6,871 research outputs found
High-speed civil transport flight- and propulsion-control technological issues
Technology advances required in the flight and propulsion control system disciplines to develop a high speed civil transport (HSCT) are identified. The mission and requirements of the transport and major flight and propulsion control technology issues are discussed. Each issue is ranked and, for each issue, a plan for technology readiness is given. Certain features are unique and dominate control system design. These features include the high temperature environment, large flexible aircraft, control-configured empennage, minimizing control margins, and high availability and excellent maintainability. The failure to resolve most high-priority issues can prevent the transport from achieving its goals. The flow-time for hardware may require stimulus, since market forces may be insufficient to ensure timely production. Flight and propulsion control technology will contribute to takeoff gross weight reduction. Similar technology advances are necessary also to ensure flight safety for the transport. The certification basis of the HSCT must be negotiated between airplane manufacturers and government regulators. Efficient, quality design of the transport will require an integrated set of design tools that support the entire engineering design team
A Deeper Look at the New Milky Way Satellites: Sagittarius II, Reticulum II, Phoenix II, and Tucana III
We present deep Magellan/Megacam stellar photometry of four recently
discovered faint Milky Way satellites: Sagittarius II (Sgr II), Reticulum II
(Ret II), Phoenix II (Phe II), and Tucana III (Tuc III). Our photometry reaches
~2-3 magnitudes deeper than the discovery data, allowing us to revisit the
properties of these new objects (e.g., distance, structural properties,
luminosity measurements, and signs of tidal disturbance). The satellite
color-magnitude diagrams show that they are all old (~13.5 Gyr) and metal-poor
([Fe/H]). Sgr II is particularly interesting as it sits in an
intermediate position between the loci of dwarf galaxies and globular clusters
in the size-luminosity plane. The ensemble of its structural parameters is more
consistent with a globular cluster classification, indicating that Sgr II is
the most extended globular cluster in its luminosity range. The other three
satellites land directly on the locus defined by Milky Way ultra-faint dwarf
galaxies of similar luminosity. Ret II is the most elongated nearby dwarf
galaxy currently known for its luminosity range. Our structural parameters for
Phe II and Tuc III suggest that they are both dwarf galaxies. Tuc III is known
to be associated with a stellar stream, which is clearly visible in our
matched-filter stellar density map. The other satellites do not show any clear
evidence of tidal stripping in the form of extensions or distortions. Finally,
we also use archival HI data to place limits on the gas content of each object.Comment: Accepted for publication in ApJ. Minor updates to match accepted
versio
Optimal, reliable estimation of quantum states
Accurately inferring the state of a quantum device from the results of
measurements is a crucial task in building quantum information processing
hardware. The predominant state estimation procedure, maximum likelihood
estimation (MLE), generally reports an estimate with zero eigenvalues. These
cannot be justified. Furthermore, the MLE estimate is incompatible with error
bars, so conclusions drawn from it are suspect. I propose an alternative
procedure, Bayesian mean estimation (BME). BME never yields zero eigenvalues,
its eigenvalues provide a bound on their own uncertainties, and it is the most
accurate procedure possible. I show how to implement BME numerically, and how
to obtain natural error bars that are compatible with the estimate. Finally, I
briefly discuss the differences between Bayesian and frequentist estimation
techniques.Comment: RevTeX; 14 pages, 2 embedded figures. Comments enthusiastically
welcomed
Reproducibility of aortic intima-media thickness in infants using edge-detection software and manual caliper measurements
Background: Aortic intima-media thickness measured by transabdominal ultrasound (aIMT) is an intermediate phenotype of cardiovascular risk. We aimed to (1) investigate the reproducibility of aIMT in a population-derived cohort of infants; (2) establish the distribution of aIMT in early infancy; (3) compare measurement by edge-detection software to that by manual sonographic calipers; and (4) assess the effect of individual and environmental variables on image quality. Methods. Participants were term infants recruited to a population-derived birth cohort study. Transabdominal ultrasound was performed at six weeks of age by one of two trained operators. Thirty participants had ultrasounds performed by both operators on the same day. Data were collected on environmental (infant sleeping, presence of a sibling, use of sucrose, timing during study visit) and individual (post-conception age, weight, gender) variables. Two readers assessed image quality and measured aIMT by edge-detection software and a subset by manual sonographic calipers. Measurements were repeated by the same reader and between readers to obtain intra-observer and inter-observer reliability. Results: Aortic IMT was measured successfully using edge-detection in 814 infants, and 290 of these infants also had aIMT measured using manual sonographic calipers. The intra-reader intra-class correlation (ICC) (n = 20) was 0.90 (95% CI 0.76, 0.96), mean difference 1.5 μm (95% LOA -39, 59). The between reader ICC using edge-detection (n = 20) was 0.92 (95% CI 0.82, 0.97) mean difference 2 μm (95% LOA -45.0, 49.0) and with manual caliper measurement (n = 290) the ICC was 0.84 (95% CI 0.80, 0.87) mean difference 5 μm (95% LOA -51.8, 61.8). Edge-detection measurements were greater than those from manual sonographic calipers (mean aIMT 618 μm (50) versus mean aIMT 563 μm (49) respectively; p < 0.001, mean difference 44 μm, 95% LOA -54, 142). With the exception of infant crying (p = 0.001), no associations were observed between individual and environmental variables and image quality. Conclusion: In a population-derived cohort of term infants, aIMT measurement has a high level of intra and inter-reader reproducibility. Measurement of aIMT using edge-detection software gives higher inter-reader ICC than manual sonographic calipers. Image quality is not substantially affected by individual and environmental factors. © 2014 McCloskey et al.; licensee BioMed Central Ltd
4f-hybridization effect on the magnetism of Nd2PdSi3, an anomalous magnetic compound
Among the members of the series R2PdSi3 (R= Rare-earths), the magnetic
behavior of the Nd compound is interesting in some respects. This compound is
considered to order ferromagnetically (below 16 K), unlike other members of
this series which order antiferromagnetically. In addition, magnetic ordering
temperature (To) is significantly enhanced with respect to de Gennes scaled
value. In order to understand the magnetism of this compound better, we have
investigated the magnetic behavior in detail (under external pressure as well)
and also of its solid solutions based on substitutions at Nd and at Si sites,
viz., on the series, Nd(2-x)(Y,La)(x)PdSi(3-y)Ge(y) (x, y= 0.2, 0.4, 0.8, and
1.2) by bulk measurements. The results overall establish that Nd2PdSi3 orders
ferromagnetically below 16 K, but antiferromagnetic component seems to set in
at very low temperatures. Notably, there is a significant suppression of To for
Y and Ge substitutions, compared to La substitution, for a given magnitude of
unit-cell volume change, however qualitatively correlating with the separation
between the layers of Nd and Pd-Si(Ge). On the basis of this observation, we
conclude that 4f(Nd) hybridization plays a major role on the magnetism of the
former solid solutions. To our knowledge, this work serves as a rare
demonstration of 4f-hybridization effects on the magnetism of a Nd-based
intermetallic compound.Comment: PRB November 2011 (accepted
Moving Towards the Post p < 0.05 Era via the Analysis of Credibility
It is now widely accepted that the techniques of null hypothesis significance testing (NHST) are routinely misused and misinterpreted by researchers seeking insight from data. There is, however, no consensus on acceptable alternatives, leaving researchers with little choice but to continue using NHST, regardless of its failings. I examine the potential for the Analysis of Credibility (AnCred) to resolve this impasse. Using real-life examples, I assess the ability of AnCred to provide researchers with a simple but robust framework for assessing study findings that goes beyond the standard dichotomy of statistical significance/nonsignificance. By extracting more insight from standard summary statistics while offering more protection against inferential fallacies, AnCred may encourage researchers to move toward the post p < 0.05 era
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