1,124 research outputs found
William A. Wheeler Correspondence
Entries include a typed letter from the Maine State Library introducing Wheeler to the Maine Author Collection, a typed letter from Wheeler on personal stationery presenting his books Ma Sez and Brunswick Yesterdays, and a typed letter from the Maine State Library on receipt of these books for the Maine Author Collection with notice that his historical book about the Maine Central Railroad was already in the lending collection and a typed note concerning an article (missing from this file) appearing in the Portland Evening Express
Revealing Relationships among Relevant Climate Variables with Information Theory
A primary objective of the NASA Earth-Sun Exploration Technology Office is to
understand the observed Earth climate variability, thus enabling the
determination and prediction of the climate's response to both natural and
human-induced forcing. We are currently developing a suite of computational
tools that will allow researchers to calculate, from data, a variety of
information-theoretic quantities such as mutual information, which can be used
to identify relationships among climate variables, and transfer entropy, which
indicates the possibility of causal interactions. Our tools estimate these
quantities along with their associated error bars, the latter of which is
critical for describing the degree of uncertainty in the estimates. This work
is based upon optimal binning techniques that we have developed for
piecewise-constant, histogram-style models of the underlying density functions.
Two useful side benefits have already been discovered. The first allows a
researcher to determine whether there exist sufficient data to estimate the
underlying probability density. The second permits one to determine an
acceptable degree of round-off when compressing data for efficient transfer and
storage. We also demonstrate how mutual information and transfer entropy can be
applied so as to allow researchers not only to identify relations among climate
variables, but also to characterize and quantify their possible causal
interactions.Comment: 14 pages, 5 figures, Proceedings of the Earth-Sun System Technology
Conference (ESTC 2005), Adelphi, M
Ensemble variational Monte Carlo for optimization of correlated excited state wave functions
Variational Monte Carlo methods have recently been applied to the calculation
of excited states; however, it is still an open question what objective
function is most effective. A promising approach is to optimize excited states
using a penalty to minimize overlap with lower eigenstates, which has the
drawback that states must be computed one at a time. We derive a general
framework for constructing objective functions with minima at the the lowest
eigenstates of a many-body Hamiltonian. The objective function uses a
weighted average of the energies and an overlap penalty, which must satisfy
several conditions. We show this objective function has a minimum at the exact
eigenstates for a finite penalty, and provide a few strategies to minimize the
objective function. The method is demonstrated using ab initio variational
Monte Carlo to calculate the degenerate first excited state of a CO molecule.Comment: 7 pages, 4 figure
Modeling Reactive Wetting when Inertial Effects are Dominant
Recent experimental studies of molten metal droplets wetting high temperature
reactive substrates have established that the majority of triple-line motion
occurs when inertial effects are dominant. In light of these studies, this
paper investigates wetting and spreading on reactive substrates when inertial
effects are dominant using a thermodynamically derived, diffuse interface model
of a binary, three-phase material. The liquid-vapor transition is modeled using
a van der Waals diffuse interface approach, while the solid-fluid transition is
modeled using a phase field approach. The results from the simulations
demonstrate an O \left( t^{-\nicefrac{1}{2}} \right) spreading rate during
the inertial regime and oscillations in the triple-line position when the metal
droplet transitions from inertial to diffusive spreading. It is found that the
spreading extent is reduced by enhancing dissolution by manipulating the
initial liquid composition. The results from the model exhibit good qualitative
and quantitative agreement with a number of recent experimental studies of
high-temperature droplet spreading, particularly experiments of copper droplets
spreading on silicon substrates. Analysis of the numerical data from the model
suggests that the extent and rate of spreading is regulated by the spreading
coefficient calculated from a force balance based on a plausible definition of
the instantaneous interface energies. A number of contemporary publications
have discussed the likely dissipation mechanism in spreading droplets. Thus, we
examine the dissipation mechanism using the entropy-production field and
determine that dissipation primarily occurs in the locality of the triple-line
region during the inertial stage, but extends along the solid-liquid interface
region during the diffusive stage
Directions of zero thermal expansion in anisotropic oxides
Figure 13. – Quadric surface visualizing the coefficients of thermal expansion of HfTiO4 at room temperature. Blue is positive, red is negative and yellow represents directions of zero thermal expansion.
Oxide materials often have anisotropic crystal structures, which can result in direction-dependent material properties. While they typically have positive coefficients of thermal expansion, it has been observed that some oxide materials can have directions of negative thermal expansion over certain temperature ranges. Such materials, having both positive and negative coefficients of thermal expansion, must also have particular directions in which the thermal expansion is zero. Using the Quadrupole Lamp Furnace (QLF) developed in the Kriven group at the University of Illinois at Urbana Champaign, high-temperature in-situ x-ray diffraction has been performed at the National Synchrotron Light Source II (NSLS II) X-ray powder diffraction beamline (XPD – 28-ID) to track directions of zero thermal expansion in orthorhombic HfTiO4. These results have important implications for the design of composites for high-temperature applications.
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BOSS-LDG: A Novel Computational Framework that Brings Together Blue Waters, Open Science Grid, Shifter and the LIGO Data Grid to Accelerate Gravitational Wave Discovery
We present a novel computational framework that connects Blue Waters, the
NSF-supported, leadership-class supercomputer operated by NCSA, to the Laser
Interferometer Gravitational-Wave Observatory (LIGO) Data Grid via Open Science
Grid technology. To enable this computational infrastructure, we configured,
for the first time, a LIGO Data Grid Tier-1 Center that can submit
heterogeneous LIGO workflows using Open Science Grid facilities. In order to
enable a seamless connection between the LIGO Data Grid and Blue Waters via
Open Science Grid, we utilize Shifter to containerize LIGO's workflow software.
This work represents the first time Open Science Grid, Shifter, and Blue Waters
are unified to tackle a scientific problem and, in particular, it is the first
time a framework of this nature is used in the context of large scale
gravitational wave data analysis. This new framework has been used in the last
several weeks of LIGO's second discovery campaign to run the most
computationally demanding gravitational wave search workflows on Blue Waters,
and accelerate discovery in the emergent field of gravitational wave
astrophysics. We discuss the implications of this novel framework for a wider
ecosystem of Higher Performance Computing users.Comment: 10 pages, 10 figures. Accepted as a Full Research Paper to the 13th
IEEE International Conference on eScienc
Leeches (Annelida: Hirudinida) of Northern Arkansas
Twenty-one lotic and lentic environments throughout central and northern Arkansas were surveyed for the presence of leeches during June 2004 and April, July - October 2005. Fourteen species of leeches {Helobdella elongata, Helobdella papillata, Helobdella stagnalis, Placobdella cryptobranchii, Placobdella multilineata, Placobdella ornata, Placobdella papillifera, Placobdella parasitica, Placobdella phaler a, Placobdella picta, Haemopis marmorata, Erpobdella fervida, Erpobdella microstoma, and Erpobdella punctata) representing 3 families were collected. Five species (H. elongata, P. cryptobranchii, P. multilineata, H. marmorata, and E. fervida) are reported from Arkansas for the first time. The natural history of the 22 species of leeches now known from Arkansas is reviewed
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