Showing papers on "Rotation published in 1991"

The ordered nature of elliptical galaxies - Implications for their intrinsic angular momenta and shapes

Abstract: The observations of rotation along the major and minor axes of 38 elliptical galaxies are analyzed to determine their intrinsic structure. Rotation along the minor axis occurs (i) as a result of projection effects in triaxial systems and/or (ii) because of real misalignment of the angular momentum axis from the intrinsic short axis, as is allowed in triaxial systems. The intrinsic angular momentum can point anywhere in the plane containing the short and long axis. The distribution of apparent misalignments is a function only of the triaxiality T of a galaxy and its intrinsic misalignment, and is independent of the flattening of the galaxy in the plane containing the short and long axis.

Neoclassical poloidal and toroidal rotation in tokamaks

Abstract: Explicit expressions for the neoclassical poloidal and toroidal rotation speeds of primary ion and impurity species are derived via the Hirshman and Sigmar moment approach. The rotation speeds of the primary ion can be significantly different from those of impurities in various interesting cases. The rapid increase of impurity poloidal rotation in the edge region of H‐mode discharges in tokamaks can be explained by a rapid steepening of the primary ion pressure gradient. Depending on ion collisionality, the poloidal rotation speed of the primary ions at the edge can be quite small and the flow direction may be opposite to that of the impurities. This may cast considerable doubts on current L to H bifurcation models based on primary ion poloidal rotation only. Also, the difference between the toroidal rotation velocities of primary ions and impurities is not negligible in various cases. In Ohmic plasmas, the parallel electric field induces a large impurity toroidal rotation close to the magnetic axis, which seems to agree with experimental observations. In the ion banana and plateau regime, there can be non‐negligible disparities between primary ion and impurity toroidal rotation velocities due to the ion density and temperature gradients. Detailed analytic expressions for the primary ion and impurity rotation speeds are presented, and the methodology for generalization to the case of several impurity species is also presented for future numerical evaluation.

3-D rotation of double-couple earthquake sources

Abstract: SUMMARY We discuss 3-D rotations by which one double-couple earthquake source can be rotated into another arbitrary double-couple. Due to the symmetry of double-couple sources, there are four such rotations. An algorithm is obtained in analytical form which is also available as a computer program solving the inverse problem of 3-D rotation of double-couple earthquake sources, i.e., for each pair of focal mechanisms or seismic moment tensor solutions the program finds all four rotations which rotate one mechanism into another. This algorithm may be used in a wide variety of studies of stress field causing earthquakes, investigations of the relationship between the focal mechanisms and the tectonic features of a seismogenic region, etc. The same inversion algorithm can be used to study the 3-D rotation of any symmetric second-rank tensor, such as the stress or strain tensor.

Axes of eye rotation and Listing's law during rotations of the head

Abstract: 1. The vestibuloocular reflex (VOR) was examined in four alert monkeys during rotations of the head about torsional, vertical, horizontal, and intermediate axes. Eye positions and axes were recorded in three dimensions (3-D). Visual targets were used to optimize gaze stabilization. 2. Axes of eye rotation during slow phases showed small but systematic deviations from collinearity with the axes of head rotation. These noncollinearities apparently resulted from vector summation of torsional, vertical, and horizontal VOR components with different gains. 3. VOR gain was lowest about a head-fixed torsional axis that was correlated with the primary gaze direction, as determined by Listing's law for saccades. As a result, rotation of the head about a partially torsional axis produced noncollinear slow phases, with axes that tilted toward Listing's plane. 4. During slow phases, eye position changed not only in the direction of rotation, but also systematically in other directions. Even axes of eye rotation within Listing's plane caused eye position to move out of the plane to a torsional position that was then held. Thus Listing's law for saccades cannot be a product of plant mechanics. 5. VOR slow phases were simulated with the use of a model that incorporated 3-D rotational kinematics into the indirect path and the oculomotor plant. This demonstrated that the observed pattern of position changes is the expected consequence of rotating the eye about a fixed axis and that to hold these positions the indirect path must employ a 3-D velocity-to-position transformation. 6. Quick phases not only corrected the violations of Listing's law produced by slow phases but anticipated them by directing the eye toward a plane rotated in the direction of head rotation. This was modeled by inputting the vestibular signal to a Listing's law operator that is shared by the quick phase and saccadic systems.

Declining rotation curves - the end of a conspiracy

Abstract: New observations of H I rotation curves at the Very Large Array have uncovered two galaxies with rotation curves declining between 1 and 3 optical radii The velocity decrease is large, more than 50 km s-1 (approximately 25% of the maximum rotation velocity), and is present on both sides of the galaxies; projection effects can be ruled out We interpret the decrease in rotation velocity as an indication of a large ratio of luminous to dark mass in the luminous regions of these systems An analysis of the current observations combined with rotation curves from the literature shows a clear correlation between peak circular velocity of a galaxy, its central surface brightness and the slope of the rotation curve in the outer parts This correlation indicates a weakening of the well-known conspiracy between luminous and dark matter, and may provide evidence in favor of the idea that dark matter is baryonic Although we do not sample the full morphological Hubble sequence, a strong correlation between slope of the rotation curve and morphological type is found This result seems to support earlier suggestions that the ratio between the mass in dark and luminous matter might be the critical parameter that controls the Hubble sequence

Ab initio potential energy surfaces and trajectory studies of A‐band photodissociation dynamics: CH3I*→CH3+I and CH3+I*

Abstract: Ab initio contracted spin–orbit configuration interaction (SOCI) calculations have been carried out to obtain potential energy surfaces of 3Q0 and 1Q1 excited states of methyl iodide as functions of all the geometrical parameters except for the three C–H stretches. The results are fitted to six‐dimensional diabatic potential functions and their couplings. Classical trajectory calculations have been performed using these potential functions. The rotation of the CH3 product in the I channel has been calculated to be perpendicular to the top axis and to have a peak at N=5 and extend up to N=8, whereas it is cold in the I* channel, in good agreement with recent experiments. The CH3 rotation is excited by the time trajectories arrive at the conical intersection region; this excitation is retained in the I‐channel product because the 1Q1 surface has a small bending force constant outside the conical intersection, whereas it is damped in the I* channel because 3Q0 still has a large bending force constant. The ca...

Effects of rotation on convective turbulence

Abstract: Laboratory experiments were carried out to investigate the effects of rotation on turbulent convection. The experimental facility was a bottom-heated, water-filled, cubical tank mounted on a turntable. The investigations were performed over a wide range of bottom buoyancy fluxes q0 and rotation rates Ω, including Ω = 0; q0 and Ω were held constant during each experiment. The depth of the water column H was fixed for the entire experimental programme. For the non-rotating experiments, the r.m.s. velocity fluctuations were found to scale well with the convective velocity , where the integral lengthscale is estimated as lr ≈ 0.25hc. The mean buoyancy gradient in the mixed layer was found to be much higher than in the corresponding non-rotating case, and the r.m.s. fluctuations and mean buoyancies were found to scale satisfactorily with (q0Ω)½. A spectral form for the temperature fluctuations in rotating convection is also proposed and is compared to the experimental results.

Symmetrical micromechanical gyroscope

Abstract: A symmetrical micromechanical gyroscope includes an inertial mass symmetrically supported about both drive and sense axes, for detecting rotational movement about an input axis Two pairs of flexures attached to diametrically opposed sides of the inertial mass support the mass within a gyroscope support frame Each of the flexures are oriented at generally a 45° angle from both the drive and the sense axes In response to an applied drive signal, the inertial mass is induced to vibrate about a drive axis which is co-planar with and orthogonal to the sense axis Both pair of flexures participate equally during rotation of the mass

Machine for converting wind energy to electrical energy

Abstract: A machine for converting wind energy into electrical energy comprising in combination a housing; propellers at the forward and rearward ends of the housing mounted on shafts for rotation upon a common horizontal axis of rotation; post means supporting a central extent of the housing for rotation in a horizontal plane to face into the wind; an alternator within the housing formed of a power take off member coupled to one shaft and a rotor coupled to another shaft for counter rotating when the propellers rotate for thereby generating electricity; centrifugal pitch control mechanisms for varying the pitch of the propellers as a function of the propeller speed; transmission mechanisms for varying the speed of rotation of the rotor and power take off member as a function of the wind speed; brake mechanisms for proportionately restraining the propellers against rotation; and an aerogovernor operatively coupled with the brake mechanisms for control thereof in response to the speed of the wind as determined by the aerogovernor.

Testing the gravitational field in elliptical galaxies - NGC 5077

Abstract: NGC 5077 is an elliptical galaxy with a disk of ionized gas along its minor axis. Observations of the structure and kinematics of this gas disk allow us to investigate both the intrinsic shape and the mass distribution of the underlying galaxy. The rotation axis of the gas disk is displaced by 23-degrees +/- 5-degrees from the apparent major axis of the galaxy, so the gas cannot lie in the equatorial plane of an axisymmetric potential. If the galaxy is triaxial and the gas disk has settled into a principal plane then there are two possible configurations, both with the gas on elliptical orbits. One is an oblate triaxial system with the gas in a plane perpendicular to the longest axis, the other is a prolate triaxial galaxy with the gas in the plane perpendicular to the shortest axis. Alternatively, the gas may lie in the warped and precessing polar ring around an oblate galaxy - in this case the gas must have been acquired recently, probably less than 10(9) yr ago. The observed rotation curve of the gas rises slowly, reaching a peak at approximately 10" from the nucleus. For circular orbits in a spherical potential, this would imply a decrease of M/L toward the center, since the core radius of the light is 1" or less. For gas on elliptic orbits, however, the precise shape of the observed rotation curve will depend on the viewing angle. If the gas lies in a warped polar ring, material further out may be seen in projection close to the center so that the observed rotation velocity is much less than the true circular speed. For NGC 5077, we construct various triaxial and oblate mass models which have constant M/L and are consistent both with the observed velocity fields of gas and stars and with the central mass-to-light ratio implied by the observed stellar velocity dispersion. Thus the slowly rising rotation curve of the gas in NGC 5077 does not require the presence of dark matter in the inner regions.

Variable diameter rotating recanalization catheter and surgical method

Abstract: According to the invention there is provided an intravascular catheter comprising an elongated flexible jacket having opposed proximal and distal ends and a central passageway extending between and interconnecting the ends. A rotating working head is located at the distal end of the jacket. A flexible drive cable extends through the passageway of the jacket, having a driving end operatively connected to the working head for rotating it, and a driven end operatively connected to a high-speed motor. The working head is rotatably mounted in a bearing sleeve which is further attached to the catheter jacket. The working head is actuated, by a actuator which adjust the a pair of tip portions from an at least initial retracted position with a first effective working diameter to an extended position with a second effective working diameter greater than the first effective diameter. Centrifugal forces generated by rotation of the cable cause the tip portions to assume the greater effective working diameter.

Development of the Wake behind a Circular Cylinder Impulsively Started into Rotatory and Rectilinear Motion: Intermediate Rotation Rates

Abstract: The temporal development of two-dimensional viscous incompressible flow generated by a circular cylinder started impulsively into steady rotatory and rectilinear motion is studied by integration of a velocity/vorticity formulation of the governing equations, using an explicit finite-difference/pseudo-spectral technique and an implementation of the Biot-Savart law. Results are presented for a Reynolds number of 200 (based on the cylinder diameter 2a and the magnitude U of the rectilinear velocity) for several values of the angular/rectilinear speed ratio alpha = (omega x a)/U (where omega is the angular speed) up to 3.25. Several aspects of the kinematics and dynamics of the flow not considered earlier are discussed. For higher values of alpha, the results indicate that for Re = 200, vortex shedding does indeed occur for alpha = 3.25. The shedding process is; however, very different from that which gives rise to the usual Karman vortex street for alpha = 0. In particular, consecutive vortices shed by the body can be shed from the same side and be of the same sense, in contrast to the nonrotating case, in which mirror-image vortices of opposite sense are shed alternately on opposite sides of the body. The implications of the results are discussed in relation to the possibility of suppressing vortex shedding by open or closed-loop control of the rotation rate.

Power driven screwdriver

Abstract: A power driven screwdriver includes a driving mechanism interposed between the drive motor and the spindle. The driving mechanism includes a first member rotatably mounted within the housing and a second member movably mounted to the first member and driven by the driver motor. A cam mechanism is interposed between the first member and the second member and is operable for transmitting rotation of the second member to the first member and for permitting the second member to move between a first position and a second position. The second member is movable from a first position to the second position as torque transmitted from the second member to the first member increases. A frictional clutch mechanism is interposed between the spindle and the first member for transmitting rotation of the first member to the spindle. A claw clutch mechanism is interposed between the spindle and the second member and is operable to be engaged when the second member is positioned at the second position.

Stability Analysis for the Head-Disk Interface in a Flexible Disk Drive

Abstract: This paper describes the modeling, theoretical formulation, and eigenvalue analysis for a combined system of a spinning flexible disk and a pair of head and suspension systems that contact the disk at opposing points on its two sides. In the analytical model a constant friction force between the sliders and disk and the slider pitch motion, as well as its transverse motion, are taken into account. From the eigenvalue analysis it is found that pitch stiffness and moment of inertia of the heads induce instability above the critical rotation speed similarly to the transverse stiffness and mass. This instability can be effectively stabilized by increasing the external damping which is spinning with the disk. It is also found that the friction force makes all forward modes unstable over the entire rotational speed range. The friction induced instability can be effectively suppressed by increasing the transverse stiffness and mass and it can be stabilized by the pitch damping and the external damping. The characteristics of instability due to the friction force qualitatively agree well with experimental results reported previously.

Evolutionary Models of Halo Stars with Rotation. I. Evidence for Differential Rotation with Depth in Stars

Abstract: Evolutionary models of metal-poor stars are computed including the effects of rotation, and their properties are compared with observations The models rotate slowly at the surface, in agreement with the observed upper limits on the rotation velocity at main-sequence turnoff; they also have substantial differential rotation with depth This differential rotation preserves a sufficient amount of internal angular momentum to explain the rapid rotation of evolved horizontal-branch stars These results hold for a wide range of angular momentum loss and transport parameter values Differences and similarities between the surface and internal rotation of solar metallicity and metal-poor models are discussed Rigidly rotating models are found to be incompatible with the observations once giant branch mass loss is taken into account Horizontal-branch rotation velocity measurements as a function of color are proposed as a test of the rotation law enforced in convection zones, and their dependence on cluster age and metallicity are discussed

The effect of the three columns of the spine on the instantaneous axis of rotation in flexion and extension.

Abstract: Instrumentation designed for stabilization and correction of spinal deformities must limit the amount of motion in flexion and extension. In flexion or extension, the vertebral bodies move about a specific point called the instantaneous axis of rotation. The ability of the implant to limit this motion is a function of its relation to the axis of rotation of the spine. The goal of this study was threefold: 1) to define the instantaneous axis of rotation of the spine in flexion and extension; 2) to study the effect of the loss of the three columns of the spine on the location of the instantaneous axis of rotation; and 3) to determine how the above parameters relate to the choice of anterior or posterior instrumentation. Ten human cadaver spines were subjected to compressive loads in flexion and extension. The columns of the spine were then destroyed in sequence at L3. The instantaneous axis of rotation for each vertebral body was found by the method of Reuleaux, and the effect of the compromise of the columns on the location of the instantaneous axis of rotation was noted. Understanding the exact location of the instantaneous axis of rotation after a specific injury would allow the clinician to objectively choose the best surgical approach and the appropriate instrumentation.

Swivelling optical connector for joining optical fiber to components and sensor including such connector

Abstract: Optical connectors adapted to join optical fibers to an optical component, each connector having an outer support to be fixedly secured to the component and provided with a housing receiving a movable element having a spherical-surface portion to which an optical fiber-holding body is connected. The spherical surface of the movable element is in contact with a mating surface of the outer support and permits pivoting or rotation of the movable element and the body housing the fiber about any axis passing through the center of the spherical surface itself. Tightening means for locking the movable element against the housing surface is provided, and such tightening means is adapted to prevent pivoting or rotation of the movable element itself by friction. The connector can be made entirely of dielectric materials.

The rotation of LAGEOS

Abstract: In view of the need of an accurate modelling of nongravitational forces on laser-tracked satellites, it is important to understand their rotational dynamics, which determines the temperature anisotropy and the ensuing radiation recoil effects. We propose a model of the torques acting on LAGEOS due to eddy currents and gravity gradient. The electromotive forces induced in the spacecraft by its rotation in the magnetic field of the Earth dissipate angular momentum and produce a precession of the spin axis; the oblate spacecraft will precess in the gravitational field of the Earth at a rate proportional to the rotation period. Therefore the gravitational torques become more and more important with time and eventually may produce a chaotic dynamics. The predicted evolution of the spin period agrees very well with the few experimental data available and corresponds to an approximately exponential growth rate of about 3 years.

Compensation for skewing of documents during a rotation through a finite angle

Abstract: The skew angle of a sheet (e.g., business form or other document) is detected by providing two sensors spaced from each other a known distance along a straight line perpendicular to the direction of conveyance of the sheet. If there is a skew, the distance travelled by the sheet leading edge between sensings by the sensors is determined, and the skew angle calculated from its tangent. First and second independent drive rollers under the sheet are driven in opposite directions of rotation to compensate for the skew angle. The rollers preferably act in conjunction with a controller (computer) to not only reorient the sheet to compensate for the skew, but also to rotate the document through a significant angle (e.g., 90°) to give the sheet a second orientation different from its initial orientation (e.g., from portrait to landscape).

Single wafer processor apparatus

Abstract: A single wafer processing apparatus includes a portable processing head that can be a portable module or a movable unit mounted to a supporting machine frame. The processing head has movable fingers adapted to grip a wafer. The fingers protrude from a protective wafer plate. Indexing and rotation monitoring assemblies are provided for automation of the wafer processing steps. A complementary processing base includes an upwardly-open bowl that receives a wafer held by the portable processing head. It has a full-diameter movable bottom wall for rapid draining purposes. Liquid and/or gas jets and nozzles supply fluids required within the bowl for processing of wafers.

Image blur correcting apparatus

Abstract: An image blur correcting apparatus includes a lens-barrel part having a lens and an imaging device, an image signal processing device for forming a video signal from an electrical signal obtained at the imaging device, a supporting body for supporting the lens-barrel part in a freely pivoting manner around a rotation axis crossing a beam axis incident to the lens-barrel part at approximately right angles, and an actuator device attached between the lens-barrel part and the supporting body for rotating the lens-barrel part. The apparatus further includes a relative angle detecting device for detecting a relative angle between the lens-barrel part and the supporting body and a device for detecting a moving vector indicating an amount of blur of the image from correlation between two frames of image information from the image signal processing means, which are continuous in view of time. Finally, the device includes an angular velocity accumulating device for calculating rotating angular velocity using a zoom multiplying factor or the like from the detected result of the moving vector.

Laser alignment and control system

Abstract: A laser alignment system includes a probe head assembly mounted for linear articulation in mutually perpendicular X, Y and Z axes, with respect to a reference plane. In a four axis version of the system, a laser probe is further mounted for rotation about a V axis relate to the reference plane. Adjustment means are provided to ensure that a laser beam emitted by the probe is perpendicular to the V axis and intersects the V axis. In a five axis version of the system, the laser probe is further rotatable about a W axis perpendicular to the reference plane. This version further incorporates a means to translate the laser beam so that the beam, when perpendicular to the reference plane, coincides with the W axis.

Snap engaging fastener system for providing rotary motion

Abstract: Disclosed is a fastener system comprising a male or stud element with a split or bifurcated head, forming two prongs, that fits inside a female or socket sleeve. Inside the socket sleeve is an internal annular ring of a smaller diameter. The stud prongs deflect radially inwardly when pushed into contact with the internal ring until the prongs pass the ring at which point they deflect radially outwardly and lock the male member within the sleeve. This locking action allows for a variety of items to be clamped together along the length of the rivet sleeve provided that at each end of the rivet there is a head of larger diameter than that of the sleeve. Each head can be replaced by any number of integrally molded items requiring a locking/mating action or where locking and rotation is desired.

Apparatus for monitoring the motion of the lumbar spine

Abstract: An apparatus is disclosed for monitoring the movement and force production of the lumbar spine during flexion and extension in each of several sagittal-frontal planes of the body, as well as during movement into he transverse (twisting) plane. The apparatus includes a rotatable platform upon which the patient is adapted to stand, and the platform is pivotable about a vertical axis, so that the platform may be pivoted to a selected angle and locked in position. A pelvic stabilization belt is mounted to the platform, and an overhead frame member is provided for rotation about a horizontal axis which is adapted to pass through the lumbro-sacral junction of the patient. An upper body yoke is mounted to the overhead frame member for rotation about a generally vertical axis which is perpendicular to the horizontal axis. An upper body engaging member is mounted to the yoke, and a control system is provided whereby the apparatus may be operated in a flexion/extension mode, or in a twisting mode, and with the foot platform in a selected angular position.