Angular velocity discrimination
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.
Van Essen, H.
2004-01-01
This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to th...
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.
Fluidic angular velocity sensor
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.
Essén, H
2003-01-01
This paper addresses the problem of the separation of rotational and internal motion. It introduces the concept of average angular velocity as the moment of inertia weighted average of particle angular velocities. It extends and elucidates the concept of Jellinek and Li (1989) of separation of the energy of overall rotation in an arbitrary (non-linear) $N$-particle system. It generalizes the so called Koenig's theorem on the two parts of the kinetic energy (center of mass plus internal) to three parts: center of mass, rotational, plus the remaining internal energy relative to an optimally translating and rotating frame.
Factors influencing perceived angular velocity
Kaiser, Mary K.; Calderone, Jack B.
1991-01-01
Angular velocity perception is examined for rotations both in depth and in the image plane and the influence of several object properties on this motion parameter is explored. Two major object properties are considered, namely, texture density which determines the rate of edge transitions for rotations in depth, i.e., the number of texture elements that pass an object's boundary per unit of time, and object size which determines the tangential linear velocities and 2D image velocities of texture elements for a given angular velocity. Results of experiments show that edge-transition rate biased angular velocity estimates only when edges were highly salient. Element velocities had an impact on perceived angular velocity; this bias was associated with 2D image velocity rather than 3D tangential velocity. Despite these biases judgements were most strongly determined by the true angular velocity. Sensitivity to this higher order motion parameter appeared to be good for rotations both in depth (y-axis) and parallel to the line of sight (z-axis).
The integration of angular velocity
Boyle, Michael
2016-01-01
A common problem in physics and engineering is determination of the orientation of an object given its angular velocity. When the direction of the angular velocity changes in time, this is a nontrivial problem involving coupled differential equations. Several possible approaches are examined, along with various improvements over previous efforts. These are then evaluated numerically by comparison to a complicated but analytically known rotation that is motivated by the important astrophysical...
Turbodrill rod angular velocity indicator
Rogachev, O.K.; Belozerova, L.P.; Konenkov, A.K.
1984-01-01
This paper outlines shortcomings of existing types of telemetry systems which resulted in production of the IChT-1 unit. Unit is intended for control of angular velocity of serially produced turbodrill rods, during drilling of wells up to 5000 m deep, and bottomhole temperatures to 100C. The paper provides a detailed description and diagrams for installing this unit.
The integration of angular velocity
Boyle, Michael
2016-01-01
A common problem in physics and engineering is determination of the orientation of an object given its angular velocity. When the direction of the angular velocity changes in time, this is a nontrivial problem involving coupled differential equations. Several possible approaches are examined, along with various improvements over previous efforts. These are then evaluated numerically by comparison to a complicated but analytically known rotation that is motivated by the important astrophysical problem of precessing black-hole binaries. It is shown that a straightforward solution directly using quaternions is most efficient and accurate, and that the norm of the quaternion is irrelevant. Integration of the generator of the rotation can also be made roughly as efficient as integration of the rotation. Both methods will typically be twice as efficient naive vector- or matrix-based methods. Implementation by means of standard general-purpose numerical integrators is stable and efficient, so that such problems can ...
Integrating rotation from angular velocity
Zupan, Eva; Saje, Miran
2011-01-01
Abstract The integration of the rotation from a given angular velocity is often required in practice. The present paper explores how the choice of the parametrization of rotation, when employed in conjuction with different numerical time-integration schemes, effects the accuracy and the computational efficiency. Three rotation parametrizations – the rotational vector, the Argyris tangential vector and the rotational quaternion – are combined with three different numerical time-integration ...
On the relation between angular momentum and angular velocity
Silva, J. P.; Tavares, J. M.
2007-01-01
Students of mechanics usually have difficulties when they learn about the rotation of a rigid body. These difficulties are rooted in the relation between angular momentum and angular velocity, because these vectors are not parallel, and we need in general to utilize a rotating frame of reference or a time dependent inertia tensor. We discuss a series of problems that introduce both difficulties.
Integrating rotation and angular velocity from curvature
Saje, Miran; Treven, Anita
2016-01-01
The problem of integrating the rotational vector from a given angular velocity vector is met in such diverse fields as the navigation, robotics, computer graphics, optical tracking and non-linear dynamics of flexible beams. For example, if the numerical formulation of non-linear dynamics of flexible beams is based on the interpolation of curvature, one needs to derive the rotation from the assumed curvature field. The relation between the angular velocity and the rotation is described by the ...
Angular velocity nonlinear observer from vector measurements
Magnis, Lionel; Petit, Nicolas
2015-01-01
The paper proposes a technique to estimate the angular velocity of a rigid body from vector measurements. Compared to the approaches presented in the literature, it does not use attitude information nor rate gyros as inputs. Instead, vector measurements are directly filtered through a nonlinear observer estimating the angular velocity. Convergence is established using a detailed analysis of the linear-time varying dynamics appearing in the estimation error equation. This equation stems from t...
Angular velocity: a new dimension in nuclei
Diamond, R.M.; Stephens, F.S.
1984-08-09
Nuclei can be studied from their ground states (approx.O(h/2..pi..)) up to angular momenta of order 100 (h/2..pi..), where they are literally pulled apart by centrifugal effects. This range of angular momenta can be viewed as resulting from cranking the nucleus around a rotation axis, where the critical variable is the cranking velocity. The calculated response of nuclei to such an imposed angular velocity corresponds well with recent observations, and includes a rich and varied interplay of collective and single-particle phenomena.
Non-Colinearity of Angular Velocity and Angular Momentum
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)
A neural circuit for angular velocity computation.
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
Samuel B Snider
2010-12-01
Full Text Available 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 neuro-mechanical 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.
Contactless Measurement of Angular Velocity using Circularly Polarized Antennas
Sipal, Vit; Narbudowicz, Adam; Ammann, Max
2014-01-01
An innovative method to measure the angular velocity using circularly polarized antennas is proposed. Due to the properties of circular polarization, the angular velocity is frequency modulated (FM) on a wireless carrier. This enables a low-cost precise continuous measurement of angular velocity using a standard FM demodulator. The hardware can be easily adapted for both high and low angular velocity values. The precise alignment angle between the antennas can be determined if the initial ant...
All-fiber sensor of angular velocity
Andreev, A.TS.; Vlasenko, O.A.; Dianov, E.M.; Diankov, G.L.; Zafirova, B.S.
1989-06-01
The paper reports the construction of an all-fiber optical sensor of angular velocity whose operation is based on the Sagnac effect in a fiber ring interferometer. An all-fiber system does not require the use of external discrete optical elements; division, polarization, and modulation functions are performed by the fiber waveguide itself. The fiber elements and sensor are constructed on the basis of slightly anisotropic fiber waveguides. The sensitivity of the device was 0.0077 deg/sq rt hr, while the zero drift was 0.5 deg/hr. 6 refs.
Motion fading is driven by perceived, not actual angular velocity.
Kohler, P J; Caplovitz, G P; Hsieh, P-J; Sun, J; Tse, P U
2010-06-01
After prolonged viewing of a slowly drifting or rotating pattern under strict fixation, the pattern appears to slow down and then momentarily stop. Here we examine the relationship between such 'motion fading' and perceived angular velocity. Using several different dot patterns that generate emergent virtual contours, we demonstrate that whenever there is a difference in the perceived angular velocity of two patterns of dots that are in fact rotating at the same angular velocity, there is also a difference in the time to undergo motion fading for those two patterns. Conversely, whenever two patterns show no difference in perceived angular velocity, even if in fact rotating at different angular velocities, we find no difference in the time to undergo motion fading. Thus, motion fading is driven by the perceived rather than actual angular velocity of a rotating stimulus. PMID:20371254
Angular velocity and centripetal acceleration relationship
Monteiro, Martín; Cabeza, Cecilia; Marti, Arturo C.; Vogt, Patrik; Kuhn, Jochen
2014-05-01
During the last few years, the growing boom of smartphones has given rise to a considerable number of applications exploiting the functionality of the sensors incorporated in these devices. A sector that has unexpectedly taken advantage of the power of these tools is physics teaching, as reflected in several recent papers. In effect, the use of smartphones has been proposed in several physics experiments spanning mechanics, electromagnetism, optics, oscillations, and waves, among other subjects. Although mechanical experiments have received considerable attention, most of them are based on the use of the accelerometer. An aspect that has received less attention is the use of rotation sensors or gyroscopes. An additional advance in the use of these devices is given by the possibility of obtaining data using the accelerometer and the gyroscope simultaneously. The aim of this paper is to consider the relation between the centripetal acceleration and the angular velocity. Instead of using a formal laboratory setup, in this experiment a smartphone is attached to the floor of a merry-go-round, found in many playgrounds. Several experiments were performed with the roundabout rotating in both directions and with the smart-phone at different distances from the center. The coherence of the measurements is shown.
Angular velocity gradients in the solar convection zone
Gilman, P.A.; Foukal, P.V.
1979-05-01
We test the hypothesis that the weak influence of rotation upon solar supergranulation, resulting in fluid particles conserving their angular momentum while moving radially, is responsible for the outward decrease in angular velocity inferred from the difference between photospheric plasma and sunspot rotation rates. This test is performed using numerical integrations of a Boussinesq spherical convection model for a thin shell at small Taylor number (implying weak influence of rotation). We find that the convection does maintain an outward decrease in angular velocity, which approaches the limit implied by angular momentum conservation as the Rayleigh number or driving for convection is increased.By examining the energetics of the motion, we verify that the dominant process maintaining the calculated angular velocity profile against viscous diffusion is the inward transport of angular momentum by the convection. Axisymmetric meridional circulation plays virtually no role in this process. We further find there is no tendency for convection weakly influenced by rotation to form an equatorial acceleration. We argue from these and earlier calculations that the origin of the Sun's latitudinal gradient of angular velocity is deep in the convection zone. At these depths there may be a strong tendency for angular velocity to be constant on cylinders, implying a positive radial gradient of angular velocity. The latitude gradient is transmitted to the photosphere by supergranulation which locally produces the negative radial gradient in the top layers. We suggest from the rotation of various magnetic features that the transition from negative to positive radial angular velocity gradient occurs near the bottom of the supergranule layer. We argue that angular momentum conservation in radially moving fluid particles should produce a similar angular velocity profile in compressible convecting fluid layers.
Demonstrating the Direction of Angular Velocity in Circular Motion
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…
Angular velocity nonlinear observer from single vector measurements
Magnis, Lionel; Petit, Nicolas
2015-01-01
The paper proposes a technique to estimate the angular velocity of a rigid body from single vector measurements. Compared to the approaches presented in the literature, it does not use attitude information nor rate gyros as inputs. Instead, vector measurements are directly filtered through a nonlinear observer estimating the angular velocity. Convergence is established using a detailed analysis of a linear-time varying dynamics appearing in the estimation error equation. This equation stems f...
Angular-velocity control approach for stance-control orthoses.
Lemaire, Edward D; Goudreau, Louis; Yakimovich, Terris; Kofman, Jonathan
2009-10-01
Currently, stance-control knee orthoses require external control mechanisms to control knee flexion during stance and allow free knee motion during the swing phase of gait. A new angular-velocity control approach that uses a rotary-hydraulic device to resist knee flexion when the knee angular velocity passes a preset threshold is presented. This angular-velocity approach for orthotic stance control is based on the premise that knee-flexion angular velocity during a knee-collapse event, such as a stumble or fall, is greater than that during walking. The new hydraulic knee-flexion control device does not require an external control mechanism to switch from free motion to stance control mode. Functional test results demonstrated that the hydraulic angular-velocity activated knee joint provided free knee motion during walking, engaged upon knee collapse, and supported body weight while the end-user recovered to a safe body position. The joint was tested to 51.6 Nm in single loading tests and passed 200,000 repeated loading cycles with a peak load of 88 Nm per cycle. The hydraulic, angular velocity activation approach has potential to improve safety and security for people with lower extremity weakness or when recovering from joint trauma. PMID:19497821
Measurement of angular velocity in the perception of rotation.
Barraza, José F; Grzywacz, Norberto M
2002-09-01
Humans are sensitive to the parameters of translational motion, namely, direction and speed. At the same time, people have special mechanisms to deal with more complex motions, such as rotations and expansions. One wonders whether people may also be sensitive to the parameters of these complex motions. Here, we report on a series of experiments that explore whether human subjects can use angular velocity to evaluate how fast a rotational motion is. In four experiments, subjects were required to perform a task of speed-of-rotation discrimination by comparing two annuli of different radii in a temporal 2AFC paradigm. Results showed that humans could rely on a sensitive measurement of angular velocity to perform this discrimination task. This was especially true when the quality of the rotational signal was high (given by the number of dots composing the annulus). When the signal quality decreased, a bias towards linear velocity of 5-80% appeared, suggesting the existence of separate mechanisms for angular and linear velocity. This bias was independent from the reference radius. Finally, we asked whether the measurement of angular velocity required a rigid rotation, that is, whether the visual system makes only one global estimate of angular velocity. For this purpose, a random-dot disk was built such that all the dots were rotating with the same tangential speed, irrespectively of radius. Results showed that subjects do not estimate a unique global angular velocity, but that they perceive a non-rigid disk, with angular velocity falling inversely proportionally with radius. PMID:12367744
Variation in Angular Velocity and Angular Acceleration of a Particle in Rectilinear Motion
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…
Alignment of angular velocity sensors for a vestibular prosthesis
DiGiovanna Jack; Carpaneto Jacopo; Micera Silvestro; Merfeld Daniel M
2012-01-01
Abstract 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 r...
Alignment of angular velocity sensors for a vestibular prosthesis.
Digiovanna, Jack; Carpaneto, Jacopo; Micera, Silvestro; Merfeld, Daniel M
2012-01-01
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. PMID:22329908
Relaxation of the Angular Velocity of Pulsars after Glitches
Sedrakian, D. M.; Hayrapetyan, M. V.; Baghdasaryan, D.
2014-03-01
The rotational dynamics of superfluid neutron stars is examined in order to study the relaxation of the angular velocity of pulsars after glitches. The motion of the neutron-proton vortex system is investigated taking the sphericity of the superfluid core and vortex pinning and depinning into account. A relaxation solution is obtained for the angular rotation velocity of pulsars after glitches. In order to compare this solution with observational data for the Vela pulsar, the inverse problem of finding the initial distribution of vortices immediately after a glitch is solved.
Angular velocity response of nanoparticles dispersed in liquid crystal
Huang, Pin-Chun; Shih, Wen-Pin
2013-06-01
A hybrid material of nanoparticles dispersed in liquid crystal changed capacitance after spinning beyond threshold angular velocity. Once the centrifugal force of nanoparticles overcomes the attractive force between liquid crystals, the nanoparticles begin to move. The order of highly viscous liquid crystals is disturbed by the nanoparticles' penetrative movement, and the dielectric constant of the liquid crystal cell changes as a result. We found that the angular velocity response of nanoparticles dispersed in liquid crystal with higher working temperature and nanoparticles' density provided higher sensitivity. The obtained results are important for the continuous improvement of liquid-crystal-based inertial sensors or nano-viscometers.
Relativistic Rotation in the Large Radius, Small Angular Velocity Limit
Klauber, Robert D.
2002-01-01
Relativistic rotation is considered in the limit of angular velocity approaching zero and radial distance approaching infinity, such that centrifugal acceleration is immeasurably small while tangent velocity remains close to the speed of light. For this case, the predictions of the traditional approach to relativistic rotation using local co-moving Lorentz frames are compared and contrasted with those of the differential geometry based non-time-orthogonal analysis approach. Different predicti...
The velocity and angular momentum of a free Dirac electron
Lin, Lu
1998-01-01
It is shown that, in Dirac theory, there is a spatial velocity of a free electron which commutes with the Hamiltonian, so it is a conserved quantity of the motion. Furthermore, there is a spatial orbital angular momentum which also commutes with the Hamiltonian and is a constant of the motion.
Angular Velocity Operator and Barnett-Pegg Formalism
Johal, R S
1997-01-01
We define a new operator within Barnett-Pegg formalism for phase angle. The physical predictions for this operator correspond to those expected of an angular velocity operator. Examples studied are particle on a circle with and without magnetic field and quantum harmonic oscillator.
Alignment of angular velocity sensors for a vestibular prosthesis
DiGiovanna Jack
2012-02-01
Full Text Available Abstract 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.
Wu, Tse-Huai; Lee, Taeyoung
2015-01-01
This paper studies a rigid body attitude tracking control problem with attitude measurements only, when angular velocity measurements are not available. An angular velocity observer is constructed such that the estimated angular velocity is guaranteed to converge to the true angular velocity asymptotically from almost all initial estimates. As it is developed directly on the special orthogonal group, it completely avoids singularities, complexities, or discontinuities caused by minimal attitu...
Global Exponential Angular Velocity Observer for Rigid Body Systems
Berkane, Soulaimane; Abdessameud, Abdelkader; Tayebi, Abdelhamid
2016-01-01
We present a uniformly globally exponentially stable hybrid angular velocity observer for rigid body systems designed directly on $SO(3)\\times\\mathbb{R}^3$. The global exponential stability result makes this observer a good candidate for a controller-observer combination with a guaranteed separation property. Simulation results are provided to demonstrate the effectiveness of the proposed hybrid observer as a part of an attitude stabilization scheme.
Adaptive Neural Network Controller for Thermogenerator Angular Velocity Stabilization System
Horvat, Krunoslav; Šoić, Ines; Kuljača, Ognjen
2013-01-01
The paper presents an analytical and simulation approach for the selection of activation functions for the class of neural network controllers for ship’s thermogenerator angular velocity stabilization system. Such systems can be found in many ships. A Lyapunov-like stability analysis is performed in order to obtain a weight update law. A number of simulations were performed to find the best activation function using integral error criteria and statistical T-tests.
GYROLESS BALL: ESTIMATION OF ANGULAR VELOCITY WITHOUT GYROSCOPE
Magnis, L; Petit, Nicolas
2015-01-01
In [MP15a, MP15b], an algorithm is proposed to estimate the angular velocity of a rigid body using only vector measurements (i.e. measurements of unknown but constant directions). The cases of a single and two vectors measurements have been addressed using similarly structured state-observers. In this note, we report experiments conducted on one such rigid body, here a wood ball, which is equipped with a smartphone. The direction sensors of the smartphone (magnetometer and accelerometer) are ...
Black Hole Statistical Mechanics and The Angular Velocity Ensemble
Thomson, Mitchell; Dyer, Charles C.
2012-01-01
An new ensemble - the angular velocity ensemble - is derived using Jaynes' method of maximising entropy subject to prior information constraints. The relevance of the ensemble to black holes is motivated by a discussion of external parameters in statistical mechanics and their absence from the Hamiltonian of general relativity. It is shown how this leads to difficulty in deriving entropy as a function of state and recovering the first law of thermodynamics from the microcanonical and canonica...
Black Hole Statistical Mechanics and The Angular Velocity Ensemble
Thomson, Mitchell
2012-01-01
An new ensemble - the angular velocity ensemble - is derived using Jaynes' method of maximising entropy subject to prior information constraints. The relevance of the ensemble to black holes is motivated by a discussion of external parameters in statistical mechanics and their absence from the Hamiltonian of general relativity. It is shown how this leads to difficulty in deriving entropy as a function of state and recovering the first law of thermodynamics from the microcanonical and canonical ensembles applied to black holes.
Changing law of launching pitching angular velocity of rotating missile
Liu Guang; Xu Bin; Jiao Xiaojuan; Zhen Tiesheng
2014-01-01
In order to provide accurate launching pitching angular velocity (LPAV) for the exterior trajectory optimization design, multi-flexible body dynamics (MFBD) technology is presented to study the changing law of LPAV of the rotating missile based on spiral guideway. An MFBD virtual prototype model of the rotating missile launching system is built using multi-body dynamics modeling technology based on the built flexible body models of key components and the special force model. The built model i...
Relativistic Rotation in the Large Radius, Small Angular Velocity Limit
Klauber, R D
2002-01-01
Relativistic rotation is considered in the limit of angular velocity approaching zero and radial distance approaching infinity, such that centrifugal acceleration is immeasurably small while tangent velocity remains close to the speed of light. For this case, the predictions of the traditional approach to relativistic rotation using local co-moving Lorentz frames are compared and contrasted with those of the differential geometry based non-time-orthogonal analysis approach. Different predictions by the two approaches imply that only the non-time-orthogonal approach is valid.
Radial and latitudinal gradients in the solar internal angular velocity
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.
Local computation of angular velocity in rotational visual motion.
Barraza, José F; Grzywacz, Norberto M
2003-07-01
Retinal images evolve continuously over time owing to self-motions and to movements in the world. Such an evolving image, also known as optic flow, if arising from natural scenes can be locally decomposed in a Bayesian manner into several elementary components, including translation, expansion, and rotation. To take advantage of this decomposition, the brain has neurons tuned to these types of motions. However, these neurons typically have large receptive fields, often spanning tens of degrees of visual angle. Can neurons such as these compute elementary optic-flow components sufficiently locally to achieve a reasonable decomposition? We show that human discrimination of angular velocity is local. Local discrimination of angular velocity requires an accurate estimation of the center of rotation within the optic-flow field. Inaccuracies in estimating the center of rotation result in a predictable systematic error when one is estimating local angular velocity. Our results show that humans make the predicted errors. We discuss how the brain might estimate the elementary components of the optic flow locally by using large receptive fields. PMID:12868642
Depth and latitude dependence of the solar internal angular velocity
Rhodes, E.J. Jr.; Cacciani, A.; Korzennik, S.; Tomczyk, S.; Ulrich, R.K.; Woodard, M.F. (Southern California Univ., Los Angeles, CA (USA) JPL, Pasadena, CA (USA) Roma I Universita (Italy) California Univ., Los Angeles (USA))
1990-03-01
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. 43 refs.
Depth and latitude dependence of the solar internal angular velocity
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.
ROTATING RINDLER SPACE TIME WITH CONSTANT ANGULAR VELOCITY
WANG YONG-CHENG
2000-01-01
A new space time metric is derived from Kerr metric if its mass and location approach to infinite in an appropriate way. The new space-time is an infinitesimal neighborhood nearby one of the two horizon poles of an infinite Kerr black hole. In other words, it is the second order infinitesimal neighborhood nearby one of the two horizon poles of a Kerr black hole. It is fiat and has event horizon and infinite red shift surface. We prove that it is a rotating Rindler space time with constant angular velocity.
Unsal, Yasin
2011-01-01
One of the subjects that is confusing and difficult for students to fully comprehend is the concept of angular velocity and linear velocity. It is the relationship between linear and angular velocity that students find difficult; most students understand linear motion in isolation. In this article, we detail the design, construction and…
Phase Resolved Angular Velocity Control of Cross Flow Turbines
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.
Recovering slant and angular velocity from a linear velocity field: modeling and psychophysics.
Domini, Fulvio; Caudek, Corrado
2003-07-01
The data from two experiments, both using stimuli simulating orthographically rotating surfaces, are presented, with the primary variable of interest being whether the magnitude of the simulated gradient was from expanding vs. contracting motion. One experiment asked observers to report the apparent slant of the rotating surface, using a gauge figure. The other experiment asked observers to report the angular velocity, using a comparison rotating sphere. The results from both experiments clearly show that observers are less sensitive to expanding than to contracting optic-flow fields. These results are well predicted by a probabilistic model which derives the orientation and angular velocity of the projected surface from the properties of the optic flow computed within an extended time window. PMID:12818345
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…
Angular velocity sensor based on a ring laser
Rodloff, R.; Bentlage, H.
1984-02-21
An angular velocity sensor based on a ring laser, wherein at any given time beam components of oppositely directed wave trains can be decoupled, having photo-receivers for the decoupled beam components, and means for the generation of signals which correspond to intensity differences of the decoupled beam components. In accordance with the invention a photo-receiver is provided for each decoupled beam and detector means is provided to analyze the output signals from the photo-receivers both for amplitude and frequency. The detector means may consist of a subtractor, a pulse-former and a counter. A rotation-direction detector may also receive an output signal from the pulse-former and feed this as a plus or minus sign into the counter.
On the Extraction of Angular Velocity from Attitude Measurements
Bar-Itzhack, I. Y.; Harman, Richard R.; Thienel, Julie K.
2006-01-01
In this paper we research the extraction of the angular rate vector from attitude information without differentiation, in particular from quaternion measurements. We show that instead of using a Kalman filter of some kind, it is possible to obtain good rate estimates, suitable for spacecraft attitude control loop damping, using simple feedback loops, thereby eliminating the need for recurrent covariance computation performed when a Kalman filter is used. This considerably simplifies the computations required for rate estimation in gyro-less spacecraft. Some interesting qualities of the Kalman filter gain are explored, proven and utilized. We examine two kinds of feedback loops, one with varying gain that is proportional to the well known Q matrix, which is computed using the measured quaternion, and the other type of feedback loop is one with constant coefficients. The latter type includes two kinds; namely, a proportional feedback loop, and a proportional-integral feedback loop. The various schemes are examined through simulations and their performance is compared. It is shown that all schemes are adequate for extracting the angular velocity at an accuracy suitable for control loop damping.
Angular Velocity Affects Trunk Muscle Strength and EMG Activation during Isokinetic Axial Rotation
Jian-Zhong Fan; Xia Liu; Guo-Xin Ni
2014-01-01
Objective. To evaluate trunk muscle strength and EMG activation during isokinetic axial rotation at different angular velocities. Method. Twenty-four healthy young men performed isokinetic axial rotation in right and left directions at 30, 60, and 120 degrees per second angular velocity. Simultaneously, surface EMG was recorded on external oblique (EO), internal oblique (IO), and latissimus dorsi (LD) bilaterally. Results. In each direction, with the increase of angular velocity, peak torque ...
Changing law of launching pitching angular velocity of rotating missile
Liu Guang
2014-10-01
Full Text Available In order to provide accurate launching pitching angular velocity (LPAV for the exterior trajectory optimization design, multi-flexible body dynamics (MFBD technology is presented to study the changing law of LPAV of the rotating missile based on spiral guideway. An MFBD virtual prototype model of the rotating missile launching system is built using multi-body dynamics modeling technology based on the built flexible body models of key components and the special force model. The built model is verified with the frequency spectrum analysis. With the flexible body contact theory and nonlinear theory of MFBD technology, the research is conducted on the influence of a series of factors on LPAV, such as launching angle change, clearance between launching canister and missile, thrust change, thrust eccentricity and mass eccentricity, etc. Through this research, some useful values of the key design parameters which are difficult to be measured in physical tests are obtained. Finally, a simplified mathematical model of the changing law of LPAV is presented through fitting virtual test results using the linear regression method and verified by physical flight tests. The research results have important significance for the exterior trajectory optimization design.
Changing law of launching pitching angular velocity of rotating missile
Liu Guang; Xu Bin; Jiao Xiaojuan; Zhen Tiesheng
2014-01-01
In order to provide accurate launching pitching angular velocity (LPAV) for the exterior trajectory optimization design, multi-flexible body dynamics (MFBD) technology is presented to study the changing law of LPAV of the rotating missile based on spiral guideway. An MFBD virtual prototype model of the rotating missile launching system is built using multi-body dynamics modeling technology based on the built flexible body models of key components and the special force model. The built model is verified with the frequency spectrum analysis. With the flexible body contact theory and nonlinear theory of MFBD technology, the research is conducted on the influence of a series of factors on LPAV, such as launching angle change, clearance between launching canister and missile, thrust change, thrust eccentricity and mass eccentricity, etc. Through this research, some useful values of the key design parameters which are difficult to be measured in physical tests are obtained. Finally, a simplified mathematical model of the changing law of LPAV is presented through fitting virtual test results using the linear regression method and verified by physical flight tests. The research results have important significance for the exterior trajectory optimization design.
Form features provide a cue to the angular velocity of rotating objects
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 l...
Task Space Angular Velocity Blending for Real-Time Trajectory Generation
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.
Marakulin, A. O.; Sazhina, O. S.; Sazhin, M. V.
2012-07-01
The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of Λ-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.
Marakulin, A. O., E-mail: marakulin@physics.msu.ru; Sazhina, O. S.; Sazhin, M. V. [Moscow State University (Russian Federation)
2012-07-15
The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of {Lambda}-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.
The possibility of the influence of adiabatic scalar perturbations on the angular velocity spectrum of extragalactic sources is considered. The multipole expansion coefficients of the angular velocity field in terms of vector spherical harmonics are calculated. We show that there is no contribution from adiabatic perturbations to the angular spectrum for a spatially flat Universe at the dusty stage, while there is a contribution only to the electric multiple coefficients at the stage of Λ-term domination. The cases of long-wavelength and short-wavelength perturbations are considered separately. The relationship between the multipole angular velocity spectrum and the primordial scalar perturbation spectrum is discussed.
Angular Velocity Affects Trunk Muscle Strength and EMG Activation during Isokinetic Axial Rotation
Jian-Zhong Fan
2014-01-01
Full Text Available Objective. To evaluate trunk muscle strength and EMG activation during isokinetic axial rotation at different angular velocities. Method. Twenty-four healthy young men performed isokinetic axial rotation in right and left directions at 30, 60, and 120 degrees per second angular velocity. Simultaneously, surface EMG was recorded on external oblique (EO, internal oblique (IO, and latissimus dorsi (LD bilaterally. Results. In each direction, with the increase of angular velocity, peak torque decreased, whereas peak power increased. During isokinetic axial rotation, contralateral EO as well as ipsilateral IO and LD acted as primary agonists, whereas, ipsilateral EO as well as contralateral IO and LD acted as primary antagonistic muscles. For each primary agonist, the root mean square values decreased with the increase of angular velocity. Antagonist coactiviation was observed at each velocity; however, it appears to be higher with the increase of angular velocity. Conclusion. Our results suggest that velocity of rotation has great impact on the axial rotation torque and EMG activity. An inverse relationship of angular velocity was suggested with the axial rotation torque as well as root mean square value of individual trunk muscle. In addition, higher velocity is associated with higher coactivation of antagonist, leading to a decrease in torque with the increase of velocity.
Rotational Doppler velocimetry to probe the angular velocity of spinning microparticles
Phillips, D.B.; Lee, M P; Speirits, F. C.; Barnett, S. M.; Simpson, S.H.; Lavery, M.P.J.; Padgett, M.J.; Gibson, G. M.
2014-01-01
Laser Doppler velocimetry is a technique used to measure linear velocity, ranging from that of exhaust gases to blood flow. A rotational analog of laser Doppler velocimetry was recently demonstrated, using a rotationally symmetric interference pattern to probe the angular velocity of a spinning object. In this work, we demonstrate the use of a diffraction-limited structured illumination pattern to measure the angular velocity of a micron-sized particle trapped and spinning at tens of Hz in an...
Edward D. Lemaire, PhD; Reza Samadi, MASc; Louis Goudreau, PEng; Jonathan Kofman, PhD, PEng
2013-01-01
A linear piston hydraulic angular-velocity-based control knee joint was designed for people with knee-extensor weakness to engage knee-flexion resistance when knee-flexion angular velocity reaches a preset threshold, such as during a stumble, but to otherwise allow free knee motion. During mechanical testing at the lowest angular-velocity threshold, the device engaged within 2 degrees knee flexion and resisted moment loads of over 150 Nm. The device completed 400,000 loading cycles without me...
Study of the mode of angular velocity damping for a spacecraft at non-standard situation
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.
Brady, J.W. Jr.; Doll, J.D.; Thompson, D.L.
1978-10-15
The angular and velocity distributions for gas/solid-surface collisions are examined. It is shown that the envelope of the scattered phase-space distribution is quite sensitive to the gas/surface interaction potential.
Direction and movement angular velocity determining of cloudiness with panoramic images of the sky
Galileiskii, Viktor P.; Elizarov, Alexey I.; Kokarev, Dmitrii V.; Morozov, Aleksandr M.
2014-11-01
This article gives a short overview to method of direction determining and visible angular velocity of movement determining of cloudiness based on set of panoramic images of cloudy sky, obtained by "Fisheye" wide-angle lens.
Evidence for changes in the angular velocity of the surface regions of the sun and stars
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.
Self-consistent anisotropic oscillator with cranked angular and vortex velocities
Rosensteel, G T
1992-01-01
The Kelvin circulation is the kinematical Hermitian observable that measures the true character of nuclear rotation. For the anisotropic oscillator, mean field solutions with fixed angular momentum and Kelvin circulation are derived in analytic form. The cranking Lagrange multipliers corresponding to the two constraints are the angular and vortex velocities. Self-consistent solutions are reported with a constraint to constant volume.
ANGULAR VELOCITY AND CORIOLIS EFFECT IN TIME-DEPENDENT QUANTUM MECHANICAL SU2 ROTATION
FAN HONG-YI; SUN MING-ZHAI
2001-01-01
Starting from a time-dependent rotation U (t) in SU2 group element space, we derive its corresponding quantum mechanical dynamic Coriolis term and the relationship between U (t) and rotational angular velocity. Throughout our discussion, the technique of integration within an ordered product of operators is fully used, which has the advantage that the correspondence between the classical rotation and the quantum rotation is in a transparent fashion. A new angular-velocity formula is also derived.
Power law in the angular velocity distribution of a granular needle
Piasecki, J.; Viot, P.
2005-01-01
We show how inelastic collisions induce a power law with exponent -3 in the decay of the angular velocity distribution of anisotropic particles with sufficiently small moment of inertia. We investigate this question within the Boltzmann kinetic theory for an elongated granular particle immersed in a bath. The power law persists so long as the collisions are inelastic for a large range of angular velocities provided the mass ratio of the anisotropic particle and the bath particles remains smal...
Angular velocity of gravitational radiation from precessing binaries and the corotating frame
Boyle, Michael
2013-01-01
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 cor...
Oegik Soegihardjo
2002-01-01
Displacement and angular velocity analysis for four bar mechanism, usually being done using graphical method. This method could be used easily for displacement and angular velocity analysis of four bar mechanism in one position. If the analysis being carried out is applied for the whole position of four bar mechanism in which the input link rotates 360o, graphical method will be inappropriate and time consuming. For this kind of situation, analytical method with the aid of computer becomes be...
Inertial Vector Based Attitude Stabilization of Rigid Body Without Angular Velocity Measurements
Benziane, L.; Benallegue, A.; Chitour, Y.; Tayebi, A.
2015-01-01
We address the problem of attitude stabilization of a rigid body, in which neither the angular velocity nor the instantaneous measurements of the attitude are used in the feedback, only body vector measurements are needed. The design of the controller is based on an angular velocity observer-like system, where a first order linear auxiliary system based directly on vector measurements is introduced. The introduction of gain matrices provides more tuning flexibility and better results compared...
Wiltshire, R. J.
2003-01-01
Einstein's equations for a Robertson-Walker fluid source endowed with rotation Einstein's equations for a Robertson-Walker fluid source endowed with rotation are presented upto and including quadratic terms in angular velocity parameter. A family of analytic solutions are obtained for the case in which the source angular velocity is purely time-dependent. A subclass of solutions is presented which merge smoothly to homogeneous rotating and non-rotating central sources. The particular solution...
Angular velocity estimation from measurement vectors of star tracker.
Liu, Hai-bo; Yang, Jun-cai; Yi, Wen-jun; Wang, Jiong-qi; Yang, Jian-kun; Li, Xiu-jian; Tan, Ji-chun
2012-06-01
In most spacecraft, there is a need to know the craft's angular rate. Approaches with least squares and an adaptive Kalman filter are proposed for estimating the angular rate directly from the star tracker measurements. In these approaches, only knowledge of the vector measurements and sampling interval is required. The designed adaptive Kalman filter can filter out noise without information of the dynamic model and inertia dyadic. To verify the proposed estimation approaches, simulations based on the orbit data of the challenging minisatellite payload (CHAMP) satellite and experimental tests with night-sky observation are performed. Both the simulations and experimental testing results have demonstrated that the proposed approach performs well in terms of accuracy, robustness, and performance. PMID:22695598
The validity of an assessment of maximum angular velocity of knee extension (KE) using a gyroscope.
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. PMID:22100108
Role of electron-molecule angular scattering in shaping the electron-velocity distribution
Kunhardt, E.E.; Tzeng, Y.
1986-09-01
Five models has been studied to elucidate the role of electron-molecule angular scattering in shaping the velocity distribution for electrons in nitrogen at E/N values of 300 and 1500 Td. The angular dependence of the differential scattering cross sections for elastic and inelastic collisions has been observed to have significant effects on the shape of the velocity distribution, the rate coefficients, and the transport parameters. The velocity distribution is most sensitive to the angular dependence of elastic scattering. Moreover, for a given elastic differential scattering cross section, variations in the angular dependence of inelastic scattering cause significant changes in the distribution. The magnitude of these changes depends on the relative action of the inelastic collisions with respect to the elastic collisions for a given energy interval, i.e., whether the scattering by the inelastic collisions is isotropic, forward, or backward in a given energy interval.
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.
A New Open-Loop Fiber Optic Gyro Error Compensation Method Based on Angular Velocity Error Modeling
Yanshun Zhang; Yajing Guo; Chunyu Li; Yixin Wang; Zhanqing Wang
2015-01-01
With the open-loop fiber optic gyro (OFOG) model, output voltage and angular velocity can effectively compensate OFOG errors. However, the model cannot reflect the characteristics of OFOG errors well when it comes to pretty large dynamic angular velocities. This paper puts forward a modeling scheme with OFOG output voltage and temperature as the input variables and angular velocity error as the output variable. Firstly, the angular ve...
Form features provide a cue to the angular velocity of rotating objects.
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. PMID:23750970
Relation between Press Intensity and Angular Velocity at a RPPP Mechanism
Şenay Baydaş; Bülent Karakaş
2011-01-01
We study some properties of RPPP. RPPP is discussed by rising with constant velocity along a given axis. The constant pressure which it stresses on a constant axis is defined by the increasing PPP. Some relations between the increase at PPP and angular velocity at R are analyzed and relations of correlation are investigated at Matlab.
Relation between Press Intensity and Angular Velocity at a RPPP Mechanism
Şenay Baydaş
2011-01-01
Full Text Available We study some properties of RPPP. RPPP is discussed by rising with constant velocity along a given axis. The constant pressure which it stresses on a constant axis is defined by the increasing PPP. Some relations between the increase at PPP and angular velocity at R are analyzed and relations of correlation are investigated at Matlab.
The angular velocity of the apsidal rotation in binary stars
Vasilev, B V
2004-01-01
The shape of a rotating star consisting of equilibrium plasma is considered. The velocity of apsidal rotation of close binary stars (periastron rotation) which depends on the star shapes is calculated. The obtained estimations are in a good agreement with the observation data of the apsidal motion in binary systems.
WU Peng-yue; XIE Shui-sheng; LI Hua-qing; YAN Ming; HUANG Guo-jie; CHENG Lei
2007-01-01
The continuous extrusion forming process for producing large section copper concave bus bar under different extrusion wheel angular velocities was studied by three-dimensional finite element technology based on software DEFORM-3D. The rigid-viscoplastic constitutive equation was employed in the model. The numerical simulation results show that the deformation body flow velocity in the die orifice increases gradually with the increase of the extrusion wheel angular velocity. But slippage between the rod and extrusion wheel occurs when the extrusion wheel angular velocity is high. The effective stress near the die orifice enhances gradually with increasing extrusion wheel angular velocity. High stress is concentrated in adjacent regions of the flash gap. The effective strain gradient is greater near the abutment than that near the die orifice. The effective strain of the product increases gradually with increasing extrusion wheel angular velocity. In the deformation process, the deformation body temperature increases remarkably due to friction and deformation. So the cooling is necessary in the region of the die and tools.
Angular velocity spread of relativistic photoelectrons induced by excimer laser irradiation
Kawai, M.; Kawamura, Y.; Toyoda, K.
1984-12-15
The angular velocity spread of relativistic photoelectrons induced by a pulsed excimer laser was measured. The energy, the current density, and the pulse duration of the accelerated photoelectron were 0.34 MeV, 0.5 A/cm/sup 2/, and 20 ns, respectively. (The method of measurement is based on measuring Larmor radius which corresponds to the transverse component of the electron velocity.)= The angular velocity spread ..beta../sub perpendicular//..beta../sub parallel/ was found to be less than 8 x 10/sup -3/, which means that the energy component due to ..beta../sub perpendicular/ was as small as < or approx. =17 eV.
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. PMID:23724603
Satellite angular velocity estimation based on star images and optical flow techniques.
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
Satellite Angular Velocity Estimation Based on Star Images and Optical Flow Techniques
Giancarmine Fasano
2013-09-01
Full Text Available 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.
Edward D. Lemaire, PhD
2013-02-01
Full Text Available A linear piston hydraulic angular-velocity-based control knee joint was designed for people with knee-extensor weakness to engage knee-flexion resistance when knee-flexion angular velocity reaches a preset threshold, such as during a stumble, but to otherwise allow free knee motion. During mechanical testing at the lowest angular-velocity threshold, the device engaged within 2 degrees knee flexion and resisted moment loads of over 150 Nm. The device completed 400,000 loading cycles without mechanical failure or wear that would affect function. Gait patterns of nondisabled participants were similar to normal at walking speeds that produced below-threshold knee angular velocities. Fast walking speeds, employed purposely to attain the angular-velocity threshold and cause knee-flexion resistance, reduced maximum knee flexion by approximately 25 degrees but did not lead to unsafe gait patterns in foot ground clearance during swing. In knee collapse tests, the device successfully engaged knee-flexion resistance and stopped knee flexion with peak knee moments of up to 235.6 Nm. The outcomes from this study support the potential for the linear piston hydraulic knee joint in knee and knee-ankle-foot orthoses for people with lower-limb weakness.
Mechanisms underlying the perceived angular velocity of a rigidly rotating object.
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. PMID:16647733
Lemaire, Edward D; Samadi, Reza; Goudreau, Louis; Kofman, Jonathan
2013-01-01
A linear piston hydraulic angular-velocity-based control knee joint was designed for people with knee-extensor weakness to engage knee-flexion resistance when knee-flexion angular velocity reaches a preset threshold, such as during a stumble, but to otherwise allow free knee motion. During mechanical testing at the lowest angular-velocity threshold, the device engaged within 2 degrees knee flexion and resisted moment loads of over 150 Nm. The device completed 400,000 loading cycles without mechanical failure or wear that would affect function. Gait patterns of nondisabled participants were similar to normal at walking speeds that produced below-threshold knee angular velocities. Fast walking speeds, employed purposely to attain the angular-velocity threshold and cause knee-flexion resistance, reduced maximum knee flexion by approximately 25 degrees but did not lead to unsafe gait patterns in foot ground clearance during swing. In knee collapse tests, the device successfully engaged knee-flexion resistance and stopped knee flexion with peak knee moments of up to 235.6 Nm. The outcomes from this study support the potential for the linear piston hydraulic knee joint in knee and knee-ankle-foot orthoses for people with lower-limb weakness. PMID:23516082
Satellite Angular Velocity Estimation Based on Star Images and Optical Flow Techniques
Giancarmine Fasano; Giancarlo Rufino; Domenico Accardo; Michele Grassi
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...
Ultrashort Laguerre-Gaussian pulses with angular and group velocity dispersion compensation.
Zeylikovich, I; Sztul, H I; Kartazaev, V; Le, T; Alfano, R R
2007-07-15
Coherent optical vortices are generated from ultrashort 6.4 fs pulses. Our results demonstrate angular dispersion compensation of ultrashort 6.4 fs Laguerre-Gaussian (LG) pulses as well as what is believed to be the first direct autocorrelation measurement of 80 fs LG amplified pulses. A reflective-mirror-based 4f-compressor is proposed to compensate the angular and group velocity dispersion of the ultrashort LG pulses. PMID:17632631
Wiltshire, R J
2003-01-01
Einstein's equations for a Robertson-Walker fluid source endowed with rotation Einstein's equations for a Robertson-Walker fluid source endowed with rotation are presented upto and including quadratic terms in angular velocity parameter. A family of analytic solutions are obtained for the case in which the source angular velocity is purely time-dependent. A subclass of solutions is presented which merge smoothly to homogeneous rotating and non-rotating central sources. The particular solution for dust endowed with rotation is presented. In all cases explicit expressions, depending sinusoidally on polar angle, are given for the density and internal supporting pressure of the rotating source. In addition to the non-zero axial velocity of the fluid particles it is shown that there is also a radial component of velocity which vanishes only at the poles. The velocity four-vector has a zero component between poles.
Limiting angular velocity of realistic relativistic neutron star models
Weber, F.; Glendenning, N.K. (California Univ., Berkeley (USA). Div. of Nuclear Science)
1991-05-01
The Keplerian velocity as well as those frequencies at which instability against gravitational radiation-reaction sets in are calculated for rotating neutron star models of gravitational mass 1.5 M{sub sun}. The investigation is based on four different, realistic neutron star matter equations of state. Our results indicate that the gravitational radiation instability sets in well below (i.e., 63-71% of) the Keplerian frequency, and that young neutron stars are limited to rotational periods greater than about 1 ms. In young and therefore hot (T {approx equal} 10{sup 10} K) neutron stars the m = 5 (+- 1) modes and in old stars after being spun up and reheated by mass accretion, the m = 4 and/or m = 3 modes may set the limit on stable rotation. (orig.).
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.
Single-axis gyroscopic motion with uncertain angular velocity about spin axis
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.
Joint Angular Velocity in Spastic Gait and the Influence of Muscle-Tendon Lengthening*
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
Resolving Two Dimensional Angular Velocity within a Rotary Tumbler
Helminiak, Nathaniel; Helminiak, David; Cariapa, Vikram; Borg, John
2015-11-01
In this study, a horizontally oriented cylindrical tumbler, filled at variable depth with cylindrical media, was rotated at various constant speeds. A monoplane layer of media was photographed with a high-speed camera and images were post processed with Particle Tracking Velocimetry (PTV) algorithms in order to resolve both the translational and rotational flow fields. Although the translational velocity fields have been well characterized, contemporary resources enabled the ability to expand upon and refine data regarding rotational characteristics of particles within a rotary tumbler. The results indicate that particles rotate according to intermittent no-slip interactions between the particles and solid body rotation. Particles within the bed, not confined to solid body rotation, exhibited behavior indicative of gearing between particles; each reacting to the tangential component of contact forming rotation chains. Furthermore, it was observed that solid body interactions corresponded to areas of confined motion, as areas of high interaction dissuaded no-slip rotation, while areas of developing flow tended towards no-slip rotation. Special thanks to: NASA Wisconsin Space Grant Consortium Program as well as Marquette University OPUS College of Engineering.
Angular and velocity distributions of NO scattered from the Pt(111) crystal surface
Guthrie, W.L.; Lin, T.; Ceyer, S.T.; Somorjai, G.A.
1982-06-15
The angular and velocity distributions of NO scattered from the Pt(111) surface have been measured for a crystal temperature range of 475--1200 K and for an incident beam energy range of 265--1390 K. Both angular and velocity distributions confirm the coexistence of inelastic and trapping-desorption scattering processes. For beams with a kinetic energy of
Gasflow style level posture sensor and angular velocity gyroscope assembled inertial sensor
无
2007-01-01
The compensational loop consisting of a gasflow style angular velocity gyroscope and gasflow level posture sensor is proposed to improve the signal of gasflow style tilt. This compensational loop could remove acceleration interfere from the signal of tilt. This assembled gasflow type inertial sensor not only measures static state angular, but also restrains the acceleration which interferes the output signal of level posture sensor in dynamic situations. Therefore, the precision of outputs signal increases greatly. Moreover, the output signal includes the angle velocity signal.
Effect of postural changes on 3D joint angular velocity during starting block phase.
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. PMID:23062070
A critical regularity condition on the angular velocity of axially symmetric Navier-Stokes equations
Zhang, Qi S.
2015-01-01
Let $v$ be the velocity of Leray-Hopf solutions to the axially symmetric three-dimensional Navier-Stokes equations. It is shown that $v$ is regular if the angular velocity $v_\\theta$ satisfies an integral condition which is critical under the standard scaling. This condition allows functions satisfying \\[ |v_\\theta(x, t)| \\le \\frac{C}{r |\\ln r|^{2+\\epsilon}}, \\quad r
Busurin, V. I.; Lwin, Naing Htoo; Tuan, Pham Anh
In this paper the possibility of microopto-electromechanical (MOEM) angular velocity and acceleration transducers based on optical tunneling effect (OTE) is considered. The generalized model of MOEM transducers with various types of sensing elements (SE) is developed, transfer functions are investigated, and the errors with various design parameters of transducers are estimated.
Ilaria Pasciuto
2015-09-01
Full Text Available 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.
Reyhanoglu, Mahmut
1996-01-01
There has been much interest over the past decade in the problem of asymptotic stabilization of the angular velocity of a rigid body with only two torque inputs. The smooth feedback laws proposed in the literature provide asymptotic stability with nonexponential convergence rates. This paper propose
State-selective velocity and angular distributions of NO molecules scattered from a graphite surface
Hager, J.; Shen, Y.R.; Walther, H.
1985-03-01
Laser ionization was used to measure the state-selective angular and velocity distributions of NO molecules scattered from a graphite surface. The data showed that at sufficiently low surface temperatures, the scattered molecules were generally composed of quasispecular reflected part and a diffusive scattered part with different translational and rotational behavior.
Reyhanoglu, Mahmut
1996-01-01
There has been much interest over the past decade in the problem of asymptotic stabilization of the angular velocity of a rigid body with only two torque inputs. The smooth feedback laws proposed in the literature provide asymptotic stability with nonexponential convergence rates. This paper proposes discontinuous feedback laws to achieve asymptotic stability with exponential convergence rates
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
Nonlinear free vibrations of centrifugally stiffened uniform beams at high angular velocity
Bekhoucha, F.; Rechak, S.; Duigou, L.; Cadou, J. M.
2016-09-01
In this paper, we study the bending nonlinear free vibrations of a centrifugally stiffened beam with uniform cross-section and constant angular velocity. The nonlinear intrinsic equations of motion used here are geometrically exact and specific to beams exhibiting large amplitude displacements and rotations associated with small strains. Based on the Timoshenko beam model, these equations are derived from Hamilton's principle, in which the warping is considered. All coupling terms are considered including Coriolis terms. The studied beams are isotropic with clamped-free boundary conditions. By combining the Galerkin method with the harmonic balance method, the equations of motion are converted into a quadratic function treated with a continuation method: the Asymptotic Numerical Method, where the generalized displacement vector is presented as a series expansion. While analysing the effect of the angular velocity, we determine the amplitude versus frequency variations which are plotted as backbone curves. Considering the first lagging and flapping modes, the changes in beam behaviour from hardening to softening are investigated and identified as a function of the angular velocity and the effect of shear. Particular attention is paid to high angular velocities for both Euler-Bernoulli and Timoshenko beams and the natural frequencies so obtained are compared with the results available in the literature.
Habituation of self-motion perception following unidirectional angular velocity steps.
Clément, Gilles; Terlevic, Robert
2016-09-01
We investigated whether the perceived angular velocity following velocity steps of 80°/s in the dark decreased with the repetition of the stimulation in the same direction. The perceptual response to velocity steps in the opposite direction was also compared before and after this unidirectional habituation training. Participants indicated their perceived angular velocity by clicking on a wireless mouse every time they felt that they had rotated by 90°. The prehabituation perceptual response decayed exponentially with a time constant of 23.9 s. After 100 velocity steps in the same direction, this time constant was 12.9 s. The time constant after velocity steps in the opposite direction was 13.4 s, indicating that the habituation of the sensation of rotation is not direction specific. The peak velocity of the perceptual response was not affected by the habituation training. The differences between the habituation characteristics of self-motion perception and eye movements confirm that different velocity storage mechanisms mediate ocular and perceptual responses. PMID:27391426
Ebersole, K T; Housh, T J; Weir, J P; Johnson, G O; Evetovich, T K; Smith, D B
2000-01-01
The purpose of the present investigation was to examine the effects of leg angular velocity on the mean power frequency (MPF) and amplitude of the mechanomyographic (MMG) signal during maximal concentric (CON) isokinetic muscle actions. Sixteen adult subjects performed maximal CON leg extensions on a calibrated Cybex 6000 dynamometer at leg angular velocities of 60 and 300 degrees.s-1. MMG was detected by a piezoelectric crystal contact sensor placed over the mid-portion of the vastus lateralis muscle. The results indicated a significant (p 0.05) in MMG MPF. These findings did not support our hypothesis that increases across velocity in MMG amplitude were due to decreases in muscle stiffness as a result of a shift in the contribution of slow and fast-twitch muscle fibers to PT production. Future research should examine the potential influence of actin-myosin cycling rate as well as limb movement on the MPF and amplitude of the MMG signal. PMID:10782358
Rotational Doppler velocimetry to probe the angular velocity of spinning microparticles
Phillips, D. B.; Lee, M. P.; Speirits, F. C.; Barnett, S. M.; Simpson, S. H.; Lavery, M. P. J.; Padgett, M. J.; Gibson, G. M.
2014-07-01
Laser Doppler velocimetry is a technique used to measure linear velocity, ranging from that of exhaust gases to blood flow. A rotational analog of laser Doppler velocimetry was recently demonstrated, using a rotationally symmetric interference pattern to probe the angular velocity of a spinning object. In this work, we demonstrate the use of a diffraction-limited structured illumination pattern to measure the angular velocity of a micron-sized particle trapped and spinning at tens of Hz in an optical trap. The technique requires no detailed knowledge of the shape of the particle, or the distribution of scatterers within it, and is independent of the particle's chirality, transparency, and birefringence. The particle is also subjected to Brownian motion, which complicates the signal by affecting the rotation rate and the rotation axis. By careful consideration of these influences, we show how the measurement is robust to both, representing a technique with which to probe the rotational motion of microscale particles.
Denis, Romain; Wilkinson, Jennifer; De Vito, Giuseppe
2011-09-01
The purpose of this study was to investigate whether changes in angular velocity would alter vastus lateralis (VL) and rectus femoris (RF) oxygenation status during maximal isokinetic knee extension exercises. Eleven recreationally active male participants randomly performed ten maximal knee extensions at 30, 60, 120 and 240° s(-1). Tissue oxygenation index (TOI) and total haemoglobin concentration ([tHb]) were acquired from the VL and RF muscles by means of near-infrared spectroscopy (NIRS). Breath-by-breath pulmonary oxygen consumption (VO(2p)) was recorded throughout the tests. Peak torque and VO(2p) significantly decreased as a function of velocity (P<0·05). Interestingly, RF and VL TOI significantly increased as a function of velocity (P<0·05), whereas [tHb] significantly decreased as a function of velocity (P<0·05). A greater number of muscle fibre recruited at slow velocity, where the torque and VO(2p) were the highest, might explain the lower VL and RF TOI observed herein. Furthermore, the increase in local blood flow (suggested by [tHb] changes) during isokinetic knee extension exercises performed at slow angular velocity might have been induced by a higher intramuscular pressure during the contraction phases as well as a greater microcirculatory vasodilatation during relaxation phases. Implementing slow-velocity isokinetic exercises in rehabilitation or other training programmes could delay the short-term anoxia generated by such exercises and result in muscle metabolism enhancement. PMID:21771253
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. PMID:18843158
Relation between the critical spin and angular velocity of a nucleus immediately after backbending
Nosov, V. G.; Kamchatnov, A. M.
2004-01-01
In nonspherical nuclei at $J = J_c + 0$ the relationship between the angular momentum and angular velocity immediately after backbending is the same as in the limiting case $J - J_c\\to\\infty$. This indicates that there is a unique type of cancellation of the deviations from a rigid-body moment of inertia in the upper phase $J>J_c$. An integral relationship is found which expresses this cancellation quantitatively. This formula permits $J_c$ to be calculated for the rotational bands of the eve...
Angular velocity of a sphere in a simple shear at small Reynolds number
Meibohm, J.; Candelier, F.; Rosén, T.; Einarsson, J.; Lundell, F.; Mehlig, B.
2016-01-01
We analyse the angular dynamics of a small neutrally buoyant sphere in a simple shear. When the effect of fluid inertia is negligible the sphere rotates at half the fluid vorticity. We compute how weak fluid inertia reduces the angular velocity, and find $\\omega_3/s \\sim -{1}/{2} +0.0540\\, {\\rm Re}_{\\rm s}^{3/2}$ where $s$ is the shear rate and ${\\rm Re}_{\\rm s}$ is the shear Reynolds number. This result differs from that derived by Lin et al. [J. Fluid Mech. 44 (1970) 1] who obtained a coeff...
A New Open-Loop Fiber Optic Gyro Error Compensation Method Based on Angular Velocity Error Modeling
Yanshun Zhang
2015-02-01
Full Text Available With the open-loop fiber optic gyro (OFOG model, output voltage and angular velocity can effectively compensate OFOG errors. However, the model cannot reflect the characteristics of OFOG errors well when it comes to pretty large dynamic angular velocities. This paper puts forward a modeling scheme with OFOG output voltage and temperature as the input variables and angular velocity error as the output variable. Firstly, the angular velocity error is extracted from OFOG output signals, and then the output voltage , temperature and angular velocity error are used as the learning samples to train a Radial-Basis-Function (RBF neural network model. Then the nonlinear mapping model over T, and is established and thus can be calculated automatically to compensate OFOG errors according to and . The results of the experiments show that the established model can be used to compensate the nonlinear OFOG errors. The maximum, the minimum and the mean square error of OFOG angular velocity are decreased by , and relative to their initial values, respectively. Compared with the direct modeling of gyro angular velocity, which we researched before, the experimental results of the compensating method proposed in this paper are further reduced by , and , respectively, so the performance of this method is better than that of the direct modeling for gyro angular velocity.
Jasiewicz, Jan M; Allum, John H J; Middleton, James W; Barriskill, Andrew; Condie, Peter; Purcell, Brendan; Li, Raymond Che Tin
2006-12-01
We report on three different methods of gait event detection (toe-off and heel strike) using miniature linear accelerometers and angular velocity transducers in comparison to using standard pressure-sensitive foot switches. Detection was performed with normal and spinal-cord injured subjects. The detection of end contact (EC), normally toe-off, and initial contact (IC) normally, heel strike was based on either foot linear accelerations or foot sagittal angular velocity or shank sagittal angular velocity. The results showed that all three methods were as accurate as foot switches in estimating times of IC and EC for normal gait patterns. In spinal-cord injured subjects, shank angular velocity was significantly less accurate (p<0.02). We conclude that detection based on foot linear accelerations or foot angular velocity can correctly identify the timing of IC and EC events in both normal and spinal-cord injured subjects. PMID:16500102
Buss, R.J.
1979-04-01
The study of seven radical-molecule reactions using the crossed molecular beam technique with supersonic nozzle beams is reported. Product angular and velocity distributions were obtained and compared with statistical calculations in order to identify dynamical features of the reactions. In the reaction of chlorine and fluorine atoms with vinyl bromide, the product energy distributions are found to deviate from predictions of the statistical model. A similar effect is observed in the reaction of chlorine atoms with 1, 2 and 3-bromopropene. The reaction of oxygen atoms with ICl and CF/sub 3/I has been used to obtain an improved value of the IO bond energy, 55.0 +- 2.0 kcal mol/sup -1/. In all reactions studied, the product energy and angular distributions are found to be coupled, and this is attributed to a kinematic effect of the conservation of angular momentum.
Analyzing angular distributions for two-step dissociation mechanisms in velocity map imaging.
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. PMID:23464815
Angular velocity of gravitational radiation from precessing binaries and the corotating frame
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 velocity of gravitational radiation from precessing binaries and the corotating frame
Boyle, Michael
2013-01-01
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...
Johnson, Michael D; Shiokawa, Hotaka; Chael, Andrew A; Doeleman, Sheperd S
2015-01-01
We show that interferometry can be applied to study irregular, rapidly rotating structures, as are expected in the turbulent accretion flow near a black hole. Specifically, we analyze the lagged covariance between interferometric baselines of similar lengths but slightly different orientations. We demonstrate that the peak in the lagged covariance indicates the direction and angular velocity of the flow. Importantly, measuring the direction of the flow as clockwise or counterclockwise on the sky breaks a degeneracy in accretion disk inclinations when analyzing time-averaged images alone. We explore the potential efficacy using three-dimensional, general relativistic magnetohydrodynamic (GRMHD) simulations, and we highlight several baseline pairs for the Event Horizon Telescope (EHT) that are well-suited to this application. These results indicate that the EHT is capable of determining the direction and angular velocity of the emitting material near Sgr A*, even for highly-inclined flows, and they suggest that...
A submicron device to rectify a square-wave angular velocity.
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. PMID:21337018
Feasibility study on an angular velocity-based damage detection method using gyroscopes
Sung, S. H.; Lee, J. H.; Park, J. W.; Koo, K. Y.; Jung, H. J.
2014-07-01
This paper proposes an angular velocity-based damage detection method using gyroscopes and investigates its feasibility. This study basically intends to enhance the performance of the existing modal flexibility-based methods by replacing accelerations measured from accelerometers with angular velocities measured from gyroscopes. In order to verify the superiority of a gyroscope in damage detection, numerical studies were performed by changing optional parameters such as damage location, severity, and measurement noise. From parametric studies, it was shown that the damage detection results using gyroscopes are more sensitive to damage and more robust to noise generated from the curvature estimation than those using accelerometers. Experimental validations were also carried out to investigate the feasibility of a gyroscope in damage detection. From the results, it was shown that the gyroscope-based damage detection method can successfully identify damage location. In conclusion, it was numerically and experimentally verified that a new damage detection approach using gyroscopes could improve damage detection ability significantly.
Feasibility study on an angular velocity-based damage detection method using gyroscopes
This paper proposes an angular velocity-based damage detection method using gyroscopes and investigates its feasibility. This study basically intends to enhance the performance of the existing modal flexibility-based methods by replacing accelerations measured from accelerometers with angular velocities measured from gyroscopes. In order to verify the superiority of a gyroscope in damage detection, numerical studies were performed by changing optional parameters such as damage location, severity, and measurement noise. From parametric studies, it was shown that the damage detection results using gyroscopes are more sensitive to damage and more robust to noise generated from the curvature estimation than those using accelerometers. Experimental validations were also carried out to investigate the feasibility of a gyroscope in damage detection. From the results, it was shown that the gyroscope-based damage detection method can successfully identify damage location. In conclusion, it was numerically and experimentally verified that a new damage detection approach using gyroscopes could improve damage detection ability significantly. (paper)
Ilaria Pasciuto; Gabriele Ligorio; Elena Bergamini; Giuseppe Vannozzi; Angelo Maria Sabatini; Aurelio Cappozzo
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 an...
Munk, W. H.; Miller, R. L.
2011-01-01
Fluctuations in the circulation of the atmosphere are associated with very small anomalies in the angular velocity of the earth. The seasonal component of these anomalies has been computed from weather maps, and is found to agree, with respect to magnitude and phase, with anomalies first reported by STOKYO in 1936 on the basis of astronomic observations. The effects of fluctuations in the oceanic circulation, and of shifting of air and water masses, have been estimated to account for not more...
Johnson, Michael D.; Loeb, Abraham; Shiokawa, Hotaka; Chael, Andrew A.; Doeleman, Sheperd S.
2015-01-01
We show that interferometry can be applied to study irregular, rapidly rotating structures, as are expected in the turbulent accretion flow near a black hole. Specifically, we analyze the lagged covariance between interferometric baselines of similar lengths but slightly different orientations. For a flow viewed close to face-on, we demonstrate that the peak in the lagged covariance indicates the direction and angular velocity of the emission pattern from the flow. Even for moderately incline...
Rotating Particle in the Near Field of the Surface at Arbitrary Direction of Angular Velocity Vector
Kyasov, A. A.; Dedkov, G. V.
2016-01-01
We study the fluctuation-electromagnetic interaction between a small rotating particle with an arbitrary direction of angular velocity vector and evanescent field of the heated surface, and obtain the general expressions for the force of attraction, rate of heating and components of torque. The particle rotation dynamics is analyzed. It is shown that during most time of motion the particle slows down provided that a quasiequilibrium thermal state has been reached, while at any initial directi...
Angular velocity distribution of a granular planar rotator in a thermalized bath
Piasecki, J.; Talbot, J.; Viot, P.
2006-01-01
The kinetics of a granular planar rotator with a fixed center undergoing inelastic collisions with bath particles is analyzed both numerically and analytically by means of the Boltzmann equation. The angular velocity distribution evolves from quasi-gaussian in the Brownian limit to an algebraic decay in the limit of an infinitely light particle. In addition, we compare this model with a planar rotator with a free center. We propose experimental tests that might confirm the predicted behaviors.
WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER
YONGHO LEE
2013-01-01
Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying th...
Angular velocity distribution of a granular planar rotator in a thermalized bath.
Piasecki, J; Talbot, J; Viot, P
2007-05-01
The kinetics of a granular planar rotator with a fixed center undergoing inelastic collisions with bath particles is analyzed both numerically and analytically by means of the Boltzmann equation. The angular velocity distribution evolves from quasi-Gaussian in the Brownian limit to an algebraic decay in the limit of an infinitely light particle. In addition, we compare this model to that of a planar rotator with a free center and discuss the prospects for experimental confirmation of these results. PMID:17677054
On the relation of Thomas rotation and angular velocity of reference frames
Matolcsi, T.; Matolcsi, M.; Tasnádi, T.
2006-01-01
In the extensive literature dealing with the relativistic phenomenon of Thomas rotation several methods have been developed for calculating the Thomas rotation angle of a gyroscope along a circular world line. One of the most appealing concepts, introduced in \\cite{rindler}, is to consider a rotating reference frame co-moving with the gyroscope, and relate the precession of the gyroscope to the angular velocity of the reference frame. A recent paper \\cite{herrera}, however, applies this princ...
Effect of postural changes on 3D joint angular velocity during starting block phase
Slawinski, Jean; Dumas, Raphaël; CHEZE, Laurence; ONTANON, Guy; BONNEFOY-MAZURE, 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 Analysis1 system was used to collect the 3D marker traje...
Cosmic web alignments with the shape, angular momentum and peculiar velocities of dark matter haloes
Forero-Romero, Jaime E.; Contreras, Sergio; Padilla, Nelson
2014-01-01
We study the alignment of dark matter haloes with the cosmic web characterized by the tidal and velocity shear fields. We focus on the alignment of their shape, angular momentum and peculiar velocities. We use a cosmological N-body simulation that allows to study dark matter halos spanning almost five orders of magnitude in mass ($10^{9}$-$10^{14}$) $h^{-1}$$M_{\\odot}$ and spatial scales of $(0.5$-$1.0)$ $h^{-1}$ Mpc to define the cosmic web. We find that the halo shape presents the strongest...
Dowling, Ariel V; Favre, Julien; Andriacchi, Thomas P
2012-09-01
The dynamic movements associated with anterior cruciate ligament (ACL) injury during jump landing suggest that limb segment angular velocity can provide important information for understanding the conditions that lead to an injury. Angular velocity measures could provide a quick and simple method of assessing injury risk without the constraints of a laboratory. The objective of this study was to assess the inter-subject variations and the sensitivity of the thigh and shank segment angular velocity in order to determine if these measures could be used to characterize jump landing mechanisms. Additionally, this study tested the correlation between angular velocity and the knee abduction moment. Thirty-six healthy participants (18 male) performed drop jumps with bilateral and unilateral landing. Thigh and shank angular velocities were measured by a wearable inertial-based system, and external knee moments were measured using a marker-based system. Discrete parameters were extracted from the data and compared between systems. For both jumping tasks, the angular velocity curves were well defined movement patterns with high inter-subject similarity in the sagittal plane and moderate to good similarity in the coronal and transverse planes. The angular velocity parameters were also able to detect differences between the two jumping tasks that were consistent across subjects. Furthermore, the coronal angular velocities were significantly correlated with the knee abduction moment (R of 0.28-0.51), which is a strong indicator of ACL injury risk. This study suggested that the thigh and shank angular velocities, which describe the angular dynamics of the movement, should be considered in future studies about ACL injury mechanisms. PMID:22938373
WIND TURBINE SIMULATION FOR TIME-DEPENDENT ANGULAR VELOCITY, TORQUE, AND POWER
YONGHO LEE
2013-02-01
Full Text Available Albeit the prediction of time-dependent properties of wind turbines is not required for common applications, such time-varying properties may play an important role during transient operations occurring due to various reasons. Unlike the conventional numerical simulations of wind turbine rotations that fix the angular velocity to an assumed value, the present work numerically simulates the time-varying turbine rotation in both unsteady and quasi-steady operation regimes, without specifying the angular velocity of the turbine a priori, but by calculating the actual time-dependent angular velocity and aerodynamic torque along with other properties in the course of simulation. In the present work, successful results obtained by an efficient computational fluid dynamics technique are shown, as a demonstration, for a vertical-axis wind turbine with a two-dimensionalSavonius rotor, and the cycle-averaged output powers are compared with experimental power curves and a theory developed on the basis of experimental observations.
Oegik Soegihardjo
2002-01-01
Full Text Available Displacement and angular velocity analysis for four bar mechanism, usually being done using graphical method. This method could be used easily for displacement and angular velocity analysis of four bar mechanism in one position. If the analysis being carried out is applied for the whole position of four bar mechanism in which the input link rotates 360o, graphical method will be inappropriate and time consuming. For this kind of situation, analytical method with the aid of computer becomes best solution for displacement and angular velocity analysis. Abstract in Bahasa Indonesia : Analisis perpindahan serta kecepatan sudut mekanisme empat batang, biasanya dilakukan secara grafis. Untuk mengidentifikasi perpindahan maupun kecepatan sudut mekanisme empat batang di satu posisi, cara grafis bisa dilakukan dengan sederhana dan cepat. Namun bila analisis dilakukan untuk mengidentifikasi perpindahan serta kecepatan mekanisme empat batang di seluruh posisi batang input yang berputar 360o, cara grafis akan memakan banyak waktu. Untuk kasus semacam ini, cara analitik dengan bantuan komputer merupakan cara penyelesaian yang tepatKata kunci: mekanisme empat batang, batang (link, perpindahan, kecepatan sudut. Kata kunci: mekanisme empat batang, batang (link, perpindahan, kecepatan sudut.
Johnson, Michael D.; Loeb, Abraham; Shiokawa, Hotaka; Chael, Andrew A.; Doeleman, Sheperd S.
2015-11-01
We show that interferometry can be applied to study irregular, rapidly rotating structures, as are expected in the turbulent accretion flow near a black hole. Specifically, we analyze the lagged covariance between interferometric baselines of similar lengths but slightly different orientations. For a flow viewed close to face-on, we demonstrate that the peak in the lagged covariance indicates the direction and angular velocity of the emission pattern from the flow. Even for moderately inclined flows, the covariance robustly estimates the flow direction, although the estimated angular velocity can be significantly biased. Importantly, measuring the direction of the flow as clockwise or counterclockwise on the sky breaks a degeneracy in accretion disk inclinations when analyzing time-averaged images alone. We explore the potential efficacy of our technique using three-dimensional, general relativistic magnetohydrodynamic simulations, and we highlight several baseline pairs for the Event Horizon Telescope (EHT) that are well-suited to this application. These results indicate that the EHT may be capable of estimating the direction and angular velocity of the emitting material near Sgr A*, and they suggest that a rotating flow may even be utilized to improve imaging capabilities.
Hewett, Timothy E; Myer, Gregory D; Zazulak, Bohdanna T
2008-09-01
Our purpose was to determine if females demonstrate decreased hamstrings to quadriceps peak torque (H/Q) ratios compared to males and if H/Q ratios increase with increased isokinetic velocity in both sexes. Maturation disproportionately increases hamstrings peak torque at high velocity in males, but not females. Therefore, we hypothesised that mature females would demonstrate decreased H/Q ratios compared to males and the difference in H/Q ratio between sexes would increase as isokinetic velocity increased. Studies that analysed the H/Q ratio with gravity corrected isokinetic strength testing reported between 1967 and 2004 were included in our review and analysis. Keywords were hamstrings/quadriceps, isokinetics, peak torque and gravity corrected. Medline and Smart databases were searched combined with cross-checked bibliographic reference lists of the publications to determine studies to be included. Twenty-two studies were included with a total of 1568 subjects (1145 male, 423 female). Males demonstrated a significant correlation between H/Q ratio and isokinetic velocity (R=0.634, p<0.0001), and a significant difference in the isokinetic H/Q ratio at the lowest angular velocity (47.8+/-2.2% at 30 degrees /s) compared to the highest velocity (81.4+/-1.1% at 360 degrees /s, p<0.001). In contrast, females did not demonstrate a significant relationship between H/Q ratio and isokinetic velocity (R=0.065, p=0.77) or a change in relative hamstrings strength as the speed increased (49.5+/-8.8% at 30 degrees /s; 51.0+/-5.7% at 360 degrees /s, p=0.84). Gender differences in isokinetic H/Q ratios were not observed at slower angular velocities. However, at high knee flexion/extension angular velocities, approaching those that occur during sports activities, significant gender differences were observed in the H/Q ratio. Females, unlike males, do not increase hamstrings to quadriceps torque ratios at velocities that approach those of functional activities. PMID:17875402
Cosmic web alignments with the shape, angular momentum and peculiar velocities of dark matter halos
Forero-Romero, Jaime E; Padilla, Nelson
2014-01-01
We study the alignment of dark matter halos with the cosmic web characterized by the tidal and velocity shear fields. We focus on the alignment of their shape, angular momentum and peculiar velocities. We use a cosmological N-body simulation that allows to study dark matter halos spanning almost five orders of magnitude in mass ($10^{9}$-$10^{14}$) $h^{-1}$$M_{\\odot}$ and spatial scales of $(0.5$-$1.0)$ $h^{-1}$ Mpc to define the cosmic web. We find that the halo shape presents the strongest alignment along the smallest tidal eigenvector, e.g. along filaments and walls, with a signal that gets stronger as the halo mass increases. In the case of the velocity shear field only massive halos $>10^{12}$ $h^{-1}$$M_{\\odot}$ tend to have their shapes aligned along the largest tidal eigenvector; that is, perpendicular to filaments and walls. For the angular momentum we find alignment signals only for halos more massive than $10^{12}$ $h^{-1}$$M_{\\odot}$ both in the tidal and velocity shear webs where the preferences ...
Li, Lin-Sen
2016-04-01
The variation of the instantaneous rotational angular velocity of the rigid Earth in the lunar-solar gravitational field is studied. The formula is derived for variation of the instantaneous angular velocity of the rigid oblate Earth using the potential function from Euler's dynamic equations. The theoretical results show that under the influence of the gravitational field of the Moon and the Sun the Earth instantaneous angular velocity varies with periodic terms, but without secular variations. Amplitudes of the periodic terms and their periods are calculated and discussed.
Constant angular velocity of the wrist during the lifting of a sphere.
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). PMID:20233128
On the constancy along cylinders of the angular velocity in the solar convection zone
Durney, B.R.
1976-03-01
If, in the absence of rotation, the Sun's convection zone is adiabatic and if in the radial and latitudinal equations of motion the main balance of forces is between pressure gradients, Coriolis forces, and buoyancy forces (which is a good approximation if differential rotation is important over the entire convection zone and the large-scale velocities are not too large), then the perturbations in the convective flux and the pole-equator differences in flux (..delta..F) are very large in the lower half of the convection zone, unless the angular velocity is constant along cylinders. The meridional velocities associated with this rotation law are not small, however, and could generate a significant ..delta..F. In this analysis compressibility was taken into account, but the latitudinal and radial dependence of the stabilizing effect of rotation on turbulent convection was neglected. (AIP)
Cosmic web alignments with the shape, angular momentum and peculiar velocities of dark matter haloes
Forero-Romero, Jaime E.; Contreras, Sergio; Padilla, Nelson
2014-09-01
We study the alignment of dark matter haloes with the cosmic web characterized by the tidal and velocity shear fields. We focus on the alignment of their shape, angular momentum and peculiar velocities. We use a cosmological N-body simulation that allows us to study dark matter haloes spanning almost five orders of magnitude in mass (109-1014) h-1 M⊙ and spatial scales of (0.5-1.0) h-1 Mpc to define the cosmic web. The strongest alignment is measured for halo shape along the smallest tidal eigenvector, e.g. along filaments and walls, with a signal that gets stronger as the halo mass increases. In the case of the velocity shear field only massive haloes >1012 h-1 M⊙ tend to have their shapes aligned along the largest tidal eigenvector, i.e. perpendicular to filaments and walls. For the angular momentum we find alignment signals only for haloes more massive than 1012 h-1 M⊙ both in the tidal and velocity shear fields where the preferences is to be parallel to the middle eigenvector; perpendicular to filaments and parallel to walls. Finally, the peculiar velocities show a strong alignment along the smallest tidal eigenvector for all halo masses; haloes move along filaments and walls. The same alignment is present with the velocity shear, albeit weaker and only for haloes less massive than 1012 h-1 M⊙. Our results show that the two different algorithms used to define the cosmic web describe different physical aspects of non-linear collapse and should be used in a complementary way to understand the cosmic web influence on galaxy evolution.
Ribeiro F
2015-06-01
Full Text Available Fernanda Ribeiro,* Pierre-Alexis Lépine,* Corine Garceau-Bolduc, Valérie Coats, Étienne Allard, François Maltais, Didier Saey Centre de recherche de l’Institut Universitaire de cardiologie et de pneumologie de Québec, Université Laval, Québec, Canada *These authors contributed equally to this workBackground: The purpose of this study was to determine and compare the test-retest reliability of quadriceps isokinetic endurance testing at two knee angular velocities in patients with chronic obstructive pulmonary disease (COPD. Methods: After one familiarization session, 14 patients with moderate to severe COPD (mean age 65±4 years; forced expiratory volume in 1 second (FEV1 55%±18% predicted performed two quadriceps isokinetic endurance tests on two separate occasions within a 5–7-day interval. Quadriceps isokinetic endurance tests consisted of 30 maximal knee extensions at angular velocities of 90° and 180° per second, performed in random order. Test-retest reliability was assessed for peak torque, muscle endurance, work slope, work fatigue index, and changes in FEV1 for dyspnea and leg fatigue from rest to the end of the test. The intraclass correlation coefficient, minimal detectable change, and limits of agreement were calculated. Results: High test-retest reliability was identified for peak torque and muscle total work at both velocities. Work fatigue index was considered reliable at 90° per second but not at 180° per second. A lower reliability was identified for dyspnea and leg fatigue scores at both angular velocities. Conclusion: Despite a limited sample size, our findings su pport the use of a 30-maximal repetition isokinetic muscle testing procedure at angular velocities of 90° and 180° per second in patients with moderate to severe COPD. Endurance measurement (total isokinetic work at 90° per second was highly reliable, with a minimal detectable change at the 95% confidence level of 10%. Peak torque and fatigue index
Angular velocity of a sphere in a simple shear at small Reynolds number
Meibohm, J; Rosén, T; Einarsson, J; Lundell, F; Mehlig, B
2016-01-01
We analyse the angular dynamics of a small neutrally buoyant sphere in a simple shear. When the effect of fluid inertia is negligible the sphere rotates at half the fluid vorticity. We compute how weak fluid inertia reduces the angular velocity, and find $\\omega_3/s \\sim -{1}/{2} +0.0540\\, {\\rm Re}_{\\rm s}^{3/2}$ where $s$ is the shear rate and ${\\rm Re}_{\\rm s}$ is the shear Reynolds number. This result differs from that derived by Lin et al. [J. Fluid Mech. 44 (1970) 1] who obtained a coefficient roughly three times larger. Our result is in good agreement with those of direct numerical simulations at small but not too small values of ${\\rm Re}_{\\rm }s$.
Fast two-position initial alignment for SINS using velocity plus angular rate measurements
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.
Angular beam width of a slit-diffracted wave with noncollinear group and phase velocities
Lock, Edwin H.
2012-12-01
Taking magnetostatic surface wave diffraction as an example, this paper theoretically investigates the 2D diffraction pattern arising in the far-field region of a ferrite slab in the case of a plane wave with noncollinear group and phase velocities incident on a wide, arbitrarily oriented slit in an opaque screen. A universal analytical formula for the angular width of a diffracted beam is derived, which is valid for magnetostatic and other types of waves in anisotropic media and structures (including metamaterials) in 2D geometries. It is shown that the angular width of a diffracted beam in an anisotropic medium can not only take values greater or less than \\lambda _0/D (where \\lambda _0 is the incident wavelength, and D is the slit width), but can also be zero under certain conditions.
Angular beam width of a slit-diffracted wave with noncollinear group and phase velocities
Taking magnetostatic surface wave diffraction as an example, this paper theoretically investigates the 2D diffraction pattern arising in the far-field region of a ferrite slab in the case of a plane wave with noncollinear group and phase velocities incident on a wide, arbitrarily oriented slit in an opaque screen. A universal analytical formula for the angular width of a diffracted beam is derived, which is valid for magnetostatic and other types of waves in anisotropic media and structures (including metamaterials) in 2D geometries. It is shown that the angular width of a diffracted beam in an anisotropic medium can not only take values greater or less than λ0/D (where λ0 is the incident wavelength, and D is the slit width), but can also be zero under certain conditions. (methodological notes)
Clark, G
2003-04-28
This report describes a feasibility study. We are interested in calculating the angular and linear velocities of a re-entry vehicle using six acceleration signals from a distributed accelerometer inertial measurement unit (DAIMU). Earlier work showed that angular and linear velocity calculation using classic nonlinear ordinary differential equation (ODE) solvers is not practically feasible, due to mathematical and numerical difficulties. This report demonstrates the theoretical feasibility of using model-based nonlinear state estimation techniques to obtain the angular and linear velocities in this problem. Practical numerical and calibration issues require additional work to resolve. We show that the six accelerometers in the DAIMU are not sufficient to provide observability, so additional measurements of the system states are required (e.g. from a Global Positioning System (GPS) unit). Given the constraint that our system cannot use GPS, we propose using the existing on-board 3-axis magnetometer to measure angular velocity. We further show that the six nonlinear ODE's for the vehicle kinematics can be decoupled into three ODE's in the angular velocity and three ODE's in the linear velocity. This allows us to formulate a three-state Gauss-Markov system model for the angular velocities, using the magnetometer signals in the measurement model. This re-formulated model is observable, allowing us to build an Extended Kalman Filter (EKF) for estimating the angular velocities. Given the angular velocity estimates from the EKF, the three ODE's for the linear velocity become algebraic, and the linear velocity can be calculated by numerical integration. Thus, we do not need direct measurements of the linear velocity to provide observability, and the technique is mathematically feasible. Using a simulation example, we show that the estimator adds value over the numerical ODE solver in the presence of measurement noise. Calculating the velocities in the
Antia, H. M.; Chitre, S. M.; Gough, D. O.
2012-01-01
A putative temporally varying circulation-free magnetic-field configuration is inferred in an equatorial segment of the solar convection zone from the helioseismologically inferred angular-velocity variation, assuming that the predominant dynamics is angular acceleration produced by the azimuthal Maxwell stress exerted by a field whose surface values are consistent with photospheric line-of-sight measurements.
Antia, H. M.; Chitre, S. M.; Gough, D. O.
2013-01-01
A putative temporally varying circulation-free magnetic-field configuration is inferred in an equatorial segment of the solar convection zone from the helioseismologically inferred angular-velocity variation, assuming that the predominant dynamics is an angular acceleration produced by the azimuthal Maxwell stress exerted by a field whose surface values are consistent with photospheric line-of-sight measurements.
A new open-loop fiber optic gyro error compensation method based on angular velocity error modeling.
Zhang, Yanshun; Guo, Yajing; Li, Chunyu; Wang, Yixin; Wang, Zhanqing
2015-01-01
With the open-loop fiber optic gyro (OFOG) model, output voltage and angular velocity can effectively compensate OFOG errors. However, the model cannot reflect the characteristics of OFOG errors well when it comes to pretty large dynamic angular velocities. This paper puts forward a modeling scheme with OFOG output voltage u and temperature T as the input variables and angular velocity error Δω as the output variable. Firstly, the angular velocity error Δω is extracted from OFOG output signals, and then the output voltage u, temperature T and angular velocity error Δω are used as the learning samples to train a Radial-Basis-Function (RBF) neural network model. Then the nonlinear mapping model over T, u and Δω is established and thus Δω can be calculated automatically to compensate OFOG errors according to T and u. The results of the experiments show that the established model can be used to compensate the nonlinear OFOG errors. The maximum, the minimum and the mean square error of OFOG angular velocity are decreased by 97.0%, 97.1% and 96.5% relative to their initial values, respectively. Compared with the direct modeling of gyro angular velocity, which we researched before, the experimental results of the compensating method proposed in this paper are further reduced by 1.6%, 1.4% and 1.42%, respectively, so the performance of this method is better than that of the direct modeling for gyro angular velocity. PMID:25734642
Akhbari, Mahsa; Shamsollahi, Mohammad,; Jutten, Christian; Coppa, Bertrand
2012-01-01
International audience 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 i...
Estimates of the solar internal angular velocity obtained with the Mt. Wilson 60-foot solar tower
Rhodes, Edward J., Jr.; Cacciani, Alessandro; Woodard, Martin; Tomczyk, Steven; Korzennik, Sylvain
1987-01-01
Estimates are obtained of the solar internal angular velocity from measurements of the frequency splittings of p-mode oscillations. A 16-day time series of full-disk Dopplergrams obtained during July and August 1984 at the 60-foot tower telescope of the Mt. Wilson Observatory is analyzed. Power spectra were computed for all of the zonal, tesseral, and sectoral p-modes from l = 0 to 89 and for all of the sectoral p-modes from l = 90 to 200. A mean power spectrum was calculated for each degree up to 89. The frequency differences of all of the different nonzonal modes were calculated for these mean power spectra.
New optimal control laws for attitude of a rigid body motion without angular velocity measurements
El-Gohary, Awad [Department of Statistics and Operational Research, Faculty of Science King Saud University, P.O. Box 2455, Riyadh 11451 (Saudi Arabia)] e-mail: aigohary@ksu.edu.sa
2005-08-01
In this paper we shall use the passive properties of Euler dynamic equations as well as the structural properties of kinematic equations in terms of Cayley-Rodrigues and Modified Rodrigues parameters to derive optimal control laws without any information about the angular velocity of the rigid body. The interesting difference in the current study is the assumption that only the kinematics attitude parameters are available for the control process. The optimal control laws ensure the optimal asymptotic stability of the rigid body motion and minimize a selecting performance are obtained in terms of the kinematics attitude parameters and their estimates. Numerical examples are presented to demonstrate the theoretical results.
The subsurface radial gradient of solar angular velocity from MDI f-mode observations
Corbard, T.; Thompson, M. J.
2001-01-01
We report quantitative analysis of the radial gradient of solar angular velocity at depths down to about 15 Mm below the solar surface for latitudes up to 75 degree using the Michelson Doppler Imager (MDI) observations of surface gravity waves (f modes) from the Solar and Heliospheric Observatory (SoHO). A negative outward gradient of around -400 nHz/R, equivalent to logarithmic gradient of the rotation frequency with respect to radius which is very close to -1, is found to be remarkably cons...
Effect of Angular Velocity on Sensors Based on Morphology Dependent Resonances
Amir R. Ali
2014-04-01
Full Text Available 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.
Structure equations of a slowly rotating, fully relativistic solid star. [Angular velocity
Quintana, H.
1976-07-01
General-relativistic elasticity theory is applied to the derivation of the structure equations for a relativistic rotating solid star with a spherically relaxable structure. The analysis is carried out to third order in the angular velocity. In this way one obtains the deformation of the star and its stress field, the change in gravitational mass, and the change in the moment of inertia. This last quantity is the key parameter needed for the application of the general-relativistic starquake theory of neutron stars.
Angular velocity variations and stability of spatially explicit prey-predator systems
Abta, Refael; Shnerb, Nadav M.
2006-01-01
The linear instability of Lotka-Volterra orbits in the homogenous manifold of a two-patch system is analyzed. The origin of these orbits instability in the absence of prey migration is revealed to be the dependence of the angular velocity on the azimuthal angle; in particular, the system desynchronizes at the exit from the slow part of the trajectory. Using this insight, an analogous model of a two coupled oscillator is presented and shown to yield the same type of linear instability. This un...
Dynamic boundary controls of a rotating body-beam system with time-varying angular velocity
Boumediène Chentouf
2004-01-01
This paper deals with feedback stabilization of a flexible beam clamped at a rigid body and free at the other end. We assume that there is no damping and the rigid body rotates with a nonconstant angular velocity. To stabilize this system, we propose a feedback law which consists of a control torque applied on the rigid body and either a dynamic boundary control moment or a dynamic boundary control force or both of them applied at the free end of the beam. Then it is ...
Effect of the starting block posture on the 3D joint angular velocity in sprinters
SLAWINSKI, J; ONTANON, G; Dumas, R; Cheze, L.; Miller, C.; MAZURE-BONNEFOY, A
2011-01-01
The aim of this study was to measure the effect of the modification of the posture during a sprint start on 3D joint angular velocity. This was performed using a 3D kinematic analysis of the whole body. Ten trained sprinters started using three different starting positions in the starting blocks (bunched, medium and elongated). They were equipped with 63 passive reflective markers, and an opto-electronic Motion Analysis® system (12 digital cameras 250 Hz) was used to collect the 3D marker tra...
Critical angular velocity of uniformly rotating white dwarfs. Technical summary report
Miketinac, M.J.
1976-05-01
The equilibrium configurations of uniformly rotating white dwarfs are calculated numerically as an application of the finite difference--finite expansion method pioneered by Stoeckly. The latest version of the Harrison--Wheeler equation of state is used, together with the post-Newtonian equations of structure. No other approximation is made. The resulting critical values for the angular velocity agree in order of magnitude with a 'crude' approximation to these values by Hartle and Thorne, but fractional differences in mean radius and in mass and eccentricities are very different. (GRA)
Effect of angular velocity on sensors based on morphology dependent resonances.
Ali, Amir R; Ioppolo, Tindaro
2014-01-01
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. PMID:24759108
Ito, Yoshifumi; Arai, Noriyuki; Ueda, Yoshio; Sugimoto, Satoshi; Okada, Shigefumi; Goto, Seiichi; Ishimura, Tsutomu (Osaka Univ., Suita (Japan). Faculty of Engineering)
1991-07-01
The angular velocity {Omega}{sub c} of the impurity ions (CV) is measured spectroscopically for the FRC (Field-Reversed-Configuration) plasmas confined in the {theta}-pinch region and translated into the confinement region with magnetic mirror field. The FRC plasma confined in the {theta}-pinch region becomes unstable due to the n=2 rotational instability which can be suppressed by the multipole magnetic field. The ion rotation in the stabilized plasma is almost equal to the velocity in the unstabilized case, suggesting that the multipole field acts on the plasma surface due to the skin effect and suppresses the instability without changing the field configuration within the separatrix radius. The FRC plasma translated in the confinement region is stable without destructive instability. The ion rotation in such a plasma indicates that a suppression mechanism of the n=2 instability exists, which is excited by the rotation in the confinement region. (author).
Velocity and angular distributions of evaporation residues from /sup 32/S-induced reactions
Hinnefeld, J.D.; Kolata, J.J.; Henderson, D.J.; Janssens, R.V.F.; Kovar, D.G.; Lesko, K.T.; Rosner, G.; Stephans, G.S.F.; van den Berg, A.M.; Wilkins, B.D.
1987-09-01
Velocity distributions of mass-resolved evaporation residues from reactions of /sup 32/S with /sup 12/C, /sup 24/Mg, /sup 27/Al, /sup 28/Si, and /sup 40/Ca have been measured at bombarding energies of 194, 239, and 278 MeV using time-of-flight techniques. In all cases, the observed shifts in the velocity centroids relative to the values expected for complete fusion are consistent with a previously reported parametrization of a threshold for onset of incomplete fusion. Angular distributions were measured and total cross sections extracted for the /sup 32/S+ /sup 24/Mg system at all three energies. A comparison with existing results for /sup 32/S+ /sup 24/Mg at lower energies, and with other systems leading to the /sup 56/Ni compound nucleus, suggests two different types of compound-nuclear limitations to complete fusion at higher energies.
Laminar flow past a spinning bullet-shaped body at moderate angular velocities
Jiménez-González, J. I.; Sanmiguel-Rojas, E.; Sevilla, A.; Martínez-Bazán, C.
2013-11-01
We present a numerical study of the flow past a spinning bullet-shaped body of length-to-diameter ratio L/D=2, focusing on the evolution of the forces and flow regimes that appear depending on the values of the two governing parameters, namely the Reynolds number, Re=ρw∞D/μ, and the dimensionless angular velocity, Ω=ωD/(2w∞), where ρ, μ and w∞ are the free-stream density, viscosity and velocity, respectively, and ω is the angular velocity of the body. The parametric study covers the range 0≤Ω≤0.4 for Re<450, corresponding to laminar flow and moderate rotation velocities. It is shown that the (Re,Ω) parameter plane can be divided into four regions, corresponding to the destabilization of several instability modes. In the range 0≤Ω≲0.2, three different flow regimes take place as Re increases keeping constant Ω: axisymmetric, frozen and spiral flow regimes respectively; the latter leading to a swirling configuration of vortices curling up around the axis, caused by a combination of the frozen mode and the vortex shedding. However, at Ω≃0.2, a new frozen spiral mode takes place for large enough values of Re, where two counter-rotating vortices spiral around the axis, as a result of a lock-in process of the vortex shedding associated to the unsteady spiral regime, being this mode the single unstable one existent for Ω≥0.225. An exhaustive study of the dependence of the drag and lift forces on Ω and Re is also presented.
Dell'Olio, Francesco; Ciminelli, Caterina; Armenise, Mario Nicola
2013-02-01
Here, we report the guidelines to be followed to optimize the design of a new angular velocity sensor based on an indium phosphide (InP) ring resonator. Optical properties of InP ring resonators have been investigated together with some significant physical effects for improving the sensor sensitivity. Three-dimensional algorithms have been utilized for the theoretical estimation of the waveguide loss. An optimized waveguide with propagation loss <0.3 dB/cm and a ring resonator with a quality factor of 1.5×106 have been designed. Performance of angular velocity sensors based on InP low-loss ring resonators has been estimated and discussed. Resolution of 10 deg/h and bias drift in the range of 0.1 to 0.3 deg/h have been evaluated for a fully integrated optical gyro including an InGaAsP/InP optical cavity having a footprint less than 24 cm2.
Repeating firing fields of CA1 neurons shift forward in response to increasing angular velocity.
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. PMID:24381284
Zilevu, Kojo S.; Kammerman, Kelly L.; Nanzer, Jeffrey A.
2013-05-01
The design of a 29.5 GHz experimental active interferometer for the measurement of the angular velocity of moving humans is presented in this paper, as well as initial measurements of walking humans. Measurement of the angular motion of moving objects is a desirable function in remote security sensing applications. Doppler radar sensors are able to measure the signature of moving humans based on micro-Doppler analysis; however, a person moving with little to no radial velocity produces negligible Doppler returns. Measurement of the angular movement of humans can be done with traditional radar techniques however the process involves either continuous tracking with narrow beamwidth or angle-of arrival estimation algorithms. Recently, the authors presented a new method of measuring the angular velocity of moving objects using interferometry. The method measures the angular velocity of an object without tracking or complex processing. The frequency shift imparted on the signal response is proportional to the angular velocity of the object as it passes through the interferometer beam pattern. The experimental system consists of a transmitter and two separate receivers with two widely spaced antennas. The received signals in each of the two channels are downconverted and digitized, and post-processed offline. Initial results of a walking person passing through the interferometer beam pattern are presented, which verify the expected operation of the receiver derived from the initial theory.
Precision angular velocity response of a fiber-optic gyroscope using a piezo-nano-rotation table
Modern fiber-optic gyroscopes are calibrated using the Earth's rotation or stepper motor actuated rotation tables. We investigated the angular velocity resolution of the Optolink SRS-1000 fiber-optic gyroscope using a piezo-activated rotation table down to angular velocity steps of 1 × 10−7 rad s−1 with an accuracy of 1.5 × 10−8 rad s−1. To our knowledge, these are the smallest velocity steps resolved and reported in the literature so far. Our results show that such a gyroscope may be also used for nanopositioning purposes in addition to its usual navigation application. (technical design note)
ZHOU Xiaoyao; ZHANG Zhiyong; FAN Dapeng
2011-01-01
The performance of any inertially stabilized platform(ISP)is strongly related to the bandwidth and accuracy of the angular velocity signals.This paper discusses the development of an optimal state estimator for sensing inertial velocity using low-cost micro-electro-mechanical systems(MEMS)sensors.A low-bandwidth gyroscope is used alone with two low-performance accelerometers to obtain the estimation.The gyroscope has its own limited dynamics and mainly contributes to the low-frequency components of the estimation.The accelerometers have inherent biases and mainly contribute to the high-frequency components of the estimation.Extensive experimental results show that the state estimator can achieve high-performance signals over a wide range of velocities without drifts in both the t- and s-domains.Furthermore,with applications in miniature inertially stabilized platforms,the control characteristic presents a significantly improvement over the existing methods.The method can be also applied to robotics,attitude estimation,and friction compensation.
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. PMID:18555699
SUN Meng; LIU Shi; LEI Jing; LI ZhiHong
2008-01-01
Cyclone separator is one of the main parts of the circulating fluidized bed (CFB) boiler. The separation efficiency of the cyclone separator is very important to the whole boiler. Electrical capacitance tomo-graphy (ECT) is a unique measuring technique with great potential in multiphase flow measurement. Experimental studies are carried out on the measurement of volumetric concentration and angular ve-locity using ECT. The former is determined through image reconstruction method, and the latter is measured by cross-correlating the capacitance fluctuations caused by the conveyed solids. The dis-tribution of void fraction in radial direction, the fluctuating characteristics, probability density function and the spectrum characteristics are analyzed. The feasibility and reliability of the method are verified by experimental results.
Calibration of the head direction network: a role for symmetric angular head velocity cells.
Stratton, Peter; Wyeth, Gordon; Wiles, Janet
2010-06-01
Continuous attractor networks require calibration. Computational models of the head direction (HD) system of the rat usually assume that the connections that maintain HD neuron activity are pre-wired and static. Ongoing activity in these models relies on precise continuous attractor dynamics. It is currently unknown how such connections could be so precisely wired, and how accurate calibration is maintained in the face of ongoing noise and perturbation. Our adaptive attractor model of the HD system that uses symmetric angular head velocity (AHV) cells as a training signal shows that the HD system can learn to support stable firing patterns from poorly-performing, unstable starting conditions. The proposed calibration mechanism suggests a requirement for symmetric AHV cells, the existence of which has previously been unexplained, and predicts that symmetric and asymmetric AHV cells should be distinctly different (in morphology, synaptic targets and/or methods of action on postsynaptic HD cells) due to their distinctly different functions. PMID:20354898
Angular velocity variations and stability of spatially explicit prey-predator systems.
Abta, Refael; Shnerb, Nadav M
2007-05-01
The linear instability of Lotka-Volterra orbits in the homogenous manifold of a two-patch system is analyzed. The origin of these orbits instability in the absence of prey migration is revealed to be the dependence of the angular velocity on the azimuthal angle; in particular, the system desynchronizes at the exit from the slow part of the trajectory. Using this insight, an analogous model of a two coupled oscillator is presented and shown to yield the same type of linear instability. This enables one to incorporate the linear instability within a recently presented general framework that allows for comparison of all known stabilization mechanisms and for simple classification of observed oscillations. PMID:17677105
Angular momentum analysis of rotational transfer of superthermal relative velocity distributions
Whiteley, T.W.J.; McCaffery, A.J. [Sussex Univ., Brighton (United Kingdom). School of Molecular Sciences
1996-12-02
An angular momentum (AM) theory is developed to calculate the relative populations of final rotational states after collision between a diatomic molecule and an atom having a narrow, superthermal velocity distribution as produced by, e.g. photolysis of a precursor species. Probability densities are derived from semiclassical expressions for energy and angular momentum assuming the classically impulsive limit with the repulsive wall modelled by a hard ellipsoid. The treatment given is general and therefore applies to molecules in which the centre-of-mass does not coincide with the centre of the potential coordinates. A transfer function for RT is derived and applied to the H + CO system. Analysis of the data allows the anisotropy to be extracted which is in good agreement with an ab initio potential surface. The method described allows one to rapidly assess the contributions from the elliptical core of the potential and from other features of the potential, and would permit more sophisticated representations of the topology to be incorporated. (Author).
Relation between the critical spin and angular velocity of a nucleus immediately after backbending
Nosov, V.G.; Kamchatnov, A.M.
1979-05-01
In nonspherical nuclei at J=J/sub c/+0 the relationship between the angular momentum and angular velocity immediately after backbending is the same as in the limiting case J-J/sub c/..-->..infinity. This indicates that there is a unique type of cancellation of the deviations from a rigid-body moment of inertia in the upper phase J>J/sub c/. An integral relationship is found which expresses this cancellation quantitatively. This formula permits J/sub c/ to be calculated for the rotational bands of the even-even nuclei studied and the results are in agreement with those obtained by other methods of locating the Curie point. For the ground state band of W/sup 170/ the cancellation of the reciprocals of the true and rigid-body moments of inertia can be verified directly. The condition for the stability of the rotation of a nonspherical nucleus is analyzed in the Appendix in close connection with the problem of a reasonable definition of the concept of a variable moment of inertia.
Relation between the critical spin and angular velocity of a nucleus immediately after backbending
Nosov, V G
1979-01-01
In nonspherical nuclei at $J = J_c + 0$ the relationship between the angular momentum and angular velocity immediately after backbending is the same as in the limiting case $J - J_c\\to\\infty$. This indicates that there is a unique type of cancellation of the deviations from a rigid-body moment of inertia in the upper phase $J>J_c$. An integral relationship is found which expresses this cancellation quantitatively. This formula permits $J_c$ to be calculated for the rotational bands of the even-even nuclei studied and the results are in agreement with those obtained by other methods of locating the Curie point. For the ground state band of W$^{170}$ the cancellation of the reciprocals of the true and rigid-body moments of inertia can be verified directly. The condition for the stability of the rotation of a nonspherical nucleus is analyzed in the Appendix in close connection with the problem of a reasonable definition of the concept of a variable moment of inertia.
Angelaki, D. E.; Hess, B. J.
1996-01-01
1. The dynamic contribution of otolith signals to three-dimensional angular vestibuloocular reflex (VOR) was studied during off-vertical axis rotations in rhesus monkeys. In an attempt to separate response components to head velocity from those to head position relative to gravity during low-frequency sinusoidal oscillations, large oscillation amplitudes were chosen such that peak-to-peak head displacements exceeded 360 degrees. Because the waveforms of head position and velocity differed in shape and frequency content, the particular head position and angular velocity sensitivity of otolith-ocular responses could be independently assessed. 2. During both constant velocity rotation and low-frequency sinusoidal oscillations, the otolith system generated two different types of oculomotor responses: 1) modulation of three-dimensional eye position and/or eye velocity as a function of head position relative to gravity, as presented in the preceding paper, and 2) slow-phase eye velocity as a function of head angular velocity. These two types of otolith-ocular responses have been analyzed separately. In this paper we focus on the angular velocity responses of the otolith system. 3. During constant velocity off-vertical axis rotations, a steady-state nystagmus was elicited that was maintained throughout rotation. During low-frequency sinusoidal off-vertical axis oscillations, dynamic otolith stimulation resulted primarily in a reduction of phase leads that characterize low-frequency VOR during earth-vertical axis rotations. Both of these effects are the result of an internally generated head angular velocity signal of otolithic origin that is coupled through a low-pass filter to the VOR. No change in either VOR gain or phase was observed at stimulus frequencies larger than 0.1 Hz. 4. The dynamic otolith contribution to low-frequency angular VOR exhibited three-dimensional response characteristics with some quantitative differences in the different response components. For
Zheng, Shiqiang; Han, Bangcheng
2013-06-01
This paper presents an integrated angular velocity measurement and attitude control system of spacecraft using magnetically suspended double-gimbal control moment gyros (MSDGCMGs). The high speed rotor of MSDGCMG is alleviated by a five-degree-of-freedom permanent magnet biased AMB control system. With this special rotor supported manner, the MSDGCMG has the function of attitude rate sensing as well as attitude control. This characteristic provides a new approach to a compact light-weight spacecraft design, which can combine these two functions into a single device. This paper discusses the principles and implementations of AMB-based angular velocity measurement. Spacecraft dynamics with DGMSCMG actuators, including the dynamics of magnetically suspended high-speed rotor, the dynamics of inner gimbal and outer gimbal, as well as the determination method of spacecraft angular velocity are modeled, respectively. The effectiveness of the proposed integrated system is also validated numerically and experimentally.
Morse, Jonathan L; Jung, Myung-Chul; Bashford, Gregory R; Hallbeck, M Susan
2006-11-01
The objective of this study was to examine the effects of gender, exertion direction, angular velocity and wrist angle on simultaneous grip force and wrist torque under the isokinetic condition. The study used 20 participants (10 males and 10 females) and included 6 angular velocities (15, 30, 45, 60, 75, and 90 degrees /s) and 2 wrist exertion directions (flexion and extension) over the wrist range of motion of 70 degrees flexion to 60 degrees extension in 5 degrees increments. Similar to other studies, males and flexion exertion produced larger forces than females and extension exertion, respectively. However, the largest forces were generated at near extreme flexion of the wrist and the dependent variable of angular velocity was not practically significant. These results can contribute to the evaluation of cumulative trauma syndromes, but there is a need for more research on the dynamic measures of the hand and wrist complex and for standard development for dynamic force measurement. PMID:16442072
Dynamic angular velocity modeling and error compensation of VG095M in the whole temperature range, based on a radial basis function (RBF) neural network, is presented in this paper. With gyro output voltage and environmental temperature as the input and angular velocity as the output, an RBF neural network model is established. The model is trained and validated by the experiment data. The fitting error of the model is 4.3818 × 10−6 deg s−1, which shows that the model has high precision. The experiment data except the data used for modeling were processed with this model. The results show that the maximum, minimum and mean square error of the angular velocity were reduced to 4.6%, 4.3% and 4.7% respectively after compensation
Modification of Angular Velocity by Inhomogeneous MRI Growth in Protoplanetary Disks
Kato, M T; Tandokoro, R; Fujimoto, M; Ida, S
2008-01-01
We have investigated evolution of magneto-rotational instability (MRI) in protoplanetary disks that have radially non-uniform magnetic field such that stable and unstable regions coexist initially, and found that a zone in which the disk gas rotates with a super-Keplerian velocity emerges as a result of the non-uniformly growing MRI turbulence. We have carried out two-dimensional resistive MHD simulations with a shearing box model. We found that if the spatially averaged magnetic Reynolds number, which is determined by widths of the stable and unstable regions in the initial conditions and values of the resistivity, is smaller than unity, the original Keplerian shear flow is transformed to the quasi-steady flow such that more flattened (rigid-rotation in extreme cases) velocity profile emerges locally and the outer part of the profile tends to be super-Keplerian. Angular momentum and mass transfer due to temporally generated MRI turbulence in the initially unstable region is responsible for the transformation...
Behavior of the angular velocity in the lower part of the solar convection zone
Durney, B. R.
1989-03-01
The solar angular velocity is expanded in Legendre polynomials. The meridional motions are restricted to one or two cells per hemisphere, and an approximation to the azimuthal equation of motion is integrated with respect to r with the help of the boundary condition at r = Rc, the lower boundary of the solar convection zone (SCZ). The Reynolds stresses appearing in the equation are estimated for the lower SCZ, and approximate expressions are derived for the turbulent viscosity coefficients (which are due to the influence of the mean flow on the turbulent velocities). It is shown that the assumption of isotropic viscosity is always open to criticism. An order-of-magnitude estimate of the different terms in the E(r) and E(theta) equations suggests that the Reynolds and viscous stresses are important only near the boundaries of the SCZ. Away from the boundaries, in the Taylor-Proudman region, the suggested balance is between Coriolis forces, pressure gradients, and buoyancy forces. 47 refs.
Zherbina, A.S.
1977-01-01
Unsteady rotation of a viscous convective layer with friction at its lower boundary is analyzed. Such friction is shown to be capable of maintaining a radial dependence of angular velocity for a long time. It is found, however, that this mechanism cannot be the cause of the sun's equatorial acceleration.
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 =…
Mandrosov, V. I.
2012-01-01
We propose a reference-free method for forming a three-dimensional image and for determining the angular velocity of a remote nonplanar object. The method is based on probing an object by laser radiation with a coherence length that is smaller or larger than the size of the object and on the use of
The subsurface radial gradient of solar angular velocity from MDI f-mode observations
Corbard, T
2001-01-01
We report quantitative analysis of the radial gradient of solar angular velocity at depths down to about 15 Mm below the solar surface for latitudes up to 75 degree using the Michelson Doppler Imager (MDI) observations of surface gravity waves (f modes) from the Solar and Heliospheric Observatory (SoHO). A negative outward gradient of around -400 nHz/R, equivalent to logarithmic gradient of the rotation frequency with respect to radius which is very close to -1, is found to be remarkably constant between the equator and 30 degree of latitude. Above 30 degree it decreases in absolute magnitude to a very small value at around 50 degree. At higher latitudes the gradient may reverse its sign: if so this reversal takes place in a thin layer extending only 5 Mm beneath the visible surface, as evidenced by the most superficial modes (with degrees l>250). The signature of the torsional oscillations is seen in this layer, but no other significant temporal variations of the gradient and value of the rotation rate there...
Cardou, Philippe, E-mail: pcardou@cim.mcgill.ca; Angeles, Jorge [McGill University, Macdonald Engineering Building, Department of Mechanical Engineering, Centre for Intelligent Machines (Canada)
2008-05-15
Two methods are available for the estimation of the angular velocity of a rigid body from point-acceleration measurements: (i) the time-integration of the angular acceleration and (ii) the square-rooting of the centripetal acceleration. The inaccuracy of the first method is due mainly to the accumulation of the error on the angular acceleration throughout the time-integration process, which does not prevent that it be used successfully in crash tests with dummies, since these experiments never last more than one second. On the other hand, the error resulting from the second method is stable through time, but becomes inaccurate whenever the rigid body angular velocity approaches zero, which occurs in many applications. In order to take advantage of the complementarity of these two methods, a fusion of their estimates is proposed. To this end, the accelerometer measurements are modeled as exact signals contaminated with bias errors and Gaussian white noise. The relations between the variables at stake are written in the form of a nonlinear state-space system in which the angular velocity and the angular acceleration are state variables. Consequently, a minimum-variance-error estimate of the state vector is obtained by means of extended Kalman filtering. The performance of the proposed estimation method is assessed by means of simulation. Apparently, the resulting estimation method is more robust than the existing accelerometer-only methods and competitive with gyroscope measurements. Moreover, it allows the identification and the compensation of any bias error in the accelerometer measurements, which is a significant advantage over gyroscopes.
Two methods are available for the estimation of the angular velocity of a rigid body from point-acceleration measurements: (i) the time-integration of the angular acceleration and (ii) the square-rooting of the centripetal acceleration. The inaccuracy of the first method is due mainly to the accumulation of the error on the angular acceleration throughout the time-integration process, which does not prevent that it be used successfully in crash tests with dummies, since these experiments never last more than one second. On the other hand, the error resulting from the second method is stable through time, but becomes inaccurate whenever the rigid body angular velocity approaches zero, which occurs in many applications. In order to take advantage of the complementarity of these two methods, a fusion of their estimates is proposed. To this end, the accelerometer measurements are modeled as exact signals contaminated with bias errors and Gaussian white noise. The relations between the variables at stake are written in the form of a nonlinear state-space system in which the angular velocity and the angular acceleration are state variables. Consequently, a minimum-variance-error estimate of the state vector is obtained by means of extended Kalman filtering. The performance of the proposed estimation method is assessed by means of simulation. Apparently, the resulting estimation method is more robust than the existing accelerometer-only methods and competitive with gyroscope measurements. Moreover, it allows the identification and the compensation of any bias error in the accelerometer measurements, which is a significant advantage over gyroscopes
Nordsiek, Freja; Huisman, Sander G.; van der Veen, Roeland C. A.; Sun, Chao; Lohse, Detlef; Lathrop, Daniel P.
2015-07-01
We present azimuthal velocity profiles measured in a Taylor-Couette apparatus, which has been used as a model of stellar and planetary accretion disks. The apparatus has a cylinder radius ratio of $\\eta = 0.716$, an aspect-ratio of $\\Gamma = 11.74$, and the plates closing the cylinders in the axial direction are attached to the outer cylinder. We investigate angular momentum transport and Ekman pumping in the Rayleigh-stable regime. The regime is linearly stable and is characterized by radially increasing specific angular momentum. We present several Rayleigh-stable profiles for shear Reynolds numbers $Re_S \\sim O(10^5) \\,$, both for $\\Omega_i > \\Omega_o > 0$ (quasi-Keplerian regime) and $\\Omega_o > \\Omega_i > 0$ (sub-rotating regime) where $\\Omega_{i,o}$ is the inner/outer cylinder rotation rate. None of the velocity profiles matches the non-vortical laminar Taylor-Couette profile. The deviation from that profile increased as solid-body rotation is approached at fixed $Re_S$. Flow super-rotation, an angular velocity greater than that of both cylinders, is observed in the sub-rotating regime. The velocity profiles give lower bounds for the torques required to rotate the inner cylinder that were larger than the torques for the case of laminar Taylor-Couette flow. The quasi-Keplerian profiles are composed of a well mixed inner region, having approximately constant angular momentum, connected to an outer region in solid-body rotation with the outer cylinder and attached axial boundaries. These regions suggest that the angular momentum is transported axially to the axial boundaries. Therefore, Taylor-Couette flow with closing plates attached to the outer cylinder is an imperfect model for accretion disk flows, especially with regard to their stability.
Ohno, Yuichi; Matsushima, Tatsuo; Uetsuka, Hiroshi
1994-01-01
The angular and velocity distributions of desorbing product CO2 were studied on a platinum(110)(1×2) surface over a wide range of CO coverages by means of angle-resolved thermal desorption combined with a cross-correlation time-of-flight (TOF) technique. Heating the coadsorption layer of CO and oxygen yields four CO2 formation peaks P1–CO2 (~400 K), P2–CO2 (300 K), P3–CO2 (250 K), and P4–CO2 (170 K)]. The angular distribution of each CO2 produced at high CO coverages consists of three desorpt...
Buss, R.J.; Coggiola, M.J.; Lee, Y.T.
1978-12-01
Several methods currently used to study unimolecular decomposition in molecular beams are discussed. Experimental product angular and velocity distributions obtained for the reaction of F, Cl with C/sub 2/H/sub 3/Br are presented. The mechanism by which conservation of angular momemtum can cause coupling of the product angular and velocity distributions in dissociation of long-lived complexes is introduced. 14 references.
Sadeghi, Jafar
2015-01-01
In order to study quark and anti-quark interaction, one should consider all effects of the medium in motion of the pair. Because the pair, is not produced at rest in QGP. So the velocity of the pair, has some effects on its interactions that should be taken into account. In this paper we apply some conformal transformations for a rotat- ing string dual to a rotating heavy quark in $AdS_3$ which construct an accelerating string dual to an accelerating quark and anti-quark pair. So, we can have a comparison between when pair has angular velocity or not. Then we can study effects of angular velocity on the accelerating quark and anti-quark which are constructed by performing special con- formal transformations, conformal SO(2,2) transformation and particular $SL(2;R)_L$ and $SL(2;R)_R$ transformation. The accelerating quark and anti-quark show different behavior with increasing in angular velocity. With useful numerical solutions we show that quark and anti-quark can deccelerate to achieve each other or accelera...
ERSOY, H. Volkan; BARIŞ, Serdar
2002-01-01
In this paper, the flow of a viscous fluid due to the non-coaxial rotations of a disk and the fluid at infinity with a slight angular velocity difference is studied. The effect of angular velocity difference on the velocity field is analyzed in detail. A perturbation series which is expressed in powers of the rotation parameter with nearly the same angular velocity and the shooting method using the fourth-order Runge-Kutta procedure are employed to solve the problem. It is proved that the r...
Arena, N.; Cavallaro, S.; Femino' , S.; Figuera, P.; Pirrone, S.; Porto, F.; Sambataro, S. (Dipartimento di Fisica, Universita di Catania, Universita di Messina, Istituto Nazionale di Fisica Nucleare, Sezione di Catania and Laboratorio Nazionale del Sud I-95129 Catania (Italy))
1991-11-01
Velocity spectra and angular and mass distributions for the evaporation residues of the {sup 32}S+{sup 12}C system at {ital E}{sup 32}S=145 MeV in the angular range 3{degree}{le}{var theta}{sub {ital L}}{le}12{degree} have been measured. In order to separate compound nucleus evaporation residues from other heavy reaction products, a kinematic analysis based on simple statistical assumptions relative to the velocity spectra was performed. The structures in the mass distribution are compared with the LILITA code predictions. The fusion excitation function of the existing results is compared with theoretical models. The total reaction cross section has been extracted by means of the modified sum of differences method.
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. PMID:23366530
Mandrosov, V. I.
2012-07-01
We propose a reference-free method for forming a threedimensional image and for determining the angular velocity of a remote nonplanar object. The method is based on probing an object by laser radiation with a coherence length that is smaller or larger than the size of the object and on the use of a screen with radial holes in the centres of which photodetectors are located, the screen being mounted in the region of the flat image of the object. A threedimensional image of the object is constructed using the visibility of the interference fringes formed behind the screen due to radiation beams scattered by the object which pass through various pairs of holes (one of the holes is fixed). The three components of the angular velocity vector of the object are determined by the power spectrum of the electric signal produced during the movement of interference fringes on a photodetector mounted behind the screen.
Gibson, S T; Cavanagh, S J; Lewis, B R [Research School of Physics and Engineering, Australian National University, Canberra ACT 0200 (Australia); Gascooke, J R [School of Chemistry, Physics and Earth Sciences, Flinders University, SA 5001 (Australia); Mabbs, R [Department of Chemistry, Washington University, St Louis MO 63930-4899 (United States); Sanov, A, E-mail: Stephen.Gibson@anu.edu.a, E-mail: Steven.Cavanagh@anu.edu.a [Department of Chemistry, University of Arizona, Tucson AZ 85721-0041 (United States)
2009-11-01
The photodetachment spectrum of O{sub 2}{sup -} has been measured at a number of wavelengths using velocity-map imaging. The electron kinetic-energy resolution (< 5 meV) is sufficient to resolve the anion fine-structure splitting, vibrational and electronic structure. The electron angular distribution varies with the electron kinetic-energy, with a different behaviour for each vibronic band.
E. A. Perdios; Kalantonis, V. S.; Perdiou, A. E.; Nikaki, A. A.
2015-01-01
The paper deals with a modification of the restricted three-body problem in which the angular velocity variation is considered in the case where the primaries are sources of radiation. In particular, the existence and stability of its equilibrium points in the plane of motion of the primaries are studied. We find that this problem admits the well-known five planar equilibria of the classical problem with the difference that the corresponding collinear points may be stable depending on the par...
Misewich, J.; Zacharias, H.; Loy, M.M.T.
1985-09-01
Infrared laser excitation has been utilized to excite part of a molecular beam of NO to a single well-defined quantum state, NO(v = 1, J = 3/2, ..cap omega.. = 1/2), which is scattered from a cleaved LiF(100) surface. Laser spectroscopic detection techniques then allow the determination of rotational and electronic distributions as well as state-specific angular and velocity distributions for scattering from a single initial vibrational-rotational state.
Yue Ji; Xingfei Li; Tengfei Wu; Cheng Chen
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 ...
Butterworth, E.M.
1979-07-01
A method previously described by Butterworth and Ipser for constructing models of rapidly rotating fluid bodies in general relativity is modified to enable construction of solutions whose sources are very highly flattened. In particular, solutions with increasing oblateness and decreasing angular velocity are exhibited. Also, a discussion is given of the possible association of the terminal of relativistic sequences by equatorial shedding and the first secular axisymmetric instability of the Maclaurin spheroids.
A. R. Gowhari-Anaraki; Djavanroodi, F.; S. Shadlou
2008-01-01
The finite element method has been used to predict the creep rupture parameter, C*-Integral for single and double-edge cracks in eight annular rotating discs under constant angular velocity with and without internal pressure. In this study, a new dimensionless creeping crack configuration factor, Q* has been introduced. Power law creeping finite element analyses have been performed and the results are presented in the form of Q* for a wide range of components and crack geometry parameters. Th...
Alpar, M.A.
1986-12-01
Model power spectra are constructed for quasi-periodic oscillations of the type observed in some galactic bulge X-ray sources. It is shown that the angular location of clumping in the boundary layer, as well as the spread in Keplerian velocities within the boundary layer, will effect the form of the power spectrum under certain conditions. The occurrence of such features in observed power spectra would yield information on the possible role of the magnetic field in clumping and on the radial velocity of matter moving through the boundary layer.
Moon, S.J.; Ro, S.T. [Seoul National University (Korea, Republic of)
1995-03-01
A simplified model for the so-called ACRT(accelerated crucible rotation technique) Bridgman crystal growth was considered in order to investigate the principal effects of the periodic variation of angular velocity. Numerical solutions were obtained for Ro=0.5, Ra=4.236*10{sup 6} and E=2.176*10{sup -3}. The effects of spin-up process combined with natural convection was investigated as a preliminary study. The spin-up time scale for the present problem was a little larger than that observed for homogeneous spin-up problems. Numerical results reveal that over a time scale of (H{sup 2}/{nu}{omega}{sub f}){sup 1/2} the forced convection due to the formation of Ekman layer predominates. When the state of rigid body rotation is attained, natural convection due to buoyancy emerges as the main driving force and then the steady-state is approached asymptotically. Based on our preliminary results with simple spin-up, several fundamental features associated with variation of rotation speed are successfully identified. When a periodic variation of angular velocity was imposed, the system response was also periodic. Due to effect of mixing, the heat transfer was enlarged. From the analysis of time-averaged Nusselt number along the bottom surface the effect of a periodic variation of angular velocity on the interface location could be indirectly identified. (author). 15 refs., 11 figs., 3 tabs.
Mass, velocity, angular and charge-state distributions from the fusion of /sup 32/S and /sup 112/Sn
Bolton, C.; Schier, W.A.; Tsoupas, N.; Enge, H.; Salomaa, M.; Sperduto, A.; Graue, A.
1978-07-01
Evaporation residues from the fusion of /sup 32/S and /sup 112/Sn at E/sub /sup 32/S/ = 160 meV were studied using an energy-mass spectrometer. The velocity selector of the energy-mass spectrometer was first utilized to measure summed fusion products as a function of velocity setting and reaction angle. In-flight mass separtion of the fusion products with the energy-mass spectrometer identified masses 141, 140, and 139 from the evaporation of three to five nucleons from the /sup 144/Dy compound nucleus. Absolute cross-section measurements are compared to theoretical predictions of the statistical evaporation model. Velocity, angular and charge state distributions of evaporation residues are also compared to calculated values.
Andrade, Marilia Dos Santos; De Lira, Claudio Andre Barbosa; Koffes, Fabiana De Carvalho; Mascarin, Naryana Cristina; Benedito-Silva, Ana Amélia; Da Silva, Antonio Carlos
2012-01-01
The purpose of this study was to determine differences in hamstrings-to-quadriceps (H/Q) peak torque ratios evaluated at different angular velocities between men and women who participate in judo, handball or soccer. A total of 166 athletes, including 58 judokas (26 females and 32 males), 39 handball players (22 females and 17 males), and 69 soccer players (17 females and 52 males), were evaluated using an isokinetic dynamometer. The H/Q isokinetic peak torque ratios were calculated at angular velocities of 1.05 rad · s⁻¹ and 5.23 rad · s⁻¹. In the analysis by gender, female soccer players produced lower H/Q peak torque ratios at 1.05 rad · s⁻¹ than males involved in the same sport. However, when H/Q peak torque ratio was assessed at 5.23 rad · s⁻¹, there were no significant differences between the sexes. In the analysis by sport, there were no differences among females at 1.05 rad · s⁻¹. In contrast, male soccer players had significantly higher H/Q peak torque ratios than judokas (66 ± 12% vs. 57 ± 14%, respectively). Female handball players produced significantly lower peak torque ratios at 5.23 rad · s⁻¹ than judokas or soccer players, whereas males presented no ratio differences among sports At 5.23 rad · s⁻¹. In the analysis by velocity, women's muscular ratios assessed at 1.05 rad · s⁻¹ were significantly lower than at 5.23 rad · s⁻¹ for all sports; among men, only judokas presented lower ratios at 1.05 rad · s⁻¹ than at 5.23 rad · s⁻¹. The present results suggest that sport modality and angular velocity influence the isokinetic strength profiles of men and women. PMID:22364375
Near-field angular distributions of high velocity ions for low-power hall thrusters
Sullivan, Regina M.; Yost, Allison; Johnson, Lee K.
2009-01-01
Experimental angular distributions of high-energy primary ions in the near-field region of a small Hall thruster between 50-200 mm downstream of the thruster exit plane at a range of centerline angles have been determined using a highly-collimated, energy-selective diagnostic probe. The measurements reveal a wide angular distribution of ions exiting the thruster channel and the formation of a strong, axially-directed jet of ions along the thruster centerline. Comparisons are made to other exp...
Yue Ji
2015-12-01
Full Text Available 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.
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. PMID:20226465
NAGAYAMA, Takumi; Omodaka, Toshihiro; Nakagawa, Akiharu; HANDA, Toshihiro; HONMA, Mareki; Kobayashi, Hideyuki; KAWAGUCHI, Noriyuki; Miyaji, Takeshi
2010-01-01
We conducted the astrometry of H2O masers in the Galactic star-forming region Onsala 1 (ON1) with VLBI Exploration of Radio Astrometry (VERA). We measured a trigonometric parallax of 0.404+/-0.017 mas, corresponding to a distance of 2.47+/-0.11 kpc. ON1 is appeared to be located near the tangent point at the Galactic longitude of 69.54 deg. We estimate the angular velocity of the Galactic rotation at Sun, the ratio of the distance from Sun to the Galactic center and the Galactic rotation velo...
Seregin, A.A.
1976-03-01
In framework of a phenomenological collective nuclear theory the dependence of the moment of inertia on the angular velocity squared is studied. It is shown that this theory may explain the S shape of dependence of J on ..omega../sup 2/ if the collective motion potential V(..beta..) has two points of inflection. Anomalies in the low-lying part of the energy spectrum of the nuclei /sup 184/Hg and /sup 186/Hg are related to inflection points of the potential.
Morioka, Y.; Tomiyama, K.; Arima, H. (Kansai Electric Power Co., Inc., Osaka (Japan)); Sawai, K.; Omata, K.; Matsushima, T.; Takagi, K.; Ishibashi, A.; Saito, H. (Toshiba Corp., Tokyo (Japan))
1993-07-01
The purpose of this newly developed equipment is to separate the power system when an out-of-step between two groups of generators within it is predicted. The out-of-step prediction method is based on the generator's angular-velocity data measured by electromagnetic sensors and gears that are fastened directly to the rotors. The equipment was tested by the large-scale power system simulator APSA (Advanced Power System Analyzer), that is installed in the Kansai Electric Power Co., Inc. The equipment also underwent a field test.
Nordsiek, F.; Huisman, S.G.; Veen, van der, J.T.; C. Sun; Lohse, D.; Lathrop, D. P.
2015-01-01
We present azimuthal velocity profiles measured in a Taylor–Couette apparatus, which has been used as a model of stellar and planetary accretion disks. The apparatus has a cylinder radius ratio of ${\\it\\eta}=0.716$η=0.716, an aspect ratio of ${\\it\\Gamma}=11.74$Γ=11.74, and the plates closing the cylinders in the axial direction are attached to the outer cylinder. We investigate angular momentum transport and Ekman pumping in the Rayleigh-stable regime. This regime is linearly stable and is ch...
Khurana, Krishan K.; Kivelson, Margaret G.
1993-01-01
The averaged angular velocity of plasma from magnetic observations is evaluated using plasma outflow rate as a parameter. New techniques are developed to calculate the normal and azimuthal components of the magnetic field in and near to the plasma sheet in a plasma sheet coordinate system. The revised field components differ substantially from the quantities used in previous analyses. With the revised field values, it appears that during the Voyager 2 flyby for an outflow rate of 2.5 x 10 exp 29 amu/s, the observed magnetic torque may be sufficient to keep the plasma in corotation to radial distances of 50 Rj in the postmidnight quadrant.
Fukutani, Atsuki; Kurihara, Toshiyuki; Isaka, Tadao
2015-01-01
Background 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). Findings 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 mo...
Zhang Zhiyong; Li Zhiqiang; Zhou Qingkun; Zhang Lianchao; Fan Dapeng
2014-01-01
To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms (ISPs) with DC motor direct-drive, the methods of modeling and compensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed experimentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified L...
Post-Glitch Relaxation of Pulsar Angular Velocity in the Context of an Inverse Problem
Hayrapetyan, M. V.; Baghdasaryan, D.
2015-06-01
The motion of the neutron-proton vortex system in neutron stars is examined taking pinning and depinning of the vortices into account. The relaxation solution of the equations for the dynamics of pulsar rotation after glitches is compared with observational data on the Vela pulsar. It is shown that the angular rotation relaxation parameters are related both to the appearance of a "density wave" of neutron vortices during a glitch and to features of the motion of the vortices between successive glitches.
Analysis of the angular sensitivity of an innovative particle velocity sensor
Honschoten, van, J.W.; Yntema, D.R.; Wiegerink, R.J.; Elwenspoek, M.
2008-01-01
Abstract—In this paper a novel micromachined acoustic sensor consisting of four heated wires is analyzed theoretically and experimentally. The presence of the chip surface of the probe in the vicinity of the wires influences the local fluid flow, while it also affects the temperature distribution in the probe by altering the direction of heat transport. Both effects result into a specific angular dependence of the sensor sensitivity. To explain this specific directionality of the sensitivity,...
Nagayama, Takumi; Nakagawa, Akiharu; Handa, Toshihiro; Honma, Mareki; Kobayashi, Hideyuki; Kawaguchi, Noriyuki; Miyaji, Takeshi
2010-01-01
We conducted the astrometry of H2O masers in the Galactic star-forming region Onsala 1 (ON1) with VLBI Exploration of Radio Astrometry (VERA). We measured a trigonometric parallax of 0.404+/-0.017 mas, corresponding to a distance of 2.47+/-0.11 kpc. ON1 is appeared to be located near the tangent point at the Galactic longitude of 69.54 deg. We estimate the angular velocity of the Galactic rotation at Sun, the ratio of the distance from Sun to the Galactic center and the Galactic rotation velocity at Sun, to be 28.7+/-1.3 km/s/kpc using the measured distance and proper motion of ON1. This value is larger than the IAU recommended value of 25.9 km/s/kpc, but consistent with other results recently obtained with the VLBI technique.
Hewett, Timothy E.; Myer, Gregory D.; Zazulak, Bohdanna T.
2007-01-01
Our purpose was to determine if females demonstrate decreased hamstrings to quadriceps peak torque (H/Q) ratios compared to males and if H/Q ratios increase with increased isokinetic velocity in both sexes. Maturation disproportionately increases hamstrings peak torque at high velocity in males, but not females. Therefore, we hypothesised that mature females would demonstrate decreased H/Q ratios compared to males and the difference in H/Q ratio between sexes would increase as isokinetic velo...
Nordsiek, Freja; van der Veen, Roeland C A; Sun, Chao; Lohse, Detlef; Lathrop, Daniel P
2014-01-01
Azimuthal velocity profiles were measured in a Taylor-Couette apparatus, which has been used as a model of stellar and planetary accretion disks. The apparatus has a cylinder radius ratio of $\\eta = 0.7158$, an aspect-ratio of $\\Gamma = 11.74$, and axial boundaries attached to the outer cylinder --- known to have significant Ekman pumping. We investigated angular momentum transport and Ekman pumping in the Rayleigh-stable regime. The regime is linearly stable and is characterized by radially increasing specific angular momentum. We measured several Rayleigh-stable profiles for shear Reynolds numbers $Re_S \\sim O\\left(10^5\\right) \\,$, both for $\\Omega_i > \\Omega_o > 0$ (quasi-Keplerian regime) and $\\Omega_o > \\Omega_i > 0$ (sub-rotating regime) where $\\Omega_{i,o}$ is the inner/outer cylinder rotation rate. None of the velocity profiles matched the non-vortical laminar Taylor-Couette profile. The deviation from that profile increased as solid-body rotation was approached at fixed $Re_S$. Flow super-rotation, a...
Shah, Abhay G; Keidl, Tobias S
2012-01-01
This is the first of two papers on computing the self-force in a radiation gauge for a particle moving in circular, equatorial orbit about a Kerr black hole. In the EMRI (extreme-mass-ratio inspiral) framework, with mode-sum renormalization, we compute the renormalized value of the quantity $h_{\\alpha\\beta}u^\\alpha u^\\beta$, gauge-invariant under gauge transformations generated by a helically symmetric gauge vector; and we find the related order $\\frak{m}$ correction to the particle's angular velocity at fixed renormalized redshift (and to its redshift at fixed angular velocity). The radiative part of the perturbed metric is constructed from the Hertz potential which is extracted from the Weyl scalar by an algebraic inversion\\cite{sf2}. We then write the spin-weighted spheroidal harmonics as a sum over spin-weighted spherical harmonics and use mode-sum renormalization to find the renormalization coefficients by matching a series in $L=\\ell+1/2$ to the large-$L$ behavior of the expression for $H := \\frac12 h_{...
Sasorova, Elena; Levin, Boris
2013-04-01
It was shown [Levin, Sasorova 2012], that a cyclic increase and decrease of the seismic activity in different time intervals was observed in spatial-temporal distributions of the earthquakes (EQ) (1900-2012) with magnitude M≥7 in northwest part of the Pacific region. The spatial-temporal analysis revealed the periodic changing of the seismic activity and the depth distributions of the strong events in different time intervals. The Earth rotation angular velocity varies with time. Increasing of the angular velocity of a celestial body rotation leads to growth of oblateness of planet, and vice versa, the oblateness is decreasing with reducing of velocity of rotation. So, well-known effect of instability leads to small pulsations of the Earth surface. The Earth crust in polar areas is compressing with increasing of angular velocity of rotating planet, and it is extensible in the equator zone. The decreasing of rotation velocity leads to opposite result. The objectives of this work is the comparative spatial-temporal analysis of the seismicity regime variation (events with M>=7.0) on the whole Earth and in the Pacific region from 1900 up to date and the Earth rotation instability. The two subsets of the worldwide NEIC (USGS) catalog were used (USGS/NEIC from 1973 up to 2012 and Significant Worldwide Earthquakes (2150 B.C. - 1994 A.D.)). The preliminary standardization of magnitudes and removal of aftershocks was fulfilled for the first mentioned above subset of events. In both cases the entire range of observations was subdivided into several 5-year intervals. The temporal EQ distributions were calculated separately for six latitudinal intervals (belts): 45°-30°N, 30°-15°N, 15°-0°N, 0°-15°S, 15°-30°S, 30°-45°S. The high latitudes do not take in consideration because of very low seismic activity in these latitudes. Separately were analyzed: the EQs with M>=8 for time interval 1900-2012, and the EQs with M>=6 for time interval 1700-1900. The data base (http
Ceyer, S.T.; Siekhaus, W.J.; Somorjai, G.A.
1981-09-01
A molecular beam surface scattering apparatus designed for the study of corrosion and catalytic surface reactions is described. The apparatus incorporates two molecular or atomic beams aimed at a surface characterized by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES), a rotatable, differentially pumped quadrupole mass spectrometer, and a versatile manipulator. Angular distributions and energy distributions as a function of angle and independent of the surface residence time can be measured. Typical data for the oxidation of deuterium to D/sub 2/O on a Pt(111) crystal surface are presented.
Ceyer, S. T.; Siekhaus, W. J.; Somorjai, G. A.
1980-11-01
A molecular beam surface scattering apparatus designed for the study of corrosion and catalyticsurfacereactions is described. The apparatus incorporates two molecular or atomic beams aimed at a surface characterized by low energy electron diffraction (LEED) and Auger electron spectroscopy (AES), a rotatable, differentially pumped quadrupole mass spectrometer, and a versatile manipulator. Angular distributions and energy distributions as a funcion of angle and independent of the surface residence time can be measured. Typical data for the oxidation of deuterium to D{sub 2}O on a Pt(lll) crystal surface are presented.
Valentini, J.J.
1976-11-01
A study of the endoergic, bimolecular reactions of F/sub 2/ with I/sub 2/, ICl, and HI in a crossed molecular beam experiment is described. The trihalogens IIF, ClIF, and HIF were directly observed as the products of these reactions. At high collision energies a second reactive channel producing IF becomes important. Product angular and velocity distributions show that this IF does not result from a four-center exchange reaction. Measured threshold energies for the formation of IIF, ClIF, and HIF yield lower bounds to the stabilities of these molecules, with respect to the separated atoms, of 69, 81, and 96 kcal/mole, respectively. Analysis of product center-of-mass angular distributions indicates that a slightly nonlinear approach is most effective in bringing about reaction to form the stable triatomic radical. Also described is a crossed molecular beam study of the Cl + Br/sub 2/ ..-->.. BrCl + Br reaction at collision energies from 6.8 to 17.7 kcal/mole. The results indicate that this reaction has the characteristics of an exoergic reaction on an attractive potential energy surface with early energy release. Reagent translational energy is very efficiently channeled into product internal energy. At high collision energy the reaction appears to approach the spectator stripping limit. Finally, a series of computer programs which can be used to carry out the requisite data analysis for crossed molecular beam reactive scattering experiments are described. These programs recover the reactive scattering center-of-mass flux distribution from the measured angular and velocity distributions of the products.
Dalton, Brian H; Power, Geoffrey A; Paturel, Justin R; Rice, Charles L
2015-06-01
The underlying factors related to the divergent findings of age-related fatigue for dynamic tasks are not well understood. The purpose here was to investigate age-related fatigability and recovery between a repeated constrained (isokinetic) and an unconstrained velocity (isotonic) task, in which participants performed fatiguing contractions at the velocity (isokinetic) or resistance (isotonic) corresponding with maximal power. To compare between tasks, isotonic torque-power relationships were constructed prior to and following both fatiguing tasks and during short-term recovery. Contractile properties were recorded from 9 old (~75 years) and 11 young (~25 years) men during three testing sessions. In the first session, maximal power was assessed, and sessions 2 and 3 involved an isokinetic or an isotonic concentric fatigue task performed until maximal power was reduced by 40 %. Compared with young, the older men performed the same number of contractions to task failure for the isokinetic task (~45 contractions), but 20 % fewer for the isotonic task (p < 0.05). Regardless of age and task, maximal voluntary isometric contraction strength, angular velocity, and power were reduced by ~30, ~13, and ~25 %, respectively, immediately following task failure, and only isometric torque was not recovered fully by 10 min. In conclusion, older men are more fatigable than the young when performing a repetitive maximal dynamic task at a relative resistance (isotonic) but not an absolute velocity (isokinetic), corresponding to maximal power. PMID:25943700
A closed form formula is given for the mean power radiated per solid angle in a given direction by a relativistic particle in cyclotronic motion with a non zero parallel velocity. The difference between emitted and received mean power for a non closed periodic motion is illustrated in this case
Corrêa, Umberto Cesar; Vilar, Luis; Davids, Keith; Renshaw, Ian
2014-01-01
The aim of this study was to investigate the influence of interpersonal interactions between players on the regulation of ball passing velocity in the team sport of futsal. For this purpose 28 sequences of play, in which passes were performed between outfield players, were selected from an elite futsal competition and analyzed using TACTO software. Relative angles between attackers and defenders were used to examine interpersonal coordination tendencies that emerged during performance. Result...
Lisitskaya, I.N.; Rudenko, V.I.; Semenova, S.V.
1979-01-01
A device has been developed which is not only a measurement convertor of high accuracy, but also a device from whose output the active power of variable current is selected (greater than one watt) to the input of an electric and hydraulic turbine velocity regulator. The device can operate at increased temperature (up to +180/sup 0/C). Results are given of an analytical study and experimental data on the shape of the curve of the output voltage of the convertor.
Modification of Angular Velocity by Inhomogeneous MRI Growth in Protoplanetary Disks
Kato, M T; Nakamura, K.; Tandokoro, R.; Fujimoto, M.; Ida, S.
2008-01-01
We have investigated evolution of magneto-rotational instability (MRI) in protoplanetary disks that have radially non-uniform magnetic field such that stable and unstable regions coexist initially, and found that a zone in which the disk gas rotates with a super-Keplerian velocity emerges as a result of the non-uniformly growing MRI turbulence. We have carried out two-dimensional resistive MHD simulations with a shearing box model. We found that if the spatially averaged magnetic Reynolds num...
Tasnim, S.; Cairns, Iver H.
2016-06-01
An analytic, self-consistent, theoretical model for the solar wind is developed that generalizes previous models to include all of the following: conservation of angular momentum, frozen-in magnetic fields, both radial (r) and azimuthal (ϕ) components of the magnetic field (Br and Bϕ) and velocity (vr and vϕ) from the inner boundary rs to 1 AU, and the detailed tracing back of observations at 1 AU to the inner boundary and all intervening (r,ϕ). The new model applies near the solar equatorial plane, assumes constant radial wind speed at each heliolongitude, and enforces corotation at the inner boundary. It is shown that the new theoretical model can be reduced to the previous models in the appropriate limits. We apply the model to two solar rotations of Wind spacecraft data, one near solar minimum (1-27 August 2010) and one near solar maximum (1-27 July 2002). The model analytically predicts the Alfvénic critical radius ra from the radial Alfvénic Mach number observed at 1 AU. Typically, the values are less than 15 solar radii, in agreement with some recent observations, and vary with longitude. Values of vϕ(r,ϕ) are predicted from the model, being always in the sense of corotation but varying in magnitude with r and ϕ. Reasonable and self-consistent results are found for Br(r,ϕ), Bϕ(r,ϕ), vϕ(r,ϕ), and n(r,ϕ) from rs to 1 AU. Both the azimuthal and radial magnetic fields at rs vary with time by more than an order of magnitude and usually |Br(rs,ϕs)|≥|Bϕ(rs,ϕs)|. Typically, though not always, magnetic contributions to the total angular momentum are small. Interestingly, however, the azimuthal flow velocities observed at 1 AU are not always in the corotation direction and usually have much larger magnitudes than predicted by the model. Conservation of angular momentum alone cannot explain these azimuthal velocities and the standard interpretation involving stream-stream interactions and dynamical behavior seems reasonable. Issues regarding the
Angular and Frequency-Dependent Wave Velocity and Attenuation in Fractured Porous Media
Carcione, José M.; Gurevich, Boris; Santos, Juan E.; Picotti, Stefano
2013-11-01
Wave-induced fluid flow generates a dominant attenuation mechanism in porous media. It consists of energy loss due to P-wave conversion to Biot (diffusive) modes at mesoscopic-scale inhomogeneities. Fractured poroelastic media show significant attenuation and velocity dispersion due to this mechanism. The theory has first been developed for the symmetry axis of the equivalent transversely isotropic (TI) medium corresponding to a poroelastic medium containing planar fractures. In this work, we consider the theory for all propagation angles by obtaining the five complex and frequency-dependent stiffnesses of the equivalent TI medium as a function of frequency. We assume that the flow direction is perpendicular to the layering plane and is independent of the loading direction. As a consequence, the behaviour of the medium can be described by a single relaxation function. We first consider the limiting case of an open (highly permeable) fracture of negligible thickness. We then compute the associated wave velocities and quality factors as a function of the propagation direction (phase and ray angles) and frequency. The location of the relaxation peak depends on the distance between fractures (the mesoscopic distance), viscosity, permeability and fractures compliances. The flow induced by wave propagation affects the quasi-shear (qS) wave with levels of attenuation similar to those of the quasi-compressional (qP) wave. On the other hand, a general fracture can be modeled as a sequence of poroelastic layers, where one of the layers is very thin. Modeling fractures of different thickness filled with CO2 embedded in a background medium saturated with a stiffer fluid also shows considerable attenuation and velocity dispersion. If the fracture and background frames are the same, the equivalent medium is isotropic, but strong wave anisotropy occurs in the case of a frameless and highly permeable fracture material, for instance a suspension of solid particles in the fluid.
Inferring the sun's internal angular velocity from observed p-mode frequency splittings
Brown, T.M.; Christensen-Dalsgaard, J.; Dziembowski, W.A.; Goode, P.; Gough, D.O. (High Altitude Observatory, Boulder, CO (USA); Aarhus Universitet (Denmark); Centrum Astronomiczne, Warsaw (Poland); New Jersey Institute of Technology, Newark (USA); Cambridge Univ. (England))
1989-08-01
The sun's internal solar velocity Omega is studied as a function of latitude and radius using the solar oscillation data of Brown and Morrow (1987). An attempt is made to separate robust inferences about the sun from artifacts of the analysis. It is found that a latitudinal variation of Omega similar to that observed at the solar surface exists throughout the sun's convection zone and that the variation of Omega with latitude persists to some extent even beneath the convection zone. 44 refs.
Zhang Zhiyong; Li Zhiqiang; Zhou Qingkun; Zhang Lianchao; Fan Dapeng
2014-01-01
To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms (ISPs) with DC motor direct-drive, the methods of modeling and com-pensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed exper-imentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified LuGre model is proposed to describe the characteristic of the friction in the prestiction regime. Furthermore, the state switch condition of the three friction regimes including presliding, gross sliding and prestiction is presented. Finally, a composite compensation controller including a nonlinear friction observer and a feedforward compensator based on the novel LuGre model is designed to restrain the nonlinear friction and to improve the control precision. Experi-mental results indicate that compared with those of the conventional proportion-integration-differentiation (PID) control method and the PID plus LuGre model-based friction compensation method, the dwell-time has decreased from 0.2 s to almost 0 s, the position error decreased to 86.7%and the peak-to-peak value of position error decreased to 80%after the novel compensation con-troller is added. It concludes that the composite compensation controller can greatly improve the control precision of the dynamic sealed ISPs.
High-Q microsphere resonators for angular velocity sensing in gyroscopes
An, Panlong [Key Laboratory of Instrumentation Science and Dynamic Measurement, Ministry of Education, Taiyuan 030051 (China); School of Science, North University of China, Taiyuan 030051 (China); Zheng, Yongqiu [Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051 (China); Yan, Shubin, E-mail: shubin-yan@nuc.edu.cn; Xue, Chenyang, E-mail: xuechenyang@nuc.edu.cn; Liu, Jun, E-mail: liuj@nuc.edu.cn [Key Laboratory of Instrumentation Science and Dynamic Measurement, Ministry of Education, Taiyuan 030051 (China); Science and Technology on Electronic Test and Measurement Laboratory, North University of China, Taiyuan 030051 (China); Wang, Wanjun [Department of Mechanical Engineering, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)
2015-02-09
A resonator gyroscope based on the Sagnac effect is proposed using a core unit that is generated by water-hydrogen flame melting. The relationship between the quality factor Q and diameter D is revealed. The Q factor of the spectral lines of the microsphere cavity coupling system, which uses tapered fibers, is found to be 10{sup 6} or more before packaging with a low refractive curable ultraviolet polymer, although it drops to approximately 10{sup 5} after packaging. In addition, a rotating test platform is built, and the transmission spectrum and discriminator curves of a microsphere cavity with Q of 3.22×10{sup 6} are measured using a semiconductor laser (linewidth less than 1 kHz) and a real-time proportional-integral circuit tracking and feedback technique. Equations fitting the relation between the voltage and angular rotation rate are obtained. According to the experimentally measured parameters, the sensitivity of the microsphere-coupled system can reach 0.095{sup ∘}/s.
High-Q microsphere resonators for angular velocity sensing in gyroscopes
An, Panlong; Zheng, Yongqiu; Yan, Shubin; Xue, Chenyang; Wang, Wanjun; Liu, Jun
2015-02-01
A resonator gyroscope based on the Sagnac effect is proposed using a core unit that is generated by water-hydrogen flame melting. The relationship between the quality factor Q and diameter D is revealed. The Q factor of the spectral lines of the microsphere cavity coupling system, which uses tapered fibers, is found to be 106 or more before packaging with a low refractive curable ultraviolet polymer, although it drops to approximately 105 after packaging. In addition, a rotating test platform is built, and the transmission spectrum and discriminator curves of a microsphere cavity with Q of 3.22 ×106 are measured using a semiconductor laser (linewidth less than 1 kHz) and a real-time proportional-integral circuit tracking and feedback technique. Equations fitting the relation between the voltage and angular rotation rate are obtained. According to the experimentally measured parameters, the sensitivity of the microsphere-coupled system can reach 0.095∘/s .
Hubble Space Telescope Angular Velocity Estimation During the Robotic Servicing Mission
Thienel, Julie K.; Sanner, Robert M.
2005-01-01
In 2004 NASA began investigation of a robotic servicing mission for the Hubble Space Telescope (HST). Such a mission would require estimates of the HST attitude and rates in order to achieve a capture by the proposed Hubble robotic vehicle (HRV). HRV was to be equipped with vision-based sensors, capable of estimating the relative attitude between HST and HRV. The inertial HST attitude is derived from the measured relative attitude and the HRV computed inertial attitude. However, the relative rate between HST and HRV cannot be measured directly. Therefore, the HST rate with respect to inertial space is not known. Two approaches are developed to estimate the HST rates. Both methods utilize the measured relative attitude and the HRV inertial attitude and rates. First, a nonlinear estimator is developed. The nonlinear approach estimates the HST rate through an estimation of the inertial angular momentum. The development includes an analysis of the estimator stability given errors in the measured attitude. Second, a linearized approach is developed. The linearized approach is a pseudo-linear Kalman filter. Simulation test results for both methods are given, including scenarios with erroneous measured attitudes. Even though the development began as an application for the HST robotic servicing mission, the methods presented are applicable to any rendezvous/capture mission involving a non-cooperative target spacecraft.
Zhang Zhiyong
2014-06-01
Full Text Available To overcome the influence of the nonlinear friction on the gimbaled servo-system of an inertial stabilized platforms (ISPs with DC motor direct-drive, the methods of modeling and compensation of the nonlinear friction are proposed. Firstly, the inapplicability of LuGre model when trying to interpret the backward angular displacement in the prestiction regime is observed experimentally and the reason is deduced theoretically. Then, based on the dynamic model of direct-drive ISPs, a modified LuGre model is proposed to describe the characteristic of the friction in the prestiction regime. Furthermore, the state switch condition of the three friction regimes including presliding, gross sliding and prestiction is presented. Finally, a composite compensation controller including a nonlinear friction observer and a feedforward compensator based on the novel LuGre model is designed to restrain the nonlinear friction and to improve the control precision. Experimental results indicate that compared with those of the conventional proportion–integration–differentiation (PID control method and the PID plus LuGre model-based friction compensation method, the dwell-time has decreased from 0.2 s to almost 0 s, the position error decreased to 86.7% and the peak-to-peak value of position error decreased to 80% after the novel compensation controller is added. It concludes that the composite compensation controller can greatly improve the control precision of the dynamic sealed ISPs.
High-Q microsphere resonators for angular velocity sensing in gyroscopes
A resonator gyroscope based on the Sagnac effect is proposed using a core unit that is generated by water-hydrogen flame melting. The relationship between the quality factor Q and diameter D is revealed. The Q factor of the spectral lines of the microsphere cavity coupling system, which uses tapered fibers, is found to be 106 or more before packaging with a low refractive curable ultraviolet polymer, although it drops to approximately 105 after packaging. In addition, a rotating test platform is built, and the transmission spectrum and discriminator curves of a microsphere cavity with Q of 3.22×106 are measured using a semiconductor laser (linewidth less than 1 kHz) and a real-time proportional-integral circuit tracking and feedback technique. Equations fitting the relation between the voltage and angular rotation rate are obtained. According to the experimentally measured parameters, the sensitivity of the microsphere-coupled system can reach 0.095∘/s
Iramina, Keiji; Kamei, Yuuichiro; Katayama, Yoshinori
2011-01-01
We developed a simple, portable and easy system to the motion of pronation and supination of the forearm. This motion was measured by wireless acceleration and angular velocity sensor. The aim of this system is evaluation of minor nervous dysfunction. It is for the screening of the developmental disorder child. In this study, in order to confirm the effectiveness of this system, the reference curve of the neuromotor development was experimentally obtained. We studied 212 participants (108 males, 104 females) aged 7 to 12 years attending the kindergarten school. We could obtain the reference curve of the neuromotor development using this system. We also investigated the difference of neuromotor function between normally developed children and a ADHD child. There is a possibility that abnormality of the minor nervous dysfunction can be detected by using this system. PMID:22256040
Variations in the angular velocity of the earth rotation and the rate of change of the pulsar period
Xia, Y.F.; Rong, J.X.
1981-09-01
The effects of the variations in the angular velocity of earth rotation on observed changes in pulsar periods are discussed. It is suggested that the variations are influential when the arrival times of the pulses are reduced from the topocenter to the barycenter of the solar system. The change in the observed pulsar period is noted to be possibly larger than the period itself. The magnitude of the effect depends on the declination of the pulsar and the altitude of the observing station, and higher declinations and latitudes result in smaller magnitudes. Finally, it is cautioned that while observing at upper or lower culmination, the effect on the rate of change of the pulsar period becomes larger.