16,986 research outputs found
The CARE 3 Phase 3 Report: Test and Evaluation
CARE 3 (Computer-Aided Reliability Estimation, version three) is a computer program designed to help estimate the reliability of complex, redundant systems; although the program can model a wide variety of redundant structures, it was developed specifically for fault-tolerant avionics systems, systems distinguished by the need for extremely reliable performance since a system failure could well result in the loss of human life. CARE 3 further generalizes the class of system structures that can be modeled and greatly expands the coverage model to take into account such effects as intermittent and transient faults, latent faults, error propagation, etc. The initial test and evaluation of CARE 3 are reported
IN-FLIGHT SHOCK-WAVE PRESSURE MEASUREMENTS ABOVE AND BELOW A BOMBER AIRPLANE AT MACH NUMBERS FROM 1.42 TO 1.69
In-flight shock wave pressure measurements above and below bomber aircraft at mach 1.42 to 1.6
Tradeoff analysis of technology needs for public service helicopters
The design requirements for a family or type of Public Service Helicopter (PSH) is examined which will satisfy the needs of municipal and state governments in the following mission areas: Emergency Medical Service--Airborne Rescue Squad; Law Enforcement; Search and Rescue; and Environmental Control (Fire Fighting, Pollution, Resource Management). The report compares both design and performance requirements as specified by the PSH user's group against current technological capabilities, RTOPS and US Army LHX design requirements. The study explores various design trade-offs and options available to the aircraft designer/manufacturer in order to meet the several criteria specified by the PSH user's group. In addition, the report includes a brief assessment of the feasibility of employing certain advanced rotorcraft designs to meet the stringent combination of operational capabilities desired by the Public Service Helicopter Users
Two universal results for Wilson loops at strong coupling
We present results for Wilson loops in strongly coupled gauge theories. The
loops may be taken around an arbitrarily shaped contour and in any field theory
with a dual IIB geometry of the form M x S^5. No assumptions about
supersymmetry are made. The first result uses D5 branes to show how the loop in
any antisymmetric representation is computed in terms of the loop in the
fundamental representation. The second result uses D3 branes to observe that
each loop defines a rich sequence of operators associated with minimal surfaces
in S^5. The action of these configurations are all computable. Both results
have features suggesting a connection with integrability.Comment: 1+12 pages. LaTeX. No figure
The implementation of performance analysis and feedback within Olympic sport: the performance analystâs perspective
The study considered performance analysis and feedback from the perspective of the performance analyst through the investigation of the âwhatâ, âhowâ, and âwhenâ of practice within a selection of Olympic sports. Twenty-three performance analysts (experience 6.4 ± 4.1 years) engaged in a structured interview (85 ± 15 minutes) regarding their processes within applied practice. Likert scales (All the time, Often, Sometimes, Rarely, Never) were used to facilitate cross sport and environment comparison. The performance analysts highlighted the experience of their coaches as the most prominent feature influencing analysis direction and time had the greatest impact upon feedback provision. The main analysis techniques used were video, profiling and performance reports. Feedback was delivered primarily either, 1) < 1-hour post-performance within sessions lasting < 10-minutes or 2) the following day within sessions lasting 25+ minutes. Video feedback was usually coach led, however data delivery was more evenly distributed between coach and analyst. Very similar processes across the participants were identified, despite a wide variety of sports and participant experience levels. The findings have begun to illustrate practice within elite sport whilst highlighting the importance and need for further practitioner-based investigation regarding the use of performance analysis and feedback within applied context
Elite coachesâ use and engagement with performance analysis within Olympic and Paralympic sport
The use and implementation of performance analysis and feedback by 18 elite Olympic/Paralympic coaches (coaching experience 16.1 ± 7.4; experience using performance analysis 8.3 ± 4.8 years) was explored via an online questionnaire (mean time to complete = 29 minutes). Likert scales were used to facilitate cross-sport comparison. Comment boxes were included to enable additional information to be provided if deemed necessary. Training goals, athlete discussion and coaching philosophy were the most prominent features influencing analysis direction. Time available had the greatest impact upon feedback provision. The main analysis techniques used were video, performance reports, and trend analysis. Coaches with greater experience delivered significantly more feedback sessions within 1-hour of performance. Feedback sessions were < 20-minutes in duration and delivered in a balanced (experienced) or mostly positive (inexperienced) approach. Feedback was delivered consistently according to a preferred schedule, face-to-face, and within an individual format. Sessions were usually coach led, however considerable value in a combined or analyst led approach was demonstrated. The findings have begun to illustrate practice within elite sport from the perspective of a key user of performance analysis, i.e. the coach, and have clear implications for practitioners by identifying the key areas coachesâ value from performance analysis
The SAMI Galaxy Survey: Satellite galaxies undergo little structural change during their quenching phase
At fixed stellar mass, satellite galaxies show higher passive fractions than
centrals, suggesting that environment is directly quenching their star
formation. Here, we investigate whether satellite quenching is accompanied by
changes in stellar spin (quantified by the ratio of the rotational to
dispersion velocity V/) for a sample of massive (10
M) satellite galaxies extracted from the SAMI Galaxy Survey. These
systems are carefully matched to a control sample of main sequence, high
central galaxies. As expected, at fixed stellar mass and
ellipticity, satellites have lower star formation rate (SFR) and spin than the
control centrals. However, most of the difference is in SFR, whereas the spin
decreases significantly only for satellites that have already reached the red
sequence. We perform a similar analysis for galaxies in the EAGLE
hydro-dynamical simulation and recover differences in both SFR and spin similar
to those observed in SAMI. However, when EAGLE satellites are matched to their
`true' central progenitors, the change in spin is further reduced and galaxies
mainly show a decrease in SFR during their satellite phase. The difference in
spin observed between satellites and centrals at 0 is primarily due to
the fact that satellites do not grow their angular momentum as fast as centrals
after accreting into bigger halos, not to a reduction of due to
environmental effects. Our findings highlight the effect of progenitor bias in
our understanding of galaxy transformation and they suggest that satellites
undergo little structural change before and during their quenching phase.Comment: 11 pages, 7 figures. Accepted for publication in MNRA
Calibrated Sub-Bundles in Non-Compact Manifolds of Special Holonomy
This paper is a continuation of math.DG/0408005. We first construct special
Lagrangian submanifolds of the Ricci-flat Stenzel metric (of holonomy SU(n)) on
the cotangent bundle of S^n by looking at the conormal bundle of appropriate
submanifolds of S^n. We find that the condition for the conormal bundle to be
special Lagrangian is the same as that discovered by Harvey-Lawson for
submanifolds in R^n in their pioneering paper. We also construct calibrated
submanifolds in complete metrics with special holonomy G_2 and Spin(7)
discovered by Bryant and Salamon on the total spaces of appropriate bundles
over self-dual Einstein four manifolds. The submanifolds are constructed as
certain subbundles over immersed surfaces. We show that this construction
requires the surface to be minimal in the associative and Cayley cases, and to
be (properly oriented) real isotropic in the coassociative case. We also make
some remarks about using these constructions as a possible local model for the
intersection of compact calibrated submanifolds in a compact manifold with
special holonomy.Comment: 20 pages; for Revised Version: Minor cosmetic changes, some
paragraphs rewritten for improved clarit
Closed trajectories of a particle model on null curves in anti-de Sitter 3-space
We study the existence of closed trajectories of a particle model on null
curves in anti-de Sitter 3-space defined by a functional which is linear in the
curvature of the particle path. Explicit expressions for the trajectories are
found and the existence of infinitely many closed trajectories is proved.Comment: 12 pages, 1 figur
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