Showing papers on "Transverse plane published in 2001"

Disk drive actuator arm with microactuated read/write head positioning

Abstract: The present invention is embodied in an actuator arm which is mounted to a primary actuator. The primary actuator positions the actuator arm, with a read/write head mounted to the actuator arm, across a data storage disk. The actuator arm comprises an inboard portion, an outboard portion and a pair of bimorph actuators. The inboard portion has a longitudinal axis and is attached to the primary actuator. The outboard portion has the read/write head mounted onto it. The pair of bimorph actuators are deflectable together in a common direction and are connected between the inboard and the outboard portions. Upon deflection of the bimorph actuators in the same direction, the outboard portion is translated along an at least nearly straight line transverse to the longitudinal axis of the inboard portion. This transverse motion allows the read/write head to be kept substantially within a plane parallel to the surface of the data storage disk, preventing damage caused by possible contact between slider and the disk surface from rolling the slider due to out-of-plane motions. Further, the use of bimorph actuators provide increased displacements of the read/write head. Also, since the head displacement is not a function of microactuator's position along the actuator arm, the actuator arm can be shorter, allowing for use in compact disk drives.

Transverse oscillations in coronal loops observed with TRACE

Abstract: We study transverse loop oscillations triggered by 17flares and filament destabilizations; only 2 such cases have been reported in the literature until now. Oscillation periods are estimated to range over a factor of ∼15, with most values between 2 and 7 min. The oscillations are excited by filament destabilizations or flares (in 6% of the 255 flares inspected, ranging from about C3 to X2). There is no clear dependence of oscillation amplitude on flare magnitude. Oscillations occur in loops that close within an active region, or in loops that connect an active region to a neighboring region or to a patch of strong flux in the quiet Sun. Some magnetic configurations are particularly prone to exhibit oscillations: two active regions showed two, and one region even three, distinct intervals with loop oscillations. The loop oscillations are not a resonance that builds up: oscillations in loops that are excited along their entire length are likely to be near the fundamental resonance mode because of that excitation profile, but asymmetrically excited oscillations clearly show propagating waves that are damped too quickly to build up a resonance, and some cases show multiple frequencies. We discuss evidence that all oscillating loops lie near magnetic separatrices that outline the large-scale topology of the field. All magnetic configurations are more complicated than a simple bipolar region, involving mixed-polarities in the interior or vicinity of the region; this may reflect that the exciting eruptions occur only in such environments, but this polarity mixing likely also introduces the large-scale separatrices that are involved. Often the oscillations occur in conjunction with gradual adjustments in loop positions in response to the triggering event. We discuss the observations in the context of two models: (a) transverse waves in coronal loops that act as wave guides and (b) strong sensitivity to changes in the field sources for field lines near separatrices. Properties that favor model b are (1) the involvement of loops at or near separatrices that outline the large-scale topology of the field, (2) the combined occurrence of oscillations and loop translations, (3) the small period spread and similar decay time scale in a set of oscillating loops in one well-observed event, and (4) the existence of loops oscillating in antiphase with footpoints close together in two cases. All other properties are compatible with either model, except the fact that almost all of the oscillations start away from the triggering event, suggestive of an outward-pushing exciting wave more in line with model a. The spread in periods from event to event suggests that the oscillations may reflect the properties of some driver mechanism that is related to the flare or mass ejection.

Parametric decay of circularly polarized Alfvén waves: Multidimensional simulations in periodic and open domains

Abstract: The nonlinear evolution of monochromatic large-amplitude circularly polarized Alfven waves subject to the decay instability is studied via numerical simulations in one, two, and three spatial dimensions. The asymptotic value of the cross helicity depends strongly on the plasma beta: in the low beta case multiple decays are observed, with about half of the energy being transferred to waves propagating in the opposite direction at lower wave numbers, for each saturation step. Correspondingly, the other half of the total transverse energy (kinetic and magnetic) goes into energy carried by the daughter compressive waves and to the associated shock heating. In higher beta conditions we find instead that the cross helicity decreases monotonically with time towards zero, implying an asymptotic balance between inward and outward Alfvenic modes, a feature similar to the observed decrease with distance in the solar wind. Although the instability mainly takes place along the propagation direction, in the two and three-dimensional case a turbulent cascade occurs also transverse to the field. The asymptotic state of density fluctuations appears to be rather isotropic, whereas a slight preferential cascade in the transverse direction is seen in magnetic field spectra. Finally, parametric decay is shown to occur also in a non-periodic domain with open boundaries, when the mother wave is continuously injected from one side. In two and three dimensions a strong transverse filamentation is found at long times, reminiscent of density ray-like features observed in the extended solar corona and pressure-balanced structures found in solar wind data.

Longitudinal and Transverse Waves in Yukawa Crystals

Abstract: A unified theoretical treatment is given of longitudinal (or compressional) and transverse modes in Yukawa crystals, including the effects of damping. Dispersion relations are obtained for hexagonal lattices in two dimensions and bcc and fcc lattices in three dimensions. Theoretical predictions are compared with two recent experiments.

Large scale flow structures and mixing processes in shallow flows

Abstract: Shallow turbulent flows occurring in wide rivers, estuaries, lakes or coastal regions, as well as the atmosphere, are readily susceptible to transverse disturbances that lead to two-dimensional coherent structures, the shallow jet, the shallow wake and the shallow mixing layer are examples of such flow patterns, three types of generation mechanisms are proposed for these flows; namely, topographical forcing, internal transverse shear instabilities, and secondary instabilities of the base flow, the large-scale coherent structures greatly influence the mixing and transport of pollutants that are released into such flows, they may also play an important role in transverse momentum exchange that controls friction in wide channel flows.

Transverse electrokinetic and microfluidic effects in micropatterned channels: Lubrication analysis for slab geometries

Abstract: Off-diagonal (transverse) effects in micropatterned geometries are predicted and analyzed within the general frame of linear-response theory, relating applied pressure gradient and electric field to flow and electric current. These effects could contribute to the design of pumps, mixers, or flow detectors. Shape and charge-density modulations are proposed as a means to obtain sizeable transverse effects, as demonstrated by focusing on simple geometries and using the lubrication approximation.

Transverse jets and jet flames. Part 2. Velocity and OH field imaging

Abstract: Detailed measurements of the velocity field in the symmetry plane of two jets and two jet flames in a crossflow are obtained using particle image velocimetry. The jets issue into a wind tunnel at density-weighted jet-to-crossflow velocity ratios r = 10 and r = 21, with corresponding Reynolds numbers 6000 and 12 800. Ensemble statistics of the velocity field are presented, and some interesting features of the entrainment process in transverse jets are discussed. Deviations from the simple behaviour predicted by the similarity analysis presented in Part 1 are highlighted. Simultaneous planar laser-induced fluorescence imaging of the OH radical is performed in selected regions of the flames. Results suggests that flame/flow interaction is strong near the lifted flamebase, but increasingly weaker further downstream.

Radio frequency magnetic field mapping of a 3 Tesla birdcage coil: experimental and theoretical dependence on sample properties.

Abstract: The RF B(1) distribution was studied, theoretically and experimentally, in phantoms and in the head of volunteers using a 3 T MRI system equipped with a birdcage coil. Agreement between numerical simulation and experiment demonstrates that B(1) distortion at high field can be explained with 3D full-Maxwell calculations. It was found that the B(1) distribution in the transverse plane is strongly dependent on the dielectric properties of the sample. We show that this is a consequence of RF penetration effects combined with RF standing wave effects. In contrast, along the birdcage coil z-axis the B(1) distribution is determined mainly by the coil geometry. In the transverse plane, the region of B(1) uniformity (within 10% of the maximum) was 15 cm with oil, 6 cm with distilled water, 11 cm with saline, and 10 cm in the head. Along z the B(1) uniformity was 9 cm with phantoms and 7 cm in the head.

High radiation efficient dual band feed horn

Abstract: A multiple mode feed horn is provided for transmitting and receiving signals. The feed horn includes a transverse electric throat section, a transverse electric profile section, and a transverse electric aperture section. The transverse electric profile section propagates a first transverse electric (TE) mode. The transverse electric aperture section propagates a second TE mode. The multiple mode feed horn prevents propagation of traverse magnetic modes from said throat section to said aperture section.

Wave-driven Turbulent Coronal Heating in Open Field Line Regions: Nonlinear Phenomenological Model

Abstract: A model is presented to investigate the driving of coronal turbulence in open field line regions, powered by low-frequency oscillatory field line motions at the coronal base. The model incorporates the combined effects of wave propagation, reflection associated with gradients of Alfven speed, and low-frequency quasi-two-dimensional turbulence, which is treated using a one-point closure phenomenology appropriate to a transverse cascade in the reduced magnetohydrodynamic regime. Considering a sample of the corona and employing open boundary conditions, we use the model to investigate the dynamical efficiency of turbulent dissipation, which competes with propagation of fluctuations away from the coronal base. We examine the dependence of the heating efficiency on wave-forcing frequency, the sensitivity to parameters controlling the Alfven speed profile, the behavior of the model for varying the phenomenological correlation length of turbulence, including asymptotic limits of negligible or very intense nonlinearities, and the confinement of turbulent dissipation to the region near the coronal base. Each of these issues may be of importance in understanding the heating of the corona and the origin of the solar wind.

Method and apparatus for stabilizing adjacent bones

Abstract: An apparatus (10) is provided for implantation into an adjacent pair of vertebral bodies (12 and 14) having first and second surfaces (17 and 19) that oppose each other. The apparatus (10), when implanted, is attached to the adjacent pair of vertebral bodies and stabilizes the vertebral bodies (12 and 14) while the vertebral bodies fuse together. The apparatus (10) comprises a platform (24) having a third surface (38) extending transverse to the first and second surfaces (17 and 19).

Two-dimensional anisotropic non-Fermi-liquid phase of coupled Luttinger liquids.

Abstract: Using bosonization techniques, we show that strong forward scattering interactions between one-dimensional spinless Luttinger liquids (LL) can stabilize a phase where charge-density wave, superconducting, and transverse single particle hopping perturbations are irrelevant. This new phase retains its LL-like properties in the directions of the chains, but with relations between exponents modified by the transverse interactions, whereas it is a perfect insulator in the transverse direction. The mechanism that stabilizes this phase is strong transverse charge-density wave fluctuations at incommensurate wave vector, which frustrates crystal formation by preventing lock-in of the in-chain density waves.

Higher-order zig-zag model for analysis of thick composite beams with inclusion of transverse normal stress and sublaminates approximations

Abstract: A modified zig-zag technical theory, suitable for the analysis of thick composite beams with rectangular cross section, general lay-up and in cylindrical bending is developed and tested. An equivalent single-layer model and a multiple-layer model are implemented. The displacement field of both these models is postulated as to allow for appropriate jumps in the strains, so that the transverse shear and the transverse normal stress and stress gradient continuity at the interfaces are met. A third-order piecewise approximation for the in-plane displacement and a fourth-order piecewise approximation for the transverse displacement are assumed in the two models. Their predictive capability is investigated in sample cases wherein the exact three-dimensional elasticity and other approximate solutions are available. On the basis of this numerical investigation, they appear to predict accurately and efficiently the displacement and stress fields of composite beams with layers of different materials.

Streamwise oscillations of a cylinder in a steady current. Part 1. Locked-on states of vortex formation and loading

Abstract: Streamwise oscillations of a circular cylinder in a steady uniform flow are investigated experimentally using a technique of high-image-density particle image velocimetry, in conjunction with instantaneous force measurements. This approach allows insight into the relationship between the loading and the patterns of vorticity and streamline topology in the near wake.In analogy with the classical locked-on state arising from transverse oscillations of a cylinder in uniform flow, it is possible to attain either locked-on or quasi-locked-on states due to streamwise oscillations. In these cases, however, the repetitive signature of the transverse force is not sinusoidal; rather, it is strongly modulated and the corresponding spectra can exhibit several sharply defined peaks. The predominant peak can vary over a remarkably wide range, extending from the subharmonic to the third harmonic of the cylinder oscillation frequency; for certain locked-on states of the transverse force signature, the spectral peak at the cylinder oscillation frequency is actually suppressed. Corresponding instantaneous traces and spectra of the in-line force simply show dominance of the spectral peak at the cylinder oscillation frequency. Further interpretation of the loading is provided in terms of Lissajous patterns of the transverse and in-line force coefficients.All of these features are related to the instantaneous patterns of vortex formation in the near wake. During a typical cycle of the cylinder oscillation, these patterns can be divided into two broad categories: Karman-like shedding; and a nearly ‘frozen’ array of shed vortices. The order of occurrence of these basic patterns during an oscillation cycle dictates the instantaneous signatures and time-averaged spectra of the transverse force.

Experimental observation of vertically polarized transverse dust-lattice wave propagating in a one-dimensional strongly coupled dust chain.

Abstract: Externally driven, vertically polarized transverse dust-lattice waves were observed in a one-dimensional strongly coupled dust chain levitated in the plasma-sheath boundary of a dc argon plasma at low gas pressure around 5 mtorr. Real and imaginary parts of the complex wave number were measured in the experiments. The experimental result clearly shows that the observed transverse dust-lattice wave propagates as a backward wave, which is in good agreement with the theoretical prediction.

Characterization of the transverse coherence of hard synchrotron radiation by intensity interferometry.

Abstract: The transverse coherence of x rays was measured with an intensity interferometer using a 120-microeV-bandwidth monochromator operating at 14.41 keV. By analyzing the transverse coherence profiles, a vertical source profile of a 25-m long undulator of SPring-8, as well as the coherence degradation by a phase object in the beam path, were quantitatively characterized.

Shielding method and apparatus using transverse slots

Abstract: A shielding method and apparatus for providing predetermined attenuation of one or more electromagnetic energy field components as the field components interact with the shield. The shield composed of a flexible strip or cylindrical body and respectively comprising a transverse conductive element or a transverse slot therein. The shields being adapted to cover an antenna mounted on a support. The shields being compatible for use in conjunction with saddle, tilted coils or multi-layered tri-axial coils to produce a pure transverse magnetic dipole electromagnetic field.

Chapter 6 Transverse mode shaping and selection in laser resonators

Abstract: This chapter discusses the transverse mode shaping and selection in laser resonators. Laser resonators are categorized as either stable or unstable. In a stable resonator, a ray launched inside the resonator parallel to the optical axis remains inside it, whereas in an unstable resonator, the ray may bounce off the resonator after a few round-trips. The chapter describes transverse modes in stable and unstable resonators, and also the numerical and analytical methods to determine the field distributions of the transverse modes. Various methods to select specific transverse modes in laser resonators, along with techniques for fabricating the needed intra-cavity elements are also described. Intra-cavity elements can be incorporated into laser resonators to shape specific transverse mode patterns and to discriminate and select a specific single mode out of the many modes that exist in the resonator. The properties of the laser output beams include beam quality, output power and field distributions. The analytical tools for describing the properties of the laser output beams, along with selected applications are discussed in the chapter.

Theory for broadband Noise of Rotor and Stator Cascades with Inhomogeneous Inflow Turbulence Including Effects of Lean and Sweep

Abstract: The problem of broadband noise generated by turbulence impinging on a downstream blade row is examined from a theoretical viewpoint. Equations are derived for sound power spectra in terms of 3 dimensional wavenumber spectra of the turbulence. Particular attention is given to issues of turbulence inhomogeneity associated with the near field of the rotor and variations through boundary layers. Lean and sweep of the rotor or stator cascade are also handled rigorously with a full derivation of the relevant geometry and definitions of lean and sweep angles. Use of the general theory is illustrated by 2 simple theoretical spectra for homogeneous turbulence. Limited comparisons are made with data from model fans designed by Pratt & Whitney, Allison, and Boeing. Parametric studies for stator noise are presented showing trends with Mach number, vane count, turbulence scale and intensity, lean, and sweep. Two conventions are presented to define lean and sweep. In the "cascade system" lean is a rotation out of its plane and sweep is a rotation of the airfoil in its plane. In the "duct system" lean is the leading edge angle viewing the fan from the front (along the fan axis) and sweep is the angle viewing the fan from the side (,perpendicular to the axis). It is shown that the governing parameter is sweep in the plane of the airfoil (which reduces the chordwise component of Mach number). Lean (out of the plane of the airfoil) has little effect. Rotor noise predictions are compared with duct turbulence/rotor interaction noise data from Boeing and variations, including blade tip sweep and turbulence axial and transverse scales are explored.

Refined Global Approximation Theory of Multilayered Plates and Shells

Abstract: A refined global approximation theory of thin multilayered anisotropic shells is developed. The effects of the laminated material response, transverse shear, and transverse normal strains are included. The material of each layer of the shell is assumed to be linearly elastic, anisotropic, homogeneous, or fiber reinforced. As unknown functions the tangential displacements of the face surfaces and transverse displacements of the face or middle surfaces of the shell are chosen. It is an important feature of the proposed theory. This fact simplifies, for example, an analysis of the contact problems and allows to elaborate universal numerical algorithms. An exact solution for the problem of the bending of homogeneous isotropic rectangular plates subjected to a sinu- soidal load has been found. Numerical solutions for the problem of the bending of multilayered composite plates and cylindrical shells have been also obtained. The influence of anisotropy, and transverse shear and transverse normal deformation response of the stress state of the shell is examined.

Subband mixing rules in circumferentially perturbed carbon nanotubes: Effects of transverse electric fields

Abstract: We analyze various potential environments such as electrodes, substrates, gate voltages, and flattening deformations in single-wall C nanotubes in terms of circumferential perturbations on nanotube surfaces. Considering the periodicity of perturbations, we derive selection rules in the subband mixing caused by perturbations. Uniform electric fields perpendicular to the tube axis induce band-gap modification such as opening and closure. Thus, locally applied transverse fields cause significant backscattering of the states near the threshold for transmission.

Geometry of phase and polarization singularities illustrated by edge diffraction and the tides

Abstract: In complex scalar fields, singularities of the phase (optical vortices, wavefront dislocations) are lines in space, or points in the plane, where the wave amplitude vanishes. Phase singularities are illustrated by zeros in edge diffraction and amphidromies in the heights of the tides. In complex vector waves, there are two sorts of polarization singularity. The polarization is purely circular on lines in space or points in the plane (C singularities); these singularities have index +/- 1/2. The polarization is purely linear on lines in space for general vector fields, and surfaces in space or lines in the plane for transverse fields (L singularities); these singularities have index +/- 1. Polarization singularities (C points and L lines) are illustrated in the pattern of tidal currents.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The influence of rays on the transverse elastic anisotropy in green wood of deciduous trees

Abstract: The green wood of twelve deciduous tree species was investigated regarding its radial and tangential moduli of elasticity measured in tension (E R and E T , respectively). In addition, the wood density and the volume fraction of rays were determined. A strong positive correlation was found between structural and stiffness properties. A simple two component model was derived for the relationship between the transverse elastic anisotropy factor (i.e., E R /E T ) of the green wood and the relative volume fraction of the axial and ray tissues. In the radial direction of the wood, the modulus of elasticity is influenced by the wood density and the volume fraction of rays; in tangential direction only the density seems to be important. However, the comparison between the elastic anisotropy and the volume fraction of rays indicates that the rays may have an indirect influence due to their shape.

Analysis of piezoelectric bimorphs and plates with segmented actuators

Abstract: Elastic plates with distributed or segmented piezoelectric layers have been analyzed using the classical laminated plate theory, the first-order shear deformation theory, and the results are compared with an analytical solution. The plate theories and the analytical solution take into account both the direct and the converse piezoelectric effects, and assume generalized plane strain deformations. The transverse displacements from both theories are in reasonable agreement. The classical lamination theory gives a discontinuous longitudinal stress at the edges of the segments whereas the analytical solution predicts a continuous curve with steep gradients. Piezoelectric bimorphs with the axis of transverse isotropy inclined at an angle to the thickness direction are also studied using the three formulations. The displacements and stresses obtained from the first-order shear deformation theory are in very good agreement with the analytical solution even for thick plates. It is advantageous to use shear bimorphs since the stresses induced in them are smaller than those in extension bimorphs. © 2001 Elsevier Science Ltd. All rights reserved.

High-concentration photovoltaic assembly for a utility-scale power generation system

Abstract: A high-concentration photovoltaic assembly ( 24 ) for use in a utility-scale solar power generation system ( 20 ) is configured to couple to a supporting tracking structure ( 22 ) of the system ( 20 ) The assembly ( 24 ) incorporates a frame ( 38 ) substantially centered in a plane ( 44 ), a plurality of substantially parallel longitudinal members ( 80 ) substantially centered in the plane ( 44 ) and coupled to the frame ( 38 ), two substantially parallel transverse members ( 82 ) substantially centered in the plane ( 44 ) and coupled to the longitudinal members ( 80 ) substantially at ends thereof, a plurality of bulkheads ( 90 ) coupled between adjacent ones of the longitudinal members ( 80 ) and configured to divide the assembly ( 24 ) into a plurality of chambers ( 94 ), a plurality of photovoltaic modules coupled to the chambers ( 94 ) upon a first side ( 48 ) of the plane ( 44 ), and a plurality of lenses ( 98 ) coupled to the chambers ( 94 ) upon a second side ( 46 ) of the plane ( 44 )