ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Other Sources  (9)
  • FLUID MECHANICS AND HEAT TRANSFER  (3)
  • MATERIALS PROCESSING  (3)
  • SOCIAL SCIENCES (GENERAL)  (2)
  • COMPUTER SYSTEMS  (1)
  • Cell & Developmental Biology
  • 1985-1989  (9)
Collection
Source
Keywords
Years
Year
  • 1
    facet.materialart.
    Unknown
    Convection and segregation in directional solidification of dilute and non-dilute binary alloys - Effects of ampoule and furnace design (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A Petrov-Galerkin/finite-element method is used to analyze the effect of furnace configuration and ampoule design on the temperature field, the convection in the melt, the shape of the melt-solid interface, and the segregation of solute in the crystal, in the directional solidification of several dilute and nondilute binary semiconductor alloys. The vertical Bridgman-Stockbarger system leads to a two-cell flow structure, and the constant gradient furnace has only a single cell near the interface. Radial temperature gradients interact with the solute field to cause the previously predicted sideways diffusive instability, and addition of a solute that is less dense than the bulk melt and that is incorporated upon solidification decreases the intensity of the flow near the interface by increasing the melt density there. The present results have application to understanding of the effects on solute segregation of microgavity solidification and of applied magnetic fields.
    Keywords: MATERIALS PROCESSING
    Type: Journal of Crystal Growth (ISSN 0022-0248); 80; 155-190
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 2
    facet.materialart.
    Unknown
    Effect of vertical magnetic field on convection and segregation in vertical Bridgman crystal growth (1988)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: A previous finite-element analysis of vertical Bridgman growth for dilute and nondilute alloys is extended to include the effect of a vertically-aligned magnetic field in the limit of zero magnetic Reynolds number. Calculations are presented for growth of a dilute gallium-germanium alloy in a vertically stabilized Bridgman-Stockbarger system and in a furnace with a uniform temperature gradient imposed along the ampoule. Steady cellular convection driven by radial temperature gradients causes good axial and radial mixing in both systems without a magnetic field. A weak magnetic field decreases the intensity of convection and the effectiveness of solute mixing. The radial nonuniformity is greatest for an intermediate field strength. Stronger fields suppress flow recirculation completely, and lead to uniform solute segregation across the crystal and to diffusion-controlled axial segregation.
    Keywords: MATERIALS PROCESSING
    Type: Journal of Crystal Growth (ISSN 0022-0248); 89; 2-3,; 339-356
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 3
    facet.materialart.
    Unknown
    Petrov-Galerkin methods for natural convection in directional solidification of binary alloys (1987)
    In:  Other Sources
    Details
    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
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 4
    facet.materialart.
    Unknown
    Third-order resonance effects and the nonlinear stability of drop oscillations (1987)
    In:  Other Sources
    Details
    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
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 5
    facet.materialart.
    Unknown
    Models for convection and segregation in the growth of HgCdTe by the vertical Bridgman method (1989)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Transport processes in the vertical Bridgman growth of Hg(1-x)Cd(x)Te were investigated by numerical analysis of an idealized quasi-steady-state model of this system. The analysis was specifically directed at an explanation for the radial and axial segregation data obtained by Szofran and Lehoczky (1984) and Szofran et al. (1984) on this system, who reported, respectively, on the observations of diffusion-controlled axial segregation and on the presence of large compositional nonuniformities of CdTe across the radius of the crystal. It is shown that the data sets of these groups can be explained by the results of a detailed analysis of heat transfer, convection, and species transport which account for thermosolutal convection in the melt and for heat transfer mechanisms that dominate the HgCdTe alloy. Predictions from this analysis is applicable to the growth of other materials, because they suggest conditions for the growth of radially uniform crystals with nearly constant axial composition profiles.
    Keywords: MATERIALS PROCESSING
    Type: Journal of Crystal Growth (ISSN 0022-0248); 96; 3, Ju; 609-627
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 6
    facet.materialart.
    Unknown
    On evaluating parallel computer systems (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A workshop was held in an attempt to program real problems on the MIT Static Data Flow Machine. Most of the architecture of the machine was specified but some parts were incomplete. The main purpose for the workshop was to explore principles for the evaluation of computer systems employing new architectures. Principles explored were: (1) evaluation must be an integral, ongoing part of a project to develop a computer of radically new architecture; (2) the evaluation should seek to measure the usability of the system as well as its performance; (3) users from the application domains must be an integral part of the evaluation process; and (4) evaluation results should be fed back into the design process. It is concluded that the general organizational principles are achievable in practice from this workshop.
    Keywords: COMPUTER SYSTEMS
    Type: NASA-CR-185399 , NAS 1.26:185399 , RIACS-TR-85.3
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 7
    facet.materialart.
    Unknown
    Space Station Freedom - A resource for aerospace education (1988)
    In:  Other Sources
    Details
    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
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 8
    facet.materialart.
    Unknown
    Dynamic centering of liquid shells (1987)
    In:  Other Sources
    Details
    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
    Format: text
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
  • 9
    facet.materialart.
    Unknown
    Scientific Literacy for the 21st Century (SL-21) (1989)
    In:  Other Sources
    Details
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...