25,514 research outputs found
Test results and facility description for a 40-kilowatt stirling engine
A 40 kilowatt Stirling engine, its test support facilities, and the experimental procedures used for these tests are described. Operating experience with the engine is discussed, and some initial test results are presente
Initial test results with a single-cylinder rhombic-drive Stirling engine
A 6 kW (8 hp), single-cylinder, rhombic-drive Stirling engine was restored to operating condition, and preliminary characterization tests run with hydrogen and helium as the working gases. Initial tests show the engine brake specific fuel consumption (BSFC) with hydrogen working gas to be within the range of BSFC observed by the Army at Fort Belvoir, Virginia, in 1966. The minimum system specific fuel consumption (SFC) observed during the initial tests with hydrogen was 669 g/kW hr (1.1 lb/hpx hr), compared with 620 g/kWx hr (1.02 lb/hpx hr) for the Army tests. However, the engine output power for a given mean compression-space pressure was lower than for the Army tests. The observed output power at a working-space pressure of 5 MPa (725 psig) was 3.27 kW (4.39 hp) for the initial tests and 3.80 kW (5.09 hp) for the Army tests. As expected, the engine power with helium was substantially lower than with hydrogen
Expanded Very Large Arrays Observations of a Proto-Cluster of Molecular Gas-Rich Galaxies at z = 4.05
We present observations of the molecular gas in the GN20 proto-cluster of galaxies at z = 4.05 using the Expanded Very Large Array (EVLA). This group of galaxies is the ideal laboratory for studying the formation of massive galaxies via luminous, gas-rich starbursts within 1.6 Gyr of the big bang. We detect three galaxies in the proto-cluster in CO 2-1 emission, with gas masses (H_2) between 10^(10) and 10^(11) × (α/0.8) M_⊙. The emission from the brightest source, GN20, is resolved with a size ~2'' and has a clear north-south velocity gradient, possibly indicating ordered rotation. The gas mass in GN20 is comparable to the stellar mass (1.3 × 10^(11) × (α/0.8) M_⊙ and 2.3 × 10^(11) M_⊙, respectively), and the sum of gas plus stellar mass is comparable to the dynamical mass of the system (~3.4 × 10^(11)[sin (i)/sin (45°)]^(–2) M_⊙), within a 5 kpc radius. There is also evidence for a tidal tail extending another 2'' north of the galaxy with a narrow velocity dispersion. GN20 may be a massive, gas-rich disk that is gravitationally disturbed, but not completely disrupted. There is one Lyman-break galaxy (BD29079) in the GN20 proto-cluster with an optical spectroscopic redshift within our search volume, and we set a 3σ limit to the molecular gas mass of this galaxy of 1.1 × 10^(10) × (α/0.8) M_⊙
Intersection of ecosystem and biodiversity concerns in the management of rangelands
Maintenance of ecological functions and disturbance regimes within ecosystems is as important as preserving species populations or their genetic structure, biotic communities, and landscapes. There is considerable dispute as to how species diversity influences productivity and stability of various ecosystem structural and dynamic attributes. Some view each and every species as making an incremental contribution to these features. Others assume that some redundancy exists. Addition or loss of species can be anecdotally shown to influence ecosystems in proportion to the role such organisms. Subtle but essential interactions are easy to overlook, however. We should try to keep all the parts until more definitive research is available on this topic. Sustainable development will require balancing resource use with maintenance of our natural legacies. Ecosystem perspectives must contribute to decisions on where the balance exists
The Harmful Addiction to the War on Drugs
Most modern societies prohibit the use of addictive drugs such as cocaine and heroin. We contend this is a mistake. They should all be legalized, forthwith, since their usage constitutes a victimless crime. But more, we also maintain that these jurisdictions are actually addicted to these unjust and harmful laws since, no matter what the logic or the evidence about the perniciousness of this legislation, it still remains on the book
XMM-Newton and Swift observations of XTE J1743-363
XTEJ1743-363 is a poorly known hard X-ray transient, that displays short and
intense flares similar to those observed from Supergiant Fast X-ray Transients.
The probable optical counterpart shows spectral properties similar to those of
an M8 III giant, thus suggesting that XTEJ1743-363 belongs to the class of the
Symbiotic X-ray Binaries. In this paper we report on the first dedicated
monitoring campaign of the source in the soft X-ray range with XMM-Newton and
Swift/XRT. T hese observations confirmed the association of XTEJ1743-363 with
the previously suggested M8 III giant and the classification of the source as a
member of the Symbiotic X-ray binaries. In the soft X-ray domain, XTEJ1743-363
displays a high absorption (~6x10^22 cm^-2 ) and variability on time scales of
hundreds to few thousand seconds, typical of wind accreting systems. A
relatively faint flare (peak X-ray flux 3x10^-11 erg/cm^2/s) lasting ~4 ks is
recorded during the XMM-Newton observation and interpreted in terms of the wind
accretion scenario.Comment: Accepted for publication on A&
Multi-wavelength observing of a forming solar-like star
V2129 Oph is a 1.35 solar mass classical T Tauri star, known to possess a
strong and complex magnetic field. By extrapolating from an observationally
derived magnetic surface map, obtained through Zeeman-Doppler imaging, models
of V2129 Oph's corona have been constructed, and used to make predictions
regarding the global X-ray emission measure, the amount of modulation of X-ray
emission, and the density of accretion shocks. In late June 2009 we will under
take an ambitious multi-wavelength, multi-observing site, and near
contemporaneous campaign, combining spectroscopic optical, nIR, UV, X-ray,
spectropolarimetric and photometric monitoring. This will allow the validity of
the 3D field topologies derived via field extrapolation to be determined.Comment: 4 pages, proceedings of the 3rd MSSL workshop on High Resolution
X-ray Spectroscopy: towards IX
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