مقالات لاتین

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      A new type of stochastic fractal for application in subsurface hydrology

      5000 تومان 4000 تومان

      Abstract
      Data suggest that many property distributions [P(x); p = property, x = length] are irregular [dP/dx discontinuous], exhibiting
      variations on all measurement scales. Logic then leads one to attempt to characterize these distributions through study of their
      increments or fluctuations [P(x+L)−P(x)], which results naturally in a statistical approach. Increment frequency distributions for a
      fixed L that fit the Levy/Gaussian family of probability density functions [PDFs] independent of position [statistically stationary in
      a spatial sense] have well-defined scaling properties characteristic of what are called self-affine stochastic fractals. Data show that
      measurements in natural systems display some of the scaling characteristics of this PDF family, but do not agree with theory in
      many important aspects. For example, increment ln(K) distributions show a consistently non-Gaussian shape for smaller values of
      L and become more Gaussian as L gets large. Particularly for smaller L, PDF tails display an approximate exponential decay and
      maintain a finite variance. In many cases they appear to be displaying a continuous change from exponential, or even subexponential,
      to Gaussian behavior with increasing L. Data supporting these observations are presented along with explanations of
      how the fractal-based concepts arise, both physically and mathematically. This is followed by the presentation and initial analysis
      of what appears to be a new type of stochastic fractal called fractional Laplace motion that displays more of the features observed in
      natural sedimentary systems.

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      Chaos theory in hydrology: important issues and interpretations

      5000 تومان 4000 تومان

      Abstract
      The application of the concept of chaos theory in hydrology has been gaining considerable interest in recent times. However,
      studies reporting the existence of chaos in hydrological processes are often criticized due to the fundamental assumptions withwhich
      the chaos identification methods have been developed, i.e. infinite and noise-free time series, and the inherent limitations of the
      hydrological time series, i.e. finite and noisy. This paper is designed: (1) to address some of the important issues in the application of
      chaos theory in hydrology; and (2) to provide possible interpretations to the results reported by past studies reporting chaos in
      hydrological processes. A brief review of some of the past studies investigating chaos in hydrological processes is presented. An
      insight into the studies reveals that most of the problems, such as data size, noise, delay time, in the application of chaos theory have
      been addressed by past studies, and caution taken in the application of the methods and interpretation of the results. The study also
      reveals that the problemof data size is not as severe as it was assumed to be,whereas the presence of noise seems to havemuchmore
      influence on the nonlinear predictionmethod than the correlation dimensionmethod.The study indicates that the presence of noise in
      the data could be an important reason for the low-prediction accuracy estimates achieved in some of the past studies. These
      observations,with the fact that most of the past studies used the correlation dimension either as a proof or as a preliminary evidence
      of chaos, suggest that the hypothesis of deterministic chaos, as the basis in those studies, for hydrological processes is valid and has
      great practical potential. q2000 Elsevier Science B.V. All rights reserved.
      Keywords: Chaos theory; Hydrological data; Identification methods; Correlation dimension; Nonlinear prediction; Data size; Noise

    • مفاهیم اولیه بورس

      50000 تومان

      مفاهیم بورس شامل:نماد معاملاتی، عرضه اولیه، حق تقدم ، دامنه نوسان و …)

    • پکیج بورس

      600000 تومان

      بسته پکیج بورس: (مقدمه و مفاهیم بورس- تحلیل تکنیکال- تحلیل بنیادی- تابلو خوانی – کندل استیک- عرضه اولیه- سهام- بورس اوارق بهادار- پول هوشمند- کار با نرم افزار مفید تریدر)