638 research outputs found
Investigation of slosh anomaly in Apollo lunar module propellant gage
Analysis of propellant sloshing in lunar module during Apollo 14 flight and resultant erroneous indication of low level of propellan
Some space shuttle tile/strain-isolator-pad sinusoidal vibration tests
Vibration tests were performed on the tile/strain-isolator-pad system used as thermal protection for the space shuttle orbiter. Experimental data on normal and in-plane vibration response and damping properties are presented. Three test specimens exhibited shear type motion during failures that occurred in the tile near the tile/strain-isolator-pad bond-line. A dynamic instability is described which has large in-plane motion at a frequency one-half that of the nominal driving frequency. Analysis shows that this phenomenon is a parametric response
Modeling, Analysis, and Optimization Issues for Large Space Structures
Topics concerning the modeling, analysis, and optimization of large space structures are discussed including structure-control interaction, structural and structural dynamics modeling, thermal analysis, testing, and design
Remote sensing study of land use and sedimentation in the Ross Barnett Reservoir, Jackson, Mississippi area
This multi-year study is aimed at focusing on the recognition of sediment and other affluents in a selected area of the Ross Barnett Reservoir. The principle objectives are the determination of land use types, effect of land use on erosion, and the correlation of sediment with land use in the area. The I2S multi-band imagery was employed in conjunction with ground truth data for both water and land use studies. The selected test site contains approximately forty square miles including forest, open land, and water in addition to residential and recreational areas
Are the Tails of Percolation Thresholds Gaussians ?
The probability distribution of percolation thresholds in finite lattices
were first believed to follow a normal Gaussian behaviour. With increasing
computer power and more efficient simulational techniques, this belief turned
to a stretched exponential behaviour, instead. Here, based on a further
improvement of Monte Carlo data, we show evidences that this question is not
yet answered at all.Comment: 7 pages including 3 figure
Cut generation for an employee timetabling problem
Motivated by an industrial application, we study a specific employee timetabling problem. Several investigations are being conducted: a lower bound by Lagrangian relaxation, a heuristic based on a cut generation process and an exact method by Benders decomposition. Experimental results on real and generated instances are reported
Réductions de domaine lagrangiennes pour le problème de minimisation des pénalités d'avance et de retard ponderées sur une machine
Cet article présente de nouvelles règles d\u27élimination pour le problème de minimisation des pénalités d\u27avance et de retard sur une machine, avec ousans dates de disponibilité. Ces règles, basées sur une décomposition lagrangienne, permettent de réduire considérablement les fenêtres d\u27exécution des tâches, et, ainsi, d\u27utiliser efficacement d\u27autres règles d\u27élimination classiques. Les expérimentations montrent que des instances comportant jusqu\u27à 70 tâches sans date de disponiblité, et 40 tâches avec dates de disponibilité, peuvent être résolues optimalement en une heure, en intégrant ces propriétés dans un branch-and-bound
Efficient Monte Carlo algorithm and high-precision results for percolation
We present a new Monte Carlo algorithm for studying site or bond percolation
on any lattice. The algorithm allows us to calculate quantities such as the
cluster size distribution or spanning probability over the entire range of site
or bond occupation probabilities from zero to one in a single run which takes
an amount of time scaling linearly with the number of sites on the lattice. We
use our algorithm to determine that the percolation transition occurs at
occupation probability 0.59274621(13) for site percolation on the square
lattice and to provide clear numerical confirmation of the conjectured
4/3-power stretched-exponential tails in the spanning probability functions.Comment: 8 pages, including 3 postscript figures, minor corrections in this
version, plus updated figures for the position of the percolation transitio
A fast Monte Carlo algorithm for site or bond percolation
We describe in detail a new and highly efficient algorithm for studying site
or bond percolation on any lattice. The algorithm can measure an observable
quantity in a percolation system for all values of the site or bond occupation
probability from zero to one in an amount of time which scales linearly with
the size of the system. We demonstrate our algorithm by using it to investigate
a number of issues in percolation theory, including the position of the
percolation transition for site percolation on the square lattice, the
stretched exponential behavior of spanning probabilities away from the critical
point, and the size of the giant component for site percolation on random
graphs.Comment: 17 pages, 13 figures. Corrections and some additional material in
this version. Accompanying material can be found on the web at
http://www.santafe.edu/~mark/percolation
Scale-invariant universal crossing probability in one-dimensional diffusion-limited coalescence
The crossing probability in the time direction is defined for an
off-equilibrium reaction-diffusion system as the probability that the system of
size L is still active at time t, in the finite-size scaling limit. Exact
results are obtained for the diffusion-limited coalescence problem in 1+1
dimensions with periodic and free boundary conditions using empty interval
methods. The crossing probability is a scale-invariant universal function of an
effective aspect ratio, L^2/Dt, which is the natural scaling variable for this
strongly anisotropic system.Comment: 12 pages, 2 figure
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