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Measurement and Modeling of Advanced Coal Conversion Processes, Volume II
A two dimensional, steady-state model for describing a variety of reactive and nonreactive flows, including pulverized coal combustion and gasification, is presented. The model, referred to as 93-PCGC-2 is applicable to cylindrical, axi-symmetric systems. Turbulence is accounted for in both the fluid mechanics equations and the combustion scheme. Radiation from gases, walls, and particles is taken into account using a discrete ordinates method. The particle phase is modeled in a lagrangian framework, such that mean paths of particle groups are followed. A new coal-general devolatilization submodel (FG-DVC) with coal swelling and char reactivity submodels has been added
New measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission
Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both
calculable from first principles using various theoretical approaches and of
interest for the understanding of a wide range of questions in many body
physics. Unfortunately, the pair correlation function inferred from
neutron scattering measurements of the differential cross section from different measurements reported in the literature are
inconsistent. We have measured the energy dependence of the total cross section
and the scattering cross section for slow neutrons with energies between
0.43~meV and 16.1~meV on liquid hydrogen at 15.6~K (which is dominated by the
parahydrogen component) using neutron transmission measurements on the hydrogen
target of the NPDGamma collaboration at the Spallation Neutron Source at Oak
Ridge National Laboratory. The relationship between the neutron transmission
measurement we perform and the total cross section is unambiguous, and the
energy range accesses length scales where the pair correlation function is
rapidly varying. At 1~meV our measurement is a factor of 3 below the data from
previous work. We present evidence that these previous measurements of the
hydrogen cross section, which assumed that the equilibrium value for the ratio
of orthohydrogen and parahydrogen has been reached in the target liquid, were
in fact contaminated with an extra non-equilibrium component of orthohydrogen.
Liquid parahydrogen is also a widely-used neutron moderator medium, and an
accurate knowledge of its slow neutron cross section is essential for the
design and optimization of intense slow neutron sources. We describe our
measurements and compare them with previous work.Comment: Edited for submission to Physical Review
The Importance of Correlations and Fluctuations on the Initial Source Eccentricity in High-Energy Nucleus-Nucleus Collisions
In this paper, we investigate various ways of defining the initial source
eccentricity using the Monte Carlo Glauber (MCG) approach. In particular, we
examine the participant eccentricity, which quantifies the eccentricity of the
initial source shape by the major axes of the ellipse formed by the interaction
points of the participating nucleons. We show that reasonable variation of the
density parameters in the Glauber calculation, as well as variations in how
matter production is modeled, do not significantly modify the already
established behavior of the participant eccentricity as a function of collision
centrality. Focusing on event-by-event fluctuations and correlations of the
distributions of participating nucleons we demonstrate that, depending on the
achieved event-plane resolution, fluctuations in the elliptic flow magnitude
lead to most measurements being sensitive to the root-mean-square, rather
than the mean of the distribution. Neglecting correlations among
participants, we derive analytical expressions for the participant eccentricity
cumulants as a function of the number of participating nucleons,
\Npart,keeping non-negligible contributions up to \ordof{1/\Npart^3}. We
find that the derived expressions yield the same results as obtained from
mixed-event MCG calculations which remove the correlations stemming from the
nuclear collision process. Most importantly, we conclude from the comparison
with MCG calculations that the fourth order participant eccentricity cumulant
does not approach the spatial anisotropy obtained assuming a smooth nuclear
matter distribution. In particular, for the Cu+Cu system, these quantities
deviate from each other by almost a factor of two over a wide range in
centrality.Comment: 18 pages, 10 figures, submitted to PR
Genetic parameters for hair characteristics and core body temperature in a multibreed Brahman-Angus herd
Thermal stress in hot humid conditions limits cattle production. The objectives for this study were to estimate genetic parameters for hair characteristics and core body temperature under low and high temperature humidity index (THI) conditions. Hair samples were collected and measured for length and diameter. Core body temperature was measured as vaginal temperature every 15 min over a 5-d period using an iButton temperature measuring device implanted in a blank CIDR in 336 heifers from the University of Florida multibreed herd (ranging from 100% Angus to 100% Brahman). Restricted maximum likelihood procedures were used to estimate heritabilities from multiple bivariate animal models using the WOMBAT program. Estimates of heritability for hair diameter, undercoat length, topcoat length, body temperature under low THI conditions, and body temperature under high THI conditions were 0.50, 0.67, 0.42, 0.32, and 0.26, respectively. The genetic parameters estimated in this study indicate a large, exploitable genetic variance which can be selected upon to improve tolerance in cattle. Breed effects for differing compositions of Brahman and Angus were also estimated. As Brahman breed composition increased by 25% undercoat length, topcoat length, body temperature under low THI conditions, and body temperature under high THI conditions decreased by 1.32 mm, 2.94 mm, 0.11 degrees C, and 0.14 degrees C, respectively. Under both low and high THI conditions, cattle with 25% Brahman breed composition or greater maintained a significantly lower body temperature than the 100% Angus breed group. The incorporation of Brahman germplasm is recommended for herds that often experience heat stress conditions in order to increase resilience to heat stress.United States Department of Agriculture (USDA
Collision geometry scaling of Au+Au pseudorapidity density from sqrt(s_NN) = 19.6 to 200 GeV
The centrality dependence of the midrapidity charged particle multiplicity in
Au+Au collisions at sqrt(s_NN) = 19.6 and 200 GeV is presented. Within a simple
model, the fraction of hard (scaling with number of binary collisions) to soft
(scaling with number of participant pairs) interactions is consistent with a
value of x = 0.13 +/- 0.01(stat) +/- 0.05(syst) at both energies. The
experimental results at both energies, scaled by inelastic p(pbar)+p collision
data, agree within systematic errors. The ratio of the data was found not to
depend on centrality over the studied range and yields a simple linear scale
factor of R_(200/19.6) = 2.03 +/- 0.02(stat) +/- 0.05(syst).Comment: 5 pages, 4 figures, submitted to PRC-R
Event-by-event fluctuations of azimuthal particle anisotropy in Au+Au collisions at sqrt(s_NN) = 200 GeV
This paper presents the first measurement of event-by-event fluctuations of
the elliptic flow parameter v_2 in Au+Au collisions at sqrt(s_NN) = 200GeV as a
function of collision centrality. The relative non-statistical fluctuations of
the v_2 parameter are found to be approximately 40%. The results, including
contributions from event-by-event elliptic flow fluctuations and from azimuthal
correlations that are unrelated to the reaction plane (non-flow correlations),
establish an upper limit on the magnitude of underlying elliptic flow
fluctuations. This limit is consistent with predictions based on spatial
fluctuations of the participating nucleons in the initial nuclear overlap
region. These results provide important constraints on models of the initial
state and hydrodynamic evolution of relativistic heavy ion collisions.Comment: 5 pages, 2 figures, Published in Phys. Rev. Lett
Non-flow correlations and elliptic flow fluctuations in gold-gold collisions at sqrt(s_NN)= 200 GeV
This paper presents results on event-by-event elliptic flow fluctuations in
Au+Au collisions at sqrt(s_NN)=200Gev, where the contribution from non-flow
correlations has been subtracted. An analysis method is introduced to measure
non-flow correlations, relying on the assumption that non-flow correlations are
most prominent at short ranges (Delta eta < 2). Assuming that non-flow
correlations are of the order that is observed in p+p collisions for long range
correlations (Delta eta > 2), relative elliptic flow fluctuations of
approximately 30-40% are observed. These results are consistent with
predictions based on spatial fluctuations of the participating nucleons in the
initial nuclear overlap region. It is found that the long range non-flow
correlations in Au+Au collisions would have to be more than an order of
magnitude stronger compared to the p+p data to lead to the observed azimuthal
anisotropy fluctuations with no intrinsic elliptic flow fluctuations.Comment: 9 pages, 7 figures, Published in Phys. Rev.
Centrality and pseudorapidity dependence of elliptic flow for charged hadrons in Au+Au collisions at sqrt(sNN) = 200 GeV
This paper describes the measurement of elliptic flow for charged particles
in Au+Au collisions at sqrt(sNN)=200 GeV using the PHOBOS detector at the
Relativistic Heavy Ion Collider (RHIC). The measured azimuthal anisotropy is
presented over a wide range of pseudorapidity for three broad collision
centrality classes for the first time at this energy. Two distinct methods of
extracting the flow signal were used in order to reduce systematic
uncertainties. The elliptic flow falls sharply with increasing eta at 200 GeV
for all the centralities studied, as observed for minimum-bias collisions at
sqrt(sNN)=130 GeV.Comment: Final published version: the most substantive change to the paper is
the inclusion of a complete description of how the errors from the hit-based
and track-based analyses are merged to produce the 90% C.L. errors quoted for
the combined results shown in Fig.
First Observation of -odd Asymmetry in Polarized Neutron Capture on Hydrogen
We report the first observation of the parity-violating 2.2 MeV gamma-ray
asymmetry in neutron-proton capture using polarized cold
neutrons incident on a liquid parahydrogen target at the Spallation Neutron
Source at Oak Ridge National Laboratory. isolates the , \mbox{} component of the weak
nucleon-nucleon interaction, which is dominated by pion exchange and can be
directly related to a single coupling constant in either the DDH meson exchange
model or pionless EFT. We measured , which implies a DDH weak coupling of
and a pionless
EFT constant of MeV. We describe the experiment, data
analysis, systematic uncertainties, and the implications of the result.Comment: 6 pages, 5 figure
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