NASA/NREN: Next Generation Internet (NGI) Activities

Various issues associated with next generation internet (NGI) and the NREN (NASA Research and Education Network) activities are presented in viewgraph form. Specific topics include: 1) NREN architecture; 2) NREN applications; and 3) NREN applied research

Fano Resonances in Mid-Infrared Spectra of Single-Walled Carbon Nanotubes

This work revisits the physics giving rise to the carbon nanotubes phonon bands in the mid- infrared. Our measurements of doped and undoped samples of single-walled carbon nanotubes in Fourier transform infrared spectroscopy show that the phonon bands exhibit an asymmetric lineshape and that their effective cross-section is enhanced upon doping. We relate these observations to electron-phonon coupling or, more specifically, to a Fano resonance phenomenon. We note that only the dopant-induced intraband continuum couples to the phonon modes and that defects induced in the sidewall increase the resonance probabilities.Comment: 5 pages, 4 figures and 1 Supplementary Information File (in pdf

Wood I-Joist Model Sensitivity to Oriented Strandboard Web Mechanical Properties

Research on wood I-joist design has often used laboratory testing, but simulation using the finite element method (FEM) offers advantages, including the possibility to separately study different joist components. The objective of this project was to perform a sensitivity analysis using FEM to determine which oriented strandboard (OSB) properties have higher impact on I-joist shear strain and deflection. OSB mechanical properties were changed from 50 to 200% of the reference value to determine their impact on web shear strain and I-joist deflection. The model was primarily sensitive to in-plane web shear stiffness, which changed I-joist deflection up to 23%. The model was also sensitive to the web tensile modulus of elasticity parallel and perpendicular to joist length and, to a lesser extent, to web shear stiffness. These properties changed I-joist deflection up to 2 and 1%, respectively. These findings will be used to plan future work to experimentally determine sensitive OSB web properties required to develop a finite element model of the mechanical behavior of wood I-joists

Impact of Initial Spacing on Plantation Black Spruce Lumber Grade Yield, Bending Properties, and MSR Yield

For decades, initial spacing of 2 m X 2 m has been used for black spruce (Picea mariana) reforestation in eastern Canada. In recent years, however, wider spacings for black spruce are being advocated to reduce establishment costs and accelerate tree growth. Wider spacings will affect not only return on investment but also the quality of products from the plantations, both of which are critical to the success of reforestation programs. As part of a multidisciplinary project, this study evaluated and quantified the impact of initial spacing on lumber grade yield, bending properties, and MSR yield in this species. Furthermore, visual grades of the plantation-grown lumber were compared for their bending properties and their compliance to the current grade requirements for bending stiffness. A total of 139 sample trees were collected from 4 different spacings (3,086, 2,500, 2,066, 1,372 trees/ha) in a 48-year-old initial spacing trial, and 849 pieces of 2-in.-thick lumber from the 4 spacings were graded visually and tested for bending strength and stiffness.With decreasing initial stand density from 3,086 to 2,066 trees/ha, branch diameter showed a steady increase. However, the 3 higher stand densities (3,086, 2,500, and 2,066 trees/ha) had a comparable Select Structural (SS) grade yield thanks to the relatively small branches in this species. Lumber strength and stiffness in those 3 spacings were also quite comparable. When the initial stand density was further reduced to 1,372 tree/ha, however, a remarkable decrease in the SS grade yield due to knots occurred, and lumber strength and stiffness also decreased significantly. The real concern occurred when the plantation-grown lumber was compared to that from natural stands currently being processed in eastern Canada. On average, the plantation-grown black spruce lumber stiffness was 28.9% lower than that of lumber from the natural stands. As a result, a high percentage of the plantation-grown lumber did not meet the bending design values. However, the percentage of the compliance to the design values tended to increase with increasing initial stand density. This article discusses the possible causes for the significantly lower bending properties of the plantation-grown lumber, and potential solutions for increasing lumber properties and the percentage of the compliance

Lockable Knee Implants and Related Methods

Total knee replacements for hinged knee implants include a tibial member, a femoral member, a hinge assembly having a laterally extending axle configured to hingedly attach the femoral member to the tibial member, and a lock mechanism in communication with the hinge assembly. The lock mechanism is configured to (i) lock the femoral member in alignment with the tibial member for a full extension or other defined stabile walking configuration to thereby allow an arthrodesis or stiff knee gait and (ii) unlock to allow the femoral and tibial members to pivot relative to each other for flexion or bending when not ambulating

Lockable Implants

Total joint replacements for implants include a first member configured to attach to a first bone, a second member configured to reside in an adjacent second bone and a locking mechanism. The locking mechanism is configured to (i) lock the first and second members in alignment for full extension or other defined stabilized configuration and (ii) unlock to allow the first and second members to pivot relative to each other for flexion or bending

High-resolution sub-millimetre diameter side-viewing all-optical ultrasound transducer based on a single dual-clad optical fibre

All-optical ultrasound (OpUS), where ultrasound is both generated and received using light, has emerged as a modality well-suited to highly miniaturised applications. In this work we present a proof-of-concept OpUS transducer built onto a single optical fibre with a highly miniaturised lateral dimension (0.4 MPa and a corresponding bandwidth >27 MHz. Concurrent ultrasound generation and reception from the transducer enabled imaging via motorised pull-back allowing image acquisition times of 4 s for an aperture of 20 mm. Image resolution was as low as ~50 µm and 190 µm in the axial and lateral extents, respectively, without the need for image reconstruction. Porcine aorta was imaged ex vivo demonstrating detailed ultrasound images. The unprecedented level of miniaturisation along with the high image quality produced by this device represents a radical new paradigm for minimally invasive imaging

Lockable Knee Implants and Related Methods

Total knee replacements for hinged knee implants include a tibial member, a femoral member, a hinge assembly having a laterally extending axle configured to hingedly attach the femoral member to the tibial member, and a lock mechanism in communication with the hinge assembly. The lock mechanism is configured to (i) lock the femoral member in alignment with the tibial member for a full extension or other defined stabile walking configuration to thereby allow an arthrodesis or stiff knee gait and (ii) unlock to allow the femoral and tibial members to pivot relative to each other for flexion or bending when not ambulating