Showing papers on "Rotation published in 1983"

Instantaneous direction changing rotation mechanism

Abstract: An instantaneous direction changing rotation mechanism in which its driving shaft and driven shaft have coincident central lines, the driving shaft can be controlled for transmission via either a direction changing train of gear with negative train value or casing of gear for driving the driven shaft for rotation in either reverse or normal direction; the intermediate bevel gear of the train of gear has a spindle extending to the exterior of the casing of gear and fixed to a brake block so that the above control can be achieved by engaging or disengaging the brake block with a barke element; a movable ring is surrounding the upper part of the casing of gear so that while the rotation of the movable ring is restricted by the sensor means, there is an angular displacement against the casing of gear for disengaging or engaging the brake element with the brake block.

Passive fiber-optic ring resonator for rotation sensing.

Abstract: A passive fiber-optic resonator technique for rotation sensing has been investigated. Preliminary data show a noise-equivalent rotation-rate sensitivity of 0.5°/h (τ= 1 sec), which is an order of magnitude above the photonshot-noise limit. The major sources of error and ways of reducing such errors are discussed.

The equilibrium and stability of rotating plasmas

Abstract: In a rotating equilibrium state, the velocity and magnetic fields are shown to share the same flux surfaces. A simplified derivation is given of a second‐order (not necessarily elliptic) partial differential equation which determines axisymmetric equilibrium states. For general configurations, equations on flux surfaces which determine the Alfven and cusp continuous spectrum are derived and the stability investigated. These equations are written without the use of any particular coordinate system. Similar equations yield a sufficient condition for global stability of axisymmetric equilibria if the flow is parallel to the magnetic field up to a rigid rotation of the plasma. This condition is also necessary for stability in a mirror configuration with no toroidal field and a pure rigid rotation.

Rotational discontinuities and the structure of the magnetopause

Abstract: Symmetric and asymmetric rotational discontinuities are studied by means of a one-dimensional computer simulation and by single-particle trajectory calculations. The numerical simulations show the symmetric rotation to be stable for both ion and electron senses of rotation with a thickness of the order of a few ion gyroradii when the rotation angle of the tangential field is 180 deg or less. Larger rotation angles tend to be unstable. In an expansive discontinuity, when the magnetic field on the downstream side of the discontinuity is larger, an expanding transition layer separating the highfield from a low-field region develops on the downstream side, and a symmetric rotational discontinuity forms at the upstream edge. The implication of these results for magnetopause structure and energy flow through the magnetopause is described.

Plasma rotation in the PDX tokamak

Abstract: Toroidal and poloidal rotation has been measured in the Poloidal Divertor Experiment (PDX) tokamak in Ohmic and neutral-beam heated plasmas in a variety of discharge conditions and in both circular and diverted configurations. Rotation velocities were deduced from Doppler shifts of magnetic dipole (M1) lines and lines of optically allowed transitions in the visible and UV regions, from Kα emission, and also from an array of magnetic pickup loops. Poloidal and toroidal rotation velocities in Ohmically heated discharges were usually less than 3 × 105 cms−1. Near the plasma edge, the toroidal rotation velocity varies with poloidal angle both before and during neutral-beam injection. No systematic poloidal rotation was observed during neutral-beam injection centred about or displaced 10 cm from the horizontal midplane, which implies that the poloidal damping time τθ < 0.5 τii consistent with theoretical estimates. The central toroidal rotation velocity during neutral-beam injection scales linearly with the quantity and is independent of plasma current and toroidal magnetic field. The toroidal rotation velocity is higher in deuterium than in hydrogen plasmas, and also in diverted discharges as compared with circular ones. Toroidal rotation decay times after injection range from 80–100 ms at the centre to 160–180 ms at half the minor radius. Modelling of the radial profile of toroidal rotation indicates a central momentum diffusivity of the order of 8 × 103 cm2s−1. This is approximately a factor of three higher than the momentum diffusivity obtained from the decay time. All present theories are inadequate in accounting for the observed damping rate of v.

The rotational spectrum of g-modes in the sun

Abstract: Observations and calculations are presented which strongly suggest that the unique sequence of rotation rates due to g-modes is active in the sun. It is found that all angular harmonics from 1 = 2-11 appear to be resolved, while higher harmonics up to at least 1 = 20 also seem to be active. The extreme narrowness of many of the spectral lines indicates that the g-modes are locked in sets of constant 1 by a local mechanism which excites the modes and possibly regulates the long-term precision of their rotation. These sets act as a system of resonant, or nearly resonant, clocks which impose a degree of periodicity upon solar activity and measure the mean solar interior rotation

Numerical study of secondary flows and roll-cell instabilities in rotating channel flow

Abstract: A numerical study is conducted on the pressure-driven laminar flow of an incompressible viscous fluid through a rectangular channel subjected to a spanwise rotation. The full nonlinear time-dependent Navier–Stokes equations are solved by a finite-difference technique for various rotation rates and Reynolds numbers in the laminar regime. At weak rotation rates, a double-vortex secondary flow appears in the transverse planes of the channel. For more rapid rotation rates, an instability occurs in the form of longitudinal roll cells in the interior of the channel. Further increases in the rotation rate leads to a restabilization of the flow to a Taylor–Proudman regime. It is found that the roll-cell and Taylor–Proudman regimes lead to a substantial distortion of the axial-velocity profiles. The specific numerical results obtained are shown to be in excellent agreement with previously obtained experimental measurements and theoretical predictions.

Rotation of a Tangle of Quantized Vortex Lines in He II

Abstract: The densities of vortex lines in He II due to rotation and axial counterflow do not simply add. With slow rotation, the critical counterflow velocity is greatly reduced. At high counterflow velocities, rotation adds fewer lines than expected, suggesting that the vortex tangle is polarized by rotation. Two critical velocities are found, the smaller of which agrees quantitatively with an explanation by Glaberson, Johnson, and Ostermeier of an instability found by Cheng, Cromar, and Donnelly.

Disc rotation servo control apparatus in a disc player

Abstract: The rotation speed of a disc rotation motor is controlled such that a synchronizing signal derived from an output signal reproduced from a disc coincides with a reference oscillation frequency. The amount of data accumulated in a memory provided for absorbing jitter of the output signal reproduced from the disc is detected. In response to a result of the detection, a control signal in the disc rotation control is corrected such that the amount of data accumulated in the memory becomes substantially constant.

Microscope stage assembly and control system

Abstract: A computerized stage assembly for a Scanning Electron Microscope including a support frame, a tilt frame pivotally coupled to the support frame, an X carriage engaged with the tilt frame for movement in an X direction, a Y carriage engaged with the X carriage for movement in a Y direction, and a pedestal carried by the Y carriage and capable of rotation around an axis substantially normal to both the X and Y directions. The tilt frame, X and Y carriages, and pedestal are moved by computer controlled step motors. The tilting and rotating of a specimen secured to the pedestal is non-eucentric, i.e. the axis of rotation or tilt is not necessarily through the point of inspection on the specimen. A method is disclosed for automatically returning an inspection point to the viewing field of the microscope after a non-eucentric rotation or tilt.

The linear strability of the flow in the narrow gap between two concentric rotating spheres

Abstract: SUMMARY The flow of a viscous fluid contained in the narrow gap between two concentric spheres rotating with different angular velocities about a common rotation axis is considered. The onset of instability of this flow is investigated analytically, and two special cases are given particular attention. In the first case the outer sphere is at rest, while in the second case the fluid is in almost rigid rotation with the inner sphere rotating slightly faster than the outer. Instability first sets in near the equator, but the critical Taylor number is greater than that for the corresponding cylinder problem. The WKBJ method is used. Difficulties which arose in previous treatments are resolved by identifying the turning points. They are located not on the real latitude axis but in its extension to the complex plane. The implementation of the procedure leads to an ordinary-differential-equation eigenvalue problem which can be solved by standard numerical techniques.

Plasma rotation measurements using spectral lines from charge‐transfer reactions

Abstract: The central toroidal rotation velocities of tokamak plasmas have been measured from the Doppler shifts of spectral lines that are excited by charge transfer of the neutral hydrogen heating beams with fully ionized oxygen.

Anti-Clockwise Rotation of the Wind Hodograph. Part I: Theoretical Study

Abstract: In a first theoretical study, the reasons for anti-clockwise rotation (clockwise rotation in the Southern Hemisphere) of the wind hodograph in the boundary layer are investigated. As observations of wind hodographs show two different kinds of anti-clockwise rotation (ACR), one frequently observed, which is highly irregular with partly ACR and the other with clear ACR, two methods have been applied. At first a two-dimensional nonlinear model which includes sea-land breezes as well as a mountain reveal partly ACR at the lee of the mountain. By analyzing the different terms in the equation for the wind vector rotation, it is shown that the pressure-gradient term is usually the leading one, and the advection term is very small. But the latter becomes important in cases of ACR. Second, a linear model is solved analytically showing that inclusion of a rotating thermal force in the ACR sense generates clear ACR. It is shown that a critical value for the phase shift between the thermal forces in the hori...

New Phenomenon of the Molecular Liquid State: Interaction of Molecular Rotation and Translation

Abstract: The technique of computer simulation is used to reveal a new and unsuspected phenomenon of the molecular liquid state which is observable by several different spectroscopic techniques. The phenomenon is explained in terms of the effect of a molecule's rotation on its own translation (or vice versa). This is directly measurable in optically active molecules, and exists for all molecules in the liquid state.

Turbo-molecular pump

Abstract: A turbo-molecular pump characterized in that three out of five degrees of freedom except the rotation around the rotational axis of a shaft are actively controlled constrainingly by a pair of magnetic radius direction bearings and a pair of magnetic axial bearings, a bell-shaped rotor provided to cover the whole of magnetic bearing and a shaft which is supported by a magnetic bearing passively constraining the remaining two degrees of freedom, and said rotor is rotated at high speed by an inner-rotor type of a driving motor provided between a radius direction bearing and axial bearing.

Measurements of plasma ion temperature and rotation velocity using the He II 4686‐Å line produced by charge transfer

Abstract: Spatially and temporally resolved values of the ion temperature and toroidal rotation velocity near the plasma axis have been obtained in neutral beam‐heated plasmas in the Doublet III tokamak from measurements of the Doppler broadening and Doppler shift of the He II 4686‐A line, excited by charge transfer reactions between fast hydrogen atoms in the beam and thermal helium ions in the plasma. The measurement technique, which uses visible optics and a multichannel detector, promises to be a straightforward method to obtain ion temperature profiles in beam‐heated tokamaks.

Three-dimensional simulations of convection in layers with tilted rotation vectors

Abstract: Three-dimensional and time-dependent numerical simulations of thermal convection are carried out for rotating layers in which the rotation vector is tilted from the vertical to represent various latitudes The vertical component of the rotation vector produces narrow convection cells and a reduced heat flux As this vertical component of the rotation vector diminishes in the lower latitudes, the vertical heat flux increases The horizontal component of the rotation vector produces striking changes in the convective motions It elongates the convection cells in a north–south direction It also tends to turn upward motions to the west and downward motions to the east in a manner that produces a large-scale circulation This circulation is directed to the west and towards the poles in the upper half of the layer and to the east and towards the equator in the bottom half Since the layer is warmer on the bottom this circulation also carries an equatorward flux of heat When the rotation vector is tilted from the vertical, angular momentum is always transported downwards and toward the equator For rapidly rotating layers, the pressure field changes in a manner that tends to balance the Coriolis force on vertical motions This results in an increase in the vertical heat flux as the rotation rate increases through a limited range of rotation rates

Solar rotation results at Mount Wilson

Abstract: Solar rotation results from Doppler velocity measurements made at Mount Wilson over a period of more than 14 years are presented based on a single reduction procedure. The observations were made with the wavelength 5250.2 A line of Fe I, and wavelength shifts of the line were simultaneously recorded. Data from 188 rotations are presented. Measurements of scattered light along with its effect on the measured rotation rate are given.

Wind-driven generator apparatus

Abstract: Disclosed is a wind-driven generator apparatus with variable pitch blades. The apparatus includes a yaw damping arrangement for resisting weathervaning rotation of a head assembly of the apparatus about a vertical axis and the apparatus further includes a pitch control mechanism for the blades which maintains the pitch substantially constant during normal operating r.p.m. of the blades but allows the blades to pitch up in an overspeed condition, and a brake mechanism for the generator shaft which includes an adjusting mechanism that compensates for wear in the brake.

Back-skewed fan

Abstract: A compact, efficient axial flow fan with blades that are rearwardly (i.e., away from the direction of fan rotation) skewed and which are oriented at a pitch ratio which continuously decreases as a function of increasing blade radius along the radially outermost 30% of the blade.

NMR experiments on rotating superfluid3He-A and3He-B and their theoretical interpretation

Abstract: We have constructed a rotating nuclear demagnetization cryostat and used it for continuous-wave NMR experiments on superfluid3He-A and3He-B. The measurements were performed in a long cylindrical geometry of 5 mm diameter, with the cylinder axis parallel to the axis of rotation and with the external magnetic field H0=284 or 142 Oe in the same direction. The angular velocity of rotation Ω was varied between 0.2 and 1.5 rad/sec, and the experiments were done under 29.3 bar pressure at temperatures between Tc=2.72 and about 1.4 mK. As a guide to the new and esoteric field of superfluid3He in rotation, we first review the general theory at some length in relatively simple terms. Pictorial explanations are often given.

Rotation rate measuring instrument

Abstract: In the rotation rate measuring instrument, two component beams derived from a light beam produced by a laser circulate around a coiled optical waveguide (radius R, length L) in opposite directions. From the phase difference between the two component beams due to the Sagnac effect, the rotation rate is determined. Before entering the optical waveguide, each of the two component beams is modulated in a modulator (5, 6) such that the phase differences (2ν+1)π/2, (2ν+5)π/2, and (2ν+3)π/2 (where ν is an arbitrary integer) exist periodically between the two component beams emerging from the optical waveguide. The drive signals for the two modulators, which exhibit periodic frequency changes of 2F, are varied in such a way that the output of an optical-to-electrical transducer (2) to which the two component beams are directed after travelling around the optical waveguide provides a constant signal. To compensate for the Sagnac phase difference, an additional frequency difference of Δf is required between the two drive signals. The rotation rate Ω is determined by the equation ##EQU1## where λ=vacuum wavelength of the light, and C=velocity of light in vacuo.

On the rotation of the polar cap potential pattern and associated polar phenomena

Abstract: Geomagnetic and radar observations indicate that the potential and convection pattern in the northern polar cap are significantly rotated clockwise with respect to the noon-midnight meridian. On the basis of simple models, some of the basic roles of the highly conductive belt (the auroral oval) on the rotation is examined. It is shown that it develops a space charge distribution along the boundaries in such a way as to rotate the potential pattern clockwise. The rotation angle is estimated as a function of the ratio of the conductivity in the auroral oval to that in the polar cap for a given set of conditions for an assumed conductivity ratio of ΣH/ΣP = 2.0.

Visual apparent movement: Transformations of size and orientation

Abstract: Sequential alternation between same-shaped stimuli differing in size (size ratio s) and orientation (angular difference v) produced a visual illusion of translation in depth and concurrent rotation. The minimum stimulus-onset asynchrony required for the appearance of a rigidly moving object was approximately a linearly increasing function of (s− 1)/(s + 1) for simple translation in depth and a linearly increasing function of v for simple rotation. The extrapolated zero intercept was lower for translation than for rotation, but estimated transformation times were additive in combined transformations. The results suggest that (a) the processes of apparent translation in depth and apparent rotation are individually sequential-additive in structure, and (b) apparent translations and rotations are combined by fine-grained alternation of steps of apparent translation and steps of apparent rotation. Similar principles account for recent data on imagined spatial transformations of visual size and orientation.