Showing papers on "Rotation published in 1995"

Endoscopic surgical apparatus with rotation lock

Abstract: A surgical instrument is disclosed for use in a wide variety of roles including grasping, dissecting, clamping, or retracting materials or tissue during surgical procedures performed either in open surgery or within the abdominal cavity. The surgical instrument includes a handle portion, a tubular body portion extending from the handle portion and defining a longitudinal axis, and tool structure associated with a distal portion of the tubular body portion. A rotation assembly is provided for effectuating rotation of the tool structure about the longitudinal axis of the body portion. Rotation locking structure is provided to lock the rotation assembly at a predetermined orientation such that it cannot be rotated with respect to the handle.

Remote center positioning device with flexible drive

Abstract: A remote center positioner used to support an instrument and provide a center of spherical rotation, remote from any bearings or mechanical supports, at a desired location of the instrument. The remote center positioner is particularly useful in laparoscopic surgery to constrain a surgical instrument to move around a fixed center of rotation remote from any bearings or mechanical supports and coincident with an entry incision in the abdominal wall.

The evolution of vortices in vertical shear. I: Initially barotropic vortices

Abstract: The behaviour of initially-barotropic vortices in vertically-sheared environmental flows is investigated. the strength and structure of the vortices used are representative of tropical cyclones. the calculations are performed using a primitive-equation numerical model on an f-plane. It is found that the initial response of the vortex to the vertical shear is to tilt in the plane of the shear. As soon as a tilt is established, the upper- and lower-level centres begin to rotate cyclonically about the mid-level centre. This rotation can be understood in terms of upper- and lower-level potential-vorticity anomalies which are displaced in the horizontal relative to one another. the flow associated with the vertical projection of each anomaly advects the other anomaly, leading to the observed cyclonic rotation. the rotation rate decreases with time, so that the direction of tilt becomes constant, but the magnitude of the tilt continues to increase. We argue that the observed rotation acts to oppose the destructive action of the vertical shear on the vortex, even in the absence of diabatic processes. The role of the vertical circulation is considered in detail. It is shown that the vertical circulation develops in a manner which is consistent with the model flow remaining balanced. It is found that the mesoscale nature of the vertical circulation leads to a distortion of the axisymmetric vortex. This results in the inner core having a smaller vertical tilt than the outer region. the vertical circulation does not act on a large enough scale to explain why the vortex is not destroyed by the vertical shear. The behaviour of the vortex is found to depend on various parameters. Results are presented where the vertical shear, the strength and size of the vortex, the Coriolis parameter, and the static stability are varied. With the exception of the vertical shear, altering any of these parameters alters the vertical penetration of a potential-vorticity anomaly. the results show that increasing the penetration depth leads to an increase in the rotation rate of the upper- and lower-level vortex centres about the mid-level centre, and to a reduction in the magnitude of the vertical tilt.

Astigmatic mirror multipass absorption cells for long-path-length spectroscopy

Abstract: A multipass absorption cell, based on an astigmatic variant of the off-axis resonator (Herriott) configuration, has been designed to obtain long path lengths in small volumes. Rotation of the mirror axes is used to obtain an effective adjustability in the two mirror radii. This allows one to compensate for errors in mirror radii that are encountered in manufacture, thereby generating the desired reentrant patterns with less-precise mirrors. Acombination of mirror rotation and separation changes can be used to reach a variety of reentrant patterns and path lengths with a fixed set of astigmatic mirrors. The accessible patterns can be determined from trajectories, as a function of rotation and separation, through a general map of reentrant solutions. Desirable patterns for long-path spectroscopy can be chosen on the basis of path length, distance of the closest beam spot from the coupling hole, and tilt insensitivity. We describe the mathematics and analysis methods for the astigmatic cell with mirror rotation and then describe the design and test of prototype cells with this concept. Two cell designs are presented, a cell with 100-m path length in a volume of 3 L and a cell with 36-m path length in a volume of 0.3 L. Tests of low-volume absorption cells that use mirror rotation, designed for fast-flow atmospheric sampling, show the validity and the usefulness of the techniques that we have developed.

Contributions of Upper Limb Segment Rotations during the Power Serve in Tennis

Abstract: In the high-velocity tennis serve, the contributions that the upper limb segments' anatomical rotations make to racket head speed at impact depend on both their angular velocity and the instantaneous position of the racket with respect to the segments' axes of rotation. Eleven high-performance tennis players were filmed at a nominal rate of 200 Hz by three Photosonics cameras while hitting a high-velocity serve. The three-dimensional (3-D) displacement histories of 11 selected landmarks were then calculated using the direct linear transformation approach, and 3-D individual segment rotations for the upper limb were calculated using vector equations (Sprigings, Marshall, Elliott, & Jennings, 1994). The major contributors to the mean linear velocity of the center of the racket head of 31.0 m · s-1 at impact were internal rotation of the upper arm (54.2%), flexion of the hand (31.0%), horizontal flexion and abduction of the upper arm (12.9%), and racket shoulder linear velocity (9.7%). Forearm extension at t...

Rotation of principal components: choice of normalization constraints

Abstract: Following a principal component analysis, it is fairly common practice to rotate some of the components, often using orthogonal rotation. It is a frequent misconception that orthogonal rotation will produce rotated components which are pairwise uncorrelated, and/or whose loadings are orthogonal In fact, it is not possible, using the standard definition of rotation, to preserve both these properties. Which of the two properties is preserved depends on the normalization chosen for the loadings, prior to rotation. The usual ‘default’ normalization leads to rotated components which possess neither property.

A modulated bias unit for rotary drilling

Abstract: A modulated bias unit, for controlling the direction of drilling of a rotary drill bit when drilling boreholes in subsurface formations, comprises a number of hydraulic actuators spaced apart around the periphery of the unit, each having a movable thrust member which is hydraulically displaceable outwardly for engagement with the formation of the borehole being drilled A selector control valve modulates the fluid pressure supplied to each actuator in synchronism with rotation of the drill bit so that, as the drill bit rotates, each movable thrust member is displaced outwardly at the same selected rotational position so as to bias the drill bit laterally and thus control the direction of drilling The control valve is a disc valve comprising two relatively rotating elements having contiguous surfaces formed of polycrystalline diamond The elements are maintained in coaxial relation by a polycrystalline diamond bearing pin which extends axially from one element and engages in a central axial bearing aperture in the other element

A phenomenological treatment of rotating turbulence

Abstract: The strong similarity between the magnetohydrodynamic (MHD) turbulence and initially isotropic turbulence subject to rotation is noted. We then apply the MHD phenomenologies of Kraichnan and Matthaeus and Zhou to rotating turbulence. When the turbulence is subject to a strong rotation, the energy spectrum is found to scale as E(k) = C_Omega (Omega epsilon)^1/2 k^-2, where Omega is the rotation rate, k is the wavenumber, and epsilon is the dissipation rate. This spectral form is consistent with a recent letter by Zeman. However, here the constant C_Omega is found to be related to the Kolmogorov constant and is estimated in the range 1.22-1.8 for the typical values of the latter constant. A `rule'' that relates spectral transfer times to the eddy turnover time and the time scale for decay of the triple correlations is deduced. A hypothesis for the triple correlation decay rate leads to the spectral law which varies between the `-5/3'' (without rotation) and `-2'' laws (with strong rotation). For intermediate rotation rates, the spectrum varies according to the value of a dimensionless parameter that measures the strength of the rotation wavenumber k_Omega =(Omega^3/epsilon)^1/2 relative to the wavenumber k. An eddy viscosity is derived with an explicit dependence on the rotation rate.

Slow rotation of the Sun's interior

Abstract: THE rotation of the Sun is not that of a rigid body; at its surface, the gas near the poles has a lower angular velocity than that near the equator(1). This latitudinal variation persists to the base of the convection zone, below which the angular velocity becomes approximately uniform(2,3). Any variations of angular velocity at much greater depths are, however, poorly constrained(4-10). Observations of solar oscillation modes have been used to probe density variations in the Sun; rotational splitting of degenerate modes, although difficult to resolve, provides important constraints on the dynamical structure(11). Here we report observations of rotationally split: modes made over a three-year period with the Birmingham Solar Oscillations Network. Our results indicate that there is a substantial region inside the Sun that is rotating more slowly than the surface. This situation seems likely to be transient-the minimum-energy state would have all the deeper regions rotating with the same angular velocity-and is at variance with our current ideas about the rotational evolution of main-sequence stars(12). We have no solution to the dynamical problem this poses.

Shape and Non-Principal Axis Spin State of Asteroid 4179 Toutatis

Abstract: Radar observations of Toutatis placed hundreds to thousands of pixels per image on the asteroid and revealed it to be a non-principal axis rotator. The radar data are used to calculate Toutatis's three-dimensional shape, spin state, and the ratios of the principal moments of inertia. Toutatis is rotating in a long-axis mode characterized by periods of 5.41 days (rotation about the long axis) and 7.35 days (average for long-axis precession), and its dimensions along the principal axes are 1.92, 2.40, and 4.60 kilometers. To within the model's uncertainties, Toutatis's density is homogeneous, or its inhomogeneities mimic the inertia tensor of a homogeneous body.

The vestibulo-ocular reflex of the squirrel monkey during eccentric rotation and roll tilt

Abstract: The vestibulo-ocular reflexes (VOR) are determined not only by angular acceleration, but also by the presence of gravity and linear acceleration. This phenomenon was studied by measuring three-dimensional nystagmic eye movements, with implanted search coils, in six male squirrel monkeys during eccentric rotation. Monkeys were rotated in the dark at a constant velocity of 200 degrees/s (centrally or 79 cm off axis) with the axis of rotation always aligned with gravity and the spinal axis of the upright monkeys. The monkey's orientation (facing-motion or back-to-motion) had a dramatic influence on the VOR. These experiments show that: (a) the axis of eye rotation always shifted toward alignment with gravito-inertial force; (b) the peak value of horizontal slow phase eye velocity was greater with the monkey facing-motion than with back-to-motion; and (c) the time constant of horizontal eye movement decay was smaller with the monkey facing-motion than with back-to-motion. All of these findings were statistically significant and consistent across monkeys. In another set of tests, the same monkeys were rapidly tilted about their naso-occipital (roll) axis. Tilted orientations of 45 degrees and 90 degrees were maintained for 1 min. Other than a compensatory angular VOR during the angular rotation, no consistent eye velocity response was observed during or following the tilt for any of the six monkeys. The absence of any eye movement response following tilt weighs against the possibility that translational linear VOR responses are due to simple high-pass filtering of the otolith signals. The VOR response during eccentric rotation was divided into the more familiar angular VOR and linear VOR components. The angular component is known to depend upon semicircular canal dynamics and central influences. The linear component of the response decays rapidly with a mean duration of only 6.6 s, while the axis of eye rotation rapidly aligns (< 10 s) with gravito-inertial force. These results are consistent with the hypothesis that the measurement of gravito-inertial force by the otolith organs is resolved into central estimates of linear acceleration and gravity, such that the central estimate of gravitational force minus the central estimate of linear acceleration approximately equals the otolith measurement of gravito-inertial force.

Local rotation angle in the structural phase-transition for the mn2+ ion in a cscacl3 crystal

Abstract: In this paper, the spin-lattice coupling coefficient G(11) for Mn2+ in the cubic phase of a CsCaCl3 crystal has been calculated from the three microscopic mechanisms which contribute to zero-field splitting. Based on this, the local rotation angle phi(T) for Mn2+ in the tetragonal phase of a CsCaCl3 crystal is estimated from the EPR zero-held splitting b(2)(0)(T). The reasonableness of the local rotation angle is discussed.

Horizontal axis wind turbine

Abstract: A horizontal axis wind turbine comprises a rotor-supporting framework, a multi-vaned rotor, an electricity-generating stator, and a rotation track. The supporting framework is constructed with a plurality of triangular sub-units. The rotor has a plurality of vanes projecting therefrom. The vanes have adjustable pitch and are encircled by a rim having a plurality of magnets. Wind induces rotation of the rim. The stator is essentially stationary and is mounted on the framework opposite the rim. As magnets on the rotating rim pass by the stator, electricity is generated. The stator uses the pull of the magnets to automatically adjust itself to align with the rotating rim. The framework is mounted on the rotation track so that the framework can continually be adjusted to maximize wind-induced rotation of the rotor.

Cordless balanced window covering

Abstract: Disclosed is a spring motor and control for use especially with window blinds. The motor comprises a storage drum having a first axis, an output drum mounted for rotation about a second axis parallel to and spaced from the first axis. A spring member is connected to and between the storage drum and the output drum to form a spring motor. The spring motor has laterally extending, spaced apart drum supports on opposite sides of the drums to support them for rotation. A coupled drive is connected to the storage and output drum whereby rotation of one of the drums in a first direction about its axis effects rotation of the other of the drums about its axis and in an opposite direction to cause winding and unwinding of the spring member between the drums. A drive actuator is connected to the coupled drive to effect rotation of the drums, and an adjustable friction member is engageable with one of the coupled drive and the drive actuator to adjustably alter the force necessary to effect movement of the coupled drive.

Planetary gear train for automatic transmission and gear shift for automatic transmission

Abstract: PROBLEM TO BE SOLVED: To easily reduce shift shock and also facilitate shift control by providing a first two-element connecting member for constantly connecting a first gear to a second ring gear (or a second sun gear). SOLUTION: A first two-element connecting member M1 integrally connects a first carrier P1 with a second ring gear R2 and a second two-element connecting member M2 connects the first two-element connecting member M1 with a third carrier P3 through a first clutch C1, while a third two-element connecting member M3 integrally connects a second carrier P2 with a third ring gear R3. A first speed gear step can be accomplished by making the first clutch C1, a second clutch C2 and a first brake B1 engage with each other. Therefore rotation of a rotation member B is regulated by input rotation from a rotation member A and fixation of a rotation member B. A first speed change gear ratio by under drive of a large reduction gear ratio to the rotation of an input shaft IS can be obtained from an output shaft OS connected to the rotation member B.

Methods for positioning a surgical instrument about a remote spherical center of rotation

Abstract: The invention is directed to a remote center positioner used to support an instrument and provide a center of spherical rotation, remote from any bearings or mechanical supports, at a desired location of the instrument. The remote center positioner is particularly useful in laparoscopic surgery to constrain a surgical instrument to move around a fixed center of rotation remote from any bearings or mechanical supports and coincident with an entry incision in the abdominal wall.

Laser processing method

Abstract: A laser processing method is to be executed by a pair of turning mirrors of which axes of rotation are arranged in mutually twisted positions, a flat field lens for converging a laser beam reflected on the pair of turning mirrors on a specified plane, and an X-Y stage which carries and moves thereon an object to be processed to which the laser beam is applied, the object having a plurality of rectangular planar areas of the same shape as each other in a matrix form and adjoining the rectangular planar areas while not overlapping the rectangular planer area nor leaving any space therebetween The method includes a first step of executing application of the laser beam of which a laser applying position is determined by the pair of turning mirrors and the flat field lens to one of the rectangular planar areas of the object, a second step of moving an X-axis stage or a Y-axis stage of the X-Y stage after the first step is completed, a third step of executing application of the laser beam to one of the rectangular planar areas which is adjacent to the rectangular planar area to which the latest application of the laser beam is performed, and a fourth step of executing the second and third steps alternately to process the plurality of rectangular planar areas of the object

Measurement of the rotation rate in the deep solar interior

Abstract: We present a measurement of solar internal rotation based on observations obtained over 3 months in early 1994 with a new instrument called LOWL. This instrument allows for the simultaneous observation of low- and intermediate-degree solar oscillations with spatial resolution. We have measured the frequency splitting of 673 multiplets with degrees ranging from 1 to 80 and inverted these to derive an estimate of the solar internal rotation profile between 0.2 and 0.85 R☉. The accuracy of this measurement ranges from ~1% in the outer regions to ~5% at 0.2 R☉ and thus places better constraints than hitherto on the rotation in the deep solar interior. We confirm earlier findings that near the base of the convection zone the solar rotation profile undergoes a transition from surface-like differential rotation to a rotation rate that is independent of latitude. In addition, we find that from the base of the convection zone down to 0.2 R☉ our measurement is consistent with rigid body rotation at a rate somewhat lower than the surface equatorial rate. The accuracy of our measurement in the deep solar interior provides a strong constraint to theories of solar and stellar angular momentum transport.

Stabilization of ideal modes by resistive walls in tokamaks with plasma rotation and its effect on the beta limit

Abstract: It is shown that pressure‐driven, ideal external modes in tokamaks can be fully stabilized by resistive walls with plasma rotation. For wall stabilized plasmas, there are two types of potentially unstable external modes: (i) the ‘‘resistive wall modes’’ that penetrate, and are nearly locked to the wall, and (ii) modes that rotate with the plasma and for which the wall acts as a good conductor. For the quickly rotating modes, the stabilizing effect of the wall increases when the wall is brought closer to the plasma, while for the resistive wall modes, the stabilization improves with increasing wall distance. When the plasma rotates at some fraction of the sound speed, there is a window of stability to both the wall‐locked and the rotating mode. The stabilization depends principally on the toroidal coupling to sound waves and is affected by ion Landau damping. Two‐dimensional stability calculations are presented to evaluate the gains in beta limit resulting from this wall stabilization for different equilibria and rotation speeds. Results are shown for advanced tokamak configurations with bootstrap fractions of ≊100%.

Reversible axial segregation of rotating granular media

Abstract: Experimental measurements of axial segregation of binary mixtures of granular media combined in a horizontal cylinder and rotated like a drum mixer are reported. While in the traditional axial segregation effect the mixture of two different sizes of granular media will separate into bands of relatively pure single concentrations along the axis of rotation, in special cases the homogeneous mixed state can be restored simply by decreasing the speed of rotation. Systematic variation of the relative diameters of the components reveal three classes of behavior: no segregation at any rotation speed, a nonreversible axial segregation, and an axial segregation at high speeds that reverses back into the mixed state at low speeds. Measurements of the dynamic angle of repose of the mixed and segregated phases as a function of rotation speed support a model for the axial segregation effect that involves a diffusion equation with an effective axial diffusion coefficient that can be negative under the conditions for which segregation occurs.

A Biological Basis for Instantaneous Centres of Rotation of the Vertebral Column

Abstract: The instantaneous centre of rotation has proven to be a useful parameter of vertebral motion. The normal location of instantaneous centres has been determined in cadavers and in normal volunteers for the cervical, thoracic and lumbar spines, and abnormal location of centres has been shown to correlate with spinal pain. However, to date, an instantaneous centre has constituted no more than a convenient mathematical summary of vertebral kinematics. It has defied resolution into biologically meaningful parameters. This study offers a novel model of vertebral motion in which the instantaneous centre of rotation can be shown to be a function of the location of the centre of reaction of a vertebra, and the intrinsic rotation and translation it undergoes. These parameters are strictly linked by equations that determine the location of an axis of rotation. These equations allow aberrations in the location of an axis to be interpreted in terms of the anatomical and pathological factors that affect the centre of reaction of the vertebra and the rotation and translation it undergoes.

Prediction of Turbulent Flow and Heat Transfer in a Ribbed Rectangular Duct With and Without Rotation

Abstract: The present study deals with the numerical prediction of turbulent flow and heat transfer in a 2:1 aspect ratio rectangular duct with ribs don the two shorter sides. The ribs are of square cross section, staggered and aligned normal (90 deg) to the main flow direction. The ratio of rib height to duct hydraulic diameter equals 0.063, and the ratio of rib spacing to rib height equals 10. The duct may be stationary or rotating. The axis of rotation is normal to the axis of the duct and parallel to the ribbed walls (i.e., the ribbed walls form the leading and the trailing faces). The problem is three dimensional and fully elliptic; hence, for computational economy, the present analysis deals only with a periodically fully developed situation where the calculation domain is limited to the region between two adjacent ribs. Turbulence is modeled with the {kappa}-{epsilon} model in conjunction with wall functions. However, since the rib height is small, use of wall functions necessitates that the Reynolds number be kept high. (Attempts to use a two-layer model that permits integration to the wall did not yield satisfactory results and such modeling issues are discussed at length.) Computations are made heremore » for Reynolds number in the range 30,000--100,000 and for Rotation number = 0 (stationary), 0.06, and 0.12. For the stationary case, the predicted heat transfer agrees well with the experimental correlations. Due to the Coriolis-induced secondary flow, rotation is found to enhance heat transfer from the trailing and the side walls, while decreasing heat transfer from the leading face. Relative to the corresponding stationary case, the effect of rotation is found to be less for a ribbed channel as compared to a smooth channel.« less

Monolithic silicon rate-gyro with integrated sensors

Abstract: A monolithic single crystal Si rate-gyro is disclosed, consisting in the preferred embodiment of an outer torsional frame (101), self-resonating with a substantial amplitude, as controlled by a four-terminal piezo torsion sensor (111), connected to an inner frame (105) by torsion hinges (103). The inner frame itself is connected to a fixed inner post (117), by a set of torsion hinges (107), defining an axis of rotation perpendicular to the first axis. Rotation of the axis of oscillation of the outer body causes the moving mass and the inner frame to tilt and oscillate at the outer frequency due to Coriolis forces, thereby periodically deforming the inner hinges in torsion. These inner hinges are likewise equipped with a four-terminal piezo voltage torsion sensor (115), giving an indication of the rate of rotation of the sensor. The design allows for good sensitivity, due to the substantial swing of the outer oscillator, its high moment of inertia, excellent Si spring characteristics, and excellent sensitivity of the torsional sensors.

Line Formation in Collapsing Cloud Cores with Rotation and Applications to B335 and IRAS 16293-2422

Abstract: We present radiative transfer models of collapsing clouds with rotation and apply them to B335 and IRAS 16293-2422, the two best candidates of protostellar collapse known to date. By including rotation in the manner of Tereby, Shu, & Cassen (1984), we can reproduce the profiles of several molecular lines not only toward the center position, but also toward a grid of positions near the center. We find that the model of B335 by Zhou et al. (1993) is not affected significantly by the presence of rotation. By including rotation, we can reproduce the observations of IRAS 16293-2422 by Menden et al. (1987); hence, we support the infall interpretations of spectral lines from IRAS 16293-2422 proposed by Walker et al. (1986). We also observed the large-scale rotation of IRAS 16293-2422 in the C(18)O J = 2 approaches 1 line. The observed rotation rate is a factor of 6 smaller than that required to explain the small-scale CS data of Menden et al. (1987). This probably means the precollapse cloud has differential rotation, possibly due to more efficient magnetic braking on large scales.