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- Hybrid approach of fractal and linguistic forecasting of winter wheat yields in Southern RússiaPublication . Kumratova, Alfira; Popova, Elena; Costa, Luís de Sousa; Shaposhnikova, OlgaThe article investigated and formed the imperatives of the impact of the external natural environment on the grain yield in the south of Russia, forcing to abandon the simplified classical concepts and methods of analysis. The author's research concept defines quantitative risk analysis, as a category, inverse forecast, which is possible only on the basis of economic and mathematical modeling. The modern theory of assessing measures of economic risks, forecasting and managing them is still far from adequate to the real needs of practical agricultural management. This determines the main feature of modern risk, which is its total and comprehensive nature. It is difficult to manage risks in regions with frequent droughts, which are classified as areas of risk farming. The methodology of studying risks in the field of agriculture is based on the study of the dynamics of the natural environment of growing crops, the conjuncture uncertainty of the external economic environment, the variability of land management technologies. Climatic and agrometeorological conditions are becoming an important factor affecting crop yields. The yield series accumulates information about the fluctuation of weather conditions and their influence on the yield, they contain information about certain regularities that synergy relates to the concept of “long-term memory”. The paper describes the features of the spectrum of climatic conditions affecting socio-economic indicators, the growth and yield of grain (winter wheat) in southern Russia, as well as the results of the implementation of the author-hybrid approach to the fractal and linguistic forecasting of winter wheat yield in southern Russia.
- Methods of nonlinear dynamics as a hybrid tool for predictive analysis and research of risk-extreme levelsPublication . Popova, Elena; Costa, Luís de Sousa; Kumratova, Alfira; Zamotajlova, DariaThe purpose of this research is to develop and adapt a complex of hybrid mathematical and instrumental methods of analysis and risk management through the prediction of natural time series with memory. The paper poses the problem of developing a constructive method for predictive analysis of time series within the current trend of using so-called “graphical tests” in the process of time series modeling using nonlinear dynamics methods. The main purpose of using graphical tests is to identify both stable and unstable quasiperiodic cycles (quasi-cycles). Modern computer technologies which allow to study in detail complex phenomena and processes were used as a toolkit for the implementation of nonlinear dynamics methods. Authors propose to use for the predictive analysis of time series a modified R=S-analysis algorithm, as well as phase analysis methods for constructing phase portraits in order to identify cycles of the studied time series and confirm the forecast. This approach differs from classical forecasting methods by implementing trends accounting and appears to the authors as a new tool for identifying the cyclical components of the considered time series. Using the proposed hybrid complex, the decision maker has more detailed information that cannot be obtained using classical statistics methods. In this paper, authors analyzed the time series of Kuban mountain river runoffs, revealed the impossibility of using the classical Hurst method for their predictive analysis and also proved the consistency of using the proposed hybrid toolkit to identify the cyclic components of the time series and predict it. The study acquires particular relevance in the light of the absence of any effective methods for predicting natural-economic time series, despite the proven need to study them and their risk-extreme levels.
- Modificação das características agrometeorológicas do sorgo pela adubação azotadaPublication . Costa, Luís de SousaO presente estudo pretende contribuir para a avaliação da influência de diferentes níveis de adubação azotada nas características agrometeorológicas de desenvolvimento e crescimento do sorgo forrageiro de regadio, nas condições edafo-climáticas do Nordeste Transmontano. Analisou-se o efeito de quatro níveis de azoto no solo na forma como o crescimento e desenvolvimento do sorgo respondem à temperatura e à radiação solar, nomeadamente em termos de crescimento em altura, evolução do número de folhas, índice de área foliar, produção de biomassa, e extracção de azoto. Esta avaliação é feita em termos dos tempos térmicos de desenvolvimento, da eficiência de utilização da radiação para a produção de matéria seca e da eficiência de utilização do azoto. O estudo decorreu na Quinta de Sta. Apolónia, em Bragança, durante 1997, 1998 e 1999, com a variedade de sorgo híbrido forrageiro Sweet Sioux IV. A aplicação de azoto aumentou as áreas foliares, a intercepção da radiação e a produção de biomassa. Contudo, aplicações de N superiores a 400 kg ha-1 não devem ser ultrapassados porque não aportam um aumento significativo de produtividade nem um aumento importante de eficiência de utilização da radiação solar, e reduzem as eficiências de recuperação e de utilização do azoto. The aim of this work is to evaluate the influence of distinct levels of soil nitrogen fertilization on the agrometeorological characteristics of development and growth of irrigated fodder sorghum in the Nordeste Transmontano (Northeastern Portugal). The effects of four levels of soil nitrogen fertilization on the responses of sorghum development and to temperature and solar radiation were analysed, namely crop height, leaf number, leaf area, biomass and nitrogen uptake. This assessment is based on the thermal time for development, on the radiation use efficiency for dry mater production and on the efficiency of nitrogen utilization. The experiments were carried out in Quinta de Sta. Apolónia, Bragança, in 1997, 1998 and 1999, with the hybrid fodder sorghum variety Sweet Sioux IV. Nitrogen fertilization increased leaf area, radiation interception and biomass production. However, nitrogen fertilization rates above 400 kg ha-1 should not be used because they do not lead to a significant increases of both yield and radiation use efficiency, and they reduce the efficiencies of nitrogen recovery and utilization.
- Hybrid instrumental means of predictive analysis of the dynamics of natural and economic processesPublication . Popova, Elena; Costa, Luís de Sousa; Kumratova, AlfiraThe purpose of the presented research is the development and adaptation of mathematical and instrumental methods of analysis and risk management through the forecasting of both economic and natural time series with memory based on the application of new mathematical methods of investigation. The paper poses the problem of developing a constructive method for predictive analysis of time series in the framework of the currently emerging trend of using so-called “graphical tests” in the process of time series’ modeling using nonlinear dynamics methods. The main purpose of using graphical tests is to identify both stable and unstable quasiperiodic cycles (quasi-cycles), the whole set of which includes a strange attractor (if one exists). New computer technologies that made it possible to study complex phenomena and processes “on a display screen” were used as instrumentation for the implementation of methods of non-linear dynamics. The proposed approach differs from classical methods of forecasting by new implementation of accounting trends (the evolution of centers and sizes of dimensional rectangles), and appears to be a new tool for identifying cyclic components of the time series in question. As a result, the person, that is making decision has more detailed information, which is impossible to obtain by the methods of classical statistics.