Showing papers on "Rotation published in 1985"

Numerical simulations of stellar convective dynamos. II. Field propagation in the convection zone

Abstract: We present numerical simulations of nonlinear, three-dimensional, time-dependent, giant-cell stellar convection and magnetic field generation. The velocity, magnetic field, and thermodynamic variables satisfy the anelastic magnetohydrodynamic equations for a stratified, rotating, spherical shell of ionized gas. The interaction of rotation and convection produces a nonlinear transport of angular momentum that maintains a differential rotation in radius and latitude. At the surface, our simulated angular velocity peaks in the equatorial region in agreement with Doppler measurements of the solar surface rotation rate; below the surface, it decreases with depth in agreement with what is inferred from the rotational frequency splitting of solar oscillations. The interaction of rotation and convection also maintains left-handed helical fluid motions in the northern hemisphere and right-handed motions in the southern hemisphere. Magnetic fields are generated by the shearing and twisting effects of the differential rotation and helical motions and are destroyed by eddy diffusion. They in turn feedback onto the velocity and thermodynamic fields via the Lorentz force and Joule heating. Although we have not continued the computation long enough to simulate a complete magnetic cycle, our solutions demonstrate how the induced magnetic fields propagate away from the equator in the opposite direction inferred from themore » solar butterfly diagram. We suggest that, instead of operating in the turbulent convective region, the solar dynamo may be operating at the base of the convection zone where our simulated helicity has the opposite sign and a smaller amplitude.« less

Deformation induced by polar motion

Abstract: Variations in the geocentric position of the earth's rotation axis (polar motion) cause deformation within the earth. The effects of this deformation on radial and horizontal positions of points on the earth's surface, on baseline lengths between those points, and on surface gravity are estimated. The effects of the oceans and of the earth's anelasticity on this deformation are found to be negligible. Peak-to-peak variations in radial motion are typically 10-20 mm over a year. Horizontal displacements are less than 7-8 mm. Variations in baseline length can be as large as 30-40 mm. Variations of up to 13 microgal in surface gravity are possible. These numbers are all small enough that they can probably not be used to learn about the earth. However, they are large enough to affect noticeably present high-quality geodetic observations.

Effect of rotation on isotropic turbulence - Computation and modelling

Abstract: This paper uses numerical simulation to analyse the effects of uniform rotation on homogeneous turbulence. Both large-eddy and full simulations were made. The results indicate that the predominant effect of rotation is to decrease the rate of dissipation of the turbulence and increase the lengthscales, especially those along the axis of rotation. These effects are a consequence of the reduction, due to the generation of inertial waves, of the net energy transfer from large eddies to small ones. Experiments are also influenced by a more complicated interaction between the rotation and the wakes of the turbulence-generating grid which modifies the nominal initial conditions in the experiment. The latter effect is accounted for in simulations by modifying the initial conditions. Finally, a two-equation model is proposed that accounts for the effects of rotation and is able to reproduce the experimental decay of the turbulent kinetic energy.

Muon Spin Rotation Spectroscopy Principles and Applications in Solid State Physics

Abstract: The muon spin rotation technique. Muon spin rotation in metals: localization, diffusion, trapping. Hyperfine fields at the +in metals. Study of dynamic effects in magnetism. Applications in superconductors. Muonium in matter. Muon spin rotation in insulators.

Influence of rotation on the near-wake development behind an impulsively started circular cylinder

Abstract: The early phase of the establishment of the flow past a circular cylinder started impulsively into rotation and translation is investigated by visualizing the flow patterns with solid tracers and by analysing qualitatively (flow topology) and quantitatively (velocity distributions and singular-point trajectories) the corresponding photographs. The range considered corresponds to moderate Reynolds numbers (Re [les ] 1000). The rotating-to-translating-speed ratio α increases from 0 to 3.25 and the motion covers a period during which the cylinder translates 4.5 or even 7 times its diameter. The details of the mechanisms of the near-wake formation are considered in particular and the increase of the flow asymmetry with increase in rotation is pointed out. Thus the existence of two regimes has been confirmed with the creation or non-creation of alternate eddies after an initial one E1 Furthermore, the new phenomena of saddle-point transposition and intermediate-eddy coalescence have been identified in the formation or shedding of respectively the odd and even subsequent eddies Ei (i = 2,3,…) when they exist. The very good agreement between these experimental data and the numerical results of Badr & Dennis (1985), obtained by solving the Navier-Stokes equations and presented in a parallel paper, confirms their respective validity and permits the determination of the flow characteristics not accessible, or accessible only with difficulty, to the present experiments. These flow properties such as drag and vorticity are capable of providing information on the Magnus effect for the former property and on unsteady separated flows for the latter.

Block rotation and deformation by strike-slip faults: 2. The properties of a type of macroscopic discontinuous deformation

Abstract: Study of the general features of deformation by systems of subparallel strike-slip faults shows that the governing constraints are kinematic: the fault blocks must remain in contact with each other and the deformed area must fit with its surroundings. As a result, fault blocks that move laterally without significant internal deformation also rotate about vertical axes relative to boundaries of the fault domain by an amount that is quantitatively related to fault slip, spacing, and orientation. Areas where left-and right-lateral faults move simultaneously are usually divided into domains that contain faults of one kind only. Deformation of such multidomain areas is nonhomogeneous, but the differences between domains can compensate for each other, so that the regional deformation is quite simple. Strike-slip faulting combined with block rotation is an efficient mechanism of deformation because modest offsets and rotations change the linear dimensions of faulted areas by several tens of percents, which may often greatly exceed the results of other types of coeval deformation. Paleomagnetic data can provide an independent measure of block rotations and should be used to supplement structural data. Block rotation changes the initial angles between right- and left-lateral faults and also their orientation relative to the stress field; the faults probably tend to rotate away from the axis of maximum compression. Rotated faults continue to move because they are weak surfaces. Since the deformation depends on geometric factors such as fault orientation and domain geometry, it is not simply related to the stress field. These properties, including rotation of material units, characterize discontinuous deformation in general.

Solar rotation as a function of depth and latitude

Abstract: A 5-day series of two-dimensional velocity images of the Sun is analysed to yield frequencies of solar p-mode oscillations with degrees between 8 and 50, with all azimuthal orders for each degree. The frequency splitting between modes with the same degree and radial order is related to the latitudinal variation of rotation, averaged over a depth range that depends on the degree. The observed splittings indicate that for 0.3R⊙ ≲r≲0.7R⊙ the solar latitudinal differential rotation is much smaller than at the surface (rotation roughly constant on spheres), and moreover that the rotation rate is close to the surface equatorial value.

Station coordinates, baselines, and Earth rotation from LAGEOS laser ranging: 1976–1984

Abstract: The orbit of the Lageos satellite is well suited as a reference frame for studying the rotation of the earth and the relative motion of points on the earth's crust. The satellite laser measurements can determine the location of a set of tracking stations in an appropriate terrestrial coordinate system. The motion of the earth's rotation axis relative to this system can be studied on the basis of the established tracking station locations. The present investigation is concerned with an analysis of 7.7 years of Lageos laser ranging data. In the first solution considered, the entire data span was used to adjust a single set of station positions simultaneously with orbit and earth rotation parameters. Attention is given to the accuracy of earth rotation parameters which are determined as an inherent part of the solution process.

Viscous effects in a collisional tokamak plasma with strong rotation

Abstract: The full viscosity tensor for an axisymmetric toroidal plasma in the collisional regime (with strong rotation) is calculated, including gyroviscosity and O(e) poloidal variations over the flux surface. It is shown that the resulting viscous force is of sufficient magnitude to account for the radial transfer of toroidal momentum that must be inferred in order to explain the rotation measurements in tokamak experiments. The consequences of a viscous force of this form and magnitude on particle transport and on the evolution of toroidal and poloidal rotation velocities are discussed.

Measurements of plasma column rotation and potential in the TM-4 tokamak

Abstract: The velocity of plasma rotation and the potential distributions are measured in the TM-4 device i n the Ohmic-heating regime. The potential is negative at the centre of the column, and its magnitude is significantly larger than the ion temperature. At the edge, the potential is positive while the rotation velocities are considerably lower than their neoclassical values.

Multi-degree of freedom mount

Abstract: @ The specification discloses a mount for an optical device having rotational and translation freedom, in particular 6 degrees of freedom in three translations along x, y and z axes and three pivotal or rotational movements about each of the axes. The mount is particularly useful in mounting scanning cameras, robotic eyes, or correlating image or pattern recognition devices for use in self-guided missiles. When used in free-flight, the three pivotal or rotational movements correspond to pitch, roll, and yaw. A semi-spherical drive means (11,12) which is rotatably journaled in a complimentary semi-spherical fixed mount. The drive means (11, 12) defines an optical axis within having interior threads. A first carrier (13) is threaded into the drive means (11,12) and translated along the z axis by rotation of the spherical drive means (11, 12). A second carrier is mounted for x, y translation within the first carrier (13). Pivotal or rotational movement about the x and y axes may occur between the first carrier (13) of the drive hemisphere, or between the drive hemisphere and the fixed mount (14). Roll movement about the z axis occurs between the first carrier (13) and the fixed mount (14).

All terrain vehicle and method of operating same

Abstract: An all terrain vehicle has two vehicle units and an articulating link which interconnects the vehicle units in tandem. Each vehicle unit has a body and a pair of spaced crawler tracks which are powered for moving the respective vehicle unit. The articulating link has two longitudinally spaced apart pitch hinge assemblies, each of which cooperates with a respective vehicle unit to permit relative rotation therebetween about a horizontal pitch axis without interference between the vehicle units. Pitch swivelling means associated with one particular pitch hinge assembly can force relative rotation about the particular pitch axis between a particular vehicle unit and the link, so that one vehicle unit can be rotated forcibly relative to the other vehicle unit to negotiate marginal terrain. The remaining pitch hinge assembly can be either freely hinged to permit rotation about the remaining pitch axis or alternatively can have a similar pitch swivelling means. The vehicle also has a yaw hinge assembly for steering, and optionally has a roll hinge assembly to permit relative rotation about the link between the vehicle units, particularly for self-righting on hard terrain, and also for additional control and versatility. A single vehicle unit can be operable independently of the other, but performance is increased considerably by utilizing at least two vehicle units in tandem connected by the articulating link. The vehicle combination can climb up or down vertical walls of limited height from hard terrain, or can negotiate a vertical wall disposed above water a height dependent on draft of the vehicle. The vehicle combination is a self-righing from an inverted position on land or immersed in water.

Induction of correct centrifugal force in a rotating mass shell

Abstract: Mach's idea of relativity of rotation is confirmed for a shell-type model of the Universe by showing that flat geometry in rotating coordinates, realising correct Coriolis and centrifugal forces, can be continuously connected through a rotating mass shell with not exactly spherical shape and latitude-dependent mass density to an asymptotically Minkowskian outside metric. The corresponding solutions of Einstein's field equations are given to second order in the angular velocity omega but it is plausible that the problem has a solution to any order of omega .

Temperature independent Faraday rotation near the band gap in Cd1-xMnxTe

Abstract: Faraday rotation spectra have been measured for Cd1−xMnxTe, 0.10≤x≤0.20, for temperatures from 213 to 373 K. At wavelengths well above the fundamental absorption edge the rotation decreases with increasing temperature. The opposite temperature dependence is found for shorter wavelengths since the rotation increases strongly when the wavelength approaches the edge and the edge moves towards longer wavelengths with increasing temperature. For each x a wavelength with temperature independent rotation can be found due to a cancellation of these effects. The large and temperature independent rotation is of great interest for optical devices such as magnetic field sensors, isolators, and modulators. By choosing 0.10≤x≤0.25 these devices would be compatible with GaAlAs emitting diodes and lasers. Optical transmission was also measured and was found to be fairly high at wavelengths of interest. A sensor design is presented, allowing dc response and very small physical dimensions.

Method and apparatus for mounting electronic parts

Abstract: In the mounting of an electronic component, a holding member is rotated by a predetermined angle prior to actual holding of the electronic parts, thereby to detect a center of the holding member from at least two positions of the rotation angle, and the rotation center of the holding member is found by a calculation based on the detected center of the holding member The position of the electronic parts against a circuit board then is corrected on the basis of a deviation between the position of the rotation center and the center of the holding member

Device for detecting the angular position of the rotor of a rotary electric machine with electronic switching

Abstract: A device for detecting the angular position of the rotor of an electric rry machine with electronic switching, comprising more particularly a disk mounted coaxially on the shaft of said rotor and comprising a radial face on which permanent magnets are fixed of alternately reversed polarity producing a magnetic field, Hall effect proximity cells disposed in the vicinity of said radial face of the disk and carried by a structure mounted for rotation on the body of said rotary machine coaxially with said axis, and adapted for detecting the axial component of the magnetic field, means allowing said structure to be locked against rotation on said body.

Satellite tracking antenna system

Abstract: A ship borne antenna using a gimballed mount for establishing a two degree of freedom unstabilized structure. A ring is mounted for rotation on a radome and carries an antenna mounted for rotation relative to the ring. The ring antenna are respectively driven by stepper motors. Variations in stability occurring by pitch, yaw or roll of the ship are corrected on a real time basis using a microprocessor that dynamically drives the ring and the antenna to maintain lock-on with a satellite.

Armboard mounting assembly

Abstract: An armboard mounting assembly including an armboard having a proximate and a distal end, an armboard mount, and a joint for pivotably interconnecting the armboard and the armboard mount for enabling rotation of the armboard about a pivot axis. The rotatable armboard and armboard mount have at least one pair of adjacent sections, and the assembly further includes friction members (or alternate grippers) for providing gripping between said adjacent sections, said friction members being responsive to a downward force on the armboard between the pivot axis and the distal end for increasing gripping between the adjacent sections and inhibiting relative rotation about the pivot axis. Depending on the materials used, the armboard mounting assembly is radiologically translucent, NMR (nuclear magnetic resonance)-compatible, or both.

Soft-X-ray tomography on Alcator C

Abstract: Using 80 miniature soft-X-ray detectors viewing along chords through a plasma cross-section at one toroidal location, tomographic reconstructions of emissivity have been obtained without the need for assuming any symmetry or rotation of the plasma. In one class of plasma discharges, it is found that a large m = 1 oscillation, which previously had been ascribed to the rotation of an MHD instability, actually is not rotating at all.

Television perspective effects system

Abstract: This invention employs an incremental technique for performing a perspective transformation on a planar television image. The equipment modifies the coefficients to a two by two matrix multiplier at the pixel or line rate. This allows for perspective generation along either the X or Y axis of the television screen. The invention will also provide perspective generation for rotation of the image about the Z axis in addition to the rotation about one of the X or Y axes.

Device for producing pulsating magnetic fields for therapeutic purposes

Abstract: A device for producing pulsating magnetic fields comprises a substrate rotatable about an axis and having disposed thereon at least one pair of magnets with a direction of magnetization substantially parallel to the rotational axis such that rotation of the substrate by 180° about its rotational axis transfers the pole faces of the magnets into each other and that there exists no symmetry of the pole faces relative to a plane which includes the rotational axis. The orientation of the pole faces of the magnets is such that during rotation of the substrate, magnetic forces are exerted radially with respect to the axis about which the substrate is rotated by drive structure provided for that purpose. In accordance with various embodiments, the magnets may be disposed upon one or both sides of the substrate and may be of rectangular, arcuate, wedge-like or other plate-like configurations.

Borehole inertial guidance system

Abstract: In order to improve the accuracy of borehole survey systems utilizing probes (18) with inertial components including inclinometers (32, 34, 36), two ring laser gyro units (42, 44) are included to provide rotation information to the system. When the probe (18) is moving in a borehole (12), inclinometer information is used to produce a synthetic rotation signal to take the place of a third gyro and the earth's rotation is used for a similar purpose in combination with signals from the two ring laser gyros (42, 44) when the probe (18) is stopped. Wire line velocity is used in combination with the inclinometer and gyro information to provide signals representing the probe velocity and position. Coordinate transformations are provided in the probe to transform the inertial signals and wire line velocity signals into earth reference coordinate system. Kalman filtering incorporates noninertial velocity data to reduce the effect of errors inherent in the generation of various input signals to the system.