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Showing papers on "Rotation published in 2004"


Patent
18 Oct 2004
TL;DR: In this paper, a tool assembly rotation mechanism is provided which includes a rotation knob, a substantially rigid tube and a flexible member interconnecting the rigid tube to the tool assembly, which provides a channel for passage of other components of the surgical stapling device.
Abstract: A surgical stapling device is disclosed which includes a handle assembly, an endoscopic body portion and a tool assembly. The tool assembly is rotatably and pivotally supported on a distal end of the endoscopic body portion. A tool assembly rotation mechanism is provided which includes a rotation knob, a substantially rigid tube and a flexible member interconnecting the rigid tube to the tool assembly. The substantially rigid tube translates rotation of the rotation knob to rotation of the flexible member and provides a channel for passage of other components of the surgical stapling device.

1,096 citations


Journal ArticleDOI
26 Nov 2004-Science
TL;DR: The minimalist nature of the [2]catenane flashing ratchet design permits certain mechanistic comparisons with the Smoluchowski-Feynman ratchet and pawl.
Abstract: The circumrotation of a submolecular fragment in either direction in a synthetic molecular structure is described. The movement of a small ring around a larger one occurs through positional displacements arising from biased Brownian motion that are kinetically captured and then directionally released. The sense of rotation is governed solely by the order in which a series of orthogonal chemical transformations is performed. The minimalist nature of the [2]catenane flashing ratchet design permits certain mechanistic comparisons with the Smoluchowski-Feynman ratchet and pawl. Even when no work has to be done against an opposing force and no net energy is used to power the motion, a finite conversion of energy is intrinsically required for the molecular motor to undergo directional rotation. Nondirectional rotation has no such requirement.

532 citations


Journal ArticleDOI
TL;DR: In this article, the authors postulate that almost any motion of an interface between two crystals can produce a coupled tangential motion of the two crystals relative to each other which is proportional to the normal motion.

393 citations


Journal ArticleDOI
TL;DR: In this article, the authors present line-profile calculations that emphasize the insensitivity of line width to rotation for fast rotators and suggest that the observational parameter v sin i may systematically underestimate the true projected equatorial rotation velocity, v e sin i by some tens of per cent for rapid rotators.
Abstract: We argue that, in general, observational studies of Be-star rotation have paid insufficient attention to the effects of equatorial gravity darkening. We present new line-profile calculations that emphasize the insensitivity of line width to rotation for fast rotators. Coupled with a critical review of observational procedures, these calculations suggest that the observational parameter v sin i may systematically underestimate the true projected equatorial rotation velocity, v e sin i, by some tens of per cent for rapid rotators. A crucial implication of this work is that Be stars may be rotating much closer to their critical velocities than is generally supposed, bringing a range of new processes into contention for the elusive physical mechanism responsible for the circumstellar disc thought to be central to the Be phenomenon.

319 citations


Journal ArticleDOI
TL;DR: A dramatic change in the appearance of the quantum gas is observed in such a fast rotation regime, the vortices which were easily detectable for a slower rotation become much less visible, and their surface density is well below the value expected for this rotation frequency domain.
Abstract: We study the rotation of a 87Rb Bose-Einstein condensate confined in a quadratic plus quartic potential. This trap configuration allows one to increase the rotation frequency of the gas above the trap frequency. In such a fast rotation regime we observe a dramatic change in the appearance of the quantum gas. The vortices which were easily detectable for a slower rotation become much less visible, and their surface density is well below the value expected for this rotation frequency domain. We discuss some possible tracks to account for this effect.

311 citations


Journal ArticleDOI
TL;DR: The physics of the hot spots on stellar surfaces and the associated variability of accreting magnetized rotating stars were investigated for the first time using fully three-dimensional magnetohydrodynamic simulations in this article.
Abstract: The physics of the hot spots on stellar surfaces and the associated variability of accreting magnetized rotating stars is investigated for the first time using fully three-dimensional magnetohydrodynamic simulations. The magnetic moment of the star, μ, is inclined relative to its rotation axis, Ω, by an angle Θ (we call this angle the "misalignment angle"), while the disk's rotation axis is parallel to Ω. A sequence of misalignment angles between Θ = 0° and 90° was investigated. The hot spots arise on the stellar surface because of the impact on the surface of magnetically channeled accretion streams. The distribution of different parameters in the hot spots reflects those in the funnel streams near the surface of the star. Typically, at small Θ the spots as observed are shaped like a bow curved around the magnetic axis, while at the largest values of Θ the spots are shaped like a bar crossing the magnetic pole. The physical parameters (density, velocity, temperature, matter, energy fluxes, etc.) increase toward the central regions of the spots; thus, the size of the spots is different at different values of these parameters. At relatively low density and temperature, the spots occupy approximately 10%-20% of the stellar surface, while at the highest values of these parameters this area may be less than 1% of the area of the star. The size of the spots increases with the accretion rate. Rotation of the star leads to the observed variability of brightness. The light curves were calculated for different values of Θ and inclination angles of the disk, i. They show a range of variability patterns, including curves with one maximum per period (at most angles Θ and i) and curves with two maxima per period (at large Θ and i). At small Θ, the funnel streams may rotate faster or slower than the star, and this may lead to quasi-periodic variability of the star. The results are of interest for understanding the variability and quasi variability of classical T Tauri stars, millisecond pulsars, and cataclysmic variables.

298 citations


Book
31 Aug 2004
TL;DR: In this article, a rotor rotor reference record was created on 2005-11-18, modified on 2016-08-08 and a dynamique reference record for dynamique was created.
Abstract: Keywords: rotor ; vibration ; rotation ; dynamique Reference Record created on 2005-11-18, modified on 2016-08-08

211 citations


Journal ArticleDOI
TL;DR: In this article, rotational splitting of two dipole (l = 1) modes (g 1 and p 1 ) was used to infer properties of the internal rotation rate of the star.
Abstract: The oscillation spectrum of v Eri is the richest known for any variable of the β Cephei type. We interpret the spectrum in terms of normal mode excitation and construct seismic models of the star. The frequency data combined with data on mean colours set the upper limit on the extent of overshooting from the convective core. We use data on rotational splitting of two dipole (l = 1) modes (g 1 and p 1 ) to infer properties of the internal rotation rate. Adopting a plausible hypothesis of nearly uniform rotation in the envelope and increasing rotation rate in the μ-gradient zone, we find that the mean rotation rate in this zone is about three times faster than in the envelope. In our standard model only the modes in the middle part of the oscillation spectrum are unstable. To account for excitation of a possible high-order g mode at v = 0.43 cd -1 as well as p modes at v > 6 cd -1 we have to invoke an overabundance of Fe in the driving zone.

182 citations


Journal ArticleDOI
Jorge Angeles1
TL;DR: In this article, the topology of a parallel manipulator for tasks involving less than six degrees of freedom is presented by resorting to qualitative reasoning, where the manipulation tasks pertain to displacements with algebraic structure of a group.
Abstract: As shown in this paper, when designing parallel manipulators for tasks involving less than six degrees of freedom, the topology can be laid out by resorting to qualitative reasoning. More specifically, the paper focuses on cases whereby the manipulation tasks pertain to displacements with the algebraic structure of a group. Besides the well-known planar and spherical displacements, this is the case of displacements involving: rotation about a given axis and translation in the direction of the same axis (cylindrical subgroup); translation in two and three dimensions (two- and three-dimensional translation subgroups); three independent translations and rotation about an axis of fixed direction, what is known as the Schonflies subgroup; and similar to the Schonflies subgroup, but with the rotation and the translation in the direction of the axis of rotation replaced by a screw displacement. For completeness, the fundamental concepts of motion representation and groups of displacements, as pertaining to rigid bodies, are first recalled. Finally, the concept of H-joint, introduced elsewhere, is generalized to two and three degrees of freedom, thereby ending up with the Π 2 -and the Π 3 -joints, respectively.

178 citations


Patent
14 Dec 2004
TL;DR: In this article, a variable valve mechanism is installed to change the operating angle and lift amount of an intake valve in accordance with the rotation position of a control shaft, and a worm wheel is secured to the control shaft.
Abstract: A variable valve mechanism is installed to change the operating angle and lift amount of an intake valve in accordance with the rotation position of a control shaft. A worm wheel is secured to the control shaft. The worm wheel is coupled to a motor actuator via a worm gear. The motor actuator is controlled during a normal operation so that the rotation position of the control shaft changes within a normal rotation range. A low-end stopper and high-end stopper are installed outside the normal rotation range to mechanically restrict the rotation of the control shaft.

157 citations


Journal ArticleDOI
TL;DR: In this paper, the authors present the results of three-dimensional simulations of core convection within A-type stars of 2 M☉, at a range of rotation rates.
Abstract: We present the results of three-dimensional simulations of core convection within A-type stars of 2 M☉, at a range of rotation rates. We consider the inner 30% by radius of such stars, thereby encompassing the convective core and some of the surrounding radiative envelope. We utilize our anelastic spherical harmonic code, which solves the compressible Navier-Stokes equations in the anelastic approximation, to examine highly nonlinear flows that can span multiple scale heights. The cores of these stars are found to rotate differentially, with central cylindrical regions of strikingly slow rotation achieved in our simulations of stars whose convective Rossby number (Roc) is less than unity. Such differential rotation results from the redistribution of angular momentum by the nonlinear convection that strongly senses the overall rotation of the star. Penetrative convective motions extend into the overlying radiative zone, yielding a prolate shape (aligned with the rotation axis) to the central region in which nearly adiabatic stratification is achieved. This is further surrounded by a region of overshooting motions, the extent of which is greater at the equator than at the poles, yielding an overall spherical shape to the domain experiencing at least some convective mixing. We assess the overshooting achieved as the stability of the radiative exterior is varied and the weak circulations that result in that exterior. The convective plumes serve to excite gravity waves in the radiative envelope, ranging from localized ripples of many scales to some remarkable global resonances.

Journal ArticleDOI
TL;DR: In this article, the authors use numerical simulations to investigate the orientation of the angular momentum axis of disk galaxies relative to their surrounding large-scale structure, and they find that this is closely related to the spatial configuration at turnaround of the material destined to form the galaxy.
Abstract: We use numerical simulations to investigate the orientation of the angular momentum axis of disk galaxies relative to their surrounding large-scale structure. We find that this is closely related to the spatial configuration at turnaround of the material destined to form the galaxy, which is often part of a coherent two-dimensional slab crisscrossed by filaments. The rotation axis is found to align very well with the intermediate principal axis of the inertia momentum tensor at this time. This orientation is approximately preserved during the ensuing collapse, so that the rotation axis of the resulting disk ends up lying on the plane traced by the protogalactic material at turnaround. This suggests a tendency for disks to align themselves so that their rotation axis is perpendicular to the minor axis of the structure defined by surrounding matter. One example of this trend is provided by our own Galaxy, where the Galactic plane is almost at right angles with the supergalactic plane (SGP) drawn by nearby galaxies; indeed, the SGP latitude of the north Galactic pole is just 6°. We have searched for a similar signature in catalogs of nearby disk galaxies, and we find a significant excess of edge-on spiral galaxies (for which the orientation of the disk rotation axis may be determined unambiguously) highly inclined relative to the SGP. This result supports the view that disk galaxies acquire their angular momentum as a consequence of early tidal torques acting during the expansion phase of the protogalactic material.

Journal ArticleDOI
TL;DR: In this article, the Taylor-Spruit dynamo theory was further developed for generating magnetic fields in radiative layers of differentially rotating stars, and it was shown that there is a complex feedback loop between the magnetic instability and the thermal instability driving meridional circulation.
Abstract: We further develop the Tayler-Spruit dynamo theory, based on the most efficient instability for generating magnetic fields in radiative layers of differentially rotating stars. We avoid the simplifying assumptions that either the μ- or the T-gradient dominates, but we treat the general case and we also account for the nonadiabatic effects, which favour the growth of the magnetic field. The general equation leads to the same analytical solutions in the limiting cases considered by Spruit (2002). Numerical models of a 15 M ○. star with a magnetic field are performed. The differences between the asymptotic solutions and the general solution demonstrate the need to use the general solution. Stars with a magnetic field rotate almost as a solid body. Several of their properties (size of the core, MS lifetimes, tracks, abundances) are closer to those of models without rotation than with rotation only. In particular, the observed N/C or N/H excesses in OB stars are better explained by our previous models with rotation only than by the present models with magnetic fields that predict no nitrogen excesses. We show that there is a complex feedback loop between the magnetic instability and the thermal instability driving meridional circulation. Equilibrium of the loop, with a small amount of differential rotation, can be reached when the velocity U magn of the growth of the magnetic instability is of the same order as the velocity U circ of the meridional circulation. This opens the possibility for further magnetic models, but at this stage we do not know the relative importance of the magnetic fields due to the Tayler instability in stellar interiors.

Journal ArticleDOI
TL;DR: In this paper, the effect of stellar rotation on the carbon ignition in a carbon-oxygen white dwarf accreting CO-rich matter was studied, and it was shown that the critical carbon ignition rate for the off-center ignition is not significantly changed by the effects of rotation, however, the mass coordinate of the ignition layer and the mass of the white dwarf at the ignition are larger than those for the corresponding nonrotating model.
Abstract: We study the effect of stellar rotation on the carbon ignition in a carbon-oxygen white dwarf accreting CO-rich matter. Including the effect of the centrifugal force of rotation, we have calculated evolutionary models up to the carbon ignition for various accretion rates. The rotational velocity at the stellar surface is set to the Keplerian velocity. The angular velocity in the stellar interior is determined by taking into account the transport of angular momentum due to turbulent viscosity. We have found that an off-center carbon ignition occurs even when the effect of stellar rotation is included if the accretion rate is sufficiently high; the critical accretion rate for the off-center ignition is hardly changed by the effect of rotation. Rotation, however, delays the ignition, i.e., the mass coordinate of the ignition layer and the mass of the white dwarf at the ignition are larger than those for the corresponding nonrotating model. The result supports our previous conclusion that a double-white dwarf merger would not be a progenitor of a Type Ia supernova (SN Ia).

Journal ArticleDOI
TL;DR: In this paper, a fully coupled non-linear integro-differential equations, describing axial, transverse and rotational motions of a uniform Euler-Bernoulli beam attached to a rotating rigid hub, are derived by using the extended Hamilton's principle.

Patent
01 Jun 2004
TL;DR: In this article, a system for moving an elongate medical device has at least one drive element for engaging and moving the elongated medical device, which is called a drive element.
Abstract: A system for moving an elongate medical device has at least one drive element for engaging and moving an elongate medical device. Various embodiments provide for moving the separate inner and outer elements of a telescoping medical device. Some systems also provide for the rotation of a rotatable distal element on a rotatable medical device or the rotation of extension element in a telescoping medical device.

Journal ArticleDOI
TL;DR: Anomalous momentum transport has been observed in Alcator C-Mod tokamak plasmas with a tangentially viewing crystal x-ray spectrometer array in this paper.
Abstract: Anomalous momentum transport has been observed in Alcator C-Mod tokamak plasmas. The time evolution of core impurity toroidal rotation velocity profiles has been measured with a tangentially viewing crystal x-ray spectrometer array. Following the L-mode to EDA (enhanced Dα) H-mode transition in both Ohmic and ion cyclotron range of frequencies heated discharges, the ensuing co-current toroidal rotation velocity, which is generated in the absence of any external momentum source, is observed to propagate in from the edge plasma to the core with a timescale of the order of the observed energy confinement time, but much less than the neo-classical momentum confinement time. The ensuing steady state toroidal rotation velocity profiles in EDA H-mode plasmas are relatively flat, with V ~ 50 km s−1, and the momentum transport can be simulated using a simple diffusion model. Assuming that the L–H transition produces an instantaneous edge source of toroidal torque (which disappears at the H- to L-mode transition), the momentum transport may be characterized by a diffusivity, with values of ~0.07 m2 s−1 during EDA H-mode and ~0.2 m2 s−1 in L-mode. These values are large compared to the calculated neo-classical momentum diffusivities, which are of the order of 0.003 m2 s−1. Velocity profiles of ELM-free H-mode plasmas are centrally peaked (with V(0) exceeding 100 km s−1 in some cases), which suggests the presence of an inward momentum pinch; the observed profiles are consistent with simulations including an edge inward convection velocity of ~10 m s−1. In EDA H-mode discharges which develop internal transport barriers, the velocity profiles become hollow in the centre, indicating the presence of a negative radial electric field well in the vicinity of the barrier foot. Upper single null diverted and inner wall limited L-mode discharges exhibit strong counter-current rotation (with V(0)~−60 km s−1 in some cases), which may be related to the observed higher H-mode power threshold in these configurations. For plasmas with locked modes, the toroidal rotation is observed to cease (V ≤ 5 km s−1).

Journal ArticleDOI
TL;DR: The stability of orbital motion about a uniformly rotating arbitrary second degree and order gravity field is investigated in this paper, where a normalized form of the equations of motion are derived and analyzed, and numerical stability criteria are proposed to evaluate the stability of initially near-circular orbits in the equatorial plane of the body.

Patent
07 Dec 2004
TL;DR: In this article, a first arm member and a second arm member are provided, where the first arm is positioned between a cam and a valve body to oscillate in synchronism with the rotation of the cam.
Abstract: A first arm member and a second arm member are provided. The first arm member is positioned between a cam and a valve body to oscillate in synchronism with the rotation of the cam. The second arm member changes the angle of the first arm member in accordance with the rotation angle of a control shaft. The temperature prevailing in the neighborhood of the control shaft and cam is detected. The rotation angle of the control shaft is corrected so as to avoid the influence of the detected temperature.

Journal ArticleDOI
TL;DR: In this article, the authors obtained a spectroscopic map of the bipolar jet from RW Aur and found that the mass ejected in the observed part of the outflow is accelerated from a region in the disk within about 0.5 (1.6) AU from the star for the blue (red) lobe.
Abstract: Using STIS on board the HST we have obtained a spectroscopic map of the bipolar jet from RW Aur. We find signatures of rotation within the first 300 AU of the jet (1.''5 from RW Aur). Both lobes rotate in the same direction (i.e. with different helicities). Toroidal velocities are in the range 5 - 30 km/s at 20 (30) AU from the symmetry axis in the blueshifted (redshifted) lobe, in line with other STIS observations and with theoretical simulations. The sense of rotation is anti-clockwise looking from the tip of the blue lobe down to the star. Rotation is more evident in the [OI] and [NII] lines and at the largest sampled distance from the axis. We derive that the mass ejected in the observed part of the outflow is accelerated from a region in the disk within about 0.5 (1.6) AU from the star for the blue (red) lobe. We estimate that the angular momentum transport rate of the jet can be two thirds or more of the estimated rate transported through the relevant portion of the disk. The magnetic lever arm (ratio rA/r0 between the Alfv`en and footpoint radii) is between 3.5 and 4.6 (accuracy 20-25%), or, the ejection index $\xi$ = d ln($\dot{M}_acc$) / d r is in the range 0.025 - 0.046 (same accuracy).These values are in the range predicted by the models, and suggest that some heating must be provided at the base of the flow. We also derive the ratio B_phi / B_p of the toroidal and poloidal components of the magnetic field at the observed location. B_phi / B_p = 3.8 +- 1.1 at 30 AU from the axis in the red lobe and -8.9 +- 2.7 at 20 AU from the axis in the blue lobe. The toroidal component is dominant, as predicted by magnetic collimation models.

Patent
01 Mar 2004
TL;DR: In this paper, a vertical axis windmill is provided where the amount of wind directed to the blades in the power producing part of rotation and the mechanical load of multiple generators is controlled by a feedback control to maintain a relatively constant rotational frequency of the shaft of the windmill.
Abstract: A vertical axis windmill is provided wherein the amount of wind directed to blades in the power producing part of rotation and the mechanical load of multiple generators is controlled by a feedback control to maintain a relatively constant rotational frequency of the shaft of the windmill. In a preferred embodiment, two wind foils extend radially outwardly from the blades to thereby provide a scoop capable of pulling in more air than would normally be received by the blades. The wind foils then direct the wind flow to the power producing part of rotation of the blades for maximum power output, when necessary. The wind foils can close to control the wind flow to the blades. The generating capacity of a plurality of generators is also controlled in response to shaft rotation to maintain substantially constant shaft rotation.

Journal ArticleDOI
TL;DR: This paper examined possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects.
Abstract: Motivated by the first detections of rotation signatures in the DG Tau jet (Bacciotti et al. [CITE]), we examine possible biases affecting the relation between detected rotation signatures and true azimuthal velocity for self-similar MHD disc winds, taking into account projection, convolution as well as excitation gradients effects. We find that computed velocity shifts are systematically smaller than the true underlying rotation curve. When outer slower streamlines dominate the emission, we predict observed shifts increasing with transverse distance to the jet axis, opposite to the true rotation profile. Determination of the full transverse rotation profile thus requires high angular resolution observations ( warm MHD disc wind models with $\lambda = 13$ and an outer radius of the disc $\simeq$3 AU are able to reproduce detected velocity shifts, while cold disc wind models ($\lambda > 50$) are ruled out for the medium-velocity component in the DG Tau jet.

Journal ArticleDOI
TL;DR: In this paper, a parametric analysis of the magnetic field and rotation of a massive stellar core was performed, and the authors found that the combination of rotation and magnetic field can lead to a jetlike prompt explosion in the direction of the rotational axis, which would not be produced by either of them alone.
Abstract: Hydrodynamics of the rotational collapse of strongly magnetized massive stellar cores has been studied numerically. Employing simplified microphysics and a two-dimensional nonrelativistic MHD code, we have performed a parametric research with respect to the strength of magnetic field and rotation, paying particular attention to the systematics of dynamics. We assume initially that the rotation is almost uniform and the magnetic field is constant in space and parallel to the rotation axis. The initial angular velocity and magnetic field strength span 1.7-6.8 rad s-1 and × 1012 G, respectively. We have found that the combination of rotation and magnetic field can lead to a jetlike prompt explosion in the direction of the rotational axis, which would not be produced by either of them alone. The range of the maximum angular velocity and field strength is 2.3 × 10-3 to 5.8 × 10-4 rad s-1 and 2.3 × 1015 to 5.6 × 1016 G, respectively, at the end of computations. Although the results appear to be consistent with those by LeBlanc & Wilson and Symbalisty, the magnetic fields behind the shock wave, not in the inner core, are the main driving factor of the jet in our models. The fields are amplified by the strong differential rotations in the region between the shock wave and the boundary of the inner and outer cores, enhanced further by the lateral matter motions induced either by an oblique shock wave (for a strong shock case) or possibly by the MRI (magnetorotational instability)-like instability (for a weak shock case). We have also calculated the gravitational wave forms in the quadrupole approximation. Although the wave form from a nonrotating magnetic core is qualitatively different from those from rotating cores, the amplitude is about an order of magnitude smaller. Otherwise, we have found no substantial difference in the first burst of gravitational waves among the magnetized and nonmagnetized models, since the bounce is mainly driven by the combination of the matter pressure and the centrifugal force.

Journal ArticleDOI
TL;DR: In this paper, the effects of rotation on wave propagation within a tire's treadband were investigated for the purpose of understanding the effect of rotating a tire on the propagation of a wave within the tire.

Journal ArticleDOI
TL;DR: In this article, the authors used the 2D multi-group, flux-limited diffusion version of the code VULCAN/2D to calculate the collapse, bounce, shock formation, and early post-bounce evolutionary phases of a core-collapse supernova for a variety of initial rotation rates.
Abstract: Using the 2D multi-group, flux-limited diffusion version of the code VULCAN/2D, that also incorporates rotation, we have calculated the collapse, bounce, shock formation, and early post-bounce evolutionary phases of a core-collapse supernova for a variety of initial rotation rates. This is the first series of such multi-group calculations undertaken in supernova theory with fully multi-D tools. We find that though rotation generates pole-to-equator angular anisotropies in the neutrino radiation fields, the magnitude of the asymmetries is not as large as previously estimated. Moreover, we find that the radiation field is always more spherically symmetric than the matter distribution, with its plumes and convective eddies. We present the dependence of the angular anisotropy of the neutrino fields on neutrino species, neutrino energy, and initial rotation rate. Only for our most rapidly rotating model do we start to see qualitatively different hydrodynamics, but for the lower rates consistent with the pre-collapse rotational profiles derived in the literature the anisotropies, though interesting, are modest. This does not mean that rotation does not play a key role in supernova dynamics. The decrease in the effective gravity due to the centripetal effect can be quite important. Rather, it means that when a realistic mapping between initial and final rotational profiles and 2D multi-group radiation-hydrodynamics are incorporated into collapse simulations the anisotropy of the radiation fields may be only a secondary, not a pivotal factor, in the supernova mechanism.

Patent
09 Jul 2004
TL;DR: In this article, a method for modeling the performance of a fixed cutter bit drilling an earth formation is presented. Butler et al. presented a method to select a drill bit and an Earth formation to be represented as drilled, simulating the bit drilling the earth formation, displaying the simulating, and adjusting at least one parameter affecting the performance.
Abstract: In one aspect, the invention provides a method for modeling the performance of a fixed cutter bit drilling an earth formation. In one embodiment, the method includes selecting a drill bit and an earth formation to be represented as drilled, simulating the bit drilling the earth formation, displaying the simulating, and adjusting at least one parameter affecting the performance. The method of design is used to make a fixed cutter drill bit. In another embodiment the method includes numerically rotating the bit, calculating bit interaction with the earth formation during the rotating, and determining the forces on the cutters during the rotation based on the calculated interaction with earth formation and empirical data.

Journal ArticleDOI
TL;DR: The first direct measurements of the very small effect of forced diurnal polar motion, successfully observed on three large ring laser gyroscopes, were reported in this article, which measured the instantaneous direction of Earth's rotation axis to a precision of 1 part in 108 when averaged over a time interval of several hours.
Abstract: [1] We report the first direct measurements of the very small effect of forced diurnal polar motion, successfully observed on three of our large ring lasers, which now measure the instantaneous direction of Earth's rotation axis to a precision of 1 part in 108 when averaged over a time interval of several hours. Ring laser gyroscopes provide a new viable technique for directly and continuously measuring the position of the instantaneous rotation axis of the Earth and the amplitudes of the Oppolzer modes. In contrast, the space geodetic techniques (very long baseline interferometry, side looking radar, GPS, etc.) contain no information about the position of the instantaneous axis of rotation of the Earth but are sensitive to the complete transformation matrix between the Earth-fixed and inertial reference frame. Further improvements of gyroscopes will provide a powerful new tool for studying the Earth's interior.

Journal ArticleDOI
TL;DR: In this paper, the authors studied the local stability of stratified, differentially rotating fluids to axisymmetric perturbations in the presence of a weak magnetic field and of finite resistivity, viscosity, and heat conductivity.
Abstract: We study the local stability of stratified, differentially rotating fluids to axisymmetric perturbations in the presence of a weak magnetic field and of finite resistivity, viscosity, and heat conductivity. This is a generalization of the Goldreich-Schubert-Fricke (GSF) double-diffusive analysis to the magnetized and resistive, triple-diffusive case. Our fifth-order dispersion relation admits a novel branch that describes a magnetized version of multidiffusive modes. We derive necessary conditions for axisymmetric stability in the inviscid and perfect-conductor (double-diffusive) limits. In each case, rotation must be constant on cylinders and angular velocity must not decrease with distance from the rotation axis for stability, irrespective of the relative strength of viscous, resistive, and heat diffusion. Therefore, in both double-diffusive limits, solid-body rotation marginally satisfies our stability criteria. The role of weak magnetic fields is essential to reach these conclusions. The triple-diffusive situation is more complex, and its stability criteria are not easily stated. Numerical analysis of our general dispersion relation confirms our analytic double-diffusive criteria but also shows that an unstable double-diffusive situation can be significantly stabilized by the addition of a third, ostensibly weaker, diffusion process. We describe a numerical application to the Sun's upper radiative zone and establish that it would be subject to unstable multidiffusive modes if moderate or strong radial gradients of angular velocity were present.

Patent
20 Apr 2004
TL;DR: In this article, a micro-electro-mechanical-system (MEMS) mirror device is proposed, which has a 2-dimensional rotational articulated hinge at a first end and a 1-dimensional rotating hinge at the second end opposite the first end.
Abstract: The invention provides a micro-electro-mechanical-system (MEMS) mirror device, comprising: a mirror having a 2-dimensional rotational articulated hinge at a first end, and having a 1-dimensional rotational articulated hinge at a second end opposite the first end; a movable cantilever connected to the mirror through the 1-dimensional rotational articulated hinge; a support structure connected to the mirror through the 2-dimensional rotational articulated hinge and connected to the movable cantilever; whereby movement of said movable cantilever causes rotation of the mirror in a first axis of rotation, and the mirror is also rotatable about a second torsional axis of rotation perpendicular to said first axis of rotation.

Journal ArticleDOI
TL;DR: Investigating observers' memory for novel objects rotating in depth suggests that dynamic information, that is, the spatiotemporal ordering of object views, provides information independent of shape or view information to a recognition system.