Showing papers on "Rotation published in 1994"

Positional feedback system for medical mattress systems

Abstract: An apparatus adjusts the pressures of a therapeutic mattress surface in accordance with the angular position of that surface. The apparatus comprises an angular position sensor and a rotation sensor which are housed together in an enclosure having a top surface in the form of a circular plate. The circular plate mounts either on the surface of the mattress or on the bottom of a bed frame supporting the mattress. The angular position and rotation sensors measure the horizontal plane referenced perpendicular to the direction of the force of gravity. The apparatus further comprises a controller blower valve assembly which processes data received from the angular position and rotation sensors to maintain, increase, or decrease the pressures within the mattress.

Computer interface or control input device for laparoscopic surgical instrument and other elongated mechanical objects

Abstract: An apparatus for interfacing the movement of a shaft with a computer includes a support, a gimbal mechanism having two degrees of freedom, and three electromechanical transducers. When a shaft is engaged with the gimbal mechanism, it can move with three degrees of freedom in a spherical coordinate space, where each degree of freedom is sensed by one of the three transducers. A fourth transducer can be used to sense rotation of the shaft around an axis. The method includes the steps of defining an origin in 3-dimensional space, physically constraining a shaft in the 3-dimensional space such that a portion of the shaft always intersects the origin and such that a portion of the shaft extending beyond the origin defines a radius in a spherical coordinate system, transducing a first electrical signal related to a first angular coordinate of the radius with a first transducer, transducing a second electrical signal related to a second angular coordinate with a second transducer, transducing a third electrical signal related to the length of the radius with a third transducer, and coupling the transducers to a computer.

Optically induced rotation of anisotropic micro‐objects fabricated by surface micromachining

Abstract: Optical trapping and directional high‐speed rotation by radiation pressure are demonstrated for anisotropic micro‐objects fabricated by reactive ion‐beam etching. These micro‐objects, which have shape dissymmetry (not bilateral symmetry but rotational symmetry) in the horizontal cross section, rotate about the laser beam axis in the designed direction in a liquid medium (e.g., water or alcohol). The rotation speed is almost proportional to the input laser power.

Noninvasive method and apparatus for determining resonance information for rotating machinery components and for anticipating component failure from changes therein

Abstract: A method and apparatus is described for determining resonant frequencies of vibration of turbine (20) and (22) and fan shafts (16) and blades, and other rotating machines (12) in which a rotating element of the machine (12) has oscillatory vibrations that modulate the fundamental frequency of rotation of the rotating machine (12). A sensor (30) monitors the machine (12), providing a train of sensor pulses or other signal representative of angular rotation of the machine (12). The signal is processed to provide a signal representative of the modulation of the fundamental frequency of rotation of the rotating machine (12), which signal is processed to provide a frequency spectrum representative of instantaneous-frequency components present. The signal spectrum is electronically processed to provide resonance-information, spectral signals representative of frequency or amplitude characteristics, or both, for the resonant vibrations. Signal-processing methods (36) include use of Fast Fourier Transform and Discrete Fourier Transform.

Inertial representation of angular motion in the vestibular system of rhesus monkeys. I. Vestibuloocular reflex.

Abstract: 1. The spatial organization of the vestibuloocular reflex (VOR) was studied in six rhesus monkeys by applying fast, short-lasting, passive head and body tilts immediately after constant-velocity rotation (+/- 90 degrees/s) about an earth-vertical axis. Two alternative hypotheses were investigated regarding the reference frame used for coding angular motion. 1) If the vestibular system is organized in head-centered coordinates, postrotatory eye velocity would decay invariably along the direction of applied head angular acceleration. 2) Alternatively, if the vestibular system codes angular motion in inertial, gravity-centered coordinates, postrotatory eye velocity would decay along the direction of gravity. 2. Horizontal VOR was studied with the monkeys upright. Pitch (roll) tilts away from upright elicited a transient vertical (torsional) VOR and shortened the time constant of the horizontal postrotatory slow phase velocity. In addition, an orthogonal torsional (after pitch tilts) or vertical (after roll tilts) response gradually built up. As a result, the eye velocity vector transiently deviated in the roll (pitch) plane and then gradually rotated in the same direction as gravity in the pitch (roll) head plane until the orthogonal component reached a peak value. Subsequently, the residual postrotatory eye velocity decayed along a line parallel to gravity. 3. The time constant of the horizontal postrotatory response was maximal in upright position (21.5 +/- 5.7 s, mean +/- SD) and minimal after tilts to prone (3.8 +/- 0.7 s), supine (4.5 +/- 1.2 s), and ear-down (5.2 +/- 1.6 s) positions. A similar dependence on head orientation relative to gravity characterized the dynamics of the resultant eye velocity vector in the pitch and roll planes. 4. Torsional VOR was studied with the monkeys in supine or prone position. Pitch (yaw) tilts from the supine or prone position toward upright (ear-down) position elicited a transient vertical (horizontal) VOR and shortened the time constant of the torsional postrotatory response while a horizontal (vertical) orthogonal component slowly built up. As a result the eye velocity vector gradually rotated in the pitch (yaw) plane until the orthogonal component reached a peak value. Subsequently residual postrotatory eye velocity decayed along a line parallel to gravity. 5. The time constant of the torsional postrotatory response in supine/prone positions was 16.5 +/- 6.8 s. After tilts from supine/prone positions toward upright position, time constants decreased and were minimal after tilts to upright position (2.7 +/- 0.7 s).(ABSTRACT TRUNCATED AT 400 WORDS)

Negative viscosity of ferrofluid under alternating magnetic field

Abstract: A stationary magnetic field induces an increase in the ferrofluid viscosity An additional resistance to the flow occurs due to the field oriented magnetic particles impeded by free rotation in a vortex flow It is shown that in an alternating, linearly polarized magnetic field the additional viscosity is positive at low frequencies of the field and negative at high frequencies The point is that an alternating field induces rotatory oscillations of the particles, but does not single out any direction of their rotation One can say that half of the particles rotate clockwise and the other half counterclockwise Hence, the macroscopic angular velocity of the particles equals zero However, this corresponds only to fluid at rest Any shear (ie, any vorticity) is sufficient to break down the degeneracy of the direction of rotation, which results in the nonzero angular velocity of the particles The occurring ‘‘spin up’’ of the flow by the rotating particles leads to the decrease of the effective viscosity,

A numerical modelling study of the geostrophic adjustment process following deep convection

Abstract: A high resolution numerical model based on the anelastic equations of motion is used to simulate the geostrophic adjustment process that follows the growth of a single, deep convective plume. Interest focuses on the form of the balanced state and the proportions of energy which go into gravity waves, dissipation and balanced flow. Three simulations are described: a non-rotating case, an intermediate rotation case (f= 10−3S−1) and a high rotation case (f= 2 × 10−3S-1). The use of these artificially high rotation rates (in the context of the terrestial atmosphere) is regarded as a device for shortening the adjustment time thereby rendering the objective of the study computationally feasible. The model simulations are two-dimensional and use an idealized specification of the moist process in which precipitation is instantaneous and no cloud is permitted. The initial state of the model atmosphere is calm and horizontally-stratified except for a warm, moist bubble near the surface. Integrations are carried out for 50000 s by which time quasi-steady flow states are achieved. In the rotating cases, the final quasi-balanced state takes the form of a well-defined lens-shaped region of uniform absolute momentum at the neutral buoyancy level and an intense, vertical shear line front extending upwards from the surface. The response is characterized by two length scales: the Rossby radius of deformation based on the depth of the convection, and a mesoscale cloud scale related to the amount of mass which convects and the rotation rate, amongst other factors. It is found that - 30% of the kinetic energy released in convection is captured in balanced flow- considerably larger than indicated in earlier studies and not dependent on the high rotation rates used here. Simple scaling arguments are used to account for the efficiency of balanced energy retention as a function of the amount of mass that convects and to define an upper bound on the amount of mass that can be convected through a single plume in a rotating environment. This is tentatively identified with a maximum possible scale for mesoscale convective systems. An analytic model for the balanced state is presented and shown to fit the simulated flow very well. The success of this model underlines the secondary role played by mixing in the numerical model.

A note on the spectra and decay of rotating homogeneous turbulence

Abstract: In this Letter, the dynamics of spectral energy transfer in rotating homogeneous turbulence is investigated. It is shown that the wave number kΩ=(Ω3/e)1/2 (defined by the rotation speed Ω and dissipation e) determines the turbulence length scale, above which rotation effects on spectral transfer and on energy spectrum form are important. From the rotation‐modified spectrum, turbulence decay laws are also inferred.

Passive earth pressures with various wall movements

Abstract: This paper presents experimental data of earth pressure acting against a vertical rigid wall, which moved into a mass of dry sand with a stress‐free horizontal surface under various wall‐movement modes. To investigate the variation of earth pressure induced by the rotation about a point above the top (RTT) and rotation about a point below the wall base (RBT) types of wall movement, the instrumented retaining‐wall facility was developed at National Chiao Tung University. Based on experimental data it is found that, for a wall under translational movement, the passive pressure distribution is linear and in good agreement with Terzaghi's prediction based on the general wedge theory. For a wall under either RTT or RBT mode, the magnitude of passive thrust and its point of application are significantly affected by the mode of wall displacement. However, if the parameter n indicating location of the center of rotation is greater than 2.0, the influence of movementmode on passive earth pressure becomes less impo...

Two-axis magnetically coupled robot

Abstract: A robot having a pair of magnetic couplings that each couple a motor in a cylindrical first chamber to an associated cylindrical ring closely spaced from the cylindrical wall of said first chamber. The robot includes a mechanism to convert rotation of each of these rings into separate motions of the robot. In the preferred embodiment, these separate motions are radial and rotational.

Strut assembly with integral bearing and spring seat

Abstract: A quarter car vehicle suspension including a wheel, a bearing having an axis of rotation, the piston rod axis aligned at an acute angle with respect to a spring axis of a coil spring of the suspension, and a spring seat integral with the bearing, wherein the bearing is located between the spring seat and the vehicle body, and wherein the axis or rotation of the bearing is substantially aligned with a spring axis and at an acute angle to the piston rod axis.

Stability analysis and large-eddy simulation of rotating turbulence with organized eddies

Abstract: Rotation strongly affects the stability of turbulent flows in the presence of large eddies. In this paper, we examine the applicability of the classic Bradshaw-Richardson criterion to flows more general than a simple combination of rotation and pure shear. Two approaches are used. Firstly the linearized theory is applied to a class of rotating two-dimensional flows having arbitrary rates of strain and vorticity and streamfunctions that are quadratic. This class includes simple shear and elliptic flows as special cases. Secondly, we describe a large-eddy simulation of initially quasi-homogeneous three-dimensional turbulence superimposed on a periodic array of two-dimensional Taylor-Green vortices in a rotating frame.The results of both approaches indicate that, for a large structure of vorticity W and subject to rotation Ω, maximum destabilization is obtained for zero tilting vorticity (½W + 2Ω = 0) whereas stability occurs for zero absolute vorticity (2Ω = 0) These results are consistent with the Bradshaw-Richardson criterion; however the numerical results show that in other cases the Bradshaw-Richardson number is not always a good indicator of the flow stability.

Image forming device having sheet conveyance device

Abstract: An image forming device for forming an image on a sheet. A pair of transport rollers are provided for transporting the sheet by their rotation so that the sheet exits from between the pair of rollers while substantially aligned with a tangent plane of both of the pair of rollers. An elongated chute is provided for guiding the sheet after the sheet exits from between the pair of transport rollers. The chute is supported so as to intersect the tangent plane to cross from one side of the tangent plane to another in the direction followed by the sheet. A toner control electrode is supported adjacent to the chute at its end opposite the transport rollers. A back electrode with an electrode tip is supported so that the electrode tip confronts the toner control electrode as separated by a space. The sheet is transported through the space as guided by the chute.

Simplimax: oblique rotation to an optimal target with simple structure

Abstract: Factor analysis and principal component analysis are usually followed by simple structure rotations of the loadings. These rotations optimize a certain criterion (e.g., varimax, oblimin), designed to measure the degree of simple structure of the pattern matrix. Simple structure can be considered optimal if a (usually large) number of pattern elements is exactly zero. In the present paper, a class of oblique rotation procedures is proposed to rotate a pattern matrix such that it optimally resembles a matrix which has an exact simple pattern. It is demonstrated that this method can recover relatively complex simple structures where other well-known simple structure rotation techniques fail.

Heat Transfer in Rotating Serpentine Passages With Selected Model Orientations for Smooth or Skewed Trip Walls

Abstract: Experiments were conducted to determine the effects of model orientation as- well as buoyancy and Coriolis forces on heat transfer in turbine blade internal coolant passages. Turbine blades have internal coolant passage surfaces at the leading and trailing edges of the airfoil with surfaces at angles that are as large as ± 50 to 60 deg to the axis of rotation. Most of the previously presented, multiple-passage, rotating heat transfer experiments have focused on radial passages aligned with the axis of rotation. The present work compares results from serpentine passages with orientations 0 and 45 deg to the axis of rotation, which simulate the coolant passages for the midchord and trailing edge regions of the rotating airfoil

Reversible axial segregation of binary mixtures of granular materials

Abstract: Measurements of axial segregation of binary mixtures of glass beads having different diameters in a rotating horizontal cylinder are reported. For rotation speeds of \ensuremath{\sim}15 rpm a mixed state quickly (within a few minutes) segregates into sharp bands of alternating large and small glass beads along the axis of rotation. Decreasing the rotation speed to \ensuremath{\sim}5 rpm causes the bands to disappear, restoring the mixed state. The process is reversible upon increasing the rotation rate, though the exact location and width of the bands vary from run to run. The axial segregation phenomena are analyzed in terms of a diffusion equation where the effective diffusion coefficient is the difference between segregating drift and normal Fickian diffusion.

A Faint Luminous Halo that May Trace the Dark Matter around Spiral Galaxy NGC~5907

Abstract: The presence of unseen halos of ``dark matter'' has long been inferred from the high rotation speeds of gas and stars in the outer parts of spiral galaxies$^{1}$. The volume density of this dark matter decreases less quickly from the galactic center than does that of the luminous mass (such as that in stars), meaning that the dark matter dominates the mass far from the center$^{1,2}$. While searching for faint starlight away from the plane of the edge-on disk galaxy \gal$^{3}$, we have found that the galaxy is surrounded by a faint luminous halo. The intensity of light from this halo falls less steeply than any known luminous component of spiral galaxies, but is consistent with the distribution of dark mass inferred from the galaxy's rotation curve.

Adjustable lumbar support

Abstract: An adjustable lumbar support for the backrest of a seat, including an elongate flexible band (3) having first and second ends attachable to sides (9) of a backrest. Drive means (24) is connected to the band (3) so as to tension the band (3) and so decrease the extent to which the band (3) curves rearwardly with respect to the ends thereof. The band (3) includes a plurality of pleats (14, 15), extending transverse to the length of the band (3) and arranged to expand or collapse in response to changes in the longitudinal tension in the band (3). As shown, the pleats (14, 15) form part of a shield overlying a tensionable strap (10). In another arrangement (not shown) the pleats are disposed between and interconnect adjacent relatively rigid rib-like elements. The drive (24) may include a motor (25) driving a screw-threaded spindle arranged at right angles thereto and connected to the band (3) so that the spindle extends in the longitudinal direction of the band (3). A carriage (28) responds to rotation of the spindle (26) so as to tension the band (3).

Endoscopic surgical instrument having curved blades

Abstract: An endoscopic surgical instrument having a handle assembly, a body portion, and a tool mechanism in which a pivoting handle pivots about a stationary handle to open and close the tool mechanism. The instrument includes a rotatable body portion, in which a rotation knob is provided on the instrument at the stationary handle so that the user may rotate the body portion, and consequently the tool mechanism, using a single hand. Furthermore, an electrocautery connection is provided which is positioned out of the line of sight of the surgeon, so that the surgeon may have an unobstructed view to the surgical site. The pivoting handle is provided with a rotatable connection point for connecting the slidable rod member to essentially eliminate radial deflection of the rod within the outer tube during opening and closing of the handles. The instrument also includes crescent-shaped blades which are curved in a plane defined by the pivot axis of the blades and the longitudinal axis of the instrument.

Magnetohydrodynamic Ekman and Stewartson Layers in a Rotating Spherical Shell

Abstract: I investigate numerically the flow of an electrically conducting fluid in a differentially rotating spherical shell, in the presence of an imposed magnetic field. For a very weak field the flow is seen to consist of an Ekman layer on the inner and outer spherical boundaries, and a Stewartson layer on the cylinder circumscribing the inner sphere and parallel to the axis of rotation, in agreement with the classical non-magnetic analysis. As the field strength is increased, the non-magnetic Ekman layers merge smoothly into magnetic Ekman-Hartmann layers, and the Stewartson layer is suppressed. In the fully magnetic regime the interior flow consists essentially of a solid-body rotation, with the precise rate determined by a torque balance between the inner and outer Ekman-Hartmann boundary layers.