Multigrid calculation of three-dimensional viscous cascade flows

NASA Technical Reports Server (NTRS)

Arnone, A.; Liou, M.-S.; Povinelli, L. A.

1991-01-01

A three-dimensional code for viscous cascade flow prediction has been developed. The space discretization uses a cell-centered scheme with eigenvalue scaling to weigh the artificial dissipation terms. Computational efficiency of a four-stage Runge-Kutta scheme is enhanced by using variable coefficients, implicit residual smoothing, and a full-multigrid method. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. A zonal, nonperiodic grid is used to minimize mesh distortion in and downstream of the throat region. Applications are presented for an annular vane with and without end wall contouring, and for a large-scale linear cascade. The calculation is validated by comparing with experiments and by studying grid dependency.

Fourier-Legendre spectral methods for incompressible channel flow

NASA Technical Reports Server (NTRS)

Zang, T. A.; Hussaini, M. Y.

1984-01-01

An iterative collocation technique is described for modeling implicit viscosity in three-dimensional incompressible wall bounded shear flow. The viscosity can vary temporally and in the vertical direction. Channel flow is modeled with a Fourier-Legendre approximation and the mean streamwise advection is treated implicitly. Explicit terms are handled with an Adams-Bashforth method to increase the allowable time-step for calculation of the implicit terms. The algorithm is applied to low amplitude unstable waves in a plane Poiseuille flow at an Re of 7500. Comparisons are made between results using the Legendre method and with Chebyshev polynomials. Comparable accuracy is obtained for the perturbation kinetic energy predicted using both discretizations.

Numerical dissipation vs. subgrid-scale modelling for large eddy simulation

NASA Astrophysics Data System (ADS)

Dairay, Thibault; Lamballais, Eric; Laizet, Sylvain; Vassilicos, John Christos

2017-05-01

This study presents an alternative way to perform large eddy simulation based on a targeted numerical dissipation introduced by the discretization of the viscous term. It is shown that this regularisation technique is equivalent to the use of spectral vanishing viscosity. The flexibility of the method ensures high-order accuracy while controlling the level and spectral features of this purely numerical viscosity. A Pao-like spectral closure based on physical arguments is used to scale this numerical viscosity a priori. It is shown that this way of approaching large eddy simulation is more efficient and accurate than the use of the very popular Smagorinsky model in standard as well as in dynamic version. The main strength of being able to correctly calibrate numerical dissipation is the possibility to regularise the solution at the mesh scale. Thanks to this property, it is shown that the solution can be seen as numerically converged. Conversely, the two versions of the Smagorinsky model are found unable to ensure regularisation while showing a strong sensitivity to numerical errors. The originality of the present approach is that it can be viewed as implicit large eddy simulation, in the sense that the numerical error is the source of artificial dissipation, but also as explicit subgrid-scale modelling, because of the equivalence with spectral viscosity prescribed on a physical basis.

Dual-modality impairment of implicit learning of letter-strings versus color-patterns in patients with schizophrenia.

PubMed

Chiu, Ming-Jang; Liu, Kristina; Hsieh, Ming H; Hwu, Hai-Gwo

2005-12-12

Implicit learning was reported to be intact in schizophrenia using artificial grammar learning. However, emerging evidence indicates that artificial grammar learning is not a unitary process. The authors used dual coding stimuli and schizophrenia clinical symptom dimensions to re-evaluate the effect of schizophrenia on various components of artificial grammar learning. Letter string and color pattern artificial grammar learning performances were compared between 63 schizophrenic patients and 27 comparison subjects. Four symptom dimensions derived from a Chinese Positive and Negative Symptom Scale ratings were correlated with patients' artificial grammar implicit learning performances along the two stimulus dimensions. Patients' explicit memory performances were assessed by verbal paired associates and visual reproduction subtests of the Wechsler Memory Scales Revised Version to provide a contrast to their implicit memory function. Schizophrenia severely hindered color pattern artificial grammar learning while the disease affected lexical string artificial grammar learning to a lesser degree after correcting the influences from age, education and the performance of explicit memory function of both verbal and visual modalities. Both learning performances correlated significantly with the severity of patients' schizophrenic clinical symptom dimensions that reflect poor abstract thinking, disorganized thinking, and stereotyped thinking. The results of this study suggested that schizophrenia affects various mechanisms of artificial grammar learning differently. Implicit learning, knowledge acquisition in the absence of conscious awareness, is not entirely intact in patients with schizophrenia. Schizophrenia affects implicit learning through an impairment of the ability of making abstractions from rules and at least in part decreasing the capacity for perceptual learning.

A framework for developing a mimetic tensor artificial viscosity for Lagrangian hydrocodes on arbitrary polygonal and polyhedral meshes (u)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lipnikov, Konstantin; Shashkov, Mikhail

2011-01-11

We construct a new mimetic tensor artificial viscosity on general polygonal and polyhedral meshes. The tensor artificial viscosity is based on a mimetic discretization of coordinate invariant operators, divergence of a tensor and gradient of a vector. The focus of this paper is on the symmetric form, div ({mu},{var_epsilon}(u)), of the tensor artificial viscosity where {var_epsilon}(u) is the symmetrized gradient of u and {mu}, is a tensor. The mimetic discretizations of this operator is derived for the case of a full tensor coefficient {mu}, that may reflect a shock direction. We demonstrate performance of the new viscosity for the Nohmore » implosion, Sedov explosion and Saltzman piston problems in both Cartesian and axisymmetric coordinate systems.« less

A computational fluid dynamics simulation of the hypersonic flight of the Pegasus(TM) vehicle using an artificial viscosity model and a nonlinear filtering method. M.S. Thesis

NASA Technical Reports Server (NTRS)

Mendoza, John Cadiz

1995-01-01

The computational fluid dynamics code, PARC3D, is tested to see if its use of non-physical artificial dissipation affects the accuracy of its results. This is accomplished by simulating a shock-laminar boundary layer interaction and several hypersonic flight conditions of the Pegasus(TM) launch vehicle using full artificial dissipation, low artificial dissipation, and the Engquist filter. Before the filter is applied to the PARC3D code, it is validated in one-dimensional and two-dimensional form in a MacCormack scheme against the Riemann and convergent duct problem. For this explicit scheme, the filter shows great improvements in accuracy and computational time as opposed to the nonfiltered solutions. However, for the implicit PARC3D code it is found that the best estimate of the Pegasus experimental heat fluxes and surface pressures is the simulation utilizing low artificial dissipation and no filter. The filter does improve accuracy over the artificially dissipative case but at a computational expense greater than that achieved by the low artificial dissipation case which has no computational time penalty and shows better results. For the shock-boundary layer simulation, the filter does well in terms of accuracy for a strong impingement shock but not as well for weaker shock strengths. Furthermore, for the latter problem the filter reduces the required computational time to convergence by 18.7 percent.

Hyperviscosity for unstructured ALE meshes

NASA Astrophysics Data System (ADS)

Cook, Andrew W.; Ulitsky, Mark S.; Miller, Douglas S.

2013-01-01

An artificial viscosity, originally designed for Eulerian schemes, is adapted for use in arbitrary Lagrangian-Eulerian simulations. Changes to the Eulerian model (dubbed 'hyperviscosity') are discussed, which enable it to work within a Lagrangian framework. New features include a velocity-weighted grid scale and a generalised filtering procedure, applicable to either structured or unstructured grids. The model employs an artificial shear viscosity for treating small-scale vorticity and an artificial bulk viscosity for shock capturing. The model is based on the Navier-Stokes form of the viscous stress tensor, including the diagonal rate-of-expansion tensor. A second-order version of the model is presented, in which Laplacian operators act on the velocity divergence and the grid-weighted strain-rate magnitude to ensure that the velocity field remains smooth at the grid scale. Unlike sound-speed-based artificial viscosities, the hyperviscosity model is compatible with the low Mach number limit. The new model outperforms a commonly used Lagrangian artificial viscosity on a variety of test problems.

Experience in using a numerical scheme with artificial viscosity at solving the Riemann problem for a multi-fluid model of multiphase flow

NASA Astrophysics Data System (ADS)

Bulovich, S. V.; Smirnov, E. M.

2018-05-01

The paper covers application of the artificial viscosity technique to numerical simulation of unsteady one-dimensional multiphase compressible flows on the base of the multi-fluid approach. The system of the governing equations is written under assumption of the pressure equilibrium between the "fluids" (phases). No interfacial exchange is taken into account. A model for evaluation of the artificial viscosity coefficient that (i) assumes identity of this coefficient for all interpenetrating phases and (ii) uses the multiphase-mixture Wood equation for evaluation of a scale speed of sound has been suggested. Performance of the artificial viscosity technique has been evaluated via numerical solution of a model problem of pressure discontinuity breakdown in a three-fluid medium. It has been shown that a relatively simple numerical scheme, explicit and first-order, combined with the suggested artificial viscosity model, predicts a physically correct behavior of the moving shock and expansion waves, and a subsequent refinement of the computational grid results in a monotonic approaching to an asymptotic time-dependent solution, without non-physical oscillations.

Relaxation and approximate factorization methods for the unsteady full potential equation

NASA Technical Reports Server (NTRS)

Shankar, V.; Ide, H.; Gorski, J.

1984-01-01

The unsteady form of the full potential equation is solved in conservation form, using implicit methods based on approximate factorization and relaxation schemes. A local time linearization for density is introduced to enable solution to the equation in terms of phi, the velocity potential. A novel flux-biasing technique is applied to generate proper forms of the artificial viscosity, to treat hyperbolic regions with shocks and sonic lines present. The wake is properly modeled by accounting not only for jumps in phi, but also for jumps in higher derivatives of phi obtained from requirements of density continuity. The far field is modeled using the Riemann invariants to simulate nonreflecting boundary conditions. Results are presented for flows over airfoils, cylinders, and spheres. Comparisons are made with available Euler and full potential results.

Long-time stability effects of quadrature and artificial viscosity on nodal discontinuous Galerkin methods for gas dynamics

NASA Astrophysics Data System (ADS)

Durant, Bradford; Hackl, Jason; Balachandar, Sivaramakrishnan

2017-11-01

Nodal discontinuous Galerkin schemes present an attractive approach to robust high-order solution of the equations of fluid mechanics, but remain accompanied by subtle challenges in their consistent stabilization. The effect of quadrature choices (full mass matrix vs spectral elements), over-integration to manage aliasing errors, and explicit artificial viscosity on the numerical solution of a steady homentropic vortex are assessed over a wide range of resolutions and polynomial orders using quadrilateral elements. In both stagnant and advected vortices in periodic and non-periodic domains the need arises for explicit stabilization beyond the numerical surface fluxes of discontinuous Galerkin spectral elements. Artificial viscosity via the entropy viscosity method is assessed as a stabilizing mechanism. It is shown that the regularity of the artificial viscosity field is essential to its use for long-time stabilization of small-scale features in nodal discontinuous Galerkin solutions of the Euler equations of gas dynamics. Supported by the Department of Energy Predictive Science Academic Alliance Program Contract DE-NA0002378.

Eye Movements in Implicit Artificial Grammar Learning

ERIC Educational Resources Information Center

Silva, Susana; Inácio, Filomena; Folia, Vasiliki; Petersson, Karl Magnus

2017-01-01

Artificial grammar learning (AGL) has been probed with forced-choice behavioral tests (active tests). Recent attempts to probe the outcomes of learning (implicitly acquired knowledge) with eye-movement responses (passive tests) have shown null results. However, these latter studies have not tested for sensitivity effects, for example, increased…

One-dimensional Lagrangian implicit hydrodynamic algorithm for Inertial Confinement Fusion applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ramis, Rafael, E-mail: rafael.ramis@upm.es

A new one-dimensional hydrodynamic algorithm, specifically developed for Inertial Confinement Fusion (ICF) applications, is presented. The scheme uses a fully conservative Lagrangian formulation in planar, cylindrical, and spherically symmetric geometries, and supports arbitrary equations of state with separate ion and electron components. Fluid equations are discretized on a staggered grid and stabilized by means of an artificial viscosity formulation. The space discretized equations are advanced in time using an implicit algorithm. The method includes several numerical parameters that can be adjusted locally. In regions with low Courant–Friedrichs–Lewy (CFL) number, where stability is not an issue, they can be adjusted tomore » optimize the accuracy. In typical problems, the truncation error can be reduced by a factor between 2 to 10 in comparison with conventional explicit algorithms. On the other hand, in regions with high CFL numbers, the parameters can be set to guarantee unconditional stability. The method can be integrated into complex ICF codes. This is demonstrated through several examples covering a wide range of situations: from thermonuclear ignition physics, where alpha particles are managed as an additional species, to low intensity laser–matter interaction, where liquid–vapor phase transitions occur.« less

Artificial viscosity in Godunov-type schemes to cure the carbuncle phenomenon

NASA Astrophysics Data System (ADS)

Rodionov, Alexander V.

2017-09-01

This work presents a new approach for curing the carbuncle instability. The idea underlying the approach is to introduce some dissipation in the form of right-hand sides of the Navier-Stokes equations into the basic method of solving Euler equations; in so doing, we replace the molecular viscosity coefficient by the artificial viscosity coefficient and calculate heat conductivity assuming that the Prandtl number is constant. For the artificial viscosity coefficient we have chosen a formula that is consistent with the von Neumann and Richtmyer artificial viscosity, but has its specific features (extension to multidimensional simulations, introduction of a threshold compression intensity that restricts additional dissipation to the shock layer only). The coefficients and the expression for the characteristic mesh size in this formula are chosen from a large number of Quirk-type problem computations. The new cure for the carbuncle flaw has been tested on first-order schemes (Godunov, Roe, HLLC and AUSM+ schemes) as applied to one- and two-dimensional simulations on smooth structured grids. Its efficiency has been demonstrated on several well-known test problems.

Fast viscosity solutions for shape from shading under a more realistic imaging model

NASA Astrophysics Data System (ADS)

Wang, Guohui; Han, Jiuqiang; Jia, Honghai; Zhang, Xinman

2009-11-01

Shape from shading (SFS) has been a classical and important problem in the domain of computer vision. The goal of SFS is to reconstruct the 3-D shape of an object from its 2-D intensity image. To this end, an image irradiance equation describing the relation between the shape of a surface and its corresponding brightness variations is used. Then it is derived as an explicit partial differential equation (PDE). Using the nonlinear programming principle, we propose a detailed solution to Prados and Faugeras's implicit scheme for approximating the viscosity solution of the resulting PDE. Furthermore, by combining implicit and semi-implicit schemes, a new approximation scheme is presented. In order to accelerate the convergence speed, we adopt the Gauss-Seidel idea and alternating sweeping strategy to the approximation schemes. Experimental results on both synthetic and real images are performed to demonstrate that the proposed methods are fast and accurate.

Improving the accuracy of central difference schemes

NASA Technical Reports Server (NTRS)

Turkel, Eli

1988-01-01

General difference approximations to the fluid dynamic equations require an artificial viscosity in order to converge to a steady state. This artificial viscosity serves two purposes. One is to suppress high frequency noise which is not damped by the central differences. The second purpose is to introduce an entropy-like condition so that shocks can be captured. These viscosities need a coefficient to measure the amount of viscosity to be added. In the standard scheme, a scalar coefficient is used based on the spectral radius of the Jacobian of the convective flux. However, this can add too much viscosity to the slower waves. Hence, it is suggested that a matrix viscosity be used. This gives an appropriate viscosity for each wave component. With this matrix valued coefficient, the central difference scheme becomes closer to upwind biased methods.

The reality of artificial viscosity

DOE PAGES

Margolin, L. G.

2018-02-24

Artificial viscosity is used in the computer simulation of high Reynolds number flows and is one of the oldest numerical artifices. In this work, I will describe the origin and the interpretation of artificial viscosity as a physical phenomenon. The basis of this interpretation is the finite scale theory, which describes the evolution of integral averages of the fluid solution over finite (length) scales. I will outline the derivation of finite scale Navier–Stokes equations and highlight the particular properties of the equations that depend on the finite scales. Those properties include enslavement, inviscid dissipation, and a law concerning the partitionmore » of total flux of conserved quantities into advective and diffusive components.« less

The reality of artificial viscosity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Margolin, L. G.

Artificial viscosity is used in the computer simulation of high Reynolds number flows and is one of the oldest numerical artifices. In this work, I will describe the origin and the interpretation of artificial viscosity as a physical phenomenon. The basis of this interpretation is the finite scale theory, which describes the evolution of integral averages of the fluid solution over finite (length) scales. I will outline the derivation of finite scale Navier–Stokes equations and highlight the particular properties of the equations that depend on the finite scales. Those properties include enslavement, inviscid dissipation, and a law concerning the partitionmore » of total flux of conserved quantities into advective and diffusive components.« less

Determining the Viscosity Coefficient for Viscoelastic Wave Propagation in Rock Bars

NASA Astrophysics Data System (ADS)

Niu, Leilei; Zhu, Wancheng; Li, Shaohua; Guan, Kai

2018-05-01

Rocks with microdefects exhibit viscoelastic behavior during stress wave propagation. The viscosity coefficient of the wave can be used to characterize the attenuation as the wave propagates in rock. In this study, a long artificial bar with a readily adjustable viscosity coefficient was fabricated to investigate stress wave attenuation. The viscoelastic behavior of the artificial bar under dynamic loading was investigated, and the initial viscoelastic coefficient was obtained based on the amplitude attenuation of the incident harmonic wave. A one-dimensional wave propagation program was compiled to reproduce the time history of the stress wave measured during the experiments, and the program was well fitted to the Kelvin-Voigt model. The attenuation and dispersion of the stress wave in long artificial viscoelastic bars were quantified to accurately determine the viscoelastic coefficient. Finally, the method used to determine the viscoelastic coefficient of a long artificial bar based on the experiments and numerical simulations was extended to determine the viscoelastic coefficient of a short rock bar. This study provides a new method of determining the viscosity coefficient of rock.

User`s guide for UTCHEM implicit (1.0) a three dimensional chemical flood simulator. Final report, September 30, 1992--December 31, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-07-01

UTCHEM IMPLICIT is a three-dimensional chemical flooding simulator. The solution scheme is fully implicit. The pressure equation and the mass conservation equations are solved simultaneously for the aqueous phase pressure and the total concentrations of each component. A third-order-in-space, second-order-in-time finite-difference method and a new total-variation-diminishing (TVD) third-order flux limiter are used to reduce numerical dispersion effects. Saturations and phase concentrations are solved in a flash routine. The major physical phenomena modeled in the simulator are: dispersion, adsorption, aqueous-oleic-microemulsion phase behavior, interfacial tension, relative permeability, capillary trapping, compositional phase viscosity, capillary pressure, phase density, polymer properties: shear thinning viscosity, inaccessiblemore » pore volume, permeability reduction, and adsorption. The following options are available in the simulator: constant or variable time-step sizes, uniform or nonuniform grid, pressure or rate constrained wells, horizontal and vertical wells.« less

Effects of heat conduction on artificial viscosity methods for shock capturing

DOE PAGES

Cook, Andrew W.

2013-12-01

Here we investigate the efficacy of artificial thermal conductivity for shock capturing. The conductivity model is derived from artificial bulk and shear viscosities, such that stagnation enthalpy remains constant across shocks. By thus fixing the Prandtl number, more physical shock profiles are obtained, only on a larger scale. The conductivity model does not contain any empirical constants. It increases the net dissipation of a computational algorithm but is found to better preserve symmetry and produce more robust solutions for strong-shock problems.

Explicit and Implicit Learning: Exploring Their Simultaneity and Immediate Effectiveness

ERIC Educational Resources Information Center

Bell, Philippa K.

2017-01-01

Do adults learn the same syntactic second language (L2) form explicitly and implicitly simultaneously during meaning-based exposure, and does the type of learning (explicit and/or implicit) affect subsequent performance. In this study, 81 anglophones completed comprehension tasks providing incidental exposure to a semi-artificial language (English…

A View of the Neural Representation of Second Language Syntax through Artificial Language Learning under Implicit Contexts of Exposure

ERIC Educational Resources Information Center

Morgan-Short, Kara; Deng, ZhiZhou; Brill-Schuetz, Katherine A.; Faretta- Stutenberg, Mandy; Wong, Patrick C. M.; Wong, Francis C. K.

2015-01-01

The current study aims to make an initial neuroimaging contribution to central implicit-explicit issues in second language (L2) acquisition by considering how implicit and explicit contexts mediate the neural representation of L2. Focusing on implicit contexts, the study employs a longitudinal design to examine the neural representation of L2…

Accuracy versus convergence rates for a three dimensional multistage Euler code

NASA Technical Reports Server (NTRS)

Turkel, Eli

1988-01-01

Using a central difference scheme, it is necessary to add an artificial viscosity in order to reach a steady state. This viscosity usually consists of a linear fourth difference to eliminate odd-even oscillations and a nonlinear second difference to suppress oscillations in the neighborhood of steep gradients. There are free constants in these differences. As one increases the artificial viscosity, the high modes are dissipated more and the scheme converges more rapidly. However, this higher level of viscosity smooths the shocks and eliminates other features of the flow. Thus, there is a conflict between the requirements of accuracy and efficiency. Examples are presented for a variety of three-dimensional inviscid solutions over isolated wings.

Representing ductile damage with the dual domain material point method

DOE PAGES

Long, C. C.; Zhang, D. Z.; Bronkhorst, C. A.; ...

2015-12-14

In this study, we incorporate a ductile damage material model into a computational framework based on the Dual Domain Material Point (DDMP) method. As an example, simulations of a flyer plate experiment involving ductile void growth and material failure are performed. The results are compared with experiments performed on high purity tantalum. We also compare the numerical results obtained from the DDMP method with those obtained from the traditional Material Point Method (MPM). Effects of an overstress model, artificial viscosity, and physical viscosity are investigated. Our results show that a physical bulk viscosity and overstress model are important in thismore » impact and failure problem, while physical shear viscosity and artificial shock viscosity have negligible effects. A simple numerical procedure with guaranteed convergence is introduced to solve for the equilibrium plastic state from the ductile damage model.« less

The Effects of Implicit Instruction on Implicit and Explicit Knowledge Development

ERIC Educational Resources Information Center

Godfroid, Aline

2016-01-01

This study extends the evidence for implicit second language (L2) learning, which comes largely from (semi-)artificial language research, to German. Upper-intermediate L2 German learners were flooded with spoken exemplars of a difficult morphological structure, namely strong, vowel-changing verbs. Toward the end of exposure, the mandatory vowel…

The Utility of Implicit Learning in the Teaching of Rules

ERIC Educational Resources Information Center

Saetrevik, Bjorn; Reber, Rolf; Sannum, Petter

2006-01-01

The potential impact of implicit learning on education has been repeatedly stressed, though little research has examined this connection directly. The current paper describes two experiments that, inspired by artificial grammar learning experiments, examine the utility of implicit learning as a method for teaching atomic bonding rules to 11-12…

The assessment of nanofluid in a Von Karman flow with temperature relied viscosity

NASA Astrophysics Data System (ADS)

Tanveer, Anum; Salahuddin, T.; Khan, Mumtaz; Alshomrani, Ali Saleh; Malik, M. Y.

2018-06-01

This work endeavor to study the heat and mass transfer viscous nanofluid features in a Von Karman flow invoking the variable viscosity mechanism. Moreover, we have extended our study in view of heat generation and uniform suction effects. The flow triggering non-linear partial differential equations are inscribed in the non-dimensional form by manipulating suitable transformations. The resulting non-linear ordinary differential equations are solved numerically via implicit finite difference scheme in conjecture with the Newton's linearization scheme afterwards. The sought solutions are plotted graphically to present comparison between MATLAB routine bvp4c and implicit finite difference schemes. Impact of different parameters on the concentration/temperature/velocity profiles are highlighted. Further Nusselt number, skin friction and Sherwood number characteristics are discussed for better exposition.

Viscosity-adjusted estimation of pressure head and pump flow with quasi-pulsatile modulation of rotary blood pump for a total artificial heart.

PubMed

Yurimoto, Terumi; Hara, Shintaro; Isoyama, Takashi; Saito, Itsuro; Ono, Toshiya; Abe, Yusuke

2016-09-01

Estimation of pressure and flow has been an important subject for developing implantable artificial hearts. To realize real-time viscosity-adjusted estimation of pressure head and pump flow for a total artificial heart, we propose the table estimation method with quasi-pulsatile modulation of rotary blood pump in which systolic high flow and diastolic low flow phased are generated. The table estimation method utilizes three kinds of tables: viscosity, pressure and flow tables. Viscosity is estimated from the characteristic that differential value in motor speed between systolic and diastolic phases varies depending on viscosity. Potential of this estimation method was investigated using mock circulation system. Glycerin solution diluted with salty water was used to adjust viscosity of fluid. In verification of this method using continuous flow data, fairly good estimation could be possible when differential pulse width modulation (PWM) value of the motor between systolic and diastolic phases was high. In estimation under quasi-pulsatile condition, inertia correction was provided and fairly good estimation was possible when the differential PWM value was high, which was not different from the verification results using continuous flow data. In the experiment of real-time estimation applying moving average method to the estimated viscosity, fair estimation could be possible when the differential PWM value was high, showing that real-time viscosity-adjusted estimation of pressure head and pump flow would be possible with this novel estimation method when the differential PWM value would be set high.

A lab-controlled simulation of a letter-speech sound binding deficit in dyslexia.

PubMed

Aravena, Sebastián; Snellings, Patrick; Tijms, Jurgen; van der Molen, Maurits W

2013-08-01

Dyslexic and non-dyslexic readers engaged in a short training aimed at learning eight basic letter-speech sound correspondences within an artificial orthography. We examined whether a letter-speech sound binding deficit is behaviorally detectable within the initial steps of learning a novel script. Both letter knowledge and word reading ability within the artificial script were assessed. An additional goal was to investigate the influence of instructional approach on the initial learning of letter-speech sound correspondences. We assigned children from both groups to one of three different training conditions: (a) explicit instruction, (b) implicit associative learning within a computer game environment, or (c) a combination of (a) and (b) in which explicit instruction is followed by implicit learning. Our results indicated that dyslexics were outperformed by the controls on a time-pressured binding task and a word reading task within the artificial orthography, providing empirical support for the view that a letter-speech sound binding deficit is a key factor in dyslexia. A combination of explicit instruction and implicit techniques proved to be a more powerful tool in the initial teaching of letter-sound correspondences than implicit training alone. Copyright © 2013 Elsevier Inc. All rights reserved.

Discontinuous Galerkin finite element method for the nonlinear hyperbolic problems with entropy-based artificial viscosity stabilization

NASA Astrophysics Data System (ADS)

Zingan, Valentin Nikolaevich

This work develops a discontinuous Galerkin finite element discretization of non- linear hyperbolic conservation equations with efficient and robust high order stabilization built on an entropy-based artificial viscosity approximation. The solutions of equations are represented by elementwise polynomials of an arbitrary degree p > 0 which are continuous within each element but discontinuous on the boundaries. The discretization of equations in time is done by means of high order explicit Runge-Kutta methods identified with respective Butcher tableaux. To stabilize a numerical solution in the vicinity of shock waves and simultaneously preserve the smooth parts from smearing, we add some reasonable amount of artificial viscosity in accordance with the physical principle of entropy production in the interior of shock waves. The viscosity coefficient is proportional to the local size of the residual of an entropy equation and is bounded from above by the first-order artificial viscosity defined by a local wave speed. Since the residual of an entropy equation is supposed to be vanishingly small in smooth regions (of the order of the Local Truncation Error) and arbitrarily large in shocks, the entropy viscosity is almost zero everywhere except the shocks, where it reaches the first-order upper bound. One- and two-dimensional benchmark test cases are presented for nonlinear hyperbolic scalar conservation laws and the system of compressible Euler equations. These tests demonstrate the satisfactory stability properties of the method and optimal convergence rates as well. All numerical solutions to the test problems agree well with the reference solutions found in the literature. We conclude that the new method developed in the present work is a valuable alternative to currently existing techniques of viscous stabilization.

A fast, time-accurate unsteady full potential scheme

NASA Technical Reports Server (NTRS)

Shankar, V.; Ide, H.; Gorski, J.; Osher, S.

1985-01-01

The unsteady form of the full potential equation is solved in conservation form by an implicit method based on approximate factorization. At each time level, internal Newton iterations are performed to achieve time accuracy and computational efficiency. A local time linearization procedure is introduced to provide a good initial guess for the Newton iteration. A novel flux-biasing technique is applied to generate proper forms of the artificial viscosity to treat hyperbolic regions with shocks and sonic lines present. The wake is properly modeled by accounting not only for jumps in phi, but also for jumps in higher derivatives of phi, obtained by imposing the density to be continuous across the wake. The far field is modeled using the Riemann invariants to simulate nonreflecting boundary conditions. The resulting unsteady method performs well which, even at low reduced frequency levels of 0.1 or less, requires fewer than 100 time steps per cycle at transonic Mach numbers. The code is fully vectorized for the CRAY-XMP and the VPS-32 computers.

Viscous compressible flow direct and inverse computation and illustrations

NASA Technical Reports Server (NTRS)

Yang, T. T.; Ntone, F.

1986-01-01

An algorithm for laminar and turbulent viscous compressible two dimensional flows is presented. For the application of precise boundary conditions over an arbitrary body surface, a body-fitted coordinate system is used in the physical plane. A thin-layer approximation of tne Navier-Stokes equations is introduced to keep the viscous terms relatively simple. The flow field computation is performed in the transformed plane. A factorized, implicit scheme is used to facilitate the computation. Sample calculations, for Couette flow, developing pipe flow, an isolated airflow, two dimensional compressor cascade flow, and segmental compressor blade design are presented. To a certain extent, the effective use of the direct solver depends on the user's skill in setting up the gridwork, the time step size and the choice of the artificial viscosity. The design feature of the algorithm, an iterative scheme to correct geometry for a specified surface pressure distribution, works well for subsonic flows. A more elaborate correction scheme is required in treating transonic flows where local shock waves may be involved.

A Hermite-based lattice Boltzmann model with artificial viscosity for compressible viscous flows

NASA Astrophysics Data System (ADS)

Qiu, Ruofan; Chen, Rongqian; Zhu, Chenxiang; You, Yancheng

2018-05-01

A lattice Boltzmann model on Hermite basis for compressible viscous flows is presented in this paper. The model is developed in the framework of double-distribution-function approach, which has adjustable specific-heat ratio and Prandtl number. It contains a density distribution function for the flow field and a total energy distribution function for the temperature field. The equilibrium distribution function is determined by Hermite expansion, and the D3Q27 and D3Q39 three-dimensional (3D) discrete velocity models are used, in which the discrete velocity model can be replaced easily. Moreover, an artificial viscosity is introduced to enhance the model for capturing shock waves. The model is tested through several cases of compressible flows, including 3D supersonic viscous flows with boundary layer. The effect of artificial viscosity is estimated. Besides, D3Q27 and D3Q39 models are further compared in the present platform.

Implicit Learning of Recursive Context-Free Grammars

PubMed Central

Rohrmeier, Martin; Fu, Qiufang; Dienes, Zoltan

2012-01-01

Context-free grammars are fundamental for the description of linguistic syntax. However, most artificial grammar learning experiments have explored learning of simpler finite-state grammars, while studies exploring context-free grammars have not assessed awareness and implicitness. This paper explores the implicit learning of context-free grammars employing features of hierarchical organization, recursive embedding and long-distance dependencies. The grammars also featured the distinction between left- and right-branching structures, as well as between centre- and tail-embedding, both distinctions found in natural languages. People acquired unconscious knowledge of relations between grammatical classes even for dependencies over long distances, in ways that went beyond learning simpler relations (e.g. n-grams) between individual words. The structural distinctions drawn from linguistics also proved important as performance was greater for tail-embedding than centre-embedding structures. The results suggest the plausibility of implicit learning of complex context-free structures, which model some features of natural languages. They support the relevance of artificial grammar learning for probing mechanisms of language learning and challenge existing theories and computational models of implicit learning. PMID:23094021

Implicit learning and reading: insights from typical children and children with developmental dyslexia using the artificial grammar learning (AGL) paradigm.

PubMed

Pavlidou, Elpis V; Williams, Joanne M

2014-07-01

We examined implicit learning in school-aged children with and without developmental dyslexia based on the proposal that implicit learning plays a significant role in mastering fluent reading. We ran two experiments with 16 typically developing children (9 to 11-years-old) and 16 age-matched children with developmental dyslexia using the artificial grammar learning (AGL) paradigm. In Experiment 1 (non-transfer task), children were trained on stimuli that followed patterns (rules) unknown to them. Subsequently, they were asked to decide from a novel set which stimuli follow the same rules (grammaticality judgments). In Experiment 2 (transfer task), training and testing stimuli differed in their superficial characteristics but followed the same rules. Again, children were asked to make grammaticality judgments. Our findings expand upon previous research by showing that children with developmental dyslexia show difficulties in implicit learning that are most likely specific to higher-order rule-like learning. These findings are discussed in relation to current theories of developmental dyslexia and of implicit learning. Copyright © 2014 Elsevier Ltd. All rights reserved.

A Dynamic Eddy Viscosity Model for the Shallow Water Equations Solved by Spectral Element and Discontinuous Galerkin Methods

NASA Astrophysics Data System (ADS)

Marras, Simone; Suckale, Jenny; Giraldo, Francis X.; Constantinescu, Emil

2016-04-01

We present the solution of the viscous shallow water equations where viscosity is built as a residual-based subgrid scale model originally designed for large eddy simulation of compressible [1] and stratified flows [2]. The necessity of viscosity for a shallow water model not only finds motivation from mathematical analysis [3], but is supported by physical reasoning as can be seen by an analysis of the energetics of the solution. We simulated the flow of an idealized wave as it hits a set of obstacles. The kinetic energy spectrum of this flow shows that, although the inviscid Galerkin solutions -by spectral elements and discontinuous Galerkin [4]- preserve numerical stability in spite of the spurious oscillations in the proximity of the wave fronts, the slope of the energy cascade deviates from the theoretically expected values. We show that only a sufficiently small amount of dynamically adaptive viscosity removes the unwanted high-frequency modes while preserving the overall sharpness of the solution. In addition, it yields a physically plausible energy decay. This work is motivated by a larger interest in the application of a shallow water model to the solution of tsunami triggered coastal flows. In particular, coastal flows in regions around the world where coastal parks made of mitigation hills of different sizes and configurations are considered as a means to deviate the power of the incoming wave. References [1] M. Nazarov and J. Hoffman (2013) "Residual-based artificial viscosity for simulation of turbulent compressible flow using adaptive finite element methods" Int. J. Numer. Methods Fluids, 71:339-357 [2] S. Marras, M. Nazarov, F. X. Giraldo (2015) "Stabilized high-order Galerkin methods based on a parameter-free dynamic SGS model for LES" J. Comput. Phys. 301:77-101 [3] J. F. Gerbeau and B. Perthame (2001) "Derivation of the viscous Saint-Venant system for laminar shallow water; numerical validation" Discrete Contin. Dyn. Syst. Ser. B, 1:89?102 [4] F. X. Giraldo and M. Restelli (2010) "High-order semi-implicit time-integrators for a triangular discontinuous Galerkin oceanic shallow water model. Int. J. Numer. Methods Fluids, 63:1077-1102

Learning of pitch and time structures in an artificial grammar setting.

PubMed

Prince, Jon B; Stevens, Catherine J; Jones, Mari Riess; Tillmann, Barbara

2018-04-12

Despite the empirical evidence for the power of the cognitive capacity of implicit learning of structures and regularities in several modalities and materials, it remains controversial whether implicit learning extends to the learning of temporal structures and regularities. We investigated whether (a) an artificial grammar can be learned equally well when expressed in duration sequences as when expressed in pitch sequences, (b) learning of the artificial grammar in either duration or pitch (as the primary dimension) sequences can be influenced by the properties of the secondary dimension (invariant vs. randomized), and (c) learning can be boosted when the artificial grammar is expressed in both pitch and duration. After an exposure phase with grammatical sequences, learning in a subsequent test phase was assessed in a grammaticality judgment task. Participants in both the pitch and duration conditions showed incidental (not fully implicit) learning of the artificial grammar when the secondary dimension was invariant, but randomizing the pitch sequence prevented learning of the artificial grammar in duration sequences. Expressing the artificial grammar in both pitch and duration resulted in disproportionately better performance, suggesting an interaction between the learning of pitch and temporal structure. The findings are relevant to research investigating the learning of temporal structures and the learning of structures presented simultaneously in 2 dimensions (e.g., space and time, space and objects). By investigating learning, the findings provide further insight into the potential specificity of pitch and time processing, and their integrated versus independent processing, as previously debated in music cognition research. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Nonlinear study of the parallel velocity/tearing instability using an implicit, nonlinear resistive MHD solver

NASA Astrophysics Data System (ADS)

Chacon, L.; Finn, J. M.; Knoll, D. A.

2000-10-01

Recently, a new parallel velocity instability has been found.(J. M. Finn, Phys. Plasmas), 2, 12 (1995) This mode is a tearing mode driven unstable by curvature effects and sound wave coupling in the presence of parallel velocity shear. Under such conditions, linear theory predicts that tearing instabilities will grow even in situations in which the classical tearing mode is stable. This could then be a viable seed mechanism for the neoclassical tearing mode, and hence a non-linear study is of interest. Here, the linear and non-linear stages of this instability are explored using a fully implicit, fully nonlinear 2D reduced resistive MHD code,(L. Chacon et al), ``Implicit, Jacobian-free Newton-Krylov 2D reduced resistive MHD nonlinear solver,'' submitted to J. Comput. Phys. (2000) including viscosity and particle transport effects. The nonlinear implicit time integration is performed using the Newton-Raphson iterative algorithm. Krylov iterative techniques are employed for the required algebraic matrix inversions, implemented Jacobian-free (i.e., without ever forming and storing the Jacobian matrix), and preconditioned with a ``physics-based'' preconditioner. Nonlinear results indicate that, for large total plasma beta and large parallel velocity shear, the instability results in the generation of large poloidal shear flows and large magnetic islands even in regimes when the classical tearing mode is absolutely stable. For small viscosity, the time asymptotic state can be turbulent.

An analysis of artificial viscosity effects on reacting flows using a spectral multi-domain technique

NASA Technical Reports Server (NTRS)

Macaraeg, M. G.; Streett, C. L.; Hussaini, M. Y.

1987-01-01

Standard techniques used to model chemically-reacting flows require an artificial viscosity for stability in the presence of strong shocks. The resulting shock is smeared over at least three computational cells, so that the thickness of the shock is dictated by the structure of the overall mesh and not the shock physics. A gas passing through a strong shock is thrown into a nonequilibrium state and subsequently relaxes down over some finite distance to an equilibrium end state. The artificial smearing of the shock envelops this relaxation zone which causes the chemical kinetics of the flow to be altered. A method is presented which can investigate these issues by following the chemical kinetics and flow kinetics of a gas passing through a fully resolved shock wave at hypersonic Mach numbers. A nonequilibrium chemistry model for air is incorporated into a spectral multidomain Navier-Stokes solution method. Since no artificial viscosity is needed for stability of the multidomain technique, the precise effect of this artifice on the chemical kinetics and relevant flow features can be determined.

Performance of children with developmental dyslexia on high and low topological entropy artificial grammar learning task.

PubMed

Katan, Pesia; Kahta, Shani; Sasson, Ayelet; Schiff, Rachel

2017-07-01

Graph complexity as measured by topological entropy has been previously shown to affect performance on artificial grammar learning tasks among typically developing children. The aim of this study was to examine the effect of graph complexity on implicit sequential learning among children with developmental dyslexia. Our goal was to determine whether children's performance depends on the complexity level of the grammar system learned. We conducted two artificial grammar learning experiments that compared performance of children with developmental dyslexia with that of age- and reading level-matched controls. Experiment 1 was a high topological entropy artificial grammar learning task that aimed to establish implicit learning phenomena in children with developmental dyslexia using previously published experimental conditions. Experiment 2 is a lower topological entropy variant of that task. Results indicated that given a high topological entropy grammar system, children with developmental dyslexia who were similar to the reading age-matched control group had substantial difficulty in performing the task as compared to typically developing children, who exhibited intact implicit learning of the grammar. On the other hand, when tested on a lower topological entropy grammar system, all groups performed above chance level, indicating that children with developmental dyslexia were able to identify rules from a given grammar system. The results reinforced the significance of graph complexity when experimenting with artificial grammar learning tasks, particularly with dyslexic participants.

Measurement of the dynamic viscosity of hybrid engine oil -Cuo-MWCNT nanofluid, development of a practical viscosity correlation and utilizing the artificial neural network

NASA Astrophysics Data System (ADS)

Aghaei, Alireza; Khorasanizadeh, Hossein; Sheikhzadeh, Ghanbar Ali

2018-01-01

The main objectives of this study have been measurement of the dynamic viscosity of CuO-MWCNTs/SAE 5w-50 hybrid nanofluid, utilization of artificial neural networks (ANN) and development of a new viscosity model. The new nanofluid has been prepared by a two-stage procedure with volume fractions of 0.05, 0.1, 0.25, 0.5, 0.75 and 1%. Then, utilizing a Brookfield viscometer, its dynamic viscosity has been measured for temperatures of 5, 15, 25, 35, 45, 55 °C. The experimental results demonstrate that the viscosity increases by increasing the nanoparticles volume fraction and decreases by increasing temperature. Based on the experimental data the maximum and minimum nanofluid viscosity enhancements, when the volume fraction increases from 0.05 to 1, are 35.52% and 12.92% for constant temperatures of 55 and 15 °C, respectively. The higher viscosity of oil engine in higher temperatures is an advantage, thus this result is important. The measured nanofluid viscosity magnitudes in various shear rates show that this hybrid nanofluid is Newtonian. An ANN model has been employed to predict the viscosity of the CuO-MWCNTs/SAE 5w-50 hybrid nanofluid and the results showed that the ANN can estimate the viscosity efficiently and accurately. Eventually, for viscosity estimation a new temperature and volume fraction based third-degree polynomial empirical model has been developed. The comparison shows that this model is in good agreement with the experimental data.

Convergence of the Critical Cooling Rate for Protoplanetary Disk Fragmentation Achieved: The Key Role of Numerical Dissipation of Angular Momentum

NASA Astrophysics Data System (ADS)

Deng, Hongping; Mayer, Lucio; Meru, Farzana

2017-09-01

We carry out simulations of gravitationally unstable disks using smoothed particle hydrodynamics (SPH) and the novel Lagrangian meshless finite mass (MFM) scheme in the GIZMO code. Our aim is to understand the cause of the nonconvergence of the cooling boundary for fragmentation reported in the literature. We run SPH simulations with two different artificial viscosity implementations and compare them with MFM, which does not employ any artificial viscosity. With MFM we demonstrate convergence of the critical cooling timescale for fragmentation at {β }{crit}≈ 3. Nonconvergence persists in SPH codes. We show how the nonconvergence problem is caused by artificial fragmentation triggered by excessive dissipation of angular momentum in domains with large velocity derivatives. With increased resolution, such domains become more prominent. Vorticity lags behind density, due to numerical viscous dissipation in these regions, promoting collapse with longer cooling times. Such effect is shown to be dominant over the competing tendency of artificial viscosity to diminish with increasing resolution. When the initial conditions are first relaxed for several orbits, the flow is more regular, with lower shear and vorticity in nonaxisymmetric regions, aiding convergence. Yet MFM is the only method that converges exactly. Our findings are of general interest, as numerical dissipation via artificial viscosity or advection errors can also occur in grid-based codes. Indeed, for the FARGO code values of {β }{crit} significantly higher than our converged estimate have been reported in the literature. Finally, we discuss implications for giant planet formation via disk instability.

Artificial fluid properties for large-eddy simulation of compressible turbulent mixing

NASA Astrophysics Data System (ADS)

Cook, Andrew W.

2007-05-01

An alternative methodology is described for large-eddy simulation (LES) of flows involving shocks, turbulence, and mixing. In lieu of filtering the governing equations, it is postulated that the large-scale behavior of a LES fluid, i.e., a fluid with artificial properties, will be similar to that of a real fluid, provided the artificial properties obey certain constraints. The artificial properties consist of modifications to the shear viscosity, bulk viscosity, thermal conductivity, and species diffusivity of a fluid. The modified transport coefficients are designed to damp out high wavenumber modes, close to the resolution limit, without corrupting lower modes. Requisite behavior of the artificial properties is discussed and results are shown for a variety of test problems, each designed to exercise different aspects of the models. When combined with a tenth-order compact scheme, the overall method exhibits excellent resolution characteristics for turbulent mixing, while capturing shocks and material interfaces in a crisp fashion.

Electrical Stimulation of Broca's Area Enhances Implicit Learning of an Artificial Grammar

ERIC Educational Resources Information Center

de Vries, Meinou H.; Barth, Andre C. R.; Maiworm, Sandra; Knecht, Stefan; Zwitserlood, Pienie; Floel, Agnes

2010-01-01

Artificial grammar learning constitutes a well-established model for the acquisition of grammatical knowledge in a natural setting. Previous neuroimaging studies demonstrated that Broca's area (left BA 44/45) is similarly activated by natural syntactic processing and artificial grammar learning. The current study was conducted to investigate the…

Modified Method of Adaptive Artificial Viscosity for Solution of Gas Dynamics Problems on Parallel Computer Systems

NASA Astrophysics Data System (ADS)

Popov, Igor; Sukov, Sergey

2018-02-01

A modification of the adaptive artificial viscosity (AAV) method is considered. This modification is based on one stage time approximation and is adopted to calculation of gasdynamics problems on unstructured grids with an arbitrary type of grid elements. The proposed numerical method has simplified logic, better performance and parallel efficiency compared to the implementation of the original AAV method. Computer experiments evidence the robustness and convergence of the method to difference solution.

High-order centered difference methods with sharp shock resolution

NASA Technical Reports Server (NTRS)

Gustafsson, Bertil; Olsson, Pelle

1994-01-01

In this paper we consider high-order centered finite difference approximations of hyperbolic conservation laws. We propose different ways of adding artificial viscosity to obtain sharp shock resolution. For the Riemann problem we give simple explicit formulas for obtaining stationary one and two-point shocks. This can be done for any order of accuracy. It is shown that the addition of artificial viscosity is equivalent to ensuring the Lax k-shock condition. We also show numerical experiments that verify the theoretical results.

A semi-implicit finite difference model for three-dimensional tidal circulation,

USGS Publications Warehouse

Casulli, V.; Cheng, R.T.

1992-01-01

A semi-implicit finite difference formulation for the numerical solution of three-dimensional tidal circulation is presented. The governing equations are the three-dimensional Reynolds equations in which the pressure is assumed to be hydrostatic. A minimal degree of implicitness has been introduced in the finite difference formula so that in the absence of horizontal viscosity the resulting algorithm is unconditionally stable at a minimal computational cost. When only one vertical layer is specified this method reduces, as a particular case, to a semi-implicit scheme for the solutions of the corresponding two-dimensional shallow water equations. The resulting two- and three-dimensional algorithm is fast, accurate and mass conservative. This formulation includes the simulation of flooding and drying of tidal flats, and is fully vectorizable for an efficient implementation on modern vector computers.

Implicit Learning Deficits among Adults with Developmental Dyslexia

ERIC Educational Resources Information Center

Kahta, Shani; Schiff, Rachel

2016-01-01

The aim of the present study was to investigate implicit learning processes among adults with developmental dyslexia (DD) using a visual linguistic artificial grammar learning (AGL) task. Specifically, it was designed to explore whether the intact learning reported in previous studies would also occur under conditions including minimal training…

The nature of declarative and nondeclarative knowledge for implicit and explicit learning.

PubMed

Kirkhart, M W

2001-10-01

Using traditional implicit and explicit artificial-grammar learning tasks, the author investigated the similarities and differences between the acquisition of declarative knowledge under implicit and explicit learning conditions and the functions of the declarative knowledge during testing. Results suggested that declarative knowledge was not predictive of or required for implicit learning but was related to consistency in implicit learning performance. In contrast, declarative knowledge was predictive of and required for explicit learning and was related to consistency in performance. For explicit learning, the declarative knowledge functioned as a guide for other behavior. In contrast, for implicit learning, the declarative knowledge did not serve as a guide for behavior but was instead a post hoc description of the most commonly seen stimuli.

GASOLINE: Smoothed Particle Hydrodynamics (SPH) code

NASA Astrophysics Data System (ADS)

N-Body Shop

2017-10-01

Gasoline solves the equations of gravity and hydrodynamics in astrophysical problems, including simulations of planets, stars, and galaxies. It uses an SPH method that features correct mixing behavior in multiphase fluids and minimal artificial viscosity. This method is identical to the SPH method used in the ChaNGa code (ascl:1105.005), allowing users to extend results to problems requiring >100,000 cores. Gasoline uses a fast, memory-efficient O(N log N) KD-Tree to solve Poisson's Equation for gravity and avoids artificial viscosity in non-shocking compressive flows.

Non-Adjacent Dependency Learning in Infants at Familial Risk of Dyslexia

ERIC Educational Resources Information Center

Kerkhoff, Annemarie; de Bree, Elise; de Klerk, Maartje; Wijnen, Frank

2013-01-01

This study tests the hypothesis that developmental dyslexia is (partly) caused by a deficit in implicit sequential learning, by investigating whether infants at familial risk of dyslexia can track non-adjacent dependencies in an artificial language. An implicit learning deficit would hinder detection of such dependencies, which mark grammatical…

On the eddy-resolving capability of high-order discontinuous Galerkin approaches to implicit LES / under-resolved DNS of Euler turbulence

NASA Astrophysics Data System (ADS)

Moura, R. C.; Mengaldo, G.; Peiró, J.; Sherwin, S. J.

2017-02-01

We present estimates of spectral resolution power for under-resolved turbulent Euler flows obtained with high-order discontinuous Galerkin (DG) methods. The '1% rule' based on linear dispersion-diffusion analysis introduced by Moura et al. (2015) [10] is here adapted for 3D energy spectra and validated through the inviscid Taylor-Green vortex problem. The 1% rule estimates the wavenumber beyond which numerical diffusion induces an artificial dissipation range on measured energy spectra. As the original rule relies on standard upwinding, different Riemann solvers are tested. Very good agreement is found for solvers which treat the different physical waves in a consistent manner. Relatively good agreement is still found for simpler solvers. The latter however displayed spurious features attributed to the inconsistent treatment of different physical waves. It is argued that, in the limit of vanishing viscosity, such features might have a significant impact on robustness and solution quality. The estimates proposed are regarded as useful guidelines for no-model DG-based simulations of free turbulence at very high Reynolds numbers.

Swallowing Mechanics Associated with Artificial Airways, Bolus Properties, and Penetration-Aspiration Status in Trauma Patients

ERIC Educational Resources Information Center

Dietsch, Angela M.; Rowley, Christopher B.; Solomon, Nancy Pearl; Pearson, William G., Jr.

2017-01-01

Purpose: Artificial airway procedures such as intubation and Sare common in the treatment of traumatic injuries, and bolus modifications may be implemented to help manage swallowing disorders. This study assessed artificial airway status, bolus properties (volume and viscosity), and the occurrence of laryngeal penetration and/or aspiration in…

Intact implicit learning in autism spectrum conditions.

PubMed

Brown, Jamie; Aczel, Balazs; Jiménez, Luis; Kaufman, Scott Barry; Grant, Kate Plaisted

2010-09-01

Individuals with autism spectrum condition (ASC) have diagnostic impairments in skills that are associated with an implicit acquisition; however, it is not clear whether ASC individuals show specific implicit learning deficits. We compared ASC and typically developing (TD) individuals matched for IQ on five learning tasks: four implicit learning tasks--contextual cueing, serial reaction time, artificial grammar learning, and probabilistic classification learning tasks--that used procedures expressly designed to minimize the use of explicit strategies, and one comparison explicit learning task, paired associates learning. We found implicit learning to be intact in ASC. Beyond no evidence of differences, there was evidence of statistical equivalence between the groups on all the implicit learning tasks. This was not a consequence of compensation by explicit learning ability or IQ. Furthermore, there was no evidence to relate implicit learning to ASC symptomatology. We conclude that implicit mechanisms are preserved in ASC and propose that it is disruption by other atypical processes that impact negatively on the development of skills associated with an implicit acquisition.

Effects of divided attention and speeded responding on implicit and explicit retrieval of artificial grammar knowledge.

PubMed

Helman, Shaun; Berry, Dianne C

2003-07-01

The artificial grammar (AG) learning literature (see, e.g., Mathews et al., 1989; Reber, 1967) has relied heavily on a single measure of implicitly acquired knowledge. Recent work comparing this measure (string classification) with a more indirect measure in which participants make liking ratings of novel stimuli (e.g., Manza & Bornstein, 1995; Newell & Bright, 2001) has shown that string classification (which we argue can be thought of as an explicit, rather than an implicit, measure of memory) gives rise to more explicit knowledge of the grammatical structure in learning strings and is more resilient to changes in surface features and processing between encoding and retrieval. We report data from two experiments that extend these findings. In Experiment 1, we showed that a divided attention manipulation (at retrieval) interfered with explicit retrieval of AG knowledge but did not interfere with implicit retrieval. In Experiment 2, we showed that forcing participants to respond within a very tight deadline resulted in the same asymmetric interference pattern between the tasks. In both experiments, we also showed that the type of information being retrieved influenced whether interference was observed. The results are discussed in terms of the relatively automatic nature of implicit retrieval and also with respect to the differences between analytic and nonanalytic processing (Whittlesea & Price, 2001).

How Explicit and Implicit Test Instructions in an Implicit Learning Task Affect Performance

PubMed Central

Witt, Arnaud; Puspitawati, Ira; Vinter, Annie

2013-01-01

Typically developing children aged 5 to 8 years were exposed to artificial grammar learning. Following an implicit exposure phase, half of the participants received neutral instructions at test while the other half received instructions making a direct, explicit reference to the training phase. We first aimed to assess whether implicit learning operated in the two test conditions. We then evaluated the differential impact of age on learning performances as a function of test instructions. The results showed that performance did not vary as a function of age in the implicit instructions condition, while age effects emerged when explicit instructions were employed at test. However, performance was affected differently by age and the instructions given at test, depending on whether the implicit learning of short or long units was assessed. These results suggest that the claim that the implicit learning process is independent of age needs to be revised. PMID:23326409

Discontinuous Galerkin method with Gaussian artificial viscosity on graphical processing units for nonlinear acoustics

NASA Astrophysics Data System (ADS)

Tripathi, Bharat B.; Marchiano, Régis; Baskar, Sambandam; Coulouvrat, François

2015-10-01

Propagation of acoustical shock waves in complex geometry is a topic of interest in the field of nonlinear acoustics. For instance, simulation of Buzz Saw Noice requires the treatment of shock waves generated by the turbofan through the engines of aeroplanes with complex geometries and wall liners. Nevertheless, from a numerical point of view it remains a challenge. The two main hurdles are to take into account the complex geometry of the domain and to deal with the spurious oscillations (Gibbs phenomenon) near the discontinuities. In this work, first we derive the conservative hyperbolic system of nonlinear acoustics (up to quadratic nonlinear terms) using the fundamental equations of fluid dynamics. Then, we propose to adapt the classical nodal discontinuous Galerkin method to develop a high fidelity solver for nonlinear acoustics. The discontinuous Galerkin method is a hybrid of finite element and finite volume method and is very versatile to handle complex geometry. In order to obtain better performance, the method is parallelized on Graphical Processing Units. Like other numerical methods, discontinuous Galerkin method suffers with the problem of Gibbs phenomenon near the shock, which is a numerical artifact. Among the various ways to manage these spurious oscillations, we choose the method of parabolic regularization. Although, the introduction of artificial viscosity into the system is a popular way of managing shocks, we propose a new approach of introducing smooth artificial viscosity locally in each element, wherever needed. Firstly, a shock sensor using the linear coefficients of the spectral solution is used to locate the position of the discontinuities. Then, a viscosity coefficient depending on the shock sensor is introduced into the hyperbolic system of equations, only in the elements near the shock. The viscosity is applied as a two-dimensional Gaussian patch with its shape parameters depending on the element dimensions, referred here as Element Centered Smooth Artificial Viscosity. Using this numerical solver, various numerical experiments are presented for one and two-dimensional test cases in homogeneous and quiescent medium. This work is funded by CEFIPRA (Indo-French Centre for the Promotion of Advance Research) and partially aided by EGIDE (Campus France).

Theories of Artificial Grammar Learning

ERIC Educational Resources Information Center

Pothos, Emmanuel M.

2007-01-01

Artificial grammar learning (AGL) is one of the most commonly used paradigms for the study of implicit learning and the contrast between rules, similarity, and associative learning. Despite five decades of extensive research, however, a satisfactory theoretical consensus has not been forthcoming. Theoretical accounts of AGL are reviewed, together…

Implicit learning: An analysis of the form and structure of a body of tacit knowledge

ERIC Educational Resources Information Center

Reber, Arthur S.; Lewis, Selma

1977-01-01

College students learned implicitly the underlying structure of an artificial language by memorizing a set of representative examples. The form and structure of their knowledge was evaluated and analyzed by: (1) solving anagrams; (2) determining well-formedness of novel letter strings; and (3) providing detailed introspective reports. (Author/MV)

The Effects of Mood, Cognitive Style, and Cognitive Ability on Implicit Learning

ERIC Educational Resources Information Center

Pretz, Jean E.; Totz, Kathryn Sentman; Kaufman, Scott Barry

2010-01-01

In an experiment with 109 undergraduates, we examined the effect of mood, cognitive style, and cognitive ability on implicit learning in the Artificial Grammar (AG) and Serial Reaction Time (SRT) tasks. Negative mood facilitated AG learning, but had no significant effect on SRT learning. Rational cognitive style predicted greater learning on both…

Artificial viscosity to cure the carbuncle phenomenon: The three-dimensional case

NASA Astrophysics Data System (ADS)

Rodionov, Alexander V.

2018-05-01

The carbuncle phenomenon (also known as the shock instability) has remained a serious computational challenge since it was first noticed and described [1,2]. In [3] the author presented a summary on this subject and proposed a new technique for curing the problem. Its idea is to introduce some dissipation in the form of right-hand sides of the Navier-Stokes equations into the basic method of solving Euler equations; in so doing, the molecular viscosity coefficient is replaced by the artificial viscosity coefficient. The new cure for the carbuncle flaw was tested and tuned for the case of using first-order schemes in two-dimensional simulations. Its efficiency was demonstrated on several well-known test problems. In this paper we extend the technique of [3] to the case of three-dimensional simulations.

Artificial Grammar Learning in Dyslexic and Nondyslexic Adults: Implications for Orthographic Learning

ERIC Educational Resources Information Center

Samara, Anna; Caravolas, Markéta

2017-01-01

Potential implicit orthographic learning deficits were investigated in adults with dyslexia. An artificial grammar learning paradigm served to assess dyslexic and typical readers' ability to exploit information about chunk frequency, letter-position patterns, and specific string similarity, all of which have analogous constructs in real…

Spreading properties of cosmetic emollients: Use of synthetic skin surface to elucidate structural effect.

PubMed

Douguet, Marine; Picard, Céline; Savary, Géraldine; Merlaud, Fabien; Loubat-Bouleuc, Nathalie; Grisel, Michel

2017-06-01

The study focuses on the impact of structural and physicochemical properties of emollients on their spreadability. Fifty-three emollients, among which esters, silicones, vegetable and mineral oils, have been characterized. Their viscosity, surface tension, density and spreadability have been measured. Vitro-skin ® , an artificial skin substitute, was used as an artificial porous substrate to measure spreadability. Two different methods have been selected to characterize spreadability, namely contact angle and spreading value. Dynamic contact angle measurements showed that emollient spreadability is first governed by spontaneous spreading and that, in a second phase, absorption and migration into the porous substrate becomes the driver of the extension of the spreading area. Statistical analysis of physicochemical and spreading value data revealed that viscosity has a major impact on the spreading behavior of emollients whatever their chemical type. A special emphasis was placed on the ester family in which chemical diversity is very wide. The results highlighted a difference between "high viscosity esters" for which viscosity is the main factor impacting spreadability and "low viscosity esters" for which structural variations (mono/diester, saturated/unsaturated chain, linear/branched chain) have to be considered in addition to viscosity. Linear regressions were used to express spreading value as a function of viscosity for each of the four emollient families tested (esters, silicones, vegetable and mineral oils). These regressions allowed the development of reliable predictive models as a powerful tool for formulators to forecast spreadability of emollients. Copyright © 2017 Elsevier B.V. All rights reserved.

Implicit Learning of Arithmetic Regularities Is Facilitated by Proximal Contrast

PubMed Central

Prather, Richard W.

2012-01-01

Natural number arithmetic is a simple, powerful and important symbolic system. Despite intense focus on learning in cognitive development and educational research many adults have weak knowledge of the system. In current study participants learn arithmetic principles via an implicit learning paradigm. Participants learn not by solving arithmetic equations, but through viewing and evaluating example equations, similar to the implicit learning of artificial grammars. We expand this to the symbolic arithmetic system. Specifically we find that exposure to principle-inconsistent examples facilitates the acquisition of arithmetic principle knowledge if the equations are presented to the learning in a temporally proximate fashion. The results expand on research of the implicit learning of regularities and suggest that contrasting cases, show to facilitate explicit arithmetic learning, is also relevant to implicit learning of arithmetic. PMID:23119101

Experiment and Artificial Neural Network Prediction of Thermal Conductivity and Viscosity for Alumina-Water Nanofluids

PubMed Central

Zhao, Ningbo; Li, Zhiming

2017-01-01

To effectively predict the thermal conductivity and viscosity of alumina (Al2O3)-water nanofluids, an artificial neural network (ANN) approach was investigated in the present study. Firstly, using a two-step method, four Al2O3-water nanofluids were prepared respectively by dispersing different volume fractions (1.31%, 2.72%, 4.25%, and 5.92%) of nanoparticles with the average diameter of 30 nm. On this basis, the thermal conductivity and viscosity of the above nanofluids were analyzed experimentally under various temperatures ranging from 296 to 313 K. Then a radial basis function (RBF) neural network was constructed to predict the thermal conductivity and viscosity of Al2O3-water nanofluids as a function of nanoparticle volume fraction and temperature. The experimental results showed that both nanoparticle volume fraction and temperature could enhance the thermal conductivity of Al2O3-water nanofluids. However, the viscosity only depended strongly on Al2O3 nanoparticle volume fraction and was increased slightly by changing temperature. In addition, the comparative analysis revealed that the RBF neural network had an excellent ability to predict the thermal conductivity and viscosity of Al2O3-water nanofluids with the mean absolute percent errors of 0.5177% and 0.5618%, respectively. This demonstrated that the ANN provided an effective way to predict the thermophysical properties of nanofluids with limited experimental data. PMID:28772913

Experiment and Artificial Neural Network Prediction of Thermal Conductivity and Viscosity for Alumina-Water Nanofluids.

PubMed

Zhao, Ningbo; Li, Zhiming

2017-05-19

To effectively predict the thermal conductivity and viscosity of alumina (Al₂O₃)-water nanofluids, an artificial neural network (ANN) approach was investigated in the present study. Firstly, using a two-step method, four Al₂O₃-water nanofluids were prepared respectively by dispersing different volume fractions (1.31%, 2.72%, 4.25%, and 5.92%) of nanoparticles with the average diameter of 30 nm. On this basis, the thermal conductivity and viscosity of the above nanofluids were analyzed experimentally under various temperatures ranging from 296 to 313 K. Then a radial basis function (RBF) neural network was constructed to predict the thermal conductivity and viscosity of Al₂O₃-water nanofluids as a function of nanoparticle volume fraction and temperature. The experimental results showed that both nanoparticle volume fraction and temperature could enhance the thermal conductivity of Al₂O₃-water nanofluids. However, the viscosity only depended strongly on Al₂O₃ nanoparticle volume fraction and was increased slightly by changing temperature. In addition, the comparative analysis revealed that the RBF neural network had an excellent ability to predict the thermal conductivity and viscosity of Al₂O₃-water nanofluids with the mean absolute percent errors of 0.5177% and 0.5618%, respectively. This demonstrated that the ANN provided an effective way to predict the thermophysical properties of nanofluids with limited experimental data.

What Artificial Grammar Learning Reveals about the Neurobiology of Syntax

ERIC Educational Resources Information Center

Petersson, Karl-Magnus; Folia, Vasiliki; Hagoort, Peter

2012-01-01

In this paper we examine the neurobiological correlates of syntax, the processing of structured sequences, by comparing FMRI results on artificial and natural language syntax. We discuss these and similar findings in the context of formal language and computability theory. We used a simple right-linear unification grammar in an implicit artificial…

A comparison of performance of several artificial intelligence methods for predicting the dynamic viscosity of TiO2/SAE 50 nano-lubricant

NASA Astrophysics Data System (ADS)

Hemmat Esfe, Mohammad; Tatar, Afshin; Ahangar, Mohammad Reza Hassani; Rostamian, Hossein

2018-02-01

Since the conventional thermal fluids such as water, oil, and ethylene glycol have poor thermal properties, the tiny solid particles are added to these fluids to increase their heat transfer improvement. As viscosity determines the rheological behavior of a fluid, studying the parameters affecting the viscosity is crucial. Since the experimental measurement of viscosity is expensive and time consuming, predicting this parameter is the apt method. In this work, three artificial intelligence methods containing Genetic Algorithm-Radial Basis Function Neural Networks (GA-RBF), Least Square Support Vector Machine (LS-SVM) and Gene Expression Programming (GEP) were applied to predict the viscosity of TiO2/SAE 50 nano-lubricant with Non-Newtonian power-law behavior using experimental data. The correlation factor (R2), Average Absolute Relative Deviation (AARD), Root Mean Square Error (RMSE), and Margin of Deviation were employed to investigate the accuracy of the proposed models. RMSE values of 0.58, 1.28, and 6.59 and R2 values of 0.99998, 0.99991, and 0.99777 reveal the accuracy of the proposed models for respective GA-RBF, CSA-LSSVM, and GEP methods. Among the developed models, the GA-RBF shows the best accuracy.

Implicit learning in children and adults with Williams syndrome.

PubMed

Don, Audrey J; Schellenberg, E Glenn; Reber, Arthur S; DiGirolamo, Kristen M; Wang, Paul P

2003-01-01

In comparison to explicit learning, implicit learning is hypothesized to be a phylogenetically older form of learning that is important in early developmental processes (e.g., natural language acquisition, socialization)and relatively impervious to individual differences in age and IQ. We examined implicit learning in a group of children and adults (9.49 years of age)with Williams syndrome (WS)and in a comparison group of typically developing individuals matched for chronological age. Participants were tested in an artificial-grammar learning paradigm and in a rotor-pursuit task. For both groups, implicit learning was largely independent of age. Both groups showed evidence of implicit learning but the comparison group outperformed the WS group on both tasks. Performance advantages for the comparison group were no longer significant when group differences in working memory or nonverbal intelligence were held constant.

Performance of Children with Developmental Dyslexia on High and Low Topological Entropy Artificial Grammar Learning Task

ERIC Educational Resources Information Center

Katan, Pesia; Kahta, Shani; Sasson, Ayelet; Schiff, Rachel

2017-01-01

Graph complexity as measured by topological entropy has been previously shown to affect performance on artificial grammar learning tasks among typically developing children. The aim of this study was to examine the effect of graph complexity on implicit sequential learning among children with developmental dyslexia. Our goal was to determine…

Second Language Acquisition of Gender Agreement in Explicit and Implicit Training Conditions: An Event-Related Potential Study

PubMed Central

Morgan-Short, Kara; Sanz, Cristina; Steinhauer, Karsten; Ullman, Michael T.

2011-01-01

This study employed an artificial language learning paradigm together with a combined behavioral/event-related potential (ERP) approach to examine the neurocognition of the processing of gender agreement, an aspect of inflectional morphology that is problematic in adult second language (L2) learning. Subjects learned to speak and comprehend an artificial language under either explicit (classroomlike) or implicit (immersionlike) training conditions. In each group, both noun-article and noun-adjective gender agreement processing were examined behaviorally and with ERPs at both low and higher levels of proficiency. Results showed that the two groups learned the language to similar levels of proficiency but showed somewhat different ERP patterns. At low proficiency, both types of agreement violations (adjective, article) yielded N400s, but only for the group with implicit training. Additionally, noun-adjective agreement elicited a late N400 in the explicit group at low proficiency. At higher levels of proficiency, noun-adjective agreement violations elicited N400s for both the explicit and implicit groups, whereas noun-article agreement violations elicited P600s for both groups. The results suggest that interactions among linguistic structure, proficiency level, and type of training need to be considered when examining the development of aspects of inflectional morphology in L2 acquisition. PMID:21359123

Visual artificial grammar learning in dyslexia: A meta-analysis.

PubMed

van Witteloostuijn, Merel; Boersma, Paul; Wijnen, Frank; Rispens, Judith

2017-11-01

Literacy impairments in dyslexia have been hypothesized to be (partly) due to an implicit learning deficit. However, studies of implicit visual artificial grammar learning (AGL) have often yielded null results. The aim of this study is to weigh the evidence collected thus far by performing a meta-analysis of studies on implicit visual AGL in dyslexia. Thirteen studies were selected through a systematic literature search, representing data from 255 participants with dyslexia and 292 control participants (mean age range: 8.5-36.8 years old). If the 13 selected studies constitute a random sample, individuals with dyslexia perform worse on average than non-dyslexic individuals (average weighted effect size=0.46, 95% CI [0.14 … 0.77], p=0.008), with a larger effect in children than in adults (p=0.041; average weighted effect sizes 0.71 [sig.] versus 0.16 [non-sig.]). However, the presence of a publication bias indicates the existence of missing studies that may well null the effect. While the studies under investigation demonstrate that implicit visual AGL is impaired in dyslexia (more so in children than in adults, if in adults at all), the detected publication bias suggests that the effect might in fact be zero. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

Numerical study of the flow in a three-dimensional thermally driven cavity

NASA Astrophysics Data System (ADS)

Rauwoens, Pieter; Vierendeels, Jan; Merci, Bart

2008-06-01

Solutions for the fully compressible Navier-Stokes equations are presented for the flow and temperature fields in a cubic cavity with large horizontal temperature differences. The ideal-gas approximation for air is assumed and viscosity is computed using Sutherland's law. The three-dimensional case forms an extension of previous studies performed on a two-dimensional square cavity. The influence of imposed boundary conditions in the third dimension is investigated as a numerical experiment. Comparison is made between convergence rates in case of periodic and free-slip boundary conditions. Results with no-slip boundary conditions are presented as well. The effect of the Rayleigh number is studied. Results are computed using a finite volume method on a structured, collocated grid. An explicit third-order discretization for the convective part and an implicit central discretization for the acoustic part and for the diffusive part are used. To stabilize the scheme an artificial dissipation term for the pressure and the temperature is introduced. The discrete equations are solved using a time-marching method with restrictions on the timestep corresponding to the explicit parts of the solver. Multigrid is used as acceleration technique.

Plasma viscosity with mass transport in spherical inertial confinement fusion implosion simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vold, E. L.; Molvig, K.; Joglekar, A. S.

2015-11-15

The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion (ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. We have implemented a Lagrangian hydrodynamic code in one-dimensional spherical geometry with plasma viscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasma viscosity andmore » to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasma viscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Plasma viscosity reduces the need for artificial viscosity to maintain numerical stability in the Lagrangian formulation and also modifies the flux-limiting needed for electron thermal conduction.« less

The P600 in Implicit Artificial Grammar Learning

ERIC Educational Resources Information Center

Silva, Susana; Folia, Vasiliki; Hagoort, Peter; Petersson, Karl Magnus

2017-01-01

The suitability of the artificial grammar learning (AGL) paradigm to capture relevant aspects of the acquisition of linguistic structures has been empirically tested in a number of EEG studies. Some have shown a syntax-related P600 component, but it has not been ruled out that the AGL P600 effect is a response to surface features (e.g.,…

Towards an explicit account of implicit learning.

PubMed

Forkstam, Christian; Petersson, Karl Magnus

2005-08-01

The human brain supports acquisition mechanisms that can extract structural regularities implicitly from experience without the induction of an explicit model. Reber defined the process by which an individual comes to respond appropriately to the statistical structure of the input ensemble as implicit learning. He argued that the capacity to generalize to new input is based on the acquisition of abstract representations that reflect underlying structural regularities in the acquisition input. We focus this review of the implicit learning literature on studies published during 2004 and 2005. We will not review studies of repetition priming ('implicit memory'). Instead we focus on two commonly used experimental paradigms: the serial reaction time task and artificial grammar learning. Previous comprehensive reviews can be found in Seger's 1994 article and the Handbook of Implicit Learning. Emerging themes include the interaction between implicit and explicit processes, the role of the medial temporal lobe, developmental aspects of implicit learning, age-dependence, the role of sleep and consolidation. The attempts to characterize the interaction between implicit and explicit learning are promising although not well understood. The same can be said about the role of sleep and consolidation. Despite the fact that lesion studies have relatively consistently suggested that the medial temporal lobe memory system is not necessary for implicit learning, a number of functional magnetic resonance studies have reported medial temporal lobe activation in implicit learning. This issue merits further research. Finally, the clinical relevance of implicit learning remains to be determined.

Development of cost-effective surfactant flooding technology. Final report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pope, G.A.; Sepehrnoori, K.

1996-11-01

Task 1 of this research was the development of a high-resolution, fully implicit, finite-difference, multiphase, multicomponent, compositional simulator for chemical flooding. The major physical phenomena modeled in this simulator are dispersion, heterogeneous permeability and porosity, adsorption, interfacial tension, relative permeability and capillary desaturation, compositional phase viscosity, compositional phase density and gravity effects, capillary pressure, and aqueous-oleic-microemulsion phase behavior. Polymer and its non-Newtonian rheology properties include shear-thinning viscosity, permeability reduction, inaccessible pore volume, and adsorption. Options of constant or variable space grids and time steps, constant-pressure or constant-rate well conditions, horizontal and vertical wells, and multiple slug injections are also availablemore » in the simulator. The solution scheme used in this simulator is fully implicit. The pressure equation and the mass-conservation equations are solved simultaneously for the aqueous-phase pressure and the total concentrations of each component. A third-order-in-space, second-order-in-time finite-difference method and a new total-variation-diminishing (TVD) third-order flux limiter are used that greatly reduce numerical dispersion effects. Task 2 was the optimization of surfactant flooding. The code UTCHEM was used to simulate surfactant polymer flooding.« less

Numerical study of drop spreading on a flat surface

NASA Astrophysics Data System (ADS)

Wang, Sheng; Desjardins, Olivier

2017-11-01

In this talk, we perform a numerical study of a droplet on a flat surface with special emphasis on capturing the spreading dynamics. The computational methodology employed is tailored for simulating large-scale two-phase flows within complex geometries. It combines a conservative level-set method to capture the liquid-gas interface, a conservative immersed boundary method to represent the solid-fluid interface, and a sub-grid curvature model at the triple-point to implicitly impose the contact angle of the liquid-gas interface. The performance of the approach is assessed in the inertial droplet spreading regime, the viscous spreading regime of high viscosity drops, and with the capillary oscillation of low viscosity droplets.

A bulk viscosity approach for shock capturing on unstructured grids

NASA Astrophysics Data System (ADS)

Shoeybi, Mohammad; Larsson, Nils Johan; Ham, Frank; Moin, Parviz

2008-11-01

The bulk viscosity approach for shock capturing (Cook and Cabot, JCP, 2005) augments the bulk part of the viscous stress tensor. The intention is to capture shock waves without dissipating turbulent structures. The present work extends and modifies this method for unstructured grids. We propose a method that properly scales the bulk viscosity with the grid spacing normal to the shock for unstructured grid for which the shock is not necessarily aligned with the grid. The magnitude of the strain rate tensor used in the original formulation is replaced with the dilatation, which appears to be more appropriate in the vortical turbulent flow regions (Mani et al., 2008). The original form of the model is found to have an impact on dilatational motions away form the shock wave, which is eliminated by a proposed localization of the bulk viscosity. Finally, to allow for grid adaptation around shock waves, an explicit/implicit time advancement scheme has been developed that adaptively identifies the stiff regions. The full method has been verified with several test cases, including 2D shock-vorticity entropy interaction, homogenous isotropic turbulence, and turbulent flow over a cylinder.

Strawberry-flavored yogurts and whey beverages: What is the sensory profile of the ideal product?

PubMed

Janiaski, D R; Pimentel, T C; Cruz, A G; Prudencio, S H

2016-07-01

This study aimed to evaluate the sensory profile and Brazilian consumers' liking of strawberry-flavored yogurts and whey beverages (fermented or nonfermented) with different fat contents that were sweetened with sugar or nonsugar sweeteners. We also determined the influence of sensory attributes on consumer preferences and the profile of the ideal product. Nonfermented whey beverages (NFWB) and "light" yogurt were less liked. The NFWB were less acidic, less viscous, and with lower smoothness of mouthcoating, sweeter and with a more intense artificial strawberry aroma (ASA) than the fermented products. Low-fat yogurts were more liked, more viscous, and had higher smoothness of mouthcoating than nonfat yogurts. Fermented-whey beverages were as liked as yogurts. Viscosity and smoothness of mouthcoating positively influenced consumer liking. The ideal product had higher levels of brightness, artificial strawberry taste, artificial strawberry aroma, and sweet taste; intermediate smoothness of mouthcoating, color, and viscosity; and low particles, acid taste, and aroma. Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.

The role of feedback in implicit and explicit artificial grammar learning: a comparison between dyslexic and non-dyslexic adults.

PubMed

Schiff, Rachel; Sasson, Ayelet; Star, Galit; Kahta, Shani

2017-10-01

The importance of feedback for learning has been firmly established over the past few decades. The question of whether feedback plays a significant role in the statistical learning abilities of adults with dyslexia, however, is currently unresolved. Here, we examined the role of feedback in grammaticality judgment, type of structural knowledge, and confidence rating in both typically developed and dyslexic adults. We implemented two artificial grammar learning experiments: implicit and explicit. The second experiment was directly analogous to the first experiment in all respects except training format: the standard memorization instruction was replaced with an explicit rule-search instruction. Each experiment was conducted with and without performance feedback. While both groups showed significantly improved learning in the feedback-based explicit artificial grammar learning task, only the typically developed adults demonstrated higher levels of conscious structural knowledge. The present study demonstrates that the basis for the grammaticality judgment of adults with dyslexia differs from that of typically developed adults, regardless of increase in the level of explicitness.

An implicit time-marching method for studying unsteady flow with massive separation

NASA Technical Reports Server (NTRS)

Osswald, G. A.; Ghia, K. N.; Chia, U.

1985-01-01

A fully implicit time-marching method is developed such that all spatial derivatives are approximated using central differences, but no use is made of any artificial dissipation. The numerical method solves the discretized equations using Alternating Direction Implicit-Block Gaussian Elimination technique. The method is implemented in the unsteady analysis, which solves the incompressible Navier-Stokes equations in terms of vorticity and stream function in generalized orthogonal coordinates. A clustered conformal C-grid is employed, and every effort is made to resolve the various length scales in the flow problem. The metric discontinuity at the branch-cut is treated appropriately using analytic continuation. Introduction of the BGE reordering permits implicit treatment of the branch cut in the numerical method. The vorticity singularity at the cusped trailing edge is also appropriately treated. This accurate and efficient implicit method is used to study flow at Re = 1000, past a 12-percent thick symmetric Joukowski airfoil at high angle of attack 30 and 53 deg.

A comparison of three approaches to compute the effective Reynolds number of the implicit large-eddy simulations

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhou, Ye; Thornber, Ben

2016-04-12

Here, the implicit large-eddy simulation (ILES) has been utilized as an effective approach for calculating many complex flows at high Reynolds number flows. Richtmyer–Meshkov instability (RMI) induced flow can be viewed as a homogeneous decaying turbulence (HDT) after the passage of the shock. In this article, a critical evaluation of three methods for estimating the effective Reynolds number and the effective kinematic viscosity is undertaken utilizing high-resolution ILES data. Effective Reynolds numbers based on the vorticity and dissipation rate, or the integral and inner-viscous length scales, are found to be the most self-consistent when compared to the expected phenomenology andmore » wind tunnel experiments.« less

Lectures series in computational fluid dynamics

NASA Technical Reports Server (NTRS)

Thompson, Kevin W.

1987-01-01

The lecture notes cover the basic principles of computational fluid dynamics (CFD). They are oriented more toward practical applications than theory, and are intended to serve as a unified source for basic material in the CFD field as well as an introduction to more specialized topics in artificial viscosity and boundary conditions. Each chapter in the test is associated with a videotaped lecture. The basic properties of conservation laws, wave equations, and shock waves are described. The duality of the conservation law and wave representations is investigated, and shock waves are examined in some detail. Finite difference techniques are introduced for the solution of wave equations and conservation laws. Stability analysis for finite difference approximations are presented. A consistent description of artificial viscosity methods are provided. Finally, the problem of nonreflecting boundary conditions are treated.

Upwind methods for the Baer–Nunziato equations and higher-order reconstruction using artificial viscosity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fraysse, F., E-mail: francois.fraysse@rs2n.eu; E. T. S. de Ingeniería Aeronáutica y del Espacio, Universidad Politécnica de Madrid, Madrid; Redondo, C.

This article is devoted to the numerical discretisation of the hyperbolic two-phase flow model of Baer and Nunziato. A special attention is paid on the discretisation of intercell flux functions in the framework of Finite Volume and Discontinuous Galerkin approaches, where care has to be taken to efficiently approximate the non-conservative products inherent to the model equations. Various upwind approximate Riemann solvers have been tested on a bench of discontinuous test cases. New discretisation schemes are proposed in a Discontinuous Galerkin framework following the criterion of Abgrall and the path-conservative formalism. A stabilisation technique based on artificial viscosity is appliedmore » to the high-order Discontinuous Galerkin method and compared against classical TVD-MUSCL Finite Volume flux reconstruction.« less

The effects of rotational flow, viscosity, thickness, and shape on transonic flutter dip phenomena

NASA Technical Reports Server (NTRS)

Reddy, T. S. R.; Srivastava, Rakesh; Kaza, Krishna Rao V.

1988-01-01

The transonic flutter dip phenomena on thin airfoils, which are employed for propfan blades, is investigated using an integrated Euler/Navier-Stokes code and a two degrees of freedom typical section structural model. As a part of the code validation, the flutter characteristics of the NACA 64A010 airfoil are also investigated. In addition, the effects of artificial dissipation models, rotational flow, initial conditions, mean angle of attack, viscosity, airfoil thickness and shape on flutter are investigated. The results obtained with a Euler code for the NACA 64A010 airfoil are in reasonable agreement with published results obtained by using transonic small disturbance and Euler codes. The two artificial dissipation models, one based on the local pressure gradient scaled by a common factor and the other based on the local pressure gradient scaled by a spectral radius, predicted the same flutter speeds except in the recovery region for the case studied. The effects of rotational flow, initial conditions, mean angle of attack, and viscosity for the Reynold's number studied seem to be negligible or small on the minima of the flutter dip.

An unconditionally stable Runge-Kutta method for unsteady flows

NASA Technical Reports Server (NTRS)

Jorgenson, Philip C. E.; Chima, Rodrick V.

1988-01-01

A quasi-three dimensional analysis was developed for unsteady rotor-stator interaction in turbomachinery. The analysis solves the unsteady Euler or thin-layer Navier-Stokes equations in a body fitted coordinate system. It accounts for the effects of rotation, radius change, and stream surface thickness. The Baldwin-Lomax eddy viscosity model is used for turbulent flows. The equations are integrated in time using a four stage Runge-Kutta scheme with a constant time step. Implicit residual smoothing was employed to accelerate the solution of the time accurate computations. The scheme is described and accuracy analyses are given. Results are shown for a supersonic through-flow fan designed for NASA Lewis. The rotor:stator blade ratio was taken as 1:1. Results are also shown for the first stage of the Space Shuttle Main Engine high pressure fuel turbopump. Here the blade ratio is 2:3. Implicit residual smoothing was used to increase the time step limit of the unsmoothed scheme by a factor of six with negligible differences in the unsteady results. It is felt that the implicitly smoothed Runge-Kutta scheme is easily competitive with implicit schemes for unsteady flows while retaining the simplicity of an explicit scheme.

Shock Capturing with PDE-Based Artificial Viscosity for an Adaptive, Higher-Order Discontinuous Galerkin Finite Element Method

DTIC Science & Technology

2008-06-01

Geometry Interpolation The function space , VpH , consists of discontinuous, piecewise-polynomials. This work used a polynomial basis for VpH such...between a piecewise-constant and smooth variation of viscosity in both a one- dimensional and multi- dimensional setting. Before continuing with the ...inviscid, transonic flow past a NACA 0012 at zero angle of attack and freestream Mach number of M∞ = 0.95. The

A Combined EOF/Variational Approach for Mapping Radar-Derived Sea Surface Currents

DTIC Science & Technology

2011-01-13

characterized by specific structure of the artificial gaps introduced into the simulated data set assess the benefits of the gap-filling technique. These...15 minutes and 1-2 km respectively. However, the back-scattered HFR signals suffer from to numerous distortions of artificial and natural origin. As a...data because information on the spatial structure of the velocity field within the gap is implicitly drawn from the idealized covariance function

Experimental study of the effects of surface mucus viscosity on the glottic cycle.

PubMed

Ayache, Stéphane; Ouaknine, Maurice; Dejonkere, Philippe; Prindere, Pierre; Giovanni, Antoine

2004-03-01

Numerous clinical findings indicate that viscosity of laryngeal mucosa is a crucial factor in glottal perfomance. Experience using experimental test benches has shown the importance of humidifying air stream used to induce vibration in excised larynges. Nevertheless, there is a lack of knowledge particularly regarding the physicochemical properties of laryngeal mucus. The purpose of this study was to research vocal fold vibration in excised larynges using artificial mucus of precisely known viscosity. Eight freshly harvested porcine larynges were examined. Parameters measured were Fo and vocal fold contact time. Measurements were performed under three conditions: basal (no fluid application on vocal cord surface), after application of a fluid of 60cP viscosity (Visc60), and after application of a fluid of 100cP viscosity (Visc100). Electroglottographic measurements were performed at two different times for each condition: 1 s after airflow onset (T1) and 6 seconds after airflow onset (T2). Statistical analysis consisted of comparing data obtained under each condition at T1 and T2. The results showed a significant decrease in Fo after application of Visc60 and Visc100 fluids and a decrease in Fo at T2. Closure time was significantly higher under Visc60 conditions and under Visc100 conditions than under basal conditions. Application of artificial mucus to the mucosa of the vocal folds lowered vibratory frequency and prolonged the contact phase. Our interpretation of this data is that the presence of mucus on the surface of the vocal folds generated superficial tension and caused adhesion, which is a source of nonlinearity in vocal vibration.

Auditory access, language access, and implicit sequence learning in deaf children.

PubMed

Hall, Matthew L; Eigsti, Inge-Marie; Bortfeld, Heather; Lillo-Martin, Diane

2018-05-01

Developmental psychology plays a central role in shaping evidence-based best practices for prelingually deaf children. The Auditory Scaffolding Hypothesis (Conway et al., 2009) asserts that a lack of auditory stimulation in deaf children leads to impoverished implicit sequence learning abilities, measured via an artificial grammar learning (AGL) task. However, prior research is confounded by a lack of both auditory and language input. The current study examines implicit learning in deaf children who were (Deaf native signers) or were not (oral cochlear implant users) exposed to language from birth, and in hearing children, using both AGL and Serial Reaction Time (SRT) tasks. Neither deaf nor hearing children across the three groups show evidence of implicit learning on the AGL task, but all three groups show robust implicit learning on the SRT task. These findings argue against the Auditory Scaffolding Hypothesis, and suggest that implicit sequence learning may be resilient to both auditory and language deprivation, within the tested limits. A video abstract of this article can be viewed at: https://youtu.be/EeqfQqlVHLI [Correction added on 07 August 2017, after first online publication: The video abstract link was added.]. © 2017 John Wiley & Sons Ltd.

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

NASA Astrophysics Data System (ADS)

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

2017-12-01

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

Concurrence of rule- and similarity-based mechanisms in artificial grammar learning.

PubMed

Opitz, Bertram; Hofmann, Juliane

2015-03-01

A current theoretical debate regards whether rule-based or similarity-based learning prevails during artificial grammar learning (AGL). Although the majority of findings are consistent with a similarity-based account of AGL it has been argued that these results were obtained only after limited exposure to study exemplars, and performance on subsequent grammaticality judgment tests has often been barely above chance level. In three experiments the conditions were investigated under which rule- and similarity-based learning could be applied. Participants were exposed to exemplars of an artificial grammar under different (implicit and explicit) learning instructions. The analysis of receiver operating characteristics (ROC) during a final grammaticality judgment test revealed that explicit but not implicit learning led to rule knowledge. It also demonstrated that this knowledge base is built up gradually while similarity knowledge governed the initial state of learning. Together these results indicate that rule- and similarity-based mechanisms concur during AGL. Moreover, it could be speculated that two different rule processes might operate in parallel; bottom-up learning via gradual rule extraction and top-down learning via rule testing. Crucially, the latter is facilitated by performance feedback that encourages explicit hypothesis testing. Copyright © 2015 Elsevier Inc. All rights reserved.

Analysis and improvement of Brinkman lattice Boltzmann schemes: bulk, boundary, interface. Similarity and distinctness with finite elements in heterogeneous porous media.

PubMed

Ginzburg, Irina; Silva, Goncalo; Talon, Laurent

2015-02-01

This work focuses on the numerical solution of the Stokes-Brinkman equation for a voxel-type porous-media grid, resolved by one to eight spacings per permeability contrast of 1 to 10 orders in magnitude. It is first analytically demonstrated that the lattice Boltzmann method (LBM) and the linear-finite-element method (FEM) both suffer from the viscosity correction induced by the linear variation of the resistance with the velocity. This numerical artefact may lead to an apparent negative viscosity in low-permeable blocks, inducing spurious velocity oscillations. The two-relaxation-times (TRT) LBM may control this effect thanks to free-tunable two-rates combination Λ. Moreover, the Brinkman-force-based BF-TRT schemes may maintain the nondimensional Darcy group and produce viscosity-independent permeability provided that the spatial distribution of Λ is fixed independently of the kinematic viscosity. Such a property is lost not only in the BF-BGK scheme but also by "partial bounce-back" TRT gray models, as shown in this work. Further, we propose a consistent and improved IBF-TRT model which vanishes viscosity correction via simple specific adjusting of the viscous-mode relaxation rate to local permeability value. This prevents the model from velocity fluctuations and, in parallel, improves for effective permeability measurements, from porous channel to multidimensions. The framework of our exact analysis employs a symbolic approach developed for both LBM and FEM in single and stratified, unconfined, and bounded channels. It shows that even with similar bulk discretization, BF, IBF, and FEM may manifest quite different velocity profiles on the coarse grids due to their intrinsic contrasts in the setting of interface continuity and no-slip conditions. While FEM enforces them on the grid vertexes, the LBM prescribes them implicitly. We derive effective LBM continuity conditions and show that the heterogeneous viscosity correction impacts them, a property also shared by FEM for shear stress. But, in contrast with FEM, effective velocity conditions in LBM give rise to slip velocity jumps which depend on (i) neighbor permeability values, (ii) resolution, and (iii) control parameter Λ, ranging its reliable values from Poiseuille bounce-back solution in open flow to zero in Darcy's limit. We suggest an "upscaling" algorithm for Λ, from multilayers to multidimensions in random extremely dispersive samples. Finally, on the positive side for LBM besides its overall versatility, the implicit boundary layers allow for smooth accommodation of the flat discontinuous Darcy profiles, quite deficient in FEM.

Implicit learning in cotton-top tamarins (Saguinus oedipus) and pigeons (Columba livia).

PubMed

Locurto, Charles; Fox, Maura; Mazzella, Andrea

2015-06-01

There is considerable interest in the conditions under which human subjects learn patterned information without explicit instructions to learn that information. This form of learning, termed implicit or incidental learning, can be approximated in nonhumans by exposing subjects to patterned information but delivering reinforcement randomly, thereby not requiring the subjects to learn the information in order to be reinforced. Following acquisition, nonhuman subjects are queried as to what they have learned about the patterned information. In the present experiment, we extended the study of implicit learning in nonhumans by comparing two species, cotton-top tamarins (Saguinus oedipus) and pigeons (Columba livia), on an implicit learning task that used an artificial grammar to generate the patterned elements for training. We equated the conditions of training and testing as much as possible between the two species. The results indicated that both species demonstrated approximately the same magnitude of implicit learning, judged both by a random test and by choice tests between pairs of training elements. This finding suggests that the ability to extract patterned information from situations in which such learning is not demanded is of longstanding origin.

Plasma viscosity with mass transport in spherical inertial confinement fusion implosion simulations

DOE PAGES

Vold, Erik Lehman; Joglekar, Archis S.; Ortega, Mario I.; ...

2015-11-20

The effects of viscosity and small-scale atomic-level mixing on plasmas in inertial confinement fusion(ICF) currently represent challenges in ICF research. Many current ICF hydrodynamic codes ignore the effects of viscosity though recent research indicates viscosity and mixing by classical transport processes may have a substantial impact on implosion dynamics. In this paper, we have implemented a Lagrangian hydrodynamic code in one-dimensional spherical geometry with plasmaviscosity and mass transport and including a three temperature model for ions, electrons, and radiation treated in a gray radiation diffusion approximation. The code is used to study ICF implosion differences with and without plasmaviscosity andmore » to determine the impacts of viscosity on temperature histories and neutron yield. It was found that plasmaviscosity has substantial impacts on ICF shock dynamics characterized by shock burn timing, maximum burn temperatures, convergence ratio, and time history of neutron production rates. Finally, plasmaviscosity reduces the need for artificial viscosity to maintain numerical stability in the Lagrangian formulation and also modifies the flux-limiting needed for electron thermal conduction.« less

The Explicit and Implicit Qualities of Alternative Fuels: Issues to Consider for Their Use in Marine Diesel Engines

DTIC Science & Technology

2008-09-30

problematic. However, such unfinished fuels are unlikely to be commercially available. Finishing those fuels by hydrotreating to remove excess...comparison, biodiesel does not meet several explicit properties because of higher acidity , viscosity, instability, pour point, and metals and ash content...would improve the remaining limiting properties of F-T and biodiesel fuels. Lubricity additives should remove the potential liability of the low

When death is not a problem: Regulating implicit negative affect under mortality salience.

PubMed

Lüdecke, Christina; Baumann, Nicola

2015-12-01

Terror management theory assumes that death arouses existential anxiety in humans which is suppressed in focal attention. Whereas most studies provide indirect evidence for negative affect under mortality salience by showing cultural worldview defenses and self-esteem strivings, there is only little direct evidence for implicit negative affect under mortality salience. In the present study, we assume that this implicit affective reaction towards death depends on people's ability to self-regulate negative affect as assessed by the personality dimension of action versus state orientation. Consistent with our expectations, action-oriented participants judged artificial words to express less negative affect under mortality salience compared to control conditions whereas state-oriented participants showed the reversed pattern. © 2015 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

Smoothed Particle Hydrodynamics Simulations of Ultrarelativistic Shocks with Artificial Viscosity

NASA Astrophysics Data System (ADS)

Siegler, S.; Riffert, H.

2000-03-01

We present a fully Lagrangian conservation form of the general relativistic hydrodynamic equations for perfect fluids with artificial viscosity in a given arbitrary background spacetime. This conservation formulation is achieved by choosing suitable Lagrangian time evolution variables, from which the generic fluid variables of rest-mass density, 3-velocity, and thermodynamic pressure have to be determined. We present the corresponding equations for an ideal gas and show the existence and uniqueness of the solution. On the basis of the Lagrangian formulation we have developed a three-dimensional general relativistic smoothed particle hydrodynamics (SPH) code using the standard SPH formalism as known from nonrelativistic fluid dynamics. One-dimensional simulations of a shock tube and a wall shock are presented together with a two-dimensional test calculation of an inclined shock tube. With our method we can model ultrarelativistic fluid flows including shocks with Lorentz factors of even 1000.

Modelling unsupervised online-learning of artificial grammars: linking implicit and statistical learning.

PubMed

Rohrmeier, Martin A; Cross, Ian

2014-07-01

Humans rapidly learn complex structures in various domains. Findings of above-chance performance of some untrained control groups in artificial grammar learning studies raise questions about the extent to which learning can occur in an untrained, unsupervised testing situation with both correct and incorrect structures. The plausibility of unsupervised online-learning effects was modelled with n-gram, chunking and simple recurrent network models. A novel evaluation framework was applied, which alternates forced binary grammaticality judgments and subsequent learning of the same stimulus. Our results indicate a strong online learning effect for n-gram and chunking models and a weaker effect for simple recurrent network models. Such findings suggest that online learning is a plausible effect of statistical chunk learning that is possible when ungrammatical sequences contain a large proportion of grammatical chunks. Such common effects of continuous statistical learning may underlie statistical and implicit learning paradigms and raise implications for study design and testing methodologies. Copyright © 2014 Elsevier Inc. All rights reserved.

Algorithm For Hypersonic Flow In Chemical Equilibrium

NASA Technical Reports Server (NTRS)

Palmer, Grant

1989-01-01

Implicit, finite-difference, shock-capturing algorithm calculates inviscid, hypersonic flows in chemical equilibrium. Implicit formulation chosen because overcomes limitation on mathematical stability encountered in explicit formulations. For dynamical portion of problem, Euler equations written in conservation-law form in Cartesian coordinate system for two-dimensional or axisymmetric flow. For chemical portion of problem, equilibrium state of gas at each point in computational grid determined by minimizing local Gibbs free energy, subject to local conservation of molecules, atoms, ions, and total enthalpy. Major advantage: resulting algorithm naturally stable and captures strong shocks without help of artificial-dissipation terms to damp out spurious numerical oscillations.

No childhood advantage in the acquisition of skill in using an artificial language rule.

PubMed

Ferman, Sara; Karni, Avi

2010-10-27

A leading notion is that language skill acquisition declines between childhood and adulthood. While several lines of evidence indicate that declarative ("what", explicit) memory undergoes maturation, it is commonly assumed that procedural ("how-to", implicit) memory, in children, is well established. The language superiority of children has been ascribed to the childhood reliance on implicit learning. Here we show that when 8-year-olds, 12-year-olds and young adults were provided with an equivalent multi-session training experience in producing and judging an artificial morphological rule (AMR), adults were superior to children of both age groups and the 8-year-olds were the poorest learners in all task parameters including in those that were clearly implicit. The AMR consisted of phonological transformations of verbs expressing a semantic distinction: whether the preceding noun was animate or inanimate. No explicit instruction of the AMR was provided. The 8-year-olds, unlike most adults and 12-year-olds, failed to explicitly uncover the semantic aspect of the AMR and subsequently to generalize it accurately to novel items. However, all participants learned to apply the AMR to repeated items and to generalize its phonological patterns to novel items, attaining accurate and fluent production, and exhibiting key characteristics of procedural memory. Nevertheless, adults showed a clear advantage in learning implicit task aspects, and in their long-term retention. Thus, our findings support the notion of age-dependent maturation in the establishment of declarative but also of procedural memory in a complex language task. In line with recent reports of no childhood advantage in non-linguistic skill learning, we propose that under some learning conditions adults can effectively express their language skill acquisition potential. Altogether, the maturational effects in the acquisition of an implicit AMR do not support a simple notion of a language skill learning advantage in children.

Artificial neural network based particle size prediction of polymeric nanoparticles.

PubMed

Youshia, John; Ali, Mohamed Ehab; Lamprecht, Alf

2017-10-01

Particle size of nanoparticles and the respective polydispersity are key factors influencing their biopharmaceutical behavior in a large variety of therapeutic applications. Predicting these attributes would skip many preliminary studies usually required to optimize formulations. The aim was to build a mathematical model capable of predicting the particle size of polymeric nanoparticles produced by a pharmaceutical polymer of choice. Polymer properties controlling the particle size were identified as molecular weight, hydrophobicity and surface activity, and were quantified by measuring polymer viscosity, contact angle and interfacial tension, respectively. A model was built using artificial neural network including these properties as input with particle size and polydispersity index as output. The established model successfully predicted particle size of nanoparticles covering a range of 70-400nm prepared from other polymers. The percentage bias for particle prediction was 2%, 4% and 6%, for the training, validation and testing data, respectively. Polymer surface activity was found to have the highest impact on the particle size followed by viscosity and finally hydrophobicity. Results of this study successfully highlighted polymer properties affecting particle size and confirmed the usefulness of artificial neural networks in predicting the particle size and polydispersity of polymeric nanoparticles. Copyright © 2017 Elsevier B.V. All rights reserved.

Dynamics and structures of transitional viscoelastic turbulence in channel flow

NASA Astrophysics Data System (ADS)

Shekar, Ashwin; Wang, Sung-Ning; Graham, Michael

2017-11-01

Introducing a trace amount of polymer into turbulent flows can result in a substantial reduction of drag. However, the mechanism is not fully understood at high levels of drag reduction. In this work we perform direct numerical simulations (DNS) of viscoelastic channel flow turbulence using a scheme that guarantees the positive-definiteness of polymer conformation tensor without artificial diffusion. Here we present the results of two parametric studies with the bulk Reynolds number fixed at 2000. First, the Weissenberg number (Wi) is kept at 100 and we vary the viscosity ratio (ratio ratio of the solvent viscosity and the total viscosity). Maximum drag reduction (MDR) is observed with viscosity ratio <0.95. As we decrease the viscosity ratio, i.e. increase polymer concentration, the mean velocity profile is almost invariant. However, this is accompanied by a decrease in velocity fluctuations but the flow stays turbulent. Turbulent kinetic energy budget analysis shows that, in this parameter regime, polymer becomes the major source of velocity fluctuations, replacing the energy transfer from the mean flow. In the second study, we fix the viscosity ratio at 0.95 and trace the Wi up to this regime and present the accompanying changes in flow quantities and structures.

Implicit solution of three-dimensional internal turbulent flows

NASA Technical Reports Server (NTRS)

Michelassi, V.; Liou, M.-S.; Povinelli, Louis A.; Martelli, F.

1991-01-01

The scalar form of the approximate factorization method was used to develop a new code for the solution of three dimensional internal laminar and turbulent compressible flows. The Navier-Stokes equations in their Reynolds-averaged form were iterated in time until a steady solution was reached. Evidence was given to the implicit and explicit artificial damping schemes that proved to be particularly efficient in speeding up convergence and enhancing the algorithm robustness. A conservative treatment of these terms at the domain boundaries was proposed in order to avoid undesired mass and/or momentum artificial fluxes. Turbulence effects were accounted for by the zero-equation Baldwin-Lomax turbulence model and the q-omega two-equation model. The flow in a developing S-duct was then solved in the laminar regime in a Reynolds number (Re) of 790 and in the turbulent regime at Re equals 40,000 by using the Baldwin-Lomax model. The Stanitz elbow was then solved by using an invicid version of the same code at M sub inlet equals 0.4. Grid dependence and convergence rate were investigated, showing that for this solver the implicit damping scheme may play a critical role for convergence characteristics. The same flow at Re equals 2.5 times 10(exp 6) was solved with the Baldwin-Lomax and the q-omega models. Both approaches show satisfactory agreement with experiments, although the q-omega model was slightly more accurate.

Assessing the Formation of Experience-Based Gender Expectations in an Implicit Learning Scenario

PubMed Central

Öttl, Anton; Behne, Dawn M.

2017-01-01

The present study investigates the formation of new word-referent associations in an implicit learning scenario, using a gender-coded artificial language with spoken words and visual referents. Previous research has shown that when participants are explicitly instructed about the gender-coding system underlying an artificial lexicon, they monitor the frequency of exposure to male vs. female referents within this lexicon, and subsequently use this probabilistic information to predict the gender of an upcoming referent. In an explicit learning scenario, the auditory and visual gender cues are necessarily highlighted prior to acqusition, and the effects previously observed may therefore depend on participants' overt awareness of these cues. To assess whether the formation of experience-based expectations is dependent on explicit awareness of the underlying coding system, we present data from an experiment in which gender-coding was acquired implicitly, thereby reducing the likelihood that visual and auditory gender cues are used strategically during acquisition. Results show that even if the gender coding system was not perfectly mastered (as reflected in the number of gender coding errors), participants develop frequency based expectations comparable to those previously observed in an explicit learning scenario. In line with previous findings, participants are quicker at recognizing a referent whose gender is consistent with an induced expectation than one whose gender is inconsistent with an induced expectation. At the same time however, eyetracking data suggest that these expectations may surface earlier in an implicit learning scenario. These findings suggest that experience-based expectations are robust against manner of acquisition, and contribute to understanding why similar expectations observed in the activation of stereotypes during the processing of natural language stimuli are difficult or impossible to suppress. PMID:28936186

Declarative and Procedural Memory as Individual Differences in Second Language Acquisition

ERIC Educational Resources Information Center

Morgan-Short, Kara; Faretta-Stutenberg, Mandy; Brill-Schuetz, Katherine A.; Carpenter, Helen; Wong, Patrick C. M.

2014-01-01

This study examined how individual differences in cognitive abilities account for variance in the attainment level of adult second language (L2) syntactic development. Participants completed assessments of declarative and procedural learning abilities. They subsequently learned an artificial L2 under implicit training conditions and received…

International Conference on Numerical Ship Hydrodynamics (6th), Held in Iowa City, Iowa on 2-5 August 1993,

DTIC Science & Technology

1994-01-01

length scales mensional hydrofoil and tip vortex flow around a F circulation three dimensional hydrofoil. The simulated mean v molecular viscosity flow...Unstructured Grid for Free Surface Flow Simulations , by T. Hino, L. Martinelli, and A. Jameson 173 "A Semi-Implicit Semi-Lagrangian Finite Element Model...Haussling Solid-Fluid Juncture Boundary Layer and Wake with Waves, by J.E. Choi and F. Stern 215 Direct Numerical and Large-Eddy Simulations of Turbulent

Numerical Simulation of Hypersonic Aerodynamics and the Computational Needs for the Design of an Aerospace Plane

DTIC Science & Technology

1992-01-01

2-layer algebraic eddy Lawrence flow, 150corner implicit (lacCormack, viscosity (Baldwin and et al. at M = 14.1 1982) Lomax, 1978) (1987) 5) NASA...for Turbulence Research NASA Ames/Stanford Summer Programme," Journal of Fluid Mechanics, Vol. 190, pp. 375-392. Hussain, A.KM.F., (1986): "Coherent...the development of a Reynolds- stress turbulence closure," Journal of Fluid Mechanics, Vol. 68, pp. 537-566. Lawrence , S. L., and A. Balakrishnan (1988

Calculation of transonic aileron buzz

NASA Technical Reports Server (NTRS)

Steger, J. L.; Bailey, H. E.

1979-01-01

An implicit finite-difference computer code that uses a two-layer algebraic eddy viscosity model and exact geometric specification of the airfoil has been used to simulate transonic aileron buzz. The calculated results, which were performed on both the Illiac IV parallel computer processor and the Control Data 7600 computer, are in essential agreement with the original expository wind-tunnel data taken in the Ames 16-Foot Wind Tunnel just after World War II. These results and a description of the pertinent numerical techniques are included.

Implicit structured sequence learning: an fMRI study of the structural mere-exposure effect

PubMed Central

Folia, Vasiliki; Petersson, Karl Magnus

2014-01-01

In this event-related fMRI study we investigated the effect of 5 days of implicit acquisition on preference classification by means of an artificial grammar learning (AGL) paradigm based on the structural mere-exposure effect and preference classification using a simple right-linear unification grammar. This allowed us to investigate implicit AGL in a proper learning design by including baseline measurements prior to grammar exposure. After 5 days of implicit acquisition, the fMRI results showed activations in a network of brain regions including the inferior frontal (centered on BA 44/45) and the medial prefrontal regions (centered on BA 8/32). Importantly, and central to this study, the inclusion of a naive preference fMRI baseline measurement allowed us to conclude that these fMRI findings were the intrinsic outcomes of the learning process itself and not a reflection of a preexisting functionality recruited during classification, independent of acquisition. Support for the implicit nature of the knowledge utilized during preference classification on day 5 come from the fact that the basal ganglia, associated with implicit procedural learning, were activated during classification, while the medial temporal lobe system, associated with explicit declarative memory, was consistently deactivated. Thus, preference classification in combination with structural mere-exposure can be used to investigate structural sequence processing (syntax) in unsupervised AGL paradigms with proper learning designs. PMID:24550865

Implicit structured sequence learning: an fMRI study of the structural mere-exposure effect.

PubMed

Folia, Vasiliki; Petersson, Karl Magnus

2014-01-01

In this event-related fMRI study we investigated the effect of 5 days of implicit acquisition on preference classification by means of an artificial grammar learning (AGL) paradigm based on the structural mere-exposure effect and preference classification using a simple right-linear unification grammar. This allowed us to investigate implicit AGL in a proper learning design by including baseline measurements prior to grammar exposure. After 5 days of implicit acquisition, the fMRI results showed activations in a network of brain regions including the inferior frontal (centered on BA 44/45) and the medial prefrontal regions (centered on BA 8/32). Importantly, and central to this study, the inclusion of a naive preference fMRI baseline measurement allowed us to conclude that these fMRI findings were the intrinsic outcomes of the learning process itself and not a reflection of a preexisting functionality recruited during classification, independent of acquisition. Support for the implicit nature of the knowledge utilized during preference classification on day 5 come from the fact that the basal ganglia, associated with implicit procedural learning, were activated during classification, while the medial temporal lobe system, associated with explicit declarative memory, was consistently deactivated. Thus, preference classification in combination with structural mere-exposure can be used to investigate structural sequence processing (syntax) in unsupervised AGL paradigms with proper learning designs.

Numerical Viscosity and the Survival of Gas Giant Protoplanets in Disk Simulations

NASA Astrophysics Data System (ADS)

Pickett, Megan K.; Durisen, Richard H.

2007-01-01

We present three-dimensional hydrodynamic simulations of a gravitationally unstable protoplanetary disk model under the condition of local isothermality. Ordinarily, local isothermality precludes the need for an artificial viscosity (AV) scheme to mediate shocks. Without AV, the disk evolves violently, shredding into dense (although short-lived) clumps. When we introduce our AV treatment in the momentum equation, but without heating due to irreversible compression, our grid-based simulations begin to resemble smoothed particle hydrodynamics (SPH) calculations, where clumps are more likely to survive many orbits. In fact, the standard SPH viscosity appears comparable in strength to the AV that leads to clump longevity in our code. This sensitivity to one numerical parameter suggests extreme caution in interpreting simulations by any code in which long-lived gaseous protoplanetary bodies appear.

Calculation of three-dimensional compressible laminar and turbulent boundary layers. An implicit finite-difference procedure for solving the three-dimensional compressible laminar, transitional, and turbulent boundary-layer equations

NASA Technical Reports Server (NTRS)

Harris, J. E.

1975-01-01

An implicit finite-difference procedure is presented for solving the compressible three-dimensional boundary-layer equations. The method is second-order accurate, unconditionally stable (conditional stability for reverse cross flow), and efficient from the viewpoint of computer storage and processing time. The Reynolds stress terms are modeled by (1) a single-layer mixing length model and (2) a two-layer eddy viscosity model. These models, although simple in concept, accurately predicted the equilibrium turbulent flow for the conditions considered. Numerical results are compared with experimental wall and profile data for a cone at an angle of attack larger than the cone semiapex angle. These comparisons clearly indicate that the numerical procedure and turbulence models accurately predict the experimental data with as few as 21 nodal points in the plane normal to the wall boundary.

An implicit solution of the three-dimensional Navier-Stokes equations for an airfoil spanning a wind tunnel. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Moitra, A.

1982-01-01

An implicit finite-difference algorithm is developed for the numerical solution of the incompressible three dimensional Navier-Stokes equations in the non-conservative primitive-variable formulation. The flow field about an airfoil spanning a wind-tunnel is computed. The coordinate system is generated by an extension of the two dimensional body-fitted coordinate generation techniques of Thompson, as well as that of Sorenson, into three dimensions. Two dimensional grids are stacked along a spanwise coordinate defined by a simple analytical function. A Poisson pressure equation for advancing the pressure in time is arrived at by performing a divergence operation on the momentum equations. The pressure at each time-step is calculated on the assumption that continuity be unconditionally satisfied. An eddy viscosity coefficient, computed according to the algebraic turbulence formulation of Baldwin and Lomax, simulates the effects of turbulence.

IMPLICIT DUAL CONTROL BASED ON PARTICLE FILTERING AND FORWARD DYNAMIC PROGRAMMING.

PubMed

Bayard, David S; Schumitzky, Alan

2010-03-01

This paper develops a sampling-based approach to implicit dual control. Implicit dual control methods synthesize stochastic control policies by systematically approximating the stochastic dynamic programming equations of Bellman, in contrast to explicit dual control methods that artificially induce probing into the control law by modifying the cost function to include a term that rewards learning. The proposed implicit dual control approach is novel in that it combines a particle filter with a policy-iteration method for forward dynamic programming. The integration of the two methods provides a complete sampling-based approach to the problem. Implementation of the approach is simplified by making use of a specific architecture denoted as an H-block. Practical suggestions are given for reducing computational loads within the H-block for real-time applications. As an example, the method is applied to the control of a stochastic pendulum model having unknown mass, length, initial position and velocity, and unknown sign of its dc gain. Simulation results indicate that active controllers based on the described method can systematically improve closed-loop performance with respect to other more common stochastic control approaches.

Divergence-Free SPH for Incompressible and Viscous Fluids.

PubMed

Bender, Jan; Koschier, Dan

2017-03-01

In this paper we present a novel Smoothed Particle Hydrodynamics (SPH) method for the efficient and stable simulation of incompressible fluids. The most efficient SPH-based approaches enforce incompressibility either on position or velocity level. However, the continuity equation for incompressible flow demands to maintain a constant density and a divergence-free velocity field. We propose a combination of two novel implicit pressure solvers enforcing both a low volume compression as well as a divergence-free velocity field. While a compression-free fluid is essential for realistic physical behavior, a divergence-free velocity field drastically reduces the number of required solver iterations and increases the stability of the simulation significantly. Thanks to the improved stability, our method can handle larger time steps than previous approaches. This results in a substantial performance gain since the computationally expensive neighborhood search has to be performed less frequently. Moreover, we introduce a third optional implicit solver to simulate highly viscous fluids which seamlessly integrates into our solver framework. Our implicit viscosity solver produces realistic results while introducing almost no numerical damping. We demonstrate the efficiency, robustness and scalability of our method in a variety of complex simulations including scenarios with millions of turbulent particles or highly viscous materials.

Finite-Difference Lattice Boltzmann Scheme for High-Speed Compressible Flow: Two-Dimensional Case

NASA Astrophysics Data System (ADS)

Gan, Yan-Biao; Xu, Ai-Guo; Zhang, Guang-Cai; Zhang, Ping; Zhang, Lei; Li, Ying-Jun

2008-07-01

Lattice Boltzmann (LB) modeling of high-speed compressible flows has long been attempted by various authors. One common weakness of most of previous models is the instability problem when the Mach number of the flow is large. In this paper we present a finite-difference LB model, which works for flows with flexible ratios of specific heats and a wide range of Mach number, from 0 to 30 or higher. Besides the discrete-velocity-model by Watari [Physica A 382 (2007) 502], a modified Lax Wendroff finite difference scheme and an artificial viscosity are introduced. The combination of the finite-difference scheme and the adding of artificial viscosity must find a balance of numerical stability versus accuracy. The proposed model is validated by recovering results of some well-known benchmark tests: shock tubes and shock reflections. The new model may be used to track shock waves and/or to study the non-equilibrium procedure in the transition between the regular and Mach reflections of shock waves, etc.

Drawing simulation by static implicit analysis with the artificial damping method

NASA Astrophysics Data System (ADS)

Oide, K.; Mihara, Y.; Kobayashi, T.; Takizawa, H.; Amaishi, T.; Umezu, Y.

2016-08-01

Wrinkling during draw is typically a local instability problem. When the structural instability is localized, there will be a local transfer of strain energy from one part of the structure to neighboring parts, and global solution methods, which is typically represented by the arc length method, may not work. So, this type of problems has to be solved either dynamically or with the artificial damping. On the other hand, the essential nature of the buckling behavior can be regarded as a static problem, even though it may be possible to raise some side issues due to the inertia effect. In this study, we traced the local buckling behavior of anisotropic elasto-plastic thin shells in Numisheet2014 BM4 using the artificial damping method.

Studying Different Tasks of Implicit Learning across Multiple Test Sessions Conducted on the Web

PubMed Central

Sævland, Werner; Norman, Elisabeth

2016-01-01

Implicit learning is usually studied through individual performance on a single task, with the most common tasks being the Serial Reaction Time (SRT) task, the Dynamic System Control (DSC) task, and Artificial Grammar Learning (AGL). Few attempts have been made to compare performance across different implicit learning tasks within the same study. The current study was designed to explore the relationship between performance on the DSC Sugar factory task and the Alternating Serial Reaction Time (ASRT) task. We also addressed another limitation of traditional implicit learning experiments, namely that implicit learning is usually studied in laboratory settings over a restricted time span lasting for less than an hour. In everyday situations, implicit learning is assumed to involve a gradual accumulation of knowledge across several learning episodes over a longer time span. One way to increase the ecological validity of implicit learning experiments could be to present the learning material repeatedly across shorter test sessions. This can most easily be done by using a web-based setup in which participants can access the material from home. We therefore created an online web-based system for measuring implicit learning that could be administered in either single or multiple sessions. Participants (n = 66) were assigned to either a single session or a multiple session condition. Learning occurred on both tasks, and awareness measures suggested that acquired knowledge was not fully conscious on either of the tasks. Learning and the degree of conscious awareness of the learned regularities were compared across conditions and tasks. On the DSC task, performance was not affected by whether learning had taken place in one or over multiple sessions. On the ASRT task, RT improvement across blocks was larger in the multiple-session condition. Learning in the two tasks was not related. PMID:27375512

Lowered pH Alters Decay but Not Speed of Tectorial Membrane Waves

NASA Astrophysics Data System (ADS)

Farrahi, Shirin; Ghaffari, Roozbeh; Freeman, Dennis M.

2011-11-01

Tectorial membrane (TM) traveling waves and mechanical shear impedances were measured in artificial endolymph baths at neutral and acidic pHs. Lowering pH from 7 to 4 significantly decreases the spatial extent of TM waves but has a relatively minor effect on wave speed. At pH 4, the imaginary component of TM shear impedance, which relates to the shear modulus, drops significantly; whereas, the real component, which relates to viscosity, is reduced less. These results suggest that shear modulus, and not viscosity, controls the extent of TM waves at lower pH.

Implicit Language Learning: Adults' Ability to Segment Words in Norwegian

ERIC Educational Resources Information Center

Kittleson, Megan M.; Aguilar, Jessica M.; Tokerud, Gry Line; Plante, Elena; Asbjornsen, Arve E.

2010-01-01

Previous language learning research reveals that the statistical properties of the input offer sufficient information to allow listeners to segment words from fluent speech in an artificial language. The current pair of studies uses a natural language to test the ecological validity of these findings and to determine whether a listener's language…

Investigating the Retention and Time Course of Phonotactic Constraint Learning from Production Experience

ERIC Educational Resources Information Center

Warker, Jill A.

2013-01-01

Adults can rapidly learn artificial phonotactic constraints such as /"f"/ "occurs only at the beginning of syllables" by producing syllables that contain those constraints. This implicit learning is then reflected in their speech errors. However, second-order constraints in which the placement of a phoneme depends on another…

The conscious, the unconscious, and familiarity.

PubMed

Scott, Ryan B; Dienes, Zoltán

2008-09-01

This article examines the role of subjective familiarity in the implicit and explicit learning of artificial grammars. Experiment 1 found that objective measures of similarity (including fragment frequency and repetition structure) predicted ratings of familiarity, that familiarity ratings predicted grammaticality judgments, and that the extremity of familiarity ratings predicted confidence. Familiarity was further shown to predict judgments in the absence of confidence, hence contributing to above-chance guessing. Experiment 2 found that confidence developed as participants refined their knowledge of the distribution of familiarity and that differences in familiarity could be exploited prior to confidence developing. Experiment 3 found that familiarity was consciously exploited to make grammaticality judgments including those made without confidence and that familiarity could in some instances influence participants' grammaticality judgments apparently without their awareness. All 3 experiments found that knowledge distinct from familiarity was derived only under deliberate learning conditions. The results provide decisive evidence that familiarity is the essential source of knowledge in artificial grammar learning while also supporting a dual-process model of implicit and explicit learning. (c) 2008 APA, all rights reserved.

The P600 in Implicit Artificial Grammar Learning.

PubMed

Silva, Susana; Folia, Vasiliki; Hagoort, Peter; Petersson, Karl Magnus

2017-01-01

The suitability of the artificial grammar learning (AGL) paradigm to capture relevant aspects of the acquisition of linguistic structures has been empirically tested in a number of EEG studies. Some have shown a syntax-related P600 component, but it has not been ruled out that the AGL P600 effect is a response to surface features (e.g., subsequence familiarity) rather than the underlying syntax structure. Therefore, in this study, we controlled for the surface characteristics of the test sequences (associative chunk strength) and recorded the EEG before (baseline preference classification) and after (preference and grammaticality classification) exposure to a grammar. After exposure, a typical, centroparietal P600 effect was elicited by grammatical violations and not by unfamiliar subsequences, suggesting that the AGL P600 effect signals a response to structural irregularities. Moreover, preference and grammaticality classification showed a qualitatively similar ERP profile, strengthening the idea that the implicit structural mere-exposure paradigm in combination with preference classification is a suitable alternative to the traditional grammaticality classification test. Copyright © 2016 Cognitive Science Society, Inc.

Effect of viscosity on tear drainage and ocular residence time.

PubMed

Zhu, Heng; Chauhan, Anuj

2008-08-01

An increase in residence time of dry eye medications including artificial tears will likely enhance therapeutic benefits. The drainage rates and the residence time of eye drops depend on the viscosity of the instilled fluids. However, a quantitative understanding of the dependence of drainage rates and the residence time on viscosity is lacking. The current study aims to develop a mathematical model for the drainage of Newtonian fluids and also for power-law non-Newtonian fluids of different viscosities. This study is an extension of our previous study on the mathematical model of tear drainage. The tear drainage model is modified to describe the drainage of Newtonian fluids with viscosities higher than the tear viscosity and power-law non-Newtonian fluids with rheological parameters obtained from fitting experimental data in literature. The drainage rate through canaliculi was derived from the modified drainage model and was incorporated into a tear mass balance to calculate the transients of total solute quantity in ocular fluids and the bioavailability of instilled drugs. For Newtonian fluids, increasing the viscosity does not affect the drainage rate unless the viscosity exceeds a critical value of about 4.4 cp. The viscosity has a maximum impact on drainage rate around a value of about 100 cp. The trends are similar for shear thinning power law fluids. The transients of total solute quantity, and the residence time agrees at least qualitatively with experimental studies. A mathematical model has been developed for the drainage of Newtonian fluids and power-law fluids through canaliculi. The model can quantitatively explain different experimental observations on the effect of viscosity on the residence of instilled fluids on the ocular surface. The current study is helpful for understanding the mechanism of fluid drainage from the ocular surface and for improving the design of dry eye treatments.

An artificial nonlinear diffusivity method for supersonic reacting flows with shocks

NASA Astrophysics Data System (ADS)

Fiorina, B.; Lele, S. K.

2007-03-01

A computational approach for modeling interactions between shocks waves, contact discontinuities and reactions zones with a high-order compact scheme is investigated. To prevent the formation of spurious oscillations around shocks, artificial nonlinear viscosity [A.W. Cook, W.H. Cabot, A high-wavenumber viscosity for high resolution numerical method, J. Comput. Phys. 195 (2004) 594-601] based on high-order derivative of the strain rate tensor is used. To capture temperature and species discontinuities a nonlinear diffusivity based on the entropy gradient is added. It is shown that the damping of 'wiggles' is controlled by the model constants and is largely independent of the mesh size and the shock strength. The same holds for the numerical shock thickness and allows a determination of the L2 error. In the shock tube problem, with fluids of different initial entropy separated by the diaphragm, an artificial diffusivity is required to accurately capture the contact surface. Finally, the method is applied to a shock wave propagating into a medium with non-uniform density/entropy and to a CJ detonation wave. Multi-dimensional formulation of the model is presented and is illustrated by a 2D oblique wave reflection from an inviscid wall, by a 2D supersonic blunt body flow and by a Mach reflection problem.

Applications of Taylor-Galerkin finite element method to compressible internal flow problems

NASA Technical Reports Server (NTRS)

Sohn, Jeong L.; Kim, Yongmo; Chung, T. J.

1989-01-01

A two-step Taylor-Galerkin finite element method with Lapidus' artificial viscosity scheme is applied to several test cases for internal compressible inviscid flow problems. Investigations for the effect of supersonic/subsonic inlet and outlet boundary conditions on computational results are particularly emphasized.

Localized Artificial Viscosity Stabilization of Discontinuous Galerkin Methods for Nonhydrostatic Mesoscale Atmospheric Modeling

DTIC Science & Technology

2014-01-01

with a Riemann flux !"#! (!! ,!!!,), where !!! denotes the solution outside the current element !. Various (approximate) Riemann solvers ...can be used to calculate the Riemann flux, and the Rusanov Riemann solver is adopted in this paper. Then Eq. (7) can be rewritten as !

Conservative, special-relativistic smoothed particle hydrodynamics

NASA Astrophysics Data System (ADS)

Rosswog, Stephan

2010-11-01

We present and test a new, special-relativistic formulation of smoothed particle hydrodynamics (SPH). Our approach benefits from several improvements with respect to earlier relativistic SPH formulations. It is self-consistently derived from the Lagrangian of an ideal fluid and accounts for the terms that stem from non-constant smoothing lengths, usually called “grad-h terms”. In our approach, we evolve the canonical momentum and the canonical energy per baryon and thus circumvent some of the problems that have plagued earlier formulations of relativistic SPH. We further use a much improved artificial viscosity prescription which uses the extreme local eigenvalues of the Euler equations and triggers selectively on (a) shocks and (b) velocity noise. The shock trigger accurately monitors the relative density slope and uses it to fine-tune the amount of artificial viscosity that is applied. This procedure substantially sharpens shock fronts while still avoiding post-shock noise. If not triggered, the viscosity parameter of each particle decays to zero. None of these viscosity triggers is specific to special relativity, both could also be applied in Newtonian SPH.The performance of the new scheme is explored in a large variety of benchmark tests where it delivers excellent results. Generally, the grad-h terms deliver minor, though worthwhile, improvements. As expected for a Lagrangian method, it performs close to perfect in supersonic advection tests, but also in strong relativistic shocks, usually considered a particular challenge for SPH, the method yields convincing results. For example, due to its perfect conservation properties, it is able to handle Lorentz factors as large as γ = 50,000 in the so-called wall shock test. Moreover, we find convincing results in a rarely shown, but challenging test that involves so-called relativistic simple waves and also in multi-dimensional shock tube tests.

Non-equilibrium radiation from viscous chemically reacting two-phase exhaust plumes

NASA Technical Reports Server (NTRS)

Penny, M. M.; Smith, S. D.; Mikatarian, R. R.; Ring, L. R.; Anderson, P. G.

1976-01-01

A knowledge of the structure of the rocket exhaust plumes is necessary to solve problems involving plume signatures, base heating, plume/surface interactions, etc. An algorithm is presented which treats the viscous flow of multiphase chemically reacting fluids in a two-dimensional or axisymmetric supersonic flow field. The gas-particle flow solution is fully coupled with the chemical kinetics calculated using an implicit scheme to calculate chemical production rates. Viscous effects include chemical species diffusion with the viscosity coefficient calculated using a two-equation turbulent kinetic energy model.

Possible benefits of catheters with lateral holes in coronary thrombus aspiration: a computational study for different clot viscosities and vacuum pressures.

PubMed

Soleimani, Sajjad; Dubini, Gabriele; Pennati, Giancarlo

2014-10-01

According to a number of clinical studies, coronary aspiration catheters are useful tools to remove a thrombus (blood clot) blocking a coronary artery. However, these thrombectomy devices may fail to remove the blood clot entirely. Few studies have been devoted to a systematic analysis of factors affecting clot aspiration. The geometric characteristics of the aspiration catheter, the physical properties of the thrombus, and the applied vacuum pressure are crucial parameters. In this study, the aspiration of a blood clot blocking a coronary bifurcation is computationally simulated. The clot is modeled as a highly viscous fluid, and a two-phase (blood and clot) problem is solved. The effects of geometric variations in the tip of the coronary catheter, including lateral hole size and location, are investigated considering different aspiration pressures and clot viscosities. A Bird-Carreau model is adopted for blood viscosity, while a power law model is used to describe the clot rheology. Computational results for blood clot aspiration show that the presence of holes in the lateral part of the tip of the catheter can be beneficial depending on clot viscosity, hole features, and applied aspiration pressure. In general, the holes are beneficial when the clot viscosity is low, while aspiration catheters without any extra lateral holes exhibit better performance for higher clot viscosity. However, when higher aspiration pressures are applied, the catheters tend to behave relatively similarly in removing clots with various viscosities, reducing the role of the clot viscosity. Copyright © 2014 International Center for Artificial Organs and Transplantation and Wiley Periodicals, Inc.

Second Language Acquisition of Gender Agreement in Explicit and Implicit Training Conditions: An Event-Related Potential Study

ERIC Educational Resources Information Center

Morgan-Short, Kara; Sanz, Cristina; Steinhauer, Karsten; Ullman, Michael T.

2010-01-01

This study employed an artificial language learning paradigm together with a combined behavioral/event-related potential (ERP) approach to examine the neurocognition of the processing of gender agreement, an aspect of inflectional morphology that is problematic in adult second language (L2) learning. Subjects learned to speak and comprehend an…

ERP evidence for hemispheric asymmetries in abstract but not exemplar-specific repetition priming.

PubMed

Küper, Kristina; Liesefeld, Anna M; Zimmer, Hubert D

2015-12-01

Implicit memory retrieval is thought to be exemplar-specific in the right hemisphere (RH) but abstract in the left hemisphere (LH). Yet, conflicting behavioral priming results illustrate that the level at which asymmetries take effect is difficult to pinpoint. In the present divided visual field experiment, we tried to address this issue by analyzing ERPs in addition to behavioral measures. Participants made a natural/artificial decision on lateralized visual objects that were either new, identical repetitions, or different exemplars of studied items. Hemispheric asymmetries did not emerge in either behavioral or late positive complex (LPC) priming effects, but did affect the process of implicit memory retrieval proper as indexed by an early frontal negativity (N350/(F)N400). Whereas exemplar-specific N350/(F)N400 priming effects emerged irrespective of presentation side, abstract implicit memory retrieval of different exemplars was contingent on right visual field presentation and the ensuing initial stimulus processing by the LH. © 2015 Society for Psychophysiological Research.

Multigrid Acceleration of Time-Accurate DNS of Compressible Turbulent Flow

NASA Technical Reports Server (NTRS)

Broeze, Jan; Geurts, Bernard; Kuerten, Hans; Streng, Martin

1996-01-01

An efficient scheme for the direct numerical simulation of 3D transitional and developed turbulent flow is presented. Explicit and implicit time integration schemes for the compressible Navier-Stokes equations are compared. The nonlinear system resulting from the implicit time discretization is solved with an iterative method and accelerated by the application of a multigrid technique. Since we use central spatial discretizations and no artificial dissipation is added to the equations, the smoothing method is less effective than in the more traditional use of multigrid in steady-state calculations. Therefore, a special prolongation method is needed in order to obtain an effective multigrid method. This simulation scheme was studied in detail for compressible flow over a flat plate. In the laminar regime and in the first stages of turbulent flow the implicit method provides a speed-up of a factor 2 relative to the explicit method on a relatively coarse grid. At increased resolution this speed-up is enhanced correspondingly.

g-Jitter Mixed Convective Slip Flow of Nanofluid past a Permeable Stretching Sheet Embedded in a Darcian Porous Media with Variable Viscosity

PubMed Central

Uddin, Mohammed J.; Khan, Waqar A.; Amin, Norsarahaida S.

2014-01-01

The unsteady two-dimensional laminar g-Jitter mixed convective boundary layer flow of Cu-water and Al2O3-water nanofluids past a permeable stretching sheet in a Darcian porous is studied by using an implicit finite difference numerical method with quasi-linearization technique. It is assumed that the plate is subjected to velocity and thermal slip boundary conditions. We have considered temperature dependent viscosity. The governing boundary layer equations are converted into non-similar equations using suitable transformations, before being solved numerically. The transport equations have been shown to be controlled by a number of parameters including viscosity parameter, Darcy number, nanoparticle volume fraction, Prandtl number, velocity slip, thermal slip, suction/injection and mixed convection parameters. The dimensionless velocity and temperature profiles as well as friction factor and heat transfer rates are presented graphically and discussed. It is found that the velocity reduces with velocity slip parameter for both nanofluids for fluid with both constant and variable properties. It is further found that the skin friction decreases with both Darcy number and momentum slip parameter while it increases with viscosity variation parameter. The surface temperature increases as the dimensionless time increases for both nanofluids. Nusselt numbers increase with mixed convection parameter and Darcy numbers and decreases with the momentum slip. Excellent agreement is found between the numerical results of the present paper with published results. PMID:24927277

User`s guide for UTCHEM-5.32m a three dimensional chemical flood simulator. Final report, September 30, 1992--December 31, 1995

DOE Office of Scientific and Technical Information (OSTI.GOV)

NONE

1996-07-01

UTCHEM is a three-dimensional chemical flooding simulator. The solution scheme is analogous to IMPES, where pressure is solved for implicitly, but concentrations rather than saturations are then solved for explicitly. Phase saturations and concentrations are then solved in a flash routine. An energy balance equation is solved explicitly for reservoir temperature. The energy balance equation includes heat flow between the reservoir and the over-and under-burden rocks. The major physical phenomena modeled in the simulator are: dispersion; dilution effects; adsorption; interfacial tension; relative permeability; capillary trapping; cation exchange; phase density; compositional phase viscosity; phase behavior (pseudoquaternary); aqueous reactions; partitioning of chemicalmore » species between oil and water; dissolution/precipitation; cation exchange reactions involving more than two cations; in-situ generation of surfactant from acidic crude oil; pH dependent adsorption; polymer properties: shear thinning viscosity; inaccessible pore volume; permeability reduction; adsorption; gel properties: viscosity; permeability reduction; adsorption; tracer properties: partitioning; adsorption; radioactive decay; reaction (ester hydrolization); temperature dependent properties: viscosity; tracer reaction; gel reactions The following options are available with UTCHEM: isothermal or non-isothermal conditions, a constant or variable time-step, constant pressure or constant rate well conditions, horizontal and vertical wells, and a radial or Cartesian geometry. Please refer to the dissertation {open_quotes}Field Scale Simulation of Chemical Flooding{close_quotes} by Naji Saad, August, 1989, for a more detailed discussion of the UTCHEM simulator and its formulation.« less

Determining a membrane's shear modulus, independent of its area-dilatation modulus, via capsule flow in a converging micro-capillary.

PubMed

Dimitrakopoulos, P; Kuriakose, S

2015-04-14

Determination of the elastic properties of the membrane of artificial capsules is essential for the better design of the various devices that are utilized in their engineering and biomedical applications. However this task is complicated owing to the combined effects of the shear and area-dilatation moduli on the capsule deformation. Based on computational investigation, we propose a new methodology to determine a membrane's shear modulus, independent of its area-dilatation modulus, by flowing strain-hardening capsules in a converging micro-capillary of comparable size under Stokes flow conditions, and comparing the experimental measurements of the capsule elongation overshooting with computational data. The capsule prestress, if any, can also be determined with the same methodology. The elongation overshooting is practically independent of the viscosity ratio for low and moderate viscosity ratios, and thus a wide range of capsule fluids can be employed. Our proposed experimental device can be readily produced via glass fabrication while owing to the continuous flow in the micro-capillary, the characterization of a large number of artificial capsules is possible.

The Role of Feedback in Implicit and Explicit Artificial Grammar Learning: A Comparison between Dyslexic and Non-Dyslexic Adults

ERIC Educational Resources Information Center

Schiff, Rachel; Sasson, Ayelet; Star, Galit; Kahta, Shani

2017-01-01

The importance of feedback for learning has been firmly established over the past few decades. The question of whether feedback plays a significant role in the statistical learning abilities of adults with dyslexia, however, is currently unresolved. Here, we examined the role of feedback in grammaticality judgment, type of structural knowledge,…

A Semi-implicit Method for Time Accurate Simulation of Compressible Flow

NASA Astrophysics Data System (ADS)

Wall, Clifton; Pierce, Charles D.; Moin, Parviz

2001-11-01

A semi-implicit method for time accurate simulation of compressible flow is presented. The method avoids the acoustic CFL limitation, allowing a time step restricted only by the convective velocity. Centered discretization in both time and space allows the method to achieve zero artificial attenuation of acoustic waves. The method is an extension of the standard low Mach number pressure correction method to the compressible Navier-Stokes equations, and the main feature of the method is the solution of a Helmholtz type pressure correction equation similar to that of Demirdžić et al. (Int. J. Num. Meth. Fluids, Vol. 16, pp. 1029-1050, 1993). The method is attractive for simulation of acoustic combustion instabilities in practical combustors. In these flows, the Mach number is low; therefore the time step allowed by the convective CFL limitation is significantly larger than that allowed by the acoustic CFL limitation, resulting in significant efficiency gains. Also, the method's property of zero artificial attenuation of acoustic waves is important for accurate simulation of the interaction between acoustic waves and the combustion process. The method has been implemented in a large eddy simulation code, and results from several test cases will be presented.

On improving the iterative convergence properties of an implicit approximate-factorization finite difference algorithm. [considering transonic flow

NASA Technical Reports Server (NTRS)

Desideri, J. A.; Steger, J. L.; Tannehill, J. C.

1978-01-01

The iterative convergence properties of an approximate-factorization implicit finite-difference algorithm are analyzed both theoretically and numerically. Modifications to the base algorithm were made to remove the inconsistency in the original implementation of artificial dissipation. In this way, the steady-state solution became independent of the time-step, and much larger time-steps can be used stably. To accelerate the iterative convergence, large time-steps and a cyclic sequence of time-steps were used. For a model transonic flow problem governed by the Euler equations, convergence was achieved with 10 times fewer time-steps using the modified differencing scheme. A particular form of instability due to variable coefficients is also analyzed.

Experimental study on the pressure and pulse wave propagation in viscoelastic vessel tubes-effects of liquid viscosity and tube stiffness.

PubMed

Ikenaga, Yuki; Nishi, Shohei; Komagata, Yuka; Saito, Masashi; Lagrée, Pierre-Yves; Asada, Takaaki; Matsukawa, Mami

2013-11-01

A pulse wave is the displacement wave which arises because of ejection of blood from the heart and reflection at vascular bed and distal point. The investigation of pressure waves leads to understanding the propagation characteristics of a pulse wave. To investigate the pulse wave behavior, an experimental study was performed using an artificial polymer tube and viscous liquid. A polyurethane tube and glycerin solution were used to simulate a blood vessel and blood, respectively. In the case of the 40 wt% glycerin solution, which corresponds to the viscosity of ordinary blood, the attenuation coefficient of a pressure wave in the tube decreased from 4.3 to 1.6 dB/m because of the tube stiffness (Young's modulus: 60 to 200 kPa). When the viscosity of liquid increased from approximately 4 to 10 mPa·s (the range of human blood viscosity) in the stiff tube, the attenuation coefficient of the pressure wave changed from 1.6 to 3.2 dB/m. The hardening of the blood vessel caused by aging and the increase of blood viscosity caused by illness possibly have opposite effects on the intravascular pressure wave. The effect of the viscosity of a liquid on the amplitude of a pressure wave was then considered using a phantom simulating human blood vessels. As a result, in the typical range of blood viscosity, the amplitude ratio of the waves obtained by the experiments with water and glycerin solution became 1:0.83. In comparison with clinical data, this value is much smaller than that seen from blood vessel hardening. Thus, it can be concluded that the blood viscosity seldom affects the attenuation of a pulse wave.

Spatial nonlinear absorption of Alfven waves by dissipative plasma taking account bremsstrahlung

NASA Astrophysics Data System (ADS)

Taiurskii, A. A.; Gavrikov, M. B.

2016-10-01

We study numerically the nonlinear absorption of a plane Alfven wave falling on the stationary boundary of dissipative plasma. This absorption is caused by such factors as the magnetic viscosity, hydrodynamic viscosity, and thermal conductivity of electrons and ions, bremsstrahlung and energy exchange between plasma components. The relevance of this investigation is due to some works, published in 2011, with regard to the heating mechanism of the solar corona and solar wind generation as a result of the absorption of plasma Alfven waves generated in the lower significantly colder layers of the Sun. Numerical analysis shows that the absorption of Alfven waves occurs at wavelengths of the order of skin depth, in which case the classical MHD equations are inapplicable. Therefore, our research is based on equations of two-fluid magnetohydrodynamics that take into account the inertia of the electrons. The implicit difference scheme proposed here for calculating plane-parallel flows of two-fluid plasma reveals a number of important patterns of absorption and thus allows us to study the dependence of the absorption on the Alfven wave frequency and the electron thermal conductivity and viscosity, as well as to evaluate the depth and the velocity of plasma heating during the penetration of Alfven waves interacting with dissipative plasma.

Stability analysis for the background equations for inflation with dissipation and in a viscous radiation bath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bastero-Gil, Mar; Cerezo, Rafael; Berera, Arjun

2012-11-01

The effects of bulk viscosity are examined for inflationary dynamics in which dissipation and thermalization are present. A complete stability analysis is done for the background inflaton evolution equations, which includes both inflaton dissipation and radiation bulk viscous effects. Three representative approaches of bulk viscous irreversible thermodynamics are analyzed: the Eckart noncausal theory, the linear and causal theory of Israel-Stewart and a more recent nonlinear and causal bulk viscous theory. It is found that the causal theories allow for larger bulk viscosities before encountering an instability in comparison to the noncausal Eckart theory. It is also shown that the causalmore » theories tend to suppress the radiation production due to bulk viscous pressure, because of the presence of relaxation effects implicit in these theories. Bulk viscosity coefficients derived from quantum field theory are applied to warm inflation model building and an analysis is made of the effects to the duration of inflation. The treatment of bulk pressure would also be relevant to the reheating phase after inflation in cold inflation dynamics and during the radiation dominated regime, although very little work in both areas has been done; the methodology developed in this paper could be extended to apply to these other problems.« less

A new flux-limited, two-dimensional, nonsymmetric tensor shock viscosity for DYNA2D: Progress report

DOE Office of Scientific and Technical Information (OSTI.GOV)

Benson, D.J.

1988-08-15

A new artificial viscosity that is being developed for DYNA2D is described in this progress report. It incorporates the one- dimensional, flux-limited viscosity developed by Randy Christensen into a two-dimensional setting. In addition, it tries to overcome some of the difficulties associated with traditional bulk viscosity formulations by using an nonsymmetric viscosity tensor. A different nonsymmetric approach (and a symmetrized version of it) is being used in SHALE by Len Margolin with great success. In a later section of this paper, the results of DYNA2D and SHALE for the ''Saltzman problem'' are compared. The general organization of this report ismore » as follows: First it presents the one-dimensional, flux-limited viscosity developed by Christensen. An nonsymmetric tensor viscosity is then developed and the addition of flux-limiting to it is discussed. The issue of boundary conditions turns out to be crucial, and some issues associated with them are unresolved. The current boundary conditions and the issues associated with them are discussed. Example calculations are also given. The current work is summarized and future work is outlined in the first chapter. This brief progress report is the basis of a future journal paper. The work presented in here is unfinished, and some of the results and algorithms will undoubtedly be changed before the final paper. No attempt has been made to survey the results of others in this report, but a limited survey will be incorporated in the journal paper. 7 refs., 39 figs.« less

Statistical Learning of Two Artificial Languages Presented Successively: How Conscious?

PubMed Central

Franco, Ana; Cleeremans, Axel; Destrebecqz, Arnaud

2011-01-01

Statistical learning is assumed to occur automatically and implicitly, but little is known about the extent to which the representations acquired over training are available to conscious awareness. In this study, we focus on whether the knowledge acquired in a statistical learning situation is available to conscious control. Participants were first exposed to an artificial language presented auditorily. Immediately thereafter, they were exposed to a second artificial language. Both languages were composed of the same corpus of syllables and differed only in the transitional probabilities. We first determined that both languages were equally learnable (Experiment 1) and that participants could learn the two languages and differentiate between them (Experiment 2). Then, in Experiment 3, we used an adaptation of the Process-Dissociation Procedure (Jacoby, 1991) to explore whether participants could consciously manipulate the acquired knowledge. Results suggest that statistical information can be used to parse and differentiate between two different artificial languages, and that the resulting representations are available to conscious control. PMID:21960981

A pressure-based semi-implicit space-time discontinuous Galerkin method on staggered unstructured meshes for the solution of the compressible Navier-Stokes equations at all Mach numbers

NASA Astrophysics Data System (ADS)

Tavelli, Maurizio; Dumbser, Michael

2017-07-01

We propose a new arbitrary high order accurate semi-implicit space-time discontinuous Galerkin (DG) method for the solution of the two and three dimensional compressible Euler and Navier-Stokes equations on staggered unstructured curved meshes. The method is pressure-based and semi-implicit and is able to deal with all Mach number flows. The new DG scheme extends the seminal ideas outlined in [1], where a second order semi-implicit finite volume method for the solution of the compressible Navier-Stokes equations with a general equation of state was introduced on staggered Cartesian grids. Regarding the high order extension we follow [2], where a staggered space-time DG scheme for the incompressible Navier-Stokes equations was presented. In our scheme, the discrete pressure is defined on the primal grid, while the discrete velocity field and the density are defined on a face-based staggered dual grid. Then, the mass conservation equation, as well as the nonlinear convective terms in the momentum equation and the transport of kinetic energy in the energy equation are discretized explicitly, while the pressure terms appearing in the momentum and energy equation are discretized implicitly. Formal substitution of the discrete momentum equation into the total energy conservation equation yields a linear system for only one unknown, namely the scalar pressure. Here the equation of state is assumed linear with respect to the pressure. The enthalpy and the kinetic energy are taken explicitly and are then updated using a simple Picard procedure. Thanks to the use of a staggered grid, the final pressure system is a very sparse block five-point system for three dimensional problems and it is a block four-point system in the two dimensional case. Furthermore, for high order in space and piecewise constant polynomials in time, the system is observed to be symmetric and positive definite. This allows to use fast linear solvers such as the conjugate gradient (CG) method. In addition, all the volume and surface integrals needed by the scheme depend only on the geometry and the polynomial degree of the basis and test functions and can therefore be precomputed and stored in a preprocessing stage. This leads to significant savings in terms of computational effort for the time evolution part. In this way also the extension to a fully curved isoparametric approach becomes natural and affects only the preprocessing step. The viscous terms and the heat flux are also discretized making use of the staggered grid by defining the viscous stress tensor and the heat flux vector on the dual grid, which corresponds to the use of a lifting operator, but on the dual grid. The time step of our new numerical method is limited by a CFL condition based only on the fluid velocity and not on the sound speed. This makes the method particularly interesting for low Mach number flows. Finally, a very simple combination of artificial viscosity and the a posteriori MOOD technique allows to deal with shock waves and thus permits also to simulate high Mach number flows. We show computational results for a large set of two and three-dimensional benchmark problems, including both low and high Mach number flows and using polynomial approximation degrees up to p = 4.

Evaluation of a research circulation control airfoil using Navier-Stokes methods

NASA Technical Reports Server (NTRS)

Shrewsbury, George D.

1987-01-01

The compressible Reynolds time averaged Navier-Stokes equations were used to obtain solutions for flows about a two dimensional circulation control airfoil. The governing equations were written in conservation form for a body-fitted coordinate system and solved using an Alternating Direction Implicit (ADI) procedure. A modified algebraic eddy viscosity model was used to define the turbulent characteristics of the flow, including the wall jet flow over the Coanda surface at the trailing edge. Numerical results are compared to experimental data obtained for a research circulation control airfoil geometry. Excellent agreement with the experimental results was obtained.

Implicit marching solution of compressible viscous subsonic flow in planar and axisymmetric ducts. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Towne, C. E.; Hoffman, J. D.

1982-01-01

A new streamwise marching procedure was developed and coded for compressible viscous subsonic flow in planar or axisymmetric ducts with or without centerbodies. The continuity, streamwise momentum, cross-flow momentum, and energy equations are written in generalized orthogonal curvilinear coordinates. To allow the use of a marching procedure, second derivatives in the streamwise momentum equation are written as the sum of a known two dimensional imposed pressure field and an unknown one dimensional viscous correction. For turbulent flow, the Reynolds stress and heat flux terms are modeled using two-layer eddy viscosity turbulence models.

Artificial Intelligence Applications to Testability.

DTIC Science & Technology

1984-10-01

general software assistant; examining testability utilization of it should wait a few years until the software assistant is a well defined product ...ago. It provides a single host which satisfies the needs of developers, product developers, and end users . As shown in table 5.10-2, it also provides...follows a trend towards more user -oriented design approaches to interactive computer systems. The implicit goal in this trend is the

Numerical simulation of steady three-dimensional flows in axial turbomachinery bladerows

NASA Astrophysics Data System (ADS)

Basson, Anton Herman

The formulation for and application of a numerical model for low Mach number steady three-dimensional flows in axial turbomachinery blade rows is presented. The formulation considered here includes an efficient grid generation scheme (particularly suited to computational grids for the analysis of turbulent turbomachinery flows) and a semi-implicit, pressure-based computational fluid dynamics scheme that directly includes artificial dissipation, applicable to viscous and inviscid flows. The grid generation technique uses a combination of algebraic and elliptic methods, in conjunction with the Minimal Residual Method, to economically generate smooth structured grids. For typical H-grids in turbomachinery bladerows, when compared to a purely elliptic grid generation scheme, the presented grid generation scheme produces grids with much improved smoothness near the leading and trailing edges, allows the use of small near wall grid spacing required by low Reynolds number turbulence models, and maintains orthogonality of the grid near the solid boundaries even for high flow angle cascades. A specialized embedded H-grid for application particularly to tip clearance flows is presented. This topology smoothly discretizes the domain without modifying the tip shape, while requiring only minor modifications to H-grid flow solvers. Better quantitative modeling of the tip clearance vortex structure than that obtained with a pinched tip approximation is demonstrated. The formulation of artificial dissipation terms for a semi-implicit, pressure-based (SIMPLE type) flow solver, is presented. It is applied to both the Euler and the Navier-Stokes equations, expressed in generalized coordinates using a non-staggered grid. This formulation is compared to some SIMPLE and time marching formulations, revealing the artificial dissipation inherent in some commonly used semi-implicit formulations. The effect of the amount of dissipation on the accuracy of the solution and the convergence rate is quantitatively demonstrated for a number of flow cases. The ability of the formulation to model complex steady turbomachinery flows is demonstrated, e.g. for pressure driven secondary flows, turbine nozzle wakes, turbulent boundary layers. The formulation's modeling of blade surface heat transfer is assessed. The numerical model is used to investigate the structure of phenomena associated with tip clearance flows in a turbine nozzle.

Social intuition as a form of implicit learning: Sequences of body movements are learned less explicitly than letter sequences

PubMed Central

Norman, Elisabeth; Price, Mark C.

2012-01-01

In the current paper, we first evaluate the suitability of traditional serial reaction time (SRT) and artificial grammar learning (AGL) experiments for measuring implicit learning of social signals. We then report the results of a novel sequence learning task which combines aspects of the SRT and AGL paradigms to meet our suggested criteria for how implicit learning experiments can be adapted to increase their relevance to situations of social intuition. The sequences followed standard finite-state grammars. Sequence learning and consciousness of acquired knowledge were compared between 2 groups of 24 participants viewing either sequences of individually presented letters or sequences of body-posture pictures, which were described as series of yoga movements. Participants in both conditions showed above-chance classification accuracy, indicating that sequence learning had occurred in both stimulus conditions. This shows that sequence learning can still be found when learning procedures reflect the characteristics of social intuition. Rule awareness was measured using trial-by-trial evaluation of decision strategy (Dienes & Scott, 2005; Scott & Dienes, 2008). For letters, sequence classification was best on trials where participants reported responding on the basis of explicit rules or memory, indicating some explicit learning in this condition. For body-posture, classification was not above chance on these types of trial, but instead showed a trend to be best on those trials where participants reported that their responses were based on intuition, familiarity, or random choice, suggesting that learning was more implicit. Results therefore indicate that the use of traditional stimuli in research on sequence learning might underestimate the extent to which learning is implicit in domains such as social learning, contributing to ongoing debate about levels of conscious awareness in implicit learning. PMID:22679467

Color change of composite resins subjected to accelerated artificial aging.

PubMed

Tornavoi, Denise Cremonezzi; Agnelli, José Augusto Marcondes; Panzeri, Heitor; Dos Reis, Andréa Cândido

2013-01-01

The aim of this study was to evaluate the influence of accelerated artificial aging (AAA) on the color change of composite resins used in dentistry. Three composite resins were evaluated: Two microhybrids and one hybrid of higher viscosity, with different amounts and sizes of filler particles, shades C2 and B2. A total of 54 specimens were obtained (18 for each composite resin), made of a Teflon matrix (15 mm in diameter and 2 mm in height). The color measurements were obtained with a Spectrophotometer, (PCB 6807 BYK Gardner) before and after AAA. Data were submitted to the Kolmogorov-Smirnov test (α >0.05), ANOVA and Tukey test (α <0.05). After statistical analysis, the color difference among composite resins with the same shades was analyzed. All composite resins showed unacceptable color changes after AAA (ΔE > 3). Considering the variable ∆E, it was observed that the color tone C2 was already statistically different for the microhybrid composite resin prior to AAA (P < 0.05) and in shade B2 for hybrid of higher viscosity and microhybrid with barium glass fluoride aluminum and silica dioxide (P < 0.01). After this process, a statistically significant difference was observed only for shade B2 between microhybrid composite resins (P < 0.01) and for hybrid of higher viscosity and microhybrid with barium glass fluoride aluminum and silica dioxide (P < 0.05). Regarding the color difference within a same composite resin group, before aging the composite resin hybrid of higher viscosity B2 showed the highest color variation rate and microhybrid with zirconium/silica C2 showed the lowest. All composite resins presented unacceptable color changes after 382 h of aging and different composite resins with same hue, presented different colors before being subjected to the aging process (B2 and C2) and after (B2). It was also observed color difference within a group of the same composite resin and same hue.

Analysis of high-incidence separated flow past airfoils

NASA Technical Reports Server (NTRS)

Chia, K. N.; Osswald, G. A.; Chia, U.

1989-01-01

An unsteady Navier-Stokes (NS) analysis is developed and used to carefully examine high-incidence aerodynamic separated flows past airfoils. Clustered conformal C-grids are employed for the 12 percent thick symmetric Joukowski airfoil as well as for the NACA 0012 airfoil with a sharp trailing edge. The clustering is controlled by appropriate one-dimensional stretching transformations. An attempt is made to resolve many of the dominant scales of an unsteady flow with massive separation, while maintaining the transformation metrics to be smooth and continuous in the entire flow field. A fully implicit time-marching alternating-direction implicit-block Gaussian elimination (ADI-BGE) method is employed, in which no use is made of any explicit artificial dissipation. Detailed results are obtained for massively separated, unsteady flow past symmetric Joukowski and NACA 0012 airfoils.

Implicit preferences: the role(s) of familiarity in the structural mere exposure effect.

PubMed

Zizak, Diane M; Reber, Arthur S

2004-06-01

In four experiments using an artificial grammar (AG) learning procedure, the authors examined the links between the "classic" mere exposure effect [heightened affect for previously encountered stimulus items (Bornstein, 1989; Zajonc, 1968)] and the "structural" mere exposure effect [greater hedonic appreciation for novel stimuli that conform to an implicitly acquired underlying rule system (Gordon & Holyoak, 1983)]. After learning, participants: (a) classified stimuli according to whether they conformed to the principles of the grammar and, (b) rated them in terms of how much they liked them. In some experiments unusual and unfamiliar symbols were used to instantiate the AG, in others highly familiar characters were used. In all cases participants showed standard AG learning. However, whether the two exposure effects emerged was dependent on symbol familiarity. Symbols with high a priori familiarity produced a structural mere exposure effect. Moderately familiar symbols produced only the classic, but not the structural, mere exposure effect. Highly unfamiliar symbols produced neither exposure effect. Results are discussed in the context of implicit learning theory and implications for a general theory of aesthetics are presented.

How Artificial Should the Treatment of a Plasma's Viscosity Be?

NASA Astrophysics Data System (ADS)

Whitney, K. G.; Velikovich, A. L.; Thornhill, J. W.; Davis, J.

1999-11-01

Electron viscosity dominates over ion viscosity and is important in describing the generation of shock fronts in highly ionizable plasmas. The sizes of shock front jumps in electron and ion temperature are determined from the magnitudes of the heat flow vector and pressure tensor, which, in turn, acquire non-negligible nonlinear contributions from the temperature and density gradients when these gradients are large. Thus, a consistent treatment of steep gradient formation in plasmas must come from investigations that include the effects of these nonlinear contributions to heat and momentum transport. Coefficients for each of five nonlinear contributions to the pressure tensor for an (r,z) Z-pinch geometry are presented and discussed in this talk. Hydrodynamic code calculations generally are not designed to provide a testbed for directly evaluating the kinetic energy dissipation that occurs at shock fronts; therefore, the strength of these nonlinear pressure tensor terms will be estimated by post-processing a Z-pinch hydrodynamics calculation and a steady-state planar shock wave calculation.

Vanishing Viscosity Approach to the Compressible Euler Equations for Transonic Nozzle and Spherically Symmetric Flows

NASA Astrophysics Data System (ADS)

Chen, Gui-Qiang G.; Schrecker, Matthew R. I.

2018-04-01

We are concerned with globally defined entropy solutions to the Euler equations for compressible fluid flows in transonic nozzles with general cross-sectional areas. Such nozzles include the de Laval nozzles and other more general nozzles whose cross-sectional area functions are allowed at the nozzle ends to be either zero (closed ends) or infinity (unbounded ends). To achieve this, in this paper, we develop a vanishing viscosity method to construct globally defined approximate solutions and then establish essential uniform estimates in weighted L p norms for the whole range of physical adiabatic exponents γ\\in (1, ∞) , so that the viscosity approximate solutions satisfy the general L p compensated compactness framework. The viscosity method is designed to incorporate artificial viscosity terms with the natural Dirichlet boundary conditions to ensure the uniform estimates. Then such estimates lead to both the convergence of the approximate solutions and the existence theory of globally defined finite-energy entropy solutions to the Euler equations for transonic flows that may have different end-states in the class of nozzles with general cross-sectional areas for all γ\\in (1, ∞) . The approach and techniques developed here apply to other problems with similar difficulties. In particular, we successfully apply them to construct globally defined spherically symmetric entropy solutions to the Euler equations for all γ\\in (1, ∞).

L1-Based Approximations of PDEs and Applications

DTIC Science & Technology

2012-09-05

the analysis of the Navier-Stokes equations. The early versions of artificial vis- cosities being overly dissipative, the interest for these technique ...Guermond, and B. Popov. Stability analysis of explicit en- tropy viscosity methods for non-linear scalar conservation equations. Math. Comp., 2012... methods for solv- ing mathematical models of nonlinear phenomena such as nonlinear conservation laws, surface/image/data reconstruction problems

[The influence of sodium hyaluronate solution and artificial tears on higher-order aberrations].

PubMed

Yamashita, Tsutomu; Ochi, Shintarou; Inoue, Yasushi; Miki, Atsushi; Kiryu, Junichi; Tabuchi, Akio

2013-12-01

To investigate the influence of sodium hyaluronate solution (HA) and artificial tears (AT) on higher-order aberrations (HOAs). Twenty four eyes of 24 normal subjects and 11 eyes of 11 dry eye patients were examined. Cornea and ocular wavefront aberrations (total, spherical-like and coma-like) were measured with a Hartmann-Shack wavefront aberrometer before and after 0.1% or 0.3% HA, AT. The consecutively obtained data of the cornea and ocular HOAs were analyzed in the central 4-mm diameter for coma-like, spherical-like and total HOAs. Average HOAs, as well as fluctuation index (FI) and stability index (SI) of the HOAs over time were compared between the two groups. In normal subjects, the AVE of all aberration parameters and FI showed an increase depending on viscosity of the HA (p < 0.001). After AT and 0.1% HA treatment the cornea aberration of the dry eye patients changed from a sawtooth pattern to a stable pattern. Cornea HOAs decreased, and the optical characteristics showed improvement after AT and 0.1% HA in the dry eye patients. HOAs increased depending on the viscosity of the HA, and optical stability worsened.

Quantum hydrodynamics: capturing a reactive scattering resonance.

PubMed

Derrickson, Sean W; Bittner, Eric R; Kendrick, Brian K

2005-08-01

The hydrodynamic equations of motion associated with the de Broglie-Bohm formulation of quantum mechanics are solved using a meshless method based upon a moving least-squares approach. An arbitrary Lagrangian-Eulerian frame of reference and a regridding algorithm which adds and deletes computational points are used to maintain a uniform and nearly constant interparticle spacing. The methodology also uses averaged fields to maintain unitary time evolution. The numerical instabilities associated with the formation of nodes in the reflected portion of the wave packet are avoided by adding artificial viscosity to the equations of motion. A new and more robust artificial viscosity algorithm is presented which gives accurate scattering results and is capable of capturing quantum resonances. The methodology is applied to a one-dimensional model chemical reaction that is known to exhibit a quantum resonance. The correlation function approach is used to compute the reactive scattering matrix, reaction probability, and time delay as a function of energy. Excellent agreement is obtained between the scattering results based upon the quantum hydrodynamic approach and those based upon standard quantum mechanics. This is the first clear demonstration of the ability of moving grid approaches to accurately and robustly reproduce resonance structures in a scattering system.

PROTEUS two-dimensional Navier-Stokes computer code, version 1.0. Volume 3: Programmer's reference

NASA Technical Reports Server (NTRS)

Towne, Charles E.; Schwab, John R.; Benson, Thomas J.; Suresh, Ambady

1990-01-01

A new computer code was developed to solve the 2-D or axisymmetric, Reynolds-averaged, unsteady compressible Navier-Stokes equations in strong conservation law form. The thin-layer or Euler equations may also be solved. Turbulence is modeled using an algebraic eddy viscosity model. The objective was to develop a code for aerospace applications that is easy to use and easy to modify. Code readability, modularity, and documentation were emphasized. The equations are written in nonorthogonal body-fitted coordinates, and solved by marching in time using a fully-coupled alternating-direction-implicit procedure with generalized first- or second-order time differencing. All terms are linearized using second-order Taylor series. The boundary conditions are treated implicitly, and may be steady, unsteady, or spatially periodic. Simple Cartesian or polar grids may be generated internally by the program. More complex geometries require an externally generated computational coordinate system. The documentation is divided into three volumes. Volume 3 is the Programmer's Reference, and describes the program structure, the FORTRAN variables stored in common blocks, and the details of each subprogram.

Explicit and Implicit Second Language Training Differentially Affect the Achievement of Native-like Brain Activation Patterns

PubMed Central

Morgan-Short, Kara; Steinhauer, Karsten; Sanz, Cristina; Ullman, Michael T.

2013-01-01

It is widely believed that adults cannot learn a foreign language in the same way that children learn a first language. However, recent evidence suggests that adult learners of a foreign language can come to rely on native-like language brain mechanisms. Here, we show that the type of language training crucially impacts this outcome. We used an artificial language paradigm to examine longitudinally whether explicit training (that approximates traditional grammar-focused classroom settings) and implicit training (that approximates immersion settings) differentially affect neural (electrophysiological) and behavioral (performance) measures of syntactic processing. Results showed that performance of explicitly and implicitly trained groups did not differ at either low or high proficiency. In contrast, electrophysiological (ERP) measures revealed striking differences between the groups’ neural activity at both proficiency levels in response to syntactic violations. Implicit training yielded an N400 at low proficiency, whereas at high proficiency, it elicited a pattern typical of native speakers: an anterior negativity followed by a P600 accompanied by a late anterior negativity. Explicit training, by contrast, yielded no significant effects at low proficiency and only an anterior positivity followed by a P600 at high proficiency. Although the P600 is reminiscent of native-like processing, this response pattern as a whole is not. Thus, only implicit training led to an electrophysiological signature typical of native speakers. Overall, the results suggest that adult foreign language learners can come to rely on native-like language brain mechanisms, but that the conditions under which the language is learned may be crucial in attaining this goal. PMID:21861686

Optimization of groundwater artificial recharge systems using a genetic algorithm: a case study in Beijing, China

NASA Astrophysics Data System (ADS)

Hao, Qichen; Shao, Jingli; Cui, Yali; Zhang, Qiulan; Huang, Linxian

2018-05-01

An optimization approach is used for the operation of groundwater artificial recharge systems in an alluvial fan in Beijing, China. The optimization model incorporates a transient groundwater flow model, which allows for simulation of the groundwater response to artificial recharge. The facilities' operation with regard to recharge rates is formulated as a nonlinear programming problem to maximize the volume of surface water recharged into the aquifers under specific constraints. This optimization problem is solved by the parallel genetic algorithm (PGA) based on OpenMP, which could substantially reduce the computation time. To solve the PGA with constraints, the multiplicative penalty method is applied. In addition, the facilities' locations are implicitly determined on the basis of the results of the recharge-rate optimizations. Two scenarios are optimized and the optimal results indicate that the amount of water recharged into the aquifers will increase without exceeding the upper limits of the groundwater levels. Optimal operation of this artificial recharge system can also contribute to the more effective recovery of the groundwater storage capacity.

Viscous real gas flowfields about three dimensional configurations

NASA Technical Reports Server (NTRS)

Balakrishnan, A.; Davy, W. C.

1983-01-01

Laminar, real gas hypersonic flowfields over a three dimensional configuration are computed using an unsteady, factored implicit scheme. Local chemical and thermodynamic properties are evaluated by an equilibrium composition method. Transport properties are obtained from individual species properties and application of a mixture rule. Numerical solutions are presented for an ideal gas and equilibrium air for free-stream Mach numbers of 13 and 15 and at various angles of attack. The effect of real gas is to decrease the shock-layer thickness resulting from decreased shock-layer temperatures and corresponding increased density. The combined effects of viscosity and real gas are to increase the subsonic layer near the wall.

The subliminal mere exposure effect does not generalize to structurally related stimuli.

PubMed

Newell, Ben R; Bright, James E H

2003-03-01

R.F. Bornstein (1994) questioned whether subliminal mere exposure effects might generalize to structurally related stimuli, thereby providing evidence for the existence of implicit learning. Two experiments examined this claim using letter string stimuli constructed according to the rules of an artificial grammar. Experiment 1 demonstrated that brief, masked exposure to grammatical strings impaired recognition but failed to produce a mere exposure effect on novel structurally related strings seen at test. Experiment 2 replicated this result but also demonstrated that a reliable mere exposure effect could be obtained, provided the same grammatical strings were presented at test. The results suggest that the structural relationship between training and test items prevents the mere exposure effect when participants are unaware of the exposure status of stimuli, and therefore provide no evidence for the existence of implicit learning.

Entropy-Based Approach To Nonlinear Stability

NASA Technical Reports Server (NTRS)

Merriam, Marshal L.

1991-01-01

NASA technical memorandum suggests schemes for numerical solution of differential equations of flow made more accurate and robust by invoking second law of thermodynamics. Proposes instead of using artificial viscosity to suppress such unphysical solutions as spurious numerical oscillations and nonlinear instabilities, one should formulate equations so that rate of production of entropy within each cell of computational grid be nonnegative, as required by second law.

Prescribed Velocity Gradients for Highly Viscous SPH Fluids with Vorticity Diffusion.

PubMed

Peer, Andreas; Teschner, Matthias

2017-12-01

Working with prescribed velocity gradients is a promising approach to efficiently and robustly simulate highly viscous SPH fluids. Such approaches allow to explicitly and independently process shear rate, spin, and expansion rate. This can be used to, e.g., avoid interferences between pressure and viscosity solvers. Another interesting aspect is the possibility to explicitly process the vorticity, e.g., to preserve the vorticity. In this context, this paper proposes a novel variant of the prescribed-gradient idea that handles vorticity in a physically motivated way. In contrast to a less appropriate vorticity preservation that has been used in a previous approach, vorticity is diffused. The paper illustrates the utility of the vorticity diffusion. Therefore, comparisons of the proposed vorticity diffusion with vorticity preservation and additionally with vorticity damping are presented. The paper further discusses the relation between prescribed velocity gradients and prescribed velocity Laplacians which improves the intuition behind the prescribed-gradient method for highly viscous SPH fluids. Finally, the paper discusses the relation of the proposed method to a physically correct implicit viscosity formulation.

An interior penalty stabilised incompressible discontinuous Galerkin-Fourier solver for implicit large eddy simulations

NASA Astrophysics Data System (ADS)

Ferrer, Esteban

2017-11-01

We present an implicit Large Eddy Simulation (iLES) h / p high order (≥2) unstructured Discontinuous Galerkin-Fourier solver with sliding meshes. The solver extends the laminar version of Ferrer and Willden, 2012 [34], to enable the simulation of turbulent flows at moderately high Reynolds numbers in the incompressible regime. This solver allows accurate flow solutions of the laminar and turbulent 3D incompressible Navier-Stokes equations on moving and static regions coupled through a high order sliding interface. The spatial discretisation is provided by the Symmetric Interior Penalty Discontinuous Galerkin (IP-DG) method in the x-y plane coupled with a purely spectral method that uses Fourier series and allows efficient computation of spanwise periodic three-dimensional flows. Since high order methods (e.g. discontinuous Galerkin and Fourier) are unable to provide enough numerical dissipation to enable under-resolved high Reynolds computations (i.e. as necessary in the iLES approach), we adapt the laminar version of the solver to increase (controllably) the dissipation and enhance the stability in under-resolved simulations. The novel stabilisation relies on increasing the penalty parameter included in the DG interior penalty (IP) formulation. The latter penalty term is included when discretising the linear viscous terms in the incompressible Navier-Stokes equations. These viscous penalty fluxes substitute the stabilising effect of non-linear fluxes, which has been the main trend in implicit LES discontinuous Galerkin approaches. The IP-DG penalty term provides energy dissipation, which is controlled by the numerical jumps at element interfaces (e.g. large in under-resolved regions) such as to stabilise under-resolved high Reynolds number flows. This dissipative term has minimal impact in well resolved regions and its implicit treatment does not restrict the use of large time steps, thus providing an efficient stabilization mechanism for iLES. The IP-DG stabilisation is complemented with a Spectral Vanishing Viscosity (SVV) method, in the z-direction, to enhance stability in the continuous Fourier space. The coupling between the numerical viscosity in the DG plane and the SVV damping, provides an efficient approach to stabilise high order methods at moderately high Reynolds numbers. We validate the formulation for three turbulent flow cases: a circular cylinder at Re = 3900, a static and pitch oscillating NACA 0012 airfoil at Re = 10000 and finally a rotating vertical-axis turbine at Re = 40000, with Reynolds based on the circular diameter, airfoil chord and turbine diameter, respectively. All our results compare favourably with published direct numerical simulations, large eddy simulations or experimental data. We conclude that the DG-Fourier high order solver, with IP-SVV stabilisation, proves to be a valuable tool to predict turbulent flows and associated statistics for both static and rotating machinery.

Local dynamic subgrid-scale models in channel flow

NASA Technical Reports Server (NTRS)

Cabot, William H.

1994-01-01

The dynamic subgrid-scale (SGS) model has given good results in the large-eddy simulation (LES) of homogeneous isotropic or shear flow, and in the LES of channel flow, using averaging in two or three homogeneous directions (the DA model). In order to simulate flows in general, complex geometries (with few or no homogeneous directions), the dynamic SGS model needs to be applied at a local level in a numerically stable way. Channel flow, which is inhomogeneous and wall-bounded flow in only one direction, provides a good initial test for local SGS models. Tests of the dynamic localization model were performed previously in channel flow using a pseudospectral code and good results were obtained. Numerical instability due to persistently negative eddy viscosity was avoided by either constraining the eddy viscosity to be positive or by limiting the time that eddy viscosities could remain negative by co-evolving the SGS kinetic energy (the DLk model). The DLk model, however, was too expensive to run in the pseudospectral code due to a large near-wall term in the auxiliary SGS kinetic energy (k) equation. One objective was then to implement the DLk model in a second-order central finite difference channel code, in which the auxiliary k equation could be integrated implicitly in time at great reduction in cost, and to assess its performance in comparison with the plane-averaged dynamic model or with no model at all, and with direct numerical simulation (DNS) and/or experimental data. Other local dynamic SGS models have been proposed recently, e.g., constrained dynamic models with random backscatter, and with eddy viscosity terms that are averaged in time over material path lines rather than in space. Another objective was to incorporate and test these models in channel flow.

The viscous lee wave problem and its implications for ocean modelling

NASA Astrophysics Data System (ADS)

Shakespeare, Callum J.; Hogg, Andrew McC.

2017-05-01

Ocean circulation models employ 'turbulent' viscosity and diffusivity to represent unresolved sub-gridscale processes such as breaking internal waves. Computational power has now advanced sufficiently to permit regional ocean circulation models to be run at sufficiently high (100 m-1 km) horizontal resolution to resolve a significant part of the internal wave spectrum. Here we develop theory for boundary generated internal waves in such models, and in particular, where the waves dissipate their energy. We focus specifically on the steady lee wave problem where stationary waves are generated by a large-scale flow acting across ocean bottom topography. We generalise the energy flux expressions of [Bell, T., 1975. Topographically generated internal waves in the open ocean. J. Geophys. Res. 80, 320-327] to include the effect of arbitrary viscosity and diffusivity. Applying these results for realistic parameter choices we show that in the present generation of models with O(1) m2s-1 horizontal viscosity/diffusivity boundary-generated waves will inevitably dissipate the majority of their energy within a few hundred metres of the boundary. This dissipation is a direct consequence of the artificially high viscosity/diffusivity, which is not always physically justified in numerical models. Hence, caution is necessary in comparing model results to ocean observations. Our theory further predicts that O(10-2) m2s-1 horizontal and O(10-4) m2s-1 vertical viscosity/diffusivity is required to achieve a qualitatively inviscid representation of internal wave dynamics in ocean models.

Automatic emotion processing as a function of trait emotional awareness: an fMRI study

PubMed Central

Lichev, Vladimir; Sacher, Julia; Ihme, Klas; Rosenberg, Nicole; Quirin, Markus; Lepsien, Jöran; Pampel, André; Rufer, Michael; Grabe, Hans-Jörgen; Kugel, Harald; Kersting, Anette; Villringer, Arno; Lane, Richard D.

2015-01-01

It is unclear whether reflective awareness of emotions is related to extent and intensity of implicit affective reactions. This study is the first to investigate automatic brain reactivity to emotional stimuli as a function of trait emotional awareness. To assess emotional awareness the Levels of Emotional Awareness Scale (LEAS) was administered. During scanning, masked happy, angry, fearful and neutral facial expressions were presented to 46 healthy subjects, who had to rate the fit between artificial and emotional words. The rating procedure allowed assessment of shifts in implicit affectivity due to emotion faces. Trait emotional awareness was associated with increased activation in the primary somatosensory cortex, inferior parietal lobule, anterior cingulate gyrus, middle frontal and cerebellar areas, thalamus, putamen and amygdala in response to masked happy faces. LEAS correlated positively with shifts in implicit affect caused by masked happy faces. According to our findings, people with high emotional awareness show stronger affective reactivity and more activation in brain areas involved in emotion processing and simulation during the perception of masked happy facial expression than people with low emotional awareness. High emotional awareness appears to be characterized by an enhanced positive affective resonance to others at an automatic processing level. PMID:25140051

Experimental investigation, model development and sensitivity analysis of rheological behavior of ZnO/10W40 nano-lubricants for automotive applications

NASA Astrophysics Data System (ADS)

Hemmat Esfe, Mohammad; Saedodin, Seyfolah; Rejvani, Mousa; Shahram, Jalal

2017-06-01

In the present study, rheological behavior of ZnO/10W40 nano-lubricant is investigated by an experimental approach. Firstly, ZnO nanoparticles of 10-30 nm were dispersed in 10W40 engine oil with solid volume fractions of 0.25-2%, then the viscosity of the composed nano-lubricant was measured in temperature ranges of 5-55 °C and in various shear rates. From analyzing the results, it was revealed that both of the base oil and nano-lubricants are non-Newtonian fluids which exhibit shear thinning behavior. Sensitivity of viscosity to the solid volume fraction enhancement was calculated by a new correlation which was proposed in terms of solid volume fraction and temperature. In order to attain an accurate model by which experimental data are predicted, an artificial neural network (ANN) with a hidden layer and 5 neurons was designed. This model was considerably accurate in predicting experimental data of dynamic viscosity as R-squared and average absolute relative deviation (AARD %) were respectively 0.9999 and 0.0502.

High speed inviscid compressible flow by the finite element method

NASA Technical Reports Server (NTRS)

Zienkiewicz, O. C.; Loehner, R.; Morgan, K.

1984-01-01

The finite element method and an explicit time stepping algorithm which is based on Taylor-Galerkin schemes with an appropriate artificial viscosity is combined with an automatic mesh refinement process which is designed to produce accurate steady state solutions to problems of inviscid compressible flow in two dimensions. The results of two test problems are included which demonstrate the excellent performance characteristics of the proposed procedures.

Influence of numerical dissipation in computing supersonic vortex-dominated flows

NASA Technical Reports Server (NTRS)

Kandil, O. A.; Chuang, A.

1986-01-01

Steady supersonic vortex-dominated flows are solved using the unsteady Euler equations for conical and three-dimensional flows around sharp- and round-edged delta wings. The computational method is a finite-volume scheme which uses a four-stage Runge-Kutta time stepping with explicit second- and fourth-order dissipation terms. The grid is generated by a modified Joukowski transformation. The steady flow solution is obtained through time-stepping with initial conditions corresponding to the freestream conditions, and the bow shock is captured as a part of the solution. The scheme is applied to flat-plate and elliptic-section wings with a leading edge sweep of 70 deg at an angle of attack of 10 deg and a freestream Mach number of 2.0. Three grid sizes of 29 x 39, 65 x 65 and 100 x 100 have been used. The results for sharp-edged wings show that they are consistent with all grid sizes and variation of the artificial viscosity coefficients. The results for round-edged wings show that separated and attached flow solutions can be obtained by varying the artificial viscosity coefficients. They also show that the solutions are independent of the way time stepping is done. Local time-stepping and global minimum time-steeping produce same solutions.

An Unsteady Preconditioning Scheme Based on Convective-Upwind Split-Pressure (CUSP) Artificial Dissipation

DTIC Science & Technology

2014-01-07

this can have a disastrous effect on convergence rate. Even if steady state is obtained for low Mach number flows (after many iterations ), the results...rally lead do a diagonally dominant left-hand-side matrix, which causes stability problems for implicit Gauss - Seidel schemes. For this reason, matrix... convergence at the stagnation point. The iterations for each airfoil is also reported in Fig. 2. Without preconditioning, dramatic efficiency problems are seen

Prior familiarity with components enhances unconscious learning of relations.

PubMed

Scott, Ryan B; Dienes, Zoltan

2010-03-01

The influence of prior familiarity with components on the implicit learning of relations was examined using artificial grammar learning. Prior to training on grammar strings, participants were familiarized with either the novel symbols used to construct the strings or with irrelevant geometric shapes. Participants familiarized with the relevant symbols showed greater accuracy when judging the correctness of new grammar strings. Familiarity with elemental components did not increase conscious awareness of the basis for discriminations (structural knowledge) but increased accuracy even in its absence. The subjective familiarity of test strings predicted grammaticality judgments. However, prior exposure to relevant symbols did not increase overall test string familiarity or reliance on familiarity when making grammaticality judgments. Familiarity with the symbols increased the learning of relations between them (bigrams and trigrams) thus resulting in greater familiarity for grammatical versus ungrammatical strings. The results have important implications for models of implicit learning.

Vectorized schemes for conical potential flow using the artificial density method

NASA Technical Reports Server (NTRS)

Bradley, P. F.; Dwoyer, D. L.; South, J. C., Jr.; Keen, J. M.

1984-01-01

A method is developed to determine solutions to the full-potential equation for steady supersonic conical flow using the artificial density method. Various update schemes used generally for transonic potential solutions are investigated. The schemes are compared for speed and robustness. All versions of the computer code have been vectorized and are currently running on the CYBER-203 computer. The update schemes are vectorized, where possible, either fully (explicit schemes) or partially (implicit schemes). Since each version of the code differs only by the update scheme and elements other than the update scheme are completely vectorizable, comparisons of computational effort and convergence rate among schemes are a measure of the specific scheme's performance. Results are presented for circular and elliptical cones at angle of attack for subcritical and supercritical crossflows.

Domain-specific learning of grammatical structure in musical and phonological sequences.

PubMed

Bly, Benjamin Martin; Carrión, Ricardo E; Rasch, Björn

2009-01-01

Artificial grammar learning depends on acquisition of abstract structural representations rather than domain-specific representational constraints, or so many studies tell us. Using an artificial grammar task, we compared learning performance in two stimulus domains in which respondents have differing tacit prior knowledge. We found that despite grammatically identical sequence structures, learning was better for harmonically related chord sequences than for letter name sequences or harmonically unrelated chord sequences. We also found transfer effects within the musical and letter name tasks, but not across the domains. We conclude that knowledge acquired in implicit learning depends not only on abstract features of structured stimuli, but that the learning of regularities is in some respects domain-specific and strongly linked to particular features of the stimulus domain.

Gravity discharge vessel revisited: An explicit Lambert W function solution

NASA Astrophysics Data System (ADS)

Digilov, Rafael M.

2017-07-01

Based on the generalized Poiseuille equation modified by a kinetic energy correction, an explicit solution for the time evolution of a liquid column draining under gravity through an exit capillary tube is derived in terms of the Lambert W function. In contrast to the conventional exponential behavior, as implied by the Poiseuille law, a new analytical solution gives a full account for the volumetric flow rate of a fluid through a capillary of any length and improves the precision of viscosity determination. The theoretical consideration may be of interest to students as an example of how implicit equations in the field of physics can be solved analytically using the Lambert function.

A numerical method for the solution of internal pipe/channel flows in laminar or turbulent motion

NASA Astrophysics Data System (ADS)

Lourenco, L.; Essers, J. A.

1981-11-01

A computer program which is useful in the solution of problems of internal turbulent or laminar flow without recirculation is described. The flow is treated in terms of parabolic boundary layer differential equations. The eddy diffusivity concept is used to model turbulent stresses. Two turbulent models are available: the Prandtl mixing length model and the Nee-Kovasznay model for the effective viscosity. Fluid is considered incompressible, but little program modification is needed to treat compressible flows. Initial conditions are prescribed as well as the boundary conditions. The differencing scheme employed is fully implicit for the dependent variables. This allows the use of relatively large forward steps without stability problems.

Visuomotor Map Determines How Visually Guided Reaching Movements are Corrected Within and Across Trials123

PubMed Central

Hirashima, Masaya

2016-01-01

Abstract When a visually guided reaching movement is unexpectedly perturbed, it is implicitly corrected in two ways: immediately after the perturbation by feedback control (online correction) and in the next movement by adjusting feedforward motor commands (offline correction or motor adaptation). Although recent studies have revealed a close relationship between feedback and feedforward controls, the nature of this relationship is not yet fully understood. Here, we show that both implicit online and offline movement corrections utilize the same visuomotor map for feedforward movement control that transforms the spatial location of visual objects into appropriate motor commands. First, we artificially distorted the visuomotor map by applying opposite visual rotations to the cursor representing the hand position while human participants reached for two different targets. This procedure implicitly altered the visuomotor map so that changes in the movement direction to the target location were more insensitive or more sensitive. Then, we examined how such visuomotor map distortion influenced online movement correction by suddenly changing the target location. The magnitude of online movement correction was altered according to the shape of the visuomotor map. We also examined offline movement correction; the aftereffect induced by visual rotation in the previous trial was modulated according to the shape of the visuomotor map. These results highlighted the importance of the visuomotor map as a foundation for implicit motor control mechanisms and the intimate relationship between feedforward control, feedback control, and motor adaptation. PMID:27275006

Visuomotor Map Determines How Visually Guided Reaching Movements are Corrected Within and Across Trials.

PubMed

Hayashi, Takuji; Yokoi, Atsushi; Hirashima, Masaya; Nozaki, Daichi

2016-01-01

When a visually guided reaching movement is unexpectedly perturbed, it is implicitly corrected in two ways: immediately after the perturbation by feedback control (online correction) and in the next movement by adjusting feedforward motor commands (offline correction or motor adaptation). Although recent studies have revealed a close relationship between feedback and feedforward controls, the nature of this relationship is not yet fully understood. Here, we show that both implicit online and offline movement corrections utilize the same visuomotor map for feedforward movement control that transforms the spatial location of visual objects into appropriate motor commands. First, we artificially distorted the visuomotor map by applying opposite visual rotations to the cursor representing the hand position while human participants reached for two different targets. This procedure implicitly altered the visuomotor map so that changes in the movement direction to the target location were more insensitive or more sensitive. Then, we examined how such visuomotor map distortion influenced online movement correction by suddenly changing the target location. The magnitude of online movement correction was altered according to the shape of the visuomotor map. We also examined offline movement correction; the aftereffect induced by visual rotation in the previous trial was modulated according to the shape of the visuomotor map. These results highlighted the importance of the visuomotor map as a foundation for implicit motor control mechanisms and the intimate relationship between feedforward control, feedback control, and motor adaptation.

Effect of chunk strength on the performance of children with developmental dyslexia on artificial grammar learning task may be related to complexity.

PubMed

Schiff, Rachel; Katan, Pesia; Sasson, Ayelet; Kahta, Shani

2017-07-01

There's a long held view that chunks play a crucial role in artificial grammar learning performance. We compared chunk strength influences on performance, in high and low topological entropy (a measure of complexity) grammar systems, with dyslexic children, age-matched and reading-level-matched control participants. Findings show that age-matched control participants' performance reflected equivalent influence of chunk strength in the two topological entropy conditions, as typically found in artificial grammar learning experiments. By contrast, dyslexic children and reading-level-matched controls' performance reflected knowledge of chunk strength only under the low topological entropy condition. In the low topological entropy grammar system, they appeared completely unable to utilize chunk strength to make appropriate test item selections. In line with previous research, this study suggests that for typically developing children, it is the chunks that are attended during artificial grammar learning and create a foundation on which implicit associative learning mechanisms operate, and these chunks are unitized to different strengths. However, for children with dyslexia, it is complexity that may influence the subsequent memorability of chunks, independently of their strength.

Flytrap-inspired robot using structurally integrated actuation based on bistability and a developable surface.

PubMed

Kim, Seung-Won; Koh, Je-Sung; Lee, Jong-Gu; Ryu, Junghyun; Cho, Maenghyo; Cho, Kyu-Jin

2014-09-01

The Venus flytrap uses bistability, the structural characteristic of its leaf, to actuate the leaf's rapid closing motion for catching its prey. This paper presents a flytrap-inspired robot and novel actuation mechanism that exploits the structural characteristics of this structure and a developable surface. We focus on the concept of exploiting structural characteristics for actuation. Using shape memory alloy (SMA), the robot actuates artificial leaves made from asymmetrically laminated carbon fiber reinforced prepregs. We exploit two distinct structural characteristics of the leaves. First, the bistability acts as an implicit actuator enabling rapid morphing motion. Second, the developable surface has a kinematic constraint that constrains the curvature of the artificial leaf. Due to this constraint, the curved artificial leaf can be unbent by bending the straight edge orthogonal to the curve. The bending propagates from one edge to the entire surface and eventually generates an overall shape change. The curvature change of the artificial leaf is 18 m(-1) within 100 ms when closing. Experiments show that these actuation mechanisms facilitate the generation of a rapid and large morphing motion of the flytrap robot by one-way actuation of the SMA actuators at a local position.

A positivity-preserving, implicit defect-correction multigrid method for turbulent combustion

NASA Astrophysics Data System (ADS)

Wasserman, M.; Mor-Yossef, Y.; Greenberg, J. B.

2016-07-01

A novel, robust multigrid method for the simulation of turbulent and chemically reacting flows is developed. A survey of previous attempts at implementing multigrid for the problems at hand indicated extensive use of artificial stabilization to overcome numerical instability arising from non-linearity of turbulence and chemistry model source-terms, small-scale physics of combustion, and loss of positivity. These issues are addressed in the current work. The highly stiff Reynolds-averaged Navier-Stokes (RANS) equations, coupled with turbulence and finite-rate chemical kinetics models, are integrated in time using the unconditionally positive-convergent (UPC) implicit method. The scheme is successfully extended in this work for use with chemical kinetics models, in a fully-coupled multigrid (FC-MG) framework. To tackle the degraded performance of multigrid methods for chemically reacting flows, two major modifications are introduced with respect to the basic, Full Approximation Storage (FAS) approach. First, a novel prolongation operator that is based on logarithmic variables is proposed to prevent loss of positivity due to coarse-grid corrections. Together with the extended UPC implicit scheme, the positivity-preserving prolongation operator guarantees unconditional positivity of turbulence quantities and species mass fractions throughout the multigrid cycle. Second, to improve the coarse-grid-correction obtained in localized regions of high chemical activity, a modified defect correction procedure is devised, and successfully applied for the first time to simulate turbulent, combusting flows. The proposed modifications to the standard multigrid algorithm create a well-rounded and robust numerical method that provides accelerated convergence, while unconditionally preserving the positivity of model equation variables. Numerical simulations of various flows involving premixed combustion demonstrate that the proposed MG method increases the efficiency by a factor of up to eight times with respect to an equivalent single-grid method, and by two times with respect to an artificially-stabilized MG method.

Second Language Processing Shows Increased Native-Like Neural Responses after Months of No Exposure

PubMed Central

Morgan-Short, Kara; Finger, Ingrid; Grey, Sarah; Ullman, Michael T.

2012-01-01

Although learning a second language (L2) as an adult is notoriously difficult, research has shown that adults can indeed attain native language-like brain processing and high proficiency levels. However, it is important to then retain what has been attained, even in the absence of continued exposure to the L2—particularly since periods of minimal or no L2 exposure are common. This event-related potential (ERP) study of an artificial language tested performance and neural processing following a substantial period of no exposure. Adults learned to speak and comprehend the artificial language to high proficiency with either explicit, classroom-like, or implicit, immersion-like training, and then underwent several months of no exposure to the language. Surprisingly, proficiency did not decrease during this delay. Instead, it remained unchanged, and there was an increase in native-like neural processing of syntax, as evidenced by several ERP changes—including earlier, more reliable, and more left-lateralized anterior negativities, and more robust P600s, in response to word-order violations. Moreover, both the explicitly and implicitly trained groups showed increased native-like ERP patterns over the delay, indicating that such changes can hold independently of L2 training type. The results demonstrate that substantial periods with no L2 exposure are not necessarily detrimental. Rather, benefits may ensue from such periods of time even when there is no L2 exposure. Interestingly, both before and after the delay the implicitly trained group showed more native-like processing than the explicitly trained group, indicating that type of training also affects the attainment of native-like processing in the brain. Overall, the findings may be largely explained by a combination of forgetting and consolidation in declarative and procedural memory, on which L2 grammar learning appears to depend. The study has a range of implications, and suggests a research program with potentially important consequences for second language acquisition and related fields. PMID:22470434

Biofluid lubrication for artificial joints

NASA Astrophysics Data System (ADS)

Pendleton, Alice Mae

This research investigated biofluid lubrication related to artificial joints using tribological and rheological approaches. Biofluids studied here represent two categories of fluids, base fluids and nanostructured biofluids. Base fluids were studied through comparison of synthetic fluids (simulated body fluid and hyaluronic acid) as well as natural biofluids (from dogs, horses, and humans) in terms of viscosity and fluid shear stress. The nano-structured biofluids were formed using molecules having well-defined shapes. Understanding nano-structured biofluids leads to new ways of design and synthesis of biofluids that are beneficial for artificial joint performance. Experimental approaches were utilized in the present research. This includes basic analysis of biofluids' property, such as viscosity, fluid shear stress, and shear rate using rheological experiments. Tribological investigation and surface characterization were conducted in order to understand effects of molecular and nanostructures on fluid lubrication. Workpiece surface structure and wear mechanisms were investigated using a scanning electron microscope and a transmission electron microscope. The surface topography was examined using a profilometer. The results demonstrated that with the adding of solid additives, such as crown ether or fullerene acted as rough as the other solids in the 3-body wear systems. In addition, the fullerene supplied low friction and low wear, which designates the lubrication purpose of this particular particle system. This dissertation is constructed of six chapters. The first chapter is an introduction to body fluids, as mentioned earlier. After Chapter II, it examines the motivation and approach of the present research, Chapter III discusses the experimental approaches, including materials, experimental setup, and conditions. In Chapter IV, lubrication properties of various fluids are discussed. The tribological properties and performance nanostructured biofluids are discussed in Chapter V, followed by summary and conclusions in Chapter VI.

An artificial viscosity method for the design of supercritical airfoils

NASA Technical Reports Server (NTRS)

Mcfadden, G. B.

1979-01-01

A numerical technique is presented for the design of two-dimensional supercritical wing sections with low wave drag. The method is a design mode of the analysis code H which gives excellent agreement with experimental results and is widely used in the aircraft industry. Topics covered include the partial differential equations of transonic flow, the computational procedure and results; the design procedure; a convergence theorem; and description of the code.

Recovery Discontinuous Galerkin Jacobian-Free Newton-Krylov Method for All-Speed Flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

HyeongKae Park; Robert Nourgaliev; Vincent Mousseau

2008-07-01

A novel numerical algorithm (rDG-JFNK) for all-speed fluid flows with heat conduction and viscosity is introduced. The rDG-JFNK combines the Discontinuous Galerkin spatial discretization with the implicit Runge-Kutta time integration under the Jacobian-free Newton-Krylov framework. We solve fully-compressible Navier-Stokes equations without operator-splitting of hyperbolic, diffusion and reaction terms, which enables fully-coupled high-order temporal discretization. The stability constraint is removed due to the L-stable Explicit, Singly Diagonal Implicit Runge-Kutta (ESDIRK) scheme. The governing equations are solved in the conservative form, which allows one to accurately compute shock dynamics, as well as low-speed flows. For spatial discretization, we develop a “recovery” familymore » of DG, exhibiting nearly-spectral accuracy. To precondition the Krylov-based linear solver (GMRES), we developed an “Operator-Split”-(OS) Physics Based Preconditioner (PBP), in which we transform/simplify the fully-coupled system to a sequence of segregated scalar problems, each can be solved efficiently with Multigrid method. Each scalar problem is designed to target/cluster eigenvalues of the Jacobian matrix associated with a specific physics.« less

PROTEUS two-dimensional Navier-Stokes computer code, version 1.0. Volume 2: User's guide

NASA Technical Reports Server (NTRS)

Towne, Charles E.; Schwab, John R.; Benson, Thomas J.; Suresh, Ambady

1990-01-01

A new computer code was developed to solve the two-dimensional or axisymmetric, Reynolds averaged, unsteady compressible Navier-Stokes equations in strong conservation law form. The thin-layer or Euler equations may also be solved. Turbulence is modeled using an algebraic eddy viscosity model. The objective was to develop a code for aerospace applications that is easy to use and easy to modify. Code readability, modularity, and documentation were emphasized. The equations are written in nonorthogonal body-fitted coordinates, and solved by marching in time using a fully-coupled alternating direction-implicit procedure with generalized first- or second-order time differencing. All terms are linearized using second-order Taylor series. The boundary conditions are treated implicitly, and may be steady, unsteady, or spatially periodic. Simple Cartesian or polar grids may be generated internally by the program. More complex geometries require an externally generated computational coordinate system. The documentation is divided into three volumes. Volume 2 is the User's Guide, and describes the program's general features, the input and output, the procedure for setting up initial conditions, the computer resource requirements, the diagnostic messages that may be generated, the job control language used to run the program, and several test cases.

Application of adaptive gridding to magnetohydrodynamic flows

DOE Office of Scientific and Technical Information (OSTI.GOV)

Schnack, D.D.; Lotatti, I.; Satyanarayana, P.

1996-12-31

The numerical simulation of the primitive, three-dimensional, time-dependent, resistive MHD equations on an unstructured, adaptive poloidal mesh using the TRIM code has been reported previously. The toroidal coordinate is approximated pseudo-spectrally with finite Fourier series and Fast-Fourier Transforms. The finite-volume algorithm preserves the magnetic field as solenoidal to round-off error, and also conserves mass, energy, and magnetic flux exactly. A semi-implicit method is used to allow for large time steps on the unstructured mesh. This is important for tokamak calculations where the relevant time scale is determined by the poloidal Alfven time. This also allows the viscosity to be treatedmore » implicitly. A conjugate-gradient method with pre-conditioning is used for matrix inversion. Applications to the growth and saturation of ideal instabilities in several toroidal fusion systems has been demonstrated. Recently we have concentrated on the details of the mesh adaption algorithm used in TRIM. We present several two-dimensional results relating to the use of grid adaptivity to track the evolution of hydrodynamic and MHD structures. Examples of plasma guns, opening switches, and supersonic flow over a magnetized sphere are presented. Issues relating to mesh adaption criteria are discussed.« less

Numerical solution of the two-dimensional time-dependent incompressible Euler equations

NASA Technical Reports Server (NTRS)

Whitfield, David L.; Taylor, Lafayette K.

1994-01-01

A numerical method is presented for solving the artificial compressibility form of the 2D time-dependent incompressible Euler equations. The approach is based on using an approximate Riemann solver for the cell face numerical flux of a finite volume discretization. Characteristic variable boundary conditions are developed and presented for all boundaries and in-flow out-flow situations. The system of algebraic equations is solved using the discretized Newton-relaxation (DNR) implicit method. Numerical results are presented for both steady and unsteady flow.

Exhaust plumes and their interaction with missile airframes - A new viewpoint

NASA Technical Reports Server (NTRS)

Dash, S. M.; Sinha, N.

1992-01-01

The present, novel treatment of missile airframe-exhaust plume interactions emphasizes their simulation via a formal solution of the Reynolds-averaged Navier-Stokes (RNS) equation and is accordingly able to address the simulation requirements of novel missiles with nonconventional/integrated propulsion systems. The method is made possible by implicit RNS codes with improved artificial dissipation models, generalized geometric capabilities, and improved two-equation turbulence models, as well as by such codes' recent incorporation of plume thermochemistry and multiphase flow effects.

Swallowing Mechanics Associated With Artificial Airways, Bolus Properties, and Penetration-Aspiration Status in Trauma Patients.

PubMed

Dietsch, Angela M; Rowley, Christopher B; Solomon, Nancy Pearl; Pearson, William G

2017-09-18

Artificial airway procedures such as intubation and tracheotomy are common in the treatment of traumatic injuries, and bolus modifications may be implemented to help manage swallowing disorders. This study assessed artificial airway status, bolus properties (volume and viscosity), and the occurrence of laryngeal penetration and/or aspiration in relation to mechanical features of swallowing. Coordinates of anatomical landmarks were extracted at minimum and maximum hyolaryngeal excursion from 228 videofluoroscopic swallowing studies representing 69 traumatically injured U.S. military service members with dysphagia. Morphometric canonical variate and regression analyses examined associations between swallowing mechanics and bolus properties based on artificial airway and penetration-aspiration status. Significant differences in swallowing mechanics were detected between extubated versus tracheotomized (D = 1.32, p < .0001), extubated versus decannulated (D = 1.74, p < .0001), and decannulated versus tracheotomized (D = 1.24, p < .0001) groups per post hoc discriminant function analysis. Tracheotomy-in-situ and decannulated subgroups exhibited increased head/neck extension and posterior relocation of the larynx. Swallowing mechanics associated with (a) penetration-aspiration status and (b) bolus properties were moderately related for extubated and decannulated subgroups, but not the tracheotomized subgroup, per morphometric regression analysis. Specific differences in swallowing mechanics associated with artificial airway status and certain bolus properties may guide therapeutic intervention in trauma-based dysphagia.

Smoothed particle hydrodynamics simulations of black hole accretion: a step to model black hole feedback in galaxies

NASA Astrophysics Data System (ADS)

Barai, Paramita; Proga, Daniel; Nagamine, Kentaro

2011-11-01

We test how accurately the smoothed particle hydrodynamics (SPH) numerical technique can follow spherically symmetric Bondi accretion. Using the 3D SPH code GADGET-3, we perform simulations of gas accretion on to a central supermassive black hole of mass 108 M⊙ within the radial range of 0.1-200 pc. We carry out simulations without and with radiative heating by a central X-ray corona and radiative cooling. For an adiabatic case, the radial profiles of hydrodynamical properties match the Bondi solution, except near the inner and outer radius of the computational domain. The deviation from the Bondi solution close to the inner radius is caused by the combination of numerical resolution, artificial viscosity and our inner boundary condition. Near the outer radius (≤200 pc), we observe either an outflow or development of a non-spherical inflow unless the outer boundary conditions are very stringently implemented. Despite these issues related to the boundary conditions, we find that adiabatic Bondi accretion can be reproduced for durations of a few dynamical times at the Bondi radius, and for longer times if the outer radius is increased. In particular, the mass inflow rate at the inner boundary, which we measure, is within 3-4 per cent of the Bondi accretion rate. With radiative heating and cooling included, the spherically accreting gas takes a longer time to reach a steady state than the adiabatic Bondi accretion runs, and in some cases does not reach a steady state even within several hundred dynamical times. We find that artificial viscosity causes excessive heating near the inner radius, making the thermal properties of the gas inconsistent with a physical solution. This overheating occurs typically only in the supersonic part of the flow, so that it does not affect the mass accretion rate. We see that increasing the X-ray luminosity produces a lower central mass inflow rate, implying that feedback due to radiative heating is operational in our simulations. With a sufficiently high X-ray luminosity, the inflowing gas is radiatively heated up, and an outflow develops. We conclude that the SPH simulations can capture the gas dynamics needed to study radiative feedback, provided artificial viscosity alters only highly supersonic part of the inflow.

Computer image analysis in obtaining characteristics of images: greenhouse tomatoes in the process of generating learning sets of artificial neural networks

NASA Astrophysics Data System (ADS)

Zaborowicz, M.; Przybył, J.; Koszela, K.; Boniecki, P.; Mueller, W.; Raba, B.; Lewicki, A.; Przybył, K.

2014-04-01

The aim of the project was to make the software which on the basis on image of greenhouse tomato allows for the extraction of its characteristics. Data gathered during the image analysis and processing were used to build learning sets of artificial neural networks. Program enables to process pictures in jpeg format, acquisition of statistical information of the picture and export them to an external file. Produced software is intended to batch analyze collected research material and obtained information saved as a csv file. Program allows for analysis of 33 independent parameters implicitly to describe tested image. The application is dedicated to processing and image analysis of greenhouse tomatoes. The program can be used for analysis of other fruits and vegetables of a spherical shape.

Freeze-dried, mucoadhesive system for vaginal delivery of the HIV microbicide, dapivirine: optimisation by an artificial neural network.

PubMed

Woolfson, A David; Umrethia, Manish L; Kett, Victoria L; Malcolm, R Karl

2010-03-30

Dapivirine mucoadhesive gels and freeze-dried tablets were prepared using a 3x3x2 factorial design. An artificial neural network (ANN) with multi-layer perception was used to investigate the effect of hydroxypropyl-methylcellulose (HPMC): polyvinylpyrrolidone (PVP) ratio (X1), mucoadhesive concentration (X2) and delivery system (gel or freeze-dried mucoadhesive tablet, X3) on response variables; cumulative release of dapivirine at 24h (Q(24)), mucoadhesive force (F(max)) and zero-rate viscosity. Optimisation was performed by minimising the error between the experimental and predicted values of responses by ANN. The method was validated using check point analysis by preparing six formulations of gels and their corresponding freeze-dried tablets randomly selected from within the design space of contour plots. Experimental and predicted values of response variables were not significantly different (p>0.05, two-sided paired t-test). For gels, Q(24) values were higher than their corresponding freeze-dried tablets. F(max) values for freeze-dried tablets were significantly different (2-4 times greater, p>0.05, two-sided paired t-test) compared to equivalent gels. Freeze-dried tablets having lower values for X1 and higher values for X2 components offered the best compromise between effective dapivirine release, mucoadhesion and viscosity such that increased vaginal residence time was likely to be achieved. Copyright (c) 2009 Elsevier B.V. All rights reserved.

Towards a versatile technique for tracking nanoparticle-mucus interaction: a step on the road

NASA Astrophysics Data System (ADS)

Nafee, N.; Schneider, M.

2014-02-01

Respiratory mucus is one of the main barriers for nanoparticle-based pulmonary delivery systems. This holds true especially for lung diseases like cystic fibrosis, where a very tenacious thick mucus layer hinders particle diffusion to the lung epithelium or the target area. Typically, mean square displacement of particles is used for mobility evaluation. In contrast, our objective is to develop a feasible technique to track directed particle penetration as a prerequisite for efficient pulmonary nanotherapy. Therefore, particle diffusion in artificial mucus was monitored based on confocal laser scanning microscopy (CLSM) and particle-mucus interaction was observed. As pharmaceutical relevant and benign materials, solid lipid nanoparticles (SLNs) were prepared by hot-melt emulsification using glyceryl behenate and different stabilizing agents such as poloxamer-407, tween-80, and polyvinyl alcohol (PVA). The diffusion of labeled SLNs in stained artificial sputum representing CF-patient sputum was verified by 3D time laps imaging. Thus, the effect of coating, particle size and mucus viscosity on nanoparticle diffusion was studied. Using image analysis software "Image J", the total fluorescent signal after 30 min in case of poloxamer-coated SLNs was 5 and 100 folds higher than tween- and PVA-coated SLNs, respectively. Nevertheless, increasing mucus viscosity reduced the diffusion of tweencoated SLNs by a factor of 10. Studying particle-mucus interaction by CLSM can be considered a promising and versatile technique.

Implicit mesh discontinuous Galerkin methods and interfacial gauge methods for high-order accurate interface dynamics, with applications to surface tension dynamics, rigid body fluid-structure interaction, and free surface flow: Part I

NASA Astrophysics Data System (ADS)

Saye, Robert

2017-09-01

In this two-part paper, a high-order accurate implicit mesh discontinuous Galerkin (dG) framework is developed for fluid interface dynamics, facilitating precise computation of interfacial fluid flow in evolving geometries. The framework uses implicitly defined meshes-wherein a reference quadtree or octree grid is combined with an implicit representation of evolving interfaces and moving domain boundaries-and allows physically prescribed interfacial jump conditions to be imposed or captured with high-order accuracy. Part one discusses the design of the framework, including: (i) high-order quadrature for implicitly defined elements and faces; (ii) high-order accurate discretisation of scalar and vector-valued elliptic partial differential equations with interfacial jumps in ellipticity coefficient, leading to optimal-order accuracy in the maximum norm and discrete linear systems that are symmetric positive (semi)definite; (iii) the design of incompressible fluid flow projection operators, which except for the influence of small penalty parameters, are discretely idempotent; and (iv) the design of geometric multigrid methods for elliptic interface problems on implicitly defined meshes and their use as preconditioners for the conjugate gradient method. Also discussed is a variety of aspects relating to moving interfaces, including: (v) dG discretisations of the level set method on implicitly defined meshes; (vi) transferring state between evolving implicit meshes; (vii) preserving mesh topology to accurately compute temporal derivatives; (viii) high-order accurate reinitialisation of level set functions; and (ix) the integration of adaptive mesh refinement. In part two, several applications of the implicit mesh dG framework in two and three dimensions are presented, including examples of single phase flow in nontrivial geometry, surface tension-driven two phase flow with phase-dependent fluid density and viscosity, rigid body fluid-structure interaction, and free surface flow. A class of techniques known as interfacial gauge methods is adopted to solve the corresponding incompressible Navier-Stokes equations, which, compared to archetypical projection methods, have a weaker coupling between fluid velocity, pressure, and interface position, and allow high-order accurate numerical methods to be developed more easily. Convergence analyses conducted throughout the work demonstrate high-order accuracy in the maximum norm for all of the applications considered; for example, fourth-order spatial accuracy in fluid velocity, pressure, and interface location is demonstrated for surface tension-driven two phase flow in 2D and 3D. Specific application examples include: vortex shedding in nontrivial geometry, capillary wave dynamics revealing fine-scale flow features, falling rigid bodies tumbling in unsteady flow, and free surface flow over a submersed obstacle, as well as high Reynolds number soap bubble oscillation dynamics and vortex shedding induced by a type of Plateau-Rayleigh instability in water ripple free surface flow. These last two examples compare numerical results with experimental data and serve as an additional means of validation; they also reveal physical phenomena not visible in the experiments, highlight how small-scale interfacial features develop and affect macroscopic dynamics, and demonstrate the wide range of spatial scales often at play in interfacial fluid flow.

Implicit mesh discontinuous Galerkin methods and interfacial gauge methods for high-order accurate interface dynamics, with applications to surface tension dynamics, rigid body fluid-structure interaction, and free surface flow: Part II

NASA Astrophysics Data System (ADS)

Saye, Robert

2017-09-01

In this two-part paper, a high-order accurate implicit mesh discontinuous Galerkin (dG) framework is developed for fluid interface dynamics, facilitating precise computation of interfacial fluid flow in evolving geometries. The framework uses implicitly defined meshes-wherein a reference quadtree or octree grid is combined with an implicit representation of evolving interfaces and moving domain boundaries-and allows physically prescribed interfacial jump conditions to be imposed or captured with high-order accuracy. Part one discusses the design of the framework, including: (i) high-order quadrature for implicitly defined elements and faces; (ii) high-order accurate discretisation of scalar and vector-valued elliptic partial differential equations with interfacial jumps in ellipticity coefficient, leading to optimal-order accuracy in the maximum norm and discrete linear systems that are symmetric positive (semi)definite; (iii) the design of incompressible fluid flow projection operators, which except for the influence of small penalty parameters, are discretely idempotent; and (iv) the design of geometric multigrid methods for elliptic interface problems on implicitly defined meshes and their use as preconditioners for the conjugate gradient method. Also discussed is a variety of aspects relating to moving interfaces, including: (v) dG discretisations of the level set method on implicitly defined meshes; (vi) transferring state between evolving implicit meshes; (vii) preserving mesh topology to accurately compute temporal derivatives; (viii) high-order accurate reinitialisation of level set functions; and (ix) the integration of adaptive mesh refinement. In part two, several applications of the implicit mesh dG framework in two and three dimensions are presented, including examples of single phase flow in nontrivial geometry, surface tension-driven two phase flow with phase-dependent fluid density and viscosity, rigid body fluid-structure interaction, and free surface flow. A class of techniques known as interfacial gauge methods is adopted to solve the corresponding incompressible Navier-Stokes equations, which, compared to archetypical projection methods, have a weaker coupling between fluid velocity, pressure, and interface position, and allow high-order accurate numerical methods to be developed more easily. Convergence analyses conducted throughout the work demonstrate high-order accuracy in the maximum norm for all of the applications considered; for example, fourth-order spatial accuracy in fluid velocity, pressure, and interface location is demonstrated for surface tension-driven two phase flow in 2D and 3D. Specific application examples include: vortex shedding in nontrivial geometry, capillary wave dynamics revealing fine-scale flow features, falling rigid bodies tumbling in unsteady flow, and free surface flow over a submersed obstacle, as well as high Reynolds number soap bubble oscillation dynamics and vortex shedding induced by a type of Plateau-Rayleigh instability in water ripple free surface flow. These last two examples compare numerical results with experimental data and serve as an additional means of validation; they also reveal physical phenomena not visible in the experiments, highlight how small-scale interfacial features develop and affect macroscopic dynamics, and demonstrate the wide range of spatial scales often at play in interfacial fluid flow.

The effect of subjective awareness measures on performance in artificial grammar learning task.

PubMed

Ivanchei, Ivan I; Moroshkina, Nadezhda V

2018-01-01

Systematic research into implicit learning requires well-developed awareness-measurement techniques. Recently, trial-by-trial measures have been widely used. However, they can increase complexity of a study because they are an additional experimental variable. We tested the effects of these measures on performance in artificial grammar learning study. Four groups of participants were assigned to different awareness measures conditions: confidence ratings, post-decision wagering, decision strategy attribution or none. Decision-strategy-attribution participants demonstrated better grammar learning and longer response times compared to controls. They also exhibited a conservative bias. Grammaticality by itself was a stronger predictor of strings endorsement in decision-strategy-attribution group compared to other groups. Confidence ratings and post-decision wagering only affected the response times. These results were supported by an additional experiment that used a balanced chunk strength design. We conclude that a decision-strategy-attribution procedure may force participants to adopt an analytical decision-making strategy and rely mostly on conscious knowledge of artificial grammar. Copyright © 2017 Elsevier Inc. All rights reserved.

Sucralose Destabilization of Protein Structure.

PubMed

Chen, Lee; Shukla, Nimesh; Cho, Inha; Cohn, Erin; Taylor, Erika A; Othon, Christina M

2015-04-16

Sucralose is a commonly employed artificial sweetener that behaves very differently than its natural disaccharide counterpart, sucrose, in terms of its interaction with biomolecules. The presence of sucralose in solution is found to destabilize the native structure of two model protein systems: the globular protein bovine serum albumin and an enzyme staphylococcal nuclease. The melting temperature of these proteins decreases as a linear function of sucralose concentration. We correlate this destabilization to the increased polarity of the molecule. The strongly polar nature is manifested as a large dielectric friction exerted on the excited-state rotational diffusion of tryptophan using time-resolved fluorescence anisotropy. Tryptophan exhibits rotational diffusion proportional to the measured bulk viscosity for sucrose solutions over a wide range of concentrations, consistent with a Stokes-Einstein model. For sucralose solutions, however, the diffusion is dependent on the concentration, strongly diverging from the viscosity predictions, and results in heterogeneous rotational diffusion.

Computation and analysis for a constrained entropy optimization problem in finance

NASA Astrophysics Data System (ADS)

He, Changhong; Coleman, Thomas F.; Li, Yuying

2008-12-01

In [T. Coleman, C. He, Y. Li, Calibrating volatility function bounds for an uncertain volatility model, Journal of Computational Finance (2006) (submitted for publication)], an entropy minimization formulation has been proposed to calibrate an uncertain volatility option pricing model (UVM) from market bid and ask prices. To avoid potential infeasibility due to numerical error, a quadratic penalty function approach is applied. In this paper, we show that the solution to the quadratic penalty problem can be obtained by minimizing an objective function which can be evaluated via solving a Hamilton-Jacobian-Bellman (HJB) equation. We prove that the implicit finite difference solution of this HJB equation converges to its viscosity solution. In addition, we provide computational examples illustrating accuracy of calibration.

Silt and gas accumulation beneath an artificial recharge spreading basin, Southwestern Utah, U.S.A.

USGS Publications Warehouse

Heilweil, V.M.; Solomon, D.K.; Ortiz, G.

2009-01-01

Sand Hollow Reservoir in southwestern Utah, USA, is operated for both surface-water storage and artificial recharge to the underlying Navajo Sandstone. The total volume of estimated artificial recharge between 2002 and 2007 is 85 million cubic meters (69,000 acre-feet). Since 2002, artificial recharge rates have generally been declining and are inversely correlated with the increasing surface area of the reservoir. Permeability testing of core samples retrieved from beneath the reservoir indicates that this decline may not be due to silt accumulation. Artificial recharge rates also show much seasonal variability. Calculations of apparent intrinsic permeability show that these variations can only partly be explained by variation in water viscosity associated with seasonal changes in water temperature. Sporadic seasonal trends in recharge rates and intrinsic permeability during 2002-2004 could be associated with the large fluctuations in reservoir elevation and wetted area. From 2005 through 2007, the reservoir was mostly full and there has been a more consistent seasonal pattern of minimum recharge rates during the summer and maximum rates during the autumn. Total dissolved-gas pressure measurements indicate the presence of biogenic gas bubbles in the shallow sediments beneath the shallower parts of Sand Hollow Reservoir when the water is warmer. Permeability reduction associated with this gas clogging may contribute to the decrease in artificial recharge rates during the spring and summer, with a subsequently increasing recharge rates in the autumn associated with a decline in volume of gas bubbles. Other possible causes for seasonal variation in artificial recharge rates require further investigation.

Third prize: the impact of fluid environment manipulation on shockwave lithotripsy artificial calculi fragmentation rates.

PubMed

Méndez-Probst, Carlos E; Fernadez, Alfonso; Erdeljan, Petar; Vanjecek, Maaike; Cadieux, Peter A; Razvi, Hassan

2011-03-01

Studies have suggested that shockwave lithotripsy (SWL) stone fragmentation rates can be affected by characteristics of the fluid media surrounding the stone, although evidence to implicate the impact of urine specific gravity (SG) is limited and inconclusive. Our aim is to further explore the impact fluid media and SGs have on stone fragmentation using a variable focus lithotripter. Artificial stones were presoaked for 24 hours in urine and then shocked in various fluid media including artificial urine (SG 1.010 control, 1.020, and 1.07), human pooled urine (HPU), degassed HPU, Pentastarch, 100% and 30% contrast, degassed 30% contrast, 100% ethanol, deionized water (dH(2)O), degassed dH(2)O, 5% glucose, Ringer lactate, 0.9% saline, glycerol, whole blood, and lubricating gel. After soaking, SWL using the Modulith SLX-F2 electromagnetic lithotripter was performed. Fragments were dried and sieved using a 4-mm diameter opening grid. Fragments >4 mm were weighed and fragmentation coefficients (FCs) calculated (pre-SWL weight - post-SWL weight)/(pre-SWL weight) × 100. Fifteen stones were shocked for each fluid group. Fluid type, viscosity, and degassing all significantly impacted stone fragmentation. While the solutions' SG, per se, did not appear to affect stone fragmentation, the use of degassed 30% contrast significantly improved stone destruction over the SG 1.010 artificial urine control (95.3% vs 71.4, P < 0.01). Furthermore, degassing improved comminution rates by increasing the number of completely fragmented stones (FC = 100%). Using degassed 30% contrast, 12/15 stones were completely fragmented, compared with only 2/15 in the control group (P = 0.007). Among the whole blood, glycerol, and lubricating gel groups, only 1/15, 0/15, and 1/15 stones reached 100% FC respectively in the narrow focus, possibly because of the detrimental impact of increased viscosity. Different fluid media can significantly affect FC in vitro. Among the various fluids tested, degassed 30% contrast significantly increased the FC and total number of completely fragmented stones.

The Overshoot Phenomenon in Geodynamics Codes

NASA Astrophysics Data System (ADS)

Kommu, R. K.; Heien, E. M.; Kellogg, L. H.; Bangerth, W.; Heister, T.; Studley, E. H.

2013-12-01

The overshoot phenomenon is a common occurrence in numerical software when a continuous function on a finite dimensional discretized space is used to approximate a discontinuous jump, in temperature and material concentration, for example. The resulting solution overshoots, and undershoots, the discontinuous jump. Numerical simulations play an extremely important role in mantle convection research. This is both due to the strong temperature and stress dependence of viscosity and also due to the inaccessibility of deep earth. Under these circumstances, it is essential that mantle convection simulations be extremely accurate and reliable. CitcomS and ASPECT are two finite element based mantle convection simulations developed and maintained by the Computational Infrastructure for Geodynamics. CitcomS is a finite element based mantle convection code that is designed to run on multiple high-performance computing platforms. ASPECT, an adaptive mesh refinement (AMR) code built on the Deal.II library, is also a finite element based mantle convection code that scales well on various HPC platforms. CitcomS and ASPECT both exhibit the overshoot phenomenon. One attempt at controlling the overshoot uses the Entropy Viscosity method, which introduces an artificial diffusion term in the energy equation of mantle convection. This artificial diffusion term is small where the temperature field is smooth. We present results from CitcomS and ASPECT that quantify the effect of the Entropy Viscosity method in reducing the overshoot phenomenon. In the discontinuous Galerkin (DG) finite element method, the test functions used in the method are continuous within each element but are discontinuous across inter-element boundaries. The solution space in the DG method is discontinuous. FEniCS is a collection of free software tools that automate the solution of differential equations using finite element methods. In this work we also present results from a finite element mantle convection simulation implemented in FEniCS that investigates the effect of using DG elements in reducing the overshoot problem.

Scheduling the blended solution as industrial CO2 absorber in separation process by back-propagation artificial neural networks.

PubMed

Abdollahi, Yadollah; Sairi, Nor Asrina; Said, Suhana Binti Mohd; Abouzari-lotf, Ebrahim; Zakaria, Azmi; Sabri, Mohd Faizul Bin Mohd; Islam, Aminul; Alias, Yatimah

2015-11-05

It is believe that 80% industrial of carbon dioxide can be controlled by separation and storage technologies which use the blended ionic liquids absorber. Among the blended absorbers, the mixture of water, N-methyldiethanolamine (MDEA) and guanidinium trifluoromethane sulfonate (gua) has presented the superior stripping qualities. However, the blended solution has illustrated high viscosity that affects the cost of separation process. In this work, the blended fabrication was scheduled with is the process arranging, controlling and optimizing. Therefore, the blend's components and operating temperature were modeled and optimized as input effective variables to minimize its viscosity as the final output by using back-propagation artificial neural network (ANN). The modeling was carried out by four mathematical algorithms with individual experimental design to obtain the optimum topology using root mean squared error (RMSE), R-squared (R(2)) and absolute average deviation (AAD). As a result, the final model (QP-4-8-1) with minimum RMSE and AAD as well as the highest R(2) was selected to navigate the fabrication of the blended solution. Therefore, the model was applied to obtain the optimum initial level of the input variables which were included temperature 303-323 K, x[gua], 0-0.033, x[MDAE], 0.3-0.4, and x[H2O], 0.7-1.0. Moreover, the model has obtained the relative importance ordered of the variables which included x[gua]>temperature>x[MDEA]>x[H2O]. Therefore, none of the variables was negligible in the fabrication. Furthermore, the model predicted the optimum points of the variables to minimize the viscosity which was validated by further experiments. The validated results confirmed the model schedulability. Accordingly, ANN succeeds to model the initial components of the blended solutions as absorber of CO2 capture in separation technologies that is able to industries scale up. Copyright © 2015 Elsevier B.V. All rights reserved.

Sleep underpins the plasticity of language production.

PubMed

Gaskell, M Gareth; Warker, Jill; Lindsay, Shane; Frost, Rebecca; Guest, James; Snowdon, Reza; Stackhouse, Abigail

2014-07-01

The constraints that govern acceptable phoneme combinations in speech perception and production have considerable plasticity. We addressed whether sleep influences the acquisition of new constraints and their integration into the speech-production system. Participants repeated sequences of syllables in which two phonemes were artificially restricted to syllable onset or syllable coda, depending on the vowel in that sequence. After 48 sequences, participants either had a 90-min nap or remained awake. Participants then repeated 96 sequences so implicit constraint learning could be examined, and then were tested for constraint generalization in a forced-choice task. The sleep group, but not the wake group, produced speech errors at test that were consistent with restrictions on the placement of phonemes in training. Furthermore, only the sleep group generalized their learning to new materials. Polysomnography data showed that implicit constraint learning was associated with slow-wave sleep. These results show that sleep facilitates the integration of new linguistic knowledge with existing production constraints. These data have relevance for systems-consolidation models of sleep. © The Author(s) 2014.

Measuring strategic control in implicit learning: how and why?

PubMed

Norman, Elisabeth

2015-01-01

Several methods have been developed for measuring the extent to which implicitly learned knowledge can be applied in a strategic, flexible manner. Examples include generation exclusion tasks in Serial Reaction Time (SRT) learning (Goschke, 1998; Destrebecqz and Cleeremans, 2001) and 2-grammar classification tasks in Artificial Grammar Learning (AGL; Dienes et al., 1995; Norman et al., 2011). Strategic control has traditionally been used as a criterion for determining whether acquired knowledge is conscious or unconscious, or which properties of knowledge are consciously available. In this paper I first summarize existing methods that have been developed for measuring strategic control in the SRT and AGL tasks. I then address some methodological and theoretical questions. Methodological questions concern choice of task, whether the measurement reflects inhibitory control or task switching, and whether or not strategic control should be measured on a trial-by-trial basis. Theoretical questions concern the rationale for including measurement of strategic control, what form of knowledge is strategically controlled, and how strategic control can be combined with subjective awareness measures.

Measuring strategic control in implicit learning: how and why?

PubMed Central

Norman, Elisabeth

2015-01-01

Several methods have been developed for measuring the extent to which implicitly learned knowledge can be applied in a strategic, flexible manner. Examples include generation exclusion tasks in Serial Reaction Time (SRT) learning (Goschke, 1998; Destrebecqz and Cleeremans, 2001) and 2-grammar classification tasks in Artificial Grammar Learning (AGL; Dienes et al., 1995; Norman et al., 2011). Strategic control has traditionally been used as a criterion for determining whether acquired knowledge is conscious or unconscious, or which properties of knowledge are consciously available. In this paper I first summarize existing methods that have been developed for measuring strategic control in the SRT and AGL tasks. I then address some methodological and theoretical questions. Methodological questions concern choice of task, whether the measurement reflects inhibitory control or task switching, and whether or not strategic control should be measured on a trial-by-trial basis. Theoretical questions concern the rationale for including measurement of strategic control, what form of knowledge is strategically controlled, and how strategic control can be combined with subjective awareness measures. PMID:26441809

Large Eddy Simulation ... Where Do We Stand? International Workshop Held in St. Petersburg Beach, Florida on 19-21 December 1990.

DTIC Science & Technology

1990-01-01

S. Orszag, Chairman 1. P. Moin Some Issues in Computation of Turbulent Flows. 2. M. Lesieur, P. Comte, X. Normand, 0. Metais and A. Silveira Spectral...Richtmeyer’s computational experience with one-dimensional shock waves (1950) indicated the value of a non-linear artificial viscosity. Charney and... computer architecture and the advantages of semi-Lagrangian advective schemes may lure large-scale atmospheric modelers back to finite-difference

Grid Effect on Spherical Shallow Water Jets Using Continuous and Discontinuous Galerkin Methods

DTIC Science & Technology

2013-01-01

The high-order Legendre -Gauss-Lobatto (LGL) points are added to the linear grid by projecting the linear elements onto the auxiliary gnomonic space...mapping, the triangles are subdivided into smaller ones by a Lagrange polynomial of order nI . The number of quadrilateral elements and grid points of...of the acceleration of gravity and the vertical height of the fluid), ν∇2 is the artificial viscosity term of viscous coefficient ν = 1× 105 m2 s−1

Convergence speeding up in the calculation of the viscous flow about an airfoil

NASA Technical Reports Server (NTRS)

Radespiel, R.; Rossow, C.

1988-01-01

A finite volume method to solve the three dimensional Navier-Stokes equations was developed. It is based on a cell-vertex scheme with central differences and explicit Runge-Kutta time steps. A good convergence for a stationary solution was obtained by the use of local time steps, implicit smoothing of the residues, a multigrid algorithm, and a carefully controlled artificial dissipative term. The method is illustrated by results for transonic profiles and airfoils. The method allows a routine solution of the Navier-Stokes equations.

The Evolution of Sonic Ecosystems

NASA Astrophysics Data System (ADS)

McCormack, Jon

This chapter describes a novel type of artistic artificial life software environment. Agents that have the ability to make and listen to sound populate a synthetic world. An evolvable, rule-based classifier system drives agent behavior. Agents compete for limited resources in a virtual environment that is influenced by the presence and movement of people observing the system. Electronic sensors create a link between the real and virtual spaces, virtual agents evolve implicitly to try to maintain the interest of the human audience, whose presence provides them with life-sustaining food.

Measuring strategic control in artificial grammar learning.

PubMed

Norman, Elisabeth; Price, Mark C; Jones, Emma

2011-12-01

In response to concerns with existing procedures for measuring strategic control over implicit knowledge in artificial grammar learning (AGL), we introduce a more stringent measurement procedure. After two separate training blocks which each consisted of letter strings derived from a different grammar, participants either judged the grammaticality of novel letter strings with respect to only one of these two grammars (pure-block condition), or had the target grammar varying randomly from trial to trial (novel mixed-block condition) which required a higher degree of conscious flexible control. Random variation in the colour and font of letters was introduced to disguise the nature of the rule and reduce explicit learning. Strategic control was observed both in the pure-block and mixed-block conditions, and even among participants who did not realise the rule was based on letter identity. This indicated detailed strategic control in the absence of explicit learning. Copyright © 2011 Elsevier Inc. All rights reserved.

Molecular Dynamics based on a Generalized Born solvation model: application to protein folding

NASA Astrophysics Data System (ADS)

Onufriev, Alexey

2004-03-01

An accurate description of the aqueous environment is essential for realistic biomolecular simulations, but may become very expensive computationally. We have developed a version of the Generalized Born model suitable for describing large conformational changes in macromolecules. The model represents the solvent implicitly as continuum with the dielectric properties of water, and include charge screening effects of salt. The computational cost associated with the use of this model in Molecular Dynamics simulations is generally considerably smaller than the cost of representing water explicitly. Also, compared to traditional Molecular Dynamics simulations based on explicit water representation, conformational changes occur much faster in implicit solvation environment due to the absence of viscosity. The combined speed-up allow one to probe conformational changes that occur on much longer effective time-scales. We apply the model to folding of a 46-residue three helix bundle protein (residues 10-55 of protein A, PDB ID 1BDD). Starting from an unfolded structure at 450 K, the protein folds to the lowest energy state in 6 ns of simulation time, which takes about a day on a 16 processor SGI machine. The predicted structure differs from the native one by 2.4 A (backbone RMSD). Analysis of the structures seen on the folding pathway reveals details of the folding process unavailable form experiment.

Evaluation of sensor arrays for engine oils using artificial oil alteration

NASA Astrophysics Data System (ADS)

Sen, Sedat; Schneidhofer, Christoph; Dörr, Nicole; Vellekoop, Michael J.

2011-06-01

With respect to varying operation conditions, only sensors directly installed in the engine can detect the current oil condition hence enabling to get the right time for the oil change. Usually, only one parameter is not sufficient to obtain reliable information about the current oil condition. For this reason, appropriate sensor principles were evaluated for the design of sensor arrays for the measurement of critical lubricant parameters. In this contribution, we report on the development of a sensor array for engine oils using laboratory analyses of used engine oils for the correlation with sensor signals. The sensor array comprises the measurement of conductivity, permittivity, viscosity and temperature as well as oil corrosiveness as a consequence of acidification of the lubricant. As a key method, rapid evaluation of the sensors was done by short term simulation of entire oil change intervals based on artificial oil alteration. Thereby, the compatibility of the sensor array to the lubricant and the oil deterioration during the artificial alteration process was observed by the sensors and confirmed by additional laboratory analyses of oil samples take.

Attentional effects on rule extraction and consolidation from speech.

PubMed

López-Barroso, Diana; Cucurell, David; Rodríguez-Fornells, Antoni; de Diego-Balaguer, Ruth

2016-07-01

Incidental learning plays a crucial role in the initial phases of language acquisition. However the knowledge derived from implicit learning, which is based on prediction-based mechanisms, may become explicit. The role that attention plays in the formation of implicit and explicit knowledge of the learned material is unclear. In the present study, we investigated the role that attention plays in the acquisition of non-adjacent rule learning from speech. In addition, we also tested whether the amount of attention during learning changes the representation of the learned material after a 24h delay containing sleep. For that, we developed an experiment run on two consecutive days consisting on the exposure to an artificial language that contained non-adjacent dependencies (rules) between words whereas different conditions were established to manipulate the amount of attention given to the rules (target and non-target conditions). Furthermore, we used both indirect and direct measures of learning that are more sensitive to implicit and explicit knowledge, respectively. Whereas the indirect measures indicated that learning of the rules occurred regardless of attention, more explicit judgments after learning showed differences in the type of learning reached under the two attention conditions. 24 hours later, indirect measures showed no further improvements during additional language exposure and explicit judgments indicated that only the information more robustly learned in the previous day, was consolidated. Copyright © 2016 The Authors. Published by Elsevier B.V. All rights reserved.

Attentional effects on rule extraction and consolidation from speech

PubMed Central

López-Barroso, Diana; Cucurell, David; Rodríguez-Fornells, Antoni; de Diego-Balaguer, Ruth

2016-01-01

Incidental learning plays a crucial role in the initial phases of language acquisition. However the knowledge derived from implicit learning, which is based on prediction-based mechanisms, may become explicit. The role that attention plays in the formation of implicit and explicit knowledge of the learned material is unclear. In the present study, we investigated the role that attention plays in the acquisition of non-adjacent rule learning from speech. In addition, we also tested whether the amount of attention during learning changes the representation of the learned material after a 24 h delay containing sleep. For that, we developed an experiment run on two consecutive days consisting on the exposure to an artificial language that contained non-adjacent dependencies (rules) between words whereas different conditions were established to manipulate the amount of attention given to the rules (target and non-target conditions). Furthermore, we used both indirect and direct measures of learning that are more sensitive to implicit and explicit knowledge, respectively. Whereas the indirect measures indicated that learning of the rules occurred regardless of attention, more explicit judgments after learning showed differences in the type of learning reached under the two attention conditions. 24 hours later, indirect measures showed no further improvements during additional language exposure and explicit judgments indicated that only the information more robustly learned in the previous day, was consolidated. PMID:27031495

Heat Generation in Axial and Centrifugal Flow Left Ventricular Assist Devices.

PubMed

Yost, Gardner; Joseph, Christine Rachel; Royston, Thomas; Tatooles, Antone; Bhat, Geetha

Despite increasing use of left ventricular assist devices (LVADs) as a surgical treatment for advanced heart failure in an era of improved outcomes with LVAD support, the mechanical interactions between these pumps and the cardiovascular system are not completely understood. We utilized an in vitro mock circulatory loop to analyze the heat production incurred by operation of an axial flow and centrifugal flow LVAD. A HeartMate II and a HeartWare HVAD were connected to an abbreviated flow loop and were implanted in a viscoelastic gel. Temperature was measured at the surface of each LVAD. Device speed and fluid viscosity were altered and, in the HeartMate II, as artificial thrombi were attached to the inflow stator, impeller, and outflow stator. The surface temperatures of both LVADs increased in all trials and reached a plateau within 80 minutes of flow initiation. Rate of heat generation and maximum system temperature were greater when speed was increased, when viscosity was increased, and when artificial thrombi were attached to the HeartMate II impeller. Normal operation of these two widely utilized LVADs results in appreciable heat generation in vitro. Increased pump loading resulted in more rapid heat generation, which was particularly severe when a large thrombus was attached to the impeller of the HeartMate II. While heat accumulation in vivo is likely minimized by greater dissipation in the blood and soft tissues, focal temperature gains with the pump housing of these two devices during long-term operation may have negative hematological consequences.

A deformable surface model for real-time water drop animation.

PubMed

Zhang, Yizhong; Wang, Huamin; Wang, Shuai; Tong, Yiying; Zhou, Kun

2012-08-01

A water drop behaves differently from a large water body because of its strong viscosity and surface tension under the small scale. Surface tension causes the motion of a water drop to be largely determined by its boundary surface. Meanwhile, viscosity makes the interior of a water drop less relevant to its motion, as the smooth velocity field can be well approximated by an interpolation of the velocity on the boundary. Consequently, we propose a fast deformable surface model to realistically animate water drops and their flowing behaviors on solid surfaces. Our system efficiently simulates water drop motions in a Lagrangian fashion, by reducing 3D fluid dynamics over the whole liquid volume to a deformable surface model. In each time step, the model uses an implicit mean curvature flow operator to produce surface tension effects, a contact angle operator to change droplet shapes on solid surfaces, and a set of mesh connectivity updates to handle topological changes and improve mesh quality over time. Our numerical experiments demonstrate a variety of physically plausible water drop phenomena at a real-time rate, including capillary waves when water drops collide, pinch-off of water jets, and droplets flowing over solid materials. The whole system performs orders-of-magnitude faster than existing simulation approaches that generate comparable water drop effects.

Harnessing Electrostatic Forces to Grow Bio-inspired Hierarchical Vascular Networks

NASA Astrophysics Data System (ADS)

Behler, Kristopher; Melrose, Zachary; Schott, Andrew; Wetzel, Eric

2012-02-01

Vascular networks provide a system for fluid distribution. Artificial vascular materials with enhanced properties are currently being developed that could ultimately be integrated into systems reliant upon fluid transport while retaining their structural properties. An uninterrupted and controllable supply of liquid is optimal for many applications such as continual self-healing materials, in-situ delivery of index matched fluids, thermal management and drug delivery systems could benefit from a bio-inspired vascular approach that combines complex network geometries with minimal processing parameters. Two such approaches to induce vascular networks are electrohydrodynamic viscous fingering (EHVF) and electrical treeing (ET). EHVF is a phenomenon that occurs when a low viscosity liquid is forced through a high viscosity fluid or matrix, resulting in branches due to capillary and viscous forces in the high viscosity material. By applying voltages of 0 -- 60 kV, finger diameter is reduced. ET is the result of partial discharges in a dielectric material. In the vicinity of a small diameter electrode, the local electric field is greater than the global dielectric strength, causing a localized, step-wise, breakdown to occur forming a highly branched interconnected structure. ET is a viable method to produce networks on a smaller, micron, scale than the products of the EHVF method.

Estimating tree bole volume using artificial neural network models for four species in Turkey.

PubMed

Ozçelik, Ramazan; Diamantopoulou, Maria J; Brooks, John R; Wiant, Harry V

2010-01-01

Tree bole volumes of 89 Scots pine (Pinus sylvestris L.), 96 Brutian pine (Pinus brutia Ten.), 107 Cilicica fir (Abies cilicica Carr.) and 67 Cedar of Lebanon (Cedrus libani A. Rich.) trees were estimated using Artificial Neural Network (ANN) models. Neural networks offer a number of advantages including the ability to implicitly detect complex nonlinear relationships between input and output variables, which is very helpful in tree volume modeling. Two different neural network architectures were used and produced the Back propagation (BPANN) and the Cascade Correlation (CCANN) Artificial Neural Network models. In addition, tree bole volume estimates were compared to other established tree bole volume estimation techniques including the centroid method, taper equations, and existing standard volume tables. An overview of the features of ANNs and traditional methods is presented and the advantages and limitations of each one of them are discussed. For validation purposes, actual volumes were determined by aggregating the volumes of measured short sections (average 1 meter) of the tree bole using Smalian's formula. The results reported in this research suggest that the selected cascade correlation artificial neural network (CCANN) models are reliable for estimating the tree bole volume of the four examined tree species since they gave unbiased results and were superior to almost all methods in terms of error (%) expressed as the mean of the percentage errors. 2009 Elsevier Ltd. All rights reserved.

Experimental investigation of the hydraulic and heat-transfer properties of artificially fractured granite.

PubMed

Luo, Jin; Zhu, Yongqiang; Guo, Qinghai; Tan, Long; Zhuang, Yaqin; Liu, Mingliang; Zhang, Canhai; Xiang, Wei; Rohn, Joachim

2017-01-05

In this paper, the hydraulic and heat-transfer properties of two sets of artificially fractured granite samples are investigated. First, the morphological information is determined using 3D modelling technology. The area ratio is used to describe the roughness of the fracture surface. Second, the hydraulic properties of fractured granite are tested by exposing samples to different confining pressures and temperatures. The results show that the hydraulic properties of the fractures are affected mainly by the area ratio, with a larger area ratio producing a larger fracture aperture and higher hydraulic conductivity. Both the hydraulic apertureand the hydraulic conductivity decrease with an increase in the confining pressure. Furthermore, the fracture aperture decreases with increasing rock temperature, but the hydraulic conductivity increases owing to a reduction of the viscosity of the fluid flowing through. Finally, the heat-transfer efficiency of the samples under coupled hydro-thermal-mechanical conditions is analysed and discussed.

Experimental investigation of the hydraulic and heat-transfer properties of artificially fractured granite

PubMed Central

Luo, Jin; Zhu, Yongqiang; Guo, Qinghai; Tan, Long; Zhuang, Yaqin; Liu, Mingliang; Zhang, Canhai; Xiang, Wei; Rohn, Joachim

2017-01-01

In this paper, the hydraulic and heat-transfer properties of two sets of artificially fractured granite samples are investigated. First, the morphological information is determined using 3D modelling technology. The area ratio is used to describe the roughness of the fracture surface. Second, the hydraulic properties of fractured granite are tested by exposing samples to different confining pressures and temperatures. The results show that the hydraulic properties of the fractures are affected mainly by the area ratio, with a larger area ratio producing a larger fracture aperture and higher hydraulic conductivity. Both the hydraulic apertureand the hydraulic conductivity decrease with an increase in the confining pressure. Furthermore, the fracture aperture decreases with increasing rock temperature, but the hydraulic conductivity increases owing to a reduction of the viscosity of the fluid flowing through. Finally, the heat-transfer efficiency of the samples under coupled hydro-thermal-mechanical conditions is analysed and discussed. PMID:28054594

A High Order Finite Difference Scheme with Sharp Shock Resolution for the Euler Equations

NASA Technical Reports Server (NTRS)

Gerritsen, Margot; Olsson, Pelle

1996-01-01

We derive a high-order finite difference scheme for the Euler equations that satisfies a semi-discrete energy estimate, and present an efficient strategy for the treatment of discontinuities that leads to sharp shock resolution. The formulation of the semi-discrete energy estimate is based on a symmetrization of the Euler equations that preserves the homogeneity of the flux vector, a canonical splitting of the flux derivative vector, and the use of difference operators that satisfy a discrete analogue to the integration by parts procedure used in the continuous energy estimate. Around discontinuities or sharp gradients, refined grids are created on which the discrete equations are solved after adding a newly constructed artificial viscosity. The positioning of the sub-grids and computation of the viscosity are aided by a detection algorithm which is based on a multi-scale wavelet analysis of the pressure grid function. The wavelet theory provides easy to implement mathematical criteria to detect discontinuities, sharp gradients and spurious oscillations quickly and efficiently.

Viscous regularization of the full set of nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations

DOE PAGES

Delchini, Marc O.; Ragusa, Jean C.; Ferguson, Jim

2017-02-17

A viscous regularization technique, based on the local entropy residual, was proposed by Delchini et al. (2015) to stabilize the nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations using an artificial viscosity technique. This viscous regularization is modulated by the local entropy production and is consistent with the entropy minimum principle. However, Delchini et al. (2015) only based their work on the hyperbolic parts of the Grey Radiation-Hydrodynamic equations and thus omitted the relaxation and diffusion terms present in the material energy and radiation energy equations. Here in this paper, we extend the theoretical grounds for the method and derive an entropy minimum principlemore » for the full set of nonequilibrium-diffusion Grey Radiation-Hydrodynamic equations. This further strengthens the applicability of the entropy viscosity method as a stabilization technique for radiation-hydrodynamic shock simulations. Radiative shock calculations using constant and temperature-dependent opacities are compared against semi-analytical reference solutions, and we present a procedure to perform spatial convergence studies of such simulations.« less

New discretization and solution techniques for incompressible viscous flow problems

NASA Technical Reports Server (NTRS)

Gunzburger, M. D.; Nicolaides, R. A.; Liu, C. H.

1983-01-01

Several topics arising in the finite element solution of the incompressible Navier-Stokes equations are considered. Specifically, the question of choosing finite element velocity/pressure spaces is addressed, particularly from the viewpoint of achieving stable discretizations leading to convergent pressure approximations. The role of artificial viscosity in viscous flow calculations is studied, emphasizing work by several researchers for the anisotropic case. The last section treats the problem of solving the nonlinear systems of equations which arise from the discretization. Time marching methods and classical iterative techniques, as well as some modifications are mentioned.

Computation of turbulent pipe and duct flow using third order upwind scheme

NASA Technical Reports Server (NTRS)

Kawamura, T.

1986-01-01

The fully developed turbulence in a circular pipe and in a square duct is simulated directly without using turbulence models in the Navier-Stokes equations. The utilized method employs a third-order upwind scheme for the approximation to the nonlinear term and the second-order Adams-Bashforth method for the time derivative in the Navier-Stokes equation. The computational results appear to capture the large-scale turbulent structures at least qualitatively. The significance of the artificial viscosity inherent in the present scheme is discussed.

Symposium on Turbulent Shear Flows (8th) Held in Munich, Germany on 9-11 September 1991. Volume 2. Sessions 19-31, Poster Sessions

DTIC Science & Technology

1991-09-01

FLAMES IN THE ATrR)S1]1 IERE USING A SECOND MOMNT TURBULENCE MODEL Hermilo RAMIREZ -LEON, Claude REY and Jean-Frangois SINI LABORATOIRE DE MECANIQUE DES...65 directly satisfied by an extended version of the C= F , ax6 aX5 artificial compressibility implicit method ( Ramirez -Leon et al,, 1991). 08 2 IR ap...the isotropization-of-production concept. For the compressible fluid case, Ramirez -Leon et al (1990) With regard to Eq (2), the right-hand side of

Comparison of Implicit Schemes for the Incompressible Navier-Stokes Equations

NASA Technical Reports Server (NTRS)

Rogers, Stuart E.

1995-01-01

For a computational flow simulation tool to be useful in a design environment, it must be very robust and efficient. To develop such a tool for incompressible flow applications, a number of different implicit schemes are compared for several two-dimensional flow problems in the current study. The schemes include Point-Jacobi relaxation, Gauss-Seidel line relaxation, incomplete lower-upper decomposition, and the generalized minimum residual method preconditioned with each of the three other schemes. The efficiency of the schemes is measured in terms of the computing time required to obtain a steady-state solution for the laminar flow over a backward-facing step, the flow over a NACA 4412 airfoil, and the flow over a three-element airfoil using overset grids. The flow solver used in the study is the INS2D code that solves the incompressible Navier-Stokes equations using the method of artificial compressibility and upwind differencing of the convective terms. The results show that the generalized minimum residual method preconditioned with the incomplete lower-upper factorization outperforms all other methods by at least a factor of 2.

Numerical Simulation of Hydrodynamics of a Heavy Liquid Drop Covered by Vapor Film in a Water Pool

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ma, W.M.; Yang, Z.L.; Giri, A.

2002-07-01

A numerical study on the hydrodynamics of a droplet covered by vapor film in water pool is carried out. Two level set functions are used as to implicitly capture the interfaces among three immiscible fluids (melt-drop, vapor and coolant). This approach leaves only one set of conservation equations for the three phases. A high-order Navier-Stokes solver, called Cubic-Interpolated Pseudo-Particle (CIP) algorithm, is employed in combination with level set approach, which allows large density ratios (up to 1000), surface tension and jump in viscosity. By this calculation, the hydrodynamic behavior of a melt droplet falling into a volatile coolant is simulated,more » which is of great significance to reveal the mechanism of steam explosion during a hypothetical severe reactor accident. (authors)« less

Numerical investigation of MHD flow of blood and heat transfer in a stenosed arterial segment

NASA Astrophysics Data System (ADS)

Majee, Sreeparna; Shit, G. C.

2017-02-01

A numerical investigation of unsteady flow of blood and heat transfer has been performed with an aim to provide better understanding of blood flow through arteries under stenotic condition. The blood is treated as Newtonian fluid and the arterial wall is considered to be rigid having deposition of plaque in its lumen. The heat transfer characteristic has been analyzed by taking into consideration of the dissipation of energy due to applied magnetic field and the viscosity of blood. The vorticity-stream function formulation has been adopted to solve the problem using implicit finite difference method by developing well known Peaceman-Rachford Alternating Direction Implicit (ADI) scheme. The quantitative profile analysis of velocity, temperature and wall shear stress as well as Nusselt number is carried out over the entire arterial segment. The streamline and temperature contours have been plotted to understand the flow pattern in the diseased artery, which alters significantly in the downstream of the stenosis in the presence of magnetic field. Both the wall shear stress and Nusselt number increases with increasing magnetic field strength. However, wall shear stress decreases and Nusselt number enhances with Reynolds number. The results show that with an increase in the magnetic field strength upto 8 T, does not causes any damage to the arterial wall, but the study is significant for assessing temperature rise during hyperthermic treatment.

Fourth order difference methods for hyperbolic IBVP's

NASA Technical Reports Server (NTRS)

Gustafsson, Bertil; Olsson, Pelle

1994-01-01

Fourth order difference approximations of initial-boundary value problems for hyperbolic partial differential equations are considered. We use the method of lines approach with both explicit and compact implicit difference operators in space. The explicit operator satisfies an energy estimate leading to strict stability. For the implicit operator we develop boundary conditions and give a complete proof of strong stability using the Laplace transform technique. We also present numerical experiments for the linear advection equation and Burgers' equation with discontinuities in the solution or in its derivative. The first equation is used for modeling contact discontinuities in fluid dynamics, the second one for modeling shocks and rarefaction waves. The time discretization is done with a third order Runge-Kutta TVD method. For solutions with discontinuities in the solution itself we add a filter based on second order viscosity. In case of the non-linear Burger's equation we use a flux splitting technique that results in an energy estimate for certain different approximations, in which case also an entropy condition is fulfilled. In particular we shall demonstrate that the unsplit conservative form produces a non-physical shock instead of the physically correct rarefaction wave. In the numerical experiments we compare our fourth order methods with a standard second order one and with a third order TVD-method. The results show that the fourth order methods are the only ones that give good results for all the considered test problems.

Discontinuous Galerkin (DG) Method for solving time dependent convection-diffusion type temperature equation : Demonstration and Comparison with Other Methods in the Mantle Convection Code ASPECT

NASA Astrophysics Data System (ADS)

He, Y.; Puckett, E. G.; Billen, M. I.; Kellogg, L. H.

2016-12-01

For a convection-dominated system, like convection in the Earth's mantle, accurate modeling of the temperature field in terms of the interaction between convective and diffusive processes is one of the most common numerical challenges. In the geodynamics community using Finite Element Method (FEM) with artificial entropy viscosity is a popular approach to resolve this difficulty, but introduce numerical diffusion. The extra artificial viscosity added into the temperature system will not only oversmooth the temperature field where the convective process dominates, but also change the physical properties by increasing the local material conductivity, which will eventually change the local conservation of energy. Accurate modeling of temperature is especially important in the mantle, where material properties are strongly dependent on temperature. In subduction zones, for example, the rheology of the cold sinking slab depends nonlinearly on the temperature, and physical processes such as slab detachment, rollback, and melting all are sensitively dependent on temperature and rheology. Therefore methods that overly smooth the temperature may inaccurately represent the physical processes governing subduction, lithospheric instabilities, plume generation and other aspects of mantle convection. Here we present a method for modeling the temperature field in mantle dynamics simulations using a new solver implemented in the ASPECT software. The new solver for the temperature equation uses a Discontinuous Galerkin (DG) approach, which combines features of both finite element and finite volume methods, and is particularly suitable for problems satisfying the conservation law, and the solution has a large variation locally. Furthermore, we have applied a post-processing technique to insure that the solution satisfies a local discrete maximum principle in order to eliminate the overshoots and undershoots in the temperature locally. To demonstrate the capabilities of this new method we present benchmark results (e.g., falling sphere), and a simple subduction models with kinematic surface boundary condition. To evaluate the trade-offs in computational speed and solution accuracy we present results for the same benchmarks using the Finite Element entropy viscosity method available in ASPECT.

Dynamics of ultra-thin polystyrene with and without a (artificial) dead layer studied by resonance enhanced dynamic light scattering

NASA Astrophysics Data System (ADS)

Vianna, S. D. B.; Lin, F. Y.; Plum, M. A.; Duran, H.; Steffen, W.

2017-05-01

Using non-invasive, marker-free resonance enhanced dynamic light scattering, the dynamics of capillary waves on ultrathin polystyrene films' coupling to the viscoelastic and mechanical properties have been studied. The dynamics of ultrathin polymer films is still debated. In particular the question of what influence either the solid substrate and/or the fluid-gas interface has on the dynamics and the mechanical properties of films of glass forming liquids as polymers is in the focus of the present research. As a consequence, e.g., viscosity close to interfaces and thus the average viscosity of very thin films are prone to change. This study is focused on atactic, non-entangled polystyrene thin films on the gold surface. A slow dynamic mode was observed with Vogel-Fulcher-Tammann temperature dependence, slowing down with decreasing film thickness. We tentatively attribute this relaxation mode to overdamped capillary waves because of its temperature dependence and the dispersion with a wave vector which was found. No signs of a more mobile layer at the air/polymer interface or of a "dead layer" at the solid/polymer interface were found. Therefore we investigated the influence of an artificially created dead layer on the capillary wave dynamics by introducing covalently bound polystyrene polymer brushes as anchors. The dynamics was slowed down to a degree more than expected from theoretical work on the increase of density close to the solid liquid interface—instead of a "dead layer" of 2 nm, the interaction seems to extend more than 10 nm into the polymer.

Computation of incompressible viscous flows through artificial heart devices with moving boundaries

NASA Technical Reports Server (NTRS)

Kiris, Cetin; Rogers, Stuart; Kwak, Dochan; Chang, I.-DEE

1991-01-01

The extension of computational fluid dynamics techniques to artificial heart flow simulations is illustrated. Unsteady incompressible Navier-Stokes equations written in 3-D generalized curvilinear coordinates are solved iteratively at each physical time step until the incompressibility condition is satisfied. The solution method is based on the pseudo compressibility approach and uses an implicit upwind differencing scheme together with the Gauss-Seidel line relaxation method. The efficiency and robustness of the time accurate formulation of the algorithm are tested by computing the flow through model geometries. A channel flow with a moving indentation is computed and validated with experimental measurements and other numerical solutions. In order to handle the geometric complexity and the moving boundary problems, a zonal method and an overlapping grid embedding scheme are used, respectively. Steady state solutions for the flow through a tilting disk heart valve was compared against experimental measurements. Good agreement was obtained. The flow computation during the valve opening and closing is carried out to illustrate the moving boundary capability.

Development of a High-Order Navier-Stokes Solver Using Flux Reconstruction to Simulate Three-Dimensional Vortex Structures in a Curved Artery Model

NASA Astrophysics Data System (ADS)

Cox, Christopher

Low-order numerical methods are widespread in academic solvers and ubiquitous in industrial solvers due to their robustness and usability. High-order methods are less robust and more complicated to implement; however, they exhibit low numerical dissipation and have the potential to improve the accuracy of flow simulations at a lower computational cost when compared to low-order methods. This motivates our development of a high-order compact method using Huynh's flux reconstruction scheme for solving unsteady incompressible flow on unstructured grids. We use Chorin's classic artificial compressibility formulation with dual time stepping to solve unsteady flow problems. In 2D, an implicit non-linear lower-upper symmetric Gauss-Seidel scheme with backward Euler discretization is used to efficiently march the solution in pseudo time, while a second-order backward Euler discretization is used to march in physical time. We verify and validate implementation of the high-order method coupled with our implicit time stepping scheme using both steady and unsteady incompressible flow problems. The current implicit time stepping scheme is proven effective in satisfying the divergence-free constraint on the velocity field in the artificial compressibility formulation. The high-order solver is extended to 3D and parallelized using MPI. Due to its simplicity, time marching for 3D problems is done explicitly. The feasibility of using the current implicit time stepping scheme for large scale three-dimensional problems with high-order polynomial basis still remains to be seen. We directly use the aforementioned numerical solver to simulate pulsatile flow of a Newtonian blood-analog fluid through a rigid 180-degree curved artery model. One of the most physiologically relevant forces within the cardiovascular system is the wall shear stress. This force is important because atherosclerotic regions are strongly correlated with curvature and branching in the human vasculature, where the shear stress is both oscillatory and multidirectional. Also, the combined effect of curvature and pulsatility in cardiovascular flows produces unsteady vortices. The aim of this research as it relates to cardiovascular fluid dynamics is to predict the spatial and temporal evolution of vortical structures generated by secondary flows, as well as to assess the correlation between multiple vortex pairs and wall shear stress. We use a physiologically (pulsatile) relevant flow rate and generate results using both fully developed and uniform entrance conditions, the latter being motivated by the fact that flow upstream of a curved artery may not have sufficient straight entrance length to become fully developed. Under the two pulsatile inflow conditions, we characterize the morphology and evolution of various vortex pairs and their subsequent effect on relevant haemodynamic wall shear stress metrics.

The Effects of Thermal Energetics on Three-dimensional Hydrodynamic Instabilities in Massive Protostellar Disks. II. High-Resolution and Adiabatic Evolutions

NASA Astrophysics Data System (ADS)

Pickett, Brian K.; Cassen, Patrick; Durisen, Richard H.; Link, Robert

2000-02-01

In this paper, the effects of thermal energetics on the evolution of gravitationally unstable protostellar disks are investigated by means of three-dimensional hydrodynamic calculations. The initial states for the simulations correspond to stars with equilibrium, self-gravitating disks that are formed early in the collapse of a uniformly rotating, singular isothermal sphere. In a previous paper (Pickett et al.), it was shown that the nonlinear development of locally isentropic disturbances can be radically different than that of locally isothermal disturbances, even though growth in the linear regime may be similar. When multiple low-order modes grew rapidly in the star and inner disk region and saturated at moderate nonlinear levels in the isentropic evolution, the same modes in the isothermal evolution led to shredding of the disk into dense arclets and ejection of material. In this paper, we (1) examine the fate of the shredded disk with calculations at higher spatial resolution than the previous simulations had and (2) follow the evolution of the same initial state using an internal energy equation rather than the assumption of locally isentropic or locally isothermal conditions. Despite the complex structure of the nonlinear features that developed in the violently unstable isothermal disk referred to above, our previous calculation produced no gravitationally independent, long-lived stellar or planetary companions. The higher resolution calculations presented here confirm this result. When the disk of this model is cooled further, prompting even more violent instabilities, the end result is qualitatively the same--a shredded disk. At least for the disks studied here, it is difficult to produce condensations of material that do not shear away into fragmented spirals. It is argued that the ultimate fate of such fragments depends on how readily local internal energy is lost. On the other hand, if a dynamically unstable disk is to survive for very long times without shredding, then some mechanism must mitigate and control any violent phenomena that do occur. The prior simulations demonstrated a marked difference in final outcome, depending upon the efficiency of disk cooling under two different, idealized thermal conditions. We have here incorporated an internal energy equation that allows for arbitrary heating and cooling. Simulations are presented for adiabatic models with and without artificial viscosity. The artificial viscosity accounts for dissipation and heating due to shocks in the code physics. The expected nonaxisymmetric instabilities occur and grow as before in these energy equation evolutions. When artificial viscosity is not present, the model protostar displays behavior between the locally isentropic and locally isothermal cases of the last paper; a strong two-armed spiral grows to nonlinear amplitudes and saturates at a level higher than in the locally isentropic case. Since the amplitude of the spiral disturbance is large, it is expected that continued transport of material and angular momentum will occur well after the end of the calculation at nearly four outer rotation periods. The spiral is not strong enough, however, to disrupt the disk as in the locally isothermal case. When artificial viscosity is present, the same disturbances reach moderate nonlinear amplitude, then heat the gas, which in turn greatly reduces their strength and effects on the disk. Additional heating in the low-density regions of the disk also leads to a gentle flow of material vertically off the computational grid. The energy equation and high-resolution isothermal calculations are used to discuss the importance and relevance of the different thermal regimes so far examined, with particular attention to applications to star and planet formation.

Plasma kinetic effects on atomistic mix in one dimension and at structured interfaces (I)

NASA Astrophysics Data System (ADS)

Yin, L.; Albright, B. J.; Vold, E. L.; Taitano, W.; Chacon, L.; Simakov, A.

2017-10-01

Kinetic effects on interfacial mix are examined using VPIC simulations. In 1D, comparisons are made to the results of analytic theory in the small Knudsen number limit. While the bulk mixing properties of interfaces are in general agreement, differences arise near the low-concentration fronts during the early evolution of a sharp interface when the species' perpendicular scattering rate dominates over the slowing down rate. In kinetic simulations, the diffusion velocities can be larger or comparable to the ion thermal speeds, and the Knudsen number can be large. Super-diffusive growth in mix widths (Δx ta where a >=1/2) is seen before transition to the slow diffusive process predicted from theory (a =1/2). Mixing at interfaces leads to persistent, bulk, hydrodynamic features in the center of mass flow profiles as a result of diffusion and momentum conservation. These conclusions are drawn from VPIC results together with simulations from the RAGE hydrodynamics code with an implementation of diffusion and viscosity from theory and an implicit Vlasov-Fokker-Planck code iFP. In perturbed 2D and 3D interfaces, it is found that 1D ambipolarity is still valid and that initial perturbations flatten out on a-few-ps time scale, implying that finite diffusivity and viscosity can slow instability growth in ICF and HED settings. Work supported by the LANL ASC and Science programs.

New discretization and solution techniques for incompressible viscous flow problems

NASA Technical Reports Server (NTRS)

Gunzburger, M. D.; Nicolaides, R. A.; Liu, C. H.

1983-01-01

This paper considers several topics arising in the finite element solution of the incompressible Navier-Stokes equations. Specifically, the question of choosing finite element velocity/pressure spaces is addressed, particularly from the viewpoint of achieving stable discretizations leading to convergent pressure approximations. Following this, the role of artificial viscosity in viscous flow calculations is studied, emphasizing recent work by several researchers for the anisotropic case. The last section treats the problem of solving the nonlinear systems of equations which arise from the discretization. Time marching methods and classical iterative techniques, as well as some recent modifications are mentioned.

Comparing AMR and SPH Cosmological Simulations. I. Dark Matter and Adiabatic Simulations

NASA Astrophysics Data System (ADS)

O'Shea, Brian W.; Nagamine, Kentaro; Springel, Volker; Hernquist, Lars; Norman, Michael L.

2005-09-01

We compare two cosmological hydrodynamic simulation codes in the context of hierarchical galaxy formation: the Lagrangian smoothed particle hydrodynamics (SPH) code GADGET, and the Eulerian adaptive mesh refinement (AMR) code Enzo. Both codes represent dark matter with the N-body method but use different gravity solvers and fundamentally different approaches for baryonic hydrodynamics. The SPH method in GADGET uses a recently developed ``entropy conserving'' formulation of SPH, while for the mesh-based Enzo two different formulations of Eulerian hydrodynamics are employed: the piecewise parabolic method (PPM) extended with a dual energy formulation for cosmology, and the artificial viscosity-based scheme used in the magnetohydrodynamics code ZEUS. In this paper we focus on a comparison of cosmological simulations that follow either only dark matter, or also a nonradiative (``adiabatic'') hydrodynamic gaseous component. We perform multiple simulations using both codes with varying spatial and mass resolution with identical initial conditions. The dark matter-only runs agree generally quite well provided Enzo is run with a comparatively fine root grid and a low overdensity threshold for mesh refinement, otherwise the abundance of low-mass halos is suppressed. This can be readily understood as a consequence of the hierarchical particle-mesh algorithm used by Enzo to compute gravitational forces, which tends to deliver lower force resolution than the tree-algorithm of GADGET at early times before any adaptive mesh refinement takes place. At comparable force resolution we find that the latter offers substantially better performance and lower memory consumption than the present gravity solver in Enzo. In simulations that include adiabatic gasdynamics we find general agreement in the distribution functions of temperature, entropy, and density for gas of moderate to high overdensity, as found inside dark matter halos. However, there are also some significant differences in the same quantities for gas of lower overdensity. For example, at z=3 the fraction of cosmic gas that has temperature logT>0.5 is ~80% for both Enzo ZEUS and GADGET, while it is 40%-60% for Enzo PPM. We argue that these discrepancies are due to differences in the shock-capturing abilities of the different methods. In particular, we find that the ZEUS implementation of artificial viscosity in Enzo leads to some unphysical heating at early times in preshock regions. While this is apparently a significantly weaker effect in GADGET, its use of an artificial viscosity technique may also make it prone to some excess generation of entropy that should be absent in Enzo PPM. Overall, the hydrodynamical results for GADGET are bracketed by those for Enzo ZEUS and Enzo PPM but are closer to Enzo ZEUS.

Study of heat transfer on physiological driven movement with CNT nanofluids and variable viscosity.

PubMed

Akbar, Noreen Sher; Kazmi, Naeem; Tripathi, Dharmendra; Mir, Nazir Ahmed

2016-11-01

With ongoing interest in CNT nanofluids and materials in biotechnology, energy and environment, microelectronics, composite materials etc., the current investigation is carried out to analyze the effects of variable viscosity and thermal conductivity of CNT nanofluids flow driven by cilia induced movement through a circular cylindrical tube. Metachronal wave is generated by the beating of cilia and mathematically modeled as elliptical wave propagation by Blake (1971). The problem is formulated in the form of nonlinear partial differential equations, which are simplified by using the dimensional analysis to avoid the complicacy of dimensional homogeneity. Lubrication theory is employed to linearize the governing equations and it is also physically appropriate for cilia movement. Analytical solutions for velocity, temperature and pressure gradient and stream function are obtained. The analytical results are numerically simulated by using the Mathematica Software and plotted the graphs for velocity profile, temperature profile, pressure gradient and stream lines for better discussion and visualization. This model is applicable in physiological transport phenomena to explore the nanotechnology in engineering the artificial cilia and ciliated tube/pipe. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

User's guide for NASCRIN: A vectorized code for calculating two-dimensional supersonic internal flow fields

NASA Technical Reports Server (NTRS)

Kumar, A.

1984-01-01

A computer program NASCRIN has been developed for analyzing two-dimensional flow fields in high-speed inlets. It solves the two-dimensional Euler or Navier-Stokes equations in conservation form by an explicit, two-step finite-difference method. An explicit-implicit method can also be used at the user's discretion for viscous flow calculations. For turbulent flow, an algebraic, two-layer eddy-viscosity model is used. The code is operational on the CDC CYBER 203 computer system and is highly vectorized to take full advantage of the vector-processing capability of the system. It is highly user oriented and is structured in such a way that for most supersonic flow problems, the user has to make only a few changes. Although the code is primarily written for supersonic internal flow, it can be used with suitable changes in the boundary conditions for a variety of other problems.

A fully vectorized numerical solution of the incompressible Navier-Stokes equations. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Patel, N.

1983-01-01

A vectorizable algorithm is presented for the implicit finite difference solution of the incompressible Navier-Stokes equations in general curvilinear coordinates. The unsteady Reynolds averaged Navier-Stokes equations solved are in two dimension and non-conservative primitive variable form. A two-layer algebraic eddy viscosity turbulence model is used to incorporate the effects of turbulence. Two momentum equations and a Poisson pressure equation, which is obtained by taking the divergence of the momentum equations and satisfying the continuity equation, are solved simultaneously at each time step. An elliptic grid generation approach is used to generate a boundary conforming coordinate system about an airfoil. The governing equations are expressed in terms of the curvilinear coordinates and are solved on a uniform rectangular computational domain. A checkerboard SOR, which can effectively utilize the computer architectural concept of vector processing, is used for iterative solution of the governing equations.

Numerical simulation of turbulent jet noise, part 2

NASA Technical Reports Server (NTRS)

Metcalfe, R. W.; Orszag, S. A.

1976-01-01

Results on the numerical simulation of jet flow fields were used to study the radiated sound field, and in addition, to extend and test the capabilities of the turbulent jet simulation codes. The principal result of the investigation was the computation of the radiated sound field from a turbulent jet. In addition, the computer codes were extended to account for the effects of compressibility and eddy viscosity, and the treatment of the nonlinear terms of the Navier-Stokes equations was modified so that they can be computed in a semi-implicit way. A summary of the flow model and a description of the numerical methods used for its solution are presented. Calculations of the radiated sound field are reported. In addition, the extensions that were made to the fundamental dynamical codes are described. Finally, the current state-of-the-art for computer simulation of turbulent jet noise is summarized.

A Penalty Method for the Numerical Solution of Hamilton-Jacobi-Bellman (HJB) Equations in Finance

NASA Astrophysics Data System (ADS)

Witte, J. H.; Reisinger, C.

2010-09-01

We present a simple and easy to implement method for the numerical solution of a rather general class of Hamilton-Jacobi-Bellman (HJB) equations. In many cases, the considered problems have only a viscosity solution, to which, fortunately, many intuitive (e.g. finite difference based) discretisations can be shown to converge. However, especially when using fully implicit time stepping schemes with their desireable stability properties, one is still faced with the considerable task of solving the resulting nonlinear discrete system. In this paper, we introduce a penalty method which approximates the nonlinear discrete system to an order of O(1/ρ), where ρ>0 is the penalty parameter, and we show that an iterative scheme can be used to solve the penalised discrete problem in finitely many steps. We include a number of examples from mathematical finance for which the described approach yields a rigorous numerical scheme and present numerical results.

Large eddy simulation of incompressible turbulent channel flow

NASA Technical Reports Server (NTRS)

Moin, P.; Reynolds, W. C.; Ferziger, J. H.

1978-01-01

The three-dimensional, time-dependent primitive equations of motion were numerically integrated for the case of turbulent channel flow. A partially implicit numerical method was developed. An important feature of this scheme is that the equation of continuity is solved directly. The residual field motions were simulated through an eddy viscosity model, while the large-scale field was obtained directly from the solution of the governing equations. An important portion of the initial velocity field was obtained from the solution of the linearized Navier-Stokes equations. The pseudospectral method was used for numerical differentiation in the horizontal directions, and second-order finite-difference schemes were used in the direction normal to the walls. The large eddy simulation technique is capable of reproducing some of the important features of wall-bounded turbulent flows. The resolvable portions of the root-mean square wall pressure fluctuations, pressure velocity-gradient correlations, and velocity pressure-gradient correlations are documented.

Nature-inspired micro-fluidic manipulation using artificial cilia

NASA Astrophysics Data System (ADS)

den Toonder, Jaap; de Goede, Judith; Khatavkar, Vinayak; Anderson, Patrick

2006-11-01

One particular micro-fluidics manipulation mechanism ``designed'' by nature is that due to a covering of beating cilia over the external surface of micro-organisms (e.g. Paramecium). A cilium can be viewed as a small hair or flexible rod (in protozoa: typical length 10 μm and diameter 0.1 μm) which is attached to the surface. We have developed polymer micro-actuators, made with standard micro-technology processing, which respond to an applied electrical or magnetic field by changing their shape. The shape and size of the polymer actuators mimics that of cilia occurring in nature. We have shown experimentally that, indeed, our artificial cilia can induce significant flow velocities of at least 75 μm/s in a fluid with a viscosity of 10 mPas. In this paper we will give an overview of our activities in developing the polymer actuators and the corresponding technology, show experimental and numerical fluid flow results, and finally assess the feasibility of applying this new and attractive micro-fluidic actuation method in functional biosensors.

Effect of artificially lengthened vocal tract on vocal fold oscillation's fundamental frequency.

PubMed

Hanamitsu, Masakazu; Kataoka, Hideyuki

2004-06-01

The fundamental frequency of vocal fold oscillation (F(0)) is controlled by laryngeal mechanics and aerodynamic properties. F(0) change per unit change of transglottal pressure (dF/dP) using a shutter valve has been studied and found to have nonlinear, V-shaped relationship with F(0). On the other hand, the vocal tract is also known to affect vocal fold oscillation. This study examined the effect of artificially lengthened vocal tract length on dF/dP. dF/dP was measured in six men using two mouthpieces of different lengths. The dF/dP graph for the longer vocal tract was shifted leftward relative to the shorter one. Using the one-mass model, the nadir of the "V" on the dF/dP graph was strongly influenced by the resonance around the first formant frequency. However, a more precise model is needed to account for the effects of viscosity and turbulence.

CAS2D: FORTRAN program for nonrotating blade-to-blade, steady, potential transonic cascade flows

NASA Technical Reports Server (NTRS)

Dulikravich, D. S.

1980-01-01

An exact, full-potential-equation (FPE) model for the steady, irrotational, homentropic and homoenergetic flow of a compressible, homocompositional, inviscid fluid through two dimensional planar cascades of airfoils was derived, together with its appropriate boundary conditions. A computer program, CAS2D, was developed that numerically solves an artificially time-dependent form of the actual FPE. The governing equation was discretized by using type-dependent, rotated finite differencing and the finite area technique. The flow field was discretized by providing a boundary-fitted, nonuniform computational mesh. The mesh was generated by using a sequence of conforming mapping, nonorthogonal coordinate stretching, and local, isoparametric, bilinear mapping functions. The discretized form of the FPE was solved iteratively by using successive line overrelaxation. The possible isentropic shocks were correctly captured by adding explicitly an artificial viscosity in a conservative form. In addition, a three-level consecutive, mesh refinement feature makes CAS2D a reliable and fast algorithm for the analysis of transonic, two dimensional cascade flows.

Correlation of individual differences in audiovisual asynchrony across stimuli and tasks: New constraints on temporal renormalization theory.

PubMed

Ipser, Alberta; Karlinski, Maayan; Freeman, Elliot D

2018-05-07

Sight and sound are out of synch in different people by different amounts for different tasks. But surprisingly, different concurrent measures of perceptual asynchrony correlate negatively (Freeman et al., 2013). Thus, if vision subjectively leads audition in one individual, the same individual might show a visual lag in other measures of audiovisual integration (e.g., McGurk illusion, Stream-Bounce illusion). This curious negative correlation was first observed between explicit temporal order judgments and implicit phoneme identification tasks, performed concurrently as a dual task, using incongruent McGurk stimuli. Here we used a new set of explicit and implicit tasks and congruent stimuli, to test whether this negative correlation persists across testing sessions, and whether it might be an artifact of using specific incongruent stimuli. None of these manipulations eliminated the negative correlation between explicit and implicit measures. This supports the generalizability and validity of the phenomenon, and offers new theoretical insights into its explanation. Our previously proposed "temporal renormalization" theory assumes that the timings of sensory events registered within the brain's different multimodal subnetworks are each perceived relative to a representation of the typical average timing of such events across the wider network. Our new data suggest that this representation is stable and generic, rather than dependent on specific stimuli or task contexts, and that it may be acquired through experience with a variety of simultaneous stimuli. Our results also add further evidence that speech comprehension may be improved in some individuals by artificially delaying voices relative to lip-movements. (PsycINFO Database Record (c) 2018 APA, all rights reserved).

Asymptotic analysis of discrete schemes for non-equilibrium radiation diffusion

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cui, Xia, E-mail: cui_xia@iapcm.ac.cn; Yuan, Guang-wei; Shen, Zhi-jun

Motivated by providing well-behaved fully discrete schemes in practice, this paper extends the asymptotic analysis on time integration methods for non-equilibrium radiation diffusion in [2] to space discretizations. Therein studies were carried out on a two-temperature model with Larsen's flux-limited diffusion operator, both the implicitly balanced (IB) and linearly implicit (LI) methods were shown asymptotic-preserving. In this paper, we focus on asymptotic analysis for space discrete schemes in dimensions one and two. First, in construction of the schemes, in contrast to traditional first-order approximations, asymmetric second-order accurate spatial approximations are devised for flux-limiters on boundary, and discrete schemes with second-ordermore » accuracy on global spatial domain are acquired consequently. Then by employing formal asymptotic analysis, the first-order asymptotic-preserving property for these schemes and furthermore for the fully discrete schemes is shown. Finally, with the help of manufactured solutions, numerical tests are performed, which demonstrate quantitatively the fully discrete schemes with IB time evolution indeed have the accuracy and asymptotic convergence as theory predicts, hence are well qualified for both non-equilibrium and equilibrium radiation diffusion. - Highlights: • Provide AP fully discrete schemes for non-equilibrium radiation diffusion. • Propose second order accurate schemes by asymmetric approach for boundary flux-limiter. • Show first order AP property of spatially and fully discrete schemes with IB evolution. • Devise subtle artificial solutions; verify accuracy and AP property quantitatively. • Ideas can be generalized to 3-dimensional problems and higher order implicit schemes.« less

Learning implicit brain MRI manifolds with deep learning

NASA Astrophysics Data System (ADS)

Bermudez, Camilo; Plassard, Andrew J.; Davis, Larry T.; Newton, Allen T.; Resnick, Susan M.; Landman, Bennett A.

2018-03-01

An important task in image processing and neuroimaging is to extract quantitative information from the acquired images in order to make observations about the presence of disease or markers of development in populations. Having a low-dimensional manifold of an image allows for easier statistical comparisons between groups and the synthesis of group representatives. Previous studies have sought to identify the best mapping of brain MRI to a low-dimensional manifold, but have been limited by assumptions of explicit similarity measures. In this work, we use deep learning techniques to investigate implicit manifolds of normal brains and generate new, high-quality images. We explore implicit manifolds by addressing the problems of image synthesis and image denoising as important tools in manifold learning. First, we propose the unsupervised synthesis of T1-weighted brain MRI using a Generative Adversarial Network (GAN) by learning from 528 examples of 2D axial slices of brain MRI. Synthesized images were first shown to be unique by performing a cross-correlation with the training set. Real and synthesized images were then assessed in a blinded manner by two imaging experts providing an image quality score of 1-5. The quality score of the synthetic image showed substantial overlap with that of the real images. Moreover, we use an autoencoder with skip connections for image denoising, showing that the proposed method results in higher PSNR than FSL SUSAN after denoising. This work shows the power of artificial networks to synthesize realistic imaging data, which can be used to improve image processing techniques and provide a quantitative framework to structural changes in the brain.

Numerical Simulations of Hypersonic Boundary Layer Transition

NASA Astrophysics Data System (ADS)

Bartkowicz, Matthew David

Numerical schemes for supersonic flows tend to use large amounts of artificial viscosity for stability. This tends to damp out the small scale structures in the flow. Recently some low-dissipation methods have been proposed which selectively eliminate the artificial viscosity in regions which do not require it. This work builds upon the low-dissipation method of Subbareddy and Candler which uses the flux vector splitting method of Steger and Warming but identifies the dissipation portion to eliminate it. Computing accurate fluxes typically relies on large grid stencils or coupled linear systems that become computationally expensive to solve. Unstructured grids allow for CFD solutions to be obtained on complex geometries, unfortunately, it then becomes difficult to create a large stencil or the coupled linear system. Accurate solutions require grids that quickly become too large to be feasible. In this thesis a method is proposed to obtain more accurate solutions using relatively local data, making it suitable for unstructured grids composed of hexahedral elements. Fluxes are reconstructed using local gradients to extend the range of data used. The method is then validated on several test problems. Simulations of boundary layer transition are then performed. An elliptic cone at Mach 8 is simulated based on an experiment at the Princeton Gasdynamics Laboratory. A simulated acoustic noise boundary condition is imposed to model the noisy conditions of the wind tunnel and the transitioning boundary layer observed. A computation of an isolated roughness element is done based on an experiment in Purdue's Mach 6 quiet wind tunnel. The mechanism for transition is identified as an instability in the upstream separation region and a comparison is made to experimental data. In the CFD a fully turbulent boundary layer is observed downstream.

A Semi-implicit Method for Resolution of Acoustic Waves in Low Mach Number Flows

NASA Astrophysics Data System (ADS)

Wall, Clifton; Pierce, Charles D.; Moin, Parviz

2002-09-01

A semi-implicit numerical method for time accurate simulation of compressible flow is presented. By extending the low Mach number pressure correction method, a Helmholtz equation for pressure is obtained in the case of compressible flow. The method avoids the acoustic CFL limitation, allowing a time step restricted only by the convective velocity, resulting in significant efficiency gains. Use of a discretization that is centered in both time and space results in zero artificial damping of acoustic waves. The method is attractive for problems in which Mach numbers are low, and the acoustic waves of most interest are those having low frequency, such as acoustic combustion instabilities. Both of these characteristics suggest the use of time steps larger than those allowable by an acoustic CFL limitation. In some cases it may be desirable to include a small amount of numerical dissipation to eliminate oscillations due to small-wavelength, high-frequency, acoustic modes, which are not of interest; therefore, a provision for doing this in a controlled manner is included in the method. Results of the method for several model problems are presented, and the performance of the method in a large eddy simulation is examined.

Implicitly defined criteria for vector optimization in technological process of hydroponic germination of wheat grain

NASA Astrophysics Data System (ADS)

Koneva, M. S.; Rudenko, O. V.; Usatikov, S. V.; Bugaets, N. A.; Tereshchenko, I. V.

2018-05-01

To reduce the duration of the process and to ensure the microbiological purity of the germinated material, an improved method of germination has been developed based on the complex use of physical factors: electrochemically activated water (ECHA-water), electromagnetic field of extremely low frequencies (EMF ELF) with round-the-clock artificial illumination by LED lamps. The increase in the efficiency of the "numerical" technology for solving computational problems of parametric optimization of the technological process of hydroponic germination of wheat grains is considered. In this situation, the quality criteria are contradictory and part of them is given by implicit functions of many variables. A solution algorithm is offered without the construction of a Pareto set in which a relatively small number of elements of a set of alternatives is used to obtain a linear convolution of the criteria with given weights, normalized to their "ideal" values from the solution of the problems of single-criterion private optimizations. The use of the proposed mathematical models describing the processes of hydroponic germination of wheat grains made it possible to intensify the germination process and to shorten the time of obtaining wheat sprouts "Altayskaya 105" for 27 hours.

The relationship between the structural mere exposure effect and the implicit learning process.

PubMed

Newell, B R; Bright, J E

2001-11-01

Three experiments are reported that investigate the relationship between the structural mere exposure effect (SMEE) and implicit learning in an artificial grammar task. Subjects were presented with stimuli generated from a finite-state grammar and were asked to memorize them. In a subsequent test phase subjects were required first to rate how much they liked novel items, and second whether or not they thought items conformed to the rules of the grammar. A small but consistent effect of grammaticality was found on subjects' liking ratings (a "structural mere exposure effect") in all three experiments, but only when encoding and testing conditions were consistent. A change in the surface representation of stimuli between encoding and test (Experiment 1), memorizing fragments of items and being tested on whole items (Experiment 2), and a mismatch of processing operations between encoding and test (Experiment 3) all removed the SMEE. In contrast, the effect of grammaticality on rule judgements remained intact in the face of all three manipulations. It is suggested that rule judgements reflect attempts to explicitly recall information about training items, whereas the SMEE can be explained in terms of an attribution of processing fluency.

A hypothetical neurological association between dehumanization and human rights abuses.

PubMed

Murrow, Gail B; Murrow, Richard

2015-07-01

Dehumanization is anecdotally and historically associated with reduced empathy for the pain of dehumanized individuals and groups and with psychological and legal denial of their human rights and extreme violence against them. We hypothesize that 'empathy' for the pain and suffering of dehumanized social groups is automatically reduced because, as the research we review suggests, an individual's neural mechanisms of pain empathy best respond to (or produce empathy for) the pain of people whom the individual automatically or implicitly associates with her or his own species. This theory has implications for the philosophical conception of 'human' and of 'legal personhood' in human rights jurisprudence. It further has implications for First Amendment free speech jurisprudence, including the doctrine of 'corporate personhood' and consideration of the potential harm caused by dehumanizing hate speech. We suggest that the new, social neuroscience of empathy provides evidence that both the vagaries of the legal definition or legal fiction of 'personhood' and hate speech that explicitly and implicitly dehumanizes may (in their respective capacities to artificially humanize or dehumanize) manipulate the neural mechanisms of pain empathy in ways that could pose more of a true threat to human rights and rights-based democracy than previously appreciated.

Using Tranformation Group Priors and Maximum Relative Entropy for Bayesian Glaciological Inversions

NASA Astrophysics Data System (ADS)

Arthern, R. J.; Hindmarsh, R. C. A.; Williams, C. R.

2014-12-01

One of the key advances that has allowed better simulations of the large ice sheets of Greenland and Antarctica has been the use of inverse methods. These have allowed poorly known parameters such as the basal drag coefficient and ice viscosity to be constrained using a wide variety of satellite observations. Inverse methods used by glaciologists have broadly followed one of two related approaches. The first is minimization of a cost function that describes the misfit to the observations, often accompanied by some kind of explicit or implicit regularization that promotes smallness or smoothness in the inverted parameters. The second approach is a probabilistic framework that makes use of Bayes' theorem to update prior assumptions about the probability of parameters, making use of data with known error estimates. Both approaches have much in common and questions of regularization often map onto implicit choices of prior probabilities that are made explicit in the Bayesian framework. In both approaches questions can arise that seem to demand subjective input. What should the functional form of the cost function be if there are alternatives? What kind of regularization should be applied, and how much? How should the prior probability distribution for a parameter such as basal slipperiness be specified when we know so little about the details of the subglacial environment? Here we consider some approaches that have been used to address these questions and discuss ways that probabilistic prior information used for regularizing glaciological inversions might be specified with greater objectivity.

Recycling ground granulated blast furnace slag as cold bonded artificial aggregate partially used in self-compacting concrete.

PubMed

Gesoğlu, Mehmet; Güneyisi, Erhan; Mahmood, Swara Fuad; Öz, Hatice Öznur; Mermerdaş, Kasım

2012-10-15

Ground granulated blast furnace slag (GGBFS), a by-product from iron industry, was recycled as artificial coarse aggregate through cold bonding pelletization process. The artificial slag aggregates (ASA) replaced partially the natural coarse aggregates in production of self-compacting concrete (SCC). Moreover, as being one of the most widely used mineral admixtures in concrete industry, fly ash (FA) was incorporated as a part of total binder content to impart desired fluidity to SCCs. A total of six concrete mixtures having various ASA replacement levels (0%, 20%, 40%, 60%, and 100%) were designed with a water-to-binder (w/b) ratio of 0.32. Fresh properties of self-compacting concretes (SCC) were observed through slump flow time, flow diameter, V-funnel flow time, and L-box filling height ratio. Compressive strength of hardened SCCs was also determined at 28 days of curing. It was observed that increasing the replacement level of ASA resulted in decrease in the amount of superplasticizer to achieve a constant slump flow diameter. Moreover, passing ability and viscosity of SCC's enhanced with increasing the amount of ASA in the concrete. The maximum compressive strength was achieved for the SCC having 60% ASA replacement. Copyright © 2012 Elsevier B.V. All rights reserved.

Development of Artificial Neural Network Model for Diesel Fuel Properties Prediction using Vibrational Spectroscopy.

PubMed

Bolanča, Tomislav; Marinović, Slavica; Ukić, Sime; Jukić, Ante; Rukavina, Vinko

2012-06-01

This paper describes development of artificial neural network models which can be used to correlate and predict diesel fuel properties from several FTIR-ATR absorbances and Raman intensities as input variables. Multilayer feed forward and radial basis function neural networks have been used to rapid and simultaneous prediction of cetane number, cetane index, density, viscosity, distillation temperatures at 10% (T10), 50% (T50) and 90% (T90) recovery, contents of total aromatics and polycyclic aromatic hydrocarbons of commercial diesel fuels. In this study two-phase training procedures for multilayer feed forward networks were applied. While first phase training algorithm was constantly the back propagation one, two second phase training algorithms were varied and compared, namely: conjugate gradient and quasi Newton. In case of radial basis function network, radial layer was trained using K-means radial assignment algorithm and three different radial spread algorithms: explicit, isotropic and K-nearest neighbour. The number of hidden layer neurons and experimental data points used for the training set have been optimized for both neural networks in order to insure good predictive ability by reducing unnecessary experimental work. This work shows that developed artificial neural network models can determine main properties of diesel fuels simultaneously based on a single and fast IR or Raman measurement.

Microstructures of superhydrophobic plant leaves - inspiration for efficient oil spill cleanup materials.

PubMed

Zeiger, Claudia; Rodrigues da Silva, Isabelle C; Mail, Matthias; Kavalenka, Maryna N; Barthlott, Wilhelm; Hölscher, Hendrik

2016-08-16

The cleanup of accidental oil spills in water is an enormous challenge; conventional oil sorbents absorb large amounts of water in addition to oil and other cleanup methods can cause secondary pollution. In contrast, fresh leaves of the aquatic ferns Salvinia are superhydrophobic and superoleophilic, and can selectively absorb oil while repelling water. These selective wetting properties are optimal for natural oil absorbent applications and bioinspired oil sorbent materials. In this paper we quantify the oil absorption capacity of four Salvinia species with different surface structures, water lettuce (Pistia stratiotes) and Lotus leaves (Nelumbo nucifera), and compare their absorption capacity to artificial oil sorbents. Interestingly, the oil absorption capacities of Salvinia molesta and Pistia stratiotes leaves are comparable to artificial oil sorbents. Therefore, these pantropical invasive plants, often considered pests, qualify as environmentally friendly materials for oil spill cleanup. Furthermore, we investigated the influence of oil density and viscosity on the oil absorption, and examine how the presence and morphology of trichomes affect the amount of oil absorbed by their surfaces. Specifically, the influence of hair length and shape is analyzed by comparing different hair types ranging from single trichomes of Salvinia cucullata to complex eggbeater-shaped trichomes of Salvinia molesta to establish a basis for improving artificial bioinspired oil absorbents.

The upwind control volume scheme for unstructured triangular grids

NASA Technical Reports Server (NTRS)

Giles, Michael; Anderson, W. Kyle; Roberts, Thomas W.

1989-01-01

A new algorithm for the numerical solution of the Euler equations is presented. This algorithm is particularly suited to the use of unstructured triangular meshes, allowing geometric flexibility. Solutions are second-order accurate in the steady state. Implementation of the algorithm requires minimal grid connectivity information, resulting in modest storage requirements, and should enhance the implementation of the scheme on massively parallel computers. A novel form of upwind differencing is developed, and is shown to yield sharp resolution of shocks. Two new artificial viscosity models are introduced that enhance the performance of the new scheme. Numerical results for transonic airfoil flows are presented, which demonstrate the performance of the algorithm.

The SPH consistency problem and some astrophysical applications

NASA Astrophysics Data System (ADS)

Klapp, Jaime; Sigalotti, Leonardo; Rendon, Otto; Gabbasov, Ruslan; Torres, Ayax

2017-11-01

We discuss the SPH kernel and particle consistency problem and demonstrate that SPH has a limiting second-order convergence rate. We also present a solution to the SPH consistency problem. We present examples of how SPH implementations that are not mathematically consistent may lead to erroneous results. The new formalism has been implemented into the Gadget 2 code, including an improved scheme for the artificial viscosity. We present results for the ``Standard Isothermal Test Case'' of gravitational collapse and fragmentation of protostellar molecular cores that produce a very different evolution than with the standard SPH theory. A further application of accretion onto a black hole is presented.

Scaling in two-fluid pinch-off

NASA Astrophysics Data System (ADS)

Pommer, Chris; Harris, Michael; Basaran, Osman

2010-11-01

The physics of two-fluid pinch-off, which arises whenever drops, bubbles, or jets of one fluid are ejected from a nozzle into another fluid, is scientifically important and technologically relevant. While the breakup of a drop in a passive environment is well understood, the physics of pinch-off when both the inner and outer fluids are dynamically active remains inadequately understood. Here, the breakup of a compound jet whose core and shell are incompressible Newtonian fluids is analyzed computationally when the interior is a "bubble" and the exterior is a liquid. The numerical method employed is an implicit method of lines ALE algorithm which uses finite elements with elliptic mesh generation and adaptive finite differences for time integration. Thus, the new approach neither starts with a priori idealizations, as has been the case with previous computations, nor is limited to length scales above that set by the wavelength of visible light as in any experimental study. In particular, three distinct responses are identified as the ratio m of the outer fluid's viscosity to the inner fluid's viscosity is varied. For small m, simulations show that the minimum neck radius r initially scales with time τ before breakup as r ˜0.58° (in accord with previous experiments and inviscid fluid models) but that r ˜τ once r becomes sufficiently small. For intermediate and large values of m, r ˜&αcirc;, where the exponent α may not equal one, once again as r becomes sufficiently small.

Spermatozoa scattering by a microchannel feature: an elastohydrodynamic model

PubMed Central

Montenegro-Johnson, T. D.; Gadêlha, H.; Smith, D. J.

2015-01-01

Sperm traverse their microenvironment through viscous fluid by propagating flagellar waves; the waveform emerges as a consequence of elastic structure, internal active moments and low Reynolds number fluid dynamics. Engineered microchannels have recently been proposed as a method of sorting and manipulating motile cells; the interaction of cells with these artificial environments therefore warrants investigation. A numerical method is presented for large-amplitude elastohydrodynamic interaction of active swimmers with domain features. This method is employed to examine hydrodynamic scattering by a model microchannel backstep feature. Scattering is shown to depend on backstep height and the relative strength of viscous and elastic forces in the flagellum. In a ‘high viscosity’ parameter regime corresponding to human sperm in cervical mucus analogue, this hydrodynamic contribution to scattering is comparable in magnitude to recent data on contact effects, being of the order of 5°–10°. Scattering can be positive or negative depending on the relative strength of viscous and elastic effects, emphasizing the importance of viscosity on the interaction of sperm with their microenvironment. The modulation of scattering angle by viscosity is associated with variations in flagellar asymmetry induced by the elastohydrodynamic interaction with the boundary feature. PMID:26064617

Ion selectivity of the Vibrio alginolyticus flagellar motor.

PubMed Central

Liu, J Z; Dapice, M; Khan, S

1990-01-01

The marine bacterium, Vibrio alginolyticus, normally requires sodium for motility. We found that lithium will substitute for sodium. In neutral pH buffers, the membrane potential and swimming speed of glycolyzing bacteria reached maximal values as sodium or lithium concentration was increased. While the maximal potentials obtained in the two cations were comparable, the maximal swimming speed was substantially lower in lithium. Over a wide range of sodium concentration, the bacteria maintained an invariant sodium electrochemical potential as determined by membrane potential and intracellular sodium measurements. Over this range the increase of swimming speed took Michaelis-Menten form. Artificial energization of swimming motility required imposition of a voltage difference in concert with a sodium pulse. The cation selectivity and concentration dependence exhibited by the motile apparatus depended on the viscosity of the medium. In high-viscosity media, swimming speeds were relatively independent of either ion type or concentration. These facts parallel and extend observations of the swimming behavior of bacteria propelled by proton-powered flagella. In particular, they show that ion transfers limit unloaded motor speed in this bacterium and imply that the coupling between ion transfers and force generation must be fairly tight. PMID:2394685

The cerebellum does more than sensory prediction error-based learning in sensorimotor adaptation tasks.

PubMed

Butcher, Peter A; Ivry, Richard B; Kuo, Sheng-Han; Rydz, David; Krakauer, John W; Taylor, Jordan A

2017-09-01

Individuals with damage to the cerebellum perform poorly in sensorimotor adaptation paradigms. This deficit has been attributed to impairment in sensory prediction error-based updating of an internal forward model, a form of implicit learning. These individuals can, however, successfully counter a perturbation when instructed with an explicit aiming strategy. This successful use of an instructed aiming strategy presents a paradox: In adaptation tasks, why do individuals with cerebellar damage not come up with an aiming solution on their own to compensate for their implicit learning deficit? To explore this question, we employed a variant of a visuomotor rotation task in which, before executing a movement on each trial, the participants verbally reported their intended aiming location. Compared with healthy control participants, participants with spinocerebellar ataxia displayed impairments in both implicit learning and aiming. This was observed when the visuomotor rotation was introduced abruptly ( experiment 1 ) or gradually ( experiment 2 ). This dual deficit does not appear to be related to the increased movement variance associated with ataxia: Healthy undergraduates showed little change in implicit learning or aiming when their movement feedback was artificially manipulated to produce similar levels of variability ( experiment 3 ). Taken together the results indicate that a consequence of cerebellar dysfunction is not only impaired sensory prediction error-based learning but also a difficulty in developing and/or maintaining an aiming solution in response to a visuomotor perturbation. We suggest that this dual deficit can be explained by the cerebellum forming part of a network that learns and maintains action-outcome associations across trials. NEW & NOTEWORTHY Individuals with cerebellar pathology are impaired in sensorimotor adaptation. This deficit has been attributed to an impairment in error-based learning, specifically, from a deficit in using sensory prediction errors to update an internal model. Here we show that these individuals also have difficulty in discovering an aiming solution to overcome their adaptation deficit, suggesting a new role for the cerebellum in sensorimotor adaptation tasks. Copyright © 2017 the American Physiological Society.

Electrospinning of Biocompatible Nanofibers

NASA Astrophysics Data System (ADS)

Coughlin, Andrew J.; Queen, Hailey A.; McCullen, Seth D.; Krause, Wendy E.

2006-03-01

Artificial scaffolds for growing cells can have a wide range of applications including wound coverings, supports in tissue cultures, drug delivery, and organ and tissue transplantation. Tissue engineering is a promising field which may resolve current problems with transplantation, such as rejection by the immune system and scarcity of donors. One approach to tissue engineering utilizes a biodegradable scaffold onto which cells are seeded and cultured, and ideally develop into functional tissue. The scaffold acts as an artificial extracellular matrix (ECM). Because a typical ECM contains collagen fibers with diameters of 50-500 nm, electrostatic spinning (electrospinning) was used to mimic the size and structure of these fibers. Electrospinning is a novel way of spinning a nonwoven web of fibers on the order of 100 nm, much like the web of collagen in an ECM. We are investigating the ability of several biocompatible polymers (e.g., chitosan and polyvinyl alcohol) to form defect-free nanofiber webs and are studying the influence of the zero shear rate viscosity, molecular weight, entanglement concentration, relaxation time, and solvent on the resulting fiber size and morphology.

A hypothetical neurological association between dehumanization and human rights abuses

PubMed Central

Murrow, Gail B.; Murrow, Richard

2015-01-01

Dehumanization is anecdotally and historically associated with reduced empathy for the pain of dehumanized individuals and groups and with psychological and legal denial of their human rights and extreme violence against them. We hypothesize that ‘empathy’ for the pain and suffering of dehumanized social groups is automatically reduced because, as the research we review suggests, an individual's neural mechanisms of pain empathy best respond to (or produce empathy for) the pain of people whom the individual automatically or implicitly associates with her or his own species. This theory has implications for the philosophical conception of ‘human’ and of ‘legal personhood’ in human rights jurisprudence. It further has implications for First Amendment free speech jurisprudence, including the doctrine of ‘corporate personhood’ and consideration of the potential harm caused by dehumanizing hate speech. We suggest that the new, social neuroscience of empathy provides evidence that both the vagaries of the legal definition or legal fiction of ‘personhood’ and hate speech that explicitly and implicitly dehumanizes may (in their respective capacities to artificially humanize or dehumanize) manipulate the neural mechanisms of pain empathy in ways that could pose more of a true threat to human rights and rights-based democracy than previously appreciated. PMID:27774198

Application of CFD to aerothermal heating problems

NASA Technical Reports Server (NTRS)

Macaraeg, M. G.

1986-01-01

Numerical solutions of the compressible Navier-Stokes equations by an alternating direction implicit scheme, applied to two experimental investigations are presented. The first is cooling by injection of a gas jet through the nose of an ogive-cone, and the second is the aerothermal environment in the gap formed by the wing and elevon section of a test model of the space shuttle. The simulations demonstrate that accurate pressure calculations are easily obtained on a coarse grid, while convergence is obtained after the residual reduces by four orders of magnitude. Accurate heating rates, however, require a fine grid solution, with convergence requiring at least a reduction of six orders of magnitude in the residual. The effect of artificial dissipation on numerical results is also assessed.

Finite area method for nonlinear supersonic conical flows

NASA Technical Reports Server (NTRS)

Sritharan, S. S.; Seebass, A. R.

1983-01-01

A fully conservative numerical method for the computation of steady inviscid supersonic flow about general conical bodies at incidence is described. The procedure utilizes the potential approximation and implements a body conforming mesh generator. The conical potential is assumed to have its best linear variation inside each mesh cell; a secondary interlocking cell system is used to establish the flux balance required to conserve mass. In the supersonic regions the scheme is symmetrized by adding artificial viscosity in conservation form. The algorithm is nearly an order of a magnitude faster than present Euler methods and predicts known results accurately and qualitative features such as nodal point lift off correctly. Results are compared with those of other investigators.

Finite area method for nonlinear conical flows

NASA Technical Reports Server (NTRS)

Sritharan, S. S.; Seebass, A. R.

1982-01-01

A fully conservative finite area method for the computation of steady inviscid flow about general conical bodies at incidence is described. The procedure utilizes the potential approximation and implements a body conforming mesh generator. The conical potential is assumed to have its best linear variation inside each mesh cell and a secondary interlocking cell system is used to establish the flux balance required to conserve mass. In the supersonic regions the scheme is desymmetrized by adding appropriate artificial viscosity in conservation form. The algorithm is nearly an order of a magnitude faster than present Euler methods and predicts known results accurately and qualitative features such as nodal point lift off correctly. Results are compared with those of other investigations.

MHD Turbulence, div B = 0 and Lattice Boltzmann Simulations

NASA Astrophysics Data System (ADS)

Phillips, Nate; Keating, Brian; Vahala, George; Vahala, Linda

2006-10-01

The question of div B = 0 in MHD simulations is a crucial issue. Here we consider lattice Boltzmann simulations for MHD (LB-MHD). One introduces a scalar distribution function for the velocity field and a vector distribution function for the magnetic field. This asymmetry is due to the different symmetries in the tensors arising in the time evolution of these fields. The simple algorithm of streaming and local collisional relaxation is ideally parallelized and vectorized -- leading to the best sustained performance/PE of any code run on the Earth Simulator. By reformulating the BGK collision term, a simple implicit algorithm can be immediately transformed into an explicit algorithm that permits simulations at quite low viscosity and resistivity. However the div B is not an imposed constraint. Currently we are examining a new formulations of LB-MHD that impose the div B constraint -- either through an entropic like formulation or by introducing forcing terms into the momentum equations and permitting simpler forms of relaxation distributions.

Computational and Experimental Flow Field Analyses of Separate Flow Chevron Nozzles and Pylon Interaction

NASA Technical Reports Server (NTRS)

Massey, Steven J.; Thomas, Russell H.; AbdolHamid, Khaled S.; Elmiligui, Alaa A.

2003-01-01

A computational and experimental flow field analyses of separate flow chevron nozzles is presented. The goal of this study is to identify important flow physics and modeling issues required to provide highly accurate flow field data which will later serve as input to the Jet3D acoustic prediction code. Four configurations are considered: a baseline round nozzle with and without a pylon, and a chevron core nozzle with and without a pylon. The flow is simulated by solving the asymptotically steady, compressible, Reynolds-averaged Navier-Stokes equations using an implicit, up-wind, flux-difference splitting finite volume scheme and standard two-equation kappa-epsilon turbulence model with a linear stress representation and the addition of a eddy viscosity dependence on total temperature gradient normalized by local turbulence length scale. The current CFD results are seen to be in excellent agreement with Jet Noise Lab data and show great improvement over previous computations which did not compensate for enhanced mixing due to high temperature gradients.

Improved Boundary Layer Module (BLM) for the Solid Performance Program (SPP)

NASA Astrophysics Data System (ADS)

Coats, D. E.; Cebeci, T.

1982-03-01

The requirements for a replacement to the Bartz boundary layer code, the standard method of computing the performance loss due to viscous effects by the solid performance program, were discussed by the propulsion community along with four nationally recognized boundary layer experts. A consensus was reached regarding the preferred features for the analysis of the replacement code. The major points that were agreed upon are: (1) finite difference methods are preferred over integral methods; (2) a single equation eddy viscosity model was considered to be adequate for the purpose of computing performance loss; (3) a variable grid capability in both coordinate directions would be required; (4) a proven finite difference algorithm which is not stability restricted should be used, that is, an implicit numerical scheme would be required; and (5) the replacement code should be able to compute both turbulent and laminar flows. The program should treat mass addition at the wall as well as being able to calculate a stagnation point starting line.

A numerical method for computing unsteady 2-D boundary layer flows

NASA Technical Reports Server (NTRS)

Krainer, Andreas

1988-01-01

A numerical method for computing unsteady two-dimensional boundary layers in incompressible laminar and turbulent flows is described and applied to a single airfoil changing its incidence angle in time. The solution procedure adopts a first order panel method with a simple wake model to solve for the inviscid part of the flow, and an implicit finite difference method for the viscous part of the flow. Both procedures integrate in time in a step-by-step fashion, in the course of which each step involves the solution of the elliptic Laplace equation and the solution of the parabolic boundary layer equations. The Reynolds shear stress term of the boundary layer equations is modeled by an algebraic eddy viscosity closure. The location of transition is predicted by an empirical data correlation originating from Michel. Since transition and turbulence modeling are key factors in the prediction of viscous flows, their accuracy will be of dominant influence to the overall results.

Computer program for solving laminar, transitional, or turbulent compressible boundary-layer equations for two-dimensional and axisymmetric flow

NASA Technical Reports Server (NTRS)

Harris, J. E.; Blanchard, D. K.

1982-01-01

A numerical algorithm and computer program are presented for solving the laminar, transitional, or turbulent two dimensional or axisymmetric compressible boundary-layer equations for perfect-gas flows. The governing equations are solved by an iterative three-point implicit finite-difference procedure. The software, program VGBLP, is a modification of the approach presented in NASA TR R-368 and NASA TM X-2458, respectively. The major modifications are: (1) replacement of the fourth-order Runge-Kutta integration technique with a finite-difference procedure for numerically solving the equations required to initiate the parabolic marching procedure; (2) introduction of the Blottner variable-grid scheme; (3) implementation of an iteration scheme allowing the coupled system of equations to be converged to a specified accuracy level; and (4) inclusion of an iteration scheme for variable-entropy calculations. These modifications to the approach presented in NASA TR R-368 and NASA TM X-2458 yield a software package with high computational efficiency and flexibility. Turbulence-closure options include either two-layer eddy-viscosity or mixing-length models. Eddy conductivity is modeled as a function of eddy viscosity through a static turbulent Prandtl number formulation. Several options are provided for specifying the static turbulent Prandtl number. The transitional boundary layer is treated through a streamwise intermittency function which modifies the turbulence-closure model. This model is based on the probability distribution of turbulent spots and ranges from zero to unity for laminar and turbulent flow, respectively. Several test cases are presented as guides for potential users of the software.

A comparison of artificial compressibility and fractional step methods for incompressible flow computations

NASA Technical Reports Server (NTRS)

Chan, Daniel C.; Darian, Armen; Sindir, Munir

1992-01-01

We have applied and compared the efficiency and accuracy of two commonly used numerical methods for the solution of Navier-Stokes equations. The artificial compressibility method augments the continuity equation with a transient pressure term and allows one to solve the modified equations as a coupled system. Due to its implicit nature, one can have the luxury of taking a large temporal integration step at the expense of higher memory requirement and larger operation counts per step. Meanwhile, the fractional step method splits the Navier-Stokes equations into a sequence of differential operators and integrates them in multiple steps. The memory requirement and operation count per time step are low, however, the restriction on the size of time marching step is more severe. To explore the strengths and weaknesses of these two methods, we used them for the computation of a two-dimensional driven cavity flow with Reynolds number of 100 and 1000, respectively. Three grid sizes, 41 x 41, 81 x 81, and 161 x 161 were used. The computations were considered after the L2-norm of the change of the dependent variables in two consecutive time steps has fallen below 10(exp -5).

Time course of changes in tear meniscus radius and blink rate after instillation of artificial tears.

PubMed

Bandlitz, Stefan; Purslow, Christine; Murphy, Paul J; Pult, Heiko

2014-08-26

Using a novel digital meniscometer (PDM), alterations in tear meniscus radius (TMR) were measured simultaneously with blink rate (BR) following the instillation of artificial tears. Central TMR and BR of 22 subjects (11 male and 11 female; mean age, 24.3 ± 2.6 SD years) were measured at baseline, and 0, 1, 5, 10, and 30 minutes after instillation of an artificial tear containing hydroxypropyl-guar and glycol (SYS) or saline (SAL). A dose of 35 μL was applied in one eye in a randomized order with a washout period between each drop. For SAL, compared to baseline TMR (0.33 ± 0.08 mm), TMR significantly increased with drop instillation (1.55 ± 0.69 mm) and at 1 minute (0.66 ± 0.36 mm; P < 0.05), but returned to baseline after 5 minutes. For SYS, TMR (0.32 ± 0.07 mm) remained significantly increased after application (1.62 ± 0.81 mm), and at 1 minute (0.81 ± 0.43 mm) and 5 minutes (0.39 ± 0.08 mm; P < 0.05). Compared to baseline BR with SAL (14.8 ± 7.7) and SYS (14.9 ± 9.4), values were significantly increased upon drop instillation (22.5 ± 11.8; 21.3 ± 11.8; P < 0.05), but returned to baseline after 1 minute. Dry eye symptoms were correlated with baseline BR (r = 0.550, P = 0.008). Results indicate that PDM can detect changes in TMR following instillation of artificial tears. Difference in residence time reflects the different viscosity of each drop. An overload with a large drop may result in an initially increased BR. Copyright 2014 The Association for Research in Vision and Ophthalmology, Inc.

Assessment of Beer Quality Based on a Robotic Pourer, Computer Vision, and Machine Learning Algorithms Using Commercial Beers.

PubMed

Gonzalez Viejo, Claudia; Fuentes, Sigfredo; Torrico, Damir D; Howell, Kate; Dunshea, Frank R

2018-05-01

Sensory attributes of beer are directly linked to perceived foam-related parameters and beer color. The aim of this study was to develop an objective predictive model using machine learning modeling to assess the intensity levels of sensory descriptors in beer using the physical measurements of color and foam-related parameters. A robotic pourer (RoboBEER), was used to obtain 15 color and foam-related parameters from 22 different commercial beer samples. A sensory session using quantitative descriptive analysis (QDA ® ) with trained panelists was conducted to assess the intensity of 10 beer descriptors. Results showed that the principal component analysis explained 64% of data variability with correlations found between foam-related descriptors from sensory and RoboBEER such as the positive and significant correlation between carbon dioxide and carbonation mouthfeel (R = 0.62), correlation of viscosity to sensory, and maximum volume of foam and total lifetime of foam (R = 0.75, R = 0.77, respectively). Using the RoboBEER parameters as inputs, an artificial neural network (ANN) regression model showed high correlation (R = 0.91) to predict the intensity levels of 10 related sensory descriptors such as yeast, grains and hops aromas, hops flavor, bitter, sour and sweet tastes, viscosity, carbonation, and astringency. This paper is a novel approach for food science using machine modeling techniques that could contribute significantly to rapid screenings of food and brewage products for the food industry and the implementation of Artificial Intelligence (AI). The use of RoboBEER to assess beer quality showed to be a reliable, objective, accurate, and less time-consuming method to predict sensory descriptors compared to trained sensory panels. Hence, this method could be useful as a rapid screening procedure to evaluate beer quality at the end of the production line for industry applications. © 2018 Institute of Food Technologists®.

Free-Lagrange methods for compressible hydrodynamics in two space dimensions

NASA Astrophysics Data System (ADS)

Crowley, W. E.

1985-03-01

Since 1970 a research and development program in Free-Lagrange methods has been active at Livermore. The initial steps were taken with incompressible flows for simplicity. Since then the effort has been concentrated on compressible flows with shocks in two space dimensions and time. In general, the line integral method has been used to evaluate derivatives and the artificial viscosity method has been used to deal with shocks. Basically, two Free-Lagrange formulations for compressible flows in two space dimensions and time have been tested and both will be described. In method one, all prognostic quantities were node centered and staggered in time. The artificial viscosity was zone centered. One mesh reconnection philosphy was that the mesh should be optimized so that nearest neighbors were connected together. Another was that vertex angles should tend toward equality. In method one, all mesh elements were triangles. In method two, both quadrilateral and triangular mesh elements are permitted. The mesh variables are staggered in space and time as suggested originally by Richtmyer and von Neumann. The mesh reconnection strategy is entirely different in method two. In contrast to the global strategy of nearest neighbors, we now have a more local strategy that reconnects in order to keep the integration time step above a user chosen threshold. An additional strategy reconnects in the vicinity of large relative fluid motions. Mesh reconnection consists of two parts: (1) the tools that permits nodes to be merged and quads to be split into triangles etc. and; (2) the strategy that dictates how and when to use the tools. Both tools and strategies change with time in a continuing effort to expand the capabilities of the method. New ideas are continually being tried and evaluated.

Numerical Modeling of a Vortex Stabilized Arcjet. Ph.D. Thesis, 1991 Final Report

NASA Technical Reports Server (NTRS)

Pawlas, Gary E.

1992-01-01

Arcjet thrusters are being actively considered for use in Earth orbit maneuvering applications. Experimental studies are currently the chief means of determining an optimal thruster configuration. Earlier numerical studies have failed to include all of the effects found in typical arcjets including complex geometries, viscosity, and swirling flow. Arcjet geometries are large area ratio converging nozzles with centerbodies in the subsonic portion of the nozzle. The nozzle walls serve as the anode while the centerbody functions as the cathode. Viscous effects are important because the Reynolds number, based on the throat radius, is typically less than 1,000. Experimental studies have shown that a swirl or circumferential velocity component stabilizes a constricted arc. This dissertation describes the equations governing flow through a constricted arcjet thruster. An assumption that the flowfield is in local thermodynamic equilibrium leads to a single fluid plasma temperature model. An order of magnitude analysis reveals the governing fluid mechanics equations are uncoupled from the electromagnetic field equations. A numerical method is developed to solve the governing fluid mechanics equations, the Thin Layer Navier-Stokes equations. A coordinate transformation is employed in deriving the governing equations to simplify the application of boundary conditions in complex geometries. An axisymmetric formulation is employed to include the swirl velocity component as well as the axial and radial velocity components. The numerical method is an implicit finite-volume technique and allows for large time steps to reach a converged steady-state solution. The inviscid fluxes are flux-split, and Gauss-Seidel line relaxation is used to accelerate convergence. Converging-diverging nozzles with exit-to-throat area ratios up to 100:1 and annular nozzles were examined. Quantities examined included Mach number and static wall pressure distributions, and oblique shock structures. As the level of swirl and viscosity in the flowfield increased the mass flow rate and thrust decreased. The technique was used to predict the flow through a typical arcjet thruster geometry. Results indicate swirl and viscosity play an important role in the complex geometry of an arcjet.

Numerical modeling of a vortex stabilized arcjet

NASA Astrophysics Data System (ADS)

Pawlas, Gary E.

1992-11-01

Arcjet thrusters are being actively considered for use in Earth orbit maneuvering applications. Experimental studies are currently the chief means of determining an optimal thruster configuration. Earlier numerical studies have failed to include all of the effects found in typical arcjets including complex geometries, viscosity, and swirling flow. Arcjet geometries are large area ratio converging nozzles with centerbodies in the subsonic portion of the nozzle. The nozzle walls serve as the anode while the centerbody functions as the cathode. Viscous effects are important because the Reynolds number, based on the throat radius, is typically less than 1,000. Experimental studies have shown that a swirl or circumferential velocity component stabilizes a constricted arc. This dissertation describes the equations governing flow through a constricted arcjet thruster. An assumption that the flowfield is in local thermodynamic equilibrium leads to a single fluid plasma temperature model. An order of magnitude analysis reveals the governing fluid mechanics equations are uncoupled from the electromagnetic field equations. A numerical method is developed to solve the governing fluid mechanics equations, the Thin Layer Navier-Stokes equations. A coordinate transformation is employed in deriving the governing equations to simplify the application of boundary conditions in complex geometries. An axisymmetric formulation is employed to include the swirl velocity component as well as the axial and radial velocity components. The numerical method is an implicit finite-volume technique and allows for large time steps to reach a converged steady-state solution. The inviscid fluxes are flux-split, and Gauss-Seidel line relaxation is used to accelerate convergence. Converging-diverging nozzles with exit-to-throat area ratios up to 100:1 and annular nozzles were examined. Quantities examined included Mach number and static wall pressure distributions, and oblique shock structures. As the level of swirl and viscosity in the flowfield increased the mass flow rate and thrust decreased.

A capillary viscometer designed for the characterization of biocompatible ferrofluids

NASA Astrophysics Data System (ADS)

Nowak, J.; Odenbach, S.

2016-08-01

Suspensions of magnetic nanoparticles are receiving a growing interest in biomedical research. These ferrofluids can, e.g., be used for the treatment of cancer, making use of the drug targeting principle or using an artificially induced heating. To enable a safe application the basic properties of the ferrofluids have to be well understood, including the viscosity of the fluids if an external magnetic field is applied. It is well known that the viscosity of ferrofluids rises if a magnetic field is applied, where the rise depends on shear rate and magnetic field strength. In case of biocompatible ferrofluids such investigations proved to be rather complicated as the experimental setup should be close to the actual application to allow justified predictions of the effects which have to be expected. Thus a capillary viscometer, providing a flow situation comparable to the flow in a blood vessel, has been designed. The glass capillary is exchangeable and different inner diameters can be used. The range of the shear rates has been adapted to the range found in the human organism. The application of an external magnetic field is enabled with two different coil setups covering the ranges of magnetic field strengths required on the one hand for a theoretical understanding of particle interaction and resulting changes in viscosity and on the other hand for values necessary for a potential biomedical application. The results show that the newly designed capillary viscometer is suitable to measure the magnetoviscous effect in biocompatible ferrofluids and that the results appear to be consistent with data measured with rotational rheometry. In addition, a strong change of the flow behaviour of a biocompatible ferrofluid was proven for ranges of the shear rate and the magnetic field strength expected for a potential biomedical application.

Three-Dimensional Incompressible Navier-Stokes Flow Computations about Complete Configurations Using a Multiblock Unstructured Grid Approach

NASA Technical Reports Server (NTRS)

Sheng, Chunhua; Hyams, Daniel G.; Sreenivas, Kidambi; Gaither, J. Adam; Marcum, David L.; Whitfield, David L.

2000-01-01

A multiblock unstructured grid approach is presented for solving three-dimensional incompressible inviscid and viscous turbulent flows about complete configurations. The artificial compressibility form of the governing equations is solved by a node-based, finite volume implicit scheme which uses a backward Euler time discretization. Point Gauss-Seidel relaxations are used to solve the linear system of equations at each time step. This work employs a multiblock strategy to the solution procedure, which greatly improves the efficiency of the algorithm by significantly reducing the memory requirements by a factor of 5 over the single-grid algorithm while maintaining a similar convergence behavior. The numerical accuracy of solutions is assessed by comparing with the experimental data for a submarine with stem appendages and a high-lift configuration.

Shear viscosity of a hadron gas and influence of resonance lifetimes on relaxation time

NASA Astrophysics Data System (ADS)

Rose, J.-B.; Torres-Rincon, J. M.; Schäfer, A.; Oliinychenko, D. R.; Petersen, H.

2018-05-01

We address a discrepancy between different computations of η /s (shear viscosity over entropy density) of hadronic matter. Substantial deviations of this coefficient are found between transport approaches mainly based on resonance propagation with finite lifetime and other (semianalytical) approaches with energy-dependent cross sections, where interactions do not introduce a timescale. We provide an independent extraction of this coefficient by using the newly developed SMASH (Simulating Many Accelerated Strongly interacting Hadrons) transport code, which is an example of a mainly resonance-based approach. We compare the results from SMASH with numerical solutions of the Boltzmann equation for simple systems using the Chapman-Enskog expansion, as well as previous results in the literature. Our conclusion is that the hadron interaction via resonance formation/decay strongly affects the transport properties of the system, resulting in significant differences in η /s with respect to other approaches where binary collisions dominate. We argue that the relaxation time of the system—which characterizes the shear viscosity—is determined by the interplay between the mean free time and the lifetime of resonances. We show how an artificial shortening of the resonance lifetimes, or the addition of a background elastic cross section nicely interpolate between the two discrepant results.

[Characteristics, stability and in vitro efficacy of cleaning products for contact lenses].

PubMed

Coiffard, L; Rivalland, P; De Roeck-Holtzhauer, Y

1995-01-01

We characterized some market products designed for cleaning contact lenses and we compared their properties to the main requirements of eye-washes. We performed several physicochemical controls including pH determination, viscosity with a Baume apparatus and the decreasing of the freezing point following the method described by the French Pharmacopea. In addition, we carried out certain analytical controls, concerning three active principles (thiomersal, chlorhexidin digluconate, hydrogen peroxide), at the opening of the different package and after accelerated aging. A microbiological control was performed when opening the product and after a simulation of a 5-day aging. We finally determined the efficacy of the products on four bacterial strains for tests and of deproteinizing products on artificial dust. The pH values obtained ranged from 4.0 (oxygenated water solutions) to 7.8. The viscosity was close to a water solution one. Contents in active substances were usually similar to those stated on the package. At opening, the bacteriological quality was excellent. But, the multidose package were highly contaminated when used. Finally decontaminating efficacy against some germs was very good for the products tested. The results obtained show that the rincing products best answer the eye-wash criteria taken as references. Their main disadvantage is their contamination in the case of multidose packaging.

A computational modeling approach for the characterization of mechanical properties of 3D alginate tissue scaffolds.

PubMed

Nair, K; Yan, K C; Sun, W

2008-01-01

Scaffold guided tissue engineering is an innovative approach wherein cells are seeded onto biocompatible and biodegradable materials to form 3-dimensional (3D) constructs that, when implanted in the body facilitate the regeneration of tissue. Tissue scaffolds act as artificial extracellular matrix providing the environment conducive for tissue growth. Characterization of scaffold properties is necessary to understand better the underlying processes involved in controlling cell behavior and formation of functional tissue. We report a computational modeling approach to characterize mechanical properties of 3D gellike biomaterial, specifically, 3D alginate scaffold encapsulated with cells. Alginate inherent nonlinearity and variations arising from minute changes in its concentration and viscosity make experimental evaluation of its mechanical properties a challenging and time consuming task. We developed an in silico model to determine the stress-strain relationship of alginate based scaffolds from experimental data. In particular, we compared the Ogden hyperelastic model to other hyperelastic material models and determined that this model was the most suitable to characterize the nonlinear behavior of alginate. We further propose a mathematical model that represents the alginate material constants in Ogden model as a function of concentrations and viscosity. This study demonstrates the model capability to predict mechanical properties of 3D alginate scaffolds.

An NPARC Turbulence Module with Wall Functions

NASA Technical Reports Server (NTRS)

Zhu, J.; Shih, T.-H.

1997-01-01

The turbulence module recently developed for the NPARC code has been extended to include wall functions. The Van Driest transformation is used so that the wall functions can be applied to both incompressible and compressible flows. The module is equipped with three two-equation K-epsilon turbulence models: Chien, Shih-Lumley and CMOTR models. Details of the wall functions as well as their numerical implementation are reported. It is shown that the inappropriate artificial viscosity in the near-wall region has a big influence on the solution of the wall function approach. A simple way to eliminate this influence is proposed, which gives satisfactory results during the code validation. The module can be easily linked to the NPARC code for practical applications.

A vortex wake capturing method for potential flow calculations

NASA Technical Reports Server (NTRS)

Murman, E. M.; Stremel, P. M.

1982-01-01

A method is presented for modifying finite difference solutions of the potential equation to include the calculation of non-planar vortex wake features. The approach is an adaptation of Baker's 'cloud in cell' algorithm developed for the stream function-vorticity equations. The vortex wake is tracked in a Lagrangian frame of reference as a group of discrete vortex filaments. These are distributed to the Eulerian mesh system on which the velocity is calculated by a finite difference solution of the potential equation. An artificial viscosity introduced by the finite difference equations removes the singular nature of the vortex filaments. Computed examples are given for the two-dimensional time dependent roll-up of vortex wakes generated by wings with different spanwise loading distributions.

Development of a New Aprepitant Liquisolid Formulation with the Aid of Artificial Neural Networks and Genetic Programming.

PubMed

Barmpalexis, Panagiotis; Grypioti, Agni; Eleftheriadis, Georgios K; Fatouros, Dimitris G

2018-02-01

In the present study, liquisolid formulations were developed for improving dissolution profile of aprepitant (APT) in a solid dosage form. Experimental studies were complemented with artificial neural networks and genetic programming. Specifically, the type and concentration of liquid vehicle was evaluated through saturation-solubility studies, while the effect of the amount of viscosity increasing agent (HPMC), the type of wetting (Soluplus® vs. PVP) and solubilizing (Poloxamer®407 vs. Kolliphor®ELP) agents, and the ratio of solid coating (microcrystalline cellulose) to carrier (colloidal silicon dioxide) were evaluated based on in vitro drug release studies. The optimum liquisolid formulation exhibited improved dissolution characteristics compared to the marketed product Emend®. X-ray diffraction (XRD), scanning electron microscopy (SEM) and a novel method combining particle size analysis by dynamic light scattering (DLS) and HPLC, revealed that the increase in dissolution rate of APT in the optimum liquisolid formulation was due to the formation of stable APT nanocrystals. Differential scanning calorimetry (DSC) and attenuated total reflection FTIR spectroscopy (ATR-FTIR) revealed the presence of intermolecular interactions between APT and liquisolid formulation excipients. Multilinear regression analysis (MLR), artificial neural networks (ANNs), and genetic programming (GP) were used to correlate several formulation variables with dissolution profile parameters (Y 15min and Y 30min ) using a full factorial experimental design. Results showed increased correlation efficacy for ANNs and GP (RMSE of 0.151 and 0.273, respectively) compared to MLR (RMSE = 0.413).

Formulation and Implementation of Nonlinear Integral Equations to Model Neural Dynamics Within the Vertebrate Retina.

PubMed

Eshraghian, Jason K; Baek, Seungbum; Kim, Jun-Ho; Iannella, Nicolangelo; Cho, Kyoungrok; Goo, Yong Sook; Iu, Herbert H C; Kang, Sung-Mo; Eshraghian, Kamran

2018-02-13

Existing computational models of the retina often compromise between the biophysical accuracy and a hardware-adaptable methodology of implementation. When compared to the current modes of vision restoration, algorithmic models often contain a greater correlation between stimuli and the affected neural network, but lack physical hardware practicality. Thus, if the present processing methods are adapted to complement very-large-scale circuit design techniques, it is anticipated that it will engender a more feasible approach to the physical construction of the artificial retina. The computational model presented in this research serves to provide a fast and accurate predictive model of the retina, a deeper understanding of neural responses to visual stimulation, and an architecture that can realistically be transformed into a hardware device. Traditionally, implicit (or semi-implicit) ordinary differential equations (OES) have been used for optimal speed and accuracy. We present a novel approach that requires the effective integration of different dynamical time scales within a unified framework of neural responses, where the rod, cone, amacrine, bipolar, and ganglion cells correspond to the implemented pathways. Furthermore, we show that adopting numerical integration can both accelerate retinal pathway simulations by more than 50% when compared with traditional ODE solvers in some cases, and prove to be a more realizable solution for the hardware implementation of predictive retinal models.

Domain-general sequence learning deficit in specific language impairment.

PubMed

Lukács, Agnes; Kemény, Ferenc

2014-05-01

Grammar-specific accounts of specific language impairment (SLI) have been challenged by recent claims that language problems are a consequence of impairments in domain-general mechanisms of learning that also play a key role in the process of language acquisition. Our studies were designed to test the generality and nature of this learning deficit by focusing on both sequential and nonsequential, and on verbal and nonverbal, domains. Twenty-nine children with SLI were compared with age-matched typically developing (TD) control children using (a) a serial reaction time task (SRT), testing the learning of motor sequences; (b) an artificial grammar learning (AGL) task, testing the extraction of regularities from auditory sequences; and (c) a weather prediction task (WP), testing probabilistic category learning in a nonsequential task. For the 2 sequence learning tasks, a significantly smaller proportion of children showed evidence of learning in the SLI than in the TD group (χ2 tests, p < .001 for the SRT task, p < .05 for the AGL task), whereas the proportion of learners on the WP task was the same in the 2 groups. The level of learning for SLI learners was comparable with that of TD children on all tasks (with great individual variation). Taken together, these findings suggest that domain-general processes of implicit sequence learning tend to be impaired in SLI. Further research is needed to clarify the relationship of deficits in implicit learning and language.

The Numerical Technique for the Landslide Tsunami Simulations Based on Navier-Stokes Equations

NASA Astrophysics Data System (ADS)

Kozelkov, A. S.

2017-12-01

The paper presents an integral technique simulating all phases of a landslide-driven tsunami. The technique is based on the numerical solution of the system of Navier-Stokes equations for multiphase flows. The numerical algorithm uses a fully implicit approximation method, in which the equations of continuity and momentum conservation are coupled through implicit summands of pressure gradient and mass flow. The method we propose removes severe restrictions on the time step and allows simulation of tsunami propagation to arbitrarily large distances. The landslide origin is simulated as an individual phase being a Newtonian fluid with its own density and viscosity and separated from the water and air phases by an interface. The basic formulas of equation discretization and expressions for coefficients are presented, and the main steps of the computation procedure are described in the paper. To enable simulations of tsunami propagation across wide water areas, we propose a parallel algorithm of the technique implementation, which employs an algebraic multigrid method. The implementation of the multigrid method is based on the global level and cascade collection algorithms that impose no limitations on the paralleling scale and make this technique applicable to petascale systems. We demonstrate the possibility of simulating all phases of a landslide-driven tsunami, including its generation, propagation and uprush. The technique has been verified against the problems supported by experimental data. The paper describes the mechanism of incorporating bathymetric data to simulate tsunamis in real water areas of the world ocean. Results of comparison with the nonlinear dispersion theory, which has demonstrated good agreement, are presented for the case of a historical tsunami of volcanic origin on the Montserrat Island in the Caribbean Sea.

Scaling of counter-current imbibition recovery curves using artificial neural networks

NASA Astrophysics Data System (ADS)

Jafari, Iman; Masihi, Mohsen; Nasiri Zarandi, Masoud

2018-06-01

Scaling imbibition curves are of great importance in the characterization and simulation of oil production from naturally fractured reservoirs. Different parameters such as matrix porosity and permeability, oil and water viscosities, matrix dimensions, and oil/water interfacial tensions have an effective on the imbibition process. Studies on the scaling imbibition curves along with the consideration of different assumptions have resulted in various scaling equations. In this work, using an artificial neural network (ANN) method, a novel technique is presented for scaling imbibition recovery curves, which can be used for scaling the experimental and field-scale imbibition cases. The imbibition recovery curves for training and testing the neural network were gathered through the simulation of different scenarios using a commercial reservoir simulator. In this ANN-based method, six parameters were assumed to have an effect on the imbibition process and were considered as the inputs for training the network. Using the ‘Bayesian regularization’ training algorithm, the network was trained and tested. Training and testing phases showed superior results in comparison with the other scaling methods. It is concluded that using the new technique is useful for scaling imbibition recovery curves, especially for complex cases, for which the common scaling methods are not designed.

StarSmasher: Smoothed Particle Hydrodynamics code for smashing stars and planets

NASA Astrophysics Data System (ADS)

Gaburov, Evghenii; Lombardi, James C., Jr.; Portegies Zwart, Simon; Rasio, F. A.

2018-05-01

Smoothed Particle Hydrodynamics (SPH) is a Lagrangian particle method that approximates a continuous fluid as discrete nodes, each carrying various parameters such as mass, position, velocity, pressure, and temperature. In an SPH simulation the resolution scales with the particle density; StarSmasher is able to handle both equal-mass and equal number-density particle models. StarSmasher solves for hydro forces by calculating the pressure for each particle as a function of the particle's properties - density, internal energy, and internal properties (e.g. temperature and mean molecular weight). The code implements variational equations of motion and libraries to calculate the gravitational forces between particles using direct summation on NVIDIA graphics cards. Using a direct summation instead of a tree-based algorithm for gravity increases the accuracy of the gravity calculations at the cost of speed. The code uses a cubic spline for the smoothing kernel and an artificial viscosity prescription coupled with a Balsara Switch to prevent unphysical interparticle penetration. The code also implements an artificial relaxation force to the equations of motion to add a drag term to the calculated accelerations during relaxation integrations. Initially called StarCrash, StarSmasher was developed originally by Rasio.

An adaptive discretization of incompressible flow using a multitude of moving Cartesian grids

NASA Astrophysics Data System (ADS)

English, R. Elliot; Qiu, Linhai; Yu, Yue; Fedkiw, Ronald

2013-12-01

We present a novel method for discretizing the incompressible Navier-Stokes equations on a multitude of moving and overlapping Cartesian grids each with an independently chosen cell size to address adaptivity. Advection is handled with first and second order accurate semi-Lagrangian schemes in order to alleviate any time step restriction associated with small grid cell sizes. Likewise, an implicit temporal discretization is used for the parabolic terms including Navier-Stokes viscosity which we address separately through the development of a method for solving the heat diffusion equations. The most intricate aspect of any such discretization is the method used in order to solve the elliptic equation for the Navier-Stokes pressure or that resulting from the temporal discretization of parabolic terms. We address this by first removing any degrees of freedom which duplicately cover spatial regions due to overlapping grids, and then providing a discretization for the remaining degrees of freedom adjacent to these regions. We observe that a robust second order accurate symmetric positive definite readily preconditioned discretization can be obtained by constructing a local Voronoi region on the fly for each degree of freedom in question in order to obtain both its stencil (logically connected neighbors) and stencil weights. Internal curved boundaries such as at solid interfaces are handled using a simple immersed boundary approach which is directly applied to the Voronoi mesh in both the viscosity and pressure solves. We independently demonstrate each aspect of our approach on test problems in order to show efficacy and convergence before finally addressing a number of common test cases for incompressible flow with stationary and moving solid bodies.

Learning and liking of melody and harmony: further studies in artificial grammar learning.

PubMed

Loui, Psyche

2012-10-01

Much of what we know and love about music is based on implicitly acquired mental representations of musical pitches and the relationships between them. While previous studies have shown that these mental representations of music can be acquired rapidly and can influence preference, it is still unclear which aspects of music influence learning and preference formation. This article reports two experiments that use an artificial musical system to examine two questions: (1) which aspects of music matter most for learning, and (2) which aspects of music matter most for preference formation. Two aspects of music are tested: melody and harmony. In Experiment 1 we tested the learning and liking of a new musical system that is manipulated melodically so that only some of the possible conditional probabilities between successive notes are presented. In Experiment 2 we administered the same tests for learning and liking, but we used a musical system that is manipulated harmonically to eliminate the property of harmonic whole-integer ratios between pitches. Results show that disrupting melody (Experiment 1) disabled the learning of music without disrupting preference formation, whereas disrupting harmony (Experiment 2) does not affect learning and memory but disrupts preference formation. Results point to a possible dissociation between learning and preference in musical knowledge. Copyright © 2012 Cognitive Science Society, Inc.

Numerical computation of viscous flow about unconventional airfoil shapes

NASA Technical Reports Server (NTRS)

Ahmed, S.; Tannehill, J. C.

1990-01-01

A new two-dimensional computer code was developed to analyze the viscous flow around unconventional airfoils at various Mach numbers and angles of attack. The Navier-Stokes equations are solved using an implicit, upwind, finite-volume scheme. Both laminar and turbulent flows can be computed. A new nonequilibrium turbulence closure model was developed for computing turbulent flows. This two-layer eddy viscosity model was motivated by the success of the Johnson-King model in separated flow regions. The influence of history effects are described by an ordinary differential equation developed from the turbulent kinetic energy equation. The performance of the present code was evaluated by solving the flow around three airfoils using the Reynolds time-averaged Navier-Stokes equations. Excellent results were obtained for both attached and separated flows about the NACA 0012 airfoil, the RAE 2822 airfoil, and the Integrated Technology A 153W airfoil. Based on the comparison of the numerical solutions with the available experimental data, it is concluded that the present code in conjunction with the new nonequilibrium turbulence model gives excellent results.

Transpiration and film cooling boundary layer computer program. Volume 1: Numerical solutions of the turbulent boundary layer equations with equilibrium chemistry

NASA Technical Reports Server (NTRS)

Levine, J. N.

1971-01-01

A finite difference turbulent boundary layer computer program has been developed. The program is primarily oriented towards the calculation of boundary layer performance losses in rocket engines; however, the solution is general, and has much broader applicability. The effects of transpiration and film cooling as well as the effect of equilibrium chemical reactions (currently restricted to the H2-O2 system) can be calculated. The turbulent transport terms are evaluated using the phenomenological mixing length - eddy viscosity concept. The equations of motion are solved using the Crank-Nicolson implicit finite difference technique. The analysis and computer program have been checked out by solving a series of both laminar and turbulent test cases and comparing the results to data or other solutions. These comparisons have shown that the program is capable of producing very satisfactory results for a wide range of flows. Further refinements to the analysis and program, especially as applied to film cooling solutions, would be aided by the acquisition of a firm data base.

Computation of oscillating airfoil flows with one- and two-equation turbulence models

NASA Technical Reports Server (NTRS)

Ekaterinaris, J. A.; Menter, F. R.

1994-01-01

The ability of one- and two-equation turbulence models to predict unsteady separated flows over airfoils is evaluated. An implicit, factorized, upwind-biased numerical scheme is used for the integration of the compressible, Reynolds-averaged Navier-Stokes equations. The turbulent eddy viscosity is obtained from the computed mean flowfield by integration of the turbulent field equations. One- and two-equation turbulence models are first tested for a separated airfoil flow at fixed angle of incidence. The same models are then applied to compute the unsteady flowfields about airfoils undergoing oscillatory motion at low subsonic Mach numbers. Experimental cases where the flow has been tripped at the leading-edge and where natural transition was allowed to occur naturally are considered. The more recently developed turbulence models capture the physics of unsteady separated flow significantly better than the standard kappa-epsilon and kappa-omega models. However, certain differences in the hysteresis effects are observed. For an untripped high-Reynolds-number flow, it was found necessary to take into account the leading-edge transitional flow region to capture the correct physical mechanism that leads to dynamic stall.

Computational Analysis of the Effect of Porosity on Shock Cell Strength at Cruise

NASA Technical Reports Server (NTRS)

Massey, Steven J.; Elmiligui, Alaa A.; Pao, S. Paul; Abdol-Hamid, Khaled S.; Hunter, Craig A.

2006-01-01

A computational flow field analysis is presented of the effect of core cowl porosity on shock cell strength for a modern separate flow nozzle at cruise conditions. The goal of this study was to identify the primary physical mechanisms by which the application of porosity can reduce shock cell strength and hence the broadband shock associated noise. The flow is simulated by solving the asymptotically steady, compressible, Reynoldsaveraged Navier-Stokes equations on a structured grid using an implicit, up-wind, flux-difference splitting finite volume scheme. The standard two-equation k - epsilon turbulence model with a linear stress representation is used with the addition of a eddy viscosity dependence on total temperature gradient normalized by local turbulence length scale. Specific issues addressed in this study were the optimal area required to weaken a shock impinging on the core cowl surface and the optimal level of porosity and placement of porous areas for reduction of the overall shock cell strength downstream. Two configurations of porosity were found to reduce downstream shock strength by approximately 50%.

A highly accurate boundary integral equation method for surfactant-laden drops in 3D

NASA Astrophysics Data System (ADS)

Sorgentone, Chiara; Tornberg, Anna-Karin

2018-05-01

The presence of surfactants alters the dynamics of viscous drops immersed in an ambient viscous fluid. This is specifically true at small scales, such as in applications of droplet based microfluidics, where the interface dynamics become of increased importance. At such small scales, viscous forces dominate and inertial effects are often negligible. Considering Stokes flow, a numerical method based on a boundary integral formulation is presented for simulating 3D drops covered by an insoluble surfactant. The method is able to simulate drops with different viscosities and close interactions, automatically controlling the time step size and maintaining high accuracy also when substantial drop deformation appears. To achieve this, the drop surfaces as well as the surfactant concentration on each surface are represented by spherical harmonics expansions. A novel reparameterization method is introduced to ensure a high-quality representation of the drops also under deformation, specialized quadrature methods for singular and nearly singular integrals that appear in the formulation are evoked and the adaptive time stepping scheme for the coupled drop and surfactant evolution is designed with a preconditioned implicit treatment of the surfactant diffusion.

Development of an explicit multiblock/multigrid flow solver for viscous flows in complex geometries

NASA Technical Reports Server (NTRS)

Steinthorsson, E.; Liou, M. S.; Povinelli, L. A.

1993-01-01

A new computer program is being developed for doing accurate simulations of compressible viscous flows in complex geometries. The code employs the full compressible Navier-Stokes equations. The eddy viscosity model of Baldwin and Lomax is used to model the effects of turbulence on the flow. A cell centered finite volume discretization is used for all terms in the governing equations. The Advection Upwind Splitting Method (AUSM) is used to compute the inviscid fluxes, while central differencing is used for the diffusive fluxes. A four-stage Runge-Kutta time integration scheme is used to march solutions to steady state, while convergence is enhanced by a multigrid scheme, local time-stepping, and implicit residual smoothing. To enable simulations of flows in complex geometries, the code uses composite structured grid systems where all grid lines are continuous at block boundaries (multiblock grids). Example results shown are a flow in a linear cascade, a flow around a circular pin extending between the main walls in a high aspect-ratio channel, and a flow of air in a radial turbine coolant passage.

Development of an explicit multiblock/multigrid flow solver for viscous flows in complex geometries

NASA Technical Reports Server (NTRS)

Steinthorsson, E.; Liou, M.-S.; Povinelli, L. A.

1993-01-01

A new computer program is being developed for doing accurate simulations of compressible viscous flows in complex geometries. The code employs the full compressible Navier-Stokes equations. The eddy viscosity model of Baldwin and Lomax is used to model the effects of turbulence on the flow. A cell centered finite volume discretization is used for all terms in the governing equations. The Advection Upwind Splitting Method (AUSM) is used to compute the inviscid fluxes, while central differencing is used for the diffusive fluxes. A four-stage Runge-Kutta time integration scheme is used to march solutions to steady state, while convergence is enhanced by a multigrid scheme, local time-stepping and implicit residual smoothing. To enable simulations of flows in complex geometries, the code uses composite structured grid systems where all grid lines are continuous at block boundaries (multiblock grids). Example results are shown a flow in a linear cascade, a flow around a circular pin extending between the main walls in a high aspect-ratio channel, and a flow of air in a radial turbine coolant passage.

Analysis of turbulent free jet hydrogen-air diffusion flames with finite chemical reaction rates

NASA Technical Reports Server (NTRS)

Sislian, J. P.

1978-01-01

The nonequilibrium flow field resulting from the turbulent mixing and combustion of a supersonic axisymmetric hydrogen jet in a supersonic parallel coflowing air stream is analyzed. Effective turbulent transport properties are determined using the (K-epsilon) model. The finite-rate chemistry model considers eight reactions between six chemical species, H, O, H2O, OH, O2, and H2. The governing set of nonlinear partial differential equations is solved by an implicit finite-difference procedure. Radial distributions are obtained at two downstream locations of variables such as turbulent kinetic energy, turbulent dissipation rate, turbulent scale length, and viscosity. The results show that these variables attain peak values at the axis of symmetry. Computed distributions of velocity, temperature, and mass fraction are also given. A direct analytical approach to account for the effect of species concentration fluctuations on the mean production rate of species (the phenomenon of unmixedness) is also presented. However, the use of the method does not seem justified in view of the excessive computer time required to solve the resulting system of equations.

NASCRIN - NUMERICAL ANALYSIS OF SCRAMJET INLET

NASA Technical Reports Server (NTRS)

Kumar, A.

1994-01-01

The NASCRIN program was developed for analyzing two-dimensional flow fields in supersonic combustion ramjet (scramjet) inlets. NASCRIN solves the two-dimensional Euler or Navier-Stokes equations in conservative form by an unsplit, explicit, two-step finite-difference method. A more recent explicit-implicit, two-step scheme has also been incorporated in the code for viscous flow analysis. An algebraic, two-layer eddy-viscosity model is used for the turbulent flow calculations. NASCRIN can analyze both inviscid and viscous flows with no struts, one strut, or multiple struts embedded in the flow field. NASCRIN can be used in a quasi-three-dimensional sense for some scramjet inlets under certain simplifying assumptions. Although developed for supersonic internal flow, NASCRIN may be adapted to a variety of other flow problems. In particular, it should be readily adaptable to subsonic inflow with supersonic outflow, supersonic inflow with subsonic outflow, or fully subsonic flow. The NASCRIN program is available for batch execution on the CDC CYBER 203. The vectorized FORTRAN version was developed in 1983. NASCRIN has a central memory requirement of approximately 300K words for a grid size of about 3,000 points.

Conformational dynamics and internal friction in homopolymer globules: equilibrium vs. non-equilibrium simulations.

PubMed

Einert, T R; Sing, C E; Alexander-Katz, A; Netz, R R

2011-12-01

We study the conformational dynamics within homopolymer globules by solvent-implicit Brownian dynamics simulations. A strong dependence of the internal chain dynamics on the Lennard-Jones cohesion strength ε and the globule size N (G) is observed. We find two distinct dynamical regimes: a liquid-like regime (for ε < ε(s) with fast internal dynamics and a solid-like regime (for ε > ε(s) with slow internal dynamics. The cohesion strength ε(s) of this freezing transition depends on N (G) . Equilibrium simulations, where we investigate the diffusional chain dynamics within the globule, are compared with non-equilibrium simulations, where we unfold the globule by pulling the chain ends with prescribed velocity (encompassing low enough velocities so that the linear-response, viscous regime is reached). From both simulation protocols we derive the internal viscosity within the globule. In the liquid-like regime the internal friction increases continuously with ε and scales extensive in N (G) . This suggests an internal friction scenario where the entire chain (or an extensive fraction thereof) takes part in conformational reorganization of the globular structure.

A study on the behaviour of high-order flux reconstruction method with different low-dissipation numerical fluxes for large eddy simulation

NASA Astrophysics Data System (ADS)

Boxi, Lin; Chao, Yan; Shusheng, Chen

2017-10-01

This work focuses on the numerical dissipation features of high-order flux reconstruction (FR) method combined with different numerical fluxes in turbulence flows. The famous Roe and AUSM+ numerical fluxes together with their corresponding low-dissipation enhanced versions (LMRoe, SLAU2) and higher resolution variants (HR-LMRoe, HR-SLAU2) are incorporated into FR framework, and the dissipation interplay of these combinations is investigated in implicit large eddy simulation. The numerical dissipation stemming from these convective numerical fluxes is quantified by simulating the inviscid Gresho vortex, the transitional Taylor-Green vortex and the homogenous decaying isotropic turbulence. The results suggest that low-dissipation enhanced versions are preferential both in high-order and low-order cases to their original forms, while the use of HR-SLAU2 has marginal improvements and the HR-LMRoe leads to degenerated solution with high-order. In high-order the effects of numerical fluxes are reduced, and their viscosity may not be dissipative enough to provide physically consistent turbulence when under-resolved.

A cell-vertex multigrid method for the Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Radespiel, R.

1989-01-01

A cell-vertex scheme for the Navier-Stokes equations, which is based on central difference approximations and Runge-Kutta time stepping, is described. Using local time stepping, implicit residual smoothing, a multigrid method, and carefully controlled artificial dissipative terms, very good convergence rates are obtained for a wide range of two- and three-dimensional flows over airfoils and wings. The accuracy of the code is examined by grid refinement studies and comparison with experimental data. For an accurate prediction of turbulent flows with strong separations, a modified version of the nonequilibrium turbulence model of Johnson and King is introduced, which is well suited for an implementation into three-dimensional Navier-Stokes codes. It is shown that the solutions for three-dimensional flows with strong separations can be dramatically improved, when a nonequilibrium model of turbulence is used.

Algebra of implicitly defined constraints for gravity as the general form of embedding theory

NASA Astrophysics Data System (ADS)

Paston, S. A.; Semenova, E. N.; Franke, V. A.; Sheykin, A. A.

2017-01-01

We consider the embedding theory, the approach to gravity proposed by Regge and Teitelboim, in which 4D space-time is treated as a surface in high-dimensional flat ambient space. In its general form, which does not contain artificially imposed constraints, this theory can be viewed as an extension of GR. In the present paper we study the canonical description of the embedding theory in this general form. In this case, one of the natural constraints cannot be written explicitly, in contrast to the case where additional Einsteinian constraints are imposed. Nevertheless, it is possible to calculate all Poisson brackets with this constraint. We prove that the algebra of four emerging constraints is closed, i.e., all of them are first-class constraints. The explicit form of this algebra is also obtained.

Anthropomorphic bias found in typically developing children is not found in children with autistic spectrum disorder.

PubMed

Chaminade, Thierry; Rosset, Delphine; Da Fonseca, David; Hodgins, Jessica K; Deruelle, Christine

2015-02-01

The anthropomorphic bias describes the finding that the perceived naturalness of a biological motion decreases as the human-likeness of a computer-animated agent increases. To investigate the anthropomorphic bias in autistic children, human or cartoon characters were presented with biological and artificial motions side by side on a touchscreen. Children were required to touch one that would grow while the other would disappear, implicitly rewarding their choice. Only typically developing controls depicted the expected preference for biological motion when rendered with human, but not cartoon, characters. Despite performing the task to report a preference, children with autism depicted neither normal nor reversed anthropomorphic bias, suggesting that they are not sensitive to the congruence of form and motion information when observing computer-animated agents' actions. © The Author(s) 2014.

Computational Fluid Dynamics of Whole-Body Aircraft

NASA Astrophysics Data System (ADS)

Agarwal, Ramesh

1999-01-01

The current state of the art in computational aerodynamics for whole-body aircraft flowfield simulations is described. Recent advances in geometry modeling, surface and volume grid generation, and flow simulation algorithms have led to accurate flowfield predictions for increasingly complex and realistic configurations. As a result, computational aerodynamics has emerged as a crucial enabling technology for the design and development of flight vehicles. Examples illustrating the current capability for the prediction of transport and fighter aircraft flowfields are presented. Unfortunately, accurate modeling of turbulence remains a major difficulty in the analysis of viscosity-dominated flows. In the future, inverse design methods, multidisciplinary design optimization methods, artificial intelligence technology, and massively parallel computer technology will be incorporated into computational aerodynamics, opening up greater opportunities for improved product design at substantially reduced costs.

Extreme learning machine for reduced order modeling of turbulent geophysical flows.

PubMed

San, Omer; Maulik, Romit

2018-04-01

We investigate the application of artificial neural networks to stabilize proper orthogonal decomposition-based reduced order models for quasistationary geophysical turbulent flows. An extreme learning machine concept is introduced for computing an eddy-viscosity closure dynamically to incorporate the effects of the truncated modes. We consider a four-gyre wind-driven ocean circulation problem as our prototype setting to assess the performance of the proposed data-driven approach. Our framework provides a significant reduction in computational time and effectively retains the dynamics of the full-order model during the forward simulation period beyond the training data set. Furthermore, we show that the method is robust for larger choices of time steps and can be used as an efficient and reliable tool for long time integration of general circulation models.

Extreme learning machine for reduced order modeling of turbulent geophysical flows

NASA Astrophysics Data System (ADS)

San, Omer; Maulik, Romit

2018-04-01

We investigate the application of artificial neural networks to stabilize proper orthogonal decomposition-based reduced order models for quasistationary geophysical turbulent flows. An extreme learning machine concept is introduced for computing an eddy-viscosity closure dynamically to incorporate the effects of the truncated modes. We consider a four-gyre wind-driven ocean circulation problem as our prototype setting to assess the performance of the proposed data-driven approach. Our framework provides a significant reduction in computational time and effectively retains the dynamics of the full-order model during the forward simulation period beyond the training data set. Furthermore, we show that the method is robust for larger choices of time steps and can be used as an efficient and reliable tool for long time integration of general circulation models.

Transonic cascade flow calculations using non-periodic C-type grids

NASA Technical Reports Server (NTRS)

Arnone, Andrea; Liou, Meng-Sing; Povinelli, Louis A.

1991-01-01

A new kind of C-type grid is proposed for turbomachinery flow calculations. This grid is nonperiodic on the wake and results in minimum skewness for cascades with high turning and large camber. Euler and Reynolds averaged Navier-Stokes equations are discretized on this type of grid using a finite volume approach. The Baldwin-Lomax eddy-viscosity model is used for turbulence closure. Jameson's explicit Runge-Kutta scheme is adopted for the integration in time, and computational efficiency is achieved through accelerating strategies such as multigriding and residual smoothing. A detailed numerical study was performed for a turbine rotor and for a vane. A grid dependence analysis is presented and the effect of artificial dissipation is also investigated. Comparison of calculations with experiments clearly demonstrates the advantage of the proposed grid.

The pros and cons of code validation

NASA Technical Reports Server (NTRS)

Bobbitt, Percy J.

1988-01-01

Computational and wind tunnel error sources are examined and quantified using specific calculations of experimental data, and a substantial comparison of theoretical and experimental results, or a code validation, is discussed. Wind tunnel error sources considered include wall interference, sting effects, Reynolds number effects, flow quality and transition, and instrumentation such as strain gage balances, electronically scanned pressure systems, hot film gages, hot wire anemometers, and laser velocimeters. Computational error sources include math model equation sets, the solution algorithm, artificial viscosity/dissipation, boundary conditions, the uniqueness of solutions, grid resolution, turbulence modeling, and Reynolds number effects. It is concluded that, although improvements in theory are being made more quickly than in experiments, wind tunnel research has the advantage of the more realistic transition process of a right turbulence model in a free-transition test.

Measuring implicit attitudes: A positive framing bias flaw in the Implicit Relational Assessment Procedure (IRAP).

PubMed

O'Shea, Brian; Watson, Derrick G; Brown, Gordon D A

2016-02-01

How can implicit attitudes best be measured? The Implicit Relational Assessment Procedure (IRAP), unlike the Implicit Association Test (IAT), claims to measure absolute, not just relative, implicit attitudes. In the IRAP, participants make congruent (Fat Person-Active: false; Fat Person-Unhealthy: true) or incongruent (Fat Person-Active: true; Fat Person-Unhealthy: false) responses in different blocks of trials. IRAP experiments have reported positive or neutral implicit attitudes (e.g., neutral attitudes toward fat people) in cases in which negative attitudes are normally found on explicit or other implicit measures. It was hypothesized that these results might reflect a positive framing bias (PFB) that occurs when participants complete the IRAP. Implicit attitudes toward categories with varying prior associations (nonwords, social systems, flowers and insects, thin and fat people) were measured. Three conditions (standard, positive framing, and negative framing) were used to measure whether framing influenced estimates of implicit attitudes. It was found that IRAP scores were influenced by how the task was framed to the participants, that the framing effect was modulated by the strength of prior stimulus associations, and that a default PFB led to an overestimation of positive implicit attitudes when measured by the IRAP. Overall, the findings question the validity of the IRAP as a tool for the measurement of absolute implicit attitudes. A new tool (Simple Implicit Procedure:SIP) for measuring absolute, not just relative, implicit attitudes is proposed. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Effect of caries infiltration technique and fluoride therapy on the colour masking of white spot lesions.

PubMed

Rocha Gomes Torres, Carlos; Borges, Alessandra Buhler; Torres, Luciana Marcondes Sarmento; Gomes, Isabela Silva; de Oliveira, Rodrigo Simões

2011-03-01

A carious lesion is initiated through the subsurface demineralization of enamel, and presents clinically as a white spot, interfering with the aesthetics. This lesion should not receive restorative treatment because it is capable of remineralization. The aim of this study was to evaluate the performance of different treatments on masking white spot lesions by assessing the colour change. Artificial white spot lesions were produced in bovine enamel of 60 cylindrical-shaped samples. The samples were randomly divided into four groups: CON (control) - immersion in artificial saliva; DF - daily application of 0.05% fluoride solution; WF - weekly application of 2% fluoride gel; and IC - resin infiltration (Icon(®) - DMG). The assessment of colour was performed by a spectrophotometer in four distinct stages: baseline, after the production of artificial caries; after 4 weeks; after 8 weeks; and after a new acid challenge. The ΔL values were calculated at each stage in relation to the baseline colour. The application of RM ANOVA revealed significant differences between the factors' treatment and time (p=0.001). For the interaction between factors there were no significant differences (p=0.27). The Tukey's test (p<0.05) was then applied and showed that the specimens treated with Icon(®) exhibited the lowest means, followed by Group DF, Group CON, and Group WF, in that order. Resin infiltration was proven to be an effective treatment for masking white spot lesions. Also, after a new acid challenge, the group infiltrated with low viscosity resin presented the lowest means of colour change. Copyright © 2011. Published by Elsevier Ltd.

Gifted Students' Implicit Beliefs about Intelligence and Giftedness

ERIC Educational Resources Information Center

Makel, Matthew C.; Snyder, Kate E.; Thomas, Chandler; Malone, Patrick S.; Putallaz, Martha

2015-01-01

Growing attention is being paid to individuals' implicit beliefs about the nature of intelligence. However, implicit beliefs about giftedness are currently underexamined. In the current study, we examined academically gifted adolescents' implicit beliefs about both intelligence and giftedness. Overall, participants' implicit beliefs about…

Nonlinear and parallel algorithms for finite element discretizations of the incompressible Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Arteaga, Santiago Egido

1998-12-01

The steady-state Navier-Stokes equations are of considerable interest because they are used to model numerous common physical phenomena. The applications encountered in practice often involve small viscosities and complicated domain geometries, and they result in challenging problems in spite of the vast attention that has been dedicated to them. In this thesis we examine methods for computing the numerical solution of the primitive variable formulation of the incompressible equations on distributed memory parallel computers. We use the Galerkin method to discretize the differential equations, although most results are stated so that they apply also to stabilized methods. We also reformulate some classical results in a single framework and discuss some issues frequently dismissed in the literature, such as the implementation of pressure space basis and non- homogeneous boundary values. We consider three nonlinear methods: Newton's method, Oseen's (or Picard) iteration, and sequences of Stokes problems. All these iterative nonlinear methods require solving a linear system at every step. Newton's method has quadratic convergence while that of the others is only linear; however, we obtain theoretical bounds showing that Oseen's iteration is more robust, and we confirm it experimentally. In addition, although Oseen's iteration usually requires more iterations than Newton's method, the linear systems it generates tend to be simpler and its overall costs (in CPU time) are lower. The Stokes problems result in linear systems which are easier to solve, but its convergence is much slower, so that it is competitive only for large viscosities. Inexact versions of these methods are studied, and we explain why the best timings are obtained using relatively modest error tolerances in solving the corresponding linear systems. We also present a new damping optimization strategy based on the quadratic nature of the Navier-Stokes equations, which improves the robustness of all the linearization strategies considered and whose computational cost is negligible. The algebraic properties of these systems depend on both the discretization and nonlinear method used. We study in detail the positive definiteness and skewsymmetry of the advection submatrices (essentially, convection-diffusion problems). We propose a discretization based on a new trilinear form for Newton's method. We solve the linear systems using three Krylov subspace methods, GMRES, QMR and TFQMR, and compare the advantages of each. Our emphasis is on parallel algorithms, and so we consider preconditioners suitable for parallel computers such as line variants of the Jacobi and Gauss- Seidel methods, alternating direction implicit methods, and Chebyshev and least squares polynomial preconditioners. These work well for moderate viscosities (moderate Reynolds number). For small viscosities we show that effective parallel solution of the advection subproblem is a critical factor to improve performance. Implementation details on a CM-5 are presented.

Implicit and explicit self-esteem in currently depressed individuals with and without suicidal ideation.

PubMed

Franck, Erik; De Raedt, Rudi; Dereu, Mieke; Van den Abbeele, Dirk

2007-03-01

In the present study, we have further explored implicit self-esteem in currently depressed individuals. Since suicidal ideation is associated with lower self-esteem in depressed individuals, we measured both implicit and explicit self-esteem in a population of currently depressed (CD) individuals, with and without suicidal ideation (SI), and in a group of non-depressed controls (ND). The results indicate that only CD individuals with SI show a discrepancy between their implicit and explicit self-esteem: that is, they exhibit high implicit and low explicit self-esteem. CD individuals without SI exhibit both low implicit and low explicit self-esteem; and ND controls exhibit both normal implicit and normal explicit self-esteem. These results provide new insights in the study of implicit self-esteem and the combination of implicit and explicit self-esteem in depression.

I like myself but I don't know why: enhancing implicit self-esteem by subliminal evaluative conditioning.

PubMed

Dijksterhuis, Ap

2004-02-01

On the basis of a conceptualization of implicit self-esteem as the implicit attitude toward the self, it was predicted that implicit self-esteem could be enhanced by subliminal evaluative conditioning. In 5 experiments, participants were repeatedly presented with trials in which the word I was paired with positive trait terms. Relative to control conditions, this procedure enhanced implicit self-esteem. The effects generalized across 3 measures of implicit self-esteem (Experiments 1-3). Furthermore, evaluative conditioning enhanced implicit self-esteem among people with low-temporal implicit self-esteem and among people with high-temporal implicit self-esteem (Experiment 4). In addition, it was shown that conditioning enhanced self-esteem to such an extent that it made participants insensitive to negative intelligence feedback (Experiments 5a and 5b). Various implications are discussed.

Understanding the Role of Reservoir Size on Probable Maximum Precipitation

NASA Astrophysics Data System (ADS)

Woldemichael, A. T.; Hossain, F.

2011-12-01

This study addresses the question 'Does surface area of an artificial reservoir matter in the estimation of probable maximum precipitation (PMP) for an impounded basin?' The motivation of the study was based on the notion that the stationarity assumption that is implicit in the PMP for dam design can be undermined in the post-dam era due to an enhancement of extreme precipitation patterns by an artificial reservoir. In addition, the study lays the foundation for use of regional atmospheric models as one way to perform life cycle assessment for planned or existing dams to formulate best management practices. The American River Watershed (ARW) with the Folsom dam at the confluence of the American River was selected as the study region and the Dec-Jan 1996-97 storm event was selected for the study period. The numerical atmospheric model used for the study was the Regional Atmospheric Modeling System (RAMS). First, the numerical modeling system, RAMS, was calibrated and validated with selected station and spatially interpolated precipitation data. Best combinations of parameterization schemes in RAMS were accordingly selected. Second, to mimic the standard method of PMP estimation by moisture maximization technique, relative humidity terms in the model were raised to 100% from ground up to the 500mb level. The obtained model-based maximum 72-hr precipitation values were named extreme precipitation (EP) as a distinction from the PMPs obtained by the standard methods. Third, six hypothetical reservoir size scenarios ranging from no-dam (all-dry) to the reservoir submerging half of basin were established to test the influence of reservoir size variation on EP. For the case of the ARW, our study clearly demonstrated that the assumption of stationarity that is implicit the traditional estimation of PMP can be rendered invalid to a large part due to the very presence of the artificial reservoir. Cloud tracking procedures performed on the basin also give indication of the formation of mesoscale convective systems (MCS) in the vicinity of dams/reservoirs that may have explicitly been triggered by their presence. The significance of this finding is that water resources managers need to consider the post-dam impact of water cycle and local climate due to the very reservoir and land use change triggered if efficient water resources management is desired. Future works of the study will include incorporation of the anthropogenic changes that occur as a result of the presence of dams/reservoirs in the forms of irrigation, urbanization and downstream wetland reduction. Similar hypothesis testing procedures will be applied to understand the combined effects of the reservoir size variation and anthropogenic changes in the extreme precipitation patterns.

Implicit cognitive aggression among young male prisoners: Association with dispositional and current aggression.

PubMed

Ireland, Jane L; Adams, Christine

2015-01-01

The current study explores associations between implicit and explicit aggression in young adult male prisoners, seeking to apply the Reflection-Impulsive Model and indicate parity with elements of the General Aggression Model and social cognition. Implicit cognitive aggressive processing is not an area that has been examined among prisoners. Two hundred and sixty two prisoners completed an implicit cognitive aggression measure (Puzzle Test) and explicit aggression measures, covering current behaviour (DIPC-R) and aggression disposition (AQ). It was predicted that dispositional aggression would be predicted by implicit cognitive aggression, and that implicit cognitive aggression would predict current engagement in aggressive behaviour. It was also predicted that more impulsive implicit cognitive processing would associate with aggressive behaviour whereas cognitively effortful implicit cognitive processing would not. Implicit aggressive cognitive processing was associated with increased dispositional aggression but not current reports of aggressive behaviour. Impulsive implicit cognitive processing of an aggressive nature predicted increased dispositional aggression whereas more cognitively effortful implicit cognitive aggression did not. The article concludes by outlining the importance of accounting for implicit cognitive processing among prisoners and the need to separate such processing into facets (i.e. impulsive vs. cognitively effortful). Implications for future research and practice in this novel area of study are indicated. Copyright © 2015 Elsevier Ltd. All rights reserved.

A Framework for Integrating Implicit Bias Recognition Into Health Professions Education.

PubMed

Sukhera, Javeed; Watling, Chris

2018-01-01

Existing literature on implicit bias is fragmented and comes from a variety of fields like cognitive psychology, business ethics, and higher education, but implicit-bias-informed educational approaches have been underexplored in health professions education and are difficult to evaluate using existing tools. Despite increasing attention to implicit bias recognition and management in health professions education, many programs struggle to meaningfully integrate these topics into curricula. The authors propose a six-point actionable framework for integrating implicit bias recognition and management into health professions education that draws on the work of previous researchers and includes practical tools to guide curriculum developers. The six key features of this framework are creating a safe and nonthreatening learning context, increasing knowledge about the science of implicit bias, emphasizing how implicit bias influences behaviors and patient outcomes, increasing self-awareness of existing implicit biases, improving conscious efforts to overcome implicit bias, and enhancing awareness of how implicit bias influences others. Important considerations for designing implicit-bias-informed curricula-such as individual and contextual variables, as well as formal and informal cultural influences-are discussed. The authors also outline assessment and evaluation approaches that consider outcomes at individual, organizational, community, and societal levels. The proposed framework may facilitate future research and exploration regarding the use of implicit bias in health professions education.

Diffusion in Zinc at High Pressure and Rheology of the Earth's Inner Core

NASA Astrophysics Data System (ADS)

Keshav, S.; van Orman, J. A.

2004-12-01

An attempt has been made here to estimate the viscosity of the Earth's inner core, and also to identify the primary mechanism by which the inner core deforms. Estimation of the viscosity and identification of the deformation mechanism(s) of the inner core require measurements of diffusion in the hcp (hexagonal close-packed, or epsilon) phase of iron, suggested to be stable at the Earth's inner-core pressure conditions. However, owing largely to experimental and analytical challenges, actual measurements on the diffusivity in this phase are non-existent. To overcome this problem, we have focused on the divalent transition metal, zinc (Zn), which has the hcp structure over a wide range of pressures. Hcp metals are known to have similar diffusivities at the same homologous temperature. A primary goal of this work was to explore the effect of increasing pressure on diffusion in zinc. Zinc has high compressibility, allowing diffusion measurements to be made on normalized pressures (P/K, pressure/bulk modulus) approaching those of Earth's core. We focused on diffusion of gold (Au), which has been extensively studied at atmospheric pressure. We find that with increasing pressure from 10 to 25 GPa, the diffusion coefficient of Au in Zn decreases, and the data at high pressures are in good agreement with that at 1 atm. However, in a plot of log D versus homologous temperature (Tm/T, where Tm is the melting point), the slope besides being slightly shallower, the high-pressure diffusivity values retrieved are higher than predicted from extrapolation of the 1 atm data. This trend is more prominent in plot of log D versus pressure, where instead of being linear, the diffusion coefficient shows a slight parabolic dependence, indicating that the activation volume decreases with pressure. High-pressure diffusivity values are higher than predicted either from homologous temperature scaling, or those retrieved assuming constant activation volume from one atmosphere data. To a good approximation, the inner core is in hydrostatic equilibrium with the surrounding fluid. The shear stress on the inner core is thought to be low, and grain sizes are larger than in the lower mantle. Temperature and pressure both influence the effective viscosity, and their role is often included in rheological models by referring the temperature to the melting temperature, Tm; the pressure dependence enters implicitly through its influence on Tm. Calculated values of viscosity of the Earth's inner core using the experimental philosophy outlined above are at least 8-9 orders of magnitude lower than estimated so far. These low viscosities have important consequences for the origin of seismic anisotropy and diffusion in the inner core. On the basis of these measurements, it appears that the inner core can quickly erase memory of deformation that occurred early in its history. Thus, search for alternative explanations of the anisotropy is required. Unraveling the clues left behind by the growth of the inner core offers the hope of new insights into the evolution of the Earth's deep interior.

A decade of studying implicit racial/ethnic bias in healthcare providers using the implicit association test.

PubMed

Maina, Ivy W; Belton, Tanisha D; Ginzberg, Sara; Singh, Ajit; Johnson, Tiffani J

2018-02-01

Disparities in the care and outcomes of US racial/ethnic minorities are well documented. Research suggests that provider bias plays a role in these disparities. The implicit association test enables measurement of implicit bias via tests of automatic associations between concepts. Hundreds of studies have examined implicit bias in various settings, but relatively few have been conducted in healthcare. The aim of this systematic review is to synthesize the current knowledge on the role of implicit bias in healthcare disparities. A comprehensive literature search of several databases between May 2015 and September 2016 identified 37 qualifying studies. Of these, 31 found evidence of pro-White or light-skin/anti-Black, Hispanic, American Indian or dark-skin bias among a variety of HCPs across multiple levels of training and disciplines. Fourteen studies examined the association between implicit bias and healthcare outcomes using clinical vignettes or simulated patients. Eight found no statistically significant association between implicit bias and patient care while six studies found that higher implicit bias was associated with disparities in treatment recommendations, expectations of therapeutic bonds, pain management, and empathy. All seven studies that examined the impact of implicit provider bias on real-world patient-provider interaction found that providers with stronger implicit bias demonstrated poorer patient-provider communication. Two studies examined the effect of implicit bias on real-world clinical outcomes. One found an association and the other did not. Two studies tested interventions aimed at reducing bias, but only one found a post-intervention reduction in implicit bias. This review reveals a need for more research exploring implicit bias in real-world patient care, potential modifiers and confounders of the effect of implicit bias on care, and strategies aimed at reducing implicit bias and improving patient-provider communication. Future studies have the opportunity to build on this current body of research, and in doing so will enable us to achieve equity in healthcare and outcomes. Copyright © 2017 Elsevier Ltd. All rights reserved.

Preparation of ion-activated in situ gel systems of scopolamine hydrobromide and evaluation of its antimotion sickness efficacy.

PubMed

Cao, Shi-lei; Zhang, Qi-zhi; Jiang, Xin-guo

2007-04-01

To develop a novel, in situ gel system for nasal delivery of scopolamine hydrobromide (SCOP) and study its efficacy on motion sickness. SCOP in situ gels at 0.2%, 0.5%, and 1.0% gellan gum concentration (w/v) were prepared, respectively, and characterized in terms of viscosity, in vitro release, and nasal ciliotoxicity. Single photon emission computing tomography technique was used to evaluate the nasal residence time of gel containing (99m)Tc tracer. The antimotion sickness efficacy produced by the in situ gel formulation was investigated in rats and compared with those achieved after subcutaneous and oral administration. The viscosity of the gellan gum formulations either in solution or in gel increased with increasing concentrations of gellan gum. Its release in vitro was moderate in artificial nasal fluid. The micrographic results showed that in situ gels were safe, without nasal ciliotoxicity. In comparison with phosphate buffer saline, a prolonged radioactivity of (99m)Tc in the rabbit nasal cavity was observed after administration of the gellan gum formulation. Intranasal SCOP in situ gel at a dose of 100 microg/kg decreased symptoms of motion sickness significantly in comparison with subcutaneous and oral administration (P<0.01). SCOP nasal in situ gel is a safe and promising therapeutic alternative to existing medications for motion sickness.

Diffusion behavior of the fluorescent proteins eGFP and Dreiklang in solvents of different viscosity monitored by fluorescence correlation spectroscopy

NASA Astrophysics Data System (ADS)

Junghans, Cornelia; Schmitt, Franz-Josef; Vukojević, Vladana; Friedrich, Thomas

2016-12-01

Fluorescence correlation spectroscopy relies on temporal autocorrelation analysis of fluorescence intensity fluctuations that spontaneously arise in systems at equilibrium due to molecular motion and changes of state that cause changes in fluorescence, such as triplet state transition, photoisomerization and other photophysical transformations, to determine the rates of these processes. The stability of a fluorescent molecule against dark state conversion is of particular concern for chromophores intended to be used as reference tags for comparing diffusion processes on multiple time scales. In this work, we analyzed properties of two fluorescent proteins, the photoswitchable Dreiklang and its parental eGFP, in solvents of different viscosity to vary the diffusion time through the observation volume element by several orders of magnitude. In contrast to eGFP, Dreiklang undergoes a dark-state conversion on the time scale of tens to hundreds of microseconds under conditions of intense fluorescence excitation, which results in artificially shortened diffusion times if the diffusional motion through the observation volume is sufficiently slowed down. Such photophysical quenching processes have also been observed in FCS studies on other photoswitchable fluorescent proteins including Citrine, from which Dreiklang was derived by genetic engineering. This property readily explains the discrepancies observed previously between the diffusion times of eGFP- and Dreiklang-labeled plasma membrane protein complexes.

Reynolds-averaged Navier-Stokes computation on tip clearance flow in a compressor cascade using an unstructured grid

NASA Astrophysics Data System (ADS)

Shin, Sangmook

2001-07-01

A three-dimensional unstructured incompressible RANS code has been developed using artificial compressibility and Spalart-Allmaras eddy viscosity model. A node-based finite volume method is used in which all flow variables are defined at the vertices of tetrahedrons in an unstructured grid. The inviscid fluxes are computed by using the Roe's flux difference splitting method, and higher order accuracy is attained by data reconstruction based on Taylor series expansion. Gauss theorem is used to formulate necessary gradients. For time integration, an implicit scheme based on linearized Euler backward method is used. A tetrahedral unstructured grid generation code has been also developed and applied to the tip clearance flow in a highly staggered cascade. Surface grids are first generated in the flow passage and blade tip by using several triangulation methods including Delaunay triangulation, advancing front method and advancing layer method. Then the whole computational domain including tip gap region is filled with prisms using the surface grids. The code has been validated by comparisons with available computational and experimental results for several test cases: inviscid flow around NACA section, laminar and turbulent flow over a flat plate, turbulent flow through double-circular arc cascade and laminar flow through a square duct with 90° bend. Finally the code is applied to a linear cascade that has GE rotor B section with tip clearance and a high stagger angle of 56.9°. The overall structure of the tip clearance flow is well predicted. Loss of loading due to tip leakage flow and reloading due to tip leakage vortex are presented. On the end wall, separation line of the tip leakage vortex and reattachment line of passage vortex are identified. Prediction of such an interaction presents a challenge to RANS computations. The effects of blade span on the flow structure have been also investigated. Two cascades with blades of aspect ratios of 0.5 and 1.0 are considered. By comparing pressure distributions on the blade, it is shown that the aspect ratio has strong effects on loading distribution on the blade although the tip gap height is very small (0.016 chord). Grid convergence study has been carried out with three different grids for pressure distributions and limiting streamlines on the end wall. (Abstract shortened by UMI.)

THOR: an open-source exo-GCM

NASA Astrophysics Data System (ADS)

Grosheintz, Luc; Mendonça, João; Käppeli, Roger; Lukas Grimm, Simon; Mishra, Siddhartha; Heng, Kevin

2015-12-01

In this talk, I will present THOR, the first fully conservative, GPU-accelerated exo-GCM (general circulation model) on a nearly uniform, global grid that treats shocks and is non-hydrostatic. THOR will be freely available to the community as a standard tool.Unlike most GCMs THOR solves the full, non-hydrostatic Euler equations instead of the primitive equations. The equations are solved on a global three-dimensional icosahedral grid by a second order Finite Volume Method (FVM). Icosahedral grids are nearly uniform refinements of an icosahedron. We've implemented three different versions of this grid. FVM conserves the prognostic variables (density, momentum and energy) exactly and doesn't require a diffusion term (artificial viscosity) in the Euler equations to stabilize our solver. Historically FVM was designed to treat discontinuities correctly. Hence it excels at resolving shocks, including those present in hot exoplanetary atmospheres.Atmospheres are generally in near hydrostatic equilibrium. We therefore implement a well-balancing technique recently developed at the ETH Zurich. This well-balancing ensures that our FVM maintains hydrostatic equilibrium to machine precision. Better yet, it is able to resolve pressure perturbations from this equilibrium as small as one part in 100'000. It is important to realize that these perturbations are significantly smaller than the truncation error of the same scheme without well-balancing. If during the course of the simulation (due to forcing) the atmosphere becomes non-hydrostatic, our solver continues to function correctly.THOR just passed an important mile stone. We've implemented the explicit part of the solver. The explicit solver is useful to study instabilities or local problems on relatively short time scales. I'll show some nice properties of the explicit THOR. An explicit solver is not appropriate for climate study because the time step is limited by the sound speed. Therefore, we are working on the first fully implicit GCM. By ESS3, I hope to present results for the advection equation.THOR is part of the Exoclimes Simulation Platform (ESP), a set of open-source community codes for simulating and understanding the atmospheres of exoplanets. The ESP also includes tools for radiative transfer and retrieval (HELIOS), an opacity calculator (HELIOS-K), and a chemical kinetics solver (VULCAN). We expect to publicly release an initial version of THOR in 2016 on www.exoclime.org.

Investigation of goal change to optimize upper-extremity motor performance in a robotic environment.

PubMed

Brewer, Bambi R; Klatzky, Roberta; Markham, Heather; Matsuoka, Yoky

2009-10-01

Robotic devices for therapy have the potential to enable intensive, fully customized home rehabilitation over extended periods for individuals with stroke and traumatic brain injury, thus empowering them to maximize their functional recovery. For robotic rehabilitation to be most effective, systems must have the capacity to assign performance goals to the user and to increment those goals to encourage performance improvement. Otherwise, individuals may plateau at an artificially low level of function. Frequent goal change is needed to motivate improvements in performance by individuals with brain injury; but because of entrenched habits, these individuals may avoid striving for goals that they perceive as becoming ever more difficult. For this reason, implicit, undetectable goal change (distortion) may be more effective than explicit goal change at optimizing the motor performance of some individuals with brain injury. This paper reviews a body of work that provides a basis for incorporating implicit goal change into a robotic rehabilitation paradigm. This work was conducted with individuals without disability to provide foundational knowledge for using goal change in a robotic environment. In addition, we compare motor performance with goal change to performance with no goal or with a static goal for individuals without brain injury. Our results show that goal change can improve motor performance when participants attend to visual feedback. Building on these preliminary results can lead to more effective robotic paradigms for the rehabilitation of individuals with brain injury, including individuals with cerebral palsy.

Unconscious Motivation. Part I: Implicit Attitudes toward L2 Speakers

ERIC Educational Resources Information Center

Al-Hoorie, Ali H.

2016-01-01

This paper reports the first investigation in the second language acquisition field assessing learners' implicit attitudes using the Implicit Association Test, a computerized reaction-time measure. Examination of the explicit and implicit attitudes of Arab learners of English (N = 365) showed that, particularly for males, implicit attitudes toward…

Public policies and reproductive technology: a feminist critique.

PubMed

Mccormack, T

1991-01-01

Reproductive technology comprises abortion, contraception, amniocentesis (more than 40 genetic disorders can be diagnosed), chorionic villus sampling, genetic screening (to reduce the risk of chromosomal defects such as Down syndrome, sickle cell anemia, Tay-Sachs disease, and cystic fibrosis), in vitro fertilization, artificial insemination by spouse or donor, the development of sperm banks, storage of frozen sperm (cryopreservation), the development of artificial wombs, techniques for predetermining the sex of a fetus, and nursery environments to maintain a fetus removed from the womb in the 1st trimester. In recent years, the demand for these services has increased because of higher infertility and the drop in the number of babies available for adoption. Surrogacy is especially controversial: it has become a symbol of the dehumanization of modern life and the exploitation of women. The feminist perspective discloses how patriarchal values about the subordinate status of women, about the nature of motherhood, infertility, and the family are both implicit and explicit in prevailing thinking about reproduction. The new technology offers women who wish to remain unmarried the opportunity to have a family, and it enables lesbian women to bear children. The research literature favors a Eurocentric nuclear family without any awareness that in Canada, and in the Western world, new forms of family life have been evolving as couples marry, divorce, and remarry. There is no awareness either that in other cultures this Eurocentric nuclear model is dysfunctional. Because of the rigid notion of the 2-parent nuclear family, the 3rd parties who are involved in either surrogate relationships or artificial insemination are deprecated. The feminist literature is more critical of the nuclear family, but it has been sometimes inconsistent on the relevant issues.

Synergistic Effect of Artificial Tears Containing Epigallocatechin Gallate and Hyaluronic Acid for the Treatment of Rabbits with Dry Eye Syndrome.

PubMed

Tseng, Ching-Li; Hung, Ya-Jung; Chen, Zhi-Yu; Fang, Hsu-Wei; Chen, Ko-Hua

2016-01-01

Dry eye syndrome (DES) is a common eye disease. Artificial tears (AT) are used to treat DES, but they are not effective. In this study, we assessed the anti-inflammatory effect of AT containing epigallocatechin gallate (EGCG) and hyaluronic acid (HA) on DES. Human corneal epithelial cells (HCECs) were used in the WST-8 assay to determine the safe dose of EGCG. Lipopolysaccharide-stimulated HCECs showing inflammation were treated with EGCG/HA. The expression of IL-1ß, IL-6, IL-8, and TNF-α was assessed by real-time PCR and AT physical properties such as the viscosity, osmolarity, and pH were examined. AT containing EGCG and HA were topically administered in a rabbit DES model established by treatment with 0.1% benzalkonium chloride (BAC). Tear secretion was assessed and fluorescein, H&E, and TUNEL staining were performed. Inflammatory cytokine levels in the corneas were also examined. The non-toxic optimal concentration of EGCG used for the treatment of HCECs in vitro was 10 μg/mL. The expression of several inflammatory genes, including IL-1ß, IL-6, IL-8, and TNF-α, was significantly inhibited in inflamed HCECs treated with 10 μg/mL EGCG and 0.1% (w/v) HA (E10/HA) compared to that in inflamed HCECs treated with either EGCG or HA alone. AT containing E10/HA mimic human tears, with similar osmolarity and viscosity and a neutral pH. Fluorescence examination of the ocular surface of mouse eyes showed that HA increased drug retention on the ocular surface. Topical treatment of DES rabbits with AT plus E10/HA increased tear secretion, reduced corneal epithelial damage, and maintained the epithelial layers and stromal structure. Moreover, the corneas of the E10/HA-treated rabbits showed fewer apoptotic cells, lower inflammation, and decreased IL-6, IL-8, and TNF-α levels. In conclusion, we showed that AT plus E10/HA had anti-inflammatory and mucoadhesive properties when used as topical eye drops and were effective for treating DES in rabbits.

Comment on "An improved gray Lattice Boltzmann model for simulating fluid flow in multi-scale porous media": Intrinsic links between LBE Brinkman schemes

NASA Astrophysics Data System (ADS)

Ginzburg, Irina

2016-02-01

In this Comment on the recent work (Zhu and Ma, 2013) [11] by Zhu and Ma (ZM) we first show that all three local gray Lattice Boltzmann (GLB) schemes in the form (Zhu and Ma, 2013) [11]: GS (Chen and Zhu, 2008; Gao and Sharma, 1994) [1,4], WBS (Walsh et al., 2009) [12] and ZM, fail to get constant Darcy's velocity in series of porous blocks. This inconsistency is because of their incorrect definition of the macroscopic velocity in the presence of the heterogeneous momentum exchange, while the original WBS model (Walsh et al., 2009) [12] does this properly. We improve the GS and ZM schemes for this and other related deficiencies. Second, we show that the ;discontinuous velocity; they recover on the stratified interfaces with their WBS scheme is inherent, in different degrees, to all LBE Brinkman schemes, including ZM scheme. None of them guarantees the stress and the velocity continuity by their implicit interface conditions, even in the frame of the two-relaxation-times (TRT) collision operator where these two properties are assured in stratified Stokes flow, Ginzburg (2007) [5]. Third, the GLB schemes are presented in work (Zhu and Ma, 2013) [11] as the alternative ones to direct, Brinkman-force based (BF) schemes (Freed, 1998; Nie and Martys, 2007) [3,8]. Yet, we show that the BF-TRT scheme (Ginzburg, 2008) [6] gets the solutions of any of the improved GLB schemes for specific, viscosity-dependent choice of its one or two local relaxation rates. This provides the principal difference between the GLB and BF: while the BF may respect the linearity of the Stokes-Brinkman equation rigorously, the GLB-TRT cannot, unless it reduces to the BF via the inverse transform of the relaxation rates. Furthermore, we show that, in limited parameter space, ;gray; schemes may run one another. From the practical point of view, permeability values obtained with the GLB are viscosity-dependent, unlike with the BF. Finally, the GLB shares with the BF a so-called anisotropy (Ginzburg, 2008; Nie and Martys, 2007) [6,8], that is, flow-direction-dependency in their effective viscosity corrections, related to the discretized spatial variation of the resistance forcing.

Numerical modeling of a vortex stabilized arcjet

NASA Astrophysics Data System (ADS)

Pawlas, Gary Edward

Arcjet thrusters are being actively considered for use in Earth orbit maneuvering applications. Satellite station-keeping is an example of a maneuvering application requiring the low thrust, high specific impulse of an arcjet. Experimental studies are currently the chief means of determining an optimal thruster configuration. Earlier numerical studies have failed to include all of the effects found in typical arcjets including complex geometries, viscosity and swirling flow. Arcjet geometries are large area ratio converging-diverging nozzles with centerbodies in the subsonic portion of the nozzle. The nozzle walls serve as the anode while the centerbody functions as the cathode. Viscous effects are important because the Reynolds number, based on the throat radius, is typically less than 1,000. Experimental studies have shown a swirl or circumferential velocity component stabilizes a constricted arc. The equations are described which governs the flow through a constricted arcjet thruster. An assumption that the flowfield is in local thermodynamic equilibrium leads to a single fluid plasma temperature model. An order of magnitude analysis reveals the governing fluid mechanics equations are uncoupled from the electromagnetic field equations. A numerical method is developed to solve the governing fluid mechanics equations, the Thin Layer Navier-Stokes equations. A coordinate transformation is used in deriving the governing equations to simplify the application of boundary conditions in complex geometries. An axisymmetric formulation is employed to include the swirl velocity component as well as the axial and redial velocity components. The numerical method is an implicit finite-volume technique and allows for large time steps to reach a converged steady-state solution. The inviscid fluxes are flux-split and Gauss-Seidel line relaxation is used to accelerate convergence. 'Converging diverging' nozzles with exit-to-throat area ratios up to 100:1 and annual nozzles were examined. Comparisons with experimental data and previous numerical results were in excellent agreement. Quantities examined included Mach number and static wall pressure distributions, and oblique shock structures.

Are implicit self-esteem measures valid for assessing individual and cultural differences?

PubMed

Falk, Carl F; Heine, Steven J; Takemura, Kosuke; Zhang, Cathy X J; Hsu, Chih-Wei

2015-02-01

Our research utilized two popular theoretical conceptualizations of implicit self-esteem: 1) implicit self-esteem as a global automatic reaction to the self; and 2) implicit self-esteem as a context/domain specific construct. Under this framework, we present an extensive search for implicit self-esteem measure validity among different cultural groups (Study 1) and under several experimental manipulations (Study 2). In Study 1, Euro-Canadians (N = 107), Asian-Canadians (N = 187), and Japanese (N = 112) completed a battery of implicit self-esteem, explicit self-esteem, and criterion measures. Included implicit self-esteem measures were either popular or provided methodological improvements upon older methods. Criterion measures were sampled from previous research on implicit self-esteem and included self-report and independent ratings. In Study 2, Americans (N = 582) completed a shorter battery of these same types of measures under either a control condition, an explicit prime meant to activate the self-concept in a particular context, or prime meant to activate self-competence related implicit attitudes. Across both studies, explicit self-esteem measures far outperformed implicit self-esteem measures in all cultural groups and under all experimental manipulations. Implicit self-esteem measures are not valid for individual or cross-cultural comparisons. We speculate that individuals may not form implicit associations with the self as an attitudinal object. © 2013 Wiley Periodicals, Inc.

Implicit self-esteem decreases in adolescence: a cross-sectional study.

PubMed

Cai, Huajian; Wu, Mingzheng; Luo, Yu L L; Yang, Jing

2014-01-01

Implicit self-esteem has remained an active research topic in both the areas of implicit social cognition and self-esteem in recent decades. The purpose of this study is to explore the development of implicit self-esteem in adolescents. A total of 599 adolescents from junior and senior high schools in East China participated in the study. They ranged in age from 11 to 18 years with a mean age of 14.10 (SD = 2.16). The degree of implicit self-esteem was assessed using the Implicit Association Test (IAT) with the improved D score as the index. Participants also completed the Rosenberg Self-Esteem Scale (α = 0.77). For all surveyed ages, implicit self-esteem was positively biased, all ts>8.59, all ps<0.001. The simple correlation between implicit self-esteem and age was significant, r =  -.25, p = 1. 10(-10). A regression with implicit self-esteem as the criterion variable, and age, gender, and age × gender interaction as predictors further revealed the significant negative linear relationship between age and implicit self-esteem, β = -0.19, t = -3.20, p = 0.001. However, explicit self-esteem manifested a reverse "U" shape throughout adolescence. Implicit self-esteem in adolescence manifests a declining trend with increasing age, suggesting that it is sensitive to developmental or age-related changes. This finding enriches our understanding of the development of implicit social cognition.

Using Implicit Measures to Highlight Science Teachers' Implicit Theories of Intelligence

ERIC Educational Resources Information Center

Mascret, Nicolas; Roussel, Peggy; Cury, François

2015-01-01

Using an innovative method, a Single-Target Implicit Association Test (ST-IAT) was created to explore the implicit theories of intelligence among science and liberal arts teachers and their relationships with their gender. The results showed that for science teachers--especially for male teachers--there was a negative implicit association between…

The Roles of Implicit Understanding of Engineering Ethics in Student Teams' Discussion.

PubMed

Lee, Eun Ah; Grohman, Magdalena; Gans, Nicholas R; Tacca, Marco; Brown, Matthew J

2017-12-01

Following previous work that shows engineering students possess different levels of understanding of ethics-implicit and explicit-this study focuses on how students' implicit understanding of engineering ethics influences their team discussion process, in cases where there is significant divergence between their explicit and implicit understanding. We observed student teams during group discussions of the ethical issues involved in their engineering design projects. Through the micro-scale discourse analysis based on cognitive ethnography, we found two possible ways in which implicit understanding influenced the discussion. In one case, implicit understanding played the role of intuitive ethics-an intuitive judgment followed by reasoning. In the other case, implicit understanding played the role of ethical insight, emotionally guiding the direction of the discussion. In either case, however, implicit understanding did not have a strong influence, and the conclusion of the discussion reflected students' explicit understanding. Because students' implicit understanding represented broader social implication of engineering design in both cases, we suggest to take account of students' relevant implicit understanding in engineering education, to help students become more socially responsible engineers.

Assessment of implicit health attitudes: a multitrait-multimethod approach and a comparison between patients with hypochondriasis and patients with anxiety disorders.

PubMed

Weck, Florian; Höfling, Volkmar

2015-01-01

Two adaptations of the Implicit Association Task were used to assess implicit anxiety (IAT-Anxiety) and implicit health attitudes (IAT-Hypochondriasis) in patients with hypochondriasis (n = 58) and anxiety patients (n = 71). Explicit anxieties and health attitudes were assessed using questionnaires. The analysis of several multitrait-multimethod models indicated that the low correlation between explicit and implicit measures of health attitudes is due to the substantial methodological differences between the IAT and the self-report questionnaire. Patients with hypochondriasis displayed significantly more dysfunctional explicit and implicit health attitudes than anxiety patients, but no differences were found regarding explicit and implicit anxieties. The study demonstrates the specificity of explicit and implicit dysfunctional health attitudes among patients with hypochondriasis.

Er:YAG and CTH:YAG laser radiation: contact versus non-contact enamel ablation and sonic-activated bulk composite placement

NASA Astrophysics Data System (ADS)

Buckova, M.; Kasparova, M.; Dostalova, T.; Jelinkova, H.; Sulc, J.; Nemec, M.; Fibrich, M.; Bradna, P.; Miyagi, M.

2013-05-01

Laser radiation can be used for effective caries removal and cavity preparation without significant thermal effects, collateral damage of tooth structure, or patient discomfort. The aim of this study was to compare the quality of tissue after contact or non-contact Er:YAG and CTH:YAG laser radiation ablation. The second goal was to increase the sealing ability of hard dental tissues using sonic-activated bulk filling material with change in viscosity during processing. The artificial caries was prepared in intact teeth to simulate a demineralized surface and then the Er:YAG or CTH:YAG laser radiation was applied. The enamel artificial caries was gently removed by the laser radiation and sonic-activated composite fillings were inserted. A stereomicroscope and then a scanning electron microscope were used to evaluate the enamel surface. Er:YAG contact mode ablation in enamel was quick and precise; the cavity was smooth with a keyhole shaped prism and rod relief arrangement without a smear layer. The sonic-activated filling material was consistently regularly distributed; no cracks or microleakage in the enamel were observed. CTH:YAG irradiation was able to clean but not ablate the enamel surface; in contact and also in non-contact mode there was evidence of melting and fusing of the enamel.

Gas Accretion onto a Supermassive Black Hole: A Step to Model AGN Feedback

NASA Astrophysics Data System (ADS)

Nagamine, K.; Barai, P.; Proga, D.

2012-08-01

We study gas accretion onto a supermassive black hole (SMBH) using the 3D SPH code GADGET-3 on scales of 0.1-200 pc. First we test our code with the spherically symmetric, adiabatic Bondi accretion problem. We find that our simulation can reproduce the expected Bondi accretion flow very well for a limited amount of time until the effect of the outer boundary starts to be visible. We also find artificial heating of gas near the inner accretion boundary due to the artificial viscosity of SPH. Second, we implement radiative cooling and heating due to X-rays, and examine the impact of thermal feedback by the central X-ray source. The accretion flow roughly follows the Bondi solution for low central X-ray luminosities; however, the flow starts to exhibit non-spherical fragmentation due to the thermal instability for a certain range of central LX, and a strong overall outflow develops for greater LX. The cold gas develops filamentary structures that fall into the central SMBH, whereas the hot gas tries to escape through the channels in between the cold filaments. Such fragmentation of accreting gas can assist in the formation of clouds around AGN, induce star-formation, and contribute to the observed variability of narrow-line regions.

Can implicit appraisal concepts produce emotion-specific effects? A focus on unfairness and anger.

PubMed

Tong, Eddie M W; Tan, Deborah H; Tan, Yan Lin

2013-06-01

This research examined whether the non-conscious activation of an implicit appraisal concept could affect responses associated with the corresponding emotion as predicted by appraisal theories. Explicit and implicit emotional responses were examined. We focused on implicit unfairness and its effect on anger. The results show that subliminal activation of implicit unfairness affected implicit anger responses (anger facial expression and latency responses to anger words) but not explicit anger feelings (i.e., reported anger). The non-conscious effect of implicit unfairness was specific to anger, as no effect on sadness, fear, and guilt was found. Copyright © 2013 Elsevier Inc. All rights reserved.

The Intergenerational Transmission of Implicit and Explicit Attitudes Toward Smoking

PubMed Central

Sherman, Steven J.; Chassin, Laurie; Presson, Clark; Seo, Dong-Chul; Macy, Jonathan T.

2009-01-01

This study examined the intergenerational transmission of implicit and explicit attitudes toward smoking, as well as the role of these attitudes in adolescents’ smoking initiation. There was evidence of intergenerational transmission of implicit attitudes. Mothers who had more positive implicit attitudes had children with more positive implicit attitudes. In turn, these positive implicit attitudes of adolescents predicted their smoking initiation 18-months later. Moreover, these effects were obtained above and beyond the effects of explicit attitudes. These findings provide the first evidence that the intergenerational transmission of implicit cognition may play a role in the intergenerational transmission of an addictive behavior. PMID:20126293

On the nature of implicit soul beliefs: when the past weighs more than the present.

PubMed

Anglin, Stephanie M

2015-06-01

Intuitive childhood beliefs in dualism may lay the foundation for implicit soul and afterlife beliefs, which may diverge from explicit beliefs formed later in adulthood. Brief Implicit Association Tests were developed to investigate the relation of implicit soul and afterlife beliefs to childhood and current beliefs. Early but not current beliefs covaried with implicit beliefs. Results demonstrated greater discrepancies in current than in childhood soul and afterlife beliefs among religious groups, and no differences in implicit beliefs. These findings suggest that implicit soul and afterlife beliefs diverge from current self-reported beliefs, stemming instead from childhood beliefs. © 2014 The British Psychological Society.

Changes of Explicit and Implicit Stigma in Medical Students during Psychiatric Clerkship.

PubMed

Wang, Peng-Wei; Ko, Chih-Hung; Chen, Cheng-Sheng; Yang, Yi-Hsin Connine; Lin, Huang-Chi; Cheng, Cheng-Chung; Tsang, Hin-Yeung; Wu, Ching-Kuan; Yen, Cheng-Fang

2016-04-01

This study examines the differences in explicit and implicit stigma between medical and non-medical undergraduate students at baseline; the changes of explicit and implicit stigma in medical undergraduate and non-medical undergraduate students after a 1-month psychiatric clerkship and 1-month follow-up period; and the differences in the changes of explicit and implicit stigma between medical and non-medical undergraduate students. Seventy-two medical undergraduate students and 64 non-medical undergraduate students were enrolled. All participants were interviewed at intake and after 1 month. The Taiwanese version of the Stigma Assessment Scale and the Implicit Association Test were used to measure the participants' explicit and implicit stigma. Neither explicit nor implicit stigma differed between two groups at baseline. The medical, but not the non-medical, undergraduate students had a significant decrease in explicit stigma during the 1-month period of follow-up. Neither the medical nor the non-medical undergraduate students exhibited a significant change in implicit stigma during the one-month of follow-up, however. There was an interactive effect between group and time on explicit stigma but not on implicit stigma. Explicit but not implicit stigma toward mental illness decreased in the medical undergraduate students after a psychiatric clerkship. Further study is needed to examine how to improve implicit stigma toward mental illness.

The Relationship of Explicit-Implicit Evaluative Discrepancy to Exercise Dropout in Middle-Aged Adults.

PubMed

Berry, Tanya R; Rodgers, Wendy M; Divine, Alison; Hall, Craig

2018-06-19

Discrepancies between automatically activated associations (i.e., implicit evaluations) and explicit evaluations of motives (measured with a questionnaire) could lead to greater information processing to resolve discrepancies or self-regulatory failures that may affect behavior. This research examined the relationship of health and appearance exercise-related explicit-implicit evaluative discrepancies, the interaction between implicit and explicit evaluations, and the combined value of explicit and implicit evaluations (i.e., the summed scores) to dropout from a yearlong exercise program. Participants (N = 253) completed implicit health and appearance measures and explicit health and appearance motives at baseline, prior to starting the exercise program. The sum of implicit and explicit appearance measures was positively related to weeks in the program, and discrepancy between the implicit and explicit health measures was negatively related to length of time in the program. Implicit exercise evaluations and their relationships to oft-cited motives such as appearance and health may inform exercise dropout.

Implicit Self-Esteem Decreases in Adolescence: A Cross-Sectional Study

PubMed Central

Cai, Huajian; Wu, Mingzheng; Luo, Yu L. L.; Yang, Jing

2014-01-01

Implicit self-esteem has remained an active research topic in both the areas of implicit social cognition and self-esteem in recent decades. The purpose of this study is to explore the development of implicit self-esteem in adolescents. A total of 599 adolescents from junior and senior high schools in East China participated in the study. They ranged in age from 11 to 18 years with a mean age of 14.10 (SD = 2.16). The degree of implicit self-esteem was assessed using the Implicit Association Test (IAT) with the improved D score as the index. Participants also completed the Rosenberg Self-Esteem Scale (α = 0.77). For all surveyed ages, implicit self-esteem was positively biased, all ts>8.59, all ps<0.001. The simple correlation between implicit self-esteem and age was significant, r = −.25, p = 1.0×10−10. A regression with implicit self-esteem as the criterion variable, and age, gender, and age × gender interaction as predictors further revealed the significant negative linear relationship between age and implicit self-esteem, β = −0.19, t = −3.20, p = 0.001. However, explicit self-esteem manifested a reverse “U” shape throughout adolescence. Implicit self-esteem in adolescence manifests a declining trend with increasing age, suggesting that it is sensitive to developmental or age-related changes. This finding enriches our understanding of the development of implicit social cognition. PMID:24587169

A nonlinear relaxation/quasi-Newton algorithm for the compressible Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Edwards, Jack R.; Mcrae, D. S.

1992-01-01

A highly efficient implicit method for the computation of steady, two-dimensional compressible Navier-Stokes flowfields is presented. The discretization of the governing equations is hybrid in nature, with flux-vector splitting utilized in the streamwise direction and central differences with flux-limited artificial dissipation used for the transverse fluxes. Line Jacobi relaxation is used to provide a suitable initial guess for a new nonlinear iteration strategy based on line Gauss-Seidel sweeps. The applicability of quasi-Newton methods as convergence accelerators for this and other line relaxation algorithms is discussed, and efficient implementations of such techniques are presented. Convergence histories and comparisons with experimental data are presented for supersonic flow over a flat plate and for several high-speed compression corner interactions. Results indicate a marked improvement in computational efficiency over more conventional upwind relaxation strategies, particularly for flowfields containing large pockets of streamwise subsonic flow.

Elliptic flow computation by low Reynolds number two-equation turbulence models

NASA Technical Reports Server (NTRS)

Michelassi, V.; Shih, T.-H.

1991-01-01

A detailed comparison of ten low-Reynolds-number k-epsilon models is carried out. The flow solver, based on an implicit approximate factorization method, is designed for incompressible, steady two-dimensional flows. The conservation of mass is enforced by the artificial compressibility approach and the computational domain is discretized using centered finite differences. The turbulence model predictions of the flow past a hill are compared with experiments at Re = 10 exp 6. The effects of the grid spacing together with the numerical efficiency of the various formulations are investigated. The results show that the models provide a satisfactory prediction of the flow field in the presence of a favorable pressure gradient, while the accuracy rapidly deteriorates when a strong adverse pressure gradient is encountered. A newly proposed model form that does not explicitly depend on the wall distance seems promising for application to complex geometries.

Prolegomena to any future mereology of the body.

PubMed

Fried, Edward

2013-10-01

Many bioethical arguments rely implicitly on the assumption that the concept of "human part" is one on which everyone must agree, because it is unambiguous. But various parties interpret this "unambiguous" term in incompatible ways, leading to contention. This article is an informal presentation of a topomereological system on whose preferred interpretation several distinct but related meanings of "human part" can be isolated: part of a human body, part of the completion of a human body, and part of a human being. A case is analyzed (the first total artificial heart (TAH) implantation), demonstrating in the process much of the apparatus of the system. By means of a casuistic methodology, the analysis is translated into recommendations for the ethical conduct of future TAH research. The more general conclusion, however, is that formal methods may provide useful tools for clarifying thought processes and organizing arguments in debates over bioethical issues.

A Least-Squares Finite Element Method for Electromagnetic Scattering Problems

NASA Technical Reports Server (NTRS)

Wu, Jie; Jiang, Bo-nan

1996-01-01

The least-squares finite element method (LSFEM) is applied to electromagnetic scattering and radar cross section (RCS) calculations. In contrast to most existing numerical approaches, in which divergence-free constraints are omitted, the LSFF-M directly incorporates two divergence equations in the discretization process. The importance of including the divergence equations is demonstrated by showing that otherwise spurious solutions with large divergence occur near the scatterers. The LSFEM is based on unstructured grids and possesses full flexibility in handling complex geometry and local refinement Moreover, the LSFEM does not require any special handling, such as upwinding, staggered grids, artificial dissipation, flux-differencing, etc. Implicit time discretization is used and the scheme is unconditionally stable. By using a matrix-free iterative method, the computational cost and memory requirement for the present scheme is competitive with other approaches. The accuracy of the LSFEM is verified by several benchmark test problems.

Computations of spray, fuel-air mixing, and combustion in a lean-premixed-prevaporized combustor

NASA Technical Reports Server (NTRS)

Dasgupta, A.; Li, Z.; Shih, T. I.-P.; Kundu, K.; Deur, J. M.

1993-01-01

A code was developed for computing the multidimensional flow, spray, combustion, and pollutant formation inside gas turbine combustors. The code developed is based on a Lagrangian-Eulerian formulation and utilizes an implicit finite-volume method. The focus of this paper is on the spray part of the code (both formulation and algorithm), and a number of issues related to the computation of sprays and fuel-air mixing in a lean-premixed-prevaporized combustor. The issues addressed include: (1) how grid spacings affect the diffusion of evaporated fuel, and (2) how spurious modes can arise through modelling of the spray in the Lagrangian computations. An upwind interpolation scheme is proposed to account for some effects of grid spacing on the artificial diffusion of the evaporated fuel. Also, some guidelines are presented to minimize errors associated with the spurious modes.

Elastic Valve Using Induced-Charge Electro-Osmosis

NASA Astrophysics Data System (ADS)

Sugioka, Hideyuki

2015-06-01

Biomimic devices using induced-charge electro-osmosis (ICEO) is interesting since they have the possibility to realize high-performance functions with simple structures and with low-energy consumption. Thus, inspired by a cilium, we propose a two-dimensional artificial elastic valve using hydrodynamic force due to ICEO with a thin elastic beam in a microfluidic channel and numerically examine the valving performance. By an implicit strongly coupled simulation technique between a fluid and an elastic structure based on the boundary-element method, along with the thin-double-layer approximation, we realize stable calculations and find that the elastic valve using ICEO functions effectively at high frequency with low applied voltages in a realistic pressure flow. Further, we also examine passive motion of the valve; i.e., it stops a reverse flow effectively and releases a forward flow in the channel. We believe that our device can be used in a wide range of microfluidic applications, such as mixers, pumps, etc.

An efficient nonlinear relaxation technique for the three-dimensional, Reynolds-averaged Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Edwards, Jack R.; Mcrae, D. S.

1993-01-01

An efficient implicit method for the computation of steady, three-dimensional, compressible Navier-Stokes flowfields is presented. A nonlinear iteration strategy based on planar Gauss-Seidel sweeps is used to drive the solution toward a steady state, with approximate factorization errors within a crossflow plane reduced by the application of a quasi-Newton technique. A hybrid discretization approach is employed, with flux-vector splitting utilized in the streamwise direction and central differences with artificial dissipation used for the transverse fluxes. Convergence histories and comparisons with experimental data are presented for several 3-D shock-boundary layer interactions. Both laminar and turbulent cases are considered, with turbulent closure provided by a modification of the Baldwin-Barth one-equation model. For the problems considered (175,000-325,000 mesh points), the algorithm provides steady-state convergence in 900-2000 CPU seconds on a single processor of a Cray Y-MP.

Developmental Dissociation Between the Maturation of Procedural Memory and Declarative Memory

PubMed Central

Finn, Amy S.; Kalra, Priya B.; Goetz, Calvin; Leonard, Julia A.; Sheridan, Margaret A.; Gabrieli, John D. E.

2015-01-01

Declarative memory and procedural memory are known to be two fundamentally different kinds of memory that are dissociable in their psychological characteristics and measurement (explicit versus implicit) and in the neural systems that subserve each kind of memory. Declarative memory abilities are known to improve from childhood through young adulthood, but the developmental maturation of procedural memory is largely unknown. We compared 10-year-old children and young adults on measures of declarative memory, working memory capacity, and four measures of procedural memory that have been strongly dissociated from declarative memory (mirror tracing, rotary pursuit, probabilistic classification, and artificial grammar). Children had lesser declarative memory ability and lesser working memory capacity than the adults, but exhibited learning equivalent to adults on all four measures of procedural memory. Declarative and procedural memory are, therefore, developmentally dissociable, with procedural memory being adult-like by age 10 and declarative memory continuing to mature into young adulthood. PMID:26560675

The embodied performance pedagogy of Jacques Lecoq

NASA Astrophysics Data System (ADS)

Kemp, Rick

2017-01-01

This article proposes that acting is a valuable area of research for the fields of Artificial Intelligence and Simulated Behaviour. This suggestion is supported through applying theories and findings from the field of embodied cognition to the performance pedagogy of French acting teacher Jacques Lecoq (1921-1999). Embodied cognition proposes that thinking and behaviour are properties of the whole human organism, not the brain alone, and that body, brain and cognition are "situated" - engaged with the surrounding environment. This thesis arises from findings that show that sensorial and motor experiences form the neural foundations for mental concepts and that sensorimotor neural networks are partially re-activated by mental and linguistic activity, leading to the concept of "embodied simulation". I give examples of the ways in which Lecoq's conceptualisation of acting technique is implicitly congruent with the principles of embodied cognition, and often explicitly anticipates its precepts.

Distinguishing the affective and cognitive bases of implicit attitudes to improve prediction of food choices.

PubMed

Trendel, Olivier; Werle, Carolina O C

2016-09-01

Eating behaviors largely result from automatic processes. Yet, in existing research, automatic or implicit attitudes toward food often fail to predict eating behaviors. Applying findings in cognitive neuroscience research, we propose and find that a central reason why implicit attitudes toward food are not good predictors of eating behaviors is that implicit attitudes are driven by two distinct constructs that often have diverging evaluative consequences: the automatic affective reactions to food (e.g., tastiness; the affective basis of implicit attitudes) and the automatic cognitive reactions to food (e.g., healthiness; the cognitive basis of implicit attitudes). More importantly, we find that the affective and cognitive bases of implicit attitudes directly and uniquely influence actual food choices under different conditions. While the affective basis of implicit attitude is the main driver of food choices, it is the only driver when cognitive resources during choice are limited. The cognitive basis of implicit attitudes uniquely influences food choices when cognitive resources during choice are plentiful but only for participants low in impulsivity. Researchers interested in automatic processes in eating behaviors could thus benefit by distinguishing between the affective and cognitive bases of implicit attitudes. Copyright © 2015 Elsevier Ltd. All rights reserved.

[The management of Dysphagia. Part 1: diagnostics].

PubMed

Schönweiler, R

2004-12-01

Patients with chronic dysphagia are often in need of artificial nutrition; though being well balanced in terms of energy and vitamins, patients are at a high risk for the loss of resistance and body weight. Dysphagia also causes a severe drawback of the overall quality of life. This paper gives an overview of the present management of dysphagia from the point of view of otolaryngologists, head-neck-surgeons, phoniatricians, and medical speech-language-voice-pathologists. The physiology of swallowing and typical symptoms of dysphagia are first explained. Then the current most important diagnostic procedures as orofacial and laryngeal function analysis, video-endoscopy, and quantitative assessments, are discussed (part 1). This also includes considerations on bolus viscosity variation, postures, swallowing maneuvers, and sensory enhancement procedures, while actual options like botulinum toxin, passy-muir speaking valve, electromyographic biofeedback, and electrostimulation are also mentioned (part 2).

Secular rotational motions and the mechanical structure of a dynamical viscoelastic earth

NASA Technical Reports Server (NTRS)

Yuen, D. A.; Sabadini, R.

1984-01-01

A survey is presented of analytical methods for computing the linear responses of the rotational axis of a layered viscoelastic earth to surface loading. Theoretical research in this area is first summarized, and the differences between the mechanical boundary conditions to be applied at the interface separating the upper and lower mantles for an adiabatically and chemically stratified mantle are discussed. Some examples of polar wander and secular variation of the spin rate from glacial excitation are presented for various types of chemical and viscosity stratifications. The effects of an artificial density jump at the base of the lithosphere in models are examined, and certain issues concerning the fluid tidal Love number for different types of density stratification are addressed. The meaning of effective plate thickness over geological time scales for rotational dynamics is discussed.

Using implicit association tests for the assessment of implicit personality self-concepts of extraversion and neuroticism in schizophrenia.

PubMed

Suslow, Thomas; Lindner, Christian; Kugel, Harald; Egloff, Boris; Schmukle, Stefan C

2014-08-30

There is evidence from research based on self-report personality measures that schizophrenia patients tend to be lower in extraversion and higher in neuroticism than healthy individuals. Self-report personality measures assess aspects of the explicit self-concept. The Implicit Association Test (IAT) has been developed to assess aspects of implicit cognition such as implicit attitudes and implicit personality traits. The present study was conducted to investigate the applicability and reliability of the IAT in schizophrenia patients and test whether they differ from healthy individuals on implicitly measured extraversion and neuroticism. The IAT and the NEO-FFI were administered as implicit and explicit measures of extraversion and neuroticism to 34 schizophrenia patients and 45 healthy subjects. For all IAT scores satisfactory to good reliabilities were observed in the patient sample. In both study groups, IAT scores were not related to NEO-FFI scores. Schizophrenia patients were lower in implicit and explicit extraversion and higher in implicit and explicit neuroticism than healthy individuals. Our data show that the IAT can be reliably applied to schizophrenia patients and suggest that they differ from healthy individuals not only in their conscious representation but also in their implicit representation of the self with regard to neuroticism and extraversion-related characteristics. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Implicit Associations and Explicit Expectancies toward Cannabis in Heavy Cannabis Users and Controls

PubMed Central

Beraha, Esther M.; Cousijn, Janna; Hermanides, Elisa; Goudriaan, Anna E.; Wiers, Reinout W.

2013-01-01

Cognitive biases, including implicit memory associations are thought to play an important role in the development of addictive behaviors. The aim of the present study was to investigate implicit affective memory associations in heavy cannabis users. Implicit positive-arousal, sedation, and negative associations toward cannabis were measured with three Single Category Implicit Association Tests (SC-IAT’s) and compared between 59 heavy cannabis users and 89 controls. Moreover, we investigated the relationship between these implicit affective associations and explicit expectancies, subjective craving, cannabis use, and cannabis related problems. Results show that heavy cannabis users had stronger implicit positive-arousal associations but weaker implicit negative associations toward cannabis compared to controls. Moreover, heavy cannabis users had stronger sedation but weaker negative explicit expectancies toward cannabis compared to controls. Within heavy cannabis users, more cannabis use was associated with stronger implicit negative associations whereas more cannabis use related problems was associated with stronger explicit negative expectancies, decreasing the overall difference on negative associations between cannabis users and controls. No other associations were observed between implicit associations, explicit expectancies, measures of cannabis use, cannabis use related problems, or subjective craving. These findings indicate that, in contrast to other substances of abuse like alcohol and tobacco, the relationship between implicit associations and cannabis use appears to be weak in heavy cannabis users. PMID:23801968

Implicit and explicit ethnocentrism: revisiting the ideologies of prejudice.

PubMed

Cunningham, William A; Nezlek, John B; Banaji, Mahzarin R

2004-10-01

Two studies investigated relationships among individual differences in implicit and explicit prejudice, right-wing ideology, and rigidity in thinking. The first study examined these relationships focusing on White Americans' prejudice toward Black Americans. The second study provided the first test of implicit ethnocentrism and its relationship to explicit ethnocentrism by studying the relationship between attitudes toward five social groups. Factor analyses found support for both implicit and explicit ethnocentrism. In both studies, mean explicit attitudes toward out groups were positive, whereas implicit attitudes were negative, suggesting that implicit and explicit prejudices are distinct; however, in both studies, implicit and explicit attitudes were related (r = .37, .47). Latent variable modeling indicates a simple structure within this ethnocentric system, with variables organized in order of specificity. These results lead to the conclusion that (a) implicit ethnocentrism exists and (b) it is related to and distinct from explicit ethnocentrism.

Gambling and Sport: Implicit Association and Explicit Intention Among Underage Youth.

PubMed

Li, En; Langham, Erika; Browne, Matthew; Rockloff, Matthew; Thorne, Hannah

2018-03-23

This study examined whether an implicit association existed between gambling and sport among underage youth in Australia, and whether this implicit association could shape their explicit intention to gamble. A sample of 14-17 year old Australian participants completed two phases of tasks, including an implicit association test based online experiment, and a post-experiment online survey. The results supported the existence of an implicit association between gambling and sport among the participants. This implicit association became stronger when they saw sport-relevant (vs. sport-irrelevant) gambling logos, or gambling-relevant (vs. gambling-irrelevant) sport names. In addition, this implicit association was positively related to the amount of sport viewing, but only among those participants who had more favorable gambling attitudes. Lastly, gambling attitudes and advertising knowledge, rather than the implicit association, turned out to be significant predictors of the explicit intention to gamble.

Hooked on a feeling: affective anti-smoking messages are more effective than cognitive messages at changing implicit evaluations of smoking

PubMed Central

Smith, Colin Tucker; De Houwer, Jan

2015-01-01

Because implicit evaluations are thought to underlie many aspects of behavior, researchers have started looking for ways to change them. We examine whether and when persuasive messages alter strongly held implicit evaluations of smoking. In smokers, an affective anti-smoking message led to more negative implicit evaluations on four different implicit measures as compared to a cognitive anti-smoking message which seemed to backfire. Additional analyses suggested that the observed effects were mediated by the feelings and emotions raised by the messages. In non-smokers, both the affective and cognitive message engendered slightly more negative implicit evaluations. We conclude that persuasive messages change implicit evaluations in a way that depends on properties of the message and of the participant. Thus, our data open new avenues for research directed at tailoring persuasive messages to change implicit evaluations. PMID:26557099

Hooked on a feeling: affective anti-smoking messages are more effective than cognitive messages at changing implicit evaluations of smoking.

PubMed

Smith, Colin Tucker; De Houwer, Jan

2015-01-01

Because implicit evaluations are thought to underlie many aspects of behavior, researchers have started looking for ways to change them. We examine whether and when persuasive messages alter strongly held implicit evaluations of smoking. In smokers, an affective anti-smoking message led to more negative implicit evaluations on four different implicit measures as compared to a cognitive anti-smoking message which seemed to backfire. Additional analyses suggested that the observed effects were mediated by the feelings and emotions raised by the messages. In non-smokers, both the affective and cognitive message engendered slightly more negative implicit evaluations. We conclude that persuasive messages change implicit evaluations in a way that depends on properties of the message and of the participant. Thus, our data open new avenues for research directed at tailoring persuasive messages to change implicit evaluations.

Adults' implicit associations to infant positive and negative acoustic cues: Moderation by empathy and gender.

PubMed

Senese, Vincenzo Paolo; Venuti, Paola; Giordano, Francesca; Napolitano, Maria; Esposito, Gianluca; Bornstein, Marc H

2017-09-01

In this study a novel auditory version of the Single Category Implicit Association Test (SC-IAT-A) was developed to investigate (a) the valence of adults' associations to infant cries and laughs, (b) moderation of implicit associations by gender and empathy, and (c) the robustness of implicit associations controlling for auditory sensitivity. Eighty adults (50% females) were administered two SC-IAT-As, the Empathy Quotient, and the Weinstein Noise Sensitivity Scale. Adults showed positive implicit associations to infant laugh and negative ones to infant cry; only the implicit associations with the infant laugh were negatively related to empathy scores, and no gender differences were observed. Finally, implicit associations to infant cry were affected by noise sensitivity. The SC-IAT-A is useful to evaluate the valence of implicit reactions to infant auditory cues and could provide fresh insights into understanding processes that regulate the quality of adult-infant relationships.

Self-Regulation and Implicit Attitudes Toward Physical Activity Influence Exercise Behavior.

PubMed

Padin, Avelina C; Emery, Charles F; Vasey, Michael; Kiecolt-Glaser, Janice K

2017-08-01

Dual-process models of health behavior posit that implicit and explicit attitudes independently drive healthy behaviors. Prior evidence indicates that implicit attitudes may be related to weekly physical activity (PA) levels, but the extent to which self-regulation attenuates this link remains unknown. This study examined the associations between implicit attitudes and self-reported PA during leisure time among 150 highly active young adults and evaluated the extent to which effortful control (one aspect of self-regulation) moderated this relationship. Results indicated that implicit attitudes toward exercise were unrelated to average workout length among individuals with higher effortful control. However, those with lower effortful control and more negative implicit attitudes reported shorter average exercise sessions compared with those with more positive attitudes. Implicit and explicit attitudes were unrelated to total weekly PA. A combination of poorer self-regulation and negative implicit attitudes may leave individuals vulnerable to mental and physical health consequences of low PA.

Abiotic Nitrous Oxide Production in Natural and Artificial Seawater

NASA Astrophysics Data System (ADS)

Ochoa, H.; Stanton, C. L.; Cavazos, A. R.; Ostrom, N. E.; Glass, J. B.

2014-12-01

The ocean contributes approximately one third of global sources of nitrous oxide (N2O) to the atmosphere. While nitrification is thought to be the dominant pathway for marine N2O production, mechanisms remain unresolved. Previous studies have carried the implicit assumption that marine N2O originates directly from enzymatic sources. However, abiotic production of N2O is possible via chemical reactions between nitrogenous intermediates and redox active trace metals in seawater. In this study, we investigated N2O production and isotopic composition in treatments with and without added hydroxylamine (NH2OH) and nitric oxide (NO), intermediates in microbial oxidation of ammonia to nitrite, and Fe(III). Addition of substrates to sterile artificial seawater was compared with filtered and unfiltered seawater from Sapelo Island, coastal Georgia, USA. N2O production was observed immediately after addition of Fe(III) in the presence of NH2OH at pH 8 in sterile artificial seawater. Highest N2O production was observed in the presence of Fe(III), NO, and NH2OH. The isotopomer site preference of abiotically produced N2O was consistent with previous studies (31 ± 2 ‰). Higher abiotic N2O production was observed in sterile artificial seawater (salinity: 35 ppt) than filtered Sapelo Island seawater (salinity: 25 ppt) whereas diluted sterile artificial seawater (18 ppt) showed lowest N2O production, suggesting that higher salinity promotes enhanced abiotic N2O production. Addition of Fe(III) to unfiltered Sapelo Island seawater stimulated N2O production. The presence of ammonia-oxidizing archaea (AOA), which lack known N2O producing enzymes, in Sapelo Island seawater was confirmed by successful amplification of the archaeal amoA gene, whereas ammonia-oxidizing bacteria (AOB), which contain N2O-producing enzymes were undetected. Given the few Fe-containing proteins present in AOA, it is likely that Fe(III) addition promoted N2O production via an abiotic vs. enzymatic N2O mechanism. Overall, this study suggests that abiotic N2O production may be occurring in marine environments where microbial ammonia oxidation occurs in the presence of elevated Fe and/or other redox-active metals, such as coastal areas, oxygen minimum zones, and near the sediment-water interface.

Using the Implicit Association Test and the Implicit Relational Assessment Procedure to Measure Attitudes toward Meat and Vegetables in Vegetarians and Meat-Eaters

ERIC Educational Resources Information Center

Barnes-Holmes, Dermot; Murtagh, Louise; Barnes-Holmes, Yvonne; Stewart, Ian

2010-01-01

The current study aimed to assess the implicit attitudes of vegetarians and non-vegetarians towards meat and vegetables, using the Implicit Association Test (IAT) and the Implicit Relational Assessment Procedure (IRAP). Both measures involved asking participants to respond, under time pressure, to pictures of meat or vegetables as either positive…

The emergence of mind and brain: an evolutionary, computational, and philosophical approach.

PubMed

Mainzer, Klaus

2008-01-01

Modern philosophy of mind cannot be understood without recent developments in computer science, artificial intelligence (AI), robotics, neuroscience, biology, linguistics, and psychology. Classical philosophy of formal languages as well as symbolic AI assume that all kinds of knowledge must explicitly be represented by formal or programming languages. This assumption is limited by recent insights into the biology of evolution and developmental psychology of the human organism. Most of our knowledge is implicit and unconscious. It is not formally represented, but embodied knowledge, which is learnt by doing and understood by bodily interacting with changing environments. That is true not only for low-level skills, but even for high-level domains of categorization, language, and abstract thinking. The embodied mind is considered an emergent capacity of the brain as a self-organizing complex system. Actually, self-organization has been a successful strategy of evolution to handle the increasing complexity of the world. Genetic programs are not sufficient and cannot prepare the organism for all kinds of complex situations in the future. Self-organization and emergence are fundamental concepts in the theory of complex dynamical systems. They are also applied in organic computing as a recent research field of computer science. Therefore, cognitive science, AI, and robotics try to model the embodied mind in an artificial evolution. The paper analyzes these approaches in the interdisciplinary framework of complex dynamical systems and discusses their philosophical impact.

I trust it, but I don't know why: effects of implicit attitudes toward automation on trust in an automated system.

PubMed

Merritt, Stephanie M; Heimbaugh, Heather; LaChapell, Jennifer; Lee, Deborah

2013-06-01

This study is the first to examine the influence of implicit attitudes toward automation on users' trust in automation. Past empirical work has examined explicit (conscious) influences on user level of trust in automation but has not yet measured implicit influences. We examine concurrent effects of explicit propensity to trust machines and implicit attitudes toward automation on trust in an automated system. We examine differential impacts of each under varying automation performance conditions (clearly good, ambiguous, clearly poor). Participants completed both a self-report measure of propensity to trust and an Implicit Association Test measuring implicit attitude toward automation, then performed an X-ray screening task. Automation performance was manipulated within-subjects by varying the number and obviousness of errors. Explicit propensity to trust and implicit attitude toward automation did not significantly correlate. When the automation's performance was ambiguous, implicit attitude significantly affected automation trust, and its relationship with propensity to trust was additive: Increments in either were related to increases in trust. When errors were obvious, a significant interaction between the implicit and explicit measures was found, with those high in both having higher trust. Implicit attitudes have important implications for automation trust. Users may not be able to accurately report why they experience a given level of trust. To understand why users trust or fail to trust automation, measurements of implicit and explicit predictors may be necessary. Furthermore, implicit attitude toward automation might be used as a lever to effectively calibrate trust.

Using the Implicit Association Test to Assess Children's Implicit Attitudes toward Smoking.

PubMed

Andrews, Judy A; Hampson, Sarah E; Greenwald, Anthony G; Gordon, Judith; Widdop, Chris

2010-09-01

The development and psychometric properties of an Implicit Association Test (IAT) measuring implicit attitude toward smoking among fifth grade children were described. The IAT with "sweets" as the contrast category resulted in higher correlations with explicit attitudes than did the IAT with "healthy foods" as the contrast category. Children with family members who smoked (versus non-smoking) and children who were high in sensation seeking (versus low) had a significantly more favorable implicit attitude toward smoking. Further, implicit attitudes became less favorable after engaging in tobacco prevention activities targeting risk perceptions of addiction. Results support the reliability and validity of this version of the IAT and illustrate its usefulness in assessing young children's implicit attitude toward smoking.

Using the Implicit Association Test to Assess Children's Implicit Attitudes toward Smoking

PubMed Central

Andrews, Judy A.; Hampson, Sarah E.; Greenwald, Anthony G.; Gordon, Judith; Widdop, Chris

2009-01-01

The development and psychometric properties of an Implicit Association Test (IAT) measuring implicit attitude toward smoking among fifth grade children were described. The IAT with “sweets” as the contrast category resulted in higher correlations with explicit attitudes than did the IAT with “healthy foods” as the contrast category. Children with family members who smoked (versus non-smoking) and children who were high in sensation seeking (versus low) had a significantly more favorable implicit attitude toward smoking. Further, implicit attitudes became less favorable after engaging in tobacco prevention activities targeting risk perceptions of addiction. Results support the reliability and validity of this version of the IAT and illustrate its usefulness in assessing young children's implicit attitude toward smoking. PMID:21566676

Power effects on implicit prejudice and stereotyping: The role of intergroup face processing.

PubMed

Schmid, Petra C; Amodio, David M

2017-04-01

Power is thought to increase discrimination toward subordinate groups, yet its effect on different forms of implicit bias remains unclear. We tested whether power enhances implicit racial stereotyping, in addition to implicit prejudice (i.e., evaluative associations), and examined the effect of power on the automatic processing of faces during implicit tasks. Study 1 showed that manipulated high power increased both forms of implicit bias, relative to low power. Using a neural index of visual face processing (the N170 component of the ERP), Study 2 revealed that power affected the encoding of White ingroup vs. Black outgroup faces. Whereas high power increased the relative processing of outgroup faces during evaluative judgments in the prejudice task, it decreased the relative processing of outgroup faces during stereotype trait judgments. An indirect effect of power on implicit prejudice through enhanced processing of outgroup versus ingroup faces suggested a potential link between face processing and implicit bias. Together, these findings demonstrate that power can affect implicit prejudice and stereotyping as well as early processing of racial ingroup and outgroup faces.

Implicit Attitudes toward the Self Over Time in Chinese Undergraduates

PubMed Central

Yang, Qing; Zhao, Yufang; Guan, Lili; Huang, Xiting

2017-01-01

Although the explicit attitudes of Chinese people toward the self over time are known (i.e., past = present < future), little is known about their implicit attitudes. Two studies were conducted to measure the implicit subjective temporal trajectory (STT) of Chinese undergraduates. Study 1 used a Go/No-go association task to measure participants’ implicit attitudes toward their past, present, and future selves. The obtained implicit STT was different from the explicit pattern found in former research. It showed that the future self was viewed to be identical to the present self and participants implicitly evaluated their present self as better than the past self. Since this comparison of the past and present selves suggested a cultural difference, we aimed to replicate this finding in Study 2. Using an implicit association test, we again found that the present self was more easily associated with positive valence than the past self. Overall, both studies reveal an implicitly inclining-flat STT (i.e., past < present = future) for Chinese undergraduates. Implications of this difference in explicit-implicit measures and the cultural differences of temporal self appraisals are discussed. PMID:29163291

Implicit Motives and Men’s Perceived Constraint in Fatherhood

PubMed Central

Ruppen, Jessica; Waldvogel, Patricia; Ehlert, Ulrike

2016-01-01

Research shows that implicit motives influence social relationships. However, little is known about their role in fatherhood and, particularly, how men experience their paternal role. Therefore, this study examined the association of implicit motives and fathers’ perceived constraint due to fatherhood. Furthermore, we explored their relation to fathers’ life satisfaction. Participants were fathers with biological children (N = 276). They were asked to write picture stories, which were then coded for implicit affiliation and power motives. Perceived constraint and life satisfaction were assessed on a visual analog scale. A higher implicit need for affiliation was significantly associated with lower perceived constraint, whereas the implicit need for power had the opposite effect. Perceived constraint had a negative influence on life satisfaction. Structural equation modeling revealed significant indirect effects of implicit affiliation and power motives on life satisfaction mediated by perceived constraint. Our findings indicate that men with a higher implicit need for affiliation experience less constraint due to fatherhood, resulting in higher life satisfaction. The implicit need for power, however, results in more perceived constraint and is related to decreased life satisfaction. PMID:27933023

Health Care Providers’ Implicit and Explicit Attitudes Toward Lesbian Women and Gay Men

PubMed Central

Riskind, Rachel G.; Nosek, Brian A.

2015-01-01

Objectives. We examined providers’ implicit and explicit attitudes toward lesbian and gay people by provider gender, sexual identity, and race/ethnicity. Methods. We examined attitudes toward heterosexual people versus lesbian and gay people in Implicit Association Test takers: 2338 medical doctors, 5379 nurses, 8531 mental health providers, 2735 other treatment providers, and 214 110 nonproviders in the United States and internationally between May 2006 and December 2012. We characterized the sample with descriptive statistics and calculated Cohen d, a standardized effect size measure, with 95% confidence intervals. Results. Among heterosexual providers, implicit preferences always favored heterosexual people over lesbian and gay people. Implicit preferences for heterosexual women were weaker than implicit preferences for heterosexual men. Heterosexual nurses held the strongest implicit preference for heterosexual men over gay men (Cohen d = 1.30; 95% confidence interval = 1.28, 1.32 among female nurses; Cohen d = 1.38; 95% confidence interval = 1.32, 1.44 among male nurses). Among all groups, explicit preferences for heterosexual versus lesbian and gay people were weaker than implicit preferences. Conclusions. Implicit preferences for heterosexual people versus lesbian and gay people are pervasive among heterosexual health care providers. Future research should investigate how implicit sexual prejudice affects care. PMID:26180976

Implicit attitudes towards homosexuality: reliability, validity, and controllability of the IAT.

PubMed

Banse, R; Seise, J; Zerbes, N

2001-01-01

Two experiments were conducted to investigate the psychometric properties of an Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998) that was adapted to measure implicit attitudes towards homosexuality. In a first experiment, the validity of the Homosexuality-IAT was tested using a known group approach. Implicit and explicit attitudes were assessed in heterosexual and homosexual men and women (N = 101). The results provided compelling evidence for the convergent and discriminant validity of the Homosexuality-IAT as a measure of implicit attitudes. No evidence was found for two alternative explanations of IAT effects (familiarity with stimulus material and stereotype knowledge). The internal consistency of IAT scores was satisfactory (alpha s > .80), but retest correlations were lower. In a second experiment (N = 79) it was shown that uninformed participants were able to fake positive explicit but not implicit attitudes. Discrepancies between implicit and explicit attitudes towards homosexuality could be partially accounted for by individual differences in the motivation to control prejudiced behavior, thus providing independent evidence for the validity of the implicit attitude measure. Neither explicit nor implicit attitudes could be changed by persuasive messages. The results of both experiments are interpreted as evidence for a single construct account of implicit and explicit attitudes towards homosexuality.

Effects of brief mindful acceptance induction on implicit dysfunctional attitudes and concordance between implicit and explicit dysfunctional attitudes.

PubMed

Keng, Shian-Ling; Seah, Stanley T H; Tong, Eddie M W; Smoski, Moria

2016-08-01

Mindfulness-based interventions have been shown to be effective in alleviating depressive symptoms. While much work has examined the effects of mindfulness training on subjective symptoms and experiences, and less is known regarding whether mindfulness training may alter relatively uncontrollable cognitive processes associated with depressed mood, particularly implicit dysfunctional attitudes. The present study examined the effects of a brief mindful acceptance induction on implicit dysfunctional attitudes and degree of concordance between implicit and explicit dysfunctional attitudes in the context of sad mood. A total of 79 adult participants with elevated depressive symptoms underwent an autobiographical mood induction procedure before being randomly assigned to mindful acceptance or thought wandering inductions. Results showed that the effect of mindful acceptance on implicit dysfunctional attitude was significantly moderated by trait mindfulness. Participants high on trait mindfulness demonstrated significant improvements in implicit dysfunctional attitudes following the mindful acceptance induction. Those low on trait mindfulness demonstrated significantly worse implicit dysfunctional attitudes following the induction. Significantly greater levels of concordance between implicit and explicit dysfunctional attitudes were observed in the mindful acceptance condition versus the thought wandering condition. The findings highlight changes in implicit dysfunctional attitudes and improvements in self-concordance as two potential mechanisms underlying the effects of mindfulness-based interventions. Copyright © 2016 Elsevier Ltd. All rights reserved.

Implicit-explicit (IMEX) Runge-Kutta methods for non-hydrostatic atmospheric models

NASA Astrophysics Data System (ADS)

Gardner, David J.; Guerra, Jorge E.; Hamon, François P.; Reynolds, Daniel R.; Ullrich, Paul A.; Woodward, Carol S.

2018-04-01

The efficient simulation of non-hydrostatic atmospheric dynamics requires time integration methods capable of overcoming the explicit stability constraints on time step size arising from acoustic waves. In this work, we investigate various implicit-explicit (IMEX) additive Runge-Kutta (ARK) methods for evolving acoustic waves implicitly to enable larger time step sizes in a global non-hydrostatic atmospheric model. The IMEX formulations considered include horizontally explicit - vertically implicit (HEVI) approaches as well as splittings that treat some horizontal dynamics implicitly. In each case, the impact of solving nonlinear systems in each implicit ARK stage in a linearly implicit fashion is also explored. The accuracy and efficiency of the IMEX splittings, ARK methods, and solver options are evaluated on a gravity wave and baroclinic wave test case. HEVI splittings that treat some vertical dynamics explicitly do not show a benefit in solution quality or run time over the most implicit HEVI formulation. While splittings that implicitly evolve some horizontal dynamics increase the maximum stable step size of a method, the gains are insufficient to overcome the additional cost of solving a globally coupled system. Solving implicit stage systems in a linearly implicit manner limits the solver cost but this is offset by a reduction in step size to achieve the desired accuracy for some methods. Overall, the third-order ARS343 and ARK324 methods performed the best, followed by the second-order ARS232 and ARK232 methods.

Characterizing Implicit Mental Health Associations across Clinical Domains

PubMed Central

Werntz, Alexandra J.; Steinman, Shari A.; Glenn, Jeffrey J.; Nock, Matthew K.; Teachman, Bethany A.

2016-01-01

Background and objectives Implicit associations are relatively uncontrollable associations between concepts in memory. The current investigation focuses on implicit associations in four mental health domains (alcohol use, anxiety, depression, and eating disorders) and how these implicit associations: a) relate to explicit associations and b) self-reported clinical symptoms within the same domains, and c) vary based on demographic characteristics (age, gender, race, ethnicity, and education). Methods Participants (volunteers over age 18 to a research website) completed implicit association (Implicit Association Tests), explicit association (self+psychopathology or attitudes toward food, using semantic differential items), and symptom measures at the Project Implicit Mental Health website tied to: alcohol use (N=12,387), anxiety (N=21,304), depression (N=24,126), or eating disorders (N=10,115). Results Within each domain, implicit associations showed small to moderate associations with explicit associations and symptoms, and predicted self-reported symptoms beyond explicit associations. In general, implicit association strength varied little by race and ethnicity, but showed small ties to age, gender, and education. Limitations This research was conducted on a public research and education website, where participants could take more than one of the studies. Conclusions Among a large and diverse sample, implicit associations in the four domains are congruent with explicit associations and self-reported symptoms, and also add to our prediction of self-reported symptoms over and above explicit associations, pointing to the potential future clinical utility and validity of using implicit association measures with diverse populations. PMID:26962979

Defensive function of persecutory delusion and discrepancy between explicit and implicit self-esteem in schizophrenia: study using the Brief Implicit Association Test

PubMed Central

Nakamura, Mitsuo; Hayakawa, Tomomi; Okamura, Aiko; Kohigashi, Mutsumi; Fukui, Kenji; Narumoto, Jin

2015-01-01

Background If delusions serve as a defense mechanism in schizophrenia patients with paranoia, then they should show normal or high explicit self-esteem and low implicit self-esteem. However, the results of previous studies are inconsistent. One possible explanation for this inconsistency is that there are two types of paranoia, “bad me” (self-blaming) paranoia and “poor me” (non-self-blaming) paranoia. We thus examined implicit and explicit self-esteem and self-blaming tendency in patients with schizophrenia and schizoaffective disorder. We hypothesized that patients with paranoia would show lower implicit self-esteem and only those with non-self-blaming paranoia would experience a discrepancy between explicit and implicit self-esteem. Methods Participants consisted of patients with schizophrenia and schizoaffective disorder recruited from a day hospital (N=71). Participants were assessed for psychotic symptoms, using the Brief Psychiatric Rating Scale (BPRS), and self-blaming tendency, using the brief COPE. We also assessed explicit self-esteem, using the Rosenberg Self-Esteem Scale (RSES), implicit self-esteem, using Brief Implicit Association Test (BIAT), and discrepancy between explicit and implicit self-esteem. Results Contrary to our hypothesis, implicit self-esteem in paranoia and nonparanoia showed no statistical difference. As expected, only patients with non-self-blaming paranoia experienced a discrepancy between explicit and implicit self-esteem; other groups showed no such discrepancy. Conclusion These results suggest that persecutory delusion plays a defensive role in non-self-blaming paranoia. PMID:25565849

Characterizing implicit mental health associations across clinical domains.

PubMed

Werntz, Alexandra J; Steinman, Shari A; Glenn, Jeffrey J; Nock, Matthew K; Teachman, Bethany A

2016-09-01

Implicit associations are relatively uncontrollable associations between concepts in memory. The current investigation focuses on implicit associations in four mental health domains (alcohol use, anxiety, depression, and eating disorders) and how these implicit associations: a) relate to explicit associations and b) self-reported clinical symptoms within the same domains, and c) vary based on demographic characteristics (age, gender, race, ethnicity, and education). Participants (volunteers over age 18 to a research website) completed implicit association (Implicit Association Tests), explicit association (self + psychopathology or attitudes toward food, using semantic differential items), and symptom measures at the Project Implicit Mental Health website tied to: alcohol use (N = 12,387), anxiety (N = 21,304), depression (N = 24,126), or eating disorders (N = 10,115). Within each domain, implicit associations showed small to moderate associations with explicit associations and symptoms, and predicted self-reported symptoms beyond explicit associations. In general, implicit association strength varied little by race and ethnicity, but showed small ties to age, gender, and education. This research was conducted on a public research and education website, where participants could take more than one of the studies. Among a large and diverse sample, implicit associations in the four domains are congruent with explicit associations and self-reported symptoms, and also add to our prediction of self-reported symptoms over and above explicit associations, pointing to the potential future clinical utility and validity of using implicit association measures with diverse populations. Copyright © 2016 Elsevier Ltd. All rights reserved.

Not explicit but implicit memory is influenced by individual perception style

PubMed Central

Tsushima, Yoshiaki

2018-01-01

Not only explicit but also implicit memory has considerable influence on our daily life. However, it is still unclear whether explicit and implicit memories are sensitive to individual differences. Here, we investigated how individual perception style (global or local) correlates with implicit and explicit memory. As a result, we found that not explicit but implicit memory was affected by the perception style: local perception style people more greatly used implicit memory than global perception style people. These results help us to make the new effective application adapting to individual perception style and understand some clinical symptoms such as autistic spectrum disorder. Furthermore, this finding might give us new insight of memory involving consciousness and unconsciousness as well as relationship between implicit/explicit memory and individual perception style. PMID:29370212

Not explicit but implicit memory is influenced by individual perception style.

PubMed

Hine, Kyoko; Tsushima, Yoshiaki

2018-01-01

Not only explicit but also implicit memory has considerable influence on our daily life. However, it is still unclear whether explicit and implicit memories are sensitive to individual differences. Here, we investigated how individual perception style (global or local) correlates with implicit and explicit memory. As a result, we found that not explicit but implicit memory was affected by the perception style: local perception style people more greatly used implicit memory than global perception style people. These results help us to make the new effective application adapting to individual perception style and understand some clinical symptoms such as autistic spectrum disorder. Furthermore, this finding might give us new insight of memory involving consciousness and unconsciousness as well as relationship between implicit/explicit memory and individual perception style.

[Effects of an implicit internal working model on attachment in information processing assessed using Go/No-Go Association Task].

PubMed

Fujii, Tsutomu; Uebuchi, Hisashi; Yamada, Kotono; Saito, Masahiro; Ito, Eriko; Tonegawa, Akiko; Uebuchi, Marie

2015-06-01

The purposes of the present study were (a) to use both a relational-anxiety Go/No-Go Association Task (GNAT) and an avoidance-of-intimacy GNAT in order to assess an implicit Internal Working Model (IWM) of attachment; (b) to verify the effects of both measured implicit relational anxiety and implicit avoidance of intimacy on information processing. The implicit IWM measured by GNAT differed from the explicit IWM measured by questionnaires in terms of the effects on information processing. In particular, in subliminal priming tasks involving with others, implicit avoidance of intimacy predicted accelerated response times with negative stimulus words about attachment. Moreover, after subliminally priming stimulus words about self, implicit relational anxiety predicted delayed response times with negative stimulus words about attachment.

Changes of explicitly and implicitly measured self-esteem in the treatment of major depression: evidence for implicit self-esteem compensation.

PubMed

Wegener, Ingo; Geiser, Franziska; Alfter, Susanne; Mierke, Jan; Imbierowicz, Katrin; Kleiman, Alexandra; Koch, Anne Sarah; Conrad, Rupert

2015-04-01

Self-esteem has been claimed to be an important factor in the development and maintenance of depression. Whereas explicit self-esteem is usually reduced in depressed individuals, studies on implicitly measured self-esteem in depression exhibit a more heterogeneous pattern of results, and the role of implicit self-esteem in depression is still ambiguous. Previous research on implicit self-esteem compensation (ISEC) revealed that implicit self-esteem can mirror processes of self-esteem compensation under conditions that threaten self-esteem. We assume that depressed individuals experience a permanent threat to their selves resulting in enduring processes of ISEC. We hypothesize that ISEC as measured by implicit self-esteem will decrease when individuals recover from depression. 45 patients with major depression received an integrative in-patient treatment in the Psychosomatic University Hospital Bonn, Germany. Depression was measured by the depression score of the Hospital Anxiety and Depression Scale (HADS-D). Self-esteem was assessed explicitly using the Rosenberg Self-Esteem Scale (RSES) and implicitly by the Implicit Association Test (IAT) and the Name Letter Test (NLT). As expected for a successful treatment of depression, depression scores declined during the eight weeks of treatment and explicit self-esteem rose. In line with our hypothesis, both measures of implicit self-esteem decreased, indicating reduced processes of ISEC. It still remains unclear, under which conditions there is an overlap of measures of implicit and explicit self-esteem. The results lend support to the concept of ISEC and demonstrate the relevance of implicit self-esteem and self-esteem compensation for the understanding of depression. Copyright © 2014 Elsevier Inc. All rights reserved.

Primary motor and premotor cortex in implicit sequence learning--evidence for competition between implicit and explicit human motor memory systems.

PubMed

Kantak, Shailesh S; Mummidisetty, Chaithanya K; Stinear, James W

2012-09-01

Implicit and explicit memory systems for motor skills compete with each other during and after motor practice. Primary motor cortex (M1) is known to be engaged during implicit motor learning, while dorsal premotor cortex (PMd) is critical for explicit learning. To elucidate the neural substrates underlying the interaction between implicit and explicit memory systems, adults underwent a randomized crossover experiment of anodal transcranial direct current stimulation (AtDCS) applied over M1, PMd or sham stimulation during implicit motor sequence (serial reaction time task, SRTT) practice. We hypothesized that M1-AtDCS during practice will enhance online performance and offline learning of the implicit motor sequence. In contrast, we also hypothesized that PMd-AtDCS will attenuate performance and retention of the implicit motor sequence. Implicit sequence performance was assessed at baseline, at the end of acquisition (EoA), and 24 h after practice (retention test, RET). M1-AtDCS during practice significantly improved practice performance and supported offline stabilization compared with Sham tDCS. Performance change from EoA to RET revealed that PMd-AtDCS during practice attenuated offline stabilization compared with M1-AtDCS and sham stimulation. The results support the role of M1 in implementing online performance gains and offline stabilization for implicit motor sequence learning. In contrast, enhancing the activity within explicit motor memory network nodes such as the PMd during practice may be detrimental to offline stabilization of the learned implicit motor sequence. These results support the notion of competition between implicit and explicit motor memory systems and identify underlying neural substrates that are engaged in this competition. © 2012 The Authors. European Journal of Neuroscience © 2012 Federation of European Neuroscience Societies and Blackwell Publishing Ltd.

Medical School Experiences Associated with Change in Implicit Racial Bias Among 3547 Students: A Medical Student CHANGES Study Report.

PubMed

van Ryn, Michelle; Hardeman, Rachel; Phelan, Sean M; Burgess, Diana J; Dovidio, John F; Herrin, Jeph; Burke, Sara E; Nelson, David B; Perry, Sylvia; Yeazel, Mark; Przedworski, Julia M

2015-12-01

Physician implicit (unconscious, automatic) bias has been shown to contribute to racial disparities in medical care. The impact of medical education on implicit racial bias is unknown. To examine the association between change in student implicit racial bias towards African Americans and student reports on their experiences with 1) formal curricula related to disparities in health and health care, cultural competence, and/or minority health; 2) informal curricula including racial climate and role model behavior; and 3) the amount and favorability of interracial contact during school. Prospective observational study involving Web-based questionnaires administered during first (2010) and last (2014) semesters of medical school. A total of 3547 students from a stratified random sample of 49 U.S. medical schools. Change in implicit racial attitudes as assessed by the Black-White Implicit Association Test administered during the first semester and again during the last semester of medical school. In multivariable modeling, having completed the Black-White Implicit Association Test during medical school remained a statistically significant predictor of decreased implicit racial bias (-5.34, p ≤ 0.001: mixed effects regression with random intercept across schools). Students' self-assessed skills regarding providing care to African American patients had a borderline association with decreased implicit racial bias (-2.18, p = 0.056). Having heard negative comments from attending physicians or residents about African American patients (3.17, p = 0.026) and having had unfavorable vs. very favorable contact with African American physicians (18.79, p = 0.003) were statistically significant predictors of increased implicit racial bias. Medical school experiences in all three domains were independently associated with change in student implicit racial attitudes. These findings are notable given that even small differences in implicit racial attitudes have been shown to affect behavior and that implicit attitudes are developed over a long period of repeated exposure and are difficult to change.

Implicit Learning as an Ability

ERIC Educational Resources Information Center

Kaufman, Scott Barry; DeYoung, Caroline G.; Gray, Jeremy R.; Jimenez, Luis; Brown, Jamie; Mackintosh, Nicholas

2010-01-01

The ability to automatically and implicitly detect complex and noisy regularities in the environment is a fundamental aspect of human cognition. Despite considerable interest in implicit processes, few researchers have conceptualized implicit learning as an ability with meaningful individual differences. Instead, various researchers (e.g., Reber,…

Implicit attitudes, emotions, and helping intentions of mental health workers toward their clients.

PubMed

Brener, Loren; Rose, Grenville; von Hippel, Courtney; Wilson, Hannah

2013-06-01

The attitudes of mental health care workers toward their clients may influence the quality of care they provide. There is growing recognition of the role of implicit attitudes in behavior toward people with stigmatized illnesses, such as mental illness, and of the need to measure these separately from explicit attitudes. Seventy-four mental health workers completed implicit and explicit measure of attitudes toward people with mental illness. The participants were also asked about their intention to help people with mental illness and their emotional reactions toward people with a mental illness. The findings show that the implicit attitudes of the health workers toward clients with a mental illness are somewhat negative despite the fact that their explicit attitudes are somewhat positive. Although both implicit and explicit attitudes predicted negative emotions, only implicit attitudes were related to helping intentions. This study highlights the association between implicit attitudes and behavioral intentions and confirms the importance of addressing implicit attitudes in mental health research.

Cultural variation in implicit independence: An extension of Kitayama et al. ().

PubMed

Park, Jiyoung; Uchida, Yukiko; Kitayama, Shinobu

2016-08-01

Previous research shows that European Americans are consistently more independent (or less interdependent) than Japanese when implicit indices are used to assess independence (vs. interdependence). The present work extended this evidence by including a novel implicit association test (IAT), as an index of implicit attitude towards independence and interdependence. Consistent with the previous findings, as compared to Japanese, Americans were significantly higher in multiple indices of implicit independence (vs. interdependence) including personal (vs. social) self-definition, experience of disengaging (vs. engaging) emotions and personal (vs. social) form of happiness. Furthermore, as compared to Japanese, Americans had a significantly more positive implicit attitude towards independence assessed with the IAT. As also observed in the previous research, explicit measures showed inconsistent cross-cultural patterns. Lastly, we observed little statistical within-culture coherence among the implicit measures of independence (vs. interdependence), consistent with a view that the implicit indices capture alternative ways for individuals to achieve the cultural mandate of independence or interdependence. © 2015 International Union of Psychological Science.

Implicit motives, explicit traits, and task and contextual performance at work.

PubMed

Lang, Jonas W B; Zettler, Ingo; Ewen, Christian; Hülsheger, Ute R

2012-11-01

Personality psychologists have long argued that explicit traits (as measured by questionnaires) channel the expression of implicit motives (as measured by coding imaginative verbal behavior) such that both interact in the prediction of relevant life outcome variables. In the present research, we apply these ideas in the context of industrial and organizational psychology and propose that 2 explicit traits work as channels for the expression of 3 core implicit motives in task and contextual job performance (extraversion for implicit affiliation and implicit power; explicit achievement for implicit achievement). As a test of these theoretical ideas, we report a study in which employees (N = 241) filled out a questionnaire booklet and worked on an improved modern implicit motive measure, the operant motive test. Their supervisors rated their task and contextual performance. Results support 4 of the 6 theoretical predictions and show that interactions between implicit motives and explicit traits increase the explained criterion variance in both task and contextual performance. (c) 2012 APA, all rights reserved.

Control of Viscous Fingering in Miscible Displacements in Porous Media with a Periodic Change of Injection Rate

NASA Astrophysics Data System (ADS)

Yuan, Q.; Zeng, F.; Knorr, K. D.; Imran, M.

2017-12-01

Context/PurposeThe viscous fingering (VF) is widely encountered in a series of miscible displacements such as CO2 sequestration and solvent-based enhanced oil recovery (EOR). Accurate prediction and effective control of its development are significant. Commercial simulators cannot capture VF because of large numerical diffusion. Moreover, previous measures for controlling VF using polymer are very expensive. In the present study, a periodic change of injection rate involving injection and extraction is used to control and reduce VF instabilities at zero cost. MethodsHighly accurate spectral method and fully implicit alternating direction implicit method are used to simulate VF with concentration-dependent diffusion (CDD) and velocity-induced dispersion (VID), although the consideration of CDD and VID may result in strong nonlinearity and stiff problem under unfavourable viscosity ratio. In-house code is developed. The VF is reduced by optimizing period and amplitude of injection rate. ResultsThe results show that the periodic change of injection rates can strongly affect VF and sweep efficiency. In particular, a period-stabilizing range is found in which the VF is reduced compared with widely used constant injection with the same amount of fluid injected. The frequent change of rate results in high sweep efficiency. The optimal injection scheme, when compared with constant injection, can improve sweep efficiency by 20-35%. InterpretationDispersion plays a key role in the mitigation of VF in periodic displacement rates. It enhances the uniform mixing of two fluids in injection stage in any period, while it can more effectively attenuate VF instabilities through the following extraction stage. Fast switch of injection and extraction can mitigate flow instability once it develops. ConclusionThis finding is very novel and significant as it is the first time to control VF instability in porous media without any additional cost. It shows great potential for EOR at zero cost.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Weston, Brian T.

This dissertation focuses on the development of a fully-implicit, high-order compressible ow solver with phase change. The work is motivated by laser-induced phase change applications, particularly by the need to develop large-scale multi-physics simulations of the selective laser melting (SLM) process in metal additive manufacturing (3D printing). Simulations of the SLM process require precise tracking of multi-material solid-liquid-gas interfaces, due to laser-induced melting/ solidi cation and evaporation/condensation of metal powder in an ambient gas. These rapid density variations and phase change processes tightly couple the governing equations, requiring a fully compressible framework to robustly capture the rapid density variations ofmore » the ambient gas and the melting/evaporation of the metal powder. For non-isothermal phase change, the velocity is gradually suppressed through the mushy region by a variable viscosity and Darcy source term model. The governing equations are discretized up to 4th-order accuracy with our reconstructed Discontinuous Galerkin spatial discretization scheme and up to 5th-order accuracy with L-stable fully implicit time discretization schemes (BDF2 and ESDIRK3-5). The resulting set of non-linear equations is solved using a robust Newton-Krylov method, with the Jacobian-free version of the GMRES solver for linear iterations. Due to the sti nes associated with the acoustic waves and thermal and viscous/material strength e ects, preconditioning the GMRES solver is essential. A robust and scalable approximate block factorization preconditioner was developed, which utilizes the velocity-pressure (vP) and velocity-temperature (vT) Schur complement systems. This multigrid block reduction preconditioning technique converges for high CFL/Fourier numbers and exhibits excellent parallel and algorithmic scalability on classic benchmark problems in uid dynamics (lid-driven cavity ow and natural convection heat transfer) as well as for laser-induced phase change problems in 2D and 3D.« less

Numerical simulation of steady and unsteady viscous flow in turbomachinery using pressure based algorithm

NASA Astrophysics Data System (ADS)

Lakshminarayana, B.; Ho, Y.; Basson, A.

1993-07-01

The objective of this research is to simulate steady and unsteady viscous flows, including rotor/stator interaction and tip clearance effects in turbomachinery. The numerical formulation for steady flow developed here includes an efficient grid generation scheme, particularly suited to computational grids for the analysis of turbulent turbomachinery flows and tip clearance flows, and a semi-implicit, pressure-based computational fluid dynamics scheme that directly includes artificial dissipation, and is applicable to both viscous and inviscid flows. The values of these artificial dissipation is optimized to achieve accuracy and convergency in the solution. The numerical model is used to investigate the structure of tip clearance flows in a turbine nozzle. The structure of leakage flow is captured accurately, including blade-to-blade variation of all three velocity components, pitch and yaw angles, losses and blade static pressures in the tip clearance region. The simulation also includes evaluation of such quantities of leakage mass flow, vortex strength, losses, dominant leakage flow regions and the spanwise extent affected by the leakage flow. It is demonstrated, through optimization of grid size and artificial dissipation, that the tip clearance flow field can be captured accurately. The above numerical formulation was modified to incorporate time accurate solutions. An inner loop iteration scheme is used at each time step to account for the non-linear effects. The computation of unsteady flow through a flat plate cascade subjected to a transverse gust reveals that the choice of grid spacing and the amount of artificial dissipation is critical for accurate prediction of unsteady phenomena. The rotor-stator interaction problem is simulated by starting the computation upstream of the stator, and the upstream rotor wake is specified from the experimental data. The results show that the stator potential effects have appreciable influence on the upstream rotor wake. The predicted unsteady wake profiles are compared with the available experimental data and the agreement is good. The numerical results are interpreted to draw conclusions on the unsteady wake transport mechanism in the blade passage.

Implicit and explicit attitudes towards conventional and complementary and alternative medicine treatments: Introduction of an Implicit Association Test.

PubMed

Green, James A; Hohmann, Cynthia; Lister, Kelsi; Albertyn, Riani; Bradshaw, Renee; Johnson, Christine

2016-06-01

This study examined associations between anticipated future health behaviour and participants' attitudes. Three Implicit Association Tests were developed to assess safety, efficacy and overall attitude. They were used to examine preference associations between conventional versus complementary and alternative medicine among 186 participants. A structural equation model suggested only a single implicit association, rather than three separate domains. However, this single implicit association predicted additional variance in anticipated future use of complementary and alternative medicine beyond explicit. Implicit measures should give further insight into motivation for complementary and alternative medicine use. © The Author(s) 2014.

Implicit cognitive processes in psychopathology: an introduction.

PubMed

Wiers, Reinout W; Teachman, Bethany A; De Houwer, Jan

2007-06-01

Implicit or automatic processes are important in understanding the etiology and maintenance of psychopathological problems. In order to study implicit processes in psychopathology, measures are needed that are valid and reliable when applied to clinical problems. One of the main topics in this special issue concerns the development and validation of new or modified implicit tests in different domains of psychopathology. The other main topic concerns the prediction of clinical outcomes and new ways to directly influence implicit processes in psychopathology. We summarize the contributions to this special issue and discuss how they further our knowledge of implicit processes in psychopathology and how to measure them.

Examining the Presence, Consequences, and Reduction of Implicit Bias in Health Care: A Narrative Review

PubMed Central

Zestcott, Colin A.; Blair, Irene V.; Stone, Jeff

2016-01-01

Recent evidence suggests that one possible cause of disparities in health outcomes for stigmatized groups is the implicit biases held by health care providers. In response, several health care organizations have called for, and developed, new training in implicit bias for their providers. This review examines current evidence on the role that provider implicit bias may play in health disparities, and whether training in implicit bias can effectively reduce the biases that providers exhibit. Directions for future research on the presence and consequences of provider implicit bias, and best practices for training to reduce such bias, will be discussed. PMID:27547105

Implicit and explicit preferences for physical attractiveness in a romantic partner: a double dissociation in predictive validity.

PubMed

Eastwick, Paul W; Eagly, Alice H; Finkel, Eli J; Johnson, Sarah E

2011-11-01

Five studies develop and examine the predictive validity of an implicit measure of the preference for physical attractiveness in a romantic partner. Three hypotheses were generally supported. First, 2 variants of the go/no-go association task revealed that participants, on average, demonstrate an implicit preference (i.e., a positive spontaneous affective reaction) for physical attractiveness in a romantic partner. Second, these implicit measures were not redundant with a traditional explicit measure: The correlation between these constructs was .00 on average, and the implicit measures revealed no reliable sex differences, unlike the explicit measure. Third, explicit and implicit measures exhibited a double dissociation in predictive validity. Specifically, explicit preferences predicted the extent to which attractiveness was associated with participants' romantic interest in opposite-sex photographs but not their romantic interest in real-life opposite-sex speed-daters or confederates. Implicit preferences showed the opposite pattern. This research extends prior work on implicit processes in romantic relationships and offers the first demonstration that any measure of a preference for a particular characteristic in a romantic partner (an implicit measure of physical attractiveness, in this case) predicts individuals' evaluation of live potential romantic partners.

Implicit Statistical Learning and Language Skills in Bilingual Children

ERIC Educational Resources Information Center

Yim, Dongsun; Rudoy, John

2013-01-01

Purpose: Implicit statistical learning in 2 nonlinguistic domains (visual and auditory) was used to investigate (a) whether linguistic experience influences the underlying learning mechanism and (b) whether there are modality constraints in predicting implicit statistical learning with age and language skills. Method: Implicit statistical learning…

Comparing the shear strength of grouted fractures: conventional methods vs biomineralisation

NASA Astrophysics Data System (ADS)

El Mountassir, G.; Tobler, D. J.; Moir, H.; Lunn, R. J.; Phoenix, V. R.

2011-12-01

For many engineering applications, such as geological disposal of nuclear waste, underground railways etc., it is necessary to limit fluid flow through fractures. The particle size of conventional cementitious grouts limits the size of fractures into which they can penetrate. To address this issue increasingly microfine and ultrafine cement grouts are becoming commercially available. Despite this the radius of penetration remains dependent on the grout viscosity alongside injection pressure, pumping rate, grout setting time and grout cohesion. As such lower viscosity aqueous solutions may have a greater radius of penetration potentially requiring fewer injection points. In addition cementitious grouts typically undergo volumetric shrinkage during setting. In many applications this change in volume may not be of particular importance but in others where a very low hydraulic conductivity is a critical design criterion, as in nuclear waste repositories, this reduction in volume may be highly significant. This study investigates the use of microbially induced carbonate precipitation (MCP) as a technique for grouting fine aperture rock fractures. Artificial fractures were created in granite cores and were subjected to conventional cementitious grouting methods and MCP. Following treatment the hydraulic and mechanical properties of the grouted fractures were investigated. The mechanical properties of grouts after setting is not usually considered to be a significant issue, but in applications which consider much longer timescales (100,000 years) grouts which result in fractures with improved strength and lower hydraulic conductivity are likely to be preferred.

Implicit affectivity in patients with borderline personality disorder.

PubMed

Dukalski, Bibiana; Quirin, Markus; Kersting, Anette; Suslow, Thomas; Donges, Uta-Susan

2017-01-01

It has been argued that borderline personality disorder (BPD) is related to an enhanced affective reactivity. According to findings from research based on self-report, individuals with BPD develop and feel more negative and less positive affect than healthy individuals. Implicit affectivity, which can be measured using indirect assessment methods, relates to processes of the impulsive, intuitive system. In the present study, implicit and explicit affectivity was examined in patients suffering from BPD compared to healthy persons. Thirty-five women with BPD and 35 healthy women participated in the study. Implicit affectivity was assessed using the Implicit Positive and Negative Affect Test (IPANAT). Measures of explicit state and trait affectivity were also administered. BPD women had lower explicit positive state and trait affect scores and higher negative state and trait affect scores than healthy women. They had also lower implicit positive affect but they did not differ from healthy women regarding implicit negative affect. Total number of comorbid disorders was correlated with both implicit positive and implicit negative affect. According to our data, BPD patients exhibit reduced implicit positive affect as well as reduced explicit positive affect compared to healthy persons. According to our IPANAT data, BPD patients are characterized by a normal disposition to develop negative affective reactions which is in line with a number of findings from psycho-physiological research on BPD. Self-reports of negative affectivity in BPD could be biased by negative distortion.

Context Effects of Alcohol Availability at Home: Implicit Alcohol Associations and the Prediction of Adolescents' Drinking Behavior.

PubMed

Peeters, Margot; Koning, Ina; Monshouwer, Karin; Vollebergh, Wilma A M; Wiers, Reinout W

2016-09-01

Recent studies suggest that the predictive effect of implicit alcohol associations is context dependent. Findings indicate that implicit associations are more easily retrieved in an alcohol-associated setting or context (e.g., bar) compared with a neutral setting. In line with this reasoning, we hypothesized that alcohol availability at home might moderate the relationship between implicit alcohol associations and future drinking behavior of adolescents. Participants were 262 at-risk adolescents (235 boys, 27 girls, adolescents with externalizing behavioral problems) with a mean age of 14.11 years (SD = 0.86, age range: 12-16 years) at baseline. Adolescents completed a questionnaire and a modified version of the Implicit Association Test (i.e., Single Category Implicit Association Test; SC-IAT). Stronger implicit alcohol associations predicted increase in frequency of alcohol use, only in adolescents who indicated that alcohol was available at home. No moderating effects were found for increase in quantity of alcohol use and problematic alcohol use, suggesting that implicit alcohol associations particularly influence the decision of whether to drink in adolescence. The findings illustrate that the availability of alcohol in the home setting influences adolescents' implicit alcohol associations and consequently affects the frequency of alcohol use. In this way, alcohol availability at home may be an important contextual factor to consider when examining the effect of implicit alcohol associations on the future drinking behavior of adolescents.

Using implicit attitudes of exercise importance to predict explicit exercise dependence symptoms and exercise behaviors.

PubMed

Forrest, Lauren N; Smith, April R; Fussner, Lauren M; Dodd, Dorian R; Clerkin, Elise M

2016-01-01

"Fast" (i.e., implicit) processing is relatively automatic; "slow" (i.e., explicit) processing is relatively controlled and can override automatic processing. These different processing types often produce different responses that uniquely predict behaviors. In the present study, we tested if explicit, self-reported symptoms of exercise dependence and an implicit association of exercise as important predicted exercise behaviors and change in problematic exercise attitudes. We assessed implicit attitudes of exercise importance and self-reported symptoms of exercise dependence at Time 1. Participants reported daily exercise behaviors for approximately one month, and then completed a Time 2 assessment of self-reported exercise dependence symptoms. Undergraduate males and females (Time 1, N = 93; Time 2, N = 74) tracked daily exercise behaviors for one month and completed an Implicit Association Test assessing implicit exercise importance and subscales of the Exercise Dependence Questionnaire (EDQ) assessing exercise dependence symptoms. Implicit attitudes of exercise importance and Time 1 EDQ scores predicted Time 2 EDQ scores. Further, implicit exercise importance and Time 1 EDQ scores predicted daily exercise intensity while Time 1 EDQ scores predicted the amount of days exercised. Implicit and explicit processing appear to uniquely predict exercise behaviors and attitudes. Given that different implicit and explicit processes may drive certain exercise factors (e.g., intensity and frequency, respectively), these behaviors may contribute to different aspects of exercise dependence.

Dissociation between implicit and explicit expectancies of cannabis use in adolescence.

PubMed

Schmits, Emilie; Maurage, Pierre; Thirion, Romain; Quertemont, Etienne

2015-12-30

Cannabis is one of the most commonly drugs used by teenagers. Expectancies about its effects play a crucial role in cannabis consumption. Various tools have been used to assess expectancies, mainly self-report questionnaires measuring explicit expectancies, but implicit measures based on experimental tasks have also been developed, measuring implicit expectancies. The aim of this study was to simultaneously assess implicit/explicit expectancies related to cannabis among adolescent users and non-users. 130 teenagers attending school (55 girls) were enrolled (Age: M=16.40 years); 43.84% had never used cannabis ("non-users") and 56.16% had used cannabis ("users"). They completed self-report questionnaires evaluating cannabis use, cannabis-related problems, effect expectancies (explicit expectancies), alcohol use, social and trait anxiety, depression, as well as three Implicit Association Tests (IAT) assessing implicit expectancies. Adolescents manifested more implicit affective associations (relaxation, excitation, negative) than neutral ones regarding cannabis. These were not related to explicit expectancies. Cannabis users reported more implicit relaxation expectancies and less negative explicit expectancies than non-users. The frequency of use and related problems were positively associated with the explicit expectancies regarding relaxation and enhancement, and were negatively associated with negative explicit expectancies and negative implicit expectancies. Findings indicate that implicit and explicit expectancies play different roles in cannabis use by adolescents. The implications for experimentation and prevention are discussed. Copyright © 2015 Elsevier Ireland Ltd. All rights reserved.

Using implicit attitudes of exercise importance to predict explicit exercise dependence symptoms and exercise behaviors

PubMed Central

Forrest, Lauren N.; Smith, April R.; Fussner, Lauren M.; Dodd, Dorian R.; Clerkin, Elise M.

2015-01-01

Objectives ”Fast” (i.e., implicit) processing is relatively automatic; “slow” (i.e., explicit) processing is relatively controlled and can override automatic processing. These different processing types often produce different responses that uniquely predict behaviors. In the present study, we tested if explicit, self-reported symptoms of exercise dependence and an implicit association of exercise as important predicted exercise behaviors and change in problematic exercise attitudes. Design We assessed implicit attitudes of exercise importance and self-reported symptoms of exercise dependence at Time 1. Participants reported daily exercise behaviors for approximately one month, and then completed a Time 2 assessment of self-reported exercise dependence symptoms. Method Undergraduate males and females (Time 1, N = 93; Time 2, N = 74) tracked daily exercise behaviors for one month and completed an Implicit Association Test assessing implicit exercise importance and subscales of the Exercise Dependence Questionnaire (EDQ) assessing exercise dependence symptoms. Results Implicit attitudes of exercise importance and Time 1 EDQ scores predicted Time 2 EDQ scores. Further, implicit exercise importance and Time 1 EDQ scores predicted daily exercise intensity while Time 1 EDQ scores predicted the amount of days exercised. Conclusion Implicit and explicit processing appear to uniquely predict exercise behaviors and attitudes. Given that different implicit and explicit processes may drive certain exercise factors (e.g., intensity and frequency, respectively), these behaviors may contribute to different aspects of exercise dependence. PMID:26195916

Decisions among the Undecided: Implicit Attitudes Predict Future Voting Behavior of Undecided Voters

PubMed Central

Lundberg, Kristjen B.; Payne, B. Keith

2014-01-01

Implicit attitudes have been suggested as a key to unlock the hidden preferences of undecided voters. Past research, however, offered mixed support for this hypothesis. The present research used a large nationally representative sample and a longitudinal design to examine the predictive utility of implicit and explicit attitude measures in the 2008 U.S. presidential election. In our analyses, explicit attitudes toward candidates predicted voting better for decided than undecided voters, but implicit candidate attitudes were predictive of voting for both decided and undecided voters. Extending our examination to implicit and explicit racial attitudes, we found the same pattern. Taken together, these results provide convergent evidence that implicit attitudes predict voting about as well for undecided as for decided voters. We also assessed a novel explanation for these effects by evaluating whether implicit attitudes may predict the choices of undecided voters, in part, because they are neglected when people introspect about their confidence. Consistent with this idea, we found that the extremity of explicit but not implicit attitudes was associated with greater confidence. These analyses shed new light on the utility of implicit measures in predicting future behavior among individuals who feel undecided. Considering the prior studies together with this new evidence, the data seem to be consistent that implicit attitudes may be successful in predicting the behavior of undecided voters. PMID:24489666

Implicit Racial/Ethnic Bias Among Health Care Professionals and Its Influence on Health Care Outcomes: A Systematic Review.

PubMed

Hall, William J; Chapman, Mimi V; Lee, Kent M; Merino, Yesenia M; Thomas, Tainayah W; Payne, B Keith; Eng, Eugenia; Day, Steven H; Coyne-Beasley, Tamera

2015-12-01

In the United States, people of color face disparities in access to health care, the quality of care received, and health outcomes. The attitudes and behaviors of health care providers have been identified as one of many factors that contribute to health disparities. Implicit attitudes are thoughts and feelings that often exist outside of conscious awareness, and thus are difficult to consciously acknowledge and control. These attitudes are often automatically activated and can influence human behavior without conscious volition. We investigated the extent to which implicit racial/ethnic bias exists among health care professionals and examined the relationships between health care professionals' implicit attitudes about racial/ethnic groups and health care outcomes. To identify relevant studies, we searched 10 computerized bibliographic databases and used a reference harvesting technique. We assessed eligibility using double independent screening based on a priori inclusion criteria. We included studies if they sampled existing health care providers or those in training to become health care providers, measured and reported results on implicit racial/ethnic bias, and were written in English. We included a total of 15 studies for review and then subjected them to double independent data extraction. Information extracted included the citation, purpose of the study, use of theory, study design, study site and location, sampling strategy, response rate, sample size and characteristics, measurement of relevant variables, analyses performed, and results and findings. We summarized study design characteristics, and categorized and then synthesized substantive findings. Almost all studies used cross-sectional designs, convenience sampling, US participants, and the Implicit Association Test to assess implicit bias. Low to moderate levels of implicit racial/ethnic bias were found among health care professionals in all but 1 study. These implicit bias scores are similar to those in the general population. Levels of implicit bias against Black, Hispanic/Latino/Latina, and dark-skinned people were relatively similar across these groups. Although some associations between implicit bias and health care outcomes were nonsignificant, results also showed that implicit bias was significantly related to patient-provider interactions, treatment decisions, treatment adherence, and patient health outcomes. Implicit attitudes were more often significantly related to patient-provider interactions and health outcomes than treatment processes. Most health care providers appear to have implicit bias in terms of positive attitudes toward Whites and negative attitudes toward people of color. Future studies need to employ more rigorous methods to examine the relationships between implicit bias and health care outcomes. Interventions targeting implicit attitudes among health care professionals are needed because implicit bias may contribute to health disparities for people of color.

Implicit Racial/Ethnic Bias Among Health Care Professionals and Its Influence on Health Care Outcomes: A Systematic Review

PubMed Central

Hall, William J.; Lee, Kent M.; Merino, Yesenia M.; Thomas, Tainayah W.; Payne, B. Keith; Eng, Eugenia; Day, Steven H.; Coyne-Beasley, Tamera

2015-01-01

Background. In the United States, people of color face disparities in access to health care, the quality of care received, and health outcomes. The attitudes and behaviors of health care providers have been identified as one of many factors that contribute to health disparities. Implicit attitudes are thoughts and feelings that often exist outside of conscious awareness, and thus are difficult to consciously acknowledge and control. These attitudes are often automatically activated and can influence human behavior without conscious volition. Objectives. We investigated the extent to which implicit racial/ethnic bias exists among health care professionals and examined the relationships between health care professionals’ implicit attitudes about racial/ethnic groups and health care outcomes. Search Methods. To identify relevant studies, we searched 10 computerized bibliographic databases and used a reference harvesting technique. Selection Criteria. We assessed eligibility using double independent screening based on a priori inclusion criteria. We included studies if they sampled existing health care providers or those in training to become health care providers, measured and reported results on implicit racial/ethnic bias, and were written in English. Data Collection and Analysis. We included a total of 15 studies for review and then subjected them to double independent data extraction. Information extracted included the citation, purpose of the study, use of theory, study design, study site and location, sampling strategy, response rate, sample size and characteristics, measurement of relevant variables, analyses performed, and results and findings. We summarized study design characteristics, and categorized and then synthesized substantive findings. Main Results. Almost all studies used cross-sectional designs, convenience sampling, US participants, and the Implicit Association Test to assess implicit bias. Low to moderate levels of implicit racial/ethnic bias were found among health care professionals in all but 1 study. These implicit bias scores are similar to those in the general population. Levels of implicit bias against Black, Hispanic/Latino/Latina, and dark-skinned people were relatively similar across these groups. Although some associations between implicit bias and health care outcomes were nonsignificant, results also showed that implicit bias was significantly related to patient–provider interactions, treatment decisions, treatment adherence, and patient health outcomes. Implicit attitudes were more often significantly related to patient–provider interactions and health outcomes than treatment processes. Conclusions. Most health care providers appear to have implicit bias in terms of positive attitudes toward Whites and negative attitudes toward people of color. Future studies need to employ more rigorous methods to examine the relationships between implicit bias and health care outcomes. Interventions targeting implicit attitudes among health care professionals are needed because implicit bias may contribute to health disparities for people of color. PMID:26469668

Racial Categorization Predicts Implicit Racial Bias in Preschool Children.

PubMed

Setoh, Peipei; Lee, Kristy J J; Zhang, Lijun; Qian, Miao K; Quinn, Paul C; Heyman, Gail D; Lee, Kang

2017-06-12

This research investigated the relation between racial categorization and implicit racial bias in majority and minority children. Chinese and Indian 3- to 7-year-olds from Singapore (N = 158) categorized Chinese and Indian faces by race and had their implicit and explicit racial biases measured. Majority Chinese children, but not minority Indian children, showed implicit bias favoring own race. Regardless of ethnicity, children's racial categorization performance correlated positively with implicit racial bias. Also, Chinese children, but not Indian children, displayed explicit bias favoring own race. Furthermore, children's explicit bias was unrelated to racial categorization performance and implicit bias. The findings support a perceptual-social linkage in the emergence of implicit racial bias and have implications for designing programs to promote interracial harmony. © 2017 The Authors. Child Development © 2017 Society for Research in Child Development, Inc.

Implicit Bias and Mental Health Professionals: Priorities and Directions for Research.

PubMed

Merino, Yesenia; Adams, Leslie; Hall, William J

2018-06-01

This Open Forum explores the role of implicit bias along the mental health care continuum, which may contribute to mental health disparities among vulnerable populations. Emerging research shows that implicit bias is prevalent among service providers. These negative or stigmatizing attitudes toward population groups are held at a subconscious level and are automatically activated during practitioner-client encounters. The authors provide examples of how implicit bias may impede access to care, clinical screening and diagnosis, treatment processes, and crisis response. They also discuss how implicit attitudes may manifest at the intersection between mental health and criminal justice institutions. Finally, they discuss the need for more research on the impact of implicit bias on health practices throughout the mental health system, including the development of interventions to address implicit bias among mental health professionals.

Implicit Monte Carlo with a linear discontinuous finite element material solution and piecewise non-constant opacity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wollaeger, Ryan T.; Wollaber, Allan B.; Urbatsch, Todd J.

2016-02-23

Here, the non-linear thermal radiative-transfer equations can be solved in various ways. One popular way is the Fleck and Cummings Implicit Monte Carlo (IMC) method. The IMC method was originally formulated with piecewise-constant material properties. For domains with a coarse spatial grid and large temperature gradients, an error known as numerical teleportation may cause artificially non-causal energy propagation and consequently an inaccurate material temperature. Source tilting is a technique to reduce teleportation error by constructing sub-spatial-cell (or sub-cell) emission profiles from which IMC particles are sampled. Several source tilting schemes exist, but some allow teleportation error to persist. We examinemore » the effect of source tilting in problems with a temperature-dependent opacity. Within each cell, the opacity is evaluated continuously from a temperature profile implied by the source tilt. For IMC, this is a new approach to modeling the opacity. We find that applying both source tilting along with a source tilt-dependent opacity can introduce another dominant error that overly inhibits thermal wavefronts. We show that we can mitigate both teleportation and under-propagation errors if we discretize the temperature equation with a linear discontinuous (LD) trial space. Our method is for opacities ~ 1/T 3, but we formulate and test a slight extension for opacities ~ 1/T 3.5, where T is temperature. We find our method avoids errors that can be incurred by IMC with continuous source tilt constructions and piecewise-constant material temperature updates.« less

A comparison of physician implicit racial bias towards adults versus children

PubMed Central

Johnson, Tiffani J.; Winger, Daniel G.; Hickey, Robert W.; Switzer, Galen E.; Miller, Elizabeth; Nguyen, Margaret B.; Saladino, Richard A.; Hausmann, Leslie R. M.

2016-01-01

Background and Objectives The general population and most physicians have implicit racial bias against black adults. Pediatricians also have implicit bias against black adults, albeit less than other specialties. There is no published research on the implicit racial attitudes of pediatricians or other physicians towards children. Our objectives were to compare implicit racial bias towards adults versus children among resident physicians working in a pediatric emergency department (ED), and to assess whether bias varied by specialty (pediatrics, emergency medicine, or other), gender, race, age, and year of training. Methods We measured implicit racial bias of residents before a pediatric ED shift using the Adult and Child Race Implicit Association Tests (IATs). Generalized linear models compared Adult and Child IAT scores and determined the association of participant demographics with Adult and Child IAT scores. Results Among 91 residents, we found moderate pro-white/anti-black bias on both the Adult (M=0.49, SD=0.34) and Child Race IAT (M=0.55, SD=0.37). There was no significant difference between Adult and Child Race IAT scores (difference=0.06, p=0.15). Implicit bias was not associated with resident demographic characteristics, including specialty. Conclusions This is the first study demonstrating that resident physicians have implicit racial bias against black children, similar to levels of bias against black adults. Bias in our study did not vary by resident demographic characteristics, including specialty, suggesting that pediatric residents are as susceptible as other physicians to implicit bias. Future studies are needed to explore how physicians’ implicit attitudes towards parents and children may impact inequities in pediatric healthcare. PMID:27620844

Evolution of midplate hotspot swells: Numerical solutions

NASA Technical Reports Server (NTRS)

Liu, Mian; Chase, Clement G.

1990-01-01

The evolution of midplate hotspot swells on an oceanic plate moving over a hot, upwelling mantle plume is numerically simulated. The plume supplies a Gaussian-shaped thermal perturbation and thermally-induced dynamic support. The lithosphere is treated as a thermal boundary layer with a strongly temperature-dependent viscosity. The two fundamental mechanisms of transferring heat, conduction and convection, during the interaction of the lithosphere with the mantle plume are considered. The transient heat transfer equations, with boundary conditions varying in both time and space, are solved in cylindrical coordinates using the finite difference ADI (alternating direction implicit) method on a 100 x 100 grid. The topography, geoid anomaly, and heat flow anomaly of the Hawaiian swell and the Bermuda rise are used to constrain the models. Results confirm the conclusion of previous works that the Hawaiian swell can not be explained by conductive heating alone, even if extremely high thermal perturbation is allowed. On the other hand, the model of convective thinning predicts successfully the topography, geoid anomaly, and the heat flow anomaly around the Hawaiian islands, as well as the changes in the topography and anomalous heat flow along the Hawaiian volcanic chain.

Interactive calculation procedure for supersonic flows. Ph.D. Thesis - Case Western Reserve Univ., 1976. Final Report

NASA Technical Reports Server (NTRS)

Tassa, Y.; Anderson, B. H.; Reshotko, E.

1977-01-01

An interactive procedure was developed for supersonic viscous flows that can be used for either two-dimensional or axisymmetric configurations. The procedure is directed to supersonic internal flows as well as those supersonic external flows that require consideration of mutual interaction between the outer flow and the boundary layer flow. The flow field is divided into two regions: an inner region which is highly viscous and mostly subsonic and an outer region where the flow is supersonic and in which viscous effects are small but not negligible. For the outer region a numerical solution is obtained by applying the method of characteristics to a system of equations which includes viscous and conduction transport terms only normal to the streamlines. The inner region is treated by a system of equations of the boundary layer type that includes higher order effects such as longitudinal and transverse curvature and normal pressure gradients. These equations are coupled and solved simultaneously in the physical coordinates by using an implicit finite difference scheme. This system can also be used to calculate laminar and turbulent boundary layers using a scalar eddy viscosity concept.

Examining the Implicit Relational Assessment Procedure: Four Preliminary Studies

ERIC Educational Resources Information Center

Drake, Chad E.; Kellum, Karen Kate; Wilson, Kelly G.; Luoma, Jason B.; Weinstein, Jonathan H.; Adams, Catherine H.

2010-01-01

The Implicit Relational Assessment Procedure (IRAP) is a relatively new measure of implicit cognition that tests cognition as relational behavior instead of an associative activity and thus may provide a more specific measure of cognitive repertoires, including those for social biases, than better known implicit measures such as the Implicit…

Explicit versus Implicit Stereotypes: "What Biases Do I Really Hold?"

ERIC Educational Resources Information Center

Morgan, Melanie

2008-01-01

This article presents an activity in which students explore the impact of implicit stereotypes in everyday interactions while examining issues of attitudinal measurement. Social cognitions that underlie stereotypes often operate implicitly and even unconsciously. Consequently, these implicit attitudes have the potential to affect the way people…

Implicit Referential Meaning with Reference to English Arabic Translation

ERIC Educational Resources Information Center

Al-Zughoul, Basem

2014-01-01

The purpose of this study is to investigate how English implicit referential meaning is translated into Arabic by analyzing sentences containing implicit referential meanings found in the novel "Harry Potter and the Prisoner of Azkaban". The analysis shows that the translation of English implicit referential meaning into Arabic can be…

Chinese Undergraduates' Explicit and Implicit Attitudes toward Persons with Disabilities

ERIC Educational Resources Information Center

Chen, Shuang; Ma, Li; Zhang, Jian-Xin

2011-01-01

The present study is aimed at examining implicit and explicit attitudes toward persons with disabilities among Chinese college students. The "Implicit Association Test" was used to measure their implicit attitudes, whereas their explicit attitudes toward persons with disabilities were measured by using a scale of three items.…

NUEN-618 Class Project: Actually Implicit Monte Carlo

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vega, R. M.; Brunner, T. A.

2017-12-14

This research describes a new method for the solution of the thermal radiative transfer (TRT) equations that is implicit in time which will be called Actually Implicit Monte Carlo (AIMC). This section aims to introduce the TRT equations, as well as the current workhorse method which is known as Implicit Monte Carlo (IMC). As the name of the method proposed here indicates, IMC is a misnomer in that it is only semi-implicit, which will be shown in this section as well.

Conditions of viscosity measurement for detecting irradiated peppers

NASA Astrophysics Data System (ADS)

Hayashi, Toru; Todoriki, Setsuko; Okadome, Hiroshi; Kohyama, Kaoru

1995-04-01

Viscosity of gelatinized suspensions of black and white peppers decreased depending upon dose. The viscosity was influenced by gelatinization and viscosity measurement conditions. The difference between unirradiated pepper and an irradiated one was larger at a higher pH and temperature for gelatinization. A viscosity parameter normalized with the starch content of pepper sample and the viscosity of a 5% suspension of corn starch could get rid of the influence of the conditions for viscosity measurement such as a type of viscometer, shear rate and temperature.

Implicit social cognition: From measures to mechanisms

PubMed Central

Nosek, Brian A.; Hawkins, Carlee Beth; Frazier, Rebecca S.

2011-01-01

Most of human cognition occurs outside of conscious awareness or conscious control. Some of these implicit processes influence social perception, judgment and action. The last fifteen years of research in implicit social cognition can be characterized as the Age of Measurement because of a proliferation of measurement methods and research evidence demonstrating their practical value for predicting human behavior. Implicit measures assess constructs that are distinct, but related, to self-report assessments, and predict variation in behavior that is not accounted for by those explicit measures. The present state of knowledge provides a foundation for the next age of implicit social cognition – clarification of the mechanisms underlying implicit measurement and how the measured constructs influence behavior. PMID:21376657

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

NASA Astrophysics Data System (ADS)

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

1998-04-01

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 methods to solve systems of conservation laws with optional source terms. The main advantage of implicit solution strategies over explicit time integration is that the restrictive constraint on the allowed time step can be (partially) eliminated, thus the computational cost is reduced. The test problems cover one and two dimensional, steady state and time accurate computations, and the solutions contain discontinuities. For each test, we confront explicit with implicit solution strategies.

46 CFR 153.2 - Definitions and acronyms.

Code of Federal Regulations, 2013 CFR

2013-10-01

... viscosity NLS includes high viscosity Category B NLS and high viscosity Category C NLS. High viscosity Category B NLS means any Category B NLS having a viscosity of at least 25 mPa.s at 20 °C and at least 25 mPa.s at the time it is unloaded. High viscosity Category C NLS means any Category C NLS having a...

46 CFR 153.2 - Definitions and acronyms.

Code of Federal Regulations, 2014 CFR

2014-10-01

... viscosity NLS includes high viscosity Category B NLS and high viscosity Category C NLS. High viscosity Category B NLS means any Category B NLS having a viscosity of at least 25 mPa.s at 20 °C and at least 25 mPa.s at the time it is unloaded. High viscosity Category C NLS means any Category C NLS having a...

Navier-Stokes Aerodynamic Simulation of the V-22 Osprey on the Intel Paragon MPP

NASA Technical Reports Server (NTRS)

Vadyak, Joseph; Shrewsbury, George E.; Narramore, Jim C.; Montry, Gary; Holst, Terry; Kwak, Dochan (Technical Monitor)

1995-01-01

The paper will describe the Development of a general three-dimensional multiple grid zone Navier-Stokes flowfield simulation program (ENS3D-MPP) designed for efficient execution on the Intel Paragon Massively Parallel Processor (MPP) supercomputer, and the subsequent application of this method to the prediction of the viscous flowfield about the V-22 Osprey tiltrotor vehicle. The flowfield simulation code solves the thin Layer or full Navier-Stoke's equation - for viscous flow modeling, or the Euler equations for inviscid flow modeling on a structured multi-zone mesh. In the present paper only viscous simulations will be shown. The governing difference equations are solved using a time marching implicit approximate factorization method with either TVD upwind or central differencing used for the convective terms and central differencing used for the viscous diffusion terms. Steady state or Lime accurate solutions can be calculated. The present paper will focus on steady state applications, although time accurate solution analysis is the ultimate goal of this effort. Laminar viscosity is calculated using Sutherland's law and the Baldwin-Lomax two layer algebraic turbulence model is used to compute the eddy viscosity. The Simulation method uses an arbitrary block, curvilinear grid topology. An automatic grid adaption scheme is incorporated which concentrates grid points in high density gradient regions. A variety of user-specified boundary conditions are available. This paper will present the application of the scalable and superscalable versions to the steady state viscous flow analysis of the V-22 Osprey using a multiple zone global mesh. The mesh consists of a series of sheared cartesian grid blocks with polar grids embedded within to better simulate the wing tip mounted nacelle. MPP solutions will be shown in comparison to equivalent Cray C-90 results and also in comparison to experimental data. Discussions on meshing considerations, wall clock execution time, load balancing, and scalability will be provided.

Implicit memory. Retention without remembering.

PubMed

Roediger, H L

1990-09-01

Explicit measures of human memory, such as recall or recognition, reflect conscious recollection of the past. Implicit tests of retention measure transfer (or priming) from past experience on tasks that do not require conscious recollection of recent experiences for their performance. The article reviews research on the relation between explicit and implicit memory. The evidence points to substantial differences between standard explicit and implicit tests, because many variables create dissociations between these tests. For example, although pictures are remembered better than words on explicit tests, words produce more priming than do pictures on several implicit tests. These dissociations may implicate different memory systems that subserve distinct memorial functions, but the present argument is that many dissociations can be understood by appealing to general principles that apply to both explicit and implicit tests. Phenomena studied under the rubric of implicit memory may have important implications in many other fields, including social cognition, problem solving, and cognitive development.

Terror management theory and self-esteem revisited: the roles of implicit and explicit self-esteem in mortality salience effects.

PubMed

Schmeichel, Brandon J; Gailliot, Matthew T; Filardo, Emily-Ana; McGregor, Ian; Gitter, Seth; Baumeister, Roy F

2009-05-01

Three studies tested the roles of implicit and/or explicit self-esteem in reactions to mortality salience. In Study 1, writing about death versus a control topic increased worldview defense among participants low in implicit self-esteem but not among those high in implicit self-esteem. In Study 2, a manipulation to boost implicit self-esteem reduced the effect of mortality salience on worldview defense. In Study 3, mortality salience increased the endorsement of positive personality descriptions but only among participants with the combination of low implicit and high explicit self-esteem. These findings indicate that high implicit self-esteem confers resilience against the psychological threat of death, and therefore the findings provide direct support for a fundamental tenet of terror management theory regarding the anxiety-buffering role of self-esteem. Copyright (c) 2009 APA, all rights reserved.

Moderators of Implicit-Explicit Exercise Cognition Concordance.

PubMed

Berry, Tanya R; Rodgers, Wendy M; Markland, David; Hall, Craig R

2016-12-01

Investigating implicit-explicit concordance can aid in understanding underlying mechanisms and possible intervention effects. This research examined the concordance between implicit associations of exercise with health or appearance and related explicit motives. Variables considered as possible moderators were behavioral regulations, explicit attitudes, and social desirability. Participants (N = 454) completed measures of implicit associations of exercise with health and appearance and questionnaire measures of health and appearance motives, attitudes, social desirability, and behavioral regulations. Attitudes significantly moderated the relationship between implicit associations of exercise with health and health motives. Identified regulations significantly moderated implicit-explicit concordance with respect to associations with appearance. These results suggest that implicit and explicit exercise-related cognitions are not necessarily independent and their relationship to each other may be moderated by attitudes or some forms of behavioral regulation. Future research that takes a dual-processing approach to exercise behavior should consider potential theoretical moderators of concordance.

Do Implicit Attitudes Predict Actual Voting Behavior Particularly for Undecided Voters?

PubMed Central

Friese, Malte; Smith, Colin Tucker; Plischke, Thomas; Bluemke, Matthias; Nosek, Brian A.

2012-01-01

The prediction of voting behavior of undecided voters poses a challenge to psychologists and pollsters. Recently, researchers argued that implicit attitudes would predict voting behavior particularly for undecided voters whereas explicit attitudes would predict voting behavior particularly for decided voters. We tested this assumption in two studies in two countries with distinct political systems in the context of real political elections. Results revealed that (a) explicit attitudes predicted voting behavior better than implicit attitudes for both decided and undecided voters, and (b) implicit attitudes predicted voting behavior better for decided than undecided voters. We propose that greater elaboration of attitudes produces stronger convergence between implicit and explicit attitudes resulting in better predictive validity of both, and less incremental validity of implicit over explicit attitudes for the prediction of voting behavior. However, greater incremental predictive validity of implicit over explicit attitudes may be associated with less elaboration. PMID:22952898

The Implicit Relational Assessment Procedure (IRAP) as a Measure of Spider Fear

ERIC Educational Resources Information Center

Nicholson, Emma; Barnes-Holmes, Dermot

2012-01-01

A greater understanding of implicit cognition can provide important information regarding the etiology and maintenance of psychological disorders. The current study sought to determine the utility of the Implicit Relational Assessment Procedure (IRAP) as a measure of implicit aversive bias toward spiders in two groups of known variation, high fear…

Implicit and Explicit Memory for Affective Passages in Temporal Lobectomy Patients

ERIC Educational Resources Information Center

Burton, Leslie A.; Rabin, Laura; Vardy, Susan Bernstein; Frohlich, Jonathan; Porter, Gwinne Wyatt; Dimitri, Diana; Cofer, Lucas; Labar, Douglas

2008-01-01

Eighteen temporal lobectomy patients (9 left, LTL; 9 right, RTL) were administered four verbal tasks, an Affective Implicit Task, a Neutral Implicit Task, an Affective Explicit Task, and a Neutral Explicit Task. For the Affective and Neutral Implicit Tasks, participants were timed while reading aloud passages with affective or neutral content,…

The Pivotal Role of Effort Beliefs in Mediating Implicit Theories of Intelligence and Achievement Goals and Academic Motivations

ERIC Educational Resources Information Center

Tempelaar, Dirk T.; Rienties, Bart; Giesbers, Bas; Gijselaers, Wim H.

2015-01-01

Empirical studies into meaning systems surrounding implicit theories of intelligence typically entail two stringent assumptions: that different implicit theories and different effort beliefs represent opposite poles on a single scale, and that implicit theories directly impact the constructs as achievement goals and academic motivations. Through…

Friendships Influence Hispanic Students' Implicit Attitudes toward White Non-Hispanics Relative to African Americans

ERIC Educational Resources Information Center

Aberson, Christopher L.; Porter, Michael K.; Gaffney, Amber M.

2008-01-01

This study examined the role of Hispanic students' friendships with White non-Hispanics (n-Hs) and African Americans (AAs) in predicting implicit and explicit prejudices toward these groups. Participants (N = 73) completed implicit and explicit attitude measures and a friendship questionnaire. Friendships were associated with implicit attitudes…

Do College Instructors Have Implicit Bias toward Latino-Accented English Speakers?

ERIC Educational Resources Information Center

Na, Eunkyung

2016-01-01

The purpose of this study was to examine the implicit attitudes of college-level instructors toward Latino-accented English and the effects of gender, teaching experience, home language, race/ethnicity, and rank on those attitudes. The auditory Implicit Association Test (IAT) was used to measure the implicit accent preferences. Participants (N =…

The Effects of Mindfulness versus Thought Suppression on Implicit and Explicit Measures of Experiential Avoidance

ERIC Educational Resources Information Center

Hooper, Nic; Villatte, Matthieu; Neofotistou, Evi; McHugh, Louise

2010-01-01

The current study aimed to provide an implicit measure of experiential avoidance (EA). Fifty undergraduate participants were exposed to an implicit (Implicit Relational Assessment Procedure: IRAP) and an explicit (Acceptance and Action Questionnaire II: AAQ II) measure of EA. Subsequently participant's response latencies on viewing a negatively…

Explicit and Implicit Stigma of Mental Illness as Predictors of the Recovery Attitudes of Assertive Community Treatment Practitioners.

PubMed

Stull, Laura G; McConnell, Haley; McGrew, John; Salyers, Michelle P

2017-01-01

While explicit negative stereotypes of mental illness are well established as barriers to recovery, implicit attitudes also may negatively impact outcomes. The current study is unique in its focus on both explicit and implicit stigma as predictors of recovery attitudes of mental health practitioners. Assertive Community Treatment practitioners (n = 154) from 55 teams completed online measures of stigma, recovery attitudes, and an Implicit Association Test (IAT). Three of four explicit stigma variables (perceptions of blameworthiness, helplessness, and dangerousness) and all three implicit stigma variables were associated with lower recovery attitudes. In a multivariate, hierarchical model, however, implicit stigma did not explain additional variance in recovery attitudes. In the overall model, perceptions of dangerousness and implicitly associating mental illness with "bad" were significant individual predictors of lower recovery attitudes. The current study demonstrates a need for interventions to lower explicit stigma, particularly perceptions of dangerousness, to increase mental health providers' expectations for recovery. The extent to which implicit and explicit stigma differentially predict outcomes, including recovery attitudes, needs further research.

How "implicit" are implicit color effects in memory?

PubMed

Zimmer, Hubert D; Steiner, Astrid; Ecker, Ullrich K H

2002-01-01

Processing colored pictures of objects results in a preference to choose the former color for a specific object in a subsequent color choice test (Wippich & Mecklenbräuker, 1998). We tested whether this implicit memory effect is independent of performances in episodic color recollection (recognition). In the study phase of Experiment 1, the color of line drawings was either named or its appropriateness was judged. We found only weak implicit memory effects for categorical color information. In Experiment 2, silhouettes were colored by subjects during the study phase. Performances in both the implicit and the explicit test were good. Selections of "old" colors in the implicit test, though, were almost completely confined to items for which the color was also remembered explicitly. In Experiment 3, we applied the opposition technique in order to check whether we could find any implicit effects regarding items for which no explicit color recollection was possible. This was not the case. We therefore draw the conclusion that implicit color preference effects are not independent of explicit recollection, and that they are probably based on the same episodic memory traces that are used in explicit tests.

The moderating role of implicit alcohol-related cognitions in hazardous alcohol use

PubMed Central

Cavanagh, Lucia; Obasi, Ezemenari M.

2015-01-01

The present study applied the Go/No-Go Association Test (GNAT; Nosek & Banaji, 2001) to measure alcohol-related implicit cognitions. Additionally, it assessed the role of implicit cognitions as a potential moderator in the relationship between explicit predictors of alcohol use and hazardous drinking behavior. University undergraduate students (N = 214) completed self-report questionnaires assessing reasons for drinking and reported alcohol use. Participants also completed two GNATs assessing implicit-alcohol-related cognitions associated with attitude (good-bad) and perceived safety (safe-dangerous). As expected, participants held implicit appraisals of alcohol as ‘‘bad’’ and ‘‘dangerous’’ in the context of nonalcoholic drinks, and as ‘‘good’’ and ‘‘safe’’ in the context of licit and illicit drugs. Implicit alcohol-related cognitions moderated the relationship between drinking to cope with negative affect and hazardous drinking and drinking due to cues or craving and hazardous drinking. These findings highlight the multidimensional nature of implicit cognitions and the role of negative implicit alcohol-related associations in moderating relationships between explicit processes and subsequent alcohol use behaviors. PMID:26989352

Controlled and implicit processes in evaluative conditioning on implicit and explicit attitudes toward alcohol and intentions to drink.

PubMed

Zerhouni, Oulmann; Bègue, Laurent; Comiran, Francisco; Wiers, Reinout W

2018-01-01

Since implicit attitudes (i.e. evaluations occurring outside of complete awareness) are highly predictive of alcohol consumption, we tested an evaluative learning procedure based on repeated pairing to a critical stimulus (i.e. alcohol, the CS) with a valenced stimulus (the US) in order to modify implicit attitudes (i.e. evaluative conditioning; EC). We hypothesized that manipulating the learning context to bolster implicit affect misattribution should strengthen EC effects on implicit attitudes toward alcohol, while encouraging deliberate processing of CS-US pairs, should strengthen EC effects on explicit attitudes. In our study (n=114 students) we manipulated whether CS-US pairs were presented simultaneously or sequentially. Recollective memory was estimated with a Process Dissociation Procedure. Both implicit and explicit attitudes were assessed immediately after the procedure. Behavioral intentions were measured directly after and one week after the EC-procedure. We found that EC with sequential presentation had a stronger impact on implicit and explicit measures and on purchase intentions immediately after the procedure and one week after. The present findings provide new evidence that (i) EC is an effective way to change implicit attitudes toward alcohol and (ii) evidence that EC may be better described by propositional rather than dual process accounts. Copyright © 2017 Elsevier Ltd. All rights reserved.

Implicit Weight Bias in Children Age 9 to 11 Years.

PubMed

Skinner, Asheley Cockrell; Payne, Keith; Perrin, Andrew J; Panter, Abigail T; Howard, Janna B; Bardone-Cone, Anna; Bulik, Cynthia M; Steiner, Michael J; Perrin, Eliana M

2017-07-01

Assess implicit weight bias in children 9 to 11 years old. Implicit weight bias was measured in children ages 9 to 11 ( N = 114) by using the Affect Misattribution Procedure. Participants were shown a test image of a child for 350 milliseconds followed by a meaningless fractal (200 milliseconds), and then they were asked to rate the fractal image as "good" or "bad." We used 9 image pairs matched on age, race, sex, and activity but differing by weight of the child. Implicit bias was the difference between positive ratings for fractals preceded by an image of a healthy-weight child and positive ratings for fractals preceded by an image of an overweight child. On average, 64% of abstract fractals shown after pictures of healthy-weight children were rated as "good," compared with 59% of those shown after pictures of overweight children, reflecting an overall implicit bias rate of 5.4% against overweight children ( P < .001). Healthy-weight participants showed greater implicit bias than over- and underweight participants (7.9%, 1.4%, and 0.3% respectively; P = .049). Implicit bias toward overweight individuals is evident in children aged 9 to 11 years with a magnitude of implicit bias (5.4%) similar to that in studies of implicit racial bias among adults. Copyright © 2017 by the American Academy of Pediatrics.

The influence of linguistic and cognitive factors on the time course of verb-based implicit causality.

PubMed

Koornneef, Arnout; Dotlačil, Jakub; van den Broek, Paul; Sanders, Ted

2016-01-01

In three eye-tracking experiments the influence of the Dutch causal connective "want" (because) and the working memory capacity of readers on the usage of verb-based implicit causality was examined. Experiments 1 and 2 showed that although a causal connective is not required to activate implicit causality information during reading, effects of implicit causality surfaced more rapidly and were more pronounced when a connective was present in the discourse than when it was absent. In addition, Experiment 3 revealed that-in contrast to previous claims-the activation of implicit causality is not a resource-consuming mental operation. Moreover, readers with higher and lower working memory capacities behaved differently in a dual-task situation. Higher span readers were more likely to use implicit causality when they had all their working memory resources at their disposal. Lower span readers showed the opposite pattern as they were more likely to use the implicit causality cue in the case of an additional working memory load. The results emphasize that both linguistic and cognitive factors mediate the impact of implicit causality on text comprehension. The implications of these results are discussed in terms of the ongoing controversies in the literature-that is, the focusing-integration debate and the debates on the source of implicit causality.

Implicit and explicit weight bias in a national sample of 4,732 medical students: the medical student CHANGES study.

PubMed

Phelan, Sean M; Dovidio, John F; Puhl, Rebecca M; Burgess, Diana J; Nelson, David B; Yeazel, Mark W; Hardeman, Rachel; Perry, Sylvia; van Ryn, Michelle

2014-04-01

To examine the magnitude of explicit and implicit weight biases compared to biases against other groups; and identify student factors predicting bias in a large national sample of medical students. A web-based survey was completed by 4,732 1st year medical students from 49 medical schools as part of a longitudinal study of medical education. The survey included a validated measure of implicit weight bias, the implicit association test, and 2 measures of explicit bias: a feeling thermometer and the anti-fat attitudes test. A majority of students exhibited implicit (74%) and explicit (67%) weight bias. Implicit weight bias scores were comparable to reported bias against racial minorities. Explicit attitudes were more negative toward obese people than toward racial minorities, gays, lesbians, and poor people. In multivariate regression models, implicit and explicit weight bias was predicted by lower BMI, male sex, and non-Black race. Either implicit or explicit bias was also predicted by age, SES, country of birth, and specialty choice. Implicit and explicit weight bias is common among 1st year medical students, and varies across student factors. Future research should assess implications of biases and test interventions to reduce their impact. Copyright © 2013 The Obesity Society.

Implicit and explicit motor sequence learning in children born very preterm.

PubMed

Jongbloed-Pereboom, Marjolein; Janssen, Anjo J W M; Steiner, K; Steenbergen, Bert; Nijhuis-van der Sanden, Maria W G

2017-01-01

Motor skills can be learned explicitly (dependent on working memory (WM)) or implicitly (relatively independent of WM). Children born very preterm (VPT) often have working memory deficits. Explicit learning may be compromised in these children. This study investigated implicit and explicit motor learning and the role of working memory in VPT children and controls. Three groups (6-9 years) participated: 20 VPT children with motor problems, 20 VPT children without motor problems, and 20 controls. A nine button sequence was learned implicitly (pressing the lighted button as quickly as possible) and explicitly (discovering the sequence via trial-and-error). Children learned implicitly and explicitly, evidenced by decreased movement duration of the sequence over time. In the explicit condition, children also reduced the number of errors over time. Controls made more errors than VPT children without motor problems. Visual WM had positive effects on both explicit and implicit performance. VPT birth and low motor proficiency did not negatively affect implicit or explicit learning. Visual WM was positively related to both implicit and explicit performance, but did not influence learning curves. These findings question the theoretical difference between implicit and explicit learning and the proposed role of visual WM therein. Copyright © 2016 Elsevier Ltd. All rights reserved.

Assessment of implicit sexual associations in non-incarcerated pedophiles.

PubMed

van Leeuwen, Matthijs L; van Baaren, Rick B; Chakhssi, Farid; Loonen, Marijke G M; Lippman, Maarten; Dijksterhuis, Ap

2013-11-01

Offences committed by pedophiles are crimes that evoke serious public concern and outrage. Although recent research using implicit measures has shown promise in detecting deviant sexual associations, the discriminatory and predictive quality of implicit tasks has not yet surpassed traditional assessment methods such as questionnaires and phallometry. The current research extended previous findings by examining whether a combination of two implicit tasks, the Implicit Association Task (IAT) and the Picture Association Task (PAT), was capable of differentiating pedophiles from non-pedophiles, and whether the PAT, which allows separate analysis for male, female, boy and girl stimulus categories, was more sensitive to specific sexual associations in pedophiles than the IAT. A total of 20 male self-reported pedophiles (10 offender and 10 non-offenders) and 20 male self-reported heterosexual controls completed the two implicit measures. Results indicated that the combination of both tasks produced the strongest results to date in detecting implicit pedophilic preferences (AUC = .97). Additionally, the PAT showed promise in decomposing the sexual associations in pedophiles. Interestingly, as there was an equal distribution of offenders and non-offenders in the pedophile group, it was possible to test for implicit association differences between these groups. This comparison showed no clear link between having these implicit sexual associations and actual offending.

Self-replicating machines in continuous space with virtual physics.

PubMed

Smith, Arnold; Turney, Peter; Ewaschuk, Robert

2003-01-01

JohnnyVon is an implementation of self-replicating machines in continuous two-dimensional space. Two types of particles drift about in a virtual liquid. The particles are automata with discrete internal states but continuous external relationships. Their internal states are governed by finite state machines, but their external relationships are governed by a simulated physics that includes Brownian motion, viscosity, and springlike attractive and repulsive forces. The particles can be assembled into patterns that can encode arbitrary strings of bits. We demonstrate that, if an arbitrary seed pattern is put in a soup of separate individual particles, the pattern will replicate by assembling the individual particles into copies of itself. We also show that, given sufficient time, a soup of separate individual particles will eventually spontaneously form self-replicating patterns. We discuss the implications of JohnnyVon for research in nanotechnology, theoretical biology, and artificial life.

Formulation, and physical, in vitro and ex vivo evaluation of transdermal ibuprofen hydrogels containing turpentine oil as penetration enhancer.

PubMed

Khan, N R; Khan, G M; Wahab, A; Khan, A R; Hussain, A; Nawaz, A; Akhlaq, M

2011-11-01

The aim of the present study was to investigate the transdermal permeation enhancing capability of turpentine oil for ibuprofen from hydrogels. Ibuprofen 1% w/v hydrogels were developed with carboxypolymethylene with and without turpentine oil. Turpentine oil was incorporated in increasing concentrations, i.e. 0.5, 1, 1.5, 2, 2.5 and 3% of the total gel formulation, and its permeation enhancing effect was examined. Gels were examined physically for pH, viscosity, spreadability, extrudability, smoothness and appearance. To study the in vitro and ex vivo permeation potential of formulated gels, permeation studies were performed with a Franz diffusion cell using cellulose membrane and excised rabbit abdominal skin. Ibuprofen hydrogel with 3% turpentine oil showed a maximum flux of 10.87 mg/cm2/h across artificial skin and 17.26 mg/cm2/h across rabbit abdominal skin.

Design of supercritical swept wings

NASA Technical Reports Server (NTRS)

Garabedian, P.; Mcfadden, G.

1982-01-01

Computational fluid dynamics are used to discuss problems inherent to transonic three-dimensional flow past supercritical swept wings. The formulation for a boundary value problem for the flow past the wing is provided, including consideration of weak shock waves and the use of parabolic coordinates. A swept wing code is developed which requires a mesh of 152 x 10 x 12 points and 200 time cycles. A formula for wave drag is calculated, based on the idea that the conservation form of the momentum equation becomes an entropy inequality measuring the drag, expressible in terms of a small-disturbance equation for a potential function in two dimensions. The entropy inequality has been incorporated in a two-dimensional code for the analysis of transonic flow over airfoils. A method of artificial viscosity is explored for optimum pressure distributions with design, and involves a free boundary problem considering speed over only a portion of the wing.

Computational fluid dynamics of airfoils and wings

NASA Technical Reports Server (NTRS)

Garabedian, P.; Mcfadden, G.

1982-01-01

It is pointed out that transonic flow is one of the fields where computational fluid dynamics turns out to be most effective. Codes for the design and analysis of supercritical airfoils and wings have become standard tools of the aircraft industry. The present investigation is concerned with mathematical models and theorems which account for some of the progress that has been made. The most successful aerodynamics codes are those for the analysis of flow at off-design conditions where weak shock waves appear. A major breakthrough was achieved by Murman and Cole (1971), who conceived of a retarded difference scheme which incorporates artificial viscosity to capture shocks in the supersonic zone. This concept has been used to develop codes for the analysis of transonic flow past a swept wing. Attention is given to the trailing edge and the boundary layer, entropy inequalities and wave drag, shockless airfoils, and the inverse swept wing code.

Heating, Cooling, and Gravitational Instabilities in Protostellar and Protoplanetary Disks

NASA Astrophysics Data System (ADS)

Pickett, B. K.; Mejia, A. C.; Durisen, R. H.

2001-12-01

We present three-dimensional hydrodynamic simulations of protostellar disk models, in order to explore how the interplay between heating and cooling regulates significant gravitational instabilities. Artificial viscosity is used to treat irreversible heating, such as would occur in shocks; volumetric cooling at several different rates is also applied throughout a broad radial region of the disk. We study the evolution of a disk that is already unstable (due to the low value of the Toomre Q parameter), and a marginally unstable disk that is cooled towards instability. The evolutions have implications for the transport of mass and angular momentum in protostellar disks, the effects of gravitational instabilities on the vertical structure of the disks, and the formation of stellar and substellar companions on dynamic time scales due to disk instabilties. This work is supported by grants from the NASA Planetary Geology and Geophysics and Origins of Solar Systems Programs.

The piecewise-linear predictor-corrector code - A Lagrangian-remap method for astrophysical flows

NASA Technical Reports Server (NTRS)

Lufkin, Eric A.; Hawley, John F.

1993-01-01

We describe a time-explicit finite-difference algorithm for solving the nonlinear fluid equations. The method is similar to existing Eulerian schemes in its use of operator-splitting and artificial viscosity, except that we solve the Lagrangian equations of motion with a predictor-corrector and then remap onto a fixed Eulerian grid. The remap is formulated to eliminate errors associated with coordinate singularities, with a general prescription for remaps of arbitrary order. We perform a comprehensive series of tests on standard problems. Self-convergence tests show that the code has a second-order rate of convergence in smooth, two-dimensional flow, with pressure forces, gravity, and curvilinear geometry included. While not as accurate on idealized problems as high-order Riemann-solving schemes, the predictor-corrector Lagrangian-remap code has great flexibility for application to a variety of astrophysical problems.

Fluid dynamic modeling of nano-thermite reactions

NASA Astrophysics Data System (ADS)

Martirosyan, Karen S.; Zyskin, Maxim; Jenkins, Charles M.; Yuki Horie, Yasuyuki

2014-03-01

This paper presents a direct numerical method based on gas dynamic equations to predict pressure evolution during the discharge of nanoenergetic materials. The direct numerical method provides for modeling reflections of the shock waves from the reactor walls that generates pressure-time fluctuations. The results of gas pressure prediction are consistent with the experimental evidence and estimates based on the self-similar solution. Artificial viscosity provides sufficient smoothing of shock wave discontinuity for the numerical procedure. The direct numerical method is more computationally demanding and flexible than self-similar solution, in particular it allows study of a shock wave in its early stage of reaction and allows the investigation of "slower" reactions, which may produce weaker shock waves. Moreover, numerical results indicate that peak pressure is not very sensitive to initial density and reaction time, providing that all the material reacts well before the shock wave arrives at the end of the reactor.

Fluid dynamic modeling of nano-thermite reactions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martirosyan, Karen S., E-mail: karen.martirosyan@utb.edu; Zyskin, Maxim; Jenkins, Charles M.

2014-03-14

This paper presents a direct numerical method based on gas dynamic equations to predict pressure evolution during the discharge of nanoenergetic materials. The direct numerical method provides for modeling reflections of the shock waves from the reactor walls that generates pressure-time fluctuations. The results of gas pressure prediction are consistent with the experimental evidence and estimates based on the self-similar solution. Artificial viscosity provides sufficient smoothing of shock wave discontinuity for the numerical procedure. The direct numerical method is more computationally demanding and flexible than self-similar solution, in particular it allows study of a shock wave in its early stagemore » of reaction and allows the investigation of “slower” reactions, which may produce weaker shock waves. Moreover, numerical results indicate that peak pressure is not very sensitive to initial density and reaction time, providing that all the material reacts well before the shock wave arrives at the end of the reactor.« less

WIND: Computer program for calculation of three dimensional potential compressible flow about wind turbine rotor blades

NASA Technical Reports Server (NTRS)

Dulikravich, D. S.

1980-01-01

A computer program is presented which numerically solves an exact, full potential equation (FPE) for three dimensional, steady, inviscid flow through an isolated wind turbine rotor. The program automatically generates a three dimensional, boundary conforming grid and iteratively solves the FPE while fully accounting for both the rotating cascade and Coriolis effects. The numerical techniques incorporated involve rotated, type dependent finite differencing, a finite volume method, artificial viscosity in conservative form, and a successive line overrelaxation combined with the sequential grid refinement procedure to accelerate the iterative convergence rate. Consequently, the WIND program is capable of accurately analyzing incompressible and compressible flows, including those that are locally transonic and terminated by weak shocks. The program can also be used to analyze the flow around isolated aircraft propellers and helicopter rotors in hover as long as the total relative Mach number of the oncoming flow is subsonic.

A new method for solving the quantum hydrodynamic equations of motion: application to two-dimensional reactive scattering.

PubMed

Pauler, Denise K; Kendrick, Brian K

2004-01-08

The de Broglie-Bohm hydrodynamic equations of motion are solved using a meshless method based on a moving least squares approach and an arbitrary Lagrangian-Eulerian frame of reference. A regridding algorithm adds and deletes computational points as needed in order to maintain a uniform interparticle spacing, and unitary time evolution is obtained by propagating the wave packet using averaged fields. The numerical instabilities associated with the formation of nodes in the reflected portion of the wave packet are avoided by adding artificial viscosity to the equations of motion. The methodology is applied to a two-dimensional model collinear reaction with an activation barrier. Reaction probabilities are computed as a function of both time and energy, and are in excellent agreement with those based on the quantum trajectory method. (c) 2004 American Institute of Physics

Quality factors and local adaption (with applications in Eulerian hydrodynamics)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowley, W.P.

1992-06-17

Adapting the mesh to suit the solution is a technique commonly used for solving both ode`s and pde`s. For Lagrangian hydrodynamics, ALE and Free-Lagrange are examples of structured and unstructured adaptive methods. For Eulerian hydrodynamics the two basic approaches are the macro-unstructuring technique pioneered by Oliger and Berger and the micro-structuring technique due to Lohner and others. Here we will describe a new micro-unstructuring technique, LAM, (for Local Adaptive Mesh) as applied to Eulerian hydrodynamics. The LAM technique consists of two independent parts: (1) the time advance scheme is a variation on the artificial viscosity method; (2) the adaption schememore » uses a micro-unstructured mesh with quadrilateral mesh elements. The adaption scheme makes use of quality factors and the relation between these and truncation errors is discussed. The time advance scheme; the adaption strategy; and the effect of different adaption parameters on numerical solutions are described.« less

Quality factors and local adaption (with applications in Eulerian hydrodynamics)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Crowley, W.P.

1992-06-17

Adapting the mesh to suit the solution is a technique commonly used for solving both ode's and pde's. For Lagrangian hydrodynamics, ALE and Free-Lagrange are examples of structured and unstructured adaptive methods. For Eulerian hydrodynamics the two basic approaches are the macro-unstructuring technique pioneered by Oliger and Berger and the micro-structuring technique due to Lohner and others. Here we will describe a new micro-unstructuring technique, LAM, (for Local Adaptive Mesh) as applied to Eulerian hydrodynamics. The LAM technique consists of two independent parts: (1) the time advance scheme is a variation on the artificial viscosity method; (2) the adaption schememore » uses a micro-unstructured mesh with quadrilateral mesh elements. The adaption scheme makes use of quality factors and the relation between these and truncation errors is discussed. The time advance scheme; the adaption strategy; and the effect of different adaption parameters on numerical solutions are described.« less

Implicit and explicit self-esteem as concurrent predictors of suicidal ideation, depressive symptoms, and loneliness.

PubMed

Creemers, Daan H M; Scholte, Ron H J; Engels, Rutger C M E; Prinstein, Mitchell J; Wiers, Reinout W

2012-03-01

The aim of the present study was to examine whether explicit and implicit self-esteem, the interaction between these two constructs, and their discrepancy are associated with depressive symptoms, suicidal ideation, and loneliness. Participants were 95 young female adults (M = 21.2 years, SD = 1.88) enrolled in higher education. We administered the Name Letter Task to measure implicit self-esteem, and the Rosenberg self-esteem scale to assess explicit self-esteem. The results indicated that explicit but not implicit self-esteem was negatively associated with depressive symptoms, suicidal ideation, and loneliness. The interaction of implicit and explicit self-esteem was associated with suicidal ideation, indicating that participants with high implicit self-esteem combined with a low explicit self-esteem showed more suicidal ideation. Furthermore, the size of the discrepancy between implicit and explicit self-esteem was positively associated with depressive symptoms, suicidal ideation, and loneliness. In addition, results showed that the direction of the discrepancy is an important: damaged self-esteem (high implicit self-esteem combined with low explicit self-esteem) was consistently associated with increased levels of depressive symptoms, suicidal ideation, and loneliness, while defensive or fragile self-esteem (high explicit and low implicit self-esteem) was not. Together, these findings provide new insights into the relationship of implicit and explicit self-esteem with depressive symptoms, suicidal ideation, and loneliness. Copyright © 2011 Elsevier Ltd. All rights reserved.

"Whether I like it or not, it's important": Implicit importance of means predicts self-regulatory persistence and success.

PubMed

Critcher, Clayton R; Ferguson, Melissa J

2016-06-01

To effectively self-regulate, people must persevere on tasks that they deem important, regardless of whether those tasks are enjoyable. Building on past work that has noted the fundamental role of implicit cognition in guiding effective self-regulation, the present paper tests whether an implicit association between goal means and importance predicts self-regulatory persistence and success. Implicit importance predicted markers of effective self-regulation-better grades, more studying and exercise, and stronger standardized testing performance-over and above, and often better than, explicit beliefs about the importance of that self-regulation, as well as implicit evaluations of those means. In particular, those for whom tasks were fairly taxing to complete (i.e., those for whom this self-regulation required effortful self-control) were those who most benefitted from the implicit association between means and importance. Moreover, when participants were reminded of recent self-regulatory failure that they believed could be overcome through hard work, implicit importance toward the means increased as if to prepare them to achieve self-regulatory persistence. A final study sought to reconcile the present findings with previous work showing the key role that implicit evaluations play in effective self-regulation. We reasoned that means are important precisely because they are associated with valued end-states. Consistent with this account, implicit evaluations of end-states predicted the implicit importance of means, which in turn predicted effective self-regulation. (PsycINFO Database Record (c) 2016 APA, all rights reserved).

Effects of pretesting implicit self-determined motivation on behavioral engagement: evidence for the mere measurement effect at the implicit level.

PubMed

Keatley, David A; Clarke, David D; Ferguson, Eamonn; Hagger, Martin S

2014-01-01

Research into individuals' intended behavior and performance has traditionally adopted explicitly measured, self-report constructs, and outcomes. More recently, research has shown that completing explicit self-report measures of constructs may effect subsequent behavior, termed the "mere measurement" effect. The aim of the present experiment was to investigate whether implicit measures of motivation showed a similar mere measurement effect on subsequent behavior. It may be the case that measuring the implicit systems affects subsequent implicit interventions (e.g., priming), observable on subsequent behavior. Priming manipulations were also given to participants in order to investigate the interaction between measurement and priming of motivation. Initially, a 2 [implicit association test (IAT: present vs. absent) ×2 (Prime: autonomous vs. absent) and a 2 (IAT: present vs. absent) × 2 (Prime: controlled vs. absent)] between participants designs were conducted, these were them combined into a 2 (IAT: present vs. absent) ×3 (Prime: autonomous vs. controlled vs. absent) between participants design, with attempts at a novel task taken as the outcome measure. Implicit measure completion significantly decreased behavioral engagement. Priming autonomous motivation significantly facilitated, and controlled motivation significantly inhibited performance. Finally, there was a significant implicit measurement × priming interaction, such that priming autonomous motivation only improved performance in the absence of the implicit measure. Overall, this research provides an insight into the effects of implicit measurement and priming of motivation and the combined effect of completing both tasks on behavior.

A specific implicit sequence learning deficit as an underlying cause of dyslexia? Investigating the role of attention in implicit learning tasks.

PubMed

Staels, Eva; Van den Broeck, Wim

2017-05-01

Recently, a general implicit sequence learning deficit was proposed as an underlying cause of dyslexia. This new hypothesis was investigated in the present study by including a number of methodological improvements, for example, the inclusion of appropriate control conditions. The second goal of the study was to explore the role of attentional functioning in implicit and explicit learning tasks. In a 2 × 2 within-subjects design 4 tasks were administered in 30 dyslexic and 38 control children: an implicit and explicit serial reaction time (RT) task and an implicit and explicit contextual cueing task. Attentional functioning was also administered. The entire learning curves of all tasks were analyzed using latent growth curve modeling in order to compare performances between groups and to examine the role of attentional functioning on the learning curves. The amount of implicit learning was similar for both groups. However, the dyslexic group showed slower RTs throughout the entire task. This group difference reduced and became nonsignificant after controlling for attentional functioning. Both implicit learning tasks, but none of the explicit learning tasks, were significantly affected by attentional functioning. Dyslexic children do not suffer from a specific implicit sequence learning deficit. The slower RTs of the dyslexic children throughout the entire implicit sequence learning process are caused by their comorbid attention problems and overall slowness. A key finding of the present study is that, in contrast to what was assumed for a long time, implicit learning relies on attentional resources, perhaps even more than explicit learning does. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

The Effects of Oncologist Implicit Racial Bias in Racially Discordant Oncology Interactions

PubMed Central

Dovidio, John F.; Gonzalez, Richard; Albrecht, Terrance L.; Chapman, Robert; Foster, Tanina; Harper, Felicity W.K.; Hagiwara, Nao; Hamel, Lauren M.; Shields, Anthony F.; Gadgeel, Shirish; Simon, Michael S.; Griggs, Jennifer J.; Eggly, Susan

2016-01-01

Purpose Health providers’ implicit racial bias negatively affects communication and patient reactions to many medical interactions. However, its effects on racially discordant oncology interactions are largely unknown. Thus, we examined whether oncologist implicit racial bias has similar effects in oncology interactions. We further investigated whether oncologist implicit bias negatively affects patients’ perceptions of recommended treatments (i.e., degree of confidence, expected difficulty). We predicted oncologist implicit bias would negatively affect communication, patient reactions to interactions, and, indirectly, patient perceptions of recommended treatments. Methods Participants were 18 non-black medical oncologists and 112 black patients. Oncologists completed an implicit racial bias measure several weeks before video-recorded treatment discussions with new patients. Observers rated oncologist communication and recorded interaction length of time and amount of time oncologists and patients spoke. Following interactions, patients answered questions about oncologists’ patient-centeredness and difficulty remembering contents of the interaction, distress, trust, and treatment perceptions. Results As predicted, oncologists higher in implicit racial bias had shorter interactions, and patients and observers rated these oncologists’ communication as less patient-centered and supportive. Higher implicit bias also was associated with more patient difficulty remembering contents of the interaction. In addition, oncologist implicit bias indirectly predicted less patient confidence in recommended treatments, and greater perceived difficulty completing them, through its impact on oncologists’ communication (as rated by both patients and observers). Conclusion Oncologist implicit racial bias is negatively associated with oncologist communication, patients’ reactions to racially discordant oncology interactions, and patient perceptions of recommended treatments. These perceptions could subsequently directly affect patient-treatment decisions. Thus, implicit racial bias is a likely source of racial treatment disparities and must be addressed in oncology training and practice. PMID:27325865

Comparison of Physician Implicit Racial Bias Toward Adults Versus Children.

PubMed

Johnson, Tiffani J; Winger, Daniel G; Hickey, Robert W; Switzer, Galen E; Miller, Elizabeth; Nguyen, Margaret B; Saladino, Richard A; Hausmann, Leslie R M

2017-03-01

The general population and most physicians have implicit racial bias against black adults. Pediatricians also have implicit bias against black adults, albeit less than other specialties. There is no published research on the implicit racial attitudes of pediatricians or other physicians toward children. Our objectives were to compare implicit racial bias toward adults versus children among resident physicians working in a pediatric emergency department, and to assess whether bias varied by specialty (pediatrics, emergency medicine, or other), gender, race, age, and year of training. We measured implicit racial bias of residents before a pediatric emergency department shift using the Adult and Child Race Implicit Association Tests (IATs). Generalized linear models compared Adult and Child IAT scores and determined the association of participant demographics with Adult and Child IAT scores. Among 91 residents, we found moderate pro-white/anti-black bias on both the Adult (mean = 0.49, standard deviation = 0.34) and Child Race IAT (mean = 0.55, standard deviation = 0.37). There was no significant difference between Adult and Child Race IAT scores (difference = 0.06, P = .15). Implicit bias was not associated with resident demographic characteristics, including specialty. This is the first study demonstrating that resident physicians have implicit racial bias against black children, similar to levels of bias against black adults. Bias in our study did not vary by resident demographic characteristics, including specialty, suggesting that pediatric residents are as susceptible as other physicians to implicit bias. Future studies are needed to explore how physicians' implicit attitudes toward parents and children may impact inequities in pediatric health care. Copyright © 2016 Academic Pediatric Association. All rights reserved.

The Effects of Oncologist Implicit Racial Bias in Racially Discordant Oncology Interactions.

PubMed

Penner, Louis A; Dovidio, John F; Gonzalez, Richard; Albrecht, Terrance L; Chapman, Robert; Foster, Tanina; Harper, Felicity W K; Hagiwara, Nao; Hamel, Lauren M; Shields, Anthony F; Gadgeel, Shirish; Simon, Michael S; Griggs, Jennifer J; Eggly, Susan

2016-08-20

Health providers' implicit racial bias negatively affects communication and patient reactions to many medical interactions. However, its effects on racially discordant oncology interactions are largely unknown. Thus, we examined whether oncologist implicit racial bias has similar effects in oncology interactions. We further investigated whether oncologist implicit bias negatively affects patients' perceptions of recommended treatments (i.e., degree of confidence, expected difficulty). We predicted oncologist implicit bias would negatively affect communication, patient reactions to interactions, and, indirectly, patient perceptions of recommended treatments. Participants were 18 non-black medical oncologists and 112 black patients. Oncologists completed an implicit racial bias measure several weeks before video-recorded treatment discussions with new patients. Observers rated oncologist communication and recorded interaction length of time and amount of time oncologists and patients spoke. Following interactions, patients answered questions about oncologists' patient-centeredness and difficulty remembering contents of the interaction, distress, trust, and treatment perceptions. As predicted, oncologists higher in implicit racial bias had shorter interactions, and patients and observers rated these oncologists' communication as less patient-centered and supportive. Higher implicit bias also was associated with more patient difficulty remembering contents of the interaction. In addition, oncologist implicit bias indirectly predicted less patient confidence in recommended treatments, and greater perceived difficulty completing them, through its impact on oncologists' communication (as rated by both patients and observers). Oncologist implicit racial bias is negatively associated with oncologist communication, patients' reactions to racially discordant oncology interactions, and patient perceptions of recommended treatments. These perceptions could subsequently directly affect patient-treatment decisions. Thus, implicit racial bias is a likely source of racial treatment disparities and must be addressed in oncology training and practice. © 2016 by American Society of Clinical Oncology.

Face puzzle—two new video-based tasks for measuring explicit and implicit aspects of facial emotion recognition

PubMed Central

Kliemann, Dorit; Rosenblau, Gabriela; Bölte, Sven; Heekeren, Hauke R.; Dziobek, Isabel

2013-01-01

Recognizing others' emotional states is crucial for effective social interaction. While most facial emotion recognition tasks use explicit prompts that trigger consciously controlled processing, emotional faces are almost exclusively processed implicitly in real life. Recent attempts in social cognition suggest a dual process perspective, whereby explicit and implicit processes largely operate independently. However, due to differences in methodology the direct comparison of implicit and explicit social cognition has remained a challenge. Here, we introduce a new tool to comparably measure implicit and explicit processing aspects comprising basic and complex emotions in facial expressions. We developed two video-based tasks with similar answer formats to assess performance in respective facial emotion recognition processes: Face Puzzle, implicit and explicit. To assess the tasks' sensitivity to atypical social cognition and to infer interrelationship patterns between explicit and implicit processes in typical and atypical development, we included healthy adults (NT, n = 24) and adults with autism spectrum disorder (ASD, n = 24). Item analyses yielded good reliability of the new tasks. Group-specific results indicated sensitivity to subtle social impairments in high-functioning ASD. Correlation analyses with established implicit and explicit socio-cognitive measures were further in favor of the tasks' external validity. Between group comparisons provide first hints of differential relations between implicit and explicit aspects of facial emotion recognition processes in healthy compared to ASD participants. In addition, an increased magnitude of between group differences in the implicit task was found for a speed-accuracy composite measure. The new Face Puzzle tool thus provides two new tasks to separately assess explicit and implicit social functioning, for instance, to measure subtle impairments as well as potential improvements due to social cognitive interventions. PMID:23805122

Unconscious Race and Class Biases among Registered Nurses: Vignette-Based Study Using Implicit Association Testing.

PubMed

Haider, Adil H; Schneider, Eric B; Sriram, N; Scott, Valerie K; Swoboda, Sandra M; Zogg, Cheryl K; Dhiman, Nitasha; Haut, Elliott R; Efron, David T; Pronovost, Peter J; Freischlag, Julie A; Lipsett, Pamela A; Cornwell, Edward E; MacKenzie, Ellen J; Cooper, Lisa A

2015-06-01

Implicit bias is an unconscious preference for a specific social group that can have adverse consequences for patient care. Acute care clinical vignettes were used to examine whether implicit race or class biases among registered nurses (RNs) impacted patient-management decisions. In a prospective study conducted among surgical RNs at the Johns Hopkins Hospital, participants were presented 8 multi-stage clinical vignettes in which patients' race or social class were randomly altered. Registered nurses were administered implicit association tests (IATs) for social class and race. Ordered logistic regression was then used to examine associations among treatment differences, race, or social class, and RN's IAT scores. Spearman's rank coefficients comparing RN's implicit (IAT) and explicit (stated) preferences were also investigated. Two hundred and forty-five RNs participated. The majority were female (n=217 [88.5%]) and white (n=203 [82.9%]). Most reported that they had no explicit race or class preferences (n=174 [71.0%] and n=108 [44.1%], respectively). However, only 36 nurses (14.7%) demonstrated no implicit race preference as measured by race IAT, and only 16 nurses (6.53%) displayed no implicit class preference on the class IAT. Implicit association tests scores did not statistically correlate with vignette-based clinical decision making. Spearman's rank coefficients comparing implicit (IAT) and explicit preferences also demonstrated no statistically significant correlation (r=-0.06; p=0.340 and r=-0.06; p=0.342, respectively). The majority of RNs displayed implicit preferences toward white race and upper social class patients on IAT assessment. However, unlike published data on physicians, implicit biases among RNs did not correlate with clinical decision making. Copyright © 2015 American College of Surgeons. Published by Elsevier Inc. All rights reserved.

Co-occurrence of social anxiety and depression symptoms in adolescence: differential links with implicit and explicit self-esteem?

PubMed

de Jong, P J; Sportel, B E; de Hullu, E; Nauta, M H

2012-03-01

Social anxiety and depression often co-occur. As low self-esteem has been identified as a risk factor for both types of symptoms, it may help to explain their co-morbidity. Current dual process models of psychopathology differentiate between explicit and implicit self-esteem. Explicit self-esteem would reflect deliberate self-evaluative processes whereas implicit self-esteem would reflect simple associations in memory. Previous research suggests that low explicit self-esteem is involved in both social anxiety and depression whereas low implicit self-esteem is only involved in social anxiety. We tested whether the association between symptoms of social phobia and depression can indeed be explained by low explicit self-esteem, whereas low implicit self-esteem is only involved in social anxiety. Adolescents during the first stage of secondary education (n=1806) completed the Revised Child Anxiety and Depression Scale (RCADS) to measure symptoms of social anxiety and depression, the Rosenberg Self-Esteem Scale (RSES) to index explicit self-esteem and the Implicit Association Test (IAT) to measure implicit self-esteem. There was a strong association between symptoms of depression and social anxiety that could be largely explained by participants' explicit self-esteem. Only for girls did implicit self-esteem and the interaction between implicit and explicit self-esteem show small cumulative predictive validity for social anxiety, indicating that the association between low implicit self-esteem and social anxiety was most evident for girls with relatively low explicit self-esteem. Implicit self-esteem showed no significant predictive validity for depressive symptoms. The findings support the view that both shared and differential self-evaluative processes are involved in depression and social anxiety.

Attitudes towards individuals with disabilities as measured by the implicit association test: a literature review.

PubMed

Wilson, Michelle Clare; Scior, Katrina

2014-02-01

Research investigating attitudes towards individuals with disabilities has largely focused on self-reported explicit attitudes. Given that factors such as social desirability may influence explicit attitudes, researchers have developed tools which instead assess less consciously controllable implicit attitudes. Considering research on implicit attitudes thus seems pertinent. A review of studies measuring implicit attitudes towards individuals with physical disabilities (visual, motor or hearing) or intellectual disabilities via the Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998) was carried out. Systematic searches of PsycINFO, CINAHL, EMBASE, ERIC, MEDLINE, PUBMED, Scopus and Web of Science databases identified relevant articles published between January 2000 and September 2012. Seventeen articles (reporting on 18 studies that employed the IAT) were identified. These investigated implicit attitudes towards individuals with; physical disabilities (N=13), intellectual disabilities (N=3), both physical and intellectual disabilities (N=1), and 'unspecified disabilities' (N=1). Across all studies, moderate to strong negative implicit attitudes were found and there was little to no association between explicit and implicit attitudes. Individuals' beliefs about the controllability of their future, sensitivity to the concept of disease, and contact with individuals with disabilities appear to be associated with implicit attitudes. A consistent pattern of moderate to strong negative implicit attitudes towards individuals with disabilities was evident. These studies provide a starting point, but methodological issues related to sampling and the employed IATs limit the generalizability of these results. Further research investigating implicit attitudes towards specific disability types, with a wider subject pool are necessary as well as further investigation of factors that contribute to these attitudes. Copyright © 2013 Elsevier Ltd. All rights reserved.

Implicit Social Cognitive Processes Underlying Victim Self and Identity: Evidence With College-Aged Adults.

PubMed

Sachs, Nicole M; Veysey, Bonita M; Rivera, Luis M

2017-11-01

Past research on victimization has relied predominantly on individuals' awareness of and willingness to self-report a victimization experience and its effect on self and identity processes. The present research adopts theoretical and methodological innovations in implicit social cognition research to provide a new perspective on how a violent victimization experience might influence identity processes outside of conscious awareness. Our main goal was to test whether individuals who have victimization experience implicitly associate the self with victims (implicit victim identity) and their stereotypes (implicit victim self-stereotyping), and the relation of these associations to explicit victim identity and self-stereotyping. Two pretests with undergraduate student participants ( Ns = 122 and 72) identified victim-related word stimuli for two Single Category Implicit Association Test (SC-IAT) measures of implicit victim identity and self-stereotyping. In Pretest Study A, participants read crime vignettes and listed words that described a victim, then in Pretest Study B, participants rated these words on victim relatedness and valence. The Main Study recruited undergraduate student participants ( N = 101) who completed the SC-IATs, self-report measures of explicit victim identity and self-stereotyping, and victimization experiences. Three of our five hypotheses were supported. Individuals with past victimization experience exhibited strong explicit victim identity and self-stereotyping, but not implicit victim identity and self-stereotyping, relative to those with no victimization experience. Explicit and implicit victim identity and self-stereotyping were unrelated. Finally, among individuals with victimization experience, a strong implicit victim identity was associated with strong implicit victim self-stereotyping. This research has implications for understanding the processes underlying revictimization and for preventing further victimization.

Long Term Memory for Noise: Evidence of Robust Encoding of Very Short Temporal Acoustic Patterns.

PubMed

Viswanathan, Jayalakshmi; Rémy, Florence; Bacon-Macé, Nadège; Thorpe, Simon J

2016-01-01

Recent research has demonstrated that humans are able to implicitly encode and retain repeating patterns in meaningless auditory noise. Our study aimed at testing the robustness of long-term implicit recognition memory for these learned patterns. Participants performed a cyclic/non-cyclic discrimination task, during which they were presented with either 1-s cyclic noises (CNs) (the two halves of the noise were identical) or 1-s plain random noises (Ns). Among CNs and Ns presented once, target CNs were implicitly presented multiple times within a block, and implicit recognition of these target CNs was tested 4 weeks later using a similar cyclic/non-cyclic discrimination task. Furthermore, robustness of implicit recognition memory was tested by presenting participants with looped (shifting the origin) and scrambled (chopping sounds into 10- and 20-ms bits before shuffling) versions of the target CNs. We found that participants had robust implicit recognition memory for learned noise patterns after 4 weeks, right from the first presentation. Additionally, this memory was remarkably resistant to acoustic transformations, such as looping and scrambling of the sounds. Finally, implicit recognition of sounds was dependent on participant's discrimination performance during learning. Our findings suggest that meaningless temporal features as short as 10 ms can be implicitly stored in long-term auditory memory. Moreover, successful encoding and storage of such fine features may vary between participants, possibly depending on individual attention and auditory discrimination abilities. Significance Statement Meaningless auditory patterns could be implicitly encoded and stored in long-term memory.Acoustic transformations of learned meaningless patterns could be implicitly recognized after 4 weeks.Implicit long-term memories can be formed for meaningless auditory features as short as 10 ms.Successful encoding and long-term implicit recognition of meaningless patterns may strongly depend on individual attention and auditory discrimination abilities.

Long Term Memory for Noise: Evidence of Robust Encoding of Very Short Temporal Acoustic Patterns

PubMed Central

Viswanathan, Jayalakshmi; Rémy, Florence; Bacon-Macé, Nadège; Thorpe, Simon J.

2016-01-01

Recent research has demonstrated that humans are able to implicitly encode and retain repeating patterns in meaningless auditory noise. Our study aimed at testing the robustness of long-term implicit recognition memory for these learned patterns. Participants performed a cyclic/non-cyclic discrimination task, during which they were presented with either 1-s cyclic noises (CNs) (the two halves of the noise were identical) or 1-s plain random noises (Ns). Among CNs and Ns presented once, target CNs were implicitly presented multiple times within a block, and implicit recognition of these target CNs was tested 4 weeks later using a similar cyclic/non-cyclic discrimination task. Furthermore, robustness of implicit recognition memory was tested by presenting participants with looped (shifting the origin) and scrambled (chopping sounds into 10− and 20-ms bits before shuffling) versions of the target CNs. We found that participants had robust implicit recognition memory for learned noise patterns after 4 weeks, right from the first presentation. Additionally, this memory was remarkably resistant to acoustic transformations, such as looping and scrambling of the sounds. Finally, implicit recognition of sounds was dependent on participant's discrimination performance during learning. Our findings suggest that meaningless temporal features as short as 10 ms can be implicitly stored in long-term auditory memory. Moreover, successful encoding and storage of such fine features may vary between participants, possibly depending on individual attention and auditory discrimination abilities. Significance Statement Meaningless auditory patterns could be implicitly encoded and stored in long-term memory.Acoustic transformations of learned meaningless patterns could be implicitly recognized after 4 weeks.Implicit long-term memories can be formed for meaningless auditory features as short as 10 ms.Successful encoding and long-term implicit recognition of meaningless patterns may strongly depend on individual attention and auditory discrimination abilities. PMID:27932941

Implicit and explicit self-esteem discrepancies in people with psychogenic nonepileptic seizures.

PubMed

Dimaro, Lian V; Roberts, Nicole A; Moghaddam, Nima G; Dawson, David L; Brown, Ian; Reuber, Markus

2015-05-01

Self-esteem (SE), or one's sense of competence and worth, is reduced in many mental and physical disorders. Low SE is associated with perceived stigma and disability and poor treatment outcomes. The present study examined implicit and explicit SE (automatic and deliberate views about the self) in people with epilepsy and people with psychogenic nonepileptic seizures (PNESs). Discrepancies between implicit SE and explicit SE have been found to correlate with psychological distress in disorders often associated with PNESs but are relatively unexplored in PNESs. We hypothesized that, compared with epilepsy, PNESs would be associated with lower self-reported SE and greater discrepancies between implicit SE and explicit SE. Thirty adults with PNESs, 25 adults with epilepsy, and 31 controls without a history of seizures were asked to complete the Rosenberg Self-esteem Scale as a measure of explicit SE and an Implicit Relational Assessment Procedure as a measure of implicit SE. The State-Trait Anxiety Inventory and Patient Health Questionnaire-15 (a somatic symptom inventory) were also administered. We found significant group differences in explicit (p<0.001) but not implicit SE. Patients with PNESs reported lower SE than the other groups. No group differences were found in implicit SE. Implicit-explicit SE discrepancies were larger in the group with PNESs than in the other groups (p<0.001). Higher frequency of PNESs (but not epileptic seizures) was associated with lower explicit SE (rs=-.83, p<0.01) and greater SE discrepancies (i.e., lower explicit relative to implicit SE; rs=.65, p<0.01). These relationships remained significant when controlling for anxiety and somatization. Patients with PNESs had lower explicit SE than those with epilepsy or healthy controls. In keeping with our expectations, there were greater discrepancies between implicit SE and explicit SE among patients with PNESs than in the other groups. Our results, including the strong relationship between PNES frequency, anxiety, and explicit-implicit SE discrepancies, support the interpretation that PNESs serve to reduce cognitive dissonance, perhaps protecting patients' implicit SE. Crown Copyright © 2015. Published by Elsevier Inc. All rights reserved.

The role of bulk viscosity on the decay of compressible, homogeneous, isotropic turbulence

NASA Astrophysics Data System (ADS)

Johnsen, Eric; Pan, Shaowu

2016-11-01

The practice of neglecting bulk viscosity in studies of compressible turbulence is widespread. While exact for monatomic gases and unlikely to strongly affect the dynamics of fluids whose bulk-to-shear viscosity ratio is small and/or of weakly compressible turbulence, this assumption is not justifiable for compressible, turbulent flows of gases whose bulk viscosity is orders of magnitude larger than their shear viscosities (e.g., CO2). To understand the mechanisms by which bulk viscosity and the associated phenomena affect compressible turbulence, we conduct DNS of freely decaying compressible, homogeneous, isotropic turbulence for ratios of bulk-to-shear viscosity ranging from 0-1000. Our simulations demonstrate that bulk viscosity increases the decay rate of turbulent kinetic energy; while enstrophy exhibits little sensitivity to bulk viscosity, dilatation is reduced by an order of magnitude within the two eddy turnover time. Via a Helmholtz decomposition of the flow, we determined that bulk viscosity damps the dilatational velocity and reduces dilatational-solenoidal exchanges, as well as pressure-dilatation coupling. In short, bulk viscosity renders compressible turbulence incompressible by reducing energy transfer between translational and internal modes.