1,554 research outputs found
JT9D engine diagnostics. Task 2: Feasibility study of measuring in-service flight loads
The feasibility of measuring JT9D propulsion system flight inertia loads on a 747 airplane is studied. Flight loads background is discussed including the current status of 747/JT9D loads knowledge. An instrumentation and test plan is formulated for an airline-owned in-service airplane and the Boeing-owned RA001 test airplane. Technical and cost comparisons are made between these two options. An overall technical feasibility evaluation is made and a cost summary presented. Conclusions and recommendations are presented in regard to using existing inertia loads data versus conducting a flight test to measure inertia loads
"Dark Matter" in Accretion Disks
Using Spitzer Space Telescope photometric observations of the eclipsing,
interacting binary WZ Sge, we have discovered that the accretion disk is far
more complex than previously believed. Our 4.5 and 8 micron time series
observations reveal that the well known gaseous accretion disk is surrounded by
an asymmetric disk of dusty material with a radius approximately 15 times
larger than the gaseous disk. This dust ring contains only a small amount of
mass and is completely invisible at optical and near-IR wavelengths, hence
consisting of "dark matter". We have produced a model dust ring using 1 micron
spherical particles with a density of 3 g/cm and with a temperature profile
ranging from 700-1500K. Our discovery about the accretion disk structure and
the presence of a larger, outer dust ring have great relevance for accretion
disks in general, including those in other interacting binary systems, pre-main
sequence stars, and active galaxies.Comment: 34 pages, 8 figures (3 in color). Accepted to Ap
p_T-fluctuations in high-energy p-p and A-A collisions
The event-by-event p_T-fluctuations in proton-proton and central Pb-Pb
collisions, which have been experimentally studied by means of the so-called
Phi-measure, are analyzed. The contribution due to the correlation which
couples the average p_T to the event multiplicity is computed. The correlation
appears to be far too weak to explain the preliminary experimental value of Phi
(p_T) in p-p interactions. The significance of the result is discussed.Comment: 5 pages, 2 figures, minor improvement
Recent atmospheric neutrino results from Soudan 2
An updated measurement of the atmospheric nu_mu/nu_e ratio-of-ratios,
0.68+-0.11+-0.06, has been obtained using a 4.6-kty exposure of the Soudan-2
iron tracking calorimeter. The L/E distributions have been analyzed for effects
of nu_mu -> nu_x oscillations, and an allowed region in the Delta m^2 vs. sin^2
2 theta plane has been determined.Comment: 3 pages, 4 figures; presented at TAUP99, the 6th Int. Workshop on
Topics in Astroparticle and Underground Physics, Sept. 6-10, 1999, College de
France, Paris, Franc
GALEX and Optical Light Curves of WX LMi, SDSSJ103100.5+202832.2 and SDSSJ121209.31+013627.7
{\it GALEX} near ultraviolet (NUV) and far-ultraviolet (FUV) light curves of
three extremely low accretion rate polars show distinct modulations in their UV
light curves. While these three systems have a range of magnetic fields from 13
to 70 MG, and of late type secondaries (including a likely brown dwarf in
SDSSJ121209.31+013627.7), the accretion rates are similar, and the UV
observations imply some mechanism is operating to create enhanced emission
zones on the white dwarf. The UV variations match in phase to the two magnetic
poles viewed in the optical in WX LMi and to the single poles evident in the
optical in SDSSJ1212109.31+013627.7 and SDSSJ103100.55+202832.2. Simple spot
models of the UV light curves show that if hot spots are responsible for the UV
variations, the temperatures are on the order of 10,000-14,000K. For the single
pole systems, the size of the FUV spot must be smaller than the NUV and in all
cases, the geometry is likely more complicated than a simple circular spot.Comment: 29 pages, 4 tables, 10 figures, Astrophysical Journal, accepte
Opening up the Pandora's box of sustainability league tables of universities: a Kafkaesque perspective
The aim of this paper is to explore the institutional impact of sustainability league tables on current university agendas. It focuses on a narrative critique of one such league table, the UK's ‘Green League Table', compiled and reported by the student campaigning NGO, ‘People & Planet’ annually between 2007 and 2013. Through a Kafkaesque perspective, this paper offers the proposition that such league tables could be acting as an institutional hegemonic mechanism for social legitimacy, through the desire by universities to show that environmental issues are effectively under control. Espoused eco-narratives of the ‘carbon targets imperative’ and ‘engagement' can serve as a form of deception, by merely embracing the narrative as a rhetorical device. Moreover, they can serve the exclusive, particularistic self-interests of a growing legion of ‘carbon managers’, ‘sustainability managers’ and ‘environmental managers' in satisfying the neo-liberal institutional drive from their vice chancellors
Discovery of Halpha satellite emission in a low state of the SW Sextantis star BB Doradus
BB Dor was observed during its low state state in 2009. Signatures of both
binary components are revealed in the average optical spectrum; no signature of
accretion is observed. Narrow emission lines of Halpha, HeI and Na-D, as well
as TiO absorption troughs trace the motion of the irradiated secondary star. We
detect two additional components in the Halpha emission line that share many
characteristics of similar "satellite" lines observed in the low state of
magnetic cataclysmic variables of AM Her type. It is the first time such
emission components are detected for an SW Sex star.Comment: 7 pages, 8 figures, accepted by MNRA
The Factory and The Beehive II. Activity and Rotation in Praesepe and the Hyades
Open clusters are collections of stars with a single, well-determined age,
and can be used to investigate the connections between angular-momentum
evolution and magnetic activity over a star's lifetime. We present the results
of a comparative study of the relationship between stellar rotation and
activity in two benchmark open clusters: Praesepe and the Hyades. As they have
the same age and roughly solar metallicity, these clusters serve as an ideal
laboratory for testing the agreement between theoretical and empirical
rotation-activity relations at 600 Myr. We have compiled a sample of
720 spectra --- more than half of which are new observations --- for 516
high-confidence members of Praesepe; we have also obtained 139 new spectra for
130 high-confidence Hyads. We have collected rotation periods () for
135 Praesepe members and 87 Hyads. To compare emission, an indicator
of chromospheric activity, as a function of color, mass, and Rossby number
, we first calculate an expanded set of values, with which we can
obtain the to bolometric luminosity ratio, ,
even when spectra are not flux-calibrated and/or stars lack reliable distances.
Our values cover a broader range of stellar masses and colors (roughly
equivalent to spectral types from K0 to M9), and exhibit better agreement
between independent calculations, than existing values. We find no difference
between the two clusters in their equivalent width or
distributions, and therefore take the merged
and data to be representative of 600-Myr-old stars. Our analysis
shows that activity in these stars is saturated for
. Above that value activity declines as a
power-law with slope , before dropping off rapidly
at ...Comment: 17 pages, 15 figures, Accepted by Ap
The fight for accretion: discovery of intermittent mass transfer in BB Doradus in the low state
Our long-term photometric monitoring of southern nova-like cataclysmic
variables with the 1.3-m SMARTS telescope found BB Doradus fading from V ~ 14.3
towards a deep low state at V ~ 19.3 in April 2008. Here we present
time-resolved optical spectroscopy of BB Dor in this faint state in 2009. The
optical spectrum in quiescence is a composite of a hot white dwarf with Teff =
30000 +- 5000 K and a M3-4 secondary star with narrow emission lines (mainly of
the Balmer series and HeI) superposed. We associate these narrow profiles with
an origin on the donor star. Analysis of the radial velocity curve of the
H-alpha emission from the donor star allowed the measurement of an orbital
period of 0.154095 +- 0.000003 d (3.69828 +- 0.00007 h), different from all
previous estimates. We detected episodic accretion events which veiled the
spectra of both stars and radically changed the line profiles within a
timescale of tens of minutes. This shows that accretion is not completely
quenched in the low state. During these accretion episodes the line wings are
stronger and their radial velocity curve is delayed by ~ 0.2 cycle, similar to
that observed in SW Sex and AM Her stars in the high state, with respect to the
motion of the white dwarf. Two scenarios are proposed to explain the extra
emission: impact of the material on the outer edge of a cold, remnant accretion
disc, or the combined action of a moderately magnetic white dwarf (B1 <~ 5 MG)
and the magnetic activity of the donor star.Comment: 10 pages, 10 figures, accepted by MNRA
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