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Security of VoIP protocols
Novotný, František ; Číka, Petr (referee) ; Krajsa, Ondřej (advisor)
This bachelor dissertation deals with the VoIP (Voice over Internet Protocol) safety. The most used transport and signal protocols employing this technology are presented first. Two extended protocols, SIP (Session Initiation Protocol) and IAX (Inter-Asterisk eXchange Protocol), as well as open source Asterisk, which is closely connected with these protocols, are shown in detail. After that, methods, attacks and threats able to assure secure transfer in the use of VoIP among users are described. Afterwards the practical part of this essay, divided into two parts, is presented. In the first part, a passive attack in the form of tapping is demonstrated, and in the second, active attacks are described which take the form of forced cancellations and forwarded calls between two communicating users. With both attacks, safety measures that could effectively prevent against their potential attacking are proposed. In the closing part, the VoIP safety is evaluated for securing a quality connection between users communicating through it.
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Compacted graphite cast iron
Švábenský, Petr ; Kaňa, Václav (referee) ; Laštovica, Jaroslav (advisor)
This labor search to summarize the known properties and methods of production of compacted graphite iron. The first part describes the structure, chemical composition, properties and uses. The second part focuses on the possibility of production of vermicular cast iron. Inoculation options and treatment and various manufacturing processes.
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Tin dioxide based semiconducting gas sensors
Gablech, Imrich ; Pytlíček, Zdeněk (referee) ; Prášek, Jan (advisor)
This project is aimed at semiconductive gas sensors based on tin dioxide. In the first part, gas sensors are divided depending on their principal of functionality. Next part is about functionality of tin dioxide gas sensors and the possibilities of active layer modification. Experimental describes gas sensor from its drawing until construction, testing and characterization. Several microelectronic technologies such as thin-film, thick-film, LTCC, spray-coating or wire-bonding were used for constructing the sensor. In the last part properties of gas sensors and differences in functionality between modified and unmodified gas sensor are summarized.
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Synthesis of core/shell quantum dots for diagnostics
Mihajlović, Ana ; Vaculovičová, Markéta (referee) ; Pekárková, Jana (advisor)
This thesis deals with biosensors based on modified semiconductor core/shell quantum dots (QDs) for diagnosis. The work is divided into four main parts. The first one discusses the theory required for the use of QDs in bioaplications, there are described methods of synthesis, modification, application and bioconjugation of QDs. In the experimental part, CdTe/ZnS QDs with core/shell structure were prepared, in which the core was modified by MPA, GSH and TGA. In the next step, these QDs were further modified using CDI, EDC and NHS as mediators in order to increase affinity to BSA (bovine serum albumine) and IgG (imunoglobuline G). Prepared conjugates were characterized by fluorescence spectroscopy (Infinite M200Pro, Tecan) and capillary electrophoresis (Agilent 7100).
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Optimization of metallurgical processes in aluminum alloys foundry
Halaška, Jan ; Lána, Ivo (referee) ; Kaňa, Václav (advisor)
Diploma thesis examines the influence of the preparation and metallurgical treatment on the mechanical properties and structure of aluminium alloys Al-Si. The experimental part was carried out at MSR Engines s.r.o. This part describes the current (sodium modification) and newly proposed (strontium modification) state of preparation and metallurgical processing of melt. There is state the course of experimental melting processes, testing of samples, evaluation of tests and observation of the impact of individual modifiers on the structure.
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Chemical modifications of polypropylene surfaces
Pospíšek, Marek ; Petrůj, Jaroslav (referee) ; Kučera, František (advisor)
Diploma thesis is focused on modification and characterization of polypropylene (PP) products surfaces by the chemical way. In theoretical part of thesis are summarized the current knowledge of this topic including characterization methods. Polypropylene surfaces were modified by acrylic monomers (acrylic acid, acrylic acid with 20 mol% content of sodium acrylate and acryl amide). Modified surfaces were characterized by infrared spectroscopy with ATR technique. The comparative parameter was carbonyl index determined from absorption peaks of functional methyl groups (2950 cm-1 ) and functional carbonyl groups (1700-1750 cm-1) of FTIR-ATR spectra. Determination of effect of initiator concentration on the modification process was done for acetophenone and benzophenone. There were determined the time dependence of carbonyl index for time from 0 to 600 s of mentioned monomers. In the same condition were modified test specimens designed for preparation of adhesive joints. Joints were bonded by cyanoacrylate adhesive that provide reaction with surface of polyacrylic acid. There were founded conditions of modification that provided strength of adhesive joints higher than strength of original PP. There were identified changes of surface roughness by using of confocal microscopy.
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Use of polymers in road constructions
Klusková, Jana ; Komenda, Radek (referee) ; Stehlík, Dušan (advisor)
The diploma thesis deals with the use of recycled polymers in asphalt mixtures. In the theoretical part of the thesis there is discussed the global issue of plastic waste including the experience of foreign countries, where this technology has already been introducted and used. The practical part is devoted to the proposal of using recycled plastic in asphalt mixture, description of used laboratory tests and the evaluating the effect of low-density polyethylen (LDPE) on the asphalt mixture type AC. There were performed tensile strenght tests, water resistant tests and stiffness modulus tests in the laboratory (E). The output of this work is an evaluation of measured values, processing of results and their interpretation depending on the possible use of this technology in Czech republic.
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Study of the effect of metallurgical and technological parameters on mechanical properties of aluminium alloys
Pešek, Jakub ; Krahula, Karel (referee) ; Zemčík, Ladislav (advisor)
Sugested thesis has been made with the intent to observe and describe the length of the modifying effect of three different types of modifiers and their effect on the mechanical properties of aluminium alloy. Next step was to process and evaluate links between mechanical properties and chemical composition. Chemical analysis and mechanical properties of cast samples were obtained. For this purpose and a method of metallographic processing was applied afterwards. The grain size was evaluated before and after the heat treatment. Measurements of the secondary dendrite branches and evaluation of the eutectic morphology were made. The hardness was measured on selected samples.
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Influence of modification and inoculation on structure and mechanical properties of aluminium alloys
Janošťák, Jan ; Lána, Ivo (referee) ; Roučka, Jaromír (advisor)
This thesis examines the influence of inoculation and modification on the internal structure and properties of aluminium-silicon alloys. The effect of inoculation by titanium and boron and modification by sodium and strontium is investigated in experimental part of the thesis. All these metallurgical interventions in the melt are tested on three types of hypoeutectic Al-Si alloys (AlSi10Mg(a), AlSi8Cu3, AlSi7Mg0,3). The experiment was carried out in cooperation with the foundry of non-ferrous metals, Aluminium Group, a.s. in Sloup.
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