Showing papers on "Transverse plane published in 1988"

Theoretical stress strain model for confined concrete

Abstract: A stress‐strain model is developed for concrete subjected to uniaxial compressive loading and confined by transverse reinforcement. The concrete section may contain any general type of confining steel: either spiral or circular hoops; or rectangular hoops with or without supplementary cross ties. These cross ties can have either equal or unequal confining stresses along each of the transverse axes. A single equation is used for the stress‐strain equation. The model allows for cyclic loading and includes the effect of strain rate. The influence of various types of confinement is taken into account by defining an effective lateral confining stress, which is dependent on the configuration of the transverse and longitudinal reinforcement. An energy balance approach is used to predict the longitudinal compressive strain in the concrete corresponding to first fracture of the transverse reinforcement by equating the strain energy capacity of the transverse reinforcement to the strain energy stored in the concret...

Axial behavior of pupil-plane filters

Abstract: The relationship between the transverse and the on-axis behaviors of various pupil-plane filters is described. Expressions for general energy constraints associated with these filters are also derived. Transverse and axial diffraction properties of filters with quadratic radial transmittance are demonstrated experimentally.

Cooperative frequency locking and stationary spatial structures in lasers

Abstract: We investigate the spontaneous emergence of transverse patterns in lasers by using both the standard two-level model and the so-called cubic approximation, which is generally valid in the threshold regions. The stationary intensity configurations fall into two distinct classes. The first includes solutions of the single-mode type with the frequency and spatial structure of one of the transverse resonances. The solutions of the second group involve the simultaneous oscillation of several cavity modes, operating in such a way as to produce a stationary intensity profile. The stationary character of these multimode configurations emerges from the fact that the transverse modes of the resonator lock onto a common frequency during the nonlinear transient. We call this phenomenon cooperative frequency locking.

Theory of ultrasound Doppler-spectra velocimetry for arbitrary beam and flow configurations

Abstract: In conventional ultrasound Doppler systems, the velocity component along the beam axis is derived from the observed frequency shift. Recently, it was verified that by using a pulsed-Doppler system with the beam transversely oriented with respect to the flow, the velocity component transverse to the beam can be derived from the edges of the spectrum. These results are generalized to take into account arbitrary angles of incidence, effects of velocity gradients, arbitrary apertures, and arbitrary source pulses. For uniform apertures and transverse flow, it has been previously shown that the Doppler output spectrum is symmetrical about zero frequency, with its width depending on the Doppler effect due to the transverse velocity and the geometry of the problem. For a beam direction oblique to the velocity, it is shown that the spectrum is now shifted, and is centered about the classical Doppler frequency. For velocity gradients and transverse flows the spectrum remains symmetrical, with the edges corresponding to the maximal velocity; however, the profile becomes peaked at the center. For oblique incidence, an asymmetrical spectrum is obtained and its edges are related to the maximal and minimal velocities within the sampling volume. >

Piezo-Hall coefficients of n-type silicon

Abstract: The effect of uniaxial mechanical stress on the Hall coefficient of n‐type silicon has been measured for various crystallographic orientations, and piezo‐Hall coefficients P12 and P11‐P44 have been derived for electron concentrations n between 1014 and 1016 cm−3 and temperatures ranging from −80 to +100 °C. In this range the piezo‐Hall effect is found to be as important as the piezoresistance effect which is understood in terms of the many‐valley band structure of silicon with anisotropic energy minima. For Hall plates in the (100) and the (110) plane of silicon the resulting longitudinal and transverse piezo‐Hall coefficients at room temperature are plotted as a function of their orientation in the plane. It turns out that the piezo‐Hall as well as the piezoresistance effects are minimized for a Hall plate in the (110) plane with the current flow roughly parallel to 〈111〉.

Notch antenna with microstrip feed

Abstract: The subject invention provides an improved conformal antenna array assembly having a strip conductor, a ground plane separated from and lying parallel to said strip conductor, said ground plane having a slot therein, said slot extending transverse to said strip conductor, a conductive planar element positioned across said slot and orthogonal to said ground plane, said conductive planar element having curved surfaces extending upwardly and outwardly from said slot. The strip conductor or microstrip and the slot-containing ground plane are separated by a dielectric material.

Effect of Finite Width on Deflection and Energy Release Rate of an Orthotropic Double Cantilever Specimen

Abstract: The problem of an orthotropic cantilevered plate subjected to a uniformly distributed end load is solved by the Rayleigh-Ritz energy method. The result is applied to laminated composite, double cantilevered specimens to estimate the effect of crack tip constraint on the transverse curvature, deflection and energy release rate. The solution is also utilized to determined finite width correction factors for fracture energy characterization tests in which neither plane stress nor plane strain conditions apply.

System and method for determining orientation of planes of imaging

Abstract: An apparatus for use in determining the orientation and location of an image plane, particularly when imaging the head of a human being, has an elongated flexible channel provided for containing an imaging-opaque fluid which is visible in the image. First and second carriers are each provided for supporting three respective portions of the elongated flexible channel at respective orientations transverse to the image plane and in predetermined space relation with respect to one another. Preferably, the portions of the said elongated flexible channel are arranged substantially as legs of a triangle. A support arrangement maintains the first and second carriers in fixed spatial relation to one another and to the head of the human being. The present invention can be used in any of several known imaging modalities by using appropriate contrast agents. After imaging, the portions of the said elongated flexible channel appear as points in the image, the location of the plane of imaging, and its orientation, being determined by analysis of the distance between such points, and the ratios of the distances between them. Such analysis can be performed by computer. Additionally, with the use of the present invention, computer analysis can be used to reconstruct a given set of consecutive image planes, such as from MRI, to match another given set of image planes, such as from PET.

Measurement of the complete (3D) velocity vector of blood flows

Abstract: The transversal crossing of ultrasound beams by moving scatterers is studied to derive a process dedicated to transverse motion estimation. A 3D blood flow model is formulated, allowing the test of various correlation algorithms to detect motion completely. Time correlation techniques giving axial displacement can be extended to transverse directions to detect 3D motion. The principle of a multiple probe is defined, and the implementation of the associated processing is demonstrated. It relies mainly on the time domain correlation processor used for axial detection, working also for transverse components. The complexity of this process is about five times that of the axial correlation processor. Feasibility of measuring this preliminary study indicates the complete velocity vector of blood flow with this approach. >

Electrostatic ion instabilities in the presence of parallel currents and transverse electric fields

Abstract: The electrostatic ion instabilities are studied for oblique propagation in the presence of magnetic field-aligned currents and transverse localized electric fields in a weakly collisional plasma. The presence of transverse electric fields result in mode excitation for magnetic field aligned current values that are otherwise stable. The electron collisions enhance the growth while ion collisions have a damping effect. These results are discussed in the context of observations of low frequency ion modes in the auroral ionosphere by radar and rocket experiments.

Technique for measuring the dielectric constant of thin materials

Abstract: A practical technique for measuring the dielectric constant of vegetation leaves and similarly thin materials is presented. A rectangular section of the leaf is placed in the transverse plane in rectangular waveguide, and the magnitude and phase of the reflection coefficient are measured over the desired frequency band using a vector network analyzer. By treating the leaf as an infinitesimally thin resistive sheet, an explicit expression for its dielectric constant is obtained in terms of the reflection coefficient. Because of the thin-sheet approximation, however, this approach is valid only at frequencies below 1.5 GHz. To extend the technique to higher frequencies, higher-order approximations are derived and their accuracies are compared to the exact dielectric-slab solution. For a material whose thickness is 0.5 mm or less, the proposed technique was found to provide accurate values of its dielectric constant up to frequencies of 12 GHz or higher. >

Conservation laws and transverse motion of energy on reflection and transmission of electromagnetic waves

Abstract: The conservation laws for the process of reflection and transmission of electromagnetic waves on a plane interface of isotropic transparent media are determined Using these laws, relations have been established between the transverse shift (TS) of a centre of gravity of reflected and transmitted wavepackets, the change of the normal component of the intrinsic Minkowski angular momentum of the electromagnetic field and the Abraham transverse momentum (or the transverse electromagnetic power flow (TPF)) The previous investigations of the TS and TPF phenomena are discussed from the point of view of conservation laws

Role of transverse effects in laser instabilities.

Abstract: We generalize the traditional Maxwell-Bloch theory of a ring laser and analyze the dynamical role of transverse effects. With the help of a suitable extension of the uniform-field limit we perform an essentially analytical study of the steady-state and linear-stability properties of a ring resonator containing a homogeneously broadened active medium. In this context we incorporate the effects of curved reflecting surfaces, the possible lack of transverse uniformity of the pump, and the detailed structure of the cavity modes. In the uniform-field limit we prove that the laser steady state is of the single-mode variety and that lack of stability can be induced in this field configuration even only a few percent above the threshold for laser action. Thus our main claim is that transverse effects can be responsible for low threshold instabilities. This explanation is more plausible to explain the observed pulsations in many lasers than what is available in terms of the traditional plane-wave theories.

On the mechanism of speed and altitude control in Drosophila melanogaster

Abstract: The total power output of tethered flying Drosophila melanogaster in still air depends on translational velocity components of image flow on the eye, whereas the orientation of the average flight force in the midsagittal plane of the fly is widely independent of visual input (Gotz, 1968) The fly does not seem to control the vertical and the horizontal force component independently Freely flying flies nevertheless generate different ratios between lift and thrust, simply by changing the inclination of their body By the combined adjustment of the body angle and the total power output a fly appears to be able to stabilize height and speed (David, 1985) Here a possible mechanism is proposed by which the appropriate torque about the transverse body axis could be generated Translational pattern motion influences the posture of the abdomen and the plane of wing oscillation Thus the position of the centre of gravity relative to the flight force vector is changed When abdomen and stroke plane deviate from an equilibrium state, a lever is generated by which the force vector will rotate the fly about its transverse axis

Ultrasonic reflection by a planar distribution of cracks

Abstract: Ultrasonic wave reflection and transmission by planar crack distributions is considered. General expressions for the reflection and transmission coefficients are derived for incident longitudinal and transverse time harmonic plane waves. For low frequencies, closed-form algebraic expressions are given in terms of the geometrical parameters, the material constants, and the incident wavefield. The results have been extended to statistical distributions, and reflection coefficients for equivalent statistical and deterministic distributions of penny-shaped cracks are compared. It is also shown that the Mode-I stress-intensity factor for a distribution of equal-sized cracks can be directly related to reflection data.

Muscle biopsy clamp

Abstract: A muscle biopsy clamp operable with one hand to securely grip and retain an excised specimen in unstressed condition. The clamping jaws are in the form of two-pronged forks lying in a plane transverse to the major plane of the instrument which includes the straight handle members, the looped finger grips and ratchet locking members between the handle members. The jaws are also angled approximately 30° with respect to the straight handle members to provide optimum visualization and maneuverability. Weakened areas are formed in the handle members permitting the finger grips to be snapped off without disturbing a gripped excised specimen so that the specimen can be placed in standard specimen jars for laboratory analysis.

Transverse elastic moduli of unidirectional fiber composites with interfacial debonding

Abstract: A mathematical model is developed to predict the transverse elastic moduli of unidirectional fiber composites. Two cases of fiber/matrix interfacial bondings are investigated: perfect bonding and complete debonding,i.e., no transferring of tensile stress on surfaces where the fiber and matrix materials are separated. Fibers are assumed to exhibit transverse isotropy, and the elastic interactions among fibers are also considered. In the analysis of the completely debonded case, the cavity formation model is adopted and the original fiber and surrounding cavities are replaced by an imaginary anisotropic inclusion. Closed form solutions of effective elastic moduli are obtained for transverse tensile and compressive moduli, and transverse shear moduli. The limiting case of fiber-like voids is also studied. Numerical results are presented for two metal matrix composites, where the optimal wetting between the fiber and matrix is difficult to be obtained and hence the interfacial bonding and transverse property have been major concerns.

Low-frequency eddy-current loss estimation in long conductors by using the moment of inertia of cross sections

Abstract: A simple method is presented to estimate low-frequency eddy-current losses in long nonmagnetic conductors of uniform cross section when subjected to axial or transverse magnetic field. The method involves calculation of the moment of inertia of the conductor cross section. In the case of transverse fields, the relationship obtained agrees with analytical results for cross sections which have a symmetry axis parallel to the incident field. For axial fields the proposed relationship agrees with the analytical expressions for circular and elliptical cross sections and gives results with reasonable accuracy for rectangular cross sections. >

Scattering of transverse-electric electromagnetic waves with a finite nonlinear film

Abstract: Exact analytical results for the scattering of a plane transverse-electric electromagnetic wave with a nonlinear thin film is derived. Optical bistable and multistable behaviors in the reflectivity as a function of the input intensity are found.

Electron spin polarization analyzers for use with synchrotron radiation

Abstract: The measurement of the spin polarization of photoelectrons emitted from a magnetic material is discussed An important consideration is the acceptance phase space of the spin analyzer relative to the phase space of the photoemitted electrons to be measured Other considerations include the magnetization direction relative to the extracted beam and whether the measurements are angle integrated or angle resolved In the longitudinal geometry where the magnetization is normal to the sample surface and along the extracted photoelectron beam, conservation of canonical angular momentum adds an additional magnetic term to the beam emittance which is absent when the magnetization is in the sample plane and transverse to the extracted beam For angle resolved measurements in the transverse geometry, the advantages of a new, low-energy (∼ 100 eV) spin analyzer which is easily movable, compact and efficient are discussed Different spin analyzers are described and compared, and an analysis of their application to different spin polarized photoemission measurement configurations is given