abstract: The lack of fungibility in Bitcoin has forced its userbase to seek out tools that can heighten their anonymity. Third-party Bitcoin mixers utilize obfuscation techniques to protect participants from blockchain analysis. In recent years, various centralized and decentralized Bitcoin mixing implementations have been proposed in academic literature. Although these methods depict a threat-free environment for users to preserve their anonymity, public Bitcoin mixers continue to be associated with theft and poor implementation. This research explores the public Bitcoin mixer ecosystem to identify if today's mixing services have adopted academically proposed solutions. This is done through real-world interactions with publicly available mixers to analyze both implementation and resistance to common threats in the mixing landscape. First, proposed decentralized and centralized mixing protocols found in literature are outlined. Then, data is presented from 19 publicly announced mixing services available on the deep web and clearnet. The services are categorized based on popularity with the Bitcoin community and experiments are conducted on five public mixing services: ChipMixer, MixTum, Bitcoin Mixer, CryptoMixer, and Sudoku Wallet. The results of the experiments highlight a clear gap between public and proposed Bitcoin mixers in both implementation and security. Today's mixing services focus on presenting users with a false sense of control to gain their trust rather then employing secure mixing techniques. As a result, the five selected services lack implementation of academically proposed techniques and display poor resistance to common mixer-related threats. / Dissertation/Thesis / Masters Thesis Computer Science 2020

The work deals with design, simulation and preparation of laboratory preparation. The main aim of the thesis is to design and implement a simple noise generator, signal sources, mixer and phase lock loop for teaching purposes.

The subject of the diploma thesis is the study of moisture resistance of macrodefect-free (MDF) cements based on calcium-aluminate cement and polyvinylalcohol used as polymer. MDF cements are perspective materials providing unique properties relative to traditional cement pastes with great potential to incoming constructional utilization. But it is known that MDF cements exhibit sensitivity to water, with swelling and reduction of strength. Therefore the work is aimed in monitoring of an organic polymer effect on the moisture resistance of MDF materials and phase changes. Aluminate cement (SECAR 51) and polyvinylalcohol/acetate copolymer have been used for the MDF cement preparation. The moisture resistance of model MDF cement samples was investigated at two different curing conditions: in the moist atmosphere and immersed in water. The influence of composition and individual curing on the properties of model MDF cement samples was observed. The characterization of MDF samples was based especially on test of flexural strength, FT-IR, EDAX and optical microscopy analyses.

The aim of the master’s thesis is to design continuous mixer for preparation of molding compounds on the performance of 1 – 3 t/hour. The first part of the thesis contains recherché from molding compound and molding compound mixers field. In the next part there is an own design of mixer containing basic calculations and strength analysis by FEM. Part of the thesis is also 3D model of the whole machine as well as drawing documentation of selected parts. At the end of thesis partial risk analysis by FMEA is made.

The aim of this diploma thesis is the structural design of continous mixer with output range 5-12 tons per hour. The work contains a brief description of mixing technology and basic parameters of similar machines. The work is devoted to the design of double-arm sand mixer with a belt conveyor. An important part of this diploma thesis is a 3D model of fundamental parts of sand mixer, as well as its composition. Based on the 3D model is elaborated strenght analysis of selected parts with finite element method. The work is accompanied by manufacturing drawings of selected components and assembly drawing of deposit of mixing blades to the shaft.

The objective of this research was to investigate the affects of various generator plate size, D/d ratio, stroke frequency and slurry concentration, for a plate type vortex ring mixer, on the drag force and power consumption. In this case CaCO3 aqueous slurry was used for the investigation. The generator plate was driven using an AC induction motor with gear type speed reducer which was controlled using a frequency inverter and a mechanism for converting rotational into translational motion. This drive system resulted in sinusoidal motion of the generator plate. The applied force, the displacement of the generator plate and the input power were measured using measurement cell developed for this purpose. The viscosity was also measured. The data were analyzed, organized and presented using appropriate graphs. The force measurement data showed that drag force was mainly affected by the size of generator plate and its oscillating frequency. Larger generator plates had greater drag force acting on them and, therefore, required more power for running. Oscillating frequency had similar effect on drag force and power consumption. However, tested CaCO3 slurry concentrations showed to have no significant affect on these two parameters. Drag force results obtained during this study are considered to be reasonably representative, while power consumption data, although representative for this system, will probably be different for different drive systems employed. / Thesis / Master of Engineering (ME)

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