35,458 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

    Remote Sensing and Problems of the Hydrosphere. A Focus for Future Research

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    The underly problems of water quality which are addressable with remote sensors are considered. The chemical, biological, geological, and physical dynamics of natural ecosystems 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

    Imperfect Knowledge Economics: Exchange Rates and Risk

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    Posing a major challenge to economic orthodoxy, Imperfect Knowledge Economics asserts that exact models of purposeful human behavior are beyond the reach of economic analysis. Roman Frydman and Michael Goldberg argue that the longstanding empirical failures of conventional economic models stem from their futile efforts to make exact predictions about the consequences of rational, self-interested behavior. Such predictions, based on mechanistic models of human behavior, disregard the importance of individual creativity and unforeseeable sociopolitical change. Scientific though these explanations may appear, they usually fail to predict how markets behave. And, the authors contend, recent behavioral models of the market are no less mechanistic than their conventional counterparts: they aim to generate exact predictions of "irrational" human behavior. Frydman and Goldberg offer a long-overdue response to the shortcomings of conventional economic models. Drawing attention to the inherent limits of economists' knowledge, they introduce a new approach to economic analysis: Imperfect Knowledge Economics (IKE). IKE rejects exact quantitative predictions of individual decisions and market outcomes in favor of mathematical models that generate only qualitative predictions of economic change. Using the foreign exchange market as a testing ground for IKE, this book sheds new light on exchange-rate and risk-premium movements, which have confounded conventional models for decades. Offering a fresh way to think about markets and representing a potential turning point in economics, Imperfect Knowledge Economics will be essential reading for economists, policymakers, and professional investors.knowledge, economic models, predictions, rational self-interest, markets, decisions, exchange rates, risk premiums

    Sub-structural Niching in Estimation of Distribution Algorithms

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    We propose a sub-structural niching method that fully exploits the problem decomposition capability of linkage-learning methods such as the estimation of distribution algorithms and concentrate on maintaining diversity at the sub-structural level. The proposed method consists of three key components: (1) Problem decomposition and sub-structure identification, (2) sub-structure fitness estimation, and (3) sub-structural niche preservation. The sub-structural niching method is compared to restricted tournament selection (RTS)--a niching method used in hierarchical Bayesian optimization algorithm--with special emphasis on sustained preservation of multiple global solutions of a class of boundedly-difficult, additively-separable multimodal problems. The results show that sub-structural niching successfully maintains multiple global optima over large number of generations and does so with significantly less population than RTS. Additionally, the market share of each of the niche is much closer to the expected level in sub-structural niching when compared to RTS

    Imperfect Knowledge, Temporal Instability and an Uncertainty Premium: Towards a Resolution of the Excess-Returns Puzzle in the Foreign Exchange Market.

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    This paper offers a refinement and explores a resolution of the excess-returns puzzle in the foreign exchange market. We find that the predictions of the forward premium are not negatively biased throughout the three decades of floating, as commonly believed, but rather are sometimes positively biased, negatively biased, unbiased or possess no predictive content depending on the subperiod examined. To explain this modified puzzle, the paper makes use of a recently developed model of the risk premium, which we have called an aggregate uncertainty premium. Our model employs an alternative approach to modeling exchange rate expectations, dubbed Imperfect Knowledge Expectations (IKE), which recognizes that rational agents do form expectations based on imperfect knowledge. Our model also makes use of a dynamic extension of the assumption of myopic loss aversion. We find that our IKE-based approach can account for the pattern of positive and negative biases estimated over three decades of floating rates.exchange rates; forward-premium anomaly; instability; imperfect knowledge expectations; risk premium
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