628 research outputs found
Atomization and mixing study
The state of the art in atomization and mixing for triplet, pentad, and coaxial injectors is described. Injectors that are applicable for LOX/hydrocarbon propellants and main chamber and fuel rich preburner/gas generator mixture ratios are of special interest. Various applicable correlating equations and parameters as well as test data found in the literature are presented. The validity, utility, and important aspects of these data and correlations are discussed and the measurement techniques used are evaluated. Propellant mixing tests performed are described and summarized, results are reported, and tentative conclusions are included
Atomization and Mixing Study
The primary objective was the obtainment of atomization and mixing performance data for a variety of typical liquid oxygen/hydrocarbon injector element designs. Such data are required to establish injector design criteria and to provide critical inputs to liquid rocket engine combustor performance and stability analysis, and computational codes and methods. Deficiencies and problems with the atomization test equipment were identified, and action initiated to resolve them. Test results of the gas/liquid mixing tests indicated that an assessment of test methods was required. A series of 71 liquid/liquid tests were performed
Detailed Phase Transition Study at M_H <= 70 GeV in a 3-dimensional --Higgs Model
We study the electroweak phase transition in an effective 3-dimensional
theory for a Higgs mass of about 70 GeV by Monte Carlo simulations. The
transition temperature and jumps of order parameters are obtained and
extrapolated to the continuum using multi-histogram techniques and finite size
analysis.Comment: Talk presented at LATTICE96(electroweak), 4 pages, 5 figure
Multiple Histogram Method for Quantum Monte Carlo
An extension to the multiple-histogram method (sometimes referred to as the
Ferrenberg-Swendsen method) for use in quantum Monte Carlo simulations is
presented. This method is shown to work well for the 2D repulsive Hubbard
model, allowing measurements to be taken over a continuous region of
parameters. The method also reduces the error bars over the range of parameter
values due the overlapping of multiple histograms. A continuous sweep of
parameters and reduced error bars allow one to make more difficult
measurements, such as Maxwell constructions used to study phase separation.
Possibilities also exist for this method to be used for other quantum systems.Comment: 4 pages, 5 figures, RevTeX, submitted to Phys. Rev. B Rapid Com
Spin and Gauge Systems on Spherical Lattices
We present results for 2D and 4D systems on lattices with topology homotopic
to the surface of a (hyper) sphere or . Finite size scaling is
studied in situations with phase transitions of first and second order type.
The Ising and Potts models exhibit the expected behaviour; for the 4D pure
gauge theory we find consistent scaling indicative of a second order
phase transition with critical exponent .Comment: 4 pages, LaTeX, 3 POSTSCRIPT figures (uuencoded
Dynamical-parameter algorithm for U(1) gauge theory
We present an algorithm for Monte Carlo simulations which is able to overcome
the suppression of transitions between the phases in compact U(1) lattice gauge
theory in 4 dimensions.Comment: 6 pages, 2 figures, uuencoded postscript file. Contribution to
LATTICE 9
Magnetic Phase Diagram of the Ferromagnetically Stacked Triangular XY Antiferromagnet: A Finite-Size Scaling Study
Histogram Monte-Carlo simulation results are presented for the magnetic-field
-- temperature phase diagram of the XY model on a stacked triangular lattice
with antiferromagnetic intraplane and ferromagnetic interplane interactions.
Finite-size scaling results at the various transition boundaries are consistent
with expectations based on symmetry arguments. Although a molecular-field
treatment of the Hamiltonian fails to reproduce the correct structure for the
phase diagram, it is demonstrated that a phenomenological Landau-type
free-energy model contains all the esstential features. These results serve to
complement and extend our earlier work [Phys. Rev. B {\bf 48}, 3840 (1993)].Comment: 5 pages (RevTex 3.0), 6 figures available upon request, CRPS 93-
Site Percolation and Phase Transitions in Two Dimensions
The properties of the pure-site clusters of spin models, i.e. the clusters
which are obtained by joining nearest-neighbour spins of the same sign, are
here investigated. In the Ising model in two dimensions it is known that such
clusters undergo a percolation transition exactly at the critical point. We
show that this result is valid for a wide class of bidimensional systems
undergoing a continuous magnetization transition. We provide numerical evidence
for discrete as well as for continuous spin models, including SU(N) lattice
gauge theories. The critical percolation exponents do not coincide with the
ones of the thermal transition, but they are the same for models belonging to
the same universality class.Comment: 8 pages, 6 figures, 2 tables. Numerical part developed; figures,
references and comments adde
Magnetic Phase Diagram of the Ferromagnetically Stacked Triangular Ising Antiferromagnet
Histogram Monte-Carlo simulation results are presented for the magnetic-field
-- temperature phase diagram of the Ising model on a stacked triangular lattice
with antiferromagnetic intraplane and ferromagnetic interplane interactions.
Finite-size scaling results for this frustrated system at three points along
the paramagnetic transition boundary are presented which strongly suggest a
line of triciritcal points at low field and a first-order transition line at
higher fields. These results are compared with the corresponding phase diagrams
from conventional mean-field theory as well as from the Monte Carlo mean-field
calculations of Netz and Berker [Phys. Rev. Lett. {\bf 66}, 377 (1991)].Comment: 6 pages (RevTex 3.0), 8 figures available upon reques
Spectral Density Study of the SU(3) Deconfining Phase Transition
We present spectral density reweighting techniques adapted to the analysis of
a time series of data with a continuous range of allowed values. In a first
application we analyze action and Polyakov line data from a Monte Carlo
simulation on lattices for the SU(3) deconfining phase
transition. We calculate partition function zeros, as well as maxima of the
specific heat and of the order parameter susceptibility. Details and warnings
are given concerning i) autocorrelations in computer time and ii) a reliable
extraction of partition function zeros. The finite size scaling analysis of
these data leads to precise results for the critical couplings , for
the critical exponent and for the latent heat . In both
cases ( and 4), the first order nature of the transition is
substantiated
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