1,720,957 research outputs found
Potential as against Restriction in CCS Strategies: the operational role of technological innovation to cut costs and to dispel distortions and doubts
No full textEXPERIMENTAL CHARACTERISATION OF LIQUID-GAS FLOWS THROUGH AN ANGLE VALVE
No full textTwo-phase flows of air and water through an angle valve have been studied. The valve, a Plexiglas replica of a 2” Willis choke valve, has been characterised previously in single phase flow.
An empirical relation between pressure drop multiplier Φtp and void fraction has been derived. A correlation is deduced for valve opening less than one to consider fluid dynamic efficiency of the valve
New perspectives in underground storage in depleted fields
No full textThe underground storage of natural gas is a procedure compatible with the optimal management of the transportation system. The amount of gas that exceeds consumption is stored underground in order to be extracted during high demand periods. Due to the structure of the gas market, greatly affected by heating gas consumption, this translates into a yearly storage cycle whereby gas is injected underground during the warmest periods of the year and retrieved in the coldest months.
The fundamental parameters for storage are:
• working gas, or maximum gas quantity that can be received during the ream cycle;
• cushion gas, or the difference between total gas volume in place in a situation of maximum flood and working gas (although it represents a fixed quantity, cushion gas is necessary to keep reservoir pressure and to allow adequate flows during the ream cycle);
• maximum gas flows allowed by the characteristics of the reservoir and the production units.
In Italy, where storage is presently carried out only in semi-depleted gas reservoirs, it is not permitted, during the injection cycle, to exceed in reservoir the original static pressure recorded at the time of discovery. This practice, however, is beginning to be successfully adopted abroad.
The storage pressure of the gas in reservoir is limited, from a technical point of view, by the ability of the cover rock to oppose the passage of the hydrocarbons and by its resistance to fracture.
Particular attention is then paid to the aptitude of the storage cover rock in preventing the passage of gas. Such property depends, on the sample scale, on the rock's chemico-physical characteristics, particularly the capillarity properties. From an experimental point of view, this study was carried out on the basis of tests run on samples of formations of the Santerno Clay type, a cover rock common to many Italian storage fields. The samples belong to four fields located at depths between 1000 and 1650 metres sub sea level.
The threshold displacement pressure of these samples was measured; that is the difference in pressure that must exist at the extremities of the sample initially saturated with water in order for it to let the gas through. This test is very burdensome, given the length of time necessary (up to several months) to perform it. The cost of the test and the need to extend the values obtained on the field scale make the possibility of correlating this parameter with the values of porous media, otherwise measurable, particularly attractive. Thus, the change of the threshold displacement pressure vis-à-vis the petrophysical (permeability and porosity), mineralogical, granulometrical and sedimentation characteristics of different samples was studied. Given the number and the varied nature of the values under consideration, the task, complex in itself, could not generate the possibility of correlating these values in reliable manner. The values of the threshold displacement pressure seem to be influenced by the content in clay minerals of the samples (Figure 1)
Applicazione di un GIS alla caratterizzazione di un ammasso roccioso per la progettazione di una grande opera sotterranea
No full textNel lavoro di caratterizzazione geologica, idrogeologica e geotecnica di un
ammasso rooccioso, interessato dalla progettazione
di un'opera di ingegneria,accade spesso di raccogliere una
notevole quantità di informazioni. spesso di natura ed origine
diversa. In questi casi risulta di particolare utilità, ai fini della interpretazione
delle effettive condizioni del sottosuolo, poter disporre di queste
informazioni in modo organizzato e di facile e diretta consultazione.
A tal fine è stato implementato un Sistema Informativo Geografico (GIS) partendo da
un software disponibile in commercio (MAPINFO), in modo da
renderlo dedicato all’impiego nella raccolta, organizzazione e rappresentazione
delle informazioni di natura geologica, idrogeologica e geotecnica
relative ad un ammasso roccioso.
Nel presente lavoro, nel descrivere sinteticamente le caratteristiche
del software inplementato, si presentano i risultati dell’applicazione di esso
alla caratterizzazione di un ammasso roccioso, appartenente alla catena appenninica
meridionale, interessato dalla progettazione e parziale esecuzione di una galleria idraulica
transappenninica di grande diametro.
L’interesse del GIS, implementato in questa sede, si ritiene risieda nel costruire uno strumento
di facile e diretta utilizzazione anche per coloro che non hanno una esperienza
specifica nel settore del sistemi informativi geografici
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
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
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