Wedge Parameters Research Articles

On-line ultrasonic density sensor for process control of liquids and slurries

An on-line ultrasonic density sensor is described in which six transducers are mounted upon a plastic wedge, the base of the wedge being in contact with a liquid or slurry. Ultrasonic beams striking the base at several angles are reflected. The amount of reflection at the plastic–liquid interface depends upon the density of the liquid ρ, the speed of sound c in the liquid, and wedge parameters. By determining the reflection coefficient at two angles, ρ and c can be determined. The sensor can be mounted in a pipeline configuration or submerged for tank applications.

Dosimetry measurement tools for commissioning Enhanced Dynamic Wedge

Measurement of Enhanced Dynamic Wedge parameters requires that the dose at a measurement point be integrated during the entire exposure as the moving jaw closes to form the dose distribution. This major difference from static fields, where dose rate measurements can be made using a single moving probe, requires major modification in measurement techniques to use devices which can measure multiple points within the field simultaneously. Each of these new tools introduce unique problems in dose measurement, which must be understood prior to their use. This paper discusses these tools.

Morphometric X-ray absorptiometry of the spine: Correlation in vivo with morphometric radiography

The diagnosis of vertebral fractures has been based on lateral thoracic and lumbar spine films and entails the determination of crush, endplate and wedge deformities of the vertebral bodies, generally between T4 and L4. Accuracy and precision of X-ray based morphometry are limited by geometric distortion and other technique-related factors. This paper proposes the use of morphometric X-ray absorptiometry (MXA) as a method which overcomes many of the limitations of morphometric radiography. MXA generates paired anteroposterior and lateral images of the spine using a scanning fan beam geometry that significantly reduces distortions inherent in the cone beam geometry used in conventional X-rays. Intra-observer precision of MXA on 41 subjects aged 65 years and older was 1 mm for vertebral height assessments and 4.7% for vertebral wedge parameters. Linear correlation with vertebral heights and wedge parameters on 32 subjects evaluated by both MXA and morphometric radiography demonstrated a root of the mean squared error of 2.1-2.4 mm and 7.0%, respectively. Vertebral deformities could be identified by MXA. The study documents the feasibility of MXA for the assessment of vertebral deformities. However, further investigation is needed to document the ability of MXA to diagnose prevalent and incident fractures.

CURVATURE: software for the analysis of curved DNA.

Software is presented to plot the sequence-dependent spatial trajectory of the DNA double helix and/or distribution of curvature along the DNA molecule. The nearest-neighbor wedge model is implemented to calculate overall DNA path using local helix parameters: helix twist angle, wedge (deflection) angle and direction (of deflection) angle. The procedures described proved to be very convenient as tools for investigation of a relationship between overall DNA curvature and its gel electrophoretic mobility. All parameters of the model had been estimated from experimental data. Using these wedge parameters the program takes, as input, any DNA sequence and calculates the likely degree of curvature at each point along the molecule. This information is displayed both graphically and in the form of simplified representations of curved double helices. The Software, CURVATURE, can thus be used to investigate possible roles of curvature in modulation of gene expression and for location of curved portions of DNA, which may play an important role in sequence-specific protein--DNA interactions.

Optimization of the wedge filter parameters for a radiotherapy treatment planning system.

When a treatment planning system uses an empirical or semianalytical approach to describe the influence of a wedge filter on a photon beam, a number of experimentally determined parameters are required. These may be found from direct measurement. However, if the beam model is sensitive to the parameters, it will be necessary to optimize the parameter values to obtain better correspondence between dose profiles calculated by the model and actual measured profiles. The procedure is time consuming if optimization is done manually. We have developed an optimization scheme, using a personal computer, to find the set of wedge parameters which will result in the best fit of calculated wedge profiles (using the beam model of the treatment planning system) to measured wedge profiles. The procedure is efficient and calculated profiles were found to match measured profiles to within 2% of the central axis value.

A self-consistent formulation for analysis and generation of non-uniform DNA structures.

A fully self-consistent formulation is described here for the analysis and generation of base-pairs in non-uniform DNA structures, in terms of various local parameters. It is shown that the internal "wedge parameters" are mathematically related to the parameters describing the base-pair orientation with respect to an external helix axis. Hence any one set of three translation and three rotation parameters are necessary and sufficient to completely describe the relative orientation of the base-pairs comprising a step (or doublet). A general procedure is outlined for obtaining an average or global helix axis from the local helix axes for each step. A graphical representation of the local helix axes in the form of a polar plot is also shown and its application for estimating the curvature of oligonucleotide structures is illustrated, with examples of both A and B type structures.

A general procedure for generation of curved DNA molecules.

A general method for generation of base-pairs in a curved DNA structure, for any prescribed values of helical parameters--unit rise (h), unit twist (theta), wedge roll (theta R) and wedge tilt (theta T), propeller twist (theta p) and displacement (D) is described. Its application for generation of uniform as well curved structures is also illustrated with some representative examples. An interesting relationship is observed between helical twist (theta), base-pair parameters theta x, theta y and the wedge parameters theta R, theta T, which has important consequences for the description and estimation of DNA curvature.

On Singularities of Scattering Amplitudes through a Convex Triangular Obstacle in Scattering Theory

A triangular grating is characterized by three parameters like period, groove depth and angle. A smooth convex triangular obstacle, forming a part of the said grating, is considered herewith for finding the Scattering amplitudes through the illuminated faced of the obstacle. Complex Fourier double transforms of the concerning wave functions has been determined for finding the Scattering amplitudes, allowing thereby the wave number to become unlimitedly large. It has been further justified that the singularities of the Scattering amplitudes occur when the concerning surface harmonics behave like distributions. In particular, the Scattering amplitudes have been determined when the Fourier transforms of the concerning wave functions behave like Dirac distributions. Finally, the expressions of relative powers of the groove fields have been determined in terms of the wedge parameters.

Analysis of a ring-type seal by the finite element method

The ring-type seal used in high speed turbogenerators contains a hydrodynamic oil film to prevent the leakage of cooling hydrogen. The ring floats on the rotor shaft and its gravity load is supported by the film. The ring-type seal must operate at a very low eccentricity in order to maintain an uninterrupted oil film around the rotor. The seal studied consisted of two lands, one plain and the other having wedges. The two lands were separated by a circumferential oil supply groove. Using the finite element method the static performance characteristics of the seal in terms of load, moment, flow, attitude angle, friction force and temperature rise were evaluated at different eccentricities for the various wedge parameters.

Dynamic Analysis of Wedge-Type Shaft Seal

The hydrodynamic seal under study here consists of two lands—one plain and the other having a wedge. The two lands are separated by a circumferential oil-supply groove. The wedge parameters significantly affect the performance of seal. The effects of various wedge parameters on dynamic stability of the hydrodynamic seal have been studied. Stiffness and damping coefficients for lateral and skew motions, critical nondimensional mass and critical nondimensional inertia have been evaluated for different wedge parameters at different eccentricities. The equations of motion of the seal center for four degrees of freedom have been derived and considering lateral and skew motions, stability studies have been made using Routh criteria.

The effect of iron powders on the utilization of permanent magnet materials in advanced motors

The properties that may be obtained in an iron powder/epoxy resin compact are discussed, and the application of this material as wedges in the armature of an axial-field d.c. machine are described. The effect of the wedge parameters on the design and performance of the machine has been studied, particularly considering the non-uniform flux density across the active diameter in a wedge. Using an electric vehicle traction motor as an example, it is shown that considerable savings in permanent magnet material are achieved by introducing wedges into the previously ironless armature, being as high as 74% with SmCo <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">5</inf> magnets.