51,117 research outputs found
A solvable non-conservative model of Self-Organized Criticality
We present the first solvable non-conservative sandpile-like critical model
of Self-Organized Criticality (SOC), and thereby substantiate the suggestion by
Vespignani and Zapperi [A. Vespignani and S. Zapperi, Phys. Rev. E 57, 6345
(1998)] that a lack of conservation in the microscopic dynamics of an SOC-model
can be compensated by introducing an external drive and thereby re-establishing
criticality. The model shown is critical for all values of the conservation
parameter. The analytical derivation follows the lines of Broeker and
Grassberger [H.-M. Broeker and P. Grassberger, Phys. Rev. E 56, 3944 (1997)]
and is supported by numerical simulation. In the limit of vanishing
conservation the Random Neighbor Forest Fire Model (R-FFM) is recovered.Comment: 4 pages in RevTeX format (2 Figures) submitted to PR
Nonuniversal Critical Spreading in Two Dimensions
Continuous phase transitions are studied in a two dimensional nonequilibrium
model with an infinite number of absorbing configurations. Spreading from a
localized source is characterized by nonuniversal critical exponents, which
vary continuously with the density phi in the surrounding region. The exponent
delta changes by more than an order of magnitude, and eta changes sign. The
location of the critical point also depends on phi, which has important
implications for scaling. As expected on the basis of universality, the static
critical behavior belongs to the directed percolation class.Comment: 21 pages, REVTeX, figures available upon reques
Investigation of thermionic energy conversion final report, 9 jul. - 9 sep. 1962
Refractory ceramic oxide for thermionic diode
White primer permits a corrosion-resistant coating of minimum weight
White primer for coating 2219 aluminum alloy supplies a base for a top coating of enamel. A formulation of pigments and vehicle results in a primer with high corrosion resistance and minimum film thickness
Phase coherence length and quantum interference patterns at step edges
The accepted approximation used to describe quantum interference patterns at
steps is shown to be incorrect. As a result, electron lifetimes determined
using it are in error by a factor 2.Comment: 3 pages, 1 figur
Evaluation of initial collector field performance at the Langley Solar Building Test Facility
The thermal performance of the solar collector field for the NASA Langley Solar Building Test Facility is given for October 1976 through January 1977. A 1,180 square meter solar collector field with seven collector designs helped to provide hot water for the building heating system and absorption air conditioner. The collectors were arranged in 12 rows with nominally 51 collectors per row. Heat transfer rates for each row were calculated and recorded along with sensor, insolation, and weather data every five minutes using a minicomputer. The agreement between the experimental and predicted collector efficiencies was generally within five percentage points
Fear and its implications for stock markets
The value of stocks, indices and other assets, are examples of stochastic
processes with unpredictable dynamics. In this paper, we discuss asymmetries in
short term price movements that can not be associated with a long term positive
trend. These empirical asymmetries predict that stock index drops are more
common on a relatively short time scale than the corresponding raises. We
present several empirical examples of such asymmetries. Furthermore, a simple
model featuring occasional short periods of synchronized dropping prices for
all stocks constituting the index is introduced with the aim of explaining
these facts. The collective negative price movements are imagined triggered by
external factors in our society, as well as internal to the economy, that
create fear of the future among investors. This is parameterized by a ``fear
factor'' defining the frequency of synchronized events. It is demonstrated that
such a simple fear factor model can reproduce several empirical facts
concerning index asymmetries. It is also pointed out that in its simplest form,
the model has certain shortcomings.Comment: 5 pages, 5 figures. Submitted to the Proceedings of Applications of
Physics in Financial Analysis 5, Turin 200
Development of corrosion inhibiting white primer final report, 26 jun. - 30 nov. 1964
Corrosion resisting white prime
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