12,451 research outputs found
Wind tunnel test IA300 analysis and results, volume 1
The analysis and interpretation of wind tunnel pressure data from the Space Shuttle wind tunnel test IA300 are presented. The primary objective of the test was to determine the effects of the Space Shuttle Main Engine (SSME) and the Solid Rocket Booster (SRB) plumes on the integrated vehicle forebody pressure distributions, the elevon hinge moments, and wing loads. The results of this test will be combined with flight test results to form a new data base to be employed in the IVBC-3 airloads analysis. A secondary objective was to obtain solid plume data for correlation with the results of gaseous plume tests. Data from the power level portion was used in conjunction with flight base pressures to evaluate nominal power levels to be used during the investigation of changes in model attitude, eleveon deflection, and nozzle gimbal angle. The plume induced aerodynamic loads were developed for the Space Shuttle bases and forebody areas. A computer code was developed to integrate the pressure data. Using simplified geometrical models of the Space Shuttle elements and components, the pressure data were integrated to develop plume induced force and moments coefficients that can be combined with a power-off data base to develop a power-on data base
Oxygen-related traps in pentacene thin films: Energetic position and implications for transistor performance
We studied the influence of oxygen on the electronic trap states in a
pentacene thin film. This was done by carrying out gated four-terminal
measurements on thin-film transistors as a function of temperature and without
ever exposing the samples to ambient air. Photooxidation of pentacene is shown
to lead to a peak of trap states centered at 0.28 eV from the mobility edge,
with trap densities of the order of 10(18) cm(-3). These trap states need to be
occupied at first and cause a reduction in the number of free carriers, i.e. a
consistent shift of the density of free holes as a function of gate voltage.
Moreover, the exposure to oxygen reduces the mobility of the charge carriers
above the mobility edge. We correlate the change of these transport parameters
with the change of the essential device parameters, i.e. subthreshold
performance and effective field-effect mobility. This study supports the
assumption of a mobility edge for charge transport, and contributes to a
detailed understanding of an important degradation mechanism of organic
field-effect transistors. Deep traps in an organic field-effect transistor
reduce the effective field-effect mobility by reducing the number of free
carriers and their mobility above the mobility edge.Comment: 13 pages, 14 figures, to be published in Phys. Rev.
Borderplex Long-Term Economic Trends to 2026
Long-term prospects for the El Paso - Ciudad Juárez borderplex economy call for steady growth. On the north side of the border, the population of El Paso is projected to reach 965 thousand by 2026, the last year of the forecast period. Real gross metropolitan product, the broadest measure of local economic activity, is expected to increase by more than 85 percent over the course of the next two decades to more than 20.7 billion by the end of the simulation period. Given this projected state of affairs, the UTEP Borderplex Econometric Model forecasts housing starts to average more than 5 thousand units per year through 2026. Substantially higher single-family home prices result under these circumstances. Demographic expansion and business growth jointly lead to greater demand for water in El Paso. As shown in Table 1, total consumption will approximate 45.8 billion gallons per year by the end of the forecast period.Border Economies; Econometric Forecasting Analysis
Infrastructure Tolls in Texas: Evidence from the Borderplex
Do changes in toll rates affect pedestrian, car, and truck traffic across the bridges between El Paso and Ciudad Juarez, Mexico? As more and more attention is paid to the use of tolls as funding mechanisms for new road and infrastructure construction in Texas, the answer to this question has policy implications not only for local and state lawmakers, but also for firms importing and exporting goods between Texas and Mexico. This article uses bridge traffic data from the Borderplex to examine the relative impact of tolls and concludes that local policymakers have more leeway than they thought in raising funds to make infrastructure improvements.Tolls; International Bridges; Border Economics
Fault Slip and Exhumation History of the Willard Thrust Sheet, Sevier Fold‐Thrust Belt, Utah: Relations to Wedge Propagation, Hinterland Uplift, and Foreland Basin Sedimentation
Zircon (U‐Th)/He (ZHe) and zircon fission track thermochronometric data for 47 samples spanning the areally extensive Willard thrust sheet within the western part of the Sevier fold‐thrust belt record enhanced cooling and exhumation during major thrust slip spanning approximately 125–90 Ma. ZHe and zircon fission track age‐paleodepth patterns along structural transects and age‐distance relations along stratigraphic‐parallel traverses, combined with thermo‐kinematic modeling, constrain the fault slip history, with estimated slip rates of ~1 km/Myr from 125 to 105 Ma, increasing to ~3 km/Myr from 105 to 92 Ma, and then decreasing as major slip was transferred onto eastern thrusts. Exhumation was concentrated during motion up thrust ramps with estimated erosion rates of ~0.1 to 0.3 km/Myr. Local cooling ages of approximately 160–150 Ma may record a period of regional erosion, or alternatively an early phase of limited... (see full abstract in article)
Detection of quantum light in the presence of noise
Detection of quantum light in the presence of dark counts and background
radiation noise is considered. The corresponding positive operator-valued
measure is obtained and photocounts statistics of quantum light in the presence
of noise is studied.Comment: 4 pages, 1 figure; misprints correcte
MOXE: An X-ray all-sky monitor for Soviet Spectrum-X-Gamma Mission
A Monitoring Monitoring X-Ray Equipment (MOXE) is being developed for the Soviet Spectrum-X-Gamma Mission. MOXE is an X-ray all-sky monitor based on array of pinhole cameras, to be provided via a collaboration between Goddard Space Flight Center and Los Alamos National Laboratory. The objectives are to alert other observers on Spectrum-X-Gamma and other platforms of interesting transient activity, and to synoptically monitor the X-ray sky and study long-term changes in X-ray binaries. MOXE will be sensitive to sources as faint as 2 milliCrab (5 sigma) in 1 day, and cover the 2 to 20 KeV band
Satellite power system: Concept development and evaluation program. Volume 3: Power transmission and reception. Technical summary and assessment
Efforts in the DOE/NASA concept development and evaluation program are discussed for the solar power satellite power transmission and reception system. A technical summary is provided together with a summary of system assessment activities. System options and system definition drivers are described. Major system assessment activities were in support of the reference system definition, solid state system studies, critical technology supporting investigations, and various system and subsystem tradeoffs. These activities are described together with reference system updates and alternative concepts for each of the subsystem areas. Conclusions reached as a result of the numerous analytical and experimental evaluations are presented. Remaining issues for a possible follow-on program are identified
Milli-second Oscillations in the Persistent and Bursting Flux of Aql X-1 During an Outburst
The Rossi X-Ray Timing Explorer observed the soft X-Ray transient Aql X-1
during its outburst in February and March 1997. We report the discovery of
quasi-periodic oscillations (QPOs) in its persistent flux with frequencies in
the range of 740 to 830 Hz, Q-value of over 100, and a fractional RMS amplitude
of (6.8 +- 0.6)%, and nearly coherent oscillations (NCOs) during a Type-I burst
with a frequency of 549 Hz. The frequency of the QPOs in the persistent flux is
correlated with the mass accretion rate on time scale of hours, but not on time
scale of days. This is most likely the manifestation in a single source of the
kHz QPO puzzle observed among many sources, i.e., on the one hand, individual
sources show a correlation between the QPO frequency and the inferred mass
accretion rate, on the other hand, the dozen or so sources with luminosities
spanning two decades have essentially the same QPO frequencies. We propose that
this multi-valued QPO frequency and mass accretion rate correlation indicates
the existence of many similar regimes of the accretion disk. These regimes,
with a very similar energy spectrum and QPO frequency, are distinguished from
each other by the mass accretion rate or the total X-ray flux. The NCOs during
the burst can be made almost perfectly coherent by taking into account a large
frequency derivative. This strongly suggests that this frequency is related to
the neutron star spin frequency. The large frequency derivative is attributable
to the expansion or contraction of the neutron star photosphere during the
burst.Comment: 6 pages, LaTex (aas2pp4), Accepted for publication in ApJ Let
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