3,079 research outputs found
Vibrations measured in the passenger cabins of two jet transport aircraft
Accelerations in the lateral and vertical directions were measured at two locations on the floor of a three-jet-engine aircraft and at two locations on the floor of a two-jet-engine aircraft during a total of 13 flights, each of which included taxiing, takeoff, ascent, cruise, descent, and landing. Accelerations over the frequency range 0 to 25 Hz were recorded continuously on magnetic tape and were synchronized with the VGH recorders in the aircraft so that vibratory accelerations could be correlated with the operating conditions of the aircraft. From the results it was indicated that the methodology used in segmenting the data, which were obtained in a continuous and repetitive manner, contributes to establishing baseline data representative of the flight characteristics of aircraft. Significant differences among flight conductions were found to occur. The lateral accelerations were approximately 15 percent of the vertical accelerations during flight but as much as 50 to 100 percent of the vertical accelerations during ground operations. The variation between the responses of the two aircraft was not statistically significant. The results also showed that more than 90 percent of the vibratory energy measured during flight occurred in the 0- to 3.0-Hz frequency range. Generally, the vibration amplitudes were normally distributed
For Us -- Pasture Renovation Paid Off
Renovating a permanent pasture may double its carrying capacity. And this cost probably will be less than you think
Best Legume for Permanent Pasture
No other pasture legume now available compares with birdsfoot trefoil in abiliity to withstand continuous grazing once it is established. Trefoil does, however, need more attention than other legumes in getting established. Here are some tips from Iowa State College agronomists
Subclustering and Luminous-Dark Matter Segregation in Galaxy Clusters
We have performed a series of N-body experiments on Connection Machine-5 in
order to simulate the formation of galaxy clusters gravitationally dominated by
a massive dark background. In accordance with previous authors we find an
extremely inhomogeneous evolution where subcondensations are continually formed
and merged. The final distribution of galaxies is more centrally condensed than
that of dark matter particles. We have analyzed the origin of this galaxy-dark
matter segregation and also the origin of subclustering leading to this effect.
We have then analysed, analytically and numerically, the dependence of final
segregation on the physical parameters characterizing the model of
protocluster. We also find that such a segregation persists even when inelastic
encounters of dark halos around galaxies are taken into account. We conclude
that this effect cannot be in general avoided in any hierarchical clustering
scenario.Comment: 26 pages plus 13 figures (4 of which, not included, available upon
request to [email protected]), postscript, Preprint OP-9303
A storage and access architecture for efficient query processing in spatial database systems
Due to the high complexity of objects and queries and also due to extremely
large data volumes, geographic database systems impose stringent requirements on their
storage and access architecture with respect to efficient query processing. Performance
improving concepts such as spatial storage and access structures, approximations, object
decompositions and multi-phase query processing have been suggested and analyzed as
single building blocks. In this paper, we describe a storage and access architecture which
is composed from the above building blocks in a modular fashion. Additionally, we incorporate
into our architecture a new ingredient, the scene organization, for efficiently
supporting set-oriented access of large-area region queries. An experimental performance
comparison demonstrates that the concept of scene organization leads to considerable
performance improvements for large-area region queries by a factor of up to 150
Stability of spherical stellar systems II : Numerical results
We have performed a series of high resolution N-body experiments on a
Connection Machine CM-5 in order to study the stability of collisionless
self-gravitating spherical systems. We interpret our results in the framework
of symplectic mechanics, which provides the definition of a new class of
particular perturbations: The preserving perturbations, which are a
generalization of the radial ones. Using models defined by the Ossipkov-Merritt
algorithm, we show that the stability of a spherical anisotropic system is
directly related to the preserving or non-preserving nature of the
perturbations acting on the system. We then generalize our results to all
spherical systems. Since the ``isotropic component'' of the linear variation of
the distribution function cannot be used to predict the stability or
instability of a spherical system, we propose a more useful stability parameter
which is derived from the ``anisotropic'' component of the linear variation.Comment: uuencoded gzip compressed postscript file containing 14 pages,
accepted for publication in MNRA
Renovation Can Double Pasture Production
Renovation is often recommended as the best method for improving pastures. Results of long-time studies are now available where renovated pastures have been compared with unimproved pastures in southern Iowa
Epidemiology of coagulase-negative staphylococci intramammary infection in dairy cattle and the effect of bacteriological culture misclassification
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