11,364 research outputs found
Indexing with coded deltas—a data compaction technique
The paper describes the coded delta scheme, which is one of the methods used by the Census Research Unit, University of Durham, for compacting the 1971 U.K. census data. It evaluates the merits and limitations of the technique in relation to the characteristics of the data set and other techniques available for compact encoding of numeric and string data
Bridges in three-dimensional granular packings: experiments and simulations
In this letter, we present the first experimental study of bridge structures
in three-dimensional dry granular packings. When bridges are small, they are
predominantly 'linear', and have an exponential size distribution. Larger,
predominantly 'complex' bridges, are confirmed to follow a power-law size
distribution. Our experiments, which use X-ray tomography, are in good
agreement with the simulations presented here, for the distribution of sizes,
end-to-end lengths, base extensions and orientations of predominantly linear
bridges. Quantitative differences between the present experiment and earlier
simulations suggest that packing fraction is an important determinant of bridge
structure.Comment: 6 pages, 7 figures, accepted by EPL (2013
Study of spin-scan imaging for outer planets missions
The constraints that are imposed on the Outer Planet Missions (OPM) imager design are of critical importance. Imager system modeling analyses define important parameters and systematic means for trade-offs applied to specific Jupiter orbiter missions. Possible image sequence plans for Jupiter missions are discussed in detail. Considered is a series of orbits that allow repeated near encounters with three of the Jovian satellites. The data handling involved in the image processing is discussed, and it is shown that only minimal processing is required for the majority of images for a Jupiter orbiter mission
Clay fine fissuring monitoring using miniature geo-electrical resistivity arrays
Abstract This article describes a miniaturised electrical imaging (resistivity tomography) technique to map the cracking pattern of a clay model. The clay used was taken from a scaled flood embankment built to study the fine fissuring due to desiccation and breaching process in flooding conditions. The potential of using a miniature array of electrodes to follow the evolution of the vertical cracks and number them during the drying process was explored. The imaging technique generated two-dimensional contoured plots of the resistivity distribution within the model before and at different stages of the desiccation process. The change in resistivity associated with the widening of the cracks were monitored as a function of time. Experiments were also carried out using a selected conductive gel to slow down the transport process into the cracks to improve the scanning capabilities of the equipment. The main vertical clay fissuring network was obtained after inversion of the experimental resistivity measurements and validated by direct observations
Experiments in randomly agitated granular assemblies close to the jamming transition
We present here the preliminary results obtained for two experiments on
randomly agitated granular assemblies using a novel way of shaking. First we
discuss the transport properties of a 2D model system undergoing classical
shaking that show the importance of large scale dynamics for this type of
agitation and offer a local view of the microscopic motions of a grain. We then
develop a new way of vibrating the system allowing for random accelerations
smaller than gravity. Using this method we study the evolution of the free
surface as well as results from a light scattering method for a 3D model
system. The final aim of these experiments is to investigate the ideas of
effective temperature on the one hand as a function of inherent states and on
the other hand using fluctuation dissipation relations.Comment: Contribution to the volume "Unifying Concepts in Granular Media and
Glasses", edt.s A. Coniglio, A. Fierro, H.J. Herrmann and M. Nicodem
Fuzzy simulation of forest road surface parameters
The problem of construction of forest roads with the use of local low-strength substandard materials and industrial waste is considered. To solve the problem, the primary task is to develop a method for estimating the parameters of road surfaces taking into account the conditions of uncertainties in the data. This technique allows us to reasonably clarify some of the regulatory parameters and improve the technology of construction of forest roads, which was the goal of the work. To formalize the task, experimental studies were performed and on the basis of these results, the statement of the task of fuzzy derivation of the function for estimating the bearing capacity of the coating was performed. The synthesis of the output function is performed by means of Matlab. © 2019 IOP Publishing Ltd. All rights reserved
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