11,268 research outputs found
Condensation in an Economic Model with Brand Competition
We present a linear agent based model on brand competition. Each agent
belongs to one of the two brands and interacts with its nearest neighbors. In
the process the agent can decide to change to the other brand if the move is
beneficial. The numerical simulations show that the systems always condenses
into a state when all agents belong to a single brand. We study the
condensation times for different parameters of the model and the influence of
different mechanisms to avoid condensation, like anti monopoly rules and brand
fidelity.Comment: Accepted in: International Journal of Modern Physics
Evaluation of methods for seismic analysis of mixed-oxide fuel fabrication plants
Guidelines are needed for selecting appropriate methods of structural analyses to evaluate the seismic hazard of mixed-oxide fuel fabrication plants. This study examines the different available methods and their applicability to fabrication plants. These results should provide a basis for establishing guidelines recommending methods of analysis to ensure safe design against seismic hazards. Using the Westinghouse Recycle Fuels Plant as representative of future mixed-oxide fuel fabrication plants, critical structures and equipment (systems, components, and piping/ducting) were identified. These included the manufacturing building and 11 different pieces of equipment. After examination of the dynamic response characteristics of the building and the different methods available to analyze equipment, appropriate methods of analyses were recommended. Because critical equipment analysis and test methods generally use floor-response spectra as their seismic input loading, several methods used to generate floor spectra were also examined. These include the time-history approach and the Kapur and Biggs approximate methods. The examination included the effect of site characteristics and both horizontal and vertical structural response. (auth
Space-Time Approach to Scattering from Many Body Systems
We present scattering from many body systems in a new light. In place of the
usual van Hove treatment, (applicable to a wide range of scattering processes
using both photons and massive particles) based on plane waves, we calculate
the scattering amplitude as a space-time integral over the scattering sample
for an incident wave characterized by its correlation function which results
from the shaping of the wave field by the apparatus. Instrument resolution
effects - seen as due to the loss of correlation caused by the path differences
in the different arms of the instrument are automatically included and analytic
forms of the resolution function for different instruments are obtained. The
intersection of the moving correlation volumes (those regions where the
correlation functions are significant) associated with the different elements
of the apparatus determines the maximum correlation lengths (times) that can be
observed in a sample, and hence, the momentum (energy) resolution of the
measurement. This geometrical picture of moving correlation volumes derived by
our technique shows how the interaction of the scatterer with the wave field
shaped by the apparatus proceeds in space and time. Matching of the correlation
volumes so as to maximize the intersection region yields a transparent,
graphical method of instrument design. PACS: 03.65.Nk, 3.80 +r, 03.75, 61.12.BComment: Latex document with 6 fig
A thermal model for adaptive competition in a market
New continuous and stochastic extensions of the minority game, devised as a
fundamental model for a market of competitive agents, are introduced and
studied in the context of statistical physics. The new formulation reproduces
the key features of the original model, without the need for some of its
special assumptions and, most importantly, it demonstrates the crucial role of
stochastic decision-making. Furthermore, this formulation provides the exact
but novel non-linear equations for the dynamics of the system.Comment: 4 RevTeX pages, 3 EPS figures. Revised versio
Enhanced winnings in a mixed-ability population playing a minority game
We study a mixed population of adaptive agents with small and large memories,
competing in a minority game. If the agents are sufficiently adaptive, we find
that the average winnings per agent can exceed that obtainable in the
corresponding pure populations. In contrast to the pure population, the average
success rate of the large-memory agents can be greater than 50 percent. The
present results are not reproduced if the agents are fed a random history,
thereby demonstrating the importance of memory in this system.Comment: 9 pages Latex + 2 figure
Structural fumigation efficacy against Tribolium castaneum in flour mills
Structural fumigations of food processing plants to manage stored-product insects have been a major component of pest management programs, but limited information on field efficacy is available. Efficacy, based on pheromone trapping data, consists of initial reduction in captures after treatment and recovery in trap captures over time after treatment (i.e., rebound). Patterns of Tribolium castaneum reduction and rebound were evaluated after 21 fumigations in two flour mills. Influence of time of year fumigation occurred, environmental conditions, and impact of other pest management tactics on efficacy was determined as well. Information generated can be used to guide fumigation decisions, including the development of risk thresholds for levels of pheromone trap captures. Keywords: Tribolium castaneum, Fumigation, Flour mills, Efficacy, Methyl bromid
Stress and Strain in Flat Piling of Disks
We have created a flat piling of disks in a numerical experiment using the
Distinct Element Method (DEM) by depositing them under gravity. In the
resulting pile, we then measured increments in stress and strain that were
associated with a small decrease in gravity. We first describe the stress in
terms of the strain using isotropic elasticity theory. Then, from a
micro-mechanical view point, we calculate the relation between the stress and
strain using the mean strain assumption. We compare the predicted values of
Young's modulus and Poisson's ratio with those that were measured in the
numerical experiment.Comment: 9 pages, 1 table, 8 figures, and 2 pages for captions of figure
Derivative spectroscopy and the continuous relaxation spectrum
Derivative spectroscopy is conventionally understood to be a collection of techniques for extracting fine structure from spectroscopic data by means of numerical differentiation. In this paper we extend the conventional interpretation of derivative spectroscopy with a view to recovering the continuous relaxation spectrum of a viscoelastic material from oscillatory shear data. To achieve this, the term “spectroscopic data” is allowed to include spectral data which have been severely broadened by the action of a strong low-pass filter. Consequently, a higher order of differentiation than is usually encountered in conventional derivative spectroscopy is required. However, by establishing a link between derivative spectroscopy and wavelet decomposition, high-order differentiation of oscillatory shear data can be achieved using specially constructed wavelet smoothing. This method of recovery is justified when the reciprocal of the Fourier transform of the filter function (convolution kernel) is an entire function, and is particularly powerful when the associated Maclaurin series converges rapidly. All derivatives are expressed algebraically in terms of scaling functions and wavelets of different scales, and the recovered relaxation spectrum is expressible in analytic form. An important feature of the method is that it facilitates local recovery of the spectrum, and is therefore appropriate for real scenarios where the oscillatory shear data is only available for a finite range of frequencies. We validate the method using synthetic data, but also demonstrate its use on real experimental data
Dynamical quenching and annealing in self-organization multiagent models
We study the dynamics of a generalized Minority Game (GMG) and of the Bar
Attendance Model (BAM) in which a number of agents self-organize to match an
attendance that is fixed externally as a control parameter. We compare the
usual dynamics used for the Minority Game with one for the BAM that makes a
better use of the available information. We study the asymptotic states reached
in both frameworks. We show that states that can be assimilated to either
thermodynamic equilibrium or quenched configurations can appear in both models,
but with different settings. We discuss the relevance of the parameter that
measures the value of the prize for winning in units of the fine for losing. We
also provide an annealing protocol by which the quenched configurations of the
GMG can progressively be modified to reach an asymptotic equlibrium state that
coincides with the one obtained with the BAM.Comment: around 20 pages, 10 figure
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