Transfer of Podokinetic Adaptation From Stepping to Hopping

2002 ◽  
Vol 87 (2) ◽  
pp. 1142-1144 ◽  
Author(s):  
Gammon M. Earhart ◽  
G. Melvill Jones ◽  
F. B. Horak ◽  
E. W. Block ◽  
K. D. Weber ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Rotating Disk ◽  
Backward Walking ◽  
Velocity Amplitude ◽  
Straight Line ◽  
Time Courses ◽  
Stepping In Place

Following stepping in-place on the surface of a rotating circular treadmill, a subject attempting to step in-place or walk in a straight line across the floor without vision will rotate relative to space. This adaptation, termed podokinetic after-rotation (PKAR), transfers to backward walking following forward walking on the rotating disk. We asked whether adaptation obtained during stepping in-place on the rotating disk would transfer to hopping on both feet. We hypothesized that subjects would demonstrate PKAR during both hopping and stepping, adding support to the hypothesis that PKAR is a centrally mediated adaptation of general locomotor trajectory that is not specific to the form of locomotion used while on the rotating disk. Subjects demonstrated PKAR during both hopping and stepping after stepping in-place on the rotating disk. The time courses of PKAR during hopping and stepping were similar, although the angular velocity amplitude of PKAR was lower in hopping than in stepping. This difference in amplitude suggests an incomplete transfer of PKAR.

scholarly journals Grip and limb force limits to turning performance in competition horses

2010 ◽  
Vol 278 (1715) ◽  
pp. 2105-2111 ◽  
Author(s):  
Huiling Tan ◽  
Alan M. Wilson
Keyword(s):  
Angular Velocity ◽  
High Speed ◽  
Small Radius ◽  
Maximum Speed ◽  
Large Radius ◽  
Centripetal Acceleration ◽  
Straight Line ◽  
Prey Interaction ◽  
The Coefficient Of Friction ◽  
Stride Parameters

Manoeuverability is a key requirement for successful terrestrial locomotion, especially on variable terrain, and is a deciding factor in predator–prey interaction. Compared with straight-line running, bend running requires additional leg force to generate centripetal acceleration. In humans, this results in a reduction in maximum speed during bend running and a published model assuming maximum limb force as a constraint accurately predicts how much a sprinter must slow down on a bend given his maximum straight-line speed. In contrast, greyhounds do not slow down or change stride parameters during bend running, which suggests that their limbs can apply the additional force for this manoeuvre. We collected horizontal speed and angular velocity of heading of horses while they turned in different scenarios during competitive polo and horse racing. The data were used to evaluate the limits of turning performance. During high-speed turns of large radius horizontal speed was lower on the bend, as would be predicted from a model assuming a limb force limit to running speed. During small radius turns the angular velocity of heading decreased with increasing speed in a manner consistent with the coefficient of friction of the hoof–surface interaction setting the limit to centripetal force to avoid slipping.

A Study on Dimension Synthesis for the Peaucellier Mechanism

2011 ◽  
Author(s):  
Jessica Buckley ◽  
Ming Z. Huang
Keyword(s):  
Angular Velocity ◽  
Velocity Profile ◽  
Kinematic Analysis ◽  
Assembly Line ◽  
Oil Wells ◽  
Straight Line ◽  
Correct Ratio ◽  
The Creation

Straight-line motion, albeit simple, manifest itself in numerous applications, from running steam engines and oil wells to manufacturing parts with straight edges and sides. The drive to maximize production creates a need for continuously running assembly-line manufacturing comprised of precise, individually optimized components. While there are many so-called straight-line generating mechanisms, few actually produce a true straight-line, most generate only approximate straight-line. Featured an eight-link rhomboidal system with length constraints, the Peaucellier mechanism is one that actually produces a true straight line intrinsically. This paper presents a study on the dimension synthesis of the Peaucellier mechanism, namely by identifying the correct ratio of linkage lengths to produce the longest straight line stroke. In addition to designing for stroke, another objective of interest is to attain a desired velocity profile along the path. Kinematic analysis of the velocity profile on the mechanism will render the creation of input angular velocity standards based on desired stroke speed. Given the stroke and velocity specifications, specific steps to size the dimensions of the mechanism developed as result of this study will be presented.

Podokinetic After-Rotation Following Unilateral and Bilateral Podokinetic Stimulation

2002 ◽  
Vol 87 (2) ◽  
pp. 1138-1141 ◽  
Author(s):  
Gammon M. Earhart ◽  
G. Melvill Jones ◽  
F. B. Horak ◽  
E. W. Block ◽  
K. D. Weber ◽  
...  
Keyword(s):  
Angular Velocity ◽  
Rotating Disk ◽  
Bilateral Stimulation ◽  
Pelvic Rotation ◽  
Eyes Closed ◽  
Stationary Surface ◽  
Unilateral Stimulation ◽  
Left And Right ◽  
Lift Off ◽  
Single Limb Support

Previous studies demonstrated an aftereffect of walking on a rotating treadmill, involving inadvertent circular navigation with eyes closed [podokinetic after-rotation (PKAR)]. We compared PKAR following unilateral and bilateral podokinetic (PK) stimulation to determine whether the left and right legs could be independently adapted. Each subject performed two sessions of PK stimulation, stepping in place with one foot on either side of the axis of a rotating disk. Subjects experienced bilateral stimulation (i.e., both left and right feet stepped on the rotating disk) in one session and unilateral stimulation (i.e., the left foot stepped on the rotating disk and the right foot stepped on a stationary surface) in the other. Following stimulation, we recorded foot lift-off and touchdown times and pelvic angular velocity while subjects stepped in place on a stationary surface. PKAR velocity following unilateral stimulation was lower than that following bilateral stimulation. Following bilateral stimulation, pelvic rotation was in the counterclockwise (CCW) direction during single-limb support on both the left and right sides. Immediately following left unilateral stimulation, subjects demonstrated CCW pelvic rotation during left single-limb support but not during right single-limb support. Across the first 13 strides, the difference between left and right sides diminished; pelvic angular velocity was then CCW during single-limb support on both sides. This suggests that both the adapted left and the unadapted right limb influenced the final PKAR response with information from the two limbs being integrated over the first few strides.

Flow Structure Transition inside Contra-Rotating Disk Cavity

2014 ◽  
Vol 602-605 ◽  
pp. 353-356
Author(s):  
Shu Xian Chen ◽  
Xue Jie Shi ◽  
Xiao Ming Tan
Keyword(s):  
Angular Velocity ◽  
Finite Volume Method ◽  
Stagnation Point ◽  
Flow Structure ◽  
Velocity Ratio ◽  
Flow Region ◽  
Rotating Disk ◽  
Structure Transition ◽  
Type Flow ◽  
Volume Method

The turbulent flow inside contra-rotating disk cavity was numerically studied based on the finite volume method. The flow structure and its transition characteristics inside a contra-rotating were studied. The flow structure varies with the angular velocity ratio Γ of the slower disk to that of the faster one. For Γ=-1, the Stewartson-type flow occurs throughout the domain. For Γ=0, the Batchelor-type flow occurs throughout the flow region. The stagnation streamlines originating from the stagnation point are formed for-1<Γ<0, and batchelor-type flow occurs radially outward of the stagnation point with Stewartson-type flow radially inward. The stagnation point moves radially outward as Γ is reduced.

Solitons and breather waves for a (2+1)-dimensional Sawada–Kotera equation

2017 ◽  
Vol 31 (22) ◽  
pp. 1750129 ◽  
Author(s):  
Shu-Liang Jia ◽  
Yi-Tian Gao ◽  
Wen-Qiang Hu ◽  
Jing-Jing Su ◽  
Gao-Fu Deng
Keyword(s):  
Soliton Solutions ◽  
Analytic Solutions ◽  
The Other ◽  
Bell Polynomials ◽  
Bilinear Forms ◽  
Ansatz Method ◽  
Velocity Amplitude ◽  
Straight Line ◽  
Time Periodic

Under investigation in this letter is a (2[Formula: see text]+[Formula: see text]1)-dimensional Sawada-Kotera equation. With the aid of the bilinear forms derived from the Bell polynomials, the Nth-order soliton solutions are obtained via the Pffafian method, and breather solutions are derived with the ansätz method. Analytic solutions obtained via the Pffafian method are the bell-type solitons. Two different kinds of the homoclinic breathers are seen, one of which is real and the other of which is complex, with two breathers interacting with each other. Homoclinic breather wave can evolve periodically along a straight line with a certain angle with the x axis and y axis, and its velocity, amplitude and width remain unchanged during the propagation. Homoclinic breather wave is not only space-periodic but also time-periodic. Interaction between the two breathers is elastic, which is similar to that of the solitons.

Large Deformation and Discontinuous Yield Analysis of Rotating Disks by Abaqus Softwares

2011 ◽  
Vol 48-49 ◽  
pp. 656-659
Author(s):  
Shao Wei Hu
Keyword(s):  
Angular Velocity ◽  
Large Deformation ◽  
Structural Design ◽  
Rotating Disk ◽  
Plastic State ◽  
Structural Elements ◽  
Rotating Disks ◽  
Rotating Disc ◽  
Yield Analysis ◽  
Rotating Discs

Rotating discs are used widely as important structural elements in mechanical engineering. In order to obtain an optimal structural design, it is necessary to estimate the angular velocity and the stress distribution of a rotating disc in fully plastic state. So Large deformation and discontinuous yield analysis of rotating disks were analyzed by ABAQUS. Moreover, continuous yield, buckling and bifurcation analysis of rotating disk with discontinuous yield were studied. Then, Minidisk model is analyzed using ABAQUS.

The existence of axially symmetric flow above a rotating disk

1971 ◽  
Vol 324 (1559) ◽  
pp. 391-414 ◽  
Keyword(s):  
Fixed Point ◽  
Angular Velocity ◽  
Boundary Value Problem ◽  
Boundary Conditions ◽  
Existence Of Solutions ◽  
Rotating Disk ◽  
Fixed Point Method ◽  
Axially Symmetric ◽  
Symmetric Flow ◽  
Shooting Technique

The paper studies the boundary-value problem arising from the behaviour of a fluid occupying the half space x > 0 above a rotating disk which is coincident with the plane x = 0 and rotates about its axis which remains fixed. The equations which describe axially symmetric solutions of this problem are f ''' + ff ''+½( g 2 – f ' 2 ) = ½ Ω 2 ∞ , g "+ fg ' = f ' g , with the boundary conditions f (0) = a , f '(0) = 0, g (0) = Ω 0 ); f '(∞) = 0, g (∞) = Ω ∞ , where a is a constant measuring possible suction at the disk, Ω 0 is the angular velocity of the disk, and Ω ∞ is an angular velocity to which the fluid is subjected at infinity. When Ω ∞ = 0, existence of solutions has previously been proved by the ‘shooting technique’. This method breaks down when Ω 0 ǂ 0 because of oscillations in the functions f and g , but in the present paper existence is first proved by a fixed point method when Ω 0 is close to Ω ∞ and then extended for all Ω 0 , with the important restriction that Ω 0 and Ω ∞ be of the same sign.

scholarly journals The highly obscured Seyfert 2 nucleus in NGC 1448 observed with MUSE

2021 ◽  
Author(s):  
R B Menezes ◽  
Patrícia da Silva ◽  
J E Steiner
Keyword(s):  
Rotating Disk ◽  
Interstellar Extinction ◽  
Seyfert Galaxies ◽  
Position Angle ◽  
Data Cube ◽  
Optical Data ◽  
Velocity Amplitude ◽  
Additional Hypothesis ◽  
The Past ◽  
The Galaxy

Abstract We present the analysis of an optical data cube of the central region of NGC 1448, obtained with MUSE. Chandra X-ray data indicate that the AGN is not located at the apparent stellar nucleus of the galaxy, but at a projected distance of 1.75 ± 0.22 arcsec (139 ± 17 pc). This is probably caused by the high interstellar extinction in the surroundings of the AGN, which corresponds to the true nucleus of the galaxy, as also proposed by previous studies. The morphology and classification of the optical line-emitting regions indicate two ionisation cones, around an axis with a position angle of PAcones = −50○ ± 7○, with emission-line spectra characteristic of Seyfert galaxies. The stellar and gas kinematics are consistent with a stellar and gas rotating disk around the nucleus, with a velocity amplitude of 125 km s−1. Two probable outflows from the AGN were detected along the region of the two ionisation cones. The AGN position does not coincide with the brightest line-emitting region at the centre of NGC 1448. That may be a consequence of the high obscuration from the AGN towards the observer (the AGN is actually Compton-thick), mostly caused by a nearly edge-on torus. An additional hypothesis is that the AGN reduced its luminosity, during the last 440 yrs, to nearly half of the value in the past. In this case, the brightest line-emitting region corresponds to a ‘light echo’ or a ‘fossil’ of the AGN in the past.

scholarly journals Podokinetic After-Rotation Is Transiently Enhanced or Reversed by Unilateral Axial Muscle Proprioceptive Stimulation

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Stefania Sozzi ◽  
Antonio Nardone ◽  
Oscar Crisafulli ◽  
Marco Schieppati
Keyword(s):  
Angular Velocity ◽  
Rotation Velocity ◽  
Whole Body ◽  
Common Mechanism ◽  
Muscle Vibration ◽  
Body Rotation ◽  
Lumbar Level ◽  
Axial Muscle ◽  
Paravertebral Muscles ◽  
Stepping In Place

Unilateral axial muscle vibration, eliciting a proprioceptive volley, is known to incite steering behavior. Whole-body rotation while stepping in place also occurs as an after-effect of stepping on a circular treadmill (podokinetic after-rotation, PKAR). Here, we tested the hypothesis that PKAR is modulated by axial muscle vibration. If both phenomena operate through a common pathway, enhancement or cancellation of body rotation would occur depending on the stimulated side when vibration is administered concurrently with PKAR. Seventeen subjects participated in the study. In one session, subjects stepped in place eyes open on the center of a platform that rotated counterclockwise 60°/s for 10 min. When the platform stopped, subjects continued stepping in place blindfolded. In other session, a vibratory stimulus (100 Hz, 2 min) was administered to right or left paravertebral muscles at lumbar level at two intervals during the PKAR. We computed angular body velocity and foot step angles from markers fixed to shoulders and feet. During PKAR, all subjects rotated clockwise. Decreased angular velocity was induced by right vibration. Conversely, when vibration was administered to the left, clockwise rotation velocity increased. The combined effect on body rotation depended on the time at which vibration was administered during PKAR. Under all conditions, foot step angle was coherent with shoulder angular velocity. PKAR results from continuous asymmetric input from the muscles producing leg rotation, while axial muscle vibration elicits a proprioceptive asymmetric input. Both conditioning procedures appear to produce their effects through a common mechanism. We suggest that both stimulations would affect our straight ahead by combining their effects in an algebraic mode.

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