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  • 1
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    Petrov-Galerkin methods for natural convection in directional solidification of binary alloys (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A Petrov-Galerkin finite element method is presented for calculation of the steady, axisymmetric thermosolutal convection and interface morphology in a model for vertical Bridgman crystal growth of nondilute binary alloys. The Petrov-Galerkin method is based on the formulation for biquadratic elements developed by Heinrich and Zienkiewicz and is introduced into the calculation of the velocity, temperature and concentration fields. The algebraic system is solved simultaneously for the field variables and interface shape by Newton's method. The results of the Petrov-Galerkin method are compared critically with those of Galerkin's method using the same finite element grids. Significant improvements in accuracy are found with the Petrov-Galerkin method only when the mesh is refined and when the formulation of the residual equations is modified to account for the mixed boundary conditions that arise at the solidification interface. Calculations for alloys with stable and unstable solute gradients show the occurrence of classical flow transitions and morphological instabilities in the solidification system.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: International Journal for Numerical Methods in Fluids (ISSN 0271-2091); 7; 761-791
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  • 2
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    Third-order resonance effects and the nonlinear stability of drop oscillations (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The three-dimensional nonlinear oscillations of an isolated, inviscid drop with surface tension are studied by a multiple timescale analysis and pre-averaging applied to the variational principle for the appropriate Lagrangian. Amplitude equations are derived which describe the generic cubic resonance caused by the spatial degeneracy of the eigenfrequencies of the linear normal modes. This resonant coupling leads to the instability of the finite amplitude axisymmetric oscillations to small nonaxisymmetric perturbations, as is demonstrated here for the three- and four-lobed normal modes. Solutions to the interaction equations that describe finite amplitude, nonaxisymmetric traveling-wave solutions are also obtained and their stability is investigated. A nongeneric cubic resonance between the two-lobed and four-lobed oscillatory modes leads to quasi-periodic motions.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Journal of Fluid Mechanics (ISSN 0022-1120); 183; 95-121
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  • 3
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    Space Station Freedom - A resource for aerospace education (1988)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The role of the International Space Station in future U.S. aerospace education efforts is discussed from a NASA perspective. The overall design concept and scientific and technological goals of the Space Station are reviewed, and particular attention is given to education projects such as the Davis Planetarium Student Space Station, the Starship McCullough, the Space Habitat, the working Space Station model in Austin, TX, the Challenger Center for Space Life Education, Space M+A+X, and the Space Science Student Involvement Program. Also examined are learning-theory aspects of aerospace education: child vs adult learners, educational objectives, teaching methods, and instructional materials.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: IAF PAPER 88-467
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  • 4
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    Dynamic centering of liquid shells (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The moderate-amplitude axisymmetric oscillations of an inviscid liquid shell surrounding an incompressible gas bubble are calculated by a multiple-time-scale expansion for initial deformations composed of two-lobed perturbations of the shell and a displacement of the bubble from the center of mass of the liquid. Two types of small-amplitude motion are identified and lead to very different nonlinear dynamic interactions, as described by the results valid up to second order in the amplitude of the initial deformation. In the 'bubble mode', the oscillations of the captive bubble and the liquid shell are exactly in phase and the bubble vibrates about its initial eccentric location. The bubble moves toward the center of the drop when the shell is perturbed into a 'sloshing mode' of oscillation where both interfaces move out of phase. These results explain the centering of liquid shells observed in several experiments.
    Keywords: FLUID MECHANICS AND HEAT TRANSFER
    Type: Physics of Fluids (ISSN 0031-9171); 30; 27-35
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  • 5
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    Space education in the context of U.S. Government multiagency efforts in science and mathematics education (1991)
    In:  Other Sources
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    Publication Date: 2019-08-27
    Description: The status of a multiagency endeavor to involve U.S. Federal agencies in the attainment of National Education Goals for the 1990's is presented. Emphasis is placed on the educational activities of NASA, which is one of 16 Federal agencies on the Federal Coordinating Council for Science, Engineering and Technology. NASA's is a prototype education program for achieving excellence in mathematics and science in the coming generations of Americans.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: IAF PAPER 91-524
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  • 6
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    Space education in the context of U.S. government multiagency efforts in science and mathematics education (1992)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The educational activities of NASA which is one of 16 agencies on the Federal Coordinating Council for Science, Engineering and Technology is discussed. NASA's education mission is to utilize its unique facilities and its specialized workforce to conduct and to leverage externally conducted science, mathematics, and technology education programs and activities. These efforts aimed at meeting the national education goals should help to preserve U.S. leadership in aeronautics, space science, and technology.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: AIAA PAPER 92-1687
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  • 7
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    NASA's educational programs (1990)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: The educational programs of NASA's Educational Affairs Division are examined. The problem of declining numbers of science and engineering students is reviewed. The various NASA educational programs are described, including programs at the elementary and secondary school levels, teacher education programs, and undergraduate, graduate, and university faculty programs. The coordination of aerospace education activities and future plans for increasing NASA educational programs are considered.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: Government Information Quarterly (ISSN 0740-624X); 7; 2, 19
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  • 8
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    Scientific Literacy for the 21st Century (SL-21) (1989)
    In:  Other Sources
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    Publication Date: 2019-08-28
    Description: A proposal called, 'Scientific Literacy for the 21st Century (SL-21)', has been introduced, suggesting ways in which NASA may work to increase scientific literacy in the U.S. The future need for an adequate supply of scientists and engineers for the space program is discussed. The principles of the SL-21 proposal are outlined. The program would emphasize education in the fields of space technologies and earth and planetary sciences. The educational elements of the proposal for teachers, students, universities, and the general adult population are described.
    Keywords: SOCIAL SCIENCES (GENERAL)
    Type: IAF PAPER 89-557
    Format: text
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