891 research outputs found
Sparger system for MMH-helium vents
Based on a calculated vent flow rate and MMH concentration, a TI-59 program was run to determine total sparger hole area for a given sparger inlet pressure. Hole diameter is determined from a mass transfer analysis in the holding tank to achieve complete capture of MMH. In addition, based on oxidation kinetics and vapor pressure data, MMh atmospheric concentrations are determined 2 ft above the holding tank
Fluorine disposal
A preliminary design of an F2 dispoal system for HELSTF is presented along with recommendations on operational policy and identification of potential operational problems. The analysis is based on sizing a system to handle two different modes of the HELSTF Fluorine Flow System (one operational and one catastrophic). This information should serve both as a guide to a final detailed design for HELSTF as well as a reference for subsequent monitoring and/or modification of the system which consists of a charcoal reactor followed by a dry soda lime scrubber
An analysis of cryotrap heat exchanger performance test data (400 area) and recommendations for a system to handle Apollo RCS engines
The current arrangement of a Platecoil heat exchanger which uses LN2 on the inside of parallel tubes, in counter flow to the test cell engine exhaust gases which are drawn through a box surrounding the plates by the existing vacuum blowers is examined. As a result of inadequate performance and special test data it was decided to redesign the system to accommodate an Apollo RCS engine
The SU(3) Beta Function from Numerical Stochastic Perturbation Theory
The SU(3) beta function is computed from Wilson loops to 20th order numerical
stochastic perturbation theory. An attempt is made to include massless
fermions, whose contribution is known analytically to 4th order. The question
whether the theory admits an infrared stable fixed point is addressed.Comment: 10 pages, 7 figures, version to be published in Physics Letters
Perturbative renormalisation of quark bilinear operators for overlap fermions with and without stout links and improved gauge action
We calculate lattice renormalisation constants of local and one-link quark
operators for overlap fermions and improved gauge actions in one-loop
perturbation theory. For the local operators we stout smear the SU(3) links in
the fermionic action. Using the popular tadpole improved L\"uscher-Weisz
actions at and we present numerical values for the Z
factors in the scheme (partly as function of the stout smearing
strength). We compare various levels of mean field (tadpole) improvement which
have been applied to our results.Comment: 7 page
Dyson instability for 2D nonlinear O(N) sigma models
For lattice models with compact field integration (nonlinear sigma models
over compact manifolds and gauge theories with compact groups) and satisfying
some discrete symmetry, the change of sign of the bare coupling g_0^2 at zero
results in a mere discontinuity in the average energy rather than the
catastrophic instability occurring in theories with integration over
arbitrarily large fields. This indicates that the large order of perturbative
series and the non-perturbative contributions should have unexpected features.
Using the large-N limit of 2-dimensional nonlinear O(N) sigma model, we discuss
the complex singularities of the average energy for complex 't Hooft coupling
lambda= g_0^2N. A striking difference with the usual situation is the absence
of cut along the negative real axis. We show that the zeros of the partition
function can only be inside a clover shape region of the complex lambda plane.
We calculate the density of states and use the result to verify numerically the
statement about the zeros. We propose dispersive representations of the
derivatives of the average energy for an approximate expression of the
discontinuity. The discontinuity is purely non-perturbative and contributions
at small negative coupling in one dispersive representation are essential to
guarantee that the derivatives become exponentially small when lambda -> 0^+ We
discuss the implications for gauge theories.Comment: 10 pages, 10 figures uses revte
Scaling of Non-Perturbatively O(a) Improved Wilson Fermions: Hadron Spectrum, Quark Masses and Decay Constants
We compute the hadron mass spectrum, the quark masses and the meson decay
constants in quenched lattice QCD with non-perturbatively improved
Wilson fermions. The calculations are done for two values of the coupling
constant, and 6.2, and the results are compared with the
predictions of ordinary Wilson fermions. We find that the improved action
reduces lattice artifacts as expected
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