62,760 research outputs found
Computation of group table alphanumeric display
Computer program, using only group elements as input data, provides machine computation of group tables used for proving theorems and algorithms of finite groups. Program is written for second generation computers
FORTRAN 4 program for computation of group tables of finite groups - Program for second generation machines
FORTRAN 4 program for second generation machines for computing group tables of finite group
FORTRAN program for computation of group table-alphanumeric display
FORTRAN program for computation of group tables, alphanumeric displa
FORTRAN program for machine computation of group tables of finite groups
FORTRAN program for computation of finite group table
NASA three-laser airborne differential absorption lidar system electronics
The system control and signal conditioning electronics of the NASA three laser airborne differential absorption lidar (DIAL) system are described. The multipurpose DIAL system was developed for the remote measurement of gas and aerosol profiles in the troposphere and lower stratosphere. A brief description and photographs of the majority of electronics units developed under this contract are presented. The precision control system; which includes a master control unit, three combined NASA laser control interface/quantel control units, and three noise pulse discriminator/pockels cell pulser units; is described in detail. The need and design considerations for precision timing and control are discussed. Calibration procedures are included
Effect of chlorine purification on oxidation resistance of some mechanical carbons
Oxidation experiments were conducted with some experimental and commercial mechanical carbons at 650 C in dry air flowing at 28 cc/sec (STP). In general, purification of these carbon-graphites with chlorine at 2800 C improved oxidation resistance. Additional improvements in oxidation resistance were obtained from purification followed by an antioxidant (zinc phosphate) treatment. For the commercial materials, purification alone gave greater oxidation resistance than the antioxidant treatment alone. The reverse, however, was the case for the experimental materials
Wear and friction of oxidation-resistant mechanical carbon graphites at 650 C in air
Studies were conducted to determine the friction and wear properties of experimental carbon-graphites. Hemispherically tipped carbon-graphite rider specimens were tested in sliding contact with rotating Inconel X-750 disks in air. A surface speed of 1.33 m/sec, a load of 500 g, and a specimen temperature of 650 C were used. Results indicate: (1) hardness is not a major factor in determining friction and wear under the conditions of these studies. (2) Friction and wear as low as or lower than those observed for a good commercial seal material were attained with some of the experimental materials studied. (3) The inclusion of boron carbide (as an oxidation inhibitor) has a strong influence on wear rate. (4) Phosphate treatment reduces the friction coefficient when boron carbide is not present in the base material
Understanding fragility in supercooled Lennard-Jones mixtures. I. Locally preferred structures
We reveal the existence of systematic variations of isobaric fragility in
different supercooled Lennard-Jones binary mixtures by performing molecular
dynamics simulations. The connection between fragility and local structures in
the bulk is analyzed by means of a Voronoi construction. We find that clusters
of particles belonging to locally preferred structures form slow, long-lived
domains, whose spatial extension increases by decreasing temperature. As a
general rule, a more rapid growth, upon supercooling, of such domains is
associated to a more pronounced super-Arrhenius behavior, hence to a larger
fragility.Comment: 14 pages, 14 figures, minor revisions, one figure adde
Understanding fragility in supercooled Lennard-Jones mixtures. II. Potential energy surface
We numerically investigated the connection between isobaric fragility and the
properties of high-order stationary points of the potential energy surface in
different supercooled Lennard-Jones mixtures. The increase of effective
activation energies upon supercooling appears to be driven by the increase of
average potential energy barriers measured by the energy dependence of the
fraction of unstable modes. Such an increase is sharper, the more fragile is
the mixture. Correlations between fragility and other properties of high-order
stationary points, including the vibrational density of states and the
localization features of unstable modes, are also discussed.Comment: 13 pages, 13 figures, minor revisions, one figure adde
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