Correlations between Angular Velocities in Selected Joints and Velocity of Table Tennis Racket during Topspin Forehand and Backhand.

PubMed

Bańkosz, Ziemowit; Winiarski, Sławomir

2018-06-01

The aim of this study was to determine the correlations between angular velocities in individual joints and racket velocity for different topspin forehand and backhand strokes in table tennis. Ten elite female table tennis players participated, presenting different kinds of topspin forehands and backhands - after a no-spin ball (FH1, BH1), after a backspin ball (FH2, BH2) and "heavy" topspin (FH3, BH3). Range of motion was measured with the BTS Smart-E (BTS Bioengineering, Milan, Italy) motion analysis system with a specially developed marker placement protocol for the upper body parts and an acoustic sensor attached to the racket to identify ball-racket contact. In forehand strokes angular velocities of internal arm rotation and adduction in shoulder joint correlated with racket velocity. Racket velocity was correlated with angular velocities (hip extension on the playing side; hip flexion on the opposite side; ankle flexion) in the case of a topspin forehand performed with maximal force -"heavy" topspin (FH3). In backhand strokes the velocities of arm abduction and shoulder girdle rotation towards the playing side correlated with racket velocity. The angular velocity of internal arm rotation and adduction in shoulder joint may be important components of a coordinated stroke, whilst angular velocity can substantially affect the racket speed when one is changing the type of stroke.

VizieR Online Data Catalog: 22-GHz water maser clouds (Richards+, 2012)

NASA Astrophysics Data System (ADS)

Richards, A. M. S.; Etoka, S.; Gray, M. D.; Lekht, E. E.; Mendoza-Torres, J. E.; Murakawa, K.; Rudnitskij, G.; Yates, J. A.

2012-07-01

Measurements of 22-GHz water maser clouds, made with the MERLIN radio interferometer. Obects presented (number of epochs): S Per (2); U Ori (4); U Her (3); IK Tau (3); RT Vir (7); W Hya (4). Results for VX Sgr were presented in Murakawa et al, 2003, Cat. J/MNRAS/344/1. The position and other properties of each patch of maser emission in each channel were measured by fitting 2D Gaussian components. The components form features corresponding to spatially distinct clouds and the properties of each cloud was calculated as described in the paper. For each cloud, we give the mean Vlsr, the total velocity extent DV, the full width half maximum DV1/2, the offsets of the cloud centroid from the assumed stellar position x, y and a (=sqrt(x2+y2), the feature largest angular size l and the peak flux density I. All velocities, angular distances and flux densities are in km/s, mas and Jy, respectively. (2 data files).

Internal Energy Dependence of Molecular Condensation Coefficients Determined from Molecular Beam Surface Scattering Experiments

DOE R&D Accomplishments Database

Sibener, S. J.; Lee, Y. T.

1978-05-01

An experiment was performed which confirms the existence of an internal mode dependence of molecular sticking probabilities for collisions of molecules with a cold surface. The scattering of a velocity selected effusive beam of CCl{sub 4} from a 90 K CC1{sub 4} ice surface has been studied at five translational velocities and for two different internal temperatures. At a surface temperature of 90 K (approx. 99% sticking probability) a four fold increase in reflected intensity was observed for the internally excited (560 K) CC1{sub 4} relative to the room temperature (298 K) CC1{sub 4} at a translational velocity of 2.5 X 10{sup 4} cm/sec. For a surface temperature of 90 K all angular distributions were found to peak 15{sup 0} superspecularly independent of incident velocity.

Texture in steel plates revealed by laser ultrasonic surface acoustic waves velocity dispersion analysis.

PubMed

Yin, Anmin; Wang, Xiaochen; Glorieux, Christ; Yang, Quan; Dong, Feng; He, Fei; Wang, Yanlong; Sermeus, Jan; Van der Donck, Tom; Shu, Xuedao

2017-07-01

A photoacoustic, laser ultrasonics based approach in an Impulsive Stimulated Scattering (ISS) implementation was used to investigate the texture in polycrystalline metal plates. The angular dependence of the 'polycrystalline' surface acoustic wave (SAW) velocity measured along regions containing many grains was experimentally determined and compared with simulated results that were based on the angular dependence of the 'single grain' SAW velocity within single grains and the grain orientation distribution. The polycrystalline SAW velocities turn out to vary with texture. The SAW velocities and their angular variations for {110} texture were found to be larger than that the ones for {111} texture or the strong γ fiber texture. The SAW velocities for {001} texture were larger than for {111} texture, but with almost the same angular dependence. The results infer the feasibility to apply angular SAW angular dispersion measurements by laser ultrasonics for on-line texture monitoring. Copyright © 2017 Elsevier B.V. All rights reserved.

Task Space Angular Velocity Blending for Real-Time Trajectory Generation

NASA Technical Reports Server (NTRS)

Volpe, Richard A. (Inventor)

1997-01-01

The invention is embodied in a method of controlling a robot manipulator moving toward a target frame F(sub 0) with a target velocity v(sub 0) including a linear target velocity v and an angular target velocity omega(sub 0) to smoothly and continuously divert the robot manipulator to a subsequent frame F(sub 1) by determining a global transition velocity v(sub 1), the global transition velocity including a linear transition velocity v(sub 1) and an angular transition velocity omega(sub 1), defining a blend time interval 2(tau)(sub 0) within which the global velocity of the robot manipulator is to be changed from a global target velocity v(sub 0) to the global transition velocity v(sub 1) and dividing the blend time interval 2(tau)(sub 0) into discrete time segments (delta)t. During each one of the discrete time segments delta t of the blend interval 2(tau)(sub 0), a blended global velocity v of the manipulator is computed as a blend of the global target velocity v(sub 0) and the global transition velocity v(sub 1), the blended global velocity v including a blended angular velocity omega and a blended linear velocity v, and then, the manipulator is rotated by an incremental rotation corresponding to an integration of the blended angular velocity omega over one discrete time segment (delta)t.

Angular velocity discrimination

NASA Technical Reports Server (NTRS)

Kaiser, Mary K.

1990-01-01

Three experiments designed to investigate the ability of naive observers to discriminate rotational velocities of two simultaneously viewed objects are described. Rotations are constrained to occur about the x and y axes, resulting in linear two-dimensional image trajectories. The results indicate that observers can discriminate angular velocities with a competence near that for linear velocities. However, perceived angular rate is influenced by structural aspects of the stimuli.

Interdependence of torque, joint angle, angular velocity and muscle action during human multi-joint leg extension.

PubMed

Hahn, Daniel; Herzog, Walter; Schwirtz, Ansgar

2014-08-01

Force and torque production of human muscles depends upon their lengths and contraction velocity. However, these factors are widely assumed to be independent of each other and the few studies that dealt with interactions of torque, angle and angular velocity are based on isolated single-joint movements. Thus, the purpose of this study was to determine force/torque-angle and force/torque-angular velocity properties for multi-joint leg extensions. Human leg extension was investigated (n = 18) on a motor-driven leg press dynamometer while measuring external reaction forces at the feet. Extensor torque in the knee joint was calculated using inverse dynamics. Isometric contractions were performed at eight joint angle configurations of the lower limb corresponding to increments of 10° at the knee from 30 to 100° of knee flexion. Concentric and eccentric contractions were performed over the same range of motion at mean angular velocities of the knee from 30 to 240° s(-1). For contractions of increasing velocity, optimum knee angle shifted from 52 ± 7 to 64 ± 4° knee flexion. Furthermore, the curvature of the concentric force/torque-angular velocity relations varied with joint angles and maximum angular velocities increased from 866 ± 79 to 1,238 ± 132° s(-1) for 90-50° knee flexion. Normalised eccentric forces/torques ranged from 0.85 ± 0.12 to 1.32 ± 0.16 of their isometric reference, only showing significant increases above isometric and an effect of angular velocity for joint angles greater than optimum knee angle. The findings reveal that force/torque production during multi-joint leg extension depends on the combined effects of angle and angular velocity. This finding should be accounted for in modelling and optimisation of human movement.

Study of the mode of angular velocity damping for a spacecraft at non-standard situation

NASA Astrophysics Data System (ADS)

Davydov, A. A.; Sazonov, V. V.

2012-07-01

Non-standard situation on a spacecraft (Earth's satellite) is considered, when there are no measurements of the spacecraft's angular velocity component relative to one of its body axes. Angular velocity measurements are used in controlling spacecraft's attitude motion by means of flywheels. The arising problem is to study the operation of standard control algorithms in the absence of some necessary measurements. In this work this problem is solved for the algorithm ensuring the damping of spacecraft's angular velocity. Such a damping is shown to be possible not for all initial conditions of motion. In the general case one of two possible final modes is realized, each described by stable steady-state solutions of the equations of motion. In one of them, the spacecraft's angular velocity component relative to the axis, for which the measurements are absent, is nonzero. The estimates of the regions of attraction are obtained for these steady-state solutions by numerical calculations. A simple technique is suggested that allows one to eliminate the initial conditions of the angular velocity damping mode from the attraction region of an undesirable solution. Several realizations of this mode that have taken place are reconstructed. This reconstruction was carried out using approximations of telemetry values of the angular velocity components and the total angular momentum of flywheels, obtained at the non-standard situation, by solutions of the equations of spacecraft's rotational motion.

Plantar-flexor Static Stretch Training Effect on Eccentric and Concentric Peak Torque – A comparative Study of Trained versus Untrained Subjects

PubMed Central

Abdel-aziem, Amr Almaz; Mohammad, Walaa Sayed

2012-01-01

The aim of this study was to examine the long-term effects of static stretching of the plantar-flexor muscles on eccentric and concentric torque and ankle dorsiflexion range of motion in healthy subjects. Seventy five healthy male volunteers, with no previous history of trauma to the calf that required surgery, absence of knee flexion contracture and no history of neurologic dysfunction or disease, systemic disease affecting the lower extremities were selected for this study. The participants were divided into three equal groups. The control group did not stretch the plantar-flexor muscles. Two Experimental groups (trained and untrained) were instructed to perform static stretching exercise of 30 second duration and 5 repetitions twice daily. The stretching sessions were carried out 5 days a week for 6 weeks. The dorsiflexion range of motion was measured in all subjects. Also measured was the eccentric and concentric torque of plantar-flexors at angular velocities of 30 and 120°/s pre and post stretching. Analysis of variance showed a significant increase in plantar-flexor eccentric and concentric torque (p < 0.05) of trained and untrained groups, and an increase in dorsiflexion range of motion (p < 0.05) at both angular velocities for the untrained group only. The static stretching program of plantar-flexors was effective in increasing the concentric and eccentric plantarflexion torque at angular velocities of 30 and 120°/s. Increases in plantar-flexors flexibility were observed in untrained subjects. PMID:23486840

A methodologic approach for normalizing angular work and velocity during isotonic and isokinetic eccentric training.

PubMed

Guilhem, Gaël; Cornu, Christophe; Guével, Arnaud

2012-01-01

Resistance exercise training commonly is performed against a constant external load (isotonic) or at a constant velocity (isokinetic). Researchers comparing the effectiveness of isotonic and isokinetic resistance-training protocols need to equalize the mechanical stimulus (work and velocity) applied. To examine whether the standardization protocol could be adjusted and applied to an eccentric training program. Controlled laboratory study. Controlled research laboratory. Twenty-one sport science male students (age = 20.6 ± 1.5 years, height = 178.0 ± 4.0 cm, mass = 74.5 ± 9.1 kg). Participants performed 9 weeks of isotonic (n = 11) or isokinetic (n = 10) eccentric training of knee extensors that was designed so they would perform the same amount of angular work at the same mean angular velocity. Angular work and angular velocity. The isotonic and isokinetic groups performed the same total amount of work (-185.2 ± 6.5 kJ and -184.4 ± 8.6 kJ, respectively) at the same angular velocity (21 ± 1°/s and 22°/s, respectively) with the same number of repetitions (8.0 and 8.0, respectively). Bland-Altman analysis showed that work (bias = 2.4%) and angular velocity (bias = 0.2%) were equalized over 9 weeks between the modes of training. The procedure developed allows angular work and velocity to be standardized over 9 weeks of isotonic and isokinetic eccentric training of the knee extensors. This method could be useful in future studies in which researchers compare neuromuscular adaptations induced by each type of training mode with respect to rehabilitating patients after musculoskeletal injury.

SDSS-IV MaNGA: stellar angular momentum of about 2300 galaxies: unveiling the bimodality of massive galaxy properties

NASA Astrophysics Data System (ADS)

Graham, Mark T.; Cappellari, Michele; Li, Hongyu; Mao, Shude; Bershady, Matthew A.; Bizyaev, Dmitry; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Drory, Niv; Law, David R.; Pan, Kaike; Thomas, Daniel; Wake, David A.; Weijmans, Anne-Marie; Westfall, Kyle B.; Yan, Renbin

2018-07-01

We measure λ _{R_e}, a proxy for galaxy specific stellar angular momentum within one effective radius, and the ellipticity, ɛ, for about 2300 galaxies of all morphological types observed with integral field spectroscopy as part of the Mapping Nearby Galaxies at Apache Point Observatory survey, the largest such sample to date. We use the (λ _{R_e}, ɛ ) diagram to separate early-type galaxies into fast and slow rotators. We also visually classify each galaxy according to its optical morphology and two-dimensional stellar velocity field. Comparing these classifications to quantitative λ _{R_e} measurements reveals tight relationships between angular momentum and galaxy structure. In order to account for atmospheric seeing, we use realistic models of galaxy kinematics to derive a general approximate analytic correction for λ _{R_e}. Thanks to the size of the sample and the large number of massive galaxies, we unambiguously detect a clear bimodality in the (λ _{R_e}, ɛ ) diagram which may result from fundamental differences in galaxy assembly history. There is a sharp secondary density peak inside the region of the diagram with low λ _{R_e} and ɛ < 0.4, previously suggested as the definition for slow rotators. Most of these galaxies are visually classified as non-regular rotators and have high velocity dispersion. The intrinsic bimodality must be stronger, as it tends to be smoothed by noise and inclination. The large sample of slow rotators allows us for the first time to unveil a secondary peak at ±90° in their distribution of the misalignments between the photometric and kinematic position angles. We confirm that genuine slow rotators start appearing above M ≥ 2 × 1011 M⊙ where a significant number of high-mass fast rotators also exist.

SDSS-IV MaNGA: Stellar angular momentum of about 2300 galaxies: unveiling the bimodality of massive galaxy properties

NASA Astrophysics Data System (ADS)

Graham, Mark T.; Cappellari, Michele; Li, Hongyu; Mao, Shude; Bershady, Matthew; Bizyaev, Dmitry; Brinkmann, Jonathan; Brownstein, Joel R.; Bundy, Kevin; Drory, Niv; Law, David R.; Pan, Kaike; Thomas, Daniel; Wake, David A.; Weijmans, Anne-Marie; Westfall, Kyle B.; Yan, Renbin

2018-03-01

We measure λ _{R_e}, a proxy for galaxy specific stellar angular momentum within one effective radius, and the ellipticity, ɛ, for about 2300 galaxies of all morphological types observed with integral field spectroscopy as part of the MaNGA survey, the largest such sample to date. We use the (λ _{R_e}, ɛ ) diagram to separate early-type galaxies into fast and slow rotators. We also visually classify each galaxy according to its optical morphology and two-dimensional stellar velocity field. Comparing these classifications to quantitative λ _{R_e} measurements reveals tight relationships between angular momentum and galaxy structure. In order to account for atmospheric seeing, we use realistic models of galaxy kinematics to derive a general approximate analytic correction for λ _{R_e}. Thanks to the size of the sample and the large number of massive galaxies, we unambiguously detect a clear bimodality in the (λ _{R_e}, ɛ ) diagram which may result from fundamental differences in galaxy assembly history. There is a sharp secondary density peak inside the region of the diagram with low λ _{R_e} and ɛ < 0.4, previously suggested as the definition for slow rotators. Most of these galaxies are visually classified as non-regular rotators and have high velocity dispersion. The intrinsic bimodality must be stronger, as it tends to be smoothed by noise and inclination. The large sample of slow rotators allows us for the first time to unveil a secondary peak at ±90○ in their distribution of the misalignments between the photometric and kinematic position angles. We confirm that genuine slow rotators start appearing above M ≥ 2 × 1011M⊙ where a significant number of high-mass fast rotators also exist.

Responses of primate caudal parabrachial nucleus and Kolliker-fuse nucleus neurons to whole body rotation

NASA Technical Reports Server (NTRS)

Balaban, Carey D.; McGee, David M.; Zhou, Jianxun; Scudder, Charles A.

2002-01-01

The caudal aspect of the parabrachial (PBN) and Kolliker-Fuse (KF) nuclei receive vestibular nuclear and visceral afferent information and are connected reciprocally with the spinal cord, hypothalamus, amygdala, and limbic cortex. Hence, they may be important sites of vestibulo-visceral integration, particularly for the development of affective responses to gravitoinertial challenges. Extracellular recordings were made from caudal PBN cells in three alert, adult female Macaca nemestrina through an implanted chamber. Sinusoidal and position trapezoid angular whole body rotation was delivered in yaw, roll, pitch, and vertical semicircular canal planes. Sites were confirmed histologically. Units that responded during rotation were located in lateral and medial PBN and KF caudal to the trochlear nerve at sites that were confirmed anatomically to receive superior vestibular nucleus afferents. Responses to whole-body angular rotation were modeled as a sum of three signals: angular velocity, a leaky integration of angular velocity, and vertical position. All neurons displayed angular velocity and integrated angular velocity sensitivity, but only 60% of the neurons were position-sensitive. These responses to vertical rotation could display symmetric, asymmetric, or fully rectified cosinusoidal spatial tuning about a best orientation in different cells. The spatial properties of velocity and integrated velocity and position responses were independent for all position-sensitive neurons; the angular velocity and integrated angular velocity signals showed independent spatial tuning in the position-insensitive neurons. Individual units showed one of three different orientations of their excitatory axis of velocity rotation sensitivity: vertical-plane-only responses, positive elevation responses (vertical plane plus ipsilateral yaw), and negative elevation axis responses (vertical plane plus negative yaw). The interactions between the velocity and integrated velocity components also produced variations in the temporal pattern of responses as a function of rotation direction. These findings are consistent with the hypothesis that a vestibulorecipient region of the PBN and KF integrates signals from the vestibular nuclei and relay information about changes in whole-body orientation to pathways that produce homeostatic and affective responses.

Attitude output feedback control for rigid spacecraft with finite-time convergence.

PubMed

Hu, Qinglei; Niu, Guanglin

2017-09-01

The main problem addressed is the quaternion-based attitude stabilization control of rigid spacecraft without angular velocity measurements in the presence of external disturbances and reaction wheel friction as well. As a stepping stone, an angular velocity observer is proposed for the attitude control of a rigid body in the absence of angular velocity measurements. The observer design ensures finite-time convergence of angular velocity state estimation errors irrespective of the control torque or the initial attitude state of the spacecraft. Then, a novel finite-time control law is employed as the controller in which the estimate of the angular velocity is used directly. It is then shown that the observer and the controlled system form a cascaded structure, which allows the application of the finite-time stability theory of cascaded systems to prove the finite-time stability of the closed-loop system. A rigorous analysis of the proposed formulation is provided and numerical simulation studies are presented to help illustrate the effectiveness of the angular-velocity observer for rigid spacecraft attitude control. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Mechanisms underlying the perceived angular velocity of a rigidly rotating object.

PubMed

Caplovitz, G P; Hsieh, P-J; Tse, P U

2006-09-01

The perceived angular velocity of an ellipse undergoing a constant rate of rotation will vary as its aspect ratio is changed. Specifically, a "fat" ellipse with a low aspect ratio will in general be perceived to rotate more slowly than a "thin" ellipse with a higher aspect ratio. Here we investigate this illusory underestimation of angular velocity in the domain where ellipses appear to be rotating rigidly. We characterize the relationship between aspect ratio and perceived angular velocity under luminance and non-luminance-defined conditions. The data are consistent with two hypotheses concerning the construction of rotational motion percepts. The first hypothesis is that perceived angular velocity is determined by low-level component-motion (i.e., motion-energy) signals computed along the ellipse's contour. The second hypothesis is that relative maxima of positive contour curvature are treated as non-component, form-based "trackable features" (TFs) that contribute to the visual system's construction of the motion percept. Our data suggest that perceived angular velocity is driven largely by component signals, but is modulated by the motion signals of trackable features, such as corners and regions of high contour curvature.

Professional tennis players' serve: correlation between segmental angular momentums and ball velocity.

PubMed

Martin, Caroline; Kulpa, Richard; Delamarche, Paul; Bideau, Benoit

2013-03-01

The purpose of the study was to identify the relationships between segmental angular momentum and ball velocity between the following events: ball toss, maximal elbow flexion (MEF), racket lowest point (RLP), maximal shoulder external rotation (MER), and ball impact (BI). Ten tennis players performed serves recorded with a real-time motion capture. Mean angular momentums of the trunk, upper arm, forearm, and the hand-racket were calculated. The anteroposterior axis angular momentum of the trunk was significantly related with ball velocity during the MEF-RLP, RLP-MER, and MER-BI phases. The strongest relationships between the transverse-axis angular momentums and ball velocity followed a proximal-to-distal timing sequence that allows the transfer of angular momentum from the trunk (MEF-RLP and RLP-MER phases) to the upper arm (RLP-MER phase), forearm (RLP-MER and MER-BI phases), and the hand-racket (MER-BI phase). Since sequence is crucial for ball velocity, players should increase angular momentums of the trunk during MEF-MER, upper arm during RLP-MER, forearm during RLP-BI, and the hand-racket during MER-BI.

Angular Distributions of Differential Electron Capture Cross Sections in Collisions Between Low-Velocity Highly-Charged Ions and Neutral Targets.

NASA Astrophysics Data System (ADS)

Waggoner, William Tracy

1990-01-01

Experimental capture cross sections d sigma / dtheta versus theta , are presented for various ions incident on neutral targets. First, distributions are presented for Ar ^{rm 8+} ions incident on H_{rm 2}, D _{rm 2}, and Ar targets. Energy gain studies indicate that capture occurs to primarily a 5d,f final state of Ar^{rm 7+} with some contributions from transfer ionization (T.I.) channels. Angular distribution spectra for all three targets are similar, with spectra having a main peak located at forward angles which is attributed to single capture events, and a secondary structure occurring at large angles which is attributed to T.I. contributions. A series of Ar^{rm 8+} on Ar spectra were collected using a retarding grid system as a low resolution energy spectrometer to resolve single capture events from T.I. events. The resulting single capture and T.I. angular distributions are presented. Results are discussed in terms of a classical deflection function employing a simple two state curve crossing model. Angular distributions for electron capture from He by C, N, O, F, and Ne ions with charge states from 5 ^+-8^+ are presented for projectile energies between 1.2 and 2.0 kV. Distributions for the same charge state but different ion species are simlar, but not identical with distributions for the 5 ^+ and 7^+ ions being strongly forward peaked, the 6^+ distributions are much less forward peaked with the O^{6+} distributions showing structure, the Ne^{8+} ion distribution appears to be an intermediate case between forward peaking and large angle scattering. These results are discussed in terms of classical deflection functions which utilize two state Coulomb diabatic curve crossing models. Finally, angular distributions are presented for electron capture from He by Ar^{rm 6+} ions at energies between 1287 eV and 296 eV. At large projectile energies the distribution is broad. As the energy decreases below 523 eV, distributions shift to forward angles with a second peak appearing outside the Coulomb angle, theta_{c} = Q/2E, which continues to grow in magnitude as the projectile energy decreases further. Results are compared with a model calculation employing a two state diabatic Coulomb curve crossing model and the classical deflection function.

Multi-segment foot kinematics after total ankle replacement and ankle arthrodesis during relatively long-distance gait.

PubMed

Rouhani, H; Favre, J; Aminian, K; Crevoisier, X

2012-07-01

This study aimed to investigate the influence of ankle osteoarthritis (AOA) treatments, i.e., ankle arthrodesis (AA) and total ankle replacement (TAR), on the kinematics of multi-segment foot and ankle complex during relatively long-distance gait. Forty-five subjects in four groups (AOA, AA, TAR, and control) were equipped with a wearable system consisting of inertial sensors installed on the tibia, calcaneus, and medial metatarsals. The subjects walked 50-m twice while the system measured the kinematic parameters of their multi-segment foot: the range of motion of joints between tibia, calcaneus, and medial metatarsals in three anatomical planes, and the peaks of angular velocity of these segments in the sagittal plane. These parameters were then compared among the four groups. It was observed that the range of motion and peak of angular velocities generally improved after TAR and were similar to the control subjects. However, unlike AOA and TAR, AA imposed impairments in the range of motion in the coronal plane for both the tibia-calcaneus and tibia-metatarsals joints. In general, the kinematic parameters showed significant correlation with established clinical scales (FFI and AOFAS), which shows their convergent validity. Based on the kinematic parameters of multi-segment foot during 50-m gait, this study showed significant improvements in foot mobility after TAR, but several significant impairments remained after AA. Copyright © 2012 Elsevier B.V. All rights reserved.

Closed-form integrator for the quaternion (euler angle) kinematics equations

NASA Technical Reports Server (NTRS)

Whitmore, Stephen A. (Inventor)

2000-01-01

The invention is embodied in a method of integrating kinematics equations for updating a set of vehicle attitude angles of a vehicle using 3-dimensional angular velocities of the vehicle, which includes computing an integrating factor matrix from quantities corresponding to the 3-dimensional angular velocities, computing a total integrated angular rate from the quantities corresponding to a 3-dimensional angular velocities, computing a state transition matrix as a sum of (a) a first complementary function of the total integrated angular rate and (b) the integrating factor matrix multiplied by a second complementary function of the total integrated angular rate, and updating the set of vehicle attitude angles using the state transition matrix. Preferably, the method further includes computing a quanternion vector from the quantities corresponding to the 3-dimensional angular velocities, in which case the updating of the set of vehicle attitude angles using the state transition matrix is carried out by (a) updating the quanternion vector by multiplying the quanternion vector by the state transition matrix to produce an updated quanternion vector and (b) computing an updated set of vehicle attitude angles from the updated quanternion vector. The first and second trigonometric functions are complementary, such as a sine and a cosine. The quantities corresponding to the 3-dimensional angular velocities include respective averages of the 3-dimensional angular velocities over plural time frames. The updating of the quanternion vector preserves the norm of the vector, whereby the updated set of vehicle attitude angles are virtually error-free.

In vivo maximal fascicle-shortening velocity during plantar flexion in humans.

PubMed

Hauraix, Hugo; Nordez, Antoine; Guilhem, Gaël; Rabita, Giuseppe; Dorel, Sylvain

2015-12-01

Interindividual variability in performance of fast movements is commonly explained by a difference in maximal muscle-shortening velocity due to differences in the proportion of fast-twitch fibers. To provide a better understanding of the capacity to generate fast motion, this study aimed to 1) measure for the first time in vivo the maximal fascicle-shortening velocity of human muscle; 2) evaluate the relationship between angular velocity and fascicle-shortening velocity from low to maximal angular velocities; and 3) investigate the influence of musculo-articular features (moment arm, tendinous tissues stiffness, and muscle architecture) on maximal angular velocity. Ultrafast ultrasound images of the gastrocnemius medialis were obtained from 31 participants during maximal isokinetic and light-loaded plantar flexions. A strong linear relationship between fascicle-shortening velocity and angular velocity was reported for all subjects (mean R(2) = 0.97). The maximal shortening velocity (V(Fmax)) obtained during the no-load condition (NLc) ranged between 18.8 and 43.3 cm/s. V(Fmax) values were very close to those of the maximal shortening velocity (V(max)), which was extrapolated from the F-V curve (the Hill model). Angular velocity reached during the NLc was significantly correlated with this V(Fmax) (r = 0.57; P < 0.001). This finding was in agreement with assumptions about the role of muscle fiber type, whereas interindividual comparisons clearly support the fact that other parameters may also contribute to performance during fast movements. Nevertheless, none of the biomechanical features considered in the present study were found to be directly related to the highest angular velocity, highlighting the complexity of the upstream mechanics that lead to maximal-velocity muscle contraction. Copyright © 2015 the American Physiological Society.

Form features provide a cue to the angular velocity of rotating objects

PubMed Central

Blair, Christopher David; Goold, Jessica; Killebrew, Kyle; Caplovitz, Gideon Paul

2013-01-01

As an object rotates, each location on the object moves with an instantaneous linear velocity dependent upon its distance from the center of rotation, while the object as a whole rotates with a fixed angular velocity. Does the perceived rotational speed of an object correspond to its angular velocity, linear velocities, or some combination of the two? We had observers perform relative speed judgments of different sized objects, as changing the size of an object changes the linear velocity of each location on the object’s surface, while maintaining the object’s angular velocity. We found that the larger a given object is, the faster it is perceived to rotate. However, the observed relationships between size and perceived speed cannot be accounted for simply by size-related changes in linear velocity. Further, the degree to which size influences perceived rotational speed depends on the shape of the object. Specifically, perceived rotational speeds of objects with corners or regions of high contour curvature were less affected by size. The results suggest distinct contour features, such as corners or regions of high or discontinuous contour curvature, provide cues to the angular velocity of a rotating object. PMID:23750970

Form features provide a cue to the angular velocity of rotating objects.

PubMed

Blair, Christopher David; Goold, Jessica; Killebrew, Kyle; Caplovitz, Gideon Paul

2014-02-01

As an object rotates, each location on the object moves with an instantaneous linear velocity, dependent upon its distance from the center of rotation, whereas the object as a whole rotates with a fixed angular velocity. Does the perceived rotational speed of an object correspond to its angular velocity, linear velocities, or some combination of the two? We had observers perform relative speed judgments of different-sized objects, as changing the size of an object changes the linear velocity of each location on the object's surface, while maintaining the object's angular velocity. We found that the larger a given object is, the faster it is perceived to rotate. However, the observed relationships between size and perceived speed cannot be accounted for simply by size-related changes in linear velocity. Further, the degree to which size influences perceived rotational speed depends on the shape of the object. Specifically, perceived rotational speeds of objects with corners or regions of high-contour curvature were less affected by size. The results suggest distinct contour features, such as corners or regions of high or discontinuous contour curvature, provide cues to the angular velocity of a rotating object. PsycINFO Database Record (c) 2014 APA, all rights reserved.

A Computational Technique to Determine the Angular Displacement, Velocity and Momentum of a Human Body.

ERIC Educational Resources Information Center

Hay, James G.; Wilson, Barry D.

The angular momentum of a human body derived from both the angular velocity and angular displacement, utilizing cinematographic records has not been adequately assessed, prior to this study. Miller (1970) obtained the angular momentum but only during the airborne phase of activity. The method used by Ramey (1973) involved a force platform, but…

Measuring Average Angular Velocity with a Smartphone Magnetic Field Sensor

ERIC Educational Resources Information Center

Pili, Unofre; Violanda, Renante

2018-01-01

The angular velocity of a spinning object is, by standard, measured using a device called a tachometer. However, by directly using it in a classroom setting, the activity is likely to appear as less instructive and less engaging. Indeed, some alternative classroom-suitable methods for measuring angular velocity have been presented. In this paper,…

The evolution of rotating stars. III - Predicted surface rotation velocities for stars which conserve total angular momentum

NASA Technical Reports Server (NTRS)

Endal, A. S.; Sofia, S.

1979-01-01

Predicted surface rotation velocities for Population I stars at 10, 7, 5, 3, and 1.5 solar masses are presented. The surface velocities were computed for angular momentum with no radial redistribution, complete redistribution, and partial redistribution as predicted by consideration of circulation currents in rotating stars. Near the main sequence, rotational effects can reduce the moment of inertia of a star, so nonrotating models underestimate the expected velocities for evolving stars. On the red giant branch, angular momentum redistribution reduces the surface velocity by a factor of 2 or more, relative to the velocity expected for no radial redistribution. This removes the discrepancy between predicted and observed rotation rates for the K giants and makes it unlikely that these stars lose significant amounts of angular momentum by stellar winds. Calculations indicate that improved observations of the red giants in the Hyades cluster can be used to determine how angular momentum is redistributed by convection

A Methodologic Approach for Normalizing Angular Work and Velocity During Isotonic and Isokinetic Eccentric Training

PubMed Central

Guilhem, Gaël; Cornu, Christophe; Guével, Arnaud

2012-01-01

Context: Resistance exercise training commonly is performed against a constant external load (isotonic) or at a constant velocity (isokinetic). Researchers comparing the effectiveness of isotonic and isokinetic resistance-training protocols need to equalize the mechanical stimulus (work and velocity) applied. Objective: To examine whether the standardization protocol could be adjusted and applied to an eccentric training program. Design: Controlled laboratory study. Setting: Controlled research laboratory. Patients or Other Participants: Twenty-one sport science male students (age = 20.6 ± 1.5 years, height = 178.0 ± 4.0 cm, mass = 74.5 ± 9.1 kg). Intervention(s): Participants performed 9 weeks of isotonic (n = 11) or isokinetic (n = 10) eccentric training of knee extensors that was designed so they would perform the same amount of angular work at the same mean angular velocity. Main Outcome Measure(s): Angular work and angular velocity. Results: The isotonic and isokinetic groups performed the same total amount of work (−185.2 ± 6.5 kJ and −184.4 ± 8.6 kJ, respectively) at the same angular velocity (21 ± 1°/s and 22°/s, respectively) with the same number of repetitions (8.0 and 8.0, respectively). Bland-Altman analysis showed that work (bias = 2.4%) and angular velocity (bias = 0.2%) were equalized over 9 weeks between the modes of training. Conclusions: The procedure developed allows angular work and velocity to be standardized over 9 weeks of isotonic and isokinetic eccentric training of the knee extensors. This method could be useful in future studies in which researchers compare neuromuscular adaptations induced by each type of training mode with respect to rehabilitating patients after musculoskeletal injury. PMID:22488276

Method for driving two-phase turbines with enhanced efficiency

NASA Technical Reports Server (NTRS)

Elliott, D. G. (Inventor)

1985-01-01

A method for driving a two phase turbine characterized by an output shaft having at least one stage including a bladed rotor connected in driving relation with the shaft is described. A two phase fluid is introduced into one stage at a known flow velocity and caused to pass through the rotor for imparing angular velocity thereto. The angular velocity of the rotor is maintained at a value such that the angular velocity of the tips of the blades of the rotor is a velocity equal to at least 50% of the velocity of the flow of the two phase fluid.

Visual processing of rotary motion.

PubMed

Werkhoven, P; Koenderink, J J

1991-01-01

Local descriptions of velocity fields (e.g., rotation, divergence, and deformation) contain a wealth of information for form perception and ego motion. In spite of this, human psychophysical performance in estimating these entities has not yet been thoroughly examined. In this paper, we report on the visual discrimination of rotary motion. A sequence of image frames is used to elicit an apparent rotation of an annulus, composed of dots in the frontoparallel plane, around a fixation spot at the center of the annulus. Differential angular velocity thresholds are measured as a function of the angular velocity, the diameter of the annulus, the number of dots, the display time per frame, and the number of frames. The results show a U-shaped dependence of angular velocity discrimination on spatial scale, with minimal Weber fractions of 7%. Experiments with a scatter in the distance of the individual dots to the center of rotation demonstrate that angular velocity cannot be assessed directly; perceived angular velocity depends strongly on the distance of the dots relative to the center of rotation. We suggest that the estimation of rotary motion is mediated by local estimations of linear velocity.

Global Plate Velocities from the Global Positioning System

NASA Technical Reports Server (NTRS)

Larson, Kristine M.; Freymueller, Jeffrey T.; Philipsen, Steven

1997-01-01

We have analyzed 204 days of Global Positioning System (GPS) data from the global GPS network spanning January 1991 through March 1996. On the basis of these GPS coordinate solutions, we have estimated velocities for 38 sites, mostly located on the interiors of the Africa, Antarctica, Australia, Eurasia, Nazca, North America, Pacific, and South America plates. The uncertainties of the horizontal velocity components range from 1.2 to 5.0 mm/yr. With the exception of sites on the Pacific and Nazca plates, the GPS velocities agree with absolute plate model predictions within 95% confidence. For most of the sites in North America, Antarctica, and Eurasia, the agreement is better than 2 mm/yr. We find no persuasive evidence for significant vertical motions (less than 3 standard deviations), except at four sites. Three of these four were sites constrained to geodetic reference frame velocities. The GPS velocities were then used to estimate angular velocities for eight tectonic plates. Absolute angular velocities derived from the GPS data agree with the no net rotation (NNR) NUVEL-1A model within 95% confidence except for the Pacific plate. Our pole of rotation for the Pacific plate lies 11.5 deg west of the NNR NUVEL-1A pole, with an angular speed 10% faster. Our relative angular velocities agree with NUVEL-1A except for some involving the Pacific plate. While our Pacific-North America angular velocity differs significantly from NUVEL-1A, our model and NUVEL-1A predict very small differences in relative motion along the Pacific-North America plate boundary itself. Our Pacific-Australia and Pacific- Eurasia angular velocities are significantly faster than NUVEL-1A, predicting more rapid convergence at these two plate boundaries. Along the East Pacific Pise, our Pacific-Nazca angular velocity agrees in both rate and azimuth with NUVFL-1A.

Variation in Angular Velocity and Angular Acceleration of a Particle in Rectilinear Motion

ERIC Educational Resources Information Center

Mashood, K. K.; Singh, V. A.

2012-01-01

We discuss the angular velocity ([image omitted]) and angular acceleration ([image omitted]) associated with a particle in rectilinear motion with constant acceleration. The discussion was motivated by an observation that students and even teachers have difficulty in ascribing rotational motion concepts to a particle when the trajectory is a…

Elbow joint angle and elbow movement velocity estimation using NARX-multiple layer perceptron neural network model with surface EMG time domain parameters.

PubMed

Raj, Retheep; Sivanandan, K S

2017-01-01

Estimation of elbow dynamics has been the object of numerous investigations. In this work a solution is proposed for estimating elbow movement velocity and elbow joint angle from Surface Electromyography (SEMG) signals. Here the Surface Electromyography signals are acquired from the biceps brachii muscle of human hand. Two time-domain parameters, Integrated EMG (IEMG) and Zero Crossing (ZC), are extracted from the Surface Electromyography signal. The relationship between the time domain parameters, IEMG and ZC with elbow angular displacement and elbow angular velocity during extension and flexion of the elbow are studied. A multiple input-multiple output model is derived for identifying the kinematics of elbow. A Nonlinear Auto Regressive with eXogenous inputs (NARX) structure based multiple layer perceptron neural network (MLPNN) model is proposed for the estimation of elbow joint angle and elbow angular velocity. The proposed NARX MLPNN model is trained using Levenberg-marquardt based algorithm. The proposed model is estimating the elbow joint angle and elbow movement angular velocity with appreciable accuracy. The model is validated using regression coefficient value (R). The average regression coefficient value (R) obtained for elbow angular displacement prediction is 0.9641 and for the elbow anglular velocity prediction is 0.9347. The Nonlinear Auto Regressive with eXogenous inputs (NARX) structure based multiple layer perceptron neural networks (MLPNN) model can be used for the estimation of angular displacement and movement angular velocity of the elbow with good accuracy.

Joint Angular Velocity in Spastic Gait and the Influence of Muscle-Tendon Lengthening*

PubMed Central

GRANATA, KEVIN P.; ABEL, MARK F.; DAMIANO, DIANE L.

2006-01-01

Background Joint angular velocity (the rate of flexion and extension of a joint) is related to the dynamics of muscle activation and force generation during walking. Therefore, the goal of this research was to examine the joint angular velocity in normal and spastic gait and changes resulting from muscle-tendon lengthening (recession and tenotomy) in patients who have spastic cerebral palsy. Methods The gait patterns of forty patients who had been diagnosed with spastic cerebral palsy (mean age, 8.3 years; range, 3.7 to 14.8 years) and of seventy-three age-matched, normally developing subjects were evaluated with three-dimensional motion analysis and electromyography. The patients who had cerebral palsy were evaluated before muscle-tendon lengthening and nine months after treatment. Results The gait patterns of the patients who had cerebral palsy were characterized by increased flexion of the knee in the stance phase, premature plantar flexion of the ankle, and reduced joint angular velocities compared with the patterns of the normally developing subjects. Even though muscle-tendon lengthening altered sagittal joint angles in gait, the joint angular velocities were generally unchanged at the hip and knee. Only the ankle demonstrated modified angular velocities, including reduced dorsiflexion velocity at foot-strike and improved dorsiflexion velocity through midstance, after treatment. Electromyographic changes included reduced amplitude of the gastrocnemius-soleus during the loading phase and decreased knee coactivity (the ratio of quadriceps and hamstring activation) at toe-off. Principal component analyses showed that, compared with joint-angle data, joint angular velocity was better able to discriminate between the gait patterns of the normal and cerebral palsy groups. Conclusions This study showed that muscle-tendon lengthening corrects biomechanical alignment as reflected by changes in sagittal joint angles. However, joint angular velocity and electromyographic data suggest that the underlying neural input remains largely unchanged at the hip and knee. Conversely, electromyographic changes and changes in velocity in the ankle indicate that the activation pattern of the gastrocnemius-soleus complex in response to stretch was altered by recession of the complex. PMID:10682726

Breaststroke swimmer's knee. A biomechanical and arthroscopic study.

PubMed

Keskinen, K; Eriksson, E; Komi, P

1980-01-01

The cause of the breaststroke swimmer's knee with medial pain of the knee joint has not been clearly identified. Breaststroke swimmers with knee pain were, therefore, examined arthroscopically. None showed any other disorders of their knees than medial synovitis in seven of nine swimmers. Since structural abnormalities could be ruled out, biomechanical analyses utilizing cinematographic techniques were used to study patients swimming in a special flume with the speed set at 90% of their best competitive performance. The results indicate that the extension and flexion and also in some cases the hip abduction and adduction movements of the whip kick were performed with high peak angular velocities. No significant differences in swimming technique among the six patients studied and three controls could be observed. It is concluded that a combination of high angular velocities at the hip and knee and external rotation of the tibia relative to the femur repeated in excessive amounts might be the primary cause for the medial synovitis documented in these patients. The breaststroker's knee thus seems to be an overuse syndrome.

Magnetometer-only attitude and angular velocity filtering estimation for attitude changing spacecraft

NASA Astrophysics Data System (ADS)

Ma, Hongliang; Xu, Shijie

2014-09-01

This paper presents an improved real-time sequential filter (IRTSF) for magnetometer-only attitude and angular velocity estimation of spacecraft during its attitude changing (including fast and large angular attitude maneuver, rapidly spinning or uncontrolled tumble). In this new magnetometer-only attitude determination technique, both attitude dynamics equation and first time derivative of measured magnetic field vector are directly leaded into filtering equations based on the traditional single vector attitude determination method of gyroless and real-time sequential filter (RTSF) of magnetometer-only attitude estimation. The process noise model of IRTSF includes attitude kinematics and dynamics equations, and its measurement model consists of magnetic field vector and its first time derivative. The observability of IRTSF for small or large angular velocity changing spacecraft is evaluated by an improved Lie-Differentiation, and the degrees of observability of IRTSF for different initial estimation errors are analyzed by the condition number and a solved covariance matrix. Numerical simulation results indicate that: (1) the attitude and angular velocity of spacecraft can be estimated with sufficient accuracy using IRTSF from magnetometer-only data; (2) compared with that of RTSF, the estimation accuracies and observability degrees of attitude and angular velocity using IRTSF from magnetometer-only data are both improved; and (3) universality: the IRTSF of magnetometer-only attitude and angular velocity estimation is observable for any different initial state estimation error vector.

Kinematic analysis of upper extremity movement during drinking in hemiplegic subjects.

PubMed

Kim, Kyung; Song, Won-Kyung; Lee, Jeongsu; Lee, Hwi-Young; Park, Dae Sung; Ko, Byung-Woo; Kim, Jongbae

2014-03-01

It is necessary to analyze the kinematic properties of a paralyzed extremity to quantitatively determine the degree of impairment of hemiplegic people during functional activities of daily living (ADL) such as a drinking task. This study aimed to identify the kinematic differences between 16 hemiplegic and 32 able-bodied participants in relation to the task phases when drinking with a cup and the kinematic strategy used during motion with respect to the gravity direction. The subjects performed a drinking task that was divided into five phases according to Murphy's phase definition: reaching, forward transport, drinking, backward transport, and returning. We found that the groups differed in terms of the movement times and the joint angles and angular velocities of the shoulder, elbow, and wrist joints. Compared to the control group, the hemiplegic participants had a larger shoulder abduction angle of at most 17.1° during all the phases, a larger shoulder flexion angle of 7.6° during the reaching phase, and a smaller shoulder flexion angle of 6.4° during the backward transporting phase. Because of these shoulder joint patterns, a smaller elbow pronation peak angle of at most 13.1° and a larger wrist extension peak angle of 12.0° were found in the motions of the hemiplegic participants, as compensation to complete the drinking task. The movement in the gravity direction during the backward transporting phase resulted in a 15.9% larger peak angular velocity for elbow extension in the hemiplegic participants compared to that of the control group. These quantitative kinematic patterns help provide an understanding of the movements of an affected extremity and can be useful in designing rehabilitation robots to assist hemiplegic people with ADL. Copyright © 2013 Elsevier Ltd. All rights reserved.

[NEII] Line Velocity Structure of Ultracompact HII Regions

NASA Astrophysics Data System (ADS)

Okamoto, Yoshiko K.; Kataza, Hirokazu; Yamashita, Takuya; Miyata, Takashi; Sako, Shigeyuki; Honda, Mitsuhiko; Onaka, Takashi; Fujiyoshi, Takuya

Newly formed massive stars are embedded in their natal molecular clouds and are observed as ultracompact HII regions. They emit strong ionic lines such as [NeII] 12.8 micron. Since Ne is ionized by UV photons of E>21.6eV which is higher than the ionization energy of hydrogen atoms the line probes the ionized gas near the ionizing stars. This enables to probe gas motion in the vicinity of recently-formed massive stars. High angular and spectral resolution observations of the [NeII] line will thus provide siginificant information on structures (e.g. disks and outflows) generated through massive star formation. We made [NeII] spectroscopy of ultracompact HII regions using the Cooled Mid-Infrared Camera and Spectrometer (COMICS) on the 8.2m Subaru Telescope in July 2002. Spatial and spectral resolutions were 0.5"" and 10000 respectively. Among the targets G45.12+0.13 shows the largest spatial variation in velocity. The brightest area of G45.12+0.13 has the largest line width in the object. The total velocity deviation amounts to 50km/s (peak to peak value) in the observed area. We report the velocity structure of [NeII] emission of G45.12+0.13 and discuss the gas motion near the ionizing star.

Evidence for the distribution of angular velocity inside the sun and stars

NASA Technical Reports Server (NTRS)

1972-01-01

A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing the distribution of angular velocity inside the sun and stars.

Non-Colinearity of Angular Velocity and Angular Momentum

ERIC Educational Resources Information Center

Burr, A. F.

1974-01-01

Discusses the principles, construction, and operation of an apparatus which serves to demonstrate the non-colinearity of the angular velocity and momentum vectors as well as the inertial tensors. Applications of the apparatus to teaching of advanced undergraduate mechanics courses are recommended. (CC)

Investigation of fluctuations in angular velocity in magnetic memory devices

NASA Technical Reports Server (NTRS)

Meshkis, Y. A.; Potsyus, Z. Y.

1973-01-01

The fluctuations in the angular velocity of individual assemblies of a precision mechanical system were analyzed. The system was composed of an electric motor and a magnetic drum which were connected by a flexible coupling. A dynamic model was constructed which took into account the absence of torsion in the rigid shafts of the electric motor drive rotor and the magnetic drum. The motion was described by Lagrange differential equations of the second kind. Curves are developed to show the nature of amplitude fluctuation of the magnetic drum angular velocity at a specific excitation frequency. Additional curves show the amplitudes of fluctuation of the magnetic drum angular velocity compared to the quantity of damping at specific frequencies.

The generalized formula for angular velocity vector of the moving coordinate system

NASA Astrophysics Data System (ADS)

Ermolin, Vladislav S.; Vlasova, Tatyana V.

2018-05-01

There are various ways for introducing the concept of the instantaneous angular velocity vector. In this paper we propose a method based on introducing of this concept by construction of the solution for the system of kinematic equations. These equations connect the function vectors defining the motion of the basis, and their derivatives. Necessary and sufficient conditions for the existence and uniqueness of the solution of this system are established. The instantaneous angular velocity vector is a solution of the algebraic system of equations. It is built explicitly. The derived formulas for the angular velocity vector generalize the earlier results, both for a basis of an affine oblique coordinate system and for an orthonormal basis.

Modelling of rotation-induced frequency shifts in whispering gallery modes

NASA Astrophysics Data System (ADS)

Venediktov, V. Yu; Kukaev, A. S.; Filatov, Yu V.; Shalymov, E. V.

2018-02-01

We study the angular velocity sensors based on whispering gallery mode resonators. Rotation of such resonators gives rise to various effects that can cause a spectral shift of their modes. Optical methods allow this shift to be determined with high precision, which can be used practically to measure the angular velocity in inertial orientation and navigation systems. The basic principles of constructing the angular velocity sensors utilising these effects are considered, their advantages and drawbacks are indicated. We also study the interrelation between the effects and the possibility of their mutual influence on each other. Based on the analytical studies of the effects, we consider the possibility of their combined application for angular velocity measurements.

Demonstrating the Direction of Angular Velocity in Circular Motion

ERIC Educational Resources Information Center

Demircioglu, Salih; Yurumezoglu, Kemal; Isik, Hakan

2015-01-01

Rotational motion is ubiquitous in nature, from astronomical systems to household devices in everyday life to elementary models of atoms. Unlike the tangential velocity vector that represents the instantaneous linear velocity (magnitude and direction), an angular velocity vector is conceptually more challenging for students to grasp. In physics…

The validity of an assessment of maximum angular velocity of knee extension (KE) using a gyroscope.

PubMed

Arai, Takeshi; Obuchi, Shuichi; Shiba, Yoshitaka; Omuro, Kazuya; Inaba, Yasuko; Kojima, Motonaga

2012-01-01

Although it is more important to assess the muscular power of the lower extremities than the strength, no simplified method for doing so has been found. The aim of this study was to assess the validity of the assessment of the angular velocity of KE using a gyroscope. Participants included 105 community-dwelling older people (55 women, 50 men, age ± standard deviation (SD) 75±5.3). Pearson correlation coefficients and Spearman rank-correlation coefficients were used to examine the relationships between the angular velocity of KE and functional performance measurements, a self-efficacy scale and health-related quality of life (HRQOL). The data from the gyroscope were significantly correlated with some physical functions such as muscle strength (r=0.304, p<0.01), and walking velocity (r=0.543, p<0.001). In addition, the joint angular velocity was significantly correlated with self-efficacy (r=0.219-0.329, p<0.01-0.05) and HRQOL (r=0.207-0.359, p<0.01-0.05). The absolute value of the correlation coefficient of angular velocity tended to be greater than that of the muscle strength for mobility functions such as walking velocity and the timed-up-and-go (TUG) test. In conclusion, it was found that the assessment of the angular velocity of the knee joint using a gyroscope could be a feasible and meaningful measurement in the geriatrics field. Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.

Spacecraft attitude sensor

NASA Technical Reports Server (NTRS)

Davidson, A. C.; Grant, M. M. (Inventor)

1973-01-01

A system for sensing the attitude of a spacecraft includes a pair of optical scanners having a relatively narrow field of view rotating about the spacecraft x-y plane. The spacecraft rotates about its z axis at a relatively high angular velocity while one scanner rotates at low velocity, whereby a panoramic sweep of the entire celestial sphere is derived from the scanner. In the alternative, the scanner rotates at a relatively high angular velocity about the x-y plane while the spacecraft rotates at an extremely low rate or at zero angular velocity relative to its z axis to provide a rotating horizon scan. The positions of the scanners about the x-y plane are read out to assist in a determination of attitude. While the satellite is spinning at a relatively high angular velocity, the angular positions of the bodies detected by the scanners are determined relative to the sun by providing a sun detector having a field of view different from the scanners.

India plate angular velocity and contemporary deformation rates from continuous GPS measurements from 1996 to 2015.

PubMed

Jade, Sridevi; Shrungeshwara, T S; Kumar, Kireet; Choudhury, Pallabee; Dumka, Rakesh K; Bhu, Harsh

2017-09-12

We estimate a new angular velocity for the India plate and contemporary deformation rates in the plate interior and along its seismically active margins from Global Positioning System (GPS) measurements from 1996 to 2015 at 70 continuous and 3 episodic stations. A new India-ITRF2008 angular velocity is estimated from 30 GPS sites, which include stations from western and eastern regions of the plate interior that were unrepresented or only sparsely sampled in previous studies. Our newly estimated India-ITRF2008 Euler pole is located significantly closer to the plate with ~3% higher angular velocity than all previous estimates and thus predicts more rapid variations in rates and directions along the plate boundaries. The 30 India plate GPS site velocities are well fit by the new angular velocity, with north and east RMS misfits of only 0.8 and 0.9 mm/yr, respectively. India fixed velocities suggest an approximate of 1-2 mm/yr intra-plate deformation that might be concentrated along regional dislocations, faults in Peninsular India, Kachchh and Indo-Gangetic plain. Relative to our newly-defined India plate frame of reference, the newly estimated velocities for 43 other GPS sites along the plate margins give insights into active deformation along India's seismically active northern and eastern boundaries.

The feasibility of measuring joint angular velocity with a gyro-sensor.

PubMed

Arai, Takeshi; Obuchi, Shuichi; Shiba, Yoshitaka; Omuro, Kazuya; Nakano, Chika; Higashi, Takuya

2008-01-01

To determine the reliability of an assessment of joint angular velocity using a gyro-sensor and to examine the relationship between ankle angular velocity and physical functions. Cross-sectional. Kinesiology laboratory. Twenty healthy young adults (mean age, 22.5 y) and 113 community-dwelling older adults (mean age, 75.1 y). Not applicable. Maximal ankle joint velocity was measured using a gyro-sensor during heel-rising and jumping with knee extended. The intraclass correlation coefficient (ICC) was used to determine the intertester and intratester reliability. The Pearson correlation coefficient was used to examine the relationships between maximal ankle joint velocity and isometric muscle strength and isokinetic muscle power in young adults and also to examine the relationships between maximal ankle joint velocity and functional performance measurements such as walking time in older adults. High reliability was found for intertester (ICC=.96) and intratester reliability (ICC=.96). The data from the gyro-sensor highly correlated with muscle strength (r range, .62-.68; P<.01) and muscle power (r range, .45-.79; P range, .01-.05). In older subjects, mobility functions significantly correlated with the angular velocity of ankle plantarflexion. Measurement of ankle angular velocity using a gyro-sensor is both reliable and feasible, with the results representing a significant correlation to muscle power and performance measurements.

Satellite angular velocity estimation based on star images and optical flow techniques.

PubMed

Fasano, Giancarmine; Rufino, Giancarlo; Accardo, Domenico; Grassi, Michele

2013-09-25

An optical flow-based technique is proposed to estimate spacecraft angular velocity based on sequences of star-field images. It does not require star identification and can be thus used to also deliver angular rate information when attitude determination is not possible, as during platform de tumbling or slewing. Region-based optical flow calculation is carried out on successive star images preprocessed to remove background. Sensor calibration parameters, Poisson equation, and a least-squares method are then used to estimate the angular velocity vector components in the sensor rotating frame. A theoretical error budget is developed to estimate the expected angular rate accuracy as a function of camera parameters and star distribution in the field of view. The effectiveness of the proposed technique is tested by using star field scenes generated by a hardware-in-the-loop testing facility and acquired by a commercial-off-the shelf camera sensor. Simulated cases comprise rotations at different rates. Experimental results are presented which are consistent with theoretical estimates. In particular, very accurate angular velocity estimates are generated at lower slew rates, while in all cases the achievable accuracy in the estimation of the angular velocity component along boresight is about one order of magnitude worse than the other two components.

Satellite Angular Velocity Estimation Based on Star Images and Optical Flow Techniques

PubMed Central

Fasano, Giancarmine; Rufino, Giancarlo; Accardo, Domenico; Grassi, Michele

2013-01-01

An optical flow-based technique is proposed to estimate spacecraft angular velocity based on sequences of star-field images. It does not require star identification and can be thus used to also deliver angular rate information when attitude determination is not possible, as during platform de tumbling or slewing. Region-based optical flow calculation is carried out on successive star images preprocessed to remove background. Sensor calibration parameters, Poisson equation, and a least-squares method are then used to estimate the angular velocity vector components in the sensor rotating frame. A theoretical error budget is developed to estimate the expected angular rate accuracy as a function of camera parameters and star distribution in the field of view. The effectiveness of the proposed technique is tested by using star field scenes generated by a hardware-in-the-loop testing facility and acquired by a commercial-off-the shelf camera sensor. Simulated cases comprise rotations at different rates. Experimental results are presented which are consistent with theoretical estimates. In particular, very accurate angular velocity estimates are generated at lower slew rates, while in all cases the achievable accuracy in the estimation of the angular velocity component along boresight is about one order of magnitude worse than the other two components. PMID:24072023

An accuracy assessment of Magellan Very Long Baseline Interferometry (VLBI)

NASA Technical Reports Server (NTRS)

Engelhardt, D. B.; Kronschnabl, G. R.; Border, J. S.

1990-01-01

Very Long Baseline Interferometry (VLBI) measurements of the Magellan spacecraft's angular position and velocity were made during July through September, 1989, during the spacecraft's heliocentric flight to Venus. The purpose of this data acquisition and reduction was to verify this data type for operational use before Magellan is inserted into Venus orbit, in August, 1990. The accuracy of these measurements are shown to be within 20 nanoradians in angular position, and within 5 picoradians/sec in angular velocity. The media effects and their calibrations are quantified; the wet fluctuating troposphere is the dominant source of measurement error for angular velocity. The charged particle effect is completely calibrated with S- and X-Band dual-frequency calibrations. Increasing the accuracy of the Earth platform model parameters, by using VLBI-derived tracking station locations consistent with the planetary ephemeris frame, and by including high frequency Earth tidal terms in the Earth rotation model, add a few nanoradians improvement to the angular position measurements. Angular velocity measurements were insensitive to these Earth platform modelling improvements.

Brushless Low-Speed dc Tachometer

NASA Technical Reports Server (NTRS)

Handlykken, M. B.

1984-01-01

Proposed tachometer produces voltages proportional to shaft angular velocity and (by differentiation) acceleration. Coil moving in homopolar field generates emf proportional to shaft angular velocity.

Comparison of sequence of trunk and arm motions between short and long official distance groups in javelin throwing.

PubMed

Liu, Hui; Leigh, Steve; Yu, Bing

2014-03-01

The purpose of this study was to determine the effects of sequences of the trunk and arm angular motions on the performance of javelin throwing. In this study, 32 male and 30 female elite javelin throwers participated and were separated into a short official distance group or a long official distance group in each gender. Three-dimensional coordinates of 21 body landmarks and 3 marks on the javelin in the best trial were collected for each subject. Joint center linear velocities and selected trunk and arm segment and joint angles and angular velocities were calculated. The times of the initiations of the selected segment and joint angular motions and maximum angular velocities were determined. The sequences of the initiations of the selected segment and joint angular motions and maximum angular velocities were compared between short and long official distance groups and between genders. The results demonstrated that short and long official distance groups employed similar sequences of the trunk and arm motions. Male and female javelin throwers employed different sequences of the trunk and arm motions. The sequences of the trunk and arm motions were different from those of the maximal joint center linear velocities.

DVL Angular Velocity Recorder

NASA Technical Reports Server (NTRS)

Liebe, Wolfgang

1944-01-01

In many studies, especially of nonstationary flight motion, it is necessary to determine the angular velocities at which the airplane rotates about its various axes. The three-component recorder is designed to serve this purpose. If the angular velocity for one flight attitude is known, other important quantities can be derived from its time rate of change, such as the angular acceleration by differentiations, or - by integration - the angles of position of the airplane - that is, the angles formed by the airplane axes with the axis direction presented at the instant of the beginning of the motion that is to be investigated.

Misperceptions of angular velocities influence the perception of rigidity in the kinetic depth effect

NASA Technical Reports Server (NTRS)

Domini, F.; Caudek, C.; Proffitt, D. R.; Kaiser, M. K. (Principal Investigator)

1997-01-01

Accuracy in discriminating rigid from nonrigid motion was investigated for orthographic projections of three-dimension rotating objects. In 3 experiments the hypothesis that magnitudes of angular velocity are misperceived in the kinetic depth effect was tested, and in 4 other experiments the hypothesis that misperceiving angular velocities leads to misperceiving rigidity was tested. The principal findings were (a) the magnitude of perceived angular velocity is derived heuristically as a function of a property of the first-order optic flow called deformation and (b) perceptual performance in discriminating rigid from nonrigid motion is accurate in cases when the variability of the deformations of the individual triplets of points of the stimulus displays favors this interpretation and not accurate in other cases.

Misperceptions of angular velocities influence the perception of rigidity in the kinetic depth effect.

PubMed

Domini, F; Caudek, C; Proffitt, D R

1997-08-01

Accuracy in discriminating rigid from nonrigid motion was investigated for orthographic projections of three-dimension rotating objects. In 3 experiments the hypothesis that magnitudes of angular velocity are misperceived in the kinetic depth effect was tested, and in 4 other experiments the hypothesis that misperceiving angular velocities leads to misperceiving rigidity was tested. The principal findings were (a) the magnitude of perceived angular velocity is derived heuristically as a function of a property of the first-order optic flow called deformation and (b) perceptual performance in discriminating rigid from nonrigid motion is accurate in cases when the variability of the deformations of the individual triplets of points of the stimulus displays favors this interpretation and not accurate in other cases.

Peak firing rates of rat anterodorsal thalamic head direction cells are higher during faster passive rotations.

PubMed

Zugaro, Michaël B; Berthoz, Alain; Wiener, Sidney I

2002-01-01

Head direction cells discharge selectively when the head of the animal is oriented in a specific direction. The goal of this study was to determine how sensory signals arising from passive rotations (e.g., triggered by vestibular stimulation and dynamic visual inputs) influence the responses of anterodorsal thalamic head direction cells in the absence of voluntary movement cues (e.g., motor command, efference copy, and associated kinesthetic signals). Three unrestrained rats consumed water from a reservoir at the center of a circular platform while passively subjected to sinusoidal rotatory oscillations at fast (153 +/- 27 degrees/s, sd) and slow (38 +/- 15 degrees/s) peak velocities. In 14 anterodorsal thalamic head direction cells, the preferred directions, angular response ranges and baseline firing rates remained stable, but the peak firing rates were, on average, 36% higher during the fast rotations (Wilcoxon matched-pairs test, p < 0.001; variation range: +11% to approximately +100%). No cell changed its peak firing rate by less than 10%, while three cells (21%) increased their peak firing rates by more than 50%. The velocity-dependent increase in peak firing rates was similar for left and right rotations, and the skewness of the directional response curves were not significantly different between left and right turns (Wilcoxon matched-pairs tests, n = 14, ns). These results show that sensory signals concerning self-movements modulate the responses of the head direction cells in the absence of active locomotion.

Evidence for changes in the angular velocity of the surface regions of the sun and stars

NASA Technical Reports Server (NTRS)

1972-01-01

A round table discussion of problems of solar and stellar spindown and theory is presented. Observational evidence of the angular momentum of the solar wind is included, emphasizing changes in the angular velocity of the surface regions of the sun and stars.

Effect of angular velocity on soleus and medial gastrocnemius H-reflex during maximal concentric and eccentric muscle contraction.

PubMed

Duclay, Julien; Robbe, Alice; Pousson, Michel; Martin, Alain

2009-10-01

At rest, the H-reflex is lower during lengthening than shortening actions. During passive lengthening, both soleus (SOL) and medial gastrocnemius (MG) H-reflex amplitudes decrease with increasing angular velocity. This study was designed to investigate whether H-reflex amplitude is affected by angular velocity during concentric and eccentric maximal voluntary contraction (MVC). Experiments were performed on nine healthy men. At a constant angular velocity of 60 degrees /s and 20 degrees /s, maximal H-reflex and M-wave potentials were evoked at rest (i.e., H(max) and M(max), respectively) and during concentric and eccentric MVC (i.e., H(sup) and M(sup), respectively). Regardless of the muscle, H(max)/M(max) was lower during lengthening than shortening actions and the H(sup)/M(sup) ratio was higher than H(max)/M(max) during lengthening actions. Whereas no action type and angular velocity effects on the MG H(sup)/M(sup) were found, the SOL H(sup)/M(sup) was lower during eccentric than concentric MVC and this depression was increased with higher angular velocity. Our findings indicate that the depression of the H-reflex amplitude during eccentric compared to concentric MVC depends mainly on the amount of inhibition induced by lengthening action. In conclusion, H-reflex should be evoked during both passive and active dynamic trials to evaluate the plasticity of the spinal loop.

Dissociative electron attachment studies on acetone

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

Prabhudesai, Vaibhav S., E-mail: vaibhav@tifr.res.in; Tadsare, Vishvesh; Ghosh, Sanat

Dissociative electron attachment (DEA) to acetone is studied in terms of the absolute cross section for various fragment channels in the electron energy range of 0–20 eV. H{sup −} is found to be the most dominant fragment followed by O{sup −} and OH{sup −} with only one resonance peak between 8 and 9 eV. The DEA dynamics is studied by measuring the angular distribution and kinetic energy distribution of fragment anions using Velocity Slice Imaging technique. The kinetic energy and angular distribution of H{sup −} and O{sup −} fragments suggest a many body break-up for the lone resonance observed. Themore » ab initio calculations show that electron is captured in the multi-centered anti-bonding molecular orbital which would lead to a many body break-up of the resonance.« less

Angular velocity estimation based on star vector with improved current statistical model Kalman filter.

PubMed

Zhang, Hao; Niu, Yanxiong; Lu, Jiazhen; Zhang, He

2016-11-20

Angular velocity information is a requisite for a spacecraft guidance, navigation, and control system. In this paper, an approach for angular velocity estimation based merely on star vector measurement with an improved current statistical model Kalman filter is proposed. High-precision angular velocity estimation can be achieved under dynamic conditions. The amount of calculation is also reduced compared to a Kalman filter. Different trajectories are simulated to test this approach, and experiments with real starry sky observation are implemented for further confirmation. The estimation accuracy is proved to be better than 10^-4  rad/s under various conditions. Both the simulation and the experiment demonstrate that the described approach is effective and shows an excellent performance under both static and dynamic conditions.

Improper trunk rotation sequence is associated with increased maximal shoulder external rotation angle and shoulder joint force in high school baseball pitchers.

PubMed

Oyama, Sakiko; Yu, Bing; Blackburn, J Troy; Padua, Darin A; Li, Li; Myers, Joseph B

2014-09-01

In a properly coordinated throwing motion, peak pelvic rotation velocity is reached before peak upper torso rotation velocity, so that angular momentum can be transferred effectively from the proximal (pelvis) to distal (upper torso) segment. However, the effects of trunk rotation sequence on pitching biomechanics and performance have not been investigated. The aim of this study was to investigate the effects of trunk rotation sequence on ball speed and on upper extremity biomechanics that are linked to injuries in high school baseball pitchers. The hypothesis was that pitchers with improper trunk rotation sequence would demonstrate lower ball velocity and greater stress to the joint. Descriptive laboratory study. Three-dimensional pitching kinematics data were captured from 72 high school pitchers. Subjects were considered to have proper or improper trunk rotation sequences when the peak pelvic rotation velocity was reached either before or after the peak upper torso rotation velocity beyond the margin of error (±3.7% of the time from stride-foot contact to ball release). Maximal shoulder external rotation angle, elbow extension angle at ball release, peak shoulder proximal force, shoulder internal rotation moment, and elbow varus moment were compared between groups using independent t tests (α < 0.05). Pitchers with improper trunk rotation sequences (n = 33) demonstrated greater maximal shoulder external rotation angle (mean difference, 7.2° ± 2.9°, P = .016) and greater shoulder proximal force (mean difference, 9.2% ± 3.9% body weight, P = .021) compared with those with proper trunk rotation sequences (n = 22). No other variables differed significantly different between groups. High school baseball pitchers who demonstrated improper trunk rotation sequences demonstrated greater maximal shoulder external rotation angle and shoulder proximal force compared with pitchers with proper trunk rotation sequences. Improper sequencing of the trunk and torso alter upper extremity joint loading in ways that may influence injury risk. As such, exercises that reinforce the use of a proper trunk rotation sequence during the pitching motion may reduce the stress placed on the structures around the shoulder joint and lead to the prevention of injuries. © 2014 The Author(s).

Three-dimensional Shock Structure of the Orion KL Outflow with IGRINS

NASA Astrophysics Data System (ADS)

Oh, Heeyoung; Pyo, Tae-Soo; Kaplan, Kyle; Yuk, In-Soo; Park, Byeong-Gon; Mace, Gregory; Park, Chan; Chun, Moo-Young; Pak, Soojong; Kim, Kang-Min; Sok Oh, Jae; Jeong, Ueejeong; Yu, Young Sam; Lee, Jae-Joon; Kim, Hwihyun; Hwang, Narae; Lee, Hye-In; Nguyen Le, Huynh Anh; Lee, Sungho; Jaffe, Daniel T.

2016-12-01

We report a study of the three-dimensional (3D) outflow structure of a 15″ × 13″ area around the H2 peak 1 in Orion KL with slit-scan observations (13 slits) using the Immersion Grating Infrared Spectrograph. The datacubes have a high-velocity resolution (˜7.5 km s-1), provide high-contrast imaging within ultra-narrow bands, and enable the detection of the main stream of the previously reported H2 outflow fingers. We identified 31 distinct fingers in the H2 1-0 S(1) λ2.122 μm emission. The line profile at each finger shows multiple-velocity peaks with a strong low-velocity component around the systemic velocity at {V}{LSR} = +8 km s-1 and high-velocity emission (| {V}{LSR}| = 45-135 km s-1), indicating a typical bow-shock. The observed radial velocity gradients of ˜4 km s-1 arcsec-1 agree well with the velocities inferred from large-scale proper motions, where the projected motion is proportional to the distance from a common origin. We construct a conceptual 3D map of the fingers with estimated inclination angles of 57°-74°. The extinction difference (ΔA v > 10 mag) between blueshifted and redshifted fingers indicates high internal extinction. The extinction, the overall angular spread, and the scale of the flow argue for an ambient medium with a very high density (105-106 cm-3), consistent with molecular line observations of the Orion Molecular Cloud core. The radial velocity gradients and the 3D distributions of the fingers together support the hypothesis of a simultaneous radial explosion of the Orion KL outflow. This paper includes data taken at The McDonald Observatory of The University of Texas at Austin.

Angular width of the Cherenkov radiation with inclusion of multiple scattering

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

Zheng, Jian, E-mail: jzheng@ustc.edu.cn

2016-06-15

Visible Cherenkov radiation can offer a method of the measurement of the velocity of charged particles. The angular width of the radiation is important since it determines the resolution of the velocity measurement. In this article, the angular width of Cherenkov radiation with inclusion of multiple scattering is calculated through the path-integral method, and the analytical expressions are presented. The condition that multiple scattering processes dominate the angular distribution is obtained.

Measurement of irregularities in angular velocities of rotating assemblies in memory devices on magnetic carriers

NASA Technical Reports Server (NTRS)

Virakas, G. I.; Matsyulevichyus, R. A.; Minkevichyus, K. P.; Potsyus, Z. Y.; Shirvinskas, B. D.

1973-01-01

Problems in measurement of irregularities in angular velocity of rotating assemblies in memory devices with rigid and flexible magnetic data carriers are discussed. A device and method for determination of change in angular velocities in various frequency and rotation rate ranges are examined. A schematic diagram of a photoelectric sensor for recording the signal pulses is provided. Mathematical models are developed to show the amount of error which can result from misalignment of the test equipment.

Transition from steady to periodic liquid-metal magnetohydrodynamic flow in a sliding electrical contact

NASA Astrophysics Data System (ADS)

Talmage, Gita; Walker, John S.; Brown, Samuel H.; Sondergaard, Neal A.

1993-09-01

In homopolar motors and generators, large dc electric currents pass through the sliding electrical contacts between rotating copper disks (rotors) and static copper surfaces shrouding the rotor tips (stators). A liquid metal in the small radial gap between the rotor tip and concentric stator surface can provide a low-resistance, low-drag electrical contact. Since there is a strong magnetic field in the region of the electrical contacts, there are large electromagnetic body forces on the liquid metal. The primary, azimuthal motion consists of simple Couette flow, plus an electromagnetically driven flow with large extremes of the azimuthal velocity near the rotor corners. The secondary flow involves the radial and axial velocity components, is driven by the centrifugal force associated with the primary flow, and is opposed by the electromagnetic body force, so that the circulation varies inversely as the square of the magnetic-field strength. Three flow regimes are identified as the angular velocity Ω of the rotor is increased. For small Ω, the primary flow is decoupled from the secondary flow. As Ω increases, the secondary flow begins to convect the azimuthal-velocity peaks radially outward, which in turn changes the centrifugal force driving the secondary flow. At some critical value of Ω, the flow becomes periodic through the coupling of the primary and secondary flows. The azimuthal-velocity peaks begin to move radially in and out with an accompanying oscillation in the secondary-flow strength.

The relationship between consistency of propulsive cycles and maximum angular velocity during wheelchair racing.

PubMed

Wang, Yong Tai; Vrongistinos, Konstantinos Dino; Xu, Dali

2008-08-01

The purposes of this study were to examine the consistency of wheelchair athletes' upper-limb kinematics in consecutive propulsive cycles and to investigate the relationship between the maximum angular velocities of the upper arm and forearm and the consistency of the upper-limb kinematical pattern. Eleven elite international wheelchair racers propelled their own chairs on a roller while performing maximum speeds during wheelchair propulsion. A Qualisys motion analysis system was used to film the wheelchair propulsive cycles. Six reflective markers placed on the right shoulder, elbow, wrist joints, metacarpal, wheel axis, and wheel were automatically digitized. The deviations in cycle time, upper-arm and forearm angles, and angular velocities among these propulsive cycles were analyzed. The results demonstrated that in the consecutive cycles of wheelchair propulsion the increased maximum angular velocity may lead to increased variability in the upper-limb angular kinematics. It is speculated that this increased variability may be important for the distribution of load on different upper-extremity muscles to avoid the fatigue during wheelchair racing.

A Study of Airplane Maneuvers with Special Reference to Angular Velocities

NASA Technical Reports Server (NTRS)

Reid, J E

1923-01-01

This investigation was undertaken by the National Advisory Committee for Aeronautics for the purpose of increasing our knowledge on the behavior of the airplane during various maneuvers and to obtain values of the maximum angular velocities and accelerations in flight. The method consisted in flying a JN4H airplane through various maneuvers while records were being taken of the control position, the air speed, the angular velocity and the acceleration along the Z axis. The results showed that the maximum angular velocity about the X axis of radians per second in a barrel roll. The maximum angular acceleration about the X axis of -2.10 radians per (second) to the 2nd power occurred in a spin, while the maximum about the Y axis was 1.40 radians per (second) to the 2nd power when pulling suddenly out of a dive. These results have direct application to the design of airplane parts, such as propeller shaft and instruments.

Effect of postural changes on 3D joint angular velocity during starting block phase.

PubMed

Slawinski, Jean; Dumas, Raphaël; Cheze, Laurence; Ontanon, Guy; Miller, Christian; Mazure-Bonnefoy, Alice

2013-01-01

Few studies have focused on the effect of posture during sprint start. The aim of this study was to measure the effect of the modification of horizontal distance between the blocks during sprint start on three dimensional (3D) joint angular velocity. Nine trained sprinters started using three different starting positions (bunched, medium and elongated). They were equipped with 63 passive reflective markers, and an opto-electronic Motion Analysis system was used to collect the 3D marker trajectories. During the pushing phase on the blocks, norm of the joint angular velocity (NJAV), 3D Euler angular velocity (EAV) and pushing time on the blocks were calculated. The results demonstrated that the decrease of the block spacing induces an opposite effect on the angular velocity of joints of the lower and the upper limbs. The NJAV of the upper limbs is greater in the bunched start, whereas the NJAV of the lower limbs is smaller. The modifications of NJAV were due to a combination of the movement of the joints in the different degrees of freedom. The medium start seems to be the best compromise because it leads, in a short pushing time, to a combination of optimal joint velocities for upper and lower segments.

Immediate compensation for variations in self-generated Coriolis torques related to body dynamics and carried objects

PubMed Central

DiZio, Paul; Lackner, James R.

2013-01-01

We have previously shown that the Coriolis torques that result when an arm movement is performed during torso rotation do not affect movement trajectory. Our purpose in the present study was to examine whether torso motion-induced Coriolis and other interaction torques are counteracted during a turn and reach (T&R) movement when the effective mass of the hand is augmented, and whether the dominant arm has an advantage in coordinating intersegmental dynamics as predicted by the dynamic dominance hypothesis (Sainburg RL. Exp Brain Res 142: 241–258, 2002). Subjects made slow and fast T&R movements in the dark to just extinguished targets with either arm, while holding or not holding a 454-g object. Movement endpoints were equally accurate at both speeds, with either hand, and in both weight conditions, but subjects tended to angularly undershoot and produce more variable endpoints for targets requiring greater torso rotation. There were no changes in endpoint accuracy or trajectory deviation over repeated movements. The dominant right arm was more stable in its control of trajectory direction across targets, whereas the nondominant left arm had an improved ability to stop accurately on the target for higher levels of interaction torques. The trajectories to more eccentric targets were straighter when performed at higher speeds but slightly more deviated when subjects held the weight. Subjects did not slow their torso velocity or change the timing of the arm and torso velocities when holding the weight, although there was a slight decrease in their hand velocity relative to the torso. The delay between the onsets of torso and finger movements was almost twice as large for the right arm than the left, suggesting the right arm was better able to account for torso rotation in the arm movement. Holding the weight increased the peak Coriolis torque by 40% at the shoulder and 45% at the elbow and, for the most eccentric target, increased the peak net torque by 12% at the shoulder and 34% at the elbow. In accordance with Sainburg's dynamic dominance hypothesis, the right arm exhibited an advantage for coordinating intersegmental dynamics, showing a more stable finger velocity in relation to the torso across targets, decreasing error variability with movement speed, and more synchronized peaks of finger relative and torso angular velocities in conditions with greater joint torque requirements. The arm used had little effect on the movement path and the magnitude of the joint torques in any of the conditions. These results indicate that compensations for forthcoming Coriolis torque variations take into account the dynamic properties of the body and of external objects, as well as the planned velocities of the torso and arm. PMID:23803330

Immediate compensation for variations in self-generated Coriolis torques related to body dynamics and carried objects.

PubMed

Pigeon, Pascale; Dizio, Paul; Lackner, James R

2013-09-01

We have previously shown that the Coriolis torques that result when an arm movement is performed during torso rotation do not affect movement trajectory. Our purpose in the present study was to examine whether torso motion-induced Coriolis and other interaction torques are counteracted during a turn and reach (T&R) movement when the effective mass of the hand is augmented, and whether the dominant arm has an advantage in coordinating intersegmental dynamics as predicted by the dynamic dominance hypothesis (Sainburg RL. Exp Brain Res 142: 241-258, 2002). Subjects made slow and fast T&R movements in the dark to just extinguished targets with either arm, while holding or not holding a 454-g object. Movement endpoints were equally accurate at both speeds, with either hand, and in both weight conditions, but subjects tended to angularly undershoot and produce more variable endpoints for targets requiring greater torso rotation. There were no changes in endpoint accuracy or trajectory deviation over repeated movements. The dominant right arm was more stable in its control of trajectory direction across targets, whereas the nondominant left arm had an improved ability to stop accurately on the target for higher levels of interaction torques. The trajectories to more eccentric targets were straighter when performed at higher speeds but slightly more deviated when subjects held the weight. Subjects did not slow their torso velocity or change the timing of the arm and torso velocities when holding the weight, although there was a slight decrease in their hand velocity relative to the torso. The delay between the onsets of torso and finger movements was almost twice as large for the right arm than the left, suggesting the right arm was better able to account for torso rotation in the arm movement. Holding the weight increased the peak Coriolis torque by 40% at the shoulder and 45% at the elbow and, for the most eccentric target, increased the peak net torque by 12% at the shoulder and 34% at the elbow. In accordance with Sainburg's dynamic dominance hypothesis, the right arm exhibited an advantage for coordinating intersegmental dynamics, showing a more stable finger velocity in relation to the torso across targets, decreasing error variability with movement speed, and more synchronized peaks of finger relative and torso angular velocities in conditions with greater joint torque requirements. The arm used had little effect on the movement path and the magnitude of the joint torques in any of the conditions. These results indicate that compensations for forthcoming Coriolis torque variations take into account the dynamic properties of the body and of external objects, as well as the planned velocities of the torso and arm.

Geodesics In A Spinning String Spacetime

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

Culetu, Hristu

2006-11-28

The geodesics equations for a rotating observer in a spinning string geometry are investigated using the Euler - Lagrange equations. For test particles with vanishing angular momentum, the radial equation of motion does not depend on the angular velocity {omega} but on the angular momentum of the string. A massless particle moves tachyonic but iteed tends asymptotically to unit velocity after a time of the order of few Planck time b. The spacetime has a horizon at r = 0, irrespective of the value of {omega} but its angular velocity is given by {omega} - 1/b. The Sagnac time delaymore » is computed proving to depend both on {omega} and the radius of the circular orbit. The velocity of an ingoing massive test particle approaches zero very close to the spinning string, as if it were rejected by it.« less

Spacecraft angular velocity estimation algorithm for star tracker based on optical flow techniques

NASA Astrophysics Data System (ADS)

Tang, Yujie; Li, Jian; Wang, Gangyi

2018-02-01

An integrated navigation system often uses the traditional gyro and star tracker for high precision navigation with the shortcomings of large volume, heavy weight and high-cost. With the development of autonomous navigation for deep space and small spacecraft, star tracker has been gradually used for attitude calculation and angular velocity measurement directly. At the same time, with the dynamic imaging requirements of remote sensing satellites and other imaging satellites, how to measure the angular velocity in the dynamic situation to improve the accuracy of the star tracker is the hotspot of future research. We propose the approach to measure angular rate with a nongyro and improve the dynamic performance of the star tracker. First, the star extraction algorithm based on morphology is used to extract the star region, and the stars in the two images are matched according to the method of angular distance voting. The calculation of the displacement of the star image is measured by the improved optical flow method. Finally, the triaxial angular velocity of the star tracker is calculated by the star vector using the least squares method. The method has the advantages of fast matching speed, strong antinoise ability, and good dynamic performance. The triaxial angular velocity of star tracker can be obtained accurately with these methods. So, the star tracker can achieve better tracking performance and dynamic attitude positioning accuracy to lay a good foundation for the wide application of various satellites and complex space missions.

Biofidelic neck influences head kinematics of parietal and occipital impacts following short falls in infants.

PubMed

Sullivan, Sarah; Coats, Brittany; Margulies, Susan S

2015-09-01

Falls are a major cause of traumatic head injury in children. Understanding head kinematics during low height falls is essential for evaluating injury risk and designing mitigating strategies. Typically, these measurements are made with commercial anthropomorphic infant surrogates, but these surrogates are designed based on adult biomechanical data. In this study, we improve upon the state-of-the-art anthropomorphic testing devices by incorporating new infant cadaver neck bending and tensile data. We then measure head kinematics following head-first falls onto 4 impact surfaces from 3 fall heights with occipital and parietal head impact locations. The biofidelic skull compliance and neck properties of the improved infant surrogate significantly influenced the measured kinematic loads, decreasing the measured impact force and peak angular accelerations, lowering the expected injury risk. Occipital and parietal impacts exhibited distinct kinematic responses in primary head rotation direction and the magnitude of the rotational velocities and accelerations, with larger angular velocities as the head rebounded after occipital impacts. Further evaluations of injury risk due to short falls should take into account the impact surface and head impact location, in addition to the fall height. Copyright © 2015 Elsevier Ltd. All rights reserved.

Biofidelic neck influences head kinematics of parietal and occipital impacts following short falls in infants

PubMed Central

Sullivan, Sarah; Coats, Brittany; Margulies, Susan S.

2015-01-01

Falls are a major cause of traumatic head injury in children. Understanding head kinematics during low height falls is essential for evaluating injury risk and designing mitigating strategies. Typically, these measurements are made with commercial anthropomorphic infant surrogates, but these surrogates are designed based on adult biomechanical data. In this study, we improve upon the state-of-the-art anthropomorphic testing devices by incorporating new infant cadaver neck bending and tensile data. We then measure head kinematics following head-first falls onto 4 impact surfaces from 3 fall heights with occipital and parietal head impact locations. The biofidelic skull compliance and neck properties of the improved infant surrogate significantly influenced the measured kinematic loads, decreasing the measured impact force and peak angular accelerations, lowering the expected injury risk. Occipital and parietal impacts exhibited distinct kinematic responses in primary head rotation direction and the magnitude of the rotational velocities and accelerations, with larger angular velocities as the head rebounded after occipital impacts. Further evaluations of injury risk due to short falls should take into account the impact surface and head impact location, in addition to the fall height. PMID:26072183

The Lower Extremity Biomechanics of Single- and Double-Leg Stop-Jump Tasks

PubMed Central

2011-01-01

The anterior cruciate ligament (ACL) injury is a common occurrence in sports requiring stop-jump tasks. Single- and double-leg stop-jump techniques are frequently executed in sports. The higher risk of ACL injury in single-leg drop landing task compared to a double-leg drop landing task has been identified. However the injury bias between single- and double-leg landing techniques has not been investigated for stop-jump tasks. The purpose of this study was to determine the differences between single- and double-leg stop-jump tasks in knee kinetics that were influenced by the lower extremity kinematics during the landing phase. Ground reaction force, lower extremity kinematics, and knee kinetics data during the landing phase were obtained from 10 subjects performing single- and double-leg stop-jump tasks, using motion-capture system and force palates. Greater peak posterior and vertical ground reaction forces, and peak proximal tibia anterior and lateral shear forces (p < 0.05) during landing phase were observed of single-leg stop-jump. Single-leg stop-jump exhibited smaller hip and knee flexion angle, and knee flexion angular velocity at initial foot contact with the ground (p < 0.05). We found smaller peak hip and knee flexion angles (p < 0.05) during the landing phase of single-leg stop-jump. These results indicate that single-leg landing may have higher ACL injury risk than double-leg landing in stop-jump tasks that may be influenced by the lower extremity kinematics during the landing phase. Key points Non-contact ACL injuries are more likely to occur during the single-leg stop-jump task than during the double-leg stop-jump task. Single-leg stop-jump exhibited greater peak proximal tibia anterior and lateral shear forces, and peak posterior and vertical ground reaction forces during the landing phase than the double-leg stop-jump task. Single-leg stop-jump exhibited smaller hip flexion angle, knee flexion angle, and knee flexion angular velocity at initial foot contact with the ground. Single-leg stop-jump exhibited greater peak knee extension and valgus moment during the landing phase than the double-leg stop-jump task. Single-leg stop-jump extended the hip joint at initial foot contact with the ground. PMID:24149308

Role of Cerebellum in Motion Perception and Vestibulo-ocular Reflex—Similarities and Disparities

PubMed Central

Shaikh, Aasef G.; Palla, Antonella; Marti, Sarah; Olasagasti, Itsaso; Optican, Lance M.; Zee, David S.; Straumann, Dominik

2012-01-01

Vestibular velocity storage enhances the efficacy of the angular vestibulo-ocular reflex (VOR) during relatively low-frequency head rotations. This function is modulated by GABA-mediated inhibitory cerebellar projections. Velocity storage also exists in perceptual pathway and has similar functional principles as VOR. However, it is not known whether the neural substrate for perception and VOR overlap. We propose two possibilities. First, there is the same velocity storage for both VOR and perception; second, there are nonoverlapping neural networks: one might be involved in perception and the other for the VOR. We investigated these possibilities by measuring VOR and perceptual responses in healthy human subjects during whole-body, constant-velocity rotation steps about all three dimensions (yaw, pitch, and roll) before and after 10 mg of 4-aminopyridine (4-AP). 4-AP, a selective blocker of inward rectifier potassium conductance, can lead to increased synchronization and precision of Purkinje neuron discharge and possibly enhance the GABAergic action. Hence 4-AP could reduce the decay time constant of the perceived angular velocity and VOR. We found that 4-AP reduced the decay time constant, but the amount of reduction in the two processes, perception and VOR, was not the same, suggesting the possibility of nonoverlapping or partially overlapping neural substrates for VOR and perception. We also noted that, unlike the VOR, the perceived angular velocity gradually built up and plateau prior to decay. Hence, the perception pathway may have additional mechanism that changes the dynamics of perceived angular velocity beyond the velocity storage. 4-AP had no effects on the duration of build-up of perceived angular velocity, suggesting that the higher order processing of perception, beyond the velocity storage, might not occur under the influence of mechanism that could be influenced by 4-AP. PMID:22777507

Neck forces and moments and head accelerations in side impact.

PubMed

Yoganandan, Narayan; Pintar, Frank A; Maiman, Dennis J; Philippens, Mat; Wismans, Jac

2009-03-01

Although side-impact sled studies have investigated chest, abdomen, and pelvic injury mechanics, determination of head accelerations and the associated neck forces and moments is very limited. The purpose of the present study was therefore to determine the temporal forces and moments at the upper neck region and head angular accelerations and angular velocities using postmortem human subjects (PMHS). Anthropometric data and X-rays were obtained, and the specimens were positioned upright on a custom-designed seat, rigidly fixed to the platform of the sled. PMHS were seated facing forward with the Frankfort plane horizontal, and legs were stretched parallel to the mid-sagittal plane. The normal curvature and alignment of the dorsal spine were maintained without initial torso rotation. A pyramid-shaped nine-accelerometer package was secured to the parietal-temporal region of the head. The test matrix consisted of groups A and B, representing the fully restrained torso condition, and groups C and D, representing the three-point belt-restrained torso condition. The change in velocity was 12.4 m/s for groups A and C, 17.9 m/s for group B, and 8.7 m/s for group D tests. Two specimens were tested in each group. Injuries were scored based on the Abbreviated Injury Scale. The head mass, center of gravity, and moment of inertia were determined for each specimen. Head accelerations and upper neck forces and moments were determined before head contact. Neck forces and moments and head angular accelerations and angular velocities are presented on a specimen-by-specimen basis. In addition, a summary of peak magnitudes of biomechanical data is provided because of their potential in serving as injury reference values characterizing head-neck biomechanics in side impacts. Though no skull fractures occurred, AIS 0 to 3 neck traumas were dependent on the impact velocity and restraint condition. Because specimen-specific head center of gravity and mass moment of inertia were determined, and a suitable instrumentation system was used for data collection and analysis, head angular accelerations and neck forces and moments determined in the present study can be used with confidence to advance impact biomechanics research. Although the sample size is limited in each group, results from these tests serve as a fundamental data set to validate finite element models and evaluate the performance and biofidelity of federalized and prototype side-impact dummies with a focus on head-neck biomechanics.

The dynamics of the Cl+C2H6→HCl(v',j')+C2H5 reaction at 0.24 eV: Is ethyl a spectator?

NASA Astrophysics Data System (ADS)

Bass, M. J.; Brouard, M.; Vallance, C.; Kitsopoulos, T. N.; Samartzis, P. C.; Toomes, R. L.

2003-10-01

The hydrogen atom abstraction reaction between Cl(2P3/2) and ethane has been studied at a mean collision energy of 0.24 eV. The experiments were performed in a coexpansion of molecular chlorine and ethane, with the atomic Cl reactants generated by laser photodissociation of Cl2 at 355 nm. HCl(v',j') products were detected quantum state selectively using (2+1) resonantly enhanced multiphoton ionization, coupled with velocity-map ion imaging. The ion images were used to determine center-of-mass angular and kinetic energy release distributions. Several analysis methods were employed and have been carefully assessed. It is shown that the single beam experiments can be used with confidence to determine both center-of-mass angular and energy release distributions. For the title reaction the angular distribution is found to be forward peaking, with on average 22% of the available energy channeled into internal excitation of the ethyl coproducts. Possible sources of this internal excitation are discussed.

Influence of resistance load on neuromuscular response to vibration training.

PubMed

Luo, Jin; Clarke, Michael; McNamara, Brian; Moran, Kieran

2009-03-01

The purpose of this study was to examine the influence of resistance load on the acute and acute residual effects of vibration training, with vibration applied directly to the bicep tendon in a maximal-effort dynamic resistance exercise (3 sets of maximal-effort bicep curls). Eleven participants were exposed to 4 training conditions in random order: exercise with 1 of 2 different loads (40% 1-repetition maximum [RM] or 70% 1RM load) combined with 1 of 2 vibration conditions (vibration [1.2 mm, 65 Hz] or sham vibration). Five minutes before and after the exercise, a set of maximal-effort bicep curls with a load of either 40 or 70% 1RM was performed as the pre- and posttraining test. Concentric elbow joint angular velocity, moment and power, and bicep root mean square electromyography (EMGrms) were measured during training and in the pre- and posttraining tests. The results show that during training (acute effect) and at 5 minutes after training (acute residual effect), vibration did not induce a significant change in EMGrms, mean and peak angular velocities, moment and power, time to peak power, and initial power at 100 milliseconds after the start of the concentric phase for either resistance load. Therefore, in aiming to train neuromuscular output using maximal-effort dynamic contractions (40 and 70% 1RM), there is no benefit in employing direct vibration, at least with a 1.2-mm amplitude and 65-Hz frequency. However, the amplitude of 1.2 mm may be too high to effectively stimulate neuromuscular output in maximal-effort dynamic contractions per se.

Determining whether a ball will land behind or in front of you: not just a combination of expansion and angular velocity.

PubMed

Brouwer, Anne-Marie; López-Moliner, Joan; Brenner, Eli; Smeets, Jeroen B J

2006-02-01

We propose and evaluate a source of information that ball catchers may use to determine whether a ball will land behind or in front of them. It combines estimates for the ball's horizontal and vertical speed. These estimates are based, respectively, on the rate of angular expansion and vertical velocity. Our variable could account for ball catchers' data of Oudejans et al. [The effects of baseball experience on movement initiation in catching fly balls. Journal of Sports Sciences, 15, 587-595], but those data could also be explained by the use of angular expansion alone. We therefore conducted additional experiments in which we asked subjects where simulated balls would land under conditions in which both angular expansion and vertical velocity must be combined for obtaining a correct response. Subjects made systematic errors. We found evidence for the use of angular velocity but hardly any indication for the use of angular expansion. Thus, if catchers use a strategy that involves combining vertical and horizontal estimates of the ball's speed, they do not obtain their estimates of the horizontal component from the rate of expansion alone.

Head Movement Dynamics During Play and Perturbed Mother-Infant Interaction

PubMed Central

Hammal, Zakia; Cohn, Jeffrey F; Messinger, Daniel S

2015-01-01

We investigated the dynamics of head movement in mothers and infants during an age-appropriate, well-validated emotion induction, the Still Face paradigm. In this paradigm, mothers and infants play normally for 2 minutes (Play) followed by 2 minutes in which the mothers remain unresponsive (Still Face), and then two minutes in which they resume normal behavior (Reunion). Participants were 42 ethnically diverse 4-month-old infants and their mothers. Mother and infant angular displacement and angular velocity were measured using the CSIRO head tracker. In male but not female infants, angular displacement increased from Play to Still-Face and decreased from Still Face to Reunion. Infant angular velocity was higher during Still-Face than Reunion with no differences between male and female infants. Windowed cross-correlation suggested changes in how infant and mother head movements are associated, revealing dramatic changes in direction of association. Coordination between mother and infant head movement velocity was greater during Play compared with Reunion. Together, these findings suggest that angular displacement, angular velocity and their coordination between mothers and infants are strongly related to age-appropriate emotion challenge. Attention to head movement can deepen our understanding of emotion communication. PMID:26640622

Experimental determination of the Yawing Moment due to Yawing Contributed by the Wing, Fuselage, and Vertical Tail of a Midwing Airplane Model

DTIC Science & Technology

1943-06-01

derivative Cnr, the rate of change of yawing-momer.t coefficient with yawing angular velocity, contributed ’by the wing, the fuselage, and the...derivative Cn , the rate of change of yawing--moraent coefficient with yawing angular velocity. Al- though theoretical methods for obtaining the...yaw. T CD -3 SYMBOLS ’n rate of change of yawing-moment coefficient with yawing angular velocity per unit of rh/2V ÖCn/d (^-’ \\ 27 J P

Measurement of Hydrodynamic Growth near Peak Velocity in an Inertial Confinement Fusion Capsule Implosion using a Self-Radiography Technique

NASA Astrophysics Data System (ADS)

Pickworth, L. A.; Hammel, B. A.; Smalyuk, V. A.; MacPhee, A. G.; Scott, H. A.; Robey, H. F.; Landen, O. L.; Barrios, M. A.; Regan, S. P.; Schneider, M. B.; Hoppe, M.; Kohut, T.; Holunga, D.; Walters, C.; Haid, B.; Dayton, M.

2016-07-01

First measurements of hydrodynamic growth near peak implosion velocity in an inertial confinement fusion (ICF) implosion at the National Ignition Facility were obtained using a self-radiographing technique and a preimposed Legendre mode 40, λ =140 μ m , sinusoidal perturbation. These are the first measurements of the total growth at the most unstable mode from acceleration Rayleigh-Taylor achieved in any ICF experiment to date, showing growth of the areal density perturbation of ˜7000 × . Measurements were made at convergences of ˜5 to ˜10 × at both the waist and pole of the capsule, demonstrating simultaneous measurements of the growth factors from both lines of sight. The areal density growth factors are an order of magnitude larger than prior experimental measurements and differed by ˜2 × between the waist and the pole, showing asymmetry in the measured growth factors. These new measurements significantly advance our ability to diagnose perturbations detrimental to ICF implosions, uniquely intersecting the change from an accelerating to decelerating shell, with multiple simultaneous angular views.

Measurement of hydrodynamic growth near peak velocity in an inertial confinement fusion capsule implosion using a self-radiography technique

DOE PAGES

Pickworth, L. A.; Hammel, B. A.; Smalyuk, V. A.; ...

2016-07-11

First measurements of hydrodynamic growth near peak implosion velocity in an inertial confinement fusion (ICF) implosion at the National Ignition Facility were obtained using a self-radiographing technique and a preimposed Legendre mode 40, λ = 140 μm, sinusoidal perturbation. These are the first measurements of the total growth at the most unstable mode from acceleration Rayleigh-Taylor achieved in any ICF experiment to date, showing growth of the areal density perturbation of ~7000×. Measurements were made at convergences of ~5 to ~10× at both the waist and pole of the capsule, demonstrating simultaneous measurements of the growth factors from both linesmore » of sight. The areal density growth factors are an order of magnitude larger than prior experimental measurements and differed by ~2× between the waist and the pole, showing asymmetry in the measured growth factors. As a result, these new measurements significantly advance our ability to diagnose perturbations detrimental to ICF implosions, uniquely intersecting the change from an accelerating to decelerating shell, with multiple simultaneous angular views.« less

Motor planning modulates sensory-motor control of collision avoidance behavior in the bullfrog, Rana catesbeiana

PubMed Central

Nakagawa, Hideki; Nishida, Yuuya

2012-01-01

Summary In this study, we examined the collision avoidance behavior of the frog, Rana catesbeiana to an approaching object in the upper visual field. The angular velocity of the frog's escape turn showed a significant positive correlation with the turn angle (r2 = 0.5741, P<0.05). A similar mechanism of velocity control has been known in head movements of the owl and in human saccades. By analogy, this suggests that the frog planned its escape velocity in advance of executing the turn, to make the duration of the escape behavior relatively constant. For escape turns less than 60°, the positive correlation was very strong (r2 = 0.7097, P<0.05). Thus, the frog controlled the angular velocity of small escape turns very accurately and completed the behavior within a constant time. On the other hand, for escape turns greater than 60°, the same correlation was not significant (r2 = 0.065, P>0.05). Thus, the frog was not able to control the velocity of the large escape turns accurately and did not complete the behavior within a constant time. In the latter case, there was a small but significant positive correlation between the threshold angular size and the angular velocity (r2 = 0.1459, P<0.05). This suggests that the threshold is controlled to compensate for the insufficient escape velocity achieved during large turn angles, and could explain a significant negative correlation between the turn angle and the threshold angular size (r2 = 0.1145, P<0.05). Thus, it is likely that the threshold angular size is also controlled by the turn angle and is modulated by motor planning. PMID:23213389

Stellar models simulating the disk-locking mechanism and the evolutionary history of the Orion Nebula cluster and NGC 2264

NASA Astrophysics Data System (ADS)

Landin, N. R.; Mendes, L. T. S.; Vaz, L. P. R.; Alencar, S. H. P.

2016-02-01

Context. Rotational evolution in young stars is described by pre-main sequence evolutionary tracks including non-gray boundary conditions, rotation, conservation of angular momentum, and simulations of disk-locking. Aims: By assuming that disk-locking is the regulation mechanism for the stellar angular velocity during the early stages of pre-main sequence evolution, we use our rotating models and observational data to constrain disk lifetimes (Tdisk) of a representative sample of low-mass stars in two young clusters, the Orion Nebula cluster (ONC) and NGC 2264, and to better understand their rotational evolution. Methods: The period distributions of the ONC and NGC 2264 are known to be bimodal and to depend on the stellar mass. To follow the rotational evolution of these two clusters' stars, we generated sets of evolutionary tracks from a fully convective configuration with low central temperatures (before D- and Li-burning). We assumed that the evolution of fast rotators can be represented by models considering conservation of angular momentum during all stages and of moderate rotators by models considering conservation of angular velocity during the first stages of evolution. With these models we estimate a mass and an age for all stars. Results: The resulting mass distribution for the bulk of the cluster population is in the ranges of 0.2-0.4 M⊙ and 0.1-0.6 M⊙ for the ONC and NGC 2264, respectively. For the ONC, we assume that the secondary peak in the period distribution is due to high-mass objects still locked in their disks, with a locking period (Plock) of ~8 days. For NGC 2264 we make two hypotheses: (1) the stars in the secondary peak are still locked with Plock = 5 days, and (2) NGC 2264 is in a later stage in the rotational evolution. Hypothesis 2 implies in a disk-locking scenario with Plock = 8 days, a disk lifetime of 1 Myr and, after that, constant angular momentum evolution. We then simulated the period distribution of NGC 2264 when the mean age of the cluster was 1 Myr. Dichotomy and bimodality appear in the simulated distribution, presenting one peak at 2 days and another one at 5-7 days, indicating that the assumption of Plock = 8 days is plausible. Our hypotheses are compared with observational disk diagnoses available in the literature for the ONC and NGC 2264, such as near-infrared excess, Hα emission, and spectral energy distribution slope in the mid-infrared. Conclusions: Disk-locking models with Plock = 8 days and 0.2 Myr ≤ Tdisk ≤ 3 Myr are consistent with observed periods of moderate rotators of the ONC. For NGC 2264, the more promising explanation for the observed period distribution is an evolution with disk-locking (with Plock near 8 days) during the first 1 Myr, approximately, but after this, the evolution continued with constant angular momentum. Full Table 1 is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A96

Single-axis gyroscopic motion with uncertain angular velocity about spin axis

NASA Technical Reports Server (NTRS)

Singh, S. N.

1977-01-01

A differential game approach is presented for studying the response of a gyro by treating the controlled angular velocity about the input axis as the evader, and the bounded but uncertain angular velocity about the spin axis as the pursuer. When the uncertain angular velocity about the spin axis desires to force the gyro to saturation a differential game problem with two terminal surfaces results, whereas when the evader desires to attain the equilibrium state the usual game with single terminal manifold arises. A barrier, delineating the capture zone (CZ) in which the gyro can attain saturation and the escape zone (EZ) in which the evader avoids saturation is obtained. The CZ is further delineated into two subregions such that the states in each subregion can be forced on a definite target manifold. The application of the game theoretic approach to Control Moment Gyro is briefly discussed.

Relationship between the size of a camphor-driven rotor and its angular velocity.

PubMed

Koyano, Yuki; Gryciuk, Marian; Skrobanska, Paulina; Malecki, Maciej; Sumino, Yutaka; Kitahata, Hiroyuki; Gorecki, Jerzy

2017-07-01

We consider a rotor made of two camphor disks glued below the ends of a plastic stripe. The disks are floating on a water surface and the plastic stripe does not touch the surface. The system can rotate around a vertical axis located at the center of the stripe. The disks dissipate camphor molecules. The driving momentum comes from the nonuniformity of surface tension resulting from inhomogeneous surface concentration of camphor molecules around the disks. We investigate the stationary angular velocity as a function of rotor radius ℓ. For large ℓ the angular velocity decreases for increasing ℓ. At a specific value of ℓ the angular velocity reaches its maximum and, for short ℓ it rapidly decreases. Such behavior is confirmed by a simple numerical model. The model also predicts that there is a critical rotor size below which it does not rotate. Within the introduced model we analyze the type of this bifurcation.

Fluidic angular velocity sensor

NASA Technical Reports Server (NTRS)

Berdahl, C. M. (Inventor)

1986-01-01

A fluidic sensor providing a differential pressure signal proportional to the angular velocity of a rotary input is described. In one embodiment the sensor includes a fluid pump having an impeller coupled to a rotary input. A housing forming a constricting fluid flow chamber is connected to the fluid input of the pump. The housing is provided with a fluid flow restrictive input to the flow chamber and a port communicating with the interior of the flow chamber. The differential pressure signal measured across the flow restrictive input is relatively noise free and proportional to the square of the angular velocity of the impeller. In an alternative embodiment, the flow chamber has a generally cylindrical configuration and plates having flow restrictive apertures are disposed within the chamber downstream from the housing port. In this embodiment, the differential pressure signal is found to be approximately linear with the angular velocity of the impeller.

Systems and Methods for Determining Inertial Navigation System Faults

NASA Technical Reports Server (NTRS)

Bharadwaj, Raj Mohan (Inventor); Bageshwar, Vibhor L. (Inventor); Kim, Kyusung (Inventor)

2017-01-01

An inertial navigation system (INS) includes a primary inertial navigation system (INS) unit configured to receive accelerometer measurements from an accelerometer and angular velocity measurements from a gyroscope. The primary INS unit is further configured to receive global navigation satellite system (GNSS) signals from a GNSS sensor and to determine a first set of kinematic state vectors based on the accelerometer measurements, the angular velocity measurements, and the GNSS signals. The INS further includes a secondary INS unit configured to receive the accelerometer measurements and the angular velocity measurements and to determine a second set of kinematic state vectors of the vehicle based on the accelerometer measurements and the angular velocity measurements. A health management system is configured to compare the first set of kinematic state vectors and the second set of kinematic state vectors to determine faults associated with the accelerometer or the gyroscope based on the comparison.

Measuring average angular velocity with a smartphone magnetic field sensor

NASA Astrophysics Data System (ADS)

Pili, Unofre; Violanda, Renante

2018-02-01

The angular velocity of a spinning object is, by standard, measured using a device called a tachometer. However, by directly using it in a classroom setting, the activity is likely to appear as less instructive and less engaging. Indeed, some alternative classroom-suitable methods for measuring angular velocity have been presented. In this paper, we present a further alternative that is smartphone-based, making use of the real-time magnetic field (simply called B-field in what follows) data gathering capability of the B-field sensor of the smartphone device as the timer for measuring average rotational period and average angular velocity. The in-built B-field sensor in smartphones has already found a number of uses in undergraduate experimental physics. For instance, in elementary electrodynamics, it has been used to explore the well-known Bio-Savart law and in a measurement of the permeability of air.

Rotating Hele-Shaw cell with a time-dependent angular velocity

NASA Astrophysics Data System (ADS)

Anjos, Pedro H. A.; Alvarez, Victor M. M.; Dias, Eduardo O.; Miranda, José A.

2017-12-01

Despite the large number of existing studies of viscous flows in rotating Hele-Shaw cells, most investigations analyze rotational motion with a constant angular velocity, under vanishing Reynolds number conditions in which inertial effects can be neglected. In this work, we examine the linear and weakly nonlinear dynamics of the interface between two immiscible fluids in a rotating Hele-Shaw cell, considering the action of a time-dependent angular velocity, and taking into account the contribution of inertia. By using a generalized Darcy's law, we derive a second-order mode-coupling equation which describes the time evolution of the interfacial perturbation amplitudes. For arbitrary values of viscosity and density ratios, and for a range of values of a rotational Reynolds number, we investigate how the time-dependent angular velocity and inertia affect the important finger competition events that traditionally arise in rotating Hele-Shaw flows.

Angularly resolved X-ray photoelectron spectroscopy investigation of PTFE after prolonged space exposure

NASA Technical Reports Server (NTRS)

Dalins, I.; Karimi, M.

1992-01-01

Monochromatized angularly resolved X-ray photoelectron spectroscopy (ARXPS) was used to study PTFE (Teflon) that had been exposed to an earth orbital environment for approximately six years. The primary interest of the research is on a very reactive component of this environment (atomic oxygen) which, because of the typical orbital velocities of a spacecraft, impinge on exposed surfaces with 5 eV energy. This presentation deals with the method of analysis, the findings as they pertain to a rather complex carbon, oxygen, and fluorine XPS peak analysis, and the character of the valence bands. An improved bias referencing method, based on ARXPS, is also demonstrated for evaluating specimen charging effects. It was found that the polymer molecule tends to resist the atomic oxygen attack by reorienting itself, so that the most electronegative CF3 groups are facing the incoming hyperthermal oxygen atoms. The implications of these findings to ground-based laboratory studies are discussed.

A novel approach to piecewise analytic agricultural machinery path reconstruction

NASA Astrophysics Data System (ADS)

Wörz, Sascha; Mederle, Michael; Heizinger, Valentin; Bernhardt, Heinz

2017-12-01

Before analysing machinery operation in fields, it has to be coped with the problem that the GPS signals of GPS receivers located on the machines contain measurement noise, are time-discrete, and the underlying physical system describing the positions, axial and absolute velocities, angular rates and angular orientation of the operating machines during the whole working time are unknown. This research work presents a new three-dimensional mathematical approach using kinematic relations based on control variables as Euler angular velocities and angles and a discrete target control problem, such that the state control function is given by the sum of squared residuals involving the state and control variables to get such a physical system, which yields a noise-free and piecewise analytic representation of the positions, velocities, angular rates and angular orientation. It can be used for a further detailed study and analysis of the problem of why agricultural vehicles operate in practice as they do.

The vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt

NASA Technical Reports Server (NTRS)

Merfeld, D. M.; Young, L. R.

1995-01-01

The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in six male squirrel monkeys during eccentric rotation. Monkeys were rotated in the dark at a constant velocity of 200 degrees/s (centrally or 79 cm off axis) with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's orientation (facing-motion or back-to-motion) had a dramatic influence on the VOR. These experiments show that: (a) the axis of eye rotation always shifted toward alignment with gravito-inertial force; (b) the peak value of horizontal slow phase eye velocity was greater with the monkey facing-motion than with back-to-motion; and (c) the time constant of horizontal eye movement decay was smaller with the monkey facing-motion than with back-to-motion. All of these findings were statistically significant and consistent across monkeys. In another set of tests, the same monkeys were rapidly tilted about their naso-occipital (roll) axis. Tilted orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the angular rotation, no consistent eye velocity response was observed during or following the tilt for any of the six monkeys. The absence of any eye movement response following tilt weighs against the possibility that translational linear VOR responses are due to simple high-pass filtering of the otolith signals. The VOR response during eccentric rotation was divided into the more familiar angular VOR and linear VOR components. The angular component is known to depend upon semicircular canal dynamics and central influences. The linear component of the response decays rapidly with a mean duration of only 6.6 s, while the axis of eye rotation rapidly aligns (< 10 s) with gravito-inertial force. These results are consistent with the hypothesis that the measurement of gravito-inertial force by the otolith organs is resolved into central estimates of linear acceleration and gravity, such that the central estimate of gravitational force minus the central estimate of linear acceleration approximately equals the otolith measurement of gravito-inertial force.

Maximum voluntary joint torque as a function of joint angle and angular velocity: model development and application to the lower limb.

PubMed

Anderson, Dennis E; Madigan, Michael L; Nussbaum, Maury A

2007-01-01

Measurements of human strength can be important during analyses of physical activities. Such measurements have often taken the form of the maximum voluntary torque at a single joint angle and angular velocity. However, the available strength varies substantially with joint position and velocity. When examining dynamic activities, strength measurements should account for these variations. A model is presented of maximum voluntary joint torque as a function of joint angle and angular velocity. The model is based on well-known physiological relationships between muscle force and length and between muscle force and velocity and was tested by fitting it to maximum voluntary joint torque data from six different exertions in the lower limb. Isometric, concentric and eccentric maximum voluntary contractions were collected during hip extension, hip flexion, knee extension, knee flexion, ankle plantar flexion and dorsiflexion. Model parameters are reported for each of these exertion directions by gender and age group. This model provides an efficient method by which strength variations with joint angle and angular velocity may be incorporated into comparisons between joint torques calculated by inverse dynamics and the maximum available joint torques.

Models of angular momentum input to a circumterrestrial swarm from encounters with heliocentric planetesimals

NASA Technical Reports Server (NTRS)

Herbert, F.; Davis, D. R.

1984-01-01

Preliminary experiments show that heliocentric planetesimals passing through the Earth environment possess significant angular momentum. However it also appears that these same planetesimals impacting a circularized circumterrestrial planetesimal swarm would likely remove angular momentum (though possibly increasing mean kinetic energy), presumably promoting both swarm infall upon the Earth and escape to heliocentric space. Only a distribution of highly eccentric satellite orbits with mean tangential velocities of a few tens of percent of local circular velocity would be immune against angular momentum loss to passing heliocentric planetesimals.

Research on the water-entry attitude of a submersible aircraft.

PubMed

Xu, BaoWei; Li, YongLi; Feng, JinFu; Hu, JunHua; Qi, Duo; Yang, Jian

2016-01-01

The water entry of a submersible aircraft, which is transient, highly coupled, and nonlinear, is complicated. After analyzing the mechanics of this process, the change rate of every variable is considered. A dynamic model is build and employed to study vehicle attitude and overturn phenomenon during water entry. Experiments are carried out and a method to organize experiment data is proposed. The accuracy of the method is confirmed by comparing the results of simulation of dynamic model and experiment under the same condition. Based on the analysis of the experiment and simulation, the initial attack angle and angular velocity largely influence the water entry of vehicle. Simulations of water entry with different initial and angular velocities are completed, followed by an analysis, and the motion law of vehicle is obtained. To solve the problem of vehicle stability and control during water entry, an approach is proposed by which the vehicle sails with a zero attack angle after entering water by controlling the initial angular velocity. With the dynamic model and optimization research algorithm, calculation is performed, and the optimal initial angular velocity of water-entry is obtained. The outcome of simulations confirms that the effectiveness of the propose approach by which the initial water-entry angular velocity is controlled.

How Angular Velocity Features and Different Gyroscope Noise Types Interact and Determine Orientation Estimation Accuracy.

PubMed

Pasciuto, Ilaria; Ligorio, Gabriele; Bergamini, Elena; Vannozzi, Giuseppe; Sabatini, Angelo Maria; Cappozzo, Aurelio

2015-09-18

In human movement analysis, 3D body segment orientation can be obtained through the numerical integration of gyroscope signals. These signals, however, are affected by errors that, for the case of micro-electro-mechanical systems, are mainly due to: constant bias, scale factor, white noise, and bias instability. The aim of this study is to assess how the orientation estimation accuracy is affected by each of these disturbances, and whether it is influenced by the angular velocity magnitude and 3D distribution across the gyroscope axes. Reference angular velocity signals, either constant or representative of human walking, were corrupted with each of the four noise types within a simulation framework. The magnitude of the angular velocity affected the error in the orientation estimation due to each noise type, except for the white noise. Additionally, the error caused by the constant bias was also influenced by the angular velocity 3D distribution. As the orientation error depends not only on the noise itself but also on the signal it is applied to, different sensor placements could enhance or mitigate the error due to each disturbance, and special attention must be paid in providing and interpreting measures of accuracy for orientation estimation algorithms.

How Angular Velocity Features and Different Gyroscope Noise Types Interact and Determine Orientation Estimation Accuracy

PubMed Central

Pasciuto, Ilaria; Ligorio, Gabriele; Bergamini, Elena; Vannozzi, Giuseppe; Sabatini, Angelo Maria; Cappozzo, Aurelio

2015-01-01

In human movement analysis, 3D body segment orientation can be obtained through the numerical integration of gyroscope signals. These signals, however, are affected by errors that, for the case of micro-electro-mechanical systems, are mainly due to: constant bias, scale factor, white noise, and bias instability. The aim of this study is to assess how the orientation estimation accuracy is affected by each of these disturbances, and whether it is influenced by the angular velocity magnitude and 3D distribution across the gyroscope axes. Reference angular velocity signals, either constant or representative of human walking, were corrupted with each of the four noise types within a simulation framework. The magnitude of the angular velocity affected the error in the orientation estimation due to each noise type, except for the white noise. Additionally, the error caused by the constant bias was also influenced by the angular velocity 3D distribution. As the orientation error depends not only on the noise itself but also on the signal it is applied to, different sensor placements could enhance or mitigate the error due to each disturbance, and special attention must be paid in providing and interpreting measures of accuracy for orientation estimation algorithms. PMID:26393606

Current Global Absolute Plate Velocities Inferred from the Trends of Hotspot Tracks: Implications for Motion between Groups of Hotspots and Comparison and Combination with Absolute Velocities Inferred from the Orientation of Seismic Anisotropy

NASA Astrophysics Data System (ADS)

Wang, C.; Gordon, R. G.; Zheng, L.

2016-12-01

Hotspot tracks are widely used to estimate the absolute velocities of plates, i.e., relative to the lower mantle. Knowledge of current motion between hotspots is important for both plate kinematics and mantle dynamics and informs the discussion on the origin of the Hawaiian-Emperor Bend. Following Morgan & Morgan (2007), we focus only on the trends of young hotspot tracks and omit volcanic propagation rates. The dispersion of the trends can be partitioned into between-plate and within-plate dispersion. Applying the method of Gripp & Gordon (2002) to the hotspot trend data set of Morgan & Morgan (2007) constrained to the MORVEL relative plate angular velocities (DeMets et al., 2010) results in a standard deviation of the 56 hotspot trends of 22°. The largest angular misfits tend to occur on the slowest moving plates. Alternatively, estimation of best-fitting poles to hotspot tracks on the nine individual plates, results in a standard deviation of trends of only 13°, a statistically significant reduction from the introduction of 15 additional adjustable parameters. If all of the between-plate misfit is due to motion of groups of hotspots (beneath different plates), nominal velocities relative to the mean hotspot reference frame range from 1 to 4 mm/yr with the lower bounds ranging from 1 to 3 mm/yr and the greatest upper bound being 8 mm/yr. These are consistent with bounds on motion between Pacific and Indo-Atlantic hotspots over the past ≈50 Ma, which range from zero (lower bound) to 8 to 13 mm/yr (upper bounds) (Koivisto et al., 2014). We also determine HS4-MORVEL, a new global set of plate angular velocities relative to the hotspots constrained to consistency with the MORVEL relative plate angular velocities, using a two-tier analysis similar to that used by Zheng et al. (2014) to estimate the SKS-MORVEL global set of absolute plate velocities fit to the orientation of seismic anisotropy. We find that the 95% confidence limits of HS4-MORVEL and SKS-MORVEL overlap substantially and that the two sets of angular velocities differ insignificantly. Thus we combine the two sets of angular velocities to estimate ABS-MORVEL, an optimal set of global angular velocities consistent with both hotspot tracks and seismic anisotropy. ABS-MORVEL has more compact confidence limits than either SKS-MORVEL or HS4-MORVEL.

An analysis of a discrete complex skill using Bernstein's stages of learning.

PubMed

Smith, D R; McCabe, D R; Wilkerson, J D

2001-08-01

The purpose of this study was to provide quantitative data about changes in coordination after practicing a racquetball forehand drive serve. Novice women (N = 10) were videotaped before and after 10 min. of practicing a racquetball forehand drive serve on Day 1, and after 10-min. practice sessions on consecutive Days 2 through 5. The PEAK5 Motion Measurement System was used to evaluate the following dependent variables: (a) range of motion of the wrist, elbow, upper torso, and pelvis from backswing to ball contact: (b) racket head velocity at ball contact; and (c) coordination. Coordination was evaluated based on analysis of the angular velocity graphs of each performance to assess sequencing and timing of the segmental contributions. Shared positive contribution was assessed between adjacent 2-segment combinations: pelvis-torso and elbow-wrist. A repeated-measures analysis of variance indicated racket velocity, pelvic rotation, and upper torso rotation significantly increased over the 5 days of practice. Although participants increased their pelvic and torso ranges of motion and racket velocity, improvement in coordination was not documented.

A study of emergency American football helmet removal techniques.

PubMed

Swartz, Erik E; Mihalik, Jason P; Decoster, Laura C; Hernandez, Adam E

2012-09-01

The purpose was to compare head kinematics between the Eject Helmet Removal System and manual football helmet removal. This quasi-experimental study was conducted in a controlled laboratory setting. Thirty-two certified athletic trainers (sex, 19 male and 13 female; age, 33 ± 10 years; height, 175 ± 12 cm; mass, 86 ± 20 kg) removed a football helmet from a healthy model under 2 conditions: manual helmet removal and Eject system helmet removal. A 6-camera motion capture system recorded 3-dimensional head position. Our outcome measures consisted of the average angular velocity and acceleration of the head in each movement plane (sagittal, frontal, and transverse), the resultant angular velocity and acceleration, and total motion. Paired-samples t tests compared each variable across the 2 techniques. Manual helmet removal elicited greater average angular velocity in the sagittal and transverse planes and greater resultant angular velocity compared with the Eject system. No differences were observed in average angular acceleration in any single plane of movement; however, the resultant angular acceleration was greater during manual helmet removal. The Eject Helmet Removal System induced greater total head motion. Although the Eject system created more motion at the head, removing a helmet manually resulted in more sudden perturbations as identified by resultant velocity and acceleration of the head. The implications of these findings relate to the care of all cervical spine-injured patients in emergency medical settings, particularly in scenarios where helmet removal is necessary. Copyright © 2012 Elsevier Inc. All rights reserved.

Influence of vision on head stabilization strategies in older adults during walking.

PubMed

Cromwell, Ronita L; Newton, Roberta A; Forrest, Gail

2002-07-01

Maintaining balance during dynamic activities is essential for preventing falls in older adults. Head stabilization contributes to dynamic balance, especially during the functional task of walking. Head stability and the role of vision in this process have not been studied during walking in older adults. Seventeen older adults (76.2 +/- 6.9 years) and 20 young adults (26.0 +/- 3.4 years) walked with their eyes open (EO), with their eyes closed (EC), and with fixed gaze (FG). Participants performed three trials of each condition. Sagittal plane head and trunk angular velocities in space were obtained using an infrared camera system with passive reflective markers. Frequency analyses of head-on-trunk with respect to trunk gains and phases were examined for head-trunk movement strategies used for head stability. Average walking velocity, cadence, and peak head velocity were calculated for each condition. Differences between age groups demonstrated that older adults decreased walking velocity in EO (p =.022). FG (p = .021), and EC (p = .022). and decreased cadence during EC (p = .007). Peak head velocity also decreased across conditions (p < .0001) for older adults. Movement patterns demonstrated increased head stability during EO. diminished head stability with EC, and improved head stability with FG as older adult patterns resembled those of young adults. Increased stability of the lower extremity outcome measures for older adults was indicated by reductions in walking velocity and cadence. Concomitant increases in head stability were related to visual tasks. Increased stability may serve as a protective mechanism to prevent falls. Further, vision facilitates the head stabilization process for older adults to compensate for age-related decrements in other sensory systems subserving dynamic balance.

Implementing a Low-Cost Long-Range Unmanned Underwater Vehicle: The SeaDiver Glider

DTIC Science & Technology

2007-01-09

25 2. Position estimation.............................................................................26 3. Angular ...calculation velocity..............................................................27 4. Angular calculation position...25 Figure 14. Angular Positions.............................................................................................27

Effects of ultrashort laser pulses on angular distributions of photoionization spectra.

PubMed

Ooi, C H Raymond; Ho, W L; Bandrauk, A D

2017-07-27

We study the photoelectron spectra by intense laser pulses with arbitrary time dependence and phase within the Keldysh framework. An efficient semianalytical approach using analytical transition matrix elements for hydrogenic atoms in any initial state enables efficient and accurate computation of the photoionization probability at any observation point without saddle point approximation, providing comprehensive three dimensional photoelectron angular distribution for linear and elliptical polarizations, that reveal the intricate features and provide insights on the photoionization characteristics such as angular dispersions, shift and splitting of photoelectron peaks from the tunneling or above threshold ionization(ATI) regime to non-adiabatic(intermediate) and multiphoton ionization(MPI) regimes. This facilitates the study of the effects of various laser pulse parameters on the photoelectron spectra and their angular distributions. The photoelectron peaks occur at multiples of 2ħω for linear polarization while  odd-ordered peaks are suppressed in the direction perpendicular to the electric field. Short pulses create splitting and angular dispersion where the peaks are strongly correlated to the angles. For MPI and elliptical polarization with shorter pulses the peaks split into doublets and the first peak vanishes. The carrier envelope phase(CEP) significantly affects the ATI spectra while the Stark effect shifts the spectra of intermediate regime to higher energies due to interference.

Influence of joint angular velocity on electrically evoked concentric force potentiation induced by stretch-shortening cycle in young adults.

PubMed

Fukutani, Atsuki; Kurihara, Toshiyuki; Isaka, Tadao

2015-01-01

During a stretch- shortening cycle (SSC), muscle force attained during concentric contractions (shortening phase) is potentiated by the preceding eccentric contractions (lengthening phase). The purpose of this study was to examine the influence of joint angular velocity on force potentiation induced by SSC (SSC effect). Twelve healthy men (age, 24.2 ± 3.2 years; height, 1.73 ± 0.05 m; body mass, 68.1 ± 11.0 kg) participated in this study. Ankle joint angle was passively moved by a dynamometer, with range of motion from dorsiflexion (DF) 15° to plantarflexion (PF) 15°. Muscle contractions were evoked by tetanic electrical stimulation. Joint angular velocity of concentric contraction was set at 30°/s and 150°/s. Magnitude of SSC effect was calculated as the ratio of joint torque obtained by concentric contraction with preliminary eccentric contraction trial relative to that obtained by concentric contraction without preliminary eccentric contraction trial. As a result, magnitude of SSC effect calculated at three joint angles was significantly larger in the 150°/s condition than in the 30°/s condition (p < 0.05). These results indicate that the magnitude of SSC effect is affected by joint angular velocity, which is larger when joint angular velocity is larger. This phenomenon would be caused by insufficient duration to increase activation level in the large joint angular velocity condition. When the duration to increase activation level is insufficient due to short contraction duration, preactivation (one of the factors of SSC effect) leads to a significant increase in joint torque.

Acute severe male hypo-testosteronemia affects central motor command in humans.

PubMed

Felici, Francesco; Bazzucchi, Ilenia; Sgrò, Paolo; Quinzi, Federico; Conti, Alessandra; Aversa, Antonio; Gizzi, Leonardo; Mezzullo, Marco; Romanelli, Francesco; Pasquali, Renato; Lenzi, Andrea; Di Luigi, Luigi

2016-06-01

To indirectly evaluate the effect of androgens on neuromuscular system in humans we analyzed if an induced short-term hypogonadal state (serum total testosterone-TT<2.3ng/ml) may affect central drive to skeletal muscle and/or muscle neuro-mechanical performance. We compared voluntary and electrically evoked muscle sEMG signals from biceps brachii in nine hypogonadal male volunteers (Hypo) and in ten healthy controls (Cont). Serum TT and dihydrotestosterone (DHT) were assayed. With respect to Hypo, Cont exhibited significantly higher median frequency content (MDF) at any angular velocity; normalized MDF [95.9% (SD=23.3) vs 73.8% (SD=9.3)]; muscle fiber conduction velocity (CV) from lowest to highest angular velocities; initial MDF at fatigue test [91.78Hz (SD=22.03) vs 70.94Hz (SD=11.06)] as well as was the normalized slope [-0.64 (SD=0.14 vs -0.5 (SD=0.11)]. In the non-fatigued state, Hypo showed a slower single twitches time to peak (TTP). In Cont, half relaxation time (HRT) decreased after fatigue while increased in Hypo (p<0.05 between groups). A significant correlation between both TT and dihydrotestosterone with MDF and CV was found during voluntary contractions only. A brief exposure to very low serum TT concentration in males seem to determine a reduced excitability of the NM system which, in turn, would favor a predominant recruitment of slow twitch MUs. Copyright © 2015 Elsevier Ltd. All rights reserved.

Relationship of spasticity to knee angular velocity and motion during gait in cerebral palsy.

PubMed

Damiano, Diane L; Laws, Edward; Carmines, Dave V; Abel, Mark F

2006-01-01

This study investigated the effects of spasticity in the hamstrings and quadriceps muscles on gait parameters including temporal spatial measures, knee position, excursion and angular velocity in 25 children with spastic diplegic cerebral palsy (CP) as compared to 17 age-matched peers. While subjects were instructed to relax, an isokinetic device alternately flexed and extended the left knee at one of the three constant velocities 30 degrees/s, 60 degrees/s and 120 degrees/s, while surface electromyography (EMG) electrodes over the biceps femoris and the rectus femoris recorded muscle activity. Patients then participated in 3D gait analysis at a self-selected speed. Results showed that, those with CP who exhibited heightened stretch responses (spasticity) in both muscles, had significantly slower knee angular velocities during the swing phase of gait as compared to those with and without CP who did not exhibit stretch responses at the joint and the tested speeds. The measured amount (torque) of the resistance to passive flexion or extension was not related to gait parameters in subjects with CP; however, the rate of change in resistance torque per unit angle change (stiffness) at the fastest test speed of 120 degrees/s showed weak to moderate relationships with knee angular velocity and motion during gait. For the subset of seven patients with CP who subsequently underwent a selective dorsal rhizotomy, knee angular extension and flexion velocity increased post-operatively, suggesting some degree of causality between spasticity and movement speed.

The effect of angular velocity and cycle on the dissipative properties of the knee during passive cyclic stretching: a matter of viscosity or solid friction.

PubMed

Nordez, A; McNair, P J; Casari, P; Cornu, C

2009-01-01

The mechanisms behind changes in mechanical parameters following stretching are not understood clearly. This study assessed the effects of joint angular velocity on the immediate changes in passive musculo-articular properties induced by cyclic stretching allowing an appreciation of viscosity and friction, and their contribution to changes in torque that occur. Ten healthy subjects performed five passive knee extension/flexion cycles on a Biodex dynamometer at five preset angular velocities (5-120 deg/s). The passive torque and knee angle were measured, and the potential elastic energy stored during the loading and the dissipation coefficient were calculated. As the stretching velocity increased, so did stored elastic energy and the dissipation coefficient. The slope of the linear relationship between the dissipation coefficient and the angular velocity was unchanged across repetitions indicating that viscosity was unlikely to be affected. A difference in the y-intercept across repetitions 1 and 5 was indicative of a change in processes associated with solid friction. Electromyographical responses to stretching were low across all joint angular velocities. Torque changes during cyclic motion may primarily involve solid friction which is more indicative of rearrangement/slipping of collagen fibers rather than the redistribution of fluid and its constituents within the muscle. The findings also suggest that it is better to stretch slowly initially to reduce the amount of energy absorption required by tissues, but thereafter higher stretching speeds can be undertaken.

Angular rate optimal design for the rotary strapdown inertial navigation system.

PubMed

Yu, Fei; Sun, Qian

2014-04-22

Due to the characteristics of high precision for a long duration, the rotary strapdown inertial navigation system (RSINS) has been widely used in submarines and surface ships. Nowadays, the core technology, the rotating scheme, has been studied by numerous researchers. It is well known that as one of the key technologies, the rotating angular rate seriously influences the effectiveness of the error modulating. In order to design the optimal rotating angular rate of the RSINS, the relationship between the rotating angular rate and the velocity error of the RSINS was analyzed in detail based on the Laplace transform and the inverse Laplace transform in this paper. The analysis results showed that the velocity error of the RSINS depends on not only the sensor error, but also the rotating angular rate. In order to minimize the velocity error, the rotating angular rate of the RSINS should match the sensor error. One optimal design method for the rotating rate of the RSINS was also proposed in this paper. Simulation and experimental results verified the validity and superiority of this optimal design method for the rotating rate of the RSINS.

Laser Pulse Shaping for Low Emittance Photo-Injector

DTIC Science & Technology

2012-06-01

It depends on the product of the beam’s transverse size and angular divergence, , (I.2) where is the standard deviation of the electron...shows the pendulum’s phase velocity as a function of the position θp. As the pendulum oscillates back and forth, its phase, or angular , velocity and...the angular divergence and size of the optical beam. The radius of the optical beam follows the equation 24 To guarantee proper transfer

On the shelf resonances of the Gulf of Carpentaria and the Arafura Sea

NASA Astrophysics Data System (ADS)

Webb, D. J.

2012-09-01

A numerical model is used to investigate the resonances of the Gulf of Carpentaria and the Arafura Sea, and the additional insights that come from extending the analysis into the complex angular velocity plane. When the model is forced at the shelf edge with physically realistic real values of the angular velocity, the response functions at points within the region show maxima and other behaviour which imply that resonances are involved but provide little additional information. The study is then extended to complex angular velocities, and the results then show a clear pattern of gravity wave and Rossby wave like resonances. The properties of the resonances are investigated and used to reinterpret the response at real values of angular velocity. It is found that in some regions the response is dominated by modes trapped between the shelf edge and the coast or between opposing coastlines. In other regions the resonances show cooperative behaviour, possibly indicating the importance of other physical processes.

Radial and latitudinal gradients in the solar internal angular velocity

NASA Technical Reports Server (NTRS)

Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain G.; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

1988-01-01

The frequency splittings of intermediate-degree (3 to 170 deg) p-mode oscillations obtained from a 16-day subset of observations were analyzed. Results show evidence for both radial and latitudinal gradients in the solar internal angular velocity. From 0.6 to 0.95 solar radii, the solar internal angular velocity increases systematically from 440 to 463 nHz, corresponding to a positive radial gradient of 66 nHz/solar radius for that portion of the solar interior. Analysis also indicates that the latitudinal differential rotation gradient which is seen at the solar surface persists throughout the convection zone, although there are indications that the differential rotation might disappear entirely below the base of the convection zone. The analysis was extended to include comparisons with additional observational studies and between earlier results and the results of additional inversions of several of the observational datasets. All the comparisons reinforce conclusions regarding the existence of radial and latitudinal gradients in the internal angular velocity.

Quasi-four-body treatment of charge transfer in the collision of protons with atomic helium: I. Thomas related mechanisms

NASA Astrophysics Data System (ADS)

Safarzade, Zohre; Fathi, Reza; Shojaei Akbarabadi, Farideh; Bolorizadeh, Mohammad A.

2018-04-01

The scattering of a completely bare ion by atoms larger than hydrogen is at least a four-body interaction, and the charge transfer channel involves a two-step process. Amongst the two-step interactions of the high-velocity single charge transfer in an anion-atom collision, there is one whose amplitude demonstrates a peak in the angular distribution of the cross sections. This peak, the so-called Thomas peak, was predicted by Thomas in a two-step interaction, classically, which could also be described through three-body quantum mechanical models. This work discusses a four-body quantum treatment of the charge transfer in ion-atom collisions, where two-step interactions illustrating a Thomas peak are emphasized. In addition, the Pauli exclusion principle is taken into account for the initial and final states as well as the operators. It will be demonstrated that there is a momentum condition for each two-step interaction to occur in a single charge transfer channel, where new classical interactions lead to the Thomas mechanism.

Relationship between cardiopulmonary responses and isokinetic moments: the optimal angular velocity for muscular endurance

PubMed Central

Lee, Chan-Bok; Eun, Denny; Kim, Kang-Ho; Park, Jae-Wan; Jee, Yong-Seok

2017-01-01

Most protocols for testing and rehabilitation for recovery and improvement of muscular endurance have been set at 180°/sec, 240°/sec, and 300°/sec. These protocols can cause confusion to clinical providers or other researchers. This study was aimed at investigating the optimal isokinetic angular speed for measuring or developing muscular endurance after assessing the relationship between cardiopulmonary responses and isokinetic moments. This study was conducted with 31 male and female college students. Graded exercise test and body composition were measured as well as the isokinetic moments of the knee muscles at three angular speeds: 180°/sec, 240°/sec, and 300°/sec. The specific isokinetic moments of knee muscles that were measured included: peak torque (PT) and total work (TW) on extensor (e) and flexor (f) of knee joints, which were denoted as ePT180, fPT180, eTW180, fTW180, ePT240, fPT240, eTW240, fTW240, ePT300, fPT300, eTW300, and fTW300 according to the three angular speeds. Spearman correlation test was used to examine the relationship between the sum means of cardiopulmonary responses and the variables of isokinetic moments. This study confirmed that the optimal angular speed for testing or training for muscular endurance was 180°/sec, which showed a stronger relationship between cardiopulmonary responses and isokinetic moments. Therefore, this angular speed is recommended for testing and training for muscular endurance of the knee joints. PMID:28503531

Relationship between cardiopulmonary responses and isokinetic moments: the optimal angular velocity for muscular endurance.

PubMed

Lee, Chan-Bok; Eun, Denny; Kim, Kang-Ho; Park, Jae-Wan; Jee, Yong-Seok

2017-04-01

Most protocols for testing and rehabilitation for recovery and improvement of muscular endurance have been set at 180°/sec, 240°/sec, and 300°/sec. These protocols can cause confusion to clinical providers or other researchers. This study was aimed at investigating the optimal isokinetic angular speed for measuring or developing muscular endurance after assessing the relationship between cardiopulmonary responses and isokinetic moments. This study was conducted with 31 male and female college students. Graded exercise test and body composition were measured as well as the isokinetic moments of the knee muscles at three angular speeds: 180°/sec, 240°/sec, and 300°/sec. The specific isokinetic moments of knee muscles that were measured included: peak torque (PT) and total work (TW) on extensor (e) and flexor (f) of knee joints, which were denoted as ePT180, fPT180, eTW180, fTW180, ePT240, fPT240, eTW240, fTW240, ePT300, fPT300, eTW300, and fTW300 according to the three angular speeds. Spearman correlation test was used to examine the relationship between the sum means of cardiopulmonary responses and the variables of isokinetic moments. This study confirmed that the optimal angular speed for testing or training for muscular endurance was 180°/sec, which showed a stronger relationship between cardiopulmonary responses and isokinetic moments. Therefore, this angular speed is recommended for testing and training for muscular endurance of the knee joints.

Double pendulum model for a tennis stroke including a collision process

NASA Astrophysics Data System (ADS)

Youn, Sun-Hyun

2015-10-01

By means of adding a collision process between the ball and racket in the double pendulum model, we analyzed the tennis stroke. The ball and the racket system may be accelerated during the collision time; thus, the speed of the rebound ball does not simply depend on the angular velocity of the racket. A higher angular velocity sometimes gives a lower rebound ball speed. We numerically showed that the proper time-lagged racket rotation increased the speed of the rebound ball by 20%. We also showed that the elbow should move in the proper direction in order to add the angular velocity of the racket.

The isokinetic strength profile of elite soccer players according to playing position

PubMed Central

Grygorowicz, Monika; Hojszyk, Radosław; Jadczak, Łukasz

2017-01-01

The aim of this study was to compare isokinetic strength performance profiles in elite soccer players across different field positions. A total of 111 elite international players of Polish Ekstraklasa (the top division in Poland) were examined during the 2010–2015 seasons. The players were classified into six positional roles: central defenders (CD), external defenders (ED), central midfielders (CM), external midfielders (EM), forwards (F), and goalkeepers (G). The concentric isokinetic strength (peak torque [PT] of quadriceps and hamstrings, H/Q ratios) was calculated for the dominant leg and the non-dominant leg at angular velocity of 1.05 rad ·s–1, whereas to assess isokinetic muscle endurance, the total work [TW] at angular velocity of 4.19 rad ·s–1, was taken into consideration. The results showed that isokinetic strength performance varies significantly among players in different playing positions. The analysis of PT for quadriceps (PT-Q) and hamstrings (PT-H) generally showed that the goalkeepers and central midfielders had lower strength levels compared to other playing positions. In the case of PT-H and hamstring/quadricep (H/Q) peak torque ratios, statistically significant differences were also noted for the legs, where mean values noted for the dominant leg were higher than for the non-dominant leg. For TW for quadriceps (TW-Q) and hamstrings (TW-H), statistically significant differences were noted only between playing positions. TW-Q values for goalkeepers were lower than for central defenders and external midfielders. TW-H values for goalkeepers were lower than for central midfielders, central defenders and external midfielders. This study showed that specific functional activity of players in individual positions on the field influences the varied profile of isokinetic strength performance. PMID:28759603

The isokinetic strength profile of elite soccer players according to playing position.

PubMed

Śliwowski, Robert; Grygorowicz, Monika; Hojszyk, Radosław; Jadczak, Łukasz

2017-01-01

The aim of this study was to compare isokinetic strength performance profiles in elite soccer players across different field positions. A total of 111 elite international players of Polish Ekstraklasa (the top division in Poland) were examined during the 2010-2015 seasons. The players were classified into six positional roles: central defenders (CD), external defenders (ED), central midfielders (CM), external midfielders (EM), forwards (F), and goalkeepers (G). The concentric isokinetic strength (peak torque [PT] of quadriceps and hamstrings, H/Q ratios) was calculated for the dominant leg and the non-dominant leg at angular velocity of 1.05 rad ·s-1, whereas to assess isokinetic muscle endurance, the total work [TW] at angular velocity of 4.19 rad ·s-1, was taken into consideration. The results showed that isokinetic strength performance varies significantly among players in different playing positions. The analysis of PT for quadriceps (PT-Q) and hamstrings (PT-H) generally showed that the goalkeepers and central midfielders had lower strength levels compared to other playing positions. In the case of PT-H and hamstring/quadricep (H/Q) peak torque ratios, statistically significant differences were also noted for the legs, where mean values noted for the dominant leg were higher than for the non-dominant leg. For TW for quadriceps (TW-Q) and hamstrings (TW-H), statistically significant differences were noted only between playing positions. TW-Q values for goalkeepers were lower than for central defenders and external midfielders. TW-H values for goalkeepers were lower than for central midfielders, central defenders and external midfielders. This study showed that specific functional activity of players in individual positions on the field influences the varied profile of isokinetic strength performance.

Do peak torque angles of muscles change following anterior cruciate ligament reconstruction using hamstring or patellar tendon graft?

PubMed

Yosmaoğlu, Hayri Baran; Baltacı, Gül; Sönmezer, Emel; Özer, Hamza; Doğan, Deha

2017-12-01

This study aims to compare the effects of anterior cruciate ligament (ACL) reconstruction using autogenous hamstring or patellar tendon graft on the peak torque angle. The study included 132 patients (103 males, 29 females; mean age 29±9 year) who were performed ACL reconstruction with autogenous hamstring or patellar tendon graft. The peak torque angles in the quadriceps and hamstring muscles were recorded using an isokinetic dynamometer. Angle of peak knee flexion torque occurred significantly earlier within the range of motion on the operated side than nonoperated side at 180°/second in the hamstring tendon group. Angle of peak knee extension torque occurred significantly earlier within the range of motion on the operated side than nonoperated side at 180°/second in the patellar tendon group. There were no statistically significant differences in the flexion and extension peak torque angles between the operated and nonoperated knees at 60°/second in both groups. The angle of peak torque at relatively high angular velocities is affected after ACL reconstruction in patients with hamstring or patellar tendon grafts. The graft donor site directly influences this parameter. This finding may be important for clinicians in terms of preventing re-injury.

Development and validity of methods for the estimation of temporal gait parameters from heel-attached inertial sensors in younger and older adults.

PubMed

Misu, Shogo; Asai, Tsuyoshi; Ono, Rei; Sawa, Ryuichi; Tsutsumimoto, Kota; Ando, Hiroshi; Doi, Takehiko

2017-09-01

The heel is likely a suitable location to which inertial sensors are attached for the detection of gait events. However, there are few studies to detect gait events and determine temporal gait parameters using sensors attached to the heels. We developed two methods to determine temporal gait parameters: detecting heel-contact using acceleration and detecting toe-off using angular velocity data (acceleration-angular velocity method; A-V method), and detecting both heel-contact and toe-off using angular velocity data (angular velocity-angular velocity method; V-V method). The aim of this study was to examine the concurrent validity of the A-V and V-V methods against the standard method, and to compare their accuracy. Temporal gait parameters were measured in 10 younger and 10 older adults. The intra-class correlation coefficients were excellent in both methods compared with the standard method (0.80 to 1.00). The root mean square errors of stance and swing time in the A-V method were smaller than the V-V method in older adults, although there were no significant discrepancies in the other comparisons. Our study suggests that inertial sensors attached to the heels, using the A-V method in particular, provide a valid measurement of temporal gait parameters. Copyright © 2017 Elsevier B.V. All rights reserved.

Effect of Range and Angular Velocity of Passive Movement on Somatosensory Evoked Magnetic Fields.

PubMed

Sugawara, Kazuhiro; Onishi, Hideaki; Yamashiro, Koya; Kojima, Sho; Miyaguchi, Shota; Kotan, Shinichi; Tsubaki, Atsuhiro; Kirimoto, Hikari; Tamaki, Hiroyuki; Shirozu, Hiroshi; Kameyama, Shigeki

2016-09-01

To clarify characteristics of each human somatosensory evoked field (SEF) component following passive movement (PM), PM1, PM2, and PM3, using high spatiotemporal resolution 306-channel magnetoencephalography and varying PM range and angular velocity. We recorded SEFs following PM under three conditions [normal range-normal velocity (NN), small range-normal velocity (SN), and small range-slow velocity (SS)] with changing movement range and angular velocity in 12 participants and calculated the amplitude, equivalent current dipole (ECD) location, and the ECD strength for each component. All components were observed in six participants, whereas only PM1 and PM3 in the other six. Clear response deflections at the ipsilateral hemisphere to PM side were observed in seven participants. PM1 amplitude was larger under NN and SN conditions, and mean ECD location for PM1 was at primary motor area. PM3 amplitude was larger under SN condition and mean ECD location for PM3 under SS condition was at primary somatosensory area. PM1 amplitude was dependent on the angular velocity of PM, suggesting that PM1 reflects afferent input from muscle spindle, whereas PM3 amplitude was dependent on the duration. The ECD for PM3 was located in the primary somatosensory cortex, suggesting that PM3 reflects cutaneous input. We confirmed the hypothesis for locally distinct generators and characteristics of each SEF component.

Contribution of irregular semicircular canal afferents to the horizontal vestibuloocular response during constant velocity rotation

NASA Technical Reports Server (NTRS)

Angelaki, D. E.; Perachio, A. A.

1993-01-01

1. The effects of constant anodal currents (100 microA) delivered bilaterally to both labyrinths on the horizontal vestibuloocular response (VOR) were studied in squirrel monkeys during steps of angular velocity in the dark. We report that bilateral anodal currents decreased eye velocity approximately 30-50% during the period of galvanic stimulation without a change in the time constant of VOR. The decrease in eye velocity, present during steps of angular velocity, was not observed during sinusoidal head rotation at 0.2, 0.5, and 1 Hz. The results suggest that responses from irregular vestibular afferents influence VOR amplitude during constant velocity rotation.

Molecular jet of IRAS 04166+2706

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

Wang, Liang-Yao; Shang, Hsien; Su, Yu-Nung

2014-01-01

The molecular outflow from IRAS 04166+2706 was mapped with the Submillimeter Array at a 350 GHz continuum and CO J = 3-2 at an angular resolution of ∼1''. The field of view covers the central arcminute, which contains the inner four pairs of knots of the molecular jet. On the channel map, conical structures are clearly present in the low-velocity range (|V – V {sub 0}| < 10 km s{sup –1}), and the highly collimated knots appear in the extremely high velocity range (50 >|V – V {sub 0}| > 30 km s{sup –1}). The higher angular resolution of ∼1''more » reveals the first blue-shifted knot (B1) that was missing in previous Plateau de Bure Interferometer observation of Santiago-García et al. at an offset of ∼6'' to the northeast of the central source. This identification completes the symmetric sequence of knots in both the blue- and red-shifted lobes of the outflow. The innermost knots R1 and B1 have the highest velocities within the sequence. Although the general features appear to be similar to previous CO J = 2-1 images in Santiago-García et al., the emission in CO J = 3-2 almost always peaks further away from the central source than that of CO J = 2-1 in the red-shifted lobe of the channel maps. This gives rise to a gradient in the line-ratio map of CO J = 3-2/J = 2-1 from head to tail within a knot. A large velocity gradient analysis suggests that the differences may reflect a higher gas kinetic temperature at the head. We also explore possible constraints imposed by the nondetection of SiO J = 8-7.« less

Alignment of angular velocity sensors for a vestibular prosthesis.

PubMed

Digiovanna, Jack; Carpaneto, Jacopo; Micera, Silvestro; Merfeld, Daniel M

2012-02-13

Vestibular prosthetics transmit angular velocities to the nervous system via electrical stimulation. Head-fixed gyroscopes measure angular motion, but the gyroscope coordinate system will not be coincident with the sensory organs the prosthetic replaces. Here we show a simple calibration method to align gyroscope measurements with the anatomical coordinate system. We benchmarked the method with simulated movements and obtain proof-of-concept with one healthy subject. The method was robust to misalignment, required little data, and minimal processing.

State Derivation of a 12-Axis Gyroscope-Free Inertial Measurement Unit

PubMed Central

Lu, Jau-Ching; Lin, Pei-Chun

2011-01-01

The derivation of linear acceleration, angular acceleration, and angular velocity states from a 12-axis gyroscope-free inertial measurement unit that utilizes four 3-axis accelerometer measurements at four distinct locations is reported. Particularly, a new algorithm which derives the angular velocity from its quadratic form and derivative form based on the context-based interacting multiple model is demonstrated. The performance of the system was evaluated under arbitrary 3-dimensional motion. PMID:22163791

Axis of Eye Rotation Changes with Head-Pitch Orientation during Head Impulses about Earth-Vertical

PubMed Central

Schubert, Michael C.; Clendaniel, Richard A.; Carey, John P.; Della Santina, Charles C.; Minor, Lloyd B.; Zee, David S.

2006-01-01

The goal of this study was to assess how the axis of head rotation, Listing's law, and eye position influence the axis of eye rotation during brief, rapid head rotations. We specifically asked how the axis of eye rotation during the initial angular vestibuloocular reflex (VOR) changed when the pitch orientation of the head relative to Earth-vertical was varied, but the initial position of the eye in the orbit and the orientation of Listing's plane with respect to the head were fixed. We measured three-dimensional eye and head rotation axes in eight normal humans using the search coil technique during head-and-trunk (whole-body) and head-on-trunk (head-only) “impulses” about an Earth-vertical axis. The head was initially oriented at one of five pitch angles (30° nose down, 15° nose down, 0°, 15° nose up, 30° nose up). The fixation target was always aligned with the nasooccipital axis. Whole-body impulses were passive, unpredictable, manual, rotations with peak-amplitude of ∼20°, peak-velocity of ∼80°/s, and peak-acceleration of ∼1000°/s2. Head-only impulses were also passive, unpredictable, manual, rotations with peak-amplitude of ∼20°, peak-velocity of ∼150°/s, and peak-acceleration of ∼3000°/s2. During whole-body impulses, the axis of eye rotation tilted in the same direction, and by an amount proportional (0.51 ± 0.09), to the starting pitch head orientation (P < 0.05). This proportionality constant decreased slightly to 0.39 ± 0.08 (P < 0.05) during head-only impulses. Using the head-only impulse data, with the head pitched up, we showed that only 50% of the tilt in the axis of eye rotation could be predicted from vectorial summation of the gains (eye velocity/head velocity) obtained for rotations about the pure yaw and roll head axes. Thus, even when the orientation of Listing's plane and eye position in the orbit are fixed, the axis of eye rotation during the VOR reflects a compromise between the requirements of Listing's law and a perfectly compensatory VOR. PMID:16552499

Lumbar Corsets Can Decrease Lumbar Motion in Golf Swing

PubMed Central

Hashimoto, Koji; Miyamoto, Kei; Yanagawa, Takashi; Hattori, Ryo; Aoki, Takaaki; Matsuoka, Toshio; Ohno, Takatoshi; Shimizu, Katsuji

2013-01-01

Swinging a golf club includes the rotation and extension of the lumbar spine. Golf-related low back pain has been associated with degeneration of the lumbar facet and intervertebral discs, and with spondylolysis. Reflective markers were placed directly onto the skin of 11young male amateur golfers without a previous history of back pain. Using a VICON system (Oxford Metrics, U.K.), full golf swings were monitored without a corset (WOC), with a soft corset (SC), and with a hard corset (HC), with each subject taking 3 swings. Changes in the angle between the pelvis and the thorax (maximum range of motion and angular velocity) in 3 dimensions (lumbar rotation, flexion-extension, and lateral tilt) were analyzed, as was rotation of the hip joint. Peak changes in lumbar extension and rotation occurred just after impact with the ball. The extension angle of the lumbar spine at finish was significantly lower under SC (38°) or HC (28°) than under WOC (44°) conditions (p < 0.05). The maximum angular velocity after impact was significantly smaller under HC (94°/sec) than under SC (177°/sec) and WOC (191° /sec) conditions, as were the lumbar rotation angles at top and finish. In contrast, right hip rotation angles at top showed a compensatory increase under HC conditions. Wearing a lumbar corset while swinging a golf club can effectively decrease lumbar extension and rotation angles from impact until the end of the swing. These effects were significantly enhanced while wearing an HC. Key points Rotational and extension forces on the lumbar spine may cause golf-related low back pain Wearing lumbar corsets during a golf swing can effectively decrease lumbar extension and rotation angles and angular velocity. Wearing lumbar corsets increased the rotational motion of the hip joint while reducing the rotation of the lumbar spine. PMID:24149729

Lumbar corsets can decrease lumbar motion in golf swing.

PubMed

Hashimoto, Koji; Miyamoto, Kei; Yanagawa, Takashi; Hattori, Ryo; Aoki, Takaaki; Matsuoka, Toshio; Ohno, Takatoshi; Shimizu, Katsuji

2013-01-01

Swinging a golf club includes the rotation and extension of the lumbar spine. Golf-related low back pain has been associated with degeneration of the lumbar facet and intervertebral discs, and with spondylolysis. Reflective markers were placed directly onto the skin of 11young male amateur golfers without a previous history of back pain. Using a VICON system (Oxford Metrics, U.K.), full golf swings were monitored without a corset (WOC), with a soft corset (SC), and with a hard corset (HC), with each subject taking 3 swings. Changes in the angle between the pelvis and the thorax (maximum range of motion and angular velocity) in 3 dimensions (lumbar rotation, flexion-extension, and lateral tilt) were analyzed, as was rotation of the hip joint. Peak changes in lumbar extension and rotation occurred just after impact with the ball. The extension angle of the lumbar spine at finish was significantly lower under SC (38°) or HC (28°) than under WOC (44°) conditions (p < 0.05). The maximum angular velocity after impact was significantly smaller under HC (94°/sec) than under SC (177°/sec) and WOC (191° /sec) conditions, as were the lumbar rotation angles at top and finish. In contrast, right hip rotation angles at top showed a compensatory increase under HC conditions. Wearing a lumbar corset while swinging a golf club can effectively decrease lumbar extension and rotation angles from impact until the end of the swing. These effects were significantly enhanced while wearing an HC. Key pointsRotational and extension forces on the lumbar spine may cause golf-related low back painWearing lumbar corsets during a golf swing can effectively decrease lumbar extension and rotation angles and angular velocity.Wearing lumbar corsets increased the rotational motion of the hip joint while reducing the rotation of the lumbar spine.

A comparison of pairs figure skaters in repeated jumps.

PubMed

Sands, William A; Kimmel, Wendy L; McNeal, Jeni R; Murray, Steven Ross; Stone, Michael H

2012-01-01

Trends in pairs figure skating have shown that increasingly difficult jumps have become an essential aspect of high-level performance, especially in the latter part of a competitive program. We compared a repeated jump power index in a 60 s repeated jump test to determine the relationship of repeated jump test to competitive rank and to measure 2D hip, knee, and ankle angles and angular velocities at 0, 20, 40, and 60 s. Eighteen National Team Pairs Figure Skaters performed a 60 s repeated jump test on a large switch-mat with timing of flight and ground durations and digital video recording. Each 60-s period was divided into 6, 10-s intervals, with power indexes (W/kg) calculated for each 10-s interval. Power index by 10-s interval repeated measures ANOVAs (RMANOVA) showed that males exceeded females at all intervals, and the highest power index interval was during 10 to 20 s for both sexes. RMANOVAs of angles and angular velocities showed main effects for time only. Power index and jumping techniques among figure skaters showed rapid and steady declines over the test duration. Power index can predict approximately 50% of competitive rank variance, and sex differences in jumping technique were rare. Key pointsThe repeated jumps test can account for about 50% of the variance in pairs ranks.Changes in technique are largely due to fatigue, but the athletes were able to maintain a maximum flexion knee angle very close to the desired 90 degrees. Changes in angular velocity and jump heights occurred as expected, again probably due to fatigue.As expected from metabolic information, the athletes' power indexes peak around 20s and decline thereafter. Coaches should be aware of this time as a boundary beyond which fatigue becomes more manifest, and use careful choreographic choices to provide rest periods that are disguised as less demanding skating elements to afford recovery.The repeated jumps test may be a helpful off-ice test of power-endurance for figure skaters.

Rotations of large inertial cubes, cuboids, cones, and cylinders in turbulence

NASA Astrophysics Data System (ADS)

Pujara, Nimish; Oehmke, Theresa B.; Bordoloi, Ankur D.; Variano, Evan A.

2018-05-01

We conduct experiments to investigate the rotations of freely moving particles in a homogeneous isotropic turbulent flow. The particles are nearly neutrally buoyant and the particle size exceeds the Kolmogorov scale so that they are too large to be considered passive tracers. Particles of several different shapes are considered including those that break axisymmetry and fore-aft symmetry. We find that regardless of shape the mean-square particle angular velocity scales as deq -4 /3, where de q is the equivalent diameter of a volume-matched sphere. This scaling behavior is consistent with the notion that velocity differences across a length de q in the flow are responsible for particle rotation. We also find that the probability density functions (PDFs) of particle angular velocity collapse for particles of different shapes and similar de q. The significance of these results is that the rotations of an inertial, nonspherical particle are only functions of its volume and not its shape. The magnitude of particle angular velocity appears log-normally distributed and individual Cartesian components show long tails. With increasing de q, the tails of the PDF become less pronounced, meaning that extreme events of angular velocity become less common for larger particles.

Catching a Rolling Stone: Dynamics and Control of a Spacecraft and an Asteroid

NASA Technical Reports Server (NTRS)

Roithmayr, Carlos M.; Shen, Haijun; Jesick, Mark C; Cornelius, David M

2013-01-01

In a recent report, a robotic spacecraft mission is proposed for the purpose of collecting a small asteroid, or a small part of a large one, and transporting it to an orbit in the Earth-Moon system. Such an undertaking will require solutions to many of the engineering problems associated with deflection of an asteroid that poses a danger to Earth. In both cases, it may be necessary for a spacecraft to approach an asteroid from a nearby position, hover for some amount of time, move with the same angular velocity as the asteroid, descend, perhaps ascend, and finally arrest the angular velocity of the asteroid. Dynamics and control in each of these activities is analyzed in order to determine the velocity increments and control torque that must be provided by a reaction control system, and the mass of the propellant that will be consumed. Two attitude control algorithms are developed, one to deal with synchronizing the spacecraft s angular velocity with that of the asteroid, and the other to arrest the asteroid s angular velocity. A novel approach is proposed for saving fuel in the latter case.

A kinematic and kinetic analysis of the sit-to-stand transfer using an ejector chair: implications for elderly rheumatoid arthritic patients.

PubMed

Munro, B J; Steele, J R; Bashford, G M; Ryan, M; Britten, N

1998-03-01

Twelve elderly female rheumatoid arthritis patients (mean age = 65.5 +/- 8.6 yr) were assessed rising from an instrumented Eser Ejector chair under four conditions: high seat (540 mm), low seat (450 mm), with and without the ejector mechanism operating. Sagittal plane motion, ground reaction forces, and vertical chair arm rest forces were recorded during each trial with the signals synchronised at initial subject head movement. When rising from a high seat, subjects displayed significantly (p < 0.05) greater time to seat off; greater trunk, knee and ankle angles at seat off; increased ankle angular displacement; decreased knee angular displacement; and decreased total net and normalised arm rest forces compared to rising from a low seat. When rising using the ejector mechanism, time to seat off and trunk and knee angle at seat off significantly increased, whereas trunk and knee angular displacement, and total net and normalised arm rest forces significantly decreased compared to rising unassisted. Regardless of seat height or ejector mechanism use, there were no significant differences in the peak, or time to peak horizontal velocity of the subjects' total body centre of mass, or net knee and ankle moments. It was concluded that increased seat height and use of the ejector mechanism facilitated sit-to-stand transfers performed by elderly female rheumatoid arthritic patients. However, using the ejector chair may be preferred by these patients compared to merely raising seat height because it does not necessitate the use of a footstool, a possible obstacle contributing to falls.

A Missile-Borne Angular Velocity Sensor Based on Triaxial Electromagnetic Induction Coils

PubMed Central

Li, Jian; Wu, Dan; Han, Yan

2016-01-01

Aiming to solve the problem of the limited measuring range for angular motion parameters of high-speed rotating projectiles in the field of guidance and control, a self-adaptive measurement method for angular motion parameters based on the electromagnetic induction principle is proposed. First, a framework with type bent “I-shape” is used to design triaxial coils in a mutually orthogonal way. Under the condition of high rotational speed of a projectile, the induction signal of the projectile moving across a geomagnetic field is acquired by using coils. Second, the frequency of the pulse signal is adjusted self-adaptively. Angular velocity and angular displacement are calculated in the form of periodic pulse counting and pulse accumulation, respectively. Finally, on the basis of that principle prototype of the sensor is researched and developed, performance of measuring angular motion parameters are tested on the sensor by semi-physical and physical simulation experiments, respectively. Experimental results demonstrate that the sensor has a wide measuring range of angular velocity from 1 rps to 100 rps with a measurement error of less than 0.3%, and the angular displacement measurement error is lower than 0.2°. The proposed method satisfies measurement requirements for high-speed rotating projectiles with an extremely high dynamic range of rotational speed and high precision, and has definite value to engineering applications in the fields of attitude determination and geomagnetic navigation. PMID:27706039

A Missile-Borne Angular Velocity Sensor Based on Triaxial Electromagnetic Induction Coils.

PubMed

Li, Jian; Wu, Dan; Han, Yan

2016-09-30

Aiming to solve the problem of the limited measuring range for angular motion parameters of high-speed rotating projectiles in the field of guidance and control, a self-adaptive measurement method for angular motion parameters based on the electromagnetic induction principle is proposed. First, a framework with type bent "I-shape" is used to design triaxial coils in a mutually orthogonal way. Under the condition of high rotational speed of a projectile, the induction signal of the projectile moving across a geomagnetic field is acquired by using coils. Second, the frequency of the pulse signal is adjusted self-adaptively. Angular velocity and angular displacement are calculated in the form of periodic pulse counting and pulse accumulation, respectively. Finally, on the basis of that principle prototype of the sensor is researched and developed, performance of measuring angular motion parameters are tested on the sensor by semi-physical and physical simulation experiments, respectively. Experimental results demonstrate that the sensor has a wide measuring range of angular velocity from 1 rps to 100 rps with a measurement error of less than 0.3%, and the angular displacement measurement error is lower than 0.2°. The proposed method satisfies measurement requirements for high-speed rotating projectiles with an extremely high dynamic range of rotational speed and high precision, and has definite value to engineering applications in the fields of attitude determination and geomagnetic navigation.

Angular momentum transfer in low velocity oblique impacts - Implications for asteroids

NASA Technical Reports Server (NTRS)

Yanagisawa, Masahisa; Eluszkiewicz, Janusz; Ahrens, Thomas J.

1991-01-01

An experimental study has been conducted for the low-velocity oblique impact efficiency of angular momentum transfer, which is defined as that fraction of incident angular momentum that is transferred to the rotation of a target. The results obtained suggest that more energetic impacts are able to transfer angular momentum more efficiently. In the cases of ricochetted projectiles, the fraction of angular momentum carried off by the ejecta was noted to be less than 30 percent. It is suggested that, if asteroid spin rates are due to mutual noncatastrophic collisions and the taxonomic classes are indicative of bulk properties, the differences between corresponding spin rates will be smaller than expected from a consideration of relative strength and density alone.

Power Stroke Angular Velocity Profiles of Archaeal A-ATP Synthase Versus Thermophilic and Mesophilic F-ATP Synthase Molecular Motors*

PubMed Central

Sielaff, Hendrik; Martin, James; Singh, Dhirendra; Biuković, Goran; Grüber, Gerhard; Frasch, Wayne D.

2016-01-01

The angular velocities of ATPase-dependent power strokes as a function of the rotational position for the A-type molecular motor A3B3DF, from the Methanosarcina mazei Gö1 A-ATP synthase, and the thermophilic motor α3β3γ, from Geobacillus stearothermophilus (formerly known as Bacillus PS3) F-ATP synthase, are resolved at 5 μs resolution for the first time. Unexpectedly, the angular velocity profile of the A-type was closely similar in the angular positions of accelerations and decelerations to the profiles of the evolutionarily distant F-type motors of thermophilic and mesophilic origins, and they differ only in the magnitude of their velocities. M. mazei A3B3DF power strokes occurred in 120° steps at saturating ATP concentrations like the F-type motors. However, because ATP-binding dwells did not interrupt the 120° steps at limiting ATP, ATP binding to A3B3DF must occur during the catalytic dwell. Elevated concentrations of ADP did not increase dwells occurring 40° after the catalytic dwell. In F-type motors, elevated ADP induces dwells 40° after the catalytic dwell and slows the overall velocity. The similarities in these power stroke profiles are consistent with a common rotational mechanism for A-type and F-type rotary motors, in which the angular velocity is limited by the rotary position at which ATP binding occurs and by the drag imposed on the axle as it rotates within the ring of stator subunits. PMID:27729450

Angular Rate Optimal Design for the Rotary Strapdown Inertial Navigation System

PubMed Central

Yu, Fei; Sun, Qian

2014-01-01

Due to the characteristics of high precision for a long duration, the rotary strapdown inertial navigation system (RSINS) has been widely used in submarines and surface ships. Nowadays, the core technology, the rotating scheme, has been studied by numerous researchers. It is well known that as one of the key technologies, the rotating angular rate seriously influences the effectiveness of the error modulating. In order to design the optimal rotating angular rate of the RSINS, the relationship between the rotating angular rate and the velocity error of the RSINS was analyzed in detail based on the Laplace transform and the inverse Laplace transform in this paper. The analysis results showed that the velocity error of the RSINS depends on not only the sensor error, but also the rotating angular rate. In order to minimize the velocity error, the rotating angular rate of the RSINS should match the sensor error. One optimal design method for the rotating rate of the RSINS was also proposed in this paper. Simulation and experimental results verified the validity and superiority of this optimal design method for the rotating rate of the RSINS. PMID:24759115

Developments in Human Centered Cueing Algorithms for Control of Flight Simulator Motion Systems

NASA Technical Reports Server (NTRS)

Houck, Jacob A.; Telban, Robert J.; Cardullo, Frank M.

1997-01-01

The authors conducted further research with cueing algorithms for control of flight simulator motion systems. A variation of the so-called optimal algorithm was formulated using simulated aircraft angular velocity input as a basis. Models of the human vestibular sensation system, i.e. the semicircular canals and otoliths, are incorporated within the algorithm. Comparisons of angular velocity cueing responses showed a significant improvement over a formulation using angular acceleration input. Results also compared favorably with the coordinated adaptive washout algorithm, yielding similar results for angular velocity cues while eliminating false cues and reducing the tilt rate for longitudinal cues. These results were confirmed in piloted tests on the current motion system at NASA-Langley, the Visual Motion Simulator (VMS). Proposed future developments by the authors in cueing algorithms are revealed. The new motion system, the Cockpit Motion Facility (CMF), where the final evaluation of the cueing algorithms will be conducted, is also described.

Walking velocity and step length adjustments affect knee joint contact forces in healthy weight and obese adults.

PubMed

Milner, Clare E; Meardon, Stacey A; Hawkins, Jillian L; Willson, John D

2018-04-28

Knee osteoarthritis is a major public health problem and adults with obesity are particularly at risk. One approach to alleviating this problem is to reduce the mechanical load at the joint during daily activity. Adjusting temporospatial parameters of walking could mitigate cumulative knee joint mechanical loads. The purpose of this study was to determine how adjustments to velocity and step length affects knee joint loading in healthy weight adults and adults with obesity. We collected three-dimensional gait analysis data on 10 adults with a normal body mass index and 10 adults with obesity during over ground walking in nine different conditions. In addition to preferred velocity and step length, we also conducted combinations of 15% increased and decreased velocity and step length. Peak tibiofemoral joint impulse and knee adduction angular impulse were reduced in the decreased step length conditions in both healthy weight adults (main effect) and those with obesity (interaction effect). Peak knee joint adduction moment was also reduced with decreased step length, and with decreased velocity in both groups. We conclude from these results that adopting shorter step lengths during daily activity and when walking for exercise can reduce mechanical stimuli associated with articular cartilage degenerative processes in adults with and without obesity. Thus, walking with reduced step length may benefit adults at risk for disability due to knee osteoarthritis. Adopting a shorter step length during daily walking activity may reduce knee joint loading and thus benefit those at risk for knee cartilage degeneration. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 9999:XX-XX, 2018. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc.

Massive star formation by accretion. II. Rotation: how to circumvent the angular momentum barrier?

NASA Astrophysics Data System (ADS)

Haemmerlé, L.; Eggenberger, P.; Meynet, G.; Maeder, A.; Charbonnel, C.; Klessen, R. S.

2017-06-01

Context. Rotation plays a key role in the star-formation process, from pre-stellar cores to pre-main-sequence (PMS) objects. Understanding the formation of massive stars requires taking into account the accretion of angular momentum during their PMS phase. Aims: We study the PMS evolution of objects destined to become massive stars by accretion, focusing on the links between the physical conditions of the environment and the rotational properties of young stars. In particular, we look at the physical conditions that allow the production of massive stars by accretion. Methods: We present PMS models computed with a new version of the Geneva Stellar Evolution code self-consistently including accretion and rotation according to various accretion scenarios for mass and angular momentum. We describe the internal distribution of angular momentum in PMS stars accreting at high rates and we show how the various physical conditions impact their internal structures, evolutionary tracks, and rotation velocities during the PMS and the early main sequence. Results: We find that the smooth angular momentum accretion considered in previous studies leads to an angular momentum barrier and does not allow the formation of massive stars by accretion. A braking mechanism is needed in order to circumvent this angular momentum barrier. This mechanism has to be efficient enough to remove more than two thirds of the angular momentum from the inner accretion disc. Due to the weak efficiency of angular momentum transport by shear instability and meridional circulation during the accretion phase, the internal rotation profiles of accreting stars reflect essentially the angular momentum accretion history. As a consequence, careful choice of the angular momentum accretion history allows circumvention of any limitation in mass and velocity, and production of stars of any mass and velocity compatible with structure equations.

Dependence of the Peak Fluxes of Solar Energetic Particles on CME 3D Parameters from STEREO and SOHO

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

Park, Jinhye; Moon, Y.-J.; Lee, Harim, E-mail: jinhye@khu.ac.kr

We investigate the relationships between the peak fluxes of 18 solar energetic particle (SEP) events and associated coronal mass ejection (CME) 3D parameters (speed, angular width, and separation angle) obtained from SOHO , and STEREO-A / B for the period from 2010 August to 2013 June. We apply the STEREO CME Analysis Tool (StereoCAT) to the SEP-associated CMEs to obtain 3D speeds and 3D angular widths. The separation angles are determined as the longitudinal angles between flaring regions and magnetic footpoints of the spacecraft, which are calculated by the assumption of a Parker spiral field. The main results are asmore » follows. (1) We find that the dependence of the SEP peak fluxes on CME 3D speed from multiple spacecraft is similar to that on CME 2D speed. (2) There is a positive correlation between SEP peak flux and 3D angular width from multiple spacecraft, which is much more evident than the relationship between SEP peak flux and 2D angular width. (3) There is a noticeable anti-correlation ( r = −0.62) between SEP peak flux and separation angle. (4) The multiple-regression method between SEP peak fluxes and CME 3D parameters shows that the longitudinal separation angle is the most important parameter, and the CME 3D speed is secondary on SEP peak flux.« less

Design and Experimental Performance of a Two Stage Partial Admission Turbine, Task B.1/B.4

NASA Technical Reports Server (NTRS)

Sutton, R. F.; Boynton, J. L.; Akian, R. A.; Shea, Dan; Roschak, Edmund; Rojas, Lou; Orr, Linsey; Davis, Linda; King, Brad; Bubel, Bill

1992-01-01

A three-inch mean diameter, two-stage turbine with partial admission in each stage was experimentally investigated over a range of admissions and angular orientations of admission arcs. Three configurations were tested in which first stage admission varied from 37.4 percent (10 of 29 passages open, 5 per side) to 6.9 percent (2 open, 1 per side). Corresponding second stage admissions were 45.2 percent (14 of 31 passages open, 7 per side) and 12.9 percent (4 open, 2 per side). Angular positions of the second stage admission arcs with respect to the first stage varied over a range of 70 degrees. Design and off-design efficiency and flow characteristics for the three configurations are presented. The results indicated that peak efficiency and the corresponding isentropic velocity ratio decreased as the arcs of admission were decreased. Both efficiency and flow characteristics were sensitive to the second stage nozzle orientation angles.

A Homing Missile Control System to Reduce the Effects of Radome Diffraction

NASA Technical Reports Server (NTRS)

Smith, Gerald L.

1960-01-01

The problem of radome diffraction in radar-controlled homing missiles at high speeds and high altitudes is considered from the point of view of developing a control system configuration which will alleviate the deleterious effects of the diffraction. It is shown that radome diffraction is in essence a kinematic feedback of body angular velocities which causes the radar to sense large apparent line-of-sight angular velocities. The normal control system cannot distinguish between the erroneous and actual line-of-sight rates, and entirely wrong maneuvers are produced which result in large miss distances. The problem is resolved by adding to the control system a special-purpose computer which utilizes measured body angular velocity to extract from the radar output true line-of-sight information for use in steering the missile. The computer operates on the principle of sampling and storing the radar output at instants when the body angular velocity is low and using this stored information for maneuvering commands. In addition, when the angular velocity is not low the computer determines a radome diffraction compensation which is subtracted from the radar output to reduce the error in the sampled information. Analog simulation results for the proposed control system operating in a coplanar (vertical plane) attack indicate a potential decrease in miss distance to an order of magnitude below that for a conventional system. Effects of glint noise, random target maneuvers, initial heading errors, and missile maneuverability are considered in the investigation.

A Kinematic Analysis of the Jumping Front-Leg Axe-Kick in Taekwondo

PubMed Central

Preuschl, Emanuel; Hassmann, Michaela; Baca, Arnold

2016-01-01

The jumping front-leg axe-kick is a valid attacking and counterattacking technique in Taekwondo competition (Streif, 1993). Yet, the existing literature on this technique is sparse (Kloiber et al., 2009). Therefore, the goal of this study was to determine parameters contributing significantly to maximum linear speed of the foot at impact. Parameters are timing of segment and joint angular velocity characteristics and segment lengths of the kicking leg. Moreover, we were interested in the prevalence of proximal-to-distal-sequencing. Three-dimensional kinematics of the kicks of 22 male Taekwondo-athletes (age: 23.3 ± 5.3 years) were recorded via a motion capturing system (Vicon Motion Systems Limited, Oxford, UK). The participants performed maximum effort kicks onto a rack-held kicking pad. Only the kick with the highest impact velocity was analysed, as it was assumed to represent the individual’s best performance. Significant Pearson correlations to impact velocity were found for pelvis tilt angular displacement (r = 0.468, p < 0.05) and for hip extension angular velocity (r = -0.446, p < 0.05) and for the timing of the minima of pelvis tilt velocity (r = -0.426, p < 0.05) and knee flexion velocity (r = -0.480, p < 0.05). Backward step linear regression analysis suggests a model consisting of three predictor variables: pelvis tilt angular displacement, hip flexion velocity at target contact and timing of pelvic tilt angular velocity minimum (adjusted R2 = 0.524). Results of Chi-Squared tests show that neither for the leg-raising period (χ2 = 2.909) of the technique, nor for the leg-lowering period a pattern of proximal-to-distal sequencing is prevalent (χ2 = 0.727). From the results we conclude that the jumping front-leg axe-kick does not follow a proximal-to-distal pattern. Raising the leg early in the technique and apprehending the upper body to be leant back during the leg-lowering period seems to be beneficial for high impact velocity. Furthermore, striking by extending the hip rather than by flexing the knee could raise impact velocity. Key points Angular velocity characteristics of the pelvis segment and the kicking leg’s hip and knee joint show no proximal-to-distal sequencing, neither for the leg-raising or leg-lowering period in a jumping front-leg axe-kick. Anthropometric parameters of taekwondo athlete’s do not influence their impact velocities. In order to raise the impact velocity in the jumping front-leg axe-kick an athlete should avoid tilting back with the torso. Instead, an upright position should be maintained. In the leg-lowering period, we suggest hitting the target by using hip extension with a rather straight knee, instead of flexing the knee. PMID:26957931

Difference in perception of angular displacement according to applied waveforms.

PubMed

Kushiro, Keisuke; Goto, Fumiyuki

2013-05-01

This study shows that the differences in the waveforms of angular rotation affect the perception and memory of angular displacement. During daily life, when we turn our head during various activities, our brain calculates how much angular displacement our head has undergone. However, how we obtain an accurate estimation of this angular displacement remains unclarified. This study aims to clarify this issue by investigating the perception and memory of passive rotation for three different waveforms of angular velocity rotation (sinusoidal (sine), triangle, and step). Thirteen healthy young subjects sitting on a servo-controlled chair were passively rotated at 60° or 120° about the earth-vertical axis by using one of these three angular velocity waveforms. They then attempted to reproduce the rotation angle by rotating the chair in the same direction in which they had been passively rotated using a handheld controller. The gain (reproduced angle/passively rotated angle) was calculated and used for the evaluation of the perception and memory of angular rotation. The gain for step rotation was larger than that for sine and triangle rotations, with statistical significance. This confirms that the difference in the waveforms of angular rotation affects the perception and memory of angular displacement.

Kinematic adaptations during running: effects of footwear, surface, and duration.

PubMed

Hardin, Elizabeth C; van den Bogert, Antonie J; Hamill, Joseph

2004-05-01

Repetitive impacts encountered during locomotion may be modified by footwear and/or surface. Changes in kinematics may occur either as a direct response to altered mechanical conditions or over time as active adaptations. : To investigate how midsole hardness, surface stiffness, and running duration influence running kinematics. In the first of two experiments, 12 males ran at metabolic steady state under six conditions; combinations of midsole hardness (40 Shore A, 70 Shore A), and surface stiffness (100 kN x m, 200 kN x m, and 350 kN x m). In the second experiment, 10 males ran for 30 min on a 12% downhill grade. In both experiments, subjects ran at 3.4 m x s on a treadmill while 2-D hip, knee, and ankle kinematics were determined using high-speed videography (200 Hz). Oxygen cost and heart rate data were also collected. Kinematic adaptations to midsole, surface, and running time were studied. Stance time, stride cycle time, and maximal knee flexion were invariant across conditions in each experiment. Increased midsole hardness resulted in greater peak ankle dorsiflexion velocity (P = 0.0005). Increased surface stiffness resulted in decreased hip and knee flexion at contact, reduced maximal hip flexion, and increased peak angular velocities of the hip, knee, and ankle. Over time, hip flexion at contact decreased, plantarflexion at toe-off increased, and peak dorsiflexion and plantarflexion velocity increased. Lower-extremity kinematics adapted to increased midsole hardness, surface stiffness, and running duration. Changes in limb posture at impact were interpreted as active adaptations that compensate for passive mechanical effects. The adaptations appeared to have the goal of minimizing metabolic cost at the expense of increased exposure to impact shock.

Power Stroke Angular Velocity Profiles of Archaeal A-ATP Synthase Versus Thermophilic and Mesophilic F-ATP Synthase Molecular Motors.

PubMed

Sielaff, Hendrik; Martin, James; Singh, Dhirendra; Biuković, Goran; Grüber, Gerhard; Frasch, Wayne D

2016-12-02

The angular velocities of ATPase-dependent power strokes as a function of the rotational position for the A-type molecular motor A 3 B 3 DF, from the Methanosarcina mazei Gö1 A-ATP synthase, and the thermophilic motor α 3 β 3 γ, from Geobacillus stearothermophilus (formerly known as Bacillus PS3) F-ATP synthase, are resolved at 5 μs resolution for the first time. Unexpectedly, the angular velocity profile of the A-type was closely similar in the angular positions of accelerations and decelerations to the profiles of the evolutionarily distant F-type motors of thermophilic and mesophilic origins, and they differ only in the magnitude of their velocities. M. mazei A 3 B 3 DF power strokes occurred in 120° steps at saturating ATP concentrations like the F-type motors. However, because ATP-binding dwells did not interrupt the 120° steps at limiting ATP, ATP binding to A 3 B 3 DF must occur during the catalytic dwell. Elevated concentrations of ADP did not increase dwells occurring 40° after the catalytic dwell. In F-type motors, elevated ADP induces dwells 40° after the catalytic dwell and slows the overall velocity. The similarities in these power stroke profiles are consistent with a common rotational mechanism for A-type and F-type rotary motors, in which the angular velocity is limited by the rotary position at which ATP binding occurs and by the drag imposed on the axle as it rotates within the ring of stator subunits. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Dopaminergic modulation of arm swing during gait among Parkinson’s disease patients

PubMed Central

Sterling, Nicholas W.; Cusumano, Joseph P.; Shaham, Noam; Piazza, Stephen J.; Liu, Guodong; Kong, Lan; Du, Guangwei; Lewis, Mechelle M.; Huang, Xuemei

2015-01-01

Background Reduced arm swing amplitude, symmetry, and coordination during gait have been reported in Parkinson’s disease (PD), but the relationship between dopaminergic depletion and these upper limb gait changes remains unclear. This study investigated the effects of dopaminergic drugs on arm swing velocity, symmetry, and coordination in PD. Methods Forearm angular velocity was recorded in 16 PD and 17 control subjects (Controls) during free walking trials. Angular velocity amplitude of each arm, arm swing asymmetry, and maximum cross-correlation were compared between control and PD groups, and between OFF- and ON-medication states among PD subjects. Results Compared to Controls, PD subjects in the OFF-medication state exhibited lower angular velocity amplitude of the slower- (p=0.0018), but not faster- (p=0.2801) swinging arm. In addition, PD subjects demonstrated increased arm swing asymmetry (p=0.0046) and lower maximum cross-correlation (p=0.0026). Following dopaminergic treatment, angular velocity amplitude increased in the slower- (p=0.0182), but not faster- (p=0.2312) swinging arm among PD subjects. Furthermore, arm swing asymmetry decreased (p=0.0386), whereas maximum cross-correlation showed no change (p=0.7436). Pre-drug angular velocity amplitude of the slower-swinging arm was correlated inversely with the change in arm swing asymmetry (R=−0.73824, p=0.0011). Conclusions This study provides quantitative evidence that reduced arm swing and symmetry in PD can be modulated by dopaminergic replacement. The lack of modulations of bilateral arm coordination suggests that additional neurotransmitters may also be involved in arm swing changes in PD. Further studies are warranted to investigate the longitudinal trajectory of arm swing dynamics throughout PD progression. PMID:25502948

Dopaminergic modulation of arm swing during gait among Parkinson's disease patients.

PubMed

Sterling, Nicholas W; Cusumano, Joseph P; Shaham, Noam; Piazza, Stephen J; Liu, Guodong; Kong, Lan; Du, Guangwei; Lewis, Mechelle M; Huang, Xuemei

2015-01-01

Reduced arm swing amplitude, symmetry, and coordination during gait have been reported in Parkinson's disease (PD), but the relationship between dopaminergic depletion and these upper limb gait changes remains unclear. We aimed to investigate the effects of dopaminergic drugs on arm swing velocity, symmetry, and coordination in PD. Forearm angular velocity was recorded in 16 PD and 17 control subjects (Controls) during free walking trials. Angular velocity amplitude of each arm, arm swing asymmetry, and maximum cross-correlation were compared between control and PD groups, and between OFF- and ON-medication states among PD subjects. Compared to Controls, PD subjects in the OFF-medication state exhibited lower angular velocity amplitude of the slower- (p = 0.0018), but not faster- (p = 0.2801) swinging arm. In addition, PD subjects demonstrated increased arm swing asymmetry (p = 0.0046) and lower maximum cross-correlation (p = 0.0026). Following dopaminergic treatment, angular velocity amplitude increased in the slower- (p = 0.0182), but not faster- (p = 0.2312) swinging arm among PD subjects. Furthermore, arm swing asymmetry decreased (p = 0.0386), whereas maximum cross-correlation showed no change (p = 0.7436). Pre-drug angular velocity amplitude of the slower-swinging arm was correlated inversely with the change in arm swing asymmetry (R = -0.73824, p = 0.0011). This study provides quantitative evidence that reduced arm swing and symmetry in PD can be modulated by dopaminergic replacement. The lack of modulations of bilateral arm coordination suggests that additional neurotransmitters may also be involved in arm swing changes in PD. Further studies are warranted to investigate the longitudinal trajectory of arm swing dynamics throughout PD progression.

Kinematics of preferred and non-preferred handballing in Australian football.

PubMed

Parrington, Lucy; Ball, Kevin; MacMahon, Clare

2015-01-01

In Australian football (AF), handballing proficiently with both the preferred and non-preferred arm is important at elite levels; yet, little information is available for handballing on the non-preferred arm. This study compared preferred and non-preferred arm handballing techniques. Optotrak Certus (100 Hz) collected three-dimensional data for 19 elite AF players performing handballs with the preferred and non-preferred arms. Position data, range of motion (ROM), and linear and angular velocities were collected and compared between preferred and non-preferred arms using dependent t-tests. The preferred arm exhibited significantly greater forearm and humerus ROM and angular velocity and significantly greater shoulder angular velocity at ball contact compared to the non-preferred arm. In addition, the preferred arm produced a significantly greater range of lateral bend and maximum lower-trunk speed, maximum strike-side hip speed and hand speed at ball contact than the non-preferred arm. The non-preferred arm exhibited a significantly greater shoulder angle and lower- and upper-trunk orientation angle, but significantly lower support-elbow angle, trunk ROM, and trunk rotation velocity compared to the preferred arm. Reduced ROM and angular velocities found in non-preferred arm handballs indicates a reduction in the degrees of freedom and a less developed skill. Findings have implication for development of handballing on the non-preferred arm.

Rotation of the asymptotic giant branch star R Doradus

NASA Astrophysics Data System (ADS)

Vlemmings, W. H. T.; Khouri, T.; Beck, E. De; Olofsson, H.; García-Segura, G.; Villaver, E.; Baudry, A.; Humphreys, E. M. L.; Maercker, M.; Ramstedt, S.

2018-05-01

High-resolution observations of the extended atmospheres of asymptotic giant branch (AGB) stars can now directly be compared to the theories that describe stellar mass loss. Using Atacama Large Millimeter/submillimeter Array (ALMA) high angular resolution (30 × 42 mas) observations, we have for the first time resolved stellar rotation of an AGB star, R Dor. We measure an angular rotation velocity of ωR sin i = (3.5 ± 0.3) × 10-9 rad s-1, which indicates a rotational velocity of |υrot sin i| = 1.0 ± 0.1 km s-1 at the stellar surface (R* = 31.2 mas at 214 GHz). The rotation axis projected on the plane of the sky has a position angle Φ = 7 ± 6°. We find that the rotation of R Dor is two orders of magnitude faster than expected for a solitary AGB star that will have lost most of its angular momentum. Its rotational velocity is consistent with angular momentum transfer from a close companion. As a companion has not been directly detected, we suggest R Dor has a low-mass, close-in companion. The rotational velocity approaches the critical velocity, set by the local sound speed in the extended envelope, and is thus expected to affect the mass-loss characteristics of R Dor.

Absolute Plate Velocities from Seismic Anisotropy

NASA Astrophysics Data System (ADS)

Kreemer, Corné; Zheng, Lin; Gordon, Richard

2015-04-01

The orientation of seismic anisotropy inferred beneath plate interiors may provide a means to estimate the motions of the plate relative to the sub-asthenospheric mantle. Here we analyze two global sets of shear-wave splitting data, that of Kreemer [2009] and an updated and expanded data set, to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. We also explore the effect of using geologically current plate velocities (i.e., the MORVEL set of angular velocities [DeMets et al. 2010]) compared with geodetically current plate velocities (i.e., the GSRM v1.2 angular velocities [Kreemer et al. 2014]). We demonstrate that the errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. The SKS-MORVEL absolute plate angular velocities (based on the Kreemer [2009] data set) are determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11° Ma-1 (95% confidence limits) right-handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2° ) differs insignificantly from that for continental lithosphere (σ=21.6° ). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4° ) than for continental lithosphere (σ=14.7° ). Two of the slowest-moving plates, Antarctica (vRMS=4 mm a-1, σ=29° ) and Eurasia (vRMS=3 mm a-1, σ=33° ), have two of the largest within-plate dispersions, which may indicate that a plate must move faster than ˜5 mm a-1 to result in seismic anisotropy useful for estimating plate motion. We will investigate if these relationships still hold with the new expanded data set and with the alternative set of relative plate angular velocities. We have found systematic differences between the SKS orientations and our predicted plate motion azimuths underneath the Arabia plate, which suggests to us either plate-scale mantle flow process not directly associated with that plate's absolute motion or intrinsic lithospheric anisotropy. We will discuss more of such discrepancies underneath other plates using the enlarged data set.

The influence of target angular velocity on visual latency difference determined using the rotating Pulfrich effect.

PubMed

Nickalls, R W

1996-09-01

Visual latency difference was determined directly in normal volunteers, using the rotating Pulfrich technique described by Nickalls [Vision Research, 26, 367-372 (1986)]. Subjects fixated a black vertical rod rotating clockwise on a horizontal turntable turning with constant angular velocity (16.6,33.3 or 44.7 revs/min) with a neutral density filter (OD 0.7 or 1.5) in front of the right eye. For all subjects the latency difference associated with the 1.5 OD filter was significantly greater (P < 0.001) with the rod rotating at 16.6 rev/min than at 33.3 revs/min. The existence of an inverse relationship between latency difference and angular velocity is hypothesized.

Angular Displacement and Velocity Sensors Based on Coplanar Waveguides (CPWs) Loaded with S-Shaped Split Ring Resonators (S-SRR).

PubMed

Naqui, Jordi; Coromina, Jan; Karami-Horestani, Ali; Fumeaux, Christophe; Martín, Ferran

2015-04-23

In this paper, angular displacement and angular velocity sensors based on coplanar waveguide (CPW) transmission lines and S-shaped split ring resonators (S-SRRs) are presented. The sensor consists of two parts, namely a CPW and an S-SRR, both lying on parallel planes. By this means, line-to-resonator magnetic coupling arises, the coupling level being dependent on the line-to-resonator relative angular orientation. The line-to-resonator coupling level is the key parameter responsible for modulating the amplitude of the frequency response seen between the CPW ports in the vicinity of the S-SRR fundamental resonance frequency. Specifically, an amplitude notch that can be visualized in the transmission coefficient is changed by the coupling strength, and it is characterized as the sensing variable. Thus, the relative angular orientation between the two parts is measured, when the S-SRR is attached to a rotating object. It follows that the rotation angle and speed can be inferred either by measuring the frequency response of the S-SRR-loaded line, or the response amplitude at a fixed frequency in the vicinity of resonance. It is in addition shown that the angular velocity can be accurately determined from the time-domain response of a carrier time-harmonic signal tuned at the S-SRR resonance frequency. The main advantage of the proposed device is its small size directly related to the small electrical size of the S-SRR, which allows for the design of compact angular displacement and velocity sensors at low frequencies. Despite the small size of the fabricated proof-of-concept prototype (electrically small structures do not usually reject signals efficiently), it exhibits good linearity (on a logarithmic scale), sensitivity and dynamic range.

Angular Displacement and Velocity Sensors Based on Coplanar Waveguides (CPWs) Loaded with S-Shaped Split Ring Resonators (S-SRR)

PubMed Central

Naqui, Jordi; Coromina, Jan; Karami-Horestani, Ali; Fumeaux, Christophe; Martín, Ferran

2015-01-01

In this paper, angular displacement and angular velocity sensors based on coplanar waveguide (CPW) transmission lines and S-shaped split ring resonators (S-SRRs) are presented. The sensor consists of two parts, namely a CPW and an S-SRR, both lying on parallel planes. By this means, line-to-resonator magnetic coupling arises, the coupling level being dependent on the line-to-resonator relative angular orientation. The line-to-resonator coupling level is the key parameter responsible for modulating the amplitude of the frequency response seen between the CPW ports in the vicinity of the S-SRR fundamental resonance frequency. Specifically, an amplitude notch that can be visualized in the transmission coefficient is changed by the coupling strength, and it is characterized as the sensing variable. Thus, the relative angular orientation between the two parts is measured, when the S-SRR is attached to a rotating object. It follows that the rotation angle and speed can be inferred either by measuring the frequency response of the S-SRR-loaded line, or the response amplitude at a fixed frequency in the vicinity of resonance. It is in addition shown that the angular velocity can be accurately determined from the time-domain response of a carrier time-harmonic signal tuned at the S-SRR resonance frequency. The main advantage of the proposed device is its small size directly related to the small electrical size of the S-SRR, which allows for the design of compact angular displacement and velocity sensors at low frequencies. Despite the small size of the fabricated proof-of-concept prototype (electrically small structures do not usually reject signals efficiently), it exhibits good linearity (on a logarithmic scale), sensitivity and dynamic range. PMID:25915590

[Evaluation of left ventricular diastolic function in canine acute myocardial ischemia using velocity vector imaging and quantitative tissue velocity imaging].

PubMed

Zhang, Chuan; Zha, Dao-Gang; DU, Rong-Sheng; Hu, Feng; Li, Sheng-Hui; Wu, Xiao-Yuan; Liu, Yi-Li

2009-07-01

To assess the value of velocity vector imaging (VVI) and quantitative tissue velocity imaging (QTVI) in assessing left ventricular diastolic function of the dogs with acute myocardial ischemia. Six healthy mongrel dogs were subjected to ligation of the left circumflex artery or left anterior descending artery to induce coronary artery stenosis of varying degrees. The mean peak diastolic velocity (Em) of the ventricular walls around the mitral annulus was recorded with VVI or QTVI in the coronary blood flow. The left ventricular end diastolic pressure (LVEDP) was measured with pigtail catheter in the left ventricle. As the coronary blood flow decreased, LVEDP was gradually increased, and Em measured by VVI or QTVI were also gradually decreased. A good linear correlation was shown between Em measured by VVI or QTVI and LVEDP (r=-0.834, P<0.001, and r=-0.68, P<0.001, respectively). A significant difference was observed in the correlation coefficient between VVI and QTVI (Z=2.625, P=0.0087). VVI and QTVI both provide good noninvasive means for measuring left ventricular diastolic function. VVI, a new echocardiographic modality without angular dependence, is better than QTVI in evaluating left ventricular diastolic function.

Optimum instantaneous impulsive orbital injection to attain a specified asymptotic velocity vector.

NASA Technical Reports Server (NTRS)

Bean, W. C.

1971-01-01

A nalysis of the necessary conditions of Battin for instantaneous orbital injection, with consideration of the uniqueness of his solution, and of the further problem which arises in the degenerate case when radius vector and asymptotic vector are separated by 180 deg. It is shown that when the angular separation between radius vector and asymptotic velocity vector satisfies theta not equal to 180 deg, there are precisely two insertion-velocity vectors which permit attainment of the target asymptotic velocity vector, one yielding posigrade, the other retrograde motion. When theta equals to 180 deg, there is a family of insertion-velocity vectors which permit attainment of a specified asymptotic velocity vector with a unique insertion-velocity vector for every arbitrary orientation of a target unit angular momentum vector.

Power law "thermalization" of ion pickup and ionospheric outflows

NASA Astrophysics Data System (ADS)

Moore, T. E.; Ofman, L.; Glocer, A.; Gershman, D. J.; Khazanov, G. V.; Paterson, W. R.

2016-12-01

One observed feature of ionospheric outflows is that the active ion heating processes produce power law tails of the core plasma velocity distribution, as well as transverse or conic peaks in the angular distributions. This characteristic is shared with hot ion distributions produced by ion pickup in the solar wind, resulting from cometary or interstellar gas ionization, and with hot ions observed around the Space Transportation System during gas releases. We revisit relevant observations and consider the hypothesis that the ion pickup thermalization process tends to produce power law (𝛋) energy distributions, using a simulation of the instability of a simple pickup (ring) distribution. Simulation results are derived for cases representative of both solar wind pickup, where ion velocities exceed the local Alfvén speed, and ionospheric pickup, where the local Alfvén speed exceeds ion velocities. The sub-Alfvenic pickup ring distribution appears to have a slow growth rate (per ion gyro period), that is, the instability evolves more slowly in the latter case than in the former. Implications for ionospheric outflow are discussed.

Synthesis of wavelet envelope in 2-D random media having power-law spectra: comparison with FD simulations

NASA Astrophysics Data System (ADS)

Sato, Haruo; Fehler, Michael C.

2016-10-01

The envelope broadening and the peak delay of the S-wavelet of a small earthquake with increasing travel distance are results of scattering by random velocity inhomogeneities in the earth medium. As a simple mathematical model, Sato proposed a new stochastic synthesis of the scalar wavelet envelope in 3-D von Kármán type random media when the centre wavenumber of the wavelet is in the power-law spectral range of the random velocity fluctuation. The essential idea is to split the random medium spectrum into two components using the centre wavenumber as a reference: the long-scale (low-wavenumber spectral) component produces the peak delay and the envelope broadening by multiple scattering around the forward direction; the short-scale (high-wavenumber spectral) component attenuates wave amplitude by wide angle scattering. The former is calculated by the Markov approximation based on the parabolic approximation and the latter is calculated by the Born approximation. Here, we extend the theory for the envelope synthesis of a wavelet in 2-D random media, which makes it easy to compare with finite difference (FD) simulation results. The synthetic wavelet envelope is analytically written by using the random medium parameters in the angular frequency domain. For the case that the power spectral density function of the random velocity fluctuation has a steep roll-off at large wavenumbers, the envelope broadening is small and frequency independent, and scattering attenuation is weak. For the case of a small roll-off, however, the envelope broadening is large and increases with frequency, and the scattering attenuation is strong and increases with frequency. As a preliminary study, we compare synthetic wavelet envelopes with the average of FD simulation wavelet envelopes in 50 synthesized random media, which are characterized by the RMS fractional velocity fluctuation ε = 0.05, correlation scale a = 5 km and the background wave velocity V0 = 4 km s-1. We use the radiation of a 2 Hz Ricker wavelet from a point source. For all the cases of von Kármán order κ = 0.1, 0.5 and 1, we find the synthetic wavelet envelopes are a good match to the characteristics of FD simulation wavelet envelopes in a time window starting from the onset through the maximum peak to the time when the amplitude decreases to half the peak amplitude.

The Study of Cobb Angular Velocity in Cervical Spine during Dynamic Extension-Flexion.

PubMed

Ren, Dong; Hu, Zhihao; Yuan, Wen

2016-04-01

A kinematic study of cervical spine. The aim of the study was to confirm the interesting manifestation observed in the dynamic images of the cervical spine movement from full-extension to full-flexion. To further explore the fine motion of total process of cervical spine movement with the new concept of Cobb angular velocity (CAV). Traditionally range of motion (ROM) is used to describe the cervical spine movement from extension to flexion. It is performed with only end position radiographs. However, these radiographs fail to explain how the elaborate movement happens. The dynamic images of the cervical spine movement from full-extension to full-flexion of 12 asymptomatic subjects were collected. After transforming these dynamic images to static lateral radiographs, we overlapped C7 cervical vertebrae of each subject and divided the total process of cervical spine movement into five equal partitions. Finally, CAV values from C2/3 to C6/7 were measured and analyzed. A broken line graph was created based on the data of CAV values. A simple motion process was observed in C2/3 and C3/4 segments. The motion processes of C4/5 and C5/6 segments exhibited a more complex track of "N" and "W" than the other segments. The peak CAV values of C4/5 and C5/6 were significantly greater than the other segments. From C2/3 to C6/7, the peak CAV value appeared in sequence. The intervertebral movements of cervical spine did not take a uniform motion form when the cervical spine moved from full-extension to full-flexion. From C2/3 to C6/7, the peak CAV value appeared in order. The C4/5 and C5/6 segments exhibited more complex kinematic characteristics in sagittal movement. This leads to C4/5 and C5/6 more vulnerable to injury and degeneration. We had a hypothesis that there was a positive correlation between injury/degeneration and complexity of intervertebral movement in the view of CAV. N/A.

Anatomy of F1-ATPase powered rotation.

PubMed

Martin, James L; Ishmukhametov, Robert; Hornung, Tassilo; Ahmad, Zulfiqar; Frasch, Wayne D

2014-03-11

F1-ATPase, the catalytic complex of the ATP synthase, is a molecular motor that can consume ATP to drive rotation of the γ-subunit inside the ring of three αβ-subunit heterodimers in 120° power strokes. To elucidate the mechanism of ATPase-powered rotation, we determined the angular velocity as a function of rotational position from single-molecule data collected at 200,000 frames per second with unprecedented signal-to-noise. Power stroke rotation is more complex than previously understood. This paper reports the unexpected discovery that a series of angular accelerations and decelerations occur during the power stroke. The decreases in angular velocity that occurred with the lower-affinity substrate ITP, which could not be explained by an increase in substrate-binding dwells, provides direct evidence that rotation depends on substrate binding affinity. The presence of elevated ADP concentrations not only increased dwells at 35° from the catalytic dwell consistent with competitive product inhibition but also decreased the angular velocity from 85° to 120°, indicating that ADP can remain bound to the catalytic site where product release occurs for the duration of the power stroke. The angular velocity profile also supports a model in which rotation is powered by Van der Waals repulsive forces during the final 85° of rotation, consistent with a transition from F1 structures 2HLD1 and 1H8E (Protein Data Bank).

Anatomy of F1-ATPase powered rotation

PubMed Central

Martin, James L.; Ishmukhametov, Robert; Hornung, Tassilo; Ahmad, Zulfiqar; Frasch, Wayne D.

2014-01-01

F1-ATPase, the catalytic complex of the ATP synthase, is a molecular motor that can consume ATP to drive rotation of the γ-subunit inside the ring of three αβ-subunit heterodimers in 120° power strokes. To elucidate the mechanism of ATPase-powered rotation, we determined the angular velocity as a function of rotational position from single-molecule data collected at 200,000 frames per second with unprecedented signal-to-noise. Power stroke rotation is more complex than previously understood. This paper reports the unexpected discovery that a series of angular accelerations and decelerations occur during the power stroke. The decreases in angular velocity that occurred with the lower-affinity substrate ITP, which could not be explained by an increase in substrate-binding dwells, provides direct evidence that rotation depends on substrate binding affinity. The presence of elevated ADP concentrations not only increased dwells at 35° from the catalytic dwell consistent with competitive product inhibition but also decreased the angular velocity from 85° to 120°, indicating that ADP can remain bound to the catalytic site where product release occurs for the duration of the power stroke. The angular velocity profile also supports a model in which rotation is powered by Van der Waals repulsive forces during the final 85° of rotation, consistent with a transition from F1 structures 2HLD1 and 1H8E (Protein Data Bank). PMID:24567403

Theoretical issues on the spontaneous rotation of axisymmetric plasmas

NASA Astrophysics Data System (ADS)

Coppi, B.; Zhou, T.

2014-09-01

An extensive series of experiments have confirmed that the observed ‘spontaneous rotation’ phenomenon in axisymmetric plasmas is related to the confinement properties of these plasmas and connected to the excitation of collective modes associated with these properties (Coppi 2000 18th IAEA Fusion Energy Conf. (Sorrento, Italy, 2000) THP 1/17, www-pub.iaea.org/MTCD/publications/PDF/csp_008c/html/node343.htm and Coppi 2002 Nucl. Fusion 42 1). In particular, radially localized modes can extract angular momentum from the plasma column from which they grow while the background plasma has to recoil in the direction opposite to that of the mode phase velocity. In the case of the excitation of the plasma modes at the edge, the loss of their angular momentum can be connected to the directed particle ejection to the surrounding medium. The recoil angular momentum is then redistributed inside the plasma column mainly by the combination of an effective viscous diffusion and an inward angular momentum transport velocity that is connected, for instance, to ion temperature gradient (ITG) driven modes. The linear and quasi-linear theories of the collisionless trapped electron modes and of the toroidal ITG driven modes are re-examined in the context of their influence on angular momentum transport. Internal modes that produce magnetic reconnection and are electromagnetic in nature, acquire characteristic phase velocity directions in high temperature regimes and become relevant to the ‘generation’ of angular momentum. The drift-tearing mode, the ‘complex’ reconnecting mode and the m0 = 1 internal mode belong to this category, the last mode acquiring different features depending on the strength of its driving factor. Toroidal velocity profiles that reproduce the experimental observations are obtained considering a global angular momentum balance equation that includes the localized sources associated with the excited internal electrostatic and electromagnetic modes besides the appropriate diffusive and the inward angular momentum transparent terms.

Biomechanical differences of arm swing countermovement jumps on sand and rigid surface performed by elite beach volleyball players.

PubMed

Giatsis, George; Panoutsakopoulos, Vassilios; Kollias, Iraklis A

2018-05-01

The purpose of this study was to investigate the possible arm swing effect on the biomechanical parameters of vertical counter movement jump due to differences of the compliance of the take-off surface. Fifteen elite male beach-volleyball players (26.2 ± 5.9 years; 1.87 ± 0.05 m; 83.4 ± 6.0 kg; mean ± standard deviation, respectively) performed counter movement jumps on sand and on a rigid surface with and without an arm swing. Results showed significant (p < .05) surface effects on the jump height, the ankle joint angle at the lowest height of the body center of mass and the ankle angular velocity. Also, significant arm swing effects were found on jump height, maximum power output, temporal parameters, range of motion and angular velocity of the hip. These findings could be attributed to the instability of the sand, which resulted in reduced peak power output due to the differences of body configuration at the lowest body position and lower limb joints' range of motion. The combined effect of the backward arm swing and the recoil of the sand that resulted in decreased resistance at ankle plantar flexion should be controlled at the preparation of selected jumping tasks in beach-volleyball.

A Neural Circuit for Angular Velocity Computation

PubMed Central

Snider, Samuel B.; Yuste, Rafael; Packer, Adam M.

2010-01-01

In one of the most remarkable feats of motor control in the animal world, some Diptera, such as the housefly, can accurately execute corrective flight maneuvers in tens of milliseconds. These reflexive movements are achieved by the halteres, gyroscopic force sensors, in conjunction with rapidly tunable wing steering muscles. Specifically, the mechanosensory campaniform sensilla located at the base of the halteres transduce and transform rotation-induced gyroscopic forces into information about the angular velocity of the fly's body. But how exactly does the fly's neural architecture generate the angular velocity from the lateral strain forces on the left and right halteres? To explore potential algorithms, we built a neuromechanical model of the rotation detection circuit. We propose a neurobiologically plausible method by which the fly could accurately separate and measure the three-dimensional components of an imposed angular velocity. Our model assumes a single sign-inverting synapse and formally resembles some models of directional selectivity by the retina. Using multidimensional error analysis, we demonstrate the robustness of our model under a variety of input conditions. Our analysis reveals the maximum information available to the fly given its physical architecture and the mathematics governing the rotation-induced forces at the haltere's end knob. PMID:21228902

A neural circuit for angular velocity computation.

PubMed

Snider, Samuel B; Yuste, Rafael; Packer, Adam M

2010-01-01

In one of the most remarkable feats of motor control in the animal world, some Diptera, such as the housefly, can accurately execute corrective flight maneuvers in tens of milliseconds. These reflexive movements are achieved by the halteres, gyroscopic force sensors, in conjunction with rapidly tunable wing steering muscles. Specifically, the mechanosensory campaniform sensilla located at the base of the halteres transduce and transform rotation-induced gyroscopic forces into information about the angular velocity of the fly's body. But how exactly does the fly's neural architecture generate the angular velocity from the lateral strain forces on the left and right halteres? To explore potential algorithms, we built a neuromechanical model of the rotation detection circuit. We propose a neurobiologically plausible method by which the fly could accurately separate and measure the three-dimensional components of an imposed angular velocity. Our model assumes a single sign-inverting synapse and formally resembles some models of directional selectivity by the retina. Using multidimensional error analysis, we demonstrate the robustness of our model under a variety of input conditions. Our analysis reveals the maximum information available to the fly given its physical architecture and the mathematics governing the rotation-induced forces at the haltere's end knob.

Bounded extremum seeking for angular velocity actuated control of nonholonomic unicycle

DOE PAGES

Scheinker, Alexander

2016-08-17

Here, we study control of the angular-velocity actuated nonholonomic unicycle, via a simple, bounded extremum seeking controller which is robust to external disturbances and measurement noise. The vehicle performs source seeking despite not having any position information about itself or the source, able only to sense a noise corrupted scalar value whose extremum coincides with the unknown source location. In order to control the angular velocity, rather than the angular heading directly, a controller is developed such that the closed loop system exhibits multiple time scales and requires an analysis approach expanding the previous work of Kurzweil, Jarnik, Sussmann, andmore » Liu, utilizing weak limits. We provide analytic proof of stability and demonstrate how this simple scheme can be extended to include position-independent source seeking, tracking, and collision avoidance of groups on autonomous vehicles in GPS-denied environments, based only on a measure of distance to an obstacle, which is an especially important feature for an autonomous agent.« less

A hybrid method for accurate star tracking using star sensor and gyros.

PubMed

Lu, Jiazhen; Yang, Lie; Zhang, Hao

2017-10-01

Star tracking is the primary operating mode of star sensors. To improve tracking accuracy and efficiency, a hybrid method using a star sensor and gyroscopes is proposed in this study. In this method, the dynamic conditions of an aircraft are determined first by the estimated angular acceleration. Under low dynamic conditions, the star sensor is used to measure the star vector and the vector difference method is adopted to estimate the current angular velocity. Under high dynamic conditions, the angular velocity is obtained by the calibrated gyros. The star position is predicted based on the estimated angular velocity and calibrated gyros using the star vector measurements. The results of the semi-physical experiment show that this hybrid method is accurate and feasible. In contrast with the star vector difference and gyro-assisted methods, the star position prediction result of the hybrid method is verified to be more accurate in two different cases under the given random noise of the star centroid.

ECG denoising using angular velocity as a state and an observation in an Extended Kalman Filter framework.

PubMed

Akhbari, Mahsa; Shamsollahi, Mohammad B; Jutten, Christian; Coppa, Bertrand

2012-01-01

In this paper an efficient filtering procedure based on Extended Kalman Filter (EKF) has been proposed. The method is based on a modified nonlinear dynamic model, previously introduced for the generation of synthetic ECG signals. The proposed method considers the angular velocity of ECG signal, as one of the states of an EKF. We have considered two cases for observation equations, in one case we have assumed a corresponding observation to angular velocity state and in the other case, we have not assumed any observations for it. Quantitative evaluation of the proposed algorithm on the MIT-BIH Normal Sinus Rhythm Database (NSRDB) shows that an average SNR improvement of 8 dB is achieved for an input signal of -4 dB.

Dynamical phenomena in fast sliding nanotube models

NASA Astrophysics Data System (ADS)

Zhang, X. H.; Santoro, G. E.; Tartaglino, U.; Tosatti, E.

2013-03-01

The experimentally known fact that coaxial carbon nanotubes can be forced to slide one inside the other stimulated in the past much detailed modelling of the dynamical sliding process. Molecular dynamics simulations of sliding coaxial nanotubes showed the existence of strong frictional peaks when, at large speed, one tube excites the other with a 'washboard' frequency that happens to resonate with some intrinsic vibration frequency. At some of these special speeds we discover a striking example of dynamical symmetry breaking taking place at the nanoscale. Even when both nanotubes are perfectly left-right symmetric and nonchiral, precisely in correspondence with the large peaks of sliding friction occurring at a series of critical sliding velocities, a nonzero angular momentum spontaneously appears. A detailed analysis shows that this internal angular momentum is of phonon origin, in particular arising from preferential excitation of a right polarized (or, with equal probability, of a left polarized) outer-tube 'pseudorotation' mode, thus spontaneously breaking their exact twofold right-left degeneracy. We present and discuss a detailed analysis of nonlinear continuum equations governing this phenomenon, showing the close similarity of this phenomenon with the well-known rotational instability of a forced string, which takes place under sufficiently strong periodic forcing of the string. We also point out new elements appearing in the present problem which are 'nano', in particular the involvement of Umklapp processes and the role of sliding nanofriction.

Convergence of excitatory and inhibitory hair cell transmitters shapes vestibular afferent responses.

PubMed

Holstein, Gay R; Rabbitt, Richard D; Martinelli, Giorgio P; Friedrich, Victor L; Boyle, Richard D; Highstein, Stephen M

2004-11-02

The vestibular semicircular canals respond to angular acceleration that is integrated to angular velocity by the biofluid mechanics of the canals and is the primary origin of afferent responses encoding velocity. Surprisingly, some afferents actually report angular acceleration. Our data indicate that hair-cell/afferent synapses introduce a mathematical derivative in these afferents that partially cancels the biomechanical integration and results in discharge rates encoding angular acceleration. We examined the role of convergent synaptic inputs from hair cells to this mathematical differentiation. A significant reduction in the order of the differentiation was observed for low-frequency stimuli after gamma-aminobutyric acid type B receptor antagonist administration. Results demonstrate that gamma-aminobutyric acid participates in shaping the temporal dynamics of afferent responses.

A Highly Miniaturized, Wireless Inertial Measurement Unit for Characterizing the Dynamics of Pitched Baseballs and Softballs

PubMed Central

McGinnis, Ryan S.; Perkins, Noel C.

2012-01-01

Baseball and softball pitch types are distinguished by the path and speed of the ball which, in turn, are determined by the angular velocity of the ball and the velocity of the ball center at the instant of release from the pitcher's hand. While radar guns and video-based motion capture (mocap) resolve ball speed, they provide little information about how the angular velocity of the ball and the velocity of the ball center develop and change during the throwing motion. Moreover, mocap requires measurements in a controlled lab environment and by a skilled technician. This study addresses these shortcomings by introducing a highly miniaturized, wireless inertial measurement unit (IMU) that is embedded in both baseballs and softballs. The resulting “ball-embedded” sensor resolves ball dynamics right on the field of play. Experimental results from ten pitches, five thrown by one softball pitcher and five by one baseball pitcher, demonstrate that this sensor technology can deduce the magnitude and direction of the ball's velocity at release to within 4.6% of measurements made using standard mocap. Moreover, the IMU directly measures the angular velocity of the ball, which further enables the analysis of different pitch types.

A new method for testing the scale-factor performance of fiber optical gyroscope

NASA Astrophysics Data System (ADS)

Zhao, Zhengxin; Yu, Haicheng; Li, Jing; Li, Chao; Shi, Haiyang; Zhang, Bingxin

2015-10-01

Fiber optical gyro (FOG) is a kind of solid-state optical gyroscope with good environmental adaptability, which has been widely used in national defense, aviation, aerospace and other civilian areas. In some applications, FOG will experience environmental conditions such as vacuum, radiation, vibration and so on, and the scale-factor performance is concerned as an important accuracy indicator. However, the scale-factor performance of FOG under these environmental conditions is difficult to test using conventional methods, as the turntable can't work under these environmental conditions. According to the phenomenon that the physical effects of FOG produced by the sawtooth voltage signal under static conditions is consistent with the physical effects of FOG produced by a turntable in uniform rotation, a new method for the scale-factor performance test of FOG without turntable is proposed in this paper. In this method, the test system of the scale-factor performance is constituted by an external operational amplifier circuit and a FOG which the modulation signal and Y waveguied are disconnected. The external operational amplifier circuit is used to superimpose the externally generated sawtooth voltage signal and the modulation signal of FOG, and to exert the superimposed signal on the Y waveguide of the FOG. The test system can produce different equivalent angular velocities by changing the cycle of the sawtooth signal in the scale-factor performance test. In this paper, the system model of FOG superimposed with an externally generated sawtooth is analyzed, and a conclusion that the effect of the equivalent input angular velocity produced by the sawtooth voltage signal is consistent with the effect of input angular velocity produced by the turntable is obtained. The relationship between the equivalent angular velocity and the parameters such as sawtooth cycle and so on is presented, and the correction method for the equivalent angular velocity is also presented by analyzing the influence of each parameter error on the equivalent angular velocity. A comparative experiment of the method proposed in this paper and the method of turntable calibration was conducted, and the scale-factor performance test results of the same FOG using the two methods were consistent. Using the method proposed in this paper to test the scale-factor performance of FOG, the input angular velocity is the equivalent effect produced by a sawtooth voltage signal, and there is no need to use a turntable to produce mechanical rotation, so this method can be used to test the performance of FOG at the ambient conditions which turntable can not work.

Analyzing angular distributions for two-step dissociation mechanisms in velocity map imaging.

PubMed

Straus, Daniel B; Butler, Lynne M; Alligood, Bridget W; Butler, Laurie J

2013-08-15

Increasingly, velocity map imaging is becoming the method of choice to study photoinduced molecular dissociation processes. This paper introduces an algorithm to analyze the measured net speed, P(vnet), and angular, β(vnet), distributions of the products from a two-step dissociation mechanism, where the first step but not the second is induced by absorption of linearly polarized laser light. Typically, this might be the photodissociation of a C-X bond (X = halogen or other atom) to produce an atom and a momentum-matched radical that has enough internal energy to subsequently dissociate (without the absorption of an additional photon). It is this second step, the dissociation of the unstable radicals, that one wishes to study, but the measured net velocity of the final products is the vector sum of the velocity imparted to the radical in the primary photodissociation (which is determined by taking data on the momentum-matched atomic cophotofragment) and the additional velocity vector imparted in the subsequent dissociation of the unstable radical. The algorithm allows one to determine, from the forward-convolution fitting of the net velocity distribution, the distribution of velocity vectors imparted in the second step of the mechanism. One can thus deduce the secondary velocity distribution, characterized by a speed distribution P(v1,2°) and an angular distribution I(θ2°), where θ2° is the angle between the dissociating radical's velocity vector and the additional velocity vector imparted to the product detected from the subsequent dissociation of the radical.

Air To Air Helicopter Fire Control Equations and Software Generation.

DTIC Science & Technology

1979-11-01

A A A A v D1. Bin), velocity (VTs, VTI. VTm). and acceleration (ATs, ATI. ATm) using the measured values of range. Rm. angular rate of the LOS W s...10 second time constant. Note that the input to each integrator also has cross channel coupling terms which are cross products of the LOS angular rate...ownship’s velocity (Vs. V1. Vm). This is subtracted from the estimated target velocity ( VsT . 01T. VmT) before the inal integration so that the

Linear and angular control of circular walking in healthy older adults and subjects with cerebellar ataxia.

PubMed

Goodworth, Adam D; Paquette, Caroline; Jones, Geoffrey Melvill; Block, Edward W; Fletcher, William A; Hu, Bin; Horak, Fay B

2012-05-01

Linear and angular control of trunk and leg motion during curvilinear navigation was investigated in subjects with cerebellar ataxia and age-matched control subjects. Subjects walked with eyes open around a 1.2-m circle. The relationship of linear to angular motion was quantified by determining the ratios of trunk linear velocity to trunk angular velocity and foot linear position to foot angular position. Errors in walking radius (the ratio of linear to angular motion) also were quantified continuously during the circular walk. Relative variability of linear and angular measures was compared using coefficients of variation (CoV). Patterns of variability were compared using power spectral analysis for the trunk and auto-covariance analysis for the feet. Errors in radius were significantly increased in patients with cerebellar damage as compared to controls. Cerebellar subjects had significantly larger CoV of feet and trunk in angular, but not linear, motion. Control subjects also showed larger CoV in angular compared to linear motion of the feet and trunk. Angular and linear components of stepping differed in that angular, but not linear, foot placement had a negative correlation from one stride to the next. Thus, walking in a circle was associated with more, and a different type of, variability in angular compared to linear motion. Results are consistent with increased difficulty of, and role of the cerebellum in, control of angular trunk and foot motion for curvilinear locomotion.

Reactive Collisions in Crossed Molecular Beams

DOE R&D Accomplishments Database

Herschbach, D. R.

1962-02-01

The distribution of velocity vectors of reaction products is discussed with emphasis on the restrictions imposed by the conservation laws. The recoil velocity that carries the products away from the center of mass shows how the energy of reaction is divided between internal excitation and translation. Similarly, the angular distributions, as viewed from the center of mass, reflect the partitioning of the total angular momentum between angular momenta of individual molecules and orbital angular momentum associated with their relative motion. Crossed-beam studies of several reactions of the type M + RI yields R + MI are described, where M = K, Rb, Cs, and R = CH{sub 3}, C{sub 3}H{sub 5}, etc. The results show that most of the energy of reaction goes into internal excitation of the products and that the angular distribution is quite anisotropic, with most of the MI recoiling backward (and R forward) with respect to the incoming K beam. (auth)

Rigidly rotating zero-angular-momentum observer surfaces in the Kerr spacetime

NASA Astrophysics Data System (ADS)

Frolov, Andrei V.; Frolov, Valeri P.

2014-12-01

A stationary observer in the Kerr spacetime has zero angular momentum if their angular velocity ω has a particular value, which depends on the position of the observer. Worldlines of such zero-angular-momentum observers (ZAMOs) with the same value of the angular velocity ω form a three-dimensional surface, which has the property that the Killing vectors generating time translation and rotation are tangent to it. We call such a surface a rigidly rotating ZAMO surface. This definition allows for a natural generalization to the surfaces inside the black hole, where ZAMO trajectories formally become spacelike. A general property of such a surface is that there exist linear combinations of the Killing vectors with constant coefficients which make them orthogonal on it. In this paper we discuss properties of the rigidly rotating ZAMO surfaces both outside and inside the black hole and the relevance of these objects to a couple of interesting physical problems.

Universal Plug-n-Play Sensor Integration for Advanced Navigation

DTIC Science & Technology

2012-03-22

Orientation (top) and Angular Velocity (bottom) . . . . . . . . . 79 IV.6 Execution of AHRS script with roscore running on separate machine . . . . . . 80...single host case only with two hosts in this scenario. The script is running 78 Figure IV.5: Plot of AHRS Orientation (top) and Angular Velocity (bottom...Component-Based System using ROS . . . . . . . . . 59 3.6 Autonomous Behavior Using Scripting . . . . . . . . . . . . . . . . . . . . 60 3.6.1 udev

Two Dimensional Steady State Eddy Current Analysis of a Spinning Conducting Cylinder

DTIC Science & Technology

2017-03-09

generate electromagnetic effects which can disrupt the electronic components contained inside the round. Finite element analyses were conducted to...which affect the magnetic field inside the cylinder were analyzed by varying the angular velocities and the electromagnetic properties (permeability and...the magnetic field distribution inside the cylinder was affected by angular velocity and the electromagnetic properties of the cylinder. 15

Characterizing the Peak in the Cosmic Microwave Background Angular Power Spectrum

NASA Astrophysics Data System (ADS)

Knox, Lloyd; Page, Lyman

2000-08-01

A peak has been unambiguously detected in the cosmic microwave background angular spectrum. Here we characterize its properties with fits to phenomenological models. We find that the TOCO and BOOM/NA data determine the peak location to be in the range 175-243 and 151-259, respectively (at 95% confidence) and determine the peak amplitude to be between ~70 and 90 μK. The peak shape is consistent with inflation-inspired flat, cold dark matter plus cosmological constant models of structure formation with adiabatic, nearly scale invariant initial conditions. It is inconsistent with open models and presents a great challenge to defect models.

Characterizing the peak in the cosmic microwave background angular power spectrum

PubMed

Knox; Page

2000-08-14

A peak has been unambiguously detected in the cosmic microwave background angular spectrum. Here we characterize its properties with fits to phenomenological models. We find that the TOCO and BOOM/NA data determine the peak location to be in the range 175-243 and 151-259, respectively (at 95% confidence) and determine the peak amplitude to be between approximately 70 and 90 &mgr;K. The peak shape is consistent with inflation-inspired flat, cold dark matter plus cosmological constant models of structure formation with adiabatic, nearly scale invariant initial conditions. It is inconsistent with open models and presents a great challenge to defect models.

Hamstrings strength imbalance in professional football (soccer) players in Australia.

PubMed

Ardern, Clare L; Pizzari, Tania; Wollin, Martin R; Webster, Kate E

2015-04-01

The aim of this study was to describe the isokinetic thigh muscle strength profile of professional male football players in Australia. Concentric (60° and 240°·s(-1)) and eccentric (30° and 120°·s(-1)) hamstrings and quadriceps isokinetic strength was measured with a HUMAC NORM dynamometer. The primary variables were bilateral concentric and eccentric hamstring and quadriceps peak torque ratios, concentric hamstring-quadriceps peak torque ratios, and mixed ratios (eccentric hamstring 30°·s(-1) ÷ concentric quadriceps 240°·s(-1)). Hamstring strength imbalance was defined as deficits in any 2 of: bilateral concentric hamstring peak torque ratio <0.86, bilateral eccentric hamstring peak torque ratio <0.86, concentric hamstring-quadriceps ratio <0.47, and mixed ratio <0.80. Fifty-five strength tests involving 42 players were conducted. Ten players (24%) were identified as having hamstring strength imbalance. Athletes with strength imbalance had significantly reduced concentric and eccentric bilateral hamstring peak torque ratios at all angular velocities tested; and reduced eccentric quadriceps peak torque (30°·s(-1)) in their stance leg, compared with those without strength imbalance. Approximately, 1 in 4 players had preseason hamstring strength imbalance; and all strength deficits were observed in the stance leg. Concentric and eccentric hamstrings strength imbalance may impact in-season football performance and could have implications for the future risk of injury.

Chaotic gas turbine subject to augmented Lorenz equations.

PubMed

Cho, Kenichiro; Miyano, Takaya; Toriyama, Toshiyuki

2012-09-01

Inspired by the chaotic waterwheel invented by Malkus and Howard about 40 years ago, we have developed a gas turbine that randomly switches the sense of rotation between clockwise and counterclockwise. The nondimensionalized expressions for the equations of motion of our turbine are represented as a starlike network of many Lorenz subsystems sharing the angular velocity of the turbine rotor as the central node, referred to as augmented Lorenz equations. We show qualitative similarities between the statistical properties of the angular velocity of the turbine rotor and the velocity field of large-scale wind in turbulent Rayleigh-Bénard convection reported by Sreenivasan et al. [Phys. Rev. E 65, 056306 (2002)]. Our equations of motion achieve the random reversal of the turbine rotor through the stochastic resonance of the angular velocity in a double-well potential and the force applied by rapidly oscillating fields. These results suggest that the augmented Lorenz model is applicable as a dynamical model for the random reversal of turbulent large-scale wind through cessation.

Uncertainties for two-dimensional models of solar rotation from helioseismic eigenfrequency splitting

NASA Technical Reports Server (NTRS)

Genovese, Christopher R.; Stark, Philip B.; Thompson, Michael J.

1995-01-01

Observed solar p-mode frequency splittings can be used to estimate angular velocity as a function of position in the solar interior. Formal uncertainties of such estimates depend on the method of estimation (e.g., least-squares), the distribution of errors in the observations, and the parameterization imposed on the angular velocity. We obtain lower bounds on the uncertainties that do not depend on the method of estimation; the bounds depend on an assumed parameterization, but the fact that they are lower bounds for the 'true' uncertainty does not. Ninety-five percent confidence intervals for estimates of the angular velocity from 1986 Big Bear Solar Observatory (BBSO) data, based on a 3659 element tensor-product cubic-spline parameterization, are everywhere wider than 120 nHz, and exceed 60,000 nHz near the core. When compared with estimates of the solar rotation, these bounds reveal that useful inferences based on pointwise estimates of the angular velocity using 1986 BBSO splitting data are not feasible over most of the Sun's volume. The discouraging size of the uncertainties is due principally to the fact that helioseismic measurements are insensitive to changes in the angular velocity at individual points, so estimates of point values based on splittings are extremely uncertain. Functionals that measure distributed 'smooth' properties are, in general, better constrained than estimates of the rotation at a point. For example, the uncertainties in estimated differences of average rotation between adjacent blocks of about 0.001 solar volumes across the base of the convective zone are much smaller, and one of several estimated differences we compute appears significant at the 95% level.

The key kinematic determinants of undulatory underwater swimming at maximal velocity.

PubMed

Connaboy, Chris; Naemi, Roozbeh; Brown, Susan; Psycharakis, Stelios; McCabe, Carla; Coleman, Simon; Sanders, Ross

2016-01-01

The optimisation of undulatory underwater swimming is highly important in competitive swimming performance. Nineteen kinematic variables were identified from previous research undertaken to assess undulatory underwater swimming performance. The purpose of the present study was to determine which kinematic variables were key to the production of maximal undulatory underwater swimming velocity. Kinematic data at maximal undulatory underwater swimming velocity were collected from 17 skilled swimmers. A series of separate backward-elimination analysis of covariance models was produced with cycle frequency and cycle length as dependent variables (DVs) and participant as a fixed factor, as including cycle frequency and cycle length would explain 100% of the maximal swimming velocity variance. The covariates identified in the cycle-frequency and cycle-length models were used to form the saturated model for maximal swimming velocity. The final parsimonious model identified three covariates (maximal knee joint angular velocity, maximal ankle angular velocity and knee range of movement) as determinants of the variance in maximal swimming velocity (adjusted-r2 = 0.929). However, when participant was removed as a fixed factor there was a large reduction in explained variance (adjusted r2 = 0.397) and only maximal knee joint angular velocity continued to contribute significantly, highlighting its importance to the production of maximal swimming velocity. The reduction in explained variance suggests an emphasis on inter-individual differences in undulatory underwater swimming technique and/or anthropometry. Future research should examine the efficacy of other anthropometric, kinematic and coordination variables to better understand the production of maximal swimming velocity and consider the importance of individual undulatory underwater swimming techniques when interpreting the data.

Sagittal plane joint kinetics during stair ascent in patients with peripheral arterial disease and intermittent claudication.

PubMed

King, Stephanie L; Vanicek, Natalie; O'Brien, Thomas D

2017-06-01

Stair negotiation poses a substantial physical demand on the musculoskeletal system and this challenging task can place individuals at risk of falls. Peripheral arterial disease (PAD) can cause intermittent claudication (IC) pain in the calf and results in altered gait mechanics during level walking. However, whether those with PAD-IC adopt alternate strategies to climb stairs is unknown. Twelve participants with PAD-IC (six bilateral and six unilateral) and 10 healthy controls were recruited and instructed to ascend a five-step staircase whilst 3D kinematic data of the lower-limbs were recorded synchronously with kinetic data from force plates embedded into the staircase on steps two and three. Limbs from the unilateral group and both limbs from the bilateral claudicants were categorised as claudicating (N=18), asymptomatic (N=6) and control (N=10). Claudicants walked more slowly than healthy controls (trend; P=<0.066). Both claudicating- and asymptomatic-limb groups had reduced propulsive GRF (P=0.025 and P=0.002, respectively) and vertical GRF (P=0.005 and P=0.001, respectively) compared to controls. The claudicating-limb group had a reduced knee extensor moment during forward continuance (P=0.060), ankle angular velocity at peak moment (P=0.039) and ankle power generation (P=0.055) compared to the controls. The slower gait speed, irrespective of laterality of symptoms, indicates functional capacity was determined by the limitations of the claudicating limb. Reduced ankle power generation and angular velocity (despite adequate plantarflexor moment) implies velocity-dependent limitations existed in the calf. The lack of notable compensatory strategies indicates reliance on an impaired muscle group to accomplish this potentially hazardous task, highlighting the importance of maintaining plantarflexor strength and power in those with PAD-IC. Copyright © 2017 Elsevier B.V. All rights reserved.

Measuring the anisotropy in the CMB

NASA Astrophysics Data System (ADS)

Page, L. A.

The CMB is perhaps the cleanest cosmological observable. Its angular spectrum may be both computed and measured to percent accuracy. The current data clearly show a rise in the angular spectrum to a peak of roughly Tl = (l(l + 1)Cl/2)1/2 80 K at l 200, and a fall at higher l. In particular, δTl at l = 400 is significantly less than at l = 200. This is shown through a combined analysis of data sets and by the TOCO data alone. For spatially flat models, a peak in the angular spectrum near l = 200 is indicated, whereas for Ω0 = 0.35 models one expects a peak near l = 400. The data clearly prefer the spatially flat models.

The Effects of Protostellar Disk Turbulence on CO Emission Lines: A Comparison Study of Disks with Constant CO Abundance versus Chemically Evolving Disks

NASA Astrophysics Data System (ADS)

Yu, Mo; Evans, Neal J., II; Dodson-Robinson, Sarah E.; Willacy, Karen; Turner, Neal J.

2017-12-01

Turbulence is the leading candidate for angular momentum transport in protoplanetary disks and therefore influences disk lifetimes and planet formation timescales. However, the turbulent properties of protoplanetary disks are poorly constrained observationally. Recent studies have found turbulent speeds smaller than what fully-developed MRI would produce (Flaherty et al.). However, existing studies assumed a constant CO/H2 ratio of 10-4 in locations where CO is not frozen-out or photo-dissociated. Our previous studies of evolving disk chemistry indicate that CO is depleted by incorporation into complex organic molecules well inside the freeze-out radius of CO. We consider the effects of this chemical depletion on measurements of turbulence. Simon et al. suggested that the ratio of the peak line flux to the flux at line center of the CO J = 3-2 transition is a reasonable diagnostic of turbulence, so we focus on that metric, while adding some analysis of the more complex effects on spatial distribution. We simulate the emission lines of CO based on chemical evolution models presented in Yu et al., and find that the peak-to-trough ratio changes as a function of time as CO is destroyed. Specifically, a CO-depleted disk with high turbulent velocity mimics the peak-to-trough ratios of a non-CO-depleted disk with lower turbulent velocity. We suggest that disk observers and modelers take into account the possibility of CO depletion when using line profiles or peak-to-trough ratios to constrain the degree of turbulence in disks. Assuming that {CO}/{{{H}}}2={10}-4 at all disk radii can lead to underestimates of turbulent speeds in the disk by at least 0.2 km s-1.

Prototype Design and Mission Analysis for a Small Satellite Exploiting Environmental Disturbances for Attitude Stabilization

DTIC Science & Technology

2016-03-01

acceleration of the shifting masses experiences a Coriolis Effect due to the angular velocity of the spacecraft. However, the perpendicular component of...angular velocity. If we neglect the Coriolis Effect in absolute acceleration, both terms become zero. Then, Equation 4.22 becomes ( )0 0 0 0 0...METHOD ......................................................83  C.  EXPLORATION OF THE ALTITUDE AND INCLINATION EFFECTS ON THE CONTROL

Knee Muscle Strength at Varying Angular Velocities and Associations with Gross Motor Function in Ambulatory Children with Cerebral Palsy

ERIC Educational Resources Information Center

Hong, Wei-Hsien; Chen, Hseih-Ching; Shen, I-Hsuan; Chen, Chung-Yao; Chen, Chia-Ling; Chung, Chia-Ying

2012-01-01

The aim of this study was to evaluate the relationships of muscle strength at different angular velocities and gross motor functions in ambulatory children with cerebral palsy (CP). This study included 33 ambulatory children with spastic CP aged 6-15 years and 15 children with normal development. Children with CP were categorized into level I (n =…

The cosmic web and the orientation of angular momenta

NASA Astrophysics Data System (ADS)

Libeskind, Noam I.; Hoffman, Yehuda; Knebe, Alexander; Steinmetz, Matthias; Gottlöber, Stefan; Metuki, Ofer; Yepes, Gustavo

2012-03-01

We use a 64 h-1 Mpc dark-matter-only cosmological simulation to examine the large-scale orientation of haloes and substructures with respect to the cosmic web. A web classification scheme based on the velocity shear tensor is used to assign to each halo in the simulation a web type: knot, filament, sheet or void. Using ˜106 haloes that span ˜3 orders of magnitude in mass, the orientation of the halo's spin and the orbital angular momentum of subhaloes with respect to the eigenvectors of the shear tensor is examined. We find that the orbital angular momentum of subhaloes tends to align with the intermediate eigenvector of the velocity shear tensor for all haloes in knots, filaments and sheets. This result indicates that the kinematics of substructures located deep within the virialized regions of a halo is determined by its infall which in turn is determined by the large-scale velocity shear, a surprising result given the virialized nature of haloes. The non-random nature of subhalo accretion is thus imprinted on the angular momentum measured at z= 0. We also find that the haloes' spin axis is aligned with the third eigenvector of the velocity shear tensor in filaments and sheets: the halo spin axis points along filaments and lies in the plane of cosmic sheets.

Rotational velocities of A-type stars. IV. Evolution of rotational velocities

NASA Astrophysics Data System (ADS)

Zorec, J.; Royer, F.

2012-01-01

Context. In previous works of this series, we have shown that late B- and early A-type stars have genuine bimodal distributions of rotational velocities and that late A-type stars lack slow rotators. The distributions of the surface angular velocity ratio Ω/Ωcrit (Ωcrit is the critical angular velocity) have peculiar shapes according to spectral type groups, which can be caused by evolutionary properties. Aims: We aim to review the properties of these rotational velocity distributions in some detail as a function of stellar mass and age. Methods: We have gathered vsini for a sample of 2014 B6- to F2-type stars. We have determined the masses and ages for these objects with stellar evolution models. The (Teff,log L/L⊙)-parameters were determined from the uvby-β photometry and the HIPPARCOS parallaxes. Results: The velocity distributions show two regimes that depend on the stellar mass. Stars less massive than 2.5 M⊙ have a unimodal equatorial velocity distribution and show a monotonical acceleration with age on the main sequence (MS). Stars more massive have a bimodal equatorial velocity distribution. Contrarily to theoretical predictions, the equatorial velocities of stars from about 1.7 M⊙ to 3.2 M⊙ undergo a strong acceleration in the first third of the MS evolutionary phase, while in the last third of the MS they evolve roughly as if there were no angular momentum redistribution in the external stellar layers. The studied stars might start in the ZAMS not necessarily as rigid rotators, but with a total angular momentum lower than the critical one of rigid rotators. The stars seem to evolve as differential rotators all the way of their MS life span and the variation of the observed rotational velocities proceeds with characteristic time scales δt ≈ 0.2 tMS, where tMS is the time spent by a star in the MS. Full Table 1 is only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/537/A120Appendices are available in electronic form at http://www.aanda.org

Isokinetic muscle performance of the hip and ankle muscles in women with fibromyalgia.

PubMed

Yetişgin, Alparslan; Tiftik, Tülay; Kara, Murat; Karabay, İlkay; Akkuş, Selami; Ersöz, Murat

2016-06-01

To compare isokinetic muscle performances of a proximal (hip) and a distal (ankle) muscle of fibromyalgia syndrome (FMS) patients with those of age- and body mass index (BMI)-matched healthy subjects. Thirty female patients with FMS (mean age: 41.5 ± 6.7 years [range, 27-54]) and 30 age- (mean age: 40.6 ± 6.0 years [range, 27-54]) and BMI-matched female healthy controls were consecutively enrolled. Demographic and clinical characteristics of the subjects were recorded. Isokinetic measurements of hip and ankle flexion and extension at angular velocities of 60°/s and 180°/s, peak torques, flexor-extensor torque ratios, muscle fatigue resistance values and average power were obtained. Mean disease duration of FMS patients was 2.4 ± 1.9 years. Mean weight, height and BMI values were 70.4 ± 12.5 kg, 159.5 ± 6.0 cm and 27.7 ± 4.7 kg/m² (FMS patients) and 69.3 ± 10.1 kg, 161.7 ± 6.2 cm and 26.6 ± 4.3 kg/m² (control subjects), respectively (all P > 0.05). All isokinetic values were statistically decreased in the FMS group when compared with the control group, except for the peak torques at angular velocity of 180°/s on flexion of the hip and extension of the ankle and the total work and average power on extension of the ankle. We did not find any correlation between isokinetic values and disease related parameters of FMS patients. In the light of our results, we may conclude that muscle strength and muscle fatigue seem to decrease in FMS patients' both proximal and distal lower extremity muscles. © 2013 Asia Pacific League of Associations for Rheumatology and Wiley Publishing Asia Pty Ltd.

A wind tunnel study on the effects of complex topography on wind turbine performance

NASA Astrophysics Data System (ADS)

Howard, Kevin; Hu, Stephen; Chamorro, Leonardo; Guala, Michele

2012-11-01

A set of wind tunnel experiments were conducted to study the response of a wind turbine under flow conditions typically observed at the wind farm scale, in complex terrain. A scale model wind turbine was placed in a fully developed turbulent boundary layer flow obtained in the SAFL Wind Tunnel. Experiments focused on the performance of a turbine model, under the effects induced by a second upwind turbine or a by three-dimensional, sinusoidal hill, peaking at the turbine hub height. High frequency measurements of fluctuating streamwise and wall normal velocities were obtained with a X-wire anemometer simultaneously with the rotor angular velocity and the turbine(s) voltage output. Velocity measurements in the wake of the first turbine and of the hill were used to determine the inflow conditions for the downwind test turbine. Turbine performance was inferred by the mean and fluctuating voltage statistics. Specific experiments were devoted to relate the mean voltage to the mean hub velocity, and the fluctuating voltage to the unsteadiness in the rotor kinematics induced by the perturbed (hill or turbine) or unperturbed (boundary layer) large scales of the incoming turbulent flow. Results show that the voltage signal can be used to assess turbine performance in complex flows.

Influence of gravity on cat vertical vestibulo-ocular reflex

NASA Technical Reports Server (NTRS)

Tomko, D. L.; Wall, C., III; Robinson, F. R.; Staab, J. P.

1988-01-01

The vertical vestibulo-ocular reflex (VOR) was recorded in cats using electro-oculography during sinusoidal angular pitch. Peak stimulus velocity was 50 deg/s over a frequency range from 0.01 to 4.0 Hz. To test the effect of gravity on the vertical VOR, the animal was pitched while sitting upright or lying on its side. Upright pitch changed the cat's orientation relative to gravity, while on-side pitch did not. The cumulative slow component position of the eye during on-side pitch was less symmetric than during upright pitch. Over the mid-frequency range (0.1 to 1.0 Hz), the average gain of the vertical VOR was 14.5 percent higher during upright pitch than during on-side pitch. At low frequencies (less than 0.05 Hz) changing head position relative to gravity raised the vertical VOR gain and kept the reflex in phase with stimulus velocity. These results indicate that gravity-sensitive mechanisms make the vertical VOR more compensatory.

Inverse problems for torsional modes.

USGS Publications Warehouse

Willis, C.

1984-01-01

Considers a spherically symmetric, non-rotating Earth consisting of an isotropic, perfect elastic material where the density and the S-wave velocity may have one or two discontinuities in the upper mantle. Shows that given the velocity throughout the mantle and the crust and given the density in the lower mantle, then the freqencies of the torsional oscillations of one angular order (one torsional spectrum), determine the density in the upper mantle and in the crust uniquely. If the velocity is known only in the lower mantle, then the frequencies of the torsional oscillations of two angular orders uniquely determine both the density and the velocity in the upper mantle and in the crust. In particular, the position and size of the discontinuities in the density and velocity are uniquely determined by two torsional spectra.-Author

A New MEMS Gyroscope Used for Single-Channel Damping

PubMed Central

Zhang, Zengping; Zhang, Wei; Zhang, Fuxue; Wang, Biao

2015-01-01

The silicon micromechanical gyroscope, which will be introduced in this paper, represents a novel MEMS gyroscope concept. It is used for the damping of a single-channel control system of rotating aircraft. It differs from common MEMS gyroscopes in that does not have a drive structure, itself, and only has a sense structure. It is installed on a rotating aircraft, and utilizes the aircraft spin to make its sensing element obtain angular momentum. When the aircraft is subjected to an angular rotation, a periodic Coriolis force is induced in the direction orthogonal to both the angular momentum and the angular velocity input axis. This novel MEMS gyroscope can thus sense angular velocity inputs. The output sensing signal is exactly an amplitude-modulation signal. Its envelope is proportional to the input angular velocity, and the carrier frequency corresponds to the spin frequency of the rotating aircraft, so the MEMS gyroscope can not only sense the transverse angular rotation of an aircraft, but also automatically change the carrier frequency over the change of spin frequency, making it very suitable for the damping of a single-channel control system of a rotating aircraft. In this paper, the motion equation of the MEMS gyroscope has been derived. Then, an analysis has been carried to solve the motion equation and dynamic parameters. Finally, an experimental validation has been done based on a precision three axis rate table. The correlation coefficients between the tested data and the theoretical values are 0.9969, 0.9872 and 0.9842, respectively. These results demonstrate that both the design and sensing mechanism are correct. PMID:25942638

Estimations of relative effort during sit-to-stand increase when accounting for variations in maximum voluntary torque with joint angle and angular velocity.

PubMed

Bieryla, Kathleen A; Anderson, Dennis E; Madigan, Michael L

2009-02-01

The main purpose of this study was to compare three methods of determining relative effort during sit-to-stand (STS). Fourteen young (mean 19.6+/-SD 1.2 years old) and 17 older (61.7+/-5.5 years old) adults completed six STS trials at three speeds: slow, normal, and fast. Sagittal plane joint torques at the hip, knee, and ankle were calculated through inverse dynamics. Isometric and isokinetic maximum voluntary contractions (MVC) for the hip, knee, and ankle were collected and used for model parameters to predict the participant-specific maximum voluntary joint torque. Three different measures of relative effort were determined by normalizing STS joint torques to three different estimates of maximum voluntary torque. Relative effort at the hip, knee, and ankle were higher when accounting for variations in maximum voluntary torque with joint angle and angular velocity (hip=26.3+/-13.5%, knee=78.4+/-32.2%, ankle=27.9+/-14.1%) compared to methods which do not account for these variations (hip=23.5+/-11.7%, knee=51.7+/-15.0%, ankle=20.7+/-10.4%). At higher velocities, the difference in calculating relative effort with respect to isometric MVC or incorporating joint angle and angular velocity became more evident. Estimates of relative effort that account for the variations in maximum voluntary torque with joint angle and angular velocity may provide higher levels of accuracy compared to methods based on measurements of maximal isometric torques.

Interaction between thorax, lumbar, and pelvis movements in the transverse plane during gait at three velocities.

PubMed

Yang, Ya-Ting; Yoshida, Yasuyuki; Hortobágyi, Tibor; Suzuki, Shuji

2013-06-01

We determined the angular range of motion and the relative timing of displacement in the thorax, lumbar spine, and pelvis in the transverse plane during treadmill walking at three velocities. Nine healthy young females walked on a treadmill for three minutes at 0.40, 0.93, and 1.47 m/s. The position of seven reflective markers and three rigs placed on the thorax, lumbar spine, and pelvis were recorded at 200 Hz by an eight-camera motion capture system. As gait velocity increased, stride length increased, cycle time decreased, and angular displacement in the thorax and L1 decreased but increased at the pelvis and L5 (all P < .05). The time of maxi- mal angular rotation occurred in the following sequence: pelvis, L5, L3, L1, and thorax (P < .001). The thorax and L1 and L3 were in-phase for shorter duration as gait velocity increased, and this reduction was especially large, approx. 32% (P < .05), between thorax and pelvis. As gait velocity increased, the pelvis rotated earlier, causing the shortening of in-phase duration between thorax and pelvis. These data suggest that, as gait velocity increases, pelvis rotation dictates trunk rotation in the transverse plane during gait in healthy young females.

Investigation of discrete states and quasidiscrete structures observed in 150Sm and 152Sm using the ( p,tγ) reaction

DOE PAGES

Peter, Humby; Simon, Anna; Beausang, C. W.; ...

2016-01-01

New levels and γ-ray transitions were identified in 150,152Sm utilizing the (p,t) reaction and particle-γ coincidence data. A large, peak-like structure observed between 2.3–3.0 MeV in excitation energy in the triton energy spectra was also investigated. The orbital angular-momentum transfer was probed by comparing the experimental angular distributions of the outgoing tritons to calculated distorted wave Born approximation curves. The angular distributions of the outgoing tritons populating the peak-like structure are remarkably similar in the two reactions and are significantly different from the angular distributions associated with the nearby continuum region. Relative partial cross sections for the observed levels, anglemore » averaged between 34 and 58 degrees, were measured. In 150Sm, 39(4)% of the strength of the peak-like structure could be accounted for by the observed discrete states. This compares with a value of 93(15)% for 152Sm« less

Investigation of discrete states and quasidiscrete structures observed in 150Sm and 152Sm using the ( p,tγ) reaction

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

Peter, Humby; Simon, Anna; Beausang, C. W.

New levels and γ-ray transitions were identified in 150,152Sm utilizing the (p,t) reaction and particle-γ coincidence data. A large, peak-like structure observed between 2.3–3.0 MeV in excitation energy in the triton energy spectra was also investigated. The orbital angular-momentum transfer was probed by comparing the experimental angular distributions of the outgoing tritons to calculated distorted wave Born approximation curves. The angular distributions of the outgoing tritons populating the peak-like structure are remarkably similar in the two reactions and are significantly different from the angular distributions associated with the nearby continuum region. Relative partial cross sections for the observed levels, anglemore » averaged between 34 and 58 degrees, were measured. In 150Sm, 39(4)% of the strength of the peak-like structure could be accounted for by the observed discrete states. This compares with a value of 93(15)% for 152Sm« less

Narrowband Angular Reflectance Properties of the Alkali Flats at White Sands, New Mexico

NASA Technical Reports Server (NTRS)

Whitlock, Charles H.; LeCroy, Stuart R.; Wheeler, Robert J.

1994-01-01

Results from helicopter measurements of the angular properties of surface reflectance for the alkali flats regions of the White Sands Missile Range are presented for the wavelength interval of 0.4 to 0.85 microns. This work was performed to allow accurate radiative transfer calculations over the region. Detailed tables and interpolation equations are given that permit other investigators to perform satellite calibrations over the alkali flats site. The effects of wavelength and soil moisture on narrowband angular reflectance are also investigated. Although there is a spectral variation in surface albedo, there is little spectral effect in Anisotropic Factor except in the forward scattering peak at solar zenith angles greater than 60 deg. The magnitude of the forward-scattering peak is also sensitive to soil moisture, with wet conditions causing a larger peak. The significance of this result is that angular reflectance properties at the center of the alkali flats usually will be different than those at the flats edge because moisture differences typically exist.

Angular distributions and mechanisms of fragmentation by relativistic heavy ions

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

Stoenner, R.W.; Haustein, P.E.; Cumming, J.B.

1984-07-23

Angular distributions of massive fragments from relativistic heavy-ion interactions are reported. Sideward peaking is observed for the light fragment /sup 37/Ar, from 25-GeV /sup 12/C+Au, while the distribution for /sup 127/Xe is strongly forward peaked. Conflicts of these observations and other existing data with predictions of models for the fragmentation process are discussed.

Close binary evolution. II. Impact of tides, wind magnetic braking, and internal angular momentum transport

NASA Astrophysics Data System (ADS)

Song, H. F.; Meynet, G.; Maeder, A.; Ekström, S.; Eggenberger, P.; Georgy, C.; Qin, Y.; Fragos, T.; Soerensen, M.; Barblan, F.; Wade, G. A.

2018-01-01

Context. Massive stars with solar metallicity lose important amounts of rotational angular momentum through their winds. When a magnetic field is present at the surface of a star, efficient angular momentum losses can still be achieved even when the mass-loss rate is very modest, at lower metallicities, or for lower-initial-mass stars. In a close binary system, the effect of wind magnetic braking also interacts with the influence of tides, resulting in a complex evolution of rotation. Aims: We study the interactions between the process of wind magnetic braking and tides in close binary systems. Methods: We discuss the evolution of a 10 M⊙ star in a close binary system with a 7 M⊙ companion using the Geneva stellar evolution code. The initial orbital period is 1.2 days. The 10 M⊙ star has a surface magnetic field of 1 kG. Various initial rotations are considered. We use two different approaches for the internal angular momentum transport. In one of them, angular momentum is transported by shear and meridional currents. In the other, a strong internal magnetic field imposes nearly perfect solid-body rotation. The evolution of the primary is computed until the first mass-transfer episode occurs. The cases of different values for the magnetic fields and for various orbital periods and mass ratios are briefly discussed. Results: We show that, independently of the initial rotation rate of the primary and the efficiency of the internal angular momentum transport, the surface rotation of the primary will converge, in a time that is short with respect to the main-sequence lifetime, towards a slowly evolving velocity that is different from the synchronization velocity. This "equilibrium angular velocity" is always inferior to the angular orbital velocity. In a given close binary system at this equilibrium stage, the difference between the spin and the orbital angular velocities becomes larger when the mass losses and/or the surface magnetic field increase. The treatment of the internal angular momentum transport has a strong impact on the evolutionary tracks in the Hertzsprung-Russell Diagram as well as on the changes of the surface abundances resulting from rotational mixing. Our modelling suggests that the presence of an undetected close companion might explain rapidly rotating stars with strong surface magnetic fields, having ages well above the magnetic braking timescale. Our models predict that the rotation of most stars of this type increases as a function of time, except for a first initial phase in spin-down systems. The measure of their surface abundances, together, when possible, with their mass-luminosity ratio, provide interesting constraints on the transport efficiencies of angular momentum and chemical species. Conclusions: Close binaries, when studied at phases predating any mass transfer, are key objects to probe the physics of rotation and magnetic fields in stars.

Afterglow Imaging and Polarization of Misaligned Structured GRB Jets and Cocoons: Breaking the Degeneracy in GRB 170817A

NASA Astrophysics Data System (ADS)

Gill, Ramandeep; Granot, Jonathan

2018-05-01

The X-ray to radio afterglow emission of GRB 170817A / GW 170817 so far scales as Fν∝ν-0.6t0.8 with observed frequency and time, consistent with a single power-law segment of the synchrotron spectrum from the external shock going into the ambient medium. This requires the effective isotropic equivalent afterglow shock energy in the visible region to increase as ˜t1.7. The two main channels for such an energy increase are (i) radial: more energy carried by slower material (in the visible region) gradually catches up with the afterglow shock and energizes it, and (ii) angular: more energy in relativistic outflow moving at different angles to our line of sight, whose radiation is initially beamed away from us but its beaming cone gradually reaches our line of sight as it decelerates. One cannot distinguish between these explanations (or combinations of them) using only the X-ray to radio Fν(t). Here we demonstrate that the most promising way to break this degeneracy is through afterglow imaging and polarization, by calculating the predicted evolution of the afterglow image (its size, shape and flux centroid) and linear polarization Π(t) for different angular and/or radial outflow structures that fit Fν(t). We consider two angular profiles - a Gaussian and a narrow core with power-law wings in energy per solid angle, as well as a (cocoon motivated) (quasi-) spherical flow with radial velocity profile. For a jet viewed off-axis (and a magnetic field produced in the afterglow shock) Π(t) peaks when the jet's core becomes visible, at ≈2tp where the lightcurve peaks at tp, and the image can be elongated with aspect ratios ≳ 2. A quasi-spherical flow has an almost circular image and a much lower Π(t) (peaking at ≈tp) and flux centroid displacement θfc (a spherical flow has Π(t) = θfc = 0 and a perfectly circular image).

Optimal simulations of ultrasonic fields produced by large thermal therapy arrays using the angular spectrum approach

PubMed Central

Zeng, Xiaozheng; McGough, Robert J.

2009-01-01

The angular spectrum approach is evaluated for the simulation of focused ultrasound fields produced by large thermal therapy arrays. For an input pressure or normal particle velocity distribution in a plane, the angular spectrum approach rapidly computes the output pressure field in a three dimensional volume. To determine the optimal combination of simulation parameters for angular spectrum calculations, the effect of the size, location, and the numerical accuracy of the input plane on the computed output pressure is evaluated. Simulation results demonstrate that angular spectrum calculations performed with an input pressure plane are more accurate than calculations with an input velocity plane. Results also indicate that when the input pressure plane is slightly larger than the array aperture and is located approximately one wavelength from the array, angular spectrum simulations have very small numerical errors for two dimensional planar arrays. Furthermore, the root mean squared error from angular spectrum simulations asymptotically approaches a nonzero lower limit as the error in the input plane decreases. Overall, the angular spectrum approach is an accurate and robust method for thermal therapy simulations of large ultrasound phased arrays when the input pressure plane is computed with the fast nearfield method and an optimal combination of input parameters. PMID:19425640

Angular distribution of diffuse reflectance from incoherent multiple scattering in turbid media.

PubMed

Gao, M; Huang, X; Yang, P; Kattawar, G W

2013-08-20

The angular distribution of diffuse reflection is elucidated with greater understanding by studying a homogeneous turbid medium. We modeled the medium as an infinite slab and studied the reflection dependence on the following three parameters: the incident direction, optical depth, and asymmetry factor. The diffuse reflection is produced by incoherent multiple scattering and is solved through radiative transfer theory. At large optical depths, the angular distribution of the diffuse reflection with small incident angles is similar to that of a Lambertian surface, but, with incident angles larger than 60°, the angular distributions have a prominent reflection peak around the specular reflection angle. These reflection peaks are found originating from the scattering within one transport mean free path in the top layer of the medium. The maximum reflection angles for different incident angles are analyzed and can characterize the structure of angular distributions for different asymmetry factors and optical depths. The properties of the angular distribution can be applied to more complex systems for a better understanding of diffuse reflection.

A measurement of the cosmic microwave background from the high Chilean Andes

NASA Astrophysics Data System (ADS)

Miller, Amber Dawn

A measurement of the angular spectrum of the Cosmic Microwave Background (CMB) between l = 50 and l = 400 is described. Data were obtained using HEMT radiometers at 30 and 40 GHz with angular resolutions of ≈1 deg and ≈0.7 deg respectively and with SIS based receivers at 144 GHz with angular resolution of ≈0.2 deg. Observations were made from Cerro Toco in the Chilean altiplano at an altitude of 17,000 feet in the Northern Chilean Andes. We find that the angular spectrum rises from l = 50 to a peak at l ≈ 200 and falls off at higher angular scales. A peak in the angular spectrum with amplitude, deltaTl ≈ 85muK is thus located for the first time with a single instrument at l ≈ 200. In addition, we find that the detected anisotropy has the spectrum of the CMB. Cosmological implications of this result are discussed.

On the Shelf Resonances of the Gulf of Carpentaria and the Arafura Sea

NASA Astrophysics Data System (ADS)

Webb, D. J.

2012-02-01

A numerical model is used to investigate the resonances of the Gulf of Carpentaria and the Arafura Sea. The model is forced at the shelf edge, first with physically realistic real values of angular velocity. The response functions at points within the region show maxima and other behaviour which imply that resonances are involved but it is difficult to be more specific. The study is then extended to complex angular velocities and the results then show a clear pattern of gravity wave and Rossby wave like resonances. The properties of the resonances are investigated and used to reinterpret the responses at real values of angular velocity. It is found that in some regions the response is dominated by modes trapped between the shelf edge and the coast or between opposing coastlines. In other regions the resonances show cooperative behaviour, possibly indicating the importance of other physical processes.

Angular velocity of gravitational radiation from precessing binaries and the corotating frame

NASA Astrophysics Data System (ADS)

Boyle, Michael

2013-05-01

This paper defines an angular velocity for time-dependent functions on the sphere and applies it to gravitational waveforms from compact binaries. Because it is geometrically meaningful and has a clear physical motivation, the angular velocity is uniquely useful in helping to solve an important—and largely ignored—problem in models of compact binaries: the inverse problem of deducing the physical parameters of a system from the gravitational waves alone. It is also used to define the corotating frame of the waveform. When decomposed in this frame, the waveform has no rotational dynamics and is therefore as slowly evolving as possible. The resulting simplifications lead to straightforward methods for accurately comparing waveforms and constructing hybrids. As formulated in this paper, the methods can be applied robustly to both precessing and nonprecessing waveforms, providing a clear, comprehensive, and consistent framework for waveform analysis. Explicit implementations of all these methods are provided in accompanying computer code.

Angular distributions of plasma edge velocity and integrated intensity: Update on specific impulse for Ablative Laser Propulsion

NASA Astrophysics Data System (ADS)

Lin, Jun; Pakhomov, Andrew V.

2005-04-01

This work concludes our discussion of the image processing technique developed earlier for determination of specific impulse (Isp) for Ablative Laser Propulsion (ALP). The plasma plumes are recorded with a time-resolved intensified charge-coupled device (ICCD) camera. The plasma was formed in vacuum (˜ 3×10-3 Torr) by focusing output pulses of a laser system (100-ps pulsewidth at 532 nm wavelength and ˜35 mJ energy) on surfaces of C (graphite), Al, Si, Fe, Cu, Zn, Sn, and Pb elements. Angular profiles for integrated intensity and plasma expansion velocity were determined for the tested elements. Such profiles were used further for assessment of specific impulse. Specific impulses derived from angular distributions of plasma expansion velocity and integral intensity appeared in excellent agreement with the data derived earlier from force measurements.

A submicron device to rectify a square-wave angular velocity.

PubMed

Moradian, A; Miri, M F

2011-02-01

We study a system composed of two thick dielectric disks separated by a thin layer of an electrolyte solution. Initially both plates have the same surface charge distribution. The surface charge distribution has no rotational symmetry. We show that the top plate experiences a torque [Formula: see text]([Formula: see text]) if it rotates about its axis by an angle [Formula: see text] . The torque can be controlled by varying the electrolyte concentration, the separation and the surface charge density of the plates. For a specific example of charged rods attached to the plates, we find [Formula: see text]([Formula: see text]) [Formula: see text] sin(4[Formula: see text]) . We also study the dynamics of the system. We consider the case where the angular velocity of the bottom disk is a square-wave signal. We find that the average angular velocity of the top disk is not zero.

Representational momentum, centripetal force, and curvilinear impetus.

PubMed

Hubbard, T L

1996-07-01

In 3 experiments, observers witnessed a target moving along a circular orbit and indicated the location at which the target vanished. The judged vanishing point was displaced forward in the direction of implied momentum and inward in the direction of implied centripetal force. In general, increases in either the angular velocity of the target or the radius length of the orbit increased the magnitude of forward displacement. If both angular velocity and radius length were varied, then increases in either angular velocity or radius length also increased the magnitude of inward displacement. The displacement patterns were consistent with hypotheses that analogues of momentum and centripetal force were incorporated into the representational system. A framework is proposed that accounts for (a) the forward and inward displacements and (b) naive-physics data on the spiral tube problem previously interpreted as suggesting a belief in a naive curvilinear-impetus principle.

Simulated cosmic microwave background maps at 0.5 deg resolution: Basic results

NASA Technical Reports Server (NTRS)

Hinshaw, G.; Bennett, C. L.; Kogut, A.

1995-01-01

We have simulated full-sky maps of the cosmic microwave background (CMB) anisotropy expected from cold dark matter (CDM) models at 0.5 deg and 1.0 deg angular resolution. Statistical properties of the maps are presented as a function of sky coverage, angular resolution, and instrument noise, and the implications of these results for observability of the Doppler peak are discussed. The rms fluctuations in a map are not a particularly robust probe of the existence of a Doppler peak; however, a full correlation analysis can provide reasonable sensitivity. We find that sensitivity to the Doppler peak depends primarily on the fraction of sky covered, and only secondarily on the angular resolution and noise level. Color plates of the simulated maps are presented to illustrate the anisotropies.

An active-optics image-motion compensation technology application for high-speed searching and infrared detection system

NASA Astrophysics Data System (ADS)

Wu, Jianping; Lu, Fei; Zou, Kai; Yan, Hong; Wan, Min; Kuang, Yan; Zhou, Yanqing

2018-03-01

An ultra-high angular velocity and minor-caliber high-precision stably control technology application for active-optics image-motion compensation, is put forward innovatively in this paper. The image blur problem due to several 100°/s high-velocity relative motion between imaging system and target is theoretically analyzed. The velocity match model of detection system and active optics compensation system is built, and active optics image motion compensation platform experiment parameters are designed. Several 100°/s high-velocity high-precision control optics compensation technology is studied and implemented. The relative motion velocity is up to 250°/s, and image motion amplitude is more than 20 pixel. After the active optics compensation, motion blur is less than one pixel. The bottleneck technology of ultra-high angular velocity and long exposure time in searching and infrared detection system is successfully broke through.

Cosmic Vorticity and the Origin Halo Spins

NASA Astrophysics Data System (ADS)

Libeskind, Noam I.; Hoffman, Yehuda; Steinmetz, Matthias; Gottlöber, Stefan; Knebe, Alexander; Hess, Steffen

2013-04-01

In the standard model of cosmology, structure emerges out of a non-rotational flow and the angular momentum of collapsing halos is induced by tidal torques. The growth of angular momentum in the linear and quasi-linear phases is associated with a shear, curl-free, flow and it is well described within the linear framework of tidal torque theory (TTT). However, TTT ceases to be applicable as halos approach turnaround when their ambient flow field becomes rotational. Subsequently, halos become embedded in a vortical flow field and the growth of their angular momentum is affected by the vorticity of their ambient velocity field. Using a cosmological simulation, we have examined the importance of the curl of the velocity field in determining halo spin, finding a significant alignment between the two: the vorticity tends to be perpendicular to the axis of the fastest collapse of the velocity shear tensor (e 1). This is independent of halo masses and cosmic web environment. Our results agree with previous findings on the tendency of halo spin to be perpendicular to e 1, and of the spin of (simulated) halos and (observed) galaxies to be aligned with the large-scale structure. It follows that angular momentum growth proceeds in two distinct phases. First, the angular momentum emerges out of a shear, curl-free, potential flow, as described by TTT. In the second phase, in which halos approach virialization, the angular momentum emerges out of a vortical flow and halo spin becomes partially aligned with the vorticity of the ambient flow field.

Chain-loaded variable resistance warm-up improves free-weight maximal back squat performance.

PubMed

Mina, Minas A; Blazevich, Anthony J; Giakas, Giannis; Seitz, Laurent B; Kay, Anthony D

2016-11-01

The acute influence of chain-loaded variable resistance exercise on subsequent free-weight one-repetition maximum (1-RM) back squat performance was examined in 16 recreationally active men. The participants performed either a free-weight resistance (FWR) or chain-loaded resistance (CLR) back squat warm-up at 85% 1-RM on two separate occasions. After a 5-min rest, the participants attempted a free-weight 1-RM back squat; if successful, subsequent 5% load additions were made until participants failed to complete the lift. During the 1-RM trials, 3D knee joint kinematics and knee extensor and flexor electromyograms (EMG) were recorded simultaneously. Significantly greater 1-RM (6.2 ± 5.0%; p < .01) and mean eccentric knee extensor EMG (32.2 ± 6.7%; p < .01) were found after the CLR warm-up compared to the FWR condition. However, no difference (p > .05) was found in concentric EMG, eccentric or concentric knee angular velocity, or peak knee flexion angle. Performing a CLR warm-up enhanced subsequent free-weight 1-RM performance without changes in knee flexion angle or eccentric and concentric knee angular velocities; thus a real 1-RM increase was achieved as the mechanics of the lift were not altered. These results are indicative of a potentiating effect of CLR in a warm-up, which may benefit athletes in tasks where high-level strength is required.

Repeated Kicking Actions in Karate: Effect on Technical Execution in Elite Practitioners.

PubMed

Quinzi, Federico; Camomilla, Valentina; Di Mario, Alberto; Felici, Francesco; Sbriccoli, Paola

2016-04-01

Training in martial arts is commonly performed by repeating a technical action continuously for a given number of times. This study aimed to investigate if the repetition of the task alters the proper technical execution, limiting the training efficacy for the technical evaluation during competition. This aim was pursued analyzing lower-limb kinematics and muscle activation during repeated roundhouse kicks. Six junior karate practitioners performed continuously 20 repetitions of the kick. Hip and knee kinematics and sEMG of vastus lateralis, biceps (BF), and rectus femoris were recorded. For each repetition, hip abduction-adduction and flexion-extension and knee flexion-extension peak angular displacements and velocities, agonist and antagonist muscle activation were computed. Moreover, to monitor for the presence of myoelectric fatigue, if any, the median frequency of the sEMG was computed. All variables were normalized with respect to their individual maximum observed during the sequence of kicks. Linear regressions were fitted to each normalized parameter to test its relationship with the repetition number. Linear-regression analysis showed that, during the sequence, the athletes modified their technique: Knee flexion, BF median frequency, hip abduction, knee-extension angular velocity, and BF antagonist activation significantly decreased. Conversely, hip flexion increased significantly. Since karate combat competitions require proper technical execution, training protocols combining severe fatigue and technical actions should be carefully proposed because of technique adaptations. Moreover, trainers and karate masters should consider including specific strength exercises for the BF and more generally for knee flexors.

Molecular Gas Properties in M83 from CO PDFs

NASA Astrophysics Data System (ADS)

Egusa, Fumi; Hirota, Akihiko; Baba, Junichi; Muraoka, Kazuyuki

2018-02-01

We have obtained 12CO(1–0) data of the nearby barred spiral galaxy M83 from Atacama Large Millimeter/submillimeter Array and Nobeyama 45 m observations. By combining these two data sets, the total CO flux has been recovered, and a high angular resolution (2\\prime\\prime corresponding to ∼40 pc at the distance of M83) has been achieved. The field of view is 3\\prime corresponding to ∼3.4 kpc and covers the galactic center, bar, and spiral arm regions. In order to investigate how these galactic structures affect gas properties, we have created a probability distribution function (PDF) of the CO integrated intensity ({I}CO}), peak temperature, and velocity dispersion for a region with each structure. We find that the {I}CO} PDF for the bar shows a bright-end tail while that for the arm does not. As the star formation efficiency is lower in the bar, this difference in PDF shape is contrary to the trend in Milky Way studies where the bright-end tail is found for star-forming molecular clouds. While the peak temperature PDFs are similar for the bar and arm regions, velocity dispersion in the bar is systematically larger than in the arm. This large velocity dispersion is likely a major cause of the bright-end tail and of suppressed star formation. We also investigate an effect of stellar feedback to PDF profiles and find that the different {I}CO} PDFs between bar and arm regions cannot be explained by the feedback effect, at least at the current spatial scale.

Absolute plate velocities from seismic anisotropy: Importance of correlated errors

NASA Astrophysics Data System (ADS)

Zheng, Lin; Gordon, Richard G.; Kreemer, Corné

2014-09-01

The errors in plate motion azimuths inferred from shear wave splitting beneath any one tectonic plate are shown to be correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. Our preferred set of angular velocities, SKS-MORVEL, is determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25 ± 0.11° Ma-1 (95% confidence limits) right handed about 57.1°S, 68.6°E. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ = 19.2°) differs insignificantly from that for continental lithosphere (σ = 21.6°). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ = 7.4°) than for continental lithosphere (σ = 14.7°). Two of the slowest-moving plates, Antarctica (vRMS = 4 mm a-1, σ = 29°) and Eurasia (vRMS = 3 mm a-1, σ = 33°), have two of the largest within-plate dispersions, which may indicate that a plate must move faster than ≈ 5 mm a-1 to result in seismic anisotropy useful for estimating plate motion. The tendency of observed azimuths on the Arabia plate to be counterclockwise of plate motion may provide information about the direction and amplitude of superposed asthenospheric flow or about anisotropy in the lithospheric mantle.

Equilibrium properties and phase diagram of two-dimensional Yukawa systems

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

Hartmann, P.; Donko, Z.; Kutasi, K.

Properties of two-dimensional strongly coupled Yukawa systems are explored through molecular dynamics simulations. An effective coupling coefficient {gamma}{sup *} for the liquid phase is introduced on the basis of the constancy of the first peak amplitude of the pair-correlation functions. Thermodynamic quantities are calculated from the pair-correlation function. The solid-liquid transition of the system is investigated through the analysis of the bond-angular order parameter. The static structure function satisfies consistency relation, attesting to the reliability of the computational method. The response is shown to be governed by the correlational part of the inverse compressibility. An analysis of the velocity autocorrelationmore » demonstrates that this latter also exhibits a universal behavior.« less

Multi-degree-of-freedom ultrasonic micromotor for guidewire and catheter navigation: The NeuroGlide actuator

NASA Astrophysics Data System (ADS)

Yun, Cheol-Ho; Yeo, Leslie Y.; Friend, James R.; Yan, Bernard

2012-04-01

A 240-μm diameter ultrasonic micromotor is presented as a potential solution for an especially difficult task in minimally invasive neurosurgery, navigating a guidewire to an injury in the neurovasculature as the first step of surgery. The peak no-load angular velocity and maximum torque were 600 rad/s and 1.6 nN-m, respectively, and we obtained rotation about all three axes. By using a burst drive scheme, open-loop position and speed control were achieved. The construction method and control scheme proposed in this study remove most of the current limitations in minimally invasive, catheter-based actuation, enabling minimally invasive vascular surgery concepts to be pursued for a broad variety of applications.

Kinematic study of O--ion formation from dissociative electron attachment to SO2

NASA Astrophysics Data System (ADS)

Jana, Irina; Nandi, Dhananjay

2018-04-01

We report a complete kinematic study of O--ion formation due to dissociative electron attachment to SO2 using the velocity slice imaging technique in the incident electron energy range over the resonances. Two resonances are observed at 5.2 and 7.5 eV, respectively. From the kinetic energy distribution, the two resonances are observed to have the same threshold energy, pointing to the fact that the two processes, giving rise to the two resonant peaks, have the same dissociation limit. From the angular distribution results we identified the involvement of an A1 and a combination of A1+B2 temporary negative-ion state(s) for the first and second resonances, respectively.

Measuring the velocity field from type Ia supernovae in an LSST-like sky survey

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

Odderskov, Io; Hannestad, Steen, E-mail: isho07@phys.au.dk, E-mail: sth@phys.au.dk

2017-01-01

In a few years, the Large Synoptic Survey Telescope will vastly increase the number of type Ia supernovae observed in the local universe. This will allow for a precise mapping of the velocity field and, since the source of peculiar velocities is variations in the density field, cosmological parameters related to the matter distribution can subsequently be extracted from the velocity power spectrum. One way to quantify this is through the angular power spectrum of radial peculiar velocities on spheres at different redshifts. We investigate how well this observable can be measured, despite the problems caused by areas with nomore » information. To obtain a realistic distribution of supernovae, we create mock supernova catalogs by using a semi-analytical code for galaxy formation on the merger trees extracted from N-body simulations. We measure the cosmic variance in the velocity power spectrum by repeating the procedure many times for differently located observers, and vary several aspects of the analysis, such as the observer environment, to see how this affects the measurements. Our results confirm the findings from earlier studies regarding the precision with which the angular velocity power spectrum can be determined in the near future. This level of precision has been found to imply, that the angular velocity power spectrum from type Ia supernovae is competitive in its potential to measure parameters such as σ{sub 8}. This makes the peculiar velocity power spectrum from type Ia supernovae a promising new observable, which deserves further attention.« less

Extra-tropical QBO signals in angular momentum and wave forcing

NASA Technical Reports Server (NTRS)

Baldwin, Mark P.; Tung, Ka Kit

1994-01-01

Although the period of the equatorial stratospheric quasi-biennal oscillation (QBO) is approximately 30 months, quasi-biennial modulation of the extratropical annual cycle may be expected to produce additional spectral peaks at approximately to produce additional spectral peaks at approximately 8.6 and 20 months in the extratropics. Using Northern Hemisphere data for 1964-78 and global data for 1978-93 it is shown that these spectral peaks are robust in both angular momentum and Eliassen-Palm flux divergence. This spectral signature represents a circulation anomaly in both hemispheres, and implies a dynamical origin to the previously observed similar spectral peaks in column ozone in the extratropics.

Inference of stress and texture from angular dependence of ultrasonic plate mode velocities

NASA Technical Reports Server (NTRS)

Thompson, R. B.; Smith, J. F.; Lee, S. S.

1986-01-01

The theory for the angular dependence of the ultrasonic wave velocity in a symmetry plane of an orthorhombic, stressed material is presented. The two waves having polarizations in this plane are shown to have velocities which can be estimated from measurements of the SH sub 0 and S sub 0 guided modes of a thin plate: the relationship being exact for the SH sub 0 mode and requiring a 10% correction for the S sub 0 mode at long wavelength. It is then shown how stress and texture can be independently inferred from various features of the angular dependence of these two velocities. From the SH sub 0 data, the ability to determine the directions and differences in magnitudes of principal stresses is described and supported by experimental data on several materials. From a combination of the SH sub 0 and S sub 0 data, a procedure is proposed for determining the coefficients W sub 400, W sub 420 and W sub 440 of an expansion of the crystallite orientation distribution function in terms of generalized Legendre functions. Possible applications in process control are indicated.

Shoulder Rotator Muscle Dynamometry Characteristics: Side Asymmetry and Correlations with Ball-Throwing Speed in Adolescent Handball Players

PubMed Central

Pontaga, Inese; Zidens, Janis

2014-01-01

The aim of the investigation was to: 1) compare shoulder external/internal rotator muscles’ peak torques and average power values and their ratios in the dominant and non-dominant arm; 2) determine correlations between shoulder rotator muscles’ peak torques, average power and ball-throwing speed in handball players. Fourteen 14 to 15-year-old male athletes with injury-free shoulders participated in the study (body height: 176 ± 7 cm, body mass 63 ± 9 kg). The tests were carried out by an isokinetic dynamometer system in the shoulder internal and external rotation movements at angular velocities of 60°/s, 90°/s and 240°/s during concentric contractions. The eccentric external– concentric internal rotator muscle contractions were performed at the velocity of 90°/s. The player threw a ball at maximal speed keeping both feet on the floor. The speed was recorded with reflected light rays. Training in handball does not cause significant side asymmetry in shoulder external/internal rotator muscle peak torques or the average power ratio. Positive correlations between isokinetic characteristics of the shoulder internal and external rotator muscles and ball-throwing speed were determined. The power produced by internal rotator muscles during concentric contractions after eccentric contractions of external rotator muscles was significantly greater in the dominant than in the non-dominant arm. Thus, it may be concluded that the shoulder eccentric external/concentric internal rotator muscle power ratio is significantly greater than this ratio in the concentric contractions of these muscles. PMID:25414738

The effect of muscle stiffness and damping on simulated impact force peaks during running.

PubMed

Nigg, B M; Liu, W

1999-08-01

It has been frequently reported that vertical impact force peaks during running change only minimally when changing the midsole hardness of running shoes. However, the underlying mechanism for these experimental observations is not well understood. An athlete has various possibilities to influence external and internal forces during ground contact (e.g. landing velocity, geometrical alignment, muscle tuning, etc.). The purpose of this study was to discuss one possible strategy to influence external impact forces acting on the athlete's body during running, the strategy to change muscle activity (muscle tuning). The human body was modeled as a simplified mass-spring-damper system. The model included masses of the upper and the lower bodies with each part of the body represented by a rigid and a non-rigid wobbling mass. The influence of mechanical properties of the human body on the vertical impact force peak was examined by varying the spring constants and damping coefficients of the spring-damper units that connected the various masses. Two types of shoe soles were modeled using a non-linear force deformation model with two sets of parameters based on the force-deformation curves of pendulum impact experiments. The simulated results showed that the regulation of the mechanical coupling of rigid and wobbling masses of the human body had an influence on the magnitude of the vertical impact force, but not on its loading rate. It was possible to produce the same impact force peaks altering specific mechanical properties of the system for a soft and a hard shoe sole. This regulation can be achieved through changes of joint angles, changes in joint angular velocities and/or changes in muscle activation levels in the lower extremity. Therefore, it has been concluded that changes in muscle activity (muscle tuning) can be used as a possible strategy to affect vertical impact force peaks during running.

Agonist and antagonist muscle activation in elite athletes: influence of age.

PubMed

Quinzi, Federico; Camomilla, Valentina; Felici, Francesco; Di Mario, Alberto; Sbriccoli, Paola

2015-01-01

Age-related neuromuscular control adaptations have been investigated mainly in untrained populations, where higher antagonist activation in adults was observed with respect to children. In elite athletes age-related differences in neuromuscular control have scarcely been investigated. Therefore, this study aims at investigating differences in co-activation about the knee joint in two groups of karate athletes belonging to the Junior (JK) and Senior (SK) age categories, performing the roundhouse kick (RK). Six SK and six JK performed the RK impacting on a punching bag. Each participant performed three attempts during which kicking limb kinematics and sEMG from the vastus lateralis (VL) and from the biceps femoris (BF) were recorded. Co-activation index during knee flexion and extension (CIF; CIE) and agonist and antagonist activation areas of VL and BF (I AGO-VL; I AGO-BF; I ANT-VL; I ANT-BF) were computed. Hip and knee range of motion, peak angular velocity and minima and maxima of lower limb angular momentum were computed. During knee extension, the SK demonstrated higher CIE, higher IANT-BF and higher total angular momentum with respect to the JK. Significant relationships were observed between I ANT-BF and total angular momentum maxima, and between I ANT-BF and age. IANT-BF is partially related to the age of the group and to joint protection upon impact. Moreover, given the very brief duration of the task, a feed-forward mechanism modulating antagonist activation partly based on the stress imposed on the knee joint could be hypothesized. This mechanism potentially involves skill dependent re-modelling of the peripheral and central nervous system.

Modified Maturity Offset Prediction Equations: Validation in Independent Longitudinal Samples of Boys and Girls.

PubMed

Kozieł, Sławomir M; Malina, Robert M

2018-01-01

Predicted maturity offset and age at peak height velocity are increasingly used with youth athletes, although validation studies of the equations indicated major limitations. The equations have since been modified and simplified. The objective of this study was to validate the new maturity offset prediction equations in independent longitudinal samples of boys and girls. Two new equations for boys with chronological age and sitting height and chronological age and stature as predictors, and one equation for girls with chronological age and stature as predictors were evaluated in serial data from the Wrocław Growth Study, 193 boys (aged 8-18 years) and 198 girls (aged 8-16 years). Observed age at peak height velocity for each youth was estimated with the Preece-Baines Model 1. The original prediction equations were included for comparison. Predicted age at peak height velocity was the difference between chronological age at prediction and maturity offset. Predicted ages at peak height velocity with the new equations approximated observed ages at peak height velocity in average maturing boys near the time of peak height velocity; a corresponding window for average maturing girls was not apparent. Compared with observed age at peak height velocity, predicted ages at peak height velocity with the new and original equations were consistently later in early maturing youth and earlier in late maturing youth of both sexes. Predicted ages at peak height velocity with the new equations had reduced variation compared with the original equations and especially observed ages at peak height velocity. Intra-individual variation in predicted ages at peak height velocity with all equations was considerable. The new equations are useful for average maturing boys close to the time of peak height velocity; there does not appear to be a clear window for average maturing girls. The new and original equations have major limitations with early and late maturing boys and girls.

Raychaudhuri equation in the self-consistent Einstein-Cartan theory with spin-density

NASA Technical Reports Server (NTRS)

Fennelly, A. J.; Krisch, Jean P.; Ray, John R.; Smalley, Larry L.

1988-01-01

The physical implications of the Raychaudhuri equation for a spinning fluid in a Riemann-Cartan spacetime is developed and discussed using the self-consistent Lagrangian based formulation for the Einstein-Cartan theory. It was found that the spin-squared terms contribute to expansion (inflation) at early times and may lead to a bounce in the final collapse. The relationship between the fluid's vorticity and spin angular velocity is clarified and the effect of the interaction terms between the spin angular velocity and the spin in the Raychaudhuri equation investigated. These results should prove useful for studies of systems with an intrinsic spin angular momentum in extreme astrophysical or cosmological problems.

A new approach to correct yaw misalignment in the spinning ultrasonic anemometer

NASA Astrophysics Data System (ADS)

Ghaemi-Nasab, M.; Davari, Ali R.; Franchini, S.

2018-01-01

Single-axis ultrasonic anemometers are the modern instruments for accurate wind speed measurements. Despite their widespread and ever increasing applications, little attention has been paid up to now to spinning ultrasonic anemometers that can accurately measure both the wind speed and its direction in a single and robust apparatus. In this study, intensive wind-tunnel tests were conducted on a spinning single-axis ultrasonic anemometer to investigate the yaw misalignment in ultrasonic wind speed measurements during the yaw rotation. The anemometer was rotating inside the test section with various angular velocities, and the experiments were performed at several combinations of wind speed and anemometer angular velocity. The instantaneous angular position of the ultrasonic signal path with wind direction was measured using an angular position sensor. For a spinning anemometer, the circulatory wake and the associated flow distortion, along with the Doppler effect, impart a phase shift in the signals measured by the anemometer, which should be added to the position data for correcting the yaw misalignment. In this paper, the experimental data are used to construct a theoretical model, based on a response surface method, to correct the phase shift for various wind speeds and anemometer rotational velocities. This model is shown to successfully correct the velocity indicated by the spinning anemometer for the phase shift due to the rotation, and can easily be used in the calibration process for such anemometers.

Angular-dependent Raman study of a- and s-plane InN

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

Filintoglou, K.; Katsikini, M., E-mail: katsiki@auth.gr; Arvanitidis, J.

2015-02-21

Angular-dependent polarized Raman spectroscopy was utilized to study nonpolar a-plane (11{sup ¯}20) and semipolar s-plane (101{sup ¯}1) InN epilayers. The intensity dependence of the Raman peaks assigned to the vibrational modes A{sub 1}(TO), E{sub 1}(TO), and E{sub 2}{sup h} on the angle ψ that corresponds to rotation around the growth axis, is very well reproduced by using expressions taking into account the corresponding Raman tensors and the experimental geometry, providing thus a reliable technique towards assessing the sample quality. The s- and a-plane InN epilayers grown on nitridated r-plane sapphire (Al{sub 2}O{sub 3}) exhibit good crystalline quality as deduced frommore » the excellent fitting of the experimental angle-dependent peak intensities to the theoretical expressions as well as from the small width of the Raman peaks. On the contrary, in the case of the s-plane epilayer grown on non-nitridated r-plane sapphire, fitting of the angular dependence is much worse and can be modeled only by considering the presence of two structural modifications, rotated so as their c-axes are almost perpendicular to each other. Although the presence of the second variant is verified by transmission electron and atomic force microscopies, angular dependent Raman spectroscopy offers a non-destructive and quick way for its quantification. Rapid thermal annealing of this sample did not affect the angular dependence of the peak intensities. The shift of the E{sub 1}(TO) and E{sub 2}{sup h} Raman peaks was used for the estimation of the strain state of the samples.« less

Isokinetic Identification of Knee Joint Torques before and after Anterior Cruciate Ligament Reconstruction

PubMed Central

Czaplicki, Adam; Jarocka, Marta; Walawski, Jacek

2015-01-01

The aim of this study was to evaluate the serial change of isokinetic muscle strength of the knees before and after anterior cruciate ligament reconstruction (ACLR) in physically active males and to estimate the time of return to full physical fitness. Extension and flexion torques were measured for the injured and healthy limbs at two angular velocities approximately 1.5 months before the surgery and 3, 6, and 12 months after ACLR. Significant differences (p ≤ 0.05) in peak knee extension and flexion torques, hamstring/quadriceps (H/Q) strength ratios, uninvolved/involved limb peak torque ratios, and the normalized work of these muscles between the four stages of rehabilitation were identified. Significant differences between extension peak torques for the injured and healthy limbs were also detected at all stages. The obtained results showed that 12 months of rehabilitation were insufficient for the involved knee joint to recover its strength to the level of strength of the uninvolved knee joint. The results helped to evaluate the progress of the rehabilitation and to implement necessary modifications optimizing the rehabilitation training program. The results of the study may also be used as referential data for physically active males of similar age. PMID:26646385

Quaternion-based study of angular velocity of the cardiac vector during myocardial ischaemia.

PubMed

Cruces, Pablo Daniel; Arini, Pedro David

2017-12-01

Early detection of acute ischaemia through non-invasive methods remains a challenge in health research. Ischaemic condition caused by a decrease in the blood supply in a cardiac region induces hypoxia and metabolic abnormalities that contribute to the electrical instability of the heart and to the development of slow conduction in damaged tissue. Herein, a percutaneous transluminal coronary angiography (PTCA) is considered as a model of supply ischaemia. We use the concept of quaternion to develop a robust method for assessing the angular velocity of cardiac vector in the orthogonal XYZ leads obtained from 92 patients undergoing the PTCA procedure. The maxima of angular velocity in both ventricular depolarization and repolarization are combined with traditional linear velocity indexes in order to obtain a detector of ischaemic episodes (Ischaemia Detector, ID). ID achieves 98%/100% of sensitivity/specificity when differentiating healthy subjects from patients with early ischaemia. Furthermore, it also shows high accuracy when the comparison is made between ischaemic subjects and patients with different non-ischaemic pathologic ST-deviations which are known to cause false positives, reaching 95%/98% of sensitivity/specificity. Moreover, the study of significant reductions (p<0.001) of angular velocity components allows extraction of distinct ischaemic common features which are useful for analyzing the dependence of vectorcardiogram signal on each site of occlusion. The sensitivity of injury location reaches values of 88% (RCA), 87% (LAD) and 80% (LCx). The high performance of the proposed method establishes a promising outcome for application in computerized assistance in clinical practice. Copyright © 2017 Elsevier B.V. All rights reserved.

Muscle activation and the isokinetic torque-velocity relationship of the human triceps surae.

PubMed

Harridge, S D; White, M J

1993-01-01

The influence of muscle activation and the time allowed for torque generation on the angle-specific torque-velocity relationship of the triceps surae was studied during plantar flexion using supramaximal electrical stimulation and a release technique on six male subjects [mean (SD) age 25 (4) years]. Torque-velocity data were obtained under different levels of constant muscle activation by varying the stimulus frequency and the time allowed for isometric torque generation prior to release and isokinetic shortening. To eliminate the effects of the frequency response on absolute torque the isokinetic data were normalized to the maximum isometric torque values at 0.44 rad. There were no significant differences in the normalized torques generated at any angular velocity using stimulus frequencies of 20, 50 or 80 Hz. When the muscle was stimulated at 50 Hz the torques obtained after a 400 ms and 1 s pre-release isometric contraction did not differ significantly. However, with no pre-release contraction significantly less torque was generated at all angular velocities beyond 1.05 rad.s-1 when compared with either the 200, 400 ms or 1 s condition. With a 200 ms pre-release contraction significantly less torque was generated at angular velocities beyond 1.05 rad.s-1 when compared with the 400 ms or 1 s conditions. It would seem that the major factor governing the shape of the torque-velocity curve at a constant level of muscle activation is the time allowed for torque generation.

Zero potential vorticity envelopes for the zonal-mean velocity of the Venus/Titan atmospheres

NASA Technical Reports Server (NTRS)

Allison, Michael; Del Genio, Anthony D.; Zhou, Wei

1994-01-01

The diagnostic analysis of numerical simulations of the Venus/Titan wind regime reveals an overlooked constraint upon the latitudinal structure of their zonal-mean angular momentum. The numerical experiments, as well as the limited planetary observations, are approximately consistent with the hypothesis that within the latitudes bounded by the wind maxima the total Ertel potential vorticity associated with the zonal-mean motion is approximately well mixed with respect to the neutral equatorial value for a stable circulation. The implied latitudinal profile of angular momentum is of the form M equal to or less than M(sub e)(cos lambda)(exp 2/Ri), where lambda is the latitude and Ri the local Richardson number, generally intermediate between the two extremes of uniform angular momentum (Ri approaches infinity) and uniform angular velocity (Ri = 1). The full range of angular momentum profile variation appears to be realized within the observed meridional - vertical structure of the Venus atmosphere, at least crudely approaching the implied relationship between stratification and zonal velocity there. While not itself indicative of a particular eddy mechanism or specific to atmospheric superrotation, the zero potential vorticity (ZPV) constraint represents a limiting bound for the eddy - mean flow adjustment of a neutrally stable baroclinic circulation and may be usefully applied to the diagnostic analysis of future remote sounding and in situ measurements from planetary spacecraft.

Signal processing related to the vestibulo-ocular reflex during combined angular rotation and linear translation of the head

NASA Technical Reports Server (NTRS)

McCrea, R. A.; Chen-Huang, C.; Peterson, B. W. (Principal Investigator)

1999-01-01

The contributions of vestibular nerve afferents and central vestibular pathways to the angular (AVOR) and linear (LVOR) vestibulo-ocular reflex were studied in squirrel monkeys during fixation of near and far targets. Irregular vestibular afferents did not appear to be necessary for the LVOR, since when they were selectively silenced with galvanic currents the LVOR was essentially unaffected during both far- and near-target viewing. The linear translation signals generated by secondary AVOR neurons in the vestibular nuclei were, on average, in phase with head velocity, inversely related to viewing distance, and were nearly as strong as AVOR-related signals. We suggest that spatial-temporal transformation of linear head translation signals to angular eye velocity commands is accomplished primarily by the addition of viewing distance multiplied, centrally integrated, otolith regular afferent signals to angular VOR pathways.

Large Angle Satellite Attitude Maneuvers

NASA Technical Reports Server (NTRS)

Cochran, J. E.; Junkins, J. L.

1975-01-01

Two methods are proposed for performing large angle reorientation maneuvers. The first method is based upon Euler's rotation theorem; an arbitrary reorientation is ideally accomplished by rotating the spacecraft about a line which is fixed in both the body and in space. This scheme has been found to be best suited for the case in which the initial and desired attitude states have small angular velocities. The second scheme is more general in that a general class of transition trajectories is introduced which, in principle, allows transfer between arbitrary orientation and angular velocity states. The method generates transition maneuvers in which the uncontrolled (free) initial and final states are matched in orientation and angular velocity. The forced transition trajectory is obtained by using a weighted average of the unforced forward integration of the initial state and the unforced backward integration of the desired state. The current effort is centered around practical validation of this second class of maneuvers. Of particular concern is enforcement of given control system constraints and methods for suboptimization by proper selection of maneuver initiation and termination times. Analogous reorientation strategies which force smooth transition in angular momentum and/or rotational energy are under consideration.

A measurement by BOOMERANG of multiple peaks in the angular power spectrum of the cosmic microwave background

NASA Technical Reports Server (NTRS)

Netterfield, C. B.; Ade, P. A. R.; Bock, J. J.; Bond, J. R.; Borrill, J.; Boscaleri, A.; Coble, K.; Contaldi, C. R.; Crill, B. P.; Bernardis, P. de;

Angular motion estimation using dynamic models in a gyro-free inertial measurement unit.

PubMed

Edwan, Ezzaldeen; Knedlik, Stefan; Loffeld, Otmar

2012-01-01

In this paper, we summarize the results of using dynamic models borrowed from tracking theory in describing the time evolution of the state vector to have an estimate of the angular motion in a gyro-free inertial measurement unit (GF-IMU). The GF-IMU is a special type inertial measurement unit (IMU) that uses only a set of accelerometers in inferring the angular motion. Using distributed accelerometers, we get an angular information vector (AIV) composed of angular acceleration and quadratic angular velocity terms. We use a Kalman filter approach to estimate the angular velocity vector since it is not expressed explicitly within the AIV. The bias parameters inherent in the accelerometers measurements' produce a biased AIV and hence the AIV bias parameters are estimated within an augmented state vector. Using dynamic models, the appended bias parameters of the AIV become observable and hence we can have unbiased angular motion estimate. Moreover, a good model is required to extract the maximum amount of information from the observation. Observability analysis is done to determine the conditions for having an observable state space model. For higher grades of accelerometers and under relatively higher sampling frequency, the error of accelerometer measurements is dominated by the noise error. Consequently, simulations are conducted on two models, one has bias parameters appended in the state space model and the other is a reduced model without bias parameters.

Angular Motion Estimation Using Dynamic Models in a Gyro-Free Inertial Measurement Unit

PubMed Central

Edwan, Ezzaldeen; Knedlik, Stefan; Loffeld, Otmar

2012-01-01

In this paper, we summarize the results of using dynamic models borrowed from tracking theory in describing the time evolution of the state vector to have an estimate of the angular motion in a gyro-free inertial measurement unit (GF-IMU). The GF-IMU is a special type inertial measurement unit (IMU) that uses only a set of accelerometers in inferring the angular motion. Using distributed accelerometers, we get an angular information vector (AIV) composed of angular acceleration and quadratic angular velocity terms. We use a Kalman filter approach to estimate the angular velocity vector since it is not expressed explicitly within the AIV. The bias parameters inherent in the accelerometers measurements' produce a biased AIV and hence the AIV bias parameters are estimated within an augmented state vector. Using dynamic models, the appended bias parameters of the AIV become observable and hence we can have unbiased angular motion estimate. Moreover, a good model is required to extract the maximum amount of information from the observation. Observability analysis is done to determine the conditions for having an observable state space model. For higher grades of accelerometers and under relatively higher sampling frequency, the error of accelerometer measurements is dominated by the noise error. Consequently, simulations are conducted on two models, one has bias parameters appended in the state space model and the other is a reduced model without bias parameters. PMID:22778586

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

Harak, B. A. de; Bartschat, K.; Martin, N. L. S.

Angular distribution and spectral (e,2e) measurements are reported for the helium autoionizing levels (2s{sup 2}){sup 1}S, (2p{sup 2}){sup 1}D, and (2s2p){sup 1}P. A special out-of-plane geometry is used where the ejected electrons are emitted in a plane perpendicular to the scattered electron direction. The kinematics are chosen so that this plane contains the momentum-transfer direction. While the recoil peak almost vanishes in the angular distribution for direct ionization, it remains significant for the autoionizing levels and exhibits a characteristic shape for each orbital angular momentum L=0,1,2. A second-order model in the projectile-target interaction correctly reproduces the observed magnitudes of themore » recoil peaks, but is a factor of 2 too large in the central out-of-plane region. Observed (e,2e) energy spectra for the three resonances over the full angular range are well reproduced by the second-order calculation. Calculations using a first-order model fail to reproduce both the magnitudes of the recoil peaks and the spectral line profiles.« less

Comparison of trunk kinematics in trunk training exercises and throwing.

PubMed

Stodden, David F; Campbell, Brian M; Moyer, Todd M

2008-01-01

Strength and conditioning professionals, as well as coaches, have emphasized the importance of training the trunk and the benefits it may have on sport performance and reducing the potential for injury. However, no data on the efficacy of trunk training support such claims. The purpose of this study was to examine the maximum differential trunk rotation and maximum angular velocities of the pelvis and upper torso of participants while they performed 4 trunk exercises (seated band rotations, cross-overs, medicine ball throws, and twisters) and compare these trunk exercise kinematics with the trunk kinematics demonstrated in actual throwing performance. Nine NCAA Division I baseball players participated in this study. Each participant's trunk kinematics was analyzed while he performed 5 repetitions of each exercise in both dominant and nondominant rotational directions. Results indicated maximum differentiated rotation in all 4 trunk exercises was similar to maximum differentiated rotation (approximately 50-60 degrees) demonstrated in throwing performance. Maximum angular velocities of the pelvis and upper torso in the trunk exercises were appreciably slower (approximately 50% or less) than the angular velocities demonstrated during throwing performance. Incorporating trunk training exercises that demonstrate sufficient trunk ranges of motion and velocities into a strength and conditioning program may help to increase ball velocity and/or decrease the risk injury.

Vestibular response to pseudorandom angular velocity input: progress report.

PubMed

Lessard, C S; Wong, W C

1987-09-01

Space motion sickness was not reported during the first Apollo missions; however, since Apollo 8 through the current Shuttle and Skylab missions, approximately 50% of the crewmembers have experienced instances of space motion sickness. One of NASA's efforts to resolve the space adaptation syndrome is to model the vestibular response for both basic knowledge and as a possible predictor of an individual's susceptibility to the disorder. This report describes a method to analyze the vestibular system when subjected to a pseudorandom angular velocity input.

Synthesis of a correcting filter with phase stabilization of the angular velocity of a synchronous motor by the feedback system method

NASA Technical Reports Server (NTRS)

Kazlauskas, K. A.; Kurlavichus, A. I.

1973-01-01

The operating characteristics of a synchronous electric motor are discussed. A system of phase stabilization of the instantaneous angular velocity of rotation of a synchronous-reaction motor is diagrammed. A mathematical model is developed to show the parameters which affect the operation of the motor. The selection of a correcting filter to use with the motor in order to reduce the reaction of the system to interference is explained.

COSMIC VORTICITY AND THE ORIGIN HALO SPINS

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

Libeskind, Noam I.; Steinmetz, Matthias; Gottloeber, Stefan

2013-04-01

In the standard model of cosmology, structure emerges out of a non-rotational flow and the angular momentum of collapsing halos is induced by tidal torques. The growth of angular momentum in the linear and quasi-linear phases is associated with a shear, curl-free, flow and it is well described within the linear framework of tidal torque theory (TTT). However, TTT ceases to be applicable as halos approach turnaround when their ambient flow field becomes rotational. Subsequently, halos become embedded in a vortical flow field and the growth of their angular momentum is affected by the vorticity of their ambient velocity field.more » Using a cosmological simulation, we have examined the importance of the curl of the velocity field in determining halo spin, finding a significant alignment between the two: the vorticity tends to be perpendicular to the axis of the fastest collapse of the velocity shear tensor (e{sub 1}). This is independent of halo masses and cosmic web environment. Our results agree with previous findings on the tendency of halo spin to be perpendicular to e{sub 1}, and of the spin of (simulated) halos and (observed) galaxies to be aligned with the large-scale structure. It follows that angular momentum growth proceeds in two distinct phases. First, the angular momentum emerges out of a shear, curl-free, potential flow, as described by TTT. In the second phase, in which halos approach virialization, the angular momentum emerges out of a vortical flow and halo spin becomes partially aligned with the vorticity of the ambient flow field.« less

Solar flares, coronal mass ejections and solar energetic particle event characteristics

NASA Astrophysics Data System (ADS)

Papaioannou, Athanasios; Sandberg, Ingmar; Anastasiadis, Anastasios; Kouloumvakos, Athanasios; Georgoulis, Manolis K.; Tziotziou, Kostas; Tsiropoula, Georgia; Jiggens, Piers; Hilgers, Alain

2016-12-01

A new catalogue of 314 solar energetic particle (SEP) events extending over a large time span from 1984 to 2013 has been compiled. The properties as well as the associations of these SEP events with their parent solar sources have been thoroughly examined. The properties of the events include the proton peak integral flux and the fluence for energies above 10, 30, 60 and 100 MeV. The associated solar events were parametrized by solar flare (SF) and coronal mass ejection (CME) characteristics, as well as related radio emissions. In particular, for SFs: the soft X-ray (SXR) peak flux, the SXR fluence, the heliographic location, the rise time and the duration were exploited; for CMEs the plane-of-sky velocity as well as the angular width were utilized. For radio emissions, type III, II and IV radio bursts were identified. Furthermore, we utilized element abundances of Fe and O. We found evidence that most of the SEP events in our catalogue do not conform to a simple two-class paradigm, with the 73% of them exhibiting both type III and type II radio bursts, and that a continuum of event properties is present. Although, the so-called hybrid or mixed events are found to be present in our catalogue, it was not possible to attribute each SEP event to a mixed/hybrid sub-category. Moreover, it appears that the start of the type III burst most often precedes the maximum of the SF and thus falls within the impulsive phase of the associated SF. At the same time, type III bursts take place within ≈5.22 min, on average, in advance from the time of maximum of the derivative of the SXR flux (Neupert effect). We further performed a statistical analysis and a mapping of the logarithm of the proton peak flux at E > 10 MeV, on different pairs of the parent solar source characteristics. This revealed correlations in 3-D space and demonstrated that the gradual SEP events that stem from the central part of the visible solar disk constitute a significant radiation risk. The velocity of the associated CMEs, as well as the SXR peak flux and fluence, are all fairly significantly correlated to both the proton peak flux and the fluence of the SEP events in our catalogue. The strongest correlation to SEP characteristics is manifested by the CME velocity.

Modeling of functional trunk muscle performance: interfacing ergonomics and spine rehabilitation in response to the ADA.

PubMed

Khalaf, K A; Parnianpour, M; Sparto, P J; Simon, S R

1997-10-01

The combination of increasing costs of musculoskeletal injuries and the implementation of the Americans with Disabilities Act (ADA) has created the need for a more objective functional understanding of dynamic trunk performance. In this study, trunk extensor and flexor strengths were measured as a function of angular position and velocity for 20 subjects performing maximum isometric and isokinetic exertions. Results indicate that trunk strength is significantly influenced by trunk angular position, trunk angular velocity, gender, and direction, as well as by the interaction between trunk angular position and velocity. Three-dimensional surfaces of trunk strength in response to trunk angular position and velocity were constructed for each subject per direction. Such data presentation is more accurate and gives better insight about the strength profile of an individual than does the traditional use of a single strength value. The joint strength capacity profiles may be combined with joint torque requirements from a manual material handling task, such as a lifting task, to compute the dynamic utilization ratio for the trunk muscles. This ratio can be used as a unified measure of both task demand and functional capacity to guide job assignment, return to work, and prognosis during the rehabilitation processes. Furthermore, the strength regressions developed in this study would provide dynamic strength limits that can be used as functional constraints in the computer simulation of physical activities, such as lifting. In light of the ADA, this would be of great value in predicting the consequences of task modifications and/or workstation alterations without subjecting an injured worker or an individual with a disability to unnecessary testing.

Velocity-free attitude coordinated tracking control for spacecraft formation flying.

PubMed

Hu, Qinglei; Zhang, Jian; Zhang, Youmin

2018-02-01

This article investigates the velocity-free attitude coordinated tracking control scheme for a group of spacecraft with the assumption that the angular velocities of the formation members are not available in control feedback. Initially, an angular velocity observer is constructed based on each individual's attitude quarternion. Then, the distributed attitude coordinated control law is designed by using the observed states, in which adaptive control method is adopted to handle the external disturbances. Stability of the overall closed-loop system is analyzed theoretically, which shows the system trajectory converges to a small set around origin with fast convergence rate. Numerical simulations are performed to demonstrate fast convergence and improved tracking performance of the proposed control strategy. Copyright © 2017 ISA. Published by Elsevier Ltd. All rights reserved.

Influence of movement parameters on area 18 neurones in the cat.

PubMed

Orban, G A; Callens, M

1977-10-24

In cats, 107 area 18 neurones with identified FR type, 10-50 degrees from the visual axis, were tested for the influence of direction, velocity and amplitude of movement. These three parameters are believed to be the primary parameters of a movement analysing system. 94% of the neurones were influenced by the direction of movement, all of them by the angular velocity and 16% by the amplitude of movement. For each of the primary parameters, tuning curves were established. Angular velocity influenced not only the response magnitude but also the response latency and the direction bias. By preparing response amplitude functions at different velocities the influence of movement duration was ruled out. The association of functional properties and RF organization suggests a model of information processing in area 18 of the cat.

Demonstrating the Conservation of Angular Momentum Using Model Cars Moving along a Rotating Rod

ERIC Educational Resources Information Center

Abdul-Razzaq, Wathiq; Golubovic, Leonardo

2013-01-01

We have developed an exciting non-traditional experiment for our introductory physics laboratories to help students to understand the principle of conservation of angular momentum. We used electric toy cars moving along a long rotating rod. As the cars move towards the centre of the rod, the angular velocity of this system increases.…

Angular Multigrid Preconditioner for Krylov-Based Solution Techniques Applied to the Sn Equations with Highly Forward-Peaked Scattering

NASA Astrophysics Data System (ADS)

Turcksin, Bruno; Ragusa, Jean C.; Morel, Jim E.

2012-01-01

It is well known that the diffusion synthetic acceleration (DSA) methods for the Sn equations become ineffective in the Fokker-Planck forward-peaked scattering limit. In response to this deficiency, Morel and Manteuffel (1991) developed an angular multigrid method for the 1-D Sn equations. This method is very effective, costing roughly twice as much as DSA per source iteration, and yielding a maximum spectral radius of approximately 0.6 in the Fokker-Planck limit. Pautz, Adams, and Morel (PAM) (1999) later generalized the angular multigrid to 2-D, but it was found that the method was unstable with sufficiently forward-peaked mappings between the angular grids. The method was stabilized via a filtering technique based on diffusion operators, but this filtering also degraded the effectiveness of the overall scheme. The spectral radius was not bounded away from unity in the Fokker-Planck limit, although the method remained more effective than DSA. The purpose of this article is to recast the multidimensional PAM angular multigrid method without the filtering as an Sn preconditioner and use it in conjunction with the Generalized Minimal RESidual (GMRES) Krylov method. The approach ensures stability and our computational results demonstrate that it is also significantly more efficient than an analogous DSA-preconditioned Krylov method.

14 CFR 25.349 - Rolling conditions.

Code of Federal Regulations, 2013 CFR

2013-01-01

...(b): (1) Conditions corresponding to steady rolling velocities must be investigated. In addition, conditions corresponding to maximum angular acceleration must be investigated for airplanes with engines or other weight concentrations outboard of the fuselage. For the angular acceleration conditions, zero...

14 CFR 25.349 - Rolling conditions.

Code of Federal Regulations, 2014 CFR

2014-01-01

...(b): (1) Conditions corresponding to steady rolling velocities must be investigated. In addition, conditions corresponding to maximum angular acceleration must be investigated for airplanes with engines or other weight concentrations outboard of the fuselage. For the angular acceleration conditions, zero...

14 CFR 25.349 - Rolling conditions.

Code of Federal Regulations, 2012 CFR

2012-01-01

...(b): (1) Conditions corresponding to steady rolling velocities must be investigated. In addition, conditions corresponding to maximum angular acceleration must be investigated for airplanes with engines or other weight concentrations outboard of the fuselage. For the angular acceleration conditions, zero...

14 CFR 25.349 - Rolling conditions.

Code of Federal Regulations, 2011 CFR

2011-01-01

...(b): (1) Conditions corresponding to steady rolling velocities must be investigated. In addition, conditions corresponding to maximum angular acceleration must be investigated for airplanes with engines or other weight concentrations outboard of the fuselage. For the angular acceleration conditions, zero...

Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. I. Normal responses

NASA Technical Reports Server (NTRS)

Minor, L. B.; Lasker, D. M.; Backous, D. D.; Hullar, T. E.; Shelhamer, M. J. (Principal Investigator)

1999-01-01

The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in five squirrel monkeys with intact vestibular function. The VOR evoked by steps of acceleration in darkness (3,000 degrees /s(2) reaching a velocity of 150 degrees /s) began after a latency of 7.3 +/- 1.5 ms (mean +/- SD). Gain of the reflex during the acceleration was 14.2 +/- 5.2% greater than that measured once the plateau head velocity had been reached. A polynomial regression was used to analyze the trajectory of the responses to steps of acceleration. A better representation of the data was obtained from a polynomial that included a cubic term in contrast to an exclusively linear fit. For sinusoidal rotations of 0.5-15 Hz with a peak velocity of 20 degrees /s, the VOR gain measured 0.83 +/- 0.06 and did not vary across frequencies or animals. The phase of these responses was close to compensatory except at 15 Hz where a lag of 5.0 +/- 0.9 degrees was noted. The VOR gain did not vary with head velocity at 0.5 Hz but increased with velocity for rotations at frequencies of >/=4 Hz (0. 85 +/- 0.04 at 4 Hz, 20 degrees /s; 1.01 +/- 0.05 at 100 degrees /s, P < 0.0001). No responses to these rotations were noted in two animals that had undergone bilateral labyrinthectomy indicating that inertia of the eye had a negligible effect for these stimuli. We developed a mathematical model of VOR dynamics to account for these findings. The inputs to the reflex come from linear and nonlinear pathways. The linear pathway is responsible for the constant gain across frequencies at peak head velocity of 20 degrees /s and also for the phase lag at higher frequencies being less than that expected based on the reflex delay. The frequency- and velocity-dependent nonlinearity in VOR gain is accounted for by the dynamics of the nonlinear pathway. A transfer function that increases the gain of this pathway with frequency and a term related to the third power of head velocity are used to represent the dynamics of this pathway. This model accounts for the experimental findings and provides a method for interpreting responses to these stimuli after vestibular lesions.

Active zone of the nucleus of the quasar 3C 273

NASA Astrophysics Data System (ADS)

Matveyenko, L. I.; Seleznev, S. V.

2017-04-01

The superfine structure of the quasar 3C 273 has been investigated at wavelengths λ = 2 and 6 cm with angular resolutions up to φ = 20 μas for epochs 2005-2014. We have identified a nozzle and a bipolar outflow: a jet and a counterjet consisting of coaxial high- and low-velocity components. The separation between the nozzles in the plane of the sky is Δ ρ = 0.84 ± 0.16 pc; the flow ejection velocity is v ≤ 0.1 c. The nozzle brightness temperature reaches T b ≈ 45 × 1012 K, φ = 20 μas, λ = 2 cm. The ejected electrons radiatively cool at a distance up to ≤4 pc. However, the jet afterglow is observed at a 8% level at a distance up to ρ ≈ 16 pc; the acceleration compensates for the radiative losses. The reduction in the emission level of the central flow at large distances determines the jet bifurcation. The counterjet shape is a mirror reflection of the initial part of the jet, suggesting a symmetry and identity of the ejected flows. The counterjet and jet nozzles are in the near and remote parts of the active region, respectively. The emission from the nozzles is absorbed by a factor of 2 and 15, respectively. The absorption decreases with increasing distance and the brightness of the jet fragments rises to its maximum at 0.5 pc from the nozzle. Arclike structures, arm fragments, are observed in the region of the nozzles. The relativistic plasma comes to the nozzles and is ejected. The brightness temperature of the arclike structures reaches 10% of the peak value, which is determined by the a smaller optical depth, the visibility in the transverse direction. The central high-velocity flow is surrounded by low-velocity components, hollow tubes being ejected as an excess angular momentum is accumulated. The remainder of the material flows along the arms toward the disk center until the next accumulation of an excess angular momentum and the process is repeated. The diameter of the outer nozzle is Ø = 25 pc and, further out, decreases exponentially; Ø n ≈ 80 exp(-1.15 n) pc. The flow kinematics, collimation, and acceleration have a vortical nature. Ring currents producing magnetic fields, which accelerate and stabilize the processes, are generated in the rotating flows (tubes). The tangential directions of the currents are observed as parallel chains of components.

Fast two-position initial alignment for SINS using velocity plus angular rate measurements

NASA Astrophysics Data System (ADS)

Chang, Guobin

2015-10-01

An improved two-position initial alignment model for strapdown inertial navigation system is proposed. In addition to the velocity, angular rates are incorporated as measurements. The measurement equations in full three channels are derived in both navigation and body frames and the latter of which is found to be preferred. The cross-correlation between the process and the measurement noises is analyzed and addressed in the Kalman filter. The incorporation of the angular rates, without introducing additional device or external signal, speeds up the convergence of estimating the attitudes, especially the heading. In the simulation study, different algorithms are tested with different initial errors, and the advantages of the proposed method compared to the conventional one are validated by the simulation results.

Analysis of nonreciprocal noise based on mode splitting in a high-Q optical microresonator

NASA Astrophysics Data System (ADS)

Yang, Zhaohua; Xiao, Yarong; Huo, Jiayan; Shao, Hui

2018-01-01

The whispering gallery mode optical microresonator offers a high quality factor, which enables it to act as the core component of a high sensitivity resonator optic gyro; however, nonreciprocal noise limits its precision. Considering the Sagnac effect, i.e. mode splitting in high-quality optical micro-resonators, we derive the explicit expression for the angular velocity versus the splitting amount, and verify the sensing mechanism by simulation using finite element method. Remarkably, the accuracy of the angular velocity measurement in the whispering gallery mode optical microresonator with a quality factor of 108 is 106 °/s. We obtain the optimal coupling position of the novel angular velocity sensing system by detecting the output transmittance spectra of different vertical coupling distances and axial coupling positions. In addition, the reason for the nonreciprocal phenomenon is determined by theoretical analysis of the evanescent distribution of a tapered fiber. These results will provide an effective method and a theoretical basis for suppression of the nonreciprocal noise.

Phase Resolved Angular Velocity Control of Cross Flow Turbines

NASA Astrophysics Data System (ADS)

Strom, Benjamin; Brunton, Steven; Polagye, Brian

2015-11-01

Cross flow turbines have a number of operational advantages for the conversion of kinetic energy in marine or fluvial currents, but they are often less efficient than axial flow devices. Here a control scheme is presented in which the angular velocity of a cross flow turbine with two straight blades is prescribed as a function of azimuthal blade position, altering the time-varying effective angle of attack. Flume experiments conducted with a scale model turbine show approximately an 80% increase in turbine efficiency versus optimal constant angular velocity and constant resistive torque control schemes. Torque, drag, and lateral forces on one- and two-bladed turbines are analyzed and interpreted with bubble flow visualization to develop a simple model that describes the hydrodynamics responsible for the observed increase in mean efficiency. Challenges associated with implementing this control scheme on commercial-scale devices are discussed. If solutions are found, the performance increase presented here may impact the future development of cross flow turbines.

Particle flow within a transonic compressor rotor passage with application to laser-Doppler velocimetry

NASA Technical Reports Server (NTRS)

Maxwell, B. R.

1975-01-01

A theoretical analysis was conducted of the dynamic behavior of micron size particles moving in the three-dimensional flow field of a rotating transonic axial-flow air compressor rotor. The particle velocity lag and angular deviation relative to the gas were determined as functions of particle diameter, mass density and radial position. Particle size and density were varied over ranges selected to correspond to typical laser-Doppler velocimeter (LDV) flow field mapping applications. It was found that the particles move essentially on gas stream surfaces and that particle tracking is relatively insensitive to the rotor radial coordinate. Velocity lag and angular deviation increased whenever particle size or mass density increased, and particle tracking was more sensitive to a change in particle diameter than to a corresponding change in mass density. Results indicated that velocity and angular deviations generally less than 1 percent and 1 degree could be achieved with 1 gm/cc tracer particles with diameters of 1 micron or less.

Simulation and experimental validation of the dynamical model of a dual-rotor vibrotactor

NASA Astrophysics Data System (ADS)

Miklós, Á.; Szabó, Z.

2015-01-01

In this work, a novel design for small vibrotactors called the Dual Excenter is presented, which makes it possible to produce vibrations with independently adjustable frequency and amplitude. This feature has been realized using two coaxially aligned eccentric rotors, which are driven by DC motors independently. The prototype of the device has been built, where mechanical components are integrated on a frame with two optical sensors for the measurement of angular velocity and phase angle. The system is equipped with a digital controller. Simulations confirm the results of analytical investigations and they allow us to model the sampling method of the signals of the angular velocity and the phase angle between the rotors. Furthermore, we model the discrete behavior of the controller, which is a PI controller for the angular velocities and a PID controller for the phase angle. Finally, simulation results are compared to experimental ones, which show that the Dual Excenter concept is feasible.

Sculling Compensation Algorithm for SINS Based on Two-Time Scale Perturbation Model of Inertial Measurements

PubMed Central

Wang, Lingling; Fu, Li

2018-01-01

In order to decrease the velocity sculling error under vibration environments, a new sculling error compensation algorithm for strapdown inertial navigation system (SINS) using angular rate and specific force measurements as inputs is proposed in this paper. First, the sculling error formula in incremental velocity update is analytically derived in terms of the angular rate and specific force. Next, two-time scale perturbation models of the angular rate and specific force are constructed. The new sculling correction term is derived and a gravitational search optimization method is used to determine the parameters in the two-time scale perturbation models. Finally, the performance of the proposed algorithm is evaluated in a stochastic real sculling environment, which is different from the conventional algorithms simulated in a pure sculling circumstance. A series of test results demonstrate that the new sculling compensation algorithm can achieve balanced real/pseudo sculling correction performance during velocity update with the advantage of less computation load compared with conventional algorithms. PMID:29346323

D = 5 Einstein-Maxwell-Chern-Simons black holes.

PubMed

Kunz, Jutta; Navarro-Lérida, Francisco

2006-03-03

Five-dimensional Einstein-Maxwell-Chern-Simons theory with a Chern-Simons coefficient lambda = 1 has supersymmetric black holes with a vanishing horizon angular velocity but finite angular momentum. Here supersymmetry is associated with a borderline between stability and instability, since for lambda > 1 a rotational instability arises, where counterrotating black holes appear, whose horizon rotates in the opposite sense to the angular momentum. For lambda > 2 black holes are no longer uniquely characterized by their global charges, and rotating black holes with vanishing angular momentum appear.

Determination of Residual Stress in Composite Materials Using Ultrasonic Waves

NASA Technical Reports Server (NTRS)

Rokhlin, S. I.

1997-01-01

The performance of high temperature composites can be significantly affected by the presence of residual stresses. These stresses arise during cooling processes from fabrication to room temperature due to mismatch of thermal expansion coefficients between matrix and fiber materials. This effect is especially pronounced in metal matrix and intermetallic composites. It can lead to plastic deformations, matrix cracking and fiber/matrix interface debonding. In this work the feasibility of ultrasonic techniques for residual stress assessment in composites is addressed. A novel technique for absolute stress determination in orthotropic materials from angular dependencies of ultrasonic velocities is described. The technique is applicable for determination of both applied and residual stresses and does not require calibration measurements on a reference sample. The important advantage of this method is that stress is determined simultaneously with stress-dependent elastic constants and is thus decoupled from the material texture. It is demonstrated that when the principal plane stress directions coincide with acoustical axes, the angular velocity data in the plane perpendicular to the stress plane may be used to determine both stress components. When the stress is off the acoustical axes, the shear and the difference of the normal stress components may be determined from the angular dependence of group velocities in the plane of stresses. Synthetic sets of experimental data corresponding to materials with different anisotropy and stress levels are used to check the applicability of the technique. The method is also verified experimentally. A high precision ultrasonic wave transmission technique is developed to measure angular dependence of ultrasonic velocities. Examples of stress determination from experimental velocity data are given. A method is presented for determination of velocities of ultrasonic waves propagating through the composite material with residual stresses. It is based on the generalized self-consistent multiple scattering model. Calculation results for longitudinal and shear ultrasonic wave velocities propagating perpendicular to the fibers direction in SCS-6/Ti composite with and without residual stresses are presented. They show that velocity changes due to presence of stresses are of order 1%.

Controlled banked turns in coleopteran flight measured by a miniature wireless inertial measurement unit.

PubMed

Li, Yao; Cao, Feng; Thang Vo Doan, Tat; Sato, Hirotaka

2016-09-28

The mechanisms and principles of insect flight have long been investigated by researchers working on micro and nano air vehicles (MAVs/NAVs). However, studies of insect flight maneuvers require high speed filming and high spatial resolution in a small experimental space, or the tethering of the insect to a fixed place. Under such artificial conditions, the insects may deviate its flying behavior from that of regular flight. In this study, we mounted a tiny wireless system, or 'backpack', on live beetles (Mecynorrhina torquata; length 62 ± 8 mm; mass 7.4 ± 1.3 g) freely flying in a large laboratory space. The backpack contains a micro inertial measurement unit (IMU) that was especially designed and manufactured for this purpose. Owing to the small mass (∼1.30 g) and dimensions (∼2.3 cm 2 ) of the backpack and the high accuracy of the IMU, we could remotely record the beetle in free flight. The free flight data revealed a strong linear correlation between the roll angle and yaw angular velocity. The strength of the correlation was quantified by the correlation coefficients and mean values. The change in roll angle preceded the change in yaw angular velocity. Moreover, there were frequent fluctuations in the roll angular velocity, which were uncorrelated with the yaw angular velocity. Apart from the strong correlation, these findings imply that Mecynorrhina torquata actively manipulates its roll rotation without coupling to the yaw rotation.

Angular momentum of the N2H+ cores in the Orion A cloud

NASA Astrophysics Data System (ADS)

Tatematsu, Ken'ichi; Ohashi, Satoshi; Sanhueza, Patricio; Nguyen Luong, Quang; Umemoto, Tomofumi; Mizuno, Norikazu

2016-04-01

We have analyzed the angular momentum of the molecular cloud cores in the Orion A giant molecular cloud observed in the N2H+ J = 1-0 line with the Nobeyama 45 m radio telescope. We have measured the velocity gradient using position-velocity diagrams passing through core centers, and made sinusoidal fits against the position angle. Twenty-seven out of 34 N2H+ cores allowed us to measure the velocity gradient without serious confusion. The derived velocity gradient ranges from 0.5 to 7.8 km s-1 pc-1. We marginally found that the specific angular momentum J/M (against the core radius R) of the Orion N2H+ cores tends to be systematically larger than that of molecular cloud cores in cold dark clouds obtained by Goodman et al., in the J/M-R relation. The ratio β of rotational to gravitational energy is derived to be β = 10-2.3±0.7, and is similar to that obtained for cold dark cloud cores in a consistent definition. The large-scale rotation of the ∫-shaped filament of the Orion A giant molecular cloud does not likely govern the core rotation at smaller scales.

The impact of Nordic walking training on the gait of the elderly.

PubMed

Ben Mansour, Khaireddine; Gorce, Philippe; Rezzoug, Nasser

2018-03-27

The purpose of the current study was to define the impact of regular practice of Nordic walking on the gait of the elderly. Thereby, we aimed to determine whether the gait characteristics of active elderly persons practicing Nordic walking are more similar to healthy adults than that of the sedentary elderly. Comparison was made based on parameters computed from three inertial sensors during walking at a freely chosen velocity. Results showed differences in gait pattern in terms of the amplitude computed from acceleration and angular velocity at the lumbar region (root mean square), the distribution (Skewness) quantified from the vertical and Euclidean norm of the lumbar acceleration, the complexity (Sample Entropy) of the mediolateral component of lumbar angular velocity and the Euclidean norm of the shank acceleration and angular velocity, the regularity of the lower limbs, the spatiotemporal parameters and the variability (standard deviation) of stance and stride durations. These findings reveal that the pattern of active elderly differs significantly from sedentary elderly of the same age while similarity was observed between the active elderly and healthy adults. These results advance that regular physical activity such as Nordic walking may counteract the deterioration of gait quality that occurs with aging.

Effect of Reduced Stiffness Dance Flooring on Lower Extremity Joint Angular Trajectories During a Ballet Jump.

PubMed

Hackney, James; Brummel, Sara; Newman, Mary; Scott, Shannon; Reinagel, Matthew; Smith, Jennifer

2015-09-01

We carried out a study to investigate how low stiffness flooring may help prevent overuse injuries of the lower extremity in dancers. It was hypothesized that performing a ballet jump (sauté) on a reduced stiffness dance floor would decrease maximum joint flexion angles and negative angular velocities at the hips, knees, or ankles compared to performing the same jump on a harder floor. The participants were 15 young adult female dancers (age range 18 to 28, mean = 20.89 ± 2.93 years) with at least 5 years of continuous ballet experience and without history of serious lower body injury, surgery, or recent pain. They performed sautés on a (low stiffness) Harlequin ® WoodSpring Floor and on a vinyl-covered hardwood on concrete floor. Maximum joint flexion angles and negative velocities at bilateral hips, knees, and ankles were measured with the "Ariel Performance Analysis System" (APAS). Paired one-tailed t-tests yielded significant decreases in maximum knee angle (average decrease = 3.4° ± 4.2°, p = 0.026) and angular negative velocity of the ankles (average decrease = 18.7°/sec ± 27.9°/sec, p = 0.009) with low stiffness flooring. If the knee angle is less acute, then the length of the external knee flexion moment arm will also be shorter and result in a smaller external knee flexion moment, given an equal landing force. Also, high velocities of eccentric muscle contraction, which are necessary to control negative angular velocity of the ankle joint, are associated with higher risk of musculotendinous injury. Hence, our findings indicate that reduced floor stiffness may indeed help decrease the likelihood of lower extremity injuries.

Comparative analyses of bicyclists and motorcyclists in vehicle collisions focusing on head impact responses.

PubMed

Wang, Xinghua; Peng, Yong; Yi, Shengen

2017-11-01

To investigate the differences of the head impact responses between bicyclists and motorcyclists in vehicle collisions. A series of vehicle-bicycle and vehicle-motorcycle lateral impact simulations on four vehicle types at seven vehicle speeds (30, 35, 40, 45, 50, 55 and 60 km/h) and three two-wheeler moving speeds (5, 7.5 and 10 km/h for bicycle, 10, 12.5 and 15 km/h for motorcycle) were established based on PC-Crash software. To further comprehensively explore the differences, additional impact scenes with other initial conditions, such as impact angle (0, π/3, 2π/3 and π) and impact position (left, middle and right part of vehicle front-end), also were supplemented. And then, extensive comparisons were accomplished with regard to average head peak linear acceleration, average head impact speed, average head peak angular acceleration, average head peak angular speed and head injury severity. The results showed there were prominent differences of kinematics and body postures for bicyclists and motorcyclists even under same impact conditions. The variations of bicyclist head impact responses with the changing of impact conditions were a far cry from that of motorcyclists. The average head peak linear acceleration, average head impact speed and average head peak angular acceleration values were higher for motorcyclists than for bicyclists in most cases, while the bicyclists received greater average head peak angular speed values. And the head injuries of motorcyclists worsened faster with increased vehicle speed. The results may provide even deeper understanding of two-wheeler safety and contribute to improve the public health affected by road traffic accidents.

Multi-body dynamic coupling mechanism for generating throwing arm velocity during baseball pitching.

PubMed

Naito, Kozo; Takagi, Tokio; Kubota, Hideaki; Maruyama, Takeo

2017-08-01

The purpose of this study was to identify the detailed mechanism how the maximum throwing arm endpoint velocity is determined by the muscular torques and non-muscular interactive torques from the perspective of the dynamic coupling among the trunk, thorax and throwing and non-throwing arm segments. The pitching movements of ten male collegiate baseball pitchers were measured by a three-dimensional motion capture system. Using the induced-segmental velocity analysis (IVA) developed in this study, the maximum fingertip velocity of the throwing arm (MFV) was decomposed into each contribution of the muscular torques, passive motion-dependent torques due to gyroscopic moment, Coriolis force and centrifugal force, and other interactive torque components. The results showed that MFV (31.6±1.7m/s) was mainly attributed to two different mechanisms. The first is the passive motion-dependent effect on increasing the angular velocities of three joints (thorax rotation, elbow extension and wrist flexion). The second is the muscular torque effect of the shoulder internal rotation (IR) torque on generating IR angular velocity. In particular, the centrifugal force-induced elbow extension motion, which was the greatest contributor among individual joint contributions, was caused primarily by the angular velocity-dependent forces associated with the humerus, thorax, and trunk rotations. Our study also found that a compensatory mechanism was achieved by the negative and positive contributions of the muscular torque components. The current IVA is helpful to understand how the rapid throwing arm movement is determined by the dynamic coupling mechanism. Copyright © 2017 Elsevier B.V. All rights reserved.

Momentum and Angular Momentum Transfer in Oblique Impacts: Implications for Asteroid Rotations

NASA Astrophysics Data System (ADS)

Yanagisawa, Masahisa; Hasegawa, Sunao; Shirogane, Nobutoshi

1996-09-01

We conducted a series of high velocity oblique impact experiments (0.66-6.7 km/s) using polycarbonate (plastic) projectiles and targets made of mortar, aluminum alloy, and mild steel. We then calculated the efficiencies of momentum transfer for small cratering impacts. They are η = (M‧Vn‧)/(mvn) and ζ = (M‧Vt‧)/(mvt), wheremandvare the mass and velocity of a projectile, andM‧ andV‧ represent those of a postimpact target. Subscripts “n” and “t” denote the components normal and tangential to the target surface at the impact point, respectively. The main findings are: (1) η increases with increasing impact velocity; (2) η is larger for mortar than for ductile metallic targets; (3) ζ for mortar targets seems to increase with the impact velocity in the velocity range less than about 2 km/s and decrease with it in the higher velocity range; (4) ζ for the aluminum alloy targets correlates negatively with incident zenith angle of the projectile. In addition to these findings on the momentum transfer, we show theoretically that “ζL” can be expressed by η and ζ for small cratering impact. Here, ζLis the spin angular momentum that the target acquires at impact divided by the collisional angular momentum due to the projectile. This is an important parameter to study the collisional evolution of asteroid rotation. For a spherical target, ζLis shown to be well approximated by ζ.

Laser plasma interaction at an early stage of laser ablation

NASA Astrophysics Data System (ADS)

Lu, Y. F.; Hong, M. H.; Low, T. S.

1999-03-01

Laser scattering and its interaction with plasma during KrF excimer laser ablation of silicon are investigated by ultrafast phototube detection. There are two peaks in an optical signal with the first peak attributed to laser scattering and the second one to plasma generation. For laser fluence above 5.8 J/cm2, the second peak rises earlier to overlap with the first one. The optical signal is fitted by a pulse distribution for the scattered laser light and a drifted Maxwell-Boltzmann distribution with a center-of-mass velocity for the plasma. Peak amplitude and its arrival time, full width at half maximum (FWHM), starting time, and termination time of the profiles are studied for different laser fluences and detection angles. Laser pulse is scattered from both the substrate and the plasma with the latter part as a dominant factor during the laser ablation. Peak amplitude of the scattered laser signal increases but its FWHM decreases with the laser fluence. Angular distribution of the peak amplitude can be fitted with cosn θ(n=4) while the detection angle has no obvious influence on the FWHM. In addition, FWHM and peak amplitude of plasma signal increase with the laser fluence. However, starting time and peak arrival time of plasma signal reduce with the laser fluence. The time interval between plasma starting and scattered laser pulse termination is proposed as a quantitative parameter to characterize laser plasma interaction. Threshold fluence for the interaction is estimated to be 3.5 J/cm2. For laser fluence above 12.6 J/cm2, the plasma and scattered laser pulse distributions tend to saturate.

Adaptation to vestibular disorientation. II, Nystagmus and vertigo following high-velocity angular accelerations.

DOT National Transportation Integrated Search

1965-09-01

Professional figure skaters who, as part of their daily routine, subject themselves to high levels of disorientation-and vertigo-producing stimuli, were given a series of laboratory tests consisting primarily of caloric irrigations and mild angular a...

Absolute Plate Velocities from Seismic Anisotropy: Importance of Correlated Errors

NASA Astrophysics Data System (ADS)

Gordon, R. G.; Zheng, L.; Kreemer, C.

2014-12-01

The orientation of seismic anisotropy inferred beneath the interiors of plates may provide a means to estimate the motions of the plate relative to the deeper mantle. Here we analyze a global set of shear-wave splitting data to estimate plate motions and to better understand the dispersion of the data, correlations in the errors, and their relation to plate speed. The errors in plate motion azimuths inferred from shear-wave splitting beneath any one tectonic plate are shown to be correlated with the errors of other azimuths from the same plate. To account for these correlations, we adopt a two-tier analysis: First, find the pole of rotation and confidence limits for each plate individually. Second, solve for the best fit to these poles while constraining relative plate angular velocities to consistency with the MORVEL relative plate angular velocities. Our preferred set of angular velocities, SKS-MORVEL, is determined from the poles from eight plates weighted proportionally to the root-mean-square velocity of each plate. SKS-MORVEL indicates that eight plates (Amur, Antarctica, Caribbean, Eurasia, Lwandle, Somalia, Sundaland, and Yangtze) have angular velocities that differ insignificantly from zero. The net rotation of the lithosphere is 0.25±0.11º Ma-1 (95% confidence limits) right-handed about 57.1ºS, 68.6ºE. The within-plate dispersion of seismic anisotropy for oceanic lithosphere (σ=19.2°) differs insignificantly from that for continental lithosphere (σ=21.6°). The between-plate dispersion, however, is significantly smaller for oceanic lithosphere (σ=7.4°) than for continental lithosphere (σ=14.7°). Two of the slowest-moving plates, Antarctica (vRMS=4 mm a-1, σ=29°) and Eurasia (vRMS=3 mm a-1, σ=33°), have two of the largest within-plate dispersions, which may indicate that a plate must move faster than ≈5 mm a-1 to result in seismic anisotropy useful for estimating plate motion.

Kinematic Description of Elite Vs. Low Level Players in Team-Handball Jump Throw

PubMed Central

Wagner, Herbert; Buchecker, Michael; von Duvillard, Serge P.; Müller, Erich

2010-01-01

The jump throw is the most applied throwing technique in team- handball (Wagner et al., 2008); however, a comprehensive analysis of 3D-kinematics of the team-handball jump throw is lacking. Therefore, the purpose of our study was: 1) to measure differences in ball release speed in team- handball jump throw and anthropometric parameters between groups of different levels of performance and (2) to analyze upper body 3D-kinematics (flexion/extension and rotation) to determine significant differences between these groups. Three-dimensional kinematic data was analyzed via the Vicon MX 13 motion capturing system (Vicon Peak, Oxford, UK) from 26 male team-handball players of different performance levels (mean age: 21.2 ± 5.0 years). The participants were instructed to throw the ball (IHF Size 3) onto a target at 8 m distance, and to hit the center of a square of 1 × 1 m at about eye level (1.75 m), with maximum ball release speed. Significant differences between elite vs. low level players were found in the ball release speed (p < 0.001), body height (p < 0.05), body weight (p < 0.05), maximal trunk internal rotation (p < 0.05), trunk flexion (p < 0.01) and forearm pronation (p < 0.05) as well as trunk flexion (p < 0.05) and shoulder internal rotation (p < 0.001) angular velocity at ball release. Results of our study suggest that team-handball players who were taller and of greater body weight have the ability to achieve a higher ball release speed in the jump throw, and that an increase in trunk flexion and rotation angular velocity improve the performance in team-handball jump throw that should result in an increase of ball release speed. Key points Team-handball players who were taller and of greater body weight have the ability to achieve a higher ball release speed. An increase in trunk flexion, trunk rotation and shoulder internal rotation angular velocity should result in an increase of ball release speed. Trunk movements are normally well observable for experienced coaches, easy correctable and therefore practical to improve the performance in team-handball jump throw of low level players during training without using complex measurement devices. PMID:24149381

Kinematic description of elite vs. Low level players in team-handball jump throw.

PubMed

Wagner, Herbert; Buchecker, Michael; von Duvillard, Serge P; Müller, Erich

2010-01-01

The jump throw is the most applied throwing technique in team- handball (Wagner et al., 2008); however, a comprehensive analysis of 3D-kinematics of the team-handball jump throw is lacking. Therefore, the purpose of our study was: 1) to measure differences in ball release speed in team- handball jump throw and anthropometric parameters between groups of different levels of performance and (2) to analyze upper body 3D-kinematics (flexion/extension and rotation) to determine significant differences between these groups. Three-dimensional kinematic data was analyzed via the Vicon MX 13 motion capturing system (Vicon Peak, Oxford, UK) from 26 male team-handball players of different performance levels (mean age: 21.2 ± 5.0 years). The participants were instructed to throw the ball (IHF Size 3) onto a target at 8 m distance, and to hit the center of a square of 1 × 1 m at about eye level (1.75 m), with maximum ball release speed. Significant differences between elite vs. low level players were found in the ball release speed (p < 0.001), body height (p < 0.05), body weight (p < 0.05), maximal trunk internal rotation (p < 0.05), trunk flexion (p < 0.01) and forearm pronation (p < 0.05) as well as trunk flexion (p < 0.05) and shoulder internal rotation (p < 0.001) angular velocity at ball release. Results of our study suggest that team-handball players who were taller and of greater body weight have the ability to achieve a higher ball release speed in the jump throw, and that an increase in trunk flexion and rotation angular velocity improve the performance in team-handball jump throw that should result in an increase of ball release speed. Key pointsTeam-handball players who were taller and of greater body weight have the ability to achieve a higher ball release speed.An increase in trunk flexion, trunk rotation and shoulder internal rotation angular velocity should result in an increase of ball release speed.Trunk movements are normally well observable for experienced coaches, easy correctable and therefore practical to improve the performance in team-handball jump throw of low level players during training without using complex measurement devices.

Poor correlation between handgrip strength and isokinetic performance of knee flexor and extensor muscles in community-dwelling elderly women.

PubMed

Felicio, Diogo Carvalho; Pereira, Daniele Sirineu; Assumpção, Alexandra Miranda; de Jesus-Moraleida, Fabianna Resende; de Queiroz, Barbara Zille; da Silva, Juscelio Pereira; de Brito Rosa, Naysa Maciel; Dias, João Marcos Domingues; Pereira, Leani Souza Máximo

2014-01-01

To investigate the correlation between handgrip strength and performance of knee flexor and extensor muscles determined using an isokinetic dynamometer in community-dwelling elderly women. This was a cross-sectional study. Sample selection for the study was made by convenience, and 221 (71.07 ± 4.93 years) community-dwelling elderly women were included. Knee flexor and extensor muscle performance was measured using an isokinetic dynamometer Biodex System 3 Pro. The isokinetic variables chosen for analysis were peak torque, peak torque/bodyweight, total work/bodyweight, total work, average power, and agonist/antagonist ratio at the angular velocities of 60°/s and 180°/s. Assessment of handgrip strength was carried out using the Jamar dynamometer. Spearman's correlation coefficient was calculated to identify intervariable correlations. Only knee flexor peak torque (60°/s) and average power (60°/s), and knee extensor peak torque (180°/s) and total work (180°/s) were significantly (P < 0.05), yet poorly, correlated with handgrip strength (r < 0.30). The majority of analyses did not show any correlation between variables assessed by isokinetic dynamometer and handgrip dynamometer. Caution is required when generalizing handgrip strength as a predictor of global muscle strength in community-dwelling elderly women. © 2013 Japan Geriatrics Society.

Activity of the 1998 Leonid Shower From the Video Records

NASA Technical Reports Server (NTRS)

Jenniskens, Peter

1999-01-01

Video observations of the Leonid shower aboard two aircraft in the 1998 Leonid multi-instrument aircraft campaign and from ground locations in China are presented. Observing at altitude proved particularly effective, with four times higher rates due to low extinction and low angular velocity at the horizon. The rates, derived from a total of 2500 Leonid meteors, trace at least two distinct dust components. One dominated the night of 1998 November 16/17. This two-day wide component was rich in bright meteors with r = N (m + 1)/N (m) approximately equal 1.5 (s = 1.4) and peaked at an influx of 3.1 +/- 0.4 x 10(exp -12) /sq m.s (for particles of mass < 7 x 10(exp -5) g) at solar longitude lambda(sub 0) approximately equal 234.52 (Eq. J2000). The other more narrow component peaked on 1998 November 17/18 at lambda(sub 0) = 235.31 +/- 0.01. Rates were elevated above the broad component between lambda(sub 0) = 235.15 and 235.40, symmetric around the current node of the parent comet 55P/Tempel-Tuttle, peaking at 5.1 +/- 0.2 x 10(exp -12) /sq m.s. The population index was higher, r = 1.8 +/- 0.1 (s = 1.7), but not as high as in past Leonid storms (r = 3.0). The flux profile of this component has an unusual asymmetric shape, which implies a blend of contributions from at least two different but relatively recent epochs of ejection. The variation of r across the profile might be due to mass-dependent ejection velocities of the narrowest component. High rates of faint meteors occurred only in an isolated five-minute interval at lambda(sub 0) = 235.198, which is likely the result of a single meteoroid breakup in space.

Fractional Fourier transform of Lorentz-Gauss vortex beams

NASA Astrophysics Data System (ADS)

Zhou, GuoQuan; Wang, XiaoGang; Chu, XiuXiang

2013-08-01

An analytical expression for a Lorentz-Gauss vortex beam passing through a fractional Fourier transform (FRFT) system is derived. The influences of the order of the FRFT and the topological charge on the normalized intensity distribution, the phase distribution, and the orbital angular momentum density of a Lorentz-Gauss vortex beam in the FRFT plane are examined. The order of the FRFT controls the beam spot size, the orientation of the beam spot, the spiral direction of the phase distribution, the spatial orientation of the two peaks in the orbital angular momentum density distribution, and the magnitude of the orbital angular momentum density. The increase of the topological charge not only results in the dark-hollow region becoming large, but also brings about detail changes in the beam profile. The spatial orientation of the two peaks in the orbital angular momentum density distribution and the phase distribution also depend on the topological charge.

Differences of the Solar Magnetic Activity Signature in Velocity and Intensity Helioseismic Observations

NASA Astrophysics Data System (ADS)

Salabert, D.; García, R. A.; Jiménez, A.

2013-12-01

The high-quality, full-disk helioseismic observations continuously collected by the spectrophotometer GOLF and the three photometers VIRGO/SPMs onboard the SoHO spacecraft for 17 years now (since April 11, 1996, apart from the SoHO “vacations”) are absolutely unique for the study of the interior of the Sun and its variability with magnetic activity. Here, we look at the differences in the low-degree oscillation p-mode frequencies between radial velocity and intensity measurements taking into account all the known features of the p-mode profiles (e.g., the opposite peak asymmetry), and of the power spectrum (e.g., the presence of the higher degrees ℓ = 4 and 5 in the signal). We show that the intensity frequencies are higher than the velocity frequencies during the solar cycle with a clear temporal dependence. The response between the individual angular degrees is also different. Time delays are observed between the temporal variations in GOLF and VIRGO frequencies. Such analysis is important in order to put new constraints and to better understand the mechanisms responsible for the temporal variations of the oscillation frequencies with the solar magnetic activity as well as their height dependences in the solar atmosphere. It is also important for the study of the stellar magnetic activity using asteroseismic data.

Distribution and Kinematics of the HCN (3-2) Emission Down to the Innermost Region in the Envelope of the O-rich Star W Hydrae

NASA Astrophysics Data System (ADS)

Muller, Sébastien; Dinh-V-Trung; He, Jin-Hua; Lim, Jeremy

2008-09-01

We report high angular resolution observations of the HCN (3-2) line emission in the circumstellar envelope of the O-rich star W Hya with the Submillimeter Array. The proximity of this star allows us to image its molecular envelope with a spatial resolution of just ~40 AU, corresponding to about 10 times the stellar diameter. We resolve the HCN (3-2) emission and find that it is centrally peaked and has a roughly spherically symmetrical distribution. This shows that HCN is formed in the innermost region of the envelope (within ~10 stellar radii), which is consistent with predictions from pulsation-driven shock chemistry models, and rules out the scenario in which HCN forms through photochemical reactions in the outer envelope. Our model suggests that the envelope decreases steeply in temperature and increases smoothly in velocity with radius, inconsistent with the standard model for mass-loss driven by radiative pressure on dust grains. We detect a velocity gradient of ~5 km s-1 in the northwest-southeast direction over the central 40 AU. This velocity gradient is reminiscent of that seen in OH maser lines, and could be caused by the rotation of the envelope or by a weak bipolar outflow.

Can You Hear That Peak? Utilization of Auditory and Visual Feedback at Peak Limb Velocity.

PubMed

Loria, Tristan; de Grosbois, John; Tremblay, Luc

2016-09-01

At rest, the central nervous system combines and integrates multisensory cues to yield an optimal percept. When engaging in action, the relative weighing of sensory modalities has been shown to be altered. Because the timing of peak velocity is the critical moment in some goal-directed movements (e.g., overarm throwing), the current study sought to test whether visual and auditory cues are optimally integrated at that specific kinematic marker when it is the critical part of the trajectory. Participants performed an upper-limb movement in which they were required to reach their peak limb velocity when the right index finger intersected a virtual target (i.e., a flinging movement). Brief auditory, visual, or audiovisual feedback (i.e., 20 ms in duration) was provided to participants at peak limb velocity. Performance was assessed primarily through the resultant position of peak limb velocity and the variability of that position. Relative to when no feedback was provided, auditory feedback significantly reduced the resultant endpoint variability of the finger position at peak limb velocity. However, no such reductions were found for the visual or audiovisual feedback conditions. Further, providing both auditory and visual cues concurrently also failed to yield the theoretically predicted improvements in endpoint variability. Overall, the central nervous system can make significant use of an auditory cue but may not optimally integrate a visual and auditory cue at peak limb velocity, when peak velocity is the critical part of the trajectory.

Ground reaction forces and knee mechanics in the weight acceptance phase of a dance leap take-off and landing.

PubMed

Kulig, Kornelia; Fietzer, Abbigail L; Popovich, John M

2011-01-01

Aesthetic constraints allow dancers fewer technique modifications than other athletes to negotiate the demands of leaping. We examined vertical ground reaction force and knee mechanics during a saut de chat performed by healthy dancers. It was hypothesized that vertical ground reaction force during landing would exceed that of take-off, resulting in greater knee extensor moments and greater knee angular stiffness. Twelve dancers (six males, six females; age 18.9 ± 1.2 years, mass 59.2 ± 9.5 kg, height 1.68 ± 0.08 m, dance training 8.9 ± 5.1 years) with no history of low back pain or lower extremity pathology participated in the study. Saut de chat data were captured using an eight-camera Vicon system and AMTI force platforms. Peak ground reaction force was 26% greater during the landing phase, but did not result in increased peak knee extensor moments. Taking into account the 67% greater knee angular displacement during landing, this resulted in less knee angular stiffness during landing. In conclusion, landing was accomplished with less knee angular stiffness despite the greater peak ground reaction force. A link between decreased joint angular stiffness and increased soft tissue injury risk has been proposed elsewhere; therefore, landing from a saut de chat may be more injurious to the knee soft tissue than take-off.

Star formation with disc accretion and rotation. I. Stars between 2 and 22 M⊙ at solar metallicity

NASA Astrophysics Data System (ADS)

Haemmerlé, L.; Eggenberger, P.; Meynet, G.; Maeder, A.; Charbonnel, C.

2013-09-01

Context. The way angular momentum is built up in stars during their formation process may have an impact on their further evolution. Aims: In the framework of the cold disc accretion scenario, we study how angular momentum builds up inside the star during its formation for the first time and what the consequences are for its evolution on the main sequence (MS). Methods: Computation begins from a hydrostatic core on the Hayashi line of 0.7 M⊙ at solar metallicity (Z = 0.014) rotating as a solid body. Accretion rates depending on the luminosity of the accreting object are considered, which vary between 1.5 × 10-5 and 1.7 × 10-3 M⊙ yr-1. The accreted matter is assumed to have an angular velocity equal to that of the outer layer of the accreting star. Models are computed for a mass-range on the zero-age main sequence (ZAMS) between 2 and 22 M⊙. Results: We study how the internal and surface velocities vary as a function of time during the accretion phase and the evolution towards the ZAMS. Stellar models, whose evolution has been followed along the pre-MS phase, are found to exhibit a shallow gradient of angular velocity on the ZAMS. Typically, the 6 M⊙ model has a core that rotates 50% faster than the surface on the ZAMS. The degree of differential rotation on the ZAMS decreases when the mass increases (for a fixed value of vZAMS/vcrit). The MS evolution of our models with a pre-MS accreting phase show no significant differences with respect to those of corresponding models computed from the ZAMS with an initial solid-body rotation. Interestingly, there exists a maximum surface velocity that can be reached through the present scenario of formation for masses on the ZAMS larger than 8 M⊙. Typically, only stars with surface velocities on the ZAMS lower than about 45% of the critical velocity can be formed for 14 M⊙ models. Reaching higher velocities would require starting from cores that rotate above the critical limit. We find that this upper velocity limit is smaller for higher masses. In contrast, there is no restriction below 8 M⊙, and the whole domain of velocities to the critical point can be reached.

Low energy electron spectroscopy of C60 in collisions with fast bare ions: Observation of GDPR peak and its angular distribution

NASA Astrophysics Data System (ADS)

Kelkar, A. H.; Misra, D.; Chatterjee, S.; Kasthurirangan, S.; Agnihotri, A.; Tribedi, L. C.

2009-11-01

We report the first direct measurement of GDPR peak in heavy ion (4 MeV/u F9+) induced secondary electron DDCS (double differential cross section) spectrum of C60 fullerene. A peak corresponding to GDPR is seen at all angles and the angular distribution, showing a dip at 90°, is in contrast with ion-atom collisions, indicating plasmon oscillations along beam direction. A comparison has also been done between C60 and other gaseous targets as well as with state-of-the art theoretical models, based on density functional methods.

Dynamics of Liquid-Filled Projectiles

DTIC Science & Technology

1976-04-01

1 Estimate of Shape of the Free Surface of the Liquid in a Liquid-Pilled Projectile During Acceleration 6 CHAPTER II. ANGULAR ACCELERATION OF THE...LIQUID IN A LIQUID-FILLED PROJECTILE DURING FLIGHT 13 Liquid "Spinup" in Configuration A 13 Angular Acceleration of the Liquid in Con... Angular Acceleration. 13 2.2 Tangential Velocity of Liquid Versus Radial Position at Several Values of Time (Liquid Configuration A) 21 2.3 Tangential

Vestibular functions and sleep in space experiments. [using rhesus and owl monkeys

NASA Technical Reports Server (NTRS)

Perachio, A. A.

1977-01-01

Physical indices of sleep were continuously monitored in an owl monkey living in a chamber continuously rotating at a constant angular velocity. The electrophysiological data obtained from chronically implanted electrodes was analyzed to determine the chronic effects of vestibular stimulation on sleep and wakefulness cycles. The interaction of linear and angular acceleration on the vestibulo-ocular reflex was investigated in three rhesus monkeys at various angular accelerations.

Analysis of the ability of catcher's masks to attenuate head accelerations on impact with a baseball.

PubMed

Shain, Kellen S; Madigan, Michael L; Rowson, Steven; Bisplinghoff, Jill; Duma, Stefan M

2010-11-01

The goals of this study were to measure the ability of catcher's masks to attenuate head accelerations on impact with a baseball and to compare these head accelerations to established injury thresholds for mild traumatic brain injury. Testing involved using a pneumatic cannon to shoot baseballs at an instrumented Hybrid III headform (a 50th percentile male head and neck) with and without a catcher's mask on the head. The ball speed was controlled from approximately 26.8 to 35.8 m/s (60-80 mph), and the regulation National Collegiate Athletic Association baseballs were used. Research laboratory. None. Catcher's masks and impact velocity. The linear and angular head accelerations of the Hybrid III headform. Peak linear resultant acceleration was 140 to 180 g without a mask and 16 to 30 g with a mask over the range of ball's speed investigated. Peak angular resultant acceleration was 19 500 to 25 700 rad/s without a mask and 2250 to 3230 rad/s with a mask. The Head Injury Criterion was 93 to 181 without a mask and 3 to 13 with a mask, and the Severity Index was 110 to 210 without a mask and 3 to 15 with a mask. Catcher's masks reduced head acceleration metrics by approximately 85%. Head acceleration metrics with a catcher's mask were significantly lower than contemporary injury thresholds, yet reports in the mass media clearly indicate that baseball impacts to the mask still occasionally result in mild traumatic brain injuries. Further research is needed to address this apparent contradiction.

Latitudinal Transport of Angular Momentum by Cellular Flows Observed with MDI

NASA Technical Reports Server (NTRS)

Hathaway, David H.; Gilman, Peter A.; Beck, John G.; Rose, M. Franklin (Technical Monitor)

2001-01-01

We have analyzed Doppler velocity images from the MDI instrument on SOHO to determine the latitudinal transport of angular momentum by the cellular photospheric flows. Doppler velocity images from 60-days in May to July of 1996 were processed to remove the p-mode oscillations, the convective blue shift, the axisymmetric flows, and any instrumental artifacts. The remaining cellular flows were examined for evidence of latitudinal angular momentum transport. Small cells show no evidence of any such transport. Cells the size of supergranules (30,000 km in diameter) show strong evidence for a poleward transport of angular momentum. This would be expected if supergranules are influenced by the Coriolis force, and if the cells are elongated in an east-west direction. We find good evidence for just such an east-west elongation of the supergranules. This elongation may be the result of differential rotation shearing the cellular structures. Data simulations of this effect support the conclusion that elongated supergranules transport angular momentum from the equator toward the poles, Cells somewhat larger than supergranules do not show evidence for this poleward transport. Further analysis of the data is planned to determine if the direction of angular momentum transport reverses for even larger cellular structures. The Sun's rapidly rotating equator must be maintained by such transport somewhere within the convection zone.

Internally versus externally mediated triggers in the acquisition of visual targets in the horizontal plane.

PubMed

Kolev, Ognyan I; Reschke, Millard F

2014-06-01

In an operational setting acquisition of visual targets using both head and eye movements can be driven by memorized sequence of commands - internal triggering (IT) or by commands issued through secondary operator - external triggering (ET). The primary objective of our research was to examine differences in target acquisition using IT compared with ET. Using a forced time optimal strategy eight subjects were required to acquire targets with angular offsets of ±20°, 30° and 60° along the horizontal plane in both IT and ET conditions. The data showed that the eye/head latency difference in IT condition is longer than that for ET, the target acquisition time is also longer for IT commands. Consistent with this finding were similar results when examining the peak head velocity and peak head acceleration. Under IT protocol head amplitude is higher than when using ET. In conclusion, the study demonstrates that the pattern of performance of target acquisition task is influenced by the way of command triggering. Copyright © 2014 Elsevier B.V. All rights reserved.

Large scale structure in universes dominated by cold dark matter

NASA Technical Reports Server (NTRS)

Bond, J. Richard

1986-01-01

The theory of Gaussian random density field peaks is applied to a numerical study of the large-scale structure developing from adiabatic fluctuations in models of biased galaxy formation in universes with Omega = 1, h = 0.5 dominated by cold dark matter (CDM). The angular anisotropy of the cross-correlation function demonstrates that the far-field regions of cluster-scale peaks are asymmetric, as recent observations indicate. These regions will generate pancakes or filaments upon collapse. One-dimensional singularities in the large-scale bulk flow should arise in these CDM models, appearing as pancakes in position space. They are too rare to explain the CfA bubble walls, but pancakes that are just turning around now are sufficiently abundant and would appear to be thin walls normal to the line of sight in redshift space. Large scale streaming velocities are significantly smaller than recent observations indicate. To explain the reported 700 km/s coherent motions, mass must be significantly more clustered than galaxies with a biasing factor of less than 0.4 and a nonlinear redshift at cluster scales greater than one for both massive neutrino and cold models.

The integration of multiple proprioceptive information: effect of ankle tendon vibration on postural responses to platform tilt.

PubMed

Hatzitaki, Vassilia; Pavlou, Marousa; Bronstein, Adolfo M

2004-02-01

Previous studies have looked at co-processing of multiple proprioceptive inputs but few have investigated the effect of separate dynamic and tonic predominantly proprioceptive disruptions applied concurrently at the same segment. The purpose of the present study was to investigate how simultaneous ankle tendon vibration, a tonic stimulus, with a dynamic toes-up (TU) or toes-down (TD) platform perturbation (1) affects postural stability and (2) influences the adaptation process. Sixteen normal subjects (ten male, six female, mean age 26 +/- 4.8 years) stood blindfolded on a moving platform with vibrators attached bilaterally over the Achilles tendons. Participants were tested in quiet stance (QS), and with five successive TU and TD tilts. All tests were conducted both with (QS+V, TU+V, TD+V) and without vibration. Centre of pressure (CoP) displacements and pitch angular trunk velocity were recorded. Results for QS+V showed a significant 1.02-cm backward CoP displacement (P<0.01) and a significant increase in trunk velocity (peak-to-peak amplitude, P<0.05; SD of trunk velocity, P<0.05). TU+V resulted in a non-significant increase of maximum backwards CoP displacement when compared to TU alone. In addition, no notable effect of vibration on other measures of CoP (pre-tilt position, SD and area of sway) and trunk velocity (peak-to-peak, SD and area of sway) indicates that TU+V does not introduce significantly greater instability compared to tilt alone. In the TD condition, vibration was found to be a stabilising influence, causing a significant shift of the mean pre-tilt position 0.85 cm backwards (P<0.01) and a substantial decrease in the area of forward CoP displacement (P<0.01). However, maximum forwards CoP displacement and trunk velocity measures were not significantly altered during TD+V. Furthermore, in neither TU nor TD was the time-course or pattern of adaptation disrupted by the additional application of vibration. In conclusion, although vibration significantly affects postural measures when applied in isolation, this finding does not hold when it is applied in combination with a more dynamic stimulus. Instead it seems that once postural stability has been disrupted the central nervous system can rapidly assess information from a weaker tonic input and utilise or suppress it appropriately, depending on its effect towards overall postural control. It can be concluded that postural responses to the concurrent application of different predominantly proprioceptive stimuli are dependent upon the type of stimulus and the ability of the central nervous system to rapidly assess and re-weigh available sensory inputs.

Imaging the photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states

PubMed Central

Marggi Poullain, Sonia; Chicharro, David V.; Zanchet, Alexandre; González, Marta G.; Rubio-Lago, Luis; Senent, María L.; García-Vela, Alberto; Bañares, Luis

2016-01-01

The photodissociation dynamics of the methyl radical from the 3s and 3pz Rydberg states have been studied using velocity map and slice ion imaging in combination with pump-probe nanosecond laser pulses. The reported translational energy and angular distributions of the H(2S) photofragment detected by (2+1) REMPI highlight different dissociation mechanisms for the 3s and 3pz Rydberg states. A narrow peak in the translational energy distribution and an anisotropic angular distribution characterizes the fast 3s photodissociation, while for the 3pz state Boltzmann-type translational energy and isotropic angular distributions are found. High level ab initio calculations have been performed in order to elucidate the photodissociation mechanisms from the two Rydberg states and to rationalize the experimental results. The calculated potential energy curves highlight a typical predissociation mechanism for the 3s state, characterized by the coupling between the 3s Rydberg state and a valence repulsive state. On the other hand, the photodissociation on the 3pz state is initiated by a predissociation process due to the coupling between the 3pz Rydberg state and a valence repulsive state and constrained, later on, by two conical intersections that allow the system to relax to lower electronic states. Such mechanism opens different reaction pathways leading to CH2 photofragments in different electronic states and inducing a transfer of energy between translational and internal modes. PMID:27296907

Changes in blood velocity following microvascular free tissue transfer.

PubMed

Hanasono, Matthew M; Ogunleye, Olubunmi; Yang, Justin S; Hartley, Craig J; Miller, Michael J

2009-09-01

Understanding how pedicle blood velocities change after free tissue transfer may enable microvascular surgeons to predict when thrombosis is most likely to occur. A 20-MHz Doppler probe was used to measure arterial and venous blood velocities prior to pedicle division and 20 minutes after anastomosis in 32 microvascular free flaps. An implantable Doppler probe was then used to measure arterial and venous blood velocities daily for 5 days. Peak arterial blood velocity averaged 30.6 cm/s prior to pedicle division and increased to 36.5 cm/s 20 minutes after anastomosis ( P < 0.05). Peak venous blood velocity averaged 7.6 cm/s prior to pedicle division and increased to 12.4 cm/s 20 minutes after anastomosis ( P < 0.05). Peak arterial blood velocities averaged 34.0, 37.7, 43.8, 37.9, 37.6 cm/s on postoperative days (PODs) 1 through 5, respectively. Peak venous blood velocities averaged 11.9, 14.5, 18.2, 16.8, 17.7 cm/s on PODs 1 through 5, respectively. The peak arterial blood velocity on POD 3, and peak venous blood velocities on PODs 2, 3, and 5 were significantly higher than 20 minutes after anastomosis ( P < 0.05). Arterial and venous blood velocities increase for the first 3 postoperative days, potentially contributing to the declining risk for pedicle thrombosis during this time period.

Differences between Doppler velocities of ions and neutral atoms in a solar prominence

NASA Astrophysics Data System (ADS)

Anan, T.; Ichimoto, K.; Hillier, A.

2017-05-01

Context. In astrophysical systems with partially ionized plasma, the motion of ions is governed by the magnetic field while the neutral particles can only feel the magnetic field's Lorentz force indirectly through collisions with ions. The drift in the velocity between ionized and neutral species plays a key role in modifying important physical processes such as magnetic reconnection, damping of magnetohydrodynamic waves, transport of angular momentum in plasma through the magnetic field, and heating. Aims: This paper aims to investigate the differences between Doppler velocities of calcium ions and neutral hydrogen in a solar prominence to look for velocity differences between the neutral and ionized species. Methods: We simultaneously observed spectra of a prominence over an active region in H I 397 nm, H I 434 nm, Ca II 397 nm, and Ca II 854 nm using a high dispersion spectrograph of the Domeless Solar Telescope at Hida observatory. We compared the Doppler velocities, derived from the shift of the peak of the spectral lines presumably emitted from optically-thin plasma. Results: There are instances when the difference in velocities between neutral atoms and ions is significant, for example 1433 events ( 3% of sets of compared profiles) with a difference in velocity between neutral hydrogen atoms and calcium ions greater than 3σ of the measurement error. However, we also found significant differences between the Doppler velocities of two spectral lines emitted from the same species, and the probability density functions of velocity difference between the same species is not significantly different from those between neutral atoms and ions. Conclusions: We interpreted the difference of Doppler velocities as being a result of the motions of different components in the prominence along the line of sight, rather than the decoupling of neutral atoms from plasma. The movie attached to Fig. 1 is available at http://www.aanda.org

Orbital-angular-momentum transfer to optically levitated microparticles in vacuum

NASA Astrophysics Data System (ADS)

Mazilu, Michael; Arita, Yoshihiko; Vettenburg, Tom; Auñón, Juan M.; Wright, Ewan M.; Dholakia, Kishan

2016-11-01

We demonstrate the transfer of orbital angular momentum to an optically levitated microparticle in vacuum. The microparticle is placed within a Laguerre-Gaussian beam and orbits the annular beam profile with increasing angular velocity as the air drag coefficient is reduced. We explore the particle dynamics as a function of the topological charge of the levitating beam. Our results reveal that there is a fundamental limit to the orbital angular momentum that may be transferred to a trapped particle, dependent upon the beam parameters and inertial forces present.

Tai Chi and vestibular rehabilitation improve vestibulopathic gait via different neuromuscular mechanisms: Preliminary report

PubMed Central

McGibbon, Chris A; Krebs, David E; Parker, Stephen W; Scarborough, Donna M; Wayne, Peter M; Wolf, Steven L

2005-01-01

Background Vestibular rehabilitation (VR) is a well-accepted exercise program intended to remedy balance impairment caused by damage to the peripheral vestibular system. Alternative therapies, such as Tai Chi (TC), have recently gained popularity as a treatment for balance impairment. Although VR and TC can benefit people with vestibulopathy, the degree to which gait improvements may be related to neuromuscular adaptations of the lower extremities for the two different therapies are unknown. Methods We examined the relationship between lower extremity neuromuscular function and trunk control in 36 older adults with vestibulopathy, randomized to 10 weeks of either VR or TC exercise. Time-distance measures (gait speed, step length, stance duration and step width), lower extremity sagittal plane mechanical energy expenditures (MEE), and trunk sagittal and frontal plane kinematics (peak and range of linear and angular velocity), were measured. Results Although gait time-distance measures were improved in both groups following treatment, no significant between-groups differences were observed for the MEE and trunk kinematic measures. Significant within groups changes, however, were observed. The TC group significantly increased ankle MEE contribution and decreased hip MEE contribution to total leg MEE, while no significant changes were found within the VR group. The TC group exhibited a positive relationship between change in leg MEE and change in trunk velocity peak and range, while the VR group exhibited a negative relationship. Conclusion Gait function improved in both groups consistent with expectations of the interventions. Differences in each group's response to therapy appear to suggest that improved gait function may be due to different neuromuscular adaptations resulting from the different interventions. The TC group's improvements were associated with reorganized lower extremity neuromuscular patterns, which appear to promote a faster gait and reduced excessive hip compensation. The VR group's improvements, however, were not the result of lower extremity neuromuscular pattern changes. Lower-extremity MEE increases corresponded to attenuated forward trunk linear and angular movement in the VR group, suggesting better control of upper body motion to minimize loss of balance. These data support a growing body of evidence that Tai Chi may be a valuable complementary treatment for vestibular disorders. PMID:15717934

Influence of Tennis Racquet Kinematics on Ball Topspin Angular Velocity and Accuracy during the Forehand Groundstroke

PubMed Central

Kwon, Sunku; Pfister, Robin; Hager, Ronald L.; Hunter, Iain; Seeley, Matthew K.

2017-01-01

Forehand groundstroke effectiveness is important for tennis success. Ball topspin angular velocity (TAV) and accuracy are important for forehand groundstroke effectiveness, and have been extensively studied, previously; despite previous, quality studies, it was unclear whether certain racquet kinematics relate to ball TAV and shot accuracy during the forehand groundstroke. This study evaluated potential relationships between (1) ball TAV and (2) forehand accuracy, and five measures of racquet kinematics: racquet head impact angle (i.e., closed or open face), horizontal and vertical racquet head velocity before impact, racquet head trajectory (resultant velocity direction, relative to horizontal) before impact, and hitting zone length (quasi-linear displacement, immediately before and after impact). Thirteen collegiate-level tennis players hit forehand groundstrokes in a biomechanics laboratory, where racquet kinematics and ball TAV were measured, and on a tennis court, to assess accuracy. Correlational statistics were used to evaluate potential relationships between racquet kinematics, and ball TAV (mixed model) and forehand accuracy (between-subjects model; α = 0.05). We observed an average (1) racquet head impact angle, (2) racquet head trajectory before impact, relative to horizontal, (3) racquet head horizontal velocity before impact, (4) racquet head vertical velocity before impact, and (5) hitting zone length of 80.4 ± 3.6˚, 18.6 ± 4.3˚, 15.4 ± 1.4 m·s-1, 6.6 ± 2.2 m·s-1, and 79.8 ± 8.6 mm, respectively; and an average ball TAV of 969 ± 375 revolutions per minute. Only racquet head impact angle and racquet head vertical velocity, before impact, significantly correlated with ball TAV (p < 0.01). None of the observed racquet kinematics significantly correlated to the measures of forehand accuracy. These results confirmed mechanical logic and indicate that increased ball TAV is associated with a more closed racquet head impact angle (ranging from 70 to 85˚, relative to the ground) and increased racquet head vertical velocity before impact. Key points The study confirmed previous research that two key racquet kinematic variables, near impact, are significantly correlated to ball topspin angular velocity, during the forehand groundstroke: racquet head impact angle (i.e., open or closed racquet face) and racquet vertical velocity, before impact. The trajectory (direction of resultant velocity) and horizontal velocity of the racquet head before impact, and length of hitting zone were not significantly correlated to ball topspin angular velocity, or shot placement accuracy, during the tennis forehand groundstroke, for skilled male players. Hitting zone length was smaller than expected for skilled tennis players performing the forehand groundstroke. PMID:29238250

Influence of snow shovel shaft configuration on lumbosacral biomechanics during a load-lifting task.

PubMed

Lewinson, Ryan T; Rouhi, Gholamreza; Robertson, D Gordon E

2014-03-01

Lower-back injury from snow shovelling may be related to excessive joint loading. Bent-shaft snow shovels are commonly available for purchase; however, their influence on lower back-joint loading is currently not known. Therefore, the purpose of this study was to compare L5/S1 extension angular impulses between a bent-shaft and a standard straight-shaft snow shovel. Eight healthy subjects participated in this study. Each completed a simulated snow-lifting task in a biomechanics laboratory with each shovel design. A standard motion analysis procedure was used to determine L5/S1 angular impulses during each trial, as well as peak L5/S1 extension moments and peak upper body flexion angle. Paired-samples t-tests (α = 0.05) were used to compare variables between shovel designs. Correlation was used to determine the relationship between peak flexion and peak moments. Results of this study show that the bent-shaft snow shovel reduced L5/S1 extension angular impulses by 16.5% (p = 0.022), decreased peak moments by 11.8% (p = 0.044), and peak flexion by 13.0% (p = 0.002) compared to the straight-shaft shovel. Peak L5/S1 extension moment magnitude was correlated with peak upper body flexion angle (r = 0.70). Based on these results, it is concluded that the bent-shaft snow shovel can likely reduce lower-back joint loading during snow shovelling, and thus may have a role in snow shovelling injury prevention. Copyright © 2013 Elsevier Ltd and The Ergonomics Society. All rights reserved.

14 CFR 29.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2014 CFR

2014-01-01

... flight path (radians, positive when axis is pointing aft); Ω=The angular velocity of rotor (radians per... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

14 CFR 27.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2011 CFR

2011-01-01

... flight path (radians, positive when axis is pointing aft); omega= The angular velocity of rotor (radians... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

14 CFR 29.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2013 CFR

2013-01-01

... flight path (radians, positive when axis is pointing aft); Ω=The angular velocity of rotor (radians per... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

14 CFR 27.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2013 CFR

2013-01-01

... flight path (radians, positive when axis is pointing aft); omega= The angular velocity of rotor (radians... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

14 CFR 29.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2012 CFR

2012-01-01

... flight path (radians, positive when axis is pointing aft); Ω=The angular velocity of rotor (radians per... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

14 CFR 29.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2011 CFR

2011-01-01

... flight path (radians, positive when axis is pointing aft); Ω=The angular velocity of rotor (radians per... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

14 CFR 27.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2014 CFR

2014-01-01

... flight path (radians, positive when axis is pointing aft); omega= The angular velocity of rotor (radians... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

14 CFR 27.339 - Resultant limit maneuvering loads.

Code of Federal Regulations, 2012 CFR

2012-01-01

... flight path (radians, positive when axis is pointing aft); omega= The angular velocity of rotor (radians... velocity component in the plane of the rotor disc to the rotational tip speed of the rotor blades, and is...

Constant angular velocity of the wrist during the lifting of a sphere.

PubMed

Chappell, P H; Metcalf, C D; Burridge, J H; Yule, V T; Pickering, R M

2010-05-01

The primary objective of the experiments was to investigate the wrist motion of a person while they were carrying out a prehensile task from a clinical hand function test. A six-camera movement system was used to observe the wrist motion of 10 participants. A very light sphere and a heavy sphere were used in the experiments to study any mass effects. While seated at a table, a participant moved a sphere over a small obstacle using their dominant hand. The participants were observed to move their wrist at a constant angular velocity. This phenomenon has not been reported previously. Theoretically, the muscles of the wrist provide an impulse of force at the start of the rotation while the forearm maintains a constant vertical force on a sphere. Light-heavy mean differences for the velocities, absolute velocities, angles and times taken showed no significant differences (p = 0.05).

Output of skeletal muscle contractions. a study of isokinetic plantar flexion in athletes.

PubMed

Fugl-Meyer, A R; Mild, K H; Hörnsten, J

1982-06-01

Maximum torques, total work and mean power of isokinetic plantar flexions were measured with simultaneous registrations. The integrated electromyograms (iEMG) were obtained by surface electrodes from all three heads of the m. triceps surae. The method applied offers possibilities for adequate description of dynamic muscular work which in the case of plantar flexion in trained man declines as a negative exponential function of angular motion velocity. The decline is parallel to that of maximum torques. The summed triceps surae iEMG was inversely proportional to the velocity and direct proportional to time suggesting that structural rather than neural factors determine the relationships between velocity of angular motion and maximum torque/total work of single Mmaneuvers. Moreover, the fact that maximum mean power as well as maximum electrical efficiency were reached at the functional velocity of toe-off during gait suggests an influence of pragmatic demands on plantar flexion mechanical output.

Movement coordination and differential kinematics of the cervical and thoracic spines in people with chronic neck pain.

PubMed

Tsang, Sharon M H; Szeto, Grace P Y; Lee, Raymond Y W

2013-07-01

Research on the kinematics and inter-regional coordination of movements between the cervical and thoracic spines in motion adds to our understanding of the performance and interplay of these spinal regions. The purpose of this study was to examine the effects of chronic neck pain on the three-dimensional kinematics and coordination of the cervical and thoracic spines during active movements of the neck. Three-dimensional spinal kinematics and movement coordination between the cervical, upper thoracic, and lower thoracic spines were examined by electromagnetic motion sensors in thirty-four individuals with chronic neck pain and thirty-four age- and gender-matched asymptomatic subjects. All subjects performed a set of free active neck movements in three anatomical planes in sitting position and at their own pace. Spinal kinematic variables (angular displacement, velocity, and acceleration) of the three defined regions, and movement coordination between regions were determined and compared between the two groups. Subjects with chronic neck pain exhibited significantly decreased cervical angular velocity and acceleration of neck movement. Cross-correlation analysis revealed consistently lower degrees of coordination between the cervical and upper thoracic spines in the neck pain group. The loss of coordination was most apparent in angular velocity and acceleration of the spine. Assessment of the range of motion of the neck is not sufficient to reveal movement dysfunctions in chronic neck pain subjects. Evaluation of angular velocity and acceleration and movement coordination should be included to help develop clinical intervention strategies to promote restoration of differential kinematics and movement coordination. Copyright © 2013 Elsevier Ltd. All rights reserved.

Segment-interaction in sprint start: Analysis of 3D angular velocity and kinetic energy in elite sprinters.

PubMed

Slawinski, J; Bonnefoy, A; Ontanon, G; Leveque, J M; Miller, C; Riquet, A; Chèze, L; Dumas, R

2010-05-28

The aim of the present study was to measure during a sprint start the joint angular velocity and the kinetic energy of the different segments in elite sprinters. This was performed using a 3D kinematic analysis of the whole body. Eight elite sprinters (10.30+/-0.14s 100 m time), equipped with 63 passive reflective markers, realised four maximal 10 m sprints start on an indoor track. An opto-electronic Motion Analysis system consisting of 12 digital cameras (250 Hz) was used to collect the 3D marker trajectories. During the pushing phase on the blocks, the 3D angular velocity vector and its norm were calculated for each joint. The kinetic energy of 16 segments of the lower and upper limbs and of the total body was calculated. The 3D kinematic analysis of the whole body demonstrated that joints such as shoulders, thoracic or hips did not reach their maximal angular velocity with a movement of flexion-extension, but with a combination of flexion-extension, abduction-adduction and internal-external rotation. The maximal kinetic energy of the total body was reached before clearing block (respectively, 537+/-59.3 J vs. 514.9+/-66.0 J; p< or =0.01). These results suggested that a better synchronization between the upper and lower limbs could increase the efficiency of pushing phase on the blocks. Besides, to understand low interindividual variances in the sprint start performance in elite athletes, a 3D complete body kinematic analysis shall be used. Copyright 2010 Elsevier Ltd. All rights reserved.

Modeling of Turbulence Generated Noise in Jets

NASA Technical Reports Server (NTRS)

Khavaran, Abbas; Bridges, James

2004-01-01

A numerically calculated Green's function is used to predict jet noise spectrum and its far-field directivity. A linearized form of Lilley's equation governs the non-causal Green s function of interest, with the non-linear terms on the right hand side identified as the source. In this paper, contributions from the so-called self- and shear-noise source terms will be discussed. A Reynolds-averaged Navier-Stokes solution yields the required mean flow as well as time- and length scales of a noise-generating turbulent eddy. A non-compact source, with exponential temporal and spatial functions, is used to describe the turbulence velocity correlation tensors. It is shown that while an exact non-causal Green's function accurately predicts the observed shift in the location of the spectrum peak with angle as well as the angularity of sound at moderate Mach numbers, at high subsonic and supersonic acoustic Mach numbers the polar directivity of radiated sound is not entirely captured by this Green's function. Results presented for Mach 0.5 and 0.9 isothermal jets, as well as a Mach 0.8 hot jet conclude that near the peak radiation angle a different source/Green's function convolution integral may be required in order to capture the peak observed directivity of jet noise.

Reverse design of a bull's eye structure for oblique incidence and wider angular transmission efficiency.

PubMed

Yamada, Akira; Terakawa, Mitsuhiro

2015-04-10

We present a design method of a bull's eye structure with asymmetric grooves for focusing oblique incident light. The design method is capable of designing transmission peaks to a desired oblique angle with capability of collecting light from a wider range of angles. The bull's eye groove geometry for oblique incidence is designed based on the electric field intensity pattern around an isolated subwavelength aperture on a thin gold film at oblique incidence, calculated by the finite difference time domain method. Wide angular transmission efficiency is successfully achieved by overlapping two different bull's eye groove patterns designed with different peak angles. Our novel design method would overcome the angular limitations of the conventional methods.

Interpersonal Coordination of Head Motion in Distressed Couples

PubMed Central

Hammal, Zakia; Cohn, Jeffrey F.; George, David T.

2015-01-01

In automatic emotional expression analysis, head motion has been considered mostly a nuisance variable, something to control when extracting features for action unit or expression detection. As an initial step toward understanding the contribution of head motion to emotion communication, we investigated the interpersonal coordination of rigid head motion in intimate couples with a history of interpersonal violence. Episodes of conflict and non-conflict were elicited in dyadic interaction tasks and validated using linguistic criteria. Head motion parameters were analyzed using Student’s paired t-tests; actor-partner analyses to model mutual influence within couples; and windowed cross-correlation to reveal dynamics of change in direction of influence over time. Partners’ RMS angular displacement for yaw and RMS angular velocity for pitch and yaw each demonstrated strong mutual influence between partners. Partners’ RMS angular displacement for pitch was higher during conflict. In both conflict and non-conflict, head angular displacement and angular velocity for pitch and yaw were strongly correlated, with frequent shifts in lead-lag relationships. The overall amount of coordination between partners’ head movement was more highly correlated during non-conflict compared with conflict interaction. While conflict increased head motion, it served to attenuate interpersonal coordination. PMID:26167256

A compensation method of lever arm effect for tri-axis hybrid inertial navigation system based on fiber optic gyro

NASA Astrophysics Data System (ADS)

Liu, Zengjun; Wang, Lei; Li, Kui; Gao, Jiaxin

2017-05-01

Hybrid inertial navigation system (HINS) is a new kind of inertial navigation system (INS), which combines advantages of platform INS, strap-down INS and rotational INS. HINS has a physical platform to isolate the angular motion as platform INS does, HINS also uses strap-down attitude algorithms and applies rotation modulation technique. Tri-axis HINS has three gimbals to isolate the angular motion in the dynamic base, in which way the system can reduce the effects of angular motion and improve the positioning precision. However, the angular motion will affect the compensation of some error parameters, especially for the lever arm effect. The lever arm effect caused by position errors between the accelerometers and rotation center cannot be ignored due to the rapid rotation of inertial measurement unit (IMU) and it will cause fluctuation and stage in velocity in HINS. The influences of angular motion on the lever arm effect compensation are analyzed firstly in this paper, and then the compensation method of lever arm effect based on the photoelectric encoders in dynamic base is proposed. Results of experiments on turntable show that after compensation, the fluctuations and stages in velocity curve disappear.

Consideration of Gravity Gradient Stabilization for Orion

DTIC Science & Technology

1989-03-01

AND ERIC ANDionl STABILIZATION TION. MAY NEED SECOND CONTROL SYSTEM TO CONTROL OVERALL ANGULAR MOMENTUM I MOMENTUM DUMPING I IN RESPONSE TO...FURTHER EXPERIENCE IS GAINED RPEFERS TO ANY DEVICE THAT MAY BEl USED Ift A PRIOCESS TOE ECHANGE ANGULAR MOMENTUM WITH THME SPACIECRAFTI BODY Figure 5...rotating with angular velocity w relative to XYZ. If unit vectors along the X, Y, and Z axes are ij, and k, respectively, the vector r can be written

Attitude guidance and tracking for spacecraft with two reaction wheels

NASA Astrophysics Data System (ADS)

Biggs, James D.; Bai, Yuliang; Henninger, Helen

2018-04-01

This paper addresses the guidance and tracking problem for a rigid-spacecraft using two reaction wheels (RWs). The guidance problem is formulated as an optimal control problem on the special orthogonal group SO(3). The optimal motion is solved analytically as a function of time and is used to reduce the original guidance problem to one of computing the minimum of a nonlinear function. A tracking control using two RWs is developed that extends previous singular quaternion stabilisation controls to tracking controls on the rotation group. The controller is proved to locally asymptotically track the generated reference motions using Lyapunov's direct method. Simulations of a 3U CubeSat demonstrate that this tracking control is robust to initial rotation errors and angular velocity errors in the controlled axis. For initial angular velocity errors in the uncontrolled axis and under significant disturbances the control fails to track. However, the singular tracking control is combined with a nano-magnetic torquer which simply damps the angular velocity in the uncontrolled axis and is shown to provide a practical control method for tracking in the presence of disturbances and initial condition errors.

Smearing model and restoration of star image under conditions of variable angular velocity and long exposure time.

PubMed

Sun, Ting; Xing, Fei; You, Zheng; Wang, Xiaochu; Li, Bin

2014-03-10

The star tracker is one of the most promising attitude measurement devices widely used in spacecraft for its high accuracy. High dynamic performance is becoming its major restriction, and requires immediate focus and promotion. A star image restoration approach based on the motion degradation model of variable angular velocity is proposed in this paper. This method can overcome the problem of energy dispersion and signal to noise ratio (SNR) decrease resulting from the smearing of the star spot, thus preventing failed extraction and decreased star centroid accuracy. Simulations and laboratory experiments are conducted to verify the proposed methods. The restoration results demonstrate that the described method can recover the star spot from a long motion trail to the shape of Gaussian distribution under the conditions of variable angular velocity and long exposure time. The energy of the star spot can be concentrated to ensure high SNR and high position accuracy. These features are crucial to the subsequent star extraction and the whole performance of the star tracker.

Modelling the vestibular head tilt response.

PubMed

Heibert, D; Lithgow, B

2005-03-01

This paper attempts to verify the existence of potentially diagnostically significant periodic signals thought to exist in recordings of neural activity originating from the vestibular nerve, following a single tilt of the head. It then attempts to find the physiological basis of this signal, in particular focusing on the mechanical response of the vestibular system. Simple mechanical models of the semi circular canals having angular velocities applied to them were looked at. A simple single canal model was simulated using CFX software. Finally, a simple model of all three canals with elastic duct walls and a moving cupula was constructed. Pressure waves within the canals were simulated using water hammer or pressure transient theory. In particular, it was investigated whether pressure waves within the utricle following a square pulse angular velocity applied to the canal(s) may be responsible for quasi-periodic oscillatory signals. The simulations showed that there are no pressure waves resonating within the canals following a square pulse angular velocity applied to the canal(s). The results show that the oscillatory signals are most likely not mechanical in origin. It was concluded that further investigation is required.

The rotation of discs around neutron stars: dependence on the Hall diffusion

NASA Astrophysics Data System (ADS)

Faghei, Kazem; Salehi, Fatemeh

2018-01-01

In this paper, we study the dynamics of a geometrically thin, steady and axisymmetric accretion disc surrounding a rotating and magnetized star. The magnetic field lines of star penetrate inside the accretion disc and are twisted due to the differential rotation between the magnetized star and the disc. We apply the Hall diffusion effect in the accreting plasma, because of the Hall diffusion plays an important role in both fully ionized plasma and weakly ionized medium. In the current research, we show that the Hall diffusion is also an important mechanism in accreting plasma around neutron stars. For the typical system parameter values associated with the accreting X-ray binary pulsar, the angular velocity of the inner regions of disc departs outstandingly from Keplerian angular velocity, due to coupling between the magnetic field of neutron star and the rotating plasma of disc. We found that the Hall diffusion is very important in inner disc and increases the coupling between the magnetic field of neutron star and accreting plasma. On the other word, the rotational velocity of inner disc significantly decreases in the presence of the Hall diffusion. Moreover, the solutions imply that the fastness parameter decreases and the angular velocity transition zone becomes broad for the accreting plasma including the Hall diffusion.

Gravitational-Wave Luminosity of Binary Neutron Stars Mergers

NASA Astrophysics Data System (ADS)

Zappa, Francesco; Bernuzzi, Sebastiano; Radice, David; Perego, Albino; Dietrich, Tim

2018-03-01

We study the gravitational-wave peak luminosity and radiated energy of quasicircular neutron star mergers using a large sample of numerical relativity simulations with different binary parameters and input physics. The peak luminosity for all the binaries can be described in terms of the mass ratio and of the leading-order post-Newtonian tidal parameter solely. The mergers resulting in a prompt collapse to black hole have the largest peak luminosities. However, the largest amount of energy per unit mass is radiated by mergers that produce a hypermassive neutron star or a massive neutron star remnant. We quantify the gravitational-wave luminosity of binary neutron star merger events, and set upper limits on the radiated energy and the remnant angular momentum from these events. We find that there is an empirical universal relation connecting the total gravitational radiation and the angular momentum of the remnant. Our results constrain the final spin of the remnant black hole and also indicate that stable neutron star remnant forms with super-Keplerian angular momentum.

Gravitational-Wave Luminosity of Binary Neutron Stars Mergers.

PubMed

Zappa, Francesco; Bernuzzi, Sebastiano; Radice, David; Perego, Albino; Dietrich, Tim

2018-03-16

We study the gravitational-wave peak luminosity and radiated energy of quasicircular neutron star mergers using a large sample of numerical relativity simulations with different binary parameters and input physics. The peak luminosity for all the binaries can be described in terms of the mass ratio and of the leading-order post-Newtonian tidal parameter solely. The mergers resulting in a prompt collapse to black hole have the largest peak luminosities. However, the largest amount of energy per unit mass is radiated by mergers that produce a hypermassive neutron star or a massive neutron star remnant. We quantify the gravitational-wave luminosity of binary neutron star merger events, and set upper limits on the radiated energy and the remnant angular momentum from these events. We find that there is an empirical universal relation connecting the total gravitational radiation and the angular momentum of the remnant. Our results constrain the final spin of the remnant black hole and also indicate that stable neutron star remnant forms with super-Keplerian angular momentum.

Male and female WorldSID and post mortem human subject responses in full-scale vehicle tests.

PubMed

Yoganandan, Narayan; Humm, John; Pintar, Frank; Rhule, Heather; Moorhouse, Kevin; Suntay, Brian; Stricklin, Jim; Rudd, Rodney; Craig, Matthew

2017-05-29

This study compares the responses of male and female WorldSID dummies with post mortem human subject (PMHS) responses in full-scale vehicle tests. Tests were conducted according to the FMVSS-214 protocols and using the U.S. Side Impact New Car Assessment Program change in velocity to match PMHS experiments, published earlier. Moving deformable barrier (MDB) tests were conducted with the male and female surrogates in the left front and left rear seats. Pole tests were performed with the male surrogate in the left front seat. Three-point belt restraints were used. Sedan-type vehicles were used from the same manufacturer with side airbags. The PMHS head was instrumented with a pyramid-shaped nine-axis accelerometer package, with angular velocity transducers on the head. Accelerometers and angular velocity transducers were secured to T1, T6, and T12 spinous processes and sacrum. Three chest bands were secured around the upper, middle, and lower thoraces. Dummy instrumentation included five infrared telescoping rods for assessment of chest compression (IR-TRACC) and a chest band at the first abdomen rib, head angular velocity transducer, and head, T1, T4, T12, and pelvis accelerometers. Morphological responses of the kinematics of the head, thoracic spine, and pelvis matched in both surrogates for each pair. The peak magnitudes of the torso accelerations were lower for the dummy than for the biological surrogate. The brain rotational injury criterion (BrIC) response was the highest in the male dummy for the MDB test and PMHS. The probability of AIS3+ injuries, based on the head injury criterion, ranged from 3% to 13% for the PMHS and from 3% to 21% for the dummy from all tests. The BrIC-based metrics ranged from 0 to 21% for the biological and 0 to 48% for the dummy surrogates. The deflection profiles from the IR-TRACC sensors were unimodal. The maximum deflections from the chest band placed on the first abdominal rib were 31.7 mm and 25.4 mm for the male and female dummies in the MDB test, and 37.4 mm for the male dummy in the pole test. The maximum deflections computed from the chest band contours at a gauge equivalent to the IR-TRACC location were 25.9 mm and 14.8 mm for the male and female dummies in the MDB test, and 37.4 mm for the male dummy in the pole test. Other data (static vehicle deformation profiles, accelerations histories of different body regions, and chest band contours for the dummy and PMHS) are given in the appendix. This is the first study to compare the responses of PMHS and male and female dummies in MDB and pole tests, done using the same recent model year vehicles with side airbag and head curtain restraints. The differences between the dummy and PMHS torso accelerations suggest the need for design improvements in the WorldSID dummy. The translation-based metrics suggest low probability of head injury. As the dummy internal sensor underrecorded the peak deflection, multipoint displacement measures are therefore needed for a more accurate quantification of deflection to improve the safety assessment of occupants.

Rotation of Giant Stars

NASA Astrophysics Data System (ADS)

Kissin, Yevgeni; Thompson, Christopher

2015-07-01

The internal rotation of post-main sequence stars is investigated, in response to the convective pumping of angular momentum toward the stellar core, combined with a tight magnetic coupling between core and envelope. The spin evolution is calculated using model stars of initial mass 1, 1.5, and 5 {M}⊙ , taking into account mass loss on the giant branches. We also include the deposition of orbital angular momentum from a sub-stellar companion, as influenced by tidal drag along with the excitation of orbital eccentricity by a fluctuating gravitational quadrupole moment. A range of angular velocity profiles {{Ω }}(r) is considered in the envelope, extending from solid rotation to constant specific angular momentum. We focus on the backreaction of the Coriolis force, and the threshold for dynamo action in the inner envelope. Quantitative agreement with measurements of core rotation in subgiants and post-He core flash stars by Kepler is obtained with a two-layer angular velocity profile: uniform specific angular momentum where the Coriolis parameter {Co}\\equiv {{Ω }}{τ }{con}≲ 1 (here {τ }{con} is the convective time), and {{Ω }}(r)\\propto {r}-1 where {Co}≳ 1. The inner profile is interpreted in terms of a balance between the Coriolis force and angular pressure gradients driven by radially extended convective plumes. Inward angular momentum pumping reduces the surface rotation of subgiants, and the need for a rejuvenated magnetic wind torque. The co-evolution of internal magnetic fields and rotation is considered in Kissin & Thompson, along with the breaking of the rotational coupling between core and envelope due to heavy mass loss.

Acute aquatic treadmill exercise improves gait and pain in people with knee osteoarthritis.

PubMed

Roper, Jaimie A; Bressel, Eadric; Tillman, Mark D

2013-03-01

To examine the acute effects of aquatic and land treadmill exercise on gait kinematics as well as the level of disease-specific and movement-related pain for individuals with osteoarthritis. Quasi-experimental crossover design. Biomechanics laboratory. Participants (N=14; age, 43-64y) diagnosed with osteoarthritis at the knee (n=12), osteoarthritis at the knee and ankle (n=1), or osteoarthritis at the knee and hip (n=1). Participants performed 3 exercise sessions separated by at least 24 hours in 1 week for each mode of exercise (aquatic treadmill and land treadmill). Gait kinematics and pain were measured before and after each intervention. The angular velocity gain score during stance for left knee extension was improved by 38% after aquatic treadmill exercise (P=.004). Similarly, during swing, the gain scores for angular velocity were also greater for left knee internal rotation and extension by 65% and 20%, respectively (P=.004, P=.008, respectively). During stance, the joint angle gain score for left hip flexion was 7.23% greater after land exercise (P=.007). During swing, the angular velocity gain score for right hip extension was significantly greater for aquatic exercise by 28% (P=.01). Only the joint angle gain score for left ankle abduction during stance was significantly higher after land exercise (4.72%, P=.003). No other joint angle gain scores for either stance or swing were significantly different for either condition (P=.06-.96). Perceived pain was 100% greater after land than aquatic treadmill exercise (P=.02). Step rate and step length were not different between conditions (P=.31-.92). An acute training period on an aquatic treadmill positively influenced joint angular velocity and arthritis-related joint pain. Acute aquatic treadmill exercise may be useful as a conservative treatment to improve angular speed of the lower-extremity joints and pain related to osteoarthritis. Copyright © 2013 American Congress of Rehabilitation Medicine. Published by Elsevier Inc. All rights reserved.

Cardiorespiratory, neuromuscular and kinematic responses to stationary running performed in water and on dry land.

PubMed

Alberton, Cristine Lima; Cadore, Eduardo Lusa; Pinto, Stephanie Santana; Tartaruga, Marcus Peikriszwili; da Silva, Eduardo Marczwski; Kruel, Luiz Fernando Martins

2011-06-01

The purpose of this study was to analyze the cardiorespiratory, neuromuscular and kinematic responses obtained during the stationary running in aquatic and dry land environments. Twelve women took part in the experimental protocol. Stationary running was performed for 4 min at three submaximal cadences and for 15 s at maximal velocity, with the collection of kinematic (peak hip angular velocity (AV)), cardiorespiratory (oxygen uptake (VO(2))) and neuromuscular variables (electromyographic (EMG) signal from the rectus femoris (RF), vastus lateralis (VL), semitendinosus (ST) and short head of the biceps femoris (BF) muscles) in land-based and water-based test protocols. Factorial ANOVA was used, with an alpha level of 0.05. AV was significantly higher when the exercise was performed on land, and became significantly higher as the execution cadence increased. Similarly, VO(2) was significantly higher in the land-based exercise and rose as cadence increased. With the increase in the submaximal execution cadences, there was no corresponding increase in the EMG signal from the VL, BF, RF and ST muscles in either environment, though such a significantly increase was seen between the submaximal cadences and the maximal velocity. Dry land presented significantly greater EMG signal responses for all muscles at the submaximal cadences, except for the ST muscle. However, at the maximal velocity, all the analyzed muscle groups showed similar responses in both environments. In summary, for both environments, cardiorespiratory responses can be maximized by increasing the submaximal cadences, while neuromuscular responses are only optimized by using maximal velocity.

An Inventory on Rotational Kinematics of a Particle: Unravelling Misconceptions and Pitfalls in Reasoning

ERIC Educational Resources Information Center

Mashood, K. K.; Singh, Vijay A.

2012-01-01

Student difficulties regarding the angular velocity ([image omitted]) and angular acceleration ([image omitted]) of a particle have remained relatively unexplored in contrast to their linear counterparts. We present an inventory comprising multiple choice questions aimed at probing misconceptions and eliciting ill-suited reasoning patterns. The…

Revealing the subfemtosecond dynamics of orbital angular momentum in nanoplasmonic vortices

NASA Astrophysics Data System (ADS)

Spektor, G.; Kilbane, D.; Mahro, A. K.; Frank, B.; Ristok, S.; Gal, L.; Kahl, P.; Podbiel, D.; Mathias, S.; Giessen, H.; Meyer zu Heringdorf, F.-J.; Orenstein, M.; Aeschlimann, M.

2017-03-01

The ability of light to carry and deliver orbital angular momentum (OAM) in the form of optical vortices has attracted much interest. The physical properties of light with a helical wavefront can be confined onto two-dimensional surfaces with subwavelength dimensions in the form of plasmonic vortices, opening avenues for thus far unknown light-matter interactions. Because of their extreme rotational velocity, the ultrafast dynamics of such vortices remained unexplored. Here we show the detailed spatiotemporal evolution of nanovortices using time-resolved two-photon photoemission electron microscopy. We observe both long- and short-range plasmonic vortices confined to deep subwavelength dimensions on the scale of 100 nanometers with nanometer spatial resolution and subfemtosecond time-step resolution. Finally, by measuring the angular velocity of the vortex, we directly extract the OAM magnitude of light.

Device for adapting continuously variable transmissions to infinitely variable transmissions with forward-neutral-reverse capabilities

DOEpatents

Wilkes, Donald F.; Purvis, James W.; Miller, A. Keith

1997-01-01

An infinitely variable transmission is capable of operating between a maximum speed in one direction and a minimum speed in an opposite direction, including a zero output angular velocity, while being supplied with energy at a constant angular velocity. Input energy is divided between a first power path carrying an orbital set of elements and a second path that includes a variable speed adjustment mechanism. The second power path also connects with the orbital set of elements in such a way as to vary the rate of angular rotation thereof. The combined effects of power from the first and second power paths are combined and delivered to an output element by the orbital element set. The transmission can be designed to operate over a preselected ratio of forward to reverse output speeds.

An Investigation of the Role of Friction in the Motion of a Tippe Top

NASA Astrophysics Data System (ADS)

Kager, Elisabeth; Howald, Craig; Kuhl, Dennis

2008-03-01

The time it takes a Tippe Top to turn over was measured as a function of friction. The reproducibility of the measured tipping time was also examined. Two experiments were conducted: One to measure a frictional figure of merit and the second to test the time it takes the Tippe Top to tip on three surfaces with varying friction. The three surfaces used were glass, Teflon, and Vinyl. Several runs of spinning Tippe Tops were recorded by means of a video camera. The data was analyzed by extracting the angular position and the angular velocity of the Tippe Top. By graphing the angular velocity vs. time and using the slope of the line, a frictional figure of merit was found. The time it took the Tippe Top to tip in each case was also determined.

Spatial orientation perception and reflexive eye movements--a perspective, an overview, and some clinical implications

NASA Technical Reports Server (NTRS)

Guedry, F. E.; Paloski, W. F. (Principal Investigator)

1996-01-01

When head motion includes a linear velocity component, eye velocity required to track an earth-fixed target depends upon: a) angular and linear head velocity, b) target distance, and c) direction of gaze relative to the motion trajectory. Recent research indicates that eye movements (LVOR), presumably otolith-mediated, partially compensate for linear velocity in small head excursions on small devices. Canal-mediated eye velocity (AVOR), otolith-mediated eye velocity (LVOR), and Ocular Torsion (OT) can be measured, one by one, on small devices. However, response dynamics that depend upon the ratio of linear to angular velocity in the motion trajectory and on subject orientation relative to the trajectory are present in a centrifuge paradigm. With this paradigm, two 3-min runs yields measures of: LVOR differentially modulated by different subject orientations in the two runs; OT dynamics in four conditions; two directions of "steady-state" OT, and two directions of AVOR. Efficient assessment of the dynamics (and of the underlying central integrative processes) may require a centrifuge radius of 1.0 meters or more. Clinical assessment of the spatial orientation system should include evaluation of central integrative processes that determine the dynamics of these responses.

Theoretical and Experimental Study of Radial Velocity Generation for Extending Bandwidth of Magnetohydrodynamic Angular Rate Sensor at Low Frequency.

PubMed

Ji, Yue; Li, Xingfei; Wu, Tengfei; Chen, Cheng

2015-12-15

The magnetohydrodynamics angular rate sensor (MHD ARS) has received much attention for its ultra-low noise in ultra-broad bandwidth and its impact resistance in harsh environments; however, its poor performance at low frequency hinders its work in long time duration. The paper presents a modified MHD ARS combining Coriolis with MHD effect to extend the measurement scope throughout the whole bandwidth, in which an appropriate radial flow velocity should be provided to satisfy simplified model of the modified MHD ARS. A method that can generate radial velocity by an MHD pump in MHD ARS is proposed. A device is designed to study the radial flow velocity generated by the MHD pump. The influence of structure and physical parameters are studied by numerical simulation and experiment of the device. The analytic expression of the velocity generated by the energized current drawn from simulation and experiment are consistent, which demonstrates the effectiveness of the method generating radial velocity. The study can be applied to generate and control radial velocity in modified MHD ARS, which is essential for the two effects combination throughout the whole bandwidth.

Theoretical and Experimental Study of Radial Velocity Generation for Extending Bandwidth of Magnetohydrodynamic Angular Rate Sensor at Low Frequency

PubMed Central

Ji, Yue; Li, Xingfei; Wu, Tengfei; Chen, Cheng

2015-01-01

The magnetohydrodynamics angular rate sensor (MHD ARS) has received much attention for its ultra-low noise in ultra-broad bandwidth and its impact resistance in harsh environments; however, its poor performance at low frequency hinders its work in long time duration. The paper presents a modified MHD ARS combining Coriolis with MHD effect to extend the measurement scope throughout the whole bandwidth, in which an appropriate radial flow velocity should be provided to satisfy simplified model of the modified MHD ARS. A method that can generate radial velocity by an MHD pump in MHD ARS is proposed. A device is designed to study the radial flow velocity generated by the MHD pump. The influence of structure and physical parameters are studied by numerical simulation and experiment of the device. The analytic expression of the velocity generated by the energized current drawn from simulation and experiment are consistent, which demonstrates the effectiveness of the method generating radial velocity. The study can be applied to generate and control radial velocity in modified MHD ARS, which is essential for the two effects combination throughout the whole bandwidth. PMID:26694393

Correcting a Widespread Error concerning the Angular Velocity of a Rotating Rigid Body.

ERIC Educational Resources Information Center

Leubner, C.

1981-01-01

Since many texts use an incorrect argument in obtaining the instantaneous velocity of a rotating body, a correct and concise derivation of this quantity for a rather general case is given. (Author/SK)

30 CFR 816.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2013 CFR

2013-07-01

... established in accordance with either the maximum peak-particle-velocity limits of paragraph (d)(2), the... in the blasting plan and approved by the regulatory authority. (2) Maximum peak particle velocity. (i... (D), from the blasting site, in feet Maximum allowable peak particle velocity (V max) for ground...

30 CFR 816.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2014 CFR

2014-07-01

... established in accordance with either the maximum peak-particle-velocity limits of paragraph (d)(2), the... in the blasting plan and approved by the regulatory authority. (2) Maximum peak particle velocity. (i... (D), from the blasting site, in feet Maximum allowable peak particle velocity (V max) for ground...

30 CFR 817.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2014 CFR

2014-07-01

... either the maximum peak-particle-velocity limits of paragraph (d)(2), the scaled-distance equation of... authority before the initiation of blasting. (2) Maximum peak-particle velocity. (i) The maximum ground... site, in feet Maximum allowable peak particle velocity (V max) for ground vibration, in inches/second 1...

30 CFR 817.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2013 CFR

2013-07-01

... either the maximum peak-particle-velocity limits of paragraph (d)(2), the scaled-distance equation of... authority before the initiation of blasting. (2) Maximum peak-particle velocity. (i) The maximum ground... site, in feet Maximum allowable peak particle velocity (V max) for ground vibration, in inches/second 1...

30 CFR 816.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2010 CFR

2010-07-01

... established in accordance with either the maximum peak-particle-velocity limits of paragraph (d)(2), the... in the blasting plan and approved by the regulatory authority. (2) Maximum peak particle velocity. (i... (D), from the blasting site, in feet Maximum allowable peak particle velocity (V max) for ground...

30 CFR 816.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2012 CFR

2012-07-01

... established in accordance with either the maximum peak-particle-velocity limits of paragraph (d)(2), the... in the blasting plan and approved by the regulatory authority. (2) Maximum peak particle velocity. (i... (D), from the blasting site, in feet Maximum allowable peak particle velocity (V max) for ground...

30 CFR 817.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2012 CFR

2012-07-01

... either the maximum peak-particle-velocity limits of paragraph (d)(2), the scaled-distance equation of... authority before the initiation of blasting. (2) Maximum peak-particle velocity. (i) The maximum ground... site, in feet Maximum allowable peak particle velocity (V max) for ground vibration, in inches/second 1...

30 CFR 817.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2010 CFR

2010-07-01

... either the maximum peak-particle-velocity limits of paragraph (d)(2), the scaled-distance equation of... authority before the initiation of blasting. (2) Maximum peak-particle velocity. (i) The maximum ground... site, in feet Maximum allowable peak particle velocity (V max) for ground vibration, in inches/second 1...

30 CFR 816.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2011 CFR

2011-07-01

... established in accordance with either the maximum peak-particle-velocity limits of paragraph (d)(2), the... in the blasting plan and approved by the regulatory authority. (2) Maximum peak particle velocity. (i... (D), from the blasting site, in feet Maximum allowable peak particle velocity (V max) for ground...

30 CFR 817.67 - Use of explosives: Control of adverse effects.

Code of Federal Regulations, 2011 CFR

2011-07-01

... either the maximum peak-particle-velocity limits of paragraph (d)(2), the scaled-distance equation of... authority before the initiation of blasting. (2) Maximum peak-particle velocity. (i) The maximum ground... site, in feet Maximum allowable peak particle velocity (V max) for ground vibration, in inches/second 1...

Visual reaction times during prolonged angular acceleration parallel the subjective perception of rotation

NASA Technical Reports Server (NTRS)

Mattson, D. L.

1975-01-01

The effect of prolonged angular acceleration on choice reaction time to an accelerating visual stimulus was investigated, with 10 commercial airline pilots serving as subjects. The pattern of reaction times during and following acceleration was compared with the pattern of velocity estimates reported during identical trials. Both reaction times and velocity estimates increased at the onset of acceleration, declined prior to the termination of acceleration, and showed an aftereffect. These results are inconsistent with the torsion-pendulum theory of semicircular canal function and suggest that the vestibular adaptation is of central origin.

Very Low Cost Expendable Harassment System Design Study. Volume 3

DTIC Science & Technology

1975-12-01

Vst = W = wf. w = g a, = a O. 3D LO * n ■ 0 = thrust horsepower anailable (hp) thrust horsepower required (hp) airspeed (mph) stall...A-113 ^rr-r-^rfr^r- "- -—’^’ iääaääiäitämäiA Hi^l^Wt^MjMW^1^-^^^ APPENDIX A-6-2 DESIGN OUTPUT VST SL VST 3K WEIGHT VST (S=17,0... angular velocity change of rolling moment from a change in yaw angular velocity change of rolling moment from a change in sideslip angle change of

Stellar Angular Momentum Distributions and Preferential Radial Migration

NASA Astrophysics Data System (ADS)

Wyse, Rosemary; Daniel, Kathryne J.

2018-04-01

I will present some results from our recent investigations into the efficiency of radial migration in stellar disks of differing angular momentum distributions, within a given adopted 2D spiral disk potential. We apply to our models an analytic criterion that determines whether or not individual stars are in orbits that could lead to radial migration around the corotation resonance. We couch our results in terms of the local stellar velocity dispersion and find that the fraction of stars that could migrate radially decreases as the velocity dispersion increases. I will discuss implications and comparisons with the results of other approaches.

Multiple Model Adaptive Attitude Control of LEO Satellite with Angular Velocity Constraints

NASA Astrophysics Data System (ADS)

Shahrooei, Abolfazl; Kazemi, Mohammad Hosein

2018-04-01

In this paper, the multiple model adaptive control is utilized to improve the transient response of attitude control system for a rigid spacecraft. An adaptive output feedback control law is proposed for attitude control under angular velocity constraints and its almost global asymptotic stability is proved. The multiple model adaptive control approach is employed to counteract large uncertainty in parameter space of the inertia matrix. The nonlinear dynamics of a low earth orbit satellite is simulated and the proposed control algorithm is implemented. The reported results show the effectiveness of the suggested scheme.

On the Origin of Rotation of a Celestial Body

NASA Astrophysics Data System (ADS)

Vujičić, V. A.

1988-03-01

The differential equations of the self-rotation of a celestial body have been evaluated. From an integral of these equations a formula for angular velocity of the celestial body was obtained. This formula after being applied to the rotation of the Sun and of the Earth gives, respectively, the following angular velocity ranges: 0.588×10-6<ω<18, 187×10-6 and 0.7533×10-5<ω<12,4266×10-5. These are up to three times narrower than those previously obtained by Savić and Kašanin [1].

Numerical Solution of the Navier-Stokes Equations for Steady Magnetohydrodynamic Flow Between Two Parallel Porous Plates with an Angular Velocity

NASA Astrophysics Data System (ADS)

Delhi Babu, R.; Ganesh, S.

2018-04-01

The Steady Laminar stream of an electrically directing thick, incompressible liquid between two parallel permeable plates of a divert within the sight of a transverse attractive field with an angular velocity when the liquid is being pulled back through both the dividers of the channel at a similar rate with a precise speed is examined. Numerical arrangement is acquired for various estimations of R (Suction Reynolds number) utilizing R-K Gill's technique and the diagrams of dimensionless functions f ' and f have been drawn.

SU-E-I-44: Some Preliminary Analysis of Angular Distribution of X-Ray Scattered On Soft Tissues

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

Ganezer, K; Krmar, M; Cvejic, Z

2015-06-15

Purpose: The angular distribution of x-radiation scattered at small angles (up to 16 degrees) from several different animal soft tissue (skin, fat, muscle, retina, etc) were measured using standard equipment devoted to study of crystal structure which provides excellent geometry conditions of measurements. showed measurable differences for different tissues. In the simplest possible case when measured samples do not differ in structure (different concentration solutions) it can be seen that intensity of scattered radiation is decreasing function of the concentration and the peak of the maximum of scattering distribution depends on the concentration as well. Methods: An x-ray scattering profilemore » usually consists of sharp diffraction peak; however some properties of the spatial profiles of scattered radiation as intensity, the peak position, height, area, FWHM, the ratio of peak heights, etc. Results: The data contained measurable differences for different tissues. In the simplest possible case when measured samples do not differ in structure (different concentration solutions) it can be seen that intensity of scattered radiation is decreasing function of the concentration and the peak of the maximum of scattering distribution depends on the concentration as well. Measurements of different samples in the very preliminary phase showed that simple biological material used in study showed slightly different scattering pattern, especially at higher angles (around 10degrees). Intensity of radiation scattered from same tissue type is very dependent on water content and several more parameters. Conclusion: This preliminary study using animal soft tissues on the angular distributions of scattered x-rays suggests that angular distributions of X-rays scattered off of soft tissues might be useful in distinguishing healthy tissue from malignant soft tissue.« less

Detection of CI line emission towards the oxygen-rich AGB star omi Ceti

NASA Astrophysics Data System (ADS)

Saberi, M.; Vlemmings, W. H. T.; De Beck, E.; Montez, R.; Ramstedt, S.

2018-05-01

We present the detection of neutral atomic carbon CI(3P1-3P0) line emission towards omi Cet. This is the first time that CI is detected in the envelope around an oxygen-rich M-type asymptotic giant branch (AGB) star. We also confirm the previously tentative CI detection around V Hya, a carbon-rich AGB star. As one of the main photodissociation products of parent species in the circumstellar envelope (CSE) around evolved stars, CI can be used to trace sources of ultraviolet (UV) radiation in CSEs. The observed flux density towards omi Cet can be reproduced by a shell with a peak atomic fractional abundance of 2.4 × 10-5 predicted based on a simple chemical model where CO is dissociated by the interstellar radiation field. However, the CI emission is shifted by 4 km s-1 from the stellar velocity. Based on this velocity shift, we suggest that the detected CI emission towards omi Cet potentially arises from a compact region near its hot binary companion. The velocity shift could, therefore, be the result of the orbital velocity of the binary companion around omi Cet. In this case, the CI column density is estimated to be 1.1 × 1019 cm-2. This would imply that strong UV radiation from the companion and/or accretion of matter between two stars is most likely the origin of the CI enhancement. However, this hypothesis can be confirmed by high-angular resolution observations.

Angular Impact Mitigation System for Bicycle Helmets to Reduce Head Acceleration and Risk of Traumatic Brain Injury

PubMed Central

Hansen, Kirk; Dau, Nathan; Feist, Florian; Deck, Caroline; Willinger, Rémy; Madey, Steven M.; Bottlang, Michael

2013-01-01

Angular acceleration of the head is a known cause of traumatic brain injury (TBI), but contemporary bicycle helmets lack dedicated mechanisms to mitigate angular acceleration. A novel Angular Impact Mitigation (AIM) system for bicycle helmets has been developed that employs an elastically suspended aluminum honeycomb liner to absorb linear acceleration in normal impacts as well as angular acceleration in oblique impacts. This study tested bicycle helmets with and without AIM technology to comparatively assess impact mitigation. Normal impact tests were performed to measure linear head acceleration. Oblique impact tests were performed to measure angular head acceleration and neck loading. Furthermore, acceleration histories of oblique impacts were analyzed in a computational head model to predict the resulting risk of TBI in the form of concussion and diffuse axonal injury (DAI). Compared to standard helmets, AIM helmets resulted in a 14% reduction in peak linear acceleration (p < 0.001), a 34% reduction in peak angular acceleration (p < 0.001), and a 22% to 32% reduction in neck loading (p < 0.001). Computational results predicted that AIM helmets reduced the risk of concussion and DAI by 27% and 44%, respectively. In conclusion, these results demonstrated that AIM technology could effectively improve impact mitigation compared to a contemporary expanded polystyrene-based bicycle helmet, and may enhance prevention of bicycle-related TBI. Further research is required. PMID:23770518

Cascaded Kalman and particle filters for photogrammetry based gyroscope drift and robot attitude estimation.

PubMed

Sadaghzadeh N, Nargess; Poshtan, Javad; Wagner, Achim; Nordheimer, Eugen; Badreddin, Essameddin

2014-03-01

Based on a cascaded Kalman-Particle Filtering, gyroscope drift and robot attitude estimation method is proposed in this paper. Due to noisy and erroneous measurements of MEMS gyroscope, it is combined with Photogrammetry based vision navigation scenario. Quaternions kinematics and robot angular velocity dynamics with augmented drift dynamics of gyroscope are employed as system state space model. Nonlinear attitude kinematics, drift and robot angular movement dynamics each in 3 dimensions result in a nonlinear high dimensional system. To reduce the complexity, we propose a decomposition of system to cascaded subsystems and then design separate cascaded observers. This design leads to an easier tuning and more precise debugging from the perspective of programming and such a setting is well suited for a cooperative modular system with noticeably reduced computation time. Kalman Filtering (KF) is employed for the linear and Gaussian subsystem consisting of angular velocity and drift dynamics together with gyroscope measurement. The estimated angular velocity is utilized as input of the second Particle Filtering (PF) based observer in two scenarios of stochastic and deterministic inputs. Simulation results are provided to show the efficiency of the proposed method. Moreover, the experimental results based on data from a 3D MEMS IMU and a 3D camera system are used to demonstrate the efficiency of the method. © 2013 ISA Published by ISA All rights reserved.

Validity and reliability of the G-Cog device for kinematic measurements.

PubMed

Chiementin, X; Crequy, S; Bertucci, W

2013-11-01

The aim of this study was to test the validity and the reliability of the G-Cog which is a new BMX powermeter allowing for the measurements of the acceleration on X-Y-Z axis (250 Hz) at the BMX rear wheel. These measurements allow computing lateral, angular, linear acceleration, angular, linear velocity and the distance. Mechanical measurements at submaximal intensities in standardized laboratory conditions and during maximal exercises in the field conditions were performed to analyse the reliability of the G-Cog accelerometers. The performances were evaluated in comparison with an industrial accelerometer and with 2 powermeters, the SRM and PowerTap. Our results in laboratory conditions show that the G-Cog measurements have low value of variation coefficient (CV=2.35%). These results suggest that the G-cog accelerometers measurements are reproducible. The ratio limits of agreement of the rear hub angular velocity differences between the SRM and the G-Cog were 1.010 × ÷ 1.024 (95%CI=0.986-1.034) and between PowerTap and G-Cog were 0.993 × ÷ 1.019 (95%CI=0.974-1.012). In conclusion, our results suggest that the G-Cog angular velocity measurements are valid and reliable compared with SRM and PowerTap and could be used to analyse the kinematics during BMX actual conditions. © Georg Thieme Verlag KG Stuttgart · New York.

Stabilization and mobility of the head and trunk in wild monkeys during terrestrial and flat-surface walks and gallops.

PubMed

Dunbar, Donald C; Badam, Gyani L; Hallgrímsson, Benedikt; Vieilledent, Stéphane

2004-02-01

This study investigated the patterns of rotational mobility (> or =20 degrees ) and stability (< or =20 degrees ) of the head and trunk in wild Indian monkeys during natural locomotion on the ground and on the flat-topped surfaces of walls. Adult hanuman langurs (Semnopithecus entellus) and bonnet macaques (Macaca radiata) of either gender were cine filmed in lateral view. Whole-body horizontal linear displacement, head and trunk pitch displacement relative to space (earth horizontal), and vertical head displacement were measured from the cine films. Head-to-trunk pitch angle was calculated from the head-to-space and trunk-to-space measurements. Locomotor velocities, cycle durations, angular segmental velocities, mean segmental positions and mean peak frequencies of vertical and angular head displacements were then calculated from the displacement data. Yaw rotations were observed qualitatively. During quadrupedal walks by both species, the head was free to rotate in the pitch and yaw planes on a stabilized trunk. By contrast, during quadrupedal gallops by both species, the trunk pitched on a stabilized head. During both gaits in both species, head and trunk pitch rotations were symmetrical about comparable mean positions in both gaits, with mean head position aligning the horizontal semicircular canals near earth horizontal. Head pitch direction countered head vertical displacement direction to varying degrees during walks and only intermittently during gallops, providing evidence that correctional head pitch rotations are not essential for gaze stabilization. Head-to-space pitch velocities were below 350 deg. s(-1), the threshold above which, at least among humans, the vestibulo-ocular reflex (VOR) becomes saturated. Mean peak frequencies of vertical translations and pitch rotations of the head ranged from 1 Hz to 2 Hz, a lower frequency range than that in which inertia is predicted to be the major stabilizer of the head in these species. Some variables, which were common to both walks and gallops in both species, are likely to reflect constraints in sensorimotor control. Other variables, which differed between the two gaits in both species, are likely to reflect kinematic differences, whereas variables that differed between the two species are attributed primarily to morphological and behavioural differences. It is concluded that either the head or the trunk can provide the nervous system with a reference frame for spatial orientation and that the segment providing that reference can change, depending upon the kinematic characteristics of the chosen gait.

[Intensification of the penicillin drying process based on the theory of short-term contact of material with a heat-exchange surface].

PubMed

Sadykov, R A; Migunov, V V

1987-01-01

The process of potassium benzylpenicillin vacuum drying was investigated. The kinetics of the process showed that a larger period of the drying process was needed for eliminating bound moisture. The influence of the angular velocity of the drier drum rotation on drying duration was studied in a short-term contact model. It was shown that intensity of drying increased with increasing velocity of the drum rotation. Experimental trials confirmed the conclusion and revealed adequacy of the relationship between the drying time and dispersion intensity in the short-term contact model. A qualitative dependence of the coefficient of convective heat exchange between the heating surface and the product on the angular velocity of the drier drum rotation was constructed.

Unveiling acoustic physics of the CMB using nonparametric estimation of the temperature angular power spectrum for Planck

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

Aghamousa, Amir; Shafieloo, Arman; Arjunwadkar, Mihir

2015-02-01

Estimation of the angular power spectrum is one of the important steps in Cosmic Microwave Background (CMB) data analysis. Here, we present a nonparametric estimate of the temperature angular power spectrum for the Planck 2013 CMB data. The method implemented in this work is model-independent, and allows the data, rather than the model, to dictate the fit. Since one of the main targets of our analysis is to test the consistency of the ΛCDM model with Planck 2013 data, we use the nuisance parameters associated with the best-fit ΛCDM angular power spectrum to remove foreground contributions from the data atmore » multipoles ℓ ≥50. We thus obtain a combined angular power spectrum data set together with the full covariance matrix, appropriately weighted over frequency channels. Our subsequent nonparametric analysis resolves six peaks (and five dips) up to ℓ ∼1850 in the temperature angular power spectrum. We present uncertainties in the peak/dip locations and heights at the 95% confidence level. We further show how these reflect the harmonicity of acoustic peaks, and can be used for acoustic scale estimation. Based on this nonparametric formalism, we found the best-fit ΛCDM model to be at 36% confidence distance from the center of the nonparametric confidence set—this is considerably larger than the confidence distance (9%) derived earlier from a similar analysis of the WMAP 7-year data. Another interesting result of our analysis is that at low multipoles, the Planck data do not suggest any upturn, contrary to the expectation based on the integrated Sachs-Wolfe contribution in the best-fit ΛCDM cosmology.« less

A Variational Property of the Velocity Distribution in a System of Material Particles

ERIC Educational Resources Information Center

Siboni, S.

2009-01-01

A simple variational property concerning the velocity distribution of a set of point particles is illustrated. This property provides a full characterization of the velocity distribution which minimizes the kinetic energy of the system for prescribed values of linear and angular momentum. Such a characterization is applied to discuss the kinetic…

Functional phases and angular momentum characteristics of Tkatchev and Kovacs.

PubMed

Irwin, Gareth; Exell, Timothy A; Manning, Michelle L; Kerwin, David G

2017-03-01

Understanding the technical requirements and underlying biomechanics of complex release and re-grasp skills on high bar allows coaches and scientists to develop safe and effective training programmes. The aim of this study was to examine the differences in the functional phases between the Tkatchev and Kovacs skills and to explain how the angular momentum demands are addressed. Images of 18 gymnasts performing 10 Tkatchevs and 8 Kovacs at the Olympic Games were recorded (50 Hz), digitised and reconstructed (3D Direct Linear Transformation). Orientation of the functional phase action, defined by the rapid flexion to extension of the shoulders and extension to flexion of the hips as the performer passed through the lower vertical, along with shoulder and hip angular kinematics, angular momentum and key release parameters (body angle, mass centre velocity and angular momentum about the mass centre and bar) were compared between skills. Expected differences in the release parameters of angle, angular momentum and velocity were observed and the specific mechanical requirement of each skill were highlighted. Whilst there were no differences in joint kinematics, hip and shoulder functional phase were significantly earlier in the circle for the Tkatchev. These findings highlight the importance of the orientation of the functional phase in the preceding giant swing and provide coaches with further understanding of the critical timing in this key phase.

Real-time three-dimensional color Doppler echocardiography for characterizing the spatial velocity distribution and quantifying the peak flow rate in the left ventricular outflow tract

NASA Technical Reports Server (NTRS)

Tsujino, H.; Jones, M.; Shiota, T.; Qin, J. X.; Greenberg, N. L.; Cardon, L. A.; Morehead, A. J.; Zetts, A. D.; Travaglini, A.; Bauer, F.;

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

Jee, I.; Komatsu, E.; Suyu, S.H., E-mail: ijee@mpa-garching.mpg.de, E-mail: komatsu@mpa-garching.mpg.de, E-mail: suyu@asiaa.sinica.edu.tw

The distance-redshift relation plays a fundamental role in constraining cosmological models. In this paper, we show that measurements of positions and time delays of strongly lensed images of a background galaxy, as well as those of the velocity dispersion and mass profile of a lens galaxy, can be combined to extract the angular diameter distance of the lens galaxy. Physically, as the velocity dispersion and the time delay give a gravitational potential (GM/r) and a mass (GM) of the lens, respectively, dividing them gives a physical size (r) of the lens. Comparing the physical size with the image positions ofmore » a lensed galaxy gives the angular diameter distance to the lens. A mismatch between the exact locations at which these measurements are made can be corrected by measuring a local slope of the mass profile. We expand on the original idea put forward by Paraficz and Hjorth, who analyzed singular isothermal lenses, by allowing for an arbitrary slope of a power-law spherical mass density profile, an external convergence, and an anisotropic velocity dispersion. We find that the effect of external convergence cancels out when dividing the time delays and velocity dispersion measurements. We derive a formula for the uncertainty in the angular diameter distance in terms of the uncertainties in the observables. As an application, we use two existing strong lens systems, B1608+656 (z{sub L}=0.6304) and RXJ1131−1231 (z{sub L}=0.295), to show that the uncertainty in the inferred angular diameter distances is dominated by that in the velocity dispersion, σ{sup 2}, and its anisotropy. We find that the current data on these systems should yield about 16% uncertainty in D{sub A} per object. This improves to 13% when we measure σ{sup 2} at the so-called sweet-spot radius. Achieving 7% is possible if we can determine σ{sup 2} with 5% precision.« less

Angular distributions in multifragmentation

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

Stoenner, R.W.; Klobuchar, R.L.; Haustein, P.E.

2006-04-15

Angular distributions are reported for {sup 37}Ar and {sup 127}Xe from 381-GeV {sup 28}Si+Au interactions and for products between {sup 24}Na and {sup 149}Gd from 28-GeV {sup 1}H+Au. Sideward peaking and forward deficits for multifragmentation products are significantly enhanced for heavy ions compared with protons. Projectile kinetic energy does not appear to be a satisfactory scaling variable. The data are discussed in terms of a kinetic-focusing model in which sideward peaking is due to transverse motion of the excited product from the initial projectile-target interaction.

Coordinated turn-and-reach movements. I. Anticipatory compensation for self-generated coriolis and interaction torques

NASA Technical Reports Server (NTRS)

Pigeon, Pascale; Bortolami, Simone B.; DiZio, Paul; Lackner, James R.

2003-01-01

When reaching movements involve simultaneous trunk rotation, additional interaction torques are generated on the arm that are absent when the trunk is stable. To explore whether the CNS compensates for such self-generated interaction torques, we recorded hand trajectories in reaching tasks involving various amplitudes and velocities of arm extension and trunk rotation. Subjects pointed to three targets on a surface slightly above waist level. Two of the target locations were chosen so that a similar arm configuration relative to the trunk would be required for reaching to them, one of these targets requiring substantial trunk rotation, the other very little. Significant trunk rotation was necessary to reach the third target, but the arm's radial distance to the body remained virtually unchanged. Subjects reached at two speeds-a natural pace (slow) and rapidly (fast)-under normal lighting and in total darkness. Trunk angular velocity and finger velocity relative to the trunk were higher in the fast conditions but were not affected by the presence or absence of vision. Peak trunk velocity increased with increasing trunk rotation up to a maximum of 200 degrees /s. In slow movements, peak finger velocity relative to the trunk was smaller when trunk rotation was necessary to reach the targets. In fast movements, peak finger velocity was approximately 1.7 m/s for all targets. Finger trajectories were more curved when reaching movements involved substantial trunk rotation; however, the terminal errors and the maximal deviation of the trajectory from a straight line were comparable in slow and fast movements. This pattern indicates that the larger Coriolis, centripetal, and inertial interaction torques generated during rapid reaches were compensated by additional joint torques. Trajectory characteristics did not vary with the presence or absence of vision, indicating that visual feedback was unnecessary for anticipatory compensations. In all reaches involving trunk rotation, the finger movement generally occurred entirely during the trunk movement, indicating that the CNS did not minimize Coriolis forces incumbent on trunk rotation by sequencing the arm and trunk motions into a turn followed by a reach. A simplified model of the arm/trunk system revealed that additional interaction torques generated on the arm during voluntary turning and reaching were equivalent to < or =1.8 g (1 g = 9.81 m/s(2)) of external force at the elbow but did not degrade performance. In slow-rotation room studies involving reaching movements during passive rotation, Coriolis forces as small as 0.2 g greatly deflect movement trajectories and endpoints. We conclude that compensatory motor innervations are engaged in a predictive fashion to counteract impending self-generated interaction torques during voluntary reaching movements.

Coordinated turn-and-reach movements. I. Anticipatory compensation for self-generated coriolis and interaction torques.

PubMed

Pigeon, Pascale; Bortolami, Simone B; DiZio, Paul; Lackner, James R

2003-01-01

When reaching movements involve simultaneous trunk rotation, additional interaction torques are generated on the arm that are absent when the trunk is stable. To explore whether the CNS compensates for such self-generated interaction torques, we recorded hand trajectories in reaching tasks involving various amplitudes and velocities of arm extension and trunk rotation. Subjects pointed to three targets on a surface slightly above waist level. Two of the target locations were chosen so that a similar arm configuration relative to the trunk would be required for reaching to them, one of these targets requiring substantial trunk rotation, the other very little. Significant trunk rotation was necessary to reach the third target, but the arm's radial distance to the body remained virtually unchanged. Subjects reached at two speeds-a natural pace (slow) and rapidly (fast)-under normal lighting and in total darkness. Trunk angular velocity and finger velocity relative to the trunk were higher in the fast conditions but were not affected by the presence or absence of vision. Peak trunk velocity increased with increasing trunk rotation up to a maximum of 200 degrees /s. In slow movements, peak finger velocity relative to the trunk was smaller when trunk rotation was necessary to reach the targets. In fast movements, peak finger velocity was approximately 1.7 m/s for all targets. Finger trajectories were more curved when reaching movements involved substantial trunk rotation; however, the terminal errors and the maximal deviation of the trajectory from a straight line were comparable in slow and fast movements. This pattern indicates that the larger Coriolis, centripetal, and inertial interaction torques generated during rapid reaches were compensated by additional joint torques. Trajectory characteristics did not vary with the presence or absence of vision, indicating that visual feedback was unnecessary for anticipatory compensations. In all reaches involving trunk rotation, the finger movement generally occurred entirely during the trunk movement, indicating that the CNS did not minimize Coriolis forces incumbent on trunk rotation by sequencing the arm and trunk motions into a turn followed by a reach. A simplified model of the arm/trunk system revealed that additional interaction torques generated on the arm during voluntary turning and reaching were equivalent to < or =1.8 g (1 g = 9.81 m/s(2)) of external force at the elbow but did not degrade performance. In slow-rotation room studies involving reaching movements during passive rotation, Coriolis forces as small as 0.2 g greatly deflect movement trajectories and endpoints. We conclude that compensatory motor innervations are engaged in a predictive fashion to counteract impending self-generated interaction torques during voluntary reaching movements.

Ground motion hazard from supershear rupture

USGS Publications Warehouse

Andrews, D.J.

2010-01-01

An idealized rupture, propagating smoothly near a terminal rupture velocity, radiates energy that is focused into a beam. For rupture velocity less than the S-wave speed, radiated energy is concentrated in a beam of intense fault-normal velocity near the projection of the rupture trace. Although confined to a narrow range of azimuths, this beam diverges and attenuates. For rupture velocity greater than the S-wave speed, radiated energy is concentrated in Mach waves forming a pair of beams propagating obliquely away from the fault. These beams do not attenuate until diffraction becomes effective at large distance. Events with supershear and sub-Rayleigh rupture velocity are compared in 2D plane-strain calculations with equal stress drop, fracture energy, and rupture length; only static friction is changed to determine the rupture velocity. Peak velocity in the sub-Rayleigh case near the termination of rupture is larger than peak velocity in the Mach wave in the supershear case. The occurrence of supershear rupture propagation reduces the most intense peak ground velocity near the fault, but it increases peak velocity within a beam at greater distances.

Methodology issues concerning the accuracy of kinematic data collection and analysis using the ariel performance analysis system

NASA Technical Reports Server (NTRS)

Wilmington, R. P.; Klute, Glenn K. (Editor); Carroll, Amy E. (Editor); Stuart, Mark A. (Editor); Poliner, Jeff (Editor); Rajulu, Sudhakar (Editor); Stanush, Julie (Editor)

1992-01-01

Kinematics, the study of motion exclusive of the influences of mass and force, is one of the primary methods used for the analysis of human biomechanical systems as well as other types of mechanical systems. The Anthropometry and Biomechanics Laboratory (ABL) in the Crew Interface Analysis section of the Man-Systems Division performs both human body kinematics as well as mechanical system kinematics using the Ariel Performance Analysis System (APAS). The APAS supports both analysis of analog signals (e.g. force plate data collection) as well as digitization and analysis of video data. The current evaluations address several methodology issues concerning the accuracy of the kinematic data collection and analysis used in the ABL. This document describes a series of evaluations performed to gain quantitative data pertaining to position and constant angular velocity movements under several operating conditions. Two-dimensional as well as three-dimensional data collection and analyses were completed in a controlled laboratory environment using typical hardware setups. In addition, an evaluation was performed to evaluate the accuracy impact due to a single axis camera offset. Segment length and positional data exhibited errors within 3 percent when using three-dimensional analysis and yielded errors within 8 percent through two-dimensional analysis (Direct Linear Software). Peak angular velocities displayed errors within 6 percent through three-dimensional analyses and exhibited errors of 12 percent when using two-dimensional analysis (Direct Linear Software). The specific results from this series of evaluations and their impacts on the methodology issues of kinematic data collection and analyses are presented in detail. The accuracy levels observed in these evaluations are also presented.

Test-retest reliability of sit-to-stand and stand-to-sit analysis in people with and without chronic non-specific low back pain.

PubMed

Pourahmadi, Mohammad Reza; Ebrahimi Takamjani, Ismail; Jaberzadeh, Shapour; Sarrafzadeh, Javad; Sanjari, Mohammad Ali; Bagheri, Rasool; Jannati, Elham

2018-06-01

Sit-to-stand (STD) and stand-to-sit (SIT) analysis can provide information on functional independence in daily activities in patients with low back pain (LBP). However, in order for measurements to be clinically useful, data on psychometric properties should be available. The main purpose was to investigate intra-rater reliability of STD and SIT tasks in participants with and without chronic non-specific LBP (CNLBP). The second purpose was to detect any differences in lumbar spine and hips sagittal plane kinematics and coordination between asymptomatic individuals and CNLBP patients during STD and SIT. Cross-sectional study. Twenty-three CNLBP patients and 23 demographically-matched controls were recruited. Ten markers were placed on specific anatomical landmarks. Participants were asked to perform STD and SIT at a preferred speed. Peak flexion angles, mean angular velocities, lumbar to hip movement ratios, and relative phase angles were measured. The procedure was repeated after 2 h and 6-8 days. Differences between two groups were analyzed using independent t-test. Intraclass correlation coefficient (ICC 3,k), standard error of measurement (SEM), and limits of agreement (LOAs) were also estimated. The ICC values showed moderate to excellent intra-rater reliability, with relatively low SEM values (≤10.17°). The 95% LOAs demonstrated that there were no differences between the measured parameters. Furthermore, CNLBP patients had limited sagittal plane angles, smaller angular velocities, and lumbar-hip dis-coordination compared to asymptomatic participants. The results indicated moderate to excellent test-retest reliability of STD and SIT analysis. Moreover, CNLBP patients had altered kinematics during STD and its reverse. Copyright © 2017 Elsevier Ltd. All rights reserved.

A contribution to calculation of the mathematical pendulum

NASA Astrophysics Data System (ADS)

Anakhaev, K. N.

2014-11-01

In this work, as a continuation of rigorous solutions of the mathematical pendulum theory, calculated dependences were obtained in elementary functions (with construction of plots) for a complete description of the oscillatory motion of the pendulum with determination of its parameters, such as the oscillation period, deviation angles, time of motion, angular velocity and acceleration, and strains in the pendulum rod (maximum, minimum, zero, and gravitational). The results of calculations according to the proposed dependences closely (≪1%) coincide with the exact tabulated data for individual points. The conditions of ascending at which the angular velocity, angular acceleration, and strains in the pendulum rod reach their limiting values equal to and 5 m 1 g, respectively, are shown. It was revealed that the angular acceleration does not depend on the pendulum oscillation amplitude; the pendulum rod strain equal to the gravitation force of the pendulum R s = m 1 g at the time instant is also independent on the amplitude. The dependences presented in this work can also be invoked for describing oscillations of a physical pendulum, mass on a spring, electric circuit, etc.

A novel HMM distributed classifier for the detection of gait phases by means of a wearable inertial sensor network.

PubMed

Taborri, Juri; Rossi, Stefano; Palermo, Eduardo; Patanè, Fabrizio; Cappa, Paolo

2014-09-02

In this work, we decided to apply a hierarchical weighted decision, proposed and used in other research fields, for the recognition of gait phases. The developed and validated novel distributed classifier is based on hierarchical weighted decision from outputs of scalar Hidden Markov Models (HMM) applied to angular velocities of foot, shank, and thigh. The angular velocities of ten healthy subjects were acquired via three uni-axial gyroscopes embedded in inertial measurement units (IMUs) during one walking task, repeated three times, on a treadmill. After validating the novel distributed classifier and scalar and vectorial classifiers-already proposed in the literature, with a cross-validation, classifiers were compared for sensitivity, specificity, and computational load for all combinations of the three targeted anatomical segments. Moreover, the performance of the novel distributed classifier in the estimation of gait variability in terms of mean time and coefficient of variation was evaluated. The highest values of specificity and sensitivity (>0.98) for the three classifiers examined here were obtained when the angular velocity of the foot was processed. Distributed and vectorial classifiers reached acceptable values (>0.95) when the angular velocity of shank and thigh were analyzed. Distributed and scalar classifiers showed values of computational load about 100 times lower than the one obtained with the vectorial classifier. In addition, distributed classifiers showed an excellent reliability for the evaluation of mean time and a good/excellent reliability for the coefficient of variation. In conclusion, due to the better performance and the small value of computational load, the here proposed novel distributed classifier can be implemented in the real-time application of gait phases recognition, such as to evaluate gait variability in patients or to control active orthoses for the recovery of mobility of lower limb joints.

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

Scheinker, Alexander

Here, we study control of the angular-velocity actuated nonholonomic unicycle, via a simple, bounded extremum seeking controller which is robust to external disturbances and measurement noise. The vehicle performs source seeking despite not having any position information about itself or the source, able only to sense a noise corrupted scalar value whose extremum coincides with the unknown source location. In order to control the angular velocity, rather than the angular heading directly, a controller is developed such that the closed loop system exhibits multiple time scales and requires an analysis approach expanding the previous work of Kurzweil, Jarnik, Sussmann, andmore » Liu, utilizing weak limits. We provide analytic proof of stability and demonstrate how this simple scheme can be extended to include position-independent source seeking, tracking, and collision avoidance of groups on autonomous vehicles in GPS-denied environments, based only on a measure of distance to an obstacle, which is an especially important feature for an autonomous agent.« less

Angular velocity integration in a fly heading circuit.

PubMed

Turner-Evans, Daniel; Wegener, Stephanie; Rouault, Hervé; Franconville, Romain; Wolff, Tanya; Seelig, Johannes D; Druckmann, Shaul; Jayaraman, Vivek

2017-05-22

Many animals maintain an internal representation of their heading as they move through their surroundings. Such a compass representation was recently discovered in a neural population in the Drosophila melanogaster central complex, a brain region implicated in spatial navigation. Here, we use two-photon calcium imaging and electrophysiology in head-fixed walking flies to identify a different neural population that conjunctively encodes heading and angular velocity, and is excited selectively by turns in either the clockwise or counterclockwise direction. We show how these mirror-symmetric turn responses combine with the neurons' connectivity to the compass neurons to create an elegant mechanism for updating the fly's heading representation when the animal turns in darkness. This mechanism, which employs recurrent loops with an angular shift, bears a resemblance to those proposed in theoretical models for rodent head direction cells. Our results provide a striking example of structure matching function for a broadly relevant computation.

Effect of surface mobility on the particle sliding along a bubble or a solid sphere.

PubMed

Wang, Weixing; Zhou, Zhiang; Nandakumar, K; Xu, Zhenghe; Masliyah, Jacob H

2003-03-01

The sliding velocity of glass beads on a spherical surface, made either of an air bubble or of a glass sphere held stationary, is measured to investigate the effect of surface mobility on the particle sliding velocity. The sliding process is recorded with a digital camera and analyzed frame by frame. The sliding glass bead was found to accelerate with increasing angular position on the collector's surface. It reaches a maximum velocity at an angular position of about 100 degrees and then, under certain conditions, the glass bead leaves the surface of the collector. The sliding velocity of the glass bead depends strongly on the surface mobility of a bubble, decreasing with decreasing surface mobility. By a mobile surface we mean one which cannot set up resistive forces to an applied stress on the surface. The sliding velocity on a rigid surface, such as a glass sphere, is much lower than that on a mobile bubble surface. The sliding velocity can be described through a modified Stokes equation. A numerical factor in the modified Stokes equation is determined by fitting the experimental data and is found to increase with decreasing surface mobility. Hydrophobic glass beads sliding on a hydrophobic glass sphere were found to stick at the point of impact without sliding if the initial angular position of the impact is less than some specific angle, which is defined as the critical sticking angle. The sticking of the glass beads can be attributed to the capillary contracting force created by the formation of a cavity due to spontaneous receding of the nonwetting liquid from the contact zone. The relationship between the critical sticking angle and the particle size is established based on the Yushchenko [J. Colloid Interface Sci. 96 (1983) 307] analysis.

Modeling and controlling a robotic convoy using guidance laws strategies.

PubMed

Belkhouche, Fethi; Belkhouche, Boumediene

2005-08-01

This paper deals with the problem of modeling and controlling a robotic convoy. Guidance laws techniques are used to provide a mathematical formulation of the problem. The guidance laws used for this purpose are the velocity pursuit, the deviated pursuit, and the proportional navigation. The velocity pursuit equations model the robot's path under various sensors based control laws. A systematic study of the tracking problem based on this technique is undertaken. These guidance laws are applied to derive decentralized control laws for the angular and linear velocities. For the angular velocity, the control law is directly derived from the guidance laws after considering the relative kinematics equations between successive robots. The second control law maintains the distance between successive robots constant by controlling the linear velocity. This control law is derived by considering the kinematics equations between successive robots under the considered guidance law. Properties of the method are discussed and proven. Simulation results confirm the validity of our approach, as well as the validity of the properties of the method. Index Terms-Guidance laws, relative kinematics equations, robotic convoy, tracking.

Stabilization of gaze during circular locomotion in light. I. Compensatory head and eye nystagmus in the running monkey

NASA Technical Reports Server (NTRS)

Solomon, D.; Cohen, B.

1992-01-01

1. A rhesus and cynomolgus monkey were trained to run around the perimeter of a circular platform in light. We call this "circular locomotion" because forward motion had an angular component. Head and body velocity in space were recorded with angular rate sensors and eye movements with electrooculography (EOG). From these measurements we derived signals related to the angular velocity of the eyes in the head (Eh), of the head on the body (Hb), of gaze on the body (Gb), of the body in space (Bs), of gaze in space (Gs), and of the gain of gaze (Gb/Bs). 2. The monkeys had continuous compensatory nystagmus of the head and eyes while running, which stabilized Gs during the slow phases. The eyes established and maintained compensatory gaze velocities at the beginning and end of the slow phases. The head contributed to gaze velocity during the middle of the slow phases. Slow phase Gb was as high as 250 degrees/s, and targets were fixed for gaze angles as large as 90-140 degrees. 3. Properties of the visual surround affected both the gain and strategy of gaze compensation in the one monkey tested. Gains of Eh ranged from 0.3 to 1.1 during compensatory gaze nystagmus. Gains of Hb varied around 0.3 (0.2-0.7), building to a maximum as Eh dropped while running past sectors of interest. Consistent with predictions, gaze gains varied from below to above unity, when translational and angular body movements with regard to the target were in opposite or the same directions, respectively. 4. Gaze moved in saccadic shifts in the direction of running during quick phases. Most head quick phases were small, and at times the head only paused during an eye quick phase. Eye quick phases were larger, ranging up to 60 degrees. This is larger than quick phases during passive rotation or saccades made with the head fixed. 5. These data indicate that head and eye nystagmus are natural phenomena that support gaze compensation during locomotion. Despite differential utilization of the head and eyes in various conditions, Gb compensated for Bs. There are various frames of reference in which an estimate of angular velocity that drives the head and eyes could be based. We infer that body in space velocity (Bs) is likely to be represented centrally to provide this signal.

Transient Performance of a Vertical Axis Wind Turbine

NASA Astrophysics Data System (ADS)

Onol, Aykut; Yesilyurt, Serhat

2016-11-01

A coupled CFD/rotor dynamics modeling approach is presented for the analysis of realistic transient behavior of a height-normalized, three-straight-bladed VAWT subject to inertial effects of the rotor and generator load which is manipulated by a feedback control under standardized wind gusts. The model employs the k- ɛ turbulence model to approximate unsteady Reynolds-averaged Navier-Stokes equations and is validated with data from field measurements. As distinct from related studies, here, the angular velocity is calculated from the rotor's equation of motion; thus, the dynamic response of the rotor is taken into account. Results include the following: First, the rotor's inertia filters large amplitude oscillations in the wind torque owing to the first-order dynamics. Second, the generator and wind torques differ especially during wind transients subject to the conservation of angular momentum of the rotor. Third, oscillations of the power coefficient exceed the Betz limit temporarily due to the energy storage in the rotor, which acts as a temporary buffer that stores the kinetic energy like a flywheel in short durations. Last, average of transient power coefficients peaks at a smaller tip-speed ratio for wind gusts than steady winds. This work was supported by the Sabanci University Internal Research Grant Program (SU-IRG-985).

Extraordinary rocks from the peak ring of the Chicxulub impact crater: P-wave velocity, density, and porosity measurements from IODP/ICDP Expedition 364

NASA Astrophysics Data System (ADS)

Christeson, G. L.; Gulick, S. P. S.; Morgan, J. V.; Gebhardt, C.; Kring, D. A.; Le Ber, E.; Lofi, J.; Nixon, C.; Poelchau, M.; Rae, A. S. P.; Rebolledo-Vieyra, M.; Riller, U.; Schmitt, D. R.; Wittmann, A.; Bralower, T. J.; Chenot, E.; Claeys, P.; Cockell, C. S.; Coolen, M. J. L.; Ferrière, L.; Green, S.; Goto, K.; Jones, H.; Lowery, C. M.; Mellett, C.; Ocampo-Torres, R.; Perez-Cruz, L.; Pickersgill, A. E.; Rasmussen, C.; Sato, H.; Smit, J.; Tikoo, S. M.; Tomioka, N.; Urrutia-Fucugauchi, J.; Whalen, M. T.; Xiao, L.; Yamaguchi, K. E.

2018-08-01

Joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub impact crater. We present P-wave velocity, density, and porosity measurements from Hole M0077A that reveal unusual physical properties of the peak-ring rocks. Across the boundary between post-impact sedimentary rock and suevite (impact melt-bearing breccia) we measure a sharp decrease in velocity and density, and an increase in porosity. Velocity, density, and porosity values for the suevite are 2900-3700 m/s, 2.06-2.37 g/cm3, and 20-35%, respectively. The thin (25 m) impact melt rock unit below the suevite has velocity measurements of 3650-4350 m/s, density measurements of 2.26-2.37 g/cm3, and porosity measurements of 19-22%. We associate the low velocity, low density, and high porosity of suevite and impact melt rock with rapid emplacement, hydrothermal alteration products, and observations of pore space, vugs, and vesicles. The uplifted granitic peak ring materials have values of 4000-4200 m/s, 2.39-2.44 g/cm3, and 8-13% for velocity, density, and porosity, respectively; these values differ significantly from typical unaltered granite which has higher velocity and density, and lower porosity. The majority of Hole M0077A peak-ring velocity, density, and porosity measurements indicate considerable rock damage, and are consistent with numerical model predictions for peak-ring formation where the lithologies present within the peak ring represent some of the most shocked and damaged rocks in an impact basin. We integrate our results with previous seismic datasets to map the suevite near the borehole. We map suevite below the Paleogene sedimentary rock in the annular trough, on the peak ring, and in the central basin, implying that, post impact, suevite covered the entire floor of the impact basin. Suevite thickness is 100-165 m on the top of the peak ring but 200 m in the central basin, suggesting that suevite flowed downslope from the collapsing central uplift during and after peak-ring formation, accumulating preferentially within the central basin.

ALMA Images of the Orion Hot Core at 349 GHz

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

Wright, M. C. H.; Plambeck, R. L., E-mail: wright@astro.berkeley.edu

We present ALMA images of the dust and molecular line emission in the Orion Hot Core at 349 GHz. At 0.″2 angular resolution the images reveal multiple clumps in an arc ∼1″ east of Orion Source I, the protostar at the center of the Kleinmann–Low Nebula, and another chain of peaks from IRc7 toward the southwest. The molecular line images show narrow filamentary structures at velocities >10 km s{sup −1} away from the heavily resolved ambient cloud velocity ∼5 km s{sup −1}. Many of these filaments trace the SiO outflow from Source I, and lie along the edges of themore » dust emission. Molecular line emission at excitation temperatures 300–2000 K, and velocities >10 km s{sup −1} from the ambient cloud, suggest that the Hot Core may be heated in shocks by the outflow from Source I or from the Becklin–Neugebauer (BN)/SrcI explosion. The spectral line observations also reveal a remarkable molecular ring, ∼2″ south of SrcI, with a diameter ∼600 au. The ring is seen in high-excitation transitions of HC{sub 3}N, HCN v 2 = 1, and SO{sub 2}. An impact of ejecta from the BN/SrcI explosion with a dense dust clump could result in the observed ring of shocked material.« less

Muscle function during jumping in frogs. I. Sarcomere length change, EMG pattern, and jumping performance.

PubMed

Lutz, G J; Rome, L C

1996-08-01

We determined the influence of temperature on muscle function during jumping to better understand how the frog muscular system is designed to generate a high level of mechanical power. Maximal jumping performance and the in vivo operating conditions of the semimembranosus muscle (SM), a hip extensor, were measured and related to the mechanical properties of the isolated SM in the accompanying paper [Muscle function during jumping in frogs. II. Mechanical properties of muscle: implication for system design. Am. J. Physiol. 271 (Cell Physiol. 40): C571-C578, 1996]. Reducing temperature from 25 to 15 degrees C caused a 1.75-fold decline in peak mechanical power generation and a proportional decline in aerial jump distance. The hip and knee joint excursions were nearly the same at both temperatures. Accordingly, sarcomeres shortened over the same range (2.4 to 1.9 microns) at both temperatures, corresponding to myofilament overlap at least 90% of maximal. At the low temperature, however, movements were made more slowly. Angular velocities were 1.2- to 1.4-fold lower, and ground contact time was increased by 1.33-fold at 15 degrees C. Average shortening velocity of the SM was only 1.2-fold lower at 15 degrees C than at 25 degrees C. The low Q10 of velocity is in agreement with that predicted for muscles shortening against an inertial load.

Wind-Tunnel Experiments for Gas Dispersion in an Atmospheric Boundary Layer with Large-Scale Turbulent Motion

NASA Astrophysics Data System (ADS)

Michioka, Takenobu; Sato, Ayumu; Sada, Koichi

2011-10-01

Large-scale turbulent motions enhancing horizontal gas spread in an atmospheric boundary layer are simulated in a wind-tunnel experiment. The large-scale turbulent motions can be generated using an active grid installed at the front of the test section in the wind tunnel, when appropriate parameters for the angular deflection and the rotation speed are chosen. The power spectra of vertical velocity fluctuations are unchanged with and without the active grid because they are strongly affected by the surface. The power spectra of both streamwise and lateral velocity fluctuations with the active grid increase in the low frequency region, and are closer to the empirical relations inferred from field observations. The large-scale turbulent motions do not affect the Reynolds shear stress, but change the balance of the processes involved. The relative contributions of ejections to sweeps are suppressed by large-scale turbulent motions, indicating that the motions behave as sweep events. The lateral gas spread is enhanced by the lateral large-scale turbulent motions generated by the active grid. The large-scale motions, however, do not affect the vertical velocity fluctuations near the surface, resulting in their having a minimal effect on the vertical gas spread. The peak concentration normalized using the root-mean-squared value of concentration fluctuation is remarkably constant over most regions of the plume irrespective of the operation of the active grid.

Bending and shear stresses developed by the instantaneous arrest of the root of a cantilever beam rotating with constant angular velocity about a transverse axis through the root

NASA Technical Reports Server (NTRS)

Stowell, Elbridge Z; Schwartz, Edward B; Houbolt, John C

1945-01-01

A theoretical investigation was made of the behavior of a cantilever beam in rotational motion about a transverse axis through the root determining the stresses, the deflections, and the accelerations that occur in the beam as a result of the arrest of motion. The equations for bending and shear stress reveal that, at a given percentage of the distance from root to tip and at a given trip velocity, the bending stresses for a particular mode are independent of the length of the beam and the shear stresses vary inversely with the length. When examined with respect to a given angular velocity instead of a given tip velocity, the equations reveal that the bending stress is proportional to the length of the beam whereas the shear stress is independent of the length. Sufficient experimental verification of the theory has previously been given in connection with another problem of the same type.

The critical role of velocity storage in production of motion sickness

NASA Technical Reports Server (NTRS)

Cohen, Bernard; Dai, Mingjia; Raphan, Theodore; Young, L. R. (Principal Investigator)

2003-01-01

We propose that motion sickness is mediated through the orientation properties of velocity storage in the vestibular system that tend to align eye velocity produced by the angular vestibulo-ocular reflex (aVOR) with gravito-inertial acceleration (GIA). (GIA is the sum of the linear accelerations acting on the head. In the absence of translational accelerations, gravity is the GIA.) We further postulate that motion sickness produced by cross-coupled vestibular stimulation can be characterized by a metric composed of the disparity between the axis of eye rotation and the GIA, the strength of the response to angular motion, and the response duration, as determined by the central vestibular time constant, that is, by the time constant of velocity storage. The nodulus and uvula of the vestibulocerebellum are likely to be the central sites where the disparity is sensed, where the vestibular time constants are habituated, and where links are made to the autonomic system to produce the symptoms and signs.

Effect of time derivative of contact area on dynamic friction

NASA Astrophysics Data System (ADS)

Arakawa, Kazuo

2014-06-01

This study investigated dynamic friction during oblique impact of a golf ball by evaluating the ball's angular velocity, contact force, and the contact area between the ball and target. The effect of the contact area on the angular velocities was evaluated, and the results indicated that the contact area plays an important role in dynamic friction. In this study, the dynamic friction force F was given by F = μN + μη dA/dt, where μ is the coefficient of friction, N is the contact force, dA/dt is the time derivative of the contact area A, and η is a coefficient associated with the contact area.

How fast can a black hole rotate?

NASA Astrophysics Data System (ADS)

Herdeiro, Carlos A. R.; Radu, Eugen

2015-11-01

Kerr black holes (BHs) have their angular momentum, J, bounded by their mass, M: Jc ≤ GM2. There are, however, known BH solutions violating this Kerr bound. We propose a very simple universal bound on the rotation, rather than on the angular momentum, of four-dimensional, stationary and axisymmetric, asymptotically flat BHs, given in terms of an appropriately defined horizon linear velocity, vH. The vH bound is simply that vH cannot exceed the velocity of light. We verify the vH bound for known BH solutions, including some that violate the Kerr bound, and conjecture that only extremal Kerr BHs saturate the vH bound.

Effect of angular velocity on sensors based on morphology dependent resonances.

PubMed

Ali, Amir R; Ioppolo, Tindaro

2014-04-22

We carried out an analysis to investigate the morphology dependent optical resonances shift (MDR) of a rotating spherical resonator. The spinning resonator experiences an elastic deformation due to the centrifugal force acting on it, leading to a shift in its MDR. Experiments are also carried out to demonstrate the MDR shifts of a spinning polydimethylsiloxane (PDMS) microsphere. The experimental results agree well with the analytical prediction. These studies demonstrated that spinning sensor based on MDR may experience sufficient shift in the optical resonances, therefore interfering with its desirable operational sensor design. Also the results show that angular velocity sensors could be designed using this principle.

Depth and latitude dependence of the solar internal angular velocity

NASA Technical Reports Server (NTRS)

Rhodes, Edward J., Jr.; Cacciani, Alessandro; Korzennik, Sylvain; Tomczyk, Steven; Ulrich, Roger K.; Woodard, Martin F.

1990-01-01

One of the design goals for the dedicated helioseismology observing state located at Mount Wilson Observatory was the measurement of the internal solar rotation using solar p-mode oscillations. In this paper, the first p-mode splittings obtained from Mount Wilson are reported and compared with those from several previously published studies. It is demonstrated that the present splittings agree quite well with composite frequency splittings obtained from the comparisons. The splittings suggest that the angular velocity in the solar equatorial plane is a function of depth below the photosphere. The latitudinal differential rotation pattern visible at the surface appears to persist at least throughout the solar convection zone.

Comparison of experiments and computations for cold gas spraying through a mask. Part 2

NASA Astrophysics Data System (ADS)

Klinkov, S. V.; Kosarev, V. F.; Ryashin, N. S.

2017-03-01

This paper presents experimental and simulation results of cold spray coating deposition using the mask placed above the plane substrate at different distances. Velocities of aluminum (mean size 30 μm) and copper (mean size 60 μm) particles in the vicinity of the mask are determined. It was found that particle velocities have angular distribution in flow with a representative standard deviation of 1.5-2 degrees. Modeling of coating formation behind the mask with account for this distribution was developed. The results of model agree with experimental data confirming the importance of particle angular distribution for coating deposition process in the masked area.

Generalized extended Navier-Stokes theory: correlations in molecular fluids with intrinsic angular momentum.

PubMed

Hansen, J S; Daivis, Peter J; Dyre, Jeppe C; Todd, B D; Bruus, Henrik

2013-01-21

The extended Navier-Stokes theory accounts for the coupling between the translational and rotational molecular degrees of freedom. In this paper, we generalize this theory to non-zero frequencies and wavevectors, which enables a new study of spatio-temporal correlation phenomena present in molecular fluids. To discuss these phenomena in detail, molecular dynamics simulations of molecular chlorine are performed for three different state points. In general, the theory captures the behavior for small wavevector and frequencies as expected. For example, in the hydrodynamic regime and for molecular fluids with small moment of inertia like chlorine, the theory predicts that the longitudinal and transverse intrinsic angular velocity correlation functions are almost identical, which is also seen in the molecular dynamics simulations. However, the theory fails at large wavevector and frequencies. To account for the correlations at these scales, we derive a phenomenological expression for the frequency dependent rotational viscosity and wavevector and frequency dependent longitudinal spin viscosity. From this we observe a significant coupling enhancement between the molecular angular velocity and translational velocity for large frequencies in the gas phase; this is not observed for the supercritical fluid and liquid state points.

Analysis of the 5 iron golf swing when hitting for maximum distance.

PubMed

Healy, Aoife; Moran, Kieran A; Dickson, Jane; Hurley, Cillian; Smeaton, Alan F; O'Connor, Noel E; Kelly, Philip; Haahr, Mads; Chockalingam, Nachiappan

2011-07-01

Most previous research on golf swing mechanics has focused on the driver club. The aim of this study was to identify the kinematic factors that contribute to greater hitting distance when using the 5 iron club. Three-dimensional marker coordinate data were collected (250 Hz) to calculate joint kinematics at eight key swing events, while a swing analyser measured club swing and ball launch characteristics. Thirty male participants were assigned to one of two groups, based on their ball launch speed (high: 52.9 ± 2.1 m · s(-1); low: 39.9 ± 5.2 m · s(-1)). Statistical analyses were used to identify variables that differed significantly between the two groups. Results showed significant differences were evident between the two groups for club face impact point and a number of joint angles and angular velocities, with greater shoulder flexion and less left shoulder internal rotation in the backswing, greater extension angular velocity in both shoulders at early downswing, greater left shoulder adduction angular velocity at ball contact, greater hip joint movement and X Factor angle during the downswing, and greater left elbow extension early in the downswing appearing to contribute to greater hitting distance with the 5 iron club.

A novel clinical evaluation method using maximum angular velocity during knee extension to assess lower extremity muscle function of older adults.

PubMed

Arai, Takeshi; Obuchi, Shuichi; Shiba, Yoshitaka

2017-11-01

The purpose of this study is to examine the utilities of maximum angular velocity (AV) assessment during knee extension (KE) using a gyroscope for clinical evaluation of exercise program for older adults. Two hundred and 4 community-dwelling older adults underwent a 3-month exercise intervention program. Outcome measures included AV during KE and other physical functions (isometric strength (IS), walking abilities, and balance functions). A correlation coefficient was used to evaluate the relationships between AV and other physical functions at baseline. The differences of physical functions before and after intervention were evaluated and the effect size of each measurement was calculated after the program. The AV measurement was significantly correlated with IS during KE (r=0.303, P<0.01) and other physical functions. Most correlation coefficients of angular velocity were greater than that of IS. All of physical assessments were significantly improved. Also, effect size of AV was greater than that of IS (d=0.45 vs. 0.42). AV of the lower extremities is useful to evaluate the effects of exercise intervention in the elderly. Copyright © 2017 Elsevier B.V. All rights reserved.

Three-dimensional simulation of the motion of a single particle under a simulated turbulent velocity field

NASA Astrophysics Data System (ADS)

Moreno-Casas, P. A.; Bombardelli, F. A.

2015-12-01

A 3D Lagrangian particle tracking model is coupled to a 3D channel velocity field to simulate the saltation motion of a single sediment particle moving in saltation mode. The turbulent field is a high-resolution three dimensional velocity field that reproduces a by-pass transition to turbulence on a flat plate due to free-stream turbulence passing above de plate. In order to reduce computational costs, a decoupled approached is used, i.e., the turbulent flow is simulated independently from the tracking model, and then used to feed the 3D Lagrangian particle model. The simulations are carried using the point-particle approach. The particle tracking model contains three sub-models, namely, particle free-flight, a post-collision velocity and bed representation sub-models. The free-flight sub-model considers the action of the following forces: submerged weight, non-linear drag, lift, virtual mass, Magnus and Basset forces. The model also includes the effect of particle angular velocity. The post-collision velocities are obtained by applying conservation of angular and linear momentum. The complete model was validated with experimental results from literature within the sand range. Results for particle velocity time series and distribution of particle turbulent intensities are presented.

Comparing performance and kinematics of throwing with a circular and whip-like wind up by experienced handball players.

PubMed

van den Tillaar, R; Zondag, A; Cabri, J

2013-12-01

The aim of this study was to compare the performance (throwing velocity of the ball) and kinematics of overarm throwing with the circular and whip-like wind up in elite handball players. Twenty-two elite handball players (11 men and 11 women) conducted both types of throws. The ball release velocity, maximal ball acceleration, maximal velocity of the end points of the five segments and maximal angles, angles at ball release and maximal angular velocities of the 11 joint movements and their timing during the throw were analyzed. Significantly higher ball release velocities (21.9 m/s vs 20.6 m/s) were reached together with higher maximal linear velocities of the end points of all segments and longer throwing time with the circular wind up than with the whip-like wind up. Furthermore, it seems that the timing and amount of maximal angular pelvis rotation was the main contributor to the difference in the maximal ball release velocity between the two wind ups. The findings support the observation that overarm throwing with the circular wind up results in higher ball releases but also a longer throwing movement in comparison to whip-like wind up throws. © 2013 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

Discovery of the Rotating Molecular Outflow and Disk in the CLASS-0/I Protostar [BHB2007]#11 in Pipe

NASA Astrophysics Data System (ADS)

Chihomi, Hara; Ryohei, Kawabe; Yoshito, Shimajiri; Junko, Ueda; Takashi, Tsukagoshi; Yasutaka, Kurono; Kazuya, Saigo; Fumitaka, Nakamura; Masao, Saito; Wilner, David

2013-07-01

The loss of angular momentum is inevitable in star formation processes, and the transportation of angular momentum by a molecular flow is widely thought to be one of the important processes. We present the results of our 2'h resolution Submillimeter Array (SMA) observations in CO, 13CO, and C18O(2-1) emissions toward a low-mass Class-0/I protostar, [BHB2007]#11 (hereafter B59#11) at the nearby star forming region, Barnard 59 in the Pipe Nebula (d=130 pc). B59#11 ejects a molecular outflow whose axis lies almost on the plane of the sky, and one of the best targets to investigate the envelope/disk rotation and the velocity structure of the molecular outflow. The 13CO and C18O observations have revealed that a compact (r ˜ 800 AU) and elongated structure of dense gas is associated with B59#11, which orients perpendicular to the outflow axis. Their distributions show the velocity gradients along their major axes, which are considered to arise from the envelope/disk rotation. The specific angular momentum is estimated to be (1.6+/-0.6)e-3 km/s pc. The power-law index of the radial profile of the rotation velocity changes from steeper one, i.e., ˜ -1 to -1/2 at a radius of 140 AU, suggesting the Keplerian disk is formed inside the radius. The central stellar mass is estimated to be ˜1.3 Msun. A collimated molecular outflow is detected from the CO observations. We found in the outflow a velocity gradient which direction is the same as that seen in the dense gas. This is interpreted to be due to the outflow rotation. The specific angular momentum of the outflow is comparable to that of the envelope, suggesting that this outflow play an important role to the ejection of the angular momentum from the envelope/disk system. This is the first case where both the Keplerian disk and the rotation of the molecular outflow were found in the Class-0 or I protostar, and provides one of good targets for ALMA to address the angular momentum ejection in course of star formation.

Full Angular Profile of the Coherent Polarization Opposition Effect

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Luck, Jean-Marc; Nieuwenhuizen, Theo M.

1999-01-01

We use the rigorous vector theory of weak photon localization for a semi-infinite medium composed of nonabsorbing Rayleigh scatterers to compute the full angular profile of the polarization opposition effect. The latter is caused by coherent backscattering of unpolarized incident light and accompanies the renowned backscattering intensity peak.

Crossed beam studies of ion-molecule reactions in methane and ammonia

NASA Technical Reports Server (NTRS)

Smith, G. P. K.; Saunders, M.; Cross, R. J., Jr.

1976-01-01

A crossed-beam apparatus is used to measure the product ion velocity and angular distributions for the following ion-molecule reactions in the relative energy range from 2 to 9 eV: CH4(+) + NH3 yields NH4(+) + CH3; CH4(+) + NH3 yields CNH5(+) + H2; NH2(+) + CH4 yields CNH4(+) + H2 (or 2H); and CH3(+) + NH3 yields CNH4(+) + H2 (or 2H). These reactions are also studied by means of deuterium labeling as a further probe of the detailed reaction dynamics. Probability contour plots for the four reactions are constructed in Cartesian velocity space, and product peaks in the plots are discussed. Relative cross sections and Q values are computed for two of the reactions as well as for the corresponding deuterium-labelled reactions. The results show that the present ion-neutral condensation reactions are highly exothermic with a deep well for the internal complex, that little hydrogen scrambling occurs, and that the energy of the reactions is released mainly as internal energy, even to the extent of producing two hydrogen atoms in some cases rather than one hydrogen atom or molecule.

Movement variability in the golf swing.

PubMed

Langdown, Ben L; Bridge, Matt; Li, Francois-Xavier

2012-06-01

Traditionally, golf biomechanics has focused upon achieving consistency in swing kinematics and kinetics, whilst variability was considered to be noise and dysfunctional. There has been a growing argument that variability is an intrinsic aspect of skilled motor performance and plays a functional role. Two types of variability are described: 'strategic shot selection' and 'movement variability'. In 'strategic shot selection', the outcome remains consistent, but the swing kinematics/kinetics (resulting in the desired ball flight) are free to vary; 'movement variability' is the changes in swing kinematics and kinetics from trial to trial when the golfer attempts to hit the same shot. These changes will emerge due to constraints of the golfer's body, the environment, and the task. Biomechanical research has focused upon aspects of technique such as elite versus non-elite kinematics, kinetics, kinematic sequencing, peak angular velocities of body segments, wrist function, ground reaction forces, and electromyography, mainly in the search for greater distance and clubhead velocity. To date very little is known about the impact of variability on this complex motor skill, and it has yet to be fully researched to determine where the trade-off between functional and detrimental variability lies when in pursuit of enhanced performance outcomes.

Brownian self-propelled particles on a sphere

NASA Astrophysics Data System (ADS)

Apaza-Pilco, Leonardo Felix; Sandoval, Mario

We present the dynamics of a Brownian self-propelled particle at low Reynolds number moving on the surface of a sphere. The effects of curvature and self-propulsion on the diffusion of the particle are elucidated by determining (numerically) the mean-square displacement of the particle's angular (azimuthal and polar) coordinates. The results show that the long time behavior of its angular mean-square displacement is linear in time. We also see that the slope of the angular MSD is proportional to the propulsion velocity and inverse to the curvature of the sphere. The angular probability distribution function (PDF) of the particle is also obtained by numerically solving its respective Smoluchowski equation.

Angular velocities, angular accelerations, and coriolis accelerations

NASA Technical Reports Server (NTRS)

Graybiel, A.

1975-01-01

Weightlessness, rotating environment, and mathematical analysis of Coriolis acceleration is described for man's biological effective force environments. Effects on the vestibular system are summarized, including the end organs, functional neurology, and input-output relations. Ground-based studies in preparation for space missions are examined, including functional tests, provocative tests, adaptive capacity tests, simulation studies, and antimotion sickness.

Transition radiation on a superlattice in finite thickness plate generated by two acoustic waves

NASA Astrophysics Data System (ADS)

Mkrtchyan, A. R.; Parazian, V. V.; Saharian, A. A.

2018-01-01

Forward transition radiation from relativistic electrons is investigated in an ultrasonic superlattice excited in a finite thickness plate by two acoustic waves. In the quasi-classical approximation formulae are derived for the vector potential of the electromagnetic field and for the spectral-angular distribution of the radiation intensity. Zone structures appear in the plate, which makes it possible (by an appropriate choice of the frequencies of the two acoustic waves) to control the spectral-angular distribution of the radiation through changes in the parameters of the medium. The acoustic waves generate new resonance peaks in the spectral and angular distribution of the radiation intensity. The heights of the peaks can be tuned by choosing the parameters of the acoustic waves. Numerical examples are presented for a plate of fused quartz.

Repeating firing fields of CA1 neurons shift forward in response to increasing angular velocity.

PubMed

Cowen, Stephen L; Nitz, Douglas A

2014-01-01

Self-motion information influences spatially-specific firing patterns exhibited by hippocampal neurons. Moreover, these firing patterns can repeat across similar subsegments of an environment, provided that there is similarity of path shape and head orientations across subsegments. The influence of self-motion variables on repeating fields remains to be determined. To investigate the role of path shape and angular rotation on hippocampal activity, we recorded the activity of CA1 neurons from rats trained to run on spiral-shaped tracks. During inbound traversals of circular-spiral tracks, angular velocity increases continuously. Under this condition, most neurons (74%) exhibited repeating fields across at least three adjacent loops. Of these neurons, 86% exhibited forward shifts in the angles of field centers relative to centers on preceding loops. Shifts were absent on squared-spiral tracks, minimal and less reliable on concentric-circle tracks, and absent on outward-bound runs on circular-spiral tracks. However, outward-bound runs on the circular-spiral track in the dark were associated with backward shifts. Together, the most parsimonious interpretation of the results is that continuous increases or decreases in angular velocity are particularly effective at shifting the center of mass of repeating fields, although it is also possible that a nonlinear integration of step counts contributes to the shift. Furthermore, the unexpected absence of field shifts during outward journeys in light (but not darkness) suggests visual cues around the goal location anchored the map of space to an allocentric reference frame.

All You Need to Know about Videodiscs: One Easy Lesson.

ERIC Educational Resources Information Center

Padgett, Helen L.

1993-01-01

Explains videodisc technology and its uses in education. Topics addressed include formats of videodiscs, including CAV discs (constant angular velocity) and CLV discs (constant linear velocity); the three industry-standard levels of interactivity; bar codes; bar-code readers; and finding information on a videodisc. (LRW)

Videodiscs in Schools: Selecting Essential Players and Videodiscs.

ERIC Educational Resources Information Center

Bennett, Priscilla

1995-01-01

Discusses the use of videodiscs in schools and suggests criteria for the selection of videodiscs and videodisc players. Topics include different videodisc formats, including CLV (constant linear velocity) and CAV (constant angular velocity); mapping; repurposing; content and age suitability; documentation; vendors; and Level I and Level II…

Modeling the vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt

NASA Technical Reports Server (NTRS)

Merfeld, D. M.; Paloski, W. H. (Principal Investigator)

1995-01-01

Model simulations of the squirrel monkey vestibulo-ocular reflex (VOR) are presented for two motion paradigms: constant velocity eccentric rotation and roll tilt about a naso-occipital axis. The model represents the implementation of three hypotheses: the "internal model" hypothesis, the "gravito-inertial force (GIF) resolution" hypothesis, and the "compensatory VOR" hypothesis. The internal model hypothesis is based on the idea that the nervous system knows the dynamics of the sensory systems and implements this knowledge as an internal dynamic model. The GIF resolution hypothesis is based on the idea that the nervous system knows that gravity minus linear acceleration equals GIF and implements this knowledge by resolving the otolith measurement of GIF into central estimates of gravity and linear acceleration, such that the central estimate of gravity minus the central estimate of acceleration equals the otolith measurement of GIF. The compensatory VOR hypothesis is based on the idea that the VOR compensates for the central estimates of angular velocity and linear velocity, which sum in a near-linear manner. During constant velocity eccentric rotation, the model correctly predicts that: (1) the peak horizontal response is greater while "facing-motion" than with "back-to-motion"; (2) the axis of eye rotation shifts toward alignment with GIF; and (3) a continuous vertical response, slow phase downward, exists prior to deceleration. The model also correctly predicts that a torsional response during the roll rotation is the only velocity response observed during roll rotations about a naso-occipital axis. The success of this model in predicting the observed experimental responses suggests that the model captures the essence of the complex sensory interactions engendered by eccentric rotation and roll tilt.

Planet Detectability in the Alpha Centauri System

NASA Astrophysics Data System (ADS)

Zhao, Lily; Fischer, Debra A.; Brewer, John; Giguere, Matt; Rojas-Ayala, Bárbara

2018-01-01

We use more than a decade of radial-velocity measurements for α {Cen} A, B, and Proxima Centauri from the High Accuracy Radial Velocity Planet Searcher, CTIO High Resolution Spectrograph, and the Ultraviolet and Visual Echelle Spectrograph to identify the M\\sin i and orbital periods of planets that could have been detected if they existed. At each point in a mass–period grid, we sample a simulated, Keplerian signal with the precision and cadence of existing data and assess the probability that the signal could have been produced by noise alone. Existing data places detection thresholds in the classically defined habitable zones at about M\\sin i of 53 {M}\\oplus for α {Cen} A, 8.4 {M}\\oplus for α {Cen} B, and 0.47 {M}\\oplus for Proxima Centauri. Additionally, we examine the impact of systematic errors, or “red noise” in the data. A comparison of white- and red-noise simulations highlights quasi-periodic variability in the radial velocities that may be caused by systematic errors, photospheric velocity signals, or planetary signals. For example, the red-noise simulations show a peak above white-noise simulations at the period of Proxima Centauri b. We also carry out a spectroscopic analysis of the chemical composition of the α {Centauri} stars. The stars have super-solar metallicity with ratios of C/O and Mg/Si that are similar to the Sun, suggesting that any small planets in the α {Cen} system may be compositionally similar to our terrestrial planets. Although the small projected separation of α {Cen} A and B currently hampers extreme-precision radial-velocity measurements, the angular separation is now increasing. By 2019, α {Cen} A and B will be ideal targets for renewed Doppler planet surveys.

Research on Free Electron Lasers

DTIC Science & Technology

1989-01-01

<exp(Aa)vo) >A = exp((YG -o/2) (67) For the exponential distribution function is another example that results from a symmetric angular spread in the...vo = 47 when there is an angular spread. This indicates that the actual peak moves to the right when 00 increases. The last term term decreases the...value of the gain at vo = F7 when either the angular spread ag or energy spread OG increases. 10. SPIE FEL Review Paper During the contracting period

Horizontal vestibuloocular reflex evoked by high-acceleration rotations in the squirrel monkey. II. Responses after canal plugging

NASA Technical Reports Server (NTRS)

Lasker, D. M.; Backous, D. D.; Lysakowski, A.; Davis, G. L.; Minor, L. B.

1999-01-01

The horizontal angular vestibuloocular reflex (VOR) evoked by high-frequency, high-acceleration rotations was studied in four squirrel monkeys after unilateral plugging of the three semicircular canals. During the period (1-4 days) that animals were kept in darkness after plugging, the gain during steps of acceleration (3, 000 degrees /s(2), peak velocity = 150 degrees /s) was 0.61 +/- 0.14 (mean +/- SD) for contralesional rotations and 0.33 +/- 0.03 for ipsilesional rotations. Within 18-24 h after animals were returned to light, the VOR gain for contralesional rotations increased to 0. 88 +/- 0.05, whereas there was only a slight increase in the gain for ipsilesional rotations to 0.37 +/- 0.07. A symmetrical increase in the gain measured at the plateau of head velocity was noted after animals were returned to light. The latency of the VOR was 8.2 +/- 0. 4 ms for ipsilesional and 7.1 +/- 0.3 ms for contralesional rotations. The VOR evoked by sinusoidal rotations of 0.5-15 Hz, +/-20 degrees /s had no significant half-cycle asymmetries. The recovery of gain for these responses after plugging was greater at lower than at higher frequencies. Responses to rotations at higher velocities for frequencies >/=4 Hz showed an increase in contralesional half-cycle gain, whereas ipsilesional half-cycle gain was unchanged. A residual response that appeared to be canal and not otolith mediated was noted after plugging of all six semicircular canals. This response increased with frequency to reach a gain of 0.23 +/- 0.03 at 15 Hz, resembling that predicted based on a reduction of the dominant time constant of the canal to 32 ms after plugging. A model incorporating linear and nonlinear pathways was used to simulate the data. The coefficients of this model were determined from data in animals with intact vestibular function. Selective increases in the gain for the linear and nonlinear pathways predicted the changes in recovery observed after canal plugging. An increase in gain of the linear pathway accounted for the recovery in VOR gain for both responses at the velocity plateau of the steps of acceleration and for the sinusoidal rotations at lower peak velocities. The increase in gain for contralesional responses to steps of acceleration and sinusoidal rotations at higher frequencies and velocities was due to an increase in the gain of the nonlinear pathway. This pathway was driven into inhibitory cutoff at low velocities and therefore made no contribution for rotations toward the ipsilesional side.

Photoelectric return-stroke velocity and peak current estimates in natural and triggered lightning

NASA Technical Reports Server (NTRS)

Mach, Douglas M.; Rust, W. David

1989-01-01

Two-dimensional photoelectric return stroke velocities from 130 strokes are presented, including 86 negative natural, 41 negative triggered, one positive triggered, and two positive natural return strokes. For strokes starting near the ground and exceeding 500 m in length, the average velocity is 1.3 + or - 0.3 X 10 to the 8th m/s for natural return strokes and 1.2 + or - 0.3 X 10 to the 8th m/s for triggered return strokes. For strokes with lengths less than 500 m, the average velocities are slightly higher. Using the transmission line model (TLM), the shortest segment one-dimensional return stroke velocity, and either the maximum or plateau electric field, it is shown that natural strokes have a peak current distribution that is lognormal with a median value of 16 kA (maximum E) or 12 kA (plateau E). Triggered lightning has a medium peak current value of 21 kA (maximum E) or 15 kA (plateau E). Correlations are found between TLM peak currents and velocities for triggered and natural subsequent return strokes, but not between TLM peak currents and natural first return stroke velocities.

The photodissociation dynamics of the ethyl radical, C2H5, investigated by velocity map imaging.

PubMed

Steinbauer, Michael; Giegerich, Jens; Fischer, Kathrin H; Fischer, Ingo

2012-07-07

The photodissociation dynamics of the ethyl radical C(2)H(5) has been investigated by velocity map imaging. Ethyl was produced by flash pyrolysis from n-propyl nitrite and excited to the à (2)A(') (3s) Rydberg state around 250 nm. The energetically most favorable reaction channel in this wavelength region is dissociation to C(2)H(4) (ethene) + H. The H-atom dissociation products were ionized in a [1+1(')] process via the 1s-2p transition. The observed translational energy distribution is bimodal: A contribution of slow H-atoms with an isotropic angular distribution peaks at low translational energies. An expectation value for the fraction of excess energy released into translation of = 0.19 is derived from the data, typical for statistical dissociation reactions. In addition, a fast H-atom channel is observed, peaking around 1.8 eV. The latter shows an anisotropic distribution with β = 0.45. It originates from a direct dissociation process within less than a rotational period. Time-delay scans with varying extraction voltages indicate the presence of two rates for the formation of H-atoms. One rate with a sub-nanosecond time constant is associated with H-atoms with large translational energy; a second one with a time constant on the order of 100 ns is associated with H-atoms formed with low translational energy. The data confirm and extend those from previous experiments and remove some inconsistencies. Possible mechanisms for the dissociation are discussed in light of the new results as well as previous ones.

The Interplay between Proto--Neutron Star Convection and Neutrino Transport in Core-Collapse Supernovae

NASA Astrophysics Data System (ADS)

Mezzacappa, A.; Calder, A. C.; Bruenn, S. W.; Blondin, J. M.; Guidry, M. W.; Strayer, M. R.; Umar, A. S.

1998-01-01

We couple two-dimensional hydrodynamics to realistic one-dimensional multigroup flux-limited diffusion neutrino transport to investigate proto-neutron star convection in core-collapse supernovae, and more specifically, the interplay between its development and neutrino transport. Our initial conditions, time-dependent boundary conditions, and neutrino distributions for computing neutrino heating, cooling, and deleptonization rates are obtained from one-dimensional simulations that implement multigroup flux-limited diffusion and one-dimensional hydrodynamics. The development and evolution of proto-neutron star convection are investigated for both 15 and 25 M⊙ models, representative of the two classes of stars with compact and extended iron cores, respectively. For both models, in the absence of neutrino transport, the angle-averaged radial and angular convection velocities in the initial Ledoux unstable region below the shock after bounce achieve their peak values in ~20 ms, after which they decrease as the convection in this region dissipates. The dissipation occurs as the gradients are smoothed out by convection. This initial proto-neutron star convection episode seeds additional convectively unstable regions farther out beneath the shock. The additional proto-neutron star convection is driven by successive negative entropy gradients that develop as the shock, in propagating out after core bounce, is successively strengthened and weakened by the oscillating inner core. The convection beneath the shock distorts its sphericity, but on the average the shock radius is not boosted significantly relative to its radius in our corresponding one-dimensional models. In the presence of neutrino transport, proto-neutron star convection velocities are too small relative to bulk inflow velocities to result in any significant convective transport of entropy and leptons. This is evident in our two-dimensional entropy snapshots, which in this case appear spherically symmetric. The peak angle-averaged radial and angular convection velocities are orders of magnitude smaller than they are in the corresponding ``hydrodynamics-only'' models. A simple analytical model supports our numerical results, indicating that the inclusion of neutrino transport reduces the entropy-driven (lepton-driven) convection growth rates and asymptotic velocities by a factor ~3 (50) at the neutrinosphere and a factor ~250 (1000) at ρ = 1012 g cm-3, for both our 15 and 25 M⊙ models. Moreover, when transport is included, the initial postbounce entropy gradient is smoothed out by neutrino diffusion, whereas the initial lepton gradient is maintained by electron capture and neutrino escape near the neutrinosphere. Despite the maintenance of the lepton gradient, proto-neutron star convection does not develop over the 100 ms duration typical of all our simulations, except in the instance where ``low-test'' intial conditions are used, which are generated by core-collapse and bounce simulations that neglect neutrino-electron scattering and ion-ion screening corrections to neutrino-nucleus elastic scattering. Models favoring the development of proto-neutron star convection either by starting with more favorable, albeit artificial (low-test), initial conditions or by including transport corrections that were ignored in our ``fiducial'' models were considered. Our conclusions nonetheless remained the same. Evidence of proto-neutron star convection in our two-dimensional entropy snapshots was minimal, and, as in our fiducial models, the angle-averaged convective velocities when neutrino transport was included remained orders of magnitude smaller than their counterparts in the corresponding hydrodynamics-only models.

Age and sex differences in ranges of motion and motion patterns.

PubMed

Hwang, Jaejin; Jung, Myung-Chul

2015-01-01

This study investigated the effects of age and sex on joint ranges of motion (ROMs) and motion patterns. Forty participants performed 18 motions using eight body segments at self-selected speeds. Older subjects showed smaller ROMs than younger subjects for 11 motions; the greatest difference in ROM was 44.9% for eversion/inversion of the foot. Older subjects also required more time than younger subjects to approach the peak angular velocity for six motions. In contrast, sex significantly affected ROMs but not motion patterns. Male subjects exhibited smaller ROMs than female subjects for four motions; the greatest sex-dependent difference in ROM was 29.7% for ulnar/radial deviation of the hand. The age and sex effects depended on the specific segments used and motions performed, possibly because of differences in anatomical structures and frequencies of use of the joints in habitual physical activities between the groups.

Peak torque and muscle balance in the knees of young U-15 and U-17 soccer athletes playing various tactical positions.

PubMed

Chiamonti Bona, Cleiton; Tourinho Filho, Hugo; Izquierdo, Mikel; Pires Ferraz, Ricardo M; Marques, Mário C

2017-01-01

Soccer is a sport that is practiced worldwide and has been investigated in its various aspects, particularly muscle strength, which is an essential motor skill for sports performance. The objective of this study was to investigate the peak torque and muscle balance on the knee extensor and flexor of young soccer players in the tactical positions of goalkeeper, defender, full back, midfielder, defensive midfielder and striker, as well as to determine which field position has the highest peak torque. Forty-nine male players were recruited and divided into two categories during the preparatory period of the season: the Under-15 (U-15) group (N.=23, mean age 14.7±0.5 years, body mass 58.2±10.5 kg, body height 168.5±7.6 cm), and the Under-17 (U-17) group (N.=26, mean age 16.8±0.4 years, body mass 69.2±7.9 kg, body height 176.2±6.6 cm). The U-17 athletes presented a higher peak torque in all the movements of flexion and extension in the two angular velocities (i.e. 60°/s and 300°/s), but only the dominant knee extensor at 300°/s was significantly different between the two categories as well as the percentage change in peak torque compared between U-15 and U-17 was always above 20%. The peak torque variation in the U-17 category (i.e. mostly above 20%) highlights a higher peak torque compared to U-15 athletes. The muscular deficit of the two categories presented a low average of 10-15%, indicating a good muscle balance between knee extensors and flexors. Finally, goalkeepers and defenders achieved the highest peak torque amongst the field positions.

Relationship between throwing velocity, muscle power, and bar velocity during bench press in elite handball players.

PubMed

Marques, Mario C; van den Tilaar, Roland; Vescovi, Jason D; Gonzalez-Badillo, Juan Jose

2007-12-01

The purpose of this study was to examine the relationship between ball-throwing velocity during a 3-step running throw and dynamic strength, power, and bar velocity during a concentric-only bench-press exercise in team-handball players. Fourteen elite senior male team-handball players volunteered to participate. Each volunteer had power and bar velocity measured during a concentric-only bench-press test with 26, 36, and 46 kg, as well as having 1-repetition-maximum (1-RMBP) strength determined. Ball-throwing velocity was evaluated with a standard 3-step running throw using a radar gun. Ball-throwing velocity was related to the absolute load lifted during the 1-RMBP (r = .637, P = .014), peak power using 36 kg (r = .586, P = .028) and 46 kg (r = .582, P = .029), and peak bar velocity using 26 kg (r = .563, P = .036) and 36 kg (r = .625, P = .017). The results indicate that throwing velocity of elite team-handball players is related to maximal dynamic strength, peak power, and peak bar velocity. Thus, a training regimen designed to improve ball-throwing velocity in elite male team-handball players should include exercises that are aimed at increasing both strength and power in the upper body.

The Fine Art of Using a Laserdisc in the Art Classroom.

ERIC Educational Resources Information Center

Porter, Sharon

1998-01-01

Laserdiscs are an efficient and flexible medium for art presentations in schools. This article discusses laserdiscs, also called videodiscs; distinguishes between constant linear velocity (CLV) and constant angular velocity (CAV) which allows more flexible access; describes the use of bar coding for access; and lists selected visual art…

Outflow structure and velocity field of Orion source. I. ALMA imaging of SiO isotopologue maser and thermal emission

NASA Astrophysics Data System (ADS)

Niederhofer, F.; Humphreys, E. M. L.; Goddi, C.

2012-12-01

Using Science Verification data from the Atacama Large Millimeter/Submillimeter Array (ALMA), we have identified and imaged five rotational transitions (J = 5-4 and J = 6-5) of the three silicon monoxide isotopologues 28SiO v = 0, 1, 2 and 29SiO v = 0 and 28Si18O v = 0 in the frequency range from 214 to 246 GHz towards the Orion BN/KL region. The emission of the ground-state 28SiO, 29SiO and 28Si18O shows an extended bipolar shape in the northeast-southwest direction at the position of Radio Source I, indicating that these isotopologues trace an outflow ( 18 km s-1, PA 50°, 5000 AU in diameter) that is driven by this embedded high-mass young stellar object (YSO). Whereas on small scales (10-1000 AU) the outflow from Source I has a well-ordered spatial and velocity structure, as probed by Very Long Baseline Interferometry (VLBI) imaging of SiO masers, the large scales (500-5000 AU) probed by thermal SiO with ALMA reveal a complex structure and velocity field, most likely related to the effects of the environment of the BN/KL region on the outflow emanating from Source I. The emission of the vibrationally-excited species peaks at the position of Source I. This emission is compact and not resolved at an angular resolution of 1farcs5 ( 600 AU at a distance of 420 pc). 2D Gaussian fitting to individual velocity channels locates emission peaks within radii of 100 AU, i.e. they trace the innermost part of the outflow. A narrow spectral profile and spatial distribution of the v = 1 J = 5-4 line similar to the masing v = 1 J = 1-0 transition, provide evidence for the most highly rotationally excited (frequency > 200 GHz) SiO maser emission associated with Source I known to date. The maser emission will enable studies of the Source I disk-outflow interface with future ALMA longest baselines.

The dynamical properties of dense filaments in the infrared dark cloud G035.39-00.33

NASA Astrophysics Data System (ADS)

Henshaw, J. D.; Caselli, P.; Fontani, F.; Jiménez-Serra, I.; Tan, J. C.

2014-05-01

Infrared dark clouds (IRDCs) are unique laboratories to study the initial conditions of high-mass star and star cluster formation. We present high-sensitivity and high-angular-resolution Institut de Radioastronomie Millimétrique (IRAM) Plateau de Bure Interferometer observations of N2H+ (1-0) towards IRDC G035.39-00.33. It is found that G035.39-00.33 is a highly complex environment, consisting of several mildly supersonic filaments (σ _NT/cs ˜ 1.5), separated in velocity by <1 km s-1. Where multiple spectral components are evident, moment analysis overestimates the non-thermal contribution to the line-width by a factor of ˜2. Large-scale velocity gradients evident in previous single-dish maps may be explained by the presence of substructure now evident in the interferometric maps. Whilst global velocity gradients are small (<0.7 km s-1 pc-1), there is evidence for dynamic processes on local scales (˜1.5-2.5 km s-1 pc-1). Systematic trends in velocity gradient are observed towards several continuum peaks. This suggests that the kinematics are influenced by dense (and in some cases, starless) cores. These trends are interpreted as either infalling material, with accretion rates ˜(7 ± 4) × 10-5 M⊙ yr-1, or expanding shells with momentum ˜24 ± 12 M⊙ km s-1. These observations highlight the importance of high-sensitivity and high-spectral-resolution data in disentangling the complex kinematic and physical structure of massive star-forming regions.