7,603 research outputs found
Building a prosperous future in which agriculture uses and produces energy efficiently and effectively
Our new challenge, opportunity, and responsibility, is energy. The USDA is determined to apply the talent and technology of agriculture to bioenergy, and others should make a point of directing their energies to support this. The road forward toward our energy future is Science and Education. This is how we can move beyond a petroleum economy to make oil dependence a thing of the past, and safeguard our environment for future generations. The USDA has started the process of getting researchers together for a large, long-term cooperative effort. We all must take actions to make sure lab results get moved toward the market, with technology transfer partnerships with industry or university spin-off startup
The Roots of Beowulf
The first Beowulf Linux commodity cluster was constructed at NASA's Goddard Space Flight Center in 1994 and its origins are a part of the folklore of high-end computing. In fact, the conditions within Goddard that brought the idea into being were shaped by rich historical roots, strategic pressures brought on by the ramp up of the Federal High-Performance Computing and Communications Program, growth of the open software movement, microprocessor performance trends, and the vision of key technologists. This multifaceted story is told here for the first time from the point of view of NASA project management
Report from the MPP Working Group to the NASA Associate Administrator for Space Science and Applications
NASA's Office of Space Science and Applications (OSSA) gave a select group of scientists the opportunity to test and implement their computational algorithms on the Massively Parallel Processor (MPP) located at Goddard Space Flight Center, beginning in late 1985. One year later, the Working Group presented its report, which addressed the following: algorithms, programming languages, architecture, programming environments, the way theory relates, and performance measured. The findings point to a number of demonstrated computational techniques for which the MPP architecture is ideally suited. For example, besides executing much faster on the MPP than on conventional computers, systolic VLSI simulation (where distances are short), lattice simulation, neural network simulation, and image problems were found to be easier to program on the MPP's architecture than on a CYBER 205 or even a VAX. The report also makes technical recommendations covering all aspects of MPP use, and recommendations concerning the future of the MPP and machines based on similar architectures, expansion of the Working Group, and study of the role of future parallel processors for space station, EOS, and the Great Observatories era
Generating methane gas from manure (1979)
At first glance, the idea of generating methane gas has considerable merit because it appears to offer at least a partial solution to two pressing problems -- the environmental crisis and the energy shortage. Unfortunately, present-day large-scale methane generation requires rather high investments in money and management which considerably reduce the practicality of the idea for the farmer. This Guide is intended to provide quantitative information so that the feasibility of methane generation can be evaluated for a given situation.Reprinted 5/79/8M
Higher-dimensional Algebra and Topological Quantum Field Theory
The study of topological quantum field theories increasingly relies upon
concepts from higher-dimensional algebra such as n-categories and n-vector
spaces. We review progress towards a definition of n-category suited for this
purpose, and outline a program in which n-dimensional TQFTs are to be described
as n-category representations. First we describe a "suspension" operation on
n-categories, and hypothesize that the k-fold suspension of a weak n-category
stabilizes for k >= n+2. We give evidence for this hypothesis and describe its
relation to stable homotopy theory. We then propose a description of
n-dimensional unitary extended TQFTs as weak n-functors from the "free stable
weak n-category with duals on one object" to the n-category of "n-Hilbert
spaces". We conclude by describing n-categorical generalizations of deformation
quantization and the quantum double construction.Comment: 36 pages, LaTeX; this version includes all 36 figure
Crossing the Brown Dwarf Desert Using Adaptive Optics: A Very Close L-Dwarf Companion to the Nearby Solar Analog HR 7672
We have found a very faint companion to the active solar analog HR 7672 (HD
190406; GJ 779; 15 Sge). Three epochs of high resolution imaging using adaptive
optics (AO) at the Gemini-North and Keck II Telescopes demonstrate that HR
7672B is a common proper motion companion, with a separation of 0.79" (14 AU)
and a 2.16 um flux ratio of 8.6 mags. Using follow-up K-band spectroscopy from
Keck AO+NIRSPEC, we measure a spectral type of L4.5+/-1.5. This is the closest
ultracool companion around a main sequence star found to date by direct
imaging. We estimate the primary has an age of 1-3 Gyr. Assuming coevality, the
companion is most likely substellar, with a mass of 55-78 Mjup based on
theoretical models. The primary star shows a long-term radial velocity trend,
and we combine the radial velocity data and AO imaging to set a firm
(model-independent) lower limit of 48 Mjup. In contrast to the paucity of brown
dwarf companions at <~4 AU around FGK dwarfs, HR 7672B implies that brown dwarf
companions do exist at separations comparable to those of the giant planets in
our own solar system. Its presence is at variance with scenarios where brown
dwarfs form as ejected stellar embryos. Moreover, since HR 7672B is likely too
massive to have formed in a circumstellar disk as planets are believed to, its
discovery suggests that a diversity of physical processes act to populate the
outer regions of exoplanetary systems.Comment: Astrophysical Journal, in pres
A New Analysis of the Exoplanet Hosting System HD 6434
The current goal of exoplanetary science is not only focused on detecting but
characterizing planetary systems in hopes of understanding how they formed,
evolved, and relate to the Solar System. The Transit Ephemeris Refinement and
Monitoring Survey (TERMS) combines both radial velocity (RV) and photometric
data in order to achieve unprecedented ground-based precision in the
fundamental properties of nearby, bright, exoplanet-hosting systems. Here we
discuss HD 6434 and its planet, HD 6434b, which has a M_p*sin(i) = 0.44 M_J
mass and orbits every 22.0170 days with an eccentricity of 0.146. We have
combined previously published RV data with new measurements to derive a
predicted transit duration of ~6 hrs, or 0.25 days, and a transit probability
of 4%. Additionally, we have photometrically observed the planetary system
using both the 0.9m and 1.0m telescopes at the Cerro Tololo Inter-American
Observatory, covering 75.4% of the predicted transit window. We reduced the
data using the automated TERMS Photometry Pipeline, developed to ensure
consistent and accurate results. We determine a dispositive null result for the
transit of HD 6434b, excluding the full transit to a depth of 0.9% and grazing
transit due to impact parameter limitations to a depth of 1.6%Comment: 9 pages, 5 figures, 3 tables, accepted to A
Generating methane gas from manure
At first glance, the idea of generating methane gas has considerable merit because it appears to offer at least a partial solution to two pressing problems -- the environmental crisis and the energy shortage. Unfortunately, present-day large-scale methane generation requires rather high investments in money and management, which considerably reduces the idea's practicality. This guide is intended to provide quantitative information so that the feasibility of methane generation can be evaluated for a given situation.Charles D. Fulhage, Dennis Sievers and James R. Fischer (Department of Agricultural Engineering)Reviewed November 2018 -- websit
Swine waste digester at the University of Missouri--Columbia
Title from JPEG cover page (University of Missouri Digital Library, viewed Feb. 19, 2010)."8/78/3M.
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