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Showing papers on "Rotation published in 1992"


Journal Article
TL;DR: In this article, an examination of the structure and previous evolution of the tachocline of the Sun is presented, assuming that the convection zone is prescribed, much as oceanographers take the wind stress on the sea surface as given.
Abstract: Acoustic sounding of the Sun reveals that the variation of angular velocity with latitude is independent of depth in the convection zone. By contrast, deep within the radiative zone, the rotation appears to be rigid. The transition between the two rotation laws occurs in a thin, unresolved layer that we here call the tachocline. This paper is an examination of the structure and previous evolution of this layer. We assume that the stress exerted by the convection zone is prescribed, much as oceanographers take the wind stress on the sea surface as given.

271 citations


Journal ArticleDOI
TL;DR: To study the VOR response to combined rotation and translation, monkeys were placed on a rate table and rotated briefly in the dark about a vertical axis that was located in front of or behind the eyes to suggest a formal model of the V OR consisting of four channels.
Abstract: 1. The vestibuloocular reflex (VOR) stabilizes images on the retina against movements of the head in space. Viewing distance, target eccentricity, and location of the axis of rotation may influence VOR responses because rotation of the head about most axes in space rotates and translates the eyes relative to visual targets. To study the VOR response to combined rotation and translation, monkeys were placed on a rate table and rotated briefly in the dark about a vertical axis that was located in front of or behind the eyes. The monkeys fixated a near or far visual target that was extinguished before the rotation. Eye movements were recorded from both eyes by the use of the search coil technique. 2. Peak eye velocity evoked by the VOR was linearly related to vergence angle for any axis of rotation. The percent change in the VOR with near target viewing relative to far target viewing at a vergence angle of 20 degrees was linearly related to the location of the axis of rotation. Axes located behind the eyes produced positive changes in VOR amplitude, and axes located in front of the eyes produced negative changes in VOR amplitude. An axis of rotation located in the coronal plane containing the centers of rotation of the eyes produced no modification of VOR amplitude. For any axis, the VOR compensated for approximately 90% of the translation of the eye relative to near targets. 3. The initial VOR response was not correct in magnitude but was refined by a series of three temporally delayed corrections of increasing complexity. The earliest VOR-evoked eye movement (10-20 ms after rotation onset) was independent of viewing distance and rotational axis location. In the next 100 ms, eye speed appeared to be sequentially modified three times: within 20 ms by viewing distance; within 30 ms by otolith translation; and within 100 ms by eye translation relative to the visual target. 4. These data suggest a formal model of the VOR consisting of four channels. Channel 1 conveys an unmodified head rotation signal with a pure delay of 10 ms. Channel 2 conveys an angular head velocity signal, modified by viewing distance with a pure delay of 20 ms, but invariant with respect to the location of the axis of rotation. Channel 3 conveys a linear head velocity signal, dependent on the location of the axis of rotation, that is modified by viewing distance with a pure delay of 30 ms.(ABSTRACT TRUNCATED AT 400 WORDS)

152 citations


Journal ArticleDOI
TL;DR: It appears to be possible to move and rotate cells or particles at will using very-high-frequency fields and media of increased relative permittivity, as shown by experimental data on levitation and rotation.

132 citations


Journal ArticleDOI
TL;DR: In three rhesus monkeys three-dimensional eye positions were measured with the dual search coil technique with a constant torsional component added to all eye positions.

121 citations


Journal ArticleDOI
TL;DR: In this paper, the authors revisited the neoclassical theory of plasma rotation in tokamaks in order to account for anomalous transport driven by a turbulence, and showed that this model yields both steep and gradual profiles for the poloidal rotation velocity at the edge corresponding to the H and L regimes of confinement.
Abstract: It is well known that usual assumptions of neoclassical theory become invalid if very large gradients occur at the plasma edge. Therefore neoclassical theory of plasma rotation in tokamaks is revisited in order to account for anomalous transport driven by a turbulence. It is shown that this model yields both steep and gradual profiles for the poloidal rotation velocity at the edge corresponding to the H and L regimes of confinement, respectively. Results and conclusions are focused on experiments employing the biased electrode technique. Regimes with fast poloidal rotation in excess of poloidal sound speed are considered with the emphasis on relaxation.

119 citations


Journal ArticleDOI
TL;DR: In this article, the spatial distribution of seismic moment tensors of earthquakes in the Aegean region over the time interval 1909-1983 was used to recover a continuous horizontal velocity field that describes the overall deformation of the lithosphere at large length scales.
Abstract: We use the spatial distribution of seismic moment tensors of earthquakes in the Aegean region over the time interval 1909–1983 to recover a continuous horizontal velocity field that describes the overall deformation of the lithosphere at large length scales. The calculated velocity field is dominated by two effects: (1) an E-W right-lateral shear of the eastern Aegean, related to motion on the North Anatolian fault becoming distributed as it enters the Aegean; and (2) a N-S extension, probably related to the sinking of the slab in the Hellenic Trench. The southern part of the central Aegean is found to be moving in a SW direction relative to Europe at a rate of about 30 mm/yr (probably a lower bound, with an error of around ± 10 mm/yr) and rotating clockwise. In the seismogenic upper crust this velocity field is accommodated by right-lateral strike-slip faults in the eastern Aegean and by normal faults that rotate clockwise in central Greece. A comparison of paleomagnetic declination data with the expected rotation of rigid elongate inclusions in the velocity field shows in most places an agreement in sense and approximate agreement in rate of rotation. Expected rotation rates of line elements are sometimes too low: probably because our derived velocity field is smoothed and unable to match locally high strain rates. There is only one part of the region where line elements are predicted to rotate in either clockwise or counterclockwise directions, depending on their orientation; this is in western Turkey, which, coincident ally, is the only place where paleomagnetic rotations in both directions have been observed. This coincidence in particular suggests to us that the analogy of rigid elongate inclusions in the velocity field, responding to forces on their bases, may be useful in predicting the senses and approximate rates of rotation of crustal blocks in deforming continental regions. The velocity field we obtain preserves the strike directions of the major faults as directions of zero length change, in spite of considerable smoothing. We use this observation to speculate that the interaction between the upper crust and the rest of the lithosphere beneath it may involve an interplay of effects. On one hand the variation of strength with direction in the crust may control the strike directions of faults that form or become reactivated and may also limit the velocity fields that are allowable. On the other hand, the fault bounded blocks may rotate in the velocity field in response to forces on their bases, which would require the velocity field to change with time if the directions of zero length change are fixed to the blocks.

116 citations


Patent
11 Feb 1992
TL;DR: In this paper, a bicycle wheel-type tension-compression support structure for a solar radiation collector system is presented, which is rotatably supported from the ground in a manner to allow for three dimensionally stable support and rotation of at least ninety degrees with respect to the ground.
Abstract: A solar radiation collector system includes a curved rim, a collector assembly including a plurality of solar radiation transducer elements passing through the plane of and connected to the curved rim, and a plurality of relatively small diameter tension members connected in distributed manner between the curved rim and the collector assembly and forming a stiff, lightweight, bicycle wheel-type tension-compression support structure. The support structure is rotatably supported from the ground in a manner to allow for three dimensionally stable support and rotation of at least ninety degrees with respect to the ground. Rotation of the bicycle wheel-type tension-compression support structure provides for a desired primary tracking motion to adjust for the apparent motion of the sun, and movement of the transducer elements provides for a second dimension adjustment for the apparent motion of the sun.

104 citations


Patent
11 Sep 1992
TL;DR: In this article, a micromechanical tuning fork gyroscope is fabricated from a unitary silicon substrate utilizing etch stop diffusions and selective anisotropic etching.
Abstract: A, micromechanical tuning fork gyroscope is fabricated from a unitary silicon substrate utilizing etch stop diffusions and selective anisotropic etching. A silicon structure is suspended over the selectively etched pit. The silicon structure includes at least first and second vibratable structures. Each vibratable structure is energizable to vibrate laterally along an axis normal to the rotation sensitive axis. The lateral vibration of the first and second vibratable structures effects simultaneous vertical movement of at least a portion of the silicon structure upon the occurrence of angular rotation of the gyroscope about the rotation sensitive axis. The vertical movement of the silicon structure is sensed, and a voltage proportional to the movement is generated, for providing an indication of angular rate of rotation detected by the gyroscope.

99 citations


Journal ArticleDOI
31 Jul 1992-Science
TL;DR: Simulated circulations converge to yield nearly the same zonal winds when initialized with both stronger or weaker rotation rates, and support the hypothesis that the observed cloud-top rotation rate is maintained by statistical balance between fluxes of momentum by thermal tides and momentum advection by mean meridional circulation.
Abstract: The cloud-level atmosphere of Venus takes little more than 4 days to complete one rotation, whereas the solid planet below has a 243-day period. Computer simulations of the circulation of the Venus middle atmosphere between 40 and 85 kilometers, as driven by solar radiation absorbed in the clouds, reproduce (i) the observed cloud-level rotation rate, (ii) strong vertical shears above and below the cloud tops, and (iii) midlatitude jets and strong poleward flow on the day side. Simulated circulations converge to yield nearly the same zonal winds when initialized with both stronger or weaker rotation rates. These results support the hypothesis that the observed cloud-top rotation rate is maintained by statistical balance between fluxes of momentum by thermal tides and momentum advection by mean meridional circulation.

95 citations


Patent
26 Feb 1992
TL;DR: A variable capacity swash plate type compressor adapted to being driven by a vehicle engine without the intervention of a solenoid clutch and having a drive shaft rotating about an axis of rotation thereof is described in this paper.
Abstract: A variable capacity swash plate type compressor adapted to being driven by a vehicle engine without the intervention of a solenoid clutch and having a drive shaft rotating about an axis of rotation thereof, a swash plate capable of nutating to cause reciprocatory suction and compression motions of pistons in cylinder bores and of pivoting about a pivoting axis thereof to change an angle of inclination thereof with respect to a plane perpendicular to the axis of the drive shaft, the swash plate being pivotable from a 0° inclination position to a large inclination angle position by setting a product of inertia of the swash plate so that a moment is automatically generated to move the swash plate from the 0° inclination position to a large inclination angle position in response to the slowest possible rotation of the swash plate.

82 citations


Journal ArticleDOI
TL;DR: In this article, the DIII-D tokamak demonstrated that discharges are more robust with regard to external nonaxisymmetric error fields as the plasma fluid rotation is increased, but more sensitive as beta is increased.
Abstract: Experimental results in the DIII-D tokamak demonstrate that discharges are more robust with regard to external nonaxisymmetric error fields as the plasma fluid rotation is increased, but more sensitive as beta is increased. In a series of discharges, the plasma fluid rotation and beta are varied by the number and type ('tangential' and/or 'perpendicular') of neutral beams. For each discharge, once rotation and plasma kinetic energy are equilibrated, an external coil is used to slowly increase the low m,n=1 resonant, static error field until a locked mode instability occurs. A larger critical error field is needed to nonlinearly induce instability in discharges spinning more rapidly. However, at higher beta, the plasmas become more unstable with increasing beta despite the faster rotation. The beta limit in tokamaks can be reduced by locked modes nonlinearly induced by modest error fields

Journal ArticleDOI
01 Jun 1992-Spine
TL;DR: The aims of this investigation were to define the instantaneous axis of rotation of the lumbar spine in rotation; and to study the effect of the loss of the anulus, facet joints, and ligamentous structures on the location of the instantaneousaxis of rotation.
Abstract: A knowledge of the rotatory motion of the vertebral bodies is needed to understand the normal biomechanical behavior of the spine. The aims of this investigation were 1) to define the instantaneous axis of rotation of the lumbar spine in rotation; and 2) to study the effect of the loss of the anulus, facet joints, and ligamentous structures on the location of the instantaneous axis of rotation. The instantaneous axis of rotation was found in 10 human cadaver thoracolumbar spines by the method of Reuleaux from superimposed serial photographs. Long-segment specimens were tested to minimize the effect of the imposed axis of the testing device. The instantaneous axis of rotation was consistently posterior to the anulus in the intact spine. With isolated destruction of the columns of the spine, the instantaneous axis of rotation migrated to the remaining intact structures. Anterior releases enhance derotation by removing the primary rotatory stabilizer. Ultimate control of a rotatory deformity or instability lies in the recognition that the anterior structures have a mechanical advantage in resisting torsion.

Patent
03 Apr 1992
TL;DR: A toroidal x-ray tube is used for rotation about a horizontal axis (170), translation along a vertical axis (172), and translation along an inverted axis (174) as discussed by the authors.
Abstract: A toroidal x-ray tube (I) is supported (II) for rotation about a horizontal axis (170), translation along a vertical axis (172), and translation along a horizontal axis (174). The x-ray tube includes a toroidal housing (A), an annular anode (B), and a cathode (0) which rotates a beam of electrons around the annular anode. A plurality of parallel connected voltage sources (901, 902, . . . , 90n) provide a sufficiently high bias voltage between the electron source and the anode that x-rays are generated. The x-ray beam passes through a compensator crystal (62), an annular window (20), a collimator (132), through a subject received in a central bore (26) of the x-ray tube, and impacts an arc segment of radiation detectors (130). The x-ray detectors are stationarily mounted outside of the plane of the annular window (FIGS. 2 and 7), nutate into the plane of the windows opposite of the origin of the x-ray beam (FIG. 6 ), rotate in part (FIG. 9 ) or rotate in full (FIG. 8 ) Angular position monitors (58, 154) determine the angular position of the cathode assembly, hence the x-ray beam, and the angular position of the detectors in the rotating detector embodiment.

Journal ArticleDOI
TL;DR: In this article, a model for the spin-down of rapidly rotating, convective stars is presented, and it is shown that a protostar accreting from a circumstellar disc reaches an equilibrium rotation period significantly below break-up.
Abstract: A model is constructed for the spin-down of rapidly rotating, convective stars. It is assumed that rotation and convection cause a star to rotate differentially, that differential rotation and convection generate a magnetic dynamo, that a magnetic dynamo gives rise to mass loss and a magnetically controlled stellar wind, and that such a wind results in angular momentum loss and hence stellar spin-down. Using the model, it is shown that a protostar accreting from a circumstellar disc reaches an equilibrium rotation period significantly below break-up

Journal ArticleDOI
TL;DR: It is shown, in a simple analytic example, that an infinitesimal amount of rotation can halt the general relativistic gravitational collapse of a pressure-free cylindrical body.
Abstract: It is shown, in a simple analytic example, that an infinitesimal amount of rotation can halt the general relativistic gravitational collapse of a pressure-free cylindrical body. The example is a thin cylindrical shell (a shell with translational symmetry and rotation symmetry), made of counterrotating dust particles. Half of the particles rotate about the symmetry axis in one direction with (conserved) angular momentum per unit rest mass α, and the other half rotate in the opposite direction with the same α. It is shown, using C-energy arguments, that the shell can never collapse to a circumference smaller than C=8παΛ, where Λ is the shell’s nonconserved mass per unit proper length. Equivalently, if R≡‖∂/∂φ∥∂/∂z‖ is the product of the lengths of the rotational and translational Killing vectors at the shell’s location and λ is the shell’s conserved rest mass per unit Killing length z, then the shell can never collapse smaller than R=4αλ. It is also shown that after its centrifugally induced bounce, the shell will oscillate radially and will radiate gravitational waves as it oscillates, the waves will carry away C energy, and this loss of C energy will force the shell to settle down to a static, equilibrium radius.

Patent
Jiri Marek1
04 Jun 1992
TL;DR: In this article, a seismic mass is displaceable in rotation is mounted within a stationary frame by two pairs of oppositely located flexible strips and either piezoresistive or capacitive detection of rotation is provided by the strips, the capacitive detector is provided with the help of parallel stationary electrodes connected to and insulated in the frame.
Abstract: From a silicon block or wafer a stationary frame is shaped and a seismic mass which is displaceable in rotation is mounted within the frame. The seismic mass is symmetrically suspended in the frame by two pairs of oppositely located flexible strips and either piezoresistive or capacitive detection of rotation is provided by the strips, the capacitive detection beeing provided with the help of parallel stationary electrodes connected to and insulated in the frame. In another embodiment an anchor stud in the center of the frame has two flexible interlaced spirals extending therefrom and their respective outer turns carry radial disposed masses with finger structures extending circumferentially in both directions. Stationary finger structures are provided to provide interfitting variable capacitors sensitive to rotary displacements.

Journal ArticleDOI
TL;DR: In this article, the authors used an argon laser beam for manipulation of wave propagation and creation of unexcitable disks, serving as artificial spiral cores, which are observed in the ruthenium-catalyzed Belousov-Zhabotinsky reaction (bromination of malonic acid).
Abstract: Dynamic features of spiral-shaped excitation waves rotating around unexcitable disks are investigated experimentally. The spiral patterns are observed in the ruthenium-catalyzed Belousov-Zhabotinsky reaction (bromination of malonic acid), in which the excitability depends on the intensity of applied illumination. Measurements are performed with a novel technique, which uses an argon laser beam for manipulation of wave propagation and creation of unexcitable disks, serving as artificial spiral cores. Rotation period, wavelength and velocity of spirals increase monotonically when the core radius is enlarged by expanding the diameter of the laser beam (0.1–3.0 mm). Rapid change of the core size is followed by a continuous relaxation process into a new dynamic state. The transient wavelengths and velocities scanned during this process provide data for a fast calculation of the dispersion relation for the investigated medium.

Journal ArticleDOI
TL;DR: In this article, the analysis of shell structures with finite displacements and rotations displacement-based and mixed finite-rotation shell elements is developed starting from consistent tensorial shell theories and the constraints for the description of the deformed normal vector have been considered at the element level as subsidiary conditions so that finite rotations in arbitrary strongly nonlinear situations can be considered without any difficulty.
Abstract: For the analysis of shell structures with finite displacements and rotations displacement-based and mixed finite-rotation shell elements are developed starting from consistent tensorial shell theories. The constraints for the description of the deformed normal vector have been considered at the element level as subsidiary conditions so that finite rotations in arbitrary strongly nonlinear situations can be considered without any difficulty. The efficiency of the finite-rotation elements is demonstrated by numerical examples.

Journal ArticleDOI
TL;DR: The relation for the angular spectra of rotated planes is evaluated, starting from the knowledge of the mono-chromatic scalar field on a given plane, and diffracted light on a tilted plane can be calculated in the frequency domain by fast-Fourier-transform algorithms.
Abstract: The relation for the angular spectra of rotated planes is evaluated, starting from the knowledge of the mono-chromatic scalar field on a given plane. Diffracted light on a tilted plane can then be calculated in the frequency domain by fast-Fourier-transform algorithms. Unlike the Fresnel and Fraunhofer approaches, this analysis does not require approximations; as a consequence, it permits any positions in space for the planes under investigation. Digital images are generated, which show the effects of rotation.

Patent
14 Jan 1992
TL;DR: In this article, a sheet-folding device having pairs of prefolding and pressure rollers (3, 4 and 8, 9, respectively) of identical diameters successively arranged for rotation in a machine frame is described.
Abstract: A sheet-folding device having pairs of prefolding and pressure rollers (3, 4 and 8, 9, respectively) of identical diameters successively arranged for rotation in a machine frame (1). A first pressure roller (8) is stationarily mounted to machine frame (1) for rotation, whereas the first prefolding roller (3) is rotatably mounted on spring-urged support members (10) which are slidable normally to the folding direction (A). The second prefolding roller (4) is mounted for rotation on shaft (14), said shaft being supported in lever arms (15) pivotally mounted to machine frame (1). Connecting arms (21) are hinged to the shaft (14) to support the second pressure roller (9) for rotation on shaft (13). The connecting arms (21) are urged by springs (18) such that, during feed-in of a prefolded stack into the nip of pressure rollers (8, 9), the springs (18) are compressed by pivoting the connecting arms (21) in a way that the pressure of the second prefolding roller (4) is increased and, thus the frictional forces exerted on the stack are enhanced.

Patent
07 Jul 1992
TL;DR: In this article, an apparatus 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 in the transverse (twisting) plane.
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 in the 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 held in the selected position. For operation in the flexion/extension mode, there is provided a lever arm which is rotatable about a horizontal axis which is adapted to pass through the lumbro-sacral junction of the patient, and a first upper body engaging member is releasably mounted to the lever arm. A first computer controlled drive motor pivotally rotates the lever arm in opposite directions in accordance with a predetermined program. An overhead frame assembly is also mounted for rotation about the horizontal axis, and a second upper body engaging member is mounted to the overhead frame assembly for rotation about a generally vertical axis which is perpendicular to the horizontal axis. Thus 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.

Journal ArticleDOI
TL;DR: In this paper, the divide-and-conquer density functional method was applied to the calculations of internal rotation energies and density of electronic states of a tetrapeptide, on comparison with the conventional Kohn-Sham method, was found to accurately describe the density of states and the small electronic energy changes in the internal rotation.
Abstract: The divide‐and‐conquer density‐functional method recently developed by Yang is applied to the calculations of internal rotation energies and density of electronic states of a tetrapeptide. The method, on comparison with the conventional Kohn–Sham method, is found to be capable of accurately describing the density of states and the small electronic energy changes in the internal rotation. The calculations further demonstrate the promise of the method for calculations of large systems beyond the reach of conventional methods.

Patent
19 Jun 1992
TL;DR: In this article, a control stick mechanism includes a hand-operated control member (10, 10') movable to swing about two axes of rotation (12, 14) about a first axis of rotation, and a reciprocating member (20) with an elongated second portion (26) axially movable along a line of reciprocation.
Abstract: Side stick controllers with isolated pitch and roll control movement may be mechanically linked. A control stick mechanism includes a hand-operated control member (10, 10') movable to swing about two axes of rotation (12, 14). A first lever member (16, 16') on the control member (10, 10') moves in response to swinging movement of the control member (10, 10') about a first axis of rotation (12). A reciprocating member (20) has a first portion (22) pivotally attached to the control member (10, 10') at a location (24) spaced from the second axis of rotation (14). The reciprocating member (20) has an elongated second portion (26) axially movable along a line of reciprocation substantially co-axial with the first axis of rotation (12) in response to swinging movement of the control member (10, 10') about the second axis of rotation (14). Movement of the first lever member (16, 16') effects operation of a first control sensor (44, 46) and movement of the reciprocating member (20) effects operation of a second control sensor (40, 42).

Journal ArticleDOI
TL;DR: In this article, the authors used helioseismic data to estimate the strength of a large-scale magnetic field in the radiative interior of the Sun and showed that the shape oblateness caused by a field at this limiting strength is about 5-10×10 −6.
Abstract: The radiative interior of the Sun could be hiding a large-scale magnetic field, which might not be axisymmetric about the observed rotation axis. Using helioseismic data, we estimate that the strength of any such relic field must be less than about 30 MG, if the field is axisymmetric about the rotation axis. The shape oblateness caused by a field at this limiting strength is about 5-10×10 −6 . Stronger fields can be accommodated by the helioseismic data if they are inclined to the rotation axis. We further conclude that the convection zone and at least the outer part of the radiative interior rotate on the same axis

Journal ArticleDOI
TL;DR: In this paper, the rotation effects on centrifugally driven instabilities in curved channel flow with a finite gap were investigated and an inviscid criterion of stability was formulated to explain the behavior of the flow when rotation and curvature effects compete to either stabilize or destabilize the flow.
Abstract: The rotation effects on centrifugally driven instabilities in curved channel flow with a finite gap are investigated. An inviscid criterion of stability is formulated to explain the behavior of the flow when rotation and curvature effects compete to either stabilize or destabilize the flow. The stability of curved Poiseuille flow with finite gap size is studied, and it is shown that the asymmetry between the directions of rotation is enhanced when the gap size increases.

Journal ArticleDOI
TL;DR: In this paper, the authors developed geometrical and mathematical relationships to explain the variation with radar range of idealized single-Doppler velocity patterns of axisymmetric rotation and divergence regions.
Abstract: Geometrical and mathematical relationships are developed to explain the variation with radar range of idealized single-Doppler velocity patterns of axisymmetric rotation and divergence regions. The velocity patterns become distorted as they approach a Doppler radar site. As a consequence, the apparent core diameters and locations of the centers of the features depart from the true values. Equations are derived to estimate the true values from the distorted Doppler velocity fields.

Patent
18 Nov 1992
TL;DR: In this article, a rotatable ultrasound transducer array is used for transesophageal echo cardiography. But the rotatable array does not have a fixed surface area.
Abstract: An endoscopic ultrasound probe for use in transesophageal echo cardiography comprises a rotatable ultrasound transducer array for obtaining two-dimensional cross-sectional images along a variety of scan planes. The array is formed of a plurality of transducer elements and rotates about an axis perpendicular to the plane of the transducer elements. The rotating array defines a circular region of rotation and has a surface area which substantially matches the area of the circular region of rotation within the probe. More specifically, the elements of the array have varying mechanical lengths such that the rotatable array may have a circular shape, a substantially circular shaped or an N-sided polygonal shape where N is an integer greater than four.

Journal ArticleDOI
15 Apr 1992-EPL
TL;DR: In this paper, an alternative explanation based on finite-size effects is proposed, which is based on a simple symmetry principle which, it is argued, underlies the phenomenon of epitaxial rotation.
Abstract: Two-dimensional and three-dimensional crystals adsorbed on crystalline substrate are often observed to be rotated, in the plane of the interface, by some apparently arbitrary angle relative to high-symmetry directions of the substrate In cases where the lattice mismatch between adsorbate and substrate can be varied, it is frequently found that the rotation angle varies with the mismatch Theoretical explanations for this epitaxial rotation have focused on the elastic properties and on commensurate structures Here, an alternative explanation is proposed, based on finite-size effects The adsorbate rotations that result from such considerations agree exactly with a simple symmetry principle which, it is argued, underlies the phenomenon of epitaxial rotation

Patent
24 Nov 1992
TL;DR: A display comprises an LED module 1 mounted for rotation on a base 2. The rotation of the LED's creates for an observer the illusion of a larger display as discussed by the authors. But the display cannot display textual or graphical information.
Abstract: A display comprises an LED module 1 mounted for rotation on a base 2. The rotation of the LED's creates for an observer the illusion of a larger display. Control of the LED's by suitable electronic circuitry makes it possible to display textual or graphical information.

Patent
21 Jan 1992
TL;DR: In this article, a pendulum-type robot is used to swing about a first axis located above and between the first and second presses, and a wrist mechanism is provided to permit rotation of the part between the presses.
Abstract: A method and system are provided for quickly and efficiently transferring a workpiece from a first work station including a first sheet metal press to a second sheet metal press by providing a pendulum-type robot, including an arm assembly mounted on a support structure to swing about a first axis located above and between the first and second presses. The arm assembly not only swings about a first axis but also rotates about a second axis orthogonal to the first axis and a third axis which is orthogonal to the second axis. During swinging movement of the arm assembly about the first axis, rotation of the arm assembly about the second and third axes allows a center of gravity of the workpiece to follow a substantially straight line path between the first and second presses. The arm assembly includes first and second four-bar linkages, which are pivotally connected together to rotate about the second axis. Preferably, a wrist mechanism is provided to permit rotation of the part between the presses. Also preferably, a counterbalance mechanism in the form of a cable balancing device is provided to support the arm assembly against gravity.