64,820 research outputs found

    Investigating techniques in the generation of support software

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    The performance of the Meta assembler processor software package previously provided for the Space Ultrareliable Modular Computer (SUMC) at the Marshall Space Flight Center (MSFC) was verified. A number of adjustments were made to the processor following the rehosting of the SUMC software development facility (S4) on a newly acquired IBM 360/65. The assembler was configured to provide cross assembly capability for various target computers

    The supersymmetric Penrose transform in six dimensions

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    We give a supersymmetric extension to the six-dimensional Penrose transform and give an integral formula for the on-shell (0, 2) supermultiplet. The relationship between super fields on space-time and twistor space is clarified and the space-time superfield constraint equations are derived from the geometry of supertwistor space. We also explain the extension to more general (0,n) supermultiplets and give twistor actions for these theories.Comment: 20 page

    The impact of Chinese import penetration on the South African manufacturing sector

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    This article uses a Chenery-type decomposition and econometric estimation to evaluate the impact of Chinese trade on production and employment in South African manufacturing from 1992 to 2010. The results suggest that increased import penetration from China caused South African manufacturing output to be 5 per cent lower in 2010 than it otherwise would have been. The estimated reduction of total employment in manufacturing as a result of trade with China is larger ā€“ in 2010 about 8 per cent ā€“ because the declines in output were concentrated on labour-intensive industries and because the increase in imports raised labour productivity within industries

    Mechanism for the failure of the Edwards hypothesis in the SK spin glass

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    The dynamics of the SK model at T=0 starting from random spin configurations is considered. The metastable states reached by such dynamics are atypical of such states as a whole, in that the probability density of site energies, p(Ī»)p(\lambda), is small at Ī»=0\lambda=0. Since virtually all metastable states have a much larger p(0)p(0), this behavior demonstrates a qualitative failure of the Edwards hypothesis. We look for its origins by modelling the changes in the site energies during the dynamics as a Markov process. We show how the small p(0)p(0) arises from features of the Markov process that have a clear physical basis in the spin-glass, and hence explain the failure of the Edwards hypothesis.Comment: 5 pages, new title, modified text, additional reference

    Expert systems for real-time monitoring and fault diagnosis

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    Methods for building real-time onboard expert systems were investigated, and the use of expert systems technology was demonstrated in improving the performance of current real-time onboard monitoring and fault diagnosis applications. The potential applications of the proposed research include an expert system environment allowing the integration of expert systems into conventional time-critical application solutions, a grammar for describing the discrete event behavior of monitoring and fault diagnosis systems, and their applications to new real-time hardware fault diagnosis and monitoring systems for aircraft

    Development of a remote digital augmentation system and application to a remotely piloted research vehicle

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    A cost-effective approach to flight testing advanced control concepts with remotely piloted vehicles is described. The approach utilizes a ground based digital computer coupled to the remotely piloted vehicle's motion sensors and control surface actuators through telemetry links to provide high bandwidth feedback control. The system was applied to the control of an unmanned 3/8-scale model of the F-15 airplane. The model was remotely augmented; that is, the F-15 mechanical and control augmentation flight control systems were simulated by the ground-based computer, rather than being in the vehicle itself. The results of flight tests of the model at high angles of attack are discussed

    Near-Term Options for a Nuclear Thermal Propulsion Flight Demonstrator

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    The Appropriations Bill passed by the US Congress in February 2019 instructed NASA to direct not less than 100,000,000forthedevelopmentofnuclearthermalpropulsion,ofwhichnotlessthan100,000,000 for the development of nuclear thermal propulsion, of which not less than 70,000,000 shall be for the design of a flight demonstration by 2024 for which a multi-year plan is required by both the House and the Senate within 180 days of enactment of this agreement." As part of NASAs response to this direction, the Advanced Concepts Office (ACO) at the Marshall Space Flight Center (MSFC) was tasked with leading a study to develop a nuclear thermal propulsion (NTP) flight demonstration (FD) concept and evaluate its feasibility with respect to the near-term schedule goal. During formulation for the NTP FD study, two perspectives emerged with regards to FD concept design. The first seeks to strictly observe the immediate near-term schedule goal, embracing a completely off-the-shelf, high-TRL approach to subsystem design and component selection. The downside to this approach is that the propulsion performance to be expected from such a design is significantly lower than what NTP promises for operational systems, and the value of the flight demo is potentially reduced due to a lack of traceability. The second approach advocates for an FD concept that shows increased traceability to the projected designs of operational systems, providing risk reduction for future NTP-enabled missions. This option comes at the cost of schedule and development risks, as it requires some new investments in nuclear reactor fuels and design. In order to understand the implications and differences between these two approaches, the ACO team elected to perform a concept design of each type, labeling the immediate near-term concept Flight Demo 1 (FD1), and the higher traceability concept Flight Demo 2 (FD2). This paper will present a summary of the mission profiles and system designs for both FD1 and FD2, identifying key drivers and challenges for each design
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