5,367 research outputs found
Sampling and handling of desert soils
Sampling and handling of desert soils - area site, transportation, processing, and storag
A hydrogen energy carrier. Volume 2: Systems analysis
A systems analysis of hydrogen as an energy carrier in the United States indicated that it is feasible to use hydrogen in all energy use areas, except some types of transportation. These use areas are industrial, residential and commercial, and electric power generation. Saturation concept and conservation concept forecasts of future total energy demands were made. Projected costs of producing hydrogen from coal or from nuclear heat combined with thermochemical decomposition of water are in the range 1.50 per million Btu of hydrogen produced. Other methods are estimated to be more costly. The use of hydrogen as a fuel will require the development of large-scale transmission and storage systems. A pipeline system similar to the existing natural gas pipeline system appears practical, if design factors are included to avoid hydrogen environment embrittlement of pipeline metals. Conclusions from the examination of the safety, legal, environmental, economic, political and societal aspects of hydrogen fuel are that a hydrogen energy carrier system would be compatible with American values and the existing energy system
A hydrogen energy carrier. Volume 1: Summary
The production, technology, transportation, and implementation of hydrogen into the energy system are discussed along with the fossil fuel cycle, hydrogen fuel cycle, and the demands for energy. The cost of hydrogen production by coal gasification; electrolysis by nuclear energy, and solar energy are presented. The legal aspects of a hydrogen economy are also discussed
Hysteresis phenomenon in deterministic traffic flows
We study phase transitions of a system of particles on the one-dimensional
integer lattice moving with constant acceleration, with a collision law
respecting slower particles. This simple deterministic ``particle-hopping''
traffic flow model being a straightforward generalization to the well known
Nagel-Schreckenberg model covers also a more recent slow-to-start model as a
special case. The model has two distinct ergodic (unmixed) phases with two
critical values. When traffic density is below the lowest critical value, the
steady state of the model corresponds to the ``free-flowing'' (or ``gaseous'')
phase. When the density exceeds the second critical value the model produces
large, persistent, well-defined traffic jams, which correspond to the
``jammed'' (or ``liquid'') phase. Between the two critical values each of these
phases may take place, which can be interpreted as an ``overcooled gas'' phase
when a small perturbation can change drastically gas into liquid. Mathematical
analysis is accomplished in part by the exact derivation of the life-time of
individual traffic jams for a given configuration of particles.Comment: 22 pages, 6 figures, corrected and improved version, to appear in the
Journal of Statistical Physic
Preparation and properties of amorphous MgB/MgO superstructures: A new model disordered superconductor
In this paper we introduce a novel method for fabricating MgB/MgO
multilayers and demonstrate the potential for using them as a new model for
disordered superconductors. In this approach we control the annealing of the
MgB to yield an interesting new class of disordered (amorphous)
superconductors with relatively high transition temperatures. The multilayers
appear to exhibit quasi-two-dimensional superconductivity with controlled
anisotropy. We discuss the properties of the multilayers as the thickness of
the components of the bilayers vary.Comment: 7 pages, 8 figure
Primary radiotherapy in progressive optic nerve sheath meningiomas: a long-term follow-up study
Background/aims: To report the outcome of primary radiotherapy in patients with progressive optic nerve sheath meningioma (ONSM). Methods: The clinical records of all patients were reviewed in a retrospective, observational, multicentre study. Results: Thirty-four consecutive patients were included. Twenty-six women and eight men received conventional or stereotactic fractionated radiotherapy, and were followed for a median 58 (range 51–156) months. Fourteen eyes (41%) showed improved visual acuity of at least two lines on the Snellen chart. In 17 (50%) eyes, the vision stabilised, while deterioration was noted in three eyes (9%). The visual outcome was not associated with age at the time of radiotherapy (p=0.83), sex (p=0.43), visual acuity at the time of presentation (p=0.22) or type of radiotherapy (p=0.35). Optic disc swelling was associated with improved visual acuity (p<0.01) and 4/11 patients with optic atrophy also showed improvement. Long-term complications were dry eyes in five patients, cataracts in three, and mild radiation retinopathy in four. Conclusion: Primary radiotherapy for patients with ONSM is associated with long-term improvement of visual acuity and few adverse effects.Peerooz Saeed, Leo Blank, Dinesh Selva, John G. Wolbers, Peter J.C.M. Nowak, Ronald B. Geskus, Ezekiel Weis, Maarten P. Mourits, Jack Rootma
Blue Dots Team Transits Working Group Review
Transiting planet systems offer an unique opportunity to observationally
constrain proposed models of the interiors (radius, composition) and
atmospheres (chemistry, dynamics) of extrasolar planets. The spectacular
successes of ground-based transit surveys (more than 60 transiting systems
known to-date) and the host of multi-wavelength, spectro-photometric follow-up
studies, carried out in particular by HST and Spitzer, have paved the way to
the next generation of transit search projects, which are currently ongoing
(CoRoT, Kepler), or planned. The possibility of detecting and characterizing
transiting Earth-sized planets in the habitable zone of their parent stars
appears tantalizingly close. In this contribution we briefly review the power
of the transit technique for characterization of extrasolar planets, summarize
the state of the art of both ground-based and space-borne transit search
programs, and illustrate how the science of planetary transits fits within the
Blue Dots perspective.Comment: 9 pages, 3 figures, to be published in the proceedings (ASP Conf.
Ser.) of the "Pathways Towards Habitable Planets" conference, held in
Barcelona (14-18 Sep 2009
Critical thickness and orbital ordering in ultrathin La0.7Sr0.3MnO3 films
Detailed analysis of transport, magnetism and x-ray absorption spectroscopy
measurements on ultrathin La0.7Sr0.3MnO3 films with thicknesses from 3 to 70
unit cells resulted in the identification of a lower critical thickness for a
non-metallic, non-ferromagnetic layer at the interface with the SrTiO3 (001)
substrate of only 3 unit cells (~12 Angstrom). Furthermore, linear dichroism
measurements demonstrate the presence of a preferred (x2-y2) in-plane orbital
ordering for all layer thicknesses without any orbital reconstruction at the
interface. A crucial requirement for the accurate study of these ultrathin
films is a controlled growth process, offering the coexistence of
layer-by-layer growth and bulk-like magnetic/transport properties.Comment: 22 pages, 6 figures, accepted for publication in Physical Review
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