Mineral scale prediction modelling : precipitation of CaCO3 scale in CO2-water alternating gas production systems

The injection of CO2 in oil reservoirs for tertiary oil recovery is one of the main Enhanced Oil Recovery (EOR) processes and it is widely used in the oil and gas industry. To prevent early gas breakthrough, CO2 is commonly injected in alternated slugs with water, in a process known as CO2 Water Alternating Gas (CO2 WAG). When such processes are carried out in carbonate reservoirs, there is the potential for calcite (CaCO3) dissolution in the reservoir and its subsequent re-precipitation in production systems, thus posing a flow assurance risk that must be carefully managed. A new thermodynamic model that addresses all of the major steps involved in the precipitation of CaCO3 scale in CO2 WAG production systems is proposed, including: i) the dissolution of injected CO2 into the reservoir brine; ii) the rock-brine interactions and the dissolution of CaCO3 rock; iii) the reactive flow and transport of aqueous components in the reservoir; iv) the partition of components between the liquid, vapour, and water phases; and v) the precipitation of CaCO3 scale as a function of decreasing pressure (and temperature) in CO2 WAG production systems (i.e. in the well and in topside equipment). Thus, an aqueous electrolyte model has been implemented and coupled with a Vapour-Liquid Equilibrium (VLE) model, a multiphase flash model, and a reactive transport model. The non-ideal behaviour of the aqueous and hydrocarbon phases (vapour and liquid) has been modelled by using respectively the Pitzer equations and an Equation of State (EOS) (Soave-Redlich-Kwong, SRK, and Peng-Robinson, PR, EOS, have been used, among others). The implementation of these models has been validated by comparing results with experimental data and/or with results obtained by using industry standard software. In addition, the impact of VLE, multiphase flash, and reactive transport calculations on the precipitation of CaCO3 scale has been investigated, by considering commonly available production data. Also, a procedure had been devised to address each step involved in the precipitation of CaCO3 scale in CO2 WAG production wells individually, and together in an integrated approach. In fact, this work focuses on building the boundaries for the CaCO3 scaling system, thus allowing to define, and work on, worst case scenarios. This gives the required information – both qualitatively and quantitatively – to manage CaCO3 scale in CO2 WAG production wells

Lithium depletion in solar analogs: age and mass effects

The main goal of this work is to evaluate the correlation between Li abundance, age, and mass. Using high-quality ESO/HARPS data (R $\simeq$ 115 000; 270 $\leq$ SNR $\leq$ 1000), we measured Li abundances via spectral synthesis of the 6707.8 \r{A} $^7$Li line in 74 solar twins and analogs. Our joint analysis of 151 Sun-like stars (72 from our sample plus 79 solar twins from a previous study) confirms the strong Li abundance-age correlation reported by other works. Mass and convective envelope size also seem to be connected with Li abundance but with lower significance. We have found a link between the presence of planets and low Li abundances in a sample of 192 stars with a high significance. Our results agree qualitatively with non-standard models, and indicate that several extra transport mechanisms must be taken into account to explain the behaviour of Li abundance for stars with different masses and ages.Comment: 10 pages, 15 figures, to appear in MNRA

Biblioteca escolar: concepção de professores em formação inicial

Se entendermos leitura (escolar) como actividade estratégica de (re)construção de sentido(s), em que o leitor interage com os textos em contexto, teremos de assumir a Biblioteca como referência na construção de leitores. Sabendo que a dinamização e o bom funcionamento da Biblioteca Escolar exigem o envolvimento dos agentes educativos, procurámos caracterizar 1) concepções, 2) papéis, 3) relações de professores estagiários com bibliotecas escolares. Para o efeito, servimo-nos de um inquérito feito a professores estagiários da Universidade do Minho. Optámos, neste estudo, por centrar a investigação nas relações estabelecidas entre professores em estágio e bibliotecas escolares por duas razões: - As bibliotecas escolares são vistas como “[…] lugar de aprendizagens múltiplas, como espaço de trabalho e de lazer de professores, alunos e funcionários e, por isso, como recurso educativo por excelência da comunidade escolar.” (Sousa et al., 2000) - A prática pedagógica proporciona ao futuro professor um desempenho em contexto real que permita desenvolver competências e atitudes necessárias para um desempenho consciente, responsável e eficaz. (Formosinho & Nisa, 2001: 54), esperando-se a sua interacção com os recursos disponíveis na instituição de formação. Assim, nesta investigação, procuraremos confirmar o estatuto especial da Biblioteca (escolar) na promoção de competências, atitudes e hábitos de leitura

Turbulence Quantification in Supercritical Nitrogen Injection: An Analysis of Turbulence Models

In Liquid Rocket Engines, higher combustion efficiencies come at the cost of the propellants exceeding their critical point conditions and entering the supercritical domain. The term fluid is used because, under these conditions, there is no longer a clear distinction between a liquid and a gas phase. The non-conventional behavior  of thermophysical properties makes the modeling of supercritical fluid flows a most challenging task. In the present work, a RANS computational method following an incompressible but variable density approach is devised on which the performance of several turbulence models is compared in conjunction with a high accuracy multi-parameter equation of state. Also, a suitable methodology to describe transport properties accounting for dense fluid corrections is applied. The results are validated against experimental data, becoming clear that there is no trend between turbulence model complexity and the quality of the produced results. For several instances, one- and two- equation turbulence models produce similar and better results than those  of Large Eddy Simulation (LES). Finally, considerations about the applicability of the tested turbulence models in supercritical simulations are given based on the results and the structural nature of each model. Keywords: Supercritial fluids, RANS turbulence modeling, Liquid rocket engine

The forums of Conimbriga and Aeminium: comparison and summary of the state of the art.

This paper presents the forums of the Roman cities of Conimbriga (Condeixa-a-Velha, Portugal) and Aeminium (Coimbra, Portugal), both of which date from the time of Augustus. The Aeminium forum was completely rebuilt in the time of Claudius/Nero, while the Conimbriga one was remodelled in the same period, before being demolished under the Flavians to make way for a completely new construction. This article offers a state-of-the-art comparison of the architectural models used in these two cities, based on the analysis and review of the available data, partly supplied by recent archaeological excavations. The geographic and chronological proximity of these two forums mean that it is of interest to compare their architectural design, which differ considerably in aspects such as volumetry, layout and the conceptual model used. The article discusses the proposals for the development of the Conimbriga forum and indicates an up-to-date bibliography for both public spaces, resulting, in the case of Aeminium, from a large-scale research and intervention project carried out in recent years

The use of 3D printing for the development of a learning tool for the visually impaired.

3D printing is a technology that allows manufacturing objects from a virtual model. The field of education has appropriated its use due to its potential to contribute to the teaching-learning process, especially for the education of the visually impaired. Visually impaired people develop their skills through alternative means, mainly using auditory and tactile landmarks as a way of obtaining information. Within the innovative perspectives for education, this study aims to propose a learning tool using 3D printing technology to build a board game employed for the use of unplugged programming language in the education of children visually impaired for their development of logical thinking skills. The learning tool production started in its modeling performed using specific software that generated 3D virtual models. Later, these files were sent to a 3D printer for printing, using the fused filament fabrication, originating physical copies of modeled objects. Then, the objects, now printed, went through a finishing process for their completion. Part of the game components received braille indications accordingly to the proposed in this study. As a result, we obtained a game prototype adapted for the visually impaired, made through 3D printing, with the potential to assist in the teaching-learning process

Effects of endoscopic thoracic sympathectomy for primary hyperhidrosis on cardiac autonomic nervous activity

ObjectiveEndoscopic thoracic sympathectomy is performed to treat primary hyperhidrosis. The second and third sympathetic thoracic ganglia excised also innervate the heart. Some studies have shown decreased heart rate but have not been conclusive regarding other cardiac effects of sympathectomy. We studied the cardiac autonomic effects of endoscopic thoracic sympathectomy in a group of patients with primary hyperhidrosis. Heart rate variability is a simple, noninvasive electrocardiographic marker reflecting the activity and balance of the sympathetic and vagal components of the autonomous nervous system.MethodsWe performed a prospective study in 38 patients with primary hyperhidrosis with 24-hour Holter recordings obtained before endoscopic thoracic sympathectomy and 6 months later.ResultsWe found statistically significant differences (P < .05) in both time and frequency domains. Parameters that evaluate global cardiac autonomic activity (total power, SD of normal R-R intervals, SD of average normal R-R intervals) and vagal activity (rhythm corresponding to percentage of normal R-R intervals with cycle greater than 50 ms relative to previous interval, square root of mean squared differences of successive normal R-R intervals, high-frequency power, high-frequency power in normalized units) were statistically significantly increased after sympathectomy. Low-frequency power in normalized units, reflecting sympathetic activity, was statistically significantly decreased after sympathectomy. Low-/high-frequency power ratio also showed a significant decrease, indicating relative decrease in sympathetic activity and increase in vagal activity.ConclusionThese results provide, for the first time to our knowledge, clear evidence of increased vagal and global cardiac autonomic activity and decreased sympathetic activity after endoscopic thoracic sympathectomy

Application of RFID Technology in Public Sectors in Brazil

RFID technology is a technology of 4.0 Industry that seeks to support logistical management by enabling data communication and allowing enhanced control of managed goods from a certain institution. One way of application is in Asset Management, granting a greater efficiency in public management, security, control and automation. This project aims to analyze the scientific production published in association to related aspects of the RFID technology at public agencies in Brazil. A systematic literature review was carried out in Science Direct and Google Scholar databases between the years 2015 and 2020. There was a total of 17 studies that addressed the RFID application in the management of mobile assets at public agencies in Brazil, which most of them being application proposals at Public Universities and Army, where the concentration of these chattel are bigger and demonstrates the efficiency of this technology on controlling tracked goods, exploiting all the advantages that this system makes possible