Showing papers on "Rotation published in 1982"

Turbulence and waves in a rotating tank

Abstract: A turbulent field is produced with an oscillating grid in a deep, rotating tank. Near the grid, the Rossby number is kept large, 0(3-33), and the turbulence is locally unaffected by rotation. Away from the grid, the scale of the turbulence increases, the r.m.s. turbulent velocity decreases, and rotation becomes increasingly important. The flow field changes dramatically at a local Rossby number of about 0.20, and thereafter remains independent of depth. The flow consists of concentrated vortices having axes approximately parallel to the rotation axis, and extending throughout the depth of the fluid above the turbulent Ekman layer. The number of vortices per unit area is a function of the grid Rossby number. The local vorticity within cores can be a factor of 50 larger than the tank vorticity 2Ω. The total relative circulation contained in the vortices remains, however, a small fraction of the tank circulation.The concentrated vortex cores support waves consisting of helical distortions, which travel along the axes of individual vortices. Isolated, travelling waves seem well-described by the vortex-soliton theory of Hasimoto (1972). The nonlinear waves transport mass, momentum and energy from the vigorously turbulent region near the grid to the rotation-dominated flow above. Interactions between waves, which are frequent occurrences, almost always result in a local breakdown of the vortex core, and small-scale turbulence production. Usually the portions of broken core reform within ½−1 rotation periods, but occasionally cores are destroyed and reformed on a much longer timescale.

Solution of an integral equation encountered in rotation therapy

Abstract: An integral equation relating the lateral absorbed dose profile of a photon beam to the resultant absorbed dose distribution during single-turn rotating-beam therapy has been set up and solved for the case of a cylindrical phantom with the axis of rotation coinciding with the axis of symmetry of the cylinder. In the first approximation the results obtained are also valid when the axis of rotation is somewhat off-centred, even in a phantom that deviates from circular symmetry, provided the rotation is performed in both clockwise and counter clockwise directions. The calculated dose profiles indicate that improved dose uniformity can be achieved using a new type of non-linear wedge-shaped filter, which can easily be designed using the derived general analytic solution to the integral equation.

Bi-axial supporting arrangement which can withstand high acceleration forces

Abstract: The invention relates to a bi-axial support of a rotatable body in a projectile for supporting said body such that it can perform small tilting motions about two mutually perpendicular axes lying in a plane, which is perpendicular to the longitudinal axis of the projectile. The support consists of a spherical or partly spherical bearing body introduced into a correspondingly spherical cup-shaped recess in a projectile-fixed part having the open end directed forwards in the motion direction of the projectile. The spherical bearing body is retained in the recess by means of two pairs of link arms defining two virtual tilting axes for the bearing body and connected to two output shafts such that a tilting motion of the body about the respective virtual axis results in a rotation of the respective output shaft and vice versa. When firing the projectile the spherical surface of the bearing body comes in metallic contact with the spherical surface of the recess, whereby the support can withstand very high acceleration forces in any direction.

Rotation of cells in an alternating electric field theory and experimental proof

Abstract: Protoplasts of Avena sativa rotate in an alternating electric field provided that at least two cells are located close to each other. An optimum frequency range (20 to 30 kHz) exists where rotation of all cells exposed to the field is observed. Below and above this frequency range, rotation of some cells is only occasionally observed. The angular velocity of rotation depends on the square of the electric field strength. At field strengths above the value leading to electrical breakdown of the cell membrane, rotation is no longer observed due to deterioration of the cells. The absolute value of the angular velocity of rotation at a given field strength depends on the arrangement of the cells in the electric field. A maximum value is obtained if the angle between the field direction and the line connecting the two cells is 45 degrees. With increasing distance between the two cells the rotation speed decreases. Furthermore, if two cells of different radii are positioned close to each other the cell with the smaller radius will rotate with a higher speed than the larger one. Rotation of cells in an alternating electric field is described theoretically by interaction between induced dipoles in adjacent cells. The optimum frequency range for rotation is related to the relaxation of the polarization process in the cell. The quadratic dependence of the angular velocity of rotation on the field strength results from the fact that the torque is the product of the external field and the induced dipole moment which is itself proportional to the external field. The theoretical and experimental results may be relevant for cyclosis (rotational streaming of cytoplasm) in living cells.

The motion of a sphere in the presence of a deformable interface

Abstract: We investigate the effect of small deformations of an initially flat fluid interface on the force and torque experienced by a nearby translating and rotating solid sphere. The small deformation problem is reformulated in terms of equivalent boundary conditions on a flat interface; this allows a separation of the rotation and translation problems, along with their respective components parallel and normal to the undeformed interface. Results for the force and torque corrections due to interface deformation are thus calculated for the four fundamental cases of translation normal and parallel to the undeformed interface, and rotation with the axis of rotation normal and parallel to the undeformed interface. These results can be superposed to obtain the force and torque on a sphere which is undergoing an arbitrary translational and/or rotational motion near the interface.

Heart valve prosthesis

Abstract: The prosthesis comprises an annular frame and a disc-shaped obturator which is coupled to the frame and is pivotable, under the action of the blood flow, between an open annular position and a closed angular position, so as to allow the flow of blood through the aperture of the annular frame in one direction and the interruption of the flow in the opposite direction, respectively. The obturator is coupled to the frame in such a way that, in the open position, it may orient itself in a direction substantially perpendicular to the plane of the frame. The side of the obturator which faces away from the central axis of the annular frame in the open angular position is defined, at least in its peripheral part, by a surface which is generated by the rotation, about the central axis of the obturator, of a curve the locus of the centers of curvature of which lies on the opposite side of this curve from a curve which generates, by rotation around the central axis, a surface defining the other side of the obturator.

Vibrating beam rotation sensor

Abstract: A rotation sensor having an integral crystal silicon cantilever beam (10) and support structure (12), an oscillator circuit (20) for generating an electrical signal vibrating the cantilever beam (10) at or near its natural resonant frequency and a piezoresistive element (22) formed at the base of the vibrating beam (10). The piezoresistive element (22) is only sensitive to the stresses induced in the beam (10) due to the rotation of the beam (10) about an axis parallel to its length.

Stacking device for paper sheets

Abstract: Paper currency notes, transported edgewise one by one, are discharged from a transport passage. Each discharged note is held between blades of a rotating blade wheel and moves along with the rotation of the wheel. The notes are then separated from the blades by a checking wall of a stacking box, and stacked in the stacking box. When a predetermined number of notes, for example 100, are stacked in the stacking box, a rotating sectional stacking member is rotated along with the wheel and stops in advance of the stacking box so as to separate the 100th note from the 101st. Since the rotation sectional stacking member has the same axis of rotation as the blade wheel and moves at the same speed, there is must less danger of disruption of the smooth flow of notes.

Fiber-Optic Rotation Sensors. Tutorial Review

Abstract: The measurement of rotation is of considerable interest in a number of areas. For example, inertial navigation systems as used in aircraft and spacecraft depend critically on accurate inertial rotation sensors. The allowable errors in rotation sensor performance depend on the particular application. Typical requirements for aircraft navigation lie between 0.01 and 0.001 degree/hour. In terms of earth rotation rate Ωe = 15 degrees/hour this becomes 10-3 to 10-4 ΩE. A number of other applications of rotation sensors exist such as surveying where the accurate determination of azimuth and geodetic latitude is important [T]. In this case performance of 10-6 ΩE or better is needed. Geophysics applications include the determination of astronomical latitude, and the monitoring of polar motion caused by wobble, rotation, precession and wandering effects [1]. A highly precise rotation sensor may be used to measure any changes in the length of the day and to detect torsional oscillations in the earth caused by earthquakes. Finally, ultraprecise sensors may find applications in relativity related experiments such as the determination of the preferred frame, dragging of inertial frames, etc. [2].

Tides in differentially rotating convective envelopes. II. The tidal coupling

Abstract: The tidal coupling between a star with an extended, differentially rotating convective envelope, and its companion in a close binary system, is calculated from the tidal velocity field derived in Paper I. The derived coupling torque can be tested using observations of RS Canum Venaticorum systems, for which a photometric wave in the light curve provides an accurate stellar rotation rate, and for which observed orbital period changes require the stars in the systems to be coupled. The coupling torque is sufficient to explain the nearly synchronous rotation of the active star in RS CVn systems, despite the observed orbital period changes, but may not be able to explain the extreme tightness of the coupling implied by the very long periods for the migration of the photometric waves in the systems. This conclusion depends on the origin of the orbital period changes, but not on the nature of the wave or the wave migration. When the coupling torque vanishes, a specific latitude at the surface of the convective star will exactly corotate with the binary system: this corotation latitude is calculated. Finally, it is shown that the additional viscous terms introduced by tides should not suppress differential rotation in binarymore » systems with RS Cvn parameters.« less

Vortex solitary waves in a rotating, turbulent flow

Abstract: Turbulent flow in a rotating container has been widely studied1–5, but here we consider an experiment in which the axis of rotation is vertical, the tank deep and a vigorous turbulence is produced near the bottom by a horizontal grid oscillating in the vertical direction. The flow within the rotating container can be envisioned to result from: (1) the disorganized, turbulent motion produced by the grid which, in the absence of rotation, would yield a random field with turbulent intensity decreasing upwards (away from the grid) and turbulent length scale increasing upwards6; (2) the organizing influence of rotation which, in the absence of turbulence, would generate a (trivial) flow having a single vertical component of vorticity, 2Ω (Ω is the tank rotation rate), uniform throughout the tank. These two competing effects combined produce a flow field which is surprisingly complex. The major feature of the flow consists of a collection of regions of highly concentrated vorticity, or vortices. These vortices extend coherently throughout the depth of the container. Waves having the form of compact, helical distortions propagate along the vortex cores. We show that the waves are well described by the vortex soliton theory of Hasimoto7.

Rotating Blade Vibration Analysis Using Shells

Abstract: Shallow shell theory and the Ritz method are employed to determine the frequencies and mode shapes of turbomachinery blades having both camber and twist, rotating with non-zero angles of attack. Frequencies obtained for different degrees of shallowness and thickness are compared with results available in the literature, obtained from finite element analyses of nonrotating blades. Frequencies are also determined for a rotating blade, showing the effects of changing the (1) angular velocity of rotation, (2) disk radius and (3) angle of attack, as well as the significance of the most important body force terms.

Wellbore inertial directional surveying system

Abstract: A wellbore inertial directional surveying system for providing a complete directional survey of an oil or gas well borehole to determine the displacement in all three directions of the borehole path relative to the well head at the surface. The information generated by the present invention is especially useful when numerous wells are drilled to different geographical targets from a single off-shore platform. Accurate knowledge of the path of the borehole allows proper well spacing and provides assurance that target formations are reached. The tool is lowered down into a borehole on the electrical cable. A computer positioned on the surface communicates with the tool via the cable. The tool contains a sensor block which is supported on a single gimbal, the rotation axis of which is aligned with the cylinder axis of the tool and, correspondingly, the borehole. The gyroscope measurement of the sensor block rotation is used in a null-seeking servo loop which essentially prevents rotation of the sensor block aboutthe gimbal axis. Angular rates of the sensor block about axes which are perpendicular to the gimbal axis are measured by gyroscopes in a manner similar to a strapped-down arrangement. Three accelerometers provide acceleration information as the tool is lowered within the borehole. The uphole computer derives position information based upon acceleration information and anular rate information. Kalman estimation techniques are used to compensate for system errors.

Errors in the center and angle of rotation of a joint: an experimental study.

Abstract: The error sensitivity in the determination of center and angle of rotations of a body joint performing planar motion is studied. A simple experiment is described to measure the errors in these two kinematic parameters as functions of errors in the input coordinates of markers. The effect of varying the marker locations and the size of motion-step is also studied. The errors in the center of rotation are found to increase dramatically when the two markers subtend angles of about 0 deg or 180 deg and when the motion step size decreases to 1 deg or less. Similar results are found for errors in the angle of rotation which, in addition, increase with decrease in the radius of the markers.

Internal rotation and gravitational quadrupole moment of the Sun

Abstract: The internal angular velocity of the Sun is estimated from observations of apparent rotational splitting of low-order low-degree global oscillations detected in fluctuations in the limb-darkening function. A sidereal rotation of 3 µHz is inferred for the deep interior; this is more than six times greater than the equatorial rotation frequency of the photosphere. The inferred angular velocity distribution does not vary strongly with latitude, and yields a gravitational quadrupole moment J2≃3.6×10−6. When combined with the results of planetary radar observations to determine (2−β+2γ)/3, a combination of Eddington–Robertson post-newtonian parameters which in general relativity is unity, a value of about 0.994 (±0.012) is thus obtained.

Rotation of an isolated cell in a rotating electric field.

Abstract: albino guinea pigs from Ffillingsdorf, Switzerland). Sensitization was performed according to the FCAT method: each animal received, on alternate days, an emulsion of the hapten (5% w/v) in a 1:1 Freund Complete Adjuvant-Saline mixture, intradermally, in the postnuchal region; each guinea pig received a total of 5 injections and rested for 2 weeks. Tests were performed by depositing 1% ethanol solution of either frullanolide on a 2 cm z area (delimited by a rubber stamp) on the dipped and shaved flank of the animal; tests were read after 24 h and scaled in the following way: 0=no reaction; 0.5=erythema covering part of the test area; 1 =erythema covering the entire test area; 2=erythema and swelling of the test area; 3 = erythema and swelling extending well beyond the test area

Apparatus for reducing starting adhesion between a magnetic disc and flying head

Abstract: In a magnetic disc memory apparatus in which a magnetic head is in contact with a surface of a magnetic disc when the disc is stationary and caused to float upon rotation of the disc, the magnetic head contacting the magnetic disc is slightly moved in the radial direction of the disc immediately before rotation of the disc, whereby the rotation of the magnetic disc is started after adhesion between the magnetic disc and the magnetic head has been obviated.

Centrifugal gas-liquid contact apparatus

Abstract: A gas-liquid contact apparatus includes a rotor having an outer wall parallel to the axis of rotation of the rotor, a permeable element mounted within the rotor for rotation therewith, inlets to supply liquid and gas to the rotor and outlets for conducting a gas and liquid respectively from the rotor The permeable element is made of a plurality of strips of permeable material in layers superimposed progressively from the outer wall inwards towards the axis of rotation, the strips being in end-to-end abutment and the abutments being circumferentially staggered in adjacent layers

Analytic Solutions for Equilibrium of Rotating Isothermal Clouds -- One-Parameter Family of Axisymmetric and Conformal Configurations--

Abstract: Equilibrium states of rotating axisymmetric isothermal gas clouds are studied and it is found that, if the linear rotation velocity is constant throughout a cloud, there exists a one· parameter family of conformal solutions which describe the equilibrium exactly The pa· rameter depends only on the ratio of the rotation velocity to the sound velocity and represents the flatness of equi·density contours in the direction of the rotation axis Two extreme values of the parameter correspond to a non· rotating spherical configuration and a rapidly-rotating thin disk Specific angular momentum on a cylindrical surface around the rotation axis is found to be proportional to the amount of mass contained inside the cylinder considered The stability of the equilibrium configurations is examined analytically as well as numer­ ically and it is found that nearly spherical configurations' are unstable to contraction and expansion as a whole, very flat configurations are unstable to ring formation and intermediate configurations are likely to be stable Finally, these equilibrium configurations are compared with the results of numerical computations which have so far been performed by many people on the collapse of rotating isothermal clouds

Piezoelectric motor with two part rotor

Abstract: A piezoelectric motor of the invention comprises a stator and a rotor one of which includes at least one first piezoelectric oscillator. The rotor consists of a first and a second parts one of which parts includes a second piezoelectric oscillator. Said parts of the rotor are mounted for relative rotation about the axis of rotation. The first part is in contact with the stator along the first surface of frictional interaction and with the second part along the second surface of frictional interaction. Each surface of frictional interaction is formed by rotation of at least one straight line length about the axis of rotation of the rotor.

Personal health care device

Abstract: A hand-held personal health care device (10) for polishing of teeth wherein the appliance containing the cleaning agent at (20) driven by means mounted in the body portion (12) with a drive shaft mounted for rotation about a first axis (40) at an angle to the axis of the output shaft (25). Driven shaft (34) mounted at the aperture end for rotation about a second axis (42) at an angle to the axis of the output shaft (25). There is an elongated link (30) coupled to finish (40) and second axis (42) to produce an oscillatory motion.

Steering wheel system

Abstract: A steering wheel mechanism which provides a driver with absolute confirmation of the direction of the orientation of the front wheels by a differential gear reduction mechanism which provides for a reduced amount of rotation of a buffer pad in comparison to the rotation of a steering wheel in which the buffer pad is located. The buffer pad contains display and switching groups which, because of the limited rotation, are easily accessible for purposes for control and ease of reading by the driver.

Nonlinear simulations of solar rotation effects in supergranules

Abstract: Nonlinear calculations for the three-dimensional and time dependent convective flow in a plane parallel layer of fluid are carried out with parameter values appropriate for supergranules on the Sun. A rotation vector is used which is tilted from the vertical to represent various latitudes. For the incompressible fluid used in this model the solar rotation produces turning motions sufficient to completely twist a fluid column in about one day. It is suggested that this effect will be greatly enhanced in a compressible fluid. The tilted rotation vector produces anisotropies and systematic Reynolds stresses which drive mean flows. The resulting flows produce a rotation rate which increases inward and a meridional circulation with poleward flow along the outer surface.

Mechanism of Flagellar Motor Rotation in Bacteria

Abstract: It has been found recently that the bacterial flagellar motor is driven by a proton flux according to its electrochemical potential gradient across the membrane. A model is presented for the mechanism of rotation of this motor, in which loose coupling is assumed between the proton flux and the motor rotation. A directional torque to rotate the motor is produced as a result of the interaction in many pairs of two kinds of molecules arranged on two rings, which is regulated by the binding of protons. The torque is calculated as a function of the electrochemical potential gradient of proton and pH values inside and outside the cell. The results of calculation are compared with experimental data and some experimental methods for further examination of the model are proposed.

Information recording/reproducing apparatus with disk having sections of different angular velocity

Abstract: In a data recording/reproducing apparatus, a DC motor is provided for rotating an optical disk. A recording/reproducing head is driven to move over the disk linearly in the radial direction of the disk, thereby defining a plurality of data-storing tracks on the disk. A motor control section is provided for controlling the rotation of the disk so as to change the angular velocity of the disk when the head tracing is changed among the track groups. While the head is tracing the tracks included in the same track group, the rotation of the disk is made constant so that the disk rotates at a constant angular speed.