40,628 research outputs found
Strong Unification
We investigate the possibility that unification occurs at strong coupling. We
show that, despite the fact the couplings pass through a strong coupling
regime, accurate predictions for their low energy values are possible because
the couplings of the theory flow to infrared fixed points. We determine the
low-energy QCD coupling in a favoured class of strong coupling models and find
it is reduced from the weak coupling predictions, lying close to the
experimentally measured value. We extend the analysis to the determination of
quark and lepton masses and show that (even without Grand Unification) the
infra-red fixed point structure may lead to good predictions for the top mass,
the bottom to tau mass ratio and . Finally we discuss the
implications for the unification scale finding it to be increased from the MSSM
value and closer to the heterotic string prediction.Comment: 12 pages, LateX, no figure
Borel singularities at small x
D.I.S. at small Bjorken is considered within the dipole cascade
formalism. The running coupling in impact parameter space is introduced in
order to parametrize effects that arise from emission of large size dipoles.
This results in a new evolution equation for the dipole cascade. Strong
coupling effects are analyzed after transforming the evolution equation in
Borel () space. The Borel singularities of the solution are discussed first
for the universal part of the dipole cascade and then for the specific process
of D.I.S. at small . In the latter case the leading infrared renormalon is
at indicating the presence of power corrections for the
small- structure functions.Comment: 5 pages, Latex (Talk presented at DIS'97, Chicago, IL
Noise addendum experimental clean combustor program, phase 1
The development of advanced CTOL aircraft engines with reduced exhaust emissions is discussed. Combustor noise information provided during the basic emissions program and used to advantage in securing reduced levels of combustion noise is included. Results are presented of internal pressure transducer measurements made during the scheduled emissions test program on ten configurations involving variations of three basic combustor designs
An Investigation of Flame Spread over Shallow Liquid Pools in Microgravity and Nonair Environments
Experiments of interest to combustion fundamentals and spacecraft fire safety investigated flame spread of alcohol fuels over shallow, 15 cm diameter pools in a 5.2 sec free-fall, microgravity facility. Results showed that, independent O2 concentration, alcohol fuel, and diluent types, microgravity flame spread rates were nearly identical to those corresponding normal-gravity flames for conditions where the normal gravity flames spread uniformly. This similarity indicated buoyancy-related convection in either phase does not affect flame spread, at least for the physical scale of the experiments. However, microgravity extinction coincided with the onset conditions for pulsating spread in normal gravity, implicating gas phase, buoyant flow as a requirement for pulsating spread. When the atmospheric nitrogen was replaced with argon, the conditions for the onset of normal-gravity pulsating flame spread and microgravity flame extinction were changed, in agreement with the expected lowering of the flash point through the thermal properties of the diluent. Helium-diluted flames, however, showed unexpected results with a shift to apparently higher flash-point temperatures and high normal gravity pulsation amplitudes
Research of low cost wind generator rotors
A feasibility program determined that it would be possible to significantly reduce the cost of manufacturing wind generator rotors by making them of cast urethane. Several high modulus urethanes which were structurally tested were developed. A section of rotor was also cast and tested showing the excellent aerodynamic surface which results. A design analysis indicated that a cost reduction of almost ten to one can be achieved with a small weight increase to achieve the same structural integrity as expected of current rotor systems
Two aspects of the Regge limit in QCD: Double Logs in Exclusive observables and Infrared Effects in Cross Sections
Two relevant points related to the application of the BFKL formalism to
phenomenology are discussed. First, we have presented a set of observables
characterizing multi-jet configurations event by event (average transverse
momentum, average azimuthal angle, average ratio of jet rapidities) which can
be used to find distinct signals of BFKL dynamics at the LHC. A numerical
analysis has been shown using the Monte Carlo event generator BFKLex, modified
to include higher-order collinear corrections in addition to the
transverse-momentum implementation of the NLO kernel. We require to have two
tagged forward/backward jets in the final state. Second, the structure of the
BFKL equation changes if infrared boundary conditions are imposed when
considering the running of the coupling. The cut in the complex angular
momentum plane becomes an infinite series of Regge poles. Integrating along a
contour off the real axis we find a strong dependence of the intercepts and
collinear regions on the choice of the boundary conditions. The mean transverse
scales dominant in the gluon ladder increase. This could have interesting
phenomenological consequences.Comment: 6 pages, presented by A. Sabio Vera at the 25th International
Workshop on Deep Inelastic Scattering and Related Topics, 3-7 April 2017,
Birmingham, U
Interconnect fatigue design for terrestrial photovoltaic modules
The results of comprehensive investigation of interconnect fatigue that has led to the definition of useful reliability-design and life-prediction algorithms are presented. Experimental data indicate that the classical strain-cycle (fatigue) curve for the interconnect material is a good model of mean interconnect fatigue performance, but it fails to account for the broad statistical scatter, which is critical to reliability prediction. To fill this shortcoming the classical fatigue curve is combined with experimental cumulative interconnect failure rate data to yield statistical fatigue curves (having failure probability as a parameter) which enable (1) the prediction of cumulative interconnect failures during the design life of an array field, and (2) the unambiguous--ie., quantitative--interpretation of data from field-service qualification (accelerated thermal cycling) tests. Optimal interconnect cost-reliability design algorithms are derived based on minimizing the cost of energy over the design life of the array field
Reconstruction of Quark Mass Matrices with Weak Basis Texture Zeroes from Experimental Input
All quark mass matrices with texture zeroes obtained through weak basis
transformations are confronted with the experimental data. The reconstruction
of the quark mass matrices M_u and M_d at the electroweak scale is performed in
a weak basis where the matrices are Hermitian and have a maximum of three
vanishing elements. The same procedure is also accomplished for the Yukawa
coupling matrices at the grand unification scale in the context of the Standard
Model and its minimal supersymmetric extension as well as of the two Higgs
doublet model. The analysis of all viable power structures on the quark Yukawa
coupling matrices that could naturally appear from a Froggatt-Nielsen mechanism
is also presented.Comment: RevTeX4, 3 tables, 21 pages; misprints corrected and one reference
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