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Showing papers on "Angular velocity published in 1980"


Journal ArticleDOI
TL;DR: In this paper, the magnetic braking of a rigidly rotating disk cloud was studied and the effect of the numerous internal reflections of nonlinear torsional Alfven waves was determined rigorously and explained physically.
Abstract: In a previous paper we studied the magnetic braking of a rigidly rotating interstellar cloud (or fragment) whose angular momentum and magnetic field vectors were mutually perpendicular. We now discuss the case of a disk cloud (of density rhol) whose angular momentum and initial magnetic field are aligned with the axis of symmetry. The cloud (or fragment) is imparted an initial angular velocity with respect to the external medium (of density rho/sub ext/). The angular velocity and magnetic field are then calculated as functions of space and time in both the disk and the external medium. The effect of the numerous internal reflections of nonlinear torsional Alfven waves in determined rigorously and explained physically. Initial conditions with and without a discontinuity in angular velocity across the disk surfaces are studied, and both cases are compared with a solution for a rigidly rotating disk. Although the transient response of the cloud structure is very different in the three cases, the loss of excess angular momentum by the cloud as a whole is insensitive to the initial conditions and can be accurately represented by the rigid rotator model if the ratio rho/sub cl//rho/sub ext/ is not close to unity.

133 citations


Journal ArticleDOI
TL;DR: In this paper, the two-dimensional shear instability of a differentially rotating star is examined and a solar-type rotation law is investigated, and it is found that for equatorial accelerations there is instability when there is a difference of 29% between the angular velocity of the equator and the poles.
Abstract: The two-dimensional (horizontal) shear instability of a differentially rotating star is examined. A solar-type rotation law is investigated. and it is found that for equatorial accelerations there is instability when there is a difference of 29% between the angular velocity of the equator and the poles.

93 citations


Journal ArticleDOI
TL;DR: Two rules are proposed which can account for the way image motion in a horizontal plane helpsyritta pipiens cope with disturbances during voluntary flight and can resolve the image motion resulting from a disturbance like a gust of wind into rotational and translational components.
Abstract: 1 Two rules are proposed which can account for the way image motion in a horizontal plane helpsSyritta pipiens cope with disturbances during voluntary flight The fly seems to assume that it moves within a stationary environment and that externally generated image motion is the result of some disturbance to its intended flight pattern and should be minimized 2 The first rule is concerned with the control of angular velocity WhenSyritta cruises with no clear goal in view it keeps the angular orientation of its body constant apart from saccade-like reorientations Thus during undisturbed flight there will be image motion all over the retina, except for regions which either look along the direction of flight or directly behindSyritta can thus assume that any image motion over these regions (the poles of the flow field) is caused by a disturbance Duringforward flight externally generated image motion only influences the fly's angular velocity if it occurs overfrontal retina (Fig 6) But when the fly movessideways with respect to its long axis, so that the pole of the flow field shifts to lateral retina, image motion confined to frontal retina no longer has any effect on angular velocity (Fig 6) It is therefore proposed that during cruising angular orientation is governed principally by image motion over the poles of the flow field 3 The second rule covers the control of translational velocity This parameter seems to be governed by externally generated image motion over a much wider area of retina It is proposed that each small region of retina influences a component of thrust at right angles to the direction of regard of that retinal region The total translational response is assumed to be caused by the summed effects of image motion over many such retinal areas Support for this rule comes from the behaviour ofSyritta when flying parallel to a vertically striped wall that moves from side to side (Fig 7) The movement of the wall influences a component of thrust parallel to the wall, whether the fly views the wall with frontal or with lateral retina 4 It is explained how these two rules can resolve the image motion resulting from a disturbance like a gust of wind into rotational and translational components

93 citations


ReportDOI
01 Apr 1980
TL;DR: In this article, nonlinear expressions are developed to relate the orientation of the deformed beam cross section, torsion, local components of bending curvature, angular velocity, and virtual rotation to deformation variables.
Abstract: Nonlinear expressions are developed to relate the orientation of the deformed beam cross section, torsion, local components of bending curvature, angular velocity, and virtual rotation to deformation variables. The deformed beam kinematic quantities are proven to be equivalent to those derived from various rotation sequences by identifying appropriate changes of variable based on fundamental uniqueness properties of the deformed beam geometry. The torsion variable used is shown to be mathematically analogous to an axial deflection variable commonly used in the literature. Rigorous applicability of Hamilton's principle to systems described by a class of quasi-coordinates that includes these variables is formally established.

74 citations


Journal ArticleDOI
TL;DR: It was concluded that there was little if any relationship between torque at a fast or slow angular velocity and the ability to vertically jump.
Abstract: The relationship between the ability to develop leg torque and performance in the vertical jump was investigated in 29 female athletes. Each subject's leg flexion, leg extension, and foot plantar flexion peak torque was determined isokinetically on a Cybex at angular velocities of 30 degrees/second and 180 degrees/second. The vertical jump was determined for each subject and correlations among the measures of torque and the vertical jump were calculated. Although the ability to produce leg power as exemplified by the vertical jump was significantly correlated with peak torque at the fast angular velocity but was not significantly correlated with peak torque at the slow angular velocity, the correlations were so low it was concluded that there was little if any relationship between torque at a fast or slow angular velocity and the ability to vertically jump.

58 citations


Journal ArticleDOI
TL;DR: In this article, the Navier-Stokes equations were used to explain the auto-rotation of an elliptic cylinder about an axis fixed perpendicular to a parallel flow by means of numerical solutions.
Abstract: Autorotation of an elliptic cylinder about an axis fixed perpendicular to a parallel flow is explained in this paper by means of numerical solutions of the Navier-Stokes equations. Potential-flow theory predicts, for constant angular velocity, half a period in which a torque supports rotation and half a period in which it opposes rotation, with vanishing torque in the average. This balance is disturbed by viscous-flow effects in such a way that, for a given angular velocity, vortex shedding either damps rotation or, under certain conditions, favours rotation. The proper interplay of those conditions, which include synchronization of vortex shedding and rate of rotation, results in auto-rotation. The numerical results for Re [les ] 400 are compared with experimental data for Re = 90000 from the literature. The agreement of the force coefficients and the large-scale flow patterns is surprisingly good.

58 citations


Patent
31 Dec 1980
TL;DR: In this paper, a steering wheel rotation detector senses whether or not the steering wheel is being rotated by sensing variations in the output from the power steering pump, which varies as a function of vehicle speed.
Abstract: A power steering apparatus includes an electric motor which drives a power steering pump. a vehicle speed detector senses the speed of the vehicle. A steering wheel rotation detector senses whether or not the steering wheel is being rotated. At low vehicle speeds, a control assembly effects operation of the electric motor to drive the power steering pump at a relatively low standby angular velocity prior to initiation of a steering operation. Upon initiation and during of the steering operation at low vehicle speeds, the control assembly effects operation of the electric motor to drive the power steering pump at an angular velocity which varies as a function of vehicle speed. When the vehicle is traveling at a relatively high speed, the control assembly causes the electric motor to drive the pump at an angular velocity which is less than the standby angular velocity, that is, at a very low speed or at a standstill. In one embodiment of the invention, rotation of the steering wheel is detected by sensing variations in the output from the power steering pump. In another embodiment of the invention, rotation of the steering wheel is detected by sensing variations in the current conducted to the electric motor which drives the power steering pump.

39 citations


Journal ArticleDOI
TL;DR: In this paper, generalized Eilenberger equations are derived for rotating superfluid 3He in the presence of a magnetic field h and finite superflow v parallel to the rotation axis, in analogy to conventional type II superconductors, the possibility of vortex solutions is discussed.
Abstract: On the basis of Gorkov's formulation of superconductivity theory, generalized Eilenberger equations are derived which apply to rotating superfluid 3He in the presence of a magnetic field h and finite superflow v. In analogy to conventional type II superconductors, the possibility of vortex solutions is discussed. An implicit equation determining the upper critical angular velocity Ωc2 as a function of temperature T, magnetic field h, and superflow Ν parallel to the rotation axis is·inferred from the linearized Eilenberger equations. In contrast to the case of slowly rotating 3He-A, the solution of the eigenvalue problem determining the order parameter δ near the upper critical angular velocity admits no coreless vortex solutions. The space-dependent amplitude of the order parameter is analogous to Abrikosov's vortex array solution, while the spin-orbit part is given either by a polar-state type or an Anderson-Brinkman-Morel (ABM)-state-type eigensolution. Among the possible eigensolutions the polar-state type yields for vanishing superflow v the highest critical rotation frequency. For finite superflow v parallel to the rotation axis, however, the ABM-state-type solution is stabilized in comparison to the polar state for |ν|≥0.2π(Tc0/TF)νF at zero temperature.

37 citations


Journal ArticleDOI
Kenichi Nanbu1
TL;DR: In this article, the authors derived a stochastic law that describes the collision process in a simulation cell for a gas of rough sphere molecules from the Boltzmann equation for a spatially uniform gas.
Abstract: The stochastic law that describes the collision process in a simulation cell was derived for a gas of rough sphere molecules from the Boltzmann equation for a spatially uniform gas. This law that determines the velocity and angular velocity of each simulated molecule after a small time increment is divided into four steps. The first step gives the collision probability of a molecule. The second step gives a probability distribution that prescribes the collision partner of the molecule. The third step gives a probability density that prescribes the direction of the line-of-centers of the collision pair. The last step gives the post-collision values of the velocity and angular velocity of the molecule.

34 citations


Journal ArticleDOI
TL;DR: In this paper, a model system of equations governing the Taylor Couette flow between two concentric cylinders is presented, which is an extension of the system given by the author in I and contains both axisymmetric and non-axisymetric Taylor vortex modes.
Abstract: With fhe aid of the Galerkin method. a model system of equations governing the Taylor­ Couette flow between two concentric cylinders is presented. which is an extension of the system given by the author in I and contains both axisymmetric and non-axisymmetric Taylor vortex modes. Direct numerical time integration of the present system shows that. with the increase of the angular velocity of the inner cylinder. the motion changes its character one after another as follows: periodic motion ~ quasi-periodic motion with two fundamental frequencies ~ periodic motion accompanied by noise ~ chaotic (noisy) motion.

33 citations


Journal ArticleDOI
TL;DR: In this article, the steady state performance of the Frost power inversion array is evaluated, assuming constant rotational velocity of the external noise environment in the sin? domain, and approximate criteria are derived for weight vector and output power deviation from optimal values.
Abstract: The steady state performance of the Frost power inversion array is evaluated, assuming constant rotational velocity of the external noise environment in the sin ? domain. The weight vector is solved implicitly in terms of a linear matrix equation. Approximate criteria are derived for weight vector and output power deviation from optimal values, which are then applied to determine the maximum scan rate of a radar sidelobe canceler.

Journal ArticleDOI
TL;DR: The weight of the evidence suggested a reformulation of the hypothesis of relational determination along the following lines: the perceived relative velocities of two objects are significantly affected by the proportions of the retinal projections of the respective movement fields traversed by the two objects in the same unit of time, even when the motion fields consist only of the objects' motion paths.
Abstract: The conventional formulation of the hypothesis of relational determination asserts that the perceived relative velocities of two or more objects depend upon their relative rates of displacement with respect to stationary referents in the visual field. Experiment 1 showed that this formulation is too restrictive by demonstrating the transposition-of-velocity effect under conditions in which two light spots moved in the absence of static visible contours and traversed unequal path lengths. Experiment 2 showed that angular velocity per unit of relative angular extent, and not relative linear or perceived extent, of the respective motion paths influences perceived relative velocity in nonarticulated space. The retinal dimensions of static visible frameworks were shown in experiment 3 to influence perceived relative velocity in a direction consistent with the conventional formulation of the relational-determination hypothesis, but the weight of the evidence suggested a reformulation along the following lines: ...

Journal ArticleDOI
TL;DR: In this article, the problem of flow between infinite eccentric disks rotating at different speeds is considered and a solution to the complete Navier-Stokes equations is obtained, and an approximate analytic solution is also presented.
Abstract: The problem of flow between infinite eccentric disks rotating at different speeds is considered and a solution to the complete Navier-Stokes equations obtained. An approximate analytic solution is also presented.

Journal ArticleDOI
TL;DR: In this article, the dynamics of molecular rototranslation are treated with an equation of motion with a non-Markovian, stochastic force/torque, and it is shown that this Mori/Kubo/Zwanzig representation is equivalent to a multidimensional Markov equation which may be identified with analytical models of the molecular motion.
Abstract: The dynamics of molecular rototranslation are treated with an equation of motion with a non-Markovian, stochastic force/torque. It is shown that this Mori/Kubo/Zwanzig representation is equivalent to a multidimensional Markov equation which may be identified with analytical models of the molecular motion. Langevin and Fokker-Planck equations for two such models are derived from the general equations of motion. The analytical results are compared with a computer simulation of the velocity/angular velocity mixed autocorrelation function, C vω(t) = for a triatomic of C 2v symmetry.

Journal ArticleDOI
TL;DR: In this article, an infinite circular cylinder, filled with viscous, incompressible fluid, is rotating as a solid body and the resulting swirl flow is susceptible to centrifugal instabilities.
Abstract: An infinite circular cylinder, filled with viscous, incompressible fluid, is rotating as a solid body. At time t=0 the angular velocity ω (t) of the cylinder is decreased in a prescribed fashion. The resulting swirl flow is susceptible to centrifugal instabilities. The method of energy is used to determine sufficient conditions, R

Proceedings ArticleDOI
01 Aug 1980
TL;DR: In this article, analytical expressions for Euler's Equations of Motion and Eulerian Angles for both symmetric and near symmetric rigid bodies under the influence of arbitrary constant body-fixed torques are given.
Abstract: Analytic expressions are found for Euler's Equations of Motion and for the Eulerian Angles for both symmetric and near symmetric rigid bodies under the influence of arbitrary constant body-fixed torques. These solutions provide the body-fixed angular velocities and the attitude of the body, respectively, as functions of time. They are of special interest in applications to spinning spacecraft (such as the Galileo Spacecraft to be launched in 1984) because they include the effect of time-varying spin rate. Thus they can be applied to spin-up and spin-down maneuvers as well as to error analysis for thruster misalignments. The solutions are given for arbitrary initial conditions in terms of Fresnel, Sine and Cosine Integrals. Numerical integration of the governing differential equations has verified that the approximate analytic solutions are very accurate in many physical situations of interest.

Patent
26 Nov 1980
TL;DR: In this article, a method and apparatus of variable structure for control of asynchronous motors is presented, which can be used to control flux, torque, angular acceleration, angular velocity, and angular position of the rotor of an asynchronous motor.
Abstract: A method and apparatus of variable structure for controlling asynchronous motors. More particularly, methods and apparatus for control of flux, torque, angular acceleration, angular velocity, and/or angular position of the rotor of an asynchronous motor, supplied through a converter having switched elements.

Journal ArticleDOI
K. Tanaka1
TL;DR: In this article, the problem of the scattering of electromagnetic waves by a rotating perfectly conducting cylinder of arbitrary geometrical cross section is solved relativistically by the point-matching method.
Abstract: The problem of the scattering of electromagnetic waves by a rotating perfectly conducting cylinder of arbitrary geometrical cross section is solved relativistically by the point-matching method. Since the formulation contains the relativistic Doppler effect due to the rotational motion of the cylinder, it can be applied to the case where the angular velocity of the cylinder is of arbitrary values. The general relativistic field-transformation formulas under the arbitrary coordinate transformations are employed to solve the problem. Numerical calculations are performed for the case of the rotating elliptic cylinder. The numerical illustrations of the angular distribution of the power density of various frequency components of the scattered waves are shown. The relativistic effect which is the Doppler effect due to the rotational motion of the cylindrical surface are discussed and compared with the results obtained by the quasistationary approximation method.

Journal ArticleDOI
TL;DR: In this article, the authors give a solution to the problem of the motion of a homogeneous incompressible simple fluid around a submerged sphere which is in steady rotation about a fixed axis.
Abstract: We give a solution to the problem of the motion of a homogeneous incompressible simple fluid around a submerged sphere which is in steady rotation about a fixed axis. The solution is complete up to fourth order in the angular velocity. By way of some explicit computations we exhibit, in a series of figures, some possible streamline fields that show secondary flow regions in the shapes of equatorial tori and/or polar caps. The aim of this study is to give support to the view that many of the non-trivial secondary flow regions that are observed in the laboratory for this problem are well within theoretical description. In our computations there are several material constants to be chosen and we make no claim that all of those we have used have any correspondence with a particular fluid substance. However, certain of those in figures 7 and 8 have been taken from the experimental literature. A discussion of our results is contained in Section 5.

01 Dec 1980
TL;DR: In this article, a shape from motion (SfM) approach is proposed to derive descriptions of rigidly rotating smooth surfaces from the orthographic projection of the motions of their surface markings.
Abstract: : The human visual system has the ability to utilize motion information to infer the shapes of surfaces. More specifically, we are able to derive descriptions of rigidly rotating smooth surfaces entirely from the orthographic projection of the motions of their surface markings. A computational analysis of this ability is proposed based on a 'shape from motion' proposition. This proposition states that given the first spatial derivatives of the orthographically projected velocity and acceleration fields of a rigidly rotating regular surface, then the angular velocity and the surface normal at each visible point on that surface are uniquely determined up to a reflection. The computational analysis proceeds in three main steps. First it is shown that surface tilt and one component of the angular velocity may be obtained entirely from the first spatial derivatives of the velocity field. Second it is shown that surface slant and the remaining two components of the angular velocity are computable if the first spatial derivatives of the acceleration field are also given. Finally the problem of constructing a velocity field from the temporally changing optic array is briefly discussed. (Author)

15 Oct 1980
TL;DR: In this paper, the dynamics of liquid drops rotating in another liquid were studied experimentally with an oil drop suspended in a neutral buoyancy tank, and new stable shapes not predicted by the theory were observed.
Abstract: The dynamics of liquid drops rotating in another liquid were studied experimentally with an oil drop suspended in a neutral buoyancy tank. New stable shapes not predicted by the theory were observed.

Patent
05 Feb 1980
TL;DR: In this paper, a method for positioning the shaft of a motor which can be subject to a rotation force in either direction of rotation by application of drive current of a respective polarity, in order to bring the shaft to a target angular position by the action of a digital control and a position sensor associated with the motor shaft, is presented.
Abstract: A method for positioning the shaft of a motor which can be subject to a rotation force in either direction of rotation by application of drive current of a respective polarity, in order to bring the shaft to a target angular position by the action of a digital control and a position sensor associated with the motor shaft for emitting a displacement step signal in response to each movement of the the shaft through an incremental angle constituting a given fraction of one cycle of shaft rotation, which includes giving the displacement step signal the form of a signal cycle of sinus-like waveform in response to each incremental angle of shaft movement, deriving from the displacement step signal a shaft movement signal having a value represented by the sum of a component proportional to the displacement step signal and a component proportional to the time derivative thereof, and, after the motor shaft has reached a defined angular speed and at the moment when the shaft position is spaced from the target position by one-half of the incremental angle, initiating a control signal having a value which decreases with time, comparing the shaft movement signal with the control signal, and varying the polarity of motor drive current in dependence on the polarity of the comparison result.

Journal ArticleDOI
TL;DR: In this article, the deformation of a circular cylindrical elastic tube rotating about its axis is examined, and the angular speed is analyzed as a function of an azimuthai deformation parameter at fixed axial extension for an arbitrary form of incompressible, isotropic elastic strain energy function.
Abstract: The deformation of a circular cylindrical elastic tube of finite wall thickness rotating about its axis is examined. A circular cylindrical deformed configuration is considered first, and the angular speed analysed as a function of an azimuthai deformation parameter at fixed axial extension for an arbitrary form of incompressible, isotropic elastic strain-energy function. This extends the analysis given previously (Haughton and Ogden, 1980) for membrane tubes. Bifurcation from a circular cylindrical configuration is then investigated. Prismatic, axisymmetric and asymmetric bifurcation modes are discussed separately. Their relative importance is assessed in relation to the wall thickness and length of the tube, the magnitude of the axial extension, and the angular speed turning-points. Numerical results are given for a specific form of strain-energy function. Amongst other results it is found that (i) for long tubes, asymmetric modes of bifurcation can occur at low values of the angular speed and before any possible axisymmetric or prismatic modes and (ii) for short tubes, there is a range of values of the axial extension (including zero) for which no bifurcation can occur during rotation.


Patent
28 Feb 1980
TL;DR: In this article, a spacecraft is deployed from a launch vehicle with linear and angular velocity, using a structural arrangement for applying a tangential, single point ejection force to the spacecraft.
Abstract: A payload such as a spacecraft is deployed from launch vehicle with linear and angular velocity, using a structural arrangement for applying a tangential, single point ejection force to the spacecraft, in which, the single point ejection force and the spacecraft/launch vehicle reaction points enclose the spacecraft center of mass and center of percussion.

Journal ArticleDOI
TL;DR: In this article, the angular velocity vector is not the time derivative of the vector which represents a finite rotation, but the relationship between the two is derived explicitly, and the relationship is shown to be linear.
Abstract: The angular velocity vector is not the time derivative of the vector which represents a finite rotation. The relationship between the two is derived explicitly.

Journal ArticleDOI
TL;DR: In this article, a miniature non-contacting displacement transducer is described, designed to measure the static and dynamic angular rotation of a shaft, using an infra-red light source, a specially constructed fibre-optic probe and a receiver.
Abstract: A miniature non-contacting displacement transducer i described, designed to measure the static and dynamic angular rotation of a shaft. The measurement techniques uses an infra-red light source, a specially constructed fibre-optic probe and a receiver. Amplitude measurements within a range of 0+or-180 degrees may be made for frequencies from 0 to 500 Hz. The transducer has continuous resolution, producing a voltage output related to instantaneous angular displacement.

Journal ArticleDOI
TL;DR: In this paper, the kinematic parameter A, the ratio of rotational velocity to forward velocity, of experimental disks was studied as a function of change of disk angle and disk velocity Disks with reduced back pressures rotated more rapidly than the conventional spherical disk.
Abstract: THE kinematic parameter A, the ratio of rotational velocity to forward velocity, of experimental disks was studied as a function of change of disk angle and disk velocity Disks with reduced back pressures rotated more rapidly than the conventional spherical disk The absolute velocity of a point on the edge of a rotating disk has a cosinal nature, the minimum velocity of which is at the lowest underground point of the disk

Journal ArticleDOI
TL;DR: In this paper, the tilting instability of a current-carrying plasma ring bedded in an external magnetic field for equilibrium can be stabilized by spinning the ring about its major axis at an angular velocity above a critical value.
Abstract: The tilting instability of a current-carrying plasma ring bedded in an external magnetic field for equilibrium can be stabilized by spinning the ring about its major axis at an angular velocity above a critical value. This value is estimated using a rigid rotor model.