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Photoelectric transport in high resistivity CdTe for gamma ray detectors
Dědič, Václav ; Šikula, Josef (referee) ; Franc, Jan (advisor)
CdTe semiconductor is a good material for the construction of X-ray and gamma ray detectors. Its physical properties are strongly influenced by an existence of deep levels in the forbidden band. This thesis deals with an influence of deep levels to the photoelectric transport in high resistivity CdTe. Experimental part of this thesis consits of measurement of slopes of Lux-Ampere characteristics of variously doped CdTe samples depended on voltage and energy of excitation. Gradients of measured guidelines of Lux-Ampere characteristics show strong dependency on an electric charge accumulated on deep levels. This thesis also contains numerical models of photoconductivity for various parameters of material.
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Photoelectric spectroscopy of deep electronic levels in high-resistance CdTe
Kubát, Jan ; Franc, Jan (advisor) ; Sopko, Bruno (referee)
CdTe is one of the most interesting X-ray and g-ray detectors' material. This work deals with influence of deep levels to photoelectric properties of CdTe. PICTS, Lux-Ampere and spectral dependences measurements at room temperature and low temperature 10K were performed on one undoped and several variously doped (Cl, Sn and Ge) samples and applied electrical fields up to 800V.cm-1. Experimental setups are introduced. Room temperature numerical solution of sample photoelectrical properties for typical midgap level using driftdiffusion and Poisson equation was performed and results are discussed. The experimentally observed slopes of Lux-ampere characteristics and energy shifts of the main photoconductivity peak with the applied voltage are explained based on a model of screening of electric field by charge accumulated on deep levels. Finally comparison with acquired experimental data is performed yielding estimates of maximum total concentration of deep levels in the samples.
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Effect of surface of semiconductor nanocrystals on their properties: investigation by laser spectroscopy
Preclíková, Jana ; Malý, Petr (advisor) ; Franc, Jan (referee)
The topic of the diploma thesis is chemical treatment of the surfaces of semiconductor nanocrystals CdS and CdSe in the form of thin nanocrystalline films prepared by chemical bath deposition. The evolution of photoluminescence and absorption spectra was investigated under treatment by water, toluene, butylamine, pyridine and hydrogen peroxide. The strongest changes were observed by samples soaked in water, pyridine and aqueous solution of pyridine. The observed effects were explained by partly dissolving of nanocrystals by water and affecting behaviour of photoexcited holes in the presence of the strong hole acceptor pyridine. The second part of this diploma thesis deals with photochromic properties of silver nanoparticles in a titanium oxide matrix. The photochromic behaviour of the samples was examined in detail. A phenomenological model of photochromic changes was suggested in analogy with the hole burning spectroscopy. In order to better understand the microscopic processes in this composite material other experiments were realized - e.g. samples were UV irradiated, or laser illuminated under lowered air pressure, pump & probe experiment. Under laser irradiation optical extinction of some nanoparticles was decreased. Simultaneously, changes of plasmon resonances of the rest of nanoparticels were...
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Methods of measuring bit rates
Franc, Jan ; Mišurec, Jiří (referee) ; Zeman, Václav (advisor)
Study and basic benchmarking methodology description of network connections based on the IP was the objective of bachelor work. I resulted above all from RFC standards, by which are directed most of Internet protocols. Particular procedures for testing are explained in RFC 2544. On the basis of parameters analysis, I suggested conception and gave shape to web application which allows identify referenced basic transfer parameters of Internet connection (downstream, upstream, latency, scattering of connection speed). Application doesn’t require no add-ons and modules on user side. It is built on server programming language PHP with usage of relational MySQL database, in which are stored data. Client scripting language JavaScript is also used. Application offers measuring of mentioned parameters both to visitors and to registered users. Matter of course is user registration; work with history of carried out measuring, sending private messages between registered users. Above whole application exists administrator account.
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Methods for the measurement of bit rates in data networks
Franc, Jan ; Martinásek, Zdeněk (referee) ; Zeman, Václav (advisor)
The target of this master's thesis were the known methods for testing the quality of transfer parameters of data networks. I have studied the RFC 2544 document to analyze these tests. From that information and by studying other existing web-based applications I was able to design a concept of my own application that will allow to measure basic quality parameters of transfers made through the Internet (the parameters: downstream, upstream, latency, variance of these and a traced route). My application doesn't require any modifications on the user's system. It's built on the server-based programming language PHP and uses the relational database engine MySQL to store measurement and user data. On the client side, it's assisted by the JavaScript scripting language. Both registered users and visitors are allowed to perform the listed measurements. Registered users are able to browse the history of their own benchmark results and also to send messages to others. There is an administrative account to oversee the operations. Another part of my thesis work is an application for Windows that performs the same measurements but does not use JavaScript.
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Analysis of internal communication in connection with IT, processes and management in a specific organization
Plachá, Alena ; Střížová, Vlasta (advisor) ; Franc, Jan (referee)
This diploma thesis primarily focuses on analysis of internal communication in a particular company and proposals for improvement. To meet this objective, first the importance of the internal communication for the company and the factors that affect it are described. After that channels and tools of internal communication and the importance of IT for communication in the company were generally defined. Then the various means of communication using IT were analyzed. Another information source used in the thesis are the results of the applied research, which was conducted among employees and management of ANAFRA company and focused on identifying critical issues that ANAFRA in the context of internal communication face. The last part of the thesis combines all of the previously gathered information and proposes solutions of the identified problems. Conclusions of the thesis may serve as referential valuable source for professionals and owners of small and medium businesses.
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