834,870 research outputs found
Recurrence Formulas for Fully Exponentially Correlated Four-Body Wavefunctions
Formulas are presented for the recursive generation of four-body integrals in
which the integrand consists of arbitrary integer powers (>= -1) of all the
interparticle distances r_ij, multiplied by an exponential containing an
arbitrary linear combination of all the r_ij. These integrals are
generalizations of those encountered using Hylleraas basis functions, and
include all that are needed to make energy computations on the Li atom and
other four-body systems with a fully exponentially correlated Slater-type basis
of arbitrary quantum numbers. The only quantities needed to start the recursion
are the basic four-body integral first evaluated by Fromm and Hill, plus some
easily evaluated three-body "boundary" integrals. The computational labor in
constructing integral sets for practical computations is less than when the
integrals are generated using explicit formulas obtained by differentiating the
basic integral with respect to its parameters. Computations are facilitated by
using a symbolic algebra program (MAPLE) to compute array index pointers and
present syntactically correct FORTRAN source code as output; in this way it is
possible to obtain error-free high-speed evaluations with minimal effort. The
work can be checked by verifying sum rules the integrals must satisfy.Comment: 10 pages, no figures, accepted by Phys. Rev. A (January 2009
Scale factor gage for fiber optics inspection device
Flexible wire device, fastened along outside of fiber bundle from viewing portion to tip, positions calibrated adjustable gage in field of view. Scale factor is determined from known magnification characteristics of fiber optics system or from graduations on gage tip
Symmetry breaking and quark-hadron duality in structure functions
We identify conditions under which a summation over nucleon resonances can
yield, via quark-hadron duality, parton model results for electromagnetic and
neutrino structure functions at large x. While a summation over the lowest even
and odd parity multiplets is sufficient to achieve duality in the symmetric
quark model, a suppression of transitions to specific final states is required
for more realistic cases incorporating SU(6) breaking. We outline several
scenarios consistent with duality, discuss their implications for the high Q^2
behavior of transition form factors, and illustrate how they can expose the
patterns in the flavor-spin dependence of inter-quark forces.Comment: 30 pages, 9 figures, to appear in Phys. Rev.
Search for methylamine in high mass hot cores
We aim to detect methylamine, CHNH, in a variety of hot cores and
use it as a test for the importance of photon-induced chemistry in ice mantles
and mobility of radicals. Specifically, CHNH cannot be formed from atom
addition to CO whereas other NH-containing molecules such as formamide,
NHCHO, can. Submillimeter spectra of several massive hot core regions were
taken with the James Clerk Maxwell Telescope. Abundances are determined with
the rotational diagram method where possible. Methylamine is not detected,
giving upper limit column densities between 1.9 6.4 10
cm for source sizes corresponding to the 100 K envelope radius. Combined
with previously obtained JCMT data analyzed in the same way, abundance ratios
of CHNH, NHCHO and CHCN with respect to each other and
to CHOH are determined. These ratios are compared with Sagittarius B2
observations, where all species are detected, and to hot core models. The
observed ratios suggest that both methylamine and formamide are overproduced by
up to an order of magnitude in hot core models. Acetonitrile is however
underproduced. The proposed chemical schemes leading to these molecules are
discussed and reactions that need further laboratory studies are identified.
The upper limits obtained in this paper can be used to guide future
observations, especially with ALMA.Comment: 14 pages, 5 figures, accepted for publication in A&
Deep Reconditioning Testing for near Earth Orbits
The problems and benefits of deep reconditioning to near Earth orbit missions with high cycle life and shallow discharge depth requirements is discussed. A simple battery level approach to deep reconditioning of nickel cadmium batteries in near Earth orbit is considered. A test plan was developed to perform deep reconditioning in direct comparison with an alternative trickle charge approach. The results demonstrate that the deep reconditioning procedure described for near Earth orbit application is inferior to the alternative of trickle charging
Evaluation of HRL condensing temperature controls
Sensitivities of condenser, radiator, and pump bypass temperature controls to control flo
The calculation of longitude and latitude from geodesic measurements
The solution of the geodesic problem for an oblate ellipsoid is developed in
terms of series. Tables are provided to simplify the computation. [This is an
English translation of F. W. Bessel, Astronomische Nachrichten 4(86), 241-254
(1825). The mathematical notation has been updated to conform to current
conventions and, in a few places, the equations have been rearranged for
clarity. Several errors have been corrected, a figure has been included, and
the tables have been recomputed.]Comment: 11 pages, including 1 figure and 4 pages of tables. Version 2 and 3
fix some minor errors. This translation was edited by Charles F. F. Karney
and Rodney E. Deakin. A transcription of the original paper is available at
arXiv:0908.1823 . For links to other 18th and 19th century papers on
geodesics, see
http://geographiclib.sourceforge.net/geodesic-papers/biblio.htm
Grain refinement control in TIG arc welding
A method for controlling grain size and weld puddle agitation in a tungsten electrode inert gas welding system to produce fine, even grain size and distribution is disclosed. In the method the frequency of dc welding voltage pulses supplied to the welding electrode is varied over a preselected frequency range and the arc gas voltage is monitored. At some frequency in the preselected range the arc gas voltage will pass through a maximum. By maintaining the operating frequency of the system at this value, maximum weld puddle agitation and fine grain structure are produced
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