A statistical study of the surface accuracy of a planar truss beam

Surface error statistics for single-layer and double-layer planar truss beams with random member-length errors were calculated using a Monte-Carlo technique in conjunction with finite-element analysis. Surface error was calculated in terms of the normal distance from a regression line to the surface nodes of the distorted beam. Results for both single-layer and double-layer beams indicate that a minimum root-mean-square surface error can be achieved by optimizing the depth-to-length ratio of a truss beam. The statically indeterminate double-layer beams can provide greater surface accuracy, though at the expense of significantly greater complexity

Component count and preliminary assembly considerations for large space truss structures

Expressions for the number of truss components per truss division are presented along with expressions for the area and dimensions of mosaic hexagonal panel arrangements. The expressions were developed by substituting the number of truss components in specific truss divisions into associated polynomial equations and solving for the coefficients of the polynomials. To assist in automated or astronaut truss/panel assembly operations, a concept for assembling a tetrahedral truss with hexagonal panels is presented. The assembly concept minimizes the exchange of truss assembly devices and panel attachment devices, assuming that the number of exchanges is a driving assembly concern

Like Peeling an Onion: An Examination of Cultural Identity Among Adult Learners

This paper describes the results of a study concerning the cultural identity of adult learners in graduate programs at the University of Georgia. Employing analytic induction research design the research team, itself a culturally diverse group of graduate students and professors, analyzes focus group transcript data. The conclusion is reached that verbal statements aside, cultural identity is complex and manifested situationally. Adult educators are advised to adopt sophisticated tools to assess learner identity issues in order to challenge learners to think more critically about their assumptions and biases toward those who are culturally different

Packaging, deployment, and panel design concepts for a truss-stiffened 7-panel precision deployable reflector with feed boom

A concept is presented for achieving a remotely deployable truss-stiffened reflector consisting of seven integrated sandwich panels that form the reflective surface, and an integrated feed boom. The concept has potential for meeting aperture size and surface precision requirements for some high-frequency microwave remote sensing applications. The packaged reflector/feed boom configuration is a self-contained unit that can be conveniently attached to a spacecraft bus. The package has a cylindrical envelope compatible with typical launch vehicle shrouds. Dynamic behavior of a deployed configuration having a 216-inch focal length and consisting of 80-inch-diameter, two-inch-thick panels is examined through finite-element analysis. Results show that the feed boom and spacecraft bus can have a large impact on the fundamental frequency of the deployed configuration. Two candidate rib-stiffened sandwich panel configurations for this application are described, and analytical results for panel mass and stiffness are presented. Results show that the addition of only a few rib stiffeners, if sufficiently deep, can efficiently improve sandwich panel stiffness

Comparison of Autoclave and Out-of-Autoclave Composites

The National Aeronautics and Space Administration (NASA) Exploration Systems Mission Directorate initiated an Advanced Composite Technology Project through the Exploration Technology Development Program in order to support the polymer composite needs for future heavy lift launch architectures. As an example, the large composite dry structural applications on Ares V inspired the evaluation of autoclave and out-of-autoclave (OOA) composite materials. A NASA and industry team selected the most appropriate materials based on component requirements for a heavy lift launch vehicle. Autoclaved and OOA composites were fabricated and results will highlight differences in processing conditions, laminate quality, as well as initial room temperature thermal and mechanical performance. Results from this study compare solid laminates that were both fiber-placed and hand-laid. Due to the large size of heavy-lift launch vehicle composite structures, there is significant potential that the uncured composite material or prepreg will experience significant out-life during component fabrication. Therefore, prepreg out-life was a critical factor examined in this comparison. In order to rigorously test material suppliers recommended out-life, the NASA/Industry team extended the out-time of the uncured composite prepreg to values that were approximately 50% beyond the manufacturers out-time limits. Early results indicate that the OOA prepreg composite materials suffered in both composite quality and mechanical property performance from their extended out-time. However, the OOA materials performed similarly to the autoclaved composites when processed within a few days of exposure to ambient "shop" floor handling. Follow on studies evaluating autoclave and OOA aluminum honeycomb core sandwich composites are planned

Rock glaciers and mountain hydrology: A review

This is the author accepted manuscript. The final version is available from Elsevier via the DOI in this record.In mountainous regions, climate change threatens cryospheric water resources, and understanding all components of the hydrological cycle is necessary for effective water resource management. Rockglaciers are climatically more resilient than glaciers and contain potentially hydrologically valuable ice volumes, and yet havereceived lessattention, even though rock glacier hydrologicalimportance may increase under future climate warming. In synthesising data from a range of global studies, we provide the first compre-hensive evaluation of the hydrological role played by rock glaciers. Weevaluate hydrological significanceover a range of temporal and spatial scales, alongsidethe complex multiple hydrological processes with which rock glaciers can interact diurnally, seasonally, annually, decadally and both at local and regional extents.We report that although no global-extent, complete inventory for rock glaciers exists currently, recent research efforts have greatly elaborated spatialcoverage.Using these research papers,we synthe-sise information on rock glacier spatial distribution, morphometric characteristics, surface and subsurface features, ice-storage and hydrological flow dynamics, water chemistry, and future resilience, from which we provide the first comprehensive evaluation of their hydrological contribution. We identify and discuss long-, intermediate-and short-term timescales for rock glacier storage, allowing a more balanced assess-ment of the contrasting perspectives regarding the relative significance of rock glacier-derived hydrological contributions compared to other water sources.We show that further empirical observations are required to gain a deeper hydrological understanding of rock glaciers, in terms of(i) their genesis and geomorpho-logical dynamics (ii) total ice/water volume; (iii) water discharge; and (iv) water quality. Lastly, we hypothesisethat at decadal and longer timescales, under future climate warming, degradation of ice within rock glaciers may represent an increasing hydrological contribution to downstream regions, and thus in-creased hydrological significance while rock glacier water stores persist.Royal Geographical SocietyNatural Environment Research Council (NERC