Showing papers on "Rotation published in 1984"
TL;DR: In this paper, the mean level of Ca n H and K emission (averaged over 15 years) is correlated with rotation period, as expected, but there is a further dependence of the emission on spectral type.
Abstract: Rotation periods are reported for 14 main-sequence stars, bringing the total number of such stars with well-determined rotation periods to 41. It is found that the mean level of their Ca n H and K emission (averaged over 15 years) is correlated with rotation period, as expected. However, there is a further dependence of the emission on spectral type. When expressed as the ratio of chromospheric flux to total bolometric flux, the emission is well correlated with the parameter Pohs/Tc, where Pohs is the observed rotation period and tc(B—V) is a theoretically-derived convective overturn time, calculated assuming a mixing length to scale height ratio a ~ 2. This finding is consonant with general predictions of dynamo theory, if the relation between chromospheric emission and dynamo-generated magnetic fields is essentially independent of rotation rate and spectral type for the stars considered. The dependence of mean chromospheric emission on rotation and spectral type is essentially the same for stars above and below the Vaughan-Preston “gap,” thus casting doubt on explanations of the gap in terms of a discontinuity in dynamo characteristics. Subject headings: Ca n emission — convection — stai
1,650 citations
TL;DR: In this article, a generalized model for the spherical collapse of a singular isothermal sphere such as protosolar and binary nebulae is defined for a sound speed of 0.35 km/sec and a rotation rate of 10 to 14th/sec.
Abstract: A generalized model which accounts for the effects of initially uniform and slow rotation is defined for the spherical collapse of a singular isothermal sphere such as protosolar and binary nebulae. An initial unstable equilibrium state is described for a sound speed of 0.35 km/sec and a rotation rate of 10 to the -14th/sec for the molecular cloud surrounding the accreting core. The total angular momentum and mass of the inner cloud is set equal to solar system values. The evolution of the collapse is traced by applying a perturbation analysis to the similarity solution for a nonrotating condition, and matched asymptotic expansions solve the hydrodynamic equations. The model is concluded a valid tool for studying star and nebular disk formation.
673 citations
TL;DR: Orthodontic forces can be treated mathematically as vectors to predict tooth movement, and the ratio between the net moment and net force on a tooth (M/F ratio) with reference to the center of resistance determines the centre of rotation.
273 citations
TL;DR: In this article, the frequency difference between prograde and retrograde sectoral solar oscillations was analyzed to determine the rotation rate of the solar interior, assuming no latitudinal dependence, and the resulting solar gravitational quadrupole moment is J2 = (1.7 + or - 0.4) x 10 to the -7th and provides a negligible contribution to current planetary tests of general relativity.
Abstract: The frequency difference between prograde and retrograde sectoral solar oscillations is analyzed to determine the rotation rate of the solar interior, assuming no latitudinal dependence. Much of the solar interior rotates slightly less rapidly than the surface, while the innermost part apparently rotates more rapidly. The resulting solar gravitational quadrupole moment is J2 = (1.7 + or - 0.4) x 10 to the -7th and provides a negligible contribution to current planetary tests of Einstein's theory of general relativity.
259 citations
27 Nov 1984-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, the magnitudinal and temporal behaviour of non-tidal variations of the Earth's rotation over the past 2700 years was evaluated. But, as would be expected if tidal friction were the only mechanism affecting the Earth’s rotation, there are also non-fractional changes present that vary on timescales ranging from decades to millennia.
Abstract: Occultations of stars by the Moon, and solar and lunar eclipses are analysed for variations in the Earth’s rotation over the past 2700 years. Although tidal braking provides the dominant, long-term torque, it is found that the rate of rotation does not decrease uniformly as would be expected if tidal friction were the only mechanism affecting the Earth’s rotation. There are also non-tidal changes present that vary on timescales ranging from decades to millennia. The magnitudinal and temporal behaviour of these non-tidal variations are evaluated in this paper.
144 citations
TL;DR: In this article, the authors observed the sectoral oscillations of the sun to determine frequency differences produced by rotation and found that most of the solar volume rotates at a rate close to that of the surface, but also that the energy generating core may rotate more rapidly than the surface.
Abstract: Prograde and retrograde sectoral oscillations of the sun have been observed so as to determine frequency differences produced by rotation. Oscillations in the frequency range 2.1-3.7 mHz and with spherical harmonic degrees from 1 to 100 have been identified. Average frequency shifts due to rotation in a sidereal reference frame are found to range from a high of about 660 nHz at degree 1 to a low of about 423 nHz at degree 6, rising to about 471 nHz at degree 100. These results indicate that most of the sun's volume rotates at a rate close to that of the surface, but also that the energy-generating core may rotate more rapidly than the surface.
135 citations
TL;DR: In this paper, the effect of rotation on the oscillation frequencies of a liquid drop is investigated under the assumptions that the drop is imbedded in a fluid of the same or different density and that the interface between drop and fluid is acted on by constant surface tension.
Abstract: The effect of rotation on the oscillation frequencies of a liquid drop is investigated under the assumptions that the drop is imbedded in a fluid of the same or different density and that the interface between drop and fluid is acted on by constant surface tension. While rotation influences the oscillations through both Coriolis force and the centrifugal distortion of the drop, only the former is important for nonaxisymmetric oscillations in first approximation, causing the predicted splitting of the frequency for the two modes that differ in circular polarization sign with respect to the axis of rotation. In axisymmetric oscillations, the centrifugal distortion and the Coriolis force combine to increase frequency in the cases where drop density exceeds that of the fluid.
99 citations
TL;DR: In this article, the two dominant, linearly independent surface-wave modes in a circular cylinder, which differ only by an azimuthal rotation of ½π and have equal natural frequencies, are nonlinearly coupled, both directly and through secondary modes.
Abstract: The two dominant, linearly independent surface-wave modes in a circular cylinder, which differ only by an azimuthal rotation of ½π and have equal natural frequencies, are nonlinearly coupled, both directly and through secondary modes. The corresponding, weakly nonlinear free oscillations are described by a pair of slowly modulated sinusoids, the amplitudes and phases of which are governed by a four-dimensional Hamiltonian system that is integrable by virtue of conservation of energy and angular momentum. The resulting solutions are harmonic in a particular, slowly rotating reference frame. Harmonic oscillations in the laboratory reference frame are realized for three special sets of initial conditions and correspond to a standing wave with a fixed nodal diameter and to two azimuthally rotating waves with opposite senses of rotation. The finite-amplitude corrections to the natural frequencies of these harmonic oscillations are calculated as functions of the aspect ratio d/a (depth/radius). A small neighbourhood of d/a = 0.1523, in which the natural frequency of the dominant axisymmetric mode approximates twice that of the two dominant antisymmetric modes, is excluded. Weak, linear damping is incorporated through a transformation that renders the evolution equations for the damped system isomorphic to those for the undamped system.
96 citations
TL;DR: The spontaneous rotation of small spherical and cylindrical objects immersed in liquid dielectrics and subjected to strong electrostatic fields was first recorded by Quincke in 1896.
Abstract: The spontaneous rotation of small spherical and cylindrical objects immersed in liquid dielectrics and subjected to strong electrostatic fields was first recorded by Quincke in 1896. The rotation was found to be threshold-dependent; and certain conditions on the relative conductivities of the liquid and solid particles were discovered necessary for the effect to be observed at all. A review of the literature shows that Quincke rotation has been rediscovered, renamed, and reexplained several times since the original work. Not all published analyses are correct. A very simple solution of the problem is described which nses the effective dipole concept. The relevance of Quincke rotation to various problems in dielectrophoresis (DEP), conduction in liquid dielectrics, etc., is discussed, and a few practical implications are considered.
94 citations
TL;DR: In four experiments, much stronger evidence for the image rotation hypothesis was found, though weak but systematic effects of frame rotation were also obtained, and additional findings pertinent to the application of the mental rotation paradigm to word recognition were discussed.
Abstract: Two hypotheses regarding mental rotation were contrasted. If subjects rotate each stimulus image to the upright (the image rotation hypothesis), then response time should depend solely on the extent of angular deviation from the upright. But if subjects rotate their frame of reference to match that of the disoriented stimulus (the frame rotation hypothesis), then response time should vary with the angular deviation between the current stimulus and the preceding stimulus. In four experiments, one involving normal and reflected letters (Experiment 1) and the other three involving lexical decisions on Hebrew letter strings (Experiments 2, 3A, and 3B), much stronger evidence for the image rotation hypothesis was found, though weak but systematic effects of frame rotation were also obtained. Increased likelihood that the same orientation would be repeated (Experiment 4) did not yield any stronger frame rotation effects. Also there was no indication of consistent individual differences in the preference for the frame rotation strategy (Experiment 3B). Additional findings pertinent to the application of the mental rotation paradigm to word recognition were discussed.
88 citations
Patent•
06 Jan 1984
TL;DR: In this article, a muscle exercise and diagnostic system which includes a lever arm, a mounting arrangement for mounting the lever arm for rotation about a fixed axis, and a connecting arrangement for connecting a selected portion of the human body to the lever-arm for rotation with the leverarm about a selected anatomical axis of rotation is described.
Abstract: A muscle exercise and diagnostic system which includes a lever arm, a mounting arrangement for mounting the lever arm for rotation about a fixed axis, and a connecting arrangement for connecting a selected portion of the human body to the lever arm for rotation with the lever arm about a selected anatomical axis of rotation. The connecting arrangement establishes a fixed tangential mounting relation and a sliding radial mounting relation between the lever arm and the body portion. This permits free radial movement of the connecting arrangement relative to the fixed axis during an exercise motion. A velocity control arrangement is coupled to the lever arm for limiting the maximum permitted rotational velocity to a value predetermined in accordance with a preselected velocity control function which includes measured values of the distances from the point of attachment to the anatomical axis and to the fixed axis. An arrangement is provided for inputting these measured values to the velocity control arrangement. One such arrangement continuously registers with a potentiometer the distance from the connection point to the fixed axis and supplies that registered distance value to the velocity control computer. The measured value of distance from connection point to anatomical axis is input by a manual dial connected to a potentiometer.
TL;DR: In this article, a new mechanism of angular momentum drain is proposed to account for the relatively slow rotation rates of intermediate-sized asteroids, and the effect of this mass loss on asteroidal rotation is calculated and shown to be a significant brake on the spins of intermediate sized asteroids.
TL;DR: In this paper, it was shown that when the planes rotate with different angular velocities about a common axis or distinct axes, there is a one parameter family of solutions for large viscosities.
Abstract: The flow of the classical linearly viscous fluid between two infinite parallel planes rotating with constant (but different) angular velocities about a common axis has received a great deal of attention during the past 60 years (cf. Parter [12]). However, until recently the assumptions which have been employed to study this problem have always led to solutions which are axisymmetric. Recently Berker [3] in his study of the flow between parallel planes rotating with the same constant angular velocities about a common axis exhibited a one parameter family of solutions that are not axisymmetric. In this study we prove that when the planes rotate with different angular velocities about a common axis or distinct axes there is a one parameter family of solutions (for “large” viscosities).
Patent•
29 Aug 1984TL;DR: In an axial flow rotary separator, each radially extending finger-like crop-engaging element of the rotor is individually and obliquely journaled on a fixed eccentric shaft.
Abstract: In an axial flow rotary separator, each radially extending finger-like crop-engaging element of the rotor is individually and obliquely journaled on a fixed eccentric shaft. Push bars spaced 90 degrees apart rotate about the axis of the separator to drive the fingers so that the finger tips describe a circular path eccentric to the separator casing and inclined to its axis. The plane of rotation of the fingers and the speed of rotation of the rotor are chosen so that the fingers maintain the crop material in an annular mat in contact with the inside wall of the casing and propel it spirally downstream. Finger element bearing housings are split for convenient assembly and repair.
Patent•
25 Oct 1984
TL;DR: In this article, a trainer-flight simulator is presented where a cockpit is gimballed on three independently-controlled axes, i.e., pitch, roll and yaw, which revolve about a planetary axis.
Abstract: Spatial disorientation trainer-flight simulator wherein a cockpit is gimballed on three independently-controlled axes, i.e., pitch, roll and yaw, which revolve about a planetary axis. Rotation of the cockpit about the planetary axis is controlled by a remote console computer. Rotation of the cockpit about the pitch and roll axes is controlled by an on board cockpit computer alone or in combination with the console computer. Rotation of the cockpit about the yaw axis is controlled by the console computer alone or in combination with the cockpit computer. Slip rings are employed at the planetary and yaw axes so as to provide 360° cockpit rotation about each axis. Rotation about each of the pitch, roll and yaw axes is effected by a high torque direct drive dc motor under control of the computers. Smooth, continuous motor operation is possible over a wide range of speeds, including sub-threshold speeds not detectable by the pilot.
Patent•
08 Mar 1984TL;DR: An X-Y input device comprises a rotatable ball, a first driven roller held in contact with the rotatable and rotatable in response to rotation of the ball, and the second driven roller having an axis of rotation extending substantially perpendicularly to that of the first driver as mentioned in this paper.
Abstract: An X-Y input device comprises a rotatable ball, a first driven roller held in contact with the rotatable ball and rotatable in response to rotation of the rotatable ball, a second driven roller held in contact with the rotatable ball and rotatable in response to rotation of the rotatable ball, the second driven roller having an axis of rotation extending substantially perpendicularly to that of the first driven roller, first rotation detector means for detecting an amount of rotation of the first driven roller, and second rotation detector means for detecting an amount of rotation of the second driven roller. The X-Y input device also includes means for imposing frictional forces between the ball and the driven rollers, stop means for stopping operation of the rotation detector means and blocking rotation of the driven rollers when the operation of the rotation detector means reaches predetermined limits, and power release means for reducing power transmitted from the ball to the rotation detector means when the operation of the rotation detector means reaches the limits.
15 Sep 1984
27 Nov 1984-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, an asymptotic method is developed to estimate the rotational splitting of sectoral five-minute solar oscillations, which can be inverted to yield the variation with depth of the Sun's angular velocity near the equatorial plane.
Abstract: An asymptotic method is developed to estimate the rotational splitting of sectoral five-minute solar oscillations. Integral formulae are obtained which can be inverted to yield the variation with depth of the Sun's angular velocity near the equatorial plane. The result is a functional of smoothed data, and does not rely on a detailed theoretical model of the Sun. The method has been tested with artificial data (computed from a theoretical solar model) of a kind similar to some real solar data obtained recently by Duvall & Harvey (Nature, Lond. 310, 19 (1984)). The results are encouraging, for they reproduce at least the broadest feature of the somewhat arbitrary angular velocity with which the theoretical model was endowed. When applied to the real data, the method yields a result similar to that derived by Duvall et al. (Nature, Lond. 310, 22 (1984)) by another procedure.
TL;DR: In this paper, the effects of Hall current and rotation on the flow of electrically conducting rarefied gas due to combined buoyant effects of thermal and mass diffusion, past an infinite porous plate in the presence of transverse magnetic have been investigated.
Abstract: Effects of Hall current and rotation on the flow of electrically conducting rarefied gas due to combined buoyant effects of thermal and mass diffusion, past an infinite porous plate in the presence of transverse magnetic have been investigated. The equations governing the flow problem have been solved and the profiles are shown on graphs. Effects ofm (Hall parameter) andE (Ekman number) on velocity are discussed.
Patent•
30 May 1984
TL;DR: In this paper, the authors proposed to improve the load detection accuracy by arranging arms of a shaft support plate spirally in an axial symmetry while a flexure easy to bend is provided parallel almost at the right angle of the length thereof near both ends thereof.
Abstract: PURPOSE:To improve the load detection accuracy by arranging arms of a shaft support plate spirally in an axial symmetry while a flexure easy to bend is provided parallel almost at the right angle of the length thereof near both ends thereof CONSTITUTION:As a measuring load displaces a shaft 22 in the Z axis direction, flexures 30 and 31 of arms 42 (42a-42d) bends so readily to incline the arms 42 slightly from the level At the same time, the center 41 is displaced in the Z axis direction while turning slightly clockwise as indicated by the arrow When the width W of the flexure 30 is very limited, there is little resistance against rotation of the center 41 at a fine angle associated with the Z-axis-wise displacement This requires no force for the displacement of the detection mechanism itself when loaded, the measuring load given is wholly applied to a load cell 23 thereby improving the load detection accuracy with such a simple construction
TL;DR: In this paper, for the first time, numerical results for two cases: (i) rotation about a common axis, and (ii) rotating about distinct axes, were reported, for two values of the Ekman number E = v/d2ω at the relative disk rotations of s = 0·8, s= 0 and s = −0·25, where s = ω2/ω1.
Abstract: Flows occurring between parallel rotating disks have recently been generalized by Parter & Rajagopal (1984) to include solutions that are not axisymmetric. They prove existence, whereas in the present paper we report, for the first time, numerical results for two cases: (i) rotation about a common axis, and (ii) rotation about distinct axes. Calculations were performed for two values of the Ekman number E = v/d2ω at the relative disk rotations of s = 0·8, s = 0 and s = −0·25, where s = ω2/ω1.
04 Jun 1984
TL;DR: In this paper, an active magnetic bearing is based on the use of forces created by a magnetic field to levitate the rotor without mechanical contact between the stationary and moving parts, and the rotor is maintained in equilibrium under the control of the electromagnetic forces.
Abstract: The active magnetic bearing is based on the use of forces created by a magnetic field to levitate the rotor without mechanical contact between the stationary and moving parts. A ferromagnetic ring fixed on the rotor “floats” in the magnetic fields generated by the electromagnets, which are mounted as two sets of opposing pairs. The current is transmitted to the electromagnetic coils through amplifiers.The four electromagnets control the rotor’s position in response to the signals transmitted from the sensors. The rotor is maintained in equilibrium under the control of the electromagnetic forces. Its position is determined by means of sensors which continuously monitor any displacements through an electronic control system.As in every control system, damping of the loop is provided by means of a phase advance command from one or more differenciating circuits of the position error signal.The capability of modifying the electromagnetic force both in terms of amplitude and phase leads to the benefit of specific properties for the application, in particular:- automatic balancing characterized by the rotation of the moving part around its main axis of inertia, and not around the axis of the bearings allowing operation without vibrations,- adjustable damping of the suspension allowing easy passing of the critical speeds of the rotor,- high and adjustable stiffness yielding maximum accuracy of rotor equilibrium position,- permanent diagnosis of machine operation due to the knowledge of all rotation characteristics (speed, loads on the bearings, position of the rotation axis, eccentricity, out-of-balance, disturbance frequency).© 1984 ASME
TL;DR: In this article, the rotation in non-eruptive limb prominences was studied and velocities of 15-75 km s-1 were found in some cases part of the prominence rotates; in others, the entire body is in rotation.
Abstract: We have studied rotation in non-eruptive limb prominences; in most cases dopplergrams could be used to confirm proper motion measurements. In some cases part of the prominence rotates; in the others, the entire body is in rotation. Velocities of 15–75 km s-1 are found. Of fifty-one prominences studied in 1978, five showed rotation.
Patent•
30 Oct 1984
TL;DR: In this paper, a system for cutting shapes from slabs of easily machinable material, such as plastic foam, under computer control is described, which can then be piled and glued together in order to build large complex volumes, to be used as models, molds or cores of fiber reinforced objects.
Abstract: A system is disclosed for cutting shapes from slabs of easily machinable material, such as plastic foam, under computer control. These shaped slabs can then be piled and glued together in order to build large complex volumes, to be used as models, molds or cores of fiber-reinforced objects. The slab of material is rotated around a fixed axis of rotation, while a cutting wire is driven in translation and tilted at various angles within a plane parallel to or containing said axis of rotation. The cutting action of the wire results from electrically induced heat and/or abrasive motions of the wire in its own direction. This cutting machine is used as a peripheral of a microcomputer, and receives from this microcomputer the signals necessary to control the electric motors driving the rotation of the slab of material and the motions of the cutting wire.
TL;DR: In this article, the identical spin rotation effect was observed in 3He↑ in the temperature range 2 < T < 6 K, and preliminary measurements of the coefficient μ which characterizes the quality factor of the spin oscillations were made.
Abstract: Spin polarized gases such as H↑ or 3He↑ can propagate damped spin waves at low temperatures; their origin is the so-called « identical spin rotation effect » in collisions between identical particles. We report here the observation of such effects in 3He↑ in the temperature range 2 < T < 6 K, and preliminary measurements of the coefficient μ which characterizes the quality factor of the spin oscillations. The measurements are in agreement with the numerical calculations of C. Lhuillier.
TL;DR: In this article, it was shown that at low collision energies the reaction cross section decreases for small H + H2(j) reactions, reaching a minimum at j = 4, then increases as j increases.
Patent•
13 Apr 1984
TL;DR: In this article, a support for a wood circular sawing machine is described, which includes a rotary eccentric member mounted for rotation on a horizontal shaft which is in alignment with the axis of the output shaft of the motor.
Abstract: In a wood circular sawing machine, a support for the circular saw which includes a rotary eccentric member mounted for rotation on a horizontal shaft which is in alignment with the axis of the output shaft of the motor, and a body which has its upper portion being mounted with the arbor of the circular saw and is provided with at its lower portion a hollow cylindrical member sleeved onto the eccentric member, wherein the body that supports the arbor can change the distance of the arbor from the axis of the output shaft of the motor by rotating the eccentric member.
Patent•
22 May 1984
TL;DR: In this article, a mass memory storage device has a plurality of optical disks that the rotation axes of each disk being mounted equidistantly from a main axis, and a transducer head is carried on the distal end of the arm and operably positioned adjacent an addressed track on the addressed disk.
Abstract: A mass memory storage device has a plurality of optical disks that the rotation axes of each disk being mounted equidistantly from a main axis. An arm is rotatably mounted about the main axis and is selectively positioned adjacent one of the addressed disks. A transducer head is carried on the distal end of the arm and is operably positioned adjacent an addressed track on the addressed disk. The arm may have two branches at its distal end where each branch carries a transducer head so that data can be read from and written to each side of the disk. Further, about each rotation axis of a disk, may be disposed a plurality of disk coaxially aligned to increase the storage capacity of the memory device.