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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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9 records

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NASA NTRS1993

Study of the Alsys implementation of the Catalogue of Interface Features and Options for the Ada language for 80386 Unix

A set of programs was written to test the functionality and performance of the Alsys Ada implementation of the Catalogue of Interface Features and Options (CIFO), a set of optional Ada packages for real-time applications. No problems were found with the task id, preemption control, or shared-data packages. Minor problems were found with the dispatching control, dynamic priority, events, non-waiting entry call, semaphore, and scheduling packages. The Alsys implementation is derived mostly from Release 2 of the CIFO standard, but includes some of the features of Release 3 and some modifications unique to Alsys. Performance measurements show that the semaphore and shared-data features are an order-of-magnitude faster than the same mechanisms using an Ada rendezvous. The non-waiting entry call is slightly faster than a standard rendezvous. The existence of errors in the implementation, the incompleteness of the documentation from the published standard impair the usefulness of this implementation. Despite those short-comings, the Alsys CIFO implementation might be of value in the development of real-time applications.

Gibson, James S.↗

NASA NTRS1972

Dissociation energies of some high temperature molecules containing aluminum

The Knudsen cell mass spectrometric method has been used to investigate the gaseous molecules Al2, AlSi,AlSiO, AlC2, Al2C2, and AlAuC2. Special attention was given to the experimental considerations and techniques needed to identify and to measure ion intensities for very low abundance molecular species. Second- and third-law procedures were used to obtain reaction enthalpies for pressure calibration independent and isomolecular exchange reactions. Dissociation energies for the molecules were derived from the measured ion intensities, free-energy functions obtained from estimated molecular constants, and auxiliary thermodynamic data. The bonding and stability of these aluminum containing molecules are compared with other similar species.

Stearns, C. A.↗

NASA NTRS1985

Studies of the Crystallization Process of Aluminum-Silicon Alloys Using a High Temperature Microscope

It is shown that primary silicon crystals grow polyhedral in super-eutectic AlSi melts and that phosphorus additives to the melt confirm the strong seeding capacity. Primary silicon exhibits strong dendritic seeding effects in eutectic silicon phases of various silicon alloys, whereas primary aluminum does not possess this capacity. Sodium addition also produces a dendritic silicon network growth in the interior of the sample that is attributed to the slower silicon diffusion velocity during cooling.

Justi, S.↗

NASA NTRS1986

Ada technology support for NASA-GSFC

Utilization of the Ada programming language and environments to perform directorate functions was reviewed. The Mission and Data Operations Directorate Network (MNET) conversion effort was chosen as the first task for evaluation and assistance. The MNET project required the rewriting of the existing Network Control Program (NCP) in the Ada programming language. The DEC Ada compiler running on the VAX under WMS was used for the initial development efforts. Stress tests on the newly delivered version of the DEC Ada compiler were performed. The new Alsys Ada compiler was purchased for the IBM PC AT. A prevalidated version of the compiler was obtained. The compiler was then validated.

Source record↗

NASA NTRS1986

Using Ada (R) on a workstation for large projects

Alsys has implemented validated Ada compilers that are hosted and targeted on a variety of microprocessor-based workstations, including the IBM PC/AT. The availability of Ada compilers for these kinds of inexpensive, widely available machines considerably enhances the development options for large efforts such as the NASA Space Station, and this is addressed from both an implementation and a user perspective. First, the issue of large program development on a workstation is discussed: how the compiler must handle this, and how an inherently decentralized approach can be managed. Next, the focus is on code efficiency and the compiler and run-time design decisions that help meet this goal are described. It is concluded with a presentation of benchmarks that are quite encouraging with respect to the run-time efficiency of Ada code compared with other languages.

Avakian, Arra S.↗

NASA NTRS1990

A study of the portability of an Ada system in the software engineering laboratory (SEL)

A particular porting effort is discussed, and various statistics on analyzing the portability of Ada and the total staff months (overall and by phase) required to accomplish the rehost, are given. This effort is compared to past experiments on the rehosting of FORTRAN systems. The discussion includes an analysis of the types of errors encountered during the rehosting, the changes required to rehost the system, experiences with the Alsys IBM Ada compiler, the impediments encountered, and the lessons learned during this study.

Jun, Linda O.↗

NASA NTRS2003

Design of Hybrid Solid Polymer Electrolytes: Structure and Properties

This paper reports synthesis, structure, and properties of novel hybrid solid polymer electrolytes (SPE's) consisting of organically modified aluminosilica (OM-ALSi), formed within a poly(ethylene oxide)-in-salt (Li triflate) phase. To alter the structure and properties we fused functionalized silanes containing poly(ethylene oxide) (PEO) tails or CN groups.

Bronstein, Lyudmila M.↗

NASA NTRS2012

ISS-Experiments of Columnar-to-Equiaxed Transition in Solidification Processing

The main topic of the research project CETSOL in the framework of the Microgravity Application Promotion (MAP) programme of the European Space Agency (ESA) is the investigation of the transition from columnar to equiaxed grain growth during solidification. Microgravity environment allows for suppression of buoyancy-driven melt flow and for growth of equiaxed grains free of sedimentation and buoyancy effects. This contribution will present first experimental results obtained in microgravity using hypo-eutectic AlSi alloys in the Materials Science Laboratory (MSL) on-board the International Space Station (ISS). The analysis of the experiments confirms the existence of a columnar to equiaxed transition, especially in the refined alloy. Temperature evolution and grain structure analysis provide critical values for the position, the temperature gradient and the solidification velocity at the columnar to equiaxed transition. These data will be used to improve modeling of solidification microstructures and grain structure on different lengths scales.

Sturz, Laszlo↗

NASA NTRS2012

Chemical Heterogeneity on Mercury's Surface Revealed by the MESSENGER X-ray Spectrometer

We present the analysis of 205 spatially resolved measurements of the surfacecomposition of Mercury from MESSENGERs X-Ray Spectrometer. The surfacefootprints of these measurements are categorized according to geological terrain. Northernsmooth plains deposits and the plains interior to the Caloris basin differ compositionallyfrom older terrain on Mercury. The older terrain generally has higher MgSi, SSi, andCaSi ratios, and a lower AlSi ratio than the smooth plains. Mercurys surface mineralogyis likely dominated by high-Mg mafic minerals (e.g., enstatite), plagioclase feldspar, andlesser amounts of Ca, Mg, andor Fe sulfides (e.g., oldhamite). The compositionaldifference between the volcanic smooth plains and the older terrain reflects differentabundances of these minerals and points to the crystallization of the smooth plains from amore chemically evolved magma source. High-degree partial melts of enstatite chondritematerial provide a generally good compositional and mineralogical match for much ofthe surface of Mercury. An exception is Fe, for which the low surface abundance onMercury is still higher than that of melts from enstatite chondrites and may indicate anexogenous contribution from meteoroid impacts.

Chemical heterogeneity↗