Showing papers on "Transverse plane published in 1994"

Localized structures and localized patterns in optical bistability.

Abstract: We study numerically a Swift-Hohenberg equation describing, in the weak dispersion limit, nascent optical bistability with transverse effects. We predict that stable localized structures, and organized clusters of them, may form in the transverse plane. These structures consist of either kinks or dips. The number and spatial distribution of these localized structures are determined by the initial conditions while their peak (bottom) intensity remains essentially constant for fixed values of the system's parameters.

Steady Inspiratory Flow in a Model Symmetric Bifurcation

Abstract: Flow in a bifurcating tube system typifying a major bronchial bifurcation is studied experimentally with a two color, two velocity component laser Doppler anemometer. The flow loop is composed of a pumping station, flow stratifiers and a constant head pressure tank; it can accommodate steady, pulsatile or oscillatory flow. The test section is a symmetric bifurcation of constant cross sectional area and has a branching angle of 70 deg. The test section is a cast of clear silicon rubber in a plexiglass mold that was milled on a numerically controlled milling machine. The flow division ratio from the parent to daughter branches is about unity. Steady flow results that model the inspiratory phase at Reynolds numbers of 518, 1036 and 2089, corresponding to Dean numbers of 98, 196 and 395, show that in the bifurcation plane velocity profiles in the daughter branches are skewed toward the inner wall. In the transverse plane, "m" shaped velocity profiles are found with low velocity at the center. Secondary flow patterns, which are responsible for such phenomena, are first observed at the axial position where the flow begins to turn. Flow separation was not observed at any point in the bifurcation.

A comparative study of two-dimensional multiple scattering techniques

Abstract: The scattering of an electromagnetic plane wave from an arbitrary configuration of parallel circular cylinders is investigated using four different techniques. The cylinders are made of perfectly conducting or homogeneous dielectric material. These techniques are a boundary value type of solution, an iterative scattering procedure, a hybrid approach based on a combination of exact and method of moments solution, and a high-frequency asymptotic approximation. The analysis is given in detail for the transverse magnetic (TM) polarization, and that for the transverse electric (TE) polarization is outlined. Numerical results are provided to show the major differences between these techniques and the validity of using circular cylinders in modeling composite two-dimensional scatterers.

Transverse particle motion in radio-frequency linear accelerators

Abstract: The transverse motion of a relativistic charged particle in a radio-frequency linear accelerator (rf linac) is examined. The spatially averaged equations of motion are derived for a particle in a periodic accelerating cavity system, and solved exactly in the ultrarelativistic limit. These solutions, along with an impulse treatment of the transients at the entrance and exit of the linac cavities, allow derivation of a linear transport matrix through the cavity. This generalized matrix is improved over previously derived results in that it is applicable to both traveling- and standing-wave structures, allows for arbitrary injection phase and spatial-harmonic content of the rf fields, and is more accurate in approximating the exact charged-particle motion.

Simulation of two-dimensional anisotropic cardiac reentry: Effects of the wavelength on the reentry characteristics

Abstract: A two-dimensional sheet model was used to study the dynamics of reentry around a zone of functional block. The sheet is a set of parallel, continuous, and uniform cables, transversely interconnected by a brick-wall arrangement of fixed resistors. In accord with experimental observations on cardiac tissue, longitudinal propagation is continuous, whereas transverse propagation exhibits discontinuous features. The width and length of the sheet are 1.5 and 5 cm, respectively, and the anisotropy ratio is fixed at approximately 4∶1. The membrane model is a mofified Beeler-Reuter formulation incorporating faster sodium current dynamics. We fixed the basic wavelength and action potential duration of the propagating impulse by dividing the time constants of the secondary inward current by an integerK. Reentry was initiated by a standard cross-shock protocol, and the rotating activity appeared as curling patterns around the point of junction (the q-point) of the activation (A) and recovery (R) fronts. The curling R front always precedes the A front and is separated from it by the excitable gap. In addition, the R front is occasionally shifted abruptly through a merging with a slow-moving triggered secondary recovery front that is dissociated from the A front and q-point. Sustained irregular reentry associated with substantial excitable gap variations was simulated with short wavelengths (K=8 andK=4). Unsustained reentry was obtained with a longer wavelength (K=2), leading to a breakup of the q-point locus and the triggering of new activation fronts.

Collapse of a transverse-mode continuum in a self-imaging photorefractively pumped ring resonator.

Abstract: We demonstrate the collapse of a continuum of transverse modes in a self-imaging ring resonator that is photorefractively pumped. The resulting localized mode has an arbitrary transverse location. The mode collapse results from placing saturable photorefractive gain and loss media in spatially conjugate resonator planes. The transverse position of the localized mode is unstable under small cavity misalignments, and it drifts across the transverse aperture while retaining its spatial form.

Biaxially oriented polyester film

Abstract: A biaxially oriented polyester film which is free from thickness unevennesses in both the longitudinal and transverse directions and has uniform physical properties in the transverse direction and a high strength in the longitudinal direction. The film has the following features: (a) an F-5 value in the longitudinal direction is 13 kg/mm2 or above, (b) the thickness unevenness in each of the longitudinal and transverse directions is 8 % or less, and (c) the transverse difference between the thermal shrinkage percentages in the longitudinal direction at 105 °C ranges from 0.02 to 0.2 % per meter in the transverse direction.

New Methodology for Seismic Design of RC Shear Walls

Abstract: An analytical approach to determine the need to provide transverse reinforcement at boundaries of reinforced concrete structural walls with rectangular, T‐shaped, or barbell‐shaped cross sections is presented. By relating the expected displacement demands on the building system to the local deformations imposed on the wall cross section, the magnitude and distribution of wall normal strain is determined. The primary variables affecting the wall‐strain distribution are found to be the ratio of wall cross‐sectional area to the floor‐plan area, the wall aspect ratio and configuration, the wall axial load, and the wall‐reinforcement ratios. Based on the computed wall‐strain distribution, required transverse steel for concrete confinement and length of the wall cross section requiring concrete confinement is computed. The wall‐strain distribution is also used to evaluate required transverse reinforcement to restrain buckling of longitudinal reinforcement. The validity of the proposed analytical approach is dem...

Glass fiber duct board with coated grooves and the method of making the same

Abstract: A glass fiber duct board has longitudinally extending, spaced-apart grooves in a major surface that facilitate the folding of the duct board into an air duct. The major surface, including the grooves, is coated with a polymeric latex coating to encapsulate glass fibers and dust within the surface of the duct board. The polymeric latex coating is applied to the surfaces of the grooves as a foam by application nozzles located downstream of groove cutting tools. The polymeric latex coating applied by the nozzles is distributed over the surfaces of the grooves and set to a predetermined thickness by wiper blades, located downstream of the nozzles, which have edge configurations complementary to the transverse configurations of the grooves being coated.

A residual-gas ionization beam profile monitor for the Heidelberg Test Storage Ring TSR

Abstract: A monitoring device for the transverse density distribution of stored heavy-ion beams, based on the detection of ionization products of the beam particles in the residual gas, has been developed for the heavy-ion Test Storage Ring (TSR) in Heidelberg. With two monitor units installed in the ring, non-destructive, sensitive measurements of the horizontal and vertical profiles of cooled stored ion beams can be performed with a spatial resolution of about ±(0.2–0.3) mm. The beam profile monitors are used to determine the transverse beam temperature, to study transverse cooling and heating mechanisms, to observe the ion beam behaviour during experiments, and to determine storage-ring parameters such as the dispersion function. The principle, technical realization and operation of these devices are described. First experimental results concerning transverse electron cooling of heavy-ion beams are discussed, in particular the measurement of cooling rates and the optimization of the alignment between the stored ion beam and the cooling electron beam.

Nonlinear transverse modes of large-aspect-ratio homogeneously broadened lasers: I. Analysis and numerical simulation.

Abstract: Transverse pattern evolution is investigated in single-longitudinal-mode two-level and Raman lasers with flat end reflectors, subjected to uniform transverse pumping. The natural nonlinear modes of the laser are identified as spatially homogeneous when the detuning from the gain peak is negative and as ``local'' plane traveling waves when the detuning is positive. The latter correspond to an off-axis emission of the laser. Stability characteristics of the underlying patterns are predicted to be quite different for one-dimensional and two-dimensional (2D) lasers. As an illustration, we provide direct numerical evidence for weakly turbulent behavior of a 2D Raman laser where Eckhaus and zigzag phase instabilities act in concert to spontaneously nucleate topological defects and ridgelike illuminated regions. Our numerics also confirm that the complicated patterns persist for finite transverse pumping as long as the characteristic width of the pump source contains a sufficient number of selected pattern wavelengths.

Transverse Shear Stresses and Their Sensitivity Coefficients in Multilayered Composite Panels

Abstract: A computational procedure is presented for the accurate determination of transverse shear stresses and their sensitivity coefficients in flat multilayered composite panels subjected to mechanical and thermal loads. The sensitivity coefficients measure the sensitivity of the transverse shear stresses to variations in the different lamination and material parameters of the panel. The panel is discretized by using either a three-field mixed finite element model based on a two-dimensional first- order shear deformation plate theory or a two-field degenerate solid element with each of the displacement components having a linear variation throughout the thickness of the laminate. The evaluation of transverse shear stresses can be conveniently divided into two phases. The first phase consists of using a superconvergent recovery technique for evaluating the in-plane stresses in the different layers. In the second phase, the transverse shear stresses are evaluated by using piecewise integration, in the thickness direction, of the three-dimensional equilibrium equations. The same procedure is used for evaluating the sensitivity coefficients of the transverse shear stresses. The effectiveness of the computational procedure is demonstrated by means of numerical examples of multilayered cross-ply panels subjected to transverse loading, uniform temperature change, and uniform temperature gradient through the thickness of the panel.more » In each case the standard of the comparison is taken to be the exact solution of the three dimensional thermoelasticity equations of the panel.« less

Transverse mode behavior in native-oxide-defined low threshold vertical-cavity lasers

Abstract: Data are presented characterizing the transverse mode behavior of AlAs/GaAs/InGaAs vertical‐cavity surface‐emitting lasers fabricated using a native‐oxide process. The native‐oxide process results in laser diodes with active regions defined to be 10, 8, and 4 μm squares. We show that the transverse lasing mode is influenced by mirror reflectivity, with significant mode changes occurring with drive current for 8–10 μm devices in the ranges of one to four times threshold. In smaller devices of 4 μm square dimension, the transverse mode at threshold appears as a lowest order mode.

Unsteady hydromagnetic free convection flow with hall current mass transfer and variable suction through a porous medium near an infinite vertical porous plate with constant heat flux

Abstract: The effects of Hall current on unsteady free convection flow of an MHD viscous incompressible fluid along an infinite vertical porous plate are investigated in the presence of a uniformly applied magnetic field acting in a plane which makes an angle α with the plane transverse to the plate. A similarity parameter, taken to be a function of time, is introduced, and the suction velocity is considered to be inversely proportional to this parameter. Similarity equations are then derived and solved numerically. The effects of the Hall parameter, the magnetic parameter and the permeability are discussed and shown graphically.

Method of correcting for axial and transverse error components in magnetometer readings during wellbore survey operations

Abstract: A method is disclosed for determining wellbore azimuth accurately, notwithstanding the corrupting influence of axial and transverse magnetic field biasing error components. A reliable value of the axial magnetic field component (Bx) is determined by minimizing the vector distance between B (as measured) and its expected value B. Preferably, this is accomplished utilizing a method of radicals to solve a quadratic equation. Given a reliable Bx, the transverse magnetic field components (Bx and Bx) can be determined from taking a number of surveys as the drillstring is rotated about. Bx and Bx can be determined by utilizing the assumption that the transverse magnetic field components should remain invariant as the drillstring is rotated.

Transverse modes, vortices and vertical-cavity surface-emitting lasers

Abstract: Injection locking dramatically modifies the phase and transverse output intensity profile of vertical-cavity surface-emitting lasers (VCSELs). Injection can induce a VCSEL to emit a high-order transverse mode. Vortices are generated by three different methods: insertion of a helicoidal phase mask, interference of two Gaussian beams, and injection locking of the TEM01 and TEM10 modes of a VCSEL to form the TEM∗01 donut mode. The first two methods stem from geometrical optics; the third method involves nonlinear mode competition in the laser cavity.

Absorbent article with fastening system to prevent drooping

Abstract: The present invention is directed to an absorbent article which is configured to prevent drooping and to improve fit. The article comprises attachment means for attaching the article about the waist of a wearer such that attachment (58) points are located on the sides of the article and behind a transverse center plane (60) of the article.

Transverse instability of energy-exchanging counterpropagating waves in photorefractive media

Abstract: The transverse instability of counterpropagating waves in photorefractive media that is due to the formation of reflection gratings is studied. We obtain new solutions for the instability threshold that account for the reflection-grating-mediated transfer of energy between the pump waves. We find that the instability threshold is minimized for equal-intensity pump beams inside the medium, corresponding to externally supplied beams of unequal intensity when there is energy coupling between the pump beams. A coupling-constant-times-interaction-length product of at least 1.1 when the coupling constant is purely real, or at least 6.3 when the coupling constant is purely imaginary, is sufficient for observation of transverse instabilities. Comparison with the physically available photorefractive coupling constant leads to the conclusion that a variety of commonly available materials should be suitable for the observation of transverse instabilities. In addition, new results for the instability threshold of a reflection-grating four-wave mixing oscillation are obtained that include the effects of direct coupling between the pump waves.

Three-Dimensional Laser Cooling of Stored and Circulating Ion Beams by Means of a Coupling Cavity

Abstract: It is shown, theoretically, that a coupling cavity; namely an rf cavity operating in the TM{sup 210} mode, when inserted in a storage ring will enhance the coupling between longitudinal and transverse degrees of freedom. As a result, it is shown that the demonstrated very effective laser cooling of the longitudinal motion, can now be extended to transverse motion; i.e., employed to cool a beam in all three directions.

Effects of transverse anisotropy on VCSEL spectra

Abstract: High resolution spectral measurements on a commercial VCSEL array are reported. The authors observe frequency splittings that result from birefringence, typically 3-22 GHz, and from transverse anisotropy between differently oriented first-order modes, typically 3-17 GHz. The spectral splittings between the various transverse modes are found to be independent of polarisation.

A review of experimental transverse Doppler studies

Abstract: The possibility of detecting useful Doppler information when the ultrasound beam is transversely oriented to the flow, has so far been studied by several authors. A new theory, in particular, has demonstrated that the focusing properties of piezoelectric transducers involve a Doppler signal bandwidth proportional to the transverse velocity component. The key element to perform reliable "transverse" Doppler experimental studies is thus an efficient spectrum analyzer, capable of performing accurate and repeatable bandwidth measurements. The authors review here experimental tests of the new theory, independently done in several laboratories by means of a specially developed computerized spectrum analyzer. The results of these tests include the demonstration that the "transverse" Doppler bandwidth is invariant with the range of cell depth and dimensions. It is also discussed how the basic transverse Doppler technique can be conveniently extended to allow the two- and three-dimensional estimation of the flow vector. Experimental evidence about the possibility of using the new theory to give a correct interpretation of in vivo transverse spectrograms is also presented. >

Existence and uniqueness of Stoneley waves

Abstract: SUMMARY The basic existence-uniqueness theory for Stoneley waves propagating along a plane interface between different isotropic elastic media is re-examined, using a matrix formulation of the secular equation. The resulting development is appreciably simpler than previous treatments of the theory. The domain of existence of Stoneley waves and the limiting curves forming its outer boundary are characterized in terms of coordinates β21/β22 and μ2/μ1 where μ1, μ2 are the shear moduli and β1, β2 the speeds of transverse plane waves in the constituent media. The equations of the limiting curves are given explicitly and exemplified numerically.

Theory of transverse modes in end-pumped microchip lasers

Abstract: I analyze the formation of transverse modes in a microchip solid-state laser with plane-parallel cavity mirrors, generalizing the traditional mean-field limit of laser theory. Owing to the balance between mode diffraction and focusing effects induced by the pump beam, the transverse dimension of the laser modes is shown to depend on the cavity Q factor. To provide further insight, a one-dimensional model for an end-pumped microchip laser is also presented. The model gives analytical solutions for the threshold and for the intensity profile of different transverse modes and allows us to study the effects of narrow pump beams. In particular, it is predicted that decreasing the dimensions of the pump beam will lead to longitudinal mode hopping with a corresponding discontinuity in the transverse-mode profile.

Method and apparatus for obtaining a signature from a fired bullet

Abstract: A method for obtaining a signature from a fired bullet is obtained by mounting the bullet to turn substantially about a longitudinal axis of the bullet, illuminating a surface of the bullet, obtaining and storing a frame image at a given position of the surface portion using microscope optics, the frame image having a transverse extent substantially transverse to the longitudinal axis, advancing the frame image position by an amount less than a transverse extent of the frame image, repeating the last two steps a plurality of times to obtain a plurality of overlapping frame images, combining the frame images to form a continuous composite image having a transverse extent much greater than the transverse extent of the frame images, and computing a signature of the composite image along a line extending in the transverse extent of the composite image. The points of the signature are determined from image data along a direction of striations in the composite image which is at an angle with respect to the transverse line and the longitudinal axis.