12,279 research outputs found
Cost/benefit analysis of advanced materials technologies for future aircraft turbine engines
The materials technologies studied included thermal barrier coatings for turbine airfoils, turbine disks, cases, turbine vanes and engine and nacelle composite materials. The cost/benefit of each technology was determined in terms of Relative Value defined as change in return on investment times probability of success divided by development cost. A recommended final ranking of technologies was based primarily on consideration of Relative Values with secondary consideration given to changes in other economic parameters. Technologies showing the most promising cost/benefits were thermal barrier coated temperature nacelle/engine system composites
Quartz crystal microbalances to measure wind velocity and air humidity
Instrument includes four temperature-sensing, Y-cut quartz crystals to determine wind direction, velocity, and temperature. Two additional AT-cut crystals are used to determine air humidity. Entire signal processing is provided by built-in electronics circuits
Wind sensor
An apparatus is described for sensing the temperature, velocity, and direction of the wind, including four temperature-dependent crystal oscillators spaced about an axis, a heater centered on the axis, and a screen through which the wind blows to pass over the crystals. In one method of operation, the frequency of the oscillators is taken when the heater is not energized, to obtain the temperature of the wind, and the frequencies of the oscillators are taken after the heater is energized to determine the direction and velocity of the wind. When the heater is energized, the wind causes the downwind crystals to achieve a higher temperature than the upwind crystals, and with the magnitude of the difference indicating the velocity of the wind
Identification of putative methanol dehydrogenase (moxF) structural genes in methylotrophs and cloning of moxF genes from Methylococcus capsulatus bath and Methylomonas albus BG8
An open-reading-frame fragment of a Methylobacterium sp. strain AM1 gene (moxF) encoding a portion of the methanol dehydrogenase structural protein has been used as a hybridization probe to detect similar sequences in a variety of methylotrophic bacteria. This hybridization was used to isolate clones containing putative moxF genes from two obligate methanotrophic bacteria, Methylococcus capsulatus Bath and Methylomonas albus BG8. The identity of these genes was confirmed in two ways. A T7 expression vector was used to produce methanol dehydrogenase protein in Escherichia coli from the cloned genes, and in each case the protein was identified by immunoblotting with antiserum against the Methylomonas albus methanol dehydrogenase. In addition, a moxF mutant of Methylobacterium strain AM1 was complemented to a methanol-positive phenotype that partially restored methanol dehydrogenase activity, using broad-host-range plasmids containing the moxF genes from each methanotroph. The partial complementation of a moxF mutant in a facultative serine pathway methanol utilizer by moxF genes from type I and type X obligate methane utilizers suggests broad functional conservation of the methanol oxidation system among gram-negative methylotrophs
Letters between A. G. Reid and William Kerr\u27s secretary
Letters concerning a position in athletic department at Utah Agricultural College
Rehabilitation following rotator cuff repair: A nested qualitative study exploring the perceptions and experiences of participants in a randomised controlled trial
Objective:
To investigate acceptability, barriers to adherence with the interventions, and which outcome measures best reflect the participants’ rehabilitation goals in a pilot and feasibility randomised controlled trial evaluating early patient-directed rehabilitation and standard rehabilitation, including sling immobilisation for four weeks, following surgical repair of the rotator cuff of the shoulder.
Design:
Nested qualitative study.
Setting:
Five English National Health Service Hospitals.
Subjects:
Nineteen patient participants who had undergone surgical repair of the rotator cuff and 10 healthcare practitioners involved in the trial.
Method:
Individual semi-structured interviews. Data were analysed thematically.
Results:
Four themes: (1) Preconceptions of early mobilisation; many participants were motivated to enter the trial for the opportunity of removing their sling and getting moving early. (2) Sling use and movement restrictions; for some, sling use for four weeks was unacceptable and contributed to their pain, rather than relieving it. (3) Tensions associated with early mobilisation; clinical tensions regarding early mobilisation and the perceived risk to the surgical repair were apparent. (4) Processes of running the trial; participants found the trial processes to be largely appropriate and acceptable, but withholding the results of the post-operative research ultrasound scan was contentious.
Conclusion:
Trial processes were largely acceptable, except for withholding results of the ultrasound scan. For some participants, use of the shoulder sling for a prolonged period after surgery was a reported barrier to standard rehabilitation whereas the concept of early mobilisation contributed tension for some healthcare practitioners due to concern about the effect on the surgical repair
Effective Critical Exponents for Dimensional Ccrossover and Quantum Systems from an Environmentally Friendly Renormalization Group
Series for the Wilson functions of an ``environmentally friendly''
renormalization group are computed to two loops, for an vector model, in
terms of the ``floating coupling'', and resummed by the Pad\'e method to yield
crossover exponents for finite size and quantum systems. The resulting
effective exponents obey all scaling laws, including hyperscaling in terms of
an effective dimensionality, {d\ef}=4-\gl, which represents the crossover in
the leading irrelevant operator, and are in excellent agreement with known
results.Comment: 10 pages of Plain Tex, Postscript figures available upon request from
[email protected], preprint numbers THU-93/18, DIAS-STP-93-1
Accuracy threshold for concatenated error detection in one dimension
Estimates of the quantum accuracy threshold often tacitly assume that it is
possible to interact arbitrary pairs of qubits in a quantum computer with a
failure rate that is independent of the distance between them. None of the many
physical systems that are candidates for quantum computing possess this
property. Here we study the performance of a concatenated error-detection code
in a system that permits only nearest-neighbor interactions in one dimension.
We make use of a new message-passing scheme that maximizes the number of errors
that can be reliably corrected by the code. Our numerical results indicate that
arbitrarily accurate universal quantum computation is possible if the
probability of failure of each elementary physical operation is below
approximately 10^{-5}. This threshold is three orders of magnitude lower than
the highest known.Comment: 7 pages, 4 figures, now with error bar
Numerical simulation of transom-stern waves
The flow field generated by a transom-stern hullform is a complex,
broad-banded, three-dimensional phenomenon marked by a large breaking wave.
This unsteady multiphase turbulent flow feature is difficult to study
experimentally and simulate numerically. The results of a set of numerical
simulations, which use the Numerical Flow Analysis (NFA) code, of the flow
around the Model 5673 transom stern at speeds covering both wet- and
dry-transom operating conditions are shown in the accompanying fluid dynamics
video. The numerical predictions for wet-transom and dry-transom conditions are
presented to demonstrate the current state of the art in the simulation of ship
generated breaking waves. The interested reader is referred to Drazen et al.
(2010) for a detailed and comprehensive comparison with experiments conducted
at the Naval Surface Warfare Center Carderock Division (NSWCCD).Comment: Fluid Dynamics Video for 2010 APS Division of Fluid Dynamics Gallery
of Fluid Motion include
Multibody aircraft study, volume 2
The potential benefits of a multibody aircraft when compared to a single body aircraft are presented. The analyses consist principally of a detailed point design analysis of three multibody and one single body aircraft, based on a selected payload of 350,000 kg (771,618 lb), for final aircraft definitions; sensitivity studies to evaluate the effects of variations in payload, wing semispan body locations, and fuel price; recommendations as to the research and technology requirements needed to validate the multibody concept. Two, two body, one, three body, and one single body aircraft were finalized for the selected payload, with DOC being the prime figure of merit. When compared to the single body, the multibody aircraft showed a reduction in DOC by as much as 11.3 percent. Operating weight was reduced up to 14 percent, and fly away cost reductions ranged from 8.6 to 13.4 percent. Weight reduction, hence cost, of the multibody aircraft resulted primarily from the wing bending relief afforded by the bodies being located outboard on the wing
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