38,475 research outputs found
Decomposition tables for experiments. II. Two--one randomizations
We investigate structure for pairs of randomizations that do not follow each
other in a chain. These are unrandomized-inclusive, independent, coincident or
double randomizations. This involves taking several structures that satisfy
particular relations and combining them to form the appropriate orthogonal
decomposition of the data space for the experiment. We show how to establish
the decomposition table giving the sources of variation, their relationships
and their degrees of freedom, so that competing designs can be evaluated. This
leads to recommendations for when the different types of multiple randomization
should be used.Comment: Published in at http://dx.doi.org/10.1214/09-AOS785 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Decomposition tables for experiments I. A chain of randomizations
One aspect of evaluating the design for an experiment is the discovery of the
relationships between subspaces of the data space. Initially we establish the
notation and methods for evaluating an experiment with a single randomization.
Starting with two structures, or orthogonal decompositions of the data space,
we describe how to combine them to form the overall decomposition for a
single-randomization experiment that is ``structure balanced.'' The
relationships between the two structures are characterized using efficiency
factors. The decomposition is encapsulated in a decomposition table. Then, for
experiments that involve multiple randomizations forming a chain, we take
several structures that pairwise are structure balanced and combine them to
establish the form of the orthogonal decomposition for the experiment. In
particular, it is proven that the properties of the design for such an
experiment are derived in a straightforward manner from those of the individual
designs. We show how to formulate an extended decomposition table giving the
sources of variation, their relationships and their degrees of freedom, so that
competing designs can be evaluated.Comment: Published in at http://dx.doi.org/10.1214/09-AOS717 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Interaction of hydrogen chloride with alumina
The influence of outgas conditions and temperature on the adsorptive properties of two aluminas Alon-c and Al6sG were studied using adsorption isotherm measurements. Alon-C and Al6SG were characterized using X-ray powder diffraction, thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and BET nitrogen surface areas. Some of these techniques were applied to two other aluminas but no isotherm data was obtained. Isotherm data and techniques applied to each alumina are summarized in tabular form
Aerodynamic interactions from reaction controls for lateral control of the M2-F2 lifting-body entry configuration at transonic and supersonic and supersonic Mach numbers
Tests were conducted in the Ames 6 by 6 foot wind tunnel to determine the interaction of reaction jets for roll control on the M2-F2 lifting-body entry vehicle. Moment interactions are presented for a Mach number range of 0.6 to 1.7, a Reynolds number range of 1.2 x 10 to the 6th power to 1.6 x 10 to the 6th power (based on model reference length), an angle-of-attack range of -9 deg to 20 deg, and an angle-of-sideslip range of -6 deg to 6 deg at an angle of attack of 6 deg. The reaction jets produce roll control with small adverse yawing moment, which can be offset by horizontal thrust component of canted jets
Interaction of hydrogen chloride with alumina
The influence of temperature, pressure, and outgas conditions on the absorption of hydrogen chloride and water vapor on both alpha and gamma alumina was studied. Characterization of the adsorbents was performed using X-ray powder diffraction, scanning electron microscopy (SEM), low temperature nitrogen adsorption desorption measurements, BET nitrogen surface area measurements and electron spectroscopy for chemical analysis (ESCA). Water vapor adsorption isotherms at 30, 40, and 50 C were measured on alpha and gamma alumina after outgassing at 80, 200, and 400 C. Both outgas temperature and adsorption temperature influenced the adsorption of water vapor on the aluminas. The water vapor adsorption was completely reversible. Alpha alumina absorbed more water per unit area than gamma alumina. Differences in the adsorption capacity for water vapor of the two aluminas were explained on the basis of ideal surface models of alpha and gamma alumina. Isosteric heats of adsorption for water vapor on the aluminas were determined over a limited range of surface coverage
Low cost fabrication development for oxide dispersion strengthened alloy vanes
Viable processes were developed for secondary working of oxide dispersion strengthened (ODS) alloys to near-net shapes (NNS) for aircraft turbine vanes. These processes were shown capable of producing required microstructure and properties for vane applications. Material cost savings of 40 to 50% are projected for the NNS process over the current procedures which involve machining from rectangular bar. Additional machining cost savings are projected. Of three secondary working processes evaluated, directional forging and plate bending were determined to be viable NNS processes for ODS vanes. Directional forging was deemed most applicable to high pressure turbine (HPT) vanes with their large thickness variations while plate bending was determined to be most cost effective for low pressure turbine (LPT) vanes because of their limited thickness variations. Since the F101 LPT vane was selected for study in this program, development of plate bending was carried through to establishment of a preliminary process. Preparation of ODS alloy plate for bending was found to be a straight forward process using currently available bar stock, providing that the capability for reheating between roll passes is available. Advanced ODS-NiCrAl and ODS-FeCrAl alloys were utilized on this program. Workability of all alloys was adequate for directional forging and plate bending, but only the ODS-FeCrAl had adequate workability for shaped preform extrustion
UAV as a Reliable Wingman: A Flight Demonstration
In this brief, we present the results from a flight experiment demonstrating two significant advances in software enabled control: optimization-based control using real-time trajectory generation and logical programming environments for formal analysis of control software. Our demonstration platform consisted of a human-piloted F-15 jet flying together with an autonomous T-33 jet. We describe the behavior of the system in two scenarios. In the first, nominal state communications were present and the autonomous aircraft maintained formation as the human pilot flew maneuvers. In the second, we imposed the loss of high-rate communications and demonstrated an autonomous safe “lost wingman” procedure to increase separation and reacquire contact. The flight demonstration included both a nominal formation flight component and an execution of the lost wingman scenario
Design and application of polycarbonate capacitors in aerospace ac power systems
Design and testing of ac polycarbonate capacitors for aerospace power system
2dF-AAOmega spectroscopy of massive stars in the Magellanic Clouds: The north-eastern region of the Large Magellanic Cloud
We present spectral classifications from optical spectroscopy of 263 massive
stars in the north-eastern region of the Large Magellanic Cloud. The observed
two-degree field includes the massive 30 Doradus star-forming region, the
environs of SN1987A, and a number of star-forming complexes to the south of 30
Dor. These are the first classifications for the majority (203) of the stars
and include eleven double-lined spectroscopic binaries. The sample also
includes the first examples of early OC-type spectra (AAOmega 30 Dor 248 and
280), distinguished by the weakness of their nitrogen spectra and by C IV 4658
emission. We propose that these stars have relatively unprocessed CNO
abundances compared to morphologically normal O-type stars, indicative of an
earlier evolutionary phase. From analysis of observations obtained on two
consecutive nights, we present radial-velocity estimates for 233 stars, finding
one apparent single-lined binary and nine (>3sigma) outliers compared to the
systemic velocity; the latter objects could be runaway stars or large-amplitude
binary systems and further spectroscopy is required to investigate their
nature.Comment: Accepted by A&
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