1,721,163 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
Differential scanning calorimetry as a powerful tool for investigation of solid-phase transformations in heating, isothermal annealing and cooling
No full textSolid-solid phase transformations play an important role for the adjustment of machining- and application-properties of metallic materials. During recent years, we developed advanced techniques to analyze solid-solid phase transformation by DSC in a very wide dynamic range. This talk will introduce these techniques, using reactions in aluminium alloys as examples. To achieve the required high dynamic range during cooling we combine three different indirect and direct measuring techniques and five types of DSC devices. Nowadays physically-based models verified with our DSC results moreover allow to predict precipitation volume fractions, solute mass fractions. Latest results on property predictions as function of cooling rate will be presented
Isothermal Nanocalorimetry of Isotactic Polypropylene
Full text linkA wide set of crystallization isotherms and the subsequent melting behavior of isotactic polypropylene (i-PP) were investigated using differential scanning calorimetry and nanocalorimetry with a very high rate in the cooling step. The latter technique offers, indeed, the distinct possibility to perform isothermal crystallization experiments at any temperature in between the glass transition and melting, as the test temperature can be reached at a cooling rate of 1000 K/s, thus, preventing crystallization during the cooling step. Isothermal tests after such fast cooling were performed at intervals of 5 K within the temperature range −15 to 90 °C, and a local exothermal overheating was observed. In particular, for each isotherm, the observed peaks were fitted using the Kolmogorov−Johnson−Mehl−Avrami model. The plot of the crystallization kinetics constant as function of temperature gives clear evidence of two kinetic processes. The subsequent heating scan performed starting from −15 °C showed an exothermic event, between 0 and 30 °C, due to the mesophase cold crystallization, for isotherms at a temperature lower than 20 °C
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
Scanning Nanocalorimetry at High Cooling Rate of Isotactic Polypropylene
Full text linkA wide set of cooling scans and subsequent melting behavior of isotactic polypropylene (i-PP) were investigated using differential scanning calorimetry and nanocalorimetry at very high cooling rate. The latter technique offers, indeed, the distinctive possibility to perform heat capacity measurements at rates of more than 1000 K/s, both in cooling and in heating, to characterize the crystallization. When the i-PP sample was solidified with cooling rate larger than 160 K/s, a novel enthalpic process was observed that was related to the mesomorphic phase formation. Furthermore, at cooling rates higher than 1000 K/s, the i-PP sample did not crystallize neither in the α nor in the mesomorphic form. The subsequent heating scan starting from −15 °C showed an exothermic event, between 0 and 30 °C, ascribed to the mesophase cold crystallization
Stability of crystal nuclei of poly (butylene isophthalate) formed near the glass transition temperature
Full text linkTammann's two-stage crystal-nuclei-development method is applied for analysis of the thermal stability of homogenously formed crystal nuclei of poly(butylene isophthalate) (PBI) as well as their possible reorganization on transferring them to the growth temperature, using fast scanning chip calorimetry. Crystal nuclei were formed at 50 °C, that is, at a temperature only slightly higher than the glass transition temperature, and developed to crystals within a pre-defined time at the growth temperature of 85 °C. The number of nuclei, overcritical at the growth temperature, was detected as a function of the transfer-conditions (maximum temperature, heating rate) by evaluation of the developed crystal fraction. For different size-distributions of crystal nuclei, as controlled by the nucleation time, there is detected distinct reduction of the nuclei number on heating to maximum temperatures higher than about 90 to 110 °C, with the latter value holding for longer nucleation time. Longer nucleation allows for both increasing the absolute nuclei number and generation of an increased fraction of larger nuclei. Heating at 1000 K/s to 140-150 °C causes "melting" of even the most stable nuclei. While direct transfer of crystal nuclei from the nucleation temperature (50 °C) to the growth temperature (85 °C) reveals negligible effect of the transfer-heating rate, in-between heating to higher temperatures is connected with distinct nuclei-reorganization above 85 °C on heating slower than 1000-10.000 K/s. The performed study not only provides specific valuable information about the thermal characteristics of crystal nuclei of PBI but also highlights the importance of proper design of Tammann's nuclei development experiment for analysis of nuclei numbers. With the evaluation of critical rates of temperature-change for suppression of non-isothermal formation of both nuclei and crystals, the kinetics of crystallization of the slow crystallizing PBI is further quantified
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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