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A class of algorithms for rational approximation of functions formally defined by power series
Corresponding sequence algorithms are defined and shown to exist for a wide range of corresponding continued fractions. Particular examples of these algorithms are given, including an algorithm for forming Pade approximants, and an error analysis is given in one case
All sky pointing attitude control system
In a strapped-down gyroscope space vehicle attitude control system, a method and apparatus are provided for gyro drift and input axis misalignment error compensation employing a sun and a star tracker and preselected vehicle calibration maneuvers. The outputs of two-axis strapped-down gyroscopes nominally aligned with the optical axis of the sun and star trackers are measured to provide gyro drift calibration, roll, pitch and yaw axis scale factors and values corresponding to the degree of nonorthogonality between the roll axis and the pitch and yaw gyro input axes and the nonorthogonality of the roll and pitch axes relative to the yaw axis. The vehicle is then rolled and yawed through precomputed angles as modified by the calibrated data stored in a digital computer, and acquires a target without recourse to external references
GRBlog: A Database for Gamma-Ray Bursts
GRBlog is an on-line database providing researchers with quick access to all
information reported in the GCN Circulars. Users of the GRBlog web site
(grad40.as.utexas.edu/grblog.php) can search the circulars and produce
afterglow light curve plots, or compile data tables. The site also offers
advanced search capabilities to aide in statistical studies or comparative
research. Most of the GCNs have already been entered into the GRBlog database,
with the remainder to follow shortly.Comment: 4 pages, 2 figures. Proceedings for the 2003 GRB Conference (Santa
Fe, NM, 2003 Sep 8-12
Repeatability, accuracy, portability, and errors of the portable alignment gyrocompass system
Portable alignment gyrocompass system accuracy, repeatability, portability, and error
GRO source candidates: (A) Nearby modest-size molecular clouds; (B) Pulsar with Wolf-Rayet companion that has lost its H-envelope
Within 100 pc of the sun there are over a hundred cirrus clouds with masses of approx. 60 solar mass and dense molecular clouds with masses of approx. 4 solar mass. If the local interstellar density of cosmic rays is also present in these clouds, the flux of neutral pion from the decay of gamma rays from the core of a cloud at a distance of 20 pc is approx. 13 x 10(exp -8) photons/sq cm/s. The flux from the more extensive cirrus cloud is approx 4 x 10(exp -7) photons/sq cm/s. A relativistic beam of particles generated by a compact stellar object and incident upon a large, close companion can be a strong gamma ray line source if more of the beam energy is used in interactions with C and O and heavier nuclei and less with H and He. This would be the case if the companion has lost its hydrogen envelope and nucleosynthesized much of its He into C, O, and Ne. Such objects are Wolf-Rayet stars and it is believed that some Wolf-Rayet stars do, in fact, have compact companions. For a beam of protons of 10(exp 37) erg/s, the flux at 1 kpc of the 4.4 MeV C-12 line could be as high as 5 x 10(exp -6) photons/sq cm/s. The fluxes of the deexcitation lines from the spallation products of O-16 are also presented
Effect of microstructure and temperature on the erosion rates and mechanisms of modified EB PVD TBCs
Thermal barrier coatings (TBCs) have now been used in gas turbine engines for a
number of decades and are now considered to be an accepted technology. As there
is a constant drive to increase the turbine entry temperature, in order to
increase engine efficiency, the coatings operate in increasingly hostile
environments. Thus there is a constant drive to both increase the temperature
capabilities of TBCs while at the same time reducing their thermal
conductivities. The thermal conductivity of standard 7 wt% yttria stabilized
zirconia (7YSZ) electron beam (EB) physical vapour deposited (PVD) TBCs can be
reduced in two ways: the first by modification of the microstructure of the TBC
and the second by addition of ternary oxides. By modifying the microstructure of
the TBC such that there are more fine pores, more photon scattering centres are
introduced into the coatings, which reduce the heat transfer by radiation. While
ternary oxides will introduce lattice defects into the coating, which increases
the phonon scattering, thus reducing the thermal conductivity via lattice
vibrations. Unfortunately, both of these methods can have a negative effect on
the erosion resistance of EB PVD TBCs. This paper compares the relative erosion
rates of ten different EB PVD TBCs tested at 90à ° impact at room temperature and
at high temperature and discusses the results in term of microstructural and
temperature effects. It was found that by modifying the coating deposition, such
that a low density coating with a highly â  featheredâ  microstructure formed,
generally resulted in an increase in the erosion rate at room temperature. When
there was a significant change between the room temperature and the high
temperature erosion mechanism it was accompanied by a significant decrease in
the erosion rate, while additions of dopents was found to significantly increase
the erosion rate at room and high temperature. However, all the modified
coatings still had a lower erosion rate than a plasma sprayed coatings. So,
although, relative to a standard 7YSZ coating, the modified coatings have a
lower erosion resistance, they still perform better than PS TBCs and their lower
thermal conductivities could make them viable alternatives to 7YSZ for use in
gas turbine en
Numerical solutions of the one-dimensional nucleon-meson cascade equations
Numerical integration of meson-nucleon cascade equations for accelerator shielding calculation
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