A critical comparison of several low Reynolds number k-epsilon turbulence models for flow over a backward facing step

NASA Technical Reports Server (NTRS)

Steffen, C. J., Jr.

1993-01-01

Turbulent backward-facing step flow was examined using four low turbulent Reynolds number k-epsilon models and one standard high Reynolds number technique. A tunnel configuration of 1:9 (step height: exit tunnel height) was used. The models tested include: the original Jones and Launder; Chien; Launder and Sharma; and the recent Shih and Lumley formulation. The experimental reference of Driver and Seegmiller was used to make detailed comparisons between reattachment length, velocity, pressure, turbulent kinetic energy, Reynolds shear stress, and skin friction predictions. The results indicated that the use of a wall function for the standard k-epsilon technique did not reduce the calculation accuracy for this separated flow when compared to the low turbulent Reynolds number techniques.

The Effect of Backward-Facing Step Height on Instability Growth and Breakdown in Swept Wing Boundary-Layer Transition

NASA Technical Reports Server (NTRS)

Eppink, Jenna L.; Wlezien, Richard W.; King, Rudolph A.; Choudhari, Meelan

2015-01-01

A low-speed experiment was performed on a swept at plate model with an imposed pressure gradient to determine the effect of a backward-facing step on transition in a stationary-cross flow dominated flow. Detailed hot-wire boundary-layer measurements were performed for three backward-facing step heights of approximately 36, 45, and 49% of the boundary-layer thickness at the step. These step heights correspond to a subcritical, nearly-critical, and critical case. Three leading-edge roughness configurations were tested to determine the effect of stationary-cross flow amplitude on transition. The step caused a local increase in amplitude of the stationary cross flow for the two larger step height cases, but farther downstream the amplitude decreased and remained below the baseline amplitude. The smallest step caused a slight local decrease in amplitude of the primary stationary cross flow mode, but the amplitude collapsed back to the baseline case far downstream of the step. The effect of the step on the amplitude of the primary cross flow mode increased with step height, however, the stationary cross flow amplitudes remained low and thus, stationary cross flow was not solely responsible for transition. Unsteady disturbances were present downstream of the step for all three step heights, and the amplitudes increased with increasing step height. The only exception is that the lower frequency (traveling crossflow-like) disturbance was not present in the lowest step height case. Positive and negative spikes in instantaneous velocity began to occur for the two larger step height cases and then grew in number and amplitude downstream of reattachment, eventually leading to transition. The number and amplitude of spikes varied depending on the step height and cross flow amplitude. Despite the low amplitude of the disturbances in the intermediate step height case, breakdown began to occur intermittently and the flow underwent a long transition region.

A dynamically adaptive multigrid algorithm for the incompressible Navier-Stokes equations: Validation and model problems

NASA Technical Reports Server (NTRS)

Thompson, C. P.; Leaf, G. K.; Vanrosendale, J.

1991-01-01

An algorithm is described for the solution of the laminar, incompressible Navier-Stokes equations. The basic algorithm is a multigrid based on a robust, box-based smoothing step. Its most important feature is the incorporation of automatic, dynamic mesh refinement. This algorithm supports generalized simple domains. The program is based on a standard staggered-grid formulation of the Navier-Stokes equations for robustness and efficiency. Special grid transfer operators were introduced at grid interfaces in the multigrid algorithm to ensure discrete mass conservation. Results are presented for three models: the driven-cavity, a backward-facing step, and a sudden expansion/contraction.

Computation of turbulent flows over backward and forward-facing steps using a near-wall Reynolds stress model

NASA Technical Reports Server (NTRS)

Ko, Sung HO

1993-01-01

Separation and reattachment of turbulent shear layers is observed in many important engineering applications, yet it is poorly understood. This has motivated many studies on understanding and predicting the processes of separation and reattachment of turbulent shear layers. Both of the situations in which separation is induced by adverse pressure gradient, or by discontinuities of geometry, have attracted attention of turbulence model developers. Formulation of turbulence closure models to describe the essential features of separated turbulent flows accurately is still a formidable task. Computations of separated flows associated with sharp-edged bluff bodies are described. For the past two decades, the backward-facing step flow, the simplest separated flow, has been a popular test case for turbulence models. Detailed studies on the performance of many turbulence models, including two equation turbulence models and Reynolds stress models, for flows over steps can be found in the papers by Thangam & Speziale and Lasher & Taulbee). These studies indicate that almost all the existing turbulence models fail to accurately predict many important features of back step flow such as reattachment length, recovery rate of the redeveloping boundary layers downstream of the reattachment point, streamlines near the reattachment point, and the skin friction coefficient. The main objectives are to calculate flows over backward and forward-facing steps using the NRSM and to make use of the newest DNS data for detailed comparison. This will give insights for possible improvements of the turbulence model.

Investigation of the capillary flow through open surface microfluidic structures

NASA Astrophysics Data System (ADS)

Taher, Ahmed; Jones, Benjamin; Fiorini, Paolo; Lagae, Liesbet

2017-02-01

The passive nature of capillary microfluidics for pumping and actuation of fluids is attractive for many applications including point of care medical diagnostics. For such applications, there is often the need to spot dried chemical reagents in the bottom of microfluidic channels after device fabrication; it is often more practical to have open surface devices (i.e., without a cover or lid). However, the dynamics of capillary driven flow in open surface devices have not been well studied for many geometries of interest. In this paper, we investigate capillary flow in an open surface microchannel with a backward facing step. An analytical model is developed to calculate the capillary pressure as the liquid-vapor interface traverses a backward facing step in an open microchannel. The developed model is validated against results from Surface Evolver liquid-vapor surface simulations and ANSYS Fluent two-phase flow simulations using the volume of fluid approach. Three different aspect ratios (inlet channel height by channel width) were studied. The analytical model shows good agreement with the simulation results from both modeling methods for all geometries. The analytical model is used to derive an expression for the critical aspect ratio (the minimum channel aspect ratio for flow to proceed across the backward facing step) as a function of contact angle.

Methicillin Resistant Staphylococcus Aureus Biofilm Formation Over A Separated Flow Region Under Steady And Pulsatile Flow Conditions

NASA Astrophysics Data System (ADS)

Salek, M. Mehdi; Martinuzzi, Robert

2012-02-01

Several researchers have observed that the formation, morphology and susceptibility of bacterial biofilms are affected by the local hydrodynamic condition and, in particular, shear stresses acting on the fluid-biofilm interface. A backwards facing step (BFS) experimental model has been widely utilized as an in vitro model to examine and characterize the effect of flow separation and recirculation zones comparable to those present within various medical devices as well as those observed in vivo. The specific geometry of BFS covers a vide range of flow features observed in physiological or environmental conditions. The hypothesis of this study is that the flow behavior and structures can effectively contribute to the transport and attachment of cells and affecting the morphology of adhered colonies as well as suspended structures (i.e. biofilm streamers). Hence, the formation of the recirculation region occurring within a backward facing step (BFS) under steady and pulsatile conditions as well as three-dimensional flow structures arising close to the side walls are investigated to correlate to biofilms behavior. This hypothesis is investigated using a backward facing step incorporated into a flow cell under steady and pulsatile flow regimes to study the growth of methicillin resistant Staphylococcus aureus (MRSA) UC18 as the study microorganism.

Stability of spanwise-modulated flows behind backward-facing steps

NASA Astrophysics Data System (ADS)

Boiko, A. V.; Dovgal, A. V.; Sorokin, A. M.

2017-10-01

An overview and synthesis of researches on development of local vortical disturbances in laminar separated flows downstream of backward-facing steps, in which the velocity field depends essentially on two variables are given. Peculiarities of transition to turbulence in such spatially inhomogeneous separated zones are discussed. The experimental data are supplemented by the linear stability characteristics of model velocity profiles of the separated flow computed using both the classical local formulation and the nonlocal approach based on the Floquet theory for partial differential equations with periodic coefficients. The results clarify the response of the local separated flows to their modulation with stationary geometrical and temperature inhomogeneities. The results can be useful for the development of new methods of laminar separation control.

POD analysis of flow over a backward-facing step forced by right-angle-shaped plasma actuator.

PubMed

Wang, Bin; Li, Huaxing

2016-01-01

This study aims to present flow control over the backward-facing step with specially designed right-angle-shaped plasma actuator and analyzed the influence of various scales of flow structures on the Reynolds stress through snapshot proper orthogonal decomposition (POD). 2D particle image velocimetry measurements were conducted on region (x/h = 0-2.25) and reattachment zone in the x-y plane over the backward-facing step at a Reynolds number of Re h  = 27,766 (based on step height [Formula: see text] and free stream velocity [Formula: see text]. The separated shear layer was excited by specially designed right-angle-shaped plasma actuator under the normalized excitation frequency St h  ≈ 0.345 along the 45° direction. The spatial distribution of each Reynolds stress component was reconstructed using an increasing number of POD modes. The POD analysis indicated that the flow dynamic downstream of the step was dominated by large-scale flow structures, which contributed to streamwise Reynolds stress and Reynolds shear stress. The intense Reynolds stress localized to a narrow strip within the shear layer was mainly affected by small-scale flow structures, which were responsible for the recovery of the Reynolds stress peak. With plasma excitation, a significant increase was obtained in the vertical Reynolds stress peak. Under the dimensionless frequencies St h  ≈ 0.345 and [Formula: see text] which are based on the step height and momentum thickness, the effectiveness of the flow control forced by the plasma actuator along the 45° direction was ordinary. Only the vertical Reynolds stress was significantly affected.

Experimental study of the flow over a backward-facing rounded ramp

NASA Astrophysics Data System (ADS)

Duriez, Thomas; Aider, Jean-Luc; Wesfreid, Jose Eduardo

2010-11-01

The backward-facing rounded ramp (BFR) is a very simple geometry leading to boundary layer separation, close to the backward facing step (BFS) flow. The main difference with the BFS flow is that the separation location depends on the incoming flow while it is fixed to the step edge for the BFS flow. Despite the simplicity of the geometry, the flow is complex and the transition process still has to be investigated. In this study we investigate the BFR flow using time-resolved PIV. For Reynolds number ranging between 300 and 12 000 we first study the time averaged properties such as the positions of the separation and reattachment, the recirculation length and the shear layer thickness. The time resolution also gives access to the characteristic frequencies of the time-dependant flow. An appropriate Fourier filtering of the flow field, around each frequency peak in the global spectrum, allows an investigation of each mode in order to extract its wavelength, phase velocity, and spatial distribution. We then sort the spectral content and relate the main frequencies to the most amplified Kelvin-Helmholtz instability mode and its harmonics, the vortex pairing, the low frequency recirculation bubble oscillation and the interactions between all these phenomena.

Hybrid mesh finite volume CFD code for studying heat transfer in a forward-facing step

NASA Astrophysics Data System (ADS)

Jayakumar, J. S.; Kumar, Inder; Eswaran, V.

2010-12-01

Computational fluid dynamics (CFD) methods employ two types of grid: structured and unstructured. Developing the solver and data structures for a finite-volume solver is easier than for unstructured grids. But real-life problems are too complicated to be fitted flexibly by structured grids. Therefore, unstructured grids are widely used for solving real-life problems. However, using only one type of unstructured element consumes a lot of computational time because the number of elements cannot be controlled. Hence, a hybrid grid that contains mixed elements, such as the use of hexahedral elements along with tetrahedral and pyramidal elements, gives the user control over the number of elements in the domain, and thus only the domain that requires a finer grid is meshed finer and not the entire domain. This work aims to develop such a finite-volume hybrid grid solver capable of handling turbulence flows and conjugate heat transfer. It has been extended to solving flow involving separation and subsequent reattachment occurring due to sudden expansion or contraction. A significant effect of mixing high- and low-enthalpy fluid occurs in the reattached regions of these devices. This makes the study of the backward-facing and forward-facing step with heat transfer an important field of research. The problem of the forward-facing step with conjugate heat transfer was taken up and solved for turbulence flow using a two-equation model of k-ω. The variation in the flow profile and heat transfer behavior has been studied with the variation in Re and solid to fluid thermal conductivity ratios. The results for the variation in local Nusselt number, interface temperature and skin friction factor are presented.

Physical modeling of vortical cross-step flow in the American paddlefish, Polyodon spathula

PubMed Central

Brooks, Hannah; Haines, Grant E.; Lin, M. Carly

2018-01-01

Vortical cross-step filtration in suspension-feeding fish has been reported recently as a novel mechanism, distinct from other biological and industrial filtration processes. Although crossflow passing over backward-facing steps generates vortices that can suspend, concentrate, and transport particles, the morphological factors affecting this vortical flow have not been identified previously. In our 3D-printed models of the oral cavity for ram suspension-feeding fish, the angle of the backward-facing step with respect to the model’s dorsal midline affected vortex parameters significantly, including rotational, tangential, and axial speed. These vortices were comparable to those quantified downstream of the backward-facing steps that were formed by the branchial arches of preserved American paddlefish in a recirculating flow tank. Our data indicate that vortices in cross-step filtration have the characteristics of forced vortices, as the flow of water inside the oral cavity provides the external torque required to sustain forced vortices. Additionally, we quantified a new variable for ram suspension feeding termed the fluid exit ratio. This is defined as the ratio of the total open pore area for water leaving the oral cavity via spaces between branchial arches that are not blocked by gill rakers, divided by the total area for water entering through the gape during ram suspension feeding. Our experiments demonstrated that the fluid exit ratio in preserved paddlefish was a significant predictor of the flow speeds that were quantified anterior of the rostrum, at the gape, directly dorsal of the first ceratobranchial, and in the forced vortex generated by the first ceratobranchial. Physical modeling of vortical cross-step filtration offers future opportunities to explore the complex interactions between structural features of the oral cavity, vortex parameters, motile particle behavior, and particle morphology that determine the suspension, concentration, and transport of particles within the oral cavity of ram suspension-feeding fish. PMID:29561890

Assessment of turbulent models for scramjet flowfields

NASA Technical Reports Server (NTRS)

Sindir, M. M.; Harsha, P. T.

1982-01-01

The behavior of several turbulence models applied to the prediction of scramjet combustor flows is described. These models include the basic two equation model, the multiple dissipation length scale variant of the two equation model, and the algebraic stress model (ASM). Predictions were made of planar backward facing step flows and axisymmetric sudden expansion flows using each of these approaches. The formulation of each of these models are discussed, and the application of the different approaches to supersonic flows is described. A modified version of the ASM is found to provide the best prediction of the planar backward facing step flow in the region near the recirculation zone, while the basic ASM provides the best results downstream of the recirculation. Aspects of the interaction of numerica modeling and turbulences modeling as they affect the assessment of turbulence models are discussed.

Effect of wall cooling on the stability of compressible subsonic flows over smooth humps and backward-facing steps

NASA Technical Reports Server (NTRS)

Al-Maaitah, Ayman A.; Nayfeh, Ali, H.; Ragab, Saad A.

1989-01-01

The effect of wall cooling on the two-dimensional linear stability of subsonic flows over two-dimensional surface imperfections is investigated. Results are presented for flows over smooth humps and backward-facing steps with Mach numbers up to 0.8. The results show that, whereas cooling decreases the viscous instability, it increases the shear-layer instability and hence it increases the growth rates in the separation region. The coexistence of more than one instability mechanism makes a certain degree of wall cooling most effective. For the Mach numbers 0.5 and 0.8, the optimum wall temperatures are about 80 pct and 60 pct of the adiabatic wall temperature, respectively. Increasing the Mach number decreases the effectiveness of cooling slightly and reduces the optimum wall temperature.

How to find home backwards? Locomotion and inter-leg coordination during rearward walking of Cataglyphis fortis desert ants.

PubMed

Pfeffer, Sarah E; Wahl, Verena L; Wittlinger, Matthias

2016-07-15

For insects, flexibility in the performance of terrestrial locomotion is a vital part of facing the challenges of their often unpredictable environment. Arthropods such as scorpions and crustaceans can switch readily from forward to backward locomotion, but in insects this behaviour seems to be less common and, therefore, is only poorly understood. Here we present an example of spontaneous and persistent backward walking in Cataglyphis desert ants that allows us to investigate rearward locomotion within a natural context. When ants find a food item that is too large to be lifted up and to be carried in a normal forward-faced orientation, they will drag the load walking backwards to their home nest. A detailed examination of this behaviour reveals a surprising flexibility of the locomotor output. Compared with forward walks with regular tripod coordination, no main coordination pattern can be assigned to rearward walks. However, we often observed leg-pair-specific stepping patterns. The front legs frequently step with small stride lengths, while the middle and the hind legs are characterized by less numerous but larger strides. But still, these specializations show no rigidly fixed leg coupling, nor are they strictly embedded within a temporal context; therefore, they do not result in a repetitive coordination pattern. The individual legs act as separate units, most likely to better maintain stability during backward dragging. © 2016. Published by The Company of Biologists Ltd.

Investigation of Particle Sampling Bias in the Shear Flow Field Downstream of a Backward Facing Step

NASA Technical Reports Server (NTRS)

Meyers, James F.; Kjelgaard, Scott O.; Hepner, Timothy E.

1990-01-01

The flow field about a backward facing step was investigated to determine the characteristics of particle sampling bias in the various flow phenomena. The investigation used the calculation of the velocity:data rate correlation coefficient as a measure of statistical dependence and thus the degree of velocity bias. While the investigation found negligible dependence within the free stream region, increased dependence was found within the boundary and shear layers. Full classic correction techniques over-compensated the data since the dependence was weak, even in the boundary layer and shear regions. The paper emphasizes the necessity to determine the degree of particle sampling bias for each measurement ensemble and not use generalized assumptions to correct the data. Further, it recommends the calculation of the velocity:data rate correlation coefficient become a standard statistical calculation in the analysis of all laser velocimeter data.

Prediction of the backflow and recovery regions in the backward facing step at various Reynolds numbers

NASA Technical Reports Server (NTRS)

Michelassi, V.; Durbin, P. A.; Mansour, N. N.

1996-01-01

A four-equation model of turbulence is applied to the numerical simulation of flows with massive separation induced by a sudden expansion. The model constants are a function of the flow parameters, and two different formulations for these functions are tested. The results are compared with experimental data for a high Reynolds-number case and with experimental and DNS data for a low Reynolds-number case. The computations prove that the recovery region downstream of the massive separation is properly modeled only for the high Re case. The problems in this case stem from the gradient diffusion hypothesis, which underestimates the turbulent diffusion.

Teaching Domestic Violence Online: A Step Forward or a Step Backward?

PubMed

Danis, Fran S

2016-10-01

With the increasing number of courses and degree programs available online, faculty may be interested in developing an online course on domestic violence. This article analyzes the similarities and differences involved in teaching about domestic violence online versus face-to-face. Highlights of course activities and notable online resources are identified including YouTube videos, webinars, online training modules, and websites. The limitations and challenges of teaching domestic violence in an asynchronous online course and recommendations for future teaching are discussed. © The Author(s) 2016.

Dynamic subfilter-scale stress model for large-eddy simulations

NASA Astrophysics Data System (ADS)

Rouhi, A.; Piomelli, U.; Geurts, B. J.

2016-08-01

We present a modification of the integral length-scale approximation (ILSA) model originally proposed by Piomelli et al. [Piomelli et al., J. Fluid Mech. 766, 499 (2015), 10.1017/jfm.2015.29] and apply it to plane channel flow and a backward-facing step. In the ILSA models the length scale is expressed in terms of the integral length scale of turbulence and is determined by the flow characteristics, decoupled from the simulation grid. In the original formulation the model coefficient was constant, determined by requiring a desired global contribution of the unresolved subfilter scales (SFSs) to the dissipation rate, known as SFS activity; its value was found by a set of coarse-grid calculations. Here we develop two modifications. We de-fine a measure of SFS activity (based on turbulent stresses), which adds to the robustness of the model, particularly at high Reynolds numbers, and removes the need for the prior coarse-grid calculations: The model coefficient can be computed dynamically and adapt to large-scale unsteadiness. Furthermore, the desired level of SFS activity is now enforced locally (and not integrated over the entire volume, as in the original model), providing better control over model activity and also improving the near-wall behavior of the model. Application of the local ILSA to channel flow and a backward-facing step and comparison with the original ILSA and with the dynamic model of Germano et al. [Germano et al., Phys. Fluids A 3, 1760 (1991), 10.1063/1.857955] show better control over the model contribution in the local ILSA, while the positive properties of the original formulation (including its higher accuracy compared to the dynamic model on coarse grids) are maintained. The backward-facing step also highlights the advantage of the decoupling of the model length scale from the mesh.

The Importance of Splat Events to the Spatiotemporal Structure of Near-Bed Fluid Velocity and Bed Load Motion Over Bed Forms: Laboratory Experiments Downstream of a Backward Facing Step

NASA Astrophysics Data System (ADS)

Leary, K. C. P.; Schmeeckle, M. W.

2017-12-01

Flow separation/reattachment on the lee side of alluvial bed forms is known to produce a complex turbulence field, but the spatiotemporal details of the associated patterns of bed load sediment transported remain largely unknown. Here we report turbulence-resolving, simultaneous measurements of bed load motion and near-bed fluid velocity downstream of a backward facing step in a laboratory flume. Two synchronized high-speed video cameras simultaneously observed bed load motion and the motion of neutrally buoyant particles in a laser light sheet 6 mm above the bed at 250 frames/s downstream of a 3.8 cm backward facing step. Particle Imaging Velocimetry (PIV) and Acoustic Doppler Velocimetry (ADV) were used to characterize fluid turbulent patterns, while manual particle tracking techniques were used to characterize bed load transport. Octant analysis, conducted using ADV data, coupled with Markovian sequence probability analysis highlights differences in the flow near reattachment versus farther downstream. Near reattachment, three distinct flow patterns are apparent. Farther downstream we see the development of a dominant flow sequence. Localized, intermittent, high-magnitude transport events are more apparent near flow reattachment. These events are composed of streamwise and cross-stream fluxes of comparable magnitudes. Transport pattern and fluid velocity data are consistent with the existence of permeable "splat events," wherein a volume of fluid moves toward and impinges on the bed (sweep) causing a radial movement of fluid in all directions around the point of impingement (outward interaction). This is congruent with flow patterns, identified with octant analysis, proximal to flow reattachment.

Extending substructure based iterative solvers to multiple load and repeated analyses

NASA Technical Reports Server (NTRS)

Farhat, Charbel

1993-01-01

Direct solvers currently dominate commercial finite element structural software, but do not scale well in the fine granularity regime targeted by emerging parallel processors. Substructure based iterative solvers--often called also domain decomposition algorithms--lend themselves better to parallel processing, but must overcome several obstacles before earning their place in general purpose structural analysis programs. One such obstacle is the solution of systems with many or repeated right hand sides. Such systems arise, for example, in multiple load static analyses and in implicit linear dynamics computations. Direct solvers are well-suited for these problems because after the system matrix has been factored, the multiple or repeated solutions can be obtained through relatively inexpensive forward and backward substitutions. On the other hand, iterative solvers in general are ill-suited for these problems because they often must restart from scratch for every different right hand side. In this paper, we present a methodology for extending the range of applications of domain decomposition methods to problems with multiple or repeated right hand sides. Basically, we formulate the overall problem as a series of minimization problems over K-orthogonal and supplementary subspaces, and tailor the preconditioned conjugate gradient algorithm to solve them efficiently. The resulting solution method is scalable, whereas direct factorization schemes and forward and backward substitution algorithms are not. We illustrate the proposed methodology with the solution of static and dynamic structural problems, and highlight its potential to outperform forward and backward substitutions on parallel computers. As an example, we show that for a linear structural dynamics problem with 11640 degrees of freedom, every time-step beyond time-step 15 is solved in a single iteration and consumes 1.0 second on a 32 processor iPSC-860 system; for the same problem and the same parallel processor, a pair of forward/backward substitutions at each step consumes 15.0 seconds.

Least-squares solution of incompressible Navier-Stokes equations with the p-version of finite elements

NASA Technical Reports Server (NTRS)

Jiang, Bo-Nan; Sonnad, Vijay

1991-01-01

A p-version of the least squares finite element method, based on the velocity-pressure-vorticity formulation, is developed for solving steady state incompressible viscous flow problems. The resulting system of symmetric and positive definite linear equations can be solved satisfactorily with the conjugate gradient method. In conjunction with the use of rapid operator application which avoids the formation of either element of global matrices, it is possible to achieve a highly compact and efficient solution scheme for the incompressible Navier-Stokes equations. Numerical results are presented for two-dimensional flow over a backward facing step. The effectiveness of simple outflow boundary conditions is also demonstrated.

Variations in backward masking with different masking stimuli: II. The effects of spatially quantised masks in the light of local contour interaction, interchannel inhibition, perceptual retouch, and substitution theories.

PubMed

Bachmann, Talis; Luiga, Iiris; Põder, Endel

2005-01-01

In part I we showed that with spatially non-overlapping targets and masks both local metacontrast-like interactions and attentional processes are involved in backward masking. In this second part we extend the strategy of varying the contents of masks to pattern masking where targets and masks overlap in space, in order to compare different masking theories. Images of human faces were backward-masked by three types of spatially quantised masks (the same faces as targets, faces different from targets, and Gaussian noise with power spectra typical for faces). Configural characteristics, rather than the spectral content of the mask, predicted the extent of masking at relatively long stimulus onset asynchronies (SOAs). This poses difficulties for the theory of transient-on-sustained inhibition as the principal mechanism of masking and also for local contour interaction being a decisive factor in pattern masking. The scale of quantisation had no effect on the masking capacity of noise masks and a strong effect on the capacity of different-face masks. Also, the decrease of configural masking with an increase in the coarseness of the quantisation of the mask highlights ambiguities inherent in the re-entrance-based substitution theory of masking. Different masking theories cannot solve the problems of masking separately. They should be combined in order to create a complex, yet comprehensible mode of interaction for the different mechanisms involved in visual backward masking.

Particle Image Velocimetry Measurements of a Two/Three-dimensional Separating/Reattaching Boundary Layer Downstream of an Axisymmetric Backward-facing Step

NASA Technical Reports Server (NTRS)

Hudy, Laura M.; Naguib, Ahmed M.; Humphreys, William M.; Bartram, Scott M.

2005-01-01

Planar Particle Image Velocimetry measurements were obtained in the separating/reattaching flow region downstream of an axisymmetric backward-facing step. Data were acquired for a two-dimensional (2D) separating boundary layer at five different Reynolds numbers based on step height (Re(sub h)), spanning 5900-33000, and for a three-dimensional (3D) separating boundary layer at Re(sub h) = 5980 and 8081. Reynolds number effects were investigated in the 2D cases using mean-velocity field, streamwise and wall-normal turbulent velocity, and Reynolds stress statistics. Results show that both the reattachment length (x(sub r)) and the secondary separation point are Reynolds number dependent. The reattachment length increased with rising Re(sub h) while the secondary recirculation region decreased in size. These and other Re(sub h) effects were interpreted in terms of changes in the separating boundary layer thickness and wall-shear stress. On the other hand, in the 3D case, it was found that the imposed cross-flow component was relatively weak in comparison to the streamwise component. As a result, the primary influences of three dimensionality only affected the near-separation region rather than the entire separation bubble.

Hot Film Velocity Measurements Downstream of a Swept Backward-Facing Step

DTIC Science & Technology

1990-08-01

WR ~4’ nol w of tdl. O64" $l"uwe. suite 424 i lV~lZdO . 00 to effice at UAqeww0fl" S4 aud ’mpeom t, 0edUOM ’l~c 004 S~ a lleq~k Dc 2010). I. AGENCY USE ...Velocity measurements were made using a single component hot film anemometer. Results from this study indicate the following: the flow in the recirculation...velocity component parallel to the step face retains a finite magnitude. Coles’ law of the wall and wake was used to corralate the data from this study. The

Selected computations of transonic cavity flows

NASA Technical Reports Server (NTRS)

Atwood, Christopher A.

1993-01-01

An efficient diagonal scheme implemented in an overset mesh framework has permitted the analysis of geometrically complex cavity flows via the Reynolds averaged Navier-Stokes equations. Use of rapid hyperbolic and algebraic grid methods has allowed simple specification of critical turbulent regions with an algebraic turbulence model. Comparisons between numerical and experimental results are made in two dimensions for the following problems: a backward-facing step; a resonating cavity; and two quieted cavity configurations. In three-dimensions the flow about three early concepts of the stratospheric Observatory For Infrared Astronomy (SOFIA) are compared to wind-tunnel data. Shedding frequencies of resolved shear layer structures are compared against experiment for the quieted cavities. The results demonstrate the progress of computational assessment of configuration safety and performance.

Incompressible Navier-Stokes Computations with Heat Transfer

NASA Technical Reports Server (NTRS)

Kiris, Cetin; Kwak, Dochan; Rogers, Stuart; Kutler, Paul (Technical Monitor)

1994-01-01

The existing pseudocompressibility method for the system of incompressible Navier-Stokes equations is extended to heat transfer problems by including the energy equation. The solution method is based on the pseudo compressibility approach and uses an implicit-upwind differencing scheme together with the Gauss-Seidel line relaxation method. Current computations use one-equation Baldwin-Barth turbulence model which is derived from a simplified form of the standard k-epsilon model equations. Both forced and natural convection problems are examined. Numerical results from turbulent reattaching flow behind a backward-facing step will be compared against experimental measurements for the forced convection case. The validity of Boussinesq approximation to simplify the buoyancy force term will be investigated. The natural convective flow structure generated by heat transfer in a vertical rectangular cavity will be studied. The numerical results will be compared by experimental measurements by Morrison and Tran.

Acoustic investigation of wall jet over a backward-facing step using a microphone phased array

NASA Astrophysics Data System (ADS)

Perschke, Raimund F.; Ramachandran, Rakesh C.; Raman, Ganesh

2015-02-01

The acoustic properties of a wall jet over a hard-walled backward-facing step of aspect ratios 6, 3, 2, and 1.5 are studied using a 24-channel microphone phased array at Mach numbers up to M=0.6. The Reynolds number based on inflow velocity and step height assumes values from Reh = 3.0 ×104 to 7.2 ×105. Flow without and with side walls is considered. The experimental setup is open in the wall-normal direction and the expansion ratio is effectively 1. In case of flow through a duct, symmetry of the flow in the spanwise direction is lost downstream of separation at all but the largest aspect ratio as revealed by oil paint flow visualization. Hydrodynamic scattering of turbulence from the trailing edge of the step contributes significantly to the radiated sound. Reflection of acoustic waves from the bottom plate results in a modulation of power spectral densities. Acoustic source localization has been conducted using a 24-channel microphone phased array. Convective mean-flow effects on the apparent source origin have been assessed by placing a loudspeaker underneath a perforated flat plate and evaluating the displacement of the beamforming peak with inflow Mach number. Two source mechanisms are found near the step. One is due to interaction of the turbulent wall jet with the convex edge of the step. Free-stream turbulence sound is found to be peaked downstream of the step. Presence of the side walls increases free-stream sound. Results of the flow visualization are correlated with acoustic source maps. Trailing-edge sound and free-stream turbulence sound can be discriminated using source localization.

On the Unsteady Shock Wave Interaction with a Backward-Facing Step: Viscous Analysis

NASA Astrophysics Data System (ADS)

Mendoza, N.; Bowersox, R. D. W.

Unsteady shock propagation through ducts with varying cross-sectional area occurs in many engineering applications, such as explosions in underground tunnels, blast shelter design, engine exhaust systems, and high-speed propulsion systems. These complex, transient flows are rich in fundamental fluid-dynamic phenomena and are excellent testbeds for improving our understanding of unsteady fluid dynamics

On the influence of airfoil deviations on the aerodynamic performance of wind turbine rotors

NASA Astrophysics Data System (ADS)

Winstroth, J.; Seume, J. R.

2016-09-01

The manufacture of large wind turbine rotor blades is a difficult task that still involves a certain degree of manual labor. Due to the complexity, airfoil deviations between the design airfoils and the manufactured blade are certain to arise. Presently, the understanding of the impact of manufacturing uncertainties on the aerodynamic performance is still incomplete. The present work analyzes the influence of a series of airfoil deviations likely to occur during manufacturing by means of Computational Fluid Dynamics and the aeroelastic code FAST. The average power production of the NREL 5MW wind turbine is used to evaluate the different airfoil deviations. Analyzed deviations include: Mold tilt towards the leading and trailing edge, thick bond lines, thick bond lines with cantilever correction, backward facing steps and airfoil waviness. The most severe influences are observed for mold tilt towards the leading and thick bond lines. By applying the cantilever correction, the influence of thick bond lines is almost compensated. Airfoil waviness is very dependent on amplitude height and the location along the surface of the airfoil. Increased influence is observed for backward facing steps, once they are high enough to trigger boundary layer transition close to the leading edge.

A Near-Wall Reynolds-Stress Closure without Wall Normals

NASA Technical Reports Server (NTRS)

Yuan, S. P.; So, R. M. C.

1997-01-01

With the aid of near-wall asymptotic analysis and results of direct numerical simulation, a new near-wall Reynolds stress model (NNWRS) is formulated based on the SSG high-Reynolds-stress model with wall-independent near-wall corrections. Only one damping function is used for flows with a wide range of Reynolds numbers to ensure that the near-wall modifications diminish away from the walls. The model is able to reproduce complicated flow phenomena induced by complex geometry, such as flow recirculation, reattachment and boundary-layer redevelopment in backward-facing step flow and secondary flow in three-dimensional square duct flow. In simple flows, including fully developed channel/pipe flow, Couette flow and boundary-layer flow, the wall effects are dominant, and the NNWRS model predicts less degree of turbulent anisotropy in the near-wall region compared with a wall-dependent near-wall Reynolds Stress model (NWRS) developed by So and colleagues. The comparison of the predictions given by the two models rectifies the misconception that the overshooting of skin friction coefficient in backward-facing step flow prevalent in those near-wall, models with wall normal is caused by he use of wall normal.

The Effect of Acoustic Forcing on Instabilities and Breakdown in Swept-Wing Flow over a Backward-Facing Step

NASA Technical Reports Server (NTRS)

Eppink, Jenna L.; Shishkov, Olga; Wlezien, Richard W.; King, Rudolph A.; Choudhari, Meelan

2016-01-01

Instability interaction and breakdown were experimentally investigated in the flow over a swept backward-facing step. Acoustic forcing was used to excite the Tollmien-Schlichting (TS) instability and to acquire phase-locked results. The phase-averaged results illustrate the complex nature of the interaction between the TS and stationary cross flow instabilities. The weak stationary cross flow disturbance causes a distortion of the TS wavefront. The breakdown process is characterized by large positive and negative spikes in velocity. The positive spikes occur near the same time and location as the positive part of the TS wave. Higher-order spectral analysis was used to further investigate the nonlinear interactions between the TS instability and the traveling cross flow disturbances. The results reveal that a likely cause for the generation of the spikes corresponds to nonlinear interactions between the TS, traveling cross flow, and stationary cross flow disturbances. The spikes begin at low amplitudes of the unsteady and steady disturbances (2-4% U (sub e) (i.e. boundary layer edge velocity)) but can achieve very large amplitudes (20-30 percent U (sub e) (i.e. boundary layer edge velocity)) that initiate an early, though highly intermittent, breakdown to turbulence.

Re-evaluation of an Optimized Second Order Backward Difference (BDF2OPT) Scheme for Unsteady Flow Applications

NASA Technical Reports Server (NTRS)

Vatsa, Veer N.; Carpenter, Mark H.; Lockard, David P.

2009-01-01

Recent experience in the application of an optimized, second-order, backward-difference (BDF2OPT) temporal scheme is reported. The primary focus of the work is on obtaining accurate solutions of the unsteady Reynolds-averaged Navier-Stokes equations over long periods of time for aerodynamic problems of interest. The baseline flow solver under consideration uses a particular BDF2OPT temporal scheme with a dual-time-stepping algorithm for advancing the flow solutions in time. Numerical difficulties are encountered with this scheme when the flow code is run for a large number of time steps, a behavior not seen with the standard second-order, backward-difference, temporal scheme. Based on a stability analysis, slight modifications to the BDF2OPT scheme are suggested. The performance and accuracy of this modified scheme is assessed by comparing the computational results with other numerical schemes and experimental data.

Passive control of coherent structures in a modified backwards-facing step flow

NASA Astrophysics Data System (ADS)

Ormonde, Pedro C.; Cavalieri, André V. G.; Silva, Roberto G. A. da; Avelar, Ana C.

2018-05-01

We study a modified backwards-facing step flow, with the addition of two different plates; one is a baseline, impermeable plate and the second a perforated one. An experimental investigation is carried out for a turbulent reattaching shear layer downstream of the two plates. The proposed setup is a model configuration to study how the plate characteristics affect the separated shear layer and how turbulent kinetic energies and large-scale coherent structures are modified. Measurements show that the perforated plate changes the mean flow field, mostly by reducing the intensity of reverse flow close to the bottom wall. Disturbance amplitudes are significantly reduced up to five step heights downstream of the trailing edge of the plate, more specifically in the recirculation region. A loudspeaker is then used to introduce phase-locked, low-amplitude perturbations upstream of the plates, and phase-averaged measurements allow a quantitative study of large-scale structures in the shear-layer. The evolution of such coherent structures is evaluated in light of linear stability theory, comparing the eigenfunction of the Kelvin-Helmholtz mode to the experimental results. We observe a close match of linear-stability eigenfunctions with phase-averaged amplitudes for the two tested Strouhal numbers. The perforated plate is found to reduce the amplitude of the Kelvin-Helmholtz coherent structures in comparison to the baseline, impermeable plate, a behavior consistent with the predicted amplification trends from linear stability.

Investigation of obstacle effect to improve conjugate heat transfer in backward facing step channel using fast simulation of incompressible flow

NASA Astrophysics Data System (ADS)

Nouri-Borujerdi, Ali; Moazezi, Arash

2018-01-01

The current study investigates the conjugate heat transfer characteristics for laminar flow in backward facing step channel. All of the channel walls are insulated except the lower thick wall under a constant temperature. The upper wall includes a insulated obstacle perpendicular to flow direction. The effect of obstacle height and location on the fluid flow and heat transfer are numerically explored for the Reynolds number in the range of 10 ≤ Re ≤ 300. Incompressible Navier-Stokes and thermal energy equations are solved simultaneously in fluid region by the upwind compact finite difference scheme based on flux-difference splitting in conjunction with artificial compressibility method. In the thick wall, the energy equation is obtained by Laplace equation. A multi-block approach is used to perform parallel computing to reduce the CPU time. Each block is modeled separately by sharing boundary conditions with neighbors. The developed program for modeling was written in FORTRAN language with OpenMP API. The obtained results showed that using of the multi-block parallel computing method is a simple robust scheme with high performance and high-order accurate. Moreover, the obtained results demonstrated that the increment of Reynolds number and obstacle height as well as decrement of horizontal distance between the obstacle and the step improve the heat transfer.

Investigation of Content and Face Validity and Reliability of Sociocultural Attitude towards Appearance Questionnaire-3 (SATAQ-3) among Female Adolescents

PubMed Central

Mousazadeh, Somayeh; Rakhshan, Mahnaz; Mohammadi, Fateme

2017-01-01

Objective: This study aimed to determine the psychometric properties of sociocultural attitude towards appearance questionnaire in female adolescents. Method: This was a methodological study. The English version of the questionnaire was translated into Persian, using forward-backward method. Then the face validity, content validity and reliability were checked. To ensure face validity, the questionnaire was given to 25 female adolescents, a psychologist and three nurses, who were required to evaluate the items with respect to problems, ambiguity, relativity, proper terms and grammar, and understandability. For content validity, 15 experts in psychology and nursing, who met the inclusion criteria, were required. They were asked to assess the qualitative of content validity. To determine the quantitative content validity, content validity index and content validity ratio were calculated. At the end, internal consistency of the items was assessed, using Cronbach’s alpha method. Results: According to the expert judgments, content validity ratio was 0.81 and content validity index was 0.91. Besides, the reliability of the questionnaire was confirmed with Cronbach’s alpha = 0.91, and physical and developmental areas showed the highest reliability indices. Conclusion: The aforementioned questionnaire could be used in researches to assess female adolescents’ self-concept. This can be a stepping-stone towards identification of problems and improvement of adolescents’ body image. PMID:28496497

A Great LEEP Backward?

ERIC Educational Resources Information Center

Allinson, Richard S.

1980-01-01

The federal government's Law Enforcement Education Program (LEEP) faces a precarious future. Three problems include: a bureaucratic tug-of-war between the Justice Department and the new Department of Education, the loss of appropriations, and a debate about the values of programs, and the types of courses and degrees offered. (MLW)

Evaluation of a wave-vector-frequency-domain method for nonlinear wave propagation

PubMed Central

Jing, Yun; Tao, Molei; Clement, Greg T.

2011-01-01

A wave-vector-frequency-domain method is presented to describe one-directional forward or backward acoustic wave propagation in a nonlinear homogeneous medium. Starting from a frequency-domain representation of the second-order nonlinear acoustic wave equation, an implicit solution for the nonlinear term is proposed by employing the Green’s function. Its approximation, which is more suitable for numerical implementation, is used. An error study is carried out to test the efficiency of the model by comparing the results with the Fubini solution. It is shown that the error grows as the propagation distance and step-size increase. However, for the specific case tested, even at a step size as large as one wavelength, sufficient accuracy for plane-wave propagation is observed. A two-dimensional steered transducer problem is explored to verify the nonlinear acoustic field directional independence of the model. A three-dimensional single-element transducer problem is solved to verify the forward model by comparing it with an existing nonlinear wave propagation code. Finally, backward-projection behavior is examined. The sound field over a plane in an absorptive medium is backward projected to the source and compared with the initial field, where good agreement is observed. PMID:21302985

Numerical solution of the incompressible Navier-Stokes equations. Ph.D. Thesis - Stanford Univ., Mar. 1989

NASA Technical Reports Server (NTRS)

Rogers, Stuart E.

1990-01-01

The current work is initiated in an effort to obtain an efficient, accurate, and robust algorithm for the numerical solution of the incompressible Navier-Stokes equations in two- and three-dimensional generalized curvilinear coordinates for both steady-state and time-dependent flow problems. This is accomplished with the use of the method of artificial compressibility and a high-order flux-difference splitting technique for the differencing of the convective terms. Time accuracy is obtained in the numerical solutions by subiterating the equations in psuedo-time for each physical time step. The system of equations is solved with a line-relaxation scheme which allows the use of very large pseudo-time steps leading to fast convergence for steady-state problems as well as for the subiterations of time-dependent problems. Numerous laminar test flow problems are computed and presented with a comparison against analytically known solutions or experimental results. These include the flow in a driven cavity, the flow over a backward-facing step, the steady and unsteady flow over a circular cylinder, flow over an oscillating plate, flow through a one-dimensional inviscid channel with oscillating back pressure, the steady-state flow through a square duct with a 90 degree bend, and the flow through an artificial heart configuration with moving boundaries. An adequate comparison with the analytical or experimental results is obtained in all cases. Numerical comparisons of the upwind differencing with central differencing plus artificial dissipation indicates that the upwind differencing provides a much more robust algorithm, which requires significantly less computing time. The time-dependent problems require on the order of 10 to 20 subiterations, indicating that the elliptical nature of the problem does require a substantial amount of computing effort.

Data-driven backward chaining

NASA Technical Reports Server (NTRS)

Haley, Paul

1991-01-01

The C Language Integrated Production System (CLIPS) cannot effectively perform sound and complete logical inference in most real-world contexts. The problem facing CLIPS is its lack of goal generation. Without automatic goal generation and maintenance, forward chaining can only deduce all instances of a relationship. Backward chaining, which requires goal generation, allows deduction of only that subset of what is logically true which is also relevant to ongoing problem solving. Goal generation can be mimicked in simple cases using forward chaining. However, such mimicry requires manual coding of additional rules which can assert an inadequate goal representation for every condition in every rule that can have corresponding facts derived by backward chaining. In general, for N rules with an average of M conditions per rule the number of goal generation rules required is on the order of N*M. This is clearly intractable from a program maintenance perspective. We describe the support in Eclipse for backward chaining which it automatically asserts as it checks rule conditions. Important characteristics of this extension are that it does not assert goals which cannot match any rule conditions, that 2 equivalent goals are never asserted, and that goals persist as long as, but no longer than, they remain relevant.

Preconditioned conjugate-gradient methods for low-speed flow calculations

NASA Technical Reports Server (NTRS)

Ajmani, Kumud; Ng, Wing-Fai; Liou, Meng-Sing

1993-01-01

An investigation is conducted into the viability of using a generalized Conjugate Gradient-like method as an iterative solver to obtain steady-state solutions of very low-speed fluid flow problems. Low-speed flow at Mach 0.1 over a backward-facing step is chosen as a representative test problem. The unsteady form of the two dimensional, compressible Navier-Stokes equations is integrated in time using discrete time-steps. The Navier-Stokes equations are cast in an implicit, upwind finite-volume, flux split formulation. The new iterative solver is used to solve a linear system of equations at each step of the time-integration. Preconditioning techniques are used with the new solver to enhance the stability and convergence rate of the solver and are found to be critical to the overall success of the solver. A study of various preconditioners reveals that a preconditioner based on the Lower-Upper Successive Symmetric Over-Relaxation iterative scheme is more efficient than a preconditioner based on Incomplete L-U factorizations of the iteration matrix. The performance of the new preconditioned solver is compared with a conventional Line Gauss-Seidel Relaxation (LGSR) solver. Overall speed-up factors of 28 (in terms of global time-steps required to converge to a steady-state solution) and 20 (in terms of total CPU time on one processor of a CRAY-YMP) are found in favor of the new preconditioned solver, when compared with the LGSR solver.

Preconditioned Conjugate Gradient methods for low speed flow calculations

NASA Technical Reports Server (NTRS)

Ajmani, Kumud; Ng, Wing-Fai; Liou, Meng-Sing

1993-01-01

An investigation is conducted into the viability of using a generalized Conjugate Gradient-like method as an iterative solver to obtain steady-state solutions of very low-speed fluid flow problems. Low-speed flow at Mach 0.1 over a backward-facing step is chosen as a representative test problem. The unsteady form of the two dimensional, compressible Navier-Stokes equations are integrated in time using discrete time-steps. The Navier-Stokes equations are cast in an implicit, upwind finite-volume, flux split formulation. The new iterative solver is used to solve a linear system of equations at each step of the time-integration. Preconditioning techniques are used with the new solver to enhance the stability and the convergence rate of the solver and are found to be critical to the overall success of the solver. A study of various preconditioners reveals that a preconditioner based on the lower-upper (L-U)-successive symmetric over-relaxation iterative scheme is more efficient than a preconditioner based on incomplete L-U factorizations of the iteration matrix. The performance of the new preconditioned solver is compared with a conventional line Gauss-Seidel relaxation (LGSR) solver. Overall speed-up factors of 28 (in terms of global time-steps required to converge to a steady-state solution) and 20 (in terms of total CPU time on one processor of a CRAY-YMP) are found in favor of the new preconditioned solver, when compared with the LGSR solver.

The Analysis of Forward and Backward Dynamic Programming for Multistage Graph

NASA Astrophysics Data System (ADS)

Sitinjak, Anna Angela; Pasaribu, Elvina; Simarmata, Justin E.; Putra, Tedy; Mawengkang, Herman

2018-01-01

Dynamic programming is an optimization approach that divides the complex problems into the simple sequences of problems in which they are interrelated leading to decisions. In the dynamic programming, there is no standard formula that can be used to make a certain formulation. In this paper we use forward and backward method to find path which have the minimum cost and to know whether they make the same final decision. Convert the problem into several successive sequential stages starting on from stages 1,2,3 and 4 for forward dynamic programming and the step back from stage 4.3,2,1 for backward dynamic programming and interconnected with a decision rule in each stage. Find the optimal solution with cost principle at next stage. Based on the characteristics of the dynamic programming, the case is divided into several stages and the decision is has to be made (xk) at each stage. The results obtained at a stage are used for the states in the next stage so that at the forward stage 1, f1 (s) is obtained and used as a consideration of the decision in the next stage. In the backward, used firstly stage 4, f4 (s) is obtained and used as a consideration of the decision in the next stage. Cost forward and backward always increase steadily, because the cost in the next stage depends on the cost in the previous stage and formed the decision of each stage by taking the smallest fk value. Therefore the forward and backward approaches have the same result.

An Experimental Study of a Separated/Reattached Flow Behind a Backward-Facing Step. Re(sub h) = 37,000

NASA Technical Reports Server (NTRS)

Jovic, Srba

1996-01-01

An experimental study was carried out to investigate turbulent structure of a two-dimensional incompressible separating/reattaching boundary layer behind a backward-facing step. Hot-wire measurement technique was used to measure three Reynolds stresses and higher-order mean products of velocity fluctuations. The Reynolds number, Re(sub h), based on the step height, h, and the reference velocity, U(sub 0), was 37,000. The upstream oncoming flow was fully developed turbulent boundary layer with the Re(sub theta) = 3600. All turbulent properties, such as Reynolds stresses, increase dramatically downstream of the step within an internally developing mixing layer. Distributions of dimensionless mean velocity, turbulent quantities and antisymmetric distribution of triple velocity products in the separated free shear layer suggest that the shear layer above the recirculating region strongly resembles free-shear mixing layer structure. In the reattachment region close to the wall, turbulent diffusion term balances the rate of dissipation since advection and production terms appear to be negligibly small. Further downstream, production and dissipation begin to dominate other transport processes near the wall indicating the growth of an internal turbulent boundary layer. In the outer region, however, the flow still has a memory of the upstream disturbance even at the last measuring station of 51 step-heights. The data show that the structure of the inner layer recovers at a much faster rate than the outer layer structure. The inner layer structure resembles the near-wall structure of a plane zero pressure-gradient turbulent boundary layer (plane TBL) by 25h to 30h, while the outer layer structure takes presumably over 100h.

Studying Turbulence Using Numerical Simulation Databases. Part 6; Proceedings of the 1996 Summer Program

NASA Technical Reports Server (NTRS)

1996-01-01

Topics considered include: New approach to turbulence modeling; Second moment closure analysis of the backstep flow database; Prediction of the backflow and recovery regions in the backward facing step at various Reynolds numbers; Turbulent flame propagation in partially premixed flames; Ensemble averaged dynamic modeling. Also included a study of the turbulence structures of wall-bounded shear flows; Simulation and modeling of the elliptic streamline flow.

Improvement of the Reynolds-stress model by a new pressure-strain correlation

NASA Technical Reports Server (NTRS)

Amano, Ryoichi S.; Chai, John C.

1988-01-01

A study is made to improve the predictions of Reynolds stresses in backward facing step flows, through modifications of the pressure-strain correlation. The mean-strain term of the pressure-strain correlation is formulated only in terms of nonisotropic turbulence in order to take the severe nonisotropic effect caused by a separating flow. This model is compared with other models and results are verified with experimental results.

Discrete maximal regularity of time-stepping schemes for fractional evolution equations.

PubMed

Jin, Bangti; Li, Buyang; Zhou, Zhi

2018-01-01

In this work, we establish the maximal [Formula: see text]-regularity for several time stepping schemes for a fractional evolution model, which involves a fractional derivative of order [Formula: see text], [Formula: see text], in time. These schemes include convolution quadratures generated by backward Euler method and second-order backward difference formula, the L1 scheme, explicit Euler method and a fractional variant of the Crank-Nicolson method. The main tools for the analysis include operator-valued Fourier multiplier theorem due to Weis (Math Ann 319:735-758, 2001. doi:10.1007/PL00004457) and its discrete analogue due to Blunck (Stud Math 146:157-176, 2001. doi:10.4064/sm146-2-3). These results generalize the corresponding results for parabolic problems.

The effects of backward walking training on balance and mobility in an individual with chronic incomplete spinal cord injury: A case report.

PubMed

Foster, Hannah; DeMark, Lou; Spigel, Pamela M; Rose, Dorian K; Fox, Emily J

2016-10-01

Individuals with incomplete spinal cord injuries (ISCIs) commonly face persistent gait impairments. Backward walking training may be a useful rehabilitation approach, providing novel gait and balance challenges. However, little is known about the effects of this approach for individuals with ISCIs. The purpose of this case report was to describe the effects of backward walking training on strength, balance, and upright mobility in an individual with chronic ISCI. A 28-year-old female, 11-years post ISCI (C4, AIS D) completed 18-sessions of backward walking training on a treadmill with partial body-weight support and overground. Training emphasized stepping practice, speed, and kinematics. Outcome measures included: Lower Extremity Motor Score, Berg Balance Scale (BBS), Sensory Organization Test (SOT), 10-Meter Walk Test (10MWT), 3-meter backward walking test, Timed Up and Go (TUG), and Activities-Specific Balance Confidence (ABC) Scale. Strength did not change. Improved balance was evident based on BBS (20 to 37/56) and SOT scores (27 to 40/100). Upright mobility improved based on TUG times (57 to 32.7 s), increased 10MWT speed (0.23 to 0.31 m/s), and backward gait speed (0.07 to 0.12 m/s). Additionally, self-reported balance confidence (ABC Scale) increased from 36.9% to 49.6%. The results suggest that backward walking may be a beneficial rehabilitation approach; examination of the clinical efficacy is warranted.

The effects of backward walking training on balance and mobility in an individual with chronic incomplete spinal cord injury: A case report

PubMed Central

Foster, Hannah; DeMark, Lou; Spigel, Pamela M.; Rose, Dorian K.; Fox, Emily J.

2016-01-01

Background/Purpose Individuals with incomplete spinal cord injuries (ISCIs) commonly face persistent gait impairments. Backward walking training may be a useful rehabilitation approach, providing novel gait and balance challenges. However, little is known about the effects of this approach for individuals with ISCIs. The purpose of this case report was to describe the effects of backward walking training on strength, balance and upright mobility in an individual with chronic ISCI. Methods A 28-year-old female, 11-years post ISCI (C4, AIS D) completed 18-sessions of backward walking training on a treadmill with partial body-weight support and overground. Training emphasized stepping practice, speed, and kinematics. Outcome measures included: Lower Extremity Motor Score, Berg Balance Scale (BBS), Sensory Organization Test (SOT); 10-Meter Walk Test (10MWT), 3-meter backward walking test, Timed Up and Go (TUG), and Activities-Specific Balance Confidence (ABC) Scale. Results Strength did not change. Improved balance was evident based on BBS (20 to 37/56) and SOT scores (27 to 40/100). Upright mobility improved based on TUG times (57 to 32.7 s), increased 10MWT speed (0.23 to 0.31 m/s), and backward gait speed (0.07 to 0.12 m/s). Additionally, self-reported balance confidence (ABC Scale) increased from 36.9% to 49.6%. Conclusions The results suggest that backward walking may be a beneficial rehabilitation approach; examination of the clinical efficacy is warranted. PMID:27482619

PETOOL: MATLAB-based one-way and two-way split-step parabolic equation tool for radiowave propagation over variable terrain

NASA Astrophysics Data System (ADS)

Ozgun, Ozlem; Apaydin, Gökhan; Kuzuoglu, Mustafa; Sevgi, Levent

2011-12-01

A MATLAB-based one-way and two-way split-step parabolic equation software tool (PETOOL) has been developed with a user-friendly graphical user interface (GUI) for the analysis and visualization of radio-wave propagation over variable terrain and through homogeneous and inhomogeneous atmosphere. The tool has a unique feature over existing one-way parabolic equation (PE)-based codes, because it utilizes the two-way split-step parabolic equation (SSPE) approach with wide-angle propagator, which is a recursive forward-backward algorithm to incorporate both forward and backward waves into the solution in the presence of variable terrain. First, the formulation of the classical one-way SSPE and the relatively-novel two-way SSPE is presented, with particular emphasis on their capabilities and the limitations. Next, the structure and the GUI capabilities of the PETOOL software tool are discussed in detail. The calibration of PETOOL is performed and demonstrated via analytical comparisons and/or representative canonical tests performed against the Geometric Optic (GO) + Uniform Theory of Diffraction (UTD). The tool can be used for research and/or educational purposes to investigate the effects of a variety of user-defined terrain and range-dependent refractivity profiles in electromagnetic wave propagation. Program summaryProgram title: PETOOL (Parabolic Equation Toolbox) Catalogue identifier: AEJS_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJS_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 143 349 No. of bytes in distributed program, including test data, etc.: 23 280 251 Distribution format: tar.gz Programming language: MATLAB (MathWorks Inc.) 2010a. Partial Differential Toolbox and Curve Fitting Toolbox required Computer: PC Operating system: Windows XP and Vista Classification: 10 Nature of problem: Simulation of radio-wave propagation over variable terrain on the Earth's surface, and through homogeneous and inhomogeneous atmosphere. Solution method: The program implements one-way and two-way Split-Step Parabolic Equation (SSPE) algorithm, with wide-angle propagator. The SSPE is, in general, an initial-value problem starting from a reference range (typically from an antenna), and marching out in range by obtaining the field along the vertical direction at each range step, through the use of step-by-step Fourier transformations. The two-way algorithm incorporates the backward-propagating waves into the standard one-way SSPE by utilizing an iterative forward-backward scheme for modeling multipath effects over a staircase-approximated terrain. Unusual features: This is the first software package implementing a recursive forward-backward SSPE algorithm to account for the multipath effects during radio-wave propagation, and enabling the user to easily analyze and visualize the results of the two-way propagation with GUI capabilities. Running time: Problem dependent. Typically, it is about 1.5 ms (for conducting ground) and 4 ms (for lossy ground) per range step for a vertical field profile of vector length 1500, on Intel Core 2 Duo 1.6 GHz with 2 GB RAM under Windows Vista.

Time Resolved Stereo Particle Image Velocimetry Measurements of the Instabilities Downstream of a Backward-Facing Step in a Swept-Wing Boundary Layer

NASA Technical Reports Server (NTRS)

Eppink, Jenna L.; Yao, Chung-Sheng

2017-01-01

Time-resolved particle image velocimetry (TRPIV) measurements are performed down-stream of a swept backward-facing step, with a height of 49% of the boundary-layer thickness. The results agree well qualitatively with previously reported hotwire measurements, though the amplitudes of the fluctuating components measured using TRPIV are higher. Nonetheless, the low-amplitude instabilities in the flow are fairly well resolved using TR- PIV. Proper orthogonal decomposition is used to study the development of the traveling cross flow and Tollmien-Schlichting (TS) instabilities downstream of the step and to study how they interact to form the large velocity spikes that ultimately lead to transition. A secondary mode within the traveling cross flow frequency band develops with a wavelength close to that of the stationary cross flow instability, so that at a certain point in the phase, it causes an increase in the spanwise modulation initially caused by the stationary cross flow mode. This increased modulation leads to an increase in the amplitude of the TS mode, which, itself, is highly modulated through interactions with the stationary cross flow. When the traveling cross flow and TS modes align in time and space, the large velocity spikes occur. Thus, these three instabilities, which are individually of low amplitude when the spikes start to occur (U'rms/Ue <0.03), interact and combine to cause a large flow disturbance that eventually leads to transition.

High-Spatial-Resolution OH PLIF Visualization in a Cavity-Stabilized Ethylene-Air Turbulent Flame

NASA Technical Reports Server (NTRS)

Geipel, Clayton M.; Rockwell, Robert D.; Chelliah, Harsha K.; Cutler, Andrew D.; Spelker, Christopher A.; Hashem, Zeid; Danehy, Paul M.

2017-01-01

High-spatial-resolution OH planar laser-induced fluorescence was measured for a premixed ethylene-air turbulent flame in an electrically-heated Mach 2 continuous-flow facility (University of Virginia Supersonic Combustion Facility, Configuration E.) The facility comprised a Mach 2 nozzle, an isolator with flush-wall fuel injectors, a combustor with optical access, and an extender. The flame was anchored at a cavity flameholder with a backward-facing step of height 9 mm. The temperature-insensitive Q1(8) transition of OH was excited using laser light of wavelength 283.55 nm. A spatial filter was used to create a laser sheet approximately 25 microns thick based on full-width at half maximum (FWHM). Extension tubes increased the magnification of an intensified camera system, achieving in-plane resolution of 40 microns based on a 50% modulation transfer function (MTF). The facility was tested with total temperature 1200 K, total pressure 300 kPa, local fuel/air equivalence ratios of approximately 0.4, and local Mach number of approximately 0.73 in the combustor. A test case with reduced total temperature and another with reduced equivalence ratio were also tested. PLIF images were acquired along a streamwise plane bisecting the cavity flameholder, from the backward facing step to 120 mm downstream of the step. The smallest observed features in the flow had width of approximately 110 microns. Flame surface density was calculated for OH PLIF images.

How to find home backwards? Navigation during rearward homing of Cataglyphis fortis desert ants.

PubMed

Pfeffer, Sarah E; Wittlinger, Matthias

2016-07-15

Cataglyphis ants are renowned for their impressive navigation skills, which have been studied in numerous experiments during forward locomotion. However, the ants' navigational performance during backward homing when dragging large food loads has not been investigated until now. During backward locomotion, the odometer has to deal with unsteady motion and irregularities in inter-leg coordination. The legs' sensory feedback during backward walking is not just a simple reversal of the forward stepping movements: compared with forward homing, ants are facing towards the opposite direction during backward dragging. Hence, the compass system has to cope with a flipped celestial view (in terms of the polarization pattern and the position of the sun) and an inverted retinotopic image of the visual panorama and landmark environment. The same is true for wind and olfactory cues. In this study we analyze for the first time backward-homing ants and evaluate their navigational performance in channel and open field experiments. Backward-homing Cataglyphis fortis desert ants show remarkable similarities in the performance of homing compared with forward-walking ants. Despite the numerous challenges emerging for the navigational system during backward walking, we show that ants perform quite well in our experiments. Direction and distance gauging was comparable to that of the forward-walking control groups. Interestingly, we found that backward-homing ants often put down the food item and performed foodless search loops around the left food item. These search loops were mainly centred around the drop-off position (and not around the nest position), and increased in length the closer the ants came to their fictive nest site. © 2016. Published by The Company of Biologists Ltd.

Development of a recursion RNG-based turbulence model

NASA Technical Reports Server (NTRS)

Zhou, YE; Vahala, George; Thangam, S.

1993-01-01

Reynolds stress closure models based on the recursion renormalization group theory are developed for the prediction of turbulent separated flows. The proposed model uses a finite wavenumber truncation scheme to account for the spectral distribution of energy. In particular, the model incorporates effects of both local and nonlocal interactions. The nonlocal interactions are shown to yield a contribution identical to that from the epsilon-renormalization group (RNG), while the local interactions introduce higher order dispersive effects. A formal analysis of the model is presented and its ability to accurately predict separated flows is analyzed from a combined theoretical and computational stand point. Turbulent flow past a backward facing step is chosen as a test case and the results obtained based on detailed computations demonstrate that the proposed recursion -RNG model with finite cut-off wavenumber can yield very good predictions for the backstep problem.

Using Backward Design in Education Research: A Research Methods Essay †

PubMed Central

Jensen, Jamie L.; Bailey, Elizabeth G.; Kummer, Tyler A.; Weber, K. Scott

2017-01-01

Education research within the STEM disciplines applies a scholarly approach to teaching and learning, with the intent of better understanding how people learn and of improving pedagogy at the undergraduate level. Most of the professionals practicing in this field have ‘crossed over’ from other disciplinary fields and thus have faced challenges in becoming experts in a new discipline. In this article, we offer a novel framework for approaching education research design called Backward Design in Education Research. It is patterned on backward curricular design and provides a three-step, systematic approach to designing education projects: 1) Define a research question that leads to a testable causal hypothesis based on a theoretical rationale; 2) Choose or design the assessment instruments to test the research hypothesis; and 3) Develop an experimental protocol that will be effective in testing the research hypothesis. This approach provides a systematic method to develop and carry out evidence-based research design. PMID:29854045

Whole-Motion Model of Perception during Forward- and Backward-Facing Centrifuge Runs

PubMed Central

Holly, Jan E.; Vrublevskis, Arturs; Carlson, Lindsay E.

2009-01-01

Illusory perceptions of motion and orientation arise during human centrifuge runs without vision. Asymmetries have been found between acceleration and deceleration, and between forward-facing and backward-facing runs. Perceived roll tilt has been studied extensively during upright fixed-carriage centrifuge runs, and other components have been studied to a lesser extent. Certain, but not all, perceptual asymmetries in acceleration-vs-deceleration and forward-vs-backward motion can be explained by existing analyses. The immediate acceleration-deceleration roll-tilt asymmetry can be explained by the three-dimensional physics of the external stimulus; in addition, longer-term data has been modeled in a standard way using physiological time constants. However, the standard modeling approach is shown in the present research to predict forward-vs-backward-facing symmetry in perceived roll tilt, contradicting experimental data, and to predict perceived sideways motion, rather than forward or backward motion, around a curve. The present work develops a different whole-motion-based model taking into account the three-dimensional form of perceived motion and orientation. This model predicts perceived forward or backward motion around a curve, and predicts additional asymmetries such as the forward-backward difference in roll tilt. This model is based upon many of the same principles as the standard model, but includes an additional concept of familiarity of motions as a whole. PMID:19208962

Advancing Detached-Eddy Simulation

DTIC Science & Technology

2007-01-01

fluxes leads to an improvement in the stability of the solution . This matrix is solved iteratively using a symmetric Gauss - Seidel procedure. Newtons sub...model (TLM) is a zonal approach, proposed by Balaras and Benocci (5) and Balaras et al. (4). The method involved the solution of filtered Navier...LES mesh. The method was subsequently used by Cabot (6) and Diurno et al. (7) to obtain the solution of the flow over a backward facing step and by

Application of a new K-tau model to near wall turbulent flows

NASA Technical Reports Server (NTRS)

Thangam, S.; Abid, R.; Speziale, Charles G.

1991-01-01

A recently developed K-tau model for near wall turbulent flows is applied to two severe test cases. The turbulent flows considered include the incompressible flat plate boundary layer with the adverse pressure gradients and incompressible flow past a backward facing step. Calculations are performed for this two-equation model using an anisotropic as well as isotropic eddy-viscosity. The model predictions are shown to compare quite favorably with experimental data.

A successful backward step correlates with hip flexion moment of supporting limb in elderly people.

PubMed

Takeuchi, Yahiko

2018-01-01

The objective of this study was to determine the positional relationship between the center of mass (COM) and the center of pressure (COP) at the time of step landing, and to examine their relationship with the joint moments exerted by the supporting limb, with regard to factors of the successful backward step response. The study population comprised 8 community-dwelling elderly people that were observed to take successive multi steps after the landing of a backward stepping. Using a motion capture system and force plate, we measured the COM, COP and COM-COP deviation distance on landing during backward stepping. In addition, we measured the moment of the supporting limb joint during backward stepping. The multi-step data were compared with data from instances when only one step was taken (single-step). Variables that differed significantly between the single- and multi-step data were used as objective variables and the joint moments of the supporting limb were used as explanatory variables in single regression analyses. The COM-COP deviation in the anteroposterior was significantly larger in the single-step. A regression analysis with COM-COP deviation as the objective variable obtained a significant regression equation in the hip flexion moment (R2 = 0.74). The hip flexion moment of supporting limb was shown to be a significant explanatory variable in both the PS and SS phases for the relationship with COM-COP distance. This study found that to create an appropriate backward step response after an external disturbance (i.e. the ability to stop after 1 step), posterior braking of the COM by a hip flexion moment are important during the single-limbed standing phase.

Recovery of forward stepping in spinal cord injured patients does not transfer to untrained backward stepping.

PubMed

Grasso, Renato; Ivanenko, Yuri P; Zago, Myrka; Molinari, Marco; Scivoletto, Giorgio; Lacquaniti, Francesco

2004-08-01

Six spinal cord injured (SCI) patients were trained to step on a treadmill with body-weight support for 1.5-3 months. At the end of training, foot motion recovered the shape and the step-by-step reproducibility that characterize normal gait. They were then asked to step backward on the treadmill belt that moved in the opposite direction relative to standard forward training. In contrast to healthy subjects, who can immediately reverse the direction of walking by time-reversing the kinematic waveforms, patients were unable to step backward. Similarly patients were unable to perform another untrained locomotor task, namely stepping in place on the idle treadmill. Two patients who were trained to step backward for 2-3 weeks were able to develop control of foot motion appropriate for this task. The results show that locomotor improvement does not transfer to untrained tasks, thus supporting the idea of task-dependent plasticity in human locomotor networks.

Numerical solutions of pulsating flow and heat transfer characteristics in a channel with a backward-facing step

NASA Astrophysics Data System (ADS)

Valencia, A.; Hinojosa, L.

The incompressible laminar flow of air and heat transfer in a channel with a backward-facing step is studied for steady cases and for pulsatile inlet conditions. For steady flows the influence of the inlet velocity profile, the height of the step and the Reynolds number on the reattachment length is investigated. A parabolic entrance profile was used for pulsatile flow. It was found with amplitude of oscillation of one by Re=100 that the primary vortex breakdown through one pulsatile cycle. The wall shear rate in the separation zone varied markedly with pulsatile flows and the wall heat transfer remained relatively constant. The time-average pulsatile heat transfer at the walls was greater as with steady flow with the same mean Reynolds number. Zusammenfassung Es wird eine zweidimensionale numerische Untersuchung des instationären Wärmeübergangs und Druckverlustes im laminar durchströmten Spaltkanal mit einer plötzlichen Kanalerweiterung dargelegt und zwar für stationäre und periodische Geschwindigkeitsprofile am Eintritt des Kanals. Für stationäre Strömungen wurden die Form des Eintrittsprofils, die Reynoldszahl und die Kanalerweiterung variiert. Als Lösung der Navier/Stokes-und der Energiegleichungen mit periodischen Randbedingungen resultiert eine oszillierende Strömung, die das Aufplatzen des Primärwirbels in einer Schwingungsperiode zur Folge hat. Der Einfluß dieser Oszillation auf den Wärmeübergang und den Strömungsverlust wurde für die maximale Amplitude und für Re=100 eingehend untersucht.

Validation of SIV measurements of turbulent characteristics in the separation region

NASA Astrophysics Data System (ADS)

Dushin, N. S.; Mikheev, N. I.; Dushina, O. A.; Zaripov, D. I.; Aslaev, A. K.

2017-11-01

Temporally and spatially resolved 2D measurements are important for the studies of complex turbulent flows. The recently developed SIV technique (Smoke Image Velocimetry), which is superior to PIV in some cases, can be used for this purpose. SIV validation results are presented for the steady turbulent backward-facing step flow measurements. Velocity profiles and Reynolds stress profiles are given for the regions of oncoming flow, reverse flow, flow reattachment and relaxation. The Reynolds number based on the step height and oncoming flow velocity at the boundary layer edge was Reh = 4834. The obtained data have been compared to LDA measurements and DNS.

Post detonation nuclear forensics

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

Davis, Jay

2014-05-09

The problem of working backwards from the debris of a nuclear explosion to attempt to attribute the event to a particular actor is singularly difficult technically. However, moving from physical information of any certainty through the political steps that would lead to national action presents daunting policy questions as well. This monograph will outline the operational and physical components of this problem and suggest the difficulty of the policy questions that remain.

Shock-Induced Heating In A Rocket Engine

NASA Technical Reports Server (NTRS)

Lagnado, Ronald R.; Raiszadeh, Farhad

1989-01-01

Misalignments give rise to hotspots on walls. Report discusses numerical simulation of flow in and near small, ringlike cavity in wall of Space Shuttle main engine at junction of main combustion chamber and nozzle. Purpose to study effects of misalignments between combustion chamber and nozzle on transfer of heat into surfaces chamber, cavity, and nozzle. Depending on specific misalignment flow encounters forward-or backward-facing step leaving chamber and entering nozzle. Results in serious losses of performance and excessive heating of walls.

Application of mean wall shear stress boundary condition to complex turbulent flows using a wall-modeled large eddy simulation

NASA Astrophysics Data System (ADS)

Cho, Minjeong; Lee, Jungil; Choi, Haecheon

2012-11-01

The mean wall shear stress boundary condition was successfully applied to turbulent channel and boundary flows using large eddy simulation without resolving near-wall region (see Lee, Cho & Choi in this book of abstracts). In the present study, we apply this boundary condition to more complex flows where flow separation and redeveloping flow exist. As a test problem, we consider flow over a backward-facing step at Reh = 22860 based on the step height. Turbulent boundary layer flow at the inlet (Reθ = 1050) is obtained using inflow generation technique by Lund et al. (1998) but with wall shear stress boundary condition. First, we prescribe the mean wall shear stress distribution obtained from DNS (Kim, 2011, Ph.D. Thesis, Stanford U.) as the boundary condition of present simulation. Here we give no-slip boundary condition at flow-reversal region. The present results are in good agreements with the flow statistics by DNS. Currently, a dynamic approach of obtaining mean wall shear stress based on the log-law is being applied to the flow having flow separation and its results will be shown in the presentation. Supported by the WCU and NRF programs.

Physical Education's Role in Public Health: Steps Forward and Backward over 20 Years and HOPE for the Future

ERIC Educational Resources Information Center

Sallis, James F.; McKenzie, Thomas L.; Beets, Michael W.; Beighle, Aaron; Erwin, Heather; Lee, Sarah

2012-01-01

The 1991 paper, "Physical Education's Role in Public Health" described the importance of physical education in addressing public health problems. On its 20th anniversary, this article reviews accomplishments in improving the health impact of physical education and identifies areas lacking progress. Major accomplishments include development of…

A velocity-pressure integrated, mixed interpolation, Galerkin finite element method for high Reynolds number laminar flows

NASA Technical Reports Server (NTRS)

Kim, Sang-Wook

1988-01-01

A velocity-pressure integrated, mixed interpolation, Galerkin finite element method for the Navier-Stokes equations is presented. In the method, the velocity variables were interpolated using complete quadratic shape functions and the pressure was interpolated using linear shape functions. For the two dimensional case, the pressure is defined on a triangular element which is contained inside the complete biquadratic element for velocity variables; and for the three dimensional case, the pressure is defined on a tetrahedral element which is again contained inside the complete tri-quadratic element. Thus the pressure is discontinuous across the element boundaries. Example problems considered include: a cavity flow for Reynolds number of 400 through 10,000; a laminar backward facing step flow; and a laminar flow in a square duct of strong curvature. The computational results compared favorable with those of the finite difference methods as well as experimental data available. A finite elememt computer program for incompressible, laminar flows is presented.

A Discontinuous Petrov-Galerkin Methodology for Adaptive Solutions to the Incompressible Navier-Stokes Equations

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

Roberts, Nathan V.; Demkowiz, Leszek; Moser, Robert

2015-11-15

The discontinuous Petrov-Galerkin methodology with optimal test functions (DPG) of Demkowicz and Gopalakrishnan [18, 20] guarantees the optimality of the solution in an energy norm, and provides several features facilitating adaptive schemes. Whereas Bubnov-Galerkin methods use identical trial and test spaces, Petrov-Galerkin methods allow these function spaces to differ. In DPG, test functions are computed on the fly and are chosen to realize the supremum in the inf-sup condition; the method is equivalent to a minimum residual method. For well-posed problems with sufficiently regular solutions, DPG can be shown to converge at optimal rates—the inf-sup constants governing the convergence aremore » mesh-independent, and of the same order as those governing the continuous problem [48]. DPG also provides an accurate mechanism for measuring the error, and this can be used to drive adaptive mesh refinements. We employ DPG to solve the steady incompressible Navier-Stokes equations in two dimensions, building on previous work on the Stokes equations, and focusing particularly on the usefulness of the approach for automatic adaptivity starting from a coarse mesh. We apply our approach to a manufactured solution due to Kovasznay as well as the lid-driven cavity flow, backward-facing step, and flow past a cylinder problems.« less

On turbulent flows dominated by curvature effects

NASA Technical Reports Server (NTRS)

Cheng, G. C.; Farokhi, S.

1992-01-01

A technique for improving the numerical predictions of turbulent flows with the effect of streamline curvature is developed. Separated flows and the flow in a curved duct are examples of flowfields where streamline curvature plays a dominant role. New algebraic formulations for the eddy viscosity incorporating the k-epsilon turbulence model are proposed to account for various effects of streamline curvature. The loci of flow reversal of the separated flows over various backward-facing steps are employed to test the capability of the proposed turbulence model in capturing the effect of local curvature.

A framework for simultaneous aerodynamic design optimization in the presence of chaos

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

Günther, Stefanie, E-mail: stefanie.guenther@scicomp.uni-kl.de; Gauger, Nicolas R.; Wang, Qiqi

Integrating existing solvers for unsteady partial differential equations into a simultaneous optimization method is challenging due to the forward-in-time information propagation of classical time-stepping methods. This paper applies the simultaneous single-step one-shot optimization method to a reformulated unsteady constraint that allows for both forward- and backward-in-time information propagation. Especially in the presence of chaotic and turbulent flow, solving the initial value problem simultaneously with the optimization problem often scales poorly with the time domain length. The new formulation relaxes the initial condition and instead solves a least squares problem for the discrete partial differential equations. This enables efficient one-shot optimizationmore » that is independent of the time domain length, even in the presence of chaos.« less

The dispersion of particles in a separated backward-facing step flow

NASA Astrophysics Data System (ADS)

Ruck, B.; Makiola, B.

1991-05-01

Flows in technical and natural circuits often involve a particulate phase. To measure the dynamics of suspended, naturally resident or artificially seeded particles in the flow, optical measuring techniques, e.g., laser Doppler anemometry (LDA) can be used advantageously. In this paper the dispersion of particles in a single-sided backward-facing step flow is investigated by LDA. The investigation is of relevance for both, two-phase flow problems in separated flows with the associated particle diameter range of 1-70 μm and the accuracy of LDA with tracer particles of different sizes. The latter is of interest for all LDA applications to measure continuous phase properties, where interest for experimental restraints require tracer diameters in the upper micrometer range, e.g., flame resistant particles for measurements inside reactors, cylinders, etc. For the experiments, a closed-loop wind tunnel with a step expansion was used. Part of this tunnel, the test section, was made of glass. The step had a height H=25 mm (channel height before the step 25 mm, after 50 mm, i.e., an expansion ratio of 2). The width of the channel was 500 mm. The length of the glass test section was chosen as 116 step heights. The wind tunnel, driven by a radial fan, allowed flow velocities up to 50 m/sec which is equivalent to ReH=105. Seeding was performed with particles of well-known size: 1, 15, 30, and 70 μm in diameter. As 1 μm tracers oil droplets were used, whereas for the upper micron range starch particles (density 1.500 kg/m3) were chosen. Starch particles have a spherical shape and are not soluble in cold water. Particle velocities were measured locally using a conventional 1-D LDA system. The measurements deliver the resultant ``flow'' field information stemming from different particle size classes. Thus, the particle behavior in the separated flow field can be resolved. The results show that with increasing particle size, the particle velocity field differs increasingly from the flow field of the continuous phase (inferred from the smallest tracers used). The velocity fluctuations successively decrease with increasing particle diameter. In separation zones, bigger particles have a lower mean velocity than smaller ones. The opposite holds for the streamwise portions of the particle velocity field, where bigger particles show a higher velocity. The measurements give detailed insight into the particle dynamics in separated flow regions. LDA-measured dividing streamlines and lines of zero velocity of different particle classes in the recirculation region have been plotted and compared. In LDA the use of tracer particles in the upper micrometer size range leads to erroneous determinations of continuous phase flow characteristics. It turned out that the dimensions of the measured recirculation zones are reduced with increasing particle diameter. The physical reasons for these findings (relaxation time of particles, Stokes numbers, etc.) are explained in detail.

Separated and Recovering Turbulent Boundary Layer Flow Behind a Backward Facing Step For Different Reynolds Numbers

NASA Technical Reports Server (NTRS)

Jovic, Srba; Kutler, Paul F. (Technical Monitor)

1994-01-01

Experimental results for a two-dimensional separated turbulent boundary layer behind a backward facing step for five different Reynolds numbers are reported. Results are presented in the form of tables, graphs and a floppy disk for an easy access of the data. Reynolds number based on the step height was varied by changing the reference velocity upstream of the step, U(sub o), and the step height, h. Hot-wire measurement techniques were used to measure three Reynolds stresses and four triple-velocity correlations. In addition, surface pressure and skin friction coefficients were measured. All hot-wire measurements were acquired in a measuring domain which excluded recirculating flow region due to the directional insensitivity of hot-wires. The downstream extent of the domain from the step was 51 h for the largest and I 14h for the smallest step height. This significant downstream length permitted extensive study of the flow recovery. Prediction of perturbed flows and their recovery is particularly attractive for popular turbulence models since variations of turbulence length and time scales and flow interactions in different regions are generally inadequately predicted. The data indicate that the flow in the free shear layer region behaves like the plane mixing layer up to about 2/3 of the mean reattachment length when the flow interaction with the wall commences the flow recovery to that of an ordinary turbulent boundary layer structure. These changes of the flow do not occur abruptly with the change of boundary conditions. A reattachment region represents a transitional region where the flow undergoes the most dramatic adjustments to the new boundary conditions. Large eddies, created in the upstream free-shear layer region, are being torn, recirculated, reentrained back into the main stream interacting with the incoming flow structure. It is foreseeable that it is quite difficult to describe the physics of this region in a rational and quantitative manner other than statistical. Downstream of the reattachment point the flow recovers at different rates near the wall, in the newly developing internal boundary layer, and in the outer part of the flow. It appears that Reynolds stresses do not fully recover up to the longest recovery length of 114 h.

Body position and direction preferences in horses during road transport.

PubMed

Smith, B L; Jones, J H; Carlson, G P; Pascoe, J R

1994-09-01

It has been hypothesised that horses have a preference for facing backward in a trailer during road transport in order to minimise shifts of body weight due to accelerations and decelerations. To determine if horses have preferences for facing forward vs. backward in a horse trailer, the authors analysed the percentages of time horses spent in different body positions and directions while standing in a moving or parked horse trailer. Body positions and directions of 8 Thoroughbred geldings were videotaped while horses were transported singly and untethered in a 4-horse stock trailer over a 32 km route of country roads; or while the same horses were untethered in the same trailer stationary in a parking lot. Analysis of the logit-transformed percentages of time horses spent in different directions indicated that they spent significantly more time facing backward when the trailer was in motion, but not when it was parked. Several horses displayed strong individual preferences for the directions they faced during road transport.

Backward masked fearful faces enhance contralateral occipital cortical activity for visual targets within the spotlight of attention

PubMed Central

Reinke, Karen S.; LaMontagne, Pamela J.; Habib, Reza

2011-01-01

Spatial attention has been argued to be adaptive by enhancing the processing of visual stimuli within the ‘spotlight of attention’. We previously reported that crude threat cues (backward masked fearful faces) facilitate spatial attention through a network of brain regions consisting of the amygdala, anterior cingulate and contralateral visual cortex. However, results from previous functional magnetic resonance imaging (fMRI) dot-probe studies have been inconclusive regarding a fearful face-elicited contralateral modulation of visual targets. Here, we tested the hypothesis that the capture of spatial attention by crude threat cues would facilitate processing of subsequently presented visual stimuli within the masked fearful face-elicited ‘spotlight of attention’ in the contralateral visual cortex. Participants performed a backward masked fearful face dot-probe task while brain activity was measured with fMRI. Masked fearful face left visual field trials enhanced activity for spatially congruent targets in the right superior occipital gyrus, fusiform gyrus and lateral occipital complex, while masked fearful face right visual field trials enhanced activity in the left middle occipital gyrus. These data indicate that crude threat elicited spatial attention enhances the processing of subsequent visual stimuli in contralateral occipital cortex, which may occur by lowering neural activation thresholds in this retinotopic location. PMID:20702500

Body configuration at first stepping-foot contact predicts backward balance recovery capacity in people with chronic stroke.

PubMed

de Kam, Digna; Roelofs, Jolanda M B; Geurts, Alexander C H; Weerdesteyn, Vivian

2018-01-01

To determine the predictive value of leg and trunk inclination angles at stepping-foot contact for the capacity to recover from a backward balance perturbation with a single step in people after stroke. Twenty-four chronic stroke survivors and 21 healthy controls were included in a cross-sectional study. We studied reactive stepping responses by subjecting participants to multidirectional stance perturbations at different intensities on a translating platform. In this paper we focus on backward perturbations. Participants were instructed to recover from the perturbations with maximally one step. A trial was classified as 'success' if balance was restored according to this instruction. We recorded full-body kinematics and computed: 1) body configuration parameters at first stepping-foot contact (leg and trunk inclination angles) and 2) spatiotemporal step parameters (step onset, step length, step duration and step velocity). We identified predictors of balance recovery capacity using a stepwise logistic regression. Perturbation intensity was also included as a predictor. The model with spatiotemporal parameters (perturbation intensity, step length and step duration) could correctly classify 85% of the trials as success or fail (Nagelkerke R2 = 0.61). In the body configuration model (Nagelkerke R2 = 0.71), perturbation intensity and leg and trunk angles correctly classified the outcome of 86% of the recovery attempts. The goodness of fit was significantly higher for the body configuration model compared to the model with spatiotemporal variables (p<0.01). Participant group and stepping leg (paretic or non-paretic) did not significantly improve the explained variance of the final body configuration model. Body configuration at stepping-foot contact is a valid and clinically feasible indicator of backward fall risk in stroke survivors, given its potential to be derived from a single sagittal screenshot.

Fish mouths as engineering structures for vortical cross-step filtration

NASA Astrophysics Data System (ADS)

Sanderson, S. Laurie; Roberts, Erin; Lineburg, Jillian; Brooks, Hannah

2016-03-01

Suspension-feeding fishes such as goldfish and whale sharks retain prey without clogging their oral filters, whereas clogging is a major expense in industrial crossflow filtration of beer, dairy foods and biotechnology products. Fishes' abilities to retain particles that are smaller than the pore size of the gill-raker filter, including extraction of particles despite large holes in the filter, also remain unexplained. Here we show that unexplored combinations of engineering structures (backward-facing steps forming d-type ribs on the porous surface of a cone) cause fluid dynamic phenomena distinct from current biological and industrial filter operations. This vortical cross-step filtration model prevents clogging and explains the transport of tiny concentrated particles to the oesophagus using a hydrodynamic tongue. Mass transfer caused by vortices along d-type ribs in crossflow is applicable to filter-feeding duck beak lamellae and whale baleen plates, as well as the fluid mechanics of ventilation at fish gill filaments.

A Study of Flow Separation in Transonic Flow Using Inviscid and Viscous Computational Fluid Dynamics (CFD) Schemes

NASA Technical Reports Server (NTRS)

Rhodes, J. A.; Tiwari, S. N.; Vonlavante, E.

1988-01-01

A comparison of flow separation in transonic flows is made using various computational schemes which solve the Euler and the Navier-Stokes equations of fluid mechanics. The flows examined are computed using several simple two-dimensional configurations including a backward facing step and a bump in a channel. Comparison of the results obtained using shock fitting and flux vector splitting methods are presented and the results obtained using the Euler codes are compared to results on the same configurations using a code which solves the Navier-Stokes equations.

Comparison of Implicit Schemes for the Incompressible Navier-Stokes Equations

NASA Technical Reports Server (NTRS)

Rogers, Stuart E.

1995-01-01

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

Linear system identification via backward-time observer models

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan; Phan, Minh

1993-01-01

This paper presents an algorithm to identify a state-space model of a linear system using a backward-time approach. The procedure consists of three basic steps. First, the Markov parameters of a backward-time observer are computed from experimental input-output data. Second, the backward-time observer Markov parameters are decomposed to obtain the backward-time system Markov parameters (backward-time pulse response samples) from which a backward-time state-space model is realized using the Eigensystem Realization Algorithm. Third, the obtained backward-time state space model is converted to the usual forward-time representation. Stochastic properties of this approach will be discussed. Experimental results are given to illustrate when and to what extent this concept works.

Large eddy simulation of a boundary layer with concave streamwise curvature

NASA Technical Reports Server (NTRS)

Lund, Thomas S.

1993-01-01

One of the most exciting recent developments in the field of large eddy simulation (LES) is the dynamic subgrid-scale model. The dynamic model concept is a general procedure for evaluating model constants by sampling a band of the smallest scales actually resolved in the simulation. To date, the procedure has been used primarily in conjunction with the Smagorinsky model. The dynamic procedure has the advantage that the value of the model constant need not be specified a priori, but rather is calculated as a function of space and time as the simulation progresses. This feature makes the dynamic model especially attractive for flows in complex geometries where it is difficult or impossible to calibrate model constants. The dynamic model was highly successful in benchmark tests involving homogeneous and channel flows. Having demonstrated the potential of the dynamic model in these simple flows, the overall direction of the LES effort at CTR shifted toward an evaluation of the model in more complex situations. The current test cases are basic engineering-type flows for which Reynolds averaged approaches were unable to model the turbulence to within engineering accuracy. Flows currently under investigation include a backward-facing step, wake behind a circular cylinder, airfoil at high angles of attack, separated flow in a diffuser, and boundary layer over a concave surface. Preliminary results from the backward-facing step and cylinder wake simulations are encouraging. Progress on the LES of a boundary layer on a concave surface is discussed. Although the geometry of a concave wall is not very complex, the boundary layer that develops on its surface is difficult to model due to the presence of streamwise Taylor-Gortler vortices. These vortices arise as a result of a centrifugal instability associated with the convex curvature.

Influence of emotion on the biomechanical organization of backward and forward step initiation.

PubMed

Yiou, Eric; Gendre, Manon; Deroche, Thomas; Le Bozec, Serge

2014-10-01

This study examined how pleasant and unpleasant emotional states influence the biomechanical organization of both forward and backward step initiation (SI). Participants (N = 31) purposely took a single step toward or away from a screen following the presentation of a pleasant (erotic), unpleasant (mutilation) or neutral (objects and landscapes) image. The main results showed that the reaction time for forward SI was shortened when individuals were exposed to pleasant pictures as compared with unpleasant pictures. The anticipatory whole-body center-of-mass velocity associated with backward SI, as well as the peak of center-of-mass velocity associated with forward SI both reached lower values when individuals were exposed to pleasant pictures as compared with neutral pictures. In contrast, unpleasant pictures did not significantly induce any change in the forward or backward SI parameters. Overall, these results obtained for whole-body approach/avoidance-like behaviors provided mitigated support for the so-called "motivational direction hypothesis."

Analysis of stability for stochastic delay integro-differential equations.

PubMed

Zhang, Yu; Li, Longsuo

2018-01-01

In this paper, we concern stability of numerical methods applied to stochastic delay integro-differential equations. For linear stochastic delay integro-differential equations, it is shown that the mean-square stability is derived by the split-step backward Euler method without any restriction on step-size, while the Euler-Maruyama method could reproduce the mean-square stability under a step-size constraint. We also confirm the mean-square stability of the split-step backward Euler method for nonlinear stochastic delay integro-differential equations. The numerical experiments further verify the theoretical results.

Lagrangian coherent structures during combustion instability in a premixed-flame backward-step combustor.

PubMed

Sampath, Ramgopal; Mathur, Manikandan; Chakravarthy, Satyanarayanan R

2016-12-01

This paper quantitatively examines the occurrence of large-scale coherent structures in the flow field during combustion instability in comparison with the flow-combustion-acoustic system when it is stable. For this purpose, the features in the recirculation zone of the confined flow past a backward-facing step are studied in terms of Lagrangian coherent structures. The experiments are conducted at a Reynolds number of 18600 and an equivalence ratio of 0.9 of the premixed fuel-air mixture for two combustor lengths, the long duct corresponding to instability and the short one to the stable case. Simultaneous measurements of the velocity field using time-resolved particle image velocimetry and the CH^{*} chemiluminescence of the flame along with pressure time traces are obtained. The extracted ridges of the finite-time Lyapunov exponent (FTLE) fields delineate dynamically distinct regions of the flow field. The presence of large-scale vortical structures and their modulation over different time instants are well captured by the FTLE ridges for the long combustor where high-amplitude acoustic oscillations are self-excited. In contrast, small-scale vortices signifying Kelvin-Helmholtz instability are observed in the short duct case. Saddle-type flow features are found to separate the distinct flow structures for both combustor lengths. The FTLE ridges are found to align with the flame boundaries in the upstream regions, whereas farther downstream, the alignment is weaker due to dilatation of the flow by the flame's heat release. Specifically, the FTLE ridges encompass the flame curl-up for both the combustor lengths, and thus act as the surrogate flame boundaries. The flame is found to propagate upstream from an earlier vortex roll-up to a newer one along the backward-time FTLE ridge connecting the two structures.

Posture alteration as a measure to accommodate uneven ground in able-bodied gait

PubMed Central

Blickhan, Reinhard; Muller, Roy; Rode, Christian

2017-01-01

Though the effects of imposed trunk posture on human walking have been studied, less is known about such locomotion while accommodating changes in ground level. For twelve able participants, we analyzed kinematic parameters mainly at touchdown and toe-off in walking across a 10-cm visible drop in ground level (level step, pre-perturbation step, step-down, step-up) with three postures (regular erect, ~30° and ~50° of trunk flexion from the vertical). Two-way repeated measures ANOVAs revealed step-specific effects of posture on the kinematic behavior of gait mostly at toe-off of the pre-perturbation step and the step-down as well as at touchdown of the step-up. In preparation to step-down, with increasing trunk flexion the discrepancy in hip−center of pressure distance, i.e. effective leg length, (shorter at toe-off versus touchdown), compared with level steps increased largely due to a greater knee flexion at toe-off. Participants rotated their trunk backwards during step-down (2- to 3-fold backwards rotation compared with level steps regardless of trunk posture) likely to control the angular momentum of their whole body. The more pronounced trunk backwards rotation in trunk-flexed walking contributed to the observed elevated center of mass (CoM) trajectories during the step-down which may have facilitated drop negotiation. Able-bodied individuals were found to recover almost all assessed kinematic parameters comprising the vertical position of the CoM, effective leg length and angle as well as hip, knee and ankle joint angles at the end of the step-up, suggesting an adaptive capacity and hence a robustness of human walking with respect to imposed trunk orientations. Our findings may provide clinicians with insight into a kinematic interaction between posture and locomotion in uneven ground. Moreover, a backward rotation of the trunk for negotiating step-down may be incorporated into exercise-based interventions to enhance gait stability in individuals who exhibit trunk-flexed postures during walking. PMID:29281712

Effect of turbulence intensity on cross-injection film cooling at a stepped or smooth endwall of a gas turbine vane passage.

PubMed

Wu, Pey-Shey; Tsai, Shen-Ta; Jhuo, Yue-Hua

2014-01-01

This study is concerned with a film cooling technique applicable to the protection of the endwalls of a gas turbine vane. In the experiments, cross-injection coolant flow from two-row, paired, inclined holes with nonintersecting centerlines was utilized. The test model is a scaled two-half vane. The levels of turbulence intensity used in the experiments are T.I. = 1.8%, 7%, and 12%. Other parameters considered in the film cooling experiments include three inlet Reynolds numbers (9.20 × 10(4), 1.24 × 10(5), and 1.50 × 10(5)), three blowing ratios (0.5, 1.0, and 2.0), and three endwall conditions (smooth endwall and stepped endwall with forward-facing or backward-facing step). Thermochromic liquid crystal (TLC) technique with steady-state heat transfer experiments was used to obtain the whole-field film cooling effectiveness. Results show that, at low turbulence intensity, increasing Reynolds number decreases the effectiveness in most of the vane passage. There is no monotonic trend of influence by Reynolds number at high turbulence intensity. The effect of blowing ratio on the effectiveness has opposite trends at low and high turbulence levels. Increasing turbulent intensity decreases the effectiveness, especially near the inlet of the vane passage. With a stepped endwall, turbulence intensity has only mild effect on the film cooling effectiveness.

Effect of Turbulence Intensity on Cross-Injection Film Cooling at a Stepped or Smooth Endwall of a Gas Turbine Vane Passage

PubMed Central

Tsai, Shen-Ta; Jhuo, Yue-Hua

2014-01-01

This study is concerned with a film cooling technique applicable to the protection of the endwalls of a gas turbine vane. In the experiments, cross-injection coolant flow from two-row, paired, inclined holes with nonintersecting centerlines was utilized. The test model is a scaled two-half vane. The levels of turbulence intensity used in the experiments are T.I. = 1.8%, 7%, and 12%. Other parameters considered in the film cooling experiments include three inlet Reynolds numbers (9.20 × 104, 1.24 × 105, and 1.50 × 105), three blowing ratios (0.5, 1.0, and 2.0), and three endwall conditions (smooth endwall and stepped endwall with forward-facing or backward-facing step). Thermochromic liquid crystal (TLC) technique with steady-state heat transfer experiments was used to obtain the whole-field film cooling effectiveness. Results show that, at low turbulence intensity, increasing Reynolds number decreases the effectiveness in most of the vane passage. There is no monotonic trend of influence by Reynolds number at high turbulence intensity. The effect of blowing ratio on the effectiveness has opposite trends at low and high turbulence levels. Increasing turbulent intensity decreases the effectiveness, especially near the inlet of the vane passage. With a stepped endwall, turbulence intensity has only mild effect on the film cooling effectiveness. PMID:24592153

Laminar supersonic flow over a backstep - A numerical solution at higher Reynolds numbers

NASA Technical Reports Server (NTRS)

Kronzon, Y.; Rom, J.; Seginer, A.

1976-01-01

The Allen-Cheng solution of the flow over a backward facing step is extended to Reynolds numbers up to 16,000 and to inflow boundary-layer height ratios as low as 0.1 by moving the downstream boundary into the recompression region and by smoothing the resulting errors. The boundary conditions in the supersonic outer flow and the downstream boundary conditions in the wake are determined by an extrapolation procedure. Computational results are compared with relevant experimental data. Fair agreement is found between the calculated base pressures and the experimental values, whereas agreement between heat transfer rates appears to be qualitative only.

A steadying effect of acoustic excitation on transitory stall

NASA Technical Reports Server (NTRS)

Zaman, K. B. M. Q.

1991-01-01

The effect of acoustic excitation on a class of separated flows with a transitional boundary layer at the point of separation is considered. Experimental results on the flow over airfoils, a two-dimensional backward-facing step, and through large angle conical diffusers are presented. In all cases, the separated flow undergoes large amplitude fluctuations, much of the energy being concentrated at unusually low frequencies. In each case, an appropriate high frequency acoustic excitation is found to be effective in reducing the fluctuations substantially. The effective excitation frequency scales on the initial boundary layer thickness and the effect is apparently achieved through acoustic tripping of the separating boundary layer.

One-equation near-wall turbulence modeling with the aid of direct simulation data

NASA Technical Reports Server (NTRS)

Rodi, W.; Mansour, N. N.; Michelassi, V.

1993-01-01

The length scales appearing in the relations for the eddy viscosity and dissipation rate in one-equation models were evaluated from direct numerical (DNS) simulation data for developed channel and boundary-layer flow at two Reynolds numbers each. To prepare the ground for the evaluation, the distribution of the most relevant mean-flow and turbulence quantities is presented and discussed, also with respect to Reynolds-number influence and to differences between channel and boundary-layer flow. An alternative model is tested as near wall component of a two-layer model by application to developed-channel, boundary-layer and backward-facing-step flows.

Regularization techniques for backward--in--time evolutionary PDE problems

NASA Astrophysics Data System (ADS)

Gustafsson, Jonathan; Protas, Bartosz

2007-11-01

Backward--in--time evolutionary PDE problems have applications in the recently--proposed retrograde data assimilation. We consider the terminal value problem for the Kuramoto--Sivashinsky equation (KSE) in a 1D periodic domain as our model system. The KSE, proposed as a model for interfacial and combustion phenomena, is also often adopted as a toy model for hydrodynamic turbulence because of its multiscale and chaotic dynamics. Backward--in--time problems are typical examples of ill-posed problem, where disturbances are amplified exponentially during the backward march. Regularization is required to solve such problems efficiently and we consider approaches in which the original ill--posed problem is approximated with a less ill--posed problem obtained by adding a regularization term to the original equation. While such techniques are relatively well--understood for linear problems, they less understood in the present nonlinear setting. We consider regularization terms with fixed magnitudes and also explore a novel approach in which these magnitudes are adapted dynamically using simple concepts from the Control Theory.

You have an idea, now what?

PubMed

Gertner, Michael

2006-11-01

The innovation process is often more important than the original idea, particularly when the ultimate goal is to improve patient care through technologically advanced products. Many physicians have great ideas; unfortunately, many of these great ideas are never translated to patient care improvements because of a misunderstanding of "the next step." In many cases, the next step is a step backward to understand the real clinical problem: "the clinical need." With the clinical need in hand, the most efficient path to a product for improved patient care can then be derived. Often, the most efficient pathway involves an appreciation of many issues, including intellectual property, regulatory pathways, finance, and clinical trial strategies. The integration of these issues underlies innovation in biomedical technology.

Masking with faces in central visual field under a variety of temporal schedules.

PubMed

Daar, Marwan; Wilson, Hugh R

2015-11-01

With a few exceptions, previous studies have explored masking using either a backward mask or a common onset trailing mask, but not both. In a series of experiments, we demonstrate the use of faces in central visual field as a viable method to study the relationship between these two types of mask schedule. We tested observers in a two alternative forced choice face identification task, where both target and mask comprised synthetic faces, and show that a simple model can successfully predict masking across a variety of masking schedules ranging from a backward mask to a common onset trailing mask and a number of intermediate variations. Our data are well accounted for by a window of sensitivity to mask interference that is centered at around 100 ms. Copyright © 2015 Elsevier Ltd. All rights reserved.

Analysis of two-equation turbulence models for recirculating flows

NASA Technical Reports Server (NTRS)

Thangam, S.

1991-01-01

The two-equation kappa-epsilon model is used to analyze turbulent separated flow past a backward-facing step. It is shown that if the model constraints are modified to be consistent with the accepted energy decay rate for isotropic turbulence, the dominant features of the flow field, namely the size of the separation bubble and the streamwise component of the mean velocity, can be accurately predicted. In addition, except in the vicinity of the step, very good predictions for the turbulent shear stress, the wall pressure, and the wall shear stress are obtained. The model is also shown to provide good predictions for the turbulence intensity in the region downstream of the reattachment point. Estimated long time growth rates for the turbulent kinetic energy and dissipation rate of homogeneous shear flow are utilized to develop an optimal set of constants for the two equation kappa-epsilon model. The physical implications of the model performance are also discussed.

Velocity-Field Measurements of an Axisymmetric Separated Flow Subjected to Amplitude-Modulated Excitation

NASA Technical Reports Server (NTRS)

Trosin, Barry James

2007-01-01

Active flow control was applied at the point of separation of an axisymmetric, backward-facing-step flow. The control was implemented by employing a Helmholtz resonator that was externally driven by an amplitude-modulated, acoustic disturbance from a speaker located upstream of the wind tunnel. The velocity field of the separating/reattaching flow region downstream of the step was characterized using hotwire velocity measurements with and without flow control. Conventional statistics of the data reveal that the separating/reattaching flow is affected by the imposed forcing. Triple decomposition along with conditional averaging was used to distinguish periodic disturbances from random turbulence in the fluctuating velocity component. A significant outcome of the present study is that it demonstrates that amplitude-modulated forcing of the separated flow alters the flow in the same manner as the more conventional method of periodic excitation.

A Semi-linear Backward Parabolic Cauchy Problem with Unbounded Coefficients of Hamilton–Jacobi–Bellman Type and Applications to Optimal Control

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

Addona, Davide, E-mail: d.addona@campus.unimib.it

2015-08-15

We obtain weighted uniform estimates for the gradient of the solutions to a class of linear parabolic Cauchy problems with unbounded coefficients. Such estimates are then used to prove existence and uniqueness of the mild solution to a semi-linear backward parabolic Cauchy problem, where the differential equation is the Hamilton–Jacobi–Bellman equation of a suitable optimal control problem. Via backward stochastic differential equations, we show that the mild solution is indeed the value function of the controlled equation and that the feedback law is verified.

Spatial Attention-Related Modulation of the N170 by Backward Masked Fearful Faces

ERIC Educational Resources Information Center

Carlson, Joshua M.; Reinke, Karen S.

2010-01-01

Facial expressions are a basic form of non-verbal communication that convey important social information to others. The relevancy of this information is highlighted by findings that backward masked facial expressions facilitate spatial attention. This attention effect appears to be mediated through a neural network consisting of the amygdala,…

Backward Masking: Evidence of Reduced Subcortical Amygdala Engagement in Autism

ERIC Educational Resources Information Center

Hall, Geoffrey B. C.; West, C. Dianne; Szatmari, Peter

2007-01-01

Recent data suggest that subthreshold presentation of emotional information is relayed to the amygdala along subcortical pathways. We examined the effect of backward masked neutral and anxious faces on the social decisions of a group of high functioning children with autism ages 7-13 years and matched controls. Participants were asked to select…

Scalability and performance of data-parallel pressure-based multigrid methods for viscous flows

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

Blosch, E.L.; Shyy, W.

1996-05-01

A full-approximation storage multigrid method for solving the steady-state 2-d incompressible Navier-Stokes equations on staggered grids has been implemented in Fortran on the CM-5, using the array aliasing feature in CM-Fortran to avoid declaring fine-grid-sized arrays on all levels while still allowing a variable number of grid levels. Thus, the storage cost scales with the number of unknowns, allowing us to consider significantly larger problems than would otherwise be possible. Timings over a range of problem sizes and numbers of processors, up to 4096 x 4096 on 512 nodes, show that the smoothing procedure, a pressure-correction technique, is scalable andmore » that the restriction and prolongation steps are nearly so. The performance obtained for the multigrid method is 333 Mflops out of the theoretical peak 4 Gflops on a 32-node CM-5. In comparison, a single-grid computation obtained 420 Mflops. The decrease is due to the inefficiency of the smoothing iterations on the coarse grid levels. W cycles cost much more and are much less efficient than V cycles, due to the increased contribution from the coarse grids. The convergence rate characteristics of the pressure-correction multigrid method are investigated in a Re = 5000 lid-driven cavity flow and a Re = 300 symmetric backward-facing step flow, using either a defect-correction scheme or a second-order upwind scheme. A heuristic technique relating the convergence tolerances for the course grids to the truncation error of the discretization has been found effective and robust. With second-order upwinding on all grid levels, a 5-level 320 x 80 step flow solution was obtained in 20 V cycles, which corresponds to a smoothing rate of 0.7, and required 25 s on a 32-node CM-5. Overall, the convergence rates obtained in the present work are comparable to the most competitive findings reported in the literature. 62 refs., 13 figs.« less

Scalability and Performance of Data-Parallel Pressure-Based Multigrid Methods for Viscous Flows

NASA Astrophysics Data System (ADS)

Blosch, Edwin L.; Shyy, Wei

1996-05-01

A full-approximation storage multigrid method for solving the steady-state 2-dincompressible Navier-Stokes equations on staggered grids has been implemented in Fortran on the CM-5,using the array aliasing feature in CM-Fortran to avoid declaring fine-grid-sized arrays on all levels while still allowing a variable number of grid levels. Thus, the storage cost scales with the number of unknowns,allowing us to consider significantly larger problems than would otherwise be possible. Timings over a range of problem sizes and numbers of processors, up to 4096 × 4096 on 512 nodes, show that the smoothing procedure, a pressure-correction technique, is scalable and that the restriction and prolongation steps are nearly so. The performance obtained for the multigrid method is 333 Mflops out of the theoretical peak 4 Gflops on a 32-node CM-5. In comparison, a single-grid computation obtained 420 Mflops. The decrease is due to the inefficiency of the smoothing iterations on the coarse grid levels. W cycles cost much more and are much less efficient than V cycles, due to the increased contribution from the coarse grids. The convergence rate characteristics of the pressure-correction multigrid method are investigated in a Re = 5000 lid-driven cavity flow and a Re = 300 symmetric backward-facing step flow, using either a defect-correction scheme or a second-order upwind scheme. A heuristic technique relating the convergence tolerances for the coarse grids to the truncation error of the discretization has been found effective and robust. With second-order upwinding on all grid levels, a 5-level 320× 80 step flow solution was obtained in 20 V cycles, which corresponds to a smoothing rate of 0.7, and required 25 s on a 32-node CM-5. Overall, the convergence rates obtained in the present work are comparable to the most competitive findings reported in the literature.

On the ``optimal'' spatial distribution and directional anisotropy of the filter-width and grid-resolution in large eddy simulation

NASA Astrophysics Data System (ADS)

Toosi, Siavash; Larsson, Johan

2017-11-01

The accuracy of an LES depends directly on the accuracy of the resolved part of the turbulence. The continuing increase in computational power enables the application of LES to increasingly complex flow problems for which the LES community lacks the experience of knowing what the ``optimal'' or even an ``acceptable'' grid (or equivalently filter-width distribution) is. The goal of this work is to introduce a systematic approach to finding the ``optimal'' grid/filter-width distribution and their ``optimal'' anisotropy. The method is tested first on the turbulent channel flow, mainly to see if it is able to predict the right anisotropy of the filter/grid, and then on the more complicated case of flow over a backward-facing step, to test its ability to predict the right distribution and anisotropy of the filter/grid simultaneously, hence leading to a converged solution. This work has been supported by the Naval Air Warfare Center Aircraft Division at Pax River, MD, under contract N00421132M021. Computing time has been provided by the University of Maryland supercomputing resources (http://hpcc.umd.edu).

A multiscale SPH particle model of the near-wall dynamics of leukocytes in flow.

PubMed

Gholami, Babak; Comerford, Andrew; Ellero, Marco

2014-01-01

A novel multiscale Lagrangian particle solver based on SPH is developed with the intended application of leukocyte transport in large arteries. In such arteries, the transport of leukocytes and red blood cells can be divided into two distinct regions: the bulk flow and the near-wall region. In the bulk flow, the transport can be modeled on a continuum basis as the transport of passive scalar concentrations. Whereas in the near-wall region, specific particle tracking of the leukocytes is required and lubrication forces need to be separately taken into account. Because of large separation of spatio-temporal scales involved in the problem, simulations of red blood cells and leukocytes are handled separately. In order to take the exchange of leukocytes between the bulk fluid and the near-wall region into account, solutions are communicated through coupling of conserved quantities at the interface between these regions. Because the particle tracking is limited to those leukocytes lying in the near-wall region only, our approach brings considerable speedup to the simulation of leukocyte circulation in a test geometry of a backward-facing step, which encompasses many flow features observed in vivo. Copyright © 2013 John Wiley & Sons, Ltd.

Pressure algorithm for elliptic flow calculations with the PDF method

NASA Technical Reports Server (NTRS)

Anand, M. S.; Pope, S. B.; Mongia, H. C.

1991-01-01

An algorithm to determine the mean pressure field for elliptic flow calculations with the probability density function (PDF) method is developed and applied. The PDF method is a most promising approach for the computation of turbulent reacting flows. Previous computations of elliptic flows with the method were in conjunction with conventional finite volume based calculations that provided the mean pressure field. The algorithm developed and described here permits the mean pressure field to be determined within the PDF calculations. The PDF method incorporating the pressure algorithm is applied to the flow past a backward-facing step. The results are in good agreement with data for the reattachment length, mean velocities, and turbulence quantities including triple correlations.

Hydrogen injection scheme influence on flow structure in supersonic combustor of constant cross-section

NASA Astrophysics Data System (ADS)

Starov, A. V.; Goldfeld, M. A.

2017-10-01

The efficiency of using two variants of hydrogen injection (distributed and non-distributed injection from vertical pylons) is experimentally investigated. The tests are performed in the attached pipeline regime with the Mach number at the model combustor entrance M=2. The combustion chamber has a backward-facing step at the entrance and slotted channels for combustion stabilization. The tested variants of injection differ basically by the shapes of the fuel jets and, correspondingly, by the hydrogen distribution over the combustor. As a result, distributed injection is found to provide faster ignition, upstream displacement of the elevated pressure region, and more intense combustion over the entire combustor volume.

Entrainment effects in periodic forcing of the flow over a backward-facing step

NASA Astrophysics Data System (ADS)

Berk, T.; Medjnoun, T.; Ganapathisubramani, B.

2017-07-01

The effect of the Strouhal number on periodic forcing of the flow over a backward-facing step (height, H ) is investigated experimentally. Forcing is applied by a synthetic jet at the edge of the step at Strouhal numbers ranging from 0.21

Kinematic Adaptations of Forward And Backward Walking on Land and in Water

PubMed Central

Cadenas-Sanchez, Cristina; Arellano, Raúl; Vanrenterghem, Jos; López-Contreras, Gracia

2015-01-01

The aim of this study was to compare sagittal plane lower limb kinematics during walking on land and submerged to the hip in water. Eight healthy adults (age 22.1 ± 1.1 years, body height 174.8 ± 7.1 cm, body mass 63.4 ± 6.2 kg) were asked to cover a distance of 10 m at comfortable speed with controlled step frequency, walking forward or backward. Sagittal plane lower limb kinematics were obtained from three dimensional video analysis to compare spatiotemporal gait parameters and joint angles at selected events using two-way repeated measures ANOVA. Key findings were a reduced walking speed, stride length, step length and a support phase in water, and step length asymmetry was higher compared to the land condition (p<0.05). At initial contact, knees and hips were more flexed during walking forward in water, whilst, ankles were more dorsiflexed during walking backward in water. At final stance, knees and ankles were more flexed during forward walking, whilst the hip was more flexed during backward walking. These results show how walking in water differs from walking on land, and provide valuable insights into the development and prescription of rehabilitation and training programs. PMID:26839602

Influence of gait speed on stability: recovery from anterior slips and compensatory stepping.

PubMed

Bhatt, T; Wening, J D; Pai, Y-C

2005-02-01

Falls precipitated by slipping are a major health concern, with the majority of all slip-related falls occurring during gait. Recent evidence shows that a faster and/or more anteriorly positioned center of mass (COM) is more stable against backward balance loss, and that compensatory stepping is the key to recovering stability upon balance loss. The purposes of this paper were to determine whether walking speed affected gait stability for backward balance loss at slip onset and touchdown of compensatory stepping, and whether compensatory stepping response resembled the regular gait pattern. Forty-seven young subjects were slipped unexpectedly either at a self-selected fast, natural or slow speed. Speed-related differences in stability at slip onset and touchdown of the subsequent compensatory step were analyzed using the COM position-velocity state. The results indicate that gait speed highly correlated with stability against backward balance loss at slip onset. The low COM velocity of the slow group was not sufficiently compensated for by a more anteriorly positioned COM associated with a shorter step length at slip onset. At touchdown of the compensatory step, the speed-related differences in stability diminished, due to the continued advantage of anterior COM positioning from a short compensatory step retained by the slow group, coupled with an increase in COM velocity. Compensatory step length and relative COM position altered as a function of gait speed, indicating the motor program for gait regulation may play a role in modulating the compensatory step.

Introducing the "Decider" Design Process

ERIC Educational Resources Information Center

Prasa, Anthony R., Jr.; Del Guercio, Ryan

2016-01-01

Engineers are faced with solving important problems every day and must follow a step-by-step design process to arrive at solutions. Students who are taught an effective design process to apply to engineering projects begin to see problems as an engineer would, consider all ideas, and arrive at the best solution. Using an effective design process…

Back off! The effect of emotion on backward step initiation.

PubMed

Bouman, Daniëlle; Stins, John F

2018-02-01

The distance regulation (DR) hypothesis states that actors are inclined to increase their distance from an unpleasant stimulus. The current study investigated the relation between emotion and its effect on the control of backward step initiation, which constitutes an avoidance-like behavior. Participants stepped backward on a force plate in response to neutral, high-arousing pleasant and high-arousing unpleasant visual emotional stimuli. Gait initiation parameters and the results of an exploratory analysis of postural sway were compared across the emotion categories using significance testing and Bayesian statistics. Evidence was found that gait initiation parameters were largely unaffected by emotional conditions. In contrast, the exploratory analysis of postural immobility showed a significant effect: highly arousing stimuli (pleasant and unpleasant) resulted in more postural sway immediately preceding gait initiation compared to neutral stimuli. This suggests that arousal, rather than valence, affects pre-step sway. These results contradict the DR hypothesis, since avoidance gait-initiation in response to unpleasant stimuli was no different compared to pleasant stimuli. Copyright © 2017 The Authors. Published by Elsevier B.V. All rights reserved.

Prediction of 3D chip formation in the facing cutting with lathe machine using FEM

NASA Astrophysics Data System (ADS)

Prasetyo, Yudhi; Tauviqirrahman, Mohamad; Rusnaldy

2016-04-01

This paper presents the prediction of the chip formation at the machining process using a lathe machine in a more specific way focusing on facing cutting (face turning). The main purpose is to propose a new approach to predict the chip formation with the variation of the cutting directions i.e., the backward and forward direction. In addition, the interaction between stress analysis and chip formation on cutting process was also investigated. The simulations were conducted using three dimensional (3D) finite element method based on ABAQUS software with aluminum and high speed steel (HSS) as the workpiece and the tool materials, respectively. The simulation result showed that the chip resulted using a backward direction depicts a better formation than that using a conventional (forward) direction.

A face versus non-face context influences amygdala responses to masked fearful eye whites.

PubMed

Kim, M Justin; Solomon, Kimberly M; Neta, Maital; Davis, F Caroline; Oler, Jonathan A; Mazzulla, Emily C; Whalen, Paul J

2016-12-01

The structure of the mask stimulus is crucial in backward masking studies and we recently demonstrated such an effect when masking faces. Specifically, we showed that activity of the amygdala is increased to fearful facial expressions masked with neutral faces and decreased to fearful expressions masked with a pattern mask-but critically both masked conditions discriminated fearful expressions from happy expressions. Given this finding, we sought to test whether masked fearful eye whites would produce a similar profile of amygdala response in a face vs non-face context. During functional magnetic resonance imaging scanning sessions, 30 participants viewed fearful or happy eye whites masked with either neutral faces or pattern images. Results indicated amygdala activity was increased to fearful vs happy eye whites in the face mask condition, but decreased to fearful vs happy eye whites in the pattern mask condition-effectively replicating and expanding our previous report. Our data support the idea that the amygdala is responsive to fearful eye whites, but that the nature of this activity observed in a backward masking design depends on the mask stimulus. © The Author (2016). Published by Oxford University Press.

Groundwater Source Identification Using Backward Fractional-Derivative Models

NASA Astrophysics Data System (ADS)

Zhang, Y.; Sun, H.; Zheng, C.

2017-12-01

The forward Fractional Advection Dispersion Equation (FADE) provides a useful model for non-Fickian transport in heterogeneous porous media. This presentation introduces the corresponding backward FADE model, to identify groundwater source location and release time. The backward method is developed from the theory of inverse problems, and the resultant backward FADE differs significantly from the traditional backward ADE because the fractional derivative is not self-adjoint and the probability density function for backward locations is highly skewed. Finally, the method is validated using tracer data from well-known field experiments.

Numerical solution of second order ODE directly by two point block backward differentiation formula

NASA Astrophysics Data System (ADS)

Zainuddin, Nooraini; Ibrahim, Zarina Bibi; Othman, Khairil Iskandar; Suleiman, Mohamed; Jamaludin, Noraini

2015-12-01

Direct Two Point Block Backward Differentiation Formula, (BBDF2) for solving second order ordinary differential equations (ODEs) will be presented throughout this paper. The method is derived by differentiating the interpolating polynomial using three back values. In BBDF2, two approximate solutions are produced simultaneously at each step of integration. The method derived is implemented by using fixed step size and the numerical results that follow demonstrate the advantage of the direct method as compared to the reduction method.

Spatio-temporal instabilities for counterpropagating waves in periodic media.

PubMed

Haus, Joseph; Soon, Boon Yi; Scalora, Michael; Bloemer, Mark; Bowden, Charles; Sibilia, Concita; Zheltikov, Alexei

2002-01-28

Nonlinear evolution of coupled forward and backward fields in a multi-layered film is numerically investigated. We examine the role of longitudinal and transverse modulation instabilities in media of finite length with a homogeneous nonlinear susceptibility c((3)). The numerical solution of the nonlinear equations by a beam-propagation method that handles backward waves is described.

Eastbound. Pioneering community participation.

PubMed

1997-03-01

The government of Indonesia has taken steps to foster economic growth in the eastern region of the country by creating a transportation infrastructure. While many parts of the region still lack sea transportation, the rate of economic growth in the region has outstripped that of the nation since 1993. In this region, clove was the major cash crop, but trade regulations have reduced the profit in clove farming. Maluku was once renowned for its fishing, but this industry is now dominated by big investors, and the region depends upon aid for backward villages and upon loans from nongovernmental organizations (NGOs) that are funneled through local self-help groups. The Yayasan Indonesia Sejahtera (YIS) has worked in eastern Indonesia since 1974 and is planning to collect data on its most urgent problems and to fund the income-generation project proposals submitted by NGOs. Among these programs are foundations that provide funds for fishermen to purchase motorized boats, loans to groups of traders, and loans for fishermen and for breeding goats and chickens. Women can also procure loans to sell groceries or for farming activities. The self-help groups of fishermen face obstacles when the weather prohibits fishing, and the farmers have problems obtaining good breeders and combating disease among their livestock. The NGOs combat problems caused by a lack of field workers and by limited funds as well as the obstacles caused by the geography of the region. Members of the self-help groups are improving their knowledge and skills, and the NGOs are improving their management capabilities to deal with these challenges.

Three-dimensional numerical study of heat transfer enhancement in separated flows

NASA Astrophysics Data System (ADS)

Kumar, Saurav; Vengadesan, S.

2017-11-01

The flow separation appears in a wide range of heat transfer applications and causes poor heat transfer performance. It motivates the study of heat transfer enhancement in laminar as well as turbulent flows over a backward facing step by means of an adiabatic fin mounted on the top wall. Recently, we have studied steady, 2-D numerical simulations in laminar flow and investigated the effect of fin length, location, and orientation. It revealed that the addition of fin causes enhancement of heat transfer and it is very effective to control the flow and thermal behavior. The fin is most effective and sensitive when it is placed exactly above the step. A slight displacement of the fin in upstream of the step causes the complete change of flow and thermal behavior. Based on the obtained 2-D results it is interesting to investigate the side wall effect in three-dimensional simulations. The comparison of two-dimensional and three-dimensional numerical simulations with the available experimental results will be presented. Special attention has to be given to capture unsteadiness in the flow and thermal field.

Application of computational fluid dynamics to the design of the Space Transportation Main Engine subscale nozzle

NASA Technical Reports Server (NTRS)

Garrett, J. L.; Syed, S. A.

1992-01-01

CFD analyses of the Space Transportation Main Engine film/dump cooled subscale nozzle are presented, with an emphasis on the timely impact of CFD in the design of the subscale nozzle secondary coolant system. Calculations were performed with the Generalized Aerodynamic Simulation Program (GASP), using a Baldwin-Lomas Turbulence model, and finite rate hydrogen-oxygen chemistry. Design iterations for both the secondary coolant cavity passage and the secondary coolant lip are presented. In addition, validation of the GASP chemistry and turbulence models by comparison with data and other CFD codes are presented for a hypersonic laminar separation corner, a backward facing step, and a 2D scramjet nozzle with hydrogen-oxygen kinetics.

A New Reynolds Stress Algebraic Equation Model

NASA Technical Reports Server (NTRS)

Shih, Tsan-Hsing; Zhu, Jiang; Lumley, John L.

1994-01-01

A general turbulent constitutive relation is directly applied to propose a new Reynolds stress algebraic equation model. In the development of this model, the constraints based on rapid distortion theory and realizability (i.e. the positivity of the normal Reynolds stresses and the Schwarz' inequality between turbulent velocity correlations) are imposed. Model coefficients are calibrated using well-studied basic flows such as homogeneous shear flow and the surface flow in the inertial sublayer. The performance of this model is then tested in complex turbulent flows including the separated flow over a backward-facing step and the flow in a confined jet. The calculation results are encouraging and point to the success of the present model in modeling turbulent flows with complex geometries.

Considering the reversibility of passive and reactive transport problems: Are forward-in-time and backward-in-time models ever equivalent?

NASA Astrophysics Data System (ADS)

Engdahl, N.

2017-12-01

Backward in time (BIT) simulations of passive tracers are often used for capture zone analysis, source area identification, and generation of travel time and age distributions. The BIT approach has the potential to become an immensely powerful tool for direct inverse modeling but the necessary relationships between the processes modeled in the forward and backward models have yet to be formally established. This study explores the time reversibility of passive and reactive transport models in a variety of 2D heterogeneous domains using particle-based random walk methods for the transport and nonlinear reaction steps. Distributed forward models are used to generate synthetic observations that form the initial conditions for the backward in time models and we consider both linear-flood and point injections. The results for passive travel time distributions show that forward and backward models are not exactly equivalent but that the linear-flood BIT models are reasonable approximations. Point based BIT models fall within the travel time range of the forward models, though their distributions can be distinctive in some cases. The BIT approximation is not as robust when nonlinear reactive transport is considered and we find that this reaction system is only exactly reversible under uniform flow conditions. We use a series of simplified, longitudinally symmetric, but heterogeneous, domains to illustrate the causes of these discrepancies between the two model types. Many of the discrepancies arise because diffusion is a "self-adjoint" operator, which causes mass to spread in the forward and backward models. This allows particles to enter low velocity regions in the both models, which has opposite effects in the forward and reverse models. It may be possible to circumvent some of these limitations using an anti-diffusion model to undo mixing when time is reversed, but this is beyond the capabilities of the existing Lagrangian methods.

Ordered Backward XPath Axis Processing against XML Streams

NASA Astrophysics Data System (ADS)

Nizar M., Abdul; Kumar, P. Sreenivasa

Processing of backward XPath axes against XML streams is challenging for two reasons: (i) Data is not cached for future access. (ii) Query contains steps specifying navigation to the data that already passed by. While there are some attempts to process parent and ancestor axes, there are very few proposals to process ordered backward axes namely, preceding and preceding-sibling. For ordered backward axis processing, the algorithm, in addition to overcoming the limitations on data availability, has to take care of ordering constraints imposed by these axes. In this paper, we show how backward ordered axes can be effectively represented using forward constraints. We then discuss an algorithm for XML stream processing of XPath expressions containing ordered backward axes. The algorithm uses a layered cache structure to systematically accumulate query results. Our experiments show that the new algorithm gains remarkable speed up over the existing algorithm without compromising on bufferspace requirement.

Least-squares finite element methods for compressible Euler equations

NASA Technical Reports Server (NTRS)

Jiang, Bo-Nan; Carey, G. F.

1990-01-01

A method based on backward finite differencing in time and a least-squares finite element scheme for first-order systems of partial differential equations in space is applied to the Euler equations for gas dynamics. The scheme minimizes the L-sq-norm of the residual within each time step. The method naturally generates numerical dissipation proportional to the time step size. An implicit method employing linear elements has been implemented and proves robust. For high-order elements, computed solutions based on the L-sq method may have oscillations for calculations at similar time step sizes. To overcome this difficulty, a scheme which minimizes the weighted H1-norm of the residual is proposed and leads to a successful scheme with high-degree elements. Finally, a conservative least-squares finite element method is also developed. Numerical results for two-dimensional problems are given to demonstrate the shock resolution of the methods and compare different approaches.

New and Emerging Problems in School Adminstration.

ERIC Educational Resources Information Center

TenHaken, Richard E.

This paper examines a number of problems facing school board members and educational administrators today and suggests some possible approaches to addressing those problems effectively. In considering each problem area, the author emphasizes its impact on the activities and responsibilities of school officials and discusses concrete steps they can…

Description and use of LSODE, the Livermore Solver for Ordinary Differential Equations

NASA Technical Reports Server (NTRS)

Radhakrishnan, Krishnan; Hindmarsh, Alan C.

1993-01-01

LSODE, the Livermore Solver for Ordinary Differential Equations, is a package of FORTRAN subroutines designed for the numerical solution of the initial value problem for a system of ordinary differential equations. It is particularly well suited for 'stiff' differential systems, for which the backward differentiation formula method of orders 1 to 5 is provided. The code includes the Adams-Moulton method of orders 1 to 12, so it can be used for nonstiff problems as well. In addition, the user can easily switch methods to increase computational efficiency for problems that change character. For both methods a variety of corrector iteration techniques is included in the code. Also, to minimize computational work, both the step size and method order are varied dynamically. This report presents complete descriptions of the code and integration methods, including their implementation. It also provides a detailed guide to the use of the code, as well as an illustrative example problem.

Two neural network algorithms for designing optimal terminal controllers with open final time

NASA Technical Reports Server (NTRS)

Plumer, Edward S.

1992-01-01

Multilayer neural networks, trained by the backpropagation through time algorithm (BPTT), have been used successfully as state-feedback controllers for nonlinear terminal control problems. Current BPTT techniques, however, are not able to deal systematically with open final-time situations such as minimum-time problems. Two approaches which extend BPTT to open final-time problems are presented. In the first, a neural network learns a mapping from initial-state to time-to-go. In the second, the optimal number of steps for each trial run is found using a line-search. Both methods are derived using Lagrange multiplier techniques. This theoretical framework is used to demonstrate that the derived algorithms are direct extensions of forward/backward sweep methods used in N-stage optimal control. The two algorithms are tested on a Zermelo problem and the resulting trajectories compare favorably to optimal control results.

Being forward not backward: lexical limits to masked priming.

PubMed

Davis, Chris; Kim, Jeesun; Forster, Kenneth I

2008-05-01

This study investigated whether masked priming is mediated by existing memory representations by determining whether nonwords targets would show repetition priming. To avoid the potential confound that nonword repetition priming would be obscured by a familiarity response bias, the standard lexical decision and naming tasks were modified to make targets unfamiliar. Participants were required to read a target string from right to left (i.e., "ECAF" should be read as "FACE") and then make a response. To examine if priming was based on lexical representations, repetition primes consisted of words when read forwards or backwards (e.g., "face", "ecaf") and nonwords (e.g., "pame", "emap"). Forward and backward primes were used to test if task instruction affected prime encoding. The lexical decision and naming tasks showed the same pattern of results: priming only occurred for forward primes with word targets (e.g., "face-ECAF"). Additional experiments to test if response priming affected the LDT indicated that the lexical status of the prime per se did not affect target responses. These results showed that the encoding of masked primes was unaffected by the novel task instruction and support the view that masked priming is due to the automatic triggering of pre-established computational processes based on stored information.

Lanczos eigensolution method for high-performance computers

NASA Technical Reports Server (NTRS)

Bostic, Susan W.

1991-01-01

The theory, computational analysis, and applications are presented of a Lanczos algorithm on high performance computers. The computationally intensive steps of the algorithm are identified as: the matrix factorization, the forward/backward equation solution, and the matrix vector multiples. These computational steps are optimized to exploit the vector and parallel capabilities of high performance computers. The savings in computational time from applying optimization techniques such as: variable band and sparse data storage and access, loop unrolling, use of local memory, and compiler directives are presented. Two large scale structural analysis applications are described: the buckling of a composite blade stiffened panel with a cutout, and the vibration analysis of a high speed civil transport. The sequential computational time for the panel problem executed on a CONVEX computer of 181.6 seconds was decreased to 14.1 seconds with the optimized vector algorithm. The best computational time of 23 seconds for the transport problem with 17,000 degs of freedom was on the the Cray-YMP using an average of 3.63 processors.

Biomechanical characteristics of adults walking forward and backward in water at different stride frequencies.

PubMed

Cadenas-Sánchez, Cristina; Arellano, Raúl; Taladriz, Sonia; López-Contreras, Gracia

2016-01-01

The aim of this study was to examine spatiotemporal characteristics and joint angles during forward and backward walking in water at low and high stride frequency. Eight healthy adults (22.1 ± 1.1 years) walked forward and backward underwater at low (50 pulses) and high frequency (80 pulses) at the xiphoid process level with arms crossed at the chest. The main differences observed were that the participants presented a greater speed (0.58 vs. 0.85 m/s) and more asymmetry of the step length (1.24 vs. 1.48) at high frequency whilst the stride and step length (0.84 vs. 0.7 m and 0.43 vs. 0.35 m, respectively) were lower compared to low frequency (P < 0.05). Support phase duration was higher at forward walking than backward walking (61.2 vs. 59.0%). At initial contact, we showed that during forward walking, the ankle and hip presented more flexion than during backward walking (ankle: 84.0 vs. 91.8º and hip: 22.8 vs. 8.0º; P < 0.001). At final stance, the knee and hip were more flexed at low frequency than at high frequency (knee: 150.0 vs. 157.0º and hip: -12.2 vs. -14.5º; P < 0.001). The knee angle showed more flexion at forward walking (134.0º) than backward walking (173.1º) (P < 0.001). In conclusion, these results show how forward and backward walking in water at different frequencies differ and contribute to a better understanding of this activity in training and rehabilitation.

Backward Channel Protection Based on Randomized Tree-Walking Algorithm and Its Analysis for Securing RFID Tag Information and Privacy

NASA Astrophysics Data System (ADS)

Choi, Wonjoon; Yoon, Myungchul; Roh, Byeong-Hee

Eavesdropping on backward channels in RFID environments may cause severe privacy problems because it means the exposure of personal information related to tags that each person has. However, most existing RFID tag security schemes are focused on the forward channel protections. In this paper, we propose a simple but effective method to solve the backward channel eavesdropping problem based on Randomized-tree walking algorithm for securing tag ID information and privacy in RFID-based applications. In order to show the efficiency of the proposed scheme, we derive two performance models for the cases when CRC is used and not used. It is shown that the proposed method can lower the probability of eavesdropping on backward channels near to ‘0.’

A stochastic maximum principle for backward control systems with random default time

NASA Astrophysics Data System (ADS)

Shen, Yang; Kuen Siu, Tak

2013-05-01

This paper establishes a necessary and sufficient stochastic maximum principle for backward systems, where the state processes are governed by jump-diffusion backward stochastic differential equations with random default time. An application of the sufficient stochastic maximum principle to an optimal investment and capital injection problem in the presence of default risk is discussed.

Visual-spatial abilities relate to mathematics achievement in children with heavy prenatal alcohol exposure

PubMed Central

Crocker, N.; Riley, E.P.; Mattson, S.N.

2014-01-01

Objective The current study examined the relationship between mathematics and attention, working memory, and visual memory in children with heavy prenatal alcohol exposure and controls. Method Fifty-six children (29 AE, 27 CON) were administered measures of global mathematics achievement (WRAT-3 Arithmetic & WISC-III Written Arithmetic), attention, (WISC-III Digit Span forward and Spatial Span forward), working memory (WISC-III Digit Span backward and Spatial Span backward), and visual memory (CANTAB Spatial Recognition Memory and Pattern Recognition Memory). The contribution of cognitive domains to mathematics achievement was analyzed using linear regression techniques. Attention, working memory and visual memory data were entered together on step 1 followed by group on step 2, and the interaction terms on step 3. Results Model 1 accounted for a significant amount of variance in both mathematics achievement measures, however, model fit improved with the addition of group on step 2. Significant predictors of mathematics achievement were Spatial Span forward and backward and Spatial Recognition Memory. Conclusions These findings suggest that deficits in spatial processing may be related to math impairments seen in FASD. In addition, prenatal alcohol exposure was associated with deficits in mathematics achievement, above and beyond the contribution of general cognitive abilities. PMID:25000323

Visual-spatial abilities relate to mathematics achievement in children with heavy prenatal alcohol exposure.

PubMed

Crocker, Nicole; Riley, Edward P; Mattson, Sarah N

2015-01-01

The current study examined the relationship between mathematics and attention, working memory, and visual memory in children with heavy prenatal alcohol exposure and controls. Subjects were 56 children (29 AE, 27 CON) who were administered measures of global mathematics achievement (WRAT-3 Arithmetic & WISC-III Written Arithmetic), attention, (WISC-III Digit Span forward and Spatial Span forward), working memory (WISC-III Digit Span backward and Spatial Span backward), and visual memory (CANTAB Spatial Recognition Memory and Pattern Recognition Memory). The contribution of cognitive domains to mathematics achievement was analyzed using linear regression techniques. Attention, working memory, and visual memory data were entered together on Step 1 followed by group on Step 2, and the interaction terms on Step 3. Model 1 accounted for a significant amount of variance in both mathematics achievement measures; however, model fit improved with the addition of group on Step 2. Significant predictors of mathematics achievement were Spatial Span forward and backward and Spatial Recognition Memory. These findings suggest that deficits in spatial processing may be related to math impairments seen in FASD. In addition, prenatal alcohol exposure was associated with deficits in mathematics achievement, above and beyond the contribution of general cognitive abilities. PsycINFO Database Record (c) 2015 APA, all rights reserved.

Optimal Control for Stochastic Delay Evolution Equations

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

Meng, Qingxin, E-mail: mqx@hutc.zj.cn; Shen, Yang, E-mail: skyshen87@gmail.com

2016-08-15

In this paper, we investigate a class of infinite-dimensional optimal control problems, where the state equation is given by a stochastic delay evolution equation with random coefficients, and the corresponding adjoint equation is given by an anticipated backward stochastic evolution equation. We first prove the continuous dependence theorems for stochastic delay evolution equations and anticipated backward stochastic evolution equations, and show the existence and uniqueness of solutions to anticipated backward stochastic evolution equations. Then we establish necessary and sufficient conditions for optimality of the control problem in the form of Pontryagin’s maximum principles. To illustrate the theoretical results, we applymore » stochastic maximum principles to study two examples, an infinite-dimensional linear-quadratic control problem with delay and an optimal control of a Dirichlet problem for a stochastic partial differential equation with delay. Further applications of the two examples to a Cauchy problem for a controlled linear stochastic partial differential equation and an optimal harvesting problem are also considered.« less

Effects of Implied Motion and Facing Direction on Positional Preferences in Single-Object Pictures.

PubMed

Palmer, Stephen E; Langlois, Thomas A

2017-07-01

Palmer, Gardner, and Wickens studied aesthetic preferences for pictures of single objects and found a strong inward bias: Right-facing objects were preferred left-of-center and left-facing objects right-of-center. They found no effect of object motion (people and cars showed the same inward bias as chairs and teapots), but the objects were not depicted as moving. Here we measured analogous inward biases with objects depicted as moving with an implied direction and speed by having participants drag-and-drop target objects into the most aesthetically pleasing position. In Experiment 1, human figures were shown diving or falling while moving forward or backward. Aesthetic biases were evident for both inward-facing and inward-moving figures, but the motion-based bias dominated so strongly that backward divers or fallers were preferred moving inward but facing outward. Experiment 2 investigated implied speed effects using images of humans, horses, and cars moving at different speeds (e.g., standing, walking, trotting, and galloping horses). Inward motion or facing biases were again present, and differences in their magnitude due to speed were evident. Unexpectedly, faster moving objects were generally preferred closer to frame center than slower moving objects. These results are discussed in terms of the combined effects of prospective, future-oriented biases, and retrospective, past-oriented biases.

The conditional moment closure method for modeling lean premixed turbulent combustion

NASA Astrophysics Data System (ADS)

Martin, Scott Montgomery

Natural gas fired lean premixed gas turbines have become the method of choice for new power generation systems due to their high efficiency and low pollutant emissions. As emission regulations for these combustion systems become more stringent, the use of numerical modeling has become an important a priori tool in designing clean and efficient combustors. Here a new turbulent combustion model is developed in an attempt to improve the state of the art. The Conditional Moment Closure (CMC) method is a new theory that has been applied to non-premixed combustion with good success. The application of the CMC method to premixed systems has been proposed, but has not yet been done. The premixed CMC method replaces the species mass fractions as independent variables with the species mass fractions that are conditioned on a reaction progress variable (RPV). Conservation equations for these new variables are then derived and solved. The general idea behind the CMC method is that the behavior of the chemical species is closely coupled to the reaction progress variable. Thus, species conservation equations that are conditioned on the RPV will have terms involving the fluctuating quantities that are much more likely to be negligible. The CMC method accounts for the interaction between scalar dissipation (micromixing) and chemistry, while de-coupling the kinetics from the bulk flow (macromixing). Here the CMC method is combined with a commercial computational fluid dynamics program, which calculates the large-scale fluid motions. The CMC model is validated by comparison to 2-D reacting backward facing step data. Predicted species, temperature and velocity fields are compared to experimental data with good success. The CMC model is also validated against the University of Washington's 3-D jet stirred reactor (JSR) data, which is an idealized lean premixed combustor. The JSR results are encouraging, but not as good as the backward facing step. The largest source of error is from the turbulence models, which are inadequate for the variable density and recirculating flows modeled here. The limitations of the turbulence models affected the calculation of the flow statistics, which are used to calculate the variance of the RPV, the scalar dissipation and the PDF.

Persisting mental health problems among AIDS-orphaned children in South Africa.

PubMed

Cluver, Lucie D; Orkin, Mark; Gardner, Frances; Boyes, Mark E

2012-04-01

  By 2008, 12 million children in sub-Saharan Africa were orphaned by AIDS. Cross-sectional studies show psychological problems for AIDS-orphaned children, but until now no longitudinal study has explored enduring psychological effects of AIDS-orphanhood in the developing world.   A 4-year longitudinal follow-up of AIDS-orphaned children with control groups of other-orphans and non-orphans. 1021 children (M = 13.4 years, 50% female, 98% isiXhosa-speaking) were interviewed in 2005 and followed up in 2009 with 71% retention (49% female, M = 16.9 years), in poor urban South African settlements. Children were interviewed using sociodemographic questionnaires and well-validated standardised scales for assessing depression, anxiety, and post-traumatic stress. Data were analysed using mixed-design ANOVA and backward-stepping regression.   AIDS-orphaned children showed higher depression, anxiety, and post-traumatic stress disorder (PTSD) scores in both 2005 and 2009 when compared with other-orphans and non-orphans. Backward-stepping regression, controlling for baseline mental health, and sociodemographic cofactors such as age, gender, and type of bereavement, revealed that being AIDS-orphaned in 2005 was associated with depression, anxiety, and PTSD scores in 2009. This was not the case for other-orphaned or non-orphaned children. Age interacted with orphan status, such that there was a steep rise in psychological distress in the AIDS-orphaned group, but no rise with age amongst other-orphans and non-orphans.   Negative mental health outcomes amongst AIDS-orphaned children are maintained and worsen over a 4-year period. It is important that psychosocial support programmes are sustained, and focus on youth as well as young children. © 2011 The Authors. Journal of Child Psychology and Psychiatry © 2011 Association for Child and Adolescent Mental Health.

A computational method for sharp interface advection.

PubMed

Roenby, Johan; Bredmose, Henrik; Jasak, Hrvoje

2016-11-01

We devise a numerical method for passive advection of a surface, such as the interface between two incompressible fluids, across a computational mesh. The method is called isoAdvector, and is developed for general meshes consisting of arbitrary polyhedral cells. The algorithm is based on the volume of fluid (VOF) idea of calculating the volume of one of the fluids transported across the mesh faces during a time step. The novelty of the isoAdvector concept consists of two parts. First, we exploit an isosurface concept for modelling the interface inside cells in a geometric surface reconstruction step. Second, from the reconstructed surface, we model the motion of the face-interface intersection line for a general polygonal face to obtain the time evolution within a time step of the submerged face area. Integrating this submerged area over the time step leads to an accurate estimate for the total volume of fluid transported across the face. The method was tested on simple two-dimensional and three-dimensional interface advection problems on both structured and unstructured meshes. The results are very satisfactory in terms of volume conservation, boundedness, surface sharpness and efficiency. The isoAdvector method was implemented as an OpenFOAM ® extension and is published as open source.

Hiding true emotions: micro-expressions in eyes retrospectively concealed by mouth movements

PubMed Central

Iwasaki, Miho; Noguchi, Yasuki

2016-01-01

When we encounter someone we dislike, we may momentarily display a reflexive disgust expression, only to follow-up with a forced smile and greeting. Our daily lives are replete with a mixture of true and fake expressions. Nevertheless, are these fake expressions really effective at hiding our true emotions? Here we show that brief emotional changes in the eyes (micro-expressions, thought to reflect true emotions) can be successfully concealed by follow-up mouth movements (e.g. a smile). In the same manner as backward masking, mouth movements of a face inhibited conscious detection of all types of micro-expressions in that face, even when viewers paid full attention to the eye region. This masking works only in a backward direction, however, because no disrupting effect was observed when the mouth change preceded the eye change. These results provide scientific evidence for everyday behaviours like smiling to dissemble, and further clarify a major reason for the difficulty we face in discriminating genuine from fake emotional expressions. PMID:26915796

Hiding true emotions: micro-expressions in eyes retrospectively concealed by mouth movements.

PubMed

Iwasaki, Miho; Noguchi, Yasuki

2016-02-26

When we encounter someone we dislike, we may momentarily display a reflexive disgust expression, only to follow-up with a forced smile and greeting. Our daily lives are replete with a mixture of true and fake expressions. Nevertheless, are these fake expressions really effective at hiding our true emotions? Here we show that brief emotional changes in the eyes (micro-expressions, thought to reflect true emotions) can be successfully concealed by follow-up mouth movements (e.g. a smile). In the same manner as backward masking, mouth movements of a face inhibited conscious detection of all types of micro-expressions in that face, even when viewers paid full attention to the eye region. This masking works only in a backward direction, however, because no disrupting effect was observed when the mouth change preceded the eye change. These results provide scientific evidence for everyday behaviours like smiling to dissemble, and further clarify a major reason for the difficulty we face in discriminating genuine from fake emotional expressions.

46 CFR 160.052-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2010 CFR

2010-10-01

... wearer in an upright or backward position with head and face out of water; (2) Have no tendency to turn a wearer face downward in the water; and (3) Be arranged so that 70 to 75 percent of the total is located... donning time for an uninitiated person. [CGD 72-163R, 38 FR 8120, Mar. 28, 1973] ...

The Amygdala Is Involved in Affective Priming Effect for Fearful Faces

ERIC Educational Resources Information Center

Yang, J.; Cao, Z.; Xu, X.; Chen, G.

2012-01-01

The object of this study was to investigate whether the amygdala is involved in affective priming effect after stimuli are encoded unconsciously and consciously. During the encoding phase, each masked face (fearful or neutral) was presented to participants six times for 17 ms each, using a backward masking paradigm. During the retrieval phase,…

Reactive Balance in Individuals With Chronic Stroke: Biomechanical Factors Related to Perturbation-Induced Backward Falling.

PubMed

Salot, Pooja; Patel, Prakruti; Bhatt, Tanvi

2016-03-01

An effective compensatory stepping response is the first line of defense for preventing a fall during sudden large external perturbations. The biomechanical factors that contribute to heightened fall risk in survivors of stroke, however, are not clearly understood. It is known that impending sensorimotor and balance deficits poststroke predispose these individuals to a risk of fall during sudden external perturbations. The purpose of this study was to examine the mechanism of fall risk in survivors of chronic stroke when exposed to sudden, slip-like forward perturbations in stance. This was a cross-sectional study. Fourteen individuals with stroke, 14 age-matched controls (AC group), and 14 young controls (YC group) were exposed to large-magnitude forward stance perturbations. Postural stability was computed as center of mass (COM) position (XCOM/BOS) and velocity (ẊCOM/BOS) relative to the base of support (BOS) at first step lift-off (LO) and touch-down (TD) and at second step TD. Limb support was quantified as vertical hip descent (Zhip) from baseline after perturbation onset. All participants showed a backward balance loss, with 71% of the stroke group experiencing a fall compared with no falls in the control groups (AC and YC groups). At first step LO, no between-group differences in XCOM/BOS and ẊCOM/BOS were noted. At first step TD, however, the stroke group had a significantly posterior XCOM/BOS and backward ẊCOM/BOS compared with the control groups. At second step TD, individuals with stroke were still more unstable (more posterior XCOM/BOS and backward ẊCOM/BOS) compared with the AC group. Individuals with stroke also showed greater peak Zhip compared with the control groups. Furthermore, the stroke group took a larger number of steps with shorter step length and delayed step initiation compared with the control groups. Although the study highlights the reactive balance deficits increasing fall risk in survivors of stroke compared with healthy adults, the study was restricted to individuals with chronic stroke only. It is likely that comparing compensatory stepping responses across different stages of recovery would enable clinicians to identify reactive balance deficits related to a specific stage of recovery. These findings suggest the inability of the survivors of stroke to regain postural stability with one or more compensatory steps, unlike their healthy counterparts. Such a response may expose them to a greater fall risk resulting from inefficient compensatory stepping and reduced vertical limb support. Therapeutic interventions for fall prevention, therefore, should focus on improving both reactive stepping and limb support. © 2016 American Physical Therapy Association.

Large-eddy simulation using the finite element method

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

McCallen, R.C.; Gresho, P.M.; Leone, J.M. Jr.

1993-10-01

In a large-eddy simulation (LES) of turbulent flows, the large-scale motion is calculated explicitly (i.e., approximated with semi-empirical relations). Typically, finite difference or spectral numerical schemes are used to generate an LES; the use of finite element methods (FEM) has been far less prominent. In this study, we demonstrate that FEM in combination with LES provides a viable tool for the study of turbulent, separating channel flows, specifically the flow over a two-dimensional backward-facing step. The combination of these methodologies brings together the advantages of each: LES provides a high degree of accuracy with a minimum of empiricism for turbulencemore » modeling and FEM provides a robust way to simulate flow in very complex domains of practical interest. Such a combination should prove very valuable to the engineering community.« less

An Element of Determinism in a Stochastic Flagellar Motor Switch

PubMed Central

Xie, Li; Altindal, Tuba; Wu, Xiao-Lun

2015-01-01

Marine bacterium Vibrio alginolyticus uses a single polar flagellum to navigate in an aqueous environment. Similar to Escherichia coli cells, the polar flagellar motor has two states; when the motor is counter-clockwise, the cell swims forward and when the motor is clockwise, the cell swims backward. V. alginolyticus also incorporates a direction randomization step at the start of the forward swimming interval by flicking its flagellum. To gain an understanding on how the polar flagellar motor switch is regulated, distributions of the forward Δf and backward Δb intervals are investigated herein. We found that the steady-state probability density functions, P(Δf) and P(Δb), of freely swimming bacteria are strongly peaked at a finite time, suggesting that the motor switch is not Poissonian. The short-time inhibition is sufficiently strong and long lasting, i.e., several hundred milliseconds for both intervals, which is readily observed and characterized. Treating motor reversal dynamics as a first-passage problem, which results from conformation fluctuations of the motor switch, we calculated P(Δf) and P(Δb) and found good agreement with the measurements. PMID:26554590

An Element of Determinism in a Stochastic Flagellar Motor Switch.

PubMed

Xie, Li; Altindal, Tuba; Wu, Xiao-Lun

2015-01-01

Marine bacterium Vibrio alginolyticus uses a single polar flagellum to navigate in an aqueous environment. Similar to Escherichia coli cells, the polar flagellar motor has two states; when the motor is counter-clockwise, the cell swims forward and when the motor is clockwise, the cell swims backward. V. alginolyticus also incorporates a direction randomization step at the start of the forward swimming interval by flicking its flagellum. To gain an understanding on how the polar flagellar motor switch is regulated, distributions of the forward Δf and backward Δb intervals are investigated herein. We found that the steady-state probability density functions, P(Δf) and P(Δb), of freely swimming bacteria are strongly peaked at a finite time, suggesting that the motor switch is not Poissonian. The short-time inhibition is sufficiently strong and long lasting, i.e., several hundred milliseconds for both intervals, which is readily observed and characterized. Treating motor reversal dynamics as a first-passage problem, which results from conformation fluctuations of the motor switch, we calculated P(Δf) and P(Δb) and found good agreement with the measurements.

Comparison of liquid rocket engine base region heat flux computations using three turbulence models

NASA Technical Reports Server (NTRS)

Kumar, Ganesh N.; Griffith, Dwaine O., II; Prendergast, Maurice J.; Seaford, C. M.

1993-01-01

The flow in the base region of launch vehicles is characterized by flow separation, flow reversals, and reattachment. Computation of the convective heat flux in the base region and on the nozzle external surface of Space Shuttle Main Engine and Space Transportation Main Engine (STME) is an important part of defining base region thermal environments. Several turbulence models were incorporated in a CFD code and validated for flow and heat transfer computations in the separated and reattaching regions associated with subsonic and supersonic flows over backward facing steps. Heat flux computations in the base region of a single STME engine and a single S1C engine were performed using three different wall functions as well as a renormalization-group based k-epsilon model. With the very limited data available, the computed values are seen to be of the right order of magnitude. Based on the validation comparisons, it is concluded that all the turbulence models studied have predicted the reattachment location and the velocity profiles at various axial stations downstream of the step very well.

Electrophysiological Correlates of Subliminal Perception of Facial Expressions in Individuals with Autistic Traits: A Backward Masking Study

PubMed Central

Vukusic, Svjetlana; Ciorciari, Joseph; Crewther, David P.

2017-01-01

People with Autism spectrum disorder (ASD) show difficulty in social communication, especially in the rapid assessment of emotion in faces. This study examined the processing of emotional faces in typically developing adults with high and low levels of autistic traits (measured using the Autism Spectrum Quotient—AQ). Event-related potentials (ERPs) were recorded during viewing of backward-masked neutral, fearful and happy faces presented under two conditions: subliminal (16 ms, below the level of visual conscious awareness) and supraliminal (166 ms, above the time required for visual conscious awareness). Individuals with low and high AQ differed in the processing of subliminal faces, with the low AQ group showing an enhanced N2 amplitude for subliminal happy faces. Some group differences were found in the condition effects, with the Low AQ showing shorter frontal P3b and N4 latencies for subliminal vs. supraliminal condition. Although results did not show any group differences on the face-specific N170 component, there were shorter N170 latencies for supraliminal vs. subliminal conditions across groups. The results observed on the N2, showing group differences in subliminal emotion processing, suggest that decreased sensitivity to the reward value of social stimuli is a common feature both of people with ASD as well as people with high autistic traits from the normal population. PMID:28588465

Electrophysiological Correlates of Subliminal Perception of Facial Expressions in Individuals with Autistic Traits: A Backward Masking Study.

PubMed

Vukusic, Svjetlana; Ciorciari, Joseph; Crewther, David P

2017-01-01

People with Autism spectrum disorder (ASD) show difficulty in social communication, especially in the rapid assessment of emotion in faces. This study examined the processing of emotional faces in typically developing adults with high and low levels of autistic traits (measured using the Autism Spectrum Quotient-AQ). Event-related potentials (ERPs) were recorded during viewing of backward-masked neutral, fearful and happy faces presented under two conditions: subliminal (16 ms, below the level of visual conscious awareness) and supraliminal (166 ms, above the time required for visual conscious awareness). Individuals with low and high AQ differed in the processing of subliminal faces, with the low AQ group showing an enhanced N2 amplitude for subliminal happy faces. Some group differences were found in the condition effects, with the Low AQ showing shorter frontal P3b and N4 latencies for subliminal vs. supraliminal condition. Although results did not show any group differences on the face-specific N170 component, there were shorter N170 latencies for supraliminal vs. subliminal conditions across groups. The results observed on the N2, showing group differences in subliminal emotion processing, suggest that decreased sensitivity to the reward value of social stimuli is a common feature both of people with ASD as well as people with high autistic traits from the normal population.

Computation and analysis of backward ray-tracing in aero-optics flow fields.

PubMed

Xu, Liang; Xue, Deting; Lv, Xiaoyi

2018-01-08

A backward ray-tracing method is proposed for aero-optics simulation. Different from forward tracing, the backward tracing direction is from the internal sensor to the distant target. Along this direction, the tracing in turn goes through the internal gas region, the aero-optics flow field, and the freestream. The coordinate value, the density, and the refractive index are calculated at each tracing step. A stopping criterion is developed to ensure the tracing stops at the outer edge of the aero-optics flow field. As a demonstration, the analysis is carried out for a typical blunt nosed vehicle. The backward tracing method and stopping criterion greatly simplify the ray-tracing computations in the aero-optics flow field, and they can be extended to our active laser illumination aero-optics study because of the reciprocity principle.

46 CFR 160.060-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2010 CFR

2010-10-01

...: (1) Be arranged to hold the wearer in an upright or backward position with head and face out of water; (2) Have no tendency to turn the wearer face downward in the water; and (3) Be arranged so that 70 to... the type designed; and (2) Facilitate donning time for an uninitiated person. [CGD 72-163R, 38 FR 8122...

A numerical solution of the supersonic flow over a rearward facing step with transverse non-reacting hydrogen injection

NASA Technical Reports Server (NTRS)

Berman, H. A.; Anderson, J. D., Jr.; Drummond, J. P.

1982-01-01

The present investigation represents an application of computational fluid dynamics to a problem associated with the flow in the combustor region of a supersonic combustion ramjet engine (scramjet). The governing equations are considered, taking into account the Navier-Stokes equations, a molecular viscosity calculation, the molecular thermal conductivity, molecular diffusion, and a turbulence model. The employed numerical solution is patterned after the explicit, time-dependent, unsplit, predictor-corrector, finite-difference method given by MacCormack (1969). The calculation is concerned with the supersonic flow over a rearward-facing step with transverse H2 injection at conditions germane to the combustor region of a scramjet engine. The H2 jet acts as an effective body which essentially shields the primary flow from the rearward-facing step, thus substantially changing the wave pattern in the primary flow.

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

NASA Astrophysics Data System (ADS)

Cox, Christopher

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

Problem Analysis: The First Step in Prevention Planning. A Prevention 101 Series Publication

ERIC Educational Resources Information Center

DeJong, William

2009-01-01

Student alcohol and other drug abuse and violence (AODV) still reign as the most serious social problems faced by U.S. institutions of higher education. To tackle these problems, campus administrators--working in conjunction with partners from the surrounding community--need to put in place an integrated set of strategies that address the mix of…

In-shoe plantar pressure distribution and lower extremity muscle activity patterns of backward compared to forward running on a treadmill.

PubMed

Sterzing, Thorsten; Frommhold, Clivia; Rosenbaum, Dieter

2016-05-01

Backward locomotion in humans occurs during leisure, rehabilitation, and competitive sports. Little is known about its general biomechanical characteristics and how it affects lower extremity loading as well as muscle coordination. Thus, the purpose of this research was to analyze in-shoe plantar pressure patterns and lower extremity muscle activity patterns for backward compared to forward running. On a treadmill, nineteen runners performed forward running at their individually preferred speed, followed by backward running at 70% of their self-selected forward speed. In-shoe plantar pressures of nine foot regions and muscular activity of nine lower extremity muscles were recorded simultaneously over a one-minute interval. Backward and forward running variables were averaged over the accumulated steps and compared with Wilcoxon-signed rank tests (p<.05). For backward compared to forward running, in-shoe plantar pressure distribution showed a load increase under metatarsal heads I and II, as well as under the medial midfoot. This was indicated by higher maximum forces and peak pressures, and by longer contact times. Muscle activity showed significantly higher mean amplitudes during backward running in the semitendinosus, rectus femoris, vastus lateralis, and gluteus medius during stance, and in the rectus femoris during swing phase, while significantly lower mean amplitudes were observed in the tibialis anterior during swing phase. Observations indicate plantar foot loading and muscle activity characteristics that are specific for the running direction. Thus, backward running may be used on purpose for certain rehabilitation tasks, aiming to strengthen respective lower extremity muscles. Furthermore, the findings are relevant for sport specific backward locomotion training. Finally, results provide an initial baseline for innovative athletic footwear development aiming to increase comfort and performance during backward running. Copyright © 2016 Elsevier B.V. All rights reserved.

Relative Effects of Forward and Backward Planning on Goal Pursuit.

PubMed

Park, Jooyoung; Lu, Fang-Chi; Hedgcock, William M

2017-11-01

Considerable research has shown that planning plays an important role in goal pursuit. But how does the way people plan affect goal pursuit? Research on this question is scarce. In the current research, we examined how planning the steps required for goal attainment in chronological order (i.e., forward planning) and reverse chronological order (i.e., backward planning) influences individuals' motivation for and perceptions of goal pursuit. Compared with forward planning, backward planning not only led to greater motivation, higher goal expectancy, and less time pressure but also resulted in better goal-relevant performance. We further demonstrated that this motivational effect occurred because backward planning allowed people to think of tasks required to reach their goals more clearly, especially when goals were complex to plan. These findings suggest that the way people plan matters just as much as whether or not they plan.

Partial Cavity Flows at High Reynolds Numbers

NASA Astrophysics Data System (ADS)

Makiharju, Simo; Elbing, Brian; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

2009-11-01

Partial cavity flows created for friction drag reduction were examined on a large-scale. Partial cavities were investigated at Reynolds numbers up to 120 million, and stable cavities with frictional drag reduction of more than 95% were attained at optimal conditions. The model used was a 3 m wide and 12 m long flat plate with a plenum on the bottom. To create the partial cavity, air was injected at the base of an 18 cm backwards-facing step 2.1 m from the leading edge. The geometry at the cavity closure was varied for different flow speeds to optimize the closure of the cavity. Cavity gas flux, thickness, frictional loads, and cavity pressures were measured over a range of flow speeds and air injection fluxes. High-speed video was used extensively to investigate the unsteady three dimensional cavity closure, the overall cavity shape and oscillations.

Calculations of turbulent separated flows

NASA Technical Reports Server (NTRS)

Zhu, J.; Shih, T. H.

1993-01-01

A numerical study of incompressible turbulent separated flows is carried out by using two-equation turbulence models of the K-epsilon type. On the basis of realizability analysis, a new formulation of the eddy-viscosity is proposed which ensures the positiveness of turbulent normal stresses - a realizability condition that most existing two-equation turbulence models are unable to satisfy. The present model is applied to calculate two backward-facing step flows. Calculations with the standard K-epsilon model and a recently developed RNG-based K-epsilon model are also made for comparison. The calculations are performed with a finite-volume method. A second-order accurate differencing scheme and sufficiently fine grids are used to ensure the numerical accuracy of solutions. The calculated results are compared with the experimental data for both mean and turbulent quantities. The comparison shows that the present model performs quite well for separated flows.

What Eye Movements Can Tell about Theory of Mind in a Strategic Game

PubMed Central

Meijering, Ben; van Rijn, Hedderik; Taatgen, Niels A.; Verbrugge, Rineke

2012-01-01

This study investigates strategies in reasoning about mental states of others, a process that requires theory of mind. It is a first step in studying the cognitive basis of such reasoning, as strategies affect tradeoffs between cognitive resources. Participants were presented with a two-player game that required reasoning about the mental states of the opponent. Game theory literature discerns two candidate strategies that participants could use in this game: either forward reasoning or backward reasoning. Forward reasoning proceeds from the first decision point to the last, whereas backward reasoning proceeds in the opposite direction. Backward reasoning is the only optimal strategy, because the optimal outcome is known at each decision point. Nevertheless, we argue that participants prefer forward reasoning because it is similar to causal reasoning. Causal reasoning, in turn, is prevalent in human reasoning. Eye movements were measured to discern between forward and backward progressions of fixations. The observed fixation sequences corresponded best with forward reasoning. Early in games, the probability of observing a forward progression of fixations is higher than the probability of observing a backward progression. Later in games, the probabilities of forward and backward progressions are similar, which seems to imply that participants were either applying backward reasoning or jumping back to previous decision points while applying forward reasoning. Thus, the game-theoretical favorite strategy, backward reasoning, does seem to exist in human reasoning. However, participants preferred the more familiar, practiced, and prevalent strategy: forward reasoning. PMID:23029341

What eye movements can tell about theory of mind in a strategic game.

PubMed

Meijering, Ben; van Rijn, Hedderik; Taatgen, Niels A; Verbrugge, Rineke

2012-01-01

This study investigates strategies in reasoning about mental states of others, a process that requires theory of mind. It is a first step in studying the cognitive basis of such reasoning, as strategies affect tradeoffs between cognitive resources. Participants were presented with a two-player game that required reasoning about the mental states of the opponent. Game theory literature discerns two candidate strategies that participants could use in this game: either forward reasoning or backward reasoning. Forward reasoning proceeds from the first decision point to the last, whereas backward reasoning proceeds in the opposite direction. Backward reasoning is the only optimal strategy, because the optimal outcome is known at each decision point. Nevertheless, we argue that participants prefer forward reasoning because it is similar to causal reasoning. Causal reasoning, in turn, is prevalent in human reasoning. Eye movements were measured to discern between forward and backward progressions of fixations. The observed fixation sequences corresponded best with forward reasoning. Early in games, the probability of observing a forward progression of fixations is higher than the probability of observing a backward progression. Later in games, the probabilities of forward and backward progressions are similar, which seems to imply that participants were either applying backward reasoning or jumping back to previous decision points while applying forward reasoning. Thus, the game-theoretical favorite strategy, backward reasoning, does seem to exist in human reasoning. However, participants preferred the more familiar, practiced, and prevalent strategy: forward reasoning.

Improving Primary School Prospective Teachers' Understanding of the Mathematics Modeling Process

ERIC Educational Resources Information Center

Bal, Aytgen Pinar; Doganay, Ahmet

2014-01-01

The development of mathematical thinking plays an important role on the solution of problems faced in daily life. Determining the relevant variables and necessary procedural steps in order to solve problems constitutes the essence of mathematical thinking. Mathematical modeling provides an opportunity for explaining thoughts in real life by making…

Managing pets with behavior problems: realistic expectations.

PubMed

Horwitz, Debra F

2008-09-01

Management solutions offer a useful tool for owners faced with behavior issues in their pets. In some cases management will improve the behavior and allow control. In other situations it may be only the first step in treatment. By offering management solutions, veterinarians can help owners with problem pets and begin the road to recovery.

Elastic scattering of 8He on 4He and 4 n system

NASA Astrophysics Data System (ADS)

Wolski, R.; Sidorchuk, S. I.; Ter-Akopian, G. M.; Fomichev, A. S.; Rodin, A. M.; Stepantsov, S. V.; Mittig, W.; Roussel-Chomaz, P.; Savajols, H.; Alamanos, N.; Auger, F.; Lapoux, V.; Raabe, R.; Tchuvil'sky, Yu. M.; Rusek, K.

2003-07-01

Elastic scattering of a 26A MeV beam of 8He on a gaseous helium target has been studied. In spite of efforts made for the observation of backward angle enhancement only upper limits could be obtained for the elastic scattering cross section at backward angles. The angular distribution of 8He nuclei scattered to CM 20°-80° was was analyzed in terms of a phenomenological Optical Model. Possible contributions from transfer reactions were estimated. The DWBA calculations indicate that the two step 2n transfer is more important than the one step 4n transfer. The transfer reaction d( 8He, 6Li)4n is discussed in terms of possible tests of a four-neutron system.

2D trajectory estimation during free walking using a tiptoe-mounted inertial sensor.

PubMed

Sagawa, Koichi; Ohkubo, Kensuke

2015-07-16

An estimation method for a two-dimensional walking trajectory during free walking, such as forward walking, side stepping and backward walking, was investigated using a tiptoe-mounted inertial sensor. The horizontal trajectory of the toe-tip is obtained by double integration of toe-tip acceleration during the moving phase in which the sensor is rotated before foot-off or after foot-contact, in addition to the swing phase. Special functions that determine the optimum moving phase as the integral duration in every one step are developed statistically using the gait cycle and the resultant angular velocity of dorsi/planter flexion, pronation/supination and inversion/eversion so that the difference between the estimated trajectory and actual one gives a minimum value during free walking with several cadences. To develop the functions, twenty healthy volunteers participated in free walking experiments in which subjects performed forward walking, side stepping to the right, side stepping to the left, and backward walking at 39 m down a straight corridor with several predetermined cadences. To confirm the effect of the developed functions, five healthy subjects participated in the free walking experiment in which each subject performed free walking with different velocities of normal, fast, and slow based on their own assessment in a square course with 7 m side. The experimentally obtained results of free walking with a combination of forward walking, backward walking, and side stepping indicate that the proposed method produces walking trajectory with high precision compared with the constant threshold method which determines swing phase using the size of the angular velocity. Copyright © 2015 Elsevier Ltd. All rights reserved.

Education Reform: A Step Forward or a Step Backward for Students with Learning Disabilities. Proceedings of a Symposium (Atlanta, Georgia, March 7-8, 1992).

ERIC Educational Resources Information Center

Learning Disabilities Association of America, Pittsburgh, PA.

This proceedings document includes 11 papers presented at a 1992 symposium on the impact of current educational reform initiatives on students with learning disabilities. Preceding the papers is a summary of the outcomes of the symposium, which are enumerated in terms of questions generated, commonalities, unresolved topics, and next steps. Papers…

Model-Free Adaptive Control for Unknown Nonlinear Zero-Sum Differential Game.

PubMed

Zhong, Xiangnan; He, Haibo; Wang, Ding; Ni, Zhen

2018-05-01

In this paper, we present a new model-free globalized dual heuristic dynamic programming (GDHP) approach for the discrete-time nonlinear zero-sum game problems. First, the online learning algorithm is proposed based on the GDHP method to solve the Hamilton-Jacobi-Isaacs equation associated with optimal regulation control problem. By setting backward one step of the definition of performance index, the requirement of system dynamics, or an identifier is relaxed in the proposed method. Then, three neural networks are established to approximate the optimal saddle point feedback control law, the disturbance law, and the performance index, respectively. The explicit updating rules for these three neural networks are provided based on the data generated during the online learning along the system trajectories. The stability analysis in terms of the neural network approximation errors is discussed based on the Lyapunov approach. Finally, two simulation examples are provided to show the effectiveness of the proposed method.

Assessment of an Unstructured-Grid Method for Predicting 3-D Turbulent Viscous Flows

NASA Technical Reports Server (NTRS)

Frink, Neal T.

1996-01-01

A method Is presented for solving turbulent flow problems on three-dimensional unstructured grids. Spatial discretization Is accomplished by a cell-centered finite-volume formulation using an accurate lin- ear reconstruction scheme and upwind flux differencing. Time is advanced by an implicit backward- Euler time-stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one-equation model, which is coupled with a wall function to reduce the number of cells in the sublayer region of the boundary layer. A systematic assessment of the method is presented to devise guidelines for more strategic application of the technology to complex problems. The assessment includes the accuracy In predictions of skin-friction coefficient, law-of-the-wall behavior, and surface pressure for a flat-plate turbulent boundary layer, and for the ONERA M6 wing under a high Reynolds number, transonic, separated flow condition.

Combined Tensor Fitting and TV Regularization in Diffusion Tensor Imaging Based on a Riemannian Manifold Approach.

PubMed

Baust, Maximilian; Weinmann, Andreas; Wieczorek, Matthias; Lasser, Tobias; Storath, Martin; Navab, Nassir

2016-08-01

In this paper, we consider combined TV denoising and diffusion tensor fitting in DTI using the affine-invariant Riemannian metric on the space of diffusion tensors. Instead of first fitting the diffusion tensors, and then denoising them, we define a suitable TV type energy functional which incorporates the measured DWIs (using an inverse problem setup) and which measures the nearness of neighboring tensors in the manifold. To approach this functional, we propose generalized forward- backward splitting algorithms which combine an explicit and several implicit steps performed on a decomposition of the functional. We validate the performance of the derived algorithms on synthetic and real DTI data. In particular, we work on real 3D data. To our knowledge, the present paper describes the first approach to TV regularization in a combined manifold and inverse problem setup.

Assessment of an Unstructured-Grid Method for Predicting 3-D Turbulent Viscous Flows

NASA Technical Reports Server (NTRS)

Frink, Neal T.

1996-01-01

A method is presented for solving turbulent flow problems on three-dimensional unstructured grids. Spatial discretization is accomplished by a cell-centered finite-volume formulation using an accurate linear reconstruction scheme and upwind flux differencing. Time is advanced by an implicit backward-Euler time-stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one-equation model, which is coupled with a wall function to reduce the number of cells in the sublayer region of the boundary layer. A systematic assessment of the method is presented to devise guidelines for more strategic application of the technology to complex problems. The assessment includes the accuracy in predictions of skin-friction coefficient, law-of-the-wall behavior, and surface pressure for a flat-plate turbulent boundary layer, and for the ONERA M6 wing under a high Reynolds number, transonic, separated flow condition.

Nonlinearly preconditioned semismooth Newton methods for variational inequality solution of two-phase flow in porous media

NASA Astrophysics Data System (ADS)

Yang, Haijian; Sun, Shuyu; Yang, Chao

2017-03-01

Most existing methods for solving two-phase flow problems in porous media do not take the physically feasible saturation fractions between 0 and 1 into account, which often destroys the numerical accuracy and physical interpretability of the simulation. To calculate the solution without the loss of this basic requirement, we introduce a variational inequality formulation of the saturation equilibrium with a box inequality constraint, and use a conservative finite element method for the spatial discretization and a backward differentiation formula with adaptive time stepping for the temporal integration. The resulting variational inequality system at each time step is solved by using a semismooth Newton algorithm. To accelerate the Newton convergence and improve the robustness, we employ a family of adaptive nonlinear elimination methods as a nonlinear preconditioner. Some numerical results are presented to demonstrate the robustness and efficiency of the proposed algorithm. A comparison is also included to show the superiority of the proposed fully implicit approach over the classical IMplicit Pressure-Explicit Saturation (IMPES) method in terms of the time step size and the total execution time measured on a parallel computer.

Modeling myosin VI stepping dynamics

NASA Astrophysics Data System (ADS)

Tehver, Riina

Myosin VI is a molecular motor that transports intracellular cargo as well as acts as an anchor. The motor has been measured to have unusually large step size variation and it has been reported to make both long forward and short inchworm-like forward steps, as well as step backwards. We have been developing a model that incorporates this diverse stepping behavior in a consistent framework. Our model allows us to predict the dynamics of the motor under different conditions and investigate the evolutionary advantages of the large step size variation.

Shear zone formation within the billet and metal flow through the die orifice in unlubricated axisymmetric forward and backward extrusion

NASA Astrophysics Data System (ADS)

Valberg, Henry; Costa, Andrè L. M.

2017-10-01

Metal flow inside the billet is known to be completely different in forward (FWE) and backward (BWE) Al-extrusion. A practical implication of this is that contamination near to the surface of the extrusion billet, or on the peripheral surface skin, tends to flow out of the die more readily in BWE than in FWE. It is therefore common in BWE to use a scalping operation on the billet to remove eventual sub-surface contamination that may be present. This additional working operation may be required in order to avoid surface quality problems on BWE profiles. In spite of the importance of metal flow in metals extrusion, there are still lack of knowledge about the topic. With recent progress in FEM-analysis for modelling deformation processing, however, it is now possible to perform accurate studies on metal flow phenomena by simulation on the computer. In our study, we are using the 3D FEM-program DEFORM® to model axisymmetric FWE and BWE in case of non-lubricated extrusion through a flat-faced die. Our primary focus is to consider the difference in appearance of shear zones present inside the extrusion billet for the two processes, including metal flow in the die mouth.

A computational method for sharp interface advection

PubMed Central

Bredmose, Henrik; Jasak, Hrvoje

2016-01-01

We devise a numerical method for passive advection of a surface, such as the interface between two incompressible fluids, across a computational mesh. The method is called isoAdvector, and is developed for general meshes consisting of arbitrary polyhedral cells. The algorithm is based on the volume of fluid (VOF) idea of calculating the volume of one of the fluids transported across the mesh faces during a time step. The novelty of the isoAdvector concept consists of two parts. First, we exploit an isosurface concept for modelling the interface inside cells in a geometric surface reconstruction step. Second, from the reconstructed surface, we model the motion of the face–interface intersection line for a general polygonal face to obtain the time evolution within a time step of the submerged face area. Integrating this submerged area over the time step leads to an accurate estimate for the total volume of fluid transported across the face. The method was tested on simple two-dimensional and three-dimensional interface advection problems on both structured and unstructured meshes. The results are very satisfactory in terms of volume conservation, boundedness, surface sharpness and efficiency. The isoAdvector method was implemented as an OpenFOAM® extension and is published as open source. PMID:28018619

Evidence for symmetry in the elementary process of bidirectional torque generation by the bacterial flagellar motor

PubMed Central

Nakamura, Shuichi; Kami-ike, Nobunori; Yokota, Jun-ichi P.; Minamino, Tohru; Namba, Keiichi

2010-01-01

The bacterial flagellar motor can rotate in both counterclockwise (CCW) and clockwise (CW) directions. It has been shown that the sodium ion-driven chimeric flagellar motor rotates with 26 steps per revolution, which corresponds to the number of FliG subunits that form part of the rotor ring, but the size of the backward step is smaller than the forward one. Here we report that the proton-driven flagellar motor of Salmonella also rotates with 26 steps per revolution but symmetrical in both CCW and CW directions with occasional smaller backward steps in both directions. Occasional shift in the stepping positions is also observed, suggesting the frequent exchange of stators in one of the 11–12 possible anchoring positions around the rotor. These observations indicate that the elementary process of torque generation by the cyclic association/dissociation of the stator with every FliG subunit along the circumference of the rotor is symmetric in CCW and CW rotation even though the structure of FliG is highly asymmetric and suggests a 180° rotation of a FliG domain for the rotor-stator interaction to reverse the direction of rotation. PMID:20876126

Stress analysis of three-dimensional roadway layout of stagger arrangement with field observation

NASA Astrophysics Data System (ADS)

Cui, Zimo; Chanda, Emmanuel; Zhao, Jingli; Wang, Zhihe

2018-01-01

Longwall top-coal caving (LTCC) has been a popular, more productive and cost-effective method for extracting thick (> 5 m) to ultra-thick coal seams in recent years. However, low-level recovery ratio of coal resources and top-coal loss above the supports at both ends of working face are long-term problems. Geological factors, such as large dip angle, soft rock, mining depth further complicate the problems. This paper proposes addressing this issue by adopting three-dimensional roadway layout of stagger arrangement (3-D RLSA). In this study, the first step was to analyse the stress environment surrounding head entry in the replacing working face based on the stress distribution characteristics at the triangular coal-pillar side in gob and the stress slip line field theory. In the second step, filed observation was conducted. Finally, an economic evaluation of the 3-D RLSA for extracting thick to ultra-thick seams was conducted.

Perturbed Partial Cavity Drag Reduction at High Reynolds Numbers

NASA Astrophysics Data System (ADS)

Makiharju, Simo; Elbing, Brian; Wiggins, Andrew; Dowling, David; Perlin, Marc; Ceccio, Steven

2010-11-01

Ventilated partial cavities were investigated at Reynolds numbers to 80 million. These cavities could be suitable for friction drag reduction on ocean going vessels and thereby lead to environmental and economical benefits. The test model was a 3.05 m wide by 12.9 m long flat plate, with a 0.18 m backward-facing step and a cavity-terminating beach, which had an adjustable slope, tilt and height. The step and beach trapped a ventilated partial cavity over the longitudinal mid-section of the model. Large-scale flow perturbations, mimicking the effect of ambient ocean waves were investigated. For the conditions tested a cavity could be maintained under perturbed flow conditions when the gas flux supplied was greater than the minimum required to maintain a cavity under steady conditions, with larger perturbations requiring more excess gas flux to maintain the cavity. High-speed video was used to observe the unsteady three dimensional cavity closure, the overall cavity shape, and the cavity oscillations. Cavities with friction drag reduction exceeding 95% were attained at optimal conditions. A simplified energy cost-benefit analysis of partial cavity drag reduction was also performed. The results suggest that PCDR could potentially lead to energy savings.

A Self-Adaptive Capacitive Compensation Technique for Body Channel Communication.

PubMed

Mao, Jingna; Yang, Huazhong; Lian, Yong; Zhao, Bo

2017-10-01

In wireless body area network, capacitive-coupling body channel communication (CC-BCC) has the potential to attain better energy efficiency over conventional wireless communication schemes. The CC-BCC scheme utilizes the human body as the forward signal transmission medium, reducing the path loss in wireless body-centric communications. However, the backward path is formed by the coupling capacitance between the ground electrodes (GEs) of transmitter (Tx) and receiver (Rx), which increases the path loss and results in a body posture dependent backward impedance. Conventional methods use a fixed inductor to resonate with the backward capacitor to compensate the path loss, while it's not effective in compensating the variable backward impedance induced by the body movements. In this paper, we propose a self-adaptive capacitive compensation (SACC) technique to address such a problem. A backward distance detector is introduced to estimate the distance between two GEs of Tx and Rx, and a backward capacitance model is built to calculate the backward capacitance. The calculated backward capacitance at varying body posture is compensated by a digitally controlled tunable inductor (DCTI). The proposed SACC technique is validated by a prototype CC-BCC system, and measurements are taken on human subjects. The measurement results show that 9dB-16 dB channel enhancement can be achieved at a backward path distance of 1 cm-10 cm.

Silent inflow condition for turbulent boundary layers

NASA Astrophysics Data System (ADS)

Gloerfelt, X.; Robinet, J.-C.

2017-12-01

The generation of a turbulent inflow is a tricky problem. In the framework of aeroacoustics, another important constraint is that the numerical strategy used to reach a turbulent state induces a spurious noise which is lower than the acoustic field of interest. For the study of noise radiated directly by a turbulent boundary layer on a flat plate, this constraint is severe since wall turbulence is a very inefficient source. That is why a method based on a transition by modal interaction using a base flow with an inflection point is proposed to cope with that. The base flow must be a solution of the equations so we use a profile behind a backward-facing step representative of experimental trip bands. A triad of resonant waves is selected by a local stability analysis of the linearized compressible equations and is added with a weak amplitude in the inlet plane. The compressible stability calculation allows the specification of the thermodynamic quantities at the inlet, which turns out to be fundamental to ensure a quiet inflow. A smooth transition is achieved with the rapid formation of Λ -shape vortices in a staggered organization as in subharmonic transition. The dominance of oblique waves promotes a rapid breakdown by the liftup mechanism of low-speed streaks. The quality of the fully turbulent state is assessed and the direct noise radiation from a turbulent boundary layer at Mach 0.5 is obtained with a very low level of spurious noise.

Optimal preconditioning of lattice Boltzmann methods

NASA Astrophysics Data System (ADS)

Izquierdo, Salvador; Fueyo, Norberto

2009-09-01

A preconditioning technique to accelerate the simulation of steady-state problems using the single-relaxation-time (SRT) lattice Boltzmann (LB) method was first proposed by Guo et al. [Z. Guo, T. Zhao, Y. Shi, Preconditioned lattice-Boltzmann method for steady flows, Phys. Rev. E 70 (2004) 066706-1]. The key idea in this preconditioner is to modify the equilibrium distribution function in such a way that, by means of a Chapman-Enskog expansion, a time-derivative preconditioner of the Navier-Stokes (NS) equations is obtained. In the present contribution, the optimal values for the free parameter γ of this preconditioner are searched both numerically and theoretically; the later with the aid of linear-stability analysis and with the condition number of the system of NS equations. The influence of the collision operator, single- versus multiple-relaxation-times (MRT), is also studied. Three steady-state laminar test cases are used for validation, namely: the two-dimensional lid-driven cavity, a two-dimensional microchannel and the three-dimensional backward-facing step. Finally, guidelines are suggested for an a priori definition of optimal preconditioning parameters as a function of the Reynolds and Mach numbers. The new optimally preconditioned MRT method derived is shown to improve, simultaneously, the rate of convergence, the stability and the accuracy of the lattice Boltzmann simulations, when compared to the non-preconditioned methods and to the optimally preconditioned SRT one. Additionally, direct time-derivative preconditioning of the LB equation is also studied.

Full-orbit and backward Monte Carlo simulation of runaway electrons

NASA Astrophysics Data System (ADS)

Del-Castillo-Negrete, Diego

2017-10-01

High-energy relativistic runaway electrons (RE) can be produced during magnetic disruptions due to electric fields generated during the thermal and current quench of the plasma. Understanding this problem is key for the safe operation of ITER because, if not avoided or mitigated, RE can severely damage the plasma facing components. In this presentation we report on RE simulation efforts centered in two complementary approaches: (i) Full orbit (6-D phase space) relativistic numerical simulations in general (integrable or chaotic) 3-D magnetic and electric fields, including radiation damping and collisions, using the recently developed particle-based Kinetic Orbit Runaway electron Code (KORC) and (ii) Backward Monte-Carlo (MC) simulations based on a recently developed efficient backward stochastic differential equations (BSDE) solver. Following a description of the corresponding numerical methods, we present applications to: (i) RE synchrotron radiation (SR) emission using KORC and (ii) Computation of time-dependent runaway probability distributions, RE production rates, and expected slowing-down and runaway times using BSDE. We study the dependence of these statistical observables on the electric and magnetic field, and the ion effective charge. SR is a key energy dissipation mechanism in the high-energy regime, and it is also extensively used as an experimental diagnostic of RE. Using KORC we study full orbit effects on SR and discuss a recently developed SR synthetic diagnostic that incorporates the full angular dependence of SR, and the location and basic optics of the camera. It is shown that oversimplifying the angular dependence of SR and/or ignoring orbit effects can significantly modify the shape and overestimate the amplitude of the spectra. Applications to DIII-D RE experiments are discussed.

Effects of visual flow direction on signs and symptoms of cybersickness.

PubMed

Mazloumi Gavgani, Alireza; Hodgson, Deborah M; Nalivaiko, Eugene

2017-01-01

Our objective was to assess the influence of visual flow direction on physiological changes and symptoms elicited by cybersickness. Twelve healthy subjects (6 male and 6 female) were exposed to a 15-min virtual ride on a rollercoaster on two different days in a counterbalanced manner, such half of participants were facing forward during the first ride while another half was facing backward. Forehead skin conductance, heart rate and HRV parameters (SDRR, RMSSD) were collected as objective measures; subjective symptoms were assessed with the Motion Sickness Assessment Questioner immediately after exposure. We found that while nausea ratings at which participants terminated the experiment did not differ between forward/backward rides, the mean ride tolerance time was significantly longer during reverse ride compared to forward ride (6.1±0.4 vs 5.0±0.5 min, respectively, p = 0.01, η2 = 0.45). Analysis of HRV parameters revealed significant reduction in both RMSSD (p = 0.02, t = 2.62, η2 = 0.43) and SDRR (p = 0.01, t = 2.90, η2 = 0.45) in the forward ride; no such changes were found in the backward ride. We also found that amplitude of phasic changes in forehead skin conductance increased significantly in both ride directions. This increase however was significantly lower (p<0.05) in backward ride when compared to the forward ride. When assessed immediately post-ride, subjects reported significantly lower (p = 0.04) subjective symptom intensity after the reverse ride compared to the forward ride. We conclude that the direction of visual flow has a significant effect on the symptoms reported by the subjects and on the physiological changes during cybersickness.

Effects of visual flow direction on signs and symptoms of cybersickness

PubMed Central

Mazloumi Gavgani, Alireza; Hodgson, Deborah M.

2017-01-01

Our objective was to assess the influence of visual flow direction on physiological changes and symptoms elicited by cybersickness. Twelve healthy subjects (6 male and 6 female) were exposed to a 15-min virtual ride on a rollercoaster on two different days in a counterbalanced manner, such half of participants were facing forward during the first ride while another half was facing backward. Forehead skin conductance, heart rate and HRV parameters (SDRR, RMSSD) were collected as objective measures; subjective symptoms were assessed with the Motion Sickness Assessment Questioner immediately after exposure. We found that while nausea ratings at which participants terminated the experiment did not differ between forward/backward rides, the mean ride tolerance time was significantly longer during reverse ride compared to forward ride (6.1±0.4 vs 5.0±0.5 min, respectively, p = 0.01, η2 = 0.45). Analysis of HRV parameters revealed significant reduction in both RMSSD (p = 0.02, t = 2.62, η2 = 0.43) and SDRR (p = 0.01, t = 2.90, η2 = 0.45) in the forward ride; no such changes were found in the backward ride. We also found that amplitude of phasic changes in forehead skin conductance increased significantly in both ride directions. This increase however was significantly lower (p<0.05) in backward ride when compared to the forward ride. When assessed immediately post-ride, subjects reported significantly lower (p = 0.04) subjective symptom intensity after the reverse ride compared to the forward ride. We conclude that the direction of visual flow has a significant effect on the symptoms reported by the subjects and on the physiological changes during cybersickness. PMID:28777827

Maximum principle for a stochastic delayed system involving terminal state constraints.

PubMed

Wen, Jiaqiang; Shi, Yufeng

2017-01-01

We investigate a stochastic optimal control problem where the controlled system is depicted as a stochastic differential delayed equation; however, at the terminal time, the state is constrained in a convex set. We firstly introduce an equivalent backward delayed system depicted as a time-delayed backward stochastic differential equation. Then a stochastic maximum principle is obtained by virtue of Ekeland's variational principle. Finally, applications to a state constrained stochastic delayed linear-quadratic control model and a production-consumption choice problem are studied to illustrate the main obtained result.

National Degree of Computerization: A Context for Evaluating Computer Education Policies in Developing Countries.

ERIC Educational Resources Information Center

Boehm, Barry W.

Developing countries should take immediate steps to avoid some of the serious problems that are now facing the United States in regard to the pool of trained computer professionals. Problem areas which should be reconciled involve a diverse range of topics from general national policy to salary structures and conversions efforts. By using the…

Preconditioned conjugate gradient methods for the Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Ajmani, Kumud; Ng, Wing-Fai; Liou, Meng-Sing

1994-01-01

A preconditioned Krylov subspace method (GMRES) is used to solve the linear systems of equations formed at each time-integration step of the unsteady, two-dimensional, compressible Navier-Stokes equations of fluid flow. The Navier-Stokes equations are cast in an implicit, upwind finite-volume, flux-split formulation. Several preconditioning techniques are investigated to enhance the efficiency and convergence rate of the implicit solver based on the GMRES algorithm. The superiority of the new solver is established by comparisons with a conventional implicit solver, namely line Gauss-Seidel relaxation (LGSR). Computational test results for low-speed (incompressible flow over a backward-facing step at Mach 0.1), transonic flow (trailing edge flow in a transonic turbine cascade), and hypersonic flow (shock-on-shock interactions on a cylindrical leading edge at Mach 6.0) are presented. For the Mach 0.1 case, overall speedup factors of up to 17 (in terms of time-steps) and 15 (in terms of CPU time on a CRAY-YMP/8) are found in favor of the preconditioned GMRES solver, when compared with the LGSR solver. The corresponding speedup factors for the transonic flow case are 17 and 23, respectively. The hypersonic flow case shows slightly lower speedup factors of 9 and 13, respectively. The study of preconditioners conducted in this research reveals that a new LUSGS-type preconditioner is much more efficient than a conventional incomplete LU-type preconditioner.

The Science of Human Nature and the Human Nature of Science

ERIC Educational Resources Information Center

Menhand, Lois

2005-01-01

In 1889, German biologist August Weissmann showed that mice whose tails are cut off do not produce short-tailed offspring. It was a step forward for science, but a step backward for civilization. Weissmann's discovery was good for science because, contrary to what many scientists had believed, acquired characteristics are not, of course,…

Literacy and the Millennium Development Goals: One Step Forward, Two Steps Backwards

ERIC Educational Resources Information Center

Gomez, Sofia Valdivielso

2005-01-01

Traditionally women have been signified to be "for others", never for themselves. This conceptualisation is also present in the discourses about literacy. The traditional discourse justifies women's literacy based on the need to improve family health, well-being, educational access, and so on. Thus, it is seen as a tool for other ends…

Bench evaluation: three face-shield CPR barrier devices.

PubMed

Simmons, M; Deao, D; Moon, L; Peters, K; Cavanaugh, S

1995-06-01

Due to the fear of disease transmission, the practice of mouth-to-mouth (M-M) rescue breathing is rarely performed; to address this concern, many types of CPR barrier devices have been developed. These include bag-valve-mask devices, mouth-to-mask devices, and face shields (FS). The purpose of this study was to measure the volumes delivered during mouth-to-face shield (M-FS) breathing, to measure the back pressure and calculate the resistance to flow through their 1-way valves, and to test for backward leak of gas through the valves. Three FS brands were evaluated: Kiss of Life (KOL), MicroSHIELD (Micro) and Res-Cue Key (RCK). Volume delivered during M-M and M-FS breathing was evaluated by 10 rescuers who used the devices while performing rescue breathing on a CPR mannequin. Back pressure was measured and resistance calculated by directing airflow through the 1-way valves. Backward leak was evaluated by measuring the O2 concentration at the rescuer side of the valve while 100% O2 was directed toward the patient side of the valve. Differences among the brands were evaluated using analysis of variance. The mean (SD) values for volumes in L were: M-M 1.00 (0.25), Micro 0.77 (0.20), RCK 0.64 (0.10), and KOL 0.24 (0.11). Mean values for back pressure in cm H2O at 50 L/min were Micro 16.7 (1.29), KOL 7.22 (0.13), and RCK 2.15 (0.16). Significant backward leak only occurred with RCK. Not one of the FSs tested met all of the requirements suggested by the American Heart Association and by the International Standards Organization.

Cracking the Illiteracy Kernel: Need for a New Model

ERIC Educational Resources Information Center

Gafoor, K. Abdul; PG, Jayasudha

2011-01-01

This paper discusses the need for new model and approach to solve the problem of illiteracy of the most backward section of the society-women among scheduled and other backward classes. The empirical support for the study is testing, interview and observation conducted on the present status of 100 from among 1,500 adult learners who attended a…

Anticipatory postural adjustments contribute to age-related changes in compensatory steps associated with unilateral perturbations.

PubMed

Hyodo, Masaki; Saito, Mayumi; Ushiba, Junichi; Tomita, Yutaka; Minami, Mihoko; Masakado, Yoshihisa

2012-07-01

Compensatory steps are essential for preventing falls following perturbations. This study aimed to explore age-related changes in compensatory steps to unilateral perturbations, specifically in terms of whether anticipatory postural adjustments (APAs) play a role in stabilizing lateral balance. Five young and five elderly male adults participated. The split-belt treadmill was used to provide bi- and unilateral perturbations, as forward or backward transitions, applied 10 times in random order. Backward steps evoked by unilateral forward perturbations were evaluated. We measured temporal characteristics, mediolateral (ML) center of mass (COM) motion, and ML step length of compensatory steps. Compensatory steps to unexpected perturbations showed delayed onset of foot-off (FO) and expanded lateral swing length in elderly compared to young subjects. Differences in COM motions and step width arose related to APAs. Elderly subjects showing APAs exhibited no significant differences in ML COM, ML COM velocity, or ML swing length compared to young subjects. However, elderly subjects without APAs showed significant changes toward instability in these parameters. The fact that APAs play a notable role, particularly in the elderly, in stability offers a new insight into preventing falls. However, APAs occurred in 29% of the steps of young and 35% of the steps of elderly subjects. If the occurrence of APAs in elderly people in response to compensatory steps was more frequent, fall risk would be reduced. Further studies, particularly into APA frequency, might contribute to improved intervention to prevent falls. Copyright © 2012 Elsevier B.V. All rights reserved.

Control of a three-dimensional turbulent shear layer by means of oblique vortices

NASA Astrophysics Data System (ADS)

Jürgens, Werner; Kaltenbach, Hans-Jakob

2018-04-01

The effect of local forcing on the separated, three-dimensional shear layer downstream of a backward-facing step is investigated by means of large-eddy simulation for a Reynolds number based on the step height of 10,700. The step edge is either oriented normal to the approaching turbulent boundary layer or swept at an angle of 40°. Oblique vortices with different orientation and spacing are generated by wavelike suction and blowing of fluid through an edge parallel slot. The vortices exhibit a complex three-dimensional structure, but they can be characterized by a wavevector in a horizontal section plane. In order to determine the step-normal component of the wavevector, a method is developed based on phase averages. The dependence of the wavevector on the forcing parameters can be described in terms of a dispersion relation, the structure of which indicates that the disturbances are mainly convected through the fluid. The introduced vortices reduce the size of the recirculation region by up to 38%. In both the planar and the swept case, the most efficient of the studied forcings consists of vortices which propagate in a direction that deviates by more than 50° from the step normal. These vortices exhibit a spacing in the order of 2.5 step heights. The upstream shift of the reattachment line can be explained by increased mixing and momentum transport inside the shear layer which is reflected in high levels of the Reynolds shear stress -ρ \\overline{u'v'}. The position of the maximum of the coherent shear stress is found to depend linearly on the wavelength, similar to two-dimensional free shear layers.

Backwards Fading to Speed Task Learning

DTIC Science & Technology

2013-09-01

estimates.) Table 1 Finalized Task List Task Domain Task Name Knot Tying Hand Cuff Rappel First Aid Fracture Bleed Map Reading* Resection...materials used. Hand Cuff . There are 10 steps in this task. To complete this task, the learner must manipulate a short length of rope (e.g...Design for Experiment 1 – Step Fade Experiment 1 (Step Fade) Task Type: Knot Tying Task Type: First Aid Task Complexity: Low (1) Hand Cuff (10

Asymptotic properties of a bold random walk

NASA Astrophysics Data System (ADS)

Serva, Maurizio

2014-08-01

In a recent paper we proposed a non-Markovian random walk model with memory of the maximum distance ever reached from the starting point (home). The behavior of the walker is different from the simple symmetric random walk only when she is at this maximum distance, where, having the choice to move either farther or closer, she decides with different probabilities. If the probability of a forward step is higher than the probability of a backward step, the walker is bold and her behavior turns out to be superdiffusive; otherwise she is timorous and her behavior turns out to be subdiffusive. The scaling behavior varies continuously from subdiffusive (timorous) to superdiffusive (bold) according to a single parameter γ ∈R. We investigate here the asymptotic properties of the bold case in the nonballistic region γ ∈[0,1/2], a problem which was left partially unsolved previously. The exact results proved in this paper require new probabilistic tools which rely on the construction of appropriate martingales of the random walk and its hitting times.

Moving backwards, moving forward: the experiences of older Filipino migrants adjusting to life in New Zealand.

PubMed

Montayre, Jed; Neville, Stephen; Holroyd, Eleanor

2017-12-01

To explore the experiences of older Filipino migrants adjusting to living permanently in New Zealand. The qualitative descriptive approach taken in this study involved 17 individual face-to-face interviews of older Filipino migrants in New Zealand. Three main themes emerged from the data. The first theme was "moving backwards and moving forward", which described how these older Filipino migrants adjusted to challenges they experienced with migration. The second theme was "engaging with health services" and presented challenges relating to the New Zealand healthcare system, including a lack of knowledge of the nature of health services, language barriers, and differences in cultural views. The third theme, "new-found home", highlighted establishing a Filipino identity in New Zealand and adjusting to the challenges of relocation. Adjustment to life in New Zealand for these older Filipino migrants meant starting over again by building new values through learning the basics and then moving forward from there.

Moving backwards, moving forward: the experiences of older Filipino migrants adjusting to life in New Zealand

PubMed Central

Montayre, Jed; Neville, Stephen; Holroyd, Eleanor

2017-01-01

ABSTRACT Purpose: To explore the experiences of older Filipino migrants adjusting to living permanently in New Zealand. Method: The qualitative descriptive approach taken in this study involved 17 individual face-to-face interviews of older Filipino migrants in New Zealand. Results: Three main themes emerged from the data. The first theme was “moving backwards and moving forward”, which described how these older Filipino migrants adjusted to challenges they experienced with migration. The second theme was “engaging with health services” and presented challenges relating to the New Zealand healthcare system, including a lack of knowledge of the nature of health services, language barriers, and differences in cultural views. The third theme, “new-found home”, highlighted establishing a Filipino identity in New Zealand and adjusting to the challenges of relocation. Conclusion: Adjustment to life in New Zealand for these older Filipino migrants meant starting over again by building new values through learning the basics and then moving forward from there. PMID:28705087

A Hybrid Backward-Forward Iterative Model for Improving Capacity Building of Earth Observations for Sustainable Societal Application

NASA Astrophysics Data System (ADS)

Hossain, F.; Iqbal, N.; Lee, H.; Muhammad, A.

2015-12-01

When it comes to building durable capacity for implementing state of the art technology and earth observation (EO) data for improved decision making, it has been long recognized that a unidirectional approach (from research to application) often does not work. Co-design of capacity building effort has recently been recommended as a better alternative. This approach is a two-way street where scientists and stakeholders engage intimately along the entire chain of actions from design of research experiments to packaging of decision making tools and each party provides an equal amount of input. Scientists execute research experiments based on boundary conditions and outputs that are defined as tangible by stakeholders for decision making. On the other hand, decision making tools are packaged by stakeholders with scientists ensuring the application-specific science is relevant. In this talk, we will overview one such iterative capacity building approach that we have implemented for gravimetry-based satellite (GRACE) EO data for improved groundwater management in Pakistan. We call our approach a hybrid approach where the initial step is a forward model involving a conventional short-term (3 day) capacity building workshop in the stakeholder environment addressing a very large audience. In this forward model, the net is cast wide to 'shortlist' a set of highly motivated stakeholder agency staffs who are then engaged more directly in 1-1 training. In the next step (the backward model), these short listed staffs are then brought back in the research environment of the scientists (supply) for 1-1 and long-term (6 months) intense brainstorming, training, and design of decision making tools. The advantage of this backward model is that it allows for a much better understanding for scientists of the ground conditions and hurdles of making a EO-based scientific innovation work for a specific decision making problem that is otherwise fundamentally impossible in conventional training workshops. We demonstrate here our experience of implementing this hybrid model for capacity building for groundwater management for Pakistan Council for Research on Water Resources (PCRWR) with the ultimate goal of empowering naitonal agencies in their ability to monitor groundwater storage changes independently from satellites.

Design of far-infrared acousto-optic tunable filter based on backward collinear interaction.

PubMed

Voloshinov, Vitaly B; Porokhovnichenko, Dmitriy L; Dyakonov, Evgeniy A

2018-04-10

The paper proposes a design of acousto-optic cell applying backward collinear interaction and acoustic mode transformation in a KRS-5 crystal. This cell may serve as an acousto-optic tunable filter for far-infrared spectral range and is able to operate both with collimated optical beams and with divergent beams forming images. The problem of acoustic mode transformation by wave reflection from the crystal facet away from symmetry planes has been solved. Polarization properties of the backward collinear interaction in optically isotropic media are discussed. Copyright © 2018 Elsevier B.V. All rights reserved.

Heavy-tailed fractional Pearson diffusions.

PubMed

Leonenko, N N; Papić, I; Sikorskii, A; Šuvak, N

2017-11-01

We define heavy-tailed fractional reciprocal gamma and Fisher-Snedecor diffusions by a non-Markovian time change in the corresponding Pearson diffusions. Pearson diffusions are governed by the backward Kolmogorov equations with space-varying polynomial coefficients and are widely used in applications. The corresponding fractional reciprocal gamma and Fisher-Snedecor diffusions are governed by the fractional backward Kolmogorov equations and have heavy-tailed marginal distributions in the steady state. We derive the explicit expressions for the transition densities of the fractional reciprocal gamma and Fisher-Snedecor diffusions and strong solutions of the associated Cauchy problems for the fractional backward Kolmogorov equation.

Real-Time Functional Magnetic Resonance Imaging Amygdala Neurofeedback Changes Positive Information Processing in Major Depressive Disorder.

PubMed

Young, Kymberly D; Misaki, Masaya; Harmer, Catherine J; Victor, Teresa; Zotev, Vadim; Phillips, Raquel; Siegle, Greg J; Drevets, Wayne C; Bodurka, Jerzy

2017-10-15

In participants with major depressive disorder who are trained to upregulate their amygdalar hemodynamic responses during positive autobiographical memory recall with real-time functional magnetic resonance imaging neurofeedback (rtfMRI-nf) training, depressive symptoms diminish. This study tested whether amygdalar rtfMRI-nf also changes emotional processing of positive and negative stimuli in a variety of behavioral and imaging tasks. Patients with major depressive disorder completed two rtfMRI-nf sessions (18 received amygdalar rtfMRI-nf, 16 received control parietal rtfMRI-nf). One week before and following rtfMRI-nf training, participants performed tasks measuring responses to emotionally valenced stimuli including a backward-masking task, which measures the amygdalar hemodynamic response to emotional faces presented for traditionally subliminal duration and followed by a mask, and the Emotional Test Battery in which reaction times and performance accuracy are measured during tasks involving emotional faces and words. During the backward-masking task, amygdalar responses increased while viewing masked happy faces but decreased to masked sad faces in the experimental versus control group following rtfMRI-nf. During the Emotional Test Battery, reaction times decreased to identification of positive faces and during self-identification with positive words and vigilance scores increased to positive faces and decreased to negative faces during the faces dot-probe task in the experimental versus control group following rtfMRI-nf. rtfMRI-nf training to increase the amygdalar hemodynamic response to positive memories was associated with changes in amygdalar responses to happy and sad faces and improved processing of positive stimuli during performance of the Emotional Test Battery. These results may suggest that amygdalar rtfMRI-nf training alters responses to emotional stimuli in a manner similar to antidepressant pharmacotherapy. Copyright © 2017 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.

On regularization and error estimates for the backward heat conduction problem with time-dependent thermal diffusivity factor

NASA Astrophysics Data System (ADS)

Karimi, Milad; Moradlou, Fridoun; Hajipour, Mojtaba

2018-10-01

This paper is concerned with a backward heat conduction problem with time-dependent thermal diffusivity factor in an infinite "strip". This problem is drastically ill-posed which is caused by the amplified infinitely growth in the frequency components. A new regularization method based on the Meyer wavelet technique is developed to solve the considered problem. Using the Meyer wavelet technique, some new stable estimates are proposed in the Hölder and Logarithmic types which are optimal in the sense of given by Tautenhahn. The stability and convergence rate of the proposed regularization technique are proved. The good performance and the high-accuracy of this technique is demonstrated through various one and two dimensional examples. Numerical simulations and some comparative results are presented.

Using Computer Output as a Vehicle for Self-Directed Study of Financial Theory: The Art of Teaching Backwards

ERIC Educational Resources Information Center

Campbell, Robert D.

2017-01-01

This paper presents an example of an approach to teaching financial theory at the college and post-graduate levels that I call "teaching backwards". In the more traditional approach, instructors begin by explaining financial theory, then proceed to give examples of the way this theory can be applied to a business problem, structuring…

Backward Blocking and Interference between Cues Are Empirically Equivalent in Non-Causally Framed Learning Tasks

ERIC Educational Resources Information Center

Luque, David; Moris, Joaquin; Orgaz, Cristina; Cobos, Pedro L.; Matute, Helena

2011-01-01

Backward blocking (BB) and interference between cues (IbC) are cue competition effects produced by very similar manipulations. In a standard BB design, both effects might occur simultaneously, which implies a potential problem for studying BB. In the present study with humans, the magnitude of both effects was compared using a non-causal scenario…

How Ants Use Vision When Homing Backward.

PubMed

Schwarz, Sebastian; Mangan, Michael; Zeil, Jochen; Webb, Barbara; Wystrach, Antoine

2017-02-06

Ants can navigate over long distances between their nest and food sites using visual cues [1, 2]. Recent studies show that this capacity is undiminished when walking backward while dragging a heavy food item [3-5]. This challenges the idea that ants use egocentric visual memories of the scene for guidance [1, 2, 6]. Can ants use their visual memories of the terrestrial cues when going backward? Our results suggest that ants do not adjust their direction of travel based on the perceived scene while going backward. Instead, they maintain a straight direction using their celestial compass. This direction can be dictated by their path integrator [5] but can also be set using terrestrial visual cues after a forward peek. If the food item is too heavy to enable body rotations, ants moving backward drop their food on occasion, rotate and walk a few steps forward, return to the food, and drag it backward in a now-corrected direction defined by terrestrial cues. Furthermore, we show that ants can maintain their direction of travel independently of their body orientation. It thus appears that egocentric retinal alignment is required for visual scene recognition, but ants can translate this acquired directional information into a holonomic frame of reference, which enables them to decouple their travel direction from their body orientation and hence navigate backward. This reveals substantial flexibility and communication between different types of navigational information: from terrestrial to celestial cues and from egocentric to holonomic directional memories. VIDEO ABSTRACT. Copyright © 2017 The Author(s). Published by Elsevier Ltd.. All rights reserved.

3D Face Modeling Using the Multi-Deformable Method

PubMed Central

Hwang, Jinkyu; Yu, Sunjin; Kim, Joongrock; Lee, Sangyoun

2012-01-01

In this paper, we focus on the problem of the accuracy performance of 3D face modeling techniques using corresponding features in multiple views, which is quite sensitive to feature extraction errors. To solve the problem, we adopt a statistical model-based 3D face modeling approach in a mirror system consisting of two mirrors and a camera. The overall procedure of our 3D facial modeling method has two primary steps: 3D facial shape estimation using a multiple 3D face deformable model and texture mapping using seamless cloning that is a type of gradient-domain blending. To evaluate our method's performance, we generate 3D faces of 30 individuals and then carry out two tests: accuracy test and robustness test. Our method shows not only highly accurate 3D face shape results when compared with the ground truth, but also robustness to feature extraction errors. Moreover, 3D face rendering results intuitively show that our method is more robust to feature extraction errors than other 3D face modeling methods. An additional contribution of our method is that a wide range of face textures can be acquired by the mirror system. By using this texture map, we generate realistic 3D face for individuals at the end of the paper. PMID:23201976

This Mechanistic Step Is ''Productive'': Organic Chemistry Students' Backward-Oriented Reasoning

ERIC Educational Resources Information Center

Caspari, I.; Weinrich, M. L.; Sevian, H.; Graulich, N.

2018-01-01

If an organic chemistry student explains that she represents a mechanistic step because ''it's a productive part of the mechanism,'' what meaning could the professor teaching the class attribute to this statement, what is actually communicated, and what does it mean for the student? The professor might think that the explanation is based on…

A Modified T-Test for Football Referees to Test Agility, Quickness and Sprint Performances

ERIC Educational Resources Information Center

Muniroglu, S.; Subak, E.

2018-01-01

The football referees perform many actions as jogging, running, sprinting, side steps and backward steps during a football match. Further, the football referees change match activities every 5-6 seconds. Many tests are being conducted to determine the physical levels and competences of football referees like 50 m running, 200 m running, 12 minutes…

Implementation and Validation of the Chien k-epsilon Turbulence Model in the Wind Navier-Stokes Code

NASA Technical Reports Server (NTRS)

Yoder, Dennis A.; Georgiadis, Nicholas J.

1999-01-01

The two equation k-epsilon turbulence model of Chien has been implemented in the WIND Navier-Stokes flow solver. Details of the numerical solution algorithm, initialization procedure, and stability enhancements are described. Results obtained with this version of the model are compared with those from the Chien k-epsilon model in the NPARC Navier-Stokes code and from the WIND SST model for three validation cases: the incompressible flow over a smooth flat plate, the incompressible flow over a backward facing step, and the shock-induced flow separation inside a transonic diffuser. The k-epsilon model results indicate that the WIND model functions very similarly to that in NPARC, though the WIND code appears to he slightly more accurate in the treatment of the near-wall region. Comparisons of the k-epsilon model results with those from the SST model were less definitive, as each model exhibited strengths and weaknesses for each particular case.

Enhancement of fine-scale mixing for fuel-rich plume combustion

NASA Astrophysics Data System (ADS)

Schadow, K. C.; Gutmark, E.; Parr, T. P.; Parr, D. M.; Wilson, K. J.; Ferrell, G. B.

1987-01-01

The effect of enhancing small-scale turbulent structures on the combustion intensity and flame stability was studied in nonreacting and reacting flows. Hot-wire anemometry was used to map the mean and turbulent flow fields of the nonreacting flows. Reacting flows were studied in a free flame and in a ducted gas-generator fuel-rich plume using Planar Laser Induced Fluorescence, a rake of thermocouples and high speed photography. A modified circular nozzle having several backward facing steps upstream of its exit was used to introduce numerous inflection points in the initial mean velocity profiles, thus producing multiple corresponding sources of small-scale turbulence generators. Cold flow tests showed turbulence increases of up to six times the initial turbulence level relative to a circular nozzle. The ensuing result was that the flame of this nozzle was more intense with a homogeneous heat release. The fuel-rich plume was stable even in supersonic speeds, and secondary ignition was obtained under conditions that prevented sustained afterburning using the circular nozzle.

A diagonal algorithm for the method of pseudocompressibility. [for steady-state solution to incompressible Navier-Stokes equation

NASA Technical Reports Server (NTRS)

Rogers, S. E.; Kwak, D.; Chang, J. L. C.

1986-01-01

The method of pseudocompressibility has been shown to be an efficient method for obtaining a steady-state solution to the incompressible Navier-Stokes equations. Recent improvements to this method include the use of a diagonal scheme for the inversion of the equations at each iteration. The necessary transformations have been derived for the pseudocompressibility equations in generalized coordinates. The diagonal algorithm reduces the computing time necessary to obtain a steady-state solution by a factor of nearly three. Implicit viscous terms are maintained in the equations, and it has become possible to use fourth-order implicit dissipation. The steady-state solution is unchanged by the approximations resulting from the diagonalization of the equations. Computed results for flow over a two-dimensional backward-facing step and a three-dimensional cylinder mounted normal to a flat plate are presented for both the old and new algorithms. The accuracy and computing efficiency of these algorithms are compared.

Comparison of two different approaches for the control of convectively unstable flows

NASA Astrophysics Data System (ADS)

Juillet, Fabien; Schmid, Peter; McKeon, Beverley; Huerre, Patrick

2011-11-01

The probably most widely used control strategy in the literature is based on the Linear Quadratic Gaussian (LQG) framework. However, this approach seems to be difficult to apply to some fluid systems. In particular, due to their high sensitivity to external noise, amplifier flows are hard to control and the classical LQG compensator may be unable to describe the noise with sufficient accuracy. Another strategy aims at directly measuring these noise sources through a sensor called ``spy.'' The LQG and the spy approaches will be presented and compared using the Ginzburg-Landau equation as a model. It will be shown that the use of a spy is particularly relevant for convectively unstable systems. In addition, the ability of Subspace Identification Methods to provide satisfactory models is demonstrated. Finally, the findings from the Ginzburg-Landau investigation are generalized and applied to a more realistic system, namely a backward-facing step at Re = 350 . Support from Ecole Polytechnique and the Partner University Fund (PUF) is gratefully acknowledged.

Blood flow and coherent vortices in the normal and aneurysmatic aortas: a fluid dynamical approach to intra-luminal thrombus formation.

PubMed

Biasetti, Jacopo; Hussain, Fazle; Gasser, T Christian

2011-10-07

Abdominal aortic aneurysms (AAAs) are frequently characterized by the development of an intra-luminal thrombus (ILT), which is known to have multiple biochemical and biomechanical implications. Development of the ILT is not well understood, and shear-stress-triggered activation of platelets could be the first step in its evolution. Vortical structures (VSs) in the flow affect platelet dynamics, which motivated the present study of a possible correlation between VS and ILT formation in AAAs. VSs educed by the λ(2)-method using computational fluid dynamics simulations of the backward-facing step problem, normal aorta, fusiform AAA and saccular AAA were investigated. Patient-specific luminal geometries were reconstructed from computed tomography scans, and Newtonian and Carreau-Yasuda models were used to capture salient rheological features of blood flow. Particularly in complex flow domains, results depended on the constitutive model. VSs developed all along the normal aorta, showing that a clear correlation between VSs and high wall shear stress (WSS) existed, and that VSs started to break up during late systole. In contrast, in the fusiform AAA, large VSs developed at sites of tortuous geometry and high WSS, occupying the entire lumen, and lasting over the entire cardiac cycle. Downward motion of VSs in the AAA was in the range of a few centimetres per cardiac cycle, and with a VS burst at that location, the release (from VSs) of shear-stress-activated platelets and their deposition to the wall was within the lower part of the diseased artery, i.e. where the thickest ILT layer is typically observed. In the saccular AAA, only one VS was found near the healthy portion of the aorta, while in the aneurysmatic bulge, no VSs occurred. We present a fluid-dynamics-motivated mechanism for platelet activation, convection and deposition in AAAs that has the potential of improving our current understanding of the pathophysiology of fluid-driven ILT growth.

Advancing parabolic operators in thermodynamic MHD models: Explicit super time-stepping versus implicit schemes with Krylov solvers

NASA Astrophysics Data System (ADS)

Caplan, R. M.; Mikić, Z.; Linker, J. A.; Lionello, R.

2017-05-01

We explore the performance and advantages/disadvantages of using unconditionally stable explicit super time-stepping (STS) algorithms versus implicit schemes with Krylov solvers for integrating parabolic operators in thermodynamic MHD models of the solar corona. Specifically, we compare the second-order Runge-Kutta Legendre (RKL2) STS method with the implicit backward Euler scheme computed using the preconditioned conjugate gradient (PCG) solver with both a point-Jacobi and a non-overlapping domain decomposition ILU0 preconditioner. The algorithms are used to integrate anisotropic Spitzer thermal conduction and artificial kinematic viscosity at time-steps much larger than classic explicit stability criteria allow. A key component of the comparison is the use of an established MHD model (MAS) to compute a real-world simulation on a large HPC cluster. Special attention is placed on the parallel scaling of the algorithms. It is shown that, for a specific problem and model, the RKL2 method is comparable or surpasses the implicit method with PCG solvers in performance and scaling, but suffers from some accuracy limitations. These limitations, and the applicability of RKL methods are briefly discussed.

Perceived facial expressions of emotion as motivational incentives: evidence from a differential implicit learning paradigm.

PubMed

Schultheiss, Oliver C; Pang, Joyce S; Torges, Cynthia M; Wirth, Michelle M; Treynor, Wendy; Derryberry, Douglas

2005-03-01

Participants (N = 216) were administered a differential implicit learning task during which they were trained and tested on 3 maximally distinct 2nd-order visuomotor sequences, with sequence color serving as discriminative stimulus. During training, 1 sequence each was followed by an emotional face, a neutral face, and no face, using backward masking. Emotion (joy, surprise, anger), face gender, and exposure duration (12 ms, 209 ms) were varied between participants; implicit motives were assessed with a picture-story exercise. For power-motivated individuals, low-dominance facial expressions enhanced and high-dominance expressions impaired learning. For affiliation-motivated individuals, learning was impaired in the context of hostile faces. These findings did not depend on explicit learning of fixed sequences or on awareness of sequence-face contingencies. Copyright 2005 APA, all rights reserved.

Coaching Family Caregivers to Become Better Problem Solvers When Caring for Persons with Advanced Cancer.

PubMed

Dionne-Odom, J Nicholas; Lyons, Kathleen D; Akyar, Imatullah; Bakitas, Marie A

2016-01-01

Family caregivers of persons with advanced cancer often take on responsibilities that present daunting and complex problems. Serious problems that go unresolved may be burdensome and result in negative outcomes for caregivers' psychological and physical health and affect the quality of care delivered to the care recipients with cancer, especially at the end of life. Formal problem-solving training approaches have been developed over the past several decades to assist individuals with managing problems faced in daily life. Several of these problem-solving principles and techniques were incorporated into ENABLE (Educate, Nurture, Advise, Before Life End), an "early" palliative care telehealth intervention for individuals diagnosed with advanced cancer and their family caregivers. A hypothetical case resembling the situations of actual caregiver participants in ENABLE that exemplifies the complex problems that caregivers face is presented, followed by presentation of an overview of ENABLE's problem-solving key principles, techniques, and steps in problem-solving support. Though more research is needed to formally test the use of problem-solving support in social work practice, social workers can easily incorporate these techniques into everyday practice.

Load-dependent ADP binding to myosins V and VI: Implications for subunit coordination and function

PubMed Central

Oguchi, Yusuke; Mikhailenko, Sergey V.; Ohki, Takashi; Olivares, Adrian O.; De La Cruz, Enrique M.; Ishiwata, Shin'ichi

2008-01-01

Dimeric myosins V and VI travel long distances in opposite directions along actin filaments in cells, taking multiple steps in a “hand-over-hand” fashion. The catalytic cycles of both myosins are limited by ADP dissociation, which is considered a key step in the walking mechanism of these motors. Here, we demonstrate that external loads applied to individual actomyosin V or VI bonds asymmetrically affect ADP affinity, such that ADP binds weaker under loads assisting motility. Model-based analysis reveals that forward and backward loads modulate the kinetics of ADP binding to both myosins, although the effect is less pronounced for myosin VI. ADP dissociation is modestly accelerated by forward loads and inhibited by backward loads. Loads applied in either direction slow ADP binding to myosin V but accelerate binding to myosin VI. We calculate that the intramolecular load generated during processive stepping is ≈2 pN for both myosin V and myosin VI. The distinct load dependence of ADP binding allows these motors to perform different cellular functions. PMID:18509050

Frogs Jump Forward: Semantic Knowledge Influences the Perception of Element Motion in the Ternus Display.

PubMed

Hsu, Patty; Taylor, J Eric T; Pratt, Jay

2015-01-01

The Ternus effect is a robust illusion of motion that produces element motion at short interstimulus intervals (ISIs; < 50 ms) and group motion at longer ISIs (> 50 ms). Previous research has shown that the nature of the stimuli (e.g., similarity, grouping), not just ISI, can influence the likelihood of perceiving element or group motion. We examined if semantic knowledge can also influence what type of illusory motion is perceived. In Experiment I, we used a modified Ternus display with pictures of frogs in a jump-ready pose facing forwards or backwards to the direction of illusory motion. Participants perceived more element motion with the forward-facing frogs and more group motion with the backward-facing frogs. Experiment 2 tested whether this effect would still occur with line drawings of frogs, or if a more life-like image was necessary. Experiment 3 tested whether this effect was due to visual asymmetries inherent in the jumping pose. Experiment 4 tested whether frogs in a "non-jumping," sedentary pose would replicate the original effect. These experiments elucidate the role of semantic knowledge in the Ternus effect. Prior knowledge of the movement of certain animate objects, in this case, frogs can also bias the perception of element or group motion.

The Noh mask effect: vertical viewpoint dependence of facial expression perception.

PubMed Central

Lyons, M J; Campbell, R; Plante, A; Coleman, M; Kamachi, M; Akamatsu, S

2000-01-01

Full-face masks, worn by skilled actors in the Noh tradition, can induce a variety of perceived expressions with changes in head orientation. Out-of-plane rotation of the head changes the two-dimensional image characteristics of the face which viewers may misinterpret as non-rigid changes due to muscle action. Three experiments with Japanese and British viewers explored this effect. Experiment 1 confirmed a systematic relationship between vertical angle of view of a Noh mask and judged affect. A forward tilted mask was more often judged happy, and one backward tilted more often judged sad. This effect was moderated by culture. Japanese viewers ascribed happiness to the mask at greater degrees of backward tilt with a reversal towards sadness at extreme forward angles. Cropping the facial image of chin and upper head contour reduced the forward-tilt reversal. Finally, the relationship between head tilt and affect was replicated with a laser-scanned human face image, but with no cultural effect. Vertical orientation of the head changes the apparent disposition of facial features and viewers respond systematically to these changes. Culture moderates this effect, and we discuss how perceptual strategies for ascribing expression to familiar and unfamiliar images may account for the differences. PMID:11413638

Free Education and Social Inequality in Ugandan Primary Schools: A Step Backward or a Step in the Right Direction?

ERIC Educational Resources Information Center

Zuze, Tia L.; Leibbrandt, Murray

2011-01-01

The intent of this study is to understand both direct and indirect resource effects in the context of a mass education system in Uganda. We find that under certain conditions, policies that promote physical resource availability can lead to substantial equity gains. A school's social composition appears to improve educational quality but it is…

Documentation of computer program VS2D to solve the equations of fluid flow in variably saturated porous media

USGS Publications Warehouse

Lappala, E.G.; Healy, R.W.; Weeks, E.P.

1987-01-01

This report documents FORTRAN computer code for solving problems involving variably saturated single-phase flow in porous media. The flow equation is written with total hydraulic potential as the dependent variable, which allows straightforward treatment of both saturated and unsaturated conditions. The spatial derivatives in the flow equation are approximated by central differences, and time derivatives are approximated either by a fully implicit backward or by a centered-difference scheme. Nonlinear conductance and storage terms may be linearized using either an explicit method or an implicit Newton-Raphson method. Relative hydraulic conductivity is evaluated at cell boundaries by using either full upstream weighting, the arithmetic mean, or the geometric mean of values from adjacent cells. Nonlinear boundary conditions treated by the code include infiltration, evaporation, and seepage faces. Extraction by plant roots that is caused by atmospheric demand is included as a nonlinear sink term. These nonlinear boundary and sink terms are linearized implicitly. The code has been verified for several one-dimensional linear problems for which analytical solutions exist and against two nonlinear problems that have been simulated with other numerical models. A complete listing of data-entry requirements and data entry and results for three example problems are provided. (USGS)

Asymptotic (h tending to infinity) absolute stability for BDFs applied to stiff differential equations. [Backward Differentiation Formulas

NASA Technical Reports Server (NTRS)

Krogh, F. T.; Stewart, K.

1984-01-01

Methods based on backward differentiation formulas (BDFs) for solving stiff differential equations require iterating to approximate the solution of the corrector equation on each step. One hope for reducing the cost of this is to make do with iteration matrices that are known to have errors and to do no more iterations than are necessary to maintain the stability of the method. This paper, following work by Klopfenstein, examines the effect of errors in the iteration matrix on the stability of the method. Application of the results to an algorithm is discussed briefly.

SPIRIT: An Evolutionally Designed Intelligent Tutoring System.

DTIC Science & Technology

1984-07-01

system’s backward reasoning approach. Instead, the student makes his moves while the mentor analyzes his progress, and whenever appropriate it...mentor in the final system makes backward reasoning explicit rather than implicit. Another problem in the second round was that the tutor did not...tutoring systems today are far less competent than the experienced tutor. One orthe reasons ror this is the lack of a well rounded theory of

Equivalent isotropic scattering formulation for transient short-pulse radiative transfer in anisotropic scattering planar media.

PubMed

Guo, Z; Kumar, S

2000-08-20

An isotropic scaling formulation is evaluated for transient radiative transfer in a one-dimensional planar slab subject to collimated and/or diffuse irradiation. The Monte Carlo method is used to implement the equivalent scattering and exact simulations of the transient short-pulse radiation transport through forward and backward anisotropic scattering planar media. The scaled equivalent isotropic scattering results are compared with predictions of anisotropic scattering in various problems. It is found that the equivalent isotropic scaling law is not appropriate for backward-scattering media in transient radiative transfer. Even for an optically diffuse medium, the differences in temporal transmittance and reflectance profiles between predictions of backward anisotropic scattering and equivalent isotropic scattering are large. Additionally, for both forward and backward anisotropic scattering media, the transient equivalent isotropic results are strongly affected by the change of photon flight time, owing to the change of flight direction associated with the isotropic scaling technique.

Culture vs. Technology: Mass Media Policy of the Netherlands Attempts a Balance.

ERIC Educational Resources Information Center

Heuterman, Thomas H.; Rennen, Toon

Telecommunications policy makers in Western Europe face the dilema of satisfying public demand for a wider range of television viewing alternatives without sacrificing national cultural integrity. The Dutch Parliament addressed this problem in 1984, 1985, and 1986 as it approved steps to implement the "Medianota," the comprehensive…

Opportunity Foregone: Education in Brazil.

ERIC Educational Resources Information Center

Birdsall, Nancy, Ed.; Sabot, Richard H., Ed.

The studies presented in this volume help readers to understand the constraints faced in addressing the key problems within the Brazilian education system. Steps to address the issues and benefits to be gained by addressing those issues are discussed. Forty-two authors reiterate that the success of Brazil's education reform will have an important…

46 CFR 160.052-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2013 CFR

2013-10-01

... the following volume of plastic foam buoyant material, determined by the displacement method: (1) Five... methods used for nonstandard buoyant vests must be equivalent to those requirements in § 160.052-5 for a... wearer in an upright or backward position with head and face out of water; (2) Have no tendency to turn a...

46 CFR 160.052-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2014 CFR

2014-10-01

... the following volume of plastic foam buoyant material, determined by the displacement method: (1) Five... methods used for nonstandard buoyant vests must be equivalent to those requirements in § 160.052-5 for a... wearer in an upright or backward position with head and face out of water; (2) Have no tendency to turn a...

46 CFR 160.052-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2012 CFR

2012-10-01

... the following volume of plastic foam buoyant material, determined by the displacement method: (1) Five... methods used for nonstandard buoyant vests must be equivalent to those requirements in § 160.052-5 for a... wearer in an upright or backward position with head and face out of water; (2) Have no tendency to turn a...

46 CFR 160.052-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2011 CFR

2011-10-01

... the following volume of plastic foam buoyant material, determined by the displacement method: (1) Five... methods used for nonstandard buoyant vests must be equivalent to those requirements in § 160.052-5 for a... wearer in an upright or backward position with head and face out of water; (2) Have no tendency to turn a...

Temporal Dynamics of Awareness for Facial Identity Revealed with ERP

ERIC Educational Resources Information Center

Genetti, Melanie; Khateb, Asaid; Heinzer, Severine; Michel, Christoph M.; Pegna, Alan J.

2009-01-01

In this study, we investigated the scalp recorded event-related potential (ERP) responses related to visual awareness. A backward masking procedure was performed while high-density EEG recordings were carried out. Subjects were asked to detect a familiar face, presented at durations that varied parametrically between 16 and 266 ms. ERPs were…

Age-related emotional bias in processing two emotionally valenced tasks.

PubMed

Allen, Philip A; Lien, Mei-Ching; Jardin, Elliott

2017-01-01

Previous studies suggest that older adults process positive emotions more efficiently than negative emotions, whereas younger adults show the reverse effect. We examined whether this age-related difference in emotional bias still occurs when attention is engaged in two emotional tasks. We used a psychological refractory period paradigm and varied the emotional valence of Task 1 and Task 2. In both experiments, Task 1 was emotional face discrimination (happy vs. angry faces) and Task 2 was sound discrimination (laugh, punch, vs. cork pop in Experiment 1 and laugh vs. scream in Experiment 2). The backward emotional correspondence effect for positively and negatively valenced Task 2 on Task 1 was measured. In both experiments, younger adults showed a backward correspondence effect from a negatively valenced Task 2, suggesting parallel processing of negatively valenced stimuli. Older adults showed similar negativity bias in Experiment 2 with a more salient negative sound ("scream" relative to "punch"). These results are consistent with an arousal-bias competition model [Mather and Sutherland (Perspectives in Psychological Sciences 6:114-133, 2011)], suggesting that emotional arousal modulates top-down attentional control settings (emotional regulation) with age.

Fine granular of shredded waste tyre for road kerb application as improvised road furniture

NASA Astrophysics Data System (ADS)

Munikanan, Vikneswaran; Yahya, Muhamad Azani; Yusof, Mohammed Alias; Radzi, Muhammad Haris Fauzan

2018-02-01

Solid waste management in Malaysia was still in a backward stage. Population growth, urbanization and rapid industrialization led to an increase in the solid waste generated by society. Solid waste management is one of the main problems faced by the community, especially in the city. Solid waste management costs of the collection, collecting, transporting waste to the landfill, is very high. The quantity of solid waste should be reduced in order to reduce government spending. Moreover, improper solid waste management caused a negative impact on people and the environment. Method of recycling is one of the best alternatives to reduce the number of solid waste. Therefore, this study was to identify methods of recycling used tires to be used in civil engineering. This study was conducted to determine the effectiveness and properties of rubber from used tires to be add in the road kerb design.

DART system analysis.

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

Boggs, Paul T.; Althsuler, Alan; Larzelere, Alex R.

2005-08-01

The Design-through-Analysis Realization Team (DART) is chartered with reducing the time Sandia analysts require to complete the engineering analysis process. The DART system analysis team studied the engineering analysis processes employed by analysts in Centers 9100 and 8700 at Sandia to identify opportunities for reducing overall design-through-analysis process time. The team created and implemented a rigorous analysis methodology based on a generic process flow model parameterized by information obtained from analysts. They also collected data from analysis department managers to quantify the problem type and complexity distribution throughout Sandia's analyst community. They then used this information to develop a communitymore » model, which enables a simple characterization of processes that span the analyst community. The results indicate that equal opportunity for reducing analysis process time is available both by reducing the ''once-through'' time required to complete a process step and by reducing the probability of backward iteration. In addition, reducing the rework fraction (i.e., improving the engineering efficiency of subsequent iterations) offers approximately 40% to 80% of the benefit of reducing the ''once-through'' time or iteration probability, depending upon the process step being considered. Further, the results indicate that geometry manipulation and meshing is the largest portion of an analyst's effort, especially for structural problems, and offers significant opportunity for overall time reduction. Iteration loops initiated late in the process are more costly than others because they increase ''inner loop'' iterations. Identifying and correcting problems as early as possible in the process offers significant opportunity for time savings.« less

Problems of older persons using a wheeled walker.

PubMed

Lindemann, Ulrich; Schwenk, Michael; Klenk, Jochen; Kessler, Max; Weyrich, Michael; Kurz, Franziska; Becker, Clemens

2016-04-01

Wheeled walkers (WWs) are used to improve mobility and for fall prevention in older persons, but not all users are satisfied with the usability of WWs. Intelligent WWs are being developed to improve the usability. The aim of this study was to support the development of intelligent WWs by investigating possible problems of using a WW. This study investigated 22 geriatric in-patients (median age 82 years) with and without their WW while opening a door against the direction of walking and passing through. Other possible problems when using WWs were identified by interview. Walking through the door was faster without than with using the WW (8.71 versus 12.86 s, p < 0.001), while interference between door and WW was documented in 41 of 44 (93 %) cases. Backward walking performance was better when using a WW with regard to gait speed, step width and walk ratio (all p < 0.002). Most referred problems when using a WW were walking downhill (83 %) and uphill (77 %) and obstacle crossing in general (77 %). Problems with opening a door against the direction of walking and the optimization of downhill and uphill walking as well as obstacle crossing should be regarded when developing an intelligent WW.

Sparse Feature Extraction for Pose-Tolerant Face Recognition.

PubMed

Abiantun, Ramzi; Prabhu, Utsav; Savvides, Marios

2014-10-01

Automatic face recognition performance has been steadily improving over years of research, however it remains significantly affected by a number of factors such as illumination, pose, expression, resolution and other factors that can impact matching scores. The focus of this paper is the pose problem which remains largely overlooked in most real-world applications. Specifically, we focus on one-to-one matching scenarios where a query face image of a random pose is matched against a set of gallery images. We propose a method that relies on two fundamental components: (a) A 3D modeling step to geometrically correct the viewpoint of the face. For this purpose, we extend a recent technique for efficient synthesis of 3D face models called 3D Generic Elastic Model. (b) A sparse feature extraction step using subspace modeling and ℓ1-minimization to induce pose-tolerance in coefficient space. This in return enables the synthesis of an equivalent frontal-looking face, which can be used towards recognition. We show significant performance improvements in verification rates compared to commercial matchers, and also demonstrate the resilience of the proposed method with respect to degrading input quality. We find that the proposed technique is able to match non-frontal images to other non-frontal images of varying angles.

Expression-invariant representations of faces.

PubMed

Bronstein, Alexander M; Bronstein, Michael M; Kimmel, Ron

2007-01-01

Addressed here is the problem of constructing and analyzing expression-invariant representations of human faces. We demonstrate and justify experimentally a simple geometric model that allows to describe facial expressions as isometric deformations of the facial surface. The main step in the construction of expression-invariant representation of a face involves embedding of the facial intrinsic geometric structure into some low-dimensional space. We study the influence of the embedding space geometry and dimensionality choice on the representation accuracy and argue that compared to its Euclidean counterpart, spherical embedding leads to notably smaller metric distortions. We experimentally support our claim showing that a smaller embedding error leads to better recognition.

Rethinking the lecture: the application of problem based learning methods to atypical contexts.

PubMed

Rogal, Sonya M M; Snider, Paul D

2008-05-01

Problem based learning is a teaching and learning strategy that uses a problematic stimulus as a means of motivating and directing students to develop and acquire knowledge. Problem based learning is a strategy that is typically used with small groups attending a series of sessions. This article describes the principles of problem based learning and its application in atypical contexts; large groups attending discrete, stand-alone sessions. The principles of problem based learning are based on Socratic teaching, constructivism and group facilitation. To demonstrate the application of problem based learning in an atypical setting, this article focuses on the graduate nurse intake from a teaching hospital. The groups are relatively large and meet for single day sessions. The modified applications of problem based learning to meet the needs of atypical groups are described. This article contains a step by step guide of constructing a problem based learning package for large, single session groups. Nurse educators facing similar groups will find they can modify problem based learning to suit their teaching context.

Forward and backward motion of artificial helical swimmers in cylindrical channels

NASA Astrophysics Data System (ADS)

Acemoglu, Alperen; Temel, Fatma Zeynep; Yesilyurt, Serhat

2013-11-01

Motion of micro swimmers in confined geometries such as channels is important due to its relevance in in vivo medical applications such as minimally invasive surgery and drug delivery. Here, swimmers with diameters 0.8 mm and lengths 2 to 3 mm are produced with a 3D printer and cylindrical Nd2Fe14B magnets are placed inside the bodies. Rotating external magnetic field is used for the actuation of artificial swimmers. Different body and tail geometries are produced and experiments are conducted with a glycerol filled circular channel. Result demonstrate that decreasing channel diameter directly affects the forward motion of the swimmer due to the increasing drag. It is observed that step-out frequency, which defines maximum frequency at which the swimmer can establish a synchronous rotation with the external magnetic field, depends on the geometry of the swimmer and the channel diameter. There are significant differences between low and high frequency motion and forward and backward swimming. Longer tails enable higher forward velocities in high frequencies than backward ones, whereas forward and backward velocities are approximately the same at low frequencies. Furthermore backward motion is more stable than the forward one; at high frequencies, swimmers travel almost at the center of the channel for backward motion, and follow a helical trajectory near the wall during the forward motion. According to simulation results there is a flow which is induced by the rotation of the swimmer rotation that affects the swimmer's trajectory. We acknowledge the support from TUBITAK (Techonological & Research Council of Turkey) under the grant no: 111M376.

Towards efficient backward-in-time adjoint computations using data compression techniques

DOE PAGES

Cyr, E. C.; Shadid, J. N.; Wildey, T.

2014-12-16

In the context of a posteriori error estimation for nonlinear time-dependent partial differential equations, the state-of-the-practice is to use adjoint approaches which require the solution of a backward-in-time problem defined by a linearization of the forward problem. One of the major obstacles in the practical application of these approaches, we found, is the need to store, or recompute, the forward solution to define the adjoint problem and to evaluate the error representation. Our study considers the use of data compression techniques to approximate forward solutions employed in the backward-in-time integration. The development derives an error representation that accounts for themore » difference between the standard-approach and the compressed approximation of the forward solution. This representation is algorithmically similar to the standard representation and only requires the computation of the quantity of interest for the forward solution and the data-compressed reconstructed solution (i.e. scalar quantities that can be evaluated as the forward problem is integrated). This approach is then compared with existing techniques, such as checkpointing and time-averaged adjoints. Lastly, we provide numerical results indicating the potential efficiency of our approach on a transient diffusion–reaction equation and on the Navier–Stokes equations. These results demonstrate memory compression ratios up to 450×450× while maintaining reasonable accuracy in the error-estimates.« less

Parallel Directionally Split Solver Based on Reformulation of Pipelined Thomas Algorithm

NASA Technical Reports Server (NTRS)

Povitsky, A.

1998-01-01

In this research an efficient parallel algorithm for 3-D directionally split problems is developed. The proposed algorithm is based on a reformulated version of the pipelined Thomas algorithm that starts the backward step computations immediately after the completion of the forward step computations for the first portion of lines This algorithm has data available for other computational tasks while processors are idle from the Thomas algorithm. The proposed 3-D directionally split solver is based on the static scheduling of processors where local and non-local, data-dependent and data-independent computations are scheduled while processors are idle. A theoretical model of parallelization efficiency is used to define optimal parameters of the algorithm, to show an asymptotic parallelization penalty and to obtain an optimal cover of a global domain with subdomains. It is shown by computational experiments and by the theoretical model that the proposed algorithm reduces the parallelization penalty about two times over the basic algorithm for the range of the number of processors (subdomains) considered and the number of grid nodes per subdomain.

How we flipped the medical classroom.

PubMed

Sharma, Neel; Lau, C S; Doherty, Iain; Harbutt, Darren

2015-04-01

Flipping the classroom centres on the delivery of print, audio or video based material prior to a lecture or class session. The class session is then dedicated to more active learning processes with application of knowledge through problem solving or case based scenarios. The rationale behind this approach is that teachers can spend their face-to-face time supporting students in deeper learning processes. In this paper we provide a background literature review on the flipped classroom along with a three step approach to flipping the classroom comprising implementing, enacting and evaluating this form of pedagogy. Our three step approach is based on actual experience of delivering a flipped classroom at the University of Hong Kong. This initiative was evaluated with positive results. We hope our experience will be transferable to other medical institutions.

Stress Studies at Kennedy Space Center: a Backward and Forward Look

NASA Technical Reports Server (NTRS)

Decker, A. I.

1971-01-01

Possible relationships between occupational and other stresses on ischemic heart disease are explored. Three procedures were used: (1) double master 2-step test, (2) dynamic ECG technique using avionics equipment, and (3) submaximal stress testing with Marco bicycle ergometer.

Two biomechanical strategies for locomotor adaptation to split-belt treadmill walking in subjects with and without transtibial amputation.

PubMed

Selgrade, Brian P; Toney, Megan E; Chang, Young-Hui

2017-02-28

Locomotor adaptation is commonly studied using split-belt treadmill walking, in which each foot is placed on a belt moving at a different speed. As subjects adapt to split-belt walking, they reduce metabolic power, but the biomechanical mechanism behind this improved efficiency is unknown. Analyzing mechanical work performed by the legs and joints during split-belt adaptation could reveal this mechanism. Because ankle work in the step-to-step transition is more efficient than hip work, we hypothesized that control subjects would reduce hip work on the fast belt and increase ankle work during the step-to-step transition as they adapted. We further hypothesized that subjects with unilateral, trans-tibial amputation would instead increase propulsive work from their intact leg on the slow belt. Control subjects reduced hip work and shifted more ankle work to the step-to-step transition, supporting our hypothesis. Contrary to our second hypothesis, intact leg work, ankle work and hip work in amputees were unchanged during adaptation. Furthermore, all subjects increased collisional energy loss on the fast belt, but did not increase propulsive work. This was possible because subjects moved further backward during fast leg single support in late adaptation than in early adaptation, compensating by reducing backward movement in slow leg single support. In summary, subjects used two strategies to improve mechanical efficiency in split-belt walking adaptation: a CoM displacement strategy that allows for less forward propulsion on the fast belt; and, an ankle timing strategy that allows efficient ankle work in the step-to-step transition to increase while reducing inefficient hip work. Copyright © 2017 Elsevier Ltd. All rights reserved.

Coaching Family Caregivers to become Better Problem Solvers when Caring for Persons with Advanced Cancer

PubMed Central

Dionne-Odom, J. Nicholas; Lyons, Kathleen D.; Akyar, Imatullah; Bakitas, Marie

2016-01-01

Family caregivers of persons with advanced cancer often take on responsibilities that present daunting and complex problems. Serious problems that go unresolved may be burdensome and result in negative outcomes for caregivers’ psychological and physical health and affect the quality of care delivered to the care recipients with cancer, especially at the end of life. Formal problem-solving training approaches have been developed over the past several decades to assist individuals with managing problems faced in daily life. Several of these problem-solving principles and techniques were incorporated into ENABLE (Educate, Nurture, Advise, Before Life End), an ‘early’ palliative care telehealth intervention for individuals diagnosed with advanced cancer and their family caregivers. A hypothetical case resembling the situations of actual caregiver participants in ENABLE that exemplifies the complex problems that caregivers face is presented followed by presentation of an overview of ENABLE’s problem-solving key principles, techniques and steps in problem-solving support. Though more research is needed to formally test the use of problem-solving support in social work practice, social workers can easily incorporate these techniques into everyday practice. PMID:27143574

New Developments of Computational Fluid Dynamics and Their Applications to Practical Engineering Problems

NASA Astrophysics Data System (ADS)

Chen, Hudong

2001-06-01

There have been considerable advances in Lattice Boltzmann (LB) based methods in the last decade. By now, the fundamental concept of using the approach as an alternative tool for computational fluid dynamics (CFD) has been substantially appreciated and validated in mainstream scientific research and in industrial engineering communities. Lattice Boltzmann based methods possess several major advantages: a) less numerical dissipation due to the linear Lagrange type advection operator in the Boltzmann equation; b) local dynamic interactions suitable for highly parallel processing; c) physical handling of boundary conditions for complicated geometries and accurate control of fluxes; d) microscopically consistent modeling of thermodynamics and of interface properties in complex multiphase flows. It provides a great opportunity to apply the method to practical engineering problems encountered in a wide range of industries from automotive, aerospace to chemical, biomedical, petroleum, nuclear, and others. One of the key challenges is to extend the applicability of this alternative approach to regimes of highly turbulent flows commonly encountered in practical engineering situations involving high Reynolds numbers. Over the past ten years, significant efforts have been made on this front at Exa Corporation in developing a lattice Boltzmann based commercial CFD software, PowerFLOW. It has become a useful computational tool for the simulation of turbulent aerodynamics in practical engineering problems involving extremely complex geometries and flow situations, such as in new automotive vehicle designs world wide. In this talk, we present an overall LB based algorithm concept along with certain key extensions in order to accurately handle turbulent flows involving extremely complex geometries. To demonstrate the accuracy of turbulent flow simulations, we provide a set of validation results for some well known academic benchmarks. These include straight channels, backward-facing steps, flows over a curved hill and typical NACA airfoils at various angles of attack including prediction of stall angle. We further provide numerous engineering cases, ranging from external aerodynamics around various car bodies to internal flows involved in various industrial devices. We conclude with a discussion of certain future extensions for complex fluids.

Flow Induced Noise from Turbulent Flow over Steps and Gaps

DTIC Science & Technology

2010-05-04

Wall Jet Facility which is detailed in Figures 2.1 through 2.3. In this facility a Cincinnati Fan variable speed centrifugal fan with model number...the flow over the multiple backward steps considered in this study The following subsections will concentrate on the oil flow visualization performed ...NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) Virginia Polytechnic Institute and State University

The amygdala is involved in affective priming effect for fearful faces.

PubMed

Yang, J; Cao, Z; Xu, X; Chen, G

2012-10-01

The object of this study was to investigate whether the amygdala is involved in affective priming effect after stimuli are encoded unconsciously and consciously. During the encoding phase, each masked face (fearful or neutral) was presented to participants six times for 17ms each, using a backward masking paradigm. During the retrieval phase, participants made a fearful/neutral judgment for each face. Half of the faces had the same valence as that seen during encoding (congruent condition) and the other half did not (incongruent condition). Participants were divided into unaware and aware groups based on their subjective and objective awareness assessments. The fMRI results showed that during encoding, the amygdala elicited stronger activation for fearful faces than neutral faces but differed in the hemisphere according to the awareness level. During retrieval, the amygdala showed a significant repetition priming effect, with the congruent faces producing less activation than the incongruent faces, especially for fearful faces. These data suggest that the amygdala is important in unconscious retrieving of memories for emotional faces whether they are encoded consciously or unconsciously. Copyright © 2012 Elsevier Inc. All rights reserved.

Preparing English Learners for Effective Peer Review in the Writers' Workshop

ERIC Educational Resources Information Center

Kim, Soo Hyon

2015-01-01

English Language Learners (ELLs) often face challenges when participating in peer review activities in writers' workshops. This article identifies some of the potential difficulties that ELL writers may experience, and provides teachers with strategies to address these problems. The author describes a simple three-step peer review training model…

Strengthening Higher Education: Simplify Student Aid & Emphasize Vital Science, Math, and Language Skills

ERIC Educational Resources Information Center

Berkowitz, Peter

2007-01-01

Higher education in America faces such formidable problems as unaffordable tuition, lack of accountability, students ill-prepared for college, declining enrollment in math and science, and too few graduates fluent in critical foreign languages. This Opportunity 08 position paper recommends that the next President should take the following steps to…

A Textbook Selection Process.

ERIC Educational Resources Information Center

Prosser, Daniel R.; Bondavalli, Bonnie J.

In response to the problem facing college faculties of choosing textbooks that are both "readable" by students and adequate in content coverage, a text selection process has been developed that can be used with or without the aid of a reading specialist. The first step in the process, a preliminary check, examines each proposed text's publication…

Study on Problems and Countermeasures of Textbook Management in China Universities

ERIC Educational Resources Information Center

Geng, Lihua

2011-01-01

Textbook management in universities is an integral component of teaching management. With gradual development of university education teaching, textbook management in China universities can no longer keep pace with the steps of the teaching management, and the work of textbook management is faced up with new challenges. This article makes an…

An Efficient Pattern Mining Approach for Event Detection in Multivariate Temporal Data

PubMed Central

Batal, Iyad; Cooper, Gregory; Fradkin, Dmitriy; Harrison, James; Moerchen, Fabian; Hauskrecht, Milos

2015-01-01

This work proposes a pattern mining approach to learn event detection models from complex multivariate temporal data, such as electronic health records. We present Recent Temporal Pattern mining, a novel approach for efficiently finding predictive patterns for event detection problems. This approach first converts the time series data into time-interval sequences of temporal abstractions. It then constructs more complex time-interval patterns backward in time using temporal operators. We also present the Minimal Predictive Recent Temporal Patterns framework for selecting a small set of predictive and non-spurious patterns. We apply our methods for predicting adverse medical events in real-world clinical data. The results demonstrate the benefits of our methods in learning accurate event detection models, which is a key step for developing intelligent patient monitoring and decision support systems. PMID:26752800

46 CFR 160.060-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2012 CFR

2012-10-01

... displacement method: (1) Five hundred cubic inches or more for the adult size, for persons weighing over 90... methods used for a nonstandard buoyant vest must be equivalent to the requirements in § 160.060-5 for...: (1) Be arranged to hold the wearer in an upright or backward position with head and face out of water...

46 CFR 160.060-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2011 CFR

2011-10-01

... displacement method: (1) Five hundred cubic inches or more for the adult size, for persons weighing over 90... methods used for a nonstandard buoyant vest must be equivalent to the requirements in § 160.060-5 for...: (1) Be arranged to hold the wearer in an upright or backward position with head and face out of water...

46 CFR 160.060-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2013 CFR

2013-10-01

... displacement method: (1) Five hundred cubic inches or more for the adult size, for persons weighing over 90... methods used for a nonstandard buoyant vest must be equivalent to the requirements in § 160.060-5 for...: (1) Be arranged to hold the wearer in an upright or backward position with head and face out of water...

46 CFR 160.060-6 - Construction-nonstandard vests.

Code of Federal Regulations, 2014 CFR

2014-10-01

... displacement method: (1) Five hundred cubic inches or more for the adult size, for persons weighing over 90... methods used for a nonstandard buoyant vest must be equivalent to the requirements in § 160.060-5 for...: (1) Be arranged to hold the wearer in an upright or backward position with head and face out of water...

Forward or Backward? (1920)

ERIC Educational Resources Information Center

Cooke, Flora J.

2011-01-01

Is it better to aim at a high ideal, with only moderate success in attainment, or is it better to be satisfied with a lower goal, one involving less effort and little responsibility? This is the question which pupils in upper grades and high school face every year. There are always some members of every class who seek the best things. They desire…

Is fear perception special? Evidence at the level of decision-making and subjective confidence.

PubMed

Koizumi, Ai; Mobbs, Dean; Lau, Hakwan

2016-11-01

Fearful faces are believed to be prioritized in visual perception. However, it is unclear whether the processing of low-level facial features alone can facilitate such prioritization or whether higher-level mechanisms also contribute. We examined potential biases for fearful face perception at the levels of perceptual decision-making and perceptual confidence. We controlled for lower-level visual processing capacity by titrating luminance contrasts of backward masks, and the emotional intensity of fearful, angry and happy faces. Under these conditions, participants showed liberal biases in perceiving a fearful face, in both detection and discrimination tasks. This effect was stronger among individuals with reduced density in dorsolateral prefrontal cortex, a region linked to perceptual decision-making. Moreover, participants reported higher confidence when they accurately perceived a fearful face, suggesting that fearful faces may have privileged access to consciousness. Together, the results suggest that mechanisms in the prefrontal cortex contribute to making fearful face perception special. © The Author (2016). Published by Oxford University Press.

Proceedings for the Annual Symposium and Exhibition on Situational Awareness in the Tactical Air Environment (3rd), Held at Piney Point, Maryland, on 2-3 June 1998

DTIC Science & Technology

1998-06-02

derived from the literature and positively reacted to by aviators - cue- recognitio 𔃻 training. This is important, because it is a first step in linking...The HMD would not only need to accommodate a wide variety of face structures, but also it must integrate with life support and protective equipment...locomotion on earth are often of considerably higher velocity than that encountered by pilots in aircraft. The fundamental problem facing pilots and other

A scalable nonlinear fluid-structure interaction solver based on a Schwarz preconditioner with isogeometric unstructured coarse spaces in 3D

NASA Astrophysics Data System (ADS)

Kong, Fande; Cai, Xiao-Chuan

2017-07-01

Nonlinear fluid-structure interaction (FSI) problems on unstructured meshes in 3D appear in many applications in science and engineering, such as vibration analysis of aircrafts and patient-specific diagnosis of cardiovascular diseases. In this work, we develop a highly scalable, parallel algorithmic and software framework for FSI problems consisting of a nonlinear fluid system and a nonlinear solid system, that are coupled monolithically. The FSI system is discretized by a stabilized finite element method in space and a fully implicit backward difference scheme in time. To solve the large, sparse system of nonlinear algebraic equations at each time step, we propose an inexact Newton-Krylov method together with a multilevel, smoothed Schwarz preconditioner with isogeometric coarse meshes generated by a geometry preserving coarsening algorithm. Here "geometry" includes the boundary of the computational domain and the wet interface between the fluid and the solid. We show numerically that the proposed algorithm and implementation are highly scalable in terms of the number of linear and nonlinear iterations and the total compute time on a supercomputer with more than 10,000 processor cores for several problems with hundreds of millions of unknowns.

A scalable nonlinear fluid–structure interaction solver based on a Schwarz preconditioner with isogeometric unstructured coarse spaces in 3D

DOE PAGES

Kong, Fande; Cai, Xiao-Chuan

2017-03-24

Nonlinear fluid-structure interaction (FSI) problems on unstructured meshes in 3D appear many applications in science and engineering, such as vibration analysis of aircrafts and patient-specific diagnosis of cardiovascular diseases. In this work, we develop a highly scalable, parallel algorithmic and software framework for FSI problems consisting of a nonlinear fluid system and a nonlinear solid system, that are coupled monolithically. The FSI system is discretized by a stabilized finite element method in space and a fully implicit backward difference scheme in time. To solve the large, sparse system of nonlinear algebraic equations at each time step, we propose an inexactmore » Newton-Krylov method together with a multilevel, smoothed Schwarz preconditioner with isogeometric coarse meshes generated by a geometry preserving coarsening algorithm. Here ''geometry'' includes the boundary of the computational domain and the wet interface between the fluid and the solid. We show numerically that the proposed algorithm and implementation are highly scalable in terms of the number of linear and nonlinear iterations and the total compute time on a supercomputer with more than 10,000 processor cores for several problems with hundreds of millions of unknowns.« less

Adaptive Greedy Dictionary Selection for Web Media Summarization.

PubMed

Cong, Yang; Liu, Ji; Sun, Gan; You, Quanzeng; Li, Yuncheng; Luo, Jiebo

2017-01-01

Initializing an effective dictionary is an indispensable step for sparse representation. In this paper, we focus on the dictionary selection problem with the objective to select a compact subset of basis from original training data instead of learning a new dictionary matrix as dictionary learning models do. We first design a new dictionary selection model via l 2,0 norm. For model optimization, we propose two methods: one is the standard forward-backward greedy algorithm, which is not suitable for large-scale problems; the other is based on the gradient cues at each forward iteration and speeds up the process dramatically. In comparison with the state-of-the-art dictionary selection models, our model is not only more effective and efficient, but also can control the sparsity. To evaluate the performance of our new model, we select two practical web media summarization problems: 1) we build a new data set consisting of around 500 users, 3000 albums, and 1 million images, and achieve effective assisted albuming based on our model and 2) by formulating the video summarization problem as a dictionary selection issue, we employ our model to extract keyframes from a video sequence in a more flexible way. Generally, our model outperforms the state-of-the-art methods in both these two tasks.

The backward phase flow and FBI-transform-based Eulerian Gaussian beams for the Schroedinger equation

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

Leung Shingyu, E-mail: masyleung@ust.h; Qian Jianliang, E-mail: qian@math.msu.ed

2010-11-20

We propose the backward phase flow method to implement the Fourier-Bros-Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schroedinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in . In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying themore » FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms.« less

The backward phase flow and FBI-transform-based Eulerian Gaussian beams for the Schrödinger equation

NASA Astrophysics Data System (ADS)

Leung, Shingyu; Qian, Jianliang

2010-11-01

We propose the backward phase flow method to implement the Fourier-Bros-Iagolnitzer (FBI)-transform-based Eulerian Gaussian beam method for solving the Schrödinger equation in the semi-classical regime. The idea of Eulerian Gaussian beams has been first proposed in [12]. In this paper we aim at two crucial computational issues of the Eulerian Gaussian beam method: how to carry out long-time beam propagation and how to compute beam ingredients rapidly in phase space. By virtue of the FBI transform, we address the first issue by introducing the reinitialization strategy into the Eulerian Gaussian beam framework. Essentially we reinitialize beam propagation by applying the FBI transform to wavefields at intermediate time steps when the beams become too wide. To address the second issue, inspired by the original phase flow method, we propose the backward phase flow method which allows us to compute beam ingredients rapidly. Numerical examples demonstrate the efficiency and accuracy of the proposed algorithms.

Unconstrained steps of myosin VI appear longest among known molecular motors.

PubMed

Ali, M Yusuf; Homma, Kazuaki; Iwane, Atsuko Hikikoshi; Adachi, Kengo; Itoh, Hiroyasu; Kinosita, Kazuhiko; Yanagida, Toshio; Ikebe, Mitsuo

2004-06-01

Myosin VI is a two-headed molecular motor that moves along an actin filament in the direction opposite to most other myosins. Previously, a single myosin VI molecule has been shown to proceed with steps that are large compared to its neck size: either it walks by somehow extending its neck or one head slides along actin for a long distance before the other head lands. To inquire into these and other possible mechanism of motility, we suspended an actin filament between two plastic beads, and let a single myosin VI molecule carrying a bead duplex move along the actin. This configuration, unlike previous studies, allows unconstrained rotation of myosin VI around the right-handed double helix of actin. Myosin VI moved almost straight or as a right-handed spiral with a pitch of several micrometers, indicating that the molecule walks with strides slightly longer than the actin helical repeat of 36 nm. The large steps without much rotation suggest kinesin-type walking with extended and flexible necks, but how to move forward with flexible necks, even under a backward load, is not clear. As an answer, we propose that a conformational change in the lifted head would facilitate landing on a forward, rather than backward, site. This mechanism may underlie stepping of all two-headed molecular motors including kinesin and myosin V.

The effects of streamline curvature and swirl on turbulent flows in curved ducts

NASA Technical Reports Server (NTRS)

Cheng, Chih-Hsiung; Farokhi, Saeed

1990-01-01

A technique for improving the numerical predictions of turbulent flows with the effect of streamline curvature is developed. Separated flows, the flow in a curved duct, and swirling flows are examples of flow fields where streamline curvature plays a dominant role. A comprehensive literature review on the effect of streamline curvature was conducted. New algebraic formulations for the eddy viscosity incorporating the kappa-epsilon turbulence model are proposed to account for various effects of streamline curvature. The loci of flow reversal of the separated flows over various backward-facing steps are employed to test the capability of the proposed turbulence model in capturing the effect of local curvature. The inclusion of the effect of longitudinal curvature in the proposed turbulence model is validated by predicting the distributions of the static pressure coefficients in an S-bend duct and in 180 degree turn-around ducts. The proposed turbulence model embedded with transverse curvature modification is substantiated by predicting the decay of the axial velocities in the confined swirling flows. The numerical predictions of different curvature effects by the proposed turbulence models are also reported.

Turbulent transport models for scramjet flowfields

NASA Technical Reports Server (NTRS)

Sindir, M. M.; Harsha, P. T.

1984-01-01

Turbulence modeling approaches were examined from the standpoint of their capability to predict the complex flowfield features observed in scramjet combustions. Thus, for example, the accuracy of each turbulence model, with respect to the prediction of recirculating flows, was examined. It was observed that for large diameter ratio axisymmetric sudden expansion flows, a choice of turbulence model was not critical because of the domination of their flowfields by pressure forces. For low diameter ratio axisymmetric sudden expansions and planar backward-facing steps flows, where turbulent shear stresses are of greater significance, the algebraic Reynolds stress approach, modified to increase its sensitivity to streamline curvature, was found to provide the best results. Results of the study also showed that strongly swirling flows provide a stringent test of turbulence model assumptions. Thus, although flows with very high swirl are not of great practical interest, they are useful for turbulence model development. Finally, it was also noted that numerical flowfields solution techniques have a strong interrelation with turbulence models, particularly with the turbulent transport models which involve source-dominated transport equations.

Erosion estimation of guide vane end clearance in hydraulic turbines with sediment water flow

NASA Astrophysics Data System (ADS)

Han, Wei; Kang, Jingbo; Wang, Jie; Peng, Guoyi; Li, Lianyuan; Su, Min

2018-04-01

The end surface of guide vane or head cover is one of the most serious parts of sediment erosion for high-head hydraulic turbines. In order to investigate the relationship between erosion depth of wall surface and the characteristic parameter of erosion, an estimative method including a simplified flow model and a modificatory erosion calculative function is proposed in this paper. The flow between the end surfaces of guide vane and head cover is simplified as a clearance flow around a circular cylinder with a backward facing step. Erosion characteristic parameter of csws3 is calculated with the mixture model for multiphase flow and the renormalization group (RNG) k-𝜀 turbulence model under the actual working conditions, based on which, erosion depths of guide vane and head cover end surfaces are estimated with a modification of erosion coefficient K. The estimation results agree well with the actual situation. It is shown that the estimative method is reasonable for erosion prediction of guide vane and can provide a significant reference to determine the optimal maintenance cycle for hydraulic turbine in the future.

Unconsciously Triggered Emotional Conflict by Emotional Facial Expressions

PubMed Central

Chen, Antao; Cui, Qian; Zhang, Qinglin

2013-01-01

The present study investigated whether emotional conflict and emotional conflict adaptation could be triggered by unconscious emotional information as assessed in a backward-masked affective priming task. Participants were instructed to identify the valence of a face (e.g., happy or sad) preceded by a masked happy or sad face. The results of two experiments revealed the emotional conflict effect but no emotional conflict adaptation effect. This demonstrates that emotional conflict can be triggered by unconsciously presented emotional information, but participants may not adjust their subsequent performance trial-by trial to reduce this conflict. PMID:23409084

A hybridized discontinuous Galerkin framework for high-order particle-mesh operator splitting of the incompressible Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Maljaars, Jakob M.; Labeur, Robert Jan; Möller, Matthias

2018-04-01

A generic particle-mesh method using a hybridized discontinuous Galerkin (HDG) framework is presented and validated for the solution of the incompressible Navier-Stokes equations. Building upon particle-in-cell concepts, the method is formulated in terms of an operator splitting technique in which Lagrangian particles are used to discretize an advection operator, and an Eulerian mesh-based HDG method is employed for the constitutive modeling to account for the inter-particle interactions. Key to the method is the variational framework provided by the HDG method. This allows to formulate the projections between the Lagrangian particle space and the Eulerian finite element space in terms of local (i.e. cellwise) ℓ2-projections efficiently. Furthermore, exploiting the HDG framework for solving the constitutive equations results in velocity fields which excellently approach the incompressibility constraint in a local sense. By advecting the particles through these velocity fields, the particle distribution remains uniform over time, obviating the need for additional quality control. The presented methodology allows for a straightforward extension to arbitrary-order spatial accuracy on general meshes. A range of numerical examples shows that optimal convergence rates are obtained in space and, given the particular time stepping strategy, second-order accuracy is obtained in time. The model capabilities are further demonstrated by presenting results for the flow over a backward facing step and for the flow around a cylinder.

High-Spatial-Resolution OH and CH2O PLIF Visualization in a Dual-Mode Scramjet Combustor

NASA Technical Reports Server (NTRS)

Geipel, Clayton M.

2017-01-01

A high-spatial-resolution planar laser-induced fluorescence (PLIF) imaging system was constructed and used to image a cavity-stabilized, premixed ethylene-air flame. The flame was created within a continuous flow, electrically-heated supersonic combustion facility consisting of a Mach 2 nozzle, an isolator with flush-wall fuel injectors, a combustor with a cavity flameholder of height 9 mm and optical access, and an extender. Tests were conducted at total temperature 1200 K, total pressure 300 kPa, equivalence ratio near 0.4 in the combustor, and Mach number near 0.6 in the combustor. A frequency-doubled Nd:YAG laser pumped a dye laser, which produced light at 283.55 nm. The beam was shaped into a light sheet with full width half-maximum 25 microns, which illuminated a streamwise plane that bisected the cavity. An intensified camera system imaged OH in this plane with a square 6.67 mm field of view and in-plane resolution 39 microns. Images were taken between the backward-facing step and 120 mm downstream of the step. OH structures as small as 110 microns were observed. CH2O was excited using 352.48 nm light; the smallest observed CH2O structures were approximately 200 microns wide. Approximately 15,000 images per species were processed and used to compute composite images.

The Coming Apart of America's Civic Culture

ERIC Educational Resources Information Center

Murray, Charles

2014-01-01

The day-to-day appraisal of the state of the nation is understandably dominated by the stories in the headlines. In "Coming Apart" (Murray, 2012), the author attempted to step back from today's headlines and take a longer view of where the nation is heading. Murray's conclusion was that we face a much more ominous long-term problem than…

Turbulent flow separation control through passive techniques

NASA Technical Reports Server (NTRS)

Lin, J. C.; Howard, F. G.; Selby, G. V.

1989-01-01

Several passive separation control techniques for controlling moderate two-dimensional turbulent flow separation over a backward-facing ramp are studied. Small transverse and swept grooves, passive porous surfaces, large longitudinal grooves, and vortex generators were among the techniques used. It was found that, unlike the transverse and longitudinal grooves of an equivalent size, the 45-deg swept-groove configurations tested tended to enhance separation.

Neighboring extremals of dynamic optimization problems with path equality constraints

NASA Technical Reports Server (NTRS)

Lee, A. Y.

1988-01-01

Neighboring extremals of dynamic optimization problems with path equality constraints and with an unknown parameter vector are considered in this paper. With some simplifications, the problem is reduced to solving a linear, time-varying two-point boundary-value problem with integral path equality constraints. A modified backward sweep method is used to solve this problem. Two example problems are solved to illustrate the validity and usefulness of the solution technique.

Student’s thinking process in solving word problems in geometry

NASA Astrophysics Data System (ADS)

Khasanah, V. N.; Usodo, B.; Subanti, S.

2018-05-01

This research aims to find out the thinking process of seventh grade of Junior High School in solve word problem solving of geometry. This research was descriptive qualitative research. The subject of the research was selected based on sex and differences in mathematical ability. Data collection was done based on student’s work test, interview, and observation. The result of the research showed that there was no difference of thinking process between male and female with high mathematical ability, and there were differences of thinking process between male and female with moderate and low mathematical ability. Also, it was found that male with moderate mathematical ability took a long time in the step of making problem solving plans. While female with moderate mathematical ability took a long time in the step of understanding the problems. The importance of knowing the thinking process of students in solving word problem solving were that the teacher knows the difficulties faced by students and to minimize the occurrence of the same error in problem solving. Teacher could prepare the right learning strategies which more appropriate with student’s thinking process.

Instructional Design-Based Research on Problem Solving Strategies

ERIC Educational Resources Information Center

Emre-Akdogan, Elçin; Argün, Ziya

2016-01-01

The main goal of this study is to find out the effect of the instructional design method on the enhancement of problem solving abilities of students. Teaching sessions were applied to ten students who are in 11th grade, to teach them problem solving strategies which are working backwards, finding pattern, adopting a different point of view,…

Computation of Turbulent Recirculating Flow in Channels, and for Impingement Cooling

NASA Technical Reports Server (NTRS)

Chang, Byong Hoon

1992-01-01

Fully elliptic forms of the transport equations have been solved numerically for two flow configurations. The first is turbulent flow in a channel with transverse rectangular ribs, and the second is impingement cooling of a plane surface. Both flows are relevant to proposed designs for active cooling of hypersonic vehicles using supercritical hydrogen as the coolant. Flow downstream of an abrupt pipe expansion and of a backward-facing step were also solved with various near-wall turbulence models as benchmark problems. A simple form of periodicity boundary condition was used for the channel flow with transverse rectangular ribs. The effects of various parameters on heat transfer in channel flow with transverse ribs and in impingement cooling were investigated using the Yap modified Jones and Launder low Reynolds number k-epsilon turbulence model. For the channel flow, predictions were in adequate agreement with experiment for constant property flow, with the results for friction superior to those for heat transfer. For impingement cooling, the agreement with experiment was generally good, but the results suggest that improved modelling of the dissipation rate of turbulence kinetic energy is required in order to obtain improved heat transfer prediction, especially near the stagnation point. The k-epsilon turbulence model was used to predict the mean flow and heat transfer for constant and variable property flows. The effect of variable properties for channel flow was investigated using the same turbulence model, but comparison with experiment yielded no clear conclusions. Also, the wall function method was modified for use in the variable properties flow with a non-adiabatic surface, and an empirical model is suggested to correctly account for the behavior of the viscous sublayer with heating.

Step Bunching: Influence of Impurities and Solution Flow

NASA Technical Reports Server (NTRS)

Chernov, A. A.; Vekilov, P. G.; Coriell, S. R.; Murray, B. T.; McFadden, G. B.

1999-01-01

Step bunching results in striations even at relatively early stages of its development and in inclusions of mother liquor at the later stages. Therefore, eliminating step bunching is crucial for high crystal perfection. At least 5 major effects causing and influencing step bunching are known: (1) Basic morphological instability of stepped interfaces. It is caused by concentration gradient in the solution normal to the face and by the redistribution of solute tangentially to the interface which redistribution enhances occasional perturbations in step density due to various types of noise; (2) Aggravation of the above basic instability by solution flowing tangentially to the face in the same directions as the steps or stabilization of equidistant step train if these flows are antiparallel; (3) Enhanced bunching at supersaturation where step velocity v increases with relative supersaturation s much faster than linear. This v(s) dependence is believed to be associated with impurities. The impurities of which adsorption time is comparable with the time needed to deposit one lattice layer may also be responsible for bunching; (4) Very intensive solution flow stabilizes growing interface even at parallel solution and step flows; (5) Macrosteps were observed to nucleate at crystal corners and edges. Numerical simulation, assuming step-step interactions via surface diffusion also show that step bunching may be induced by random step nucleation at the facet edge and by discontinuity in the step density (a ridge) somewhere in the middle of a face. The corresponding bunching patterns produce the ones observed in experiment. The nature of step bunching generated at the corners and edges and by dislocation step sources, as well as the also relative importance and interrelations between mechanisms 1-5 is not clear, both from experimental and theoretical standpoints. Furthermore, several laws controlling the evolution of existing step bunches have been suggested, though unambiguous conclusions are still missing. Addressing these issues is the major goal of the present project. The theory addressing the above problem, experimental methods, several figures which include: (1) the spatial wave numbers at which the system is neutrally stable as a function of growth velocity for linear kinetics and supersaturation for nonlinear kinetics; (2) a schematic of the experiment of lysozyme crystal growing under conditions of natural convection; (3) fluctuations in time, t, of the normal growth rate, R(t), vicinal slope, p(t) and Fourier Spectra of R(t), discussions and conclusions are presented.

Experimental instruction in photonics for high school students: approaches to managing problems faced

NASA Astrophysics Data System (ADS)

Choong, Zhengyang

2017-08-01

Student research projects are increasingly common at the K-12 level. However, students often face difficulties in the course of their school research projects such as setting realistic timelines and expectations, handling problems stemming from a lack of self-confidence, as well as being sufficiently disciplined for sustained communication and experimentation. In this work, we explore manifestations of these problems in the context of a photonics project, characterising the spectrum of the breakdown flash from Silicon Avalanche Photodiodes. We report on the process of planning and building the setup, data collection, analysis and troubleshooting, as well as the technical and human problems at each step. Approaches that were found to be helpful in managing the aforementioned problems are discussed, including an attention to detail during experimental work, as well as communicating in a forthcoming manner. Œe former allowed for clearer planning and the setting of quantifiable proximal goals; the latter helped in motivating discipline, and also helped in the understanding of research as an iterative learning process without a clear definition of success or failure.

3 CFR - Continuation of the National Emergency With Respect to the Actions and Policies of Certain...

Code of Federal Regulations, 2013 CFR

2013-01-01

... steps backward in the development of democratic governance and respect for human rights. The actions and... or institutions, to commit human rights abuses related to political repression, including detentions... against political opposition, civil society, and independent media. The government arbitrarily arrested...

Schooling Makes You Smarter: What Teachers Need to Know about IQ

ERIC Educational Resources Information Center

Nisbett, Richard E.

2013-01-01

In 1994, America took a giant step backward in understanding intelligence and how it can be cultivated. Richard Herrnstein, a psychology professor at Harvard University, and Charles Murray, a political scientist with the American Enterprise Institute, published "The Bell Curve," a best-selling book that was controversial among…

Sonoma Developmental Curriculum: Instructional Programs. Volume II.

ERIC Educational Resources Information Center

Adams, Patrick, Ed.; And Others

The guide presents instructional materials for teaching developmentally delayed children from birth to 6 years old. The following five instructional areas are covered (with sample activities in parentheses): gross motor (demonstrates a tonic-neck reflex, demonstrates ability to bear almost full weight, and crawls backward down three steps); fine…

Particle rejuvenation of Rao-Blackwellized sequential Monte Carlo smoothers for conditionally linear and Gaussian models

NASA Astrophysics Data System (ADS)

Nguyen, Ngoc Minh; Corff, Sylvain Le; Moulines, Éric

2017-12-01

This paper focuses on sequential Monte Carlo approximations of smoothing distributions in conditionally linear and Gaussian state spaces. To reduce Monte Carlo variance of smoothers, it is typical in these models to use Rao-Blackwellization: particle approximation is used to sample sequences of hidden regimes while the Gaussian states are explicitly integrated conditional on the sequence of regimes and observations, using variants of the Kalman filter/smoother. The first successful attempt to use Rao-Blackwellization for smoothing extends the Bryson-Frazier smoother for Gaussian linear state space models using the generalized two-filter formula together with Kalman filters/smoothers. More recently, a forward-backward decomposition of smoothing distributions mimicking the Rauch-Tung-Striebel smoother for the regimes combined with backward Kalman updates has been introduced. This paper investigates the benefit of introducing additional rejuvenation steps in all these algorithms to sample at each time instant new regimes conditional on the forward and backward particles. This defines particle-based approximations of the smoothing distributions whose support is not restricted to the set of particles sampled in the forward or backward filter. These procedures are applied to commodity markets which are described using a two-factor model based on the spot price and a convenience yield for crude oil data.

Effects of an aft facing step on the surface of a laminar flow glider wing

NASA Technical Reports Server (NTRS)

Sandlin, Doral R.; Saiki, Neal

1993-01-01

A motor glider was used to perform a flight test study on the effects of aft facing steps in a laminar boundary layer. This study focuses on two dimensional aft facing steps oriented spanwise to the flow. The size and location of the aft facing steps were varied in order to determine the critical size that will force premature transition. Transition over a step was found to be primarily a function of Reynolds number based on step height. Both of the step height Reynolds numbers for premature and full transition were determined. A hot film anemometry system was used to detect transition.

Efficient feature subset selection with probabilistic distance criteria. [pattern recognition

NASA Technical Reports Server (NTRS)

Chittineni, C. B.

1979-01-01

Recursive expressions are derived for efficiently computing the commonly used probabilistic distance measures as a change in the criteria both when a feature is added to and when a feature is deleted from the current feature subset. A combinatorial algorithm for generating all possible r feature combinations from a given set of s features in (s/r) steps with a change of a single feature at each step is presented. These expressions can also be used for both forward and backward sequential feature selection.

Barriers to and Reasons for Treatment Initiation Among Gambling Help-line Callers.

PubMed

Khayyat-Abuaita, Ula; Ostojic, Dragana; Wiedemann, Ashley; Arfken, Cynthia L; Ledgerwood, David M

2015-08-01

Identifying barriers to seeking treatment is essential for increasing problem gambler treatment initiation in the community, given that as few as 1 in 10 problem gamblers ever seek treatment. Further, many problem gamblers who take the initial step of contacting problem gambling help-lines do not subsequently go on to attend face-to-face treatment. There is limited research examining reasons for attending treatment among this population. This study addressed these gaps in the literature by examining barriers and attractions to treatment among callers to the State of Michigan Problem Gambling Help-line. In total, 143 callers (n = 86 women) completed the Barriers to Treatment for Problem Gambling (BTPG) questionnaire and responded to open-ended questions regarding barriers to and reasons for treatment initiation, as part of a telephone interview. Greater endorsement of barriers to treatment was associated with a lower likelihood of initiating treatment, especially perceived absence of problem and treatment unavailability. Correspondingly, problem gamblers who identified more reasons to attend treatment were more likely to attend, with positive treatment perceptions being the most influential. These findings can help get people into treatment by addressing barriers and fostering reasons for attending treatment, as well as reminding clinicians of the importance of identifying and addressing individual treatment barriers among patients with problem gambling.

Mechanisms for anterior cruciate ligament injuries in badminton.

PubMed

Kimura, Yuka; Ishibashi, Yasuyuki; Tsuda, Eiichi; Yamamoto, Yuji; Tsukada, Harehiko; Toh, Satoshi

2010-12-01

A high incidence of anterior cruciate ligament (ACL) injuries related to sports activities has been reported; however, the injury situation of ACL injury in badminton has not been elucidated. This study investigated the mechanism of ACL injury in badminton using a questionnaire. Information on injury mechanism was gathered from interviews with six male and 15 female badminton players who received a non-contact ACL injury playing badminton and underwent ACL reconstruction. The most common injury mechanism (10 of 21 injuries) was single-leg landing after overhead stroke. Nine of 10 players had injured the knee opposite to the racket-hand side. The second most frequent injury mechanism (eight of 21 injuries) was plant-and-cut while side-stepping or backward stepping. All eight players injured the knee of the racket-hand side. Eleven injuries occurred in the rear court, and six of the 11 injuries occurred during single-leg landing after an overhead stroke. The knee opposite to the racket-hand side tended to sustain the ACL injuries during single-leg landing after a backhand overhead stroke, whereas the knee of the racket-hand side tended to be injured by plant-and-cut during side or backward stepping. These injury patterns appear to be due to specific movements during badminton.

Reduction of sludge production from WWTP using thermal pretreatment and enhanced anaerobic methanisation.

PubMed

Graja, S; Chauzy, J; Fernandes, P; Patria, L; Cretenot, D

2005-01-01

The objective of the study presented here was to investigate the performance of an enhanced two-step anaerobic process for the treatment of WWTP sludge. This process was developed to answer the urgent need currently faced by WWTP operators to reduce the production of biosolids, for which disposal pathways are facing increasing difficulties. A pilot plant was operated on a full-scale WWTP (2,500 p.e.) over a period of 4 months. It consisted of a thermal pre-treatment of excess sludge at 175 degrees C and 40 min, followed by dewatering and methanisation of the centrate in a fixed-film reactor. The thermal lysis had a two-fold enhancing effect on sludge reduction efficiency: firstly, it allowed a decrease of the HRT in the methaniser to 2.9 days and secondly, it yielded biosolids with a high dewaterability. This contributed to further reductions in the final volume of sludge to be disposed of. The two-step process achieved a sludge reduction efficiency of 65% as TSS, thus giving an interesting treatment option for WWTP facing sludge disposal problems.

Reversible Reasoning and the Working Backwards Problem Solving Strategy

ERIC Educational Resources Information Center

Ramful, Ajay

2015-01-01

Making sense of mathematical concepts and solving mathematical problems may demand different forms of reasoning. These could be either domain-based, such as algebraic, geometric or statistical reasoning, while others are more general such as inductive/deductive reasoning. This article aims at giving visibility to a particular form of reasoning…

Cross-cultural equivalence in translations of the oral health impact profile.

PubMed

MacEntee, Michael I; Brondani, Mario

2016-04-01

The Oral Health Impact Profile (OHIP) has been translated for comparisons across cultural boundaries. This report on a systematic search of literature published between 1994 and 2014 aims to identify an acceptable method of translating psychometric instruments for cross-cultural equivalence, and how they were used to translate the OHIP. An electronic search used the keywords 'cultural adaptation', 'validation', 'Oral Health Impact Profile' and 'OHIP' in MEDLINE and EMBASE databases supplemented by reference links and grey literature. It included papers on methods of cross-cultural translation and translations of the OHIP for dentulous adults and adolescents, and excluded papers without translational details or limited to specific disorders. The search identified eight steps to cross-cultural equivalence, and 36 (plus three supplemental) translations of the OHIP. The steps involve assessment of (i) forward/backward translation by committee, (ii) constructs, (iii) item interpretations, (iv) interval scales, (v) convergent validity, (vi) discriminant validity, (vii) responsiveness to clinical change and (viii) pilot tests. Most (>60%) of the translations involved forward/backward translation by committee, item interpretations, interval scales, convergence, discrimination and pilot tests, but fewer assessed the underlying theory (47%) or responsiveness to clinical change (28%). An acceptable method for translating quality of life-related psychometric instruments for cross-cultural equivalence has eight procedural steps, and most of the 36 OHIP translations involved at least five of the steps. Only translations to Saudi Arabian Arabic, Chinese Mandarin, German and Japanese used all eight steps to claim cultural equivalence with the original OHIP. © 2015 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Effects of narrow-base walking and dual tasking on gait spatiotemporal characteristics in anterior cruciate ligament-injured adults compared to healthy adults.

PubMed

Mazaheri, Masood; Negahban, Hossein; Soltani, Maryam; Mehravar, Mohammad; Tajali, Shirin; Hessam, Masumeh; Salavati, Mahyar; Kingma, Idsart

2017-08-01

The present experiment was conducted to examine the hypothesis that challenging control through narrow-base walking and/or dual tasking affects ACL-injured adults more than healthy control adults. Twenty male ACL-injured adults and twenty healthy male adults walked on a treadmill at a comfortable speed under two base-of-support conditions, normal-base versus narrow-base, with and without a cognitive task. Gait patterns were assessed using mean and variability of step length and mean and variability of step velocity. Cognitive performance was assessed using the number of correct counts in a backward counting task. Narrow-base walking resulted in a larger decrease in step length and a more pronounced increase in variability of step length and of step velocity in ACL-injured adults than in healthy adults. For most of the gait parameters and for backward counting performance, the dual-tasking effect was similar between the two groups. ACL-injured adults adopt a more conservative and more unstable gait pattern during narrow-base walking. This can be largely explained by deficits of postural control in ACL-injured adults, which impairs gait under more balance-demanding conditions. The observation that the dual-tasking effect did not differ between the groups may be explained by the fact that walking is an automatic process that involves minimal use of attentional resources, even after ACL injury. Clinicians should consider the need to include aspects of terrain complexity, such as walking on a narrow walkway, in gait assessment and training of patients with ACL injury. III.

A backward Monte Carlo method for efficient computation of runaway probabilities in runaway electron simulation

NASA Astrophysics Data System (ADS)

Zhang, Guannan; Del-Castillo-Negrete, Diego

2017-10-01

Kinetic descriptions of RE are usually based on the bounced-averaged Fokker-Planck model that determines the PDFs of RE. Despite of the simplification involved, the Fokker-Planck equation can rarely be solved analytically and direct numerical approaches (e.g., continuum and particle-based Monte Carlo (MC)) can be time consuming specially in the computation of asymptotic-type observable including the runaway probability, the slowing-down and runaway mean times, and the energy limit probability. Here we present a novel backward MC approach to these problems based on backward stochastic differential equations (BSDEs). The BSDE model can simultaneously describe the PDF of RE and the runaway probabilities by means of the well-known Feynman-Kac theory. The key ingredient of the backward MC algorithm is to place all the particles in a runaway state and simulate them backward from the terminal time to the initial time. As such, our approach can provide much faster convergence than the brute-force MC methods, which can significantly reduce the number of particles required to achieve a prescribed accuracy. Moreover, our algorithm can be parallelized as easy as the direct MC code, which paves the way for conducting large-scale RE simulation. This work is supported by DOE FES and ASCR under the Contract Numbers ERKJ320 and ERAT377.

Modeling biological problems in computer science: a case study in genome assembly.

PubMed

Medvedev, Paul

2018-01-30

As computer scientists working in bioinformatics/computational biology, we often face the challenge of coming up with an algorithm to answer a biological question. This occurs in many areas, such as variant calling, alignment and assembly. In this tutorial, we use the example of the genome assembly problem to demonstrate how to go from a question in the biological realm to a solution in the computer science realm. We show the modeling process step-by-step, including all the intermediate failed attempts. Please note this is not an introduction to how genome assembly algorithms work and, if treated as such, would be incomplete and unnecessarily long-winded. © The Author(s) 2018. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

The Efficacy of a Home-School Intervention for Preschoolers with Challenging Behaviors: A Randomized Controlled Trial of Preschool First Step to Success

ERIC Educational Resources Information Center

Feil, Edward G.; Frey, Andy; Walker, Hill M.; Small, Jason W.; Seeley, John R.; Golly, Annemieke; Forness, Steven R.

2014-01-01

The field of early intervention is currently faced with the challenge of reducing the prevalence of antisocial behavior in children. Longitudinal outcomes research indicates that increased antisocial behavior and impairments in social competence skills during the preschool years often serve as harbingers of future adjustment problems in a number…

A Calculating Web Site Could Ignite a New Campus "Math War"

ERIC Educational Resources Information Center

Young, Jeffrey R.

2009-01-01

The long-running debate over whether students should be allowed to wield calculators during mathematics exams may soon seem quaint. The latest dilemma facing professors is whether to let students turn to a Web site called WolframAlpha, which not only solves complex math problems, but also can spell out the steps leading to those solutions. In…

Emotion Unchained: Facial Expression Modulates Gaze Cueing under Cognitive Load.

PubMed

Pecchinenda, Anna; Petrucci, Manuel

2016-01-01

Direction of eye gaze cues spatial attention, and typically this cueing effect is not modulated by the expression of a face unless top-down processes are explicitly or implicitly involved. To investigate the role of cognitive control on gaze cueing by emotional faces, participants performed a gaze cueing task with happy, angry, or neutral faces under high (i.e., counting backward by 7) or low cognitive load (i.e., counting forward by 2). Results show that high cognitive load enhances gaze cueing effects for angry facial expressions. In addition, cognitive load reduces gaze cueing for neutral faces, whereas happy facial expressions and gaze affected object preferences regardless of load. This evidence clearly indicates a differential role of cognitive control in processing gaze direction and facial expression, suggesting that under typical conditions, when we shift attention based on social cues from another person, cognitive control processes are used to reduce interference from emotional information.

Emotion Unchained: Facial Expression Modulates Gaze Cueing under Cognitive Load

PubMed Central

Petrucci, Manuel

2016-01-01

Direction of eye gaze cues spatial attention, and typically this cueing effect is not modulated by the expression of a face unless top-down processes are explicitly or implicitly involved. To investigate the role of cognitive control on gaze cueing by emotional faces, participants performed a gaze cueing task with happy, angry, or neutral faces under high (i.e., counting backward by 7) or low cognitive load (i.e., counting forward by 2). Results show that high cognitive load enhances gaze cueing effects for angry facial expressions. In addition, cognitive load reduces gaze cueing for neutral faces, whereas happy facial expressions and gaze affected object preferences regardless of load. This evidence clearly indicates a differential role of cognitive control in processing gaze direction and facial expression, suggesting that under typical conditions, when we shift attention based on social cues from another person, cognitive control processes are used to reduce interference from emotional information. PMID:27959925

Experimental Evidence on Iterated Reasoning in Games

PubMed Central

Grehl, Sascha; Tutić, Andreas

2015-01-01

We present experimental evidence on two forms of iterated reasoning in games, i.e. backward induction and interactive knowledge. Besides reliable estimates of the cognitive skills of the subjects, our design allows us to disentangle two possible explanations for the observed limits in performed iterated reasoning: Restrictions in subjects’ cognitive abilities and their beliefs concerning the rationality of co-players. In comparison to previous literature, our estimates regarding subjects’ skills in iterated reasoning are quite pessimistic. Also, we find that beliefs concerning the rationality of co-players are completely irrelevant in explaining the observed limited amount of iterated reasoning in the dirty faces game. In addition, it is demonstrated that skills in backward induction are a solid predictor for skills in iterated knowledge, which points to some generalized ability of the subjects in iterated reasoning. PMID:26312486

The response of turbine engine rotors to interference rubs

NASA Technical Reports Server (NTRS)

Kascak, A. F.

1980-01-01

A method was developed for the direct integration of a rotor dynamics system experiencing a blade loss induced rotor rub. Both blade loss and rotor rub were simulated on a rotor typical of a small gas turbine. A small change in the coefficient of friction (from 0.1 to 0.2) caused the rotor to change from forward to backward whirl and to theoretically destroy itself in a few rotations. This method provides an analytical capability to study the susceptibility of rotors to rub induced backward whirl problems.

Hysteresis and Phase Transitions in a Lattice Regularization of an Ill-Posed Forward-Backward Diffusion Equation

NASA Astrophysics Data System (ADS)

Helmers, Michael; Herrmann, Michael

2018-03-01

We consider a lattice regularization for an ill-posed diffusion equation with a trilinear constitutive law and study the dynamics of phase interfaces in the parabolic scaling limit. Our main result guarantees for a certain class of single-interface initial data that the lattice solutions satisfy asymptotically a free boundary problem with a hysteretic Stefan condition. The key challenge in the proof is to control the microscopic fluctuations that are inevitably produced by the backward diffusion when a particle passes the spinodal region.

Beliefs about Creativity: Views of Tertiary Students in Hong Kong

ERIC Educational Resources Information Center

Ho, Kwok Keung; Soh, Kay Cheng; Ho, Belinda

2006-01-01

Background: Creativity is associated with many pet beliefs, unfounded or based on limited personal experiences and observations. Aims: The intention of the present study is to take the research one step backward to look at possible antecedents of beliefs regarding creativity, as such knowledge has implications for education where creativity is…

Steps forward, backward, and sideways: Intravenous lipid emulsions for critically ill neonates

USDA-ARS?s Scientific Manuscript database

A neonatologist doesn't need long-term memory to recall caring for babies who developed severe cholestasis leading to death or the need for a liver and/or intestinal transplant. Fortunately, there is no doubt that the situation has improved dramatically in the past 5 years. Cholestasis is resolving ...

A security/safety survey of long term care facilities.

PubMed

Acorn, Jonathan R

2010-01-01

What are the major security/safety problems of long term care facilities? What steps are being taken by some facilities to mitigate such problems? Answers to these questions can be found in a survey of IAHSS members involved in long term care security conducted for the IAHSS Long Term Care Security Task Force. The survey, the author points out, focuses primarily on long term care facilities operated by hospitals and health systems. However, he believes, it does accurately reflect the security problems most long term facilities face, and presents valuable information on security systems and practices which should be also considered by independent and chain operated facilities.

The use of ARL trajectories for the evaluation of precipitation chemistry data

Treesearch

John M. Miller; James N. Galloway; Gene E. Likens

1976-01-01

One of the major problems in interpreting precipitation chemistry data is determining the possible source areas of the materials found in the precipitation. To investigate this problem, the trajectory program developed at Air Resources Laboratories (NOAA) was used to compute five-day backward air trajectories from Ithaca, New York.

Effects of Progressive Body Weight Support Treadmill Forward and Backward Walking Training on Stroke Patients' Affected Side Lower Extremity's Walking Ability.

PubMed

Kim, Kyunghoon; Lee, Sukmin; Lee, Kyoungbo

2014-12-01

[Purpose] The purpose of the present study was to examine the effects of progressive body weight supported treadmill forward and backward walking training (PBWSTFBWT), progressive body weight supported treadmill forward walking training (PBWSTFWT), progressive body weight supported treadmill backward walking training (PBWSTBWT), on stroke patients' affected side lower extremity's walking ability. [Subjects and Methods] A total of 36 chronic stroke patients were divided into three groups with 12 subjects in each group. Each of the groups performed one of the progressive body weight supported treadmill training methods for 30 minute, six times per week for three weeks, and then received general physical therapy without any other intervention until the follow-up tests. For the assessment of the affected side lower extremity's walking ability, step length of the affected side, stance phase of the affected side, swing phase of the affected side, single support of the affected side, and step time of the affected side were measured using optogait and the symmetry index. [Results] In the within group comparisons, all the three groups showed significant differences between before and after the intervention and in the comparison of the three groups, the PBWSTFBWT group showed more significant differences in all of the assessed items than the other two groups. [Conclusion] In the present study progressive body weight supported treadmill training was performed in an environment in which the subjects were actually walked, and PBWSTFBWT was more effective at efficiently training stroke patients' affected side lower extremity's walking ability.

Spatial Disorientation in Gondola Centrifuges Predicted by the Form of Motion as a Whole in 3-D

PubMed Central

Holly, Jan E.; Harmon, Katharine J.

2009-01-01

INTRODUCTION During a coordinated turn, subjects can misperceive tilts. Subjects accelerating in tilting-gondola centrifuges without external visual reference underestimate the roll angle, and underestimate more when backward-facing than when forward-facing. In addition, during centrifuge deceleration, the perception of pitch can include tumble while paradoxically maintaining a fixed perceived pitch angle. The goal of the present research was to test two competing hypotheses: (1) that components of motion are perceived relatively independently and then combined to form a three-dimensional perception, and (2) that perception is governed by familiarity of motions as a whole in three dimensions, with components depending more strongly on the overall shape of the motion. METHODS Published experimental data were used from existing tilting-gondola centrifuge studies. The two hypotheses were implemented formally in computer models, and centrifuge acceleration and deceleration were simulated. RESULTS The second, whole-motion oriented, hypothesis better predicted subjects' perceptions, including the forward-backward asymmetry and the paradoxical tumble upon deceleration. Important was the predominant stimulus at the beginning of the motion as well as the familiarity of centripetal acceleration. CONCLUSION Three-dimensional perception is better predicted by taking into account familiarity with the form of three-dimensional motion. PMID:19198199

Development of face recognition: Dynamic causal modelling of MEG data.

PubMed

He, Wei; Johnson, Blake W

2018-04-01

Electrophysiological studies of adults indicate that brain activity is enhanced during viewing of repeated faces, at a latency of about 250 ms after the onset of the face (M250/N250). The present study aimed to determine if this effect was also present in preschool-aged children, whose brain activity was measured in a custom-sized pediatric MEG system. The results showed that, unlike adults, face repetition did not show any significant modulation of M250 amplitude in children; however children's M250 latencies were significantly faster for repeated than non-repeated faces. Dynamic causal modelling (DCM) of the M250 in both age groups tested the effects of face repetition within the core face network including the occipital face area (OFA), the fusiform face area (FFA), and the superior temporal sulcus (STS). DCM revealed that repetition of identical faces altered both forward and backward connections in children and adults; however the modulations involved inputs to both FFA and OFA in adults but only to OFA in children. These findings suggest that the amplitude-insensitivity of the immature M250 may be due to a weaker connection between the FFA and lower visual areas. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

Large-eddy simulations with wall models

NASA Technical Reports Server (NTRS)

Cabot, W.

1995-01-01

The near-wall viscous and buffer regions of wall-bounded flows generally require a large expenditure of computational resources to be resolved adequately, even in large-eddy simulation (LES). Often as much as 50% of the grid points in a computational domain are devoted to these regions. The dense grids that this implies also generally require small time steps for numerical stability and/or accuracy. It is commonly assumed that the inner wall layers are near equilibrium, so that the standard logarithmic law can be applied as the boundary condition for the wall stress well away from the wall, for example, in the logarithmic region, obviating the need to expend large amounts of grid points and computational time in this region. This approach is commonly employed in LES of planetary boundary layers, and it has also been used for some simple engineering flows. In order to calculate accurately a wall-bounded flow with coarse wall resolution, one requires the wall stress as a boundary condition. The goal of this work is to determine the extent to which equilibrium and boundary layer assumptions are valid in the near-wall regions, to develop models for the inner layer based on such assumptions, and to test these modeling ideas in some relatively simple flows with different pressure gradients, such as channel flow and flow over a backward-facing step. Ultimately, models that perform adequately in these situations will be applied to more complex flow configurations, such as an airfoil.

Canopy-wake dynamics: the failure of the constant flux layer

NASA Astrophysics Data System (ADS)

Stefan, H. G.; Markfort, C. D.; Porte-Agel, F.

2013-12-01

The atmospheric boundary layer adjustment at the abrupt transition from a canopy (forest) to a flat surface (land or water) was investigated in a wind tunnel experiment. Detailed measurements examining the effect of canopy turbulence on flow separation, reduced surface shear stress and wake recovery are compared to data for the classical case of a solid backward-facing step. Results provide new insights into the data interpretation for flux estimation by eddy-covariance and flux gradient methods and for the assessment of surface boundary conditions in turbulence models of the atmospheric boundary layer in complex landscapes and over water bodies affected by canopy wakes. The wind tunnel results indicate that the wake of a forest canopy strongly affects surface momentum flux within a distance of 35 - 100 times the step or canopy height, and mean turbulence quantities require distances of at least 100 times the canopy height to adjust to the new surface. The near-surface mixing length in the wake exhibits characteristic length scales of canopy flows at the canopy edge, of the flow separation in the near wake and adjusts to surface layer scaling in the far wake. Components of the momentum budget are examined individually to determine the impact of the wake. The results demonstrate why a constant flux layer does not form until far downwind in the wake. An empirical model for surface shear stress distribution from a forest to a clearing or lake is proposed.

Evaluation of a parallel implementation of the learning portion of the backward error propagation neural network: experiments in artifact identification.

PubMed Central

Sittig, D. F.; Orr, J. A.

1991-01-01

Various methods have been proposed in an attempt to solve problems in artifact and/or alarm identification including expert systems, statistical signal processing techniques, and artificial neural networks (ANN). ANNs consist of a large number of simple processing units connected by weighted links. To develop truly robust ANNs, investigators are required to train their networks on huge training data sets, requiring enormous computing power. We implemented a parallel version of the backward error propagation neural network training algorithm in the widely portable parallel programming language C-Linda. A maximum speedup of 4.06 was obtained with six processors. This speedup represents a reduction in total run-time from approximately 6.4 hours to 1.5 hours. We conclude that use of the master-worker model of parallel computation is an excellent method for obtaining speedups in the backward error propagation neural network training algorithm. PMID:1807607

Visuospatial working memory for locations, colours, and binding in typically developing children and in children with dyslexia and non-verbal learning disability.

PubMed

Garcia, Ricardo Basso; Mammarella, Irene C; Tripodi, Doriana; Cornoldi, Cesare

2014-03-01

This study examined forward and backward recall of locations and colours and the binding of locations and colours, comparing typically developing children - aged between 8 and 10 years - with two different groups of children of the same age with learning disabilities (dyslexia in one group, non-verbal learning disability [NLD] in the other). Results showed that groups with learning disabilities had different visuospatial working memory problems and that children with NLD had particular difficulties in the backward recall of locations. The differences between the groups disappeared, however, when locations and colours were bound together. It was concluded that specific processes may be involved in children in the binding and backward recall of different types of information, as they are not simply the resultant of combining the single processes needed to recall single features. © 2013 The British Psychological Society.

A Right Worth Fighting for

ERIC Educational Resources Information Center

Blakeley, Richard

2010-01-01

The statutory right to request time to train for all employees is the right way forward for UK plc and for workers. The coalition government not implementing this legislation in full would be a backward step. The author says this with such certainty because the status quo in which a third of employers don't train their workers and 10 million…

Dance Education in an Era of Racial Backlash: Moving Forward as We Step Backwards

ERIC Educational Resources Information Center

Kerr-Berry, Julie A.

2012-01-01

The field of dance education is not immune to conflicted discourses about race in the United States. This article investigates the subject of race, education, and dance, and problematizes current postracial discourses in postsecondary education. It examines the implications of race and ethnicity in a number of critical areas, such as faculty and…

Sub-optimal control of unsteady boundary layer separation and optimal control of Saltzman-Lorenz model

NASA Astrophysics Data System (ADS)

Sardesai, Chetan R.

The primary objective of this research is to explore the application of optimal control theory in nonlinear, unsteady, fluid dynamical settings. Two problems are considered: (1) control of unsteady boundary-layer separation, and (2) control of the Saltzman-Lorenz model. The unsteady boundary-layer equations are nonlinear partial differential equations that govern the eruptive events that arise when an adverse pressure gradient acts on a boundary layer at high Reynolds numbers. The Saltzman-Lorenz model consists of a coupled set of three nonlinear ordinary differential equations that govern the time-dependent coefficients in truncated Fourier expansions of Rayleigh-Renard convection and exhibit deterministic chaos. Variational methods are used to derive the nonlinear optimal control formulations based on cost functionals that define the control objective through a performance measure and a penalty function that penalizes the cost of control. The resulting formulation consists of the nonlinear state equations, which must be integrated forward in time, and the nonlinear control (adjoint) equations, which are integrated backward in time. Such coupled forward-backward time integrations are computationally demanding; therefore, the full optimal control problem for the Saltzman-Lorenz model is carried out, while the more complex unsteady boundary-layer case is solved using a sub-optimal approach. The latter is a quasi-steady technique in which the unsteady boundary-layer equations are integrated forward in time, and the steady control equation is solved at each time step. Both sub-optimal control of the unsteady boundary-layer equations and optimal control of the Saltzman-Lorenz model are found to be successful in meeting the control objectives for each problem. In the case of boundary-layer separation, the control results indicate that it is necessary to eliminate the recirculation region that is a precursor to the unsteady boundary-layer eruptions. In the case of the Saltzman-Lorenz model, it is possible to control the system about either of the two unstable equilibrium points representing clockwise and counterclockwise rotation of the convection roles in a parameter regime for which the uncontrolled solution would exhibit deterministic chaos.

Attentional demands and postural recovery: the effects of aging.

PubMed

Brown, L A; Shumway-Cook, A; Woollacott, M H

1999-04-01

Cognitive demands associated with balance and locomotion may contribute to the incidence of falling among older adults. This study addressed issues related to the effects of aging on the attentional demands of recovering from an external disturbance to balance. This research also investigated whether performing a secondary cognitive task differentially affects postural recovery in young versus older adults. Fifteen young and 10 healthy older adults were exposed to a series of balance disturbances. Attentional demands were assessed using a dual task paradigm where postural recovery served as the primary task, and counting backwards served as a concurrent secondary cognitive task. The effect of the counting task was assessed by comparing kinematic variables related to feet-in-place and stepping recovery strategies. Recovering upright stance was found to be attentionally demanding in both age groups. The type of recovery strategy did not influence attentional demands in young adults; however, a hierarchy of increasing attentional demands between the ankle strategy and compensatory stepping was apparent among older adults. In addition, stepping appears to be more attentionally demanding for older adults than for younger adults. Counting backwards did not affect the type of strategy used; however, it did affect the kinematics of stepping. For both age groups, steps occurred when the center of mass was located in a more central location within the base of support when the secondary task was added. The ability to recover a stable posture following an external perturbation is more attentionally demanding for older adults than for younger adults. This would suggest that for some older adults, an increased risk for loss of balance and falls may result if sufficient attentional resources are not allocated to the task of postural recovery.

Perceptions of family caregivers of cancer patients about the challenges of caregiving: a qualitative study.

PubMed

Nemati, Shahnaz; Rassouli, Maryam; Ilkhani, Mahnaz; Baghestani, Ahmad Reza

2018-03-01

The experience of caring for a family member with cancer is associated with several care-related problems and challenges for the caregiver. The comprehensive and in-depth understanding of the trials and tribulations of caregiving can be a step towards resolving the problems faced by family caregivers of these patients. The present study aimed to explore challenges faced by Iranian family caregivers of cancer patients. The present qualitative study was conducted through in-depth semi-structured interviews held with 21 family caregivers of cancer patients selected through purposive sampling. Interviews continued until saturation of data. All interviews were recorded, transcribed and analysed through conventional content analysis. The codes extracted from interviews produced four main themes, including 'confusion', 'uncertainty', 'disintegration' and 'setback', which collectively caused suffering for family caregivers. Care provided in an atmosphere of suffering and discontent diminishes caregiver's quality of life and quality of patient care. Health planners should therefore consider the challenges and sufferings faced by family caregivers and should seek to obviate them through appropriate plans. © 2017 Nordic College of Caring Science.

Toward open set recognition.

PubMed

Scheirer, Walter J; de Rezende Rocha, Anderson; Sapkota, Archana; Boult, Terrance E

2013-07-01

To date, almost all experimental evaluations of machine learning-based recognition algorithms in computer vision have taken the form of "closed set" recognition, whereby all testing classes are known at training time. A more realistic scenario for vision applications is "open set" recognition, where incomplete knowledge of the world is present at training time, and unknown classes can be submitted to an algorithm during testing. This paper explores the nature of open set recognition and formalizes its definition as a constrained minimization problem. The open set recognition problem is not well addressed by existing algorithms because it requires strong generalization. As a step toward a solution, we introduce a novel "1-vs-set machine," which sculpts a decision space from the marginal distances of a 1-class or binary SVM with a linear kernel. This methodology applies to several different applications in computer vision where open set recognition is a challenging problem, including object recognition and face verification. We consider both in this work, with large scale cross-dataset experiments performed over the Caltech 256 and ImageNet sets, as well as face matching experiments performed over the Labeled Faces in the Wild set. The experiments highlight the effectiveness of machines adapted for open set evaluation compared to existing 1-class and binary SVMs for the same tasks.

Towards an Efficient Flooding Scheme Exploiting 2-Hop Backward Information in MANETs

NASA Astrophysics Data System (ADS)

Le, Trong Duc; Choo, Hyunseung

Flooding is an indispensable operation for providing control or routing functionalities to mobile ad hoc networks (MANETs). Previously, many flooding schemes have been studied with the intention of curtailing the problems of severe redundancies, contention, and collisions in traditional implementations. A recent approach with relatively high efficiency is 1HI by Liu et al., which uses only 1-hop neighbor information. The scheme achieves local optimality in terms of the number of retransmission nodes with time complexity &Theta(n log n), where n is the number of neighbors of a node; however, this method tends to make many redundant transmissions. In this paper, we present a novel flooding algorithm, 2HBI (2-hop backward information), that efficiently reduces the number of retransmission nodes and solves the broadcast storm problem in ad hoc networks using our proposed concept, “2-hop backward information.” The most significant feature of the proposed algorithm is that it does not require any extra communication overhead other than the exchange of 1-hop HELLO messages but maintains high deliverability. Comprehensive computer simulations show that the proposed scheme significantly reduces redundant transmissions in 1HI and in pure flooding, up to 38% and 91%, respectively; accordingly it alleviates contention and collisions in networks.

Adhesion of leukocytes under oscillating stagnation point conditions: a numerical study.

PubMed

Walker, P G; Alshorman, A A; Westwood, S; David, T

2002-01-01

Leukocyte recruitment from blood to the endothelium plays an important role in atherosclerotic plaque formation. Cells show a primary and secondary adhesive process with primary bonds responsible for capture and rolling and secondary bonds for arrest. Our objective was to investigate the role played by this process on the adhesion of leukocytes in complex flow. Cells were modelled as rigid spheres with spring like adhesion molecules which formed bonds with endothelial receptors. Models of bond kinetics and Newton's laws of motion were solved numerically to determine cell motion. Fluid force was obtained from the local shear rate obtained from a CFD simulation of the flow over a backward facing step.In stagnation point flow the shear rate near the stagnation point has a large gradient such that adherent cells in this region roll to a high shear region preventing permanent adhesion. This is enhanced if a small time dependent perturbation is imposed upon the stagnation point. For lower shear rates the cell rolling velocity may be such that secondary bonds have time to form. These bonds resist the lower fluid forces and consequently there is a relatively large permanent adhesion region.

A note on supersonic flow control with nanosecond plasma actuator

NASA Astrophysics Data System (ADS)

Zheng, J. G.; Cui, Y. D.; Li, J.; Khoo, B. C.

2018-04-01

A concept study on supersonic flow control using nanosecond pulsed plasma actuator is conducted by means of numerical simulation. The nanosecond plasma discharge is characterized by the generation of a micro-shock wave in ambient air and a residual heat in the discharge volume arising from the rapid heating of near-surface gas by the quick discharge. The residual heat has been found to be essential for the flow separation control over aerodynamic bodies like airfoil and backward-facing step. In this study, novel experiment is designed to utilize the other flow feature from discharge, i.e., instant shock wave, to control supersonic flow through shock-shock interaction. Both bow shock in front of a blunt body and attached shock anchored at the tip of supersonic projectile are manipulated via the discharged-induced shock wave in an appropriate manner. It is observed that drag on the blunt body is reduced appreciably. Meanwhile, a lateral force on sharp-edged projectile is produced, which can steer the body and give it an effective angle of attack. This opens a promising possibility for extending the applicability of this flow control technique in supersonic flow regime.

Introducing the pro-coagulant contact system in the numerical assessment of device-related thrombosis.

PubMed

Méndez Rojano, Rodrigo; Mendez, Simon; Nicoud, Franck

2018-06-01

Thrombosis is a major concern in blood-coated medical devices. Contact activation, which is the initial part of the coagulation cascade in device-related thrombosis, is not considered in current thrombus formation models. In the present study, pro-coagulant reactions including the contact activation system are coupled with a fluid solver in order to evaluate the potential of the contact system to initiate thrombin production. The biochemical/fluid model is applied to a backward-facing step configuration, a flow configuration that frequently appears in medical devices. In contrast to the in vivo thrombosis models in which a specific thrombotic zone (injury region) is set a priori by the user to initiate the coagulation reaction, a reactive surface boundary condition is applied to the whole device wall. Simulation results show large thrombin concentration in regions related to recirculation zones without the need of an a priori knowledge of the thrombus location. The numerical results align well with the regions prone to thrombosis observed in experimental results reported in the literature. This approach could complement thrombus formation models that take into account platelet activity and thrombus growth to optimize a wide range of medical devices.

Time-dependent and outflow boundary conditions for Dissipative Particle Dynamics

PubMed Central

Lei, Huan; Fedosov, Dmitry A.; Karniadakis, George Em

2011-01-01

We propose a simple method to impose both no-slip boundary conditions at fluid-wall interfaces and at outflow boundaries in fully developed regions for Dissipative Particle Dynamics (DPD) fluid systems. The procedure to enforce the no-slip condition is based on a velocity-dependent shear force, which is a generalized force to represent the presence of the solid-wall particles and to maintain locally thermodynamic consistency. We show that this method can be implemented in both steady and time-dependent fluid systems and compare the DPD results with the continuum limit (Navier-Stokes) results. We also develop a force-adaptive method to impose the outflow boundary conditions for fully developed flow with unspecified outflow velocity profile or pressure value. We study flows over the backward-facing step and in idealized arterial bifurcations using a combination of the two new boundary methods with different flow rates. Finally, we explore the applicability of the outflow method in time-dependent flow systems. The outflow boundary method works well for systems with Womersley number of O(1), i.e., when the pressure and flowrate at the outflow are approximately in-phase. PMID:21499548

Stepped Care Versus Direct Face-to-Face Cognitive Behavior Therapy for Social Anxiety Disorder and Panic Disorder: A Randomized Effectiveness Trial.

PubMed

Nordgreen, Tine; Haug, Thomas; Öst, Lars-Göran; Andersson, Gerhard; Carlbring, Per; Kvale, Gerd; Tangen, Tone; Heiervang, Einar; Havik, Odd E

2016-03-01

The aim of this study was to assess the effectiveness of a cognitive behavioral therapy (CBT) stepped care model (psychoeducation, guided Internet treatment, and face-to-face CBT) compared with direct face-to-face (FtF) CBT. Patients with panic disorder or social anxiety disorder were randomized to either stepped care (n=85) or direct FtF CBT (n=88). Recovery was defined as meeting two of the following three criteria: loss of diagnosis, below cut-off for self-reported symptoms, and functional improvement. No significant differences in intention-to-treat recovery rates were identified between stepped care (40.0%) and direct FtF CBT (43.2%). The majority of the patients who recovered in the stepped care did so at the less therapist-demanding steps (26/34, 76.5%). Moderate to large within-groups effect sizes were identified at posttreatment and 1-year follow-up. The attrition rates were high: 41.2% in the stepped care condition and 27.3% in the direct FtF CBT condition. These findings indicate that the outcome of a stepped care model for anxiety disorders is comparable to that of direct FtF CBT. The rates of improvement at the two less therapist-demanding steps indicate that stepped care models might be useful for increasing patients' access to evidence-based psychological treatments for anxiety disorders. However, attrition in the stepped care condition was high, and research regarding the factors that can improve adherence should be prioritized. Copyright © 2015. Published by Elsevier Ltd.

Efficient Integration of Coupled Electrical-Chemical Systems in Multiscale Neuronal Simulations

PubMed Central

Brocke, Ekaterina; Bhalla, Upinder S.; Djurfeldt, Mikael; Hellgren Kotaleski, Jeanette; Hanke, Michael

2016-01-01

Multiscale modeling and simulations in neuroscience is gaining scientific attention due to its growing importance and unexplored capabilities. For instance, it can help to acquire better understanding of biological phenomena that have important features at multiple scales of time and space. This includes synaptic plasticity, memory formation and modulation, homeostasis. There are several ways to organize multiscale simulations depending on the scientific problem and the system to be modeled. One of the possibilities is to simulate different components of a multiscale system simultaneously and exchange data when required. The latter may become a challenging task for several reasons. First, the components of a multiscale system usually span different spatial and temporal scales, such that rigorous analysis of possible coupling solutions is required. Then, the components can be defined by different mathematical formalisms. For certain classes of problems a number of coupling mechanisms have been proposed and successfully used. However, a strict mathematical theory is missing in many cases. Recent work in the field has not so far investigated artifacts that may arise during coupled integration of different approximation methods. Moreover, in neuroscience, the coupling of widely used numerical fixed step size solvers may lead to unexpected inefficiency. In this paper we address the question of possible numerical artifacts that can arise during the integration of a coupled system. We develop an efficient strategy to couple the components comprising a multiscale test problem in neuroscience. We introduce an efficient coupling method based on the second-order backward differentiation formula (BDF2) numerical approximation. The method uses an adaptive step size integration with an error estimation proposed by Skelboe (2000). The method shows a significant advantage over conventional fixed step size solvers used in neuroscience for similar problems. We explore different coupling strategies that define the organization of computations between system components. We study the importance of an appropriate approximation of exchanged variables during the simulation. The analysis shows a substantial impact of these aspects on the solution accuracy in the application to our multiscale neuroscientific test problem. We believe that the ideas presented in the paper may essentially contribute to the development of a robust and efficient framework for multiscale brain modeling and simulations in neuroscience. PMID:27672364

Efficient Integration of Coupled Electrical-Chemical Systems in Multiscale Neuronal Simulations.

PubMed

Brocke, Ekaterina; Bhalla, Upinder S; Djurfeldt, Mikael; Hellgren Kotaleski, Jeanette; Hanke, Michael

2016-01-01

Multiscale modeling and simulations in neuroscience is gaining scientific attention due to its growing importance and unexplored capabilities. For instance, it can help to acquire better understanding of biological phenomena that have important features at multiple scales of time and space. This includes synaptic plasticity, memory formation and modulation, homeostasis. There are several ways to organize multiscale simulations depending on the scientific problem and the system to be modeled. One of the possibilities is to simulate different components of a multiscale system simultaneously and exchange data when required. The latter may become a challenging task for several reasons. First, the components of a multiscale system usually span different spatial and temporal scales, such that rigorous analysis of possible coupling solutions is required. Then, the components can be defined by different mathematical formalisms. For certain classes of problems a number of coupling mechanisms have been proposed and successfully used. However, a strict mathematical theory is missing in many cases. Recent work in the field has not so far investigated artifacts that may arise during coupled integration of different approximation methods. Moreover, in neuroscience, the coupling of widely used numerical fixed step size solvers may lead to unexpected inefficiency. In this paper we address the question of possible numerical artifacts that can arise during the integration of a coupled system. We develop an efficient strategy to couple the components comprising a multiscale test problem in neuroscience. We introduce an efficient coupling method based on the second-order backward differentiation formula (BDF2) numerical approximation. The method uses an adaptive step size integration with an error estimation proposed by Skelboe (2000). The method shows a significant advantage over conventional fixed step size solvers used in neuroscience for similar problems. We explore different coupling strategies that define the organization of computations between system components. We study the importance of an appropriate approximation of exchanged variables during the simulation. The analysis shows a substantial impact of these aspects on the solution accuracy in the application to our multiscale neuroscientific test problem. We believe that the ideas presented in the paper may essentially contribute to the development of a robust and efficient framework for multiscale brain modeling and simulations in neuroscience.

Preschool motor skills following physical and occupational therapy services among non-disabled very low birth weight children.

PubMed

Watkins, Stephanie; Jonsson-Funk, Michele; Brookhart, M Alan; Rosenberg, Steven A; O'Shea, T Michael; Daniels, Julie

2014-05-01

Children born very low birth weight (VLBW) are at an increased risk of delayed development of motor skills. Physical and occupational therapy services may reduce this risk. Among VLBW children, we evaluated whether receipt of physical or occupational therapy services between 9 months and 2 years of age is associated with improved preschool age motor ability. Using data from the Early Childhood Longitudinal Study Birth Cohort we estimated the association between receipt of therapy and the following preschool motor milestones: skipping eight consecutive steps, hopping five times, standing on one leg for 10 seconds, walking backwards six steps on a line, and jumping distance. We used propensity score methods to adjust for differences in baseline characteristics between children who did and did not receive physical or occupational therapy, since children receiving therapy may be at higher risk of impairment. We applied propensity score weights and modeled the estimated effect of therapy on the distance that the child jumped using linear regression. We modeled all other end points using logistic regression. Treated VLBW children were 1.70 times as likely to skip eight steps (RR 1.70, 95 % CI 0.84, 3.44) compared to the untreated group and 30 % more likely to walk six steps backwards (RR 1.30, 95 % CI 0.63, 2.71), although these differences were not statistically significant. We found little effect of therapy on other endpoints. Providing therapy to VLBW children during early childhood may improve select preschool motor skills involving complex motor planning.

Air stepping in response to optic flows that move Toward and Away from the neonate.

PubMed

Barbu-Roth, Marianne; Anderson, David I; Desprès, Adeline; Streeter, Ryan J; Cabrol, Dominique; Trujillo, Michael; Campos, Joseph J; Provasi, Joëlle

2014-07-01

To shed further light on the perceptual regulation of newborn stepping, we compared neonatal air stepping in response to optic flows simulating forward or backward displacement with stepping forward on a surface. Twenty-two 3-day-olds performed four 60 s trials in which they stepped forward on a table (Tactile) or in the air in response to a pattern that moved toward (Toward) or away (Away) from them or was static (Static). Significantly more steps were taken in the Tactile and Toward conditions than the Static condition. The Away condition was intermediate to the other conditions. The knee joint activity across the entire trial was significantly greater in the Toward than the Away condition. Within-limb kinematics and between-limb coordination were very similar for steps taken in the air and on the table, particularly in the Toward and Tactile conditions. These findings highlight that visual and tactile stimulation can equally elicit neonatal stepping. © 2013 Wiley Periodicals, Inc.

Opportunities to utilize traditional phenological knowledge to support adaptive management of social-ecological systems vulnerable to changes in climate and fire regimes

Treesearch

Christopher A. Armatas; Tyron J. Venn; Brooke B. McBride; Alan E. Watson; Steve J. Carver

2016-01-01

The field of adaptive management has been embraced by researchers and managers in the United States as an approach to improve natural resource stewardship in the face of uncertainty and complex environmental problems. Integrating multiple knowledge sources and feedback mechanisms is an important step in this approach. Our objective is to contribute to the...

Statement of David Crosland, Acting Commissioner, Immigration & Naturalization Service, Before the Subcommittee on Immigration, Refugees, and International Law, Judiciary Committee, on Haitian Refugees on June 17, 1980.

ERIC Educational Resources Information Center

Crosland, David

Since the early 1970s, Haitians have been arriving in the United States in increasing numbers. Since 1977, the Immigration and Naturalization Service has taken several steps in response to this influx and to problems Haitian refugees face regarding asylum, exclusion, and deportation. One major decision resulted in new regulations that would…

The impact of conflicting spatial representations in airborne unmanned aerial system sensor control

DTIC Science & Technology

2016-02-01

Their methodology, however, was limited – participants were only seated in a forward configured seat in a civilian aircraft and only rudimentary...a starboard seat , facing towards the center of the aircraft , great discord between these spatial representations and their relevant sensory inputs...configuration provided space for three participants to be run at a time in three different seating orientations: forward, backward, and center of the aircraft

Constrained-transport Magnetohydrodynamics with Adaptive Mesh Refinement in CHARM

NASA Astrophysics Data System (ADS)

Miniati, Francesco; Martin, Daniel F.

2011-07-01

We present the implementation of a three-dimensional, second-order accurate Godunov-type algorithm for magnetohydrodynamics (MHD) in the adaptive-mesh-refinement (AMR) cosmological code CHARM. The algorithm is based on the full 12-solve spatially unsplit corner-transport-upwind (CTU) scheme. The fluid quantities are cell-centered and are updated using the piecewise-parabolic method (PPM), while the magnetic field variables are face-centered and are evolved through application of the Stokes theorem on cell edges via a constrained-transport (CT) method. The so-called multidimensional MHD source terms required in the predictor step for high-order accuracy are applied in a simplified form which reduces their complexity in three dimensions without loss of accuracy or robustness. The algorithm is implemented on an AMR framework which requires specific synchronization steps across refinement levels. These include face-centered restriction and prolongation operations and a reflux-curl operation, which maintains a solenoidal magnetic field across refinement boundaries. The code is tested against a large suite of test problems, including convergence tests in smooth flows, shock-tube tests, classical two- and three-dimensional MHD tests, a three-dimensional shock-cloud interaction problem, and the formation of a cluster of galaxies in a fully cosmological context. The magnetic field divergence is shown to remain negligible throughout.

Regional source identification using Lagrangian stochastic particle dispersion and HYSPLIT backward-trajectory models.

PubMed

Koracin, Darko; Vellore, Ramesh; Lowenthal, Douglas H; Watson, John G; Koracin, Julide; McCord, Travis; DuBois, David W; Chen, L W Antony; Kumar, Naresh; Knipping, Eladio M; Wheeler, Neil J M; Craig, Kenneth; Reid, Stephen

2011-06-01

The main objective of this study was to investigate the capabilities of the receptor-oriented inverse mode Lagrangian Stochastic Particle Dispersion Model (LSPDM) with the 12-km resolution Mesoscale Model 5 (MM5) wind field input for the assessment of source identification from seven regions impacting two receptors located in the eastern United States. The LSPDM analysis was compared with a standard version of the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) single-particle backward-trajectory analysis using inputs from MM5 and the Eta Data Assimilation System (EDAS) with horizontal grid resolutions of 12 and 80 km, respectively. The analysis included four 7-day summertime events in 2002; residence times in the modeling domain were computed from the inverse LSPDM runs and HYPSLIT-simulated backward trajectories started from receptor-source heights of 100, 500, 1000, 1500, and 3000 m. Statistics were derived using normalized values of LSPDM- and HYSPLIT-predicted residence times versus Community Multiscale Air Quality model-predicted sulfate concentrations used as baseline information. From 40 cases considered, the LSPDM identified first- and second-ranked emission region influences in 37 cases, whereas HYSPLIT-MM5 (HYSPLIT-EDAS) identified the sources in 21 (16) cases. The LSPDM produced a higher overall correlation coefficient (0.89) compared with HYSPLIT (0.55-0.62). The improvement of using the LSPDM is also seen in the overall normalized root mean square error values of 0.17 for LSPDM compared with 0.30-0.32 for HYSPLIT. The HYSPLIT backward trajectories generally tend to underestimate near-receptor sources because of a lack of stochastic dispersion of the backward trajectories and to overestimate distant sources because of a lack of treatment of dispersion. Additionally, the HYSPLIT backward trajectories showed a lack of consistency in the results obtained from different single vertical levels for starting the backward trajectories. To alleviate problems due to selection of a backward-trajectory starting level within a large complex set of 3-dimensional winds, turbulence, and dispersion, results were averaged from all heights, which yielded uniform improvement against all individual cases.

Proposal of digital interface for the system of the air conditioner's remote control: analysis of the system of feedback.

PubMed

da Silva de Queiroz Pierre, Raisa; Kawada, Tarô Arthur Tavares; Fontes, André Guimarães

2012-01-01

Develop a proposal of digital interface for the system of the remote control, that functions as support system during the manipulation of air conditioner adjusted for the users in general, from ergonomic parameters, objectifying the reduction of the problems faced for the user and improving the process. 20 people with questionnaire with both qualitative and quantitative level. Linear Method consists of a sequence of steps in which the input of one of them depends on the output from the previous one, although they are independent. The process of feedback, when necessary, must occur within each step separately.

Renaissance or a Backward Step? Disparities and Tensions in Two New Swedish Pathways in VET

ERIC Educational Resources Information Center

Berglund, Ingrid; Loeb, Ingrid Henning

2013-01-01

This article builds on results from studies of two new pathways in Swedish upper secondary VET. A major reform was launched in 2011 and the restructuring was presented by the Minister of Education as a "renaissance for VET education". The conclusion of the Upper Secondary Commission is that "students shall be more specialised within…

Correlating Lagrangian structures with forcing in two-dimensional flow

NASA Astrophysics Data System (ADS)

Ouellette, Nicholas; Hogg, Charlie; Liao, Yang

2015-11-01

Lagrangian coherent structures (LCSs) are the dominant transport barriers in unsteady, aperiodic flows, and their role in organizing mixing and transport has been well documented. However, nearly all that is known about LCSs has been gleaned from passive observations: they are computed in a post-processing step after a flow has been observed, and used to understand why the mixing and transport proceeded as it did. Here, we instead take a first step toward controlling the presence or locations of LCSs by studying the relationship between LCSs and external forcing in an experimental quasi-two-dimensional weakly turbulent flow. We find that the likelihood of finding a repelling LCS at a given location is positively correlated with the mean strain rate injected at that point and negatively correlated with the mean speed, and that it is not correlated with the vorticity. We also find that mean time between successive LCSs appearing at a fixed location is related to the structure of the forcing field. Finally, we demonstrate a surprising difference in our results between LCSs computed forward and backwards in time, with forward-time (repelling) LCSs showing much more correlation with the forcing than backwards-time (attracting) LCSs.

Effects of progressive backward body weight suppoted treadmill training on gait ability in chronic stroke patients: A randomized controlled trial.

PubMed

Kim, Kyung Hun; Lee, Kyoung Bo; Bae, Young-Hyeon; Fong, Shirley S M; Lee, Suk Min

2017-10-23

A stroke patient with hemiplegic gait is generally described as being slow and asymmetric. Body weight-supported treadmill training and backward gait training are recent additions to therapeutic gait trainings that may help improve gait in stroke patient with hemiplegic gait. Therefore, we examined the effect of progressive backward body weight-supported treadmill training on gait in chronic stroke patients with hemiplegic gait. Thirty subjects were divided to the experimental and control groups. The experimental group consisted of 15 patients and underwent progressive backward body weight-supported treadmill training. The control group consisted of 15 patients and underwent general treadmill gait training five times per week, for a total of four weeks. The OptoGait was used to analyze gait kinematics, and the dynamic gait index (DGI) and results of the 6-minute walk test were used as the clinical evaluation indicators. A follow-up test was carried out four weeks later to examine persistence of exercise effects. The experimental group showed statistically significant results in all dependent variables week four compared to the control group. However, until the eighth week, only the dependent variables, of affected step length (ASL), stride length (SL), and DGI differed significantly between the two groups. This study verified that progressive bodyweight-supported treadmill training had a positive influence on the temporospatial characteristics of gait and clinical gait evaluation index in chronic stroke patients.

J. E. W. Wallin's Diagnostic Theory for Classifying the Feeble-Minded and Backward in Early Twentieth-Century Public Schools in America

ERIC Educational Resources Information Center

Yoshii, Ryo

2016-01-01

In the late nineteenth and early twentieth centuries, American psychologists began addressing problems related to the intellectual capacity of students enrolled in public schools. This paper focuses on the role and influence of psychologists in addressing these problems, specifically the difficulty of classifying students deemed feeble-minded and…

School's Out-Gone Fishing!

ERIC Educational Resources Information Center

Lancaster, Ron

2016-01-01

Can you solve the following Problem? There are 200 fish in an aquarium, and 99 percent of them are guppies. How many guppies must be removed to reduce the tank's guppy population to 98 percent? The key to this problem is to work backward by using the data given in figure 2 to determine the surface area of the top of the aquarium; then determine…

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

NASA Astrophysics Data System (ADS)

Witte, J. H.; Reisinger, C.

2010-09-01

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

Continuous-Time Public Good Contribution Under Uncertainty: A Stochastic Control Approach

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

Ferrari, Giorgio, E-mail: giorgio.ferrari@uni-bielefeld.de; Riedel, Frank, E-mail: frank.riedel@uni-bielefeld.de; Steg, Jan-Henrik, E-mail: jsteg@uni-bielefeld.de

In this paper we study continuous-time stochastic control problems with both monotone and classical controls motivated by the so-called public good contribution problem. That is the problem of n economic agents aiming to maximize their expected utility allocating initial wealth over a given time period between private consumption and irreversible contributions to increase the level of some public good. We investigate the corresponding social planner problem and the case of strategic interaction between the agents, i.e. the public good contribution game. We show existence and uniqueness of the social planner’s optimal policy, we characterize it by necessary and sufficient stochasticmore » Kuhn–Tucker conditions and we provide its expression in terms of the unique optional solution of a stochastic backward equation. Similar stochastic first order conditions prove to be very useful for studying any Nash equilibria of the public good contribution game. In the symmetric case they allow us to prove (qualitative) uniqueness of the Nash equilibrium, which we again construct as the unique optional solution of a stochastic backward equation. We finally also provide a detailed analysis of the so-called free rider effect.« less

Effects of age and lean direction on the threshold of single-step balance recovery in younger, middle-aged and older adults.

PubMed

Carbonneau, Evelyne; Smeesters, Cécile

2014-01-01

Several studies have quantified and compared balance recovery between healthy younger and older adults, using a variety of large postural perturbations and loss of balance directions. However, to the best of our knowledge, no studies at the threshold of balance recovery, where avoiding a fall is not always possible, have included middle-aged adults. We thus determined the maximum lean angle from which 20 younger, 16 middle-aged and 16 older healthy adults could be suddenly released and still recover balance using a single step for forward, sideways and backward leans. Results showed that the maximum lean angles of younger adults were 23% greater than middle-aged adults and 48% greater than older adults. The maximum lean angles for forward leans were 23% greater than sideways leans and 22% greater than backward leans. These declines with age and lean direction were associated with declines in response initiation, execution and geometry. Finally exponential regressions showed that the critical ages at which the ability to recover balance and avoid a fall significantly decreases were 51.0, 60.6 and 69.9 yrs for forward, sideways and backward leans, respectively. Therefore, we have demonstrated that age affects the ability to recover balance nearly a decade earlier than the rate of falls. Future studies should thus not only include older adults over 65 yrs, but also middle-aged adults under 65 yrs, or recruit all ages from 18 to 85 yrs. Finally, the critical ages identified in this study may justify an earlier screening of aging adults to prevent future falls, especially the first fall. Copyright © 2013 Elsevier B.V. All rights reserved.

Multicell migration tracking within angiogenic networks by deep learning-based segmentation and augmented Bayesian filtering.

PubMed

Wang, Mengmeng; Ong, Lee-Ling Sharon; Dauwels, Justin; Asada, H Harry

2018-04-01

Cell migration is a key feature for living organisms. Image analysis tools are useful in studying cell migration in three-dimensional (3-D) in vitro environments. We consider angiogenic vessels formed in 3-D microfluidic devices (MFDs) and develop an image analysis system to extract cell behaviors from experimental phase-contrast microscopy image sequences. The proposed system initializes tracks with the end-point confocal nuclei coordinates. We apply convolutional neural networks to detect cell candidates and combine backward Kalman filtering with multiple hypothesis tracking to link the cell candidates at each time step. These hypotheses incorporate prior knowledge on vessel formation and cell proliferation rates. The association accuracy reaches 86.4% for the proposed algorithm, indicating that the proposed system is able to associate cells more accurately than existing approaches. Cell culture experiments in 3-D MFDs have shown considerable promise for improving biology research. The proposed system is expected to be a useful quantitative tool for potential microscopy problems of MFDs.

Cubic-panorama image dataset analysis for storage and transmission

NASA Astrophysics Data System (ADS)

Salehi, Saeed; Dubois, Eric

2013-02-01

In this paper we address the problem of disparity estimation required for free navigation in acquired cubicpanorama image datasets. A client server based scheme is assumed and a remote user is assumed to seek information at each navigation step. The initial compression of such image datasets for storage as well as the transmission of the required data is addressed in this work. Regarding the compression of such data for storage, a fast method that uses properties of the epipolar geometry together with the cubic format of panoramas is used to estimate disparity vectors efficiently. Assuming the use of B pictures, the concept of forward and backward prediction is addressed. Regarding the transmission stage, a new disparity vector transcoding-like scheme is introduced and a frame conversion scenario is addressed. Details on how to pick the best vector among candidate disparity vectors is explained. In all the above mentioned cases, results are compared both visually through error images as well as using the objective measure of Peak Signal to Noise Ratio (PSNR) versus time.

A Chess-Like Game for Teaching Engineering Students to Solve Large System of Simultaneous Linear Equations

NASA Technical Reports Server (NTRS)

Nguyen, Duc T.; Mohammed, Ahmed Ali; Kadiam, Subhash

2010-01-01

Solving large (and sparse) system of simultaneous linear equations has been (and continues to be) a major challenging problem for many real-world engineering/science applications [1-2]. For many practical/large-scale problems, the sparse, Symmetrical and Positive Definite (SPD) system of linear equations can be conveniently represented in matrix notation as [A] {x} = {b} , where the square coefficient matrix [A] and the Right-Hand-Side (RHS) vector {b} are known. The unknown solution vector {x} can be efficiently solved by the following step-by-step procedures [1-2]: Reordering phase, Matrix Factorization phase, Forward solution phase, and Backward solution phase. In this research work, a Game-Based Learning (GBL) approach has been developed to help engineering students to understand crucial details about matrix reordering and factorization phases. A "chess-like" game has been developed and can be played by either a single player, or two players. Through this "chess-like" open-ended game, the players/learners will not only understand the key concepts involved in reordering algorithms (based on existing algorithms), but also have the opportunities to "discover new algorithms" which are better than existing algorithms. Implementing the proposed "chess-like" game for matrix reordering and factorization phases can be enhanced by FLASH [3] computer environments, where computer simulation with animated human voice, sound effects, visual/graphical/colorful displays of matrix tables, score (or monetary) awards for the best game players, etc. can all be exploited. Preliminary demonstrations of the developed GBL approach can be viewed by anyone who has access to the internet web-site [4]!

Computer-Aided Diagnosis Systems for Lung Cancer: Challenges and Methodologies

PubMed Central

El-Baz, Ayman; Beache, Garth M.; Gimel'farb, Georgy; Suzuki, Kenji; Okada, Kazunori; Elnakib, Ahmed; Soliman, Ahmed; Abdollahi, Behnoush

2013-01-01

This paper overviews one of the most important, interesting, and challenging problems in oncology, the problem of lung cancer diagnosis. Developing an effective computer-aided diagnosis (CAD) system for lung cancer is of great clinical importance and can increase the patient's chance of survival. For this reason, CAD systems for lung cancer have been investigated in a huge number of research studies. A typical CAD system for lung cancer diagnosis is composed of four main processing steps: segmentation of the lung fields, detection of nodules inside the lung fields, segmentation of the detected nodules, and diagnosis of the nodules as benign or malignant. This paper overviews the current state-of-the-art techniques that have been developed to implement each of these CAD processing steps. For each technique, various aspects of technical issues, implemented methodologies, training and testing databases, and validation methods, as well as achieved performances, are described. In addition, the paper addresses several challenges that researchers face in each implementation step and outlines the strengths and drawbacks of the existing approaches for lung cancer CAD systems. PMID:23431282

Backward bifurcation and optimal control of Plasmodium Knowlesi malaria

NASA Astrophysics Data System (ADS)

Abdullahi, Mohammed Baba; Hasan, Yahya Abu; Abdullah, Farah Aini

2014-07-01

A deterministic model for the transmission dynamics of Plasmodium Knowlesi malaria with direct transmission is developed. The model is analyzed using dynamical system techniques and it shows that the backward bifurcation occurs for some range of parameters. The model is extended to assess the impact of time dependent preventive (biological and chemical control) against the mosquitoes and vaccination for susceptible humans, while treatment for infected humans. The existence of optimal control is established analytically by the use of optimal control theory. Numerical simulations of the problem, suggest that applying the four control measure can effectively reduce if not eliminate the spread of Plasmodium Knowlesi in a community.

Control of photon storage time using phase locking.

PubMed

Ham, Byoung S

2010-01-18

A photon echo storage-time extension protocol is presented by using a phase locking method in a three-level backward propagation scheme, where phase locking serves as a conditional stopper of the rephasing process in conventional two-pulse photon echoes. The backward propagation scheme solves the critical problems of extremely low retrieval efficiency and pi rephasing pulse-caused spontaneous emission noise in photon echo based quantum memories. The physics of the storage time extension lies in the imminent population transfer from the excited state to an auxiliary spin state by a phase locking control pulse. We numerically demonstrate that the storage time is lengthened by spin dephasing time.

Earth Entry Requirements for Mars, Europa and Enceladus Sample Return Missions: A Thermal Protection System Perspective

NASA Technical Reports Server (NTRS)

Venkatapathy, Ethiraj; Gage, Peter; Ellerby, Don; Mahzari, Milad; Peterson, Keith; Stackpoole, Mairead; Young, Zion

2016-01-01

This oral presentation will be given at the 13th International Planetary Probe Workshop on June 14th, 2016 and will cover the drivers for reliability and the challenges faced in selecting and designing the thermal protection system (TPS). In addition, an assessment is made on new emerging TPS related technologies that could help with designs to meet the planetary protection requirements to prevent backward (Earth) contamination by biohazardous samples.

Amphipathic amines affect membrane excitability in paramecium: role for bilayer couple.

PubMed Central

Browning, J L; Nelson, D L

1976-01-01

Amphipathic amines and local anesthetics stimulated reversal of the ciliary beating direction in wild-type Paramecium. Ca++ influx across the surface membrane and the consequent increase in internal Ca++ causes ciliary reversal and backward swimming. Mutant cells of the "Pawn" class, which lack a "gating" mechanism for regulating Ca++ influx, did not swim backwards in the presence of local anesthetics. Local anesthetics stimulated the passive efflux of K+ but had no effect on the active transport of K+ or Ca++. Apparently passive influx of Ca++ also was stimulated by local anesthetics as evidenced by their effects on swimming direction. These data can be interpreted in terms of the "bilayer couple" hypothesis of Sheetz and Singer [(1974) Proc. Nat. Acad. Sci. USA 71, 4457-4461]: amphipathic drugs affect cells by asymmetric insertion into one face of the lipid bilayer. As predicted by this hypothesis, the drugs' effects were seen only after a short time lag, and quaternary amines were less effective than tertiary amines. The effect on behavior was caused by any of several amphipathic cations, and the relative potency was a function of their hydrophobicity. Amphipathic anions, which according to the hypothesis would insert into the opposite face of the lipid bilayer, had little effect on ciliary reversal. Asymmetric perturbation of the lipid bilayer with amphipathic cations may trigger the opening of the Ca++ gate. Images PMID:1061147

Infants' understanding of false labeling events: the referential roles of words and the speakers who use them.

PubMed

Koenig, Melissa A; Echols, Catharine H

2003-04-01

The four studies reported here examine whether 16-month-old infants' responses to true and false utterances interact with their knowledge of human agents. In Study 1, infants heard repeated instances either of true or false labeling of common objects; labels came from an active human speaker seated next to the infant. In Study 2, infants experienced the same stimuli and procedure; however, we replaced the human speaker of Study 1 with an audio speaker in the same location. In Study 3, labels came from a hidden audio speaker. In Study 4, a human speaker labeled the objects while facing away from them. In Study 1, infants looked significantly longer to the human agent when she falsely labeled than when she truthfully labeled the objects. Infants did not show a similar pattern of attention for the audio speaker of Study 2, the silent human of Study 3 or the facing-backward speaker of Study 4. In fact, infants who experienced truthful labeling looked significantly longer to the facing-backward labeler of Study 4 than to true labelers of the other three contexts. Additionally, infants were more likely to correct false labels when produced by the human labeler of Study 1 than in any of the other contexts. These findings suggest, first, that infants are developing a critical conception of other human speakers as truthful communicators, and second, that infants understand that human speakers may provide uniquely useful information when a word fails to match its referent. These findings are consistent with the view that infants can recognize differences in knowledge and that such differences can be based on differences in the availability of perceptual experience.

Improving flow patterns and spillage characteristics of a box-type commercial kitchen hood.

PubMed

Huang, Rong Fung; Chen, Jia-Kun; Han, Meng-Ji; Priyambodo, Yusuf

2014-01-01

A conventional box-type commercial kitchen hood and its improved version (termed the "IQV commercial kitchen hood") were studied using the laser-assisted smoke flow visualization technique and tracer-gas (sulfur hexafluoride) detection methods. The laser-assisted smoke flow visualization technique qualitatively revealed the flow field of the hood and the areas apt for leakages of hood containment. The tracer-gas concentration detection method measured the quantitative leakage levels of the hood containment. The oil mists that were generated in the conventional box-type commercial kitchen hood leaked significantly into the environment from the areas near the front edges of ceiling and side walls. Around these areas, the boundary-layer separation occurred, inducing highly unsteady and turbulent recirculating flow, and leading to spillages of hood containment due to inappropriate aerodynamic design at the front edges of the ceiling and side walls. The tracer-gas concentration measurements on the conventional box-type commercial kitchen hood showed that the sulfur hexafluoride concentrations detected at the hood face attained very large values on an order of magnitude about 10(3)-10(4) ppb. By combining the backward-offset narrow suction slot, deflection plates, and quarter-circular arcs at the hood entrance, the IQV commercial kitchen hood presented a flow field containing four backward-inclined cyclone flow structures. The oil mists generated by cooking were coherently confined in these upward-rising cyclone flow structures and finally exhausted through the narrow suction slot. The tracer-gas concentration measurements on the IQV commercial kitchen hood showed that the order of magnitude of the sulfur hexafluoride concentrations detected at the hood face is negligibly small--only about 10(0) ppb across the whole hood face.

Multi-Time Step Service Restoration for Advanced Distribution Systems and Microgrids

DOE PAGES

Chen, Bo; Chen, Chen; Wang, Jianhui; ...

2017-07-07

Modern power systems are facing increased risk of disasters that can cause extended outages. The presence of remote control switches (RCSs), distributed generators (DGs), and energy storage systems (ESS) provides both challenges and opportunities for developing post-fault service restoration methodologies. Inter-temporal constraints of DGs, ESS, and loads under cold load pickup (CLPU) conditions impose extra complexity on problem formulation and solution. In this paper, a multi-time step service restoration methodology is proposed to optimally generate a sequence of control actions for controllable switches, ESSs, and dispatchable DGs to assist the system operator with decision making. The restoration sequence is determinedmore » to minimize the unserved customers by energizing the system step by step without violating operational constraints at each time step. The proposed methodology is formulated as a mixed-integer linear programming (MILP) model and can adapt to various operation conditions. Furthermore, the proposed method is validated through several case studies that are performed on modified IEEE 13-node and IEEE 123-node test feeders.« less

Multi-Time Step Service Restoration for Advanced Distribution Systems and Microgrids

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

Chen, Bo; Chen, Chen; Wang, Jianhui

Modern power systems are facing increased risk of disasters that can cause extended outages. The presence of remote control switches (RCSs), distributed generators (DGs), and energy storage systems (ESS) provides both challenges and opportunities for developing post-fault service restoration methodologies. Inter-temporal constraints of DGs, ESS, and loads under cold load pickup (CLPU) conditions impose extra complexity on problem formulation and solution. In this paper, a multi-time step service restoration methodology is proposed to optimally generate a sequence of control actions for controllable switches, ESSs, and dispatchable DGs to assist the system operator with decision making. The restoration sequence is determinedmore » to minimize the unserved customers by energizing the system step by step without violating operational constraints at each time step. The proposed methodology is formulated as a mixed-integer linear programming (MILP) model and can adapt to various operation conditions. Furthermore, the proposed method is validated through several case studies that are performed on modified IEEE 13-node and IEEE 123-node test feeders.« less

Controlling Wavebreaking in a Viscous Fluid Conduit

NASA Astrophysics Data System (ADS)

Anderson, Dalton; Maiden, Michelle; Hoefer, Mark

2015-11-01

This poster will present a new technique in the experimental investigation of dispersive hydrodynamics. In shallow water flows, internal ocean waves, superfluids, and optical media, wave breaking can be resolved by a dispersive shock wave (DSW). In this work, an experimental method to control the location of DSW formation (gradient catastrophe) is explained. The central idea is to convert an initial value problem (Riemann problem) into an equivalent boundary value problem. The system to which this technique is applied is a fluid conduit resulting from high viscosity contrast between a buoyant interior and heavier exterior fluid. The conduit cross-sectional area is modeled by a nonlinear, conservative, dispersive, third order partial differential equation. Using this model, the aim is to predict the breaking location of a DSW by controlling one boundary condition. An analytical expression for this boundary condition is derived by solving the dispersionless equation backward in time from the desired step via the method of characteristics. This is used in experiment to generate an injection rate profile for a high precision piston pump. This translates to the desired conduit shape. Varying the jump height and desired breaking location indicates good control of DSW formation. This result can be improved by deriving a conduit profile by numerical simulation of the full model equation. Controlling the breaking location of a DSW allows for the investigation of dynamics independent of the boundary. Support provided by NSF CAREER DMS-1255422 , NSF EXTREEMS.

Steps for arm and trunk actions of overhead forehand stroke used in badminton games across skill levels.

PubMed

Wang, Jianyu; Liu, Wenhao; Moffit, Jeffrey

2009-08-01

The purpose of this study was to examine arm and trunk actions in overhead forehand strokes used in badminton games across skill levels. The participants were 80 students (40 boys, 40 girls) who were randomly selected from video recordings of 300 students ages 16 to 19 years. The videotaped performances of overhead forehand strokes were coded based on three steps of arm action (elbow flexion, elbow and humeral flexion, and upward backswing) and three steps of trunk action (no trunk action, forward-backward movement, and trunk rotation). Students across the four skill levels exhibited different patterns of arm and trunk actions. Students at advanced levels used more mature arm and trunk actions.

Crystallographic control of surface structure on the sectoral zoning of iron in a diopside from Orford nickel mine (Quebec), Canada

NASA Astrophysics Data System (ADS)

Paquette, J.; Zangooi, A.; Thornton, K.

2004-05-01

The influence of surface structure on partitioning between mineral and melt (or solution) has been noted by other workers in a handful of minerals, including calcite, dolomite, apatite, topaz and diamond. Each one of these minerals displays at least one crystallographic face where steps present during crystal growth are not equivalent by symmetry. When this is the case, sectors grown at the edge of these steps commonly show differential incorporation of minor or trace elements. In the diopside investigated here, electron probe microanalyses performed on the as-grown (100) surface of several crystals show concentric and sectoral zoning defined by variations in Fe content. Atomic force microscopy (AFM) was used to study the surfaces of the three crystallographic forms present on the diopside crystals, with the goal of relating the compositional zoning to the surface structure of the faces. The dominant {100} faces are covered with growth hillocks consisting of four vicinal faces defined by steps parallel to [010] and [001]. The steps are often bunched into macrosteps and the resulting hillocks are visible optically. The steps along the two crystallographic directions show significant differences in straightness and smoothness that indicate non-equivalent kinetics. The wavier steps correspond to Fe-enriched areas within the {100} sectors. The {010} faces, next in morphological importance, are dominated by a single step orientation and show no differential incorporation. They display topography related to polysynthetic twinning. The {110} faces are much smaller and very few show resolvable steps. Sector zoning (i.e. diffential partitioning among non-equivalent crystallographic faces) has been described in the past from pyroxenes. Explanations have invoked either differences in surface structure among non-equivalent faces or their unequal growth rates. This particular occurrence indicates that trace element incorporation is, in fact, highly site-specific and that significant compositioinal zoning can be induced on a single face without invoking the effect of growth rate. The natural diopside crystals from the Orford nickel mine (Brompton, Quebec) show a unusual bladed habit flattened on {100} faces. Exceptional fluid chemistry during crystallization may therefore be required for the persistence of steps responsible for differential incorporation. Nevertheless, whenever this zoning is present, the trace element involved cannot be expected to reflect thermodynamic equilibrium between the solid and the fluid from which it crystallized.

Stepping Backwards in Development: Integrating Developmental Speech Perception with Lexical and Phonological Development--A Commentary on Stoel-Gammon's "Relationships between Lexical and Phonological Development in Young Children"

ERIC Educational Resources Information Center

Zamuner, Tania S.

2011-01-01

Within the subfields of linguistics, traditional approaches tend to examine different phenomena in isolation. As Stoel-Gammon (this issue) correctly states, there is little interaction between the subfields. However, for a more comprehensive understanding of language acquisition in general and, more specifically, lexical and phonological…

Solutions to time variant problems of real-time expert systems

NASA Technical Reports Server (NTRS)

Yeh, Show-Way; Wu, Chuan-Lin; Hung, Chaw-Kwei

1988-01-01

Real-time expert systems for monitoring and control are driven by input data which changes with time. One of the subtle problems of this field is the propagation of time variant problems from rule to rule. This propagation problem is even complicated under a multiprogramming environment where the expert system may issue test commands to the system to get data and to access time consuming devices to retrieve data for concurrent reasoning. Two approaches are used to handle the flood of input data. Snapshots can be taken to freeze the system from time to time. The expert system treats the system as a stationary one and traces changes by comparing consecutive snapshots. In the other approach, when an input is available, the rules associated with it are evaluated. For both approaches, if the premise condition of a fired rule is changed to being false, the downstream rules should be deactivated. If the status change is due to disappearance of a transient problem, actions taken by the fired downstream rules which are no longer true may need to be undone. If a downstream rule is being evaluated, it should not be fired. Three mechanisms for solving this problem are discussed: tracing, backward checking, and censor setting. In the forward tracing mechanism, when the premise conditions of a fired rule become false, the premise conditions of downstream rules which have been fired or are being evaluated due to the firing of that rule are reevaluated. A tree with its root at the rule being deactivated is traversed. In the backward checking mechanism, when a rule is being fired, the expert system checks back on the premise conditions of the upstream rules that result in evaluation of the rule to see whether it should be fired. The root of the tree being traversed is the rule being fired. In the censor setting mechanism, when a rule is to be evaluated, a censor is constructed based on the premise conditions of the upstream rules and the censor is evaluated just before the rule is fired. Unlike the backward checking mechanism, this one does not search the upstream rules. This paper explores the details of implementation of the three mechanisms.

Stability analysis of an implicitly defined labor market model

NASA Astrophysics Data System (ADS)

Mendes, Diana A.; Mendes, Vivaldo M.

2008-06-01

Until very recently, the pervasive existence of models exhibiting well-defined backward dynamics but ill-defined forward dynamics in economics and finance has apparently posed no serious obstacles to the analysis of their dynamics and stability, despite the problems that may arise from possible erroneous conclusions regarding theoretical considerations and policy prescriptions from such models. A large number of papers have dealt with this problem in the past by assuming the existence of symmetry between forward and backward dynamics, even in the case when the map cannot be invertible either forward or backwards. However, this procedure has been seriously questioned over the last few years in a series of papers dealing with implicit difference equations and inverse limit spaces. This paper explores the search and matching labor market model developed by Bhattacharya and Bunzel [J. Bhattacharya, H. Bunzel, Chaotic Planning Solution in the Textbook Model of Equilibrium Labor Market Search and Matching, Mimeo, Iowa State University, 2002; J. Bhattacharya, H. Bunzel, Economics Bulletin 5 (19) (2003) 1-10], with the following objectives in mind: (i) to show that chaotic dynamics may still be present in the model for acceptable parameter values, (ii) to clarify some open questions related with the admissible dynamics in the forward looking setting, by providing a rigorous proof of the existence of cyclic and chaotic dynamics through the application of tools from symbolic dynamics and inverse limit theory.

Illumination normalization of face image based on illuminant direction estimation and improved Retinex.

PubMed

Yi, Jizheng; Mao, Xia; Chen, Lijiang; Xue, Yuli; Rovetta, Alberto; Caleanu, Catalin-Daniel

2015-01-01

Illumination normalization of face image for face recognition and facial expression recognition is one of the most frequent and difficult problems in image processing. In order to obtain a face image with normal illumination, our method firstly divides the input face image into sixteen local regions and calculates the edge level percentage in each of them. Secondly, three local regions, which meet the requirements of lower complexity and larger average gray value, are selected to calculate the final illuminant direction according to the error function between the measured intensity and the calculated intensity, and the constraint function for an infinite light source model. After knowing the final illuminant direction of the input face image, the Retinex algorithm is improved from two aspects: (1) we optimize the surround function; (2) we intercept the values in both ends of histogram of face image, determine the range of gray levels, and stretch the range of gray levels into the dynamic range of display device. Finally, we achieve illumination normalization and get the final face image. Unlike previous illumination normalization approaches, the method proposed in this paper does not require any training step or any knowledge of 3D face and reflective surface model. The experimental results using extended Yale face database B and CMU-PIE show that our method achieves better normalization effect comparing with the existing techniques.

The temporal advantage for individuating objects of expertise: perceptual expertise is an early riser.

PubMed

Curby, Kim M; Gauthier, Isabel

2009-06-10

The identification of faces has a temporal advantage over that of other object categories. The orientation-specific nature of this advantage suggests that it stems from our extensive experience and resulting expertise with upright faces. While experts can identify objects faster than novices, it is unclear exactly how the temporal dynamics of identification are changed by expertise and whether the nature of this temporal advantage is similar for face and non-face objects of expertise. Here, we titrated encoding time using a backward-masking paradigm with variable stimulus-mask onset-asynchronies and mapped the resulting effect on recognition for upright and inverted faces (Experiment 1) and for cars among car experts and car novices (Experiment 2). Performance for upright faces and cars among car experts rose above chance between 33 and 70 ms before that for inverted faces or cars among car novices. A shifted exponential function fitted to these data suggested that performance started to rise earlier for experts than for novices, but that additional encoding time increased performance at a similar rate. Experience influences the availability of information early in processing, possibly through the recruitment of more category-selective neurons, while the rate of perceptual processing may be less flexible and limited by inherent physiological constraints.

The P1-RKDG method for two-dimensional Euler equations of gas dynamics

NASA Technical Reports Server (NTRS)

Cockburn, Bernardo; Shu, Chi-Wang

1991-01-01

A class of nonlinearly stable Runge-Kutta local projection discontinuous Galerkin (RKDG) finite element methods for conservation laws is investigated. Two dimensional Euler equations for gas dynamics are solved using P1 elements. The generalization of the local projections, which for scalar nonlinear conservation laws was designed to satisfy a local maximum principle, to systems of conservation laws such as the Euler equations of gas dynamics using local characteristic decompositions is discussed. Numerical examples include the standard regular shock reflection problem, the forward facing step problem, and the double Mach reflection problem. These preliminary numerical examples are chosen to show the capacity of the approach to obtain nonlinearly stable results comparable with the modern nonoscillatory finite difference methods.

Subject independent facial expression recognition with robust face detection using a convolutional neural network.

PubMed

Matsugu, Masakazu; Mori, Katsuhiko; Mitari, Yusuke; Kaneda, Yuji

2003-01-01

Reliable detection of ordinary facial expressions (e.g. smile) despite the variability among individuals as well as face appearance is an important step toward the realization of perceptual user interface with autonomous perception of persons. We describe a rule-based algorithm for robust facial expression recognition combined with robust face detection using a convolutional neural network. In this study, we address the problem of subject independence as well as translation, rotation, and scale invariance in the recognition of facial expression. The result shows reliable detection of smiles with recognition rate of 97.6% for 5600 still images of more than 10 subjects. The proposed algorithm demonstrated the ability to discriminate smiling from talking based on the saliency score obtained from voting visual cues. To the best of our knowledge, it is the first facial expression recognition model with the property of subject independence combined with robustness to variability in facial appearance.

Revenge Pornography: Mental Health Implications and Related Legislation.

PubMed

Kamal, Mudasir; Newman, William J

2016-09-01

Revenge pornography, also known as nonconsensual pornography, is a subtype of cyberharassment/cyberstalking, and a serious problem facing society in the Internet age. Revenge pornography can result in lifelong mental health consequences for victims, damaged relationships, and social isolation. Recently, a growing number of states have recognized the importance of this phenomenon and have enacted legislation that criminalizes it. The technology industry has also taken steps to assist victims of revenge pornography by creating web forms to request removal of links leading to the explicit content. The Cyber Civil Rights Initiative (CCRI) has been instrumental in promoting public awareness of this often overlooked problem and in providing services for victims. Although important steps have been made, greater recognition of the gravity of this problem and the mental health implications of revenge pornography is needed to expand legislation criminalizing such acts. A federal criminal law, in particular, is much overdue. Mental health professionals must understand the dimensions of revenge pornography to be able to identify and address the consequences in both forensic and clinical settings. © 2016 American Academy of Psychiatry and the Law.

Performance Engineering as an Expert System.

ERIC Educational Resources Information Center

Harmon, Paul

1984-01-01

Considers three powerful techniques--heuristics, context trees, and search via backward chaining--that a knowledge engineer might employ to develop an expert system to automate performance engineering, i.e., the branch of instructional technology that focuses on the problems of business and industry. (MBR)

An experimental investigation of the separating/reattaching flow over a backstep

NASA Technical Reports Server (NTRS)

Jovic, Srboljub

1993-01-01

This progress report covers the grant period from March until the end of January 1993. Extensive data reduction and analysis of single and two-point measurements for a backward-facing experiment were performed. Pertinent results are presented in two conference papers which are appended to this report. The titles of the papers are as follows: (1) 'Two-point correlation measurements in a recovering turbulent boundary layer'; and (2) 'An experimental study on the recovery of a turbulent boundary layer downstream of the reattachment'.

Looking Backward, Looking Forward: The Long, Torturous Struggle with Mosquitoes.

PubMed

Patterson, Gordon M

2016-10-19

The American anti-mosquito movement grew out of the discovery of the role of mosquitoes in transferring pathogens and public concern about pest and nuisance mosquitoes in the late 1800s. In the 20th century, organized mosquito control in the United States passed through three eras: mechanical, chemical, and integrated mosquito control. Mosquito control in the 21st century faces the challenge of emerging pathogens, invasive mosquito species, and balancing concerns about the environment with effective control strategies.

Ultrafast forward and backward electron transfer dynamics of coumarin 337 in hydrogen-bonded anilines as studied with femtosecond UV-pump/IR-probe spectroscopy.

PubMed

Ghosh, Hirendra N; Verma, Sandeep; Nibbering, Erik T J

2011-02-10

Femtosecond infrared spectroscopy is used to study both forward and backward electron transfer (ET) dynamics between coumarin 337 (C337) and the aromatic amine solvents aniline (AN), N-methylaniline (MAN), and N,N-dimethylaniline (DMAN), where all the aniline solvents can donate an electron but only AN and MAN can form hydrogen bonds with C337. The formation of a hydrogen bond with AN and MAN is confirmed with steady state FT-IR spectroscopy, where the C═O stretching vibration is a direct marker mode for hydrogen bond formation. Transient IR absorption measurements in all solvents show an absorption band at 2166 cm(-1), which has been attributed to the C≡N stretching vibration of the C337 radical anion formed after ET. Forward electron transfer dynamics is found to be biexponential with time constants τ(ET)(1) = 500 fs, τ(ET)(2) = 7 ps in all solvents. Despite the presence of hydrogen bonds of C337 with the solvents AN and MAN, no effect has been found on the forward electron transfer step. Because of the absence of an H/D isotope effect on the forward electron transfer reaction of C337 in AN, hydrogen bonds are understood to play a minor role in mediating electron transfer. In contrast, direct π-orbital overlap between C337 and the aromatic amine solvents causes ultrafast forward electron transfer dynamics. Backward electron transfer dynamics, in contrast, is dependent on the solvent used. Standard Marcus theory explains the observed backward electron transfer rates.

JPRS Report, Soviet Union, Political Affairs

DTIC Science & Technology

1989-05-17

be the envy of many large cities. A child with infantile cerebral palsy can be given a free course of The conversation with R. Dovlyatshoyev, deputy...Social sciences face quite a few serious problems. They international relations, active work is being conducted so re ace quide a benefious proess to...at the Sum- mer Games in Seoul. With regard to medals won, they This will allow us to take a major step forward in solving were in the top 10, having

KIVA-Update June 2012

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

Carrington, David B

2012-06-07

Development of a fractional step, a Predictor-Corrector Split (PCS), or what is often known as a projection method combining hp-adaptive system in a Finite Element Method (FEM) for combustion modeling has been achieved. This model will advance the accuracy and range of applicability of the KIVA combustion model and software used typically for internal combustion engine modeling. This abstract describes a PCS hp-adaptive FEM model for turbulent reactive flow spanning all velocity regimes and fluids that is being developed for the new KIVA combustion algorithm, particularly for internal combustion engines. The method and general solver is applicable to Newtonian andmore » non- Newtonian fluids and also for incompressible solids, porous media, solidification modeling, and fluid structure interaction problems. The fuel injection and injector modeling could easily benefit from the capability of solving the fluid structure interaction problem in an injector, helping to understand cycle to cycle variation and cavitation. This is just one example where the new algorithm differs from the old, in addition to handling Conjugate Heat Transfer (CHT), although there a numerous features that makes the new system more robust and accurate. In these ways, the PCS hp-adaptive algorithm does not compete with commercial software packages, those often used in conjunction with the currently distributed KIVA codes for engine combustion modeling. In addition, choosing a local ALE method on immersed moving parts represented by overset grid that is 2nd order spatially accurate, allows for easy grid generation from CAD to fluid grid while also provide for robustness in handling any possible moving parts configuration without any code modifications. The combined methods employed produce a minimal amount of computational effort as compared to fully resolved grids at the same accuracy. We demonstrate the solver on benchmark problems for the all flow regimes as follows: (1) 2-D backward-facing step using h-adaption, (2) 2-D driven cavity, (3) 2-D natural convection in a differentially heat cavity with h-adaptation, (4) NACA 0012 airfoil in 2-D, (5) supersonic flows over compression ramps, (6) 2-D natural convection in a differentially heat cavity with hp-adaptation, (7) 3-D natural convection in a differentially heat sphere with hp-adaptation. In addition, we show the new moving parts algorithm for working for a 2-D piston; the immersed moving parts method also for valves and pistons, vanes, etc... The movement is performed using an overset grid method and is 2nd order accurate in space, and never produces a tangle grid, that is, robust system at any resolution and any parts configuration. We also show CHT for the currently distributed KIVA-4mpi software and some fairly automatic grid generation using Sandia's Cubit unstructured grid generator. A new electronic web-based manual for KIVA-4 has been developed as well.« less

A special purpose knowledge-based face localization method

NASA Astrophysics Data System (ADS)

Hassanat, Ahmad; Jassim, Sabah

2008-04-01

This paper is concerned with face localization for visual speech recognition (VSR) system. Face detection and localization have got a great deal of attention in the last few years, because it is an essential pre-processing step in many techniques that handle or deal with faces, (e.g. age, face, gender, race and visual speech recognition). We shall present an efficient method for localization human's faces in video images captured on mobile constrained devices, under a wide variation in lighting conditions. We use a multiphase method that may include all or some of the following steps starting with image pre-processing, followed by a special purpose edge detection, then an image refinement step. The output image will be passed through a discrete wavelet decomposition procedure, and the computed LL sub-band at a certain level will be transformed into a binary image that will be scanned by using a special template to select a number of possible candidate locations. Finally, we fuse the scores from the wavelet step with scores determined by color information for the candidate location and employ a form of fuzzy logic to distinguish face from non-face locations. We shall present results of large number of experiments to demonstrate that the proposed face localization method is efficient and achieve high level of accuracy that outperforms existing general-purpose face detection methods.

An application of forward-backward difference approximation method on the optimal control problem in the transmission of tuberculosis model

NASA Astrophysics Data System (ADS)

Rahmah, Z.; Subartini, B.; Djauhari, E.; Anggriani, N.; Supriatna, A. K.

2017-03-01

Tuberculosis (TB) is a disease that is infected by the bacteria Mycobacterium tuberculosis. The World Health Organization (WHO) recommends to implement the Baccilus Calmete Guerin (BCG) vaccine in toddler aged two to three months to be protected from the infection. This research explores the numerical simulation of forward-backward difference approximation method on the model of TB transmission considering this vaccination program. The model considers five compartments of sub-populations, i.e. susceptible, vaccinated, exposed, infected, and recovered human sub-populations. We consider here the vaccination as a control variable. The results of the simulation showed that vaccination can indeed reduce the number of infected human population.

An algorithm for generating modular hierarchical neural network classifiers: a step toward larger scale applications

NASA Astrophysics Data System (ADS)

Roverso, Davide

2003-08-01

Many-class learning is the problem of training a classifier to discriminate among a large number of target classes. Together with the problem of dealing with high-dimensional patterns (i.e. a high-dimensional input space), the many class problem (i.e. a high-dimensional output space) is a major obstacle to be faced when scaling-up classifier systems and algorithms from small pilot applications to large full-scale applications. The Autonomous Recursive Task Decomposition (ARTD) algorithm is here proposed as a solution to the problem of many-class learning. Example applications of ARTD to neural classifier training are also presented. In these examples, improvements in training time are shown to range from 4-fold to more than 30-fold in pattern classification tasks of both static and dynamic character.

Two-step superresolution approach for surveillance face image through radial basis function-partial least squares regression and locality-induced sparse representation

NASA Astrophysics Data System (ADS)

Jiang, Junjun; Hu, Ruimin; Han, Zhen; Wang, Zhongyuan; Chen, Jun

2013-10-01

Face superresolution (SR), or face hallucination, refers to the technique of generating a high-resolution (HR) face image from a low-resolution (LR) one with the help of a set of training examples. It aims at transcending the limitations of electronic imaging systems. Applications of face SR include video surveillance, in which the individual of interest is often far from cameras. A two-step method is proposed to infer a high-quality and HR face image from a low-quality and LR observation. First, we establish the nonlinear relationship between LR face images and HR ones, according to radial basis function and partial least squares (RBF-PLS) regression, to transform the LR face into the global face space. Then, a locality-induced sparse representation (LiSR) approach is presented to enhance the local facial details once all the global faces for each LR training face are constructed. A comparison of some state-of-the-art SR methods shows the superiority of the proposed two-step approach, RBF-PLS global face regression followed by LiSR-based local patch reconstruction. Experiments also demonstrate the effectiveness under both simulation conditions and some real conditions.

Stability of numerical integration techniques for transient rotor dynamics

NASA Technical Reports Server (NTRS)

Kascak, A. F.

1977-01-01

A finite element model of a rotor bearing system was analyzed to determine the stability limits of the forward, backward, and centered Euler; Runge-Kutta; Milne; and Adams numerical integration techniques. The analysis concludes that the highest frequency mode determines the maximum time step for a stable solution. Thus, the number of mass elements should be minimized. Increasing the damping can sometimes cause numerical instability. For a uniform shaft, with 10 mass elements, operating at approximately the first critical speed, the maximum time step for the Runge-Kutta, Milne, and Adams methods is that which corresponds to approximately 1 degree of shaft movement. This is independent of rotor dimensions.

Theoretical face pressure and drag characteristics of forward-facing steps in supersonic turbulent boundary layers

NASA Technical Reports Server (NTRS)

Patel, D. K.; Czarnecki, K. R.

1975-01-01

A theoretical investigation of the pressure distributions and drag characteristics was made for forward facing steps in turbulent flow at supersonic speeds. An approximate solution technique proposed by Uebelhack has been modified and extended to obtain a more consistent numerical procedure. A comparison of theoretical calculations with experimental data generally indicated good agreement over the experimentally available range of ratios of step height to boundary layer thickness from 7 to 0.05.

Development and acceleration of unstructured mesh-based cfd solver

NASA Astrophysics Data System (ADS)

Emelyanov, V.; Karpenko, A.; Volkov, K.

2017-06-01

The study was undertaken as part of a larger effort to establish a common computational fluid dynamics (CFD) code for simulation of internal and external flows and involves some basic validation studies. The governing equations are solved with ¦nite volume code on unstructured meshes. The computational procedure involves reconstruction of the solution in each control volume and extrapolation of the unknowns to find the flow variables on the faces of control volume, solution of Riemann problem for each face of the control volume, and evolution of the time step. The nonlinear CFD solver works in an explicit time-marching fashion, based on a three-step Runge-Kutta stepping procedure. Convergence to a steady state is accelerated by the use of geometric technique and by the application of Jacobi preconditioning for high-speed flows, with a separate low Mach number preconditioning method for use with low-speed flows. The CFD code is implemented on graphics processing units (GPUs). Speedup of solution on GPUs with respect to solution on central processing units (CPU) is compared with the use of different meshes and different methods of distribution of input data into blocks. The results obtained provide promising perspective for designing a GPU-based software framework for applications in CFD.

Backward Dependencies and in-Situ wh-Questions as Test Cases on How to Approach Experimental Linguistics Research That Pursues Theoretical Linguistics Questions

PubMed Central

Pablos, Leticia; Doetjes, Jenny; Cheng, Lisa L.-S.

2018-01-01

The empirical study of language is a young field in contemporary linguistics. This being the case, and following a natural development process, the field is currently at a stage where different research methods and experimental approaches are being put into question in terms of their validity. Without pretending to provide an answer with respect to the best way to conduct linguistics related experimental research, in this article we aim at examining the process that researchers follow in the design and implementation of experimental linguistics research with a goal to validate specific theoretical linguistic analyses. First, we discuss the general challenges that experimental work faces in finding a compromise between addressing theoretically relevant questions and being able to implement these questions in a specific controlled experimental paradigm. We discuss the Granularity Mismatch Problem (Poeppel and Embick, 2005) which addresses the challenges that research that is trying to bridge the representations and computations of language and their psycholinguistic/neurolinguistic evidence faces, and the basic assumptions that interdisciplinary research needs to consider due to the different conceptual granularity of the objects under study. To illustrate the practical implications of the points addressed, we compare two approaches to perform linguistic experimental research by reviewing a number of our own studies strongly grounded on theoretically informed questions. First, we show how linguistic phenomena similar at a conceptual level can be tested within the same language using measurement of event-related potentials (ERP) by discussing results from two ERP experiments on the processing of long-distance backward dependencies that involve coreference and negative polarity items respectively in Dutch. Second, we examine how the same linguistic phenomenon can be tested in different languages using reading time measures by discussing the outcome of four self-paced reading experiments on the processing of in-situ wh-questions in Mandarin Chinese and French. Finally, we review the implications that our findings have for the specific theoretical linguistics questions that we originally aimed to address. We conclude with an overview of the general insights that can be gained from the role of structural hierarchy and grammatical constraints in processing and the existing limitations on the generalization of results. PMID:29375417

Backward Dependencies and in-Situ wh-Questions as Test Cases on How to Approach Experimental Linguistics Research That Pursues Theoretical Linguistics Questions.

PubMed

Pablos, Leticia; Doetjes, Jenny; Cheng, Lisa L-S

2017-01-01

The empirical study of language is a young field in contemporary linguistics. This being the case, and following a natural development process, the field is currently at a stage where different research methods and experimental approaches are being put into question in terms of their validity. Without pretending to provide an answer with respect to the best way to conduct linguistics related experimental research, in this article we aim at examining the process that researchers follow in the design and implementation of experimental linguistics research with a goal to validate specific theoretical linguistic analyses. First, we discuss the general challenges that experimental work faces in finding a compromise between addressing theoretically relevant questions and being able to implement these questions in a specific controlled experimental paradigm. We discuss the Granularity Mismatch Problem (Poeppel and Embick, 2005) which addresses the challenges that research that is trying to bridge the representations and computations of language and their psycholinguistic/neurolinguistic evidence faces, and the basic assumptions that interdisciplinary research needs to consider due to the different conceptual granularity of the objects under study. To illustrate the practical implications of the points addressed, we compare two approaches to perform linguistic experimental research by reviewing a number of our own studies strongly grounded on theoretically informed questions. First, we show how linguistic phenomena similar at a conceptual level can be tested within the same language using measurement of event-related potentials (ERP) by discussing results from two ERP experiments on the processing of long-distance backward dependencies that involve coreference and negative polarity items respectively in Dutch. Second, we examine how the same linguistic phenomenon can be tested in different languages using reading time measures by discussing the outcome of four self-paced reading experiments on the processing of in-situ wh -questions in Mandarin Chinese and French. Finally, we review the implications that our findings have for the specific theoretical linguistics questions that we originally aimed to address. We conclude with an overview of the general insights that can be gained from the role of structural hierarchy and grammatical constraints in processing and the existing limitations on the generalization of results.

Ready or Not: Insufficient Collaboration between Department of Education and CUNY Could Hinder Effectiveness and Future Growth of Programs Designed to Improve Students' College Readiness Levels

ERIC Educational Resources Information Center

Colton, Tara

2006-01-01

This new report shows that while some of New York's college readiness programs have grown significantly in the last few years, there have also been some disappointing steps backward. For instance, the Bloomberg administration backed away from an initiative launched in 2000 by CUNY Chancellor Matthew Goldstein and then-New York City Schools…

Family functioning mediates adaptation in caregivers of individuals with Rett syndrome.

PubMed

Lamb, Amanda E; Biesecker, Barbara B; Umstead, Kendall L; Muratori, Michelle; Biesecker, Leslie G; Erby, Lori H

2016-11-01

The objective of this study was to investigate factors related to family functioning and adaptation in caregivers of individuals with Rett syndrome (RS). A cross-sectional quantitative survey explored the relationships between demographics, parental self-efficacy, coping methods, family functioning and adaptation. A forward-backward, step-wise model selection procedure was used to evaluate variables associated with both family functioning and adaptation. Analyses also explored family functioning as a mediator of the relationship between other variables and adaptation. Bivariate analyses (N=400) revealed that greater parental self-efficacy, a greater proportion of problem-focused coping, and a lesser proportion of emotion-focused coping were associated with more effective family functioning. In addition, these key variables were significantly associated with greater adaptation, as was family functioning, while controlling for confounders. Finally, regression analyses suggest family functioning as a mediator of the relationships between three variables (parental self-efficacy, problem-focused coping, and emotion-focused coping) with adaptation. This study demonstrates the potentially predictive roles of expectations and coping methods and the mediator role of family functioning in adaptation among caregivers of individuals with RS, a chronic developmental disorder. A potential target for intervention is strengthening of caregiver competence in the parenting role to enhance caregiver adaptation. Published by Elsevier Ireland Ltd.

Finite Volume Element (FVE) discretization and multilevel solution of the axisymmetric heat equation

NASA Astrophysics Data System (ADS)

Litaker, Eric T.

1994-12-01

The axisymmetric heat equation, resulting from a point-source of heat applied to a metal block, is solved numerically; both iterative and multilevel solutions are computed in order to compare the two processes. The continuum problem is discretized in two stages: finite differences are used to discretize the time derivatives, resulting is a fully implicit backward time-stepping scheme, and the Finite Volume Element (FVE) method is used to discretize the spatial derivatives. The application of the FVE method to a problem in cylindrical coordinates is new, and results in stencils which are analyzed extensively. Several iteration schemes are considered, including both Jacobi and Gauss-Seidel; a thorough analysis of these schemes is done, using both the spectral radii of the iteration matrices and local mode analysis. Using this discretization, a Gauss-Seidel relaxation scheme is used to solve the heat equation iteratively. A multilevel solution process is then constructed, including the development of intergrid transfer and coarse grid operators. Local mode analysis is performed on the components of the amplification matrix, resulting in the two-level convergence factors for various combinations of the operators. A multilevel solution process is implemented by using multigrid V-cycles; the iterative and multilevel results are compared and discussed in detail. The computational savings resulting from the multilevel process are then discussed.

Data assimilation experiments using the diffusive back and forth nudging for the NEMO ocean model

NASA Astrophysics Data System (ADS)

Ruggiero, G. A.; Ourmières, Y.; Cosme, E.; Blum, J.; Auroux, D.; Verron, J.

2014-07-01

The Diffusive Back and Forth Nudging (DBFN) is an easy-to-implement iterative data assimilation method based on the well-known Nudging method. It consists in a sequence of forward and backward model integrations, within a given time window, both of them using a feedback term to the observations. Therefore in the DBFN, the Nudging asymptotic behavior is translated into an infinite number of iterations within a bounded time domain. In this method, the backward integration is carried out thanks to what is called backward model, which is basically the forward model with reversed time step sign. To maintain numeral stability the diffusion terms also have their sign reversed, giving a diffusive character to the algorithm. In this article the DBFN performance to control a primitive equation ocean model is investigated. In this kind of model non-resolved scales are modeled by diffusion operators which dissipate energy that cascade from large to small scales. Thus, in this article the DBFN approximations and their consequences on the data assimilation system set-up are analyzed. Our main result is that the DBFN may provide results which are comparable to those produced by a 4Dvar implementation with a much simpler implementation and a shorter CPU time for convergence.

Forward-facing steps induced transition in a subsonic boundary layer

NASA Astrophysics Data System (ADS)

Zh, Hui; Fu, Song

2017-10-01

A forward-facing step (FFS) immersed in a subsonic boundary layer is studied through a high-order flux reconstruction (FR) method to highlight the flow transition induced by the step. The step height is a third of the local boundary-layer thickness. The Reynolds number based on the step height is 720. Inlet disturbances are introduced giving rise to streamwise vortices upstream of the step. It is observed that these small-scale streamwise structures interact with the step and hairpin vortices are quickly developed after the step leading to flow transition in the boundary layer.

Rapid stepping test towards virtual visual objects: Feasibility and convergent validity in older adults.

PubMed

Hutzler, Yeshayahu; Korsensky, Olga; Laufer, Yocheved

2017-01-01

Rapid voluntary stepping has been recognized as an important measure of balance control. The purpose of this study was to assess the feasibility and convergent validity of a Rapid Stepping Test protocol utilizing a virtual reality SeeMeTM system (VR-RST) in elderly ambulatory and independent individuals living in a community residential home. Associations between step execution times determined by the system and the Activities-specific Balance Confidence (ABC) Questionnaire, and clinical measures of balance performance in the MiniBESTest and Timed Up and Go (TUG) test, were established in 60 participants (mean age 88.2 ± 5.0 years). All participants completed the study. The correlations of the ABC questionnaire and the clinical tests with VR-RST forward and backward stepping were moderate (ρ rage 0.42-0.52), and weak to moderate with sideward stepping (ρ rage 0.32-0.52). Moderate to strong correlations were found across stepping directions (ρ rage 0.45-0.87). Findings support the test's feasibility and validity and confirm the utility of the VR-RST as an assessment tool in an elderly population.

Stability analysis of implicit time discretizations for the Compton-scattering Fokker-Planck equation

NASA Astrophysics Data System (ADS)

Densmore, Jeffery D.; Warsa, James S.; Lowrie, Robert B.; Morel, Jim E.

2009-09-01

The Fokker-Planck equation is a widely used approximation for modeling the Compton scattering of photons in high energy density applications. In this paper, we perform a stability analysis of three implicit time discretizations for the Compton-Scattering Fokker-Planck equation. Specifically, we examine (i) a Semi-Implicit (SI) scheme that employs backward-Euler differencing but evaluates temperature-dependent coefficients at their beginning-of-time-step values, (ii) a Fully Implicit (FI) discretization that instead evaluates temperature-dependent coefficients at their end-of-time-step values, and (iii) a Linearized Implicit (LI) scheme, which is developed by linearizing the temperature dependence of the FI discretization within each time step. Our stability analysis shows that the FI and LI schemes are unconditionally stable and cannot generate oscillatory solutions regardless of time-step size, whereas the SI discretization can suffer from instabilities and nonphysical oscillations for sufficiently large time steps. With the results of this analysis, we present time-step limits for the SI scheme that prevent undesirable behavior. We test the validity of our stability analysis and time-step limits with a set of numerical examples.

Steps in the bacterial flagellar motor.

PubMed

Mora, Thierry; Yu, Howard; Sowa, Yoshiyuki; Wingreen, Ned S

2009-10-01

The bacterial flagellar motor is a highly efficient rotary machine used by many bacteria to propel themselves. It has recently been shown that at low speeds its rotation proceeds in steps. Here we propose a simple physical model, based on the storage of energy in protein springs, that accounts for this stepping behavior as a random walk in a tilted corrugated potential that combines torque and contact forces. We argue that the absolute angular position of the rotor is crucial for understanding step properties and show this hypothesis to be consistent with the available data, in particular the observation that backward steps are smaller on average than forward steps. We also predict a sublinear speed versus torque relationship for fixed load at low torque, and a peak in rotor diffusion as a function of torque. Our model provides a comprehensive framework for understanding and analyzing stepping behavior in the bacterial flagellar motor and proposes novel, testable predictions. More broadly, the storage of energy in protein springs by the flagellar motor may provide useful general insights into the design of highly efficient molecular machines.

Application of FUN3D and CFL3D to the Third Workshop on CFD Uncertainty Analysis

NASA Technical Reports Server (NTRS)

Rumsey, C. L.; Thomas, J. L.

2008-01-01

Two Reynolds-averaged Navier-Stokes computer codes - one unstructured and one structured - are applied to two workshop cases (for the 3rd Workshop on CFD Uncertainty Analysis, held at Instituto Superior Tecnico, Lisbon, in October 2008) for the purpose of uncertainty analysis. The Spalart-Allmaras turbulence model is employed. The first case uses the method of manufactured solution and is intended as a verification case. In other words, the CFD solution is expected to approach the exact solution as the grid is refined. The second case is a validation case (comparison against experiment), for which modeling errors inherent in the turbulence model and errors/uncertainty in the experiment may prevent close agreement. The results from the two computer codes are also compared. This exercise verifies that the codes are consistent both with the exact manufactured solution and with each other. In terms of order property, both codes behave as expected for the manufactured solution. For the backward facing step, CFD uncertainty on the finest grid is computed and is generally very low for both codes (whose results are nearly identical). Agreement with experiment is good at some locations for particular variables, but there are also many areas where the CFD and experimental uncertainties do not overlap.

Wave Driven Fluid-Sediment Interactions over Rippled Beds

NASA Astrophysics Data System (ADS)

Foster, Diane; Nichols, Claire

2008-11-01

Empirical investigations relating vortex shedding over rippled beds to oscillatory flows date back to Darwin in 1883. Observations of the shedding induced by oscillating forcing over fixed beds have shown vortical structures to reach maximum strength at 90 degrees when the horizontal velocity is largest. The objective of this effort is to examine the vortex generation and ejection over movable rippled beds in a full-scale, free surface wave environment. Observations of the two-dimensional time-varying velocity field over a movable sediment bed were obtained with a submersible Particle Image Velocimetry (PIV) system in two wave flumes. One wave flume was full scale and had a natural sand bed and the other flume had an artificial sediment bed with a specific gravity of 1.6. Full scale observations over an irregularly rippled bed show that the vortices generated during offshore directed flow over the steeper bed form slope were regularly ejected into the water column and were consistent with conceptual models of the oscillatory flow over a backward facing step. The results also show that vortices remain coherent during ejection when the background flow stalls (i.e. both the velocity and acceleration temporarily approach zero). These results offer new insight into fluid sediment interaction over rippled beds.

Fluoroscopy guided percutaneous renal access in prone position

PubMed Central

Sharma, Gyanendra R; Maheshwari, Pankaj N; Sharma, Anshu G; Maheshwari, Reeta P; Heda, Ritwik S; Maheshwari, Sakshi P

2015-01-01

Percutaneous nephrolithotomy is a very commonly done procedure for management of renal calculus disease. Establishing a good access is the first and probably the most crucial step of this procedure. A proper access is the gateway to success. However, this crucial step has the steepest learning curve for, in a fluoroscopy guided access, it involves visualizing a three dimensional anatomy on a two dimensional fluoroscopy screen. This review describes the anatomical basis of the renal access. It provides a literature review of all aspects of percutaneous renal access along with the advances that have taken place in this field over the years. The article describes a technique to determine the site of skin puncture, the angle and depth of puncture using a simple mathematical principle. It also reviews the common problems faced during the process of puncture and dilatation and describes the ways to overcome them. The aim of this article is to provide the reader a step by step guide for percutaneous renal access. PMID:25789297

Translation and articulation in biological motion perception.

PubMed

Masselink, Jana; Lappe, Markus

2015-08-01

Recent models of biological motion processing focus on the articulational aspect of human walking investigated by point-light figures walking in place. However, in real human walking, the change in the position of the limbs relative to each other (referred to as articulation) results in a change of body location in space over time (referred to as translation). In order to examine the role of this translational component on the perception of biological motion we designed three psychophysical experiments of facing (leftward/rightward) and articulation discrimination (forward/backward and leftward/rightward) of a point-light walker viewed from the side, varying translation direction (relative to articulation direction), the amount of local image motion, and trial duration. In a further set of a forward/backward and a leftward/rightward articulation task, we additionally tested the influence of translational speed, including catch trials without articulation. We found a perceptual bias in translation direction in all three discrimination tasks. In the case of facing discrimination the bias was limited to short stimulus presentation. Our results suggest an interaction of articulation analysis with the processing of translational motion leading to best articulation discrimination when translational direction and speed match articulation. Moreover, we conclude that the global motion of the center-of-mass of the dot pattern is more relevant to processing of translation than the local motion of the dots. Our findings highlight that translation is a relevant cue that should be integrated in models of human motion detection.

The Obstacles for the Teaching of 8th Grade TR History of Revolution and Kemalism Course According to the Constructivist Approach (An Example of Exploratory Sequential Mixed Method Design)

ERIC Educational Resources Information Center

Karademir, Yavuz; Demir, Selcuk Besir

2015-01-01

The aim of this study is to ascertain the problems social studies teachers face in the teaching of topics covered in 8th grade TRHRK Course. The study was conducted in line with explanatory sequential mixed method design, which is one of the mixed research method, was used. The study involves three phases. In the first step, exploratory process…

Attitudes to face transplantation: results of a public engagement exercise at the Royal Society Summer Science Exhibition.

PubMed

Clarke, Alex; Simmons, Jon; White, Paul; Withey, Simon; Butler, Peter E M

2006-01-01

Hettiaratchy and Butler (Lancet 2002;360:5-6) framed face transplantation as the next logical step on the reconstructive ladder for severe facial injury, in particular, pan-facial burns. The procedure formed the basis for a Royal College of Surgeons of England working party report. Ethical, surgical, and psychological issues were identified as research priorities before face transplantation is attempted in the United Kingdom. Public engagement is a vital mechanism if people are to be informed about the risks and benefits of the technique and ultimately to be able to consent to either receiving or donating facial tissue. To sample public opinion about the procedure, 304 people attending the Royal Society Summer Science Exhibition were sampled by online questionnaire to determine their attitude toward face transplantation. Although people were more cautious about face transplantation when comparing this with solid-organ transplantation, most of the sample were in favor of the procedure, whether receiving a donor face or donating their own face after their death. Only 10% were against the idea in principle. Concerns about altered identity were not a barrier to face transplantation for 69% of the sample, with most people appropriately identifying the long-term problems of immunosuppression as the issue that most concerned them. There is a substantial population of people who, given the right circumstances, would contemplate face transplantation for themselves and would be willing to donate their own face for transplantation after their death.

Sequence-dependent base pair stepping dynamics in XPD helicase unwinding

PubMed Central

Qi, Zhi; Pugh, Robert A; Spies, Maria; Chemla, Yann R

2013-01-01

Helicases couple the chemical energy of ATP hydrolysis to directional translocation along nucleic acids and transient duplex separation. Understanding helicase mechanism requires that the basic physicochemical process of base pair separation be understood. This necessitates monitoring helicase activity directly, at high spatio-temporal resolution. Using optical tweezers with single base pair (bp) resolution, we analyzed DNA unwinding by XPD helicase, a Superfamily 2 (SF2) DNA helicase involved in DNA repair and transcription initiation. We show that monomeric XPD unwinds duplex DNA in 1-bp steps, yet exhibits frequent backsteps and undergoes conformational transitions manifested in 5-bp backward and forward steps. Quantifying the sequence dependence of XPD stepping dynamics with near base pair resolution, we provide the strongest and most direct evidence thus far that forward, single-base pair stepping of a helicase utilizes the spontaneous opening of the duplex. The proposed unwinding mechanism may be a universal feature of DNA helicases that move along DNA phosphodiester backbones. DOI: http://dx.doi.org/10.7554/eLife.00334.001 PMID:23741615

Variations of cortisol, fatigue and sleep disturbances in sound engineers: effect of job task and fast backward-rotating shifts.

PubMed

Vangelova, Katia K

2008-01-01

The aim was to study the effect of job task and fast backward-rotating shifts on the time-of-day variations of cortisol, fatigue, and sleep disturbances in broadcasting sound engineers. The concentration of saliva cortisol and ratings of stress, sleepiness, and fatigue were followed at 3-hour intervals during the fast backward-rotating shifts in 26 sound engineers: 14 subjects from control rooms, aged 45.1 +/- 7.3 years, and 12 subjects working in direct transmissions, aged 51.7 +/- 6.0 years. Saliva cortisol was assessed using an radioimmunology kit. The participants reported for stress symptoms after the shifts and filled a sleep diary. The effects of job task, shift, and time-of-day were analyzed by tests of between-subjects effects (SPSS). Cortisol retained the typical diurnal pattern with a highly significant effect of the shift. The job task and the shift interacted significantly. Higher cortisol values during the morning and night shifts in engineers working in direct transmissions were found. Their stress ratings were also higher, as well as the ratings of sleepiness and fatigue. The quality of sleep was worse in engineers working in direct transmissions. In conclusion, our data indicate that stress and fast backward-rotating shifts in sound engineers working in direct transmissions affect physiological stress markers such as cortisol and increase sleepiness, fatigue, and sleep problems.

Coordination of rapid stepping with arm pointing: anticipatory changes and step adaptation.

PubMed

Yiou, Eric; Schneider, Cyril; Roussel, Didier

2007-06-01

The present study explored whether rapid stepping is influenced by the coordination of an arm pointing task. Nine participants were instructed to (a) point the index finger of the dominant arm towards a target from the standing posture, (b) initiate a rapid forward step with the contralateral leg, and (c) synchronize stepping and pointing (combined task). Force plate and ankle muscle electromyography (EMG) recordings were contrasted between (b) and (c). In the combined task, the arm acceleration trace most often peaked around foot-off, coinciding with a 15% increase in the forward acceleration of the center of gravity (CoG). Backward displacement of the center of foot pressure at foot-off, duration of anticipatory postural adjustments (APAs) and ankle muscle EMG activity remained unchanged. In contrast, durations of swing phase and whole step were reduced and step length was smaller in the combined task. A reduction in the swing phase was correlated with an increased CoG forward acceleration at foot-off. Changes in the biomechanics of step initiation during the combined task might be ascribed to the postural dynamics elicited by arm pointing, and not to a modulation of the step APAs programming.

Facial expressions and speech acts: experimental evidences on the role of the upper face as an illocutionary force indicating device in language comprehension.

PubMed

Domaneschi, Filippo; Passarelli, Marcello; Chiorri, Carlo

2017-08-01

Language scientists have broadly addressed the problem of explaining how language users recognize the kind of speech act performed by a speaker uttering a sentence in a particular context. They have done so by investigating the role played by the illocutionary force indicating devices (IFIDs), i.e., all linguistic elements that indicate the illocutionary force of an utterance. The present work takes a first step in the direction of an experimental investigation of non-verbal IFIDs because it investigates the role played by facial expressions and, in particular, of upper-face action units (AUs) in the comprehension of three basic types of illocutionary force: assertions, questions, and orders. The results from a pilot experiment on production and two comprehension experiments showed that (1) certain upper-face AUs seem to constitute non-verbal signals that contribute to the understanding of the illocutionary force of questions and orders; (2) assertions are not expected to be marked by any upper-face AU; (3) some upper-face AUs can be associated, with different degrees of compatibility, with both questions and orders.

Walk this way: approaching bodies can influence the processing of faces.

PubMed

Pilz, Karin S; Vuong, Quoc C; Bülthoff, Heinrich H; Thornton, Ian M

2011-01-01

A highly familiar type of movement occurs whenever a person walks towards you. In the present study, we investigated whether this type of motion has an effect on face processing. We took a range of different 3D head models and placed them on a single, identical 3D body model. The resulting figures were animated to approach the observer. In a first series of experiments, we used a sequential matching task to investigate how the motion of an approaching person affects immediate responses to faces. We compared observers' responses following approach sequences to their performance with figures walking backwards (receding motion) or remaining still. Observers were significantly faster in responding to a target face that followed an approach sequence, compared to both receding and static primes. In a second series of experiments, we investigated long-term effects of motion using a delayed visual search paradigm. After studying moving or static avatars, observers searched for target faces in static arrays of varying set sizes. Again, observers were faster at responding to faces that had been learned in the context of an approach sequence. Together these results suggest that the context of a moving body influences face processing, and support the hypothesis that our visual system has mechanisms that aid the encoding of behaviourally-relevant and familiar dynamic events. Copyright © 2010 Elsevier B.V. All rights reserved.

A judicious multiple hypothesis tracker with interacting feature extraction

NASA Astrophysics Data System (ADS)

McAnanama, James G.; Kirubarajan, T.

2009-05-01

The multiple hypotheses tracker (mht) is recognized as an optimal tracking method due to the enumeration of all possible measurement-to-track associations, which does not involve any approximation in its original formulation. However, its practical implementation is limited by the NP-hard nature of this enumeration. As a result, a number of maintenance techniques such as pruning and merging have been proposed to bound the computational complexity. It is possible to improve the performance of a tracker, mht or not, using feature information (e.g., signal strength, size, type) in addition to kinematic data. However, in most tracking systems, the extraction of features from the raw sensor data is typically independent of the subsequent association and filtering stages. In this paper, a new approach, called the Judicious Multi Hypotheses Tracker (jmht), whereby there is an interaction between feature extraction and the mht, is presented. The measure of the quality of feature extraction is input into measurement-to-track association while the prediction step feeds back the parameters to be used in the next round of feature extraction. The motivation for this forward and backward interaction between feature extraction and tracking is to improve the performance in both steps. This approach allows for a more rational partitioning of the feature space and removes unlikely features from the assignment problem. Simulation results demonstrate the benefits of the proposed approach.

Past, present and future of spike sorting techniques

PubMed Central

Rey, Hernan Gonzalo; Pedreira, Carlos; Quian Quiroga, Rodrigo

2015-01-01

Spike sorting is a crucial step to extract information from extracellular recordings. With new recording opportunities provided by the development of new electrodes that allow monitoring hundreds of neurons simultaneously, the scenario for the new generation of algorithms is both exciting and challenging. However, this will require a new approach to the problem and the development of a common reference framework to quickly assess the performance of new algorithms. In this work, we review the basic concepts of spike sorting, including the requirements for different applications, together with the problems faced by presently available algorithms. We conclude by proposing a roadmap stressing the crucial points to be addressed to support the neuroscientific research of the near future. PMID:25931392

The Disestablishment of U.S. Joint Forces Command: A Step Backward in Jointness

DTIC Science & Technology

2011-06-01

and the less than stellar 1983 rescue of a few medical students from the island of Grenada (Operation Urgent Fury), Congress passed the Goldwater...an opportunity for dialogue and a source of basic joint doctrine, it was widely ignored despite increasing tension and preparation for the Second... basic unity of effort appeared lacking even with dialogue like the Key West Agreements. Dr. William Niskanen, with the CATO Institute, described the

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

Klimsiak, Tomasz, E-mail: tomas@mat.umk.pl; Rozkosz, Andrzej, E-mail: rozkosz@mat.umk.pl

In the paper we consider the problem of valuation of American options written on dividend-paying assets whose price dynamics follow the classical multidimensional Black and Scholes model. We provide a general early exercise premium representation formula for options with payoff functions which are convex or satisfy mild regularity assumptions. Examples include index options, spread options, call on max options, put on min options, multiply strike options and power-product options. In the proof of the formula we exploit close connections between the optimal stopping problems associated with valuation of American options, obstacle problems and reflected backward stochastic differential equations.

Alexithymia and psychosocial problems among Italian preadolescents. A latent class analysis approach.

PubMed

Mannarini, Stefania; Balottin, Laura; Toldo, Irene; Gatta, Michela

2016-10-01

The study, conducted on Italian preadolscents aged 11 to 13 belonging to the general population, aims to investigate the relationship between the emotional functioning, namely, alexithymia, and the risk of developing behavioral and emotional problems measured using the Strength and Difficulty Questionnaire. The latent class analysis approach allowed to identify two latent variables, accounting for the internalizing (emotional symptoms and difficulties in emotional awareness) and for the externalizing problems (conduct problems and hyperactivity, problematic relationships with peers, poor prosocial behaviors and externally oriented thinking). The two latent variables featured two latent classes: the difficulty in dealing with problems and the strength to face problems that was representative of most of the healthy participants with specific gender differences. Along with the analysis of psychopathological behaviors, the study of resilience and strengths can prove to be a key step in order to develop valuable preventive approaches to tackle psychiatric disorders. © 2016 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

Six Sigma Approach to Improve Stripping Quality of Automotive Electronics Component – a case study

NASA Astrophysics Data System (ADS)

Razali, Noraini Mohd; Murni Mohamad Kadri, Siti; Con Ee, Toh

2018-03-01

Lacking of problem solving skill techniques and cooperation between support groups are the two obstacles that always been faced in actual production line. Inadequate detail analysis and inappropriate technique in solving the problem may cause the repeating issues which may give impact to the organization performance. This study utilizes a well-structured six sigma DMAIC with combination of other problem solving tools to solve product quality problem in manufacturing of automotive electronics component. The study is concentrated at the stripping process, a critical process steps with highest rejection rate that contribute to the scrap and rework performance. The detail analysis is conducted in the analysis phase to identify the actual root cause of the problem. Then several improvement activities are implemented and the results show that the rejection rate due to stripping defect decrease tremendously and the process capability index improved from 0.75 to 1.67. This results prove that the six sigma approach used to tackle the quality problem is substantially effective.

Administrator Preparation: Looking Backwards and Forwards

ERIC Educational Resources Information Center

Bridges, Edwin

2012-01-01

Purpose: The purpose of this paper was to conduct a critical analysis of the origins and implementation of problem-based learning in educational administration as a window into the limitations of this approach and more generally administrator preparation. Design/methodology/approach: The author reviewed the published work of the originator from…

Effects of Cueing in Auditory Temporal Masking

ERIC Educational Resources Information Center

Zhang, Ting; Formby, Craig

2007-01-01

Purpose: In a landmark study, B. A. Wright et al. (1997) reported an apparent backward-masking deficit in language-learning-impaired children. Subsequently, the controversial interpretation of those results has been influential in guiding treatments for childhood language problems. This study revisited the temporal-masking paradigm reported by B.…

Auditory Backward Masking Deficits in Children with Reading Disabilities

ERIC Educational Resources Information Center

Montgomery, Christine R.; Morris, Robin D.; Sevcik, Rose A.; Clarkson, Marsha G.

2005-01-01

Studies evaluating temporal auditory processing among individuals with reading and other language deficits have yielded inconsistent findings due to methodological problems (Studdert-Kennedy & Mody, 1995) and sample differences. In the current study, seven auditory masking thresholds were measured in fifty-two 7- to 10-year-old children (26…

Solving Rational Expectations Models Using Excel

ERIC Educational Resources Information Center

Strulik, Holger

2004-01-01

Simple problems of discrete-time optimal control can be solved using a standard spreadsheet software. The employed-solution method of backward iteration is intuitively understandable, does not require any programming skills, and is easy to implement so that it is suitable for classroom exercises with rational-expectations models. The author…

The Emergence of the Technical Generalist.

ERIC Educational Resources Information Center

Collins, Paul D.

Social problems are manifested earlier at home and particularly on the job by alienated, depressed, estranged, dissatisfied, poorly motivated employees who steal or are frequently absent. Some say the education of the young must be specialized to ensure productivity, but emphasis on job requirements seems to be a backward view. Education should be…

Optimal insecticide-treated bed-net coverage and malaria treatment in a malaria-HIV co-infection model.

PubMed

Mohammed-Awel, Jemal; Numfor, Eric

2017-03-01

We propose and study a mathematical model for malaria-HIV co-infection transmission and control, in which malaria treatment and insecticide-treated nets are incorporated. The existence of a backward bifurcation is established analytically, and the occurrence of such backward bifurcation is influenced by disease-induced mortality, insecticide-treated bed-net coverage and malaria treatment parameters. To further assess the impact of malaria treatment and insecticide-treated bed-net coverage, we formulate an optimal control problem with malaria treatment and insecticide-treated nets as control functions. Using reasonable parameter values, numerical simulations of the optimal control suggest the possibility of eliminating malaria and reducing HIV prevalence significantly, within a short time horizon.

Five conversations: reflections of stakeholders on the impact of the ethnocultural communities facing AIDS study.

PubMed

Willms, D; Bhatia, R; Lowe, J; Niemi, F; Stewart, D; Westmoreland-Traore, J

1996-01-01

This paper reports on issues identified in conversations held between one of the Ethnocultural Communities Facing AIDS Study (ECFA) investigators and five stakeholders associated with this experiment in collaborative and participatory research. The stakeholders reflect on their experiences in partnering with university-based researchers, resistance in ethnocultural communities to being researched, and the next steps implicated by the research in question. The problem of HIV/AIDS in ethnocultural communities in Canada is, relative to the mainstream, also viewed as a symbol of disadvantage in these communities. The stakeholders suggest that to address these deeper concerns, there must be vital, dynamic, and enduring communication between researchers, community representatives, and government at all levels, in the process of identifying solutions and implementing them in the present.

Kruskal-Wallis-based computationally efficient feature selection for face recognition.

PubMed

Ali Khan, Sajid; Hussain, Ayyaz; Basit, Abdul; Akram, Sheeraz

2014-01-01

Face recognition in today's technological world, and face recognition applications attain much more importance. Most of the existing work used frontal face images to classify face image. However these techniques fail when applied on real world face images. The proposed technique effectively extracts the prominent facial features. Most of the features are redundant and do not contribute to representing face. In order to eliminate those redundant features, computationally efficient algorithm is used to select the more discriminative face features. Extracted features are then passed to classification step. In the classification step, different classifiers are ensemble to enhance the recognition accuracy rate as single classifier is unable to achieve the high accuracy. Experiments are performed on standard face database images and results are compared with existing techniques.

Don't make me angry, you wouldn't like me when I'm angry: Volitional choices to act or inhibit are modulated by subliminal perception of emotional faces.

PubMed

Parkinson, Jim; Garfinkel, Sarah; Critchley, Hugo; Dienes, Zoltan; Seth, Anil K

2017-04-01

Volitional action and self-control-feelings of acting according to one's own intentions and in being control of one's own actions-are fundamental aspects of human conscious experience. However, it is unknown whether high-level cognitive control mechanisms are affected by socially salient but nonconscious emotional cues. In this study, we manipulated free choice decisions to act or withhold an action by subliminally presenting emotional faces: In a novel version of the Go/NoGo paradigm, participants made speeded button-press responses to Go targets, withheld responses to NoGo targets, and made spontaneous, free choices to execute or withhold the response for Choice targets. Before each target, we presented emotional faces, backwards masked to render them nonconscious. In Intentional trials, subliminal angry faces made participants more likely to voluntarily withhold the action, whereas fearful and happy faces had no effects. In a second experiment, the faces were made supraliminal, which eliminated the effects of angry faces on volitional choices. A third experiment measured neural correlates of the effects of subliminal angry faces on intentional choice using EEG. After replicating the behavioural results found in Experiment 1, we identified a frontal-midline theta component-associated with cognitive control processes-which is present for volitional decisions, and is modulated by subliminal angry faces. This suggests a mechanism whereby subliminally presented "threat" stimuli affect conscious control processes. In summary, nonconscious perception of angry faces increases choices to inhibit, and subliminal influences on volitional action are deep seated and ecologically embedded.

Superior Recognition Performance for Happy Masked and Unmasked Faces in Both Younger and Older Adults

PubMed Central

Svärd, Joakim; Wiens, Stefan; Fischer, Håkan

2012-01-01

In the aging literature it has been shown that even though emotion recognition performance decreases with age, the decrease is less for happiness than other facial expressions. Studies in younger adults have also revealed that happy faces are more strongly attended to and better recognized than other emotional facial expressions. Thus, there might be a more age independent happy face advantage in facial expression recognition. By using a backward masking paradigm and varying stimulus onset asynchronies (17–267 ms) the temporal development of a happy face advantage, on a continuum from low to high levels of visibility, was examined in younger and older adults. Results showed that across age groups, recognition performance for happy faces was better than for neutral and fearful faces at durations longer than 50 ms. Importantly, the results showed a happy face advantage already during early processing of emotional faces in both younger and older adults. This advantage is discussed in terms of processing of salient perceptual features and elaborative processing of the happy face. We also investigate the combined effect of age and neuroticism on emotional face processing. The rationale was previous findings of age-related differences in physiological arousal to emotional pictures and a relation between arousal and neuroticism. Across all durations, there was an interaction between age and neuroticism, showing that being high in neuroticism might be disadvantageous for younger, but not older adults’ emotion recognition performance during arousal enhancing tasks. These results indicate that there is a relation between aging, neuroticism, and performance, potentially related to physiological arousal. PMID:23226135

Facial detection using deep learning

NASA Astrophysics Data System (ADS)

Sharma, Manik; Anuradha, J.; Manne, H. K.; Kashyap, G. S. C.

2017-11-01

In the recent past, we have observed that Facebook has developed an uncanny ability to recognize people in photographs. Previously, we had to tag people in photos by clicking on them and typing their name. Now as soon as we upload a photo, Facebook tags everyone on its own. Facebook can recognize faces with 98% accuracy which is pretty much as good as humans can do. This technology is called Face Detection. Face detection is a popular topic in biometrics. We have surveillance cameras in public places for video capture as well as security purposes. The main advantages of this algorithm over other are uniqueness and approval. We need speed and accuracy to identify. But face detection is really a series of several related problems: First, look at a picture and find all the faces in it. Second, focus on each face and understand that even if a face is turned in a weird direction or in bad lighting, it is still the same person. Third select features which can be used to identify each face uniquely like size of the eyes, face etc. Finally, compare these features to data we have to find the person name. As a human, your brain is wired to do all of this automatically and instantly. In fact, humans are too good at recognizing faces. Computers are not capable of this kind of high-level generalization, so we must teach them how to do each step in this process separately. The growth of face detection is largely driven by growing applications such as credit card verification, surveillance video images, authentication for banking and security system access.

A high-order Lagrangian-decoupling method for the incompressible Navier-Stokes equations

NASA Technical Reports Server (NTRS)

Ho, Lee-Wing; Maday, Yvon; Patera, Anthony T.; Ronquist, Einar M.

1989-01-01

A high-order Lagrangian-decoupling method is presented for the unsteady convection-diffusion and incompressible Navier-Stokes equations. The method is based upon: (1) Lagrangian variational forms that reduce the convection-diffusion equation to a symmetric initial value problem; (2) implicit high-order backward-differentiation finite-difference schemes for integration along characteristics; (3) finite element or spectral element spatial discretizations; and (4) mesh-invariance procedures and high-order explicit time-stepping schemes for deducing function values at convected space-time points. The method improves upon previous finite element characteristic methods through the systematic and efficient extension to high order accuracy, and the introduction of a simple structure-preserving characteristic-foot calculation procedure which is readily implemented on modern architectures. The new method is significantly more efficient than explicit-convection schemes for the Navier-Stokes equations due to the decoupling of the convection and Stokes operators and the attendant increase in temporal stability. Numerous numerical examples are given for the convection-diffusion and Navier-Stokes equations for the particular case of a spectral element spatial discretization.

State Tracking and Fault Diagnosis for Dynamic Systems Using Labeled Uncertainty Graph.

PubMed

Zhou, Gan; Feng, Wenquan; Zhao, Qi; Zhao, Hongbo

2015-11-05

Cyber-physical systems such as autonomous spacecraft, power plants and automotive systems become more vulnerable to unanticipated failures as their complexity increases. Accurate tracking of system dynamics and fault diagnosis are essential. This paper presents an efficient state estimation method for dynamic systems modeled as concurrent probabilistic automata. First, the Labeled Uncertainty Graph (LUG) method in the planning domain is introduced to describe the state tracking and fault diagnosis processes. Because the system model is probabilistic, the Monte Carlo technique is employed to sample the probability distribution of belief states. In addition, to address the sample impoverishment problem, an innovative look-ahead technique is proposed to recursively generate most likely belief states without exhaustively checking all possible successor modes. The overall algorithms incorporate two major steps: a roll-forward process that estimates system state and identifies faults, and a roll-backward process that analyzes possible system trajectories once the faults have been detected. We demonstrate the effectiveness of this approach by applying it to a real world domain: the power supply control unit of a spacecraft.

Tetrahedral Finite-Volume Solutions to the Navier-Stokes Equations on Complex Configurations

NASA Technical Reports Server (NTRS)

Frink, Neal T.; Pirzadeh, Shahyar Z.

1998-01-01

A review of the algorithmic features and capabilities of the unstructured-grid flow solver USM3Dns is presented. This code, along with the tetrahedral grid generator, VGRIDns, is being extensively used throughout the U.S. for solving the Euler and Navier-Stokes equations on complex aerodynamic problems. Spatial discretization is accomplished by a tetrahedral cell-centered finite-volume formulation using Roe's upwind flux difference splitting. The fluxes are limited by either a Superbee or MinMod limiter. Solution reconstruction within the tetrahedral cells is accomplished with a simple, but novel, multidimensional analytical formula. Time is advanced by an implicit backward-Euler time-stepping scheme. Flow turbulence effects are modeled by the Spalart-Allmaras one-equation model, which is coupled with a wall function to reduce the number of cells in the near-wall region of the boundary layer. The issues of accuracy and robustness of USM3Dns Navier-Stokes capabilities are addressed for a flat-plate boundary layer, and a full F-16 aircraft with external stores at transonic speed.

Embodied Cognition is Not What you Think it is

PubMed Central

Wilson, Andrew D.; Golonka, Sabrina

2013-01-01

The most exciting hypothesis in cognitive science right now is the theory that cognition is embodied. Like all good ideas in cognitive science, however, embodiment immediately came to mean six different things. The most common definitions involve the straight-forward claim that “states of the body modify states of the mind.” However, the implications of embodiment are actually much more radical than this. If cognition can span the brain, body, and the environment, then the “states of mind” of disembodied cognitive science won’t exist to be modified. Cognition will instead be an extended system assembled from a broad array of resources. Taking embodiment seriously therefore requires both new methods and theory. Here we outline four key steps that research programs should follow in order to fully engage with the implications of embodiment. The first step is to conduct a task analysis, which characterizes from a first person perspective the specific task that a perceiving-acting cognitive agent is faced with. The second step is to identify the task-relevant resources the agent has access to in order to solve the task. These resources can span brain, body, and environment. The third step is to identify how the agent can assemble these resources into a system capable of solving the problem at hand. The last step is to test the agent’s performance to confirm that agent is actually using the solution identified in step 3. We explore these steps in more detail with reference to two useful examples (the outfielder problem and the A-not-B error), and introduce how to apply this analysis to the thorny question of language use. Embodied cognition is more than we think it is, and we have the tools we need to realize its full potential. PMID:23408669

Sparse Regression as a Sparse Eigenvalue Problem

NASA Technical Reports Server (NTRS)

Moghaddam, Baback; Gruber, Amit; Weiss, Yair; Avidan, Shai

2008-01-01

We extend the l0-norm "subspectral" algorithms for sparse-LDA [5] and sparse-PCA [6] to general quadratic costs such as MSE in linear (kernel) regression. The resulting "Sparse Least Squares" (SLS) problem is also NP-hard, by way of its equivalence to a rank-1 sparse eigenvalue problem (e.g., binary sparse-LDA [7]). Specifically, for a general quadratic cost we use a highly-efficient technique for direct eigenvalue computation using partitioned matrix inverses which leads to dramatic x103 speed-ups over standard eigenvalue decomposition. This increased efficiency mitigates the O(n4) scaling behaviour that up to now has limited the previous algorithms' utility for high-dimensional learning problems. Moreover, the new computation prioritizes the role of the less-myopic backward elimination stage which becomes more efficient than forward selection. Similarly, branch-and-bound search for Exact Sparse Least Squares (ESLS) also benefits from partitioned matrix inverse techniques. Our Greedy Sparse Least Squares (GSLS) generalizes Natarajan's algorithm [9] also known as Order-Recursive Matching Pursuit (ORMP). Specifically, the forward half of GSLS is exactly equivalent to ORMP but more efficient. By including the backward pass, which only doubles the computation, we can achieve lower MSE than ORMP. Experimental comparisons to the state-of-the-art LARS algorithm [3] show forward-GSLS is faster, more accurate and more flexible in terms of choice of regularization

Further insight into self-face recognition in schizophrenia patients: Why ambiguity matters.

PubMed

Bortolon, Catherine; Capdevielle, Delphine; Salesse, Robin N; Raffard, Stephane

2016-03-01

Although some studies reported specifically self-face processing deficits in patients with schizophrenia disorder (SZ), it remains unclear whether these deficits rather reflect a more global face processing deficit. Contradictory results are probably due to the different methodologies employed and the lack of control of other confounding factors. Moreover, no study has so far evaluated possible daily life self-face recognition difficulties in SZ. Therefore, our primary objective was to investigate self-face recognition in patients suffering from SZ compared to healthy controls (HC) using an "objective measure" (reaction time and accuracy) and a "subjective measure" (self-report of daily self-face recognition difficulties). Twenty-four patients with SZ and 23 HC performed a self-face recognition task and completed a questionnaire evaluating daily difficulties in self-face recognition. Recognition task material consisted in three different faces (the own, a famous and an unknown) being morphed in steps of 20%. Results showed that SZ were overall slower than HC regardless of the face identity, but less accurate only for the faces containing 60%-40% morphing. Moreover, SZ and HC reported a similar amount of daily problems with self/other face recognition. No significant correlations were found between objective and subjective measures (p > 0.05). The small sample size and relatively mild severity of psychopathology does not allow us to generalize our results. These results suggest that: (1) patients with SZ are as capable of recognizing their own face as HC, although they are susceptible to ambiguity; (2) there are far less self recognition deficits in schizophrenia patients than previously postulated. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stepped inlet optical panel

DOEpatents

Veligdan, James T.

2001-01-01

An optical panel includes stacked optical waveguides having stepped inlet facets collectively defining an inlet face for receiving image light, and having beveled outlet faces collectively defining a display screen for displaying the image light channeled through the waveguides by internal reflection.

12. DETAIL VIEW OF STEPPED CONCRETE GRAVITY DAM FACE AND ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

12. DETAIL VIEW OF STEPPED CONCRETE GRAVITY DAM FACE AND ROCK OUTCROPPING, WITH LAKE IN BACKGROUND, SHOWN AT MINIMUM WATER FLOW, LOOKING SOUTHEAST (UPSTREAM) - Van Arsdale Dam, South Fork of Eel River, Ukiah, Mendocino County, CA

The effect of cane use on the compensatory step following posterior perturbations.

PubMed

Hall, Courtney D; Jensen, Jody L

2004-08-01

The compensatory step is a critical component of the balance response and is impaired in older fallers. The purpose of this research was to examine whether utilization of a cane modified the compensatory step response following external posterior perturbations. Single subject withdrawal design was employed. Single subject statistical analysis--the standard deviation bandwidth-method--supplemented visual analysis of the data. Four older adults (range: 73-83 years) with balance impairment who habitually use a cane completed this study. Subjects received a series of sudden backward pulls that were large enough to elicit compensatory stepping. We examined the following variables both with and without cane use: timing of cane loading relative to step initiation and center of mass acceleration, stability margin, center of mass excursion and velocity, step length and width. No participant loaded the cane prior to initiation of the first compensatory step. There was no effect of cane use on the stability margin, nor was there an effect of cane use on center of mass excursion or velocity, or step length or width. These data suggest that cane use does not necessarily improve balance recovery following an external posterior perturbation when the individual is forced to rely on compensatory stepping. Instead these data suggest that the strongest factor in modifying step characteristics is experience with the perturbation.

Diagnostic, design and implementation of an integrated model of care in France: a bottom-up process with a continuous leadership

PubMed Central

de Stampa, Matthieu; Vedel, Isabelle; Mauriat, Claire; Bagaragaza, Emmanuel; Routelous, Christelle; Bergman, Howard; Lapointe, Liette; Cassou, Bernard; Ankri, Joel; Henrard, Jean-Claude

2010-01-01

Purpose To present an innovative bottom-up and pragmatic strategy used to implement a new integrated care model in France for community-dwelling elderly people with complex needs. Context Sustaining integrated care is difficult, in large part because of problems encountered securing the participation of health care and social service professionals and, in particular, general practitioners (GPs). Case description In the first step, a diagnostic study was conducted with face-to-face interviews to gather data on current practices from a sample of health and social stakeholders working with elderly people. In the second step, an integrated care model called Coordination Personnes Agées (COPA) was designed by the same major stakeholders in order to define its detailed characteristics based on the local context. In the third step, the model was implemented in two phases: adoption and maintenance. This strategy was carried out by a continuous and flexible leadership throughout the process, initially with a mixed leadership (clinician and researcher) followed by a double one (clinician and managers of services) in the implementation phase. Conclusions The implementation of this bottom-up and pragmatic strategy relied on establishing a collaborative dynamic among health and social stakeholders. This enhanced their involvement throughout the implementation phase, particularly among the GPs, and allowed them to support the change practices and services arrangements.

Green design assessment of electromechanical products based on group weighted-AHP

NASA Astrophysics Data System (ADS)

Guo, Jinwei; Zhou, MengChu; Li, Zhiwu; Xie, Huiguang

2015-11-01

Manufacturing industry is the backbone of a country's economy while environmental pollution is a serious problem that human beings must face today. The green design of electromechanical products based on enterprise information systems is an important method to solve the environmental problem. The question on how to design green products must be answered by excellent designers via both advanced design methods and effective assessment methods of electromechanical products. Making an objective and precise assessment of green design is one of the problems that must be solved when green design is conducted. An assessment method of green design on electromechanical products based on Group Weighted-AHP (Analytic Hierarchy Process) is proposed in this paper, together with the characteristics of green products. The assessment steps of green design are also established. The results are illustrated via the assessment of a refrigerator design.

Influence of gait mode and body orientation on following a walking avatar.

PubMed

Meerhoff, L Rens A; de Poel, Harjo J; Jowett, Tim W D; Button, Chris

2017-08-01

Regulating distance with a moving object or person is a key component of human movement and of skillful interpersonal coordination. The current set of experiments aimed to assess the role of gait mode and body orientation on distance regulation using a cyclical locomotor tracking task in which participants followed a virtual leader. In the first experiment, participants moved in the backward-forward direction while the body orientation of the virtual leader was manipulated (i.e., facing towards, or away from the follower), hence imposing an incongruence in gait mode between leader and follower. Distance regulation was spatially less accurate when followers walked backwards. Additionally, a clear trade-off was found between spatial leader-follower accuracy and temporal synchrony. Any perceptual effects were overshadowed by the effect of one's gait mode. In the second experiment we examined lateral following. The results suggested that lateral following was also constrained strongly by perceptual information presented by the leader. Together, these findings demonstrated how locomotor tracking depends on gait mode, but also on the body orientation of whoever is being followed. Copyright © 2017 Elsevier B.V. All rights reserved.

Forward Monte Carlo Computations of Polarized Microwave Radiation

NASA Technical Reports Server (NTRS)

Battaglia, A.; Kummerow, C.

2000-01-01

Microwave radiative transfer computations continue to acquire greater importance as the emphasis in remote sensing shifts towards the understanding of microphysical properties of clouds and with these to better understand the non linear relation between rainfall rates and satellite-observed radiance. A first step toward realistic radiative simulations has been the introduction of techniques capable of treating 3-dimensional geometry being generated by ever more sophisticated cloud resolving models. To date, a series of numerical codes have been developed to treat spherical and randomly oriented axisymmetric particles. Backward and backward-forward Monte Carlo methods are, indeed, efficient in this field. These methods, however, cannot deal properly with oriented particles, which seem to play an important role in polarization signatures over stratiform precipitation. Moreover, beyond the polarization channel, the next generation of fully polarimetric radiometers challenges us to better understand the behavior of the last two Stokes parameters as well. In order to solve the vector radiative transfer equation, one-dimensional numerical models have been developed, These codes, unfortunately, consider the atmosphere as horizontally homogeneous with horizontally infinite plane parallel layers. The next development step for microwave radiative transfer codes must be fully polarized 3-D methods. Recently a 3-D polarized radiative transfer model based on the discrete ordinate method was presented. A forward MC code was developed that treats oriented nonspherical hydrometeors, but only for plane-parallel situations.

Unconscious processing of facial affect in children and adolescents.

PubMed

Killgore, William D S; Yurgelun-Todd, Deborah A

2007-01-01

In a previous study, with adults, we demonstrated that the amygdala and anterior cingulate gyrus are differentially responsive to happy and sad faces presented subliminally. Because the ability to perceive subtle facial signals communicating sadness is an important aspect of prosocial development, and is critical for empathic behavior, we examined this phenomenon from a developmental perspective using a backward masking paradigm. While undergoing functional magnetic resonance imaging (fMRI), 10 healthy adolescent children were presented with a series of happy and sad facial expressions, each lasting 20 ms and masked immediately by a neutral face to prevent conscious awareness of the affective expression. Relative to fixation baseline, masked sad faces activated the right amygdala, whereas masked happy faces failed to activate any of the regions of interest. Direct comparison between masked happy and sad faces revealed valence specific differences in the anterior cingulate gyrus. When the data were compared statistically to our previous sample of adults, the adolescent group showed significantly greater activity in the right amygdala relative to the adults during the masked sad condition. Groups also differed in several non-hypothesized regions. Development of unconscious perception from adolescence into adulthood appears to be accompanied by reduced activity within limbic affect processing systems, and perhaps increased involvement of other cortical and cerebellar systems.

Updating QR factorization procedure for solution of linear least squares problem with equality constraints.

PubMed

Zeb, Salman; Yousaf, Muhammad

2017-01-01

In this article, we present a QR updating procedure as a solution approach for linear least squares problem with equality constraints. We reduce the constrained problem to unconstrained linear least squares and partition it into a small subproblem. The QR factorization of the subproblem is calculated and then we apply updating techniques to its upper triangular factor R to obtain its solution. We carry out the error analysis of the proposed algorithm to show that it is backward stable. We also illustrate the implementation and accuracy of the proposed algorithm by providing some numerical experiments with particular emphasis on dense problems.

Auditory abilities of speakers who persisted, or recovered, from stuttering

PubMed Central

Howell, Peter; Davis, Stephen; Williams, Sheila M.

2006-01-01

Objective The purpose of this study was to see whether participants who persist in their stutter have poorer sensitivity in a backward masking task compared to those participants who recover from their stutter. Design The auditory sensitivity of 30 children who stutter was tested on absolute threshold, simultaneous masking, backward masking with a broadband and with a notched noise masker. The participants had been seen and diagnosed as stuttering at least 1 year before their 12th birthday. The participants were assessed again at age 12 plus to establish whether their stutter had persisted or recovered. Persistence or recovery was based on participant's, parent's and researcher's assessment and Riley's [Riley, G. D. (1994). Stuttering severity instrument for children and adults (3rd ed.). Austin, TX: Pro-Ed.] Stuttering Severity Instrument-3. Based on this assessment, 12 speakers had persisted and 18 had recovered from stuttering. Results Thresholds differed significantly between persistent and recovered groups for the broadband backward-masked stimulus (thresholds being higher for the persistent group). Conclusions Backward masking performance at teenage is one factor that distinguishes speakers who persist in their stutter from those who recover.

 Education objectives: Readers of this article should: (1) explain why auditory factors have been implicated in stuttering; (2) summarise the work that has examined whether peripheral, and/or central, hearing are problems in stuttering; (3) explain how the hearing ability of persistent and recovered stutterers may differ; (4) discuss how hearing disorders have been implicated in other language disorders. PMID:16920188

[Eugenics: progress or backward movement?].

PubMed

González de Cancino, Emilssen

2007-01-01

Throughout this article there is a critical analysis of how genetics presents a dilemma for "human progress". So much so, that the legal world aims to create unequivocal norms and guarantees in relation with eugenics in order to avoid attempting against human dignity. The document makes the reader reflect on the ethical problems that eugenics can entail.

A Backwards Binding Construction in Zapotec.

ERIC Educational Resources Information Center

Black, Cheryl A.

Many of the Zapotecan (Mexico) languages have a unique way of signaling co-reference between the subject and the possessor of the object: the subject is null. Analysis of such a construction is problematic to current theories of anaphoric construction. In this analysis, the construction is described and the theoretical problem is underlined by…

Engaging Contexts for the Game of Nim

ERIC Educational Resources Information Center

Reeves, Charles A.; Gleichowski, Rosemarie Reeves

2007-01-01

Middle school teachers realize the value of students playing games in mathematics classes if those games emphasize problem-solving strategies, algebraic reasoning, or spatial sense. This article describes various versions of the traditional game of nim and shows how working backward can be used to find a winning strategy. The link is then made…

Adaptive Search through Constraint Violations

DTIC Science & Technology

1990-01-01

procedural) knowledge? Different methodologies are used to investigate these questions: Psychological experiments, computer simulations, historical studies...learns control knowledge through adaptive search. Unlike most other psychological models of skill acquisition, HS is a model of analytical, or...Newzll, 1986; VanLehn, in press). Psychological models of skill acquisition employ different problem solving mechanisms (forward search, backward

Integration Moves Backward in the 70s

ERIC Educational Resources Information Center

Coffin, Gregory C.

1973-01-01

Suggests that the failure of (1) school boards and superintendents to recognize the evil inherent in segragated schools -- both black and white -- and their lack of courage in dealing with the problem and (2) educators to recognize the subtle and not so subtle racial bias of their curriculum, curricular materials, personnel, and staffing practices…

Local error estimates for discontinuous solutions of nonlinear hyperbolic equations

NASA Technical Reports Server (NTRS)

Tadmor, Eitan

1989-01-01

Let u(x,t) be the possibly discontinuous entropy solution of a nonlinear scalar conservation law with smooth initial data. Suppose u sub epsilon(x,t) is the solution of an approximate viscosity regularization, where epsilon greater than 0 is the small viscosity amplitude. It is shown that by post-processing the small viscosity approximation u sub epsilon, pointwise values of u and its derivatives can be recovered with an error as close to epsilon as desired. The analysis relies on the adjoint problem of the forward error equation, which in this case amounts to a backward linear transport with discontinuous coefficients. The novelty of this approach is to use a (generalized) E-condition of the forward problem in order to deduce a W(exp 1,infinity) energy estimate for the discontinuous backward transport equation; this, in turn, leads one to an epsilon-uniform estimate on moments of the error u(sub epsilon) - u. This approach does not follow the characteristics and, therefore, applies mutatis mutandis to other approximate solutions such as E-difference schemes.

A synergetic combination of small and large neighborhood schemes in developing an effective procedure for solving the job shop scheduling problem.

PubMed

Amirghasemi, Mehrdad; Zamani, Reza

2014-01-01

This paper presents an effective procedure for solving the job shop problem. Synergistically combining small and large neighborhood schemes, the procedure consists of four components, namely (i) a construction method for generating semi-active schedules by a forward-backward mechanism, (ii) a local search for manipulating a small neighborhood structure guided by a tabu list, (iii) a feedback-based mechanism for perturbing the solutions generated, and (iv) a very large-neighborhood local search guided by a forward-backward shifting bottleneck method. The combination of shifting bottleneck mechanism and tabu list is used as a means of the manipulation of neighborhood structures, and the perturbation mechanism employed diversifies the search. A feedback mechanism, called repeat-check, detects consequent repeats and ignites a perturbation when the total number of consecutive repeats for two identical makespan values reaches a given threshold. The results of extensive computational experiments on the benchmark instances indicate that the combination of these four components is synergetic, in the sense that they collectively make the procedure fast and robust.

Backward Planning a Craniomaxillofacial Trauma Curriculum for the Surgical Workforce in Low-Resource Settings.

PubMed

Shaye, David A; Tollefson, Travis; Shah, Irfan; Krishnan, Gopal; Matic, Damir; Figari, Marcelo; Lim, Thiam Chye; Aniruth, Sunil; Schubert, Warren

2018-06-06

Trauma is a significant contributor to global disease, and low-income countries disproportionately shoulder this burden. Education and training are critical components in the effort to address the surgical workforce shortage. Educators can tailor training to a diverse background of health professionals in low-resource settings using competency-based curricula. We present a process for the development of a competency-based curriculum for low-resource settings in the context of craniomaxillofacial (CMF) trauma education. CMF trauma surgeons representing 7 low-, middle-, and high-income countries conducted a standardized educational curriculum development program. Patient problems related to facial injuries were identified and ranked from highest to lowest morbidity. Higher morbidity problems were categorized into 4 modules with agreed upon competencies. Methods of delivery (lectures, case discussions, and practical exercises) were selected to optimize learning of each competency. A facial injuries educational curriculum (1.5 days event) was tailored to health professionals with diverse training backgrounds who care for CMF trauma patients in low-resource settings. A backward planned, competency-based curriculum was organized into four modules titled: acute (emergent), eye (periorbital injuries and sight preserving measures), mouth (dental injuries and fracture care), and soft tissue injury treatments. Four courses have been completed with pre- and post-course assessments completed. Surgeons and educators from a diverse geographic background found the backward planning curriculum development method effective in creating a competency-based facial injuries (trauma) course for health professionals in low-resource settings, where contextual aspects of shortages of surgical capacity, equipment, and emergency transportation must be considered.

Gender Differences in Neural Responses to Perceptually Invisible Fearful Face—An ERP Study

PubMed Central

Lee, Seung A.; Kim, Chai-Youn; Shim, Miseon; Lee, Seung-Hwan

2017-01-01

Women tend to respond to emotional stimuli differently from men. This study aimed at investigating whether neural responses to perceptually “invisible” emotional stimuli differ between men and women by exploiting event-related potential (ERP). Forty healthy participants (21 women) were recruited for the main experiment. A control experiment was conducted by excluding nine (7 women) participants from the main experiment and replacing them with additional ten (6 women) participants (total 41 participants) where Beck's Anxiety Inventory (BAI) and Beck's Depression Inventory (BDI) scores were controlled. Using the visual backward masking paradigm, either a fearful or a neutral face stimulus was presented in varied durations (subthreshold, near-threshold, or suprathreshold) followed by a mask. Participants performed a two-alternative forced choice (2-AFC) emotion discrimination task on each face. Behavioral analysis showed that participants were unaware of masked stimuli of which duration was the shortest and, therefore, processed at subthreshold. Nevertheless, women showed significantly larger response in P100 amplitude to subthreshold fearful faces than men. This result remained consistent in the control experiment. Our findings indicate gender-differences in neural response to subthreshold emotional face, which is reflected in the early processing stage. PMID:28184189

Oxytocin attenuates neural reactivity to masked threat cues from the eyes.

PubMed

Kanat, Manuela; Heinrichs, Markus; Schwarzwald, Ralf; Domes, Gregor

2015-01-01

The neuropeptide oxytocin has recently been shown to modulate covert attention shifts to emotional face cues and to improve discrimination of masked facial emotions. These results suggest that oxytocin modulates facial emotion processing at early perceptual stages prior to full evaluation of the emotional expression. Here, we used functional magnetic resonance imaging to examine whether oxytocin alters neural responses to backwardly masked angry and happy faces while controlling for attention to the eye vs the mouth region. Intranasal oxytocin administration reduced amygdala reactivity to masked emotions when attending to salient facial features, ie, the eyes of angry faces and the mouth of happy faces. In addition, oxytocin decreased neural responses within the fusiform gyrus and brain stem areas, as well as functional coupling between the amygdala and the fusiform gyrus specifically for threat cues from the eyes. Effects of oxytocin on brain activity were not attributable to differences in behavioral performance, as oxytocin had no impact on mere emotion detection. Our results suggest that oxytocin attenuates neural correlates of early arousal by threat signals from the eye region. As reduced threat sensitivity may increase the likelihood of engaging in social interactions, our findings may have important implications for clinical states of social anxiety.

Metabolite concentrations, fluxes and free energies imply efficient enzyme usage

DOE PAGES

Park, Junyoung O.; Rubin, Sara A.; Xu, Yi -Fan; ...

2016-05-02

In metabolism, available free energy is limited and must be divided across pathway steps to maintain a negative Δ G throughout. For each reaction, Δ G is log proportional both to a concentration ratio (reaction quotient to equilibrium constant) and to a flux ratio (backward to forward flux). In this paper, we use isotope labeling to measure absolute metabolite concentrations and fluxes in Escherichia coli, yeast and a mammalian cell line. We then integrate this information to obtain a unified set of concentrations and Δ G for each organism. In glycolysis, we find that free energy is partitioned so asmore » to mitigate unproductive backward fluxes associated with Δ G near zero. Across metabolism, we observe that absolute metabolite concentrations and Δ G are substantially conserved and that most substrate (but not inhibitor) concentrations exceed the associated enzyme binding site dissociation constant ( K m or K i). Finally, the observed conservation of metabolite concentrations is consistent with an evolutionary drive to utilize enzymes efficiently given thermodynamic and osmotic constraints.« less

Spontaneous reverse movement of mRNA-bound tRNA through the ribosome.

PubMed

Konevega, Andrey L; Fischer, Niels; Semenkov, Yuri P; Stark, Holger; Wintermeyer, Wolfgang; Rodnina, Marina V

2007-04-01

During the translocation step of protein synthesis, a complex of two transfer RNAs bound to messenger RNA (tRNA-mRNA) moves through the ribosome. The reaction is promoted by an elongation factor, called EF-G in bacteria, which, powered by GTP hydrolysis, induces an open, unlocked conformation of the ribosome that allows for spontaneous tRNA-mRNA movement. Here we show that, in the absence of EF-G, there is spontaneous backward movement, or retrotranslocation, of two tRNAs bound to mRNA. Retrotranslocation is driven by the gain in affinity when a cognate E-site tRNA moves into the P site, which compensates the affinity loss accompanying the movement of peptidyl-tRNA from the P to the A site. These results lend support to the diffusion model of tRNA movement during translocation. In the cell, tRNA movement is biased in the forward direction by EF-G, which acts as a Brownian ratchet and prevents backward movement.

[PedsQL™ 4.0 Generic Core Infant Scales Parents Report for infants (ages 13-24 months). Linguistic validation from original US English version to Italian version].

PubMed

González-Melado, F J; Di Ciommo, V M; Di Pietro, M; Chiarini Testa, M B; Cutrera, R

2013-10-01

The purpose of this research was to show the translation and linguistic validation of the PedsQL™ 4.0 Generic Core Infant Scales Parents Report for Infants (ages 13-24 months) from its original English version to Italian language. The linguistic validation consists in three steps: a) different forward translations from the original US English instrument to Italian; this step includes the drawing of a "reconciliation" version (version 1); b) backward translations from the Italian reconciliation version to US English; c) patient testing: the second version of the questionnaire (obtained after the backward translations) has to be tested on a panel of a minimum of 5 respondents, throughout cognitive interviewing methodology, in order to obtain the final italian version of the PedsQL™ Parents Report for Infants (ages 13-24 months). In this report we summarize the third step of this process. To study the content validity, the applicability and comprehension of our questionnarie translation, we tested it through a qualitative methodology in a sample of parents whose children were hospitalized in Bambino Gesù Children's Hospital with two different kinds of interview: 4 parents responded to the questions posed through a "thinkaloud interview" and 3 parents responded to the questionnaire and to a "respondent debriefing" interview. We modified the main question of each section and also one of the possible answer in order to maintain the Italian translation that appeared in others PedsQL™. We did not modify the questions of each section because respondents expressed that are clearly comprehensible and easy to understand.

MO-DE-207A-07: Filtered Iterative Reconstruction (FIR) Via Proximal Forward-Backward Splitting: A Synergy of Analytical and Iterative Reconstruction Method for CT

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

Gao, H

Purpose: This work is to develop a general framework, namely filtered iterative reconstruction (FIR) method, to incorporate analytical reconstruction (AR) method into iterative reconstruction (IR) method, for enhanced CT image quality. Methods: FIR is formulated as a combination of filtered data fidelity and sparsity regularization, and then solved by proximal forward-backward splitting (PFBS) algorithm. As a result, the image reconstruction decouples data fidelity and image regularization with a two-step iterative scheme, during which an AR-projection step updates the filtered data fidelity term, while a denoising solver updates the sparsity regularization term. During the AR-projection step, the image is projected tomore » the data domain to form the data residual, and then reconstructed by certain AR to a residual image which is in turn weighted together with previous image iterate to form next image iterate. Since the eigenvalues of AR-projection operator are close to the unity, PFBS based FIR has a fast convergence. Results: The proposed FIR method is validated in the setting of circular cone-beam CT with AR being FDK and total-variation sparsity regularization, and has improved image quality from both AR and IR. For example, AIR has improved visual assessment and quantitative measurement in terms of both contrast and resolution, and reduced axial and half-fan artifacts. Conclusion: FIR is proposed to incorporate AR into IR, with an efficient image reconstruction algorithm based on PFBS. The CBCT results suggest that FIR synergizes AR and IR with improved image quality and reduced axial and half-fan artifacts. The authors was partially supported by the NSFC (#11405105), the 973 Program (#2015CB856000), and the Shanghai Pujiang Talent Program (#14PJ1404500).« less

Nonconscious attention bias to threat is correlated with anterior cingulate cortex gray matter volume: a voxel-based morphometry result and replication.

PubMed

Carlson, Joshua M; Beacher, Felix; Reinke, Karen S; Habib, Reza; Harmon-Jones, Eddie; Mujica-Parodi, Lilianne R; Hajcak, Greg

2012-01-16

An important aspect of the fear response is the allocation of spatial attention toward threatening stimuli. This response is so powerful that modulations in spatial attention can occur automatically without conscious awareness. Functional neuroimaging research suggests that the amygdala and anterior cingulate cortex (ACC) form a network involved in the rapid orienting of attention to threat. A hyper-responsive attention bias to threat is a common component of anxiety disorders. Yet, little is known of how individual differences in underlying brain morphometry relate to variability in attention bias to threat. Here, we performed two experiments using dot-probe tasks that measured individuals' attention bias to backward masked fearful faces. We collected whole-brain structural magnetic resonance images and used voxel-based morphometry to measure brain morphometry. We tested the hypothesis that reduced gray matter within the amygdala and ACC would be associated with reduced attention bias to threat. In Experiment 1, we found that backward masked fearful faces captured spatial attention and that elevated attention bias to masked threat was associated with greater ACC gray matter volumes. In Experiment 2, this association was replicated in a separate sample. Thus, we provide initial and replicating evidence that ACC gray matter volume is correlated with biased attention to threat. Importantly, we demonstrate that variability in affective attention bias within the healthy population is associated with ACC morphometry. This result opens the door for future research into the underlying brain morphometry associated with attention bias in clinically anxious populations. Copyright © 2011 Elsevier Inc. All rights reserved.

Transport in the Subtropical Lowermost Stratosphere during CRYSTAL-FACE

NASA Technical Reports Server (NTRS)

Pittman, Jasna V.; Weinstock, elliot M.; Oglesby, Robert J.; Sayres, David S.; Smith, Jessica B.; Anderson, James G.; Cooper, Owen R.; Wofsy, Steven C.; Xueref, Irene; Gerbig, Cristoph;

The rid-redundant procedure in C-Prolog

NASA Technical Reports Server (NTRS)

Chen, Huo-Yan; Wah, Benjamin W.

1987-01-01

C-Prolog can conveniently be used for logical inferences on knowledge bases. However, as similar to many search methods using backward chaining, a large number of redundant computation may be produced in recursive calls. To overcome this problem, the 'rid-redundant' procedure was designed to rid all redundant computations in running multi-recursive procedures. Experimental results obtained for C-Prolog on the Vax 11/780 computer show that there is an order of magnitude improvement in the running time and solvable problem size.

Single molecule thermodynamics in biological motors.

PubMed

Taniguchi, Yuichi; Karagiannis, Peter; Nishiyama, Masayoshi; Ishii, Yoshiharu; Yanagida, Toshio

2007-04-01

Biological molecular machines use thermal activation energy to carry out various functions. The process of thermal activation has the stochastic nature of output events that can be described according to the laws of thermodynamics. Recently developed single molecule detection techniques have allowed each distinct enzymatic event of single biological machines to be characterized providing clues to the underlying thermodynamics. In this study, the thermodynamic properties in the stepping movement of a biological molecular motor have been examined. A single molecule detection technique was used to measure the stepping movements at various loads and temperatures and a range of thermodynamic parameters associated with the production of each forward and backward step including free energy, enthalpy, entropy and characteristic distance were obtained. The results show that an asymmetry in entropy is a primary factor that controls the direction in which the motor will step. The investigation on single molecule thermodynamics has the potential to reveal dynamic properties underlying the mechanisms of how biological molecular machines work.

Notes on the Prediction of Shock-induced Boundary-layer Separation

NASA Technical Reports Server (NTRS)

Lange, Roy H.

1953-01-01

The present status of available information relative to the prediction of shock-induced boundary-layer separation is discussed. Experimental results showing the effects of Reynolds number and Mach number on the separation of both laminar and turbulent boundary layer are given and compared with available methods for predicting separation. The flow phenomena associated with separation caused by forward-facing steps, wedges, and incident shock waves are discussed. Applications of the flat-plate data to problems of separation on spoilers, diffusers, and scoop inlets are indicated for turbulent boundary layers.

The ASSIST: Bringing Information and Software Together for Scientists

NASA Technical Reports Server (NTRS)

Mandel, Eric

1997-01-01

The ASSIST was developed as a step toward overcoming the problems faced by researchers when trying to utilize complex and often conflicting astronomical data analysis systems. It implements a uniform graphical interface to analysis systems, documentation, data, and organizational memory. It is layered on top of the Answer Garden Substrate (AGS), a system specially designed to facilitate the collection and dissemination of organizational memory. Under the AISRP program, we further developed the ASSIST to make it even easier for researchers to overcome the difficulties of accessing software and information in a complex computer environment.

Milne problem for non-absorbing medium with extremely anisotropic scattering kernel in the case of specular and diffuse reflecting boundaries

NASA Astrophysics Data System (ADS)

Güleçyüz, M. Ç.; Şenyiğit, M.; Ersoy, A.

2018-01-01

The Milne problem is studied in one speed neutron transport theory using the linearly anisotropic scattering kernel which combines forward and backward scatterings (extremely anisotropic scattering) for a non-absorbing medium with specular and diffuse reflection boundary conditions. In order to calculate the extrapolated endpoint for the Milne problem, Legendre polynomial approximation (PN method) is applied and numerical results are tabulated for selected cases as a function of different degrees of anisotropic scattering. Finally, some results are discussed and compared with the existing results in literature.

Early ERP Modulation for Task-Irrelevant Subliminal Faces.

PubMed

Pegna, Alan J; Darque, Alexandra; Berrut, Claire; Khateb, Asaid

2011-01-01

A number of investigations have reported that emotional faces can be processed subliminally, and that they give rise to specific patterns of brain activation in the absence of awareness. Recent event-related potential (ERP) studies have suggested that electrophysiological differences occur early in time (<200 ms) in response to backward-masked emotional faces. These findings have been taken as evidence of a rapid non-conscious pathway, which would allow threatening stimuli to be processed rapidly and subsequently allow appropriate avoidance action to be taken. However, for this to be the case, subliminal processing should arise even if the threatening stimulus is not attended. This point has in fact not yet been clearly established. In this ERP study, we investigated whether subliminal processing of fearful faces occurs outside the focus of attention. Fourteen healthy participants performed a line judgment task while fearful and non-fearful (happy or neutral) faces were presented both subliminally and supraliminally. ERPs were compared across the four experimental conditions (i.e., subliminal and supraliminal; fearful and non-fearful). The earliest differences between fearful and non-fearful faces appeared as an enhanced posterior negativity for the former at 170 ms (the N170 component) over right temporo-occipital electrodes. This difference was observed for both subliminal (p < 0.05) and supraliminal presentations (p < 0.01). Our results confirm that subliminal processing of fearful faces occurs early in the course of visual processing, and more importantly, that this arises even when the subject's attention is engaged in an incidental task.

Flexible climate modeling systems: Lessons from Snowball Earth, Titan and Mars

NASA Astrophysics Data System (ADS)

Pierrehumbert, R. T.

2007-12-01

Climate models are only useful to the extent that real understanding can be extracted from them. Most leading- edge problems in climate change, paleoclimate and planetary climate require a high degree of flexibility in terms of incorporating model physics -- for example in allowing methane or CO2 to be a condensible substance instead of water vapor. This puts a premium on model design that allows easy modification, and on physical parameterizations that are close to fundamentals with as little empirical ad-hoc formulation as possible. I will provide examples from two approaches to this problem we have been using at the University of Chicago. The first is the FOAM general circulation model, which is a clean single-executable Fortran-77/c code supported by auxiliary applications in Python and Java. The second is a new approach based on using Python as a shell for assembling building blocks in compiled-code into full models. Applications to Snowball Earth, Titan and Mars, as well as pedagogical uses, will be discussed. One painful lesson we have learned is that Fortran-95 is a major impediment to portability and cross-language interoperability; in this light the trend toward Fortran-95 in major modelling groups is seen as a significant step backwards. In this talk, I will focus on modeling projects employing a full representation of atmospheric fluid dynamics, rather than "intermediate complexity" models in which the associated transports are parameterized.

Copyright at the Bedside: Should We Stop the Spread?

PubMed Central

Feldman, Robin; Newman, John

2014-01-01

We recently published an article in the New England Journal of Medicine describing a crisis in cognitive testing, as doctors and medical researchers increasingly face copyright claims in sets of questions used for testing mental state. We encouraged the creation of a cultural norm in medicine, in which medical researchers would ensure continued availability of their tests through open source licensing for any copyrights that might exist. In this piece, we consider the legal side of the question. Although copyrights are being copiously asserted in medical testing, are those rights valid, and should they be upheld? The legal precedents in this area are anything but clear, and the courts are divided in the few analogous circumstances that have arisen. We examine analogies in standardized testing, computer compilations and baseball pitching forms to consider the marvelous question of how to conceptualize a process—which is the purview of patent law—when that process consists of words—which are the purview of copyright law. We also look from an economics perspective at the issue of investment and value creation in the development of de facto standards. Legal scholars are so often in the position of looking backwards, teasing out solutions to problems that have developed within a doctrinal or theoretical area. Rarely does one have the opportunity to affect the course of events before problems become so deeply entrenched that they are intractable. This is such a moment, and the legal and medical fields should take advantage of the opportunities presented. PMID:25221427

Classification of burn wounds using support vector machines

NASA Astrophysics Data System (ADS)

Acha, Begona; Serrano, Carmen; Palencia, Sergio; Murillo, Juan Jose

2004-05-01

The purpose of this work is to improve a previous method developed by the authors for the classification of burn wounds into their depths. The inputs of the system are color and texture information, as these are the characteristics observed by physicians in order to give a diagnosis. Our previous work consisted in segmenting the burn wound from the rest of the image and classifying the burn into its depth. In this paper we focus on the classification problem only. We already proposed to use a Fuzzy-ARTMAP neural network (NN). However, we may take advantage of new powerful classification tools such as Support Vector Machines (SVM). We apply the five-folded cross validation scheme to divide the database into training and validating sets. Then, we apply a feature selection method for each classifier, which will give us the set of features that yields the smallest classification error for each classifier. Features used to classify are first-order statistical parameters extracted from the L*, u* and v* color components of the image. The feature selection algorithms used are the Sequential Forward Selection (SFS) and the Sequential Backward Selection (SBS) methods. As data of the problem faced here are not linearly separable, the SVM was trained using some different kernels. The validating process shows that the SVM method, when using a Gaussian kernel of variance 1, outperforms classification results obtained with the rest of the classifiers, yielding an error classification rate of 0.7% whereas the Fuzzy-ARTMAP NN attained 1.6 %.

Anticipatory postural adjustments for altering direction during walking.

PubMed

Xu, Dali; Carlton, Les G; Rosengren, Karl S

2004-09-01

The authors examined how individuals adapt their gait and regulate their body configuration before altering direction during walking. Eight young adults were asked to change direction during walking with different turning angles (0 degree, 45 degree, 90 degree), pivot foot (left, right), and walking speeds (normal and fast). The authors used video and force platform systems to determine participants' whole-body center of mass and the center of pressure during the step before they changed direction. The results showed that anticipatory postural adjustments occurred during the prior step and occurred earlier for the fast walking speed. Anticipatory postural adjustments were affected by all 3 variables (turn angle, pivot foot, and speed). Participants leaned backward and sideward on the prior step in anticipation of the turn. Those findings indicate that the motor system uses central control mechanisms to predict the required anticipatory adjustments and organizes the body configuration on the basis of the movement goal.

A universal pathway for kinesin stepping.

PubMed

Clancy, Bason E; Behnke-Parks, William M; Andreasson, Johan O L; Rosenfeld, Steven S; Block, Steven M

2011-08-14

Kinesin-1 is an ATP-driven, processive motor that transports cargo along microtubules in a tightly regulated stepping cycle. Efficient gating mechanisms ensure that the sequence of kinetic events proceeds in the proper order, generating a large number of successive reaction cycles. To study gating, we created two mutant constructs with extended neck-linkers and measured their properties using single-molecule optical trapping and ensemble fluorescence techniques. Owing to a reduction in the inter-head tension, the constructs access an otherwise rarely populated conformational state in which both motor heads remain bound to the microtubule. ATP-dependent, processive backstepping and futile hydrolysis were observed under moderate hindering loads. On the basis of measurements, we formulated a comprehensive model for kinesin motion that incorporates reaction pathways for both forward and backward stepping. In addition to inter-head tension, we found that neck-linker orientation is also responsible for ensuring gating in kinesin.

Backward distraction osteogenesis in a patient with severe mandibular micrognathia.

PubMed

Mitsukawa, Nobuyuki; Morishita, Tadashi; Saiga, Atsuomi; Akita, Shinsuke; Kubota, Yoshitaka; Satoh, Kaneshige

2013-09-01

Maxillary skeletal prognathism can involve severe mandibular micrognathia with marked mandibular retrognathism or hypoplasia. For patients with such a condition, a conventional treatment is mandibular advancement by sagittal split ramus osteotomy (SSRO). This procedure has problems such as insufficient advancement, instability of jaw position, and postoperative relapse. Thus, in recent years, mandibular distraction osteogenesis has been used in some patients. Mandibular distraction has many advantages, but an ideal occlusion is difficult to achieve using this procedure. That is, 3-dimensional control cannot be attained using an internal device that is unidirectional. This report describes a case of severe mandibular micrognathia in a 14-year-old girl treated using backward distraction osteogenesis. This procedure was first reported by Ishii et al (Jpn J Jaw Deform 2004; 14:49) and involves a combination of SSRO and ramus distraction osteogenesis. In the present study, intermaxillary fixation in centric occlusion was performed after osteotomy, and proximal bone segments were distracted in a posterosuperior direction. This procedure is a superior surgical technique that avoids the drawbacks of SSRO and conventional mandibular distraction. However, it applies a large load to the temporomandibular joints and requires thorough management. Thus, careful evaluation needs to be made of the indication for backward distraction osteogenesis.

Enhancing multi-step quantum state tomography by PhaseLift

NASA Astrophysics Data System (ADS)

Lu, Yiping; Zhao, Qing

2017-09-01

Multi-photon system has been studied by many groups, however the biggest challenge faced is the number of copies of an unknown state are limited and far from detecting quantum entanglement. The difficulty to prepare copies of the state is even more serious for the quantum state tomography. One possible way to solve this problem is to use adaptive quantum state tomography, which means to get a preliminary density matrix in the first step and revise it in the second step. In order to improve the performance of adaptive quantum state tomography, we develop a new distribution scheme of samples and extend it to three steps, that is to correct it once again based on the density matrix obtained in the traditional adaptive quantum state tomography. Our numerical results show that the mean square error of the reconstructed density matrix by our new method is improved to the level from 10-4 to 10-9 for several tested states. In addition, PhaseLift is also applied to reduce the required storage space of measurement operator.

Sequential Reactions of Surface-Tethered Glycolytic Enzymes

PubMed Central

Mukai, Chinatsu; Bergkvist, Magnus; Nelson, Jacquelyn L.; Travis, Alexander J.

2014-01-01

SUMMARY The development of complex hybrid organic-inorganic devices faces several challenges, including how they can generate energy. Cells face similar challenges regarding local energy production. Mammalian sperm solve this problem by generating ATP down the flagellar principal piece by means of glycolytic enzymes, several of which are tethered to a cytoskeletal support via germ cell-specific targeting domains. Inspired by this design, we have produced recombinant hexokinase type 1 and glucose-6-phosphate isomerase capable of oriented immobilization on a nickel-nitrilotriacetic acid modified surface. Specific activities of enzymes tethered via this strategy were substantially higher than when randomly adsorbed. Furthermore, these enzymes showed sequential activities when tethered onto the same surface. This is the first demonstration of surface-tethered pathway components showing sequential enzymatic activities, and it provides a first step toward reconstitution of glycolysis on engineered hybrid devices. PMID:19778729

Three-dimensional unstructured grid Euler computations using a fully-implicit, upwind method

NASA Technical Reports Server (NTRS)

Whitaker, David L.

1993-01-01

A method has been developed to solve the Euler equations on a three-dimensional unstructured grid composed of tetrahedra. The method uses an upwind flow solver with a linearized, backward-Euler time integration scheme. Each time step results in a sparse linear system of equations which is solved by an iterative, sparse matrix solver. Local-time stepping, switched evolution relaxation (SER), preconditioning and reuse of the Jacobian are employed to accelerate the convergence rate. Implicit boundary conditions were found to be extremely important for fast convergence. Numerical experiments have shown that convergence rates comparable to that of a multigrid, central-difference scheme are achievable on the same mesh. Results are presented for several grids about an ONERA M6 wing.

The extended functional neuroanatomy of emotional processing biases for masked faces in major depressive disorder.

PubMed

Victor, Teresa A; Furey, Maura L; Fromm, Stephen J; Bellgowan, Patrick S F; Öhman, Arne; Drevets, Wayne C

2012-01-01

Major depressive disorder (MDD) is associated with a mood-congruent processing bias in the amygdala toward face stimuli portraying sad expressions that is evident even when such stimuli are presented below the level of conscious awareness. The extended functional anatomical network that maintains this response bias has not been established, however. To identify neural network differences in the hemodynamic response to implicitly presented facial expressions between depressed and healthy control participants. Unmedicated-depressed participants with MDD (n=22) and healthy controls (HC; n=25) underwent functional MRI as they viewed face stimuli showing sad, happy or neutral face expressions, presented using a backward masking design. The blood-oxygen-level dependent (BOLD) signal was measured to identify regions where the hemodynamic response to the emotionally valenced stimuli differed between groups. The MDD subjects showed greater BOLD responses than the controls to masked-sad versus masked-happy faces in the hippocampus, amygdala and anterior inferotemporal cortex. While viewing both masked-sad and masked-happy faces relative to masked-neutral faces, the depressed subjects showed greater hemodynamic responses than the controls in a network that included the medial and orbital prefrontal cortices and anterior temporal cortex. Depressed and healthy participants showed distinct hemodynamic responses to masked-sad and masked-happy faces in neural circuits known to support the processing of emotionally valenced stimuli and to integrate the sensory and visceromotor aspects of emotional behavior. Altered function within these networks in MDD may establish and maintain illness-associated differences in the salience of sensory/social stimuli, such that attention is biased toward negative and away from positive stimuli.

Mitigating Toxic Planktonic Cyanobacterial Blooms in Aquatic Ecosystems Facing Increasing Anthropogenic and Climatic Pressures

PubMed Central

2018-01-01

Toxic planktonic cyanobacterial blooms are a pressing environmental and human health problem. Blooms are expanding globally and threatening sustainability of our aquatic resources. Anthropogenic nutrient enrichment and hydrological modifications, including water diversions and reservoir construction, are major drivers of bloom expansion. Climatic change, i.e., warming, more extreme rainfall events, and droughts, act synergistically with human drivers to exacerbate the problem. Bloom mitigation steps, which are the focus of this review, must consider these dynamic interactive factors in order to be successful in the short- and long-term. Furthermore, these steps must be applicable along the freshwater to marine continuum connecting streams, lakes, rivers, estuarine, and coastal waters. There is an array of physical, chemical, and biological approaches, including flushing, mixing, dredging, application of algaecides, precipitating phosphorus, and selective grazing, that may arrest and reduce bloom intensities in the short-term. However, to ensure long term, sustainable success, targeting reductions of both nitrogen and phosphorus inputs should accompany these approaches along the continuum. Lastly, these strategies should accommodate climatic variability and change, which will likely modulate and alter nutrient-bloom thresholds. PMID:29419777

Validation of Supersonic Film Cooling Modeling for Liquid Rocket Engine Applications

NASA Technical Reports Server (NTRS)

Morris, Christopher I.; Ruf, Joseph H.

2010-01-01

Topics include: upper stage engine key requirements and design drivers; Calspan "stage 1" results, He slot injection into hypersonic flow (air); test articles for shock generator diagram, slot injector details, and instrumentation positions; test conditions; modeling approach; 2-d grid used for film cooling simulations of test article; heat flux profiles from 2-d flat plate simulations (run #4); heat flux profiles from 2-d backward facing step simulations (run #43); isometric sketch of single coolant nozzle, and x-z grid of half-nozzle domain; comparison of 2-d and 3-d simulations of coolant nozzles (run #45); flowfield properties along coolant nozzle centerline (run #45); comparison of 3-d CFD nozzle flow calculations with experimental data; nozzle exit plane reduced to linear profile for use in 2-d film-cooling simulations (run #45); synthetic Schlieren image of coolant injection region (run #45); axial velocity profiles from 2-d film-cooling simulation (run #45); coolant mass fraction profiles from 2-d film-cooling simulation (run #45); heat flux profiles from 2-d film cooling simulations (run #45); heat flux profiles from 2-d film cooling simulations (runs #47, #45, and #47); 3-d grid used for film cooling simulations of test article; heat flux contours from 3-d film-cooling simulation (run #45); and heat flux profiles from 3-d and 2-d film cooling simulations (runs #44, #46, and #47).

High-Resolution OH and CH2O Visualization in a Premixed Cavity-Anchored Ethylene-Air Flame in a M = 0.6 Flowfield

NASA Technical Reports Server (NTRS)

Geipel, Clayton M.; Rockwell, Robert D.; Chelliah, Harsha K.; Cutler, Andrew D.; Spelker, Christopher A.; Hashem, Zeid; Danehy, Paul M.

2017-01-01

OH and CH2O were imaged in a premixed, cavity-anchored, ethylene-air turbulent flame using a high resolution planar laser-induced fluorescence (PLIF) system. The electrically-heated, continuous flow facility (UVa Supersonic Combustion Facility, Configuration E) consisted of a Mach 2 nozzle, an isolator with fuel injectors, a test section with a cavity flame holder and optical access, and an extender. Standard test conditions comprised total temperature 1200 K, total pressure 300 kPa, local equivalence ratio near 0.4, and local Mach number near 0.6. OH PLIF data was also collected for a case with reduced total temperature and another with reduced equivalence ratio. OH and CH2O were excited in separate experiments with light sheets at 283.55 nm and 352.48 nm, respectively. A light sheet of approximate thickness 25 ?m illuminated the stream-wise midplane. This plane was imaged for 120 mm downstream of the backward-facing step. The intensified camera system imaged OH with magnification 1.97, a square 6.67 mm field of view, and in-plane resolution of 39 ?m. The smallest observed OH structures observed were approximately 100 ?m wide. The CH2O PLIF image signal was much weaker; the smallest observed structures were approximately 200 ?m wide. Composite fluorescence images were computed for the observed area.

A Realizable Reynolds Stress Algebraic Equation Model

NASA Technical Reports Server (NTRS)

Shih, Tsan-Hsing; Zhu, Jiang; Lumley, John L.

1993-01-01

The invariance theory in continuum mechanics is applied to analyze Reynolds stresses in high Reynolds number turbulent flows. The analysis leads to a turbulent constitutive relation that relates the Reynolds stresses to the mean velocity gradients in a more general form in which the classical isotropic eddy viscosity model is just the linear approximation of the general form. On the basis of realizability analysis, a set of model coefficients are obtained which are functions of the time scale ratios of the turbulence to the mean strain rate and the mean rotation rate. The coefficients will ensure the positivity of each component of the mean rotation rate. These coefficients will ensure the positivity of each component of the turbulent kinetic energy - realizability that most existing turbulence models fail to satisfy. Separated flows over backward-facing step configurations are taken as applications. The calculations are performed with a conservative finite-volume method. Grid-independent and numerical diffusion-free solutions are obtained by using differencing schemes of second-order accuracy on sufficiently fine grids. The calculated results are compared in detail with the experimental data for both mean and turbulent quantities. The comparison shows that the present proposal significantly improves the predictive capability of K-epsilon based two equation models. In addition, the proposed model is able to simulate rotational homogeneous shear flows with large rotation rates which all conventional eddy viscosity models fail to simulate.

Steps in Solution Growth: Revised Gibbs-Thomson Law, Turbulence and Morphological Stability

NASA Technical Reports Server (NTRS)

Chernov, A. A.; Rashkovich, L. N.; Vekilov, P. G.

2004-01-01

Two groups of new phenomena revealed by AFM and high resolution optical interferometry on crystal faces growing from solutions will be discussed. 1. Spacing between strongly polygonized spiral steps with low less than 10(exp -2) kink density on lysozyme and K- biphtalate do not follow the Burton-cabrera-Frank theory. The critical length of the yet immobile first Short step segment adjacent to a pinning defect (dislocation, stacking fault) is many times longer than that following from the step free energy. The low-kink density steps are typical of many growth conditions and materials, including low temperature gas phase epitaxy and MBE. 2. The step bunching pattern on the approx. 1 cm long { 110) KDP face growing from the turbulent solution flow (Re (triple bonds) 10(exp 4), solution flow rate approx. 1 m/s) suggests that the step bunch height does not increase infinitely as the bunch path on the crystal face rises, as is usually observed on large KDP crystals. The mechanism controlling the maximal bunch width and height is based on the drag of the solution depleted by the step bunch down thc solution stream. It includes splitting, coagulation and interlacing of bunches

The Effect of Forward-Facing Steps on Stationary Crossflow Instability Growth and Breakdown

NASA Technical Reports Server (NTRS)

Eppink, Jenna L.

2018-01-01

The e?ect of a forward-facing step on stationary cross?ow transition was studied using standard stereo particle image velocimetry (PIV) and time-resolved PIV. Step heights ranging from 53 to 71% of the boundary-layer thickness were studied in detail. The steps above a critical step height of approximately 60% of the boundary-layer thickness had a signi?cant impact on the stationary cross?ow growth downstream of the step. For the critical cases, the stationary cross?ow amplitude grew suddenly downstream of the step, decayed for a short region, then grew again. The adverse pressure gradient upstream of the step resulted in a region of cross?ow reversal. A secondary set of vortices, rotating in the opposite direction to the primary vortices, developed underneath the uplifted primary vortices. The wall-normal velocity disturbance (V' ) created by these secondary vortices impacted the step, and is believed to feed into the strong vortex that developed downstream of the step. A large but very short negative cross?ow region formed for a short region downstream of the step due to a sharp inboard curvature of the streamlines near the wall. For the larger step height cases, a cross?ow-reversal region formed just downstream of the strong negative cross?ow region. This cross?ow reversal region is believed to play an important role in the growth of the stationary cross?ow vortices downstream of the step, and may be a good indication of the critical forward-facing step height.

Specific problems in visual cognition of dyslexic readers: Face discrimination deficits predict dyslexia over and above discrimination of scrambled faces and novel objects.

PubMed

Sigurdardottir, Heida Maria; Fridriksdottir, Liv Elisabet; Gudjonsdottir, Sigridur; Kristjánsson, Árni

2018-06-01

Evidence of interdependencies of face and word processing mechanisms suggest possible links between reading problems and abnormal face processing. In two experiments we assessed such high-level visual deficits in people with a history of reading problems. Experiment 1 showed that people who were worse at face matching had greater reading problems. In experiment 2, matched dyslexic and typical readers were tested, and difficulties with face matching were consistently found to predict dyslexia over and above both novel-object matching as well as matching noise patterns that shared low-level visual properties with faces. Furthermore, ADHD measures could not account for face matching problems. We speculate that reading difficulties in dyslexia are partially caused by specific deficits in high-level visual processing, in particular for visual object categories such as faces and words with which people have extensive experience. Copyright © 2018 Elsevier B.V. All rights reserved.

Boggle Logic Puzzles: Minimal Solutions

ERIC Educational Resources Information Center

Needleman, Jonathan

2013-01-01

Boggle logic puzzles are based on the popular word game Boggle played backwards. Given a list of words, the problem is to recreate the board. We explore these puzzles on a 3 x 3 board and find the minimum number of three-letter words needed to create a puzzle with a unique solution. We conclude with a series of open questions.

Evaluation of Instructors and Students' Reaction to Undesired Classroom Behaviours from a Professional Perspective

ERIC Educational Resources Information Center

Pepe, Kadir; Bozkurt, Ibrahim

2011-01-01

Nowadays, it is seen that student behaviours that disturb the learning environment have come up as crucial problems in education and training applications and they set learning backward. This research aims to define the opinions of instructors and students on preventing the undesired classroom behaviours that disturb education and to evaluate…

A problem-solving routine for improving hospital operations.

PubMed

Ghosh, Manimay; Sobek Ii, Durward K

2015-01-01

The purpose of this paper is to examine empirically why a systematic problem-solving routine can play an important role in the process improvement efforts of hospitals. Data on 18 process improvement cases were collected through semi-structured interviews, reports and other documents, and artifacts associated with the cases. The data were analyzed using a grounded theory approach. Adherence to all the steps of the problem-solving routine correlated to greater degrees of improvement across the sample. Analysis resulted in two models. The first partially explains why hospital workers tended to enact short-term solutions when faced with process-related problems; and tended not seek longer-term solutions that prevent problems from recurring. The second model highlights a set of self-reinforcing behaviors that are more likely to address problem recurrence and result in sustained process improvement. The study was conducted in one hospital setting. Hospital managers can improve patient care and increase operational efficiency by adopting and diffusing problem-solving routines that embody three key characteristics. This paper offers new insights on why caregivers adopt short-term approaches to problem solving. Three characteristics of an effective problem-solving routine in a healthcare setting are proposed.

The Work Organization of Long-Haul Truck Drivers and the Association With Body Mass Index.

PubMed

Hege, Adam; Apostolopoulos, Yorghos; Perko, Mike; Sönmez, Sevil; Strack, Robert

2016-07-01

The aim of this study was to examine relationships between work organization features of work hours, work schedules, and job stress with body mass indexes (BMIs) of long-haul truck drivers. Face-to-face survey data were collected first, followed by collection of anthropometric measures including height and weight (n = 260). Logistic regression (backward stepwise model) was used to identify significant predictors of BMI and to analyze odds ratios. Mean BMI was 33.40 kg/m, with 64.2% obese (BMI > 30 kg/m) and 18.4% extreme/morbidly obese (BMI > 40 kg/m). Working more than 11 daily hours was associated with statistically significant increased odds for being extreme obese. Findings suggest that longer work hours (>11 hours daily) have a major influence on odds for obesity among this population. The results align with recent NIOSH calls for integrated approaches to worker health.

Local Approximation and Hierarchical Methods for Stochastic Optimization

NASA Astrophysics Data System (ADS)

Cheng, Bolong

In this thesis, we present local and hierarchical approximation methods for two classes of stochastic optimization problems: optimal learning and Markov decision processes. For the optimal learning problem class, we introduce a locally linear model with radial basis function for estimating the posterior mean of the unknown objective function. The method uses a compact representation of the function which avoids storing the entire history, as is typically required by nonparametric methods. We derive a knowledge gradient policy with the locally parametric model, which maximizes the expected value of information. We show the policy is asymptotically optimal in theory, and experimental works suggests that the method can reliably find the optimal solution on a range of test functions. For the Markov decision processes problem class, we are motivated by an application where we want to co-optimize a battery for multiple revenue, in particular energy arbitrage and frequency regulation. The nature of this problem requires the battery to make charging and discharging decisions at different time scales while accounting for the stochastic information such as load demand, electricity prices, and regulation signals. Computing the exact optimal policy becomes intractable due to the large state space and the number of time steps. We propose two methods to circumvent the computation bottleneck. First, we propose a nested MDP model that structure the co-optimization problem into smaller sub-problems with reduced state space. This new model allows us to understand how the battery behaves down to the two-second dynamics (that of the frequency regulation market). Second, we introduce a low-rank value function approximation for backward dynamic programming. This new method only requires computing the exact value function for a small subset of the state space and approximate the entire value function via low-rank matrix completion. We test these methods on historical price data from the PJM Interconnect and show that it outperforms the baseline approach used in the industry.

The design and implementation of an Interactive Computerised Decision Support Framework (ICDSF) as a strategy to improve nursing students' clinical reasoning skills.

PubMed

Hoffman, Kerry; Dempsey, Jennifer; Levett-Jones, Tracy; Noble, Danielle; Hickey, Noelene; Jeong, Sarah; Hunter, Sharyn; Norton, Carol

2011-08-01

This paper describes the conceptual design and testing of an Interactive Computerised Decision Support Framework (ICDSF) which was constructed to enable student nurses to "think like a nurse." The ICDSF was based on a model of clinical reasoning. Teaching student nurses to reason clinically is important as poor clinical reasoning skills can lead to "failure-to rescue" of deteriorating patients. The framework of the ICDSF was based on nursing concepts to encourage deep learning and transferability of knowledge. The principles of active student participation, situated cognition to solve problems, authenticity, and cognitive rehearsal were used to develop the ICDSF. The ICDSF was designed in such a way that students moved through it in a step-wise fashion and were required to achieve competency at each step before proceeding to the next. The quality of the ICDSF was evaluated using a questionairre survey, students' written comments and student assessment measures on a pilot and the ICDSF. Overall students were highly satisfied with the clinical scenarios of the ICDSF and believed they were an interesting and useful way to engage in authentic clinical learning. They also believed the ICDSF was useful in developing cognitive skills such as clinical reasoning, problem-solving and decision-making. Some reported issues were the need for good technical support and the lack of face to face contact when using e-learning. Some students also believed the ICDSF was less useful than actual clinical placements. Copyright © 2010 Elsevier Ltd. All rights reserved.

Who reports sexual function problems? Empirical evidence from Britain's 2000 National Survey of Sexual Attitudes and Lifestyles

PubMed Central

Mercer, C; Fenton, K; Johnson, A; Copas, A; Macdowall, W; Erens, B; Wellings, K

2005-01-01

Objective: To identify sociodemographic, sexual, and health behavioural and attitudinal factors associated with reporting sexual function problems. Methods: A probability sample survey of 11 161 men and women aged 16–44 years resident in Britain in 2000. Data collected by a combination of computer assisted face to face and self interviewing. Outcomes were self report of a range of sexual function problems, considered as "any problems" (1+ lasting 1+ months in the past year) and "persistent problems" (1+ lasting 6+ months in the past year), and associations with sociodemographic, behavioural, and attitudinal variables. Results: Both "any" and "persistent" sexual function problems were more commonly reported by women than men. A variety of sociodemographic factors were associated with both measures but differed by gender. For example, the adjusted odds ratio (AOR) for reporting any problems for married v single respondents was 0.70 (95% confidence interval (CI) 0.57 to 0.87) v 1.31 (95% CI 1.10 to 1.56) for men and women, respectively. Sexual behaviours significantly associated with reporting sexual function problems included competence at first sex, paying for sex in the past 5 years, number of occasions of sex and masturbation, both in the past 4 weeks. For men (only), reporting STI diagnosis(es) was significantly associated with reporting "any" problems (AOR 2.1, 95% CI 1.4 to 3.2) and "persistent" problems (AOR 2.1, 95% CI 1.1 to 3.9). Both measures were significantly more likely among men and women who reported communication difficulties with their partners, with AORs in excess of 1.9. Conclusions: Sexual fulfilment is an important part of sexual health. Understanding factors associated with reporting sexual problems, and recognising that such factors maybe partnership specific, is an important step towards improving our understanding of sexual function and thus improving the provision of care and support available. PMID:16199738

Cumulative childhood interpersonal trauma is associated with reduced cortical differentiation between threat and non-threat faces in posttraumatic stress disorder adults.

PubMed

Chu, Denise A; Bryant, Richard A; Gatt, Justine M; Harris, Anthony Wf

2018-03-01

Posttraumatic stress disorder and childhood trauma frequently co-occur. Both are associated with abnormal neural responses to salient emotion stimuli. As childhood trauma is a risk factor for posttraumatic stress disorder, differentiating between their neurophysiological effects is necessary to elucidate the neural pathways by which childhood trauma exposure contributes to increased posttraumatic stress disorder risks. Face-specific N170 evoked response potentials for backward-masked (non-conscious) and conscious threat (fear, angry) and non-threat (happy) faces were measured in 77 adults (18-64 years old, 64% women, 78% right-handed) symptomatic for posttraumatic stress disorder. Differences in N170 peak amplitudes for fear-versus-happy and angry-versus-happy faces at bilateral temporo-occipital (T5, T6) sites were computed. The effect of cumulative exposure to childhood interpersonal trauma, other childhood trauma, adult trauma, depression and posttraumatic stress disorder symptom severity on the N170 response was assessed using hierarchical multiple regression analyses. T5 N170 peak amplitudes for non-conscious fear-versus-happy faces were inversely related to cumulative childhood interpersonal trauma after accounting for socio-demographic, clinical symptom and other trauma factors. Posttraumatic stress disorder Avoidance was positively associated with N170 peak amplitudes for non-conscious fear-versus-happy faces, primarily due to reduced N170 responsivity to happy faces. Childhood interpersonal trauma exposure is associated with reduced discrimination between fear and happy faces, while avoidance symptom severity is associated with dampened responsivity to automatically processed happy faces in posttraumatic stress disorder adults. Results are discussed in terms of the likely contributions of impaired threat discrimination and deficient reward processing during neural processing of salient emotion stimuli, to increased risks of posttraumatic stress disorder onset and chronicity in childhood interpersonal trauma-exposed adults.

Aerodynamic losses calculation of a turbine blade with film cooling with forward and backward injection by numerical method

NASA Astrophysics Data System (ADS)

Prajapati, Anil

Thermal efficiency and power output of gas turbines can be increased by increasing the turbine blade inlet temperature. However, the main problem is the durability of the turbine blade due to the thermal stress on it at high temperature. This has led to the development of film cooling technology, in which coolant is injected from a series of cooling holes made on the blade surface to form an insulating blanket over the blade surface. However, it has to pay the aerodynamic penalties due to the injection of coolant, which are not fully understood. Pressure loss coefficient is one of the easy and widely used parameters to determine the aerodynamic loss occurred on a turbine blade. The losses occurred on the turbine blade with forward injection and backward injection cooling are studied at a different blowing ratios by a numerical simulation, which shows that the loss is higher in the case of backward injection than in forward injection. Fan-shaped cooling holes are also considered to compare with the cylindrical holes. It is observed that the loss is increased due to the fan-shaped holes in the forward injection whereas there is not a substantial difference due to the fan-shaped holes in the backward injection. The aerodynamic loss due to the location of coolant injection is studied by using injection from the leading edge, pressure side, suction side and trailing edge respectively. The study is performed to determine the effect of incidence angles and coolant injection angles on the aerodynamic loss.

Improving Causal Inferences in Meta-analyses of Longitudinal Studies: Spanking as an Illustration.

PubMed

Larzelere, Robert E; Gunnoe, Marjorie Lindner; Ferguson, Christopher J

2018-05-24

To evaluate and improve the validity of causal inferences from meta-analyses of longitudinal studies, two adjustments for Time-1 outcome scores and a temporally backwards test are demonstrated. Causal inferences would be supported by robust results across both adjustment methods, distinct from results run backwards. A systematic strategy for evaluating potential confounds is also introduced. The methods are illustrated by assessing the impact of spanking on subsequent externalizing problems (child age: 18 months to 11 years). Significant results indicated a small risk or a small benefit of spanking, depending on the adjustment method. These meta-analytic methods are applicable for research on alternatives to spanking and other developmental science topics. The underlying principles can also improve causal inferences in individual studies. © 2018 Society for Research in Child Development.

Fractal analyses reveal independent complexity and predictability of gait

PubMed Central

Dierick, Frédéric; Nivard, Anne-Laure

2017-01-01

Locomotion is a natural task that has been assessed for decades and used as a proxy to highlight impairments of various origins. So far, most studies adopted classical linear analyses of spatio-temporal gait parameters. Here, we use more advanced, yet not less practical, non-linear techniques to analyse gait time series of healthy subjects. We aimed at finding more sensitive indexes related to spatio-temporal gait parameters than those previously used, with the hope to better identify abnormal locomotion. We analysed large-scale stride interval time series and mean step width in 34 participants while altering walking direction (forward vs. backward walking) and with or without galvanic vestibular stimulation. The Hurst exponent α and the Minkowski fractal dimension D were computed and interpreted as indexes expressing predictability and complexity of stride interval time series, respectively. These holistic indexes can easily be interpreted in the framework of optimal movement complexity. We show that α and D accurately capture stride interval changes in function of the experimental condition. Walking forward exhibited maximal complexity (D) and hence, adaptability. In contrast, walking backward and/or stimulation of the vestibular system decreased D. Furthermore, walking backward increased predictability (α) through a more stereotyped pattern of the stride interval and galvanic vestibular stimulation reduced predictability. The present study demonstrates the complementary power of the Hurst exponent and the fractal dimension to improve walking classification. Our developments may have immediate applications in rehabilitation, diagnosis, and classification procedures. PMID:29182659

Linear system identification via backward-time observer models

NASA Technical Reports Server (NTRS)

Juang, Jer-Nan; Phan, Minh Q.

1992-01-01

Presented here is an algorithm to compute the Markov parameters of a backward-time observer for a backward-time model from experimental input and output data. The backward-time observer Markov parameters are decomposed to obtain the backward-time system Markov parameters (backward-time pulse response samples) for the backward-time system identification. The identified backward-time system Markov parameters are used in the Eigensystem Realization Algorithm to identify a backward-time state-space model, which can be easily converted to the usual forward-time representation. If one reverses time in the model to be identified, what were damped true system modes become modes with negative damping, growing as the reversed time increases. On the other hand, the noise modes in the identification still maintain the property that they are stable. The shift from positive damping to negative damping of the true system modes allows one to distinguish these modes from noise modes. Experimental results are given to illustrate when and to what extent this concept works.

Quantum Physics, Fields and Closed Timelike Curves: The D-CTC Condition in Quantum Field Theory

NASA Astrophysics Data System (ADS)

Tolksdorf, Jürgen; Verch, Rainer

2018-01-01

The D-CTC condition has originally been proposed by David Deutsch as a condition on states of a quantum communication network that contains "backward time-steps" in some of its branches. It has been argued that this is an analogue for quantum processes in the presence of closed timelike curves (CTCs). The unusual properties of states of quantum communication networks that fulfill the D-CTC condition have been discussed extensively in recent literature. In this work, the D-CTC condition is investigated in the framework of quantum field theory in the local, operator-algebraic approach due to Haag and Kastler. It is shown that the D-CTC condition cannot be fulfilled in states that are analytic in the energy, or satisfy the Reeh-Schlieder property, for a certain class of processes and initial conditions. On the other hand, if a quantum field theory admits sufficiently many uncorrelated states across acausally related spacetime regions (as implied by the split property), then the D-CTC condition can always be fulfilled approximately to arbitrary precision. As this result pertains to quantum field theory on globally hyperbolic spacetimes where CTCs are absent, one may conclude that interpreting the D-CTC condition as characteristic for quantum processes in the presence of CTCs could be misleading, and should be regarded with caution. Furthermore, a construction of the quantized massless Klein-Gordon field on the Politzer spacetime, often viewed as spacetime analogue for quantum communication networks with backward time-steps, is proposed in this work.

Exemplar-Based Image Inpainting Using a Modified Priority Definition.

PubMed

Deng, Liang-Jian; Huang, Ting-Zhu; Zhao, Xi-Le

2015-01-01

Exemplar-based algorithms are a popular technique for image inpainting. They mainly have two important phases: deciding the filling-in order and selecting good exemplars. Traditional exemplar-based algorithms are to search suitable patches from source regions to fill in the missing parts, but they have to face a problem: improper selection of exemplars. To improve the problem, we introduce an independent strategy through investigating the process of patches propagation in this paper. We first define a new separated priority definition to propagate geometry and then synthesize image textures, aiming to well recover image geometry and textures. In addition, an automatic algorithm is designed to estimate steps for the new separated priority definition. Comparing with some competitive approaches, the new priority definition can recover image geometry and textures well.

Past, present and future of spike sorting techniques.

PubMed

Rey, Hernan Gonzalo; Pedreira, Carlos; Quian Quiroga, Rodrigo

2015-10-01

Spike sorting is a crucial step to extract information from extracellular recordings. With new recording opportunities provided by the development of new electrodes that allow monitoring hundreds of neurons simultaneously, the scenario for the new generation of algorithms is both exciting and challenging. However, this will require a new approach to the problem and the development of a common reference framework to quickly assess the performance of new algorithms. In this work, we review the basic concepts of spike sorting, including the requirements for different applications, together with the problems faced by presently available algorithms. We conclude by proposing a roadmap stressing the crucial points to be addressed to support the neuroscientific research of the near future. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.