11,896 research outputs found
Synchronization and Stability in Noisy Population Dynamics
We study the stability and synchronization of predator-prey populations
subjected to noise. The system is described by patches of local populations
coupled by migration and predation over a neighborhood. When a single patch is
considered, random perturbations tend to destabilize the populations, leading
to extinction. If the number of patches is small, stabilization in the presence
of noise is maintained at the expense of synchronization. As the number of
patches increases, both the stability and the synchrony among patches increase.
However, a residual asynchrony, large compared with the noise amplitude, seems
to persist even in the limit of infinite number of patches. Therefore, the
mechanism of stabilization by asynchrony recently proposed by R. Abta et. al.,
combining noise, diffusion and nonlinearities, seems to be more general than
first proposed.Comment: 3 pages, 3 figures. To appear in Phys. Rev.
Belief heterogeneity and survival in incomplete markets
In complete markets economies (Sandroni [16]), or in economies with Pareto optimal outcomes (Blume and Easley [10]), the market selection hypothesis holds, as long as traders have identical discount factors. Traders who survive must have beliefs that merge with the truth. We show that in incomplete markets, regardless of traders’ discount factors, the market selects for a range of beliefs, at least some of which do not merge with the truth. We also show that impatient traders with incorrect beliefs can survive and that these incorrect beliefs impact prices. These beliefs may be chosen so that they are far from the truth
Gestão do Laboratório de Análise de Sementes da Embrapa Milho e Sorgo.
A implantação do sistema de gestão da qualidade, composto de Manual da Qualidade com todos os requisitos da direção e de requisitos técnicos, segundo a norma ABNT ISO/IEC 17025: 2005, e dos procedimentos operacionais padrão de atividades relacionadas aos ensaios em análises de sementes, proporciona resultados de análises rastreáveis, com controle de qualidade, e exatidão nos resultados para comercialização de sementes e segurança dos clientes. Este trabalho vem demonstrar a capacitação da equipe técnica, o laboratório de sementes equipado adequadamente e a qualidade dos resultados para os clientes internos e externos à Embrapa Milho e Sorgo.bitstream/item/56242/1/doc-130.pd
Improved Simulation of the Mass Charging for ASTROD I
The electrostatic charging of the test mass in ASTROD I (Astrodynamical Space
Test of Relativity using Optical Devices I) mission can affect the quality of
the science data as a result of spurious Coulomb and Lorentz forces. To
estimate the size of the resultant disturbances, credible predictions of
charging rates and the charging noise are required. Using the GEANT4 software
toolkit, we present a detailed Monte Carlo simulation of the ASTROD I test mass
charging due to exposure of the spacecraft to galactic cosmic-ray (GCR) protons
and alpha particles (3He, 4He) in the space environment. A positive charging
rate of 33.3 e+/s at solar minimum is obtained. This figure reduces by 50% at
solar maximum. Based on this charging rate and factoring in the contribution of
minor cosmic-ray components, we calculate the acceleration noise and stiffness
associated with charging. We conclude that the acceleration noise arising from
Coulomb and Lorentz effects are well below the ASTROD I acceleration noise
limit at 0.1 mHz both at solar minimum and maximum. The coherent Fourier
components due to charging are investigated, it needs to be studied carefully
in order to ensure that these do not compromise the quality of science data in
the ASTROD I mission.Comment: 20 pages, 14 figures, submitted to International Journal of Modern
Physics
Interrelações entre variáveis associadas à precocidade, ao crescimento e ao teor de nutrientes absorvidos de mamoeiro.
bitstream/CNPAT/7830/1/pd_7.pd
Generalized Involution Models for Wreath Products
We prove that if a finite group has a generalized involution model, as
defined by Bump and Ginzburg, then the wreath product also has a
generalized involution model. This extends the work of Baddeley concerning
involution models for wreath products. As an application, we construct a
Gelfand model for wreath products of the form with abelian, and
give an alternate proof of a recent result due to Adin, Postnikov, and Roichman
describing a particularly elegant Gelfand model for the wreath product \ZZ_r
\wr S_n. We conclude by discussing some notable properties of this
representation and its decomposition into irreducible constituents, proving a
conjecture of Adin, Roichman, and Postnikov's.Comment: 29 page
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