1,051 research outputs found
Space storable thrustor investigation Final report
Design and performance of space storable liquid FLOX methane thrustor of refractory composite material
Wide range operation of advanced low NOx combustors for supersonic high-altitude aircraft gas turbines
An initial rig program tested the Jet Induced Circulation (JIC) and Vortex Air Blast (VAB) systems in small can combustor configurations for NOx emissions at a simulated high altitude, supersonic cruise condition. The VAB combustor demonstrated the capability of meeting the NOx goal of 1.0 g NO2/kg fuel at the cruise condition. In addition, the program served to demonstrate the limited low-emissions range available from the lean, premixed combustor. A follow-on effort was concerned with the problem of operating these lean, premixed combustors with acceptable emissions at simulated engine idle conditions. Various techniques have been demonstrated that allow satisfactory operation on both the JIC and VAB combustors at idle with CO emissions below 20 g/kg fuel. The VAB combustor was limited by flashback/autoignition phenomena at the cruise conditions to a pressure of 8 atmospheres. The JIC combustor was operated up to the full design cruise pressure of 14 atmospheres without encountering an autoignition limitation although the NOx levels, in the 2-3 g NO2/kg fuel range, exceeded the program goal
Is M82 X-1 Really An Intermediate-Mass Black Hole? X-ray Spectral and Timing Evidence
Ultra-luminous X-ray sources (ULXs) with apparent luminosities up to 100's of
times the Eddington luminosity for a neutron star have been discovered in
external galaxies. The existence of intermediate mass black holes has been
proposed to explain these sources. We present evidence for an intermediate-mass
black hole in the ULX M82 X-1 based on the spectral features and timing (QPO)
properties of the X-radiation from this source. We revisited XMM Newton and
RXTE data for M82 X-1 obtained in 2001 and 1997 for XMM and RXTE respectively.
We show for these observations that the source is either in transition or in a
high/soft state with photon spectral indices 2.1 and 2.7 respectively. We
confirm the early determination of the QPO frequency ~ 55 mHz in this source by
Strohmayer & Mushotzky and identify this as the low frequency QPO for the
source. We apply a new method to determine the BH mass of M82 X-1. The method
uses the index-QPO low frequency correlation that has been recently been
established in galactic black hole candidates GRS 1915+105, XTE J1550-564, 4U
1630-47 and others. Using scaling arguments and the correlation derived from
consideration of galactic BHs, we conclude that M82 X-1 is an intermediate BH
with a mass of the order of 1000 solar masses.Comment: 7 pages and 3 figures. Accepted for publication in ApJ Letters,
v.614, 2004, October 2
Interference of diffraction and transition radiation and its application as a beam divergence diagnostic
We have observed the interference of optical diffraction radiation (ODR) and
optical transition radiation (OTR) produced by the interaction of a
relativistic electron beam with a micromesh foil and a mirror. The production
of forward directed ODR from electrons passing through the holes and wires of
the mesh and their separate interactions with backward OTR from the mirror are
analyzed with the help of a simulation code. By careful choice of the micromesh
properties, mesh-mirror spacing, observation wavelength and filter band pass,
the interference of the ODR produced from the unperturbed electrons passing
through the open spaces of the mesh and OTR from the mirror are observable
above a broad incoherent background from interaction of the heavily scattered
electrons passing through the mesh wires. These interferences (ODTRI) are
sensitive to the beam divergence and can be used to directly diagnose this
parameter. We compare experimental divergence values obtained using ODTRI,
conventional OTRI, for the case when front foil scattering is negligible, and
computed values obtained from transport code calculations and multiple screen
beam size measurements. We obtain good agreement in all cases.Comment: 40 pages 18 Figures. accepted for publication in PRSTA
When Lights Are Low
https://digitalcommons.library.umaine.edu/mmb-vp/2497/thumbnail.jp
Cephalopod Brains: An Overview of Current Knowledge to Facilitate Comparison With Vertebrates.
Cephalopod and vertebrate neural-systems are often highlighted as a traditional example of convergent evolution. Their large brains, relative to body size, and complexity of sensory-motor systems and behavioral repertoires offer opportunities for comparative analysis. Despite various attempts, questions on how cephalopod 'brains' evolved and to what extent it is possible to identify a vertebrate-equivalence, assuming it exists, remain unanswered. Here, we summarize recent molecular, anatomical and developmental data to explore certain features in the neural organization of cephalopods and vertebrates to investigate to what extent an evolutionary convergence is likely. Furthermore, and based on whole body and brain axes as defined in early-stage embryos using the expression patterns of homeodomain-containing transcription factors and axonal tractography, we describe a critical analysis of cephalopod neural systems showing similarities to the cerebral cortex, thalamus, basal ganglia, midbrain, cerebellum, hypothalamus, brain stem, and spinal cord of vertebrates. Our overall aim is to promote and facilitate further, hypothesis-driven, studies of cephalopod neural systems evolution
Multi-component measurements of the Jefferson Lab energy recovery linac electron beam using optical transition and diffraction radiation
High brightness electron accelerators, such as energy recovery linacs (ERL),
often have complex particle distributions that can create difficulties in beam
transport as well as matching to devices such as wigglers used to generate
radiation from the beam. Optical transition radiation (OTR), OTR interferometry
(OTRI) and optical diffraction-transition radiation interferometry (ODTRI) have
proven to be effective tools for diagnosing both the spatial and angular
distributions of charged particle beams. OTRI and ODTRI have been used to
measure rms divergences and optical transverse phase space mapping has been
demonstrated using OTRI. In this work we present the results of diagnostic
experiments using OTR and ODR conducted at the Jefferson Laboratory 115 MeV ERL
which show the presence of two separate components within the spatial and
angular distributions of the beam. By assuming a correlation between the
spatial and angular features we estimate an rms emittance value for each of the
two components.Comment: 25 pages, 10 figures; accepted for publication in PRSTAB; minor
formatting errors correcte
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