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Sample records for advective flow paradigm

  1. Instabilities of advection-dominated accretion flows

    CERN Document Server

    Chen, X

    1996-01-01

    Accretion disk instabilities are briefly reviewed. Some details are given to the short-wavelength thermal instabilities and the convective instabilities. Time-dependent calculations of two-dimensional advection-dominated accretion flows are presented.

  2. Preheated Advection Dominated Accretion Flow

    CERN Document Server

    Park, M G; Park, Myeong-Gu; Ostriker, Jeremiah P.

    2001-01-01

    All high temperature accretion solutions including ADAF are physically thick, so outgoing radiation interacts with the incoming flow, sharing as much or more resemblance with classical spherical accretion flows as with disk flows. We examine this interaction for the popular ADAF case. We find that without allowance for Compton preheating, a very restricted domain of ADAF solution is permitted and with Compton preheating included a new high temperature PADAF branch appears in the solution space. In the absence of preheating, high temperature flows do not exist when the mass accretion rate mdot == Mdot c^2 / L_E >~ 10^-1.5. Below this mass accretion rate, a roughly conical region around the hole cannot sustain high temperature ions and electrons for all flows having mdot >~ 10^-4, which may lead to a funnel possibly filled with a tenuous hot outgoing wind. If the flow starts at large radii with the usual equilibrium temperature ~10^4 K, the critical mass accretion rate is much lower, mdot exist. However, above ...

  3. Vertical structure of Advection dominated Accretion Flows

    CERN Document Server

    Zeraatgari, Fateme Zahra

    2015-01-01

    We solve the set of hydrodynamic (HD) equations for optically thin Advection Dominated Accretion Flows (ADAFs) by assuming radially self-similar in spherical coordinate system $ (r, \\theta, \\phi) $. The disk is considered to be steady state and axi-symmetric. We define the boundary conditions at the pole and the equator of the disk and to avoid singularity at the rotation axis, the disk is taken to be symmetric with respect to this axis. Moreover, only the $ \\tau_{r \\phi} $ component of viscous stress tensor is assumed and we have set $ v_{\\theta} = 0 $. The main purpose of this study is to investigate the variation of dynamical quantities of the flow in the vertical direction by finding an analytical solution. As a consequence, we found that the advection parameter, $ f^{adv} $, varies along the $ \\theta $ direction and reaches to its maximum near the rotation axis. Our results also show that, in terms of no-outflow solution, thermal equilibrium still exists and consequently advection cooling can balance vis...

  4. Advection of nematic liquid crystals by chaotic flow

    CERN Document Server

    O'Naraigh, Lennon

    2016-01-01

    Consideration is given to the effects of inhomogeneous shear flow (both regular and chaotic) on nematic liquid crystals in a planar two-dimensional geometry. The Landau-de Gennes equation coupled to an externally-prescribed flow field is the basis for the study: this is solved numerically in a periodic spatial domain. The focus is on a limiting case where the advection is passive, such that variations in the liquid-crystal properties do not feed back into the equation of motion for the uid velocity. The numerical simulations demonstrate that the coarsening of the liquid-crystal domains is arrested by the ow. The nature of the arrest is different depending on whether the flow is regular or chaotic. For the specific case where tumbling is important, the flow has a strong effect on the the liquid-crystal morphology: this provides a mechanism for controlling the shape of the liquid-crystal domains.

  5. Implementation of Two Component Advective Flow Solution in XSPEC

    CERN Document Server

    Debnath, Dipak; Mondal, Santanu

    2014-01-01

    Spectral and Temporal properties of black hole candidates can be explained reasonably well using Chakrabarti-Titarchuk solution of two component advective flow (TCAF). This model requires two accretion rates, namely, the Keplerian disk accretion rate and the halo accretion rate, the latter being composed of a sub-Keplerian, low angular momentum flow which may or may not develop a shock. In this solution, the relevant parameter is the relative importance of the halo (which creates the Compton cloud region) rate with respect to the Keplerian disk rate (soft photon source). Though this model has been used earlier to manually fit data of several black hole candidates quite satisfactorily, for the first time, we made it user friendly by implementing it into XSPEC software of GSFC/NASA. This enables any user to extract physical parameters of the accretion flows, such as two accretion rates, the shock location, the shock strength etc. for any black hole candidate. We provide some examples of fitting a few cases usin...

  6. Standing Shock Instability in Advection-Dominated Accretion Flows

    CERN Document Server

    Le, Truong; Wolff, Michael T; Becker, Peter A; Putney, Joy

    2015-01-01

    Depending on the values of the energy and angular momentum per unit mass in the gas supplied at large radii, inviscid advection-dominated accretion flows can display velocity profiles with either pre-shock deceleration or pre-shock acceleration. Nakayama has shown that these two types of flow configurations are expected to have different stability properties. By employing the Chevalier & Imamura linearization method and the Nakayama instability boundary conditions, we discover that there are regions of parameters space where disk/shocks with outflows can be stable or unstable. In region of instability, we find that pre-shock deceleration is always unstable to the zeroth mode with zero frequency of oscillation, but is always stable to the fundamental and overtones. Furthermore, we also find that pre-shock acceleration is always unstable to the zeroth mode, and that the fundamental and overtones become increasingly less stable as the shock location moves away from the horizon when the disk half-height expan...

  7. Is the accretion flow in NGC 4258 advection-dominated?

    CERN Document Server

    Lasota, J P; Chen, X; Krolik, J H; Narayan, R; Yi, I

    1995-01-01

    The mass of the central black hole in the active galaxy NGC 4258 (M106) has been measured to be M=3.6\\times10^7\\Msun (Miyoshi et al. 1995). The Eddington luminosity corresponding to this mass is L_E=4.5\\times10^{45} erg s^{-1}. By contrast the X-ray luminosity of the nucleus of NGC 4258 between 2-10 keV is (4\\pm 1)\\times10^{40}~{\\rm erg\\,s^{-1}} while the optical/UV luminosity is less than 1.5\\times10^{42} ~{\\rm erg\\,s^{-1}}. The luminosity of NGC 4258 is therefore extremely sub-Eddington, L\\sim10^{-5}L_E in X-rays and L\\sim3\\times10^{-4} L_E even if we take the maximum optical/UV luminosity. Assuming the usual accretion efficiency of 0.1 would imply accretion rates orders of magnitude lower than in Seyfert galaxies and quasars. We show that the properties of the AGN in NGC 4258 can be explained by an accretion flow in the form of a very hot, optically-thin plasma which advects most of the viscously generated thermal energy into the central black hole and radiates only a small fraction of the energy. In this ...

  8. Subsurface barrier design alternatives for confinement and controlled advection flow

    International Nuclear Information System (INIS)

    Various technologies and designs are being considered to serve as subsurface barriers to confine or control contaminant migration from underground waste storage or disposal structures containing radioactive and hazardous wastes. Alternatives including direct-coupled flood and controlled advection designs are described as preconceptual examples. Prototype geotechnical equipment for testing and demonstration of these alternative designs tested at the Hanford Geotechnical Development and Test Facility and the Hanford Small-Tube Lysimeter Facility include mobile high-pressure injectors and pumps, mobile transport and pumping units, vibratory and impact pile drivers, and mobile batching systems. Preliminary laboratory testing of barrier materials and additive sequestering agents have been completed and are described

  9. Accretion discs around black holes two dimensional, advection cooled flows

    CERN Document Server

    Igumenshchev, I V; Abramowicz, M A; Igumenshchev, Igor V; Chen, Xingming; Abramowicz, Marek Artur

    1995-01-01

    Two-dimensional accretion flows near black holes have been investigated by time-dependent hydrodynamical calculations. We assume that the flow is axisymmetric and that radiative losses of internal energy are negligible, so that the disc is geometrically thick and hot. Accretion occurs due to the overflow of the effective potential barrier near the black hole, similar to the case of the Roche lobe overflowing star in a binary system. We make no pre-assumptions on the properties of the flow, instead our models evolve self-consistently from an initially non-accreting state. The viscosity is due to the the small-scale turbulence and it is described by the \\alpha-viscosity prescription. We confirm earlier suggestions that viscous accretion flows are convectively unstable. We found that the instability produces transient eddies of various length-scales. The eddies contribute to the strength of the viscosity in the flow by redistributing the angular momentum. They also introduce low amplitude oscillatory variations ...

  10. Spectrum of Optically Thin Advection Dominated Accretion Flow around a Black Hole Application to Sgr A*

    CERN Document Server

    Manmoto, T; Kusunose, M

    1997-01-01

    The global structure of optically thin advection dominated accretion flows which are composed of two-temperature plasma around black holes is calculated. We adopt the full set of basic equations including the advective energy transport in the energy equation for the electrons. The spectra emitted by the optically thin accretion flows are also investigated. The radiation mechanisms which are taken into accout are bremsstrahlung, synchrotron emission, and Comptonization. The calculation of the spectra and that of the structure of the accretion flows are made to be completely consistent by calculating the radiative cooling rate at each radius. As a result of the advection domination for the ions, the heat transport from the ions to the electrons becomes practically zero and the radiative cooling balances with the advective heating in the energy equation of the electrons. Following up on the successful work of Narayan et al. (1995), we applied our model to the spectrum of Sgr A*. We find that the spectrum of Sgr ...

  11. Chaotic advection and heat transfer in two similar 2-D periodic flows and in their corresponding 3-D periodic flows

    Science.gov (United States)

    Vinsard, G.; Dufour, S.; Saatdjian, E.; Mota, J. P. B.

    2016-03-01

    Chaotic advection can effectively enhance the heat transfer rate between a boundary and fluids with high Prandtl number. These fluids are usually highly viscous and thus turbulent agitation is not a viable solution since the energy required to mix the fluid would be prohibitive. Here, we analyze previously obtained results on chaotic advection and heat transfer in two similar 2-D periodic flows and on their corresponding 3-D periodic flows when an axial velocity component is superposed. The two flows studied are the flow between eccentric rotating cylinders and the flow between confocal ellipses. For both of these flows the analysis is simplified because the Stokes equations can be solved analytically to obtain a closed form solution. For both 2-D periodic flows, we show that chaotic heat transfer is enhanced by the displacement of the saddle point location during one period. Furthermore, the enhancement by chaotic advection in the elliptical geometry is approximately double that obtained in the cylindrical geometry because there are two saddle points instead of one. We also explain why, for high eccentricity ratios, there is no heat transfer enhancement in the cylindrical geometry. When an axial velocity component is added to both of these flows so that they become 3-D, previous work has shown that there is an optimum modulation frequency for which chaotic advection and heat transfer enhancement is a maximum. Here we show that the optimum modulation frequency can be derived from results without an axial flow. We also explain by physical arguments other previously unanswered questions in the published data.

  12. Self-Similar Solutions for Viscous and Resistive Advection Dominated Accretion Flows

    Indian Academy of Sciences (India)

    Kazem Faghei

    2012-03-01

    In this paper, self-similar solutions of resistive advection dominated accretion flows (ADAF) in the presence of a pure azimuthal magnetic field are investigated. The mechanism of energy dissipation is assumed to be the viscosity and the magnetic diffusivity due to turbulence in the accretion flow. It is assumed that the magnetic diffusivity and the kinematic viscosity are not constant and vary by position and -prescription is used for them. In order to solve the integrated equations that govern the behavior of the accretion flow, a self-similar method is used. The solutions show that the structure of accretion flow depends on the magnetic field and the magnetic diffusivity. As the radial infall velocity and the temperature of the flow increase by magnetic diffusivity, the rotational velocity decreases. Also, the rotational velocity for all selected values of magnetic diffusivity and magnetic field is sub-Keplerian. The solutions show that there is a certain amount of magnetic field for which rotational velocity of the flow becomes zero. This amount of the magnetic field depends upon the gas properties of the disc, such as adiabatic index and viscosity, magnetic diffusivity, and advection parameters. The mass accretion rate increases by adding the magnetic diffusivity and the solutions show that in high magnetic pressure, the ratio of the mass accretion rate to the Bondi accretion rate is reduced with an increase in magnetic pressure. Also, the study of Lundquist and magnetic Reynolds numbers based on resistivity indicates that the linear growth of magnetorotational instability (MRI) of the flow reduces by resistivity. This property is qualitatively consistent with resistive magnetohydrodynamics (MHD) simulations.

  13. Advection Dominated Accretion Flows in the Kerr Metric; 1, Basic Equations

    CERN Document Server

    Gammie, C F; Gammie, Charles F.; Popham, Robert

    1997-01-01

    We write down and solve equations describing steady state, optically thin, advection-dominated accretion onto a Kerr black hole. The mean flow, described by the relativistic fluid equations, is axisymmetric and vertically averaged. The effect of turbulence in the flow is represented by a viscous shear stress. Our treatment differs in several important ways from earlier work: we use a causal prescription for the shear stress, we do not assume the relativistic enthalpy is unity (this is important for rapidly rotating holes), and we use a relativistic equation of state. We present several representative solutions and use them to evaluate the importance of relativistic effects, to check our approximations, and to evaluate the robustness of the input physics. Detailed properties of the solutions are described in an accompanying paper.

  14. Signature of Accretion Shocks in Emitted Radiation From a Two Temperature Advective Flows Around Black Holes

    CERN Document Server

    Mandal, S; Mandal, Samir; Chakrabarti, Sandip K.

    2005-01-01

    Centrifugal barrier supported boundary layer (CENBOL) of a black hole affects the spectrum exactly in the same way the boundary layer of a neutron star does. The CENBOL is produced due to standing or oscillating shock waves and these shocks accelerate electrons very efficiently and produce a power-law distribution. The accelerated particles in turn emit synchrotron radiation in presence of the magnetic field. We study the spectral properties of an accretion disk as a function of the shock strength, compression ratio, flow accretion rate and flow geometry. In the absence of a satisfactory description of magnetic fields inside the advective disk, we consider the presence of only stochastic fields and use the ratio of the field energy density to the gravitational energy density to be a parameter. Not surprisingly, stronger fields produce stronger humps due to synchrotron radiation. We not only include `conventional' synchrotron emission and Comptonization due to Maxwell-Bolzmann electrons in the gas, we also com...

  15. Correlation networks from flows. The case of forced and time-dependent advection-diffusion dynamics

    CERN Document Server

    Tupikina, Liubov; López, Cristóbal; Hernández-García, Emilio; Marwan, Norbert; Kurths, Jürgen

    2016-01-01

    Complex network theory provides an elegant and powerful framework to statistically investigate different types of systems such as society, brain or the structure of local and long-range dynamical interrelationships in the climate system. Network links in climate networks typically imply information, mass or energy exchange. However, the specific connection between oceanic or atmospheric flows and the climate network's structure is still unclear. We propose a theoretical approach for verifying relations between the correlation matrix and the climate network measures, generalizing previous studies and overcoming the restriction to stationary flows. Our methods are developed for correlations of a scalar quantity (temperature, for example) which satisfies an advection-diffusion dynamics in the presence of forcing and dissipation. Our approach reveals that correlation networks are not sensitive to steady sources and sinks and the profound impact of the signal decay rate on the network topology. We illustrate our r...

  16. Dynamics of Magnetic Flux Tubes in an Advective Flow around a Black Hole

    Science.gov (United States)

    Deb, Arnab; Chakrabarti, Sandip Kumar; Giri, Kinsuk

    2016-07-01

    Magnetic fields cannibalized by an accretion flow would very soon have a dominant toroidal component. Without changing the topology, we study the movements of these flux tubes inside a geometrically thick advective disk which undergo centrifugal pressure supported shocks. We also consider the effects of the flux tubes on the flow. We use a finite element method (Total Variation Diminishing) for this purpose and specifically focussed whether the flux tubes contribute to changes in outflow properties in terms of its collimation and outflow rates. It is seen that depending upon the cross sectional radius of the flux tubes (which control the drag force), these field lines may move towards the central object or oscillate vertically before eventually escaping out of the funnel wall (pressure zero surface). These interesting results obtained with and without flux tubes point to the role the flux tubes play in collimation of jets and outflows.

  17. Study of Accretion processes Around Black Holes becomes Science: Tell Tale Observational Signatures of Two Component Advective Flows

    CERN Document Server

    Chakrabarti, Sandip K

    2016-01-01

    An accretion flow around a black hole has a saddle type sonic point just outside the event horizon to guarantee that the flow enters the black hole supersonically. This feature exclusively present in strong gravity limit makes its marks in every observation of black hole candidates. Another physical sonic point is present (as in a Bondi flow) even in weak gravity. Every aspect of spectral or temporal properties of every black hole can be understood using this transonic or advective flow having more than one saddle type points. This most well known and generalized solution with viscosity and radiative transfer has been verified by numerical simulations also. Spectra, computed for various combinations of the standard Keplerian, and advective sub-Keplerian components match accurately with those from satellite observations. Standing, oscillating and propagatory oscillating shocks are produced due to centrifugal barrier of the advective component. The post-shock region acts as the Compton cloud producing the power...

  18. Multiscale numerical methods for passive advection-diffusion in incompressible turbulent flow fields

    Science.gov (United States)

    Lee, Yoonsang; Engquist, Bjorn

    2016-07-01

    We propose a seamless multiscale method which approximates the macroscopic behavior of the passive advection-diffusion equations with steady incompressible velocity fields with multi-spatial scales. The method uses decompositions of the velocity fields in the Fourier space, which are similar to the decomposition in large eddy simulations. It also uses a hierarchy of local domains with different resolutions as in multigrid methods. The effective diffusivity from finer scale is used for the next coarser level computation and this process is repeated up to the coarsest scale of interest. The grids are only in local domains whose sizes decrease depending on the resolution level so that the overall computational complexity increases linearly as the number of different resolution grids increases. The method captures interactions between finer and coarser scales but has to sacrifice some of interactions between different scales. The proposed method is numerically tested with 2D examples including a successful approximation to a continuous spectrum flow.

  19. Correlation Networks from Flows. The Case of Forced and Time-Dependent Advection-Diffusion Dynamics.

    Directory of Open Access Journals (Sweden)

    Liubov Tupikina

    Full Text Available Complex network theory provides an elegant and powerful framework to statistically investigate different types of systems such as society, brain or the structure of local and long-range dynamical interrelationships in the climate system. Network links in climate networks typically imply information, mass or energy exchange. However, the specific connection between oceanic or atmospheric flows and the climate network's structure is still unclear. We propose a theoretical approach for verifying relations between the correlation matrix and the climate network measures, generalizing previous studies and overcoming the restriction to stationary flows. Our methods are developed for correlations of a scalar quantity (temperature, for example which satisfies an advection-diffusion dynamics in the presence of forcing and dissipation. Our approach reveals that correlation networks are not sensitive to steady sources and sinks and the profound impact of the signal decay rate on the network topology. We illustrate our results with calculations of degree and clustering for a meandering flow resembling a geophysical ocean jet.

  20. Correlation Networks from Flows. The Case of Forced and Time-Dependent Advection-Diffusion Dynamics.

    Science.gov (United States)

    Tupikina, Liubov; Molkenthin, Nora; López, Cristóbal; Hernández-García, Emilio; Marwan, Norbert; Kurths, Jürgen

    2016-01-01

    Complex network theory provides an elegant and powerful framework to statistically investigate different types of systems such as society, brain or the structure of local and long-range dynamical interrelationships in the climate system. Network links in climate networks typically imply information, mass or energy exchange. However, the specific connection between oceanic or atmospheric flows and the climate network's structure is still unclear. We propose a theoretical approach for verifying relations between the correlation matrix and the climate network measures, generalizing previous studies and overcoming the restriction to stationary flows. Our methods are developed for correlations of a scalar quantity (temperature, for example) which satisfies an advection-diffusion dynamics in the presence of forcing and dissipation. Our approach reveals that correlation networks are not sensitive to steady sources and sinks and the profound impact of the signal decay rate on the network topology. We illustrate our results with calculations of degree and clustering for a meandering flow resembling a geophysical ocean jet. PMID:27128846

  1. Volume of Fluid (VOF) type advection methods in two-phase flow: a comparative study

    CERN Document Server

    Aniszewski, Wojciech; Marek, Maciej

    2014-01-01

    In this paper, four distinct approaches to Volume of Fluid (VOF) computational method are compared. Two of the methods are the 'simplified' VOF formulations, in that they do not require geometrical interface reconstruction. The assessment is made possible by implementing all four approaches into the same code as a switchable options. This allows to rule out possible influence of other parts of numerical scheme, be it the discretisation of Navier-Stokes equations or chosen approximation of curvature, so that we are left with conclusive arguments because only one factor differs the compared methods. The comparison is done in the framework of CLSVOF (Coupled Level Set Volume of Fluid), so that all four methods are coupled with Level Set interface, which is used to compute pressure jump via the GFM (Ghost-Fluid Method). Results presented include static advections, full N-S solutions in laminar and turbulent flows. The paper is aimed at research groups who are implementing VOF methods in their computations or inte...

  2. Temporal Variability from the Two-Component Advective Flow Solution and Its Observational Evidence

    Science.gov (United States)

    Dutta, Broja G.; Chakrabarti, Sandip K.

    2016-09-01

    In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of the energy-dependent temporal properties in different variability timescales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high-inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclination black hole source GX 339-4 during its 2006-07 outburst using RXTE/PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase, the time lag increases with time. We find a systematic evolution of QPO frequency and hard lags in these outbursts. In XTE J1550-564, the lag changes from hard to soft (i.e., from a positive to a negative value) at a crossing frequency (ν c) of ˜3.4 Hz. We present possible mechanisms to explain the lag behavior of high and low-inclination sources within the framework of a single two-component advective flow model.

  3. Investigating redox processes under diffusive and advective flow conditions using a coupled omics and synchrotron approach

    Science.gov (United States)

    Kemner, K. M.; Boyanov, M.; Flynn, T. M.; O'Loughlin, E. J.; Antonopoulos, D. A.; Kelly, S.; Skinner, K.; Mishra, B.; Brooks, S. C.; Watson, D. B.; Wu, W. M.

    2015-12-01

    FeIII- and SO42--reducing microorganisms and the mineral phases they produce have profound implications for many processes in aquatic and terrestrial systems. In addition, many of these microbially-catalysed geochemical transformations are highly dependent upon introduction of reactants via advective and diffusive hydrological transport. We have characterized microbial communities from a set of static microcosms to test the effect of ethanol diffusion and sulfate concentration on UVI-contaminated sediment. The spatial distribution, valence states, and speciation of both U and Fe were monitored in situ throughout the experiment by synchrotron x-ray absorption spectroscopy, in parallel with solution measurements of pH and the concentrations of sulfate, ethanol, and organic acids. After reaction initiation, a ~1-cm thick layer of sediment near the sediment-water (S-W) interface became visibly dark. Fe XANES spectra of the layer were consistent with the formation of FeS. Over the 4 year duration of the experiment, U LIII-edge XANES indicated reduction of U, first in the dark layer and then throughout the sediment. Next, the microcosms were disassembled and samples were taken from the overlying water and different sediment regions. We extracted DNA and characterized the microbial community by sequencing 16S rRNA gene amplicons with the Illumina MiSeq platform and found that the community evolved from its originally homogeneous composition, becoming significantly spatially heterogeneous. We have also developed an x-ray accessible column to probe elemental transformations as they occur along the flow path in a porous medium with the purpose of refining reactive transport models (RTMs) that describe coupled physical and biogeochemical processes in environmental systems. The elemental distribution dynamics and the RTMs of the redox driven processes within them will be presented.

  4. Modeling size segregation of bidisperse granular flow: the roles of segregation, advection, and diffusion

    OpenAIRE

    Fan, Yi; Schlick, Conor; Isner, Austin; Ottino, Julio; Umbanhowar, Paul; Richard, Lueptow

    2014-01-01

    Segregation of granular materials composed of different-sized particles has important repercussions in various industrial processes and natural phenomena, but predicting size segregation remains a challenging problem. To address this problem, we have developed a theoretical model that captures the interplay between advection, segregation, and diffusion in size bidisperse granular materials. The fluxes associated with these three driving factors depend on the underlying kinematics, whose chara...

  5. Modeling Three-Dimensional Groundwater Flow and Advective Contaminant Transport at a Heterogeneous Mountainous Site in Support of Remediation Strategy

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Quanlin; Birkholzer, Jens T.; Javandel, Iraj; Jordan, Preston D.

    2004-01-14

    A calibrated groundwater flow model for a contaminated site can provide substantial information for assessing and improving hydraulic measures implemented for remediation. A three-dimensional transient groundwater flow model was developed for a contaminated mountainous site, at which interim corrective measures were initiated to limit further spreading of contaminants. This flow model accounts for complex geologic units that vary considerably in thickness, slope, and hydrogeologic properties, as well as large seasonal fluctuations of the groundwater table and flow rates. Other significant factors are local recharge from leaking underground storm drains and recharge from steep uphill areas. The zonation method was employed to account for the clustering of high and low hydraulic conductivities measured in a geologic unit. A composite model was used to represent the bulk effect of thin layers of relatively high hydraulic conductivity found within bedrock of otherwise low conductivity. The inverse simulator ITOUGH2 was used to calibrate the model for the distribution of rock properties. The model was initially calibrated using data collected between 1994 and 1996. To check the validity of the model, it was subsequently applied to predicting groundwater level fluctuation and groundwater flux between 1996 and 1998. Comparison of simulated and measured data demonstrated that the model is capable of predicting the complex flow reasonably well. Advective transport was approximated using pathways of particles originating from source areas of the plumes. The advective transport approximation was in good agreement with the trend of contaminant plumes observed over the years. The validated model was then refined to focus on a subsection of the large system. The refined model was subsequently used to assess the efficiency of hydraulic measures implemented for remediation.

  6. A conservative orbital advection scheme for simulations of magnetized shear flows with the PLUTO code

    CERN Document Server

    Mignone, A; Stute, M; Kolb, S M; Muscianisi, G

    2012-01-01

    Explicit numerical computations of super-fast differentially rotating disks are subject to the time-step constraint imposed by the Courant condition. When the bulk orbital velocity largely exceeds any other wave speed the time step is considerably reduced and a large number of steps may be necessary to complete the computation. We present a robust numerical scheme to overcome the Courant limitation by extending the algorithm previously known as FARGO (Fast Advection in Rotating Gaseous Objects) to the equations of magnetohydrodynamics (MHD). The proposed scheme conserves total angular momentum and energy to machine precision and works in Cartesian, cylindrical, or spherical coordinates. The algorithm is implemented in the PLUTO code for astrophysical gasdynamics and is suitable for local or global simulations of accretion or proto-planetary disk models. By decomposing the total velocity into an average azimuthal contribution and a residual term, the algorithm solves the MHD equations through a linear transpor...

  7. Spectral Properties of a Two Component and Two Temperature Advective Flow

    CERN Document Server

    Mandal, S; Mandal, Samir; Chakrabarti, Sandip K.

    2005-01-01

    Low angular momentum accretion flows very often have centrifugal pressure supported standing shock waves which can accelerate flow particles. The accelerated particles in turn emit synchrotron radiation in presence of magnetic fields. Efficient cooling of the electrons reduces its temperature in comparison to the protons. In this paper, we assume two temperature flows to explore this property of shocks and present an example of the emitted radiation spectrum.

  8. Characterization of GX 339-4 outburst of 2010-11: analysis by XSPEC using two component advective flow model

    Science.gov (United States)

    Debnath, Dipak; Mondal, Santanu; Chakrabarti, Sandip K.

    2015-02-01

    We study spectral properties of GX 339-4 during its 2010-11 outburst with two component advective flow (TCAF) model after its inclusion in XSPEC as a table model. We compare results fitted by TCAF model with combined disc blackbody and power-law model. For a spectral fit, we use 2.5-25 keV spectral data of the Proportional Counter Array instrument onboard RXTE satellite. From our fit, accretion flow parameters such as Keplerian (disc) rate, sub-Keplerian (halo) rate, location and strength of shock are extracted. We quantify how the disc and the halo rates vary during the entire outburst. We study how the halo to disc accretion rate ratio (ARR), quasi-periodic oscillations (QPOs), shock locations and its strength vary when the system passes through hard, hard-intermediate, soft-intermediate and soft states. We find pieces of evidence of monotonically increasing and decreasing nature of QPO frequencies depending on the variation of ARR during rising and declining phases. Interestingly, on days of transition from hard state to hard-intermediate spectral state (during the rising phase) or vice-versa (during decline phase), ARR is observed to be locally maximum. Non-constancy of ARR while obtaining reasonable fits points to the presence of two independent components in the flow.

  9. Characterization of GX 339-4 outburst of 2010-11: Analysis by XSPEC using Two Component Advective Flow model

    CERN Document Server

    Debnath, Dipak; Chakrabarti, Sandip K

    2013-01-01

    We study the spectral properties of the Galactic transient black hole candidate (BHC) GX 339-4 during its 2010-11 outburst with Two Component (Keplerian and sub-Keplerian) Advective Flow (TCAF) model after its inclusion in XSPEC as a local model. We also compare our TCAF model fitted results with combined disk black body (DBB) and power-law (PL) model fitted spectral results and find similar types of smooth variation in thermal (Keplerian or disk black body) as well as non-thermal (power-law or sub-Keplerian) fluxes. For spectral fit, we use 2.5-25 keV spectral data of PCA instrument onboard RXTE satellite. From the TCAF model fit, accretion flow parameters, such as the Keplerian (disk) rate, sub-Keplerian (halo) rate, location of the shock and strength of the shock are extracted. Our study provides a comprehensive understanding of the mass accretion processes and properties of the accretion disk around the BHC during the outburst phases. Based on the comparison of the halo to disk accretion rate ratio (ARR) ...

  10. Frontiers of chaotic advection

    CERN Document Server

    Aref, Hassan; Budišić, Marko; Cartwright, Julyan H E; Clercx, Herman J H; Feudel, Ulrike; Golestanian, Ramin; Gouillart, Emmanuelle; Guer, Yves Le; van Heijst, GertJan F; Krasnopolskaya, Tatyana S; MacKay, Robert S; Meleshko, Vyacheslav V; Metcalfe, Guy; Mezić, Igor; de Moura, Alessandro P S; Omari, Kamal El; Piro, Oreste; Speetjens, Michel F M; Sturman, Rob; Thiffeault, Jean-Luc; Tuval, Idan

    2014-01-01

    We review the present position of and survey future perspectives in the physics of chaotic advection; the field that emerged three decades ago at the intersection of fluid mechanics and nonlinear dynamics, which encompasses a range of applications with length scales ranging from micrometers to hundreds of kilometers, including systems as diverse as mixing and thermal processing of viscous fluids, micro-fluidics, biological flows, and large-scale dispersion of pollutants in oceanographic and atmospheric flows.

  11. Temporal variability from the two-component advective flow solution and its observational evidence

    CERN Document Server

    Dutta, Broja G

    2016-01-01

    In the propagating oscillatory shock model, the oscillation of the post-shock region, i.e., the Compton cloud, causes the observed low-frequency quasi-periodic oscillations (QPOs). The evolution of QPO frequency is explained by the systematic variation of the Compton cloud size, i.e., the steady radial movement of the shock front, which is triggered by the cooling of the post-shock region. Thus, analysis of energy-dependent temporal properties in different variability time scales can diagnose the dynamics and geometry of accretion flows around black holes. We study these properties for the high inclination black hole source XTE J1550-564 during its 1998 outburst and the low-inclination black hole source GX 339-4 during its 2006-07 outburst using RXTE/PCA data, and we find that they can satisfactorily explain the time lags associated with the QPOs from these systems. We find a smooth decrease of the time lag as a function of time in the rising phase of both sources. In the declining phase the time lag increase...

  12. Sweet and Sour: Attenuating Sulfidogenesis in an Advective Flow Column System with Perchlorate or Nitrate Treatment

    Science.gov (United States)

    Engelbrektson, A. L.; Hubbard, C. G.; Piceno, Y.; Boussina, A.; Jin, Y.; Dubinsky, E. A.; Tom, L.; Hu, P.; Conrad, M. E.; Anderson, G. L.; Coates, J. D.

    2013-12-01

    Hydrogen sulfide (H2S) biogenesis in oil reservoirs is a primary cause of souring and of associated costs in reservoir and pipeline maintenance. In addition to the corrosive effects of the H2S itself, abiotic and biological oxidation also generates sulfuric acid, further degrading metallic surfaces. Amending these environments with perchlorate (ClO4-) resolves these problems by inhibition of biological sulfate reduction and re-oxidation of H2S to elemental sulfur by dissimilatory (per)chlorate reducing bacteria (DPRB). Triplicate flow through columns packed with San Francisco bay sediment were flushed with bay water ([SO4=] = 25-30 mM) containing yeast extract with 50 mM inhibitor concentrations (NO3-or ClO4-) decreasing to 25 mM and finally 12.5 mM. Influent and effluent geochemistry was monitored and DNA was prepared from the sediment bed for microbial community analysis. Souring was reversed by both treatments (at 50 mM) compared to the control columns that had no ion addition. Nitrate began to re-sour when treatment concentration was decreased to 25 mM but treatment had to be decreased to 12.5 mM before the perchlorate treated columns began to re-sour. However, the treated columns re-soured to a lesser extent than the control columns. Phylochip microbial community analyses indicated microbial community shifts and phylogenetic clustering by treatment. Isotopic analysis of sulfate showed trends that broadly agreed with the geochemistry but also suggested further sulfur cycling was occurring. This study indicates that perchlorate shows great promise as an inhibitor of sulfidogenesis in natural communities and provides insight into which organisms are involved in this process.

  13. Analytical solutions for benchmarking cold regions subsurface water flow and energy transport models: one-dimensional soil thaw with conduction and advection

    Science.gov (United States)

    Kurylyk, Barret L.; McKenzie, Jeffrey M; MacQuarrie, Kerry T. B.; Voss, Clifford I.

    2014-01-01

    Numerous cold regions water flow and energy transport models have emerged in recent years. Dissimilarities often exist in their mathematical formulations and/or numerical solution techniques, but few analytical solutions exist for benchmarking flow and energy transport models that include pore water phase change. This paper presents a detailed derivation of the Lunardini solution, an approximate analytical solution for predicting soil thawing subject to conduction, advection, and phase change. Fifteen thawing scenarios are examined by considering differences in porosity, surface temperature, Darcy velocity, and initial temperature. The accuracy of the Lunardini solution is shown to be proportional to the Stefan number. The analytical solution results obtained for soil thawing scenarios with water flow and advection are compared to those obtained from the finite element model SUTRA. Three problems, two involving the Lunardini solution and one involving the classic Neumann solution, are recommended as standard benchmarks for future model development and testing.

  14. Mean vertical velocities and flow tilt angles at a fetch-limited forest site in the context of carbon dioxide vertical advection

    Directory of Open Access Journals (Sweden)

    E. Dellwik

    2009-08-01

    Full Text Available An analysis of flow angles from a fetch-limited beech forest site with clearings is presented. Flow angles and vertical velocities from two types of sonic anemometers as well as a ground based remote sensing lidar were analysed. Instead of using rotations, where zero-flow angles were assumed for neutral flow, the data from the instruments were interpreted in relation to the terrain.

    Uncertainties regarding flow distortion and limited sampling time (statistical uncertainty were evaluated and found to be significant. Especially for one of the sonic anemometers, relatively small changes in the flow distortion correction could change the sign of mean vertical velocities taken during stable atmospheric stratification relative to the neutral flow. Despite the uncertainties, it was possible to some extent to relate both positive and negative mean flow angles to features in the terrain.

    Conical and linear scans with a remote sensing lidar were evaluated for estimation of vertical velocities and flow angles. The results of the vertical conical scans were promising, and yielded negative flow angles for a sector where the forest is fetch-limited. However, more data and analysis is needed for a complete evaluation of the technique. The horizontal linear scans showed the variability of the mean wind speed field. A vertical velocity was calculated from different focusing distances, but this estimate yielded unrealistically high vertical velocities, due to neglect of the transversal wind component.

    The vertical advection term was calculated using the measured mean flow angles at the mast and profile measurements of carbon dioxide, but it is not recommended to use in relation with the flux measurement as the vertical velocity measured at the mast is most likely not representative for the whole forest.

  15. Evaporation of Accretion Disks around Black Holes: The Disk-Corona Transition and the Connection to the Advection-dominated Accretion Flow.

    Science.gov (United States)

    Liu; Yuan; Meyer; Meyer-Hofmeister; Xie

    1999-12-10

    We apply the disk-corona evaporation model (Meyer & Meyer-Hofmeister) originally derived for dwarf novae to black hole systems. This model describes the transition of a thin cool outer disk to a hot coronal flow. The mass accretion rate determines the location of this transition. For a number of well-studied black hole binaries, we take the mass flow rates derived from a fit of the advection-dominated accretion flow (ADAF) model to the observed spectra (for a review, see Narayan, Mahadevan, & Quataert) and determine where the transition of accretion via a cool disk to a coronal flow/ADAF would be located for these rates. We compare this with the observed location of the inner disk edge, as estimated from the maximum velocity of the Halpha emission line. We find that the transition caused by evaporation agrees with this determination in stellar disks. We also show that the ADAF and the "thin outer disk + corona" are compatible in terms of the physics in the transition region. PMID:10566989

  16. Steady-state and transient models of groundwater flow and advective transport, Eastern Snake River Plain aquifer, Idaho National Laboratory and vicinity, Idaho

    Science.gov (United States)

    Ackerman, Daniel J.; Rousseau, Joseph P.; Rattray, Gordon W.; Fisher, Jason C.

    2010-01-01

    Three-dimensional steady-state and transient models of groundwater flow and advective transport in the eastern Snake River Plain aquifer were developed by the U.S. Geological Survey in cooperation with the U.S. Department of Energy. The steady-state and transient flow models cover an area of 1,940 square miles that includes most of the 890 square miles of the Idaho National Laboratory (INL). A 50-year history of waste disposal at the INL has resulted in measurable concentrations of waste contaminants in the eastern Snake River Plain aquifer. Model results can be used in numerical simulations to evaluate the movement of contaminants in the aquifer. Saturated flow in the eastern Snake River Plain aquifer was simulated using the MODFLOW-2000 groundwater flow model. Steady-state flow was simulated to represent conditions in 1980 with average streamflow infiltration from 1966-80 for the Big Lost River, the major variable inflow to the system. The transient flow model simulates groundwater flow between 1980 and 1995, a period that included a 5-year wet cycle (1982-86) followed by an 8-year dry cycle (1987-94). Specified flows into or out of the active model grid define the conditions on all boundaries except the southwest (outflow) boundary, which is simulated with head-dependent flow. In the transient flow model, streamflow infiltration was the major stress, and was variable in time and location. The models were calibrated by adjusting aquifer hydraulic properties to match simulated and observed heads or head differences using the parameter-estimation program incorporated in MODFLOW-2000. Various summary, regression, and inferential statistics, in addition to comparisons of model properties and simulated head to measured properties and head, were used to evaluate the model calibration. Model parameters estimated for the steady-state calibration included hydraulic conductivity for seven of nine hydrogeologic zones and a global value of vertical anisotropy. Parameters

  17. On the disappearance of broad-line region in low-luminosity active galactic nuclei: the role of the outflows from advection dominated accretion flows

    CERN Document Server

    Cao, Xinwu

    2010-01-01

    The broad-line region (BLR) disappears in many low-luminosity AGNs, the reason of which is still controversial. The BLRs in AGNs are believed to be associated with the outflows from the accretion disks. Most of the low-luminosity AGNs (LLAGNs) contain advection dominated accretion flows (ADAFs), which are very hot and have a positive Bernoulli parameter. ADAFs are therefore associated with strong outflows. We estimate the cooling of the outflows from the ADAFs, and find that the gases in such hot outflows always cannot be cooled efficiently by bremsstrahlung radiation. The ADAF may co-exist with the standard disk, i.e., the inner ADAF connects to the outer thin accretion disk at radius R_tr, in the sources accreting at slightly lower than the critical rate. For the ADAFs with >0.001 L_edd, a secondary small inner cold disk is suggested to co-exist with the ADAF due to the condensation process. We estimate the Compton cooling of the outflow, of which the soft seed photons either come from the outer cold disk o...

  18. The advection-dominated accretion flow+thin accretion disk model for two low-luminosity active galactic nuclei: M81 and NGC 4579

    Institute of Scientific and Technical Information of China (English)

    Ya-Di Xu; Xin-Wu Cao

    2009-01-01

    It was found that advection-dominated accretion flow (ADAF)+thin disk model calculations can reproduce the observed spectral energy distributions (SEDs) of two low- luminosity active galactic nuclei (AGNs), provided they are accreting at ~ 0.01 - 0.03 Eddington rates and the thin disks are truncated to ADAFs at~ 100Rs (Rs is the Schwarzschild radius) for M81 and NGC 4579 (Quataert et al. 1999). However, the black hole masses adopted in their work are about one order of magnitude lower than recent measurements on these two sources. Adopting the well estimated black hole masses, our ADAF+thin disk model calculations can reproduce the observed SEDs of these two low- luminosity AGNs, if the black hole is accreting at 2.5 × 10-4 Eddington rates with the thin disk truncated at Rtr = 120Rs for M81 ((m) = 3.3 × 10-3 and Rtr = 80Rs are required for NGC 4579). The transition zones with temperature from the thin disk with 104 - 105 to~109 - 1010 K in the ADAF will inevitably emit thermal X-ray lines, which provides a useful diagnosis of their physical properties. The observed widths of the thermal X-ray iron lines at(~)6.8 keV are consistent with Doppler broadening by Keplerian motion of the gases in the transition zones at~100Rs. We use the structure of the transition zone between the ADAF and the thin disk derived by assuming the turbulent diffusive heat mechanism to calculate their thermal X-ray line emission with the standard software package Astrophysical Plasma Emission Code (APEC). Comparing them with the equivalent widths of the observed thermal X-ray iron lines in these two sources, we find that the turbulent diffusive heat mechanism seems to be unable to reproduce the ob- served thermal X-ray line emission. The test of the evaporation model for the accretion mode transition with the observed thermal X-ray line emission is briefly discussed.

  19. A New Paradigm for Flow Analyses and a Novel Technique to Enhance the Thrust from Scarfed Nozzles

    Science.gov (United States)

    Chang, I-Shih; Chang, Sin-Chung; Glick, Robert L.; Chang, Chau-Lyan; Glick, Mailyn P.

    2008-01-01

    A new flow analysis paradigm and a novel technique to enhance scarfed nozzle thrust are presented. The new paradigm, the space-time Conservation Element and Solution Element (CESE) method, a truly unsteady and genuinely multi-dimensional flow solver that provides accurate solutions for Euler and Navier-Stokes flows, is well suited for next generation flow analyses.In this study, the space-time CESE method was applied to solve scarfed nozzles flow-fields. Nozzle scarfing is frequently used for vectoring control of a space propulsion sub-system; it reduces nozzle weight and length and lowers nozzle thrust. A novel technique to enhance scarfed nozzles' thrust is discussed and investigated. Results of 2D and 3D flow analyses are presented.

  20. GPS Imaging of Solid Earth's Flex and Flow: A New Paradigm

    Science.gov (United States)

    Blewitt, G.; Hammond, W. C.; Kreemer, C.

    2015-12-01

    Geodetic GPS data analysis has gone through several paradigm shifts since the 1980s. Initially GPS was used in relative positioning mode to leverage and densify the existing global VLBI network. In the 1990s the new paradigm was to analyze GPS as a self-contained system, in which the global network of GPS stations and satellite orbits could be estimated simultaneously. Computational resources limit this approach to a few hundred stations (n ~ 100), with O(n4) computational complexity. Since the last decade, the new paradigm is to estimate GPS orbits first, followed by precise point positioning of single stations with O(n) complexity. This allows for parallel processing of an unlimited number of stations. The Nevada Geodetic Laboratory currently updates GPS time series for over 13,500 stations every week, a number that has been doubling every ~3 years. In some parts of the world, the inter-station distance between GPS stations that we process is now approaching ~10 km. This now brings us to a new paradigm, "GPS Imaging," for which we use thousands of GPS stations in different continents to generate smooth, yet detailed maps of vertical land motion. Our prototype images show that the striking, first-order signal in North America and Europe is large scale uplift and subsidence from mantle flow driven by Glacial Isostatic Adjustment. Thus we are imaging deep Earth processes with unprecedented scope, resolution and accuracy. At regional scales, the images reveal that anthropogenic lithospheric processes can dominate vertical land motion in extended regions. We have developed prototype techniques that form a foundation to make "GPS Imaging" operational: (1) an automatic, robust estimator of station velocity that is insensitive to prevalent step discontinuities, outliers, seasonality, and heteroscedasticity; (2) a realistic estimate of the velocity errors based on subsampling; (3) a filter of common-mode noise that is globally seamless; (4) a median spatial filter to

  1. On the tensorial nature of advective porosity

    Science.gov (United States)

    Neuman, Shlomo P.

    2005-02-01

    Field tracer tests indicate that advective porosity, the quantity relating advective velocity to Darcy flux, may exhibit directional dependence. Hydraulic anisotropy explains some but not all of the reported directional results. The present paper shows mathematically that directional variations in advective porosity may arise simply from incomplete mixing of an inert tracer between directional flow channels within a sampling (or support) volume ω of soil or rock that may be hydraulically isotropic or anisotropic. In the traditional fully homogenized case, our theory yields trivially a scalar advective porosity equal to the interconnected porosity ϕ, thus explaining neither the observed directional effects nor the widely reported experimental finding that advective porosity is generally smaller than ϕ. We consider incomplete mixing under conditions in which the characteristic time tD of longitudinal diffusion along channels across ω is much shorter than the characteristic time tH required for homogenization through transverse diffusion between channels. This may happen where flow takes place preferentially through relatively conductive channels and/or fractures of variable orientation separated by material that forms a partial barrier to diffusive transport. Our solution is valid for arbitrary channel Peclet numbers on a correspondingly wide range of time scales tD ⩽ t ≪ tH. It shows that the tracer center of mass is advected at a macroscopic velocity which is generally not collinear with the macroscopic Darcy flux and exceeds it in magnitude. These two vectors are related through a second-rank symmetric advective dispersivity tensor Φ. If the permeability k of ω is a symmetric positive-definite tensor, so is Φ. However, the principal directions and values of these two tensors are generally not the same; whereas those of k are a fixed property of the medium and the length-scale of ω, those of Φ depend additionally on the direction and magnitude of the

  2. Optically-thick accretion discs with advection

    Institute of Scientific and Technical Information of China (English)

    陈林红; 吴枚; 尚仁成

    2002-01-01

    The structures of optically-thick accretion discs with radial advection have been investigated by the iteration and integration algorithms. The advective cooling term changes mostly the inner part of disc solution, and even results in an optically-thick advection-dominated accretion flow (ADAF). Three distinct branches-the outer Shakura-Sunyaev disc (SSD), the inner ADAF and the middle transition layer-are found for a super-Eddington disc. The SSD-ADAF transition radius can be estimated as 18(M/ME)RG where RG is the Schwarzschild radius, M is the mass accretion rate and ME is the Eddington accretion rate. SSD solutions calculated with the iteration and integration methods are identical, while ADAF solutions obtained by these two methods differ greatly. Detailed algorithms and their differences have been analysed. The iteration algorithm is not self-consistent, since it implies that the dimensionless advection factor ξ is invariant, but in the inner ADAF region the variation of ξ is not negligible. The integration algorithm is always effective for the whole region of an optically-thick disc if the accretion rate is no smaller than 10-4ME. For optically-thin discs, the validity of these two algorithms is different. We suggest that the integration method be employed to calculate the global solution of a disc model without assuming ξ to be a constant. We also discuss its application to the emergent continuum spectrum in order to explain observational facts.

  3. Advection around ventilated U-shaped burrows: A model study

    Science.gov (United States)

    Brand, Andreas; Lewandowski, JöRg; Hamann, Enrico; Nützmann, Gunnar

    2013-05-01

    Advective transport in the porous matrix of sediments surrounding burrows formed by fauna such as Chironomus plumosus has been generally neglected. A positron emission tomography study recently revealed that the pumping activity of the midge larvae can indeed induce fluid flow in the sediment. We present a numerical model study which explores the conditions at which advective transport in the sediment becomes relevant. A 0.15 m deep U-shaped burrow with a diameter of 0.002 m within the sediment was represented in a 3-D domain. Fluid flow in the burrow was calculated using the Navier-Stokes equation for incompressible laminar flow in the burrow, and flow in the sediment was described by Darcy's law. Nonreactive and reactive transport scenarios were simulated considering diffusion and advection. The pumping activity of the model larva results in considerable advective flow in the sediment at reasonable high permeabilities with flow velocities of up to 7.0 × 10-6 m s-1 close to the larva for a permeability of 3 × 10-12 m2. At permeabilities below 7 × 10-13 m2 advection is negligible compared to diffusion. Reactive transport simulations using first-order kinetics for oxygen revealed that advective flux into the sediment downstream of the pumping larva enhances sedimentary uptake, while the advective flux into the burrow upstream of the larvae inhibits diffusive sedimentary uptake. Despite the fact that both effects cancel each other with respect to total solute uptake, the advection-induced asymmetry in concentration distribution can lead to a heterogeneous solute and redox distribution in the sediment relevant to complex reaction networks.

  4. Using the Statecharts paradigm for simulation of patient flow in surgical care.

    Science.gov (United States)

    Sobolev, Boris; Harel, David; Vasilakis, Christos; Levy, Adrian

    2008-03-01

    Computer simulation of patient flow has been used extensively to assess the impacts of changes in the management of surgical care. However, little research is available on the utility of existing modeling techniques. The purpose of this paper is to examine the capacity of Statecharts, a system of graphical specification, for constructing a discrete-event simulation model of the perioperative process. The Statecharts specification paradigm was originally developed for representing reactive systems by extending the formalism of finite-state machines through notions of hierarchy, parallelism, and event broadcasting. Hierarchy permits subordination between states so that one state may contain other states. Parallelism permits more than one state to be active at any given time. Broadcasting of events allows one state to detect changes in another state. In the context of the peri-operative process, hierarchy provides the means to describe steps within activities and to cluster related activities, parallelism provides the means to specify concurrent activities, and event broadcasting provides the means to trigger a series of actions in one activity according to transitions that occur in another activity. Combined with hierarchy and parallelism, event broadcasting offers a convenient way to describe the interaction of concurrent activities. We applied the Statecharts formalism to describe the progress of individual patients through surgical care as a series of asynchronous updates in patient records generated in reaction to events produced by parallel finite-state machines representing concurrent clinical and managerial activities. We conclude that Statecharts capture successfully the behavioral aspects of surgical care delivery by specifying permissible chronology of events, conditions, and actions. PMID:18390170

  5. Chaotic advection at the pore scale: Mechanisms, upscaling and implications for macroscopic transport

    Science.gov (United States)

    Lester, D. R.; Trefry, M. G.; Metcalfe, G.

    2016-11-01

    The macroscopic spreading and mixing of solute plumes in saturated porous media is ultimately controlled by processes operating at the pore scale. Whilst the conventional picture of pore-scale mechanical dispersion and molecular diffusion leading to persistent hydrodynamic dispersion is well accepted, this paradigm is inherently two-dimensional (2D) in nature and neglects important three-dimensional (3D) phenomena. We discuss how the kinematics of steady 3D flow at the pore scale generate chaotic advection-involving exponential stretching and folding of fluid elements-the mechanisms by which it arises and implications of microscopic chaos for macroscopic dispersion and mixing. Prohibited in steady 2D flow due to topological constraints, these phenomena are ubiquitous due to the topological complexity inherent to all 3D porous media. Consequently 3D porous media flows generate profoundly different fluid deformation and mixing processes to those of 2D flow. The interplay of chaotic advection and broad transit time distributions can be incorporated into a continuous-time random walk (CTRW) framework to predict macroscopic solute mixing and spreading. We show how these results may be generalised to real porous architectures via a CTRW model of fluid deformation, leading to stochastic models of macroscopic dispersion and mixing which both honour the pore-scale kinematics and are directly conditioned on the pore-scale architecture.

  6. High Order Semi-Lagrangian Advection Scheme

    Science.gov (United States)

    Malaga, Carlos; Mandujano, Francisco; Becerra, Julian

    2014-11-01

    In most fluid phenomena, advection plays an important roll. A numerical scheme capable of making quantitative predictions and simulations must compute correctly the advection terms appearing in the equations governing fluid flow. Here we present a high order forward semi-Lagrangian numerical scheme specifically tailored to compute material derivatives. The scheme relies on the geometrical interpretation of material derivatives to compute the time evolution of fields on grids that deform with the material fluid domain, an interpolating procedure of arbitrary order that preserves the moments of the interpolated distributions, and a nonlinear mapping strategy to perform interpolations between undeformed and deformed grids. Additionally, a discontinuity criterion was implemented to deal with discontinuous fields and shocks. Tests of pure advection, shock formation and nonlinear phenomena are presented to show performance and convergence of the scheme. The high computational cost is considerably reduced when implemented on massively parallel architectures found in graphic cards. The authors acknowledge funding from Fondo Sectorial CONACYT-SENER Grant Number 42536 (DGAJ-SPI-34-170412-217).

  7. Advective turbulent transport in the fluid plasma

    Science.gov (United States)

    Min, Byung-Hoon; An, Chan-Yong; Kim, Chang-Bae

    2013-10-01

    The Hasegawa-Wakatani model (HWM) has been employed in pedagogical analyses of the physics behind the behavior of the tokamak plasmas. In addition to the geometric simplicity HWM has an appealing feature of sustaining autonomous quasi-steady state, unstable modes providing the power that is being transported by the nonlinear interactions and is eventually dissipated by the collisional damping at small scales. Emergence of the zonal flow out of the turbulence is a main candidate to cause the transition from the low plasma confinement to the high mode. In the study of such LH transition with the HWM, the adiabaticity parameter has been shown to play an important role in forcing the zonal flow that results in the regulation of the drift-wave turbulence. Instead of concentrating on the physics of the feedback loop between the turbulence and the zonal flow the present study focuses on the presence of the advective transport of the energy. Numerical simulations of HWM are performed and the connections between the advective transport and the zonal flow will be presented. This work was supported by the Supercpmputing Center/Korea Institute of Science and Technology Information with supercomputing resources including technical support (KSC-2013-C1-009).

  8. A generalized advection dispersion equation

    Indian Academy of Sciences (India)

    Abdon Atangana

    2014-02-01

    This paper examines a possible effect of uncertainties, variability or heterogeneity of any dynamic system when being included in its evolution rule; the notion is illustrated with the advection dispersion equation, which describes the groundwater pollution model. An uncertain derivative is defined; some properties of the operator are presented. The operator is used to generalize the advection dispersion equation. The generalized equation differs from the standard equation in four properties. The generalized equation is solved via the variational iteration technique. Some illustrative figures are presented.

  9. How to Determine Losses in a Flow Field: A Paradigm Shifttowards the Second Law Analysis

    Directory of Open Access Journals (Sweden)

    Heinz Herwig

    2014-05-01

    Full Text Available Assuming that CFD solutions will be more and more used to characterizelosses in terms of drag for external flows and head loss for internal flows, we suggest toreplace single-valued data, like the drag force or a pressure drop, by field information aboutthe losses. These information are gained when the entropy generation in the flow field isanalyzed, an approach that often is called second law analysis (SLA, referring to the secondlaw of thermodynamics. We show that this SLA approach is straight-forward, systematicand helpful when it comes to the physical interpretation of the losses in a flow field. Variousexamples are given, including external and internal flows, two phase flow, compressible flowand unsteady flow. Finally, we show that an energy transfer within a certain process can beput into a broader perspective by introducing the entropic potential of an energy.

  10. Theory of advection-driven long range biotic transport

    Science.gov (United States)

    We propose a simple mechanistic model to examine the effects of advective flow on the spread of fungal diseases spread by wind-blown spores. The model is defined by a set of two coupled non-linear partial differential equations for spore densities. One equation describes the long-distance advectiv...

  11. Fast multigrid solution of the advection problem with closed characteristics

    Energy Technology Data Exchange (ETDEWEB)

    Yavneh, I. [Israel Inst. of Technology, Haifa (Israel); Venner, C.H. [Univ. of Twente, Enschede (Netherlands); Brandt, A. [Weizmann Inst. of Science, Rehovot (Israel)

    1996-12-31

    The numerical solution of the advection-diffusion problem in the inviscid limit with closed characteristics is studied as a prelude to an efficient high Reynolds-number flow solver. It is demonstrated by a heuristic analysis and numerical calculations that using upstream discretization with downstream relaxation-ordering and appropriate residual weighting in a simple multigrid V cycle produces an efficient solution process. We also derive upstream finite-difference approximations to the advection operator, whose truncation terms approximate {open_quotes}physical{close_quotes} (Laplacian) viscosity, thus avoiding spurious solutions to the homogeneous problem when the artificial diffusivity dominates the physical viscosity.

  12. Nucleosynthesis in Advective Accretion Disks Around Galactic and Extra-Galactic Black Holes

    CERN Document Server

    Mukhopadhyay, B

    1998-01-01

    We compute the nucleosynthesis of materials inside advective disks around black holes. We show that composition of incoming matter can change significantly depending on the accretion rate and accretion disks. These works are improvements on the earlier works in thick accretion disks of Chakrabarti, Jin & Arnett (1987) in presence of advection in the flow.

  13. The multifractal structure of chaotically advected chemical fields

    CERN Document Server

    Neufeld, Z; Hernández-García, E; Tél, T; Neufeld, Zoltan; Lopez, Cristobal; Hernandez-Garcia, Emilio; Tel, Tamas

    1999-01-01

    The structure of the concentration field of a decaying substance produced by chemical sources and advected by a smooth incompressible two-dimensional flow is investigated. We focus our attention on the non-uniformities of the Hölder exponent of the resulting filamental chemical field. They appear most evidently in the case of open flows where irregularities of the field exhibit strong spatial intermittency as they are restricted to a fractal manifold. Non-uniformities of the Hölder exponent of the chemical field in closed flows appears as a consequence of the non-uniform stretching of the fluid elements. We study how this affects the scaling exponents of the structure functions, displaying anomalous scaling, and relate the scaling exponents to the distribution of finite-time Lyapunov exponents of the advection dynamics. Theoretical predictions are compared with numerical experiments.

  14. Computation of Mass-Outflow Rates From Advective Accretion Disks Around Black Holes

    CERN Document Server

    Das, T K

    1998-01-01

    We self-consistently compute the mass outflow rate from a mass inflow using the conditions in the centrifugal barrier of an advective flow. Our detailed result agrees with the theoretical estimates given in Chakrabarti (1997; astro-ph/9801079).

  15. Advective and diffusive contributions to reactive gas transport during pyrite oxidation in the unsaturated zone

    DEFF Research Database (Denmark)

    Binning, Philip John; Postma, Diederik Jan; Russel, T.F.;

    2007-01-01

    at depth in the unsaturated zone, a pressure gradient is created between the reactive zone and the ground surface, causing a substantial advective air flow into the subsurface. To determine the balance between advective and diffusive transport, a one-dimensional multicomponent unsaturated zone gas...... flows at steady state. However, greater pressure gradients are found in low-permeability soils. In transient cases, advective fluxes depend on the initial conditions and can be far greater than diffusive fluxes. In contrast to steady state conditions the transient case is sensitive to other model...

  16. Oceanic heat advection to the Arctic in the last Millennium

    OpenAIRE

    Spielhagen, Robert F.; Werner, Kirstin; Aagaard-Sørensen, Steffen; Zamelczyk, Katarzyna; Kandiano, Evguenia; Budeus, Gereon; Husum, Katrine; Marchitto, Thomas M.; Hald, Morten

    2011-01-01

    EGU2011-8738 At present, the Arctic is responding faster to global warming than most other areas on earth, as indicated by rising air temperatures, melting glaciers and ice sheets and a decline of the sea ice cover. As part of the meridional overturning circulation which connects all ocean basins and influences global climate, northward flowing Atlantic Water is the major means of heat and salt advection towards the Arctic where it strongly affects the sea ice distribution. Records of its ...

  17. Non-linear thermal engineering, chaotic advection and mixing; Thermique non-lineaire, melange et advection chaotique

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-12-31

    This conference day was jointly organized by the `university group of thermal engineering (GUT)` and the French association of thermal engineers. This book of proceedings contains 7 papers entitled: `energy spectra of a passive scalar undergoing advection by a chaotic flow`; `analysis of chaotic behaviours: from topological characterization to modeling`; `temperature homogeneity by Lagrangian chaos in a direct current flow heat exchanger: numerical approach`; ` thermal instabilities in a mixed convection phenomenon: nonlinear dynamics`; `experimental characterization study of the 3-D Lagrangian chaos by thermal analogy`; `influence of coherent structures on the mixing of a passive scalar`; `evaluation of the performance index of a chaotic advection effect heat exchanger for a wide range of Reynolds numbers`. (J.S.)

  18. Cellwise conservative unsplit advection for the volume of fluid method

    Science.gov (United States)

    Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri

    2015-02-01

    We present a cellwise conservative unsplit (CCU) advection scheme for the volume of fluid method (VOF) in 2D. Contrary to other schemes based on explicit calculations of the flux balances, the CCU advection adopts a cellwise approach where the pre-images of the control volumes are traced backwards through the flow map. The donating regions of the fluxes are calculated via the streaklines of the grid intersections, represented as polygonal chains whose vertices are determined by backward tracing of particles injected in the flow at different times. High order accuracy is obtained from the fourth-order Runge-Kutta method, where intermediate velocities along pathlines are determined with quadratic temporal and bicubic spatial interpolations. The volumes of the donating regions are corrected in order to fulfill the discrete continuity of incompressible flows. Consequently, the calculation produces non-overlapping donating regions and pre-images with conforming edges to their neighbors, resulting in the conservativeness and the boundedness (liquid volume fraction inside the interval [ 0 , 1 ]) of the CCU advection scheme. Finally, the update of the liquid volume fractions is computed from the intersections of the pre-image polygons with the reconstructed interfaces. The CCU scheme is tested on several benchmark tests for the VOF advection, together with the standard piecewise linear interface calculation (PLIC). The geometrical errors of the CCU compare favorably with other unsplit VOF-PLIC schemes. Finally, potential improvements of the VOF method with the use of more precise interface representation techniques and the future extension of the CCU scheme to 3D are discussed.

  19. Verification of Advective Bar Elements Implemented in the Aria Thermal Response Code.

    Energy Technology Data Exchange (ETDEWEB)

    Mills, Brantley [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2016-01-01

    A verification effort was undertaken to evaluate the implementation of the new advective bar capability in the Aria thermal response code. Several approaches to the verification process were taken : a mesh refinement study to demonstrate solution convergence in the fluid and the solid, visually examining the mapping of the advective bar element nodes to the surrounding surfaces, and a comparison of solutions produced using the advective bars for simple geometries with solutions from commercial CFD software . The mesh refinement study has shown solution convergence for simple pipe flow in both temperature and velocity . Guidelines were provided to achieve appropriate meshes between the advective bar elements and the surrounding volume. Simulations of pipe flow using advective bars elements in Aria have been compared to simulations using the commercial CFD software ANSYS Fluent (r) and provided comparable solutions in temperature and velocity supporting proper implementation of the new capability. Verification of Advective Bar Elements iv Acknowledgements A special thanks goes to Dean Dobranich for his guidance and expertise through all stages of this effort . His advice and feedback was instrumental to its completion. Thanks also goes to Sam Subia and Tolu Okusanya for helping to plan many of the verification activities performed in this document. Thank you to Sam, Justin Lamb and Victor Brunini for their assistance in resolving issues encountered with running the advective bar element model. Finally, thanks goes to Dean, Sam, and Adam Hetzler for reviewing the document and providing very valuable comments.

  20. Toward enhanced subsurface intervention methods using chaotic advection.

    Science.gov (United States)

    Trefry, Michael G; Lester, Daniel R; Metcalfe, Guy; Ord, Alison; Regenauer-Lieb, Klaus

    2012-01-01

    Many intervention activities in the terrestrial subsurface involve the need to recover/emplace distributions of scalar quantities (e.g. dissolved phase concentrations or heat) from/in volumes of saturated porous media. These scalars can be targeted by pump-and-treat methods or by amendment technologies. Application examples include in-situ leaching for metals, recovery of dissolved contaminant plumes, or utilizing heat energy in geothermal reservoirs. While conventional pumping methods work reasonably well, costs associated with maintaining pumping schedules are high and improvements in efficiency would be welcome. In this paper we discuss how transient switching of the pressure at different wells can intimately control subsurface flow, generating a range of "programmed" flows with various beneficial characteristics. Some programs produce chaotic flows which accelerate mixing, while others create encapsulating flows which can isolate fluid zones for lengthy periods. In a simplified model of an aquifer subject to balanced pumping, chaotic flow topologies have been predicted theoretically and verified experimentally using Hele-Shaw cells. Here, a survey of the key characteristics of chaotic advection is presented. Mathematical methods are used to show how these characteristics may translate into practical situations involving regional flows and heterogeneity. The results are robust to perturbations, and withstand significant aquifer heterogeneity. It is proposed that chaotic advection may form the basis of new efficient technologies for groundwater interventions.

  1. Cellwise conservative unsplit advection for the volume of fluid method

    DEFF Research Database (Denmark)

    Comminal, Raphaël; Spangenberg, Jon; Hattel, Jesper Henri

    2015-01-01

    We present a cellwise conservative unsplit (CCU) advection scheme for the volume of fluid method (VOF) in 2D. Contrary to other schemes based on explicit calculations of the flux balances, the CCU advection adopts a cellwise approach where the pre-images of the control volumes are traced...... improvements of the VOF method with the use of more precise interface representation techniques and the future extension of the CCU scheme to 3D are discussed. ©2014 Elsevier Inc. All rights reserved.......-order Runge–Kutta method, where intermediate velocities along pathlines are determined with quadratic temporal and bicubic spatial interpolations. The volumes of the donating regions are corrected in order to fulfill the discrete continuity of incompressible flows. Consequently, the calculation produces non...

  2. Turbulent dynamo with advective magnetic helicity flux

    CERN Document Server

    Del Sordo, Fabio; Brandenburg, Axel

    2012-01-01

    Many astrophysical bodies harbor magnetic fields that are thought to be sustained by dynamo processes. However, it has been argued that the production of large-scale magnetic fields by a mean-field dynamo is strongly suppressed at large magnetic Reynolds numbers owing to the conservation of magnetic helicity. This phenomenon is known as catastrophic quenching. Advection of magnetic field toward the outer boundaries and away from the dynamo is expected to alleviate such quenching. Examples are stellar and galactic winds. Such advection might be able to overcome the constraint imposed by the conservation of magnetic helicity, transporting a fraction of it outside the domain in which the dynamo operates. We study how the dynamo process is affected by advection. In particular, we study the relative roles played by advective and diffusive fluxes of magnetic helicity. We do this by performing direct numerical simulations of a turbulent dynamo of alpha^2 type driven by forced turbulence in a Cartesian domain in the ...

  3. Effect of Ionic Advection on Electroosmosis over Charge Surfaces: Beyond the Weak Field Limit

    CERN Document Server

    Ghosh, Uddipta

    2015-01-01

    The present study deals with the effect of ionic advection on electroosmotic flow over charge modulated surfaces in a generalized paradigm when the classically restrictive "weak field" limit may be relaxed. Going beyond the commonly portrayed weak field limit (i.e, the externally applied electric field is over-weighed by the surface-induced electrical potential, towards charge distribution in an electrified wall-adhering layer) for electroosmotic transport, we numerically solve the coupled full set of Poisson-Nernst-Planck (PNP) and Navier-Stokes equations, in a semi-infinite domain, bounded at the bottom by a charged wall. Further, in an effort to obtain deeper physical insight, we solve the simplified forms of the relevant governing equations for low surface potential in two separate asymptotic limits: (i) a regular perturbation solution for Low Ionic Peclet number (Pe), where Pe is employed as the gauge function and (ii) a matched asymptotic solution for O(1) Pe in the Thin Electric Double Layer (EDL) limi...

  4. Waste dissolution with chemical reaction, diffusion and advection

    International Nuclear Information System (INIS)

    This paper extends the mass-transfer analysis to include the effect of advective transport in predicting the steady-state dissolution rate, with a chemical-reaction-rate boundary condition at the surface of a waste form of arbitrary shape. This new theory provides an analytic means of predicting the ground-water velocities at which dissolution rate in a geologic environment will be governed entirely to the chemical reaction rate. As an illustration, we consider the steady-state potential flow of ground water in porous rock surrounding a spherical waste solid. 3 refs., 2 figs

  5. Local and nonlocal advected invariants and helicities in magnetohydrodynamics and gas dynamics I: Lie dragging approach

    International Nuclear Information System (INIS)

    In this paper advected invariants and conservation laws in ideal magnetohydrodynamics (MHD) and gas dynamics are obtained using Lie dragging techniques. There are different classes of invariants that are advected or Lie dragged with the flow. Simple examples are the advection of the entropy S (a 0-form), and the conservation of magnetic flux (an invariant 2-form advected with the flow). The magnetic flux conservation law is equivalent to Faraday's equation. The gauge condition for the magnetic helicity to be advected with the flow is determined. Different variants of the helicity in ideal fluid dynamics and MHD including: fluid helicity, cross helicity and magnetic helicity are investigated. The fluid helicity conservation law and the cross-helicity conservation law in MHD are derived for the case of a barotropic gas. If the magnetic field lies in the constant entropy surface, then the gas pressure can depend on both the entropy and the density. In these cases the conservation laws are local conservation laws. For non-barotropic gases, we obtain nonlocal conservation laws for fluid helicity and cross helicity by using Clebsch variables. These nonlocal conservation laws are the main new results of the paper. Ertel's theorem and potential vorticity, the Hollman invariant, and the Godbillon–Vey invariant for special flows for which the magnetic helicity is zero are also discussed. (paper)

  6. Discrete Lie Advection of Differential Forms

    CERN Document Server

    Mullen, P; Pavlov, D; Durant, L; Tong, Y; Kanso, E; Marsden, J E; Desbrun, M

    2009-01-01

    In this paper, we present a numerical technique for performing Lie advection of arbitrary differential forms. Leveraging advances in high-resolution finite volume methods for scalar hyperbolic conservation laws, we first discretize the interior product (also called contraction) through integrals over Eulerian approximations of extrusions. This, along with Cartan's homotopy formula and a discrete exterior derivative, can then be used to derive a discrete Lie derivative. The usefulness of this operator is demonstrated through the numerical advection of scalar fields and 1-forms on regular grids.

  7. Paradigm Shift

    OpenAIRE

    Besancenot, Damien; Dogguy, Habib

    2011-01-01

    This paper analyses the consequences of young researchers' scientifc choice on the dynamics of sciences. We develop a simple two state mean field game model to analyze the competition between two paradigms based on Kuhn's theory of scientifc revolutions. At the beginning of their career, young researchers choose the paradigm in which they want to work according to social and personal motivations. Despite the possibility of multiple equilibria the model exhibits at least one stable solution in...

  8. Metamorphism during temperature gradient with undersaturated advective airflow in a snow sample

    Science.gov (United States)

    Ebner, Pirmin Philipp; Schneebeli, Martin; Steinfeld, Aldo

    2016-04-01

    Snow at or close to the surface commonly undergoes temperature gradient metamorphism under advective flow, which alters its microstructure and physical properties. Time-lapse X-ray microtomography is applied to investigate the structural dynamics of temperature gradient snow metamorphism exposed to an advective airflow in controlled laboratory conditions. Cold saturated air at the inlet was blown into the snow samples and warmed up while flowing across the sample with a temperature gradient of around 50 K m-1. Changes of the porous ice structure were observed at mid-height of the snow sample. Sublimation occurred due to the slight undersaturation of the incoming air into the warmer ice matrix. Diffusion of water vapor opposite to the direction of the temperature gradient counteracted the mass transport of advection. Therefore, the total net ice change was negligible leading to a constant porosity profile. However, the strong recrystallization of water molecules in snow may impact its isotopic or chemical content.

  9. Asymmetric spreading in highly advective, disordered environments

    OpenAIRE

    Carpenter, John H.; Dahmen, Karin A.

    2005-01-01

    Spreading of bacteria in a highly advective, disordered environment is examined. Predictions of super-diffusive spreading for a simplified reaction-diffusion equation are tested. Concentration profiles display anomalous growth and super-diffusive spreading. A perturbation analysis yields a crossover time between diffusive and super-diffusive behavior. The time's dependence on the convection velocity and disorder is tested. Like the simplified equation, the full linear reaction-diffusion equat...

  10. Distributed Parallel Particle Advection using Work Requesting

    Energy Technology Data Exchange (ETDEWEB)

    Muller, Cornelius; Camp, David; Hentschel, Bernd; Garth, Christoph

    2013-09-30

    Particle advection is an important vector field visualization technique that is difficult to apply to very large data sets in a distributed setting due to scalability limitations in existing algorithms. In this paper, we report on several experiments using work requesting dynamic scheduling which achieves balanced work distribution on arbitrary problems with minimal communication overhead. We present a corresponding prototype implementation, provide and analyze benchmark results, and compare our results to an existing algorithm.

  11. Influence of porewater advection on denitrification in carbonate sands: Evidence from repacked sediment column experiments

    DEFF Research Database (Denmark)

    Santos, Isaac R.; Eyre, Bradley D.; Glud, Ronnie N.

    2012-01-01

    Porewater flow enhances mineralization rates in organic-poor permeable sands. Here, a series of sediment column experiments were undertaken to assess the potential effect of advective porewater transport on denitrification in permeable carbonate sands collected from Heron Island (Great Barrier Reef...

  12. Chaotic advection in 2D anisotropic porous media

    Science.gov (United States)

    Varghese, Stephen; Speetjens, Michel; Trieling, Ruben; Toschi, Federico

    2015-11-01

    Traditional methods for heat recovery from underground geothermal reservoirs employ a static system of injector-producer wells. Recent studies in literature have shown that using a well-devised pumping scheme, through actuation of multiple injector-producer wells, can dramatically enhance production rates due to the increased scalar / heat transport by means of chaotic advection. However the effect of reservoir anisotropy on kinematic mixing and heat transport is unknown and has to be incorporated and studied for practical deployment in the field. As a first step, we numerically investigate the effect of anisotropy (both magnitude and direction) on (chaotic) advection of passive tracers in a time-periodic Darcy flow within a 2D circular domain driven by periodically reoriented diametrically opposite source-sink pairs. Preliminary results indicate that anisotropy has a significant impact on the location, shape and size of coherent structures in the Poincare sections. This implies that the optimal operating parameters (well spacing, time period of well actuation) may vary strongly and must be carefully chosen so as to enhance subsurface transport. This work is part of the research program of the Foundation for Fundamental Research on Matter (FOM), which is part of Netherlands Organisation for Scientific Research (NWO). This research program is co-financed by Shell Global Solutions International B.V.

  13. A cryogenic circulating advective multi-pass absorption cell

    Science.gov (United States)

    Stockett, M. H.; Lawler, J. E.

    2012-03-01

    A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 107 cm-3. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

  14. OBSERVATION OF MAGNETIC RECONNECTION DRIVEN BY GRANULAR SCALE ADVECTION

    Energy Technology Data Exchange (ETDEWEB)

    Zeng Zhicheng; Cao Wenda [Center for Solar-Terrestrial Research, New Jersey Institute of Technology, 323 Martin Luther King Blvd., Newark, NJ 07102 (United States); Ji Haisheng [Big Bear Solar Observatory, 40386 North Shore Lane, Big Bear City, CA 92314 (United States)

    2013-06-01

    We report the first evidence of magnetic reconnection driven by advection in a rapidly developing large granule using high spatial resolution observations of a small surge event (base size {approx} 4'' Multiplication-Sign 4'') with the 1.6 m aperture New Solar Telescope at the Big Bear Solar Observatory. The observations were carried out in narrowband (0.5 A) He I 10830 A and broadband (10 A) TiO 7057 A. Since He I 10830 A triplet has a very high excitation level and is optically thin, its filtergrams enable us to investigate the surge from the photosphere through the chromosphere into the lower corona. Simultaneous space data from the Atmospheric Imaging Assembly and Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory were used in the analysis. It is shown that the surge is spatio-temporally associated with magnetic flux emergence in the rapidly developing large granule. During the development of the granule, its advecting flow ({approx}2 km s{sup -1}) squeezed the magnetic flux into an intergranular lane area, where a magnetic flux concentration was formed and the neighboring flux with opposite magnetic polarity was canceled. During the cancellation, the surge was produced as absorption in He I 10830 A filtergrams while simultaneous EUV brightening occurred at its base. The observations clearly indicate evidence of a finest-scale reconnection process driven by the granule's motion.

  15. Semi-Lagrangian advection-propagation (SLAP) scheme for three-dimensional interface tracking

    Science.gov (United States)

    Aldredge, R. C.

    2010-06-01

    A fully three-dimensional semi-Lagrangian scheme is developed for computing the evolution of advected self-propagating surfaces (e.g., premixed flames) governed by a level-set advection-propagation equation. The scheme provides third-order spatial accuracy and shape preservation. Example numerical simulations of three-dimensional front propagation are presented to illustrate the capability of the scheme of capturing cusp formation and associated surface-area annihilation as well as the formation and consumption of detached closed-surface pockets behind fronts propagating in highly vortical flow.

  16. Fluctuating paradigm

    OpenAIRE

    Simmons, L. W.; Tomkins, J. L.; Kotiaho, J. S.; Hunt, J.

    1999-01-01

    A prominent paradigm in evolutionary biology over the last ten years has been the role of fluctuating asymmetry in sexual selection. Fluctuating asymmetry in bilaterally paired traits, and in particular sexual traits, has been proposed to be a reliable indicator of individual quality and the focus of selection through sexual competition and attractiveness. We surveyed the literature on fluctuating asymmetry and sexual selection and found a marked chronological decline in the proportion of stu...

  17. Development of Multigrid Methods for diffusion, Advection, and the incompressible Navier-Stokes Equations

    Energy Technology Data Exchange (ETDEWEB)

    Gjesdal, Thor

    1997-12-31

    This thesis discusses the development and application of efficient numerical methods for the simulation of fluid flows, in particular the flow of incompressible fluids. The emphasis is on practical aspects of algorithm development and on application of the methods either to linear scalar model equations or to the non-linear incompressible Navier-Stokes equations. The first part deals with cell centred multigrid methods and linear correction scheme and presents papers on (1) generalization of the method to arbitrary sized grids for diffusion problems, (2) low order method for advection-diffusion problems, (3) attempt to extend the basic method to advection-diffusion problems, (4) Fourier smoothing analysis of multicolour relaxation schemes, and (5) analysis of high-order discretizations for advection terms. The second part discusses a multigrid based on pressure correction methods, non-linear full approximation scheme, and papers on (1) systematic comparison of the performance of different pressure correction smoothers and some other algorithmic variants, low to moderate Reynolds numbers, and (2) systematic study of implementation strategies for high order advection schemes, high-Re flow. An appendix contains Fortran 90 data structures for multigrid development. 160 refs., 26 figs., 22 tabs.

  18. Reconciling paradigms of abnormal pulmonary blood flow and quasi-malignant cellular alterations in pulmonary arterial hypertension.

    Science.gov (United States)

    Happé, C M; Szulcek, R; Voelkel, N F; Bogaard, H J

    2016-08-01

    In pulmonary arterial hypertension (PAH) structural and functional abnormalities of the small lung vessels interact and lead to a progressive increase in pulmonary vascular resistance and right heart failure. A current pathobiological concept characterizes PAH as a 'quasi-malignant' disease focusing on cancer-like alterations in endothelial cells (EC) and the importance of their acquired apoptosis-resistant, hyper-proliferative phenotype in the process of vascular remodeling. While changes in pulmonary blood flow (PBF) have been long-since recognized and linked to the development of PAH, little is known about a possible relationship between an altered PBF and the quasi-malignant cell phenotype in the pulmonary vascular wall. This review summarizes recognized and hypothetical effects of an abnormal PBF on the pulmonary vascular bed and links these to quasi-malignant changes found in the pulmonary endothelium. Here we describe that abnormal PBF does not only trigger a pulmonary vascular cell growth program, but may also maintain the cancer-like phenotype of the endothelium. Consequently, normalization of PBF and EC response to abnormal PBF may represent a treatment strategy in patients with established PAH. PMID:26804008

  19. A Computational Method for Sharp Interface Advection

    CERN Document Server

    Roenby, Johan; Jasak, Hrvoje

    2016-01-01

    We devise a numerical method for passive advection of a surface, such as the interface between two incompressible fluids, across a computational mesh. The method is called isoAdvector, and is developed for general meshes consisting of arbitrary polyhedral cells. The algorithm is based on the volume of fluid (VOF) idea of calculating the volume of one of the fluids transported across the mesh faces during a time step. The novelty of the isoAdvector concept consists in two parts: First, we exploit an isosurface concept for modelling the interface inside cells in a geometric surface reconstruction step. Second, from the reconstructed surface, we model the motion of the face-interface intersection line for a general polygonal face to obtain the time evolution within a time step of the submerged face area. Integrating this submerged area over the time step leads to an accurate estimate for the total volume of fluid transported across the face. The method was tested on simple 2D and 3D interface advection problems ...

  20. Perturbation analysis of steady and unsteady electrohydrodynamic chaotic advection inside translating drops

    Science.gov (United States)

    Wu, Fan; Vainchtein, Dmitri; Ward, Thomas

    2015-08-01

    A drop translating in the presence of an electric field is studied analytically. The flow is a combination of a Hadamard-Rybczynski and a Taylor circulation due to the translation and electric field, respectively. We consider chaotic advection that is generated by (1) tilting and (2) time-dependent modulation of the electric field. For the analysis we consider small perturbations in time and space to what is otherwise an integrable flow. By using a robust analytical technique we find an adiabatic invariant (AI) for the system by averaging the equations of motion. The chaotic advection is due to quasirandom jumps of the AI after crossing the separatrix of the unperturbed flow. We demonstrate that the asymptotic analysis leads to a set of criteria that can be used to optimize stirring in these systems.

  1. Effects of advection on the seasonal abundance patterns of three species of planktonic calanoid copepods in Dabob Bay, Washington

    Science.gov (United States)

    Osgood, Kenric E.; Frost, Bruce W.

    1996-08-01

    The copepodid stage abundances of Calanus marshallae, Calanus pacificus and Metridia pacifica in Dabob Bay, Washington were followed through two years. Based on the species' life histories, vertical distributions, abundances inside and outside the bay, and the hydrographic setting, times when advection was important were explored. During the first study-year, 1973, advection acted to keep the copepod concentrations inside and outside Dabob Bay similar through the early summer. During the summer, a period of very little advective exchange, the copepod concentrations diverged at the two stations. In the fall, when advection picked up again, the copepod concentrations at the two stations once again became similar. During the summer of the other study-year, 1982, flow of deep water into Dabob Bay occurred. This may have caused some of the differences observed in the abundances of the copepods during the summer of 1982 vs 1973. Due in part to the advective events, the seasonal abundance patterns of the copepods could not be predicted based upon their locally expressed life history patterns. The most striking example of this was C. pacificus. Its population decreased during the spring and increased during the fall, despite having its major reproductive peak in the spring. Advective effects clearly contributed to this.

  2. An objective method for computing advective surface velocities from sequential infrared satellite images

    Science.gov (United States)

    Emery, W. J.; Thomas, A. C.; Collins, M. J.; Crawford, W. R.; Mackas, D. L.

    1986-11-01

    Using cross correlations between sequential infrared satellite images, an objective technique is developed to compute advective sea surface velocities. Cross correlations are computed in 32 × 32 pixel search (second image) and 22 × 22 template (first image) windows from gradients of sea surface temperature computed from the satellite images. Velocity vectors, computed from sequential images of the British Columbia coastal ocean, generally appear coherent and consistent with the seasonal surface current in the region. During periods of strong wind forcing, as indicated by maps of sea level pressure, the image advective velocities are stronger and more coherent spatially and appear to cross surface temperature gradients; when winds are weaker, the advective velocities correspond better with the infrared temperature patterns, suggesting the increased contribution of the geostrophic current to the surface flow. Velocities determined from coincident, near-surface drogued (5-10 m) buoys, positioned every half hour by internal LORAN-C units in mid-June, show excellent agreement with the image advective velocities. In addition, conductivity, temperature, and depth (CTD) measurements (taken during the buoy tracking) confirm the homogeneity of the upper 10 m, and CTD-derived geostrophic currents are consistent with both buoy and sequential image displacement velocities.

  3. Thermal instability of advection-dominated disks against local perturbations

    CERN Document Server

    Kato, S; Chen, X; Kato, Shoji; Abramowicz, Marek Artur; Chen, Xingming

    1995-01-01

    Thermal instability is examined for advection-dominated one-temperature accretion disks. We consider axisymmetric perturbations with short wavelength in the radial direction. The viscosity is assumed to be sufficiently small for the vertical hydrostatic balance to hold in perturbed states. The type of viscosity is given either by the \\alpha-viscosity or by a diffusion-type stress tensor. Optically thick disks are found to be in general more unstable than optically thin ones. When the thermal diffusion is present, the optically thin disks become stable, but the optically thick disks are still unstable. The instability of the advection-dominated disks is different from that of the geometrically thin disks without advection. In the case of no advection, the thermal mode behaves under no appreciable surface density change. In the case of advection-dominated disks, however, the thermal mode occurs with no appreciable pressure change (compared with the density change), when local perturbations are considered. The v...

  4. Predicting salt advection in groundwater from saline aquaculture ponds

    Science.gov (United States)

    Verrall, D. P.; Read, W. W.; Narayan, K. A.

    2009-01-01

    SummaryThis paper predicts saltwater advection in groundwater from leaky aquaculture ponds. A closed form solution for the potential function, stream function and velocity field is derived via the series solutions method. Numerically integrating along different streamlines gives the location (or advection front) of saltwater throughout the domain for any predefined upper time limit. Extending this process produces a function which predicts advection front location against time. The models considered in this paper are easily modified given knowledge of the required physical parameters.

  5. Didaktiske paradigmer og refleksion

    DEFF Research Database (Denmark)

    Christensen, Torben Spanget

    2014-01-01

    this article. A possible utilitarian didactical paradigm, already indicated by Krogh as a historical paradigm prominent in our time, is also discussed. It is suggested that reflection could be seen as a normative response to the utilitarian paradigm, and not as a paradigm in its own right. It is concluded...... that reflection must be understood as an overarching cultural phenomenon and a very important qualification of all Nielsen’s paradigms, and also a possible utilitarian paradigm, because it has the potential to add dynamic elements to the more or less static didactic paradigms. Thus the semiotic analysis may...

  6. Transmission pricing: paradigms and methodologies

    Energy Technology Data Exchange (ETDEWEB)

    Shirmohammadi, Dariush [Pacific Gas and Electric Co., San Francisco, CA (United States); Vieira Filho, Xisto; Gorenstin, Boris [Centro de Pesquisas de Energia Eletrica (CEPEL), Rio de Janeiro, RJ (Brazil); Pereira, Mario V.P. [Power System Research, Rio de Janeiro, RJ (Brazil)

    1994-12-31

    In this paper we describe the principles of several paradigms and methodologies for pricing transmission services. The paper outlines some of the main characteristics of these paradigms and methodologies such as where they may be used for best results. Due to their popularity, power flow based MW-mile and short run marginal cost pricing methodologies will be covered in some detail. We conclude the paper with examples of the application of these two pricing methodologies for pricing transmission services in Brazil. (author) 25 refs., 2 tabs.

  7. Contribution of Advective and Non-advective Heat Fluxes to the Heat Budget of a Shallow Lagoon

    Directory of Open Access Journals (Sweden)

    Rodríguez-Rodríguez Miguel

    2005-01-01

    Full Text Available The heat budget in a shallow lagoon has been established from field measurements at a bihourly scale. Information on the main advective and non-advective heat fluxes were collected during year 2003 at Nueva lagoon (Almería, Southern Spain. Heat storage data was obtained from a thermistor chain located in the deepest part of the lagoon and meteorological information was acquired using an automatic meteorological station placed near the lagoon's shore. In addition, estimation of evaporation was inferred from climatic approaches. Inputs of heat energy were dominated by radiative fluxes, with received net radiation accounting on average for around 95% of the non-advective total gains and radiation losses accounting for around 70% of the non-advective total losses. Sensible heat transfer from/to the atmosphere constituted the second energy input (4% and output (20%, although heat losses by evaporation were also significant. Conduction of heat into the sediments was a relatively constant form of energy loss but constitutes a minor contribution on the overall heat budget. Considerable variability was evident in non-advective heat fluxes at different time scales, from diel to seasonal. In relation to advective heat fluxes, groundwater and irrigation surpluses added to the heat storage of Nueva lagoon, whereas heat advected via precipitation was negligible.

  8. Benthic solute exchange and carbon mineralization in two shallow subtidal sandy sediments: Effect of advective pore-water exchange

    DEFF Research Database (Denmark)

    Cook, Perran L. M.; Wenzhofer, Frank; Glud, Ronnie N.;

    2007-01-01

    proceeded predominantly through sulfate reduction when benthic mineralization rates were high and advective pore-water flow low as a result of poorly developed topography. Previous studies of benthic mineralization in shallow sandy sediments have generally ignored these dynamics and, hence, have overlooked...

  9. Analytical Solutions of the Space-Time Fractional Derivative of Advection Dispersion Equation

    Directory of Open Access Journals (Sweden)

    Abdon Atangana

    2013-01-01

    Full Text Available Fractional advection-dispersion equations are used in groundwater hydrology to model the transport of passive tracers carried by fluid flow in porous medium. A space-time fractional advection-dispersion equation (FADE is a generalization of the classical ADE in which the first-order space derivative is replaced with Caputo or Riemann-Liouville derivative of order , and the second-order space derivative is replaced with the Caputo or the Riemann-Liouville fractional derivative of order . We derive the solution of the new equation in terms of Mittag-Leffler functions using Laplace transfrom. Some examples are given. The results from comparison let no doubt that the FADE is better in prediction than ADE.

  10. Advective-diffusive mass transfer in fractured porous media with variable rock matrix block size.

    Science.gov (United States)

    Sharifi Haddad, Amin; Hassanzadeh, Hassan; Abedi, Jalal

    2012-05-15

    Traditional dual porosity models do not take into account the effect of matrix block size distribution on the mass transfer between matrix and fracture. In this study, we introduce the matrix block size distributions into an advective-diffusive solute transport model of a divergent radial system to evaluate the mass transfer shape factor, which is considered as a first-order exchange coefficient between the fracture and matrix. The results obtained lead to a better understanding of the advective-diffusive mass transport in fractured porous media by identifying two early and late time periods of mass transfer. Results show that fractured rock matrix block size distribution has a great impact on mass transfer during early time period. In addition, two dimensionless shape factors are obtained for the late time, which depend on the injection flow rate and the distance of the rock matrix from the injection point.

  11. New complex variable meshless method for advection-diffusion problems

    Institute of Scientific and Technical Information of China (English)

    Wang Jian-Fei; Cheng Yu-Min

    2013-01-01

    In this paper,an improved complex variable meshless method (ICVMM) for two-dimensional advection-diffusion problems is developed based on improved complex variable moving least-square (ICVMLS) approximation.The equivalent functional of two-dimensional advection-diffusion problems is formed,the variation method is used to obtain the equation system,and the penalty method is employed to impose the essential boundary conditions.The difference method for two-point boundary value problems is used to obtain the discrete equations.Then the corresponding formulas of the ICVMM for advection-diffusion problems are presented.Two numerical examples with different node distributions are used to validate and investigate the accuracy and efficiency of the new method in this paper.It is shown that ICVMM is very effective for advection-diffusion problems,and has a good convergent character,accuracy,and computational efficiency.

  12. Anomalous scaling of a scalar field advected by turbulence

    Energy Technology Data Exchange (ETDEWEB)

    Kraichnan, R.H. [Robert H. Kraichnan, Inc., Santa Fe, NM (United States)

    1995-12-31

    Recent work leading to deduction of anomalous scaling exponents for the inertial range of an advected passive field from the equations of motion is reviewed. Implications for other turbulence problems are discussed.

  13. A spatial SIS model in advective heterogeneous environments

    Science.gov (United States)

    Cui, Renhao; Lou, Yuan

    2016-09-01

    We study the effects of diffusion and advection for a susceptible-infected-susceptible epidemic reaction-diffusion model in heterogeneous environments. The definition of the basic reproduction number R0 is given. If R0 globally asymptotically stable. Asymptotic behaviors of R0 for advection rate and mobility of the infected individuals (denoted by dI) are established, and the existence of the endemic equilibrium when R0 > 1 is studied. The effects of diffusion and advection rates on the stability of the DFE are further investigated. Among other things, we find that if the habitat is a low-risk domain, there may exist one critical value for the advection rate, under which the DFE changes its stability at least twice as dI varies from zero to infinity, while the DFE is unstable for any dI when the advection rate is larger than the critical value. These results are in strong contrast with the case of no advection, where the DFE changes its stability at most once as dI varies from zero to infinity.

  14. A Method for Measuring Subcanopy CO2 Advection

    Science.gov (United States)

    Staebler, R. M.; Fitzjarrald, D. R.

    2004-12-01

    Underestimation of nocturnal CO2 respiration under calm conditions remains an unsolved problem at many forest flux stations, and several groups are currently investigating the direct measurement of horizontal advection of CO2. This presentation will describe a systematic, relatively low-cost methodology developed to determine whether horizontal mean transport of CO2 accounts for the missing CO2 at the Harvard Forest (Petersham, MA). This methodology includes the characterization of subcanopy motions, determining the appropriate size of the subcanopy network required to make the measurements, developing a method of integrating the measurements in the vertical, and determining the required averaging time. Measurements were conducted over 4 years and produced data for 310 nights covering all seasons. Subcanopy flows were decoupled from the flows aloft 75% of the time. Conditions conducive to the generation of negative buoyancy near the forest floor, necessary for drainage flows to develop, were given in 92% of all nights. The occurrence of nocturnal drainage flows correlated well with "missing flux" problems ("deficit nights"), prompting us to propose an improvement on the commonly used friction velocity criterion (which requires u* to be larger than some empirical cut-off for the eddy fluxes to be considered credible). The "negative buoyancy forcing fraction", i.e. negative buoyancy as a fraction of the sum of the dynamic driving forces, can be shown to predict deficit nights significantly better than the u* cut-off. The appropriate horizontal size of the network of wind and CO2 sensors at the Harvard Forest was shown to be on the order of 100 m, ensuring that sensors were generally observing coherent processes on this scale or larger and thus displaying some correlation. Horizontal transport of CO2 was found to be restricted to the bottom ~10 m of the forest, facilitating the development of a method of integrating the horizontal CO2 gradients in the vertical

  15. Energetics of lateral eddy diffusion/advection:Part III. Energetics of horizontal and isopycnal diffusion/advection

    Institute of Scientific and Technical Information of China (English)

    HUANG Rui Xin

    2014-01-01

    Gravitational Potential Energy (GPE) change due to horizontal/isopycnal eddy diffusion and advection is examined. Horizontal/isopycnal eddy diffusion is conceptually separated into two steps:stirring and sub-scale diffusion. GPE changes associated with these two steps are analyzed. In addition, GPE changes due to stirring and subscale diffusion associated with horizontal/isopycnal advection in the Eulerian coordinates are analyzed. These formulae are applied to the SODA data for the world oceans. Our analysis indicates that horizontal/isopycnal advection in Eulerian coordinates can introduce large artificial diffusion in the model. It is shown that GPE source/sink in isopycnal coordinates is closely linked to physical property distribution, such as temperature, salinity and velocity. In comparison with z-coordinates, GPE source/sink due to stir-ring/cabbeling associated with isopycnal diffusion/advection is much smaller. Although isopycnal coordi-nates may be a better choice in terms of handling lateral diffusion, advection terms in the traditional Eule-rian coordinates can produce artificial source of GPE due to cabbeling associated with advection. Reducing such numerical errors remains a grand challenge.

  16. Stationary spots and stationary arcs induced by advection in a one-activator, two-inhibitor reactive system.

    Science.gov (United States)

    Berenstein, Igal; Bullara, Domenico; De Decker, Yannick

    2014-09-01

    This paper studies the spatiotemporal dynamics of a reaction-diffusion-advection system corresponding to an extension of the Oregonator model, which includes two inhibitors instead of one. We show that when the reaction-diffusion, two-dimensional problem displays stationary patterns the addition of a plug flow can induce the emergence of new types of stationary structures. These patterns take the form of spots or arcs, the size and the spacing of which can be controlled by the flow.

  17. Advection-condensation of water vapor with coherent stirring: a stochastic approach

    Science.gov (United States)

    Tsang, Yue-Kin; Vanneste, Jacques; Vallis, Geoffrey

    2015-11-01

    The dynamics of atmospheric water is an essential ingredient of weather and climate. Water vapor, in particular, is an important greenhouse gas whose distribution has a strong impact on climate. To gain insight into the factors controlling the distribution of atmospheric moisture, we study an advection-condensation model in which water vapor is passively advected by a prescribed velocity and condensation acts as a sink that maintains the specific humidity below a prescribed, spatially dependent saturation value. The velocity consists of two parts: a single vortex representing large-scale coherent flow (e.g. the Hadley cell) and a white noise component mimicking small-scale turbulence. Steady-state is achieved in the presence of a moisture source at a boundary. We formulate this model as a set of stochastic differential equations. In the fast advection limit, analytical expression for the water vapor distribution is obtained by matched asymptotics. This allows us to make various predictions including the dependence of total precipitation on the vortex strength. These analytical results are verified by Monte Carlo simulations. This work is supported by the UK EPSRC Grant EP/I028072/1 and the Feasibility Fund from the UK EPSRC Network ReCoVER.

  18. Heat transfer enhancement utilizing chaotic advection in coiled tube heat exchangers

    International Nuclear Information System (INIS)

    The present study introduced a novel chaotic coil heat exchanger utilizing chaotic advection to enhance heat transfer at low Reynolds numbers. Using Lagrangian tracing of fluid particles and their sensitivity to the initial condition and fluid element calculations, it was shown that mixing was significantly increased due to the chaotic advection. Heat transfer performance in the coil and chaotic configuration was visualized by isotherms contours of temperature in different cross-sections. In order to evaluate the hydraulic-thermal performance of heat exchangers, Nusselt numbers and friction factor were calculated and comparison was made between the two configurations. Numerical calculations revealed that the chaotic coil configuration displayed heat transfer enhancement of 4–26% relative to the fully developed Nusselt numbers in the regular coil with only 5–8% change in the pressure drop. - Highlights: • A novel chaotic coil heat exchanger is introduced in this study. • It is shown that mixing is increased significantly due to the altered chaotic advection mechanism. • By increasing the Reynolds number, results show impressive enhancement in chaotic heat exchanger performance. • Reorientation in chaotic flow leads to higher pressure loss than that in the normal helical coil

  19. Clay with Desiccation Cracks is an Advection Dominated Environment

    Science.gov (United States)

    Baram, S.; Kurtzman, D.; Sher, Y.; Ronen, Z.; Dahan, O.

    2012-04-01

    , indicating deep soil evaporation. Daily fluctuation of the air temperature in the desiccation cracks supported thermally induced air convection within the cracks void and could explain the deep soil salinization process. Combination of all the abovementioned observations demonstrated that the formation of desiccation cracks network in dispersive clay sediments generates a bulk advection dominated environment for both air and water flow, and that the reference to clay sediments as "hydrologically safe" should to be reconsidered.

  20. Round window membrane intracochlear drug delivery enhanced by induced advection.

    Science.gov (United States)

    Borkholder, David A; Zhu, Xiaoxia; Frisina, Robert D

    2014-01-28

    Delivery of therapeutic compounds to the inner ear via absorption through the round window membrane (RWM) has advantages over direct intracochlear infusions; specifically, minimizing impact upon functional hearing measures. However, previous reports show that significant basal-to-apical concentration gradients occur, with the potential to impact treatment efficacy. Here we present a new approach to inner ear drug delivery with induced advection aiding distribution of compounds throughout the inner ear in the murine cochlea. Polyimide microtubing was placed near the RWM niche through a bullaostomy into the middle ear cavity allowing directed delivery of compounds to the RWM. We hypothesized that a posterior semicircular canalostomy would induce apical flow from the patent cochlear aqueduct to the canalostomy due to influx of cerebral spinal fluid. To test this hypothesis, young adult CBA/CaJ mice were divided into two groups: bullaostomy approach only (BA) and bullaostomy+canalostomy (B+C). Cochlear function was evaluated by distortion product otoacoustic emission (DPOAE) and auditory brainstem response (ABR) thresholds during and after middle ear infusion of salicylate in artificial perilymph (AP), applied near the RWM. The mice recovered for 1week, and were re-tested. The results demonstrate there was no significant impact on auditory function utilizing the RWM surgical procedure with or without the canalostomy, and DPOAE thresholds were elevated reversibly during the salicylate infusion. Comparing the threshold shifts for both methods, the B+C approach had more of a physiological effect than the BA approach, including at lower frequencies representing more apical cochlear locations. Unlike mouse cochleostomies, there was no deleterious auditory functional impact after 1week recovery from surgery. The B+C approach had more drug efficacy at lower frequencies, underscoring potential benefits for more precise control of delivery of inner ear therapeutic compounds.

  1. Effect of advection on variations in zooplankton at a single location near Cabo Nazca, Peru

    Energy Technology Data Exchange (ETDEWEB)

    Smith, S L; Brink, K H; Santander, H; Cowles, T J; Huyer, A

    1980-04-01

    Temporal variations in the biomass and species composition of zooplankton at a single midshelf station in an upwelling area off Peru can be explained to a large extent by onshore-offshore advection in the upper 20 m of the water column. During periods of strong or sustained near-surface onshore flow, peaks in biomass of zooplankton were observed at midshelf and typically oceanic species of copepod were collected. In periods of offshore flow at the surface, a copepod capable of migrating into oxygen-depleted layers deeper than 30 m was collected. A simple translocation model of advection applied to the cross-shelf distribution of Paracalanus parvus suggests that the fluctuations in P. pavus observed in the midshelf time-series were closely related to onshore-offshore flow in the upper 20 m. Fluctuations in abundance of the numerically dominant copepod, Acartia tonsa, were apparently affected by near surface flow also. The population age-structure suggests that A. tonsa was growing at maximal rates, due in part to its positive feeding response to the dinoflagellate/diatom assemblage of phytoplankton.

  2. Paradigms of polyamory.

    Science.gov (United States)

    Zambrano, M

    1999-01-01

    SUMMARY The paradigm theory of Thomas Kuhn is used as a framework to discuss alternative ways of intimacy. The author discusses the implications of structuring actual lesbian relationships by a paradigm of monogamy among Latin-American women. The author proposes that creating alternative paradigms of multiple relationships would be useful for many lesbians as models for alternative life patterns.

  3. Positioning Theory in Paradigms

    Institute of Scientific and Technical Information of China (English)

    FU Xiao-qiu

    2015-01-01

    This article discusses the importance of theory and paradigm to a researcher. It starts from introducing and analyzing the definition of the two terms, by using the theories in the field of intercultural communication as examples. To a good researcher, he needs not only clarifying the paradigm his research is positioned, but also integrating the theories in his paradigm.

  4. Accuracy of spectral and finite difference schemes in 2D advection problems

    DEFF Research Database (Denmark)

    Naulin, V.; Nielsen, A.H.

    2003-01-01

    In this paper we investigate the accuracy of two numerical procedures commonly used to solve 2D advection problems: spectral and finite difference (FD) schemes. These schemes are widely used, simulating, e.g., neutral and plasma flows. FD schemes have long been considered fast, relatively easy...... that the accuracy of FD schemes can be significantly improved if one is careful in choosing an appropriate FD scheme that reflects conservation properties of the nonlinear terms and in setting up the grid in accordance with the problem....

  5. 2.5-dimensional solution of the advective accretion disk:a self-similar approach

    Institute of Scientific and Technical Information of China (English)

    Shubhrangshu Ghosh; Banibrata Mukhopadhyay

    2009-01-01

    We provide a 2.5-dimensional solution to a complete set of viscous hydrodynamical equations describing accretion-induced outflows and plausible jets around black holes/compact objects. We prescribe a self-consistent advective disk-outflow coupling model, which explicitly includes the information of vertical flux. Inter-connecting dynamics of an inflow-outflow system essentially upholds the conservation laws. We provide a set of analytical family of solutions through a self-similar approach. The flow parameters of the disk-outflow system depend strongly on the viscosity parameter α and the cooling factor f.

  6. Features of a rare advection-radiation fog event

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    To investigate effects of atmospheric pollutants on fog nature, a comprehensive in situ observation project was implemented in the northern suburb of Nanjing, in December of 2006. For December 24-27 there occurred a heavy fog lasting 4 d in succession. This event is of rare characteristics, namely long persistence, high concentration, tall fog top, acid fog water and explosive growth. Detailed analysis along with the causes of the fog was presented. The evidence suggests that the fog was generated by nighttime radiative cooling, maintained and developed under effects of warm, wet advection. As a result, it is an advection-radiation fog event.

  7. Measurements on, and modelling of diffusive and advective radon transport in soil

    DEFF Research Database (Denmark)

    Graff, E.R. van der; Witteman, G.A.A.; Spoel, W.H. van der;

    1994-01-01

    Results are presented of measurements on radon transport in soil under controlled conditions with a laboratory facility consisting of a stainless steel vessel (height and diameter 2 m) filled with a uniform column of sand. At several depths under the sand surface, probes are radially inserted...... into the vessel to measure the radon concentration in the soil gas. To study advective radon transport a perforated circular box is placed in the sand close to the bottom of the vessel. By pressurising this box, an air flow through the sand column is induced. Radon concentration profiles were measured without...... an air flow as a function of time, and for several values of the air flow, equilibrium radon concentration profiles were measured....

  8. Simulating magnetised plasma with the versatile advection code

    NARCIS (Netherlands)

    Keppens, R.; Toth, G.; Palma, J. M. L.; Dongarra, J.; Hernandez, V.

    1999-01-01

    Matter in the universe mainly consists of plasma. The dynamics of plasmas is controlled by magnetic fields. To simulate the evolution of magnetised plasma, we solve the equations of magnetohydrodynamics using the Versatile Advection Code (VAC). To demonstrate the versatility of VAC, we present calcu

  9. Consistency Problem with Tracer Advection in the Atmospheric Model GAMIL

    Institute of Scientific and Technical Information of China (English)

    ZHANG Kai; WAN Hui; WANG Bin; ZHANG Meigen

    2008-01-01

    The radon transport test,which is a widely used test case for atmospheric transport models,is carried out to evaluate the tracer advection schemes in the Grid-Point Atmospheric Model of IAP-LASG (GAMIL).TWO of the three available schemes in the model are found to be associated with significant biases in the polar regions and in the upper part of the atmosphere,which implies potentially large errors in the simulation of ozone-like tracers.Theoretical analyses show that inconsistency exists between the advection schemes and the discrete continuity equation in the dynamical core of GAMIL and consequently leads to spurious sources and sinks in the tracer transport equation.The impact of this type of inconsistency is demonstrated by idealized tests and identified as the cause of the aforementioned biases.Other potential effects of this inconsistency are also discussed.Results of this study provide some hints for choosing suitable advection schemes in the GAMIL model.At least for the polar-region-concentrated atmospheric components and the closely correlated chemical species,the Flux-Form Semi-Lagrangian advection scheme produces more reasonable simulations of the large-scale transport processes without significantly increasing the computational expense.

  10. Advective and diffusive cosmic ray transport in galactic haloes

    CERN Document Server

    Heesen, Volker; Krause, Marita; Beck, Rainer; Stein, Yelena

    2016-01-01

    We present 1D cosmic ray transport models, numerically solving equations of pure advection and diffusion for the electrons and calculating synchrotron emission spectra. We find that for exponential halo magnetic field distributions advection leads to approximately exponential radio continuum intensity profiles, whereas diffusion leads to profiles that can be better approximated by a Gaussian function. Accordingly, the vertical radio spectral profiles for advection are approximately linear, whereas for diffusion they are of `parabolic' shape. We compare our models with deep ATCA observations of two edge-on galaxies, NGC 7090 and 7462, at $\\lambda\\lambda$ 22 and 6 cm. Our result is that the cosmic ray transport in NGC 7090 is advection dominated with $V=150^{+80}_{-30}~\\rm km\\,s^{-1}$, and that the one in NGC 7462 is diffusion dominated with $D=3.0\\pm 1.0 \\times 10^{28}E_{\\rm GeV}^{0.5}~\\rm cm^2\\,s^{-1}$. NGC 7090 has both a thin and thick radio disc with respective magnetic field scale heights of $h_{\\rm B1}=0...

  11. Fractional gradient and its application to the fractional advection equation

    OpenAIRE

    D'Ovidio, M; Garra, R.

    2013-01-01

    In this paper we provide a definition of fractional gradient operators, related to directional derivatives. We develop a fractional vector calculus, providing a probabilistic interpretation and mathematical tools to treat multidimensional fractional differential equations. A first application is discussed in relation to the d-dimensional fractional advection-dispersion equation. We also study the connection with multidimensional L\\'evy processes.

  12. Statement of Cash Flows - Concrete Aspect of the Convergence of Global Accounting in the Context of the Paradigm of New Economy

    OpenAIRE

    Gheorghe Lepadatu

    2013-01-01

    Statement of cash flows presents useful information about changing the company's financial position, allowing assessing the enterprise’s ability to generate future cash flows and cash equivalents in the operating, investing and financing activities and their appropriate use. Treasury forecasts are intended to contribute to financial security and enterprise profitability by reducing financial costs. Treasury of an economic entity can be considered its strong point. The manner in which they man...

  13. Energetics of lateral eddy diffusion/advection:Part IV. Energetics of diffusion/advection in sigma coordinates and other coordinates

    Institute of Scientific and Technical Information of China (English)

    HUANG Rui Xin

    2014-01-01

    Gravitational potential energy (GPE) source and sink due to stirring and cabbeling associated with sigma dif-fusion/advection is analyzed. It is shown that GPE source and sink is too big, and they are not closely linked to physical property distribution, such as temperature, salinity and velocity. Although the most frequently quoted advantage of sigma coordinate models are their capability of dealing with topography;the exces-sive amount of GPE source and sink due to stirring and cabbeling associated with sigma diffusion/advec-tion diagnosed from our analysis raises a very serious question whether the way lateral diffusion/advection simulated in the sigma coordinates model is physically acceptable. GPE source and sink in three coordinates is dramatically different in their magnitude and patterns. Overall, in terms of simulating lateral eddy diffu-sion and advection isopycnal coordinates is the best choice and sigma coordinates is the worst. The physical reason of the excessive GPE source and sink in sigma coordinates is further explored in details. However, even in the isopycnal coordinates, simulation based on the Eulerian coordinates can be contaminated by the numerical errors associated with the advection terms.

  14. Single Wake Meandering, Advection and Expansion - An analysis using an adapted Pulsed Lidar and CFD LES-ACL simulations

    DEFF Research Database (Denmark)

    Machefaux, Ewan; Larsen, Gunner Chr.; Troldborg, Niels;

    2013-01-01

    In this paper, single wake characteristics have been studied both experimentally and numerically. Firstly, the wake is studied experimentally using full-scale measurements from an adapted focused pulsed lidar system, which potentially gives more insight into the wake dynamics as compared to class...... using the EllipSys3D flow solver using Large Eddy Simulation (LES) and Actuator Line Technique (ACL) to model the rotor. Discrepancies due to the uncertainties on the wake advection velocity are observed and discussed....

  15. Single Wake Meandering, Advection and Expansion - An analysis using an adapted Pulsed Lidar and CFD LES-ACL simulations

    DEFF Research Database (Denmark)

    In this paper, single wake characteristics have been studied both experimentally and numerically. Firstly, the wake is studied experimentally using full-scale measurements from an adapted focused pulsed lidar system, which potentially gives more insight into the wake dynamics as compared to class...... using the EllipSys3D flow solver using Large Eddy Simulation (LES) and Actuator Line Technique (ACL) to model the rotor. Discrepancies due to the uncertainties on the wake advection velocity are observed and discussed....

  16. An Integrative Paradigm

    Science.gov (United States)

    Hammack, Phillip L.

    2005-01-01

    Through the application of life course theory to the study of sexual orientation, this paper specifies a new paradigm for research on human sexual orientation that seeks to reconcile divisions among biological, social science, and humanistic paradigms. Recognizing the historical, social, and cultural relativity of human development, this paradigm…

  17. Phase mixing versus nonlinear advection in drift-kinetic plasma turbulence

    Science.gov (United States)

    Schekochihin, A. A.; Parker, J. T.; Highcock, E. G.; Dellar, P. J.; Dorland, W.; Hammett, G. W.

    2016-04-01

    > A scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g. drift-wave turbulence driven by ion temperature gradients) is proposed, with account taken both of the nonlinear advection of the perturbed particle distribution by fluctuating flows and of its phase mixing, which is caused by the streaming of the particles along the mean magnetic field and, in a linear problem, would lead to Landau damping. It is found that it is possible to construct a consistent theory in which very little free energy leaks into high velocity moments of the distribution function, rendering the turbulent cascade in the energetically relevant part of the wavenumber space essentially fluid-like. The velocity-space spectra of free energy expressed in terms of Hermite-moment orders are steep power laws and so the free-energy content of the phase space does not diverge at infinitesimal collisionality (while it does for a linear problem); collisional heating due to long-wavelength perturbations vanishes in this limit (also in contrast with the linear problem, in which it occurs at the finite rate equal to the Landau damping rate). The ability of the free energy to stay in the low velocity moments of the distribution function is facilitated by the `anti-phase-mixing' effect, whose presence in the nonlinear system is due to the stochastic version of the plasma echo (the advecting velocity couples the phase-mixing and anti-phase-mixing perturbations). The partitioning of the wavenumber space between the (energetically dominant) region where this is the case and the region where linear phase mixing wins its competition with nonlinear advection is governed by the `critical balance' between linear and nonlinear time scales (which for high Hermite moments splits into two thresholds, one demarcating the wavenumber region where phase mixing predominates, the other where plasma echo does).

  18. Advection of passive magnetic field by the Gaussian velocity field with finite correlations in time and spatial parity violation

    Science.gov (United States)

    Jurčišinová, E.; Jurčišin, M.

    2013-03-01

    Using the field theoretic renormalization group technique the model of passively advected weak magnetic field by an incompressible isotropic helical turbulent flow is investigated up to the second order of the perturbation theory (two-loop approximation) in the framework of an extended Kazantsev-Kraichnan model of kinematic magnetohydrodynamics. Statistical fluctuations of the velocity field are taken in the form of a Gaussian distribution with zero mean and defined noise with finite correlations in time. The two-loop analysis of all possible scaling regimes is done and the influence of helicity on the stability of scaling regimes is discussed and shown in the plane of exponents ɛ - η, where ɛ characterizes the energy spectrum of the velocity field in the inertial range E ∞ k 1 - 2ɛ, and η is related to the correlation time at the wave number k which is scaled as k -2 + η. It is shown that in non-helical case the scaling regimes of the present vector model are completely identical and have also the same properties as those obtained in the corresponding model of passively advected scalar field. Besides, it is also shown that when the turbulent environment under consideration is helical then the properties of the scaling regimes in models of passively advected scalar and vector (magnetic) fields are essentially different. The results demonstrate the importance of the presence of a symmetry breaking in a given turbulent environment for investigation of the influence of an internal tensor structure of the advected field on the inertial range scaling properties of the model under consideration and will be used in the analysis of the influence of helicity on the anomalous scaling of correlation functions of passively advected magnetic field.

  19. Advection equation analysed by two-timing method

    CERN Document Server

    Vladimirov, V A

    2016-01-01

    The aim of this paper is to study and classify the multiplicity of distinguished limits and asymptotic solutions for the advection equation with a general oscillating velocity field with the systematic use of the two-timing method. Our results are: (i) the dimensionless advection equation contains two independent small parameters, which represent the ratio of two characteristic time-scales and the spatial amplitudes of oscillations; the scaling of the variables and parameters contains Strouhal number; (ii) an infinite sequence of distinguished limits has been identified; this sequence corresponds to the successive degenerations of a drift velocity; (iii) we have derived the averaged and oscillatory equations for the first four distinguished limits; derivations are performed up to the forth orders in small parameters; (v) we have shown, that each distinguish limit solution generates an infinite number of parametric solutions; these solutions differ from each other by the slow time-scale and the amplitude of pr...

  20. Features of a rare advection-radiation event

    Institute of Scientific and Technical Information of China (English)

    PU MeiJuan; ZHANG GuoZheng; YAN WenLian; LI ZiHua

    2008-01-01

    To investigate effects of atmospheric pollutants on fog nature,a comprehensive in situ observation project was implemented in the northern suburb of Nanjing,in December of 2006. For December 24-27 there occurred a heavy fog lasting 4 d in succession. This event is of rare characteristics,namely long persistence,high concentration,tall fog top,acid fog water and explosive growth. Detailed analysis along with the causes of the fog was presented. The evidence suggests that the fog was generated by nighttime radiative cooling,maintained and developed under effects of warm,wet advection. As a result,it is an advection-radiation fog event.

  1. Influences of tidal energy advection on the surface energy balance in a mangrove forest

    Directory of Open Access Journals (Sweden)

    J. G. Barr

    2012-08-01

    Full Text Available Mangrove forests are ecosystems susceptible to changing water levels and temperatures due to climate change as well as perturbations resulting from tropical storms. Numerical models can be used to project mangrove forest responses to regional and global environmental changes, and the reliability of these models depends on surface energy balance closure. However, for tidal ecosystems, the surface energy balance is complex because the energy transport associated with tidal activity remains poorly understood. This study aimed to quantify impacts of tidal flows on energy dynamics within a mangrove ecosystem. To address the research objective, an intensive study was conducted in a mangrove forest located along the Shark River in the Everglades National Park, FL. Forest-atmosphere energy exchanges were quantified with an eddy covariance system deployed on a flux tower. The lateral energy transport associated with tidal activity was calculated based on a coupled mass and energy balance approach. The mass balance included tidal flows and accumulation of water on the forest floor. The energy balance included temporal changes in enthalpy, resulting from tidal flows and temperature changes in the water column. By serving as a net sink or a source of available energy, tidal flows reduced the impact of high radiational loads on the mangrove forest. Including tidal energy advection in the surface energy balance improved the 30-min daytime energy closure from 73% to 82% over the study period. Also, the cumulative sum of energy output improved from 79% to 91% of energy input during the study period. Results indicated that tidal inundation provides an important mechanism for heat removal and that tidal exchange should be considered in surface energy budgets of coastal ecosystems. Results also demonstrated the importance of including tidal energy advection in mangrove biophysical models that are used for predicting ecosystem response to changing climate and

  2. Simulation of advective dominant transport in porous material by discontinuous finite elements methods

    International Nuclear Information System (INIS)

    When transport in porous media is advection-dominated, the classical convection-dispersion equation behaves like an hyperbolic partial differential equation. Special numerical methods are then necessary to reduce numerical dispersion and/or spurious oscillations. Discontinuous Galerkin finite element methods are good candidates to solve this problem. At the discontinuities between two adjacent elements, numerical advective fluxes are calculated using one-dimensional approximate Riemann solvers. The method is stabilized with a multidimensional slope limiter which introduces small amounts of numerical diffusion when sharp concentration fronts occur. For a 2-dimensional domain and quadrangular elements, two space approximations are compared: a linear approximation (P1) based on average concentration value and average gradients (i.e. 3 degrees of freedom) and a bilinear approximation (Q1) based on nodal values of the concentration (i.e. 4 degrees of freedom). Numerical experiments based on structured or unstructured meshes and unidirectional or rotating flow have been run. For the same number of unknowns we show that: 1) the P1 approximation provides more accurate results than the Q1 approximation in simple configuration (structured meshes and unidirectional flow); 2) both approximations provide the same results for not too complicated configurations like structured meshes and rotating flow; 3) Q1 approximation provides more accurate results in complex situations like rotating flow on a unstructured mesh. However, because the required CPU time for the P1 approximation is much less than for the Q1 approximation, the P1 approximation was always found to be more efficient (in terms of CPU time for a given error) compared to the Q1 approximation. (authors)

  3. Lattice Boltzmann method for the fractional advection-diffusion equation.

    Science.gov (United States)

    Zhou, J G; Haygarth, P M; Withers, P J A; Macleod, C J A; Falloon, P D; Beven, K J; Ockenden, M C; Forber, K J; Hollaway, M J; Evans, R; Collins, A L; Hiscock, K M; Wearing, C; Kahana, R; Villamizar Velez, M L

    2016-04-01

    Mass transport, such as movement of phosphorus in soils and solutes in rivers, is a natural phenomenon and its study plays an important role in science and engineering. It is found that there are numerous practical diffusion phenomena that do not obey the classical advection-diffusion equation (ADE). Such diffusion is called abnormal or superdiffusion, and it is well described using a fractional advection-diffusion equation (FADE). The FADE finds a wide range of applications in various areas with great potential for studying complex mass transport in real hydrological systems. However, solution to the FADE is difficult, and the existing numerical methods are complicated and inefficient. In this study, a fresh lattice Boltzmann method is developed for solving the fractional advection-diffusion equation (LabFADE). The FADE is transformed into an equation similar to an advection-diffusion equation and solved using the lattice Boltzmann method. The LabFADE has all the advantages of the conventional lattice Boltzmann method and avoids a complex solution procedure, unlike other existing numerical methods. The method has been validated through simulations of several benchmark tests: a point-source diffusion, a boundary-value problem of steady diffusion, and an initial-boundary-value problem of unsteady diffusion with the coexistence of source and sink terms. In addition, by including the effects of the skewness β, the fractional order α, and the single relaxation time τ, the accuracy and convergence of the method have been assessed. The numerical predictions are compared with the analytical solutions, and they indicate that the method is second-order accurate. The method presented will allow the FADE to be more widely applied to complex mass transport problems in science and engineering.

  4. NUMERICAL SIMULATIONS OF SEA ICE WITH DIFFERENT ADVECTION SCHEMES

    Institute of Scientific and Technical Information of China (English)

    LIU Xi-ying

    2011-01-01

    Numerical simulations are carried out for sea ice with four different advection schemes to study their effects on the simulation results.The sea ice model employed here is the Sea Ice Simulator (SIS) of the Geophysical Fluid Dynamics Laboratory (GFDL) Modular Ocean Model version 4b (MOM4b) and the four advection schemes are, the upwind scheme originally used in the SIS, the Multi-Dimensional Positive Advection (MDPA) scheme, the Incremental Remapping Scheme (IRS) and the Two Step Shape Preserving (TSSP) scheme.The latter three schemes are newly introduced.To consider the interactions between sea ice and ocean, a mixed layer ocean model is introduced and coupled to the SIS.The coupled model uses a tri-polar coordinate with 120×65 grids,covering the whole earth globe, in the horizontal plane.Simulation results in the northern high latitudes are analyzed.In all simulations, the model reproduces the seasonal variation of sea ice in the northern high latitudes well.Compared with the results from the observation, the sea ice model produces some extra sea ice coverage in the Greenland Sea and Barents Sea in winter due to the exclusion of ocean current effects and the smaller simulated sea ice thickness in the Arctic basin.There are similar features among the results obtained with the introduced three advection schemes.The simulated sea ice thickness with the three newly introduced schemes are all smaller than that of the upwind scheme and the simulated sea ice velocities of movement are all smaller than that of the upwind scheme.There are more similarities shared in the results obtained with the MPDA and TSSP schemes.

  5. Oscillatory convection in binary mixtures: thermodiffusion, solutal buoyancy, and advection

    OpenAIRE

    Jung, D.; Matura, P.; Luecke, M.

    2005-01-01

    The role of thermodiffusive generation of concentration fluctuations via the Soret effect, their contribution to the buoyancy forces that drive convection, the advective mixing effect of the latter, and the diffusive homogenisation are compared and elucidated for oscillatory convection. Numerically obtained solutions of the field equations in the form of spatially extended relaxed traveling waves, of standing waves, and of the transient growth of standing waves and their transition to traveli...

  6. Lattice Boltzmann method for the fractional advection-diffusion equation

    Science.gov (United States)

    Zhou, J. G.; Haygarth, P. M.; Withers, P. J. A.; Macleod, C. J. A.; Falloon, P. D.; Beven, K. J.; Ockenden, M. C.; Forber, K. J.; Hollaway, M. J.; Evans, R.; Collins, A. L.; Hiscock, K. M.; Wearing, C.; Kahana, R.; Villamizar Velez, M. L.

    2016-04-01

    Mass transport, such as movement of phosphorus in soils and solutes in rivers, is a natural phenomenon and its study plays an important role in science and engineering. It is found that there are numerous practical diffusion phenomena that do not obey the classical advection-diffusion equation (ADE). Such diffusion is called abnormal or superdiffusion, and it is well described using a fractional advection-diffusion equation (FADE). The FADE finds a wide range of applications in various areas with great potential for studying complex mass transport in real hydrological systems. However, solution to the FADE is difficult, and the existing numerical methods are complicated and inefficient. In this study, a fresh lattice Boltzmann method is developed for solving the fractional advection-diffusion equation (LabFADE). The FADE is transformed into an equation similar to an advection-diffusion equation and solved using the lattice Boltzmann method. The LabFADE has all the advantages of the conventional lattice Boltzmann method and avoids a complex solution procedure, unlike other existing numerical methods. The method has been validated through simulations of several benchmark tests: a point-source diffusion, a boundary-value problem of steady diffusion, and an initial-boundary-value problem of unsteady diffusion with the coexistence of source and sink terms. In addition, by including the effects of the skewness β , the fractional order α , and the single relaxation time τ , the accuracy and convergence of the method have been assessed. The numerical predictions are compared with the analytical solutions, and they indicate that the method is second-order accurate. The method presented will allow the FADE to be more widely applied to complex mass transport problems in science and engineering.

  7. Paradigms for machine learning

    Science.gov (United States)

    Schlimmer, Jeffrey C.; Langley, Pat

    1991-01-01

    Five paradigms are described for machine learning: connectionist (neural network) methods, genetic algorithms and classifier systems, empirical methods for inducing rules and decision trees, analytic learning methods, and case-based approaches. Some dimensions are considered along with these paradigms vary in their approach to learning, and the basic methods are reviewed that are used within each framework, together with open research issues. It is argued that the similarities among the paradigms are more important than their differences, and that future work should attempt to bridge the existing boundaries. Finally, some recent developments in the field of machine learning are discussed, and their impact on both research and applications is examined.

  8. A high order characteristic discontinuous Galerkin scheme for advection on unstructured meshes

    Science.gov (United States)

    Lee, D.; Lowrie, R.; Petersen, M.; Ringler, T.; Hecht, M.

    2016-11-01

    A new characteristic discontinuous Galerkin (CDG) advection scheme is presented. In contrast to standard discontinuous Galerkin schemes, the test functions themselves follow characteristics in order to ensure conservation and the edges of each element are also traced backwards along characteristics in order to create a swept region, which is integrated in order to determine the mass flux across the edge. Both the accuracy and performance of the scheme are greatly improved by the use of large Courant-Friedrichs-Lewy numbers for a shear flow test case and the scheme is shown to scale sublinearly with the number of tracers being advected, outperforming a standard flux corrected transport scheme for 10 or more tracers with a linear basis. Moreover the CDG scheme may be run to arbitrarily high order spatial accuracy and on unstructured grids, and is shown to give the correct order of error convergence for piecewise linear and quadratic bases on regular quadrilateral and hexahedral planar grids. Using a modal Taylor series basis, the scheme may be made monotone while preserving conservation with the use of a standard slope limiter, although this reduces the formal accuracy of the scheme to first order. The second order scheme is roughly as accurate as the incremental remap scheme with nonlocal gradient reconstruction at half the horizontal resolution. The scheme is being developed for implementation within the Model for Prediction Across Scales (MPAS) Ocean model, an unstructured grid finite volume ocean model.

  9. Early Holocene variability in the Arctic Gateway - High-resolution records reflecting Atlantic Water advection and ice coverage

    Science.gov (United States)

    Spielhagen, Robert F.; Bauch, Henning A.; Maudrich, Martin; Not, Christelle; Telesinski, Maciej M.; Werner, Kirstin

    2015-04-01

    The Arctic Gateway between Greenland and Svalbard is the main passage for the advection of Atlantic Water to the Arctic Ocean. Water temperature and intensity of this advection largely determine the degree of ice coverage which is fed by sea ice export from the north. Supported by a maximum in insolation, the Early Holocene was a period of extraordinarily strong advection and relatively high near-surface water temperatures in the eastern Nordic Seas (cf. Risebrobakken et al., 2011, Paleoceanography v. 26). Here we present a synthesis of radiocarbon-dated records from the northern and western part of this area, reaching from the SW Greenland Sea (73°N) to the Yermak Plateau (81°N) and revealing temporal and spatial differences in the development of the so-called Holocene Thermal Maximum (HTM). In the northern part of this region, the HTM started ca. 11-10.5 ka as indicated by rapidly increasing amounts of subpolar planktic foraminifers in the sediments. In the eastern Fram Strait and on the Yermak Plateau, our records of (sub)millennial scale resolution show that the maximum influx terminated already 2,000 years later (9-8 ka). Most likely, this development went along with a N-S relocation of the sea ice margin. According to the current stratigraphic model for a core with submillennial-scale resolution from Vesterisbanken seamount (73°N) in the Greenland Sea, the timing was different there. Increasing total amounts of planktic foraminifers in the sediment indicate an early (11-10 ka) reduction in sea ice coverage also in this region. However, evidence from subpolar planktic foraminifers for maximum Atlantic Water advection is younger (9-6 ka) than in the north. Apparently, the site in the SW Greenland Sea was affected by Atlantic Water in the Greenland Gyre that decoupled from the northward flowing Norwegian Atlantic Current/Westspitsbergen Current south of the Fram Strait. Thus, in a suite of events, strong Atlantic Water advection first affected the

  10. The nature and role of advection in advection-diffusion equations used for modelling bed load transport

    Science.gov (United States)

    Ancey, Christophe; Bohorquez, Patricio; Heyman, Joris

    2016-04-01

    The advection-diffusion equation arises quite often in the context of sediment transport, e.g., for describing time and space variations in the particle activity (the solid volume of particles in motion per unit streambed area). Stochastic models can also be used to derive this equation, with the significant advantage that they provide information on the statistical properties of particle activity. Stochastic models are quite useful when sediment transport exhibits large fluctuations (typically at low transport rates), making the measurement of mean values difficult. We develop an approach based on birth-death Markov processes, which involves monitoring the evolution of the number of particles moving within an array of cells of finite length. While the topic has been explored in detail for diffusion-reaction systems, the treatment of advection has received little attention. We show that particle advection produces nonlocal effects, which are more or less significant depending on the cell size and particle velocity. Albeit nonlocal, these effects look like (local) diffusion and add to the intrinsic particle diffusion (dispersal due to velocity fluctuations), with the important consequence that local measurements depend on both the intrinsic properties of particle displacement and the dimensions of the measurement system.

  11. The MOND paradigm

    OpenAIRE

    Milgrom, Mordehai

    2008-01-01

    I review briefly different aspects of the MOND paradigm, with emphasis on phenomenology, epitomized here by many MOND laws of galactic motion--analogous to Kepler's laws of planetary motion. I then comment on the possible roots of MOND in cosmology, possibly the deepest and most far reaching aspect of MOND. This is followed by a succinct account of existing underlying theories. I also reflect on the implications of MOND's successes for the dark matter (DM) paradigm: MOND predictions imply tha...

  12. Development (Paradigm) Failures

    OpenAIRE

    Hodler, Roland

    2011-01-01

    Over time the international development community has advocated various development paradigms, but countries following these paradigms have often performed poorly. I provide an explanation for this poor performance. In my model the political leader of a developing country chooses a policy and whether to implement it in an honest or corrupt manner. These choices affect domestic production and aid inflows. Production is high when productive capacity is high, and when the policy is appropriate i...

  13. The role of phase dynamics in a stochastic model of a passively advected scalar

    CERN Document Server

    Moradi, Sara

    2016-01-01

    Collective synchronous motion of the phases is introduced in a model for the stochastic passive advection-diffusion of a scalar with external forcing. The model for the phase coupling dynamics follows the well known Kuramoto model paradigm of limit-cycle oscillators. The natural frequencies in the Kuramoto model are assumed to obey a given scale dependence through a dispersion relation of the drift-wave form $-\\beta\\frac{k}{1+k^2}$, where $\\beta$ is a constant representing the typical strength of the gradient. The present aim is to study the importance of collective phase dynamics on the characteristic time evolution of the fluctuation energy and the formation of coherent structures. Our results show that the assumption of a fully stochastic phase state of turbulence is more relevant for high values of $\\beta$, where we find that the energy spectrum follows a $k^{-7/2}$ scaling. Whereas for lower $\\beta$ there is a significant difference between a-synchronised and synchronised phase states, and one could expe...

  14. The role of phase dynamics in a stochastic model of a passively advected scalar

    Science.gov (United States)

    Moradi, Sara; Anderson, Johan

    2016-05-01

    Collective synchronous motion of the phases is introduced in a model for the stochastic passive advection-diffusion of a scalar with external forcing. The model for the phase coupling dynamics follows the well known Kuramoto model paradigm of limit-cycle oscillators. The natural frequencies in the Kuramoto model are assumed to obey a given scale dependence through a dispersion relation of the drift-wave form -βk/1 +k2 , where β is a constant representing the typical strength of the gradient. The present aim is to study the importance of collective phase dynamics on the characteristic time evolution of the fluctuation energy and the formation of coherent structures. Our results show that the assumption of a fully stochastic phase state of turbulence is more relevant for high values of β, where we find that the energy spectrum follows a k-7 /2 scaling. Whereas for lower β there is a significant difference between a-synchronised and synchronised phase states, one could expect the formation of coherent modulations in the latter case.

  15. Advection and diffusion in random media implications for sea surface temperature anomalies

    CERN Document Server

    Piterbarg, Leonid I

    1997-01-01

    The book presents the foundations of the theory of turbulent transport within the context of stochastic partial differential equations. It serves to establish a firm connection between rigorous and non-rigorous results concerning turbulent diffusion. Mathematically all of the issues addressed in this book are concentrated around a single linear equation: stochastic advection-diffusion (transport) equation. There is no attempt made to derive universal statistics for turbulent flow. Instead emphasis is placed on a statistical description of a passive scalar (tracer) under given velocity statistics. An application concerning transport of sea surface temperature anomalies reconciles the developed theory and a highly practical issue of modern physical oceanography by using the newly designed inversion techniques which take advantage of powerful maximum likelihood and autoregressive estimators. Audience: Graduate students and researchers in mathematics, fluid dynamics, and physical oceanography.

  16. Local- and field-scale stochastic-advective vertical solute transport in horizontally heterogeneous unsaturated soils

    Science.gov (United States)

    Ojha, Richa; Prakash, A.; Govindaraju, Rao S.

    2014-08-01

    Description of field-scale solute transport in unsaturated soils is essential for assessing the degree of contamination, estimating fluxes past a control plane and for designing remedial measures. The flow field is usually described by numerical solution of the Richards equation followed by numerical solution of the advection-dispersion equation to describe contaminant movement. These numerical solutions are highly complex, and do not provide the insights that are possible from simpler analytical representations. In this study, analytical solutions at the local scale are developed to describe purely advective vertical transport of a conservative solute along the principle characteristic of the flow field. Local-scale model development is simplified by using a sharp-front approximation for water movement. These local solutions are then upscaled to field-scale solute transport by adopting a lognormally distributed horizontal hydraulic conductivity field to represent the natural heterogeneity observed in field soils. Analytical expressions are developed for the mean behavior of solute transport at the field scale. Comparisons with experimental observations find that trends of field-scale solute behavior are reasonably reproduced by the model. The accuracy of the proposed solution improves with increasing spatial variability in the hydraulic conductivity as revealed by further comparisons with numerical results of the Richards equation-based field-scale solute movement. In some cases, the sharp-front approximation may lead to anomalous field-scale behavior depending on the role of pre and postponded conditions in the field, and this limitation is discussed. The proposed method shows promise for describing field-scale solute movement in loamy sand and sandy loam soils.

  17. Multiple anisotropic collisions for advection-diffusion Lattice Boltzmann schemes

    Science.gov (United States)

    Ginzburg, Irina

    2013-01-01

    This paper develops a symmetrized framework for the analysis of the anisotropic advection-diffusion Lattice Boltzmann schemes. Two main approaches build the anisotropic diffusion coefficients either from the anisotropic anti-symmetric collision matrix or from the anisotropic symmetric equilibrium distribution. We combine and extend existing approaches for all commonly used velocity sets, prescribe most general equilibrium and build the diffusion and numerical-diffusion forms, then derive and compare solvability conditions, examine available anisotropy and stable velocity magnitudes in the presence of advection. Besides the deterioration of accuracy, the numerical diffusion dictates the stable velocity range. Three techniques are proposed for its elimination: (i) velocity-dependent relaxation entries; (ii) their combination with the coordinate-link equilibrium correction; and (iii) equilibrium correction for all links. Two first techniques are also available for the minimal (coordinate) velocity sets. Even then, the two-relaxation-times model with the isotropic rates often gains in effective stability and accuracy. The key point is that the symmetric collision mode does not modify the modeled diffusion tensor but it controls the effective accuracy and stability, via eigenvalue combinations of the opposite parity eigenmodes. We propose to reduce the eigenvalue spectrum by properly combining different anisotropic collision elements. The stability role of the symmetric, multiple-relaxation-times component, is further investigated with the exact von Neumann stability analysis developed in diffusion-dominant limit.

  18. Horizontal advection, diffusion and plankton spectra at the sea surface.

    Science.gov (United States)

    Bracco, A.; Clayton, S.; Pasquero, C.

    2009-04-01

    Plankton patchiness is ubiquitous in the oceans, and various physical and biological processes have been proposed as its generating mechanisms. However, a coherent statement on the problem is missing, due to both a small number of suitable observations and to an incomplete understanding of the properties of reactive tracers in turbulent media. Abraham (1998) suggested that horizontal advection may be the dominant process behind the observed distributions of phytoplankton and zooplankton, acting to mix tracers with longer reaction times (Rt) down to smaller scales. Conversely, Mahadevan and Campbell (2002) attributed the relative distributions of sea surface temperature and phytoplankton to small scale upwelling, where tracers with longer Rt are able to homogenize more than those with shorter reaction times. Neither of the above mechanisms can explain simultaneously the (relative) spectral slopes of temperature, phytoplankton and zooplankton. Here, with a simple advection model and a large suite of numerical experiments, we concentrate on some of the physical processes influencing the relative distributions of tracers at the ocean surface, and we investigate: 1) the impact of the spatial scale of tracer supply; 2) the role played by coherent eddies on the distribution of tracers with different Rt; 3) the role of diffusion (so far neglected). We show that diffusion determines the distribution of temperature, regardless of the nature of the forcing. We also find that coherent structures together with differential diffusion of tracers with different Rt impact the tracer distributions. This may help in understanding the highly variable nature of observed plankton spectra.

  19. Investigation of the influence of groundwater advection on energy extraction rates for sustainable borehole heat exchanger operation

    Science.gov (United States)

    Schelenz, Sophie; Dietrich, Peter; Vienken, Thomas

    2016-04-01

    A sustainable thermal exploitation of the shallow subsurface requires a precise understanding of all relevant heat transport processes. Currently, planning practice of shallow geothermal systems (especially for systems neglected or strongly simplified. The presented study proves that those simplifications of complex geological and hydrogeological subsurface characteristics are insufficient for a precise evaluation of site-specific energy extraction rates. Based on synthetic model scenarios with varying subsurface conditions (groundwater flow velocity and aquifer thickness) the impact of advection on induced long term temperature changes in 5 and 10 m distance of the borehole heat exchanger is presented. Extending known investigations, this study enhances the evaluation of shallow geothermal energy extraction rates by considering conductive and advective heat transport under varying aquifer thicknesses. Further, it evaluates the impact of advection on installation lengths of the borehole heat exchanger to optimize the initial financial investment. Finally, an evaluation approach is presented that classifies relevant heat transport processes according to their Péclet number to enable a first quantitative assessment of the subsurface energy regime and recommend further investigation and planning procedures.

  20. Paradigms and pragmatic constructivism

    DEFF Research Database (Denmark)

    Nørreklit, Hanne; Nørreklit, Lennart; Mitchell, Falconer

    2010-01-01

    to the analysis of the comment on their past paper. Findings - In addressing each of the issues in turn the authors clarify their analysis. Originality/value - The paper provides an argument for the development of a paradigm for accounting practice derived from the use of pragmatic constructivism....

  1. Paradigms in object recognition

    International Nuclear Information System (INIS)

    A broad range of approaches has been proposed and applied for the complex and rather difficult task of object recognition that involves the determination of object characteristics and object classification into one of many a priori object types. Our paper revises briefly the three main different paradigms in pattern recognition, namely Bayesian statistics, neural networks, and expert systems. (author)

  2. New Paradigms For Asteroid Formation

    CERN Document Server

    Johansen, Anders; Cuzzi, Jeffrey N; Morbidelli, Alessandro; Gounelle, Matthieu

    2015-01-01

    Asteroids and meteorites provide key evidence on the formation of planetesimals in the Solar System. Asteroids are traditionally thought to form in a bottom-up process by coagulation within a population of initially km-scale planetesimals. However, new models challenge this idea by demonstrating that asteroids of sizes from 100 to 1000 km can form directly from the gravitational collapse of small particles which have organised themselves in dense filaments and clusters in the turbulent gas. Particles concentrate passively between eddies down to the smallest scales of the turbulent gas flow and inside large-scale pressure bumps and vortices. The streaming instability causes particles to take an active role in the concentration, by piling up in dense filaments whose friction on the gas reduces the radial drift compared to that of isolated particles. In this chapter we review new paradigms for asteroid formation and compare critically against the observed properties of asteroids as well as constraints from meteo...

  3. Experimental tsunami deposits: Linking hydrodynamics to sediment entrainment, advection lengths and downstream fining

    Science.gov (United States)

    Johnson, Joel P. L.; Delbecq, Katie; Kim, Wonsuck; Mohrig, David

    2016-01-01

    A goal of paleotsunami research is to quantitatively reconstruct wave hydraulics from sediment deposits in order to better understand coastal hazards. Simple models have been proposed to predict wave heights and velocities, based largely on deposit grain size distributions (GSDs). Although seemingly consistent with some recent tsunamis, little independent data exist to test these equations. We conducted laboratory experiments to evaluate inversion assumptions and uncertainties. A computer-controlled lift gate instantaneously released ~ 6.5 m3 of water into a 32 m flume with shallow ponded water, creating a hydraulic bore that transported sand from an upstream source dune. Differences in initial GSDs and ponded water depths influenced entrainment, transport, and deposition. While the source dune sand was fully suspendable based on size alone, experimental tsunamis produced deposits dominated by bed load sand transport in the upstream ~ 1/3 of the flume and suspension-dominated transport downstream. The suspension deposits exhibited downstream fining and thinning. At 95% confidence, a published advection-settling model predicts time-averaged flow depths to approximately a factor of two, and time-averaged downstream flow velocities to within a factor of 1.5. Finally, reasonable scaling is found between flume and field cases by comparing flow depths, inundation distances, Froude numbers, Rouse numbers and grain size trends in suspension-dominated tsunami deposits, justifying laboratory study of sediment transport and deposition by tsunamis.

  4. Advection from the North Atlantic as the Forcing of Winter Greenhouse Effect Over Europe

    Science.gov (United States)

    Otterman, J.; Angell, J.; Atlas, R.; Bungato, D.; Shubert, S.; Starr, David OC.; Susskind, J.; Wu, M.-L. C.

    2002-01-01

    In winter, large interannual fluctuations in the surface temperature are observed over central Europe. Comparing warm February 1990 with cold February 1996, a satellite-retrieved surface (skin) temperature difference of 9.8 K is observed for the region 50-60 degrees N; 5-35 degrees E. Previous studies show that advection from the North Atlantic constitutes the forcing to such fluctuations. The advection is quantified by Index I(sub na), the average of the ocean-surface wind speed over the eastern North Atlantic when the direction is from the southwest (when the wind is from another direction, it counts as a zero speed to the average). Average I(sub na) for February 1990 was 10.6 m/s, but for February 1996 I(sub na) was only 2.4 m/s. A large value of I(sub na) means a strong southwesterly flow which brings warm and moist air into central Europe at low level, producing a steeper tropospheric lapse rate. Strong ascending motions at 700 mb are observed in association with the occurrence of enhanced warm, moist advection from the ocean in February 1990 producing clouds and precipitation. Total precipitable water and cloud-cover fraction have larger values in February 1990 than in 1996. The difference in the greenhouse effect between these two scenarios, this reduction in heat loss to space, can be translated into a virtual radiative heating of 2.6 W/square m above the February 1990 surface/atmosphere system, which contributes to a warming of the surface on the order of 2.6 K. Accepting this estimate as quantitatively meaningful, we evaluate the direct effect, the rise in the surface temperature in Europe as a result of maritime-air inflow, as 7.2 K (9.8 K-2.6 K). Thus, fractional reinforcement by the greenhouse effect is 2.6/7.2, or 36%, a substantial positive feedback.

  5. Groundwater flux characterization using distributed temperature sensing: Separating advection from thermal conduction

    Science.gov (United States)

    Liu, G.; Knobbe, S.; Butler, J. J., Jr.

    2015-12-01

    Direct measurement of groundwater flux is difficult to obtain in the field so hydrogeologists often use easily-detectable environmental tracers, such as heat or chemicals, as an indirect way to characterize flux. Previously, we developed a groundwater flux characterization (GFC) probe by using distributed temperature sensing (DTS) to monitor the temperature responses to active heating in a well. The temperature responses were consistent with the hydraulic conductivity profiles determined at the same location, and provided high-resolution information (approx. 1.5 cm) about vertical variations in horizontal flux through the screen. One of the key assumptions in the previous GFC approach was that the vertical variations in the thermal conductivity of the aquifer materials near the well are negligible, so that the temperature differences with depth are primarily a result of groundwater flux instead of thermal conduction. Although this assumption is likely valid for wells constructed with an artificial filter pack, it might become questionable for wells with natural filter packs (such as the wells constructed by direct push where the sediments are allowed to directly collapse onto the well screen). In this work, we develop a new procedure for separating advection from thermal conduction during GFC measurement. In addition to the normal open-screen GFC profiling, an impermeable sleeve was used so that heating tests could be performed without advective flow entering the well. The heating tests under sleeved conditions were primarily controlled by the thermal conduction around the well, and therefore could be used to remove the impact of thermal conduction from the normal GFC results obtained under open-screen conditions. This new procedure was tested in a laboratory sandbox, where a series of open-screen and sleeved GFC tests were performed under different flow rates. Results indicated that for the tested range of rates (Darcy velocity 0 - 0.78 m/d), the relation between

  6. Finite amplitude gravity waves: Harmonics, advective steepening, breaking and saturation

    Science.gov (United States)

    Weinstock, J.

    1985-01-01

    A simple theory is presented which determines details of the breaking and saturation of a gravity wave as it propagates upward in the atmosphere. Breaking and saturation are here due to nonlinear advection analogous to the breaching of a surface wave and to the breaking of a planetary wave. Much simplification is obtained by the assumption that in a wave packet consisting of a primary wave and its harmonics, the primary wave remains dominant. This assumption, referred to a quasi-monochromatic approximation, is suggested by observations. Determined by this approximate theory are: a detailed picture of the waveform as it steepens and breaks; harmonics of the wave; the turbulence generation; and an underlying relationship between superadiabatic lapse rate and saturation by wave-wave interactions.

  7. On the Structure of Advective Accretion Disks At High Luminosity

    CERN Document Server

    Artemova, I V; Igumenshchev, I V; Novikov, I D; Artemova, Ioulia V.; Bisnovatyi-Kogan, Gennadi S.; Igumenshchev, Igor V.; Novikov, Igor D.

    2001-01-01

    Global solutions of optically thick advective accretion disks around blackholes are constructed. The solutions are obtained by solving numerically a setof ordinary differential equations corresponding to a steady axisymmetricgeometrically thin disk. We pay special attention to consistently satisfy theregularity conditions at singular points of the equations. For this reason weanalytically expand a solution at the singular point, and use coefficients ofthe expansion in our iterative numerical procedure. We obtain consistenttransonic solutions in a wide range of values of the viscosity parameter alphaand mass acretion rate. We compare two different form of viscosity: one takesthe shear stress to be proportional to the pressure, while the other uses theangular velocity gradient-dependent stress. We find that there are two singular points in solutions corresponding to thepressure-proportional shear stress. The inner singular point locates close tothe last stable orbit around black hole. This point changes its typ...

  8. Modeling contaminant transport in homogeneous porous media with fractional advection-dispersion equation

    Institute of Scientific and Technical Information of China (English)

    HUANG Guanhua; HUANG Quanzhong; ZHAN Hongbin; CHEN Jing; XIONG Yunwu; FENG Shaoyuan

    2005-01-01

    The newly developed Fractional Advection-Dispersion Equation (FADE), which is FADE was extended and used in this paper for modelling adsorbing contaminant transport by adding an adsorbing term. A parameter estimation method and its corresponding FORTRAN based program named FADEMain were developed on the basis of Nonlinear Least Square Algorithm and the analytical solution for one-dimensional FADE under the conditions of step input and steady state flow. Data sets of adsorbing contaminants Cd and NH4+-N transport in short homogeneous soil columns and conservative solute NaCI transport in a long homogeneous soil column, respectively were used to estimate the transport parameters both by FADEMain and the advection-dispersion equation (ADE) based program CXTFIT2.1. Results indicated that the concentration simulated by FADE agreed well with the measured data. Compared to the ADE model, FADE can provide better simulation for the concentration in the initial lower concentration part and the late higher concentration part of the breakthrough curves for both adsorbing contaminants. The dispersion coefficients for ADE were from 0.13 to 7.06 cm2/min, while the dispersion coefficients for FADE ranged from 0.119 to 3.05 cm1.856/min for NaCI transport in the long homogeneous soil column. We found that the dispersion coefficient of FADE increased with the transport distance, and the relationship between them can be quantified with an exponential function. Less scale-dependent was also found for the dispersion coefficient of FADE with respect to ADE.

  9. A mass-conserving advection scheme for offline simulation of scalar transport in coastal ocean models

    Science.gov (United States)

    Gillibrand, P. A.; Herzfeld, M.

    2016-05-01

    We present a flux-form semi-Lagrangian (FFSL) advection scheme designed for offline scalar transport simulation with coastal ocean models using curvilinear horizontal coordinates. The scheme conserves mass, overcoming problems of mass conservation typically experienced with offline transport models, and permits long time steps (relative to the Courant number) to be used by the offline model. These attributes make the method attractive for offline simulation of tracers in biogeochemical or sediment transport models using archived flow fields from hydrodynamic models. We describe the FFSL scheme, and test it on two idealised domains and one real domain, the Great Barrier Reef in Australia. For comparison, we also include simulations using a traditional semi-Lagrangian advection scheme for the offline simulations. We compare tracer distributions predicted by the offline FFSL transport scheme with those predicted by the original hydrodynamic model, assess the conservation of mass in all cases and contrast the computational efficiency of the schemes. We find that the FFSL scheme produced very good agreement with the distributions of tracer predicted by the hydrodynamic model, and conserved mass with an error of a fraction of one percent. In terms of computational speed, the FFSL scheme was comparable with the semi-Lagrangian method and an order of magnitude faster than the full hydrodynamic model, even when the latter ran in parallel on multiple cores. The FFSL scheme presented here therefore offers a viable mass-conserving and computationally-efficient alternative to traditional semi-Lagrangian schemes for offline scalar transport simulation in coastal models.

  10. Advection, dispersion, and filtration of fine particles within emergent vegetation of the Florida Everglades

    Science.gov (United States)

    Huang, Y.H.; Saiers, J.E.; Harvey, J.W.; Noe, G.B.; Mylon, S.

    2008-01-01

    The movement of particulate matter within wetland surface waters affects nutrient cycling, contaminant mobility, and the evolution of the wetland landscape. Despite the importance of particle transport in influencing wetland form and function, there are few data sets that illuminate, in a quantitative way, the transport behavior of particulate matter within surface waters containing emergent vegetation. We report observations from experiments on the transport of 1 ??m latex microspheres at a wetland field site located in Water Conservation Area 3A of the Florida Everglades. The experiments involved line source injections of particles inside two 4.8-m-long surface water flumes constructed within a transition zone between an Eleocharis slough and Cladium jamaicense ridge and within a Cladium jamaicense ridge. We compared the measurements of particle transport to calculations of two-dimensional advection-dispersion model that accounted for a linear increase in water velocities with elevation above the ground surface. The results of this analysis revealed that particle spreading by longitudinal and vertical dispersion was substantially greater in the ridge than within the transition zone and that particle capture by aquatic vegetation lowered surface water particle concentrations and, at least for the timescale of our experiments, could be represented as an irreversible, first-order kinetics process. We found generally good agreement between our field-based estimates of particle dispersion and water velocity and estimates determined from published theory, suggesting that the advective-dispersive transport of particulate matter within complex wetland environments can be approximated on the basis of measurable properties of the flow and aquatic vegetation. Copyright 2008 by the American Geophysical Union.

  11. The Nature of Paradigms and Paradigm Shifts in Music Education

    Science.gov (United States)

    Panaiotidi, Elvira

    2005-01-01

    In this paper, the author attempts to extend the paradigm approach into the philosophy of music education and to build upon this basis a model for structuring music education discourse. The author begins with an examination of Peter Abbs' account of paradigms and paradigm shifts in arts education. Then she turns to Kuhn's conception and to his…

  12. A high-order splitting scheme for the advection-diffusion equation of pollutants

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A high-order splitting scheme for the advection-diffusion equation of pollutants is proposed in this paper. The multidimensional advection-diffusion equation is splitted into several one-dimensional equations that are solved by the scheme. Only three spatial grid points are needed in each direction and the scheme has fourth-order spatial accuracy. Several typically pure advection and advection-diffusion problems are simulated. Numerical results show that the accuracy of the scheme is much higher than that of the classical schemes and the scheme can be efficiently solved with little programming effort.

  13. Research Paradigm of Displaced Aggression

    OpenAIRE

    Tanno, Syota

    2013-01-01

    A review of research paradigm of displaced aggression is presented. The author arranged the Japanese wording of displaced aggression, summarized the historical transition of research on displaced aggression, and reviewed research paradigm of displaced aggression.

  14. Yoga, Sundhed og Paradigme

    OpenAIRE

    Andersen, Anna Bjerning Berg; Nielsen, Anna Sabine; Zunda, Daniella

    2014-01-01

    Our focal point and core concepts in this paper are science, health and yoga. Our main concern is to shed light on the understanding of these three concepts and how it varies, depending on the scientific approach these concepts are dealt with. The problem statement of this paper is thereby: How is it possible to argue, based on Kuhn's paradigm theory, that yoga/ayurveda and medical science represent fundamentally different views on health, yoga and science? We choose two scientific ap...

  15. Advective Heat Transport in an Unconfined Aquifer Induced by the Field Injection of an Open-Loop Groundwater Heat Pump

    Directory of Open Access Journals (Sweden)

    Stefano L. Russo

    2010-01-01

    Full Text Available Problem statement: The increasing diffusion of low-enthalpy geothermal open-loop Groundwater Heat Pumps (GWHP providing buildings air conditioning requires a careful assessment of the overall effects on groundwater system, especially in the urban areas. The impact on the groundwater temperature in the surrounding area of the re-injection well is directly linked to the aquifer properties. Physical processes affecting heat transport within an aquifer include advection (or convection and hydrodynamic thermodispersion (diffusion and mechanical dispersion. If the groundwater flows, the advective components tend to dominate the heat transfer process within the aquifer and the diffusion can be considered negligible. This study illustrates the experimental results derived from the groundwater monitoring in the surrounding area of an injection well connected to an open-loop GWHP plant which has been installed in the "Politecnico di Torino" (NW Italy for cooling some of the university buildings. Groundwater pumping and injection interfere only with the upper unconfined aquifer. Approach: After the description of the hydrogeological setting the authors examined the data deriving from multiparameter probes installed inside the pumping well (P2, the injection well (P4 and a downgradient piezometer (S2. Data refers to the summer 2009. To control the aquifer thermal stratification some multi-temporal temperature logs have been performed in the S2. Results: After the injection of warm water in P4 the plume arrived after 30 days in the S2. That delay is compatible with the calculated plume migration velocity (1.27 m d-1 and their respective distance (35 m. The natural temperature in the aquifer due to the switching-off of the GWHP plant has been reached after two month. The Electrical Conductivity (EC values tend to vary out of phase with the temperature. The temperature logs in the S2 highlighted a thermal stratification in the aquifer due to a low vertical

  16. Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone

    Energy Technology Data Exchange (ETDEWEB)

    Bachand, P.A.M., E-mail: Philip.Bachand@Tetratech.com [Tetra Tech, Davis, CA (United States); Bachand, S. [Tetra Tech, Davis, CA (United States); Fleck, J.; Anderson, F. [U.S. Geological Survey, California Water Science Center, Sacramento, CA (United States); Windham-Myers, L. [U.S. Geological Survey, National Research Program, Menlo Park, CA (United States)

    2014-06-01

    The current state of science and engineering related to analyzing wetlands overlooks the importance of transpiration and risks data misinterpretation. In response, we developed hydrologic and mass budgets for agricultural wetlands using electrical conductivity (EC) as a natural conservative tracer. We developed simple differential equations that quantify evaporation and transpiration rates using flow rates and tracer concentrations at wetland inflows and outflows. We used two ideal reactor model solutions, a continuous flow stirred tank reactor (CFSTR) and a plug flow reactor (PFR), to bracket real non-ideal systems. From those models, estimated transpiration ranged from 55% (CFSTR) to 74% (PFR) of total evapotranspiration (ET) rates, consistent with published values using standard methods and direct measurements. The PFR model more appropriately represents these non-ideal agricultural wetlands in which check ponds are in series. Using a flux model, we also developed an equation delineating the root zone depth at which diffusive dominated fluxes transition to advective dominated fluxes. This relationship is similar to the Peclet number that identifies the dominance of advective or diffusive fluxes in surface and groundwater transport. Using diffusion coefficients for inorganic mercury (Hg) and methylmercury (MeHg) we calculated that during high ET periods typical of summer, advective fluxes dominate root zone transport except in the top millimeters below the sediment–water interface. The transition depth has diel and seasonal trends, tracking those of ET. Neglecting this pathway has profound implications: misallocating loads along different hydrologic pathways; misinterpreting seasonal and diel water quality trends; confounding Fick's First Law calculations when determining diffusion fluxes using pore water concentration data; and misinterpreting biogeochemical mechanisms affecting dissolved constituent cycling in the root zone. In addition, our

  17. Flow

    DEFF Research Database (Denmark)

    2009-01-01

    Flow er en positiv, koncentreret tilstand, hvor al opmærksomhed er samlet om en bestemt aktivitet, som er så krævende og engagerende, at man må anvende mange mentale ressourcer for at klare den. Tidsfornemmelsen forsvinder, og man glemmer sig selv. 'Flow' er den første af en række udsendelser om...

  18. Correcting transport errors during advection of aerosol and cloud moment sequences in eulerian models

    Energy Technology Data Exchange (ETDEWEB)

    McGraw R.

    2012-03-01

    Moment methods are finding increasing usage for simulations of particle population balance in box models and in more complex flows including two-phase flows. These highly efficient methods have nevertheless had little impact to date for multi-moment representation of aerosols and clouds in atmospheric models. There are evidently two reasons for this: First, atmospheric models, especially if the goal is to simulate climate, tend to be extremely complex and take many man-years to develop. Thus there is considerable inertia to the implementation of novel approaches. Second, and more fundamental, the nonlinear transport algorithms designed to reduce numerical diffusion during advection of various species (tracers) from cell to cell, in the typically coarse grid arrays of these models, can and occasionally do fail to preserve correlations between the moments. Other correlated tracers such as isotopic abundances, composition of aerosol mixtures, hydrometeor phase, etc., are subject to this same fate. In the case of moments, this loss of correlation can and occasionally does give rise to unphysical moment sets. When this happens the simulation can come to a halt. Following a brief description and review of moment methods, the goal of this paper is to present two new approaches that both test moment sequences for validity and correct them when they fail. The new approaches work on individual grid cells without requiring stored information from previous time-steps or neighboring cells.

  19. Algebraic dynamics solution to and algebraic dynamics algorithm for nonlinear advection equation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Algebraic dynamics approach and algebraic dynamics algorithm for the solution of nonlinear partial differential equations are applied to the nonlinear advection equa-tion. The results show that the approach is effective for the exact analytical solu-tion and the algorithm has higher precision than other existing algorithms in nu-merical computation for the nonlinear advection equation.

  20. Analytical solution for the advection-dispersion transport equation in layered media

    Science.gov (United States)

    The advection-dispersion transport equation with first-order decay was solved analytically for multi-layered media using the classic integral transform technique (CITT). The solution procedure used an associated non-self-adjoint advection-diffusion eigenvalue problem that had the same form and coef...

  1. Investigation of density-dependent gas advection of trichloroethylene: Experiment and a model validation exercise

    Science.gov (United States)

    Lenhard, R. J.; Oostrom, M.; Simmons, C. S.; White, M. D.

    1995-07-01

    An experiment was conducted to evaluate whether vapor-density effects are significant in transporting volatile organic compounds (VOC's) with high vapor pressure and molecular mass through the subsurface. Trichloroethylene (TCE) was chosen for the investigation because it is a common VOC contaminant with high vapor pressure and molecular mass. For the investigation, a 2-m-long by 1-m-high by 7.5-cm-thick flow cell was constructed with a network of sampling ports. The flow cell was packed with sand, and a water table was established near the lower boundary. Liquid TCE was placed near the upper boundary of the flow cell in a chamber from which vapors could enter and migrate through the sand. TCE concentrations in the gas phase were measured by extracting 25-μl gas samples with an air-tight syringe and analyzing them with a gas chromatograph. The evolution of the TCE gas plume in the sand was investigated by examining plots of TCE concentrations over the domain for specific times and for particular locations as a function of time. To help in this analysis, a numerical model was developed that can predict the simultaneous movements of a gas, a nonaqueous liquid and water in porous media. The model also considers interphase mass transfer by employing the phase equilibrium assumption. The model was tested with one- and two-dimensional analytical solutions of fluid flow before it was used to simulate the experiment. Comparisons between experimental data and simulation results when vapor-density effects are considered were very good. When vapor-density effects were ignored, agreement was poor. These analyses suggest that vapor-density effects should be considered and that density-driven vapor advection may be an important mechanism for moving VOC's with high vapor pressures and molecular mass through the subsurface.

  2. Flow

    DEFF Research Database (Denmark)

    Knoop, Hans Henrik

    2006-01-01

    FLOW. Orden i hovedet på den fede måde Oplevelsesmæssigt er flow-tilstanden kendetegnet ved at man er fuldstændig involveret, fokuseret og koncentreret; at man oplever stor indre klarhed ved at vide hvad der skal gøres, og i hvilket omfang det lykkes; at man ved at det er muligt at løse opgaven...

  3. Mass loss from advective accretion disc around rotating black holes

    CERN Document Server

    Aktar, Ramiz; Nandi, Anuj

    2015-01-01

    We examine the properties of the outflowing matter from an advective accretion disc around a spinning black hole. During accretion, rotating matter experiences centrifugal pressure supported shock transition that effectively produces a virtual barrier around the black hole in the form of post-shock corona (hereafter, PSC). Due to shock compression, PSC becomes hot and dense that eventually deflects a part of the inflowing matter as bipolar outflows because of the presence of extra thermal gradient force. In our approach, we study the outflow properties in terms of the inflow parameters, namely specific energy (${\\mathcal E}$) and specific angular momentum ($\\lambda$) considering the realistic outflow geometry around the rotating black holes. We find that spin of the black hole ($a_k$) plays an important role in deciding the outflow rate $R_{\\dot m}$ (ratio of mass flux of outflow and inflow), in particular, $R_{\\dot m}$ is directly correlated with $a_k$ for the same set of inflow parameters. It is found that ...

  4. Paradigm, science and society

    Directory of Open Access Journals (Sweden)

    N.T. van der Merwe

    1975-03-01

    Full Text Available The subject of my contribution to the Taljaard Festschrift is focused on a cardinal aspect of the contemporary discussion in the area of theory of science, namely the relationship between science and society', and in this connection especially the role ascribed by certain scholars to paradigms in the practice of science. Because of its bridge function, the first task will be a global getting acquainted with some characteristic accents in contemporary theory of science. If this is successful, it can hopefully open up avenues for a view of the relationship of the remaining two components of the above mentioned subject.

  5. SUSTAINABLE DEVELOPMENT PARADIGM - SYNOPSIS

    Directory of Open Access Journals (Sweden)

    Constantinescu Andreea

    2014-07-01

    Full Text Available Even if sustainable development is a concept that gained quite recently its scientific prestige, through contribution of researchers its content has upgraded to a high degree of conceptual luggage and, through contribution from governance representatives, has gained an impressive good-practice background. Allowing the use of different methodological premises and conceptual tools, sustainable development paradigm is equipped with all the elements that would allow the opening of new horizons of knowledge. Based on the facility which can operate the concept of sustainable development, the European Union aims to develop both a more competitive economy based on environmental protection as well as a new governance of economic policy. This on one hand demonstrates the sustainable development ability to irradiate creativity towards the establishment of interdisciplinary bridges and on the other hand explains the growing interest of researchers interested in the problem of analyzing in detail this fruitful concept. Launched first as a theoretical framework to serve justify actions responsible for weighting economic growth, the concept of Sustainable Development has quickly become a topic of ethical debate circumscribed to the area of perfectibility of human nature to the necessity registry. In this regard, the philosophical content of this paradigm could not remain outside researchers concerns, who want to provide both policy makers and the general public a wide range of evidence to demonstrate the viability of this paradigm. Academia waits until maximization of the contribution of governance to achieve sustainable economic development, which consists in conjunction of this upward path with the momentum given by public policy sync, perfectly adapted for globalization era and all crises to come. However, because this concept based its structure and composition on three pillars, equally important economy, society and environment any attempt to strengthen

  6. Challenging the Innovation Paradigm

    CERN Document Server

    Sveiby, Karl Erik; Segercrantz, Beata

    2012-01-01

    Innovation is almost always seen as a "good thing". Challenging the Innovation Paradigm is a critical analysis of the innovation frenzy and contemporary innovation research. The one-sided focus on desirable effects of innovation misses many opportunities to reduce the undesirable consequences. Authors in this book show how systemic effects outside the innovating firms reduce the net benefits of innovation for individual employees, customers, as well as for society as a whole - also the innovators' own organizations. This book analyzes the dominant discourses that construct and recons

  7. Marketing! Where is Paradigm?

    Directory of Open Access Journals (Sweden)

    Deosir Flávio Lobo de Castro Júnior

    2015-09-01

    Full Text Available The quantitative- qualitative debate is not a new discussion. The aim of this study therefore is to check through the concept of paradigm, new perspectives to understand the academic research in marketing, developments of marketing thinking and methodologies used in the studies of quality of service. Without pretending to exhaust the subject and present a final conclusion, studies that point to the need and importance of qualitative research, as it helps the researcher to better understand the complex nature of the social world in which we live are presented. According to Santana and Gomes (2007, after examining the discussion of Hegel and Kant, reason and conclude that epistemology itself are historical buildings and evolve from contradictions. This article is divided into five moments. The first part presents besides introducing the constitution of the goals of this theoretical essay. The second part presents a brief discussion of the concept of paradigm and marketing. The third part presents a historical retrospective of marketing and its evolution from its schools from studies of Miranda and Arruda (2004. The fourth part presents the methodology of the studies on quality of services and finally the fifth part presents the final considerations.

  8. Numerical and analytical approaches to an advection-diffusion problem at small Reynolds number and large P\\'eclet number

    CERN Document Server

    Fuller, Nathaniel J

    2016-01-01

    Obtaining a detailed understanding of the physical interactions between a cell and its environment often requires information about the flow of fluid surrounding the cell. Cells must be able to effectively absorb and discard material in order to survive. Strategies for nutrient acquisition and toxin disposal, which have been evolutionarily selected for their efficacy, should reflect knowledge of the physics underlying this mass transport problem. Motivated by these considerations, in this paper we consider a two-dimensional advection-diffusion problem at small Reynolds number and large P\\'eclet number. We discuss the problem of mass transport for a circular cell in a uniform far-field flow. We approach the problem numerically, and also analytically through a rescaling of the concentration boundary layer. A biophysically motivated first-passage problem for the absorption of material by the cell demonstrates quantitative agreement between the numerical and analytical approaches.

  9. Differentiating transpiration from evaporation in seasonal agricultural wetlands and the link to advective fluxes in the root zone

    Science.gov (United States)

    Bachand, P.A.M.; S. Bachand,; Fleck, Jacob A.; Anderson, Frank E.; Windham-Myers, Lisamarie

    2014-01-01

    The current state of science and engineering related to analyzing wetlands overlooks the importance of transpiration and risks data misinterpretation. In response, we developed hydrologic and mass budgets for agricultural wetlands using electrical conductivity (EC) as a natural conservative tracer. We developed simple differential equations that quantify evaporation and transpiration rates using flowrates and tracer concentrations atwetland inflows and outflows. We used two ideal reactormodel solutions, a continuous flowstirred tank reactor (CFSTR) and a plug flow reactor (PFR), to bracket real non-ideal systems. From those models, estimated transpiration ranged from 55% (CFSTR) to 74% (PFR) of total evapotranspiration (ET) rates, consistent with published values using standard methods and direct measurements. The PFR model more appropriately represents these nonideal agricultural wetlands in which check ponds are in series. Using a fluxmodel, we also developed an equation delineating the root zone depth at which diffusive dominated fluxes transition to advective dominated fluxes. This relationship is similar to the Peclet number that identifies the dominance of advective or diffusive fluxes in surface and groundwater transport. Using diffusion coefficients for inorganic mercury (Hg) and methylmercury (MeHg) we calculated that during high ET periods typical of summer, advective fluxes dominate root zone transport except in the top millimeters below the sediment–water interface. The transition depth has diel and seasonal trends, tracking those of ET. Neglecting this pathway has profound implications: misallocating loads along different hydrologic pathways; misinterpreting seasonal and diel water quality trends; confounding Fick's First Law calculations when determining diffusion fluxes using pore water concentration data; and misinterpreting biogeochemicalmechanisms affecting dissolved constituent cycling in the root zone. In addition,our understanding of internal

  10. Summertime influences of tidal energy advection on the surface energy balance in a mangrove forest

    Directory of Open Access Journals (Sweden)

    J. G. Barr

    2013-01-01

    Full Text Available Mangrove forests are ecosystems susceptible to changing water levels and temperatures due to climate change as well as perturbations resulting from tropical storms. Numerical models can be used to project mangrove forest responses to regional and global environmental changes, and the reliability of these models depends on surface energy balance closure. However, for tidal ecosystems, the surface energy balance is complex because the energy transport associated with tidal activity remains poorly understood. This study aimed to quantify impacts of tidal flows on energy dynamics within a mangrove ecosystem. To address the research objective, an intensive 10-day study was conducted in a mangrove forest located along the Shark River in the Everglades National Park, FL, USA. Forest–atmosphere turbulent exchanges of energy were quantified with an eddy covariance system installed on a 30-m-tall flux tower. Energy transport associated with tidal activity was calculated based on a coupled mass and energy balance approach. The mass balance included tidal flows and accumulation of water on the forest floor. The energy balance included temporal changes in enthalpy, resulting from tidal flows and temperature changes in the water column. By serving as a net sink or a source of available energy, flood waters reduced the impact of high radiational loads on the mangrove forest. Also, the regression slope of available energy versus sink terms increased from 0.730 to 0.754 and from 0.798 to 0.857, including total enthalpy change in the water column in the surface energy balance for 30-min periods and daily daytime sums, respectively. Results indicated that tidal inundation provides an important mechanism for heat removal and that tidal exchange should be considered in surface energy budgets of coastal ecosystems. Results also demonstrated the importance of including tidal energy advection in mangrove biophysical models that are used for predicting ecosystem

  11. The role of a delay time on the spatial structure of chaotically advected reactive scalars

    CERN Document Server

    Tzella, Alexandra

    2009-01-01

    The stationary-state spatial structure of reacting scalar fields, chaotically advected by a two-dimensional large-scale flow, is examined for the case for which the reaction equations contain delay terms. Previous theoretical investigations have shown that, in the absence of delay terms and in a regime where diffusion can be neglected (large P\\'eclet number), the emergent spatial structures are filamental and characterized by a single scaling regime with a H\\"older exponent that depends on the rate of convergence of the reactive processes and the strength of the stirring measured by the average stretching rate. In the presence of delay terms, we show that for sufficiently small scales all interacting fields should share the same spatial structure, as found in the absence of delay terms. Depending on the strength of the stirring and the magnitude of the delay time, two further scaling regimes that are unique to the delay system may appear at intermediate length scales. An expression for the transition length s...

  12. Phase mixing vs. nonlinear advection in drift-kinetic plasma turbulence

    CERN Document Server

    Schekochihin, A A; Highcock, E G; Dellar, P J; Dorland, W; Hammett, G W

    2015-01-01

    A scaling theory of long-wavelength electrostatic turbulence in a magnetised, weakly collisional plasma (e.g., drift-wave turbulence driven by temperature gradients) is proposed, with account taken both of the nonlinear advection of the perturbed particle distribution by fluctuating ExB flows and of its phase mixing, which is caused by the streaming of the particles along the mean magnetic field and, in a linear problem, would lead to Landau damping. A consistent theory is constructed in which very little free energy leaks into high velocity moments of the distribution, rendering the turbulent cascade in the energetically relevant part of the wave-number space essentially fluid-like. The velocity-space spectra of free energy expressed in terms of Hermite-moment orders are steep power laws and so the free-energy content of the phase space does not diverge at infinitesimal collisionality (while it does for a linear problem); collisional heating due to long-wavelength perturbations vanishes in this limit (also i...

  13. The Peter Pan paradigm

    Directory of Open Access Journals (Sweden)

    Larson Janet E

    2008-01-01

    Full Text Available Abstract Genetic and environmental agents that disrupt organogenesis are numerous and well described. Less well established, however, is the role of delay in the developmental processes that yield functionally immature tissues at birth. Evidence is mounting that organs do not continue to develop postnatally in the context of these organogenesis insults, condemning the patient to utilize under-developed tissues for adult processes. These poorly differentiated organs may appear histologically normal at birth but with age may deteriorate revealing progressive or adult-onset pathology. The genetic and molecular underpinning of the proposed paradigm reveals the need for a comprehensive systems biology approach to evaluate the role of maternal-fetal environment on organogenesis. You may delay, but time will not Benjamin Franklin USA Founding Father

  14. A diffusive Fisher-KPP equation with free boundaries and time-periodic advections

    OpenAIRE

    Sun, Ningkui; Lou, Bendong; Zhou, Maolin

    2016-01-01

    We consider a reaction-diffusion-advection equation of the form: $u_t=u_{xx}-\\beta(t)u_x+f(t,u)$ for $x\\in (g(t),h(t))$, where $\\beta(t)$ is a $T$-periodic function representing the intensity of the advection, $f(t,u)$ is a Fisher-KPP type of nonlinearity, $T$-periodic in $t$, $g(t)$ and $h(t)$ are two free boundaries satisfying Stefan conditions. This equation can be used to describe the population dynamics in time-periodic environment with advection. Its homogeneous version (that is, both $...

  15. Paradigms for parasite conservation.

    Science.gov (United States)

    Dougherty, Eric R; Carlson, Colin J; Bueno, Veronica M; Burgio, Kevin R; Cizauskas, Carrie A; Clements, Christopher F; Seidel, Dana P; Harris, Nyeema C

    2016-08-01

    Parasitic species, which depend directly on host species for their survival, represent a major regulatory force in ecosystems and a significant component of Earth's biodiversity. Yet the negative impacts of parasites observed at the host level have motivated a conservation paradigm of eradication, moving us farther from attainment of taxonomically unbiased conservation goals. Despite a growing body of literature highlighting the importance of parasite-inclusive conservation, most parasite species remain understudied, underfunded, and underappreciated. We argue the protection of parasitic biodiversity requires a paradigm shift in the perception and valuation of their role as consumer species, similar to that of apex predators in the mid-20th century. Beyond recognizing parasites as vital trophic regulators, existing tools available to conservation practitioners should explicitly account for the unique threats facing dependent species. We built upon concepts from epidemiology and economics (e.g., host-density threshold and cost-benefit analysis) to devise novel metrics of margin of error and minimum investment for parasite conservation. We define margin of error as the risk of accidental host extinction from misestimating equilibrium population sizes and predicted oscillations, while minimum investment represents the cost associated with conserving the additional hosts required to maintain viable parasite populations. This framework will aid in the identification of readily conserved parasites that present minimal health risks. To establish parasite conservation, we propose an extension of population viability analysis for host-parasite assemblages to assess extinction risk. In the direst cases, ex situ breeding programs for parasites should be evaluated to maximize success without undermining host protection. Though parasitic species pose a considerable conservation challenge, adaptations to conservation tools will help protect parasite biodiversity in the face of

  16. Paradigms for parasite conservation.

    Science.gov (United States)

    Dougherty, Eric R; Carlson, Colin J; Bueno, Veronica M; Burgio, Kevin R; Cizauskas, Carrie A; Clements, Christopher F; Seidel, Dana P; Harris, Nyeema C

    2016-08-01

    Parasitic species, which depend directly on host species for their survival, represent a major regulatory force in ecosystems and a significant component of Earth's biodiversity. Yet the negative impacts of parasites observed at the host level have motivated a conservation paradigm of eradication, moving us farther from attainment of taxonomically unbiased conservation goals. Despite a growing body of literature highlighting the importance of parasite-inclusive conservation, most parasite species remain understudied, underfunded, and underappreciated. We argue the protection of parasitic biodiversity requires a paradigm shift in the perception and valuation of their role as consumer species, similar to that of apex predators in the mid-20th century. Beyond recognizing parasites as vital trophic regulators, existing tools available to conservation practitioners should explicitly account for the unique threats facing dependent species. We built upon concepts from epidemiology and economics (e.g., host-density threshold and cost-benefit analysis) to devise novel metrics of margin of error and minimum investment for parasite conservation. We define margin of error as the risk of accidental host extinction from misestimating equilibrium population sizes and predicted oscillations, while minimum investment represents the cost associated with conserving the additional hosts required to maintain viable parasite populations. This framework will aid in the identification of readily conserved parasites that present minimal health risks. To establish parasite conservation, we propose an extension of population viability analysis for host-parasite assemblages to assess extinction risk. In the direst cases, ex situ breeding programs for parasites should be evaluated to maximize success without undermining host protection. Though parasitic species pose a considerable conservation challenge, adaptations to conservation tools will help protect parasite biodiversity in the face of

  17. MDMA and the "ecstasy paradigm".

    Science.gov (United States)

    Cole, Jon C

    2014-01-01

    For nearly 30 years, there has been a steady flow of research papers highlighting the dangers of MDMA and the implications for ecstasy users. After such a long time, it would be reasonable to expect that these dangers would be obvious due to the large number of ecstasy users. The available evidence does not indicate that there are millions of ecstasy users experiencing any problems linked to their ecstasy use. The "precautionary principle" suggests that, in the absence of knowing for certain, "experts" should argue that MDMA be avoided. However, this may have been taken too far, as the dire warnings do not seem to be reducing with the lack of epidemiological evidence of clinically relevant problems. The "ecstasy paradigm" is one way of articulating this situation, in that the needs of research funders and publication bias lead to a specific set of subcultural norms around what information is acceptable in the public domain. By digging a little deeper, it is easy to find problems with the evidence base that informs the public debate around MDMA. The key question is whether it is acceptable to maintain this status quo given the therapeutic potential of MDMA.

  18. Passive advection of a vector field: Anisotropy, finite correlation time, exact solution, and logarithmic corrections to ordinary scaling.

    Science.gov (United States)

    Antonov, N V; Gulitskiy, N M

    2015-10-01

    In this work we study the generalization of the problem considered in [Phys. Rev. E 91, 013002 (2015)] to the case of finite correlation time of the environment (velocity) field. The model describes a vector (e.g., magnetic) field, passively advected by a strongly anisotropic turbulent flow. Inertial-range asymptotic behavior is studied by means of the field theoretic renormalization group and the operator product expansion. The advecting velocity field is Gaussian, with finite correlation time and preassigned pair correlation function. Due to the presence of distinguished direction n, all the multiloop diagrams in this model vanish, so that the results obtained are exact. The inertial-range behavior of the model is described by two regimes (the limits of vanishing or infinite correlation time) that correspond to the two nontrivial fixed points of the RG equations. Their stability depends on the relation between the exponents in the energy spectrum E∝k(⊥)(1-ξ) and the dispersion law ω∝k(⊥)(2-η). In contrast to the well-known isotropic Kraichnan's model, where various correlation functions exhibit anomalous scaling behavior with infinite sets of anomalous exponents, here the corrections to ordinary scaling are polynomials of logarithms of the integral turbulence scale L. PMID:26565343

  19. Horizontal Advection and Mixing of Pollutants in the Urban Atmospheric Environment

    Science.gov (United States)

    Magnusson, S. P.; Entekhabi, D.; Britter, R.; Norford, L.; Fernando, H. J.

    2013-12-01

    Although urban air quality and its impacts on the public health have long been studied, the increasing urbanization is raising concerns on how to better control and mitigate these health impacts. A necessary element in predicting exposure levels is fundamental understanding of flow and dispersion in urban canyons. The complex topology of building structures and roads requires the resolution of turbulence phenomena within urban canyons. The use of dense and low porosity construction material can lead to rapid heating in response to direct solar exposure due to large thermal mass. Hence thermal and buoyancy effects may be as important as mechanically-forced or shear-induced flows. In this study, the transport of pollutants within the urban environment, as well as the thermal and advection effects, are investigated. The focus is on the horizontal transport or the advection effects within the urban environment. With increased urbanization and larger and more spread cities, concern about how the upstream air quality situation can affect downstream areas. The study also examines the release and the dispersion of hazardous material. Due to the variety and complexity of urban areas around the world, the urban environment is simplified into adjacent two-dimensional urban street canyons. Pollutants are released inside each canyon. Computational Fluid Dynamics (CFD) simulations are applied to evaluate and quantify the flow rate out of each canyon and also the exchange of pollutants between the canyons. Imagine a row of ten adjacent urban street canyons of aspect ratio 1 with horizontal flow perpendicular to it as shown in the attached figure. C is the concentration of pollutants. The first digit indicates in what canyon the pollutant is released and the second digit indicates the location of that pollutant. For example, C3,4 is the concentration of pollutant released inside canyon 3 measured in canyon 4. The same amount of pollution is released inside the ten street canyons

  20. Boundary value problemfor multidimensional fractional advection-dispersion equation

    Directory of Open Access Journals (Sweden)

    Khasambiev Mokhammad Vakhaevich

    2015-05-01

    authors first considered the boundary value problem for stationary equation for mass transfer in super-diffusion conditions and abnormal advection. Then the solution of the problem is explicitly given. The solution is obtained by the Fourier’s method.The obtained results will be useful in liquid filtration theory in fractal medium and for modeling the temperature variations in the heated bar.

  1. Naturalistic Inquiry: Paradigm and Method.

    Science.gov (United States)

    Lotto, Linda S.

    Despite the rhetoric acclaiming it as a new paradigm, educational researchers have tended to treat naturalistic inquiry as a new or alternative method employed within the dominant, rationalistic paradigm. Spokespersons for naturalistic inquiry tend to concentrate on what one does differently rather than how one perceives what one is doing…

  2. Site use of advective flux probes for soil gas and soil analysis

    International Nuclear Information System (INIS)

    The success of soil vapor as a means of assessing subsurface conditions depends upon the volatility of the compounds and the ability of the vapor to migrate through soil pores. Normally, soil gas techniques are not considered valid for poorly volatile compounds or tight soils. Both of these factors can be overcome by a simultaneous application of heat and vacuum with heated gas streams or use of a liquid solution, combined with a means of creating an artificially porous substrate out of compacted poorly permeable soils. Special points and bits have been devised to fit on a miniature hollow stem shaft. The point receives a continuous flow of heated air or liquid which volatilises or dissolves organics from porous or pulverized soil as the point penetrates. The re-circulation of gas or fluid then transports the adsorbed organics to the surface for chromatographic analysis. A comparison of vapor pressures of different organics versus absolute temperatures can be used to extrapolate the extension of soil gas detection. Heavy oils, creosotes, naphthalenes, turpenes, and quinolines, all compounds whose boiling points exist in excess of 200 degrees C, can be analyzed by soil vapor techniques. Samples of the organic were obtained by either direct injection on to a heated GC column or by liquid chromatographic processing. The paper compares current vacuum procedures with those obtained from the advective flux procedure. The compounds are plotted on a grid of boiling point, vapor pressure, and aqueous solubility. A site containing soil contaminated with a mixture of light to heavy petroleum products was analyzed with enhanced hot gas and liquid flow. A comparison between the compounds analyzed is presented for both techniques

  3. Advective surface velocity in the north west Pacific derived from NOAA AVHRR images

    Digital Repository Service at National Institute of Oceanography (India)

    Pankajakshan, T.; Akiyama, M.; Okada, Y.; Sugimori, Y.

    Using sequential AVHRR images in November 1983, nearsurface advective velocities are derived in the region Kuroshio south of Japan. For deriving the velocities two methods are used. One is the Method of Cross Correlation (MCC), using image pair...

  4. Rigorous upper bounds for fluid and plasma transport due to passive advection

    Energy Technology Data Exchange (ETDEWEB)

    Krommes, J.A.; Smith, R.A.; Kim, C.B.

    1987-07-01

    The formulation of variational principles for transport due to passive advection is described. A detailed account of the work has been published elsewhere. In the present paper, the motivations, philosophy, and implications of the method are briefly discussed. 15 refs.

  5. Implicit and semi-implicit schemes in the Versatile Advection Code: numerical tests

    NARCIS (Netherlands)

    Toth, G.; Keppens, R.; Botchev, M. A.

    1998-01-01

    We describe and evaluate various implicit and semiimplicit time integration schemes applied to the numerical simulation of hydrodynamical and magnetohydrodynamical problems. The schemes were implemented recently in the software package Versatile Advection Code, which uses modern shock capturing meth

  6. Solving the Advection-Diffusion Equations in Biological Contexts using the Cellular Potts Model

    CERN Document Server

    Dan, D; Chen, K; Glazier, J A; Dan, Debasis; Mueller, Chris; Chen, Kun; Glazier, James A.

    2005-01-01

    The Cellular Potts Model (CPM) is a robust, cell-level methodology for simulation of biological tissues and morphogenesis. Both tissue physiology and morphogenesis depend on diffusion of chemical morphogens in the extra-cellular fluid or matrix (ECM). Standard diffusion solvers applied to the cellular potts model use finite difference methods on the underlying CPM lattice. However, these methods produce a diffusing field tied to the underlying lattice, which is inaccurate in many biological situations in which cell or ECM movement causes advection rapid compared to diffusion. Finite difference schemes suffer numerical instabilities solving the resulting advection-diffusion equations. To circumvent these problems we simulate advection-diffusion within the framework of the CPM using off-lattice finite-difference methods. We define a set of generalized fluid particles which detach advection and diffusion from the lattice. Diffusion occurs between neighboring fluid particles by local averaging rules which approxi...

  7. Wright functions governed by fractional directional derivatives and fractional advection diffusion equations

    CERN Document Server

    D'Ovidio, Mirko

    2012-01-01

    We consider fractional directional derivatives and establish some connection with stable densities. Solutions to advection equations involving fractional directional derivatives are presented and some properties investigated. In particular we obtain solutions written in terms of Wright functions by exploiting operational rules involving the shift operator. We also consider fractional advection diffusion equations involving fractional powers of the negative Laplace operator and directional derivatives of fractional order and discuss the probabilistic interpretations of solutions.

  8. Modifying SEBAL ET Algorithm to account for advection by using daily averages of weather data

    Science.gov (United States)

    Mkhwanazi, M. M.; Chavez, J. L.

    2013-12-01

    The use of Remote Sensing (RS) in crop evapotranspiration (ET) estimation is aimed at improving agricultural water management. The Surface Energy Balance Algorithm for Land (SEBAL) is one of several methods that have been developed for this purpose. This has been a preferred model as it requires minimal climate data. However, it has a noted downside of underestimating ET under advective conditions. This is primarily due to the use of evaporative fraction (EF) to extrapolate instantaneous ET to daily values, with the assumption that EF is constant throughout the day. A modified SEBAL model was used in this study, which requires daily averages of weather data to estimate advection which is then introduced into the 24-hour ET sub-model of SEBAL. The study was carried out in southeastern Colorado, a semi-arid area where afternoon advection is a common feature. ET estimated using the original and modified SEBAL was compared to the lysimeter-measured ET. Results showed that the modified SEBAL algorithm performed better in estimating daily ET in overall, but especially on days when there was advection. On non-advective days, the original SEBAL was more accurate. It is therefore recommended that the modified SEBAL be used only on advective days, and guidelines to help identify such days were proposed.

  9. Characterization of the role of heterogeneous advection and diffusion on transport in weathered and fractured granite

    Science.gov (United States)

    Guihéneuf, N.; Boisson, A.; Bour, O.; Le Borgne, T.; Marechal, J.; Nigon, B.; Wajiddudin, M.; Ahmed, S.

    2013-12-01

    The prediction of transport in weathered and fractured rocks is critical as it represents the primary control of contaminant transfer from the subsurface in many parts of the world. This is the case in Southern India, where the subsurface is composed mainly of weathered and fractured granite and where the overexploitation of the groundwater resource since the 70's has led to high water table depletion and strong groundwater quality deterioration. One key issue for modelling transport in such systems is to quantify the respective role of advective heterogeneities and matrix diffusion, which can both lead to strongly non Fickian transport properties. We investigate this question by analysing tracer test experiments performed under different flow configurations at a fractured granite experimental site located in Andhra Pradesh (India). We performed both convergent and push-pull tracer tests within the same fracture and at different scales. Three convergent tracer tests were performed with a solution of fluorescein for different pumping rate and for different distances between injection and pumping boreholes: 6, 30 and 41 meters. To evaluate diffusive process, we performed two long-duration push-pull tests (push time of 3 hours) with a solution of two conservative tracers of different diffusion coefficient (fluorescein and sodium chloride). We performed also six others push-pull tests with only fluorescein but for a variable push times of 14 min and 55 min with or without resting time of about 60 min. The late-time behaviour on the breakthrough curves (BTCs) obtained for all convergent tracer tests showed a power-law slope of -2. Two of them showed an inflexion in the BTCs suggesting the existence of two independent flow paths and thus a highly channelized flow. The long-duration push-pull tests showed similar late-time behaviour with a power-law slope of -2.2 for both tracers. The six others push-pull tests showed a variation of power-law exponent from -3 to -2

  10. Planktonic interactions and chaotic advection in Langmuir circulation

    DEFF Research Database (Denmark)

    Bees, Martin Alan; Mezic, I.; McGlade, J.

    1998-01-01

    The role of unsteady laminar flows for planktonic communities is investigated. Langmuir circulation is used, as a typical medium-scale structure, to illustrate mechanisms for the generation of plankton patches. Two behaviours are evident: chaotic regions that help to spread plankton and locally...

  11. On the importance of aqueous diffusion and electrostatic interactions in advection-dominated transport in saturated porous media

    DEFF Research Database (Denmark)

    Rolle, Massimo

    2015-01-01

    Diffusion and compound-specific mixing significantly affect conservative and reactive transport in groundwater. The variability of diffusion coefficients for different solutes has a relevant impact on their displacement at different scales, not only under diffusion-dominated regimes but also under...... to multicomponent ionic dispersion: the dispersive fluxes of the different ions are cross-coupled due to the effects of Coulombic interactions. Such effects are illustrated in flow-through experiments in saturated porous media. Simple strong electrolytes were selected as tracers and their transport was studied...... under different advection-dominated conditions and in homogeneous and heterogeneous porous media. The interpretation of the experimental results requires a multicomponent modeling approach with an accurate description of local hydrodynamic dispersion and explicitly accounting for the cross...

  12. Multidimensional supernova simulations with approximative neutrino transport. II. Convection and the advective-acoustic cycle in the supernova core

    CERN Document Server

    Scheck, L; Foglizzo, T; Kifonidis, K

    2007-01-01

    By 2D hydrodynamic simulations including a detailed equation of state and neutrino transport, we investigate the interplay between different non-radial hydrodynamic instabilities that play a role during the postbounce accretion phase of collapsing stellar cores. The convective mode of instability, which is driven by negative entropy gradients caused by neutrino heating or by time variations of the shock strength, can be identified clearly by the development of typical Rayleigh-Taylor mushrooms. However, in cases where the gas in the postshock region is rapidly advected towards the gain radius, the growth of such a buoyancy instability can be suppressed. In such a situation the shocked flow nevertheless can develop non-radial asymmetry with an oscillatory growth of the amplitude. This phenomenon was previously termed ``standing accretion shock instability'' (SASI) by Blondin et al. (2003). It is shown here that the oscillation period of the SASI observed in our simulations agrees well with the one estimated fo...

  13. Functional reactive paradigm advantages for Android development

    OpenAIRE

    SUTULA ALEXANDER

    2015-01-01

    This article describes conceptual difference between imperative, reactive paradigms and functional reactive style advantages in Android development. Solutions of imperative paradigm main problems are described.

  14. Phase dependent advection-diffusion in drift wave - zonal flow turbulence

    CERN Document Server

    Moradi, Sara

    2016-01-01

    In plasma turbulence theory, due to the complexity of the system with many non-linearly interacting waves, the dynamics of the phases is often disregarded and the so-called random-phase approximation (RPA) is used assuming the existence of a Chirikov-like criterion for the onset of wave stochasticity. The dynamical amplitudes are represented as complex numbers, $\\psi = \\psi_r + i\\psi_i = ae^{i\\theta}$, with the amplitudes slowly varying whereas the phases are rapidly varying and, in particular, distributed uniformly over the interval $[0;2\\pi)$. However, one could expect that the phase dynamics can play a role in the self-organisation and the formation of coherent structures. In the same manner it is also expected that the RPA falls short to take coherent interaction between phases into account. In this work therefore, we studied the role of phase dynamics and the coupling of phases between different modes on the characteristic time evolution of the turbulent. We assume a simple turbulent system where the so-...

  15. Signatures of Accretion Shocks in Broadband Spectrum of Advective Flows Around Black Holes

    CERN Document Server

    Mandal, S; Mandal, Samir; Chakrabarti, Sandip K.

    2005-01-01

    We compute the effects of the centrifugal pressure supported shock waves on the emitted spectrum from an accretion disk primarily consisting of low angular momentum matter. Electrons are very efficiently accelerated by the accretion shock and acquire power-law distribution. The accelerated particles in turn emit synchrotron radiation in presence of a stochastic magnetic field in equipartition with the gas. Efficient cooling of the electrons by these soft photons reduces its temperature in comparison to the protons. We explore the nature of the broadband spectra by using Comptonization, bremsstrahlung and synchrotron emission. We then show that there could be two crossing points in a broadband spectrum, one near $\\sim 10 keV$ and the other $\\sim 300-400$KeV.

  16. Advection of the salt wedge and evolution of the internal flow structure in the Rotterdam Waterway

    NARCIS (Netherlands)

    De Nijs, M.A.J.; Pietrzak, J.D.; Winterwerp, J.C.

    2011-01-01

    An analysis of field measurements recorded over a tidal cycle in the Rotterdam Waterway is presented. These measurements are the first to elucidate the processes influencing the along-channel current structure and the excursion of the salt wedge in this estuary. The salt wedge structure remained sta

  17. Diagnosis of a Moist Thermodynamic Advection Parameter in Heavy-Rainfall Events

    Institute of Scientific and Technical Information of China (English)

    WU Xiandu; RAN Lingkun; CHU Yanli

    2011-01-01

    A moist thermodynamic advection parameter, defined as an absolute value of the dot product of horizontal gradients of three-dimensional potential temperature advection and general potential temperature, is introduced to diagnose frontal heavy rainfall events in the north of China. It is shown that the parameter is closely related to observed 6-h accumulative surface rainfall and simulated cloud hydrometeors. Since the parameter is capable of describing the typical vertical structural characteristics of dynamic, thermodynamic and water vapor fields above a strong precipitation region near the front surface, it may serve as a physical tracker to detect precipitable weather systems near to a front.A tendency equation of the parameter was derived in Cartesian coordinates and calculated with the simulation output data of a heavy rainfall event. Results revealed that the advection of the parameter by the three-dimensional velocity vector, the covariance of potential temperature advection by local change of the velocity vector and general potential temperature, and the interaction between potential temperature advection and the source or sink of general potential temperature, accounted for local change in the parameter. This indicated that the parameter was determined by a combination of dynamic processes and cloud microphysical processes.

  18. First-Order Hyperbolic System Method for Time-Dependent Advection-Diffusion Problems

    Science.gov (United States)

    Mazaheri, Alireza; Nishikawa, Hiroaki

    2014-01-01

    A time-dependent extension of the first-order hyperbolic system method for advection-diffusion problems is introduced. Diffusive/viscous terms are written and discretized as a hyperbolic system, which recovers the original equation in the steady state. The resulting scheme offers advantages over traditional schemes: a dramatic simplification in the discretization, high-order accuracy in the solution gradients, and orders-of-magnitude convergence acceleration. The hyperbolic advection-diffusion system is discretized by the second-order upwind residual-distribution scheme in a unified manner, and the system of implicit-residual-equations is solved by Newton's method over every physical time step. The numerical results are presented for linear and nonlinear advection-diffusion problems, demonstrating solutions and gradients produced to the same order of accuracy, with rapid convergence over each physical time step, typically less than five Newton iterations.

  19. Health Inequities: Evaluation of Two Paradigms

    Science.gov (United States)

    Ashcroft, Rachelle

    2010-01-01

    Social work practice in health is shaped by underlying paradigms. To effectively target health inequities, practitioners need to consider appropriate paradigms. In this exploration of how six health paradigms shape theory and practice, the two health paradigms that most attended to health inequalities are social determinants of health and…

  20. Advective transport observations with MODPATH-OBS--documentation of the MODPATH observation process

    Science.gov (United States)

    Hanson, R.T.; Kauffman, L.K.; Hill, M.C.; Dickinson, J.E.; Mehl, S.W.

    2013-01-01

    The MODPATH-OBS computer program described in this report is designed to calculate simulated equivalents for observations related to advective groundwater transport that can be represented in a quantitative way by using simulated particle-tracking data. The simulated equivalents supported by MODPATH-OBS are (1) distance from a source location at a defined time, or proximity to an observed location; (2) time of travel from an initial location to defined locations, areas, or volumes of the simulated system; (3) concentrations used to simulate groundwater age; and (4) percentages of water derived from contributing source areas. Although particle tracking only simulates the advective component of conservative transport, effects of non-conservative processes such as retardation can be approximated through manipulation of the effective-porosity value used to calculate velocity based on the properties of selected conservative tracers. This program can also account for simple decay or production, but it cannot account for diffusion. Dispersion can be represented through direct simulation of subsurface heterogeneity and the use of many particles. MODPATH-OBS acts as a postprocessor to MODPATH, so that the sequence of model runs generally required is MODFLOW, MODPATH, and MODPATH-OBS. The version of MODFLOW and MODPATH that support the version of MODPATH-OBS presented in this report are MODFLOW-2005 or MODFLOW-LGR, and MODPATH-LGR. MODFLOW-LGR is derived from MODFLOW-2005, MODPATH 5, and MODPATH 6 and supports local grid refinement. MODPATH-LGR is derived from MODPATH 5. It supports the forward and backward tracking of particles through locally refined grids and provides the output needed for MODPATH_OBS. For a single grid and no observations, MODPATH-LGR results are equivalent to MODPATH 5. MODPATH-LGR and MODPATH-OBS simulations can use nearly all of the capabilities of MODFLOW-2005 and MODFLOW-LGR; for example, simulations may be steady-state, transient, or a combination

  1. Methods and Algorithms for Solving Inverse Problems for Fractional Advection-Dispersion Equations

    KAUST Repository

    Aldoghaither, Abeer

    2015-11-12

    Fractional calculus has been introduced as an e cient tool for modeling physical phenomena, thanks to its memory and hereditary properties. For example, fractional models have been successfully used to describe anomalous di↵usion processes such as contaminant transport in soil, oil flow in porous media, and groundwater flow. These models capture important features of particle transport such as particles with velocity variations and long-rest periods. Mathematical modeling of physical phenomena requires the identification of pa- rameters and variables from available measurements. This is referred to as an inverse problem. In this work, we are interested in studying theoretically and numerically inverse problems for space Fractional Advection-Dispersion Equation (FADE), which is used to model solute transport in porous media. Identifying parameters for such an equa- tion is important to understand how chemical or biological contaminants are trans- ported throughout surface aquifer systems. For instance, an estimate of the di↵eren- tiation order in groundwater contaminant transport model can provide information about soil properties, such as the heterogeneity of the medium. Our main contribution is to propose a novel e cient algorithm based on modulat-ing functions to estimate the coe cients and the di↵erentiation order for space FADE, which can be extended to general fractional Partial Di↵erential Equation (PDE). We also show how the method can be applied to the source inverse problem. This work is divided into two parts: In part I, the proposed method is described and studied through an extensive numerical analysis. The local convergence of the proposed two-stage algorithm is proven for 1D space FADE. The properties of this method are studied along with its limitations. Then, the algorithm is generalized to the 2D FADE. In part II, we analyze direct and inverse source problems for a space FADE. The problem consists of recovering the source term using final

  2. Evaporative loss from irrigated interrows in a highly advective semi-arid agricultural area

    Science.gov (United States)

    Agam, Nurit; Evett, Steven R.; Tolk, Judy A.; Kustas, William P.; Colaizzi, Paul D.; Alfieri, Joseph G.; McKee, Lynn G.; Copeland, Karen S.; Howell, Terry A.; Chávez, Jose L.

    2012-12-01

    Agricultural productivity has increased in the Texas High Plains at the cost of declining water tables, putting at risk the sustainability of the Ogallala Aquifer as a principal source of water for irrigated agriculture. This has led area producers to seek alternative practices that can increase water use efficiency (WUE) through more careful management of water. One potential way of improving WUE is by reducing soil evaporation (E), thus reducing overall evapotranspiration (ET). Before searching for ways to reduce E, it is first important to quantify E and understand the factors that determine its magnitude. The objectives of this study were (1) to quantify E throughout part of the growing season for irrigated cotton in a strongly advective semi-arid region; (2) to study the effects of LAI, days after irrigation, and measurement location within the row on the E/ET fraction; and (3) to study the ability of microlysimeter (ML) measures of E combined with sap flow gage measures of transpiration (T) to accurately estimate ET when compared with weighing lysimeter ET data and to assess the E/T ratio. The research was conducted in an irrigated cotton field at the Conservation & Production Research Laboratory of the USDA-ARS, Bushland, TX. ET was measured by a large weighing lysimeter, and E was measured by 10 microlysimeters that were deployed in two sets of 5 across the interrow. In addition, 10 heat balance sap flow gages were used to determine T. A moderately good agreement was found between the sum E + T and ET (SE = 1 mm or ˜10% of ET). It was found that E may account for >50% of ET during early stages of the growing season (LAI < 0.2), significantly decreasing with increase in LAI to values near 20% at peak LAI of three. Measurement location within the north-south interrows had a distinct effect on the diurnal pattern of E, with a shift in time of peak E from west to east, a pattern that was governed by the solar radiation reaching the soil surface. However, total

  3. Large-eddy Advection in Evapotranspiration Estimates from an Array of Eddy Covariance Towers

    Science.gov (United States)

    Lin, X.; Evett, S. R.; Gowda, P. H.; Colaizzi, P. D.; Aiken, R.

    2014-12-01

    Evapotranspiration was continuously measured by an array of eddy covariance systems and large weighting lysimeter in a sorghum in Bushland, Texas in 2014. The advective divergence from both horizontal and vertical directions were measured through profile measurements above canopy. All storage terms were integrated from the depth of soil heat flux plate to the height of eddy covariance measurement. Therefore, a comparison between the eddy covariance system and large weighing lysimeter was conducted on hourly and daily basis. The results for the discrepancy between eddy covariance towers and the lysimeter will be discussed in terms of advection and storage contributions in time domain and frequency domain.

  4. Identification of advective entry of soil-gas radon into a crawl space covered with sheets of polyethylene foil

    International Nuclear Information System (INIS)

    To assess the effectiveness of mitigative measures against radon (222Rn) entry into houses, experiments were conducted in a crawl-space house where the dirt floor of the crawl space was covered with sheets of 0.23 mm polyethylene foil fixed to the walls. The radon concentration was measured below the foil and in the crawl space together with environmental variables such as indoor-outdoor pressure differences. The experimental data was analyzed using various types of models including a simplistic mass-balance model, a regression model, and a two-dimensional numerical model based on Darcy flow or soil gas and combined diffusive and advective transport of radon. The main outcome of the work was that: (i) The soil-gas entry rate per pascal depressurization was at the order of 1 m3 h-1, (ii) the stack-related part of the depressurization of the crawl space (approx. 0.1 Pa deg. C-1) was controlled by the temperature difference between the living room of the house and the outdoors (not by the difference between the crawl space and the outdoors), (iii) that part of the wind-related depressurization that was measured by the pressure transducers seemed to force radon into the crawl space in the same proportion as the stack-related part of the depressurization, (iv) the ratio of advective and diffusive entry was approx. 0.7, when the crawl space was depressurized 1.5 Pa, (v) the effective diffusivity of the foil was found to be three orders of magnitude larger than that measured in the laboratory (the enhanced diffusivity was most likely caused by leaks in the foil and by mixing fans located in the crawl space), and (vi) there was no measurable mitigative impact of having the sheets of foil on the crawl-space floor even if the crawl space was artificially pressurized or depressurized. (au) 28 tabs., 36 ills., 61 refs

  5. Towards reduction of Paradigm coordination models

    OpenAIRE

    Andova, S.; Groenewegen, L. P. J.; Vink, de, E.P.; Aceto, Luca; Mousavi, M.R.

    2011-01-01

    The coordination modelling language Paradigm addresses collaboration between components in terms of dynamic constraints. Within a Paradigm model, component dynamics are consistently specified at a detailed and a global level of abstraction. To enable automated verification of Paradigm models, a translation of Paradigm into process algebra has been defined in previous work. In this paper we investigate, guided by a client-server example, reduction of Paradigm models based on a notion of global...

  6. Cultural Paradigms in Management Sciences

    Directory of Open Access Journals (Sweden)

    Lukasz Sulkowski

    2013-09-01

    Full Text Available Purpose: The purpose of this paper is to present an idea for understanding cultural processes in the organizational discourse from the perspective of four paradigms in management sciences based on the concept of G. Burrell and G. Morgan.Methodology: The author has elaborated a valuable list of structures of the scientifi c theory based on the respective paradigms and has compared cultural paradigms in management sciences. The methodology involves an analysis of classical and recent world literature. Nowadays there is no consensus on the defi nitions, types or research models of organizational culture.Originality: In the literature on the subject we can fi nd many, sometimes contradictory cultural research studies that require further analysis. Precisely because of the diversity and complexity of cultural issues in management sciences a multi-paradigmatic analysis is necessary. The paper presents a proposal for a pluralistic approach to the theory and methodology of cultural studies in management sciences.

  7. CNN a paradigm for complexity

    CERN Document Server

    Chua, Leon O

    1998-01-01

    Revolutionary and original, this treatise presents a new paradigm of EMERGENCE and COMPLEXITY, with applications drawn from numerous disciplines, including artificial life, biology, chemistry, computation, physics, image processing, information science, etc.CNN is an acronym for Cellular Neural Networks when used in the context of brain science, or Cellular Nonlinear Networks, when used in the context of emergence and complexity. A CNN is modeled by cells and interactions: cells are defined as dynamical systems and interactions are defined via coupling laws. The CNN paradigm is a universal Tur

  8. Bayesian test and Kuhn's paradigm

    Institute of Scientific and Technical Information of China (English)

    Chen Xiaoping

    2006-01-01

    Kuhn's theory of paradigm reveals a pattern of scientific progress,in which normal science alternates with scientific revolution.But Kuhn underrated too much the function of scientific test in his pattern,because he focuses all his attention on the hypothetico-deductive schema instead of Bayesian schema.This paper employs Bayesian schema to re-examine Kuhn's theory of paradigm,to uncover its logical and rational components,and to illustrate the tensional structure of logic and belief,rationality and irrationality,in the process of scientific revolution.

  9. The synthesis paradigm in genetics.

    Science.gov (United States)

    Rice, William R

    2014-02-01

    Experimental genetics with model organisms and mathematically explicit genetic theory are generally considered to be the major paradigms by which progress in genetics is achieved. Here I argue that this view is incomplete and that pivotal advances in genetics--and other fields of biology--are also made by synthesizing disparate threads of extant information rather than generating new information from experiments or formal theory. Because of the explosive expansion of information in numerous "-omics" data banks, and the fragmentation of genetics into numerous subdisciplines, the importance of the synthesis paradigm will likely expand with time.

  10. Paradigms in Physics Education Research

    CERN Document Server

    Robertson, Amy D; McKagan, Sarah B

    2013-01-01

    Physics education research (PER) includes three distinct paradigms: quantitative research, qualitative research, and question-driven research. Quantitative PER seeks reproducible, representative patterns and relationships; human behavior is seen as dictated by lawful (albeit probabilistic) relationships. Qualitative PER seeks to refine and develop theory by linking theory to cases; human action is seen as shaped by the meanings that participants make of their local environments. Question-driven physics education researchers prioritize questions over the pursuit of local meanings or abstract relationships. We illustrate each paradigm with interviews with physics education researchers and examples of published PER.

  11. Convection-Dominated Accretion Flows with Radiative Cooling

    Institute of Scientific and Technical Information of China (English)

    LI Shuang-Liang; XUE Li; LU Ju-Fu

    2007-01-01

    @@ By numerically solving the set of basic equations describing black hole accretion flows with low accretion rates,we show that although the dynamical structure of these flows is essentially unaffected by radiative processes in comparison with the case in which the radiation is not considered, the radiative cooling can be more important than the advective cooling in the flow's convection-dominated zone, and this result may have implications to distinguish observationally convection-dominated accretion flows from advection-dominated accretion flows.

  12. Paradigms of mangroves in treatment of anthropogenic wastewater pollution.

    Science.gov (United States)

    Ouyang, Xiaoguang; Guo, Fen

    2016-02-15

    Mangroves have been increasingly recognized for treating wastewater from aquaculture, sewage and other sources with the overwhelming urbanization trend. This study clarified the three paradigms of mangroves in disposing wastewater contaminants: natural mangroves, constructed wetlands (including free water surface and subsurface flow) and mangrove-aquaculture coupling systems. Plant uptake is the common major mechanism for nutrient removal in all the paradigms as mangroves are generally nitrogen and phosphorus limited. Besides, sediments accrete and provide substrates for microbial activities, thereby removing organic matter and nutrients from wastewater in natural mangroves and constructed wetlands. Among the paradigms, the mangrove-aquaculture coupling system was determined to be the optimal alternative for aquaculture wastewater treatment by multi-criterion decision making. Sensitivity analysis shows variability of alternative ranking but underpins the coupling system as the most environment-friendly and cost-efficient option. Mangrove restoration is expected to be achievable if aquaculture ponds are planted with mangrove seedlings, creating the coupling system.

  13. Paradigms of mangroves in treatment of anthropogenic wastewater pollution.

    Science.gov (United States)

    Ouyang, Xiaoguang; Guo, Fen

    2016-02-15

    Mangroves have been increasingly recognized for treating wastewater from aquaculture, sewage and other sources with the overwhelming urbanization trend. This study clarified the three paradigms of mangroves in disposing wastewater contaminants: natural mangroves, constructed wetlands (including free water surface and subsurface flow) and mangrove-aquaculture coupling systems. Plant uptake is the common major mechanism for nutrient removal in all the paradigms as mangroves are generally nitrogen and phosphorus limited. Besides, sediments accrete and provide substrates for microbial activities, thereby removing organic matter and nutrients from wastewater in natural mangroves and constructed wetlands. Among the paradigms, the mangrove-aquaculture coupling system was determined to be the optimal alternative for aquaculture wastewater treatment by multi-criterion decision making. Sensitivity analysis shows variability of alternative ranking but underpins the coupling system as the most environment-friendly and cost-efficient option. Mangrove restoration is expected to be achievable if aquaculture ponds are planted with mangrove seedlings, creating the coupling system. PMID:26706768

  14. Advection of magnetic flux by accretion disks around neutron stars

    Science.gov (United States)

    Flores-Tulian, S.; Reisenegger, A.

    The aim of our research is to address why millisecond pulsars have relatively weak surface magnetic fields, of about 10^8 G, with a narrow spread. We propose that the accretion of plasma from the companion star fully screens the original neutron star field, but the accretion disk carries additional magnetic flux from the companion star, or itself can generate field by means of dynamo processes. For a strongly magnetized star, the field prevents the disk from approaching the star. The accretion is along the field lines and deposits the matter on the polar cap. Then, the accreted plasma flows, dragging with itself the magnetic field lines, from the pole to the equator (Payne & Melatos 2004). In a following stage, when the star becomes non-magnetic, because the field has been buried, the disk touches the star. We suggest that some effective mechanism of magnetic flux transport such as that proposed by Spruit & Uzdensky 2005 (or Bisnovatyi-Kogan & Lovelace 2007), operates and necessarily leads to a "strongly magnetized disk''. It becomes laminar because the magneto-rotational instability saturates (it is considered to be responsible for turbulence in the disk), and the magnetic difussivity is negligible. Then, the loss of angular momentum allowing the accretion is only caused by the magneto-centrifugal disk-wind (Blandford & Payne 1982). Meanwhile, the wind-driven transport of the magnetic flux by the disk re-magnetizes the star. This process continues until the Lorentz force due to the star's magnetic field forbids any further accretion of matter and magnetic flux, in the Ideal Magneto-Hydro-Dynamics approach. Additional of material can fall onto the star (but at lower rate) if some instability process sets in, allowing the diffusion of mass through the magnetic field lines (e.g the Interchange Instability, Spruit & Taam 1990). All these processes might lead to an asymptotic magnetic field of 10^8 G,as is inferred from observations. We are developing a self

  15. Satellite-advection based solar forecasting: lessons learned and progress towards probabalistic solar forecasting

    Science.gov (United States)

    Rogers, M. A.

    2015-12-01

    Using satellite observations from GOES-E and GOES-W platforms in concert with GFS-derived cloud-level winds and a standalone radiative transfer model, an advection-derived forecast for surface GHI over the continental United States, with intercomparison between forecasts for four zones over the CONUS and Central Pacific with SURFRAD results. Primary sources for error in advection-based forecasts, primarily driven by false- or mistimed ramp events are discussed, with identification of error sources quantified along with techniques used to improve advection-based forecasts to approximately 10% MAE for designated surface locations. Development of a blended steering wind product utilizing NWP output combined with satellite-derived winds from AMV techniques to improve 0-1 hour advection forecasts will be discussed. Additionally, the use of two years' of solar forecast observations in the development of a prototype probablistic forecast for ramp events will be shown, with the intent of increasing the use of satellite-derived forecasts for grid operators and optimizing integration of renewable resources into the power grid. Elements of the work were developed under the 'Public-Private-Academic Partnership to Advance Solar Power Forecasting' project spearheaded by the National Center for Atmospheric Research.

  16. Shell model for time-correlated random advection of passive scalars

    DEFF Research Database (Denmark)

    Andersen, Ken Haste; Muratore-Ginanneschi, P.

    1999-01-01

    We study a minimal shell model for the advection of a passive scalar by a Gaussian time-correlated velocity field. The anomalous scaling properties of the white noise limit are studied analytically. The effect of the time correlations are investigated using perturbation theory around the white...

  17. Large aperture scintillometer used over a homogeneous irrigated area, partly affected by regional advection

    NARCIS (Netherlands)

    Hoedjes, J.C.B.; Zuurbier, R.M.; Watts, J.C.

    2002-01-01

    Scintillometer measurements were collected over an irrigated wheat field in a semi-arid region in northwest Mexico. Conditions were unstable in the morning and stable during the afternoon, while latent heat fluxes remained high throughout the day. Regional advection was observed during near-neutral

  18. Exact analytical solutions for contaminant transport in rivers 1. The equilibrium advection-dispersion equation

    Science.gov (United States)

    Analytical solutions of the advection-dispersion equation and related models are indispensable for predicting or analyzing contaminant transport processes in streams and rivers, as well as in other surface water bodies. Many useful analytical solutions originated in disciplines other than surface-w...

  19. Implicit and semi-implicit schemes in the Versatile Advection Code : numerical tests

    NARCIS (Netherlands)

    Tóth, G.; Keppens, R.; Botchev, M.A.

    1998-01-01

    We describe and evaluate various implicit and semi-implicit time integration schemes applied to the numerical simulation of hydrodynamical and magnetohydrodynamical problems. The schemes were implemented recently in the software package Versatile Advection Code, which uses modern shock capturing met

  20. Isoline retrieval: An optimal sounding method for validation of advected contours

    CERN Document Server

    Mills, Peter

    2012-01-01

    The study of chaotic mixing is important for its potential to improve our understanding of fluid systems. Contour advection simulations provide a good model of the phenomenon by tracking the evolution of one or more contours or isolines of a trace substance to a high level of precision. The most accurate method of validating an advected contour is to divide the tracer concentration into discrete ranges and perform a maximum likelihood classification, a method that we term, "isoline retrieval." Conditional probabilities generated as a result provide excellent error characterization. In this study, a water vapour isoline of 0.001 mass-mixing-ratio is advected over five days in the upper troposphere and compared with high-resolution AMSU (Advanced Microwave Sounding Unit) satellite retrievals. The goal is to find the same fine-scale, chaotic mixing in the isoline retrievals as seen in the advection simulations. Some of the filaments generated by the simulations show up in the conditional probabilities as areas o...

  1. Comparison of different computer platforms for running the Versatile Advection Code

    NARCIS (Netherlands)

    Toth, G.; Keppens, R.; Sloot, P.; Bubak, M.; Hertzberger, B.

    1998-01-01

    The Versatile Advection Code is a general tool for solving hydrodynamical and magnetohydrodynamical problems arising in astrophysics. We compare the performance of the code on different computer platforms, including work stations and vector and parallel supercomputers. Good parallel scaling can be a

  2. The Paradigm of Distributed Creativity

    DEFF Research Database (Denmark)

    Glaveanu, Vlad Petre

    This presentation aims to focus on and develop the notion of distributed creativity from a cultural psychological perspective. It will start by outlining the need for a cultural psychological paradigm of creative expression and argue that this perspective is primarily concerned with what can...

  3. Explaining (Missing) Regulator Paradigm Shifts

    DEFF Research Database (Denmark)

    Wigger, Angela; Buch-Hansen, Hubert

    2014-01-01

    of competition regulation is heaving into sight. It sets out to explain this from the vantage point of a critical political economy perspective, which identifies the circumstances under which a crisis can result in a regulatory paradigm shift. Contrasting the current situation with the shift in EC/EU competition...

  4. Quantification of numerical diffusivity due to TVD schemes in the advection equation

    Science.gov (United States)

    Bidadi, Shreyas; Rani, Sarma L.

    2014-03-01

    In this study, the numerical diffusivity νnum inherent to the Roe-MUSCL scheme has been quantified for the scalar advection equation. The Roe-MUSCL scheme employed is a combination of: (1) the standard extension of the original Roe's formulation to the advection equation, and (2) van Leer's Monotone Upwind Scheme for Conservation Laws (MUSCL) technique that applies a linear variable reconstruction in a cell along with a scaled limiter function. An explicit expression is derived for the numerical diffusivity in terms of the limiter function, the distance between the cell centers on either side of a face, and the face-normal velocity. The numerical diffusivity formulation shows that a scaled limiter function is more appropriate for MUSCL in order to consistently recover the central-differenced flux at the maximum value of the limiter. The significance of the scaling factor is revealed when the Roe-MUSCL scheme, originally developed for 1-D scenarios, is applied to 2-D scalar advection problems. It is seen that without the scaling factor, the MUSCL scheme may not necessarily be monotonic in multi-dimensional scenarios. Numerical diffusivities of the minmod, superbee, van Leer and Barth-Jesperson TVD limiters were quantified for four problems: 1-D advection of a step function profile, and 2-D advection of step, sinusoidal, and double-step profiles. For all the cases, it is shown that the superbee scheme provides the lowest numerical diffusivity that is also most confined to the vicinity of the discontinuity. The minmod scheme is the most diffusive, as well as active in regions away from high gradients. As expected, the grid resolution study demonstrates that the magnitude and the spatial extent of the numerical diffusivity decrease with increasing resolution.

  5. Improving estimates of ecosystem metabolism by reducing effects of tidal advection on dissolved oxygen time series-Abstract

    Science.gov (United States)

    Continuous time series of dissolved oxygen (DO) have been used to compute estimates of metabolism in aquatic ecosystems. Central to this open water or "Odum" method is the assumption that the DO time is not strongly affected by advection and that effects due to advection or mixin...

  6. Analytical solutions of the one-dimensional advection-dispersion solute transport equation subject to time-dependent boundary conditions

    Science.gov (United States)

    Analytical solutions of the advection-dispersion solute transport equation remain useful for a large number of applications in science and engineering. In this paper we extend the Duhamel theorem, originally established for diffusion type problems, to the case of advective-dispersive transport subj...

  7. Mathematical Modeling of Electrolyte Flow Dynamic Patterns and Volumetric Flow Penetrations in the Flow Channel over Porous Electrode Layered System in Vanadium Flow Battery with Serpentine Flow Field Design

    CERN Document Server

    Ke, Xinyou; Alexander, J Iwan D; Savinell, Robert F

    2016-01-01

    In this work, a two-dimensional mathematical model is developed to study the flow patterns and volumetric flow penetrations in the flow channel over the porous electrode layered system in vanadium flow battery with serpentine flow field design. The flow distributions at the interface between the flow channel and porous electrode are examined. It is found that the non-linear pressure distributions can distinguish the interface flow distributions under the ideal plug flow and ideal parabolic flow inlet boundary conditions. However, the volumetric flow penetration within the porous electrode beneath the flow channel through the integration of interface flow velocity reveals that this value is identical under both ideal plug flow and ideal parabolic flow inlet boundary conditions. The volumetric flow penetrations under the advection effects of flow channel and landing/rib are estimated. The maximum current density achieved in the flow battery can be predicted based on the 100% amount of electrolyte flow reactant ...

  8. Scalar transport in compressible flow

    OpenAIRE

    Vergassola, M.; Avellaneda, M.

    1996-01-01

    Transport of scalar fields in compressible flow is investigated. The effective equations governing the transport at scales large compared to those of the advecting flow are derived by using multi-scale techniques. Ballistic transport generally takes place when both the solenoidal and the potential components of the velocity do not vanish, despite of the fact that it has zero average value. The calculation of the effective ballistic velocity $V_b$ is reduced to the solution of one auxiliary eq...

  9. 3D IBFV : Hardware-Accelerated 3D Flow Visualization

    NARCIS (Netherlands)

    Telea, Alexandru; Wijk, Jarke J. van

    2003-01-01

    We present a hardware-accelerated method for visualizing 3D flow fields. The method is based on insertion, advection, and decay of dye. To this aim, we extend the texture-based IBFV technique for 2D flow visualization in two main directions. First, we decompose the 3D flow visualization problem in a

  10. Particulate export vs lateral advection in the Antarctic Polar Front (Southern Pacific Ocean)

    Science.gov (United States)

    Tesi, T.; Langone, L.; Ravaioli, M.; Capotondi, L.; Giglio, F.

    2012-04-01

    The overarching goal of our study was to describe and quantify the influence of lateral advection relative to the vertical export in the Antarctic Polar Front (Southern Pacific Ocean). In areas where lateral advection of particulate material is significant, budgets of bioactive elements can be inaccurate if fluxes through the water column and to the seabed are exclusively interpreted as passive sinking of particles. However, detailed information on the influence of lateral advection in the water column in the southern ocean is lacking. With this in mind, our study focused between the twilight zone (i.e. mesopelagic) and the benthic nepheloid layer to understand the relative importance of lateral flux with increasing water depth. Measurements were performed south of the Antarctic Polar Front for 1 year (January 10th 1999-January 3rd 2000) at 900, 1300, 2400, and 3700 m from the sea surface. The study was carried out using a 3.5 km long mooring line instrumented with sediment traps, current meters and sensors of temperature and conductivity. Sediment trap samples were characterized via several parameters including total mass flux, elemental composition (organic carbon, total nitrogen, biogenic silica, and calcium carbonate), concentration of metals (aluminum, iron, barium, and manganese), 210Pb activity, and foraminifera taxonomy. High fluxes of biogenic particles were observed in both summer 1999 and 2000 as a result of seasonal algal blooms associated with sea ice retreat and water column stratification. During no-productive periods, several high energy events occurred and resulted in advecting resuspended biogenic particles from flat-topped summits of the Pacific Antarctic Ridge. Whereas the distance between seabed and uppermost sediment traps was sufficient to avoid lateral advection processes, resuspension was significant in the lowermost sediment traps accounting for ~60 and ~90% of the material caught at 2400 and 3700 m, respectively. Samples collected during

  11. Black hole evaporation: a paradigm

    International Nuclear Information System (INIS)

    A paradigm describing black hole evaporation in non-perturbative quantum gravity is developed by combining two sets of detailed results: (i) resolution of the Schwarzschild singularity using quantum geometry methods and (ii) time evolution of black holes in the trapping and dynamical horizon frameworks. Quantum geometry effects introduce a major modification in the traditional spacetime diagram of black hole evaporation, providing a possible mechanism for recovery of information that is classically lost in the process of black hole formation. The paradigm is developed directly in the Lorentzian regime and necessary conditions for its viability are discussed. If these conditions are met, much of the tension between expectations based on spacetime geometry and structure of quantum theory would be resolved

  12. Understanding the land management paradigm

    DEFF Research Database (Denmark)

    Enemark, Stig

    2006-01-01

    There is a worldwide need to build understanding of the land management paradigm and for institutional development to establish sustainable national concepts. This includes creation and adoption of a policy on land development, and an approach that combines the land administration/cadastre/land r......There is a worldwide need to build understanding of the land management paradigm and for institutional development to establish sustainable national concepts. This includes creation and adoption of a policy on land development, and an approach that combines the land administration....../cadastre/land registration function with topographic mapping. The author seeks to awaken more awareness of global trends in this area, recognising that the systems design involved is always unique....

  13. SEBAL-A: A Remote Sensing ET Algorithm that Accounts for Advection with Limited Data. Part I: Development and Validation

    Directory of Open Access Journals (Sweden)

    Mcebisi Mkhwanazi

    2015-11-01

    Full Text Available The Surface Energy Balance Algorithm for Land (SEBAL is one of the remote sensing (RS models that are increasingly being used to determine evapotranspiration (ET. SEBAL is a widely used model, mainly due to the fact that it requires minimum weather data, and also no prior knowledge of surface characteristics is needed. However, it has been observed that it underestimates ET under advective conditions due to its disregard of advection as another source of energy available for evaporation. A modified SEBAL model was therefore developed in this study. An advection component, which is absent in the original SEBAL, was introduced such that the energy available for evapotranspiration was a sum of net radiation and advected heat energy. The improved SEBAL model was termed SEBAL-Advection or SEBAL-A. An important aspect of the improved model is the estimation of advected energy using minimal weather data. While other RS models would require hourly weather data to be able to account for advection (e.g., METRIC, SEBAL-A only requires daily averages of limited weather data, making it appropriate even in areas where weather data at short time steps may not be available. In this study, firstly, the original SEBAL model was evaluated under advective and non-advective conditions near Rocky Ford in southeastern Colorado, a semi-arid area where afternoon advection is common occurrence. The SEBAL model was found to incur large errors when there was advection (which was indicated by higher wind speed and warm and dry air. SEBAL-A was then developed and validated in the same area under standard surface conditions, which were described as healthy alfalfa with height of 40–60 cm, without water-stress. ET values estimated using the original and modified SEBAL were compared to large weighing lysimeter-measured ET values. When the SEBAL ET was compared to SEBAL-A ET values, the latter showed improved performance, with the ET Mean Bias Error (MBE reduced from −17

  14. Crises and paradigms in macroeconomics

    OpenAIRE

    Malcolm Sawyer

    2010-01-01

    Contrasts are drawn between mainstream macroeconomics (with the 'New Consensus in Macroeconomics' taken as the current manifestation) and heterodox macroeconomics and their abilities to comprehend the financial crises and world wide recession of 2007 – 09 for macroeconomic paradigms is discussed. Specifically, the contrasting ways in which the two schools of thought treat unemployment, human behaviour, aggregate and money and credit are discussed. It is concluded that the events of 2007 –...

  15. Membrane Paradigm and Holographic Hydrodynamics

    Energy Technology Data Exchange (ETDEWEB)

    Eling, Christopher [SISSA, Via Bonomea 265, 34136 Trieste, Italy and INFN Sezione di Trieste, Via Valerio 2, 34127 Trieste (Italy); Neiman, Yasha; Oz, Yaron, E-mail: cteling@sissa.it, E-mail: yashula@gmail.com, E-mail: yaronoz@post.tau.ac.il [Raymond and Beverly Sackler School of Physics and Astronomy, Tel-Aviv University, Tel-Aviv 69978 (Israel)

    2011-09-22

    We discuss recent work showing that in certain cases the membrane paradigm equations governing the dynamics of black hole horizons can be recast as relativistic conservation law equations. In the context of gauge/gravity dualities, these equations are interpreted as defining the viscous hydrodynamics of a holographically dual relativistic field theory. Using this approach, one can derive the viscous transport coefficients and the form of the entropy current for field theories dual to gravity plus matter fields.

  16. Emergent Gravity Paradigm: Recent Progress

    CERN Document Server

    Padmanabhan, T

    2014-01-01

    Research during the last one decade or so suggests that the gravitational field equations in a large class of theories (including, but not limited to, general relativity) have the same status as the equations of, say, gas dynamics or elasticity. This paradigm provides a refreshingly different way of interpreting spacetime dynamics and highlights the fact that several features of classical gravitational theories have direct thermodynamic interpretation. I review the recent progress in this approach, achieved during the last few years.

  17. Employee discipline: a changing paradigm.

    Science.gov (United States)

    Raper, J L; Myaya, S N

    1993-12-01

    To increase the receptiveness of health care supervisors to a broader meaning of discipline and to simulate investigation of nontraditional methods of encouragement to employees who fail to meet minimum standards of conduct and thereby negatively affect the quality of patient care, a subjectively realistic view of the implications of the traditional punitive disciplinary paradigm is presented. Through the use of a case study, the authors present, explain, and apply the contemporary concept of discipline without punishment as first described by J. Huberman.

  18. Political Market. Paradigms and Realities

    Directory of Open Access Journals (Sweden)

    Vasile Macoviciuc

    2012-06-01

    Full Text Available The paper Political Market. Paradigms and Realities, by Simona Busoi, is an important contribution and a spadework within our specialized literature. Recently issued by Editura ASE (The Bucharest Academy of Economic Studies Publishing House, in the collection “Et in Arcadia ego”, it offers to the readers a synthesis of the literature destined to the study of political phenomena from an economic point of view, but also a lucid analysis of the Romanian political market.

  19. The Afrocentric Paradigm: Contours and Definitions.

    Science.gov (United States)

    Mazama, Ama

    2001-01-01

    Defines and describes Afrocentricity, suggesting that Afrocentricity within the academic context is best understood as a paradigm. Explains how Afrocentricity meets the definition of a paradigm, examining the affective, cognitive, and conative aspects of the Afrocentric paradigm (metaphysical and sociological) and looking at the structural and…

  20. Towards reduction of Paradigm coordination models

    NARCIS (Netherlands)

    Andova, S.; Groenewegen, L.P.J.; Vink, E.P. de; Aceto, L.; Mousavi, M.R.

    2011-01-01

    The coordination modelling language Paradigm addresses collaboration between components in terms of dynamic constraints. Within a Paradigm model, component dynamics are consistently specified at a detailed and a global level of abstraction. To enable automated verification of Paradigm models, a tran

  1. Orphism as a scientific paradigm

    Directory of Open Access Journals (Sweden)

    Biernat Przemyslaw

    2012-01-01

    Full Text Available In my essay I would like to examine current interpretative paradigm, which western scholarship cast on heterogenous and ambiguous data first to create and then to modify the notion of ‘orphism’. In case of paradigms preceding the actual one, the role which ‘orphism’ played in contemporary theories and controversies centered around the question of its significance for emergence of Christianity is well known. That is why in my work I would like to focus on deconstruction of interpretative consensus, elaborated in recent years, which is to be found in such works as Martin West’s The Orphic Poems (1983, Ritual Texts for the Afterlife. Orpheus and the Bacchic Gold Tablets by Fritz Graf and Sarah Iles-Johnston (2007 or monumental Orfeo y la tradición órfica. Un reencuentro (2008 edited by Alberto Bernabé. What is significant, inasmuch as we can write the history of Athenian religion or the history of Hellenistic kings’ worship, we still cannot write the history of orphism. In formulation of all these scholars it is an ahistorical phenomenon, a hidden constant in the sphere of Greek religion, never expressed directly and entirely, but always alluded to y ancient authors. I find difficult to agree with such a statement. The aim of my inquiry is to reveal assumptions of current paradigm, which are hidden in it, but leave a distinct impression on data.

  2. Poverty eradication: a new paradigm.

    Science.gov (United States)

    Pethe, V P

    1998-08-01

    This article offers a new paradigm for eradicating poverty in India. It was assumed incorrectly by Mahatma Gandhi that a good society without mass poverty would follow after independence. India copied Western models of development and developed giant factories, big dams, and megacities. Agriculture did not expand the number of jobs for people. The Western paradigm failed in India because of the false assumption of "trickle down" of income to the masses. The targeted programs to the poor did not directly benefit enough of the poor. Mega-industrialization led to reduced employment and higher skill needs. The model failed mainly because it was a proxy and relied on indirect ways of reaching the poor. The models failed to be adapted to conditions in India. The Swadeshi paradigm is a direct model for addressing mass poverty. Poverty is affected by immediate, intermediate, and ultimate determinants. Poverty begets social and economic problems, such as ignorance, ill health, high fertility, unemployment, and crime. In India and developing countries, mass poverty results from under use of human resources; lack of equal opportunities; and an outdated non-egalitarian social structure, an unjust global economic order, human cruelty, and erosion of ethical values. Indians are squandering their precious resources mimicking Western consumerism. Poverty leads to rapid population growth. People become productive assets with universal literacy, compulsory and free education, health services and sanitation, vocational training, and work ethics. India needs people-oriented policies with less emphasis on capital accumulation. PMID:12294462

  3. Poverty eradication: a new paradigm.

    Science.gov (United States)

    Pethe, V P

    1998-08-01

    This article offers a new paradigm for eradicating poverty in India. It was assumed incorrectly by Mahatma Gandhi that a good society without mass poverty would follow after independence. India copied Western models of development and developed giant factories, big dams, and megacities. Agriculture did not expand the number of jobs for people. The Western paradigm failed in India because of the false assumption of "trickle down" of income to the masses. The targeted programs to the poor did not directly benefit enough of the poor. Mega-industrialization led to reduced employment and higher skill needs. The model failed mainly because it was a proxy and relied on indirect ways of reaching the poor. The models failed to be adapted to conditions in India. The Swadeshi paradigm is a direct model for addressing mass poverty. Poverty is affected by immediate, intermediate, and ultimate determinants. Poverty begets social and economic problems, such as ignorance, ill health, high fertility, unemployment, and crime. In India and developing countries, mass poverty results from under use of human resources; lack of equal opportunities; and an outdated non-egalitarian social structure, an unjust global economic order, human cruelty, and erosion of ethical values. Indians are squandering their precious resources mimicking Western consumerism. Poverty leads to rapid population growth. People become productive assets with universal literacy, compulsory and free education, health services and sanitation, vocational training, and work ethics. India needs people-oriented policies with less emphasis on capital accumulation.

  4. Modeling the adsorption of Cr(III) from aqueous solution onto Agave lechuguilla biomass: study of the advective and dispersive transport.

    Science.gov (United States)

    Romero-González, J; Walton, J C; Peralta-Videa, J R; Rodríguez, E; Romero, J; Gardea-Torresdey, J L

    2009-01-15

    The biosorption of Cr(III) onto packed columns of Agave lechuguilla was analyzed using an advective-dispersive (AD) model and its analytical solution. Characteristic parameters such as axial dispersion coefficients, retardation factors, and distribution coefficients were predicted as functions of inlet ion metal concentration, time, flow rate, bed density, cross-sectional column area, and bed length. The root-mean-square-error (RMSE) values 0.122, 0.232, and 0.285 corresponding to the flow rates of 1, 2, and 3 (10(-3))dm3min(-1), respectively, indicated that the AD model provides an excellent approximation of the simulation of lumped breakthrough curves for the adsorption of Cr(III) by lechuguilla biomass. Therefore, the model can be used for design purposes to predict the effect of varying operational conditions. PMID:18462882

  5. iCFD: Interpreted Computational Fluid Dynamics – Degeneration of CFD to one-dimensional advection-dispersion models using statistical experimental design – The secondary clarifier

    DEFF Research Database (Denmark)

    Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat;

    2015-01-01

    The present study aims at using statistically designed computational fluid dynamics (CFD) simulations as numerical experiments for the identification of one-dimensional (1-D) advection-dispersion models – computationally light tools, used e.g., as sub-models in systems analysis. The objective...... is to develop a new 1-D framework, referred to as interpreted CFD (iCFD) models, in which statistical meta-models are used to calculate the pseudo-dispersion coefficient (D) as a function of design and flow boundary conditions. The method – presented in a straightforward and transparent way – is illustrated...... using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor...

  6. Object-oriented implementations of the MPDATA advection equation solver in C++, Python and Fortran

    CERN Document Server

    Arabas, Sylwester; Jaruga, Anna; Fijałkowski, Maciej

    2013-01-01

    Three object-oriented implementations of a prototype solver of the advection equation are introduced. Presented programs are based on Blitz++ (C++), NumPy (Python), and Fortran's built-in array containers. The solvers include an implementation of the Multidimensional Positive-Definite Advective Transport Algorithm (MPDATA). The introduced codes exemplify how the application of object-oriented programming (OOP) techniques allows to reproduce the mathematical notation used in the literature within the program code. The introduced codes serve as a basis for discussion on the tradeoffs of the programming language choice. The main angles of comparison are code brevity and syntax clarity (and hence maintainability and auditability) as well as performance. In case of Python, a significant performance gain is observed when switching from the standard interpreter (CPython) to the PyPy implementation of Python. Entire source code of all three implementations is embedded in the text and is licensed under the terms of th...

  7. Estimation and correction of advection effects with single and multiple, conventional and Doppler radars

    Science.gov (United States)

    Gal-Chen, T.

    1981-01-01

    The laws of fluid motion are invariant under a Gallilean transformation. For a perfect observing system, the data analysis should, therefore, also be invariant under a Gallilean transformation. This invariance is often not preserved in practical observing systems. In this connection, it is often advisable to perform mesoscale analysis in a frame moving with respect to the earth's surface. In the present investigation the velocity of such a frame is referred to as an advection velocity. The investigation is concerned with remaining problems regarding the Gallilean transformation. The establishment of a frame of reference for the achievement of maximum coherence is considered, taking into account the case of given nonsimultaneous observations of scalars or Cartesian vectors. It is found that advection speed can be estimated objectively if a scalar or Cartesian vector can be observed directly and if, in addition, the time and position of each observation is approximately known.

  8. Numerical Solution of Advection-Diffusion Equation Using a Sixth-Order Compact Finite Difference Method

    Directory of Open Access Journals (Sweden)

    Gurhan Gurarslan

    2013-01-01

    Full Text Available This study aims to produce numerical solutions of one-dimensional advection-diffusion equation using a sixth-order compact difference scheme in space and a fourth-order Runge-Kutta scheme in time. The suggested scheme here has been seen to be very accurate and a relatively flexible solution approach in solving the contaminant transport equation for Pe≤5. For the solution of the present equation, the combined technique has been used instead of conventional solution techniques. The accuracy and validity of the numerical model are verified through the presented results and the literature. The computed results showed that the use of the current method in the simulation is very applicable for the solution of the advection-diffusion equation. The present technique is seen to be a very reliable alternative to existing techniques for these kinds of applications.

  9. An advection-diffusion model for cross-field runaway electron transport in perturbed magnetic fields

    CERN Document Server

    Särkimäki, Konsta; Decker, Joan; Varje, Jari; Kurki-Suonio, Taina

    2016-01-01

    Disruption-generated runaway electrons (RE) present an outstanding issue for ITER. The predictive computational studies of RE generation rely on orbit-averaged computations and, as such, they lack the effects from the magnetic field stochasticity. Since stochasiticity is naturally present in post-disruption plasma, and externally induced stochastization offers a prominent mechanism to mitigate RE avalanche, we present an advection-diffusion model that can be used to couple an orbit-following code to an orbit-averaged tool in order to capture the cross-field transport and to overcome the latter's limitation. The transport coefficients are evaluated via a Monte Carlo method. We show that the diffusion coefficient differs significantly from the well-known Rechester-Rosenbluth result. We also demonstrate the importance of including the advection: it has a two-fold role both in modelling transport barriers created by magnetic islands and in amplifying losses in regions where the islands are not present.

  10. Improvement of the One-dimensional Vertical Advection-diffusion Model in Seawater

    Institute of Scientific and Technical Information of China (English)

    王保栋; 单宝田; 战闰; 王修林

    2003-01-01

    The classical 1-D vertical advection-diffusion model was improved in this work. Themain advantages of the improved model over the previous one are: 1 ) The applicable condition ofthe 1-D model is made clear in the improved model, in that it is substantively applicable only to avertical domain on which two end-member water masses are mixing. 2) The substitution of parame-ter f(z) in the equation of the classical 1-D model with end-member fraction f1 makes the modelmore precisely and easily solved. 3 ) All the terms in the improved model equation have specificphysical meanings, which makes the model easily understood. Practical application of the improvedmodel to predict the vertical profiles of dissolved oxygen and micronutrients in abyssal ocean waterof the North Pacific proved that the improvement of the 1-D advection-diffusion model is successfuland practicable.

  11. A balancing domain decomposition method by constraints for advection-diffusion problems

    Energy Technology Data Exchange (ETDEWEB)

    Tu, Xuemin; Li, Jing

    2008-12-10

    The balancing domain decomposition methods by constraints are extended to solving nonsymmetric, positive definite linear systems resulting from the finite element discretization of advection-diffusion equations. A pre-conditioned GMRES iteration is used to solve a Schur complement system of equations for the subdomain interface variables. In the preconditioning step of each iteration, a partially sub-assembled finite element problem is solved. A convergence rate estimate for the GMRES iteration is established, under the condition that the diameters of subdomains are small enough. It is independent of the number of subdomains and grows only slowly with the subdomain problem size. Numerical experiments for several two-dimensional advection-diffusion problems illustrate the fast convergence of the proposed algorithm.

  12. Approximate Solution of Time-Fractional Advection-Dispersion Equation via Fractional Variational Iteration Method

    Directory of Open Access Journals (Sweden)

    Birol İbiş

    2014-01-01

    Full Text Available This paper aims to obtain the approximate solution of time-fractional advection-dispersion equation (FADE involving Jumarie’s modification of Riemann-Liouville derivative by the fractional variational iteration method (FVIM. FVIM provides an analytical approximate solution in the form of a convergent series. Some examples are given and the results indicate that the FVIM is of high accuracy, more efficient, and more convenient for solving time FADEs.

  13. Numerical Solution of Advection-Diffusion Equation Using a Sixth-Order Compact Finite Difference Method

    OpenAIRE

    Gurhan Gurarslan; Halil Karahan; Devrim Alkaya; Murat Sari; Mutlu Yasar

    2013-01-01

    This study aims to produce numerical solutions of one-dimensional advection-diffusion equation using a sixth-order compact difference scheme in space and a fourth-order Runge-Kutta scheme in time. The suggested scheme here has been seen to be very accurate and a relatively flexible solution approach in solving the contaminant transport equation for Pe≤5. For the solution of the present equation, the combined technique has been used instead of conventional solution techniques. The accuracy and...

  14. A New Evapotranspiration Model Accounting for Advection and Its Validation during SMEX02

    OpenAIRE

    Yongmin Yang; Hongbo Su; Renhua Zhang; Jianjun Wu; Jianwei Qi

    2013-01-01

    Based on the crop water stress index (CWSI) concept, a new model was proposed to account for advection to estimate evapotranspiration. Both local scale evaluation with sites observations and regional scale evaluation with a remote dataset from Landsat 7 ETM+ were carried out to assess the performance of this model. Local scale evaluation indicates that this newly developed model can effectively characterize the daily variations of evapotranspiration and the predicted results show good agreeme...

  15. ADVECTION AND DIFFUSION OF POISONOUS GAS CONTAMINANT RELEASED FROM BOTTOM SLUDGE IN OPEN CHANNEL

    Institute of Scientific and Technical Information of China (English)

    WU Zhou-hu

    2004-01-01

    In some cases, poisonous contaminants may be released from bottom sludge in open channels. The equation of advection and diffusion for the related problem was analyzed in this paper. The conditions for the definite solution to the equation were given. The analytic solution of poisonous gas concentration distribution was worked out. The reasonableness of this solution was discussed. The result is also of significance for other similar problems.

  16. Carbon dioxide seasonality in dynamically ventilated caves: the role of advective fluxes

    Science.gov (United States)

    Lang, Marek; Faimon, Jiří; Godissart, Jean; Ek, Camille

    2016-07-01

    The seasonality in cave CO2 levels was studied based on (1) a new data set from the dynamically ventilated Comblain-au-Pont Cave (Dinant Karst Basin, Belgium), (2) archive data from Moravian Karst caves, and (3) published data from caves worldwide. A simplified dynamic model was proposed for testing the effect of all conceivable CO2 fluxes on cave CO2 levels. Considering generally accepted fluxes, i.e., the direct diffusive flux from soils/epikarst, the indirect flux derived from dripwater degassing, and the input/output fluxes linked to cave ventilation, gives the cave CO2 level maxima of 1.9 × 10-2 mol m-3 (i.e., ˜ 440 ppmv), which only slightly exceed external values. This indicates that an additional input CO2 flux is necessary for reaching usual cave CO2 level maxima. The modeling indicates that the additional flux could be a convective advective CO2 flux from soil/epikarst driven by airflow (cave ventilation) and enhanced soil/epikarstic CO2 concentrations. Such flux reaching up to 170 mol s-1 is capable of providing the cave CO2 level maxima up to 3 × 10-2 mol m-3 (70,000 ppmv). This value corresponds to the maxima known from caves worldwide. Based on cave geometry, three types of dynamic caves were distinguished: (1) the caves with the advective CO2 flux from soil/epikarst at downward airflow ventilation mode, (2) the caves with the advective soil/epikarstic flux at upward airflow ventilation mode, and (3) the caves without any soil/epikarstic advective flux. In addition to CO2 seasonality, the model explains both the short-term and seasonal variations in δ13C in cave air CO2.

  17. Advective loss of overwintering Calanus finmarchicus from the Faroe-Shetland Channel

    DEFF Research Database (Denmark)

    Rullyanto, Arief; Jonasdottir, Sigrun H.; Visser, Andre W.

    2015-01-01

    , a regionally important secondary producer. Using a high resolution hydrodynamic model, MIKE 3 FM, we simulate the overflow of deep water and estimate the associated loss rate of C. finmarchicus as a function of the water depth strata within which they reside. We estimate a net advective loss from the Norwegian...... is to be entrained into warmer waters of the North Atlantic Basin, a habitat that appears to be unsuitable for successful overwintering. (C) 2015 Elsevier Ltd. All rights reserved....

  18. Radiation Pressure-supported Accretion Disks: Vertical Structure, Energy Advection, and Convective Stability

    CERN Document Server

    Gu, Wei-Min

    2012-01-01

    By taking into account the local energy balance per unit volume between the viscous heating and the advective cooling plus the radiative cooling, we investigate the vertical structure of radiation pressure-supported accretion disks in spherical coordinates. Our solutions show that the photosphere of the disk is close to the polar axis and therefore the disk seems to be extremely thick. However, the profile of density implies that most of the accreted matter exists in a moderate range around the equatorial plane. We show that the well-known polytropic relation between the pressure and the density is unsuitable for describing the vertical structure of radiation pressure-supported disks. More importantly, we find that the energy advection is significant even for slightly sub-Eddington accretion disks. We argue that the non-negligible advection may help to understand why the standard thin disk model is likely to be inaccurate above \\sim 0.3 Eddington luminosity, which was found by some works on the black hole spi...

  19. A Comparative Study of Indoor Radon Contributed by Diffusive and Advective Transport through Intact Concrete

    Science.gov (United States)

    Chauhan, R. P.; Kumar, Amit

    The present work is aimed that out of diffusive and advective transport which is dominant process for indoor radon entry under normal room conditions. For this purpose the radon diffusion coefficient and permeability of concrete were measured by specially designed experimental set up. The radon diffusion coefficient of concrete was measured by continuous radon monitor. The measured value was (3.78 ± 0.39)×10-8 m2/s and found independent of the radon gas concentration in source chamber. The radon permeability of concrete varied between 1.85×10-17 to 1.36×10-15 m2 for the bulk pressure difference fewer than 20 Pa to 73.3 kPa. From the measured diffusion coefficient and absolute permeability, the radon flux from the concrete surface having concentrations gradient 12-40 kBq/m3 and typical floor thickness 0.1 m was calculated by the application of Fick and Darcy laws. Using the measured flux attributable to diffusive and advective transport, the indoor radon concentration for a typical Indian model room having dimension (5×6×7) m3 was calculated under average room ventilation (0.63 h-1). The results showed that the contribution of diffusive transport through intact concrete is dominant over the advective transport, as expected from the low values of concrete permeability.

  20. Backward Calculation Based on the Advection and Diffusion of Oil Spills on the Sea Surface

    Institute of Scientific and Technical Information of China (English)

    LIU Hao; YIN Baoshu; LIN Jianguo

    2005-01-01

    In the light of the problem of oil pollution brought about by ships, in this paper we present the concept of backward tracing oil spills. In the course of backward calculation of the two-dimensional convection & diffusion equation, on the one hand,the advection term itself has the strong unilateral property, which means information in the upper reaches is transmitted downstream via the advection term; on the other hand,because of the opposite direction of calculation, it is essential for information to be conveyed upstream by means of the advection term. In addition, unlike that in the forward calculation, the diffusion term in the backward calculation is prone to accumulate errors, and thus renders the whole scheme unstable. Therefore, we adopt the central difference to deal with both the convectional term and the diffusion term. By examining two practical examples (1) under the unlimited boundary condition, and (2) under the limited boundary condition, it is proven that this method could achieve fundamentally satisfactory results not only in the open ocean but also in the closed or semi-closed bay.

  1. Parallel simulation of particle transport in an advection field applied to volcanic explosive eruptions

    Science.gov (United States)

    Künzli, Pierre; Tsunematsu, Kae; Albuquerque, Paul; Falcone, Jean-Luc; Chopard, Bastien; Bonadonna, Costanza

    2016-04-01

    Volcanic ash transport and dispersal models typically describe particle motion via a turbulent velocity field. Particles are advected inside this field from the moment they leave the vent of the volcano until they deposit on the ground. Several techniques exist to simulate particles in an advection field such as finite difference Eulerian, Lagrangian-puff or pure Lagrangian techniques. In this paper, we present a new flexible simulation tool called TETRAS (TEphra TRAnsport Simulator) based on a hybrid Eulerian-Lagrangian model. This scheme offers the advantages of being numerically stable with no numerical diffusion and easily parallelizable. It also allows us to output particle atmospheric concentration or ground mass load at any given time. The model is validated using the advection-diffusion analytical equation. We also obtained a good agreement with field observations of the tephra deposit associated with the 2450 BP Pululagua (Ecuador) and the 1996 Ruapehu (New Zealand) eruptions. As this kind of model can lead to computationally intensive simulations, a parallelization on a distributed memory architecture was developed. A related performance model, taking into account load imbalance, is proposed and its accuracy tested.

  2. Vertical advection and nocturnal deposition of ozone over a boreal pine forest

    Directory of Open Access Journals (Sweden)

    Ü. Rannik

    2008-10-01

    Full Text Available Night-time ozone deposition for a Scots pine forest in Southern Finland was studied at the SMEAR II measurement station by evaluating the turbulent eddy covariance (EC, storage change and vertical advection fluxes. Similarly to night-time carbon dioxide flux, the eddy-covariance flux of ozone was decreasing with turbulence intensity (friction velocity, and storage change of the compound did not compensate the reduction (well-known night-time measurement problem. Accounting for vertical advection resulted in invariance of ozone deposition rate on turbulence intensity. This was also demonstrated for carbon dioxide, verified by independent measurements of NEE by chamber systems. The result highlights the importance of advection when considering the exchange measurements of any scalar. Analysis of aerodynamic and laminar boundary layer resistances by the model approach indicated that the surface resistance and/or chemical sink strength was limiting ozone deposition. The possible aerial ozone sink by known fast chemical reactions with sesquiterpenes and NO explain only a minor fraction of ozone sink. Thus the deposition is controlled either by stomatal uptake or surface reactions or both of them, the mechanisms not affected by turbulence intensity. Therefore invariance of deposition flux on turbulence intensity is expected also from resistance and chemical sink analysis.

  3. Some numerical studies of interface advection properties of level set method

    Indian Academy of Sciences (India)

    A Salih; S Ghosh Moulic

    2009-04-01

    In this paper, we discuss the results of a series of tests carried out to assess the level set methodology for capturing interfaces between two immiscible fluids. The tests are designed to investigate the accuracy of convection process, the preservation of interface shape, and the mass conservation properties of individual fluids. These test cases involve the advection of interfaces of different shapes exposed to translation, rotation, deformation, and shear flow. Prescribed solenoidal velocity fields are used and no attempt is made to couple the advection of the level set function with the momentum equations. For the solution of level set equation we have employed first-order upwind scheme, MacCormack method, second-order ENO scheme, and fifth-order WENO scheme. Our studies show that the level set method perform well when higher-order schemes are used for the solution of advection equation. However, for certain type of shearing and vortical velocity fields mass conservation is an issue on coarser meshes even with higher order schemes. Finer mesh must be used in such situations to reduce numerical diffusion.

  4. A Babcock-Leighton solar dynamo model with multi-cellular meridional circulation in advection- and diffusion-dominated regimes

    CERN Document Server

    Belucz, Bernadett; Forgacs-Dajka, Emese

    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 presence of a weak, second, high-latitude reverse cell speeds up the cycle and slightly enhances the poleward branch in butterfly diagram, whereas the presence of a second cell in depth reverses the tilt of butterfly wing to an anti-solar type. A butterfly diagram constructed from 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...

  5. Dissecting diffusive and advective motion in colloidal sedimentation by multi-speckle Ultra-Small-Angle XPCS

    Science.gov (United States)

    Möller, Johannes; Narayanan, Theyencheri

    In colloidal suspensions internal or external fields can induce directed motions of particles in addition to Brownian diffusion. Here, gradients in temperature or chemical potential, shear flow as well as gravity can act as an external field. Examples for internal motions can be found in synthetic self-propelling particles and microorganisms, generally coined as active matter. We present multi-speckle X-ray photon correlation spectroscopy measurements in the Ultra-Small-Angle scattering range which probes an expanded length scale comparable to DLS and optical microscopy. To demonstrate the advanced capabilities, we show measurements probing the motions within a settling suspension of sub-micron sized silica particles. A global fitting procedure has been applied to separate the diffusive and advective contributions to the particle dynamics. With this, macroscopic parameters such as the sedimentation velocity can be probed on a microscopic level in highly opaque and concentrated systems, which are in general difficult to access for optical investigations. This procedure may prove its value for investigating various kinds of non-equilibrium systems.

  6. GRMHD Simulations of Magnetized Advection Dominated Accretion on a Non-Spinning Black Hole: Outflows and Convection

    CERN Document Server

    Narayan, Ramesh; Penna, Robert F; Kulkarni, Akshay K

    2012-01-01

    We present results from two long-duration GRMHD simulations of an advection-dominated accretion flow around a non-spinning black hole. The first simulation was designed to avoid significant accumulation of magnetic flux around the black hole. This simulation was run for a time of 200,000GM/c^3 and achieved inflow equilibrium out to a radius \\sim 100GM/c^2. Up to this radius, we do not see significant mass outflow. We estimate that, if at all, only at radii \\gsim 300GM/c^2 does the mass outflow rate (\\dot{M}_{\\rm out}) exceed the net mass inflow rate into the black hole (\\dot{M}_{\\rm BH}). The second simulation was designed to achieve substantial magnetic flux accumulation around the black hole in a magnetically arrested disc. This simulation was run for a time of only 100,000GM/c^3. Nevertheless, because the mean radial velocity was several times larger than in the first simulation, it reached inflow equilibrium out to a radius \\sim 200GM/c^2. The mass outflow rate is larger, though even in this case, $\\dot{M...

  7. X-ray Variability as a Probe of Advection-Dominated Accretion in Low-Luminosity AGN

    CERN Document Server

    Ptak, A; Mushotzky, R F; Serlemitsos, P J; Griffiths, R

    1998-01-01

    As a class, LINERs and Low-Luminosity AGN tend to show little or no significant short-term variability (i.e., with time-scales less than a day). This is a marked break for the trend of increased variability in Seyfert 1 galaxies with decreased luminosity. We propose that this difference is due to the lower accretion rate in LINERs and LLAGN which is probably causing the accretion flow to be advection-dominated. This results in a larger characteristic size for the X-ray producing region than is the case in ``normal'' AGN. Short-term variability may be caused by a localized instability or occultation events, but we note that such events would likely be accompanied by broad-band spectral changes. Since the ADAF is more compact in a Kerr metric, it is possible that the X-ray emission from ADAFs around rotating blackholes would be more variable than X-ray emission from ADAFs in a Schwarzchild metric. Similar variability arguments also apply to other wavelengths, and accordingly multiwavelength monitoring of LLAGN ...

  8. LABORATORY-SCALE STUDY ON REACTIVE CONTAMINANT TRANSPORT IN SOIL BY MEANS OF ONE-DIMENSIONAL ADVECTIVE DISPERSIVE MODELS

    Directory of Open Access Journals (Sweden)

    Vincenzo Comegna

    2012-06-01

    Full Text Available We measured adsorption and transport of cadmium (Cd in the presence of Ca2+ and Na+ salts of varying ionic strengths and pH by using batch and miscible displacement experiments, carried out on undisturbed and homogenized soil columns. A fluvent-vertic soil was used in this study. In the column experiment a clear effect of ionic strength on breakthrough curves (BTCs of Cd2+ was observed when the Na+ concentration was increased from 0.02 to 0.2 M. The effect of increasing the Ca2+ concentration on Cd2+ absorption and transport was relatively less pronounced than that recorded for the Na+ solution. At low pH values, H+ ions competed strongly with Cd2+ ions and, at a high pH, precipitation was the main process taking place for Cd2+ sorption. The reliability of the advection- dispersion equation (ADE was tested. When implemented within the least-squares method, the model produced a sufficiently precise space-time distribution of Cd2+ ion concentrations. The results of this study demonstrated also, that laboratory leaching experiments, when performed on homogenized soil columns, can greatly underestimate Cd2+ ions transport in the field and that preferential flow can increase the mobility and velocity of cadmium movement to the groundwater.

  9. Ferrofluid flow for TOUGH2

    Energy Technology Data Exchange (ETDEWEB)

    Oldenburg, Curtis; Moridis, George

    1998-03-24

    We have developed EOS7M, a ferrofluid flow and transport module for TOUGH2. EOS7M calculates the magnetic forces on ferrofluid caused by an external magnetic field and allows simulation of flow and advective transport of ferrofluid-water mixtures through porous media. Such flow problems are strongly coupled and well suited to the TOUGH2 framework. Preliminary applications of EOS7M to some simple pressure and flow problems for which experiments were carried out in the lab show good qualitative agreement with the laboratory results.

  10. Identification of advective entry of soil-gas radon into a crawl space covered with sheets of polyethylene foil

    Energy Technology Data Exchange (ETDEWEB)

    Andersen, C. [Risoe National Lab., Dept. of Nucl. Safety Res. and Nucl. Facilities, Roskilde (Denmark); Koopmanns, M.; Meijer, R.J. de [Kernfysische Versneller Inst., Environmental Radioactivity Res., Groningen (Netherlands)

    1996-04-01

    To assess the effectiveness of mitigative measures against radon ({sup 222}Rn) entry into houses, experiments were conducted in a crawl-space house where the dirt floor of the crawl space was covered with sheets of 0.23 mm polyethylene foil fixed to the walls. The radon concentration was measured below the foil and in the crawl space together with environmental variables such as indoor-outdoor pressure differences. The experimental data was analyzed using various types of models including a simplistic mass-balance model, a regression model, and a two-dimensional numerical model based on Darcy flow or soil gas and combined diffusive and advective transport of radon. The main outcome of the work was that: (i) The soil-gas entry rate per pascal depressurization was at the order of 1 m{sup 3} h{sup -1}, (ii) the stack-related part of the depressurization of the crawl space (approx. 0.1 Pa deg. C{sup -1}) was controlled by the temperature difference between the living room of the house and the outdoors (not by the difference between the crawl space and the outdoors), (iii) that part of the wind-related depressurization that was measured by the pressure transducers seemed to force radon into the crawl space in the same proportion as the stack-related part of the depressurization, (iv) the ratio of advective and diffusive entry was approx. 0.7, when the crawl space was depressurized 1.5 Pa, (v) the effective diffusivity of the foil was found to be three orders of magnitude larger than that measured in the laboratory (the enhanced diffusivity was most likely caused by leaks in the foil and by mixing fans located in the crawl space), and (vi) there was no measurable mitigative impact of having the sheets of foil on the crawl-space floor even if the crawl space was artificially pressurized or depressurized. (au) 28 tabs., 36 ills., 61 refs.

  11. Modelling the observed vertical transport of {sup 7}Be in specific soils with advection dispersion model

    Energy Technology Data Exchange (ETDEWEB)

    Torres Astorga, Romina; Velasco, Hugo; Valladares, Diego L.; Lohaiza, Flavia; Ayub, Jimena Juri; Rizzotto, Marcos [Grupo de Estudios Ambientales. Instituto de Matematica Aplicada San Luis - Universidad Nacional de San Luis - CONICET, San Luis (Argentina)

    2014-07-01

    {sup 7}Be is a short-lived environmental radionuclide, produced in the upper atmosphere by spallation of nitrogen and oxygen by cosmic rays. After of the production by the nuclear reaction, {sup 7}Be diffuses through the atmosphere until it attaches to atmospheric aerosols. Subsequently, it is deposited on the earth surface mainly as wet fallout. The main physical processes which transport {sup 7}Be in soil are diffusion and advection by water. Migration parameters and measurements confirm that sorption is the main physical process, which confines {sup 7}Be concentration to soil surface. The literature data show that in soils, {sup 7}Be is concentrated near the surface (0-2 cm) as it is adsorbed onto clay minerals after its deposition on the soil surface and does not penetrate deeper into soils due to its short half-life. The maximum mass activity density of {sup 7}Be is found at the point of input of the radionuclide, i.e. at the surface of the soil column, showing a exponential distribution profile typical of a purely diffusive transport. Many studies applying the advection dispersion models have been reported in the literature in order to modelling the transport of {sup 137}Cs in soils. On them, the models are used to achieve information of the mechanisms that govern the transport, i. e. the model is used to explain the soil profile of radionuclide. The effective dispersion coefficient and the apparent advection velocity of radionuclide in soil are also obtained by fitting the analytical solution of the model equation to measured depth distributions of the radionuclide. In this work, the advective dispersive transport model with linear sorption is used to analyze the vertical migration process of {sup 7}Be in soils of undisturbed or reference sites. The deposition history is approximated by pulse-like input functions and time dependent analytical solution of equation model is obtained. The values of dispersion coefficient and apparent advection velocity obtained

  12. International Politics: A Desirable Paradigm

    Institute of Scientific and Technical Information of China (English)

    Xia Aiding; Feng Shuai

    2007-01-01

    This article first traces the origin of four concepts: International Politics (IP), International Relations (IR), World Politics (WP) and Global Politics (GP) and discusses the similarities among these four paradigms. It then analyses their application both at home and abroad. Finally, it argues for the desirability of selecting the concept of IP in academic training, thus facilitating practical application of concepts. It asserts that this will not only enhance academic discussion about IP among different Chinese schools of thought, but also help blazing new ideas.

  13. New Indivisible Planetary Science Paradigm

    OpenAIRE

    Herndon, J. Marvin

    2013-01-01

    I present here a new, indivisible planetary science paradigm, a wholly self-consistent vision of the nature of matter in the Solar System, and dynamics and energy sources of planets. Massive-core planets formed by condensing and raining-out from within giant gaseous protoplanets at high pressures and high temperatures. Earth's complete condensation included a 300 Earth-mass gigantic gas/ice shell that compressed the rocky kernel to about 66% of Earth's present diameter. T-Tauri eruptions stri...

  14. Psychiatry beyond the current paradigm.

    LENUS (Irish Health Repository)

    Bracken, Pat

    2012-12-01

    A series of editorials in this Journal have argued that psychiatry is in the midst of a crisis. The various solutions proposed would all involve a strengthening of psychiatry\\'s identity as essentially \\'applied neuroscience\\'. Although not discounting the importance of the brain sciences and psychopharmacology, we argue that psychiatry needs to move beyond the dominance of the current, technological paradigm. This would be more in keeping with the evidence about how positive outcomes are achieved and could also serve to foster more meaningful collaboration with the growing service user movement.

  15. Hypothesis Formation, Paradigms, and Openness

    Directory of Open Access Journals (Sweden)

    Conrad P. Pritscher

    2008-01-01

    Full Text Available A part of hypothesis formation, while necessary for scientific investigation, is beyond direct observation. Powerful hypothesis formation is more than logical and is facilitated by mind­opening. As Percy Bridgeman, Nobel laureate, said, science is: “Nothing more than doing one's damnedest with one's mind, no holds barred.” This paper suggests more open schooling helps generate more open hypothesizing which helps one do one's damnedest with one's mind. It is hypothesized that a more open process of hypothesis formation may help schools and society forge new ways of living and learning so that more people more often can do their damnedest with their mind. This writing does not offer a new paradigm but rather attempts to elaborate on the notion that new paradigms are difficult to form without openness to what was previously quasi­unthinkable. More on these topics and issues is included in the author's Reopening Einstein's Thought: About What Can't Be Learned From Textbooks ­­to be published by Sense Publishers in June 2008.

  16. Flow visualization in science and mathematics

    Energy Technology Data Exchange (ETDEWEB)

    Max, Nelson; Correa, Carlos; Muelder, Chris; Yan Shi; Chen, Cheng-Kai; Ma, Kwan-Liu, E-mail: max@cs.ucdavis.ed [Department of Computer Science, University of California, Davis 1 Shields Ave., Davis California, 95616 (United States)

    2009-07-01

    We present several methods for visualizing motion, vector fields, and flows, including polygonal surface advection, visibility driven transfer functions, feature extraction and tracking, and motion frequency analysis and enhancement. They are applied to chaotic attractors, turbulent vortices, supernovae, and seismic data.

  17. Numerical Modeling of Deep Mantle Convection: Advection and Diffusion Schemes for Marker Methods

    Science.gov (United States)

    Mulyukova, Elvira; Dabrowski, Marcin; Steinberger, Bernhard

    2013-04-01

    Thermal and chemical evolution of Earth's deep mantle can be studied by modeling vigorous convection in a chemically heterogeneous fluid. Numerical modeling of such a system poses several computational challenges. Dominance of heat advection over the diffusive heat transport, and a negligible amount of chemical diffusion results in sharp gradients of thermal and chemical fields. The exponential dependence of the viscosity of mantle materials on temperature also leads to high gradients of the velocity field. The accuracy of many numerical advection schemes degrades quickly with increasing gradient of the solution, while the computational effort, in terms of the scheme complexity and required resolution, grows. Additional numerical challenges arise due to a large range of length-scales characteristic of a thermochemical convection system with highly variable viscosity. To examplify, the thickness of the stem of a rising thermal plume may be a few percent of the mantle thickness. An even thinner filament of an anomalous material that is entrained by that plume may consitute less than a tenth of a percent of the mantle thickness. We have developed a two-dimensional FEM code to model thermochemical convection in a hollow cylinder domain, with a depth- and temperature-dependent viscosity representative of the mantle (Steinberger and Calderwood, 2006). We use marker-in-cell method for advection of chemical and thermal fields. The main advantage of perfoming advection using markers is absence of numerical diffusion during the advection step, as opposed to the more diffusive field-methods. However, in the common implementation of the marker-methods, the solution of the momentum and energy equations takes place on a computational grid, and nodes do not generally coincide with the positions of the markers. Transferring velocity-, temperature-, and chemistry- information between nodes and markers introduces errors inherent to inter- and extrapolation. In the numerical scheme

  18. ENVIRONMENTALISM AND CLASSIC PARADIGMS OF INTERNATIONAL RELATIONS

    OpenAIRE

    D. D. Miniaeva

    2014-01-01

    This article examines an environmentalism integration process into Three classical paradigms of international relations theory (Liberalism, Realism and Marxism) into Three classical paradigms of international relations theory (Liberalism, Realism and Marxism). The main purpose of this study is to reveal the result of this integration. Methods used in this article include analysis and comparison of "ecological" paradigms on selected parameters (the nature of international relations, actors, ta...

  19. Performance Analysis of high-order remap-type advection scheme on icosahedral-hexagonal grid

    Science.gov (United States)

    Mittal, Rashmi; Dubey, Sarvesh; Saxena, Vaibhav; Meurdesoif, Yann

    2014-05-01

    A comparative performance analysis on computational cost of second order advection schemes FF-CSLAM (Flux form conservative semi-Lagrangian multi-tracer transport scheme) and it's two simplifications on Icosahedral grid has been presented. Tracer transport is one of the main building blocks in atmospheric models and hence their performance greatly determines the overall performance of the model. FF-CSLAM falls in the category of arbitrary Lagrangian Eulerian (ALE) scheme. It exploits the finite volume formulation and therefore it is inherently conservative. Flux-area through edges are approximated with great circle arcs in an upwind fashion. Bi-quadratic sub-grid scale reconstructions using weighted least-squares method is employed to approximate trace field. Area integrals on the overlapped region of flux-area and static Eulerian meshes are evaluated via line-integrals. A brief description of implementation of FF-CSLAM on icosahedral -hexagonal meshes along with and its numerical accuracy in terms of standard test cases will be presented. A comparative analysis of the computational overhead is necessary to assess the suitability of FF-CSLAM for massively parallel and multi-threading computer architectures in comparison to other advection schemes implemented on icosahedral grids. The main focus of this work is to present the implementation of the shared memory parallelization and to describe the memory access pattern of the numerical scheme. FF-CSLAM is a remap-type advection scheme, thus extra calculation are done in comparison to the other advection schemes. The additional computations are associated with the search required to find the overlap area between the area swept through the edge and the underlining grid. But the experiments shows that the associated computational overhead is minimal for multi-tracer transport. It will be shown that for the Courant Number less than one, FF-CSLAM, the computations are not expensive. Since the grid cells are arranged in

  20. Really TVD advection schemes for the depth-integrated transport equation

    Science.gov (United States)

    Mercier, Ch.; Delhez, E. J. M.

    This paper explores the use of TVD advection schemes to solve the depth-integrated transport equation for tracers in finite volume marine models. Numerical experiments show that the blind application of the usual TVD schemes and associated flux limiters can lead to non-TVD solutions when applied in complex geometries. Spatial and/or temporal variations of the local bathymetry can indeed break the TVD property of the usual schemes. Really TVD schemes can be recovered by taking into account the local depth and its variations in the formulation of the flux limiters. Using this approach, a generalized superbee limiter is introduced and validated.

  1. Variational Integration for Ideal MHD with Built-in Advection Equations

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yao [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Qin, Hong [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Burby, J. W. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States); Bhattacharjee, A. [Princeton Plasma Physics Lab. (PPPL), Princeton, NJ (United States)

    2014-08-05

    Newcomb's Lagrangian for ideal MHD in Lagrangian labeling is discretized using discrete exterior calculus. Variational integrators for ideal MHD are derived thereafter. Besides being symplectic and momentum preserving, the schemes inherit built-in advection equations from Newcomb's formulation, and therefore avoid solving them and the accompanying error and dissipation. We implement the method in 2D and show that numerical reconnection does not take place when singular current sheets are present. We then apply it to studying the dynamics of the ideal coalescence instability with multiple islands. The relaxed equilibrium state with embedded current sheets is obtained numerically.

  2. Preconditioned iterative methods for space-time fractional advection-diffusion equations

    Science.gov (United States)

    Zhao, Zhi; Jin, Xiao-Qing; Lin, Matthew M.

    2016-08-01

    In this paper, we propose practical numerical methods for solving a class of initial-boundary value problems of space-time fractional advection-diffusion equations. First, we propose an implicit method based on two-sided Grünwald formulae and discuss its stability and consistency. Then, we develop the preconditioned generalized minimal residual (preconditioned GMRES) method and preconditioned conjugate gradient normal residual (preconditioned CGNR) method with easily constructed preconditioners. Importantly, because resulting systems are Toeplitz-like, fast Fourier transform can be applied to significantly reduce the computational cost. We perform numerical experiments to demonstrate the efficiency of our preconditioners, even in cases with variable coefficients.

  3. The determination of an unknown source for a space fractional advection dispersion equation

    KAUST Repository

    Aldoghaither, Abeer

    2014-09-01

    In this paper, we are interested in the estimation of the source term for a space fractional advection dispersion equation using concentration and flux measurements at final time. An example of application is the identification of contamination source in groundwater transport. We propose to use the socalled modulating functions method which has been introduced for parameters estimation. This method allows to transfer the estimation problem into solving a system of algebraic equations. Numerical examples are given to illustrate the effectiveness and the robustness of the proposed method. Finally, a comparison between a Tikhonov-based optimization method and the modulating functions approach is presented.

  4. Identifying space-dependent coefficients and the order of fractionality in fractional advection diffusion equation

    CERN Document Server

    Maryshev, Boris; Latrille, Christelle; Néel, Marie-Christine

    2016-01-01

    Tracer tests in natural porous media sometimes show abnormalities that suggest considering a fractional variant of the Advection Diffusion Equation supplemented by a time derivative of non-integer order. We are describing an inverse method for this equation: it finds the order of the fractional derivative and the coefficients that achieve minimum discrepancy between solution and tracer data. Using an adjoint equation divides the computational effort by an amount proportional to the number of freedom degrees, which becomes large when some coefficients depend on space. Method accuracy is checked on synthetical data, and applicability to actual tracer test is demonstrated.

  5. Convergence to a propagating front in a degenerate Fisher-KPP equation with advection

    CERN Document Server

    Alfaro, Matthieu

    2011-01-01

    We consider a Fisher-KPP equation with density-dependent diffusion and advection, arising from a chemotaxis-growth model. We study its behavior as a small parameter, related to the thickness of a diffuse interface, tends to zero. We analyze, for small times, the emergence of transition layers induced by a balance between reaction and drift effects. Then we investigate the propagation of the layers. Convergence to a free-boundary limit problem is proved and a sharp estimate of the thickness of the layers is provided.

  6. Variational integration for ideal magnetohydrodynamics with built-in advection equations

    International Nuclear Information System (INIS)

    Newcomb's Lagrangian for ideal magnetohydrodynamics (MHD) in Lagrangian labeling is discretized using discrete exterior calculus. Variational integrators for ideal MHD are derived thereafter. Besides being symplectic and momentum-preserving, the schemes inherit built-in advection equations from Newcomb's formulation, and therefore avoid solving them and the accompanying error and dissipation. We implement the method in 2D and show that numerical reconnection does not take place when singular current sheets are present. We then apply it to studying the dynamics of the ideal coalescence instability with multiple islands. The relaxed equilibrium state with embedded current sheets is obtained numerically

  7. Understanding the land management paradigm

    DEFF Research Database (Denmark)

    Enemark, Stig

    2006-01-01

    Land management is the process by which the resources of land are put into good effect. Land management encompasses all activities associated with the management of land and natural resources that are required to achieve sustainable development. Land Administration Systems (LAS) are institutional...... development towards the capacity to design, build, and manage Land Administration Systems that incorporate sustainable land policies and efficient spatial data infrastructures.......Land management is the process by which the resources of land are put into good effect. Land management encompasses all activities associated with the management of land and natural resources that are required to achieve sustainable development. Land Administration Systems (LAS) are institutional...... frameworks complicated by the tasks they must perform, by national cultural, political and judicial settings, and by technology. This paper facilitates an overall understanding of the land management paradigm. This paper assists sharing LAS among countries with diverse legal systems and institutional...

  8. Emerging Paradigms in Machine Learning

    CERN Document Server

    Jain, Lakhmi; Howlett, Robert

    2013-01-01

    This  book presents fundamental topics and algorithms that form the core of machine learning (ML) research, as well as emerging paradigms in intelligent system design. The  multidisciplinary nature of machine learning makes it a very fascinating and popular area for research.  The book is aiming at students, practitioners and researchers and captures the diversity and richness of the field of machine learning and intelligent systems.  Several chapters are devoted to computational learning models such as granular computing, rough sets and fuzzy sets An account of applications of well-known learning methods in biometrics, computational stylistics, multi-agent systems, spam classification including an extremely well-written survey on Bayesian networks shed light on the strengths and weaknesses of the methods. Practical studies yielding insight into challenging problems such as learning from incomplete and imbalanced data, pattern recognition of stochastic episodic events and on-line mining of non-stationary ...

  9. Datacubes as a Service Paradigm

    Science.gov (United States)

    Rossi, Angelo Pio; Baumann, Peter

    2016-04-01

    Spatio-temporal data sets often can be represented conveniently through datacubes as a common unifying paradigm. Flexible, scalable services can be offered based on the concept of a datacube query language while hiding the technicalities, thereby allowing user-friendly visual data interaction. One of today's most influential initiatives in Big Geo Data is EarthServer which is paving the way for flexible, scalable datacube services based on innovative NewSQL technology (Fig. 1). Researchers from Europe, the US and recently Australia have teamed up to rigorously materialize the datacube paradigm for Earth Observation, ocean, meteorological, and planetary science. EarthServer has established client and server technology for such spatio-temporal datacubes strictly based on the open datacube standards, OGC WCS and WPCS. The underlying scalable array engine, rasdaman, enables direct interaction, including 3-D visualization, what-if scenarios, common EO data processing, and general analytics on regular and irregular grids. Integration of datacube and metadata retrieval, together with advanced visualization based on NASA WorldWind, are geared towards an effective, user-friendly access and analysis. Conversely, EarthServer is significantly shaping the ISO, OGC, and INSPIRE Big Data standards landscape by being specification editor. Phase 1 of EarthServer has advanced scalable array data¬base technology into 100+ TB services; in phase 2, a federation of Petabyte datacubes is being built in Europe and Australia to perform ad-hoc querying and merging. Phase 1 reviewers have attested rasdaman to "significantly transform the way that scientists in different areas of Earth Science will be able to access and use data in a way that hitherto was not possible". Altogether, these large-scale deployments prove that datacubes are a convenient model for presenting users with a simple, consolidated view on the massive amount of data files gathered - "a cube tells more than a million

  10. Transient eddy current flow metering

    Science.gov (United States)

    Forbriger, J.; Stefani, F.

    2015-10-01

    Measuring local velocities or entire flow rates in liquid metals or semiconductor melts is a notorious problem in many industrial applications, including metal casting and silicon crystal growth. We present a new variant of an old technique which relies on the continuous tracking of a flow-advected transient eddy current that is induced by a pulsed external magnetic field. This calibration-free method is validated by applying it to the velocity of a spinning disk made of aluminum. First tests at a rig with a flow of liquid GaInSn are also presented.

  11. Transient eddy current flow metering

    CERN Document Server

    Forbriger, Jan

    2015-01-01

    Measuring local velocities or entire flow rates in liquid metals or semiconductor melts is a notorious problem in many industrial applications, including metal casting and silicon crystal growth. We present a new variant of an old technique which relies on the continuous tracking of a flow-advected transient eddy current that is induced by a pulsed external magnetic field. This calibration-free method is validated by applying it to the velocity of a spinning disk made of aluminum. First tests at a rig with a flow of liquid GaInSn are also presented.

  12. Contribution of velocity-vorticity correlations to the frictional drag in wall-bounded turbulent flows

    Science.gov (United States)

    Yoon, Min; Ahn, Junsun; Hwang, Jinyul; Sung, Hyung Jin

    2016-08-01

    The relationship between the frictional drag and the velocity-vorticity correlations in wall-bounded turbulent flows is derived from the mean vorticity equation. A formula for the skin friction coefficient is proposed and evaluated with regards to three canonical wall-bounded flows: turbulent boundary layer, turbulent channel flow, and turbulent pipe flow. The frictional drag encompasses four terms: advective vorticity transport, vortex stretching, viscous, and inhomogeneous terms. Drag-reduced channel flow with the slip condition is used to test the reliability of the formula. The advective vorticity transport and vortex stretching terms are found to dominate the contributions to the frictional drag.

  13. Space-Time Fractional Diffusion-Advection Equation with Caputo Derivative

    Directory of Open Access Journals (Sweden)

    José Francisco Gómez Aguilar

    2014-01-01

    Full Text Available An alternative construction for the space-time fractional diffusion-advection equation for the sedimentation phenomena is presented. The order of the derivative is considered as 0<β, γ≤1 for the space and time domain, respectively. The fractional derivative of Caputo type is considered. In the spatial case we obtain the fractional solution for the underdamped, undamped, and overdamped case. In the temporal case we show that the concentration has amplitude which exhibits an algebraic decay at asymptotically large times and also shows numerical simulations where both derivatives are taken in simultaneous form. In order that the equation preserves the physical units of the system two auxiliary parameters σx and σt are introduced characterizing the existence of fractional space and time components, respectively. A physical relation between these parameters is reported and the solutions in space-time are given in terms of the Mittag-Leffler function depending on the parameters β and γ. The generalization of the fractional diffusion-advection equation in space-time exhibits anomalous behavior.

  14. An advective-spectral-mixed method for time-dependent many-body Wigner simulations

    CERN Document Server

    Xiong, Yunfeng; Shao, Sihong

    2016-01-01

    As a phase space language for quantum mechanics, the Wigner function approach bears a close analogy to classical mechanics and has been drawing growing attention, especially in simulating quantum many-body systems. However, deterministic numerical solutions have been almost exclusively confined to one-dimensional one-body systems and few results are reported even for one-dimensional two-body problems. This paper serves as the first attempt to solve the time-dependent many-body Wigner equation through a grid-based advective-spectral-mixed method. The main feature of the method is to resolve the linear advection in $(\\bm{x},t)$-space by an explicit three-step characteristic scheme coupled with the piecewise cubic spline interpolation, while the Chebyshev spectral element method in $\\bm k$-space is adopted for accurate calculation of the nonlocal pseudo-differential term. Not only the time step of the resulting method is not restricted by the usual CFL condition and thus a large time step is allowed, but also th...

  15. Modeling of advection-diffusion-reaction processes using transport dissipative particle dynamics

    Science.gov (United States)

    Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-11-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. In particular, the transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of Lagrangian particles. To validate the proposed tDPD model and the boundary conditions, three benchmark simulations of one-dimensional diffusion with different boundary conditions are performed, and the results show excellent agreement with the theoretical solutions. Also, two-dimensional simulations of ADR systems are performed and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, an application of tDPD to the spatio-temporal dynamics of blood coagulation involving twenty-five reacting species is performed to demonstrate the promising biological applications of the tDPD model. Supported by the DOE Center on Mathematics for Mesoscopic Modeling of Materials (CM4) and an INCITE grant.

  16. Striped pattern selection by advective reaction-diffusion systems: resilience of banded vegetation on slopes.

    Science.gov (United States)

    Siero, E; Doelman, A; Eppinga, M B; Rademacher, J D M; Rietkerk, M; Siteur, K

    2015-03-01

    For water-limited arid ecosystems, where water distribution and infiltration play a vital role, various models have been set up to explain vegetation patterning. On sloped terrains, vegetation aligned in bands has been observed ubiquitously. In this paper, we consider the appearance, stability, and bifurcations of 2D striped or banded patterns in an arid ecosystem model. We numerically show that the resilience of the vegetation bands is larger on steeper slopes by computing the stability regions (Busse balloons) of striped patterns with respect to 1D and transverse 2D perturbations. This is corroborated by numerical simulations with a slowly decreasing water input parameter. Here, long wavelength striped patterns are unstable against transverse perturbations, which we also rigorously prove on flat ground through an Evans function approach. In addition, we prove a "Squire theorem" for a class of two-component reaction-advection-diffusion systems that includes our model, showing that the onset of pattern formation in 2D is due to 1D instabilities in the direction of advection, which naturally leads to striped patterns. PMID:25833449

  17. Energetics of lateral eddy diffusion/advection:Part I. Thermodynamics and energetics of vertical eddy diffusion

    Institute of Scientific and Technical Information of China (English)

    HUANG Rui Xin

    2014-01-01

    Two important nonlinear properties of seawater thermodynamics linked to changes of water density, cab-beling and elasticity (compressibility), are discussed. Eddy diffusion and advection lead to changes in den-sity;as a result, gravitational potential energy of the system is changed. Therefore, cabbeling and elasticity play key roles in the energetics of lateral eddy diffusion and advection. Vertical eddy diffusion is one of the key elements in the mechanical energy balance of the global oceans. Vertical eddy diffusion can be con-ceptually separated into two steps:stirring and subscale diffusion. Vertical eddy stirring pushes cold/dense water upward and warm/light water downward;thus, gravitational potential energy is increased. During the second steps, water masses from different places mix through subscale diffusion, and water density is increased due to cabbeling. Using WOA01 climatology and assuming the vertical eddy diffusivity is equal to a constant value of 2×103 Pa2/s, the total amount of gravitational potential energy increase due to vertical stirring in the world oceans is estimated at 263 GW. Cabbeling associated with vertical subscale diffusion is a sink of gravitational potential energy, and the total value of energy lost is estimated at 73 GW. Therefore, the net source of gravitational potential energy due to vertical eddy diffusion for the world oceans is estimated at 189 GW.

  18. Optimizing zonal advection of the Advanced Research WRF (ARW) dynamics for Intel MIC

    Science.gov (United States)

    Mielikainen, Jarno; Huang, Bormin; Huang, Allen H.

    2014-10-01

    The Weather Research and Forecast (WRF) model is the most widely used community weather forecast and research model in the world. There are two distinct varieties of WRF. The Advanced Research WRF (ARW) is an experimental, advanced research version featuring very high resolution. The WRF Nonhydrostatic Mesoscale Model (WRF-NMM) has been designed for forecasting operations. WRF consists of dynamics code and several physics modules. The WRF-ARW core is based on an Eulerian solver for the fully compressible nonhydrostatic equations. In the paper, we will use Intel Intel Many Integrated Core (MIC) architecture to substantially increase the performance of a zonal advection subroutine for optimization. It is of the most time consuming routines in the ARW dynamics core. Advection advances the explicit perturbation horizontal momentum equations by adding in the large-timestep tendency along with the small timestep pressure gradient tendency. We will describe the challenges we met during the development of a high-speed dynamics code subroutine for MIC architecture. Furthermore, lessons learned from the code optimization process will be discussed. The results show that the optimizations improved performance of the original code on Xeon Phi 5110P by a factor of 2.4x.

  19. Is This the Paradigm Shift We Need?

    Science.gov (United States)

    Mirvis, Jonathan

    2012-01-01

    Dr. Woocher's essay, states Mirvis, is seminal in the field of Jewish education. It proposes a new paradigm for Jewish education in North America. This proposed paradigm is supported by a comprehensive multi-disciplinary research drawing on literature from education, philosophy, history, sociology, psychology, and economics. The essay reflects a…

  20. Towards a New Paradigm of Moral Personhood

    Science.gov (United States)

    Frimer, Jeremy A.; Walker, Lawrence J.

    2008-01-01

    Moral psychology is between paradigms. Kohlberg's model of moral rationality has proved inadequate in explaining action; yet its augmentation--moral personality--awaits empirical embodiment. This article addresses some critical issues in developing a comprehensive empirical paradigm of moral personhood. Is a first-person or a third-person…

  1. The cognitive paradigm and the immunological homunculus.

    Science.gov (United States)

    Cohen, I R

    1992-12-01

    In last month's issue of Immunology Today, Irun Cohen discussed the inadequacies of the clonal selection paradigm and proposed a cognitive paradigm in which preformed internal images guide and restrict the process of clonal activation. Here he clarifies the nature of these internal images, during on concrete examples from the image of infection and the image of self, the immunological homunculus.

  2. Programming Paradigms in Computer Science Education

    OpenAIRE

    Bolshakova, Elena

    2005-01-01

    Main styles, or paradigms of programming – imperative, functional, logic, and object-oriented – are shortly described and compared, and corresponding programming techniques are outlined. Programming languages are classified in accordance with the main style and techniques supported. It is argued that profound education in computer science should include learning base programming techniques of all main programming paradigms.

  3. Two-dimensional circulation and mixing in the far field of a surface-advected river plume

    Science.gov (United States)

    Mazzini, Piero L. F.; Chant, Robert J.

    2016-06-01

    Field observations of the Hudson River plume are presented to discuss circulation and mixing in the far field of this coastally trapped buoyant flow. The plume was surface advected and propagated downshelf near the internal wave speed. The plume outflow was characterized by a two-layer bulge-like feature but became continuously stratified and vertically sheared in the far field, where Richardson numbers are generally below 0.5. High-frequency velocity and backscatter data from a moored ADCP revealed strong vertical and horizontal oscillatory motions at the front with a wavelength approximately 7-8 times the plume thickness, consistent with Kelvin-Helmholtz instabilities. These motions quickly died out after 2-3 cycles. The combination of vertical shear and stratification in the plume leads to a buoyancy flux toward the nose of the plume, which competes with mixing. However, the continued salinity increase of the plume as it propagated downshelf indicates that mixing overcomes this delivery of freshwater to the plume front. A simple 2-D model is developed, which relates the time rate-of-change of the plume salinity to: (1) salt entrainment due to vertical mixing, and (2) freshwater flux and salt removal due to the vertical shear of the stratified plume. Estimates of an entrainment coefficient from this model are consistent with previous estimates from the near field of a river outflow. A scaling of the plume width is obtained by assuming that vertical shears are controlled by both thermal wind and a critical Richardson number. This scaling yields plume widths that are consistent with previous laboratory studies.

  4. Speed and structure of turbulent fronts in pipe flow

    CERN Document Server

    Song, Baofang; Hof, Björn; Avila, Marc

    2016-01-01

    The dynamics of laminar-turbulent fronts in pipe flow is investigated for Reynolds numbers between Re=1900 and Re=5500 using extensive direct numerical simulations. In this range the flow undergoes a continuous transition from localised puffs to weakly expanding and ultimately to strongly expanding turbulent slugs (Barkley et al. 2015). We here investigate the physical distinction between these two types of slug by analysing time-resolved statistics of their downstream fronts in the frame moving at the bulk turbulent advection speed. While weak fronts travel slower than the bulk turbulent advection speed, implying local relaminarisation, strong fronts travel faster and so feed on the laminar flow ahead. At Re$\\approx$2900 the downstream front speed becomes faster than the advection speed, marking the onset of strong fronts. We argue that large temporal fluctuations of production and dissipation at the laminar-turbulent interface drive the dynamical switches between the two types of front observed up to Re$\\si...

  5. An oblique membrane paradigm for cosmological horizon

    CERN Document Server

    Wang, Tower

    2014-01-01

    The membrane paradigm is a formalism for studying the event horizon of black holes. After analyzing it with some technical details and realizing it in the Reissner-Nordstrom black hole, we extend the paradigm to cosmological horizons. A standard membrane paradigm is established for the pure de Sitter horizon, and an oblique membrane paradigm is proposed for the trapping horizon of the Friedmann-Lemaitre-Robertson-Walker universe. In the latter case, the cosmological stretched horizon is oblique, thus the running of renormalization parameter is nonzero in the timelike direction and gives a correction to the membrane pressure. In this paradigm, the cosmological equations come from continuity equations of the membrane fluid and the bulk fluid respectively.

  6. The Physical and Cognitive Paradigms in Information Retrieval Research.

    Science.gov (United States)

    Ellis, David

    1992-01-01

    Explores the role of paradigms in information retrieval research and discusses the nature of a paradigm and the applicability of the paradigm concept to a multidisciplinary field such as information science. The features of the physical paradigm and the cognitive paradigm are outlined, and their origins, nature, and role are examined. (55…

  7. Study of a model for correcting the effects of horizontal advection on surface fluxes measurement based on remote sensing

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    <正>As well known, the methods of remote sensing and Bowen Ratio for retrieving surface flux are based on energy balance closure; however, in most cases, surface energy observed in experiment is lack of closure. There are two main causes for this: one is from the errors of the observation devices and the differences of their observational scale; the other lies in the effect of horizontal advection on the surface flux measurement. Therefore, it is very important to estimate the effects of horizontal advection quantitatively. Based on the local advection theory and the surface experiment, a model has been proposed for correcting the effect of horizontal advection on surface flux measurement, in which the relationship between the fetch of the measurement and pixel size for remote sensed data was considered. By means of numerical simulations, the sensitivities of the main parameters in the model and the scaling problems of horizontal advection were analyzed. At last, by using the observational data acquired in agricultural field with relatively homogeneous surface, the model was validated.

  8. New Indivisible Planetary Science Paradigm

    CERN Document Server

    Herndon, J Marvin

    2013-01-01

    I present here a new, indivisible planetary science paradigm, a wholly self-consistent vision of the nature of matter in the Solar System, and dynamics and energy sources of planets. Massive-core planets formed by condensing and raining-out from within giant gaseous protoplanets at high pressures and high temperatures. Earth's complete condensation included a 300 Earth-mass gigantic gas/ice shell that compressed the rocky kernel to about 66% of Earth's present diameter. T-Tauri eruptions stripped the gases away from the inner planets and stripped a portion of Mercury's incompletely condensed protoplanet, and transported it to the region between Mars and Jupiter where it fused with in-falling oxidized condensate from the outer regions of the Solar System and formed the parent matter of ordinary chondrite meteorites, the main-Belt asteroids, and veneer for the inner planets, especially Mars. In response to decompression-driven planetary volume increases, cracks form to increase surface area and mountain ranges ...

  9. Metacognition: A new cognitive paradigm

    Directory of Open Access Journals (Sweden)

    Kankaraš Miloš

    2004-01-01

    Full Text Available This article reviews concept of metacognition, defined as: (a knowledge about ones own cognitive activity, (b strategies to monitor and regulate cognitive activity and behavior, and (c subjective or metacognitive experiences which comes from some changes or temporary difficulties in cognitive functioning. While describing different conceptualizations of metacognition, its development, fields of application, relation with intelligence, and its constrictions and ambiguity, we attempt to present new and emerging metacognitive paradigm, which is, for a relatively short period, succeeded to improve, expand, and redefine wide range of theoretical and practical fields in psychology, on new and original way. How do we become conscious of our own cognitive processes? What role and significance that consciousness has, what is the functional level above thinking processes and how that level, which monitor and control cognitive activity, works. Metacognition is concept that presents, as so far, the most important insight in those human mind areas, which, although very important, remained on the margin of psychological investigations until now.

  10. Life behind cell walls: paradigm lost, paradigm regained.

    Science.gov (United States)

    Lamport, D T

    2001-09-01

    This review of the living cell wall and its protein components is in two parts. The first is anecdotal. A personal account spanning over 40 years research may perhaps be an antidote to one stereotypical view of scientists as detached and humorless. The second part deals with the meaning of function, particularly as it applies to hydroxyproline-rich glycoproteins. Function is a difficult word to define objectively. However, with help from such luminaries as Humpty Dumpty: "A word means what I want it to mean, neither more nor less," and Wittgenstein: "Giving examples of usage ... is the only way to talk about meaning," it is possible to construct a ziggurat representing increasingly complex levels of organization from molecular structure to ecology. Forty years ago I suggested that hydroxyproline-rich structural proteins played a key role in cell wall functioning. But because the bulk of the wall is carbohydrate, there has been an understandable resistance to paradigm change. Expansins, paradoxically, contribute greatly to this resistance because their modus operandi as cell-wall-loosening proteins is based on the idea that they break hydrogen bonds between polysaccharide chains allowing slippage. However, this view is not consistent with the recent discovery [Grobe et al. (1999) Eur. J. Biochem 263: 33-40] that beta-expansins may be proteases, as it implies that the extensin network is not a straightjacket but a substrate for expansin in muro. Such a direct role for extensins in both negative and positive regulation of cell expansion and elongation may constitute a major morphogenetic mechanism operating at all levels of plant growth and development.

  11. Differential patterns of divergence in ocean drifters: Implications for larval flatfish advection and recruitment

    Science.gov (United States)

    Wilderbuer, Thomas; Duffy-Anderson, Janet T.; Stabeno, Phyllis; Hermann, Albert

    2016-05-01

    In an effort to better understand the physics of the eastern Bering Sea shelf current as it relates to flatfish advection to favorable near-shore areas, sets of multiple, satellite-tracked, oceanic drifters were released in 2010, 2012 and 2013. The release sites and dates were chosen to coincide with known spawning locations for northern rock sole (Lepidopsetta polyxystra) and known time of larval emergence. The drifters were drogued 5-each at 20 and 40 m in 2010 and 2012, and 4 at 40 m and 2 at 20 m in 2013. The locations of drifters were used to calculate divergence over a 90-day period that corresponds to the larval pelagic duration of Bering Sea shelf northern rock sole. Results indicate that there are alternating periods of positive and negative divergence with an overall trend toward drifter separation after 90 days, roughly the end of the rock sole planktonic larval period. Examination of the drifter behavior at the hourly scale indicates that semi-daily tidal forcing is the primary mechanism of drifter divergence and convergence. Field observations of early-stage northern rock sole larval distributions over the same period indicate that predominant oceanographic advection is northerly over the continental shelf among preflexion stages, though juveniles are predominantly found in nursery areas located ~ 400 km eastward and inshore. Evidence from drifter deployments suggests that behavioral movements during the postflexion and early juvenile larval phases that optimize eastward periodicity of tidal cycles is a viable mechanism to enhance eastward movement of northern rock sole larvae to favorable nursery grounds. A regional ocean modeling system (ROMS) was implemented to track the different rates of dispersion in simulations both with and without tidal forcing, and was used to estimate effective horizontal eddy diffusion in the case of both isobaric (fixed-depth) and Lagrangian (neutrally buoyant) particles. The addition of tidal forcing had a pronounced

  12. Developing a modified SEBAL algorithm that is responsive to advection by using limited weather data

    Science.gov (United States)

    Mkhwanazi, Mcebisi

    The use of Remote Sensing ET algorithms in water management, especially for agricultural purposes is increasing, and there are more models being introduced. The Surface Energy Balance Algorithm for Land (SEBAL) and its variant, Mapping Evapotranspiration with Internalized Calibration (METRIC) are some of the models that are being widely used. While SEBAL has several advantages over other RS models, including that it does not require prior knowledge of soil, crop and other ground details, it has the downside of underestimating evapotranspiration (ET) on days when there is advection, which may be in most cases in arid and semi-arid areas. METRIC, however has been modified to be able to account for advection, but in doing so it requires hourly weather data. In most developing countries, while accurate estimates of ET are required, the weather data necessary to use METRIC may not be available. This research therefore was meant to develop a modified version of SEBAL that would require minimal weather data that may be available in these areas, and still estimate ET accurately. The data that were used to develop this model were minimum and maximum temperatures, wind data, preferably the run of wind in the afternoon, and wet bulb temperature. These were used to quantify the advected energy that would increase ET in the field. This was a two-step process; the first was developing the model for standard conditions, which was described as a healthy cover of alfalfa, 40-60 cm tall and not short of water. Under standard conditions, when estimated ET using modified SEBAL was compared with lysimeter-measured ET, the modified SEBAL model had a Mean Bias Error (MBE) of 2.2 % compared to -17.1 % from the original SEBAL. The Root Mean Square Error (RMSE) was lower for the modified SEBAL model at 10.9 % compared to 25.1 % for the original SEBAL. The modified SEBAL model, developed on an alfalfa field in Rocky Ford, was then tested on other crops; beans and wheat. It was also tested on

  13. Dynamics of Finite-Size Particles in Chaotic Fluid Flows

    Science.gov (United States)

    Cartwright, Julyan H. E.; Feudel, Ulrike; Károlyi, György; de Moura, Alessandro; Piro, Oreste; Tél, Tamás

    We review recent advances on the dynamics of finite-size particles advected by chaotic fluid flows, focusing on the phenomena caused by the inertia of finite-size particles which have no counterpart in traditionally studied passive tracers. Particle inertia enlarges the phase space and makes the advection dynamics much richer than the passive tracer dynamics, because particles' trajectories can diverge from the trajectories of fluid parcels. We cover both confined and open flow regimes, and we also discuss the dynamics of interacting particles, which can undergo fragmentation and coagulation.

  14. Ostracism Online: A social media ostracism paradigm.

    Science.gov (United States)

    Wolf, Wouter; Levordashka, Ana; Ruff, Johanna R; Kraaijeveld, Steven; Lueckmann, Jan-Matthis; Williams, Kipling D

    2015-06-01

    We describe Ostracism Online, a novel, social media-based ostracism paradigm designed to (1) keep social interaction experimentally controlled, (2) provide researchers with the flexibility to manipulate the properties of the social situation to fit their research purposes, (3) be suitable for online data collection, (4) be convenient for studying subsequent within-group behavior, and (5) be ecologically valid. After collecting data online, we compared the Ostracism Online paradigm with the Cyberball paradigm (Williams & Jarvis Behavior Research Methods, 38, 174-180, 2006) on need-threat and mood questionnaire scores (van Beest & Williams Journal of Personality and Social Psychology 91, 918-928, 2006). We also examined whether ostracized targets of either paradigm would be more likely to conform to their group members than if they had been included. Using a Bayesian analysis of variance to examine the individual effects of the different paradigms and to compare these effects across paradigms, we found analogous effects on need-threat and mood. Perhaps because we examined conformity to the ostracizers (rather than neutral sources), neither paradigm showed effects of ostracism on conformity. We conclude that Ostracism Online is a cost-effective, easy to use, and ecologically valid research tool for studying the psychological and behavioral effects of ostracism. PMID:24878596

  15. Analysis of Field Synergy on Heat Transfer Enhancement in Chaotic Advection%混沌对流强化传热的场协同分析

    Institute of Scientific and Technical Information of China (English)

    王永庆; 董其伍; 刘敏珊; 王丹

    2011-01-01

    Based on the numerical results of fluid flow and heat transfer in a chaotic advection channel by a-dopting periodic model, heat transfer enhancement in chaotic advection is analysed by using the field synergy principle. The synergy between velocity and temperature fields on the cross section in the duct was analyzed, and the relationship in the chaotic duct between the Nusselt number and the average vector product of velocity and temperature gradient, and average synergy angle in different Reynolds numbers were studied, which were compared with that in the regular straight channel. It is found that the chaotic channel resulted in the different distribution of velocity field, which changed temperature fields. The synergy of velocity and temperature fields is improved, which enhances heat transfer in chaotic channel. The Nusselt number changes monotonously with the vector product of velocity and temperature gradient, and the fundamental mechanism of heat transfer enhancement in chaotic advection is the improvement of synergy between velocity and temperature fields.%基于采用周期性计算模型得到的混沌对流流道内的流体流动与传热数值计算结果,应用场协同原理,对混沌对流内强化传热进行分析.分析了混沌流道截面上流场与温度场的协同关系,讨论了流道内不同雷诺数下Nusselt数与平均流速与温度梯度矢量积和平均协同角的对应变化趋势,并与普通直流道内层流下的流动与传热场协同情况进行了对比.结果表明,混沌流道改变了流体在流道内速度场的分布,流场的变化影响了温度场的分布,使得两场的协同效果得到明显的改善,从而强化传热.在整个流道内,混沌对流的Nusselt数与速度和温度梯度两矢量的点积具有相同变化关系,混沌对流强化传热的根本机理是改善了两场的协同关系.

  16. The cognitive paradigm ontology: design and application.

    Science.gov (United States)

    Turner, Jessica A; Laird, Angela R

    2012-01-01

    We present the basic structure of the Cognitive Paradigm Ontology (CogPO) for human behavioral experiments. While the experimental psychology and cognitive neuroscience literature may refer to certain behavioral tasks by name (e.g., the Stroop paradigm or the Sternberg paradigm) or by function (a working memory task, a visual attention task), these paradigms can vary tremendously in the stimuli that are presented to the subject, the response expected from the subject, and the instructions given to the subject. Drawing from the taxonomy developed and used by the BrainMap project ( www.brainmap.org ) for almost two decades to describe key components of published functional imaging results, we have developed an ontology capable of representing certain characteristics of the cognitive paradigms used in the fMRI and PET literature. The Cognitive Paradigm Ontology is being developed to be compliant with the Basic Formal Ontology (BFO), and to harmonize where possible with larger ontologies such as RadLex, NeuroLex, or the Ontology of Biomedical Investigations (OBI). The key components of CogPO include the representation of experimental conditions focused on the stimuli presented, the instructions given, and the responses requested. The use of alternate and even competitive terminologies can often impede scientific discoveries. Categorization of paradigms according to stimulus, response, and instruction has been shown to allow advanced data retrieval techniques by searching for similarities and contrasts across multiple paradigm levels. The goal of CogPO is to develop, evaluate, and distribute a domain ontology of cognitive paradigms for application and use in the functional neuroimaging community.

  17. Preconditioned time-difference methods for advection-diffusion-reaction equations

    Energy Technology Data Exchange (ETDEWEB)

    Aro, C.; Rodrigue, G. [Lawrence Livermore National Lab., CA (United States); Wolitzer, D. [California State Univ., Hayward, CA (United States)

    1994-12-31

    Explicit time differencing methods for solving differential equations are advantageous in that they are easy to implement on a computer and are intrinsically very parallel. The disadvantage of explicit methods is the severe restrictions placed on stepsize due to stability. Stability bounds for explicit time differencing methods on advection-diffusion-reaction problems are generally quite severe and implicit methods are used instead. The linear systems arising from these implicit methods are large and sparse so that iterative methods must be used to solve them. In this paper the authors develop a methodology for increasing the stability bounds of standard explicit finite differencing methods by combining explicit methods, implicit methods, and iterative methods in a novel way to generate new time-difference schemes, called preconditioned time-difference methods.

  18. Numerical Identification of Multiparameters in the Space Fractional Advection Dispersion Equation by Final Observations

    Directory of Open Access Journals (Sweden)

    Dali Zhang

    2012-01-01

    Full Text Available This paper deals with an inverse problem for identifying multiparameters in 1D space fractional advection dispersion equation (FADE on a finite domain with final observations. The parameters to be identified are the fractional order, the diffusion coefficient, and the average velocity in the FADE. The forward problem is solved by a finite difference scheme, and then an optimal perturbation regularization algorithm is introduced to determine the three parameters simultaneously. Numerical inversions are performed both with the accurate data and noisy data, and several factors having influences on realization of the algorithm are discussed. The inversion solutions are in good approximations to the exact solutions demonstrating the efficiency of the proposed algorithm.

  19. Analytical Solutions of a Fractional Diffusion-advection Equation for Solar Cosmic-Ray Transport

    Science.gov (United States)

    Litvinenko, Yuri E.; Effenberger, Frederic

    2014-12-01

    Motivated by recent applications of superdiffusive transport models to shock-accelerated particle distributions in the heliosphere, we analytically solve a one-dimensional fractional diffusion-advection equation for the particle density. We derive an exact Fourier transform solution, simplify it in a weak diffusion approximation, and compare the new solution with previously available analytical results and with a semi-numerical solution based on a Fourier series expansion. We apply the results to the problem of describing the transport of energetic particles, accelerated at a traveling heliospheric shock. Our analysis shows that significant errors may result from assuming an infinite initial distance between the shock and the observer. We argue that the shock travel time should be a parameter of a realistic superdiffusive transport model.

  20. Analytical solutions of a fractional diffusion-advection equation for solar cosmic-ray transport

    CERN Document Server

    Litvinenko, Yuri E

    2014-01-01

    Motivated by recent applications of superdiffusive transport models to shock-accelerated particle distributions in the heliosphere, we solve analytically a one-dimensional fractional diffusion-advection equation for the particle density. We derive an exact Fourier transform solution, simplify it in a weak diffusion approximation, and compare the new solution with previously available analytical results and with a semi-numerical solution based on a Fourier series expansion. We apply the results to the problem of describing the transport of energetic particles, accelerated at a traveling heliospheric shock. Our analysis shows that significant errors may result from assuming an infinite initial distance between the shock and the observer. We argue that the shock travel time should be a parameter of a realistic superdiffusive transport model.

  1. Advection of pollutants by internal solitary waves in oceanic and atmospheric stable stratifications

    Directory of Open Access Journals (Sweden)

    G. W. Haarlemmer

    1998-01-01

    Full Text Available When a pollutant is released into the ocean or atmosphere under turbulent conditions, even a steady release is captured by large eddies resulting in localized patches of high concentration of the pollutant. If such a cloud of pollutant subsequently enters a stable stratification-either a pycnocline or thermocline-then internal waves are excited. Since large solitary internal waves have a recirculating core, pollutants may be trapped in the sclitary wave, and advected large distances through the waveguide provided by the stratification. This paper addresses the mechanisms, through computer and physical simulation, by which a localized release of a dense pollutant results in solitary waves that trap the pollutant or disperse the pollutant faster than in the absence of the waves.

  2. Moments Preserving and high-resolution Semi-Lagrangian Advection Scheme

    CERN Document Server

    Becerra-Sagredo, Julián; Mandujano, Francisco

    2014-01-01

    We present a forward semi-Lagrangian numerical method for systems of transport equations able to advect smooth and discontinuous fields with high-order accuracy. The numerical scheme is composed of an integration of the transport equations along the trajectory of material elements in a moving grid and a reconstruction of the fields in a reference regular mesh using a non-linear mapping and adaptive moment-preserving interpolations. The non-linear mapping allows for the arbitrary deformation of material elements. Additionally, interpolations can represent discontinuous fields using adaptive-order interpolation near jumps detected with a slope-limiter function. Due to the large number of operations during the interpolations, a serial implementation of this scheme is computationally expensive. The scheme has been accelerated in many-core parallel architectures using a thread per grid node and parallel data gathers. We present a series of tests that prove the scheme to be an attractive option for simulating advec...

  3. Temporal signatures of advective versus diffusive radon transport at a geothermal zone in Central Nepal

    Energy Technology Data Exchange (ETDEWEB)

    Richon, Patrick, E-mail: patrick.richon@cea.f [CEA, DAM, DIF, F-91297 Arpajon (France); Equipe Geologie des Systemes Volcaniques, Institut de Physique du Globe, 1 rue Jussieu, F-75238 Paris cedex 05 (France); Universite Paris Diderot, Sorbonne Paris Cite (France); Perrier, Frederic [Equipe de Geomagnetisme, Institut de Physique du Globe, 1 rue Jussieu, F-75238 Paris cedex 05 (France); Universite Paris Diderot, Sorbonne Paris Cite (France), CNRS (UMR 7154) (France); Koirala, Bharat Prasad [National Seismological Centre, Department of Mines and Geology, Lainchaur, Kathmandu (Nepal); Girault, Frederic [Equipe de Geomagnetisme, Institut de Physique du Globe, 1 rue Jussieu, F-75238 Paris cedex 05 (France); Universite Paris Diderot, Sorbonne Paris Cite (France), CNRS (UMR 7154) (France); Bhattarai, Mukunda; Sapkota, Soma Nath [National Seismological Centre, Department of Mines and Geology, Lainchaur, Kathmandu (Nepal)

    2011-02-15

    Temporal variation of radon-222 concentration was studied at the Syabru-Bensi hot springs, located on the Main Central Thrust zone in Central Nepal. This site is characterized by several carbon dioxide discharges having maximum fluxes larger than 10 kg m{sup -2} d{sup -1}. Radon concentration was monitored with autonomous Barasol{sup TM} probes between January 2008 and November 2009 in two small natural cavities with high CO{sub 2} concentration and at six locations in the soil: four points having a high flux, and two background reference points. At the reference points, dominated by radon diffusion, radon concentration was stable from January to May, with mean values of 22 {+-} 6.9 and 37 {+-} 5.5 kBq m{sup -3}, but was affected by a large increase, of about a factor of 2 and 1.6, respectively, during the monsoon season from June to September. At the points dominated by CO{sub 2} advection, by contrast, radon concentration showed higher mean values 39.0 {+-} 2.6 to 78 {+-} 1.4 kBq m{sup -3}, remarkably stable throughout the year with small long-term variation, including a possible modulation of period around 6 months. A significant difference between the diffusion dominated reference points and the advection-dominated points also emerged when studying the diurnal S{sub 1} and semi-diurnal S{sub 2} periodic components. At the advection-dominated points, radon concentration did not exhibit S{sub 1} or S{sub 2} components. At the reference points, however, the S{sub 2} component, associated with barometric tide, could be identified during the dry season, but only when the probe was installed at shallow depth. The S{sub 1} component, associated with thermal and possibly barometric diurnal forcing, was systematically observed, especially during monsoon season. The remarkable short-term and long-term temporal stability of the radon concentration at the advection-dominated points, which suggests a strong pressure source at depth, may be an important asset to detect

  4. Numerical calculation of tidal current with UTOPIA scheme for advection and application to Osaka Bay

    Science.gov (United States)

    Komoda, Jun; Matsuyama, Masaji

    UTOPIA scheme was applied to advection term for the numerical calculation of tide and tidal current to reproduce the strong tidal current realistically. Numerical model is constructed by boundary-fitted coordinate method vertically using Arakawa A grid in space. The new method is designed to suppress a numerical oscillation usually induced by Arakawa A grid. UTOPIA scheme was confirmed to be suitable to express a strong current around complicated topography. This model was applied to the tidal calculation for M2 constituent in Osaka Bay with two narrow straits, i.e., Akashi and Tomogashima straits. The tidal currents obtained in this model agree with them observed at monitoring stations, and the four eddies in the bay were also reproduced as the residual currents, i.e., tide induced transient eddy (TITE). The generation, growth and lifetime of the eddies also were investigated.

  5. A self-organizing Lagrangian particle method for adaptive-resolution advection-diffusion simulations

    Science.gov (United States)

    Reboux, Sylvain; Schrader, Birte; Sbalzarini, Ivo F.

    2012-05-01

    We present a novel adaptive-resolution particle method for continuous parabolic problems. In this method, particles self-organize in order to adapt to local resolution requirements. This is achieved by pseudo forces that are designed so as to guarantee that the solution is always well sampled and that no holes or clusters develop in the particle distribution. The particle sizes are locally adapted to the length scale of the solution. Differential operators are consistently evaluated on the evolving set of irregularly distributed particles of varying sizes using discretization-corrected operators. The method does not rely on any global transforms or mapping functions. After presenting the method and its error analysis, we demonstrate its capabilities and limitations on a set of two- and three-dimensional benchmark problems. These include advection-diffusion, the Burgers equation, the Buckley-Leverett five-spot problem, and curvature-driven level-set surface refinement.

  6. Temporal signatures of advective versus diffusive radon transport at a geothermal zone in Central Nepal

    International Nuclear Information System (INIS)

    Temporal variation of radon-222 concentration was studied at the Syabru-Bensi hot springs, located on the Main Central Thrust zone in Central Nepal. This site is characterized by several carbon dioxide discharges having maximum fluxes larger than 10 kg m-2 d-1. Radon concentration was monitored with autonomous BarasolTM probes between January 2008 and November 2009 in two small natural cavities with high CO2 concentration and at six locations in the soil: four points having a high flux, and two background reference points. At the reference points, dominated by radon diffusion, radon concentration was stable from January to May, with mean values of 22 ± 6.9 and 37 ± 5.5 kBq m-3, but was affected by a large increase, of about a factor of 2 and 1.6, respectively, during the monsoon season from June to September. At the points dominated by CO2 advection, by contrast, radon concentration showed higher mean values 39.0 ± 2.6 to 78 ± 1.4 kBq m-3, remarkably stable throughout the year with small long-term variation, including a possible modulation of period around 6 months. A significant difference between the diffusion dominated reference points and the advection-dominated points also emerged when studying the diurnal S1 and semi-diurnal S2 periodic components. At the advection-dominated points, radon concentration did not exhibit S1 or S2 components. At the reference points, however, the S2 component, associated with barometric tide, could be identified during the dry season, but only when the probe was installed at shallow depth. The S1 component, associated with thermal and possibly barometric diurnal forcing, was systematically observed, especially during monsoon season. The remarkable short-term and long-term temporal stability of the radon concentration at the advection-dominated points, which suggests a strong pressure source at depth, may be an important asset to detect possible temporal variations associated with the seismic cycle. - Graphical abstract: Radon

  7. Bias adjustment and advection interpolation of long-term high resolution radar rainfall series

    DEFF Research Database (Denmark)

    Thorndahl, Søren Liedtke; Nielsen, Jesper Ellerbæk; Rasmussen, Michael R.

    2014-01-01

    known to depend on the changing drop size distribution of the specific rain. This creates a transient bias between the radar rainfall and the ground observations due to seasonal changes of the drop size distribution as well as other atmospheric effects and effects related to the radar observational...... technology. In this study different bias adjustment techniques is investigated, developing a complete 10-year dataset (2002–2012) of high spatio-temporal resolution radar rainfall based on a radar observations from a single C-band radar from Denmark. Results show that hourly adjustment mean field bias...... adjustment outperform daily mean field bias adjustment with regards to estimation of rainfall totals and peak rain rates. Furthermore, it is demonstrated that radar rainfall estimates can be improved significantly by implementation of a novel advection interpolation technique....

  8. An advective diffusion process on hot wasted water discharged to a depression angle direction into water

    International Nuclear Information System (INIS)

    Effect of change in wasted water from nuclear or fossil fuel power plants discharging direction from horizontal one to depression angle one on an advective diffusion process of hot wasted water was investigated. As a result, it could be confirmed that an effect of depression angle jet discharge on water temperature reduction and so forth could be applied present experimental equation on horizontal discharging by a coordinate transformation of various factors with discharging water angle. And, a judgement equation to obtain a limiting area of hot wasted water affecting with bed surface was obtained by using distance from the lowest point of jet to the sea bed, inner diameter of discharging pipe, and field number for parameters, to elucidate its effectiveness. Furthermore, a diagram to estimate an effect of depression angle discharging water in the area on water temperature reduction and so forth was also proposed. (G.K.)

  9. On the stability of Godunov-projection methods for incompressible flow

    Energy Technology Data Exchange (ETDEWEB)

    Minion, M.L. [New York Univ., NY (United States)

    1996-02-01

    An analysis of the stability of certain numerical methods for the linear advection-diffusion equation in two dimensions is performed. The advection-diffusion equation is studied because it is a linearized version of the Navier-Stokes equations, the evolution equation for density in Boussinesq flows, and a simplified form of the equations for bulk thermodynamic temperature and mass fraction in reacting flows. It is found that various methods currently in use which are based on a Crank-Nicholson type temporal discretization utilizing second-order Godunov methods for explicitly calculating advective terms suffer from a time-step restriction which depends on the coefficients of diffusive terms. A simple modification in the computation of the advective derivatives results in a method with a stability condition that is independent of the magnitude of the coefficients of the diffusive terms. 19 refs., 9 figs., 1 tab.

  10. Emergence and decline of scientific paradigms

    DEFF Research Database (Denmark)

    Bornholdt, S.; Jensen, Mogens Høgh; Sneppen, Kim

    2011-01-01

    Scientific paradigms have a tendency to rise fast and decline slowly. This asymmetry reflects the difficulty in developing a truly original idea, compared to the ease at which a concept can be eroded by numerous modifications. Here we formulate a model for the emergence and spread of ideas which...... deals with this asymmetry by constraining the ability of agents to return to already abandoned concepts. The model exhibits a fairly regular pattern of global paradigm shifts, where older paradigms are eroded and subsequently replaced by new ones. The model sets the theme for a new class of pattern...

  11. Fuzzy Hybrid Deliberative/Reactive Paradigm (FHDRP)

    Science.gov (United States)

    Sarmadi, Hengameth

    2004-01-01

    This work aims to introduce a new concept for incorporating fuzzy sets in hybrid deliberative/reactive paradigm. After a brief review on basic issues of hybrid paradigm the definition of agent-based fuzzy hybrid paradigm, which enables the agents to proceed and extract their behavior through quantitative numerical and qualitative knowledge and to impose their decision making procedure via fuzzy rule bank, is discussed. Next an example performs a more applied platform for the developed approach and finally an overview of the corresponding agents architecture enhances agents logical framework.

  12. Contemporary Treatment Paradigms in Keratoconus.

    Science.gov (United States)

    McGhee, Charles N J; Kim, Bia Z; Wilson, Peter J

    2015-10-01

    The past 20 years have witnessed an explosion in our knowledge of keratoconus, accompanied by a radical transformation of management options. A 2-hit hypothesis proposes an underlying genetic predisposition coupled with external environmental factors, including eye rubbing and atopy. The variable prevalence and natural history have been better defined including significant cone progression in middle age. Therefore, current management must include early diagnosis, regular monitoring, and treatment of environmental cofactors. Spectacles and contact lenses remain fundamental to the optical management of keratoconus. Intrastromal corneal ring segments have been increasingly used, providing improvement in the corneal shape, corrected visual acuity, and contact lens wear. However, like contact lenses, intrastromal corneal ring segments do not treat the underlying disease process. Therefore, current approaches must also consider treatments to minimize keratoconus progression. Fortunately, there is increasing evidence that corneal collagen crosslinking will halt or slow progression in most cases. Until relatively recently, penetrating keratoplasty was the preferred intervention for advanced keratoconus, with long-term success in the region of 90%; however, the greatest risk of failure remains endothelial allograft rejection. Deep anterior lamellar keratoplasty has emerged in the new millennium as a preferred approach to conserve the host endothelium and avoid rejection. Nonetheless, the overall superiority of deep anterior lamellar keratoplasty compared with penetrating keratoplasty, in terms of optical and survival benefits, is still debated. This perspective provides an overview of our current knowledge of keratoconus and current management options. A step-ladder approach to managing keratoconus is outlined to provide the practitioner with a contemporary management paradigm.

  13. Gas transmission : a paradigm shift

    International Nuclear Information System (INIS)

    The evolution of energy markets in North America was discussed. The investment opportunities that are possible in a deregulated energy market, be it in production or in the generation of energy commodities, in the development of midstream infrastructure, or in the provision of energy services, were outlined. Deregulation of crude oil, natural gas and electricity has resulted in significant changes in the structure of energy markets and the way in which customers are served. One of the advantages of competition regarding power generation is that it has turned energy into a commodity which has resulted in greater customer choice and efficiency. As one example of midstream infrastructure development, the Alliance Pipeline project was described. This project was conceived as a means to enhance the value of western Canadian natural gas. The 1,900 mile pipeline will run from British Columbia, through Alberta into Chicago where it will interconnect with the North American gas transmission grid. The pipeline is an efficient means of transporting energy from Western Canada to North American markets, and Alliance, as a lowest cost transporter, will continue to put pressure on the traditional infrastructure to become even more competitive at the margin. As such, Alliance represents a paradigm shift in energy transportation, and serves as an excellent example of the type of investment opportunity that a deregulated market can provide. It was suggested that innovation and competition in a deregulated North American energy market will continue to increase. As electricity is deregulated, the energy market will respond more quickly to changes in supply and demand than it did in the past, in an effort to satisfy the needs of investors and customers. This will provide increased opportunities for restructuring and further competition

  14. Smoothed particle hydrodynamics model for Landau-Lifshitz-Navier-Stokes and advection-diffusion equations

    Science.gov (United States)

    Kordilla, Jannes; Pan, Wenxiao; Tartakovsky, Alexandre

    2014-12-01

    We propose a novel smoothed particle hydrodynamics (SPH) discretization of the fully coupled Landau-Lifshitz-Navier-Stokes (LLNS) and stochastic advection-diffusion equations. The accuracy of the SPH solution of the LLNS equations is demonstrated by comparing the scaling of velocity variance and the self-diffusion coefficient with kinetic temperature and particle mass obtained from the SPH simulations and analytical solutions. The spatial covariance of pressure and velocity fluctuations is found to be in a good agreement with theoretical models. To validate the accuracy of the SPH method for coupled LLNS and advection-diffusion equations, we simulate the interface between two miscible fluids. We study formation of the so-called "giant fluctuations" of the front between light and heavy fluids with and without gravity, where the light fluid lies on the top of the heavy fluid. We find that the power spectra of the simulated concentration field are in good agreement with the experiments and analytical solutions. In the absence of gravity, the power spectra decay as the power -4 of the wavenumber—except for small wavenumbers that diverge from this power law behavior due to the effect of finite domain size. Gravity suppresses the fluctuations, resulting in much weaker dependence of the power spectra on the wavenumber. Finally, the model is used to study the effect of thermal fluctuation on the Rayleigh-Taylor instability, an unstable dynamics of the front between a heavy fluid overlaying a light fluid. The front dynamics is shown to agree well with the analytical solutions.

  15. Transport dissipative particle dynamics model for mesoscopic advection-diffusion-reaction problems

    Science.gov (United States)

    Li, Zhen; Yazdani, Alireza; Tartakovsky, Alexandre; Karniadakis, George Em

    2015-07-01

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic dissipative particle dynamics (DPD) framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between tDPD particles, and the advection is implicitly considered by the movements of these Lagrangian particles. An analytical formula is proposed to relate the tDPD parameters to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the conventional DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.

  16. Interpretation of Isopycnal Layer Thickness Advection in Terms of Eddy-Topography Interaction

    Science.gov (United States)

    Liu, Chuanyu; Koehl, Armin; Stammer, Detlef

    2013-04-01

    Spatially varying amplitude of the eddy isopycnal layer thickness diffusivity Kgm and the layer thickness advection Kgmskew of the modified Gent and McWilliams parameterization are estimated using two different approaches: the adjoint estimation from a global data assimilation system and the inversion calculation according to divergent buoyancy eddy flux-mean buoyancy gradient relation using results from idealized eddy resolving numerical models with various bottom topographies. This work focuses on the properties of Kgmskew. From the adjoint estimation, large Kgmskew values are found along meandering currents and predominantly positive (negative) over the deep ocean and negative (positive) over seamounts in the southern (northern) hemisphere, implying close relation to the 'Neptune effect" parameterization by Holloway in which the eddy induced mean velocity stream function is represented by -fHL, where H is the bottom depth, f the Coriolis parameter and L a length scale. In the inversion calculation, divergent buoyancy eddy fluxes are obtained by removing the rotational components from the total buoyancy eddy fluxes through Helmholtz-Hodge decomposition. Though subject to topographic length scale, the inversed Kgmskew reveals characteristics of both f and H, and interactions with the mean current, inter-confirming the adjoint estimation results. Applying this parameterization for Kgmskew in the general circulation model produces cold domes and anti-cyclonic circulations over seamounts, which reduces common model biases there. By construction, the original thickness advection Kgmskew redistributes potential energy and the original "Neptune effect" parameterization improves potential vorticity conservation, applying the latter into the former as suggested in the present study thus more correctly reproduces the potential vorticity structure over a sloping topography while conserving the total potential energy.

  17. Empirical modeling of single-wake advection and expansion using full-scale pulsed lidar-based measurements

    DEFF Research Database (Denmark)

    Machefaux, Ewan; Larsen, Gunner Chr.; Troldborg, Niels;

    2015-01-01

    In the present paper, single-wake dynamics have been studied both experimentally and numerically. The use of pulsed lidar measurements allows for validation of basic dynamic wake meandering modeling assumptions. Wake center tracking is used to estimate the wake advection velocity experimentally and...... expansion fairly well in the far wake but lacks accuracy in the outer region of the near wake. An empirical relationship, relating maximum wake induction and wake advection velocity, is derived and linked to the characteristics of a spherical vortex structure. Furthermore, a new empirical model for single...

  18. Arbitrary-order difference schemes for solving linear advection equations with constant coefficients by the Godunov method with antidiffusion

    Science.gov (United States)

    Moiseev, N. Ya.; Silant'eva, I. Yu.

    2008-07-01

    An approach to the construction of second-and higher order accurate difference schemes in time and space is described for solving the linear one-and multidimensional advection equations with constant coefficients by the Godunov method with antidiffusion. The differential approximations for schemes of up to the fifth order are constructed and written. For multidimensional advection equations with constant coefficients, it is shown that Godunov schemes with splitting over spatial variables are preferable, since they have a smaller truncation error than schemes without splitting. The high resolution and efficiency of the difference schemes are demonstrated using test computations.

  19. The safety implications of emerging software paradigms

    International Nuclear Information System (INIS)

    This paper addresses some of the emerging software paradigms that may be used in developing safety-critical software applications. Paradigms considered in this paper include knowledge-based systems, neural networks, genetic algorithms, and fuzzy systems. It presents one view of the software verification and validation activities that should be associated with each paradigm. The paper begins with a discussion of the historical evolution of software verification and validation. Next, a comparison is made between the verification and validation processes used for conventional and emerging software systems. Several verification and validation issues for the emerging paradigms are discussed and some specific research topics are identified. This work is relevant for monitoring and control at nuclear power plants

  20. Paradigms and Principles Shaping Educational Design Research

    NARCIS (Netherlands)

    McKenney, Susan

    2014-01-01

    McKenney, S. (2013). Paradigms and Principles Shaping Educational Design Research. Invited panel presentation at the annual meeting of the European Association for Research on Learning and Instruction. August 27-31, Munich.

  1. Yakov Zeldovich and the Cosmic Web Paradigm

    CERN Document Server

    Einasto, Jaan

    2014-01-01

    I discuss the formation of the modern cosmological paradigm. In more detail I describe the early study of dark matter and cosmic web and the role of Yakov Zeldovich in the formation of the present concepts on these subjects.

  2. Flow dynamics around downwelling submarine canyons

    Directory of Open Access Journals (Sweden)

    J. M. Spurgin

    2014-05-01

    Full Text Available Flow dynamics around a downwelling submarine canyon were analysed with the Massachusetts Institute of Technology general circulation model. Blanes Canyon (Northwest Mediterranean was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby number and Burger number were used to determine the significance of Coriolis acceleration and stratification (respectively and their impacts on flow dynamics. A new non-dimensional parameter (χ was introduced to determine the significance of vertical variations in stratification. Some simulations do see brief periods of upwards displacement of water during the 10 day model period, however, the presence of the submarine canyon is found to enhance downwards advection of density in all model scenarios. High Burger numbers lead to negative vorticity and a trapped anticyclonic eddy within the canyon, as well as an increased density anomaly. Low Burger numbers lead to positive vorticity, cyclonic circulation and weaker density anomalies. Vertical variations in stratification affect zonal jet placement. Under the same forcing conditions, the zonal jet is pushed offshore in more uniformly stratified domains. Offshore jet location generates upwards density advection away from the canyon, while onshore jets generate downwards density advection everywhere within the model domain. Increasing Rossby values across the canyon axis, as well as decreasing Burger values, increase negative vertical flux at shelf break depth (150 m. Increasing Rossby numbers lead to stronger downwards advection of a passive tracer (nitrate as well as stronger vorticity within the canyon. Results from previous studies were explained within this new dynamic framework.

  3. Flow dynamics around downwelling submarine canyons

    Directory of Open Access Journals (Sweden)

    J. M. Spurgin

    2014-10-01

    Full Text Available Flow dynamics around a downwelling submarine canyon were analysed with the Massachusetts Institute of Technology general circulation model. Blanes Canyon (northwestern Mediterranean was used for topographic and initial forcing conditions. Fourteen scenarios were modelled with varying forcing conditions. Rossby and Burger numbers were used to determine the significance of Coriolis acceleration and stratification (respectively and their impacts on flow dynamics. A new non-dimensional parameter (χ was introduced to determine the significance of vertical variations in stratification. Some simulations do see brief periods of upwards displacement of water during the 10-day model period; however, the presence of the submarine canyon is found to enhance downwards advection of density in all model scenarios. High Burger numbers lead to negative vorticity and a trapped anticyclonic eddy within the canyon, as well as an increased density anomaly. Low Burger numbers lead to positive vorticity, cyclonic circulation, and weaker density anomalies. Vertical variations in stratification affect zonal jet placement. Under the same forcing conditions, the zonal jet is pushed offshore in more uniformly stratified domains. The offshore jet location generates upwards density advection away from the canyon, while onshore jets generate downwards density advection everywhere within the model domain. Increasing Rossby values across the canyon axis, as well as decreasing Burger values, increase negative vertical flux at shelf break depth (150 m. Increasing Rossby numbers lead to stronger downwards advection of a passive tracer (nitrate, as well as stronger vorticity within the canyon. Results from previous studies are explained within this new dynamic framework.

  4. Engineering paradigms and anthropogenic global change

    Science.gov (United States)

    Bohle, Martin

    2016-04-01

    This essay discusses 'paradigms' as means to conceive anthropogenic global change. Humankind alters earth-systems because of the number of people, the patterns of consumption of resources, and the alterations of environments. This process of anthropogenic global change is a composite consisting of societal (in the 'noosphere') and natural (in the 'bio-geosphere') features. Engineering intercedes these features; e.g. observing stratospheric ozone depletion has led to understanding it as a collateral artefact of a particular set of engineering choices. Beyond any specific use-case, engineering works have a common function; e.g. civil-engineering intersects economic activity and geosphere. People conceive their actions in the noosphere including giving purpose to their engineering. The 'noosphere' is the ensemble of social, cultural or political concepts ('shared subjective mental insights') of people. Among people's concepts are the paradigms how to shape environments, production systems and consumption patterns given their societal preferences. In that context, engineering is a means to implement a given development path. Four paradigms currently are distinguishable how to make anthropogenic global change happening. Among the 'engineering paradigms' for anthropogenic global change, 'adaptation' is a paradigm for a business-as-usual scenario and steady development paths of societies. Applying this paradigm implies to forecast the change to come, to appropriately design engineering works, and to maintain as far as possible the current production and consumption patterns. An alternative would be to adjust incrementally development paths of societies, namely to 'dovetail' anthropogenic and natural fluxes of matter and energy. To apply that paradigm research has to identify 'natural boundaries', how to modify production and consumption patterns, and how to tackle process in the noosphere to render alterations of common development paths acceptable. A further alternative

  5. International business and the eclectic paradigm

    DEFF Research Database (Denmark)

    The eclectic paradigm has become the dominant theoretical basis in the study of international business, multinational corporations and internationalization since 1980. However, developments such as economic globalization and the subsequent growth of global and alliance capitalism have fundamentally......, finance, evolutionary economics, resource-based theory or strategic management? Can it be utilized to explain new developments in international business and economics? Do these require new ideas and concepts to be integrated within the eclectic paradigm? What are the new challenges to which international...

  6. Aqueous semi-solid flow cell: demonstration and analysis

    Energy Technology Data Exchange (ETDEWEB)

    Li, Z; Smith, KC; Dong, YJ; Baram, N; Fan, FY; Xie, J; Limthongkul, P; Carter, WC; Chiang, YM

    2013-01-01

    An aqueous Li-ion flow cell using suspension-based flow electrodes based on the LiTi2(PO4)(3)-LiFePO4 couple is demonstrated. Unlike conventional flow batteries, the semi-solid approach utilizes fluid electrodes that are electronically conductive. A model of simultaneous advection and electrochemical transport is developed and used to separate flow-induced losses from those due to underlying side reactions. The importance of plug flow to achieving high energy efficiency in flow batteries utilizing highly non-Newtonian flow electrodes is emphasized.

  7. New Indivisible Planetary Science Paradigm: Consequence of Questioning Popular Paradigms

    Science.gov (United States)

    Marvin Herndon, J.

    2014-05-01

    Progress in science involves replacing less precise understanding with more precise understanding. In science and in science education one should always question popular ideas; ask "What's wrong with this picture?" Finding limitations, conflicts or circumstances that require special ad hoc consideration sometimes is the key to making important discoveries. For example, from thermodynamic considerations, I found that the 'standard model of solar system formation' leads to insufficiently massive planetary cores. That understanding led me to discover a new indivisible planetary science paradigm. Massive-core planets formed by condensing and raining-out from within giant gaseous protoplanets at high pressures and high temperatures, accumulating heterogeneously on the basis of volatility with liquid core-formation preceding mantle-formation; the interior states of oxidation resemble that of the Abee enstatite chondrite. Core-composition was established during condensation based upon the relative solubilities of elements, including uranium, in liquid iron in equilibrium with an atmosphere of solar composition at high pressures and high temperatures. Uranium settled to the central region and formed planetary nuclear fission reactors, producing heat and planetary magnetic fields. Earth's complete condensation included a ~300 Earth-mass gigantic gas/ice shell that compressed the rocky kernel to about 66% of Earth's present diameter. T-Tauri eruptions, associated with the thermonuclear ignition of the Sun, stripped the gases away from the Earth and the inner planets. The T-Tauri outbursts stripped a portion of Mercury's incompletely condensed protoplanet and transported it to the region between Mars and Jupiter where it fused with in-falling oxidized condensate from the outer regions of the Solar System, forming the parent matter of ordinary chondrite meteorites, the main-Belt asteroids, and veneer for the inner planets, especially Mars. With its massive gas/ice shell

  8. The Underlying Social Dynamics of Paradigm Shifts

    Science.gov (United States)

    Claro, Francisco; Fuentes, Miguel Angel

    2015-01-01

    We develop here a multi-agent model of the creation of knowledge (scientific progress or technological evolution) within a community of researchers devoted to such endeavors. In the proposed model, agents learn in a physical-technological landscape, and weight is attached to both individual search and social influence. We find that the combination of these two forces together with random experimentation can account for both i) marginal change, that is, periods of normal science or refinements on the performance of a given technology (and in which the community stays in the neighborhood of the current paradigm); and ii) radical change, which takes the form of scientific paradigm shifts (or discontinuities in the structure of performance of a technology) that is observed as a swift migration of the knowledge community towards the new and superior paradigm. The efficiency of the search process is heavily dependent on the weight that agents posit on social influence. The occurrence of a paradigm shift becomes more likely when each member of the community attaches a small but positive weight to the experience of his/her peers. For this parameter region, nevertheless, a conservative force is exerted by the representatives of the current paradigm. However, social influence is not strong enough to seriously hamper individual discovery, and can act so as to empower successful individual pioneers who have conquered the new and superior paradigm. PMID:26418255

  9. The Underlying Social Dynamics of Paradigm Shifts.

    Directory of Open Access Journals (Sweden)

    Carlos Rodriguez-Sickert

    Full Text Available We develop here a multi-agent model of the creation of knowledge (scientific progress or technological evolution within a community of researchers devoted to such endeavors. In the proposed model, agents learn in a physical-technological landscape, and weight is attached to both individual search and social influence. We find that the combination of these two forces together with random experimentation can account for both i marginal change, that is, periods of normal science or refinements on the performance of a given technology (and in which the community stays in the neighborhood of the current paradigm; and ii radical change, which takes the form of scientific paradigm shifts (or discontinuities in the structure of performance of a technology that is observed as a swift migration of the knowledge community towards the new and superior paradigm. The efficiency of the search process is heavily dependent on the weight that agents posit on social influence. The occurrence of a paradigm shift becomes more likely when each member of the community attaches a small but positive weight to the experience of his/her peers. For this parameter region, nevertheless, a conservative force is exerted by the representatives of the current paradigm. However, social influence is not strong enough to seriously hamper individual discovery, and can act so as to empower successful individual pioneers who have conquered the new and superior paradigm.

  10. The Underlying Social Dynamics of Paradigm Shifts.

    Science.gov (United States)

    Rodriguez-Sickert, Carlos; Cosmelli, Diego; Claro, Francisco; Fuentes, Miguel Angel

    2015-01-01

    We develop here a multi-agent model of the creation of knowledge (scientific progress or technological evolution) within a community of researchers devoted to such endeavors. In the proposed model, agents learn in a physical-technological landscape, and weight is attached to both individual search and social influence. We find that the combination of these two forces together with random experimentation can account for both i) marginal change, that is, periods of normal science or refinements on the performance of a given technology (and in which the community stays in the neighborhood of the current paradigm); and ii) radical change, which takes the form of scientific paradigm shifts (or discontinuities in the structure of performance of a technology) that is observed as a swift migration of the knowledge community towards the new and superior paradigm. The efficiency of the search process is heavily dependent on the weight that agents posit on social influence. The occurrence of a paradigm shift becomes more likely when each member of the community attaches a small but positive weight to the experience of his/her peers. For this parameter region, nevertheless, a conservative force is exerted by the representatives of the current paradigm. However, social influence is not strong enough to seriously hamper individual discovery, and can act so as to empower successful individual pioneers who have conquered the new and superior paradigm.

  11. Spectral analysis of large-eddy advection in ET from eddy covariance towers and a large weighting lysimeter

    Science.gov (United States)

    Evapotranspiration was continuously measured by an array of eddy covariance systems and large weighting lysimeter in a cotton field in Bushland, Texas. The advective divergence from both horizontal and vertical directions were measured through profile measurements above canopy. All storage terms wer...

  12. Dynamical structure of magnetized dissipative accretion flow around black holes

    OpenAIRE

    Sarkar, Biplob; Das, Santabrata

    2016-01-01

    We study the global structure of optically thin, advection dominated, magnetized accretion flow around black holes. We consider the magnetic field to be turbulent in nature and dominated by the toroidal component. With this, we obtain the complete set of accretion solutions for dissipative flows where bremsstrahlung process is regarded as the dominant cooling mechanism. We show that rotating magnetized accretion flow experiences virtual barrier around black hole due to centrifugal repulsion t...

  13. On vertical advection truncation errors in terrain-following numerical models: Comparison to a laboratory model for upwelling over submarine canyons

    Science.gov (United States)

    Allen, S. E.; Dinniman, M. S.; Klinck, J. M.; Gorby, D. D.; Hewett, A. J.; Hickey, B. M.

    2003-01-01

    Submarine canyons which indent the continental shelf are frequently regions of steep (up to 45°), three-dimensional topography. Recent observations have delineated the flow over several submarine canyons during 2-4 day long upwelling episodes. Thus upwelling episodes over submarine canyons provide an excellent flow regime for evaluating numerical and physical models. Here we compare a physical and numerical model simulation of an upwelling event over a simplified submarine canyon. The numerical model being evaluated is a version of the S-Coordinate Rutgers University Model (SCRUM). Careful matching between the models is necessary for a stringent comparison. Results show a poor comparison for the homogeneous case due to nonhydrostatic effects in the laboratory model. Results for the stratified case are better but show a systematic difference between the numerical results and laboratory results. This difference is shown not to be due to nonhydrostatic effects. Rather, the difference is due to truncation errors in the calculation of the vertical advection of density in the numerical model. The calculation is inaccurate due to the terrain-following coordinates combined with a strong vertical gradient in density, vertical shear in the horizontal velocity and topography with strong curvature.

  14. Wind-driven gas networks and star formation in galaxies: reaction-advection hydrodynamic simulations

    Science.gov (United States)

    Chappell, David; Scalo, John

    2001-07-01

    The effects of wind-driven star formation feedback on the spatio-temporal organization of stars and gas in galaxies is studied using two-dimensional intermediate-representational quasi-hydrodynamical simulations. The model retains only a reduced subset of the physics, including mass and momentum conservation, fully non-linear fluid advection, inelastic macroscopic interactions, threshold star formation, and momentum forcing by winds from young star clusters on the surrounding gas. Expanding shells of swept-up gas evolve through the action of fluid advection to form a `turbulent' network of interacting shell fragments which have the overall appearance of a web of filaments (in two dimensions). A new star cluster is formed whenever the column density through a filament exceeds a critical threshold based on the gravitational instability criterion for an expanding shell, which then generates a new expanding shell after some time delay. A filament-finding algorithm is developed to locate the potential sites of new star formation. The major result is the dominance of multiple interactions between advectively distorted shells in controlling the gas and star morphology, gas velocity distribution and mass spectrum of high mass density peaks, and the global star formation history. The gas morphology strongly resembles the model envisioned by Norman & Silk, and observations of gas in the Large Magellanic Cloud (LMC)Q1 and local molecular clouds. The dependence of the frequency distribution of present-to-past average global star formation rate on a number of parameters is investigated. Bursts of star formation only occur when the time-averaged star formation rate per unit area is low, or the system is small. Percolation does not play a role. The broad distribution observed in late-type galaxies can be understood as a result of either small size or small metallicity, resulting in larger shell column densities required for gravitational instability. The star formation rate

  15. PARADIGM FOR CONTEMPORARY SYMBOLIC REALITY

    Directory of Open Access Journals (Sweden)

    Elena Korableva

    2013-12-01

    Full Text Available Objective: Civilization development in its concrete historical specificity is embodied in symbolic forms that require interpretation and understanding of its meaning. Info communication symbolic reality sets new parameters of self-determination rights, creates a new type of information behavior. Adequate entry into the modern social context requires analysis of the basic concepts of symbolic reality of human existence, and its contemporary sound. The dialectical materialist methodology allows us to investigate human immersion in contradictive meanings of the era, the skills of interaction with the increased flow of information, the ability to determine information needs and use this information right way as well as the ability to analyze this information. Scientific novelty is reflected in axiological evolutionary approach to the analysis of reproduction in the sign and symbol of the spiritual and the practical forms of human multidimensional realities of their existence in their specific historical context. Conclusions: 1 Persons' immersion into the space of cultural and historical symbolic processes determines the content of their socialization which is a process of self-identification in the symbolic reality, the process of entering the subject-shaped field of human culture; 2 An adequate model of signs and symbols reflects the diversity of information flows, that is the synthesis of a specific objective and true knowledge, its interpretation and value. Herewith, a lot of interpretations, pluralism and diversity of axiological points of view to understanding objective reality are obvious; 3 The use of signs becomes like a code or the language for communication between people. The interpretation of clip-culture determines the adequacy and efficiency of action based on the identified meanings and values of diverse information and communication symbolic reality.

  16. ENVIRONMENTALISM AND CLASSIC PARADIGMS OF INTERNATIONAL RELATIONS

    Directory of Open Access Journals (Sweden)

    D. D. Miniaeva

    2014-06-01

    Full Text Available This article examines an environmentalism integration process into Three classical paradigms of international relations theory (Liberalism, Realism and Marxism into Three classical paradigms of international relations theory (Liberalism, Realism and Marxism. The main purpose of this study is to reveal the result of this integration. Methods used in this article include analysis and comparison of "ecological" paradigms on selected parameters (the nature of international relations, actors, targets, tools, processes. Results of research show that the beginning of the XXI century is distinguished by the development of new types of political concepts that explain interaction of elements in modern international relations in the area of environmental protection. The reason of these changes lies in the phenomena of environmentalism integration into Three paradigms of international relations. However, we cannot say that any of the examined paradigms accumulated all features of environmentalism without their modification. Better to say, it's rather similar to adaptation of environmental ideas. Therefore, to understand modern international relations processes, it is necessary to take into account their environmental element. Purchase on Elibrary.ru > Buy nowDOI: http://dx.doi.org/10.12731/2070-7568-2014-3-4

  17. Evaluating the advective Brewer-Dobson circulation in three reanalyses for the period 1979-2012

    Science.gov (United States)

    Abalos, Marta; Legras, Bernard; Ploeger, Felix; Randel, William J.

    2015-08-01

    Most chemistry-climate models show an intensification of the Brewer-Dobson circulation (BDC) in the stratosphere associated with increasing greenhouse gas emissions and ozone depletion in the last decades, but this trend remains to be confirmed in observational data. In this work the evolution of the advective BDC for the period 1979-2012 is evaluated and compared in three modern reanalyses (ERA-Interim, MERRA, and JRA-55). Three different estimates of the BDC are computed for each reanalysis, one based on the definition of the residual circulation and two indirect estimates derived from momentum and thermodynamic balances. The comparison among the nine estimates shows substantial uncertainty in the mean magnitude (˜40%) but significant common variability. The tropical upwelling series show variability linked to the stratospheric quasi-biennial oscillation and to El Niño-Southern Oscillation (ENSO) and also reflect extreme events such as major sudden stratospheric warmings and volcanic eruptions. The trend analysis suggests a strengthening of tropical upwelling of around 2-5%/decade throughout the layer 100-10 hPa. The global spatial structure of the BDC trends provides evidence of an overall acceleration of the circulation in both hemispheres, with qualitative agreement among the estimates. The global BDC trends are mainly linked to changes in the boreal winter season and can be tracked to long-term increases in the resolved wave drag in both hemispheres.

  18. The advective Brewer-Dobson circulation in three reanalyses (1979-2012)

    Science.gov (United States)

    Abalos, Marta; Legras, Bernard; Ploeger, Felix; Randel, William

    2015-04-01

    Most chemistry-climate models predict an intensification of the Brewer-Dobson circulation in the stratosphere in the last decades, but this trend remains to be confirmed in observational data. In this work the evolution of the advective BDC for the period 1979-2012 is evaluated and compared in three modern reanalyses (ERA-Interim, MERRA and JRA-55). Three different estimates of the BDC are computed for each reanalysis, one based on the definition of the residual circulation and two indirect estimates derived from momentum and thermodynamic balance. The comparison among the nine estimates shows substantial uncertainty in the mean magnitude but significant common variability. The trend analysis suggests an intensification in tropical upwelling throughout the layer 100-10 hPa. Globally, an acceleration of the circulation is observed in both hemispheres, with qualitative agreement among the estimates. The global BDC trends are mainly due to changes in the DJF circulation and can be tracked to changes in the resolved wave drag in both hemispheres, which are highly consistent in the three reanalyses.

  19. Bound-Preserving Discontinuous Galerkin Methods for Conservative Phase Space Advection in Curvilinear Coordinates

    CERN Document Server

    Endeve, Eirik; Xing, Yulong; Mezzacappa, Anthony

    2014-01-01

    We extend the positivity-preserving method of Zhang & Shu (2010, JCP, 229, 3091-3120) to simulate the advection of neutral particles in phase space using curvilinear coordinates. The ability to utilize these coordinates is important for non-equilibrium transport problems in general relativity and also in science and engineering applications with specific geometries. The method achieves high-order accuracy using Discontinuous Galerkin (DG) discretization of phase space and strong stability-preserving, Runge-Kutta (SSP-RK) time integration. Special care in taken to ensure that the method preserves strict bounds for the phase space distribution function $f$; i.e., $f\\in[0,1]$. The combination of suitable CFL conditions and the use of the high-order limiter proposed in Zhang & Shu (2010) is sufficient to ensure positivity of the distribution function. However, to ensure that the distribution function satisfies the upper bound, the discretization must, in addition, preserve the divergence-free property of ...

  20. Far-from-equilibrium sheared colloidal liquids: Disentangling relaxation, advection, and shear-induced diffusion

    KAUST Repository

    Lin, Neil Y. C.

    2013-12-01

    Using high-speed confocal microscopy, we measure the particle positions in a colloidal suspension under large-amplitude oscillatory shear. Using the particle positions, we quantify the in situ anisotropy of the pair-correlation function, a measure of the Brownian stress. From these data we find two distinct types of responses as the system crosses over from equilibrium to far-from-equilibrium states. The first is a nonlinear amplitude saturation that arises from shear-induced advection, while the second is a linear frequency saturation due to competition between suspension relaxation and shear rate. In spite of their different underlying mechanisms, we show that all the data can be scaled onto a master curve that spans the equilibrium and far-from-equilibrium regimes, linking small-amplitude oscillatory to continuous shear. This observation illustrates a colloidal analog of the Cox-Merz rule and its microscopic underpinning. Brownian dynamics simulations show that interparticle interactions are sufficient for generating both experimentally observed saturations. © 2013 American Physical Society.

  1. Helical turbulent Prandtl number in the $A$ model of passive advection: Two loop approximation

    CERN Document Server

    Hnatič, Michal

    2016-01-01

    Using the field theoretic renormalization group technique in the two-loop approximation, turbulent Prandtl numbers are obtained in the general $A$ model of passive vector advected by fully developed turbulent velocity field with violation of spatial parity introduced via continuous parameter $\\rho$ ranging from $\\rho=0$ (no violation of spatial parity) to $|\\rho|=1$ (maximum violation of spatial parity). In non-helical environments, we demonstrate that $A$ is restricted to $-1.723 \\leq A \\leq 2.800$ (rounded on the last presented digit) due to the constraints of two-loop calculations. When $\\rho >0.749$ restrictions may be removed. Furthermore, three physically important cases $A \\in \\{-1, 0, 1\\}$ are shown to lie deep within the allowed interval of $A$ for all values of $\\rho$. For the model of linearized Navier-Stokes equations ($A = -1$) up to date unknown helical values of turbulent Prandtl number have been shown to equal $1$ regardless of parity violation. Furthermore, we have shown that interaction para...

  2. A New Evapotranspiration Model Accounting for Advection and Its Validation during SMEX02

    Directory of Open Access Journals (Sweden)

    Yongmin Yang

    2013-01-01

    Full Text Available Based on the crop water stress index (CWSI concept, a new model was proposed to account for advection to estimate evapotranspiration. Both local scale evaluation with sites observations and regional scale evaluation with a remote dataset from Landsat 7 ETM+ were carried out to assess the performance of this model. Local scale evaluation indicates that this newly developed model can effectively characterize the daily variations of evapotranspiration and the predicted results show good agreement with the site observations. For all the 6 corn sites, the coefficient of determination (R2 is 0.90 and the root mean square difference (RMSD is 58.52W/m2. For all the 6 soybean sites, the R2 and RMSD are 0.85 and 49.46W/m2, respectively. Regional scale evaluation shows that the model can capture the spatial variations of evapotranspiration at the Landsat-based scale. Clear spatial patterns were observed at the Landsat-based scale and are closely related to the dominant land covers, corn and soybean. Furthermore, the surface resistance derived from instantaneous CWSI was applied to the Penman-Monteith equation to estimate daily evapotranspiration. Overall, results indicate that this newly developed model is capable of estimating reliable surface heat fluxes using remotely sensed data.

  3. Transport dissipative particle dynamics model for mesoscopic advection- diffusion-reaction problems

    Energy Technology Data Exchange (ETDEWEB)

    Zhen, Li; Yazdani, Alireza; Tartakovsky, Alexandre M.; Karniadakis, George E.

    2015-07-07

    We present a transport dissipative particle dynamics (tDPD) model for simulating mesoscopic problems involving advection-diffusion-reaction (ADR) processes, along with a methodology for implementation of the correct Dirichlet and Neumann boundary conditions in tDPD simulations. tDPD is an extension of the classic DPD framework with extra variables for describing the evolution of concentration fields. The transport of concentration is modeled by a Fickian flux and a random flux between particles, and an analytical formula is proposed to relate the mesoscopic concentration friction to the effective diffusion coefficient. To validate the present tDPD model and the boundary conditions, we perform three tDPD simulations of one-dimensional diffusion with different boundary conditions, and the results show excellent agreement with the theoretical solutions. We also performed two-dimensional simulations of ADR systems and the tDPD simulations agree well with the results obtained by the spectral element method. Finally, we present an application of the tDPD model to the dynamic process of blood coagulation involving 25 reacting species in order to demonstrate the potential of tDPD in simulating biological dynamics at the mesoscale. We find that the tDPD solution of this comprehensive 25-species coagulation model is only twice as computationally expensive as the DPD simulation of the hydrodynamics only, which is a significant advantage over available continuum solvers.

  4. Existence of solutions to boundary value problems arising from the fractional advection dispersion equation

    Directory of Open Access Journals (Sweden)

    Lingju Kong

    2013-04-01

    Full Text Available We study the existence of multiple solutions to the boundary value problem $$displaylines{ frac{d}{dt}Big(frac12{}_0D_t^{-eta}(u'(t+frac12{}_tD_T^{-eta}(u'(t Big+lambda abla F(t,u(t=0,quad tin [0,T],cr u(0=u(T=0, }$$ where $T>0$, $lambda>0$ is a parameter, $0leqeta<1$, ${}_0D_t^{-eta}$ and ${}_tD_T^{-eta}$ are, respectively, the left and right Riemann-Liouville fractional integrals of order $eta$, $F: [0,T]imesmathbb{R}^Nomathbb{R}$ is a given function. Our interest in the above system arises from studying the steady fractional advection dispersion equation. By applying variational methods, we obtain sufficient conditions under which the above equation has at least three solutions. Our results are new even for the special case when $eta=0$. Examples are provided to illustrate the applicability of our results.

  5. On the advection of tracer by eddies on the beta-plane: A numerical study

    Directory of Open Access Journals (Sweden)

    E. S. Benilov

    1999-01-01

    Full Text Available The evolution of tracer "injected" into an equivalent barotropic eddy on the beta-plane is examined numerically. The eddy is governed by the standard quasigeostrophic equation, and the concentration of tracer is governed by the advection equation with diffusion. At the initial moment of time, the streamfunction and distribution of tracer are both radially or elliptically symmetric. After the first 10-30 days, a spirallike strip, where the gradient of concentration is large, develops in the tracer field, whereas the eddy remains smooth for a relatively long time. To put this conclusion in quantitative terms, a "tracer variability indicator" is introduced and shown to grow much faster than a similar characteristic of the potential vorticity field (notwithstanding the fact that the tracer concentration and PV satisfy the same governing equation. A simple explanation as to why the tracer is more affected by filamentation than PV is provided for eddies with small Burger number. It is demonstrated that the high-gradient strip develops, unless stopped by turbulent diffusion, into an inversion (non-monotonicity of the tracer concentration field. Finally, the results of simulations are compared to the spiral patterns in the real-life eddies observed in the East Australian Current.

  6. Central Arctic Ocean freshwater during a period of anomalous melt and advection in 2015

    Science.gov (United States)

    Rabe, Benjamin; Korhonen, Meri; Hoppmann, Mario; Ricker, Robert; Hendricks, Stefan; Krumpen, Thomas; Beckers, Justin; Schauer, Ursula

    2016-04-01

    During the recent decade the Arctic Ocean has shown several years of very low sea-ice extent and an increase in liquid freshwater. Yet, the processes underlying the interannual variability are still not fully understood. Hydrographic observations by ship campaigns and autonomous platforms reveal that summer 2015 showed above average liquid freshwater in the upper ocean of the central Arctic. Surface temperatures and sea level pressure were also higher than the average of the preceeding two decades. From hydrographic observations and atmospheric reanalysis data we show that this liquid freshwater anomaly is associated with above average sea-ice melt and intensified northward Ekman transport. We, further, found significant amounts of Pacific Water in the upper water column, from the mixed-layer to the upper halocline. Our results suggest that the freshening was due to both advection of low-salinity water from the direction of the Siberian shelves, the Beaufort Gyre and the Bering Strait, and enhance sea-ice melt.

  7. Bad behavior of Godunov mixed methods for strongly anisotropic advection-dispersion equations

    Science.gov (United States)

    Mazzia, Annamaria; Manzini, Gianmarco; Putti, Mario

    2011-09-01

    We study the performance of Godunov mixed methods, which combine a mixed-hybrid finite element solver and a Godunov-like shock-capturing solver, for the numerical treatment of the advection-dispersion equation with strong anisotropic tensor coefficients. It turns out that a mesh locking phenomenon may cause ill-conditioning and reduce the accuracy of the numerical approximation especially on coarse meshes. This problem may be partially alleviated by substituting the mixed-hybrid finite element solver used in the discretization of the dispersive (diffusive) term with a linear Galerkin finite element solver, which does not display such a strong ill conditioning. To illustrate the different mechanisms that come into play, we investigate the spectral properties of such numerical discretizations when applied to a strongly anisotropic diffusive term on a small regular mesh. A thorough comparison of the stiffness matrix eigenvalues reveals that the accuracy loss of the Godunov mixed method is a structural feature of the mixed-hybrid method. In fact, the varied response of the two methods is due to the different way the smallest and largest eigenvalues of the dispersion (diffusion) tensor influence the diagonal and off-diagonal terms of the final stiffness matrix. One and two dimensional test cases support our findings.

  8. Effect of organic compounds for the advection of actinide elements in the environments

    Energy Technology Data Exchange (ETDEWEB)

    Muraoka, Susumu; Nagao, Seiya; Tanaka, Tadao [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment; Hiraki, Keizo; Nakaguchi, Yuzuru; Suzuki, Yasuhiro

    1998-01-01

    The aim of this studies is understood the effects of humic substances for the advection of actinide elements in the environments. These substances are a major role of dissolved organic matter in natural waters. In order to obtain the informations on the structure of metal-humic substances complexes, these substances were studied by fluorescence spectroscopy. Observation the spectrum forms, peak positions of maximum intensity are related to these informations on the chemical structures and functional groups in organic compounds. Using three-dimensional excitation emission matrix (3-D EEM) spectroscopy, the characteristics of metal-humic substances complexes were studied. Observation the wavelengths and fluorescence intensity of the peaks were varied between humic substances before the complex to the metal and these substances after ones. Understanding the fluorescence properties of metal-humic substances complexes, working program of the 3-D EEM spectroscopy was studied to obtaining detailed data collection. New program was applied to copper-humic acid complex, the peak positions which different with before the complex and after ones were recorded. This program is supported by the interpreation of fluorescence properties in the metal-humic substances by the 3-D EEM spectroscopy. (author)

  9. Organizational improvement using Organizational paradigms with the support of people paradigms

    Directory of Open Access Journals (Sweden)

    Md. Shariful Alam

    2011-02-01

    Full Text Available An organization is a vital part of social environment. Different parts of organization have great impact to the environment. On the other hand the different organizational strategy helps to improve the efficiency of organization and customer satisfaction. The people and tools of organization help to organization to work properly. This paper mainly describes about the organizational paradigms and people paradigms also the way how the people paradigms facilitate the organizational paradigms to improve the organizational architecture for better performance. This paper describes the different aspects of organizational like Information system strategy, Information system planning, Business process reengineering etc also End user computing, Knowledge management, Expert system of people paradigms.And finally there is a combination between those. Keywords: Business process reengineering, Customer satisfaction, end used computing, In Information System Strategy, knowledge management, Organizational improvement.

  10. New Paradigms in Internet Computing

    CERN Document Server

    Tripathy, Piyu; Naik, Sagar

    2013-01-01

    The renaissance of internet has reached the mainstream that is named as Web 2.0. People are now using the web to build things they have never thought of earlier. Experts take a step forward to what we contribute, and extend it and give back to the society, i.e. really the boon of internet computing. It has revolutionized the current business environment, not as a mere computing tool, but offers versatile services and increase the productive flow of information. It is a new dimension in computing systems by which companies can curtail their operating expenses, by hosting and operating through the internet. Now the users can access the required information by means of any device connected with an internet. The challenge ahead for implementing this versatile system is that the software and technology has to be developed and deployed simultaneously vis-a-vis safeguarding the security and privacy of information.             This book encompasses various research and developments in Internet technology a...

  11. Elastic instability in stratified core annular flow

    CERN Document Server

    Bonhomme, Oriane; Leng, Jacques; Colin, Annie

    2010-01-01

    We study experimentally the interfacial instability between a layer of dilute polymer solution and water flowing in a thin capillary. The use of microfluidic devices allows us to observe and quantify in great detail the features of the flow. At low velocities, the flow takes the form of a straight jet, while at high velocities, steady or advected wavy jets are produced. We demonstrate that the transition between these flow regimes is purely elastic -- it is caused by viscoelasticity of the polymer solution only. The linear stability analysis of the flow in the short-wave approximation captures quantitatively the flow diagram. Surprisingly, unstable flows are observed for strong velocities, whereas convected flows are observed for low velocities. We demonstrate that this instability can be used to measure rheological properties of dilute polymer solutions that are difficult to assess otherwise.

  12. Emergence and decline of scientific paradigms.

    Science.gov (United States)

    Bornholdt, S; Jensen, M H; Sneppen, K

    2011-02-01

    Scientific paradigms have a tendency to rise fast and decline slowly. This asymmetry reflects the difficulty in developing a truly original idea, compared to the ease at which a concept can be eroded by numerous modifications. Here we formulate a model for the emergence and spread of ideas which deals with this asymmetry by constraining the ability of agents to return to already abandoned concepts. The model exhibits a fairly regular pattern of global paradigm shifts, where older paradigms are eroded and subsequently replaced by new ones. The model sets the theme for a new class of pattern formation models, where local dynamics breaks the detailed balance in a way that prevents old states from defending themselves against new nucleating or invading states. The model allows for frozen events in terms of the coexistence of multiple metastable states. PMID:21405444

  13. A Paradigm for Spreadsheet Engineering Methodologies

    CERN Document Server

    Grossman, Thomas A

    2008-01-01

    Spreadsheet engineering methodologies are diverse and sometimes contradictory. It is difficult for spreadsheet developers to identify a spreadsheet engineering methodology that is appropriate for their class of spreadsheet, with its unique combination of goals, type of problem, and available time and resources. There is a lack of well-organized, proven methodologies with known costs and benefits for well-defined spreadsheet classes. It is difficult to compare and critically evaluate methodologies. We present a paradigm for organizing and interpreting spreadsheet engineering recommendations. It systematically addresses the myriad choices made when developing a spreadsheet, and explicitly considers resource constraints and other development parameters. This paradigm provides a framework for evaluation, comparison, and selection of methodologies, and a list of essential elements for developers or codifiers of new methodologies. This paradigm identifies gaps in our knowledge that merit further research.

  14. Phase transitions in paradigm shift models.

    Directory of Open Access Journals (Sweden)

    Huiseung Chae

    Full Text Available Two general models for paradigm shifts, deterministic propagation model (DM and stochastic propagation model (SM, are proposed to describe paradigm shifts and the adoption of new technological levels. By defining the order parameter m based on the diversity of ideas, Δ, it is studied when and how the phase transition or the disappearance of a dominant paradigm occurs as a cost C in DM or an innovation probability α in SM increases. In addition, we also investigate how the propagation processes affect the transition nature. From analytical calculations and numerical simulations m is shown to satisfy the scaling relation m=1-f(C/N for DM with the number of agents N. In contrast, m in SM scales as m=1-f(α(aN.

  15. The influence of advection on the short term CO2-budget in and above a forest canopy

    Science.gov (United States)

    Feigenwinter, C.; Vogt, R.; Bernhofer, C.

    2003-04-01

    The investigation of advective effects in complex terrain requires an experimental setup, which is capable to precisely measure the horizontal concentration gradients of a property (i.e. CO2). For this purpose, the CARBOEUROFLUX site in Tharandt (Germany) was completed with additional measurements to account for the entire mass balance of CO2 in a soil-vegetation-atmosphere volume during the AFO 2000 VERTIKO MORE 1 campaign (Sep/Oct 2001) in close cooperation with IHM TU Dresden. Net Ecosystem Exchange is calculated by the conservation equation, in which the horizontal advection term is undoubtedly the less known and less investigated term. The large scatter of horizontal and vertical advection during 13 consecutive days of available 30-min values is supposed to be mainly natural and not due to measurement errors. The latter were minimized by measuring the horizontal CO2 concentration differences at the three edges of a prism volume at two heights (2 m and 26 m a.g.l.) with the same IRGA gas analyser additionally to the single profile measurements at 7 levels at each edge point. Wind vectors were simultaneously measured at two levels (0.5 m and 2.5 m) in the trunk space with carefully calibrated sonics. From these measurements profiles of the horizontal CO2 gradient (amount and direction) and of the mean horizontal wind vector are constructed. These profiles are supposed to be representative for the closer surroundings of the site. The horizontal advection in a certain layer depends essentially on the horizontal wind vector and CO2 gradient (amount and direction). It is very sensitive to smallest changes in input variables and thus, their derivation from profile measurements is actually the crucial task. It is shown that the direction of the horizontal concentration gradient as well as the horizontal wind vector is often height dependent. A minimum and a maximum scenario for the horizontal advection term gives gain of 10..30 g CO2 m-2 d-1 compared to a mean loss of

  16. Experimental studies of coherent structures in an advection-reaction-diffusion system

    Science.gov (United States)

    Gowen, Savannah; Solomon, Tom

    2015-08-01

    We present experimental studies of reaction front propagation in a single vortex flow with an imposed external wind. The fronts are produced by the excitable, ferroin-catalyzed Belousov-Zhabotinsky chemical reaction. The flow is generated using an electromagnetic forcing technique: an almost-radial electrical current interacts with a magnetic field from a magnet below the fluid layer to produce the vortex. The magnet is mounted on crossed translation stages allowing for movement of the vortex through the flow. Reaction fronts triggered in or in front of the moving vortex form persistent structures that are seen experimentally for time-independent (constant motion), time-periodic, and time-aperiodic flows. These results are examined with the use of burning invariant manifolds that act as one-way barriers to front motion in the flows. We also explore the usefulness of finite-time Lyapunov exponent fields as an instrument for analyzing front propagation behavior in a fluid flow.

  17. « Les OGM face aux nouveaux paradigmes de la biologie »

    Directory of Open Access Journals (Sweden)

    Grosclaude Jeanne

    2009-03-01

    Full Text Available The assessment and risk management of GMOs are inherited from the paradigm of molecular biology born in the 1960s and from theories of evolutionary biology dominant in the years that saw the onset of GMOs. But these paradigms have been greatly challenged by recent advances in these disciplines : the dissolution of the concept of gene, the identification of epigenetic phenomena transmitted hereditarily, the discovery of the new continent of microRNAs, the metapopulation theory, the ability to trace gene flow over long distances, imply otherwise consider the properties of a genetically modified organism, whether or not dedicated to the dispersion in the environment. A symposium organized last february in Paris, in the framework of the ANR GMOs was designed to take the measure of these transformations of the paradigms of biology and to let clear how these results force to rethink the impacts of GMOs in the light of the new biology.

  18. Time-series of turbulent flow in a pipe measured with PIV

    DEFF Research Database (Denmark)

    Meyer, Knud Erik; Westerweel, Jerry

    1999-01-01

    Measurements with particle image velocimetry of the fully developed flow of water in a pipe with a Reynolds number of 5370 are presented. The measurements are taken with a frame rate high enough to capture the same flow structure on 2 or 3 frames. This makes it possible to estimate advection...

  19. On the Radial Structure of Radiatively Inefficient Accretion Flows with Convection

    CERN Document Server

    Abramowicz, M A; Quataert, E; Narayan, R; Abramowicz, Marek Artur; Igumenshchev, Igor V.; Quataert, Eliot; Narayan, Ramesh

    2002-01-01

    We consider the radial structure of radiatively inefficient hydrodynamic accretion flows around black holes. We show that low-viscosity flows consist of two zones: an outer convection-dominated zone and an inner advection-dominated zone. The transition between these two zones occurs at ~50 Schwarzschild radii.

  20. Metabolic engineering: the ultimate paradigm for continuous pharmaceutical manufacturing.

    Science.gov (United States)

    Yadav, Vikramaditya G; Stephanopoulos, Gregory

    2014-07-01

    Research and development (R&D) expenditures by pharmaceutical companies doubled over the past decade, yet candidate attrition rates and development times rose markedly during this period. Understandably, companies have begun downsizing their pipelines and diverting investments away from R&D in favor of manufacturing. It is estimated that transitioning to continuous manufacturing could enable companies to compete for a share in emerging markets. Accordingly, the model for continuous manufacturing that has emerged commences with the conversion of late-stage intermediates into the active pharmaceutical ingredient (API) in a series of continuous flow reactors, followed by continuous solid processing to form finished tablets. The use of flow reactions for API synthesis will certainly generate purer products at higher yields in shorter times compared to equivalent batch reactions. However, transitioning from batch to flow configuration simply alleviates transport limitations within the reaction milieu. As the catalogue of reactions used in flow syntheses is a subset of batch-based chemistries, molecules such as natural products will continue to evade drug prospectors. Also, it is uncertain whether flow synthesis can deliver improvements in the atom and energy economies of API production at the scales that would achieve the levels of revenue growth targeted by companies. Instead, it is argued that implementing metabolic engineering for the production of oxidized scaffolds as gateway molecules for flow-based addition of electrophiles is a more effective and scalable strategy for accessing natural product chemical space. This new paradigm for manufacturing, with metabolic engineering as its engine, would also permit rapid optimization of production variables and allow facile scale-up from gram to ton scale to meet material requirements for clinical trials, thus recasting manufacturing as a tool for discovery.

  1. A modified TVD scheme for the advection of two or more variables with consideration for their sum

    Science.gov (United States)

    Mercier, Christophe Y. M.; Delhez, Eric J. M.

    2010-10-01

    Total variation diminishing (TVD) advection schemes are known to produce results that are free from some of the numerical artifacts (no overshooting, no spurious oscillation, small diffusion) that can spoil the physical significance of the results. When two or more tracers are advected separately using a TVD scheme, the sum of these variables can however exhibit some inappropriate behaviors. The total variation of the sum will not necessarily be non- increasing and local artificial oscillations and extrema can appear. We show that these can be avoided with only minor perturbations of the original solution by adjusting the slope limiters used for the different variables. If the sum of these variables has some physical significance, for instance as refinement of a larger model compartment, the correction procedure introduced in this paper should be used to ensure a physically meaningful solution.

  2. A study of a WENO-TVD finite volume scheme for the numerical simulation of atmospheric advective and convective phenomena

    CERN Document Server

    Kalise, Dante

    2011-01-01

    We present a WENO-TVD scheme for the simulation of atmospheric phenomena. The scheme considers a spatial discretization via a second-order TVD flux based upon a flux-centered limiter approach, which makes use of high-order accurate extrapolated values arising from a WENO reconstruction procedure. Time discretization is performed with a third order RK-TVD scheme, and splitting is used for the inclusion of source terms. We present a comprehensive performance study of the method in atmospheric applications involving advective and convective motion. We present a set of tests for space-dependent linear advection, where we assess convergence and robustness with respect to the parameters of the scheme. We apply the method to approximate the 2D Euler equations in a series of tests for atmospheric convection.

  3. Groundwater age, life expectancy and transit time distributions in advective-dispersive systems: 1. Generalized reservoir theory

    CERN Document Server

    Cornaton, F; 10.1016/j.advwatres.2005.10.009

    2011-01-01

    We present a methodology for determining reservoir groundwater age and transit time probability distributions in a deterministic manner, considering advective-dispersive transport in steady velocity fields. In a first step, we propose to model the statistical distribution of groundwater age at aquifer scale by means of the classical advection-dispersion equation for a conservative and nonreactive tracer, associated to proper boundary conditions. The evaluated function corresponds to the density of probability of the random variable age, age being defined as the time elapsed since the water particles entered the aquifer. An adjoint backward model is introduced to characterize the life expectancy distribution, life expectancy being the time remaining before leaving the aquifer. By convolution of these two distributions, groundwater transit time distributions, from inlet to outlet, are fully defined for the entire aquifer domain. In a second step, an accurate and efficient method is introduced to simulate the tr...

  4. Gamma irradiation test report of simulated grout specimens for gas generation/liquid advection

    International Nuclear Information System (INIS)

    This report presents the results from an irradiation test performed on four specimens of grout that were fabricated from synthetic Double Shell Slurry Feed (DSSF) liquid waste. The objective was to investigate the radiolytic generation of gases and the potential for advective rejection of waste liquids from the grout matrix and to provide experimental information for the validation of the C-Cubed calculated model. It has been demonstrated that a number of gases can be formed within the grout due to radiolytic decomposition of various chemical components that make up the grout. This observation leads to the conjecture that the potential exists for the rejection of a portion of the 60 vol% free liquid from the grout matrix driven by pressurization by these gases. It was found that, for the specimen geometries used in this test series, and for peak radiation dose accumulation rates on the order of 4 to 60 times of the initial rate expected in the grout vaults (300 Rads/hr), no liquid rejection was observed from 2% to 35% of the target exposure expected in the grout vaults (1E+08 Rads). When the irradiation rate exceeded the projected grout vault dose rate by a factor of 200 a small amount of liquid rejection was observed from one of two specimens that had received 20% more than the goal exposure. Because of the differences in the magnitudes of the relative radiation field strengths between this study and an actual grout vault, it is concluded that the potential for liquid rejection by internal gas pressurization from presently configured grout waste forms is very low for the expected conditions

  5. Advective heat transport in the upper carbonate aquifer beneath Winnipeg, Manitoba

    Energy Technology Data Exchange (ETDEWEB)

    Ferguson, G.A.G.; Woodbury, A.D. [Manitoba Univ., Winnipeg, MB (Canada). Dept. of Civil Engineering

    2003-07-01

    Air conditioning and industrial cooling in Winnipeg, Manitoba requires large volumes of groundwater, with the bulk of this water pumped from the Upper Carbonate Aquifer. Pumping takes place at the erosional surface of several dipping Paleozoic carbonate units beneath the city. To prevent excessive drawdown, wastewater from these processes is reinjected into the aquifer. Heat loading from the surface, combined with this practice, leads to the creation of areas of elevated temperature within the Upper Carbonate Aquifer. An industrial area located in eastern Winnipeg is the site of the largest of these anomalies, where the aquifer's permeability is enhanced by the presence of conduits and discrete fractures. The use of numerical modeling showed that the greatest temperature anomalies occur where there are very high permeabilities, especially in the form of conduits and discrete fractures. Groundwater velocities are increased by these factors, and could result in the creation of plumes of heated water. Plumes of heated water are less likely to occur where the aquifer is thicker and conduits are absent, due to advective heat transport becoming focused between the injection well and the production well in lower permeability situations. These areas also correspond to the areas of decreased transmissivity in several parts of the Upper Carbonate Aquifer, and may not be capable of producing the required volumes of groundwater for thermal applications. Taking into account these permeability features in planning and design of non-consumptive groundwater systems in the Upper Carbonate Aquifer helps to minimize both drawdown and changes in aquifer temperature. 8 refs., 2 figs.

  6. Abrupt cooling associated with the oceanic Rossby wave and lateral advection during CINDY2011

    Science.gov (United States)

    Seiki, Ayako; Katsumata, Masaki; Horii, Takanori; Hasegawa, Takuya; Richards, Kelvin J.; Yoneyama, Kunio; Shirooka, Ryuichi

    2013-10-01

    The cooperative Indian Ocean experiment on intraseasonal variability in the Year 2011 (CINDY2011) was conducted to capture atmospheric and oceanic characteristics of the Madden-Julian Oscillation (MJO) in the central Indian Ocean from late 2011 to early 2012. During CINDY2011, the research vessel (R/V) MIRAI stayed at 8°S, 80.5°E for two months during the special observing period (SOP). Intraseasonal convection associated with the MJO was organized in the central Indian Ocean in late October and late November during the SOP. In the middle of November, both sea surface temperature (SST) and mixed layer temperature decreased suddenly when cold low salinity water intruded into the upper layer around the R/V MIRAI. This intrusion was accompanied by a surface current change from southwestward to westward/west-northwestward associated with the passage of the annual oceanic downwelling Rossby wave. The mixed layer heat budget analysis shows that horizontal advection plays an important role in the abrupt cooling whereas the net surface heat flux cannot account for the cooling. This is an interesting result because the associated downwelling Rossby wave is usually considered to increase SST through a reduction of entrainment cooling. In addition, for the second MJO event convection was activated around 20 November over the central north and equatorial Indian Ocean but not in the south. It is suggested that the cooler surface waters (as seen at the location of the R/V MIRAI) tended to suppress the initial atmospheric convection, resulting in the lagged convective onset in the end of November over the central south Indian Ocean.

  7. Chaotic Advection in Multi-component Melts for the Manufacture of Composite Materials

    Science.gov (United States)

    Zumbrunnen, David

    2011-10-01

    Several forces arise when different liquids are placed into contact. The relative importance of these forces depends on the sizes and shapes of liquid domains and also on molecular characteristics of the liquids. When the liquids are agitated and in the absence of interdiffusion, a composite structure results that is defined by the spatial extent and size of each liquid domain in the presence of the other. Shaking a bottle with about equal parts of water and oil gives a structure that resembles a household sponge, for example. If the oil volume is much smaller than the water volume, oil droplets result instead. In polymer blends and composites, the structure can have feature sizes at the micron scale or smaller. Little has been known about the variety of structural types that can be formed because current information is based on mixing machinery that intrinsically restricts structural outcomes. This shortcoming has important consequences because physical properties of composite materials obtained by solidifying the structured liquids depend appreciably on structure characteristics. A recent approach to overcome this shortcoming makes use of chaotic advection to establish conditions that organize liquid domains into numerous thin layers. A multi-layer construction undergoes morphological changes in situ. Progressive structure development arises, whereby a specific structure leads in sequence to a morphologically different structure. A new manufacturing technology has resulted which allows control of the internal structure in extruded plastic materials. Micro- and nanostructured materials have been obtained. On-line process control allows rapid optimization of physical properties. In this presentation, the underlying physics will be described, examples of novel materials and their applications will be shown, and research opportunities will be highlighted.

  8. Characteristics of the surface layer above a row crop in the presence of local advection

    Energy Technology Data Exchange (ETDEWEB)

    Figuerola, P.I. [Universidad de Buenos Aires, Buenos Aires (Argentina)]. E-mail: figuerol@at.fcen.uba.ar; Berliner, P.R. [Blaustein Institute for Desert Research, Ben-Gurion University of the Negev (Israel)

    2006-04-15

    In some arid land, the irrigated fields are not contiguous and are surrounded by large patches of bare land. During the summer time and rainless season, the solar radiation flux is high and the surface temperature during daylight in the dry bare areas, is much higher than that of the air. The sensible heat generated over these areas may be advected to the irrigated fields. The crops are usually planted in rows and the irrigation systems used (trickle) do not wet the whole surface, the dry bare soil between the rows may develop high soil surface temperatures and lead to convective activity inside the canopy above the bare soil. Advection from the surrounding fields and convective activity inside the canopy affect the layer above the crop. We studied the surface layer above an irrigated tomato field planted in Israel's Negev desert. The crop was planted in rows, trickle irrigated and the distance between the outer edges of two adjacent rows was 0.36 m at the time of measurement. The gradients in temperature and water vapor pressure were obtained at various heights above the canopy using a Bowen ratio machine. The residual in the energy balance equation was used as a criterion to determine the equilibrium layer. During the morning, unstable conditions prevail, and the equilibrium layer was between Z/h {approx} 1.9 and 2.4. In some particular circumstances, in the late morning, the bare soil between the rows reached extremely high temperatures and during conditions with low wind speeds free convection was identified. During these hours the residuals of the energy budget to the heights Z/h = 1.5 and 2.4 were significantly different from zero and an extremely large variability was evident for the Z/h = 3.2 layer. Local advection took place during the afternoon resulting in an increase in the stability of the uppermost measured layer and propagated slowly downwards. The equilibrium layer was between Z/h {approx} 1.5 to 2.4. The residuals were significantly different

  9. Late Glacial – Holocene climate variability and sedimentary environments on northern continental shelves Zonal and meridional Atlantic Water advection

    OpenAIRE

    Sørensen, Steffen Aagaard

    2011-01-01

    The overall objective for this PhD-study was to further advance the understanding of the oceanographic variability and development in the Nordic Seas during the Late Glacial and the Holocene and towards the present. The focus is specifically on the poleward Atlantic Water advection along the continental margins of Norway, into the SW Barents Sea and along the West Spitsbergen slope. Four high resolution sediment cores retrieved from northern continental shelve allowed examination of spatial a...

  10. The roles of vertical advection and eddy diffusion in the equatorial mesospheric semi-annual oscillation (MSAO

    Directory of Open Access Journals (Sweden)

    R. L. Gattinger

    2013-08-01

    Full Text Available Observations of the mesospheric semi-annual oscillation (MSAO in the equatorial region have been reported dating back several decades. Seasonal variations in both species densities and airglow emissions are well documented. The extensive observations available offer an excellent case study for comparison with model simulations. A broad range of MSAO measurements is summarised with emphasis on the 80–100 km region. The objective here is not to address directly the complicated driving forces of the MSAO, but rather to employ a combination of observations and model simulations to estimate the limits of some of the underlying dynamical processes. Photochemical model simulations are included for near-equinox and near-solstice conditions, the two times with notable differences in the observed MSAO parameters. Diurnal tides are incorporated in the model to facilitate comparisons of observations made at different local times. The roles of water vapour as the "driver" species and ozone as the "response" species are examined to test for consistency between the model results and observations. The simulations suggest the interactions between vertical eddy diffusion and background vertical advection play a significant role in the MSAO phenomenon. Further, the simulations imply there are rigid limits on vertical advection rates and eddy diffusion rates. For August at the Equator, 90 km altitude, the derived eddy diffusion rate is approximately 1 × 106 cm2 s−1 and the vertical advection is upwards at 0.8 cm s−1. For April the corresponding values are 4 × 105 cm2 s−1 and 0.1 cm s−1. These results from the current 1-D model simulations will need to be verified by a full 3-D simulation. Exactly how vertical advection and eddy diffusion are related to gravity wave momentum as discussed by Dunkerton (1982 three decades ago remains to be addressed.

  11. Advective Heat Transport in an Unconfined Aquifer Induced by the Field Injection of an Open-Loop Groundwater Heat Pump

    OpenAIRE

    Stefano L. Russo; Glenda Taddia

    2010-01-01

    Problem statement: The increasing diffusion of low-enthalpy geothermal open-loop Groundwater Heat Pumps (GWHP) providing buildings air conditioning requires a careful assessment of the overall effects on groundwater system, especially in the urban areas. The impact on the groundwater temperature in the surrounding area of the re-injection well is directly linked to the aquifer properties. Physical processes affecting heat transport within an aquifer include advection (or convection) and hydro...

  12. Crouzeix-Raviart MsFEM with Bubble Functions for Diffusion and Advection-Diffusion in Perforated Media

    OpenAIRE

    Degond, Pierre; Lozinski, Alexei; Muljadi, Bagus Putra; Narski, Jacek

    2013-01-01

    The adaptation of Crouzeix - Raviart finite element in the context of multiscale finite element method (MsFEM) is studied and implemented on diffusion and advection-diffusion problems in perforated media. It is known that the approximation of boundary condition on coarse element edges when computing the multiscale basis functions critically influences the eventual accuracy of any MsFEM approaches. The weakly enforced continuity of Crouzeix - Raviart function space across element edges leads t...

  13. Reinforcing the Afrocentric Paradigm: A Theoretical Project

    Science.gov (United States)

    Sams, Timothy E.

    2010-01-01

    Thomas Kuhn's 1962 groundbreaking work, "The Scientific Revolution," established the process for creating, and the components of, a disciplinary paradigm. This "scientific revolution" has evolved to become the standard for determining a field's claim to disciplinary status. In 2001 and 2003, Ama Mazama, used Kuhn's model to establish the…

  14. A Review of Process Modeling Language Paradigms

    Institute of Scientific and Technical Information of China (English)

    MA Qin-hai; GUAN Zhi-min; LI Ying; ZHAO Xi-nan

    2002-01-01

    Process representation or modeling plays an important role in business process engineering.Process modeling languages can be evaluated by the extent to which they provide constructs useful for representing and reasoning about the aspects of a process, and subsequently are chosen for a certain purpose.This paper reviews process modeling language paradigms and points out their advantages and disadvantages.

  15. Toward an Ecological Paradigm in Adventure Programming

    Science.gov (United States)

    Beringer, Almut

    2004-01-01

    Many forms of adventure therapy, in particular wilderness therapy, rely on challenges in the outdoors to achieve objectives of client change. While nature is drawn on as a medium for therapy and healing, some adventure therapists give nature little if any mention when it comes to explaining therapeutic success. The dominant paradigm in psychology…

  16. Augmenting the ADDIE Paradigm for Instructional Design

    Science.gov (United States)

    Ni, Xiaopeng; Branch, Robert Maribe

    2008-01-01

    The authors discuss topics appropriate for augmenting the ADDIE paradigm for instructional design. The topics selected are based on data from a study of working professionals who successfully completed an instructional design and technology certificate program and who identified related topics that they regarded as beneficial. The participants…

  17. New Paradigms for Computer Aids to Invention.

    Science.gov (United States)

    Langston, M. Diane

    Many people are interested in computer aids to rhetorical invention and want to know how to evaluate an invention aid, what the criteria are for a good one, and how to assess the trade-offs involved in buying one product or another. The frame of reference for this evaluation is an "old paradigm," which treats the computer as if it were paper, but…

  18. Empirical Testing of an Affective Learning Paradigm.

    Science.gov (United States)

    Asmus, Edward P., Jr.

    1980-01-01

    This investigation of a college music course examined the effectiveness of a cyclical affective learning paradigm based on the premise that student affect toward a course of instruction will dictate, in part, cognitive performance. Results suggest that teachers would be better advised to concentrate on cognitive instruction than on affect.…

  19. Haptics in computer music : a paradigm shift

    CERN Document Server

    Castagné, Nicolas; Florens, Jean-Loup; Luciani, Annie

    2010-01-01

    With an historical point of view combined with a bibliographic overview, the article discusses the idea that haptic force feedback transducers correspond with a paradigm shift in our real-time tools for creating music. So doing, il shows that computer music may be regarded as a major field of research and application for haptics.

  20. Has the Education Paradigm Begun to Shift?

    Science.gov (United States)

    Chadwick, Clifton B.

    2014-01-01

    The author reviews various elements of what may be considered as evidence that the long-awaited shift in the education paradigm is actually happening. Concepts like student-centered learning, attainment-based evaluation, knowledge-based constructivism, and effort-based intelligence are growing, are being more widely recognized as important, and…

  1. Production planning development and paradigm integration

    Directory of Open Access Journals (Sweden)

    Galina Ledneva

    2009-12-01

    Full Text Available The paper reviews principles of different concepts of enterprise management including a theory of constrains, a Balanced Scorecard, lean production, Six Sigma. The authors believe that creating some mix or integration of these paradigms can bring extraordinary effect for production management. As example the modified Balanced Scorecard based on constraints and its application on Magnitorsk metallurgical enterprise in Russia is described.

  2. Operationalizing Social Justice Counseling: Paradigm to Practice

    Science.gov (United States)

    Lewis, Judith A.

    2011-01-01

    Social justice counseling, like all humanistic models, recognizes the dignity of each human being, affirms the right of all people to choose and work toward their own goals, and asserts the importance of service to community. The social justice paradigm brings a special emphasis on the role of the environment. (Contains 1 figure and 1 table.)

  3. A new paradigm for doing Reformed dogmatics

    Directory of Open Access Journals (Sweden)

    G. J. Spykman

    1992-06-01

    Full Text Available When discussing Reformational Theology: A New Paradigm for Doing Dogmatics some people may call it my opus magnum. Perhaps time 'will tell. The book has only recently - early 1992 - entered the marketplace of theological ideas. How critic readers and reviewers respond will go a long way toward settling the case.

  4. Den postmoderna stadens två paradigm

    DEFF Research Database (Denmark)

    Nielsen, Tom

    2005-01-01

    the attention of politicians, planners and architects today is focused on the individual, not the collective. But the policy of the third way has no counterpart in an urbanism torn between two paradigms. Tom Nielsen paints the picture of what has to urban development since the welfare state...

  5. ACCOUNTING PARADIGMS WHICH FAVOR HISTORICAL COST

    OpenAIRE

    Valentin Gabriel CRISTEA

    2014-01-01

    Henning Kirkegaard shows that the evolution of accounting is to shift from one paradigm to another . Business continuity perspective should guide the company into the future , without confine it exclusively in the past. Accounting in its classical form , however, can not be dissociated from the historical cost evaluation .

  6. 06472 Abstracts Collection - XQuery Implementation Paradigms

    NARCIS (Netherlands)

    Boncz, Peter A.; Grust, Torsten; Siméon, Jerome; Keulen, van Maurice; Boncz, P.A.; Grust, T.; Siméon, J.; Keulen, van M.

    2007-01-01

    From 19.11.2006 to 22.11.2006, the Dagstuhl Seminar 06472 ``XQuery Implementation Paradigms'' was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were disc

  7. 06472 Abstracts Collection - XQuery Implementation Paradigms

    NARCIS (Netherlands)

    Boncz, P.A.; Grust, T.; Siméon, J.; Keulen, M. van

    2007-01-01

    From 19.11.2006 to 22.11.2006, the Dagstuhl Seminar 06472 "XQuery Implementation Paradigms" was held in the International Conference and Research Center (IBFI), Schloss Dagstuhl. During the seminar, several participants presented their current research, and ongoing work and open problems were discus

  8. Redesigning Higher Education: Embracing a New Paradigm

    Science.gov (United States)

    Watson, William R.; Watson, Sunnie Lee

    2014-01-01

    Higher education is under enormous pressure to transform itself and embrace a new paradigm. Operating under an outdated model that no longer aligns with the realities of modern society, institutions of higher education are recognizing the need to drastically remake themselves or possibly cease to exist. This article explores the current landscape…

  9. Dark matter and the neutrino portal paradigm

    CERN Document Server

    González-Macías, Vannia; Wudka, José

    2016-01-01

    A simple extension of the Standard Model (SM) that provides an explicit realization of the dark-matter (DM) neutrino-portal paradigm is presented. The leading interactions between the dark sector, containing scalars and relic fermions, and the SM involve neutrinos. This model meets all observational constraints.

  10. ACCOUNTING PARADIGMS WHICH FAVOR HISTORICAL COST

    Directory of Open Access Journals (Sweden)

    Valentin Gabriel CRISTEA

    2014-05-01

    Full Text Available Henning Kirkegaard shows that the evolution of accounting is to shift from one paradigm to another . Business continuity perspective should guide the company into the future , without confine it exclusively in the past. Accounting in its classical form , however, can not be dissociated from the historical cost evaluation .

  11. Transparency and public participation - the need for a new paradigm

    International Nuclear Information System (INIS)

    Increasing openness, public participation and transparency are considered important for decision-making in public issues. Transparency serves two purposes; for the awareness of decision-makers and for public insight and influence. However, the increasing complexity of today's society, the complexity of decision processes and the complexity of the underlying factual basis are all factors that work against transparency and participation. Furthermore, the decision-making context in controversial issues is not only set up by the factual basis provided by the experts, but also by stakeholder pressure groups, lobbyists and extensive media coverage. The seemingly unlimited availability of information on the Internet and the continuous information flow in TV channels does not make it easier for the layman to get insight and clarity. This paper starts with a discussion about the expert role, a definition of transparency and three rationales for public participation. The two areas of nuclear waste disposal and biotechnology are then used to illustrate problems with transparency, but also initiatives for improving the situation. Frameworks for the evaluation of participative processes are described, as well as the role of media in making complex issues transparent. A central theme in the paper is the need for a shift from the 'experts-agenda paradigm' to the 'values-first paradigm'. We end up with suggestions for how transparency and public participation can be enhanced for the sake of democratic development: 1. We must have a multi-perspective starting point. Participants in participative processes should represent a broad spectrum of views. People must hear each other out to achieve common understanding that there are a variety of legitimate perspectives to consider. 2. The RISCOM model has been shown both innovative and workable in the nuclear waste area. We should extend its application to other areas, biotechnology being one primary candidate. 3. Experiences from

  12. Transparency and public participation - the need for a new paradigm

    Energy Technology Data Exchange (ETDEWEB)

    Andersson, Kjell [Karinta-Konsult, Taeby (Sweden)

    2001-07-01

    Increasing openness, public participation and transparency are considered important for decision-making in public issues. Transparency serves two purposes; for the awareness of decision-makers and for public insight and influence. However, the increasing complexity of today's society, the complexity of decision processes and the complexity of the underlying factual basis are all factors that work against transparency and participation. Furthermore, the decision-making context in controversial issues is not only set up by the factual basis provided by the experts, but also by stakeholder pressure groups, lobbyists and extensive media coverage. The seemingly unlimited availability of information on the Internet and the continuous information flow in TV channels does not make it easier for the layman to get insight and clarity. This paper starts with a discussion about the expert role, a definition of transparency and three rationales for public participation. The two areas of nuclear waste disposal and biotechnology are then used to illustrate problems with transparency, but also initiatives for improving the situation. Frameworks for the evaluation of participative processes are described, as well as the role of media in making complex issues transparent. A central theme in the paper is the need for a shift from the 'experts-agenda paradigm' to the 'values-first paradigm'. We end up with suggestions for how transparency and public participation can be enhanced for the sake of democratic development: 1. We must have a multi-perspective starting point. Participants in participative processes should represent a broad spectrum of views. People must hear each other out to achieve common understanding that there are a variety of legitimate perspectives to consider. 2. The RISCOM model has been shown both innovative and workable in the nuclear waste area. We should extend its application to other areas, biotechnology being one primary candidate. 3

  13. The bereitschaftspotential paradigm in investigating voluntary movement organization in humans using magnetoencephalography (MEG).

    Science.gov (United States)

    Kristeva-Feige, R; Rossi, S; Feige, B; Mergner, T; Lücking, C H; Rossini, P M

    1997-02-01

    In 1965, Kornhuber and Deecke first described the bereitschaftspotential (BP), a paradigm for investigating the organization of voluntary movement in humans, using electroencephalography (EEG). This paradigm has since been used in many studies for investigating motor control in healthy humans and patients. Over the last years, the advantages of magnetoencephalography (MEG) have been applied to the BP paradigm by a number of researchers. The main advantage of magnetoencephalography over electroencephalography is that MEG has a higher localization accuracy. This is due to the fact that the different structures of the head (brain, liquor cerebrospinalis, skull and scalp) influence the magnetic fields less than the volume current flow that causes the EEG. Additionally, the MEG is reference free, so that the localization of sources with a given precision is easier for MEG than it is for EEG. The present protocol shows in detail how the bereitschaftspotential paradigm can be applied using MEG. Some additional paradigms for investigating motor plasticity, somatosensory gating, Parkinson disease, and the efference copy theory are suggested as well.

  14. Implementation of the Semi-Lagrangian Advection Scheme on a Quasi-Uniform Overset Grid on a Sphere

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The semi-Lagrangian advection scheme is implemented on a new quasi-uniform overset (Yin-Yang) grid on the sphere. The Yin-Yang grid is a newly developed grid system in spherical geometry with two perpendicularly-oriented latitude-longitude grid components (called Yin and Yang respectively) that overlapp each other, and this effectively avoids the coordinate singularity and the grid convergence near the poles. In this overset grid, the way of transferring data between the Yin and Yang components is the key to maintaining the accuracy and robustness in numerical solutions. A numerical interpolation for boundary data exchange, which maintains the accuracy of the original advection scheme and is computationally efficient, is given in this paper. A standard test of the solid-body advection proposed by Williamson is carried out on the Yin-Yang grid. Numerical results show that the quasi-uniform Yin-Yang grid can get around the problems near the poles, and the numerical accuracy in the original semi-Lagrangian scheme is effectively maintained in the Yin-Yang grid.

  15. In situ observations of dehydrated air parcels advected horizontally in the Tropical Tropopause Layer of the western Pacific

    Directory of Open Access Journals (Sweden)

    F. Hasebe

    2007-01-01

    Full Text Available Water vapor observations by chilled-mirror hygrometers were conducted at Bandung, Indonesia (6.90° S, 107.60° E and Tarawa, Kiribati (1.35° N, 172.91° E in December 2003 to examine the efficiency of dehydration during horizontal advection in the tropical tropopause layer (TTL. Trajectory analyses based on bundles of isentropic trajectories suggest that the modification of air parcels' identity due to irreversible mixing by the branching-out and merging-in of nearby trajectories is found to be an important factor, in addition to the routes air parcels follow, for interpreting the water vapor concentrations observed by chilled-mirror frostpoint hygrometers in the TTL. Clear correspondence between the observed water vapor concentration and the estimated temperature history of air parcels is found showing that drier air parcels were exposed to lower temperatures than were more humid ones during advection. Although the number of observations is quite limited, the water content in the observed air parcels on many occasions was more than that expected from the minimum saturation mixing ratio during horizontal advection prior to sonde observations.

  16. Advection and starvation cause krill (Euphausia pacifica) decreases in 2005 Northern California coastal populations: Implications from a model study

    Science.gov (United States)

    Dorman, Jeffrey G.; Powell, Thomas M.; Sydeman, William J.; Bograd, Steven J.

    2011-02-01

    A decrease in krill abundance during 2005 in regions of the California Current has been hypothesized to have had immediate (seabird) and long-term (salmon) negative impacts on upper trophic level predators. We use a suite of coupled models to examine the population biology and spatial and temporal distribution of the krill species Euphausia pacifica during the winter/spring of 2001, a “normal” year, and 2005, an “anomalous” year, to determine if this hypothesis is supported mechanistically. Ocean conditions were simulated using the Regional Ocean Modeling System (ROMS), which forced an individual-based model parameterized to simulate the population biology of E. pacifica. Poleward transport during winter 2005 advected particles north of Cape Mendocino, away from seabirds and salmon feeding in the Gulf of the Farallons region. Few of the particles that were advected north in 2005 returned to their region of release throughout the model run time (200 days). Moreover, the “condition” of those particles remaining within the domain was poor in 2005, with greater mortality from starvation and a decreased mean particle weight. Our results indicate that both physical processes (anomalous northern advection) and biological processes (greater starvation and less weight per individual) contributed to reduced krill availability to predators in the northern California region during 2005, and that the productivity and survival of seabirds and salmonids is dependent on krill during critical life history stages.

  17. Analytical solutions to the fractional advection-diffusion equation with time-dependent pulses on the boundary

    Science.gov (United States)

    Rubbab, Qammar; Mirza, Itrat Abbas; Qureshi, M. Zubair Akbar

    2016-07-01

    The time-fractional advection-diffusion equation with Caputo-Fabrizio fractional derivatives (fractional derivatives without singular kernel) is considered under the time-dependent emissions on the boundary and the first order chemical reaction. The non-dimensional problem is formulated by using suitable dimensionless variables and the fundamental solutions to the Dirichlet problem for the fractional advection-diffusion equation are determined using the integral transforms technique. The fundamental solutions for the ordinary advection-diffusion equation, fractional and ordinary diffusion equation are obtained as limiting cases of the previous model. Using Duhamel's principle, the analytical solutions to the Dirichlet problem with time-dependent boundary pulses have been obtained. The influence of the fractional parameter and of the drift parameter on the solute concentration in various spatial positions was analyzed by numerical calculations. It is found that the variation of the fractional parameter has a significant effect on the solute concentration, namely, the memory effects lead to the retardation of the mass transport.

  18. A Study on the Effect of Fracture Aperture Variability on Advective Transport in aFractured Shale using Discrete Fracture Network Modeling

    Science.gov (United States)

    Makedonska, N.; Karra, S.; Painter, S. L.; Viswanathan, H.; Gable, C. W.

    2014-12-01

    's Manual: A Massively Parallel Reactive Flow andTransport Model for describing Surface and Subsurface Processes, 2014. [3] Makedonska N., Painter S.L., Karra S., and Gable C.W., NumericalExperiments on Advective Transport in Large Three-Dimensional DFNs,Abstract H53A-1398 ,2013, AGU, San-Francisco, CA, 9-13 Dec.

  19. Aspects of numerical and representational methods related to the finite-difference simulation of advective and dispersive transport of freshwater in a thin brackish aquifer

    Science.gov (United States)

    Merritt, M.L.

    1993-01-01

    The simulation of the transport of injected freshwater in a thin brackish aquifer, overlain and underlain by confining layers containing more saline water, is shown to be influenced by the choice of the finite-difference approximation method, the algorithm for representing vertical advective and dispersive fluxes, and the values assigned to parametric coefficients that specify the degree of vertical dispersion and molecular diffusion that occurs. Computed potable water recovery efficiencies will differ depending upon the choice of algorithm and approximation method, as will dispersion coefficients estimated based on the calibration of simulations to match measured data. A comparison of centered and backward finite-difference approximation methods shows that substantially different transition zones between injected and native waters are depicted by the different methods, and computed recovery efficiencies vary greatly. Standard and experimental algorithms and a variety of values for molecular diffusivity, transverse dispersivity, and vertical scaling factor were compared in simulations of freshwater storage in a thin brackish aquifer. Computed recovery efficiencies vary considerably, and appreciable differences are observed in the distribution of injected freshwater in the various cases tested. The results demonstrate both a qualitatively different description of transport using the experimental algorithms and the interrelated influences of molecular diffusion and transverse dispersion on simulated recovery efficiency. When simulating natural aquifer flow in cross-section, flushing of the aquifer occurred for all tested coefficient choices using both standard and experimental algorithms. ?? 1993.

  20. Is the Coastal Ocean a Source of Mercury to Marine Advective Fog

    Science.gov (United States)

    Heim, W. A.; Weiss-Penzias, P. S.; Fernandez, D.; Byington, A.; Bonnema, A.; Beebe, C.; Chiswell, H.; Olson, A.; Coale, K. H.

    2014-12-01

    Marine advective fog is a common feature along the California coast during the summer season. This fog provides an important water source to many endemic fauna and flora. Studies are underway to better understand the chemical makeup of Pacific marine fog as it is an important input to the hydrologic cycle. We report results from our study focused on investigating the potential for coastal ocean upwelling to contribute volatile organic mercury to the overlying atmosphere where it could be incorporated into cloud droplets as monomethyl mercury (MMHg). Preliminary research by this group has indicated that fog water inputs to certain coastal locations may contribute up to 99% of the MMHg flux to land compared to the MMHg flux in rain. Mercury measurements, including total mercury (Hgt), MMHg, elemental mercury (Hg0), and dimethyl mercury (DMHg), were made to unfiltered water collected from depth profiles at 12 stations from Big Sur to Trinidad Head over the California shelf during summer 2014. Profiles of Hgt ranged from 0.3-2.4 pM and were similar to other reported measurements of Hgt for the North Pacific. A large range in concentration was observed for MMHg (10-540 fM) with elevated values generally occurring below the oxycline (>50m). Concentrations of Hg0 were 0.06 to 0.57 pM with elevated concentrations at depth relative to surface values. Depth profiles of DMHg were similar to MMHg and concentrations were measured from 10-295 fM with highest concentrations observed below the oxycline. Surface concentrations of DMHg averaged 40 ± 22 fM. Given the observed profiles for DMHg and the fact that it is sparingly soluble in water, a net flux of DMHg to the atmosphere is likely occurring. Based on these findings and the fact that MMHg and DMHg concentrations in the coastal ocean were highest in the low oxygen zone, we speculate that mercury is methylated in the water column and/or sediments as DMHg and that this water is upwelled seasonally in the coastal zones and

  1. iCFD: Interpreted Computational Fluid Dynamics - Degeneration of CFD to one-dimensional advection-dispersion models using statistical experimental design - The secondary clarifier.

    Science.gov (United States)

    Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat; Plósz, Benedek Gy

    2015-10-15

    The present study aims at using statistically designed computational fluid dynamics (CFD) simulations as numerical experiments for the identification of one-dimensional (1-D) advection-dispersion models - computationally light tools, used e.g., as sub-models in systems analysis. The objective is to develop a new 1-D framework, referred to as interpreted CFD (iCFD) models, in which statistical meta-models are used to calculate the pseudo-dispersion coefficient (D) as a function of design and flow boundary conditions. The method - presented in a straightforward and transparent way - is illustrated using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor screening study and system understanding, 50 different sets of design and flow conditions are selected using Latin Hypercube Sampling (LHS). The boundary condition sets are imposed on a 2-D axi-symmetrical CFD simulation model of the SST. In the framework, to degenerate the 2-D model structure, CFD model outputs are approximated by the 1-D model through the calibration of three different model structures for D. Correlation equations for the D parameter then are identified as a function of the selected design and flow boundary conditions (meta-models), and their accuracy is evaluated against D values estimated in each numerical experiment. The evaluation and validation of the iCFD model structure is carried out using scenario simulation results obtained with parameters sampled from the corners of the LHS experimental region. For the studied SST, additional iCFD model development was carried out in terms of (i) assessing different density current sub-models; (ii) implementation of a combined flocculation, hindered, transient and compression settling velocity function; and (iii

  2. iCFD: Interpreted Computational Fluid Dynamics - Degeneration of CFD to one-dimensional advection-dispersion models using statistical experimental design - The secondary clarifier.

    Science.gov (United States)

    Guyonvarch, Estelle; Ramin, Elham; Kulahci, Murat; Plósz, Benedek Gy

    2015-10-15

    The present study aims at using statistically designed computational fluid dynamics (CFD) simulations as numerical experiments for the identification of one-dimensional (1-D) advection-dispersion models - computationally light tools, used e.g., as sub-models in systems analysis. The objective is to develop a new 1-D framework, referred to as interpreted CFD (iCFD) models, in which statistical meta-models are used to calculate the pseudo-dispersion coefficient (D) as a function of design and flow boundary conditions. The method - presented in a straightforward and transparent way - is illustrated using the example of a circular secondary settling tank (SST). First, the significant design and flow factors are screened out by applying the statistical method of two-level fractional factorial design of experiments. Second, based on the number of significant factors identified through the factor screening study and system understanding, 50 different sets of design and flow conditions are selected using Latin Hypercube Sampling (LHS). The boundary condition sets are imposed on a 2-D axi-symmetrical CFD simulation model of the SST. In the framework, to degenerate the 2-D model structure, CFD model outputs are approximated by the 1-D model through the calibration of three different model structures for D. Correlation equations for the D parameter then are identified as a function of the selected design and flow boundary conditions (meta-models), and their accuracy is evaluated against D values estimated in each numerical experiment. The evaluation and validation of the iCFD model structure is carried out using scenario simulation results obtained with parameters sampled from the corners of the LHS experimental region. For the studied SST, additional iCFD model development was carried out in terms of (i) assessing different density current sub-models; (ii) implementation of a combined flocculation, hindered, transient and compression settling velocity function; and (iii

  3. Code Component Composition Reuse Is a New Programming Paradigm

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    After describing the characteristics of programming paradigm,this pap er introduces the approach of code component composition reuse in detail, propos es and discusses viewpoint that code component composition reuse is a kind of ne w programming paradigm. This paper also specifies the characteristics of this ne w programming paradigm in detail, and points out some issues that must be resolv ed for using this new programming paradigm.

  4. Paradigm Shifts in the Treatment of Appendicitis.

    Science.gov (United States)

    Mak, Grace Zee; Loeff, Deborah S

    2016-07-01

    Acute appendicitis is the most common cause of emergent surgery in children. Historically, surgical dogma dictated emergent appendectomy due to concern for impending perforation. Recently, however, there has been a paradigm shift in both the understanding of its pathophysiology as well as its treatment to more nonoperative management. No longer is it considered a spectrum from uncomplicated appendicitis inevitably progressing to complicated appendicitis over time. Rather, uncomplicated and complicated appendicitis are now considered two distinct pathophysiologic entities. This change requires not only educating the patients and their families but also the general practitioners who will be managing treatment expectations and caring for patients long term. In this article, we review the pathophysiology of appendicitis, including the differentiation between uncomplicated and complicated appendicitis, as well as the new treatment paradigms. [Pediatr Ann. 2016;45(7):e235-e240.]. PMID:27403670

  5. Security Issues in Mobile Agent Paradigm

    Directory of Open Access Journals (Sweden)

    Nitin Jain

    2011-05-01

    Full Text Available A mobile Agent is a Software program that migrates from node tonode of a heterogeneous network. They are goal-oriented i.e. workautonomously towards a goal, capable of suspending their executionon one platform and moving to other where they can resumeexecution using resources of these nodes and they meet and interactwith other agents. Agents may be stationary, always resident at asingle platform or mobile, capable of moving among differentplatforms at different time. The mobile agent paradigm providesmany benefits in developments of distributed application at the sametime introduce new requirements for security issues with thesesystems. In this paper we try to focus mainly on security issues thatarise when mobile agent paradigm comes into play.

  6. Web Content Analysis: Expanding the Paradigm

    Science.gov (United States)

    Herring, Susan C.

    Are established methods of content analysis (CA) adequate to analyze web content, or should new methods be devised to address new technological developments? This article addresses this question by contrasting narrow and broad interpretations of the concept of web content analysis. The utility of a broad interpretation that subsumes the narrow one is then illustrated with reference to research on weblogs (blogs), a popular web format in which features of HTML documents and interactive computer-mediated communication converge. The article concludes by proposing an expanded Web Content Analysis (WebCA) paradigm in which insights from paradigms such as discourse analysis and social network analysis are operationalized and implemented within a general content analytic framework.

  7. Paradigms for Realizing Machine Learning Algorithms.

    Science.gov (United States)

    Agneeswaran, Vijay Srinivas; Tonpay, Pranay; Tiwary, Jayati

    2013-12-01

    The article explains the three generations of machine learning algorithms-with all three trying to operate on big data. The first generation tools are SAS, SPSS, etc., while second generation realizations include Mahout and RapidMiner (that work over Hadoop), and the third generation paradigms include Spark and GraphLab, among others. The essence of the article is that for a number of machine learning algorithms, it is important to look beyond the Hadoop's Map-Reduce paradigm in order to make them work on big data. A number of promising contenders have emerged in the third generation that can be exploited to realize deep analytics on big data. PMID:27447253

  8. A New Paradigm for Chemical Engineering?

    DEFF Research Database (Denmark)

    Gani, Rafiqul

    material, energy usage and waste generation without compromising the economic value of the enterprise. Responding to these challenges requires a new insight into the characteristics of a sustainable system, for example, how to incorporate the product, the process and the related supply chain within...... the system boundary under investigation? A fundamental rethinking of how to identify the needed chemicals based products and how to design, build and operate the corresponding production units, is necessary. Indeed, the chemical industry today is changed from the chemical industry of forty years ago. Clear...... businesses has been observed. There is an increasing trend within the chemical industry to focus on products and the sustainable processes that can make them. Do these changes point to a paradigm shift in chemical engineering as a discipline? Historically, two previous paradigm shifts in chemical engineering...

  9. BMS invariance and the membrane paradigm

    Science.gov (United States)

    Penna, Robert F.

    2016-03-01

    The Bondi-van der Burg-Metzner-Sachs (BMS) group is the asymptotic symmetry group of asymptotically flat spacetime. It is infinite dimensional and entails an infinite number of conservation laws. According to the black hole membrane paradigm, null infinity (in asymptotically flat spacetime) and black hole event horizons behave like fluid membranes. The fluid dynamics of the membrane is governed by an infinite set of symmetries and conservation laws. Our main result is to point out that the infinite set of symmetries and conserved charges of the BMS group and the membrane paradigm are the same. This relationship has several consequences. First, it sheds light on the physical interpretation of BMS conservation laws. Second, it generalizes the BMS conservation laws to arbitrary subregions of arbitrary null surfaces. Third, it clarifies the identification of the superrotation subgroup of the BMS group. We briefly comment on the black hole information problem.

  10. Mixing Paradigms for More Comprehensible Models

    DEFF Research Database (Denmark)

    Westergaard, Michael; Slaats, Tijs

    2013-01-01

    Petri nets efficiently model both data- and control-flow. Control-flow is either modeled explicitly as flow of a specific kind of data, or implicit based on the data-flow. Explicit modeling of control-flow is useful for well-known and highly structured processes, but may make modeling of abstract...... features of models, or processes which are highly dynamic, overly complex. Declarative modeling, such as is supported by Declare and DCR graphs, focus on control-flow, but does not specify it explicitly; instead specifications come in the form of constraints on the order or appearance of tasks...... or abstract processes. In addition to enriching both procedural processes in the form of Petri nets and declarative processes, we also support a flow from modeling only abstract data- and control-flow of a model towards a more explicit control-flow model if so desired. We define our combined approach...

  11. A molecular dynamics test of the Navier-Stokes-Fourier paradigm for compressible gaseous continua

    CERN Document Server

    Brenner, Howard; Reese, Jason M

    2013-01-01

    Knudsen's pioneering experimental and theoretical work performed more than a century ago pointed to the fact that the Navier-Stokes-Fourier (NSF) paradigm is inapplicable to compressible gases at Knudsen numbers (Kn) beyond the continuum range, namely to noncontinua. However, in the case of continua, wherein Kn approaches zero asymptotically, it is nevertheless (implicitly) assumed in the literature that the compressible NSF equations remain applicable. Surprisingly, this belief appears never to have been critically tested; rather, most tests of the viability of the NSF equations for continuum flows have, to date, effectively been limited to incompressible fluids, namely liquids. Given that bivelocity hydrodynamic theory has recently raised fundamental questions about the validity of the NSF equations for compressible continuum gas flows, we deemed it worthwhile to test the validity of the NSF paradigm for the case of continua. Although our proposed NSF test does not, itself, depend upon the correctness of th...

  12. Consumers’ Empowerement for a New Marketing Paradigm

    OpenAIRE

    Victor Danciu

    2013-01-01

    The marketing practices of the companies show that not all of them are observing ethical and moral standards and they manipulate the consumers. This paper has as main goal to examine the most usual unethical techniques, the present status of consumers’ power and how more power could work for a new marketing paradigm. There are many unethical marketing techniques which could be found in deceptive product recipes, packaging, promotion, prices and in other areas. Most consumers have no appropria...

  13. Security Issues in Mobile Agent Paradigm

    OpenAIRE

    Nitin Jain; Neeraj Singla

    2011-01-01

    A mobile Agent is a Software program that migrates from node tonode of a heterogeneous network. They are goal-oriented i.e. workautonomously towards a goal, capable of suspending their executionon one platform and moving to other where they can resumeexecution using resources of these nodes and they meet and interactwith other agents. Agents may be stationary, always resident at asingle platform or mobile, capable of moving among differentplatforms at different time. The mobile agent paradigm...

  14. The Knowledge Society: A Sustainability Paradigm

    Directory of Open Access Journals (Sweden)

    Naim Hamdija Afgan

    2010-10-01

    Full Text Available This paper defines the knowledge society as a human structured organisation based on contemporary developed knowledge and representing new quality of life support systems. It implies the need for a full understanding of distribution of knowledge, access to information and the capability to transfer information into a knowledge. The understanding of knowledge is the central challenge when defining a knowledge society. From our present perception of knowledge society, it is of interest to emphasize the role of the knowledge society in future development of human society. The life support systems are essential pillars of human society development. In this respect knowledge society represents a new paradigm for future development and it is strongly correlated to sustainable development. For this reason the sustainability paradigm of knowledge society is a potential frame for human society development leading to social cohesion, economic competitiveness and stability, use of resources and economic development, safeguarding biodiversity and the ecosystem.In order to verify the mutual relation between knowledge society and sustainability, we have to introduce the difference between these two terms. The knowledge society is based on the agglomeration of eco-knowledge, env-knowledge and soc-knowledge, it may be evaluated as the complex knowledge of quality of life support systems. We have to introduce metrics which will allow us to present knowledge as the paradigm of the number of indicators for verifying progress made.Sustainability metrics are designed to consolidate measures of economic, environmental and social performance of any system. It can be understood as a pattern for evaluation of the available knowledge about systems and their performance. In particular the decision-making process for the selection of the system under consideration must be based on the available knowledge. The link between knowledge and sustainability makes it possible for

  15. Using Participatory Paradigm to Learn Human Behaviour

    OpenAIRE

    Taillandier, Patrick; Chu, Thanh-Quang

    2009-01-01

    International audience Since the end of the seventies, the utilisation of multi-agents simulations has spread out. A typical use of these simulations concerns the modelling of human behaviour. In this application case, a key point to ensure the simulation realism is the definition of the agent behaviour. Unfortunately, designing such behaviour is often complex. In order to help the definition of such behaviour, we propose an approach based on the participatory paradigm. In our approach, a ...

  16. Imaging deductive reasoning and the new paradigm

    OpenAIRE

    Mike Oaksford

    2015-01-01

    There has been a great expansion of research into human reasoning at all of Marr’s explanatory levels. There is a tendency for this work to progress within a level largely ignoring the others which can lead to slippage between levels (Chater, Oaksford, Nakisa, & Reddington, 2003). It is argued that recent brain imaging research on deductive reasoning—implementational level—has largely ignored the new paradigm in reasoning—computational level (Over, 2009). Consequently, recent imaging results ...

  17. Human Resources Development: A Paradigm Shift?

    OpenAIRE

    Corner, Lorraine

    1993-01-01

    A paradigm shift is taking place in contemporary understanding of the role of human resources in development. Support for the supply-sided human capital model rests on the proposition, not yet established empirically, that it leads to more rapid rates of development than alternative approaches. The human resources development strategy stresses that human resources are both producers and the intended beneficiaries of development. It thus focuses on the achievement of human development directly...

  18. Paradigms of Migration: From Integration to Transnationalism

    OpenAIRE

    Christian Giordano

    2010-01-01

    This article provides a critical analysis from the viewpoint of social anthropology of the different theoretic approaches that also set the tone of current debates on immigration in Europe and elsewhere. We begin by retracing the models developed and popularized since the 1960s to discuss the integration theory and Marxist reflections on the rise of class consciousness in immigrants. The article illustrates the paradigm shift that occurred in the 1990s that takes into account the role of the ...

  19. A new paradigm of health education

    DEFF Research Database (Denmark)

    From, Ditte-Marie

    2016-01-01

    This article draws upon research exploring school-based community practices of health education for overweight children and their families. In accordance with the existing critique of the ‘obesity epidemic’ and medico-scientific discourses around food and exercise, this article challenges the pre...... learning. This, I argue, calls for a shift into a new paradigm of health education by regarding the promotion of health as a reflexive learning practice....

  20. Quality improvement through the paradigm of learning

    OpenAIRE

    Hafford-Letchfield, Trish; Lavender, Peter

    2015-01-01

    Purpose - If we are to achieve meaningful participation and co-production for older people in care, more radical approaches are required. This project explores an innovation where older people using social care were matched to community based learning mentors to develop partnerships within which learning interventions were facilitated. We explore how the concept of learning might be used as a paradigm to raise the quality of care in institutionalised settings using a co-productive and relati...

  1. Changing the Cultural Paradigm to Meet Emerging Requirements

    Science.gov (United States)

    Robbins, William W.

    2007-01-01

    This viewgraph presentation reviews changes that are required in Space Transportation. This new transportation paradigm from the reliance on the Space Shuttle to a mixture of space transportation vehicles, i.e., the Russian Progress, vehicle, the Japanese HTV, the European ATV and other commercial orbital transportation systems, requires a new cultural paradigm. This new paradigm is outlined, and reviewed.

  2. Paradigm Adherence and Personality Correlates across Mental Health Professions

    Science.gov (United States)

    Rauscher, Laura Anne

    2012-01-01

    Paradigm adherence has been developed as a meta-theoretical approach to organize and to classify the multitude of different theories of counseling and psychotherapy. Four paradigms have been identified in the literature: The Organic-Medical, The Psychological, The Systemic-Relational, and the Social Constructivist paradigms. Only one other study…

  3. Investigation of structure and properties of novel multi-layer clay nanocomposite films produced controllably by continuous chaotic advection blending

    Science.gov (United States)

    Mahesha, Chaitra

    A unique processing technique based on chaotic advection developed at Clemson University and shown to controllably produce structured materials in the past was employed to produce structured nanocomposites with a high degree of clay orientation as well as localization of platelets within layers of nanoscale thicknesses. Continuous lengths of nanocomposites with different clay contents were extruded in the form of films by feeding separately melts of virgin polyamide-6 polymer and polyamide 6-clay masterbatch into a continuous chaotic advection blender. A variety of composite structures were producible at fixed clay compositions. The internal structure was characterized by transmission electron microscopy (TEM), x-ray diffraction (XRD) and differential scanning calorimetry (DSC). Nanocomposites with novel in-situ multi-layered structures and a high degree of platelet orientation were formed by the recursive stretching and folding of the melt domains due to chaotic advection. Clay platelets were localized within discrete regions to form alternating virgin and platelet-rich layers leading to a hierarchical structure with multiple nano-scales. The thicknesses of the layers reduced with prolonged chaotic advection, eventually leading to nanocomposites in which the multi-layering was no longer discernible. The oriented platelets appeared to be homogenously dispersed through the bulk of the nanocomposite. Investigation of the morphology of the matrix by XRD showed that the homogeneity of the crystalline phase and the orientation of polymer chains parallel to the film surface increased with increased chaotic advection. Also, as the layer thickness reduced, the number of polymer chains restricted by clay platelets increased causing the gamma-crystalline fraction to increase. While XRD results suggested a change in total crystallinity with chaotic advection and clay content but without a specific trend, no change in crystallinity was measured by DSC. Such contradictions are

  4. Biological robustness: paradigms, mechanisms, and systems principles.

    Science.gov (United States)

    Whitacre, James Michael

    2012-01-01

    Robustness has been studied through the analysis of data sets, simulations, and a variety of experimental techniques that each have their own limitations but together confirm the ubiquity of biological robustness. Recent trends suggest that different types of perturbation (e.g., mutational, environmental) are commonly stabilized by similar mechanisms, and system sensitivities often display a long-tailed distribution with relatively few perturbations representing the majority of sensitivities. Conceptual paradigms from network theory, control theory, complexity science, and natural selection have been used to understand robustness, however each paradigm has a limited scope of applicability and there has been little discussion of the conditions that determine this scope or the relationships between paradigms. Systems properties such as modularity, bow-tie architectures, degeneracy, and other topological features are often positively associated with robust traits, however common underlying mechanisms are rarely mentioned. For instance, many system properties support robustness through functional redundancy or through response diversity with responses regulated by competitive exclusion and cooperative facilitation. Moreover, few studies compare and contrast alternative strategies for achieving robustness such as homeostasis, adaptive plasticity, environment shaping, and environment tracking. These strategies share similarities in their utilization of adaptive and self-organization processes that are not well appreciated yet might be suggestive of reusable building blocks for generating robust behavior. PMID:22593762

  5. Biological Robustness: Paradigms, Mechanisms, and Systems Principles

    Directory of Open Access Journals (Sweden)

    James Michael Whitacre

    2012-05-01

    Full Text Available Robustness has been studied through the analysis of data sets, simulations, and a variety of experimental techniques that each have their own limitations but together confirm the ubiquity of biological robustness. Recent trends suggest that different types of perturbation (e.g. mutational, environmental are commonly stabilized by similar mechanisms, and system sensitivities often display a long-tailed distribution with relatively few perturbations representing the majority of sensitivities. Conceptual paradigms from network theory, control theory, complexity science, and natural selection have been used to understand robustness, however each paradigm has a limited scope of applicability and there has been little discussion of the conditions that determine this scope or the relationships between paradigms. Systems properties such as modularity, bow-tie architectures, degeneracy, and other topological features are often positively associated with robust traits, however common underlying mechanisms are rarely mentioned. For instance, many system properties support robustness through functional redundancy or through response diversity with responses regulated by competitive exclusion and cooperative facilitation. Moreover, few studies compare and contrast alternative strategies for achieving robustness such as homeostasis, adaptive plasticity, environment shaping, and environment tracking. These strategies share similarities in their utilization of adaptive and self-organization processes that are not well appreciated yet might be suggestive of reusable building blocks for generating robust behavior.

  6. Shifting paradigms: Reflecting Germanys European policy

    Directory of Open Access Journals (Sweden)

    Nicola Staeck

    1999-03-01

    Full Text Available Germany's presidency of the European Council in the first half of 1999 has focused the attention of schlolars on Germany's attitude towards the EU. Germany's European policy has been guided from the beginning by a pro-European vision of 'the house of Europe'. The hypothesis of the article is that this paradigm of German European policy is in flux. Via a constructivist approach it is argued that we are observing a paradigm shift away from a visionary towards a pragmatic European policy which is oriented around efficiency criteria and national interest. Evidence is given by analysing the following propositions: (1 the advocates of a European vision have vanished in Germany, and the broad coalition in society towards Europe is crumbling; (2 at the same time the discussion on Europe has become highly politicised; (3 in addition, important German institutions such as the Federal Constitutional Court (Bundesverfassungsgericht are reluctant to (re-strengthen the European idea; and (4 the fit between Germany's and the EU's institutional setting supports the change in paradigm. In conclusion it is argued that Germany is on its way to changing its role from that of a supporting participant to that of a self-confident active player.

  7. Toward a Metatheoretical Integration of Developmental Paradigms

    Directory of Open Access Journals (Sweden)

    Mark W. Antley

    2010-07-01

    Full Text Available This paper shows how a partial consilience might be achieved in the field of human development by means of principles from general systems theory. The author concurs with Sameroff (1989 that it is possible to interpret the mechanistic, organisimic, and contextualist paradigms/worldviews (Goldhaber, 2000; Pepper, 1970 in terms of general systems theory. The author selects a major developmentalist from each paradigm and interprets that scholar’s work in terms of systems principles. The following developmentalists were selected: Arnold Sameroff (contextualism, Erik Erickson (organicism, and Albert Bandura (mechanism. The systems principles employed are wholeness and order, self-stabilization, self-reorganization, hierarchical interaction, and dialectical contradiction (Sameroff, 1989. The author addresses the conflicting presuppositions of the major paradigms in order to provide for their theoretical subsuming under systems theory. Finally, the author notes areas of inconsistency that will need to be resolved in the future and calls for further scholarship to translate developmental theory in terms of general systems theory for the benefit of students, scholars, consultants and other practitioners familiar with systems theory.

  8. The rise of fully turbulent flow

    CERN Document Server

    Barkley, Dwight; Mukund, Vasudevan; Lemoult, Grégoire; Avila, Marc; Hof, Björn

    2015-01-01

    Over a century of research into the origin of turbulence in wallbounded shear flows has resulted in a puzzling picture in which turbulence appears in a variety of different states competing with laminar background flow. At slightly higher speeds the situation changes distinctly and the entire flow is turbulent. Neither the origin of the different states encountered during transition, nor their front dynamics, let alone the transformation to full turbulence could be explained to date. Combining experiments, theory and computer simulations here we uncover the bifurcation scenario organising the route to fully turbulent pipe flow and explain the front dynamics of the different states encountered in the process. Key to resolving this problem is the interpretation of the flow as a bistable system with nonlinear propagation (advection) of turbulent fronts. These findings bridge the gap between our understanding of the onset of turbulence and fully turbulent flows.

  9. Wireless Communications and Networking Technologies for Smart Grid: Paradigms and Challenges

    OpenAIRE

    Fang, Xi; Yang, Dejun; Xue, Guoliang

    2011-01-01

    Smart grid, regarded as the next generation power grid, uses two-way flows of electricity and information to create a widely distributed automated energy delivery network. In this work we present our vision on smart grid from the perspective of wireless communications and networking technologies. We present wireless communication and networking paradigms for four typical scenarios in the future smart grid and also point out the research challenges of the wireless communication and networking ...

  10. Wireless Communications and Networking Technologies for Smart Grid: Paradigms and Challenges

    CERN Document Server

    Fang, Xi; Xue, Guoliang

    2011-01-01

    Smart grid, regarded as the next generation power grid, uses two-way flows of electricity and information to create a widely distributed automated energy delivery network. In this work we present our vision on smart grid from the perspective of wireless communications and networking technologies. We present wireless communication and networking paradigms for four typical scenarios in the future smart grid and also point out the research challenges of the wireless communication and networking technologies used in smart grid

  11. Parity properties of an advection dominated solar alpha 2Omega -dynamo

    Science.gov (United States)

    Bonanno, A.; Elstner, D.; Rüdiger, G.; Belvedere, G.

    We present the results of numerical simulations of the solar dynamo both for given rotation law and meridional flow in the case of a low eddy diffusivity of the order of 1011 cm2/s known from the sunspot decay. If the helioseismologically derived internal solar rotation law is considered, a model without meridional flow of high magnetic Reynolds number (corresponding to low eddy diffusivity) fails in all the three issues in comparison with the observations. However, a meridional flow with equatorial drift at the bottom of the convection zone of few meters by second can indeed enforce the equatorward migration of the toroidal magnetic field belts similar to the observed butterfly diagram but, the solution has only a dipolar parity if the (positive) alpha -effect is located at the base of the convection zone rather than at the top.

  12. Heat advection processes leading to El Niño events as depicted by an ensemble of ocean assimilation products

    Science.gov (United States)

    Ballester, Joan; Bordoni, Simona; Petrova, Desislava; Rodó, Xavier

    2016-06-01

    The oscillatory nature of El Niño-Southern Oscillation results from an intricate superposition of near-equilibrium balances and out-of-phase disequilibrium processes between the ocean and the atmosphere. The main objective of the present work is to perform an exhaustive spatiotemporal analysis of the upper ocean heat budget in an ensemble of state-of-the-art ocean assimilation products. We put specific emphasis on the ocean heat advection mechanisms, and their representation in individual ensemble members and in the different stages of the ENSO oscillation leading to EN events. Our analyses consistently show that the initial subsurface warming in the western equatorial Pacific is advected to the central Pacific by the equatorial undercurrent, which, together with the equatorward advection associated with anomalies in both the meridional temperature gradient and circulation at the level of the thermocline, explains the heat buildup in the central Pacific during the recharge phase. We also find that the recharge phase is characterized by an increase of meridional tilting of the thermocline, as well as a southward upper-ocean cross-equatorial mass transport resulting from Ekman-induced anomalous vertical motion in the off-equatorial regions. Although differences between data sets are generally small, and anomalies tend to have the same sign, the differences in the magnitude of the meridional term are seen to be key for explaining the different propagation speed of the subsurface warming tendency along the thermocline. The only exception is GECCO, which does not produce the patterns of meridional surface Ekman divergence (subsurface Sverdrup convergence) in the western and central equatorial Pacific.

  13. A POSTERIORI ENERGY-NORM ERROR ESTIMATES FOR ADVECTION-DIFFUSION EQUATIONS APPROXIMATED BY WEIGHTED INTERIOR PENALTY METHODS

    Institute of Scientific and Technical Information of China (English)

    Alexandre Ern; Annette F.Stephansen

    2008-01-01

    We propose and analyze a posteriori energy-norm error estimates for weighted interior penalty discontinuous Galerkin approximations of advection-diffusion-reaction equations with heterogeneous and anisotropic diffusion.The weights,which play a key role in the analysis.depend on the diffusion tensor and are used to formulate the consistency terms in the discontinuous Galerkin method.The error upper bounds,in which all the constants are specified.consist of three terms:a residual estimator which depends only on the elementwise fluctuation of the discrete solution residual,a diffusive flux estimator where the weights used in the method enter explicitly,and a non-conforming estimator which is nonzero because of the use of discontinuous finite element spaces.The three estimators can be bounded locally by the approximation error.A particular attention is given to the dependency on problem parameters of the constants in the local lower error bounds,For moderate advection.it.is shown that full robustness with respect to diffusion heterogeneities is achieved owing to the specific design of the weights in the discontinuous Galerkin method,while diffusion anisotropies remain purely local and impact the constants through the square root of the condition number of the diffusion tensor.For dominant advection,the local lower error bounds can be written with constants involving a cut-off for the ratio of local mesh size to the reciprocal of the square root of the lowest local eignevalue of the diffusion tensor.

  14. Quantifying advective and nonstationary effects on eddy fluxes in the AmeriFlux network

    Energy Technology Data Exchange (ETDEWEB)

    Fitzjarrald, David R

    2012-12-19

    Our goal was to study the flows within and above of a forested area and assess the degree to which horizontal subcanopy motions transport significant amounts of CO2. This process can explain why ecosystem respiration appears to be underestimated on calm nights. It is essential to understand the physical and biological mechanisms that determine relevant processes that occur on these suspect nights.

  15. Improving estimates of ecosystem metabolism by reducing effects of tidal advection on dissolved oxygen time series

    Science.gov (United States)

    In aquatic systems, time series of dissolved oxygen (DO) have been used to compute estimates of ecosystem metabolism. Central to this open-water method is the assumption that the DO time series is a Lagrangian specification of the flow field. However, most DO time series are coll...

  16. Computation of diffusion coefficients for waters of Gauthami Godavari estuary using one-dimensional advection-diffusion model

    Digital Repository Service at National Institute of Oceanography (India)

    Jyothi, D.; Murty, T.V.R.; Sarma, V.V.; Rao, D.P.

    of Marine Sciences Vol. 29, June 2000, pp. 185-187 Short Communication Computation of diffusion coefficients for waters of Gauthami Godavari estuary using one-dimensional advection-diffusion model D Jyothi, T V Ramana Murty, V V Sarma & D P Rao National.... - Jan.) Y2(x) = 8.55283 x + 17.5469 (Jan. - April) These equations would be more useful to get diffusion coefficients for any point along the channel axis, which in turn, helps to compute the concentration of pollutant along the axis of estuary. Thus...

  17. ADVECTION-DIFFUSION NUMERICAL MODEL OF AN AIR POLLUTANT EMITTED FROM AN AREA SOURCE OF PRIMARY POLLUTANT WITH WET DEPOSITION

    Directory of Open Access Journals (Sweden)

    C M SURESHA

    2012-01-01

    Full Text Available A two dimensional advection-diffusion numerical model of air pollutant emitted from an area source of primary pollutant with wet deposition is presented. We study the effect of removal mechanism i.e. wet deposition on primary pollutant with respect to distance and height for stable and neutral cases. The numerical model has been solved by using Crank-Nicolson implicit finite difference technique. Concentration contours are plotted and results are analysed for primary pollutant in stable and neutral atmospheric situations for various meteorological parameters.

  18. Regional and inter-annual variability in Atlantic zooplankton en route to the Arctic Ocean: potential effects of multi-path Atlantic water advection through Fram Strait and the Barents Sea

    Science.gov (United States)

    Kwasniewski, Slawomir; Gluchowska, Marta; Trudnowska, Emilia; Ormanczyk, Mateusz; Walczowski, Waldemar; Beszczynska-Moeller, Agnieszka

    2016-04-01

    The Arctic is among the regions where the climate change effects on ecosystem will be the most rapid and consequential, with Arctic amplification recognized as an integral part of the process. Great part of the changes are forced by advection of warm waters from the North Atlantic and the expected modifications of Arctic marine ecosystem will be induced not only by changing environmental conditions but also as a result of introducing Atlantic biota. Thus, the knowledge of physical and biological heterogeneity of Atlantic inflow is requisite for understanding the effects of climate change on biological diversity and ecosystem functioning in the Arctic. The complex and variable two-branched structure of the Atlantic Water flow via Fram Strait and the Barents Sea most likely has a strong influence on the ocean biology in these regions, especially in the pelagic realm. Zooplankton are key components of marine ecosystems which form essential links between primary producers and grazer/predator consumers, thus they are important for functioning of the biological carbon pump. Changes in zooplankton distribution and abundance may have cascading effects on ecosystem functioning, with regulatory effects on climate. Based on data collected in summers of 2012-2014, within the scope of the Polish-Norwegian PAVE research project, we investigate zooplankton distribution, abundance and selected structural characteristics of communities, in relation to water mass properties in the Atlantic Water complex flow to the Arctic Ocean. The main questions addressed here are: what are the differences in zooplankton patterns between the Fram Strait and Barents Sea branches, and how does the inter-annual variability of Atlantic Water advection relate to changes in zooplankton? The results of the investigation are precondition for foreseeing changes in the pelagic realm in the Arctic Ocean and are necessary for constructing and tuning plankton components of ecosystem models.

  19. Inevitable suicide: a new paradigm in psychiatry.

    Science.gov (United States)

    Sadock, Benjamin J

    2012-05-01

    The author suggests that a new paradigm may be needed which holds that some suicides may be inevitable. The goal of this paradigm would be to diminish the sense of failure and inadequacy felt by many psychiatrists who experience the suicide of a patient and to increase understanding of the unique biopsychosocial profile of those whose suicides appear to be inevitable. The author stresses that this proposed paradigm should not be misconstrued as therapeutic nihilism but rather should serve to stimulate efforts to treat this patient population more effectively. Risk factors that place individuals at high risk for suicide are reviewed, including presence of a mental illness, genetic predisposition, and factors such as a history of abuse, divorce, unemployment, male gender, recent discharge from a psychiatric hospital, prior suicide attempts, alcohol or other substance abuse, a history of panic attacks, and persistent suicidal thoughts, especially if coupled with a plan. The author notes that, in those suicides that appear to have been inevitable, risk factors are not only numerous but at the extreme end of profound pathology. The example of Ernest Hemingway is used to illustrate how such a combination of risk factors may have contributed to his eventual suicide. Psychiatrists, like other doctors, may have to acknowledge that some psychiatric disorders are associated with a high mortality rate as a natural outcome. This could lead to heightened vigilance, a more realistic view of what can and cannot be achieved with therapy, and efforts to improve the quality of life of patients at high risk for suicide with the goal of reducing this risk and prolonging their lives. (Journal of Psychiatric Practice 2012;18:221-224). PMID:22617088

  20. Three paradigms for the analysis of corruption

    Directory of Open Access Journals (Sweden)

    Alberto Vannucci

    2015-10-01

    Full Text Available In the last decades a growing awareness emerged of the relevance of corruption as an hidden factor which may negatively affect political and economic decision-making processes. In spite of a lively scientific debate there is no general consensus on a commonly accepted definition of what corruption is.The A. distinguishes three main paradigms, focusing on different (though not irreconcilable variables.The first is the economic paradigm, which usually takes the principal-agent model of corruption as its founding pillar. In this paradigm corruption is considered the outcome of rational individual choices, and its spread within a certain organization is influenced by the factors defining the structure of expected costs and rewards.A second approach – the cultural paradigm – looks at the differences in cultural traditions, social norms and interiorized values which shape individuals’ moral preferences and consideration of his social and institutional role. These are a leading forces that can push a corrupt public or private agent (not to violate legal norms.A third neo-institutional approach considers also mechanisms which allow the internal regulation of social interactions within corrupt networks, and their effects on individuals’ beliefs and preferences. Though the corrupt agreements cannot be enforced with legal sanctions, several informal, non-written rules, contractual provisos and conventions may regulate the corrupt exchange between agent and corruptor.The A. underlines that corruption is the outcome of a multitude of individual and collective choices which change public opinion towards corruption and its diffusion throughout the state, markets and civil society. There is no univocal recipe to deal with anti-bribery measures, since corruption is a complex and multifaceted phenomenon.Reforms aimed at dismantling systemic corruption have to be finely tuned against its hidden governance structures, i.e. its internal regulation of

  1. Power and shifting paradigm in translation

    Directory of Open Access Journals (Sweden)

    Martin Djovčoš

    2011-06-01

    Full Text Available The paper deals with interrelation of dominant ideology and its influence on the translation and publishing policy as reflected on the example of Slovakia. The introductory part is devoted to theoretical framework for the research drawing upon the works of Slovak and foreign translation scholars. The analytical part is contrastive; it presents publishing tendencies in selected dominant vs dependent cultures within the periods of opposing ideologies (socialistic vs democratic regimes. It clearly shows the shift of paradigm and the place of "small cultures" in the intercultural dialogue/monologue.

  2. An adaptive paradigm for human space settlement

    Science.gov (United States)

    Smith, Cameron M.

    2016-02-01

    Because permanent space settlement will be multigenerational it will have to be viable on ecological timescales so far unfamiliar to those planning space exploration. Long-term viability will require evolutionary and adaptive planning. Adaptations in the natural world provide many lessons for such planning, but implementing these lessons will require a new, evolutionary paradigm for envisioning and carrying out Earth-independent space settlement. I describe some of these adaptive lessons and propose some cognitive shifts required to implement them in a genuinely evolutionary approach to human space settlement.

  3. Trace elements as paradigms of developmental neurotoxicants

    DEFF Research Database (Denmark)

    Grandjean, Philippe; Herz, Katherine T

    2015-01-01

    several decades ago so that past and cumulated exposures could be easily characterized through analysis of biological samples, e.g. blood and urine. The first compelling evidence resulted from unfortunate poisoning events that allowed scrutiny of long-term outcomes of acute exposures that occurred during...... early development. Pursuant to this documentation, prospective studies of children's cohorts that applied sensitive neurobehavioral methods supported the notion that the brain is uniquely vulnerable to toxic damage during early development. Lead, methylmercury, and arsenic thereby serve as paradigm...

  4. Paradigms-Shift in Set Theory

    OpenAIRE

    DePauli-Schimanovich, Werner

    2008-01-01

    In this article the author claims that there is a paradigm shift from ZFC to NFUM and further to NACT - due to philosophical reasons, not mathematical ones. The goal is to construct systems where every "Not-Properclass" is a set! With help of Non-Monotonic Logic, the consistent systems NACT-MoonW, NACT*W, and NACT-SunW are producing "largest possible universes" of sets. Using self-evident philosophical principles, three approximations are suggested: NACT+NFUM-closed (to NACT*), NACT&ZFC4+(GCH...

  5. Chua's circuit a paradigm for chaos

    CERN Document Server

    1993-01-01

    For uninitiated researchers, engineers, and scientists interested in a quick entry into the subject of chaos, this book offers a timely collection of 55 carefully selected papers covering almost every aspect of this subject. Because Chua's circuit is endowed with virtually every bifurcation phenomena reported in the extensive literature on chaos, and because it is the only chaotic system which can be easily built by a novice, simulated in a personal computer, and tractable mathematically, it has become a paradigm for chaos, and a vehicle for illustrating this ubiquitous phenomenon. Its supreme

  6. Genes and human behavior: the emerging paradigm.

    Science.gov (United States)

    Drew, A P

    1997-03-01

    The physical properties of human beings and other organisms as well as their social behavioral traits are manifestations of both genetic inheritance and environment. Recent behavioral research has indicated that certain characteristics or behaviors--such as schizophrenia, divorce, and homosexuality--are highly heritable and are not governed exclusively by social environment. A balanced view of human behavior includes the effects of social learning as well as of genetically determined behavior. A new paradigm promotes enhanced understanding and acceptance of human diversity, be it cultural, racial, or sexual, and has the potential to unite scientists and theologians by creating common grounds of understanding. PMID:15719495

  7. High order finite difference methods with subcell resolution for advection equations with stiff source terms

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Wei [Deprartment of Mathematics. Florida Intl Univ., Miami, FL (United States); Shu, Chi-Wang [Division of Applied Mathematics. Brown Univ., Providence, RI (United States); Yee, H.C. [NASA Ames Research Center (ARC), Moffett Field, Mountain View, CA (United States); Sjögreen, Björn [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2012-01-01

    A new high order finite-difference method utilizing the idea of Harten ENO subcell resolution method is proposed for chemical reactive flows and combustion. In reaction problems, when the reaction time scale is very small, e.g., orders of magnitude smaller than the fluid dynamics time scales, the governing equations will become very stiff. Wrong propagation speed of discontinuity may occur due to the underresolved numerical solution in both space and time. The present proposed method is a modified fractional step method which solves the convection step and reaction step separately. In the convection step, any high order shock-capturing method can be used. In the reaction step, an ODE solver is applied but with the computed flow variables in the shock region modified by the Harten subcell resolution idea. For numerical experiments, a fifth-order finite-difference WENO scheme and its anti-diffusion WENO variant are considered. A wide range of 1D and 2D scalar and Euler system test cases are investigated. Studies indicate that for the considered test cases, the new method maintains high order accuracy in space for smooth flows, and for stiff source terms with discontinuities, it can capture the correct propagation speed of discontinuities in very coarse meshes with reasonable CFL numbers.

  8. Parity properties of an advection-dominated solar $\\alpha^2\\Om$-dynamo

    CERN Document Server

    Bonanno, A; Rüdiger, G; Belvedere, G

    2002-01-01

    We have developed a high-precision code which solves the kinematic dynamo problem both for given rotation law and meridional flow in the case of a low eddy diffusivity of the order of $10^{11}$ cm$^2$/s known from the sunspot decay. All our models work with an \\alf-effect which is positive (negative) in the northern (southern) hemisphere. It is concentrated in radial layers located either at the top or at the bottom of the convection zone. We have also considered an \\alf-effect uniformly distributed in all the convection zone. In the present paper the main attention is focused on i) the parity of the solution, ii) the form of the butterfly diagram and iii) the phase relation of the resulting field components. If the helioseismologically derived internal solar rotation law is considered, a model without meridional flow of high magnetic Reynolds number (corresponding to low eddy diffusivity) fails in all the three issues in comparison with the observations. However, a meridional flow with equatorial drift at th...

  9. Parity properties of an advection-dominated solar alpha 2 Omega-dynamo

    Science.gov (United States)

    Bonanno, A.; Elstner, D.; Rüdiger, G.; Belvedere, G.

    2002-08-01

    We have developed a high-precision code which solves the kinematic dynamo problem both for given rotation law and meridional flow in the case of a low eddy diffusivity of the order of 1011 cm2 s-1 known from the sunspot decay. All our models work with an alpha -effect which is positive (negative) in the northern (southern) hemisphere. It is concentrated in radial layers located either at the top or at the bottom of the convection zone. We have also considered an alpha -effect uniformly distributed in all the convection zone. In the present paper the main attention is focused on i) the parity of the solution, ii) the form of the butterfly diagram and iii) the phase relation of the resulting field components. If the helioseismologically derived internal solar rotation law is considered, a model without meridional flow of high magnetic Reynolds number (corresponding to low eddy diffusivity) fails in all the three issues in comparison with the observations. However, a meridional flow with equatorial drift at the bottom of the convection zone of few meters by second can indeed enforce the equatorward migration of the toroidal magnetic field belts similar to the observed butterfly diagram but, the solution has only a dipolar parity if the (positive) alpha -effect is located at the base of the convection zone rather than at the top. We can, therefore, confirm the main results of a similar study by Dikpati & Gilman (\\cite{Dikpati01}).

  10. Experimental test of scaling of mixing by chaotic advection in droplets moving through microfluidic channels.

    Science.gov (United States)

    Song, Helen; Bringer, Michelle R; Tice, Joshua D; Gerdts, Cory J; Ismagilov, Rustem F

    2003-12-01

    This letter describes an experimental test of a simple argument that predicts the scaling of chaotic mixing in a droplet moving through a winding microfluidic channel. Previously, scaling arguments for chaotic mixing have been described for a flow that reduces striation length by stretching, folding, and reorienting the fluid in a manner similar to that of the baker's transformation. The experimentally observed flow patterns within droplets (or plugs) resembled the baker's transformation. Therefore, the ideas described in the literature could be applied to mixing in droplets to obtain the scaling argument for the dependence of the mixing time, t~(aw/U)log(Pe), where w [m] is the cross-sectional dimension of the microchannel, a is the dimensionless length of the plug measured relative to w, U [m s(-1)] is the flow velocity, Pe is the Péclet number (Pe=wU/D), and D [m(2)s(-1)] is the diffusion coefficient of the reagent being mixed. Experiments were performed to confirm the scaling argument by varying the parameters w, U, and D. Under favorable conditions, submillisecond mixing has been demonstrated in this system.

  11. PyFR: An open source framework for solving advection-diffusion type problems on streaming architectures using the flux reconstruction approach

    Science.gov (United States)

    Witherden, F. D.; Farrington, A. M.; Vincent, P. E.

    2014-11-01

    High-order numerical methods for unstructured grids combine the superior accuracy of high-order spectral or finite difference methods with the geometric flexibility of low-order finite volume or finite element schemes. The Flux Reconstruction (FR) approach unifies various high-order schemes for unstructured grids within a single framework. Additionally, the FR approach exhibits a significant degree of element locality, and is thus able to run efficiently on modern streaming architectures, such as Graphical Processing Units (GPUs). The aforementioned properties of FR mean it offers a promising route to performing affordable, and hence industrially relevant, scale-resolving simulations of hitherto intractable unsteady flows within the vicinity of real-world engineering geometries. In this paper we present PyFR, an open-source Python based framework for solving advection-diffusion type problems on streaming architectures using the FR approach. The framework is designed to solve a range of governing systems on mixed unstructured grids containing various element types. It is also designed to target a range of hardware platforms via use of an in-built domain specific language based on the Mako templating engine. The current release of PyFR is able to solve the compressible Euler and Navier-Stokes equations on grids of quadrilateral and triangular elements in two dimensions, and hexahedral elements in three dimensions, targeting clusters of CPUs, and NVIDIA GPUs. Results are presented for various benchmark flow problems, single-node performance is discussed, and scalability of the code is demonstrated on up to 104 NVIDIA M2090 GPUs. The software is freely available under a 3-Clause New Style BSD license (see www.pyfr.org). Catalogue identifier: AETY_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AETY_v1_0.html Program obtainable from: CPC Program Library, Queen’s University, Belfast, N. Ireland Licensing provisions: New style BSD license No. of lines in

  12. Solution of the advection-dispersion equation by a finite-volume eulerian-lagrangian local adjoint method

    Science.gov (United States)

    Healy, R.W.; Russell, T.F.

    1992-01-01

    A finite-volume Eulerian-Lagrangian local adjoint method for solution of the advection-dispersion equation is developed and discussed. The method is mass conservative and can solve advection-dominated ground-water solute-transport problems accurately and efficiently. An integrated finite-difference approach is used in the method. A key component of the method is that the integral representing the mass-storage term is evaluated numerically at the current time level. Integration points, and the mass associated with these points, are then forward tracked up to the next time level. The number of integration points required to reach a specified level of accuracy is problem dependent and increases as the sharpness of the simulated solute front increases. Integration points are generally equally spaced within each grid cell. For problems involving variable coefficients it has been found to be advantageous to include additional integration points at strategic locations in each well. These locations are determined by backtracking. Forward tracking of boundary fluxes by the method alleviates problems that are encountered in the backtracking approaches of most characteristic methods. A test problem is used to illustrate that the new method offers substantial advantages over other numerical methods for a wide range of problems.

  13. In situ investigation of rapid subsurface flow: Identification of relevant spatial structures beyond heterogeneity

    OpenAIRE

    Jackisch, Conrad; Angermann, Lisa; Allroggen, Niklas; Sprenger, Matthias; Blume, Theresa; Weiler, Markus; Tronicke, Jens; Zehe, Erwin

    2016-01-01

    Rapid subsurface flow in structured soils facilitates fast vertical and lateral redistribution of event water. Despite their significance and omnipresence the related processes are challenging hydrological exploration, monitoring, modeling and theory. One reason for this is that flow processes at high velocities are difficult to observe in the subsurface. Another reason is that advective flow is channeled in distinct connected structures several orders of magnitude smaller than commonly resol...

  14. A model of the free surface dynamics of shallow turbulent flows

    OpenAIRE

    Nichols, A.; Tait, S.; Horoshenkov, K.; Shepherd, S

    2016-01-01

    Understanding the dynamic free surface of geophysical flows has the potential to enable direct inference of the flow properties based on measurements of the free surface. An important step is to understand the inherent response of free surfaces in depth-limited flows. Here a model is presented to demonstrate that free surface oscillatory spatial correlation patterns result from individual surface features oscillating vertically as they advect over space and time. Comparison with laboratory ob...

  15. Numerical Methods for Chemically Reacting Fluid Flow Computation under Low-Mach Number Approximation

    OpenAIRE

    Arima, Toshiyuki

    2006-01-01

    A mathematical model of environmental fluid is presented to describe fluid flow motions with large density variations. Moreover the associated numerical methods are discussed. The model of environmental fluid is formulated as an unsteady low-Mach number flow based on the compressible Navier-Stokes equations. For low-Mach number flows, the acoustic effects are assumed to be weak relative to the advection effects. Under this assumption, detailed acoustic effects can be removed fr...

  16. Comparison of transport and attachment behaviors of Cryptosporidium parvum oocysts and oocyst-sized microspheres being advected through three minerologically different granular porous media

    Science.gov (United States)

    Mohanram, A.; Ray, C.; Harvey, R.W.; Metge, D.W.; Ryan, J.N.; Chorover, J.; Eberl, D.D.

    2010-01-01

    In order to gain more information about the fate of Cryptosporidium parvum oocysts in tropical volcanic soils, the transport and attachment behaviors of oocysts and oocyst-sized polystyrene microspheres were studied in the presence of two soils. These soils were chosen because of their differing chemical and physical properties, i.e., an organic-rich (43-46% by mass) volcanic ash-derived soil from the island of Hawaii, and a red, iron (22-29% by mass), aluminum (29-45% by mass), and clay-rich (68-76% by mass) volcanic soil from the island of Oahu. A third agricultural soil, an organic- (13% by mass) and quartz-rich (40% by mass) soil from Illinois, was included for reference. In 10-cm long flow-through columns, oocysts and microspheres advecting through the red volcanic soil were almost completely (98% and 99%) immobilized. The modest breakthrough resulted from preferential flow-path structure inadvertently created by soil-particle aggregation during the re-wetting process. Although a high (99%) removal of oocysts and microsphere within the volcanic ash soil occurred initially, further examination revealed that transport was merely retarded because of highly reversible interactions with grain surfaces. Judging from the slope of the substantive and protracted tail of the breakthrough curve for the 1.8-??m microspheres, almost all (>99%) predictably would be recovered within ~4000 pore volumes. This suggests that once contaminated, the volcanic ash soil could serve as a reservoir for subsequent contamination of groundwater, at least for pathogens of similar size or smaller. Because of the highly reversible nature of organic colloid immobilization in this soil type, C. parvum could contaminate surface water should overland flow during heavy precipitation events pick up near-surface grains to which they are attached. Surprisingly, oocyst and microsphere attachment to the reference soil from Illinois appeared to be at least as sensitive to changes in pH as was observed

  17. Comparison of transport and attachment behaviors of Cryptosporidium parvum oocysts and oocyst-sized microspheres being advected through three minerologically different granular porous media.

    Science.gov (United States)

    Mohanram, Arvind; Ray, Chittaranjan; Harvey, Ronald W; Metge, David W; Ryan, Joseph N; Chorover, Jon; Eberl, D D

    2010-10-01

    In order to gain more information about the fate of Cryptosporidium parvum oocysts in tropical volcanic soils, the transport and attachment behaviors of oocysts and oocyst-sized polystyrene microspheres were studied in the presence of two soils. These soils were chosen because of their differing chemical and physical properties, i.e., an organic-rich (43-46% by mass) volcanic ash-derived soil from the island of Hawaii, and a red, iron (22-29% by mass), aluminum (29-45% by mass), and clay-rich (68-76% by mass) volcanic soil from the island of Oahu. A third agricultural soil, an organic- (13% by mass) and quartz-rich (40% by mass) soil from Illinois, was included for reference. In 10-cm long flow-through columns, oocysts and microspheres advecting through the red volcanic soil were almost completely (98% and 99%) immobilized. The modest breakthrough resulted from preferential flow-path structure inadvertently created by soil-particle aggregation during the re-wetting process. Although a high (99%) removal of oocysts and microsphere within the volcanic ash soil occurred initially, further examination revealed that transport was merely retarded because of highly reversible interactions with grain surfaces. Judging from the slope of the substantive and protracted tail of the breakthrough curve for the 1.8-μm microspheres, almost all (>99%) predictably would be recovered within ∼4000 pore volumes. This suggests that once contaminated, the volcanic ash soil could serve as a reservoir for subsequent contamination of groundwater, at least for pathogens of similar size or smaller. Because of the highly reversible nature of organic colloid immobilization in this soil type, C. parvum could contaminate surface water should overland flow during heavy precipitation events pick up near-surface grains to which they are attached. Surprisingly, oocyst and microsphere attachment to the reference soil from Illinois appeared to be at least as sensitive to changes in pH as was

  18. Passage of American shad: paradigms and realities

    Science.gov (United States)

    Haro, Alex; Castro-Santos, Theodore

    2012-01-01

    Despite more than 250 years of development, the passage of American shad Alosa sapidissima at dams and other barriers frequently remains problematic. Few improvements in design based on knowledge of the swimming, schooling, and migratory behaviors of American shad have been incorporated into passage structures. Large-scale technical fishways designed for the passage of adult salmonids on the Columbia River have been presumed to have good performance for American shad but have never been rigorously evaluated for this species. Similar but smaller fishway designs on the East Coast frequently have poor performance. Provision of effective downstream passage for both juvenile and postspawning adult American shad has been given little consideration in most passage projects. Ways to attract and guide American shad to both fishway entrances and downstream bypasses remain marginally understood. The historical development of passage structures for American shad has resulted in assumptions and paradigms about American shad behavior and passage that are frequently unsubstantiated by supporting data or appropriate experimentation. We propose that many of these assumptions and paradigms are either unfounded or invalid and that significant improvements to American shad upstream and downstream passage can be made via a sequential program of behavioral experimentation, application of experimental results to the physical and hydraulic design of new structures, and controlled tests of large-scale prototype structures in the laboratory and field.

  19. Imaging Deductive Reasoning and the New Paradigm

    Directory of Open Access Journals (Sweden)

    Mike eOaksford

    2015-02-01

    Full Text Available There has been a great expansion of research into human reasoning at all of Marr’s explanatory levels. There is a tendency for this work to progress within a level largely ignoring the others which can lead to slippage between levels (Chater, Oaksford, Nakisa, & Reddington, 2003. It is argued that recent brain imaging research on deductive reasoning—implementational level—has largely ignored the new paradigm in reasoning—computational level (Over, 2009. Consequently, recent imaging results are reviewed with the focus on how they relate to the new paradigm. The imaging results are drawn primarily from a recent meta-analysis by Prado, Chadha, and Booth (2011 but further imaging results are also reviewed where relevant. Three main observations are made. First, the main function of the core brain region identified is most likely elaborative, defeasible reasoning not deductive reasoning. Second, the subtraction methodology and the meta-analytic approach may remove all traces of content specific System 1 processes thought to underpin much human reasoning. Third, interpreting the function of the brain regions activated by a task depends on theories of the function that a task engages. When there are multiple interpretations of that function, interpreting what an active brain region is doing is not clear cut. It is concluded that there is a need to more tightly connect brain activation to function, which could be achieved using formalized computational level models and a parametric variation approach.

  20. Imaging deductive reasoning and the new paradigm.

    Science.gov (United States)

    Oaksford, Mike

    2015-01-01

    There has been a great expansion of research into human reasoning at all of Marr's explanatory levels. There is a tendency for this work to progress within a level largely ignoring the others which can lead to slippage between levels (Chater et al., 2003). It is argued that recent brain imaging research on deductive reasoning-implementational level-has largely ignored the new paradigm in reasoning-computational level (Over, 2009). Consequently, recent imaging results are reviewed with the focus on how they relate to the new paradigm. The imaging results are drawn primarily from a recent meta-analysis by Prado et al. (2011) but further imaging results are also reviewed where relevant. Three main observations are made. First, the main function of the core brain region identified is most likely elaborative, defeasible reasoning not deductive reasoning. Second, the subtraction methodology and the meta-analytic approach may remove all traces of content specific System 1 processes thought to underpin much human reasoning. Third, interpreting the function of the brain regions activated by a task depends on theories of the function that a task engages. When there are multiple interpretations of that function, interpreting what an active brain region is doing is not clear cut. It is concluded that there is a need to more tightly connect brain activation to function, which could be achieved using formalized computational level models and a parametric variation approach. PMID:25774130

  1. Towards a New Paradigm in Education

    Directory of Open Access Journals (Sweden)

    Garry Jacobs

    2014-05-01

    Full Text Available A new paradigm in human development must be founded upon a new paradigm in education. A human-centered educational system is needed whose aim is the fullest development of the capacities of each individual. Today humanity is on the cusp of a major transition in education, our most powerful instrument for conscious social evolution. Quality education can now be made universally accessible and affordable. Equally important, future education must be made relevant to the rapidly changing needs of society, the increasingly sophisticated demands of the labor market, the growing shortage of attitudes and skills need to promote entrepreneurship and full employment, the values needed for social harmony and problem solving, and the individuality needed for leadership, independent thinking and creativity. The coming revolution in education spurred by the breakthrough in online learning has made all of these goals achievable. New technology can facilitate a shift from the drudgery of passive knowledge transfer and memorization to the exhilaration of active learning that fosters curiosity, discovery and original thinking. It can also help break down the intellectual boundaries between disciplines, making possible a more comprehensive, transdisciplinary, integrated approach to knowledge. A revolution in higher education is upon us.

  2. Consumers’ Empowerement for a New Marketing Paradigm

    Directory of Open Access Journals (Sweden)

    Victor Danciu

    2013-09-01

    Full Text Available The marketing practices of the companies show that not all of them are observing ethical and moral standards and they manipulate the consumers. This paper has as main goal to examine the most usual unethical techniques, the present status of consumers’ power and how more power could work for a new marketing paradigm. There are many unethical marketing techniques which could be found in deceptive product recipes, packaging, promotion, prices and in other areas. Most consumers have no appropriate powers and tools to counteract the manipulation techniques and feel they have fewer rights than the marketers. The current state of empowerment of the consumer show that the European consumers are not in the best position in the market as the Consumer Empowerment Index proves. This matter of facts emphasizes a strong need for a better empowerment of the consumers. The consumer which has more power and wisely use it could improve the balance of power in the market. But the consumers should have a proactive buying behavior in order to get such results. These revolutionary consumers attack the structural roots of the social, economic and political problems which produces a new market ideology as a part of the new tier of transnational institutional ideology. This consumer behavior may have a strong influence toward a new marketing paradigm.

  3. Testing the membrane paradigm with holography

    CERN Document Server

    de Boer, Jan; Pinzani-Fokeeva, Natalia

    2014-01-01

    One version of the membrane paradigm states that as far as outside observers are concerned, black holes can be replaced by a dissipative membrane with simple physical properties located at the stretched horizon. We demonstrate, in the AdS/CFT context, that such a membrane paradigm is incomplete in several aspects. We argue that it generically fails to capture the massive quasinormal modes, unless we replace the stretched horizon by the true horizon, and show this explicitly for a scalar field in a BTZ background. We also consider linearized metric perturbations of a five-dimensional AdS-Schwarzschild black brane and show that a spurious excitation appears in the long-wavelength response that is only removed from the spectrum when the stretched horizon is replaced by ingoing boundary conditions at the true horizon. We interpret this excitation in terms of an additional Goldstone boson that appears due to symmetry breaking by the classical solution ending on the stretched horizon rather than the true horizon.

  4. Tolerance of sexual harassment: a laboratory paradigm.

    Science.gov (United States)

    Angelone, David J; Mitchell, Damon; Carola, Kara

    2009-12-01

    The present study attempted to develop a laboratory analogue for the study of tolerance for sexual harassment by using an online speed-dating paradigm. In that context, the relation between participants' sexual harassment attitudes, perpetrator attractiveness, perpetrator status, and perceived dating potential of the perpetrator were examined as factors influencing participants' tolerance of sexually harassing behavior. Participants were 128 female college students from a small northeastern public university. Results indicated that attractiveness, high social status, and attitudinal beliefs about sexual harassment were all predictive of tolerance for sexual harassment, providing preliminary support for the validity of this paradigm. In addition, participants' self reported likelihood to date a bogus male dating candidate was also predictive of tolerance for sexual harassment, over and above the aforementioned variables, suggesting that dating potential can play a role in perceptions of sexual harassment. Further, this experiment demonstrated that perceptions of sexual harassment can be assessed using the in vivo measurement of behavior. In addition, using an online environment not only provides a contemporary spin and adds a greater degree of external validity compared to other sexual harassment analogues, it also reduces any risk of potential physical sexual contact for participants. PMID:19030980

  5. Osteoporosis: Modern Paradigms for Last Century's Bones.

    Science.gov (United States)

    Kruger, Marlena C; Wolber, Frances M

    2016-01-01

    The skeleton is a metabolically active organ undergoing continuously remodelling. With ageing and menopause the balance shifts to increased resorption, leading to a reduction in bone mineral density and disruption of bone microarchitecture. Bone mass accretion and bone metabolism are influenced by systemic hormones as well as genetic and lifestyle factors. The classic paradigm has described osteoporosis as being a "brittle bone" disease that occurs in post-menopausal, thin, Caucasian women with low calcium intakes and/or vitamin D insufficiency. However, a study of black women in Africa demonstrated that higher proportions of body fat did not protect bone health. Isoflavone interventions in Asian postmenopausal women have produced inconsistent bone health benefits, due in part to population heterogeneity in enteric bacterial metabolism of daidzein. A comparison of women and men in several Asian countries identified significant differences between countries in the rate of bone health decline, and a high incidence rate of osteoporosis in both sexes. These studies have revealed significant differences in genetic phenotypes, debunking long-held beliefs and leading to new paradigms in study design. Current studies are now being specifically designed to assess genotype differences between Caucasian, Asian, African, and other phenotypes, and exploring alternative methodology to measure bone architecture. PMID:27322315

  6. Long Period Variables: questioning the pulsation paradigm

    CERN Document Server

    Berlioz-Arthaud, Paul

    2016-01-01

    Long period variables, among them Miras, are thought to be pulsating. Under this approach the whole star inflates and deflates along a period that can vary from 100 to 900 days; that pulsation is assumed to produce shock waves on the outer layers of the star that propagate into the atmosphere and could account for the increase in luminosity and the presence of emission lines in the spectra of these stars. However, this paradigm can seriously be questioned from a theoretical point of view. First, in order to maintain a radial pulsation, the spherical symmetry of the star must be preserved: how can it be reconciled with the large convective cells present in these stars? or when close companions are detected? Secondly, how different radial and non-radial pulsation modes of a sphere could be all damped except one radial mode? These problems have no solution and significantly weigh on the pulsation paradigm. Acknowledging this inconsistency, we show that a close companion around these stars could account for the s...

  7. Locating the Doctoral Study in the "Paradigm Skirmishes": Challenges and Prospects for Adopting a Paradigm Cradle

    Science.gov (United States)

    Ruto-Korir, Rose; Lubbe, Carien

    2010-01-01

    It is important to understand the thought patterns of students and supervisors that underlie the choice of paradigm and determine the progression of doctoral studies as an integral part of articulating scholarship at the doctoral level and subsequently, to completing the research. This paper traces a student's and a supervisor's thought patterns…

  8. Parity properties of an advection-dominated solar $\\alpha^2\\Om$-dynamo

    OpenAIRE

    Bonanno, A.; Elstner, D.; Ruediger, G.; G. Belvedere

    2002-01-01

    We have developed a high-precision code which solves the kinematic dynamo problem both for given rotation law and meridional flow in the case of a low eddy diffusivity of the order of $10^{11}$ cm$^2$/s known from the sunspot decay. All our models work with an \\alf-effect which is positive (negative) in the northern (southern) hemisphere. It is concentrated in radial layers located either at the top or at the bottom of the convection zone. We have also considered an \\alf-effect uniformly dist...

  9. Revisiting System Paradigms from the Viewpoint of Manufacturing Sustainability

    OpenAIRE

    Zhuming Bi

    2011-01-01

    A system paradigm is an abstract representation of system; it includes system architecture used to determine the types and numbers of components and their relations in the system. The design of system paradigm relies on customers’ requirements and the characteristics of the manufacturing environment. Many system paradigms and design guidelines have been proposed for a variety of customers’ needs including functions, cost, quality, personalization, and lead time of products. However, the c...

  10. Organizations, Paradigms, and People: The Challenge of KM Interventions

    Science.gov (United States)

    Bailey, Teresa; Burton, Yvette

    1999-01-01

    This paper presents viewgraphs on Knowledge Management (KM) and how these interventions are put into practice by organizations and society. The topics include: 1) The Multiple Paradigm Tool; 2) Four Paradigms: tool for the Analyzing Organizations; 3) Assumptions About the Nature of Social Science; 4) Assumptions About the Nature of Society; 5) Schools of Sociological and Organizational Theory; 6) Meaning and Metaphors in the Four Paradigms; and 7) Possibilities and Conclusions.

  11. Paradigm Shift from Current Manufacturing to Social Manufacturing

    OpenAIRE

    Mohajeri, Babak

    2015-01-01

    The emergent phenomenon of social manufacturing is disrupting industries all over the world. Social manufacturing represents a new collaborative manufacturing paradigm. The shift from the current manufacturing paradigm to social manufacturing is facilitated by rapid development of mobile technologies, new digital manufacturing, and online social networks. There are already successful businesses that build upon the social manufacturing paradigm, e.g., in finance, hospitality, and transportatio...

  12. Permafrost thaw in a nested groundwater-flow system

    Science.gov (United States)

    McKenzie, Jeffery M.; Voss, Clifford I.

    2013-01-01

    Groundwater flow in cold regions containing permafrost accelerates climate-warming-driven thaw and changes thaw patterns. Simulation analyses of groundwater flow and heat transport with freeze/thaw in typical cold-regions terrain with nested flow indicate that early thaw rate is particularly enhanced by flow, the time when adverse environmental impacts of climate-warming-induced permafrost loss may be severest. For the slowest climate-warming rate predicted by the Intergovernmental Panel on Climate Change (IPCC), once significant groundwater flow begins, thick permafrost layers can vanish in several hundred years, but survive over 1,000 years where flow is minimal. Large-scale thaw depends mostly on the balance of heat advection and conduction in the supra-permafrost zone. Surface-water bodies underlain by open taliks allow slow sub-permafrost flow, with lesser influence on regional thaw. Advection dominance over conduction depends on permeability and topography. Groundwater flow around permafrost and flow through permafrost impact thaw differently; the latter enhances early thaw rate. Air-temperature seasonality also increases early thaw. Hydrogeologic heterogeneity and topography strongly affect thaw rates/patterns. Permafrost controls the groundwater/surface-water-geomorphology system; hence, prediction and mitigation of impacts of thaw on ecology, chemical exports and infrastructure require improved hydrogeology/permafrost characterization and understanding

  13. Interaction of monopoles, dipoles, and turbulence with a shear flow

    Science.gov (United States)

    Marques Rosas Fernandes, V. H.; Kamp, L. P. J.; van Heijst, G. J. F.; Clercx, H. J. H.

    2016-09-01

    Direct numerical simulations have been conducted to examine the evolution of eddies in the presence of large-scale shear flows. The numerical experiments consist of initial-value-problems in which monopolar and dipolar vortices as well as driven turbulence are superposed on a plane Couette or Poiseuille flow in a periodic two-dimensional channel. The evolution of the flow has been examined for different shear rates of the background flow and different widths of the channel. Results found for retro-grade and pro-grade monopolar vortices are consistent with those found in the literature. Boundary layer vorticity, however, can significantly modify the straining and erosion of monopolar vortices normally seen for unbounded domains. Dipolar vortices are shown to be much more robust coherent structures in a large-scale shear flow than monopolar eddies. An analytical model for their trajectories, which are determined by self-advection and advection and rotation by the shear flow, is presented. Turbulent kinetic energy is effectively suppressed by the shearing action of the background flow provided that the shear is linear (Couette flow) and of sufficient strength. Nonlinear shear as present in the Poiseuille flow seems to even increase the turbulence strength especially for high shear rates.

  14. The use of repetition suppression paradigms in developmental cognitive neuroscience.

    Science.gov (United States)

    Nordt, Marisa; Hoehl, Stefanie; Weigelt, Sarah

    2016-07-01

    Repetition suppression paradigms allow a more detailed look at brain functioning than classical paradigms and have been applied vigorously in adult cognitive neuroscience. These paradigms are well suited for studies in the field of developmental cognitive neuroscience as they can be applied without collecting a behavioral response and across all age groups. Furthermore, repetition suppression paradigms can be employed in various neuroscience techniques, such as functional magnetic resonance imaging (fMRI), functional near-infrared spectroscopy (fNIRS), electroencephalography (EEG) and magnetoencephalography (MEG). In the present article we review studies using repetition suppression paradigms in developmental cognitive neuroscience covering the age range from infancy to adolescence. Our first goal is to point out characteristics of developmental repetition suppression effects. In doing so, we discuss the relationship of the direction of repetition effects (suppression vs enhancement) with developmental factors, and address the question how the direction of repetition effects might be related to looking-time effects in behavioral infant paradigms, the most prominently used behavioral measure in infant research. To highlight the potential of repetition suppression paradigms, our second goal is to provide an overview on the insights recently obtained by applying repetition paradigms in neurodevelopmental studies, including research on children with autism spectrum disorders (ASDs). We conclude that repetition suppression paradigms are valuable tools for investigating neurodevelopmental processes, while at the same time we highlight the necessity for further studies that disentangle methodological and developmental factors. PMID:27161033

  15. Environmental Pressures,Management Imperatives, and Competing Paradigms in Educational Administration

    Institute of Scientific and Technical Information of China (English)

    LUO Jia ying

    2002-01-01

    Across much of the westernized world, environmental pressures have transformed the context of public educational administration. In particular, the changing world economy, decline of confidence in the welfare state, and adverse social trends have generated strong pressures for change in the organization and performance of education systems, and for nothing less than a paradigm shift in educational management.Together, these social forces have produced three interconnected imperatives for educational administrators:a productivity imperative, an accountability imperative, and a community imperative. Efforts to respond to these imperatives have generated tensions between competing paradigms in educational management. This article discusses the environmental pressures noted above, the resulting three imperatives, and the tensions flowing from these developments.

  16. Shifting the Climate Finance Paradigm: Nine Key Challenges for Developed Countries

    Energy Technology Data Exchange (ETDEWEB)

    Curtin, Joseph

    2013-03-13

    In 2009, developed countries committed to part-funding the cost of adapting to the impacts of climate change and of low carbon development in developing countries. From 2010 to 2012, fast start finance began to flow from developed country exchequers. However, the climate finance paradigm is now shifting. A transition from loans and grants provided from scarce exchequer resources to innovative instruments for leveraging private capital and mitigating investment risk is required in the coming period. But what are the implications for developed countries? This policy brief explores the policy context defining the current climate finance debate; examines the extent to which commitments have been met; and identifies nine key challenges for developed countries as they enter the new climate finance paradigm, drawing on the lessons of the fast start finance period. This is the second in a series of Environment Nexus policy briefs by leading experts in the fields of agriculture, energy, climate change and water.

  17. Diffusive transport in Stokeslet flow and its application to plankton ecology

    DEFF Research Database (Denmark)

    Thygesen, Uffe Høgsbro; Kiørboe, Thomas

    2006-01-01

    In this paper we consider the advective/diffusive transport of a solute near a hovering zooplankter. We approximate the fluid flow with that of a Stokeslet, corresponding to the plankter exerting a point force on the water, and assume that the plankter acts as a point source for the transported...

  18. Front Speed Enhancement by Incompressible Flows in Three or Higher Dimensions

    Science.gov (United States)

    El Smaily, Mohammad; Kirsch, Stéphane

    2014-07-01

    We study, in dimensions N ≥ 3, the family of first integrals of an incompressible flow: these are functions whose level surfaces are tangential to the streamlines of the advective incompressible field. One main motivation for this study comes from earlier results proving that the existence of nontrivial first integrals of an incompressible flow q is the main key that leads to a "linear speed up" by a large advection of pulsating traveling fronts solving a reaction-advection-diffusion equation in a periodic heterogeneous framework. The family of first integrals is not well understood in dimensions N ≥ 3 due to the randomness of the trajectories of q and this is in contrast with the case N = 2. By looking at the domain of propagation as a union of different components produced by the advective field, we provide more information about first integrals and we give a class of incompressible flows which exhibit "ergodic components" of positive Lebesgue measure (and hence are not shear flows) and which, under certain sharp geometric conditions, speed up the KPP fronts linearly with respect to the large amplitude. In the proofs, we establish a link between incompressibility, ergodicity, first integrals and the dimension to give a sharp condition about the asymptotic behavior of the minimal KPP speed in terms of the configuration of ergodic components.

  19. Measurement of Flow Velocity and Inference of Liquid Viscosity in a Microfluidic Channel by Fluorescence Photobleaching

    DEFF Research Database (Denmark)

    Carroll, Nick J.; Jensen, Kaare Hartvig; Parsa, Shima;

    2014-01-01

    downstream of the initial front position. We fit an exact solution of the advection diffusion equation to the fluorescence intensity recovery curve to determine the average flow velocity and the diffusion coefficient of the tracer dye. The dye diffusivity is correlated to solute concentration to infer...

  20. Stability of Streamline Upwind Petrov-Galerkin (SUPG) finite elements for transient advection-diffusion problems.

    Energy Technology Data Exchange (ETDEWEB)

    Shadid, John Nicolas; Bochev, Pavel Blagoveston; Gunzburger, Max Donald (Florida State University, Tallahasse, FL)

    2003-09-01

    Implicit time integration coupled with SUPG discretization in space leads to additional terms that provide consistency and improve the phase accuracy for convection dominated flows. Recently, it has been suggested that for small Courant numbers these terms may dominate the streamline diffusion term, ostensibly causing destabilization of the SUPG method. While consistent with a straightforward finite element stability analysis, this contention is not supported by computational experiments and contradicts earlier Von-Neumann stability analyses of the semidiscrete SUPG equations. This prompts us to re-examine finite element stability of the fully discrete SUPG equations. A careful analysis of the additional terms reveals that, regardless of the time step size, they are always dominated by the consistent mass matrix. Consequently, SUPG cannot be destabilized for small Courant numbers. Numerical results that illustrate our conclusions are reported.