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  • Other Sources  (83)
  • COMMUNICATIONS AND RADAR  (34)
  • FLUID MECHANICS AND HEAT TRANSFER  (32)
  • Animals
  • Chemical Engineering
  • Humans
  • Life and Medical Sciences
  • SPACE SCIENCES
  • STRUCTURAL MECHANICS
  • 1990-1994
  • 1980-1984  (83)
  • 1981  (83)
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  • 1990-1994
  • 1980-1984  (83)
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  • 1
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    System data communication structures for active-control transport aircraft, volume 1 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Candidate data communication techniques are identified, including dedicated links, local buses, broadcast buses, multiplex buses, and mesh networks. The design methodology for mesh networks is then discussed, including network topology and node architecture. Several concepts of power distribution are reviewed, including current limiting and mesh networks for power. The technology issues of packaging, transmission media, and lightning are addressed, and, finally, the analysis tools developed to aid in the communication design process are described. There are special tools to analyze the reliability and connectivity of networks and more general reliability analysis tools for all types of systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165773 , NAS 1.26:165773 , R-1469-VOL-1
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 2
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    System data communication structures for active-control transport aircraft, volume 2 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The application of communication structures to advanced transport aircraft are addressed. First, a set of avionic functional requirements is established, and a baseline set of avionics equipment is defined that will meet the requirements. Three alternative configurations for this equipment are then identified that represent the evolution toward more dispersed systems. Candidate communication structures are proposed for each system configuration, and these are compared using trade off analyses; these analyses emphasize reliability but also address complexity. Multiplex buses are recognized as the likely near term choice with mesh networks being desirable for advanced, highly dispersed systems.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-165774 , NAS 1.26:165774 , R-1469-VOL-2
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 3
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    Burst statistics of Viterbi decoding (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: A mathematical model of Viterbi decoder burst error performance is presented. This model allows for computer generation of Viterbi-like error sequences quickly and inexpensively for applications where large amounts of data are required. The model is corroborated through comparisons with actual software decoder simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: The Telecommun. and Data Acquisition Progr. Rept. 42-64; p 187-193
    Format: text
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    NASA TECHNICAL REPORTS
  • 4
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    New results on antenna arraying, part 1 (1981)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: Baseband combining with and without combined carrier referencing for antenna arrays are compared under two scenarios for the Voyager 2 Uranus encounter. The combined carrier reference scheme is estimated to outperform the baseband only scheme by less than 0.3 dB E (sub b)/N (sub 0) at a bit error probability of 0.005. These results were attained both with mathematical modeling and software Viterbi decoder simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: Telecommun. and Data Acquisition; p 105-111
    Format: text
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    NASA TECHNICAL REPORTS
  • 5
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    Interplanetary magnetic clouds at 1 AU (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Magnetic clouds are defined as regions with a radial dimension approximately 0.25 AU (at 1 AU) in which the magnetic field strength is high and the magnetic field direction changes appreciably by means of rotation of one component of B nearly parallel to a plane. The magnetic field geometry in such a magnetic cloud is consistent with that of a magnetic loop, but it cannot be determined uniquely. Forty-five clouds were identified in interplanetary data obtained near Earth between 1967 and 1978; at least one cloud passed the Earth every three months. Three classes of clouds were identified, corresponding to the association of a cloud with a shock, a stream interface, or a CME. There are approximately equal numbers of clouds in each class, and the three types of clouds might be different manifestations of a coronal transient. The magnetic pressure inside the clouds is higher than the ion pressure and the sum is higher than the pressure of the material outside of the cloud.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: NASA-TM-82114
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 6
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    On the error statistics of Viterbi decoding and the performance of concatenated codes (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Computer simulation results are presented on the performance of convolutional codes of constraint lengths 7 and 10 concatenated with the (255, 223) Reed-Solomon code (a proposed NASA standard). These results indicate that as much as 0.8 dB can be gained by concatenating this Reed-Solomon code with a (10, 1/3) convolutional code, instead of the (7, 1/2) code currently used by the DSN. A mathematical model of Viterbi decoder burst-error statistics is developed and is validated through additional computer simulations.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-164858 , JPL-PUB-81-9
    Format: application/pdf
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  • 7
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    Entropy encoding applied to a video DM bit stream (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: This paper investigates bandwidth compression of delta modulated video signals using a variety of novel techniques. The video signal is encoded at 16 MHz with an adaptive delta modulator (ADM) using the Song video mode algorithm. One method of achieving bandwidth compression is through the detection and reduction of steady state patterns in the DM bit stream. Further reduction is obtained by deleting the horizontal and vertical drive information. Finally, a modified ADM algorithm is introduced to increase the frequency of steady state patterns. When the modified ADM is combined with entropy coding a 30-50% data compression can be realized.
    Keywords: COMMUNICATIONS AND RADAR
    Type: In: ICC ''81; International Conference on Communications; Jun 14, 1981 - Jun 18, 1981; Denver, CO
    Format: text
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  • 8
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    An analytical tool for simulating Large AMplitude Propellant Slosh (1981)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The development of a multiple-mass, nonlinear, finite-element analytical model - the Large AMplitude Propellant Slosh model (LAMPS) in two- and three-dimensional versions, is described. The model is used in predicting the forces on the Space Shuttle external tank caused by large amplitude motion of propellant fluid. Comparisons between measured propellant reorientation forces and those predicted by the LAMPS models are presented, and it is concluded that the model provides a cost effective, experimentally verified approach to a complicated nonlinear problem.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: AIAA PAPER 81-0500 , Conference on Structures, Structural Dynamics and Materials; Apr 06, 1981 - Apr 08, 1981; Atlanta, GA
    Format: text
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  • 9
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    SP mountain data analysis (1981)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: An analysis of synthetic aperture radar data of SP Mountain was undertaken to demonstrate the use of digital image processing techniques to aid in geologic interpretation of SAR data. These data were collected with the ERIM X- and L-band airborne SAR using like- and cross-polarizations. The resulting signal films were used to produce computer compatible tapes, from which four-channel imagery was generated. Slant range-to-ground range and range-azimuth-scale corrections were made in order to facilitate image registration; intensity corrections were also made. Manual interpretation of the imagery showed that L-band represented the geology of the area better than X-band. Several differences between the various images were also noted. Further digital analysis of the corrected data was done for enhancement purposes. This analysis included application of an MSS differencing routine and development of a routine for removal of relief displacement. It was found that accurate registration of the SAR channels is critical to the effectiveness of the differencing routine. Use of the relief displacement algorithm on the SP Mountain data demonstrated the feasibility of the technique.
    Keywords: COMMUNICATIONS AND RADAR
    Type: NASA-CR-169471 , NAS 1.26:169471 , ERIM-148000-1-F
    Format: application/pdf
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    NASA TECHNICAL REPORTS
  • 10
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    Virtual center arraying (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Methods to increase the amount of data that can be received from outer planet missions are described with emphasis on antenna arraying systems designed to increase the total effective aperture of the receiving system. One such method is virtual center arraying (VCA). In VCA, a combined carrier reference is derived at a point that is, conceptually, the geometric center of the array. This point need not coincide with any of the actual antennas of the array. A noise analysis of the VCA system is given along with formulas for the phase jitter as a function of loop bandwidths and the amount of loop damping. If the ratio of the loop bandwidths of the center loop to the vertex loops is greater than 100, then the jitter is very nearly equal to that expected for ideal combined carrier referencing.
    Keywords: COMMUNICATIONS AND RADAR
    Type: the Telecommun. and Data Acquisition Rept.; p 47-52
    Format: text
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