39,132 research outputs found
Aeroplane design study STOL airliner (A71). Part 1- configuration description and data
The interest in STOL airliners was reflected in the
choice of a 100-118 passenger short range aircraft of this
type as the 1971 design project. In addition to the use of
the study for detailed investigation by the students of
Aircraft Design it also served as the basis for an
investigation of the low speed lift and control problems
of STOL aircraft.
This report is concerned with a description of the
configuration adopted and specification of geometric and
aerodynamic data. As such it is the first part of the
complete reporting of the investigation, subsequent parts
being concerned with the more detailed work.
The aircraft was designed to operate from 2000 ft long
single runways and have a cruising speed of up to 11 - 0.83
at 30,000 ft altitude. The estimated gross weight is
115,000 lb and when landing at 100,000 lb weight the approach
speed is 79 knots. The high lift coefficients necessitated
by this are obtained either by externally blown jet flaps or
an augmenter wing arrangement
Equality of P-partition generating functions
To every labeled poset (P,\omega), one can associate a quasisymmetric
generating function for its (P,\omega)-partitions. We ask: when do two labeled
posets have the same generating function? Since the special case corresponding
to skew Schur function equality is still open, a complete classification of
equality among (P,\omega) generating functions is likely too much to expect.
Instead, we determine necessary conditions and separate sufficient conditions
for two labeled posets to have equal generating functions. We conclude with a
classification of all equalities for labeled posets with small numbers of
linear extensions.Comment: 24 pages, 19 figures. Incorporates minor changes suggested by the
referees. To appear in Annals of Combinatoric
ELECTRONIC MARKET USE BY OKLAHOMA LAMB PRODUCERS
Socioeconomic and production system characteristics of a sample of Oklahoma sheep producers were employed to examine the decision to use or not use an electronic market for slaughter lambs. Producer attributes that influence electronic market use were identified with qualitative choice models. The results help identify characteristics of electronic markets which influence their success. The findings also have implications about educational opportunities for cooperative extension.Livestock Production/Industries, Marketing,
A qualitative exploration of consumers’ perceived impacts, behavioural reactions, and future reflections of the EU Tobacco Products Directive (2017) as applied to electronic cigarettes
Background: Electronic cigarette regulations included in the Tobacco Products Directive (TPD), Article 20, implemented in Europe by May 2017, aimed to improve safety for e-cigarette consumers, and prevent uptake among non-smokers, particularly young people. Before implementation, there were significant concerns from consumers, industry, and some in the scientific community about the potential negative impact of the TPD on people using e-cigarettes to stay stopped from smoking. To date, there is limited evidence on how the TPD has affected consumers. This study aimed to add insight into how consumers perceived and experienced the regulations. Methods: Qualitative data, collected between March 2018 and March 2019, relating to participant views of the TPD were extracted from 160 interviews/extended surveys of e-cigarette consumers as part of a wider study into e-cigarette use trajectories (ECtra study). Data were thematically analysed. Results: Awareness of the TPD amongst consumers was not universal. Participants’ smoking behaviour did not appear to be influenced by the legislation. Participants were reassured by manufacturing regulations and requirements for ingredients labels. Participants responded negatively to changes perceived to cause inconvenience and extra plastic waste. The product restrictions prompted some participants to purchase non-compliant products illegally, potentially putting their safety at risk. Conclusions: E-cigarette regulation should focus on ensuring product safety. Raising awareness of the TPD amongst consumers and smokers could be beneficial
Aeroplane design study STOL airliner (A71). Part 3- low speed lift and control
The potential application of advanced forms of aircraft
control to civil operation appears to be capable of being split
into two areas. First, those aircraft which are very large,
whose rotary inertia tends to reduce the effectiveness of
conventional controls. Second, those aircraft whose
specification dictates that the aeroplane be flown at very low
speed. Again conventional controls become inefficient due to
decreased aerodynamic efficiency.
The second category of aircraft has been considered in
the form of an STOL aircraft. The control problems of an STOL
aircraft with a 2000 ft runway capability (Ref.10) have been
examined. It has been found that the aircraft is unstable
and could require autostabilisation. None of the conventional
controls were satisfactory and each required augmentation.
The single strip crosswind requirement penalises the design
most heavily since this requires over half of the extra control
power necessary. The total augmentation for blowing air
amounts to an equivalent thrust of approximately 6700 lb.
This is equivalent to 11.5 per cent of the total installed
aircraft thrust
Saving Planetary Systems: Dead Zones & Planetary Migration
The tidal interaction between a disk and a planet leads to the planet's
migration. A long-standing question regarding this mechanism is how to stop the
migration before planets plunge into their central stars. In this paper, we
propose a new, simple mechanism to significantly slow down planet migration,
and test the possibility by using a hybrid numerical integrator to simulate the
disk-planet interaction. The key component of the scenario is the role of low
viscosity regions in protostellar disks known as dead zones, which affect
planetary migration in two ways. First of all, it allows a smaller-mass planet
to open a gap, and hence switch the faster type I migration to the slower type
II migration. Secondly, a low viscosity slows down type II migration itself,
because type II migration is directly proportional to the viscosity. We present
numerical simulations of planetary migration by using a hybrid symplectic
integrator-gas dynamics code. Assuming that the disk viscosity parameter inside
the dead zone is (alpha=1e-4-1e-5), we find that, when a low-mass planet (e.g.
1-10 Earth masses) migrates from outside the dead zone, its migration is
stopped due to the mass accumulation inside the dead zone. When a low-mass
planet migrates from inside the dead zone, it opens a gap and slows down its
migration. A massive planet like Jupiter, on the other hand, opens a gap and
slows down inside the dead zone, independent of its initial orbital radius. The
final orbital radius of a Jupiter mass planet depends on the dead zone's
viscosity. For the range of alpha's noted above, this can vary anywhere from 7
AU, to an orbital radius of 0.1 AU that is characteristic of the hot Jupiters.Comment: 38 pages, 14 figures, some changes in text and figures, accepted for
publication in Ap
Mapping and Characterizing Subtidal Oyster Reefs Using Acoustic Techniques, Underwater Videography and Quadrat Counts
Populations of the eastern oyster Crassostrea virginica have been in long-term decline in most areas. A major hindrance to effective oyster management has been lack of a methodology for accurately and economically obtaining data on their distribution and abundance patterns. Here, we describe early results from studies aimed at development of a mapping and monitoring protocol involving acoustic techniques, underwater videography, and destructive sampling (excavated quadrats). Two subtidal reefs in Great Bay, New Hampshire, were mapped with side-scan sonar and with videography by systematically imaging multiple sampling cells in a grid covering the same areas. A single deployment was made in each cell, and a 5-10-s recording was made of a 0.25-m2 area; the location of each image was determined using a differential global position system. A still image was produced for each of the cells and all (n = 40 or 44) were combined into a single photomontage overlaid onto a geo-referenced base map for each reef using Arc View geographic information system. Quadrat (0.25 m2 ) samples were excavated from 9 or 10 of the imaged areas on each reef, and all live oysters were counted and measured. Intercomparisons of the acoustic, video, and quadrat data suggest: (1) acoustic techniques and systematic videography can readily delimit the boundaries of oyster reefs; (2) systematic videography can yield quantitative data on shell densities and information on reef structure; and (3) some combination of acoustics, systematic videography, and destructive sampling can provide spatially detailed information on oyster reef characteristics
IMPACTS FROM CAPTIVE SUPPLIES ON FED CATTLE TRANSACTION PRICES
Increased use of noncash-price procurement methods has concerned cattlemen for the past several years. This research estimated impacts of captive supplies on transaction prices for fed cattle. Negative relationships were found between transaction prices and percentage deliveries from the inventory of forward contracted and marketing agreement cattle. However, impacts from the absolute size of the total captive supply inventory were not significant. Price differences were found among procurement methods with forward contract prices being much lower. On balance, captive supplies had small but often negative effects on fed cattle transaction prices.Demand and Price Analysis,
A novel laser ranging system for measurement of ground-to-satellite distances
A technique was developed for improving the precision of laser ranging measurements of ground-to-satellite distances. The method employs a mode-locked laser transmitter and utilizes an image converter tube equipped with deflection plates in measuring the time of flight of the laser pulse to a distant retroreflector and back. Samples of the outgoing and returning light pulses are focussed on the photocathode of the image converter tube, whose deflection plates are driven by a high-voltage 120 MHz sine wave derived from a very stable oscillator. From the relative positions of the images produced at the output phosphor by the two light pulses, it is possible to make a precise determination of the fractional amount by which the time of flight exceeds some large integral multiple of the period of the deflection sinusoid
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