5,731 research outputs found
Primeness, semiprimeness and localisation in Iwasawa algebras
Necessary and sufficient conditions are given for the completed group
algebras of a compact p-adic analytic group with coefficient ring the p-adic
integers or the field of p elements to be prime, semiprime and a domain.
Necessary and sufficient conditions for the localisation at semiprime ideals
related to the augmentation ideals of closed normal subgroups are found. Some
information is obtained about the Krull and global dimensions of the
localisations. The results extend and complete work of A. Neumann and J. Coates
et al
Structural tailoring of counter rotation propfans
The STAT program was designed for the optimization of single rotation, tractor propfan designs. New propfan designs, however, generally consist of two counter rotating propfan rotors. STAT is constructed to contain two levels of analysis. An interior loop, consisting of accurate, efficient approximate analyses, is used to perform the primary propfan optimization. Once an optimum design has been obtained, a series of refined analyses are conducted. These analyses, while too computer time expensive for the optimization loop, are of sufficient accuracy to validate the optimized design. Should the design prove to be unacceptable, provisions are made for recalibration of the approximate analyses, for subsequent reoptimization
Verification of TG-61 dose for synchrotron-produced monochromatic x-ray beams using fluence-normalized MCNP5 calculations
Ion chamber dosimetry is being used to calibrate dose for cell irradiations
designed to investigate photoactivated Auger electron therapy at the Louisiana
State University CAMD synchrotron facility. This study performed a dosimetry
intercomparison for synchrotron-produced monochromatic x-ray beams at 25 and 35
keV. Ion chamber depth-dose measurements in a PMMA phantom were compared with
the product of MCNP5 Monte Carlo calculations of dose per fluence and measured
incident fluence. Monochromatic beams of 25 and 35 keV were generated on the
tomography beamline at CAMD. A cylindrical, air-equivalent ion chamber was used
to measure the ionization created in a 10x10x10-cm3 PMMA phantom for depths
from 0.6 to 7.7 cm. The American Association of Physicists in Medicine TG-61
protocol was applied to convert measured ionization into dose. Photon fluence
was determined using a NaI detector to make scattering measurements of the beam
from a thin polyethylene target at angles 30 degrees to 60 degrees.
Differential Compton and Rayleigh scattering cross sections obtained from
xraylib, an ANSI C library for x-ray-matter interactions, were applied to
derive the incident fluence. MCNP5 simulations of the irradiation geometry
provided the dose deposition per photon fluence as a function of depth in the
phantom. At 25 keV the fluence-normalized MCNP5 dose overestimated the
ion-chamber measured dose by an average of 7.2+/-3.0% to 2.1+/-3.0% for PMMA
depths from 0.6 to 7.7 cm, respectively. At 35 keV the fluence-normalized MCNP5
dose underestimated the ion-chamber measured dose by an average of 1.0+/-3.4%
to 2.5+/-3.4%, respectively. These results showed that TG-61 ion chamber
dosimetry, used to calibrate dose output for cell irradiations, agreed with
fluence-normalized MCNP5 calculations to within approximately 7% and 3% at 25
and 35 keV, respectively.Comment: 22 pages, 5 figure
Trumpet slices of the Schwarzschild-Tangherlini spacetime
We study families of time-independent maximal and 1+log foliations of the
Schwarzschild-Tangherlini spacetime, the spherically-symmetric vacuum black
hole solution in D spacetime dimensions, for D >= 4. We identify special
members of these families for which the spatial slices display a trumpet
geometry. Using a generalization of the 1+log slicing condition that is
parametrized by a constant n we recover the results of Nakao, Abe, Yoshino and
Shibata in the limit of maximal slicing. We also construct a numerical code
that evolves the BSSN equations for D=5 in spherical symmetry using
moving-puncture coordinates, and demonstrate that these simulations settle down
to the trumpet solutions.Comment: 11 pages, 6 figures, submitted to PR
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