ON APPROXIMATION OF VALUE FUNCTIONS FOR CONTROLLED DISCONTINUOUS RANDOM PROCESSES

Best approximation for classes of random processes

We consider the best approximation order for classes of random processes. The close relationship between the smoothness properties of a function and the best rate of its linear approximation is one of the basic ideas of conventional (determinis-tic) approximation theory. We investigate similar properties for random functions. HH older's class of random processes is studied in more detail. Sever...

On Padé Approximation of Some Practical Functions

Nonlinear Approximation of Random Functions

Given an orthonormal basis and a certain class X of vectors in a Hilbert space H, consider the following nonlinear approximation process: approach a vector x ∈ X by keeping only its N largest coordinates, and let N go to infinity. In this paper, we study the accuracy of this process in the case where H = L(I), and we use either the trigonometric system or a wavelet basis to expand this space. T...

A weak approximation for the Extrema's distributions of Levy processes

‎Suppose that $X_{t}$ is a one-dimensional and real-valued L'evy‎ ‎process started from $X_0=0$‎, ‎which ({bf 1}) its nonnegative‎ ‎jumps measure $nu$ satisfying $int_{Bbb‎ ‎R}min{1,x^2}nu(dx)

study of hash functions based on chaotic maps

توابع درهم نقش بسیار مهم در سیستم های رمزنگاری و پروتکل های امنیتی دارند. در سیستم های رمزنگاری برای دستیابی به احراز درستی و اصالت داده دو روش مورد استفاده قرار می گیرند که عبارتند از توابع رمزنگاری کلیددار و توابع درهم ساز. توابع درهم ساز، توابعی هستند که هر متن با طول دلخواه را به دنباله ای با طول ثابت تبدیل می کنند. از جمله پرکاربردترین و معروف ترین توابع درهم می توان توابع درهم ساز md4, md...