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  • 1
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    Microstructure characterization by angle-resolved scatter and comparison to measurements made by other techniques (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: The theory and measurement of angle-resolved scatter are described. Values of rms roughness that were obtained by using this technique to characterize four different materials are compared with values that were obtained by using a total integrated scatter measuring instrument, an optical profiler, and a mechanical profiler. The spatial frequency bandwidths and modulation transfer functions of the four instruments are different, and results are described in light of these differences.
    Keywords: INSTRUMENTATION AND PHOTOGRAPHY
    Type: Applied Optics (ISSN 0003-6935); 31; 1426-143
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  • 2
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    16-QAM and trellis-coded 16-QAM on nonlinear channels (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The use of 16-QAM on bandlimited nonlinear satellite channels, in uncoded and trellis-coded form, for bandwidth efficient modulation (ideally 4 bps/Hz) is discussed. To avoid severe degradation due to AM/AM and AM/PM distortion, or to avoid the need for large back-off, predistorting the 16-QAM constellation at the modulator is considered. Performance for varying back-off settings for uncoded and coded 16-QAM is simulated, and it is found that the four-state trellis code has a coding gain of about 8 dB, larger than expected based on linear channel analysis, while the 16-state code gains only marginally beyond this.
    Keywords: COMMUNICATIONS AND RADAR
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  • 3
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    Supersonic STOVL fighter concepts featuring the hybrid tandem-fan propulsion system (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Current research on vertical- or short-takeoff-and-landing (V/STOL) aircraft is concentrating on developing a multirole-capable fighter. Several V/STOL concepts being studied show a capability performing for short-takeoff and vertical-landing (STOVL) missions. This paper is concerned with a propulsion concept which promises added flexibility in mission performance: the hybrid-tandem fan. This propulsion concept is combined with four aircraft planforms and the performance of each is evaluated on a representative mission. The four aircraft planforms used in the study are a conventional wing-tail, a forward-swept wing and canard, a delta-wing and canard, and an oblique wing and tail. The mission was chosen so that the four aircraft all had approximately the same gross takeoff weight. The four designs are compared at various phases of the mission.
    Keywords: AIRCRAFT DESIGN, TESTING AND PERFORMANCE
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  • 4
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    Rate 5/6 Trellis-coded 8-PSK (1986)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Some new short constraint length codes are described for satellite channels which are constant-envelope and which have spectral and energy efficiencies intermediate to other recent coded techniques, namely r = 2/3 coded 8-PSK and r = 3/4 coded 16-PSK. Two intervals of 8-PSK transmission are used to form a modulation base for r = 5/6 Trellis codes. A particularly attractive design is an eight-state code, producing 6.2 dB gain on the Gaussian channel over uncoded 8-PSK, yet sacrificing only 16 percent in spectral efficiency.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications (ISSN 0090-6778); Com-34; 1045-104
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  • 5
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    Convolutional coding combined with continuous phase modulation (1985)
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    Publication Date: 2011-08-19
    Description: Background theory and specific coding designs for combined coding/modulation schemes utilizing convolutional codes and continuous-phase modulation (CPM) are presented. In this paper the case of r = 1/2 coding onto a 4-ary CPM is emphasized, with short-constraint length codes presented for continuous-phase FSK, double-raised-cosine, and triple-raised-cosine modulation. Coding buys several decibels of coding gain over the Gaussian channel, with an attendant increase of bandwidth. Performance comparisons in the power-bandwidth tradeoff with other approaches are made.
    Keywords: COMMUNICATIONS AND RADAR
    Type: IEEE Transactions on Communications (ISSN 0090-6778); COM-33; 20-29
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  • 6
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    An improved algorithm for evaluating trellis phase codes (1984)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A method is described for evaluating the minimum distance parameters of trellis phase codes, including CPFSK, partial response FM, and more importantly, coded CPM (continuous phase modulation) schemes. The algorithm provides dramatically faster execution times and lesser memory requirements than previous algorithms. Results of sample calculations and timing comparisons are included.
    Keywords: CYBERNETICS
    Type: IEEE Transactions on Information Theory (ISSN 0018-9448); IT-30; 846-851
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  • 7
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    On the representation matrices of the spin permutation group (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A method is presented for the determination of the representation matrices of the spin permutation group (symmetric group), a detailed knowledge of these matrices being required in the study of the electronic structure of atoms and molecules. The method is characterized by the use of two different coupling schemes. Unlike the Yamanouchi spin algebraic scheme, the method is not recursive. The matrices for the fundamental transpositions can be written down directly in one of the two bases. The method results in a computationally significant reduction in the number of matrix elements that have to be stored when compared with, say, the standard Young tableaux group theoretical approach.
    Keywords: NUCLEAR AND HIGH-ENERGY PHYSICS
    Type: Journal of Chemical Physics; 67; Dec. 1
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  • 8
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    Diagrammatic perturbation theory - The ground state of the carbon monosulfide molecule (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Diagrammatic many-body perturbation theory is employed in a study of the ground state of the carbon monosulfide molecule for bond lengths close to the equilibrium value. The calculations are complete through third order in the energy within the algebraic approximation. Two different zero-order Hamiltonians are considered, and all two-, three-, and four-body terms are determined for the corresponding perturbation expansions. Many-body effects are found to be very important. Pade approximants to the energy expansion are constructed, and upper bounds evaluated. Almost 53 percent of the estimated correlation energy is recovered. The variation of components of the correlation energy with nuclear separation is investigated. Spectroscopic constants are also calculated.
    Keywords: INORGANIC AND PHYSICAL CHEMISTRY
    Type: Journal of Chemical Physics; 67; Nov. 15
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  • 9
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    Theoretical study of the thioformyl ion (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The equilibrium structure of the thioformyl ion has been determined from an ab initio matrix Hartree-Fock calculation, and an estimated rotation constant has been derived. A rotation constant of 21.7 GHz is obtained for HCS(+); the corresponding constant for DCS(+) is 18.3 GHz. If the vibration-rotation interaction constants for HCS(+) are assumed to be the same as those for HCP, then the rotation constant is 21.6 GHz, while the vibration-rotation constants of DCP give a rotation constant of 18.3 GHz for DCS(+).
    Keywords: NUCLEAR AND HIGH-ENERGY PHYSICS
    Type: Astrophysical Journal; vol. 220
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  • 10
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    Theoretical study of isocyanoacetylene and the isocyanoethynyl radical (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Quantum mechanical calculations, using the matrix Hartree-Fock model, have been performed to obtain estimates of the rotation constants of the isocyanoacetylene molecule and the isocyanoethynyl radical which may be detectable in space. A rotation constant of 5076 MHz is calculated for HC2NC, while for the radical C2NC the value 5458 MHz is obtained.
    Keywords: ATOMIC AND MOLECULAR PHYSICS
    Type: Astrophysical Journal; vol. 220
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