Persistence and origin of the lunar core dynamo

Science.gov (United States)

Suavet, Clément; Weiss, Benjamin P.; Cassata, William S.; Shuster, David L.; Gattacceca, Jérôme; Chan, Lindsey; Garrick-Bethell, Ian; Head, James W.; Grove, Timothy L.; Fuller, Michael D.

2013-01-01

The lifetime of the ancient lunar core dynamo has implications for its power source and the mechanism of field generation. Here, we report analyses of two 3.56-Gy-old mare basalts demonstrating that they were magnetized in a stable and surprisingly intense dynamo magnetic field of at least ∼13 μT. These data extend the known lifetime of the lunar dynamo by ∼160 My and indicate that the field was likely continuously active until well after the final large basin-forming impact. This likely excludes impact-driven changes in rotation rate as the source of the dynamo at this time in lunar history. Rather, our results require a persistent power source like precession of the lunar mantle or a compositional convection dynamo. PMID:23650386

Numerical models of planetary dynamos

International Nuclear Information System (INIS)

Glatzmaier, G.A.; Roberts, P.H.

1992-01-01

We describe a nonlinear, axisymmetric, spherical-shell model of planetary dynamos. This intermediate-type dynamo model requires a prescribed helicity field (the alpha effect) and a prescribed buoyancy force or thermal wind (the omega effect) and solves for the axisymmetric time-dependent magnetic and velocity fields. Three very different time dependent solutions are obtained from different prescribed sets of alpha and omega fields

Helicity, Reconnection, and Dynamo Effects

International Nuclear Information System (INIS)

Ji, Hantao

1998-01-01

The inter-relationships between magnetic helicity, magnetic reconnection, and dynamo effects are discussed. In laboratory experiments, where two plasmas are driven to merge, the helicity content of each plasma strongly affects the reconnection rate, as well as the shape of the diffusion region. Conversely, magnetic reconnection events also strongly affect the global helicity, resulting in efficient helicity cancellation (but not dissipation) during counter-helicity reconnection and a finite helicity increase or decrease (but less efficiently than dissipation of magnetic energy) during co-helicity reconnection. Close relationships also exist between magnetic helicity and dynamo effects. The turbulent electromotive force along the mean magnetic field (alpha-effect), due to either electrostatic turbulence or the electron diamagnetic effect, transports mean-field helicity across space without dissipation. This has been supported by direct measurements of helicity flux in a laboratory plasma. When the dynamo effect is driven by electromagnetic turbulence, helicity in the turbulent field is converted to mean-field helicity. In all cases, however, dynamo processes conserve total helicity except for a small battery effect, consistent with the observation that the helicity is approximately conserved during magnetic relaxation

Present state of the theory of a MHD-dynamo

Energy Technology Data Exchange (ETDEWEB)

Soward, A M; Roberts, P H

1976-01-01

A review is given of the state of the theory of a MHD-dynamo, that is, the theory of self-excited magnetic fields in homogeneous moving liquids. A description is given of two basic approaches-the turbulent dynamos of Steinbeck, Krause and Redler and the high-conductivity dynamo of Braginski, and a look is also taken at the relation between these dynamos. Finally a look is taken at the results of recent studies of the total problem of a MHD-dynamo, that is, at the results of recent attempts to solve the electro- and hydrodynamic equations and to obtain self-excited fields. 6 figs., 122 ref. (SJR)

The magnetic universe geophysical and astrophysical dynamo theory

CERN Document Server

Rüdiger, Günther

2004-01-01

Magnetism is one of the most pervasive features of the Universe, with planets, stars and entire galaxies all having associated magnetic fields. All of these fields are generated by the motion of electrically conducting fluids, the so-called dynamo effect. The precise details of what drives the motion, and indeed what the fluid consists of, differ widely though. In this work the authors draw upon their expertise in geophysical and astrophysical MHD to explore some of these phenomena, and describe the similarities and differences between different magnetized objects. They also explain why magn

The Hottest Hot Jupiters May Host Atmospheric Dynamos

Energy Technology Data Exchange (ETDEWEB)

Rogers, T. M. [Department of Mathematics and Statistics, Newcastle University, Newcastle upon Tyne (United Kingdom); McElwaine, J. N. [Planetary Science Institute, Tucson, AZ 85721 (United States)

2017-06-01

Hot Jupiters have proven themselves to be a rich class of exoplanets that test our theories of planetary evolution and atmospheric dynamics under extreme conditions. Here, we present three-dimensional magnetohydrodynamic simulations and analytic results that demonstrate that a dynamo can be maintained in the thin, stably stratified atmosphere of a hot Jupiter, independent of the presumed deep-seated dynamo. This dynamo is maintained by conductivity variations arising from strong asymmetric heating from the planets’ host star. The presence of a dynamo significantly increases the surface magnetic field strength and alters the overall planetary magnetic field geometry, possibly affecting star–planet magnetic interactions.

Integral equation approach to time-dependent kinematic dynamos in finite domains

International Nuclear Information System (INIS)

Xu Mingtian; Stefani, Frank; Gerbeth, Gunter

2004-01-01

The homogeneous dynamo effect is at the root of cosmic magnetic field generation. With only a very few exceptions, the numerical treatment of homogeneous dynamos is carried out in the framework of the differential equation approach. The present paper tries to facilitate the use of integral equations in dynamo research. Apart from the pedagogical value to illustrate dynamo action within the well-known picture of the Biot-Savart law, the integral equation approach has a number of practical advantages. The first advantage is its proven numerical robustness and stability. The second and perhaps most important advantage is its applicability to dynamos in arbitrary geometries. The third advantage is its intimate connection to inverse problems relevant not only for dynamos but also for technical applications of magnetohydrodynamics. The paper provides the first general formulation and application of the integral equation approach to time-dependent kinematic dynamos, with stationary dynamo sources, in finite domains. The time dependence is restricted to the magnetic field, whereas the velocity or corresponding mean-field sources of dynamo action are supposed to be stationary. For the spherically symmetric α 2 dynamo model it is shown how the general formulation is reduced to a coupled system of two radial integral equations for the defining scalars of the poloidal and toroidal field components. The integral equation formulation for spherical dynamos with general stationary velocity fields is also derived. Two numerical examples - the α 2 dynamo model with radially varying α and the Bullard-Gellman model - illustrate the equivalence of the approach with the usual differential equation method. The main advantage of the method is exemplified by the treatment of an α 2 dynamo in rectangular domains

A two-billion-year history for the lunar dynamo.

Science.gov (United States)

Tikoo, Sonia M; Weiss, Benjamin P; Shuster, David L; Suavet, Clément; Wang, Huapei; Grove, Timothy L

2017-08-01

Magnetic studies of lunar rocks indicate that the Moon generated a core dynamo with surface field intensities of ~20 to 110 μT between at least 4.25 and 3.56 billion years ago (Ga). The field subsequently declined to lunar dynamo by at least 1 billion years. Such a protracted history requires an extraordinarily long-lived power source like core crystallization or precession. No single dynamo mechanism proposed thus far can explain the strong fields inferred for the period before 3.56 Ga while also allowing the dynamo to persist in such a weakened state beyond ~2.5 Ga. Therefore, our results suggest that the dynamo was powered by at least two distinct mechanisms operating during early and late lunar history.

MHD turbulent dynamo in astrophysics: Theory and numerical simulation

Science.gov (United States)

Chou, Hongsong

2001-10-01

This thesis treats the physics of dynamo effects through theoretical modeling of magnetohydrodynamic (MHD) systems and direct numerical simulations of MHD turbulence. After a brief introduction to astrophysical dynamo research in Chapter 1, the following issues in developing dynamic models of dynamo theory are addressed: In Chapter 2, nonlinearity that arises from the back reaction of magnetic field on velocity field is considered in a new model for the dynamo α-effect. The dependence of α-coefficient on magnetic Reynolds number, kinetic Reynolds number, magnetic Prandtl number and statistical properties of MHD turbulence is studied. In Chapter 3, the time-dependence of magnetic helicity dynamics and its influence on dynamo effects are studied with a theoretical model and 3D direct numerical simulations. The applicability of and the connection between different dynamo models are also discussed. In Chapter 4, processes of magnetic field amplification by turbulence are numerically simulated with a 3D Fourier spectral method. The initial seed magnetic field can be a large-scale field, a small-scale magnetic impulse, and a combination of these two. Other issues, such as dynamo processes due to helical Alfvénic waves and the implication and validity of the Zeldovich relation, are also addressed in Appendix B and Chapters 4 & 5, respectively. Main conclusions and future work are presented in Chapter 5. Applications of these studies are intended for astrophysical magnetic field generation through turbulent dynamo processes, especially when nonlinearity plays central role. In studying the physics of MHD turbulent dynamo processes, the following tools are developed: (1)A double Fourier transform in both space and time for the linearized MHD equations (Chapter 2 and Appendices A & B). (2)A Fourier spectral numerical method for direct simulation of 3D incompressible MHD equations (Appendix C).

Ionospheric disturbance dynamo

International Nuclear Information System (INIS)

Blanc, M.; Richmond, A.D.

1980-01-01

A numerical simulation study of the thermospheric winds produced by auroral heating during magnetic storms, and of their global dynamo effects, establishes the main features of the ionospheric disturbanc dynamo. Driven by auroral heating, a Hadley cell is created with equatorward winds blowing above about 120 km at mid-latitudes. The transport of angular momentum by these winds produces a subrotation of the midlatitude thermosphere, or westward motion with respect to the earth. The westward winds in turn drive equatorward Pedersen currents which accumulate charge toward the equator, resulting in the generation of a poleward electric field, a westward E x B drift, and an eastward current. When realistic local time conductivity variations are simulated, the eastward mid-latitude current is found to close partly via lower latitudes, resulting in an 'anti-Sq' type of current vortex. Both electric field and current at low latitudes thus vary in opposition to their normal quiet-day behavior. This total pattern of distrubance winds, electric fields, and currents is superimposed upon the background quiet-day pattern. When the neutral winds are artificially confined on the nightside, the basic pattern of predominantly westward E x B plasma drifts still prevails on the nightside but no longer extends into the dayside. Considerable observational evidence exists, suggesting that the ionospheric disturbance dynamo has an appreciable influence on storm-time ionospheric electric fields at middle and low latitudes

Planetary Dynamos: Investigations of Saturn and Ancient Mars

Energy Technology Data Exchange (ETDEWEB)

Stanley, Sabine [University of Toronto

2012-04-18

Magnetic field observations by spacecraft missions have provided vital information on planetary dynamos. The four giant planets as well as Earth, Mercury and Ganymede have observable magnetic fields generated by active dynamos. In contrast, Moon and Mars only have remanent crustal fields from dynamo action in their early histories. A variety of magnetic field morphologies and intensities can be found in the solar system. We have found that some of the differences between planetary magnetic fields can be explained as the result of the presence of boundary thermal variations or stably-stratified layers. In this talk, I will discuss how dynamos are affected by these complications and discuss the implications for Mars’ magnetic dichotomy and Saturn’s extremely axisymmetric magnetic field.

Measurement of the dynamo effect in a plasma

International Nuclear Information System (INIS)

Ji, H.; Prager, S.C.; Almagri, A.F.; Sarff, J.S.; Hirano, Y.; Toyama, H.

1995-11-01

A series of the detailed experiments has been conducted in three laboratory plasma devices to measure the dynamo electric field along the equilibrium field line (the α effect) arising from the correlation between the fluctuating flow velocity and magnetic field. The fluctuating flow velocity is obtained from probe measurement of the fluctuating E x B drift and electron diamagnetic drift. The three major findings are (1) the α effect accounts for the dynamo current generation, even in the time dependence through a ''sawtooth'' cycle; (2) at low collisionality the dynamo is explained primarily by the widely studied pressureless Magnetohydrodynamic (MHD) model, i.e., the fluctuating velocity is dominated by the E x B drift; (3) at high collisionality, a new ''electron diamagnetic dynamo'' is observed, in which the fluctuating velocity is dominated by the diamagnetic drift. In addition, direct measurements of the helicity flux indicate that the dynamo activity transports magnetic helicity from one part of the plasma to another, but the total helicity is roughly conserved, verifying J.B. Taylor's conjecture

The effect of collisionality and diamagnetism on the plasma dynamo

International Nuclear Information System (INIS)

Ji, H.; Yagi, Y.; Hattori, K.; Hirano, Y.; Shimada, T.; Maejima, Y.; Hayase, K.; Almagri, A.F.; Prager, S.C.; Sarff, J.S.

1995-01-01

Fluctuation-induced dynamo forces are measured over a wide range of electron collisionality in the edge of TPE-1RM20 Reversed-Field Pinch (RFP). In the collisionless region the Magnetohydrodynamic (MHD) dynamo alone can sustain the parallel current, while in the collisional region a new dynamo mechanism resulting from the fluctuations in the electron diamagnetic drift becomes dominant. A comprehensive picture of the RFP dynamo emerges by combining with earlier results from MST and REPUTE RFPs

Saturn Dynamo Model (Invited)

Science.gov (United States)

Glatzmaier, G. A.

2010-12-01

There has been considerable interest during the past few years about the banded zonal winds and global magnetic field on Saturn (and Jupiter). Questions regarding the depth to which the intense winds extend below the surface and the role they play in maintaining the dynamo continue to be debated. The types of computer models employed to address these questions fall into two main classes: general circulation models (GCMs) based on hydrostatic shallow-water assumptions from the atmospheric and ocean modeling communities and global non-hydrostatic deep convection models from the geodynamo and solar dynamo communities. The latter class can be further divided into Boussinesq models, which do not account for density stratification, and anelastic models, which do. Recent efforts to convert GCMs to deep circulation anelastic models have succeeded in producing fluid flows similar to those obtained from the original deep convection anelastic models. We describe results from one of the original anelastic convective dynamo simulations and compare them to a recent anelastic dynamo benchmark for giant gas planets. This benchmark is based on a polytropic reference state that spans five density scale heights with a radius and rotation rate similar to those of our solar system gas giants. The resulting magnetic Reynolds number is about 3000. Better spatial resolution will be required to produce more realistic predictions that capture the effects of both the density and electrical conductivity stratifications and include enough of the turbulent kinetic energy spectrum. Important additional physics may also be needed in the models. However, the basic models used in all simulation studies of the global dynamics of giant planets will hopefully first be validated by doing these simpler benchmarks.

Turbulent Liquid Metal Dynamo Experiments

International Nuclear Information System (INIS)

Forest, Cary

2007-01-01

The self-generation of magnetic fields in planets and stars--the dynamo effect--is a long-standing problem of magnetohydrodynamics and plasma physics. Until recently, research on the self-excitation process has been primarily theoretical. In this talk, I will begin with a tutorial on how magnetic fields are generated in planets and stars, describing the 'Standard Model' of self-excitation known as the alpha-omega dynamo. In this model, axisymmetric differential rotation can produce the majority of the magnetic field, but some non-axisymmetric, turbulence driven currents are also necessary. Understanding the conversion of turbulent kinetic energy in the fluid motion into electrical currents and thus magnetic fields, is a major challenge for both experiments and theory at this time. I will then report on recent results from a 1 meter diameter, spherical, liquid sodium dynamo experiment at the University of Wisconsin, in which the first clear evidence for these turbulence driven currents has been observed.

Mean-field theory and self-consistent dynamo modeling

International Nuclear Information System (INIS)

Yoshizawa, Akira; Yokoi, Nobumitsu

2001-12-01

Mean-field theory of dynamo is discussed with emphasis on the statistical formulation of turbulence effects on the magnetohydrodynamic equations and the construction of a self-consistent dynamo model. The dynamo mechanism is sought in the combination of the turbulent residual-helicity and cross-helicity effects. On the basis of this mechanism, discussions are made on the generation of planetary magnetic fields such as geomagnetic field and sunspots and on the occurrence of flow by magnetic fields in planetary and fusion phenomena. (author)

Magnetic Helicities and Dynamo Action in Magneto-rotational Turbulence

Energy Technology Data Exchange (ETDEWEB)

Bodo, G.; Rossi, P. [INAF/Osservatorio Astrofisico di Torino, Strada Osservatorio 20, I-10025 Pino Torinese (Italy); Cattaneo, F. [Department of Astronomy and Astrophysics, The University of Chicago, 5640 S. Ellis Avenue, Chicago IL 60637 (United States); Mignone, A., E-mail: bodo@oato.inaf.it [Dipartimento di Fisica, Università degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino (Italy)

2017-07-10

We examine the relationship between magnetic flux generation, taken as an indicator of large-scale dynamo action, and magnetic helicity, computed as an integral over the dynamo volume, in a simple dynamo. We consider dynamo action driven by magneto-rotational turbulence (MRT) within the shearing-box approximation. We consider magnetically open boundary conditions that allow a flux of helicity in or out of the computational domain. We circumvent the problem of the lack of gauge invariance in open domains by choosing a particular gauge—the winding gauge—that provides a natural interpretation in terms of the average winding number of pairwise field lines. We use this gauge precisely to define and measure the helicity and the helicity flux for several realizations of dynamo action. We find in these cases that the system as a whole does not break reflectional symmetry and that the total helicity remains small even in cases when substantial magnetic flux is generated. We find no particular connection between the generation of magnetic flux and the helicity or the helicity flux through the boundaries. We suggest that this result may be due to the essentially nonlinear nature of the dynamo processes in MRT.

Energy transfers in dynamos with small magnetic Prandtl numbers

KAUST Repository

Kumar, Rohit

2015-06-25

We perform numerical simulation of dynamo with magnetic Prandtl number Pm = 0.2 on 10243 grid, and compute the energy fluxes and the shell-to-shell energy transfers. These computations indicate that the magnetic energy growth takes place mainly due to the energy transfers from large-scale velocity field to large-scale magnetic field and that the magnetic energy flux is forward. The steady-state magnetic energy is much smaller than the kinetic energy, rather than equipartition; this is because the magnetic Reynolds number is near the dynamo transition regime. We also contrast our results with those for dynamo with Pm = 20 and decaying dynamo. © 2015 Taylor & Francis.

Transitions in rapidly rotating convection dynamos

Science.gov (United States)

Tilgner, A.

2013-12-01

It is commonly assumed that buoyancy in the fluid core powers the geodynamo. We study here the minimal model of a convection driven dynamo, which is a horizontal plane layer in a gravity field, filled with electrically conducting fluid, heated from below and cooled from above, and rotating about a vertical axis. Such a plane layer may be viewed as a local approximation to the geophysically more relevant spherical geometry. The numerical simulations have been run on graphics processing units with at least 960 cores. If the convection is driven stronger and stronger at fixed rotation rate, the flow behaves at some point as if it was not rotating. This transition shows in the scaling of the heat transport which can be used to distinguish slow from rapid rotation. One expects dynamos to behave differently in these two flow regimes. But even within the convection flows which are rapidly rotating according to this criterion, it will be shown that different types of dynamos exist. In one state, the magnetic field strength obeys a scaling indicative of a magnetostrophic balance, in which the Lorentz force is in equilibrium with the Coriolis force. The flow in this case is helical. A different state exists at higher magnetic Reynolds numbers, in which the magnetic energy obeys a different scaling law and the helicity of the flow is much reduced. As one increases the Rayleigh number, all other parameters kept constant, one may find both types of dynamos separated by an interval of Rayleigh numbers in which there are no dynamos at all. The effect of these transitions on energy dissipation and mean field generation have also been studied.

Differential rotation and the solar dynamo

International Nuclear Information System (INIS)

Stix, M.

1976-01-01

A number of numerical models for the generation of mean magnetic fields is examined and the fields are compared with the mean field of the Sun. In particular, αω-dynamos, which are based on differential rotation and cyclonic turbulence, are studied in the case of cylindrical surfaces of isorotation. Such dynamos have an oscillatory antisymmetric field as the most easily excited mode. Only models with an angular velocity which increases with increasing depth appear to be compatible with observations. A search for oscillatory ω x j-dynamos, where the α-effect is replaced by a different mean electric field perpendicular to the rotation vector ω and the mean current density j is also made. Oscillatory modes do exist for models with radial shear. Their migration is equatorwards for inwards increasing angular velocity. (orig./BJ) [de

Efficiency Measurement Using a Motor-Dynamo Module

Science.gov (United States)

Ng, Pun-hon; Wong, Siu-ling; Mak, Se-yuen

2009-01-01

In this article, we describe a simple method which can be used to measure the efficiency of a low power dc motor, a motor-converted dynamo and a coupled motor-dynamo module as a function of the speed of rotation. The result can also be used to verify Faraday's law of electromagnetic induction. (Contains 1 table and 8 figures.)

Physical conditions for Jupiter-like dynamo models

Science.gov (United States)

Duarte, Lúcia D. V.; Wicht, Johannes; Gastine, Thomas

2018-01-01

The Juno mission will measure Jupiter's magnetic field with unprecedented precision and provide a wealth of additional data that will allow us to constrain the planet's interior structure and dynamics. Here we analyse 66 different numerical simulations in order to explore the sensitivity of the dynamo-generated magnetic field to the planets interior properties. Jupiter field models based on pre-Juno data and up-to-date interior models based on ab initio simulations serve as benchmarks. Our results suggest that Jupiter-like magnetic fields can be found for a number of different models. These complement the steep density gradients in the outer part of the simulated shell with an electrical conductivity profile that mimics the low conductivity in the molecular hydrogen layer and thus renders the dynamo action in this region largely unimportant. We find that whether we assume an ideal gas or use the more realistic interior model based on ab initio simulations makes no difference. However, two other factors are important. A low Rayleigh number leads to a too strong axial dipole contribution while the axial dipole dominance is lost altogether when the convective driving is too strong. The required intermediate range that yields Jupiter-like magnetic fields depends on the other system properties. The second important factor is the convective magnetic Reynolds number radial profile Rmc(r), basically a product of the non-axisymmetric flow velocity and electrical conductivity. We find that the depth where Rmc exceeds about 50 is a good proxy for the top of the dynamo region. When the dynamo region sits too deep, the axial dipole is once more too dominant due to geometric reasons. Extrapolating our results to Jupiter and the result suggests that the Jovian dynamo extends to 95% of the planetary radius. The zonal flow system in our simulations is dominated by an equatorial jet which remains largely confined to the molecular layer. Where the jet reaches down to higher

An Experimental MHD Dynamo

International Nuclear Information System (INIS)

Forest, C. B.

2002-01-01

The project is designed to understand current and magnetic field generation in plasmas and other magnetohydrodynamic systems. The experiments will investigate the generation of a dynamo using liquid Na

A long-lived lunar dynamo driven by continuous mechanical stirring.

Science.gov (United States)

Dwyer, C A; Stevenson, D J; Nimmo, F

2011-11-09

Lunar rocks contain a record of an ancient magnetic field that seems to have persisted for more than 400 million years and which has been attributed to a lunar dynamo. Models of conventional dynamos driven by thermal or compositional convection have had difficulty reproducing the existence and apparently long duration of the lunar dynamo. Here we investigate an alternative mechanism of dynamo generation: continuous mechanical stirring arising from the differential motion, due to Earth-driven precession of the lunar spin axis, between the solid silicate mantle and the liquid core beneath. We show that the fluid motions and the power required to drive a dynamo operating continuously for more than one billion years and generating a magnetic field that had an intensity of more than one microtesla 4.2 billion years ago are readily obtained by mechanical stirring. The magnetic field is predicted to decrease with time and to shut off naturally when the Moon recedes far enough from Earth that the dissipated power is insufficient to drive a dynamo; in our nominal model, this occurred at about 48 Earth radii (2.7 billion years ago). Thus, lunar palaeomagnetic measurements may be able to constrain the poorly known early orbital evolution of the Moon. This mechanism may also be applicable to dynamos in other bodies, such as large asteroids.

THE TURBULENT DYNAMO IN HIGHLY COMPRESSIBLE SUPERSONIC PLASMAS

Energy Technology Data Exchange (ETDEWEB)

Federrath, Christoph [Research School of Astronomy and Astrophysics, The Australian National University, Canberra, ACT 2611 (Australia); Schober, Jennifer [Universität Heidelberg, Zentrum für Astronomie, Institut für Theoretische Astrophysik, Albert-Ueberle-Strasse 2, D-69120 Heidelberg (Germany); Bovino, Stefano; Schleicher, Dominik R. G., E-mail: christoph.federrath@anu.edu.au [Institut für Astrophysik, Georg-August-Universität Göttingen, Friedrich-Hund-Platz 1, D-37077 Göttingen (Germany)

2014-12-20

The turbulent dynamo may explain the origin of cosmic magnetism. While the exponential amplification of magnetic fields has been studied for incompressible gases, little is known about dynamo action in highly compressible, supersonic plasmas, such as the interstellar medium of galaxies and the early universe. Here we perform the first quantitative comparison of theoretical models of the dynamo growth rate and saturation level with three-dimensional magnetohydrodynamical simulations of supersonic turbulence with grid resolutions of up to 1024{sup 3} cells. We obtain numerical convergence and find that dynamo action occurs for both low and high magnetic Prandtl numbers Pm = ν/η = 0.1-10 (the ratio of viscous to magnetic dissipation), which had so far only been seen for Pm ≥ 1 in supersonic turbulence. We measure the critical magnetic Reynolds number, Rm{sub crit}=129{sub −31}{sup +43}, showing that the compressible dynamo is almost as efficient as in incompressible gas. Considering the physical conditions of the present and early universe, we conclude that magnetic fields need to be taken into account during structure formation from the early to the present cosmic ages, because they suppress gas fragmentation and drive powerful jets and outflows, both greatly affecting the initial mass function of stars.

Magnetohydrodynamic dynamos in the presence of fossil magnetic fields

International Nuclear Information System (INIS)

Boyer, D.W.

1982-01-01

A fossil magnetic field embedded in the radiative core of the Sun has been thought possible for some time now. However, such a fossil magnetic field has, a priori, not been considered a visible phenomenon due to the effects of turbulence in the solar convection zone. Since a well developed theory (referred to herein as magnetohydrodynamic dynamo theory) exists for describing the regeneration of magnetic fields in astrophysical objects like the Sun, it is possible to quantitatively evaluate the interaction of a fossil magnetic field with the magnetohydrodynamic dynamo operating in the solar convection zone. In this work, after a brief description of the basic dynamo equations, a spherical model calculation of the solar dynamo is introduced. First, the interaction of a fossil magnetic field with a dynamo in which the regeneration mechanisms of cyclonic convection and large-scale, nonuniform rotation are confined to spherical shells is calculated. It is argued that the amount of amplification or suppression of a fossil magnetic field will be smallest for a uniform distribution of cyclonic convection and nonuniform rotation, as expected in the Sun. Secondly, the interaction of a fossil magnetic field with a dynamo having a uniform distribution of cyclonic convection and large-scale, nonuniform rotation is calculated. It is found that the dipole or quadrupole moments of a fossil magnetic field are suppressed by factors of -0.35 and -0.37, respectively

Magnetic reversals from planetary dynamo waves.

Science.gov (United States)

Sheyko, Andrey; Finlay, Christopher C; Jackson, Andrew

2016-11-24

A striking feature of many natural dynamos is their ability to undergo polarity reversals. The best documented example is Earth's magnetic field, which has reversed hundreds of times during its history. The origin of geomagnetic polarity reversals lies in a magnetohydrodynamic process that takes place in Earth's core, but the precise mechanism is debated. The majority of numerical geodynamo simulations that exhibit reversals operate in a regime in which the viscosity of the fluid remains important, and in which the dynamo mechanism primarily involves stretching and twisting of field lines by columnar convection. Here we present an example of another class of reversing-geodynamo model, which operates in a regime of comparatively low viscosity and high magnetic diffusivity. This class does not fit into the paradigm of reversal regimes that are dictated by the value of the local Rossby number (the ratio of advection to Coriolis force). Instead, stretching of the magnetic field by a strong shear in the east-west flow near the imaginary cylinder just touching the inner core and parallel to the axis of rotation is crucial to the reversal mechanism in our models, which involves a process akin to kinematic dynamo waves. Because our results are relevant in a regime of low viscosity and high magnetic diffusivity, and with geophysically appropriate boundary conditions, this form of dynamo wave may also be involved in geomagnetic reversals.

Bipolar Jets Launched by a Mean-field Accretion Disk Dynamo

Science.gov (United States)

Fendt, Christian; Gaßmann, Dennis

2018-03-01

By applying magnetohydrodynamic simulations, we investigate the launching of jets driven by a disk magnetic field generated by a mean-field disk dynamo. Extending our earlier studies, we explore the bipolar evolution of the disk α 2Ω-dynamo and the outflow. We confirm that a negative dynamo-α leads to a dipolar field geometry, whereas positive values generate quadrupolar fields. The latter remain mainly confined to the disk and cannot launch outflows. We investigate a parameter range for the dynamo-α ranging from a critical value below which field generation is negligible, {α }0,{crit}=-0.0005, to α 0 = ‑1.0. For weak | {α }0| ≤slant 0.07, two magnetic loop structures with opposite polarity may arise, which leads to reconnection and disturbs the field evolution and accretion-ejection process. For a strong dynamo-α, a higher poloidal magnetic energy is reached, roughly scaling with {E}mag}∼ | {α }0| , which also leads to higher accretion and ejection rates. The terminal jet speed is governed by the available magnetic energy and increases with the dynamo-α. We find jet velocities on the order of the inner disk Keplerian velocity. For a strong dynamo-α, oscillating dynamo modes may occur that can lead to a pulsed ejection. This is triggered by an oscillating mode in the toroidal field component. The oscillation period is comparable to the Keplerian timescale in the launching region, thus too short to be associated with the knots in observed jets. We find a hemispherically asymmetric evolution for the jet and counter-jet in the mass flux and field structure.

Systematic parameter study of dynamo bifurcations in geodynamo simulations

Science.gov (United States)

Petitdemange, Ludovic

2018-04-01

We investigate the nature of the dynamo bifurcation in a configuration applicable to the Earth's liquid outer core, i.e. in a rotating spherical shell with thermally driven motions with no-slip boundaries. Unlike in previous studies on dynamo bifurcations, the control parameters have been varied significantly in order to deduce general tendencies. Numerical studies on the stability domain of dipolar magnetic fields found a dichotomy between non-reversing dipole-dominated dynamos and the reversing non-dipole-dominated multipolar solutions. We show that, by considering weak initial fields, the above transition disappears and is replaced by a region of bistability for which dipolar and multipolar dynamos coexist. Such a result was also observed in models with free-slip boundaries in which the geostrophic zonal flow can develop and participate to the dynamo mechanism for non-dipolar fields. We show that a similar process develops in no-slip models when viscous effects are reduced sufficiently. The following three regimes are distinguished: (i) Close to the onset of convection (Rac) with only the most critical convective mode (wave number) being present, dynamos set in supercritically in the Ekman number regime explored here and are dipole-dominated. Larger critical magnetic Reynolds numbers indicate that they are particularly inefficient. (ii) in the range 3 10) , the relative importance of zonal flows increases with Ra in non-magnetic models. The field topology depends on the magnitude of the initial magnetic field. The dipolar branch has a subcritical behavior whereas the multipolar branch has a supercritical behavior. By approaching more realistic parameters, the extension of this bistable regime increases. A hysteretic behavior questions the common interpretation for geomagnetic reversals. Far above the dynamo threshold (by increasing the magnetic Prandtl number), Lorentz forces contribute to the first order force balance, as predicted for planetary dynamos. When

Stable Alfven wave dynamo action in the reversed field pinch

International Nuclear Information System (INIS)

Werley, K.A.

1984-01-01

Recent advances in linear resistive MHD stability analysis are used to calculate the quasi-linear dynamo mean electromotive force of Alfven waves. This emf is incorporated into a one-dimensional transport and mean-field evolution code. The changing equilibrium is then fed back to the stability code to complete a computational framework that self-consistently evaluates a dynamic plasma dynamo. Static quasi-linear Alfven wave calculations have shown that dynamo emfs on the order of eta vector J are possible. This suggested a possible explanation of RFP behavior and a new (externally driven) mechanism for extending operation and controlling field profiles (possibly reducing plasma transport). This thesis demonstrates that the dynamo emf can quickly induce plasma currents whose emf cancels the dynamo effect. This thesis also contains extensive studies of resistive Alfven wave properties. This includes behavior versus spectral location, magnetic Reynolds number and wave number

Mean-field magnetohydrodynamics and dynamo theory

CERN Document Server

Krause, F

2013-01-01

Mean-Field Magnetohydrodynamics and Dynamo Theory provides a systematic introduction to mean-field magnetohydrodynamics and the dynamo theory, along with the results achieved. Topics covered include turbulence and large-scale structures; general properties of the turbulent electromotive force; homogeneity, isotropy, and mirror symmetry of turbulent fields; and turbulent electromotive force in the case of non-vanishing mean flow. The turbulent electromotive force in the case of rotational mean motion is also considered. This book is comprised of 17 chapters and opens with an overview of the gen

Solar and Stellar Dynamos Saas-Fee Advanced Course 39 Swiss Society for Astrophysics and Astronomy

CERN Document Server

2013-01-01

Astrophysical dynamos are at the heart of cosmic magnetic fields of a wide range of scales, from planets and stars to entire galaxies. This book presents a thorough, step-by-step introduction to solar and stellar dynamos. Looking first at the ultimate origin of cosmic seed magnetic fields, the antagonists of field amplification are next considered: resistive decay, flux expulsion, and flows ruled out by anti-dynamo theorems. Two kinematic flows that can act as dynamos are then studied: the Roberts cell and the CP-flow. Mean-field electrodynamics and derivation of the mean-field dynamo equations lead to the alpha Omega-dynamo, the flux transport dynamo, and dynamos based on the Babcock-Leighton mechanism. Alternatives to the mean-field theory are also presented, as are global MHD dynamo simulations. Fluctuations and grand minima in the solar cycle are discussed in terms of dynamo modulations through stochastic forcing and nonlinear effects. The book concludes with an overview of the major challenges in underst...

Sleuthing the Dynamo: the Final Frontier

Science.gov (United States)

Ayres, Thomas

1996-07-01

Innovative technologies are opening new windows into the Sun;from its hidden interior to the far reaches of its turbulentouter envelope: rare-earth detectors for solar neutrinos; theGONG project for helioseismology; SOHO for high-resolutionXUV spectroscopy, and YOHKOH for coronal X-ray imaging. Atthe same time, a fleet of space observatories--ROSAT, EUVE,ASCA, and HST itself--are providing unprecedented views ofthe vacuum-UV and X-ray emissions of stars in our Galacticneighborhood. These seemingly unrelated developments are infact deeply connected. A central issue of solar-stellarphysics is the nature and origin of magnetic activity: thelink between the interior dynamics of a late-type star and theviolent state of its outermost coronal layers. As solarphysicists are unlocking the secrets of the hydromagneticDynamo deep inside the Sun, we and others have beendocumenting the early evolution of the Dynamo and itsassociated external gas-dynamic activity. In particular, wehave obtained HST/FOS spectra of ten young solar-type starsin three nearby open clusters--the Hyades, Pleiades, andAlpha Persei--ranging in age from 50 Myr to 600 Myr. We havesupplemented the HST spectroscopy with deep ROSAT pointings, and ground-based studies. Here, we will continue the HSTside of our project by obtaining FUV spectra of two AlphaPerseids from our original program (but not yet observed),and high-S/N follow-up measurements of the hyperactive PleiadH II 314.

Outsourcing an Effective Postdischarge Call Program

Science.gov (United States)

Meek, Kevin L.; Williams, Paula; Unterschuetz, Caryn J.

2018-01-01

To improve patient satisfaction ratings and decrease readmissions, many organizations utilize internal staff to complete postdischarge calls to recently released patients. Developing, implementing, monitoring, and sustaining an effective call program can be challenging and have eluded some of the renowned medical centers in the country. Using collaboration with an outsourced vendor to bring state-of-the-art call technology and staffed with specially trained callers, health systems can achieve elevated levels of engagement and satisfaction for their patients postdischarge. PMID:29494453

Magnetorotational Dynamo Action in the Shearing Box

Science.gov (United States)

Walker, Justin; Boldyrev, Stanislav

2017-10-01

Magnetic dynamo action caused by the magnetorotational instability is studied in the shearing-box approximation with no imposed net magnetic flux. Consistent with recent studies, the dynamo action is found to be sensitive to the aspect ratio of the box: it is much easier to obtain in tall boxes (stretched in the direction normal to the disk plane) than in long boxes (stretched in the radial direction). Our direct numerical simulations indicate that the dynamo is possible in both cases, given a large enough magnetic Reynolds number. To explain the relatively larger effort required to obtain the dynamo action in a long box, we propose that the turbulent eddies caused by the instability most efficiently fold and mix the magnetic field lines in the radial direction. As a result, in the long box the scale of the generated strong azimuthal (stream-wise directed) magnetic field is always comparable to the scale of the turbulent eddies. In contrast, in the tall box the azimuthal magnetic flux spreads in the vertical direction over a distance exceeding the scale of the turbulent eddies. As a result, different vertical sections of the tall box are permeated by large-scale nonzero azimuthal magnetic fluxes, facilitating the instability. NSF AGS-1261659, Vilas Associates Award, NSF-Teragrid Project TG-PHY110016.

Energy fluxes in helical magnetohydrodynamics and dynamo action

Indian Academy of Sciences (India)

... large-scale magnetic field arising due to non-helical interactions and (2) inverse energy flux of magnetic energy caused by helical interactions. Based on our flux results, a primitive model for galactic dynamo has been constructed. Our calculations yield dynamo time-scale for a typical galaxy to be of the order of 108 years.

A THREE-DIMENSIONAL BABCOCK-LEIGHTON SOLAR DYNAMO MODEL

International Nuclear Information System (INIS)

Miesch, Mark S.; Dikpati, Mausumi

2014-01-01

We present a three-dimensional (3D) kinematic solar dynamo model in which poloidal field is generated by the emergence and dispersal of tilted sunspot pairs (more generally bipolar magnetic regions, or BMRs). The axisymmetric component of this model functions similarly to previous 2.5 dimensional (2.5D, axisymmetric) Babcock-Leighton (BL) dynamo models that employ a double-ring prescription for poloidal field generation but we generalize this prescription into a 3D flux emergence algorithm that places BMRs on the surface in response to the dynamo-generated toroidal field. In this way, the model can be regarded as a unification of BL dynamo models (2.5D in radius/latitude) and surface flux transport models (2.5D in latitude/longitude) into a more self-consistent framework that builds on the successes of each while capturing the full 3D structure of the evolving magnetic field. The model reproduces some basic features of the solar cycle including an 11 yr periodicity, equatorward migration of toroidal flux in the deep convection zone, and poleward propagation of poloidal flux at the surface. The poleward-propagating surface flux originates as trailing flux in BMRs, migrates poleward in multiple non-axisymmetric streams (made axisymmetric by differential rotation and turbulent diffusion), and eventually reverses the polar field, thus sustaining the dynamo. In this Letter we briefly describe the model, initial results, and future plans

Dynamos and MHD theory of turbulence suppression

International Nuclear Information System (INIS)

Yoshizawa, Akira; Yokoi, Nobumitsu; Itoh, Sanae-I; Itoh, Kimitaka

2003-12-01

Characteristics of electrically-conducting media are reviewed from the macroscopic viewpoint based on the mean-field magnetohydrodynamics, while being compared with the methodology and knowledge in fluid mechanics. The themes covered in this review range from the generation mechanism of stellar magnetic fields (dynamo) to transport properties in fusion. The primary concern here is to see the characteristics common to these apparently different phenomena, within the framework of the mean-field theory. Owing to the intrinsic limitation of the approach, the present discussions are limited more or less to specific aspects of phenomena. They are supplemented with the reference to theoretical, numerical, and observational approaches intrinsic to each theme. In the description of dynamo phenomena, an emphasis is put on the cross-helicity dynamo. Features common to the stellar magnetic-field generation and the rotational-motion drive in toroidal plasmas are illustrated on this basis. (author)

Energy transfers and magnetic energy growth in small-scale dynamo

KAUST Repository

Kumar, Rohit Raj; Verma, Mahendra K.; Samtaney, Ravi

2013-01-01

In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulations for the magnetic Prandtl number Pm = 20

A Model of the Turbulent Electric Dynamo in Multi-Phase Media

Science.gov (United States)

Dementyeva, Svetlana; Mareev, Evgeny

2016-04-01

Many terrestrial and astrophysical phenomena witness the conversion of kinetic energy into electric energy (the energy of the quasi-stationary electric field) in conducting media, which is natural to treat as manifestations of electric dynamo by analogy with well-known theory of magnetic dynamo. Such phenomena include thunderstorms and lightning in the Earth's atmosphere and atmospheres of other planets, electric activity caused by dust storms in terrestrial and Martian atmospheres, snow storms, electrical discharges occurring in technological setups, connected with intense mixing of aerosol particles like in the milling industry. We have developed a model of the large-scale turbulent electric dynamo in a weakly conducting medium, containing two heavy-particle components. We have distinguished two main classes of charging mechanisms (inductive and non-inductive) in accordance with the dependence or independence of the electric charge, transferred during a particle collision, on the electric field intensity and considered the simplified models which demonstrate the possibility of dynamo realization and its specific peculiarities for these mechanisms. Dynamo (the large-scale electric field growth) appears due to the charge separation between the colliding and rebounding particles. This process is may be greatly intensified by the turbulent mixing of particles with different masses and, consequently, different inertia. The particle charge fluctuations themselves (small-scale dynamo), however, do not automatically mean growth of the large-scale electric field without a large-scale asymmetry. Such an asymmetry arises due to the dependence of the transferred charge magnitude on the electric field intensity in the case of the inductive mechanism of charge separation, or due to the gravity and convection for non-inductive mechanisms. We have found that in the case of the inductive mechanism the large-scale dynamo occurs if the medium conductivity is small enough while the

On self-exciting coupled Faraday disk homopolar dynamos driving series motors

Science.gov (United States)

Moroz, Irene M.; Hide, Raymond; Soward, Andrew M.

1998-06-01

We present the results of a preliminary analytical and numerical study of one of the simpler members of a hierarchy of N (where N ≥ 1) coupled self-exciting Faraday disk homopolar dynamos, incorporating motors as additional electrical elements driven by the dynamo-generated current, as proposed by Hide (1997). The hierarchy is a generalisation of a single disk dynamo ( N = 1) with just one electric motor in the system, and crucially, incorporating effects due to mechanical friction in both the disk and the motor, as investigated by Hide et al. (1996). This is describable by a set of three coupled autonomous nonlinear ordinary differential equations, which, due to the presence of the motor, has solutions corresponding to co-existing periodic states of increasing complexity, as well as to chaotic dynamics. We consider the case of two such homopolar dynamos ( N = 2) with generally dissimilar characteristics but coupled together magnetically, with the aim of determining the extent to which this coupled system differs in its behaviour from the single disk dynamo with a series motor (Hide et al. 1996). In the case when the units are identical, the behaviour of the double dynamo system (after initial transients have decayed away) is identical to that of the single dynamo system, with solutions (including “synchronised chaos”) locked in both amplitude and phase. When there is no motor in the system and the coefficient of mechanical friction in the disks is small, these transients resemble the well-known ‘non-synchronous’, but structurally unstable Rikitake solution.

GRAND MINIMA AND EQUATORWARD PROPAGATION IN A CYCLING STELLAR CONVECTIVE DYNAMO

Energy Technology Data Exchange (ETDEWEB)

Augustson, Kyle; Miesch, Mark [High Altitude Observatory, Center Green 1, Boulder, CO 80301 (United States); Brun, Allan Sacha [Laboratoire AIM Paris-Saclay, CEA/DSM–CNRS–Université Paris Diderot, IRFU/SAp, Gif-sur-Yvette (France); Toomre, Juri [JILA and Department of Astrophysical and Planetary Sciences, University of Colorado, Boulder, CO 80309 (United States)

2015-08-20

The 3D MHD Anelastic Spherical Harmonic code, using slope-limited diffusion, is employed to capture convective and dynamo processes achieved in a global-scale stellar convection simulation for a model solar-mass star rotating at three times the solar rate. The dynamo-generated magnetic fields possesses many timescales, with a prominent polarity cycle occurring roughly every 6.2 years. The magnetic field forms large-scale toroidal wreaths, whose formation is tied to the low Rossby number of the convection in this simulation. The polarity reversals are linked to the weakened differential rotation and a resistive collapse of the large-scale magnetic field. An equatorial migration of the magnetic field is seen, which is due to the strong modulation of the differential rotation rather than a dynamo wave. A poleward migration of magnetic flux from the equator eventually leads to the reversal of the polarity of the high-latitude magnetic field. This simulation also enters an interval with reduced magnetic energy at low latitudes lasting roughly 16 years (about 2.5 polarity cycles), during which the polarity cycles are disrupted and after which the dynamo recovers its regular polarity cycles. An analysis of this grand minimum reveals that it likely arises through the interplay of symmetric and antisymmetric dynamo families. This intermittent dynamo state potentially results from the simulation’s relatively low magnetic Prandtl number. A mean-field-based analysis of this dynamo simulation demonstrates that it is of the α-Ω type. The timescales that appear to be relevant to the magnetic polarity reversal are also identified.

Simulation study of dynamo structure in reversed field pinch

International Nuclear Information System (INIS)

Nagata, A.; Sato, K.I.; Ashida, H.; Amano, T.

1992-10-01

The dynamo structure in the reversed field pinch (RFP) is studied through the nonlinear dynamics of single-helicity mode. Simulation is concentrated upon the physical structure of nonlinear interactions of the plasma flow and magnetic fluctuation. The result indicates that when the initial equilibrium profile is deformed by resistive diffusion, the radial flow is driven near the core of the plasma. As this flow forms a vortex structure and magnetic fluctuation grows radially, the dynamo electric field is spirally induced just inside the reversal surface and then the toroidal flux is increased. This dynamo electric field correlates to nonlinear evolution of the kinetic energy of m=1 mode, and the increase of the toroidal flux is originated in the growth process of the magnetic energy of this mode. Consequently, the RFP configuration can be sustained by the single-helicity evolution of m=1 mode alone, and the electric field induced by the interactions of the toroidal velocity and the radial magnetic field is the most dominant source on the dynamo action. (author)

Gravitational dynamos and the low-frequency geomagnetic secular variation.

Science.gov (United States)

Olson, P

2007-12-18

Self-sustaining numerical dynamos are used to infer the sources of low-frequency secular variation of the geomagnetic field. Gravitational dynamo models powered by compositional convection in an electrically conducting, rotating fluid shell exhibit several regimes of magnetic field behavior with an increasing Rayleigh number of the convection, including nearly steady dipoles, chaotic nonreversing dipoles, and chaotic reversing dipoles. The time average dipole strength and dipolarity of the magnetic field decrease, whereas the dipole variability, average dipole tilt angle, and frequency of polarity reversals increase with Rayleigh number. Chaotic gravitational dynamos have large-amplitude dipole secular variation with maximum power at frequencies corresponding to a few cycles per million years on Earth. Their external magnetic field structure, dipole statistics, low-frequency power spectra, and polarity reversal frequency are comparable to the geomagnetic field. The magnetic variability is driven by the Lorentz force and is characterized by an inverse correlation between dynamo magnetic and kinetic energy fluctuations. A constant energy dissipation theory accounts for this inverse energy correlation, which is shown to produce conditions favorable for dipole drift, polarity reversals, and excursions.

SpF: Enabling Petascale Performance for Pseudospectral Dynamo Models

Science.gov (United States)

Jiang, W.; Clune, T.; Vriesema, J.; Gutmann, G.

2013-12-01

Pseudospectral (PS) methods possess a number of characteristics (e.g., efficiency, accuracy, natural boundary conditions) that are extremely desirable for dynamo models. Unfortunately, dynamo models based upon PS methods face a number of daunting challenges, which include exposing additional parallelism, leveraging hardware accelerators, exploiting hybrid parallelism, and improving the scalability of global memory transposes. Although these issues are a concern for most models, solutions for PS methods tend to require far more pervasive changes to underlying data and control structures. Further, improvements in performance in one model are difficult to transfer to other models, resulting in significant duplication of effort across the research community. We have developed an extensible software framework for pseudospectral methods called SpF that is intended to enable extreme scalability and optimal performance. High-level abstractions provided by SpF unburden applications of the responsibility of managing domain decomposition and load balance while reducing the changes in code required to adapt to new computing architectures. The key design concept in SpF is that each phase of the numerical calculation is partitioned into disjoint numerical 'kernels' that can be performed entirely in-processor. The granularity of domain-decomposition provided by SpF is only constrained by the data-locality requirements of these kernels. SpF builds on top of optimized vendor libraries for common numerical operations such as transforms, matrix solvers, etc., but can also be configured to use open source alternatives for portability. SpF includes several alternative schemes for global data redistribution and is expected to serve as an ideal testbed for further research into optimal approaches for different network architectures. In this presentation, we will describe the basic architecture of SpF as well as preliminary performance data and experience with adapting legacy dynamo codes

3-dimensional simulation of dynamo effect of reversed field pinch

International Nuclear Information System (INIS)

Koide, Shinji.

1990-09-01

A non-linear numerical simulation of the dynamo effect of a reversed field pinch (RFP) with finite beta is presented. It is shown that the m=-1, n=(9,10,11,....,19) modes cause the dynamo effect and sustain the field reversed configuration. The role of the m=0 modes on the dynamo effect is carefully examined. Our simulation shows that the magnetic field fluctuation level scales as S -0.2 or S -0.3 in the range of 10 3 5 , while Nebel, Caramana and Schnack obtained the fluctuation level is independent of S for a pressureless RFP plasma. (author)

Stellar rotation, dynamo, electromagnetic braking, age an lithium burning

International Nuclear Information System (INIS)

Schatzmann, E.

1989-01-01

After an introduction describing the problem and the observational tests of the theory a consistant model of the dynamo mechanism in rotating star is presented. This provides for the electromagnetic braking a law Ω ∼ (1.t/t c har) -3 / 4 , in good agreement with the observations. This rests on the hypothesis that the main contribution to the EM braking is due to the magnetic field present in bipolar magnetic spots at the surface of the stellar disk. The premain sequence EM braking provides an initial angular velocity on arrival on the main sequence which is slightly smaller than the angular velocity when the dynamo turns on. Starting the dynamo takes place when the level at which the (αΩ) dynamo number becomes larger than one drops below the ionization level of hydrogen. Before that time, the surface dynamo mechanism would take place in a region of low ionization, where the magnetic Reynods number is so small that dissipation overtakes the building of the magnetic field. Turbulent mixing with a turbulent diffusion coefficient proportional to Ω 2 provides a consistant picture of the time and mass dependance of the surface abundance of Lithium. When the level of Li-burning is sufficiently far from the bottom of the convective zone an asymptotic value of lithium abundance is reached. This can explain the anomalous Li abundance of pop.II stars. (author). 40 refs

Stellar convection and dynamo theory

Energy Technology Data Exchange (ETDEWEB)

Jennings, R L

1989-10-01

In considering the large scale stellar convection problem the outer layers of a star are modelled as two co-rotating plane layers coupled at a fluid/fluid interface. Heating from below causes only the upper fluid to convect, although this convection can penetrate into the lower fluid. Stability analysis is then used to find the most unstable mode of convection. With parameters appropriate to the Sun the most unstable mode is steady convection in thin cells (aspect ratio {approx equal} 0.2) filling the convection zone. There is negligible vertical motion in the lower fluid, but considerable thermal penetration, and a large jump in helicity at the interface, which has implications for dynamo theory. An {alpha}{omega} dynamo is investigated in isolation from the convection problem. Complexity is included by allowing both latitudinal and time dependence in the magnetic fields. The nonlinear dynamics of the resulting partial differential equations are analysed in considerable detail. On varying the main control parameter D (the dynamo number), many transitions of behaviour are found involving many forms of time dependence, but not chaos. Further, solutions which break equatorial symmetry are common and provide a theoretical explanation of solar observations which have this symmetry. Overall the behaviour was more complicated than expected. In particular, there were multiple stable solutions at fixed D, meaning that similar stars can have very different magnetic patterns, depending upon their history. (author).

Small-scale dynamo at low magnetic Prandtl numbers

Science.gov (United States)

Schober, Jennifer; Schleicher, Dominik; Bovino, Stefano; Klessen, Ralf S.

2012-12-01

The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude, fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(ℓ)∝ℓϑ, where v(ℓ) is the eddy velocity at a scale ℓ. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with ϑ=1/3 to highly compressible Burgers turbulence with ϑ=1/2. In this work, we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the evolution of the small-scale magnetic field, using the WKB approximation. In the limit of low magnetic Prandtl numbers, the growth rate is proportional to Rm(1-ϑ)/(1+ϑ). We furthermore discuss the critical magnetic Reynolds number Rmcrit, which is required for small-scale dynamo action. The value of Rmcrit is roughly 100 for Kolmogorov turbulence and 2700 for Burgers. Furthermore, we discuss that Rmcrit provides a stronger constraint in the limit of low Pm than it does for large Pm. We conclude that the small-scale dynamo can operate in the regime of low magnetic Prandtl numbers if the magnetic Reynolds number is large enough. Thus, the magnetic field amplification on small scales can take place in a broad range of physical environments and amplify week magnetic seed fields on short time scales.

Small-scale dynamo at low magnetic Prandtl numbers.

Science.gov (United States)

Schober, Jennifer; Schleicher, Dominik; Bovino, Stefano; Klessen, Ralf S

2012-12-01

The present-day Universe is highly magnetized, even though the first magnetic seed fields were most probably extremely weak. To explain the growth of the magnetic field strength over many orders of magnitude, fast amplification processes need to operate. The most efficient mechanism known today is the small-scale dynamo, which converts turbulent kinetic energy into magnetic energy leading to an exponential growth of the magnetic field. The efficiency of the dynamo depends on the type of turbulence indicated by the slope of the turbulence spectrum v(ℓ)∝ℓ^{ϑ}, where v(ℓ) is the eddy velocity at a scale ℓ. We explore turbulent spectra ranging from incompressible Kolmogorov turbulence with ϑ=1/3 to highly compressible Burgers turbulence with ϑ=1/2. In this work, we analyze the properties of the small-scale dynamo for low magnetic Prandtl numbers Pm, which denotes the ratio of the magnetic Reynolds number, Rm, to the hydrodynamical one, Re. We solve the Kazantsev equation, which describes the evolution of the small-scale magnetic field, using the WKB approximation. In the limit of low magnetic Prandtl numbers, the growth rate is proportional to Rm^{(1-ϑ)/(1+ϑ)}. We furthermore discuss the critical magnetic Reynolds number Rm_{crit}, which is required for small-scale dynamo action. The value of Rm_{crit} is roughly 100 for Kolmogorov turbulence and 2700 for Burgers. Furthermore, we discuss that Rm_{crit} provides a stronger constraint in the limit of low Pm than it does for large Pm. We conclude that the small-scale dynamo can operate in the regime of low magnetic Prandtl numbers if the magnetic Reynolds number is large enough. Thus, the magnetic field amplification on small scales can take place in a broad range of physical environments and amplify week magnetic seed fields on short time scales.

A spherical Taylor-Couette dynamo

Science.gov (United States)

Marcotte, Florence; Gissinger, Christophe

2016-04-01

We present a new scenario for magnetic field amplification in the planetary interiors where an electrically conducting fluid is confined in a differentially rotating, spherical shell (spherical Couette flow) with thin aspect-ratio. When the angular momentum sufficiently decreases outwards, a primary hydrodynamic instability is widely known to develop in the equatorial region, characterized by pairs of counter-rotating, axisymmetric toroidal vortices (Taylor vortices) similar to those observed in cylindrical Couette flow. We characterize the subcritical dynamo bifurcation due to this spherical Taylor-Couette flow and study its evolution as the flow successively breaks into wavy and turbulent Taylor vortices for increasing Reynolds number. We show that the critical magnetic Reynolds number seems to reach a constant value as the Reynolds number is gradually increased. The role of global rotation on the dynamo threshold and the implications for planetary interiors are finally discussed.

Towards the geophysical regime in numerical dynamo models: studies of rapidly-rotating convection driven dynamos with low Pm and constant heat flux boundary conditions

DEFF Research Database (Denmark)

Sheyko, A.A.; Finlay, Chris; Marti, P.

We present a set of numerical dynamo models with the convection strength varied by a factor of 30 and the ratio of magnetic to viscous diffusivities by a factor of 20 at rapid rotation rates (E =nu/(2 Omega d^2 ) = 10-6 and 10-7 ) using a heat flux outer BC. This regime has been little explored...... on the structure of the dynamos and how this changes in relation to the selection of control parameters, a comparison with the proposed rotating convection and dynamo scaling laws, energy spectra of steady solutions and inner core rotation rates. Magnetic field on the CMB. E=2.959*10-7, Ra=6591.0, Pm=0.05, Pr=1....

Magnetic field saturation in the Riga dynamo experiment.

Science.gov (United States)

Gailitis, A; Lielausis, O; Platacis, E; Dement'ev, S; Cifersons, A; Gerbeth, G; Gundrum, T; Stefani, F; Christen, M; Will, G

2001-04-02

After the dynamo experiment in November 1999 [A. Gailitis et al., Phys. Rev. Lett. 84, 4365 (2000)] had shown magnetic field self-excitation in a spiraling liquid metal flow, in a second series of experiments emphasis was placed on the magnetic field saturation regime as the next principal step in the dynamo process. The dependence of the strength of the magnetic field on the rotation rate is studied. Various features of the saturated magnetic field are outlined and possible saturation mechanisms are discussed.

The Dynamo package for tomography and subtomogram averaging: components for MATLAB, GPU computing and EC2 Amazon Web Services.

Science.gov (United States)

Castaño-Díez, Daniel

2017-06-01

Dynamo is a package for the processing of tomographic data. As a tool for subtomogram averaging, it includes different alignment and classification strategies. Furthermore, its data-management module allows experiments to be organized in groups of tomograms, while offering specialized three-dimensional tomographic browsers that facilitate visualization, location of regions of interest, modelling and particle extraction in complex geometries. Here, a technical description of the package is presented, focusing on its diverse strategies for optimizing computing performance. Dynamo is built upon mbtools (middle layer toolbox), a general-purpose MATLAB library for object-oriented scientific programming specifically developed to underpin Dynamo but usable as an independent tool. Its structure intertwines a flexible MATLAB codebase with precompiled C++ functions that carry the burden of numerically intensive operations. The package can be delivered as a precompiled standalone ready for execution without a MATLAB license. Multicore parallelization on a single node is directly inherited from the high-level parallelization engine provided for MATLAB, automatically imparting a balanced workload among the threads in computationally intense tasks such as alignment and classification, but also in logistic-oriented tasks such as tomogram binning and particle extraction. Dynamo supports the use of graphical processing units (GPUs), yielding considerable speedup factors both for native Dynamo procedures (such as the numerically intensive subtomogram alignment) and procedures defined by the user through its MATLAB-based GPU library for three-dimensional operations. Cloud-based virtual computing environments supplied with a pre-installed version of Dynamo can be publicly accessed through the Amazon Elastic Compute Cloud (EC2), enabling users to rent GPU computing time on a pay-as-you-go basis, thus avoiding upfront investments in hardware and longterm software maintenance.

Stable Alfven-wave dynamo action in the reversed-field pinch

International Nuclear Information System (INIS)

Werley, K.A.

1984-01-01

Previous theoretical work has suggested that Alfven waves may be related to the anomalous toroidal magnetic flux generation and extended (over classical expectations) discharge times observed in the reversed-field pinch. This thesis examines the dynamo action of stable Alfven waves as a means of generating toroidal flux. Recent advances in linear resistive MHD stability analysis are used to calculate the quasi-linear dynamo mean electromotive force of Alfven waves. This emf is incorporated into a one-dimensional transport and mean-field evolution code. The changing equilibrium is then fed back to the stability code to complete a computational framework that self-consistently evaluates a dynamic plasma dynamo. This technique is readily extendable to other plasmas in which dynamic stable model action is of interest. Such plasmas include Alfven wave current-drive and plasma heating for fusion devices, as well as astrophysical and geophysical dynamo systems. This study also contains extensive studies of resistive Alfven wave properties. This includes behavior versus spectral location, magnetic Reynolds number and wave number

A wet, heterogeneous lunar interior: Lower mantle and core dynamo evolution

Science.gov (United States)

Evans, A. J.; Zuber, M. T.; Weiss, B. P.; Tikoo, S. M.

2014-05-01

While recent analyses of lunar samples indicate the Moon had a core dynamo from at least 4.2-3.56 Ga, mantle convection models of the Moon yield inadequate heat flux at the core-mantle boundary to sustain thermal core convection for such a long time. Past investigations of lunar dynamos have focused on a generally homogeneous, relatively dry Moon, while an initial compositionally stratified mantle is the expected consequence of a postaccretionary lunar magma ocean. Furthermore, recent re-examination of Apollo samples and geophysical data suggests that the Moon contains at least some regions with high water content. Using a finite element model, we investigate the possible consequences of a heterogeneously wet, compositionally stratified interior for the evolution of the Moon. We find that a postoverturn model of mantle cumulates could result in a core heat flux sufficiently high to sustain a dynamo through 2.5 Ga and a maximum surface, dipolar magnetic field strength of less than 1 μT for a 350-km core and near ˜2 μT for a 450-km core. We find that if water was transported or retained preferentially in the deep interior, it would have played a significant role in transporting heat out of the deep interior and reducing the lower mantle temperature. Thus, water, if enriched in the lower mantle, could have influenced core dynamo timing by over 1.0 Gyr and enhanced the vigor of a lunar core dynamo. Our results demonstrate the plausibility of a convective lunar core dynamo even beyond the period currently indicated by the Apollo samples.

Feasible homopolar dynamo with sliding liquid-metal contacts

OpenAIRE

Priede, Jānis; Avalos-Zúñiga, Raúl

2013-01-01

We present a feasible homopolar dynamo design consisting of a flat, multi-arm spiral coil, which is placed above a fast-spinning metal ring and connected to the latter by sliding liquid-metal electrical contacts. Using a simple, analytically solvable axisymmetric model, we determine the optimal design of such a setup. For small contact resistance, the lowest magnetic Reynolds number, Rm~34.6, at which the dynamo can work, is attained at the optimal ratio of the outer and inner radii of the ri...

Dynamical Regimes and the Dynamo Bifurcation in Geodynamo Simulations

Science.gov (United States)

Petitdemange, L.

2017-12-01

We investigate the nature of the dynamo bifurcation in a configuration applicable to the Earth's liquid outer core : in a rotating spherical shell with thermally driven motions with no-slip boundaries. Unlike previous studies on dynamo bifurcations, the control parameters have been varied significantly in order to deduce general tendencies. Numerical studies on the stability domain of dipolar magnetic fields found a dichotomy between non-reversing dipole-dominated dynamos and the reversing non-dipole-dominated multipolar solutions. We show that, by considering weak initial fields, the above transition is replaced by a region of bistability for which dipolar and multipolar dynamos coexist. Such a result was also observed in models with free-slip boundaries in which the strong shear of geostrophic zonal flows can develop and gives rise to non-dipolar fields. We show that a similar process develops in no-slip models when viscous effects are reduced sufficiently.Close to the onset of convection (Rac), the axial dipole grows exponentially in the kinematic phase and saturation occurs by marginally changing the flow structure close to the dynamo threshold Rmc. The resulting bifurcation is then supercritical.In the range 3RacIf (Ra/Ra_c>10), important zonal flows develop in non-magnetic models with low viscosity. The field topology depends on the initial magnetic field. The dipolar branch has a subcritical behaviour whereas the multipolar branch is supercritical. By approaching more realistic parameters, the extension of this bistable regime increases (lower Rossby numbers). An hysteretic behaviour questions the common interpretation for geomagnetic reversals. Far above Rm_c$, the Lorentz force becomes dominant, as it is expected in planetary cores.

Spectral gaps, inertial manifolds and kinematic dynamos

Energy Technology Data Exchange (ETDEWEB)

Nunez, Manuel [Departamento de Analisis Matematico, Universidad de Valladolid, 47005 Valladolid (Spain)]. E-mail: mnjmhd@am.uva.es

2005-10-17

Inertial manifolds are desirable objects when ones wishes a dynamical process to behave asymptotically as a finite-dimensional ones. Recently [Physica D 194 (2004) 297] these manifolds are constructed for the kinematic dynamo problem with time-periodic velocity. It turns out, however, that the conditions imposed on the fluid velocity to guarantee the existence of inertial manifolds are too demanding, in the sense that they imply that all the solutions tend exponentially to zero. The inertial manifolds are meaningful because they represent different decay rates, but the classical dynamos where the magnetic field is maintained or grows are not covered by this approach, at least until more refined estimates are found.

A study of the required Rayleigh number to sustain dynamo with various inner core radius

Science.gov (United States)

Nishida, Y.; Katoh, Y.; Matsui, H.; Kumamoto, A.

2017-12-01

It is widely accepted that the geomagnetic field is sustained by thermal and compositional driven convections of a liquid iron alloy in the outer core. The generation process of the geomagnetic field has been studied by a number of MHD dynamo simulations. Recent studies of the ratio of the Earth's core evolution suggest that the inner solid core radius ri to the outer liquid core radius ro changed from ri/ro = 0 to 0.35 during the last one billion years. There are some studies of dynamo in the early Earth with smaller inner core than the present. Heimpel et al. (2005) revealed the Rayleigh number Ra of the onset of dynamo process as a function of ri/ro from simulation, while paleomagnetic observation shows that the geomagnetic field has been sustained for 3.5 billion years. While Heimpel and Evans (2013) studied dynamo processes taking into account the thermal history of the Earth's interior, there were few cases corresponding to the early Earth. Driscoll (2016) performed a series of dynamo based on a thermal evolution model. Despite a number of dynamo simulations, dynamo process occurring in the interior of the early Earth has not been fully understood because the magnetic Prandtl numbers in these simulations are much larger than that for the actual outer core.In the present study, we performed thermally driven dynamo simulations with different aspect ratio ri/ro = 0.15, 0.25 and 0.35 to evaluate the critical Ra for the thermal convection and required Ra to maintain the dynamo. For this purpose, we performed simulations with various Ra and fixed the other control parameters such as the Ekman, Prandtl, and magnetic Prandtl numbers. For the initial condition and boundary conditions, we followed the dynamo benchmark case 1 by Christensen et al. (2001). The results show that the critical Ra increases with the smaller aspect ratio ri/ro. It is confirmed that larger amplitude of buoyancy is required in the smaller inner core to maintain dynamo.

New Mexico Liquid Metal αω -dynamo experiment: Most Recent Progress

Science.gov (United States)

Si, Jiahe; Sonnenfeld, Richard; Colgate, Art; Li, Hui

2017-10-01

The goal of the New Mexico Liquid Metal αω -dynamo experiment is to demonstrate a galactic dynamo can be generated through two phases, the ω-phase and α-phase by two semi-coherent flows in laboratory. We have demonstrated an 8-fold poloidal-to-toroidal flux amplification from differential rotation (the ω-effect) by minimizing turbulence in our apparatus. To demonstrate the α-effect, major upgrades are needed. The upgrades include building a helicity injection facility, mounting new 100hp motors and new sensors, designing a new data acquisition system capable of transmitting data from about 80 sensors in a high speed rotating frame with an overall 200kS/sec sampling rate. We hope the upgrade can be utilized to answer the question of whether a self-sustaining αω -dynamo can be implemented with a realistic lab fluid flow field, as well as to obtain more details to understand dynamo action in highly turbulent Couette flow.

Energy transfers and magnetic energy growth in small-scale dynamo

KAUST Repository

Kumar, Rohit Raj

2013-12-01

In this letter we investigate the dynamics of magnetic energy growth in small-scale dynamo by studying energy transfers, mainly energy fluxes and shell-to-shell energy transfers. We perform dynamo simulations for the magnetic Prandtl number Pm = 20 on 10243 grid using the pseudospectral method. We demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers moves towards lower wave numbers as dynamo evolves, which is the reason why the integral scale of the magnetic field increases with time. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. Copyright © EPLA, 2013.

Nonlinear dynamo in the intracluster medium

Science.gov (United States)

Beresnyak, Andrey; Miniati, Francesco

2018-05-01

Hot plasma in galaxy clusters, the intracluster medium is observed to be magnetized with magnetic fields of around a μG and the correlation scales of tens of kiloparsecs, the largest scales of the magnetic field so far observed in the Universe. Can this magnetic field be used as a test of the primordial magnetic field in the early Universe? In this paper, we argue that if the cluster field was created by the nonlinear dynamo, the process would be insensitive to the value of the initial field. Our model combines state of the art hydrodynamic simulations of galaxy cluster formation in a fully cosmological context with nonlinear dynamo theory. Initial field is not a parameter in this model, yet it predicts magnetic scale and strength compatible with observations.

Turbulent transport coefficients in spherical wedge dynamo simulations of solar-like stars

Science.gov (United States)

Warnecke, J.; Rheinhardt, M.; Tuomisto, S.; Käpylä, P. J.; Käpylä, M. J.; Brandenburg, A.

2018-01-01

Aims: We investigate dynamo action in global compressible solar-like convective dynamos in the framework of mean-field theory. Methods: We simulate a solar-type star in a wedge-shaped spherical shell, where the interplay between convection and rotation self-consistently drives a large-scale dynamo. To analyze the dynamo mechanism we apply the test-field method for azimuthally (φ) averaged fields to determine the 27 turbulent transport coefficients of the electromotive force, of which six are related to the α tensor. This method has previously been used either in simulations in Cartesian coordinates or in the geodynamo context and is applied here for the first time to fully compressible simulations of solar-like dynamos. Results: We find that the φφ-component of the α tensor does not follow the profile expected from that of kinetic helicity. The turbulent pumping velocities significantly alter the effective mean flows acting on the magnetic field and therefore challenge the flux transport dynamo concept. All coefficients are significantly affected by dynamically important magnetic fields. Quenching as well as enhancement are being observed. This leads to a modulation of the coefficients with the activity cycle. The temporal variations are found to be comparable to the time-averaged values and seem to be responsible for a nonlinear feedback on the magnetic field generation. Furthermore, we quantify the validity of the Parker-Yoshimura rule for the equatorward propagation of the mean magnetic field in the present case.

Modeling the Solar Convective Dynamo and Emerging Flux

Science.gov (United States)

Fan, Y.

2017-12-01

Significant advances have been made in recent years in global-scale fully dynamic three-dimensional convective dynamo simulations of the solar/stellar convective envelopes to reproduce some of the basic features of the Sun's large-scale cyclic magnetic field. It is found that the presence of the dynamo-generated magnetic fields plays an important role for the maintenance of the solar differential rotation, without which the differential rotation tends to become anti-solar (with a faster rotating pole instead of the observed faster rotation at the equator). Convective dynamo simulations are also found to produce emergence of coherent super-equipartition toroidal flux bundles with a statistically significant mean tilt angle that is consistent with the mean tilt of solar active regions. The emerging flux bundles are sheared by the giant cell convection into a forward leaning loop shape with its leading side (in the direction of rotation) pushed closer to the strong downflow lanes. Such asymmetric emerging flux pattern may lead to the observed asymmetric properties of solar active regions.

DYNAMO-HIA--a Dynamic Modeling tool for generic Health Impact Assessments.

Directory of Open Access Journals (Sweden)

Stefan K Lhachimi

Full Text Available BACKGROUND: Currently, no standard tool is publicly available that allows researchers or policy-makers to quantify the impact of policies using epidemiological evidence within the causal framework of Health Impact Assessment (HIA. A standard tool should comply with three technical criteria (real-life population, dynamic projection, explicit risk-factor states and three usability criteria (modest data requirements, rich model output, generally accessible to be useful in the applied setting of HIA. With DYNAMO-HIA (Dynamic Modeling for Health Impact Assessment, we introduce such a generic software tool specifically designed to facilitate quantification in the assessment of the health impacts of policies. METHODS AND RESULTS: DYNAMO-HIA quantifies the impact of user-specified risk-factor changes on multiple diseases and in turn on overall population health, comparing one reference scenario with one or more intervention scenarios. The Markov-based modeling approach allows for explicit risk-factor states and simulation of a real-life population. A built-in parameter estimation module ensures that only standard population-level epidemiological evidence is required, i.e. data on incidence, prevalence, relative risks, and mortality. DYNAMO-HIA provides a rich output of summary measures--e.g. life expectancy and disease-free life expectancy--and detailed data--e.g. prevalences and mortality/survival rates--by age, sex, and risk-factor status over time. DYNAMO-HIA is controlled via a graphical user interface and is publicly available from the internet, ensuring general accessibility. We illustrate the use of DYNAMO-HIA with two example applications: a policy causing an overall increase in alcohol consumption and quantifying the disease-burden of smoking. CONCLUSION: By combining modest data needs with general accessibility and user friendliness within the causal framework of HIA, DYNAMO-HIA is a potential standard tool for health impact assessment based

When did the lunar core dynamo cease?

Science.gov (United States)

Tikoo, S. M.; Weiss, B. P.; Shuster, D. L.; Fuller, M.

2013-12-01

Remanent magnetization in the lunar crust and in returned Apollo samples has long suggested that the Moon formed a metallic core and an ancient dynamo magnetic field. Recent paleomagnetic investigations of lunar samples demonstrate that the Moon had a core dynamo which produced ~30-110 μT surface fields between at least 4.2 and 3.56 billion years ago (Ga). Tikoo et al. (1) recently found that the field declined to below several μT by 3.19 Ga. However, given that even values of a few μT are at the upper end of the intensities predicted by dynamo theory for this late in lunar history, it remains uncertain when the lunar dynamo actually ceased completely. Determining this requires a young lunar rock with extraordinarily high magnetic recording fidelity. With this goal, we are conducting a new analysis of young regolith breccia 15498. Although the breccia's age is currently uncertain, the presence of Apollo 15-type mare basalt clasts provides an upper limit constraint of ~3.3 Ga, while trapped Ar data suggest a lithification age of ~1.3 Ga. In stark contrast to the multidomain character of virtually all lunar crystalline rocks, the magnetic carriers in 15498 are on average pseudo-single domain to superparamagnetic, indicating that the sample should provide high-fidelity paleointensity records. A previous alternating field (AF) and thermal demagnetization study of 15498 by Gose et al. (2) observed that the sample carries stable remanent magnetization which persists to unblocking temperatures of at least 650°C. Using a modified Thellier technique, they reported a paleointensity of 2 μT. Although this value may have been influenced by spurious remanence acquired during pretreatment with AF demagnetization, our results confirm the presence of an extremely stable (blocked to coercivities >290 mT) magnetization in the glassy matrix. We also found that this magnetization is largely unidirectional across mutually oriented subsamples. The cooling timescale of this rock (~1

Sharing programming resources between Bio* projects through remote procedure call and native call stack strategies

DEFF Research Database (Denmark)

Prins, Pjotr; Goto, Naohisa; Yates, Andrew

2012-01-01

Open-source software (OSS) encourages computer programmers to reuse software components written by others. In evolutionary bioinformatics, OSS comes in a broad range of programming languages, including C/C++, Perl, Python, Ruby, Java, and R. To avoid writing the same functionality multiple times...... for different languages, it is possible to share components by bridging computer languages and Bio* projects, such as BioPerl, Biopython, BioRuby, BioJava, and R/Bioconductor. In this chapter, we compare the two principal approaches for sharing software between different programming languages: either by remote...... procedure call (RPC) or by sharing a local call stack. RPC provides a language-independent protocol over a network interface; examples are RSOAP and Rserve. The local call stack provides a between-language mapping not over the network interface, but directly in computer memory; examples are R bindings, RPy...

Energy transfers in large-scale and small-scale dynamos

Science.gov (United States)

Samtaney, Ravi; Kumar, Rohit; Verma, Mahendra

2015-11-01

We present the energy transfers, mainly energy fluxes and shell-to-shell energy transfers in small-scale dynamo (SSD) and large-scale dynamo (LSD) using numerical simulations of MHD turbulence for Pm = 20 (SSD) and for Pm = 0.2 on 10243 grid. For SSD, we demonstrate that the magnetic energy growth is caused by nonlocal energy transfers from the large-scale or forcing-scale velocity field to small-scale magnetic field. The peak of these energy transfers move towards lower wavenumbers as dynamo evolves, which is the reason for the growth of the magnetic fields at the large scales. The energy transfers U2U (velocity to velocity) and B2B (magnetic to magnetic) are forward and local. For LSD, we show that the magnetic energy growth takes place via energy transfers from large-scale velocity field to large-scale magnetic field. We observe forward U2U and B2B energy flux, similar to SSD.

Faraday rotation signatures of fluctuation dynamos in young galaxies

Science.gov (United States)

Sur, Sharanya; Bhat, Pallavi; Subramanian, Kandaswamy

2018-03-01

Observations of Faraday rotation through high-redshift galaxies have revealed that they host coherent magnetic fields that are of comparable strengths to those observed in nearby galaxies. These fields could be generated by fluctuation dynamos. We use idealized numerical simulations of such dynamos in forced compressible turbulence up to rms Mach number of 2.4 to probe the resulting rotation measure (RM) and the degree of coherence of the magnetic field. We obtain rms values of RM at dynamo saturation of the order of 45-55 per cent of the value expected in a model where fields are assumed to be coherent on the forcing scale of turbulence. We show that the dominant contribution to the RM in subsonic and transonic cases comes from the general sea of volume filling fields, rather than from the rarer structures. However, in the supersonic case, strong field regions as well as moderately overdense regions contribute significantly. Our results can account for the observed RMs in young galaxies.

Impact of Convection on Surface Fluxes Observed During LASP/DYNAMO 2011

Science.gov (United States)

2014-12-01

20  Figure 8.  FFM maneuver used in the LASP/DYNAMO experiment (from Wang et al. 2013...Atmosphere Response Experiment DYNAMO Dynamics of Madden-Julian Oscillation EM electro-magnetic EO electro-optical FFM flight-level flux mapping FVS...level flux mapping ( FFM ) modules. Convection modules consisted of dropsonde cloud survey or radar convective element maneuver. Dropsonde modules

A Single Mode Study of a Quasi-Geostrophic Convection-Driven Dynamo Model

Science.gov (United States)

Plumley, M.; Calkins, M. A.; Julien, K. A.; Tobias, S.

2017-12-01

Planetary magnetic fields are thought to be the product of hydromagnetic dynamo action. For Earth, this process occurs within the convecting, turbulent and rapidly rotating outer core, where the dynamics are characterized by low Rossby, low magnetic Prandtl and high Rayleigh numbers. Progress in studying dynamos has been limited by current computing capabilities and the difficulties in replicating the extreme values that define this setting. Asymptotic models that embrace these extreme parameter values and enforce the dominant balance of geostrophy provide an option for the study of convective flows with actual relevance to geophysics. The quasi-geostrophic dynamo model (QGDM) is a multiscale, fully-nonlinear Cartesian dynamo model that is valid in the asymptotic limit of low Rossby number. We investigate the QGDM using a simplified class of solutions that consist of a single horizontal wavenumber which enforces a horizontal structure on the solutions. This single mode study is used to explore multiscale time stepping techniques and analyze the influence of the magnetic field on convection.

A basal magma ocean dynamo to explain the early lunar magnetic field

Science.gov (United States)

Scheinberg, Aaron L.; Soderlund, Krista M.; Elkins-Tanton, Linda T.

2018-06-01

The source of the ancient lunar magnetic field is an unsolved problem in the Moon's evolution. Theoretical work invoking a core dynamo has been unable to explain the magnitude of the observed field, falling instead one to two orders of magnitude below it. Since surface magnetic field strength is highly sensitive to the depth and size of the dynamo region, we instead hypothesize that the early lunar dynamo was driven by convection in a basal magma ocean formed from the final stages of an early lunar magma ocean; this material is expected to be dense, radioactive, and metalliferous. Here we use numerical convection models to predict the longevity and heat flow of such a basal magma ocean and use scaling laws to estimate the resulting magnetic field strength. We show that, if sufficiently electrically conducting, a magma ocean could have produced an early dynamo with surface fields consistent with the paleomagnetic observations.

Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. II. Simulations

Science.gov (United States)

Schober, Jennifer; Rogachevskii, Igor; Brandenburg, Axel; Boyarsky, Alexey; Fröhlich, Jürg; Ruchayskiy, Oleg; Kleeorin, Nathan

2018-05-01

Using direct numerical simulations (DNS), we study laminar and turbulent dynamos in chiral magnetohydrodynamics with an extended set of equations that accounts for an additional contribution to the electric current due to the chiral magnetic effect (CME). This quantum phenomenon originates from an asymmetry between left- and right-handed relativistic fermions in the presence of a magnetic field and gives rise to a chiral dynamo. We show that the magnetic field evolution proceeds in three stages: (1) a small-scale chiral dynamo instability, (2) production of chiral magnetically driven turbulence and excitation of a large-scale dynamo instability due to a new chiral effect (α μ effect), and (3) saturation of magnetic helicity and magnetic field growth controlled by a conservation law for the total chirality. The α μ effect becomes dominant at large fluid and magnetic Reynolds numbers and is not related to kinetic helicity. The growth rate of the large-scale magnetic field and its characteristic scale measured in the numerical simulations agree well with theoretical predictions based on mean-field theory. The previously discussed two-stage chiral magnetic scenario did not include stage (2), during which the characteristic scale of magnetic field variations can increase by many orders of magnitude. Based on the findings from numerical simulations, the relevance of the CME and the chiral effects revealed in the relativistic plasma of the early universe and of proto-neutron stars are discussed.

MHD dynamo action in space plasmas

International Nuclear Information System (INIS)

Faelthammar, C.G.

1984-05-01

Electric currents are now recognized to play a major role in the physical process of the Earths magnetosphere as well as in distant astrophysical plasmas. In driving these currents MHD dynamos as well as generators of a thermoelectric nature are important. The primary source of power for the Earths magnetospheric process is the solar wind, which supplies a voltage of the order of 200 kV across the magnetosphere. The direction of the large-scale solar wind electric field varies of many different time scales. The power input to the magnetosphere is closely correlated with the direction of the large-scale solar wind electric field in such a fashion as to mimick the response of a half-wave rectifier with a down-to-dusk conduction direction. Behind this apparently simple response there are complex plasma physical processes that are still very incompletely understood. They are intimately related to auroras, magnetic storms, radiation belts and changes in magnetospheric plasma populations. Similar dynamo actions should occur at other planets having magnetospheres. Recent observations seem to indicate that part of the power input to the Earths magnetosphere comes through MHD dynamo action of a forced plasma flow inside the flanks of the magnetopause and may play a role in other parts of the magnetosphere, too. An example of a cosmical MHD connected to a solid load is the corotating plasma of Jupiters inner magnetosphere, sweeping past the plants inner satelites. In particular the electric currents thereby driven to and from the satellite Io have attracted considerable interest.(author)

Large-scale dynamo action due to α fluctuations in a linear shear flow

Science.gov (United States)

Sridhar, S.; Singh, Nishant K.

2014-12-01

We present a model of large-scale dynamo action in a shear flow that has stochastic, zero-mean fluctuations of the α parameter. This is based on a minimal extension of the Kraichnan-Moffatt model, to include a background linear shear and Galilean-invariant α-statistics. Using the first-order smoothing approximation we derive a linear integro-differential equation for the large-scale magnetic field, which is non-perturbative in the shearing rate S , and the α-correlation time τα . The white-noise case, τα = 0 , is solved exactly, and it is concluded that the necessary condition for dynamo action is identical to the Kraichnan-Moffatt model without shear; this is because white-noise does not allow for memory effects, whereas shear needs time to act. To explore memory effects we reduce the integro-differential equation to a partial differential equation, valid for slowly varying fields when τα is small but non-zero. Seeking exponential modal solutions, we solve the modal dispersion relation and obtain an explicit expression for the growth rate as a function of the six independent parameters of the problem. A non-zero τα gives rise to new physical scales, and dynamo action is completely different from the white-noise case; e.g. even weak α fluctuations can give rise to a dynamo. We argue that, at any wavenumber, both Moffatt drift and Shear always contribute to increasing the growth rate. Two examples are presented: (a) a Moffatt drift dynamo in the absence of shear and (b) a Shear dynamo in the absence of Moffatt drift.

Magnetic field dynamos and magnetically triggered flow instabilities

Science.gov (United States)

Stefani, F.; Albrecht, T.; Arlt, R.; Christen, M.; Gailitis, A.; Gellert, M.; Giesecke, A.; Goepfert, O.; Herault, J.; Kirillov, O. N.; Mamatsashvili, G.; Priede, J.; Rüdiger, G.; Seilmayer, M.; Tilgner, A.; Vogt, T.

2017-07-01

The project A2 of the LIMTECH Alliance aimed at a better understanding of those magnetohydrodynamic instabilities that are relevant for the generation and the action of cosmic magnetic fields. These comprise the hydromagnetic dynamo effect and various magnetically triggered flow instabilities, such as the magnetorotational instability and the Tayler instability. The project was intended to support the experimental capabilities to become available in the framework of the DREsden Sodium facility for DYNamo and thermohydraulic studies (DRESDYN). An associated starting grant was focused on the dimensioning of a liquid metal experiment on the newly found magnetic destabilization of rotating flows with positive shear. In this survey paper, the main results of these two projects are summarized.

Non-linear dynamo waves in an incompressible medium when the turbulence dissipative coefficients depend on temperature

Directory of Open Access Journals (Sweden)

A. D. Pataraya

1997-01-01

Full Text Available Non-linear α-ω; dynamo waves existing in an incompressible medium with the turbulence dissipative coefficients depending on temperature are studied in this paper. We investigate of α-ω solar non-linear dynamo waves when only the first harmonics of magnetic induction components are included. If we ignore the second harmonics in the non-linear equation, the turbulent magnetic diffusion coefficient increases together with the temperature, the coefficient of turbulent viscosity decreases, and for an interval of time the value of dynamo number is greater than 1. In these conditions a stationary solution of the non-linear equation for the dynamo wave's amplitude exists; meaning that the magnetic field is sufficiently excited. The amplitude of the dynamo waves oscillates and becomes stationary. Using these results we can explain the existence of Maunder's minimum.

Sharing programming resources between Bio* projects through remote procedure call and native call stack strategies.

Science.gov (United States)

Prins, Pjotr; Goto, Naohisa; Yates, Andrew; Gautier, Laurent; Willis, Scooter; Fields, Christopher; Katayama, Toshiaki

2012-01-01

Open-source software (OSS) encourages computer programmers to reuse software components written by others. In evolutionary bioinformatics, OSS comes in a broad range of programming languages, including C/C++, Perl, Python, Ruby, Java, and R. To avoid writing the same functionality multiple times for different languages, it is possible to share components by bridging computer languages and Bio* projects, such as BioPerl, Biopython, BioRuby, BioJava, and R/Bioconductor. In this chapter, we compare the two principal approaches for sharing software between different programming languages: either by remote procedure call (RPC) or by sharing a local call stack. RPC provides a language-independent protocol over a network interface; examples are RSOAP and Rserve. The local call stack provides a between-language mapping not over the network interface, but directly in computer memory; examples are R bindings, RPy, and languages sharing the Java Virtual Machine stack. This functionality provides strategies for sharing of software between Bio* projects, which can be exploited more often. Here, we present cross-language examples for sequence translation, and measure throughput of the different options. We compare calling into R through native R, RSOAP, Rserve, and RPy interfaces, with the performance of native BioPerl, Biopython, BioJava, and BioRuby implementations, and with call stack bindings to BioJava and the European Molecular Biology Open Software Suite. In general, call stack approaches outperform native Bio* implementations and these, in turn, outperform RPC-based approaches. To test and compare strategies, we provide a downloadable BioNode image with all examples, tools, and libraries included. The BioNode image can be run on VirtualBox-supported operating systems, including Windows, OSX, and Linux.

A comprehensive view of solar-terrestrial relationships in terms of a chain of four dynamo-powered plasma acceleration processes

International Nuclear Information System (INIS)

Akasofu, S.-I.

1983-01-01

This paper emphasizes an effort to link processes which relate solar activity and magnetospheric disturbances in terms of energy transfer through a chain of four elements. In this view, each element is explicitly thought to be powered by a dynamo, namely the solar wind generation dynamo, the solar flare dynamo, the solar wind-magnetosphere dynamo and the aurora dynamo, respectively. Each dynamo powers a plasma acceleration process by the Lorentz force and the plasma flows thus generated are the solar wind, the flare-generated solar wind disturbance, the magnetospheric plasma convection and the ionospheric convection, respectively. Each plasma flow conveys the energy from one element to the next in the chain. Some of the kinetic energy of the photospheric plasma is eventually deposited in the polar ionosphere as heat energy. (author)

Instrumental Implementation of an Experiment to Demonstrate αω -dynamos in Accretion Disks

Science.gov (United States)

Si, Jiahe; Sonnenfeld, Richard; Colgate, Art; Li, Hui; Nornberg, Mark

2016-10-01

The New Mexico Liquid Metal αω -dynamo experiment is aimed to demonstrate a galactic dynamo. Our goal is to generate the ω-effect and α-effect by two semi-coherent flows in laboratory. Two coaxial cylinders are used to generate Taylor-Couette flows to simulate the differential rotation of accretion disks. Plumes induced by jets injected into the Couette flows are expected to produce helicities necessary for the α-effect. We have demonstrated an 8-fold poloidal-to-toroidal flux amplification from differential rotation (the ω-effect) by minimizing turbulence in our apparatus. To demonstrate the α-effect, the experimental apparatus is undergoing significant upgrade. We have constructed a helicity injection facility, and are also designing and testing a new data acquisition system capable of transmitting data in a high speed rotating frame. Additional magnetic field diagnostics will also be included. The upgrade is intended to answer the question of whether a self-sustaining αω -dynamo can be constructed with a realistic fluid flow field, as well as to obtain more details to understand dynamo action in highly turbulent Couette flow.

Simulations of Dynamo and Magnetorotational Instability in Madison Plasma Experiments and Astrophysical Disks

Energy Technology Data Exchange (ETDEWEB)

Ebrahimi, Fatima [Princeton Univ., NJ (United States). Dept. of Astrophysical Sciences

2018-02-22

Magnetic fields are observed to exist on all scales in many astrophysical sources such as stars, galaxies, and accretion discs. Understanding the origin of large scale magnetic fields, whereby the field emerges on spatial scales large compared to the fluctuations, has been a particularly long standing challenge. Our physics objective are: 1) what are the minimum ingredients for large-scale dynamo growth? 2) could a large-scale magnetic field grow out of turbulence and sustained despite the presence of dissipation? These questions are fundamental for understanding the large-scale dynamo in both laboratory and astrophysical plasmas. Here, we report major new findings in the area of Large-Scale Dynamo (magnetic field generation).

Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. I. Theory

Energy Technology Data Exchange (ETDEWEB)

Rogachevskii, Igor; Kleeorin, Nathan [Department of Mechanical Engineering, Ben-Gurion University of the Negev, P.O. Box 653, Beer-Sheva 84105 (Israel); Ruchayskiy, Oleg [Discovery Center, Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen (Denmark); Boyarsky, Alexey [Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, Niels Bohrweg 2, 2333 CA Leiden (Netherlands); Fröhlich, Jürg [Institute of Theoretical Physics, ETH Hönggerberg, CH-8093 Zurich (Switzerland); Brandenburg, Axel; Schober, Jennifer, E-mail: gary@bgu.ac.il [Nordita, KTH Royal Institute of Technology and Stockholm University, Roslagstullsbacken 23, SE-10691 Stockholm (Sweden)

2017-09-10

The magnetohydrodynamic (MHD) description of plasmas with relativistic particles necessarily includes an additional new field, the chiral chemical potential associated with the axial charge (i.e., the number difference between right- and left-handed relativistic fermions). This chiral chemical potential gives rise to a contribution to the electric current density of the plasma ( chiral magnetic effect ). We present a self-consistent treatment of the chiral MHD equations , which include the back-reaction of the magnetic field on a chiral chemical potential and its interaction with the plasma velocity field. A number of novel phenomena are exhibited. First, we show that the chiral magnetic effect decreases the frequency of the Alfvén wave for incompressible flows, increases the frequencies of the Alfvén wave and of the fast magnetosonic wave for compressible flows, and decreases the frequency of the slow magnetosonic wave. Second, we show that, in addition to the well-known laminar chiral dynamo effect, which is not related to fluid motions, there is a dynamo caused by the joint action of velocity shear and chiral magnetic effect. In the presence of turbulence with vanishing mean kinetic helicity, the derived mean-field chiral MHD equations describe turbulent large-scale dynamos caused by the chiral alpha effect, which is dominant for large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an interaction of the chiral magnetic effect and fluctuations of the small-scale current produced by tangling magnetic fluctuations (which are generated by tangling of the large-scale magnetic field by sheared velocity fluctuations). These dynamo effects may have interesting consequences in the dynamics of the early universe, neutron stars, and the quark–gluon plasma.

Laminar and Turbulent Dynamos in Chiral Magnetohydrodynamics. I. Theory

International Nuclear Information System (INIS)

Rogachevskii, Igor; Kleeorin, Nathan; Ruchayskiy, Oleg; Boyarsky, Alexey; Fröhlich, Jürg; Brandenburg, Axel; Schober, Jennifer

2017-01-01

The magnetohydrodynamic (MHD) description of plasmas with relativistic particles necessarily includes an additional new field, the chiral chemical potential associated with the axial charge (i.e., the number difference between right- and left-handed relativistic fermions). This chiral chemical potential gives rise to a contribution to the electric current density of the plasma ( chiral magnetic effect ). We present a self-consistent treatment of the chiral MHD equations , which include the back-reaction of the magnetic field on a chiral chemical potential and its interaction with the plasma velocity field. A number of novel phenomena are exhibited. First, we show that the chiral magnetic effect decreases the frequency of the Alfvén wave for incompressible flows, increases the frequencies of the Alfvén wave and of the fast magnetosonic wave for compressible flows, and decreases the frequency of the slow magnetosonic wave. Second, we show that, in addition to the well-known laminar chiral dynamo effect, which is not related to fluid motions, there is a dynamo caused by the joint action of velocity shear and chiral magnetic effect. In the presence of turbulence with vanishing mean kinetic helicity, the derived mean-field chiral MHD equations describe turbulent large-scale dynamos caused by the chiral alpha effect, which is dominant for large fluid and magnetic Reynolds numbers. The chiral alpha effect is due to an interaction of the chiral magnetic effect and fluctuations of the small-scale current produced by tangling magnetic fluctuations (which are generated by tangling of the large-scale magnetic field by sheared velocity fluctuations). These dynamo effects may have interesting consequences in the dynamics of the early universe, neutron stars, and the quark–gluon plasma.

Tracing control of chaos for the coupled dynamos dynamical system

International Nuclear Information System (INIS)

Wang Xuedi; Tian Lixin

2004-01-01

This paper introduces a new method for the coupled dynamos dynamical system, which can be applied to the decision of the chaotic behavior of the system. And research the tracing control of the chaos for the coupled dynamos dynamical system by gradually changing the driving parameter for the chaos. With the different design of controllers, the numerical simulation results show the relation between the chaotic behavior and the changes of the parameter value. Furthermore, the result shows the difference of the controllers. In the mean time, it reveals the process of the orbit's gradual changing with the parameter value

THE MEAN-FIELD SOLAR DYNAMO WITH A DOUBLE CELL MERIDIONAL CIRCULATION PATTERN

Energy Technology Data Exchange (ETDEWEB)

Pipin, V. V. [Institute of Solar-Terrestrial Physics, Russian Academy of Sciences, Irkutsk, 664033 (Russian Federation); Kosovichev, A. G. [Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)

2013-10-10

Recent helioseismology findings, as well as advances in direct numerical simulations of global dynamics of the Sun, have indicated that in each solar hemisphere meridional circulation may form more than one cell along the radius in the convection zone. In particular, recent helioseismology results revealed a double-cell structure of the meridional circulation. We investigate properties of a mean-field solar dynamo with such double-cell meridional circulation. The dynamo model also includes the realistic profile of solar differential rotation (including the tachocline and subsurface shear layer) and takes into account effects of turbulent pumping, anisotropic turbulent diffusivity, and conservation of magnetic helicity. Contrary to previous flux-transport dynamo models, we find that the dynamo model can robustly reproduce the basic properties of the solar magnetic cycles for a wide range of model parameters and circulation speeds. The best agreement with observations is achieved when the surface meridional circulation speed is about 12 m s{sup –1}. For this circulation speed, the simulated sunspot activity shows good synchronization with the polar magnetic fields. Such synchronization was indeed observed during previous sunspot Cycles 21 and 22. We compare theoretical and observed phase diagrams of the sunspot number and the polar field strength and discuss the peculiar properties of Cycle 23.

Sustainment dynamo reexamined: nonlocal electrical conductivity of plasma in a stochastic magnetic field

International Nuclear Information System (INIS)

Jacobson, A.R.; Moses, R.W.

1984-01-01

The plasma dynamo is both an intriguing and a practical concept. The intrigue derives from attempting to explain naturally occurring and man-made plasmas whose strong field-aligned currents j/sub parallel/ apparently disobey the most naive Ohm's law j/sub parallel/ = sigma/sub parallel/E/sub parallel/. The practical importance derives from the dynamo's role both in formation and in sustainment of reversed-field pinch (RFP) and Spheromak fusion plasmas. We will examine certain features of the documented quasi-steady discharges on ZT-40M, and RFP in apparent need of a sustainment dynamo. We will show that the tail electrons (which carry j/sub parallel/) are probably wandering (along stochastic B Vector-field lines) over much of the minor radius in one mean-free-path

Energy fluxes in helical magnetohydrodynamics and dynamo action

Indian Academy of Sciences (India)

Kinetic and magnetic helicities do not affect the renormalized parameters, ... Generation of magnetic field in plasma, usually referred to as 'dynamo', is one of the ..... energy fluxes for the inertial-range wave numbers where the same power.

The metastable dynamo model of stellar rotational evolution

International Nuclear Information System (INIS)

Brown, Timothy M.

2014-01-01

This paper introduces a new empirical model for the rotational evolution of Sun-like stars—those with surface convection zones and non-convective interior regions. Previous models do not match the morphology of observed (rotation period)-color diagrams, notably the existence of a relatively long-lived 'C-sequence' of fast rotators first identified by Barnes. This failure motivates the Metastable Dynamo Model (MDM) described here. The MDM posits that stars are born with their magnetic dynamos operating in a mode that couples very weakly to the stellar wind, so their (initially very short) rotation periods at first change little with time. At some point, this mode spontaneously and randomly changes to a strongly coupled mode, the transition occurring with a mass-dependent lifetime that is of the order of 100 Myr. I show that with this assumption, one can obtain good fits to observations of young clusters, particularly for ages of 150-200 Myr. Previous models and the MDM both give qualitative agreement with the morphology of the slower-rotating 'I-sequence' stars, but none of them have been shown to accurately reproduce the stellar-mass-dependent evolution of the I-sequence stars, especially for clusters older than a few hundred million years. I discuss observational experiments that can test aspects of the MDM, and speculate that the physics underlying the MDM may be related to other situations described in the literature, in which stellar dynamos may have a multi-modal character.

Feasible homopolar dynamo with sliding liquid-metal contacts

International Nuclear Information System (INIS)

Priede, Jānis; Avalos-Zúñiga, Raúl

2013-01-01

We present a feasible homopolar dynamo design consisting of a flat, multi-arm spiral coil, which is placed above a fast-spinning metal ring and connected to the latter by sliding liquid-metal electrical contacts. Using a simple, analytically solvable axisymmetric model, we determine the optimal design of such a setup. For small contact resistance, the lowest magnetic Reynolds number, Rm≈34.6, at which the dynamo can work, is attained at the optimal ratio of the outer and inner radii of the rings R i /R o ≈0.36 and the spiral pitch angle 54.7°. In a setup of two copper rings with the thickness of 3 cm, R i =10 cm and R o =30 cm, self-excitation of the magnetic field is expected at a critical rotation frequency around 10 Hz

A Study of Stochastic Resonance in the Periodically Forced Rikitake Dynamo

Directory of Open Access Journals (Sweden)

Chien-Chih Chen Chih-Yuan Tseng

2007-01-01

Full Text Available The geodynamo has widely been thought to be an intuitive and selfsustained model of the Earth¡¦s magnetic field. In this paper, we elucidate how a periodic signal could be embedded in the geomagnetic filed via the mechanism of stochastic resonance in a forced Rikitake dynamo. Based on the stochastic resonance observed in the periodically forced Rikitake dynamo, we thus suggest a common triggering for geomagnetic reversal and glacial events. Both kinds of catastrophes may result from the cyclic variation of the Earth¡¦s orbital eccentricity.

EFFECTS OF FOSSIL MAGNETIC FIELDS ON CONVECTIVE CORE DYNAMOS IN A-TYPE STARS

International Nuclear Information System (INIS)

Featherstone, Nicholas A.; Toomre, Juri; Browning, Matthew K.; Brun, Allan Sacha

2009-01-01

The vigorous magnetic dynamo action achieved within the convective cores of A-type stars may be influenced by fossil magnetic fields within their radiative envelopes. We study such effects through three-dimensional simulations that model the inner 30% by radius of a 2 M sun A-type star, capturing the convective core and a portion of the overlying radiative envelope within our computational domain. We employ the three-dimensional anelastic spherical harmonic code to model turbulent dynamics within a deep rotating spherical shell. The interaction between a fossil field and the core dynamo is examined by introducing a large-scale magnetic field into the radiative envelope of a mature A star dynamo simulation. We find that the inclusion of a twisted toroidal fossil field can lead to a remarkable transition in the core dynamo behavior. Namely, a super-equipartition state can be realized in which the magnetic energy built by dynamo action is 10-fold greater than the kinetic energy of the convection itself. Such strong-field states may suggest that the resulting Lorentz forces should seek to quench the flows, yet we have achieved super-equipartition dynamo action that persists for multiple diffusion times. This is achieved by the relative co-alignment of the flows and magnetic fields in much of the domain, along with some lateral displacements of the fastest flows from the strongest fields. Convection in the presence of such strong magnetic fields typically manifests as 4-6 cylindrical rolls aligned with the rotation axis, each possessing central axial flows that imbue the rolls with a helical nature. The roll system also possesses core-crossing flows that couple distant regions of the core. We find that the magnetic fields exhibit a comparable global topology with broad, continuous swathes of magnetic field linking opposite sides of the convective core. We have explored several poloidal and toroidal fossil field geometries, finding that a poloidal component is essential

Effect of metallic walls on dynamos generated by laminar boundary-driven flow in a spherical domain.

Science.gov (United States)

Guervilly, Céline; Wood, Toby S; Brummell, Nicholas H

2013-11-01

We present a numerical study of dynamo action in a conducting fluid encased in a metallic spherical shell. Motions in the fluid are driven by differential rotation of the outer metallic shell, which we refer to as "the wall." The two hemispheres of the wall are held in counter-rotation, producing a steady, axisymmetric interior flow consisting of differential rotation and a two-cell meridional circulation with radial inflow in the equatorial plane. From previous studies, this type of flow is known to maintain a stationary equatorial dipole by dynamo action if the magnetic Reynolds number is larger than about 300 and if the outer boundary is electrically insulating. We vary independently the thickness, electrical conductivity, and magnetic permeability of the wall to determine their effect on the dynamo action. The main results are the following: (a) Increasing the conductivity of the wall hinders the dynamo by allowing eddy currents within the wall, which are induced by the relative motion of the equatorial dipole field and the wall. This processes can be viewed as a skin effect or, equivalently, as the tearing apart of the dipole by the differential rotation of the wall, to which the field lines are anchored by high conductivity. (b) Increasing the magnetic permeability of the wall favors dynamo action by constraining the magnetic field lines in the fluid to be normal to the wall, thereby decoupling the fluid from any induction in the wall. (c) Decreasing the wall thickness limits the amplitude of the eddy currents, and is therefore favorable for dynamo action, provided that the wall is thinner than the skin depth. We explicitly demonstrate these effects of the wall properties on the dynamo field by deriving an effective boundary condition in the limit of vanishing wall thickness.

Pre-Service Teachers' Uses of and Barriers from Adopting Computer-Assisted Language Learning (CALL) Programs

Science.gov (United States)

Samani, Ebrahim; Baki, Roselan; Razali, Abu Bakar

2014-01-01

Success in implementation of computer-assisted language learning (CALL) programs depends on the teachers' understanding of the roles of CALL programs in education. Consequently, it is also important to understand the barriers teachers face in the use of computer-assisted language learning (CALL) programs. The current study was conducted on 14…

Anelastic spherical dynamos with radially variable electrical conductivity

Science.gov (United States)

Dietrich, W.; Jones, C. A.

2018-05-01

A series of numerical simulations of the dynamo process operating inside gas giant planets has been performed. We use an anelastic, fully nonlinear, three-dimensional, benchmarked MHD code to evolve the flow, entropy and magnetic field. Our models take into account the varying electrical conductivity, high in the ionised metallic hydrogen region, low in the molecular outer region. Our suite of electrical conductivity profiles ranges from Jupiter-like, where the outer hydrodynamic region is quite thin, to Saturn-like, where there is a thick non-conducting shell. The rapid rotation leads to the formation of two distinct dynamical regimes which are separated by a magnetic tangent cylinder - mTC. Outside the mTC there are strong zonal flows, where Reynolds stress balances turbulent viscosity, but inside the mTC Lorentz force reduces the zonal flow. The dynamic interaction between both regions induces meridional circulation. We find a rich diversity of magnetic field morphologies. There are Jupiter-like steady dipolar fields, and a belt of quadrupolar dominated dynamos spanning the range of models between Jupiter-like and Saturn-like conductivity profiles. This diversity may be linked to the appearance of reversed sign helicity in the metallic regions of our dynamos. With Saturn-like conductivity profiles we find models with dipolar magnetic fields, whose axisymmetric components resemble those of Saturn, and which oscillate on a very long time-scale. However, the non-axisymmetric field components of our models are at least ten times larger than those of Saturn, possibly due to the absence of any stably stratified layer.

Ion heating and MHD dynamo fluctuations in the reversed field pinch

International Nuclear Information System (INIS)

Scime, E.; Hokin, S.; Watts, C.; Mattor, N.

1992-01-01

Ion temperature measurements, time resolved to 10 μs, have been made in the Madison Symmetric Torus reversed-field pinch with a five channel charge exchange analyzer. The ion temperature, T i ∼ 200 eV for I = 350 kA, increases by as much as 100% during discrete dynamo bursts in MST discharges. Magnetic field fluctuations in the range 0.5--5 MHz were also measured. Structure in the fluctuation frequency spectrum at the ion cyclotron frequency appears as the bursts terminate, suggesting that the mechanism of ion heating involves the dissipation of dynamo fluctuations at ion gyro-orbit scales

IMPACT OF A REALISTIC DENSITY STRATIFICATION ON A SIMPLE SOLAR DYNAMO CALCULATION

Energy Technology Data Exchange (ETDEWEB)

Cardoso, Elisa; Lopes, Ilidio, E-mail: ilidio.lopes@ist.utl.pt [Centro Multidisciplinar de Astrofisica, Instituto Superior Tecnico, Av. Rovisco Pais, 1049-001 Lisboa (Portugal)

2012-09-20

In our Sun, the magnetic cycle is driven by the dynamo action occurring inside the convection zone, beneath the surface. Rotation couples with plasma turbulent motions to produce organized magnetic fields that erupt at the surface and undergo relatively regular cycles of polarity reversal. Among others, the axisymmetric dynamo models have been proved to be a quite useful tool to understand the dynamical processes responsible for the evolution of the solar magnetic cycle and the formation of the sunspots. Here, we discuss the role played by the radial density stratification on the critical layers of the Sun on the solar dynamo. The current view is that a polytropic description of the density stratification from beneath the tachocline region up to the Sun's surface is sufficient for the current precision of axisymmetric dynamo models. In this work, by using an up-to-date density profile obtained from a standard solar model, which is itself consistent with helioseismic data, we show that the detailed peculiarities of the density in critical regions of the Sun's interior, such as the tachocline, the base of the convection zone, the layers of partial ionization of hydrogen and helium, and the super-adiabatic layer, play a non-negligible role on the evolution of the solar magnetic cycle. Furthermore, we found that the chemical composition of the solar model plays a minor role in the formation and evolution of the solar magnetic cycle.

IMPACT OF A REALISTIC DENSITY STRATIFICATION ON A SIMPLE SOLAR DYNAMO CALCULATION

International Nuclear Information System (INIS)

Cardoso, Elisa; Lopes, Ilídio

2012-01-01

In our Sun, the magnetic cycle is driven by the dynamo action occurring inside the convection zone, beneath the surface. Rotation couples with plasma turbulent motions to produce organized magnetic fields that erupt at the surface and undergo relatively regular cycles of polarity reversal. Among others, the axisymmetric dynamo models have been proved to be a quite useful tool to understand the dynamical processes responsible for the evolution of the solar magnetic cycle and the formation of the sunspots. Here, we discuss the role played by the radial density stratification on the critical layers of the Sun on the solar dynamo. The current view is that a polytropic description of the density stratification from beneath the tachocline region up to the Sun's surface is sufficient for the current precision of axisymmetric dynamo models. In this work, by using an up-to-date density profile obtained from a standard solar model, which is itself consistent with helioseismic data, we show that the detailed peculiarities of the density in critical regions of the Sun's interior, such as the tachocline, the base of the convection zone, the layers of partial ionization of hydrogen and helium, and the super-adiabatic layer, play a non-negligible role on the evolution of the solar magnetic cycle. Furthermore, we found that the chemical composition of the solar model plays a minor role in the formation and evolution of the solar magnetic cycle.

Dynamo generation of magnetic fields in three-dimensional space: Solar cycle main flux tube formation and reversals

International Nuclear Information System (INIS)

Yoshimura, H.

1983-01-01

Dynamo processes as a magnetic field generation mechanism in astrophysics can be described essentially by movement and deformation of magnetic field lines due to plasma fluid motions. A basic element of the processes is a kinematic problem. As an important prototype of these processes, we investigate the case of the solar magnetic cycle. To follow the movement and deformation, we solve magnetohydrodynamic (MHD) equations by a numerical method with a prescribed velocity field. A simple combination of differential rotation and global convection, given by a linear analysis of fluid dynamics in a rotating sphere, can perpetually create and reverse great magnetic flux tubes encircling the Sun. We call them the main flux tubes of the solar cycle. They are progenitors of small-scale flux ropes of the solar activity. This shows that magnetic field generation by fluid motions is, in fact, possible and that MHD equations have a new type of oscillatory solution. The solar cycle can be identified with one of such oscillatory solutions. This means that we can follow detailed stages of the field generation and reversal processes of the dynamo by continuously observing the Sun. It is proposed that the magnetic flux tube formation by streaming plasma flows exemplified here could be a universal mechanism of flux tube formation in astrophysics

Integración de sensores medioambientales con BIM: casos de estudio usando Arduino, Dynamo, y Revit API

OpenAIRE

Kensek, K. M.

2014-01-01

This paper investigates the feasibility of connecting environmental sensors such as light, humidity, or CO2 receptors to a building information model (BIM). A base case was created in Rhino; using Grasshopper and Firefly, a simple digital model responded to lighting-levels detected by a photoresistor on an Arduino board. The case study was duplicated using Revit Architecture, a popular BIM software, and Dynamo, a visual programming environment, in an innovative application. Another case study...

Steady-state dynamo and current drive in a nonuniform bounded plasma

International Nuclear Information System (INIS)

Mett, R.R.; Taylor, J.B.

1991-03-01

Current drive due to helicity injection and dynamo effect are examined in an inhomogeneous bounded plasma. Averaged over a magnetic surface, there is in general no dynamo effect independent of resistivity -- contrary to the results found previously for an unbounded plasma. The dynamo field is calculated explicitly for an incompressible visco-resistive fluid in the plane-slab model. In accord with our general conclusion, outside the Alfven resonant layer it is proportional to the resistivity. Within the resonant layer there is a contribution which is enhanced, relative to its value outside the layer, by a factor (ωa 2 /(η + ν)), where ω is the wave frequency, a the plasma radius, η the magnetic diffusivity, and ν the kinematic viscosity. However, this contribution vanishes when integrated across the layer. The average field in the layer is enhanced by factor (ωa 2 /(η + ν)) 2/3 and is proportional to the shear in the magnetic field and the cube root of the gradient of the Alfven speed. These results are interpreted in terms of helicity balance, and reconciled with the infinite medium calculations. 15 refs

BABCOCK–LEIGHTON SOLAR DYNAMO: THE ROLE OF DOWNWARD PUMPING AND THE EQUATORWARD PROPAGATION OF ACTIVITY

International Nuclear Information System (INIS)

Karak, Bidya Binay; Cameron, Robert

2016-01-01

The key elements of the Babcock–Leighton dynamos are the generation of poloidal field through decay and the dispersal of tilted bipolar active regions and the generation of toroidal field through the observed differential rotation. These models are traditionally known as flux transport dynamo models as the equatorward propagations of the butterfly wings in these models are produced due to an equatorward flow at the bottom of the convection zone. Here we investigate the role of downward magnetic pumping near the surface using a kinematic Babcock–Leighton model. We find that the pumping causes the poloidal field to become predominately radial in the near-surface shear layer, which allows the negative radial shear to effectively act on the radial field to produce a toroidal field. We observe a clear equatorward migration of the toroidal field at low latitudes as a consequence of the dynamo wave even when there is no meridional flow in the deep convection zone. Both the dynamo wave and the flux transport type solutions are thus able to reproduce some of the observed features of the solar cycle including the 11-year periodicity. The main difference between the two types of solutions is the strength of the Babcock–Leighton source required to produce the dynamo action. A second consequence of the magnetic pumping is that it suppresses the diffusion of fields through the surface, which helps to allow an 11-year cycle at (moderately) larger values of magnetic diffusivity than have previously been used.

BABCOCK–LEIGHTON SOLAR DYNAMO: THE ROLE OF DOWNWARD PUMPING AND THE EQUATORWARD PROPAGATION OF ACTIVITY

Energy Technology Data Exchange (ETDEWEB)

Karak, Bidya Binay; Cameron, Robert, E-mail: bkarak@ucar.edu [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany)

2016-11-20

The key elements of the Babcock–Leighton dynamos are the generation of poloidal field through decay and the dispersal of tilted bipolar active regions and the generation of toroidal field through the observed differential rotation. These models are traditionally known as flux transport dynamo models as the equatorward propagations of the butterfly wings in these models are produced due to an equatorward flow at the bottom of the convection zone. Here we investigate the role of downward magnetic pumping near the surface using a kinematic Babcock–Leighton model. We find that the pumping causes the poloidal field to become predominately radial in the near-surface shear layer, which allows the negative radial shear to effectively act on the radial field to produce a toroidal field. We observe a clear equatorward migration of the toroidal field at low latitudes as a consequence of the dynamo wave even when there is no meridional flow in the deep convection zone. Both the dynamo wave and the flux transport type solutions are thus able to reproduce some of the observed features of the solar cycle including the 11-year periodicity. The main difference between the two types of solutions is the strength of the Babcock–Leighton source required to produce the dynamo action. A second consequence of the magnetic pumping is that it suppresses the diffusion of fields through the surface, which helps to allow an 11-year cycle at (moderately) larger values of magnetic diffusivity than have previously been used.

Integration of Environmental Sensors with BIM: case studies using Arduino, Dynamo, and the Revit API

Directory of Open Access Journals (Sweden)

Kensek, K. M.

2014-12-01

Full Text Available This paper investigates the feasibility of connecting environmental sensors such as light, humidity, or CO2 receptors to a building information model (BIM. A base case was created in Rhino; using Grasshopper and Firefly, a simple digital model responded to lighting-levels detected by a photoresistor on an Arduino board. The case study was duplicated using Revit Architecture, a popular BIM software, and Dynamo, a visual programming environment, in an innovative application. Another case study followed a similar procedure by implementing the Revit API directly instead of using Dynamo. Then the process was reversed to demonstrate that not only could data could be sent from sensors to change the 3D model, but changes to parameters of a 3D model could effect a physical model through the use of actuators. It is intended that these virtual/physical prototypes could be used as the basis for testing intelligent façade systems before constructing full size mock-ups.Este estudio investiga la posibilidad de conectar sensores ambientales como de luz, humedad, o dióxido de carbono con un modelo de información de un edificio (siglas BIM en inglés. Un caso base fue creado en Rhino; usando Grasshopper and Firefly, donde un simple modelo digital respondió a niveles de luz detectados por un foto resistor en una tarjeta Arduino. El caso de estudio fue duplicado usando Revit Architecture, una herramienta popular en BIM, y Dynamo, un ambiente de programación gráfica, en una creativa aplicación. Un segundo caso de estudio siguió un procedimiento similar implementando Revit API directamente en vez de usar Dynamo. Entonces el proceso fue revertido para demostrar que no solamente la información podría ser enviada desde sensores para cambiar el modelo tridimensional, pero cambios en los parámetros de un modelo tridimensional podrían afectar un modelo físico mediante el uso de actuadores. Se espera que esos modelos virtuales puedan ser usados como base para

Energy transfers in dynamos with small magnetic Prandtl numbers

KAUST Repository

Kumar, Rohit; Verma, Mahendra K.; Samtaney, Ravi

2015-01-01

We perform numerical simulation of dynamo with magnetic Prandtl number Pm = 0.2 on 10243 grid, and compute the energy fluxes and the shell-to-shell energy transfers. These computations indicate that the magnetic energy growth takes place mainly due

Dynamo Scaling Laws for Uranus and Neptune: The Role of Convective Shell Thickness on Dipolarity

Science.gov (United States)

Stanley, Sabine; Yunsheng Tian, Bob

2017-10-01

Previous dynamo scaling law studies (Christensen and Aubert, 2006) have demonstrated that the morphology of a planet’s magnetic field is determined by the local Rossby number (Ro_l): a non-dimensional diagnostic variable that quantifies the ratio of inertial forces to Coriolis forces on the average length scale of the flow. Dynamos with Ro_l ~ 0.1 produce multipolar magnetic fields. Scaling studies have also determined the dependence of the local Rossby number on non-dimensional parameters governing the system - specifically the Ekman, Prandtl, magnetic Prandtl and flux-based Rayleigh numbers (Olson and Christensen, 2006). When these scaling laws are applied to the planets, it appears that Uranus and Neptune should have dipole-dominated fields, contrary to observations. However, those scaling laws were derived using the specific convective shell thickness of the Earth’s core. Here we investigate the role of convective shell thickness on dynamo scaling laws. We find that the local Rossby number depends exponentially on the convective shell thickness. Including this new dependence on convective shell thickness, we find that the dynamo scaling laws now predict that Uranus and Neptune reside deeply in the multipolar regime, thereby resolving the previous contradiction with observations.

MAGNETIC QUENCHING OF TURBULENT DIFFUSIVITY: RECONCILING MIXING-LENGTH THEORY ESTIMATES WITH KINEMATIC DYNAMO MODELS OF THE SOLAR CYCLE

International Nuclear Information System (INIS)

Munoz-Jaramillo, Andres; Martens, Petrus C. H.; Nandy, Dibyendu

2011-01-01

The turbulent magnetic diffusivity in the solar convection zone is one of the most poorly constrained ingredients of mean-field dynamo models. This lack of constraint has previously led to controversy regarding the most appropriate set of parameters, as different assumptions on the value of turbulent diffusivity lead to radically different solar cycle predictions. Typically, the dynamo community uses double-step diffusivity profiles characterized by low values of diffusivity in the bulk of the convection zone. However, these low diffusivity values are not consistent with theoretical estimates based on mixing-length theory, which suggest much higher values for turbulent diffusivity. To make matters worse, kinematic dynamo simulations cannot yield sustainable magnetic cycles using these theoretical estimates. In this work, we show that magnetic cycles become viable if we combine the theoretically estimated diffusivity profile with magnetic quenching of the diffusivity. Furthermore, we find that the main features of this solution can be reproduced by a dynamo simulation using a prescribed (kinematic) diffusivity profile that is based on the spatiotemporal geometric average of the dynamically quenched diffusivity. This bridges the gap between dynamically quenched and kinematic dynamo models, supporting their usage as viable tools for understanding the solar magnetic cycle.

Boundary effects on the MHD dynamo in laboratory plasmas

International Nuclear Information System (INIS)

Ho, Y.L.; Prager, S.C.

1989-07-01

In recent laboratory experiments, a dynamo-like mechanism has been demonstrated in which a portion of the axisymmetric component of the magnetic field is believed to be sustained by 3D spatial fluctuations in the field and flow. With a conducting shell at the plasma surface, past MHD computation shows that sustainment arises from fluctuations which cause magnetic reconnection. If the conducting wall is retracted from the plasma surface, the fluctuations are amplified and the dynamo sustainment is still active for the times studied, but an increased energy input to the plasma is required through the applied electric field. The retraction of the conducting wall enhances the helicity dissipation rate by the intersection of the fields with the resistive surface which bounds the plasma. This enhanced helicity dissipation is balanced by the helicity injection that accompanies the increased applied electric field. 17 refs., 7 figs., 1 tab

Time-resolved observation of discrete and continuous MHD dynamo in the reversed-field pinch edge

International Nuclear Information System (INIS)

Ji, H.; Almagri, A.F.; Prager, S.C.; Sarff, J.S.

1994-01-01

We report the first experimental verification of the MHD dynamo in the RFP. A burst of magnetohydrodynamic (MHD) dynamo electric field is observed during the sawtooth crash, followed by an increase in the local parallel current in the MST RFP edge. By measuring each term, the parallel MHD mean-field Ohm's law is observed to hold within experimental error bars both between and during sawtooth crashes

Solar Dynamo Driven by Periodic Flow Oscillation

Science.gov (United States)

Mayr, Hans G.; Hartle, Richard E.; Einaudi, Franco (Technical Monitor)

2001-01-01

We have proposed that the periodicity of the solar magnetic cycle is determined by wave mean flow interactions analogous to those driving the Quasi Biennial Oscillation in the Earth's atmosphere. Upward propagating gravity waves would produce oscillating flows near the top of the radiation zone that in turn would drive a kinematic dynamo to generate the 22-year solar magnetic cycle. The dynamo we propose is built on a given time independent magnetic field B, which allows us to estimate the time dependent, oscillating components of the magnetic field, (Delta)B. The toroidal magnetic field (Delta)B(sub phi) is directly driven by zonal flow and is relatively large in the source region, (Delta)(sub phi)/B(sub Theta) much greater than 1. Consistent with observations, this field peaks at low latitudes and has opposite polarities in both hemispheres. The oscillating poloidal magnetic field component, (Delta)B(sub Theta), is driven by the meridional circulation, which is difficult to assess without a numerical model that properly accounts for the solar atmosphere dynamics. Scale-analysis suggests that (Delta)B(sub Theta) is small compared to B(sub Theta) in the dynamo region. Relative to B(sub Theta), however, the oscillating magnetic field perturbations are expected to be transported more rapidly upwards in the convection zone to the solar surface. As a result, (Delta)B(sub Theta) (and (Delta)B(sub phi)) should grow relative to B(sub Theta), so that the magnetic fields reverse at the surface as observed. Since the meridional and zonai flow oscillations are out of phase, the poloidal magnetic field peaks during times when the toroidal field reverses direction, which is observed. With the proposed wave driven flow oscillation, the magnitude of the oscillating poloidal magnetic field increases with the mean rotation rate of the fluid. This is consistent with the Bode-Blackett empirical scaling law, which reveals that in massive astrophysical bodies the magnetic moment tends

Saturation of the turbulent dynamo.

Science.gov (United States)

Schober, J; Schleicher, D R G; Federrath, C; Bovino, S; Klessen, R S

2015-08-01

The origin of strong magnetic fields in the Universe can be explained by amplifying weak seed fields via turbulent motions on small spatial scales and subsequently transporting the magnetic energy to larger scales. This process is known as the turbulent dynamo and depends on the properties of turbulence, i.e., on the hydrodynamical Reynolds number and the compressibility of the gas, and on the magnetic diffusivity. While we know the growth rate of the magnetic energy in the linear regime, the saturation level, i.e., the ratio of magnetic energy to turbulent kinetic energy that can be reached, is not known from analytical calculations. In this paper we present a scale-dependent saturation model based on an effective turbulent resistivity which is determined by the turnover time scale of turbulent eddies and the magnetic energy density. The magnetic resistivity increases compared to the Spitzer value and the effective scale on which the magnetic energy spectrum is at its maximum moves to larger spatial scales. This process ends when the peak reaches a characteristic wave number k☆ which is determined by the critical magnetic Reynolds number. The saturation level of the dynamo also depends on the type of turbulence and differs for the limits of large and small magnetic Prandtl numbers Pm. With our model we find saturation levels between 43.8% and 1.3% for Pm≫1 and between 2.43% and 0.135% for Pm≪1, where the higher values refer to incompressible turbulence and the lower ones to highly compressible turbulence.

RED DWARF DYNAMO RAISES PUZZLE OVER INTERIORS OF LOWEST-MASS STARS

Science.gov (United States)

2002-01-01

NASA's Hubble Space Telescope has uncovered surprising evidence that powerful magnetic fields might exist around the lowest mass stars in the universe, which are near the threshold of stellar burning processes. 'New theories will have to be developed to explain how these strong fields are produced, since conventional models predict that these low mass red dwarfs should have very weak or no magnetic fields,' says Dr. Jeffrey Linsky of the Joint Institute for Laboratory Astrophysics (JILA) in Boulder, Colorado. 'The Hubble observations provide clear evidence that very low mass red dwarf stars must have some form of dynamo to amplify their magnetic fields.' His conclusions are based upon Hubble's detection of a high-temperature outburst, called a flare, on the surface of the extremely small, cool red dwarf star Van Biesbroeck 10 (VB10) also known as Gliese 752B. Stellar flares are caused by intense, twisted magnetic fields that accelerate and contain gasses which are much hotter than a star's surface. Explosive flares are common on the Sun and expected for stars that have internal structures similar to our Sun's. Stars as small as VB10 are predicted to have a simpler internal structure than that of the Sun and so are not expected to generate the electric currents required for magnetic fields that drive flares. Besides leading to a clearer understanding of the interior structure of the smallest red dwarf stars known, these unexpected results might possibly shed light on brown dwarf stars. A brown dwarf is a long-sought class of astronomical object that is too small to shine like a star through nuclear fusion processes, but is too large to be considered a planet. 'Since VB10 is nearly a brown dwarf, it is likely brown dwarfs also have strong magnetic fields,' says Linsky. 'Additional Hubble searches for flares are needed to confirm this prediction.' A QUARTER-MILLION DEGREE TORCH The star VB10 and its companion star Gliese 752A make up a binary system located 19 light

Magnetic fluctuation induced transport and edge dynamo measurements in the MST reversed-field pinch

International Nuclear Information System (INIS)

Hokin, S.; Fiksel, G.; Ji, H.

1994-09-01

Probe measurements in MST indicate that RFP particle and energy loss is governed by magnetic fluctuations inside r/a = 0.8, with energy carried out convectively by superthermal electrons. The radial loss rate is lower than the Rechester-Rosenbluth level, presumably due to the establishment of a restraining ambipolar potential. Several aspects of these measurements contradict the Kinetic Dynamo Theory, while the MHD dynamo EMF is measured to be large enough to drive the edge current carried by these superthermal electrons

Some consequences of shear on galactic dynamos with helicity fluxes

Science.gov (United States)

Zhou, Hongzhe; Blackman, Eric G.

2017-08-01

Galactic dynamo models sustained by supernova (SN) driven turbulence and differential rotation have revealed that the sustenance of large-scale fields requires a flux of small-scale magnetic helicity to be viable. Here we generalize a minimalist analytic version of such galactic dynamos to explore some heretofore unincluded contributions from shear on the total turbulent energy and turbulent correlation time, with the helicity fluxes maintained by either winds, diffusion or magnetic buoyancy. We construct an analytic framework for modelling the turbulent energy and correlation time as a function of SN rate and shear. We compare our prescription with previous approaches that include only rotation. The solutions depend separately on the rotation period and the eddy turnover time and not just on their ratio (the Rossby number). We consider models in which these two time-scales are allowed to be independent and also a case in which they are mutually dependent on radius when a radial-dependent SN rate model is invoked. For the case of a fixed rotation period (or a fixed radius), we show that the influence of shear is dramatic for low Rossby numbers, reducing the correlation time of the turbulence, which, in turn, strongly reduces the saturation value of the dynamo compared to the case when the shear is ignored. We also show that even in the absence of winds or diffusive fluxes, magnetic buoyancy may be able to sustain sufficient helicity fluxes to avoid quenching.

Large-scale dynamo of accretion disks around supermassive nonrotating black holes

Directory of Open Access Journals (Sweden)

Poplavsky A.L.

2006-01-01

Full Text Available In this paper one presents an analytical model of accretion disk magnetosphere dynamics around supermassive nonrotating black holes in the centers of active galactic nuclei. Based on general relativistic equations of magneto hydrodynamics, the nonstationary solutions for time-dependent dynamo action in the accretion disks, spatial and temporal distribution of magnetic field are found. It is shown that there are two distinct stages of dynamo process: the transient and the steady-state regimes, the induction of magnetic field at t > 6:6665 x 1011GM/c3 s becomes stationary, magnetic field is located near the innermost stable circular orbit, and its value rises up to ~ 105 G. Applications of such systems with nonrotating black holes in real active galactic nuclei are discussed.

Magnetic and velocity fields in a dynamo operating at extremely small Ekman and magnetic Prandtl numbers

Science.gov (United States)

Šimkanin, Ján; Kyselica, Juraj

2017-12-01

Numerical simulations of the geodynamo are becoming more realistic because of advances in computer technology. Here, the geodynamo model is investigated numerically at the extremely low Ekman and magnetic Prandtl numbers using the PARODY dynamo code. These parameters are more realistic than those used in previous numerical studies of the geodynamo. Our model is based on the Boussinesq approximation and the temperature gradient between upper and lower boundaries is a source of convection. This study attempts to answer the question how realistic the geodynamo models are. Numerical results show that our dynamo belongs to the strong-field dynamos. The generated magnetic field is dipolar and large-scale while convection is small-scale and sheet-like flows (plumes) are preferred to a columnar convection. Scales of magnetic and velocity fields are separated, which enables hydromagnetic dynamos to maintain the magnetic field at the low magnetic Prandtl numbers. The inner core rotation rate is lower than that in previous geodynamo models. On the other hand, dimensional magnitudes of velocity and magnetic fields and those of the magnetic and viscous dissipation are larger than those expected in the Earth's core due to our parameter range chosen.

A NEW SIMPLE DYNAMO MODEL FOR STELLAR ACTIVITY CYCLE

Energy Technology Data Exchange (ETDEWEB)

Yokoi, N.; Hamba, F. [Institute of Industrial Science, University of Tokyo, Tokyo 153-8505 (Japan); Schmitt, D. [Max-Planck Institut für Sonnensystemforschung, Göttingen D-37077 (Germany); Pipin, V., E-mail: nobyokoi@iis.u-tokyo.ac.jp [Institute of Solar–Terrestrial Physics, Russian Academy of Science, Irkutsk 664033 (Russian Federation)

2016-06-20

A new simple dynamo model for stellar activity cycle is proposed. By considering an inhomogeneous flow effect on turbulence, it is shown that turbulent cross helicity (velocity–magnetic-field correlation) enters the expression of turbulent electromotive force as the coupling coefficient for the mean absolute vorticity. This makes the present model different from the current α –Ω-type models in two main ways. First, in addition to the usual helicity ( α ) and turbulent magnetic diffusivity ( β ) effects, we consider the cross-helicity effect as a key ingredient of the dynamo process. Second, the spatiotemporal evolution of cross helicity is solved simultaneously with the mean magnetic fields. The basic scenario is as follows. In the presence of turbulent cross helicity, the toroidal field is induced by the toroidal rotation. Then, as in usual models, the α effect generates the poloidal field from the toroidal one. This induced poloidal field produces a turbulent cross helicity whose sign is opposite to the original one (negative production). With this cross helicity of the reversed sign, a reversal in field configuration starts. Eigenvalue analyses of the simplest possible model give a butterfly diagram, which confirms the above scenario and the equatorward migrations, the phase relationship between the cross helicity and magnetic fields. These results suggest that the oscillation of the turbulent cross helicity is a key for the activity cycle. The reversal of the cross helicity is not the result of the magnetic-field reversal, but the cause of the latter. This new model is expected to open up the possibility of the mean-field or turbulence closure dynamo approaches.

Solar Physics at Evergreen: Solar Dynamo and Chromospheric MHD

Science.gov (United States)

Zita, E. J.; Maxwell, J.; Song, N.; Dikpati, M.

2006-12-01

We describe our five year old solar physics research program at The Evergreen State College. Famed for its cloudy skies, the Pacific Northwest is an ideal location for theoretical and remote solar physics research activities. Why does the Sun's magnetic field flip polarity every 11 years or so? How does this contribute to the magnetic storms Earth experiences when the Sun's field reverses? Why is the temperature in the Sun's upper atmosphere millions of degrees higher than the Sun's surface temperature? How do magnetic waves transport energy in the Sun’s chromosphere and the Earth’s atmosphere? How does solar variability affect climate change? Faculty and undergraduates investigate questions such as these in collaboration with the High Altitude Observatory (HAO) at the National Center for Atmospheric Research (NCAR) in Boulder. We will describe successful student research projects, logistics of remote computing, and our current physics investigations into (1) the solar dynamo and (2) chromospheric magnetohydrodynamics.

Nonlinear quenching of current fluctuations in a self-exciting homopolar dynamo

Science.gov (United States)

Hide, R.

In the interpretation of geomagnetic polarity reversals with their highly variable frequency over geological time it is necessary, as with other irregularly fluctuating geophysical phenomena, to consider the relative importance of forced contributions associated with changing boundary conditions and of free contributions characteristic of the behaviour of nonlinear systems operating under fixed boundary conditions. New evidence -albeit indirect- in favour of the likely predominance of forced contributions is provided by the discovery reported here of the possibility of complete quenching by nonlineax effects of current fluctuations in a self-exciting homopolar dynamo with its single Faraday disk driven into rotation with angular speed y(τ) (where τ denotes time) by a steady applied couple. The armature of an electric motor connected in series with the coil of the dynamo is driven into rotation' with angular speed z(τ) by a torque xf (x) due to Lorentz forces associated with the electric current x(τ) in the system (just as certain parts of the spectrum of eddies within the liquid outer core are generated largely by Lorentz forces associated with currents generated by the self-exciting magnetohydrodynamic (MHD) geodynamo). The discovery is based on bifurcation analysis supported by computational studies of the following (mathematically novel) autonomous set of nonlinear ordinary differential equations: dx/dt = x(y - 1) - βzf(x), dy/dt = α(1 - x²) - κy, dz/dt = xf (x) -λz, where f (x) = 1 - ɛ + ɛσx, in cases when the dimensionless parameters (α, β, κ, λ, σ) are all positive and 0 ≤ ɛ ≤ 1. Within those regions of (α, β, κ, λ, σ) parameter space where the applied couple, as measured by α, is strong enough for persistent dynamo action (i.e. x ≠ 0) to occur at all, there are in general extensive regions where x(τ) exhibits large amplitude regular or irregular (chaotic) fluctuations. But these fluctuating régimes shrink in size as increases

Degenerate Hopf bifurcation in a self-exciting Faraday disc dynamo

Indian Academy of Sciences (India)

Weiquan Pan

2017-05-31

May 31, 2017 ... Recently, self-exciting Faraday disk dynamo is also a topic of con- cern [16–20]. ..... Hopf bifurcation. (a) Projected on the x–z plane and (b) pro- ... Key Lab of Com- plex System Optimization and Big Data Processing. (No.

Solar Internal Rotation and Dynamo Waves: A Two Dimensional ...

Indian Academy of Sciences (India)

tribpo

Solar Internal Rotation and Dynamo Waves: A Two Dimensional. Asymptotic Solution in the Convection Zone ... We calculate here a spatial 2 D structure of the mean magnetic field, adopting real profiles of the solar internal ... of the asymptotic solution in low (middle) and high (right panel) latitudes. field is shifted towards the ...

An update of Leighton's solar dynamo model

Science.gov (United States)

Cameron, R. H.; Schüssler, M.

2017-03-01

In 1969, Leighton developed a quasi-1D mathematical model of the solar dynamo, building upon the phenomenological scenario of Babcock published in 1961. Here we present a modification and extension of Leighton's model. Using the axisymmetric component (longitudinal average) of the magnetic field, we consider the radial field component at the solar surface and the radially integrated toroidal magnetic flux in the convection zone, both as functions of latitude. No assumptions are made with regard to the radial location of the toroidal flux. The model includes the effects of (I) turbulent diffusion at the surface and in the convection zone; (II) poleward meridional flow at the surface and an equatorward return flow affecting the toroidal flux; (III) latitudinal differential rotation and the near-surface layer of radial rotational shear; (iv) downward convective pumping of magnetic flux in the shear layer; and (v) flux emergence in the form of tilted bipolar magnetic regions treated as a source term for the radial surface field. While the parameters relevant for the transport of the surface field are taken from observations, the model condenses the unknown properties of magnetic field and flow in the convection zone into a few free parameters (turbulent diffusivity, effective return flow, amplitude of the source term, and a parameter describing the effective radial shear). Comparison with the results of 2D flux transport dynamo codes shows that the model captures the essential features of these simulations. We make use of the computational efficiency of the model to carry out an extended parameter study. We cover an extended domain of the 4D parameter space and identify the parameter ranges that provide solar-like solutions. Dipole parity is always preferred and solutions with periods around 22 yr and a correct phase difference between flux emergence in low latitudes and the strength of the polar fields are found for a return flow speed around 2 m s-1, turbulent

Helicity--vorticity turbulent pumping of magnetic fields in the solar dynamo

OpenAIRE

Pipin, V. V.

2012-01-01

The interaction of helical convective motions and differential rotation in the solar convection zone results in turbulent drift of a large-scale magnetic field. We discuss the pumping mechanism and its impact on the solar dynamo.

Ion heating and MHD dynamo fluctuations in the reversed field pinch

International Nuclear Information System (INIS)

Scime, E.E.

1992-05-01

Ion temperature measurements, time resolved to 10 μs, have been made in the Madison Symmetric Torus (MST) reversed field pinch (RFP) with a five channel charge exchange analyzer. The characteristic anomalously high ion temperature of RFP discharges has been observed in the MST. The evolution of the ion and electron temperature, as well as density and charge exchange power loss, were measured for a series of reproducible discharges. The ion heating expected from collisional processes with the electrons is calculated and shown too small to explain the measured ion temperatures. The charge exchange determined ion temperature is also compared to measurements of the thermally broadened CV 227.1 nm line. The ion temperature, T i ∼ 250 eV for I = 360 kA, increases by more than 100% during discrete dynamo bursts in MST discharges. Magnetic field fluctuations in the range 0.5 endash 5 MHz were also measured during the dynamo bursts. Structure in the fluctuation frequency spectrum at the ion cyclotron frequency appears as the bursts terminate, suggesting that the mechanism of ion heating involves the dissipation of dynamo fluctuations at ion cyclotron frequencies. Theoretical models for ion heating are reviewed and discussed in light of the experimental results. Similar electron heating mechanisms may be responsible for the discrepancy between measured and expected loop voltages in the RFP. The electrons, as well as the ions, may be heated by turbulent mechanisms, and a RFP energy budget including such phenomena is described

New computation results for the solar dynamo

International Nuclear Information System (INIS)

Csada, I.K.

1983-01-01

The analytical solution to the solar dynamo equation leads to a relatively simple algorythm for the computation in terms of kinematic models. The internal and external velocities taken to be in the form of axisymmetric meridional circulation and differential rotation, respectively. Pure radial expanding motions in the corona are also taken into consideration. Numerical results are presented in terms of the velocity parameters for the period of field reversal, decay time, magnitudes and phases of the first four multipoles. (author)

A PROPOSED PARADIGM FOR SOLAR CYCLE DYNAMICS MEDIATED VIA TURBULENT PUMPING OF MAGNETIC FLUX IN BABCOCK–LEIGHTON-TYPE SOLAR DYNAMOS

Energy Technology Data Exchange (ETDEWEB)

Hazra, Soumitra; Nandy, Dibyendu [Department of Physical Sciences, Indian Institute of Science Education and Research, Kolkata (India)

2016-11-20

At present, the Babcock–Leighton flux transport solar dynamo models appear to be the most promising models for explaining diverse observational aspects of the sunspot cycle. The success of these flux transport dynamo models is largely dependent upon a single-cell meridional circulation with a deep equatorward component at the base of the Sun’s convection zone. However, recent observations suggest that the meridional flow may in fact be very shallow (confined to the top 10% of the Sun) and more complex than previously thought. Taken together, these observations raise serious concerns on the validity of the flux transport paradigm. By accounting for the turbulent pumping of magnetic flux, as evidenced in magnetohydrodynamic simulations of solar convection, we demonstrate that flux transport dynamo models can generate solar-like magnetic cycles even if the meridional flow is shallow. Solar-like periodic reversals are recovered even when meridional circulation is altogether absent. However, in this case, the solar surface magnetic field dynamics does not extend all the way to the polar regions. Very importantly, our results demonstrate that the Parker–Yoshimura sign rule for dynamo wave propagation can be circumvented in Babcock–Leighton dynamo models by the latitudinal component of turbulent pumping, which can generate equatorward propagating sunspot belts in the absence of a deep, equatorward meridional flow. We also show that variations in turbulent pumping coefficients can modulate the solar cycle amplitude and periodicity. Our results suggest the viability of an alternate magnetic flux transport paradigm—mediated via turbulent pumping—for sustaining solar-stellar dynamo action.

A PROPOSED PARADIGM FOR SOLAR CYCLE DYNAMICS MEDIATED VIA TURBULENT PUMPING OF MAGNETIC FLUX IN BABCOCK–LEIGHTON-TYPE SOLAR DYNAMOS

International Nuclear Information System (INIS)

Hazra, Soumitra; Nandy, Dibyendu

2016-01-01

At present, the Babcock–Leighton flux transport solar dynamo models appear to be the most promising models for explaining diverse observational aspects of the sunspot cycle. The success of these flux transport dynamo models is largely dependent upon a single-cell meridional circulation with a deep equatorward component at the base of the Sun’s convection zone. However, recent observations suggest that the meridional flow may in fact be very shallow (confined to the top 10% of the Sun) and more complex than previously thought. Taken together, these observations raise serious concerns on the validity of the flux transport paradigm. By accounting for the turbulent pumping of magnetic flux, as evidenced in magnetohydrodynamic simulations of solar convection, we demonstrate that flux transport dynamo models can generate solar-like magnetic cycles even if the meridional flow is shallow. Solar-like periodic reversals are recovered even when meridional circulation is altogether absent. However, in this case, the solar surface magnetic field dynamics does not extend all the way to the polar regions. Very importantly, our results demonstrate that the Parker–Yoshimura sign rule for dynamo wave propagation can be circumvented in Babcock–Leighton dynamo models by the latitudinal component of turbulent pumping, which can generate equatorward propagating sunspot belts in the absence of a deep, equatorward meridional flow. We also show that variations in turbulent pumping coefficients can modulate the solar cycle amplitude and periodicity. Our results suggest the viability of an alternate magnetic flux transport paradigm—mediated via turbulent pumping—for sustaining solar-stellar dynamo action.

A COUPLED 2 × 2D BABCOCK–LEIGHTON SOLAR DYNAMO MODEL. II. REFERENCE DYNAMO SOLUTIONS

International Nuclear Information System (INIS)

Lemerle, Alexandre; Charbonneau, Paul

2017-01-01

In this paper we complete the presentation of a new hybrid 2 × 2D flux transport dynamo (FTD) model of the solar cycle based on the Babcock–Leighton mechanism of poloidal magnetic field regeneration via the surface decay of bipolar magnetic regions (BMRs). This hybrid model is constructed by allowing the surface flux transport (SFT) simulation described in Lemerle et al. to provide the poloidal source term to an axisymmetric FTD simulation defined in a meridional plane, which in turn generates the BMRs required by the SFT. A key aspect of this coupling is the definition of an emergence function describing the probability of BMR emergence as a function of the spatial distribution of the internal axisymmetric magnetic field. We use a genetic algorithm to calibrate this function, together with other model parameters, against observed cycle 21 emergence data. We present a reference dynamo solution reproducing many solar cycle characteristics, including good hemispheric coupling, phase relationship between the surface dipole and the BMR-generating internal field, and correlation between dipole strength at cycle maximum and peak amplitude of the next cycle. The saturation of the cycle amplitude takes place through the quenching of the BMR tilt as a function of the internal field. The observed statistical scatter about the mean BMR tilt, built into the model, acts as a source of stochasticity which dominates amplitude fluctuations. The model thus can produce Dalton-like epochs of strongly suppressed cycle amplitude lasting a few cycles and can even shut off entirely following an unfavorable sequence of emergence events.

A COUPLED 2 × 2D BABCOCK–LEIGHTON SOLAR DYNAMO MODEL. II. REFERENCE DYNAMO SOLUTIONS

Energy Technology Data Exchange (ETDEWEB)

Lemerle, Alexandre; Charbonneau, Paul, E-mail: lemerle@astro.umontreal.ca, E-mail: paulchar@astro.umontreal.ca [Département de physique, Université de Montréal, 2900 Boulevard Édouard-Montpetit, Montréal, QC, H3T 1J4 (Canada)

2017-01-10

In this paper we complete the presentation of a new hybrid 2 × 2D flux transport dynamo (FTD) model of the solar cycle based on the Babcock–Leighton mechanism of poloidal magnetic field regeneration via the surface decay of bipolar magnetic regions (BMRs). This hybrid model is constructed by allowing the surface flux transport (SFT) simulation described in Lemerle et al. to provide the poloidal source term to an axisymmetric FTD simulation defined in a meridional plane, which in turn generates the BMRs required by the SFT. A key aspect of this coupling is the definition of an emergence function describing the probability of BMR emergence as a function of the spatial distribution of the internal axisymmetric magnetic field. We use a genetic algorithm to calibrate this function, together with other model parameters, against observed cycle 21 emergence data. We present a reference dynamo solution reproducing many solar cycle characteristics, including good hemispheric coupling, phase relationship between the surface dipole and the BMR-generating internal field, and correlation between dipole strength at cycle maximum and peak amplitude of the next cycle. The saturation of the cycle amplitude takes place through the quenching of the BMR tilt as a function of the internal field. The observed statistical scatter about the mean BMR tilt, built into the model, acts as a source of stochasticity which dominates amplitude fluctuations. The model thus can produce Dalton-like epochs of strongly suppressed cycle amplitude lasting a few cycles and can even shut off entirely following an unfavorable sequence of emergence events.

Low-latitude plasma drifts from a simulation of the global atmospheric dynamo

International Nuclear Information System (INIS)

Crain, D.J.; Heelis, R.A.; Bailey, G.J.; Richmond, A.D.

1993-01-01

The authors work with a dynamo model to address questions about plasma drifts in the E region, primarily at low latitudes. Tidal winds have been known to have a big influence on electric fields in the E region, and magnetic fields and ion drifts in the equatorial F region. Recent work has centered on self consistency in simulations, using realistic wind distributions, 3-D current distributions, and more accurate measures of the currents and conductivities. The wind dynamo in the ionosphere is well accepted as the main source of electric fields in the low and mid latitudes. The authors present a self consistent model of the plasma distribution and the dynamo driven electric potential distribution. Their results are compared with other simulations. A major concern in their model was reproducing ion drift observations in the equatorial region. Their conclusion is that the F region plays a significant role in the low latitude dyanamo effects, much larger than was previously assumed. When they build into their model realistic ionospheric conditions, allow for appropriate wind distributions, and allow a self consistent redistribution of plasma in the night, they find the model simulates measured ion drifts more closely. Their model is normalized against observations at Jicamarca. By allowing E x B drifts in the ionosphere, and F region zonal winds they can reproduce many of the night changes in the ion drifts at Jicamarca

Stochastic disk dynamo as a model of reversals of the Earth's magnetic field

International Nuclear Information System (INIS)

Ito, H.M.

1988-01-01

A stochastic model is given of a system composed of N similar disk dynamos interacting with one another. The time evolution of the system is governed by a master equation of the class introduced by van Kampen as relevant to stochastic macrosystems. In the model, reversals of the Earth's magnetic field are regarded as large deviations caused by a small random force of O(N/sup -1/2/) from one of the field polarities to the other. Reversal processes are studied by simulation, which shows that the model explains well the activities of the paleomagnetic field inclusive of statistical laws of the reversal sequence and the intensity distribution. Comparison are made between the model and dynamical disk dynamo models

Effects due to induced azimuthal eddy currents in a self-exciting Faraday disk homopolar dynamo with a nonlinear series motor. I.. Two special cases

Science.gov (United States)

Hide, Raymond; Moroz, Irene M.

1999-10-01

The elucidation of the behaviour of physically realistic self-exciting Faraday-disk dynamos bears inter alia on attempts by theoretical geophysicists to interpret observations of geomagnetic polarity reversals. Hide [The nonlinear differential equations governing a hierarchy of self-exciting coupled Faraday-disk homopolar dynamos, Phys. Earth Planet. Interiors 103 (1997) 281-291; Nonlinear quenching of current fluctuations in a self-exciting homopolar dynamo, Nonlinear Processes in Geophysics 4 (1998) 201-205] has introduced a novel 4-mode set of nonlinear ordinary differential equations to describe such a dynamo in which a nonlinear electric motor is connected in series with the coil. The applied couple, α, driving the disk is steady and the Lorentz couple driving the motor is a quadratic function, x(1-ɛ)+ɛσx 2, of the dynamo-generated current x, with 0≤ɛ≤1. When there are no additional biasing effects due to background magnetic fields etc., the behaviour of the dynamo is determined by eight independent non-negative control parameters. These include ρ, proportional to the resistance of the disk to azimuthal eddy currents, and β, an inverse measure of the moment of inertia of the armature of the motor. When β=0 (the case when the motor is absent and ɛ and σ are redundant) and ρ -1≠0 , the 4-mode dynamo equations reduce to the 3-mode Lorenz equations, which can behave chaotically [E. Knobloch, Chaos in the segmented disc dynamo, Phys. Lett. A 82 (1981) 439-440]. When β≠0 but ρ -1=0 , the 4-mode set of equations reduces to a 3-mode dynamo [R. Hide (1997), see above], which can also behave chaotically when ɛ=0 [R. Hide, A.C. Skeldon, D.J. Acheson, A study of two novel self-exciting single-disk homopolar dynamos: theory, Proc. R. Soc. Lond. A 452 (1996) 1369-1395] but not when ɛ=1 [R. Hide (1998), see above]. In the latter case, however, all persistent fluctuations are completely quenched [R. Hide (1998), see above]. In this paper we investigate

Nonlinear quenching of current fluctuations in a self-exciting homopolar dynamo

Directory of Open Access Journals (Sweden)

R. Hide

1997-01-01

Full Text Available In the interpretation of geomagnetic polarity reversals with their highly variable frequency over geological time it is necessary, as with other irregularly fluctuating geophysical phenomena, to consider the relative importance of forced contributions associated with changing boundary conditions and of free contributions characteristic of the behaviour of nonlinear systems operating under fixed boundary conditions.  New evidence -albeit indirect- in favour of the likely predominance of forced contributions is provided by the discovery reported here of the possibility of complete quenching by nonlineax effects of current fluctuations in a self-exciting homopolar dynamo with its single Faraday disk driven into rotation with angular speed y(τ (where τ denotes time by a steady applied couple.  The armature of an electric motor connected in series with the coil of the dynamo is driven into rotation' with angular speed z(τ by a torque xf (x due to Lorentz forces associated with the electric current x(τ in the system (just as certain parts of the spectrum of eddies within the liquid outer core are generated largely by Lorentz forces associated with currents generated by the self-exciting magnetohydrodynamic (MHD geodynamo.   The discovery is based on bifurcation analysis supported by computational studies of the following (mathematically novel autonomous set of nonlinear ordinary differential equations: dx/dt = x(y - 1 - βzf(x, dy/dt = α(1 - x² - κy, dz/dt = xf (x -λz,          where f (x = 1 - ε + εσx, in cases when the dimensionless parameters (α, β, κ, λ, σ are all positive and 0 ≤ ε ≤ 1. Within those regions of (α, β, κ, λ, σ parameter space where the applied couple, as measured by α, is strong enough for persistent dynamo action (i.e. x ≠ 0 to occur at all, there are in general extensive regions where x(τ exhibits large amplitude regular or irregular (chaotic fluctuations.  But these fluctuating r

Recovery from Maunder-like Grand Minima in a Babcock–Leighton Solar Dynamo Model

Science.gov (United States)

Karak, Bidya Binay; Miesch, Mark

2018-06-01

The Sun occasionally goes through Maunder-like extended grand minima when its magnetic activity drops considerably from the normal activity level for several decades. Many possible theories have been proposed to explain the origin of these minima. However, how the Sun managed to recover from such inactive phases every time is even more enigmatic. The Babcock–Leighton type dynamos, which are successful in explaining many features of the solar cycle remarkably well, are not expected to operate during grand minima due to the lack of a sufficient number of sunspots. In this Letter, we explore the question of how the Sun could recover from grand minima through the Babcock–Leighton dynamo. In our three-dimensional dynamo model, grand minima are produced spontaneously as a result of random variations in the tilt angle of emerging active regions. We find that the Babcock–Leighton process can still operate during grand minima with only a minimal number of sunspots, and that the model can emerge from such phases without the need for an additional generation mechanism for the poloidal field. The essential ingredient in our model is a downward magnetic pumping, which inhibits the diffusion of the magnetic flux across the solar surface.

MAGNETIC CYCLES IN A DYNAMO SIMULATION OF FULLY CONVECTIVE M-STAR PROXIMA CENTAURI

Energy Technology Data Exchange (ETDEWEB)

Yadav, Rakesh K.; Wolk, Scott J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Christensen, Ulrich R. [Max-Planck-Institut für Sonnensystemforschung, Justus-von-Liebig-Weg 3, D-37077 Göttingen (Germany); Poppenhaeger, Katja, E-mail: rakesh.yadav@cfa.harvard.edu [Astrophysics Research Center, Queen’s University Belfast, Belfast BT7 1NN (United Kingdom)

2016-12-20

The recent discovery of an Earth-like exoplanet around Proxima Centauri has shined a spot light on slowly rotating fully convective M-stars. When such stars rotate rapidly (period ≲20 days), they are known to generate very high levels of activity that is powered by a magnetic field much stronger than the solar magnetic field. Recent theoretical efforts are beginning to understand the dynamo process that generates such strong magnetic fields. However, the observational and theoretical landscape remains relatively uncharted for fully convective M-stars that rotate slowly. Here, we present an anelastic dynamo simulation designed to mimic some of the physical characteristics of Proxima Centauri, a representative case for slowly rotating fully convective M-stars. The rotating convection spontaneously generates differential rotation in the convection zone that drives coherent magnetic cycles where the axisymmetric magnetic field repeatedly changes polarity at all latitudes as time progress. The typical length of the “activity” cycle in the simulation is about nine years, in good agreement with the recently proposed activity cycle length of about seven years for Proxima Centauri. Comparing our results with earlier work, we hypothesis that the dynamo mechanism undergoes a fundamental change in nature as fully convective stars spin down with age.

A DOUBLE-RING ALGORITHM FOR MODELING SOLAR ACTIVE REGIONS: UNIFYING KINEMATIC DYNAMO MODELS AND SURFACE FLUX-TRANSPORT SIMULATIONS

International Nuclear Information System (INIS)

Munoz-Jaramillo, Andres; Martens, Petrus C. H.; Nandy, Dibyendu; Yeates, Anthony R.

2010-01-01

The emergence of tilted bipolar active regions (ARs) and the dispersal of their flux, mediated via processes such as diffusion, differential rotation, and meridional circulation, is believed to be responsible for the reversal of the Sun's polar field. This process (commonly known as the Babcock-Leighton mechanism) is usually modeled as a near-surface, spatially distributed α-effect in kinematic mean-field dynamo models. However, this formulation leads to a relationship between polar field strength and meridional flow speed which is opposite to that suggested by physical insight and predicted by surface flux-transport simulations. With this in mind, we present an improved double-ring algorithm for modeling the Babcock-Leighton mechanism based on AR eruption, within the framework of an axisymmetric dynamo model. Using surface flux-transport simulations, we first show that an axisymmetric formulation-which is usually invoked in kinematic dynamo models-can reasonably approximate the surface flux dynamics. Finally, we demonstrate that our treatment of the Babcock-Leighton mechanism through double-ring eruption leads to an inverse relationship between polar field strength and meridional flow speed as expected, reconciling the discrepancy between surface flux-transport simulations and kinematic dynamo models.

Dynamos of the Sun, Stars, and Planets - Preface

Science.gov (United States)

Stix, M.

2005-04-01

The conference ``Dynamos of the Sun, Stars, and Planets'' was organized by the Kiepenheuer-Institut für Sonnenphysik Freiburg, and was held at the University of Freiburg from 4th to 6th October 2004. About 50 participants attended the conference, with 8 review lectures, 20 contributed talks, and 6 posters. With only few exceptions, these contributions appear in the present issue of Astronomische Nachrichten. This preface summarizes the discussion of the closing session.

Pembuatan Kakas Pendeteksi Unused Method pada Kode Program PHP dengan Framework CodeIgniter Menggunakan Call Graph

Directory of Open Access Journals (Sweden)

Divi Galih Prasetyo Putri

2014-03-01

Full Text Available Proses evolusi dan perawatan dari sebuah sistem merupakan proses yang sangat penting dalam rekayasa perangkat lunak tidak terkecuali pada aplikasi web. Pada proses ini kebanyakan pengembang tidak lagi berpatokan pada rancangan sistem. Hal ini menyebabkan munculnya unused method. Bagian-bagian program ini tidak lagi terpakai namun masih berada dalam sistem. Keadaan ini meningkatkan kompleksitas dan mengurangi tingkat understandability sistem. Guna mendeteksi adanya unused method pada progam diperlukan teknik untuk melakukan code analysis. Teknik static analysis yang digunakan memanfaatkan call graph yang dibangun dari kode program untuk mengetahui adanya unused method. Call graph dibangun berdasarkan pemanggilan antar method. Aplikasi ini mendeteksi unused method pada kode program PHP yang dibangun menggunakan framework CodeIgniter. Kode program sebagai inputan diurai kedalam bentuk Abstract Syntax Tree (AST yang kemudian dimanfaatkan untuk melakukan analisis terhadap kode program. Proses analisis tersebut kemudian menghasilkan sebuah call graph. Dari call graph yang dihasilkan dapat dideteksi method-method mana saja yang tidak berhasil ditelusuri dan tergolong kedalam unused method. Kakas telah diuji coba pada 5 aplikasi PHP dengan hasil  rata-rata nilai presisi sistem sebesar 0.749 dan recall sebesar 1.

Reducing and measuring fluctuations in the MST RFP: Enhancement of energy confinement and measurement of the MHD dynamo

International Nuclear Information System (INIS)

Den Hartog, D.J.; Almagri, A.F.

1996-09-01

A three- to five-fold enhancement of the energy confinement time in a reversed-field pinch (RFP) has been achieved in the Madison Symmetric Torus (MST) by reducing the amplitude of tearing mode fluctuations responsible for anomalous transport in the core of the RFP. By applying a transient poloidal inductive electric field to flatten the current density profile, the fluctuation amplitude b/B decreases from 1.5% to 0.8%, the electron temperature T e0 increases from 250 eV to 370 eV, the ohmic input power decreases from 4.5 MW to approximately 1.5 MW, the poloidal beta β 0 increases from 6% to 9%, and the energy confinement time τ E increases from 1 ms to ∼5 ms in I φ = 340 kA plasmas with density n = 1 x 10 19 m -3 . Current profile control methods are being developed for the RFP in a program to eliminate transport associated with these current-gradient-driven fluctuations. In addition to controlling the amplitude of the tearing modes, we are vigorously pursuing an understanding of the physics of these fluctuations. In particular, plasma flow, both equilibrium and fluctuating, plays a critical role in a diversity of physical phenomena in MST. The key results: 1) Edge probe measurements show that the MHD dynamo is active in low collisionality plasmas, while at high collisionality a new mechanism, the 'electron diamagnetic dynamo,' is observed. 2) Core spectroscopic measurements show that the toroidal velocity fluctuations of the plasma are coherent with the large-scale magnetic tearing modes; the scalar product of these two fluctuating quantities is similar to that expected for the MHD dynamo electromotive force. 3) Toroidal plasma flow in MST exhibits large radial shear and can be actively controlled, including unlocking locked discharges, by modifying E r with a robust biased probe. 24 refs

Solar activity simulation and forecast with a flux-transport dynamo

Science.gov (United States)

Macario-Rojas, Alejandro; Smith, Katharine L.; Roberts, Peter C. E.

2018-06-01

We present the assessment of a diffusion-dominated mean field axisymmetric dynamo model in reproducing historical solar activity and forecast for solar cycle 25. Previous studies point to the Sun's polar magnetic field as an important proxy for solar activity prediction. Extended research using this proxy has been impeded by reduced observational data record only available from 1976. However, there is a recognised need for a solar dynamo model with ample verification over various activity scenarios to improve theoretical standards. The present study aims to explore the use of helioseismology data and reconstructed solar polar magnetic field, to foster the development of robust solar activity forecasts. The research is based on observationally inferred differential rotation morphology, as well as observed and reconstructed polar field using artificial neural network methods via the hemispheric sunspot areas record. Results show consistent reproduction of historical solar activity trends with enhanced results by introducing a precursor rise time coefficient. A weak solar cycle 25, with slow rise time and maximum activity -14.4% (±19.5%) with respect to the current cycle 24 is predicted.

A simple stochastic model for dipole moment fluctuations in numerical dynamo simulations

Directory of Open Access Journals (Sweden)

Domenico G. eMeduri

2016-04-01

Full Text Available Earth's axial dipole field changes in a complex fashion on many differenttime scales ranging from less than a year to tens of million years.Documenting, analysing, and replicating this intricate signalis a challenge for data acquisition, theoretical interpretation,and dynamo modelling alike. Here we explore whether axial dipole variationscan be described by the superposition of a slow deterministic driftand fast stochastic fluctuations, i.e. by a Langevin-type system.The drift term describes the time averaged behaviour of the axial dipole variations,whereas the stochastic part mimics complex flow interactions over convective time scales.The statistical behaviour of the system is described by a Fokker-Planck equation whichallows useful predictions, including the average rates of dipole reversals and excursions.We analyse several numerical dynamo simulations, most of which havebeen integrated particularly long in time, and also the palaeomagneticmodel PADM2M which covers the past 2 Myr.The results show that the Langevin description provides a viable statistical modelof the axial dipole variations on time scales longer than about 1 kyr.For example, the axial dipole probability distribution and the average reversalrate are successfully predicted.The exception is PADM2M where the stochastic model reversal rate seems too low.The dependence of the drift on the axial dipolemoment reveals the nonlinear interactions that establish thedynamo balance. A separate analysis of inductive and diffusive magnetic effectsin three dynamo simulations suggests that the classical quadraticquenching of induction predicted by mean-field theory seems at work.

Non-kinematic Flux-transport Dynamos Including the Effects of Diffusivity Quenching

Energy Technology Data Exchange (ETDEWEB)

Ichimura, Chiaki; Yokoyama, Takaaki [Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

2017-04-10

Turbulent magnetic diffusivity is quenched when strong magnetic fields suppress turbulent motion in a phenomenon known as diffusivity quenching. Diffusivity quenching can provide a mechanism for amplifying magnetic field and influencing global velocity fields through Lorentz force feedback. To investigate this effect, we conducted mean field flux-transport dynamo simulations that included the effects of diffusivity quenching in a non-kinematic regime. We found that toroidal magnetic field strength is amplified by up to approximately 1.5 times in the convection zone as a result of diffusivity quenching. This amplification is much weaker than that in kinematic cases as a result of Lorentz force feedback on the system’s differential rotation. While amplified toroidal fields lead to the suppression of equatorward meridional flow locally near the base of the convection zone, large-scale equatorward transport of magnetic flux via meridional flow, which is the essential process of the flux-transport dynamo, is sustainable in our calculations.

Linear astrophysical dynamos in rotating spheres: Differential rotation, anisotropic turbulent magnetic diffusivity, and solar-stellar cycle magnetic parity

International Nuclear Information System (INIS)

Yoshimura, H.; Wang, Z.; Wu, F.

1984-01-01

Differential rotation dependence of the selection mechanism for magnetic parity of solar and stellar cycles is studied by assuming various differential rotation profiles inn the dynamo equation. The parity selection depends on propagation direction of oscillating magnetic fields in the form of dynamo waves which propagate along isorotation surfaces. When there is any radial gradient in the differential rotation, dynamo waves propagate either equatorward or poleward. In the former case, field systems of the two hemispheres approach each other and collide at the equator. Then, odd parity is selected. In the latter case, field systems of the two hemispheres recede from each other and do not collide at the equator, an even parity is selected. Thus the equatorial migration of wings of the butterfly iagram of the solar cycle and its odd parity are intrinsically related. In the case of purely latitudibnal differential rotation, dynamo waves propagate purely radially and growth rates of odd and even modes are nearly the same even when dynamo strength is weak when the parity selection mechanism should work most efficiently. In this case, anisotropy of turbulent diffusivity is a decisive factor to separate odd and even modes. Unlike in the case of radial-gradient-dominated differential rotation in which any difference between diffusivities for poloidal and toroidal fields enhancess the parity selection without changing the parity, the parity selection in the case of latitudinal-gradient-dominated differential rotation depends on the difference of diffusivities for poloidal and toroidal fields. When diffusivity for poloidal fields iss larger than that for toroidal fields, odd parity is selected; and when diffusivity for toroidal fields is larger, even parity is selected

Bounds on the growth of the magnetic energy for the Hall kinematic dynamo equation

Energy Technology Data Exchange (ETDEWEB)

Nunez, Manuel [Departamento de Analisis Matematico Universidad de Valladolid 47005 Valladolid (Spain)

2005-09-09

While the magnetic induction equation in plasmas, governing kinematic dynamos, is a linear one admitting exponential growth of the magnetic energy for certain velocity fields, the addition of the Hall term turns it into a nonlinear parabolic equation. Local existence of solutions may be proved, but in contrast with the magnetohydrodynamics case, for a number of boundary conditions the magnetic energy grows at most linearly in time for stationary velocity fields, and like the square of the time in the general case. It appears that the Hall effect enhances diffusivity in some way to compensate for the positive contribution of the transport of the magnetic field by the flow occurring in fast dynamos.

75 FR 53640 - Call for Applications for the International Buyer Program Calendar Year 2012

Science.gov (United States)

2010-09-01

... addition, the applicant should describe in detail the international marketing program to be conducted for... DEPARTMENT OF COMMERCE International Trade Administration [Docket No.: 100806330-0330-01] Call for Applications for the International Buyer Program Calendar Year 2012 AGENCY: International Trade Administration...

76 FR 54428 - Call for Applications for the International Buyer Program Calendar Year 2013

Science.gov (United States)

2011-09-01

... in detail the international marketing program to be conducted for the event, and explain how efforts... DEPARTMENT OF COMMERCE International Trade Administration [Docket No. 110729450-1450-01] Call for Applications for the International Buyer Program Calendar Year 2013 AGENCY: International Trade Administration...

Generation of a Magnetic Field by Dynamo Action in a Turbulent Flow of Liquid Sodium

International Nuclear Information System (INIS)

Monchaux, R.; Chiffaudel, A.; Daviaud, F.; Dubrulle, B.; Gasquet, C.; Marie, L.; Ravelet, F.; Berhanu, M.; Fauve, S.; Mordant, N.; Petrelis, F.; Bourgoin, M.; Moulin, M.; Odier, Ph.; Pinton, J.-F.; Volk, R.

2007-01-01

We report the observation of dynamo action in the von Karman sodium experiment, i.e., the generation of a magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold corresponds to a magnetic Reynolds number R m ∼30. A mean magnetic field of the order of 40 G is observed 30% above threshold at the flow lateral boundary. The rms fluctuations are larger than the corresponding mean value for two of the components. The scaling of the mean square magnetic field is compared to a prediction previously made for high Reynolds number flows

Dynamo Tests for Stratification Below the Core-Mantle Boundary

Science.gov (United States)

Olson, P.; Landeau, M.

2017-12-01

Evidence from seismology, mineral physics, and core dynamics points to a layer with an overall stable stratification in the Earth's outer core, possibly thermal in origin, extending below the core-mantle boundary (CMB) for several hundred kilometers. In contrast, energetic deep mantle convection with elevated heat flux implies locally unstable thermal stratification below the CMB in places, consistent with interpretations of non-dipole geomagnetic field behavior that favor upwelling flows below the CMB. Here, we model the structure of convection and magnetic fields in the core using numerical dynamos with laterally heterogeneous boundary heat flux in order to rationalize this conflicting evidence. Strongly heterogeneous boundary heat flux generates localized convection beneath the CMB that coexists with an overall stable stratification there. Partially stratified dynamos have distinctive time average magnetic field structures. Without stratification or with stratification confined to a thin layer, the octupole component is small and the CMB magnetic field structure includes polar intensity minima. With more extensive stratification, the octupole component is large and the magnetic field structure includes intense patches or high intensity lobes in the polar regions. Comparisons with the time-averaged geomagnetic field are generally favorable for partial stratification in a thin layer but unfavorable for stratification in a thick layer beneath the CMB.

Accretion disc dynamo activity in local simulations spanning weak-to-strong net vertical magnetic flux regimes

Science.gov (United States)

Salvesen, Greg; Simon, Jacob B.; Armitage, Philip J.; Begelman, Mitchell C.

2016-03-01

Strongly magnetized accretion discs around black holes have attractive features that may explain enigmatic aspects of X-ray binary behaviour. The structure and evolution of these discs are governed by a dynamo-like mechanism, which channels part of the accretion power liberated by the magnetorotational instability (MRI) into an ordered toroidal magnetic field. To study dynamo activity, we performed three-dimensional, stratified, isothermal, ideal magnetohydrodynamic shearing box simulations. The strength of the self-sustained toroidal magnetic field depends on the net vertical magnetic flux, which we vary across almost the entire range over which the MRI is linearly unstable. We quantify disc structure and dynamo properties as a function of the initial ratio of mid-plane gas pressure to vertical magnetic field pressure, β _0^mid = p_gas / p_B. For 10^5 ≥ β _0^mid ≥ 10 the effective α-viscosity parameter scales as a power law. Dynamo activity persists up to and including β _0^mid = 10^2, at which point the entire vertical column of the disc is magnetic pressure dominated. Still stronger fields result in a highly inhomogeneous disc structure, with large density fluctuations. We show that the turbulent steady state βmid in our simulations is well matched by the analytic model of Begelman et al. describing the creation and buoyant escape of toroidal field, while the vertical structure of the disc can be broadly reproduced using this model. Finally, we discuss the implications of our results for observed properties of X-ray binaries.

Minerva: using a software program to improve resident performance during independent call

Science.gov (United States)

Itri, Jason N.; Redfern, Regina O.; Cook, Tessa; Scanlon, Mary H.

2010-03-01

We have developed an application called Minerva that allows tracking of resident discrepancy rates and missed cases. Minerva mines the radiology information system (RIS) for preliminary interpretations provided by residents during independent call and copies both the preliminary and final interpretations to a database. Both versions are displayed for direct comparison by Minerva and classified as 'in agreement', 'minor discrepancy' or 'major discrepancy' by the resident program director. Minerva compiles statistics comparing minor, major and total discrepancy rates for individual residents relative to the overall group. Discrepant cases are categorized according to date, modality and body part and reviewed for trends in missed cases. The rate of minor, major and total discrepancies for residents on-call at our institution was similar to rates previously published, including a 2.4% major discrepancy rate for second year radiology residents in the DePICTORS study and a 2.6% major discrepancy rate for resident at a community hospital. Trend analysis of missed cases was used to generate a topic-specific resident missed case conference on acromioclavicular (AC) joint separation injuries, which resulted in a 75% decrease in the number of missed cases related to AC separation subsequent to the conference. Using a software program to track of minor and major discrepancy rates for residents taking independent call using modified RadPeer scoring guidelines provides a competency-based metric to determine resident performance. Topic-specific conferences using the cases identified by Minerva can result in a decrease in missed cases.

Utilizing Facebook and Automated Telephone Calls to Increase Adoption of a Local Smoke Alarm Installation Program.

Science.gov (United States)

Frattaroli, Shannon; Schulman, Eric; McDonald, Eileen M; Omaki, Elise C; Shields, Wendy C; Jones, Vanya; Brewer, William

2018-05-17

Innovative strategies are needed to improve the prevalence of working smoke alarms in homes. To our knowledge, this is the first study to report on the effectiveness of Facebook advertising and automated telephone calls as population-level strategies to encourage an injury prevention behavior. We examine the effectiveness of Facebook advertising and automated telephone calls as strategies to enroll individuals in Baltimore City's Fire Department's free smoke alarm installation program. We directed our advertising efforts toward Facebook users eligible for the Baltimore City Fire Department's free smoke alarm installation program and all homes with a residential phone line included in Baltimore City's automated call system. The Facebook campaign targeted Baltimore City residents 18 years of age and older. In total, an estimated 300 000 Facebook users met the eligibility criteria. Facebook advertisements were delivered to users' desktop and mobile device newsfeeds. A prerecorded message was sent to all residential landlines listed in the city's automated call system. By the end of the campaign, the 3 advertisements generated 456 666 impressions reaching 130 264 Facebook users. Of the users reached, 4367 individuals (1.3%) clicked the advertisement. The automated call system included approximately 90 000 residential phone numbers. Participants attributed 25 smoke alarm installation requests to Facebook and 458 to the automated call. Facebook advertisements are a novel approach to promoting smoke alarms and appear to be effective in exposing individuals to injury prevention messages. However, converting Facebook message recipients to users of a smoke alarm installation program occurred infrequently in this study. Residents who participated in the smoke alarm installation program were more likely to cite the automated call as the impetus for their participation. Additional research is needed to understand the circumstances and strategies to effectively use the social

FPGA Implementation of Blue Whale Calls Classifier Using High-Level Programming Tool

Directory of Open Access Journals (Sweden)

Mohammed Bahoura

2016-02-01

Full Text Available In this paper, we propose a hardware-based architecture for automatic blue whale calls classification based on short-time Fourier transform and multilayer perceptron neural network. The proposed architecture is implemented on field programmable gate array (FPGA using Xilinx System Generator (XSG and the Nexys-4 Artix-7 FPGA board. This high-level programming tool allows us to design, simulate and execute the compiled design in Matlab/Simulink environment quickly and easily. Intermediate signals obtained at various steps of the proposed system are presented for typical blue whale calls. Classification performances based on the fixed-point XSG/FPGA implementation are compared to those obtained by the floating-point Matlab simulation, using a representative database of the blue whale calls.

Spectroscopic measurement of the MHD dynamo in the MST reversed field pinch

International Nuclear Information System (INIS)

Chapman, J.T.

1998-09-01

The author has directly observed the coupling of ion velocity fluctuations and magnetic field fluctuations to produce an MHD dynamo electric field in the interior of the MST reversed field pinch. Chord averaged ion velocity fluctuations were measured with a fast spectroscopic diagnostic which collects line radiation from intrinsic carbon impurities simultaneously along two lines of sight. The chords employed for the measurements resolved long wavelength velocity fluctuations of several km/s at 8--20 kHz as tiny, fast Doppler shifts in the emitted line profile. During discrete dynamo events the velocity fluctuations, like the magnetic fluctuations, increase dramatically. The toroidal and poloidal chords with impact parameters of 0.3 a and 0.6 a respectively, resolved fluctuation wavenumbers with resonance surfaces near or along the lines of sight indicating a radial velocity fluctuation width for each mode which spans only a fraction of the plasma radius. The phase between the measured toroidal velocity fluctuations and the magnetic fluctuations matches the predictions of resistive MHD while the poloidal velocity fluctuations exhibit a phase consistent with the superposition of MHD effects and the advection of a mean flow gradient past the poloidal line of sight. Radial velocity fluctuations resolved by a chord through the center of the plasma were small compared to the poloidal and toroidal fluctuations and exhibited low coherence with the magnetic fluctuations. The ensembled nonlinear product of the ion velocity fluctuations and fluctuations in the magnetic field indicates a substantial dynamo electric field which peaks during the periods of spontaneous flux generation

Spectroscopic measurement of the MHD dynamo in the MST reversed field pinch

Energy Technology Data Exchange (ETDEWEB)

Chapman, James Tharp [Univ. of Wisconsin, Madison, WI (United States)

1998-09-01

The author has directly observed the coupling of ion velocity fluctuations and magnetic field fluctuations to produce an MHD dynamo electric field in the interior of the MST reversed field pinch. Chord averaged ion velocity fluctuations were measured with a fast spectroscopic diagnostic which collects line radiation from intrinsic carbon impurities simultaneously along two lines of sight. The chords employed for the measurements resolved long wavelength velocity fluctuations of several km/s at 8-20 kHz as tiny, fast Doppler shifts in the emitted line profile. During discrete dynamo events the velocity fluctuations, like the magnetic fluctuations, increase dramatically. The toroidal and poloidal chords with impact parameters of 0.3 a and 0.6 a respectively, resolved fluctuation wavenumbers with resonance surfaces near or along the lines of sight indicating a radial velocity fluctuation width for each mode which spans only a fraction of the plasma radius. The phase between the measured toroidal velocity fluctuations and the magnetic fluctuations matches the predictions of resistive MHD while the poloidal velocity fluctuations exhibit a phase consistent with the superposition of MHD effects and the advection of a mean flow gradient past the poloidal line of sight. Radial velocity fluctuations resolved by a chord through the center of the plasma were small compared to the poloidal and toroidal fluctuations and exhibited low coherence with the magnetic fluctuations. The ensembled nonlinear product of the ion velocity fluctuations and fluctuations in the magnetic field indicates a substantial dynamo electric field which peaks during the periods of spontaneous flux generation.

A BABCOCK–LEIGHTON SOLAR DYNAMO MODEL WITH MULTI-CELLULAR MERIDIONAL CIRCULATION IN ADVECTION- AND DIFFUSION-DOMINATED REGIMES

Energy Technology Data Exchange (ETDEWEB)

Belucz, Bernadett; Forgács-Dajka, Emese [Eötvös University, Department of Astronomy, 1518 Budapest, Pf. 32 (Hungary); Dikpati, Mausumi, E-mail: bbelucz@astro.elte.hu, E-mail: dikpati@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, 3080 Center Green, Boulder, CO 80307-3000 (United States)

2015-06-20

Babcock–Leighton type-solar dynamo models with single-celled meridional circulation are successful in reproducing many solar cycle features. Recent observations and theoretical models of meridional circulation do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular circulation patterns in a Babcock–Leighton solar dynamo in advection- and diffusion-dominated regimes. We show from simulations that the presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in the butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of the butterfly wing to an antisolar type. A butterfly diagram constructed from the middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a meridional circulation containing four cells in latitude behaves distinctly differently in the two regimes, producing solar-like butterfly diagrams with fast cycles in the higher diffusivity regime, and complex branches in butterfly diagrams in the lower diffusivity regime. We also find that dynamo solutions for a four-celled pattern, two in radius and two in latitude, prefer to quickly relax to quadrupolar parity if the bottom flow speed is strong enough, of similar order of magnitude as the surface flow speed.

A BABCOCK–LEIGHTON SOLAR DYNAMO MODEL WITH MULTI-CELLULAR MERIDIONAL CIRCULATION IN ADVECTION- AND DIFFUSION-DOMINATED REGIMES

International Nuclear Information System (INIS)

Belucz, Bernadett; Forgács-Dajka, Emese; Dikpati, Mausumi

2015-01-01

Babcock–Leighton type-solar dynamo models with single-celled meridional circulation are successful in reproducing many solar cycle features. Recent observations and theoretical models of meridional circulation do not indicate a single-celled flow pattern. We examine the role of complex multi-cellular circulation patterns in a Babcock–Leighton solar dynamo in advection- and diffusion-dominated regimes. We show from simulations that the presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in the butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of the butterfly wing to an antisolar type. A butterfly diagram constructed from the middle of convection zone yields a solar-like pattern, but this may be difficult to realize in the Sun because of magnetic buoyancy effects. Each of the above cases behaves similarly in higher and lower magnetic diffusivity regimes. However, our dynamo with a meridional circulation containing four cells in latitude behaves distinctly differently in the two regimes, producing solar-like butterfly diagrams with fast cycles in the higher diffusivity regime, and complex branches in butterfly diagrams in the lower diffusivity regime. We also find that dynamo solutions for a four-celled pattern, two in radius and two in latitude, prefer to quickly relax to quadrupolar parity if the bottom flow speed is strong enough, of similar order of magnitude as the surface flow speed

Lorentz violation bounds from torsion trace fermion sector and galaxy M51 data and chiral dynamos

Energy Technology Data Exchange (ETDEWEB)

Garcia de Andrade, L.C. [IF-UERJ, Departamento de Fisica Teorica, Rio de Janeiro, RJ (Brazil)

2017-06-15

Earlier we have computed a Lorentz violation (LV) bound for torsion terms via galactic dynamos and found bounds similar to the one obtained by Kostelecky et al. (Phys Rev Lett 100:111102, 2008) which is of the order of 10{sup -31} GeV. Their result was found making use of the axial torsion vector in terms of Dirac spinors and minimal torsion coupling in flat space-time of fermions. In this paper, a torsion dynamo equation obtained using the variation of the torsion trace and galaxy M51 data of 500 pc are used to place an upper bound of 10{sup -26} GeV in LV, which agrees with the one by Kostelecky and his group using an astrophysical framework background. Their lowest bound was obtained in earth laboratory using dual masers. One of the purposes of this paper is to apply the Faraday self-induction magnetic equation, recently extended to torsioned space-time, by the author to show that it lends support to physics in Riemann-Cartan space-time, in several distinct physical backgrounds. Backreaction magnetic effects are used to obtain the LV bounds. Previously Bamba et al. (JCAP 10:058, 2012) have used the torsion trace in their teleparallel investigation of the IGMF, with the argument that the torsion trace leads to less weaker effects than the other irreducible components of the torsion tensor. LV is computed in terms of a chiral-torsion-like current in the new dynamo equation analogous to the Dvornikov and Semikoz dynamo equation with chiral magnetic currents. Making use of the chiral-torsion dynamo equation we estimate the LV bounds in the early universe to be of the order of 10{sup -24} GeV, which was the order of the charged-lepton sector. Our main result is that it is possible to obtain more stringent bounds than the ones found in the fermion sector of astrophysics in the new revised 2017 data table for CPT and Lorentz violation by Kostelecky and Mewes. They found in several astrophysical backgrounds, orders of magnitude such as 10{sup -24} and 10{sup -23} Ge

First Numerical Simulations of Turbulent Dynamos Driven by Libration, Precession and Tides in Triaxial Ellipsoids - An Alternative Route for Planetary Magnetism

Science.gov (United States)

Le Bars, M.; Kanuganti, S. R.; Favier, B.

2017-12-01

Most of the time, planetary dynamos are - tacitly or not - associated with thermo-solutal convection. The convective dynamo model has indeed proven successful to explain the current Earth's magnetic field. However, its results are sometimes difficult to reconcile with observational data and its validity can be questioned for several celestial bodies. For instance, the small size of the Moon and Ganymede makes it difficult to maintain a sufficient temperature gradient to sustain convection and to explain their past and present magnetic fields, respectively. The same caveat applies to the growing number of planetesimals shown to have generated magnetic fields in their early history. Finally, the energy budget of the early Earth is difficult to reconcile with a convective dynamo before the onset of inner core growth. Significant effort has thus been put into finding new routes for planetary dynamo. In particular, the rotational dynamics of planets, moons and small bodies, where their average spinning motion is periodically perturbed by the small mechanical forcings of libration, precession and/or tides, is now widely accepted as an efficient source of core turbulence. The underlying mechanism relies on a parametric instability where the inertial waves of the rotating fluid core are resonantly excited by the small forcing, leading to exponential growth and bulk filling intense motions, pumping their energy from the orbital dynamics. Dynamos driven by mechanical forcing have been suggested for the Moon, Mars, Io, the early Earth, etc. However, the real dynamo capacity of the corresponding flows has up-to-now been studied only in very limited cases, with simplified spherical/spheroidal geometries and/or overly viscous fluids. We will present here the first numerical simulations of dynamos driven by libration, precession and tides, in the triaxial ellipsoidal geometry and in the turbulent regime relevant for planetary cores. We will describe the numerical techniques

Post discharge issues identified by a call-back program: identifying improvement opportunities.

Science.gov (United States)

Ojeda, Patricia I; Kara, Areeba

2017-12-01

The period following discharge from the hospital is one of heightened vulnerability. Discharge instructions serve as a guide during this transition. Yet, clinicians receive little feedback on the quality of this document that ties into the patients' experience. We reviewed the issues voiced by discharged patients via a call-back program and compared them to the discharge instructions they had received. At our institution, patients receive an automated call forty-eight hours following discharge inquiring about progress. If indicated by the response to the call, they are directed to a nurse who assists with problem solving. We reviewed the nursing documentation of these encounters for a period of nine months. The issues voiced were grouped into five categories: communication, medications, durable medical equipment/therapies, follow up and new or ongoing symptoms. The discharge instructions given to each patient were reviewed. We retrieved data on the number of discharges from each specialty from the hospital over the same period. A total of 592 patients voiced 685 issues. The numbers of patients discharged from medical or surgical services identified as having issues via the call-back line paralleled the proportions discharged from medical and surgical services from the hospital during the same period. Nearly a quarter of the issues discussed had been addressed in the discharge instructions. The most common category of issues was related to communication deficits including missing or incomplete information which made it difficult for the patient to enact or understand the plan of care. Medication prescription related issues were the next most common. Resource barriers and questions surrounding medications were often unaddressed. Post discharge issues affect patients discharged from all services equally. Data from call back programs may provide actionable targets for improvement, identify the inpatient team's 'blind spots' and be used to provide feedback to clinicians.

Ab Initio Simulations of a Supernova-driven Galactic Dynamo in an Isolated Disk Galaxy

Energy Technology Data Exchange (ETDEWEB)

Butsky, Iryna [Astronomy Department, University of Washington, Seattle, WA 98195 (United States); Zrake, Jonathan; Kim, Ji-hoon; Yang, Hung-I; Abel, Tom [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Menlo Park, CA 94025 (United States)

2017-07-10

We study the magnetic field evolution of an isolated spiral galaxy, using isolated Milky Way–mass galaxy formation simulations and a novel prescription for magnetohydrodynamic (MHD) supernova feedback. Our main result is that a galactic dynamo can be seeded and driven by supernova explosions, resulting in magnetic fields whose strength and morphology are consistent with observations. In our model, supernovae supply thermal energy and a low-level magnetic field along with their ejecta. The thermal expansion drives turbulence, which serves a dual role by efficiently mixing the magnetic field into the interstellar medium and amplifying it by means of a turbulent dynamo. The computational prescription for MHD supernova feedback has been implemented within the publicly available ENZO code and is fully described in this paper. This improves upon ENZO 's existing modules for hydrodynamic feedback from stars and active galaxies. We find that the field attains microgauss levels over gigayear timescales throughout the disk. The field also develops a large-scale structure, which appears to be correlated with the disk’s spiral arm density structure. We find that seeding of the galactic dynamo by supernova ejecta predicts a persistent correlation between gas metallicity and magnetic field strength. We also generate all-sky maps of the Faraday rotation measure from the simulation-predicted magnetic field, and we present a direct comparison with observations.

Mean-field dynamos: The old concept and some recent developments. Karl Schwarzschild Award Lecture 2013

Science.gov (United States)

Rädler, K.-H.

This article elucidates the basic ideas of electrodynamics and magnetohydrodynamics of mean fields in turbulently moving conducting fluids. It is stressed that the connection of the mean electromotive force with the mean magnetic field and its first spatial derivatives is in general neither local nor instantaneous and that quite a few claims concerning pretended failures of the mean-field concept result from ignoring this aspect. In addition to the mean-field dynamo mechanisms of α2 and α Ω type several others are considered. Much progress in mean-field electrodynamics and magnetohydrodynamics results from the test-field method for calculating the coefficients that determine the connection of the mean electromotive force with the mean magnetic field. As an important example the memory effect in homogeneous isotropic turbulence is explained. In magnetohydrodynamic turbulence there is the possibility of a mean electromotive force that is primarily independent of the mean magnetic field and labeled as Yoshizawa effect. Despite of many efforts there is so far no convincing comprehensive theory of α quenching, that is, the reduction of the α effect with growing mean magnetic field, and of the saturation of mean-field dynamos. Steps toward such a theory are explained. Finally, some remarks on laboratory experiments with dynamos are made.

47 CFR 22.921 - 911 call processing procedures; 911-only calling mode.

Science.gov (United States)

2010-10-01

... programming in the mobile unit that determines the handling of a non-911 call and permit the call to be... CARRIER SERVICES PUBLIC MOBILE SERVICES Cellular Radiotelephone Service § 22.921 911 call processing procedures; 911-only calling mode. Mobile telephones manufactured after February 13, 2000 that are capable of...

Paleomagnetic evidence for dynamo activity driven by inward crystallisation of a metallic asteroid

Science.gov (United States)

Bryson, James F. J.; Weiss, Benjamin P.; Harrison, Richard J.; Herrero-Albillos, Julia; Kronast, Florian

2017-08-01

The direction in which a planetary core solidifies has fundamental implications for the feasibility and nature of dynamo generation. Although Earth's core is outwardly solidifying, the cores of certain smaller planetary bodies have been proposed to inwardly solidify due to their lower central pressures. However, there have been no unambiguous observations of inwardly solidified cores or the relationship between this solidification regime and planetary magnetic activity. To address this gap, we present the results of complimentary paleomagnetic techniques applied to the matrix metal and silicate inclusions within the IVA iron meteorites. This family of meteorites has been suggested to originate from a planetary core that had its overlaying silicate mantle removed by collisions during the early solar system. This process is thought to have produced a molten ball of metal that cooled rapidly and has been proposed to have inwardly solidified. Recent thermal evolution models of such a body predict that it should have generated an intense, multipolar and time-varying dynamo field. This field could have been recorded as a remanent magnetisation in the outer, cool layers of a solid crust on the IVA parent core. We find that the different components in the IVA iron meteorites display a range of paleomagnetic fidelities, depending crucially on the cooling rate of the meteorite. In particular, silicate inclusions in the quickly cooled São João Nepomuceno meteorite are poor paleomagnetic recorders. On the other hand, the matrix metal and some silicate subsamples from the relatively slowly cooled Steinbach meteorite are far better paleomagnetic recorders and provide evidence of an intense (≳100 μT) and directionally varying (exhibiting significant changes on a timescale ≲200 kyr) magnetic field. This is the first demonstration that some iron meteorites record ancient planetary magnetic fields. Furthermore, the observed field intensity, temporal variability and dynamo

Inertial effects on thermochemically driven convection and hydromagnetic dynamos in a spherical shell

Czech Academy of Sciences Publication Activity Database

Šimkanin, Ján; Kyselica, Juraj; Guba, P.

2018-01-01

Roč. 212, č. 3 (2018), s. 2194-2205 ISSN 0956-540X Institutional support: RVO:67985530 Keywords : composition and structure of the core * dynamo * nonlinear differential equations * numerical modelling Subject RIV: DE - Earth Magnetism, Geodesy, Geography Impact factor: 2.414, year: 2016

A Set of Free Cross-Platform Authoring Programs for Flexible Web-Based CALL Exercises

Science.gov (United States)

O'Brien, Myles

2012-01-01

The Mango Suite is a set of three freely downloadable cross-platform authoring programs for flexible network-based CALL exercises. They are Adobe Air applications, so they can be used on Windows, Macintosh, or Linux computers, provided the freely-available Adobe Air has been installed on the computer. The exercises which the programs generate are…

Turbulent Diffusion of the Geomagnetic Field and Dynamo Theories

OpenAIRE

Filippi, Enrico

2016-01-01

The thesis deals with the Dynamo Theories of the Earth’s Magnetic Field and mainly deepens the turbulence phenomena in the fluid Earth’s core. Indeed, we think that these phenomena are very important to understand the recent decay of the geomagnetic field. The thesis concerns also the dynamics of the outer core and some very rapid changes of the geomagnetic field observed in the Earth’s surface and some aspects regarding the (likely) isotropic turbulence in the Magnetohydrodynamics. These top...

A homopolar disc dynamo experiment with liquid metal contacts

OpenAIRE

Avalos-Zúñiga, R. A.; Priede, J.; Bello-Morales, C. E.

2017-01-01

We present experimental results of a homopolar disc dynamo constructed at CICATA-Quer\\'etaro in Mexico. The device consists of a flat, multi-arm spiral coil which is placed above a fast-spinning metal disc and connected to the latter by sliding liquid-metal electrical contacts. Theoretically, self-excitation of the magnetic field is expected at the critical magnetic Reynolds number Rm~45, which corresponds to a critical rotation rate of about 10 Hz. We measured the magnetic field above the di...

Sudden transitions and grand variations in the solar dynamo, past and future

NARCIS (Netherlands)

de Jager, C.; Duhau, S.

2012-01-01

The solar dynamo is the exotic dance of the sun's two major magnetic field components, the poloidal and the toroidal, interacting in anti-phase. On the basis of new data on the geomagnetic aa index, we improve our previous forecast of the properties of the current Schwabe cycle #24. Its maximum will

The aurora and the magnetosphere - The Chapman Memorial Lecture. [dynamo theory development, 1600-present

Science.gov (United States)

Akasofu, S.-I.

1974-01-01

Review of recent progress in magnetospheric physics, in particular, in understanding the magnetospheric substorm. It is shown that a number of magnetospheric phenomena can now be understood by viewing the solar wind-magnetosphere interaction as an MHD dynamo; auroral phenomena are powered by the dynamo. Also, magnetospheric responses to variations of the north-south and east-west components of the interplanetary magnetic field have been identified. The magnetospheric substorm is entirely different from the responses of the magnetosphere to the southward component of the interplanetary magnetic field. It may be associated with the formation of a neutral line within the plasma sheet and with an enhanced reconnection along the line. A number of substorm-associated phenomena can be understood by noting that the new neutral line formation is caused by a short-circuiting of a part of the magnetotail current.

Energy coupling function and solar wind-magnetosphere dynamo

International Nuclear Information System (INIS)

Kan, J.R.; Lee, L.C.

1979-01-01

The power delivered by the solar wind dynamo to the open magnetosphere is calculated based on the concept of field line reconnection, independent of the MHD steady reconnection theories. By recognizing a previously overlooked geometrical relationship between the reconnection electric field and the magnetic field, the calculated power is shown to be approximately proportional to the Akasofu-Perreault energy coupling function for the magnetospheric substorm. In addition to the polar cap potential, field line reconnection also gives rise to parallel electric fields on open field lines in the high-latitude cusp and the polar cap reions

Finite correlation time effects in kinematic dynamo problem

International Nuclear Information System (INIS)

Schekochihin, A.A.; Kulsrud, R.M.

2000-01-01

One-point statistics of the magnetic fluctuations in kinematic regime with large Prandtl number and non delta-correlated in time advecting velocity field are studied. A perturbation expansion in the ratio of the velocity correlation time to the dynamo growth time is constructed in the spirit of the Kliatskin-Tatarskii functional method and carried out to first order. The convergence properties are improved compared to the commonly used van Kampen-Terwiel method. The zeroth-order growth rate of the magnetic energy is estimated to be reduced (in three dimensions) by approximately 40%. This reduction is quite close to existing numerical results

Dynamo dominated accretion and energy flow: The mechanism of active galactic nuclei

Energy Technology Data Exchange (ETDEWEB)

Colgate, S.A.; Li, H.

1998-12-31

An explanation of the magnetic fields of the universe, the central mass concentration of galaxies, the massive black hole of every galaxy, and the AGN phenomena has been an elusive goal. The authors suggest here the outlines of such a theoretical understanding and point out where the physical understanding is missing. They believe there is an imperative to the sequence of mass flow and hence energy flow in the collapse of a galactic mass starting from the first non-linearity appearing in structure formation following decoupling. This first non-linearity of a two to one density fluctuation, the Lyman-{alpha} clouds, ultimately leads to the emission spectra of the phenomenon of AGN, quasars, blazars, etc. The over-arching physical principle is the various mechanisms for the transport of angular momentum. They believe they have now understood the new physics of two of these mechanisms that have previously been illusive and as a consequence they impose strong constraints on the initial conditions of the mechanisms for the subsequent emission of the gravitational binding energy. The new phenomena described are: (1) the Rossby vortex mechanism of the accretion disk {alpha}-viscosity, and (2) the mechanism of the {alpha}-{Omega} dynamo in the accretion disk. The Rossby vortex mechanism leads to a prediction of the black hole mass and rate of energy release and the {alpha}-{Omega} dynamo leads to the generation of the magnetic flux of the galaxy (and the far greater magnetic flux of clusters) and separately explains the primary flux of energy emission as force-free magnetic energy density. This magnetic flux and magnetic energy density separately are the necessary consequence of the saturation of a dynamo created by the accretion disk with a gain greater than unity.

Mixed Sequence Reader: A Program for Analyzing DNA Sequences with Heterozygous Base Calling

Science.gov (United States)

Chang, Chun-Tien; Tsai, Chi-Neu; Tang, Chuan Yi; Chen, Chun-Houh; Lian, Jang-Hau; Hu, Chi-Yu; Tsai, Chia-Lung; Chao, Angel; Lai, Chyong-Huey; Wang, Tzu-Hao; Lee, Yun-Shien

2012-01-01

The direct sequencing of PCR products generates heterozygous base-calling fluorescence chromatograms that are useful for identifying single-nucleotide polymorphisms (SNPs), insertion-deletions (indels), short tandem repeats (STRs), and paralogous genes. Indels and STRs can be easily detected using the currently available Indelligent or ShiftDetector programs, which do not search reference sequences. However, the detection of other genomic variants remains a challenge due to the lack of appropriate tools for heterozygous base-calling fluorescence chromatogram data analysis. In this study, we developed a free web-based program, Mixed Sequence Reader (MSR), which can directly analyze heterozygous base-calling fluorescence chromatogram data in .abi file format using comparisons with reference sequences. The heterozygous sequences are identified as two distinct sequences and aligned with reference sequences. Our results showed that MSR may be used to (i) physically locate indel and STR sequences and determine STR copy number by searching NCBI reference sequences; (ii) predict combinations of microsatellite patterns using the Federal Bureau of Investigation Combined DNA Index System (CODIS); (iii) determine human papilloma virus (HPV) genotypes by searching current viral databases in cases of double infections; (iv) estimate the copy number of paralogous genes, such as β-defensin 4 (DEFB4) and its paralog HSPDP3. PMID:22778697

The importance of wind-flux feedbacks during the November CINDY-DYNAMO MJO event

Science.gov (United States)

Riley Dellaripa, Emily; Maloney, Eric; van den Heever, Susan

2015-04-01

High-resolution, large-domain cloud resolving model (CRM) simulations probing the importance of wind-flux feedbacks to Madden-Julian Oscillation (MJO) convection are performed for the November 2011 CINDY-DYNAMO MJO event. The work is motivated by observational analysis from RAMA buoys in the Indian Ocean and TRMM precipitation retrievals that show a positive correlation between MJO precipitation and wind-induced surface fluxes, especially latent heat fluxes, during and beyond the CINDY-DYNAMO time period. Simulations are done using Colorado State University's Regional Atmospheric Modeling System (RAMS). The domain setup is oceanic and spans 1000 km x 1000 km with 1.5 km horizontal resolution and 65 stretched vertical levels centered on the location of Gan Island - one of the major CINDY-DYNAMO observation points. The model is initialized with ECMWF reanalysis and Aqua MODIS sea surface temperatures. Nudging from ECMWF reanalysis is applied at the domain periphery to encourage realistic evolution of MJO convection. The control experiment is run for the entire month of November so both suppressed and active, as well as, transitional phases of the MJO are modeled. In the control experiment, wind-induced surface fluxes are activated through the surface bulk aerodynamic formula and allowed to evolve organically. Sensitivity experiments are done by restarting the control run one week into the simulation and controlling the wind-induced flux feedbacks. In one sensitivity experiment, wind-induced surface flux feedbacks are completely denied, while in another experiment the winds are kept constant at the control simulations mean surface wind speed. The evolution of convection, especially on the mesoscale, is compared between the control and sensitivity simulations.

Learning Based Approach for Optimal Clustering of Distributed Program's Call Flow Graph

Science.gov (United States)

Abofathi, Yousef; Zarei, Bager; Parsa, Saeed

Optimal clustering of call flow graph for reaching maximum concurrency in execution of distributable components is one of the NP-Complete problems. Learning automatas (LAs) are search tools which are used for solving many NP-Complete problems. In this paper a learning based algorithm is proposed to optimal clustering of call flow graph and appropriate distributing of programs in network level. The algorithm uses learning feature of LAs to search in state space. It has been shown that the speed of reaching to solution increases remarkably using LA in search process, and it also prevents algorithm from being trapped in local minimums. Experimental results show the superiority of proposed algorithm over others.

Chaotic Dynamos Generated by a Turbulent Flow of Liquid Sodium

International Nuclear Information System (INIS)

Ravelet, F.; Monchaux, R.; Aumaitre, S.; Chiffaudel, A.; Daviaud, F.; Dubrulle, B.; Berhanu, M.; Fauve, S.; Mordant, N.; Petrelis, F.; Bourgoin, M.; Odier, Ph.; Plihon, N.; Pinton, J.-F.; Volk, R.

2008-01-01

We report the observation of several dynamical regimes of the magnetic field generated by a turbulent flow of liquid sodium (VKS experiment). Stationary dynamos, transitions to relaxation cycles or to intermittent bursts, and random field reversals occur in a fairly small range of parameters. Large scale dynamics of the magnetic field result from the interactions of a few modes. The low dimensional nature of these dynamics is not smeared out by the very strong turbulent fluctuations of the flow

77 FR 24766 - Call for Proposals for a Micro Support Program on International Conflict Resolution and...

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2012-04-25

... UNITED STATES INSTITUTE OF PEACE Call for Proposals for a Micro Support Program on International Conflict Resolution and Peacebuilding For Immediate Release AGENCY: United States Institute of Peace. ACTION: Notice. SUMMARY: Micro Support Program on International Conflict Resolution and Peacebuilding...

77 FR 61740 - Call for Applications for the International Buyer Program-Calendar Years 2014 and 2015

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2012-10-11

... should describe in detail the international marketing program to be conducted for the event, and explain... DEPARTMENT OF COMMERCE International Trade Administration [Docket No. 120913451-2451-01] Call for Applications for the International Buyer Program-- Calendar Years 2014 and 2015 AGENCY: International Trade...

78 FR 68814 - Call for Applications for the International Buyer Program Calendar Year 2015

Science.gov (United States)

2013-11-15

... overseas markets and corresponds to marketing opportunities as identified by ITA. Previous international... overseas. In addition, the applicant should describe in detail the international marketing program to be... DEPARTMENT OF COMMERCE International Trade Administration [Docket No.: 131030913-3913-01] Call for...

Dynamo: A Model Transition Framework for Dynamic Stability Control and Body Mass Manipulation

Science.gov (United States)

2011-11-01

driving at high speed, and you turn the steering wheel hard to the right and slam on the brakes, then you will end up in the oversteer regime. At the...sensors (GPS, IMU, LIDAR ) for vehicle control. Figure 17: Dynamo high-speed small UGV hardware platform We will perform experiments to measure the MTC

Turbulent Dynamo Amplification of Magnetic Fields in Laser-Produced Plasmas: Simulations and Experiments

Science.gov (United States)

Tzeferacos, P.; Rigby, A.; Bott, A.; Bell, A.; Bingham, R.; Casner, A.; Cattaneo, F.; Churazov, E.; Forest, C.; Katz, J.; Koenig, M.; Li, C.-K.; Meinecke, J.; Petrasso, R.; Park, H.-S.; Remington, B.; Ross, J.; Ryutov, D.; Ryu, D.; Reville, B.; Miniati, F.; Schekochihin, A.; Froula, D.; Lamb, D.; Gregori, G.

2017-10-01

The universe is permeated by magnetic fields, with strengths ranging from a femtogauss in the voids between the filaments of galaxy clusters to several teragauss in black holes and neutron stars. The standard model for cosmological magnetic fields is the nonlinear amplification of seed fields via turbulent dynamo. We have conceived experiments to demonstrate and study the turbulent dynamo mechanism in the laboratory. Here, we describe the design of these experiments through large-scale 3D FLASH simulations on the Mira supercomputer at ANL, and the laser-driven experiments we conducted with the OMEGA laser at LLE. Our results indicate that turbulence is capable of rapidly amplifying seed fields to near equipartition with the turbulent fluid motions. This work was supported in part from the ERC (FP7/2007-2013, No. 256973 and 247039), and the U.S. DOE, Contract No. B591485 to LLNL, FWP 57789 to ANL, Grant No. DE-NA0002724 and DE-SC0016566 to the University of Chicago, and DE-AC02-06CH11357 to ANL.

Magnetism, dynamo action and the solar-stellar connection

Directory of Open Access Journals (Sweden)

Allan Sacha Brun

2017-09-01

Full Text Available Abstract The Sun and other stars are magnetic: magnetism pervades their interiors and affects their evolution in a variety of ways. In the Sun, both the fields themselves and their influence on other phenomena can be uncovered in exquisite detail, but these observations sample only a moment in a single star’s life. By turning to observations of other stars, and to theory and simulation, we may infer other aspects of the magnetism—e.g., its dependence on stellar age, mass, or rotation rate—that would be invisible from close study of the Sun alone. Here, we review observations and theory of magnetism in the Sun and other stars, with a partial focus on the “Solar-stellar connection”: i.e., ways in which studies of other stars have influenced our understanding of the Sun and vice versa. We briefly review techniques by which magnetic fields can be measured (or their presence otherwise inferred in stars, and then highlight some key observational findings uncovered by such measurements, focusing (in many cases on those that offer particularly direct constraints on theories of how the fields are built and maintained. We turn then to a discussion of how the fields arise in different objects: first, we summarize some essential elements of convection and dynamo theory, including a very brief discussion of mean-field theory and related concepts. Next we turn to simulations of convection and magnetism in stellar interiors, highlighting both some peculiarities of field generation in different types of stars and some unifying physical processes that likely influence dynamo action in general. We conclude with a brief summary of what we have learned, and a sampling of issues that remain uncertain or unsolved.

Is a deep one-cell meridional circulation essential for the flux transport solar dynamo?

International Nuclear Information System (INIS)

Hazra, Gopal; Karak, Bidya Binay; Choudhuri, Arnab Rai

2014-01-01

The solar activity cycle is successfully modeled by the flux transport dynamo, in which the meridional circulation of the Sun plays an important role. Most of the kinematic dynamo simulations assume a one-cell structure of the meridional circulation within the convection zone, with the equatorward return flow at its bottom. In view of the recent claims that the return flow occurs at a much shallower depth, we explore whether a meridional circulation with such a shallow return flow can still retain the attractive features of the flux transport dynamo (such as a proper butterfly diagram, the proper phase relation between the toroidal and poloidal fields). We consider additional cells of the meridional circulation below the shallow return flow—both the case of multiple cells radially stacked above one another and the case of more complicated cell patterns. As long as there is an equatorward flow in low latitudes at the bottom of the convection zone, we find that the solar behavior is approximately reproduced. However, if there is either no flow or a poleward flow at the bottom of the convection zone, then we cannot reproduce solar behavior. On making the turbulent diffusivity low, we still find periodic behavior, although the period of the cycle becomes unrealistically large. In addition, with a low diffusivity, we do not get the observed correlation between the polar field at the sunspot minimum and the strength of the next cycle, which is reproduced when diffusivity is high. On introducing radially downward pumping, we get a more reasonable period and more solar-like behavior even with low diffusivity.

Is a deep one-cell meridional circulation essential for the flux transport solar dynamo?

Energy Technology Data Exchange (ETDEWEB)

Hazra, Gopal; Karak, Bidya Binay; Choudhuri, Arnab Rai, E-mail: ghazra@physics.iisc.ernet.in [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

2014-02-20

The solar activity cycle is successfully modeled by the flux transport dynamo, in which the meridional circulation of the Sun plays an important role. Most of the kinematic dynamo simulations assume a one-cell structure of the meridional circulation within the convection zone, with the equatorward return flow at its bottom. In view of the recent claims that the return flow occurs at a much shallower depth, we explore whether a meridional circulation with such a shallow return flow can still retain the attractive features of the flux transport dynamo (such as a proper butterfly diagram, the proper phase relation between the toroidal and poloidal fields). We consider additional cells of the meridional circulation below the shallow return flow—both the case of multiple cells radially stacked above one another and the case of more complicated cell patterns. As long as there is an equatorward flow in low latitudes at the bottom of the convection zone, we find that the solar behavior is approximately reproduced. However, if there is either no flow or a poleward flow at the bottom of the convection zone, then we cannot reproduce solar behavior. On making the turbulent diffusivity low, we still find periodic behavior, although the period of the cycle becomes unrealistically large. In addition, with a low diffusivity, we do not get the observed correlation between the polar field at the sunspot minimum and the strength of the next cycle, which is reproduced when diffusivity is high. On introducing radially downward pumping, we get a more reasonable period and more solar-like behavior even with low diffusivity.

Introduction to Plasma Dynamo, Reconnection and Shocks

Energy Technology Data Exchange (ETDEWEB)

Intrator, Thomas P. [Los Alamos National Laboratory

2012-08-30

In our plasma universe, most of what we can observe is composed of ionized gas, or plasma. This plasma is a conducting fluid, which advects magnetic fields when it flows. Magnetic structure occurs from the smallest planetary to the largest cosmic scales. We introduce at a basic level some interesting features of non linear magnetohydrodynamics (MHD). For example, in our plasma universe, dynamo creates magnetic fields from gravitationally driven flow energy in an electrically conducting medium, and conversely magnetic reconnection annihilates magnetic field and accelerates particles. Shocks occur when flows move faster than the local velocity (sonic or Alfven speed) for the propagation of information. Both reconnection and shocks can accelerate particles, perhaps to gigantic energies, for example as observed with 10{sup 20} eV cosmic rays.

Evidence favoring an internally generated dynamo in the H chondrite parent planetesimal from the Forest Vale meteorite

Science.gov (United States)

Getzin, B. L.; Bryson, J. F. J.; Weiss, B. P.; Gattacceca, J.

2016-12-01

Chondritic meteorites are traditionally assumed to originate from undifferentiated asteroids due to their unmelted texture and composition. This implies that their parent bodies should not have formed a core or generated a dynamo. However, recent measurements of the H chondrite Portales Valley (Bryson et al., this meeting) observed post-accretional remanent magnetization interpreted as a record of a core dynamo, indicating that some chondrite parent bodies were partially differentiated. However, it has been proposed that the H chondrites may have been magnetized instead by a crustal remanent field. If this crustal magnetization was imparted by an early external source, such as nebular fields or even the solar wind, then the magnetization of H chondrites may not require a core dynamo. To test this hypothesis, we measured the magnetic properties of the Forest Vale H4 ordinary chondrite. Forest Vale cooled quickly (10000 K/My) and so would have acquired magnetization that represents the bulk of the H chondrite parent body's crust during the first 10 My of the solar system. Based on alternating field and pressure demagnetization experiments of natural remanent magnetization (NRM) and anhysteretic remanent magnetization, we conclude that Forest Vale contains no ancient magnetization and, due to its poor intrinsic magnetic recording properties, is unable to acquire a magnetization that is stable against even weak shocks (0.2 GPa). Furthermore, we show that a crust composed of Forest-Vale-like material magnetized by the upper limit field intensities expected for the nebula and solar wind fields (50 μT and 1 μT, respectively) produces an insufficient crustal remanent field (<2.5 μT and <0.045 μT, respectively) to explain the paleointensity recorded by Portales Valley ( 10 μT). Thus, we conclude that the field that magnetization Portales Valley is unlikely to be from a crustal remanence magnetized by early external fields, favoring a partially differentiated asteroid

Generation of dynamo waves by spatially separated sources in the Earth and other celestial bodies

Science.gov (United States)

Popova, E.

2017-12-01

The amplitude and the spatial configuration of the planetary and stellar magnetic field can changing over the years. Celestial bodies can have cyclic, chaotic or unchanging in time magnetic activity which is connected with a dynamo mechanism. This mechanism is based on the consideration of the joint influence of the alpha-effect and differential rotation. Dynamo sources can be located at different depths (active layers) of the celestial body and can have different intensities. Application of this concept allows us to get different forms of solutions and some of which can include wave propagating inside the celestial body. We analytically showed that in the case of spatially separated sources of magnetic field each source generates a wave whose frequency depends on the physical parameters of its source. We estimated parameters of sources required for the generation nondecaying waves. We discus structure of such sources and matter motion (including meridional circulation) in the liquid outer core of the Earth and active layers of other celestial bodies.

TURBULENCE AND DYNAMO IN GALAXY CLUSTER MEDIUM: IMPLICATIONS ON THE ORIGIN OF CLUSTER MAGNETIC FIELDS

International Nuclear Information System (INIS)

Xu Hao; Collins, David C.; Norman, Michael L.; Li Hui; Li Shengtai

2009-01-01

We present self-consistent cosmological magnetohydrodynamic (MHD) simulations that simultaneously follow the formation of a galaxy cluster and the magnetic field ejection by an active galactic nucleus (AGN). We find that the magnetic fields ejected by the AGNs, though initially distributed in relatively small volumes, can be transported throughout the cluster and be further amplified by the intracluster medium (ICM) turbulence during the cluster formation process. The ICM turbulence is shown to be generated and sustained by the frequent mergers of smaller halos. Furthermore, a cluster-wide dynamo process is shown to exist in the ICM and amplify the magnetic field energy and flux. The total magnetic energy in the cluster can reach ∼10 61 erg while micro Gauss (μG) fields can distribute over ∼ Mpc scales throughout the whole cluster. This finding shows that magnetic fields from AGNs, being further amplified by the ICM turbulence through small-scale dynamo processes, can be the origin of cluster-wide magnetic fields.

An analytic interface dynamo over a shear layer of finite depth

OpenAIRE

Petrovay, K.; Kerekes, A.; Erdélyi, R.

2010-01-01

Parker's analytic Cartesian interface dynamo is generalized to the case of a shear layer of finite thickness and low resistivity ("tachocline"), bounded by a perfect conductor ("radiative zone") on the one side, and by a highly diffusive medium ("convective zone") supporting an $\\alpha$-effect on the other side. In the limit of high diffusivity contrast between the shear layer and the diffusive medium, thought to be relevant for the Sun, a pair of exact dispersion relations for the growth rat...

Angular momentum transport and dynamo action in the sun - Implications of recent oscillation measurements

International Nuclear Information System (INIS)

Gilman, P. A.; Morrow, C. A.; Deluca, E. E.

1989-01-01

The implications of a newly proposed picture of the sun's internal rotation (Brown et al., 1989; Morrow, 1988) for the distribution and transport of angular momentum and for the solar dynamo are considered. The new results, derived from an analysis of solar acoustic oscillations, affect understanding of how momentum is cycled in the sun and provide clues as to how and where the solar dynamo is driven. The data imply that the only significant radial gradient of angular velocity exists in a transitional region between the bottom of the convection zone, which is rotating like the solar surface, and the top of the deep interior, which is rotating rigidly at a rate intermediate between the equatorial and polar rates at the surface. Thus the radial gradient must change sign at the latitude where the angular velocity of the surface matches that of the interior. These inferences suggest that the cycle of angular momentum that produces the observed latitudinal differential rotation in the convection zone may be coupled to layers of the interior beneath the convection zone. 35 refs

Solar Cycle Variability Induced by Tilt Angle Scatter in a Babcock-Leighton Solar Dynamo Model

Science.gov (United States)

Karak, Bidya Binay; Miesch, Mark

2017-09-01

We present results from a three-dimensional Babcock-Leighton (BL) dynamo model that is sustained by the emergence and dispersal of bipolar magnetic regions (BMRs). On average, each BMR has a systematic tilt given by Joy’s law. Randomness and nonlinearity in the BMR emergence of our model produce variable magnetic cycles. However, when we allow for a random scatter in the tilt angle to mimic the observed departures from Joy’s law, we find more variability in the magnetic cycles. We find that the observed standard deviation in Joy’s law of {σ }δ =15^\\circ produces a variability comparable to the observed solar cycle variability of ˜32%, as quantified by the sunspot number maxima between 1755 and 2008. We also find that tilt angle scatter can promote grand minima and grand maxima. The time spent in grand minima for {σ }δ =15^\\circ is somewhat less than that inferred for the Sun from cosmogenic isotopes (about 9% compared to 17%). However, when we double the tilt scatter to {σ }δ =30^\\circ , the simulation statistics are comparable to the Sun (˜18% of the time in grand minima and ˜10% in grand maxima). Though the BL mechanism is the only source of poloidal field, we find that our simulations always maintain magnetic cycles even at large fluctuations in the tilt angle. We also demonstrate that tilt quenching is a viable and efficient mechanism for dynamo saturation; a suppression of the tilt by only 1°-2° is sufficient to limit the dynamo growth. Thus, any potential observational signatures of tilt quenching in the Sun may be subtle.

Statistical Mechanics of Turbulent Dynamos

Science.gov (United States)

Shebalin, John V.

2014-01-01

Incompressible magnetohydrodynamic (MHD) turbulence and magnetic dynamos, which occur in magnetofluids with large fluid and magnetic Reynolds numbers, will be discussed. When Reynolds numbers are large and energy decays slowly, the distribution of energy with respect to length scale becomes quasi-stationary and MHD turbulence can be described statistically. In the limit of infinite Reynolds numbers, viscosity and resistivity become zero and if these values are used in the MHD equations ab initio, a model system called ideal MHD turbulence results. This model system is typically confined in simple geometries with some form of homogeneous boundary conditions, allowing for velocity and magnetic field to be represented by orthogonal function expansions. One advantage to this is that the coefficients of the expansions form a set of nonlinearly interacting variables whose behavior can be described by equilibrium statistical mechanics, i.e., by a canonical ensemble theory based on the global invariants (energy, cross helicity and magnetic helicity) of ideal MHD turbulence. Another advantage is that truncated expansions provide a finite dynamical system whose time evolution can be numerically simulated to test the predictions of the associated statistical mechanics. If ensemble predictions are the same as time averages, then the system is said to be ergodic; if not, the system is nonergodic. Although it had been implicitly assumed in the early days of ideal MHD statistical theory development that these finite dynamical systems were ergodic, numerical simulations provided sufficient evidence that they were, in fact, nonergodic. Specifically, while canonical ensemble theory predicted that expansion coefficients would be (i) zero-mean random variables with (ii) energy that decreased with length scale, it was found that although (ii) was correct, (i) was not and the expected ergodicity was broken. The exact cause of this broken ergodicity was explained, after much

Exact axially symmetric galactic dynamos

Science.gov (United States)

Henriksen, R. N.; Woodfinden, A.; Irwin, J. A.

2018-05-01

We give a selection of exact dynamos in axial symmetry on a galactic scale. These include some steady examples, at least one of which is wholly analytic in terms of simple functions and has been discussed elsewhere. Most solutions are found in terms of special functions, such as associated Lagrange or hypergeometric functions. They may be considered exact in the sense that they are known to any desired accuracy in principle. The new aspect developed here is to present scale-invariant solutions with zero resistivity that are self-similar in time. The time dependence is either a power law or an exponential factor, but since the geometry of the solution is self-similar in time we do not need to fix a time to study it. Several examples are discussed. Our results demonstrate (without the need to invoke any other mechanisms) X-shaped magnetic fields and (axially symmetric) magnetic spiral arms (both of which are well observed and documented) and predict reversing rotation measures in galaxy haloes (now observed in the CHANG-ES sample) as well as the fact that planar magnetic spirals are lifted into the galactic halo.

The nonlinear differential equations governing a hierarchy of self-exciting coupled Faraday-disk homopolar dynamos

Science.gov (United States)

Hide, Raymond

1997-02-01

This paper discusses the derivation of the autonomous sets of dimensionless nonlinear ordinary differential equations (ODE's) that govern the behaviour of a hierarchy of related electro-mechanical self-exciting Faraday-disk homopolar dynamo systems driven by steady mechanical couples. Each system comprises N interacting units which could be arranged in a ring or lattice. Within each unit and connected in parallel or in series with the coil are electric motors driven into motion by the dynamo, all having linear characteristics, so that nonlinearity arises entirely through the coupling between components. By introducing simple extra terms into the equations it is possible to represent biasing effects arising from impressed electromotive forces due to thermoelectric or chemical processes and from the presence of ambient magnetic fields. Dissipation in the system is due not only to ohmic heating but also to mechanical friction in the disk and the motors, with the latter agency, no matter how weak, playing an unexpectedly crucial rôle in the production of régimes of chaotic behaviour. This has already been demonstrated in recent work on a case of a single unit incorporating just one series motor, which is governed by a novel autonomous set of nonlinear ODE's with three time-dependent variables and four control parameters. It will be of mathematical as well as geophysical and astrophysical interest to investigate systematically phase and amplitude locking and other types of behaviour in the more complicated cases that arise when N > 1, which can typically involve up to 6 N dependent variables and 19 N-5 control parameters. Even the simplest members of the hierarchy, with N as low as 1, 2 or 3, could prove useful as physically-realistic low-dimensional models in theoretical studies of fluctuating stellar and planetary magnetic fields. Geomagnetic polarity reversals could be affected by the presence of the Earth's solid metallic inner core, driven like an electric motor

Tidal excitation of elliptical instability in the Martian core: Possible mechanism for generating the core dynamo

Science.gov (United States)

Arkani-Hamed, J.; Seyed-Mahmoud, B.; Aldridge, K. D.; Baker, R. E.

2008-06-01

We propose a causal relationship between the creation of the giant impact basins on Mars by a large asteroid, ruptured when it entered the Roche limit, and the excitation of the Martian core dynamo. Our laboratory experiments indicate that the elliptical instability of the Martian core can be excited if the asteroid continually exerts tidal forces on Mars for ~20,000 years. Our numerical experiments suggest that the growth-time of the instability was 5,000-15,000 years when the asteroid was at a distance of 50,000-75,000 km. We demonstrate the stability of the orbital motion of an asteroid captured by Mars at a distance of 100,000 km in the presence of the Sun and Jupiter. We also present our results for the tidal interaction of the asteroid with Mars. An asteroid captured by Mars in prograde fashion can survive and excite the elliptical instability of the core for only a few million years, whereas a captured retrograde asteroid can excite the elliptical instability for hundreds of millions of years before colliding with Mars. The rate at which tidal energy dissipates in Mars during this period is over two orders of magnitude greater than the rate at which magnetic energy dissipates. If only 1% of the tidal energy dissipation is partitioned to the core, sufficient energy would be available to maintain the core dynamo. Accordingly, a retrograde asteroid is quite capable of exciting an elliptical instability in the Martian core, thus providing a candidate process to drive a core dynamo.

APL MITRA extensions to graphics. Call programs written in another language with APL MITRA

International Nuclear Information System (INIS)

Ouanes, Mohamed Kamel

1978-01-01

This study concerns: - A new way of using APL to deal with graphics problems. For this, the extensions to the APL-MITRA interpreter are: - the definition of graphic variables, - the creation of a graphic environment using new graphic system variables (□AX, □CA, □MΦ), - dealing with a set of primitive graphic system functions (□GΦ, □GI, □GR, □GF, □GC) which handle graphic input/output operations on a Tektronix console (4000 series, especially the 4013 and 4015). A new system function (□CI) which permits APL programs to call programs written in other languages. (author) [fr

A model of the solar cycle driven by the dynamo action of the global convection in the solar convection zone

International Nuclear Information System (INIS)

Yoshimura, H.

1976-01-01

Extensive numerical studies of the dynamo equations due to the global convection are presented to simulate the solar cycle and to open the way to study general stellar magnetic cycles. The dynamo equations which represent the longitudinally-averaged magnetohydrodynamical action (mean magnetohydrodynamics) of the global convection under the influence of the rotation in the solar convection zone are considered here as an initial boundary-value problem. The latitudinal and radial structure of the dynamo action consisting of a generation action due to the differential rotation and a regeneration action due to the global convection is parameterized in accordance with the structure of the rotation and of the global convection. This is done especially in such a way as to represent the presence of the two cells of the regeneration action in the radial direction in which the action has opposite signs, which is typical of the regeneration action of the global convection. The effects of the dynamics of the global convection (e.g., the effects of the stratification of the physical conditions in the solar convection zone) are presumed to be all included in those parameters used in the model and they are presumed not to alter the results drastically since these effects are only to change the structure of the regeneration action topologically. (Auth.)

Role of asymmetric meridional circulation in producing north-south asymmetry in a solar cycle dynamo model

Energy Technology Data Exchange (ETDEWEB)

Belucz, Bernadett [Eötvös University, Department of Astronomy, 1518 Budapest, Pf. 32 (Hungary); Dikpati, Mausumi [High Altitude Observatory, National Center for Atmospheric Research, 3080 Center Green, Boulder, CO 80307-3000 (United States)

2013-12-10

Solar cycles in the north and south hemispheres differ in cycle length, amplitude, profile, polar fields, and coronal structure. To show what role differences in meridional flow could play in producing these differences, we present the results of three sets of numerical simulations from a flux transport dynamo in which one property of meridional circulation has been changed in the south only. The changes are in amplitude and the presence of a second cell in latitude or in depth. An ascending phase speedup causes weakening of polar and toroidal fields; a speed decrease in a late descending phase does not change amplitudes. A long-duration speed increase leads to lower toroidal field peaks but unchanged polar field peaks. A second high-latitude circulation cell in an ascending phase weakens the next polar and toroidal field peaks, and the ascending phase is lengthened. A second cell in a late descending phase speeds up the cycle. A long-duration second cell leads to a poleward branch of the butterfly diagram and weaker polar fields. A second cell in depth reverses the tilt of the butterfly wing, decreasing polar fields when added during an ascending phase and increasing them during a late descending phase. A long-duration presence of a second cell in radius evolves the butterfly diagram far away from the observed one, with different dynamo periods in low and high latitudes. Thus, a second cell in depth is unlikely to persist more than a few years if the solar dynamo is advection-dominated. Our results show the importance of time variation and north-south asymmetry in meridional circulation in producing differing cycles in the north and south.

Role of asymmetric meridional circulation in producing north-south asymmetry in a solar cycle dynamo model

International Nuclear Information System (INIS)

Belucz, Bernadett; Dikpati, Mausumi

2013-01-01

Solar cycles in the north and south hemispheres differ in cycle length, amplitude, profile, polar fields, and coronal structure. To show what role differences in meridional flow could play in producing these differences, we present the results of three sets of numerical simulations from a flux transport dynamo in which one property of meridional circulation has been changed in the south only. The changes are in amplitude and the presence of a second cell in latitude or in depth. An ascending phase speedup causes weakening of polar and toroidal fields; a speed decrease in a late descending phase does not change amplitudes. A long-duration speed increase leads to lower toroidal field peaks but unchanged polar field peaks. A second high-latitude circulation cell in an ascending phase weakens the next polar and toroidal field peaks, and the ascending phase is lengthened. A second cell in a late descending phase speeds up the cycle. A long-duration second cell leads to a poleward branch of the butterfly diagram and weaker polar fields. A second cell in depth reverses the tilt of the butterfly wing, decreasing polar fields when added during an ascending phase and increasing them during a late descending phase. A long-duration presence of a second cell in radius evolves the butterfly diagram far away from the observed one, with different dynamo periods in low and high latitudes. Thus, a second cell in depth is unlikely to persist more than a few years if the solar dynamo is advection-dominated. Our results show the importance of time variation and north-south asymmetry in meridional circulation in producing differing cycles in the north and south.

Computer simulation of a magnetohydrodynamic dynamo II

International Nuclear Information System (INIS)

Kageyama, Akira; Sato, Tetsuya.

1994-11-01

We performed a computer simulation of a magnetohydrodynamic dynamo in a rapidly rotating spherical shell. Extensive parameter runs are carried out changing the electrical resistivity. It is found that the total magnetic energy can grow more than ten times larger than the total kinetic energy of the convection motion when the resistivity is sufficiently small. When the resistivity is relatively large and the magnetic energy is comparable or smaller than the kinetic energy, the convection motion maintains its well-organized structure. However, when the resistivity is small and the magnetic energy becomes larger than the kinetic energy, the well-organized convection motion is highly disturbed. The generated magnetic field is organized as a set of flux tubes which can be divided into two categories. The magnetic field component parallel to the rotation axis tends to be confined inside the anticyclonic columnar convection cells. On the other hand, the component perpendicular to the rotation axis is confined outside the convection cells. (author)

The 3D Elevation Program initiative: a call for action

Science.gov (United States)

Sugarbaker, Larry J.; Constance, Eric W.; Heidemann, Hans Karl; Jason, Allyson L.; Lukas, Vicki; Saghy, David L.; Stoker, Jason M.

2014-01-01

The 3D Elevation Program (3DEP) initiative is accelerating the rate of three-dimensional (3D) elevation data collection in response to a call for action to address a wide range of urgent needs nationwide. It began in 2012 with the recommendation to collect (1) high-quality light detection and ranging (lidar) data for the conterminous United States (CONUS), Hawaii, and the U.S. territories and (2) interferometric synthetic aperture radar (ifsar) data for Alaska. Specifications were created for collecting 3D elevation data, and the data management and delivery systems are being modernized. The National Elevation Dataset (NED) will be completely refreshed with new elevation data products and services. The call for action requires broad support from a large partnership community committed to the achievement of national 3D elevation data coverage. The initiative is being led by the U.S. Geological Survey (USGS) and includes many partners—Federal agencies and State, Tribal, and local governments—who will work together to build on existing programs to complete the national collection of 3D elevation data in 8 years. Private sector firms, under contract to the Government, will continue to collect the data and provide essential technology solutions for the Government to manage and deliver these data and services. The 3DEP governance structure includes (1) an executive forum established in May 2013 to have oversight functions and (2) a multiagency coordinating committee based upon the committee structure already in place under the National Digital Elevation Program (NDEP). The 3DEP initiative is based on the results of the National Enhanced Elevation Assessment (NEEA) that was funded by NDEP agencies and completed in 2011. The study, led by the USGS, identified more than 600 requirements for enhanced (3D) elevation data to address mission-critical information requirements of 34 Federal agencies, all 50 States, and a sample of private sector companies and Tribal and local

Partitioning a call graph

NARCIS (Netherlands)

Bisseling, R.H.; Byrka, J.; Cerav-Erbas, S.; Gvozdenovic, N.; Lorenz, M.; Pendavingh, R.A.; Reeves, C.; Röger, M.; Verhoeven, A.; Berg, van den J.B.; Bhulai, S.; Hulshof, J.; Koole, G.; Quant, C.; Williams, J.F.

2006-01-01

Splitting a large software system into smaller and more manageable units has become an important problem for many organizations. The basic structure of a software system is given by a directed graph with vertices representing the programs of the system and arcs representing calls from one program to

77 FR 74828 - Call for Applications for the International Buyer Program Calendar Years 2014 and 2015

Science.gov (United States)

2012-12-18

... DEPARTMENT OF COMMERCE International Trade Administration [Docket No. 120913451-2681-02] Call for Applications for the International Buyer Program Calendar Years 2014 and 2015 AGENCY: International Trade... the DOC and trade show organizers to benefit U.S. firms exhibiting at selected events and provides...

Latitudinal profile of the ionospheric disturbance dynamo magnetic signature: comparison with the DP2 magnetic disturbance

Directory of Open Access Journals (Sweden)

K. Z. Zaka

2009-09-01

Full Text Available During magnetic storms, the auroral electrojets intensification affects the thermospheric circulation on a global scale. This process which leads to electric field and current disturbance at middle and low latitudes, on the quiet day after the end of a storm, has been attributed to the ionospheric disturbance dynamo (Ddyn. The magnetic field disturbance observed as a result of this process is the reduction of the H component amplitude in the equatorial region which constitutes the main characteristic of the ionospheric disturbance dynamo process, associated with a westward electric current flow. The latitudinal profile of the Ddyn disturbance dynamo magnetic signature exhibits an eastward current at mid latitudes and a westward one at low latitudes with a substantial amplification at the magnetic equator. Such current flow reveals an "anti-Sq" system established between the mid latitudes and the equatorial region and opposes the normal Sq current vortex. However, the localization of the eastward current and consequently the position and the extent of the "anti-Sq" current vortex changes from one storm to another. Indeed, for a strong magnetic storm, the eastward current is well established at mid latitudes about 45° N and for a weak magnetic storm, the eastward current is established toward the high latitudes (about 60° N, near the Joule heating region, resulting in a large "anti-Sq" current cell. The latitudinal profile of the Ddyn disturbance as well as the magnetic disturbance DP2 generated by the mechanism of prompt penetration of the magnetospheric convection electric field in general, show a weak disturbance at the low latitudes with a substantial amplification at the magnetic equator. Due to the intensity of the storm, the magnitude of the DP2 appears higher than the Ddyn over the American and Asian sector contrary to the African sector.

Using dynamo theory to predict the sunspot number during solar cycle 21

Science.gov (United States)

Schatten, K. H.; Scherrer, P. H.; Svalgaard, L.; Wilcox, J. M.

1978-01-01

On physical grounds it is suggested that the polar field strength of the sun near a solar minimum is closely related to the solar activity of the following cycle. Four methods of estimating the polar magnetic field strength of the sun near solar minimum are employed to provide an estimate of the yearly mean sunspot number of cycle 21 at solar maximum of 140 + or - 20. This estimate may be considered a first-order attempt to predict the cycle activity using one parameter of physical importance based upon dynamo theory.

NONLINEAR DYNAMO IN A ROTATING ELECTRICALLY CONDUCTING FLUID

Directory of Open Access Journals (Sweden)

M. I. Kopp

2017-05-01

Full Text Available We found a new large-scale instability, which arises in the rotating conductive fluid with small-scale turbulence. Turbulence is generated by small-scale external force with a low Reynolds number. The theory is built simply by the method of multiscale asymptotic expansions. Nonlinear equations for vortex and magnetic perturbations obtained in the third order for small Reynolds number. It is shown that the combined effects of the Coriolis force and the small external forces in a rotating conducting fluid possible large-scale instability. The large-scale increments of the instability, correspond to generation as the vortex and magnetic disturbances. This type of instability is classified as hydrodynamic and MHD alpha-effect. We studied the stationary regimes of nonlinear equations of magneto-vortex dynamo. In the limit of weakly conducting fluid found stationary solutions in the form of helical kinks. In the limit of high conductivity fluid was obtained stationary solutions in the form of nonlinear periodic waves and kinks.

Marketing Residential Treatment Programs for Eating Disorders: A Call for Transparency.

Science.gov (United States)

Attia, Evelyn; Blackwood, Kristy L; Guarda, Angela S; Marcus, Marsha D; Rothman, David J

2016-06-01

Residential behavioral treatment is a growing sector of the health care industry and is used by a large proportion of adolescent and adult patients with eating disorders. These programs and the organizations that own them have developed extensive marketing strategies that target clinicians and include promotional gifts, meals, travel reimbursement, and continuing education credit. Legislation and policy changes have limited these types of activities when conducted by the pharmaceutical industry, and awareness of conflicts of interest associated with clinician-targeted advertising of drugs and devices has increased. However, similar practices by the behavioral health care industry have evolved without oversight. The authors urge clinicians to consider how marketing strategies by treatment facilities may influence their referral behaviors and call for improved transparency regarding gifts and payments from treatment facilities.

Hidden hyperchaos and electronic circuit application in a 5D self-exciting homopolar disc dynamo

Science.gov (United States)

Wei, Zhouchao; Moroz, Irene; Sprott, J. C.; Akgul, Akif; Zhang, Wei

2017-03-01

We report on the finding of hidden hyperchaos in a 5D extension to a known 3D self-exciting homopolar disc dynamo. The hidden hyperchaos is identified through three positive Lyapunov exponents under the condition that the proposed model has just two stable equilibrium states in certain regions of parameter space. The new 5D hyperchaotic self-exciting homopolar disc dynamo has multiple attractors including point attractors, limit cycles, quasi-periodic dynamics, hidden chaos or hyperchaos, as well as coexisting attractors. We use numerical integrations to create the phase plane trajectories, produce bifurcation diagram, and compute Lyapunov exponents to verify the hidden attractors. Because no unstable equilibria exist in two parameter regions, the system has a multistability and six kinds of complex dynamic behaviors. To the best of our knowledge, this feature has not been previously reported in any other high-dimensional system. Moreover, the 5D hyperchaotic system has been simulated using a specially designed electronic circuit and viewed on an oscilloscope, thereby confirming the results of the numerical integrations. Both Matlab and the oscilloscope outputs produce similar phase portraits. Such implementations in real time represent a new type of hidden attractor with important consequences for engineering applications.

FamSeq: a variant calling program for family-based sequencing data using graphics processing units.

Directory of Open Access Journals (Sweden)

Gang Peng

2014-10-01

Full Text Available Various algorithms have been developed for variant calling using next-generation sequencing data, and various methods have been applied to reduce the associated false positive and false negative rates. Few variant calling programs, however, utilize the pedigree information when the family-based sequencing data are available. Here, we present a program, FamSeq, which reduces both false positive and false negative rates by incorporating the pedigree information from the Mendelian genetic model into variant calling. To accommodate variations in data complexity, FamSeq consists of four distinct implementations of the Mendelian genetic model: the Bayesian network algorithm, a graphics processing unit version of the Bayesian network algorithm, the Elston-Stewart algorithm and the Markov chain Monte Carlo algorithm. To make the software efficient and applicable to large families, we parallelized the Bayesian network algorithm that copes with pedigrees with inbreeding loops without losing calculation precision on an NVIDIA graphics processing unit. In order to compare the difference in the four methods, we applied FamSeq to pedigree sequencing data with family sizes that varied from 7 to 12. When there is no inbreeding loop in the pedigree, the Elston-Stewart algorithm gives analytical results in a short time. If there are inbreeding loops in the pedigree, we recommend the Bayesian network method, which provides exact answers. To improve the computing speed of the Bayesian network method, we parallelized the computation on a graphics processing unit. This allowed the Bayesian network method to process the whole genome sequencing data of a family of 12 individuals within two days, which was a 10-fold time reduction compared to the time required for this computation on a central processing unit.

Turchin's Relation for Call-by-Name Computations: A Formal Approach

OpenAIRE

Antonina Nepeivoda

2016-01-01

Supercompilation is a program transformation technique that was first described by V. F. Turchin in the 1970s. In supercompilation, Turchin's relation as a similarity relation on call-stack configurations is used both for call-by-value and call-by-name semantics to terminate unfolding of the program being transformed. In this paper, we give a formal grammar model of call-by-name stack behaviour. We classify the model in terms of the Chomsky hierarchy and then formally prove that Turchin's rel...

A Coupled 2 × 2D Babcock-Leighton Solar Dynamo Model. I. Surface Magnetic Flux Evolution

Science.gov (United States)

Lemerle, Alexandre; Charbonneau, Paul; Carignan-Dugas, Arnaud

2015-09-01

The need for reliable predictions of the solar activity cycle motivates the development of dynamo models incorporating a representation of surface processes sufficiently detailed to allow assimilation of magnetographic data. In this series of papers we present one such dynamo model, and document its behavior and properties. This first paper focuses on one of the model’s key components, namely surface magnetic flux evolution. Using a genetic algorithm, we obtain best-fit parameters of the transport model by least-squares minimization of the differences between the associated synthetic synoptic magnetogram and real magnetographic data for activity cycle 21. Our fitting procedure also returns Monte Carlo-like error estimates. We show that the range of acceptable surface meridional flow profiles is in good agreement with Doppler measurements, even though the latter are not used in the fitting process. Using a synthetic database of bipolar magnetic region (BMR) emergences reproducing the statistical properties of observed emergences, we also ascertain the sensitivity of global cycle properties, such as the strength of the dipole moment and timing of polarity reversal, to distinct realizations of BMR emergence, and on this basis argue that this stochasticity represents a primary source of uncertainty for predicting solar cycle characteristics.

A COUPLED 2 × 2D BABCOCK–LEIGHTON SOLAR DYNAMO MODEL. I. SURFACE MAGNETIC FLUX EVOLUTION

International Nuclear Information System (INIS)

Lemerle, Alexandre; Charbonneau, Paul; Carignan-Dugas, Arnaud

2015-01-01

The need for reliable predictions of the solar activity cycle motivates the development of dynamo models incorporating a representation of surface processes sufficiently detailed to allow assimilation of magnetographic data. In this series of papers we present one such dynamo model, and document its behavior and properties. This first paper focuses on one of the model’s key components, namely surface magnetic flux evolution. Using a genetic algorithm, we obtain best-fit parameters of the transport model by least-squares minimization of the differences between the associated synthetic synoptic magnetogram and real magnetographic data for activity cycle 21. Our fitting procedure also returns Monte Carlo-like error estimates. We show that the range of acceptable surface meridional flow profiles is in good agreement with Doppler measurements, even though the latter are not used in the fitting process. Using a synthetic database of bipolar magnetic region (BMR) emergences reproducing the statistical properties of observed emergences, we also ascertain the sensitivity of global cycle properties, such as the strength of the dipole moment and timing of polarity reversal, to distinct realizations of BMR emergence, and on this basis argue that this stochasticity represents a primary source of uncertainty for predicting solar cycle characteristics

A COUPLED 2 × 2D BABCOCK–LEIGHTON SOLAR DYNAMO MODEL. I. SURFACE MAGNETIC FLUX EVOLUTION

Energy Technology Data Exchange (ETDEWEB)

Lemerle, Alexandre; Charbonneau, Paul; Carignan-Dugas, Arnaud, E-mail: lemerle@astro.umontreal.ca, E-mail: paulchar@astro.umontreal.ca [Département de physique, Université de Montréal, 2900 boul. Édouard-Montpetit, Montréal, QC, H3T 1J4 (Canada)

2015-09-01

The need for reliable predictions of the solar activity cycle motivates the development of dynamo models incorporating a representation of surface processes sufficiently detailed to allow assimilation of magnetographic data. In this series of papers we present one such dynamo model, and document its behavior and properties. This first paper focuses on one of the model’s key components, namely surface magnetic flux evolution. Using a genetic algorithm, we obtain best-fit parameters of the transport model by least-squares minimization of the differences between the associated synthetic synoptic magnetogram and real magnetographic data for activity cycle 21. Our fitting procedure also returns Monte Carlo-like error estimates. We show that the range of acceptable surface meridional flow profiles is in good agreement with Doppler measurements, even though the latter are not used in the fitting process. Using a synthetic database of bipolar magnetic region (BMR) emergences reproducing the statistical properties of observed emergences, we also ascertain the sensitivity of global cycle properties, such as the strength of the dipole moment and timing of polarity reversal, to distinct realizations of BMR emergence, and on this basis argue that this stochasticity represents a primary source of uncertainty for predicting solar cycle characteristics.

A Video-Based CALL Program for Proficient and Less-Proficient L2 Learners' Comprehension Ability, Incidental Vocabulary Acquisition

Science.gov (United States)

Lin, Lu-Fang

2010-01-01

This study investigates first whether news video in a computer-assisted language learning (CALL) program can foster second language (L2) comprehension and incidental acquisition of adjectives, nouns, and verbs. Second, this study examines the relationship between the participants' vocabulary acquisition and their video comprehension. The…

Jamaican Call-In Radio: A Uses and Gratification Analysis.

Science.gov (United States)

Surlin, Stuart H.

Noting that radio call-in programs seem to contain the elements for active audience involvement and participation, a study was conducted to examine the hypothesis that information gain and surveillance are the primary gratifications sought through call-in radio programs, especially in a culture that has a strong oral tradition and relatively few…

DYNAMO: Distributed Leisure Yacht-Carried Sensor-Network for Atmosphere and Marine Data Crowdsourcing Applications

DEFF Research Database (Denmark)

Montella, Raffaele; Kosta, S.; Foster, I.

2018-01-01

Data crowdsourcing is a increasingly pervasive and lifestyle-changing technology, due to the flywheel effect that results from the interaction between the internet of things and cloud computing. In smart cities, for example, many initiatives harvest valuable data from citizen sensors. However, th...... weather and marine predictions via the use of data assimilation methods. We show our preliminary results about the DYNAMO Daemon, a SignalK server we embedded in the native level of the Android operating system enabling the data gathering and transfer from vessels to the cloud....

The Ghost in the Machine: Are "Teacherless" CALL Programs Really Possible?

Science.gov (United States)

Davies, Ted; Williamson, Rodney

1998-01-01

Reflects critically on pedagogical issues in the production of computer-assisted language learning (CALL) courseware and ways CALL has affected the practice of language learning. Concludes that if CALL is to reach full potential, it must be more than a simple medium of information; it should provide a teaching/learning process, with the real…

Turchin's Relation for Call-by-Name Computations: A Formal Approach

Directory of Open Access Journals (Sweden)

Antonina Nepeivoda

2016-07-01

Full Text Available Supercompilation is a program transformation technique that was first described by V. F. Turchin in the 1970s. In supercompilation, Turchin's relation as a similarity relation on call-stack configurations is used both for call-by-value and call-by-name semantics to terminate unfolding of the program being transformed. In this paper, we give a formal grammar model of call-by-name stack behaviour. We classify the model in terms of the Chomsky hierarchy and then formally prove that Turchin's relation can terminate all computations generated by the model.

Dynamo action and magnetic buoyancy in convection simulations with vertical shear

Science.gov (United States)

Guerrero, G.; Käpylä, P.

2011-10-01

A hypothesis for sunspot formation is the buoyant emergence of magnetic flux tubes created by the strong radial shear at the tachocline. In this scenario, the magnetic field has to exceed a threshold value before it becomes buoyant and emerges through the whole convection zone. In this work we present the results of direct numerical simulations of compressible turbulent convection that include a vertical shear layer. Like the solar tachocline, the shear is located at the interface between convective and stable layers. We follow the evolution of a random seed magnetic field with the aim of study under what conditions it is possible to excite the dynamo instability and whether the dynamo generated magnetic field becomes buoyantly unstable and emerges to the surface as expected in the flux-tube context. We find that shear and convection are able to amplify the initial magnetic field and form large-scale elongated magnetic structures. The magnetic field strength depends on several parameters such as the shear amplitude, the thickness and location of the shear layer, and the magnetic Reynolds number (Rm). Models with deeper and thicker shear layers allow longer storage and are more favorable for generating a mean magnetic field. Models with higher Rm grow faster but saturate at slightly lower levels. Whenever the toroidal magnetic field reaches amplitudes greater a threshold value which is close to the equipartition value, it becomes buoyant and rises into the convection zone where it expands and forms mushroom shape structures. Some events of emergence, i.e., those with the largest amplitudes of the amplified field, are able to reach the very uppermost layers of the domain. These episodes are able to modify the convective pattern forming either broader convection cells or convective eddies elongated in the direction of the field. However, in none of these events the field preserves its initial structure. The back-reaction of the magnetic field on the fluid is also

Energetic Approach to Investigation of Chaotic Behavior of Low-Dimensional Dynamic Systems and its Illustration on a Two-Disc Rikitake Dynamo

Czech Academy of Sciences Publication Activity Database

Pánek, D.; Hrušák, J.; Doležel, Ivo

2007-01-01

Roč. 43, č. 596 (2007), s. 46-51 ISSN 0321-0499 R&D Projects: GA ČR(CZ) GA102/07/0496 Institutional research plan: CEZ:AV0Z20570509 Keywords : chaotic behavior * low-dimensional chaotic systems * Rikitake dynamo Subject RIV: JA - Electronics ; Optoelectronics, Electrical Engineering

Kinematic Dynamo Action in the Presence of a Large Scale Velocity

Science.gov (United States)

Carvalho, J. C.

1990-11-01

RESUMEN. Se investiga la influencia de Un campo de velocidades de ran escala sobre la acci6n del tur bulento. Usando Un proceso de expansi6n, las soluciones se encuentran en el del movimiento lobal y de cizalla pequeflo y para randes de Reynolds. Se calcula la re jeneraci6n tica hasta un orden en el de expansi6n usando convectivas ciclotr6nicas para el campo turbulento de velocidad. ABSTRACT. The influence a scale velocity field upon the kinernatic turbulent dynamo action is . Usinj an expansion process, the solutions are found in the limit of small bulk motion and shear, and for Reynolds number. The majnetic is calculated up to second order in the expansion parameter usin cyclonic convective cells for the turbulent velocity field. Key o'td : HYDROMAGNETICS

Non-linear quenching of current fluctuations in a self-exciting homopolar dynamo, proved by feedback system theory

OpenAIRE

A. M. de Paor

1998-01-01

International audience; Hide (Nonlinear Processes in Geophysics, 1998) has produced a new mathematical model of a self-exciting homopolar dynamo driving a series- wound motor, as a continuing contribution to the theory of the geomagnetic field. By a process of exact perturbation analysis, followed by combination and partial solution of differential equations, the complete nonlinear quenching of current fluctuations reported by Hide in the case that a parameter ? has the value 1 is proved via ...

A synthetic operational account of call-by-need evaluation

DEFF Research Database (Denmark)

Zerny, Ian; Danvy, Olivier

2013-01-01

. The syntactic theory was initiated by Ariola, Felleisen, Maraist, Odersky and Wadler and is prevalent today to reason equationally about lazy programs, on par with Barendregt et al.'s term graphs. Nobody knows, however, how the theory of call by need compares to the practice of call by need: all that is known...... machine implementing lazy evaluation. The machines are intensionally compatible with extensional reasoning about lazy programs and they are lock-step equivalent. Each machine functionally corresponds to a natural semantics for call by need in the style of Launchbury, though for non-preprocessed λ...

UNDERSTANDING SOLAR TORSIONAL OSCILLATIONS FROM GLOBAL DYNAMO MODELS

International Nuclear Information System (INIS)

Guerrero, G.; Smolarkiewicz, P. K.; Pino, E. M. de Gouveia Dal; Kosovichev, A. G.; Mansour, N. N.

2016-01-01

The phenomenon of solar “torsional oscillations” (TO) represents migratory zonal flows associated with the solar cycle. These flows are observed on the solar surface and, according to helioseismology, extend through the convection zone. We study the origin of the TO using results from a global MHD simulation of the solar interior that reproduces several of the observed characteristics of the mean-flows and magnetic fields. Our results indicate that the magnetic tension (MT) in the tachocline region is a key factor for the periodic changes in the angular momentum transport that causes the TO. The torque induced by the MT at the base of the convection zone is positive at the poles and negative at the equator. A rising MT torque at higher latitudes causes the poles to speed up, whereas a declining negative MT torque at the lower latitudes causes the equator to slow-down. These changes in the zonal flows propagate through the convection zone up to the surface. Additionally, our results suggest that it is the magnetic field at the tachocline that modulates the amplitude of the surface meridional flow rather than the opposite as assumed by flux-transport dynamo models of the solar cycle.

Integrating heterogeneous healthcare call centers.

Science.gov (United States)

Peschel, K M; Reed, W C; Salter, K

1998-01-01

In a relatively short period, OHS has absorbed multiple call centers supporting different LOBs from various acquisitions, functioning with diverse standards, processes, and technologies. However, customer and employee satisfaction is predicated on OHS's ability to thoroughly integrate these heterogeneous call centers. The integration was initiated and has successfully progressed through a balanced program of focused leadership and a defined strategy which includes site consolidation, sound performance management philosophies, and enabling technology. Benefits have already been achieved with even more substantive ones to occur as the integration continues to evolve.

Call Forecasting for Inbound Call Center

Directory of Open Access Journals (Sweden)

Peter Vinje

2009-01-01

Full Text Available In a scenario of inbound call center customer service, the ability to forecast calls is a key element and advantage. By forecasting the correct number of calls a company can predict staffing needs, meet service level requirements, improve customer satisfaction, and benefit from many other optimizations. This project will show how elementary statistics can be used to predict calls for a specific company, forecast the rate at which calls are increasing/decreasing, and determine if the calls may stop at some point.

Evolution of pulsarmagnetism by virtue of a Faraday dynamo mechanism

International Nuclear Information System (INIS)

Heintzmann, H.; Novello, M.

1983-01-01

The evidence that radio-pulsars are slowed-down and Roentgen - pulsars accelerated predominantly by magnetic torques is now very strong. Angular momentum is transferred away from the neutron star to the velocity-of-light cylinder or from the Alfven - cylinder down to the neutron star by means of a magnetic spring the physical origin of which is an appropriate current flowing along the magnetic field lines. As this current must be closed at the neutron star's surface and no Hall-Field can be built-up a Faraday dynamo mechanism is set up. It is pointed out that this mechanism could switch -off a radio pulsar or turn-on a Roentgen pulsar. Many disconcerting pulsar observations could thus be explained, if radio pulsars can be reactivated in the galactic plane by means of accretion of matter in dense clouds and if Roentgenpulsars must first create a sufficiently strong magnetic field to function as a regularly pulsed emitter. (Author) [pt

Data acquisition in a high-speed rotating frame for New Mexico Institute of Mining and Technology liquid sodium αω dynamo experiment.

Science.gov (United States)

Si, Jiahe; Colgate, Stirling A; Li, Hui; Martinic, Joe; Westpfahl, David

2013-10-01

New Mexico Institute of Mining and Technology liquid sodium αω-dynamo experiment models the magnetic field generation in the universe as discussed in detail by Colgate, Li, and Pariev [Phys. Plasmas 8, 2425 (2001)]. To obtain a quasi-laminar flow with magnetic Reynolds number R(m) ~ 120, the dynamo experiment consists of two co-axial cylinders of 30.5 cm and 61 cm in diameter spinning up to 70 Hz and 17.5 Hz, respectively. During the experiment, the temperature of the cylinders must be maintained to 110 °C to ensure that the sodium remains fluid. This presents a challenge to implement a data acquisition (DAQ) system in such high temperature, high-speed rotating frame, in which the sensors (including 18 Hall sensors, 5 pressure sensors, and 5 temperature sensors, etc.) are under the centrifugal acceleration up to 376g. In addition, the data must be transmitted and stored in a computer 100 ft away for safety. The analog signals are digitized, converted to serial signals by an analog-to-digital converter and a field-programmable gate array. Power is provided through brush/ring sets. The serial signals are sent through ring/shoe sets capacitively, then reshaped with cross-talk noises removed. A microcontroller-based interface circuit is used to decode the serial signals and communicate with the data acquisition computer. The DAQ accommodates pressure up to 1000 psi, temperature up to more than 130 °C, and magnetic field up to 1000 G. First physics results have been analyzed and published. The next stage of the αω-dynamo experiment includes the DAQ system upgrade.

ESTIMATING THE DEEP SOLAR MERIDIONAL CIRCULATION USING MAGNETIC OBSERVATIONS AND A DYNAMO MODEL: A VARIATIONAL APPROACH

Energy Technology Data Exchange (ETDEWEB)

Hung, Ching Pui; Jouve, Laurène; Brun, Allan Sacha [Laboratoire AIM Paris-Saclay, CEA/IRFU Université Paris-Diderot CNRS/INSU, F-91191 Gif-Sur-Yvette (France); Fournier, Alexandre [Institut de Physique du Globe de Paris, Sorbonne Paris Cité, Université Paris Diderot UMR 7154 CNRS, F-75005 Paris (France); Talagrand, Olivier [Laboratoire de météorologie dynamique, UMR 8539, Ecole Normale Supérieure, Paris Cedex 05 (France)

2015-12-01

We show how magnetic observations of the Sun can be used in conjunction with an axisymmetric flux-transport solar dynamo model in order to estimate the large-scale meridional circulation throughout the convection zone. Our innovative approach rests on variational data assimilation, whereby the distance between predictions and observations (measured by an objective function) is iteratively minimized by means of an optimization algorithm seeking the meridional flow that best accounts for the data. The minimization is performed using a quasi-Newton technique, which requires knowledge of the sensitivity of the objective function to the meridional flow. That sensitivity is efficiently computed via the integration of the adjoint flux-transport dynamo model. Closed-loop (also known as twin) experiments using synthetic data demonstrate the validity and accuracy of this technique for a variety of meridional flow configurations, ranging from unicellular and equatorially symmetric to multicellular and equatorially asymmetric. In this well-controlled synthetic context, we perform a systematic study of the behavior of our variational approach under different observational configurations by varying their spatial density, temporal density, and noise level, as well as the width of the assimilation window. We find that the method is remarkably robust, leading in most cases to a recovery of the true meridional flow to within better than 1%. These encouraging results are a first step toward using this technique to (i) better constrain the physical processes occurring inside the Sun and (ii) better predict solar activity on decadal timescales.

ESTIMATING THE DEEP SOLAR MERIDIONAL CIRCULATION USING MAGNETIC OBSERVATIONS AND A DYNAMO MODEL: A VARIATIONAL APPROACH

International Nuclear Information System (INIS)

Hung, Ching Pui; Jouve, Laurène; Brun, Allan Sacha; Fournier, Alexandre; Talagrand, Olivier

2015-01-01

We show how magnetic observations of the Sun can be used in conjunction with an axisymmetric flux-transport solar dynamo model in order to estimate the large-scale meridional circulation throughout the convection zone. Our innovative approach rests on variational data assimilation, whereby the distance between predictions and observations (measured by an objective function) is iteratively minimized by means of an optimization algorithm seeking the meridional flow that best accounts for the data. The minimization is performed using a quasi-Newton technique, which requires knowledge of the sensitivity of the objective function to the meridional flow. That sensitivity is efficiently computed via the integration of the adjoint flux-transport dynamo model. Closed-loop (also known as twin) experiments using synthetic data demonstrate the validity and accuracy of this technique for a variety of meridional flow configurations, ranging from unicellular and equatorially symmetric to multicellular and equatorially asymmetric. In this well-controlled synthetic context, we perform a systematic study of the behavior of our variational approach under different observational configurations by varying their spatial density, temporal density, and noise level, as well as the width of the assimilation window. We find that the method is remarkably robust, leading in most cases to a recovery of the true meridional flow to within better than 1%. These encouraging results are a first step toward using this technique to (i) better constrain the physical processes occurring inside the Sun and (ii) better predict solar activity on decadal timescales

Non-linear quenching of current fluctuations in a self-exciting homopolar dynamo, proved by feedback system theory

Science.gov (United States)

de Paor, A. M.

Hide (Nonlinear Processes in Geophysics, 1998) has produced a new mathematical model of a self-exciting homopolar dynamo driving a series- wound motor, as a continuing contribution to the theory of the geomagnetic field. By a process of exact perturbation analysis, followed by combination and partial solution of differential equations, the complete nonlinear quenching of current fluctuations reported by Hide in the case that a parameter ɛ has the value 1 is proved via the Popov theorem from feedback system stability theory.

Measurements of the large-scale direct-current Earth potential and possible implications for the geomagnetic dynamo.

Science.gov (United States)

1985-07-05

The magnitude of the large-scale direct-current earth potential was measured on a section of a recently laid transatlantic telecommunications cable. Analysis of the data acquired on the 4476-kilometer cable yielded a mean direct-current potential drop of less than about 0.072 +/- 0.050 millivolts per kilometer. Interpreted in terms of a generation of the potential by the earth's geodynamo, such a small value of the mean potential implies that the toroidal and poloidal magnetic fields of the dynamo are approximately equal at the core-mantle boundary.

Glasbury Bridge 1: The Jumper. Close Call.

Science.gov (United States)

Journal of Adventure Education and Outdoor Leadership, 1994

1994-01-01

Describes an incident in which a group of 10th-grade students in a 1-week outdoor residential program in the Wye Valley (Great Britain) defied program rules, drank alcohol, and had a close call with a near-drowning. Discusses five strategies for dealing with such groups coalesced around a rebellious leader. (SV)

Emergence of Magnetic Flux Generated in a Solar Convective Dynamo. I. The Formation of Sunspots and Active Regions, and The Origin of Their Asymmetries

Energy Technology Data Exchange (ETDEWEB)

Chen, Feng; Rempel, Matthias; Fan, Yuhong, E-mail: chenfeng@ucar.edu [High Altitude Observatory, NCAR, P.O. Box 3000, Boulder, CO, 80307 (United States)

2017-09-10

We present a realistic numerical model of sunspot and active region formation based on the emergence of flux bundles generated in a solar convective dynamo. To this end, we use the magnetic and velocity fields in a horizontal layer near the top boundary of the solar convective dynamo simulation to drive realistic radiative-magnetohydrodynamic simulations of the uppermost layers of the convection zone. The main results are as follows. (1) The emerging flux bundles rise with the mean speed of convective upflows and fragment into small-scale magnetic elements that further rise to the photosphere, where bipolar sunspot pairs are formed through the coalescence of the small-scale magnetic elements. (2) Filamentary penumbral structures form when the sunspot is still growing through ongoing flux emergence. In contrast to the classical Evershed effect, the inflow seems to prevail over the outflow in a large part of the penumbra. (3) A well-formed sunspot is a mostly monolithic magnetic structure that is anchored in a persistent deep-seated downdraft lane. The flow field outside the spot shows a giant vortex ring that comprises an inflow below 15 Mm depth and an outflow above 15 Mm depth. (4) The sunspots successfully reproduce the fundamental properties of the observed solar active regions, including the more coherent leading spots with a stronger field strength, and the correct tilts of bipolar sunspot pairs. These asymmetries can be linked to the intrinsic asymmetries in the magnetic and flow fields adapted from the convective dynamo simulation.

Reducing juvenile delinquency with automated cell phone calls.

Science.gov (United States)

Burraston, Bert O; Bahr, Stephen J; Cherrington, David J

2014-05-01

Using a sample of 70 juvenile probationers (39 treatment and 31 controls), we evaluated the effectiveness of a rehabilitation program that combined cognitive-behavioral training and automated phone calls. The cognitive-behavioral training contained six 90-min sessions, one per week, and the phone calls occurred twice per day for the year following treatment. Recidivism was measured by whether they were rearrested and the total number of rearrests during the 1st year. To test the impact of the phone calls, those who received phone calls were divided into high and low groups depending on whether they answered more or less than half of their phone calls. Those who completed the class and answered at least half of their phone calls were less likely to have been arrested and had fewer total arrests.

Non-linear quenching of current fluctuations in a self-exciting homopolar dynamo, proved by feedback system theory

Directory of Open Access Journals (Sweden)

A. M. de Paor

1998-01-01

Full Text Available Hide (Nonlinear Processes in Geophysics, 1998 has produced a new mathematical model of a self-exciting homopolar dynamo driving a series- wound motor, as a continuing contribution to the theory of the geomagnetic field. By a process of exact perturbation analysis, followed by combination and partial solution of differential equations, the complete nonlinear quenching of current fluctuations reported by Hide in the case that a parameter ε has the value 1 is proved via the Popov theorem from feedback system stability theory.

Responding to the call for globalization in nursing education: the implementation of the transatlantic double-degree program.

Science.gov (United States)

Hornberger, Cynthia A; Erämaa, Sirkka; Helembai, Kornélia; McCartan, Patrick J; Turtiainen, Tarja

2014-01-01

Increased demand for nurses worldwide has highlighted the need for a flexible nursing workforce eligible for licensure in multiple countries. Nursing's curricular innovation mirrors the call for reform within higher education including globalization of curricula (E. J. S. Hovenga, 2004; D. Nayyar, 2008; B. J. G. Wood, S. M. Tapsall, & G. N. Soutar, 2005), increased opportunities for student mobility exchanges, dialogue between different academic traditions, and mutual understanding and transparency between universities (J. González & R. Wagenaar, 2005). The European Union (EU) and United States have combined efforts to achieve these objectives by creating the Atlantis program in 2007 (U.S. Department of Education, 2011). This article describes experiences of four nursing programs participating in an Atlantis project to develop a double-degree baccalaureate program for undergraduate nursing students. Early learnings include increasing awareness and appreciation of essential curricular and performance competencies of the baccalaureate-prepared professional nurse. Challenges include language competency; variations in curriculum, cultural norms, student expectations, and learning assessment; and philosophical differences regarding first-level professional nurse preparation as specialist versus generalist. The Transatlantic Double Degree program has successfully implemented the double-degree program. Members have gained valuable insights into key issues surrounding the creation of a more uniform, yet flexible, educational standard between our countries. © 2014.

STELLAR EVIDENCE THAT THE SOLAR DYNAMO MAY BE IN TRANSITION

International Nuclear Information System (INIS)

Metcalfe, Travis S.; Egeland, Ricky; Van Saders, Jennifer

2016-01-01

Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation–age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a critical Rossby number (Ro ∼ 2). We compile published chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation–age relations. We use these data along with a sample of well-characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun may be in a transitional evolutionary phase, and that its magnetic cycle might represent a special case of stellar dynamo theory.

STELLAR EVIDENCE THAT THE SOLAR DYNAMO MAY BE IN TRANSITION

Energy Technology Data Exchange (ETDEWEB)

Metcalfe, Travis S. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder CO 80301 (United States); Egeland, Ricky [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder CO 80307 (United States); Van Saders, Jennifer [Carnegie Observatories, 813 Santa Barbara Street, Pasadena CA 91101 (United States)

2016-07-20

Precise photometry from the Kepler space telescope allows not only the measurement of rotation in solar-type field stars, but also the determination of reliable masses and ages from asteroseismology. These critical data have recently provided the first opportunity to calibrate rotation–age relations for stars older than the Sun. The evolutionary picture that emerges is surprising: beyond middle-age the efficiency of magnetic braking is dramatically reduced, implying a fundamental change in angular momentum loss beyond a critical Rossby number (Ro ∼ 2). We compile published chromospheric activity measurements for the sample of Kepler asteroseismic targets that were used to establish the new rotation–age relations. We use these data along with a sample of well-characterized solar analogs from the Mount Wilson HK survey to develop a qualitative scenario connecting the evolution of chromospheric activity to a fundamental shift in the character of differential rotation. We conclude that the Sun may be in a transitional evolutionary phase, and that its magnetic cycle might represent a special case of stellar dynamo theory.

Magnetorotational instability and dynamo action in gravito-turbulent astrophysical discs

Science.gov (United States)

Riols, A.; Latter, H.

2018-02-01

Though usually treated in isolation, the magnetorotational and gravitational instabilities (MRI and GI) may coincide at certain radii and evolutionary stages of protoplanetary discs and active galactic nuclei. Their mutual interactions could profoundly influence several important processes, such as accretion variability and outbursts, fragmentation and disc truncation, or large-scale magnetic field production. Direct numerical simulations of both instabilities are computationally challenging and remain relatively unexplored. In this paper, we aim to redress this neglect via a set of 3D vertically stratified shearing-box simulations, combining self-gravity and magnetic fields. We show that gravito-turbulence greatly weakens the zero-net-flux MRI. In the limit of efficient cooling (and thus enhanced GI), the MRI is completely suppressed, and yet strong magnetic fields are sustained by the gravito-turbulence. This turbulent `spiral wave' dynamo may have widespread application, especially in galactic discs. Finally, we present preliminary work showing that a strong net-vertical-flux revives the MRI and supports a magnetically dominated state in which the GI is secondary.

Instrument calls and real-time code for laboratory automation

International Nuclear Information System (INIS)

Taber, L.; Ames, H.S.; Yamauchi, R.K.; Barton, G.W. Jr.

1978-01-01

These programs are the result of a joint Lawrence Livermore Laboratory and Environmental Protection Agency project to automate water quality laboratories. They form the interface between the analytical instruments and the BASIC language programs for data reduction and analysis. They operate on Data General NOVA 840's at Cincinnati and Chicago and on a Data General ECLIPSE C330 at Livermore. The operating system consists of unmodified RDOS, Data General's disk operating system, and Data General's multiuser BASIC modified to provide the instrument CALLs and other functions described. Instruments automated at various laboratories include Technicon AutoAnalyzers, atomic absorption spectrophotometers, total organic carbon analyzers, an emission spectrometer, an electronic balance, sample changers, and an optical spectrophotometer. Other instruments may be automated using these same CALLs, or new CALLs may be written as described

Perilaku Kreatif Pekerja Call Center: Peran Komunikasi dan Dukungan Training Center

Directory of Open Access Journals (Sweden)

Nugroho J. Setiadi

2013-11-01

Full Text Available Call center business in Indonesia is growing rapidly worldwide. This condition has had repercussions for a growing number of call center workers needed. They are forced to be more creative in performing their duties. This study aims to determine the role of communication and training center in supporting the creative performance of workers in call centers. The survey was conducted by distributing questionnaires to 100 respondents (employees of the 3 major companies in the field of telecommunication services in Indonesia. Regression analysis was used to analyze the data to examine the role of communication and training support center on creative performance. The results indicated that communication and training support center significantly influence the creative behavior in call center workers. Communication quality shown in the telecommunication service provider companies, such as the media quality, simplicity of information, dissemination of information, loads of information, and accuracy of messages, has shown good quality. In addition, the training program has shown its support for call center workers in the form of program effectiveness through research and data collection, determining the materials, training methods, choosing a coach, preparing facilities, selecting and implementing the program.

Plasma response to sustainment with imposed-dynamo current drive in HIT-SI and HIT-SI3

Science.gov (United States)

Hossack, A. C.; Jarboe, T. R.; Chandra, R. N.; Morgan, K. D.; Sutherland, D. A.; Penna, J. M.; Everson, C. J.; Nelson, B. A.

2017-07-01

The helicity injected torus—steady inductive (HIT-SI) program studies efficient, steady-state current drive for magnetic confinement plasmas using a novel experimental method. Stable, high-beta spheromaks have been sustained using steady, inductive current drive. Externally induced loop voltage and magnetic flux are oscillated together so that helicity and power injection are always positive, sustaining the edge plasma current indefinitely. Imposed-dynamo current drive (IDCD) theory further shows that the entire plasma current is sustained. The method is ideal for low aspect ratio, toroidal geometries with closed flux surfaces. Experimental studies of spheromak plasmas sustained with IDCD have shown stable magnetic profiles with evidence of pressure confinement. New measurements show coherent motion of a stable spheromak in response to the imposed perturbations. On the original device two helicity injectors were mounted on either side of the spheromak and the injected mode spectrum was predominantly n  =  1. Coherent, rigid motion indicates that the spheromak is stable and a lack of plasma-generated n  =  1 energy indicates that the maximum q is maintained below 1 during sustainment. Results from the HIT-SI3 device are also presented. Three inductive helicity injectors are mounted on one side of the spheromak flux conserver. Varying the relative injector phasing changes the injected mode spectrum which includes n  =  2, 3, and higher modes.

Steven MacCall: Winner of LJ's 2010 Teaching Award

Science.gov (United States)

Berry, John N., III

2010-01-01

This article profiles Steven L. MacCall, winner of "Library Journal's" 2010 Teaching Award. An associate professor at the School of Library and Information Studies (SLIS) at the University of Alabama, Tuscaloosa, MacCall was nominated by Kathie Popadin, known as "Kpop" to the members of her cohort in the online MLIS program at SLIS. Sixteen of…

DYNAMO: a Mars upper atmosphere package for investigating solar wind interaction and escape processes, and mapping Martian fields

DEFF Research Database (Denmark)

Chassefiere, E.; Nagy, A.; Mandea, M.

2004-01-01

DYNAMO is a small multi-instrument payload aimed at characterizing current atmospheric escape, which is still poorly constrained, and improving gravity and magnetic field representations, in order to better understand the magnetic, geologic and thermal history of Mars. The internal structure...... of periapsis 170 km), and in a lesser extent 2a, offers an unprecedented opportunity to investigate by in situ probing the chemical and dynamical properties of the deep ionosphere, thermosphere, and the interaction between the atmosphere and the solar wind, and therefore the present atmospheric escape rate...

Southeast regional and state trends in anuran occupancy from calling survey data (2001-2013) from the North American Amphibian Monitoring Program

Science.gov (United States)

Villena Carpio, Oswaldo; Royle, J. Andrew; Weir, Linda; Foreman, Tasha M.; Gazenski, Kimberly D.; Campbell Grant, Evan H.

2016-01-01

We present the first regional trends in anuran occupancy for eight states of the southeastern United States, based on 13 y (2001–2013) of North American Amphibian Monitoring Program (NAAMP) data. The NAAMP is a longterm monitoring program in which observers collect anuran calling observation data at fixed locations along random roadside routes. We assessed occupancy trends for 14 species. We found weak evidence for a general regional pattern of decline in calling anurans within breeding habitats along roads in the southeastern USA over the last 13 y. Two species had positive regional trends with 95% posterior intervals that did not include zero (Hyla cinerea and Pseudacris crucifer). Five other species also showed an increasing trend, while eight species showed a declining trend, although 95% posterior intervals included zero. We also assessed state level trends for 107 species/state combinations. Of these, 14 showed a significant decline and 12 showed a significant increase in occupancy (i.e., credible intervals did not include zero for these 26 trends).

New solar telescope in Big Bear: evidence for super-diffusivity and small-scale solar dynamos?

International Nuclear Information System (INIS)

Goode, Philip R; Abramenko, Valentyna; Yurchyshyn, Vasyl

2012-01-01

The 1.6 m clear aperture New Solar Telescope (NST) in Big Bear Solar Observatory (BBSO) is now providing the highest resolution solar data ever. These data have revealed surprises about the Sun on small-scales including the observation that bright points (BPs), which can be used as proxies for the intense, compact magnetic elements that are apparent in photospheric intergranular lanes. The BPs are ever more numerous on ever smaller spatial scales as though there were no limit to how small the BPs can be. Here we discuss high resolution NST data on BPs that provide support for the ideas that a turbulent regime of super-diffusivity dominates in the quiet Sun, and there are local dynamos operating near the solar surface. (comment)

Answering the Call: How Group Mentoring Makes a Difference

Science.gov (United States)

Altus, Jillian

2015-01-01

Mentoring programs answer the call for social justice for many students who are in success-inhibiting environments. This study employed a case study design to investigate the perceived benefits from a group mentoring program. Data was collected from pre- and post-assessments focus groups, and artifacts. Four participant benefits were revealed:…

SMALL-SCALE AND GLOBAL DYNAMOS AND THE AREA AND FLUX DISTRIBUTIONS OF ACTIVE REGIONS, SUNSPOT GROUPS, AND SUNSPOTS: A MULTI-DATABASE STUDY

Energy Technology Data Exchange (ETDEWEB)

Muñoz-Jaramillo, Andrés; Windmueller, John C.; Amouzou, Ernest C.; Longcope, Dana W. [Department of Physics, Montana State University, Bozeman, MT 59717 (United States); Senkpeil, Ryan R. [Department of Physics, Purdue University, West Lafayette, IN 47907 (United States); Tlatov, Andrey G. [Kislovodsk Mountain Astronomical Station of the Pulkovo Observatory, Kislovodsk 357700 (Russian Federation); Nagovitsyn, Yury A. [Pulkovo Astronomical Observatory, Russian Academy of Sciences, St. Petersburg 196140 (Russian Federation); Pevtsov, Alexei A. [National Solar Observatory, Sunspot, NM 88349 (United States); Chapman, Gary A.; Cookson, Angela M. [San Fernando Observatory, Department of Physics and Astronomy, California State University Northridge, Northridge, CA 91330 (United States); Yeates, Anthony R. [Department of Mathematical Sciences, Durham University, South Road, Durham DH1 3LE (United Kingdom); Watson, Fraser T. [National Solar Observatory, Tucson, AZ 85719 (United States); Balmaceda, Laura A. [Institute for Astronomical, Terrestrial and Space Sciences (ICATE-CONICET), San Juan (Argentina); DeLuca, Edward E. [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Martens, Petrus C. H., E-mail: munoz@solar.physics.montana.edu [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303 (United States)

2015-02-10

In this work, we take advantage of 11 different sunspot group, sunspot, and active region databases to characterize the area and flux distributions of photospheric magnetic structures. We find that, when taken separately, different databases are better fitted by different distributions (as has been reported previously in the literature). However, we find that all our databases can be reconciled by the simple application of a proportionality constant, and that, in reality, different databases are sampling different parts of a composite distribution. This composite distribution is made up by linear combination of Weibull and log-normal distributions—where a pure Weibull (log-normal) characterizes the distribution of structures with fluxes below (above) 10{sup 21}Mx (10{sup 22}Mx). Additionally, we demonstrate that the Weibull distribution shows the expected linear behavior of a power-law distribution (when extended to smaller fluxes), making our results compatible with the results of Parnell et al. We propose that this is evidence of two separate mechanisms giving rise to visible structures on the photosphere: one directly connected to the global component of the dynamo (and the generation of bipolar active regions), and the other with the small-scale component of the dynamo (and the fragmentation of magnetic structures due to their interaction with turbulent convection)

Measurement of core velocity fluctuations and the dynamo in a reversed-field pinch

International Nuclear Information System (INIS)

Den Hartog, D.J.; Craig, D.; Fiksel, G.; Fontana, P.W.; Prager, S.C.; Sarff, J.S.; Chapman, J.T.

1998-01-01

Plasma flow velocity fluctuations have been directly measured in the high temperature magnetically confined plasma in the Madison Symmetric Torus (MST) Reversed-Field Pinch (RFP). These measurements show that the flow velocity fluctuations are correlated with magnetic field fluctuations. This initial measurement is subject to limitations of spatial localization and other uncertainties, but is evidence for sustainment of the RFP magnetic field configuration by the magnetohydrodynamic (MHD) dynamo. Both the flow velocity and magnetic field fluctuations are the result of global resistive MHD modes of helicity m = 1, n = 5--10 in the core of MST. Chord-averaged flow velocity fluctuations are measured in the core of MST by recording the Doppler shift of impurity line emission with a specialized high resolution and throughput grating spectrometer. Magnetic field fluctuations are recorded with a large array of small edge pickup coils, which allows spectral decomposition into discrete modes and subsequent correlation with the velocity fluctuation data

Northeast regional and state trends in anuran occupancy from calling survey data (2001-2011) from the North American Amphibian Monitoring Program

Science.gov (United States)

Weir, Linda A.; Royle, Andy; Gazenski, Kimberly D.; Villena Carpio, Oswaldo

2014-01-01

We present the first regional trends in anuran occupancy from North American Amphibian Monitoring Program (NAAMP) data from 11 northeastern states using an 11 years of data. NAAMP is a long-term monitoring program where observers collect data at assigned random roadside routes using a calling survey technique. We assessed occupancy trends for 17 species. Eight species had statistically significant regional trends, of these seven were negative (Anaxyrus fowleri, Acris crepitans, Pseudacris brachyphona, Pseudacris feriarum-kalmi complex, Lithobates palustris, Lithobates pipiens, and Lithobates sphenocephalus) and one was positive (Hyla versicolor-chrysoscelis complex). We also assessed state level trends for 101 species/state combinations, of these 29 showed a significant decline and nine showed a significant increase in occupancy.

Inhibitors of calling behavior of Plodia interpunctella.

Science.gov (United States)

Hirashima, Akinori; Shigeta, Yoko; Eiraku, Tomohiko; Kuwano, Eiichi

2003-01-01

Some octopamine agonists were found to suppress the calling behavior of the stored product Indian meal moth, Plodia interpunctella. Compounds were screened using a calling behavior bioassay using female P. interpunctella. Four active derivatives, with inhibitory activity at the nanomolar range, were identified in order of decreasing activity: 2-(1-phenylethylamino)-2-oxazoline > 2-(2-ethyl,6-methylanilino)oxazolidine > 2-(2-methyl benzylamino)-2-thiazoline > 2-(2,6-diethylanilino)thiazolidine. Three-dimensional pharmacophore hypotheses were built from a set of 15 compounds. Among the ten common-featured models generated by the program Catalyst/HipHop, a hypothesis including a hydrogen-bond acceptor lipid, a hydrophobic aromatic and two hydrophobic aliphatic features was considered to be essential for inhibitory activity in the calling behavior. Active compounds mapped well onto all the hydrogen-bond acceptor lipid, hydrophobic aromatic and hydrophobic aliphatic features of the hypothesis. On the other hand, less active compounds were shown not to achieve the energetically favorable conformation that is found in the active molecules in order to fit the 3D common-feature pharmacophore models. The present studies demonstrate that inhibition of calling behavior is via an octopamine receptor.

Inhibitors of calling behavior of Plodia interpunctella

Directory of Open Access Journals (Sweden)

Akinori Hirashima

2003-01-01

Full Text Available Some octopamine agonists were found to suppress the calling behavior of the stored product Indian meal moth, Plodia interpunctella. Compounds were screened using a calling behavior bioassay using female P. interpunctella. Four active derivatives, with inhibitory activity at the nanomolar range, were identified in order of decreasing activity: 2-(1-phenylethylamino-2-oxazoline > 2-(2-ethyl,6-methylanilinooxazolidine > 2-(2-methyl benzylamino-2-thiazoline > 2-(2,6-diethylanilinothiazolidine. Three-dimensional pharmacophore hypotheses were built from a set of 15 compounds. Among the ten common-featured models generated by the program Catalyst/HipHop, a hypothesis including a hydrogen-bond acceptor lipid, a hydrophobic aromatic and two hydrophobic aliphatic features was considered to be essential for inhibitory activity in the calling behavior. Active compounds mapped well onto all the hydrogen-bond acceptor lipid, hydrophobic aromatic and hydrophobic aliphatic features of the hypothesis. On the other hand, less active compounds were shown not to achieve the energetically favorable conformation that is found in the active molecules in order to fit the 3D common-feature pharmacophore models. The present studies demonstrate that inhibition of calling behavior is via an octopamine receptor.

Blended call center with idling times during the call service

NARCIS (Netherlands)

Legros, Benjamin; Jouini, Oualid; Koole, Ger

We consider a blended call center with calls arriving over time and an infinitely backlogged amount of outbound jobs. Inbound calls have a non-preemptive priority over outbound jobs. The inbound call service is characterized by three successive stages where the second one is a break; i.e., there is

RIEGER-TYPE PERIODICITY DURING SOLAR CYCLES 14–24: ESTIMATION OF DYNAMO MAGNETIC FIELD STRENGTH IN THE SOLAR INTERIOR

Energy Technology Data Exchange (ETDEWEB)

Gurgenashvili, Eka; Zaqarashvili, Teimuraz V.; Kukhianidze, Vasil; Ramishvili, Giorgi; Shergelashvili, Bidzina [Abastumani Astrophysical Observatory at Ilia State University, Tbilisi, Georgia (United States); Oliver, Ramon; Ballester, Jose Luis [Departament de Física, Universitat de les Illes Balears, E-07122, Palma de Mallorca (Spain); Hanslmeier, Arnold [IGAM, Institute of Physics, University of Graz, Universitätsplatz 5, A-8010 Graz (Austria); Poedts, Stefaan, E-mail: teimuraz.zaqarashvili@uni-graz.at [Centre for Mathematical Plasma Astrophysics, Department of Mathematics, KU Leuven, Celestijnenlaan 200B, B-3001, Leuven (Belgium)

2016-07-20

Solar activity undergoes a variation over timescales of several months known as Rieger-type periodicity, which usually occurs near maxima of sunspot cycles. An early analysis showed that the periodicity appears only in some cycles and is absent in other cycles. But the appearance/absence during different cycles has not been explained. We performed a wavelet analysis of sunspot data from the Greenwich Royal Observatory and the Royal Observatory of Belgium during cycles 14–24. We found that the Rieger-type periods occur in all cycles, but they are cycle dependent: shorter periods occur during stronger cycles. Our analysis revealed a periodicity of 185–195 days during the weak cycles 14–15 and 24 and a periodicity of 155–165 days during the stronger cycles 16–23. We derived the dispersion relation of the spherical harmonics of the magnetic Rossby waves in the presence of differential rotation and a toroidal magnetic field in the dynamo layer near the base of the convection zone. This showed that the harmonics of fast Rossby waves with m = 1 and n = 4, where m ( n ) indicates the toroidal (poloidal) wavenumbers, perfectly fit with the observed periodicity. The variation of the toroidal field strength from weaker to stronger cycles may lead to the different periods found in those cycles, which explains the observed enigmatic feature of the Rieger-type periodicity. Finally, we used the observed periodicity to estimate the dynamo field strength during cycles 14–24. Our estimations suggest a field strength of ∼40 kG for the stronger cycles and ∼20 kG for the weaker cycles.

Magnetostrophic Rotating Magnetoconvection

Science.gov (United States)

King, Eric; Aurnou, Jonathan

2016-11-01

Planetary magnetic fields are generated by turbulent convection within their vast interior liquid metal cores. Although direct observation is not possible, this liquid metal circulation is thought to be dominated by the controlling influences of Coriolis and Lorentz forces. Theory famously predicts that local-scale convection naturally settles into the so-called magnetostrophic state, where the Coriolis and Lorentz forces partially cancel, and convection is optimally efficient. To date, no laboratory experiments have reached the magnetostrophic regime in turbulent liquid metal convection. Furthermore, computational dynamo simulations have as yet failed to produce a globally magnetostrophic dynamo, which has led some to question the existence of the magnetostrophic state. Here, we present results from the first turbulent magnetostrophic rotating magnetoconvection experiments using the liquid metal gallium. We find that turbulent convection in the magnetostrophic regime is, in fact, maximally efficient. The experimental results clarify these previously disparate results, suggesting that the fluid dynamics saturate in magnetostrophic balance within turbulent liquid metal, planetary cores. The authors thank the NSF Geophysics Program for financial support.

A dynamo theory prediction for solar cycle 22: Sunspot number, radio flux, exospheric temperature, and total density at 400 km

Science.gov (United States)

Schatten, K. H.; Hedin, A. E.

1986-01-01

Using the dynamo theory method to predict solar activity, a value for the smoothed sunspot number of 109 + or - 20 is obtained for solar cycle 22. The predicted cycle is expected to peak near December, 1990 + or - 1 year. Concommitantly, F(10.7) radio flux is expected to reach a smoothed value of 158 + or - 18 flux units. Global mean exospheric temperature is expected to reach 1060 + or - 50 K and global total average total thermospheric density at 400 km is expected to reach 4.3 x 10 to the -15th gm/cu cm + or - 25 percent.

A dynamo theory prediction for solar cycle 22 - Sunspot number, radio flux, exospheric temperature, and total density at 400 km

Science.gov (United States)

Schatten, K. H.; Hedin, A. E.

1984-01-01

Using the 'dynamo theory' method to predict solar activity, a value for the smoothed sunspot number of 109 + or - 20 is obtained for solar cycle 22. The predicted cycle is expected to peak near December, 1990 + or - 1 year. Concommitantly, F(10.7) radio flux is expected to reach a smoothed value of 158 + or - 18 flux units. Global mean exospheric temperature is expected to reach 1060 + or - 50 K and global total average total thermospheric density at 400 km is expected to reach 4.3 x 10 to the -15th gm/cu cm + or - 25 percent.

High Magnetic Shear Gain in a Liquid Sodium Stable Couette Flow Experiment: A Prelude to an α-Ω Dynamo

International Nuclear Information System (INIS)

Colgate, Stirling A.; Beckley, Howard; Si, Jiahe; Martinic, Joe; Westpfahl, David; Slutz, James; Westrom, Cebastian; Klein, Brianna; Schendel, Paul; Scharle, Cletus; McKinney, Travis; Ginanni, Rocky; Bentley, Ian; Mickey, Timothy; Ferrel, Regnar; Li, Hui; Pariev, Vladimir; Finn, John

2011-01-01

The Ω phase of the liquid sodium α-Ω dynamo experiment at New Mexico Institute of Mining and Technology in cooperation with Los Alamos National Laboratory has demonstrated a high toroidal field B φ that is ≅8xB r , where B r is the radial component of an applied poloidal magnetic field. This enhanced toroidal field is produced by the rotational shear in stable Couette flow within liquid sodium at a magnetic Reynolds number Rm≅120. Small turbulence in stable Taylor-Couette flow is caused by Ekman flow at the end walls, which causes an estimated turbulence energy fraction of (δv/v) 2 ∼10 -3 .

Generation of large-scale vortives in compressible helical turbulence

International Nuclear Information System (INIS)

Chkhetiani, O.G.; Gvaramadze, V.V.

1989-01-01

We consider generation of large-scale vortices in compressible self-gravitating turbulent medium. The closed equation describing evolution of the large-scale vortices in helical turbulence with finite correlation time is obtained. This equation has the form similar to the hydromagnetic dynamo equation, which allows us to call the vortx genertation effect the vortex dynamo. It is possible that principally the same mechanism is responsible both for amplification and maintenance of density waves and magnetic fields in gaseous disks of spiral galaxies. (author). 29 refs

GROUP POLICY BASED AUTHENTICATION ON INCOMING CALLS FOR ANDROID SMARTPHONES

OpenAIRE

Sunita M. Kumbhar, Prof. Z.M Shaikh

2016-01-01

The numbers of Smartphone users increasing day by day. Hence, there is need to propose advanced Group Policy based Authentication for incoming calls for Android phone. Android platform provides a variety of functions that support the programming of face recognition, as in image processing. Group policy based authentication scheme increases the security which restricts the access of incoming call form un-authorized user. To solve problems, related to face recognition should be applied in the p...

Core flow inversion tested with numerical dynamo models

Science.gov (United States)

Rau, Steffen; Christensen, Ulrich; Jackson, Andrew; Wicht, Johannes

2000-05-01

We test inversion methods of geomagnetic secular variation data for the pattern of fluid flow near the surface of the core with synthetic data. These are taken from self-consistent 3-D models of convection-driven magnetohydrodynamic dynamos in rotating spherical shells, which generate dipole-dominated magnetic fields with an Earth-like morphology. We find that the frozen-flux approximation, which is fundamental to all inversion schemes, is satisfied to a fair degree in the models. In order to alleviate the non-uniqueness of the inversion, usually a priori conditions are imposed on the flow; for example, it is required to be purely toroidal or geostrophic. Either condition is nearly satisfied by our model flows near the outer surface. However, most of the surface velocity field lies in the nullspace of the inversion problem. Nonetheless, the a priori constraints reduce the nullspace, and by inverting the magnetic data with either one of them we recover a significant part of the flow. With the geostrophic condition the correlation coefficient between the inverted and the true velocity field can reach values of up to 0.65, depending on the choice of the damping parameter. The correlation is significant at the 95 per cent level for most spherical harmonic degrees up to l=26. However, it degrades substantially, even at long wavelengths, when we truncate the magnetic data sets to l currents, similar to those seen in core-flow models derived from geomagnetic data, occur in the equatorial region. However, the true flow does not contain this flow component. The results suggest that some meaningful information on the core-flow pattern can be retrieved from secular variation data, but also that the limited resolution of the magnetic core field could produce serious artefacts.

Sharing Programming Resources Between Bio* Projects Through Remote Procedure Call and Native Call Stack Strategies

NARCIS (Netherlands)

Prins, J.C.P.; Goto, N.; Yates, A.; Gautier, L.; Willis, S.; Fields, C.; Katayama, T.

2012-01-01

Open-source software (OSS) encourages computer programmers to reuse software components written by others. In evolutionary bioinformatics, OSS comes in a broad range of programming languages, including C/C++, Perl, Python, Ruby, Java, and R. To avoid writing the same functionality multiple times for

Stretching and joint mobilization exercises reduce call-center operators' musculoskeletal discomfort and fatigue

Directory of Open Access Journals (Sweden)

Denise Helena de Castro Lacaze

2010-01-01

Full Text Available AIM: We sought to evaluate musculoskeletal discomfort and mental and physical fatigue in the call-center workers of an airline company before and after a supervised exercise program compared with rest breaks during the work shift. INTRODUCTION: This was a longitudinal pilot study conducted in a flight-booking call-center for an airline in São Paulo, Brazil. Occupational health activities are recommended to decrease the negative effects of the call-center working conditions. In practice, exercise programs are commonly recommended for computer workers, but their effects have not been studied in call-center operators. METHODS: Sixty-four call-center operators participated in this study. Thirty-two subjects were placed into the experimental group and attended a 10-min daily exercise session for 2 months. Conversely, 32 participants were placed into the control group and took a 10-min daily rest break during the same period. Each subject was evaluated once a week by means of the Corlett-Bishop body map with a visual analog discomfort scale and the Chalder fatigue questionnaire. RESULTS: Musculoskeletal discomfort decreased in both groups, but the reduction was only statistically significant for the spine and buttocks (p=0.04 and the sum of the segments (p=0.01 in the experimental group. In addition, the experimental group showed significant differences in the level of mental fatigue, especially in questions related to memory Rienzo, #181ff and tiredness (p=0.001. CONCLUSIONS: Our preliminary results demonstrate that appropriately designed and supervised exercise programs may be more efficient than rest breaks in decreasing discomfort and fatigue levels in call-center operators.

Dynamic call center routing policies using call waiting and agent idle times

NARCIS (Netherlands)

Chan, W.; Koole, G.M.; L'Ecuyer, P.

2014-01-01

We study call routing policies for call centers with multiple call types and multiple agent groups. We introduce new weight-based routing policies where each pair (call type, agent group) is given a matching priority defined as an affine combination of the longest waiting time for that call type and

A model of the solar cycle driven by the dynamo action of the global convection in the solar convection zone

International Nuclear Information System (INIS)

Yoshimura, H.

1975-01-01

The dynamo equation which represents the longitudinally averaged magnetohydrodynamical action of the global convection influenced by the rotation in the solar convection zone is solved numerically to simulate the solar cycle as an initial boundary-value problem. The radial and latitudinal structure of the dynamo action is parametrized in accordance with the structure of the rotation, and of the global convection especially in such a way as to represent the presence of the two cells of the regeneration action in the radial direction in which the action has opposite signs, which is typical of the regeneration action of the global convection. A nonlinear process is included by assuming that part of the magnetic field energy is dissipated when the magnetic field strength exceeds some critical value; the formation of active regions and subsequent dissipations are thus simulated. By adjusting the parameters within a reasonable range, oscillatory solutions are obtained to simulate the solar cycle with the period of the right order of magnitude and with the patterns of evolution of the latitudinal distribution of the toroidal component of the magnetic field similar to the observed Butterfly Diagram of sunspots. The evolution of the latitudinal distribution of the radial component of the magnetic field shows patterns similar to the Butterfly Diagram, but having two branches of different polarity in each hemisphere. The development of the radial structure of the magnetic field associated with the solar cycle is presented. The importance of the poleward migrating branch of the Butterfly Diagram is emphasized in relation to the relative importance of the role of the latitudinal and radial shears of the differential rotation

Finite-correlation-time effects in the kinematic dynamo problem

International Nuclear Information System (INIS)

Schekochihin, Alexander A.; Kulsrud, Russell M.

2001-01-01

Most of the theoretical results on the kinematic amplification of small-scale magnetic fluctuations by turbulence have been confined to the model of white-noise-like (δ-correlated in time) advecting turbulent velocity field. In this work, the statistics of the passive magnetic field in the diffusion-free regime are considered for the case when the advecting flow is finite-time correlated. A new method is developed that allows one to systematically construct the correlation-time expansion for statistical characteristics of the field such as its probability density function or the complete set of its moments. The expansion is valid provided the velocity correlation time is smaller than the characteristic growth time of the magnetic fluctuations. This expansion is carried out up to first order in the general case of a d-dimensional arbitrarily compressible advecting flow. The growth rates for all moments of the magnetic-field strength are derived. The effect of the first-order corrections due to the finite correlation time is to reduce these growth rates. It is shown that introducing a finite correlation time leads to the loss of the small-scale statistical universality, which was present in the limit of the δ-correlated velocity field. Namely, the shape of the velocity time-correlation profile and the large-scale spatial structure of the flow become important. The latter is a new effect, that implies, in particular, that the approximation of a locally-linear shear flow does not fully capture the effect of nonvanishing correlation time. Physical applications of this theory include the small-scale kinematic dynamo in the interstellar medium and protogalactic plasmas

Call for proposals for the Joint Canada-Israel Health Research ...

International Development Research Centre (IDRC) Digital Library (Canada)

23 nov. 2017 ... Call for proposals for the Joint Canada-Israel Health Research Program 2018 competition ... developmental neurobiology; neuro-immunology; neuroendocrinology; regenerative medicine in brain disease; cellular and molecular basis of cognition; modeling brain function; imaging of neural processes ...

Induction by Coinduction and Control Operators in Call-by-Name

Directory of Open Access Journals (Sweden)

Yoshihiko Kakutani

2013-09-01

Full Text Available This paper studies emulation of induction by coinduction in a call-by-name language with control operators. Since it is known that call-by-name programming languages with control operators cannot have general initial algebras, interaction of induction and control operators is often restricted to effect-free functions. We show that some class of such restricted inductive types can be derived from full coinductive types by the power of control operators. As a typical example of our results, the type of natural numbers is represented by the type of streams. The underlying idea is a counterpart of the fact that some coinductive types can be expressed by inductive types in call-by-name pure language without side-effects.

Evaluation of a Postdischarge Call System Using the Logic Model.

Science.gov (United States)

Frye, Timothy C; Poe, Terri L; Wilson, Marisa L; Milligan, Gary

2018-02-01

This mixed-method study was conducted to evaluate a postdischarge call program for congestive heart failure patients at a major teaching hospital in the southeastern United States. The program was implemented based on the premise that it would improve patient outcomes and overall quality of life, but it had never been evaluated for effectiveness. The Logic Model was used to evaluate the input of key staff members to determine whether the outputs and results of the program matched the expectations of the organization. Interviews, online surveys, reviews of existing patient outcome data, and reviews of publicly available program marketing materials were used to ascertain current program output. After analyzing both qualitative and quantitative data from the evaluation, recommendations were made to the organization to improve the effectiveness of the program.

What Do Monkey Calls Mean?

Science.gov (United States)

Schlenker, Philippe; Chemla, Emmanuel; Zuberbühler, Klaus

2016-12-01

A field of primate linguistics is gradually emerging. It combines general questions and tools from theoretical linguistics with rich data gathered in experimental primatology. Analyses of several monkey systems have uncovered very simple morphological and syntactic rules and have led to the development of a primate semantics that asks new questions about the division of semantic labor between the literal meaning of monkey calls, additional mechanisms of pragmatic enrichment, and the environmental context. We show that comparative studies across species may validate this program and may in some cases help in reconstructing the evolution of monkey communication over millions of years. Copyright © 2016. Published by Elsevier Ltd.

A mechanism for the dynamo terms to sustain closed-flux current, including helicity balance, by driving current which crosses the magnetic field

Energy Technology Data Exchange (ETDEWEB)

Jarboe, T. R.; Nelson, B. A.; Sutherland, D. A. [University of Washington, Seattle, Washington 98195 (United States)

2015-07-15

An analysis of imposed dynamo current drive (IDCD) [T.R. Jarboe et al., Nucl. Fusion 52 083017 (2012)] reveals: (a) current drive on closed flux surfaces seems possible without relaxation, reconnection, or other flux-surface-breaking large events; (b) the scale size of the key physics may be smaller than is often computationally resolved; (c) helicity can be sustained across closed flux; and (d) IDCD current drive is parallel to the current which crosses the magnetic field to produce the current driving force. In addition to agreeing with spheromak data, IDCD agrees with selected tokamak data.

“Computer Assisted Language Learning” (CALL

Directory of Open Access Journals (Sweden)

Nazlı Gündüz

2005-10-01

Full Text Available This article will provide an overview of computers; an overview of the history of CALL, itspros and cons, the internet, World Wide Web, Multimedia, and research related to the uses of computers in the language classroom. Also, it also aims to provide some background for the beginnerson using the Internet in language classes today. It discusses some of the common types of Internetactivities that are being used today, what the minimum requirements are for using the Internet forlanguage learning, and some easy activities you can adapt for your classes. Some special terminology related to computers will also be used in this paper. For example, computer assisted language learning(CALL refers to the sets of instructions which need to be loaded into the computer for it to be able to work in the language classroom. It should be borne in mind that CALL does not refer to the use of acomputer by a teacher to type out a worksheet or a class list or preparing his/her own teaching alone.Hardware refers to any computer equipment used, including the computer itself, the keyboard, screen (or the monitor, the disc-drive, and the printer. Software (computer programs refers to the sets of instructions which need to be loaded into the computer for it to be able to work.

Understanding Short-Term Nonmigrating Tidal Variability in the Ionospheric Dynamo Region from SABER Using Information Theory and Bayesian Statistics

Science.gov (United States)

Kumari, K.; Oberheide, J.

2017-12-01

Nonmigrating tidal diagnostics of SABER temperature observations in the ionospheric dynamo region reveal a large amount of variability on time-scales of a few days to weeks. In this paper, we discuss the physical reasons for the observed short-term tidal variability using a novel approach based on Information theory and Bayesian statistics. We diagnose short-term tidal variability as a function of season, QBO, ENSO, and solar cycle and other drivers using time dependent probability density functions, Shannon entropy and Kullback-Leibler divergence. The statistical significance of the approach and its predictive capability is exemplified using SABER tidal diagnostics with emphasis on the responses to the QBO and solar cycle. Implications for F-region plasma density will be discussed.

Magnetostrophic balance as the optimal state for turbulent magnetoconvection.

Science.gov (United States)

King, Eric M; Aurnou, Jonathan M

2015-01-27

The magnetic fields of Earth and other planets are generated by turbulent convection in the vast oceans of liquid metal within them. Although direct observation is not possible, this liquid metal circulation is thought to be dominated by the controlling influences of planetary rotation and magnetic fields through the Coriolis and Lorentz forces. Theory famously predicts that planetary dynamo systems naturally settle into the so-called magnetostrophic state, where the Coriolis and Lorentz forces partially cancel, and convection is optimally efficient. Although this magnetostrophic theory correctly predicts the strength of Earth's magnetic field, no laboratory experiments have reached the magnetostrophic regime in turbulent liquid metal convection. Furthermore, computational dynamo simulations have as yet failed to produce a magnetostrophic dynamo, which has led some to question the existence of the magnetostrophic state. Here, we present results from the first, to our knowledge, turbulent, magnetostrophic convection experiments using the liquid metal gallium. We find that turbulent convection in the magnetostrophic regime is, in fact, maximally efficient. The experimental results clarify these previously disparate results, suggesting that the dynamically optimal magnetostrophic state is the natural expression of turbulent planetary dynamo systems.

Sudden transitions and grand variations in the solar dynamo, past and future☆

Directory of Open Access Journals (Sweden)

De Jager Cornelis

2012-06-01

Full Text Available The solar dynamo is the exotic dance of the sun’s two major magnetic field components, the poloidal and the toroidal, interacting in anti-phase. On the basis of new data on the geomagnetic aa index, we improve our previous forecast of the properties of the current Schwabe cycle #24. Its maximum will occur in 2013.5 and the maximum sunspot number Rmax will then be 62 ± 12, which is within the bounds of our earlier forecasts. The subsequent analysis, based on a phase diagram, which is a diagram showing the relation between maximum sunspot numbers and minimum geomagnetic aa index values leads to the conclusion that a new Grand Episode in solar activity has started in 2008. From the study of the natural oscillations in the sunspot number time series, as found by an analysis based on suitable wavelet base functions, we predict that this Grand Episode will be of the Regular Oscillations type, which is the kind of oscillations that also occurred between 1724 and 1924. Previous expectations of a Grand (Maunder-type Minimum of solar activity cannot be supported. We stress the significance of the Hallstatt periodicity for determining the character of the forthcoming Grand Episodes. No Grand Minimum is expected to occur during the millennium that has just started.

Perceiving a calling, living a calling, and job satisfaction: testing a moderated, multiple mediator model.

Science.gov (United States)

Duffy, Ryan D; Bott, Elizabeth M; Allan, Blake A; Torrey, Carrie L; Dik, Bryan J

2012-01-01

The current study examined the relation between perceiving a calling, living a calling, and job satisfaction among a diverse group of employed adults who completed an online survey (N = 201). Perceiving a calling and living a calling were positively correlated with career commitment, work meaning, and job satisfaction. Living a calling moderated the relations of perceiving a calling with career commitment and work meaning, such that these relations were more robust for those with a stronger sense they were living their calling. Additionally, a moderated, multiple mediator model was run to examine the mediating role of career commitment and work meaning in the relation of perceiving a calling and job satisfaction, while accounting for the moderating role of living a calling. Results indicated that work meaning and career commitment fully mediated the relation between perceiving a calling and job satisfaction. However, the indirect effects of work meaning and career commitment were only significant for individuals with high levels of living a calling, indicating the importance of living a calling in the link between perceiving a calling and job satisfaction. Implications for research and practice are discussed. (c) 2012 APA, all rights reserved.

Call Center Capacity Planning

DEFF Research Database (Denmark)

Nielsen, Thomas Bang

in order to relate the results to the service levels used in call centers. Furthermore, the generic nature of the approximation is demonstrated by applying it to a system incorporating a dynamic priority scheme. In the last paper Optimization of overflow policies in call centers, overflows between agent......The main topics of the thesis are theoretical and applied queueing theory within a call center setting. Call centers have in recent years become the main means of communication between customers and companies, and between citizens and public institutions. The extensively computerized infrastructure...... in modern call centers allows for a high level of customization, but also induces complicated operational processes. The size of the industry together with the complex and labor intensive nature of large call centers motivates the research carried out to understand the underlying processes. The customizable...

Calle Blanco

Directory of Open Access Journals (Sweden)

Gonzalo Cerda Brintrup

1988-06-01

Full Text Available Importante arteria, que comunica el sector del puerto con la plaza. Las más imponentes construcciones se sucedían de un modo continuo, encaramándose a ambos lados de la empinada calle. Antes del gran incendio de 1936 grandes casonas de madera destacaban en calle Irarrázabal y en la esquina de ésta con calle Blanco, la más hermosa construcción pertenecía a don Alberto Oyarzún y la casa vecina hacia Blanco era de don Mateo Miserda, limitada por arriba con la casa de don Augusto Van Der Steldt y ésta era seguida de la casa de don David Barrientos provista de cuatro cúpulas en las esquinas y de un amplio corredor en el frontis. Todas estas construcciones de madera fueron destruidas en el gran incendio de 1936.

A small-scale dynamo in feedback-dominated galaxies - III. Cosmological simulations

Science.gov (United States)

Rieder, Michael; Teyssier, Romain

2017-12-01

Magnetic fields are widely observed in the Universe in virtually all astrophysical objects, from individual stars to entire galaxies, even in the intergalactic medium, but their specific genesis has long been debated. Due to the development of more realistic models of galaxy formation, viable scenarios are emerging to explain cosmic magnetism, thanks to both deeper observations and more efficient and accurate computer simulations. We present here a new cosmological high-resolution zoom-in magnetohydrodynamic (MHD) simulation, using the adaptive mesh refinement technique, of a dwarf galaxy with an initially weak and uniform magnetic seed field that is amplified by a small-scale dynamo (SSD) driven by supernova-induced turbulence. As first structures form from the gravitational collapse of small density fluctuations, the frozen-in magnetic field separates from the cosmic expansion and grows through compression. In a second step, star formation sets in and establishes a strong galactic fountain, self-regulated by supernova explosions. Inside the galaxy, the interstellar medium becomes highly turbulent, dominated by strong supersonic shocks, as demonstrated by the spectral analysis of the gas kinetic energy. In this turbulent environment, the magnetic field is quickly amplified via a SSD process and is finally carried out into the circumgalactic medium by a galactic wind. This realistic cosmological simulation explains how initially weak magnetic seed fields can be amplified quickly in early, feedback-dominated galaxies, and predicts, as a consequence of the SSD process, that high-redshift magnetic fields are likely to be dominated by their small-scale components.

Recombinant Programming

OpenAIRE

Pawlak , Renaud; Cuesta , Carlos; Younessi , Houman

2004-01-01

This research report presents a promising new approach to computation called Recombinant Programming. The novelty of our approach is that it separates the program into two layers of computation: the recombination and the interpretation layer. The recombination layer takes sequences as inputs and allows the programmer to recombine these sequences through the definition of cohesive code units called extensions. The output of such recombination is a mesh that can be used by the interpretation la...

Perceiving a Calling, Living a Calling, and Job Satisfaction: Testing a Moderated, Multiple Mediator Model

Science.gov (United States)

Duffy, Ryan D.; Bott, Elizabeth M.; Allan, Blake A.; Torrey, Carrie L.; Dik, Bryan J.

2012-01-01

The current study examined the relation between perceiving a calling, living a calling, and job satisfaction among a diverse group of employed adults who completed an online survey (N = 201). Perceiving a calling and living a calling were positively correlated with career commitment, work meaning, and job satisfaction. Living a calling moderated…

Behavioral Preferences for Individual Securities : The Case for Call Warrants and Call Options

NARCIS (Netherlands)

Ter Horst, J.R.; Veld, C.H.

2002-01-01

Since 1998, large investment banks have flooded the European capital markets with issues of call warrants.This has led to a unique situation in the Netherlands, where now call warrants, traded on the stock exchange, and long-term call options, traded on the options exchange, exist.Both entitle their

A call-by-value lambda-calculus with lists and control

Directory of Open Access Journals (Sweden)

Robbert Krebbers

2012-10-01

Full Text Available Calculi with control operators have been studied to reason about control in programming languages and to interpret the computational content of classical proofs. To make these calculi into a real programming language, one should also include data types. As a step into that direction, this paper defines a simply typed call-by-value lambda calculus with the control operators catch and throw, a data type of lists, and an operator for primitive recursion (a la Goedel's T. We prove that our system satisfies subject reduction, progress, confluence for untyped terms, and strong normalization for well-typed terms.

Secure, web-accessible call rosters for academic radiology departments.

Science.gov (United States)

Nguyen, A V; Tellis, W M; Avrin, D E

2000-05-01

Traditionally, radiology department call rosters have been posted via paper and bulletin boards. Frequently, changes to these lists are made by multiple people independently, but often not synchronized, resulting in confusion among the house staff and technical staff as to who is on call and when. In addition, multiple and disparate copies exist in different sections of the department, and changes made would not be propagated to all the schedules. To eliminate such difficulties, a paperless call scheduling application was developed. Our call scheduling program allowed Java-enabled web access to a database by designated personnel from each radiology section who have privileges to make the necessary changes. Once a person made a change, everyone accessing the database would see the modification. This eliminates the chaos resulting from people swapping shifts at the last minute and not having the time to record or broadcast the change. Furthermore, all changes to the database were logged. Users are given a log-in name and password and can only edit their section; however, all personnel have access to all sections' schedules. Our applet was written in Java 2 using the latest technology in database access. We access our Interbase database through the DataExpress and DB Swing (Borland, Scotts Valley, CA) components. The result is secure access to the call rosters via the web. There are many advantages to the web-enabled access, mainly the ability for people to make changes and have the changes recorded and propagated in a single virtual location and available to all who need to know.

Dynamos in asymptotic-giant-branch stars as the origin of magnetic fields shaping planetary nebulae.

Science.gov (United States)

Blackman, E G; Frank, A; Markiel, J A; Thomas, J H; Van Horn, H M

2001-01-25

Planetary nebulae are thought to be formed when a slow wind from the progenitor giant star is overtaken by a subsequent fast wind generated as the star enters its white dwarf stage. A shock forms near the boundary between the winds, creating the relatively dense shell characteristic of a planetary nebula. A spherically symmetric wind will produce a spherically symmetric shell, yet over half of known planetary nebulae are not spherical; rather, they are elliptical or bipolar in shape. A magnetic field could launch and collimate a bipolar outflow, but the origin of such a field has hitherto been unclear, and some previous work has even suggested that a field could not be generated. Here we show that an asymptotic-giant-branch (AGB) star can indeed generate a strong magnetic field, having as its origin a dynamo at the interface between the rapidly rotating core and the more slowly rotating envelope of the star. The fields are strong enough to shape the bipolar outflows that produce the observed bipolar planetary nebulae. Magnetic braking of the stellar core during this process may also explain the puzzlingly slow rotation of most white dwarf stars.

The Nature of Grand Minima and Maxima from Fully Nonlinear Flux Transport Dynamos

Energy Technology Data Exchange (ETDEWEB)

Inceoglu, Fadil; Arlt, Rainer [Leibniz-Institute for Astrophysics Potsdam, An der Sternwarte 16, D-14482, Potsdam (Germany); Rempel, Matthias, E-mail: finceoglu@aip.de [High Altitude Observatory, National Center for Atmospheric Research, P.O. Box 3000, Boulder, CO 80307 (United States)

2017-10-20

We aim to investigate the nature and occurrence characteristics of grand solar minimum and maximum periods, which are observed in the solar proxy records such as {sup 10}Be and {sup 14}C, using a fully nonlinear Babcock–Leighton type flux transport dynamo including momentum and entropy equations. The differential rotation and meridional circulation are generated from the effect of turbulent Reynolds stress and are subjected to back-reaction from the magnetic field. To generate grand minimum- and maximum-like periods in our simulations, we used random fluctuations in the angular momentum transport process, namely the Λ-mechanism, and in the Babcock–Leighton mechanism. To characterize the nature and occurrences of the identified grand minima and maxima in our simulations, we used the waiting time distribution analyses, which reflect whether the underlying distribution arises from a random or a memory-bearing process. The results show that, in the majority of the cases, the distributions of grand minima and maxima reveal that the nature of these events originates from memoryless processes. We also found that in our simulations the meridional circulation speed tends to be smaller during grand maximum, while it is faster during grand minimum periods. The radial differential rotation tends to be larger during grand maxima, while it is smaller during grand minima. The latitudinal differential rotation, on the other hand, is found to be larger during grand minima.

Comparison of Large eddy dynamo simulation using dynamic sub-grid scale (SGS) model with a fully resolved direct simulation in a rotating spherical shell

Science.gov (United States)

Matsui, H.; Buffett, B. A.

2017-12-01

The flow in the Earth's outer core is expected to have vast length scale from the geometry of the outer core to the thickness of the boundary layer. Because of the limitation of the spatial resolution in the numerical simulations, sub-grid scale (SGS) modeling is required to model the effects of the unresolved field on the large-scale fields. We model the effects of sub-grid scale flow and magnetic field using a dynamic scale similarity model. Four terms are introduced for the momentum flux, heat flux, Lorentz force and magnetic induction. The model was previously used in the convection-driven dynamo in a rotating plane layer and spherical shell using the Finite Element Methods. In the present study, we perform large eddy simulations (LES) using the dynamic scale similarity model. The scale similarity model is implement in Calypso, which is a numerical dynamo model using spherical harmonics expansion. To obtain the SGS terms, the spatial filtering in the horizontal directions is done by taking the convolution of a Gaussian filter expressed in terms of a spherical harmonic expansion, following Jekeli (1981). A Gaussian field is also applied in the radial direction. To verify the present model, we perform a fully resolved direct numerical simulation (DNS) with the truncation of the spherical harmonics L = 255 as a reference. And, we perform unresolved DNS and LES with SGS model on coarser resolution (L= 127, 84, and 63) using the same control parameter as the resolved DNS. We will discuss the verification results by comparison among these simulations and role of small scale fields to large scale fields through the role of the SGS terms in LES.

A Debate over the Teaching of a Legacy Programming Language in an Information Technology (IT) Program

Science.gov (United States)

Ali, Azad; Smith, David

2014-01-01

This paper presents a debate between two faculty members regarding the teaching of the legacy programming course (COBOL) in a Computer Science (CS) program. Among the two faculty members, one calls for the continuation of teaching this language and the other calls for replacing it with another modern language. Although CS programs are notorious…

Creating a vision for your medical call center.

Science.gov (United States)

Barr, J L; Laufenberg, S; Sieckman, B L

1998-01-01

MCC technologies and applications that can have a positive impact on managed care delivery are almost limitless. As you determine your vision, be sure to have in mind the following questions: (1) Do you simply want an efficient front end for receiving calls? (2) Do you want to offer triage services? (3) Is your organization ready for a fully functional "electronic physician's office?" Understand your organization's strategy. Where are you going, not only today but five years from now? That information is essential to determine your vision. Once established, your vision will help determine what you need and whether you should build or outsource. Vendors will assist in cost/benefit analysis of their equipment, but do not lose sight of internal factors such as "prior inclination" costs in the case of a nurse triage program. The technology is available to take your vision to its outer reaches. With the projected increase in utilization of call center services, don't let your organization be left behind!

Call Centre- Computer Telephone Integration

Directory of Open Access Journals (Sweden)

Dražen Kovačević

2012-10-01

Full Text Available Call centre largely came into being as a result of consumerneeds converging with enabling technology- and by the companiesrecognising the revenue opportunities generated by meetingthose needs thereby increasing customer satisfaction. Regardlessof the specific application or activity of a Call centre, customersatisfaction with the interaction is critical to the revenuegenerated or protected by the Call centre. Physical(v, Call centreset up is a place that includes computer, telephone and supervisorstation. Call centre can be available 24 hours a day - whenthe customer wants to make a purchase, needs information, orsimply wishes to register a complaint.

Portable and Accurate Collection of Calling-Context-Sensitive Bytecode Metrics for the Java Virtual Machine

DEFF Research Database (Denmark)

Sarimbekov, Aibek; Sewe, Andreas; Binder, Walter

2011-01-01

Calling-context profiles and dynamic metrics at the bytecode level are important for profiling, workload characterization, program comprehension, and reverse engineering. Prevailing tools for collecting calling-context profiles or dynamic bytecode metrics often provide only incomplete information...... that compute various dynamic bytecode metrics from the profiles. As a case-study and tutorial on the use of JP2, we use it for crossprofiling for an embedded Java processor....

Diurnal Cycle of ITCZ Convection during the MJO Suppressed Phase in DYNAMO

Science.gov (United States)

Ciesielski, P. E.; Johnson, R. H.; Schubert, W. H.

2017-12-01

During the special observing period of the Dynamics of the MJO (DYNAMO) experiment, conducted over the Indian Ocean from 1 October to 30 November 2011, two sounding arrays - one north and one south of the equator, referred to here as the NSA and SSA, respectively - took 4-8 soundings/day. We augment this 3-h dataset with observations of radiation and rainfall to investigate the diurnal cycle of convection during the suppressed phase of the October MJO. During this 14-day period when convection was suppressed over the NSA but prominent over the SSA, the circulation over the sounding arrays could be characterized as a local Hadley cell embedded within a monsoonal flow. Strong rising motion was present within the ITCZ and compensating subsidence over the NSA. A prominent diurnal pulsing of this cell was observed, impacting conditions on both sides of the equator, with the cell running strongest in the early morning hours (05-08 LT) and notably weakening later in the day (17-20LT). The reduction in evening subsidence over the NSA may have assisted the moistening of the low to mid-troposphere there during the pre-onset stage of the MJO. Apparent heating Q1 within the ITCZ exhibits a diurnal evolution from early morning bottom-heavy profiles to weaker daytime top-heavy profiles. Making use of the weak temperature gradient approximation, results suggest that direct radiative effects played a dominant role in controlling diurnal variations of vertical motion and convection within the ITCZ while non-radiative processes were more prominent over the NSA.

Perspectives on a 'Sit Less, Move More' Intervention in Australian Emergency Call Centres.

Science.gov (United States)

Chau, Josephine Y; Engelen, Lina; Burks-Young, Sarah; Daley, Michelle; Maxwell, Jen-Kui; Milton, Karen; Bauman, Adrian

2016-01-01

Prolonged sitting is associated with increased risk of chronic diseases. Workplace programs that aim to reduce sitting time (sit less) and increase physical activity (move more) have targeted desk-based workers in corporate and university settings with promising results. However, little is known about 'move more, sit less' programs for workers in other types of jobs and industries, such as shift workers. This formative research examines the perceptions of a 'sit less, move more' program in an Australian Emergency Call Centre that operates 24 hours per day, 7 days per week. Participants were employees (N = 39, 72% female, 50% aged 36-55 years) recruited from Emergency Services control centres located in New South Wales, Australia. The 'sit less, move more' intervention, consisting of emails, posters and timer lights, was co-designed with the management team and tailored to the control centre environment and work practices, which already included electronic height-adjustable sit-stand workstations for all call centre staff. Participants reported their perceptions and experiences of the intervention in a self-report online questionnaire, and directly to the research team during regular site visits. Questionnaire topics included barriers and facilitators to standing while working, mental wellbeing, effects on work performance, and workplace satisfaction. Field notes and open-ended response data were analysed in an iterative process during and after data collection to identify the main themes. Whilst participants already had sit-stand workstations, use of the desks in the standing position varied and sometimes were contrary to expectations (e.g, less tired standing than sitting; standing when experiencing high call stress). Participants emphasised the "challenging" and "unrelenting" nature of their work. They reported sleep issues ("always tired"), work stress ("non-stop demands"), and feeling mentally and physically drained due to shift work and length of shifts

Call cultures in orang-utans?

Directory of Open Access Journals (Sweden)

Serge A Wich

Full Text Available BACKGROUND: Several studies suggested great ape cultures, arguing that human cumulative culture presumably evolved from such a foundation. These focused on conspicuous behaviours, and showed rich geographic variation, which could not be attributed to known ecological or genetic differences. Although geographic variation within call types (accents has previously been reported for orang-utans and other primate species, we examine geographic variation in the presence/absence of discrete call types (dialects. Because orang-utans have been shown to have geographic variation that is not completely explicable by genetic or ecological factors we hypothesized that this will be similar in the call domain and predict that discrete call type variation between populations will be found. METHODOLOGY/PRINCIPAL FINDINGS: We examined long-term behavioural data from five orang-utan populations and collected fecal samples for genetic analyses. We show that there is geographic variation in the presence of discrete types of calls. In exactly the same behavioural context (nest building and infant retrieval, individuals in different wild populations customarily emit either qualitatively different calls or calls in some but not in others. By comparing patterns in call-type and genetic similarity, we suggest that the observed variation is not likely to be explained by genetic or ecological differences. CONCLUSION/SIGNIFICANCE: These results are consistent with the potential presence of 'call cultures' and suggest that wild orang-utans possess the ability to invent arbitrary calls, which spread through social learning. These findings differ substantially from those that have been reported for primates before. First, the results reported here are on dialect and not on accent. Second, this study presents cases of production learning whereas most primate studies on vocal learning were cases of contextual learning. We conclude with speculating on how these findings might

Large-scale flows, sheet plumes and strong magnetic fields in a rapidly rotating spherical dynamo

Science.gov (United States)

Takahashi, F.

2011-12-01

Mechanisms of magnetic field intensification by flows of an electrically conducting fluid in a rapidly rotating spherical shell is investigated. Bearing dynamos of the Eartn and planets in mind, the Ekman number is set at 10-5. A strong dipolar solution with magnetic energy 55 times larger than the kinetic energy of thermal convection is obtained. In a regime of small viscosity and inertia with the strong magnetic field, convection structure consists of a few large-scale retrograde flows in the azimuthal direction and sporadic thin sheet-like plumes. The magnetic field is amplified through stretching of magnetic lines, which occurs typically through three types of flow: the retrograde azimuthal flow near the outer boundary, the downwelling flow of the sheet plume, and the prograde azimuthal flow near the rim of the tangent cylinder induced by the downwelling flow. It is found that either structure of current loops or current sheets is accompanied in each flow structure. Current loops emerge as a result of stretching the magnetic lines along the magnetic field, wheres the current sheets are formed to counterbalance the Coriolis force. Convection structure and processes of magnetic field generation found in the present model are distinct from those in models at larger/smaller Ekman number.

Three-dimensional dynamo-thermo-elastic analysis of a functionally graded cylindrical shell with piezoelectric layers by DQ-FD coupled

International Nuclear Information System (INIS)

Akbari Alashti, R.; Khorsand, M.

2012-01-01

Three-dimensional elastic analysis is carried out for functionally graded cylindrical shells bonded with piezoelectric layers subjected to dynamic and thermal loads. Material properties are assumed to be graded in the radial direction obeying a simple power law with constant Poisson's ratio. Two versions of differential quadrature (DQ) method coupled with the finite difference (FD) method are employed to discretize the governing differential equations in space and time domains. The convergence is studied and results of the axisymmetric loadings are verified with reported results. Effects of the grading index of material properties, thermal gradient, boundary conditions, thickness of piezoelectric layers and electric excitation on stress, displacement, electric and temperature fields are presented. Highlights: ► Dynamo-thermo-elastic analysis of an FGM shell with piezoelectric layer is carried out. ► Governing equations are solved by DQ-FD coupled. ► Effects of grading index, temperature difference and piezoelectric thickness are presented.

The difficult medical emergency call

DEFF Research Database (Denmark)

Møller, Thea Palsgaard; Kjærulff, Thora Majlund; Viereck, Søren

2017-01-01

BACKGROUND: Pre-hospital emergency care requires proper categorization of emergency calls and assessment of emergency priority levels by the medical dispatchers. We investigated predictors for emergency call categorization as "unclear problem" in contrast to "symptom-specific" categories and the ......BACKGROUND: Pre-hospital emergency care requires proper categorization of emergency calls and assessment of emergency priority levels by the medical dispatchers. We investigated predictors for emergency call categorization as "unclear problem" in contrast to "symptom-specific" categories...... and the effect of categorization on mortality. METHODS: Register-based study in a 2-year period based on emergency call data from the emergency medical dispatch center in Copenhagen combined with nationwide register data. Logistic regression analysis (N = 78,040 individuals) was used for identification...

BUSINESS MODELS FOR EXTENDING OF 112 EMERGENCY CALL CENTER CAPABILITIES WITH E-CALL FUNCTION INSERTION

Directory of Open Access Journals (Sweden)

Pop Dragos Paul

2010-12-01

Full Text Available The present article concerns present status of implementation in Romania and Europe of eCall service and the proposed business models regarding eCall function implementation in Romania. eCall system is used for reliable transmission in case of crush between In Vehicle System and Public Service Answering Point, via the voice channel of cellular and Public Switched Telephone Network (PSTN. eCall service could be initiated automatically or manual the driver. All data presented in this article are part of researches made by authors in the Sectorial Contract Implementation study regarding eCall system, having as partners ITS Romania and Electronic Solution, with the Romanian Ministry of Communication and Information Technology as beneficiary.

Использование продукции Autodesk и Dynamo в тоннелестроении

OpenAIRE

Мусиенко, Ю. А.

2017-01-01

In this article the speech about expediency of application of BIM of modeling will go to tunneling. We will review a concrete example of modeling of a tunnel with application of a linking of Revit and Dynamo. I will tell you about benefits on economic indicators and you will be pleasantly surprised.

Convective Cold Pool Structure and Boundary Layer Recovery in DYNAMO

Science.gov (United States)

Savarin, A.; Chen, S. S.; Kerns, B. W.; Lee, C.; Jorgensen, D. P.

2012-12-01

One of the key factors controlling convective cloud systems in the Madden-Julian Oscillation (MJO) over the tropical Indian Ocean is the property of the atmospheric boundary layer. Convective downdrafts and precipitation from the cloud systems produce cold pools in the boundary layer, which can inhibit subsequent development of convection. The recovery time is the time it takes for the boundary layer to return to pre convective conditions. It may affect the variability of the convection on various time scales during the initiation of MJO. This study examines the convective cold pool structure and boundary layer recovery using the NOAA WP-3D aircraft observations, include the flight-level, Doppler radar, and GPS dropsonde data, collected during the Dynamics of MJO (DYNAMO) field campaign from November-December 2011. The depth and strength of convective cold pools are defined by the negative buoyancy, which can be computed from the dropsonde data. Convective downdraft can be affected by environmental water vapor due to entrainment. Mid-level dry air observed during the convectively suppressed phase of MJO seems to enhance convective downdraft, making the cold pools stronger and deeper. Recovery of the cold pools in the boundary layer is determined by the strength and depth of the cold pools and also the air-sea heat and moisture fluxes. Given that the water vapor and surface winds are distinct for the convectively active and suppressed phases of MJO over the Indian Ocean, the aircraft data are stratified by the two different large-scale regimes of MJO. Preliminary results show that the strength and depth of the cold pools are inversely correlated with the surrounding mid-level moisture. During the convectively suppressed phase, the recovery time is ~5-20 hours in relative weak wind condition with small air-sea fluxes. The recovery time is generally less than 6 hours during the active phase of MJO with moist mid-levels and stronger surface wind and air-sea fluxes.

Assessing call centers’ success:

Directory of Open Access Journals (Sweden)

Hesham A. Baraka

2013-07-01

This paper introduces a model to evaluate the performance of call centers based on the Delone and McLean Information Systems success model. A number of indicators are identified to track the call center’s performance. Mapping of the proposed indicators to the six dimensions of the D&M model is presented. A Weighted Call Center Performance Index is proposed to assess the call center performance; the index is used to analyze the effect of the identified indicators. Policy-Weighted approach was used to assume the weights with an analysis of different weights for each dimension. The analysis of the different weights cases gave priority to the User satisfaction and net Benefits dimension as the two outcomes from the system. For the input dimensions, higher priority was given to the system quality and the service quality dimension. Call centers decision makers can use the tool to tune the different weights in order to reach the objectives set by the organization. Multiple linear regression analysis was used in order to provide a linear formula for the User Satisfaction dimension and the Net Benefits dimension in order to be able to forecast the values for these two dimensions as function of the other dimensions

78 FR 76218 - Rural Call Completion

Science.gov (United States)

2013-12-17

... calls to rural areas, and enforce restrictions against blocking, choking, reducing, or restricting calls... to alert the Commission of systemic problems receiving calls from a particular originating long... associated with completing calls to rural areas. These rules will also enhance our ability to enforce...

Long-distance calls in Neotropical primates

Directory of Open Access Journals (Sweden)

Oliveira Dilmar A.G.

2004-01-01

Full Text Available Long-distance calls are widespread among primates. Several studies concentrate on such calls in just one or in few species, while few studies have treated more general trends within the order. The common features that usually characterize these vocalizations are related to long-distance propagation of sounds. The proposed functions of primate long-distance calls can be divided into extragroup and intragroup ones. Extragroup functions relate to mate defense, mate attraction or resource defense, while intragroup functions involve group coordination or alarm. Among Neotropical primates, several species perform long-distance calls that seem more related to intragroup coordination, markedly in atelines. Callitrichids present long-distance calls that are employed both in intragroup coordination and intergroup contests or spacing. Examples of extragroup directed long-distance calls are the duets of titi monkeys and the roars and barks of howler monkeys. Considerable complexity and gradation exist in the long-distance call repertoires of some Neotropical primates, and female long-distance calls are probably more important in non-duetting species than usually thought. Future research must focus on larger trends in the evolution of primate long-distance calls, including the phylogeny of calling repertoires and the relationships between form and function in these signals.

Automatic Construction of Java Programs from Functional Program Specifications

OpenAIRE

Md. Humayun Kabir

2015-01-01

This paper presents a novel approach to construct Java programs automatically from the input functional program specifications on natural numbers from the constructive proofs of the input specifications using an inductive theorem prover called Poiti'n. The construction of a Java program from the input functional program specification involves two phases. The theorem prover is used to construct a higher order functional (HOF) program from the input specification expressed as an existential the...

Community-Based Art Education and Performance: Pointing to a Place Called Home

Science.gov (United States)

Washington, G. E.

2011-01-01

Can art make a difference? This is a call for a new sense of interconnectivity among visual art programs in and out of schools. This common ground will be found in the embodiment of performance, critical reflection, and social change within art learning. One goal of this article is to encourage educators to use the "verbs of art" for…

Where Do Data Go When They Die? Attaining Data Salvation Through the Establishment of a Solar Dynamo Dataverse

Science.gov (United States)

Munoz-Jaramillo, Andres

2016-05-01

The arrival of a highly interconnected digital age with practically limitless data storage capacity has brought with it a significant shift in which scientific data is stored and distributed (i.e. from being in the hands of a small group of scientists to being openly and freely distributed for anyone to use). However, the vertiginous speed at which hardware, software, and the nature of the internet changes has also sped up the rate at which data is lost due to formatting obsolescence and loss of access.This poster is meant to advertise the creation of a highly permanent data repository (within the context of Harvard's Dataverse), curated to contain datasets of high relevance for the study, and prediction of the solar dynamo, solar cycle, and long-term solar variability. This repository has many advantages over traditional data storage like the assignment of unique DOI identifiers for each database (making it easier for scientist to directly cite them), and the automatic versioning of each database so that all data are able to attain salvation.

Sleep Quality of Call Handlers Employed in International Call Centers in National Capital Region of Delhi, India.

Science.gov (United States)

Raja, J D; Bhasin, S K

2016-10-01

Call center sector in India is a relatively new and fast growing industry driving employment and growth in modern India today. Most international call centers in National Capital Region (NCR) of Delhi operate at odd work hours corresponding to a time suitable fortheir international customers. The sleep quality of call handlers employed in these call centers is in jeopardy owing to their altered sleep schedule. To assess the sleep quality and determine its independent predictors among call handlers employed in international call centers in NCR of Delhi. A cross-sectional questionnaire-based study was conducted on 375 call handlers aged 18-39 years employed in international call centers in NCR of Delhi. Sleep quality was assessed using Athens Insomnia scale along with a pre-tested, structured questionnaire. The mean age of respondents was 24.6 (SD 2.4) years. 78% of participants were male. 83.5% of respondents were unmarried. 44.3% of call handlers were cigarette smokers. Physical ailments were reported by 37% call handlers. 77.6% of call handlers had somesuspicion of insomnia or suspected insomnia; the rest had no sleep problem. Smoking, poor social support, heavy workload, lack of relaxation facility at office, and prolonged travel time to office were independent predictors of sleep quality (pSafeguarding their health becomes an occupational health challenge to public health specialists.

Callings and Organizational Behavior

Science.gov (United States)

Elangovan, A. R.; Pinder, Craig C.; McLean, Murdith

2010-01-01

Current literature on careers, social identity and meaning in work tends to understate the multiplicity, historical significance, and nuances of the concept of calling(s). In this article, we trace the evolution of the concept from its religious roots into secular realms and develop a typology of interpretations using occupation and religious…

Uncertain call likelihood negatively affects sleep and next-day cognitive performance while on-call in a laboratory environment.

Science.gov (United States)

Sprajcer, Madeline; Jay, Sarah M; Vincent, Grace E; Vakulin, Andrew; Lack, Leon; Ferguson, Sally A

2018-05-11

On-call working arrangements are employed in a number of industries to manage unpredictable events, and often involve tasks that are safety- or time-critical. This study investigated the effects of call likelihood during an overnight on-call shift on self-reported pre-bed anxiety, sleep and next-day cognitive performance. A four-night laboratory-based protocol was employed, with an adaptation, a control and two counterbalanced on-call nights. On one on-call night, participants were instructed that they would definitely be called during the night, while on the other on-call night they were told they may be called. The State-Trait Anxiety Inventory form x-1 was used to investigate pre-bed anxiety, and sleep was assessed using polysomnography and power spectral analysis of the sleep electroencephalographic analysis. Cognitive performance was assessed four times daily using a 10-min psychomotor vigilance task. Participants felt more anxious before bed when they were definitely going to be called, compared with the control and maybe conditions. Conversely, participants experienced significantly less non-rapid eye movement and stage two sleep and poorer cognitive performance when told they may be called. Further, participants had significantly more rapid eye movement sleep in the maybe condition, which may be an adaptive response to the stress associated with this on-call condition. It appears that self-reported anxiety may not be linked with sleep outcomes while on-call. However, this research indicates that it is important to take call likelihood into consideration when constructing rosters and risk-management systems for on-call workers.

Occupational voice demands and their impact on the call-centre industry

Directory of Open Access Journals (Sweden)

Duffy OM

2009-04-01

Full Text Available Abstract Background Within the last decade there has been a growth in the call-centre industry in the UK, with a growing awareness of the voice as an important tool for successful communication. Occupational voice problems such as occupational dysphonia, in a business which relies on healthy, effective voice as the primary professional communication tool, may threaten working ability and occupational health and safety of workers. While previous studies of telephone call-agents have reported a range of voice symptoms and functional vocal health problems, there have been no studies investigating the use and impact of vocal performance in the communication industry within the UK. This study aims to address a significant gap in the evidence-base of occupational health and safety research. The objectives of the study are: 1. to investigate the work context and vocal communication demands for call-agents; 2. to evaluate call-agents' vocal health, awareness and performance; and 3. to identify key risks and training needs for employees and employers within call-centres. Methods and design This is an occupational epidemiological study, which plans to recruit call-centres throughout the UK and Ireland. Data collection will consist of three components: 1. interviews with managers from each participating call-centre to assess their communication and training needs; 2. an online biopsychosocial questionnaire will be administered to investigate the work environment and vocal demands of call-agents; and 3. voice acoustic measurements of a random sample of participants using the Multi-dimensional Voice Program (MDVP. Qualitative content analysis from the interviews will identify underlying themes and issues. A multivariate analysis approach will be adopted using Structural Equation Modelling (SEM, to develop voice measurement models in determining the construct validity of potential factors contributing to occupational dysphonia. Quantitative data will be

A Remarkable Recent Transition in the Solar Dynamo

NARCIS (Netherlands)

de Jager, C.; Akasofu, S.-I.; Duhau, S.; Livingston, W.C.; Nieuwenhuijzen, H.; Potgieter, M.S.

2016-01-01

We summarize the major aspects of the remarkable, fairly long lasting period(∼ 2005 to ∼ 2010) of low solar activity, that we will call the Transition. It is the transitionalstage between the Grand Maximum of the 20th century and a forthcoming (most probablyRegular) episode of solar activity. The

Implementation and quality assessment of a pharmacy services call center for outpatient pharmacies and specialty pharmacy services in an academic health system.

Science.gov (United States)

Rim, Matthew H; Thomas, Karen C; Chandramouli, Jane; Barrus, Stephanie A; Nickman, Nancy A

2018-05-15

The implementation and quality assessment of a pharmacy services call center (PSCC) for outpatient pharmacies and specialty pharmacy services within an academic health system are described. Prolonged wait times in outpatient pharmacies or hold times on the phone affect the ability of pharmacies to capture and retain prescriptions. To support outpatient pharmacy operations and improve quality, a PSCC was developed to centralize handling of all outpatient and specialty pharmacy calls. The purpose of the PSCC was to improve the quality of pharmacy telephone services by (1) decreasing the call abandonment rate, (2) improving the speed of answer, (3) increasing first-call resolution, (4) centralizing all specialty pharmacy and prior authorization calls, (5) increasing labor efficiency and pharmacy capacities, (6) implementing a quality evaluation program, and (7) improving workplace satisfaction and retention of outpatient pharmacy staff. The PSCC centralized pharmacy calls from 9 pharmacy locations, 2 outpatient clinics, and a specialty pharmacy. Since implementation, the PSCC has achieved and maintained program goals, including improved abandonment rate, speed of answer, and first-call resolution. A centralized 24-7 support line for specialty pharmacy patients was also successfully established. A quality calibration program was implemented to ensure service quality and excellent patient experience. Additional ongoing evaluations measure the impact of the PSCC on improving workplace satisfaction and retention of outpatient pharmacy staff. The design and implementation of the PSCC have significantly improved the health system's patient experiences, efficiency, and quality. Copyright © 2018 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

Online and call center referral for endocrine surgical pathology within institutions.

Science.gov (United States)

Dhillon, Vaninder K; Al Khadem, Mai G; Tufano, Ralph P; Russell, Jonathon O

2017-10-08

We hypothesized that self-referred patients to academic centers will be equally distributed between general surgery and otolaryngology departments that perform thyroid surgery. We sought to quantify disparities in the assignment of these self-referred patients who may reach an institution through call centers or online pathways. Cross-sectional survey. Key words "thyroid surgery" and "thyroid cancer" were used along with the name of the Accreditation Council for Graduate Medical Education-listed otolaryngology program in both Google and Bing search engines. The top three search results for departments were reviewed, and a tally was given to general surgery (GS), otolaryngology-head and neck surgery (OLHNS), or neither. A multidisciplinary center with both GS and OLHNS was recorded as "equitable." Telephone calls were tallied if they were directed to GS or OLHNS. Out of 400 program tallies, 117 (29.25%) patients were directed to GS and 50 (12.5%) were directed to OLHNS. An additional 181 (45.25%) were directed to neither group ("neither") (P call survey had 62 patients (62%) assigned to a general surgeon, as opposed to 38 (38%) for OLHNS (P < .05). Five institutions offered a multidisciplinary group when searching with Bing, and 11 were found by searching with Google. There is not an equal distribution of self-referred patients with thyroid surgical pathology. It may be important to increase the online presence of OLHNS surgeons who perform thyroid surgery at academic medical institutions. Multidisciplinary centers focused on thyroid and parathyroid surgical disease represents one model of assigning self-referred patients. NA Laryngoscope, 2017. © 2017 The American Laryngological, Rhinological and Otological Society, Inc.

Care and calls

DEFF Research Database (Denmark)

Paasch, Bettina Sletten

-centred care through the use of tactile resources and embodied orientations while they attend to the phone call. Experienced nurses Thus perform multiactivity by distributing attention towards both the patient and the phone, and the analysis shows that their concrete ways of doing so depend on the complex...... they are telephoned during interactions with patients are not universal. Indeed different strategies have evolved in other hospital departments. Not only does this thesis contribute insights into the way nurses manage phone calls during interactions with patients, but by subscribing to a growing body of embodied...... of human interaction....

Pain Psychology: A Global Needs Assessment and National Call to Action

Science.gov (United States)

Scheman, Judith; Davin, Sara; Burns, John W.; Murphy, Jennifer L.; Wilson, Anna C.; Kerns, Robert D.; Mackey, Sean C.

2016-01-01

Objective. The Institute of Medicine and the draft National Pain Strategy recently called for better training for health care clinicians. This was the first high-level needs assessment for pain psychology services and resources in the United States. Design. Prospective, observational, cross-sectional. Methods. Brief surveys were administered online to six stakeholder groups (psychologists/therapists, individuals with chronic pain, pain physicians, primary care physicians/physician assistants, nurse practitioners, and the directors of graduate and postgraduate psychology training programs). Results. 1,991 responses were received. Results revealed low confidence and low perceived competency to address physical pain among psychologists/therapists, and high levels of interest and need for pain education. We found broad support for pain psychology across stakeholder groups, and global support for a national initiative to increase pain training and competency in U.S. therapists. Among directors of graduate and postgraduate psychology training programs, we found unanimous interest for a no-cost pain psychology curriculum that could be integrated into existing programs. Primary barriers to pain psychology include lack of a system to identify qualified therapists, paucity of therapists with pain training, limited awareness of the psychological treatment modality, and poor insurance coverage. Conclusions. This report calls for transformation within psychology predoctoral and postdoctoral education and training and psychology continuing education to include and emphasize pain and pain management. A system for certification is needed to facilitate quality control and appropriate reimbursement. There is a need for systems to facilitate identification and access to practicing psychologists and therapists skilled in the treatment of pain. PMID:26803844

Opportunity to Participate in ESSE 21: The 2003 Call for Participation

Science.gov (United States)

Ruzek, M.; Johnson, D. R.

2003-12-01

Earth System Science Education for the 21st Century (ESSE 21), sponsored by NASA through the Universities Space Research Association (USRA), is a collaborative undergraduate/graduate education program offering small grants to colleges and universities to engage a diverse interdisciplinary community of faculty and scientists in the development of courses, curricula and degree programs and sharing of learning resources focused on the fundamental understanding and application of Earth system principles for the classroom and laboratory. Through an expanded focus including partnerships with minority institutions, ESSE 21 is further developing broadly based courses, educational resources, electronic learning materials and degree programs that extend Earth system science concepts in both undergraduate and graduate classrooms and laboratories. These resources emphasizing the fundamentals of Earth system science advance the nation's broader agenda for improving science, technology, engineering and mathematics competency. The thrust to establish Earth system and global change science within the classrooms of colleges and universities is critical to laying and extending the foundation for knowledge-based decision making in the 21st century by both scientists and society in an effort to achieve sustainability. ESSE 21 released a Call for Participation (CFP) in the Fall of 2002 soliciting proposals from undergraduate institutions to create and adopt undergraduate and graduate level Earth system science content in courses, curricula and degree programs. In February 2003, twelve college and university teams were competitively selected through the CFP as the Year 1 and Year 2 Program participants. Eight of the participating teams are from minority institutions. The goal for all is to effect systemic change through developing Earth system science learning materials, courses, curricula, degree tracks or programs, and departments that are self-sustaining in the coming decades. ESSE

How to call the Fire Brigade

CERN Multimedia

2003-01-01

The telephone numbers for the CERN Fire Brigade are: 74444 for emergency calls 74848 for other calls Note The number 112 will stay in use for emergency calls from "wired" telephones, however, from mobile phones it leads to non-CERN emergency services.

Global Comparative Public Administration: Are Graduate Programs Responding to the Call?

Science.gov (United States)

Manoharan, Aroon P.; Mirbel, Wendel; Carrizales, Tony J.

2018-01-01

Within the past two decades, globalization has led to increased literature on comparative public administration (CPA) research, and it has enhanced analyses of administrative systems in various societies. Our paper examines CPA education among Master of Public Administration and Master of Public Policy programs in the United States. The findings…

Restoring rape survivors: justice, advocacy, and a call to action.

Science.gov (United States)

Koss, Mary P

2006-11-01

Rape results in mental and physical health, social, and legal consequences. For the latter, restorative justice-based programs might augment community response, but they generate controversy among advocates and policy makers. This article identifies survivors' needs and existing community responses to them. Survivors feel their legal needs are most poorly met due to justice system problems that can be summarized as attrition, retraumatization, and disparate treatment across gender, class, and ethnic lines. Empirical data support each problem and the conclusion that present justice options are inadequate. The article concludes by identifying common ground in advocacy and restorative justice goals and calls for a holistic approach to the needs of rape survivors that includes advocating for expanded justice alternatives. A call to action is issued to implement restorative alternatives to expand survivor choice and offender accountability. Conventional and restorative justice are often viewed as mutually exclusive whereas the author argues they are complementary.

Using Semantic Similarity In Automated Call Quality Evaluator For Call Centers

Directory of Open Access Journals (Sweden)

Ria A. Sagum

2015-08-01

Full Text Available Conversation between the agent and client are being evaluated manually by a quality assurance officer QA. This job is only one of the responsibilities being done by a QA and particularly eat ups a lot of time for them which lead to late evaluation results that may cause untimely response of the company to concerns raised by their clients. This research developed an application software that automates and evaluates the quality assurance in business process outsourcing companies or customer service management implementing sentence similarity. The developed system includes two modules speaker diarization which includes transcription and question and answer extraction and similarity checker which checks the similarity between the extracted answer and the answer of the call center agent to a question. The system was evaluated for Correctness of the extracted answers and accurateness of the evaluation for a particular call. Audio conversations were tested for the accuracy of the transcription module which has an accuracy of 27.96. The Precision Recall and F-measure of the extracted answer was tested as 78.03 96.26 and 86.19 respectively. The Accuracy of the system in evaluating a call is 70.

Perspectives on a ‘Sit Less, Move More’ Intervention in Australian Emergency Call Centres

Directory of Open Access Journals (Sweden)

Michelle Daley

2016-05-01

Full Text Available Background: Prolonged sitting is associated with increased risk of chronic diseases. Workplace programs that aim to reduce sitting time (sit less and increase physical activity (move more have targeted desk-based workers in corporate and university settings with promising results. However, little is known about ‘move more, sit less’ programs for workers in other types of jobs and industries, such as shift workers. This formative research examines the perceptions of a ‘sit less, move more’ program in an Australian Emergency Call Centre that operates 24 hours per day, 7 days per week. Methods: Participants were employees (N = 39, 72% female, 50% aged 36–55 years recruited from Emergency Services control centres located in New South Wales, Australia. The ‘sit less, move more’ intervention, consisting of emails, posters and timer lights, was co-designed with the management team and tailored to the control centre environment and work practices, which already included electronic height-adjustable sit-stand workstations for all call centre staff. Participants reported their perceptions and experiences of the intervention in a self-report online questionnaire, and directly to the research team during regular site visits. Questionnaire topics included barriers and facilitators to standing while working, mental wellbeing, effects on work performance, and workplace satisfaction. Field notes and open-ended response data were analysed in an iterative process during and after data collection to identify the main themes. Results: Whilst participants already had sit-stand workstations, use of the desks in the standing position varied and sometimes were contrary to expectations (e.g, less tired standing than sitting; standing when experiencing high call stress. Participants emphasised the “challenging” and “unrelenting” nature of their work. They reported sleep issues (“always tired”, work stress (“non-stop demands”, and feeling

Calling in Work: Secular or Sacred?

Science.gov (United States)

Steger, Michael F.; Pickering, N. K.; Shin, J. Y.; Dik, B. J.

2010-01-01

Recent scholarship indicates that people who view their work as a calling are more satisfied with their work and their lives. Historically, calling has been regarded as a religious experience, although modern researchers frequently have adopted a more expansive and secular conceptualization of calling, emphasizing meaning and personal fulfillment…

Orion: a web-based application designed to monitor resident and fellow performance on-call.

Science.gov (United States)

Itri, Jason N; Kim, Woojin; Scanlon, Mary H

2011-10-01

Radiology residency and fellowship training provides a unique opportunity to evaluate trainee performance and determine the impact of various educational interventions. We have developed a simple software application (Orion) using open-source tools to facilitate the identification and monitoring of resident and fellow discrepancies in on-call preliminary reports. Over a 6-month period, 19,200 on-call studies were interpreted by 20 radiology residents, and 13,953 on-call studies were interpreted by 25 board-certified radiology fellows representing eight subspecialties. Using standard review macros during faculty interpretation, each of these reports was classified as "agreement", "minor discrepancy", and "major discrepancy" based on the potential to impact patient management or outcome. Major discrepancy rates were used to establish benchmarks for resident and fellow performance by year of training, modality, and subspecialty, and to identify residents and fellows demonstrating a significantly higher major discrepancy rate compared with their classmates. Trends in discrepancies were used to identify subspecialty-specific areas of increased major discrepancy rates in an effort to tailor the didactic and case-based curriculum. A series of missed-case conferences were developed based on trends in discrepancies, and the impact of these conferences is currently being evaluated. Orion is a powerful information technology tool that can be used by residency program directors, fellowship programs directors, residents, and fellows to improve radiology education and training.

Hornbills can distinguish between primate alarm calls.

Science.gov (United States)

Rainey, Hugo J.; Zuberbühler, Klaus; Slater, Peter J. B.

2004-01-01

Some mammals distinguish between and respond appropriately to the alarm calls of other mammal and bird species. However, the ability of birds to distinguish between mammal alarm calls has not been investigated. Diana monkeys (Cercopithecus diana) produce different alarm calls to two predators: crowned eagles (Stephanoaetus coronatus) and leopards (Panthera pardus). Yellow-casqued hornbills (Ceratogymna elata) are vulnerable to predation by crowned eagles but are not preyed on by leopards and might therefore be expected to respond to the Diana monkey eagle alarm call but not to the leopard alarm call. We compared responses of hornbills to playback of eagle shrieks, leopard growls, Diana monkey eagle alarm calls and Diana monkey leopard alarm calls and found that they distinguished appropriately between the two predator vocalizations as well as between the two Diana monkey alarm calls. We discuss possible mechanisms leading to these responses. PMID:15209110

The North American Amphibian Monitoring Program. [abstract

Science.gov (United States)

Griffin, J.

1998-01-01

The North American Amphibian Monitoring Program has been under development for the past three years. The monitoring strategy for NAAMP has five main prongs: terrestrial salamander surveys, calling surveys, aquatic surveys, western surveys, and atlassing. Of these five, calling surveys were selected as one of the first implementation priorities due to their friendliness to volunteers of varying knowledge levels, relative low cost, and the fact that several groups had already pioneered the techniques involved. While some states and provinces had implemented calling surveys prior to NAAMP, like WI and IL, most states and provinces had little or no history of state/provincewide amphibian monitoring. Thus, the majority of calling survey programs were initiated in the past two years. To assess the progress of this pilot phase, a program review was conducted on the status of the NAAMP calling survey program, and the results of that review will be presented at the meeting. Topics to be discussed include: who is doing what where, extent of route coverage, the continuing random route discussions, quality assurance, strengths and weaknesses of calling surveys, reliability of data, and directions for the future. In addition, a brief overview of the DISPro project will be included. DISPro is a new amphibian monitoring program in National Parks, funded by the Demonstration of Intensive Sites Program (DISPro) through the EPA and NPS. It will begin this year at Big Bend and Shenandoah National Parks. The purpose of the DISPro Amphibian Project will be to investigate relationships between environmental factors and stressors and the distribution, abundance, and health of amphibians in these National Parks. At each Park, amphibian long-term monitoring protocols will be tested, distributions and abundance of amphibians will be mapped, and field research experiments will be conducted to examine stressor effects on amphibians (e.g., ultraviolet radiation, contaminants, acidification).

The dynomak: An advanced spheromak reactor concept with imposed-dynamo current drive and next-generation nuclear power technologies

Energy Technology Data Exchange (ETDEWEB)

Sutherland, D.A., E-mail: das1990@uw.edu; Jarboe, T.R.; Morgan, K.D.; Pfaff, M.; Lavine, E.S.; Kamikawa, Y.; Hughes, M.; Andrist, P.; Marklin, G.; Nelson, B.A.

2014-04-15

A high-β spheromak reactor concept has been formulated with an estimated overnight capital cost that is competitive with conventional power sources. This reactor concept utilizes recently discovered imposed-dynamo current drive (IDCD) and a molten salt (FLiBe) blanket system for first wall cooling, neutron moderation and tritium breeding. Currently available materials and ITER-developed cryogenic pumping systems were implemented in this concept from the basis of technological feasibility. A tritium breeding ratio (TBR) of greater than 1.1 has been calculated using a Monte Carlo N-Particle (MCNP5) neutron transport simulation. High temperature superconducting tapes (YBCO) were used for the equilibrium coil set, substantially reducing the recirculating power fraction when compared to previous spheromak reactor studies. Using zirconium hydride for neutron shielding, a limiting equilibrium coil lifetime of at least thirty full-power years has been achieved. The primary FLiBe loop was coupled to a supercritical carbon dioxide Brayton cycle due to attractive economics and high thermal efficiencies. With these advancements, an electrical output of 1000 MW from a thermal output of 2486 MW was achieved, yielding an overall plant efficiency of approximately 40%.

From nestling calls to fledgling silence: adaptive timing of change in response to aerial alarm calls.

Science.gov (United States)

Magrath, Robert D; Platzen, Dirk; Kondo, Junko

2006-09-22

Young birds and mammals are extremely vulnerable to predators and so should benefit from responding to parental alarm calls warning of danger. However, young often respond differently from adults. This difference may reflect: (i) an imperfect stage in the gradual development of adult behaviour or (ii) an adaptation to different vulnerability. Altricial birds provide an excellent model to test for adaptive changes with age in response to alarm calls, because fledglings are vulnerable to a different range of predators than nestlings. For example, a flying hawk is irrelevant to a nestling in a enclosed nest, but is dangerous to that individual once it has left the nest, so we predict that young develop a response to aerial alarm calls to coincide with fledging. Supporting our prediction, recently fledged white-browed scrubwrens, Sericornis frontalis, fell silent immediately after playback of their parents' aerial alarm call, whereas nestlings continued to calling despite hearing the playback. Young scrubwrens are therefore exquisitely adapted to the changing risks faced during development.

Staffing to Maximize Profit for Call Centers with Impatient and Repeat-Calling Customers

Directory of Open Access Journals (Sweden)

Jun Gong

2015-01-01

Full Text Available Motivated by call center practice, we study the optimal staffing of many-server queues with impatient and repeat-calling customers. A call center is modeled as an M/M/s+M queue, which is developed to a behavioral queuing model in which customers come and go based on their satisfaction with waiting time. We explicitly take into account customer repeat behavior, which implies that satisfied customers might return and have an impact on the arrival rate. Optimality is defined as the number of agents that maximize revenues net of staffing costs, and we account for the characteristic that revenues are a direct function of staffing. Finally, we use numerical experiments to make certain comparisons with traditional models that do not consider customer repeat behavior. Furthermore, we indicate how managers might allocate staffing optimally with various customer behavior mechanisms.

Program auto

International Nuclear Information System (INIS)

Rawool-Sullivan, M.W.; Plagnol, E.

1990-01-01

The program AUTO was developed to be used in the analysis of dE vs E type spectra. This program is written in FORTRAN and calculates dE vs E lines in MeV. The provision is also made in the program to convert these lines from MeV to ADC channel numbers to facilitate the comparison with the raw data from the experiments. Currently the output of this program can be plotted with the display program, called VISU, but it can also be used independent of the program VISU, with little or no modification in the actual fortran code. The program AUTO has many useful applications. In this article the program AUTO is described along with its applications

Peafowl antipredator calls encode information about signalers.

Science.gov (United States)

Yorzinski, Jessica L

2014-02-01

Animals emit vocalizations that convey information about external events. Many of these vocalizations, including those emitted in response to predators, also encode information about the individual that produced the call. The relationship between acoustic features of antipredator calls and information relating to signalers (including sex, identity, body size, and social rank) were examined in peafowl (Pavo cristatus). The "bu-girk" antipredator calls of male and female peafowl were recorded and 20 acoustic parameters were automatically extracted from each call. Both the bu and girk elements of the antipredator call were individually distinctive and calls were classified to the correct signaler with over 90% and 70% accuracy in females and males, respectively. Females produced calls with a higher fundamental frequency (F0) than males. In both females and males, body size was negatively correlated with F0. In addition, peahen rank was related to the duration, end mean frequency, and start harmonicity of the bu element. Peafowl antipredator calls contain detailed information about the signaler and can potentially be used by receivers to respond to dangerous situations.

BUFO PARDALIS (ANURA: BUFONIDAE): MATING CALL AND ...

African Journals Online (AJOL)

the calls of one of these species, Bufo pardalis. Hewitt, were not analysed by Tandy & Keith. (1972). Furthennore there is some confusion in the literature regarding the mating call of this species. For these reasons this mating call is here clarified. The mating call of B. pardaiis was first described by Ranger (in Hewitt 1935) as ...

Impact of mobility on call block, call drops and optimal cell size in small cell networks

OpenAIRE

Ramanath , Sreenath; Voleti , Veeraruna Kavitha; Altman , Eitan

2011-01-01

We consider small cell networks and study the impact of user mobility. Assuming Poisson call arrivals at random positions with random velocities, we discuss the characterization of handovers at the boundaries. We derive explicit expressions for call block and call drop probabilities using tools from spatial queuing theory. We also derive expressions for the average virtual server held up time. These expressions are used to derive optimal cell sizes for various profile of velocities in small c...

Answering the Call of the Web: UVA Crafts a Innovative Web Certification Program for Its Staff.

Science.gov (United States)

Lee, Sandra T.

2000-01-01

Describes the development of a Web Certification Program at the University of Virginia. This program offers certificates at three levels: Web Basics, Web Designer, and Web Master. The paper focuses on: determination of criteria for awarding certificates; program status; program evaluation and program effectiveness; and future plans for the Web…

From Systematic Review to Call for Action.

Science.gov (United States)

Sawin, Erika Metzler; Sobel, Linda L; Annan, Sandra L; Schminkey, Donna L

2017-06-01

Intimate partner violence (IPV) is a global public health and criminal justice concern with significant impacts; especially high rates are seen among rural Hispanic American (HA) communities, the fastest growing population in the United States. They experience additional barriers to care including extreme poverty, lesser education, gender norms, and language and immigration issues. A systematic literature review was conducted using Cooper's framework to identify evidence supporting associations between interventions and prevention, reduction, and elimination of IPV among rural HA women. Searches conducted on databases including CINAHL, PubMed, Medline, Women's Studies International, MedicLatina, and JSTOR used the MeSH terms Hispanic Americans (Latino/a and Hispanic), domestic violence, and intimate partner violence. Selected studies were published between January 1, 2000, and January 1, 2014. Of the 617 yielded articles, only 6 met the inclusion criteria. Of these, none closely examined rurality or provided valid and reliable measures of outcomes, instead reporting program descriptions and suggested interventions. We identify key findings to guide program, screening, and tool development. Our study identifies a gap in knowledge, research, and effective practices and issues a call for action to create evidence-based tools to prevent, reduce, and eliminate IPV in these underserved populations.

A theory of the Earth's magnetic field and of sunspots, based on a self-excited dynamo incorporating the Hall effect

Directory of Open Access Journals (Sweden)

A. de Paor

2001-01-01

Full Text Available A new viewpoint on the generation and maintenance of the Earth's magnetic field is put forward, which integrates self-exciting dynamo theory with the possibility of energy coupling along orthogonal axes provided by the Hall effect. A nonlinear third-order system is derived, with a fourth equation serving as an observer of unspecified geophysical processes which could result in field reversal. Lyapunov analysis proves that chaos is not intrinsic to this system. Relative constancy of one of the variables produces pseudo equilibrium in a second order subsystem and allows for self-excitation of the geomagnetic field. Electromagnetic analysis yields expressions for key parameters. Models for secular variations recorded at London, Palermo and at the Cape of Good Hope over the past four hundred years are offered. Offset of the Earth's magnetic axis from the geographic axis is central to time-varying declination, but its causes have not yet been established. Applicability of the model to the explanation of sunspot activity is outlined. A corroborating experiment published by Peter Barlow in 1831 is appended.

PyCPR - a python-based implementation of the Conjugate Peak Refinement (CPR) algorithm for finding transition state structures.

Science.gov (United States)

Gisdon, Florian J; Culka, Martin; Ullmann, G Matthias

2016-10-01

Conjugate peak refinement (CPR) is a powerful and robust method to search transition states on a molecular potential energy surface. Nevertheless, the method was to the best of our knowledge so far only implemented in CHARMM. In this paper, we present PyCPR, a new Python-based implementation of the CPR algorithm within the pDynamo framework. We provide a detailed description of the theory underlying our implementation and discuss the different parts of the implementation. The method is applied to two different problems. First, we illustrate the method by analyzing the gauche to anti-periplanar transition of butane using a semiempirical QM method. Second, we reanalyze the mechanism of a glycyl-radical enzyme, namely of 4-hydroxyphenylacetate decarboxylase (HPD) using QM/MM calculations. In the end, we suggest a strategy how to use our implementation of the CPR algorithm. The integration of PyCPR into the framework pDynamo allows the combination of CPR with the large variety of methods implemented in pDynamo. PyCPR can be used in combination with quantum mechanical and molecular mechanical methods (and hybrid methods) implemented directly in pDynamo, but also in combination with external programs such as ORCA using pDynamo as interface. PyCPR is distributed as free, open source software and can be downloaded from http://www.bisb.uni-bayreuth.de/index.php?page=downloads . Graphical Abstract PyCPR is a search tool for finding saddle points on the potential energy landscape of a molecular system.

External GSM phone calls now made simpler

CERN Multimedia

2007-01-01

On 2 July, the IT/CS Telecom Service introduced a new service making external calls from CERN GSM phones easier. A specific prefix is no longer needed for calls outside CERN. External calls from CERN GSM phones are to be simplified. It is no longer necessary to use a special prefix to call an external number from the CERN GSM network.The Telecom Section of the IT/CS Group is introducing a new system that will make life easier for GSM users. It is no longer necessary to use a special prefix (333) to call an external number from the CERN GSM network. Simply dial the number directly like any other Swiss GSM customer. CERN currently has its own private GSM network with the Swiss mobile operator, Sunrise, covering the whole of Switzerland. This network was initially intended exclusively for calls between CERN numbers (replacing the old beeper system). A special system was later introduced for external calls, allowing them to pass thr...

Call Duration Characteristics based on Customers Location

Directory of Open Access Journals (Sweden)

Žvinys Karolis

2014-05-01

Full Text Available Nowadays a lot of different researches are performed based on call duration distributions (CDD analysis. However, the majority of studies are linked with social relationships between the people. Therefore the scarcity of information, how the call duration is associated with a user's location, is appreciable. The goal of this paper is to reveal the ties between user's voice call duration and the location of call. For this reason we analyzed more than 5 million calls from real mobile network, which were made over the base stations located in rural areas, roads, small towns, business and entertainment centers, residential districts. According to these site types CDD’s and characteristic features for call durations are given and discussed. Submitted analysis presents the users habits and behavior as a group (not an individual. The research showed that CDD’s of customers being them in different locations are not equal. It has been found that users at entertainment, business centers are tend to talk much shortly, than people being at home. Even more CDD can be distorted strongly, when machinery calls are evaluated. Hence to apply a common CDD for a whole network it is not recommended. The study also deals with specific parameters of call duration for distinguished user groups, the influence of network technology for call duration is considered.

"You're being paged!" outcomes of a nursing home on-call role-playing and longitudinal curriculum.

Science.gov (United States)

Yuasa, Misuzu; Bell, Christina L; Inaba, Michiko; Tamura, Bruce K; Ahsan, Samina; Saunders, Valisa; Masaki, Kamal

2013-11-01

Effectively handling telephone calls about nursing home (NH) residents is an important skill for healthcare professionals, but little formal training is typically provided. The objective of the current study was to describe and evaluate the effectiveness of a novel structured role-playing didactic session followed by an on-call NH longitudinal clinical experience. The effectiveness of the structured role-playing didactic session was compared in different learners, including geriatric medicine fellows (n = 10), family medicine residents and faculty (n = 14), nurse practitioner students (n = 31), and other learners (n = 7). The curriculum focused on common problems encountered while caring for NH residents during on-call periods. Learners rated themselves using an 18-item pre/post questionnaire including five attitude and 13 skills questions, using a 1-to-5 Likert scale. T-tests were used to compare means before and after sessions. Significant improvements were found in overall mean attitudes and skills scores. For all learners, the greatest improvements were seen in "comfort in managing residents at the NH," "managing feeding or gastrostomy tube dislodgement," "identifying different availability of medications, laboratory studies, and procedures in NH," and "describing steps to send NH residents to the emergency department." Geriatric medicine fellows' attitudes and skills improved significantly after the longitudinal clinical experience. The faculty survey demonstrated improved documentation, communication, and fellows' management of on-call problems after curriculum implementation. This novel curriculum used role-playing to provide training for on-call management of NH residents. This curriculum has been successfully disseminated on a national geriatrics educational resource website (POGOe) and is applicable to geriatric medicine fellowships, internal medicine and family medicine residency programs, and other training programs. © 2013, Copyright the Authors

INTEGRATING CORPUS-BASED RESOURCES AND NATURAL LANGUAGE PROCESSING TOOLS INTO CALL

Directory of Open Access Journals (Sweden)

Pascual Cantos Gomez

2002-06-01

Full Text Available This paper ainis at presenting a survey of computational linguistic tools presently available but whose potential has been neither fully considered not exploited to its full in modern CALL. It starts with a discussion on the rationale of DDL to language learning, presenting typical DDL-activities. DDL-software and potential extensions of non-typical DDL-software (electronic dictionaries and electronic dictionary facilities to DDL . An extended section is devoted to describe NLP-technology and how it can be integrated into CALL, within already existing software or as stand alone resources. A range of NLP-tools is presentcd (MT programs, taggers, lemn~atizersp, arsers and speech technologies with special emphasis on tagged concordancing. The paper finishes with a number of reflections and ideas on how language technologies can be used efficiently within the language learning context and how extensive exploration and integration of these technologies might change and extend both modern CAI,I, and the present language learning paradigiii..

Stoked nondynamos: sustaining field in magnetically non-closed systems

International Nuclear Information System (INIS)

Byington, B M; Brummell, N H; Stone, J M; Gough, D O

2014-01-01

Much effort has gone into identifying and classifying systems that might be capable of dynamo action, i.e. capable of generating and sustaining magnetic field indefinitely against dissipative effects in a conducting fluid. However, it is difficult, if not almost technically impossible, to derive a method of determining in both an absolutely conclusive and a pragmatic manner whether a system is a dynamo or not in the nonlinear regime. This problem has generally been examined only for closed systems, despite the fact that most realistic situations of interest are not strictly closed. Here we examine the even more complex problem of whether a known nondynamo closed system can be distinguished pragmatically from a true dynamo when a small input of magnetic field to the system is allowed. We call such systems ‘stoked nondynamos’ owing to the ‘stoking’ or augmentation of the magnetic field in the system. It may seem obvious that magnetic energy can be sustained in such systems since there is an external source, but crucial questions remain regarding what level is maintained and whether such nondynamo systems can be distinguished from a true dynamo. In this paper, we perform 3D nonlinear numerical simulations with time-dependent ABC forcing possessing known dynamo properties. We find that magnetic field can indeed be maintained at a significant stationary level when stoking a system that is a nondynamo when not stoked. The maintained state results generally from an eventual rough balance of the rates of input and decay of magnetic field. We find that the relevance of this state is dictated by a parameter κ representing the correlation of the resultant field with the stoking forcing function. The interesting regime is where κ is small but non-zero, as this represents a middle ground between a state where the stoking has no effect on the pre-existing nondynamo properties and a state where the effect of stoking is easily detectable. We find that in this regime, (a

Care and Calls

DEFF Research Database (Denmark)

Paasch, Bettina Sletten

on the enactment of care but also on patient safety. Nurses working in various hospital departments have developed different strategies for handling mobile phone calls when with a patient. Additional research into the ways nurses successfully or unsuccessfully enact care and ensure patient safety when they answer......In Danish hospitals, nurses have been equipped with a mobile work phone to improve their availability and efficiency. On the phones nurses receive internal and external phone conversations, patient calls, and alarms from electronic surveillance equipment. For safety reasons the phones cannot...... be switched off or silenced; they consequently ring during all activities and also during interactions with patients. A possible tension thus arises when nurses have to be both caring and sensitive towards the patient and simultaneously be efficient and available and answer their phone. The present paper...

Calling under pressure: short-finned pilot whales make social calls during deep foraging dives.

Science.gov (United States)

Jensen, Frants H; Perez, Jacobo Marrero; Johnson, Mark; Soto, Natacha Aguilar; Madsen, Peter T

2011-10-22

Toothed whales rely on sound to echolocate prey and communicate with conspecifics, but little is known about how extreme pressure affects pneumatic sound production in deep-diving species with a limited air supply. The short-finned pilot whale (Globicephala macrorhynchus) is a highly social species among the deep-diving toothed whales, in which individuals socialize at the surface but leave their social group in pursuit of prey at depths of up to 1000 m. To investigate if these animals communicate acoustically at depth and test whether hydrostatic pressure affects communication signals, acoustic DTAGs logging sound, depth and orientation were attached to 12 pilot whales. Tagged whales produced tonal calls during deep foraging dives at depths of up to 800 m. Mean call output and duration decreased with depth despite the increased distance to conspecifics at the surface. This shows that the energy content of calls is lower at depths where lungs are collapsed and where the air volume available for sound generation is limited by ambient pressure. Frequency content was unaffected, providing a possible cue for group or species identification of diving whales. Social calls may be important to maintain social ties for foraging animals, but may be impacted adversely by vessel noise.

Do market participants learn from conference calls?

NARCIS (Netherlands)

Roelofsen, E.; Verbeeten, F.; Mertens, G.

2014-01-01

We examine whether market participants learn from the information that is disseminated during the Q-and-A section of conference calls. Specifically, we investigate whether stock prices react to information on intangible assets provided during conference calls, and whether conference calls

After-hours/on-call experience during primary care nurse practitioner education utilizing standard scenarios and simulated patients.

Science.gov (United States)

Kelly, Michelle M; Blunt, Elizabeth; Nestor, Kelly

2017-12-01

Few nurse practitioner (NP) programs include an after-hours/on-call component in their clinical preparation of NP students. This role is expected in many primary and specialty care practices, and is one that students feel unprepared to competently navigate. Utilizing simulated callers as patients or parents, NP students participated in a simulated after-hours/on-call experience that included receiving the call, managing the patient, and submitting documentation of the encounter. Students completed pre- and postparticipation evaluations, and were evaluated by the simulated patient callers and faculty using standardized evaluation tools. NP students rated the experience as an educationally valuable experience despite feeling anxious and nervous about the experience. Several essential skills were identified including critical thinking, clear communication, self-confidence, and access to resources. After participation NP students were more receptive to an NP position with an on-call component. Inclusion of a simulated on-call experience is a feasible component of NP education and should be added to the NP curriculum. ©2017 American Association of Nurse Practitioners.

Fundamental Magnetofluid Physics Studies on the Swarthmore Spheromak Experiment: Reconnection and Sustainment

International Nuclear Information System (INIS)

Brown, M.R.

2001-01-01

The general goal of the Magnetofluids Laboratory at Swarthmore College is to understand how magnetofluid kinetic energy can be converted to magnetic energy as it is in the core of the earth and sun (the dynamo problem) and to understand how magnetic energy can be rapidly converted back to kinetic energy and heat as it is in solar flares (the magnetic reconnection problem). Magnetic reconnection has been studied using the Swarthmore Spheromak Experiment (SSX) which was designed and built under this Junior Faculty Grant. In SSX we generate and merge two rings of magnetized plasma called spheromaks and study their interaction. The spheromaks have many properties similar to solar flares so this work is directly relevant to basic solar physics. In addition, since the spheromak is a magnetic confinement fusion configuration, issues of formation and stability have direct impact on the fusion program

Introduction to parallel programming

CERN Document Server

Brawer, Steven

1989-01-01

Introduction to Parallel Programming focuses on the techniques, processes, methodologies, and approaches involved in parallel programming. The book first offers information on Fortran, hardware and operating system models, and processes, shared memory, and simple parallel programs. Discussions focus on processes and processors, joining processes, shared memory, time-sharing with multiple processors, hardware, loops, passing arguments in function/subroutine calls, program structure, and arithmetic expressions. The text then elaborates on basic parallel programming techniques, barriers and race

HOW TO CALL THE CERN FIRE BRIGADE

CERN Multimedia

2002-01-01

The telephone numbers of the CERN Fire Brigade are: 74444 for emergency calls 74848 for other calls Note The number 112 will stay in use for emergency calls from 'wired' telephones, however, from mobile phones it leads to non-CERN emergency services.  

HOW TO CALL THE CERN FIRE BRIGADE

CERN Multimedia

2002-01-01

The telephone numbers of the CERN Fire Brigade are: 74444 for emergency calls 74848 for other calls Note The number 112 will stay in use for emergency calls from 'wired' telephones, however, from mobile phones it leads to non-CERN emergency services.

HOW TO CALL THE CERN FIRE BRIGADE

CERN Multimedia

2001-01-01

The telephone numbers of the CERN Fire Brigade are: 74444 for emergency calls 74848 for other calls Note The number 112 will stay in use for emergency calls from 'wired' telephones, however, from mobile phones it leads to non-CERN emergency services.

HOW TO CALL THE CERN FIRE BRIGADE

CERN Multimedia

2001-01-01

The telephone numbers of the CERN Fire Brigade are: 74444 for emergency calls 74848 for other calls Note: the number 112 will stay in use for emergency calls from 'wired' telephones, however, from mobile phones it leads to non-CERN emergency services.

Motivační program organizace

OpenAIRE

Černá, Lenka

2013-01-01

This thesis deals with the motivation program of the company and its basis. The thesis focuses on the analysis and the comparison of motivation theories that have influence on the creation of motivation programs. In addition to traditional motivation theories is a crucial part of the thesis devoted to the so-called new motivation theories. The new motivation theories are called because of their development during last thirty years. The main aspects of the comparison of motivation theories in ...

Telephone calls by individuals with cancer.

Science.gov (United States)

Flannery, Marie; McAndrews, Leanne; Stein, Karen F

2013-09-01

To describe symptom type and reporting patterns found in spontaneously initiated telephone calls placed to an ambulatory cancer center practice. Retrospective, descriptive. Adult hematology oncology cancer center. 563 individuals with a wide range of oncology diagnoses who initiated 1,229 telephone calls to report symptoms. Raw data were extracted from telephone forms using a data collection sheet with 23 variables obtained for each phone call, using pre-established coding criteria. A literature-based, investigator-developed instrument was used for the coding criteria and selection of which variables to extract. Symptom reporting, telephone calls, pain, and symptoms. A total of 2,378 symptoms were reported by telephone during the four months. At least 10% of the sample reported pain (38%), fatigue (16%), nausea (16%), swelling (12%), diarrhea (12%), dyspnea (10%), and anorexia (10%). The modal response was to call only one time and to report only one symptom (55%). Pain emerged as the symptom that most often prompted an individual to pick up the telephone and call. Although variation was seen in symptom reporting, an interesting pattern emerged with an individual reporting on a solitary symptom in a single telephone call. The emergence of pain as the primary symptom reported by telephone prompted educational efforts for both in-person clinic visit management of pain and prioritizing nursing education and protocol management of pain reported by telephone. Report of symptoms by telephone can provide nurses unique insight into patient-centered needs. Although pain has been an important focus of education and research for decades, it remains a priority for individuals with cancer. A wide range in symptom reporting by telephone was evident.

Firefighter health and fitness assessment: a call to action.

Science.gov (United States)

Storer, Thomas W; Dolezal, Brett A; Abrazado, Marlon L; Smith, Denise L; Batalin, Maxim A; Tseng, Chi-Hong; Cooper, Christopher B

2014-03-01

Sudden cardiac deaths experienced by firefighters in the line of duty account for the largest proportion of deaths annually. Several fire service standards for fitness and wellness have been recommended but currently only 30% of U.S. fire departments are implementing programs for this purpose. The Department of Homeland Security Science and Technology Directorate has initiated the Physiological Health Assessment System for Emergency Responders (PHASER) program aiming to reduce these line-of-duty deaths through an integration of medical science and sensor technologies. Confirming previous reports, PHASER comprehensive risk assessment has identified lack of physical fitness with propensity for overexertion as a major modifiable risk factor. We sought to determine if current levels of fitness and cardiovascular disease (CVD) risk factors in a contemporary cohort of firefighters were better than those reported over the past 30 years. Fifty-one firefighters from a Southern California department were characterized for physical fitness and CVD risk factors using standard measures. Overall, physical fitness and risk factors were not different from previous reports of firefighter fitness and most subjects did not achieve recommended fitness standards. Considering the lack of widespread implementation of wellness/fitness programs in the U.S. fire service together with our findings that low physical fitness and the presence of CVD risk factors persist, we issue a call to action among health and fitness professionals to assist the fire service in implementing programs for firefighters that improve fitness and reduce CVD risk factors. Fitness professionals should be empowered to work with fire departments lending their expertise to guide programs that achieve these objectives, which may then lead to reduced incidence of sudden cardiac death or stroke.

Calling to Nursing: Concept Analysis.

Science.gov (United States)

Emerson, Christie

The aims of this article are (a) to analyze the concept of a calling as it relates nursing and (b) to develop a definition of calling to nursing with the detail and clarity needed to guide reliable and valid research. The classic steps described by Walker and Avant are used for the analysis. Literature from several disciplines is reviewed including vocational psychology, Christian career counseling, sociology, organizational management, and nursing. The analysis provides an operational definition of a calling to nursing and establishes 3 defining attributes of the concept: (a) a passionate intrinsic motivation or desire (perhaps with a religious component), (b) an aspiration to engage in nursing practice, as a means of fulfilling one's purpose in life, and (c) the desire to help others as one's purpose in life. Antecedents to the concept are personal introspection and cognitive awareness. Positive consequences to the concept are improved work meaningfulness, work engagement, career commitment, personal well-being, and satisfaction. Negative consequences of having a calling might include willingness to sacrifice well-being for work and problems with work-life balance. Following the concept analysis, philosophical assumptions, contextual factors, interdisciplinary work, research opportunities, and practice implications are discussed.

EMERGENCY CALLS

CERN Multimedia

Medical Service

2001-01-01

IN URGENT NEED OF A DOCTOR GENEVA EMERGENCY SERVICES GENEVA AND VAUD 144 FIRE BRIGADE 118 POLICE 117 CERN FIREMEN 767-44-44 ANTI-POISONS CENTRE Open 24h/24h 01-251-51-51 Patient not fit to be moved, call family doctor, or: GP AT HOME, open 24h/24h 748-49-50 Association Of Geneva Doctors Emergency Doctors at home 07h-23h 322 20 20 Patient fit to be moved: HOPITAL CANTONAL CENTRAL 24 Micheli-du-Crest 372-33-11 ou 382-33-11 EMERGENCIES 382-33-11 ou 372-33-11 CHILDREN'S HOSPITAL 6 rue Willy-Donzé 372-33-11 MATERNITY 32 bvd.de la Cluse 382-68-16 ou 382-33-11 OPHTHALMOLOGY 22 Alcide Jentzer 382-33-11 ou 372-33-11 MEDICAL CENTRE CORNAVIN 1-3 rue du Jura 345 45 50 HOPITAL DE LA TOUR Meyrin EMERGENCIES 719-61-11 URGENCES PEDIATRIQUES 719-61-00 LA TOUR MEDICAL CENTRE 719-74-00 European Emergency Call 112 FRANCE EMERGENCY SERVICES 15 FIRE BRIGADE 18 POLICE 17 CERN FIREMEN AT HOME 00-41-22-767-44-44 ANTI-POISONS CENTRE Open 24h/24h 04-72-11-69-11 All doctors ...

The visco-elastic multilayer program VEROAD

NARCIS (Netherlands)

Hopman, P.C.

1996-01-01

The mathematical principles and derivation of a linear visco-elastic multilayer computer program are described. The mathematical derivation is based on Fourier Transformation. The program is called VEROAD, which is an acronym for Visco-Elastic ROad Analysis Delft. The program allows calculation of

TPMG Northern California appointments and advice call center.

Science.gov (United States)

Conolly, Patricia; Levine, Leslie; Amaral, Debra J; Fireman, Bruce H; Driscoll, Tom

2005-08-01

Kaiser Permanente (KP) has been developing its use of call centers as a way to provide an expansive set of healthcare services to KP members efficiently and cost effectively. Since 1995, when The Permanente Medical Group (TPMG) began to consolidate primary care phone services into three physical call centers, the TPMG Appointments and Advice Call Center (AACC) has become the "front office" for primary care services across approximately 89% of Northern California. The AACC provides primary care phone service for approximately 3 million Kaiser Foundation Health Plan members in Northern California and responds to approximately 1 million calls per month across the three AACC sites. A database records each caller's identity as well as the day, time, and duration of each call; reason for calling; services provided to callers as a result of calls; and clinical outcomes of calls. We here summarize this information for the period 2000 through 2003.

Evolution of advertisement calls in African clawed frogs

Science.gov (United States)

Tobias, Martha L.; Evans, Ben J.; Kelley, Darcy B.

2014-01-01

Summary For most frogs, advertisement calls are essential for reproductive success, conveying information on species identity, male quality, sexual state and location. While the evolutionary divergence of call characters has been examined in a number of species, the relative impacts of genetic drift or natural and sexual selection remain unclear. Insights into the evolutionary trajectory of vocal signals can be gained by examining how advertisement calls vary in a phylogenetic context. Evolution by genetic drift would be supported if more closely related species express more similar songs. Conversely, a poor correlation between evolutionary history and song expression would suggest evolution shaped by natural or sexual selection. Here, we measure seven song characters in 20 described and two undescribed species of African clawed frogs (genera Xenopus and Silurana) and four populations of X. laevis. We identify three call types — click, burst and trill — that can be distinguished by click number, call rate and intensity modulation. A fourth type is biphasic, consisting of two of the above. Call types vary in complexity from the simplest, a click, to the most complex, a biphasic call. Maximum parsimony analysis of variation in call type suggests that the ancestral type was of intermediate complexity. Each call type evolved independently more than once and call type is typically not shared by closely related species. These results indicate that call type is homoplasious and has low phylogenetic signal. We conclude that the evolution of call type is not due to genetic drift, but is under selective pressure. PMID:24723737

Using Pill Identification Calls to Poison Centers as a Marker of Drug Abuse at Three Texas Military Bases.

Science.gov (United States)

Ng, Patrick C; Maddry, Joseph K; Sessions, Daniel; Borys, Douglas J; Bebarta, Vikhyat S

2017-11-01

Opioid abuse is a growing problem in civilian communities, and it has developed in the military as well. Telephone calls to poison centers requesting pill identification (ID) is a marker of drug abuse. This study identifies the number of pill ID calls made to the poison centers from areas containing and surrounding three Texas military bases during an 8-year period. We performed a retrospective observational study identifying calls to certified poison centers in Texas from 2002 to 2009 that identified hydrocodone tablets and other pain medications. We noted the calls made from ZIP codes containing and surrounding the three largest military bases in Texas. We reviewed 75,537 drug ID calls for any drug from the ZIP codes of interest. Total drug ID calls increased 105% and the number of calls for hydrocodone increased 463%. In our study most of the drug ID calls from military communities in Texas were for hydrocodone. The rate of calls for hydrocodone increased more than the rate of calls for other analgesics from 2002 to 2009. Using drug ID calls as a surrogate of drug abuse, our results suggest that hydrocodone abuse has increased within military communities and that poison center data can be a reliable surrogate for prescription drug abuse near military bases. Future studies are needed to further understand the extent of this problem in military and civilian communities. We can use this information to heighten awareness, influence prescription practices, establish practice guidelines, and develop educational programs to mitigate the increasing rate of prescription analgesic abuse in the United States.

Person-Centered Care in the Home Setting for Parkinson’s Disease: Operation House Call Quality of Care Pilot Study

Directory of Open Access Journals (Sweden)

Nawaz Hack

2015-01-01

Full Text Available Objective. (1 To evaluate the feasibility of implementing and evaluating a home visit program for persons with Parkinson’s disease (PD in a rural setting. (2 To have movement disorders fellows coordinate and manage health care delivery. Background. The University of Florida, Center for Movement Disorders and Neurorestoration established Operation House Call to serve patients with PD who could not otherwise afford to travel to an expert center or to pay for medical care. PD is known to lead to significant disability, frequent hospitalization, early nursing home placement, and morbidity. Methods. This was designed as a quality improvement project. Movement disorders fellows travelled to the home(s of underserved PD patients and coordinated their clinical care. The diagnosis of Parkinson’s disease was confirmed using standardized criteria, and the Unified Parkinson’s Disease Rating Scale was performed and best treatment practices were delivered. Results. All seven patients have been followed up longitudinally every 3 to 6 months in the home setting, and they remain functional and independent. None of the patients have been hospitalized for PD related complications. Each patient has a new updatable electronic medical record. All Operation House Call cases are presented during video rounds for the interdisciplinary PD team to make recommendations for care (neurology, neurosurgery, neuropsychology, psychiatry, physical therapy, occupational therapy, speech therapy, and social work. One Operation House Call patient has successfully received deep brain stimulation (DBS. Conclusion. This program is a pilot program that has demonstrated that it is possible to provide person-centered care in the home setting for PD patients. This program could provide a proof of concept for the construction of a larger visiting physician or nurse program.

A type-driven approach to concrete meta programming.

NARCIS (Netherlands)

J.J. Vinju (Jurgen)

2005-01-01

textabstractApplications that manipulate programs as data are called meta programs. Examples of meta programs are compilers, source-to-source translators and code generators. Meta programming can be supported by the ability to represent program fragments in concrete syntax instead of abstract

MAGNETIC HELICITY FLUX IN THE PRESENCE OF SHEAR

International Nuclear Information System (INIS)

Hubbard, Alexander; Brandenburg, Axel

2011-01-01

Magnetic helicity has risen to be a major player in dynamo theory, with the helicity of the small-scale field being linked to the dynamo saturation process for the large-scale field. It is a nearly conserved quantity, which allows its evolution equation to be written in terms of production and flux terms. The flux term can be decomposed in a variety of fashions. One particular contribution that has been expected to play a significant role in dynamos in the presence of mean shear was isolated by Vishniac and Cho. Magnetic helicity fluxes are explicitly gauge dependent however, and the correlations that have come to be called the Vishniac-Cho flux were determined in the Coulomb gauge, which turns out to be fraught with complications in shearing systems. While the fluxes of small-scale helicity are explicitly gauge dependent, their divergences can be gauge independent. We use this property to investigate magnetic helicity fluxes of the small-scale field through direct numerical simulations in a shearing-box system and find that in a numerically usable gauge the divergence of the small-scale helicity flux vanishes, while the divergence of the Vishniac-Cho flux remains finite. We attribute this seeming contradiction to the existence of horizontal fluxes of small-scale magnetic helicity with finite divergences.

Magnetic Helicity Flux in the Presence of Shear

Science.gov (United States)

Hubbard, Alexander; Brandenburg, Axel

2011-01-01

Magnetic helicity has risen to be a major player in dynamo theory, with the helicity of the small-scale field being linked to the dynamo saturation process for the large-scale field. It is a nearly conserved quantity, which allows its evolution equation to be written in terms of production and flux terms. The flux term can be decomposed in a variety of fashions. One particular contribution that has been expected to play a significant role in dynamos in the presence of mean shear was isolated by Vishniac & Cho. Magnetic helicity fluxes are explicitly gauge dependent however, and the correlations that have come to be called the Vishniac-Cho flux were determined in the Coulomb gauge, which turns out to be fraught with complications in shearing systems. While the fluxes of small-scale helicity are explicitly gauge dependent, their divergences can be gauge independent. We use this property to investigate magnetic helicity fluxes of the small-scale field through direct numerical simulations in a shearing-box system and find that in a numerically usable gauge the divergence of the small-scale helicity flux vanishes, while the divergence of the Vishniac-Cho flux remains finite. We attribute this seeming contradiction to the existence of horizontal fluxes of small-scale magnetic helicity with finite divergences.

Deaf and hard of hearing social workers accessing their profession: a call to action.

Science.gov (United States)

Sheridan, Martha A; White, Barbara J; Mounty, Judith L

2010-01-01

This article aims to familiarize the social work profession with a paradox in its midst. Culturally sensitive and accessible services for deaf and hard of hearing people can often best be provided by social workers who are themselves deaf and hard of hearing, who have specialized language and communication skills, as well as unique cultural knowledge of this population at risk. Yet, deaf and hard of hearing graduates of social work education programs routinely experience difficulties accessing the profession. Addressing this paradox calls for creative collaborations among professional social work organizations, social work education programs, policymakers, and deaf and hard of hearing social workers.

29 CFR 785.17 - On-call time.

Science.gov (United States)

2010-07-01

... On-call time. An employee who is required to remain on call on the employer's premises or so close... employee who is not required to remain on the employer's premises but is merely required to leave word at his home or with company officials where he may be reached is not working while on call. (Armour & Co...

CALLING AQUARIUM LOVERS...

CERN Multimedia

2002-01-01

CERN's anemones will soon be orphans. We are looking for someone willing to look after the aquarium in the main building, for one year. If you are interested, or if you would like more information, please call 73830. (The anemones living in the aquarium thank you in anticipation.)

Calling 911! What role does the pediatrician play?

Science.gov (United States)

Grossman, Devin; Kunkov, Sergey; Kaplan, Carl; Crain, Ellen F

2013-06-01

The objective of this study was to compare admission rates and medical interventions among children whose caregivers called their child's primary care provider (PCP) before taking an ambulance to the pediatric emergency department (PED) versus those who did not. This was a prospective cohort study of patients brought to an urban, public hospital PED via emergency medical system (EMS). Children were included if the caregiver called 911 to have them transported via EMS and was present in the PED. The main variable was whether the child's PCP was called before EMS utilization. Study outcomes were medical interventions, such as intravenous line insertion or laboratory tests, and hospital admission. χ Test and logistic regression were used to evaluate the relationship of the main variable to the study outcomes. Six hundred fourteen patients met inclusion criteria and were enrolled. Five hundred eighty-five patients (95.3%) were reported to have a PCP. Seventy-four caregivers (12.1%) called their child's PCP before calling EMS. Two hundred seventy-seven patients (45.1%) had medical interventions performed; of these, 42 (15.2%) called their PCP (P = 0.03). Forty-two patients (6.8%) were admitted; among these, 14 (33.3%) called their PCP (P < 0.01). Adjusting for triage level, patients whose caregiver called the PCP before calling EMS were 3.2 times (95% confidence interval, 1.9-5.2 times) more likely to be admitted and 1.7 times (95% confidence interval, 1.1-2.9 times) more likely to have a medical intervention compared with patients whose caregivers did not call their child's PCP. Children were more likely to be admitted or require a medical intervention if their caregiver called their PCP before calling EMS. The availability of a PCP for telephone triage may help to optimize EMS utilization.

2APL: a practical agent programming language

NARCIS (Netherlands)

Dastani, M.M.

2008-01-01

This article presents a BDI-based agent-oriented programming language, called 2APL (A Practical Agent Programming Language). This programming language facilitates the implementation ofmulti-agent systems consisting of individual agents thatmay share and access external environments. It realizes

Indico CONFERENCE: Define the Call for Abstracts

CERN Multimedia

CERN. Geneva; Ferreira, Pedro

2017-01-01

In this tutorial, you will learn how to define and open a call for abstracts. When defining a call for abstracts, you will be able to define settings related to the type of questions asked during a review of an abstract, select the users who will review the abstracts, decide when to open the call for abstracts, and more.

Developing an English for Specific Purpose Curriculum for Asian Call Centres: How Theory Can Inform Practice

Science.gov (United States)

Lockwood, Jane

2012-01-01

The primary focus of this article is the investigation of how current applied linguistic research into the nature of call centre communication breakdown in business processing outsourcing (BPO) sites such as India and the Philippines, can impact English communications training program content and design for this industry. It is argued that a…

Call for Research

International Development Research Centre (IDRC) Digital Library (Canada)

Marie-Isabelle Beyer

2014-10-03

Oct 3, 2014 ... 5.Submission process. 6.Eligibility criteria. 7.Selection Process. 8. Format and requirements. 9.Evaluation criteria. 10.Country clearance requirements. 11. .... It is envisaged that through this call a single consortium will undertake 6-8 projects within a total budget of up to ... principle qualify for IDRC's support.

The function of migratory bird calls

DEFF Research Database (Denmark)

Reichl, Thomas; Andersen, Bent Bach; Larsen, Ole Næsbye

The function of migratory bird calls: do they influence orientation and navigation?   Thomas Reichl1, Bent Bach Andersen2, Ole Naesbye Larsen2, Henrik Mouritsen1   1Institute of Biology, University of Oldenburg, Oldenburg, D-26111 Oldenburg, Germany 2Institute of Biology, University of Southern...... migration and to stimulate migratory restlessness in conspecifics. We wished to test if conspecific flight calls influence the flight direction of a nocturnal migrant, the European Robin (Erithacus rubecula), i.e. if flight calls help migrants keeping course. Wild caught birds showing migratory restlessness...... the experimental bird could be activated successively to simulate a migrating Robin cruising E-W, W-E, S-N or N-S at a chosen height (mostly about 40 m), at 10 m/s and emitting Robin flight calls of 80 dB(A) at 1 m. The simulated flight of a "ding" sound served as a control. During an experiment the bird was first...

Bridging the Otolaryngology Peer Review Knowledge Gap: A Call for a Residency Development Program.

Science.gov (United States)

Schmalbach, Cecelia E

2016-07-01

Current otolaryngology literature and future scientific direction rely heavily on a rigorous peer review process. Just as manuscripts warrant thoughtful review with constructive feedback to the authors, the same can be said for critiques written by novice peer reviewers. Formal scientific peer review training programs are lacking. Recognizing this knowledge gap, Otolaryngology-Head and Neck Surgery is excited to offer its new Resident Reviewer Development Program. All otolaryngology residents who are postgraduate year 2 and above and in excellent academic standing are eligible to participate in this mentored program, during which they will conduct 6 manuscript reviews under the direction of a seasoned reviewer in his or her subspecialty area of interest. By completing reviews alongside a mentor, participants gain the required skills to master the peer review process-a first step that often leads to journal editorial board and associate editor invitations. © American Academy of Otolaryngology—Head and Neck Surgery Foundation 2016.

An empirical analysis of the corporate call decision

International Nuclear Information System (INIS)

Carlson, M.D.

1998-01-01

An economic study of the the behaviour of financial managers of utility companies was presented. The study examined whether or not an option pricing based model of the call decision does a better job of explaining callable preferred share prices and call decisions compared to other models. In this study, the Rust (1987) empirical technique was extended to include the use of information from preferred share prices in addition to the call decisions. Reasonable estimates were obtained from data of shares of the Pacific Gas and Electric Company (PGE) for the transaction costs associated with a call. It was concluded that the managers of the PGE clearly take into account the value of the option to delay the call when making their call decisions

Perceived Calling and Work Engagement Among Nurses.

Science.gov (United States)

Ziedelis, Arunas

2018-03-01

The purpose of this study was to explore the relationship of perceived calling and work engagement in nursing over and above major work environment factors. In all, 351 nurses from various health care institutions completed the survey. Data were collected about the most demanding aspects of nursing, major job resources, the degree to which nursing is perceived as a meaningful calling, work engagement, and main demographic information. Hierarchical linear regression was applied to assess the relation between perceived calling and work engagement, while controlling for demographic and work environment factors, and perceived calling was significantly related to two out of three components of nurses' work engagement. The highest association was found with dedication component, and vigor component was related insignificantly. Results have shown that perceived calling might motivate nurses to engage in their work even in burdensome environment, although possible implications for the occupational well-being of nurses themselves remains unclear.

On-call work and health: a review

Directory of Open Access Journals (Sweden)

Botterill Jackie S

2004-12-01

Full Text Available Abstract Many professions in the fields of engineering, aviation and medicine employ this form of scheduling. However, on-call work has received significantly less research attention than other work patterns such as shift work and overtime hours. This paper reviews the current body of peer-reviewed, published research conducted on the health effects of on-call work The health effects studies done in the area of on-call work are limited to mental health, job stress, sleep disturbances and personal safety. The reviewed research suggests that on-call work scheduling can pose a risk to health, although there are critical gaps in the literature.

Systems configured to distribute a telephone call, communication systems, communication methods and methods of routing a telephone call to a service representative

Science.gov (United States)

Harris, Scott H.; Johnson, Joel A.; Neiswanger, Jeffery R.; Twitchell, Kevin E.

2004-03-09

The present invention includes systems configured to distribute a telephone call, communication systems, communication methods and methods of routing a telephone call to a customer service representative. In one embodiment of the invention, a system configured to distribute a telephone call within a network includes a distributor adapted to connect with a telephone system, the distributor being configured to connect a telephone call using the telephone system and output the telephone call and associated data of the telephone call; and a plurality of customer service representative terminals connected with the distributor and a selected customer service representative terminal being configured to receive the telephone call and the associated data, the distributor and the selected customer service representative terminal being configured to synchronize, application of the telephone call and associated data from the distributor to the selected customer service representative terminal.

Assessing the effects of employee assistance programs: a review of employee assistance program evaluations.

OpenAIRE

Colantonio, A.

1989-01-01

Employee assistance programs have grown at a dramatic rate, yet the effectiveness of these programs has been called into question. The purpose of this paper was to assess the effectiveness of employee assistance programs (EAPs) by reviewing recently published EAP evaluations. All studies evaluating EAPs published since 1975 from peer-reviewed journals in the English language were included in this analysis. Each of the articles was assessed in the following areas: (a) program description (subj...

A qualitative content analysis of peer mentoring video calls in adolescents with chronic illness.

Science.gov (United States)

Ahola Kohut, Sara; Stinson, Jennifer; Forgeron, Paula; van Wyk, Margaret; Harris, Lauren; Luca, Stephanie

2018-05-01

This article endeavored to determine the topics of discussion during open-ended peer mentoring between adolescents and young adults living with chronic illness. This study occurred alongside a study of the iPeer2Peer Program. Fifty-two calls (7 mentor-mentee pairings) were audio recorded, transcribed verbatim, and analyzed using inductive coding with an additional 30 calls (21 mentor-mentee pairings) coded to ensure representativeness of the data. Three categories emerged: (1) illness impact (e.g., relationships, school/work, self-identity, personal stories), (2) self-management (e.g., treatment adherence, transition to adult care, coping strategies), and (3) non-illness-related adolescent issues (e.g., post-secondary goals, hobbies, social environments). Differences in discussed topics were noted between sexes and by diagnosis. Peer mentors provided informational, appraisal, and emotional support to adolescents.

No Call for Action? Why There Is No Union (Yet in Philippine Call Centers

Directory of Open Access Journals (Sweden)

Niklas Reese

2013-01-01

Full Text Available This contribution presents findings from a qualitative study which focused on young urban professionals in the Philippines who work(ed in international call centers – workplaces usually characterized by job insecurity and other forms of precarity, factory-like working conditions, and disembeddedness. Nevertheless, trade unions in these centers have not come into existence. Why collective action is not chosen by call center agents as an option to tackle the above mentioned problems – this is what the research project this article is based on tried to understand. After outlining some workrelated problems identified by Filipino call center agents, the article will focus on the strategies the agents employ to counter these problems (mainly accommodation and everyday resistance. By highlighting five objective and five subjective reasons (or reasons by circumstances and reasons by framing, we conclude that it is not repressive regulation policies, but rather the formative power and the internalization of discourses of rule within individual life strategies that are preventing the establishment of unions and other collective action structures.

VENVAL : a plywood mill cost accounting program

Science.gov (United States)

Henry Spelter

1991-01-01

This report documents a package of computer programs called VENVAL. These programs prepare plywood mill data for a linear programming (LP) model that, in turn, calculates the optimum mix of products to make, given a set of technologies and market prices. (The software to solve a linear program is not provided and must be obtained separately.) Linear programming finds...

Europlanet-2020 NA1 Exchange Program

Science.gov (United States)

Genzer, M.; Szego, K.; Haukka, H.; Harri, A.-M.

2017-09-01

The task of Exchange Program of NA1 is to support the activities of EPN2020 with experts and scientific exchange whenever it is needed. Short visits (up to 1 week) with the goal of improving infrastructure facilities and services offered to the scientific community are supported from this task. Since the start of the EPN2020 in September 2015 we have received and approved 14 applications for exchange program travel. More general and specifically targeted calls are planned for the future. The calls are announced on Europlanet-2020 NA1 web site.

Debugging a high performance computing program

Science.gov (United States)

Gooding, Thomas M.

2013-08-20

Methods, apparatus, and computer program products are disclosed for debugging a high performance computing program by gathering lists of addresses of calling instructions for a plurality of threads of execution of the program, assigning the threads to groups in dependence upon the addresses, and displaying the groups to identify defective threads.

Effectiveness of the Call in Beach Volleyball Attacking Play

Directory of Open Access Journals (Sweden)

Künzell Stefan

2014-12-01

Full Text Available In beach volleyball the setter has the opportunity to give her or his hitter a “call”. The call intends that the setter suggests to her or his partner where to place the attack in the opponent’s court. The effectiveness of a call is still unknown. We investigated the women’s and men’s Swiss National Beach Volleyball Championships in 2011 and analyzed 2185 attacks. We found large differences between female and male players. While men called in only 38.4% of attacks, women used calls in 85.5% of attacks. If the male players followed a given call, 63% of the attacks were successful. The success rate of attacks without any call was 55.8% and 47.6% when the call was ignored. These differences were not significant (χ2(2 = 4.55, p = 0.103. In women’s beach volleyball, the rate of successful attacks was 61.5% when a call was followed, 35% for attacks without a call, and 42.6% when a call was ignored. The differences were highly significant (χ2(2 = 23.42, p < 0.0005. Taking into account the findings of the present study, we suggested that the call was effective in women’s beach volleyball, while its effect in men’s game was unclear. Considering the quality of calls we indicate that there is a significant potential to increase the effectiveness of a call.

Call for volunteers

CERN Document Server

2008-01-01

CERN is calling for volunteers from all members of the Laboratory for organizing the two exceptional Open days.CERN is calling for volunteers from all members of the Laboratory’s personnel to help with the organisation of these two exceptional Open Days, for the visits of CERN personnel and their families on the Saturday and above all for the major public Open Day on the Sunday. As for the 50th anniversary in 2004, the success of the Open Days will depend on a large number of volunteers. All those working for CERN as well as retired members of the personnel can contribute to making this event a success. Many guides will be needed at the LHC points, for the activities at the surface and to man the reception and information points. The aim of these major Open Days is to give the local populations the opportunity to discover the fruits of almost 20 years of work carried out at CERN. We are hoping for some 2000 volunteers for the two Open Days, on the Saturday from 9 a.m. to ...

Perpetual Cancellable American Call Option

OpenAIRE

Emmerling, Thomas J.

2010-01-01

This paper examines the valuation of a generalized American-style option known as a Game-style call option in an infinite time horizon setting. The specifications of this contract allow the writer to terminate the call option at any point in time for a fixed penalty amount paid directly to the holder. Valuation of a perpetual Game-style put option was addressed by Kyprianou (2004) in a Black-Scholes setting on a non-dividend paying asset. Here, we undertake a similar analysis for the perpetua...

Leveraging management information in improving call centre productivity

Directory of Open Access Journals (Sweden)

Manthisana Mosese

2016-04-01

Objectives: This research explored the use of management information and its impact on two fundamental functions namely, improving productivity without compromising the quality of service, in the call centre of a well-known South African fashion retailer, Edcon. Following the implementation of the call centre technology project the research set out to determine how Edcon can transform their call centre to improve productivity and customer service through effective utilisation of their management information. Method: Internal documents and reports were analysed to provide the basis of evaluation between the measures of productivity prior to and post the implementation of a technology project at Edcon’s call centre. Semi-structured in-depth and group interviews were conducted to establish the importance and use of management information in improving productivity and customer service. Results: The results indicated that the availability of management information has indeed contributed to improved efficiency at the Edcon call centre. Although literature claims that there is a correlation between a call centre technology upgrade and improvement in performance, evident in the return on investment being realised within a year or two of implementation, it fell beyond the scope of this study to investigate the return on investment for Edcon’s call centre. Conclusion: Although Edcon has begun realising benefits in improved productivity in their call centre from their available management information, information will continue to play a crucial role in supporting management with informed decisions that will improve the call centre operations. [pdf to follow

Smart Grid Technology and Consumer Call Center Readiness

OpenAIRE

Schamber, Kelsey L.

2010-01-01

The following reasearch project deals with utility call center readiness to address customer concerns and questions about the Smart Grid and smart meter technology. Since consumer engagement is important for the benefits of the Smart Grid to be realized, the readiness and ability of utilities to answer consumer questions is an important issue. Assessing the readiness of utility call centers to address pertinant customer concerns was accomplished by calling utility call centers with Smart Grid...

Medical Decisions of Pediatric Residents Turn Riskier after a 24-Hour Call with No Sleep.

Science.gov (United States)

Aran, Adi; Wasserteil, Netanel; Gross, Itai; Mendlovic, Joseph; Pollak, Yehuda

2017-01-01

Despite a gradual reduction in the workload during residency, 24-hour calls are still an integral part of most training programs. While sleep deprivation increases the risk propensity, the impact on medical risk taking has not been studied. This study aimed to assess the clinical decision making and psychomotor performance of pediatric residents following a limited nap time during a 24-hour call. A neurocognitive battery (IntegNeuro) and a medical decision questionnaire were completed by 44 pediatric residents at 2 time points: after a 24-hour call and following 3 nights with no calls (sleep ≥5 hours). To monitor sleep, residents wore actigraphs and completed sleep logs. Nap time during the shift was change in risk taking) or 2 to 3 hours (4% decreased risk taking) (difference between groups, P = 0.001). Risk-taking tendency inversely correlated with sustained attention scores (Pearson = -0.433, P = 0.003). Sustained attention was the neurocognitive domain most affected by sleep deprivation (effect size = 0.29, P = 0.025). This study suggests that residents napping less than an hour during a night shift are prone to riskier clinical decisions. Hence, enabling residents to nap at least 1 hour during shifts is recommended. © The Author(s) 2016.

Mobile telephones: a comparison of radiated power between 3G VoIP calls and 3G VoCS calls.

Science.gov (United States)

Jovanovic, Dragan; Bragard, Guillaume; Picard, Dominique; Chauvin, Sébastien

2015-01-01

The purpose of this study is to assess the mean RF power radiated by mobile telephones during voice calls in 3G VoIP (Voice over Internet Protocol) using an application well known to mobile Internet users, and to compare it with the mean power radiated during voice calls in 3G VoCS (Voice over Circuit Switch) on a traditional network. Knowing that the specific absorption rate (SAR) is proportional to the mean radiated power, the user's exposure could be clearly identified at the same time. Three 3G (High Speed Packet Access) smartphones from three different manufacturers, all dual-band for GSM (900 MHz, 1800 MHz) and dual-band for UMTS (900 MHz, 1950 MHz), were used between 28 July and 04 August 2011 in Paris (France) to make 220 two-minute calls on a mobile telephone network with national coverage. The places where the calls were made were selected in such a way as to describe the whole range of usage situations of the mobile telephone. The measuring equipment, called "SYRPOM", recorded the radiation power levels and the frequency bands used during the calls with a sampling rate of 20,000 per second. In the framework of this study, the mean normalised power radiated by a telephone in 3G VoIP calls was evaluated at 0.75% maximum power of the smartphone, compared with 0.22% in 3G VoCS calls. The very low average power levels associated with use of 3G devices with VoIP or VoCS support the view that RF exposure resulting from their use is far from exceeding the basic restrictions of current exposure limits in terms of SAR.

Computer Vision Syndrome among Call Center Employees at Telecommunication Company in Bandung

Directory of Open Access Journals (Sweden)

Ghea Nursyifa

2016-06-01

Full Text Available Background: The occurrence of Computer Vision Syndrome (CVS at the workplace has increased within decades due to theprolonged use of computers. Knowledge of CVS is necessary in order to develop an awareness of how to prevent and alleviate itsprevalence . The objective of this study was to assess the knowledge of CVS among call center employees and to explore the most frequent CVS symptom experienced by the workers. Methods: A descriptive cross sectional study was conducted during the period of September to November 2014 at Telecommunication Company in Bandung using a questionnaire consisting of 30 questions. Out of the 30 questions/statements, 15 statements were about knowledge of CVS and other 15 questions were about the occurrence of CVS and its symptoms. In this study 125 call center employees participated as respondents using consecutive sampling. The level of knowledge was divided into 3 categories: good (76–100%, fair (75–56% and poor (<56%. The collected data was presented in frequency tabulation. Results: There was 74.4% of the respondents had poor knowledge of CVS. The most symptom experienced by the respondents was asthenopia. Conclusions: The CVS occurs in call center employees with various symptoms and signs. This situation is not supported by good knowledge of the syndrome which can hamper prevention programs.

The Wireless Nursing Call System

DEFF Research Database (Denmark)

Jensen, Casper Bruun

2006-01-01

This paper discusses a research project in which social scientists were involved both as analysts and supporters during a pilot with a new wireless nursing call system. The case thus exemplifies an attempt to participate in developing dependable health care systems and offers insight into the cha......This paper discusses a research project in which social scientists were involved both as analysts and supporters during a pilot with a new wireless nursing call system. The case thus exemplifies an attempt to participate in developing dependable health care systems and offers insight...

The renewal of hydroelectric concessions in competitive call

International Nuclear Information System (INIS)

2013-01-01

This document discusses various issues associated with the planned competitive call on the French hydraulic power plants. The principles of this competitive call for hydroelectric concessions are first addressed: administrative regime of concessions, competitive call process, criteria of selection of the concession holder, case of 'concession of valleys', potential competitors. It outlines and discusses the difficulties of this competitive call: France is the single country to implement this procedure; it concerns a national asset; it questions the guarantee of a future use of equipment at best for the energy benefits of French consumers; the competitive call is a nice idea indeed but extremely complex. A note discusses the profitability aspects of Plants for Transfer of Energy by Pumping

Assertion checking environment (ACE) for formal verification of C programs

International Nuclear Information System (INIS)

Sharma, Babita; Dhodapkar, S.D.; Ramesh, S.

2003-01-01

In this paper we describe an Assertion Checking Environment (ACE) for compositional verification of programs, which are written in an industrially sponsored safe subset of C programming language called MISRA C [Guidelines for the Use of the C Language in Vehicle Based Software, 1998]. The theory is based on Hoare logic [Commun. ACM 12 (1969) 576] and the C programs are verified using static assertion checking technique. First the functional specifications of the program, captured in the form of pre- and post-conditions for each C function, are derived from the specifications. These pre- and post-conditions are then introduced as assertions (also called annotations or formal comments) in the program code. The assertions are then proved formally using ACE and theorem proving tool called Stanford Temporal Prover [The Stanford Temporal Prover User's Manual, 1998]. ACE has been developed by us and consists mainly of a translator c2spl, a GUI and some utility programs. The technique and tools developed are targeted towards verification of real-time embedded software

Alma-0: an imperative language that supports declarative programming

NARCIS (Netherlands)

K.R. Apt (Krzysztof); J. Brunekreef; V. Partinton; A. Schaerf

1997-01-01

textabstractWe describe here an implemented small programming language, called Alma, that augments the expressive power of imperative programming by a limited number of features inspired by the logic programming paradigm. These additions encourage declarative programming and make it a more

EGS4 benchmark program

International Nuclear Information System (INIS)

Yasu, Y.; Hirayama, H.; Namito, Y.; Yashiro, S.

1995-01-01

This paper proposes EGS4 Benchmark Suite which consists of three programs called UCSAMPL4, UCSAMPL4I and XYZDOS. This paper also evaluates optimization methods of recent RISC/UNIX systems, such as IBM, HP, DEC, Hitachi and Fujitsu, for the benchmark suite. When particular compiler option and math library were included in the evaluation process, system performed significantly better. Observed performance of some of the RISC/UNIX systems were beyond some so-called Mainframes of IBM, Hitachi or Fujitsu. The computer performance of EGS4 Code System on an HP9000/735 (99MHz) was defined to be the unit of EGS4 Unit. The EGS4 Benchmark Suite also run on various PCs such as Pentiums, i486 and DEC alpha and so forth. The performance of recent fast PCs reaches that of recent RISC/UNIX systems. The benchmark programs have been evaluated with correlation of industry benchmark programs, namely, SPECmark. (author)

Linking Calling Orientations to Organizational Attachment via Organizational Instrumentality

Science.gov (United States)

Cardador, M. Teresa; Dane, Erik; Pratt, Michael G.

2011-01-01

Despite an emerging interest in callings, researchers know little about whether calling orientations matter in the workplace. We explore the under-examined relationship between a calling orientation and employees' attachment to their organizations. Although some theory suggests that callings may be negatively related to organizational attachment,…

The Influence of Judgment Calls on Meta-Analytic Findings.

Science.gov (United States)

Tarrahi, Farid; Eisend, Martin

2016-01-01

Previous research has suggested that judgment calls (i.e., methodological choices made in the process of conducting a meta-analysis) have a strong influence on meta-analytic findings and question their robustness. However, prior research applies case study comparison or reanalysis of a few meta-analyses with a focus on a few selected judgment calls. These studies neglect the fact that different judgment calls are related to each other and simultaneously influence the outcomes of a meta-analysis, and that meta-analytic findings can vary due to non-judgment call differences between meta-analyses (e.g., variations of effects over time). The current study analyzes the influence of 13 judgment calls in 176 meta-analyses in marketing research by applying a multivariate, multilevel meta-meta-analysis. The analysis considers simultaneous influences from different judgment calls on meta-analytic effect sizes and controls for alternative explanations based on non-judgment call differences between meta-analyses. The findings suggest that judgment calls have only a minor influence on meta-analytic findings, whereas non-judgment call differences between meta-analyses are more likely to explain differences in meta-analytic findings. The findings support the robustness of meta-analytic results and conclusions.

Optimal scheduling in call centers with a callback option

OpenAIRE

Legros , Benjamin; Jouini , Oualid; Koole , Ger

2016-01-01

International audience; We consider a call center model with a callback option, which allows to transform an inbound call into an outbound one. A delayed call, with a long anticipated waiting time, receives the option to be called back. We assume a probabilistic customer reaction to the callback offer (option). The objective of the system manager is to characterize the optimal call scheduling that minimizes the expected waiting and abandonment costs. For the single-server case, we prove that ...

Flight calls and orientation

DEFF Research Database (Denmark)

Larsen, Ole Næsbye; Andersen, Bent Bach; Kropp, Wibke

2008-01-01

flight calls was simulated by sequential computer controlled activation of five loudspeakers placed in a linear array perpendicular to the bird's migration course. The bird responded to this stimulation by changing its migratory course in the direction of that of the ‘flying conspecifics' but after about......  In a pilot experiment a European Robin, Erithacus rubecula, expressing migratory restlessness with a stable orientation, was video filmed in the dark with an infrared camera and its directional migratory activity was recorded. The flight overhead of migrating conspecifics uttering nocturnal...... 30 minutes it drifted back to its original migration course. The results suggest that songbirds migrating alone at night can use the flight calls from conspecifics as additional cues for orientation and that they may compare this information with other cues to decide what course to keep....

Lunar phases and crisis center telephone calls.

Science.gov (United States)

Wilson, J E; Tobacyk, J J

1990-02-01

The lunar hypothesis, that is, the notion that lunar phases can directly affect human behavior, was tested by time-series analysis of 4,575 crisis center telephone calls (all calls recorded for a 6-month interval). As expected, the lunar hypothesis was not supported. The 28-day lunar cycle accounted for less than 1% of the variance of the frequency of crisis center calls. Also, as hypothesized from an attribution theory framework, crisis center workers reported significantly greater belief in lunar effects than a non-crisis-center-worker comparison group.

Correlates of Gay-Related Name-Calling in Schools

Science.gov (United States)

Slaatten, Hilde; Hetland, Jørn; Anderssen, Norman

2015-01-01

The aim of this study was to examine whether attitudes about gay-related name-calling, social norms concerning gay-related name-calling among co-students, teacher intervention, and school-related support would predict whether secondary school pupils had called another pupil a gay-related name during the last month. A total of 921 ninth-grade…

47 CFR 90.241 - Radio call box operations.

Science.gov (United States)

2010-10-01

... remains on for a period in excess of three minutes. The automatic cutoff system must be designed so the... Public Safety Pool for highway call box systems subject to the following requirements: (1) Call box... effective radiated power (ERP). (3) The height of a call box antenna may not exceed 6.1 meters (20 feet...

A Temporal Concurrent Constraint Programming Calculus

DEFF Research Database (Denmark)

Palamidessi, Catuscia; Valencia Posso, Frank Darwin

2001-01-01

The tcc model is a formalism for reactive concurrent constraint programming. In this paper we propose a model of temporal concurrent constraint programming which adds to tcc the capability of modeling asynchronous and non-deterministic timed behavior. We call this tcc extension the ntcc calculus...

Coaching "Callings" throughout the Adult Life Cycle.

Science.gov (United States)

Hudson, Frederic M.

2001-01-01

The process of "callings" continues throughout life. Coaching can connect the present to the future in a meaningful way. Callings represent a value shift requiring revision of the nature and scope of one's central purpose in life and meaningful activities. (JOW)

Robust Programming by Example

OpenAIRE

Bishop , Matt; Elliott , Chip

2011-01-01

Part 2: WISE 7; International audience; Robust programming lies at the heart of the type of coding called “secure programming”. Yet it is rarely taught in academia. More commonly, the focus is on how to avoid creating well-known vulnerabilities. While important, that misses the point: a well-structured, robust program should anticipate where problems might arise and compensate for them. This paper discusses one view of robust programming and gives an example of how it may be taught.

MAGNETIC ACTIVITY CYCLES IN THE EXOPLANET HOST STAR ε ERIDANI

International Nuclear Information System (INIS)

Metcalfe, T. S.; Mathur, S.; Buccino, A. P.; Mauas, P. J. D.; Petrucci, R.; Brown, B. P.; Soderblom, D. R.; Henry, T. J.; Hall, J. C.; Basu, S.

2013-01-01

The active K2 dwarf ε Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in ε Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95 ± 0.03 years and 12.7 ± 0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called 'active' and 'inactive' sequences as proposed by Böhm-Vitense. Finally, based on the observed properties of ε Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.

Performance indicators for call centers with impatience

NARCIS (Netherlands)

Jouini, O.; Koole, G.M.; Roubos, A.

2013-01-01

An important feature of call center modeling is the presence of impatient customers. This article considers single-skill call centers including customer abandonments. A number of different service-level definitions are structured, including all those used in practice, and the explicit computation of

Calling, is there anything special about it?

African Journals Online (AJOL)

2016-07-15

Jul 15, 2016 ... when a pastor is installed or a new candidate is ordained, 'The one who calls you is faithful .... extension to secular work of the dignity of a calling' (Fowler ... For Luther, therefore, the private life of devotion exercised in the.

Ultrasound call detection in capybara

Directory of Open Access Journals (Sweden)

Selene S.C. Nogueira

2012-07-01

Full Text Available The vocal repertoire of some animal species has been considered a non-invasive tool to predict distress reactivity. In rats ultrasound emissions were reported as distress indicator. Capybaras[ vocal repertoire was reported recently and seems to have ultrasound calls, but this has not yet been confirmed. Thus, in order to check if a poor state of welfare was linked to ultrasound calls in the capybara vocal repertoire, the aim of this study was to track the presence of ultrasound emissions in 11 animals under three conditions: 1 unrestrained; 2 intermediately restrained, and 3 highly restrained. The ultrasound track identified frequencies in the range of 31.8±3.5 kHz in adults and 33.2±8.5 kHz in juveniles. These ultrasound frequencies occurred only when animals were highly restrained, physically restrained or injured during handling. We concluded that these calls with ultrasound components are related to pain and restraint because they did not occur when animals were free of restraint. Thus we suggest that this vocalization may be used as an additional tool to assess capybaras[ welfare.

Relabeling the Medications We Call Antidepressants

Directory of Open Access Journals (Sweden)

David Antonuccio

2012-01-01

Full Text Available This paper raises the question about whether the data on the medications we call antidepressants justify the label of antidepressant. The authors argue that a true antidepressant should be clearly superior to placebo, should offer a risk/benefit balance that exceeds that of alternative treatments, should not increase suicidality, should not increase anxiety and agitation, should not interfere with sexual functioning, and should not increase depression chronicity. Unfortunately, these medications appear to fall short on all of these dimensions. Many of the “side effects” of these medications have larger effect sizes than the antidepressant effect size. To call these medications antidepressants may make sense from a marketing standpoint but may be misleading from a scientific perspective. Consumers deserve a label that more accurately reflects the data on the largest effects and helps them understand the range of effects from these medications. In other words, it may make just as much sense to call these medications antiaphrodisiacs as antidepressants because the negative effects on libido and sexual functioning are so common. It can be argued that a misleading label may interfere with our commitment to informed consent. Therefore, it may be time to stop calling these medications antidepressants.

Directory of Post-Secondary Retailing and Marketing Vocational Programs.

Science.gov (United States)

American Vocational Association, Inc., Washington, DC.

This directory lists 357 general and 135 special retailing and marketing vocational programs at the post secondary level. Institutions vary somewhat in the identification of general programs; for example, they may be called retailing, merchandising, marketing, mid-management, or distributive education programs. Specialized programs offered by…

The Barbados Emergency Ambulance Service: High Frequency of Nontransported Calls

Directory of Open Access Journals (Sweden)

Sherwin E. Phillips

2012-01-01

Full Text Available Objectives. There are no published studies on the Barbados Emergency Ambulance Service and no assessment of the calls that end in nontransported individuals. We describe reasons for the nontransport of potential clients. Methods. We used the Emergency Medical Dispatch (Medical Priority Dispatch System instrument, augmented with five local call types, to collect information on types of calls. The calls were categorised under 7 headings. Correlations between call types and response time were calculated. Results. Most calls were from the category medical (54%. Nineteen (19% percent of calls were in the non-transported category. Calls from call type Cancelled accounted for most of these and this was related to response time, while Refused service was inversely related (. Conclusions. The Barbados Ambulance Service is mostly used by people with a known illness and for trauma cases. One-fifth of calls fall into a category where the ambulance is not used often due to cancellation which is related to response time. Other factors such as the use of alternative transport are also important. Further study to identify factors that contribute to the non-transported category of calls is necessary if improvements in service quality are to be made.

Mini Project Programming Exams

DEFF Research Database (Denmark)

Nørmark, Kurt; Thomsen, Lone Leth; Torp, Kristian

2008-01-01

A number of different types of final programming exams used or considered at the Department of Computer Science, Aalborg University, are identified and analyzed. Based on this analysis, a new type of programming exam is introduced called a Mini Project Programming (MIP) exam. MIP is a group...... years. The MIP exam is a compromise between (1) a long problem-based project exam and (2) a short oral or written programming exam. It is concluded that the strengths of MIP are the high degree of realism in the exam assignment and comprehensiveness relative to the course syllabus. The main challenge...

Make a 21st century phone call

CERN Multimedia

Katarina Anthony

2014-01-01

Want to avoid roaming charges? Click to call anyone at CERN? How about merging your CERN landline with your existing smartphone? That's all easily done with Lync, CERN's new opt-in service that can take your calls to the next level.   The Lync application on Windows (left) and iPhone (right). Lync unites CERN's traditional telephone service with the digital sphere. "Lync gives you the gift of mobility, by letting you access your CERN landline on the go," explains Pawel Grzywaczewski, service manager of the Lync system. "Once you've registered your CERN telephone with the service, you can run the Lync application and make calls from a range of supported devices. No matter where you are in the world - be it simply out to lunch or off at an international conference - you can make a CERN call as though you were in the office. All you need is an Internet connection!" Following a recent upgrade, CERN's Lync service now has...

Turnover intentions in a call center: The role of emotional dissonance, job resources, and job satisfaction.

Directory of Open Access Journals (Sweden)

Margherita Zito

Full Text Available Turnover intentions refer to employees' intent to leave the organization and, within call centers, it can be influenced by factors such as relational variables or the perception of the quality of working life, which can be affected by emotional dissonance. This specific job demand to express emotions not felt is peculiar in call centers, and can influence job satisfaction and turnover intentions, a crucial problem among these working contexts. This study aims to detect, within the theoretical framework of the Job Demands-Resources Model, the role of emotional dissonance (job demand, and two resources, job autonomy and supervisors' support, in the perception of job satisfaction and turnover intentions among an Italian call center.The study involved 318 call center agents of an Italian Telecommunication Company. Data analysis first performed descriptive statistics through SPSS 22. A path analysis was then performed through LISREL 8.72 and tested both direct and indirect effects.Results suggest the role of resources in fostering job satisfaction and in decreasing turnover intentions. Emotional dissonance reveals a negative relation with job satisfaction and a positive relation with turnover. Moreover, job satisfaction is negatively related with turnover and mediates the relationship between job resources and turnover.This study contributes to extend the knowledge about the variables influencing turnover intentions, a crucial problem among call centers. Moreover, the study identifies theoretical considerations and practical implications to promote well-being among call center employees. To foster job satisfaction and reduce turnover intentions, in fact, it is important to make resources available, but also to offer specific training programs to make employees and supervisors aware about the consequences of emotional dissonance.

Turnover intentions in a call center: The role of emotional dissonance, job resources, and job satisfaction.

Science.gov (United States)

Zito, Margherita; Emanuel, Federica; Molino, Monica; Cortese, Claudio Giovanni; Ghislieri, Chiara; Colombo, Lara

2018-01-01

Turnover intentions refer to employees' intent to leave the organization and, within call centers, it can be influenced by factors such as relational variables or the perception of the quality of working life, which can be affected by emotional dissonance. This specific job demand to express emotions not felt is peculiar in call centers, and can influence job satisfaction and turnover intentions, a crucial problem among these working contexts. This study aims to detect, within the theoretical framework of the Job Demands-Resources Model, the role of emotional dissonance (job demand), and two resources, job autonomy and supervisors' support, in the perception of job satisfaction and turnover intentions among an Italian call center. The study involved 318 call center agents of an Italian Telecommunication Company. Data analysis first performed descriptive statistics through SPSS 22. A path analysis was then performed through LISREL 8.72 and tested both direct and indirect effects. Results suggest the role of resources in fostering job satisfaction and in decreasing turnover intentions. Emotional dissonance reveals a negative relation with job satisfaction and a positive relation with turnover. Moreover, job satisfaction is negatively related with turnover and mediates the relationship between job resources and turnover. This study contributes to extend the knowledge about the variables influencing turnover intentions, a crucial problem among call centers. Moreover, the study identifies theoretical considerations and practical implications to promote well-being among call center employees. To foster job satisfaction and reduce turnover intentions, in fact, it is important to make resources available, but also to offer specific training programs to make employees and supervisors aware about the consequences of emotional dissonance.

Turnover intentions in a call center: The role of emotional dissonance, job resources, and job satisfaction

Science.gov (United States)

Zito, Margherita; Molino, Monica; Cortese, Claudio Giovanni; Ghislieri, Chiara; Colombo, Lara

2018-01-01

Background Turnover intentions refer to employees’ intent to leave the organization and, within call centers, it can be influenced by factors such as relational variables or the perception of the quality of working life, which can be affected by emotional dissonance. This specific job demand to express emotions not felt is peculiar in call centers, and can influence job satisfaction and turnover intentions, a crucial problem among these working contexts. This study aims to detect, within the theoretical framework of the Job Demands-Resources Model, the role of emotional dissonance (job demand), and two resources, job autonomy and supervisors’ support, in the perception of job satisfaction and turnover intentions among an Italian call center. Method The study involved 318 call center agents of an Italian Telecommunication Company. Data analysis first performed descriptive statistics through SPSS 22. A path analysis was then performed through LISREL 8.72 and tested both direct and indirect effects. Results Results suggest the role of resources in fostering job satisfaction and in decreasing turnover intentions. Emotional dissonance reveals a negative relation with job satisfaction and a positive relation with turnover. Moreover, job satisfaction is negatively related with turnover and mediates the relationship between job resources and turnover. Conclusion This study contributes to extend the knowledge about the variables influencing turnover intentions, a crucial problem among call centers. Moreover, the study identifies theoretical considerations and practical implications to promote well-being among call center employees. To foster job satisfaction and reduce turnover intentions, in fact, it is important to make resources available, but also to offer specific training programs to make employees and supervisors aware about the consequences of emotional dissonance. PMID:29401507

Intelligent programs-expert systems

Energy Technology Data Exchange (ETDEWEB)

Gledhill, V X

1982-01-01

In recent years, computer scientists have developed what are called expert systems. These programs have three fundamental components: a knowledge base, which changes with experience; an inference engine which enables the program to make decisions; and an interface that allows the program to communicate with the person using the system. Expert systems have been developed successfully in areas such as medical diagnosis, geology, and computer maintenance. This paper describes the evolution and basic principles of expert systems and give some examples of their use.

Sleep Quality of Call Handlers Employed in International Call Centers in National Capital Region of Delhi, India

Directory of Open Access Journals (Sweden)

JD Raja

2016-10-01

suspicion of insomnia or suspected insomnia; the rest had no sleep problem. Smoking, poor social support, heavy workload, lack of relaxation facility at office, and prolonged travel time to office were independent predictors of sleep quality (p<0.05. Conclusion: Call handlers have to compromise upon their sleep owing to the contemporary work settings in call centers. Safeguarding their health becomes an occupational health challenge to public health specialists.

Consumer Experiences Calling Toll-Free Corporate Hotlines.

Science.gov (United States)

Martin, Charles L.; Smart, Denise T.

1994-01-01

Finds that dimensions that contribute to caller satisfaction (of toll-free corporate hotlines) included operator characteristics such as knowledge, courtesy, and interest; specific behaviors such as apologizing for a problem, thanking the consumer for calling, and encouraging them to call again; and reducing time placed on "hold." (SR)

Call center performance with direct response advertising

NARCIS (Netherlands)

M. Kiygi Calli (Meltem); M. Weverbergh (Marcel); Ph.H.B.F. Franses (Philip Hans)

2017-01-01

textabstractThis study investigates the manpower planning and the performance of a national call center dealing with car repairs and on the road interventions. We model the impact of advertising on the capacity required. The starting point is a forecasting model for the incoming calls, where we take

Advertisement call of Scinax camposseabrai (Bokermann, 1968) (Anura: Hylidae), with comments on the call of three species of the Scinax ruber clade.

Science.gov (United States)

Novaes, Gabriel; Zina, Juliana

2016-02-25

Scinax camposseabrai was allocated into the Scinax ruber clade by Caramaschi & Cardoso (2006) by overall similarities as snout not pointed, breeding in open areas, and an advertisement calls with multipulsed notes. This assumption about the call was based solely on an onomatopoeia provided by Bokermann (1968). Herein we provide a formal description of the advertisement call of S. camposseabrai and compare it with described calls of other S. ruber clade species. Additionally, we provide descriptions of the advertisement calls of three sympatric species of the S. ruber clade: S. eurydice (Bokermann), S. pachycrus (Miranda-Ribeiro) and S. cf. x-signatus.

[Emotional well-being and discomfort at work in call center].

Science.gov (United States)

Emanuel, Federica; Colombo, Lara; Ghislieri, Chiara

2014-01-01

The theme of well-being and discomfort at work has attracted increasing interest in recent years. The present study, according to Job Demands-Resources model (JD-R), inquires the effects of personal (optimism, internal locus of control) and organizational resources (job autonomy, supervisors and colleagues support) and general (work-to-family conflict, workload) and context specific demands (emotional dissonance) on emotional well-being and discomfort at work in call centre employees. This research was conducted through an online questionnaire, composed by measures present in scientific literature, filled out individually by call center agents (N = 507) of the same telecommunication firm. Data analysis (PASW 18) provides: descriptive statistics, correlations and multiple regressions. Personal and organizational resources improve emotional well-being at work, except for colleagues support. Optimism and supervisors support reduce emotional discomfort at work. Among organizational demands, work-family conflict and emotional dissonance increase emotional discomfort at work and, to a lesser extent, reduce the emotional well-being at work. The results, according to theoretical model, highlight the different role of demands and resources on emotional well-being and discomfort at work. The results suggest organizational politics and investments to promote emotional well-being at work, in particular training program to support emotional skills, training for supervisors, increasing job autonomy and support to work-family balance.

Environmental constraints and call evolution in torrent-dwelling frogs.

Science.gov (United States)

Goutte, Sandra; Dubois, Alain; Howard, Samuel D; Marquez, Rafael; Rowley, Jodi J L; Dehling, J Maximilian; Grandcolas, Philippe; Rongchuan, Xiong; Legendre, Frédéric

2016-04-01

Although acoustic signals are important for communication in many taxa, signal propagation is affected by environmental properties. Strong environmental constraints should drive call evolution, favoring signals with greater transmission distance and content integrity in a given calling habitat. Yet, few empirical studies have verified this prediction, possibly due to a shortcoming in habitat characterization, which is often too broad. Here we assess the potential impact of environmental constraints on the evolution of advertisement call in four groups of torrent-dwelling frogs in the family Ranidae. We reconstruct the evolution of calling site preferences, both broadly categorized and at a finer scale, onto a phylogenetic tree for 148 species with five markers (∼3600 bp). We test models of evolution for six call traits for 79 species with regard to the reconstructed history of calling site preferences and estimate their ancestral states. We find that in spite of existing morphological constraints, vocalizations of torrent-dwelling species are most probably constrained by the acoustic specificities of torrent habitats and particularly their high level of ambient noise. We also show that a fine-scale characterization of calling sites allows a better perception of the impact of environmental constraints on call evolution. © 2016 The Author(s). Evolution © 2016 The Society for the Study of Evolution.

Attitude of Farmers towards Kisan Call Centres

Directory of Open Access Journals (Sweden)

Shely Mary Koshy

2017-09-01

Full Text Available The present study was conducted to measure the attitude of farmers in Kerala, India towards Kisan Call Centre (KCC. Kisan Call Centre provides free agricultural advisory services to every citizen involved in agriculture through a toll free number. One hundred and fifty farmers who have utilized the Kisan Call Centre service were selected from the database of KCC. The results showed that the respondents had moderately favourable attitude towards KCC followed by highly favourable attitude. The variables digital divide, temporal awareness on KCC, satisfaction towards KCC and utilization of KCC were found to have a positive correlation with the attitude of respondents towards KCC.

Too close to call

DEFF Research Database (Denmark)

Kurrild-Klitgaard, Peter

2012-01-01

a number of other frequent explanations and is found to be quite robust. When augmented with approval ratings for incumbent presidents, the explanatory power increases to 83 pct. and only incorrectly calls one of the last 15 US presidential elections. Applied to the 2012 election as a forecasting model...

A call for surveys

DEFF Research Database (Denmark)

Bernstein, Philip A.; Jensen, Christian S.; Tan, Kian-Lee

2012-01-01

The database field is experiencing an increasing need for survey papers. We call on more researchers to set aside time for this important writing activity. The database field is growing in population, scope of topics covered, and the number of papers published. Each year, thousands of new papers ...

Call centers with a postponed callback offer

NARCIS (Netherlands)

B. Legros (Benjamin); S. Ding (Sihan); R.D. van der Mei (Rob); O. Jouini (Oualid)

2017-01-01

textabstractWe study a call center model with a postponed callback option. A customer at the head of the queue whose elapsed waiting time achieves a given threshold receives a voice message mentioning the option to be called back later. This callback option differs from the traditional ones found in

Ostomy Home Skills Program

Medline Plus

Full Text Available ... Call for Abstracts Hotel Accommodations Travel Information 2017 Presentations Education Education Overview Division of Education About the ... the College Maintenance of Certification Quality Quality Quality Electronic Health Records (EHR) Incentive Program Physician Quality Reporting ...

Effect of an art brut therapy program called go beyond the schizophrenia (GBTS) on prison inmates with schizophrenia in mainland China-A randomized, longitudinal, and controlled trial.

Science.gov (United States)

Qiu, Hong-Zhong; Ye, Zeng-Jie; Liang, Mu-Zi; Huang, Yue-Qun; Liu, Wei; Lu, Zhi-Dong

2017-09-01

Creative arts therapies are proven to promote an interconnection between body and mind, but there are major obstacles for providing therapeutic services in prisons due to inmates' inherent mistrust for verbal disclosure and rigid self-defenses, especially among inmates with schizophrenia. Thus, we developed a structured and quantitative art brut therapy program called go beyond the schizophrenia to actually measure the benefits of art therapy on prison inmates in mainland China. Upon completion of the program, the intervention group reported a decrease in anxiety, depression, anger, and negative psychiatric symptoms and showed better compliance with rules, socialization with peers, compliance with medications, and regular sleeping patterns after 16 weekly sessions of go beyond the schizophrenia. This article concludes that the art brut therapy was effective for the inmates with schizophrenia in mainland China and provides encouraging data on how to enhance mental health for inmates with schizophrenia. Art brut therapy can reduce emotional distress and negative psychiatric symptoms among Chinese inmates. Arts brut therapy can enhance Chinese inmates' compliance with rules, socialization with peers, compliance with medicines, and regular sleeping patterns. Arts brut therapy in conjunction with medication is highly recommended for recovery of Chinese inmates with schizophrenia, especially for patients with negative symptoms. Copyright © 2017 John Wiley & Sons, Ltd.

Outpatient outcomes and satisfaction in pediatric population: data from the postoperative phone call.

Science.gov (United States)

Brenn, B Randall; Choudhry, Dinesh K; Sacks, Karen

2016-02-01

Quality and patient/parent satisfaction are goals for pediatric perioperative services. As part of the implementation of our operating room electronic medical record (EMR), a postoperative phone call questionnaire was developed to assess patients discharged after outpatient surgery. The goal of this initiative was to determine the rate of common postoperative complications and understand reasons for patient/parent dissatisfaction. Institutional Review Board approval was obtained for chart review. The postoperative phone call survey was attempted by our postanesthesia care unit nursing staff on all pediatric outpatients. The call was attempted for 3 days. From 2009 to 2013, more than 37 000 phone records existed in our EMR, Epic Optime (Epic Systems, Verona, WI). These data were extracted to a business intelligence (BI) program, QlikView (Qliktech, Radnor, PA, USA). A BI dashboard was constructed to obtain phone call results for any given time frame from monthly to spanning several years. Complications were logged as 4-point severity rating scales (none, mild, moderate, severe) with descriptions for each level. The BI dashboard calculated the overall and rates by severity for the following: (i) nausea, (ii) vomiting, (iii) pain, (iv) bleeding, (v) hoarseness, and (vi) difficulty eating. Of 42 688 outpatient cases, 37 620 postoperative phone calls were completed for an overall response rate of 88%. Pain, at 11.1%, was the highest reported postoperative complication. The rate of dissatisfaction was reported to be 0.31%. Most patients reporting dissatisfaction (62%) did not report any complications. Contingency coefficient showed that there was little relationship between satisfaction and presence of complications. A postoperative phone survey is cost-effective and appreciated by patients. We found that satisfaction with our perioperative services was not related to the rates of reported complications. Although reducing complications is of utmost importance

The Role of Analyst Conference Calls in Capital Markets

NARCIS (Netherlands)

E.M. Roelofsen (Erik)

2010-01-01

textabstractMany firms conduct a conference call with analysts shortly after the quarterly earnings announcement. In these calls, management discusses the completed quarter, and analysts can ask questions. Due to SEC requirements, conference calls in the United States are virtually always live

Revisiting the rotating call schedule in less than 80 hours per week.

Science.gov (United States)

Roses, Robert E; Foley, Paul J; Paulson, Emily C; Pray, Lori; Kelz, Rachel R; Williams, Noel N; Morris, Jon B

2009-01-01

The Accreditation Council for Graduate Medical Education (ACGME) work-hour restrictions have prompted many surgical training programs to adopt a night-float resident coverage system (NF). Dissatisfaction with NF prompted us to transition to a rotating junior resident call model (Q4) with 24-hour call shifts at the outset of the 2007-2008 academic year. We performed a prospective study to determine the influence of this transition on resident education, morale, and quality of life, as well as on ACGME work rule compliance and American Board of Surgery In-Training Examination (ABSITE) scores. Residents were surveyed after 1 year of NF and again 1 year after the introduction of Q4. Responses to a series of statements about the influence of the call model (NF or Q4) on educational opportunities and morale were solicited. The survey used a 5-point Likert response scale (1 = complete disagreement to 5 = complete agreement). Median values of participant responses were calculated and compared using the Wilcoxon rank-sum test. Compliance with ACGME work rules, ABSITE scores, and operative case logs from the 2006-2007 and 2007-2008 academic years were also compared. Residents were significantly more enthusiastic about Q4 compared with NF, particularly when asked about the influence these systems had on morale (median response = 4.0 [Q4] compared with 2.0 [NF]; p = 0.001) and engagement of residents by the teaching faculty (median response = 4.0 [Q4] compared with 1.0 [NF]; p = 0.001). Case logs revealed a similar operative experience for first-year residents irrespective of the call schedule (p = 0.51). Excellent compliance with ACGME work rules was maintained as reflected by the percentage of monthly 80-hour violations per resident months worked (3% [Q4] compared with 0.7% [NF]). No difference was observed in the ABSITE scores of first-year residents (a mean percentile point increase of 1 was found after the introduction of Q4). Educational opportunities, compliance with

Individual and contextual variation in Thomas langur male loud calls

NARCIS (Netherlands)

Wich, S.A.; Koski, S.; Vries, Han de; Schaik, Carel P. van

2003-01-01

Individual and contextual differences in male loud calls of wild Thomas langurs (Presbytis thomasi) were studied in northern Sumatra, Indonesia. Loud calls were given in the following contexts: morning calls, vocal responses to other groups, between-group encounter calls and alarmcalls. Loud

Help Options in CALL: A Systematic Review

Science.gov (United States)

Cardenas-Claros, Monica S.; Gruba, Paul A.

2009-01-01

This paper is a systematic review of research investigating help options in the different language skills in computer-assisted language learning (CALL). In this review, emerging themes along with is-sues affecting help option research are identified and discussed. We argue that help options in CALL are application resources that do not only seem…

The Call to Teach and Teacher Hopefulness

Science.gov (United States)

Bullough, Robert V., Jr.; Hall-Kenyon, Kendra M.

2011-01-01

The purpose of this paper is to explore teacher motivation and well-being. Our analysis focuses on two central concepts, the notion of a "calling to teach" and of teacher "hopefulness." Data from 205 preservice and inservice teachers were collected to determine teachers' sense of calling and level of hope. Results indicate that overwhelmingly,…

Examining calling as a double-edged sword for employability

NARCIS (Netherlands)

Lysova, Evgenia I.; Jansen, Paul G.W.; Khapova, Svetlana N.; Plomp, Judith; Tims, Maria

2018-01-01

Using a two-study design (total N = 1232), this paper examines the relationship between calling and employability. We suggest that, on the one hand, calling can positively relate to employability due to individuals’ engagement in proactive professional development (PPD). On the other hand, calling

Identification of sympatric bat species by the echolocation calls

Institute of Scientific and Technical Information of China (English)

2008-01-01

One hundred and thirty-eight echolocation calls of 63 free-flying individuals of five bat species (Rhinolophus ferrumequinum,Myotis formosus,Myotis ikonnikovi,Myotis daubentoni and Murina leucogaster)were recorded (by ultrasonic bat detector (D980)) in Zhi'an village of Jilin Province,China.According to the frequency-time spectra,these calls were categorized into two types:FM/CF (constant frequency) / FM (R.ferrumequinum) and FM (frequency modulated)(M.formosus,M.ikonnikovi,M.daubentoni and M.leucogaster).Sonograms of the calls of R.ferrumequinum could easily be distinguished from those of the other four species.For the calls of the remaining four species,six echolocation call parameters,including starting frequency,ending frequency,peak frequency duration,longest inter-pulse interval and shortest inter-pulse interval,were examined by stepwise discriminant analysis.The results show that 84.1% of calls were correctly classified,which indicates that these parameters of echolocation calls play an important role in identifying bat species.These parameters can be used to test the accuracy of general predictions based on bats' morphology in the same forest and can provide essential information for assessing patterns of bat habitat use.

Heart rate variability changes in physicians working on night call.

Science.gov (United States)

Malmberg, Birgitta; Persson, Roger; Flisberg, Per; Ørbaek, Palle

2011-03-01

Adverse effects by night-call duty have become an important occupational health issue. The aim of this study was to investigate whether the heart rate variability (HRV) differed during recovery from day work and night-call duty between distinct physician specialities. We studied the impact of a 16-h night-call duty on autonomic balance, measured by HRV, among two physician groups differing with respect to having to deal with life-threatening conditions while on call. Nineteen anaesthesiologists (ANEST) and 16 paediatricians and ear, nose and throat surgeons (PENT) were monitored by ambulatory digital Holter electrocardiogram (ECG). Heart rate variability was analysed between 21:00 and 22:00 after an ordinary workday, on night call and in the evening post-call. Absolute and normalized high-frequency power (HF, HFnu) were the main outcome variables, expressing parasympathetic influence on the heart. ANEST had lower HF power than PENT while on night call and post-daytime work (p work compared with post-night-call duty (p balance and did not differ between specialities. However, the less dynamic HRV after daytime work and during night-call duty in the ANEST group may indicate a higher physiological stress level. These results may contribute to the improvement of night-call schedules within the health care sector.

The relation between media promotions and service volume for a statewide tobacco quitline and a web-based cessation program

Directory of Open Access Journals (Sweden)

Schillo Barbara A

2011-12-01

Full Text Available Abstract Background This observational study assessed the relation between mass media campaigns and service volume for a statewide tobacco cessation quitline and stand-alone web-based cessation program. Methods Multivariate regression analysis was used to identify how weekly calls to a cessation quitline and weekly registrations to a web-based cessation program are related to levels of broadcast media, media campaigns, and media types, controlling for the impact of external and earned media events. Results There was a positive relation between weekly broadcast targeted rating points and the number of weekly calls to a cessation quitline and the number of weekly registrations to a web-based cessation program. Additionally, print secondhand smoke ads and online cessation ads were positively related to weekly quitline calls. Television and radio cessation ads and radio smoke-free law ads were positively related to web program registration levels. There was a positive relation between the number of web registrations and the number of calls to the cessation quitline, with increases in registrations to the web in 1 week corresponding to increases in calls to the quitline in the subsequent week. Web program registration levels were more highly influenced by earned media and other external events than were quitline call volumes. Conclusion Overall, broadcast advertising had a greater impact on registrations for the web program than calls to the quitline. Furthermore, registrations for the web program influenced calls to the quitline. These two findings suggest the evolving roles of web-based cessation programs and Internet-use practices should be considered when creating cessation programs and media campaigns to promote them. Additionally, because different types of media and campaigns were positively associated with calls to the quitline and web registrations, developing mass media campaigns that offer a variety of messages and communicate through

Heavy Ion Collisions at the LHC - Last Call for Predictions

Energy Technology Data Exchange (ETDEWEB)

Armesto, N; Borghini, N; Jeon, S; Wiedemann, U A; Abreu, S; Akkelin, V; Alam, J; Albacete, J L; Andronic, A; Antonuv, D; Arleo, F; Armesto, N; Arsene, I C; Barnafoldi, G G; Barrette, J; Bauchle, B; Becattini, F; Betz, B; Bleicher, M; Bluhm, M; Boer, D; Bopp, F W; Braun-Munzinger, P; Bravina, L; Busza, W; Cacciari, M; Capella, A; Casalderrey-Solana, J; Chatterjee, R; Chen, L; Cleymans, J; Cole, B A; delValle, Z C; Csernai, L P; Cunqueiro, L; Dainese, A; de Deus, J D; Ding, H; Djordjevic, M; Drescher, H; Dremin, I M; Dumitru, A; El, A; Engel, R; d' Enterria, D; Eskola, K J; Fai, G; Ferreiro, E G; Fries, R J; Frodermann, E; Fujii, H; Gale, C; Gelis, F; Goncalves, V P; Greco, V; Gyulassy, M; van Hees, H; Heinz, U; Honkanen, H; Horowitz, W A; Iancu, E; Ingelman, G; Jalilian-Marian, J; Jeon, S; Kaidalov, A B; Kampfer, B; Kang, Z; Karpenko, I A; Kestin, G; Kharzeev, D; Ko, C M; Koch, B; Kopeliovich, B; Kozlov, M; Kraus, I; Kuznetsova, I; Lee, S H; Lednicky, R; Letessier, J; Levin, E; Li, B; Lin, Z; Liu, H; Liu, W; Loizides, C; Lokhtin, I P; Machado, M T; Malinina, L V; Managadze, A M; Mangano, M L; Mannarelli, M; Manuel, C; Martinez, G; Milhano, J G; Mocsy, A; Molnar, D; Nardi, M; Nayak, J K; Niemi, H; Oeschler, H; Ollitrault, J; Paic, G; Pajares, C; Pantuev, V S; Papp, G; Peressounko, D; Petreczky, P; Petrushanko, S V; Piccinini, F; Pierog, T; Pirner, H J; Porteboeuf, S; Potashnikova, I; Qin, G Y; Qiu, J; Rafelski, J; Rajagopal, K; Ranft, J; Rapp, R; Rasanen, S S; Rathsman, J; Rau, P; Redlich, K; Renk, T; Rezaeian, A H; Rischke, D; Roesler, S; Ruppert, J; Ruuskanen, P V; Salgado, C A; Sapeta, S; Sarcevic, I; Sarkar, S; Sarycheva, L I; Schmidt, I; Shoski, A I; Sinha, B; Sinyukov, Y M; Snigirev, A M; Srivastava, D K; Stachel, J; Stasto, A; Stocker, H; Teplov, C Y; Thews, R L; Torrieri, G; Pop, V T; Triantafyllopoulos, D N; Tuchin, K L; Turbide, S; Tywoniuk, K; Utermann, A; Venugopalan, R; Vitev, I; Vogt, R; Wang, E; Wang, X N; Werner, K; Wessels, E; Wheaton, S; Wicks, S; Wiedemann, U A; Wolschin, G; Xiao, B; Xu, Z; Yasui, S; Zabrodin, E; Zapp, K; Zhang, B

2008-02-25

In August 2006, the CERN Theory Unit announced to restructure its visitor program and to create a 'CERN Theory Institute', where 1-3 month long specific programs can take place. The first such Institute was held from 14 May to 10 June 2007, focusing on 'Heavy Ion Collisions at the LHC - Last Call for Predictions'. It brought together close to 100 scientists working on the theory of ultra-relativistic heavy ion collisions. The aim of this workshop was to review and document the status of expectations and predictions for the heavy ion program at the Large Hadron Collider LHC before its start. LHC will explore heavy ion collisions at {approx} 30 times higher center of mass energy than explored previously at the Relativistic Heavy Ion Collider RHIC. So, on the one hand, the charge of this workshop provided a natural forum for the exchange of the most recent ideas, and allowed to monitor how the understanding of heavy ion collisions has evolved in recent years with the data from RHIC, and with the preparation of the LHC experimental program. On the other hand, the workshop aimed at a documentation which helps to distinguish pre- from post-dictions. An analogous documentation of the 'Last Call for Predictions' [1] was prepared prior to the start of the heavy-ion program at the Relativistic Heavy Ion Collider RHIC, and it proved useful in the subsequent discussion and interpretation of RHIC data. The present write-up is the documentation of predictions for the LHC heavy ion program, received or presented during the CERN TH Institute. The set-up of the CERN TH Institute allowed us to aim for the wide-most coverage of predictions. There were more than 100 presentations and discussions during the workshop. Moreover, those unable to attend could still participate by submitting predictions in written form during the workshop. This followed the spirit that everybody interested in making a prediction had the right to be heard. To arrive at a concise

Calling under pressure: Short-finned pilot whales make social calls during deep foraging dives

DEFF Research Database (Denmark)

Jensen, Frants Havmand; Marrero Perez, Jacobo; Johnson, Mark

2011-01-01

Toothed whales rely on sound to echolocate prey and communicate with conspecifics, but little is known about how extreme pressure affects pneumatic sound production in deep-diving species with a limited air supply. The short-finned pilot whale (Globicephala macrorhynchus) is a highly social species...... among the deep-diving toothed whales, in which individuals socialize at the surface but leave their social group in pursuit of prey at depths of up to 1000 m. To investigate if these animals communicate acoustically at depth and test whether hydrostatic pressure affects communication signals, acoustic...... DTAGs logging sound, depth and orientation were attached to 12 pilot whales. Tagged whales produced tonal calls during deep foraging dives at depths of up to 800 m. Mean call output and duration decreased with depth despite the increased distance to conspecifics at the surface. This shows...

A Call to Action: Addressing the Childhood Obesity Epidemic through Comprehensive School Counseling Programs

Science.gov (United States)

Belser, Christopher T.; Morris, Jessica A.; Hasselbeck, Jennifer M.

2012-01-01

The need for school-based interventions targeting the childhood obesity epidemic has been well documented. The risk factors associated with childhood obesity are physical, mental, psychosocial, academic, and economic. With training in developing comprehensive programs and interventions, professional school counselors are positioned to assist…

Frogs Call at a Higher Pitch in Traffic Noise

Directory of Open Access Journals (Sweden)

Kirsten M. Parris

2009-06-01

Full Text Available Male frogs call to attract females for mating and to defend territories from rival males. Female frogs of some species prefer lower-pitched calls, which indicate larger, more experienced males. Acoustic interference occurs when background noise reduces the active distance or the distance over which an acoustic signal can be detected. Birds are known to call at a higher pitch or frequency in urban noise, decreasing acoustic interference from low-frequency noise. Using Bayesian linear regression, we investigated the effect of traffic noise on the pitch of advertisement calls in two species of frogs, the southern brown tree frog (Litoria ewingii and the common eastern froglet (Crinia signifera. We found evidence that L. ewingii calls at a higher pitch in traffic noise, with an average increase in dominant frequency of 4.1 Hz/dB of traffic noise, and a total effect size of 123 Hz. This frequency shift is smaller than that observed in birds, but is still large enough to be detected by conspecific frogs and confer a significant benefit to the caller. Mathematical modelling predicted a 24% increase in the active distance of a L. ewingii call in traffic noise with a frequency shift of this size. Crinia signifera may also call at a higher pitch in traffic noise, but more data are required to be confident of this effect. Because frog calls are innate rather than learned, the frequency shift demonstrated by L. ewingii may represent an evolutionary adaptation to noisy conditions. The phenomenon of frogs calling at a higher pitch in traffic noise could therefore constitute an intriguing trade-off between audibility and attractiveness to potential mates.

Solar Field Mapping and Dynamo Behavior

Directory of Open Access Journals (Sweden)

Kenneth H. Schatten

2012-01-01

Full Text Available We discuss the importance of the Sun’s large-scale magnetic field to the Sun-Planetary environment. This paper narrows its focus down to the motion and evolution of the photospheric large-scale magnetic field which affects many environments throughout this region. For this purpose we utilize a newly developed Netlogo cellular automata model. The domain of this algorithmic model is the Sun’s photosphere. Within this computational space are placed two types of entities or agents; one may refer to them as bluebirds and cardinals; the former carries outward magnetic flux and the latter carries out inward magnetic flux. One may simply call them blue and red agents. The agents provide a granularity with discrete changes not present in smooth MHD models; they undergo three processes: birth, motion, and death within the photospheric domain. We discuss these processes, as well as how we are able to develop a model that restricts its domain to the photosphere and allows the deeper layers to be considered only through boundary conditions. We show the model’s ability to mimic a number of photospheric magnetic phenomena: the solar cycle (11-year oscillations, the Waldmeier effect, unipolar magnetic regions (e.g. sectors and coronal holes, Maunder minima, and the march/rush to the poles involving the geometry of magnetic field reversals. We also discuss why the Sun sometimes appears as a magnetic monopole, which of course requires no alteration of Maxwell’s equations.

New degradation call admission control for increasing WCDMA system capacity

Institute of Scientific and Technical Information of China (English)

Liu Ningqing; Lu Zhi; Gu Xuemai

2006-01-01

Propose a new degradation call admission control(DCAC)scheme, which can be used in wideband code division multiple access communication system. So-called degradation is that non-real time call has the characteristic of variable bit rate, so decreasing its bit rate can reduce the load of the system, consequently the system can admit new call which should be blocked when the system is close to full load, therefore new call's access probability increases. This paper brings forward design project and does system simulation, simulation proves that DCAC can effectively decrease calls' blocking probability and increase the total number of the on-line users.

Implications of Structured Programming for Machine Architecture

NARCIS (Netherlands)

Tanenbaum, A.S.

1978-01-01

Based on an empirical study of more than 10,000 lines of program text written in a GOTO-less language, a machine architecture specifically designed for structured programs is proposed. Since assignment, CALL, RETURN, and IF statements together account for 93 percent of all executable statements,

De novo SNP calling from RAD sequences for a mink (Neovison vison) specific genotyping assay

DEFF Research Database (Denmark)

Thirstrup, Janne Pia; Pujolar, José Martin; Larsen, Peter F

2013-01-01

mink from Brown and Black color types were obtained. A mean of 49,789,860.2 (± 9,813,587.2) raw reads of high quality per sample were sequenced. SNPs were called using the software pipeline Stacks. The populations program was used to estimate population structure and genetic divergence between the two...

The Role of Calling in Military Engagement

Science.gov (United States)

2017-06-01

depression , hopelessness, emotional and behavior problems , and have lower levels of neuroticism (Oladipo et al., 2013; Suldo & Huebner, 2004; Gilman...retention? Data from surveys of Naval Postgraduate School students reveal many work-related correlations with calling and calling’s positive effects. My...retention? Data from surveys of Naval Postgraduate School students reveal many work-related correlations with calling and calling’s positive effects

Adult meerkats modify close call rate in the presence of pups

Institute of Scientific and Technical Information of China (English)

Megan T.WYMAN; Pearl R.RIVERS; Coline MULLER; Pauline TONI; Marta B.MANSER

2017-01-01

In animals,signaling behavior is often context-dependent,with variation in the probability of emitting certain signals dependent on fitness advantages.Senders may adjust signaling rate depending on receiver identity,presence of audiences,or noise masking the signal,all of which can affect the benefits and costs of signal production.In the cooperative breeding meerkat Suricata suricatta,group members emit soft contact calls,termed as "close calls",while foraging in order to maintain group cohesion.Here,we investigated how the close calling rate during foraging was affected by the presence of pups,that produce continuous,noisy begging calls as they follow older group members.Adults decreased their overall close call rate substantially when pups were foraging with the group in comparison to periods when no pups were present.We suggest this decrease was likely due to a masking effect of the loud begging calls,which makes the close call function of maintaining group cohesion partly redundant as the centrally located begging calls can be used instead to maintain cohesion.There was some support that adults use close calls strategically to attract specific pups based on fitness advantages,that is,as the philopatric sex,females should call more than males and more to female pups than male pups.Dominant females called more than dominant males when a pup was in close proximity,while subordinates showed no sex-based differences.The sex of the nearest pup did not affect the calling rate of adults.The study shows that meerkats modify their close call production depending on benefits gained from calling and provides an example of the flexible use of one calling system in the presence of another,here contact calls versus begging calls,within the same species.

Adult meerkats modify close call rate in the presence of pups.

Science.gov (United States)

Wyman, Megan T; Rivers, Pearl R; Muller, Coline; Toni, Pauline; Manser, Marta B

2017-06-01

In animals, signaling behavior is often context-dependent, with variation in the probability of emitting certain signals dependent on fitness advantages. Senders may adjust signaling rate depending on receiver identity, presence of audiences, or noise masking the signal, all of which can affect the benefits and costs of signal production. In the cooperative breeding meerkat Suricata suricatta , group members emit soft contact calls, termed as "close calls", while foraging in order to maintain group cohesion. Here, we investigated how the close calling rate during foraging was affected by the presence of pups, that produce continuous, noisy begging calls as they follow older group members. Adults decreased their overall close call rate substantially when pups were foraging with the group in comparison to periods when no pups were present. We suggest this decrease was likely due to a masking effect of the loud begging calls, which makes the close call function of maintaining group cohesion partly redundant as the centrally located begging calls can be used instead to maintain cohesion. There was some support that adults use close calls strategically to attract specific pups based on fitness advantages, that is, as the philopatric sex, females should call more than males and more to female pups than male pups. Dominant females called more than dominant males when a pup was in close proximity, while subordinates showed no sex-based differences. The sex of the nearest pup did not affect the calling rate of adults. The study shows that meerkats modify their close call production depending on benefits gained from calling and provides an example of the flexible use of one calling system in the presence of another, here contact calls versus begging calls, within the same species.

Acoustic model optimisation for a call routing system

CSIR Research Space (South Africa)

Kleynhans, N

2012-11-01

Full Text Available Secretary system and provides background on some application-specific ASR issues. Section III details the ASR development effort as well as corpus selection and design. Our experiments are described Fig. 1. High level AutoSecretary call flow. in Section IV... and results and a discussion are presented in Section V. Lastly, the conclusion and possible future work appear in Section VI. II. BACKGROUND A. AutoSecretary IVR System Figure 1 shows the high level call flow of the AutoSecretary call routing system...

Program with Ixquic

Directory of Open Access Journals (Sweden)

Carmen Ramos

2017-06-01

Full Text Available The goal of this paper is to explain the story telling, game design, game play and how is the interaction with the game Program with Ixquic. Here is the description about the new approach to this video game I called Program with Ixquic. Initially focused on an educational video game but now is a hybrid, now has more levels and provides moments of great fun, where each player can have some much fun in each different level and environments of interaction.

Evidence That Calls-Based and Mobility Networks Are Isomorphic.

Directory of Open Access Journals (Sweden)

Michele Coscia

Full Text Available Social relations involve both face-to-face interaction as well as telecommunications. We can observe the geography of phone calls and of the mobility of cell phones in space. These two phenomena can be described as networks of connections between different points in space. We use a dataset that includes billions of phone calls made in Colombia during a six-month period. We draw the two networks and find that the call-based network resembles a higher order aggregation of the mobility network and that both are isomorphic except for a higher spatial decay coefficient of the mobility network relative to the call-based network: when we discount distance effects on the call connections with the same decay observed for mobility connections, the two networks are virtually indistinguishable.

Calle y Saberes en Movimiento

Directory of Open Access Journals (Sweden)

Laura Daniela Aguirre Aguilar

2010-01-01

Full Text Available En México el rezago, el ausentismo, la deserción escolar, el trabajo a temprana edad y el inicio de una vida en la calle, en repetidas ocasiones son consecuencia de un núcleo familiar desarticulado o de una débil relación intrafamiliar, así como de una condición socioeconómica en desventaja. Ante esta problemática, la Secretaría de Educación Pública, instancia gubernamental encargada de garantizar una educación de calidad para la población, trabaja coordinadamente con organizaciones de la sociedad civil e instancias públicas, para la reintegración a los espacios educativos de los niños, niñas y jóvenes en situación de calle.

Magnetohydrodynamics of accretion disks

International Nuclear Information System (INIS)

Torkelsson, U.

1994-04-01

The thesis consists of an introduction and summary, and five research papers. The introduction and summary provides the background in accretion disk physics and magnetohydrodynamics. The research papers describe numerical studies of magnetohydrodynamical processes in accretion disks. Paper 1 is a one-dimensional study of the effect of magnetic buoyancy on a flux tube in an accretion disk. The stabilizing influence of an accretion disk corona on the flux tube is demonstrated. Paper 2-4 present numerical simulations of mean-field dynamos in accretion disks. Paper 11 verifies the correctness of the numerical code by comparing linear models to previous work by other groups. The results are also extended to somewhat modified disk models. A transition from an oscillatory mode of negative parity for thick disks to a steady mode of even parity for thin disks is found. Preliminary results for nonlinear dynamos at very high dynamo numbers are also presented. Paper 3 describes the bifurcation behaviour of the nonlinear dynamos. For positive dynamo numbers it is found that the initial steady solution is replaced by an oscillatory solution of odd parity. For negative dynamo numbers the solution becomes chaotic at sufficiently high dynamo numbers. Paper 4 continues the studies of nonlinear dynamos, and it is demonstrated that a chaotic solution appears even for positive dynamo numbers, but that it returns to a steady solution of mixed parity at very high dynamo numbers. Paper 5 describes a first attempt at simulating the small-scale turbulence of an accretion disk in three dimensions. There is only find cases of decaying turbulence, but this is rather due to limitations of the simulations than that turbulence is really absent in accretion disks

House Calls in Private Practice.

Science.gov (United States)

Whittington, Ronaele

1985-01-01

Relates the experiences of a social worker in private practice who offered house calls as an ongoing setting for counseling and psychotherapy to individuals and families. Describes advantages and disadvantages, liability, and target populations. (JAC)

Inbound Call Centers and Emotional Dissonance in the Job Demands - Resources Model.

Science.gov (United States)

Molino, Monica; Emanuel, Federica; Zito, Margherita; Ghislieri, Chiara; Colombo, Lara; Cortese, Claudio G

2016-01-01

employees in coping with emotional labor and to promote well-being in inbound call centers. In detail, results showed the need to improve training programs in order to enhance employees' emotion regulation skills, and to introduce human resource practices aimed at clarifying emotional requirements of the job.

Non-linguistic analysis of call center conversations

CERN Document Server

Kopparapu, Sunil Kumar

2014-01-01

The book focuses on the part of the audio conversation not related to language such as speaking rate (in terms of number of syllables per unit time) and emotion centric features. This text examines using non-linguistics features to infer information from phone calls to call centers. The author analyzes 'how' the conversation happens and not 'what' the conversation is about by audio signal processing and analysis.

Implementation of SQLite database support in program gama-local

Directory of Open Access Journals (Sweden)

Vaclav Petras

2012-03-01

Full Text Available The program gama-local is a part of GNU Gama project and allows adjustment of local geodetic networks. Before realization of this project the program gama-local supported only XML as an input. I designed and implemented support for the SQLite database and thanks to this extension gama-local can read input data from the SQLite database. This article is focused on the specifics of the use of callback functions in C++ using the native SQLite C/C++ Application Programming Interface. The article provides solution to safe calling of callback functions written in C++. Callback functions are called from C library and C library itself is used by C++ program. Provided solution combines several programing techniques which are described in detail, so this article can serve as a cookbook even for beginner programmers.  This project was accomplished within my bachelor thesis.

[Work-family conflict in call center].

Science.gov (United States)

Ghislieri, Chiara; Ricotta, Simona; Colombo, Lara

2012-01-01

The working environment of call centers, which have seen a significant growth in recent years, has been the subject of several studies aiming at understanding its specific dynamics, with particular attention to the possible causes of stress and discomfort. Despite the fact that the work-family conflict is considered a source of stress responsible for undermining workers' well-being, and as such has been explored in many work environments, there is still very little research specific to call centers. This study had the following aims: to explore work-family conflict perceived by call-center operators taking account of any differences related to respondents'professional and personal characteristics; to understand which demands and resources can have an impact on work-family conflict in this context. The study was carried out on a sample of 898 call center operators in a telecommunications company through the administration of a self-reporting questionnaire. Data analysis included: t-test, one-way analysis of variance, linear correlations and multiple regressions. A higher perception of work-family conflict among workers having a full-time contract was observed compared to those having part-time contracts. Multiple regression analysis identified as sources of influence on work-family conflict: emotional dissonance, uneasiness due customer dissatisfaction, workload, avoidance coping and working hours. Work-family conflict in the context studied is not particularly critical: it is in part influenced by professional and personal characteristics of respondents and primarily caused by work demands. Managerial implications are discussed, especially referred to training activities.

Symbolic Game Semantics for Model Checking Program Families

DEFF Research Database (Denmark)

Dimovski, Aleksandar

2016-01-01

represent program families with infinite integers as so-called (finite-state) featured symbolic automata. Specifically designed model checking algorithms are then employed to verify safety of all programs from a family at once and pinpoint those programs that are unsafe (respectively, safe). We present...... a prototype tool implementing this approach, and we illustrate it with several examples....

Investigating CALL in the Classroom: Situational Variables to Consider

Directory of Open Access Journals (Sweden)

Darlene Liutkus

2012-01-01

Full Text Available A new paradigm in second language pedagogy has Computer Assisted Language Learning (CALL playing a significant role. Much of the literature to-date claims that CALL can have a positive impact on students’ second language acquisition (SLA. Mixed method of research produces data to investigate if CALL positively affects student language proficiency, motivation and autonomy. Classroom observation of participants in their natural environment is a qualitative technique used but has situational variables that could skew results if not structured. A questionnaire is a quantitative tool that can offer insight regarding participants’ perception of performance but can contradict what the researcher has observed. This paper will take an in-depth look at variables such as: instructor’s pedagogical application; blending CALL into the curriculum; types of CALL implemented; feedback received and their implications for design of the data collection tools

Implementing a short-term loyalty program : case: Bosch Lawn & Garden and the Ventum short-term loyalty program

OpenAIRE

Logvinova, Veronika

2015-01-01

In 2015, one of the Bosch Home and Garden divisions, Bosch Lawn and Garden, has made a strategic decision to adopt a points-based short-term loyalty program called Ventum LG in the German supermarkets and petrol stations. It was decided that the base of this program will be completed Ventum PT short-term loyalty program which was managed by another division, Bosch Power Tools, and proved to be successful. This thesis aims to evaluate the worthiness of the Ventum LG loyalty program for Bosch L...

PENGARUH PERMAINAN CALL CARDS TERHADAP HASIL BELAJAR DAN AKTIVITAS PEMBELAJARAN BIOLOGI

Directory of Open Access Journals (Sweden)

A. Machin

2012-10-01

Full Text Available Tujuan penelitian untuk mengetahui pengaruh permainan call cards terhadap hasil belajar dan aktivitas pembelajaran. Aktivitas pembelajaran yang diukur meliputi aktivitas individual siswa dan kinerja guru. Penelitian ini merupakan penelitian eksperimental. Hasil penelitian menunjukkan bahwa media permainan call cards berkontribusi sebesar 46% terhadap hasil belajar siswa. Hasil belajar siswa yang diberi media permainan call cards lebih baik daripada hasil belajar siswa yang tidak diberi mediapermainan call cards. Dengan demikian, media permainan call cards dapat menjadi alternatif dalam pencapaian hasil belajar biologi yang lebih baik.   Research purposes to determine the effect of call cards game against learning outcomes and learning activities. Learning activities that were measured included the activity of individual student and teacher performance. This research was experimental. The results showed that the media play call cards account for 46% of the student learning outcomes. Learning outcomes of students who were given media cards call the game better than the learning outcomes of students who were not given mediapermainan call cards. Thus, the media play call cards can be an alternative in achieving the learning outcomes of biology better.

MAGNETIC ACTIVITY CYCLES IN THE EXOPLANET HOST STAR {epsilon} ERIDANI

Energy Technology Data Exchange (ETDEWEB)

Metcalfe, T. S.; Mathur, S. [Space Science Institute, 4750 Walnut Street, Suite 205, Boulder, CO 80301 (United States); Buccino, A. P.; Mauas, P. J. D.; Petrucci, R. [Instituto de Astronomia y Fisica del Espacio (CONICET), C.C. 67 Sucursal 28, C1428EHA-Buenos Aires (Argentina); Brown, B. P. [Department of Astronomy and Center for Magnetic Self-Organization, University of Wisconsin, Madison, WI 53706-1582 (United States); Soderblom, D. R. [Space Telescope Science Institute, 3700 San Martin Dr., Baltimore, MD 21218 (United States); Henry, T. J. [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30302 (United States); Hall, J. C. [Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States); Basu, S. [Department of Astronomy, Yale University, P.O. Box 208101, New Haven, CT 06520 (United States)

2013-02-01

The active K2 dwarf {epsilon} Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in {epsilon} Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed by the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95 {+-} 0.03 years and 12.7 {+-} 0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called 'active' and 'inactive' sequences as proposed by Boehm-Vitense. Finally, based on the observed properties of {epsilon} Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.

Penentuan Nilai Opsi Call Eropa Dengan Pembayaran Dividen

Directory of Open Access Journals (Sweden)

Diana Purwandari

2016-08-01

Full Text Available Fluktuasi harga saham menyebabkan perdagangan saham memiliki resiko. Opsi merupakan alternatif untuk mengurangi resiko dalam perdagangan saham. Opsi Eropa adalah suatu kontrak keuangan yang memberikan hak, bukan kewajiban, kepada holder, untuk membeli atau menjual aset pokok dari writer pada saat jatuh tempo dengan harga yang sudah ditentukan. Model penilaian harga opsi yang banyak diterima dalam bidang finansial adalah model Black-Scholes. Tujuan dari penelitian ini adalah mengetahui pengaruh pembagian dividen terhadap harga saham dan menentukan nilai opsi call Eropa dengan pembayaran dividen pada waktu yang telah ditentukan. Nilai opsi call Eropa dengan pembayaran dividen pada waktu yang telah ditentukan diperoleh menggunakan integrasi numerik dengan metode Simpson sebesar 12,6388.Kata kunci: opsi call Eropa, model Black-Scholes, dividen, metode Simpson.ABSTRACT Fluctuations in stock prices lead stock trading risk. An alternative options to reduce the risk in stock trading. European option is a financial contract that gives the right, but not the obligation, to the holder, to buy or sell the underlying asset of the writer at the maturity date at a price specified. Option price valuation models are widely accepted in the field of finance is the Black-Scholes model. The purpose of this study is to determine the effect of dividend distribution to the stock price and determine the value of the European call option with dividend payments at a predetermined time. Value of the European call option with dividend payments at a predetermined time obtained using numerical integration with Simpson method of 12,6388.Key words: European call options, Black-Scholes model, dividend, Simpson method.

Leveraging Call Center Logs for Customer Behavior Prediction

Science.gov (United States)

Parvathy, Anju G.; Vasudevan, Bintu G.; Kumar, Abhishek; Balakrishnan, Rajesh

Most major businesses use business process outsourcing for performing a process or a part of a process including financial services like mortgage processing, loan origination, finance and accounting and transaction processing. Call centers are used for the purpose of receiving and transmitting a large volume of requests through outbound and inbound calls to customers on behalf of a business. In this paper we deal specifically with the call centers notes from banks. Banks as financial institutions provide loans to non-financial businesses and individuals. Their call centers act as the nuclei of their client service operations and log the transactions between the customer and the bank. This crucial conversation or information can be exploited for predicting a customer’s behavior which will in turn help these businesses to decide on the next action to be taken. Thus the banks save considerable time and effort in tracking delinquent customers to ensure minimum subsequent defaulters. Majority of the time the call center notes are very concise and brief and often the notes are misspelled and use many domain specific acronyms. In this paper we introduce a novel domain specific spelling correction algorithm which corrects the misspelled words in the call center logs to meaningful ones. We also discuss a procedure that builds the behavioral history sequences for the customers by categorizing the logs into one of the predefined behavioral states. We then describe a pattern based predictive algorithm that uses temporal behavioral patterns mined from these sequences to predict the customer’s next behavioral state.

On-call emergency workload of a general surgical team.

Science.gov (United States)

Jawaid, Masood; Raza, Syed Muhammad; Alam, Shams Nadeem; Manzar, S

2009-01-01

To examine the on-call emergency workload of a general surgical team at a tertiary care teaching hospital to guide planning and provision of better surgical services. During six months period from August to January 2007; all emergency calls attended by general surgical team of Surgical Unit II in Accident and Emergency department (A and E) and in other units of Civil, Hospital Karachi, Pakistan were prospectively recorded. Data recorded includes timing of call, diagnosis, operation performed and outcome apart from demography. Total 456 patients (326 males and 130 females) were attended by on-call general surgery team during 30 emergency days. Most of the calls, 191 (41.9%) were received from 8 am to 5 pm. 224 (49.1%) calls were of abdominal pain, with acute appendicitis being the most common specific pathology in 41 (9.0%) patients. Total 73 (16.0%) calls were received for trauma. Total 131 (28.7%) patients were admitted in the surgical unit for urgent operation or observation while 212 (46.5%) patients were discharged from A and E. 92 (20.1%) patients were referred to other units with medical referral accounts for 45 (9.8%) patients. Total 104 (22.8%) emergency surgeries were done and the most common procedure performed was appendicectomy in 34 (32.7%) patients. Major workload of on-call surgical emergency team is dealing with the acute conditions of abdomen. However, significant proportion of patients are suffering from other conditions including trauma that require a holistic approach to care and a wide range of skills and experience. These results have important implications in future healthcare planning and for the better training of general surgical residents.

MEDICAL SERVICE - URGENT CALLS

CERN Multimedia

Service Médical

2000-01-01

IN URGENT NEED OF A DOCTOR GENEVA: EMERGENCY SERVICES GENEVA AND VAUD 144 FIRE BRIGADE 118 POLICE 117 CERN FIREMEN 767-44-44 ANTI-POISONS CENTRE Open 24h/24h 01-251-51-51 Patient not fit to be moved, call family doctor, or: GP AT HOME: Open 24h/24h 748-49-50 AMG- Association Of Geneva Doctors: Emergency Doctors at home 07h-23h 322 20 20 Patient fit to be moved: HOPITAL CANTONAL CENTRAL 24 Micheli-du-Crest 372-33-11 ou 382-33-11 EMERGENCIES 382-33-11 ou 372-33-11 CHILDREN'S HOSPITAL 6 rue Willy-Donzé 372-33-11 MATERNITY 32 bvd.de la Cluse 382-68-16 ou 382-33-11 OPHTHALMOLOGY 22 Alcide Jentzer 382-33-11 ou 372-33-11 MEDICAL CENTRE CORNAVIN 1-3 rue du Jura 345 45 50 HOPITAL DE LA TOUR Meyrin 719-61-11 EMERGENCIES 719-61-11 CHILDREN'S EMERGENCIES 719-61-00 LA TOUR MEDICAL CENTRE 719-74-00 European Emergency Call 112   FRANCE: EMERGENCY SERVICES 15 FIRE BRIGADE 18 POLICE 17 CERN FIREMEN AT HOME 00-41-22-767-44-44 ...

Analysis of jitter due to call-level fluctuations

NARCIS (Netherlands)

M.R.H. Mandjes (Michel)

2005-01-01

textabstractIn communication networks used by constant bit rate applications, call-level dynamics (i.e., entering and leaving calls) lead to fluctuations in the load, and therefore also fluctuations in the delay (jitter). By intentionally delaying the packets at the destination, one can transform

A THEORETICAL STUDY OF THE BUILD-UP OF THE SUN’S POLAR MAGNETIC FIELD BY USING A 3D KINEMATIC DYNAMO MODEL

Energy Technology Data Exchange (ETDEWEB)

Hazra, Gopal; Choudhuri, Arnab Rai [Department of Physics, Indian Institute of Science, Bangalore, 560012 (India); Miesch, Mark S., E-mail: ghazra@physics.iisc.ernet.in, E-mail: arnab@physics.iisc.ernet.in, E-mail: miesch@ucar.edu [High Altitude Observatory, National Center for Atmospheric Research, Boulder, CO 80301 (United States)

2017-01-20

We develop a three-dimensional kinematic self-sustaining model of the solar dynamo in which the poloidal field generation is from tilted bipolar sunspot pairs placed on the solar surface above regions of strong toroidal field by using the SpotMaker algorithm, and then the transport of this poloidal field to the tachocline is primarily caused by turbulent diffusion. We obtain a dipolar solution within a certain range of parameters. We use this model to study the build-up of the polar magnetic field and show that some insights obtained from surface flux transport models have to be revised. We present results obtained by putting a single bipolar sunspot pair in a hemisphere and two symmetrical sunspot pairs in two hemispheres. We find that the polar fields produced by them disappear due to the upward advection of poloidal flux at low latitudes, which emerges as oppositely signed radial flux and which is then advected poleward by the meridional flow. We also study the effect that a large sunspot pair, violating Hale’s polarity law, would have on the polar field. We find that there would be some effect—especially if the anti-Hale pair appears at high latitudes in the mid-phase of the cycle—though the effect is not very dramatic.

Tree Notation: an antifragile program notation

OpenAIRE

Yunits, Breck

2017-01-01

This paper presents Tree Notation, a new simple, universal syntax. Language designers can invent new programming languages, called Tree Languages, on top of Tree Notation. Tree Languages have a number of advantages over traditional programming languages. We include a Visual Abstract to succinctly display the problem and discovery. Then we describe the problem--the BNF to abstract syntax tree (AST) parse step--and introduce the novel solution we discovered: a new family of 2D programming langu...

Implementation of the results of scientific investigations in the framework of the branch task comprehensive program called Health

Energy Technology Data Exchange (ETDEWEB)

Kochin, I.V.; Martynenko, O.N.; Berestizhevskii, S.I.; Eshchenko, N.E.

1987-01-01

A draft is evaluated for a research program on health hazards and occupational diseases in coking plants in the USSR. The research program would be a component of the Health program for 1986-1990 approved by the authorities. The following structure of the research program is recommended for the coking industry in the Ukrainian SSR: research on social and socio-economic factors which influence health of coking plant employees (development of standard survey, development of questionnaires), examinations of state of health of coking plant personnel on the basis of statistical data (determining most frequent disease in coking plant personnel, calculating indices which describe disease frequency, assessment of disease structure), investigations into disease dependence on social and socio-economic factors as well as safety conditions (development of mathematical models which describe effects of various social and economic factors on general state of health and diseases of coking plant personnel, classification of personnel in coking plant considering state of health and socio-economic factors (development of computer programs and algorithms), development of computer programs for health control in coking plants and reducing economic losses caused by absence associated with diseases and accidents.

Learners Programming Language a Helping System for Introductory Programming Courses

Directory of Open Access Journals (Sweden)

MUHAMMAD SHUMAIL NAVEED

2016-07-01

Full Text Available Programming is the core of computer science and due to this momentousness a special care is taken in designing the curriculum of programming courses. A substantial work has been conducted on the definition of programming courses, yet the introductory programming courses are still facing high attrition, low retention and lack of motivation. This paper introduced a tiny pre-programming language called LPL (Learners Programming Language as a ZPL (Zeroth Programming Language to illuminate novice students about elementary concepts of introductory programming before introducing the first imperative programming course. The overall objective and design philosophy of LPL is based on a hypothesis that the soft introduction of a simple and paradigm specific textual programming can increase the motivation level of novice students and reduce the congenital complexities and hardness of the first programming course and eventually improve the retention rate and may be fruitful in reducing the dropout/failure level. LPL also generates the equivalent high level programs from user source program and eventually very fruitful in understanding the syntax of introductory programming languages. To overcome the inherent complexities of unusual and rigid syntax of introductory programming languages, the LPL provide elementary programming concepts in the form of algorithmic and plain natural language based computational statements. The initial results obtained after the introduction of LPL are very encouraging in motivating novice students and improving the retention rate.