1,720,975 research outputs found
High-pressure methane jet: Analysis of the jet-obstacle interaction
Full text linkThe study of unplanned high-pressure gas releases is of paramount importance in the industrial safety framework because of the possible large consequences, both in case of flammable and toxic substances leakage. In addition, if an obstacle is involved in the release, it is known that the main effect on the jet behavior is the enhancement of the risk area. Pointing out the importance to consider the obstacle presence, among the various available numerical approaches, the sole reliable tool able to correctly model the scenario of a jet interacting with an obstacle seems to be the Computational Fluid Dynamics (CFD). This work lies in the context outlined through the examination of a realistic unignited high-pressure methane jet interacting with a realistic obstacle placed along its axis via CFD simulations: a stationary 65-bara unignited methane jet outflowing from a one-inch diameter hole and a medium size horizontal cylindrical tank are the building blocks of the realistic scenario. The aim is to deeply investigate how the distance between obstacle and jet orifice modifies the jet behavior. In particular, the final purposes are: i) to establish when the obstacle most influences the jet cloud extent and, ii) to assess when the obstacle influence expires. Moreover, a sensitivity analysis on the obstacle shape and size is conducted for comparison purposes
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Evaluation of serum CA549, CA M26 and CA M29 levels in the post-operative follow-up of breast cancer patients
No full textGround influence on high-pressure methane jets: Practical tools for risk assessment
Full text linkHigh-pressure gaseous methane release is a relevant safety-related problem mainly in the Oil and Gas industry. As well documented, the reason for these safety concerns is connected with the severe consequences of the domino effect subsequent to the possible ignition. In risk assessment activities, estimation of the damage area is of primary importance in order to draw up proper safety guidelines. To do this, loss prevention specialists use quick and well-established numerical tools (i.e., integral models) in their daily activities. However, the presence of an obstacle in the flow field of the jet (e.g., the ground) is a more probable situation to deal with. It is known that integral models fail in this kind of scenario, leading to unreliable predictions. Hence, the present work investigates how an industrial ground surface influences the LFL cloud size of a horizontal high-pressure methane jet. An innovative quick procedure is proposed allowing to determine the height below which the ground begins to influence the LFL cloud size and the extent of such influence. Therefore, this procedure allows practitioners to establish when integral models can be used and when not to use them, and also provides a simple and reliable alternative to their use. These analytical instruments are derived from an extensive computational fluid dynamics analysis performed with Ansys Fluent 19.0
Safety evaluations on unignited high-pressure methane jets impacting a spherical obstacle
Full text linkNowadays methane is a fossil fuel widely used both in industries and in civil appliances. From the safety point of view, due to its flammability, its use implies hazards for people and assets. The hazardous area related to a high-pressure jet of methane arising from an accidental loss of containment requires the estimation of the distance at which the methane concentration falls below the Lower Flammability limit. Such a topic is well covered in the literature when considering free jet conditions, i.e., jets that do not interact with any equipment or surface. The same cannot be said for high pressure jets impacting an obstacle. In this context, the present work focuses on studying high pressure methane jets impacting spherical obstacles by means of Computational Fluid Dynamics with the aim of giving some insights about such a jet-obstacle interaction, possibly providing a brief by-hand procedure that, only based on known scenario information, allows to estimate the maximum extent of the unignited high-pressure jet when interacting with a spherical obstacle
Evaluation of serum CA15-3 determination with CEA and TPA in the post-operative follow-up of breast cancer patients
No full textGround influence on high-pressure methane jets: Different concentration clouds scenarios
No full textBecause of their relevant consequences (in particular, associated with domino effect), accidental highpressure flammable gas releases are one of the major hazards in the industrial safety framework. It is likely that the accidental loss of containment can involve obstacles that, as a matter of fact, are present in any process facility. As obstacle, flat surfaces (e.g., walls, ground, etc.), equipment (e.g., tanks, pipes, etc.) or structures can be counted. Focusing on the scenario of an accidental high-pressure unignited methane jet interacting with an obstacle, this work investigates how the proximity to the ground influences the jet cloud extent when considering different concentrations of methane in air. Varying the height above the ground of the source term, the effect of the ground was systematically studied through an extensive Computational Fluid Dynamics analysis. Thanks to the sensitivity analysis performed, the main achievement is the demonstration that methane releases observed at different concentrations in air, from sources at different pressures and outflowing from accidental holes of different sizes are similarly influenced by the ground presence. The conclusion of the present work is that, the assessment of the hazardous area extent of the flammable release at any concentration of interest can be evaluated exploit an analytical model specifically derived, providing a useful alternative of practical precision to more expensive CFD computations. This way, for this specific accidental scenario, delineating the area involved within the flammability limits become easier and faster
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