National Repository of Grey Literature 6 records found  Search took 0.00 seconds. 
Importance and occurrence of chromium in hydrogeology
Sadloň, Matúš ; Nedvěd, Jakub (advisor) ; Šantrůček, Jaromír (referee)
in English Chromium, particularly its two most stable oxidation states - hexavalent and trivalent chromium - plays a very significant role in the environment. While trivalent chromium is an essential nutrient both for humans and plants, hexavalent chromium proved to be one of the most dangerous contaminants negatively affecting people and the environment on a wide- ranging scale. This thesis aims to provide a complex overview of chromium occurrence in various natural systems, its physical and chemical properties as well as its mobility in the environment. Furthermore, the thesis will describe two case studies (from Greece and India), which illustrate both the natural and anthropogenic sources of hexavalent chromium contamination. Due to its mutagenic and carcinogenic properties, a complex set of remediation methods was suggested for hexavalent chromium removal, including both in-situ and ex-situ ones. Given their proven record in successful elimination of hexavalent chromium contamination from groundwater, in-situ methods are being utilised far more frequently nowadays; these will be explained more comprehensively. The most notable categories of in- situ remediation methods include biological and chemical reduction, chemical precipitation and chemical sorption. Besides these, other promising...
Mathematical model of groundwater flow affected by circulation wells
Nedvěd, Jakub
In this thesis, I focused on numerical modelling of groundwater flow in the vicinity of groundwater circulation well (GCW). The thesis can be devided to two parts. In the first one, I created a simple numerical model of GCW. I used a cylindrical flow domain because of the radial symmetry of the problem. The task was to find out which parameters have the biggest influence on groundwater flow. It was found that the hydrogeological settings and hydraulic properties have more considerable effect on GW flow than the well construction parameters. Distance between the well screens is the only important construction parameter, other parameters can be neglected. However, we cannot neglect the influence of hydraulic properties of the porous medium. Considering the radius of influence of GCW, the presence of aquitards and anisotropy of layers affect the groundwater flow around the well seriously. These two parameters cause the extension of the radius of influence, which leads to a longer path of the particle of water. The travel time of particles increases too this slows down the remediation. A big influence has also an intensity of natural groundwater flow in the area because it decreases the radius of influence of the well. In the second part I created a numerical model of pilot site Velká Hleďsebe to investigate...
Mathematical model of groundwater flow affected by circulation wells
Nedvěd, Jakub ; Mls, Jiří (advisor) ; Ondovčin, Tomáš (referee)
In this thesis, I focused on numerical modelling of groundwater flow in the vicinity of groundwater circulation well (GCW). The thesis can be devided to two parts. In the first one, I created a simple numerical model of GCW. I used a cylindrical flow domain because of the radial symmetry of the problem. The task was to find out which parameters have the biggest influence on groundwater flow. It was found that the hydrogeological settings and hydraulic properties have more considerable effect on GW flow than the well construction parameters. Distance between the well screens is the only important construction parameter, other parameters can be neglected. However, we cannot neglect the influence of hydraulic properties of the porous medium. Considering the radius of influence of GCW, the presence of aquitards and anisotropy of layers affect the groundwater flow around the well seriously. These two parameters cause the extension of the radius of influence, which leads to a longer path of the particle of water. The travel time of particles increases too this slows down the remediation. A big influence has also an intensity of natural groundwater flow in the area because it decreases the radius of influence of the well. In the second part I created a numerical model of pilot site Velká Hleďsebe to investigate...
Circulation wells and their mathematical modelling
Nedvěd, Jakub ; Mls, Jiří (advisor) ; Šantrůček, Jaromír (referee)
Groundwater is our priceless natural resource and it is our duty to protect it and to take care of its quality. That is the reason why several techniques of pollution removal have been developed; the Groundwater Circulation Well technique (GCW) is one of them. This system enables us to clean contaminated groundwater effectively and in-situ (it means that there is no need to extract groundwater to the surface). This thesis is aimed at collecting and presenting our actual knowledge of the most common GCW systems. In the first part of the thesis the basic kinds of the GCW are introduced and their principles are presented. The remediation mechanisms are further described with respect to the character of the particular contamination. The chemical and biological processes controlling the contaminant degradation are described. Several experiments that were carried out and monitored in order to study the efficiency of GCWs are presented. In the last part of the thesis the mathematical modelling of GCWs is introduced. The partial differential equations governing the processes of flow and mass transport in the well surrounding parts of aquifers are presented and the corresponding initial and boundary conditions are formulated. The obtained numerical results and conclusions of their comparison with measured data are...
Mixture distributions
Nedvěd, Jakub ; Malá, Ivana (advisor) ; Bílková, Diana (referee)
Object of this thesis is to construct a mixture model of earnings of the Czech households. In first part are described characteristics of mixtures of statistical distributions with the focus on the mixtures of normal distibutions. In practical part of this thesis are constructed models with parameters extimations based on the data from EU-SILC. Models made by graphical method, EM algorithm and method of maximum likelihood. The quality of models is measured by Akaike information criterion.
The use of the lognormal distribution in analysing of earning
Nedvěd, Jakub ; Malá, Ivana (advisor) ; Bílková, Diana (referee)
Object of this thesis is to verify the possibility of use the lognormal distribution as a revenue-distribution model. This text describes characteristics of lognormal distribution and methods of estimating its parameters. Thesis is focused on three-parametric lognormal distribution, because it is most common in this dilemma. Using data from Informational system of average earnings this thesis finds out quality of models. There are described options of usage the lognormal distribution in analyzing revenues. At the end of this essay is suggested an easy analysis of differences between revenue-frequency distribution in the years 2000 and 2010. The thesis demonstrates the fact that the curve of lognormal distribution density function is applicable model which is reliable especially in the wide central part of revenue-distribution.

See also: similar author names
1 Nedvěd, Jaroslav
3 Nedvěd, Jiří
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