5,828 research outputs found
Power corrections to the transition form factor and pion distribution amplitudes
Employing the standard hard-scattering approach and the running coupling
method we calculate a class of power-suppressed corrections to the electromagnetic transition form
factor (FF) arising from the end-point
integration regions. In the investigations we use a hard-scattering amplitude
of the subprocess , symmetrized under
exchange important for exclusive
processes containing two external photons. In the computations the pion model
distribution amplitudes (DA's) with one and two non-asymptotic terms are
employed. The obtained predictions are compared with the CLEO data and
constraints on the DA parameters and at the
normalization point are extracted. Further restrictions on
the pion DA's are deduced from the experimental data on the electromagnetic FF
.Comment: 23 pages, 6 figures; the version published in Phys. Rev. D69, 094010
(2004
Symmetrized mean-field description of magnetic instabilities in k-(BEDT-TTF)_2Cu[N(CN)]_2 Y salts
We present a novel and convenient mean-field method, and apply it to study
the metallic/antiferromagnetic interface of k-(BEDT-TTF)_2Cu[N(CN)]_2 Y organic
superconductors (BEDT_TTF is bis-ethylen-dithio-tetrathiafulvalene, Y=Cl, Br).
The method, which fully exploits the crystal symmetry, allows one to obtain the
mean-field solution of the 2D Hubbard model for very large lattices, up to
6x10^5 sites, yielding a reliable description of the phase boundary in a wide
region of the parameter space. The metal/antiferromagnet transtion appears to
be second order, except for a narrow region of the parameter space, where the
transition is very sharp and possibly first order. The cohexistence of metallic
and antiferromagnetic properties is only observed for the transient state in
the case of smooth second order transitions. The relevance of the present
resaults to the complex experimental behavior of centrosymmetric k-phase
BEDT-TTF salts is discussed.Comment: 9 pages in PS format, 7 figures (included in PS), 1 tabl
Post-Demagnetization Performance Assessment for Interior Permanent Magnet AC Machines
This paper assesses the post-demagnetization performance of interior permanent magnet (IPM) ac machines by employing the more accurate recoil line approach based on a 2-D transient finite-element analysis (FEA). The method predicts continuous demagnetization of each magnet element undergoing partial demagnetization and evaluates the machine behavior after an event of short-circuit faults across its terminals. Along with the short-circuit faults, a failure in a drive controller or a position sensor, which may lead to a reverse voltage across the machine terminals that can eventually be more fatal and can cause significant reduction in the performance due to high levels of demagnetization, is analyzed as the worst case scenario. The FE predicted post-demagnetization performance is validated by experimental measurements in which a six-phase IPM machine designed for electric vehicle traction is allowed to lose its synchronization with the inverter when forced to operate on a torque-speed envelope, which is way beyond the drive voltage setting
Spatial variability of available nutrients in soil in nearly level fields in northeastern Saskatchewan
Non-Peer Reviewe
High transverse momentum suppression and surface effects in Cu+Cu and Au+Au collisions within the PQM model
We study parton suppression effects in heavy-ion collisions within the Parton
Quenching Model (PQM). After a brief summary of the main features of the model,
we present comparisons of calculations for the nuclear modification and the
away-side suppression factor to data in Au+Au and Cu+Cu collisions at 200 GeV.
We discuss properties of light hadron probes and their sensitivity to the
medium density within the PQM Monte Carlo framework.Comment: Comments: 6 pages, 8 figures. To appear in the proceedings of Hot
Quarks 2006: Workshop for Young Scientists on the Physics of
Ultrarelativistic Nucleus-Nucleus Collisions, Villasimius, Italy, 15-20 May
200
Direct photons in d+Au collisions at s_(NN)**(1/2)=200GeV with STAR
Results are presented of an ongoing analysis of direct photon production in
s_(NN)=200GeV deuteron-gold collisions with the STAR experiment at RHIC. A
significant excess of direct photons is observed near mid-rapidity 0<y<1 and
found to be consistent with next-to-leading order pQCD calculations including
the contribution from fragmentation photons.Comment: 4 pages, 4 figures, HotQuarks 200
Evaluating the Usability of Automatically Generated Captions for People who are Deaf or Hard of Hearing
The accuracy of Automated Speech Recognition (ASR) technology has improved,
but it is still imperfect in many settings. Researchers who evaluate ASR
performance often focus on improving the Word Error Rate (WER) metric, but WER
has been found to have little correlation with human-subject performance on
many applications. We propose a new captioning-focused evaluation metric that
better predicts the impact of ASR recognition errors on the usability of
automatically generated captions for people who are Deaf or Hard of Hearing
(DHH). Through a user study with 30 DHH users, we compared our new metric with
the traditional WER metric on a caption usability evaluation task. In a
side-by-side comparison of pairs of ASR text output (with identical WER), the
texts preferred by our new metric were preferred by DHH participants. Further,
our metric had significantly higher correlation with DHH participants'
subjective scores on the usability of a caption, as compared to the correlation
between WER metric and participant subjective scores. This new metric could be
used to select ASR systems for captioning applications, and it may be a better
metric for ASR researchers to consider when optimizing ASR systems.Comment: 10 pages, 8 figures, published in ACM SIGACCESS Conference on
Computers and Accessibility (ASSETS '17
Nitrogen fertilization improves quantity and quality of organic matter in a grassland soil
Non-Peer Reviewe
Biomass accumulation and nutrient uptake of cereals at different growth stages in the parkland region of Saskatchewan
Non-Peer ReviewedField experiments were conducted with spring wheat (cv. AC Barrie - CWRS and cv. AC Taber - CPS), barley (cv. AC Oxbow - malt and cv. AC Lacombe - feed) and oats (cv. CDC Boyer or CDC Pacer) in 1998 and 1999 at Melfort, Saskatchewan, Canada, to determine biomass accumulation and nutrient uptake in cereal crops at different growth stages, and their relationship. All cereal crops followed a similar pattern of biomass and
nutrient accumulation, which increased at early growth stages, reached at maximum and then decreased at late growth stages. Cereal crops usually reached their maximum biomass at late milk to full ripening stages (72-90 days after emergence), although some cultivars had a several days difference between the two years. Maximum biomass accumulation rate was 164-204 kg ha-1d-1 for wheat, 211-308 kg ha-1d-1 for barley and 185-217g ha-1d-1 for oats. Maximum uptake of nutrients usually occurred at beginning of flower to late milk (63-82 days after emergence) in both years. Maximum accumulation rate of N, P, K and S was 2.0-4.7, 0.3-0.4, 2.4-5.1 and 0.3-0.5 kg ha-1d-1 for wheat, 2.4-5.2, 0.3-0.5, 3.1-7.6 and 0.4-0.8 kg ha-1d-1 for barley, and 2.7-3.6, 0.3, 4.2-4.7 and 0.4-0.5 kg ha-1d-1 for oats, respectively. Both seed yield and nutrient uptake were lower in 1999 than in 1998, due to differences in weather conditions in the growing season in the two years. In summary, maximum nutrient accumulation rate occurred earlier than maximum biomass accumulation rate, and maximum nutrient uptake occurred earlier than maximum biomass. This indicates that in order to get high seed yields, there should be sufficient supply of nutrients to ensure higher nutrient uptake rate at tillering to stem elongation growth stage first, then a higher biomass accumulation rate at early to late boot growth stage, a greater nutrient uptake at beginning of flower to late milk growth stage, and a greater biomass at late milk to full ripening growth stage. This also suggests that sufficient supply of nutrients from soil/fertilizers at early growth stages is of great importance for high-yield crop production systems
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