627 research outputs found
Investigation of warm fog properties and fog modification concepts Annual summary report
Ground based and aerial seeding of warm fog with hygroscopic materials and computer modeling of fog response to seedin
Project Fog Drops 5. Task 1: A numerical model of advection fog. Task 2: Recommendations for simplified individual zero-gravity cloud physics experiments
A two-dimensional numerical model was used to investigate the formation of marine advection fog. The model predicts the evolution of potential temperature, horizontal wind, water vapor content, and liquid water content in a vertical cross section of the atmosphere as determined by vertical turbulent transfer and horizontal advection, as well as radiative cooling and drop sedimentation. The model is designed to simulate the formation, development, or dissipation of advection fog in response to transfer of heat and moisture between the atmosphere and the surface as driven by advection over horizontal discontinuities in the surface temperature. Results from numerical simulations of advection fog formation are discussed with reference to observations of marine fog. A survey of candidate fog or cloud microphysics experiments which might be performed in the low gravity environment of a shuttle-type spacecraft in presented. Recommendations are given for relatively simple experiments which are relevent to fog modification problems
Investigation of warm fog properties and fog modification concepts
Warm fog seeding to determine potential of various sized and unsized hygroscopic chemicals for fog dissipatio
Globular Cluster Systems in Brightest Cluster Galaxies. III: Beyond Bimodality
We present new deep photometry of the rich globular cluster (GC) systems
around the Brightest Cluster Galaxies UGC 9799 (Abell 2052) and UGC 10143
(Abell 2147), obtained with the HST ACS and WFC3 cameras. For comparison, we
also present new reductions of similar HST/ACS data for the Coma supergiants
NGC 4874 and 4889. All four of these galaxies have huge cluster populations (to
the radial limits of our data, comprising from 12000 to 23000 clusters per
galaxy). The metallicity distribution functions (MDFs) of the GCs can still be
matched by a bimodal-Gaussian form where the metal-rich and metal-poor modes
are separated by ~0.8 dex, but the internal dispersions of each mode are so
large that the total MDF becomes very broad and nearly continuous from [Fe/H] =
-2.4 to Solar. There are, however, significant differences between galaxies in
the relative numbers of \emph{metal-rich} clusters, suggesting that they
underwent significantly different histories of mergers with massive, gas-rich
halos. Lastly, the proportion of metal-poor GCs rises especially rapidly
outside projected radii R > 4 R_eff, suggesting the importance of accreted
dwarf satellites in the outer halo. Comprehensive models for the formation of
GCs as part of the hierarchical formation of their parent galaxies will be
needed to trace the systematic change in structure of the MDF with galaxy mass,
from the distinctly bimodal form in smaller galaxies up to the broad continuum
that we see in the very largest systems.Comment: In press for Astrophysical Journa
axial form factor from bubble chamber experiments
A careful reanalysis of both Argonne National Laboratory and Brookhaven
National Laboratory data for weak single pion production is done. We consider
deuteron nuclear effects and normalization (flux) uncertainties in both
experiments. We demonstrate that these two sets of data are in good agreement.
For the dipole parametrization of , we obtain , GeV. As an application we present the discussion of
the uncertainty of the neutral current 1 production cross section,
important for the T2K neutrino oscillation experiment.Comment: 16 pages, 8 figures, 2 table
Recommended from our members
Long-range transport of pollutants in the Pacific Northwest
Air quality impacts associated with future utility and industrial siting as defined by the business as usual scenario have been analyzed. This analysis is based on assumptions regarding emission rates, implementation of Best Available Current Technology (BACT), siting data generated by the ORNL regional studies program, and a regional scale transport, transformation, and removal model for SO/sub 2/, sulfates, and particulates. Results of this assessment show that industrial siting in the Portland-Seattle area may be constrained due to regulations for Prevention of Significant Deterioration (PSD) in terms of both incremental SO/sub 2/ and particulate concentrations at sites near Class I areas. Topography influences the concentration patterns of the pollutants. Generally, these patterns reflect the wind flow characteristics but are modified by dry deposition processes. Maximum predicted ground-level concentrations of SO/sub 2/, sulfate, and particulates occur with 63 km of the source. Over 80% of the sulfur emissions in the Pacific Northwest US will ultimately be deposited within the region. The percentage deposited for industrial sources is slightly higher than utility sources due to the lower effective release height
Statistical Mechanics of the Quantum K-Satisfiability problem
We study the quantum version of the random -Satisfiability problem in the
presence of the external magnetic field applied in the transverse
direction. We derive the replica-symmetric free energy functional within static
approximation and the saddle-point equation for the order parameter: the
distribution of functions of magnetizations. The order parameter is
interpreted as the histogram of probability distributions of individual
magnetizations. In the limit of zero temperature and small transverse fields,
to leading order in magnetizations become relevant in
addition to purely classical values of . Self-consistency
equations for the order parameter are solved numerically using Quasi Monte
Carlo method for K=3. It is shown that for an arbitrarily small
quantum fluctuations destroy the phase transition present in the classical
limit , replacing it with a smooth crossover transition. The
implications of this result with respect to the expected performance of quantum
optimization algorithms via adiabatic evolution are discussed. The
replica-symmetric solution of the classical random -Satisfiability problem
is briefly revisited. It is shown that the phase transition at T=0 predicted by
the replica-symmetric theory is of continuous type with atypical critical
exponents.Comment: 35 pages, 23 figures; changed abstract, improved discussion in the
introduction, added references, corrected typo
A New Technique for Finding Needles in Haystacks: A Geometric Approach to Distinguishing Between a New Source and Random Fluctuations
We propose a new test statistic based on a score process for determining the
statistical significance of a putative signal that may be a small perturbation
to a noisy experimental background. We derive the reference distribution for
this score test statistic; it has an elegant geometrical interpretation as well
as broad applicability. We illustrate the technique in the context of a model
problem from high-energy particle physics. Monte Carlo experimental results
confirm that the score test results in a significantly improved rate of signal
detection.Comment: 5 pages, 4 figure
Direct CP violation for decay in QCD factorization
In the framework of QCD factorization, based on the first order of isospin
violation, we study direct CP violation in the decay of including the effect of
mixing. We find that the CP violating asymmetry is large via
mixing mechanism when the invariant mass of the
pair is in the vicinity of the resonance. For the decay of
, the maximum
CP violating asymmetries can reach about 46%. We also discuss the possibility
to observe the predicted CP violating asymmetries at the LHC
Likelihood scan of the Super-Kamiokande I time series data
In this work a detailed spectral analysis of the time series of the 8B solar
neutrino flux published by the Super-Kamiokande Collaboration is presented,
performed through a likelihood scan approach. Preliminarily a careful review of
the analysis methodology is given, showing that the traditional periodicity
search via the Lomb-Scargle periodogram is a special case of a more general
likelihood based method. Since the data are published together with the
relevant asymmetric errors, it is then shown how the likelihood analysis can be
performed either with or without a prior error averaging. A key point of this
work is the detailed illustration of the mathematical model describing the
statistical properties of the estimated spectra obtained in the various cases,
which is also validated through extensive Monte Carlo computations; the model
includes a calculation for the prediction of the possible alias effects. In the
successive investigation of the data, such a model is used to derive objective,
mathematical predictions which are quantitatively compared with the features
observed in the experimental spectra. This article clearly demonstrates that
the handling of the errors is the origin of the discrepancy between published
null observations and claimed significant periodicity in the same SK-I data
sample. Moreover, the comprehensive likelihood analysis with asymmetric errors
developed in this work provides results which cannot exclude the null
hypothesis of constant rate, even though some indications stemming from the
model at odd with such conclusion point towards the desirability of additional
investigations with alternative methods to shed further light on the
characteristics of the data.Comment: 49 pages, 38 figures. Calculation of the asymmetric likelihood
revised. Accepted fo publication on Physical Review
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