28,495 research outputs found
Crack growth measured on flat and curved surfaces at cryogenic temperatures
Multiple element continuity gage measures plane stress crack growth plus surface crack growth under plane strain conditions. The gage measures flat and curved surfaces and operates at cryogenic temperatures
Ablation article and method
An ablation article, such as a conical heat shield, having an ablating surface is provided with at least one discrete area of at least one seed material, such as aluminum. When subjected to ablation conditions, the seed material is ablated. Radiation emanating from the ablated seed material is detected to analyze ablation effects without disturbing the ablation surface. By providing different seed materials having different radiation characteristics, the ablating effects on various areas of the ablating surface can be analyzed under any prevailing ablation conditions. The ablating article can be provided with means for detecting the radiation characteristics of the ablated seed material to provide a self-contained analysis unit
A Calibrated Measurement of the Near-IR Continuum Sky Brightness Using Magellan/FIRE
We characterize the near-IR sky background from 308 observations with the
FIRE spectrograph at Magellan. A subset of 105 observations selected to
minimize lunar and thermal effects gives a continuous, median spectrum from
0.83 to 2.5 microns which we present in electronic form. The data are used to
characterize the broadband continuum emission between atmospheric OH features
and correlate its properties with observing conditions such as lunar angle and
time of night. We find that the moon contributes significantly to the
inter-line continuum in the Y and J bands whereas the observed H band continuum
is dominated by the blended Lorentzian wings of multiple OH line profiles even
at R=6000. Lunar effects may be mitigated in Y and J through careful scheduling
of observations, but the most ambitious near-IR programs will benefit from
allocation during dark observing time if those observations are not limited by
read noise. In Y and J our measured continuum exceeds space-based average
estimates of the Zodiacal light, but it is not readily identified with known
terrestrial foregrounds. If further measurements confirm such a fundamental
background, it would impact requirements for OH-suppressed instruments
operating in this regime.Comment: 25 pages, 11 figures, accepted to PAS
Less than perfect quantum wavefunctions in momentum-space: How phi(p) senses disturbances in the force
We develop a systematic approach to determine the large |p| behavior of the
momentum-space wavefunction, phi(p), of a one-dimensional quantum system for
wich the position-space wavefunction, psi(x), has a discontinuous derivative at
any order. We find that if the k-th derivative of the potential energy function
has a discontinuity, there is a corresponding discontinuity in psi^{(k+2)}(x)
at the same point. This discontinuity leads directly to a power-law tail in the
momentum-space wavefunction proportional to 1/p^{k+3}. A number of familiar
pedagogical examples are examined in this context, leading to a general
derivation of the result.Comment: 22 pages, 2 figures. To appear in Am. J. Phy
Near-Infrared InGaAs Detectors for Background-limited Imaging and Photometry
Originally designed for night-vision equipment, InGaAs detectors are
beginning to achieve background-limited performance in broadband imaging from
the ground. The lower cost of these detectors can enable multi-band
instruments, arrays of small telescopes, and large focal planes that would be
uneconomical with high-performance HgCdTe detectors. We developed a camera to
operate the FLIR AP1121 sensor using deep thermoelectric cooling and
up-the-ramp sampling to minimize noise. We measured a dark current of 163-
s pix, a read noise of 87- up-the-ramp, and a well depth of
80k-. Laboratory photometric testing achieved a stability of 230 ppm
hr, which would be required for detecting exoplanet transits. InGaAs
detectors are also applicable to other branches of near-infrared time-domain
astronomy, ranging from brown dwarf weather to gravitational wave follow-up.Comment: Submitted to Proc. SPIE, Astronomical Telescopes + Instrumentation
(2014
Saturn orbiter mission study
A preliminary analysis of the important aspects of missions orbiting the planet Saturn is provided. Orbital missions to Saturn is given serious consideration for the 1980's, or after flybys by Pioneer 10/G and Mariner Jupiter-Saturn 1977. An attempt is made to characterize Saturn orbiters in detail so that comparisons with Jupiter missions can be made. The scientific objectives of Saturn exploration are grouped under four topics: (1) the atmosphere, (2) the magnetosphere, (3) the rings, and (4) the satellites
Apollo experience report: Real-time display system
The real time display system used in the Apollo Program is described; the systematic organization of the system, which resulted from hardware/software trade-offs and the establishment of system criteria, is emphasized. Each basic requirement of the real time display system was met by a separate subsystem. The computer input multiplexer subsystem, the plotting display subsystem, the digital display subsystem, and the digital television subsystem are described. Also described are the automated display design and the generation of precision photographic reference slides required for the three display subsystems
An evaluation of the total quality management implementation strategy for the advanced solid rocket motor project at NASA's Marshall Space Flight Center
An evaluation of the NASA's Marshall Space Flight Center (MSFC) strategy to implement Total Quality Management (TQM) in the Advanced Solid Rocket Motor (ASRM) Project is presented. The evaluation of the implementation strategy reflected the Civil Service personnel perspective at the project level. The external and internal environments at MSFC were analyzed for their effects on the ASRM TQM strategy. Organizational forms, cultures, management systems, problem solving techniques, and training were assessed for their influence on the implementation strategy. The influence of ASRM's effort was assessed relative to its impact on mature projects as well as future projects at MSFC
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