3,405 research outputs found
Design and Use of a Large-Scale Liquid Helium Conversion System
A large-scale liquid helium (LHe) to high-pressure (HP) gas conversion system has been implemented at the John F. Kennedy Space Center (KSC). Helium is used by the Space Shuttle, Titan, Atlas, and Delta programs for prelaunch processing, during launch count-down, and for postlaunch securing. The first phase of modifications to the Compressor Converter Facility (CCF), operational in April 1998, allowed the facility to accept bulk liquid helium from tanker containers and to off-load the helium at super-critical pressures. The second phase of modifications, planned to be operational by January 2001, will implement a 227-cubic-meter (m(sup 3)) on-site liquid helium storage system. This paper describes the design and operation of the current system and discusses the design and implementation for the second phase system
The fear of bad smell: Health risk awareness related to using waste in agricultural production in Vietnam
Waste watersWater reuseAgricultural productionFish farmingIrrigation waterPublic healthRisksSkin diseasesOrganic fertilizersWomen
Directed network modules
A search technique locating network modules, i.e., internally densely
connected groups of nodes in directed networks is introduced by extending the
Clique Percolation Method originally proposed for undirected networks. After
giving a suitable definition for directed modules we investigate their
percolation transition in the Erdos-Renyi graph both analytically and
numerically. We also analyse four real-world directed networks, including
Google's own webpages, an email network, a word association graph and the
transcriptional regulatory network of the yeast Saccharomyces cerevisiae. The
obtained directed modules are validated by additional information available for
the nodes. We find that directed modules of real-world graphs inherently
overlap and the investigated networks can be classified into two major groups
in terms of the overlaps between the modules. Accordingly, in the
word-association network and among Google's webpages the overlaps are likely to
contain in-hubs, whereas the modules in the email and transcriptional
regulatory networks tend to overlap via out-hubs.Comment: 21 pages, 10 figures, version 2: added two paragaph
Experimental investigation of the Landau-Pomeranchuk-Migdal effect in low-Z targets
In the CERN NA63 collaboration we have addressed the question of the
potential inadequacy of the commonly used Migdal formulation of the
Landau-Pomeranchuk-Migdal (LPM) effect by measuring the photon emission by 20
and 178 GeV electrons in the range 100 MeV - 4 GeV, in targets of
LowDensityPolyEthylene (LDPE), C, Al, Ti, Fe, Cu, Mo and, as a reference
target, Ta. For each target and energy, a comparison between simulated values
based on the LPM suppression of incoherent bremsstrahlung is shown, taking
multi-photon effects into account. For these targets and energies, we find that
Migdal's theoretical formulation is adequate to a precision of better than
about 5%, irrespective of the target substance.Comment: 8 pages, 13 figure
A direct D-bar reconstruction algorithm for recovering a complex conductivity in 2-D
A direct reconstruction algorithm for complex conductivities in
, where is a bounded, simply connected Lipschitz
domain in , is presented. The framework is based on the
uniqueness proof by Francini [Inverse Problems 20 2000], but equations relating
the Dirichlet-to-Neumann to the scattering transform and the exponentially
growing solutions are not present in that work, and are derived here. The
algorithm constitutes the first D-bar method for the reconstruction of
conductivities and permittivities in two dimensions. Reconstructions of
numerically simulated chest phantoms with discontinuities at the organ
boundaries are included.Comment: This is an author-created, un-copyedited version of an article
accepted for publication in [insert name of journal]. IOP Publishing Ltd is
not responsible for any errors or omissions in this version of the manuscript
or any version derived from it. The Version of Record is available online at
10.1088/0266-5611/28/9/09500
Neutron Resonance Spectroscopy of 106Pd, and 108Pd from 20–2000 eV
Parity nonconserving asymmetries have been measured in p-wave resonances of 106Pd and 108Pd. The data analysis requires knowledge of the neutron resonance parameters. Transmission and capture γ-ray yields were measured for En=20–2000 eV with the time-of-flight method at the Los Alamos Neutron Science Center (LANSCE). A total of 28 resonances in 106Pd and 32 resonances in 108Pd were studied. The resonance parameters for 106Pd are new for all except one resonance. In 108Pd six new resonances were observed and the precision improved for many of the resonance parameters. A Bayesian analysis was used to assign orbital angular momentum for the resonances studied
Experimental investigations of synchrotron radiation at the onset of the quantum regime
The classical description of synchrotron radiation fails at large Lorentz
factors, , for relativistic electrons crossing strong transverse
magnetic fields . In the rest frame of the electron this field is comparable
to the so-called critical field T. For quantum corrections are essential for the description of
synchrotron radiation to conserve energy. With electrons of energies 10-150 GeV
penetrating a germanium single crystal along the axis, we have
experimentally investigated the transition from the regime where classical
synchrotron radiation is an adequate description, to the regime where the
emission drastically changes character; not only in magnitude, but also in
spectral shape. The spectrum can only be described by quantum synchrotron
radiation formulas. Apart from being a test of strong-field quantum
electrodynamics, the experimental results are also relevant for the design of
future linear colliders where beamstrahlung - a closely related process - may
limit the achievable luminosity.Comment: 11 pages, 18 figures, submitted to PR
Parity Nonconservation in 106Pd and 108Pd Neutron Resonances
Parity nonconservation (PNC) has been studied in the neutron p-wave resonances of 106Pd and 108Pd in the energy range of 20 to 2000 eV. Longitudinal asymmetries in p-wave capture cross sections are measured using longitudinally polarized neutrons incident on ∼20-g metal-powder targets at LANSCE. A CsI γ-ray detector array measures capture cross section asymmetries as a function of neutron energy which is determined by the neutron time-of-flight method. A total of 21 p-wave resonances in 106Pd and 21 p-wave resonances in 108Pd were studied. One statistically significant PNC effect was observed in106Pd, and no effects were observed in 108Pd. For 106Pd a weak spreading width of Γw=34-28+47×10-7 eV was obtained. For 108Pd an upper limit on the weak spreading width of Γw\u3c12×10-7 eV was determined at the 68% confidence level
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