1,720,964 research outputs found
Experimental study of aqueous foam generation and transport in a horizontal pipe for deliquification purposes
No full textThis work presents and analyses the results of experimental activities aimed at a preliminary characterization of foamy flows for pipeline dewatering, in order to assess whether the addition of surfactants may effectively reduce the liquid holdup in horizontal pipelines. Static tests were run to compare the foam cycle (generation and decay) for three commercial surfactants and to choose the most suitable one. Dynamic tests with the selected product were performed in a 20 m long, 60 mm i.d. Plexiglas® pipe, where a 0.3% wt. solution of surfactant in tap water was pumped after mixing with an air flow at nearly atmospheric pressure and temperature. Superficial velocities ranged between 0.03 m/s and 0.05 m/s for water and between 1.5 m/s and 11.5 m/s for air, which would determine stratified/stratified wavy flows in the case of pure water-air flow, i.e. the benchmark case. Due to the presence of the surfactant, foam formed in the mixing section, which implied a significant change in the flow patterns that were photographically recorded and classified into three main types: plug, stratified wavy and stratified with foam entrainment, as far as the air superficial velocity was increased at constant water superficial velocity. The associated pressure drop, linearly distributed along the pipeline, resulted greater than the benchmark value in all the operating conditions, with a dramatic increase (even more than 100%) for plug flows. On the other hand, the percentage relative difference was found to lower with increasing the air superficial velocity, apart for stratified wavy flows where it seemed to keep constant at about 3.3%. Finally, a theoretical model for stratified flows was used to relate the pressure drop to the void fraction in order to get at least an approximate indication of the liquid load reduction due to the surfactant addition, which ranged between 6% and 39%
Probabilistic analysis of risk and mitigation of deepwater well blowouts and oil spills
Get PDFThe development of robust risk assessment procedures for offshore oil and gas operations is a major element for the assessment of the potential feedback between planned activities and the environment. We illustrate a methodological and computational framework conducive to (1) a quantitative risk analysis of deepwater well barrier failures and subsequent hydrocarbon release to the environment and (2) the analysis of the value of the deployment of conventional and/or innovative mitigation measures. Our methodological framework is grounded on historical records and combines the use of Dynamic Event Trees and Decision Trees from which we estimate probability of occurrence and impact of post-blowout events. Each sequence of response actions, which are undertaken immediately after the event or in the subsequent days, is considered within the context of appropriately structured event paths. This approach is conducive to an estimate of the expected value of key decisions and underlying technologies, with an emphasis on their potential to reduce the oil spill volume, which can critically impact the environment. Our study yields an original comparative analysis of diverse intervention strategies, and forms a basis to guiding future efforts towards the development and deployment of technologies and operating procedures yielding maximum benefit in terms of safety of operations and environmental protection
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Analysis of electrical heating technologies from a flow assurance point of view
Get PDFLAUREA MAGISTRALEIl petrolio facilmente estraibile è finito, tuttavia la domanda mondiale di combustibili liquidi è in continuo aumento. Per questo motivo le compagnie petrolifere stanno concentrando i loro sforzi nell’esplorazione e sfruttamento di giacimenti in acque sempre più profonde, tuttavia solo grandi giacimenti possono essere sfruttati per via del tremendo impegno economico. Collegare giacimenti marginali con delle infrastrutture già esistenti è fondamentale per ridurre i costi e quindi per produrre da riserve che altrimenti non sarebbero economicamente sfruttabili. La gestione del flusso di idrocarburi, tuttavia, diventa critica per lunghe distanze, per via della deposizione di cere e di idrati che possono completamente ostruire la condotta. In pratica diversi metodi, come ad esempio l’iniezione di inibitori chimici, vengono usati per mantenere il flusso di idrocarburi. Le tecnologie tradizionali tuttavia sono estremamente costose e quindi non possono essere economicamente applicate su condotte lunghe. In questo scenario le tecnologie di riscaldamento attivo possono essere applicate per ridurre i costi e produrre da campi marginali. Lo scopo di questa tesi è di analizzare le varie tecnologie di riscaldamento elettrico dal punto di vista termo-fluido dinamico. Per confrontare le differenti soluzioni diversi modelli sono stati implementati in MATLAB®. I modelli sono stati validati con l’ausilio del simulatore commerciale OLGA. I modelli sono successivamente stati applicati in un caso studio in regime stazionario e per un’analisi preliminare in regime transitorio. Dai risultati ottenuti è possibile capire che l’impiego delle tecnologie di riscaldamento elettrico è fondamentale per evitare la deposizione di cere e idrati e che l’impiego in combinazione con materiali molto isolanti è cruciale per limitare la potenza necessaria per riscaldare la linea.“Easy-to-reach” oil is finished. However, the world demand of liquid fuels is constantly rising. For this reason, Oil&Gas companies are focusing their effort in the exploitation of deep and ultra-deep offshore fields. To justify the economical commitment only large and giant fields can be exploited. Long tie backs to existing facilities are crucial to exploit small fields, which production otherwise will result uneconomical. However, flow assurance issues, such as wax and hydrate deposition, becomes critical. In this context more cost-effective flow assurance technologies must be employed to enable the production from such fields. One of the most promising technology is Active Heating, which is by definition the injection of heat into a production system. In this work steady-state electrical heating simulators have been implemented in MATLAB® in order to compare the different technologies from a flow assurance point of view. The fluid dynamic validity of the models is verified with the aid of the commercial software OLGA®. The models are then applied to a case study to extract general considerations. A preliminary transient analysis has been also performed to compare the different technologies. From the results, is possible to understand that the employment of the active heating technologies is fundamental to avoid solid depositions during normal flowing conditions. Furthermore, the technologies allow to maintain the temperature during a shut-down and warm-up the fluids during a cold start-up. The installation of high-performance insulating material is necessary to reduce the power requirement of the different active heating technologies
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