Showing papers on "Rotation published in 1998"

Vortex dynamics in three-dimensional continuous myocardium with fiber rotation: Filament instability and fibrillation.

Abstract: Wave propagation in ventricular muscle is rendered highly anisotropic by the intramural rotation of the fiber This rotational anisotropy is especially important because it can produce a twist of electrical vortices, which measures the rate of rotation (in degree/mm) of activation wavefronts in successive planes perpendicular to a line of phase singularity, or filament This twist can then significantly alter the dynamics of the filament This paper explores this dynamics via numerical simulation After a review of the literature, we present modeling tools that include: (i) a simplified ionic model with three membrane currents that approximates well the restitution properties and spiral wave behavior of more complex ionic models of cardiac action potential (Beeler-Reuter and others), and (ii) a semi-implicit algorithm for the fast solution of monodomain cable equations with rotational anisotropy We then discuss selected results of a simulation study of vortex dynamics in a parallelepipedal slab of ventricular muscle of varying wall thickness (S) and fiber rotation rate (theta(z)) The main finding is that rotational anisotropy generates a sufficiently large twist to destabilize a single transmural filament and cause a transition to a wave turbulent state characterized by a high density of chaotically moving filaments This instability is manifested by the propagation of localized disturbances along the filament and has no previously known analog in isotropic excitable media These disturbances correspond to highly twisted and distorted regions of filament, or "twistons," that create vortex rings when colliding with the natural boundaries of the ventricle Moreover, when sufficiently twisted, these rings expand and create additional filaments by further colliding with boundaries This instability mechanism is distinct from the commonly invoked patchy failure or wave breakup that is not observed here during the initial instability For modified Beeler-Reuter-like kinetics with stable reentry in two dimensions, decay into turbulence occurs in the left ventricle in about one second above a critical wall thickness in the range of 4-6 mm that matches experiment However this decay is suppressed by uniformly decreasing excitability Specific experiments to test these results, and a method to characterize the filament density during fibrillation are discussed Results are contrasted with other mechanisms of fibrillation and future prospects are summarized (c)1998 American Institute of Physics

A New class of unstable modes of rotating relativistic stars

Abstract: The first numerical study of axial (toroidal) pulsation modes of a slowly rotating relativistic star is presented. The calculation includes terms of first order in ≡ Ω(R3/M)1/2 1 (R is the radius, M is the mass, and Ω is the rotation frequency of the star) and accounts for effects due to the Coriolis force. Effects due to the centrifugal flattening of the star enter at order 2 and are not included in the analysis. It is shown that increased rotation tends to decrease the damping times for prograde modes, while retrograde modes become longer lived. Specifically, we show that rotation affects the axial gravitational wave w-modes in this way. We also present the first relativistic calculation of the so-called r-modes (analogous to Rossby waves in the Earth's oceans). These have frequencies of the same order of magnitude as the rotation frequency of the star. The presented results indicate that the r-modes are unstable due to the emission of gravitational radiation for all rotating perfect fluid stars. This is interesting, since the previously considered gravitational wave instability associated with (for example) the f-mode of the star sets in at a critical rotation rate. Because they are also unstable for the slowest rotating stars, the r-modes may well be of considerable astrophysical importance.

A Ka-band microstrip reflectarray with elements having variable rotation angles

Abstract: This paper demonstrates a novel means of achieving cophasal far-field radiation for a circularly polarized microstrip reflectarray with elements having variable rotation angles. Two Ka-band half-meter microstrip reflectarrays have been fabricated and tested. Both are believed to be the electrically largest reflectarrays ever developed using microstrip patches. One, a conventional design, has identical square patches with variable-length microstrip phase-delay lines attached. The other has identical square patches with identical microstrip phase-delay lines but different element rotation angles. Both antennas demonstrated excellent performance with more than 55% aperture efficiencies, but the one with variable rotation angles resulted in better overall performance. A brief mathematical analysis is presented to validate this "rotational element" approach. With this approach, a means of scanning the main beam of the reflectarray over a wide angular region without any RF beamformer by using miniature or micromachined motors is viable.

The transepicondylar axis approximates the optimal flexion axis of the knee

Abstract: The traditional understanding of knee kinematics holds that no single fixed axis of rotation exists in the knee. In contrast, a recent hypothesis suggests that knee kinematics are better described simply as two simultaneous rotations occurring about fixed axes. Knee flexion and extension occurs about an optimal flexion axis fixed in the femur, whereas tibial internal and external rotations occur about a longitudinal rotation axis fixed in the tibia. No other translations or rotations exist. This hypothesis has been tested. Tibiofemoral kinematics were measured for 15 cadaveric knees undergoing a realistic loadbearing activity (simulated squatting). An optimization technique was used to identify the locations of the optimal flexion and longitudinal rotation axes such that simultaneous rotations about them could best represent the measured kinematics. The optimal flexion axis was compared with the transepicondylar axis defined by bony landmarks. The longitudinal rotation axis was found to pass through the medial joint compartment. The optimal flexion axis passed through the centers of the posterior femoral condyles. No significant difference was found between the optimal flexion and transepicondylar axes. To an average accuracy of better than 3.4 mm in translation, and 2.9 degrees in orientation, knee kinematics were represented successfully by simple rotations about the optimal flexion and longitudinal rotation axes. The optimal flexion axis is fixed in the femur and can be considered the true flexion axis of the knee. The transepicondylar axis axis, which is identified easily by palpation, closely approximates the optimal flexion axis.

The Equilibrium Tide Model for Tidal Friction

Abstract: We derive from first principles the equations governing (a) the quadrupole tensor of a star distorted both by rotation and by the presence of a companion in a possibly eccentric orbit; (b) a functional form for the dissipative force of tidal friction, based on the concept that the rate of energy loss from a time-dependent tide should be a positive-definite function of the rate of change of the quadrupole tensor as seen in the frame that rotates with the star; and (c) the equations governing the rates of change of the magnitude and the direction of the stellar rotation, the orbital period and eccentricity, based on the concept of the Laplace-Runge-Lenz vector. Our analysis leads relatively simply to a closed set of equations, valid for arbitrary inclination of the stellar spin to the orbit. The results are equivalent to classical results based on the rather less clear principle that the tidal bulge lags behind the line of centers by some time determined by the rate of dissipation. Our analysis gives the effective lag time as a function of the dissipation rate and the quadrupole moment. We discuss briefly some possible applications of the formulation.

Mental and manual rotation

Abstract: The relation between mental and manual rotation was investigated in 2 experiments. Experiment 1 compared the response times (RTs) of mental rotation about 4 axes in space with the RTs shown in the same task when participants were allowed to reorient the stimuli by means of rotational hand movements. For the 3 Cartesian axes, RT functions were quantitatively indistinguishable. Experiment 2 investigated interference between mental rotation and 4 kinds of simultaneously executed hand movements that did not reorient the stimuli. Interference was observed only when axes of manual and mental rotation coincided in space. Regardless of the hand used, concordant rotational directions facilitated, whereas discordant directions inhibited, mental rotation. The results suggest that mental object rotation and rotatory object manipulation share a common process that is thought to control he dynamics of both imagined and actually performed object reorientation.

Long nonlinear surface and internal gravity waves in a rotating ocean

Abstract: Nonlinear dynamics of surface and internal waves in a stratified ocean under the influence of the Earth's rotation is discussed Attention is focussed upon guided waves long compared to the ocean depth The effect of rotation on linear processes is reviewed in detail as well as the existing nonlinear models describing weakly and strongly nonlinear dynamics of long waves The influence of rotation on small-scale waves and two-dimensional effects are also briefly considered Some estimates of the influence of the Earth's rotation on the parameters of real oceanic waves are presented and related to observational and numerical data

Experimental studies of the physical mechanism determining the radial electric field and its radial structure in a toroidal plasma

Abstract: Experimental studies on radial structures of plasma rotation and radial electric field in toroidal plasmas are reviewed. In this context, the perpendicular and parallel viscosities that determine the toroidal/poloidal rotation velocity and radial electric field profiles are discussed. Experimental studies of parallel viscosity and the comparison with the neoclassical values in heliotron/torsatron and stellarator devices, are described. The anomalous perpendicular viscosity, which is dominant in dictating the toroidal rotation in tokamaks, is also discussed. Even without external momentum input, plasma rotation and radial electric field are sustained by non-ambipolar flux of off-diagonal terms of the transport matrix. The effects of radial electric field shear and the bulk rotation velocity shear on the improvement of particle, momentum and heat transport in bulk and edge plasma regimes are also discussed.

Bed system for radiation therapy.

Abstract: In a treatment bed system for radiation therapy a rotation drive mechanism (relative isocentric rotation drive mechanism, rolling rotation drive mechanism, and pitching rotation drive mechanism) for rotating the bed independently around three axes (i, r, and p) perpendicular with respect to a patient each other and a parallel transfer mechanism (X-axis direction transfer mechanism, Z-axis direction transfer mechanism, and Y-axis direction transfer mechanism) for transferring the bed independently in parallel in the directions of three axes (X, Z, and Y) perpendicular with respect to a floor surface each other are provided. Thereby, the irradiation from arbitrary directions and distances to a patient held stationary on the bed can be performed.

The structure and dynamics of vorticity and rate of strain in incompressible homogeneous turbulence

Abstract: The structure and dynamics of vorticity ω and rate of strain S are studied using direct numerical simulations (DNS) of incompressible homogeneous isotropic turbulence. In particular, characteristics of the pressure Hessian Π, which describe non-local interaction of ω and S, are presented. Conditional Lagrangian statistics which distinguish high-amplitude events in both space and time are used to investigate the physical processes associated with their evolution. The dynamics are examined on the principal strain basis which distinguishes vortex stretching and induced rotation of the principal axes of S. The latter mechanism is associated with misaligned ω with respect to S, a condition which predominates in isotropic turbulence and is dynamically significant, particularly in rotation-dominated regions of the flow. Locally-induced rotation of the principal axes acts to orient ω towards the direction of either the intermediate or most compressive principal strain. The tendency towards compressive straining of ω is manifested at the termini of the high-amplitude tube-like structures in the flow. Non-locally-induced rotation, associated with Π, tends to counteract the locally-induced rotation. This is due to the strong alignment between ω and the eigenvector of Π corresponding to its smallest eigenvalue and is indicative of the controlling influence of the proximate structure on the dynamics. High-amplitude rotation-dominated regions deviate from Burgers vortices due to the misalignment of ω. Although high-amplitude strain-dominated regions are promoted primarily by local dynamics, the associated spatial structure is less organized and more discontinuous than that of rotation-dominated regions.

Helioseismic determination of the solar gravitational quadrupole moment

Abstract: 1 I N T RO D U C T I O N For observations that are well resolved in space and in time the oscillation of the Sun can be decomposed into its pulsation eigenmodes, which are products of functions of radius and of spherical harmonic functions. Each mode, and therefore each measured oscillation frequency, is uniquely identified by three numbers: the radial order n, and the degree l and the azimuthal order m of the spherical harmonic. The solar rotation produces oscillation frequencies that are split into multiplets. The relationship between the mode frequencies and the rotation is 2p nnlm 1 nnl 1m 2m 1⁄4 …1

Hybrid drive system

Abstract: In a state a vehicle is stopped at an intersection, an infinitely variable transmission is in a neutral position, a motor/generator rotates with a low speed, an oil pump and an auxiliary equipment are in rotating state. At that time, an input clutch is disengaged, and the internal engine is stopped. When the vehicle is started, a continuously variable transmission performs continuous shift control from the neutral position using hydraulic pressure from an oil pump, and the rotation of the motor/generator is transmitted to drive wheels via a ring gear of a planetary gear. After the vehicle has started driving, the input clutch is engaged and the internal engine is started. The vehicle is driven while the motor/generator assists driving or the motor/generator charges batteries based on operation of the internal engine.

Observations of central toroidal rotation in ICRF heated Alcator C-Mod plasmas

Abstract: Impurity toroidal rotation has been observed in the centre of Alcator C-Mod ion cyclotron range of frequencies (ICRF) heated plasmas, from the Doppler shifts of argon X ray lines. Rotation velocities greater than 1.2 × 107 cm/s (ω = 200 krad/s) in the co-current direction have been observed in H mode discharges that had no direct momentum input. There is a correlation between the increase in the central impurity rotation velocity and the increase in the plasma stored energy (confinement enhancement), induced by ICRF heating, although other factors may be at play. The toroidal rotation velocity is highest near the magnetic axis, and decreases with increasing minor radius. A radial electric field of 300 V/cm at r/a = 0.3 has been inferred from the force balance equation. The direction of the rotation changes when the plasma current direction is reversed, remaining co-current. Impurity toroidal rotation in ICRF heated plasmas is in the direction opposite to the rotation in ohmic L mode plasmas; co-current rotation has also been observed during purely ohmic H modes. When the ICRF heating is turned off, the toroidal rotation decays with a characteristic time of order 50 ms, similar to the energy confinement time, and much shorter than the calculated neoclassical momentum damping time.

Torsional micro-mechanical mirror system

Abstract: A torsional micro-mechanical mirror system includes a mirror assembly rotatably supported by a torsional mirror support assembly for rotational movement over and within a cavity in a base. The cavity is sized sufficiently to allow unimpeded rotation of the mirror assembly. The mirror assembly includes a support structure for supporting a reflective layer. The support structure is coplanar with and formed from the same wafer as the base. The torsional mirror support assembly includes at least one torsion spring formed of an electroplated metal. An actuator assembly is operative to apply a driving force to torsionally drive the torsional mirror support assembly, whereby torsional motion of the torsional mirror support assembly causes rotational motion of the mirror assembly. In another embodiment, a magnetic actuator assembly is provided to drive the mirror assembly. Other actuator assemblies are operative to push on the mirror assembly or provide electrodes spaced across the gap between the mirror assembly and the base. A process for fabricating the torsional micro-mirror is provided. The torsional micro-mirror is useful in various applications such as in biaxial scanner or video display systems.

Atomic Contributions to the Optical Rotation Angle as a Quantitative Probe of Molecular Chirality

Abstract: Chiral molecules are characterized by a specific rotation angle, the angle through which plane-polarized light is rotated on passing through an enantiomerically enriched solution. Recent developments in methodology allow computation of both the sign and the magnitude of these rotation angles. However, a general strategy for assigning the individual contributions that atoms and functional groups make to the optical rotation angle and, more generally, to the molecular chirality has remained elusive. Here, a method to determine the atomic contributions to the optical rotation angle is reported. This approach links chemical structure with optical rotation angle and provides a quantitative measure of molecular asymmetry propagation from a center, axis, or plane of chirality.

Charged particle beam irradiation apparatus and method of irradiation with charged particle beam

Abstract: A charged particle beam irradiation apparatus includes two electromagnets arranged in series along a direction of an incident axis of a charged particle beam, for deflecting the charged particle beam in opposite directions, an energy modulator including a cylindrical member having a length and a distribution of wall thickness in a circumferential direction, a first rotational drive for rotating the cylindrical member around a rotation axis, and a detector for detecting the angular position of the cylindrical member. The energy modulator is disposed at a downstream side of the scanning electromagnets so that the deflected charged particle beam passes through the rotation axis. The apparatus includes an energy degrader for limiting energy of the charged particle beam, and a second rotational drive for rotating the scanning electromagnets and the energy modulator together around the incident axis of the charged particle beam.

Angular acceleration measurement: a review

Abstract: This paper gives a review of sensors, methods, and algorithms available for the measurement of angular acceleration. The emphasis is in delay-sensitive, real-time applications. Although the angular acceleration can be measured indirectly using either a rotating angle sensor or a velocity sensor, the noise-amplification problem related to the differentiation process has motivated the efforts to develop transducers for direct sensing of angular acceleration. Direct measuring of linear acceleration is widely in everyday use, but the angular acceleration sensors, particularly those with unlimited rotation angle, can still be considered as emerging devices. Consequently, there exist two principal challenges for the research and development community: to develop economical and accurate angular accelerometers with unlimited rotation range, and to create wideband indirect techniques with small lag and high signal-to-error ratio.

Power output device and method of stopping prime mover in the power output device

Abstract: A power output device is provided with a planetary gear, an engine having a crank shaft coupled to the planetary gear, a motor secured to a sun gear and a motor secured to a ring gear. Even if there is no need to continue operation of the engine, the engine is not immediately stopped in view of the charge amount of a battery. For example, in the D (drive) range, a processing for stopping rotation of the engine with a predetermined deceleration is performed only if an ABS device is out of operation, the cancellation of reaction force is possible and the vehicle speed is within a predetermined range. Consequently, it is possible to stop the engine while preventing the reaction force from causing a sense of shock to the driver.

Submersible appartus for generating electricity and associated method

Abstract: A fully submersible apparatus for generating electricity from liquid flow as in an ocean or river current. A buoyant structure is fully submersible and has at least one pair of counter-rotating side-by-side motors with a plurality of angularly spaced radial vanes each having a plurality of rotatable subvanes such that current impinging upon the motor will impinge on a closed or solid vane to effect rotation of the motor and its shaft during a first phase of the rotational cycle and will impinge on open vanes for free passage therethrough on the return or second phase of rotation of the motor. Motors may also be provided with vanes in overlying and underlying relationship. An associated method is provided.

The Distribution of Nearby Stars in Velocity Space

Abstract: From the tangential velocities of stars all over the sky, one can, in a statistical way, infer their 3D velocity distribution. An application to Hipparcos data reveals rich structure in the planar stellar motions: there are several moving groups, increasing in number with stellar type but decreasing in importance. A distinct group of outward moving stars with low rotation velocities might be associated with the Galactic bar: growing a bar in a smooth model for the Galactic disk results in such a group, provided the Sun is outside the outer Lindblad resonance (OLR) and the orientation angle with the bar is in the first quadrant. The vertical motions show less structure, but the mean increases for large rotational velocities, which can be nicely explained by a warp of the outer stellar disk.

Turbulent Compressible Convection with Rotation. II. Mean Flows and Differential Rotation

Abstract: The e†ects of rotation on turbulent, compressible convection within stellar envelopes are studied through three-dimensional numerical simulations conducted within a local f-plane model. This work seeks to understand the types of di†erential rotation that can be established in convective envelopes of stars like the Sun, for which recent helioseismic observations suggest an angular velocity pro-le with depth and latitude at variance with many theoretical predictions. This paper analyzes the mechanisms that are responsible for the mean (horizontally averaged) zonal and meridional Nows that are produced by convection inNuenced by Coriolis forces. The compressible convection is considered for a range of Rayleigh, Taylor, and Prandtl (and thus Rossby) numbers encompassing both laminar and turbulent Now conditions under weak and strong rotational constraints. When the nonlinearities are moderate, the e†ects of rotation on the resulting laminar cellular convec- tion leads to distinctive tilts of the cell boundaries away from the vertical. These yield correlations between vertical and horizontal motions that generate Reynolds stresses that can drive mean Nows, inter- pretable as di†erential rotation and meridional circulations. Under more vigorous forcing, the resulting turbulent convection involves complicated and contorted Nuid particle trajectories, with few clear corre- lations between vertical and horizontal motions, punctuated by an evolving and intricate downNow network that can extend over much of the depth of the layer. Within such networks are some coherent structures of vortical downNow that tend to align with the rotation axis. These yield a novel turbulent alignment mechanism, distinct from the laminar tilting of cellular boundaries, that can provide the prin- cipal correlated motions and thus Reynolds stresses and subsequently mean Nows. The emergence of such coherent structures that can persist amidst more random motions is a characteristic of turbulence with symmetries broken by rotation and strati-cation. Such structure is here found to play a crucial role in de-ning the mean zonal and meridional Nows that coexist with the convection. Though they are subject to strong inertial oscillations, the strength and type of the mean Nows are determined by a com- bination of the laminar tilting and the turbulent alignment mechanisms. Varying the parameters pro- duces a wide range of mean motions. Among these, some turbulent solutions exhibit a mean zonal velocity pro-le that is nearly constant with depth, much as deduced by helioseismology at midlatitudes within the Sun. The solutions exhibit a de-nite handedness, with the direction of the persistent mean Nows often prescribing a spiral with depth near the boundaries, also in accord with helioseismic deduc- tions. The mean helicity has a pro-le that is positive in the upper portion of the domain and negative in the lower portion, a property bearing on magnetic dynamo processes that may be realized within such rotating layers of turbulent convection. Subject headings: convection E stars: interiors E stars: rotation E Sun: rotation E turbulence

Aperture Synthesis C18O J = 1-0 Observations of L1551 IRS 5: Detailed Structure of the Infalling Envelope*

Abstract: We report aperture synthesis C18O J = 1-0 observations of L1551 IRS 5 with a spatial resolution of 28 × 25 using the Nobeyama Millimeter Array. We have detected an emission component centrally condensed around IRS 5, as well as a diffuse component extending in the north-south direction from the centrally condensed component. The centrally condensed component, 2380 × 1050 AU in size, is elongated in the direction perpendicular to the outflow axis, indicating the existence of a flattened circumstellar envelope around L1551 IRS 5. The mass of the centrally condensed component is estimated to be 0.062 M☉. The position-velocity (P-V) diagrams reveal that the velocity field in the centrally condensed component is composed of infall and slight rotation. The infall velocity in the outer part is equal to the free-fall velocity around a central mass of ~0.1 M☉, e.g., 0.5 km s-1 at r = 700 AU, whereas the rotation velocity, 0.24 km s-1 at the same radius, gets prominent at inner radii with a radial dependence of r-1. We make up P-V diagrams for the model envelopes with vertical structure, in which the matter falls under the gravity and eventually settles down in Keplerian rotation inside the centrifugal radius, and compare them with the observed P-V diagrams of the centrally condensed component. The main characteristics of the observed P-V diagrams are reproduced by either (1) an envelope with a moderately flattened density distribution, or (2) a spherical envelope with a bipolar cavity whose half-opening angle is about 50°. Detailed comparison of the observed and model P-V diagrams suggests that the C18O J = 1-0 emission from the outer part of the centrally condensed component is well reproduced with the models with the central mass ~0.15 M☉ and the mass infall rate ~6 × 10-6 M☉ yr-1. However, the higher velocity features of the emission near the star cannot be reproduced unless the central mass is taken to be ~0.5 M☉. These facts suggest either that the gas pressure and/or magnetic force dilute the effect of the gravity in the outer part of the envelope, or that the velocity structure inside the centrifugal radius deviates significantly from the Keplerian rotation.

Drum type washing machine

Abstract: PURPOSE: To effectively suppress generated vibration by connecting a dynamic vibration-absorbing system to an external tank in a drum type washing machine for which a drum for housing laundry is housed rotatably around a horizontal axis inside the external tank elastically supported by a frame. CONSTITUTION: For this drum type washing machine, the external tank 2 is elastically supported by an external tank suspension spring 4 in the inside of the frame 1, the drum 21 is housed rotatably around the horizontal axis inside the external tank 2. A motor 3 for driving the drum is attached to the lower surface of the external tank 2 and is connected through a power transmission mechanism to the rotary shaft of the drum 21. In this drum type washing machine, a washing water tank 5 is connected to the lower surface of the external tank 2 in a suspended state through a damper 7 and a leaf spring 8. Then, in the case of turning auxiliary mass constituted of the washing water tank 5 to a set fixed value, the output of a vibration sensor 9 is supplied to a control circuit 90, the rotation amount of the motor 6 for adjusting a spring constant is controlled and the spring constant of the leaf spring 8 is adjusted to an optimum value by a spring constant adjusting slider 61.

The Magnetic Stability of Spin-Dependent Tunneling Devices

Abstract: The tunneling resistance between two ferromagnetic metal layers that are separated by a thin insulator depends on the relative orientation of the magnetization M of each layer. In a memory device, independent switching of the magnetically soft layer is achieved by making the other layer either exchange-biased or magnetically hard. The repeated reversal of M of the soft layer by field cycling can demagnetize the other magnetically hard layer and thus erase the tunnel junction9s memory. The M of exchange-biased structures was stable at least to 107cycles, whereas in hard structures, M generally decayed logarithmically with the number of field cycles. The decay was very sensitive to the thickness of the hard layer and the composition of the soft layer. However, no decay was observed when the moment reversal was accomplished by coherent rotation, establishing that demagnetization results from the formation and motion of domain walls in the soft layer during field cycling.

Wellbore wash nozzle system

Abstract: A wash nozzle for wellbore washing operations has been invented, the wash nozzle, in one aspect having a central mandrel with a top, a bottom, and a fluid flow bore therethrough from top to bottom, at least one mandrel port through the central mandrel for fluid flow from within the central mandrel's fluid flow bore to an exterior of the central mandrel, a hollow sleeve rotatably mounted around the central mandrel, and at least one sleeve port through the sleeve for fluid flow from within the sleeve from the exterior of the central mandrel to an exterior of the sleeve, the at least one sleeve port defined by a wall on the sleeve. In one aspect the wash nozzle includes apparatus for selective rotation of the sleeve about the mandrel. In one aspect flow through the wash nozzle is stopped to effect sleeve rotation and, in one particular aspect, flow through the nozzle is then re-established. Methods have been invented using such wash nozzles for wellbore washing operations and/or cuttings removal.

The wave modes in ducted swirling flows

Abstract: The small amplitude wave modes inside a ducted inviscid, compressible swirling flow are investigated. In order to avoid possible mathematical ambiguities arising from the use of an inviscid flow model, the wave modes are cast as the solution of an initial boundary value problem. Two families of propagating waves are found. The acoustic modes are supported by the compressibility effect of the flow. The rotational modes are sustained by the centrifugal force field associated with the mean flow rotation. Two cases, one with a free vortex swirl and the other with a rigid body swirl, are investigated in some depth. Numerical results are provided. The effect of swirl on the propagation characteristics of the acoustic modes and the effect of compressibility on those of the rotational modes are found to be relatively insignificant.

Rotatable electrode device

Abstract: An apparatus for thermal treatment of a tissue mass having an elongated housing having a proximal and a distal end and defining a longitudinal axis, and further including at least two electrodes supported at its distal end and mounted for rotation to facilitate entry and passage through a tissue mass. A drive shaft may be disposed within the elongated housing and operatively engageable with the electrodes for causing their rotational movement. The apparatus may include an electrode gear and a drive shaft gear in cooperative engagement whereby rotation of the drive shaft causes corresponding rotation of the electrodes. Preferably, a motor is operatively connected to the drive shaft causing its rotational movement. Desirably, the distal end of the electrodes are threaded. A method for thermally treating a tissue mass is disclosed.

Actuator for independent axial and rotational actuation of a catheter or similar elongated object

Abstract: An actuator is used in a surgical simulation system that simulates the catheterization of cardiac or peripheral vasculature. The simulation system provides haptic feedback to a user of a catheter or similar elongated object coupled to the system. The actuator includes sensors that generate sense signals indicative of axial translation and rotation of the object by the user. The sense signals are provided to a workstation executing a simulation program. In response to the sense signals, the workstation calculates axial forces and torques to be applied to the object as haptic feedback to the user, and generates drive signals representing the calculated axial forces and torques. Mechanisms within the actuator respond to the drive signals by applying corresponding axial force and torque to a rigid tube that is mechanically coupled to the object. One embodiment of the actuator includes a carriage assembly for holding the rigid tube between a pair of opposed pinch wheels. The carriage assembly rotates to rotate the object about its longitudinal axis, and the pinch wheels rotate to translate the object axially. Another actuator embodiment includes a first bearing mounted on a rotary actuator and a second bearing mounted on a sliding linear actuator. The rigid tube has a square cross section for secure engagement by the second actuator. The linear actuator grips the tube and allows it to freely rotate about its longitudinal axis.