30,407 research outputs found

    Remote Sensing and Problems of the Hydrosphere

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    A discussion of freshwater and marine systems is presented including areas of the classification of lakes, identification and quantification of major functional groups of phytoplankton, sources and sinks of biochemical factors, and temporal and regional variability of surface features. Atmospheric processes linked to hydrospheric process through the transfer of matter via aerosols and gases are discussed. Particle fluxes to the aquatic environment and global geochemical problems are examined

    Properties of Nucleon Resonances by means of a Genetic Algorithm

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    We present an optimization scheme that employs a Genetic Algorithm (GA) to determine the properties of low-lying nucleon excitations within a realistic photo-pion production model based upon an effective Lagrangian. We show that with this modern optimization technique it is possible to reliably assess the parameters of the resonances and the associated error bars as well as to identify weaknesses in the models. To illustrate the problems the optimization process may encounter, we provide results obtained for the nucleon resonances Δ\Delta(1230) and Δ\Delta(1700). The former can be easily isolated and thus has been studied in depth, while the latter is not as well known experimentally.Comment: 12 pages, 10 figures, 3 tables. Minor correction

    Imperfect Knowledge and Asset Price Dynamics: Modeling the Forecasting of Rational Agents, Dynamic Prospect Theory and Uncertainty Premia on Foreign Exchange.

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    Models using the Rational Expectations Hypothesis (REH) are widely recognized to be inconsistent with the observed behavior of premia in financial markets, as well as other features of asset price dynamics. Moreover, many reasons have been advanced as to why the REH cannot generally represent, even approximately, the expectations behavior of individually rational agents. In this paper, we develop a new model of the equilibrium premium in the foreign exchange market that replaces the REH with the Imperfect Knowledge Forecasting (IKF) framework. Because we maintain that agents must cope with imperfect knowledge and that they are not grossly irrational, our IKF approach imposes only qualitative conditions on the formation of individual forecasting models and their updating. We also develop a dynamic extension of the original formulation of Kahneman and Tversky’s prospect theory. We find that under IKF and dynamic prospect theory, the equilibrium premium on foreign exchange is positively related to the gap between the aggregate forecast of the exchange rate and its historical benchmark level. We test this implication, using survey data on the German mark-U.S. dollar exchange rate, and find that the behavior of the ex ante premium on foreign exchange is consistent with our model of the premium.exchange rates; risk premium; imperfect knowledge; individual rationality; expectations; prospect theory
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