1,720,984 research outputs found
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
Two-Scale Analysis of The Dissolution of Calcite in Geothermal Sandstone Reservoirs: An Experimental and Numerical Study
No full textExperimental studies and three dimensional finite element core scale and field scale models were used to study the effect of calcite dissolution on low-enthalpy sandstone geothermal reservoirs. A series of core flooding experiments were conducted, monitoring the porosity and permeability at 150 ◦C and 20 bars back pressure to see the effect of calcite dissolution by Glutamic acid Di-Acetic acid (GLDA). These experiments are supported by the critical salt concentration and critical fines migration velocity tests in order to ensure that any pressure variations in the core is due to the injected chelating agent and not due to other mechanical effects or chemically damaging reactions. This data obtained is then used in a core scale finite element model to obtain the corresponding kinetic and dissolution parameters. These parameters are then implemented on a field scale (homogeneous and heterogeneous) reservoir model to see the effect of calcite dissolution on the well productivity. Process based facies modelling is utilised to construct realistic heterogeneous reservoir models. In an effort to understand the effect of flow direction in the reservoir, samples were tested for the critical velocity of fines migration in three directions and it was observed that the critical velocity of fines migration in the different samples were similar, showing the homogeneous nature of the samples. From the homogeneous field scale model, for a given volume of acid injected, the effect of calcite dissolution was analysed for 5, 10, 30 and 50% calcite concentration in the reservoir. The estimated values of well productivity and equivalent permeability for 10, 30 and 50% calcite concentration were found to be in a decreasing order with 10% having the highest value. Interestingly, in the case of 5% calcite concentration the well productivity and equivalent permeability were estimated the lowest. In the case of power required by the pump the 5% calcite concentration required the highest power while the 10%, 30% and 50% were found to be in a increasing order with 10% calcite concentration requiring the least power. Although the acid penetration for the 5% calcite concentration was the furthest, the permeability improvement was too low to have a positive impact on the equivalent permeability, well productivity and power required by the pump. From the heterogeneous model, it was observed that the lifetime of the reservoir increases with increasing stimulation. This model could be used as a predictive tool for estimating the lifetime increment for a given volume of acid injected. Our simulation results show that the penetration depth (acid front) of acid is highly affected by the radial flow characteristics in field scale simulations, as the penetration depth is not linearly correlated to the volume of acid injected.Civil Engineering and GeosciencesGeoscience & EngineeringApplied Earth Science
Oil foam interaction: Simulation of foam displacement with oil
No full textFoam injection is a promising method to improve sweep efficiency for gas flooding in enhanced oil recovery (EOR). The effect of oil on foam is a complex phenomenon and for this reason three phase foam simulations have shown to be difficult in the past. Initially the objective of this simulation study was getting a better understanding of relating composition paths for foam displacements on the ternary diagram to the gas mobility reduction factor on the same diagram (Dharma, 2013). However, there were unexpected numerical problems during the course of the study and consequently the objective of the thesis has been changed. The new focus of the research is investigating the different problems that are encountered with three-phase foam simulations. Additionally an attempt is made to overcome the problems by changing the numerical method and adding a capillary diffusion coefficient. Two cases are examined, both showing oscillations using the STARSTM foam model. Firstly, a Finite Volume Method (FVM) model has been created. This simple single point upstream scheme without diffusion is tested and used to study the challenging cases of Namdar Zanganeh et al. (2009) and Dharma (2013). In both researches oscillations between the foam and no-foam region appear. Research on the case of Namdar Zanganeh et al. is presented; the same difficulties occur using the FVM method. The oscillations cannot be overcome by using extremely small time steps and grid size. Hence this is a fundamental problem for finite volume grids with a single point up-wind scheme and no diffusion. The FVM script is extended with a capillary diffusion coefficient to approximate the effect of capillary pressure gradient and Finite Element Method (FEM) is in an attempt to overcome the problems encountered. The addition of the capillary diffusion coefficient makes the oscillations between the foam and no-foam region disappear and shocks to states predicted by Namdar Zanganeh et al. are present. The forward shock is broad, but it appears to be a shock. The velocity of the slow shock is too fast. For the FEM simulation COMSOL is used, with this numerical method no oscillations occur. However, a shock to a state not predicted by Namdar Zanganeh et al. (2009) is present. Moreover, a travelling ’shock’ does not advance at all, on the time scale studied. Additionally, research on the case of Dharma (2013) is presented. For this case the oscillations disappear using the FVM. This means the oscillations are a result of the higher order FVM used by Dharma. However, the result is not optimal since new complications arise: non-monotonically moving shocks. A study on this abnormality is carried out and results obtained are for a number of cases compared to the work of Dharma. The FVMresults in this research show similar behaviour as Dharma found. An intermediate oil bank is found at a different saturation this most likely because of the use of a different oil relative permeability function.Petroleum EngineeringGeoscience & EngineeringCivil Engineering and Geoscience
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
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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
Thermally-enhanced oil recovery from stranded fields: Synergy potential for geothermal and oil exploitation
No full textAccepted author manuscriptReservoir EngineeringApplied Geolog
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
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