86,078 research outputs found
Nuclear radiation environment analysis for thermoelectric outer planet spacecraft
Neutron and gamma ray transport calculations were performed using Monte Carlo methods and a three-dimensional geometric model of the spacecraft. The results are compared with similar calculations performed for an earlier design
Rocketdyne's advanced coal slurry pumping program
The Rocketdyne Division of Rockwell International Corporation is conducting a program for the engineering, fabrication, and testing of an experimental/prototype high-capacity, high-pressure centrifugal slurry feed pump for coal liquefaction purposes. The abrasion problems in a centrifugal slurry pump are primarily due to the manner in which the hard, solid particles contained in the slurry are transported through the hydraulic flow passages within the pump. The abrasive particles can create scraping, grinding, cutting, and sandblasting effects on the various exposed parts of the pump. These critical areas involving abrasion and impact erosion wear problems in a centrifugal pump are being addressed by Rocketdyne. The mechanisms of abrasion and erosion are being studied through hydrodynamic analysis, materials evaluation, and advanced design concepts
Thermocapillary flows and their stability: Effects of surface layers and combination
The theoretical analysis of the fluid mechanics and heat transfer of motions driven by surface tension gradients (Marangoni convection) was researched. Convection accompanying the process of growing high quality single crystals from the melt in a micro-g environment was examined. The geometries considered include two dimensional liquid filled slots and axisymmetric float-zone configurations
An evaluation of auroral all-sky camera observations
From photometric, all-sky camera, and visual observations
of a moderate auroral display, it is found that the
all-sky camera compares favorably with the visual observer
in detecting and recording auroral forms. The visual
observer can make instantaneous observations and so can
detect rapid changes and auroral forms lasting only a few
seconds, whereas the poorer time resolution of the all-sky
camera prevents it from recording very short-lived phenonema.
However, the ability of the all-sky camera to accurately
record the shape and intensity of the majority of auroral
forms allows it to yield more precise and complete information
about these aspects of auroral morphology than is
normally obtained through visual observation.Ye
User's manual for MacPASCO
A user's manual is presented for MacPASCO, which is an interactive, graphic, preprocessor for panel design. MacPASCO creates input for PASCO, an existing computer code for structural analysis and sizing of longitudinally stiffened composite panels. MacPASCO provides a graphical user interface which simplifies the specification of panel geometry and reduces user input errors. The user draws the initial structural geometry and reduces user input errors. The user draws the initial structural geometry on the computer screen, then uses a combination of graphic and text inputs to: refine the structural geometry; specify information required for analysis such as panel load and boundary conditions; and define design variables and constraints for minimum mass optimization. Only the use of MacPASCO is described, since the use of PASCO has been documented elsewhere
Improved space radiation shielding methods
The computing software that was used to perform the charged particle radiation transport analysis and shielding design for the Mariner Jupiter/Saturn 1977 spacecraft is described. Electron fluences, energy spectra and dose rates obtained with this software are presented and compared with independent computer calculations
Thermocapillary flows and their stability: Effects of surface layers and contamination
The fluid mechanics and heat transfer of motions driven by surface tension gradients (Marangoni convection) were analyzed theoretically to obtain an understanding of the convection accompanying the process of growing high quality single crystals from the melt in a mu-g environment. The geometries considered include two dimensional liquid filled slots and axisymmetric float zone configurations
Surface-tension induced instabilities: Effects of lateral boundaries
Convection in circular and rectangular cylinders is analyzed. The governing equations and boundary conditions are formulated, linear and nonlinear stability theory are considered, and the physical implications of the theory are discussed
ASCA observations of massive medium-distant clusters of galaxies. II
We have selected seven medium-distant clusters of galaxies (z ~ 0.1 - 0.3)
for multi-wavelength observations with the goal of investigating their
dynamical state. Following Paper I (Pierre et al. 1999) which reported the ASCA
results about two of them, we present here the analysis of the ASCA
observations of the other five clusters; RXJ1023.8-2715 (A3444),
RXJ1031.6-2607, RXJ1050.5-0236 (A1111), RXJ1203.2-2131(A1451), and
RXJ1314.5-2517. Except for RXJ1031.6, whose X-ray emission turned out to be
dominated by an AGN, the ASCA spectra are well fitted by a one-temperature thin
thermal plasma model. We compare the temperature-luminosity relation of our
clusters with that of nearby ones (z<0.1). Two clusters, RXJ1050.5 and
RXJ1023.8, show larger luminosities than the bulk of clusters at similar
temperatures, which suggests the presence of a cooling flow. The temperature
vs. iron-abundance relationship of our sample is consistent with that of nearby
clusters.Comment: 9 pages, 20 figures, A&AS in pres
Genetic algorithms: a pragmatic, non-parametric approach to exploratory analysis of questionnaires in educational research
Data from a survey to determine student attitudes to their courses are used as an example to show how genetic algorithms can be used in the analysis of questionnaire data. Genetic algorithms provide a means of generating logical rules which predict one variable in a data set by relating it to others. This paper explains the principle underlying genetic algorithms and gives a non-mathematical description of the means by which rules are generated. A commercially available computer program is used to apply genetic algorithms to the survey data. The results are discussed
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