Showing papers on "Transverse plane published in 1993"

Articular facets of the human spine. Quantitative three-dimensional anatomy.

Abstract: This study provides the quantitative three-dimensional surface anatomy of the articular facets for the entire human vertebral column based on a study of 276 vertebrae. Means and standard errors of the means for linear, angular, and area dimensions of the superior and inferior articular facets were measured for all vertebrae from C2 to L5. Facet orientations were described as angles with respect to the sagittal and transverse planes and also as card angles. The plane angles are similar to the angles seen on traditional radiographic views--radiographs and computed tomographic scans. The card angles, a new concept, are better at helping visualize the three-dimensional orientations of the facets. Excluding the superior C2 facet, the following minimum and maximum dimensions were found for the facets from C3 to L5: width = 9.6-16.3 mm; height = 10.2-18.4; surface area = 72.3-211.9 mm2; interfacet width = 20.8-40.6; interfacet height = 12.2-33.0 mm; transverse plane angle = 41.0-86.0; sagittal plane angle = 67.4-154.8; X-card angle = 41.0-86.0; and Y-card angle = 5.8-66.1. The quantitative anatomy of the facets may improve the understanding of the spinal anatomy, help improve the clinical diagnosis and treatment, and provide the necessary data for constructing more realistic mathematical models of the spine.

Three‐dimensional fluid simulations of the nonlinear drift‐resistive ballooning modes in tokamak edge plasmas

Abstract: A three‐dimensional study of the turbulence and sheared flow generated by the drift‐resistive ballooning modes in tokamak edge plasmas has been completed. The fluid simulations show that 10%–15% percent density fluctuations can develop in the nonlinear state when the self‐consistently generated shear flow is suppressed. These modes are also found to give rise to poloidally asymmetric particle transport. Characteristic scale lengths of these fluctuations are isotropic in the plane transverse to B and smaller than the connection length along the field line. Sheared poloidal flow is self‐consistently driven by both the Reynolds stress and the Stringer mechanisms. In the presence of self‐consistent shear flow, the transverse spectrum is no longer isotropic transverse to B. The vortices become elongated in the poloidal direction. Also, there is a substantial reduction in both the level of fluctuations of the density and potential and the associated particle transport. These features are in qualitative agreement with L–H transitions observed in tokamaks.

Transverse mode control of vertical-cavity top-surface-emitting lasers

Abstract: Transverse mode characteristics and control for vertical-cavity top-surface-emitting lasers (VCSELs) are discussed. A spatial filtering concept for the control of VCSEL transverse modes that allows over 1.5-mW single TEM/sub 00/ transverse mode emission to be routinely achieved from continuous-wave electrically excited VCSELs is introduced. Without spatial filtering, L-I and V-I kinks are observed. >

Transverse cracking and stiffness reduction in composite laminates

Abstract: A study of transverse cracking mechanism in composite laminates is presented using a singular hybrid finite element model. The model provides the global structural response as well as the precise local crack-tip stress fields. An elasticity basis for the problem is established by employing Lekhnitskii's complex variable potentials and method of eigenfunction expansion. Stress singularities associated with the transverse crack are obtained by decomposing the deformation into the symmetric and antisymmetric modes and proper boundary conditions. A singular hybrid element is thereby formulated based on the variational principle of a modified hybrid functional to incorporate local crack singularities. Axial stiffness reduction due to transverse cracking is studied. The results are shown to be in very good agreement with the existing experimental data. Comparison with simple shear lag analysis is also given. The effects of stress intensity factors and strain energy density on the increase of crack density are analyzed. The results reveal that the parameters approach definite limits when crack densities are saturated, an evidence of the existence of characteristic damage state.

Stability and confinement of nonrelativistic sheet electron beams with periodic cusped magnetic focusing

Abstract: Sheet electron beams focused by periodically cusped magnetic (PCM) fields are stable against low‐frequency velocity‐shear instabilities (such as diocotron mode). This is in contrast to more familiar unstable behavior in uniform solenoidal magnetic fields. Two rectangular‐cross‐section magnetic configurations capable of focusing in both transverse dimensions are investigated: (i) a closed‐side two‐plane PCM configuration that is topologically equivalent to conventional round‐cross‐section PPM focusing; and (ii) an open‐side configuration that uses ponderomotive PCM focusing in the vertical plane and simple vzBy Lorentz force focusing in the horizontal plane. Both configurations are capable of stable sheet beam confinement. The open‐side configuration appears more practical both for focusing and for realizing matched (cold) beam conditions in which the beam envelope is free from oscillations. For realistic beams with finite emittance, the existence of a matched cold beam solution implies less emittance grow...

Two-dimensional spreading of a granular avalanche down an inclined plane Part I. theory

Abstract: This paper is concerned with the motion of an unconfined finite mass of a granular material released from rest on an inclined plane. The granular mass is treated as a frictional Coulomb-like continuum with a Coulomb-like basal friction law. Depth averaged equations are deduced from the three-dimensional dynamical equations by scaling the equations and imposing the shallowness assumption that the moving piles are long and wide but not deep. Several distinguished limits for small depth to length and depth to width ratios can be analysed. We develop an approximate theory based upon the full dynamical equations parallel to the inclined plane and imposed hydrostatic pressure conditions perpendicular to it. The resulting model equations are then applied to construct either yet simpler model equations or else solutions for particular cases. In a first application the transverse distributions of the velocity fields and of the depth profile are prescribed, while representative values of these functions (such as the cross sectional averages or maxima) as functions of time and the downhill coordinate are left unspecified. For these quantities evolution equations are obtained from a lateral averaging of the vertically averaged equations. In a second application approximate similarity solutions of the spatially two-dimensional equations are derived. The depth and velocity profiles for the moving mass are determined in analytical form, and the evolution equation for the total length and the total width of the pile is integrated numerically. A parameter study illustrates the performance of the model.

Buckling or transverse deflections of unsymmetrically laminated plates subjected to in-plane loads

Abstract: Numerous research publications purport to give in-plane buckling loads for unsymmetrically laminated composite plates. In many of these cases, bifurcation buckling is impossible; that is, transverse deflection is initiated, regardless of the magnitude of the loading. In the present work, finite element studies are made of four types of unsymmetrical laminates, including antisymmetrical ones. Twelve sets of edge constraints are considered. Maximum values of transverse deflection are determined for uniform and linearly varying in-plane boundary forces, including uniaxial, biaxial, and shear. Cases where the plate remains flat are thereby also identified. Results confirm a theoretical analysis previously made. Cases for which improper buckling results are often reported in the published literature are identified.

Improving transverse actuation of piezoceramics using interdigitated surface electrodes

Abstract: The possibility of using interdigitated surface electrode patterns to improve the transverse actuation capability of electroceramic actuators is investigated. This pattern produces nonuniform electrical fields in the plane of the wafer which utilize the longitudinal piezoelectric effect to generate larger, more anisotropic planar actuation than conventional piezoelectric devices. Analytical models are developed for a representative electroceramic volume element of a piezoelectric wafer with interdigitated electrodes. These models incorporate full electromechanical coupling through the constitutive relations and are solved using approximate energy methods. The analytical models are compared to piezoelectric finite element solutions. The analysis predicts a range of electrode thickness and spacings which can increase the achievable transverse actuation. An experimental program was performed to validate the analytical results. The experimental results verified the analytical prediction of highly orthotropic large magnitude in plane strains.© (1993) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Particle acceleration in reconnecting current sheets

Abstract: We study motions of charged particles in reconnecting current sheets (CS) which have both transverse (perpendicular to the current sheet plane) and longitudinal (parallel to the electric current inside the sheet) components of the magnetic field. Such CS, called non-neutral, are formed in regions of magnetic field line reconnection in the solar atmosphere. We develop an analytical technique which allows us to reproduce previous results concerning the influence of transverse fields on particle motion and acceleration. This technique also allows us to evaluate the effect of the longitudinal field. The latter increases considerably the efficiency of particle acceleration in CS. The energizing of electrons during the main phase of solar flares can be interpreted as their acceleration in non-neutral CS.

Instrumentation for distal targeting of locking screws in intramedullary nails

Abstract: The instrumentation is used by orthopaedic surgeons for accurate and rapid placement of distal locking screws in intramedullary nails. A probe inserted into the intramedullary nail positions two electromagnetic drive coils with their magnetic axes parallel to and at a fixed offset from the axis of a transverse hole to be drilled. The drive coils generate alternating magnetic fields over intermittent and non-overlapping time intervals in a manner that provides independent sources of positional information. A hand-held guide, containing a drill bushing and four receiving coils with the same offset as the drive coils, when moved about in the vicinity of the probe, produces a corresponding movement of graphical images on a display screen. The graphical images provide intuitive information as to how the guide must be moved to accurately align the drill bushing with the axis of the transverse hole. With the aid of continuous visual information on the display screen, the surgeon holds the guide and bushing in proper position while making a stab incision to the bone, while drilling or driving a trocar through the near and far cortices of the bone, and while inserting and fastening the locking screw. The intrumentation enables distal targeting by surgeons without specialized training or experience and eliminates the need for C-arm x-ray machines that increase operating room costs and increase the risk of radiation exposure to the patient and the surgeon.

Development of the acetabulum and hip: computed tomography analysis of the axial plane

Abstract: Acetabular growth and development in the axial plane was evaluated by computed tomography (CT) scan. One hundred seventy normal hips of children ranging in age from 6 months to 17 years were evaluated for axial acetabular index, anterior and posterior center-edge angles (CEA), and acetabular anteversion. The acetabulum deepens and becomes increasingly spherical with time until the age of 13 years. Little further change in acetabular shape occurs once the triradiate cartilage closes. Closure ensues between the ages of 11 and 13 years, occurring slightly earlier in girls. Posterior bony coverage of the femoral head is greater than anterior coverage at all times. Acetabular anteversion showed little change as the acetabulum developed. Establishing normal values for axial development of the hip and acetabulum allows a better three-dimensional concept of the different pathologic conditions and aids in treatment planning.

A Study of the Opening Displacement of Transverse Cracks in Cross-Ply Laminates

Abstract: Transverse cracks in cross-ply laminates are investigated experimentally to reveal the essential characteristics of their opening displacement under tensile loads. The average crack opening displacement is studied as a function of the longitudinal overall strain and the effects of matrix toughness and transverse ply thickness on this parameter are examined. The interactive effects between closely spaced transverse cracks are also ex- amined and found to be significant. Implications of the experimentally observed features on the micromechanics and continuum damage type models are discussed.

Solenoidal, octopolar, transverse gradient coils

Abstract: A structure provides a gradient field useful in magnetic resonance imaging. Axially aligned, solenoidal-like coils are symmetrically distributed around the perimeter of the bore of a superconducting magnet in an MRI system so as to produce transverse gradients in the X and Y directions with exceptionally high efficiency and exceptionally low acoustic noise. Opposed solenoidal endcoils may be added to reduce axial flux leakage by generating an axial quadrupolar field. Radially aligned coils may be positioned near each end of the axial coils to reduce leakage flux by adding a transverse quadrupolar field to form a resulting octopolar field. Typically, the solenoid-like coils have a mean radius of about 15% of the radius of that of the imaging ellipsoidal region. A thick-walled stainless steel, copper and resin cylinder may be used to simplify gradient shielding problems. Silver plated bronze or stainless steel sheet is used as an rf shield.

Closure device for a cylindrical housing

Abstract: In combination with a cylindrical housing, a closure cap including a transverse end wall and cylindrical shell defining a bore and open end. A sealing device arranged between the bore and open end has an outer cylindrical sealing surface mating with an inner cylindrical sealing surface on the housing. A coupling device is arranged between the closure cap and cylindrical housing and includes three spiral webs on the inner surface of the closure cap shell between a first and second transverse plane. The first plane is remote from the end wall and the second plane is close to the end wall, each web having respective ends in the first and second plane, the ends in the first plane being circumferentially spaced from the ends in the second plane by an angle of less than 120 degrees. Three guide lugs radially extend from the cylindrical housing for engagement with the webs, the guide lugs being circumferentially spaced from each other by an angle of about 120 degrees. The second place has a distance from the transverse end wall of the closure cap which exceeds the length of the guide lugs extending parallel to the longitudinal axis of the housing.

Towed array shape estimation using Kalman filters-theoretical models

Abstract: The dynamical behavior of a thin flexible array towed through the water is described by the Paidoussis equation. By discretizing this equation in space and time a finite-dimensional state-space representation is obtained where the states are the transverse displacements of the array from linearity in either the horizontal or vertical plane. The form of the transition matrix in the state-space representation describes the propagation of transverse displacements down the array. The outputs of depth sensors and compasses located along the array are shown to be related in a simple, linear manner to the states. From this state-space representation a Kalman filter which recursively estimates the transverse displacements and hence the array shape is derived. It is shown how the properties of the Kalman filter reflect the physics of the propagation of motion down the array. Solutions of the Riccati equation are used to predict the mean square error of the Kalman filter estimates of the transverse displacements. >

Particle aggregation method and apparatus.

Abstract: A sample (e.g. 52) of liquid with suspended particles is contained in a tube (10) and subjected to a standing wave ultrasound field transverse to the tube (10), the standing wave exhibiting a progressive change in pressure amplitude transverse to the tube, so that particles in suspension are displaced transversely of the tube to one or more predetermined regions: exposure of the sample to the standing wave is then terminated and the particles are allowed to settle, and inspected to determine whether they remain aggregated or whether they dissociate. The ultrasound field is produced by a transducer (20) of tubular form encircling the tube (10). The invention may be used for the agglutination of particles or cells via cross-bridging molecules in immuno-agglutination assays.

Excitation field synthesis as a means for obtaining enhanced axial resolution in fluorescence microscopes

Abstract: For fundamental reasons, fluorescence microscopes are more limited in axial, as opposed to transverse, resolution. By giving the excitation field a particular axial structure, this limitation can be partially alleviated, as in confocal scanning or two-photon scanning, or even in optical sectioning microscopy in cases where the object occupies only a small part of the field of view. Standing-wave fluorescence microscopy (SWFM) is a direct imaging method in which the specimen is excited by a 3-D field of planar interference fringes oriented parallel to the object focal plane of the microscope. By shifting the position of the nodal planes of this field relative to the specimen, structures that are normally obscured under uniform excitation become resolved. We demonstrate that, in very thin biological specimens, this optical subsectioning increases axial resolution by an order of magnitude, to 0.04 μm. In comparison to confocal scanning, SWFM resolves fine axial structure with more than 10-fold greater speed, and with similarly-reduced photobleaching. We also discuss the more general case of excitation field synthesis (EFS), in which standing wave fields differing in node spacing can be overlapped or time-multiplexed in the specimen so that the average field is non-periodic and peaked at the object focal plane. A transfer function model is given to show that for weakly-refractive specimens of arbitrary thickness, such as single cells or cell monolayers, EFS should lead to a fivefold improvement in axial resolution.

Ultrasonic cutting device

Abstract: An ultrasonic cutting device includes a transducer, an ultrasonic horn and a cutting blade. The transducer generates ultrasonic vibrations in a direction having a longitudinal axis, and the ultrasonic horn has a nodal point and at least three projections extending, respectively, to vibrating faces equidistantly away from and symmetrically about the nodal point, one of the vibrating faces being connected to the transducer so that, in operation, the ultrasonic horn is vibrated. The cutting blade is connected to one of the vibrating faces of the ultrasonic horn which is not connected to the transducer and is positioned in a plane transverse to the longitudinal axis of vibrations so that, in operation, the blade is vibrated.

A waveguide transverse slot for array applications

Abstract: The characteristics of a radiating rectangular transverse slot in a rectangular waveguide have been studied. A moment method solution is used with entire basis expansion and testing functions (Galerkin) including the effect of wall thickness. The results are presented in terms of normalized resistance and reactance versus slot length and frequency. Excellent agreement with a previous pulse basis solution is found, as well as with measured data. An array of resonantly spaced transverse slots radiates large grating lobes. A spatial filter using baffles to suppress the grating lobes is described, suppressed. The effect of the baffles on the transverse slot impedance is analyzed for the case of baffles with infinite height. >

Phase diagrams of transverse Ising film

Abstract: Applying the effective-field theory, we study the phase diagrams of a transverse Ising film. The phase diagrams show that, for JS/J Rc, Tc is larger than the surface critical temperature Tsc of the semi-infinite system and as JS/J is increased further, Tc (except Tc of the film with two layers) rapidly approaches Tsc. We also calculate the critical transverse field hc and Tc as a function of the film thickness.

Windscreen wiper with elongated, curved backbone

Abstract: A windscreen wiper includes an elongate curved backbone which is of a resiliently flexible material and which has a connecting formation at a position intermediate its length for connection to a displacing and force applying member. The backbone has a free-form curved profile in a plane, thereby to define a transverse axis perpendicular to the plane. The backbone further has a suitably varying transverse cross-sectional profile along its length such that if it is clamped at its connecting formation and a test force of 1N applied at a tip in a direction that is parallel to the transverse axis, the tip is displaced less than 1.0 mm.

On the structure of solar and stellar coronae - Loops and loop heat transport

Abstract: We discuss the principal constraints on mechanisms for structuring and heating the outer atmospheres - the coronae - of stars. We argue that the essential cause of highly localized heating in the coronae of stars like the sun is the spatially intermittent nature of stellar surface magnetic fields, and that the spatial scale of the resulting coronal structures is related to the spatial structure of the photospheric fields. We show that significant constraints on coronal heating mechanisms derive from the observed variations in coronal emission, and, in addition, show that the observed structuring perpendicular to coronal magnetic fields imposes severe constraints on mechanisms for heat dispersal in the low-beta atmosphere. In particular, we find that most of commonly considered mechanisms for heat dispersal, such as anomalous diffusion due to plasma turbulence or magnetic field line stochasticity, are much too slow to account for the observed rapid heating of coronal loops. The most plausible mechanism appears to be reconnection at the interface between two adjacent coronal flux bundles. Based on a model invoking hyperresistivity, we show that such a mechanism naturally leads to dominance of isolated single bright coronal loops and to bright coronal plasma structures whose spatial scale transverse to the local magnetic field is comparable to observed dimensions of coronal X-ray loops.

An analysis of transverse electric scattering from a rectangular channel in a conducting plane

Abstract: The problem of transverse electric plane wave scattering from a rectangular channel which is engraved in a perfect conducting plane is investigated. A Fourier transform technique is employed to express the scattered field in the spectral domain in terms of parallel-plate waveguide modes. The boundary conditions are enforced on the conducting surface and the channel aperture to obtain simultaneous equations for the transmitted field inside the channel. The simultaneous equations are solved to represent the transmitted field in a series form. By using the stationary phase approximation, the exact expression for the far-zone scattered field is obtained and the echo width behavior is numerically studied in terms of the scattering angle, frequency, and channel size. It is found that the behavior of the echo width versus the channel depth exibits resonance irrespective of the size of the channel width. An approximate series expression (Kirchhoff solution) for the echo width is valid for high-frequency scattering regimes (a > 2 λ). We also present an approximate closed form solution for nadir backscattering which is valid when a > 0.2λ.

On pressure-shear plate impact for studying the kinetics of stress-induced phase transformations

Abstract: Pressure-shear plate impact experiments are proposed for studying the kinetics of stress-induced phase transformations. The purpose of this paper is to determine loading conditions and specimen orientations which can be expected to activate a single habit plane variant parallel to the impact plane, thereby simplifying the study of the kinetics of the transformation through monitoring the wave profiles associated with the propagating phase boundary. The Wechsler-Lieberman-Read phenomenological theory was used to determine habit plane indices and directions of shape deformation for a CuAlNi shape memory alloy which undergoes a martensitic phase transformation under stress. Elastic waves generated by pressure-shear impact were analyzed for wave propagation in the direction of the normal to a habit plane. A critical resolved shear stress criterion was used to predict variants which are expected to be activated for a range of impact velocities and relative magnitudes of the normal and transverse components of the impact velocity.

Interpretive gridding by anisotropic kriging

Abstract: Most interpolation algorithms perform poorly on data sampled along profiles crossing features whose length scales are small along the profiles but large transverse to them, such as lineaments. Rather than reproducing the linear features, these algorithms create a series of closures around the profiles. By introducing additional information into the algorithm, in particular by using an anisotropic covariance model for kriging that contains a priori information about the lineations, more realistic results can be obtained. An algorithm of this type produces a much more reasonable map of aeromagnetic data from the Cobb Offset zone of the Juan de Fuca Ridge than either minimum curvature gridding or isotropic kriging.