Science.gov

Sample records for damping direct implicit

  1. Electromagnetic direct implicit PIC simulation

    SciTech Connect

    Langdon, A.B.

    1983-03-29

    Interesting modelling of intense electron flow has been done with implicit particle-in-cell simulation codes. In this report, the direct implicit PIC simulation approach is applied to simulations that include full electromagnetic fields. The resulting algorithm offers advantages relative to moment implicit electromagnetic algorithms and may help in our quest for robust and simpler implicit codes.

  2. Parallelizing alternating direction implicit solver on GPUs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We present a parallel Alternating Direction Implicit (ADI) solver on GPUs. Our implementation significantly improves existing implementations in two aspects. First, we address the scalability issue of existing Parallel Cyclic Reduction (PCR) implementations by eliminating their hardware resource con...

  3. Directed compact percolation near a damp wall with biased growth

    NASA Astrophysics Data System (ADS)

    Lonsdale, H.; Owczarek, A. L.

    2012-11-01

    The model of directed compact percolation near a damp wall is generalized to allow for a bias in the growth of a cluster, either towards or away from the wall. The percolation probability for clusters beginning with seed width m, any distance from the wall, is derived exactly by solving the associated recurrences. It is found that the general biased case near a damp wall leads to a critical exponent β = 1, in line with the dry biased case, which differs from the unbiased damp/dry exponent β = 2.

  4. Direct structural damping identification method using complex FRFs

    NASA Astrophysics Data System (ADS)

    Arora, Vikas

    2015-03-01

    Most of the identification methods are based only on the viscous damping model and uses modal data. In this paper, a new FRF-based direct structural damping identification method is proposed. The proposed method is a direct method and identifies structural damping matrix explicitly. As the new method is a FRF-based method, it overcomes the problem of closely spaced modes for damping identification. The accuracy of identified structural damping matrix depends upon the accuracy of finite element model. In this paper, FRF-based model updating method is used to obtain accurate mass and stiffness matrices. Thus, the procedure to obtain accurate structural damping matrix is a two-step procedure. In the first step, mass and stiffness matrices are updated and in the second step, structural damping matrix is identified using updated mass and stiffness matrices, which are obtained in the previous step. The effectiveness of the new method is demonstrated by three numerical examples and one experimental example. The numerical studies of lumped mass system, fixed-fixed beam and L-shaped frame structure are carried out. The effects of coordinate incompleteness, ill-conditioning and robustness of method under presence of noise are investigated. The proposed method is able to predict FRFs accurately for the frequency range covering the modes considered. However, beyond the considered modes, the predicted FRFs do not match the experimental FRFs. It is suggested in this work that ill-conditioning problem should be dealt by considering all the modes in the frequency range of interest. The performance of the proposed method is investigated for cases of light, medium and heavily damped structures. The numerical studies are followed by experimental case study of cantilever beam structure. The effectiveness of the proposed method is evaluated by comparing the predicted and the experimental FRFs. The results have shown that the proposed method is able to predict accurately the

  5. No direction home: Extinction is affected by implicit motion.

    PubMed

    Riddoch, M Jane; Bodley Scott, Sarah; Humphreys, Glyn W

    2010-05-01

    Following lesions to (usually) the right parietal lobe, patients may fail to report stimuli on their contralesional side if a stimulus is also presented ipsilesionally. The problem can be ameliorated if the stimuli form part of a common action (e.g., a bottle pouring into a glass), when the contralesional item may be brought to awareness. We examined whether this improved awareness depended on implied motion from one object to another. This was tested using pairs of stimuli in which one had implied motion towards or away from the other stimulus. The results showed that patients were more aware of the presence of two objects on trials when one object had implied motion towards the other, compared with when motion was directed away from the second object. This held when the implied motion was in the contralesional as well as when it was in the ipsilesional field. In a single case, this effect held even when the direction of motion could not be explicitly discriminated. The data suggest that motion was coded implicitly and that it helped to link objects together as a perceptual unit. Coding objects as a single perceptual unit reduces the spatial bias in selection that produces extinction. PMID:19664764

  6. Performance and optimization of direct implicit time integration schemes for use in electrostatic particle simulation codes

    SciTech Connect

    Procassini, R.J.; Birdsall, C.K.; Morse, E.C.; Cohen, B.I.

    1988-01-01

    Implicit time integration schemes allow for the use of larger time steps than conventional explicit methods, thereby extending the applicability of kinetic particle simulation methods. This paper will describe a study of the performance and optimization of two such direct implicit schemes, which are used to follow the trajectories of charged particles in an electrostatic, particle-in-cell plasma simulation code. The direct implicit method that was used for this study is an alternative to the moment-equation implicit method. 10 refs., 7 figs., 4 tabs.

  7. Analytical modeling of squeeze air film damping of biomimetic MEMS directional microphone

    NASA Astrophysics Data System (ADS)

    Ishfaque, Asif; Kim, Byungki

    2016-08-01

    Squeeze air film damping is introduced in microelectromechanical systems due to the motion of the fluid between two closely spaced oscillating micro-structures. The literature is abundant with different analytical models to address the squeeze air film damping effects, however, there is a lack of work in modeling the practical sensors like directional microphones. Here, we derive an analytical model of squeeze air film damping of first two fundamental vibration modes, namely, rocking and bending modes, of a directional microphone inspired from the fly Ormia ochracea's ear anatomy. A modified Reynolds equation that includes compressibility and rarefaction effects is used in the analysis. Pressure distribution under the vibrating diaphragm is derived by using Green's function. From mathematical modeling of the fly's inspired mechanical model, we infer that bringing the damping ratios of both modes in the critical damping range enhance the directional sensitivity cues. The microphone parameters are varied in derived damping formulas to bring the damping ratios in the vicinity of critical damping, and to show the usefulness of the analytical model in tuning the damping ratios of both modes. The accuracy of analytical damping results are also verified by finite element method (FEM) using ANSYS. The FEM results are in full compliance with the analytical results.

  8. Children Can Implicitly, but Not Voluntarily, Direct Attention in Time

    PubMed Central

    Johnson, Katherine A.; Burrowes, Emma; Coull, Jennifer T.

    2015-01-01

    Children are able to use spatial cues to orient their attention to discrete locations in space from around 4 years of age. In contrast, no research has yet investigated the ability of children to use informative cues to voluntarily predict when an event will occur in time. The spatial and temporal attention task was used to determine whether children were able to voluntarily orient their attention in time, as well as in space: symbolic spatial and temporal cues predicted where or when an imperative target would appear. Thirty typically developing children (average age 11 yrs) and 32 adults (average age 27 yrs) took part. Confirming previous findings, adults made use of both spatial and temporal cues to optimise behaviour, and were significantly slower to respond to invalidly cued targets in either space or time. Children were also significantly slowed by invalid spatial cues, demonstrating their use of spatial cues to guide expectations. In contrast, children’s responses were not slowed by invalid temporal cues, suggesting that they were not using the temporal cue to voluntarily orient attention through time. Children, as well as adults, did however demonstrate signs of more implicit forms of temporal expectation: RTs were faster for long versus short cue-target intervals (the variable foreperiod effect) and slower when the preceding trial’s cue-target interval was longer than that on the current trial (sequential effects). Overall, our results suggest that although children implicitly made use of the temporally predictive information carried by the length of the current and previous trial’s cue-target interval, they could not deliberately use symbolic temporal cues to speed responses. The developmental trajectory of the ability to voluntarily use symbolic temporal cues is therefore delayed, relative both to the use of symbolic (arrow) spatial cues, and to the use of implicit temporal information. PMID:25881188

  9. Damping effects of capacitive comb fingers on biomimetic MEMS directional microphone

    NASA Astrophysics Data System (ADS)

    Roth, John; Touse, Michael; Sinibaldi, Jose; Karunasiri, Gamani

    2011-03-01

    MEMS directional sound sensors that use two coupled wings moving in air are subjected to viscous damping. The amplitude of oscillation of the sensors is read out by measuring the capacitance of interdigitated comb fingers along the edges of the wings. In this presentation, effects of damping on MEMS sensors with and without comb fingers will be described. It was found that the sensors with comb fingers have a significantly larger damping indicating that the longer perimeter due to combs is responsible for the observed increase. However, the increase in damping reduces the quality factor which improves the response time of the device. This work is supported by NSF.

  10. Explicit Control of Implicit Responses: Simple Directives can alter IAT Performance.

    PubMed

    Wallaert, Matthew; Ward, Andrew; Mann, Traci

    2010-03-01

    Research has begun to reveal the malleability of implicit prejudice. One measure of this construct, the race Implicit Association Test (IAT), represents a widely-used tool to assess individuals' positive and negative associations with different racial groups. In two studies, we demonstrate the capacity of salient pressures to alter implicit racial responses. In Study 1, an enhancement of promoting pressures through an explicit instruction to stereotype was sufficient to increase pro-White bias on the IAT. In Study 2, an enhancement of inhibiting pressures through a simple instruction to avoid stereotyping was sufficient to reduce pro-White bias. Taken together, the studies suggest that implicit prejudice is amenable to voluntary control through the use of simple, direct means. PMID:21769299

  11. How Transcranial Direct Current Stimulation Can Modulate Implicit Motor Sequence Learning and Consolidation: A Brief Review.

    PubMed

    Savic, Branislav; Meier, Beat

    2016-01-01

    The purpose of this review is to investigate how transcranial direct current stimulation (tDCS) can modulate implicit motor sequence learning and consolidation. So far, most of the studies have focused on the modulating effect of tDCS for explicit motor learning. Here, we focus explicitly on implicit motor sequence learning and consolidation in order to improve our understanding about the potential of tDCS to affect this kind of unconscious learning. Specifically, we concentrate on studies with the serial reaction time task (SRTT), the classical paradigm for measuring implicit motor sequence learning. The influence of tDCS has been investigated for the primary motor cortex, the premotor cortex, the prefrontal cortex, and the cerebellum. The results indicate that tDCS above the primary motor cortex gives raise to the most consistent modulating effects for both implicit motor sequence learning and consolidation. PMID:26903837

  12. How Transcranial Direct Current Stimulation Can Modulate Implicit Motor Sequence Learning and Consolidation: A Brief Review

    PubMed Central

    Savic, Branislav; Meier, Beat

    2016-01-01

    The purpose of this review is to investigate how transcranial direct current stimulation (tDCS) can modulate implicit motor sequence learning and consolidation. So far, most of the studies have focused on the modulating effect of tDCS for explicit motor learning. Here, we focus explicitly on implicit motor sequence learning and consolidation in order to improve our understanding about the potential of tDCS to affect this kind of unconscious learning. Specifically, we concentrate on studies with the serial reaction time task (SRTT), the classical paradigm for measuring implicit motor sequence learning. The influence of tDCS has been investigated for the primary motor cortex, the premotor cortex, the prefrontal cortex, and the cerebellum. The results indicate that tDCS above the primary motor cortex gives raise to the most consistent modulating effects for both implicit motor sequence learning and consolidation. PMID:26903837

  13. Three-dimensional viscous-flow computations using a directionally hybrid implicit-explicit procedure

    NASA Astrophysics Data System (ADS)

    Rizk, Y. M.; Chaussee, D. S.

    A new, directionally dependent, hybrid numerical algorithm for solving the unsteady, three-dimensional Navier-Stokes equations has been developed and used to compute the viscous supersonic flow over complex configurations, which may generate local regions of embedded subsonic or streamwise separated flows or both. The new hybrid implicit-explicit algorithm is derived from the more general implicit Beam-Warming algorithm and is particularly suitable for viscous computations in which the grid spacing in the direction outward from the body is considerably smaller than the spacing in the other two directions. Numerical results obtained from both the hybrid and implicit schemes are presented and compared on the basis of numerical stability, convergence history, and computer and core memory requirements.

  14. The implicit "go": masked action cues directly mobilize mental effort.

    PubMed

    Gendolla, Guido H E; Silvestrini, Nicolas

    2010-10-01

    In this study, we examined the hypothesis that masked general action and inaction cues that are processed during a cognitive task directly mobilize effort exerted during the task. Participants were randomly assigned to an action-prime condition, an inaction-prime condition, or a control condition and performed a Sternberg short-term memory task. The intensity of effort the participants exerted during the task was estimated by measuring their heart responses (cardiac preejection period, PEP) during task performance. As expected, exposure to masked action cues resulted in stronger PEP reactivity than exposure to masked inaction cues. PEP reactivity in the control group fell in between reactivity when action cues were used and reactivity when inaction cues were used. Participants' task performance revealed a corresponding pattern: Reaction times were the shortest in the action-prime condition, increased in the control condition, and increased further in the inaction-prime condition. These results show that masked action cues and inaction cues directly influence the intensity of effort exerted in the performance of a task. PMID:20861511

  15. Quadratic Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Quadratic friction involves a discontinuous damping term in equations of motion in order that the frictional force always opposes the direction of the motion. Perhaps for this reason this topic is usually omitted from beginning texts in differential equations and physics. However, quadratic damping is more realistic than viscous damping in many…

  16. An extension of A-stability to alternating direction implicit methods

    NASA Technical Reports Server (NTRS)

    Warming, R. F.; Beam, R. M.

    1978-01-01

    An alternating direction implicit (ADI) scheme was constructed by the method of approximate factorization. An A-stable linear multistep method (LMM) was used to integrate a model two-dimensional hyperbolic-parabolic partial differential equation. Sufficient conditions for the A-stability of the LMM were determined by applying the theory of positive real functions to reduce the stability analysis of the partial differential equations to a simple algebraic test. A linear test equation for partial differential equations is defined and then used to analyze the stability of approximate factorization schemes. An ADI method for the three-dimensional heat equation is also presented.

  17. An alternating-direction-implicit algorithm for the unsteady potential equation in conservation form

    NASA Technical Reports Server (NTRS)

    Chipman, R. R.

    1980-01-01

    An implicit finite difference scheme for an efficient computation of unsteady potential flow about airfoils is presented. The formulation uses density and velocity potential as dependent variables, and is cast in conservation form to assure the theoretically correct determination of shockwave location and speed. To enable boundary conditions to be imposed directly on the airfoil surface, a time varying sheared rectilinear coordinate transformation is employed. Calculated time history solutions on a pulsating airfoil are compared with the results of another unsteady transonic code. It is concluded that the method has excellent numerical stability and gives accurate solutions with sharply resolved shocks.

  18. Perceived azimuth direction is exaggerated: Converging evidence from explicit and implicit measures

    PubMed Central

    Li, Zhi; Durgin, Frank H.

    2016-01-01

    Recent observations suggest that perceived visual direction in the sagittal plane (angular direction in elevation, both upward and downward from eye level) is exaggerated. Foley, Ribeiro-Filho, and Da Silva's (2004) study of perceived size of exocentric ground extent implies that perceived angular direction in azimuth may also be exaggerated. In the present study, we directly examined whether perceived azimuth direction is overestimated. In Experiment 1, numeric estimates of azimuth direction (−48° to 48° relative to straight ahead) were obtained. The results showed a linear exaggeration in perceived azimuth direction with a gain of about 1.26. In Experiment 2, a perceptual extent-matching task served as an implicit measure of perceived azimuth direction. Participants matched an egocentric distance in one direction to a frontal extent in nearly the opposite direction. The angular biases implied by the matching data well replicated Foley et al.'s finding and were also fairly consistent with the azimuth bias function found in Experiment 1, although a slight overall shift was observed between the results of the two experiments. Experiment 3, in which half the observers were tilted sideways while making frontal/depth extent comparisons, suggested that the discrepancy between the results of Experiment 1 and 2 can partially be explained by a retinal horizontal vertical illusion affecting distance estimation tasks. Overall the present study provides converging evidence to suggest that the perception of azimuth direction is overestimated. PMID:26756174

  19. A pre-conditioned implicit direct forcing based immersed boundary method for incompressible viscous flows

    NASA Astrophysics Data System (ADS)

    Park, Hyunwook; Pan, Xiaomin; Lee, Changhoon; Choi, Jung-Il

    2016-06-01

    A novel immersed boundary (IB) method based on an implicit direct forcing (IDF) scheme is developed for incompressible viscous flows. The key idea for the present IDF method is to use a block LU decomposition technique in momentum equations with Taylor series expansion to construct the implicit IB forcing in a recurrence form, which imposes more accurate no-slip boundary conditions on the IB surface. To accelerate the IB forcing convergence during the iterative procedure, a pre-conditioner matrix is introduced in the recurrence formulation of the IB forcing. A Jacobi-type parameter is determined in the pre-conditioner matrix by minimizing the Frobenius norm of the matrix function representing the difference between the IB forcing solution matrix and the pre-conditioner matrix. In addition, the pre-conditioning parameter is restricted due to the numerical stability in the recurrence formulation. Consequently, the present pre-conditioned IDF (PIDF) enables accurate calculation of the IB forcing within a few iterations. We perform numerical simulations of two-dimensional flows around a circular cylinder and three-dimensional flows around a sphere for low and moderate Reynolds numbers. The result shows that PIDF yields a better imposition of no-slip boundary conditions on the IB surfaces for low Reynolds number with a fairly larger time step than IB methods with different direct forcing schemes due to the implicit treatment of the diffusion term for determining the IB forcing. Finally, we demonstrate the robustness of the present PIDF scheme by numerical simulations of flow around a circular array of cylinders, flows around a falling sphere, and two sedimenting spheres in gravity.

  20. The DIPSI (Direct Implicit Plasma Surface Interactions) computer code user's manual

    SciTech Connect

    Procassini, R.J. . Dept. of Nuclear Engineering); Cohen, B.I. )

    1990-06-01

    DIPSI (Direct Implicit Plasma Surface Interactions) is a one-dimensional, bounded particle-in-cell (PIC) simulation code designed to investigate the interaction of plasma with a solid surface, such as a limiter or divertor plate in a tokamak fusion device. Plasma confinement and transport may be studied in a system which includes an applied magnetic field (oriented normal to the solid surface) and/or a self-consistent electrostatic potential. The PIC code DIPSI is an offshoot of the PIC code TESS (Tandem Experiment Simulation Studies) which was developed to study plasma confinement in mirror devices. The codes DIPSI and TESS are direct descendants of the PIC code ES1 that was created by A. B. Langdon. This document provides the user with a brief description of the methods used in the code and a tutorial on the use of the code. 11 refs., 2 tabs.

  1. Direct cortical mapping via solving partial differential equations on implicit surfaces.

    PubMed

    Shi, Yonggang; Thompson, Paul M; Dinov, Ivo; Osher, Stanley; Toga, Arthur W

    2007-06-01

    In this paper, we propose a novel approach for cortical mapping that computes a direct map between two cortical surfaces while satisfying constraints on sulcal landmark curves. By computing the map directly, we can avoid conventional intermediate parameterizations and help simplify the cortical mapping process. The direct map in our method is formulated as the minimizer of a flexible variational energy under landmark constraints. The energy can include both a harmonic term to ensure smoothness of the map and general data terms for the matching of geometric features. Starting from a properly designed initial map, we compute the map iteratively by solving a partial differential equation (PDE) defined on the source cortical surface. For numerical implementation, a set of adaptive numerical schemes are developed to extend the technique of solving PDEs on implicit surfaces such that landmark constraints are enforced. In our experiments, we show the flexibility of the direct mapping approach by computing smooth maps following landmark constraints from two different energies. We also quantitatively compare the metric preserving property of the direct mapping method with a parametric mapping method on a group of 30 subjects. Finally, we demonstrate the direct mapping method in the brain mapping applications of atlas construction and variability analysis. PMID:17379568

  2. Direct path from microscopic mechanics to Debye shielding, Landau damping and wave-particle interaction

    NASA Astrophysics Data System (ADS)

    Escande, D. F.; Elskens, Yves; Doveil, F.

    2015-02-01

    The derivation of Debye shielding and Landau damping from the N-body description of plasmas is performed directly by using Newton’s second law for the N-body system. This is done in a few steps with elementary calculations using standard tools of calculus and no probabilistic setting. Unexpectedly, Debye shielding is encountered together with Landau damping. This approach is shown to be justified in the one-dimensional case when the number of particles in a Debye sphere becomes large. The theory is extended to accommodate a correct description of trapping and chaos due to Langmuir waves. On top of their well-known production of collisional transport, the repulsive deflections of electrons are shown to produce shielding, in such a way that each particle is shielded by all other ones, while keeping in uninterrupted motion.

  3. Wide-angle full-vector beam propagation method based on an alternating direction implicit preconditioner.

    PubMed

    Chui, Siu Lit; Lu, Ya Yan

    2004-03-01

    Wide-angle full-vector beam propagation methods (BPMs) for three-dimensional wave-guiding structures can be derived on the basis of rational approximants of a square root operator or its exponential (i.e., the one-way propagator). While the less accurate BPM based on the slowly varying envelope approximation can be efficiently solved by the alternating direction implicit (ADI) method, the wide-angle variants involve linear systems that are more difficult to handle. We present an efficient solver for these linear systems that is based on a Krylov subspace method with an ADI preconditioner. The resulting wide-angle full-vector BPM is used to simulate the propagation of wave fields in a Y branch and a taper. PMID:15005407

  4. Three-Dimensional Viscous Alternating Direction Implicit Algorithm and Strategies for Shape Optimization

    NASA Technical Reports Server (NTRS)

    Pandya, Mohagna J.; Baysal, Oktay

    1997-01-01

    A gradient-based shape optimization based on quasi-analytical sensitivities has been extended for practical three-dimensional aerodynamic applications. The flow analysis has been rendered by a fully implicit, finite-volume formulation of the Euler and Thin-Layer Navier-Stokes (TLNS) equations. Initially, the viscous laminar flow analysis for a wing has been compared with an independent computational fluid dynamics (CFD) code which has been extensively validated. The new procedure has been demonstrated in the design of a cranked arrow wing at Mach 2.4 with coarse- and fine-grid based computations performed with Euler and TLNS equations. The influence of the initial constraints on the geometry and aerodynamics of the optimized shape has been explored. Various final shapes generated for an identical initial problem formulation but with different optimization path options (coarse or fine grid, Euler or TLNS), have been aerodynamically evaluated via a common fine-grid TLNS-based analysis. The initial constraint conditions show significant bearing on the optimization results. Also, the results demonstrate that to produce an aerodynamically efficient design, it is imperative to include the viscous physics in the optimization procedure with the proper resolution. Based upon the present results, to better utilize the scarce computational resources, it is recommended that, a number of viscous coarse grid cases using either a preconditioned bi-conjugate gradient (PbCG) or an alternating-direction-implicit (ADI) method, should initially be employed to improve the optimization problem definition, the design space and initial shape. Optimized shapes should subsequently be analyzed using a high fidelity (viscous with fine-grid resolution) flow analysis to evaluate their true performance potential. Finally, a viscous fine-grid-based shape optimization should be conducted, using an ADI method, to accurately obtain the final optimized shape.

  5. Implicit Statistical Learning Is Directly Associated with the Acquisition of Syntax

    ERIC Educational Resources Information Center

    Kidd, Evan

    2012-01-01

    This article reports on an individual differences study that investigated the role of implicit statistical learning in the acquisition of syntax in children. One hundred children ages 4 years 5 months through 6 years 11 months completed a test of implicit statistical learning, a test of explicit declarative learning, and standardized tests of…

  6. End-point impedance measurements across dominant and nondominant hands and robotic assistance with directional damping.

    PubMed

    Erden, Mustafa Suphi; Billard, Aude

    2015-06-01

    The goal of this paper is to perform end-point impedance measurements across dominant and nondominant hands while doing airbrush painting and to use the results for developing a robotic assistance scheme. We study airbrush painting because it resembles in many ways manual welding, a standard industrial task. The experiments are performed with the 7 degrees of freedom KUKA lightweight robot arm. The robot is controlled in admittance using a force sensor attached at the end-point, so as to act as a free-mass and be passively guided by the human. For impedance measurements, a set of nine subjects perform 12 repetitions of airbrush painting, drawing a straight-line on a cartoon horizontally placed on a table, while passively moving the airbrush mounted on the robot's end-point. We measure hand impedance during the painting task by generating sudden and brief external forces with the robot. The results show that on average the dominant hand displays larger impedance than the nondominant in the directions perpendicular to the painting line. We find the most significant difference in the damping values in these directions. Based on this observation, we develop a "directional damping" scheme for robotic assistance and conduct a pilot study with 12 subjects to contrast airbrush painting with and without robotic assistance. Results show significant improvement in precision with both dominant and nondominant hands when using robotic assistance. PMID:25148680

  7. Alternating-direction implicit numerical solution of the time-dependent, three-dimensional, single fluid, resistive magnetohydrodynamic equations

    SciTech Connect

    Finan, C.H. III

    1980-12-01

    Resistive magnetohydrodynamics (MHD) is described by a set of eight coupled, nonlinear, three-dimensional, time-dependent, partial differential equations. A computer code, IMP (Implicit MHD Program), has been developed to solve these equations numerically by the method of finite differences on an Eulerian mesh. In this model, the equations are expressed in orthogonal curvilinear coordinates, making the code applicable to a variety of coordinate systems. The Douglas-Gunn algorithm for Alternating-Direction Implicit (ADI) temporal advancement is used to avoid the limitations in timestep size imposed by explicit methods. The equations are solved simultaneously to avoid syncronization errors.

  8. Fast wave-front reconstruction by solving the Sylvester equation with the alternating direction implicit method

    NASA Astrophysics Data System (ADS)

    Ren, Hongwu; Dekany, Richard

    2004-07-01

    Large degree-of-freedom real-time adaptive optics (AO) control requires reconstruction algorithms that are computationally efficient and readily parallelized for hardware implementation. In particular, we find the wave-front reconstruction for the Hudgin and Fried geometry can be cast into a form of the well-known Sylvester equation using the Kronecker product properties of matrices. We derive the filters and inverse filtering formulas for wave-front reconstruction in two-dimensional (2-D) Discrete Cosine Transform (DCT) domain for these two geometries using the Hadamard product concept of matrices and the principle of separable variables. We introduce a recursive filtering (RF) method for the wave-front reconstruction on an annular aperture, in which, an imbedding step is used to convert an annular-aperture wave-front reconstruction into a squareaperture wave-front reconstruction, and then solving the Hudgin geometry problem on the square aperture. We apply the Alternating Direction Implicit (ADI) method to this imbedding step of the RF algorithm, to efficiently solve the annular-aperture wave-front reconstruction problem at cost of order of the number of degrees of freedom, O(n). Moreover, the ADI method is better suited for parallel implementation and we describe a practical real-time implementation for AO systems of order 3,000 actuators.

  9. Field simulation of axisymmetric plasma screw pinches by alternating-direction-implicit methods

    SciTech Connect

    Lambert, M.A.

    1996-06-01

    An axisymmetric plasma screw pinch is an axisymmetric column of ionized gaseous plasma radially confined by forces from axial and azimuthal currents driven in the plasma and its surroundings. This dissertation is a contribution to detailed, high resolution computer simulation of dynamic plasma screw pinches in 2-d {ital rz}-coordinates. The simulation algorithm combines electron fluid and particle-in-cell (PIC) ion models to represent the plasma in a hybrid fashion. The plasma is assumed to be quasineutral; along with the Darwin approximation to the Maxwell equations, this implies application of Ampere`s law without displacement current. Electron inertia is assumed negligible so that advective terms in the electron momentum equation are ignored. Electrons and ions have separate scalar temperatures, and a scalar plasma electrical resistivity is assumed. Altemating-direction-implicit (ADI) methods are used to advance the electron fluid drift velocity and the magnetic fields in the simulation. The ADI methods allow time steps larger than allowed by explicit methods. Spatial regions where vacuum field equations have validity are determined by a cutoff density that invokes the quasineutral vacuum Maxwell equations (Darwin approximation). In this dissertation, the algorithm was first checked against ideal MM stability theory, and agreement was nicely demonstrated. However, such agreement is not a new contribution to the research field. Contributions to the research field include new treatments of the fields in vacuum regions of the pinch simulation. The new treatments predict a level of magnetohydrodynamic turbulence near the bulk plasma surface that is higher than predicted by other methods.

  10. Low frequency, electrodynamic simulation of kinetic plasmas with the DArwin Direct Implicit Particle-In-Cell (DADIPIC) method

    SciTech Connect

    Gibbons, M.R.

    1995-06-01

    This dissertation describes a new algorithm for simulating low frequency, kinetic phenomena in plasmas. DArwin Direct Implicit Particle-in-Cell (DADIPIC), as its name implies, is a combination of the Darwin and direct implicit methods. One of the difficulties in simulating plasmas lies in the enormous disparity between the fundamental scale lengths of a plasma and the scale lengths of the phenomena of interest. The objective is to create models which can ignore the fundamental constraints without eliminating relevant plasma properties. Over the past twenty years several PIC methods have been investigated for overcoming the constraints on explicit electrodynamic PIC. These models eliminate selected high frequency plasma phenomena while retaining kinetic phenomena at low frequency. This dissertation shows that the combination of Darwin and Direct Implicit allows them to operate better than they have been shown to operate in the past. Through the Darwin method the hyperbolic Maxwell`s equations are reformulated into a set of elliptic equations. Propagating light waves do not exist in the formulation so the Courant constraint on the time step is eliminated. The Direct Implicit method is applied only to the electrostatic field with the result that electrostatic plasma oscillations do not have to be resolved for stability. With the elimination of these constraints spatial and temporal discretization can be much larger than that possible with explicit, electrodynamic PIC. The code functions in a two dimensional Cartesian region and has been implemented with all components of the particle velocities, the E-field, and the B-field. Internal structures, conductors or dielectrics, may be placed in the simulation region, can be set at desired potentials, and driven with specified currents.

  11. Magnetic Damping For Maglev

    DOE PAGESBeta

    Zhu, S.; Cai, Y.; Rote, D. M.; Chen, S. S.

    1998-01-01

    Magnetic damping is one of the important parameters that control the response and stability of maglev systems. An experimental study to measure magnetic damping directly is presented. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters, such as conductivity, gap, excitation frequency, and oscillation amplitude, on magnetic damping. The experimental technique is capable of measuring all of the magnetic damping coefficients, some of which cannot be measured indirectly.

  12. A high-damping magnetorheological elastomer with bi-directional magnetic-control modulus for potential application in seismology

    NASA Astrophysics Data System (ADS)

    Yu, Miao; Qi, Song; Fu, Jie; Zhu, Mi

    2015-09-01

    A high-damping magnetorheological elastomer (MRE) with bi-directional magnetic-control modulus is developed. This MRE was synthesized by filling NdFeB particles into polyurethane (PU)/ epoxy (EP) interpenetrating network (IPN) structure. The anisotropic samples were prepared in a permanent magnetic field and magnetized in an electromagnetic field of 1 T. Dynamic mechanical responses of the MRE to applied magnetic fields are investigated through magneto-rheometer, and morphology of MREs is observed via scanning electron microscope (SEM). Test result indicates that when the test field orientation is parallel to that of the sample's magnetization, the shear modulus of sample increases. On the other hand, when the orientation is opposite to that of the sample's magnetization, shear modulus decreases. In addition, this PU/EP IPN matrix based MRE has a high-damping property, with high loss factor and can be controlled by applying magnetic field. It is expected that the high damping property and the ability of bi-directional magnetic-control modulus of this MRE offer promising advantages in seismologic application.

  13. A high-damping magnetorheological elastomer with bi-directional magnetic-control modulus for potential application in seismology

    SciTech Connect

    Yu, Miao Qi, Song; Fu, Jie; Zhu, Mi

    2015-09-14

    A high-damping magnetorheological elastomer (MRE) with bi-directional magnetic-control modulus is developed. This MRE was synthesized by filling NdFeB particles into polyurethane (PU)/ epoxy (EP) interpenetrating network (IPN) structure. The anisotropic samples were prepared in a permanent magnetic field and magnetized in an electromagnetic field of 1 T. Dynamic mechanical responses of the MRE to applied magnetic fields are investigated through magneto-rheometer, and morphology of MREs is observed via scanning electron microscope (SEM). Test result indicates that when the test field orientation is parallel to that of the sample's magnetization, the shear modulus of sample increases. On the other hand, when the orientation is opposite to that of the sample's magnetization, shear modulus decreases. In addition, this PU/EP IPN matrix based MRE has a high-damping property, with high loss factor and can be controlled by applying magnetic field. It is expected that the high damping property and the ability of bi-directional magnetic-control modulus of this MRE offer promising advantages in seismologic application.

  14. Effects of counterion valency on the damping of phonons propagating along the axial direction of liquid-crystalline DNA

    NASA Astrophysics Data System (ADS)

    Liu, Yun; Chen, Sow-Hsin; Berti, Debora; Baglioni, Piero; Alatas, Ahmet; Sinn, Harald; Alp, Ercan; Said, Ayman

    2005-12-01

    The phonon propagation and damping along the axial direction of films of aligned 40wt% calf-thymus DNA rods are studied by inelastic x-ray scattering (IXS). The IXS spectra are analyzed with the generalized three effective eigenmode theory, from which we extract the dynamic structure factor S (Q,E) as a function of transferred energy E =ℏω, and the magnitude of the transferred wave vector Q. S (Q,E) of a DNA sample typically consists of three peaks, one central Rayleigh scattering peak, and two symmetric Stokes and anti-Stokes Brillouin side peaks. By analyzing the Brillouin peaks, the phonon excitation energy and damping can be extracted at different Q values from about 4 to 30nm-1. A high-frequency sound speed is obtained from the initial slope of the linear portion of the dispersion relation below Q =4nm-1. The high-frequency sound speed obtained in this Q range is 3100m /s, which is about twice faster than the ultrasound speed of 1800m/s, measured by Brillouin light scattering at Q ˜0.01nm-1 at the similar hydration level. Our observations provide further evidence of the strong coupling between the internal dynamics of a DNA molecule and the dynamics of the solvent. The effect on damping and propagation of phonons along the axial direction of DNA rods due to divalent and trivalent counterions has been studied. It is found that the added multivalent counterions introduce stronger phonon damping. The phonons at the range between ˜12.5 and ˜22.5nm-1 are overdamped by the added counterions according to our model analyses. The intermediate scattering function is extracted and it shows a clear two-step relaxation with the fast relaxation time ranging from 0.1 to 4ps.

  15. Direct Numerical Simulation of Interfacial Flows: Implicit Sharp-Interface Method (I-SIM)

    SciTech Connect

    Robert Nourgaliev; Theo Theofanous; HyeongKae Park; Vincent Mousseau; Dana Knoll

    2008-01-01

    In recent work (Nourgaliev, Liou, Theofanous, JCP in press) we demonstrated that numerical simulations of interfacial flows in the presence of strong shear must be cast in dynamically sharp terms (sharp interface treatment or SIM), and that moreover they must meet stringent resolution requirements (i.e., resolving the critical layer). The present work is an outgrowth of that work aiming to overcome consequent limitations on the temporal treatment, which become still more severe in the presence of phase change. The key is to avoid operator splitting between interface motion, fluid convection, viscous/heat diffusion and reactions; instead treating all these non-linear operators fully-coupled within a Newton iteration scheme. To this end, the SIM’s cut-cell meshing is combined with the high-orderaccurate implicit Runge-Kutta and the “recovery” Discontinuous Galerkin methods along with a Jacobian-free, Krylov subspace iteration algorithm and its physics-based preconditioning. In particular, the interfacial geometry (i.e., marker’s positions and volumes of cut cells) is a part of the Newton-Krylov solution vector, so that the interface dynamics and fluid motions are fully-(non-linearly)-coupled. We show that our method is: (a) robust (L-stable) and efficient, allowing to step over stability time steps at will while maintaining high-(up to the 5th)-order temporal accuracy; (b) fully conservative, even near multimaterial contacts, without any adverse consequences (pressure/velocity oscillations); and (c) highorder-accurate in spatial discretization (demonstrated here up to the 12th-order for smoothin-the-bulk-fluid flows), capturing interfacial jumps sharply, within one cell. Performance is illustrated with a variety of test problems, including low-Mach-number “manufactured” solutions, shock dynamics/tracking with slow dynamic time scales, and multi-fluid, highspeed shock-tube problems. We briefly discuss preconditioning, and we introduce two physics

  16. Utilising HVDC to damp power oscillations

    SciTech Connect

    Smed, T.; Andersson, G. . Dept. of Electric Power Systems)

    1993-04-01

    In this paper, damping of slow oscillations with active and reactive power modulation of HVDC-links is analyzed with the aim of gaining a physical insight into the problem. The analysis shows that active power modulation is efficient when applied to a short mass-scaled electrical distance from one of the swinging machines, and reactive power modulation is most efficient when there exists a well-defined power flow direction and the modulation is made at a point close to the electrical midpoint between the swinging machines. It is shown that the intuitively appealing feedback signals frequency and derivative of the voltage are appropriate for active and reactive power modulation, respectively. The impact of the constraints imposed by the HVDC equations are analyzed, and it is determined when the implicit reactive power modulation resulting from constant [gamma] control may be detrimental for the damping.

  17. Matching is not Naming: A direct comparison of lexical manipulations in explicit and implicit reading tasks

    PubMed Central

    Vogel, Alecia C.; Petersen, Steven E.; Schlaggar, Bradley L.

    2014-01-01

    The neurobiological basis of reading is of considerable interest, yet analyzing data from subjects reading words aloud during functional MRI data collection can be difficult. Therefore, many investigators use surrogate tasks such as visual matching or rhyme matching to eliminate the need for spoken output. Use of these tasks has been justified by the presumption of “automatic activation” of reading-related neural processing when a word is viewed. We have tested the efficacy of using a non-reading task for studying “reading effects” by directly comparing BOLD activity in subjects performing a visual matching task and an item naming task on words, pseudowords (meaningless but legal letter combinations), and nonwords (meaningless and illegal letter combinations). When compared directly, there is significantly more activity during the naming task in “reading-related” regions such as the inferior frontal gyrus (IFG) and supramarginal gyrus. More importantly, there are differing effects of lexicality in the tasks. A whole-brain task (matching vs naming) by string type (word vs pseudoword vs nonword) by BOLD timecourse analysis identifies regions showing this three-way interaction, including the left IFG and left angular gyrus (AG). In the majority of the identified regions (including the left IFG and left AG), there is a string type by timecourse interaction in the naming but not the matching task. These results argue that the processing performed in specific regions is contingent on task, even in reading-related regions, and is thus non-automatic. Such differences should be taken into consideration when designing studies intended to investigate reading. PMID:22711620

  18. New observations directly measuring the full continuous sizes of high redshift damped Lya systems

    NASA Astrophysics Data System (ADS)

    Cooke, Jeff; O'Meara, John

    2016-01-01

    The formation and evolution of galaxies requires large reservoirs of cold, neutral gas. The damped Lyman-α systems (DLAs), seen in absorption towards distant quasars and gamma ray bursts, are predicted to be the dominant reservoirs for this gas. Detailed properties of DLAs have been studied extensively for decades with great success. However, their size, fundamental in understanding their nature, has remained elusive, as quasar and gamma ray burst sightlines only probe comparatively tiny areas of the foreground DLAs. Here, we introduce a new approach to measure the full extent of DLAs in the sightlines to extended background sources. We present the discovery of z ~ 2 DLAs with column densities as high as log N(HI) = 21.1 ±0.4 cm-2 covering 90-100% of the luminous extent of background galaxies. Estimates of the sizes of the background galaxies range from a minimum of a few kpc2, to ˜100 kpc2, and demonstrate that high-column density neutral gas can span continuous areas 108-1010 times larger than previously explored in quasar or gamma ray burst sightlines. The DLAs are from our pilot survey that searches Lyman break and Lyman continuum galaxies at high redshift. The low luminosities, large sizes, and mass contents (~106-109 M⊙) implied by the early data suggest that DLAs contain the necessary fuel for galaxies, with many systems consistent with relatively massive, low-luminosity primeval galaxies.

  19. Implicit and semi-implicit schemes: Algorithms

    NASA Astrophysics Data System (ADS)

    Keppens, R.; Tóth, G.; Botchev, M. A.; van der Ploeg, A.

    1999-06-01

    This study formulates general guidelines to extend an explicit code with a great variety of implicit and semi-implicit time integration schemes. The discussion is based on their specific implementation in the Versatile Advection Code, which is a general purpose software package for solving systems of non-linear hyperbolic (and/or parabolic) partial differential equations, using standard high resolution shock capturing schemes. For all combinations of explicit high resolution schemes with implicit and semi-implicit treatments, it is shown how second-order spatial and temporal accuracy for the smooth part of the solutions can be maintained. Strategies to obtain steady state and time accurate solutions implicitly are discussed. The implicit and semi-implicit schemes require the solution of large linear systems containing the Jacobian matrix. The Jacobian matrix itself is calculated numerically to ensure the generality of this implementation. Three options are discussed in terms of applicability, storage requirements and computational efficiency. One option is the easily implemented matrix-free approach, but the Jacobian matrix can also be calculated by using a general grid masking algorithm, or by an efficient implementation for a specific Lax-Friedrich-type total variation diminishing (TVD) spatial discretization. The choice of the linear solver depends on the dimensionality of the problem. In one dimension, a direct block tridiagonal solver can be applied, while in more than one spatial dimension, a conjugate gradient (CG)-type iterative solver is used. For advection-dominated problems, preconditioning is needed to accelerate the convergence of the iterative schemes. The modified block incomplete LU-preconditioner is implemented, which performs very well. Examples from two-dimensional hydrodynamic and magnetohydrodynamic computations are given. They model transonic stellar outflow and recover the complex magnetohydrodynamic bow shock flow in the switch-on regime

  20. Awareness of Implicit Attitudes

    PubMed Central

    Hahn, Adam; Judd, Charles M.; Hirsh, Holen K.; Blair, Irene V.

    2013-01-01

    Research on implicit attitudes has raised questions about how well people know their own attitudes. Most research on this question has focused on the correspondence between measures of implicit attitudes and measures of explicit attitudes, with low correspondence interpreted as showing that people have little awareness of their implicit attitudes. We took a different approach and directly asked participants to predict their results on upcoming IAT measures of implicit attitudes toward five different social groups. We found that participants were surprisingly accurate in their predictions. Across four studies, predictions were accurate regardless of whether implicit attitudes were described as true attitudes or culturally learned associations (Studies 1 and 2), regardless of whether predictions were made as specific response patterns (Study 1) or as conceptual responses (Studies 2–4), and regardless of how much experience or explanation participants received before making their predictions (Study 4). Study 3 further suggested that participants’ predictions reflected unique insight into their own implicit responses, beyond intuitions about how people in general might respond. Prediction accuracy occurred despite generally low correspondence between implicit and explicit measures of attitudes, as found in prior research. All together, the research findings cast doubt on the belief that attitudes or evaluations measured by the IAT necessarily reflect unconscious attitudes. PMID:24294868

  1. Examining implicit bias of physicians who care for individuals with spinal cord injury: A pilot study and future directions

    PubMed Central

    Hausmann, Leslie R. M.; Myaskovsky, Larissa; Niyonkuru, Christian; Oyster, Michelle L.; Switzer, Galen E.; Burkitt, Kelly H.; Fine, Michael J.; Gao, Shasha; Boninger, Michael L.

    2015-01-01

    Context Despite evidence that healthcare providers have implicit biases that can impact clinical interactions and decisions, implicit bias among physicians caring for individuals with spinal cord injury (SCI) has not been examined. Objective Conduct a pilot study to examine implicit racial bias of SCI physicians and its association with functioning and wellbeing for individuals with SCI. Design Combined data from cross-sectional surveys of individuals with SCI and their SCI physicians. Setting Four national SCI Model Systems sites. Participants Individuals with SCI (N = 162) and their SCI physicians (N = 14). Outcome measures SCI physicians completed online surveys measuring implicit racial (pro-white/anti-black) bias. Individuals with SCI completed questionnaires assessing mobility, physical independence, occupational functioning, social integration, self-reported health, depression, and life satisfaction. We used multilevel regression analyses to examine the associations of physician bias and outcomes of individuals with SCI. Results Physicians had a mean bias score of 0.62 (SD = 0.35), indicating a strong pro-white/anti-black bias. Greater physician bias was associated with disability among individuals with SCI in the domain of social integration (odds ratio = 4.80, 95% confidence interval (CI) = 1.44, 16.04), as well as higher depression (B = 3.24, 95% CI = 1.06, 5.41) and lower life satisfaction (B = −4.54, 95% CI= −8.79, −0.28). Conclusion This pilot study indicates that SCI providers are susceptible to implicit racial bias and provides preliminary evidence that greater implicit racial bias of physicians is associated with poorer psychosocial health outcomes for individuals with SCI. It demonstrates the feasibility of studying implicit bias among SCI providers and provides guidance for future research on physician bias and patient outcomes. PMID:24621034

  2. Magnetic damping for maglev

    SciTech Connect

    Chen, S.S.; Zhu, S.; Cai, Y.; Rote, D.M.

    1994-12-31

    Magnetic damping is one of the important parameters to control the response and stability of maglev systems. An experimental study is presented to measure the magnetic damping using a direct method. A plate attached to a permanent magnet levitated on a rotating drum was tested to investigate the effect of various parameters on magnetic damping such as conductivity, gap, excitation frequency, and oscillation amplitude. The experimental technique is capable of measuring all magnetic damping coefficients, some of which can not be measured by an indirect method.

  3. Some effects of nonlinear variation in the directional-stability and damping-in-yawing derivatives on the lateral stability of an airplane

    NASA Technical Reports Server (NTRS)

    Sternfield, Leonard

    1951-01-01

    A theoretical investigation has been made to determine the effect of nonlinear stability derivatives on the lateral stability of an airplane. Motions were calculated on the assumption that the directional-stability and the damping-in-yawing derivatives are functions of the angle of sideslip. The application of the Laplace transform to the calculation of an airplane motion when certain types of nonlinear derivatives are present is described in detail. The types of nonlinearities assumed correspond to the condition in which the values of the directional-stability and damping-in-yawing derivatives are zero for small angle of sideslip.

  4. Implicit CAPTCHAs

    NASA Astrophysics Data System (ADS)

    Baird, Henry S.; Bentley, Jon L.

    2004-12-01

    We propose a design methodology for "implicit" CAPTCHAs to relieve drawbacks of present technology. CAPTCHAs are tests administered automatically over networks that can distinguish between people and machines and thus protect web services from abuse by programs masquerading as human users. All existing CAPTCHAs' challenges require a significant conscious effort by the person answering them -- e.g. reading and typing a nonsense word -- whereas implicit CAPTCHAs may require as little as a single click. Many CAPTCHAs distract and interrupt users, since the challenge is perceived as an irrelevant intrusion; implicit CAPTCHAs can be woven into the expected sequence of browsing using cues tailored to the site. Most existing CAPTCHAs are vulnerable to "farming-out" attacks in which challenges are passed to a networked community of human readers; by contrast, implicit CAPTCHAs are not "fungible" (in the sense of easily answerable in isolation) since they are meaningful only in the specific context of the website that is protected. Many existing CAPTCHAs irritate or threaten users since they are obviously tests of skill: implicit CAPTCHAs appear to be elementary and inevitable acts of browsing. It can often be difficult to detect when CAPTCHAs are under attack: implicit CAPTCHAs can be designed so that certain failure modes are correlated with failed bot attacks. We illustrate these design principles with examples.

  5. Implicit CAPTCHAs

    NASA Astrophysics Data System (ADS)

    Baird, Henry S.; Bentley, Jon L.

    2005-01-01

    We propose a design methodology for "implicit" CAPTCHAs to relieve drawbacks of present technology. CAPTCHAs are tests administered automatically over networks that can distinguish between people and machines and thus protect web services from abuse by programs masquerading as human users. All existing CAPTCHAs' challenges require a significant conscious effort by the person answering them -- e.g. reading and typing a nonsense word -- whereas implicit CAPTCHAs may require as little as a single click. Many CAPTCHAs distract and interrupt users, since the challenge is perceived as an irrelevant intrusion; implicit CAPTCHAs can be woven into the expected sequence of browsing using cues tailored to the site. Most existing CAPTCHAs are vulnerable to "farming-out" attacks in which challenges are passed to a networked community of human readers; by contrast, implicit CAPTCHAs are not "fungible" (in the sense of easily answerable in isolation) since they are meaningful only in the specific context of the website that is protected. Many existing CAPTCHAs irritate or threaten users since they are obviously tests of skill: implicit CAPTCHAs appear to be elementary and inevitable acts of browsing. It can often be difficult to detect when CAPTCHAs are under attack: implicit CAPTCHAs can be designed so that certain failure modes are correlated with failed bot attacks. We illustrate these design principles with examples.

  6. Implicit and Multigrid Method for Ideal Multigrid Convergence: Direct Numerical Simulation of Separated Flow Around NACA 0012 Airfoil

    NASA Technical Reports Server (NTRS)

    Liu, Chao-Qun; Shan, H.; Jiang, L.

    1999-01-01

    Numerical investigation of flow separation over a NACA 0012 airfoil at large angles of attack has been carried out. The numerical calculation is performed by solving the full Navier-Stokes equations in generalized curvilinear coordinates. The second-order LU-SGS implicit scheme is applied for time integration. This scheme requires no tridiagonal inversion and is capable of being completely vectorized, provided the corresponding Jacobian matrices are properly selected. A fourth-order centered compact scheme is used for spatial derivatives. In order to reduce numerical oscillation, a sixth-order implicit filter is employed. Non-reflecting boundary conditions are imposed at the far-field and outlet boundaries to avoid possible non-physical wave reflection. Complex flow separation and vortex shedding phenomenon have been observed and discussed.

  7. Landau damping

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-10-01

    Section 2.5.8 of the Handbook of Accelerator Physics and Engineering on Landau damping is rewritten. An solvable example is first given to demonstrate the interplay between Landau damping and decoherence. This example is an actual one when the beam oscillatory motion is driven by a wake force. The dispersion relation is derived and its implication on Landau damping is illustrated. The rest of the article touches on the Landau damping of transverse and longitudinal beam oscillations. The stability criteria are given for a bunched beam and the changes of the criteria when the beam is lengthened and becomes unbunched.

  8. Coulomb Damping

    ERIC Educational Resources Information Center

    Fay, Temple H.

    2012-01-01

    Viscous damping is commonly discussed in beginning differential equations and physics texts but dry friction or Coulomb friction is not despite dry friction being encountered in many physical applications. One reason for avoiding this topic is that the equations involve a jump discontinuity in the damping term. In this article, we adopt an energy…

  9. Time-asymptotic solutions of the Navier-Stokes equation for free shear flows using an alternating-direction implicit method

    NASA Technical Reports Server (NTRS)

    Rudy, D. H.; Morris, D. J.

    1976-01-01

    An uncoupled time asymptotic alternating direction implicit method for solving the Navier-Stokes equations was tested on two laminar parallel mixing flows. A constant total temperature was assumed in order to eliminate the need to solve the full energy equation; consequently, static temperature was evaluated by using algebraic relationship. For the mixing of two supersonic streams at a Reynolds number of 1,000, convergent solutions were obtained for a time step 5 times the maximum allowable size for an explicit method. The solution diverged for a time step 10 times the explicit limit. Improved convergence was obtained when upwind differencing was used for convective terms. Larger time steps were not possible with either upwind differencing or the diagonally dominant scheme. Artificial viscosity was added to the continuity equation in order to eliminate divergence for the mixing of a subsonic stream with a supersonic stream at a Reynolds number of 1,000.

  10. Evidence for Implicit Learning in Syntactic Comprehension

    ERIC Educational Resources Information Center

    Fine, Alex B.; Jaeger, T. Florian

    2013-01-01

    This study provides evidence for implicit learning in syntactic comprehension. By reanalyzing data from a syntactic priming experiment (Thothathiri & Snedeker, 2008), we find that the error signal associated with a syntactic prime influences comprehenders' subsequent syntactic expectations. This follows directly from error-based implicit learning…

  11. An Implicit LU/AF FDTD Method

    NASA Technical Reports Server (NTRS)

    Beggs, John H.; Briley, W. Roger

    2001-01-01

    There has been some recent work to develop two and three-dimensional alternating direction implicit (ADI) FDTD schemes. These ADI schemes are based upon the original ADI concept developed by Peaceman and Rachford and Douglas and Gunn, which is a popular solution method in Computational Fluid Dynamics (CFD). These ADI schemes work well and they require solution of a tridiagonal system of equations. A new approach proposed in this paper applies a LU/AF approximate factorization technique from CFD to Maxwell s equations in flux conservative form for one space dimension. The result is a scheme that will retain its unconditional stability in three space dimensions, but does not require the solution of tridiagonal systems. The theory for this new algorithm is outlined in a one-dimensional context for clarity. An extension to two and threedimensional cases is discussed. Results of Fourier analysis are discussed for both stability and dispersion/damping properties of the algorithm. Results are presented for a one-dimensional model problem, and the explicit FDTD algorithm is chosen as a convenient reference for comparison.

  12. Vibration damping method and apparatus

    DOEpatents

    Redmond, James M.; Barney, Patrick S.; Parker, Gordon G.; Smith, David A.

    1999-01-01

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof.

  13. Vibration damping method and apparatus

    DOEpatents

    Redmond, J.M.; Barney, P.S.; Parker, G.G.; Smith, D.A.

    1999-06-22

    The present invention provides vibration damping method and apparatus that can damp vibration in more than one direction without requiring disassembly, that can accommodate varying tool dimensions without requiring re-tuning, and that does not interfere with tool tip operations and cooling. The present invention provides active dampening by generating bending moments internal to a structure such as a boring bar to dampen vibration thereof. 38 figs.

  14. CHEMICAL ENRICHMENT OF DAMPED Ly{alpha} SYSTEMS AS A DIRECT CONSTRAINT ON POPULATION III STAR FORMATION

    SciTech Connect

    Kulkarni, Girish; Hennawi, Joseph F.; Rollinde, Emmanuel; Vangioni, Elisabeth

    2013-08-01

    Observations of damped Ly{alpha} absorbers (DLAs) can be used to measure gas-phase metallicities at large cosmological look-back times with high precision. Furthermore, relative abundances can still be measured accurately deep into the reionization epoch (z > 6) using transitions redward of Ly{alpha}, even though Gunn-Peterson absorption precludes measurement of neutral hydrogen. In this paper, we study the chemical evolution of DLAs using a model for the coupled evolution of galaxies and the intergalactic medium (IGM), which is constrained by a variety of observations. Our goal is to explore the influence of Population III stars on the abundance patterns of DLAs to determine the degree to which abundance measurements can discriminate between different Population III stellar initial mass functions (IMFs). We include effects, such as inflows onto galaxies due to cosmological accretion and outflows from galaxies due to supernova feedback. A distinct feature of our model is that it self-consistently calculates the effect of Population III star formation on the reionization of an inhomogeneous IGM, thus allowing us to calculate the thermal evolution of the IGM and implement photoionization feedback on low-mass galaxy formation. We find that if the critical metallicity of Population III to II/I transition is {approx}< 10{sup -4} Z{sub Sun }, then the cosmic Population III star formation rate drops to zero for z < 8. Nevertheless, at high redshift (z {approx} 6), chemical signatures of Population III stars remain in low-mass galaxies (halo mass {approx}< 10{sup 9} M{sub Sun }). This is because photoionization feedback suppresses star formation in these galaxies until relatively low redshift (z {approx} 10), and the chemical record of their initial generation of Population III stars is retained. We model DLAs as these low-mass galaxies, and assign to them a mass-dependent H I absorption cross-section in order to predict the expected distribution of DLA abundance ratios

  15. On the Formation and Persistence of Implicit Attitudes: New Evidence from the Implicit Relational Assessment Procedure (IRAP)

    ERIC Educational Resources Information Center

    Hughes, Sean; Barnes-Holmes, Dermot

    2011-01-01

    Research increasingly supports the Implicit Relational Assessment Procedure (IRAP) as a measure capable of providing a sensitive index of preexisting implicit attitudes and cognitions. The current study constitutes the first attempt to determine if the IRAP is also sensitive to implicit attitudes engineered through either direct relational…

  16. Cognitive control: a role for implicit learning?

    PubMed

    Deroost, Natacha; Vandenbossche, Jochen; Zeischka, Peter; Coomans, Daphné; Soetens, Eric

    2012-09-01

    We investigated the influence of implicit learning on cognitive control. In a sequential Stroop task, participants implicitly learned a sequence placed on the color of the Stroop words. In Experiment 1, Stroop conflict was lower in sequenced than in random trials (learning-improved control). However, as these results were derived from an interaction between learning and conflict, they could also be explained by improved implicit learning (difference between random and sequenced trials), under incongruent compared with congruent trials (control-improved learning). Therefore, we further unraveled the direction of the interaction in 2 additional experiments. In Experiment 2, participants who learned the color sequence were no better at resolving conflict than participants who did not undergo sequence training. This shows that implicit knowledge does not directly reduce conflict (no learning-improved control). In Experiment 3, the amount of conflict did not directly improve learning either (no control-improved learning). However, conflict had a significant impact on the expression of implicit learning, as most knowledge was expressed under the highest amount of conflict. Thus, task-optimization was accomplished by an increased reliance on implicit sequence knowledge under high conflict. These findings demonstrate that implicit learning processes can be flexibly recruited to support cognitive control functions. PMID:22428719

  17. Haptics-based dynamic implicit solid modeling.

    PubMed

    Hua, Jing; Qin, Hong

    2004-01-01

    This paper systematically presents a novel, interactive solid modeling framework, Haptics-based Dynamic Implicit Solid Modeling, which is founded upon volumetric implicit functions and powerful physics-based modeling. In particular, we augment our modeling framework with a haptic mechanism in order to take advantage of additional realism associated with a 3D haptic interface. Our dynamic implicit solids are semi-algebraic sets of volumetric implicit functions and are governed by the principles of dynamics, hence responding to sculpting forces in a natural and predictable manner. In order to directly manipulate existing volumetric data sets as well as point clouds, we develop a hierarchical fitting algorithm to reconstruct and represent discrete data sets using our continuous implicit functions, which permit users to further design and edit those existing 3D models in real-time using a large variety of haptic and geometric toolkits, and visualize their interactive deformation at arbitrary resolution. The additional geometric and physical constraints afford more sophisticated control of the dynamic implicit solids. The versatility of our dynamic implicit modeling enables the user to easily modify both the geometry and the topology of modeled objects, while the inherent physical properties can offer an intuitive haptic interface for direct manipulation with force feedback. PMID:15794139

  18. Technical report series on global modeling and data assimilation. Volume 2: Direct solution of the implicit formulation of fourth order horizontal diffusion for gridpoint models on the sphere

    NASA Technical Reports Server (NTRS)

    Li, Yong; Moorthi, S.; Bates, J. Ray; Suarez, Max J.

    1994-01-01

    High order horizontal diffusion of the form K Delta(exp 2m) is widely used in spectral models as a means of preventing energy accumulation at the shortest resolved scales. In the spectral context, an implicit formation of such diffusion is trivial to implement. The present note describes an efficient method of implementing implicit high order diffusion in global finite difference models. The method expresses the high order diffusion equation as a sequence of equations involving Delta(exp 2). The solution is obtained by combining fast Fourier transforms in longitude with a finite difference solver for the second order ordinary differential equation in latitude. The implicit diffusion routine is suitable for use in any finite difference global model that uses a regular latitude/longitude grid. The absence of a restriction on the timestep makes it particularly suitable for use in semi-Lagrangian models. The scale selectivity of the high order diffusion gives it an advantage over the uncentering method that has been used to control computational noise in two-time-level semi-Lagrangian models.

  19. Directly Imaging Damped Ly-Alpha Galaxies at Redshifts Greater Than 2. III: The Star Formation Rates of Neutral Gas Reservoirs at Redshifts of Approximately 2.7

    NASA Technical Reports Server (NTRS)

    Fumagalli, Michele; OMeara, John M.; Prochaska, J. Xavier; Rafelski, Marc; Kanekar, Nissim

    2014-01-01

    We present results from a survey designed to probe the star formation properties of 32 damped Ly alpha systems (DLAs) at redshifts of approximately 2.7. By using the "double-DLA" technique that eliminates the glare of the bright background quasars, we directly measure the rest-frame FUV flux from DLAs and their neighbouring galaxies. At the position of the absorbing gas, we place stringent constraints on the unobscured star formation rates (SFRs) of DLAs to 2 sigma limits of psi less than 0.09-0.27 solar mass yr(exp -1), corresponding to SFR surface densities sigma(sub sfr) less than 10(exp -2.6)-10(exp -1.5) solar mass yr(exp -1) kpc(exp -2). The implications of these limits for the star formation law, metal enrichment, and cooling rates of DLAs are examined. By studying the distribution of impact parameters as a function of SFRs for all the galaxies detected around these DLAs, we place new direct constraints on the bright end of the UV luminosity function of DLA hosts. We find that less than or equal to 13% of the hosts have psi greater than or equal to 2 solar mass yr(exp -1) at impact parameters b(sub dla) less than or equal to (psi/solar mass yr(exp -1))(exp 0.8) + 6 kpc, differently from current samples of confirmed DLA galaxies. Our observations also disfavor a scenario in which the majority of DLAs arise from bright LBGs at distances 20 less than or equal to b(sub dla) less than 100 kpc. These new findings corroborate a picture in which DLAs do not originate from highly star forming systems that are coincident with the absorbers, and instead suggest that DLAs are associated with faint, possibly isolated, star-forming galaxies. Potential shortcomings of this scenario and future strategies for further investigation are discussed.

  20. Evidence for implicit learning in syntactic comprehension.

    PubMed

    Fine, Alex B; Florian Jaeger, T

    2013-04-01

    This study provides evidence for implicit learning in syntactic comprehension. By reanalyzing data from a syntactic priming experiment (Thothathiri & Snedeker, 2008), we find that the error signal associated with a syntactic prime influences comprehenders' subsequent syntactic expectations. This follows directly from error-based implicit learning accounts of syntactic priming, but it is unexpected under accounts that consider syntactic priming a consequence of temporary increases in base-level activation. More generally, the results raise questions about the principles underlying the maintenance of implicit statistical knowledge relevant to language processing, and about possible functional motivations for syntactic priming. PMID:23363004

  1. Implicit plasma simulation

    SciTech Connect

    Langdon, A.B.

    1985-03-03

    Implicit time integration methods have been used extensively in numerical modelling of slowly varying phenomena in systems that also support rapid variation. Examples include diffusion, hydrodynamics and reaction kinetics. This article discussed implementation of implicit time integration in plasma codes of the ''particle-in-cell'' family, and the benefits to be gained.

  2. Implicit Kalman filtering

    NASA Technical Reports Server (NTRS)

    Skliar, M.; Ramirez, W. F.

    1997-01-01

    For an implicitly defined discrete system, a new algorithm for Kalman filtering is developed and an efficient numerical implementation scheme is proposed. Unlike the traditional explicit approach, the implicit filter can be readily applied to ill-conditioned systems and allows for generalization to descriptor systems. The implementation of the implicit filter depends on the solution of the congruence matrix equation (A1)(Px)(AT1) = Py. We develop a general iterative method for the solution of this equation, and prove necessary and sufficient conditions for convergence. It is shown that when the system matrices of an implicit system are sparse, the implicit Kalman filter requires significantly less computer time and storage to implement as compared to the traditional explicit Kalman filter. Simulation results are presented to illustrate and substantiate the theoretical developments.

  3. Wall modeling for implicit large-eddy simulation and immersed-interface methods

    NASA Astrophysics Data System (ADS)

    Chen, Zhen Li; Hickel, Stefan; Devesa, Antoine; Berland, Julien; Adams, Nikolaus A.

    2014-02-01

    We propose and analyze a wall model based on the turbulent boundary layer equations (TBLE) for implicit large-eddy simulation (LES) of high Reynolds number wall-bounded flows in conjunction with a conservative immersed-interface method for mapping complex boundaries onto Cartesian meshes. Both implicit subgrid-scale model and immersed-interface treatment of boundaries offer high computational efficiency for complex flow configurations. The wall model operates directly on the Cartesian computational mesh without the need for a dual boundary-conforming mesh. The combination of wall model and implicit LES is investigated in detail for turbulent channel flow at friction Reynolds numbers from Re τ = 395 up to Re τ =100,000 on very coarse meshes. The TBLE wall model with implicit LES gives results of better quality than current explicit LES based on eddy viscosity subgrid-scale models with similar wall models. A straightforward formulation of the wall model performs well at moderately large Reynolds numbers. A logarithmic-layer mismatch, observed only at very large Reynolds numbers, is removed by introducing a new structure-based damping function. The performance of the overall approach is assessed for two generic configurations with flow separation: the backward-facing step at Re h = 5,000 and the periodic hill at Re H = 10,595 and Re H = 37,000 on very coarse meshes. The results confirm the observations made for the channel flow with respect to the good prediction quality and indicate that the combination of implicit LES, immersed-interface method, and TBLE-based wall modeling is a viable approach for simulating complex aerodynamic flows at high Reynolds numbers. They also reflect the limitations of TBLE-based wall models.

  4. Solution Accounts for Structural Damping

    NASA Technical Reports Server (NTRS)

    Roussos, L. A.; Hyer, M. W.; Thornton, E. A.

    1982-01-01

    New analytical technique determines dynamic response of damped structures dominated by internal structural damping mechanisms. Though structural damping is often negligible compared with damping due to air friction and friction in joints, structural damping can be of major importance in structures having heavy damping treatments or in outer-space structures. Finite-element model includes nonlinear, nonviscous internal damping.

  5. Effects of vertical fins near the nose of the fuselage on the directional and damping-in-yaw stability derivatives of an airplane model under steady-state and oscillatory conditions

    NASA Technical Reports Server (NTRS)

    Queijo, M J; Wells, Evalyn G

    1956-01-01

    A wind-tunnel investigation has been made at low speed to determine the effects of vertical fins placed ahead of the vertical tail on the directional stability and damping-in-yaw characteristics of a swept-wing model under steady-state oscillatory conditions. Various sizes of fins were used above and below the fuselage center line. The vertical-tail size also was varied.

  6. Intergroup anxiety effects on implicit racial evaluation and stereotyping.

    PubMed

    Amodio, David M; Hamilton, Holly K

    2012-12-01

    How does intergroup anxiety affect the activation of implicit racial evaluations and stereotypes? Given the common basis of social anxiety and implicit evaluative processes in memory systems linked to classical conditioning and affect, we predicted that intergroup anxiety would amplify implicit negative racial evaluations. Implicit stereotyping, which is associated primarily with semantic memory systems, was not expected to increase as a function of intergroup anxiety. This pattern was observed among White participants preparing to interact with Black partners, but not those preparing to interact with White partners. These findings shed new light on how anxiety, often elicited in real-life intergroup interactions, can affect the operation of implicit racial biases, suggesting that intergroup anxiety has more direct implications for affective and evaluative forms of implicit bias than for implicit stereotyping. These findings also support a memory-systems model of the interplay between emotion and cognition in the context of social behavior. PMID:22775128

  7. 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

  8. Damped leaf flexure hinge

    NASA Astrophysics Data System (ADS)

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage.

  9. Damped leaf flexure hinge.

    PubMed

    Chen, Zhong; Chen, Guisheng; Zhang, Xianmin

    2015-05-01

    Flexure-based mechanism like compliant actuation system embeds complex dynamics that will reduce the control bandwidth and limits their dynamic positioning precision. This paper presents a theoretical model of a leaf flexure hinge with damping layers using strain energy method and Kelvin damping model. The modified loss factor of the damped leaf flexure hinge is derived, and the equivalent viscous damping coefficient of the damped leaf hinge is obtained, which could be used to improve the pseudo-rigid-model. The free vibration signals of the hinge in three different damping configurations are measured. The experimental modal analysis also is performed on the three kinds of damped leaf flexure hinges in order to evaluate their 1st order bending natural frequency and vibration-suppressing effects. The evaluation of modified loss factor model also is performed. The experimental results indicate that the constrained layer damping can enhance the structure damping of the hinge even if only single damping layer each side, the modified loss factor model can get good predicts of a damped leaf flexure hinge in the frequency range below 1st order natural frequency, and it is necessary that the dimensional parameters of the damping layers and basic layer of the hinge should be optimized for simplification at the mechanism's design stage. PMID:26026549

  10. Damping constant estimation in magnetoresistive readers

    SciTech Connect

    Stankiewicz, Andrzej Hernandez, Stephanie

    2015-05-07

    The damping constant is a key design parameter in magnetic reader design. Its value can be derived from bulk or sheet film ferromagnetic resonance (FMR) line width. However, dynamics of nanodevices is usually defined by presence of non-uniform modes. It triggers new damping mechanisms and produces stronger damping than expected from traditional FMR. This work proposes a device-level technique for damping evaluation, based on time-domain analysis of thermally excited stochastic oscillations. The signal is collected using a high bandwidth oscilloscope, by direct probing of a biased reader. Recorded waveforms may contain different noise signals, but free layer FMR is usually a dominating one. The autocorrelation function is a reflection of the damped oscillation curve, averaging out stochastic contributions. The damped oscillator formula is fitted to autocorrelation data, producing resonance frequency and damping constant values. Restricting lag range allows for mitigation of the impact of other phenomena (e.g., reader instability) on the damping constant. For a micromagnetically modeled reader, the technique proves to be much more accurate than the stochastic FMR line width approach. Application to actual reader waveforms yields a damping constant of ∼0.03.

  11. Damping constant estimation in magnetoresistive readers

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Andrzej; Hernandez, Stephanie

    2015-05-01

    The damping constant is a key design parameter in magnetic reader design. Its value can be derived from bulk or sheet film ferromagnetic resonance (FMR) line width. However, dynamics of nanodevices is usually defined by presence of non-uniform modes. It triggers new damping mechanisms and produces stronger damping than expected from traditional FMR. This work proposes a device-level technique for damping evaluation, based on time-domain analysis of thermally excited stochastic oscillations. The signal is collected using a high bandwidth oscilloscope, by direct probing of a biased reader. Recorded waveforms may contain different noise signals, but free layer FMR is usually a dominating one. The autocorrelation function is a reflection of the damped oscillation curve, averaging out stochastic contributions. The damped oscillator formula is fitted to autocorrelation data, producing resonance frequency and damping constant values. Restricting lag range allows for mitigation of the impact of other phenomena (e.g., reader instability) on the damping constant. For a micromagnetically modeled reader, the technique proves to be much more accurate than the stochastic FMR line width approach. Application to actual reader waveforms yields a damping constant of ˜0.03.

  12. Predictive models of implicit and explicit attitudes.

    PubMed

    Perugini, Marco

    2005-03-01

    Explicit attitudes have long been assumed to be central factors influencing behaviour. A recent stream of studies has shown that implicit attitudes, typically measured with the Implicit Association Test (IAT), can also predict a significant range of behaviours. This contribution is focused on testing different predictive models of implicit and explicit attitudes. In particular, three main models can be derived from the literature: (a) additive (the two types of attitudes explain different portion of variance in the criterion), (b) double dissociation (implicit attitudes predict spontaneous whereas explicit attitudes predict deliberative behaviour), and (c) multiplicative (implicit and explicit attitudes interact in influencing behaviour). This paper reports two studies testing these models. The first study (N = 48) is about smoking behaviour, whereas the second study (N = 109) is about preferences for snacks versus fruit. In the first study, the multiplicative model is supported, whereas the double dissociation model is supported in the second study. The results are discussed in light of the importance of focusing on different patterns of prediction when investigating the directive influence of implicit and explicit attitudes on behaviours. PMID:15901390

  13. Landau damping of auroral hiss

    NASA Technical Reports Server (NTRS)

    Morgan, D. D.; Gurnett, D. A.; Menietti, J. D.; Winningham, J. D.; Burch, J. L.

    1994-01-01

    Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit omega/k(sub parallel) to values of 3.4 x 10(exp 4) km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, omega/k(sub parallel) is limited to values greater than 6.8 x 10(exp 4) km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that omega/k(sub parallel) corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities.

  14. Landau damping of auroral hiss

    SciTech Connect

    Morgan, D.D.; Gurnett, D.A.; Menietti, J.D.; Winningham, J.D.; Burch, J.L.

    1994-02-01

    Auroral hiss is observed to propagate over distances comparable to an Earth radius from its source in the auroral oval. The role of Landau damping is investigated for upward propagating auroral hiss. By using a ray tracing code and a simplified model of the distribution function, the effect of Landau damping is calculated for auroral hiss propagation through the environment around the auroral oval. Landau damping is found to be the likely mechanism for explaining some of the one-sided auroral hiss funnels observed by Dynamics Explorer 1. It is also found that Landau damping puts a lower limit on the wavelength of auroral hiss. Poleward of the auroral oval, Landau damping is found in a typical case to limit {omega}/k{parallel} to values of 3.4 x 10{sup 4} km/s or greater, corresponding to resonance energies of 3.2 keV or greater and wavelengths of 2 km or greater. For equatorward propagation, {omega}/k{parallel} is limited to values greater than 6.8 x 10{sup 4} km/s, corresponding to resonance energies greater than 13 keV and wavelengths greater than 3 km. Independent estimates based on measured ratios of the magnetic to electric field intensity also show that {omega}/k{parallel} corresponds to resonance energies greater than 1 keV and wavelengths greater than 1 km. These results lead to the difficulty that upgoing electron beams sufficiently energetic to directly generate auroral hiss of the inferred wavelength are not usually observed. A partial transmission mechanism utilizing density discontinuities oblique to the magnetic field is proposed for converting auroral hiss to wavelengths long enough to avoid damping of the wave over long distances. Numerous reflections of the wave in an upwardly flared density cavity could convert waves to significantly increased wavelengths and resonance velocities. 36 refs., 12 figs., 4 tabs.

  15. Implicit Attitudes in Prosopagnosia

    PubMed Central

    Knutson, Kristine M.; DeTucci, Karen A.; Grafman, Jordan

    2011-01-01

    We studied a male with acquired prosopagnosia using a battery of implicit association tests (IATs) to investigate whether observing faces varying by social category would activate the patient’s implicit social biases. We also asked him to categorize faces explicitly by race, gender, and political party. The patient, G.B., was marginally slower to categorize black compared to white faces. He showed congruency effects in the race and celebrity IATs, but not in the gender or political IATs. These results indicate that G.B. possesses an implicit social sensitivity to certain facial stimuli despite an inability to overtly recognize familiar faces. The results demonstrate that social biases can be retrieved based on facial stimuli via pathways bypassing the fusiform gyri. Thus the IAT effect can be added to the list of covert recognition effects found in prosopagnosia. PMID:21414330

  16. Implicit Spacecraft Gyro Calibration

    NASA Technical Reports Server (NTRS)

    Harman, Richard; Bar-Itzhack, Itzhack Y.

    2003-01-01

    This paper presents an implicit algorithm for spacecraft onboard instrument calibration, particularly to onboard gyro calibration. This work is an extension of previous work that was done where an explicit gyro calibration algorithm was applied to the AQUA spacecraft gyros. The algorithm presented in this paper was tested using simulated data and real data that were downloaded from the Microwave Anisotropy Probe (MAP) spacecraft. The calibration tests gave very good results. A comparison between the use of the implicit calibration algorithm used here with the explicit algorithm used for AQUA spacecraft indicates that both provide an excellent estimation of the gyro calibration parameters with similar accuracies.

  17. RMS active damping augmentation

    NASA Technical Reports Server (NTRS)

    Gilbert, Michael G.; Scott, Michael A.; Demeo, Martha E.

    1992-01-01

    The topics are presented in viewgraph form and include: RMS active damping augmentation; potential space station assembly benefits to CSI; LaRC/JSC bridge program; control law design process; draper RMS simulator; MIMO acceleration control laws improve damping; potential load reduction benefit; DRS modified to model distributed accelerations; accelerometer location; Space Shuttle aft cockpit simulator; simulated shuttle video displays; SES test goals and objectives; and SES modifications to support RMS active damping augmentation.

  18. Emotion and Implicit Timing

    PubMed Central

    Droit-Volet, Sylvie

    2016-01-01

    This study examined the effects of emotion on implicit timing. In the implicit timing task used, the participants did not receive any temporal instructions. Instead they were simply asked and trained to press a key as quickly as possible after a stimulus (response stimulus) that was separated from a preceding stimulus by a given temporal interval (reference interval duration). However, in the testing phase, the interval duration was the reference interval duration or a shorter or longer interval duration. In addition, the participants attended two sessions: a first baseline session in which no stimulus was presented during the inter-stimulus intervals, and a second emotional session in which emotional facial expressions (angry, neutral and sad facial expressions) were presented during these intervals. Results showed faster RTs for interval durations close to the reference duration in both the baseline and the emotional conditions and yielded a U-shaped curve. This suggests that implicit processing of time persists in emotional contexts. In addition, the RT was faster for the facial expressions of anger than for those of neutrality and sadness. However, the U-shaped RT curve did not peak clearly at a shorter interval duration for the angry than for the other facial expressions. This lack of time distortion in an implicit timing task in response to arousing emotional stimuli questions the idea of an automatic speeding-up of the interval clock system involved in the representation of time. PMID:27380409

  19. Sexual Murderers' Implicit Theories

    ERIC Educational Resources Information Center

    Beech, Anthony; Fisher, Dawn; Ward, Tony

    2005-01-01

    Interviews with 28 sexual murderers were subjected to grounded theory analysis. Five implicit theories (ITs) were identified: dangerous world, male sex drive is uncontrollable, entitlement, women as sexual objects, and women as unknowable. These ITs were found to be identical to those identified in the literature as being present in rapists. The…

  20. Decoherence and Landau-Damping

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2005-12-01

    The terminologies, decoherence and Landau damping, are often used concerning the damping of a collective instability. This article revisits the difference and relation between decoherence and Landau damping. A model is given to demonstrate how Landau damping affects the rate of damping coming from decoherence.

  1. Saturation of Gyrokinetic Turbulence through Damped Eigenmodes

    SciTech Connect

    Hatch, D. R.; Terry, P. W.; Jenko, F.; Merz, F.; Nevins, W. M.

    2011-03-18

    In the context of toroidal gyrokinetic simulations, it is shown that a hierarchy of damped modes is excited in the nonlinear turbulent state. These modes exist at the same spatial scales as the unstable eigenmodes that drive the turbulence. The larger amplitude subdominant modes are weakly damped and exhibit smooth, large-scale structure in velocity space and in the direction parallel to the magnetic field. Modes with increasingly fine-scale structure are excited to decreasing amplitudes. In aggregate, damped modes define a potent energy sink. This leads to an overlap of the spatial scales of energy injection and peak dissipation, a feature that is in contrast with more traditional turbulent systems.

  2. Turbine blade damping study

    NASA Technical Reports Server (NTRS)

    Dominic, R. J.

    1984-01-01

    Research results and progress on the performance of bladed systems is reported the different topics discussed include: the study of turbine blade damping; forced vibrations of friction damped beam moistures in two dimensions; and a users manual for a computer program for dynamic analysis of bladed systems.

  3. Damped acceleration cavities

    SciTech Connect

    Palmer, R.B.

    1988-07-01

    Structures with slots to strongly damp higher order longitudinal and transverse modes should allow the use, in linear colliders, of multiple bunches, and thus attain luminosities of over 10/sup 34/cm/sup /minus/2/sec/sup /minus/1/. Preliminary measurements on model structures suggest that such damping can be achieved. 10 refs., 9 figs.

  4. 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,…

  5. Turbojet engine blade damping

    NASA Technical Reports Server (NTRS)

    Srinivasan, A. V.; Cutts, D. G.; Sridhar, S.

    1981-01-01

    The potentials of various sources of nonaerodynamic damping in engine blading are evaluated through a combination of advanced analysis and testing. The sources studied include material hysteresis, dry friction at shroud and root disk interfaces as well as at platform type external dampers. A limited seris of tests was conducted to evaluate damping capacities of composite materials (B/AL, B/AL/Ti) and thermal barrier coatings. Further, basic experiments were performed on titanium specimens to establish the characteristics of sliding friction and to determine material damping constants J and n. All the tests were conducted on single blades. Mathematical models were develthe several mechanisms of damping. Procedures to apply this data to predict damping levels in an assembly of blades are developed and discussed.

  6. Approach for Selection of Rayleigh Damping Parameters Used for Time History Analysis

    SciTech Connect

    R. E. Spears; S. R. Jensen

    2012-12-01

    Nonlinearities, whether geometric or material, need to be addressed in seismic analysis. One good analysis method that can address these nonlinearities is direct time integration with Rayleigh damping. Modal damping is the damping typically specified in seismic analysis Codes and Standards. Modal damping is constant for all frequencies where Rayleigh damping varies with frequency. An approach is proposed here for selection of Rayleigh damping coefficients to be used in seismic analyses that is consistent with given Modal damping. The approach uses the difference between the modal damping response and the Rayleigh damping response along with effective mass properties of the model being evaluated to match overall system response levels. This paper provides a simple example problem to demonstrate the approach. It also provides results for a finite element model representing an existing piping system. Displacement, acceleration, and stress results are compared from model runs using modal damping and model runs using Rayleigh damping with coefficients selected using the proposed method.

  7. Damping models in elastography

    NASA Astrophysics Data System (ADS)

    McGarry, Matthew D. J.; Berger, Hans-Uwe; Van Houten, Elijah E. W.

    2007-03-01

    Current optimization based Elastography reconstruction algorithms encounter difficulties when the motion approaches resonant conditions, where the model does a poor job of approximating the real behavior of the material. Model accuracy can be improved through the addition of damping effects. These effects occur in-vivo due to the complex interaction between microstructural elements of the tissue; however reconstruction models are typically formulated at larger scales where the structure can be treated as a continuum. Attenuation behavior in an elastic continuum can be described as a mixture of inertial and viscoelastic damping effects. In order to develop a continuum damping model appropriate for human tissue, the behavior of each aspect of this proportional, or Rayleigh damping needs to be characterized. In this paper we investigate the nature of these various damping representations with a goal of best describing in-vivo behavior of actual tissue in order to improve the accuracy and performance of optimization based elastographic reconstruction. Inertial damping effects are modelled using a complex density, where the imaginary part is equivalent to a damping coefficient, and the effects of viscoelasticity are modelled through the use of complex shear moduli, where the real and imaginary parts represent the storage and loss moduli respectively. The investigation is carried out through a combination of theoretical analysis, numerical experiment, investigation of gelatine phantoms and comparison with other continua such as porous media models.

  8. Spatial cyclotron damping

    NASA Technical Reports Server (NTRS)

    Olson, C. L.

    1970-01-01

    To examine spatial electron cyclotron damping in a uniform Vlasov plasma, it is noted that the plasma response to a steady-state transverse excitation consists of several terms (dielectric-pole, free-streaming, and branch-cut), but that the cyclotron-damped pole term is the dominant term for z l = c/w sub ce provided (w sub pe/w sub ce) squared (c/a) is much greater than 1. If the latter inequality does not hold, then the free-streaming and branch-cut terms persist well past z = c/w sub ce as w sub 1 approaches w sub ce, making experimental measurement of cyclotron damping essentially impossible. Considering only (w sub pe/w sub ce) squared (c/a) is much greater than 1, it is shown how collisional effects should be estimated and how a finite-width excitation usually has little effect on the cyclotron-damped part of the response. Criteria is established concerning collisional damping, measurable damping length sizes, and allowed uncertainty in the magnetic field Beta. Results of numerical calculations, showing the regions in the appropriate parameter spaces that meet these criteria, are presented. From these results, one can determine the feasibility of, or propose parameter values for, an experiment designed to measure spatial cyclotron damping. It is concluded that the electron temperature T sub e should be at least 1 ev., and preferably 10 ev. or higher, for a successful experiment.

  9. Passively damped vibration welding system and method

    DOEpatents

    Tan, Chin-An; Kang, Bongsu; Cai, Wayne W.; Wu, Tao

    2013-04-02

    A vibration welding system includes a controller, welding horn, an anvil, and a passive damping mechanism (PDM). The controller generates an input signal having a calibrated frequency. The horn vibrates in a desirable first direction at the calibrated frequency in response to the input signal to form a weld in a work piece. The PDM is positioned with respect to the system, and substantially damps or attenuates vibration in an undesirable second direction. A method includes connecting the PDM having calibrated properties and a natural frequency to an anvil of an ultrasonic welding system. Then, an input signal is generated using a weld controller. The method includes vibrating a welding horn in a desirable direction in response to the input signal, and passively damping vibration in an undesirable direction using the PDM.

  10. Experimental and analytical estimation of damping in beams and plates with damping treatments

    NASA Astrophysics Data System (ADS)

    Liu, Wanbo

    constant material properties, this analytical power input method directly takes into account the frequency-dependent material properties of the viscoelastic material using the MSC/NASTRAN direct frequency response solution. Features of each method are compared and summarized. Especially, (1) the complex frequency-dependency of viscoelastic materials used in constrained layer damping is modeled using MSC Patran/NASTRAN; (2) a new procedure of estimating loss factors is presented, using the concept of the power input method. Particle damping is also investigated. A fluid analogy is proposed and applied to composite beams and metallic plates. Results show that the fluid analogy can effectively estimate peak damping frequencies and peak damping levels. Both experimental and analytical loss factor results for various engineering structures are presented and discussed.

  11. STREAK damping. Technical report

    SciTech Connect

    Baker, J.; Peyton, S.; Freiberg, H.

    1989-12-01

    This report documents a study aimed at improving the damping in STREAK. A form and value for an artificial viscosity is recommended which appears to control ringing and overshoots without overdamping.

  12. Dependence of Kambersky damping on Fermi level and spin orientation

    SciTech Connect

    Qu, T.; Victora, R. H.

    2014-05-07

    Kambersky damping represents the loss of magnetic energy from the electrons to the lattice through the spin orbit interaction. It is demonstrated that, for bcc Fe-based transition metal alloys, the logarithm of the energy loss is proportional to the density of states at the Fermi level. Both inter and intraband damping are calculated for spins at arbitrary angle to the previously examined [001] direction. Although the easy axis 〈100〉 shows isotropic relaxation and achieves the minimum damping value of 0.002, other directions, such as 〈110〉, show substantial anisotropic damping.

  13. An Implicit Characteristic Based Method for Electromagnetics

    NASA Technical Reports Server (NTRS)

    Beggs, John H.; Briley, W. Roger

    2001-01-01

    An implicit characteristic-based approach for numerical solution of Maxwell's time-dependent curl equations in flux conservative form is introduced. This method combines a characteristic based finite difference spatial approximation with an implicit lower-upper approximate factorization (LU/AF) time integration scheme. This approach is advantageous for three-dimensional applications because the characteristic differencing enables a two-factor approximate factorization that retains its unconditional stability in three space dimensions, and it does not require solution of tridiagonal systems. Results are given both for a Fourier analysis of stability, damping and dispersion properties, and for one-dimensional model problems involving propagation and scattering for free space and dielectric materials using both uniform and nonuniform grids. The explicit Finite Difference Time Domain Method (FDTD) algorithm is used as a convenient reference algorithm for comparison. The one-dimensional results indicate that for low frequency problems on a highly resolved uniform or nonuniform grid, this LU/AF algorithm can produce accurate solutions at Courant numbers significantly greater than one, with a corresponding improvement in efficiency for simulating a given period of time. This approach appears promising for development of dispersion optimized LU/AF schemes for three dimensional applications.

  14. DAMPs, ageing, and cancer: The 'DAMP Hypothesis'.

    PubMed

    Huang, Jin; Xie, Yangchun; Sun, Xiaofang; Zeh, Herbert J; Kang, Rui; Lotze, Michael T; Tang, Daolin

    2015-11-01

    Ageing is a complex and multifactorial process characterized by the accumulation of many forms of damage at the molecular, cellular, and tissue level with advancing age. Ageing increases the risk of the onset of chronic inflammation-associated diseases such as cancer, diabetes, stroke, and neurodegenerative disease. In particular, ageing and cancer share some common origins and hallmarks such as genomic instability, epigenetic alteration, aberrant telomeres, inflammation and immune injury, reprogrammed metabolism, and degradation system impairment (including within the ubiquitin-proteasome system and the autophagic machinery). Recent advances indicate that damage-associated molecular pattern molecules (DAMPs) such as high mobility group box 1, histones, S100, and heat shock proteins play location-dependent roles inside and outside the cell. These provide interaction platforms at molecular levels linked to common hallmarks of ageing and cancer. They can act as inducers, sensors, and mediators of stress through individual plasma membrane receptors, intracellular recognition receptors (e.g., advanced glycosylation end product-specific receptors, AIM2-like receptors, RIG-I-like receptors, and NOD1-like receptors, and toll-like receptors), or following endocytic uptake. Thus, the DAMP Hypothesis is novel and complements other theories that explain the features of ageing. DAMPs represent ideal biomarkers of ageing and provide an attractive target for interventions in ageing and age-associated diseases. PMID:25446804

  15. Damping of nanomechanical resonators.

    PubMed

    Unterreithmeier, Quirin P; Faust, Thomas; Kotthaus, Jörg P

    2010-07-01

    We study the transverse oscillatory modes of nanomechanical silicon nitride strings under high tensile stress as a function of geometry and mode index m≤9. Reproducing all observed resonance frequencies with classical elastic theory we extract the relevant elastic constants. Based on the oscillatory local strain we successfully predict the observed mode-dependent damping with a single frequency-independent fit parameter. Our model clarifies the role of tensile stress on damping and hints at the underlying microscopic mechanisms. PMID:20867737

  16. Processing implicit control: evidence from reading times

    PubMed Central

    McCourt, Michael; Green, Jeffrey J.; Lau, Ellen; Williams, Alexander

    2015-01-01

    Sentences such as “The ship was sunk to collect the insurance” exhibit an unusual form of anaphora, implicit control, where neither anaphor nor antecedent is audible. The non-finite reason clause has an understood subject, PRO, that is anaphoric; here it may be understood as naming the agent of the event of the host clause. Yet since the host is a short passive, this agent is realized by no audible dependent. The putative antecedent to PRO is therefore implicit, which it normally cannot be. What sorts of representations subserve the comprehension of this dependency? Here we present four self-paced reading time studies directed at this question. Previous work showed no processing cost for implicit vs. explicit control, and took this to support the view that PRO is linked syntactically to a silent argument in the passive. We challenge this conclusion by reporting that we also find no processing cost for remote implicit control, as in: “The ship was sunk. The reason was to collect the insurance.” Here the dependency crosses two independent sentences, and so cannot, we argue, be mediated by syntax. Our Experiments 1–4 examined the processing of both implicit (short passive) and explicit (active or long passive) control in both local and remote configurations. Experiments 3 and 4 added either “3 days ago” or “just in order” to the local conditions, to control for the distance between the passive and infinitival verbs, and for the predictability of the reason clause, respectively. We replicate the finding that implicit control does not impose an additional processing cost. But critically we show that remote control does not impose a processing cost either. Reading times at the reason clause were never slower when control was remote. In fact they were always faster. Thus, efficient processing of local implicit control cannot show that implicit control is mediated by syntax; nor, in turn, that there is a silent but grammatically active argument in

  17. Mitigation of two-plasmon decay in direct-drive inertial confinement fusion through the manipulation of ion-acoustic and Langmuir wave damping

    SciTech Connect

    Myatt, J. F.; Short, R. W.; Maximov, A. V.; Vu, H. X.; DuBois, D. F.; Russell, D. A.; Zhang, J.

    2013-05-15

    The extended Zakharov model of the two-plasmon decay instability in an inhomogeneous plasma [D. F. DuBois et al., Phys. Rev. Lett. 74, 3983 (1995); D. A. Russell and D. F. DuBois, Phys. Rev. Lett. 86, 428 (2001)] is further generalized to include the evolution of the electron distribution function in the quasi-linear approximation [cf., e.g., K. Y. Sanbonmatsu et al. Phys. Plasmas 7, 2824 (2000); D. A. Russell et al., paper presented at the Workshop on SRS/SBS Saturation, Wente Vineyards, Livermore, CA, 2–5 April 2002]. This makes it possible to investigate anomalous absorption of laser light and hot electron production due to the two-plasmon decay instability of multiple overlapping electromagnetic waves. Scalings of hot-electron production in the (stationary) nonlinearly saturated regime relevant to recent experiments [B. Yaakobi et al., Phys. Plasmas 19, 012704 (2012); D. H. Froula et al., Phys. Rev. Lett. 108, 165003 (2012)] have been obtained. They indicate a sensitivity to ion-acoustic wave (IAW) damping and to the collisional absorption of Langmuir waves. Such a sensitivity might be exploited in inertial confinement fusion target design by the use of mid-Z ablators.

  18. Mitigation of two-plasmon decay in direct-drive inertial confinement fusion through the manipulation of ion-acoustic and Langmuir wave damping

    NASA Astrophysics Data System (ADS)

    Myatt, J. F.; Vu, H. X.; DuBois, D. F.; Russell, D. A.; Zhang, J.; Short, R. W.; Maximov, A. V.

    2013-05-01

    The extended Zakharov model of the two-plasmon decay instability in an inhomogeneous plasma [D. F. DuBois et al., Phys. Rev. Lett. 74, 3983 (1995); D. A. Russell and D. F. DuBois, Phys. Rev. Lett. 86, 428 (2001)] is further generalized to include the evolution of the electron distribution function in the quasi-linear approximation [cf., e.g., K. Y. Sanbonmatsu et al. Phys. Plasmas 7, 2824 (2000); D. A. Russell et al., paper presented at the Workshop on SRS/SBS Saturation, Wente Vineyards, Livermore, CA, 2-5 April 2002]. This makes it possible to investigate anomalous absorption of laser light and hot electron production due to the two-plasmon decay instability of multiple overlapping electromagnetic waves. Scalings of hot-electron production in the (stationary) nonlinearly saturated regime relevant to recent experiments [B. Yaakobi et al., Phys. Plasmas 19, 012704 (2012); D. H. Froula et al., Phys. Rev. Lett. 108, 165003 (2012)] have been obtained. They indicate a sensitivity to ion-acoustic wave (IAW) damping and to the collisional absorption of Langmuir waves. Such a sensitivity might be exploited in inertial confinement fusion target design by the use of mid-Z ablators.

  19. Damping modeling in Timoshenko beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Wang, Y.

    1992-01-01

    Theoretical and numerical results of damping model studies for composite material beams using the Timoshenko theory is presented. Based on the damping models developed for Euler-Bernoulli beams, the authors develop damping methods for both bending and shear in investigation of Timoshenko beams. A computational method for the estimation of the damping parameters is given. Experimental data with high-frequency excitation were used to test Timoshenko beam equations with different types of damping models for bending and shear in various combinations.

  20. Implicit measure for yoga research: Yoga implicit association test

    PubMed Central

    Ilavarasu, Judu V; Rajesh, Sasidharan K; Hankey, Alex

    2014-01-01

    Context: The implicit association test (IAT), a new tool for yoga research is presented. Implicit measures could be used in those situations where (1) The construct is difficult to self-report, (2) there is a threat of social desirability. Clinically, we can assess cognitive dissonance by evaluating incongruence between implicit and explicit measures. Explicit preferences are self-reported. Implicit preferences are what we inherently believe, often without our conscious awareness. Aims: The primary objective of this study is to provide a bird's eye view of the field, implicit cognition, with emphasis on the IAT and the secondary objective is to illustrate through an example of our study to develop an implicit tool to assess implicit preference toward yoga. Settings and Design: A total of 5 independent samples of total 69 students undergoing short and long-term yoga courses in a Yoga University were assessed for their implicit and explicit preferences towards yoga. Materials and Methods: The yoga-IAT (Y-IAT), explicit self-rating scale was administered through computers using the Inquisit program by Millisecond Software. Experimental and scoring materials are provided. Results: A moderate preference toward yoga was detected, with a lower implicit-explicit congruence, reflecting possible confound of social desirability in the self-report of preference toward yoga. Conclusions: Implicit measures may be used in the yoga field to assess constructs, which are difficult to self-report or may have social desirability threat. Y-IAT may be used to evaluate implicit preference toward yoga. PMID:25035621

  1. Adapting implicit methods to parallel processors

    SciTech Connect

    Reeves, L.; McMillin, B.; Okunbor, D.; Riggins, D.

    1994-12-31

    When numerically solving many types of partial differential equations, it is advantageous to use implicit methods because of their better stability and more flexible parameter choice, (e.g. larger time steps). However, since implicit methods usually require simultaneous knowledge of the entire computational domain, these methods axe difficult to implement directly on distributed memory parallel processors. This leads to infrequent use of implicit methods on parallel/distributed systems. The usual implementation of implicit methods is inefficient due to the nature of parallel systems where it is common to take the computational domain and distribute the grid points over the processors so as to maintain a relatively even workload per processor. This creates a problem at the locations in the domain where adjacent points are not on the same processor. In order for the values at these points to be calculated, messages have to be exchanged between the corresponding processors. Without special adaptation, this will result in idle processors during part of the computation, and as the number of idle processors increases, the lower the effective speed improvement by using a parallel processor.

  2. Experiments with particle damping

    NASA Astrophysics Data System (ADS)

    Hollkamp, Joseph J.; Gordon, Robert W.

    1998-06-01

    High cycle fatigue in jet engines is a current military concern. The vibratory stresses that cause fatigue can be reduced by adding damping. However, the high temperatures that occur in the gas turbine greatly hinder the application of mature damping technologies. One technology which may perform in the harsh environment is particle damping. Particle damping involves placing metallic or ceramic particles inside structural cavities. As the cavity vibrates, energy is dissipated through particle collisions. Performance is influenced by many parameters including the type, shape, and size of the particles; the amount of free volume for the particles to move in; density of the particles; and the level of vibration. This paper presents results from a series of experiments designed to gain an appreciation of the important parameters. The experimental setup consists of a cantilever beam with drilled holes. These holes are partially filled with particles. The types of particles, location of the particles, fill level, and other parameters are varied. Damping is estimated for each configuration. Trends in the results are studied to determine the influence of the varied parameter.

  3. Damped flexible seal

    DOEpatents

    DuBois, Neil J.; Amaral, Antonio M.

    1992-10-27

    A damped flexible seal assembly for a torpedo isolates the tailcone thereof rom vibrational energy present in the drive shaft assembly. A pair of outside flanges, each of which include an inwardly facing groove and an O-ring constrained therein, provide a watertight seal against the outer non-rotating surface of the drive shaft assembly. An inside flange includes an outwardly-facing groove and an O-ring constrained therein, and provides a watertight seal against the inner surface of the tail cone. Two cast-in-place elastomeric seals provide a watertight seal between the flanges and further provide a damping barrier between the outside flanges and the inside flanges for damping vibrational energy present in the drive shaft assembly before the energy can reach the tailcone through the seal assembly.

  4. DAMPs and autophagy

    PubMed Central

    Zhang, Qiuhong; Kang, Rui; Zeh, III, Herbert J.; Lotze, Michael T.; Tang, Daolin

    2013-01-01

    Autophagy is a lysosome-mediated catabolic process involving the degradation of intracellular contents (e.g., proteins and organelles) as well as invading microbes (e.g., parasites, bacteria and viruses). Multiple forms of cellular stress can stimulate this pathway, including nutritional imbalances, oxygen deprivation, immunological response, genetic defects, chromosomal anomalies and cytotoxic stress. Damage-associated molecular pattern molecules (DAMPs) are released by stressed cells undergoing autophagy or injury, and act as endogenous danger signals to regulate the subsequent inflammatory and immune response. A complex relationship exists between DAMPs and autophagy in cellular adaption to injury and unscheduled cell death. Since both autophagy and DAMPs are important for pathogenesis of human disease, it is crucial to understand how they interplay to sustain homeostasis in stressful or dangerous environments. PMID:23388380

  5. Introduction to DAMPE event reconstruction (On behalf of DAMPE collaboration)

    NASA Astrophysics Data System (ADS)

    Zang, Jingjing

    2016-07-01

    The Dark Matter Particle Explorer (DAMPE) is a high energy particle physics experiment satellite, launched on 17 Dec 2015. To measure basic attributes of cosmic ray particles, DAMPE is equipped with four sub-detectors, BGO calorimeter (BGO), plastic scintillator detector (PSD), silicon tungsten tracker (STK) and neutron detector (NUD). On orbit, the high energy particle data are acquired and recorded by well-designed Data Acquisition system. After that, a series of elaborate event reconstruction algorithms are implemented to determine the energy, direction and particle ID of each event. The energy reconstruction algorithm firstly treats the sum of the BGO crystal energy as the overall energy estimator and various corrections are performed to calculate energy leakage from side and back of the calorimeter. The track reconstruction starts with cluster finding in STK, then shower axis of BGO and barycentre of clusters are used to extract seed of tracks. These seeds will be projected on the next layer by Kalman Filter method which will finally give location and direction of particle tracks. Based on shower development in BGO and tracks reconstructed by STK, we also combine data from PSD and NUD and developed a series of algorithms to evaluate particle's charge and identification. In this talk, we will describe technical strategies of event reconstruction and provide their basic performance.

  6. Damping of long-wavelength kinetic alfven fluctuations: linear theory

    SciTech Connect

    Gary, S Peter; Borovsky, Joseph E

    2008-01-01

    The full electromagnetic linear dispersion equation for kinetic Alfven fluctuations in a homogeneous, isotropic, Maxwellian electron-proton plasma is solved numerically in the long wavelength limit. The solutions are summarized by an analytic expression for the damping rate of such modes at propagation sufficiently oblique to the background magnetic field B{sub o} which scales as k{sub {perpendicular}}{sup 2} k{sub {parallel}} where the subscripts denote directions relative to B{sub o}. This damping progressively (although not monotonically) increases with increasing electron {beta}, corresponding to four distinct damping regimes: nonresonant, electron Landau, proton Landau, and proton transit-time damping.

  7. Implicit Sequence Learning in Children.

    ERIC Educational Resources Information Center

    Meulemans, Thierry; Van der Linden, Martial; Perruchet, Pierre

    1998-01-01

    Examined implicit learning ability in 6- and 10-year olds and adults as assessed by a serial reaction-time task, along with retention of knowledge after one week and explicit knowledge developed by children. Found no age-related difference in serial reaction-time performance, consistent with the idea that implicit learning abilities may be…

  8. The Neuropharmacology of Implicit Learning

    PubMed Central

    Uddén, Julia; Folia, Vasiliki; Petersson, Karl Magnus

    2010-01-01

    Two decades of pharmacologic research on the human capacity to implicitly acquire knowledge as well as cognitive skills and procedures have yielded surprisingly few conclusive insights. We review the empirical literature of the neuropharmacology of implicit learning. We evaluate the findings in the context of relevant computational models related to neurotransmittors such as dopamine, serotonin, acetylcholine and noradrenalin. These include models for reinforcement learning, sequence production, and categorization. We conclude, based on the reviewed literature, that one can predict improved implicit acquisition by moderately elevated dopamine levels and impaired implicit acquisition by moderately decreased dopamine levels. These effects are most prominent in the dorsal striatum. This is supported by a range of behavioral tasks in the empirical literature. Similar predictions can be made for serotonin, although there is yet a lack of support in the literature for serotonin involvement in classical implicit learning tasks. There is currently a lack of evidence for a role of the noradrenergic and cholinergic systems in implicit and related forms of learning. GABA modulators, including benzodiazepines, seem to affect implicit learning in a complex manner and further research is needed. Finally, we identify allosteric AMPA receptors modulators as a potentially interesting target for future investigation of the neuropharmacology of procedural and implicit learning. PMID:21629444

  9. Implicit Theories of Peer Relationships

    ERIC Educational Resources Information Center

    Rudolph, Karen D.

    2010-01-01

    This research investigated the role of children's implicit theories of peer relationships in their psychological, emotional, and behavioral adjustment. Participants included 206 children (110 girls; 96 boys; M age = 10.13 years, SD = 1.16) who reported on their implicit theories of peer relationships, social goal orientation, need for approval,…

  10. Process Damping Parameters

    NASA Astrophysics Data System (ADS)

    Turner, Sam

    2011-12-01

    The phenomenon of process damping as a stabilising effect in milling has been encountered by machinists since milling and turning began. It is of great importance when milling aerospace alloys where maximum surface speed is limited by excessive tool wear and high speed stability lobes cannot be attained. Much of the established research into regenerative chatter and chatter avoidance has focussed on stability lobe theory with different analytical and time domain models developed to expand on the theory first developed by Trusty and Tobias. Process damping is a stabilising effect that occurs when the surface speed is low relative to the dominant natural frequency of the system and has been less successfully modelled and understood. Process damping is believed to be influenced by the interference of the relief face of the cutting tool with the waveform traced on the cut surface, with material properties and the relief geometry of the tool believed to be key factors governing performance. This study combines experimental trials with Finite Element (FE) simulation in an attempt to identify and understand the key factors influencing process damping performance in titanium milling. Rake angle, relief angle and chip thickness are the variables considered experimentally with the FE study looking at average radial and tangential forces and surface compressive stress. For the experimental study a technique is developed to identify the critical process damping wavelength as a means of measuring process damping performance. For the range of parameters studied, chip thickness is found to be the dominant factor with maximum stable parameters increased by a factor of 17 in the best case. Within the range studied, relief angle was found to have a lesser effect than expected whilst rake angle had an influence.

  11. Damping seals for turbomachinery

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L.

    1985-01-01

    Rotor whirl stabilization of high performance turbomachinery which operates at supercritical speed is discussed. Basic whirl driving forces are reviewed. Stabilization and criteria are discussed. Damping seals are offered as a solution to whirl and high vibration problems. Concept, advantages, retrofitting, and limits of damping seals are explained. Dynamic and leakage properties are shown to require a rough stator surface for stability and efficiency. Typical seal characteristics are given for the case of the high pressure oxidizer turbopump of the Space Shuttle. Ways of implementation and bearing load effects are discussed.

  12. Note: Tesla transformer damping

    NASA Astrophysics Data System (ADS)

    Reed, J. L.

    2012-07-01

    Unexpected heavy damping in the two winding Tesla pulse transformer is shown to be due to small primary inductances. A small primary inductance is a necessary condition of operability, but is also a refractory inefficiency. A 30% performance loss is demonstrated using a typical "spiral strip" transformer. The loss is investigated by examining damping terms added to the transformer's governing equations. A significant alteration of the transformer's architecture is suggested to mitigate these losses. Experimental and simulated data comparing the 2 and 3 winding transformers are cited to support the suggestion.

  13. Implicit race attitudes predict trustworthiness judgments and economic trust decisions.

    PubMed

    Stanley, Damian A; Sokol-Hessner, Peter; Banaji, Mahzarin R; Phelps, Elizabeth A

    2011-05-10

    Trust lies at the heart of every social interaction. Each day we face decisions in which we must accurately assess another individual's trustworthiness or risk suffering very real consequences. In a global marketplace of increasing heterogeneity with respect to nationality, race, and multiple other social categories, it is of great value to understand how implicitly held attitudes about group membership may support or undermine social trust and thereby implicitly shape the decisions we make. Recent behavioral and neuroimaging work suggests that a common mechanism may underlie the expression of implicit race bias and evaluations of trustworthiness, although no direct evidence of a connection exists. In two behavioral studies, we investigated the relationship between implicit race attitude (as measured by the Implicit Association Test) and social trust. We demonstrate that race disparity in both an individual's explicit evaluations of trustworthiness and, more crucially, his or her economic decisions to trust is predicted by that person's bias in implicit race attitude. Importantly, this relationship is robust and is independent of the individual's bias in explicit race attitude. These data demonstrate that the extent to which an individual invests in and trusts others with different racial backgrounds is related to the magnitude of that individual's implicit race bias. The core dimension of social trust can be shaped, to some degree, by attitudes that reside outside conscious awareness and intention. PMID:21518877

  14. Implicit negotiation beliefs and performance: experimental and longitudinal evidence.

    PubMed

    Kray, Laura J; Haselhuhn, Michael P

    2007-07-01

    The authors argue that implicit negotiation beliefs, which speak to the expected malleability of negotiating ability, affect performance in dyadic negotiations. They expected negotiators who believe negotiating attributes are malleable (incremental theorists) to outperform negotiators who believe negotiating attributes are fixed (entity theorists). In Study 1, they gathered evidence of convergent and discriminant validity for the implicit negotiation belief construct. In Study 2, they examined the impact of implicit beliefs on the achievement goals that negotiators pursue. In Study 3, they explored the causal role of implicit beliefs on negotiation performance by manipulating negotiators' implicit beliefs within dyads. They also identified perceived ability as a moderator of the link between implicit negotiation beliefs and performance. In Study 4, they measured negotiators' beliefs in a classroom setting and examined how these beliefs affected negotiation performance and overall performance in the course 15 weeks later. Across all performance measures, incremental theorists outperformed entity theorists. Consistent with the authors' hypotheses, incremental theorists captured more of the bargaining surplus and were more integrative than their entity theorist counterparts, suggesting implicit theories are important determinants of how negotiators perform. Implications and future directions are discussed. PMID:17605588

  15. Damping seal for turbomachinery

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L. (Inventor)

    1985-01-01

    A damping seal between a high speed rotor member and stator member that separates pressurized fluid compartments is described. It is characterized by the rotor member having a smooth outer surface and the stator member having its bore surface roughened by a plurality of pockets or depressions.

  16. Exotic damping ring lattices

    SciTech Connect

    Palmer, R.B.

    1987-05-01

    This paper looks at, and compares three types of damping ring lattices: conventional, wiggler lattice with finite ..cap alpha.., wiggler lattice with ..cap alpha.. = 0, and observes the attainable equilibrium emittances for the three cases assuming a constraint on the attainable longitudinal impedance of 0.2 ohms. The emittance obtained are roughly in the ratio 4:2:1 for these cases.

  17. Bounce-harmonic Landau Damping of Plasma Waves

    NASA Astrophysics Data System (ADS)

    Anderegg, Francois

    2015-11-01

    We present measurement of plasma wave damping, spanning the temperature regimes of direct Landau damping, bounce-harmonic Landau damping, inter-species drag damping, and viscous damping. Direct Landau damping is dominant at high temperatures, but becomes negligible as v damping, controlled by an applied ``squeeze'' potential, which generates harmonics in the wave potential and in the particle dynamics. A particle moving in z experiences a non-sinusoidal mode potential caused by the squeeze, producing high spatial harmonics with lower phase velocity. These harmonics are Landau damped even when the mode phase velocity vph is large compared to the thermal velocity v , since the nth harmonic is resonant with a particle bouncing at velocity vb =vph / n . Here we increase the bounce harmonics through applied squeeze potential; but some harmonics are always present in finite length systems. For our centered squeeze geometry, theory shows that only odd harmonics are generated, and predicts the Landau damping rate from vph / n . Experimentally, the squeeze potential increases the wave damping and reduces its frequency. The frequency shift occurs because the squeeze potential reduces the number of particle where the mode velocity is the largest, therefore reducing the mode frequency. We observe an increase in the damping proportional to Vs2,and a frequency reduction proportional to Vs , in quantitative agreement with theory. Wave-coherent laser induced fluorescence allows direct observation of bounce resonances on the particle distribution, here predominantly at vph / 3 . A clear increase of the bounce harmonics is visible on the particle distribution when the squeeze potential is applied. Supported by NSF Grant PHY-1414570, and DOE Grants DE-SC0002451 and DE-SC0008693.

  18. Study of modal coupling procedures for the shuttle: A matrix method for damping synthesis

    NASA Technical Reports Server (NTRS)

    Hasselman, T. K.

    1972-01-01

    The damping method was applied successfully to real structures as well as analytical models. It depends on the ability to determine an appropriate modal damping matrix for each substructure. In the past, modal damping matrices were assumed diagonal for lack of being able to determine the coupling terms which are significant in the general case of nonproportional damping. This problem was overcome by formulating the damped equations of motion as a linear perturbation of the undamped equations for light structural damping. Damped modes are defined as complex vectors derived from the complex frequency response vectors of each substructure and are obtained directly from sinusoidal vibration tests. The damped modes are used to compute first order approximations to the modal damping matrices. The perturbation approach avoids ever having to solve a complex eigenvalue problem.

  19. Implicit emotion perception in schizophrenia.

    PubMed

    Trémeau, Fabien; Antonius, Daniel; Todorov, Alexander; Rebani, Yasmina; Ferrari, Kelsey; Lee, Sang Han; Calderone, Daniel; Nolan, Karen A; Butler, Pamela; Malaspina, Dolores; Javitt, Daniel C

    2015-12-01

    Explicit but not implicit facial emotion perception has been shown to be impaired in schizophrenia. In this study, we used newly developed technology in social neuroscience to examine implicit emotion processing. It has been shown that when people look at faces, they automatically infer social traits, and these trait judgments rely heavily on facial features and subtle emotion expressions even with neutral faces. Eighty-one individuals with schizophrenia or schizoaffective disorder and 62 control subjects completed a computer task with 30 well-characterized neutral faces. They rated each face on 10 trait judgments: attractive, mean, trustworthy, intelligent, dominant, fun, sociable, aggressive, emotionally stable and weird. The degree to which trait ratings were predicted by objectively-measured subtle emotion expressions served as a measure of implicit emotion processing. Explicit emotion recognition was also examined. Trait ratings were significantly predicted by subtle facial emotional expressions in controls and patients. However, impairment in the implicit emotion perception of fear, happiness, anger and surprise was found in patients. Moreover, these deficits were associated with poorer everyday problem-solving skills and were relatively independent of explicit emotion recognition. Implicit emotion processing is impaired in patients with schizophrenia or schizoaffective disorder. Deficits in implicit and explicit emotion perception independently contribute to the patients' poor daily life skills. More research is needed to fully understand the role of implicit and explicit processes in the functional deficits of patients, in order to develop targeted and useful remediation interventions. PMID:26473695

  20. Damping formulas and experimental values of damping in flutter models

    NASA Technical Reports Server (NTRS)

    Coleman, Robert P

    1940-01-01

    The problem of determining values of structural damping for use in flutter calculations is discussed. The concept of equivalent viscous damping is reviewed and its relation to the structural damping coefficient g introduced in NACA Technical Report No. 685 is shown. The theory of normal modes is reviewed and a number of methods are described for separating the motions associated with different modes. Equations are developed for use in evaluating the damping parameters from experimental data. Experimental results of measurements of damping in several flutter models are presented.

  1. Damping and spectral formation of upstream whistlers

    SciTech Connect

    Orlowski, D.S.; Russell, C.T.; Krauss-Varban, D.

    1995-09-01

    Previous studies have indicated that damping rates of upstream whistlers strongly depend on the details of the electron distribution function. Moreover, detailed analysis of Doppler shift and the whistler dispersion relation indicate that upstream whistlers propagate obliquely in a finite band of frequencies. In this paper we present results of a kinetic calculation of damping lengths of wideband whistlers using the sum of seven drifting bi-Maxwellian electron distributions as a best fit to the ISEE 1 electron data. For two cases, when upstream whistlers are observed, convective damping lengths derived from ISEE magnetic field and ephemeris data are compared with theoretical results. We find that the calculated convective damping lengths are consistent with the data and that upstream whistlers remain marginally stable. We also show that the slope of plasma frame spectra of upstream whistlers, obtained by direct fitting of the observed spectra, is between 5 and 7. The overall spectral, wave, and particle characteristics, proximity to the shock, as well as propagation and damping properties indicated that these waves cannot be generated locally. Instead, the observed upstream whistlers arise in the shock ramp, most likely by a variety of cross-field drift and/or anisotropy driven instabilities. 57 refs., 11 figs.

  2. Resolving photons from cosmic ray in DAMPE

    NASA Astrophysics Data System (ADS)

    Xu, Zunlei; Chang, Jin; Li, Xiang; Dong, TieKuang; Zang, Jingjing

    2016-07-01

    The Dark Matter Particle Explorer(DAMPE), which took to the skies on 17 December, is designed for high energy cosmic ray ion detection. The proportion of photons in the cosmic ray is very small, so it's difficult to distinguish between photons and 'background', but necessary for any DAMPE gamma-ray science goals.The paper present a algorithm to identify photons from 'background' mainly by the tracker/converter, which promote pair conversion and measure the directions of incident particles, and an anticoincidence detector,featuring an array of plastic scintillator to detect the charged particles.The method has been studied by simulating using the GEANT4 Monte Carlo simulation code and adjusted by the BeamTest at CERN in December,2014.In addition,DAMPE photon detection capabilities can be checked using the flight data.

  3. Turbine blade damping device with controlled loading

    SciTech Connect

    Marra, John J.

    2015-09-29

    A damping structure for a turbomachine rotor. The damping structure including an elongated snubber element including a first snubber end rigidly attached to a first blade and extending toward an adjacent second blade, and an opposite second snubber end positioned adjacent to a cooperating surface associated with the second blade. The snubber element has a centerline extending radially inwardly in a direction from the first blade toward the second blade along at least a portion of the snubber element between the first and second snubber ends. Rotational movement of the rotor effects relative movement between the second snubber end and the cooperating surface to position the second snubber end in frictional engagement with the cooperating surface with a predetermined damping force determined by a centrifugal force on the snubber element.

  4. Saturation of gyrokinetic turbulence through damped eigenmodes.

    PubMed

    Hatch, D R; Terry, P W; Jenko, F; Merz, F; Nevins, W M

    2011-03-18

    In the context of toroidal gyrokinetic simulations, it is shown that a hierarchy of damped modes is excited in the nonlinear turbulent state. These modes exist at the same spatial scales as the unstable eigenmodes that drive the turbulence. The larger amplitude subdominant modes are weakly damped and exhibit smooth, large-scale structure in velocity space and in the direction parallel to the magnetic field. Modes with increasingly fine-scale structure are excited to decreasing amplitudes. In aggregate, damped modes define a potent energy sink. This leads to an overlap of the spatial scales of energy injection and peak dissipation, a feature that is in contrast with more traditional turbulent systems. PMID:21469869

  5. Turbine blade damping device with controlled loading

    SciTech Connect

    Marra, John J

    2013-09-24

    A damping structure for a turbomachine rotor. The damping structure including an elongated snubber element including a first snubber end rigidly attached to a first blade and extending toward an adjacent second blade, and an opposite second snubber end positioned adjacent to a cooperating surface associated with the second blade. The snubber element has a centerline extending radially inwardly in a direction from the first blade toward the second blade along at least a portion of the snubber element between the first and second snubber ends. Rotational movement of the rotor effects relative movement between the second snubber end and the cooperating surface to position the second snubber end in frictional engagement with the cooperating surface with a predetermined damping force determined by a centrifugal force on the snubber element.

  6. Priming Implicit Prosody: Prosodic Boundaries and Individual Differences.

    PubMed

    Jun, Sun-Ah; Bishop, Jason

    2015-12-01

    Using the structural priming paradigm, the present study explores predictions made by the implicit prosody hypothesis (IPH) by testing whether an implicit prosodic boundary generated from a silently read sentence influences attachment preference for a novel, subsequently read sentence. Results indicate that such priming does occur, as evidenced by an effect on relative clause attachment. In particular, priming an implicit boundary directly before a relative clause--cued by commas in orthography--encouraged high attachment of that relative clause, although the size of the effect depended somewhat on individual differences in pragmatic/communication skills (as measured by the Autism Spectrum Quotient). Thus, in addition to supporting the basic claims of the IPH, the present study demonstrates the relevance of such individual differences to sentence processing, and that implicit prosodic structure, like syntactic structure, can be primed. PMID:27483740

  7. The Medial Temporal Lobe Supports Conceptual Implicit Memory

    PubMed Central

    Wang, Wei-Chun; Lazzara, Michele M.; Ranganath, Charan; Knight, Robert T.; Yonelinas, Andrew P.

    2010-01-01

    Summary The medial temporal lobe (MTL) is generally thought to be critical for explicit, but not implicit, memory. Here, we demonstrate that the perirhinal cortex (PRc), within the MTL, plays a role in conceptually-driven implicit memory. Amnesic patients with MTL lesions that converged on the left PRc exhibited deficits on two conceptual implicit tasks (i.e., exemplar generation and semantic decision). A separate functional magnetic resonance imaging (fMRI) study in healthy subjects indicated that PRc activation during encoding of words was predictive of subsequent exemplar generation. Moreover, across subjects, the magnitude of the fMRI and behavioral conceptual priming effects were directly related. Additionally, the PRc region implicated in the fMRI study was the same region of maximal lesion overlap in the patients with impaired conceptual priming. These patient and imaging results converge to suggest that the PRc plays a critical role in conceptual implicit memory, and possibly conceptual processing in general. PMID:21144998

  8. Relaxation damping in oscillating contacts

    PubMed Central

    Popov, M.; Popov, V.L.; Pohrt, R.

    2015-01-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed. PMID:26549011

  9. Relaxation damping in oscillating contacts

    NASA Astrophysics Data System (ADS)

    Popov, M.; Popov, V. L.; Pohrt, R.

    2015-11-01

    If a contact of two purely elastic bodies with no sliding (infinite coefficient of friction) is subjected to superimposed oscillations in the normal and tangential directions, then a specific damping appears, that is not dependent on friction or dissipation in the material. We call this effect “relaxation damping”. The rate of energy dissipation due to relaxation damping is calculated in a closed analytic form for arbitrary axially-symmetric contacts. In the case of equal frequency of normal and tangential oscillations, the dissipated energy per cycle is proportional to the square of the amplitude of tangential oscillation and to the absolute value of the amplitude of normal oscillation, and is dependent on the phase shift between both oscillations. In the case of low frequency tangential oscillations with superimposed high frequency normal oscillations, the dissipation is proportional to the ratio of the frequencies. Generalization of the results for macroscopically planar, randomly rough surfaces as well as for the case of finite friction is discussed.

  10. 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…

  11. Damping seals for turbomachinery

    NASA Technical Reports Server (NTRS)

    Vonpragenau, G. L.

    1982-01-01

    A rotor seal is proposed that restricts leakage like a labyrinth seal, but extends the stabilizing speed range beyond twice the first critical speed. The dynamic parameters were derived from bulk flow equations without requiring a dominant axial flow. The flow is considered incompressible and turbulent. Damping seals are shown to be feasible for extending the speed range of high performance turbomachinery beyond the limit imposed by conventional seals.

  12. An advanced implicit solver for MHD

    NASA Astrophysics Data System (ADS)

    Udrea, Bogdan

    A new implicit algorithm has been developed for the solution of the time-dependent, viscous and resistive single fluid magnetohydrodynamic (MHD) equations. The algorithm is based on an approximate Riemann solver for the hyperbolic fluxes and central differencing applied on a staggered grid for the parabolic fluxes. The algorithm employs a locally aligned coordinate system that allows the solution to the Riemann problems to be solved in a natural direction, normal to cell interfaces. The result is an original scheme that is robust and reduces the complexity of the flux formulas. The evaluation of the parabolic fluxes is also implemented using a locally aligned coordinate system, this time on the staggered grid. The implicit formulation employed by WARP3 is a two level scheme that was applied for the first time to the single fluid MHD model. The flux Jacobians that appear in the implicit scheme are evaluated numerically. The linear system that results from the implicit discretization is solved using a robust symmetric Gauss-Seidel method. The code has an explicit mode capability so that implementation and test of new algorithms or new physics can be performed in this simpler mode. Last but not least the code was designed and written to run on parallel computers so that complex, high resolution runs can be per formed in hours rather than days. The code has been benchmarked against analytical and experimental gas dynamics and MHD results. The benchmarks consisted of one-dimensional Riemann problems and diffusion dominated problems, two-dimensional supersonic flow over a wedge, axisymmetric magnetoplasmadynamic (MPD) thruster simulation and three-dimensional supersonic flow over intersecting wedges and spheromak stability simulation. The code has been proven to be robust and the results of the simulations showed excellent agreement with analytical and experimental results. Parallel performance studies showed that the code performs as expected when run on parallel

  13. 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.

  14. Methods for improving damping. Part 3: Damping material data

    NASA Astrophysics Data System (ADS)

    1992-12-01

    ESDU 92001 presents modulus and loss factor for 27 damping materials in the form of reduced temperature nomograms which allow the effects of frequency and temperature on those properties to be considered simultaneously. The data were supplied by 5 manufacturers, and their addresses in the UK and US are provided. The information is a necessary input in computational procedures, described in ESDU 91013, dealing with the application of layered damping treatments to beam- and plate-like structures. Notes are included on the measurement and reliability of the damping quantities that affect the variability allowances to be made when assessing a damping treatment for a particular application. Factors to be considered when selecting a damping material are discussed. Approximate relationships between the elastic properties of damping materials are given.

  15. Passively Damped Laminated Piezoelectric Shell Structures with Integrated Electric Networks

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitris A.

    1999-01-01

    Multi-field mechanics are presented for curvilinear piezoelectric laminates interfaced with distributed passive electric components. The equations of motion for laminated piezoelectric shell structures with embedded passive electric networks are directly formulated and solved using a finite element methodology. The modal damping and frequencies of the piezoelectric shell are calculated from the poles of the system. Experimental and numerical results are presented for the modal damping and frequency of composite beams with a resistively shunted piezoceramic patch. The modal damping and frequency of plates, cylindrical shells and cylindrical composite blades with piezoelectric-resistor layers are predicted. Both analytical and experimental studies illustrate a unique dependence of modal damping and frequencies on the shunting resistance and show the effect of structural shape and curvature on piezoelectric damping.

  16. Integrating Implicit Induction Proofs into Certified Proof Environments

    NASA Astrophysics Data System (ADS)

    Stratulat, Sorin

    We give evidence of the direct integration and automated checking of implicit induction-based proofs inside certified reasoning environments, as that provided by the Coq proof assistant. This is the first step of a long term project focused on 1) mechanically certifying implicit induction proofs generated by automated provers like Spike, and 2) narrowing the gap between automated and interactive proof techniques inside proof assistants such that multiple induction steps can be executed completely automatically and mutual induction can be treated more conveniently. Contrary to the current approaches of reconstructing implicit induction proofs into scripts based on explicit induction tactics that integrate the usual proof assistants, our checking methodology is simpler and fits better for automation. The underlying implicit induction principles are separated and validated independently from the proof scripts that consist in a bunch of one-to-one translations of implicit induction proof steps. The translated steps can be checked independently, too, so the validation process fits well for parallelisation and for the management of large proof scripts. Moreover, our approach is more general; any kind of implicit induction proof can be considered because the limitations imposed by the proof reconstruction techniques no longer exist. An implementation that integrates automatic translators for generating fully checkable Coq scripts from Spike proofs is reported.

  17. [Using the Implicit Association Test (IAT) to measure implicit shyness].

    PubMed

    Aikawa, Atsushi; Fujii, Tsutomu

    2011-04-01

    Previous research has shown that implicitly measured shyness predicted spontaneous shy behavior in social situations, while explicit self-ratings of shyness predicted controlled shy behavior (Asendorpf, Banse, & Mücke, 2002). The present study examined whether these same results would be replicated in Japan. In Study 1, college students (N=47) completed a shyness Implicit Association Test (IAT for shyness) and explicit self-ratings of shyness. In Study 2, friends (N=69) of the Study 1 participants rated those participants on various personality scales. Covariance structure analysis, revealed that only implicit self-concept measured by the shyness IAT predicted other-rated high interpersonal tension (spontaneous shy behavior). Also, only explicit self-concept predicted other-rated low praise seeking (controlled shy behavior). The results of this study are similar to the findings of the previous research. PMID:21706822

  18. Linking the river to the estuary: influence of river discharge on tidal damping

    NASA Astrophysics Data System (ADS)

    Cai, H.; Savenije, H. H. G.; Toffolon, M.

    2013-07-01

    The effect of river discharge on tidal damping in estuaries is explored within one consistent theoretical framework where analytical solutions are obtained by solving four implicit equations, i.e., the phase lag, the scaling, the damping and the celerity equation. In this approach the damping equation is obtained by subtracting the envelope curves of high water and low water occurrence, taking into account that the flow velocity consists of a tidal and river discharge component. Different approximations of the friction term are considered in deriving the damping equation, resulting in as many analytical solutions. In this framework it is possible to show that river discharge affects tidal damping primarily through the friction term. The application to the Modaomen and Yangtze estuaries demonstrates that the influence of river discharge on tidal damping can be significant in the upstream part of an estuary where the ratio of river flow to tidal flow amplitude is substantial. The analytical model is able to describe the main tidal dynamics with realistic roughness values in the upper part of the estuary, while a model with negligible river discharge can be made to fit observations only with unrealistically high roughness values. Moreover, the damping equation can be used to estimate river discharge on the basis of observed tidal damping, which makes the proposed analytical model a tool to obtain indirect information about quantities that are difficult to measure in the tidal region.

  19. Flux-driven algebraic damping of m = 1 diocotron mode

    NASA Astrophysics Data System (ADS)

    Chim, Chi Yung; O'Neil, Thomas M.

    2016-07-01

    Recent experiments with pure electron plasmas in a Malmberg-Penning trap have observed the algebraic damping of m = 1 diocotron modes. Transport due to small field asymmetries produces a low density halo of electrons moving radially outward from the plasma core, and the mode damping begins when the halo reaches the resonant radius r = Rw at the wall of the trap. The damping rate is proportional to the flux of halo particles through the resonant layer. The damping is related to, but distinct from, spatial Landau damping, in which a linear wave-particle resonance produces exponential damping. This paper explains with analytic theory the new algebraic damping due to particle transport by both mobility and diffusion. As electrons are swept around the "cat's eye" orbits of the resonant wave-particle interaction, they form a dipole (m = 1) density distribution. From this distribution, the electric field component perpendicular to the core displacement produces E × B-drift of the core back to the axis, that is, damps the m = 1 mode. The parallel component produces drift in the azimuthal direction, that is, causes a shift in the mode frequency.

  20. Damping measurements in flowing water

    NASA Astrophysics Data System (ADS)

    Coutu, A.; Seeley, C.; Monette, C.; Nennemann, B.; Marmont, H.

    2012-11-01

    Fluid-structure interaction (FSI), in the form of mass loading and damping, governs the dynamic response of water turbines, such as Francis turbines. Water added mass and damping are both critical quantities in evaluating the dynamic response of the turbine component. Although the effect of fluid added mass is well documented, fluid damping, a critical quantity to limit vibration amplitudes during service, and therefore to help avoiding possible failure of the turbines, has received much less attention in the literature. This paper presents an experimental investigation of damping due to FSI. The experimental setup, designed to create dynamic characteristics similar to the ones of Francis turbine blades is discussed, together with the experimental protocol and examples of measurements obtained. The paper concludes with the calculated damping values and a discussion on the impact of the observed damping behaviour on the response of hydraulic turbine blades to FSI.

  1. On damping mechanisms in beams

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Inman, D. J.

    1989-01-01

    A partial differential equation model of a cantilevered beam with a tip mass at its free end is used to study damping in a composite. Four separate damping mechanisms consisting of air damping, strain rate damping, spatial hysteresis and time hysteresis are considered experimentally. Dynamic tests were performed to produce time histories. The time history data is then used along with an approximate model to form a sequence of least squares problems. The solution of the least squares problem yields the estimated damping coefficients. The resulting experimentally determined analytical model is compared with the time histories via numerical simulation of the dynamic response. The procedure suggested here is compared with a standard modal damping ratio model commonly used in experimental modal analysis.

  2. Magnetically Damped Furnace (MDF)

    NASA Technical Reports Server (NTRS)

    1998-01-01

    The Magnetically Damped Furnace (MDF) breadboard is being developed in response to NASA's mission and goals to advance the scientific knowledge of microgravity research, materials science, and related technologies. The objective of the MDF is to dampen the fluid flows due to density gradients and surface tension gradients in conductive melts by introducing a magnetic field during the sample processing. The MDF breadboard will serve as a proof of concept that the MDF performance requirements can be attained within the International Space Station resource constraints.

  3. Propagation and damping of broadband upstream whistlers

    NASA Technical Reports Server (NTRS)

    Orlowski, D. S.; Russell, C. T.; Krauss-Varban, D.; Omidi, N.; Thomsen, M. F.

    1995-01-01

    Previous studies indicated that damping rates of upstream whistlers strongly depend on the details of the electron distribution function. Moreover, detailed analysis of Doppler-shift and whistler dispersion relation indicated that upstream whistlers propagate obliquely in a broad band. In this paper we present results of a kinetic calculation of damping lengths of wide-band whistlers using the sum of 7-drifting bi-Maxwellian electron distributions as a best fit to the International Sun Earth Explorer (ISEE) 1 electron data. For 2 cases, when upstream whistlers are observed, convective damping lengths derived from ISEE magnetic field and ephemeris data are compared with theoretical results. We find that the calculated convective damping lengths are consistent with the data and that upstream whistlers remain marginally stable. We also show that the slope of plasma frame spectra of upstream whistlers, obtained by direct fitting of the observed spectra is between 5 and 7 with a sharp lower frequency cutoff corresponding to a wavelength of about one ion inertial length. When the solar wind velocity is directed largely along the wave normal of the upstream whistlers the polariztion of the right hand waves becomes reversed and low frequencies are switched to high resulting in a peaked spectrum with a strong high frequency cutoff. The overall spectral, wave and particle characteristics, proximity to the shock as well as propagation and damping properties indicate that these waves cannot be generated locally. Instead the observed upstream whistlers arise in the shock ramp most likely by a variety of cross-field drift and/or anisotropy driven instabilities.

  4. Asymptotic behavior of tidal damping in alluvial estuaries

    NASA Astrophysics Data System (ADS)

    Cai, Huayang; Savenije, Hubert H. G.

    2013-11-01

    Tidal wave propagation can be described analytically by a set of four implicit equations, i.e., the phase lag equation, the scaling equation, the damping equation, and the celerity equation. It is demonstrated that this system of equations has an asymptotic solution for an infinite channel, reflecting the balance between friction and channel convergence. Subsequently, explicit expressions for the tidal amplitude and velocity amplitude are derived, which are different from the generally assumed exponential damping equation that follows from linearizing the friction term. Analysis of the asymptotic behavior demonstrates that exponential damping of the tidal amplitude is only correct for a frictionless wave or an ideal estuary (no damping). However, in estuaries with modest damping (near ideal) it provides a reasonable approximation. In natural estuaries, there is generally a need to take account of local variability of, e.g., depth and friction, by subdividing the estuary into multiple reaches. This is illustrated with an example of the Scheldt estuary, which has been gradually deepened for navigation purpose over the last half century. The analytical model is used to study the effect of this deepening on the tidal dynamics in the main navigation channel, demonstrating that the navigation channel will become "overamplified" when it reaches a depth larger than the critical depth. In the case of overamplification, a further increase of the depth reduces the amplification until critical convergence (condition for a frictionless standing wave) is reached asymptotically. Finally, based on the ratio between the tidal amplitude at the seaward boundary and the asymptotic tidal amplitude, estuaries can be classified into damped, amplified, or ideal estuaries, which is illustrated with 23 real estuaries.

  5. The Joint Damping Experiment (JDX)

    NASA Technical Reports Server (NTRS)

    Folkman, Steven L.; Bingham, Jeff G.; Crookston, Jess R.; Dutson, Joseph D.; Ferney, Brook D.; Ferney, Greg D.; Rowsell, Edwin A.

    1997-01-01

    The Joint Damping Experiment (JDX), flown on the Shuttle STS-69 Mission, is designed to measure the influence of gravity on the structural damping of a high precision three bay truss. Principal objectives are: (1) Measure vibration damping of a small-scale, pinjointed truss to determine how pin gaps give rise to gravity-dependent damping rates; (2) Evaluate the applicability of ground and low-g aircraft tests for predicting on-orbit behavior; and (3) Evaluate the ability of current nonlinear finite element codes to model the dynamic behavior of the truss. Damping of the truss was inferred from 'Twang' tests that involve plucking the truss structure and recording the decay of the oscillations. Results are summarized as follows. (1) Damping, rates can change by a factor of 3 to 8 through changing the truss orientation; (2) The addition of a few pinned joints to a truss structure can increase the damping by a factor as high as 30; (3) Damping is amplitude dependent; (4) As gravity induced preloads become large (truss long axis perpendicular to gravity vector) the damping is similar to non-pinjointed truss; (5) Impacting in joints drives higher modes in structure; (6) The torsion mode disappears if gravity induced preloads are low.

  6. New concepts for damping rings

    SciTech Connect

    Raimondi, P.; Wolski, A.

    2002-05-30

    The requirements for very low emittance and short damping time in the damping rings of future linear colliders, naturally lead to very small beta functions and dispersion in the ring arcs. This makes it difficult to make chromatic correction while maintaining good dynamics. We have therefore developed a lattice with very simple arcs (designed to give the best product of emittance and damping time), and with separate chromatic correction in a dedicated section. The chromatic correction is achieved using a series of non-interleaved sextupole pairs. The performance of such a solution is comparable to that of current damping ring designs, while there are a number of potential advantages.

  7. Posture modulates implicit hand maps.

    PubMed

    Longo, Matthew R

    2015-11-01

    Several forms of somatosensation require that afferent signals be informed by stored representations of body size and shape. Recent results have revealed that position sense relies on a highly distorted body representation. Changes of internal hand posture produce plastic alterations of processing in somatosensory cortex. This study therefore investigated how such postural changes affect implicit body representations underlying position sense. Participants localised the knuckles and tips of each finger in external space in two postures: the fingers splayed (Apart posture) or pressed together (Together posture). Comparison of the relative locations of the judgments of each landmark were used to construct implicit maps of represented hand structure. Spreading the fingers apart produced increases in the implicit representation of hand size, with no apparent effect on hand shape. Thus, changes of internal hand posture produce rapid modulation of how the hand itself is represented, paralleling the known effects on somatosensory cortical processing. PMID:26117153

  8. Active Damping Using Distributed Anisotropic Actuators

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Cabell, Randolph H.; Quinones, Juan D.; Wier, Nathan C.

    2010-01-01

    A helicopter structure experiences substantial high-frequency mechanical excitation from powertrain components such as gearboxes and drive shafts. The resulting structure-borne vibration excites the windows which then radiate sound into the passenger cabin. In many cases the radiated sound power can be reduced by adding damping. This can be accomplished using passive or active approaches. Passive treatments such as constrained layer damping tend to reduce window transparency. Therefore this paper focuses on an active approach utilizing compact decentralized control units distributed around the perimeter of the window. Each control unit consists of a triangularly shaped piezoelectric actuator, a miniature accelerometer, and analog electronics. Earlier work has shown that this type of system can increase damping up to approximately 1 kHz. However at higher frequencies the mismatch between the distributed actuator and the point sensor caused control spillover. This paper describes new anisotropic actuators that can be used to improve the bandwidth of the control system. The anisotropic actuators are composed of piezoelectric material sandwiched between interdigitated electrodes, which enables the application of the electric field in a preferred in-plane direction. When shaped correctly the anisotropic actuators outperform traditional isotropic actuators by reducing the mismatch between the distributed actuator and point sensor at high frequencies. Testing performed on a Plexiglas panel, representative of a helicopter window, shows that the control units can increase damping at low frequencies. However high frequency performance was still limited due to the flexible boundary conditions present on the test structure.

  9. Measurement of damping of graphite expoxy materials

    NASA Technical Reports Server (NTRS)

    Crocker, M. J.

    1985-01-01

    During this period damping measurements were made on the cylindrical graphite epoxy specimen using the forced-vibration test method. The specimen was carefully mounted directly on the shaker through the supporting ring and the impedance head. This was done to simulate an idealized free-free boundary condition at the two edges. The damping ratio value and the natural frequency (first mode) obtained in this experiment were 0.13% and 508.75 Hz respectively. In order to check the damping induced by the supporting ring, measurements were made with the top half of the ring removed. The specimen then was supported only by the bottom half of the ring (half ring). It was observed that the natural frequency of the specimen (first mode) increased of a value of 552.5 Hz due to the influence of the reduced mass of the supporting ring. But the damping ratio value obtained was the same as that obtained with full supporting ring, namely 0.13%.

  10. Active damping of spacecraft structural appendage vibrations

    NASA Technical Reports Server (NTRS)

    Fedor, Joseph V. (Inventor)

    1990-01-01

    An active vibration damper system, for bending in two orthogonal directions and torsion, in each of three mutually perpendicular axes is located at the extremities of the flexible appendages of a space platform. The system components for each axis includes: an accelerometer, filtering and signal processing apparatus, and a DC motor-inertia wheel torquer. The motor torquer, when driven by a voltage proportional to the relative vibration tip velocity, produces a reaction torque for opposing and therefore damping a specific modal velocity of vibration. The relative tip velocity is obtained by integrating the difference between the signal output from the accelerometer located at the end of the appendage with the output of a usually carried accelerometer located on a relatively rigid body portion of the space platform. A selector switch, with sequential stepping logic or highest modal vibration energy logic, steps to another modal tip velocity channel and receives a signal voltage to damp another vibration mode. In this manner, several vibration modes can be damped with a single sensor/actuator pair. When a three axis damper is located on each of the major appendages of the platform, then all of the system vibration modes can be effectively damped.

  11. The DAMPE mission

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Guo, Jianhua; Chang, Jin; Cai, Mingsheng

    2016-07-01

    The DArk Matter Particle Explorer (DAMPE) was launched into space on Dec.17, 2015 to a 500km dawn-to-dusk sun-synchronous orbit aiming at detecting high energy electron(gamma) as well as cosmic heavy ions up to 10TeV and 1PeV respectively to try to understand the mechanisms of particle acceleration in celestial sources and the propagation of cosmic rays in the Galaxy, to probe the nature of dark matter, a form of matter necessary to account for gravitational effects observed in very large scale structures such as anomalies in the rotation of galaxies and the gravitational lensing of light by galaxy clusters that cannot be accounted for by the quantity of observed matter , and to study the high-energy behavior of gamma-ray bursts, pulsars, Active Galaxy Nuclei and other transients,etc. After months' commissioning, DAMPE has been in the observational mode. This paper reports the status of its detectors and latest results collected so far.

  12. On the computational efficiency of particle dynamics simulations in the radiation belt: comparison between implicit and semi-implicit schemes

    NASA Astrophysics Data System (ADS)

    Camporeale, E.; Delzanno, G.; Zaharia, S. G.; Koller, J.

    2012-12-01

    The particle dynamics in the Earth's radiation belt is generally modeled by means of a two-dimensional diffusion equation for the particle distribution function in energy and pitch angle. In this work we survey and compare different numerical schemes for the solution of the diffusion equation, with the goal of outlining which is the optimal strategy from a numerical point of view. We focus on the general (and more computationally challenging) case where the mixed terms in the diffusion tensor are retained. We compare fully-implicit and semi-implicit schemes. For the former we have analyzed a direct solver based on a LU decomposition routine for sparse matrices, and an iterative ILU-preconditioned GMRES. For the semi-implicit scheme we have studied an Alternating Direction Implicit scheme. We present a convergence study for a realistic case that shows that the timestep and grid size are strongly constrained by the desired accuracy of the solution. We show that the fully-implicit scheme is to be preferred in most cases as the more computationally efficient.

  13. On the numerical simulation of particle dynamics in the radiation belt: 1. Implicit and semi-implicit schemes

    NASA Astrophysics Data System (ADS)

    Camporeale, E.; Delzanno, G. L.; Zaharia, S.; Koller, J.

    2013-06-01

    The particle dynamics in the Earth's radiation belt is generally modeled by means of a two-dimensional diffusion equation for the particle distribution function in energy and pitch angle. The goal of this paper is to survey and compare different numerical schemes for the solution of the diffusion equation, and to outline the optimal strategy from a numerical point of view. We focus on the general (and more computationally challenging) case where the mixed terms in the diffusion tensor are retained. In Part 1, we compare fully implicit and semi-implicit schemes. For the former, we have analyzed a direct solver based on a LU decomposition routine for sparse matrices, and an iterative incomplete LU preconditioned Generalized Minimal REsidual solver. For the semi-implicit scheme, we have studied an alternating direction implicit scheme. We present a convergence study for a realistic case that shows that the time step and grid size are strongly constrained by the desired accuracy of the solution. We show that the fully implicit scheme is to be preferred in most cases as the more computationally efficient.

  14. The Latest Results from DAMPE

    NASA Astrophysics Data System (ADS)

    Chang, Jin

    2016-07-01

    DArk Matter Particle Explorer (DAMPE) successfully launched on Dec.17, 2015 is the first Chinese astronomical satellite that can measure 2 GeV-10 TeV electrons and gamma-rays with unprecedented energy resolution. In this talk I will introduce the design, the beam-test, the on-orbit calibration and some preliminary results of DAMPE.

  15. Damping Vibration at an Impeller

    NASA Technical Reports Server (NTRS)

    Hager, J. A.; Rowan, B. F.

    1982-01-01

    Vibration of pump shaft is damped at impeller--where vibration-induced deflections are greatest--by shroud and seal. Damping reduces vibrational motion of shaft at bearings and load shaft places on them. Flow through clearance channel absorbs vibration energy.

  16. Surge-damping vacuum valve

    DOEpatents

    Bullock, Jack C.; Kelly, Benjamin E.

    1980-01-01

    A valve having a mechanism for damping out flow surges in a vacuum system which utilizes a slotted spring-loaded disk positioned adjacent the valve's vacuum port. Under flow surge conditions, the differential pressure forces the disk into sealing engagement with the vacuum port, thereby restricting the flow path to the slots in the disk damping out the flow surge.

  17. Damping seal verification setup

    NASA Technical Reports Server (NTRS)

    Cappel, K. L.

    1985-01-01

    The heart of the Space Shuttle Main Engine (SSME) is a set of turbopumps that propel cryogenic fluids at very high pressures and flow rates, at rotor speeds up to 37,000 rpm. Bushing seals that cause the flow in the fluid film to become turbulent, by means of a multiplicity of pockets, were shown theoretically not only to inhibit subsynchronous whirl, but to reduce leakage as well. However, experimental data that relate these two desirable characteristics to such parameters as pocket depth, Reynolds number (based on clearance and axial flow rate), and rotating speed are limited. To obtain the required data, NASA's Marshall Space Flight Center (MSFC) commissioned Wyle Laboratories to design, build and operate a test rig in which the damping efficacy and leakage reduction of typical candidate seals are to be evaluated.

  18. Photon and electron Landau damping in quantum plasmas

    NASA Astrophysics Data System (ADS)

    Mendonça, J. T.; Serbeto, A.

    2016-09-01

    Using a quantum kinetic description, we establish a general expression for the dispersion relation of electron plasma waves in the presence of an arbitrary spectrum of electromagnetic waves. This includes both electron and photon Landau damping. The quantum kinetic description allows us to compare directly these two distinct processes, and to show that they are indeed quite similar. The present work also extends previous results on photon Landau damping onto the quantum domain.

  19. Damping measurements using operational data

    SciTech Connect

    James, G.H.; Carne, T.G.; Veers, P.S.

    1996-08-01

    The authors have measured modal damping using strain-gauge data from an operating wind turbine. This new technique for measuring modal damping is easier and less expensive than previously used methods. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. The authors have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-m Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control.

  20. Changing theories of change: strategic shifting in implicit theory endorsement.

    PubMed

    Leith, Scott A; Ward, Cindy L P; Giacomin, Miranda; Landau, Enoch S; Ehrlinger, Joyce; Wilson, Anne E

    2014-10-01

    People differ in their implicit theories about the malleability of characteristics such as intelligence and personality. These relatively chronic theories can be experimentally altered, and can be affected by parent or teacher feedback. Little is known about whether people might selectively shift their implicit beliefs in response to salient situational goals. We predicted that, when motivated to reach a desired conclusion, people might subtly shift their implicit theories of change and stability to garner supporting evidence for their desired position. Any motivated context in which a particular lay theory would help people to reach a preferred directional conclusion could elicit shifts in theory endorsement. We examine a variety of motivated situational contexts across 7 studies, finding that people's theories of change shifted in line with goals to protect self and liked others and to cast aspersions on disliked others. Studies 1-3 demonstrate how people regulate their implicit theories to manage self-view by more strongly endorsing an incremental theory after threatening performance feedback or memories of failure. Studies 4-6 revealed that people regulate the implicit theories they hold about favored and reviled political candidates, endorsing an incremental theory to forgive preferred candidates for past gaffes but leaning toward an entity theory to ensure past failings "stick" to opponents. Finally, in Study 7, people who were most threatened by a previously convicted child sex offender (i.e., parents reading about the offender moving to their neighborhood) gravitated most to the entity view that others do not change. Although chronic implicit theories are undoubtedly meaningful, this research reveals a previously unexplored source of fluidity by highlighting the active role people play in managing their implicit theories in response to goals. PMID:25222649

  1. Damping Bearings In High-Speed Turbomachines

    NASA Technical Reports Server (NTRS)

    Von Pragenau, George L.

    1994-01-01

    Paper presents comparison of damping bearings with traditional ball, roller, and hydrostatic bearings in high-speed cryogenic turbopumps. Concept of damping bearings described in "Damping Seals and Bearings for a Turbomachine" (MFS-28345).

  2. Implicit Cognition and the Maintenance and Treatment of Major Depression

    ERIC Educational Resources Information Center

    Friedman, Michael A.; Whisman, Mark A.

    2004-01-01

    Although extensive research has identified the role of consciously expressed cognition in the onset and maintenance of depression, much less work has directly examined the role of nonconscious, automatic, implicit cognition biases and depression. Further, whereas there is evidence of changes in self-report measures of cognition following cognitive…

  3. Semantic Generalization in Implicit Language Learning

    ERIC Educational Resources Information Center

    Paciorek, Albertyna; Williams, John N.

    2015-01-01

    Despite many years of investigation into implicit learning in nonlinguistic domains, the potential for implicit learning to deliver the kinds of generalizations that underlie natural language competence remains unclear. In a series of experiments, we investigated implicit learning of the semantic preferences of novel verbs, specifically, whether…

  4. Measuring individual differences in implicit cognition: the implicit association test.

    PubMed

    Greenwald, A G; McGhee, D E; Schwartz, J L

    1998-06-01

    An implicit association test (IAT) measures differential association of 2 target concepts with an attribute. The 2 concepts appear in a 2-choice task (2-choice task (e.g., flower vs. insect names), and the attribute in a 2nd task (e.g., pleasant vs. unpleasant words for an evaluation attribute). When instructions oblige highly associated categories (e.g., flower + pleasant) to share a response key, performance is faster than when less associated categories (e.g., insect & pleasant) share a key. This performance difference implicitly measures differential association of the 2 concepts with the attribute. In 3 experiments, the IAT was sensitive to (a) near-universal evaluative differences (e.g., flower vs. insect), (b) expected individual differences in evaluative associations (Japanese + pleasant vs. Korean + pleasant for Japanese vs. Korean subjects), and (c) consciously disavowed evaluative differences (Black + pleasant vs. White + pleasant for self-described unprejudiced White subjects). PMID:9654756

  5. Distinct developmental trajectories for explicit and implicit timing.

    PubMed

    Droit-Volet, Sylvie; Coull, Jennifer T

    2016-10-01

    Adults and children aged 5 and 8years were given explicit and implicit timing tasks. These tasks were based on the same temporal representation (the temporal interval between two signals), but in the explicit task participants received overt instructions to judge the duration of the interval, whereas in the implicit task they did not receive any temporal instructions and were asked only to press as quickly as possible after the second signal. In addition, participants' cognitive capacities were assessed with different neuropsychological tests. The results showed that temporal variability (i.e., the spread of performance around the reference interval) decreased as a function of age in the explicit task, being higher in the 5-year-olds than in the 8-year-olds and adults. The higher variability in the youngest children was directly linked to their limited cognitive capacity. By contrast, temporal variability in the implicit timing task remained constant across the different age groups and was unrelated to cognitive capacity. Processing of time, therefore, was independent of age in the implicit task but changed with age in the explicit task, thereby demonstrating distinct developmental trajectories for explicit and implicit timing. PMID:27295205

  6. Implicit measures in social cognition. research: their meaning and use.

    PubMed

    Fazio, Russell H; Olson, Michael A

    2003-01-01

    Behavioral scientists have long sought measures of important psychological constructs that avoid response biases and other problems associated with direct reports. Recently, a large number of such indirect, or "implicit," measures have emerged. We review research that has utilized these measures across several domains, including attitudes, self-esteem, and stereotypes, and discuss their predictive validity, their interrelations, and the mechanisms presumably underlying their operation. Special attention is devoted to various priming measures and the Implicit Association Test, largely due to their prevalence in the literature. We also attempt to clarify several unresolved theoretical and empirical issues concerning implicit measures, including the nature of the underlying constructs they purport to measure, the conditions under which they are most likely to relate to explicit measures, the kinds of behavior each measure is likely to predict, their sensitivity to context, and the construct's potential for change. PMID:12172003

  7. Angular biasing in implicit Monte-Carlo

    SciTech Connect

    Zimmerman, G.B.

    1994-10-20

    Calculations of indirect drive Inertial Confinement Fusion target experiments require an integrated approach in which laser irradiation and radiation transport in the hohlraum are solved simultaneously with the symmetry, implosion and burn of the fuel capsule. The Implicit Monte Carlo method has proved to be a valuable tool for the two dimensional radiation transport within the hohlraum, but the impact of statistical noise on the symmetric implosion of the small fuel capsule is difficult to overcome. We present an angular biasing technique in which an increased number of low weight photons are directed at the imploding capsule. For typical parameters this reduces the required computer time for an integrated calculation by a factor of 10. An additional factor of 5 can also be achieved by directing even smaller weight photons at the polar regions of the capsule where small mass zones are most sensitive to statistical noise.

  8. Formation and damping of relativistic strong shocks

    NASA Astrophysics Data System (ADS)

    Anile, A. M.; Miller, J. C.; Motta, S.

    1983-06-01

    Results are presented from a detailed study of the formation of strong relativistic shocks from simple waves and their subsequent damping. Basic results in relativistic hydrodynamics are first reviewed, and the transport equation for the shock amplitude is derived which permits the exact calculation of the characteristic damping time for an arbitrary initial shock profile. A basic formalism for the numerical treatment of the problem is set up using a Lagrangian formulation with the rest mass as a distance coordinate. Some results derived directly from the Rankine-Hugoniot relations are presented, and numerical results are given for the case of a purely compressive initial sine pulse propagating into a static uniform medium. The calculations confirm the qualitative nature of the effect fund by Liang and Baker (1977).

  9. 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. PMID:26471802

  10. Analytical Modeling of Squeeze Film Damping in Dual Axis Torsion Microactuators

    NASA Astrophysics Data System (ADS)

    Moeenfard, Hamid

    2015-10-01

    In this paper, problem of squeeze film damping in dual axis torsion microactuators is modeled and closed form expressions are provided for damping torques around tilting axes of the actuator. The Reynolds equation which governs the pressure distribution underneath the actuator is linearized. The resulting equation is then solved analytically. The obtained pressure distribution is used to calculate the normalized damping torques around tilting axes of the actuator. Dependence of the damping torques on the design parameters of the dual axis torsion actuator is studied. It is observed that with proper selection of the actuator's aspect ratio, damping torque along one of the tilting directions can be eliminated. It is shown that when the tilting angles of the actuator are small, squeeze film damping would act like a linear viscous damping. The results of this paper can be used for accurate dynamical modeling and control of torsion dual axis microactuators.

  11. Theoretical study of interfacial damping in perpendicular anisotropy superlattices along multiple crystal orientations

    NASA Astrophysics Data System (ADS)

    Qu, T.; Victora, R. H.

    2016-06-01

    Damping, representing the loss of magnetic energy from the electrons to the lattice through the spin-orbit interaction, is calculated for Co/Pt and Co/Pd superlattices grown along the (001), (111), and (011) orientations. The damping consists of two contributions: interfacial and, usually, bulk. The interfacial damping shows dependence on the superlattice orientation. The origin of the interfacial damping is due to both the distorted electronic states at the interface and the spin-orbit interaction in the weakly polarized nonmagnetic Pt/Pd layers deposited on Co layers. The density of states around the Fermi level provides the spin-flip channels and closely correlates with the damping value. The damping shows asymmetry in the two transverse directions of the spin for spins at most angles. The damping for out-of-plane magnetization can be as much as 1.7 times larger than that of in-plane magnetization.

  12. Semi-implicit and fully implicit shock-capturing methods for hyperbolic conservation laws with stiff source terms

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Shinn, J. L.

    1986-01-01

    Some numerical aspects of finite-difference algorithms for nonlinear multidimensional hyperbolic conservation laws with stiff nonhomogenous (source) terms are discussed. If the stiffness is entirely dominated by the source term, a semi-implicit shock-capturing method is proposed provided that the Jacobian of the soruce terms possesses certain properties. The proposed semi-implicit method can be viewed as a variant of the Bussing and Murman point-implicit scheme with a more appropriate numerical dissipation for the computation of strong shock waves. However, if the stiffness is not solely dominated by the source terms, a fully implicit method would be a better choice. The situation is complicated by problems that are higher than one dimension, and the presence of stiff source terms further complicates the solution procedures for alternating direction implicit (ADI) methods. Several alternatives are discussed. The primary motivation for constructing these schemes was to address thermally and chemically nonequilibrium flows in the hypersonic regime. Due to the unique structure of the eigenvalues and eigenvectors for fluid flows of this type, the computation can be simplified, thus providing a more efficient solution procedure than one might have anticipated.

  13. Semi-implicit and fully implicit shock-capturing methods for hyperbolic conservation laws with stiff source terms

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Shinn, Judy L.

    1987-01-01

    Some numerical aspects of finite-difference algorithms for nonlinear multidimensional hyperbolic conservation laws with stiff nonhomogeneous (source) terms are discussed. If the stiffness is entirely dominated by the source term, a semi-implicit shock-capturing method is proposed provided that the Jacobian of the source terms possesses certain properties. The proposed semi-implicit method can be viewed as a variant of the Bussing and Murman point-implicit scheme with a more appropriate numerical dissipation for the computation of strong shock waves. However, if the stiffness is not solely dominated by the source terms, a fully implicit method would be a better choice. The situation is complicated by problems that are higher than one dimension, and the presence of stiff source terms further complicates the solution procedures for alternating direction implicit (ADI) methods. Several alternatives are discussed. The primary motivation for constructing these schemes was to address thermally and chemically nonequilibrium flows in the hypersonic regime. Due to the unique structure of the eigenvalues and eigenvectors for fluid flows of this type, the computation can be simplified, thus providing a more efficient solution procedure than one might have anticipated.

  14. Self-Damping Sprung Wheel

    NASA Technical Reports Server (NTRS)

    Weddendorf, Bruce

    1993-01-01

    Self-damping sprung wheel provides shock-absorbing suspension for wheelchair, reducing user's discomfort when traversing rough terrain or obstacles. Pair of self-damping sprung wheels installed in place of conventional large rear wheels of standard wheelchair, which user operates in conventional manner. Rim deflects in vicinity of contact with ground or floor. Includes inner and outer hoops bending when obstacle encountered. Shear deformation of elastomeric hoop between them absorbs energy. Thus, three hoops act together as damping spring. Alternative version of wheel designed for bicycle.

  15. Universal single level implicit algorithm for gasdynamics

    NASA Technical Reports Server (NTRS)

    Lombard, C. K.; Venkatapthy, E.

    1984-01-01

    A single level effectively explicit implicit algorithm for gasdynamics is presented. The method meets all the requirements for unconditionally stable global iteration over flows with mixed supersonic and supersonic zones including blunt body flow and boundary layer flows with strong interaction and streamwise separation. For hyperbolic (supersonic flow) regions the method is automatically equivalent to contemporary space marching methods. For elliptic (subsonic flow) regions, rapid convergence is facilitated by alternating direction solution sweeps which bring both sets of eigenvectors and the influence of both boundaries of a coordinate line equally into play. Point by point updating of the data with local iteration on the solution procedure at each spatial step as the sweeps progress not only renders the method single level in storage but, also, improves nonlinear accuracy to accelerate convergence by an order of magnitude over related two level linearized implicit methods. The method derives robust stability from the combination of an eigenvector split upwind difference method (CSCM) with diagonally dominant ADI(DDADI) approximate factorization and computed characteristic boundary approximations.

  16. Revealing children's implicit spelling representations.

    PubMed

    Critten, Sarah; Pine, Karen J; Messer, David J

    2013-06-01

    Conceptualizing the underlying representations and cognitive mechanisms of children's spelling development is a key challenge for literacy researchers. Using the Representational Redescription model (Karmiloff-Smith), Critten, Pine and Steffler (2007) demonstrated that the acquisition of phonological and morphological knowledge may be underpinned by increasingly explicit levels of spelling representation. However, their proposal that implicit representations may underlie early 'visually based' spelling remains unresolved. Children (N = 101, aged 4-6 years) were given a recognition task (Critten et al., 2007) and a novel production task, both involving verbal justifications of why spellings are correct/incorrect, strategy use and word pattern similarity. Results for both tasks supported an implicit level of spelling characterized by the ability to correctly recognize/produce words but the inability to explain operational strategies or generalize knowledge. Explicit levels and multiple representations were also in evidence across the two tasks. Implications for cognitive mechanisms underlying spelling development are discussed. PMID:23659891

  17. Measurements of Aerodynamic Damping in the MIT Transonic Rotor

    NASA Technical Reports Server (NTRS)

    Crawley, E. F.

    1981-01-01

    A method was developed and demonstrated for the direct measurement of aerodynamic forcing and aerodynamic damping of a transonic compressor. The method is based on the inverse solution of the structural dynamic equations of motion of the blade disk system in order to determine the forces acting on the system. The disturbing and damping forces acting on a given blade are determined if the equations of motion are expressed in individual blade coordinates. If the structural dynamic equations are transformed to multiblade coordinates, the damping can be measured for blade disk modes, and related to a reduced frequency and interblade phase angle. In order to measure the aerodynamic damping in this way, the free response to a known excitation is studied.

  18. Ego depletion impairs implicit learning.

    PubMed

    Thompson, Kelsey R; Sanchez, Daniel J; Wesley, Abigail H; Reber, Paul J

    2014-01-01

    Implicit skill learning occurs incidentally and without conscious awareness of what is learned. However, the rate and effectiveness of learning may still be affected by decreased availability of central processing resources. Dual-task experiments have generally found impairments in implicit learning, however, these studies have also shown that certain characteristics of the secondary task (e.g., timing) can complicate the interpretation of these results. To avoid this problem, the current experiments used a novel method to impose resource constraints prior to engaging in skill learning. Ego depletion theory states that humans possess a limited store of cognitive resources that, when depleted, results in deficits in self-regulation and cognitive control. In a first experiment, we used a standard ego depletion manipulation prior to performance of the Serial Interception Sequence Learning (SISL) task. Depleted participants exhibited poorer test performance than did non-depleted controls, indicating that reducing available executive resources may adversely affect implicit sequence learning, expression of sequence knowledge, or both. In a second experiment, depletion was administered either prior to or after training. Participants who reported higher levels of depletion before or after training again showed less sequence-specific knowledge on the post-training assessment. However, the results did not allow for clear separation of ego depletion effects on learning versus subsequent sequence-specific performance. These results indicate that performance on an implicitly learned sequence can be impaired by a reduction in executive resources, in spite of learning taking place outside of awareness and without conscious intent. PMID:25275517

  19. [Psychological theory and implicit sociology.].

    PubMed

    Sévigny, R

    1983-01-01

    This text is based on the hypothesis that every theory on the psychology of personality must inevitably, in one manner or another, have a sociological referent, that is to say, it must refer to a body of knowledge which deals with a diversity of social contexts and their relations to individuals. According to this working hypothesis, such a sociology is implicit. This text then discusses a group of theoretical approaches in an effort to verify this hypothesis. This approach allows the extrication of diverse forms or diverse expressions of this implicit sociology within this context several currents are rapidly explored : psychoanalysis, behaviorism, gestalt, classical theory of needs. The author also comments on the approach, inspired by oriental techniques or philosophies, which employs the notion of myth to deepen self awareness. Finally, from the same perspective, he comments at greater length on the work of Carl Rogers, highlighting the diverse form of implicit sociology. In addition to Carl Rogers, this text refers to Freud, Jung, Adler, Reich, Perls, Goodman, Skinner as well as to Ginette Paris and various analysts of Taoism. In conclusion, the author indicates the significance of his analysis from double viewpoint of psychological theory and practice. PMID:17093766

  20. Enhancing the damping of wind turbine rotor blades, the DAMPBLADE project

    NASA Astrophysics Data System (ADS)

    Chaviaropoulos, P. K.; Politis, E. S.; Lekou, D. J.; Sørensen, N. N.; Hansen, M. H.; Bulder, B. H.; Winkelaar, D.; Lindenburg, C.; Saravanos, D. A.; Philippidis, T. P.; Galiotis, C.; Hansen, M. O. L.; Kossivas, T.

    2006-01-01

    A research programme enabling the development of damped wind turbine blades, having the acronym DAMPBLADE, has been supported by the EC under its 5th Framework Programme. In DAMPBLADE the following unique composite damping mechanisms were exploited aiming to increase the structural damping: tailoring of laminate damping anisotropy, damping layers and damped polymer matrices. Additional objectives of the project were the development of the missing critical analytical technologies enabling the explicit modelling of composite structural damping and a novel composite blade design capacity enabling the direct prediction of aeroelastic stability and fatigue life; the development and characterization of damped composite materials; and the evaluation of new technology via the design and fabrication of damped prototype blades and their full-scale laboratory testing. After 4 years of work a 19 m glass/polyester damped blade was designed, manufactured and tested using the know-how acquired. Modal analysis of this blade at the testing facility of CRES showed a nearly 80% increase in the damping ratio of both the first flap and lag modes compared with the earlier, standard, design practice. Copyright

  1. Gilbert damping in noncollinear ferromagnets.

    PubMed

    Yuan, Zhe; Hals, Kjetil M D; Liu, Yi; Starikov, Anton A; Brataas, Arne; Kelly, Paul J

    2014-12-31

    The precession and damping of a collinear magnetization displaced from its equilibrium are well described by the Landau-Lifshitz-Gilbert equation. The theoretical and experimental complexity of noncollinear magnetizations is such that it is not known how the damping is modified by the noncollinearity. We use first-principles scattering theory to investigate transverse domain walls (DWs) of the important ferromagnetic alloy Ni80Fe20 and show that the damping depends not only on the magnetization texture but also on the specific dynamic modes of Bloch and Néel DWs in ways that were not theoretically predicted. Even in the highly disordered Ni80Fe20 alloy, the damping is found to be remarkably nonlocal. PMID:25615368

  2. Damping measurements using operational data

    SciTech Connect

    James, G.H.; Carne, T.G.; Veers, P.S.

    1991-01-01

    We have measured modal damping using strain-gauge data from an operating wind turbine. Previously, such measurements were difficult and expensive. Auto-correlation and cross-correlation functions of the strain-gauge data have been shown to consist of decaying sinusoids which correspond to the modal frequencies and damping ratios of the wind turbine. We have verified the method by extracting damping values from an analytically generated data set. Actual operating response data from the DOE/Sandia 34-meter Test Bed has been used to calculate modal damping ratios as a function of rotor rotation rate. This capability will allow more accurate fatigue life prediction and control. 16 refs., 3 figs., 2 tabs.

  3. Implicit solution of three-dimensional internal turbulent flows

    NASA Technical Reports Server (NTRS)

    Michelassi, V.; Liou, M.-S.; Povinelli, L. A.

    1990-01-01

    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 are iterated in time until a steady solution is reached. Evidence is 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 domain boundaries is proposed in order to avoid undesired mass and/or momentum artificial fluxes. Turbulence effects are accounted for by the zero-equation Baldwin-Lomax turbulence model and the q-omega two-equation model. For the first, an investigation on the model behavior in case of multiple boundaries is performed. The flow in a developing S-duct is then solved in the laminar regime at Reynolds number (Re) 790 and in the turbulent regime at Re=40,000 using the Baldwin-Lomax model . The Stanitz elbow is then solved using an inviscid version of the same code at M(sub inlet)=0.4. Grid dependence and convergence rate are investigated showing that for this solver the implicit damping scheme may play a critical role for convergence characteristics. The same flow at Re=2.5x10(exp 6) is solved with the Baldwin-Lomax and the q-omega models. Both approaches showed satisfactory agreement with experiments, although the q-omega model is slightly more accurate.

  4. The effects of the space environment on damping materials and damping designs on flexible structures

    NASA Technical Reports Server (NTRS)

    Kluesener, M. F.

    1984-01-01

    The effects of space environments on damping materials and damping designs on flexible structures were investigated. The following items were examined: damping of flexible spacecraft appendages; composite loss factor (n sub s) vs. time in high vacuum for damped test beams and damping of flexible structures. The STEP experiments show inherent damping of flexible structures in space effective possible damping design configurations for space structures, effects of passively damped components on the system loss factor of flexible structures and the effect of space environment on properties of damping materials.

  5. Implicit frictional-contact model for soft particle systems

    NASA Astrophysics Data System (ADS)

    Nezamabadi, Saeid; Radjai, Farhang; Averseng, Julien; Delenne, Jean-Yves

    2015-10-01

    We introduce a novel numerical approach for the simulation of soft particles interacting via frictional contacts. This approach is based on an implicit formulation of the Material Point Method, allowing for large particle deformations, combined with the Contact Dynamics method for the treatment of unilateral frictional contacts between particles. This approach is both precise due to the treatment of contacts with no regularization and artificial damping parameters, and robust due to implicit time integration of both bulk degrees of freedom and relative contact velocities at the nodes representing the contact points. By construction, our algorithm is capable of handling arbitrary particle shapes and deformations. We illustrate this approach by two simple 2D examples: a Hertz contact and a rolling particle on an inclined plane. We also investigate the compaction of a packing of circular particles up to a solid fraction well above the jamming limit of hard particles. We find that, for the same level of deformation, the solid fraction in a packing of frictional particles is above that of a packing of frictionless particles as a result of larger particle shape change.

  6. Accessibility effects on implicit social cognition: the role of knowledge activation and retrieval experiences.

    PubMed

    Gawronski, Bertram; Bodenhausen, Galen V

    2005-11-01

    Performance on measures of implicit social cognition has been shown to vary as a function of the momentary accessibility of relevant information. The present research investigated the mechanisms underlying accessibility effects of self-generated information on implicit measures. Results from 3 experiments demonstrate that measures based on response compatibility processes (e.g., Implicit Association Test, affective priming with an evaluative decision task) are influenced by subjective feelings pertaining to the ease of retrieving relevant information from memory, whereas measures based on stimulus compatibility processes (e.g., semantic priming with a lexical-decision task) are influenced by direct knowledge activation in associative memory. These results indicate that the mediating mechanisms underlying context effects on implicit measures can differ as a function of the task even when these tasks show similar effects on a superficial level. Implications for research on implicit social cognition and the ease-of-retrieval effect are discussed. PMID:16351361

  7. Implicit adaptive mesh refinement for 2D reduced resistive magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Philip, Bobby; Chacón, Luis; Pernice, Michael

    2008-10-01

    An implicit structured adaptive mesh refinement (SAMR) solver for 2D reduced magnetohydrodynamics (MHD) is described. The time-implicit discretization is able to step over fast normal modes, while the spatial adaptivity resolves thin, dynamically evolving features. A Jacobian-free Newton-Krylov method is used for the nonlinear solver engine. For preconditioning, we have extended the optimal "physics-based" approach developed in [L. Chacón, D.A. Knoll, J.M. Finn, An implicit, nonlinear reduced resistive MHD solver, J. Comput. Phys. 178 (2002) 15-36] (which employed multigrid solver technology in the preconditioner for scalability) to SAMR grids using the well-known Fast Adaptive Composite grid (FAC) method [S. McCormick, Multilevel Adaptive Methods for Partial Differential Equations, SIAM, Philadelphia, PA, 1989]. A grid convergence study demonstrates that the solver performance is independent of the number of grid levels and only depends on the finest resolution considered, and that it scales well with grid refinement. The study of error generation and propagation in our SAMR implementation demonstrates that high-order (cubic) interpolation during regridding, combined with a robustly damping second-order temporal scheme such as BDF2, is required to minimize impact of grid errors at coarse-fine interfaces on the overall error of the computation for this MHD application. We also demonstrate that our implementation features the desired property that the overall numerical error is dependent only on the finest resolution level considered, and not on the base-grid resolution or on the number of refinement levels present during the simulation. We demonstrate the effectiveness of the tool on several challenging problems.

  8. On the destabilizing effect of damping on discrete and continuous circulatory systems

    NASA Astrophysics Data System (ADS)

    Luongo, Angelo; D`Annibale, Francesco

    2014-12-01

    The 'Ziegler paradox', concerning the destabilizing effect of damping on elastic systems loaded by nonconservative positional forces, is addressed. The paper aims to look at the phenomenon in a new perspective, according to which no surprising discontinuities in the critical load exist between undamped and damped systems. To show that the actual critical load is found as an (infinitesimal) perturbation of one of the infinitely many sub-critically loaded undamped systems. A series expansion of the damped eigenvalues around the distinct purely imaginary undamped eigenvalues is performed, with the load kept as a fixed, although unknown, parameter. The first sensitivity of the eigenvalues, which is found to be real, is zeroed, so that an implicit expression for the critical load multiplier is found, which only depends on the 'shape' of damping, being independent of its magnitude. An interpretation is given of the destabilization paradox, by referring to the concept of 'modal damping', according to which the sign of the projection of the damping force on the eigenvector of the dual basis, and not on the eigenvector itself, is the true responsible for stability. The whole procedure is explained in detail for discrete systems, and successively extended to continuous systems. Two sample structures are studied for illustrative purposes: the classical reverse double-pendulum under a follower force and a linear visco-elastic beam under a follower force and a dead load.

  9. Implicit Social Biases in People With Autism.

    PubMed

    Birmingham, Elina; Stanley, Damian; Nair, Remya; Adolphs, Ralph

    2015-11-01

    Implicit social biases are ubiquitous and are known to influence social behavior. A core diagnostic criterion of autism spectrum disorders (ASD) is abnormal social behavior. We investigated the extent to which individuals with ASD might show a specific attenuation of implicit social biases, using Implicit Association Tests (IATs) involving social (gender, race) and nonsocial (nature, shoes) categories. High-functioning adults with ASD showed intact but reduced IAT effects relative to healthy control participants. We observed no selective attenuation of implicit social (vs. nonsocial) biases in our ASD population. To extend these results, we supplemented our healthy control data with data collected from a large online sample from the general population and explored correlations between autistic traits and IAT effects. We observed no systematic relationship between autistic traits and implicit social biases in our online and control samples. Taken together, these results suggest that implicit social biases, as measured by the IAT, are largely intact in ASD. PMID:26386014

  10. Implicit Media Knowledge Experiments & Results

    NASA Astrophysics Data System (ADS)

    Ly, Muy-Chu; Germaneau, Alexis

    2011-08-01

    Implicit Media Knowledge aims to provide relevant information related to visual media without effort. It is based on the analysis of media usage from several users (e.g. a community). Algorithms based on clustering methods that extract relevant information (e.g. tags, taxonomy trees) related to a media from its usage are detailed. To validate our new approach, we propose to apply our concept and algorithms on a specific media use such as the analysis of how multiple users organize their media files. Significant results of two experiments will be highlighted. Perspectives of our work will be finally presented.

  11. Age Differences in Implicit Interference

    PubMed Central

    Ikier, Simay; Hasher, Lynn

    2006-01-01

    We assessed age differences in interference effects in priming by using fragment completion. In Experiment 1, noninterfering filler words preceded critical targets at study, and priming was age invariant. In Experiment 2, the same target items had interfering competitors at the beginning of the list, such that both the target and the competitor were legitimate solutions to a fragment. Having two responses to a cue was disruptive for older adults, but not for younger adults. Younger and older adults differ in their susceptibility to interference in implicit tasks, and interference may play a role in influencing the magnitude of age differences in priming. PMID:16960231

  12. An implicit Smooth Particle Hydrodynamic code

    SciTech Connect

    Charles E. Knapp

    2000-04-01

    An implicit version of the Smooth Particle Hydrodynamic (SPH) code SPHINX has been written and is working. In conjunction with the SPHINX code the new implicit code models fluids and solids under a wide range of conditions. SPH codes are Lagrangian, meshless and use particles to model the fluids and solids. The implicit code makes use of the Krylov iterative techniques for solving large linear-systems and a Newton-Raphson method for non-linear corrections. It uses numerical derivatives to construct the Jacobian matrix. It uses sparse techniques to save on memory storage and to reduce the amount of computation. It is believed that this is the first implicit SPH code to use Newton-Krylov techniques, and is also the first implicit SPH code to model solids. A description of SPH and the techniques used in the implicit code are presented. Then, the results of a number of tests cases are discussed, which include a shock tube problem, a Rayleigh-Taylor problem, a breaking dam problem, and a single jet of gas problem. The results are shown to be in very good agreement with analytic solutions, experimental results, and the explicit SPHINX code. In the case of the single jet of gas case it has been demonstrated that the implicit code can do a problem in much shorter time than the explicit code. The problem was, however, very unphysical, but it does demonstrate the potential of the implicit code. It is a first step toward a useful implicit SPH code.

  13. The "exaptation" of linguistic implicit strategies.

    PubMed

    Lombardi Vallauri, Edoardo

    2016-01-01

    Implicit strategies are known to increase persuasion performances. Implicits of content (vagueness, implicatures) and implicits of responsibility (presuppositions, topics) will be compared semiotically to non-linguistic implicits such as images and sounds. The results of psycholinguistic and neurolinguistic experiments will be used to propose that presuppositions and topics arose in language as means to spare addressees processing effort on already known contents, but they were subsequently "exapted" to spare effort on unknown marginal contents, and eventually to reduce the probability for doubtful contents to be processed thoroughly and rejected. This will be shown by many examples from commercial advertising and political propaganda. PMID:27478723

  14. The development of implicit gender attitudes.

    PubMed

    Dunham, Yarrow; Baron, Andrew Scott; Banaji, Mahzarin R

    2016-09-01

    The development course of implicit and explicit gender attitudes between the ages of 5 and adulthood is investigated. Findings demonstrate that implicit and explicit own-gender preferences emerge early in both boys and girls, but implicit own-gender preferences are stronger in young girls than boys. In addition, female participants' attitudes remain largely stable over development, whereas male participants' implicit and explicit attitudes show an age-related shift towards increasing female positivity. Gender attitudes are an anomaly in that social evaluations dissociate from social status, with both male and female participants tending to evaluate female more positively than male. PMID:26260250

  15. Implicit dose-response curves.

    PubMed

    Pérez Millán, Mercedes; Dickenstein, Alicia

    2015-06-01

    We develop tools from computational algebraic geometry for the study of steady state features of autonomous polynomial dynamical systems via elimination of variables. In particular, we obtain nontrivial bounds for the steady state concentration of a given species in biochemical reaction networks with mass-action kinetics. This species is understood as the output of the network and we thus bound the maximal response of the system. The improved bounds give smaller starting boxes to launch numerical methods. We apply our results to the sequential enzymatic network studied in Markevich et al. (J Cell Biol 164(3):353-359, 2004) to find nontrivial upper bounds for the different substrate concentrations at steady state. Our approach does not require any simulation, analytical expression to describe the output in terms of the input, or the absence of multistationarity. Instead, we show how to extract information from effectively computable implicit dose-response curves, with the use of resultants and discriminants. We moreover illustrate in the application to an enzymatic network, the relation between the exact implicit dose-response curve we obtain symbolically and the standard hysteresis diagram provided by a numerical ode solver. The setting and tools we propose could yield many other results adapted to any autonomous polynomial dynamical system, beyond those where it is possible to get explicit expressions. PMID:25008963

  16. Implicit binding of facial features during change blindness.

    PubMed

    Lyyra, Pessi; Mäkelä, Hanna; Hietanen, Jari K; Astikainen, Piia

    2014-01-01

    Change blindness refers to the inability to detect visual changes if introduced together with an eye-movement, blink, flash of light, or with distracting stimuli. Evidence of implicit detection of changed visual features during change blindness has been reported in a number of studies using both behavioral and neurophysiological measurements. However, it is not known whether implicit detection occurs only at the level of single features or whether complex organizations of features can be implicitly detected as well. We tested this in adult humans using intact and scrambled versions of schematic faces as stimuli in a change blindness paradigm while recording event-related potentials (ERPs). An enlargement of the face-sensitive N170 ERP component was observed at the right temporal electrode site to changes from scrambled to intact faces, even if the participants were not consciously able to report such changes (change blindness). Similarly, the disintegration of an intact face to scrambled features resulted in attenuated N170 responses during change blindness. Other ERP deflections were modulated by changes, but unlike the N170 component, they were indifferent to the direction of the change. The bidirectional modulation of the N170 component during change blindness suggests that implicit change detection can also occur at the level of complex features in the case of facial stimuli. PMID:24498165

  17. Reduced Variance for Material Sources in Implicit Monte Carlo

    SciTech Connect

    Urbatsch, Todd J.

    2012-06-25

    Implicit Monte Carlo (IMC), a time-implicit method due to Fleck and Cummings, is used for simulating supernovae and inertial confinement fusion (ICF) systems where x-rays tightly and nonlinearly interact with hot material. The IMC algorithm represents absorption and emission within a timestep as an effective scatter. Similarly, the IMC time-implicitness splits off a portion of a material source directly into the radiation field. We have found that some of our variance reduction and particle management schemes will allow large variances in the presence of small, but important, material sources, as in the case of ICF hot electron preheat sources. We propose a modification of our implementation of the IMC method in the Jayenne IMC Project. Instead of battling the sampling issues associated with a small source, we bypass the IMC implicitness altogether and simply deterministically update the material state with the material source if the temperature of the spatial cell is below a user-specified cutoff. We describe the modified method and present results on a test problem that show the elimination of variance for small sources.

  18. Timoshenko systems with indefinite damping

    NASA Astrophysics Data System (ADS)

    Muñoz Rivera, Jaime E.; Racke, Reinhard

    2008-05-01

    We consider the Timoshenko system in a bounded domain . The system has an indefinite damping mechanism, i.e. with a damping function a=a(x) possibly changing sign, present only in the equation for the rotation angle. We shall prove that the system is still exponentially stable under the same conditions as in the positive constant damping case, and provided and , for [epsilon] small enough. The decay rate will be described explicitly. In the arguments, we shall also give a new proof of exponential stability for the constant case . Moreover, we give a precise description of the decay rate and demonstrate that the system has the spectrum determined growth (SDG) property, i.e. the type of the induced semigroup coincides with the spectral bound for its generator.

  19. 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…

  20. 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 PMID:26075407

  1. Parallel Explicit and Implicit Control of Reaching

    PubMed Central

    Mazzoni, Pietro; Wexler, Nancy S.

    2009-01-01

    Background Human movement can be guided automatically (implicit control) or attentively (explicit control). Explicit control may be engaged when learning a new movement, while implicit control enables simultaneous execution of multiple actions. Explicit and implicit control can often be assigned arbitrarily: we can simultaneously drive a car and tune the radio, seamlessly allocating implicit or explicit control to either action. This flexibility suggests that sensorimotor signals, including those that encode spatially overlapping perception and behavior, can be accurately segregated to explicit and implicit control processes. Methodology/Principal Findings We tested human subjects' ability to segregate sensorimotor signals to parallel control processes by requiring dual (explicit and implicit) control of the same reaching movement and testing for interference between these processes. Healthy control subjects were able to engage dual explicit and implicit motor control without degradation of performance compared to explicit or implicit control alone. We then asked whether segregation of explicit and implicit motor control can be selectively disrupted by studying dual-control performance in subjects with no clinically manifest neurologic deficits in the presymptomatic stage of Huntington's disease (HD). These subjects performed successfully under either explicit or implicit control alone, but were impaired in the dual-control condition. Conclusion/Significance The human nervous system can exert dual control on a single action, and is therefore able to accurately segregate sensorimotor signals to explicit and implicit control. The impairment observed in the presymptomatic stage of HD points to a possible crucial contribution of the striatum to the segregation of sensorimotor signals to multiple control processes. PMID:19847295

  2. Damped vacuum states of light

    NASA Astrophysics Data System (ADS)

    Philbin, T. G.

    2016-09-01

    We consider one-dimensional propagation of quantum light in the presence of a block of material, with a full account of dispersion and absorption. The electromagnetic zero-point energy for some frequencies is damped (suppressed) by the block below the free-space value, while for other frequencies it is increased. We also calculate the regularized (Casimir) zero-point energy at each frequency and find that it too is damped below the free-space value (zero) for some frequencies. The total Casimir energy is positive.

  3. Structural damping studies at cryogenic temperatures

    NASA Technical Reports Server (NTRS)

    Young, Clarence P., Jr.; Buehrle, Ralph D.

    1994-01-01

    Results of an engineering study to measure changes in structural damping properties of two cryogenic wind tunnel model systems and two metallic test specimens at cryogenic temperatures are presented. Data are presented which indicate overall, a trend toward reduced structural damping at cryogenic temperatures (-250 degrees F) when compared with room temperature damping properties. The study was focused on structures and materials used for model systems tested in the National Transonic Facility (NTF). The study suggests that the significant reductions in damping at extremely cold temperatures are most likely associated with changes in mechanical joint compliance damping rather than changes in material (solid) damping.

  4. Implicit and Explicit Instruction of Spelling Rules

    ERIC Educational Resources Information Center

    Kemper, M. J.; Verhoeven, L.; Bosman, A. M. T.

    2012-01-01

    The study aimed to compare the differential effectiveness of explicit and implicit instruction of two Dutch spelling rules. Students with and without spelling disabilities were instructed a spelling rule either implicitly or explicitly in two experiments. Effects were tested in a pretest-intervention-posttest control group design. Experiment 1…

  5. Understanding Implicit Bias: What Educators Should Know

    ERIC Educational Resources Information Center

    Staats, Cheryl

    2016-01-01

    The desire to ensure the best for children is precisely why educators should become aware of the concept of implicit bias: the attitudes or stereotypes that affect our understanding, actions, and decisions in an unconscious manner. Operating outside of our conscious awareness, implicit biases are pervasive, and they can challenge even the most…

  6. Implicit and Explicit Exercise and Sedentary Identity

    ERIC Educational Resources Information Center

    Berry, Tanya R.; Strachan, Shaelyn M.

    2012-01-01

    We examined the relationship between implicit and explicit "exerciser" and "sedentary" self-identity when activated by stereotypes. Undergraduate participants (N = 141) wrote essays about university students who either liked to exercise or engage in sedentary activities. This was followed by an implicit identity task and an explicit measure of…

  7. Implicit and Explicit Learning of Languages.

    ERIC Educational Resources Information Center

    McDermott, James E.

    1999-01-01

    Discusses theoretical and practical issues connected with implicit and explicit learning of languages. Explicit learning is knowledge expressed in the form of rules or definitions; implicit knowledge can be inferred to exist because of observed performance but cannot be clearly described. Hypothesizes why explicit learning can lead to implicit…

  8. Altered Implicit Category Learning in Anorexia Nervosa

    PubMed Central

    Shott, Megan E.; Filoteo, J. Vincent; Jappe, Leah M.; Pryor, Tamara; Maddox, W. Todd; Rollin, Michael D.H.; Hagman, Jennifer O.; Frank, Guido K.W.

    2012-01-01

    Objective Recent research has identified specific cognitive deficits in patients with anorexia nervosa (AN), including impairment in executive functioning and attention. Another such cognitive process, implicit category learning has been less studied in AN. This study examined whether implicit category learning is impaired in AN. Method Twenty-one women diagnosed with AN and 19 control women (CW) were administered an implicit category learning task in which they were asked to categorize simple perceptual stimuli (Gabor patches) into one of two categories. Category membership was based on a linear integration (i.e., an implicit task) of two stimulus dimensions (orientation and spatial frequency of the stimulus). Results AN individuals were less accurate on implicit category learning relative to age-matched CW. Model-based analyses indicated that, even when AN individuals used the appropriate (i.e., implicit) strategy they were still impaired relative to CW who also used the same strategy. In addition, task performance in AN patients was worse the higher they were in self-reported novelty seeking and the lower they were in sensitivity to punishment. Conclusions These results indicate that AN patients have implicit category learning deficits, and given this type of learning is thought to be mediated by striatal dopamine pathways, AN patients may have deficits in these neural systems. The finding of significant correlations with novelty seeking and sensitivity to punishment suggests that feedback sensitivity is related to implicit learning in AN. PMID:22201300

  9. Psychometric Intelligence Dissociates Implicit and Explicit Learning

    ERIC Educational Resources Information Center

    Gebauer, Guido F.; Mackintosh, Nicholas J.

    2007-01-01

    The hypothesis that performance on implicit learning tasks is unrelated to psychometric intelligence was examined in a sample of 605 German pupils. Performance in artificial grammar learning, process control, and serial learning did not correlate with various measures of intelligence when participants were given standard implicit instructions.…

  10. Implicit solvers for unstructured meshes

    NASA Technical Reports Server (NTRS)

    Venkatakrishnan, V.; Mavriplis, Dimitri J.

    1991-01-01

    Implicit methods were developed and tested for unstructured mesh computations. The approximate system which arises from the Newton linearization of the nonlinear evolution operator is solved by using the preconditioned GMRES (Generalized Minimum Residual) technique. Three different preconditioners were studied, namely, the incomplete LU factorization (ILU), block diagonal factorization, and the symmetric successive over relaxation (SSOR). The preconditioners were optimized to have good vectorization properties. SSOR and ILU were also studied as iterative schemes. The various methods are compared over a wide range of problems. Ordering of the unknowns, which affects the convergence of these sparse matrix iterative methods, is also studied. Results are presented for inviscid and turbulent viscous calculations on single and multielement airfoil configurations using globally and adaptively generated meshes.

  11. Implicit restart Lanczos as an eigensolver

    NASA Astrophysics Data System (ADS)

    Rajaie Khorasani, Reza; Dumont, Randall S.

    2009-03-01

    This paper investigates the efficiency of the implicit restart Lanczos and simple (without reorthogonalization) Lanczos algorithms, as eigensolvers for large scale computations in molecular and chemical physics. Using the cardioid billiard and the hydrogen cyanide/hydrogen isocyanide (HCN/HNC) molecule as model systems we demonstrate superior efficiency of implicit restart Lanczos compared to the simple Lanczos algorithm. A modified implementation of implicit restart Lanczos is also presented which works with a smaller Krylov space—with associated savings in memory—and can handle larger basis sets than the usual implicit restart Lanczos. It also enables getting all eigenpairs of a matrix, or all eigenvalues below a threshold (where the number of such is not known before hand), which is more difficult with the usual implicit restart algorithm.

  12. Implicit restart Lanczos as an eigensolver.

    PubMed

    Rajaie Khorasani, Reza; Dumont, Randall S

    2009-03-01

    This paper investigates the efficiency of the implicit restart Lanczos and simple (without reorthogonalization) Lanczos algorithms, as eigensolvers for large scale computations in molecular and chemical physics. Using the cardioid billiard and the hydrogen cyanide/hydrogen isocyanide (HCN/HNC) molecule as model systems we demonstrate superior efficiency of implicit restart Lanczos compared to the simple Lanczos algorithm. A modified implementation of implicit restart Lanczos is also presented which works with a smaller Krylov space-with associated savings in memory-and can handle larger basis sets than the usual implicit restart Lanczos. It also enables getting all eigenpairs of a matrix, or all eigenvalues below a threshold (where the number of such is not known before hand), which is more difficult with the usual implicit restart algorithm. PMID:19392082

  13. 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

  14. Dealing with damping-off

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Damping-off is a common disease that rots and kills both seeds and recently germinated seedlings. The disease is caused by number of different soilborne pathogens, including true fungi (Botrytis, Fusarium, and Rhizoctonia species) and oomycetes (Phytophthora and Pythium species). The seedlings of mo...

  15. Red cell DAMPs and inflammation.

    PubMed

    Mendonça, Rafaela; Silveira, Angélica A A; Conran, Nicola

    2016-09-01

    Intravascular hemolysis, or the destruction of red blood cells in the circulation, can occur in numerous diseases, including the acquired hemolytic anemias, sickle cell disease and β-thalassemia, as well as during some transfusion reactions, preeclampsia and infections, such as those caused by malaria or Clostridium perfringens. Hemolysis results in the release of large quantities of red cell damage-associated molecular patterns (DAMPs) into the circulation, which, if not neutralized by innate protective mechanisms, have the potential to activate multiple inflammatory pathways. One of the major red cell DAMPs, heme, is able to activate converging inflammatory pathways, such as toll-like receptor signaling, neutrophil extracellular trap formation and inflammasome formation, suggesting that this DAMP both activates and amplifies inflammation. Other potent DAMPs that may be released by the erythrocytes upon their rupture include heat shock proteins (Hsp), such as Hsp70, interleukin-33 and Adenosine 5' triphosphate. As such, hemolysis represents a major inflammatory mechanism that potentially contributes to the clinical manifestations that have been associated with the hemolytic diseases, such as pulmonary hypertension and leg ulcers, and likely plays a role in specific complications of sickle cell disease such as endothelial activation, vaso-occlusive processes and tissue injury. PMID:27251171

  16. Frequency and damping rate of fast sausage waves

    SciTech Connect

    Farahani, S. Vasheghani; Van Doorsselaere, T.; Goossens, M.; Hornsey, C.

    2014-02-01

    We investigate the frequency and damping rate of fast axisymmetric waves that are subject to wave leakage for a one-dimensional magnetic cylindrical structure in the solar corona. We consider the ideal magnetohydrodynamic (MHD) dispersion relation for axisymmetric MHD waves superimposed on a straight magnetic cylinder in the zero β limit, similar to a jet or loop in the solar corona. An analytic study accompanied by numerical calculations has been carried out to model the frequency, damping rate, and phase speed of the sausage wave around the cut-off frequency and in the long wavelength limit. Analytic expressions have been obtained based on equations around the points of interest. They are linear approximations of the dependence of the sausage frequency on the wave number around the cut-off wavelength for both leaky and non-leaky regimes and in the long wavelength limit. Moreover, an expression for the damping rate of the leaky sausage wave has been obtained both around the cut-off frequency and in the long wavelength limit. These analytic results are compared with numerical computations. The expressions show that the complex frequencies are mainly dominated by the density ratio. In addition, it is shown that the damping eventually becomes independent of the wave number in the long wavelength limit. We conclude that the sausage mode damping directly depends on the density ratios of the internal and external media where the damping declines in higher density contrasts. Even in the long wavelength limit, the sausage mode is weakly damped for high-density contrasts. As such, sausage modes could be observed for a significant number of periods in high-density contrast loops or jets.

  17. Damped Oscillator with Delta-Kicked Frequency

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1996-01-01

    Exact solutions of the Schrodinger equation for quantum damped oscillator subject to frequency delta-kick describing squeezed states are obtained. The cases of strong, intermediate, and weak damping are investigated.

  18. Nutation damping in viscoelastic tumbling rotators

    NASA Astrophysics Data System (ADS)

    Frouard, Julien; Efroimsky, Michael

    2015-11-01

    Presently, 138 asteroids show signs of being in non-principal spin states (Warner et al. 2009, updated September 2015). Such spin is often called `tumble' or `wobble'. The instantaneous rotation axis of a wobbling body performs nutation about the direction of the (conserved) angular-momentum vector. Incited by collisions and YORP, wobble is mitigated by internal dissipation due to the nutation-caused alternating stresses inside the asteroid.The knowledge of the timescale related to the damping of the nutation angle is complementary to the knowledge of the timescales associated with collisions and YORP. Previous evaluations of the nutation relaxation rate were based on an inherently inconsistent approach that may be called "Q-model". First, the elastic energy in a periodically deforming rotator was calculated in assumption of the deformation being elastic. Therefrom, the energy dissipation rate was determined by introducing an ad hoc quality factor Q. This ignored the fact that friction (and the ensuing existence of Q) is due to deviation from elasticity.We use the viscoelastic Maxwell model which naturally implies dissipation (as any other viscoelastic model would). In this approach, we compute the power and damping time for an oblate ellipsoid and a prism. Now, the viscosity assumes the role of the product μQ in the empirical Q-model, with μ being the rigidity. Contrarily to the Q-model, our model naturally gives a null dissipation for a shape tending to a sphere. We also explore when the constant part of the stress can be ignored in the derivation of the damping time. The neglect of prestressing turns out to be legitimate for the mean viscosity exceeding a certain threshold value.

  19. The Nonlinear Landau Damping Rate of a Driven Plasma Wave

    SciTech Connect

    Benisti, D; Strozzi, D J; Gremillet, L; Morice, O

    2009-08-04

    In this Letter, we discuss the concept of the nonlinear Landau damping rate, {nu}, of a driven electron plasma wave, and provide a very simple, practical, analytic formula for {nu} which agrees very well with results inferred from Vlasov simulations of stimulated Raman scattering. {nu} actually is more complicated an operator than a plain damping rate, and it may only be seen as such because it assumes almost constant values before abruptly dropping to 0. The decrease of {nu} to 0 is moreover shown to occur later when the wave amplitude varies in the direction transverse to its propagation.

  20. Kraus representation of a damped harmonic oscillator and its application

    SciTech Connect

    Liu Yuxi; Oezdemir, Sahin K.; Miranowicz, Adam; Imoto, Nobuyuki

    2004-10-01

    By definition, the Kraus representation of a harmonic oscillator suffering from the environment effect, modeled as the amplitude damping or the phase damping, is directly given by a simple operator algebra solution. As examples and applications, we first give a Kraus representation of a single qubit whose computational basis states are defined as bosonic vacuum and single particle number states. We further discuss the environment effect on qubits whose computational basis states are defined as the bosonic odd and even coherent states. The environment effects on entangled qubits defined by two different kinds of computational basis are compared with the use of fidelity.

  1. Linking the river to the estuary: influence of river discharge on tidal damping

    NASA Astrophysics Data System (ADS)

    Cai, H.; Savenije, H. H. G.; Toffolon, M.

    2014-01-01

    The effect of river discharge on tidal damping in estuaries is explored within one consistent theoretical framework where analytical solutions are obtained by solving four implicit equations, i.e. the phase lag, the scaling, the damping and the celerity equation. In this approach the damping equation is obtained by subtracting the envelope curves of high water and low water occurrence, taking into account that the flow velocity consists of a tidal and river discharge component. Different approximations of the friction term are considered in deriving the damping equation, resulting in as many analytical solutions. In this framework it is possible to show that river discharge affects tidal damping primarily through the friction term. It appears that the residual slope, due to nonlinear friction, can have a substantial influence on tidal wave propagation when including the effect of river discharge. An iterative analytical method is proposed to include this effect, which significantly improved model performance in the upper reaches of an estuary. The application to the Modaomen and Yangtze estuaries demonstrates that the proposed analytical model is able to describe the main tidal dynamics with realistic roughness values in the upper part of the estuary where the ratio of river flow to tidal flow amplitude is substantial, while a model with negligible river discharge can be made to fit observations only with unrealistically high roughness values.

  2. Squeezed states of damped oscillator chain

    NASA Technical Reports Server (NTRS)

    Manko, O. V.

    1993-01-01

    The Caldirola-Kanai model of one-dimensional damped oscillator is extended to the chain of coupled parametric oscillators with damping. The correlated and squeezed states for the chain of coupled parametric oscillators with damping are constructed. Based on the concept of the integrals of motion, it is demonstrated how squeezing phenomenon arises due to parametric excitation.

  3. Modulation of effective damping constant using spin Hall effect

    SciTech Connect

    Kasai, Shinya Kondou, Kouta; Sukegawa, Hiroaki; Mitani, Seiji; Tsukagoshi, Kazuhito; Otani, Yoshichika

    2014-03-03

    We have investigated modulation of the effective damping constant α{sub eff} via spin currents through the spin Hall effect for Permalloy/Pt bilayer films with various thicknesses. The observed linear and sinusoidal dependences of current density and field direction on α{sub eff} are in agreement with the analytical model. By comparing the thickness dependence of spin Hall angle obtained from the damping modulation with that previously obtained by spin-torque-induced ferromagnetic resonance, we show that there is no clear extrinsic contribution in the present method. We also show the large modulation of the effective damping constant (down to ∼20%) in the high-current-density region.

  4. The development of implicit attitudes. Evidence of race evaluations from ages 6 and 10 and adulthood.

    PubMed

    Baron, Andrew Scott; Banaji, Mahzarin R

    2006-01-01

    To understand the origin and development of implicit attitudes, we measured race attitudes in White American 6-year-olds, 10-year-olds, and adults by first developing a child-oriented version of the Implicit Association Test (Child IAT). Remarkably, implicit pro-White/anti-Black bias was evident even in the youngest group, with self-reported attitudes revealing bias in the same direction. In 10-year-olds and adults, the same magnitude of implicit race bias was observed, although self-reported race attitudes became substantially less biased in older children and vanished entirely in adults, who self-reported equally favorable attitudes toward Whites and Blacks. These data are the first to show an asymmetry in the development of implicit and explicit race attitudes, with explicit attitudes becoming more egalitarian and implicit attitudes remaining stable and favoring the in-group across development. We offer a tentative suggestion that mean levels of implicit and explicit attitudes diverge around age 10. PMID:16371144

  5. Research on the damping properties of Fe12O19Sr/the polyurethane elastomer composite

    NASA Astrophysics Data System (ADS)

    Li, Y.; Qin, Yan; Sun, P. C.; Huang, Z. X.

    2016-07-01

    Magnetic elastomer composite is a promising damping material. In this paper, both strontium ferrite (Fe12O19Sr) powders and polyurethane elastomer which were mixed by mechanical blending method were used as the magnetic filler and as the matrix respectively, the properties of the magnetic damping composite materials were studied. The results show that the magnetic properties of the magnetic elastomers composite are enhanced with the ferrite loading. The mechanical properties and Shore hardness are highly influenced by mass fraction of ferrite particles. The damping properties of magnetic elastomer composite reach best when the strontium ferrite loading is 15phr, and the damping properties deteriorate when the loading continue increasing. The damping properties of the composites with the X direction of magnetization are better than that with Y direction of magnetization.

  6. Implicit social learning in relation to autistic-like traits.

    PubMed

    Hudson, Matthew; Nijboer, Tanja C W; Jellema, Tjeerd

    2012-12-01

    We investigated if variation in autistic traits in the typically-developed population (using the Autism-spectrum Quotient, AQ) influenced implicit learning of social information. In the learning phase, participants repeatedly observed two identities whose gaze and expression conveyed either a pro- or antisocial disposition. These identities were then employed in a gaze-cueing paradigm. Participants made speeded responses to a peripheral target that was spatially pre-cued by a non-predictive gaze direction. The low AQ group (n = 50) showed a smaller gaze-cueing effect for the antisocial than for the prosocial identity. The high AQ group (n = 48) showed equivalent gaze-cueing for both identities. Others' intentions/dispositions can be learned implicitly and affect subsequent responses to their behavior. This ability is impaired with increasing levels of autistic traits. PMID:22447071

  7. Passive damping for space truss structures

    NASA Technical Reports Server (NTRS)

    Chen, Gun-Shing; Wada, Ben K.

    1988-01-01

    Theoretical and experimental studies of passive damping techniques in truss-type structures are presented, with emphasis on the use of viscoelastic damping in the parallel load path. The constraining member length is shown to be a convenient design variable for enhancing damping performance. Results are presented for integral damping members made of thin-wall aluminum tubes, concentric constraining members, and viscoelastic materials in a six-bay truss structure at low frequency and low dynamic strain conditions. Integral members with graphite/epoxy constraining members exhibited relatively low damping values due to the possible polymer interaction during the cocure stage.

  8. Forced oscillations with linear and nonlinear damping

    NASA Astrophysics Data System (ADS)

    Li, Aijun; Ma, Li; Keene, David; Klingel, Joshua; Payne, Marvin; Wang, Xiao-jun

    2016-01-01

    A general solution is derived for the differential equations of forced oscillatory motion with both linear damping ( ˜v ) and nonlinear damping ( ˜v2 ). Experiments with forced oscillators are performed using a flat metal plate with a drag force due to eddy currents and a flat piece of stiffened cardboard with a drag force due to air resistance serving as the linear and nonlinear damping, respectively. Resonance of forced oscillations for different damping forces and quality factors is demonstrated. The experimental measurements and theoretical calculations are in good agreement, and damping constants are determined.

  9. 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

  10. Clipped viscous damping with negative stiffness for semi-active cable damping

    NASA Astrophysics Data System (ADS)

    Weber, F.; Boston, C.

    2011-04-01

    This paper investigates numerically and experimentally clipped viscous damping with negative stiffness for semi-active cable damping. From simulations it is concluded that unclipped and clipped viscous damping with negative stiffness is equivalent to unclipped and clipped LQR. It is shown that optimized unclipped viscous damping with negative stiffness generates critical cable damping by an anti-node at the actuator position. The resulting curvature at the actuator position is larger than the curvature close to the anchors due to the disturbance forces which may lead to premature cable fatigue at the actuator position. Optimized clipped viscous damping with negative stiffness does not show this drawback, can be implemented using a semi-active damper and produces twice as much cable damping as optimal viscous damping. Close to the optimal tuning, it leads to approximately the same control force as optimal semi-active friction damping with negative stiffness, which explains the superior cable damping. The superior damping results from the negative stiffness that increases the damper motion. Clipped viscous damping with negative stiffness is validated on a strand cable with a magneto-rheological damper. The measured cable damping is twice that achieved by emulated viscous damping, which confirms the numerical results. A tuning rule for clipped viscous damping with negative stiffness of real cables with flexural rigidity is given.

  11. Implicit collaboration of sensor systems

    NASA Astrophysics Data System (ADS)

    Hintz, Kenneth J.

    2004-08-01

    The concept of goal lattices for the evaluation of potential sensor actions can be used to cause a multiplicity of heterogeneous sensor systems to collaborate. Previously goal lattices have been used to compute the value to a sensor system of taking a particular action in terms of how well that action contributes to the accomplishment of the topmost goals. This assumes that each sensor system is autonomous and only responsible to itself. If the topmost goals of each sensor system's goal lattice has adjoined to it two additional goals, namely "collaboration" and "altruism", then the value system is extended to include servicing requests from other systems. Two aircraft on a common mission can each benefit from measurements taken by the other aircraft either to confirm their own measurements, to create a pseudo-sensor, or to extend the area of coverage. The altruism goal indicates how much weight a sensor management system (SMS) will give in responding to a measurement request from any other system. The collaboration goal indicates how much weight will be given to responding to a measurement request from specific systems which are defined as being part of a collaborating group. By varying the values of the altruism and collaboration goals of each system, either locally or globally, various levels of implicit cooperation among sensor systems can be caused to emerge.

  12. Human infant faces provoke implicit positive affective responses in parents and non-parents alike.

    PubMed

    Senese, Vincenzo Paolo; De Falco, Simona; Bornstein, Marc H; Caria, Andrea; Buffolino, Simona; Venuti, Paola

    2013-01-01

    Human infants' complete dependence on adult caregiving suggests that mechanisms associated with adult responsiveness to infant cues might be deeply embedded in the brain. Behavioural and neuroimaging research has produced converging evidence for adults' positive disposition to infant cues, but these studies have not investigated directly the valence of adults' reactions, how they are moderated by biological and social factors, and if they relate to child caregiving. This study examines implicit affective responses of 90 adults toward faces of human and non-human (cats and dogs) infants and adults. Implicit reactions were assessed with Single Category Implicit Association Tests, and reports of childrearing behaviours were assessed by the Parental Style Questionnaire. The results showed that human infant faces represent highly biologically relevant stimuli that capture attention and are implicitly associated with positive emotions. This reaction holds independent of gender and parenthood status and is associated with ideal parenting behaviors. PMID:24282537

  13. Human Infant Faces Provoke Implicit Positive Affective Responses in Parents and Non-Parents Alike

    PubMed Central

    Senese, Vincenzo Paolo; De Falco, Simona; Bornstein, Marc H.; Caria, Andrea; Buffolino, Simona; Venuti, Paola

    2013-01-01

    Human infants' complete dependence on adult caregiving suggests that mechanisms associated with adult responsiveness to infant cues might be deeply embedded in the brain. Behavioural and neuroimaging research has produced converging evidence for adults' positive disposition to infant cues, but these studies have not investigated directly the valence of adults' reactions, how they are moderated by biological and social factors, and if they relate to child caregiving. This study examines implicit affective responses of 90 adults toward faces of human and non-human (cats and dogs) infants and adults. Implicit reactions were assessed with Single Category Implicit Association Tests, and reports of childrearing behaviours were assessed by the Parental Style Questionnaire. The results showed that human infant faces represent highly biologically relevant stimuli that capture attention and are implicitly associated with positive emotions. This reaction holds independent of gender and parenthood status and is associated with ideal parenting behaviors. PMID:24282537

  14. Implicit Flux Feedback Control for Magnetic Bearings

    NASA Astrophysics Data System (ADS)

    Keith, Frederick Joseph

    Design and implementation of a dynamic system that includes magnetic bearings is dependent on knowledge of the relationship between the command input to the magnetic actuator and the force that the bearing actually applies to the rotor (or other structure) being controlled. Traditional designs relate the bearing coil current to the developed bearing force; unfortunately, the current-to-force relationship is not invariant to magnetic hysteresis, magnetic saturation, eddy current effects, or changes in the bearing air gap length. To overcome these limitations, an approach known as implicit flux feedback is explored. Since the gap force in a magnetic circuit is directly related to the flux in that gap, measuring the gap flux and employing it as a feedback state results in a bearing with an improved command -to-force relation which is less subject to the error sources mentioned above. Confirmation of the flux-to-force relationship is accomplished via experiments on a test apparatus specifically designed to allow simultaneous force and flux measurements on a single-axis magnetic bearing (using both laminated and solid magnetic components). Successful implementation of the flux feedback algorithm simplifies the control system design of magnetic bearing systems by providing a more accurate, well characterized actuator model, and, by overcoming such effects as hysteresis, saturation, eddy currents and gap dependence, this approach provides magnetic bearings which exhibit significantly improved dynamic performance.

  15. An implicit spatial memory alignment effect.

    PubMed

    Cerles, Mélanie; Gomez, Alice; Rousset, Stéphane

    2015-09-01

    The memory alignment effect is the advantage of reasoning from a perspective which is aligned with the frame of reference used to encode an environment in memory. It usually occurs when participants have to consciously take a perspective to perform a spatial memory task. The present experiment assesses whether the memory alignment effect can occur without requiring to consciously take a given perspective, when the misaligned perspective is only perceptively provided. In others words, does the memory alignment effect still arise when it is only implicitly prompted? Thirty participants learned a sequence of four objects' positions in a room from a north-as-up survey perspective. During the testing phase, they had to point to the direction of a target object from another object ('the reference') with a fixed north-up orientation. The background behind the reference object displayed either a uniform color (control condition) or a misaligned ground-level perspective. The latter displayed a reference object's position information which was either congruent with the studied environment (congruent misaligned condition) or incongruent (incongruent misaligned condition). Mean pointing errors were higher in the congruent misaligned condition than in the control condition, whereas the incongruent misaligned condition did not differ from the control one. The present study shows that the memory alignment effect can arise without requiring a conscious misaligned perspective taking. Moreover, the perceived misaligned perspective must share the same spatial content as the memorized spatial representation in order to induce an alignment effect. PMID:26233526

  16. Computational fluid mechanics utilizing the variational principle of modeling damping seals

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The pressure solution for incompressible flow was investigated in support of a computational fluid mechanics model which simulates the damping seals considered for use in the space shuttle main engine turbomachinery. Future work directions are discussed briefly.

  17. Lay dispositionism and implicit theories of personality.

    PubMed

    Chiu, C Y; Hong, Y Y; Dweck, C S

    1997-07-01

    Lay dispositionism refers to lay people's tendency to use traits as the basic unit of analysis in social perception (L. Ross & R. E. Nisbett, 1991). Five studies explored the relation between the practices indicative of lay dispositionism and people's implicit theories about the nature of personal attributes. As predicted, compared with those who believed that personal attributes are malleable (incremental theorists), those who believed in fixed traits (entity theorists) used traits or trait-relevant information to make stronger future behavioral predictions (Studies 1 and 2) and made stronger trait inferences from behavior (Study 3). Moreover, the relation between implicit theories and lay dispositionism was found in both the United States (a more individualistic culture) and Hong Kong (a more collectivistic culture), suggesting this relation to be generalizable across cultures (Study 4). Finally, an experiment in which implicit theories were manipulated provided preliminary evidence for the possible causal role of implicit theories in lay dispositionism (Study 5). PMID:9216077

  18. Implicit learning and acquisition of music.

    PubMed

    Rohrmeier, Martin; Rebuschat, Patrick

    2012-10-01

    Implicit learning is a core process for the acquisition of a complex, rule-based environment from mere interaction, such as motor action, skill acquisition, or language. A body of evidence suggests that implicit knowledge governs music acquisition and perception in nonmusicians and musicians, and that both expert and nonexpert participants acquire complex melodic, harmonic, and other features from mere exposure. While current findings and computational modeling largely support the learning of chunks, some results indicate learning of more complex structures. Despite the body of evidence, more research is required to support the cross-cultural validity of implicit learning and to show that core and more complex music theoretical features are acquired implicitly. PMID:23060126

  19. 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…

  20. Implicit Association Tests of Attitudes toward Persons with Disabilities

    ERIC Educational Resources Information Center

    Thomas, Adrian; Vaughn, Edwin D.; Doyle, Andrea; Bubb, Robert

    2014-01-01

    The authors assessed 3 of the currently available implicit association tests designed to measure attitudes toward persons with disabilities. The Revised Multiple Disability Implicit Association Test, the Implicit Association Test for Attitudes Toward Athletes With Disabilities, and the Disability Attitude Implicit Association Test were related to…

  1. Implicit solution of large-scale radiation diffusion problems

    SciTech Connect

    Brown, P N; Graziani, F; Otero, I; Woodward, C S

    2001-01-04

    In this paper, we present an efficient solution approach for fully implicit, large-scale, nonlinear radiation diffusion problems. The fully implicit approach is compared to a semi-implicit solution method. Accuracy and efficiency are shown to be better for the fully implicit method on both one- and three-dimensional problems with tabular opacities taken from the LEOS opacity library.

  2. Influence of inhomogeneous damping distribution on sound radiation properties of complex vibration modes in rectangular plates

    NASA Astrophysics Data System (ADS)

    Unruh, Oliver

    2016-09-01

    In order to reduce noise emitted by vibrating structures additional damping treatments such as constraint layer damping or embedded elastomer layers can be used. To save weight and cost, the additional damping is often placed at some critical locations of the structure, what leads to spatially inhomogeneous distribution of damping. This inhomogeneous distribution of structural damping leads to an occurrence of complex vibration modes, which are no longer dominated by pure standing waves, but by a superposition of travelling and standing waves. The existence of complex vibration modes raises the question about their influence on sound radiation. Previous studies on the sound radiation of complex modes of rectangular plates reveal, that, depending on the direction of travelling waves, the radiation efficiency of structural modes can slightly decrease or significantly increase. These observations have been made using a rectangular plate with a simple inhomogeneous damping configuration which includes a single plate boundary with a higher structural damping ratio. In order to answer the question about the influence of other possible damping configurations on the sound radiation properties, this paper addresses the self- and mutual-radiation efficiencies of the resulting complex vibration modes. Numerical simulations are used for the calculation of complex structural modes of different inhomogeneous damping configurations with varying geometrical form and symmetry. The evaluation of self- and mutual-radiation efficiencies reveals that primarily the symmetry properties of the inhomogeneous damping distribution affect the sound radiation characteristics. Especially the asymmetric distributions of inhomogeneous damping show a high influence on the investigated acoustic metrics. The presented study also reveals that the acoustic cross-coupling between structural modes, which is described by the mutual-radiation efficiencies, generally increases with the presence of

  3. A procedure for the evaluation of damping effects in composite laminated structures

    NASA Astrophysics Data System (ADS)

    Vescovini, Riccardo; Bisagni, Chiara

    2015-10-01

    The paper presents an approach based on experimental tests and numerical simulations for taking into account damping effects during the design and the analysis of composite structures. The experiments are conducted using the Dynamic Mechanical Analysis (DMA) and unidirectional coupons are tested to characterize the damping properties of the plies. Starting from these results, first order shear deformation theory is applied to determine the damping properties of the laminate, which are then used in the context of a numerical procedure based on finite element analyses and strain energy method. The results are presented for an aircraft stiffened panel, illustrating the evaluation of the specific damping capacities of the structure, and performing direct transient analyses to investigate the effect of damping on the panel response to pulse loadings.

  4. Implicit methods for efficient musculoskeletal simulation and optimal control

    PubMed Central

    van den Bogert, Antonie J.; Blana, Dimitra; Heinrich, Dieter

    2011-01-01

    The ordinary differential equations for musculoskeletal dynamics are often numerically stiff and highly nonlinear. Consequently, simulations require small time steps, and optimal control problems are slow to solve and have poor convergence. In this paper, we present an implicit formulation of musculoskeletal dynamics, which leads to new numerical methods for simulation and optimal control, with the expectation that we can mitigate some of these problems. A first order Rosenbrock method was developed for solving forward dynamic problems using the implicit formulation. It was used to perform real-time dynamic simulation of a complex shoulder arm system with extreme dynamic stiffness. Simulations had an RMS error of only 0.11 degrees in joint angles when running at real-time speed. For optimal control of musculoskeletal systems, a direct collocation method was developed for implicitly formulated models. The method was applied to predict gait with a prosthetic foot and ankle. Solutions were obtained in well under one hour of computation time and demonstrated how patients may adapt their gait to compensate for limitations of a specific prosthetic limb design. The optimal control method was also applied to a state estimation problem in sports biomechanics, where forces during skiing were estimated from noisy and incomplete kinematic data. Using a full musculoskeletal dynamics model for state estimation had the additional advantage that forward dynamic simulations, could be done with the same implicitly formulated model to simulate injuries and perturbation responses. While these methods are powerful and allow solution of previously intractable problems, there are still considerable numerical challenges, especially related to the convergence of gradient-based solvers. PMID:22102983

  5. Targeting damage-associated molecular pattern molecules (DAMPs) and DAMP receptors in melanoma.

    PubMed

    Boone, Brian A; Lotze, Michael T

    2014-01-01

    Damage-associated molecular pattern molecules (DAMPs) are proteins released from cells under stress due to nutrient deprivation, hypoxia, trauma, or treatment with chemotherapy, among a variety of other causes. When released, DAMPs activate innate immunity, providing a pathway to a systemic inflammatory response in the absence of infection. By regulating inflammation in the tumor microenvironment, promoting angiogenesis, and increasing autophagy with evasion of apoptosis, DAMPs facilitate cancer growth. DAMPs and DAMP receptors have a key role in melanoma pathogenesis. Due to their crucial role in the development of melanoma and chemoresistance, DAMPs represent intriguing targets at a time when novel treatments are desperately needed. PMID:24258998

  6. The Effect of Gender Stereotypes on Explicit and Implicit Career Preferences

    ERIC Educational Resources Information Center

    Gadassi, Reuma; Gati, Itamar

    2009-01-01

    The present study compared gender differences in directly reported and indirectly derived career preferences and tested the hypothesis that individuals' implicit preferences would show less gender-biased occupational choices than their directly elicited ones. Two hundred sixty-six visitors to a career-related Internet site were asked to (a) list 5…

  7. ICAN/DAMP-integrated composite analyzer with damping analysis capabilities: User's manual

    NASA Technical Reports Server (NTRS)

    Saravanos, Dimitrious A.; Sanfeliz, Jose G.

    1992-01-01

    This manual describes the use of the computer code ICAN/DAMP (Integrated Composite Analyzer with Damping Analysis Capabilities) for the prediction of damping in polymer-matrix composites. The code is written in FORTRAN 77 and is a version of the ICAN (Integrated Composite ANalyzer) computer program. The code incorporates a new module for synthesizing the material damping from micromechanics to laminate level. Explicit micromechanics equations based on hysteretic damping are programmed relating the on-axis damping capacities to the fiber and matrix properties and fiber volume ratio. The damping capacities of unidirectional composites subjected to off-axis loading are synthesized from on-axis damping values. The hygrothermal effect on the damping performance of unidirectional composites caused by temperature and moisture variation is modeled along with the damping contributions from interfacial friction between broken fibers and matrix. The temperature rise is continuously vibrating composite plies and composite laminates is also estimated. The ICAN/DAMP user's manual provides descriptions of the damping analysis module's functions, structure, input requirements, output interpretation, and execution requirements. It only addresses the changes required to conduct the damping analysis and is used in conjunction with the 'Second Generation Integrated Composite Analyzer (ICAN) Computer Code' user's manual (NASA TP-3290).

  8. Viscous damping for base isolated structures

    SciTech Connect

    Lee, D.; Hussain, S.; Retamal, E.

    1995-12-01

    Seismic Base Isolation can use elastomeric pads, sliding plates or inverted pendulums. Each method can include an energy dissipation means, but only as some kind of hysteretic damping. Hysteretic damping has limitations in terms of energy absorption and may tend to excite higher modes in some cases. It`s possible to avoid these problems with viscous dampers. Viscous damping adds energy dissipation through loads that are 900 out of phase with bending and shear loads so even with damping levels as high as 40% of critical adverse side effects tend to be minimal. This paper presents basic theory of viscous damping, and also describes a sample project. Viscous dampers being built for the new San Bernardino Medical Center reduce both deflections and loads by 50% compared with high damping elastomer base isolation bearings by themselves.

  9. Global Asymptotic Behavior of Iterative Implicit Schemes

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sweby, P. K.

    1994-01-01

    The global asymptotic nonlinear behavior of some standard iterative procedures in solving nonlinear systems of algebraic equations arising from four implicit linear multistep methods (LMMs) in discretizing three models of 2 x 2 systems of first-order autonomous nonlinear ordinary differential equations (ODEs) is analyzed using the theory of dynamical systems. The iterative procedures include simple iteration and full and modified Newton iterations. The results are compared with standard Runge-Kutta explicit methods, a noniterative implicit procedure, and the Newton method of solving the steady part of the ODEs. Studies showed that aside from exhibiting spurious asymptotes, all of the four implicit LMMs can change the type and stability of the steady states of the differential equations (DEs). They also exhibit a drastic distortion but less shrinkage of the basin of attraction of the true solution than standard nonLMM explicit methods. The simple iteration procedure exhibits behavior which is similar to standard nonLMM explicit methods except that spurious steady-state numerical solutions cannot occur. The numerical basins of attraction of the noniterative implicit procedure mimic more closely the basins of attraction of the DEs and are more efficient than the three iterative implicit procedures for the four implicit LMMs. Contrary to popular belief, the initial data using the Newton method of solving the steady part of the DEs may not have to be close to the exact steady state for convergence. These results can be used as an explanation for possible causes and cures of slow convergence and nonconvergence of steady-state numerical solutions when using an implicit LMM time-dependent approach in computational fluid dynamics.

  10. Subliminal strengthening: improving older individuals' physical function over time with an implicit-age-stereotype intervention.

    PubMed

    Levy, Becca R; Pilver, Corey; Chung, Pil H; Slade, Martin D

    2014-12-01

    Negative age stereotypes that older individuals assimilate from their culture predict detrimental outcomes, including worse physical function. We examined, for the first time, whether positive age stereotypes, presented subliminally across multiple sessions in the community, would lead to improved outcomes. Each of 100 older individuals (age=61-99 years, M=81) was randomly assigned to an implicit-positive-age-stereotype-intervention group, an explicit-positive-age-stereotype-intervention group, a combined implicit- and explicit-positive-age-stereotype-intervention group, or a control group. Interventions occurred at four 1-week intervals. The implicit intervention strengthened positive age stereotypes, which strengthened positive self-perceptions of aging, which, in turn, improved physical function. The improvement in these outcomes continued for 3 weeks after the last intervention session. Further, negative age stereotypes and negative self-perceptions of aging were weakened. For all outcomes, the implicit intervention's impact was greater than the explicit intervention's impact. The physical-function effect of the implicit intervention surpassed a previous study's 6-month-exercise-intervention's effect with participants of similar ages. The current study's findings demonstrate the potential of directing implicit processes toward physical-function enhancement over time. PMID:25326508