Impact of Geo-distribution and Mining Pools on Blockchains: A Study of Ethereum

Given the large adoption and economical impact of permissionless blockchains, the complexity of the underlying systems and the adversarial environment in which they operate, it is fundamental to properly study and understand the emergent behavior and properties of these systems. We describe our experience on a detailed, one-month study of the Ethereum network from several geographically dispersed observation points. We leverage multiple geographic vantage points to assess the key pillars of Ethereum, namely geographical dispersion, network efficiency, blockchain efficiency and security, and the impact of mining pools. Among other new findings, we identify previously undocumented forms of selfish behavior and show that the prevalence of powerful mining pools exacerbates the geographical impact on block propagation delays. Furthermore, we provide a set of open measurement and processing tools, as well as the data set of the collected measurements, in order to promote further research on understanding permissionless blockchains.Comment: To appear in 50th IEEE/IFIP International Conference on Dependable Systems and Networks (DSN), 202

Molecular analysis of anterior endoderm during Xenopus development: a funtional and genomic approach

Tese de doutoramento em Biologia (Biologia do Desenvolvimento), apresentada à Universidade de Lisboa através da Faculdade de Ciências, 2008Fundação para a Ciência e Tecnologia (FCT), (SFHR/BD/10035/2002

Consuming durable goods when stock markets jump: a strategic asset allocation approach

Agents derive their utilities from consumption over time. In this paper we consider an agent that invests in thefinancial market and in consumption goods. The agent has an infinite time horizon and a utility that depends on consumption at each point in time, consuming both a durable good and a perishable good. There are costs for transacting the durable good. We show that an agent who does not consider the impact of jumps in the return process of risky assets will make suboptimal decisions, not only regarding the fraction of wealth invested in the stock market, but also with respect to the timing for trading on the durable good.Optimal asset allocation, durable consumption good, transaction costs.

Gas mass-flow meters: Principles and applications

Gas mass-flow meters (GMFM) for original equipment manufacturers (OEM) applications are presently found in a relatively easy and cheap way. GMFM may be applied in a number of different situations but technical formation concerning its principles of measurement and applications are still misleading. In this paper, the principles of GMFM measurement are discussed and the operating parameters are clarified. A concept of gas mass-flow response factor is introduced and further used in a model for gas mass-flow measurement that is suitable to any gas mixture of known composition. In addition, a model for the application of GMFM to dynamic volumetric methods of dilution is presented and generalized

Vibration Analysis of Gas Turbine’s Transportation Carrigage and Warranty Issues

Case StudiesThis paper describes the investigation of whether the vibration shock limits were exceeded on the transportation of 2 gas turbines. This investigation was requested due to an improper suspension type of the carriage used in the transport and the OEM consideration if vibration limits were exceeded during the route. It ultimately lead to a contractual impasse where the OEM required full bearing inspection prior to commissioning as a prerequisite to maintain the warranty on the equipment which the client did not agree to follow without further investigation

Behaviour Monitorization of a 13m High Gabions Wall

The paper refers a gabions retaining wall, located at Belas, about 30 km Northeast of Lisbon, in the North perimeter of an Organic Valorisation Central (Valorsul). After the wall completion some pathology occurred and it was detected that it had been partially executed with marl limestone blocks that loose mechanical resistance under rainy water. The wall was then demolished and rebuilt with adequate material. During the earth fill execution the wall was monitorized with a superficial topographical survey. The results obtained and the respective conclusions are referred

Project management metrics and creation of an operational dashboard

Mestrado Bolonha em Mathematical FinanceThis report describes my 3-month internship at Unipartner IT Services S.A., that occurred from March to June 2022. This internship focused on activities mainly related to project management. Unipartner IT Services S.A is an information technology services company that works with government organizations, financial institutions and commercial companies with the aim of solving the most demanding IT and business challenges. During this internship, I performed a gap analysis between the information available in the client’s database and a set of performance metrics that needed to be computed, with the objective of understanding what information was missing, and to improve the quality of the service provided. Understanding and analysing the project management process was an important task prior to all others: it was essential learning what to do and how to do it, depending on the characteristics of contracts and clients at hand. I also created a dashboard in Power BI, based on the company’s database (Azure DevOps), gathering all information regarding contracts, that can be presented to a client in order to illustrate the progress.info:eu-repo/semantics/publishedVersio