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Evaluation of actual sulphur supply in soil and forecast of its development in the Czech Republic
Vojtěch, Jaroslav ; Kulhánek, Martin (advisor) ; Sedlář, Ondřej (referee)
This thesis contains summary information about the importance of sulphur as an important macrobiogenic element in plant nutrition, as well as about sulphur cycle in soil, development of sulphur content in recent years and possibilities of sulphur supply to crops being grown.
Sulphur is an important macroelement in plant nutrition and it is part of important amino acids, vitamins and proteins. Sulphur content in crops predetermines the quantity and quality of harvested products.
Sulphur in our latitudes entered in soil particularly due to atmospheric depositions. With desulphurization of power plants, there has been a significant decline in sulphur entering soil in recent decades, from an approximate figure of 120 kg of pure sulphur per hectare in 1990 to mere 6 8 kg of sulphur per hectare in 2013. Due to small intake of sulphur in soil, plants that draw off large amounts of sulphur and due to the fact that sulphur is swiftly washed off from the topsoil to deeper soil layers where it is inaccessible to the crops, there is often lack of sulphur in the nourishment of crops being grown, which regards both sulphur demanding crops, such as oil crops, and crops such as cereals where lack of sulphur has not manifested itself as much so far.
Soil contains sulphur in an inorganic and organic form. Inorganic sulphur in agricultural land is represented to a lesser extent than organic sulphur, but it is the main source of plant available sulphur and it is a highlydynamic soil component. In soil, it is usually contained in the form of sulphates. Intake of sulphates and their concentration in the soil solution impacts pH, amount of Fe and Al oxides and behaviour of soil colloids. We can influence the content of inorganic sulphur by supplying mineral fertilizers, but we cannot increase the overall long-term supply of sulphur in soil in this way. Long-term and main supply of sulphur in soil is represented by organic sulphur bound in sulphur amino acids, sulfolipids, sulphonic acids and sulphated polysaccharides. We can influence this component of the overall sulphur content by organic fertilization, green manuring, afterharvest residues and sewage sludge application.
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Distribution of the accurate optical frequency and time via photonic networks in the Czech Republic
Číp, Ondřej ; Čížek, Martin ; Pravdová, Lenka ; Hucl, Václav ; Řeřucha, Šimon ; Hrabina, Jan ; Lešundák, Adam ; Mikel, Břetislav ; Lazar, Josef ; Vojtěch, J. ; Smotlacha, V.
To verify the stability of the frequency of optical clock an intensive research in the transmission of stable frequency via optical fibers is in progress for many years. Interconnection of large cities and metropolitan networks with optical fiber running DWDM allowing to transfer many optical signals in parallel over one fiber at the same time contributes significantly to troubleshoot the problem. Between nodes of ISI Brno and the main center of CESNET there are several dedicated bi-directional channels through the DWDM technology. The first tests are ongoing with the transfer of accurate time, which are using the possibility of bi-directional communication over a single fiber, thus the phase delay including Doppler shift are reflected on the two signals as well. From periodic measurements can subsequently be evaluated daily, weekly and seasonal fluctuations of the delay and after deduction of such data from the measured data a mutual stability of used time normal can be determined. The second technique is a full compensation of phase of the laser wave through active control of phase changes of the wave during its transmission from the ISI to the node of CESNET. At present, a characterization of the behavior of individual system elements, including their commissioning is in progress.
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Optical infrastructure for time and frequency transfer
Smotlacha, V. ; Vojtěch, J. ; Kuna, Alexander
The paper describes optical infrastructure for time and frequency transfer in the Czech republic. The infrastructure is heterogeneous and utilises resources of the Czech academic optical network. It allows to interconnect Cesium standards in distant sites with the national time and frequency laboratory and to distribute accurate time and stable frequency. We also present results and compare them with other methods of time transfer
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Extreme Value Theory in Operational Risk Management
Vojtěch, Jan ; Kahounová, Jana (advisor) ; Řezanková, Hana (referee) ; Orsáková, Martina (referee)
Currently, financial institutions are supposed to analyze and quantify a new type of banking risk, known as operational risk. Financial institutions are exposed to this risk in their everyday activities. The main objective of this work is to construct an acceptable statistical model of capital requirement computation. Such a model must respect specificity of losses arising from operational risk events. The fundamental task is represented by searching for a suitable distribution, which describes the probabilistic behavior of losses arising from this type of risk. There is a strong utilization of the Pickands-Balkema-de Haan theorem used in extreme value theory. Roughly speaking, distribution of a random variable exceeding a given high threshold, converges in distribution to generalized Pareto distribution. The theorem is subsequently used in estimating the high percentile from a simulated distribution. The simulated distribution is considered to be a compound model for the aggregate loss random variable. It is constructed as a combination of frequency distribution for the number of losses random variable and the so-called severity distribution for individual loss random variable. The proposed model is then used to estimate a fi -nal quantile, which represents a searched amount of capital requirement. This capital requirement is constituted as the amount of funds the bank is supposed to retain, in order to make up for the projected lack of funds. There is a given probability the capital charge will be exceeded, which is commonly quite small. Although a combination of some frequency distribution and some severity distribution is the common way to deal with the described problem, the final application is often considered to be problematic. Generally, there are some combinations for severity distribution of two or three, for instance, lognormal distributions with different location and scale parameters. Models like these usually do not have any theoretical background and in particular, the connecting of distribution functions has not been conducted in the proper way. In this work, we will deal with both problems. In addition, there is a derivation of maximum likelihood estimates of lognormal distribution for which hold F_LN(u) = p, where u and p is given. The results achieved can be used in the everyday practices of financial institutions for operational risks quantification. In addition, they can be used for the analysis of a variety of sample data with so-called heavy tails, where standard distributions do not offer any help. As an integral part of this work, a CD with source code of each function used in the model is included. All of these functions were created in statistical programming language, in S-PLUS software. In the fourth annex, there is the complete description of each function and its purpose and general syntax for a possible usage in solving different kinds of problems.
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