1,720,977 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
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
Statistical modelling of the narrow gap gas metal arc welding process
Full text linkThe J-laying technique for the construction of offshore pipelines requires a fast welding process that can produce sound welds in the horizontal-vertical position. The suitability of narrow gap gas metal arc welding (NG-GMA W) process for this application was previously demonstrated.
The present programme studied the influence of process parameters on the fusion characteristics of NG-GMA welding in a range of different shielding gas compositions and welding positions. Statistical techniques were employed for both designing the experimental programme and to process the data generated. A partial factorial design scheme was used to investigate the influence of input variables and their interaction in determining weld bead shape. Modelling equations were developed by multiple linear regression to represent different characteristics of the weld bead. Transformation of the response variable based on the Cox-Box method was commonly used to simplify the model format. Modelling results were analysed by graphical techniques including surface plots and a multiplot approach was developed in order to graphically assess the influence of up to four input variables on the bead shape.
Conditions for acceptable bead formation were determined and the process sensitivity to minor changes in input parameters assessed. Asymmetrical base metal fusion in horizontalvertical welding is discussed and techniques to improve fusion presented.
At the same time, the interaction between the power supply output characteristic and the bead geometry was studied for narrow gap joints and the effect of shielding gas composition on both process stability and fusion of the base metal was assessed. An arc instability mode that is strongly influenced by arc length, power supply characteristic and shielding gas composition was demonstrated and its properties investigated. An optimized shielding gas composition for narrow gap process was suggested
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
Welding C-Mn steels using the pulsed current MIG welding process
No full textThe welding of C-Mn steels using the pulsed current MIG welding
process was investigated. Following initial work on the basic fusion
characteristics, the process was applied to the production of closed
butt joint linepipe welding and narrow gap welding (in the flat and
H-V positions).
The initial stage of the work covered the determination of pulse
parameters for controlled metal transfer with a variety of wires and
shielding gases. Basic bead-on-plate fusion characteristics were
investigated 1n all welding positions and quantified in terms of the
major welding variables of current and travel speed. Welding position
was shown to have no effect on fusion behaviour.
Successful full penetration closed butt root welds were produced in
all welding positions. Heat input was shown to be the factor
controlling bead dimensions. Close control over welding parameters
are needed to maintain consistent bead sizes. Complete joint
simulations were also made. The vertical-up technique was shown to
give superior fusion characteristics with the process producing
excellent quality results in all positions.
Narrow gap MIG welding was shown to be feasible without wire manipulation
at gap widths below 12 mm in the flat position. A wire manipulation
technique gave excellent fusion characteristics with gap
widths greater than 12 mm. A computer program was devised as a guide
to the selection of process parameters and possible fusion behaviour.
Modelling considerations showed that H-V position narrow gap welding
would be feasible only with gap widths less than 10 ... A short
experimental programme validated the predictions of fusion behaviour
by the model and indicated the direction for future development work
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
Chevron cracking in steel weld metals
Full text linkA less well known form of transverse cracking in carbon manganese and low alloy steel weld metals, generally referred to as chevron cracking, has been found in a large number of industrial welds. These cracks are characterized by their macroscopic orientation, which is approximately transverse to the welding direction and at 45 with the plane of the plates (in a butt joint), and by the staircase morphology, which is easily recognized under microscopical examination. A special test was designed to reproduce these cracks under laboratory controlled conditions and a large number of welds was carried out. Chevron cracks were found in the tests with medium strength weld metals deposited by submerged arc with a basic agglomerated flux and by manual metal arc with basic and cellulosic electrodes. No chevron cracks were observed in the welds with rutile electrodes. High temperature baking of the submerged arc flux and the basic electrodes eliminated or reduced markedly the incidence of cracking in all cases indicating that hydrogen was the main factor controlling the cracking occurrence. Cont/d
Metal transfer in MIG welding
Full text linkThe metal transfer process in MIG welding has been investigated. The
heat balance of the melting process, forces acting on the wire tip and
droplets, and droplet movement were examined quantitatively both under
steady current and pulsed current conditions. A novel transistorised
power source was employed for precision current adjustment which with
the use of high speed cinephotography and careful metallographic
techniques has allowed a re-assessment of current theories to be made.
A new metal transfer mode designated as ’Drop Spray* has been discovered.
This transfer mode is located between the well known globular and
spray transfer modes and only occurs in a very narrow current range of
20A, but it has several important features.
The relationship between metal transfer mode and the welding variables
has been established quantitatively for the first time. It was found that
the extension resistance and heat content of droplets are determined by
current and hence metal transfer modes. The amount of spatter and fume
was also found to be determined by transfer mode.
Metal transfer under pulsed current was also investigated. It was found
that the metal transfer modes under pulsed current are the same as that
of steady current. It was also found that the first drop of every pulse
is of drop spray mode and the subsequent droplets will be stream spray.
Careful observations and measurements have been made at various stages
of the current pulse to enable greater understanding of the influence of
the pulse parameters.
Based on the results mentioned above, a concept of controlled MIG welding
was proposed, based on the control of metal transfer mode. By this
concept any predetermined feature of conventional MIG welding can be
achieved consistently and repeatedly.
As an application of the proposed concept, drop spray transfer was
reproduced over a wide current range by means of metal transfer control.
A new controlled MIG process designated as ’controlled drop spray MIG'
has been developed which features high efficiency, all positional ability,
freedom from spatter, low fume generation and good bead appearance. The
preliminary bead on plate trial shows that all the expected results have
been achieved although many more trials are necessary to fully prove the process.Ph
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