Showing papers on "Transverse plane published in 2003"

Impact parameter space interpretation for generalized parton distributions

Abstract: The Fourier transform of generalized parton distribution functions at ξ = 0 describes the distribution of partons in the transverse plane. The physical significance of these impact parameter dependent parton distribution functions is discussed. In particular, it is shown that they satisfy positivity constraints which justify their physical interpretation as a probability density. The generalized parton distribution H is related to impact parameter distribution of unpolarized quarks for an unpolarized nucleon, $\tilde{H}$ is related to the distribution of longitudinally polarized quarks in a longitudinally polarized nucleon, and E is related to the distortion of the unpolarized quark distribution in the transverse plane when the nucleon has transverse polarization. The magnitude of the resulting transverse flavor dipole moment can be related to the anomalous magnetic moment for that flavor in a model independent way.

Closure device and methods for making and using them

Abstract: A clip for engaging tissue includes a generally annular-shaped body defining a plane and disposed about a central axis extending normal to the plane. The body includes alternating inner and outer curved regions, defining a zigzag pattern about a periphery of the clip. The body is biased towards a planar configuration lying in the plane and deflectable towards a transverse configuration extending out of the plane. Tines extend from the inner curved regions, the tines being oriented towards the central axis in the planar configuration, and parallel to the central axis in the transverse configuration. The tines may include primary tines and secondary tines that are shorter than the primary tines. The primary tines may be disposed on opposing inner curved regions and oriented towards one another such that they overlap in the planar configuration.

Electromechanical characterisation of dielectric elastomer planar actuators: comparative evaluation of different electrode materials and different counterloads

Abstract: This work intends to extend the electromechanical characterisation of dielectric elastomer actuators. Planar actuators were realised with a 50m-thick film of an acrylic elastomer coated with compliant electrodes. The isotonic transverse strain, the isometric transverse stress and the driving current, due to a 2 s high voltage impulse, were measured for four electrode materials (thickened electrolyte solution, graphite spray, carbon grease and graphite powder), four transverse prestress values (19.6, 29.4, 39.2 and 49.0 kPa) and different driving voltages (up to the dielectric breakdown voltage). Results showed that the electrode material and prestress strongly influence the electromechanical performances of the devices. Actuators with graphite spray electrodes and transverse prestress of 39.2 kPa exhibited an isotonic transverse strain of 6% at 49 V/m, with a driving current per unit electrode area of 3.5 A/cm 2 , and an isometric transverse stress of 49 kPa at 42 V/m. An electromechanical coupling efficiency of 10% at 21 V/m was calculated for actuators with thickened electrolyte solution electrodes and a transverse prestress of 29.4 kPa. The presented data permits to choose the best electrode material and the best prestress value (among those tested), to obtain the maximum isotonic transverse strain, the maximum isometric transverse stress or the maximum efficiency for different ranges of applied electric field. © 2003 Elsevier B.V. All rights reserved.

Mechanisms on Transverse Motions in Turbulent Wall Flows

Abstract: ▪ Abstract Drag reduction in wall-bounded flows can be achieved by transverse motions imposed by passive means, e.g., riblets, or by external forcing, such as wall oscillation or transverse traveling-wave excitation. In this article, we review possible physical mechanisms responsible for turbulent drag reduction and corresponding near-wall flow modification.

Spontaneously generated X-shaped light bullets.

Abstract: We observe the formation of an intense optical wave packet fully localized in all dimensions, i.e., both longitudinally (in time) and in the transverse plane, with an extension of a few tens of fsec and microns, respectively. Our measurements show that the self-trapped wave is an X-shaped light bullet spontaneously generated from a standard laser wave packet via the nonlinear material response (i.e., second-harmonic generation), which extend the soliton concept to a new realm, where the main hump coexists with conical tails which reflect the symmetry of linear dispersion relationship.

Non-linear analysis of functionally graded plates under transverse and in-plane loads

Abstract: Large deflection and postbuckling responses of functionally graded rectangular plates under transverse and in-plane loads are investigated by using a semi-analytical approach. Material properties are assumed to be temperature-dependent, and graded in the thickness direction according to a simple power law distribution in terms of the volume fractions of the constituents. The plate is assumed to be clamped on two opposite edges and the remaining two edges may be simply supported or clamped or may have elastic rotational edge constraints. The formulations are based on the classical plate theory, accounting for the plate-foundation interaction effects by a two-parameter model (Pasternak-type), from which Winkler elastic foundation can be treated as a limiting case. A perturbation technique in conjunction with one-dimensional differential quadrature approximation and Galerkin procedure are employed in the present analysis. The numerical illustrations concern the large deflection and postbuckling behavior of functional graded plates with two pairs of constituent materials. Effects played by volume fraction, the character of boundary conditions, plate aspect ratio, foundation stiffness, initial compressive stress as well as initial transverse pressure are studied.

Observational tests of damping by resonant absorption in coronal loop oscillations

Abstract: One of the proposed damping mechanisms of coronal (transverse) loop oscillations in the kink mode is resonant absorption as a result of the Alfven speed variation at the outer boundary of coronal loops. Analytical expressions for the period and damping time exist for loop models with thin nonuniform boundaries. They predict a linear dependency of the ratio of the damping time to the period on the thickness of the nonuniform boundary layer. Ruderman and Roberts used a sinusoidal variation of the density in the nonuniform boundary layer and obtained the corresponding analytical expression for the damping time. Here we measure the thickness of the nonuniform layer in oscillating loops for 11 events, by forward-fitting of the cross-sectional density profile ne(r) and line-of-sight integration to the cross-sectional fluxes F(r) observed with TRACE 171 A. This way we model the internal (ni) and external electron density (ne) of the coronal plasma in oscillating loops. This allows us to test the theoretically predicted damping rates for thin boundaries as a function of the density ratio χ = ne/ni. Since the observations show that the loops have nonuniform density profiles, we also use numerical results for damping rates to determine the value of χ for the loops. We find that the density ratio predicted by the damping time, χLEDA = 0.53 ± 0.12, is a factor of ≈1.2-3.5 higher than the density ratio estimated from the background fluxes, χ = 0.30 ± 0.16. The lower densities modeled from the background fluxes are likely to be a consequence of the neglected hotter plasma that is not detected with the TRACE 171 A filter. Taking these corrections into account, resonant absorption predicts damping times of kink-mode oscillations that are commensurable with the observed ones and provides a new diagnostic of the density contrast of oscillating loops.

Three-dimensional imaging of the human retina by high-speed optical coherence tomography

Abstract: Conventional optical coherence tomography is based on A-scans, i.e., the fast scan direction is the z-direction. While this technique has been successfully demonstrated for two-dimensional cross sectional imaging of various tissues, it is rather slow if three-dimensional information is to be obtained. We report on a new technique that combines the transverse scanning approach of a confocal scanning laser ophthalmoscope with the depth sectioning capability of OCT. A stable high-frequency carrier is generated by use of an acousto optic modulator, and high frame rate is obtained by using a resonant scanning mirror for the priority scan (x-direction). Our prototype instrument records 64 transverse images consisting of 256x128 pixels in 1.2 seconds, thus providing the fastest retinal 3D OCT scanning system reported so far. We demonstrate the capabilities of our system by measuring and imaging the fovea and the optic nerve head region of healthy human volunteers in vivo.

Mechanical method and apparatus for bilateral tissue fastening

Abstract: A mechanical system for bilaterally securing skin tissue preferably utilizes a tissue manipulator apparatus to approximate a portion of an interior surface of each of two pieces of living dermis tissue along a vertical interface below an exterior surface without overlapping either interior surface across the vertical interface. An applicator apparatus includes a driving head portion positioned in the vertical interface and at least partially below the exterior surface and a handle portion positioned at least partially above the exterior surface. The applicator apparatus bilaterally drives at least one portion of the fastener through each piece of the living dermis tissue behind the interior surface of that piece of tissue such that the fastener is positioned below the exterior surface and a portion of the fastener is positioned generally transverse to the vertical interface.

Transverse dimensions of chorus in the source region

Abstract: We report measurement of whistler-mode chorus by the four Cluster spacecraft at close separations. We focus our analysis on the generation region close to the magnetic equatorial plane at a radial distance of 4.4 Earth's radii. We use both linear and rank correlation analysis to define perpendicular dimensions of the sources of chorus elements below one half of the electron cyclotron frequency. Correlation is significant throughout the range of separation distances of 60-260 km parallel to the field line and 7-100 km in the perpendicular plane. At these scales, the correlation coefficient is independent for parallel separations, and decreases with perpendicular separation. The observations are consistent with a statistical model of the source region assuming individual sources as gaussian peaks of radiated power with a common half-width of 35 km perpendicular to the magnetic field. This characteristic scale is comparable to the wavelength of observed waves.

Polarization-vortex-driven second-harmonic generation.

Abstract: Polarization vortices exist in the focus of a class of vector beams, the lowest order of which possess full vector symmetry about the axis of propagation of the beam. At high numerical apertures these beams are known to exhibit large, local, longitudinal fields in the focal region. At an interface these fields can be many times stronger than the largest available transverse component and are therefore candidates for a variety of different experiments in surface physics. The observation of vortex-driven surface second-harmonic generation at smooth metal and semiconductor surfaces and thin films is reported. By comparing the response to that of a purely transverse field, we show that the smooth surface responds primarily to the longitudinal field component.

Effects of Bathymetry, Friction, and Rotation on Estuary-Ocean Exchange

Abstract: An analytical model that includes pressure gradient, friction, and the earth’s rotation in both components of the flow is used to study the transverse structure of estuarine exchange flows and the nature of transverse circulation in estuaries of arbitrary bathymetry. Analytical results are obtained for generic bathymetry and also over real depth distributions and are compared with observations. This study extends previous efforts on the topic of transverse structure of density-induced exchange flows in three main aspects: 1) the analytical model explores any arbitrary bathymetry; 2) the results reflect transverse asymmetries, relative to a midchannel centerline, associated with the effects of the earth’s rotation; and 3) the transverse circulation produced by the analytical model is examined in detail. Analytical results over generic bathymetry show, in addition to the already reported dependence of exchange flow structure on the Ekman number, two new features. First, the transverse structure of along-estuary flows shows the earth’s rotation effects, even in relatively narrow systems, thus producing transverse asymmetries in these flows. The asymmetries disappear under strongly frictional (high Ekman number) conditions, thus illustrating the previously documented pattern of inflow in channels and outflows over shoals for typical estuaries. Second, transverse flows resemble a ‘‘sideways gravitational circulation’’ when frictional effects are apparent (Ekman number greater than ;0.1) responding to a transverse balance between pressure gradient and friction. These transverse flows reverse direction under very weak friction and reflect Coriolis deflection of along-estuary flows, that is, geostrophic dynamics. All examples of observed flows are satisfactorily explained by the dynamics included in the analytical model.

Does the transverse electric zero mode contribute to the Casimir effect for a metal

Abstract: The finite-temperature Casimir free energy, entropy, and internal energy are considered anew for a conventional parallel-plate configuration, in the light of current discussions in the literature. In the case of an "ideal" metal, characterized by a refractive index equal to infinity for all frequencies, we recover, via a somewhat unconventional method, conventional results for the temperature dependence, meaning that the zero-frequency transverse electric mode contributes the same as the transverse magnetic mode. For a real metal, however, approximately obeying the Drude dispersive model at low frequencies, we find that the zero-frequency transverse electric mode does not contribute at all. This would appear to lead to an observable temperature dependence and a violation of the third law of thermodynamics. It had been suggested that the source of the difficulty was the behavior of the reflection coefficient for perpendicular polarization but we show that this is not the case. By introducing a simplified model for the Casimir interaction, consisting of two harmonic oscillators interacting via a third one, we illustrate the behavior of the transverse electric field. Numerical results are presented based on the refractive index for gold. A linear temperature correction to the Casimir force between parallel plates is indeed found which should be observable in room-temperature experiments, but this does not entail any thermodynamic inconsistency.

Two-dimensional solitons in Bose-Einstein condensates with a disk-shaped trap

Abstract: We consider, both analytically and numerically, the evolution of two-dimensional (2D) nonlinear matter-wave pulses in a Bose-Einstein condensate with a disk-shaped trap and repulsive atom-atom interactions. Due to the strong confinement in the axial direction the sound speed of the system is c=(1/2 1/4)c 0, where c 0 is the corresponding value without the trap. From the 3D order-parameter equation of the condensate, we derive a soliton-bearing Kadomtsev-Petriashvili equation with positive dispersion. When the trapping potential is weak in two transverse directions, a low-depth plane dark soliton can propagate in the condensate with a changing profile but preserving its structure down to the boundary of the condensate. We show that high-depth plane dark solitons are unstable to long-wavelength transverse disturbances. The instability appears as a longitudinal modulation of the soliton amplitude decaying into vortices. We also show how a dark lumplike 2D nonlinear excitation can be excited in the system. Furthermore, a dark lump decaying algebraically in two spatial directions can propagate rather stable in the condensate, but disappears near the boundary of the condensate where two vortices are nucleated. The vortices move in opposite directions along the boundary and when meeting merge creating a new lump. Finally, we also provide results for head-on and oblique collisions of two lumps in the system.

Dns of velocity and thermal fields in turbulent channel flow with transverse-rib roughness

Abstract: A detailed knowledge of both velocity and thermal fields in wall turbulence disturbed by a row of ribs on the wall is important for clarifying the chief factors of fluid and thermal dynamics related to the control of heat transfer. In this study, in order to elucidate the effects of roughness on the statistical quantities in the velocity and thermal fields, direct numerical simulations (DNS) of heat transfer in turbulent channel flows with transverse-rib roughness have been performed by varying their spacing, width and height, in which the turbulent heat transfer with k-type and d-type roughness walls are simulated. It is found that since turbulent mixing is promoted by arranging ribs, the distributions of mean velocity and temperature become markedly asymmetric. Systematic variations of secondary flow patterns between ribs are clearly identified. The best heat transfer performance is found to be obtained with the k-type roughness.

Directional velocity estimation using focusing along the flow direction. I: theory and simulation

Abstract: A new method for directional velocity estimation is presented. The method uses beam formation along the flow direction to generate data in which the correct velocity magnitude can be directly estimated from the shift in position of the received consecutive signals. The shift is found by cross-correlating the beamformed lines. The approach can find the velocity in any direction, including transverse to the traditionally emitted ultrasound beam. The velocity estimation is studied through extensive simulations using Field II. A 128-element, 7-MHz linear array is used. A parabolic velocity profile with a peak velocity of 0.5 m/s is simulated for different beam-to-flow angles and for different emit foci. At 45/spl deg/ the relative standard deviation over the profile is 1.6% for a transmit focus at 40 mm. At 90/spl deg/ the approach gave a relative standard deviation of 6.6% with a transmit focus of 80 mm, when using 8 pulse-echo lines and stationary echo canceling. Pulsatile flow in the femoral artery was also simulated using Womersley's flow model. A purely transverse flow profile could be obtained with a relative standard deviation of less than 10% over the whole cardiac cycle using 8 pulse emissions for each imaging direction, which is sufficient to show clinically relevant transverse color flow images.

Scaling distributions of quarks, mesons, and proton for all p T , energy, and centrality

Abstract: We present the evidences for the existence of a universal scaling behavior of the production of $\pi^0$ at all transverse momenta in heavy-ion collisions at all centralities and all collision energies The corresponding scaling behavior of the quarks is then derived just before the quarks recombine with antiquarks to form the pions The degradation effect of the dense medium on the quark $p_T$ is derived from the scaling distribution In the recombination model it is then possible to calculate the $p_T$ distributions of the produced proton and kaon, which are scaling also Experimentally verifiable predictions are made Implications of the existence of the scaling behavior are discussed

Transverse Optical Mode in a One-Dimensional Yukawa Chain

Abstract: A transverse optical mode was observed in a one-dimensional Yukawa chain. Charged particles, suspended in a strongly coupled dusty plasma, were arranged in a 1D periodic structure. Particle displacement in the direction perpendicular to the chain was restored by the confining potential. The dispersion relation of phonons was measured, verifying that the optical mode has negative dispersion, with phase and group velocities that are oppositely directed. A theoretical dispersion relation is presented and compared to the experiment and a molecular dynamics simulation.

Method and apparatus for directional resistivity measurement while drilling

Abstract: A measurement-while-drilling or logging while drilling method and apparatus for determining the azimuth of providing magnetic field in a remote formation layer in the vicinity of a down hole resistivity tool. A cross-component magnetic field with substantially orthogonal transmitter and receiver coils is provided. The coil planes are either substantially orthogonal (coaxial coils) or parallel (transverse coils) with respect to, the longitudinal axis of the tool body. The coils are placed on the tool body having an external surface and a plurality of rooves are cut in the external surface of the tool body and oriented substantially horizontally with respect to the longitudinal axis of the tool body for the coils and oriented vertically with respect to the longitudinal axis of the tool body for the coaxial coils. A transverse and coaxial coil are placed in the grooves for transmission or reception of a cross-component transverse magnetic field.

Analysis and Prediction of Transverse Mixing Coefficients in Natural Channels

Abstract: An experimental study has been undertaken using a naturally formed meandering channel to obtain unique tracer and hydrodynamic data. The velocity data presented are from laser Doppler anemometer measurements; tracer data were collected using an array of fluorometers in continuous flow through mode. Techniques for the prediction of the primary and secondary velocity flow fields are explored, and shown to be accurate. Analysis of the tracer data by the generalized method of moments using the cumulative transverse discharge approach is undertaken. The coefficient of transverse mixing is shown to exhibit considerable longitudinal variation over the meander cycle. A new integrated approach for predicting transverse mixing coefficients is developed and explored and has been validated against the data set. This approach requires only three parameters as input, namely, longitudinal planform curvature, cross-sectional shape, and total discharge, and has been shown capable of accurately predicting the longitudinal variation of the transverse mixing coefficient over the meander cycle.

Cylindrical dust acoustic waves with transverse perturbation

Abstract: The nonlinear dust acoustic waves in dusty plasmas with the combined effects of bounded cylindrical geometry and the transverse perturbation are studied. Using the perturbation method, a cylindrical Kadomtsev–Petviashvili (CKP) equation that describes the dust acoustic waves is deduced for the first time. A particular solution of this CKP equation is also obtained. It is shown that the dust acoustic solitary waves can exist in the CKP equation.

Continuous monitoring of three-dimensional resin flow through a fibre preform

Abstract: A basic requirement for an accurate numerical simulation of the resin transfer moulding process is a set of exact permeability coefficients of the applied textile reinforcement. The permeabilities are usually obtained from the measurement of flow front propagation through a stack of planar fibre preforms. While measuring the in-plane flow is considered as rather simple, the detection of a flow front that moves perpendicular to the laminate plane emerges to be difficult. Therefore, the knowledge of the transverse impregnation behaviour is still sparse and transverse permeability values were determined for a very few fabrics only. The knowledge of an exact transverse permeability is important for the three-dimensional simulation of flow through thick sectioned parts and for specific RTM-related processes like resin film infusion or SCRIMP®. This paper addresses the monitoring of flow front propagation utilizing ultrasound transmission. A testing rig was developed for monitoring three-dimensional ellipsoidal impregnation, which is induced by point injection. Two multidirectional non-crimped fabrics were characterised by the three-dimensional measurement. For the determination of the transverse permeability the three-dimensional filling was emulated by a numerical flow simulation software.

Front and back instability of a liquid film on a slightly inclined plate

Abstract: We study the transverse instability of a liquid ridge on horizontal and inclined substrates using a film evolution equation based on a long wave approximation. The equation incorporates an additional pressure term—the disjoining pressure—accounting for the effective interaction of the film with the substrate. On a horizontal substrate the dominant instability mode is varicose, but may turn into a zigzag mode on a slightly inclined substrate depending on the inclination angle and the ridge volume. For larger angles or volumes the instabilities at the front and back decouple. The linear stability properties of a one-dimensional transverse ridgelike state are studied in detail, and an energy analysis is used to demonstrate that the disjoining pressure provides the dominant instability mechanism at both the front and the back, while the body force is responsible for the main differences between these two instabilities. An amplitude equation for the time evolution of perturbations with small transverse wave numbers is derived that predicts correctly the linear crossing of the most dangerous eigenvalues at zero wave number in the inclined case, in contrast to the situation on a horizontal substrate.

Polarization of wave modes in a two-dimensional hexagonal lattice using a complex (dusty) plasma

Abstract: Wave spectra corresponding to the random particle motion in a monolayer Yukawa crystal were studied for various directions of propagation. It was found that there are two wave modes with a polarization alternating between the longitudinal and transverse. In the long-wavelength regime, the modes became purely longitudinal and transverse as was known before. In the short-wavelength regime the spectra strongly depended on the wavelength and the direction of propagation. The results obtained from the experiment, theory, and simulation agreed well with each other.

Improved vectorial finite-element BPM analysis for transverse anisotropic media

Abstract: An efficient finite-element vector beam propagation formulation for dielectric media with transverse anisotropy is thoroughly presented. This formulation is expressed in terms of the magnetic field's transverse components and includes perfectly matched layers at the truncated boundaries and the wide-angle Pade approach. Several key examples demonstrate the usefulness and effectiveness of the present scheme.

Measurement of the transverse Spitzer resistivity during collisional magnetic reconnection

Abstract: Measurement of the transverse resistivity was carried out in a reconnecting current sheet where the mean free path for the Coulomb collision is smaller than the thickness of the sheet. In a collisional neutral sheet without a guide field, the transverse resistivity is directly related to the reconnection rate. A remarkable agreement is found between the measured resistivity and the classical value derived by Spitzer. In his calculation the transverse resistivity for the electrons is higher than the parallel resistivity by a factor of 1.96. The measured values have verified this theory to within 30% errors.

In-plane and out-of-plane transverse susceptibility in close-packed arrays of monodisperse Fe nanoparticles

Abstract: The transverse susceptibility (TS) of arrays of self-assembled Fe nanoparticles has been studied using a sensitive radio-frequency resonant technique. Symmetrically located broad peaks in the TS data are observed below the blocking temperature as the applied field is swept from positive to negative saturation. These peaks occur at the effective anisotropy fields $(\ifmmode\pm\else\textpm\fi{}{H}_{K})$ with the peak width determined by the distribution in ${H}_{K}$ in the nanoparticle array system. These features are observed to be strongly affected by dipolar interactions as well as thermal relaxation. Systematically tracking the evolution of the TS curves across the superparamagnetic transition reveals distinct temperature ranges over which thermal activation and dipolar energy overcome the effective magnetic anisotropy energy. Hysteresis loops measured using a superconducting quantum interference device magnetometer indicate a smaller coercive field for in-plane field orientation compared to that for out-of-plane orientation. This is also reflected in the TS measurements. A comparison of the TS over a wide range in temperature and magnetic fields, applied in plane and out of plane, reveals the distinct influence of variation in dipolar interaction strengths for the two geometries.