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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. The direct measurement of structural mass, stiffness and damping properties

    NASA Astrophysics Data System (ADS)

    Lee, H. G.; Dobson, B. J.

    1991-02-01

    A method is described for directly evaluating the spatial properties (i.e., mass, stiffness and damping) of a structure from experimentally measured frequency response data. The resulting structural model can be compared directly with an equivalent finite element idealization. The effects of model reduction, such as the Guyan method, which can be employed to ensure that the experimental and theoretical models contain comparable degrees of freedom, are discussed. It is shown that it is possible to detect regions within the structure at which differences exist between the experimental and theoretical models. Further, it is demonstrated that the resulting experimentally derived models can be used to predict the effects of structural modifications upon the frequency response behaviour of the structure.

  4. 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.

  5. Children can implicitly, but not voluntarily, direct attention in time.

    PubMed

    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.

  6. Solution of the field equations for 2-D electromagnetic direct implicit plasma simulation

    NASA Astrophysics Data System (ADS)

    Hewett, D. W.; Langdon, A. B.

    1985-01-01

    A direct implicit particle-in-cell (PIC) simulation model with full electromagnetic (EM) effects has been implemented in 2-D Cartesian geometry. The model, implemented with the D1 time differencing scheme, was first implemented in a 1-D electrostatic (ES) version to gain some experience with spatial differencing in forms suitable for extension to the full EM field in two dimensions. The implicit EM field solve is considerably different from the implicit ES code. The EM field calculation requires an inductive part as well as the electrostatic and the B field must be self-consistently advanced.

  7. Investigation of an incompressible flow along a corner by an alternating direction implicit method

    NASA Technical Reports Server (NTRS)

    Goglia, G. L.; Patel, D. K.

    1977-01-01

    The axial corner flow is analyzed for the incompressible laminar boundary layer flow. The governing equations are derived from the Navier-Stokes equations by neglecting second derivative terms of the axial direction. An alternating direction implicit method is used to solve the equations in primitive variables.

  8. Alternating direction implicit methods for parabolic equations with a mixed derivative

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    Alternating direction implicit (ADI) schemes for two-dimensional parabolic equations with a mixed derivative are constructed by using the class of all A sub 0-stable linear two-step methods in conjunction with the method of approximation factorization. The mixed derivative is treated with an explicit two-step method which is compatible with an implicit A sub 0-stable method. The parameter space for which the resulting ADI schemes are second order accurate and unconditionally stable is determined. Some numerical examples are given.

  9. Intelligent damping layer under a plate subjected to a pair of masses moving in opposite directions

    NASA Astrophysics Data System (ADS)

    Bajer, Czesław; Pisarski, Dominik; Szmidt, Tomasz; Dyniewicz, Bartłomiej

    2017-04-01

    Reducing displacements of a plate vibrating under a pair of masses traveling in opposite directions can be improved by adding a smart subsoil instead of a classical damping layer. We propose a material that acts according to the instantaneous state of the plate, i.e., its displacements and velocity. Such an intelligent damping layer reduces vertical displacements even by 40%-60%, depending on the type of load and the assumed objective function. Existing materials enable the application of the proposed layer in a semi-active mode. The passive mode can be applied with materials exhibiting direction-dependent viscosity.

  10. 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…

  11. Direct heuristic dynamic programming for damping oscillations in a large power system.

    PubMed

    Lu, Chao; Si, Jennie; Xie, Xiaorong

    2008-08-01

    This paper applies a neural-network-based approximate dynamic programming method, namely, the direct heuristic dynamic programming (direct HDP), to a large power system stability control problem. The direct HDP is a learning- and approximation-based approach to addressing nonlinear coordinated control under uncertainty. One of the major design parameters, the controller learning objective function, is formulated to directly account for network-wide low-frequency oscillation with the presence of nonlinearity, uncertainty, and coupling effect among system components. Results include a novel learning control structure based on the direct HDP with applications to two power system problems. The first case involves static var compensator supplementary damping control, which is used to provide a comprehensive evaluation of the learning control performance. The second case aims at addressing a difficult complex system challenge by providing a new solution to a large interconnected power network oscillation damping control problem that frequently occurs in the China Southern Power Grid.

  12. 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

  13. 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.

  14. 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.

  15. Direct Cortical Mapping via Solving Partial Differential Equations on Implicit Surfaces

    PubMed Central

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

    2007-01-01

    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

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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…

  1. 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.

  2. High-order implicit residual smoothing time scheme for direct and large eddy simulations of compressible flows

    NASA Astrophysics Data System (ADS)

    Cinnella, P.; Content, C.

    2016-12-01

    Restrictions on the maximum allowable time step of explicit time integration methods for direct and large eddy simulations of compressible turbulent flows at high Reynolds numbers can be very severe, because of the extremely small space steps used close to solid walls to capture tiny and elongated boundary layer structures. A way of increasing stability limits is to use implicit time integration schemes. However, the price to pay is a higher computational cost per time step, higher discretization errors and lower parallel scalability. In quest for an implicit time scheme for scale-resolving simulations providing the best possible compromise between these opposite requirements, we develop a Runge-Kutta implicit residual smoothing (IRS) scheme of fourth-order accuracy, based on a bilaplacian operator. The implicit operator involves the inversion of scalar pentadiagonal systems, for which efficient parallel algorithms are available. The proposed method is assessed against two explicit and two implicit time integration techniques in terms of computational cost required to achieve a threshold level of accuracy. Precisely, the proposed time scheme is compared to four-stages and six-stages low-storage Runge-Kutta method, to the second-order IRS and to a second-order backward scheme solved by means of matrix-free quasi-exact Newton subiterations. Numerical results show that the proposed IRS scheme leads to reductions in computational time by a factor 3 to 5 for an accuracy comparable to that of the corresponding explicit Runge-Kutta scheme.

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

    SciTech Connect

    Lambert, Michael Allen

    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 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.

  4. Implicit Causality, Implicit Consequentiality and Semantic Roles

    ERIC Educational Resources Information Center

    Crinean, Marcelle; Garnham, Alan

    2006-01-01

    Stewart, Pickering, and Sanford (1998) reported a new type of semantic inference, implicit consequentiality, which they suggest is comparable to, although not directly related to, the well-documented phenomenon of implicit causality. It is our contention that there is a direct relation between these two semantic phenomena but that this relation…

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

    SciTech Connect

    Gibbons, Matthew Richard

    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.

  6. Alternating direction implicit technique and quantum evolution within the hydrodynamical formulation of Schrödinger's equation

    NASA Astrophysics Data System (ADS)

    Dey, Bijoy K.; Askar, Attila; Rabitz, H.

    1998-11-01

    An alternative method of quantum dynamics is presented. The method is based on the hydrodynamical formulation of the time-dependent Schrödinger equation originally given by David Bohm in his quest for establishing a hidden variable alternative to the quantum mechanics. A new alternating direction implicit technique has been employed to decouple many-dimensional hydrodynamical equations into a set of one-dimensional equations which have been solved numerically by adopting a recently developed flux corrected transport algorithm. We apply the method to describe the dynamics of a quantum particle in three spatial dimensions where analytical solutions are known.

  7. Magnetic Damping For Maglev

    DOE PAGES

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

    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.

  8. 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.

  9. 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.

  10. Implicit short- and long-term memory direct our gaze in visual search.

    PubMed

    Kruijne, Wouter; Meeter, Martijn

    2016-04-01

    Visual attention is strongly affected by the past: both by recent experience and by long-term regularities in the environment that are encoded in and retrieved from memory. In visual search, intertrial repetition of targets causes speeded response times (short-term priming). Similarly, targets that are presented more often than others may facilitate search, even long after it is no longer present (long-term priming). In this study, we investigate whether such short-term priming and long-term priming depend on dissociable mechanisms. By recording eye movements while participants searched for one of two conjunction targets, we explored at what stages of visual search different forms of priming manifest. We found both long- and short- term priming effects. Long-term priming persisted long after the bias was present, and was again found even in participants who were unaware of a color bias. Short- and long-term priming affected the same stage of the task; both biased eye movements towards targets with the primed color, already starting with the first eye movement. Neither form of priming affected the response phase of a trial, but response repetition did. The results strongly suggest that both long- and short-term memory can implicitly modulate feedforward visual processing.

  11. Complex-envelope alternating-direction-implicit FDTD method for simulating active photonic devices with semiconductor/solid-state media.

    PubMed

    Singh, Gurpreet; Ravi, Koustuban; Wang, Qian; Ho, Seng-Tiong

    2012-06-15

    A complex-envelope (CE) alternating-direction-implicit (ADI) finite-difference time-domain (FDTD) approach to treat light-matter interaction self-consistently with electromagnetic field evolution for efficient simulations of active photonic devices is presented for the first time (to our best knowledge). The active medium (AM) is modeled using an efficient multilevel system of carrier rate equations to yield the correct carrier distributions, suitable for modeling semiconductor/solid-state media accurately. To include the AM in the CE-ADI-FDTD method, a first-order differential system involving CE fields in the AM is first set up. The system matrix that includes AM parameters is then split into two time-dependent submatrices that are then used in an efficient ADI splitting formula. The proposed CE-ADI-FDTD approach with AM takes 22% of the time as the approach of the corresponding explicit FDTD, as validated by semiconductor microdisk laser simulations.

  12. Implicit coding of location and direction in a familiar, real-world "vista" space.

    PubMed

    Sulpizio, Valentina; Boccia, Maddalena; Guariglia, Cecilia; Galati, Gaspare

    2017-02-15

    Keeping oriented in the surrounding space requires an accurate representation of one's spatial position and facing direction. Although previous studies provided evidence of specific spatial codes for position and direction within room-sized and large-scale navigational environments, little is known about the mechanisms by which these spatial quantities are represented in a real small-scale environment. Here, we used two spatial tasks requiring participants to encode their own position and facing direction on a series of pictures taken from a familiar circular square. Crucially, directions and positions were incidentally manipulated, so that when participants were required to encode their current position in the square, the perceived direction across consecutive trials was the same, and vice versa. We found a behavioral advantage (priming effect: reduced reaction times and increased accuracy) for repeated directions and positions, even in the absence of any explicit demand to encode either of them. The advantage was higher for repeated directions, indicating that representation of one's own direction is more automatic than representation of one's own location. Furthermore, priming effects were partially mediated by gender: females (but not males) showed a stronger priming effect for repeated directions than for repeated positions. Finally, although priming effects were not linearly related to the physical distances between consecutive positions and directions, they revealed a rough preservation of real-world distance relationships.

  13. 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

  14. 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.

  15. 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.

  16. 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

  17. 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.

  18. 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…

  19. Performance of arrays of direct-driven wave energy converters under optimal power take-off damping

    NASA Astrophysics Data System (ADS)

    Wang, Liguo; Engström, Jens; Leijon, Mats; Isberg, Jan

    2016-08-01

    It is well known that the total power converted by a wave energy farm is influenced by the hydrodynamic interactions between wave energy converters, especially when they are close to each other. Therefore, to improve the performance of a wave energy farm, the hydrodynamic interaction between converters must be considered, which can be influenced by the power take-off damping of individual converters. In this paper, the performance of arrays of wave energy converters under optimal hydrodynamic interaction and power take-off damping is investigated. This is achieved by coordinating the power take-off damping of individual converters, resulting in optimal hydrodynamic interaction as well as higher production of time-averaged power converted by the farm. Physical constraints on motion amplitudes are considered in the solution, which is required for the practical implementation of wave energy converters. Results indicate that the natural frequency of a wave energy converter under optimal damping will not vary with sea states, but the production performance of a wave energy farm can be improved significantly while satisfying the motion constraints.

  20. 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.

  1. 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.

  2. 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.

  3. 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…

  4. 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.

  5. 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

  6. An improved semi-implicit method for structural dynamics analysis

    NASA Technical Reports Server (NTRS)

    Park, K. C.

    1982-01-01

    A semi-implicit algorithm is presented for direct time integration of the structural dynamics equations. The algorithm avoids the factoring of the implicit difference solution matrix and mitigates the unacceptable accuracy losses which plagued previous semi-implicit algorithms. This substantial accuracy improvement is achieved by augmenting the solution matrix with two simple diagonal matrices of the order of the integration truncation error.

  7. 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…

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. How explicit and implicit test instructions in an implicit learning task affect performance.

    PubMed

    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.

  15. 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.

  16. Quasienergy formulation of damped response theory.

    PubMed

    Kristensen, Kasper; Kauczor, Joanna; Kjaergaard, Thomas; Jørgensen, Poul

    2009-07-28

    We present a quasienergy-based formulation of damped response theory where a common effective lifetime parameter has been introduced for all excited states in terms of complex excitation energies. The introduction of finite excited state lifetimes leads to a set of (complex) damped response equations, which have the same form to all orders in the perturbation. An algorithm is presented for solving the damped response equations in Hartree-Fock theory and Kohn-Sham density functional theory. The use of the quasienergy formulation allows us to obtain directly the computationally simplest expressions for damped response functions by applying a set of response parameter elimination rules, which minimize the total number of damped response equations to be solved. In standard response theory broadened absorption spectra are obtained by ad hoc superimposing lineshape functions onto the absorption stick spectra, whereas an empirical lineshape function common to all excitations is an integrated part of damped response theory. By superimposing the lineshape functions inherent in damped response theory onto the stick spectra of standard response theory, we show that the absorption spectra obtained in standard and damped response theory calculations are identical. We demonstrate that damped response theory may be applied to obtain absorption spectra in all frequency ranges, also those that are not readily addressed using standard response theory. This makes damped response theory an effective tool, e.g., for determining absorption spectra for large molecules, where the density of the excited states may be very high, and where standard response theory therefore is not applicable in practice. A thorough comparison is given between our formulation of damped response theory and the formulation by Norman et al. [J. Chem. Phys. 123, 194103 (2005)].

  17. Probabilities in implicit learning.

    PubMed

    Tseng, Philip; Hsu, Tzu-Yu; Tzeng, Ovid J L; Hung, Daisy L; Juan, Chi-Hung

    2011-01-01

    The visual system possesses a remarkable ability in learning regularities from the environment. In the case of contextual cuing, predictive visual contexts such as spatial configurations are implicitly learned, retained, and used to facilitate visual search-all without one's subjective awareness and conscious effort. Here we investigated whether implicit learning and its facilitatory effects are sensitive to the statistical property of such implicit knowledge. In other words, are highly probable events learned better than less probable ones even when such learning is implicit? We systematically varied the frequencies of context repetition to alter the degrees of learning. Our results showed that search efficiency increased consistently as contextual probabilities increased. Thus, the visual contexts, along with their probability of occurrences, were both picked up by the visual system. Furthermore, even when the total number of exposures was held constant between each probability, the highest probability still enjoyed a greater cuing effect, suggesting that the temporal aspect of implicit learning is also an important factor to consider in addition to the effect of mere frequency. Together, these findings suggest that implicit learning, although bypassing observers' conscious encoding and retrieval effort, behaves much like explicit learning in the sense that its facilitatory effect also varies as a function of its associative strengths.

  18. Reducing explicit and implicit outgroup prejudice via direct and extended contact: The mediating role of self-disclosure and intergroup anxiety.

    PubMed

    Turner, Rhiannon N; Hewstone, Miles; Voci, Alberto

    2007-09-01

    In 4 studies, the authors investigated mediators of the effect of cross-group friendship. In Study 1, cross-group friendship among White elementary school children predicted more positive explicit outgroup attitude toward South Asians, mediated by self-disclosure and intergroup anxiety. In Study 2, cross-group friendship and extended contact among White and South Asian high school students positively predicted explicit outgroup attitude, mediated by self-disclosure and intergroup anxiety. Study 3 replicated these findings in a larger independent sample. In all 3 studies, exposure to the outgroup positively predicted implicit outgroup attitude. Study 4 further showed that self-disclosure improved explicit outgroup attitude via empathy, importance of contact, and intergroup trust. The authors discuss the theoretical and practical implications of these findings, which argue for the inclusion of self-disclosure as a key component of social interventions to reduce prejudice.

  19. Engineered damping treatments

    NASA Astrophysics Data System (ADS)

    Oh, J.; Ray, Manas C.; Baz, Amr M.

    2001-07-01

    Engineered Damping Treatments (EDT) that have high damping characteristics per unit volume are presented. The EDT's under consideration, consist of cellular viscoelastic damping matrices with optimally selected cell configuration, size and distribution. The cellular topology of the EDT's is designed using Computer-Aided-Design (CAD) strategies and the obtained optimal configurations will be manufactured using the state-of-the-art technology of Rapid Prototyping (RP). The EDT's are modeled using the finite element method in an attempt to determine the optimal topologies that maximize the strain energy, maximize the damping characteristics and minimize the total weight. The CAD files of the prototypes of the EDT's. The damping characteristics of the manufactured EDT's are evaluated and compared with the corresponding characteristics obtained by conventional solid damping treatments in order to emphasize the importance of using optimally configured damping treatment to achieve high damping characteristics. The presented procedures are invaluable for designing efficient damping treatments for many military and civilian structures whose vibrations and noise must be effectively controlled.

  20. Critically damped quantum search.

    PubMed

    Mizel, Ari

    2009-04-17

    Although measurement and unitary processes can accomplish any quantum evolution in principle, thinking in terms of dissipation and damping can be powerful. We propose a modification of Grover's algorithm in which the idea of damping plays a natural role. Remarkably, we find that there is a critical damping value that divides between the quantum O(sqrt[N]) and classical O(N) search regimes. In addition, by allowing the damping to vary in a fashion we describe, one obtains a fixed-point quantum search algorithm in which ignorance of the number of targets increases the number of oracle queries only by a factor of 1.5.

  1. 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.

  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. Implicit self and identity.

    PubMed

    Devos, Thierry; Banaji, Mahzarin R

    2003-10-01

    Recent advances in research on implicit social cognition offer an opportunity to challenge common assumptions about self and identity. In the present article, we critically review a burgeoning line of research on self-related processes known to occur outside conscious awareness or conscious control. Our discussion focuses on these implicit self-related processes as they unfold in the context of social group memberships. That is, we show that group memberships can shape thoughts, preferences, motives, goals, or behaviors without the actor's being aware of such an influence or having control over such expressions. As such, this research brings to the fore facets of the self that often contrast with experiences of reflexive consciousness and introspection. Far from being rigid or monolithic, these processes are highly flexible, context-sensitive, and deeply rooted in socio-structural realities. As such, work on implicit self and identity renew thinking about the interplay between the individual and the collective.

  4. 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.

  5. Variations of hybrid damping

    NASA Astrophysics Data System (ADS)

    Lam, Margaretha J.; Inman, Daniel J.; Saunders, William R.

    1998-06-01

    Damping is important to structures and can be achieved through the addition of viscoelastic materials (VEM). The damping of the VEM is enhanced if a constraining layer is attached to the VEM. If this constraining layer is active, the treatment is called active constrained layer damping (ACLD). In the last few years, ACLD has proven to be superior in vibration control to active or passive damping. The active element makes ACLD more effective than passive constrained layer damping. It also provides a fail-safe in case of breakdown of the active element that is not present for purely active control. It is shown that the control effort needed to damp vibration using ACLD can be significantly higher than purely active control. In order to combine the inherent damping of passive control with the effectiveness of the active element, this paper will explore different variations of active, passive and hybrid damping. Some of the variations include: passive constrained layer damping (PCLD) separate from active element but on the same side of beam, PCLD separate from active on the opposite side of the beam, and active element underneath PCLD. The discretized system equations will be obtained using assumed modes method and Lagrange's equation. The damping will be modeled using the Golla-Hughes-McTavish (GHM) method. The optimal placement and size of the active, passive, ACLD and hybrid treatments will be found using different schemes. The issue of overshoot and settling time of the output and control force using LQR will be addressed, as well as the control effort, passive and active vibration suppression, and LQR cost function. It will be shown that the hybrid treatments are capable of greater vibration control for lower control effort for different optimization schemes. 31

  6. Implicit Understanding of Belief.

    ERIC Educational Resources Information Center

    Clements, Wendy A.; Perner, Josef

    1994-01-01

    Implicit understanding of false belief was investigated by monitoring where preschoolers looked in anticipation of a protagonist reappearing, when the protagonist mistakenly thinks that his desired object is in a different place from where it really is. Two-year olds erroneously looked at the object's real location whereas most older children…

  7. 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.

  8. 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,…

  9. 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.

  10. Brain Networks of Explicit and Implicit Learning

    PubMed Central

    Yang, Jing; Li, Ping

    2012-01-01

    Are explicit versus implicit learning mechanisms reflected in the brain as distinct neural structures, as previous research indicates, or are they distinguished by brain networks that involve overlapping systems with differential connectivity? In this functional MRI study we examined the neural correlates of explicit and implicit learning of artificial grammar sequences. Using effective connectivity analyses we found that brain networks of different connectivity underlie the two types of learning: while both processes involve activation in a set of cortical and subcortical structures, explicit learners engage a network that uses the insula as a key mediator whereas implicit learners evoke a direct frontal-striatal network. Individual differences in working memory also differentially impact the two types of sequence learning. PMID:22952624

  11. 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.

  12. Damping in Space Constructions

    NASA Astrophysics Data System (ADS)

    de Vreugd, Jan; de Lange, Dorus; Winters, Jasper; Human, Jet; Kamphues, Fred; Tabak, Erik

    2014-06-01

    Monolithic structures are often used in optomechanical designs for space applications to achieve high dimensional stability and to prevent possible backlash and friction phenomena. The capacity of monolithic structures to dissipate mechanical energy is however limited due to the high Q-factor, which might result in high stresses during dynamic launch loads like random vibration, sine sweeps and shock. To reduce the Q-factor in space applications, the effect of constrained layer damping (CLD) is investigated in this work. To predict the damping increase, the CLD effect is implemented locally at the supporting struts in an existing FE model of an optical instrument. Numerical simulations show that the effect of local damping treatment in this instrument could reduce the vibrational stresses with 30-50%. Validation experiments on a simple structure showed good agreement between measured and predicted damping properties. This paper presents material characterization, material modeling, numerical implementation of damping models in finite element code, numerical results on space hardware and the results of validation experiments.

  13. Implicit learning as an ability.

    PubMed

    Kaufman, Scott Barry; Deyoung, Colin G; Gray, Jeremy R; Jiménez, Luis; Brown, Jamie; Mackintosh, Nicholas

    2010-09-01

    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, 1993; Stanovich, 2009) have suggested that individual differences in implicit learning are minimal relative to individual differences in explicit learning. In the current study of English 16-17year old students, we investigated the association of individual differences in implicit learning with a variety of cognitive and personality variables. Consistent with prior research and theorizing, implicit learning, as measured by a probabilistic sequence learning task, was more weakly related to psychometric intelligence than was explicit associative learning, and was unrelated to working memory. Structural equation modeling revealed that implicit learning was independently related to two components of psychometric intelligence: verbal analogical reasoning and processing speed. Implicit learning was also independently related to academic performance on two foreign language exams (French, German). Further, implicit learning was significantly associated with aspects of self-reported personality, including intuition, Openness to Experience, and impulsivity. We discuss the implications of implicit learning as an ability for dual-process theories of cognition, intelligence, personality, skill learning, complex cognition, and language acquisition.

  14. Damped flexible seal

    SciTech Connect

    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.

  15. 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.

  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. Implicit working memory

    PubMed Central

    Hassin, Ran R.; Bargh, John A.; Engell, Andrew D.; McCulloch, Kathleen C.

    2009-01-01

    Working Memory (WM) plays a crucial role in many high-level cognitive processes (e.g., reasoning, decision making, goal pursuit and cognitive control). The prevalent view holds that active components of WM are predominantly intentional and conscious. This conception is oftentimes expressed explicitly, but it is best reflected in the nature of major WM tasks: All of them are blatantly explicit. We developed two new WM paradigms that allow for an examination of the role of conscious awareness in WM. Results from five studies show that WM can operate unintentionally and outside of conscious awareness, thus suggesting that the current view should be expanded to include implicit WM. PMID:19442537

  18. 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.

  19. 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.

  20. The DAMPE Neutron Detector

    NASA Astrophysics Data System (ADS)

    Yan, Zhang; Tao, Ma; Yongyi, Huang

    2016-07-01

    The first Chinese space observatory DAMPE (DArk Matter Particle Explorer) was successfully launched on Dec. 17th, 2015. One major scientific object of DAMPE is to measure electrons between 5GeV to 10TeV with excellent energy resolution (1.5% at 800GeV) to search for possible dark matter signatures. The detector consists of four subsystems: a plastic scintillator detector (PSD), a silicon-tungsten tracker (STK), a BGO calorimeter (BGO), and a neutron detector (NUD). The NUD on board DAMPE is designed to detect moderated neutrons via the boron capture of thermal neutrons in boron-doped plastics. Given the fact that hadron showers initiated in the BGO calorimeter by incident nuclei tend to be followed by significantly more neutron activities comparing to electromagnetic cascades triggered by electrons, the NUD provides an additional order of magnitude hadron rejection capability to improve the overall e/p discrimination of DAMPE up to 10 ^{5}. Preliminary analysis of the in-orbit data is given, together with comparisons to the results obtained by a detailed GEANT4 simulation of the NUD instrument.

  1. 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.

  2. Radiation damping on cryoprobes.

    PubMed

    Shishmarev, Dmitry; Otting, Gottfried

    2011-12-01

    Radiation damping on 600 and 800 MHz cryoprobes was investigated. The phase angle β between a vector 90° phase shifted to the precessing magnetization and the rf field induced in the coil was found to depend markedly on whether an FID was being acquired or not. The magnitude of the radiation damping field was sufficiently strong to restore 95% of the equilibrium water magnetization of a 90% H2O sample in a 5 mm sample tube within about 5 ms following a 165° pulse. This can be exploited in water flip-back versions of NOESY and TOCSY experiments of proteins, but care must be taken to limit the effect of the radiation damping field from the water on the Ha protons. Long water-selective pulses can be applied only following corrections. We developed a program for correcting pulse shapes if β is non-zero. The WATERGATE scheme is shown to be insensitive to imperfections introduced by radiation damping.

  3. Parallel Implicit Algorithms for CFD

    NASA Technical Reports Server (NTRS)

    Keyes, David E.

    1998-01-01

    The main goal of this project was efficient distributed parallel and workstation cluster implementations of Newton-Krylov-Schwarz (NKS) solvers for implicit Computational Fluid Dynamics (CFD.) "Newton" refers to a quadratically convergent nonlinear iteration using gradient information based on the true residual, "Krylov" to an inner linear iteration that accesses the Jacobian matrix only through highly parallelizable sparse matrix-vector products, and "Schwarz" to a domain decomposition form of preconditioning the inner Krylov iterations with primarily neighbor-only exchange of data between the processors. Prior experience has established that Newton-Krylov methods are competitive solvers in the CFD context and that Krylov-Schwarz methods port well to distributed memory computers. The combination of the techniques into Newton-Krylov-Schwarz was implemented on 2D and 3D unstructured Euler codes on the parallel testbeds that used to be at LaRC and on several other parallel computers operated by other agencies or made available by the vendors. Early implementations were made directly in Massively Parallel Integration (MPI) with parallel solvers we adapted from legacy NASA codes and enhanced for full NKS functionality. Later implementations were made in the framework of the PETSC library from Argonne National Laboratory, which now includes pseudo-transient continuation Newton-Krylov-Schwarz solver capability (as a result of demands we made upon PETSC during our early porting experiences). A secondary project pursued with funding from this contract was parallel implicit solvers in acoustics, specifically in the Helmholtz formulation. A 2D acoustic inverse problem has been solved in parallel within the PETSC framework.

  4. Nutational Damping Revisited

    NASA Astrophysics Data System (ADS)

    Burns, J. A.; Sharma, I.

    2000-10-01

    Motivated by the recent detection of complex rotational states for several asteroids and comets, as well as by the ongoing and planned spacecraft missions to such bodies, which should allow their rotational states to be accurately determined, we revisit the problem of the nutational damping of small solar system bodies. The nutational damping of asteroids has been approximately analyzed by Prendergast (1958), Burns and Safronov (1973), and Efroimsky and Lazarian (2000). Many other similar dynamical studies concern planetary wobble decay (e.g., Peale 1973; Yoder and Ward 1979), interstellar dust grain alignment (e.g., Purcell 1979; Lazarian and Efroimsky 1999) and damping of Earth's Chandler wobble (Lambeck 1980). Recall that rotational energy loss for an isolated body aligns the body's angular momentum vector with its axis of maximum inertia. Assuming anelastic dissipation, simple dimensional analysis determines a functional form of the damping timescale, on which all the above authors agree. However, the numerical coefficients of published results are claimed to differ by orders of magnitude. Differences have been ascribed to absent physics, to solutions that fail to satisfy boundary conditions perfectly, and to unphysical choices for the Q parameter. The true reasons for the discrepancy are unclear since, despite contrary claims, the full 3D problem (nutational damping of an anelastic ellipsoid) is analytically intractable so far. To move the debate forward, we compare the solution of a related 2D problem to the expressions found previously, and we present results from a finite element model. On this basis, we feel that previous rates for the decay of asteroidal tumbling (Harris 1994), derived from Burns and Safronov (1973), are likely to be accurate, at least to a factor of a few. Funded by NASA.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  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. The neuropharmacology of implicit learning.

    PubMed

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

    2010-12-01

    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.

  11. The repressed and implicit knowledge.

    PubMed

    Talvitie, Vesa; Ihanus, Juhani

    2002-12-01

    The distinction between implicit (non-conscious) and explicit (conscious) knowledge made by cognitive scientists is applied to the psychoanalytic idea of repressed contents. The consequences of repression are suggested to have been caused by implicit representations. Repressed memories can also be treated in terms of explicit representations, which are prevented from becoming activated. Implicit knowledge cannot, however, be made conscious, and thus the idea of becoming conscious of the repressed desires and fears that have never been conscious is contradictory. This tension may be relieved by reconceptualising the idea of becoming conscious of the repressed. It is suggested that this could be seen as creating explicit knowledge about the effects of implicit representations. By applying the implicit/explicit knowledge distinction, psychoanalytic ideas concerning the repressed could be connected to current views in the domain of cognitive orientation.

  12. Damping of Crank-Nicolson error oscillations.

    PubMed

    Britz, D; Østerby, O; Strutwolf, J

    2003-07-01

    The Crank-Nicolson (CN) simulation method has an oscillatory response to sharp initial transients. The technique is convenient but the oscillations make it less popular. Several ways of damping the oscillations in two types of electrochemical computations are investigated. For a simple one-dimensional system with an initial singularity, subdivision of the first time interval into a number of equal subintervals (the Pearson method) works rather well, and so does division with exponentially increasing subintervals, where however an optimum expansion parameter must be found. This method can be computationally more expensive with some systems. The simple device of starting with one backward implicit (BI, or Laasonen) step does damp the oscillations, but not always sufficiently. For electrochemical microdisk simulations which are two-dimensional in space and using CN, the use of a first BI step is much more effective and is recommended. Division into subintervals is also effective, and again, both the Pearson method and exponentially increasing subintervals methods are effective here. Exponentially increasing subintervals are often considerably more expensive computationally. Expanding intervals over the whole simulation period, although capable of satisfactory results, for most systems will require more cpu time compared with subdivision of the first interval only.

  13. 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

  14. Translational damping on high-frequency flapping wings

    NASA Astrophysics Data System (ADS)

    Parks, Perry A.

    Flapping fliers such as insects and birds depend on passive translational and rotational damping to terminate quick maneuvers and to provide a source of partial stability in an otherwise unstable dynamic system. Additionally, passive translational and rotational damping reduce the amount of active kinematic changes that must be made to terminate maneuvers and maintain stability. The study of flapping-induced damping phenomena also improves the understanding of micro air vehicle (MAV) dynamics needed for the synthesis of effective flight control strategies. Aerodynamic processes which create passive translational and rotational damping as a direct result of symmetric flapping with no active changes in wing kinematics have been previously studied and were termed flapping counter-force (FCF) and flapping counter-torque (FCT), respectively. In this first study of FCF measurement in air, FCF generation is measured using a pendulum system designed to isolate and measure the relationship of translational flapping-induced damping with wingbeat frequency for a 2.86 gram mechanical flapper equipped with real cicada wings. Analysis reveals that FCF generation and wingbeat frequency are directly proportional, as expected from previous work. The quasi-steady FCF model using Blade-Element-Theory is used as an estimate for translational flapping-induced damping. In most cases, the model proves to be accurate in predicting the relationship between flapping-induced damping and wingbeat frequency. "Forward-backward" motion proves to have the strongest flapping-induced damping while "up-down" motion has the weakest.

  15. 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.

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

    PubMed Central

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

    2011-01-01

    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

  17. Implicit and explicit representations of hand position in tool use.

    PubMed

    Rand, Miya K; Heuer, Herbert

    2013-01-01

    Understanding the interactions of visual and proprioceptive information in tool use is important as it is the basis for learning of the tool's kinematic transformation and thus skilled performance. This study investigated how the CNS combines seen cursor positions and felt hand positions under a visuo-motor rotation paradigm. Young and older adult participants performed aiming movements on a digitizer while looking at rotated visual feedback on a monitor. After each movement, they judged either the proprioceptively sensed hand direction or the visually sensed cursor direction. We identified asymmetric mutual biases with a strong visual dominance. Furthermore, we found a number of differences between explicit and implicit judgments of hand directions. The explicit judgments had considerably larger variability than the implicit judgments. The bias toward the cursor direction for the explicit judgments was about twice as strong as for the implicit judgments. The individual biases of explicit and implicit judgments were uncorrelated. Biases of these judgments exhibited opposite sequential effects. Moreover, age-related changes were also different between these judgments. The judgment variability was decreased and the bias toward the cursor direction was increased with increasing age only for the explicit judgments. These results indicate distinct explicit and implicit neural representations of hand direction, similar to the notion of distinct visual systems.

  18. How implicit is visual statistical learning?

    PubMed

    Bertels, Julie; Franco, Ana; Destrebecqz, Arnaud

    2012-09-01

    In visual statistical learning, participants learn the statistical regularities present in a sequence of visual shapes. A recent study (Kim, Seitz, Feenstra, & Shams, 2009) suggests that visual statistical learning occurs implicitly, as it is not accompanied by conscious awareness of these regularities. However, that interpretation of the data depends on 2 unwarranted assumptions concerning the nature and sensitivity of the tasks used to measure learning. In a replication of this study, we used a 4-choice completion task as a direct measure of learning, in addition to an indirect measure consisting of a rapid serial visual presentation task. Moreover, binary confidence judgments were recorded after each completion trial. This way, we measured systematically the extent to which sequence knowledge was available to consciousness. Supporting the notion that the role of unconscious knowledge was overestimated in Kim et al.'s study, our results reveal that participants' performance cannot be exclusively accounted for by implicit knowledge.

  19. Radiation Damping in a Focusing Channel

    NASA Astrophysics Data System (ADS)

    Ruth, Ronald D.

    1996-05-01

    In electron storage rings synchrotron radiation leads to the damping of the three degrees of freedom of the particle trajectory towards a stable closed orbit transversely and a fixed stable phase longitudinally. At the same time, the emission of discrete quanta leads to diffusion in all three degrees of freedom. These two competing effects result in an equilibrium beam emittance that depends upon the parameters of the storage ring. In the case above, the radiation in the bending fields dominates, and the radiation due to the focusing fields is either neglected or taken into account perturbatively. In this talk we study the opposite case, a continuous focusing channel in which the radiation and its reaction are dominated by the strong focusing field. If there is a bending field, it is much weaker than the focusing field. In such focusing systems, we find that the radiation is synchrotron-like for larger betatron oscillation amplitudes and undulator-like for smaller amplitudes. However, quantum excitation is absent for any oscillation amplitude, and the damping exhibits asymmetry in favor of the transverse degree of freedom as the amplitude becomes smaller. In the undulator regime, the damping turns into exponential in the transverse direction, much faster than the total energy damping in this system. In principle, the particle could damp to the transverse ground state of the harmonic oscillator, reaching a minimum normalized emittance, γ ɛ_min = hbar/2mc, limited only by the uncertainty principle. In the case of a bent focusing system, we find that the lack of quantum excitation and asymmetric damping still hold provided that the bending field is sufficiently weak.

  20. Implicit Self-Evaluations Predict Changes in Implicit Partner Evaluations

    PubMed Central

    McNulty, James K.; Baker, Levi R.; Olson, Michael A.

    2014-01-01

    Do people who feel good about themselves have better relations with others? Although the notion that they do is central to both classic and modern theories, there is little strong evidence to support it. We argue that one reason for the lack of evidence is that prior research has relied exclusively on explicit measures of self- and relationship evaluations. The current longitudinal study of newlywed couples used explicit measures of self-, relationship, and partner evaluations as well as implicit measures of self- and partner evaluations to examine the link between self-evaluations and changes in relationship evaluations over the first three years of marriage. Whereas explicit self-evaluations were unrelated to changes in all interpersonal measures, implicit self-evaluations positively predicted changes in implicit partner evaluations. This finding joins others in highlighting the importance of automatic processes and implicit measures to the study of close interpersonal relationships. PMID:24958686

  1. 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.

  2. 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…

  3. 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.

  4. Implicit Numerical Methods in Meteorology

    NASA Technical Reports Server (NTRS)

    Augenbaum, J.

    1984-01-01

    The development of a fully implicit finite-difference model, whose time step is chosen solely to resolve accurately the physical flow of interest is discussed. The method is based on an operator factorization which reduces the dimensionality of the implicit approach: at each time step only (spatially) one-dimensional block-tridiagonal linear systems must be solved. The scheme uses two time levels and is second-order accurate in time. Compact implicit spatial differences are used, yielding fourth-order accuracy both vertically and horizontally. In addition, the development of a fully interactive computer code is discussed. With this code the user will have a choice of models, with various levels of accuracy and sophistication, which are imbedded, as subsets of the fully implicit 3D code.

  5. 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.

  6. On damping mechanisms in beams

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    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.

  7. 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.

  8. 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.

  9. Benchmarking the Multidimensional Stellar Implicit Code MUSIC

    NASA Astrophysics Data System (ADS)

    Goffrey, T.; Pratt, J.; Viallet, M.; Baraffe, I.; Popov, M. V.; Walder, R.; Folini, D.; Geroux, C.; Constantino, T.

    2017-03-01

    We present the results of a numerical benchmark study for the MUltidimensional Stellar Implicit Code (MUSIC) based on widely applicable two- and three-dimensional compressible hydrodynamics problems relevant to stellar interiors. MUSIC is an implicit large eddy simulation code that uses implicit time integration, implemented as a Jacobian-free Newton Krylov method. A physics based preconditioning technique which can be adjusted to target varying physics is used to improve the performance of the solver. The problems used for this benchmark study include the Rayleigh-Taylor and Kelvin-Helmholtz instabilities, and the decay of the Taylor-Green vortex. Additionally we show a test of hydrostatic equilibrium, in a stellar environment which is dominated by radiative effects. In this setting the flexibility of the preconditioning technique is demonstrated. This work aims to bridge the gap between the hydrodynamic test problems typically used during development of numerical methods and the complex flows of stellar interiors. A series of multidimensional tests were performed and analysed. Each of these test cases was analysed with a simple, scalar diagnostic, with the aim of enabling direct code comparisons. As the tests performed do not have analytic solutions, we verify MUSIC by comparing it to established codes including ATHENA and the PENCIL code. MUSIC is able to both reproduce behaviour from established and widely-used codes as well as results expected from theoretical predictions. This benchmarking study concludes a series of papers describing the development of the MUSIC code and provides confidence in future applications.

  10. 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.

  11. 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.

  12. 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.

  13. Discrete-layered damping model of multilayer plate with account of internal damping

    NASA Astrophysics Data System (ADS)

    Paimushin, V. N.; Gazizullin, R. K.

    2016-11-01

    Construction of discrete-layered damping model of multilayer plate in small displacement and deformations with account of internal damping of layers of Thompson- Kelvin-Voight model is presented. Based on derived equations, analytical solution is given to the static damping problem of simply supported single-layer rectangular plate subjected to uniformly distributed pressure, which is applied to one of its boundary planes. Convergence to the three-dimensional case is analysed for the obtained solution with respect to the dependence on dimension of mesh in the thickness direction of plate. For thin plates, dimension reduction of the formulated problem is set on the basis of simplifying hypothesis applied for each layer.

  14. Backup nutation damping strategy for the Galileo spacecraft

    NASA Technical Reports Server (NTRS)

    Eke, Fidelis O.; Eke, Estelle M.

    1989-01-01

    A discussion is presented of the design and testing of remedial measures that can be taken to achieve reasonable nutation damping of the Galileo spacecraft in the event of failure of its boom damper in flight. One scheme exploits the effects of payload motion on the nutational stability of a spinning spacecraft. However, the spacecraft-motion-compensation algorithm can only be used if the scan platform bore sight is pointed in a direction chosen to produce rapid damping of spacecraft nutation. A second method suggested for nutation damping is a thruster-based open-loop control algorithm, utilizing a pair of thrusters as actuators.

  15. 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.

  16. Vibration Damping Response of Composite Materials

    DTIC Science & Technology

    1991-04-01

    to predict the vibration damping of these coposites. L lein Irauu, .. rii. se i-s foi tesi specimel gC-miLtrics oSl0y, so that - material...manner that the strain in the x direction was determined. This development results in the transverse strain given as av (x,y,z) avO (x,y)ei~ t a 2wO(xy) ei

  17. 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.

  18. 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.

  19. 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.

  20. Atomistic Mechanisms for Viscoelastic Damping in Inorganic Solids

    NASA Astrophysics Data System (ADS)

    Ranganathan, Raghavan

    the microstructural length-scale of the composite. The second class of materials consist of structurally heterogeneous binary alloys that are either ordered, random or glassy. Vastly different mechanisms for viscoelastic damping arise for the three structures - random alloy and glass are observed to exhibit significant damping owing to large anharmonicity in the coupling between vibrational modes, which is a direct consequence of the chemical heterogeneity. Additionally, at low shear frequencies, glass exhibits significant long-time scale structural relaxation that results in persistent damping over a large range of frequencies. Finally, a critical analysis of various factors that affect damping in inorganic glasses is made. We show that damping in glasses exhibits a striking commonality - at high frequencies, vibrational anharmonicity leads to a peak in damping for all glasses commensurate with the range of vibrational frequencies of the glass; at intermediate and low frequencies, structural relaxation leads to persistent, nearly-constant damping. The frequency-dependent damping mechanisms and structure-property relations observed with respect to damping are expected to enable the design of novel structures with favorable damping characteristics.

  1. Implicit emotional awareness in frontotemporal dementia.

    PubMed

    Ibáñez, Agustín; Velásquez, María Marcela; Caro, Miguel Martorell; Manes, Facundo

    2013-01-01

    The preserved "implicit awareness" in patients with Alzheimer disease (AD) presenting anosognosia has opened a new branch of research regarding explicit-implicit integration. The behavioral variant of frontotemporal dementia (bvFTD), contrary to AD, would present impaired anosognosia-related implicit awareness due to a dysfunctional implicit integration of contextual information caused by an abnormal fronto-insular-temporal network. Loss of insight and anosognosia are pervasive in bvFTD, but no reports have assessed the implicit emotional awareness in this condition. We emphasize the need to investigate and extend our knowledge of implicit contextual integration impairments and their relation with anosognosia in bvFTD vs AD.

  2. The Implicit Learning of Mappings between Forms and Contextually Derived Meanings

    ERIC Educational Resources Information Center

    Leung, Janny H. C.; Williams, John N.

    2011-01-01

    The traditional implicit learning literature has focused primarily on the abstraction of statistical regularities in form-form connections. More attention has been recently directed toward the implicit learning of form-meaning connections, which might be crucial in the acquisition of natural languages. The current article reports evidence for…

  3. 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.

  4. Bearing-Cartridge Damping Seal

    NASA Technical Reports Server (NTRS)

    Goggins, David G.; Scharrer, Joseph K.; Chen, Wei C.

    1991-01-01

    In proposed design for improved ball-bearing cartridge, damping seal in form of thin-layer fluid journal bearing incorporated into cartridge. Damping seal acts as auxiliary bearing, relieving bearing balls of significant portions of both static and dynamic bearing loads. Damping from seal reduces dynamic loads even further by reducing amplitude of vibrations in second vibrational mode of rotor, which mode occurs when rotor turning at nearly full operating speed. Intended for use in high-pressure-oxygen turbopump of Space Shuttle main engine, also applicable to other turbomachinery bearings.

  5. 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.

  6. 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.

  7. 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.

  8. Electrorheologically damped impact system

    NASA Astrophysics Data System (ADS)

    Hardt, Lee R.

    1991-05-01

    An impact switch is described having a housing containing a rigid coaxial conductor entering one end. An inner cylindrical contact extends axially inward from and beyond the in housing end of an outer tubular contact which has a spiral spring extending axially from within a recess therein. The free end of the spring supports a mass spaced from the end of the inner contact. The contacts, spring and mass are enclosed within a flexible shroud spaced from the inner wall of the housing. The space between the shroud and housing contains an electrorheological fluid, the viscosity of which is a function of the voltage supplied by two electrodes extending through the housing and into the fluid. The voltage controlled viscosity permits control of damping of the shroud, mass, and spring movements in response to impact caused switch deceleration and control of time for switch closure and fuze delay by means of mass contact with the inner cylindrical contact, or spring contact with the outer tubular contact.

  9. Landau damping in space plasmas

    NASA Technical Reports Server (NTRS)

    Thorne, Richard M.; Summers, Danny

    1991-01-01

    The Landau damping of electrostatic Langmuir waves and ion-acoustic waves in a hot, isotropic, nonmagnetized, generalized Lorentzian plasma is analyzed using the modified plasma dispersion function. Numerical solutions for the real and imaginary parts of the wave frequency omega sub 0 - (i)(gamma) have been obtained as a function of the normalized wave number (k)(lambda sub D), where lambda sub D is the electron Debye length. For both particle distributions the electrostatic modes are found to be strongly damped at short wavelengths. At long wavelengths, this damping becomes less severe, but the attenuation of Langmuir waves is much stronger for a generalized Lorentzian plasma than for a Maxwellian plasma. It is concluded that Landau damping of ion-acoustic waves is only slightly affected by the presence of a high energy tail, but is strongly dependent on the ion temperature.

  10. 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.

  11. Fully Implicit Numerical Methods for the Baroclinic Primitive Equations

    NASA Technical Reports Server (NTRS)

    Cohn, S. E.; Isaacson, E.

    1984-01-01

    A fully implicit code was developed to solve the three-dimensional primitive equations of atmospheric flow. The scheme is second order accurate in time and fourth order accurate in the horizontal and vertical directions. Furthermore, as a result of being fully implicit, the time step is not restricted by the mesh spacing near the poles, nor by the speed of inertia-gravity waves. Rather, the time step, deltat is determined simply by the requirement that it be small enough to adequately resolve the atmospheric flow of interest. The accuracy and efficiency of current models for fine grids should be significantly improved.

  12. Implicit Learning of Nonlocal Musical Rules: Implicitly Learning More Than Chunks

    ERIC Educational Resources Information Center

    Kuhn, Gustav; Dienes, Zoltan

    2005-01-01

    Dominant theories of implicit learning assume that implicit learning merely involves the learning of chunks of adjacent elements in a sequence. In the experiments presented here, participants implicitly learned a nonlocal rule, thus suggesting that implicit learning can go beyond the learning of chunks. Participants were exposed to a set of…

  13. Simple suppression of radiation damping.

    PubMed

    Khitrin, A K; Jerschow, Alexej

    2012-12-01

    Radiation damping is known to cause line-broadening and frequency shifts of strong resonances in NMR spectra. While several techniques exist for the suppression of these effects, many require specialized hardware, or are only compatible with the presence of few strong resonances. We describe a simple pulse sequence for radiation damping suppression in spectra with many strong resonances. The sequence can be used as-is to generate simple spectra or as a signal excitation part in more advanced experiments.

  14. 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…

  15. Integrating Implicit Bias into Counselor Education

    ERIC Educational Resources Information Center

    Boysen, Guy A.

    2010-01-01

    The author reviews the empirical and theoretical literature on implicit bias as it relates to counselor education. Counselor educators can integrate implicit bias into the concepts of multicultural knowledge, awareness, and skill. Knowledge about implicit bias includes its theoretical explanation, measurement, and impact on counseling. Awareness…

  16. Turbomachinery rotor support with damping

    NASA Technical Reports Server (NTRS)

    Vonpragenau, George L. (Inventor)

    1990-01-01

    Damping seals, damping bearings, and a support sleeve are presented for the ball bearings of a high speed rotor. The ball bearings consist of a duplex set having the outer races packaged tightly within the sleeve while the sleeve provides a gap with a support member so that the bearings may float with the sleeve. The sleeve has a web extending radially between the pair of outer races and acts in conjunction with one or more springs to apply an axial preload to the outer races. The sleeves have a series of slits which provide the sleeve with a spring-like quality so that the spring acts to center the rotor upon which the bearings are mounted during start up and shut down. A damping seal or a damping bearing may be used in conjunction with the ball bearings and supporting sleeve, the damping seal and damping bearing having rotor portions including rigid outer surfaces mounted within the bore of a stator portion having triangular shaped pockets on the surface facing the rotor. Axial gates are provided between adjacent pockets in sections of the stator permitting fluid to flow with less resistance axially relative to the flow of fluids circumferentially between the rotor and the stator.

  17. Damping characterization in large structures

    NASA Technical Reports Server (NTRS)

    Eke, Fidelis O.; Eke, Estelle M.

    1991-01-01

    This research project has as its main goal the development of methods for selecting the damping characteristics of components of a large structure or multibody system, in such a way as to produce some desired system damping characteristics. The main need for such an analytical device is in the simulation of the dynamics of multibody systems consisting, at least partially, of flexible components. The reason for this need is that all existing simulation codes for multibody systems require component-by-component characterization of complex systems, whereas requirements (including damping) often appear at the overall system level. The main goal was met in large part by the development of a method that will in fact synthesize component damping matrices from a given system damping matrix. The restrictions to the method are that the desired system damping matrix must be diagonal (which is almost always the case) and that interbody connections must be by simple hinges. In addition to the technical outcome, this project contributed positively to the educational and research infrastructure of Tuskegee University - a Historically Black Institution.

  18. Generation of Delaunay meshes in implicit domains with edge sharpening

    NASA Astrophysics Data System (ADS)

    Belokrys-Fedotov, A. I.; Garanzha, V. A.; Kudryavtseva, L. N.

    2016-11-01

    A variational algorithm for the construction of 3D Delaunay meshes in implicit domains with a nonsmooth boundary is proposed. The algorithm is based on the self-organization of an elastic network in which each Delaunay edge is interpreted as an elastic strut. The elastic potential is constructed as a combination of the repulsion potential and the sharpening potential. The sharpening potential is applied only on the boundary and is used to minimize the deviation of the outward normals to the boundary faces from the direction of the gradient of the implicit function. Numerical experiments showed that in the case when the implicit function specifying the domain is considerably different from the signed distance function, the use of the sharpening potential proposed by Belyaev and Ohtake in 2002 leads to the mesh instability. A stable version of the sharpening potential is proposed. The numerical experiments showed that acceptable Delaunay meshes for complex shaped domains with sharp curved boundary edges can be constructed.

  19. Training Implicit Social Anxiety Associations: An Experimental Intervention

    PubMed Central

    Clerkin, Elise M.; Teachman, Bethany A.

    2010-01-01

    The current study investigates an experimental anxiety reduction intervention among a highly socially anxious sample (N=108; n=36 per Condition; 80 women). Using a conditioning paradigm, our goal was to modify implicit social anxiety associations to directly test the premise from cognitive models that biased cognitive processing may be causally related to anxious responding. Participants were trained to preferentially process non-threatening information through repeated pairings of self-relevant stimuli and faces indicating positive social feedback. As expected, participants in this positive training condition (relative to our two control conditions) displayed less negative implicit associations following training, and were more likely to complete an impromptu speech (though they did not report less anxiety during the speech). These findings offer partial support for cognitive models and indicate that implicit associations are not only correlated with social anxiety, they may be causally related to anxiety reduction as well. PMID:20102788

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

    PubMed

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

    2016-12-22

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

  1. Consider the source: persuasion of implicit evaluations is moderated by source credibility.

    PubMed

    Smith, Colin Tucker; De Houwer, Jan; Nosek, Brian A

    2013-02-01

    The long history of persuasion research shows how to change explicit, self-reported evaluations through direct appeals. At the same time, research on how to change implicit evaluations has focused almost entirely on techniques of retraining existing evaluations or manipulating contexts. In five studies, we examined whether direct appeals can change implicit evaluations in the same way as they do explicit evaluations. In five studies, both explicit and implicit evaluations showed greater evidence of persuasion following information presented by a highly credible source than a source low in credibility. Whereas cognitive load did not alter the effect of source credibility on explicit evaluations, source credibility had an effect on the persuasion of implicit evaluations only when participants were encouraged and able to consider information about the source. Our findings reveal the relevance of persuasion research for changing implicit evaluations and provide new ideas about the processes underlying both types of evaluation.

  2. 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.

  3. 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.

  4. 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.

  5. Spin-orbit precession damping in transition metal ferromagnets (invited)

    NASA Astrophysics Data System (ADS)

    Gilmore, K.; Idzerda, Y. U.; Stiles, M. D.

    2008-04-01

    We provide a simple explanation, based on an effective field, for the precession damping rate due to the spin-orbit interaction. Previous effective field treatments of spin-orbit damping include only variations of the state energies with respect to the magnetization direction, an effect referred to as the breathing Fermi surface. Treating the interaction of the rotating spins with the orbits as a perturbation, we include also changes in the state populations in the effective field. In order to investigate the quantitative differences between the damping rates of iron, cobalt, and nickel, we compute the dependence of the damping rate on the density of states and the spin-orbit parameter. There is a strong correlation between the density of states and the damping rate. The intraband terms of the damping rate depend on the spin-orbit parameter cubed, while the interband terms are proportional to the spin-orbit parameter squared. However, the spectrum of band spacings is also an important quantity and does not appear to depend in a simple way on material parameters.

  6. Design and responses of Butterworth and critically damped digital filters.

    PubMed

    Robertson, D Gordon E; Dowling, James J

    2003-12-01

    For many years the Butterworth lowpass filter has been used to smooth many kinds of biomechanical data, despite the fact that it is underdamped and therefore overshoots and/or undershoots data during rapid transitions. A comparison of the conventional Butterworth filter with a critically damped filter shows that the critically damped filter not only removes the undershooting and overshooting, but has a superior rise time during rapid transitions. While analog filters always create phase distortion, both the critically damped and Butterworth filters can be modified to become zero-lag filters when the data are processed in both the forward and reverse directions. In such cases little improvement is realized by applying multiple passes. The Butterworth filter has superior 'roll-off' (attenuation of noise above the cutoff frequency) than the critically damped filter, but by increasing the number of passes of the critically damped filter the same 'roll-off' can be achieved. In summary, the critically damped filter was shown to have superior performance in the time domain than the Butterworth filter, but for data that need to be double differentiated (e.g. displacement data) the Butterworth filter may still be the better choice.

  7. Spin amplification in solution magnetic resonance using radiation damping.

    PubMed

    Walls, Jamie D; Huang, Susie Y; Lin, Yung-Ya

    2007-08-07

    The sensitive detection of dilute solute spins is critical to biomolecular NMR. In this work, a spin amplifier for detecting dilute solute magnetization is developed using the radiation damping interaction in solution magnetic resonance. The evolution of the solvent magnetization, initially placed along the unstable -z direction, is triggered by the radiation damping field generated by the dilute solute magnetization. As long as the radiation damping field generated by the solute is larger than the corresponding thermal noise field generated by the sample coil, the solute magnetization can effectively trigger the evolution of the water magnetization under radiation damping. The coupling between the solute and solvent magnetizations via the radiation damping field can be further improved through a novel bipolar gradient scheme, which allows solute spins with chemical shift differences much greater than the effective radiation damping field strength to affect the solvent magnetizations more efficiently. Experiments performed on an aqueous acetone solution indicate that solute concentrations on the order of 10(-5) that of the solvent concentration can be readily detected using this spin amplifier.

  8. 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.

  9. [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.

  10. Damping mechanisms of a pendulum

    NASA Astrophysics Data System (ADS)

    Dolfo, Gilles; Castex, Daniel; Vigué, Jacques

    2016-11-01

    In this paper, we study the damping mechanisms of a pendulum. The originality of our setup is the use of a metal strip suspension and the development of extremely sensitive electric measurements of the pendulum velocity and position. Their sensitivity is absolutely necessary for a reliable measurement of the pendulum damping time constant because this measurement is possible only for very low oscillation amplitudes, when air friction forces quadratic in velocity have a negligible contribution to the observed damping. We have thus carefully studied damping by air friction forces, which is the dominant mechanism for large values of the Reynolds number Re but which is negligible in the Stokes regime, {Re} ∼ 1. In this last case, we have found that the dominant damping is due to internal friction in the metal strip, a universal effect called anelasticity, and, for certain frequencies, to resonant coupling to the support of the pendulum. All our measurements are well explained by theory. We believe this paper would be of interest to students in an undergraduate classical mechanics course.

  11. Increased damping in irregular resonators

    NASA Astrophysics Data System (ADS)

    Sapoval, Bernard; Asch, Mark; Felix, Simon; Filoche, Marcel

    2005-04-01

    The relation between shape and damping of shallow acoustical cavities has been studied numerically in the case where the dissipation occurs only on the cavity walls. It is first found that whatever the type of geometrical irregularity, many, but not all the modes are localized. It is shown that the localization mechanism is what is called weak localization. The more irregular, the smaller the quality factors are found. However this effect is very different for the non-localized and the localized modes. For non-localized modes the damping increases roughly proportionally to the cavity surface. The localized modes are even more damped. These results generalize the results already obtained both numerically and experimentally on prefractal acoustical cavities. [B. Sapoval, O. Haeberle, and S. Russ, J. Acoust. Soc. Am. 102, 2014-2019 (1997); B. Hebert, B. Sapoval, and S. Russ, ibid. 105, 1567-1576 (1999)].

  12. Increased damping of irregular resonators.

    PubMed

    Russ, S; Sapoval, B

    2002-03-01

    It is shown that fractal drums and jagged geometry resonators may be more damped than ordinary Euclidean systems. Several damping mechanisms are examined and studied by numerical calculations. The results depend on the dissipation mechanisms but globally they increase with localization, frequency, and the irregularity of the resonator. The increased dissipation is due to the uneven spatial distribution of the vibrational amplitude in two different ways. First, it is related to the partial confinement of the vibrational modes. Secondly, increased dissipation may be due to singularities in the amplitude distribution. This is the case when a few points exist where the vibration is pinned to zero inducing local logarithmic singularities. This last effect can be spectacular: a single defect can dominate the surface damping by viscous forces of a square drum.

  13. Implicit associations with popularity in early adolescence: an approach-avoidance analysis.

    PubMed

    Lansu, Tessa A M; Cillessen, Antonius H N; Karremans, Johan C

    2012-01-01

    This study examined 241 early adolescents' implicit and explicit associations with popularity. The peer status and gender of both the targets and the perceivers were considered. Explicit associations with popularity were assessed with sociometric methods. Implicit associations with popularity were assessed with an approach-avoidance task (AAT). Explicit evaluations of popularity were positive, but implicit associations were negative: Avoidance reactions to popular peers were faster than approach reactions. Interactions with the status of the perceiver indicated that unpopular participants had stronger negative implicit reactions to popular girls than did popular participants. This study demonstrated a negative reaction to popularity that cannot be revealed with explicit methods. The study of implicit processes with methods such as the AAT is a new and important direction for peer relations research.

  14. Linearized Implicit Numerical Method for Burgers' Equation

    NASA Astrophysics Data System (ADS)

    Mukundan, Vijitha; Awasthi, Ashish

    2016-12-01

    In this work, a novel numerical scheme based on method of lines (MOL) is proposed to solve the nonlinear time dependent Burgers' equation. The Burgers' equation is semi discretized in spatial direction by using MOL to yield system of nonlinear ordinary differential equations in time. The resulting system of nonlinear differential equations is integrated by an implicit finite difference method. We have not used Cole-Hopf transformation which gives less accurate solution for very small values of kinematic viscosity. Also, we have not considered nonlinear solvers that are computationally costlier and take more running time.In the proposed scheme nonlinearity is tackled by Taylor series and the use of fully discretized scheme is easy and practical. The proposed method is unconditionally stable in the linear sense. Furthermore, efficiency of the proposed scheme is demonstrated using three test problems.

  15. Temporal course of implicit emotion regulation during a Priming-Identify task: an ERP study.

    PubMed

    Wang, Yi; Li, Xuebing

    2017-02-02

    Implicit emotion regulation defined as goal-driven processes modulates emotion experiences and responses automatically without awareness. However, the temporal course of implicit emotion regulation is not clear. To address these issues, we adopted a new Priming-identify task (PI task) to manipulate implicit emotion regulation directly and observed the changes of early (N170), middle (early posterior negativity, EPN), and late event-related potentials (ERPs) components (late positivity potentials, LPP) under the different implicit emotion regulation conditions. The behavioral results indicated that the PI task manipulated subjective emotion experience effectively by priming emotion regulation goals. The ERP results found that implicit emotion regulation induced more negative N170 without altering the EPN and the LPP amplitudes, indicating that implicit emotion regulation occured automatically in the early perceptual stage not in the late selective attention stage of emotion processing. The correlation analysis also found the enlarged N170 was associated with decreased negative emotion subjective rating, suggesting that the N170 was probably an effective index of implicit emotion regulation. These observations imply that implicit emotion regulation probabbly occurs in the early stage of emotion processing automatically without consciousness.

  16. Temporal course of implicit emotion regulation during a Priming-Identify task: an ERP study

    PubMed Central

    Wang, Yi; Li, Xuebing

    2017-01-01

    Implicit emotion regulation defined as goal-driven processes modulates emotion experiences and responses automatically without awareness. However, the temporal course of implicit emotion regulation is not clear. To address these issues, we adopted a new Priming-identify task (PI task) to manipulate implicit emotion regulation directly and observed the changes of early (N170), middle (early posterior negativity, EPN), and late event-related potentials (ERPs) components (late positivity potentials, LPP) under the different implicit emotion regulation conditions. The behavioral results indicated that the PI task manipulated subjective emotion experience effectively by priming emotion regulation goals. The ERP results found that implicit emotion regulation induced more negative N170 without altering the EPN and the LPP amplitudes, indicating that implicit emotion regulation occured automatically in the early perceptual stage not in the late selective attention stage of emotion processing. The correlation analysis also found the enlarged N170 was associated with decreased negative emotion subjective rating, suggesting that the N170 was probably an effective index of implicit emotion regulation. These observations imply that implicit emotion regulation probabbly occurs in the early stage of emotion processing automatically without consciousness. PMID:28150801

  17. The Dynamics of Some 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 2 x 2 systems of first-order autonomous nonlinear ordinary differential equations is analyzed using the theory of dynamical systems. With the aid of parallel Connection Machines (CM-2 and CM-5), the associated bifurcation diagrams as a function of the time step, and the complex behavior of the associated 'numerical basins of attraction' of these iterative implicit schemes are revealed and compared. Studies showed that all of the four implicit LMMs exhibit a drastic distortion and segmentation but less shrinkage of the basin of attraction of the true solution than standard explicit methods. The numerical basins of attraction of a noniterative implicit procedure mimic more closely the basins of attraction of the differential equations than the iterative implicit procedures for the four implicit LMMs.

  18. Vibration Damping Circuit Card Assembly

    NASA Technical Reports Server (NTRS)

    Hunt, Ronald Allen (Inventor)

    2016-01-01

    A vibration damping circuit card assembly includes a populated circuit card having a mass M. A closed metal container is coupled to a surface of the populated circuit card at approximately a geometric center of the populated circuit card. Tungsten balls fill approximately 90% of the metal container with a collective mass of the tungsten balls being approximately (0.07) M.

  19. 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.

  20. Surfactant damping of water waves

    NASA Astrophysics Data System (ADS)

    Lapham, Gary S.; Dowling, David R.; Schultz, William W.

    1997-11-01

    The most well known and perhaps most important distinguishing characteristic of a water surface laden with surfactant is the profound increase in small-wave damping with the addition of even small amounts of surfactant material. It would seem to follow that damping increases with increasing surfactant concentration. This is undoubtedly true for some surfactants, however our experiments with a soluble surfactant show that it is possible to increase surfactant concentration and measure a decrease in damping. While the increased concentration is accompanied by a dramatic decrease in measured static surface tension, some of the capillary-wave frequency regime is less damped. Experimental measurements of the real and imaginary parts of the wave speed are compared with existing theory where at least one other physical quantity besides surface tension is needed to properly model the interface. Our on-going work with insoluble surfactants may also provide an example of this type of behavior for materials that do not readily transfer to and from the bulk water. [Supported by the Office of Naval Research

  1. 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...

  2. 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.

  3. An implicit Smooth Particle Hydrodynamic code

    SciTech Connect

    Knapp, Charles E.

    2000-05-01

    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.

  4. SPACE LAUNCH VEHICLE FULL-SCALE DAMPING TESTS

    DTIC Science & Technology

    The wind study portion of testing showed that the SLV gantry tower is sufficiently stable to be used as a base for forced oscillation of the vehicle...experimental damping factors agreed reasonably well with the results of previous tests. Increased confidence in the recent SLV ground wind restrictions has been the direct result of this test.

  5. 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.

  6. 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.

  7. 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.

  8. Implicit Binding of Facial Features During Change Blindness

    PubMed Central

    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

  9. 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.

  10. 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.

  11. 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.

  12. 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

  13. 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…

  14. 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.

  15. 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.

  16. A novel approach to the analysis of squeezed-film air damping in microelectromechanical systems

    NASA Astrophysics Data System (ADS)

    Yang, Weilin; Li, Hongxia; Chatterjee, Aveek N.; Elfadel, Ibrahim (Abe M.; Ender Ocak, Ilker; Zhang, TieJun

    2017-01-01

    Squeezed-film damping (SFD) is a phenomenon that significantly affects the performance of micro-electro-mechanical systems (MEMS). The total damping force in MEMS mainly include the viscous damping force and elastic damping force. Quality factor (Q factor) is usually used to evaluate the damping in MEMS. In this work, we measure the Q factor of a resonator through experiments in a wide range of pressure levels. In fact, experimental characterizations of MEMS have some limitations because it is difficult to conduct experiments at very high vacuum and also hard to differentiate the damping mechanisms from the overall Q factor measurements. On the other hand, classical theoretical analysis of SFD is restricted to strong assumptions and simple geometries. In this paper, a novel numerical approach, which is based on lattice Boltzmann simulations, is proposed to investigate SFD in MEMS. Our method considers the dynamics of squeezed air flow as well as fluid-solid interactions in MEMS. It is demonstrated that Q factor can be directly predicted by numerical simulation, and our simulation results agree well with experimental data. Factors that influence SFD, such as pressure, oscillating amplitude, and driving frequency, are investigated separately. Furthermore, viscous damping and elastic damping forces are quantitatively compared based on comprehensive simulation. The proposed numerical approach as well as experimental characterization enables us to reveal the insightful physics of squeezed-film air damping in MEMS.

  17. Implicit bias, awareness and imperfect cognitions.

    PubMed

    Holroyd, Jules

    2015-05-01

    Are individuals responsible for behaviour that is implicitly biased? Implicitly biased actions are those which manifest the distorting influence of implicit associations. That they express these 'implicit' features of our cognitive and motivational make up has been appealed to in support of the claim that, because individuals lack the relevant awareness of their morally problematic discriminatory behaviour, they are not responsible for behaving in ways that manifest implicit bias. However, the claim that such influences are implicit is, in fact, not straightforwardly related to the claim that individuals lack awareness of the morally problematic dimensions of their behaviour. Nor is it clear that lack of awareness does absolve from responsibility. This may depend on whether individuals culpably fail to know something that they should know. I propose that an answer to this question, in turn, depends on whether other imperfect cognitions are implicated in any lack of the relevant kind of awareness. In this paper I clarify our understanding of 'implicitly biased actions' and then argue that there are three different dimensions of awareness that might be at issue in the claim that individuals lack awareness of implicit bias. Having identified the relevant sense of awareness I argue that only one of these senses is defensibly incorporated into a condition for responsibility, rejecting recent arguments from Washington & Kelly for an 'externalist' epistemic condition. Having identified what individuals should - and can - know about their implicitly biased actions, I turn to the question of whether failures to know this are culpable. This brings us to consider the role of implicit biases in relation to other imperfect cognitions. I conclude that responsibility for implicitly biased actions may depend on answers to further questions about their relationship to other imperfect cognitions.

  18. A time-implicit numerical method and benchmarks for the relativistic Vlasov–Ampere equations

    DOE PAGES

    Carrie, Michael; Shadwick, B. A.

    2016-01-04

    Here, we present a time-implicit numerical method to solve the relativistic Vlasov–Ampere system of equations on a two dimensional phase space grid. The time-splitting algorithm we use allows the generalization of the work presented here to higher dimensions keeping the linear aspect of the resulting discrete set of equations. The implicit method is benchmarked against linear theory results for the relativistic Landau damping for which analytical expressions using the Maxwell-Juttner distribution function are derived. We note that, independently from the shape of the distribution function, the relativistic treatment features collective behaviors that do not exist in the non relativistic case.more » The numerical study of the relativistic two-stream instability completes the set of benchmarking tests.« less

  19. A time-implicit numerical method and benchmarks for the relativistic Vlasov–Ampere equations

    SciTech Connect

    Carrie, Michael; Shadwick, B. A.

    2016-01-04

    Here, we present a time-implicit numerical method to solve the relativistic Vlasov–Ampere system of equations on a two dimensional phase space grid. The time-splitting algorithm we use allows the generalization of the work presented here to higher dimensions keeping the linear aspect of the resulting discrete set of equations. The implicit method is benchmarked against linear theory results for the relativistic Landau damping for which analytical expressions using the Maxwell-Juttner distribution function are derived. We note that, independently from the shape of the distribution function, the relativistic treatment features collective behaviors that do not exist in the non relativistic case. The numerical study of the relativistic two-stream instability completes the set of benchmarking tests.

  20. Cocured damped layers in composite structure

    SciTech Connect

    Rotz, C.A. ); Barrett, D.J. )

    1992-01-01

    A study was made on the feasibility of laminating and cocuring graphite fiber-epoxy prepreg with plies of commercially available damping materials for form beams and hat-stiffened panels. Experiments showed that cocuring did not adversely affect the damping materials and that excellent structural damping properties could be obtained. The construction of the hat-stiffened panels proved that complex parts containing damping materials could be fabricated. Dynamic testing of these components showed that internal architectural features could be designed to promote damping in primary structure.

  1. Why Explicit Knowledge Cannot Become Implicit Knowledge

    ERIC Educational Resources Information Center

    VanPatten, Bill

    2016-01-01

    In this essay, I review one of the conclusions in Lindseth (2016) published in "Foreign Language Annals." That conclusion suggests that explicit learning and practice (what she called form-focused instruction) somehow help the development of implicit knowledge (or might even become implicit knowledge). I argue for a different…

  2. 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…

  3. 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.…

  4. 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…

  5. 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…

  6. Implicit Relational Effects in Associative Recognition

    ERIC Educational Resources Information Center

    Algarabel, S.; Pitarque, A.; Combita, L. M.; Rodriguez, L. A.

    2013-01-01

    We study the contribution of implicit relatedness to associative recognition in two experiments. In the first experiment, we showed an implicit improvement in recognition when the stimulus elements of each word pair shared common letters and they were unpaired at test. Moreover, when asked to study the stimuli under divided attention, recollection…

  7. 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…

  8. SPATIAL DAMPING OF PROPAGATING KINK WAVES DUE TO RESONANT ABSORPTION: EFFECT OF BACKGROUND FLOW

    SciTech Connect

    Soler, R.; Goossens, M.; Terradas, J.

    2011-06-20

    Observations show the ubiquitous presence of propagating magnetohydrodynamic (MHD) kink waves in the solar atmosphere. Waves and flows are often observed simultaneously. Due to plasma inhomogeneity in the direction perpendicular to the magnetic field, kink waves are spatially damped by resonant absorption. The presence of flow may affect the wave spatial damping. Here, we investigate the effect of longitudinal background flow on the propagation and spatial damping of resonant kink waves in transversely nonuniform magnetic flux tubes. We combine approximate analytical theory with numerical investigation. The analytical theory uses the thin tube (TT) and thin boundary (TB) approximations to obtain expressions for the wavelength and the damping length. Numerically, we verify the previously obtained analytical expressions by means of the full solution of the resistive MHD eigenvalue problem beyond the TT and TB approximations. We find that the backward and forward propagating waves have different wavelengths and are damped on length scales that are inversely proportional to the frequency as in the static case. However, the factor of proportionality depends on the characteristics of the flow, so that the damping length differs from its static analog. For slow, sub-Alfvenic flows the backward propagating wave gets damped on a shorter length scale than in the absence of flow, while for the forward propagating wave the damping length is longer. The different properties of the waves depending on their direction of propagation with respect to the background flow may be detected by the observations and may be relevant for seismological applications.

  9. Implicit measures: A normative analysis and review.

    PubMed

    De Houwer, Jan; Teige-Mocigemba, Sarah; Spruyt, Adriaan; Moors, Agnes

    2009-05-01

    Implicit measures can be defined as outcomes of measurement procedures that are caused in an automatic manner by psychological attributes. To establish that a measurement outcome is an implicit measure, one should examine (a) whether the outcome is causally produced by the psychological attribute it was designed to measure, (b) the nature of the processes by which the attribute causes the outcome, and (c) whether these processes operate automatically. This normative analysis provides a heuristic framework for organizing past and future research on implicit measures. The authors illustrate the heuristic function of their framework by using it to review past research on the 2 implicit measures that are currently most popular: effects in implicit association tests and affective priming tasks. (PsycINFO Database Record (c) 2009 APA, all rights reserved).

  10. 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.

  11. Implicit social cognition: from measures to mechanisms.

    PubMed

    Nosek, Brian A; Hawkins, Carlee Beth; Frazier, Rebecca S

    2011-04-01

    Most human cognition occurs outside conscious awareness or conscious control. Some of these implicit processes influence social perception, judgment and action. The past 15 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.

  12. Implicit Social Biases in People with Autism

    PubMed Central

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

    2015-01-01

    Implicit social biases are ubiquitous and are known to influence social behavior. A core diagnostic criterion of Autism Spectrum Disorder (ASD) is abnormal social behavior. Here we investigated the extent to which individuals with ASD might show a specific attenuation of implicit social biases, using the Implicit Association Test (IAT) across Social (gender, race) and Nonsocial (flowers/insect, shoes) categories. High-functioning adults with ASD showed intact but reduced IAT effects relative to healthy controls. Importantly, we observed no selective attenuation of implicit social (vs. nonsocial) biases in our ASD population. To extend these results, we collected data from a large online sample of the general population, and explored correlations between autistic traits and IAT effects. No associations were found between autistic traits and IAT effects for any of the categories tested in our online sample. Taken together, these results suggest that implicit social biases, as measured by the IAT, are largely intact in ASD. PMID:26386014

  13. Implicit sequence learning with competing explicit cues.

    PubMed

    Jiménez, L; Méndez, C

    2001-05-01

    Previous research has shown that the expression of implicit sequence learning is eliminated in a choice reaction time task when an explicit cue allows participants to accurately predict the next stimulus (Cleeremans, 1997), but that two contingencies predicting the same outcome can be learned and expressed simultaneously when both of them remain implicit (Jiménez & Méndez, 1999). Two experiments tested the hypothesis that it is the deliberate use of explicit knowledge that produces the inhibitory effects over the expression of implicit sequence learning. However, the results of these experiments do not support this hypothesis, rather showing that implicit learning is acquired and expressed regardless of the influence of explicit knowledge. These results are interpreted as reinforcing the thesis about the automatic nature of both the acquisition and the expression of implicit sequence learning. The contradictory results reported by Cleeremans are attributed to a floor effect derived from the use of a special type of explicit cue.

  14. GRIM: General Relativistic Implicit Magnetohydrodynamics

    NASA Astrophysics Data System (ADS)

    Chandra, Mani; Foucart, Francois; Gammie, Charles F.

    2017-02-01

    GRIM (General Relativistic Implicit Magnetohydrodynamics) evolves a covariant extended magnetohydrodynamics model derived by treating non-ideal effects as a perturbation of ideal magnetohydrodynamics. Non-ideal effects are modeled through heat conduction along magnetic field lines and a difference between the pressure parallel and perpendicular to the field lines. The model relies on an effective collisionality in the disc from wave-particle scattering and velocity-space (mirror and firehose) instabilities. GRIM, which runs on CPUs as well as on GPUs, combines time evolution and primitive variable inversion needed for conservative schemes into a single step using only the residuals of the governing equations as inputs. This enables the code to be physics agnostic as well as flexible regarding time-stepping schemes.

  15. Reducing Prejudice With Labels: Shared Group Memberships Attenuate Implicit Bias and Expand Implicit Group Boundaries.

    PubMed

    Scroggins, W Anthony; Mackie, Diane M; Allen, Thomas J; Sherman, Jeffrey W

    2016-02-01

    In three experiments, we used a novel Implicit Association Test procedure to investigate the impact of group memberships on implicit bias and implicit group boundaries. Results from Experiment 1 indicated that categorizing targets using a shared category reduced implicit bias by increasing the extent to which positivity was associated with Blacks. Results from Experiment 2 revealed that shared group membership, but not mere positivity of a group membership, was necessary to reduce implicit bias. Quadruple process model analyses indicated that changes in implicit bias caused by shared group membership are due to changes in the way that targets are evaluated, not to changes in the regulation of evaluative bias. Results from Experiment 3 showed that categorizing Black targets into shared group memberships expanded implicit group boundaries.

  16. Radiation damping in real time.

    PubMed

    Mendes, A C; Takakura, F I

    2001-11-01

    We study the nonequilibrium dynamics of a charge interacting with its own radiation, which originates the radiation damping. The real-time equation of motion for the charge and the associated Langevin equation is found in classical limit. The equation of motion for the charge allows one to obtain the frequency-dependent coefficient of friction. In the lowest order we find that although the coefficient of static friction vanishes, there is dynamical dissipation represented by a non-Markovian dissipative kernel.

  17. 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.

  18. 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

  19. 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.

  20. Single-Target Implicit Association Tests (ST-IAT) Predict Voting Behavior of Decided and Undecided Voters in Swiss Referendums

    PubMed Central

    Raccuia, Livio

    2016-01-01

    Undecided voters represent a major challenge to political pollsters. Recently, political psychologists have proposed the use of implicit association tests (IAT) to measure implicit attitudes toward political parties and candidates and predict voting behavior of undecided voters. A number of studies have shown that both implicit and explicit (i.e., self-reported) attitudes contribute to the prediction of voting behavior. More importantly, recent research suggests that implicit attitudes may be more useful for predicting the vote of undecided voters in the case of specific political issues rather than elections. Due to its direct-democratic political system, Switzerland represents an ideal place to investigate the predictive validity of IATs in the context of political votes. In this article, I present evidence from three studies in which both explicit and implicit measures were used ahead of the vote on four different referendums. Explicit measures predicted voting better than implicit attitudes for decided voters while implicit and explicit attitudes were equally good predictors among undecided voters. In addition, implicit attitudes predicted voting behavior descriptively, but not significantly better for undecided voters while, also from a descriptive point of view, explicit attitudes predicted voting better for decided respondents. In sum, results suggest that, as argued in previous research, the predictive value of implicit attitudes may be higher in the context of issue-related votes but still not as high as initially hoped-for. PMID:27732617

  1. Implicit training of nonnative speech stimuli.

    PubMed

    Vlahou, Eleni L; Protopapas, Athanassios; Seitz, Aaron R

    2012-05-01

    Learning nonnative speech contrasts in adulthood has proven difficult. Standard training methods have achieved moderate effects using explicit instructions and performance feedback. In this study, the authors question preexisting assumptions by demonstrating a superiority of implicit training procedures. They trained 3 groups of Greek adults on a difficult Hindi contrast (a) explicitly, with feedback (Experiment 1), or (b) implicitly, unaware of the phoneme distinctions, with (Experiment 2) or without (Experiment 3) feedback. Stimuli were natural recordings of consonant-vowel syllables with retroflex and dental unvoiced stops by a native Hindi speaker. On each trial, participants heard pairs of tokens from both categories and had to identify the retroflex sounds (explicit condition) or the sounds differing in intensity (implicit condition). Unbeknownst to participants, in the implicit conditions, target sounds were always retroflex, and distractor sounds were always dental. Post-training identification and discrimination tests showed improved performance of all groups, compared with a baseline of untrained Greek listeners. Learning was most robust for implicit training without feedback. It remains to be investigated whether implicitly trained skills can generalize to linguistically relevant phonetic categories when appropriate variability is introduced. These findings challenge traditional accounts on the role of feedback in phonetic training and highlight the importance of implicit, reward-based mechanisms.

  2. Nonlinear damping identification from transient data

    NASA Astrophysics Data System (ADS)

    Smith, Clifford B.; Wereley, Norman M.

    1999-06-01

    To study new damping augmentation methods for helicopter rotor systems, accurate and reliable nonlinear damping identification techniques are needed. For example, current studies on applications of magnetorheological (MR) dampers for rotor stability augmentation suggest that a strong Coulomb damping characteristic will be manifested as the field applied to the MR fluid is maximized. Therefore, in this work, a single degree of freedom (SDOF) system having either nonlinear Coulomb or quadratic damping is considered. This paper evaluates three analyses for identifying damping from transient test data; an FFT-based moving block analysis, an analysis based on a periodic Fourier series decomposition, and a Hilbert transform based technique. Analytical studies are used to determine the effects of block length, noise, and error in identified modal frequency on the accuracy of the identified damping level. The FFT-based moving block has unacceptable performance for systems with nonlinear damping. These problems were remedied in the Fourier series based analysis and acceptable performance is obtained for nonlinear damping identification from both this technique and the Hilbert transform based method. To more closely simulate a helicopter rotor system test, these techniques were then applied to a signal composed of two closely spaced modes. This data was developed to simulate a response containing the first lag and 1/rev modes. The primary mode of interest (simulated lag mode) had either Coulomb or quadratic damping, and the close mode (1/rev) was either undamped or had a specified viscous damping level. A comprehensive evaluation of the effects of close mode amplitude, frequency, and damping level was performed. A classifier was also developed to identify the dominant damping mechanism in a signal of 'unknown' composition. This classifier is based on the LMS error of a fit of the analytical envelope expression to the experimentally identified envelope signal. In most

  3. Applications of implicit BGK scheme in near-continuum flow

    NASA Astrophysics Data System (ADS)

    Li, Qibing; Fu, Song

    2006-07-01

    The implicit gas-kinetic Bhatnagar-Gross-Krook (BGK) scheme and kinetic boundary conditions are introduced and applied to the study of two typical flows in the near continuum regime, the hypersonic flow around a hollow cylinder flare and the flow in microchannels. The grid convergent numerical results in hypersonic flow agree well with experimental measurements and direct simulation Monte Carlo (DSMC) studies. For the low-speed microchannel flow, the present simulated results show good agreement with analytic solutions deduced from Navier-Stokes (NS) equations with slip conditions and DSMC computations. The implicit technology is found to be able to greatly improve the efficiency, which is expected to be a truly practical tool for the flow in micro-electro-mechanical systems (MEMS). The present study reveals the good performance of the BGK scheme in simulations of both high-speed and low-speed viscous flow in near continuum regime.

  4. 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

  5. Radiation damping and reciprocity in nuclear magnetic resonance: the replacement of the filling factor.

    PubMed

    Tropp, James; Van Criekinge, Mark

    2010-09-01

    The basic equation describing radiation damping in nuclear magnetic resonance (NMR) is rewritten by means of the reciprocity principle, to remove the dependence of the damping constant upon filling factor - a parameter which is neither uniquely defined for easily measured. The new equation uses instead the transceive efficiency, i.e. the peak amplitude of the radiofrequency B field in laboratory coordinates, divided by the square root of the resistance of the detection coil, for which a simple and direct means of measurement exists. We use the efficiency to define the intrinsic damping constant, i.e. that which obtains when both probe and preamplifier are perfectly matched to the system impedance. For imperfect matching of the preamp, it is shown that the damping constant varies with electrical distance to the probe, and equations are given and simulations performed, to predict the distance dependence, which (for lossless lines) is periodic modulo a half wavelength. Experimental measurements of the radiation-damped free induction NMR signal of protons in neat water are performed at a static B field strength of 14.1T; and an intrinsic damping constant measured using the variable line method. For a sample of 5mm diameter, in an inverse detection probe we measure an intrinsic damping constant of 204 s(-1), corresponding to a damping linewidth of 65 Hz for small tip angles. The predicted intrinsic linewidth, based upon three separate measurements of the efficiency, is 52.3 Hz, or 80% of the measured value.

  6. Optimum vibration absorber (tuned mass damper) design for linear damped systems subjected to random loads

    NASA Astrophysics Data System (ADS)

    Tigli, Omer F.

    2012-06-01

    Optimum design of dynamic vibration absorbers (DVAs) installed on linear damped systems that are subjected to random loads is studied and closed-form design formulas are provided. Three cases are considered in the optimization process: Minimizing the variance of the displacement, velocity and acceleration of the main mass. Exact optimum design parameters for the velocity case, which to the best knowledge of the author do not exist in the literature, are derived for the first time. Exact solutions are found to be directly applicable for practical use with no simplification needed. For displacement and acceleration cases, a solution for the optimum absorber frequency ratio is obtained as a function of optimum absorber damping ratio. Numerical simulations indicate that optimum absorber damping ratio is not significantly related to the structural damping, especially when the displacement variance is minimized. Therefore, optimum damping ratio derived for undamped systems is proposed for damped systems for the displacement case. When acceleration variance is minimized, however, the optimum damping ratio derived for undamped systems is found not as accurate for damped systems. Therefore, a more accurate approximate expression is derived. Numerical comparisons with published approximate expressions at the same level of complexity indicated that proposed design formula yield more accurate estimates. Another important finding of the paper is that for specific applications where all of the response parameters are desired to be minimized simultaneously, DVAs designed per velocity criteria provide the best overall performance with the least complexity in the design equations.

  7. Structural damage identification using damping: a compendium of uses and features

    NASA Astrophysics Data System (ADS)

    Cao, M. S.; Sha, G. G.; Gao, Y. F.; Ostachowicz, W.

    2017-04-01

    The vibration responses of structures under controlled or ambient excitation can be used to detect structural damage by correlating changes in structural dynamic properties extracted from responses with damage. Typical dynamic properties refer to modal parameters: natural frequencies, mode shapes, and damping. Among these parameters, natural frequencies and mode shapes have been investigated extensively for their use in damage characterization by associating damage with reduction in local stiffness of structures. In contrast, the use of damping as a dynamic property to represent structural damage has not been comprehensively elucidated, primarily due to the complexities of damping measurement and analysis. With advances in measurement technologies and analysis tools, the use of damping to identify damage is becoming a focus of increasing attention in the damage detection community. Recently, a number of studies have demonstrated that damping has greater sensitivity for characterizing damage than natural frequencies and mode shapes in various applications, but damping-based damage identification is still a research direction ‘in progress’ and is not yet well resolved. This situation calls for an overall survey of the state-of-the-art and the state-of-the-practice of using damping to detect structural damage. To this end, this study aims to provide a comprehensive survey of uses and features of applying damping in structural damage detection. First, we present various methods for damping estimation in different domains including the time domain, the frequency domain, and the time-frequency domain. Second, we investigate the features and applications of damping-based damage detection methods on the basis of two predominant infrastructure elements, reinforced concrete structures and fiber-reinforced composites. Third, we clarify the influential factors that can impair the capability of damping to characterize damage. Finally, we recommend future research directions

  8. 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).

  9. Implicit theories of intelligence, perceived academic competence, and school achievement: testing alternative models.

    PubMed

    Gonida, Eleftheria; Kiosseoglou, Grigoris; Leondari, Angeliki

    2006-01-01

    In the present study 3 alternative causal models concerning the relationships between implicit theories of intelligence, perceived academic competence, and school achievement were tested. The direction of changes in implicit theories and perceived competence during early adolescence also was examined. A total of 187 fifth and sixth graders were tested and retested a year later, when they were sixth and seventh graders, respectively. Cross-lagged regression analyses indicated that school achievement determined the adoption of a particular implicit theory through the mediation of perceived competence. Implicit theories were found to change toward the adoption of more incremental beliefs and perceived academic competence declined; however, high achievers, as compared with their low- and middle-level classmates, adopted more incremental beliefs and had significantly higher perceived competence.

  10. 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

  11. Damped transverse oscillations of interacting coronal loops

    NASA Astrophysics Data System (ADS)

    Soler, Roberto; Luna, Manuel

    2015-10-01

    Damped transverse oscillations of magnetic loops are routinely observed in the solar corona. This phenomenon is interpreted as standing kink magnetohydrodynamic waves, which are damped by resonant absorption owing to plasma inhomogeneity across the magnetic field. The periods and damping times of these oscillations can be used to probe the physical conditions of the coronal medium. Some observations suggest that interaction between neighboring oscillating loops in an active region may be important and can modify the properties of the oscillations. Here we theoretically investigate resonantly damped transverse oscillations of interacting nonuniform coronal loops. We provide a semi-analytic method, based on the T-matrix theory of scattering, to compute the frequencies and damping rates of collective oscillations of an arbitrary configuration of parallel cylindrical loops. The effect of resonant damping is included in the T-matrix scheme in the thin boundary approximation. Analytic and numerical results in the specific case of two interacting loops are given as an application.

  12. Conformal structure-preserving method for damped nonlinear Schrödinger equation

    NASA Astrophysics Data System (ADS)

    Fu, Hao; Zhou, Wei-En; Qian, Xu; Song, Song-He; Zhang, Li-Ying

    2016-11-01

    In this paper, we propose a conformal momentum-preserving method to solve a damped nonlinear Schrödinger (DNLS) equation. Based on its damped multi-symplectic formulation, the DNLS system can be split into a Hamiltonian part and a dissipative part. For the Hamiltonian part, the average vector field (AVF) method and implicit midpoint method are employed in spatial and temporal discretizations, respectively. For the dissipative part, we can solve it exactly. The proposed method conserves the conformal momentum conservation law in any local time-space region. With periodic boundary conditions, this method also preserves the total conformal momentum and the dissipation rate of momentum exactly. Numerical experiments are presented to demonstrate the conservative properties of the proposed method. Project supported by the National Natural Science Foundation of China (Grant Nos. 11571366, 11501570, and 11601514) and the Open Foundation of State Key Laboratory of High Performance Computing of China (Grant No. JC15-02-02).

  13. Flexible explicit but rigid implicit learning in a visuomotor adaptation task.

    PubMed

    Bond, Krista M; Taylor, Jordan A

    2015-06-01

    There is mounting evidence for the idea that performance in a visuomotor rotation task can be supported by both implicit and explicit forms of learning. The implicit component of learning has been well characterized in previous experiments and is thought to arise from the adaptation of an internal model driven by sensorimotor prediction errors. However, the role of explicit learning is less clear, and previous investigations aimed at characterizing the explicit component have relied on indirect measures such as dual-task manipulations, posttests, and descriptive computational models. To address this problem, we developed a new method for directly assaying explicit learning by having participants verbally report their intended aiming direction on each trial. While our previous research employing this method has demonstrated the possibility of measuring explicit learning over the course of training, it was only tested over a limited scope of manipulations common to visuomotor rotation tasks. In the present study, we sought to better characterize explicit and implicit learning over a wider range of task conditions. We tested how explicit and implicit learning change as a function of the specific visual landmarks used to probe explicit learning, the number of training targets, and the size of the rotation. We found that explicit learning was remarkably flexible, responding appropriately to task demands. In contrast, implicit learning was strikingly rigid, with each task condition producing a similar degree of implicit learning. These results suggest that explicit learning is a fundamental component of motor learning and has been overlooked or conflated in previous visuomotor tasks.

  14. Vitreous Enamel Damping Material Development.

    DTIC Science & Technology

    1982-11-01

    PROCEDURES 3 2.1. EXPERIMENTAL 3 2.1.1. GLASS PREPARATION 3 2.1.2. METHOD OF COATING APPLICATION 3 2.1.3. VIBRATION DAMPING MEASUREMENTS 3 2.2. CALCULATION OF...discussion in this report. fL 2 SECTION II TECHNICAL PROCEDURES 2.1 EXPERIMENTAL 2.1.1 Glass Preparation All of the compositions, except the standard...After heat treatments of composition "B", a- cristobalite and devitrite (Na20.3CaO-6SiO 2) appear as crystalline phases; a- cristobalite being the major

  15. CHARACTERIZATION OF DAMPING IN BOLTED LAP JOINTS

    SciTech Connect

    C. MALONEY; D. PEAIRS; ET AL

    2000-08-01

    The dynamic response of a jointed beam was measured in laboratory experiments. The data were analyzed and the system was mathematically modeled to establish plausible representations of joint damping behavior. Damping is examined in an approximate, local linear framework using log decrement and half power bandwidth approaches. in addition, damping is modeled in a nonlinear framework using a hybrid surface irregularities model that employs a bristles-construct. Experimental and analytical results are presented.

  16. Radiation damping in metal nanoparticle pairs.

    PubMed

    Dahmen, Christian; Schmidt, Benjamin; von Plessen, Gero

    2007-02-01

    The radiation damping rate of plasmon resonances in pairs of spherical gold nanoparticles is calculated. The radiative line width of the plasmon resonance indicates significant far-field coupling between the nanoparticles over distances many times the particle diameter. The radiation damping of the coupled particle-plasmon mode alternates between superradiant and subradiant behavior when the particle spacing is varied. At small particle spacings where near-field coupling occurs, the radiation damping rate lies far below that of an isolated particle.

  17. 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.

  18. Psychometric intelligence dissociates implicit and explicit learning.

    PubMed

    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. Under an explicit rule discovery instruction, however, a significant relationship between performance on the learning tasks and intelligence appeared. This finding provides support for Reber's hypothesis that implicit learning, in contrast to explicit learning, is independent of intelligence, and confirms thereby the distinction between the 2 modes of learning. However, because there were virtually no correlations among the 3 learning tasks, the assumption of a unitary ability of implicit learning was not supported.

  19. Implicit SPH v. 1.0

    SciTech Connect

    Kim, Kyungjoo; Parks, Michael L.; Perego, Mauro; Trask, Nathanial; Pan, Wenxiao

    2016-11-09

    ISPH code is developed to solve multi-physics meso-scale flow problems using implicit SPH method. In particular, the code can provides solutions for incompressible, multi phase flow and electro-kinetic flows

  20. Hysteretic damping in rotordynamics: An equivalent formulation

    NASA Astrophysics Data System (ADS)

    Genta, Giancarlo; Amati, Nicola

    2010-10-01

    The hysteretic damping model cannot be applied to time domain dynamic simulations: this is a well-known feature that has been discussed in the literature since the time when analog computers were widespread. The constant equivalent damping often introduced to overcome this problem is also discussed, and its limitations are stated, in particular those linked with its application in rotordynamics to simulate rotating damping. An alternative model based on the nonviscous damping (NVD) model, but with a limited number of additional degrees of freedom, is proposed, and the relevant equations are derived. Some examples show applications to the rotordynamics field.

  1. Viscous damped space structure for reduced jitter

    NASA Technical Reports Server (NTRS)

    Wilson, James F.; Davis, L. Porter

    1987-01-01

    A technique to provide modal vibration damping in high performance space structures was developed which uses less than one once of incompressible fluid. Up to 50 percent damping can be achieved which can reduce the settling times of the lowest structural mode by as much as 50 to 1. This concept allows the designers to reduce the weight of the structure while improving its dynamic performance. Damping by this technique is purely viscous and has been shown by test to be linear over 5 orders of input magnitude. Amplitudes as low as 0.2 microinch were demonstrated. Damping in the system is independent of stiffness and relatively insensitive to temperature.

  2. Material Damping Experiments at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Levine, Marie; White, Christopher

    2003-01-01

    A unique experimental facility has been designed to measure damping of materials at cryogenic temperatures. The test facility pays special attention to removing other sources of damping in the measurement by avoiding frictional interfaces, decoupling the test specimen from the support system, and by using a non-contacting measurement device; Damping data is obtained for materials (AI, GrEp, Be, Fused Quartz), strain amplitudes (less than 10-6 ppm), frequencies (20Hz-330Hz) and temperatures (20K-293K) relevant to future precision optical space missions. The test data shows a significant decrease in viscous damping at cryogenic temperatures and can be as low as 10-4%, but the amount of the damping decrease is a function of frequency and material. Contrary to the other materials whose damping monotonically decreased with temperature, damping of Fused Quartz increased substantially at cryo, after reaching a minimum at around l50 K. The damping is also shown to be insensitive to strain for low strain levels. At room temperatures, the test data correlates well to the analytical predictions of the Zener damping model. Discrepancies at cryogenic temperatures between the model predictions and the test data are observed.

  3. Spatial damping of propagating sausage waves in coronal cylinders

    NASA Astrophysics Data System (ADS)

    Guo, Ming-Zhe; Chen, Shao-Xia; Li, Bo; Xia, Li-Dong; Yu, Hui

    2015-09-01

    Context. Sausage modes are important in coronal seismology. Spatially damped propagating sausage waves were recently observed in the solar atmosphere. Aims: We examine how wave leakage influences the spatial damping of sausage waves propagating along coronal structures modeled by a cylindrical density enhancement embedded in a uniform magnetic field. Methods: Working in the framework of cold magnetohydrodynamics, we solve the dispersion relation (DR) governing sausage waves for complex-valued, longitudinal wavenumber k at given real angular frequencies ω. For validation purposes, we also provide analytical approximations to the DR in the low-frequency limit and in the vicinity of ωc, the critical angular frequency separating trapped from leaky waves. Results: In contrast to the standing case, propagating sausage waves are allowed for ω much lower than ωc. However, while able to direct their energy upward, these low-frequency waves are subject to substantial spatial attenuation. The spatial damping length shows little dependence on the density contrast between the cylinder and its surroundings, and depends only weakly on frequency. This spatial damping length is of the order of the cylinder radius for ω ≲ 1.5vAi/a, where a and vAi are the cylinder radius and the Alfvén speed in the cylinder, respectively. Conclusions: If a coronal cylinder is perturbed by symmetric boundary drivers (e.g., granular motions) with a broadband spectrum, wave leakage efficiently filters out the low-frequency components.

  4. Implicit attitudes in sexuality: gender differences.

    PubMed

    Geer, James H; Robertson, Gloria G

    2005-12-01

    This study examined the role of gender in both implicit and explicit attitudes toward sexuality. Implicit attitudes are judgments or evaluations of social objects that are automatically activated, often without the individual's conscious awareness of the causation. In contrast, explicit attitudes are judgments or evaluations that are well established in awareness. As described in Oliver and Hyde's (1993) meta-analysis of self-report (explicit) data, women report greater negative attitudes toward sexuality than do men. In the current study, we used the Sexual Opinion Survey (SOS) developed by Fisher, Byrne, White, and Kelley (1988) to index explicit attitudes and the Implicit Association Test (IAT) developed by Greenwald, McGhee, and Schwartz (1998) to index implicit attitudes. Research has demonstrated that the IAT reveals attitudes that participants may be reluctant to express. Independent variables examined were participant gender, social acceptability of sexual words, and order of associated evaluations in the IAT (switching from positive to negative evaluations or the reverse). The IAT data revealed a significant Order x Gender interaction that showed that women had more negative implicit attitudes toward sexuality than did men. There was also a significant Order x Acceptability interaction, indicating that implicit attitudes were more strongly revealed when the sexual words used in the IAT were more socially unacceptable. As expected, on the SOS, women had more negative explicit attitudes toward sexuality. There was no significant correlation between explicit and implicit attitudes. These data suggest that at both automatic (implicit) and controlled (explicit) levels of attitudes, women harbor more negative feelings toward sex than do men.

  5. Implicit measures of association in psychopathology research.

    PubMed

    Roefs, Anne; Huijding, Jorg; Smulders, Fren T Y; MacLeod, Colin M; de Jong, Peter J; Wiers, Reinout W; Jansen, Anita T M

    2011-01-01

    Studies obtaining implicit measures of associations in Diagnostic and Statistical Manual of Mental Disorders (4th ed., Text Revision; American Psychiatric Association, 2000) Axis I psychopathology are organized into three categories: (a) studies comparing groups having a disorder with controls, (b) experimental validity studies, and (c) incremental and predictive validity studies. In the first category, implicit measures of disorder-relevant associations were consistent with explicit beliefs for some disorders (e.g., specific phobia), but for other disorders evidence was either mixed (e.g., panic disorder) or inconsistent with explicit beliefs (e.g., pain disorder). For substance use disorders and overeating, expected positive and unexpected negative associations with craved substances were found consistently. Contrary to expectation, implicit measures of self-esteem were consistently positive for patients with depressive disorder, social phobia, and body dysmorphic disorder. In the second category, short-term manipulations of disorder-relevant states generally affected implicit measures as expected. Therapeutic interventions affected implicit measures for one type of specific phobia, social phobia, and panic disorder, but not for alcohol use disorders or obesity. In the third category, implicit measures had predictive value for certain psychopathological behaviors, sometimes moderated by the availability of cognitive resources (e.g., for alcohol and food, only when cognitive resources were limited). The strengths of implicit measures include (a) converging evidence for dysfunctional beliefs regarding certain disorders and consistent new insights for other disorders and (b) prediction of some psychopathological behaviors that explicit measures cannot explain. Weaknesses include (a) that findings were inconsistent for some disorders, raising doubts about the validity of the measures, and (b) that understanding of the concept "implicit" is incomplete.

  6. Superconductive material and magnetic field for damping and levitation support and damping of cryogenic instruments

    NASA Technical Reports Server (NTRS)

    Dolgin, Benjamin P. (Inventor)

    1994-01-01

    A superconductive load bearing support without a mechanical contact and vibration damping for cryogenic instruments in space is presented. The levitation support and vibration damping is accomplished by the use of superconducting magnets and the 'Meissner' effect. The assembly allows for transfer of vibration energy away from the cryogenic instrument which then can be damped by the use of either an electronic circuit or conventional vibration damping mean.

  7. 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…

  8. 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…

  9. Retroactive interference effects in implicit memory.

    PubMed

    Eakin, Deborah K; Smith, Robert

    2012-09-01

    One source of evidence for separate explicit and implicit memory systems is that explicit but not implicit memory is impacted by interference (e.g., Graf & Schacter, 1987). The present experiment examined whether retroactive interference (RI) effects could be obtained in implicit memory when a strong test of RI was used. People studied an original list of word pairs (e.g., COTTON-PRIZE) using the typical RI paradigm. During the interpolated phase, participants studied either interference pairs for which the same cue was re-paired with a different target (e.g., COTTON-PRINT) or novel pairs (e.g., HOST-VASE). RI was tested with the modified opposition cued recall test (Eakin, Schreiber, & Sergent-Marshall, 2003). The original-list cue was presented along with the beginning stem of its target (e.g., COTTON-PRI-) and a hint (e.g., not PRINT). RI effects were obtained for explicit and implicit memory. Taken together with prior research finding proactive interference effects in implicit memory, the findings indicate that implicit memory is not immune from retroactive interference.

  10. Damped Lyman-α Systems

    NASA Astrophysics Data System (ADS)

    Petitjean, P.; Ledoux, C.

    Recently, Prochaska & Wolfe (1997) have used Keck spectra of 17 DLA absorbers to investigate the kinematics of the neutral gas using unsaturated low excitation transitions such as Si iiλ 1808. They show that the absorption profiles are inconsistent with models of galactic haloes with random motions, spherically infalling gas and slowly rotating hot disks. The CDM model (Kauffmann 1996) is rejected as it produces disks with rotation velocities too small to account for the large observed velocity broadening of the absorption lines. Models of thick disks (h ~0.3 R, where h is the vertical scale and R the radius) with large rotational velocity (v 225kms-1) can reproduce the data. By combining new data on five damped systems with information gathered in the literature, we study the kinematics of the low and high-ionization phases in a sample of 26 damped Lyman-α systems in the redshift range 1.17 - 4.38. We show that the broader the line the more asymmetric, as expected in case rotation dominates the line broadening. However this correlation does not hold for velocities larger than 150 km/s indicating that evidence for rotational motions if any is restricted to velocity broadenings Δ V < 150kms-1. The systems with Δ V > 200kms-1 are peculiar with kinematics consistent with random motions. They show sub-systems as those expected if the objects are in the process of merging.

  11. Acoustic transducer with damping means

    DOEpatents

    Smith, Richard W.; Adamson, Gerald E.

    1976-11-02

    An ultrasonic transducer specifically suited to high temperature sodium applications is described. A piezoelectric active element is joined to the transducer faceplate by coating the faceplate and juxtaposed active element face with wetting agents specifically compatible with the bonding procedure employed to achieve the joint. The opposite face of the active element is fitted with a backing member designed to assure continued electrical continuity during adverse operating conditions which can result in the fracturing of the active element. The fit is achieved employing a spring-loaded electrode operably arranged to electrically couple the internal transducer components, enclosed in a hermetically sealed housing, to accessory components normally employed in transducer applications. Two alternative backing members are taught for assuring electrical continuity. The first employs a resilient, discrete multipoint contact electrode in electrical communication with the active element face. The second employs a resilient, elastomeric, electrically conductive, damped member in electrical communication with the active element face in a manner to effect ring-down of the transducer. Each embodiment provides continued electrical continuity within the transducer in the event the active element fractures, while the second provides the added benefit of damping.

  12. Tuned vibration absorbers with nonlinear viscous damping for damped structures under random load

    NASA Astrophysics Data System (ADS)

    Shum, K. M.

    2015-06-01

    The classical problem for the application of a tuned vibration absorber is to minimize the response of a structural system, such as displacement, velocity, acceleration or to maximize the energy dissipated by tuned vibration absorber. The development of explicit optimal absorber parameters is challenging for a damped structural system since the fixed points no longer exist in the frequency response curve. This paper aims at deriving a set of simple design formula of tuned vibration absorber with nonlinear viscous damping based on the frequency tuning for harmonic load for a damped structural system under white noise excitation. The vibration absorbers being considered include tuned mass damper (TMD) and liquid column vibration absorber (LCVA). Simple approximate expression for the standard deviation velocity response of tuned vibration absorber for damped primary structure is also derived in this study to facilitate the estimation of the damping coefficient of TMD with nonlinear viscous damping and the head loss coefficient of LCVA. The derived results indicate that the higher the structural inherent damping the smaller the supplementary damping provided by a tuned vibration absorber. Furthermore, the optimal damping of tuned vibration absorber is shown to be independent of structural damping when it is tuned using the frequency tuning for harmonic load. Finally, the derived closed-form expressions are demonstrated to be capable of predicting the optimal parameters of tuned vibration absorbers with sufficient accuracy for preliminary design of tuned vibration absorbers with nonlinear viscous damping for a damped primary structure.

  13. Aeromechanical stability augmentation of helicopters using enhanced active constrained layer damping treatment on rotor flex beams

    NASA Astrophysics Data System (ADS)

    Badre Alam, Askari

    This thesis presents a study conducted to explore the feasibility of employing Enhanced Active Constrained Layer (EACL) damping treatment in helicopter rotor systems to alleviate aeromechanical instability. The central idea is to apply the EACL treatment on the flexbeams of soft in-plane bearingless main rotors (BMRs) and increase the damping of the first lag mode. In this research, it is explored whether EACL damping treatment can provide sufficient damping in rotor system without exceeding the physical design limits of actuators. To study the feasibility of the EACL damping treatment, a finite element based mathematical model of a rotor with EACL damping treatment on flexbeam is developed. A bench top experiment is conducted to verify the mathematical model. It is shown that the experimental results correlate well with the analytical results. A derivative controller, with control voltage based on the flexbeam tip transverse velocity, is used in this investigation. A filter is developed to remove 1/rev component of the feedback signal. An optimization study is conducted to understand the influence of EACL design parameters on the performance of the damping treatment. A study is conducted to analyze delamination of EACL damping treatment. In this study, a new finite element model is developed that is capable of accurately predicting both, the performance and interlaminar stresses in EACL damping treatment. A new configuration of PCL damping treatment is developed by tapering the constraining layer at the free ends. As compared to a conventional PCL, this configuration has significantly lower interlaminar stresses and similar damping performance. A study is conducted to compare ACL with purely active configuration. It was shown that in ACL configuration, the interlaminar stresses are an-order-of-magnitude lower than the purely active configuration for similar damping levels. A new ACL configuration is designed by changing the poling direction of the PZT constraining

  14. The ROSETTA PHILAE Lander damping mechanism as probe for the Comet soil strength.

    NASA Astrophysics Data System (ADS)

    Roll, R.

    2015-10-01

    The ROSETTA Lander is equipped with an one axis damping mechanism to dissipate kinetic energy during the touch down. This damping is necessary to avoid damages to the Lander by a hard landing shock and more important to avoid re-bouncing from ground with high velocity. The damping mechanism works best for perpendicular impact, which means the velocity vector is parallel to the damper axis and all three feet touch the ground at the same time. That is usually not the case. Part of the impact energy can be transferred into rotational energy at ground contact if the impact is not perpendicular. This energy will lift up the Lander from the ground if the harpoons and the hold down thruster fail, as happen in mission. The damping mechanism itself is an electrical generator, driven by a spindle inside a telescopic tube. This tube was extended in mission for landing by 200mm. A maximum damping length of 140mm would be usually required to compensate a landing velocity of 1m/s, if the impact happens perpendicular on hard ground. After landing the potentiometer of the telescopic tube reading shows a total damping length of only 42,5mm. The damping mechanism and the overall mechanical behavior of the Lander at touch down are well tested and characterized and transferred to a multi-body computer model. The incoming and outgoing flightpath of PHILAE allow via computer-simulation the reconstruction of the touch down. It turns out, that the outgoing flight direction is dominated by the local ground slope and that the damping length is strongly dependent on the soil strength. Damping of soft comet ground must be included to fit the damping length measured. Scenario variations of the various feet contact with different local surface features (stone or regolith) and of different soil models finally lead to a restricted range for the soil strength at the touch down area.

  15. Simulation Study of Electronic Damping of Microphonic Vibrations in Superconducting Cavities

    SciTech Connect

    Alicia Hofler; Jean Delayen

    2005-05-01

    Electronic damping of microphonic vibrations in superconducting rf cavities involves an active modulation of the cavity field amplitude in order to induce ponderomotive forces that counteract the effect of ambient vibrations on the cavity frequency. In lightly beam loaded cavities, a reduction of the microphonics-induced frequency excursions leads directly to a reduction of the rf power required for phase and amplitude stabilization. Jefferson Lab is investigating such an electronic damping scheme that could be applied to the JLab 12 GeV upgrade, the RIA driver, and possibly to energy-recovering superconducting linacs. This paper discusses a model and presents simulation results for electronic damping of microphonic vibrations.

  16. 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

  17. Implicit methods for efficient musculoskeletal simulation and optimal control.

    PubMed

    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.

  18. Measuring Mentalizing Ability: A Within-Subject Comparison between an Explicit and Implicit Version of a Ball Detection Task

    PubMed Central

    Nijhof, Annabel D.; Brass, Marcel; Bardi, Lara; Wiersema, Jan R.

    2016-01-01

    The concept of mentalizing has been widely studied, but almost exclusively through tasks with explicit instructions. Recent studies suggest that people also mentalize on a more implicit level. However, to our knowledge, no study to date has directly contrasted the effects of implicit and explicit mentalizing processes on an implicit dependent measure within-subjects. We implemented this by using two versions of an object detection task, differing only on secondary catch questions. We hypothesized that if explicit mentalizing relies on complementary processes beyond those underlying implicit mentalizing, this would be reflected in enhanced belief effects in the explicit version. Twenty-eight healthy adults watched movies in which, during the first phase, both they themselves and another agent formed a belief about the location of a ball, and although irrelevant, these beliefs could influence their ball detection reaction times in the second phase. After this response phase, there were occasional catch questions that were different for the explicit and implicit task version. Finally, self-report measures of autism spectrum disorder (ASD) symptomatology were included, as the literature suggests that ASD is related to a specific deficit in implicit mentalizing. Both in the explicit and implicit version, belief conditions had a significant effect on reaction times, with responses being slower when neither the participant nor the other agent expected the ball to be present compared to all other conditions. Importantly, after the implicit version, participants reported no explicit mentalizing awareness. In our neurotypical sample, ASD symptoms were not found to correlate with either explicit or implicit mentalizing. In conclusion, the reaction time patterns in the explicit and implicit version of the task show strikingly similar effects of mentalizing, indicating that participants processed beliefs to the same extent regardless of whether they mentalized explicitly or

  19. 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.

  20. Study for ILC Damping Ring at KEKB

    SciTech Connect

    Flanagan, J.W.; Fukuma, H.; Kanazawa, K.I.; Koiso, H.; Masuzawa, M.; Ohmi, Kazuhito; Ohnishi, Y.; Oide, Katsunobu; Suetsugu, Y.; Tobiyama, M.; Pivi, M.; /SLAC

    2011-11-04

    ILC damping ring consists of very low emittance electron and positron storage rings. It is necessary for ILC damping ring to study electron cloud effects in such low emittance positron ring. We propose a low emittance operation of KEKB to study the effects.

  1. Understanding the Damped SHM without ODEs

    ERIC Educational Resources Information Center

    Ng, Chiu-king

    2016-01-01

    Instead of solving ordinary differential equations (ODEs), the damped simple harmonic motion (SHM) is surveyed qualitatively from basic mechanics and quantitatively by the instrumentality of a graph of velocity against displacement. In this way, the condition b ? [square root]4mk for the occurrence of the non-oscillating critical damping and…

  2. Bending rate damping in elastic systems

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Wang, Y.; Fabiano, R. H.

    1989-01-01

    Preliminary results of an investigation of the bending rate damping model for elastic structures are presented. A model for which the internal damping term is physically plausible and which can accomodate cantilevered boundary conditions is discussed. The model formulation and mathematical foundations are given, and numerical results are discussed.

  3. Damping device for a stationary labyrinth seal

    NASA Technical Reports Server (NTRS)

    El-Aini, Yehia M. (Inventor); Mitchell, William S. (Inventor); Roberts, Lawrence P. (Inventor); Montgomery, Stuart K. (Inventor); Davis, Gary A. (Inventor)

    2010-01-01

    A stationary labyrinth seal system includes a seal housing having an annular cavity, a plurality of damping devices, and a retaining ring. The damping devices are positioned within the annular cavity and are maintained within the annular cavity by the retaining ring.

  4. Magnetic dipole oscillations and radiation damping

    NASA Astrophysics Data System (ADS)

    Stump, Daniel R.; Pollack, Gerald L.

    1997-01-01

    We consider the problem of radiation damping for a magnetic dipole oscillating in a magnetic field. An equation for the radiation reaction torque is derived, and the damping of the oscillations is described. Also discussed are runaway solutions for a rotating magnetic dipole moving under the influence of the reaction torque, with no external torque.

  5. DAMPs from Cell Death to New Life

    PubMed Central

    Vénéreau, Emilie; Ceriotti, Chiara; Bianchi, Marco Emilio

    2015-01-01

    Our body handles tissue damage by activating the immune system in response to intracellular molecules released by injured tissues [damage-associated molecular patterns (DAMPs)], in a similar way as it detects molecular motifs conserved in pathogens (pathogen-associated molecular patterns). DAMPs are molecules that have a physiological role inside the cell, but acquire additional functions when they are exposed to the extracellular environment: they alert the body about danger, stimulate an inflammatory response, and finally promote the regeneration process. Beside their passive release by dead cells, some DAMPs can be secreted or exposed by living cells undergoing a life-threatening stress. DAMPs have been linked to inflammation and related disorders: hence, inhibition of DAMP-mediated inflammatory responses is a promising strategy to improve the clinical management of infection- and injury-elicited inflammatory diseases. However, it is important to consider that DAMPs are not only danger signals but also central players in tissue repair. Indeed, some DAMPs have been studied for their role in tissue healing after sterile or infection-associated inflammation. This review is focused on two exemplary DAMPs, HMGB1 and adenosine triphosphate, and their contribution to both inflammation and tissue repair. PMID:26347745

  6. 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.

  7. Resistive-Wall Instability in the Damping Rings of the ILC

    SciTech Connect

    Wang, L.; Bane, K.L.F.; Raubenheimer, T.; Ross, M.; /SLAC

    2006-07-05

    In the damping rings of the International Linear Collider (ILC), the resistive-wall instability is one of the dominant transverse instabilities. This instability directly influences the choice of material and aperture of the vacuum pipe, and the parameters of the transverse feedback system. This paper investigates the resistive-wall instabilities in an ILC damping ring under various conditions of beam pipe material, aperture, and fill pattern.

  8. The Implicit Relational Assessment Procedure (IRAP) as a Measure of Implicit Relative Preferences: A First Study

    ERIC Educational Resources Information Center

    Power, Patricia; Barnes-Holmes, Dermot; Barnes-Holmes, Yvonne; Stewart, Ian

    2009-01-01

    The Implicit Relational Assessment Procedure (IRAP) was designed to examine implicit beliefs or attitudes. In Experiment 1, response latencies obtained from Irish participants on the IRAP showed a strong preference for Irish over Scottish and American over African. In contrast, responses to explicit Likert measures diverged from the IRAP…

  9. Landau damping in a turbulent setting

    SciTech Connect

    Plunk, G. G.

    2013-03-15

    To address the problem of Landau damping in kinetic turbulence, we consider the forcing of the linearized Vlasov equation by a stationary random source. It is found that the time-asymptotic density response is dominated by resonant particle interactions that are synchronized with the source. The energy consumption of this response is calculated, implying an effective damping rate, which is the main result of this paper. Evaluating several cases, it is found that the effective damping rate can differ from the Landau damping rate in magnitude and also, remarkably, in sign. A limit is demonstrated in which the density and current become phase-locked, which causes the effective damping to be negligible; this result offers a fresh perspective from which to reconsider recent observations of kinetic turbulence satisfying critical balance.

  10. Damping characteristics of damaged fiber composite components

    NASA Technical Reports Server (NTRS)

    Eberle, K.

    1986-01-01

    Defects in fiber composite components produce changes with respect to the vibrational characteristics of the material. These changes can be recognized in the form of a frequency shift or an alteration of the damping process. The present investigation is concerned with questions regarding the possibility of a utilization of the changes in suitable defect-detecting inspection procedures. A description is given of a method for measuring the damping characteristics of a specimen. This method provides a spectrum of the damping coefficients of the sample as a basis for a comprehensive evaluation of the damping behavior. The correlation between defects and change in the damping characteristics is demonstrated with the aid of results obtained in measurements involving specimens of carbon-fiber composites and a component consisting of glass-fiber-reinforced plastics.

  11. Magnetic damping of rotation. [in satellites

    NASA Technical Reports Server (NTRS)

    Opik, E. J.

    1977-01-01

    Based on Wilson's (1977) article on the magnetic effects on space vehicles and other celestial bodies, the magnetic damping of rotation is considered. The inadequacy of the interstellar magnetic field in overcoming solar wind shielding and thus influencing the rotation of bodies is described. The ionospheric shielding of the interstellar field is discussed along with the permeability and magnetic damping by the solar or stellar wind. Star formation and angular momentum is discussed and attention is given to the magnetic damping of unshielded small bodies. Calculations of the rate for damping through random particle impact are made. Theories concerning the rotation of asteroids and the origin of meteorites are reviewed. The shielding process of ionospheric plasmas is outlined and the damping effect of the geomagnetic field on the rotation of artificial satellites is evaluated.

  12. VIBRATION DAMPING AND SHOCK MOUNT

    DOEpatents

    Stevens, D.J.; Forman, G.W.

    1963-12-10

    A shock absorbing mount in which vibrations are damped by an interference fit between relatively movable parts of the mount is described. A pair of generally cup-shaped parts or members have skirt portions disposed in an oppositely facing nesting relationship with the skirt of one member frictionally engaging the skirt of the other. The outermost skirt may be slotted to provide spring-like segments which embrace the inner skirt for effecting the interference fit. Belleville washers between the members provide yieldable support for a load carried by the mount. When a resonant frequency of vibration forces acting upon the moumt attains a certain level the kinetic energy of these forces is absorbed by sliding friction between the parts. (AEC)

  13. Large space structure damping design

    NASA Technical Reports Server (NTRS)

    Pilkey, W. D.; Haviland, J. K.

    1983-01-01

    Several FORTRAN subroutines and programs were developed which compute complex eigenvalues of a damped system using different approaches, and which rescale mode shapes to unit generalized mass and make rigid bodies orthogonal to each other. An analytical proof of a Minimum Constrained Frequency Criterion (MCFC) for a single damper is presented. A method to minimize the effect of control spill-over for large space structures is proposed. The characteristic equation of an undamped system with a generalized control law is derived using reanalysis theory. This equation can be implemented in computer programs for efficient eigenvalue analysis or control quasi synthesis. Methods to control vibrations in large space structure are reviewed and analyzed. The resulting prototype, using electromagnetic actuator, is described.

  14. Circulating Mitochondrial DAMPs Are Not Effective Inducers of Proteinuria and Kidney Injury in Rodents

    PubMed Central

    Xia, Hong; Liang, Yaojun; Wang, Xiao; Bao, Wenduona; Yun, Shifeng; Ye, Yuting; Zheng, Chunxia; Liu, Zhihong; Shi, Shaolin

    2015-01-01

    Mitochondria in eukaryotic cells are derived from bacteria in evolution. Like bacteria, mitochondria contain DNA with unmethylated CpG motifs and formyl peptides, both of which have recently been shown to be damage associated molecular patterns (DAMPs) and induce immune response and cell injury. Based on the facts that circulating mitochondrial DAMPs (mtDAMPs) are increased in the patients of trauma or burn injury who also have proteinuria, that mtDAMPs can activate immune cells which in turn secrete glomerular permeability factors, that renal intrinsic cells express a variety of DAMP receptors, and that mtDAMPs can directly increase endothelial cell permeability in vitro, we hypothesized that mtDAMPs may be novel circulating factors inducing proteinuria and kidney injury. We tested this hypothesis by directly injecting mtDAMPs into rodents and examining urinary protein and kidney histology. We prepared mtDAMP samples, including mitochondrial DNA (mtDNA) and mitochondrial debris (MTD), from rodent liver. In mice, injection of mtDNA for 20 μg/ml initial concentration in circulation (much higher than the clinical range), did not cause any renal manifestations. However, an increased dose leading to 45 μg/ml initial concentration in circulation resulted in a transient, slight increase in urinary albumin. In rats, MTD injection resulting in 450 μg/ml initial concentration of MTD protein in circulation, which was much higher than the clinical range, caused mild, transient proteinuria and lung lesions. Multiple injections of such large amount of either mtDNA or MTD into rodents on 3 consecutive days also failed in inducing proteinuria and kidney injury. In summary, clinical levels of circulating mtDAMPs do not induce proteinuria and clinically irrelevant high levels of mtDAMPs cause only a transient and slight increase in urinary protein in rodents, suggesting that circulating mtDAMPs may not be responsible for the proteinuria and kidney injury in patients with trauma

  15. Implicit unified gas-kinetic scheme for steady state solutions in all flow regimes

    NASA Astrophysics Data System (ADS)

    Zhu, Yajun; Zhong, Chengwen; Xu, Kun

    2016-06-01

    This paper presents an implicit unified gas-kinetic scheme (UGKS) for non-equilibrium steady state flow computation. The UGKS is a direct modeling method for flow simulation in all regimes with the updates of both macroscopic flow variables and microscopic gas distribution function. By solving the macroscopic equations implicitly, a predicted equilibrium state can be obtained first through iterations. With the newly predicted equilibrium state, the evolution equation of the gas distribution function and the corresponding collision term can be discretized in a fully implicit way for fast convergence through iterations as well. The lower-upper symmetric Gauss-Seidel (LU-SGS) factorization method is implemented to solve both macroscopic and microscopic equations, which improves the efficiency of the scheme. Since the UGKS is a direct modeling method and its physical solution depends on the mesh resolution and the local time step, a physical time step needs to be fixed before using an implicit iterative technique with a pseudo-time marching step. Therefore, the physical time step in the current implicit scheme is determined by the same way as that in the explicit UGKS for capturing the physical solution in all flow regimes, but the convergence to a steady state speeds up through the adoption of a numerical time step with large CFL number. Many numerical test cases in different flow regimes from low speed to hypersonic ones, such as the Couette flow, cavity flow, and the flow passing over a cylinder, are computed to validate the current implicit method. The overall efficiency of the implicit UGKS can be improved by one or two orders of magnitude in comparison with the explicit one.

  16. Active vibration control using an inertial actuator with internal damping.

    PubMed

    Paulitsch, Christoph; Gardonio, Paolo; Elliott, Stephen J

    2006-04-01

    Collocated direct velocity feedback with ideal point force actuators mounted on structures is unconditionally stable and generates active damping. When inertial actuators are used to generate the control force, the system can become unstable even for moderate velocity feedback gains due to an additional -180 degree phase lag introduced by the fundamental axial resonant mode of the inertial actuator. In this study a relative velocity sensor is used to implement an inner velocity feedback loop that generates internal damping in a lightweight, electrodynamic, inertial actuator. Simulation results for a model problem with the actuator mounted on a clamped plate show that, when internal relative velocity feedback is used in addition to a conventional external velocity feedback loop, there is an optimum combination of internal and external velocity feedback gains, which, for a given gain margin, maximizes vibration reduction. These predictions are validated in experiments with a specially built lightweight inertial actuator.

  17. Comments on Landau damping due to synchrotron frequency spread

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2005-01-01

    An inductive/space-charge impedance shifts the synchrotron frequency downwards above/below transition, but it is often said that the coherent synchrotron frequency of the bunch is not shifted in the rigid-dipole mode. On the other hand, the incoherent synchrotron frequency due to the sinusoidal rf always spreads in the downward direction. This spread will therefore not be able to cover the coherent synchrotron frequency, implying that there will not be any Landau damping no matter how large the frequency spread is. By studying the dispersion relation, it is shown that the above argument is incorrect, and there will be Landau damping if there is sufficient frequency spread. The main reason is that the coherent frequency of the rigid-dipole mode will no longer remain unshifted in the presence of a synchrotron frequency spread.

  18. DAMPE silicon tracker on-board data compression algorithm

    NASA Astrophysics Data System (ADS)

    Dong, Yi-Fan; Zhang, Fei; Qiao, Rui; Peng, Wen-Xi; Fan, Rui-Rui; Gong, Ke; Wu, Di; Wang, Huan-Yu

    2015-11-01

    The Dark Matter Particle Explorer (DAMPE) is an upcoming scientific satellite mission for high energy gamma-ray, electron and cosmic ray detection. The silicon tracker (STK) is a subdetector of the DAMPE payload. It has excellent position resolution (readout pitch of 242 μm), and measures the incident direction of particles as well as charge. The STK consists of 12 layers of Silicon Micro-strip Detector (SMD), equivalent to a total silicon area of 6.5 m2. The total number of readout channels of the STK is 73728, which leads to a huge amount of raw data to be processed. In this paper, we focus on the on-board data compression algorithm and procedure in the STK, and show the results of initial verification by cosmic-ray measurements. Supported by Strategic Priority Research Program on Space Science of Chinese Academy of Sciences (XDA040402) and National Natural Science Foundation of China (1111403027)

  19. Précis of implicit nationalism.

    PubMed

    Hassin, Ran R; Ferguson, Melissa J; Kardosh, Rasha; Porter, Shanette C; Carter, Travis J; Dudareva, Veronika

    2009-06-01

    While the study of nationalism has received much attention throughout the social sciences and humanities, the experimental investigation of it lags behind. In this paper we review recent advances in the examination of implicit nationalism. In the first set of experiments we survey, the Palestinian, Israeli, Italian, and Russian flags were primed (or not, in the control conditions) and their effects on political thought and behavior were tested. In the second set the American or the Israeli flag was primed (or not) and prejudice toward African-Americans or Palestinians (respectively) was examined. The results of all experiments suggest that the implicit activation of national cues has far-reaching implications on political thought and behavior as well as on attitudes toward minorities. Under the assumption that the image of national flags is associated in memory with national ideologies, these results suggest that national ideologies can be implicitly pursued in a way that significantly affects our thoughts and behaviors.

  20. Emotion and Implicit Timing: The Arousal Effect

    PubMed Central

    Droit-Volet, Sylvie; Berthon, Mickaël

    2017-01-01

    This study tested the effects of emotion on implicit time judgment. The participants did not receive any overt temporal instructions. They were simply trained to respond as quickly as possible after a response signal, which was separated from a warning signal by a reference temporal interval. In the testing phase, the inter-signal interval was shorter, equal or longer than the reference interval and was filled by emotional pictures (EP) of different arousal levels: high, moderate, and low. The results showed a U-shaped curve of reaction time plotted against the interval duration, indicating an implicit processing of time. However, this RT-curve was shifted toward the left, with a significantly lower peak time for the high-arousal than for the low-arousal EP. This emotional time distortion in an implicit timing task suggests an automatic effect of emotion on the internal clock rate. PMID:28261125

  1. State-Based Implicit Coordination and Applications

    NASA Technical Reports Server (NTRS)

    Narkawicz, Anthony J.; Munoz, Cesar A.

    2011-01-01

    In air traffic management, pairwise coordination is the ability to achieve separation requirements when conflicting aircraft simultaneously maneuver to solve a conflict. Resolution algorithms are implicitly coordinated if they provide coordinated resolution maneuvers to conflicting aircraft when only surveillance data, e.g., position and velocity vectors, is periodically broadcast by the aircraft. This paper proposes an abstract framework for reasoning about state-based implicit coordination. The framework consists of a formalized mathematical development that enables and simplifies the design and verification of implicitly coordinated state-based resolution algorithms. The use of the framework is illustrated with several examples of algorithms and formal proofs of their coordination properties. The work presented here supports the safety case for a distributed self-separation air traffic management concept where different aircraft may use different conflict resolution algorithms and be assured that separation will be maintained.

  2. Implicit solvent methods for free energy estimation

    PubMed Central

    Decherchi, Sergio; Masetti, Matteo; Vyalov, Ivan; Rocchia, Walter

    2014-01-01

    Solvation is a fundamental contribution in many biological processes and especially in molecular binding. Its estimation can be performed by means of several computational approaches. The aim of this review is to give an overview of existing theories and methods to estimate solvent effects giving a specific focus on the category of implicit solvent models and their use in Molecular Dynamics. In many of these models, the solvent is considered as a continuum homogenous medium, while the solute can be represented at the atomic detail and at different levels of theory. Despite their degree of approximation, implicit methods are still widely employed due to their trade-off between accuracy and efficiency. Their derivation is rooted in the statistical mechanics and integral equations disciplines, some of the related details being provided here. Finally, methods that combine implicit solvent models and molecular dynamics simulation, are briefly described. PMID:25193298

  3. Testosterone abolishes implicit subordination in social anxiety.

    PubMed

    Terburg, David; Syal, Supriya; Rosenberger, Lisa A; Heany, Sarah J; Stein, Dan J; Honk, Jack van

    2016-10-01

    Neuro-evolutionary theories describe social anxiety as habitual subordinate tendencies acquired through a recursive cycle of social defeat and submissive reactions. If so, the steroid hormone testosterone might be of therapeutic value, as testosterone is a main force behind implicit dominance drive in many species including humans. We combined these two theories to investigate whether the tendency to submit to the dominance of others is an implicit mechanism in social anxiety (Study-1), and whether this can be relieved through testosterone administration (Study-2). Using interactive eye-tracking we demonstrate that socially anxious humans more rapidly avert gaze from subliminal angry eye contact (Study-1). We replicate this effect of implicit subordination in social anxiety in an independent sample, which is subsequently completely abolished after a single placebo-controlled sublingual testosterone administration (Study-2). These findings provide crucial evidence for hormonal and behavioral treatment strategies that specifically target mechanisms of dominance and subordination in social anxiety.

  4. AN IMPLICIT"DRIFT-LORENTZ" PARTICLE MOVER FOR PLASMA AND BEAM SIMULATIONS

    SciTech Connect

    Friedman, A.; Grote, D.P.; Vay, J.-L; Cohen, R.H.

    2008-07-15

    In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventionalparticle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.

  5. An Implicit "Drift-Lorentz" Mover for Plasma and Beam Simulations

    SciTech Connect

    Cohen, R H; Friedman, A; Grote, D P; Vay, J

    2009-02-12

    In order to efficiently perform particle simulations in systems with widely varying magnetization, we developed a drift-Lorentz mover, which interpolates between full particle dynamics and drift kinetics in such a way as to preserve a physically correct gyroradius and particle drifts for both large and small ratios of the timestep to the cyclotron period. In order to extend applicability of the mover to systems with plasma frequency exceeding the cyclotron frequency such as one may have with fully neutralized drift compression of a heavy-ion beam we have developed an implicit version of the mover. A first step in this direction, in which the polarization charge was added to the field solver, was described previously. Here we describe a fully implicit algorithm (which is analogous to the direct-implicit method for conventional particle-in-cell simulation), summarize a stability analysis of it, and describe several tests of the resultant code.

  6. Validation Of Equivalent Viscous Damping Methodologies

    NASA Astrophysics Data System (ADS)

    Vaquer Araujo, Xavier; Fransen, S. H. J. A.; Germes, S.; Thiry, N.

    2012-07-01

    An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain. To obtain accurate predictions of the satellite’s dynamic environment it is essential that the damping of the system is correctly defined and taken into account within the resolution methodologies for the Coupled Loads Analysis (CLA). When working with finite element models, the materials’ damping is characterized by structural damping ratios. In addition, most of the load cases present in the CLA are transient excitations so the resolution of the equations of motion must be done in the time domain. Unfortunately, transient analyses cannot be carried out using structural damping models. Thus, a transformation from a structural to a viscous damping characterization is necessary. Nevertheless, this transformation is not trivial. There exist many methodologies aiming at computing an equivalent viscous damping matrix of the system so it can be used in transient analyses. This paper describes the results obtained in the validation of equivalent viscous damping methodologies used in the European Space Agency. This work permitted to identify the limitations of these methodologies and to come up with an enhanced methodology that predicts more reliable results.

  7. SLC positron damping ring optics design

    SciTech Connect

    Delahaye, J.P.; Rivkin, L.

    1984-12-01

    The basic SLAC Linear Collider operation scheme assumes the use of two damping rings, one for the e/sup -/, one for the e/sup +/, in order to reduce the colliding beam normalized emittances to 30..pi.. ..mu..radm hence raising the corresponding luminosity by a factor 170. The e/sup -/ damping ring which optics was designed by H. Wiedemann, has been extensively studied and modelled since it's completion at the end of 1982. The e/sup +/ damping ring to be built soon will be based on the same design except for some modifications resulting from the studies on the e/sup -/ damping ring which clearly pointed out two major optics weak points: the extracted normalized emittances are 30 to 60% bigger than the design values, which already left no margin for unavoidable blow-up between the damping rings and the SLC interaction point, and the chromaticity correction based on distributed sextupole components provided by shaping the ends of the bending magnet poles was insufficient. Moreover the QDI quadrupoles introduce a strong coupling between transverse planes due to an undesirable skew component. The present note describes the basic modifications of the ring lattice and main equipment positions in order to improve the first two points in the Positron Damping Ring. The QDI quadrupole design has already been modified and magnets of a new type will be implemented in both damping rings.

  8. Material damping experiments at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Levine, Marie B.; White, Christopher

    2003-12-01

    NASA's James Webb Space Telescope (JWST) will be operating at temperatures below 40K to image in the infrared. The 7-m class telescope will require nanometric jitter stability of the optical elements such as the primary and secondary mirrors. Of particular concern is the vibration response of these cryogenic systems when subjected to on-board disturbance sources such as the reaction wheels, the amplitude of which is governed by damping. Unfortunately there is relatively little data available for flight grade materials at these temperatures and within the frequency bands of interest. The paper will describe the experimental setup designed to measure viscous damping to values as low 10^-4%. The tests measure damping from room temperature all the way down to 20K in a controlled thermal and disturbance free environment. Data is obtained for strain levels of about 0.1 micro-strain down to nano-strains to verify vibration level effects on material damping. Damping is also measured for several frequencies in the range of 20Hz to 300Hz to assess the trend of damping as a function of vibrational frequency. Data for several materials, such as Aluminum, Beryllium, Quartz, and various composites are presented. The data is compared to analytical predictions using the Zener damping theory and is shown to match well at room temperature but to disagree at colder temperatures.

  9. The influence of complexes on implicit learning.

    PubMed

    Shin, Yong-Wook; Lee, Joong-Sun; Han, Oh-Su; Rhi, Bou-Yong

    2005-04-01

    A century ago, Jung looked into the unconscious through complexes by using word association tests. Jung wrote, 'modern psychology with its investigation of complexes has opened up a psychic taboo area riddled with hopes and fears', and complexes remain an unexplored taboo area of research. In the present study, we have investigated the influence of complexes on unconscious cognitive processing, in particular on implicit learning. We have found that complexes shown to disturb conscious cognitive processing in fact enhanced the attention of the subjects and their performance on an implicit learning task. These results suggest that complexes are not just abstractions, but have various actual influences on both conscious and unconscious processing.

  10. Experimental verification of damping mechanisms in a composite beam

    NASA Technical Reports Server (NTRS)

    Cudney, Harley H.; Inman, Daniel J.

    1989-01-01

    A method of estimating the distributed damping parameters based on the measured modal parameters (frequency and damping ratios) was derived. Three different mathematical models were used to model the damping mechanism of a quasi-isotropic pultruded cantilevered beam. These three models were (1) viscous (air) damping, (2) strain rate damping, and (3) both viscous and strain rate damping. The eigenvalues of the partial differential equation model were found to be uninfluenced by any of the three assumed damping models. Values were obtained for each of the damping models as well as the modulus of elasticity of the beam. It was found that the two-parameter damping model provided the best fit to measured modal data. However, the two-parameter damping model could only reproduce the measured damping ratios to within 85 percent.

  11. Investigation on the mechanism of damping behavior of magnetorheological elastomers

    NASA Astrophysics Data System (ADS)

    Yang, Jie; Gong, Xinglong; Deng, Huaxia; Qin, Lijun; Xuan, Shouhu

    2012-12-01

    Magnetorheological elastomers (MREs) are a group of smart materials which have many applications such as dynamic vibration absorbers, engine mounts, and so on. The damping behavior is important for applications of MREs. However, the mechanism of the damping of MREs has not been investigated thoroughly. In this study, MREs are modeled as special particle reinforced composites with magneto-induced properties and the mechanism of the damping behavior of MREs is investigated theoretically and experimentally. It has been found that there are three types of damping property in MREs: the intrinsic damping, the interface damping and the magneto-mechanical damping. The presented damping model is successfully validated by damping tests on a series of MRE samples. Furthermore, the relationships between the damping properties and formulas of MREs are discussed; this provides guidance for the manufacture of MREs with various damping properties.

  12. Nonlinear Landau damping of Alfven waves.

    NASA Technical Reports Server (NTRS)

    Hollweg, J. V.

    1971-01-01

    Demonstration that large-amplitude linearly or elliptically polarized Alfven waves propagating parallel to the average magnetic field can be dissipated by nonlinear Landau damping. The damping is due to the longitudinal electric field associated with the ion sound wave which is driven (in second order) by the Alfven wave. The damping rate can be large even in a cold plasma (beta much less than 1, but not zero), and the mechanism proposed may be the dominant one in many plasmas of astrophysical interest.

  13. A Resonant Damping Study Using Piezoelectric Materials

    NASA Technical Reports Server (NTRS)

    Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

    2008-01-01

    Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

  14. Oscillation damped movement of suspended objects

    SciTech Connect

    Jones, J.F.; Petterson, B.J.

    1988-01-01

    Transportation of objects using overhead cranes or manipulators can induce pendulum motion of the object. Residual oscillation from transportation typically must be damped or allowed to decay before the next process can take place. By properly programming the acceleration of the transporting device (e.g., crane) an oscillation damped transport and swing free stop is obtainable. This paper reviews the theory associated with oscillation damped trajectories for simply suspended objects and describes a particular implementation using a CIMCORP XR 6100 gantry robot. 8 refs., 7 figs., 1 tab.

  15. Damping measurements of laminated composite materials and aluminum using the hysteresis loop method

    NASA Astrophysics Data System (ADS)

    Abramovich, H.; Govich, D.; Grunwald, A.

    2015-10-01

    The damping characteristics of composite laminates made of Hexply 8552 AGP 280-5H (fabric), used for structural elements in aeronautical vehicles, have been investigated in depth using the hysteresis loop method and compared to the results for aluminum specimens (2024 T351). It was found that the loss factor, η, obtained by the hysteresis loop method is linearly dependent only on the applied excitation frequency and is independent of the preloading and the stress amplitudes. For the test specimens used in the present tests series, it was found that the damping of the aluminum specimens is higher than the composite ones for longitudinal direction damping, while for bending vibrations the laminates exhibited higher damping values.

  16. Turbine blade friction damping study

    NASA Technical Reports Server (NTRS)

    Dominic, R. J.

    1985-01-01

    A lumped parameter method, implemented on a VAX 11/780 computer shows that the primary parameters affecting the performance of the friction damper of the first stage turbine of the SSME high pressure fuel pump are: the damper-blade coefficient of friction; the normal force applied to the friction interface; the amplitude of the periodic forcing function; the relative phase angle of the forcing functions for adjacent blades bridged by a damper (effectively, the engine order of the forcing function); and the amount of hysteretic damping that acts to limit the vibration amplitude of the blade in its resonance modes. The low order flexural resonance vibration modes of HPFTP blades without dampers, with production dampers, and with two types of lightweight experimental dampers were evaluated in high speed spin pit tests. Results agree with those of the analytical study in that blades fitted with production friction dampers experienced the airfoil-alone flexural resonance mode, while those without dampers or with lighter weight dampers did not. No blades fitted with dampers experienced the whole blade flexural resonance mode during high speed tests, while those without dampers did.

  17. Eigensolutions of non-proportionally damped systems based on continuous damping sensitivity

    NASA Astrophysics Data System (ADS)

    Lázaro, Mario

    2016-02-01

    The viscous damping model has been widely used to represent dissipative forces in structures under mechanical vibrations. In multiple degree of freedom systems, such behavior is mathematically modeled by a damping matrix, which in general presents non-proportionality, that is, it does not become diagonal in the modal space of the undamped problem. Eigensolutions of non-proportional systems are usually estimated assuming that the modal damping matrix is diagonally dominant (neglecting the off-diagonal terms) or, in the general case, using the state-space approach. In this paper, a new closed-form expression for the complex eigenvalues of non-proportionally damped system is proposed. The approach is derived assuming small damping and involves not only the diagonal terms of the modal damping matrix, but also the off-diagonal terms, which appear under higher order. The validity of the proposed approach is illustrated through a numerical example.

  18. High and Mighty: Implicit Associations between Space and Social Status

    PubMed Central

    Gagnon, Stephanie A.; Brunyé, Tad T.; Robin, Cynthia; Mahoney, Caroline R.; Taylor, Holly A.

    2011-01-01

    Figurative language and our perceptuo-motor experiences frequently associate social status with physical space. In three experiments we examine the source and extent of these associations by testing whether people implicitly associate abstract social status indicators with concrete representations of spatial topography (level versus mountainous land) and relatively abstract representations of cardinal direction (south and north). Experiment 1 demonstrates speeded performance during an implicit association test (Greenwald et al., 1998) when average social status is paired with level topography and high status with mountainous topography. Experiments 2 and 3 demonstrate a similar effect but with relatively abstract representations of cardinal direction (south and north), with speeded performance when average and powerful social status are paired with south and north coordinate space, respectively. Abstract concepts of social status are perceived and understood in an inherently spatial world, resulting in powerful associations between abstract social concepts and concrete and abstract notions of physical axes. These associations may prove influential in guiding daily judgments and actions. PMID:22013428

  19. Random vibrations of quadratic damping systems. [optimum damping analysis for automobile suspension system

    NASA Technical Reports Server (NTRS)

    Sireteanu, T.

    1974-01-01

    An oscillating system with quadratic damping subjected to white noise excitation is replaced by a nonlinear, statistically equivalent system for which the associated Fokker-Planck equation can be exactly solved. The mean square responses are calculated and the optimum damping coefficient is determined with respect to the minimum mean square acceleration criteria. An application of these results to the optimization of automobile suspension damping is given.

  20. Simplified Model of Nonlinear Landau Damping

    SciTech Connect

    N. A. Yampolsky and N. J. Fisch

    2009-07-16

    The nonlinear interaction of a plasma wave with resonant electrons results in a plateau in the electron distribution function close to the phase velocity of the plasma wave. As a result, Landau damping of the plasma wave vanishes and the resonant frequency of the plasma wave downshifts. However, this simple picture is invalid when the external driving force changes the plasma wave fast enough so that the plateau cannot be fully developed. A new model to describe amplification of the plasma wave including the saturation of Landau damping and the nonlinear frequency shift is proposed. The proposed model takes into account the change of the plasma wave amplitude and describes saturation of the Landau damping rate in terms of a single fluid equation, which simplifies the description of the inherently kinetic nature of Landau damping. A proposed fluid model, incorporating these simplifications, is verified numerically using a kinetic Vlasov code.

  1. Roll Damping Characterisation Program: User Guide

    DTIC Science & Technology

    2014-06-01

    sallying test. The Defence Science and Technology Organisation (DSTO) have developed a software-based tool called the Roll Damping Characterisation...Murray Riding Maritime Division Murray obtained a Bachelor of Science (Honours) Degree from the

  2. Electron beam depolarization in a damping ring

    SciTech Connect

    Minty, M.

    1993-04-01

    Depolarization of a polarized electron beam injected into a damping ring is analyzed by extending calculations conventionally applied to proton synchrotrons. Synchrotron radiation in an electron ring gives rise to both polarizing and depolarizing effects. In a damping ring, the beam is stored for a time much less than the time for self polarization. Spin flip radiation may therefore be neglected. Synchrotron radiation without spin flips, however, must be considered as the resonance strength depends on the vertical betatron oscillation amplitude which changes as the electron beam is radiation damped. An expression for the beam polarization at extraction is derived which takes into account radiation damping. The results are applied to the electron ring at the Stanford Linear Collider and are compared with numerical matrix formalisms.

  3. Oscillation damping means for magnetically levitated systems

    DOEpatents

    Post, Richard F.

    2009-01-20

    The present invention presents a novel system and method of damping rolling, pitching, or yawing motions, or longitudinal oscillations superposed on their normal forward or backward velocity of a moving levitated system.

  4. Modification of spastic gait through mechanical damping.

    PubMed

    Maki, B E; Rosen, M J; Simon, S R

    1985-01-01

    The effect of dissipative mechanical loads on spastic gait has been studied, to evaluate the feasibility of using mechanically damped orthoses to effect functional improvements in the gait of spastic patients. This concept is based on a hypothesis citing uninhibited, velocity-dependent stretch reflexes as a possible causal factor in spastic gait abnormalities, such as equinus and back-kneeing. In order to screen potential experimental subjects and to quantify velocity-dependent reflex behaviour, ankle rotation experiments and filmed gait analysis were performed. The results supported the existence of a velocity threshold. Orthosis simulation experiments were performed with one spastic subject, using a wearable, computer-controlled, electromechanical, below-knee orthosis simulator to apply a variety of damping loads to the ankle as the subject walked. Results indicated that appropriate damping can improve local joint kinematics. The damping causes a reduction in muscle stretch velocity which apparently results in reduced spastic reflex activity.

  5. Collisional damping of the geodesic acoustic mode

    SciTech Connect

    Gao Zhe

    2013-03-15

    The frequency and damping rate of the geodesic acoustic mode (GAM) is revisited by using a gyrokinetic model with a number-conserving Krook collision operator. It is found that the damping rate of the GAM is non-monotonic as the collision rate increases. At low ion collision rate, the damping rate increases linearly with the collision rate; while as the ion collision rate is higher than v{sub ti}/R, where v{sub ti} and R are the ion thermal velocity and major radius, the damping rate decays with an increasing collision rate. At the same time, as the collision rate increases, the GAM frequency decreases from the (7/4+{tau})v{sub ti}/R to (1+{tau})v{sub ti}/R, where {tau} is the ratio of electron temperature to ion temperature.

  6. Recollective performance advantages for implicit memory tasks.

    PubMed

    Sheldon, Signy A M; Moscovitch, Morris

    2010-10-01

    A commonly held assumption is that processes underlying explicit and implicit memory are distinct. Recent evidence, however, suggests that they may interact more than previously believed. Using the remember-know procedure the current study examines the relation between recollection, a process thought to be exclusive to explicit memory, and performance on two implicit memory tasks, lexical decision and word stem completion. We found that, for both implicit tasks, words that were recollected were associated with greater priming effects than were words given a subsequent familiarity rating or words that had been studied but were not recognised (misses). Broadly, our results suggest that non-voluntary processes underlying explicit memory also benefit priming, a measure of implicit memory. More specifically, given that this benefit was due to a particular aspect of explicit memory (recollection), these results are consistent with some strength models of memory and with Moscovitch's (2008) proposal that recollection is a two-stage process, one rapid and unconscious and the other more effortful and conscious.

  7. Development of Implicit and Explicit Category Learning

    ERIC Educational Resources Information Center

    Huang-Pollock, Cynthia L.; Maddox, W. Todd; Karalunas, Sarah L.

    2011-01-01

    We present two studies that examined developmental differences in the implicit and explicit acquisition of category knowledge. College-attending adults consistently outperformed school-age children on two separate information-integration paradigms due to children's more frequent use of an explicit rule-based strategy. Accuracy rates were also…

  8. Implicit Social Scaling from an Institutional Perspective

    ERIC Educational Resources Information Center

    D'Epifanio, Giulio

    2009-01-01

    The methodological question concerns constructing a cardinal social index, in order to assess performances of social agents, taking into account implicit political judgments. Based on the formal structure of a Choquet's expected utility, index construction demands quantification of levels of a meaningful ordinal indicator of overall performance.…

  9. Crosslinguistic Differences in Implicit Language Learning

    ERIC Educational Resources Information Center

    Leung, Janny H. C.; Williams, John N.

    2014-01-01

    We report three experiments that explore the effect of prior linguistic knowledge on implicit language learning. Native speakers of English from the United Kingdom and native speakers of Cantonese from Hong Kong participated in experiments that involved different learning materials. In Experiment 1, both participant groups showed evidence of…

  10. On stiffly stable implicit linear multistep methods.

    NASA Technical Reports Server (NTRS)

    Cooke, C. H.

    1972-01-01

    The motivation to increase the step size with no degradation of numerical accuracy and stability has led to the discovery of particular members of the class of stiffly stable implicit linear multistep algorithms. Sufficient conditions for a consistent linear multistep method to be stiffly stable are given. These conditions involve properties of the stability mapping from the extended complex plane onto itself.

  11. Thinking Styles in Implicit and Explicit Learning

    ERIC Educational Resources Information Center

    Xie, Qiuzhi; Gao, Xiangping; King, Ronnel B.

    2013-01-01

    This study investigated whether individual differences in thinking styles influence explicit and implicit learning. Eighty-seven university students in China participated in this study. Results indicated that performance in the explicit learning condition was positively associated with Type I thinking styles (i.e. legislative and liberal styles)…

  12. Strategic Game Moves Mediate Implicit Science Learning

    ERIC Educational Resources Information Center

    Rowe, Elizabeth; Baker, Ryan S.; Asbell-Clarke, Jodi

    2015-01-01

    Educational games have the potential to be innovative forms of learning assessment, by allowing us to not just study their knowledge but the process that takes students to that knowledge. This paper examines the mediating role of players' moves in digital games on changes in their pre-post classroom measures of implicit science learning. We…

  13. Implicit theories and ability emotional intelligence.

    PubMed

    Cabello, Rosario; Fernández-Berrocal, Pablo

    2015-01-01

    Previous research has shown that people differ in their implicit theories about the essential characteristics of intelligence and emotions. Some people believe these characteristics to be predetermined and immutable (entity theorists), whereas others believe that these characteristics can be changed through learning and behavior training (incremental theorists). The present study provides evidence that in healthy adults (N = 688), implicit beliefs about emotions and emotional intelligence (EI) may influence performance on the ability-based Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT). Adults in our sample with incremental theories about emotions and EI scored higher on the MSCEIT than entity theorists, with implicit theories about EI showing a stronger relationship to scores than theories about emotions. Although our participants perceived both emotion and EI as malleable, they viewed emotions as more malleable than EI. Women and young adults in general were more likely to be incremental theorists than men and older adults. Furthermore, we found that emotion and EI theories mediated the relationship of gender and age with ability EI. Our findings suggest that people's implicit theories about EI may influence their emotional abilities, which may have important consequences for personal and professional EI training.

  14. Implicit theories and ability emotional intelligence

    PubMed Central

    Cabello, Rosario; Fernández-Berrocal, Pablo

    2015-01-01

    Previous research has shown that people differ in their implicit theories about the essential characteristics of intelligence and emotions. Some people believe these characteristics to be predetermined and immutable (entity theorists), whereas others believe that these characteristics can be changed through learning and behavior training (incremental theorists). The present study provides evidence that in healthy adults (N = 688), implicit beliefs about emotions and emotional intelligence (EI) may influence performance on the ability-based Mayer-Salovey-Caruso Emotional Intelligence Test (MSCEIT). Adults in our sample with incremental theories about emotions and EI scored higher on the MSCEIT than entity theorists, with implicit theories about EI showing a stronger relationship to scores than theories about emotions. Although our participants perceived both emotion and EI as malleable, they viewed emotions as more malleable than EI. Women and young adults in general were more likely to be incremental theorists than men and older adults. Furthermore, we found that emotion and EI theories mediated the relationship of gender and age with ability EI. Our findings suggest that people’s implicit theories about EI may influence their emotional abilities, which may have important consequences for personal and professional EI training. PMID:26052309

  15. Implicit Theories about Everyday Problem Solving.

    ERIC Educational Resources Information Center

    Herbert, Margaret E.; Dionne, Jean-Paul

    Mental models or implicit theories held by adults about everyday problem solving were studied. Research questions were posed to 12 male and 12 female adults, aged 25 to 60 years, from a wide range of educational and occupational orientations. Subjects were interviewed in pairs. Verbal Protocol Analysis was used to analyze the data from two…

  16. Identifying, Quantifying, Extracting and Enhancing Implicit Parallelism

    ERIC Educational Resources Information Center

    Agarwal, Mayank

    2009-01-01

    The shift of the microprocessor industry towards multicore architectures has placed a huge burden on the programmers by requiring explicit parallelization for performance. Implicit Parallelization is an alternative that could ease the burden on programmers by parallelizing applications "under the covers" while maintaining sequential semantics…

  17. Implicit Training of Nonnative Speech Stimuli

    ERIC Educational Resources Information Center

    Vlahou, Eleni L.; Protopapas, Athanassios; Seitz, Aaron R.

    2012-01-01

    Learning nonnative speech contrasts in adulthood has proven difficult. Standard training methods have achieved moderate effects using explicit instructions and performance feedback. In this study, the authors question preexisting assumptions by demonstrating a superiority of implicit training procedures. They trained 3 groups of Greek adults on a…

  18. Implicit Assumptions in High Potentials Recruitment

    ERIC Educational Resources Information Center

    Posthumus, Jan; Bozer, Gil; Santora, Joseph C.

    2016-01-01

    Purpose: Professionals of human resources (HR) use different criteria in practice than they verbalize. Thus, the aim of this research was to identify the implicit criteria used for the selection of high-potential employees in recruitment and development settings in the pharmaceutical industry. Design/methodology/approach: A semi-structured…

  19. Implicit variational principle for contact Hamiltonian systems

    NASA Astrophysics Data System (ADS)

    Wang, Kaizhi; Wang, Lin; Yan, Jun

    2017-02-01

    We establish an implicit variational principle for the contact Hamiltonian systems generated by the Hamiltonian H(x, u, p) with respect to the contact 1-form α =\\text{d}u-p\\text{d}x under Tonelli and Lipschitz continuity conditions.

  20. Implicit Learning of Semantic Preferences of Verbs

    ERIC Educational Resources Information Center

    Paciorek, Albertyna; Williams, John N.

    2015-01-01

    Previous studies of semantic implicit learning in language have only examined learning grammatical form-meaning connections in which learning could have been supported by prior linguistic knowledge. In this study we target the domain of verb meaning, specifically semantic preferences regarding novel verbs (e.g., the preference for a novel verb to…

  1. Implicit Measures of Association in Psychopathology Research

    ERIC Educational Resources Information Center

    Roefs, Anne; Huijding, Jorg; Smulders, Fren T. Y.; MacLeod, Colin M.; de Jong, Peter J.; Wiers, Reinout W.; Jansen, Anita T. M.

    2011-01-01

    Validity;Measures (Individuals);Studies obtaining implicit measures of associations in "Diagnostic and Statistical Manual of Mental Disorders" (4th ed., Text Revision; American Psychiatric Association, 2000) Axis I psychopathology are organized into three categories: (a) studies comparing groups having a disorder with controls, (b) experimental…

  2. Implicit Reading in Chinese Pure Alexia

    ERIC Educational Resources Information Center

    Shan, Chunlei; Zhu, Renjing; Xu, Mingwei; Luo, Benyan; Weng, Xuchu

    2010-01-01

    A number of recent studies have shown that some patients with pure alexia display evidence of implicit access to lexical and semantic information about words that they cannot read explicitly. This phenomenon has not been investigated systematically in Chinese patients. We report here a case study of a Chinese patient who met the criteria for pure…

  3. Three-dimensional implicit lambda methods

    NASA Technical Reports Server (NTRS)

    Napolitano, M.; Dadone, A.

    1983-01-01

    This paper derives the three dimensional lambda-formulation equations for a general orthogonal curvilinear coordinate system and provides various block-explicit and block-implicit methods for solving them, numerically. Three model problems, characterized by subsonic, supersonic and transonic flow conditions, are used to assess the reliability and compare the efficiency of the proposed methods.

  4. Implicit emotion regulation affects outcome evaluation.

    PubMed

    Yang, Qiwei; Tang, Ping; Gu, Ruolei; Luo, Wenbo; Luo, Yue-jia

    2015-06-01

    Efficient implicit emotion regulation processes, which run without awareness, are important for human well-being. In this study, to investigate the influence of implicit emotion regulation on psychological and electrophysiological responses to gains and losses, participants were required to select between two Chinese four-character idioms to match the meaning of the third one before they performed a monetary gambling task. According to whether their meanings were related to emotion regulation, the idioms fell into two categories. Event-related potentials and self-rating emotional experiences to outcome feedback were recorded during the task. Priming emotion regulation reduced subjective emotional experience to both gains and losses and the amplitudes of the feedback-related negativity, while the P3 component was not influenced. According to these results, we suggest that the application of implicit emotion regulation effectively modulated the subjective emotional experience and the motivational salience of current outcomes without the cost of cognitive resources. This study implicates the potential significance of implicit emotion regulation in decision-making processes.

  5. Spatial versus time hysteresis in damping mechanisms

    NASA Technical Reports Server (NTRS)

    Banks, H. T.; Fabiano, R. H.; Wang, Y.; Inman, D. J.; Cudney, H., Jr.

    1988-01-01

    A description is given of continuing investigations on the task of estimating internal damping mechanisms in flexible structures. Specifically, two models for internal damping in Euler-Bernoulli beams are considered: spatial hysteresis and time hysteresis. A theoretically sound computational algorithm for estimation is described, and experimental results are discussed. It is concluded that both models perform well in the sense that they accurately predict response for the experiments conducted.

  6. Microscale damping using thin film active materials

    NASA Astrophysics Data System (ADS)

    Kerrigan, Catherine A.; Ho, Ken K.; Mohanchandra, K. P.; Carman, Gregory P.

    2007-04-01

    This paper focuses on understanding and developing a new approach to dampen MEMS structures using both experiments and analytical techniques. Thin film Nitinol and thin film Terfenol-D are evaluated as a damping solution to the micro scale damping problem. Stress induced twin boundary motion in Nitinol is used to passively dampen potentially damaging vibrations. Magnetic domain wall motion is used to passively dampen vibration in Terfenol-D. The thin films of Nitinol, Nitinol/Silicon laminates and Nitinol/Terfenol-D/Nickel laminates have been produced using a sputter deposition process and damping properties have been evaluated. Dynamic testing shows substantial damping (tan δ) measurable in each case. Nitinol film samples were tested in the Differential Scanning Calorimetry (DSC) to determine phase transformation temperatures. The twin boundary mechanism by which energy absorption occurs is present at all points below the Austenite start temperature (approximately 69°C in our film) and therefore allows damping at cold temperatures where traditional materials fail. Thin film in the NiTi/Si laminate was found to produce substantially higher damping (tan δ = 0.28) due to the change in loading condition. The NiTi/Si laminate sample was tested in bending allowing the twin boundaries to be reset by cyclic tensile and compressive loads. The thin film Terfenol-D in the Nitinol/Terfenol-D/Nickel laminate was shown to produce large damping (tan δ = 0.2). In addition to fabricating and testing, an analytical model of a heterogeneous layered thin film damping material was developed and compared to experimental work.

  7. Turbine blade with tuned damping structure

    DOEpatents

    Campbell, Christian X.; Messmann, Stephen J.

    2015-09-01

    A turbine blade is provided comprising: a root; an airfoil comprising an external wall extending radially from the root and having a radially outermost portion; and a damping structure. The external wall may comprise first and second side walls joined together to define an inner cavity of the airfoil. The damping structure may be positioned within the airfoil inner cavity and coupled to the airfoil so as to define a tuned mass damper.

  8. Analysis of nonlinear damping properties of carbon

    NASA Astrophysics Data System (ADS)

    Kazakova, Olga I.; Smolin, Igor Yu.; Bezmozgiy, Iosif M.

    2016-11-01

    This paper describes research results of nonlinear damping properties of carbon fiber reinforced plastics. The experimental and computational research is performed on flat composite specimens with the gradual structure complication (from 1 to 12 layers). Specimens are subjected to three types of testing which are modal, harmonic and transient analyses. Relationships between the amplitude response and damping ratio are obtained by means of the analysis of variance as the result of this research.

  9. Quantum damped oscillator I: Dissipation and resonances

    SciTech Connect

    Chruscinski, Dariusz

    2006-04-15

    Quantization of a damped harmonic oscillator leads to so called Bateman's dual system. The corresponding Bateman's Hamiltonian, being a self-adjoint operator, displays the discrete family of complex eigenvalues. We show that they correspond to the poles of energy eigenvectors and the corresponding resolvent operator when continued to the complex energy plane. Therefore, the corresponding generalized eigenvectors may be interpreted as resonant states which are responsible for the irreversible quantum dynamics of a damped harmonic oscillator.

  10. Aerospace Structures Technology Damping Design Guide. Volume 3. Damping Material Data

    DTIC Science & Technology

    1985-12-01

    1.1 DAMPING MATERIAL PROPERTIES 1 3 1.2 THE STANDARIZED MATERIAL DATA I 1.2.1 Nomogram Cover Sheet 3 ’ 1.2.2 The Reduced Nomogram 4 1.2.3 Reading...MATERIALS 6 2 DAMPING MATERIAL PROPERTY DATA 14 3 STRUCTURAL EPOXIES AND OTHER MATERIALS 469 3.1 STRUCTURAL EPOXIES 469 3.2 STRUCTURAL PLASTICS 477 3.3...Data Listing II 6 Temperature Shift Function and Its Properties 12 7 Typical TCA Plot 13 8 Quick Reference Chart for Damping Materials 15 9 Damping vs

  11. Transient analysis for damping identification in rotating composite beams with integral damping layers

    NASA Astrophysics Data System (ADS)

    Smith, Clifford B.; Wereley, Norman M.

    1996-10-01

    The first objective of this paper is to evaluate the performance of damping identification algorithms. The second objective is to determine the feasibility of damping augmentation in rotating composite beams via passive constrained layer damping (PCLD). Damping identification schemes were applied to four rectangular cross-section laminated composite beams with cocured integral damping layers over the span of the beam. The cocured beam consisted of a twenty-ply balanced and symmetric cross-ply Gr/Ep composite host structure, a top and bottom damping layer of viscoelastic material (VEM), and a 2-ply Gr/Ep constraining layer sandwiching the viscoelastic material to the host structure. Four VEM thicknesses were considered: 0, 5, 10, and 15 mils. The cantilevered beams were tested at rotational speeds ranging from 0 to 900 RPM in a vacuum chamber. Excitation in bending was provided using piezo actuators, and the bending response was measured using full strain gauge bridges. Transient data were analysed using logarithmic decrement, a Hilbert transform technique, and an FFT- based moving block analysis. When compared to the beam with no VEM, a 19.2% volume fraction (15 mil layer) of viscoelastic in the beam produced a 400% increase in damping ratio in the non-rotating case, while at 900 RPM, the damping ratio increased only 360%. Overall structural damping was reduced as a function of RPM, due to centrifugal stiffening.

  12. Damping effects in doped graphene: The relaxation-time approximation

    NASA Astrophysics Data System (ADS)

    Kupčić, I.

    2014-11-01

    The dynamical conductivity of interacting multiband electronic systems derived by Kupčić et al. [J. Phys.: Condens. Matter 90, 145602 (2013), 10.1088/0953-8984/25/14/145602] is shown to be consistent with the general form of the Ward identity. Using the semiphenomenological form of this conductivity formula, we have demonstrated that the relaxation-time approximation can be used to describe the damping effects in weakly interacting multiband systems only if local charge conservation in the system and gauge invariance of the response theory are properly treated. Such a gauge-invariant response theory is illustrated on the common tight-binding model for conduction electrons in doped graphene. The model predicts two distinctly resolved maxima in the energy-loss-function spectra. The first one corresponds to the intraband plasmons (usually called the Dirac plasmons). On the other hand, the second maximum (π plasmon structure) is simply a consequence of the Van Hove singularity in the single-electron density of states. The dc resistivity and the real part of the dynamical conductivity are found to be well described by the relaxation-time approximation, but only in the parametric space in which the damping is dominated by the direct scattering processes. The ballistic transport and the damping of Dirac plasmons are thus the problems that require abandoning the relaxation-time approximation.

  13. The single category implicit association test as a measure of implicit social cognition.

    PubMed

    Karpinski, Andrew; Steinman, Ross B

    2006-07-01

    The Single Category Implicit Association Test (SC-IAT) is a modification of the Implicit Association Test that measures the strength of evaluative associations with a single attitude object. Across 3 different attitude domains--soda brand preferences, self-esteem, and racial attitudes--the authors found evidence that the SC-IAT is internally consistent and makes unique contributions in the ability to understand implicit social cognition. In a 4th study, the authors investigated the susceptibility of the SC-IAT to faking or self-presentational concerns. Once participants with high error rates were removed, no significant self-presentation effect was observed. These results provide initial evidence for the reliability and validity of the SC-IAT as an individual difference measure of implicit social cognition.

  14. Validation of equivalent viscous damping methodologies

    NASA Astrophysics Data System (ADS)

    Vaquer Araujo, Xavier; Fransen, Sebastiaan H. J. A.; Germès, Sylvain; Thiry, Nicolas

    2013-06-01

    An important step in the design and verification process of spacecraft structures is the coupled dynamic analysis with the launch vehicle in the low-frequency domain. To obtain accurate predictions of the satellite's dynamic environment, it is essential that the damping of the system is correctly defined and taken into account within the resolution methodologies for the coupled loads analysis (CLA). When working with finite element models, the materials' damping is characterized by structural damping ratios. In addition, most of the load cases present in the CLA are transient excitations, and so the resolution of the equations of motion must be done in the time domain. Unfortunately, in the CLA, transient analyses cannot be carried out using structural damping models. Thus, a transformation from a structural to a viscous damping characterization is necessary in this case. Nevertheless, this transformation is not trivial. There exist many methodologies for computing an equivalent viscous damping (EqVD) matrix of the system which can be used in transient analyses. This paper describes the results obtained from the validation of EqVD methodologies used in the European Space Agency. This work identifies the limitations of these methodologies and comes up with an enhanced methodology that predicts more reliable results.

  15. The effect of motive-trait interaction on satisfaction of the implicit need for affiliation among German and Cameroonian adults.

    PubMed

    Hofer, Jan; Busch, Holger; Schneider, Carolin

    2015-04-01

    Research provided evidence that personality traits influence the realization of implicit motives: Extraversion supported the successful realization of the implicit motives for affiliation and power, whereas introversion deflected implicit motives away from significant goals and created difficulties in goal attainment. Based on those findings on motive-trait interaction, we tested whether the traits of Neuroticism, Agreeableness, and Extraversion affect the satisfaction of the implicit affiliation motive (i.e., the need for establishing and maintaining close relationships with other people) approximately 18 months later. Data on personality traits, the implicit affiliation motive, and need satisfaction were assessed from 244 Cameroonian and German adults. As expected, across cultural groups, Neuroticism constrains but Agreeableness supports the realization of the implicit affiliation motive. No significant results could be found for Extraversion, even if the effect was in the assumed direction. The findings support the argument that different significant personality components ought to be taken into account in research on implicit motives and their psychological and behavioral correlates.

  16. Phrase Length Matters: The Interplay between Implicit Prosody and Syntax in Korean "Garden Path" Sentences

    ERIC Educational Resources Information Center

    Hwang, Hyekyung; Steinhauer, Karsten

    2011-01-01

    In spoken language comprehension, syntactic parsing decisions interact with prosodic phrasing, which is directly affected by phrase length. Here we used ERPs to examine whether a similar effect holds for the on-line processing of written sentences during silent reading, as suggested by theories of "implicit prosody." Ambiguous Korean sentence…

  17. Hybrid Damping System for an Electronic Equipment Mounting Shelf

    NASA Technical Reports Server (NTRS)

    Voracek, David; Kolkailah, Faysal A.; Cavalli, J. R.; Elghandour, Eltahry

    1997-01-01

    The objective of this study was to design and construct a vibration control system for an electronic equipment shelf to be evaluated in the NASA Dryden FTF-11. The vibration control system was a hybrid system which included passive and active damping techniques. Passive damping was fabricated into the equipment shelf using ScothDamp(trademark) damping film and aluminum constraining layers. Active damping was achieved using a two channel active control circuit employing QuickPack(trademark) sensors and actuators. Preliminary Chirp test results indicated passive damping smoothed the frequency response while active damping reduced amplitudes of the frequency response for most frequencies below 500Hz.

  18. Hybrid Damping System for an Electronic Equipment Mounting Shelf

    NASA Technical Reports Server (NTRS)

    Voracek, David; Kolkailah, Faysal A.; Cavalli, J. R.; Elghandour, Eltahry

    1997-01-01

    The objective of this study was to design and construct a vibration control system for an electronic equipment shelf to be evaluated in the NASA Dryden FTF-II. The vibration control system was a hybrid system which included passive and active damping techniques. Passive damping was fabricated into the equipment shelf using ScothDamp(trademark) damping film and aluminum constraining layers. Active damping was achieved using a two channel active control circuit employing QuickPack(trademark) sensors and actuators. Preliminary Chirp test results indicated passive damping smoothed the frequency response while active damping reduced amplitudes of the frequency response for most frequencies below 500Hz.

  19. Questioning Children: Interactional Evidence of Implicit Bias in Medical Interviews

    ERIC Educational Resources Information Center

    Stivers, Tanya; Majid, Asifa

    2007-01-01

    Social psychologists have shown experimentally that implicit race bias can influence an individual's behavior. Implicit bias has been suggested to be more subtle and less subject to cognitive control than more explicit forms of racial prejudice. Little is known about how implicit bias is manifest in naturally occurring social interaction. This…

  20. Implicit Referential Meaning with Reference to English Arabic Translation

    ERIC Educational Resources Information Center

    Al-Zughoul, Basem

    2014-01-01

    The purpose of this study is to investigate how English implicit referential meaning is translated into Arabic by analyzing sentences containing implicit referential meanings found in the novel "Harry Potter and the Prisoner of Azkaban". The analysis shows that the translation of English implicit referential meaning into Arabic can be…

  1. Implicit Statistical Learning and Language Skills in Bilingual Children

    ERIC Educational Resources Information Center

    Yim, Dongsun; Rudoy, John

    2013-01-01

    Purpose: Implicit statistical learning in 2 nonlinguistic domains (visual and auditory) was used to investigate (a) whether linguistic experience influences the underlying learning mechanism and (b) whether there are modality constraints in predicting implicit statistical learning with age and language skills. Method: Implicit statistical learning…

  2. Constraints on Implicit Learning of Grammatical Form-Meaning Connections

    ERIC Educational Resources Information Center

    Leung, Janny H. C.; Williams, John N.

    2012-01-01

    Although there is good evidence for implicit learning of associations between forms, little work has investigated implicit learning of form-meaning connections, and the findings are somewhat contradictory. Two experiments were carried out using a novel reaction time methodology to investigate implicit learning of grammatical form-meaning…

  3. Implicit associations in cybersex addiction: Adaption of an Implicit Association Test with pornographic pictures.

    PubMed

    Snagowski, Jan; Wegmann, Elisa; Pekal, Jaro; Laier, Christian; Brand, Matthias

    2015-10-01

    Recent studies show similarities between cybersex addiction and substance dependencies and argue to classify cybersex addiction as a behavioral addiction. In substance dependency, implicit associations are known to play a crucial role, and such implicit associations have not been studied in cybersex addiction, so far. In this experimental study, 128 heterosexual male participants completed an Implicit Association Test (IAT; Greenwald, McGhee, & Schwartz, 1998) modified with pornographic pictures. Further, problematic sexual behavior, sensitivity towards sexual excitation, tendencies towards cybersex addiction, and subjective craving due to watching pornographic pictures were assessed. Results show positive relationships between implicit associations of pornographic pictures with positive emotions and tendencies towards cybersex addiction, problematic sexual behavior, sensitivity towards sexual excitation as well as subjective craving. Moreover, a moderated regression analysis revealed that individuals who reported high subjective craving and showed positive implicit associations of pornographic pictures with positive emotions, particularly tended towards cybersex addiction. The findings suggest a potential role of positive implicit associations with pornographic pictures in the development and maintenance of cybersex addiction. Moreover, the results of the current study are comparable to findings from substance dependency research and emphasize analogies between cybersex addiction and substance dependencies or other behavioral addictions.

  4. Explicit and Implicit Processes Constitute the Fast and Slow Processes of Sensorimotor Learning.

    PubMed

    McDougle, Samuel D; Bond, Krista M; Taylor, Jordan A

    2015-07-01

    A popular model of human sensorimotor learning suggests that a fast process and a slow process work in parallel to produce the canonical learning curve (Smith et al., 2006). Recent evidence supports the subdivision of sensorimotor learning into explicit and implicit processes that simultaneously subserve task performance (Taylor et al., 2014). We set out to test whether these two accounts of learning processes are homologous. Using a recently developed method to assay explicit and implicit learning directly in a sensorimotor task, along with a computational modeling analysis, we show that the fast process closely resembles explicit learning and the slow process approximates implicit learning. In addition, we provide evidence for a subdivision of the slow/implicit process into distinct manifestations of motor memory. We conclude that the two-state model of motor learning is a close approximation of sensorimotor learning, but it is unable to describe adequately the various implicit learning operations that forge the learning curve. Our results suggest that a wider net be cast in the search for the putative psychological mechanisms and neural substrates underlying the multiplicity of processes involved in motor learning.

  5. A critical role of the human hippocampus in an electrophysiological measure of implicit memory

    PubMed Central

    Addante, Richard James

    2015-01-01

    The hippocampus has traditionally been thought to be critical for conscious explicit memory but not necessary for unconscious implicit memory processing. In a recent study of a group of mild amnesia patients with evidence of MTL damage limited to the hippocampus, subjects were tested on a direct test of item recognition confidence while electroencephalogram (EEG) was acquired, and revealed intact measures of explicit memory from 400–600ms (mid-frontal old-new effect, FN400). The current investigation re-analyzed this data to study event-related potentials (ERPs) of implicit memory, using a recently developed procedure that eliminated declarative memory differences. Prior ERP findings from this technique were first replicated in two independent matched control groups, which exhibited reliable implicit memory effects in posterior scalp regions from 400–600 msec, which were topographically dissociated from the explicit memory effects of familiarity. However, patients were found to be dramatically impaired in implicit memory effects relative to control subjects, as quantified by a reliable condition × group interaction. Several control analysis were conducted to consider alternative factors that could account for the results, including outliers, sample size, age, or contamination by explicit memory, and each of these factors were systematically ruled out. Results suggest that the hippocampus plays a fundamental role in aspects of memory processing that is beyond conscious awareness. The current findings therefore indicate that both memory systems of implicit and explicit memory may rely upon the same neural structures – but function in different physiological ways. PMID:25562828

  6. Inductive reasoning and implicit memory: evidence from intact and impaired memory systems.

    PubMed

    Girelli, Luisa; Semenza, Carlo; Delazer, Margarete

    2004-01-01

    In this study, we modified a classic problem solving task, number series completion, in order to explore the contribution of implicit memory to inductive reasoning. Participants were required to complete number series sharing the same underlying algorithm (e.g., +2), differing in both constituent elements (e.g., 2468 versus 57911) and correct answers (e.g., 10 versus 13). In Experiment 1, reliable priming effects emerged, whether primes and targets were separated by four or ten fillers. Experiment 2 provided direct evidence that the observed facilitation arises at central stages of problem solving, namely the identification of the algorithm and its subsequent extrapolation. The observation of analogous priming effects in a severely amnesic patient strongly supports the hypothesis that the facilitation in number series completion was largely determined by implicit memory processes. These findings demonstrate that the influence of implicit processes extends to higher level cognitive domain such as induction reasoning.

  7. Viscous damping and spring force calculation of regularly perforated MEMS microstructures in the Stokes' approximation

    PubMed Central

    Homentcovschi, Dorel; Murray, Bruce T.; Miles, Ronald N.

    2013-01-01

    There are a number of applications for microstructure devices consisting of a regular pattern of perforations, and many of these utilize fluid damping. For the analysis of viscous damping and for calculating the spring force in some cases, it is possible to take advantage of the regular hole pattern by assuming periodicity. Here a model is developed to determine these quantities based on the solution of the Stokes' equations for the air flow. Viscous damping is directly related to thermal-mechanical noise. As a result, the design of perforated microstructures with minimal viscous damping is of real practical importance. A method is developed to calculate the damping coefficient in microstructures with periodic perforations. The result can be used to minimize squeeze film damping. Since micromachined devices have finite dimensions, the periodic model for the perforated microstructure has to be associated with the calculation of some frame (edge) corrections. Analysis of the edge corrections has also been performed. Results from analytical formulas and numerical simulations match very well with published measured data. PMID:24058267

  8. FORWARD MODELING OF PROPAGATING SLOW WAVES IN CORONAL LOOPS AND THEIR FREQUENCY-DEPENDENT DAMPING

    SciTech Connect

    Mandal, Sudip; Banerjee, Dipankar; Magyar, Norbert; Yuan, Ding; Doorsselaere, Tom Van

    2016-03-20

    Propagating slow waves in coronal loops exhibit a damping that depends upon the frequency of the waves. In this study we aim to investigate the relationship of the damping length (L{sub d}) with the frequency of the propagating wave. We present a 3D coronal loop model with uniform density and temperature and investigate the frequency-dependent damping mechanism for the four chosen wave periods. We include the thermal conduction to damp the waves as they propagate through the loop. The numerical model output has been forward modeled to generate synthetic images of SDO/AIA 171 and 193 Å channels. The use of forward modeling, which incorporates the atomic emission properties into the intensity images, allows us to directly compare our results with the real observations. The results show that the damping lengths vary linearly with the periods. We also measure the contributions of the emission properties on the damping lengths by using density values from the simulation. In addition to that we have also calculated the theoretical dependence of L{sub d} with wave periods and showed that it is consistent with the results we obtained from the numerical modeling and earlier observations.

  9. Damping of Alfvén Waves by Turbulence and Its Consequences: From Cosmic-ray Streaming to Launching Winds

    NASA Astrophysics Data System (ADS)

    Lazarian, A.

    2016-12-01

    This paper considers turbulent damping of Alfvén waves in magnetized plasmas. We identify two cases of damping, one related to damping of cosmic-ray streaming instability, the other related to damping of Alfvén waves emitted by a macroscopic wave source, e.g., a stellar atmosphere. The physical difference between the two cases is that in the former case the generated waves are emitted with respect to the local direction of the magnetic field, and in the latter, waves are emitted with respect to the mean field. The scaling of damping is different in the two cases. We explore effects of turbulence in the regimes from sub-Alfvénic to super-Alfvénic to obtain analytical expressions for the damping rates and define the ranges of applicability of these expressions. In describing the damping of the streaming instability, we find that for sub-Alfvénic turbulence, the range of cosmic-ray energies influenced by weak turbulence is unproportionally large compared to the range of scales where weak turbulence is present. On the contrary, the range of cosmic-ray energies affected by strong Alfvénic turbulence is rather limited. A number of astrophysical applications of the process ranging from launching of stellar and galactic winds to propagation of cosmic rays in galaxies and clusters of galaxies is considered. In particular, we discuss how to reconcile the process of turbulent damping with the observed isotropy of the Milky Way cosmic rays.

  10. Multigrid Methods for Fully Implicit Oil Reservoir Simulation

    NASA Technical Reports Server (NTRS)

    Molenaar, J.

    1996-01-01

    In this paper we consider the simultaneous flow of oil and water in reservoir rock. This displacement process is modeled by two basic equations: the material balance or continuity equations and the equation of motion (Darcy's law). For the numerical solution of this system of nonlinear partial differential equations there are two approaches: the fully implicit or simultaneous solution method and the sequential solution method. In the sequential solution method the system of partial differential equations is manipulated to give an elliptic pressure equation and a hyperbolic (or parabolic) saturation equation. In the IMPES approach the pressure equation is first solved, using values for the saturation from the previous time level. Next the saturations are updated by some explicit time stepping method; this implies that the method is only conditionally stable. For the numerical solution of the linear, elliptic pressure equation multigrid methods have become an accepted technique. On the other hand, the fully implicit method is unconditionally stable, but it has the disadvantage that in every time step a large system of nonlinear algebraic equations has to be solved. The most time-consuming part of any fully implicit reservoir simulator is the solution of this large system of equations. Usually this is done by Newton's method. The resulting systems of linear equations are then either solved by a direct method or by some conjugate gradient type method. In this paper we consider the possibility of applying multigrid methods for the iterative solution of the systems of nonlinear equations. There are two ways of using multigrid for this job: either we use a nonlinear multigrid method or we use a linear multigrid method to deal with the linear systems that arise in Newton's method. So far only a few authors have reported on the use of multigrid methods for fully implicit simulations. Two-level FAS algorithm is presented for the black-oil equations, and linear multigrid for

  11. Introduction to the scientific application system of DAMPE (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. The science data processing and payload operation maintenance for DAMPE will be provided by the DAMPE Scientific Application System (SAS) at the Purple Mountain Observatory (PMO) of Chinese Academy of Sciences. SAS is consisted of three subsystems - scientific operation subsystem, science data and user management subsystem and science data processing subsystem. In cooperation with the Ground Support System (Beijing), the scientific operation subsystem is responsible for proposing observation plans, monitoring the health of satellite, generating payload control commands and participating in all activities related to payload operation. Several databases developed by the science data and user management subsystem of DAMPE methodically manage all collected and reconstructed science data, down linked housekeeping data, payload configuration and calibration data. Under the leadership of DAMPE Scientific Committee, this subsystem is also responsible for publication of high level science data and supporting all science activities of the DAMPE collaboration. The science data processing subsystem of DAMPE has already developed a series of physics analysis software to reconstruct basic information about detected cosmic ray particle. This subsystem also maintains the high performance computing system of SAS to processing all down linked science data and automatically monitors the qualities of all produced data. In this talk, we will describe all functionalities of whole DAMPE SAS system and show you main performances of data processing ability.

  12. On the modal damping ratios of shear-type structures equipped with Rayleigh damping systems

    NASA Astrophysics Data System (ADS)

    Trombetti, T.; Silvestri, S.

    2006-04-01

    The effects of added manufactured viscous dampers upon shear-type structures are analytically investigated here for the class of Rayleigh damping systems. The definitions of mass proportional damping (MPD) and stiffness proportional damping (SPD) systems are briefly recalled and their physical counterpart is derived. From basic physics, a detailed mathematical demonstration that the first modal damping ratio of a structure equipped with the MPD system is always larger than the first modal damping ratio of a structure equipped with the SPD system is provided here. All results are derived for the class of structures characterised by constant values of lateral stiffness and storey mass, under the equal "total size" constraint. The paper also provides closed form demonstrations of other properties of modal damping ratios which further indicate that the MPD and the SPD systems are respectively characterised by the largest and the smallest damping efficiency among Rayleigh damping systems subjected to base excitation. A numerical application with realistic data corresponding to an actual seven-storey building structure is presented to illustrate and verify the theoretical findings.

  13. Parametric effects of CFL number and artificial smoothing on numerical solutions using implicit approximate factorization algorithm

    NASA Technical Reports Server (NTRS)

    Daso, E. O.

    1986-01-01

    An implicit approximate factorization algorithm is employed to quantify the parametric effects of Courant number and artificial smoothing on numerical solutions of the unsteady 3-D Euler equations for a windmilling propeller (low speed) flow field. The results show that propeller global or performance chracteristics vary strongly with Courant number and artificial dissipation parameters, though the variation is such less severe at high Courant numbers. Candidate sets of Courant number and dissipation parameters could result in parameter-dependent solutions. Parameter-independent numerical solutions can be obtained if low values of the dissipation parameter-time step ratio are used in the computations. Furthermore, it is realized that too much artificial damping can degrade numerical stability. Finally, it is demonstrated that highly resolved meshes may, in some cases, delay convergence, thereby suggesting some optimum cell size for a given flow solution. It is suspected that improper boundary treatment may account for the cell size constraint.

  14. Neural networks underlying implicit and explicit moral evaluations in psychopathy

    PubMed Central

    Yoder, K J; Harenski, C; Kiehl, K A; Decety, J

    2015-01-01

    Psychopathy, characterized by symptoms of emotional detachment, reduced guilt and empathy and a callous disregard for the rights and welfare of others, is a strong risk factor for immoral behavior. Psychopathy is also marked by abnormal attention with downstream consequences on emotional processing. To examine the influence of task demands on moral evaluation in psychopathy, functional magnetic resonance imaging was used to measure neural response and functional connectivity in 88 incarcerated male subjects (28 with Psychopathy Checklist Revised (PCL-R) scores ⩾30) while they viewed dynamic visual stimuli depicting interpersonal harm and interpersonal assistance in two contexts, implicit and explicit. During the implicit task, high psychopathy was associated with reduced activity in the dorsolateral prefrontal cortex and caudate when viewing harmful compared with helpful social interactions. Functional connectivity seeded in the right amygdala and right temporoparietal junction revealed decreased coupling with the anterior cingulate cortex (ACC), anterior insula, striatum and ventromedial prefrontal cortex. In the explicit task, higher trait psychopathy predicted reduced signal change in ACC and amygdala, accompanied by decreased functional connectivity to temporal pole, insula and striatum, but increased connectivity with dorsal ACC. Psychopathy did not influence behavioral performance in either task, despite differences in neural activity and functional connectivity. These findings provide the first direct evidence that hemodynamic activity and neural coupling within the salience network are disrupted in psychopathy, and that the effects of psychopathy on moral evaluation are influenced by attentional demands. PMID:26305476

  15. Neural networks underlying implicit and explicit moral evaluations in psychopathy.

    PubMed

    Yoder, K J; Harenski, C; Kiehl, K A; Decety, J

    2015-08-25

    Psychopathy, characterized by symptoms of emotional detachment, reduced guilt and empathy and a callous disregard for the rights and welfare of others, is a strong risk factor for immoral behavior. Psychopathy is also marked by abnormal attention with downstream consequences on emotional processing. To examine the influence of task demands on moral evaluation in psychopathy, functional magnetic resonance imaging was used to measure neural response and functional connectivity in 88 incarcerated male subjects (28 with Psychopathy Checklist Revised (PCL-R) scores ⩾ 30) while they viewed dynamic visual stimuli depicting interpersonal harm and interpersonal assistance in two contexts, implicit and explicit. During the implicit task, high psychopathy was associated with reduced activity in the dorsolateral prefrontal cortex and caudate when viewing harmful compared with helpful social interactions. Functional connectivity seeded in the right amygdala and right temporoparietal junction revealed decreased coupling with the anterior cingulate cortex (ACC), anterior insula, striatum and ventromedial prefrontal cortex. In the explicit task, higher trait psychopathy predicted reduced signal change in ACC and amygdala, accompanied by decreased functional connectivity to temporal pole, insula and striatum, but increased connectivity with dorsal ACC. Psychopathy did not influence behavioral performance in either task, despite differences in neural activity and functional connectivity. These findings provide the first direct evidence that hemodynamic activity and neural coupling within the salience network are disrupted in psychopathy, and that the effects of psychopathy on moral evaluation are influenced by attentional demands.

  16. Effects of damping wigglers on beam dynamics in the NLC damping rings

    SciTech Connect

    Wolski, Andrzej; Wu, Ying

    2001-06-16

    To achieve the required damping time in the main damping rings for the Next Linear Collider (NLC), a wiggler will be required in each ring with integrated squared field strength up to 110 T{sup 2}m. There are concerns that nonlinear components of the wiggler field will damage the dynamic aperture of the ring, leading to poor injection efficiency. Severe effects from an insertion device have been observed and corrected in SPEAR 2. In this paper, we describe a model that we have developed to study the effects of the damping wiggler, compare the predictions of the model with actual experience in the case of the SPEAR 2 wiggler, and consider the predicted effects of current damping wiggler design on the NLC main damping rings.

  17. Ferroelectric control of anisotropic damping in multiferroic tunnel junctions

    NASA Astrophysics Data System (ADS)

    Wang, Yan; Zhang, Ning; Berakdar, Jamal; Jia, Chenglong

    2015-10-01

    The magnetoelectric effect on nonlocal magnetization dynamics is theoretically investigated in normal-metal/ferroelectric-insulator/ferromagnetic tunnel junctions. In addition to the Rashba spin-orbit interaction (SOI) originating from loss of parity symmetry at the interfaces, the topology of interfacial spiral spins triggered by ferroelectric polarization acts with an effective SOI that is electrically controllable. These spin-dependent interactions result in an anisotropic Gilbert damping with C2 v symmetry. The findings are of a direct relevance for the utilization of composite multiferroics for devices that rely on electrically controlled magnetic switching.

  18. Gilbert damping in magnetic layered systems

    NASA Astrophysics Data System (ADS)

    Barati, E.; Cinal, M.; Edwards, D. M.; Umerski, A.

    2014-07-01

    The Gilbert damping constant present in the phenomenological Landau-Lifshitz-Gilbert equation describing the dynamics of magnetization is calculated for ferromagnetic metallic films as well as Co/nonmagnet (NM) bilayers. The calculations are done within a realistic nine-orbital tight-binding model including spin-orbit coupling. The convergence of the damping constant expressed as a sum over the Brillouin zone is remarkably improved by introducing finite temperature into the electronic occupation factors and subsequent summation over the Matsubara frequencies. We investigate how the Gilbert damping constant depends on the ferromagnetic film thickness as well as on the thickness of the nonmagnetic cap in Co/NM bilayers (NM=Cu, Pd, Ag, Pt, and Au). The obtained theoretical dependence of the damping constant on the electron-scattering rate, describing the average lifetime of electronic states, varies substantially with the ferromagnetic film thickness and it differs significantly from the dependence for bulk ferromagnetic metals. The presence of nonmagnetic caps is found to largely enhance the magnetic damping in Co/NM bilayers in accordance with experimental data. Unlike Cu, Ag, and Au a particularly strong enhancement is obtained for Pd and Pt caps. This is attributed to the combined effect of the large spin-orbit couplings of Pd and Pt and the simultaneous presence of d states at the Fermi level in these two metals. The calculated Gilbert damping constant also shows an oscillatory dependence on the thicknesses of both ferromagnetic and nonmagnetic parts of the investigated systems which is attributed to quantum-well states. Finally, the expression for contributions to the damping constant from individual atomic layers is derived. The obtained distribution of layer contributions in Co/Pt and Co/Pd bilayers proves that the enhanced damping which affects the dynamics of the magnetization in the Co film originates mainly from a region within the nonmagnetic part of the

  19. Offline consolidation in implicit sequence learning.

    PubMed

    Meier, Beat; Cock, Josephine

    2014-08-01

    The goal of this study was to investigate offline memory consolidation with regard to general motor skill learning and implicit sequence-specific learning. We trained young adults on a serial reaction time task with a retention interval of either 24 h (Experiment 1) or 1 week (Experiment 2) between two sessions. We manipulated sequence complexity (deterministic vs probabilistic) and motor responses (unimanual or vs bimanual). We found no evidence of offline memory consolidation for sequence-specific learning with either interval (in the sense of no deterioration over the interval but no further improvement either). However, we did find evidence of offline enhancement of general motor skill learning with both intervals, independent of kind of sequence or kind of response. These results suggest that general motor skill learning, but not sequence-specific learning, appears to be enhanced during offline intervals in implicit sequence learning.

  20. Radiation damping in microcoil NMR probes

    NASA Astrophysics Data System (ADS)

    Krishnan, V. V.

    2006-04-01

    Radiation damping arises from the field induced in the receiver coil by large bulk magnetization and tends to selectively drive this magnetization back to equilibrium much faster than relaxation processes. The demand for increased sensitivity in mass-limited samples has led to the development of microcoil NMR probes that are capable of obtaining high quality NMR spectra with small sample volumes (nL-μL). Microcoil probes are optimized to increase sensitivity by increasing either the sample-to-coil ratio (filling factor) of the probe or quality factor of the detection coil. Though radiation damping effects have been studied in standard NMR probes, these effects have not been measured in the microcoil probes. Here a systematic evaluation of radiation damping effects in a microcoil NMR probe is presented and the results are compared with similar measurements in conventional large volume samples. These results show that radiation-damping effects in microcoil probe is much more pronounced than in 5 mm probes, and that it is critically important to optimize NMR experiments to minimize these effects. As microcoil probes provide better control of the bulk magnetization, with good RF and B0 inhomogeneity, in addition to negligible dipolar field effects due to nearly spherical sample volumes, these probes can be used exclusively to study the complex behavior of radiation damping.

  1. Radiation damping in microcoil NMR probes.

    PubMed

    Krishnan, V V

    2006-04-01

    Radiation damping arises from the field induced in the receiver coil by large bulk magnetization and tends to selectively drive this magnetization back to equilibrium much faster than relaxation processes. The demand for increased sensitivity in mass-limited samples has led to the development of microcoil NMR probes that are capable of obtaining high quality NMR spectra with small sample volumes (nL-microL). Microcoil probes are optimized to increase sensitivity by increasing either the sample-to-coil ratio (filling factor) of the probe or quality factor of the detection coil. Though radiation damping effects have been studied in standard NMR probes, these effects have not been measured in the microcoil probes. Here a systematic evaluation of radiation damping effects in a microcoil NMR probe is presented and the results are compared with similar measurements in conventional large volume samples. These results show that radiation-damping effects in microcoil probe is much more pronounced than in 5 mm probes, and that it is critically important to optimize NMR experiments to minimize these effects. As microcoil probes provide better control of the bulk magnetization, with good RF and B0 inhomogeneity, in addition to negligible dipolar field effects due to nearly spherical sample volumes, these probes can be used exclusively to study the complex behavior of radiation damping.

  2. Anti-damping effect of radiation reaction

    NASA Astrophysics Data System (ADS)

    Wang, G.; Li, H.; Shen, Y. F.; Yuan, X. Z.; Zi, J.

    2010-01-01

    The anti-damping effect of radiation reaction, which means the radiation reaction does non-negative work on a radiating charge, is investigated at length by using the Lorentz-Dirac equation (LDE) for the motion of a point charge respectively acted on by (a) a pure electric field, (b) a pure magnetic field and (c) the fields of an electromagnetic wave. We found that the curvature of the charge's trajectory plays an important role in the radiation reaction force, and the anti-damping effect cannot take place for the real macroscopic motions of a point charge. The condition for this anti-damping effect to take place is that the gradient of the external force field must exceed a certain value over the region of magnitude of the classical radius of massive charges (~10-15 m). Our results are potentially helpful to lessen the controversy on LDE and justify it as the correct classical equation describing the radiating charge's motion. If this anti-damping effect of LDE were a real existing physical process, it could serve as a mechanism within the context of classical electrodynamics for the stability of hydrogen atoms. Using the picture of an electron in quantum electrodynamics, namely the negative bare charge surrounded by the polarized positive charges of vacuum, we can obtain a reasonable explanation for the energy transferred to the electron during the occurrence of the anti-damping effect, on which the venerable work of Wheeler and Feynman has thrown some light.

  3. Damping by branching: a bioinspiration from trees.

    PubMed

    Theckes, B; Langre, E de; Boutillon, X

    2011-12-01

    Man-made slender structures are known to be sensitive to high levels of vibration due to their flexibility which often cause irreversible damage. In nature, trees repeatedly endure large amplitudes of motion, mostly caused by strong climatic events, yet with minor or no damage in most cases. A new damping mechanism inspired by the architecture of trees is identified here and characterized in the simplest tree-like structure, a Y-shaped branched structure. Through analytical and numerical analyses of a simple two-degree-of-freedom model, branching is shown to be the key ingredient in this protective mechanism that we call damping-by-branching. It originates in the geometrical nonlinearities so that it is specifically efficient to damp out large amplitudes of motion. A more realistic model, using flexible beam approximation, shows that the mechanism is robust. Finally, two bioinspired architectures are analyzed, showing significant levels of damping achieved via branching with typically 30% of the energy being dissipated in one oscillation. This concept of damping-by-branching is of simple practical use in the design of very slender and flexible structures subjected to extreme dynamical loadings.

  4. Machine Understanding of Human Implicit Intention

    DTIC Science & Technology

    2013-05-18

    Cognitive Neurodynamics , Hokkaido, Japan, June 2011, Hokkaido, Japan (Plenary Talk) - Soo-Young Lee, Implicit Intention Recognition and Hierarchical...subject’s response with the accuracy of about 80% by SVM. 15. SUBJECT TERMS Brain Science and Engineering; Cognitive Neuroscience; Human-Computer...oscillations have been related to a variety of functions such as perception, cognition , sleep, etc. For a long time, researchers have found the sensory and

  5. RESONANTLY DAMPED PROPAGATING KINK WAVES IN LONGITUDINALLY STRATIFIED SOLAR WAVEGUIDES

    SciTech Connect

    Soler, R.; Verth, G.; Goossens, M.; Terradas, J.

    2011-07-20

    It has been shown that resonant absorption is a robust physical mechanism for explaining the observed damping of magnetohydrodynamic kink waves in the solar atmosphere due to naturally occurring plasma inhomogeneity in the direction transverse to the direction of the magnetic field. Theoretical studies of this damping mechanism were greatly inspired by the first observations of post-flare standing kink modes in coronal loops using the Transition Region and Coronal Explorer. More recently, these studies have been extended to explain the attenuation of propagating coronal kink waves observed by the Coronal Multi-Channel Polarimeter. In the present study, for the first time we investigate the properties of propagating kink waves in solar waveguides including the effects of both longitudinal and transverse plasma inhomogeneity. Importantly, it is found that the wavelength is only dependent on the longitudinal stratification and the amplitude is simply a product of the two effects. In light of these results the advancement of solar atmospheric magnetoseismology by exploiting high spatial/temporal resolution observations of propagating kink waves in magnetic waveguides to determine the length scales of the plasma inhomogeneity along and transverse to the direction of the magnetic field is discussed.

  6. Method Developed for Noninterference Measurement of Blade Damping

    NASA Technical Reports Server (NTRS)

    Kurkov, Anatole P.

    2004-01-01

    Although noninterference optical instrumentation has been previously used to monitor and measure rotor blade vibrations, it has not been used at the NASA Glenn Research Center for the determination of damping. This article describes such a measurement in Glenn's Spin Rig facility. The optical system was chosen because installation of the slip rig for this particular configuration was not feasible, ruling out strain gauge instrumentation. The shaft in this facility was suspended with two radial magnetic bearings, and the excitation was supplied to the bearings by a signal generator. For the first mode, the direction of excitation force was always perpendicular to the blade as described by Morrison. The preceding graph shows blade displacements, as measured by an optical probe during a frequency sweep designed to locate the first mode resonance. The resonance determines the frequency at which the shaft is excited. Because the sampling rate was fixed to only once per revolution with these transducers, and the first mode frequency was much larger than the rotational frequency, the data in this figure were undersampled with an apparent frequency that was only 1 Hz at the beginning of the sweep, about 14 Hz at the maximum amplitude, and about 20 Hz at the end of the sweep. The true excitation frequency varied during the sweep from 320 to 340 Hz, and the resonance occurred at 334 Hz. Damping is determined by applying a frequency burst to the shaft. Upon cessation of the burst, the blade undergoes free decay. The apparent damping is then obtained by a least squares fit of the theoretical cosine decay function through the experimental points. The following graph illustrates this procedure. Because of frequency aliasing, the apparent measured damping must be divided by the ratio of the true resonant frequency to the apparent measured frequency to obtain the true damping. Note that the contribution of the shaft vibration to the blade vibration could be neglected because it

  7. Helicopter rotor lag damping augmentation based on a radial absorber and Coriolis coupling

    NASA Astrophysics Data System (ADS)

    Byers, Lynn Karen

    A radial vibration absorber is proposed to augment rotor lag damping. Modeled as a discrete mass restrained by a damped spring and moving along the spanwise direction within the rotor blade, it introduces damping into the lag mode of the blade through strong Coriolis coupling. A two-degree-of-freedom model is developed and used to examine the effectiveness of the radial absorber in transferring damping to the rotor lag mode. Results demonstrate that it is possible to introduce a significant amount of damping in the lag mode with a relatively small absorber mass, and the corresponding amplitudes of 1/rev periodic motions are not excessively large. The lag mode damping and 1/rev motions are also compared with the results achieved for an embedded chordwise inertial damper. A classical six-degree-of-freedom aeromechanical stability analysis is augmented with two absorber cyclic degrees of freedom in the nonrotating frame to examine the effect of the radial absorber on aeromechanical stability characteristics. These results indicate that ground resonance instability is eliminated for the range of absorber parameters considered, and in most cases, the stability margins are significant. A rotor blade with a discrete radial vibration absorber is also analyzed to examine the effect of the absorber on rotor blade and hub loads. The rotor blade is modeled as an elastic beam undergoing flap and lag bending, with the absorber modeled as a discrete mass restrained by a damped spring, moving in the spanwise direction within the rotor blade. Results indicate that the addition of the absorber does not detrimentally affect the blade spanwise and root loads, as well as steady and vibratory hub loads. Finally, device concepts and implementation possibilities are considered for the embedded radial vibration absorber.

  8. Toward a meaningful metric of implicit prejudice.

    PubMed

    Blanton, Hart; Jaccard, James; Strauts, Erin; Mitchell, Gregory; Tetlock, Philip E

    2015-09-01

    [Correction Notice: An Erratum for this article was reported in Vol 100(5) of Journal of Applied Psychology (see record 2015-40760-001). there are errors in some of the values listed in Table 6 that do not alter any of the conclusions or substantive statements in the original article. The corrected portion of Table 6 is in the correction. The positive intercepts in this table represent the estimated IAT score when the criterion has a value of zero (suggesting attitudinal neutrality), except in the equation examining voter preference in Greenwald et al. (2009), where the intercept estimated the IAT score of Obama voters.] The modal distribution of the Implicit Association Test (IAT) is commonly interpreted as showing high levels of implicit prejudice among Americans. These interpretations have fueled calls for changes in organizational and legal practices, but such applications are problematic because the IAT is scored on an arbitrary psychological metric. The present research was designed to make the IAT metric less arbitrary by determining the scores on IAT measures that are associated with observable racial or ethnic bias. By reexamining data from published studies, we found evidence that the IAT metric is "right biased," such that individuals who are behaviorally neutral tend to have positive IAT scores. Current scoring conventions fail to take into account these dynamics and can lead to faulty inferences about the prevalence of implicit prejudice.

  9. Implicit constitutive relations for nonlinear magnetoelastic bodies

    PubMed Central

    Bustamante, R.; Rajagopal, K. R.

    2015-01-01

    Implicit constitutive relations that characterize the response of elastic bodies have greatly enhanced the arsenal available at the disposal of the analyst working in the field of elasticity. This class of models were recently extended to describe electroelastic bodies by the present authors. In this paper, we extend the development of implicit constitutive relations to describe the behaviour of elastic bodies that respond to magnetic stimuli. The models that are developed provide a rational way to describe phenomena that have hitherto not been adequately described by the classical models that are in place. After developing implicit constitutive relations for magnetoelastic bodies undergoing large deformations, we consider the linearization of the models within the context of small displacement gradients. We then use the linearized model to describe experimentally observed phenomena which the classical linearized magnetoelastic models are incapable of doing. We also solve several boundary value problems within the context of the models that are developed: extension and shear of a slab, and radial inflation and extension of a cylinder. PMID:25792968

  10. Implicit constitutive relations for nonlinear magnetoelastic bodies.

    PubMed

    Bustamante, R; Rajagopal, K R

    2015-03-08

    Implicit constitutive relations that characterize the response of elastic bodies have greatly enhanced the arsenal available at the disposal of the analyst working in the field of elasticity. This class of models were recently extended to describe electroelastic bodies by the present authors. In this paper, we extend the development of implicit constitutive relations to describe the behaviour of elastic bodies that respond to magnetic stimuli. The models that are developed provide a rational way to describe phenomena that have hitherto not been adequately described by the classical models that are in place. After developing implicit constitutive relations for magnetoelastic bodies undergoing large deformations, we consider the linearization of the models within the context of small displacement gradients. We then use the linearized model to describe experimentally observed phenomena which the classical linearized magnetoelastic models are incapable of doing. We also solve several boundary value problems within the context of the models that are developed: extension and shear of a slab, and radial inflation and extension of a cylinder.

  11. Implicit Shape Parameterization for Kansei Design Methodology

    NASA Astrophysics Data System (ADS)

    Nordgren, Andreas Kjell; Aoyama, Hideki

    Implicit shape parameterization for Kansei design is a procedure that use 3D-models, or concepts, to span a shape space for surfaces in the automotive field. A low-dimensional, yet accurate shape descriptor was found by Principal Component Analysis of an ensemble of point-clouds, which were extracted from mesh-based surfaces modeled in a CAD-program. A theoretical background of the procedure is given along with step-by-step instructions for the required data-processing. The results show that complex surfaces can be described very efficiently, and encode design features by an implicit approach that does not rely on error-prone explicit parameterizations. This provides a very intuitive way to explore shapes for a designer, because various design features can simply be introduced by adding new concepts to the ensemble. Complex shapes have been difficult to analyze with Kansei methods due to the large number of parameters involved, but implicit parameterization of design features provides a low-dimensional shape descriptor for efficient data collection, model-building and analysis of emotional content in 3D-surfaces.

  12. Passive damping concepts for slender columns in space structures

    NASA Technical Reports Server (NTRS)

    Razzaq, Z.; Ekhelikar, R. K.

    1985-01-01

    An experimental and theoretical study of three different passive damping concepts is conducted for a slender member with partial rotational end restraints. Over a hundred full-scale natural vibration experiments were conducted to evaluate the effectiveness of mass-string, polyethylene tubing, and chain damping concepts. The damping properties obtained from the experiments were used in the approximate analyses based on the partial differential equation of motion for the problem. The comparison of the experimental and the theoretical deflection-time relations shows that the velocity-dependent damping model used in the theory is adequate. From the experimental results, the effect of end connection friction and induced axial forces on damping is identified. The definition of an efficiency index is proposed based on the damping ratio and the mass of a given passive damping device. Using this definition, the efficiencies of the three damping devices are compared. The polyethylene tubing concept resulted into a low damping efficiency.

  13. Laminar flow control with distributed surface actuation: damping Tollmien-Schlichting waves with active surface displacement

    NASA Astrophysics Data System (ADS)

    Goldin, Nikolas; King, Rudibert; Pätzold, Andreas; Nitsche, Wolfgang; Haller, Daniel; Woias, Peter

    2013-03-01

    Control strategies for laminar flow control above an unswept wing are investigated. An actuation method based on a flexible membrane displaced by multiple piezo-polymer composite elements is developed for wind tunnel experiments. A model predictive control algorithm is applied to control the multi-bar actuator. The direct negative superposition method of damping Tollmien-Schlichting waves is compared to a biomimetic approach imitating the damping mechanisms of a compliant skin. In both cases, a model predictive control algorithm is applied to control the multi-bar actuator segments. For the biomimetic approach, reduced, real-time solvable models of compliant surfaces are developed and parametrized by direct optimization and according to numerically generated optimal wall properties. Damping results of up to 85 % RMS value are achieved, shifting the onset of transition about 100 mm downstream with a single actuation membrane. Additional experiments with cascaded multiple membranes show the potential for a further shift.

  14. Highly damped kinematic coupling for precision instruments

    DOEpatents

    Hale, Layton C.; Jensen, Steven A.

    2001-01-01

    A highly damped kinematic coupling for precision instruments. The kinematic coupling provides support while causing essentially no influence to its nature shape, with such influences coming, for example, from manufacturing tolerances, temperature changes, or ground motion. The coupling uses three ball-cone constraints, each combined with a released flexural degree of freedom. This arrangement enables a gain of higher load capacity and stiffness, but can also significantly reduce the friction level in proportion to the ball radius divided by the distance between the ball and the hinge axis. The blade flexures reduces somewhat the stiffness of the coupling and provides an ideal location to apply constrained-layer damping which is accomplished by attaching a viscoelastic layer and a constraining layer on opposite sides of each of the blade flexures. The three identical ball-cone flexures provide a damped coupling mechanism to kinematically support the projection optics system of the extreme ultraviolet lithography (EUVL) system, or other load-sensitive apparatus.

  15. Measurement of damping of graphite epoxy materials

    NASA Technical Reports Server (NTRS)

    Crocker, M. J.

    1985-01-01

    The design of an experiment to measure the damping of a cylindrical graphite-epoxy specimen with a three point support and a knife edge support is described as well as equipment used in tests conducted to determine the influence of the support at the two ends of the specimen and to simulate an idealized free-free boundary condition at the two edges. A curve fitting technique is being used to process the frequency response data obtained. Experiments conducted on the thin plate specimen also reveal the influence of the end support condition on the damping ratio of the specimen. The damping ratio values measured for both specimens appear to be strongly influenced by the shape of the specimen and appear to depend on length and fiber orientation as well as the presence of discontinuities such as sharp bends, corners, and notches.

  16. Radiation damping in focusing-dominated systems

    SciTech Connect

    Huang, Zhirong; Chen, Pisin; Ruth, R.D.

    1995-06-01

    A quasi-classical method is developed to calculate the radiation damping of a relativistic particle in a straight, continuous focusing system. In one limiting case where the pitch angle of the particle {theta}{sub p} is much larger than the radiation opening angle 1/{gamma}, the radiation power spectrum is similar to synchrotron radiation and the relative damping rate of the transverse action is proportional to the relative energy loss rate. In the other limiting case where {theta}{sub p} {much_lt} 1/{gamma}, the radiation is dipole in nature and the relative damping rate of the transverse action is energy-independent and is much faster than the relative energy rate. Quantum excitation to the transverse action is absent in this focusing channel. These results can be extended to bent systems provided that the focusing field dominates over the bending field.

  17. Viscous damping of perforated planar micromechanical structures

    PubMed Central

    Homentcovschi, D.; Miles, R.N.

    2008-01-01

    The paper gives an analytical approximation to the viscous damping coefficient due to the motion of a gas between a pair of closely spaced fluctuating plates in which one of the plates contains a regular system of circular holes. These types of structures are important parts of many microelectromechanical devices realized in MEMS technology as microphones, microaccelerometers, resonators, etc. The pressure satisfies a Reynolds’ type equation with coefficients accounting for all the important effects: compressibility of the gas, inertia and possibly slip of the gas on the plates. An analytical expression for the optimum number of circular holes which assure a minimum value of the total damping coefficient is given. This value realizes an equilibrium between the squeeze-film damping and the viscous resistance of the holes. The paper also provides analytical design formulas to be used in the case of regular circular perforated plates. PMID:19365579

  18. Biomimetic Gradient Polymers with Enhanced Damping Capacities.

    PubMed

    Wang, Dong; Zhang, Huan; Guo, Jing; Cheng, Beichen; Cao, Yuan; Lu, Shengjun; Zhao, Ning; Xu, Jian

    2016-04-01

    Designing gradient structures, mimicking biological materials, such as pummelo peels and tendon, is a promising strategy for developing advanced materials with superior energy damping capacities. Here a facile and effective approach for fabricating polymers with composition gradients at millimeter length scale is presented. The gradient thiol-ene polymers (TEPs) are created by the use of density difference of ternary thiol-ene-ene precursors and the subsequent photo-crosslinking via thiol-ene reaction. The compositional gradients are analyzed via differential scanning calorimeter (DSC), compressive modulus testing, atomic force microscopy (AFM) indentation, and swelling measurements. In contrast to homogeneous TEPs networks, the resultant gradient polymer shows a broader effective damping temperature range combining with good mechanical properties. The present result provides an effective route toward high damping materials by the fabrication of gradient structures.

  19. Fluid damping of cylindrical liquid storage tanks.

    PubMed

    Habenberger, Joerg

    2015-01-01

    A method is proposed in order to calculate the damping effects of viscous fluids in liquid storage tanks subjected to earthquakes. The potential equation of an ideal fluid can satisfy only the boundary conditions normal to the surface of the liquid. To satisfy also the tangential interaction conditions between liquid and tank wall and tank bottom, the potential flow is superimposed by a one-dimensional shear flow. The shear flow in this boundary layer yields to a decrease of the mechanical energy of the shell-liquid-system. A damping factor is derived from the mean value of the energy dissipation in time. Depending on shell geometry and fluid viscosity, modal damping ratios are calculated for the convective component.

  20. Effects of Reliability and Global Context on Explicit and Implicit Measures of Sensed Hand Position in Cursor-Control Tasks

    PubMed Central

    Rand, Miya K.; Heuer, Herbert

    2016-01-01

    In a cursor-control task in which the motion of the cursor is rotated randomly relative to the movement of the hand, the sensed directions of hand and cursor are mutually biased. In our previous study, we used implicit and explicit measures of the bias of sensed hand direction toward the direction of the cursor and found different characteristics. The present study serves to explore further differences and commonalities of these measures. In Experiment 1, we examined the effects of different relative reliabilities of visual and proprioceptive information on the explicitly and implicitly assessed bias of sensed hand direction. In two conditions, participants made an aiming movement and returned to the start position immediately or after a delay of 6 s during which the cursor was no longer visible. The unimodal proprioceptive information on final hand position in the delayed condition served to increase its relative reliability. As a result, the bias of sensed hand direction toward the direction of the cursor was reduced for the explicit measure, with a complementary increase of the bias of sensed cursor direction, but unchanged for the implicit measure. In Experiment 2, we examined the influence of global context, specifically of the across-trial sequence of judgments of hand and cursor direction. Both explicitly and implicitly assessed biases of sensed hand direction did not significantly differ between the alternated condition (trial-to-trial alternations of judgments of hand and cursor direction) and the blocked condition (judgments of hand or cursor directions in all trials). They both substantially decreased from the alternated to the randomized condition (random sequence of judgments of hand and cursor direction), without a complementary increase of the bias of sensed cursor direction. We conclude that our explicit and implicit measures are equally sensitive to variations of coupling strength as induced by the variation of global context in Experiment 2, but

  1. Lag-stabilized force feedback damping

    SciTech Connect

    Petterson, B.J.; Robinett, R.D.; Werner, J.C.

    1991-05-01

    A lag-stabilized, force feedback controller for damping initial and residual oscillations of a planar, cantilevered flexible arm has been analytically developed and experimentally implemented on a commercial robot. The controller feeds back force sensor measurements that are delayed in time and proportional to the displacement (angular orientation) of the arm in order to damp the oscillation. As a result of the lag (contrary to popular belief), the controlled robot system is stable and provides tunable performance on a Cincinnati Milacron T3-786 robot. 3 refs., 9 figs., 2 tabs.

  2. Particle systems and nonlinear Landau damping

    SciTech Connect

    Villani, Cédric

    2014-03-15

    Some works dealing with the long-time behavior of interacting particle systems are reviewed and put into perspective, with focus on the classical Kolmogorov–Arnold–Moser theory and recent results of Landau damping in the nonlinear perturbative regime, obtained in collaboration with Clément Mouhot. Analogies are discussed, as well as new qualitative insights in the theory. Finally, the connection with a more recent work on the inviscid Landau damping near the Couette shear flow, by Bedrossian and Masmoudi, is briefly discussed.

  3. Optimal piezoelectric switching technique for vibration damping

    NASA Astrophysics Data System (ADS)

    Neubauer, Marcus; Oleskiewicz, Robert

    2007-04-01

    This paper describes piezoelectric switching techniques for vibration damping. The dynamical behaviour of a piezoceramics connected to a switching LR shunt and the dissipated energy are obtained using a fundamental piezoelectric model. All calculations are performed in a normalized way and highlight the influence of the electromechanical coupling coefficient of the piezoceramics and the shunt parameters. For the first time, a precise result for the dynamics of a shunted piezoceramics is derived. The analytic results are used to determine the optimal switching sequence and external branch parameters in order to maximize the damping performance. The results are validated by measurements of a clamped beam.

  4. Wind turbine blade with viscoelastic damping

    DOEpatents

    Sievers, Ryan A.; Mullings, Justin L.

    2017-01-10

    A wind turbine blade (60) damped by viscoelastic material (54, 54A-F) sandwiched between stiffer load-bearing sublayers (52A, 52B, 56A, 56B) in portions of the blade effective to damp oscillations (38) of the blade. The viscoelastic material may be located in one or more of: a forward portion (54A) of the shell, an aft portion (54D) of the shell, pressure and suction side end caps (54B) of an internal spar, internal webbing walls (54C, 54E), and a trailing edge core (54F).

  5. Inertia-Wheel Vibration-Damping System

    NASA Technical Reports Server (NTRS)

    Fedor, Joseph V.

    1990-01-01

    Proposed electromechanical system would damp vibrations in large, flexible structure. In active vibration-damping system motors and reaction wheels at tips of appendages apply reaction torques in response to signals from accelerometers. Velocity signal for vibrations about one axis processes into control signal to oppose each of n vibrational modes. Various modes suppressed one at a time. Intended primarily for use in spacecraft that has large, flexible solar panels and science-instrument truss assembly, embodies principle of control interesting in its own right and adaptable to terrestrial structures, vehicles, and instrument platforms.

  6. Damping Goes the Distance in Golf

    NASA Technical Reports Server (NTRS)

    2004-01-01

    In the late 1980s, Dr. Benjamin Dolgin of NASA s Jet Propulsion Laboratory developed a concept for a high-damping graphite/viscoelastic material for the Strategic Defense Initiative (popularly referred to as "Star Wars"), as part of a space-based laser anti-missile program called "Asterix." Dolgin drummed up this concept with the intention of stabilizing weapons launch platforms in space, where there is no solid ground to firmly support these structures. Without the inclusion of high-damping material, the orbital platforms were said to vibrate for 20 minutes after force was applied - a rate deemed "unacceptable" by leaders of the Strategic Defense Initiative.

  7. Mechanical Design of the DAMPE BGO Calorimeter

    NASA Astrophysics Data System (ADS)

    Hu, Yiming; Wu, Jian; Feng, Changqing; Zhang, Yunlong; Chen, Dengyi; Chang, Jin

    The Dark Matter Particle Explorer, DAMPE, is a new designed satellite developed for the CASs new Innovation 2020 program. As the main component of DAMPE, the new designed BGO calorimeter consists of 308 BGO Crystals coupled with photomultiplier tube.The reliability and safety of the BGO Calorimeter structure play a very important role in the operation of whole detector. During the rocket launch, the calorimeter structure should be stable against vibration and environmental factors to ensure detector works in good conditions. In this article, we make the BGO calorimeter structure design, and then prove that it will work in the environments of rocket launch and flight.

  8. Delay of Transition Using Forced Damping

    NASA Technical Reports Server (NTRS)

    Exton, Reginald J.

    2014-01-01

    Several experiments which have reported a delay of transition are analyzed in terms of the frequencies of the induced disturbances generated by different flow control elements. Two of the experiments employed passive stabilizers in the boundary layer, one leading-edge bluntness, and one employed an active spark discharge in the boundary layer. It is found that the frequencies generated by the various elements lie in the damping region of the associated stability curve. It is concluded that the creation of strong disturbances in the damping region stabilizes the boundary-layer and delays the transition from laminar to turbulent flow.

  9. Implicit Statistical Learning in Language Processing: Word Predictability is the Key

    PubMed Central

    Conway, Christopher M.; Baurnschmidt, Althea; Huang, Sean; Pisoni, David B.

    2010-01-01

    Fundamental learning abilities related to the implicit encoding of sequential structure have been postulated to underlie language acquisition and processing. However, there is very little direct evidence to date supporting such a link between implicit statistical learning and language. In three experiments using novel methods of assessing implicit learning and language abilities, we show that sensitivity to sequential structure -- as measured by improvements to immediate memory span for structurally-consistent input sequences -- is significantly correlated with the ability to use knowledge of word predictability to aid speech perception under degraded listening conditions. Importantly, the association remained even after controlling for participant performance on other cognitive tasks, including short-term and working memory, intelligence, attention and inhibition, and vocabulary knowledge. Thus, the evidence suggests that implicit learning abilities are essential for acquiring long-term knowledge of the sequential structure of language -- i.e., knowledge of word predictability – and that individual differences on such abilities impact speech perception in everyday situations. These findings provide a new theoretical rationale linking basic learning phenomena to specific aspects of spoken language processing in adults, and may furthermore indicate new fruitful directions for investigating both typical and atypical language development. PMID:19922909

  10. Who owns implicit attitudes? Testing a metacognitive perspective.

    PubMed

    Cooley, Erin; Payne, B Keith; Loersch, Chris; Lei, Ryan

    2015-01-01

    Metacognitive inferences about ownership for one's implicit attitudes have the power to turn implicit bias into explicit prejudice. In Study 1, participants were assigned to construe their implicit attitudes toward gay men as belonging to themselves (owned) or as unrelated to the self (disowned). Construing one's implicit responses as owned led to greater implicit-explicit attitude correspondence. In Study 2, we measured ownership for implicit attitudes as well as self-esteem. We predicted that ownership inferences would dictate explicit attitudes to the degree that people had positive views of the self. Indeed, higher ownership for implicit bias was associated with greater implicit-explicit attitude correspondence, and this effect was driven by participants high in self-esteem. Finally, in Study 3, we manipulated inferences of ownership and measured self-esteem. Metacognitions of ownership affected implicit-explicit attitude correspondence but only among those with relatively high self-esteem. We conclude that subjective inferences about implicit bias affect explicit prejudice.

  11. Genetic and Environmental Sources of Implicit and Explicit Self-Esteem and Affect: Results from a Genetically Sensitive Multi-group Design.

    PubMed

    Stieger, Stefan; Kandler, Christian; Tran, Ulrich S; Pietschnig, Jakob; Voracek, Martin

    2017-03-01

    In today's world, researchers frequently utilize indirect measures of implicit (i.e., automatic, spontaneous) evaluations. The results of several studies have supported the usefulness of these measures in predicting behavior, as compared to utilizing direct measures of explicit (i.e., purposeful, deliberate) evaluations. A current, under-debate issue concerns the origin of these implicit evaluations. The present genetically sensitive multi-group study analyzed data from 223 twin pairs and 222 biological core families to estimate possible genetic and environmental sources of individual differences in implicit and explicit self-esteem and affect. The results show that implicit self-esteem and affect maintain a substantial genetic basis, but demonstrate little influence from the shared environment by siblings (e.g., shared familial socialization in childhood). A bivariate analysis found that implicit and explicit evaluations of the same construct share a common genetic core which aligns with the motivation and opportunity as determinants (MODE) model.

  12. Gaming mindsets: implicit theories in serious game learning.

    PubMed

    Lee, Yu-Hao; Heeter, Carrie; Magerko, Brian; Medler, Ben

    2012-04-01

    Individuals' beliefs about the malleability of their abilities may predict their response and outcome in learning from serious games. Individuals with growth mindsets believe their abilities can develop with practice and effort, whereas individuals with fixed mindsets believe their abilities are static and cannot improve. This study uses survey and gameplay server data to examine the implicit theory of intelligence in the context of serious game learning. The findings show that growth mindset players performed better than fixed mindset players, their mistakes did not affect their attention to the game, and they read more learning feedback than fixed mindset players. In addition, growth mindset players were more likely to actively seek difficult challenges, which is often essential to self-directed learning. General mindset measurements and domain-specific measurements were also compared. These findings suggest that players' psychological attributes should be considered when designing and applying serious games.

  13. Implicit flux-split schemes for the Euler equations

    NASA Technical Reports Server (NTRS)

    Thomas, J. L.; Walters, R. W.; Van Leer, B.

    1985-01-01

    Recent progress in the development of implicit algorithms for the Euler equations using the flux-vector splitting method is described. Comparisons of the relative efficiency of relaxation and spatially-split approximately factored methods on a vector processor for two-dimensional flows are made. For transonic flows, the higher convergence rate per iteration of the Gauss-Seidel relaxation algorithms, which are only partially vectorizable, is amply compensated for by the faster computational rate per iteration of the approximately factored algorithm. For supersonic flows, the fully-upwind line-relaxation method is more efficient since the numerical domain of dependence is more closely matched to the physical domain of dependence. A hybrid three-dimensional algorithm using relaxation in one coordinate direction and approximate factorization in the cross-flow plane is developed and applied to a forebody shape at supersonic speeds and a swept, tapered wing at transonic speeds.

  14. Gaming Mindsets: Implicit Theories in Serious Game Learning

    PubMed Central

    Heeter, Carrie; Magerko, Brian; Medler, Ben

    2012-01-01

    Abstract Individuals' beliefs about the malleability of their abilities may predict their response and outcome in learning from serious games. Individuals with growth mindsets believe their abilities can develop with practice and effort, whereas individuals with fixed mindsets believe their abilities are static and cannot improve. This study uses survey and gameplay server data to examine the implicit theory of intelligence in the context of serious game learning. The findings show that growth mindset players performed better than fixed mindset players, their mistakes did not affect their attention to the game, and they read more learning feedback than fixed mindset players. In addition, growth mindset players were more likely to actively seek difficult challenges, which is often essential to self-directed learning. General mindset measurements and domain-specific measurements were also compared. These findings suggest that players' psychological attributes should be considered when designing and applying serious games. PMID:22165916

  15. A Geometric Treatment of Implicit Differential-Algebraic Equations

    NASA Astrophysics Data System (ADS)

    Rabier, P. J.; Rheinboldt, W. C.

    A differential-geometric approach for proving the existence and uniqueness of implicit differential-algebraic equations is presented. It provides for a significant improvement of an earlier theory developed by the authors as well as for a completely intrinsic definition of the index of such problems. The differential-algebraic equation is transformed into an explicit ordinary differential equation by a reduction process that can be abstractly defined for specific submanifolds of tangent bundles here called reducible π-submanifolds. Local existence and uniqueness results for differential-algebraic equations then follow directly from the final stage of this reduction by means of an application of the standard theory of ordinary differential equations.

  16. Damping of the wrist joint during voluntary movement.

    PubMed

    Milner, T E; Cloutier, C

    1998-10-01

    Damping characteristics of the musculoskeletal system were investigated during rapid voluntary wrist flexion movements. Oscillations about the final position were induced by introducing a load with the characteristics of negative damping, which artificially reduced the damping of the wrist. Subjects responded to increases in the negatively damped load by stronger cocontraction of wrist flexor and extensor muscles during the stabilization phase of the movement. However, their ability to counteract the effects of the negatively damped load diminished as the negative damping increased. Consequently, the number and frequency of oscillations increased. The oscillations were accompanied by phase-locked muscle activity superimposed on underlying tonic muscle activation. The wrist stiffness and damping coefficient increased with the increased cocontraction that accompanied more negatively damped loads, although changes in the damping coefficient were less systematic than the stiffness. Analysis of successive half-cycles of the oscillation revealed that the wrist stiffness and damping coefficient increased, despite decreasing muscle activation, as oscillation amplitude and velocity declined. This indicates that the inverse dependence of the damping coefficient on oscillation velocity contributes significantly to damping of joint motion. It is suggested that this property helps to offset a negative contribution to damping from the stretch reflex.

  17. Chemical Interface Damping Depends on Electrons Reaching the Surface.

    PubMed

    Foerster, Benjamin; Joplin, Anneli; Kaefer, Katharina; Celiksoy, Sirin; Link, Stephan; Sönnichsen, Carsten

    2017-03-28

    Metallic nanoparticles show extraordinary strong light absorption near their plasmon resonance, orders of magnitude larger compared to nonmetallic nanoparticles. This "antenna" effect has recently been exploited to transfer electrons into empty states of an attached material, for example to create electric currents in photovoltaic devices or to induce chemical reactions. It is generally assumed that plasmons decay into hot electrons, which then transfer to the attached material. Ultrafast electron-electron scattering reduces the lifetime of hot electrons drastically in metals and therefore strongly limits the efficiency of plasmon induced hot electron transfer. However, recent work has revived the concept of plasmons decaying directly into an interfacial charge transfer state, thus avoiding the intermediate creation of hot electrons. This direct decay mechanism has mostly been neglected, and has been termed chemical interface damping (CID). CID manifests itself as an additional damping contribution to the homogeneous plasmon line width. In this study, we investigate the size dependence of CID by following the plasmon line width of gold nanorods during the adsorption process of thiols on the gold surface with single particle spectroscopy. We show that CID scales inversely with the effective path length of electrons, i.e., the average distance of electrons to the surface. Moreover, we compare the contribution of CID to other competing plasmon decay channels and predict that CID becomes the dominating plasmon energy decay mechanism for very small gold nanorods.

  18. Nonlinear Landau damping and Alfven wave dissipation

    NASA Technical Reports Server (NTRS)

    Vinas, Adolfo F.; Miller, James A.

    1995-01-01

    Nonlinear Landau damping has been often suggested to be the cause of the dissipation of Alfven waves in the solar wind as well as the mechanism for ion heating and selective preacceleration in solar flares. We discuss the viability of these processes in light of our theoretical and numerical results. We present one-dimensional hybrid plasma simulations of the nonlinear Landau damping of parallel Alfven waves. In this scenario, two Alfven waves nonresonantly combine to create second-order magnetic field pressure gradients, which then drive density fluctuations, which in turn drive a second-order longitudinal electric field. Under certain conditions, this electric field strongly interacts with the ambient ions via the Landau resonance which leads to a rapid dissipation of the Alfven wave energy. While there is a net flux of energy from the waves to the ions, one of the Alfven waves will grow if both have the same polarization. We compare damping and growth rates from plasma simulations with those predicted by Lee and Volk (1973), and also discuss the evolution of the ambient ion distribution. We then consider this nonlinear interaction in the presence of a spectrum of Alfven waves, and discuss the spectrum's influence on the growth or damping of a single wave. We also discuss the implications for wave dissipation and ion heating in the solar wind.

  19. The Stochastic Nonlinear Damped Wave Equation

    SciTech Connect

    Barbu, V. Da Prato, G.

    2002-12-19

    We prove the existence of an invariant measure for the transition semigroup associated with a nonlinear damped stochastic wave equation in R{sup n} of the Klein-Gordon type. The uniqueness of the invariant measure and the structure of the corresponding Kolmogorov operator are also studied.

  20. Radiation damping in pulsed Gaussian beams

    NASA Astrophysics Data System (ADS)

    Harvey, Chris; Marklund, Mattias

    2012-01-01

    We consider the effects of radiation damping on the electron dynamics in a Gaussian-beam model of a laser field. For high intensities, i.e., with dimensionless intensity a0≫1, it is found that the dynamics divides into three regimes. For low-energy electrons (low initial γ factor, γ0) the radiation damping effects are negligible. At higher energies, but still at 2γ0damping alters the final displacement and the net energy change of the electron. For 2γ0>a0 one is in a regime of radiation-reaction-induced electron capture. This capture is found to be stable with respect to the spatial properties of the electron beam and results in a significant energy loss of the electrons. In this regime the plane-wave model of the laser field provides a good description of the dynamics, whereas for lower energies the Gaussian-beam and plane-wave models differ significantly. Finally the dynamics is considered for the case of an x-ray free-electron laser field. It is found that the significantly lower intensities of such fields inhibit the damping effects.

  1. Scattering Theory of Mesoscopic Gilbert Damping

    NASA Astrophysics Data System (ADS)

    Brataas, Arne

    2010-03-01

    Magnetic damping determines the performance of magnetic devices including high-frequency oscillators, hard drives, magnetic random access memories, magnetic logic devices, and magnetic field sensors. The drive to improve these devices, to reduce the response time of sensors and the physical dimensions has led to a greater focus on studying the friction force a changing magnetization experiences. We study the magnetization dynamics of single domain ferromagnets and domain walls in contact with a thermal bath by scattering theory. We recover the Landau-Lifshitz-Gilbert equation and express the Gilbert damping tensor in terms of the scattering matrix [1,2]. Dissipation of magnetic energy equals energy current pumped out of the system by the time-dependent magnetization, with separable spin-relaxation induced bulk and spin-pumping generated interface contributions [3]. The scattering theory of Gilbert damping is suitable for first-principles calculations that include disorder and spin-orbit coupling on an equal footing [4]. In linear response, our scattering theory for the Gilbert damping tensor is equivalent with the Kubo formalism. [4pt] [1] A. Brataas, Y. Tserkovnyak, and G. E. W. Bauer, Phys. Rev. Lett. 101, 037207 (2008). [0pt] [2] K. M. D. Hals, A. K. Nguyen, and A. Brataas, Phys. Rev. Lett. 102, 256601 (2009). [0pt] [3] Y. Tserkovnyak, A. Brataas, G. E. W. Bauer, and B. I. Halperin, Rev. Mod. Phys. 77, 1375 (2005). [0pt] [4] A. A. Starikov, P. J. Kelly, A. Brataas, Y. Tserkovnyak, and G. E. W. Bauer, unpublished.

  2. The DAMPE experiment: first data from space

    NASA Astrophysics Data System (ADS)

    De Mitri, Ivan

    2017-03-01

    The DAMPE satellite has been successfully launched in orbit on December 2015. The science goals of the mission include the study of high energy cosmic ray electrons, photons, protons and nuclei in a wide energy range: 109 - 1014 eV. A report on the mission status will be presented, together with on-orbit detector performance and first data coming from space.

  3. Vibration damping for the Segmented Mirror Telescope

    NASA Astrophysics Data System (ADS)

    Maly, Joseph R.; Yingling, Adam J.; Griffin, Steven F.; Agrawal, Brij N.; Cobb, Richard G.; Chambers, Trevor S.

    2012-09-01

    The Segmented Mirror Telescope (SMT) at the Naval Postgraduate School (NPS) in Monterey is a next-generation deployable telescope, featuring a 3-meter 6-segment primary mirror and advanced wavefront sensing and correction capabilities. In its stowed configuration, the SMT primary mirror segments collapse into a small volume; once on location, these segments open to the full 3-meter diameter. The segments must be very accurately aligned after deployment and the segment surfaces are actively controlled using numerous small, embedded actuators. The SMT employs a passive damping system to complement the actuators and mitigate the effects of low-frequency (<40 Hz) vibration modes of the primary mirror segments. Each of the six segments has three or more modes in this bandwidth, and resonant vibration excited by acoustics or small disturbances on the structure can result in phase mismatches between adjacent segments thereby degrading image quality. The damping system consists of two tuned mass dampers (TMDs) for each of the mirror segments. An adjustable TMD with passive magnetic damping was selected to minimize sensitivity to changes in temperature; both frequency and damping characteristics can be tuned for optimal vibration mitigation. Modal testing was performed with a laser vibrometry system to characterize the SMT segments with and without the TMDs. Objectives of this test were to determine operating deflection shapes of the mirror and to quantify segment edge displacements; relative alignment of λ/4 or better was desired. The TMDs attenuated the vibration amplitudes by 80% and reduced adjacent segment phase mismatches to acceptable levels.

  4. The DAMPE silicon-tungsten tracker

    NASA Astrophysics Data System (ADS)

    Azzarello, P.; Ambrosi, G.; Asfandiyarov, R.; Bernardini, P.; Bertucci, B.; Bolognini, A.; Cadoux, F.; Caprai, M.; De Mitri, I.; Domenjoz, M.; Dong, Y.; Duranti, M.; Fan, R.; Fusco, P.; Gallo, V.; Gargano, F.; Gong, K.; Guo, D.; Husi, C.; Ionica, M.; La Marra, D.; Loparco, F.; Marsella, G.; Mazziotta, M. N.; Mesa, J.; Nardinocchi, A.; Nicola, L.; Pelleriti, G.; Peng, W.; Pohl, M.; Postolache, V.; Qiao, R.; Surdo, A.; Tykhonov, A.; Vitillo, S.; Wang, H.; Weber, M.; Wu, D.; Wu, X.; Zhang, F.

    2016-09-01

    The DArk Matter Particle Explorer (DAMPE) is a spaceborne astroparticle physics experiment, launched on 17 December 2015. DAMPE will identify possible dark matter signatures by detecting electrons and photons in the 5 GeV-10 TeV energy range. It will also measure the flux of nuclei up to 100 TeV, for the study of the high energy cosmic ray origin and propagation mechanisms. DAMPE is composed of four sub-detectors: a plastic strip scintillator, a silicon-tungsten tracker-converter (STK), a BGO imaging calorimeter and a neutron detector. The STK is composed of six tracking planes of 2 orthogonal layers of single-sided micro-strip detectors, for a total detector surface of ca. 7 m2. The STK has been extensively tested for space qualification. Also, numerous beam tests at CERN have been done to study particle detection at silicon module level, and at full detector level. After description of the DAMPE payload and its scientific mission, we will describe the STK characteristics and assembly. We will then focus on some results of single ladder performance tests done with particle beams at CERN.

  5. Chiral damping of magnetic domain walls.

    PubMed

    Jué, Emilie; Safeer, C K; Drouard, Marc; Lopez, Alexandre; Balint, Paul; Buda-Prejbeanu, Liliana; Boulle, Olivier; Auffret, Stephane; Schuhl, Alain; Manchon, Aurelien; Miron, Ioan Mihai; Gaudin, Gilles

    2016-03-01

    Structural symmetry breaking in magnetic materials is responsible for the existence of multiferroics, current-induced spin-orbit torques and some topological magnetic structures. In this Letter we report that the structural inversion asymmetry (SIA) gives rise to a chiral damping mechanism, which is evidenced by measuring the field-driven domain-wall (DW) motion in perpendicularly magnetized asymmetric Pt/Co/Pt trilayers. The DW dynamics associated with the chiral damping and those with Dzyaloshinskii-Moriya interaction (DMI) exhibit identical spatial symmetry. However, both scenarios are differentiated by their time reversal properties: whereas DMI is a conservative effect that can be modelled by an effective field, the chiral damping is purely dissipative and has no influence on the equilibrium magnetic texture. When the DW motion is modulated by an in-plane magnetic field, it reveals the structure of the internal fields experienced by the DWs, allowing one to distinguish the physical mechanism. The chiral damping enriches the spectrum of physical phenomena engendered by the SIA, and is essential for conceiving DW and skyrmion devices owing to its coexistence with DMI (ref. ).

  6. Apparatus and method of preloading vibration-damping bellows

    DOEpatents

    Cutburth, Ronald W.

    1988-01-01

    An improved vibration damping bellows mount or interconnection is disclosed. In one aspect, the bellows is compressively prestressed along its length to offset vacuum-generated tensile loads and thereby improve vibration damping characteristics.

  7. Experimental determination of material damping using vibration analyzer

    NASA Technical Reports Server (NTRS)

    Chowdhury, Mostafiz R.; Chowdhury, Farida

    1990-01-01

    Structural damping is an important dynamic characteristic of engineering materials that helps to damp vibrations by reducing their amplitudes. In this investigation, an experimental method is illustrated to determine the damping characteristics of engineering materials using a dual channel Fast Fourier Transform (FFT) analyzer. A portable Compaq III computer which houses the analyzer, is used to collect the dynamic responses of three metal rods. Time-domain information is analyzed to obtain the logarithmic decrement of their damping. The damping coefficients are then compared to determine the variation of damping from material to material. The variations of damping from one point to another of the same material, due to a fixed point excitation, and the variable damping at a fixed point due to excitation at different points, are also demonstrated.

  8. Implicit and explicit learning in individuals with agrammatic aphasia.

    PubMed

    Schuchard, Julia; Thompson, Cynthia K

    2014-06-01

    Implicit learning is a process of acquiring knowledge that occurs without conscious awareness of learning, whereas explicit learning involves the use of overt strategies. To date, research related to implicit learning following stroke has been largely restricted to the motor domain and has rarely addressed implications for language. The present study investigated implicit and explicit learning of an auditory word sequence in 10 individuals with stroke-induced agrammatic aphasia and 18 healthy age-matched participants using an adaptation of the Serial Reaction Time task. Individuals with aphasia showed significant learning under implicit, but not explicit, conditions, whereas age-matched participants learned under both conditions. These results suggest significant implicit learning ability in agrammatic aphasia. Furthermore, results of an auditory sentence span task indicated working memory deficits in individuals with agrammatic aphasia, which are discussed in relation to explicit and implicit learning processes.

  9. Implicit social cognition: attitudes, self-esteem, and stereotypes.

    PubMed

    Greenwald, A G; Banaji, M R

    1995-01-01

    Social behavior is ordinarily treated as being under conscious (if not always thoughtful) control. However, considerable evidence now supports the view that social behavior often operates in an implicit or unconscious fashion. The identifying feature of implicit cognition is that past experience influences judgment in a fashion not introspectively known by the actor. The present conclusion--that attitudes, self-esteem, and stereotypes have important implicit modes of operation--extends both the construct validity and predictive usefulness of these major theoretical constructs of social psychology. Methodologically, this review calls for increased use of indirect measures--which are imperative in studies of implicit cognition. The theorized ordinariness of implicit stereotyping is consistent with recent findings of discrimination by people who explicitly disavow prejudice. The finding that implicit cognitive effects are often reduced by focusing judges' attention on their judgment task provides a basis for evaluating applications (such as affirmative action) aimed at reducing such unintended discrimination.

  10. Embedded diagonally implicit Runge-Kutta algorithms on parallel computers

    NASA Astrophysics Data System (ADS)

    van der Houwen, P. J.; Sommeijer, B. P.; Couzy, W.

    1992-01-01

    This paper investigates diagonally implicit Runge-Kutta methods in which the implicit relations can be solved in parallel and are singly diagonal-implicit on each processor. The algorithms are based on diagonally implicit iteration of fully implicit Runge-Kutta methods of high order. The iteration scheme is chosen in such a way that the resulting algorithm is A(α ) -stable or L(α ) -stable with α equal or very close to π /2 . In this way, highly stable, singly diagonal-implicit Runge-Kutta methods of orders up to 10 can be constructed. Because of the iterative nature of the methods, embedded formulas of lower orders are automatically available, allowing a strategy for step and order variation.

  11. Resistor-damped electromechanical lever blocks

    NASA Astrophysics Data System (ADS)

    Zago, Lorenzo; Genequand, Pierre M.; Kjelberg, Ivar

    1998-06-01

    The paper presents an innovative technical solution which provides a combined damping and isolation interface with the appropriate transmissibility characteristics between a vibrating base and a sensitive payload, typically an optical terminal/telescope. The novelty of the solution is primarily found in the implementation of uncoupling and magnification of the incurred vibrations by means of flexures combined with the implementation of energy dissipation by means of a linear electro-magnetic actuator to constitute a passive integrated resistor-damped electromechanic lever block. By means of frictionless flexible lever systems, the amplitude of the payload vibrations is adapted to the optimal range of the actuator with a magnification by a factor ranging typically between 10 and 30. Passive viscous damping is obtained by simply short-circuiting the electro-magnetic motor and can be adapted by setting the impedance of the shorting connection. The desired stiffness is provided by the passive springs of the elastic motor suspension and by the stiffness of the lever flexure blades. The mobile mass of the motors also provide a reaction mass which, like damping and stiffness, is amplified by the square of the lever factor. A theoretical model of resistor-damped electromechanical lever blocks has been established. A particular property is it the good attenuation of excited vibrations only over a set frequency range. Above this range the interface properties rejoin the ones of a rigid connection. This performance makes this type of isolators particularly suitable for integration into multi-layer vibration control systems where sensitive equipment is protected by a mix of passive and active damping/isolation devices acting optimally at different frequency ranges. Experiments performed with a dummy load (80 Kg) representative of a satellite based optical terminal demonstrated the efficiency of the system in protecting the payload by passive damping for vibration excitations

  12. Implicitly learned suppression of irrelevant spatial locations.

    PubMed

    Leber, Andrew B; Gwinn, Rachael E; Hong, Yoolim; O'Toole, Ryan J

    2016-12-01

    How do we ignore a salient, irrelevant stimulus whose location is predictable? A variety of studies using instructional manipulations have shown that participants possess the capacity to exert location-based suppression. However, for the visual search challenges we face in daily life, we are not often provided explicit instructions and are unlikely to consciously deliberate on what our best strategy might be. Instead, we might rely on our past experience-in the form of implicit learning-to exert strategic control. In this paper, we tested whether implicit learning could drive spatial suppression. In Experiment 1, participants searched displays in which one location contained a target, while another contained a salient distractor. An arrow cue pointed to the target location with 70 % validity. Also, unbeknownst to the participants, the same arrow cue predicted the distractor location with 70 % validity. Results showed facilitated RTs to the predicted target location, confirming target enhancement. Critically, distractor interference was reduced at the predicted distractor location, revealing that participants used spatial suppression. Further, we found that participants had no explicit knowledge of the cue-distractor contingencies, confirming that the learning was implicit. In Experiment 2, to seek further evidence for suppression, we modified the task to include occasional masked probes following the arrow cue; we found worse probe identification accuracy at the predicted distractor location than control locations, providing converging evidence that observers spatially suppressed the predicted distractor locations. These results reveal an ecologically desirable mechanism of suppression, which functions without the need for conscious knowledge or externally guided instructions.

  13. Neural Patterns of the Implicit Association Test

    PubMed Central

    Healy, Graham F.; Boran, Lorraine; Smeaton, Alan F.

    2015-01-01

    The Implicit Association Test (IAT) is a reaction time based categorization task that measures the differential associative strength between bipolar targets and evaluative attribute concepts as an approach to indexing implicit beliefs or biases. An open question exists as to what exactly the IAT measures, and here EEG (Electroencephalography) has been used to investigate the time course of ERPs (Event-related Potential) indices and implicated brain regions in the IAT. IAT-EEG research identifies a number of early (250–450 ms) negative ERPs indexing early-(pre-response) processing stages of the IAT. ERP activity in this time range is known to index processes related to cognitive control and semantic processing. A central focus of these efforts has been to use IAT-ERPs to delineate the implicit and explicit factors contributing to measured IAT effects. Increasing evidence indicates that cognitive control (and related top-down modulation of attention/perceptual processing) may be components in the effective measurement of IAT effects, as factors such as physical setting or task instruction can change an IAT measurement. In this study we further implicate the role of proactive cognitive control and top-down modulation of attention/perceptual processing in the IAT-EEG. We find statistically significant relationships between D-score (a reaction-time based measure of the IAT-effect) and early ERP-time windows, indicating where more rapid word categorizations driving the IAT effect are present, they are at least partly explainable by neural activity not significantly correlated with the IAT measurement itself. Using LORETA, we identify a number of brain regions driving these ERP-IAT relationships notably involving left-temporal, insular, cingulate, medial frontal and parietal cortex in time regions corresponding to the N2- and P3-related activity. The identified brain regions involved with reduced reaction times on congruent blocks coincide with those of previous studies

  14. Predicting film genres with implicit ideals.

    PubMed

    Olney, Andrew McGregor

    2012-01-01

    We present a new approach to defining film genre based on implicit ideals. When viewers rate the likability of a film, they indirectly express their ideal of what a film should be. Across six studies we investigate the category structure that emerges from likability ratings and the category structure that emerges from the features of film. We further compare these data-driven category structures with human annotated film genres. We conclude that film genres are structured more around ideals than around features of film. This finding lends experimental support to the notion that film genres are set of shifting, fuzzy, and highly contextualized psychological categories.

  15. Predicting Film Genres with Implicit Ideals

    PubMed Central

    Olney, Andrew McGregor

    2013-01-01

    We present a new approach to defining film genre based on implicit ideals. When viewers rate the likability of a film, they indirectly express their ideal of what a film should be. Across six studies we investigate the category structure that emerges from likability ratings and the category structure that emerges from the features of film. We further compare these data-driven category structures with human annotated film genres. We conclude that film genres are structured more around ideals than around features of film. This finding lends experimental support to the notion that film genres are set of shifting, fuzzy, and highly contextualized psychological categories. PMID:23423823

  16. A diagonally inverted LU implicit multigrid scheme

    NASA Technical Reports Server (NTRS)

    Yokota, Jeffrey W.; Caughey, David A.; Chima, Rodrick V.

    1988-01-01

    A new Diagonally Inverted LU Implicit scheme is developed within the framework of the multigrid method for the 3-D unsteady Euler equations. The matrix systems that are to be inverted in the LU scheme are treated by local diagonalizing transformations that decouple them into systems of scalar equations. Unlike the Diagonalized ADI method, the time accuracy of the LU scheme is not reduced since the diagonalization procedure does not destroy time conservation. Even more importantly, this diagonalization significantly reduces the computational effort required to solve the LU approximation and therefore transforms it into a more efficient method of numerically solving the 3-D Euler equations.

  17. Extraction of implicit information in biosignals.

    PubMed

    Lu, W; Xia, L

    1997-12-01

    The first part of this paper explains the meaning of implicit information in biosignals. Image reconstruction from projections and ECG inverse problem are two typical examples. In the second part the limitation of conventional ECG inverse problem study is discussed, that is, the excitation propagation process that was not included in inverse study. In the third part a new approach to ECG inverse problem studies is introduced. To verify the new method, we used this method to localize the ventricular preexcitation site with simulated body surface potentials of WPW syndrome. The experimental results show that the inversely recovered preexcitation sites are in close agreement with the true preexcitation site.

  18. Implicit Degenerate Evolution Equations and Applications.

    DTIC Science & Technology

    1980-07-01

    implicit evolution equations divides historically into three cases. The first and certainly the easiest is where 9 0 A - is Lipschitz or monotone in...on all V, and its Yoshida pproximation A - )’I(I - J,), a monotone Lipschitz function defined on all V. For u e V we have AA(u) e A(JA(u)). We denote...a) (u (t) + (v (t)) + BAlu t)) - f(t) dt (3.2.b) vXlt) e AluAlt) t e (0,T] Since (I + A) - 1 and BX are both Lipschitz continuous from V to V, (3.2

  19. Nonlinear damping of coherent transverse oscillations of a beam in hadron cyclic accelerators and colliders

    NASA Astrophysics Data System (ADS)

    Ivanov, I. N.; Melnikov, V. A.

    1997-02-01

    The correlation between the requirements for the quality of a beam and parameters of systems of damping of transverse coherent oscillations for modern hadron accelerators and colliders is considered. Special attention is directed to systems in which the signal in the kicker is not proportional to the signal of the pickup. It is shown that a nonlinear mode of suppression can provide a greater damping rate. Limiting beam blow-up at injection and accumulation is made possible by an appropriate choice of the discrimination level of the pickup signal.

  20. Nonlinear damping and quasi-linear modelling.

    PubMed

    Elliott, S J; Ghandchi Tehrani, M; Langley, R S

    2015-09-28

    The mechanism of energy dissipation in mechanical systems is often nonlinear. Even though there may be other forms of nonlinearity in the dynamics, nonlinear damping is the dominant source of nonlinearity in a number of practical systems. The analysis of such systems is simplified by the fact that they show no jump or bifurcation behaviour, and indeed can often be well represented by an equivalent linear system, whose damping parameters depend on the form and amplitude of the excitation, in a 'quasi-linear' model. The diverse sources of nonlinear damping are first reviewed in this paper, before some example systems are analysed, initially for sinusoidal and then for random excitation. For simplicity, it is assumed that the system is stable and that the nonlinear damping force depends on the nth power of the velocity. For sinusoidal excitation, it is shown that the response is often also almost sinusoidal, and methods for calculating the amplitude are described based on the harmonic balance method, which is closely related to the describing function method used in control engineering. For random excitation, several methods of analysis are shown to be equivalent. In general, iterative methods need to be used to calculate the equivalent linear damper, since its value depends on the system's response, which itself depends on the value of the equivalent linear damper. The power dissipation of the equivalent linear damper, for both sinusoidal and random cases, matches that dissipated by the nonlinear damper, providing both a firm theoretical basis for this modelling approach and clear physical insight. Finally, practical examples of nonlinear damping are discussed: in microspeakers, vibration isolation, energy harvesting and the mechanical response of the cochlea.

  1. Disentangling Rheumatoid Arthritis Patients’ Implicit and Explicit Attitudes toward Methotrexate

    PubMed Central

    Linn, Annemiek J.; Vandeberg, Lisa; Wennekers, Annemarie M.; Vervloet, Marcia; van Dijk, Liset; van den Bemt, Bart J. F.

    2016-01-01

    Medication non-adherence is a major public health problem that has been termed an ‘invisible epidemic.’ Non-adherence is not only associated with negative clinical consequences but can also result in substantial healthcare costs. Up to now, effective adherence interventions are scarce and a more comprehensive model of adherence determinants is required to target the determinants for not taking the medication as prescribed. Current approaches only included explicit attitudes such as self-reported evaluations of medication as determinants, neglecting the role of associative processes that shape implicit attitudes. Implicit processes can predict daily behavior more accurately than explicit attitudes. Our aim is to assess explicit and implicit attitudes toward medication and explore the relation with beliefs, adherence and clinical (laboratory) outcomes in chronically ill patients. Fifty two Rheumatic Arthritis (RA) patients’ attitudes toward Methotrexate (MTX) were explicitly (self-reported) and implicitly (Single-Category Implicit Association Test) assessed and related to the Beliefs about Medicine Questionnaire, the Compliance Questionnaire on Rheumatology and laboratory parameters [Erythrocyte Sedimentation Rate (ESR), C-Reactive Protein (CRP)]. Results show that explicit attitudes were positive and health-related. Implicit attitudes were, however, negative and sickness-related. Half of the patients displayed explicitly positive but implicitly negative attitudes. Explicit attitudes were positively related to ESR. A positive relationship between implicit attitudes and disease duration was observed. In this study, we have obtained evidence suggesting that the measurement of implicit attitudes and associations provides different information than explicit, self-reported attitudes toward medication. Since patients’ implicit attitudes deviated from explicit attitudes, we can conclude that the relationship between implicit attitudes and medication adherence is

  2. On Existence and Uniqueness Results for Nonsmooth Implicit Differential Equations

    NASA Astrophysics Data System (ADS)

    You, Xiong; Wu, Xinyuan; Chen, Zhaoxia; Yang, Hongli; Fang, Yonglei

    2008-09-01

    The classical implicit function theorem gives conditions that the function is Fréchet differentiable and the derivative is surjective. In this short article they are generalized to conditions of Lipschitz and monotone type. The newly obtained implicit function theorems are used to derive two sets of sufficient conditions for the existence and uniqueness of solutions to the initial value problems of nonsmooth implicit differential equations.

  3. GPU accelerating technique for rendering implicitly represented vasculatures.

    PubMed

    Hong, Qingqi; Wang, Beizhan; Li, Qingde; Li, Yan; Wu, Qingqiang

    2014-01-01

    With the flooding datasets of medical Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), implicit modeling techniques are increasingly applied to reconstruct the human organs, especially the vasculature. However, displaying implicitly represented geometric objects arises heavy computational burden. In this study, a Graphics Processing Unit (GPU) accelerating technique was developed for high performance rendering of implicitly represented objects, especially the vasculatures. The experimental results suggested that the rendering performance was greatly enhanced via exploiting the advantages of modern GPUs.

  4. Applications of implicit restarting in optimization and control Dan Sorensen

    SciTech Connect

    Sorensen, D.

    1996-12-31

    Implicit restarting is a technique for combining the implicitly shifted QR mechanism with a k-step Arnoldi or Lanczos factorization to obtain a truncated form of the implicitly shifted QR-iteration suitable for large scale eigenvalue problems. The software package ARPACK based upon this technique has been successfully used to solve large scale symmetric and nonsymmetric (generalized) eigenvalue problems arising from a variety of applications.

  5. The Effects of Implicit Instruction on Implicit and Explicit Knowledge Development

    ERIC Educational Resources Information Center

    Godfroid, Aline

    2016-01-01

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

  6. Measuring Implicit Attitudes of 4-Year-Olds: The Preschool Implicit Association Test

    ERIC Educational Resources Information Center

    Cvencek, Dario; Greenwald, Anthony G.; Meltzoff, Andrew N.

    2011-01-01

    The Preschool Implicit Association Test (PSIAT) is an adaptation of an established social cognition measure (IAT) for use with preschool children. Two studies with 4-year-olds found that the PSIAT was effective in evaluating (a) attitudes toward commonly liked objects ("flowers"="good") and (b) gender attitudes ("girl"="good" or "boy"="good"). The…

  7. Functional Imaging of Implicit Marijuana Associations during performance on an Implicit Association Test (IAT)

    PubMed Central

    Ames, Susan L.; Grenard, Jerry L.; Stacy, Alan W.; Xiao, Lin; He, Qinghua; Wong, Savio W.; Xue, Gui; Wiers, Reinout W.; Bechara, Antoine

    2013-01-01

    This research evaluated the neural correlates of implicit associative memory processes (habit-based processes) through the imaging (fMRI) of a marijuana Implicit Association Test. Drug-related associative memory effects have been shown to consistently predict level of drug use. To observe differences in neural activity of associative memory effects, this study compared 13 heavy marijuana users and 15 non-using controls, ranging in age from 18 to 25, during performance of a marijuana Implicit Association Test (IAT). Group by condition interactions in the putamen, caudate, and right inferior frontal gyrus were observed. Relative to non-users, marijuana users showed greater bilateral activity in the dorsal striatum (caudate and putamen) during compatible trials focused on perceived positive outcomes of use. Alternatively, relative to the marijuana-using group, the non-users showed greater activity in the right inferior frontal gyrus during incompatible trials, which require more effortful processing of information. Further, relative to fixation, heavy users showed bilateral activity in the caudate and putamen, hippocampus and some frontal regions during compatible trials and no significant activity during incompatible trials. The non-using group showed greater activity in frontal regions during incompatible trials relative to fixation and no significant activity during compatible trials. These findings are consistent with a dual process framework of appetitive behaviors proposing that (1) implicit associations underlying habit are mediated through neural circuitry dependent on the striatum, and (2) deliberative/controlled behaviors are mediated through circuitry more dependent on the prefrontal cortex. PMID:24029699

  8. Inflammatory and fibrotic responses of cardiac fibroblasts to myocardial damage associated molecular patterns (DAMPs).

    PubMed

    Turner, Neil A

    2016-05-01

    Cardiac fibroblasts (CF) are well-established as key regulators of extracellular matrix (ECM) turnover in the context of myocardial remodelling and fibrosis. Recently, this cell type has also been shown to act as a sensor of myocardial damage by detecting and responding to damage-associated molecular patterns (DAMPs) upregulated with cardiac injury. CF express a range of innate immunity pattern recognition receptors (TLRs, NLRs, IL-1R1, RAGE) that are stimulated by a host of different DAMPs that are evident in the injured or remodelling myocardium. These include intracellular molecules released by necrotic cells (heat shock proteins, high mobility group box 1 protein, S100 proteins), proinflammatory cytokines (interleukin-1α), specific ECM molecules up-regulated in response to tissue injury (fibronectin-EDA, tenascin-C) or molecules modified by a pathological environment (advanced glycation end product-modified proteins observed with diabetes). DAMP receptor activation on fibroblasts is coupled to altered cellular function including changes in proliferation, migration, myofibroblast transdifferentiation, ECM turnover and production of fibrotic and inflammatory paracrine factors, which directly impact on the heart's ability to respond to injury. This review gives an overview of the important role played by CF in responding to myocardial DAMPs and how the DAMP/CF axis could be exploited experimentally and therapeutically.

  9. Implicit fear and effort-related cardiac response.

    PubMed

    Chatelain, Mathieu; Gendolla, Guido H E

    2015-10-01

    Based on the Implicit-Affect-Primes-Effort (IAPE) model (Gendolla, 2012, 2015), two experiments tested the impact of fear primes on effort-related cardiac response. The main dependent variable was reactivity of cardiac pre-ejection period (PEP) during the performance of cognitive tasks. The IAPE model predicts that activation of implicit fear and sadness results in stronger PEP responses during task performance than activation of implicit happiness or anger. To test this, Experiment 1 exposed participants to masked facial expressions of fear, anger, or happiness while they performed a cognitive "parity task". As expected, PEP responses in the implicit fear condition were stronger than in both the implicit anger and happiness conditions. Experiment 2 conceptually replicated the implicit fear effect and revealed, as expected, stronger PEP responses for implicit fear and sadness than implicit anger during a "mental concentration" task. The findings provide the first evidence for the systematic impact of implicit fear on effort-related cardiac response and complete the existing evidence for the IAPE model.

  10. Implicit schemes and parallel computing in unstructured grid CFD

    NASA Technical Reports Server (NTRS)

    Venkatakrishnam, V.

    1995-01-01

    The development of implicit schemes for obtaining steady state solutions to the Euler and Navier-Stokes equations on unstructured grids is outlined. Applications are presented that compare the convergence characteristics of various implicit methods. Next, the development of explicit and implicit schemes to compute unsteady flows on unstructured grids is discussed. Next, the issues involved in parallelizing finite volume schemes on unstructured meshes in an MIMD (multiple instruction/multiple data stream) fashion are outlined. Techniques for partitioning unstructured grids among processors and for extracting parallelism in explicit and implicit solvers are discussed. Finally, some dynamic load balancing ideas, which are useful in adaptive transient computations, are presented.

  11. Implicit TVD schemes for hyperbolic conservation laws in curvilinear coordinates

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Harten, A.

    1985-01-01

    The Harten (1983, 1984) total variation-diminishing (TVD) schemes, constituting a one-parameter explicit and implicit, second-order-accurate family, have the property of not generating spurious oscillations when applied to one-dimensional, nonlinear scalar hyperbolic conservation laws and constant coefficient hyperbolic systems. These methods are presently extended to the multidimensional hyperbolic conservation laws in curvilinear coordinates. Means by which to linearize the implicit operator and solution strategies, in order to improve the computation efficiency of the implicit algorithm, are discussed. Numerical experiments with steady state airfoil calculations indicate that the proposed linearized implicit TVD schemes are accurate and robust.

  12. Damped and zero-damped quasinormal modes of charged, nearly extremal black holes

    NASA Astrophysics Data System (ADS)

    Zimmerman, Aaron; Mark, Zachary

    2016-02-01

    Despite recent progress, the complete understanding of the perturbations of charged, rotating black holes as described by the Kerr-Newman metric remains an open and fundamental problem in relativity. In this study, we explore the existence of families of quasinormal modes of Kerr-Newman black holes whose decay rates limit to zero at extremality, called zero-damped modes in past studies. We review the nearly extremal and WKB approximation methods for spin-weighted scalar fields (governed by the Dudley-Finley equation) and give an accounting of the regimes where scalar zero-damped and damped modes exist. Using Leaver's continued fraction method, we verify that these approximations give accurate predictions for the frequencies in their regimes of validity. In the nonrotating limit, we argue that gravito-electromagnetic perturbations of nearly extremal Reissner-Nordström black holes have zero-damped modes in addition to the well-known spectrum of damped modes. We provide an analytic formula for the frequencies of these modes, verify their existence using a numerical search, and demonstrate the accuracy of our formula. These results, along with recent numerical studies, point to the existence of a simple universal equation for the frequencies of zero-damped gravito-electromagnetic modes of Kerr-Newman black holes, whose precise form remains an open question.

  13. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    SciTech Connect

    Lee, H. K.; Barsukov, I.; Swartz, A. G.; Kim, B.; Yang, L.; Hwang, H. Y.; Krivorotov, I. N.

    2016-05-16

    In this paper, we report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO3 (LSMO) and Pt capped LSMO thin films on SrTiO3 (001) substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1) × 10-3, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect in Pt. Our research demonstrates efficient spin transport across the Pt/LSMO interface.

  14. Influence of damping on the frequency-dependent polarizabilities of doped quantum dot

    NASA Astrophysics Data System (ADS)

    Pal, Suvajit; Ghosh, Manas

    2014-09-01

    We investigate the profiles of diagonal components of frequency-dependent linear (αxx and αyy), and first nonlinear (βxxx and βyyy) optical response of repulsive impurity doped quantum dots. The dopant impurity potential chosen assumes Gaussian form. The study principally focuses on investigating the role of damping on the polarizability components. In view of this the dopant is considered to be propagating under damped condition which is otherwise linear inherently. The frequency-dependent polarizabilities are then analyzed by placing the doped dot to a periodically oscillating external electric field of given intensity. The damping strength, in conjunction with external oscillation frequency and confinement potentials, fabricate the polarizability components in a fascinating manner which is adorned with emergence of maximization, minimization, and saturation. The discrimination in the values of the polarizability components in x and y-directions has also been addressed in the present context.

  15. Modeling structural damping for solids having distinct shear and dilatational loss factors

    NASA Technical Reports Server (NTRS)

    Kalinowski, A. J.

    1978-01-01

    For steady state time harmonic problems (rigid format 8), the NASTRAN program as currently configured treats internal structural damping through the introduction of a single structural element damping coefficient that typically is viewed as the ratio of the complex to real modulus of elasticity. For problems dealing with two or three dimensional dynamic linear viscoelasticity (e.g. a Kelvin-Voigt viscoelastic model), the present NASTRAN capability cannot directly handle this situation wherein two independent damping coefficients are required to properly model the dissipation phenomenon. A technique is presented whereby the user can adapt the standard versions of NASTRAN (without resorting to either DMAP and/or FORTRAN coding changes) for the purpose of treating this class of problem.

  16. Model Condensation for Non-Classically Damped SYSTEMS—PART i: Static Condensation

    NASA Astrophysics Data System (ADS)

    Qu, Z.-Q.; Jung, Y.; Selvam, R. P.

    2003-09-01

    Three condensation methods for the model reduction of non-classically damped systems are presented. One is defined in the displacement space and the other two are defined in the state space. Since the damping and inertia forces on all degrees of freedom of the full model are ignored, these algorithms are considered as the static condensation. One advantage of these condensation methods is that the explicit forms of the reduced stiffness, mass, and damping matrices can be directly obtained from the reduced model. These explicit reduced system matrices are very useful in further dynamic analyses. These approaches are compared from the assumptions, condensation matrices, computational work and the reduced system matrices. With the introduction of the generalised inverse of matrix, the method defined in the displacement space is extended and one variant is derived. Numerical examples, one three-degree-of-freedom discrete system and one floating raft isolation system, are applied to demonstrate the features of these methods.

  17. Magnetic anisotropy, damping, and interfacial spin transport in Pt/LSMO bilayers

    DOE PAGES

    Lee, H. K.; Barsukov, I.; Swartz, A. G.; ...

    2016-05-16

    In this paper, we report ferromagnetic resonance measurements of magnetic anisotropy and damping in epitaxial La0.7Sr0.3MnO3 (LSMO) and Pt capped LSMO thin films on SrTiO3 (001) substrates. The measurements reveal large negative perpendicular magnetic anisotropy and a weaker uniaxial in-plane anisotropy that are unaffected by the Pt cap. The Gilbert damping of the bare LSMO films is found to be low α = 1.9(1) × 10-3, and two-magnon scattering is determined to be significant and strongly anisotropic. The Pt cap increases the damping by 50% due to spin pumping, which is also directly detected via inverse spin Hall effect inmore » Pt. Our research demonstrates efficient spin transport across the Pt/LSMO interface.« less

  18. Redistribution of energy flow in a material due to damping.

    PubMed

    Li, Xin; Pierce, Donna M; Arnoldus, Henk F

    2011-02-01

    The field lines of energy flow of the radiation emitted by a linear dipole in free space are straight lines, running radially outward from the source. When the dipole is embedded in a medium, the field lines are curves when the imaginary part of the relative permittivity is finite. It is shown that due to the damping in the material all radiation is emitted in directions perpendicular to the dipole axis, whereas for a dipole in free space the radiation is emitted in all directions except along the dipole axis. It is also shown that some field lines in the near field form semiloops. Energy flowing along these semiloops is absorbed by the material and does not contribute to the radiative power in the far field.

  19. Shades of American Identity: Implicit Relations between Ethnic and National Identities.

    PubMed

    Devos, Thierry; Mohamed, Hafsa

    2014-11-01

    The issue of ethnic diversity and national identity in an immigrant nation such as the USA is a recurrent topic of debate. We review and integrate research examining the extent to which the American identity is implicitly granted or denied to members of different ethnic groups. Consistently, European Americans are implicitly conceived of as being more American than African, Asian, Latino, and even Native Americans. This implicit American = White effect emerges when explicit knowledge or perceptions point in the opposite direction. The propensity to deny the American identity to members of ethnic minorities is particularly pronounced when targets (individuals or groups) are construed through the lenses of ethnic identities. Implicit ethnic-national associations fluctuate as a function of perceivers' ethnic identity and political orientation, but also contextual or situational factors. The tendency to equate being American with being White accounts for the strength of national identification (among European Americans) and behavioral responses including hiring recommendations and voting intentions. The robust propensity to deny the American identity to ethnic minority groups reflects an exclusionary national identity.

  20. Preserved implicit mentalizing in schizophrenia despite poor explicit performance: evidence from eye tracking

    PubMed Central

    Roux, Paul; Smith, Pauline; Passerieux, Christine; Ramus, Franck

    2016-01-01

    Schizophrenia has been characterized by an impaired mentalizing. It has been suggested that distinguishing implicit from explicit processes is crucial in social cognition, and only the latter might be affected in schizophrenia. Two other questions remain open: (1) Is schizophrenia characterized by an hypo- or hyper attribution of intentions? (2) Is it characterized by a deficit in the attribution of intention or of contingency? To test these three questions, spontaneous mentalizing was tested in 29 individuals with schizophrenia and 29 control subjects using the Frith-Happé animations, while eye movements were recorded. Explicit mentalizing was measured from participants’ verbal descriptions and was contrasted with implicit mentalizing measured through eye tracking. As a group, patients made less accurate and less intentional descriptions of the goal-directed and theory of mind animations. No group differences were found in the attribution of contingency. Eye tracking results revealed that patients and controls showed a similar modulation of eye movements in response to the mental states displayed in the Frith-Happé animations. To conclude, in this paradigm, participants with schizophrenia showed a dissociation between explicit and implicit mentalizing, with a decrease in the explicit attribution of intentions, whereas their eye movements suggested a preserved implicit perception of intentions. PMID:27703225

  1. Mind-sets matter: a meta-analytic review of implicit theories and self-regulation.

    PubMed

    Burnette, Jeni L; O'Boyle, Ernest H; VanEpps, Eric M; Pollack, Jeffrey M; Finkel, Eli J

    2013-05-01

    This review builds on self-control theory (Carver & Scheier, 1998) to develop a theoretical framework for investigating associations of implicit theories with self-regulation. This framework conceptualizes self-regulation in terms of 3 crucial processes: goal setting, goal operating, and goal monitoring. In this meta-analysis, we included articles that reported a quantifiable assessment of implicit theories and at least 1 self-regulatory process or outcome. With a random effects approach used, meta-analytic results (total unique N = 28,217; k = 113) across diverse achievement domains (68% academic) and populations (age range = 5-42; 10 different nationalities; 58% from United States; 44% female) demonstrated that implicit theories predict distinct self-regulatory processes, which, in turn, predict goal achievement. Incremental theories, which, in contrast to entity theories, are characterized by the belief that human attributes are malleable rather than fixed, significantly predicted goal setting (performance goals, r = -.151; learning goals, r = .187), goal operating (helpless-oriented strategies, r = -.238; mastery-oriented strategies, r = .227), and goal monitoring (negative emotions, r = -.233; expectations, r = .157). The effects for goal setting and goal operating were stronger in the presence (vs. absence) of ego threats such as failure feedback. Discussion emphasizes how the present theoretical analysis merges an implicit theory perspective with self-control theory to advance scholarship and unlock major new directions for basic and applied research.

  2. Mindfulness practice: A promising approach to reducing the effects of clinician implicit bias on patients.

    PubMed

    Burgess, Diana J; Beach, Mary Catherine; Saha, Somnath

    2017-02-01

    Like the population at large, health care providers hold implicit racial and ethnic biases that may contribute to health care disparities. Little progress has been made in identifying and implementing effective strategies to address these normal but potentially harmful unconscious cognitive processes. We propose that meditation training designed to increase healthcare providers' mindfulness skills is a promising and potentially sustainable way to address this problem. Emerging evidence suggests that mindfulness practice can reduce the provider contribution to healthcare disparities through several mechanisms including: reducing the likelihood that implicit biases will be activated in the mind, increasing providers' awareness of and ability to control responses to implicit biases once activated, increasing self-compassion and compassion toward patients, and reducing internal sources of cognitive load (e.g., stress, burnout, and compassion fatigue). Mindfulness training may also have advantages over current approaches to addressing implicit bias because it focuses on the development of skills through practice, promotes a nonjudgmental approach, can circumvent resistance some providers feel when directly confronted with evidence of racism, and constitutes a holistic approach to promoting providers' well-being. We close with suggestions for how a mindfulness approach can be practically implemented and identify potential challenges and research gaps to be addressed.

  3. Shades of American Identity: Implicit Relations between Ethnic and National Identities

    PubMed Central

    Devos, Thierry; Mohamed, Hafsa

    2015-01-01

    The issue of ethnic diversity and national identity in an immigrant nation such as the USA is a recurrent topic of debate. We review and integrate research examining the extent to which the American identity is implicitly granted or denied to members of different ethnic groups. Consistently, European Americans are implicitly conceived of as being more American than African, Asian, Latino, and even Native Americans. This implicit American = White effect emerges when explicit knowledge or perceptions point in the opposite direction. The propensity to deny the American identity to members of ethnic minorities is particularly pronounced when targets (individuals or groups) are construed through the lenses of ethnic identities. Implicit ethnic–national associations fluctuate as a function of perceivers’ ethnic identity and political orientation, but also contextual or situational factors. The tendency to equate being American with being White accounts for the strength of national identification (among European Americans) and behavioral responses including hiring recommendations and voting intentions. The robust propensity to deny the American identity to ethnic minority groups reflects an exclusionary national identity. PMID:27011765

  4. Context effects in auditory implicit memory.

    PubMed

    Besken, Miri; Mulligan, Neil W

    2010-10-01

    The context effect in implicit memory is the finding that presentation of words in meaningful context reduces or eliminates repetition priming compared to words presented in isolation. Virtually all of the research on the context effect has been conducted in the visual modality but preliminary results raise the question of whether context effects are less likely in auditory priming. Context effects in the auditory modality were systematically examined in five experiments using the auditory implicit tests of word-fragment and word-stem completion. The first three experiments revealed the classical context effect in auditory priming: Words heard in isolation produced substantial priming, whereas there was little priming for the words heard in meaningful passages. Experiments 4 and 5 revealed that a meaningful context is not required for the context effect to be obtained: Words presented in an unrelated audio stream produced less priming than words presented individually and no more priming than words presented in meaningful passages. Although context effects are often explained in terms of the transfer-appropriate processing (TAP) framework, the present results are better explained by Masson and MacLeod's (2000) reduced-individuation hypothesis.

  5. Implicit integration methods for dislocation dynamics

    NASA Astrophysics Data System (ADS)

    Gardner, D. J.; Woodward, C. S.; Reynolds, D. R.; Hommes, G.; Aubry, S.; Arsenlis, A.

    2015-03-01

    In dislocation dynamics simulations, strain hardening simulations require integrating stiff systems of ordinary differential equations in time with expensive force calculations, discontinuous topological events and rapidly changing problem size. Current solvers in use often result in small time steps and long simulation times. Faster solvers may help dislocation dynamics simulations accumulate plastic strains at strain rates comparable to experimental observations. This paper investigates the viability of high-order implicit time integrators and robust nonlinear solvers to reduce simulation run times while maintaining the accuracy of the computed solution. In particular, implicit Runge-Kutta time integrators are explored as a way of providing greater accuracy over a larger time step than is typically done with the standard second-order trapezoidal method. In addition, both accelerated fixed point and Newton's method are investigated to provide fast and effective solves for the nonlinear systems that must be resolved within each time step. Results show that integrators of third order are the most effective, while accelerated fixed point and Newton's method both improve solver performance over the standard fixed point method used for the solution of the nonlinear systems.

  6. Implicit integration methods for dislocation dynamics

    DOE PAGES

    Gardner, D. J.; Woodward, C. S.; Reynolds, D. R.; ...

    2015-01-20

    In dislocation dynamics simulations, strain hardening simulations require integrating stiff systems of ordinary differential equations in time with expensive force calculations, discontinuous topological events, and rapidly changing problem size. Current solvers in use often result in small time steps and long simulation times. Faster solvers may help dislocation dynamics simulations accumulate plastic strains at strain rates comparable to experimental observations. Here, this paper investigates the viability of high order implicit time integrators and robust nonlinear solvers to reduce simulation run times while maintaining the accuracy of the computed solution. In particular, implicit Runge-Kutta time integrators are explored as a waymore » of providing greater accuracy over a larger time step than is typically done with the standard second-order trapezoidal method. In addition, both accelerated fixed point and Newton's method are investigated to provide fast and effective solves for the nonlinear systems that must be resolved within each time step. Results show that integrators of third order are the most effective, while accelerated fixed point and Newton's method both improve solver performance over the standard fixed point method used for the solution of the nonlinear systems.« less

  7. Implicit integration methods for dislocation dynamics

    SciTech Connect

    Gardner, D. J.; Woodward, C. S.; Reynolds, D. R.; Hommes, G.; Aubry, S.; Arsenlis, A.

    2015-01-20

    In dislocation dynamics simulations, strain hardening simulations require integrating stiff systems of ordinary differential equations in time with expensive force calculations, discontinuous topological events, and rapidly changing problem size. Current solvers in use often result in small time steps and long simulation times. Faster solvers may help dislocation dynamics simulations accumulate plastic strains at strain rates comparable to experimental observations. Here, this paper investigates the viability of high order implicit time integrators and robust nonlinear solvers to reduce simulation run times while maintaining the accuracy of the computed solution. In particular, implicit Runge-Kutta time integrators are explored as a way of providing greater accuracy over a larger time step than is typically done with the standard second-order trapezoidal method. In addition, both accelerated fixed point and Newton's method are investigated to provide fast and effective solves for the nonlinear systems that must be resolved within each time step. Results show that integrators of third order are the most effective, while accelerated fixed point and Newton's method both improve solver performance over the standard fixed point method used for the solution of the nonlinear systems.

  8. Eye Movements in Implicit Artificial Grammar Learning.

    PubMed

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

    2017-03-13

    Artificial grammar learning (AGL) has been probed with forced-choice behavioral tests (active tests). Recent attempts to probe the outcomes of learning (implicitly acquired knowledge) with eye-movement responses (passive tests) have shown null results. However, these latter studies have not tested for sensitivity effects, for example, increased eye movements on a printed violation. In this study, we tested for sensitivity effects in AGL tests with (Experiment 1) and without (Experiment 2) concurrent active tests (preference- and grammaticality classification) in an eye-tracking experiment. Eye movements discriminated between sequence types in passive tests and more so in active tests. The eye-movement profile did not differ between preference and grammaticality classification, and it resembled sensitivity effects commonly observed in natural syntax processing. Our findings show that the outcomes of implicit structured sequence learning can be characterized in eye tracking. More specifically, whole trial measures (dwell time, number of fixations) showed robust AGL effects, whereas first-pass measures (first-fixation duration) did not. Furthermore, our findings strengthen the link between artificial and natural syntax processing, and they shed light on the factors that determine performance differences in preference and grammaticality classification tests. (PsycINFO Database Record

  9. On state representations of nonlinear implicit systems

    NASA Astrophysics Data System (ADS)

    Pereira da Silva, Paulo Sergio; Batista, Simone

    2010-03-01

    This work considers a semi-implicit system Δ, that is, a pair (S, y), where S is an explicit system described by a state representation ? , where x(t) ∈ ℝ n and u(t) ∈ ℝ m , which is subject to a set of algebraic constraints y(t) = h(t, x(t), u(t)) = 0, where y(t) ∈ ℝ l . An input candidate is a set of functions v = (v 1, …, v s ), which may depend on time t, on x, and on u and its derivatives up to a finite order. The problem of finding a (local) proper state representation ż = g(t, z, v) with input v for the implicit system Δ is studied in this article. The main result shows necessary and sufficient conditions for the solution of this problem, under mild assumptions on the class of admissible state representations of Δ. These solvability conditions rely on an integrability test that is computed from the explicit system S. The approach of this article is the infinite-dimensional differential geometric setting of Fliess, Lévine, Martin, and Rouchon (1999) ('A Lie-Bäcklund Approach to Equivalence and Flatness of Nonlinear Systems', IEEE Transactions on Automatic Control, 44(5), (922-937)).

  10. Hysteresis as an implicit prior in tactile spatial decision making.

    PubMed

    Thiel, Sabrina D; Bitzer, Sebastian; Nierhaus, Till; Kalberlah, Christian; Preusser, Sven; Neumann, Jane; Nikulin, Vadim V; van der Meer, Elke; Villringer, Arno; Pleger, Burkhard

    2014-01-01

    Perceptual decisions not only depend on the incoming information from sensory systems but constitute a combination of current sensory evidence and internally accumulated information from past encounters. Although recent evidence emphasizes the fundamental role of prior knowledge for perceptual decision making, only few studies have quantified the relevance of such priors on perceptual decisions and examined their interplay with other decision-relevant factors, such as the stimulus properties. In the present study we asked whether hysteresis, describing the stability of a percept despite a change in stimulus property and known to occur at perceptual thresholds, also acts as a form of an implicit prior in tactile spatial decision making, supporting the stability of a decision across successively presented random stimuli (i.e., decision hysteresis). We applied a variant of the classical 2-point discrimination task and found that hysteresis influenced perceptual decision making: Participants were more likely to decide 'same' rather than 'different' on successively presented pin distances. In a direct comparison between the influence of applied pin distances (explicit stimulus property) and hysteresis, we found that on average, stimulus property explained significantly more variance of participants' decisions than hysteresis. However, when focusing on pin distances at threshold, we found a trend for hysteresis to explain more variance. Furthermore, the less variance was explained by the pin distance on a given decision, the more variance was explained by hysteresis, and vice versa. Our findings suggest that hysteresis acts as an implicit prior in tactile spatial decision making that becomes increasingly important when explicit stimulus properties provide decreasing evidence.

  11. Using implicit association tests for the assessment of implicit personality self-concepts of extraversion and neuroticism in schizophrenia.

    PubMed

    Suslow, Thomas; Lindner, Christian; Kugel, Harald; Egloff, Boris; Schmukle, Stefan C

    2014-08-30

    There is evidence from research based on self-report personality measures that schizophrenia patients tend to be lower in extraversion and higher in neuroticism than healthy individuals. Self-report personality measures assess aspects of the explicit self-concept. The Implicit Association Test (IAT) has been developed to assess aspects of implicit cognition such as implicit attitudes and implicit personality traits. The present study was conducted to investigate the applicability and reliability of the IAT in schizophrenia patients and test whether they differ from healthy individuals on implicitly measured extraversion and neuroticism. The IAT and the NEO-FFI were administered as implicit and explicit measures of extraversion and neuroticism to 34 schizophrenia patients and 45 healthy subjects. For all IAT scores satisfactory to good reliabilities were observed in the patient sample. In both study groups, IAT scores were not related to NEO-FFI scores. Schizophrenia patients were lower in implicit and explicit extraversion and higher in implicit and explicit neuroticism than healthy individuals. Our data show that the IAT can be reliably applied to schizophrenia patients and suggest that they differ from healthy individuals not only in their conscious representation but also in their implicit representation of the self with regard to neuroticism and extraversion-related characteristics.

  12. Implicit and explicit attitudes towards conventional and complementary and alternative medicine treatments: Introduction of an Implicit Association Test.

    PubMed

    Green, James A; Hohmann, Cynthia; Lister, Kelsi; Albertyn, Riani; Bradshaw, Renee; Johnson, Christine

    2016-06-01

    This study examined associations between anticipated future health behaviour and participants' attitudes. Three Implicit Association Tests were developed to assess safety, efficacy and overall attitude. They were used to examine preference associations between conventional versus complementary and alternative medicine among 186 participants. A structural equation model suggested only a single implicit association, rather than three separate domains. However, this single implicit association predicted additional variance in anticipated future use of complementary and alternative medicine beyond explicit. Implicit measures should give further insight into motivation for complementary and alternative medicine use.

  13. Molecular and Translational Classifications of DAMPs in Immunogenic Cell Death

    PubMed Central

    Garg, Abhishek D.; Galluzzi, Lorenzo; Apetoh, Lionel; Baert, Thais; Birge, Raymond B.; Bravo-San Pedro, José Manuel; Breckpot, Karine; Brough, David; Chaurio, Ricardo; Cirone, Mara; Coosemans, An; Coulie, Pierre G.; De Ruysscher, Dirk; Dini, Luciana; de Witte, Peter; Dudek-Peric, Aleksandra M.; Faggioni, Alberto; Fucikova, Jitka; Gaipl, Udo S.; Golab, Jakub; Gougeon, Marie-Lise; Hamblin, Michael R.; Hemminki, Akseli; Herrmann, Martin; Hodge, James W.; Kepp, Oliver; Kroemer, Guido; Krysko, Dmitri V.; Land, Walter G.; Madeo, Frank; Manfredi, Angelo A.; Mattarollo, Stephen R.; Maueroder, Christian; Merendino, Nicolò; Multhoff, Gabriele; Pabst, Thomas; Ricci, Jean-Ehrland; Riganti, Chiara; Romano, Erminia; Rufo, Nicole; Smyth, Mark J.; Sonnemann, Jürgen; Spisek, Radek; Stagg, John; Vacchelli, Erika; Vandenabeele, Peter; Vandenberk, Lien; Van den Eynde, Benoit J.; Van Gool, Stefaan; Velotti, Francesca; Zitvogel, Laurence; Agostinis, Patrizia

    2015-01-01

    The immunogenicity of malignant cells has recently been acknowledged as a critical determinant of efficacy in cancer therapy. Thus, besides developing direct immunostimulatory regimens, including dendritic cell-based vaccines, checkpoint-blocking therapies, and adoptive T-cell transfer, researchers have started to focus on the overall immunobiology of neoplastic cells. It is now clear that cancer cells can succumb to some anticancer therapies by undergoing a peculiar form of cell death that is characterized by an increased immunogenic potential, owing to the emission of the so-called “damage-associated molecular patterns” (DAMPs). The emission of DAMPs and other immunostimulatory factors by cells succumbing to immunogenic cell death (ICD) favors the establishment of a productive interface with the immune system. This results in the elicitation of tumor-targeting immune responses associated with the elimination of residual, treatment-resistant cancer cells, as well as with the establishment of immunological memory. Although ICD has been characterized with increased precision since its discovery, several questions remain to be addressed. Here, we summarize and tabulate the main molecular, immunological, preclinical, and clinical aspects of ICD, in an attempt to capture the essence of this phenomenon, and identify future challenges for this rapidly expanding field of investigation. PMID:26635802

  14. Surface Plasmon Damping Quantified with an Electron Nanoprobe

    PubMed Central

    Bosman, Michel; Ye, Enyi; Tan, Shu Fen; Nijhuis, Christian A.; Yang, Joel K. W.; Marty, Renaud; Mlayah, Adnen; Arbouet, Arnaud; Girard, Christian; Han, Ming-Yong

    2013-01-01

    Fabrication and synthesis of plasmonic structures is rapidly moving towards sub-nanometer accuracy in control over shape and inter-particle distance. This holds the promise for developing device components based on novel, non-classical electro-optical effects. Monochromated electron energy-loss spectroscopy (EELS) has in recent years demonstrated its value as a qualitative experimental technique in nano-optics and plasmonic due to its unprecedented spatial resolution. Here, we demonstrate that EELS can also be used quantitatively, to probe surface plasmon kinetics and damping in single nanostructures. Using this approach, we present from a large (>50) series of individual gold nanoparticles the plasmon Quality factors and the plasmon Dephasing times, as a function of energy/frequency. It is shown that the measured general trend applies to regular particle shapes (rods, spheres) as well as irregular shapes (dendritic, branched morphologies). The combination of direct sub-nanometer imaging with EELS-based plasmon damping analysis launches quantitative nanoplasmonics research into the sub-nanometer realm. PMID:23425921

  15. Enhanced Damping for Capillary Bridge Oscillation Using Velocity Feedback

    NASA Technical Reports Server (NTRS)

    Wei, Wei; Thiessen, David B.; Marston, Philip L.

    2004-01-01

    The stability of cylindrical liquid bridges in reduced gravity is affected by ambient vibrations of the spacecraft. Such vibrations are expected to excite capillary modes of the bridge. The lowest-order unstable mode is particularly susceptible to vibration as the length of the bridge approaches the stability limit. This low-order mode is known as the (2,0) mode and is an axisymmetric varicose mode of one wavelength in the axial direction. In this work, an optical system is used to detect the (2,0)-mode amplitude. The derivative of the error signal produced by this detector is used to produce the appropriate voltages on a pair of ring electrodes which are concentric with the bridge. A mode-coupled Maxwell stress profile is thus generated in proportional to the modal velocity. Depending on the sign of the gain, the damping of the capillary oscillation can be either increased or decreased. This effect has been demonstrated in Plateau-tank experiments. Increasing the damping of the capillary modes on free liquid surfaces in space could be beneficial for containerless processing and other novel technologies.

  16. Enhanced Damping for Capillary Bridge Oscillation Using Velocity Feedback

    NASA Technical Reports Server (NTRS)

    Wei, Wei; Thiessen, David B.; Marston, Philip L.

    2004-01-01

    The stability of cylindrical liquid bridges in reduced gravity is affected by ambient vibrations of the spacecraft. Such vibrations are expected to excite capillary modes of the bridge. The lowest-order unstable mode is particularly susceptible to vibration as the length of the bridge approaches the stability limit. This low-order mode is known as the (2,0) mode and is an axisymmetric varicose mode of one wavelength in the axial direction. In this work, an optical system is used to detect the (2,0)-mode amplitude. The derivative of the error signal produced by this detector is used to produce the appropriate voltages on a pair of ring electrodes which are concentric with the bridge. A mode-coupled Maxwell stress profile is thus generated in proportional to the modal velocity. Depending on the sign of the gain, the damping of the capillary oscillation can be either increased or decreased. This effect has been demonstrated in Plateau-tank experiments. Increasing the damping of the capillary modes on free liquid surfaces in space could be beneficial for containerless processing and other novel technologies. [work supported by NASA

  17. IBW and fast wave launching and damping on TFTR

    SciTech Connect

    Hosea, J.C.; Bell, R.; Hill, K.; LeBlanc, B.; Majeski, R.; Nazikian, R.; Ono, M.; Phillips, C.K.; Rogers, J.H.; Schilling, G.; Wilson, J.R.; DIppolito, D.A.; Myra, J.R.; Bush, C.E.; Hanson, G.R.

    1997-04-01

    Antennas to provide direct IBW excitation and to improve the launched spectrum and power handling for mode converted (MC) IBW excitation have been installed on TFTR to support studies of transport barrier formation inside the TFTR plasma. Initial IBW launching/heating experiments have been performed at f{sub RF}{approx}76MHz and 50.6 MHz for several antenna and plasma positions, several magnetic fields (D, T, H, {sup 3}He resonances), and with and without neutral beam injection. Although the measured surface density profiles in front of the antenna should theoretically support IBW launching to the plasma core via EPW excitation, loading resistance parameter dependence and heating results suggest that the wave energy is being deposited mostly in the plasma periphery. The potential roles of surface fast wave and near field excitation/damping on the IBW performance are discussed. Also MC IBW damping of the fast wave has been significantly improved through the removal of lithium 7 from the plasma. {copyright} {ital 1997 American Institute of Physics.}

  18. IBW and Fast Wave Launching and Damping on TFTR

    SciTech Connect

    First Author = J.C. Hosea

    1997-01-01

    Antennas to provide direct IBW (ion-Bernstein wave) excitation and to improve the launched spectrum and power handling for mode-coverted (MC) IBW excitation have been installed on TFTR (Tokamak Fusion Test Reactor) to support studies of transport barrier formation inside the TFTR plasma. Initial IBW launching/heating experiments have been performed at f(subscript) rf (nonsubsript) = 76 MHz and 50.6 MHz for several antenna and plasma positions, several mangetic fields [D, T, H, (superscript) 3 (nonsuperscript) He resonances], and with and without neutral-beam injection. Although the measured surface density profiles in front of the antenna should theoretically support IBW launching to the plasma core via EPW (electron plasma wave) excitation, loading resistance parameter dependence and heating results suggest that the wave energy is being deposited mostly in the plasma periphery. The potential roles of surface fast-wave and near-field excitation/damping on the IBW performance are discussed. Also MC IBW damping of the fast wave has been significantly improved through the removal of lithium 7 from the plasma.

  19. Fast damping in mismatched high intensity beam transportation

    NASA Astrophysics Data System (ADS)

    Variale, V.

    2001-08-01

    A very fast damping of beam envelope oscillation amplitudes was recently observed in simulations of high intensity beam transport, through periodic FODO cells, in mismatched conditions [V. Variale, Nuovo Cimento Soc. Ital. Fis. 112A, 1571-1582 (1999) and T. Clauser et al., in Proceedings of the Particle Accelerator Conference, New York, 1999 (IEEE, Piscataway, NJ, 1999), p. 1779]. A Landau damping mechanism was proposed at the origin of observed effect. In this paper, to further investigate the source of this fast damping, extensive simulations have been carried out. The results presented here support the interpretation of the mechanism at the origin of the fast damping as a Landau damping effect.

  20. Determining material damping type by comparing modal frequency estimators.

    PubMed

    Anthony, D K; Simón, F; Juan, Jesús

    2009-09-01

    The accuracy of modal frequency and damping estimators for non-lightly damped single degree of freedom systems depend on the response parameter used as well as the damping mechanism. Therefore, in order to make accurate modal parameter measurements, the damping mechanism at play must be known to be either viscous or hysteretic a priori. Here, comparisons between the evaluated frequency values are used to glean this information. The damping mechanism of an experimental system (consisting of resilient layer and mass plate) is then determined using two simple modal parameter estimators and applying statistical methods.

  1. Effects of Landau-Lifshitz-Gilbert damping on domain growth.

    PubMed

    Kudo, Kazue

    2016-12-01

    Domain patterns are simulated by the Landau-Lifshitz-Gilbert (LLG) equation with an easy-axis anisotropy. If the Gilbert damping is removed from the LLG equation, it merely describes the precession of magnetization with a ferromagnetic interaction. However, even without the damping, domains that look similar to those of scalar fields are formed, and they grow with time. It is demonstrated that the damping has no significant effects on domain growth laws and large-scale domain structure. In contrast, small-scale domain structure is affected by the damping. The difference in small-scale structure arises from energy dissipation due to the damping.

  2. Effects of damping on mode shapes, volume 1

    NASA Technical Reports Server (NTRS)

    Gates, R. M.

    1977-01-01

    Displacement, velocity, and acceleration admittances were calculated for a realistic NASTRAN structural model of space shuttle for three conditions: liftoff, maximum dynamic pressure and end of solid rocket booster burn. The realistic model of the orbiter, external tank, and solid rocket motors included the representation of structural joint transmissibilities by finite stiffness and damping elements. Methods developed to incorporate structural joints and their damping characteristics into a finite element model of the space shuttle, to determine the point damping parameters required to produce realistic damping in the primary modes, and to calculate the effect of distributed damping on structural resonances through the calculation of admittances.

  3. Improved Contact Algorithms for Implicit FE Simulation of Sheet Forming

    NASA Astrophysics Data System (ADS)

    Zhuang, S.; Lee, M. G.; Keum, Y. T.; Wagoner, R. H.

    2007-05-01

    Implicit finite element simulations of sheet forming processes do not always converge, particularly for complex tool geometries and rapidly changing contact. The SHEET-3 program exhibits remarkable stability and strong convergence by use of its special N-CFS algorithm and a sheet normal defined by the mesh, but these features alone do not always guarantee convergence and accuracy. An improved contact capability within the N-CFS algorithm is formulated taking into account sheet thickness within the framework of shell elements. Two imaginary surfaces offset from the mid-plane of shell elements are implemented along the mesh normal direction. An efficient contact searching algorithm based on the mesh-patch tool description is formulated along the mesh normal direction. The contact search includes a general global searching procedure and a new local searching procedure enforcing the contact condition along the mesh normal direction. The processes of unconstrained cylindrical bending and drawing through a drawbead are simulated to verify the accuracy and convergence of the improved contact algorithm.

  4. Logistic Mixed Models to Investigate Implicit and Explicit Belief Tracking

    PubMed Central

    Lages, Martin; Scheel, Anne

    2016-01-01

    We investigated the proposition of a two-systems Theory of Mind in adults’ belief tracking. A sample of N = 45 participants predicted the choice of one of two opponent players after observing several rounds in an animated card game. Three matches of this card game were played and initial gaze direction on target and subsequent choice predictions were recorded for each belief task and participant. We conducted logistic regressions with mixed effects on the binary data and developed Bayesian logistic mixed models to infer implicit and explicit mentalizing in true belief and false belief tasks. Although logistic regressions with mixed effects predicted the data well a Bayesian logistic mixed model with latent task- and subject-specific parameters gave a better account of the data. As expected explicit choice predictions suggested a clear understanding of true and false beliefs (TB/FB). Surprisingly, however, model parameters for initial gaze direction also indicated belief tracking. We discuss why task-specific parameters for initial gaze directions are different from choice predictions yet reflect second-order perspective taking. PMID:27853440

  5. An Initial Investigation of the Effects of Turbulence Models on the Convergence of the RK/Implicit Scheme

    NASA Technical Reports Server (NTRS)

    Swanson, R. C.; Rossow, C.-C.

    2008-01-01

    A three-stage Runge-Kutta (RK) scheme with multigrid and an implicit preconditioner has been shown to be an effective solver for the fluid dynamic equations. This scheme has been applied to both the compressible and essentially incompressible Reynolds-averaged Navier-Stokes (RANS) equations using the algebraic turbulence model of Baldwin and Lomax (BL). In this paper we focus on the convergence of the RK/implicit scheme when the effects of turbulence are represented by either the Spalart-Allmaras model or the Wilcox k-! model, which are frequently used models in practical fluid dynamic applications. Convergence behavior of the scheme with these turbulence models and the BL model are directly compared. For this initial investigation we solve the flow equations and the partial differential equations of the turbulence models indirectly coupled. With this approach we examine the convergence behavior of each system. Both point and line symmetric Gauss-Seidel are considered for approximating the inverse of the implicit operator of the flow solver. To solve the turbulence equations we use a diagonally dominant alternating direction implicit (DDADI) scheme. Computational results are presented for three airfoil flow cases and comparisons are made with experimental data. We demonstrate that the two-dimensional RANS equations and transport-type equations for turbulence modeling can be efficiently solved with an indirectly coupled algorithm that uses the RK/implicit scheme for the flow equations.

  6. A soft damping function for dispersion corrections with less overfitting.

    PubMed

    Ucak, Umit V; Ji, Hyunjun; Singh, Yashpal; Jung, Yousung

    2016-11-07

    The use of damping functions in empirical dispersion correction schemes is common and widespread. These damping functions contain scaling and damping parameters, and they are usually optimized for the best performance in practical systems. In this study, it is shown that the overfitting problem can be present in current damping functions, which can sometimes yield erroneous results for real applications beyond the nature of training sets. To this end, we present a damping function called linear soft damping (lsd) that suffers less from this overfitting. This linear damping function damps the asymptotic curve more softly than existing damping functions, attempting to minimize the usual overcorrection. The performance of the proposed damping function was tested with benchmark sets for thermochemistry, reaction energies, and intramolecular interactions, as well as intermolecular interactions including nonequilibrium geometries. For noncovalent interactions, all three damping schemes considered in this study (lsd, lg, and BJ) roughly perform comparably (approximately within 1 kcal/mol), but for atomization energies, lsd clearly exhibits a better performance (up to 2-6 kcal/mol) compared to other schemes due to an overfitting in lg and BJ. The number of unphysical parameters resulting from global optimization also supports the overfitting symptoms shown in the latter numerical tests.

  7. A soft damping function for dispersion corrections with less overfitting

    NASA Astrophysics Data System (ADS)

    Ucak, Umit V.; Ji, Hyunjun; Singh, Yashpal; Jung, Yousung

    2016-11-01

    The use of damping functions in empirical dispersion correction schemes is common and widespread. These damping functions contain scaling and damping parameters, and they are usually optimized for the best performance in practical systems. In this study, it is shown that the overfitting problem can be present in current damping functions, which can sometimes yield erroneous results for real applications beyond the nature of training sets. To this end, we present a damping function called linear soft damping (lsd) that suffers less from this overfitting. This linear damping function damps the asymptotic curve more softly than existing damping functions, attempting to minimize the usual overcorrection. The performance of the proposed damping function was tested with benchmark sets for thermochemistry, reaction energies, and intramolecular interactions, as well as intermolecular interactions including nonequilibrium geometries. For noncovalent interactions, all three damping schemes considered in this study (lsd, lg, and BJ) roughly perform comparably (approximately within 1 kcal/mol), but for atomization energies, lsd clearly exhibits a better performance (up to 2-6 kcal/mol) compared to other schemes due to an overfitting in lg and BJ. The number of unphysical parameters resulting from global optimization also supports the overfitting symptoms shown in the latter numerical tests.

  8. Relativity Damps OPEP in Nuclear Matter

    NASA Astrophysics Data System (ADS)

    Banerjee, Manoj K.

    1998-09-01

    Using a relativistic Dirac--Brueckner analysis the OPEP contribution to the ground state energy of nuclear matter is studied. In the study the pion is derivative-coupled. We find that the role of the tensor force in the saturation mechanism is substantially reduced compared to its dominant role in a usual nonrelativistic treatment. We show that the damping of derivative-coupled OPEP is actually due to the decrease of M*/M with increasing density. We point out that if derivative-coupled OPEP is the preferred form of nuclear effective Lagrangian nonrelativistic treatment of nuclear matter is in trouble. Lacking the notion of M* it cannot replicate the damping. We suggest an examination of the feasibility of using pseudoscalar coupled πN interaction before reaching a final conclusion about nonrelativistic treatment of nuclear matter.

  9. Nonlinear Landau damping in the ionosphere

    NASA Technical Reports Server (NTRS)

    Kiwamoto, Y.; Benson, R. F.

    1978-01-01

    A model is presented to explain the non-resonant waves which give rise to the diffuse resonance observed near 3/2 f sub H by the Alouette and ISIS topside sounders, where f sub H is the ambient electron cyclotron frequency. In a strictly linear analysis, these instability driven waves will decay due to Landau damping on a time scale much shorter than the observed time duration of the diffuse resonance. Calculations of the nonlinear wave particle coupling coefficients, however, indicate that the diffuse resonance wave can be maintained by the nonlinear Landau damping of the sounder stimulated 2f sub H wave. The time duration of the diffuse resonance is determined by the transit time of the instability generated and nonlinearly maintained diffuse resonance wave from the remote short lived hot region back to the antenna. The model is consistent with the Alouette/ISIS observations, and clearly demonstrates the existence of nonlinear wave-particle interactions in the ionosphere.

  10. Harmonic cavities for the NLC damping rings

    SciTech Connect

    de Santis, S.; Wolski, A.

    2003-05-29

    To achieve high luminosity, a linear collider needs damping rings to produce beams with very small transverse emittances. In the NLC, design constraints place the Main Damping Rings in a parameter regime where intrabeam scattering (IBS) is likely to be a limitation on the emittance, and hence on the final luminosity. It is possible to mitigate the effects of IBS by lengthening the bunch: this may be achieved by redesigning the lattice with higher momentum compaction, or by use of higher harmonic cavities. Here, we consider the latter approach. We estimate the required bunch lengthening that might be needed, outline some appropriate parameters for the harmonic cavities, and discuss some of the effects that might be introduced or exacerbated by the cavities, such as synchronous phase variation along the bunch train.

  11. Movers and shakers: granular damping in microgravity.

    PubMed

    Bannerman, M N; Kollmer, J E; Sack, A; Heckel, M; Mueller, P; Pöschel, T

    2011-07-01

    The response of an oscillating granular damper to an initial perturbation is studied using experiments performed in microgravity and granular dynamics simulations. High-speed video and image processing techniques are used to extract experimental data. An inelastic hard sphere model is developed to perform simulations and the results are in excellent agreement with the experiments. In line with previous work, a linear decay of the amplitude is observed. Although this behavior is typical for a friction-damped oscillator, through simulation it is shown that this effect is still present even when friction forces are absent. A simple expression is developed which predicts the optimal damping conditions for a given amplitude and is independent of the oscillation frequency and particle inelasticities.

  12. Relativity damps OPEP in nuclear matter

    SciTech Connect

    Banerjee, M.K.

    1998-06-01

    Using a relativistic Dirac-Brueckner analysis the OPEP contribution to the ground state energy of nuclear matter is studied. In the study the pion is derivative-coupled. The author finds that the role of the tensor force in the saturation mechanism is substantially reduced compared to its dominant role in a usual nonrelativistic treatment. He shows that the damping of derivative-coupled OPEP is actually due to the decrease of M{sup *}/M with increasing density. He points out that if derivative-coupled OPEP is the preferred form of nuclear effective lagrangian nonrelativistic treatment of nuclear matter is in trouble. Lacking the notion of M{sup *} it cannot replicate the damping. He suggests an examination of the feasibility of using pseudoscalar coupled {pi}N interaction before reaching a final conclusion about nonrelativistic treatment of nuclear matter.

  13. Enthalpy damping for the steady Euler equations

    NASA Technical Reports Server (NTRS)

    Jespersen, D. C.

    1984-01-01

    For inviscid steady flow problems where the enthalpy is constant at steady state, it was previously proposed to use the difference between the local enthalpy and the steady state enthalpy as a driving term to accelerate convergence of iterative schemes. This idea is analyzed, both on the level of the partial differential equation and on the level of a particular finite difference scheme. It is shown that for the two-dimensional unsteady Euler equations, a hyperbolic system with eigenvalues on the imaginary axis, there is no enthalpy damping strategy which moves all the eigenvalues into the open left half plane. For the numerical scheme, however, the analysis shows and examples verify that enthalpy damping is potentially effective in accelerating convergence to steady state.

  14. Enthalpy damping for the steady Euler equations

    NASA Technical Reports Server (NTRS)

    Jespersen, D. C.

    1985-01-01

    For inviscid steady flow problems where the enthalpy is constant at steady state, it was previously proposed to use the difference between the local enthalpy and the steady state enthalpy as a driving term to accelerate convergence of iterative schemes. This idea is analyzed, both on the level of the partial differential equation and on the level of a particular finite difference scheme. It is shown that for the two-dimensional unsteady Euler equations, a hyperbolic system with eigenvalues on the imaginary axis, there is no enthalpy damping strategy which moves all the eigenvalues into the open left half plane. For the numerical scheme, however, the analysis shows and examples verify that enthalpy damping is potentially effective in accelerating convergence to steady state.

  15. On the damping capacity of cast irons

    NASA Astrophysics Data System (ADS)

    Golovin, S. A.

    2012-07-01

    The treatment of experimental data on the amplitude-dependent internal friction (ADIF) in terms of various theoretical models has revealed a staged character and the main mechanisms of the processes of energy dissipation in graphite with increasing amplitude of vibrations upon cyclic loading. It is shown that the level of the damping capacity of lamellar cast iron depends on the relationship between the elastic and strength characteristics of graphite and the matrix phase. In cast irons with a rigid matrix structure (pearlite, martensite), the energy dissipation is determined by the volume fraction and morphology of the initial graphite phase. In cast irons with a softer metallic phase (ferrite), the contact interaction of graphite inclusions with the matrix and the properties of the matrix introduce additional sources of high damping.

  16. Pressurized fluid damping of nanoelectromechanical systems.

    PubMed

    Svitelskiy, Oleksiy; Sauer, Vince; Liu, Ning; Cheng, Kar-Mun; Finley, Eric; Freeman, Mark R; Hiebert, Wayne K

    2009-12-11

    Interactions of nanoscale structures with fluids are of current interest both in the elucidation of fluid dynamics at these small scales, and in determining the ultimate performance of nanoelectromechanical systems outside of vacuum. We present a comprehensive study of nanomechanical damping in three gases (He, N2, CO2), and liquid CO2. Resonant dynamics in multiple devices of varying size and frequency is measured over 10 decades of pressure (1 mPa-20 MPa) using time-domain stroboscopic optical interferometry. The wide pressure range allows full exploration of the regions of validity of Newtonian and non-Newtonian flow damping models. Observing free molecular flow behavior extending above 1 atm, we find a fluid relaxation time model to be valid throughout, but not beyond, the non-Newtonian regime, and a Newtonian flow vibrating spheres model to be valid in the viscous limit.

  17. Development of Transverse Modes Damped DLA Structure

    SciTech Connect

    Jing, C.; Kanareykin, A.; Schoessow, P.; Gai, W.; Konecny, R.; Power, J. G.; Conde, M.

    2009-01-22

    As the dimensions of accelerating structures become smaller and beam intensities higher, the transverse wakefields driven by the beam become quite large with even a slight misalignment of the beam from the geometric axis. These deflection modes can cause inter-bunch beam breakup and intra-bunch head-tail instabilities along the beam path, and thus BBU control becomes a critical issue. All new metal based accelerating structures, like the accelerating structures developed at SLAC or power extractors at CLIC, have designs in which the transverse modes are heavily damped. Similarly, minimizing the transverse wakefield modes (here the HEMmn hybrid modes in Dielectric-Loaded Accelerating (DLA) structures) is also very critical for developing dielectric based high energy accelerators. In this paper, we present the design of a 7.8 GHz transverse mode damped DLA structure currently under construction, along with plans for the experimental program.

  18. Active Vibration Damping of Solar Arrays

    NASA Astrophysics Data System (ADS)

    Reinicke, Gunar; Baier, Horst; Grillebeck, Anton; Scharfeld, Frank; Hunger, Joseph; Abou-El-Ela, A.; Lohberg, Andreas

    2012-07-01

    Current generations of large solar array panels are lightweight and flexible constructions to reduce net masses. They undergo strong vibrations during launch. The active vibration damping is one convenient option to reduce vibration responses and limit stresses in facesheets. In this study, two actuator concepts are used for vibration damping. A stack interface actuator replaces a panel hold down and is decoupled from bending moments and shear forces. Piezoelectric patch actuators are used as an alternative, where the number, position and size of actuators are mainly driven by controllability analyses. Linear Quadratic Gaussian control is used to attenuate vibrations of selected mode shapes with both actuators. Simulations as well as modal and acoustic tests show the feasibility of selected actuator concepts.

  19. Plasmon damping in graphene out of equilibrium

    NASA Astrophysics Data System (ADS)

    Sun, Zhiyuan; Basov, Dimitri; Fogler, Michael

    Motivated by recent experiments with graphene under high photoexcitation, we study theoretically plasmons of graphene in the two-temperature regime, i.e., the regime where electrons are much hotter than the lattice. We calculate the plasmon damping due to scattering of electrons by acoustic phonons, which is the dominant intrinsic contribution in clean graphene. As the system relaxes to equilibrium, the plasmon frequency adiabatically changes with time. We show that this causes a partial compensation of the plasmon damping. A similar mechanism may apply to another collective mode (the energy wave) predicted to exist in graphene in the low-frequency hydrodynamic regime. Implications for infrared and THz pump-probe experiments are discussed.

  20. Wakefield Damping for the CLIC Crab Cavity

    SciTech Connect

    Ambattu, P.K.; Burt, G.; Dexter, A.C.; Carter, R.G.; Khan, V.; Jones, R.M.; Dolgashev, V.; /SLAC

    2011-12-01

    A crab cavity is required in the CLIC to allow effective head-on collision of bunches at the IP. A high operating frequency is preferred as the deflection voltage required for a given rotation angle and the RF phase tolerance for a crab cavity are inversely proportional to the operating frequency. The short bunch spacing of the CLIC scheme and the high sensitivity of the crab cavity to dipole kicks demand very high damping of the inter-bunch wakes, the major contributor to the luminosity loss of colliding bunches. This paper investigates the nature of the wakefields in the CLIC crab cavity and the possibility of using various damping schemes to suppress them effectively.

  1. The impact damped harmonic oscillator in free decay

    NASA Technical Reports Server (NTRS)

    Brown, G. V.; North, C. M.

    1987-01-01

    The impact-damped oscillator in free decay is studied by using time history solutions. A large range of oscillator amplitude is covered. The amount of damping is correlated with the behavior of the impacting mass. There are three behavior regimes: (1) a low amplitude range with less than one impact per cycle and very low damping, (2) a useful middle amplitude range with a finite number of impacts per cycle, and (3) a high amplitude range with an infinite number of impacts per cycle and progressively decreasing damping. For light damping the impact damping in the middle range is: (1) proportional to impactor mass, (2) additive to proportional damping, (3) a unique function of vibration amplitude, (4) proportional to 1-epsilon, where epsilon is the coefficient of restitution, and (5) very roughly inversely proportional to amplitude. The system exhibits jump phenomena and period doublings. An impactor with 2 percent of the oscillator's mass can produce a loss factor near 0.1.

  2. On the velocity space discretization for the Vlasov-Poisson system: Comparison between implicit Hermite spectral and Particle-in-Cell methods

    NASA Astrophysics Data System (ADS)

    Camporeale, E.; Delzanno, G. L.; Bergen, B. K.; Moulton, J. D.

    2016-01-01

    We describe a spectral method for the numerical solution of the Vlasov-Poisson system where the velocity space is decomposed by means of an Hermite basis, and the configuration space is discretized via a Fourier decomposition. The novelty of our approach is an implicit time discretization that allows exact conservation of charge, momentum and energy. The computational efficiency and the cost-effectiveness of this method are compared to the fully-implicit PIC method recently introduced by Markidis and Lapenta (2011) and Chen et al. (2011). The following examples are discussed: Langmuir wave, Landau damping, ion-acoustic wave, two-stream instability. The Fourier-Hermite spectral method can achieve solutions that are several orders of magnitude more accurate at a fraction of the cost with respect to PIC.

  3. Damping in Ferrous Shape Memory Alloys

    DTIC Science & Technology

    1993-08-01

    time it has been proposed that the solution lies in the approach of energy dissipation by using metallic structural materials which have inherent...and automotive manufacturing plants, has never achieved commercial producton . 1-b. Ferromagnetic alloys, such as Fe-Cr alloys High damping Fe-Cr alloys...Pre-exsiring mar~en-si,ýe worms orwie treenred orieL a ion ! A Lr cow s SL AL 14- L AL Figure 26. Schematic illustration of various processes involved

  4. Fluidic Technology Investigation - Suspension Damping Simulations

    DTIC Science & Technology

    1977-01-01

    IF (w (I LT’ CVM)~4$1 IF ( Wrf 1 0 i CmpY MX2)V?1112wW~ CALL ORPArIP:(Pcx) pP,i.,IERR) .......-or pi i v~,R4p CAlLA (QAI)Rr7,4,?,T.ERR) T F Z (I ~LT C V...Damper Damping Devices Suspension Systems Shock Absorbers Adaptive Suspension Systems Hydro -Fluidics 20. ABSTRACT (Continue on reverse side if necessary

  5. Robot vibration control using inertial damping forces

    NASA Technical Reports Server (NTRS)

    Lee, Soo Han; Book, Wayne J.

    1991-01-01

    This paper concerns the suppression of the vibration of a large flexible robot by inertial forces of a small robot which is located at the tip of the large robot. A controller for generating damping forces to a large robot is designed based on the two time scale model. The controller does not need to calculate the quasi-steady variables and is efficient in computation. Simulation results show the effectiveness of the inertial forces and the controller designed.

  6. Robot vibration control using inertial damping forces

    NASA Technical Reports Server (NTRS)

    Lee, Soo Han; Book, Wayne J.

    1989-01-01

    The suppression is examined of the vibration of a large flexible robot by inertial forces of a small robot which is located at the tip of the large robot. A controller for generating damping forces to a large robot is designed based on the two time scale mode. The controller does not need to calculate the quasi-steady state variables and is efficient in computation. Simulation results show the effectiveness of the inertial forces and the controller designed.

  7. Damping Materials, Finite Elements and Special Projects.

    DTIC Science & Technology

    1982-12-01

    made of either Haynes Alloy Number 188, Hastalloy C, Hastalloy X, or 17 - 4PH stainless steel Hastalloy X. Figure 1.26 is a schematic of the test...Motors Corporation (DDA), conducted a cooperative effort to characterize a DDA proprietary temperature damping material. The UDRI supplied two 17 - 4PH ...range at which the 17 - 4PH stainless steel beams could be tested. Serious discrepancy was noted between the structural loss factors derived from the room

  8. Fluency Does Not Express Implicit Knowledge of Artificial Grammars

    ERIC Educational Resources Information Center

    Scott, Ryan B.; Dienes, Zoltan

    2010-01-01

    It is commonly held that implicit knowledge expresses itself as fluency. A perceptual clarification task was used to examine the relationship between perceptual processing fluency, subjective familiarity, and grammaticality judgments in a task frequently used to produce implicit knowledge, artificial grammar learning (AGL). Four experiments…

  9. Implicit Approach-Avoidance Associations for Craved Food Cues

    ERIC Educational Resources Information Center

    Kemps, Eva; Tiggemann, Marika; Martin, Rachel; Elliott, Mecia

    2013-01-01

    Implicit approach associations are well documented for substances such as alcohol, tobacco, and illicit drugs. This study reports two experiments designed to establish and modify such associations specifically in the food craving domain. Experiment 1 used a pictorial implicit association task to examine approach-avoidance associations with…

  10. The Existence of Implicit Racial Bias in Nursing Faculty

    ERIC Educational Resources Information Center

    Fitzsimmons, Kathleen A.

    2009-01-01

    This study examined the existence of implicit racial bias in nursing faculty using the Implicit Association Test (IAT). It was conducted within a critical race theory framework where race was seen as a permanent, pervasive, and systemic condition, not an individual process. The study was fueled by data showing continued disparate academic and…

  11. Explicit versus Implicit Questioning: Inviting All Children to Think Mathematically

    ERIC Educational Resources Information Center

    Parks, Amy Noelle

    2010-01-01

    Background/Context: Open-ended, or implicit, questioning has been described as central to reform teaching in mathematics. However, concerns about equity have caused some researchers to question whether this kind of teaching is productive for all children. Purpose: This study explores the role that implicit and explicit questions played in…

  12. Qualitative Differences between Implicit and Explicit Sequence Learning

    ERIC Educational Resources Information Center

    Jimenez, Luis; Vaquero, Joaquin M. M.; Lupianez, Juan

    2006-01-01

    Four experiments investigate the differences between implicit and explicit sequence learning concerning their resilience to structural and superficial task changes. A superficial change that embedded the SRT task in the context of a selection task, while maintaining the sequence, did selectively hinder the expression of implicit learning. In…

  13. Preservice and Inservice Teachers' Implicit Theories of Intelligence

    ERIC Educational Resources Information Center

    Jones, Brett D.; Bryant, Lauren H.; Snyder, Jennifer Dee; Malone, David

    2012-01-01

    Implicit theories of intelligence (i.e., individuals' beliefs about the nature of intelligence, such as whether it is fixed or changeable) are important because they are related to individuals' behaviors and their beliefs in other areas (Sternberg, 2000). Implicit theories of intelligence are especially important in educational settings because…

  14. Using Multidimensional Scaling to Explore Biases in Implicit Job Theories.

    ERIC Educational Resources Information Center

    McNelis, Kathleen

    The mention of a job title can trigger descriptive and evaluative associations, suggesting that people possess shared job knowledge. This study focused on the concept of implicit job theory and explored the nature of implicit theories to understand the types of information people rely on when they think about jobs and the biases that might exist.…

  15. Implicit Motives and Men’s Perceived Constraint in Fatherhood

    PubMed Central

    Ruppen, Jessica; Waldvogel, Patricia; Ehlert, Ulrike

    2016-01-01

    Research shows that implicit motives influence social relationships. However, little is known about their role in fatherhood and, particularly, how men experience their paternal role. Therefore, this study examined the association of implicit motives and fathers’ perceived constraint due to fatherhood. Furthermore, we explored their relation to fathers’ life satisfaction. Participants were fathers with biological children (N = 276). They were asked to write picture stories, which were then coded for implicit affiliation and power motives. Perceived constraint and life satisfaction were assessed on a visual analog scale. A higher implicit need for affiliation was significantly associated with lower perceived constraint, whereas the implicit need for power had the opposite effect. Perceived constraint had a negative influence on life satisfaction. Structural equation modeling revealed significant indirect effects of implicit affiliation and power motives on life satisfaction mediated by perceived constraint. Our findings indicate that men with a higher implicit need for affiliation experience less constraint due to fatherhood, resulting in higher life satisfaction. The implicit need for power, however, results in more perceived constraint and is related to decreased life satisfaction. PMID:27933023

  16. Measuring Explicit and Implicit Knowledge: A Psychometric Study in SLA

    ERIC Educational Resources Information Center

    Ebadi, Mandana Rohollahzadeh; Abedalaziz, Nabeel; Saad, Mohd Rashid Mohd

    2015-01-01

    Lack of valid means of measuring explicit and implicit knowledge in acquisition of second language is a concern issue in investigations of explicit and implicit learning. This paper endeavors to validate the use of four tests (i.e., Untimed Judgment Grammatical Test, UJGT; Test of Metalinguistic Knowledge, TMK; Elicited Oral Imitation Test, EOIT;…

  17. Explicit- and Implicit Bullying Attitudes in Relation to Bullying Behavior

    ERIC Educational Resources Information Center

    van Goethem, Anne A. J.; Scholte, Ron H. J.; Wiers, Reinout W.

    2010-01-01

    The main aim of this study was to examine whether an assessment of implicit bullying attitudes could add to the prediction of bullying behavior after controlling for explicit bullying attitudes. Primary school children (112 boys and 125 girls, M age = 11 years, 5 months) completed two newly developed measures of implicit bullying attitudes (a…

  18. Implicit and Explicit Learning in Individuals with Agrammatic Aphasia

    ERIC Educational Resources Information Center

    Schuchard, Julia; Thompson, Cynthia K.

    2014-01-01

    Implicit learning is a process of acquiring knowledge that occurs without conscious awareness of learning, whereas explicit learning involves the use of overt strategies. To date, research related to implicit learning following stroke has been largely restricted to the motor domain and has rarely addressed implications for language. The present…

  19. The Ms. Stereotype Revisited: Implicit and Explicit Facets

    ERIC Educational Resources Information Center

    Malcolmson, Kelly A.; Sinclair, Lisa

    2007-01-01

    Implicit and explicit stereotypes toward the title Ms. were examined. Participants read a short description of a target person whose title of address varied (Ms., Mrs., Miss, Mr.). They then rated the person on agentic and communal traits and completed an Implicit Association Test. Replicating earlier research (Dion, 1987), at an explicit level,…

  20. Implicit and Explicit Knowledge in Second Language Acquisition

    ERIC Educational Resources Information Center

    Rebuschat, Patrick; Williams, John N.

    2012-01-01

    Language development is frequently characterized as a process where learning proceeds implicitly, that is, incidentally and in absence of awareness of what was learned. This article reports the results of two experiments that investigated whether second language acquisition can also result in implicit knowledge. Adult learners were trained on an…

  1. Teaching about Implicit Prejudices and Stereotypes: A Pedagogical Demonstration

    ERIC Educational Resources Information Center

    Adams, Virgil H., III; Devos, Thierry; Rivera, Luis M.; Smith, Heather; Vega, Luis A.

    2014-01-01

    Social psychology instructors from five distinct state universities in California examined the effect of incorporating the implicit association test (IAT) in a teaching module on students' perceived knowledge of implicit biases and motivation to control prejudice. Students (N = 258) completed a knowledge survey on prejudice, stereotypes, and…

  2. Implicit Race/Ethnic Prejudice in Mexican Americans

    ERIC Educational Resources Information Center

    Garza, Christelle Fabiola; Gasquoine, Philip Gerard

    2013-01-01

    Implicit race/ethnic prejudice was assessed using Spanish- and English-language versions of an Implicit Association Test that used Hispanic/Anglo first names and pleasant/unpleasant words as stimuli. This test was administered to a consecutive sample of Mexican American adults residing in the Rio Grande Valley region of Texas of whom about…

  3. Measuring Implicit and Explicit Attitudes toward Foreign-Accented Speech

    ERIC Educational Resources Information Center

    Pantos, Andrew J.

    2010-01-01

    The purpose of this research was to investigate the nature of listeners' attitudes toward foreign-accented speech and the manner in which those attitudes are formed. This study measured 165 participants' implicit and explicit attitudes toward US- and foreign-accented audio stimuli. Implicit attitudes were measured with an audio Implicit…

  4. Implicit and Explicit Recasts in L2 Oral French Interaction

    ERIC Educational Resources Information Center

    Erlam, Rosemary; Loewen, Shawn

    2010-01-01

    This laboratory-based study of second- and third-year American university students learning French examines the effectiveness of implicit and explicit corrective feedback on noun-adjective agreement errors. The treatment consisted of one hour of interactive tasks. Implicit feedback was operationalized as a single recast with interrogative…

  5. Collisional damping rates for plasma waves

    NASA Astrophysics Data System (ADS)

    Tigik, S. F.; Ziebell, L. F.; Yoon, P. H.

    2016-06-01

    The distinction between the plasma dynamics dominated by collisional transport versus collective processes has never been rigorously addressed until recently. A recent paper [P. H. Yoon et al., Phys. Rev. E 93, 033203 (2016)] formulates for the first time, a unified kinetic theory in which collective processes and collisional dynamics are systematically incorporated from first principles. One of the outcomes of such a formalism is the rigorous derivation of collisional damping rates for Langmuir and ion-acoustic waves, which can be contrasted to the heuristic customary approach. However, the results are given only in formal mathematical expressions. The present brief communication numerically evaluates the rigorous collisional damping rates by considering the case of plasma particles with Maxwellian velocity distribution function so as to assess the consequence of the rigorous formalism in a quantitative manner. Comparison with the heuristic ("Spitzer") formula shows that the accurate damping rates are much lower in magnitude than the conventional expression, which implies that the traditional approach over-estimates the importance of attenuation of plasma waves by collisional relaxation process. Such a finding may have a wide applicability ranging from laboratory to space and astrophysical plasmas.

  6. Synchrosqueezed wavelet transform for damping identification

    NASA Astrophysics Data System (ADS)

    Mihalec, Marko; Slavič, Janko; Boltežar, Miha

    2016-12-01

    Synchrosqueezing is a procedure for improving the frequency localization of a continuous wavelet transform. This research focuses on using a synchrosqueezed wavelet transform (SWT) to determine the damping ratios of a vibrating system using a free-response signal. While synchrosqueezing is advantageous due to its localisation in the frequency, damping identification with the original SWT is not sufficiently accurate. Here, the synchrosqueezing was researched in detail, and it was found that an error in the frequency occurs as a result of the numerical calculation of the preliminary frequencies. If this error were to be compensated, a better damping identification would be expected. To minimize the frequency-shift error, three different strategies are investigated: the scale-dependent coefficient method, the shifted-coefficient method and the autocorrelated-frequency method. Furthermore, to improve the SWT, two synchrosqueezing criteria are introduced: the average SWT and the proportional SWT. Finally, the proposed modifications are tested against close modes and the noise in the signals. It was numerically and experimentally confirmed that the SWT with the proportional criterion offers better frequency localization and performs better than the continuous wavelet transform when tested against noisy signals.

  7. A comparison of viscoelastic damping models

    NASA Technical Reports Server (NTRS)

    Slater, Joseph C.; Belvin, W. Keith; Inman, Daniel J.

    1993-01-01

    Modern finite element methods (FEM's) enable the precise modeling of mass and stiffness properties in what were in the past overwhelmingly large and complex structures. These models allow the accurate determination of natural frequencies and mode shapes. However, adequate methods for modeling highly damped and high frequency dependent structures did not exist until recently. The most commonly used method, Modal Strain Energy, does not correctly predict complex mode shapes since it is based on the assumption that the mode shapes of a structure are real. Recently, many techniques have been developed which allow the modeling of frequency dependent damping properties of materials in a finite element compatible form. Two of these methods, the Golla-Hughes-McTavish method and the Lesieutre-Mingori method, model the frequency dependent effects by adding coordinates to the existing system thus maintaining the linearity of the model. The third model, proposed by Bagley and Torvik, is based on the Fractional Calculus method and requires fewer empirical parameters to model the frequency dependence at the expense of linearity of the governing equations. This work examines the Modal Strain Energy, Golla-Hughes-McTavish and Bagley and Torvik models and compares them to determine the plausibility of using them for modeling viscoelastic damping in large structures.

  8. Metallic materials for mechanical damping capacity applications

    NASA Astrophysics Data System (ADS)

    Crăciun, R. C.; Stanciu, S.; Cimpoeșu, R.; (Dragoș Ursanu, A. I.; Manole, V.; Paraschiv, P.; Chicet, D. L.

    2016-08-01

    Some metallic materials exhibit good damping capacity of mechanical energy into thermal energy. This property along with the others metallic characteristics make this materials interesting for a big number of applications. These materials can be used as bumpers in different applications including automotive field. Beside grey cast iron and shape memory alloys few new metallic materials are presented for the supposition of high damping capacity. We analyze the causes that increase the internal friction of some metallic materials and possibilities to enhance this property through different mechanical, physical or chemical methods. Shape memory alloys, especially those based on copper, present a different damping capacity on martensite, austenite or transition state. In the transformation range M ↔A, which in case of copper base shape memory alloys is quite large, the metallic intelligent materials present a high internal friction, almost comparable with natural rubber behavior that can transform mechanical energy into thermal energy till a certain value of the external solicitation. These materials can be used as noise or small vibrations bumpers or even as shock absorbers in automotive industry.

  9. Active damping of the SOFIA Telescope assembly

    NASA Astrophysics Data System (ADS)

    Keas, Paul J.; Dunham, Edward; Lampater, Ulrich; Pfüller, Enrico; Teufel, Stefan; Roeser, Hans-Peter; Wiedemann, Manuel; Wolf, Jürgen

    2012-09-01

    The NASA/DLR Stratospheric Observatory for Infrared Astronomy (SOFIA) employs a 2.5-meter reflector telescope in a Boeing 747SP. The telescope is housed in an open cavity and is subjected to aeroacoustic and inertial disturbances in flight. To meet pointing requirements, SOFIA must achieve a pointing stability of approximately 0.5 arcseconds RMS. An active damping control system is being developed for SOFIA to reduce image jitter and image degradation due to resonance of the telescope assembly. Our paper discusses the history of the active damping design for SOFIA, from early concepts to the current implementation which has recently completed a ground and flight testing for proof-of-concept. We describe some milestones in the analysis and testing of the telescope assembly which guided the development of the vibration control system. The control synthesis approach and current implementation of the active damping control system is presented. Finally, we summarize the performance observed in early flight tests and the steps that are currently foreseen to completing the development of this system.

  10. Random Response of Linear Hysteretic Damping

    SciTech Connect

    Floris, Claudio

    2008-07-08

    The probabilistic characterization of the response of a single-degree-of-freedom (SDOF) oscillator with linear hysteretic damping excited by ground motion described by zero mean stationary Gaussian processes is achieved by profiting from a steady-state solution of the motion equation, valid when the excitation is given by the superposition of harmonics. The model of linear hysteretic damping has been introduced to fit damping mechanisms in which the dissipation rate is independent of frequency, and mathematically it is described by the Hilbert transform of the response. Though this model is debated since it violates the principle of causality, its intrinsic simplicity makes it preferable to other models. The steady-state solution of the motion equation proposed in this paper allows a closed form evaluation of the respone mean square value. However, the numerical examples show that this quantity is affected by the mechanism of energy dissipation only when this is large. On the contrary, for a low capacity of dissipation the response mean square value is rather insensitive to the dissipation mechanism.

  11. The Impact of Cognitive Stressors in the Emergency Department on Physician Implicit Racial Bias

    PubMed Central

    Johnson, Tiffani J.; Hickey, Robert W.; Switzer, Galen E.; Miller, Elizabeth; Winger, Daniel G.; Nguyen, Margaret; Saladino, Richard A.; Hausmann, Leslie R. M.

    2016-01-01

    Objectives The emergency department (ED) is characterized by stressors (e.g. fatigue, stress, time-pressure, and complex decision-making) that can pose challenges to delivering high quality, equitable care. Although it has been suggested that characteristics of the ED may exacerbate reliance on cognitive heuristics, no research has directly investigated whether stressors in the ED impact physician racial bias, a common heuristic. We seek to determine if physicians have different levels of implicit racial bias post-ED shift versus pre-shift, and to examine associations between demographics and cognitive stressors with bias. Methods This repeated measures study of resident physicians in a pediatric ED used electronic pre- and post-shift assessments of implicit racial bias, demographics, and cognitive stressors. Implicit bias was measured using the Race Implicit Association Test (IAT). Linear regression models compared differences in IAT scores pre- to post-shift, and determined associations between participant demographics and cognitive stressors with post-shift IAT and pre- to post-shift difference scores. Results Participants (n=91) displayed moderate pro-white/anti-black bias on pre-shift (M=0.50, SD=0.34, d=1.48) and post-shift (M=0.55, SD=0.39, d=1.40) IAT scores. Overall, IAT scores did not differ pre-shift to post-shift (mean increase=0.05, 95% CI −0.02,0.14, d=0.13). Sub-analyses revealed increased pre- to post-shift bias among participants working when the ED was more overcrowded (mean increase=0.09, 95% CI 0.01,0.17, d=0.24) and among those caring for >10 patients (mean increase=0.17, 95% CI 0.05,0.27, d=0.47). Residents’ demographics (including specialty), fatigue, busyness, stressfulness, and number of shifts were not associated with post-shift IAT or difference scores. In multivariable models, ED overcrowding was associated with greater post-shift bias (coefficient=0.11 per 1 unit of NEDOCS score, SE=0.05, 95% CI 0.00,0.21). Conclusions While

  12. The nondiscriminating heart: lovingkindness meditation training decreases implicit intergroup bias.

    PubMed

    Kang, Yoona; Gray, Jeremy R; Dovidio, John F

    2014-06-01

    Although meditation is increasingly accepted as having personal benefits, less is known about the broader impact of meditation on social and intergroup relations. We tested the effect of lovingkindness meditation training on improving implicit attitudes toward members of 2 stigmatized social outgroups: Blacks and homeless people. Healthy non-Black, nonhomeless adults (N = 101) were randomly assigned to 1 of 3 conditions: 6-week lovingkindness practice, 6-week lovingkindness discussion (a closely matched active control), or waitlist control. Decreases in implicit bias against stigmatized outgroups (as measured by Implicit Association Test) were observed only in the lovingkindness practice condition. Reduced psychological stress mediated the effect of lovingkindness practice on implicit bias against homeless people, but it did not mediate the reduced bias against Black people. These results suggest that lovingkindness meditation can improve automatically activated, implicit attitudes toward stigmatized social groups and that this effect occurs through distinctive mechanisms for different stigmatized social groups.

  13. The time course of explicit and implicit categorization.

    PubMed

    Smith, J David; Zakrzewski, Alexandria C; Herberger, Eric R; Boomer, Joseph; Roeder, Jessica L; Ashby, F Gregory; Church, Barbara A

    2015-10-01

    Contemporary theory in cognitive neuroscience distinguishes, among the processes and utilities that serve categorization, explicit and implicit systems of category learning that learn, respectively, category rules by active hypothesis testing or adaptive behaviors by association and reinforcement. Little is known about the time course of categorization within these systems. Accordingly, the present experiments contrasted tasks that fostered explicit categorization (because they had a one-dimensional, rule-based solution) or implicit categorization (because they had a two-dimensional, information-integration solution). In Experiment 1, participants learned categories under unspeeded or speeded conditions. In Experiment 2, they applied previously trained category knowledge under unspeeded or speeded conditions. Speeded conditions selectively impaired implicit category learning and implicit mature categorization. These results illuminate the processing dynamics of explicit/implicit categorization.

  14. Mode- and size-dependent Landau-Lifshitz damping in magnetic nanostructures: evidence for nonlocal damping.

    PubMed

    Nembach, Hans T; Shaw, Justin M; Boone, Carl T; Silva, T J

    2013-03-15

    We demonstrate a strong dependence of the effective damping on the nanomagnet size and the particular spin-wave mode that can be explained by the theory of intralayer transverse-spin pumping. The effective Landau-Lifshitz damping is measured optically in individual, isolated nanomagnets as small as 100 nm. The measurements are accomplished by use of a novel heterodyne magneto-optical microwave microscope with unprecedented sensitivity. Experimental data reveal multiple standing spin-wave modes that we identify by use of micromagnetic modeling as having either localized or delocalized character, described generically as end and center modes. The damping parameter of the two modes depends on both the size of the nanomagnet as well as the particular spin-wave mode that is excited, with values that are enhanced by as much as 40% relative to that measured for an extended film. Contrary to expectations based on the ad hoc consideration of lithography-induced edge damage, the damping for the end mode decreases as the size of the nanomagnet decreases. The data agree with the theory for damping caused by the flow of intralayer transverse spin currents driven by the magnetization curvature. These results have serious implications for the performance of nanoscale spintronic devices such as spin-torque-transfer magnetic random access memory.

  15. Implicit Riemann solvers for the Pn equations.

    SciTech Connect

    Mehlhorn, Thomas Alan; McClarren, Ryan; Brunner, Thomas A.; Holloway, James Paul

    2005-03-01

    The spherical harmonics (P{sub n}) approximation to the transport equation for time dependent problems has previously been treated using Riemann solvers and explicit time integration. Here we present an implicit time integration method for the P n equations using Riemann solvers. Both first-order and high-resolution spatial discretization schemes are detailed. One facet of the high-resolution scheme is that a system of nonlinear equations must be solved at each time step. This nonlinearity is the result of slope reconstruction techniques necessary to avoid the introduction of artifical extrema in the numerical solution. Results are presented that show auspicious agreement with analytical solutions using time steps well beyond the CFL limit.

  16. Domain decomposition for implicit solvation models.

    PubMed

    Cancès, Eric; Maday, Yvon; Stamm, Benjamin

    2013-08-07

    This article is the first of a series of papers dealing with domain decomposition algorithms for implicit solvent models. We show that, in the framework of the COSMO model, with van der Waals molecular cavities and classical charge distributions, the electrostatic energy contribution to the solvation energy, usually computed by solving an integral equation on the whole surface of the molecular cavity, can be computed more efficiently by using an integral equation formulation of Schwarz's domain decomposition method for boundary value problems. In addition, the so-obtained potential energy surface is smooth, which is a critical property to perform geometry optimization and molecular dynamics simulations. The purpose of this first article is to detail the methodology, set up the theoretical foundations of the approach, and study the accuracies and convergence rates of the resulting algorithms. The full efficiency of the method and its applicability to large molecular systems of biological interest is demonstrated elsewhere.

  17. Implicit familiarity processing in congenital prosopagnosia.

    PubMed

    Avidan, Galia; Behrmann, Marlene

    2008-03-01

    A particularly interesting and somewhat puzzling finding in the face-processing literature is that, despite the absence of overt recognition of most faces, many patients with acquired prosopagnosia (AP) exhibit evidence of intact covert face recognition of the very same faces. This phenomenon has important implications for the understanding of the mechanism underlying AP and, by extension, the mechanism underlying normal face processing. Here, we set out to examine whether individuals with congenital prosopagnosia (CP) exhibit a similar dissociation between overt and covert face recognition. We first confirmed that all six of our CP individuals were significantly impaired in face recognition in comparison with controls. Participants then completed a matching task with both famous and unknown faces in which they decided whether two consecutive images have the same identity or not. Critically, the level of face familiarity was orthogonal to the task at hand and this enabled us to examine whether the familiarity of a face enhanced identity matching, a finding which would implicate implicit face processing. As expected, the CP individuals were slower and less accurate than the control participants. More importantly, like the controls, the CP individuals were faster and more accurate at matching famous compared with unknown faces. Also, for both groups, matching performance on unrecognized famous faces fell at an intermediate level between performance on explicitly recognized famous faces and faces which are unknown. These results provide the first solid evidence for the existence of implicit familiarity processing in CP and suggest that, despite the marked impairment in explicit face recognition, these individuals still have some familiarity representation which manifests in the form of covert recognition. We discuss possible models to account for the apparent dissociation of overt and covert face processing in CPR.

  18. Implicit phonological priming during visual word recognition.

    PubMed

    Wilson, Lisa B; Tregellas, Jason R; Slason, Erin; Pasko, Bryce E; Rojas, Donald C

    2011-03-15

    Phonology is a lower-level structural aspect of language involving the sounds of a language and their organization in that language. Numerous behavioral studies utilizing priming, which refers to an increased sensitivity to a stimulus following prior experience with that or a related stimulus, have provided evidence for the role of phonology in visual word recognition. However, most language studies utilizing priming in conjunction with functional magnetic resonance imaging (fMRI) have focused on lexical-semantic aspects of language processing. The aim of the present study was to investigate the neurobiological substrates of the automatic, implicit stages of phonological processing. While undergoing fMRI, eighteen individuals performed a lexical decision task (LDT) on prime-target pairs including word-word homophone and pseudoword-word pseudohomophone pairs with a prime presentation below perceptual threshold. Whole-brain analyses revealed several cortical regions exhibiting hemodynamic response suppression due to phonological priming including bilateral superior temporal gyri (STG), middle temporal gyri (MTG), and angular gyri (AG) with additional region of interest (ROI) analyses revealing response suppression in the left lateralized supramarginal gyrus (SMG). Homophone and pseudohomophone priming also resulted in different patterns of hemodynamic responses relative to one another. These results suggest that phonological processing plays a key role in visual word recognition. Furthermore, enhanced hemodynamic responses for unrelated stimuli relative to primed stimuli were observed in midline cortical regions corresponding to the default-mode network (DMN) suggesting that DMN activity can be modulated by task requirements within the context of an implicit task.

  19. The absence of intraband scattering in a consistent theory of Gilbert damping in pure metallic ferromagnets

    NASA Astrophysics Data System (ADS)

    Edwards, D. M.

    2016-03-01

    Damping of magnetization dynamics in a ferromagnetic metal, arising from spin-orbit coupling, is usually characterised by the Gilbert parameter α. Recent calculations of this quantity, using a formula due to Kambersky, find that it is infinite for a perfect crystal owing to an intraband scattering term which is of third order in the spin-orbit parameter ξ. This surprising result conflicts with recent work by Costa and Muniz who study damping numerically by direct calculation of the dynamical transverse susceptibility in the presence of spin-orbit coupling. We resolve this inconsistency by following the approach of Costa and Muniz for a slightly simplified model where it is possible to calculate α analytically. We show that to second order in ξ one retrieves the Kambersky result for α, but to higher order one does not obtain any divergent intraband terms. The present work goes beyond that of Costa and Muniz by pointing out the necessity of including the effect of long-range Coulomb interaction in calculating damping for large ξ. A direct derivation of the Kambersky formula is given which shows clearly the restriction of its validity to second order in ξ so that no intraband scattering terms appear. This restriction has an important effect on the damping over a substantial range of impurity content and temperature. The experimental situation is discussed.

  20. A transient FETI methodology for large-scale parallel implicit computations in structural mechanics

    NASA Technical Reports Server (NTRS)

    Farhat, Charbel; Crivelli, Luis; Roux, Francois-Xavier

    1992-01-01

    Explicit codes are often used to simulate the nonlinear dynamics of large-scale structural systems, even for low frequency response, because the storage and CPU requirements entailed by the repeated factorizations traditionally found in implicit codes rapidly overwhelm the available computing resources. With the advent of parallel processing, this trend is accelerating because explicit schemes are also easier to parallelize than implicit ones. However, the time step restriction imposed by the Courant stability condition on all explicit schemes cannot yet -- and perhaps will never -- be offset by the speed of parallel hardware. Therefore, it is essential to develop efficient and robust alternatives to direct methods that are also amenable to massively parallel processing because implicit codes using unconditionally stable time-integration algorithms are computationally more efficient when simulating low-frequency dynamics. Here we present a domain decomposition method for implicit schemes that requires significantly less storage than factorization algorithms, that is several times faster than other popular direct and iterative methods, that can be easily implemented on both shared and local memory parallel processors, and that is both computationally and communication-wise efficient. The proposed transient domain decomposition method is an extension of the method of Finite Element Tearing and Interconnecting (FETI) developed by Farhat and Roux for the solution of static problems. Serial and parallel performance results on the CRAY Y-MP/8 and the iPSC-860/128 systems are reported and analyzed for realistic structural dynamics problems. These results establish the superiority of the FETI method over both the serial/parallel conjugate gradient algorithm with diagonal scaling and the serial/parallel direct method, and contrast the computational power of the iPSC-860/128 parallel processor with that of the CRAY Y-MP/8 system.