The paper describes qualitative analysis of contaminant transport in a homogeneous, isotropic aquifer where first order chemical reaction at the boundary and nonlinear decay act simultaneously. In order to analyze the relative merits, two types of disposal scheme are considered; (i) Scenario I: longer duration with low input concentration and (ii) Scenario II: short duration with higher input concentration. The governing advective-dispersion equation is solved numerically by employing ADI scheme under finite difference method. We apply the method of moments to investigate mean concentration distribution and other statistical parameters such as central moment, coefficients of skewness (β2 ) and kurtosis (β 3 ). The mean concentration distribution ( Cm ) is computed by applying Edgeworth’s asymptotic series for non-Gaussian curves involving Hermite polynomials ( Hn ). The forward displacement of centroid ( Xg ) with time, deviations of mean concentration distribution from Gaussianity and breakthrough curves have been examined. and Príspevok obsahuje kvalitatívnu analýzu transportu kontaminantov v homogénnej, izotropnej zvodni, na hraniciach ktorej simultánne prebiehajú chemické reakcie prvého rádu a nelineárny rozpad. Aby sme mohli posúdiť relatívne výhody spôsobu analýzy, použili sme dva typy schém; (i) Scenár I: nízka koncentrácia vstupov a ich dlhšie trvanie; (ii) Scenár II: krátko trvajúce vysoké koncentrácie vstupov. Advektívnodisperzná rovnica je riešená numericky, s využitím schémy ADI v rámci metódy konečných rozdielov. Na určovanie rozdelenia priemerných koncentrácií a iných štatistických parametrov, ako je centrálny moment, koeficient šikmosti (β2 ) a strmosť (β 3 ) , použili sme metódu momentov. Rozdelenie priemerných koncentrácií ( Cm ) sme vypočítali aplikáciou Edgeworthových asymptotických radov negaussovských kriviek, obsahujúcich Hermitove polynómy ( Hn ). Študovali sme dopredný posun centroidu ( Xg ) v závislosti od času, odchýlky od priemerných hodnôt rozdelenia priemerných koncentrácií od gaussovských, a určili sme tiež prienikové krivky.
The paper is aimed at a modeling of transonic flow of steam with pressure and temperature range corresponding to conditions in steam turbines. A possibility of the droplet size spectra reconstruction is discussed. Numerical results are compared to experimental data for nozzle flow. and Obsahuje seznam literatury
We discuss three estimation methods: the method of moments, probability weighted moments, and L-moments for the scale parameter and the extreme value index in the generalized Pareto distribution under linear normalization. Moreover, we adapt these methods to use for the generalized Pareto distribution under power and exponential normalizations. A simulation study is conducted to compare the three methods on the three models and determine which is the best, which turned out to be the probability weighted moments. A new computational technique for improving fitting quality is proposed and tested on two real-world data sets using the probability weighted moments. We looked back at various maximal data sets that had previously been addressed in the literature and for which the generalized extreme value distribution under linear normalization had failed to adequately explain them. We use the suggested procedure to find good fits.