25,187 research outputs found
Flight tests on a torquemeter installed on Gipsy Queen 71 engine on dove aircraft
The torquemeter failed at 178 hrs. 50 minutes flying.
Torquemeter powers compared with engine powers deduced from maker's
curves give the following results:
1) At low BHP readings the torquemeter tends to over-read
2) At high BHP readings the torquemeter tends to under-read
Pilot reliability investigation: final report on agreement PD/28/035/ADM
The feasibility of constructing a device to give a measure
of pilot reliability has been investigated. A rig to meet the proposals
made by BLEU has been designed and basic circuits constructed and tested
for accuracy of operation and reliability. An estimate of the materials
required and the cost of construction has been made.
The rig has been designed to be subject operated for twentyfour
tests before requiring attention, and devices have been incorporated
to indicate unserviceability and prevent operation if starting cond4 tions
are not correct.
Switching sequences typical of the final period of an autoland
approach are demanded verbally by magnetic tape replay equipment and the
performance of the subject measured. The test consists of two phases;
a preparatory or "unloaded" phase, and a "loaded" phase during which
the subject performs a tracking task in addition to the switching
sequence. The performance of the subject is recorded on veeder counters
for both phases of the test in the form of actions demanded, actions
taken and actions taken during a memory period. A measure of performance
of the tracking task is also given by veeder counter
Passive and active seismic isolation for gravitational radiation detectors and other instruments
Some new passive and active methods for reducing the effects of seismic disturbances on suspended masses are described, with special reference to gravitational radiation detectors in which differential horizontal motions of two or more suspended test masses are monitored. In these methods it is important to be able to determine horizontal seismic accelerations independent of tilts of the ground. Measurement of changes in inclination of the suspension wire of a test mass, relative to a direction defined by a reference arm of long period of oscillation, makes it possible to carry this out over the frequency range of interest for earth-based gravitational radiation detectors. The signal obtained can then be used to compensate for the effects of seismic disturbances on the test mass if necessary. Alternatively the signal corresponding to horizontal acceleration can be used to move the point from which the test mass is suspended in such a way as to reduce the effect of the seismic disturbance and also damp pendulum motions of the suspended test mass. Experimental work with an active anti-seismic system of this type is described
On the pathwidth of almost semicomplete digraphs
We call a digraph {\em -semicomplete} if each vertex of the digraph has at
most non-neighbors, where a non-neighbor of a vertex is a vertex such that there is no edge between and in either direction.
This notion generalizes that of semicomplete digraphs which are
-semicomplete and tournaments which are semicomplete and have no
anti-parallel pairs of edges. Our results in this paper are as follows. (1) We
give an algorithm which, given an -semicomplete digraph on vertices
and a positive integer , in time either
constructs a path-decomposition of of width at most or concludes
correctly that the pathwidth of is larger than . (2) We show that there
is a function such that every -semicomplete digraph of pathwidth
at least has a semicomplete subgraph of pathwidth at least .
One consequence of these results is that the problem of deciding if a fixed
digraph is topologically contained in a given -semicomplete digraph
admits a polynomial-time algorithm for fixed .Comment: 33pages, a shorter version to appear in ESA 201
Cylindrical, periodic surface lattice â theory, dispersion analysis, and experiment
A two-dimensional surface lattice of cylindrical topology obtained via perturbing the inner surface of a cylinder is considered. Periodic perturbations of the surface lead to observation of high-impedance, dielectric-like media and resonant coupling of surface and non-propagating volume fields. This allows synthesis of tailored-for-purpose "coating" material with dispersion suitable, for instance, to mediate a Cherenkov type interaction. An analytical model of the lattice is discussed and coupled-wave equations are derived. Variations of the lattice dispersive properties with variation of parameters are shown, illustrating the tailoring of the structure's electromagnetic properties. Experimental results are presented showing agreement with the theoretical model
Tweed in Martensites: A Potential New Spin Glass
We've been studying the ``tweed'' precursors above the martensitic transition
in shape--memory alloys. These characteristic cross--hatched modulations occur
for hundreds of degrees above the first--order shape--changing transition. Our
two--dimensional model for this transition, in the limit of infinite elastic
anisotropy, can be mapped onto a spin--glass Hamiltonian in a random field. We
suggest that the tweed precursors are a direct analogy of the spin--glass
phase. The tweed is intermediate between the high--temperature cubic phase and
the low--temperature martensitic phase in the same way as the spin--glass phase
can be intermediate between ferromagnet and antiferromagnet.Comment: 18 pages and four figures (included
Risk factors associated with brucella seropositivity in sheep and goats in Duhok Province, Iraq
Sera from 432 small ruminants (335 sheep and 97 goats) from 72 farms in Duhok Province, northern Iraq, were collected to investigate risk factors associated with brucellosis seropositivity. Serum samples were tested using the Rose Bengal test (RBT) and an indirect enzyme-linked immunosorbent assay (iELISA). Using parallel interpretation, RBT and iELISA results showed that 31.7% (95% confidence interval (CI): 26.1, 36.3) of sheep and 34.0% (95% CI: 24.7, 44.3) of goats had antibodies against Brucella in the study area. A random-effects multivariable logistic regression model indicated that a higher chance of being seropositive (odds ratio (OR) = 1.7; 95% 1.4; 2.2) was associated with an increase in the age of animals. The odds of Brucella seropositivity in flocks where sheep and goats grazed together was 2.0 times higher (95% CI: 1.08; 3.9) compared to flocks where sheep and goats grazed separately. The odds of Brucella seropositivity in small ruminants was 2.2 higher (95% CI: 1.2; 4.3) for animals originating from farms with a history of goat abortion in the preceding 12 months. In contrast, for every 1000 Iraqi Dinars (~0.85 US Dollar) spent by the farmers on control of Brucella in their flocks, the odds of Brucella seropositivity decreased significantly (OR = 0.9, p-value = 0.021). The final model also indicated significant differences in Brucella seropositivity between the different districts of Duhok Province. This study provides a contribution to the epidemiology of brucellosis in small ruminants in northern Iraq
Information requirements for enterprise systems
In this paper, we discuss an approach to system requirements engineering, which is based on using models of the responsibilities assigned to agents in a multi-agency system of systems. The responsibility models serve as a basis for identifying the stakeholders that should be considered in establishing the requirements and provide a basis for a structured approach, described here, for information requirements elicitation. We illustrate this approach using a case study drawn from civil emergency management
Influence of 100% and 40% oxygen on penumbral blood flow, oxygen level, and T2*-weighted MRI in a rat stroke model
Accurate imaging of the ischemic penumbra is a prerequisite for acute clinical stroke research. T2* magnetic resonance imaging (MRI) combined with an oxygen challenge (OC) is being developed to detect penumbra based on changes in blood deoxyhemoglobin. However, inducing OC with 100% O2 induces sinus artefacts on human scans and influences cerebral blood flow (CBF), which can affect T2* signal. Therefore, we investigated replacing 100% O2 OC with 40% O2 OC (5âminutes 40% O2 versus 100% O2) and determined the effects on blood pressure (BP), CBF, tissue pO2, and T2* signal change in presumed penumbra in a rat stroke model. Probes implanted into penumbra and contralateral cortex simultaneously recorded pO2 and CBF during 40% O2 (n=6) or 100% O2 (n=8) OC. In a separate MRI study, T2* signal change to 40% O2 (n=6) and 100% O2 (n=5) OC was compared. Oxygen challenge (40% and 100% O2) increased BP by 8.2% and 18.1%, penumbra CBF by 5% and 15%, and penumbra pO2 levels by 80% and 144%, respectively. T2* signal significantly increased by 4.56%±1.61% and 8.65%±3.66% in penumbra compared with 2.98%±1.56% and 2.79%±0.66% in contralateral cortex and 1.09%±0.82% and â0.32%±0.67% in ischemic core, respectively. For diagnostic imaging, 40% O2 OC could provide sufficient T2* signal change to detect penumbra with limited influence in BP and CBF
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