25,414 research outputs found
Design, fabrication, and test of a steel spar wind turbine blade
The design and fabrication of wind turbine blades based on 60 foot steel spars are discussed. Performance and blade load information is given and compared to analytical prediction. In addition, performance is compared to that of the original MOD-O aluminum blades. Costs for building the two blades are given, and a projection is made for the cost in mass production. Design improvements to reduce weight and improve fatigue life are suggested
Missing heavy flavor backgrounds to Higgs boson production
We investigate characteristics of the signal and backgrounds for Higgs boson
decay into WW at the Fermilab Tevatron and CERN Large Hadron Collider. In the
the lepton-pair-plus-missing-energy final state, we show that the background
receives an important contribution from semileptonic decays of heavy flavors.
Lepton isolation cuts provide too little suppression of these heavy flavor
contributions, and an additional 4 to 8 orders-of-magnitude suppression must
come from physics cuts. We demonstrate that an increase of the minimum
transverse momentum of nonleading leptons in multilepton events is one
effective way to achieve the needed suppression, without appreciable loss of
the Higgs boson signal. Such a cut would impact the efficiency of searches for
supersymmetry as well. We emphasize the importance of direct measurement of the
lepton background from heavy flavor production.Comment: 23 pgs., 10 figs, revtex4, 1 Ref. added, minor typos corrected, to
appear in Phys. Rev.
An experimentally robust technique for halo measurement using the IPM at the Fermilab Booster
We propose a model-independent quantity, , to characterize non-Gaussian
tails in beam profiles observed with the Fermilab Booster Ion Profile Monitor.
This quantity can be considered a measure of beam halo in the Booster. We use
beam dynamics and detector simulations to demonstrate that is superior to
kurtosis as an experimental measurement of beam halo when realistic beam
shapes, detector effects and uncertainties are taken into account. We include
the rationale and method of calculation for in addition to results of the
experimental studies in the Booster where we show that is a useful halo
discriminator
Theoretical Characterization of the Interface in a Nonequilibrium Lattice System
The influence of nonequilibrium bulk conditions on the properties of the
interfaces exhibited by a kinetic Ising--like model system with nonequilibrium
steady states is studied. The system is maintained out of equilibrium by
perturbing the familiar spin--flip dynamics at temperature T with
completely--random flips; one may interpret these as ideally simulating some
(dynamic) impurities. We find evidence that, in the present case, the
nonequilibrium mechanism adds to the basic thermal one resulting on a
renormalization of microscopic parameters such as the probability of
interfacial broken bonds. On this assumption, we develop theory for the
nonequilibrium "surface tension", which happens to show a non--monotonous
behavior with a maximum at some finite T. It ensues, in full agreement with
Monte Carlo simulations, that interface fluctuations differ qualitatively from
the equilibrium case, e.g., the interface remains rough at zero--T. We discuss
on some consequences of these facts for nucleation theory, and make some
explicit predictions concerning the nonequilibrium droplet structure.Comment: 10 pages, 7 figures, submitted to Phys. Re
Wind turbine generator rotor blade concepts with low cost potential
Four processed for producing blades are examined. Two use filament winding techniques and two involve filling a mold or form to produce all or part of a blade. The processes are described and a comparison is made of cost, material properties, design and free vibration characteristics. Conclusions are made regarding the feasibility of each process to produce low cost, structurally adequate blades
Filtrations on the knot contact homology of transverse knots
We construct a new invariant of transverse links in the standard contact
structure on R^3. This invariant is a doubly filtered version of the knot
contact homology differential graded algebra (DGA) of the link. Here the knot
contact homology of a link in R^3 is the Legendrian contact homology DGA of its
conormal lift into the unit cotangent bundle S^*R^3 of R^3, and the filtrations
are constructed by counting intersections of the holomorphic disks of the DGA
differential with two conormal lifts of the contact structure. We also present
a combinatorial formula for the filtered DGA in terms of braid representatives
of transverse links and apply it to show that the new invariant is independent
of previously known invariants of transverse links.Comment: 23 pages, v2: minor corrections suggested by refere
Weak Localization Thickness Measurements of Si:P Delta-Layers
We report on our results for the characterization of Si:P delta-layers grown
by low temperature molecular beam epitaxy. Our data shows that the effective
thickness of a delta-layer can be obtained through a weak localization analysis
of electrical transport measurements performed in perpendicular and parallel
magnetic fields. An estimate of the diffusivity of phosphorous in silicon is
obtained by applying this method to several samples annealed at 850 Celsius for
intervals of zero to 15 minutes. With further refinements, this may prove to be
the most precise method of measuring delta-layer widths developed to date,
including that of Secondary Ion Mass Spectrometry analysis
Probing the Interstellar Medium using HI absorption and emission towards the W3 HII region
HI spectra towards the W3 HII complex are presented and used to probe the
Galactic structure and interstellar medium conditions between us and this
region. The overall shape of the spectra is consistent with the predictions of
the Two-Arm Spiral Shock model wherein the gas found in the -40 km/s to -50
km/s range has been accelerated by some 20 km/s from its rotation curve
velocity. Spin temperatures of ~100 K are derived for the Local Arm gas, lower
than found in a previous, similar study towards DR 7. For the interarm region,
values on the order of 300 K are found, implying a negligible filling factor
for the Cold Neutral Medium (<< 1%). Some of the absorbing gas at velocities
near -40 km/s is confirmed to be associated with the HII regions.Comment: 23 pages, 6 figures, accepted for publication in the Astronomical
Journa
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