10,878 research outputs found
Flight test evaluation of a separate surface attitude command control system on a Beech 99 airplane
A joint NASA/university/industry program was conducted to flight evaluate a potentially low cost separate surface implementation of attitude command in a Beech 99 airplane. Saturation of the separate surfaces was the primary cause of many problems during development. Six experienced professional pilots who made simulated instrument flight evaluations experienced improvements in airplane handling qualities in the presence of turbulence and a reduction in pilot workload. For ride quality, quantitative data show that the attitude command control system results in all cases of airplane motion being removed from the uncomfortable ride region
Development of systems and techniques for landing an aircraft using onboard television
A flight program was conducted to develop a landing technique with which a pilot could consistently and safely land a remotely piloted research vehicle (RPRV) without outside visual reference except through television. Otherwise, instrumentation was standard. Such factors as the selection of video parameters, the pilot's understanding of the television presentation, the pilot's ground cockpit environment, and the operational procedures for landing were considered. About 30 landings were necessary for a pilot to become sufficiently familiar and competent with the test aircraft to make powered approaches and landings with outside visual references only through television. When steep approaches and landings were made by remote control, the pilot's workload was extremely high. The test aircraft was used as a simulator for the F-15 RPRV, and as such was considered to be essential to the success of landing the F-15 RPRV
Singular values of some modular functions
We study the properties of special values of the modular functions obtained
from Weierstrass P-function at imaginary quadratic points.Comment: 19 pages,corrected typo
A discourse analysis of trainee teacher identity in online discussion forums
Teacher education involves an identity transformation for trainees from being a student to being a teacher. This discourse analysis examined the online discussion board communications of a cohort of trainee teachers to better understand the situated identities of the trainees and how they were presented online. Their discussion board posts were the primary method of communication during placement periods and, as such, provided insight into how the trainees situated their identities in terms of being a student or being a teacher. During the analysis, the community boundaries, language and culture were explored along with the tutor's power and role in the identity transformation process. This involved looking at the lexis used by the students, the use of pronouns to refer to themselves and others such as teachers and pupils, the types of messages allowed in the community and the effect of the tutor's messages on their communication. The research found that the trainees felt comfortable with teaching but did not feel like teachers during the course. Tutors and school teachers need to develop an awareness of the dual nature of trainees' identities and help promote the transition from student to teacher. In the beginning of the course, trainees should be familiarised with teacher vocabulary and practical concepts in addition to pedagogical theory. Towards the end of the course, trainee identity as teachers could be promoted through the use of authentic assessments that mirror real teacher tasks and requirements
Tandem concentrator solar cells with 30 percent (AMO) power conversion efficiency
Very high efficiency concentrator solar panels are envisioned as economical and reliable electrical power subsystems for space based platforms of the future. GaAs concentrator cells with very high efficiencies and good sub-bandgap transmissions can be fabricated on standard wafers. GaSb booster cell development is progressing very well; performance characteristics are still improving dramatically. Consistent GaAs/GaSb stacked cell AMO efficiencies greater than 30 percent are expected
Stick-Slip Motion and Phase Transition in a Block-Spring System
We study numerically stick slip motions in a model of blocks and springs
being pulled slowly. The sliding friction is assumed to change dynamically with
a state variable. The transition from steady sliding to stick-slip is
subcritical in a single block and spring system. However, we find that the
transition is continuous in a long chain of blocks and springs. The size
distribution of stick-slip motions exhibits a power law at the critical point.Comment: 8 figure
Local political leadership and the modernisation of local government
Political leadership has been a key element of central governmentâs attempts to âmoderniseâ local government over the past decade, within a discourse that emphasised âstrongâ and âvisibleâ leadership and the role of leaders and leadership in driving change within local authorities. In the context of such an approach, and also taking account of academic discourse, this article draws upon interviews with nearly thirty individuals in leadership positions in local authorities in England, Scotland and Wales to assess their experiences of leadership and their views of some aspects of the role and work of councils. It suggests that whilst there is broad convergence between the aspirations of government and the narratives that emerge from these leaders on some aspects of local political leadership, there are also differences, perhaps most notably over the relationship between changes to decision making structures and the loci of political power
Paleomagnetic constraints on deformation of superfast-spread oceanic crust exposed at Pito Deep Rift
The uppermost oceanic crust produced at the superfast spreading (âŒ142 km Ma â1, fullâspreading rate) southern East Pacific Rise (EPR) during the Gauss Chron is exposed in a tectonic window along the northeastern wall of the Pito Deep Rift. Paleomagnetic analysis of fully oriented dike (62) and gabbro (5) samples from two adjacent study areas yield bootstrapped mean remanence directions of 38.9° ± 8.1°, â16.7° ± 15.6°, n = 23 (Area A) and 30.4° ± 8.0°, â25.1° ± 12.9°, n = 44 (Area B), both are significantly distinct from the Geocentric Axial Dipole expected direction at 23° S. Regional tectonics and outcropâscale structural data combined with bootstrapped remanence directions constrain models that involve a sequence of three rotations that result in dikes restored to subvertical orientations related to (1) inwardâtilting of crustal blocks during spreading (Area A = 11°, Area B = 22°), (2) clockwise, verticalâaxis rotation of the Easter Microplate (A = 46°, B = 44°), and (3) block tilting at Pito Deep Rift (A = 21°, B = 10°). These data support a structural model for accretion at the southern EPR in which outcropâscale faulting and block rotation accommodates spreadingârelated subaxial subsidence that is generally less than that observed in crust generated at a fast spreading rate exposed at Hess Deep Rift. These data also support previous estimates for the clockwise rotation of crust adjacent to the Easter Microplate. Dike sample natural remanent magnetization (NRM) has an arithmetic mean of 5.96 A/m ± 3.76, which suggests that they significantly contribute to observed magnetic anomalies from fastâ to superfastâspread crust
Direct evidence from anisotropy of magnetic susceptibility for lateral melt migration at superfast spreading centers
Rare, faultâbounded escarpments expose natural cross sections of ocean crust in several areas and provide an unparalleled opportunity to study the end products of tectonic and magmatic processes that operated at depth beneath oceanic spreading centers. We mapped the geologic structure of ocean crust produced at the East Pacific Rise (EPR) and now exposed along steep cliffs of the Pito Deep Rift near the northern edge of the Easter microplate. The upper oceanic crust in this area is typified by basaltic lavas underlain by a sheeted dike complex comprising northeast striking, moderately to steeply southeast dipping dikes. Paleomagnetic remanence of oriented blocks of dikes collected with both Alvin and Jason II indicate clockwise rotation of âŒ61° related to rotation of the microplate indicating structural coupling between the microplate and crust of the Nazca Plate to the north. The consistent southeast dip of dikes formed as the result of tilting at the EPR shortly after their injection. Anisotropy of magnetic susceptibility of dikes provides wellâdefined magmatic flow directions that are dominantly dikeâparallel and shallowly plunging. Corrected to their original EPR orientation, magma flow is interpreted as nearâhorizontal and parallel to the ridge axis. These data provide the first direct evidence from sheeted dikes in ocean crust for alongâaxis magma transport. These results also suggest that lateral transport in dikes is important even at fast spreading ridges where a laterally continuous subaxial magma chamber is present
Qualitative effects on safety and construction materials of 1300 deg F sodium-potassium spray in air and nitrogen
Shielding material evaluation for resistance to sodium potassium fires in air and nitroge
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