565 research outputs found
USAF solar thermal applications overview
Process heat applications were compared to solar thermal technologies. The generic process heat applications were analyzed for solar thermal technology utilization, using SERI's PROSYS/ECONOMAT model in an end use matching analysis and a separate analysis was made for solar ponds. Solar technologies appear attractive in a large number of applications. Low temperature applications at sites with high insolation and high fuel costs were found to be most attractive. No one solar thermal technology emerges as a clearly universal or preferred technology, however,, solar ponds offer a potential high payoff in a few, selected applications. It was shown that troughs and flat plate systems are cost effective in a large number of applications
Liquid-Gas Phase Transition in Nuclear Equation of State
A canonical ensemble model is used to describe a caloric curve of nuclear
liquid-gas phase transition. Allowing a discontinuity in the freeze out density
from one spinodal density to another for a given initial temperature, the
nuclear liquid-gas phase transition can be described as first order. Averaging
over various freeze out densities of all the possible initial temperatures for
a given total reaction energy, the first order characteristics of liquid-gas
phase transition is smeared out to a smooth transition. Two experiments, one at
low beam energy and one at high beam energy show different caloric behaviors
and are discussed.Comment: 12 pages in Revtex including two Postscript figure
Temperature determination from the lattice gas model
Determination of temperature from experimental data has become important in
searches for critical phenomena in heavy ion collisions. Widely used methods
are ratios of isotopes (which rely on chemical and thermal equilibrium),
population ratios of excited states etc. Using the lattice gas model we propose
a new observable: where is the charge multiplicity and
is the charge of the fragmenting system. We show that the reduced multiplicity
is a good measure of the average temperature of the fragmenting system.Comment: 11 pages, 2 ps file
An investigation of standard thermodynamic quantities as determined via models of nuclear multifragmentation
Both simple and sophisticated models are frequently used in an attempt to
understand how real nuclei breakup when subjected to large excitation energies,
a process known as nuclear multifragmentation. Many of these models assume
equilibriumthermodynamics and produce results often interpreted as evidence of
a phase transition. This work examines one class of models and employs standard
thermodynamical procedure to explore the possible existence and nature of a
phase transition. The role of various terms, e.g. Coulomb and surface energy,
is discussed.Comment: 19 two-column format pages with 24 figure
One-loop chiral amplitudes of Moller scattering process
The high energy amplitudes of the large angles Moller scattering are
calculated in frame of chiral basis in Born and 1-loop QED level. Taking into
account as well the contribution from emission of soft real photons the compact
relations free from infrared divergences are obtained. The expressions for
separate chiral amplitudes contribution to the cross section are in agreement
with renormalization group predictions.Comment: 15 pages, 3 figure
Microcanonical studies concerning the recent experimental evaluations of the nuclear caloric curve
The microcanonical multifragmentation model from [Al. H. Raduta and Ad. R.
Raduta, Phys. Rev. C 55, 1344 (1997); 56, 2059 (1997); 59, 323 (1999)] is
refined and improved by taking into account the experimental discrete levels
for fragments with and by including the stage of sequential decay of
the primary excited fragments. The caloric curve is reevaluated and the heat
capacity at constant volume curve is represented as a function of excitation
energy and temperature. The sequence of equilibrated sources formed in the
reactions studied by the ALADIN group (Au+Au at 600, 800 and
1000 MeV/nucleon bombarding energy) is deduced by fitting simultaneously the
model predicted mean multiplicity of intermediate mass fragments ()
and charge asymmetry of the two largest fragments () versus bound
charge () on the corresponding experimental data. Calculated HeLi
isotopic temperature curves as a function of the bound charge are compared with
the experimentally deduced ones.Comment: 13 pages, 4 figure
Effect of Flow on Caloric Curve for Finite Nuclei
In a finite temperature Thomas-Fermi theory, we construct caloric curves for
finite nuclei enclosed in a freeze-out volume few times the normal nuclear
volume, with and without inclusion of flow. Without flow, the caloric curve
indicates a smooth liquid-gas phase transition whereas with flow, the
transition may be very sharp. We discuss these results in the context of two
recent experiments, one for heavy symmetric system (Au + Au at 600A MeV) and
the other for highly asymmetric system (Au + C at 1A GeV) where different
behaviours in the caloric curves are seen.Comment: 11 pages revtex; 4 figs; version to appear in Phys. Rev. Let
Isotope thermometery in nuclear multifragmentation
A systematic study of the effect of fragmentfragment interaction, quantum
statistics, -feeding and collective flow is made in the extraction of
the nuclear temperature from the double ratio of the isotopic yields in the
statistical model of one-step (Prompt) multifragmentation. Temperature is also
extracted from the isotope yield ratios generated in the sequential
binary-decay model. Comparison of the thermodynamic temperature with the
extracted temperatures for different isotope ratios show some anomaly in both
models which is discussed in the context of experimentally measured caloric
curves.Comment: uuencoded gzipped file containing 20 pages of text in REVTEX format
and 12 figures (Postscript files). Physical Review C (in press
Correlated Strength in Nuclear Spectral Function
We have carried out an (e,e'p) experiment at high momentum transfer and in
parallel kinematics to measure the strength of the nuclear spectral function
S(k,E) at high nucleon momenta k and large removal energies E. This strength is
related to the presence of short-range and tensor correlations, and was known
hitherto only indirectly and with considerable uncertainty from the lack of
strength in the independent-particle region. This experiment confirms by direct
measurement the correlated strength predicted by theory.Comment: 4 pages, 2 figures, accepted by Phys. Rev. Let
A Measurement of the Electric Form Factor of the Neutron through at (GeV/c)
We report the first measurement of the neutron electric form factor
via using a solid polarized target. was
determined from the beam-target asymmetry in the scattering of longitudinally
polarized electrons from polarized deuterated ammonia, ND. The
measurement was performed in Hall C at Thomas Jefferson National Accelerator
Facility (TJNAF) in quasi free kinematics with the target polarization
perpendicular to the momentum transfer. The electrons were detected in a
magnetic spectrometer in coincidence with neutrons in a large solid angle
segmented detector. We find at (GeV/c).Comment: Latex2e 5 pages, 3 figure
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