Showing papers on "Rotation published in 1972"

Rotation of the Corsica–Sardinia Microplate

Abstract: This article summarizes the available data that can be used to date the rotation of the small Corsica–Sardinia plate and points out the types of investigation that could clarify the problem further.

Force-free magnetic-field structures and their role in solar activity.

Abstract: Magnetic-field structures in solar active regions are expected to be substantially force-free. A method is proposed for calculating such structures by numerical methods. The method is applied to the study of the magnetic-field pattern associated with a sunspot of one polarity surrounded by a magnetic region of opposite polarity when the sunspot rotates with respect to the surrounding region. Rotation introduces a toroidal component of magnetic field, and the associated pressure leads to inflation of the magnetic field pattern. If the differential rotation exceeds about 180 deg, the force-free magnetic field has energy greater than that of an open magnetic-field configuration with the same photospheric boundary conditions. It is concluded that, beyond this point, the force-free field structure is metastable and can be converted into an open field structure by an explosive MHD instability.

Hydromagnetic convection in a rapidly rotating fluid layer

Abstract: The linear stability of a rotating, electrically conducting viscous layer, heated from below and cooled from above, and lying in a uniform magnetic field is examined, using the Boussinesq approximation. Several orientations of the magnetic field and rotation axes are considered under a variety of different surface conditions. The analysis is, however, limited to large Taylor numbers, T , and large Hartmann numbers, M . (These are non-dimensional measures of the rotation rate and magnetic field strength, respectively.) Except when field and rotation are both vertical, the most unstable mode at marginal stability has the form of a horizontal roll whose orientation depends in a complex way on the directions and strengths of the field and angular velocity. For example, when the field is horizontal and the rotation is vertical, the roll is directed parallel to the field, provided that the field is sufficiently weak. In this case, the Rayleigh number, R (the non-dimensional measure of the applied temperature contrast) must reach a critical value, R c , which is O ( T 2/5 ) before convection will occur. If, however, the field is sufficiently strong [ T = O ( M 4 )], the roll makes an acute angle with the direction of the field, and R c = O ( T 1/2 ), i.e. the critical Rayleigh number is much smaller than when the magnetic field is absent. Also, in this case the mean applied temperature gradient and the wavelength of the tesselated convection pattern are both independent of viscosity when the layer is marginally stable. Furthermore, the Taylor-Proudman theorem and its extension to the hydromagnetic case are no longer applicable even qualitatively. Over the interior of the layer, however, the Coriolis forces to which the convective motions are subjected are, to leading order, balanced by the Lorentz forces. The results obtained in this paper have a bearing on the possibility of a thermally driven steady hydromagnetic dynamo.

Studies of Floating Liquid Zones in Simulated Zero Gravity

Abstract: Floating liquid zones of water/ethanol solutions were suspended between glass tubes inside mineral oil. When the densities of the two liquids were equal, there was no net gravitational force acting on the interface between them. The shape stability of this interface was studied under conditions of density imbalance and end‐member rotation. Cylindrical, conical, and spherical zone shapes were investigated. Our results show that the generally accepted Heywang criterion for the stability of cylindrical liquid zones is no longer valid under reduced gravitational conditions. The convective flow patterns in the zone due to rotation have been studied in detail and show the existence of distinctly different flow regimes. In all cases the outer liquid rotated more slowly than the end faces and so resulted in Taylor‐Proudman‐type axial flow. However the liquid near the rotation axis behaved quite differently; for equal isorotation of the end faces, a central core of liquid rotated as a solid core at the same rate as the imposed velocity, while for equal counterrotation, the central core of liquid showed a zero angular velocity. The implications of these studies for crystal growth are considered.

On the hydromagnetic stability of a rotating fluid annulus

Abstract: A non-dissipative fluid rotates uniformly in the annular region between two infinitely long cylinders and is permeated by a magnetic field varying with distance from the axis of rotation. The hydromagnetic stability of this system is examined theoretically. When the magnetic field is azimuthal the system can always be rendered stable to axisymmetric disturbances by sufficiently rapid rotation (Michael 1954). Unless the magnetic field everywhere decreases with radius, however, the system may be unstable to non-axisymmetric disturbances even when the rotation speed exceeds a typical Alfven speed by many orders of magnitude. ‘Slow’ hydromagnetic waves, akin to those invoked in a recent theory of the geomagnetic secular variation (Hide 1966), may then be generated by the spatial variations of the magnetic field. All unstable waves so generated propagate against the basic rotation, i.e. ‘westward’, when the field is azimuthal, and this property is in fact remarkably insensitive to variations in both magnitude and direction of the imposed field.

Mariner 9 celestial mechanics experiment: gravity field and pole direction of Mars.

Abstract: Analysis of the Mariner 9 radio-tracking data shows that the Martian gravity field is rougher than that of earth or the moon, and that the accepted direction of the Mars rotation axis is in error by about 0.5 deg. Contours of equivalent surface heights deduced from a sixth-degree solution for the Martian gravity field are presented. These contours represent the deviations from sphericity of a uniformly dense body with an external potential which is given by the first sixth-degree solution. In addition to Doppler observations, ranging or group-delay measurements have been made regularly since orbit insertion.

Rotatable finned heat transfer device

Abstract: A heat transfer device includes first and second members mounted for continuous relative rotation in either of a clockwise or a counterclockwise direction while maintaining substantially equally sized gaps between a plurality of equally spaced concentric fins which are alternately disposed in overlapping relationship.

Resonance Rotation of Celestial Bodies and Cassini's Laws

Abstract: Celestial body rotation about its center of mass, taking into account the body orbit evolution, is considered. Non-linear evolution equations of motion are constructed. Empirical Cassini's laws describing the Moon motion result from these equations as their stationary points. Bifurcation conditions of steady motions are written out and conditions of their stability are investigated. Hypothesis of Mercury's resonance motion analogous to the ‘motion by Cassini’ is discussed. Consequences of this hypothesis are considered.

Title Not Available

Abstract: In an air supported vehicle a steering and traction wheel is mounted for vertical movement so as to contact the floor in all vertical positions into which the vehicle is moved by the air support The steering axis of the wheel is offset so that driving rotation of the wheel develops steering torque A locking mechanism or clutch holds the wheel and its mounting against steering rotation until such rotation is required, and the wheel and its mounting may be locked in desired positions

Electron beam therapy unit

Abstract: An electron beam therapy unit in which an electron beam source and a shield are mounted on the opposed horizontally extending arms of a U-frame mounted for rotation about a horizontal axis, and a patient support is pivotally attached at off-centre positions to three planet gears which are rotatable about fixed axis and mesh with a rotatable sun gear. As the U-frame is rotated a gear train connected to it rotates one of the planet gears, which rotates the other planet gears through the sun gear, so that the patient support is rotated along a circular path around the U-frame axis of rotation so that the patient is always diametrically opposite the electron beam source.

Adaptive braking wheel speed sensor

Abstract: An electromagnetic probe is installed in the differential housing of an automotive vehicle. The probe includes a substantially U-shaped core piece having a base which abuts a permanent magnet and pair of generally parallel arms which extend through the centers of a pair of coils. The arms extend into close poximity with circumferentially spaced teeth formed on the differential frame and on one of the axles. Since rotation of the teeth past the legs changes the reluctance path of the magnet, a pulsed output will be generated in the coils, the frequency of which varies directly according to the speed of rotation of the frame and of the axle. Since the frame rotates at substantially the same speed as the vehicle drive shaft or at some known fraction of that speed, and since the drive shaft rotates at the average speed of the left and right axles, by determining the speed of rotation of the frame and of one of the axles, the speed of rotation of the other axle may be readily determined, thereby providing intelligence of the speed of rotation of both of the vehicle''s rear axles by using only the single probe. This speed sensor is particularly useful in automotive adaptive braking systems.

Manipulator with drive motors

Abstract: The manipulator arm is pivoted at its mid-point on a laterally displaced shoulder pin coupled to a rotatable body which has a horizontal axis on one side of said arm and serves to rotate the complete manipulator assembly about said axis. A drive-motor block which produces a continuous balancing action about the shoulder-pin axis is pivotally mounted on one end of the manipulator arm in laterally displaced relation thereto. A wide range of angular motion is thus imparted by cable-type transmission means to a fore-arm which is rotated about an elbow pin or in azimuth and to a tong unit which is subjected to movements of elevation, rotation and closure.

Balancing system for a rotating mass

Abstract: Three different types of unbalance are detected and corrected while a gyroscopic inertial flywheel is continuously spinning. The gyroscope is mounted in an integrated test and correction apparatus comprising an angularly positionable mount supported on a shaker table. The mount supports a test chamber in which the spinning gyroscope is located in a low viscosity, low density atmosphere. Windows are formed in the chamber on opposite sides permitting lasers fixed on the mount to be aimed at the flywheel to burn off selected portions of its mass. A safety system is arranged within the chamber to detect whether the spot at which a given laser beam is aimed has already received a laser burn. Mass unbalance is determined, with the spin axis polar, by rotating the gyroscopic reference axes 90° and recording the drift at two orientations. Radial unbalance is determined by imparting a reciprocating motion along the spin axis by means of the shaker table at the same rate as the rotation of the flywheel. By shifting the phase of the vibratory motion relative to the rotation of the flywheel, a maximum signal proportional to the radial unbalance is sensed by one of the gyro pick-offs. Modulation is determined directly by detecting the amplitude of a modulating signal on the pick-off signal. An automated closed-loop procedure determines the correct pattern of laser burns on the flywheel to minimize the unbalances.

Apparatus for milling road surfaces

Abstract: Apparatus and method for milling road surfaces wherein a motor driven rotatable roller, equipped with hard-metal cutters, is moved horizontally at a uniform level relative to the road surface, the level being such that the cutters engage the road surface during rotation of the roller. In accordance with the present invention, the roller is rotated in a direction opposite to the direction of forward movement of the axis of the roller relative to the road surface. That is, the cutters mill the road surface in a direction of forward movement of the axis of the roller. The apparatus of the invention further includes means for varying the level of the roller, and for varying the tilt of the roller relative to the road surface.

Molecular Rotation in Liquids. Conditional Fast Rotational Diffusion

Abstract: The theory of finite step rotational Brownian motion is generalized to anisotropic rotators. It is assumed that fast rotational diffusion will occur with the event of a ``hard'' collision between molecules. An expression for the rotational correlation time τ2 is given which is anisotropic and depends on the orientation of the z principal axis of the quadrupolar or dipolar interaction with respect to the principal axes of the rotational diffusion tensor. A general expression for the product of the spin‐rotational correlation time (τ1) and τ2 is given. The quasilattice random flight model is generalized with the aid of an expression for the collision frequency given by Einwohner and Alder. The microcanonical conditional rotation model of Atkins et al. is reformulated to the case of rotation upon a hard collision.

Solar rotation as determined from OSO-4 EUV spectroheliograms.

Abstract: Spectroheliograms obtained in extreme ultraviolet (EUV) lines and the Lyman continuum are used to determine the rotation rate of the solar chromosphere, transition region, and corona. A cross-correlation analysis of the observations indicates the presence of differential rotation through the chromosphere and transition region. The rotation rate does not vary with height. The average sidereal rotation rate is given by ω (deg day−1) = 13.46 - 2.99 sin2B where B is the solar latitude. This rate agrees with spectroscopic determinations of the photospheric rotation rate, but is slower by ∼ 1 deg day−1) = 13.46 - 2.99 sin2 than rates determined from the apparent motion of photospheric magnetic fields and from the brightest points of active regions observed in the EUV. The corona does not clearly show differential rotation as do the chromosphere and transition region.

Propagation of internal gravity waves in perfectly conducting fluids with shear flow, rotation and transverse magnetic field

Abstract: The propagation of internal Alfven-inertio-gravitational waves in a Boussinesq inviscid adiabatic perfectly conducting shear flow with rotation is investigated in the presence of a transverse magnetic field. It is shown that the effect of the rotational nature of electromagnetic force and Coriolis force is that linear momentum is not conserved anywhere in the fluid even at critical levels, whereas the angular momentum flux is conserved everywhere in the fluid except at the critical levels at which the Doppler-shifted frequency Ωd = 0, + ΩA or ± Ω ± (Ω2 + Ω2A)½, where ΩA is the Alfven frequency and Ω is the Coriolis frequency, and the angular momentum is transferred to the mean flow there by Alfven-inertio-gravitational waves. Asymptotic solutions to the wave equation are obtained near the critical levels and it is shown that the effect of the Lorentz force on the waves at the critical levels is to increase the process of critical layer absorption. The condition for neglection of rotation for higher frequency waves is also obtained and is found to be the same in both hydrodynamic and hydro-magnetic flows.

Angular orientation measuring apparatus

Abstract: An optical device using a wedge deviation technique for the measurement of the angular orientation about the axis of rotation of one body relative to another. The device employs a passive target, which may be a linear reticle, on one body and optical measuring means on the second body. The measuring means has an optical element such as a prism assembly to split the image of spaced apart portions of the linear target into two transposed halves which are viewed by suitable means such as a telescope. An optical wedge assembly centered in the line of sight on the axis of rotation between the telescope and the target can be used as the optical element. When the target reticle lies in the plane described by the optically deviated split field of view of the telescope, an unbroken line is perceived through the telescope. When rotation about the line of sight occurs in one body with respect to the other, a linear displacement of one half of the split image of the target with respect to the other occurs. The amount of rotation of the optical measuring means required to bring the split image back into coincidence is correlated against a calibrated scale to give an indication of the amount of angular displacement about the axis of rotation that had occured. In a further embodiment, an arrangement of mirrors rather than a wedge assembly is used to produce the split image in the optical measuring means.