7,499 research outputs found
Big-Step Semantics
With the popularity of model-driven methodologies, and the abundance of modelling languages, a major question for a requirements engineer is: which language is suitable for modelling a system under study? We address this question from a semantic point-of-view for big-step modelling languages (BSMLs). BSMLs are a popular class of behavioural modelling languages in which a model can respond to an environmental input by executing multiple, possibly concurrent, transitions. We deconstruct the semantics of a large class of BSMLs into high-level, orthogonal semantic aspects and discuss the relative advantages and disadvantages of the semantic options for each of these aspects to allow a requirements engineer to compare and choose the right BSML. We accompany our presentation with many modelling examples that illustrate the differences between a set of relevant semantic options.
Desorption of hydrocarbon chains by association with ionic and nonionic surfactants under flow as a mechanism for enhanced oil recovery
The need to extract oil from wells where it is embedded on the surfaces of
rocks has led to the development of new and improved enhanced oil recovery
techniques. One of those is the injection of surfactants with water vapor,
which promotes desorption of oil that can then be extracted using pumps, as the
surfactants encapsulate the oil in foams. However, the mechanisms that lead to
the optimal desorption of oil and the best type of surfactants to carry out
desorption are not well known yet, which warrants the need to carry out basic
research on this topic. In this work, we report non equilibrium dissipative
particle dynamics simulations of model surfactants and oil molecules adsorbed
on surfaces, with the purpose of studying the efficiency of the surfactants to
desorb hydrocarbon chains, that are found adsorbed over flat surfaces. The
model surfactants studied correspond to nonionic and cationic surfactants, and
the hydrocarbon desorption is studied as a function of surfactant concentration
under increasing Poiseuille flow. We obtain various hydrocarbon desorption
isotherms for every model of surfactant proposed, under flow. Nonionic
surfactants are found to be the most effective to desorb oil and the mechanisms
that lead to this phenomenon are presented and discussed.Comment: 10 figures; to appear in Scientific Report
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