Showing papers on "Transverse plane published in 1992"

Permeability of Unidirectional Reinforcements for RTM

Abstract: The permeability of an idealized unidirectional reinforcement consisting of regularly ordered, parallel fibres is derived starting from first principles (Navier-Stokes equations) both for flow along and for flow perpendicular to the fibres. First, an approx imate analytical solution for transverse flow is derived which differs from the Kozeny- Carman equation for the permeability of a porous medium [9] in that the transverse flow stops when the maximum fibre volume fraction is reached. The solution for flow along the fibres has the same form as the Kozeny-Carman equation. A comparison shows excellent agreement between a numerical solution of the full flow equations and the approximate one at medium to high fibre volume fractions (V f > 0.35). The theoretical predictions of permeability were tested in a specially designed mould. The results from the experiments with an unsaturated polyester resin (Jotun PO-2454) and the unidirectional reinforcement did in all cases show excellent agreement with results pre...

Theory of stress transfer in a 0°—90°—0° cross-ply laminate containing a parallel array of transverse cracks

Abstract: Two new analytical methods have been developed that can predict the stress transfer between the 0 and 90° plies in a 0°—90°—0° cross-ply laminate containing transverse cracks. Account is taken of thermal residual stresses arising from a mismatch in thermal expansion coefficients of the 0 and 90° plies. The first method is based on a 2-D model which assumes that generalised plane strain conditions prevail. The theoretical approach retains all relevant stress and displacement components, and satisfies exactly the equilibrium equations, the interface conditions, and other boundary conditions involving stresses. The stress—strain—temperature relations are satisfied either exactly or in an average sense. The 2-D representation can be used to predict the stress and displacement fields for a laminate containing parallel transverse cracks. In this paper the solutions are used to estimate the dependence of the longitudinal values of Young's modulus, Poisson's ratio, and thermal expansion coefficient on the density of transverse cracks. The second analytical method extends the 2-D model so that it can apply to 3-D problems which arise, for example, when edge effects or orthogonal cracking are to be taken into account. For the special case of very large laminate widths the 2- and 3-D models predict results which are very close to each other for both glass fibre/epoxy and carbon fibre/epoxy laminates. It is shown how the 3-D model can be used to predict the transverse Young's modulus and thermal expansion coefficient. Theoretical predictions of the dependence of Poisson's ratio on transverse crack density indicate that experimental measurements can be sensitive to the strain measurement technique used, and to specimen width when using a transverse extensometer. Theoretical predictions, for glass fibre/epoxy and carbon fibre/epoxy laminates, of the dependence of Young's modulus and Poisson's ratio on the crack density are compared with some experimental results.

Modeling of cylindrical objects by circular dielectric and conducting cylinders

Abstract: The scattering of an incident plane wave from an array of parallel circular dielectric and/or conducting cylinders is derived rigorously using a boundary value approach. Both transverse electric (TE) and transverse magnetic (TM) polarized incident plane waves are considered. The validity and accuracy of the method are verified by comparing the numerical results with those based on other available methods. The advantage of the proposed analysis is the simplicity and efficiency in computation. The modeling of two-dimensional objects of arbitrary cross section and composite material is outlined and sample numerical results are presented to illustrate the versatility of the method. >

Characterization of near-wall hydrodynamic lift forces using sedimentation field-flow fractionation

Abstract: In field-flow fractionation (FFF), a family of high resolution techniques for the separation of particles and polymers, the measured retention time of entrained particles eluting through a thin (50-500 μm) parallel plate channel is determined by the transverse forces acting on the particles during their migration. For particles in the size range ∼l-100μm an applied transverse driving force (in the present case sedimentation) rapidly brings the particles into balance with hydrodynamic lift forces, so that the two force vectors are equal in magnitude but opposite in direction. By subjecting latex microspheres of known size and density to a specified rotation rate in a centrifuge, the applied sedimentation force is known and thus the magnitude of the lift forces is immediately obtained. The transverse particle position can be determined from the measured particle retention time. Thus lift forces can be determined as a function of particle size, transverse position, and flowrate. This strategy has be...

Bed-load transport on transverse slope.I

Abstract: Bed-load particles tend to move downslope in response to gravity and downstream in response to fluid drag. The effect of gravity becomes particularly important when the downslope gravitational force has a component normal to the streamwise direction. Such phenomena as bank erosion, bed topography in river bends, sediment sorting, and stream braiding are strongly influenced by transverse bed-load transport under the influence of gravity. Here, the problem is analyzed from a consideration of the dynamics of saltating grains. Simultaneous solution of the streamwise and transverse equations of motion for a grain saltating on a transversely tilting bed of moderate slope allows a determination of mean particle trajectory. This mean trajectory, while predominately directed in the streamwise direction, includes a transverse downslope component as well. The results are used to determine a relation for the ratio of transverse to streamwise bed-load transport. This ratio increases with increasing transverse slope and decreases with increasing streamwise shear stress. The relation is compared with observations as well as existing relations obtained from simpler considerations.

Circumstantial evidence for transverse flow in 200A GeV S+S collisions.

Abstract: The hadronic spectra of 200A GeV S+S collisions are analyzed assuming thermal emission of particles including resonance decays. While the rapidity distributions suggest a longitudinal flow almost independent of the temperature, the transverse momentum spectra exhibit an ambiguity between transverse flow and temperature, which cannot be resolved by the spectra of the heavier particles. However, in a theoretical model for the global hydrodynamic expansion with a dynamical freeze-out criteron, we find that almost inevitably a sizable transverse flow develops, which is in quantitative agreement with the data.

Compression Failure of Quasibrittle Material: Nonlocal Microplane Model

Abstract: The previously presented constitutive model of microplane type for nonlinear triaxial behavior and fracture of concrete is used in nonlocal finite element analysis of compression failure in plane strain rectangular specimens. For specimens with sliding rigid platens there is a bifurcation of the loading path at the beginning of postpeak softening; a symmetric (primary) path exists but the actual (stable) path is the nonsymmetric (secondary) path, involving an inclined shear‐expansion band that consists of axial splitting cracks and is characterized by transverse expansion. The secondary path is indicated by the first eigenvalue of the tangent stiffness matrix but can be more easily obtained if a slight nonsymmetry is introduced into the finite element model. In specimens with bonded rigid platens there is no bifurcation; they fail symmetrically, by two inclined shear‐expansion bands that consist of axial splitting cracks. The transverse expansion produces transverse tension in the adjacent material, which...

Equivalent boundary conditions for thin orthotropic layer between two solids: reflection, refraction, and interface waves.

Abstract: Boundary conditions for an interface between two solids are introduced to model a thin orthotropic interface layer. The plane of symmetry of the layer material coincides with the incidence plane. Boundary conditions relating stresses and displacements on both sides of the interface are obtained from an asymptotic representation of the three‐dimensional solutions for an interface layer whose thickness is small compared to the wavelength. The results for anisotropic boundary conditions are a generalization of our previous results [S. I. Rokhlin and Y. J. Wang, J. Acoust. Soc. Am. 89, 505–515 (1991)] for an isotropic viscoelastic layer. The interface boundary conditions obtained contain interface stiffness and inertia and terms involving coupling between normal and tangential stresses and displacements. The applicability of such boundary conditions is analyzed by comparison with exact solutions for reflection. As in the isotropic case, fundamental boundary‐layer conditions are introduced containing only one transverse or normal mass or stiffness. It is shown that the solution for more accurate interface boundary conditions, which include two inertia elements and two stiffness elements, can be decomposed into a sum of fundamental solutions. Interface waves along such an interface are considered. Characteristic equations for these waves are obtained in closed form for different types of approximate boundary conditions and the velocities calculated from them are compared to the exact solution. It is shown that retention of the terms describing coupling between normal and transverse stresses and displacements is essential for calculating the velocity of an antisymmetric interface wave.

Large-eddy simulation of turbulent flow and heat transfer in plane and rib-roughened channels

Abstract: Large-eddy simulation results are presented and discussed for turbulent flow and heat transfer in a plane channel with and without transverse square ribs on one of the walls. They were obtained with the finite-difference code Harwell-FLOW3D, Release 2, by using the PISOC pressure-velocity coupling algorithm, central differencing in space, and Crank-Nicolson time stepping. A simple Smagorinsky model, with van Driest damping near the walls, was implemented to model subgrid scale effects. Periodic boundary conditions were imposed in the streamwise and spanwise directions. The Reynolds number based on hydraulic diameter (twice the channel height) ranged from 10 000 to 40 000. Results are compared with experimental data, k-ϵ predictions, and previous large-eddy simulations.

Low profile electrical connector

Abstract: An electrical connector includes a dielectric housing having a terminal-receiving passage defining a terminal-insertion axis for receiving a mating terminal member. A stamped and formed sheet metal contact member has a contact end disposed in the passage and a terminal end projecting from the housing. The housing has top and bottom walls, with the terminal-receiving passage extending in a direction therebetween. A slot is provided in a side wall of the housing communicating with the passage. The contact end of the contact member is inserted into the slot and is generally planar and has a terminal-receiving slot. The plane of the contact end and the slot are disposed generally transverse to the terminal-insertion axis. The contact member includes an intermediate portion located adjacent the contact end to provide additional flexiblity to the contact arms at the contact end.

Transient response of thick circular and square bars subjected to transverse elastic impact

Abstract: The objective of the studies presented in this paper was to understand the transient response of thick circular and square bars subjected to transverse elastic point impact. It is shown that the transient response is composed of a number of resonant frequencies caused by cross‐sectional modes of vibration. The individual cross‐sectional modes and their corresponding natural frequencies were determined using plane strain and three‐dimensional finite‐element models of circular and square cross sections. The first few modes for both circular and square cross sections are shown. Subsequently, three‐dimensional finite‐element models of circular and square bars were used to determine the transient response caused by transverse point impact. To verify the results obtained from the numerical models, experimental studies were performed on a 0.4‐m‐diam circular bar and a 0.3‐m square bar. These specimens were representative of full‐size concrete columns—typical barlike structural elements. The results of these experimental studies were in excellent agreement with those obtained from the finite‐element analyses. A future paper will present the results obtained from numerical and experimental studies on rectangular bars.

Kinematics of the ankle: a hinge axis model.

Abstract: We used a mechanical method to locate the axis of rotation of the talocrural joint. A single constant axis of rotation was found just distal to the tips of the malleoli. The paths of light-emitting diodes mounted on a talar pin were recorded with time lapse photography during flexion-extension. These paths were analyzed both in the sagittal plane and in a plane perpendicular to the axis of rotation. Sagittal plane studies were distorted by perspective error. The plane used to analyze joint motion or shape must be the plane of motion. Models of the talocrural joint for gait analysis, reconstructive surgery and prosthetic design should have a single offset axis of rotation.

Two-Dimensional Effects and Design Criteria for Convective Extended Surfaces

Abstract: An analysis of the thermal performance of convective extended surfaces is presented that takes into account the primary function of the fins, which is to augment the heat transfer. The measure of the heat transfer augmentation is expressed by the removal number Nr, which we proposed should be O(10). It is shown that in order to satisfy this criterion the transverse Biot number hw/k must be of the order of 0.01. Further, it is argued that the fin is fully utilized if the aspect number is O(1). These criteria, Bi; = O(0.01) and u = 0(1), offer guidelines for designing fins and are applicable to longitudinal, annular, and pin fins, of uniform thickness or tapered profile. They must substitute the criterion that is frequently used, Bi < I, which was derived from the analysis of longitudinal fins. A very important consequence of this investigation is that fins designed to meet the above criteria can be analyzed using the classical one-dimensional method without introducing any appreciable error.

Momentum distributions in reactions with radioactive beams.

Abstract: We investigate the longitudinal and transverse momentum distributions of charged fragments originating from reactions with radioactive, neutron-rich beams. It is shown that the width of the narrow peak of the longitudinal momentum distribution is insensitive to the details of the collision and the size of the target nucleus. In contrast, the width of the peripheral region from which transversely moving particles originate is significantly narrowed via absorption of the outgoing neutrons. This diffractively broadens the width of their transverse momentum distribution, in a manner which depends on details of the collision, and so makes the transverse distribution less reliable than the longitudinal one for measuring the size of the original neutron halo.

Vacuum Field Fluctuations and Spontaneous Emission in a Dielectric Slab

Abstract: The electromagnetic field is quantized on the basis of the complete set of spatial modes of a plane dielectric slab of arbitrary thickness and refractive index but infinite transverse dimensions, located in otherwise empty three-dimensional space. The vacuum field fluctuations and spontaneous emission rates are evaluated as functions of position both inside and outside the slab. The source-field operator is derived for emission by atoms inside the slab, in the direction perpendicular to its surfaces. Particular attention is given to the possibility of suppressing spontaneous emission by placing atoms in, or close to, a dielectric slab.

The primary position of the eyes, the resetting saccade, and the transverse visual head plane. Head movements around the cervical joints.

Abstract: Photographic and video analyses show that the primary position of the eyes is a natural constant position in alert normal humans, and the eyes are automatically saccadically reset to this position from any displacement of the visual line The primary position is not dependent on fixation, the fusion reflex, gravity, or the head position The primary position is defined anatomically by head and eye planes and lines that are localized by photography, magnetic resonance imaging, and x-rays of the head and neck The eyes are in the primary position when the principal (horizontal) retinal plane is coplanar with the transverse visual head (brain) plane (TVHP), and the equatorial plane of the eye is coplanar with a fixed orbital plane (Listing's plane) Evidence is presented to indicate an active neurologic basis for the primary position instead of passive mechanical forces A different understanding of the primary position and the conception of the TVHP may be valuable in analyzing oculomotor defects

Magnetic properties of a transverse Ising film with s = 1/2

Abstract: A transverse Ising film, for s=1/2, with a body-centred cubic structure and two (001) surfaces is studied by means of the effective-field theory with correlations. The layer magnetizations and average magnetization of the film as functions of temperature and transverse field are calculated numerically and some interesting results are obtained.

Two-mode optical fiber accelerometer.

Abstract: A novel interferometric accelerometer is described and demonstrated by using a two-mode, elliptical-core optical fiber. A loop of fiber bends when subjected to acceleration normal to its plane, which causes a differential phase shift between the LP01 and LP11 modes. This optical phase shift is directly measured at the output of a phase-sensitive detector by using an in-fiber double-frequency conversion technique. Preliminary results indicate a scale factor of 2 rad/g, with a sensitivity and bias stability of 30 mg. Signal-processing electronics employed to measure the rotation rate in a fiber gyroscope could potentially be used to reduce short-term noise to the 1–10-μg range. Cross talk between the sensitive axis and one of the transverse axes is virtually null.

Die stamping press having ccd camera system for automatic 3-axis die registration.

Abstract: In a die cutting press (16), a registration system for successively positioning a die unit (34) in predetermined relationship to defined areas of an elongated material (56) includes servomotors (60, 68) for moving the die unit (34) in a direction transverse to the path of travel of the material (56), and for rotating the die unit (34) relative to the material (56). At least one camera (96) is provided for receiving images, and is focused on predetermined locations relative to the die unit (34). Reference image data representative of the desired position of the indicia within the images received by the camera (96) is compared with the images actually received and longitudinal, lateral and angular difference data is generated which is representative of this difference. In response to the generated data, the material (56) and die unit (34) are shifted to compensate for the difference in position so that proper registration is achieved.

Theoretical Basis of Field-Flow Fractionation

Abstract: In field-flow fractionation (FFF), macromolecular or particulate species (including colloids and particles up to about 50 μm) are separated in thin flow channels under the influence of a transverse external field. The separation relies on the non-uniform distribution of the species molecules or particles in the channel cross-section. In the ideal case corresponding to molecules or particles of negligible size and a uniform applied field, the migration toward one of the channel walls is countered by Brownian motion resulting in an exponential transverse concentration profile. This characterizes the Brownian, or normal, mode of operation in FFF. Interactions of species with nonuniform fields, transverse gradients, the flow of carrier fluid, and/or the channel walls may result in quite different transverse concentration profiles. These profiles distinguish the non-Brownian modes of operation.

Coupling impedance of a single hole in a thick-wall beam pipe.

Abstract: The coupling impedance of a hole in a thick-wall beam pipe has been calculated for hole dimensions that are small compared to the wavelength. In particular, the longitudinal and transverse coupling impedances are shown to be proportional to the difference between the transverse magnetic susceptibility and the electric polarizability of the inside surface of the hole, and these quantities are themselves proportional to the cube of the hole dimensions

Quantification of back motion during asymmetric lifting.

Abstract: The objective of this study was to determine how trunk motion characteristics (in all three planes of the trunk) change as a free dynamic lifting task becomes more asymmetric. Trunk motion characteristics included range of motion, velocity (peak and average), and acceleration. Previous studies have shown that trunk motion characteristics affect trunk strength as well as the action of the trunk musculature. These trunk motion characteristics were quantified as a function of seven task asymmetries and three task weights. The experimental task required the subject to lift materials in positions commonly seen in the workplace. The range of motion, peak velocity, average velocity, and peak acceleration in each plane of the body were documented during the tasks. Generally, trunk motion characteristics in all three planes increased with an increase in task asymmetry. However, with an increase in task weight all the sagittal plane parameters and one transverse plane parameter decreased. Models were constructed to predict trunk motion characteristics given a task asymmetry and weight. When these motion components were compared to dynamic strength estimates from previous studies it was found that dynamic asymmetric lifts could reduce available strength up to 21% of maximum static strength. The results provide new insight into factors associated with the risk of developing low back disorders.

Chaotic Responses of a Two-Degree-of-Freedom Elastic-Plastic Beam Model to Short Pulse Loading

Abstract: The paper discusses chaotic response behavior of a beam model whose ends are fixed, so that shallow arch action prevails after moderate plastic straining has occurred due to a short pulse of transverse loading. Examples of anomalous displacement-time histories of a uniform beam are first shown. These motivated the present study of a two-degree-of-freedom model of Shanley type. Calculations confirm these behaviors as symptoms of chaotic unpredictability . Evidence of chaos is seen in displacement-time histories, in phase plane and power spectral diagrams, and especially in extreme sensitivity to parameters. The exponential nature of the latter is confirmed by calculations of conventional Lyapunov exponents and also by a direct method. The two-degree-of-freedom model allows use of the energy approach found helpful for the single-degree-of-freedom model (Borino et al., 1989). The strain energy is plotted as a surface over the displacement coordinate plane, which depends on the plastic strains. Contrasting with the single-degree-of-freedom case, the energy diagram illuminates the possibility of chaotic vibrations in an initial phase, and the eventual transition to a smaller amplitude nonchaotic vibration which is finally damped out. Properties of the response are further illustrated by samples of solution trajectories in a fixed total energy plane and by related Poincare section plots.

Longitudinal-transverse interference structure function of 2H.

Abstract: The interference structure function {ital f}{sub 01}, the transverse structure function {ital f}{sub 11}, and the longitudinal structure function {ital f}{sub 00} have been determined in a {sup 2}H({ital e},{ital e}{prime}{ital p}) experiment at a four-momentum transfer {ital Q}{sup 2}=0.21 (GeV/{ital c}){sup 2}. The {ital f}{sub 00} and {ital f}{sub 11} data are in agreement both with a nonrelativistic calculation that includes the effects of final-state interaction (FSI), meson-exchange currents, and isobar configurations, and with a relativistic calculation that only includes FSI effects. The {ital f}{sub 01} data demonstrate the relevance of a relativistic approach even at this low value of the momentum transfer.

The Prominence / Corona Transition Region in Transverse Magnetic Fields

Abstract: An emission measure analysis is performed for the Prominence-Corona Transition Region (PCTR) under the assumption that the cool matter of quiescent filaments is contained in long, thin magnetic flux loops imbedded in hot coronal cavity gas. Consequently, there is a transition region around each thread. Comparison of the model and observations implies that the temperature gradient is perpendicular to the magnetic lines of force in the lower part of the PCTR (T < 105 K). It is shown that in this layer the heating given by the divergence of the transverse conduction fails to account for the observed UV and EUV emission by several orders of magnitude. It is, therefore, suggested that the heating of these layers could be due to dissipation of Alfven waves. In the high-temperature layers (T ≥ 105 K), where the plasma β ≥ 1, the temperature gradient is governed by radiative cooling balancing conductive heating from the surrounding hot coronal gas. Also in these outer layers the presence of magnetic fields reduces notably the thermal conduction relative to the ideal field-free case. Numerical modelling gives good agreement with observed DEM; the inferred value of the flux carried by Alfven waves, as well as that of the damping length, greatly support the suggested form of heating. The model assumes that about 1/3 of the volume is occupied by threads and the rest by hot coronal cavity matter. The brightness of the EUV emission will depend on the angle between the thread structure and the line of sight, which may lead to a difference in brightness from observations at the limb and on the disk.

Surgical knife blade for making sutureless incisions in the eye and methods therefor

Abstract: A surgical knife blade includes a cutting blade for penetrating tissue of the eye. First indicia is carried on the cutting blade proximally spaced from a tip thereof for being aligned with an external surface of the tissue when the cutting blade is inserted tip first in the tissue to form an initial incision having a depth equal to the distance that the first indicia is spaced proximally from the tip. The cutting edge is configured to form a subsurface tunnel within the thickness of the tissue when the cutting blade is moved from the initial incision along a plane transverse to the plane of the initial incision. Second indicia is carried on the blade proximally spaced from the tip for being aligned relative to the initial incision to gauge the length of the subsurface tunnel. A method of making sutureless incisions in the eye includes the steps of inserting the knife blade in the tissue along a plane transverse to the tissue to form the initial incision, aligning the first indicia with the external surface to obtain a depth for the initial incision equal to the distance that the first indicia is spaced from the tip, moving the knife blade from the initial incision along a plane transverse to a plane of the initial incision to form the subsurface tunnel, aligning the second indicia relative to the initial incision to gauge the length of the tunnel and making a second incision from the tunnel through the tissue along a plane transverse to the plane of the tunnel.