Diffusion bonding of titanium to simulate S-1C fuel tankage components

Developing fabrication methods for diffusion bonding of titanium alloys to meet SIC fuel tank design criteri

Fracture surface characteristics of notched angleplied graphite/epoxy composites

Composite fracture surface characteristics and related fracture modes have been investigated through extensive microscopic inspections of the fracture surfaces of notched angleplied graphite/epoxy laminates. The investigation involved 4 ply laminates of the configuration + or - theta (s) where theta = 0 deg, 3 deg, 5 deg, 10 deg, 15 deg, 30 deg, 45 deg, 60 deg, 75 deg, and 90 deg. Two-inch wide tensile specimens with 0.25 in. by 0.05 in. through-slits centered across the width were tested to fracture. The fractured surfaces were then removed and examined using a scanning electron microscope. Evaluation of the photomicrographs combined with analytical results obtained using the CODSTRAN computer code culminated in a unified set of fracture criteria for determining the mode of fracture in notched angleplied graphite/epoxy laminates

MSFC evaluation of the space fabrication demonstration system (beam builder)

The beam builder, designed and manufactured as a ground demonstration model, is a precursor to a machine for use in the space environment, transportable by the space shuttle. The beam builder has the capability to automatically fabricate triangular truss beams in low Earth orbit with a highly reliable machine that requires a minimum of in-space maintenance and repair. A performance assessment of the beam builder, which was fabricated from commercial hardware is given

Management system requirements for wireless systems beyond 3G

This paper presents a comprehensive description of various management system requirements for systems beyond 3G, which have been identified as a result of the Software Based Systems activities within the Mobile VCE Core 2 program. Specific requirements for systems beyond 3G are discussed and potential technologies to address them proposed. The analysis has been carried out from network, service and security viewpoints

Longitudinal variations, the opposition effect and monochromatic albedos for Mars

Magnitude at zero phase, phase coefficient, and monochromatic albedo computed for Mars as function of wavelengt

Solar dynamic power systems for space station

The Parabolic Offset Linearly Actuated Reflector (POLAR) solar dynamic module was selected as the baseline design for a solar dynamic power system aboard the space station. The POLAR concept was chosen over other candidate designs after extensive trade studies. The primary advantages of the POLAR concept are the low mass moment of inertia of the module about the transverse boom and the compactness of the stowed module which enables packaging of two complete modules in the Shuttle orbiter payload bay. The fine pointing control system required for the solar dynamic module has been studied and initial results indicate that if disturbances from the station are allowed to back drive the rotary alpha joint, pointing errors caused by transient loads on the space station can be minimized. This would allow pointing controls to operate in bandwidths near system structural frequencies. The incorporation of the fine pointing control system into the solar dynamic module is fairly straightforward for the three strut concentrator support structure. However, results of structural analyses indicate that this three strut support is not optimum. Incorporation of a vernier pointing system into the proposed six strut support structure is being studied

Coulomb Oscillations of Indium-doped ZnO Nanowire Transistors in a Magnetic Field

We report on the observation of Coulomb oscillations from localized quantum dots superimposed on the normal hopping current in ZnO nanowire transistors. The Coulomb oscillations can be resolved up to 20 K. Positive anisotropic magnetoresistance has been observed due to the Lorentz force on the carrier motion. Magnetic field-induced tunneling barrier transparency results in an increase of oscillation amplitude with increasing magnetic field. The energy shift as a function of magnetic field indicates electron wavefunction modification in the quantum dots.Comment: 16 pages, 6 figure

Contrasting life-history traits and population dynamics in two co-existing gastrointestinal nematodes of Svalbard reindeer

By definition, parasites are expected to have fitness consequences for their hosts by reducing survival and fecundity. If such events are density dependent they may play a regulatory role in their host's dynamics. However, there are few studies in the wild that provide empirical evidence to support these suppositions. To understand the impact of parasites it is necessary to explore the interactions between parasite and host and the mechanisms that regulate nematode populations. The aims of this work are to: 1) identify the species specific patterns of infection; 2) investigate the interactions between and within nematode species and 3) examine the regulatory mechanisms that control nematode fecundity. The distribution of parasites between hosts and the variation between years, seasons, reindeer age and location are also examined. Nematode infections of Svalbard reindeer are dominated by two species: Ostertagia gruehneri and Marshallagia marshalli and their contrasting life-histories and population dynamics highlights the importance of investigating at the level of individual species. For 0. gruehneri, there is significant annual variation but no strong seasonal pattern in abundance. Susceptible calves do not acquire infection until their second summer. Egg output is highly seasonal with a peak in July and controlled through density dependent effects on worm development. In contrast M marshalli, shows a strong seasonal cycle which does not vary between years and the peak occurs in late winter suggesting winter transmission. Egg output is low and also confined to the winter months. The quantification of these traits is important in allowing parameterisation of models with data from the study system. In many studies parameters are estimated from studies of domestic host parasite systems and these may be inappropriate in this natural system. The role of immunity and arrested development and the relationship between transmission and environmental heterogeneity are discussed