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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
Effect of second phase distribution and morphology on the bake hardening behavior of dual phase steels
No full textThe present scenario of rapid boom in automotive industry has ushered tremendous
improvement and growth in the steel processing technology. Advanced High Strength Steels
(AHSS) have fulfilled most of the aspects concerning better utilization and fabrication of
light weight steels for automobile applications. Various grades of AHSS have been processed
over the past few decades, however, the search for even better mechanical properties and
subsequently fuel efficient-light weight structures has deemed a deep research prospect in
dual phase steels (DP steels), a category of AHSS. DP steels is the most commonly used
AHSS grade for automotive industry. Dual Phase steels also known as DP steels consist of a
hard martensite/ or bainite phase embedded within a softer ferrite phase. This peculiar
combination of a hard phase (martensite) and a soft phase (ferrite) provides a perfect balance
of strength and ductility in these steels. The typical production process of DP steels involves
inter-critical annealing of low carbon steels which is followed by a rapid quenching or
cooling techniques to obtain DP microstructure wherein, martensite is distributed along the
grain boundaries of the ferrite grains. DP steels are mostly used for fabricating the exterior
members of automobile bodies like the roof or floor panels and the cross member regions.
The finished or heavily formed (simulated by pre-straining in this research work) auto-body
is given a finishing paint curing treatment which helps in proper curing or adhesion of the
paint coat over the entire exterior panels in the vehicles. This finishing operation is
industrially referred to as the Bake Hardening treatment. The term hardening is associated
with the improvement in final yield strength of the automobile body after this treatment. The
increase in final yield strength is due to the presence of free or available interstitial solute
carbon atoms in DP steels during its processing. These interstitial solute atoms upon
receiving sufficient diffusion energy (during baking treatment) pin or lock the dislocations
created during various forming operations (stamping, bending, extrusion etc.) thus, a rise in
final yield strength is always obtained. Hence, in addition to curing of the paint coat, the dent
resistance of the final component also improves at no extra production cost. In the present
research work, bake hardening characteristics of a conventionally processed DP steel viz.
Continuous Annealing Line (CAL) process was evaluated against a modified Continuous
Annealing Line (mod-CAL) process. A typical industrial continuous annealing line (CAL)
process was employed to anneal a 67% cold rolled steel to obtain the dual phase
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microstructure. Subsequent to this conventional annealing, the steel was now subjected to an
improved process (mod-CAL) with modified initial heating rate and peak annealing
temperature. The processed specimens (through CAL and mod-CAL respectively) were
further pre-strained in the range 1–5 % followed by the bake hardening treatment at 170
for 20 minutes. It was observed that the CAL processed specimen showed a peak of about 70
MPa in bake-hardening index at 2 % pre-strain level. At higher pre-strain values (in excess
of 2 %), a gradual drop in bake-hardening index was observed. On the contrary, the mod-
CAL processed specimens showed near uniform bake-hardening response at all pre-strain
levels and a decrease could be noted above 4% pre-strain. The evolving microstructure at
each stage of annealing process and after bake-hardening treatment was studied using field
emission scanning electron microscopy. The microstructure analysis distinctly revealed the
differences in the martensite spatial distribution and interface morphologies developed by the
two annealing processes. The modified process showed predominant formation of martensite
within the ferrite grains with serrated lath martensite interfaces. This nature of the martensite
was considered responsible for the observed improvement in the bake-hardening response.
Furthermore, along with improved bake-hardening response, negligible loss in tensile
ductility was also noted. This behavior was correlated with delayed micro-crack initiation at
martensite interface due to the serrated nature of the lath martensite
Effect of Inter-critical Annealing Parameters on the Recrystallization, Austenite Formation and Stabilization in a Dual Phase Steel
No full textME, MEDAdvanced high strength steels (AHSS) have been developed in the last few decades especially
for automotive applications due to their remarkable properties combining high strength and good
ductility. DP steels are the most common grade of advanced high strength steels which are
produced through inter-critical annealing of a low carbon steel followed by an accelerated
cooling to obtain the ferrite-martensite (dual phase) microstructure. The strength of DP steels is
manipulated by the amount of martensite and ductility by the size and distribution of this phase.
The fraction of martensite formed depends upon the austenite amount available during the intercritical
annealing process. So, it is always important to understand the kinetics of ferrite
recrystallization and austenite formation during the annealing of cold rolled sheets. The present
work focuses on understanding the effect of intercritical annealing parameters (viz. annealing
temperature, soaking time periods etc.) on ferrite recrystallization, austenite formation and its
stabilization during the production of dual phase steel from a low carbon cold rolled steel. The
main effort of this research work has been to arrive at the combination of annealing process
parameters to produce the desired ferrite-martensite structures. For the study, commercial
software viz. Thermo-Calc (3.0) and JMat-Pro (7.0) have been used to predict the various
annealing parameters. The predicted values have been compared with the experimental values
and a significant variation has been observed in the results. It has been concluded that the
annealing parameters clearly affect the phenomenon of ferrite recrystallization, and austenite
formation and its stabilization during the production of dual phase steels. Hence, this study is
very helpful in understanding the synergistic effect of ferrite recrystallization and austenite phase
transformation behaviour in dual phase steels to tailor design the mechanical properties by
microstructure control
Inter-critical Annealing of a Lean Composition Steel under Controlled Cooling to Produce Multiphase Microstructure
No full textME, MEDIn the past years, there has been growth in the search and use of new advanced materials in the transport industry. So far, conventional steel is the main material for car bodies, but there is a growing demand for other materials to decrease the weight of cars and thereby saving costs, energy and environment. Also, the increasing safety requirements in the automotive industry has forced search for new materials. The different parts need to be as light as possible, but with sufficient strength and ductility. Hereby, multiphase steels like dual phase and TRIP (Transformed Induced Plasticity) steels are important because of their high strength in combination with good formability. Various methods have been used for the production of these steels to get best outcomes. However, extremely limited work has been reported for the production of dual/ multiphase steels with controlled cooling and using a lean chemistry. The present experimental work reports on the methods of production of dual/ multiphase steels (tensile strength range 500–800 MPa; ductility in the range 12–33%) with ferrite/ martensite, ferrite/ bainite/ martensite and ferrite/ martensite/ austenite/ bainite multiphase structures. These structures were obtained in a normalized steel of very lean chemistry (0.11C, 1.8Mn, and 0.325 Si) subjected to inter-critical annealing and soaking followed by controlled cooling in an annealing simulator. Dual phase structures were produced by inter-critical annealing followed by direct cooling to room temperature to achieve high strengths. Multiphase microstructures were produced by holding in the bainitic and martensitic range to get various combinations of strength and ductility (multi-functional). The present work also compares the results for annealing process obtained through experimental investigations and through software predictions. Finally, micro-mechanical modeling has been done for steel with dual phase structure The true stress- strain curves obtained through actual tensile experiments closely matched with the true stress- strain curves predicted by micro-mechanical modelling
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
A new annealing route for industrial processing of dual phase steels to obtain improved mechanical properties
No full textDual-phase (DP) steels offer high potential of weight reduction without sacrificing
mechanical properties for their application in automotive industry. They derive their
properties through the second hard phase (martensite/ bainite) in a ferrite matrix. DP steels
are mostly produced through the continuous annealing process route in the industry because
of the requirement of high production rates, uniformity in properties, and leaner chemistry
design feasibility. Important mechanical properties which are desirable for the final
components include absence of yield point, low yield point to ultimate tensile strength, high
strain hardenability along with high ductility etc.
The main objective of the present work was to improve the mechanical properties of a low
carbon Si based ferrite-martensite DP steel by tailoring the second phase (martensite)
morphology, distribution, and size in the ferrite matrix. An existing conventional continuous
annealing process (CAL) route was modified to develop an improved annealing process route
suitable for industrial usage. A custom designed annealing simulator (capable of simulating
conditions similar to industrial continuous annealing lines) was used to simulate the various
annealing processes. Several combinations of processing routes depending on the governing
mechanisms such as, ferrite recrystallization, pearlite dissolution, and phase transformation
etc. were investigated for their effect on the morphology, and distribution of the martensite
phase and the resulting mechanical properties. The main focus of the current work was to
study the effect of heating rates, isothermal annealing temperatures, and soaking time periods
(with no changes in cooling regime of conventional CAL) on the morphology, and
distribution of martensite phase. Further, the effect of combining thermal cycling as a pretreatment
to conventional CAL processing was also investigated. It was observed that by
varying the above stated annealing parameters, it was possible to trigger the ferrite
recrystallization, pearlite dissolution, and phase transformation at various stages of the
annealing process cycle. All such changes resulted in change of martensite morphology,
distribution, and even grain size and thus affected the final mechanical properties of DP steel.
This entire experimentation effort resulted in the development of a new processing route
called “Continuous Heating Annealing Process (CHAP)” that gave strength levels of 625
MPa with ductility similar to that obtained with the conventional CAL process with a
significant improvement in strain hardening exponent. Thus, the present research provided a
new annealing route (without any major changes in the conventional CAL process) for
processing of DP steels with improved strength-ductility combinatio
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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