3,682 research outputs found
Preparation of simulated lunar samples Final report
Techniques for shock loading and recovering mineral samples in simulated lunar condition
Electrochemical deposition of silver crystals aboard Skylab 4
Silver crystals were grown aboard Skylab 4 by an electro-chemical reaction and subsequently returned to earth for comparison with crystals grown at 1- and 5-g. Both the Skylab and earth-grown crystals show a variety of structures. Certain tendencies in structure dependency on gravity level, however, can be discerned. In addition, downward growing dendrite streamers; upward growing chunky crystal streamers; growth along an air/liquid interface; and ribbon, film, and fiber crystal habits were observed in experiments conducted on the ground with solutions of varying concentrations. It was also observed that the crystal structures of space and ground electro-deposited silver crystals were very similar to the structures of germanium selenide and germanium telluride crystals grown in space and on the ground by a vapor transport technique. Consideration of the data leads to the conclusions that: (1) the rate of electrochemical displacement of silver ions from a 5 percent aqueous solution by copper is predominantly diffussion controlled in space and kinetically controlled in 1- and higher-g because of augmentation of mass transport by convection; (2) downward and upward crystal streamers are the result of gravity-driven convection, the flow patterns of which can be delineated. Lateral growths along an air/liquid interface are the result of surface-tension-driven convection, the pattern of which also can be delineated; (3) electrolysis in space or low-g environments can produce either dendritic crystals with more perfect microcrystalline structures or massive, single crystals with fewer defects than those grown on ground or at higher g-levels. Ribbons or films of space-grown silicon crystals would find a ready market for electronic substrate and photocell applications. Space-grown dendritic, metal crystals present the possibility of unique catalysts. Large perfect crystals of various materials are desired for a number of electronic and optical applications; and (4) vapor transport growth of germanium selenide and germanium telluride is affected by convection mechanisms similar to the mechanisms hypothesized for the electrochemical deposition of silver crystals. Evidence and considerations leading to the preceding summaries and conclusions are presented. The implications of the findings and conclusions for technological applications are discussed, and recommendations for further experiments are presented
SMP: A solid modeling program
A prototype solid modeling program, SMP, developed by CSC for Langley Research Center (LaRC) is documented in this paper. The SMP software is employed by the System and Experiments Branch (SEB) of the Space Systems Division (SSD) for preliminary space station design, but is intended as a general purpose tool. The SMP document provides details concerning: the basic geometric modeling primitives and associated operators, the data representation scheme utilized to structure the geometric model, the available commands for both editing and displaying the solid model, the interactive user interface and the input/output interfaces to external software, and the utility of the package in the LaRC computing environment. The document is sufficiently detailed to serve both as a user's guide and reference manual
Computer generated animation and movie production at LARC: A case study
The process of producing computer generated 16mm movies using the MOVIE.BYU software package developed by Brigham Young University and the currently available hardware technology at the Langley Research Center is described. A general overview relates the procedures to a specific application. Details are provided which describe the data used, preparation of a storyboard, key frame generation, the actual animation, title generation, filming, and processing/developing the final product. Problems encountered in each of these areas are identified. Both hardware and software problems are discussed along with proposed solutions and recommendations
Variant supercurrent multiplets
In N = 1 rigid supersymmetric theories, there exist three standard
realizations of the supercurrent multiplet corresponding to the (i) old
minimal, (ii) new minimal and (iii) non-minimal off-shell formulations for N =
1 supergravity. Recently, Komargodski and Seiberg in arXiv:1002.2228 put
forward a new supercurrent and proved its consistency, although in the past it
was believed not to exist. In this paper, three new variant supercurrent
multiplets are proposed. Implications for supergravity-matter systems are
discussed.Comment: 11 pages; V2: minor changes in sect. 3; V3: published version; V4:
typos in eq. (2.3) corrected; V5: comments and references adde
SMP: A solid modeling program version 2.0
The Solid Modeling Program (SMP) provides the capability to model complex solid objects through the composition of primitive geometric entities. In addition to the construction of solid models, SMP has extensive facilities for model editing, display, and analysis. The geometric model produced by the software system can be output in a format compatible with existing analysis programs such as PATRAN-G. The present version of the SMP software supports six primitives: boxes, cones, spheres, paraboloids, tori, and trusses. The details for creating each of the major primitive types is presented. The analysis capabilities of SMP, including interfaces to existing analysis programs, are discussed
Generalized BF Theory in Superspace as Underlying Theory of 11D Supergravity
We construct a generalized BF theory in superspace that can embed
eleven-dimensional supergravity theory. Our topological BF theory can
accommodate all the necessary Bianchi identities for teleparallel superspace
supergravity in eleven-dimensions, as the simplest but nontrivial solutions to
superfield equations for our superspace action. This indicates that our theory
may have solutions other than eleven-dimensional supergravity, accommodating
generalized theories of eleven-dimensional supergravity. Therefore our
topological theory can be a good candidate for the low energy limit of
M-theory, as an underlying fundamental theory providing a `missing link'
between eleven-dimensional supergravity and M-theory.Comment: 16 pages, latex, two new paragraphs in section 4 and in Concluding
Remarks with two new reference
Ectoplasm & Superspace Integration Measure for 2D Supergravity with Four Spinorial Supercurrents
Building on a previous derivation of the local chiral projector for a two
dimensional superspace with eight real supercharges, we provide the complete
density projection formula required for locally supersymmetrical theories in
this context. The derivation of this result is shown to be very efficient using
techniques based on the Ectoplasmic construction of local measures in
superspace.Comment: 18 pages, LaTeX; V2: minor changes, typos corrected, references
added; V3: version to appear in J. Phys. A: Math. Theor., some comments and
references added to address a referee reques
Variant supercurrents and Noether procedure
Consistent supercurrent multiplets are naturally associated with linearized
off-shell supergravity models. In arXiv:1002.4932 we presented the hierarchy of
such supercurrents which correspond to all the models for linearized 4D N = 1
supergravity classified a few years ago. Here we analyze the correspondence
between the most general supercurrent given in arXiv:1002.4932 and the one
obtained eight years ago in hep-th/0110131 using the superfield Noether
procedure. We apply the Noether procedure to the general N = 1 supersymmetric
nonlinear sigma-model and show that it naturally leads to the so-called
S-multiplet, revitalized in arXiv:1002.2228.Comment: 6 page
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