Rectangular Cross-sectional Shape Research Articles

Nano-patterning of a hydrogen silsesquioxane resist with reduced linewidth fluctuations

A new resist system providing small linewidth fluctuation has been developed for nanolithography. Hydrogen silsesquioxane (HSQ) resist used here has a small polymer size because of its three-dimensional framework. This framework reduces the size of aggregates in the resist film which strongly influence linewidth fluctuation of resist patterns. The scission of SiH bonds in HSQ by e-beam leads to the crosslinking required for the nega-patterning. In addition, the application of a TMAH developer realizes higher contrast and less thickness loss. Consequently, 20-nm-wide nega-patterns with a rectangular cross-sectional shape are successfully formed with linewidth fluctuation less than 2 nm.

Conditions for a direct band gap in Si quantum wires

The condition for a direct band gap in Si quantum wires is investigated within the effective mass theory for wires coherent in every direction perpendicular to the wire direction. The condition is calculated using the equivalent condition that the minimum energy of the one-dimensional sub-bands of electrons is at the Γ-point, because holes always have a minimum energy at this point. It is shown that only Si quantum wires on the {100} plane can have a direct band gap. In particular, 〈100〉-oriented Si quantum wires have a direct band gap regardless of their cross-sectional shape. For wires other than 〈100〉-oriented ones, the condition of a direct band gap for rectangular, elliptic, triangular and trapezoidal cross-sectional shapes is investigated, assuming that the confinement potential is infinitely high in order to have the condition determined only by their cross-sectional shape and direction independently of their cross-sectional size. In all cases, wires have a direct band gap when the ratio of wire height (size perpendicular to the {100} plane) to width (size parallel to the {100} plane) decreases, and 〈110〉-oriented wires have the largest ratio of height to width for a direct band gap.

Selective growth of gallium nitride layers with a rectangular cross-sectional shape and stimulated emission from the optical waveguides observed by photopumping

Selective growth of GaN layers on sapphire substrates is investigated for low-loss optical waveguide structures of active and passive photonic devices. When growth conditions, such as nitridation of the substrate surface and growth temperature, are adjusted to achieve high-density uniform nucleation on the substrate, we found that the cross-sectional shape of GaN waveguides has a rectangular structure with smooth top and side surfaces. At 77 K, we observed stimulated emission from the cleaved facet of an optically pumped selectively grown GaN waveguide with a width of 6 μm and a cavity length of 800 μm. Line narrowing was also achieved: with the full width at half-maximum of the emission spectra decreasing from 11 to 2 nm by increasing a pump power density from 0.013 to 0.05 MW/cm2.

Structural Study of Cholesteryl Anthraquinone-2-carboxylate (CAQ) Physical Organogels by Neutron and X-ray Small Angle Scattering

Physical organogels of cholesteryl anthraquinone-2-carboxylate (CAQ) and an organic liquid have been studied by small-angle neutron and X-ray scattering techniques. The gel structure consists of long and rigid fibers of CAQ interconnected in swollen lyotropic microdomains. The nature of the “junction zones” of the three-dimensional network is dependent upon the type of liquid component. In decane, they consist of bundles of several hexagonal-like arrangements of cylindrical aggregates (diameter ca. 102 A). In alkane/alcohol mixtures, a merging process toward a more compact lamellar-like structure occurs progressively with increasing alcohol content. In pure 1-alkanols, the aggregates may have a more rectangular cross-sectional shape (ribbons). Schlieren optical textures confirm the inhomogeneity of the orientation of thread-like structures in the birefringent materials. When the structural features of CAQ gels are compared to those of other low-molecular weight gelators, the nature of the link between the...

Description of velocity field of currents in canals taking turbulence characteristics into account

1. It has been shown that in canals of rectangular cross-sectional shape, the vector of the full turbulence stresses forms with the flow direction an angle equal to 65°, and the value of this angle does not depend on the distance to the solid boundary. 2. It was demonstrated that the shearing stresses are proportional to the vector of the full turbulence stresses and that the proportionality coefficient is constant. 3. We established the type of relation of the velocity gradient with respect to the vector of the full turbulence stresses, which is correct to the limit of the external layer in canals with rectangular cross-sectional shapes. 4. A new equation is proposed for calculation of the velocity gradient in canals by means of the vector of full turbulence stresses.

Natural vibrations and waves in pretwisted rods

A finite element method is presented for studying natural vibrations and waves in pretwisted rods. The analysis is based on three-dimensional elasticity using a coordinate system that rotates with the cross-section. Finite element modeling occurs over the cross-section, so that arbitrary geometry and inhomogeneous, anisotropic material properties can be accommodated. The variationally derived equations of motions are partial differential equations in terms of the axial coordinate and time. Specifying the solution as a harmonic wave form leads to an algebraic eigensystem from which the natural frequencies and corresponding modal patterns of vibration can be extracted. Because of the pretwist, the harmonic wave forms for extension/torsion waves and flexural waves must be expressed separately. Two examples, a homogeneous, isotropic bar and a two-layer ±30° angle-ply composite bar where both have the same rectangular cross-sectional shape, are given to illustrate the method of analysis and the physical behavior of these two members.

The effect of geometry on source mechanisms of fricative consonants

Mechanical models of the vocal tract have often been used to measure source parameters needed for transmission-line models of fricative consonants. Since such theoretical models are based on the assumptions that source and filter are independent and that only one-dimensional sound propagation need be considered, the mechanical models generally have had highly idealized shapes. In this paper, experiments with two sets of more realistic models are reported; these were conducted in order to establish source parameters such as source location, degree of distribution and spectral characteristics. Both sets of models have midsagittal profiles copied from X-rays; one set also has a correct area function, with rectangular cross-sectional shapes throughout. Results suggest that although the area function is sufficient for predicting filter parameters, it is inadequate for predicting source parameters: small changes in the tract shape at or downstream of the constriction, which do not affect the area function significantly, do affect source parameters, and the radiated sound, significantly. In order to model the source mechanism accurately, for a transmission line or any other representation, it appears that the three-dimensional shape of the vocal tract at and anterior to the constriction must be considered.

Measurement of refractive indices of homogeneous fibers with regular or irregular transverse sections

Seven fibers of different cross-sectional shape are studied interferometrically using multiple-beam Fizeau fringes. These fibers are of circular, rectangular, triangular, trilobal, elliptical, kidney, and dog-bone cross-sectional shapes. The areas enclosed under the interference fringe shift is considered to represent the optical path difference integrated across the fiber. This principal is applied to nylon 6 fibers of trilobal cross-sectional shape. The described method is suitable for the measurement of refractive indices of any fiber with regular or irregular transverse sections. Microinterferograms are given for illustration.

Interferometric determination of the refractive indices, birefringence and homogeneity of a polymer thin film

An experimental illustration using microinterferometry is given as a qualitative and quantitative method for determining the refractive indices, birefringence and estimating of the homogeneity of polymer thin film. Multiple-beam Fizeau fringes in transmission were applied for sliced polymer of rectangular cross-sectional shape. Thin film optical parameters could be determined from the shape of Fizeau fringes obtained experimentally. The applicability and advantage of this method have been discussed from the point of view of thin film microscopy. Illustrations were made using photomicrographs.

Loosening of the femoral component after use of the medullary-plug cementing technique. Follow-up note with a minimum five-year follow-up.

Of the 171 total hip replacements reported on previously that had had a minimum length of follow-up of two years, 117 replacements in 104 patients were analyzed at a minimum of five years postoperatively (average, seventy-four months; range, sixty to ninety-four months) to assess the rate of loosening of the femoral component. At the time of cementing of the femoral component, the medullary canal had been plugged with a bolus of bone cement and then filled with doughy Simplex-P methylmethacrylate in a retrograde fashion using a cement gun. The femoral components, made of a chromium-cobalt alloy, had a rectangular cross-sectional shape to the stem and a medial collar. Three categories of loosening were used: definite (requiring radiographic evidence of migration of the component or the cement), probable (requiring evidence of a complete radiolucent zone at the bone-cement interface on one radiograph or more), and possible (a radiolucent zone at the cement-bone interface of more than 49 per cent but less than 100 per cent on one radiograph or more). One femoral component had been removed for aseptic loosening at another hospital, leaving the patient with a resection arthroplasty. One other (1.7 per cent) was definitely loose. No femoral component was categorized as probably loose, and only two were possibly loose.

Sound reproducing device

An improved sound reproducing device which includes a housing, an acoustic diaphragm and drive means for driving the acoustic diaphragm. Corrugated compliant coupling means is provided for supporting the acoustic diaphragm with respect to the housing in a predetermined lateral position for longitudinal movement relative thereto. The compliant coupling means has a lateral cross-sectional shape which is noncircular so that the acoustic diaphragm is centered in a predetermined lateral position but which allows freedom of movement in the longitudinal direction. The drive means provides the relative longitudinal movement between the acoustic diaphragm and the housing. In a preferred embodiment, the corrugated compliant coupling has a rectangular cross-sectional shape.

Analysis of TEM modes in dielectric waveguides, by a variational method

In this paper, a method of analysis of dielectric waveguides using a variational method is presented. This method can be applied to dielectric waveguides with any general permittivity distribution. As examples, numerical calculations for dielectric waveguides with rectangular cross-sectional shape and quadratic inhomogeneous permittivity distribution are given.