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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A tumbler and pore water expression device to prepare homogeneous samples for the extraction of free chloride in cement paste

Delport, D.J., Potgieter-Vermaak, S.S., Potgieter, J.H. January 2013 (has links)
Published Article / Corrosion of rebar in concrete is commonly associated with the free chloride in the pore water in the cement matrix. Knowing the quantity of chloride in concrete is important because chloride can promote corrosion of steel reinforcement when moisture and oxygen are present. The problem ofphysical extraction and the measurement of the free chloride content in pore water solutions extracted from cement pastes has received attention in literature but has not been explained in full detail. However, the variability of results obtained from the different methods used by various investigators only serves to confuse the issue. This investigation describes the use of a tumbler designed to prepare homogeneous samples and the use of a pore water expression device designed to extract free chloride in cement paste and concrete samples.
2

The Dark Flows of Cryptocurrency : an overview of money flow behaviors in Bitcoin transactions related to online criminal activities and Bitcoin mixers

Olsson, Anton, Andersson, Daniel January 2024 (has links)
The decentralized and pseudonymous nature of cryptocurrencies like Bitcoin has made it easier for criminal entities to engage in illicit activities online compared to relying on traditional currency systems. Detecting these activities is vital to preventing and combating such abuse. We employ a data collection tool based on a Depth First Search algorithm to follow the largest receivers from 10 illicit starting addresses in each abuse type; Darknet, Blackmail, Tumbler, and Ransomware. The results from our two searches showed that money tends to be concentrated to one or two receivers and that all abuse types rely heavily on so-called Two-Transaction addresses. These addresses are only used once, likely as intermediaries to obfuscate money flow, potentially within the inner layer of Bitcoin Tumblers. The results also showed behaviors within the abuse types that were both consistent with and divergent from existing research. Furthermore, similarities and unique behaviors across the abuse types were identified. Expanding the dataset with deeper searches could yield clearer patterns in money flow behavior. Additionally, increasing the number of data collection points could enhance the analysis. Finally, the starting addresses significantly impacted the trustworthiness and reliability of our results. We hope our findings, lessons, and developed tools will aid future research and the development of strategies to combat online abuse.

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