Coaxial Wires Research Articles

Intense THz laser effects on off-axis donor impurities in GaAs–AlGaAs coaxial quantum well wires

The binding energy of an off-axis shallow-donor impurity in a GaAs coaxial cylindrical quantum well-wire under the action of an intense, high-frequency laser field is calculated using a variational procedure within the effective-mass approximation. We take into account the laser dressing effects on both the impurity Coulomb potential and the confinement potential. Numerical calculations of the ground state subband energy levels based on a finite element method are performed for different barrier thicknesses and laser field parameters. Our model indicates a possible tuning of the well potential shape along the laser polarization direction. Strong distortions of the electron probability density under intense laser field conditions are also predicted. The study proves that the presence of the laser field partially breaks down the degeneracy of the states for donors symmetrically positioned within the structure. The results obtained show that the impurity energy levels in coaxial quantum wires can be significantly modified and controlled by intense laser fields.

Modelling of Wire Melting Behaviour of Coaxial Hybrid Solid Wire in Gas Metal Arc Welding in a Pure Argon Shielding Gas

Coaxial multi layer solid wires (coaxial hybrid solid wires) have been developed in order to stabilize welding in pure Ar shielding gas. This coaxial hybrid solid wire has a double structure, the composition of inner part and outer part is different. The wire melting behaviour of coaxial hybrid solid wire is different from that of conventional solid wires because the electric current path and the heat transfer behaviour depend on the characteristics of inner and outer materials. Therefore, in order to obtain stable welding, to combine appropriate materials for inner part and outer part is necessary. To understand the influence of the material properties of the inner part and outer part on the wire melting behaviour, a simulation model for wire melting has been developed. The influences of the melting temperature, the specific heat, and the thermal conductivity on wire melting behaviour were examined. Simulations show that the shape of the solid wire tip is affected by changing melting temperature and specific heat of the inner part. Furthermore, these changes have a large effect on the length of the wire extension. The thermal conductivity effects on wire tip shape and temperature distribution, but has little effect on the wire extension.

Analytical expressions of the electrical conductivity and the temperature coefficient of resistivity of two thin coaxial metallic wires

Assuming, that the sources of scattering act independently in the two thin coaxial metallic wires, and introducing the mean free path describing the Fuchs–Sondheimer effect, an apparent size effect is then defined. The aim of this paper is to show that the size effects in the thin coaxial metallic wires can be examined as well by using initially the theoretical formulations proposed in the case of a single wire and of the thin double-layer metal films. Simple analytical expressions of the electrical conductivity and the temperature coefficient of resistivity are therefore proposed.

Deactivation force-deflection behavior of multistranded stainless steel wires

This investigation measured the deactivation (unloading) force-deflection behavior of selected multistranded stainless steel orthodontic wires. The guidelines from the revised American National Standards Institute/American Dental Association Specification No. 32 for orthodontic wires (type 2, nonlinear elasticity) were used to perform a 3-point bending test to obtain data for the deactivation force levels at 3, 2, 1, and 0.5 mm, and permanent deformation values. The study tested 20 wire designs: triple-stranded twisted wires, 5- and 6-stranded coaxial wires, and 8- and 9-stranded braided rectangular wires of selected cross-sections. Twenty specimens were tested for each wire design. The specification guidelines for testing provided a means for obtaining comparative unloading force delivery data for the deflections tested. Multistranded wires of significantly different cross-section, weave, and strand number fell within relatively narrow ranges of force delivery at the 0.5-mm (1.7-42.7 grams-force [gmf]) and 1-mm (31.1-134.2 gmf) deflections and wider ranges of force levels at the 2-mm (57.0-320.5 gmf) and 3-mm (72.5-451.8 gmf) deflections. All wires exhibited some permanent deformation, but none averaged greater than 0.66 mm. The testing also showed that multistranded wires of significantly different design exhibit similar force levels. The guidelines of the revised Specification No. 32 yielded deactivation data with regard to force delivery and provided comparisons of the wire designs tested.

Theoretical investigation of elastic flexural properties for multistranded orthodontic archwires.

The bending and torsional stresses during flexure were detailed and simplified for a single twisted strand, which emulates a spring. General expressions were derived to evaluate the elastic properties (i.e., strength, stiffness, and range) of multistranded wires by combining the effects of a number of outer twisted strands, with or without an inner strand. Specific expressions were solved for single-stranded, twisted, and coaxial wires. Initially, we considered the following multistranded wire configurations: two- (twin), three- (triple), four-strand (quad) twisted, and coaxial wires. The elastic properties of the twin and quad wires were essentially subsets of the triple wire. For a given overall wire diameter (D) and helix angle (alpha), the ranges of multistranded wires were independent of wire configurations. By varying the alpha from 45 to 85 degrees, the D from 0.394 to 0.546 mm (15.5 to 21.5 mil), and the stress at the proportional limit from 1.03 to 3.28 GPa (150 to 475 ksi), the theoretical elastic properties of triple and coaxial stainless steel wires matched many of the properties of conventional nickel titanium leveling wires.

Enhancing wire-composite bond strength of bonded retainers with wire surface treatment

Bonded orthodontic retainers with wires embedded in composite resin are commonly used for orthodontic retention. The purpose of this study was to test, in vitro, various wire surface treatments to determine the optimal method of enhancing the wire-composite bond strength. Coaxial wires and stainless steel wires with different surface treatments were bonded to bovine enamel and then pulled along their long axes with an Instron universal testing machine. Wire surface treatments included placing a right-angle bend in the wire, microetching the wire, and treating the wire with adhesion promoters; combinations of treatments were also examined. The results demonstrated a 24-fold increase in the wire-composite bond strength of wire that was microetched (sandblasted), compared with that of untreated straight wire. The difference between the amount of force required to break the bond produced by microetching alone (246.1 ± 46.0 MPa) and that required for the bonds produced by the retentive bend (87.8 ± 16.3 MPa), the adhesion promoters (silane, 11.0 ± 3.1 MPa; Metal Primer, 28.5 ± 15.8 MPa), or for any combination of surface treatments, was statistically significant. Microetching a stainless steel wire produced a higher wire-composite bond strength than that obtained from a coaxial wire (113.5 ± 27.5 MPa). The results of this study indicate that microetching or sandblasting a stainless steel wire significantly increases the strength of the wire-composite bond. (Am J Orthod Dentofacial Orthop 2001;119:625-31)

The Binding Energies of Shallow Donor Impurities in GaAs–(Ga,Al)As Coaxial Quantum-Well Wires

The Binding Energies of Shallow Donor Impurities in GaAs–(Ga,Al)As Coaxial Quantum-Well Wires

The Binding Energies of Shallow Donor Impurities in GaAs-(Ga,Al)As Coaxial Quantum-Well Wires

The Binding Energies of Shallow Donor Impurities in GaAs-(Ga,Al)As Coaxial Quantum-Well Wires

Electron-phonon interaction in complicated semiconductor coaxial cylindrical quantum wires

Electron-phonon interaction in complicated semiconductor coaxial cylindrical quantum wires

Electron spectrum in a quantum superlattice with cylindrical symmetry

A quantum superlattice with axial symmetry, a heterostructure in which two semiconductor materials in the form of coaxial wires with a nanosize cross section are in contact with one another and form a periodic structure in the radial direction, is studied. It is shown that the electron energy spectrum consists of alternating allowed and forbidden bands. The electron dispersion law is studied for different values of the period of the potential, thicknesses of the semiconductor layers, and radius of the inner crystal of the system. It is shown that the coherent electron effective mass of the quantum superlattice is a tensor: The longitudinal component is close in value to the electron effective mass of the semiconductor material characterizing the quantum well of the superlattice and the radial component depends strongly on the period of the potential, the thicknesses of the coaxial semiconductor layers, and the core radius of the heterosystem, taking on positive or negative values in different allowed bands.

Distal end cutters--efficiency, safety and design.

This investigation aimed to evaluate the efficiency of a range of different distal end cutters in cutting and holding the ends of orthodontic arch wires. Fourteen different types of distal end cutter were used to cut a range of orthodontic arch wires under standard conditions. The arch wires comprised nickel-titanium and stainless steel wires of different dimensions, as well as twist flex and coaxial wires. The number of times each wire was successfully cut and held by each cutter was recorded. Significant differences in performance between the cutters were noted, particularly in holding the cut distal ends. Small diameter nickel-titanium wires were significantly less well held than heavier grade or stainless steel wires. Twist flex and coaxial wires were less easily cut cleanly than nickel-titanium and plain stainless steel wires.

Determination of the interfacial tension by thermal grooving and zero creep in coaxial wires—theory

A model based on the thermal grooving and zero creep theory is developed to allow absolute measurements of the interfacial energy between two materials in the shape of bamboo coaxial wires.

Perturbed motions of a bubble rising in a vertical tube

Experiments are reported in which long air bubbles rising in liquid-filled vertical tubes were perturbed by coaxial wires. Distinctly different flow regimes were found to arise as the thickness of the wire was varied. The breaking of axial symmetry observed in the experiments is discussed in the light of ideas from bifurcation theory.

Simulation of SREMP Coupling to Buried Cables

Experimental results that simulate SREMP coupling to buried cables are presented for bare wires, branched wires, and coaxial wires. Comparisons with two theoretical approaches are presented for bare wires, and excellent agreement is obtained with test results.

Comments on the Experiments of Bodner and of Fitzgerald and Woodward on Laterally Vibrating Beams under Axial Tension

Bodner and Fitzgerald and Woodward have described dynamic tests on beams of aluminum alloy and polytetrafluoroethylene, respectively, in which the laterally vibrating bars were subjected to tension by coaxial wires. In both cases, the direct effect of the wires was disregarded. This paper presents an analysis of the wire-bar systems, based on the theories of vibrating bars and strings. The calculations show that resonance patterns generally resembling those found experimentally should be expected.

Mutual inductance and force between two coaxial helical wires

Mutual inductance and force between two coaxial helical wires