Study of fluid transients in closed conduits progress report no. 64-5, 1-30 nov. 1964

Fluid transients in closed conduit

Low-density polybenzimidazole foams for thermal insulation and fire protection

Fire-resistant and nonsmoking foam can be prepared in desirable density range of 24 to 50 kg/cu m by controlled thermal crosslinking of polybenzimidazole prepolymer. Reproducible foams of specific density can be produced by controlling volative content and melting temperature of prepolymer

Systems development of a stall/spin research facility using remotely controlled/augmented aircraft models. Volume 1: Systems overview

A ground based, general purpose, real time, digital control system simulator (CSS) is specified, developed, and integrated with the existing instrumentation van of the testing facility. This CSS is built around a PDP-11/55, and its operational software was developed to meet the dual goal of providing the immediate capability to represent the F-18 drop model control laws and the flexibility for expansion to represent more complex control laws typical of control configured vehicles. Overviews of the two CSS's developed are reviewed as well as the overall system after their integration with the existing facility. Also the latest version of the F-18 drop model control laws (REV D) is described and the changes needed for its incorporation in the digital and analog CSS's are discussed

Coherent cross-talk and parametric driving of matter-wave vortices

We show that the interaction between vortices and sound waves in atomic Bose-Einstein condensates can be elucidated in a double-well trap: with one vortex in each well, the sound emitted by each precessing vortex can be driven into the opposing vortex (if of the same polarity). This cross-talk leads to a periodic exchange of energy between the vortices which is long-range and highly efficient. The increase in vortex energy (obtained by numerical simulations of the Gross-Pitaevskii equation) is significant and experimentally observable as a migration of the vortex to higher density over just a few precession periods. Similar effects can be controllably engineered by introducing a precessing localised obstacle into one well as an artificial generator of sound, thereby demonstrating the parametric driving of energy into a vortex.Comment: 12 pages, 13 figure

Relaxation of strained silicon on Si0.5Ge0.5 virtual substrates

Strain relaxation has been studied in tensile strained silicon layers grown on Si0.5Ge0.5 virtual substrates, for layers many times the critical thickness, using high resolution x-ray diffraction. Layers up to 30 nm thick were found to relax less than 2% by the glide of preexisting 60° dislocations. Relaxation is limited because many of these dislocations dissociate into extended stacking faults that impede the dislocation glide. For thicker layers, nucleated microtwins were observed, which significantly increased relaxation to 14%. All these tensile strained layers are found to be much more stable than layers with comparable compressive strain

Study of fluid transients in closed conduits annual report no. 1

Atmospheric density effect on computation of earth satellite orbit

Optimization of aircraft seat cushion fire blocking layers

This report describes work completed by the National Aeronautics and Space Administration - for the Federal Aviation Administration Technical Center. The purpose of this work was to examine the potential of fire blocking mechanisms for aircraft seat cushions in order to provide an optimized seat configuration with adequate fire protection and minimum weight. Aluminized thermally stable fabrics were found to provide adequate fire protection when used in conjunction with urethane foams, while maintaining minimum weight and cost penalty

Geomorphic evidence for ancient seas on Mars

Geomorphic evidence is presented for ancient seas on Mars. Several features, similar to terrestrial lacustrine and coastal features, were identified along the northern plains periphery from Viking images. The nature of these features argues for formation in a predominantly liquid, shallow body of standing water. Such a shallow sea would require either relatively rapid development of shoreline morphologies or a warmer than present climate at the time of outflow channel formation

Curvilinear ridges and related features in southwest Cydonia Mensae, Mars

Examined is a region on Mars in southwest Cydonia Mensae (32 deg lat., 17 deg long.) just northwest of the lowland/upland boundary escarpment. The dominant morphological features in this region are the clusters of large massifs and plateau outliers (PI), knobby material (K), and smooth lowland plains (Ps). Surrounding the clusters and linking many isolated knobs is a system of curvilinear ridges and arcuate terrain boundaries which tend to separate the massifs and knobs from the smooth plains. Curvilinear ridges are arcuate to nearly linear and smoother in plan than wrinkle ridges and show no apparent correlation with regional structural grain. They are typically 5 to 10 km long but can range from as little as 2 or 3 km to greater than 50 km long. The widths vary from about 100 m to as much as 2 km. Curvilinear ridges are most numerous within 100 km of the lowland/upland boundary escarpment and are associated with massifs and knobby terrain. Arcuate terrain boundaries appear between units of different apparent albedo or arcuate breaks in slope