18 research outputs found
IdĹ‘sorok analĂzise Ă©s sztochasztikus fraktál modellek tanulmányozása alkalmazásokkal = Time series analysis and fractal models with applications
Frakcionális Ornstein-Uhlenbeck lepedĹ‘ tulajdonságait vizsgáltuk abbĂłl a szempontbĂłl, hogy olyan modellt konstruáljunk, aminek spektruma az origĂł környezetĂ©ben nem izotrĂłp mĂłdon viselkedik. A LĂ©vy-Flight-ok (közel stabilis LĂ©vy-folyamtok) fontos szerepet játszanak a nem Gauss jelensĂ©gek vizsgálatában. Egzakt eredmĂ©nyeket bizonyĂtottunk a LĂ©vy-Flight-ok aszimptotikus egĂ©sz Ă©s tört rendű momentumaira, ezzel összefĂĽggĂ©sben sikerĂĽlt kimutatni ezek multi-fraktál tulajdonságát. A nemlineáris vektor Ă©rtĂ©kű regressziĂł problĂ©májával foglalkoztunk, amikor a megfigyelĂ©sek hibája stacionárius eloszlásĂş. Egzakt formulát adtunk meg a paramĂ©ter becslĂ©sek aszimptotikus szĂłrásmátrixára, Ă©s alkalmaztuk eredmĂ©nyĂĽnket valĂłdi adatokra is. A magfĂĽggvĂ©nyes sűrűsĂ©gfĂĽggvĂ©ny becslĂ©s aszimptotikus normalitását bizonyĂtottuk Ăşgy, hogy a mezĹ‘t egyre nagyobb tartományon figyeljĂĽk meg, de közben megfigyelĂ©si helyeket is sűrĂtjĂĽk. KiderĂĽl, hogy az aszimptotikus kovariancia fĂĽgg a sávszĂ©lessĂ©g Ă©s az osztĂłpontok távolságának arányátĂłl. | The Fractional Ornstein-Uhlenbeck sheet is investigated, non-isotropic stationary model is constructed and applied for real data. We showed that LĂ©vy-Flights are fractals and proved asymptotical formulae for moments and cumulants.with integer and fractal order. Functional limit theorems are proved for a sequence of Galton-Watson processes with immigration, where the offspring mean tends to its critical value 1 under weak conditions for the variances of offspring and immigration processes. Int he limit theorems the norming factors depend on these variances. We proved the asymptotic normality of the kernel density estimates in 2D. The asymptotic covariance is shown to be dependent of the ratio of the window size and distance between point on the lattice. The nonlinear multiple regression with stationary errors is investigated. A clear formula is given for the asymptotic variance of the parameter estimator and it is applied for the identification of fitting models to real data
Renormalization group of and convergence to the LISDLG process
The LISDLG process denoted by J(t) is defined in Iglói and Terdik [ESAIM: PS 7 (2003) 23–86] by a
functional limit theorem as the limit of ISDLG processes. This paper gives a
more general limit representation of J(t). It is shown that process J(t)
has its own renormalization group and that J(t) can be represented as the
limit process of the renormalization operator flow applied to the elements of
some set of stochastic processes. The latter set consists of IGSDLG processes
which are generalizations of the ISDLG process
Superposition of Diffusions with Linear Generator and its Multifractal Limit Process
In this paper a new multifractal stochastic process called Limit of the
Integrated Superposition of Diffusion processes with Linear differencial
Generator (LISDLG) is presented which realistically characterizes the network
traffic multifractality. Several properties of the LISDLG model are presented
including long range dependence, cumulants, logarithm of the characteristic
function, dilative stability, spectrum and bispectrum. The model captures
higher-order statistics by the cumulants. The relevance and validation of the
proposed model are demonstrated by real data of Internet traffic.