1,720,974 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Grain sorghum in the hybrid-era, 1957-2008: yield with hybrid advancement and improved agronomic practices
Get PDFDoctor of PhilosophyDepartment of AgronomyScott A. StaggenborgGrain sorghum yield has notably increased from the beginning of hybrid production and commercialization in the late 1950s. The yield increases were the result of improved agronomic practices and hybrid advancement. The objectives of my research were: (1) to determine the magnitude of yield change in the hybrid era in irrigated and rain fed sorghum production, (2) to determine the contribution of agronomic and hybrid changes for yield in the hybrid era, (3) to investigate changes in sorghum morphology, physiology, and water use that contributed to yield increases, (4) to investigate changes that accompanied yield increase with hybrid improvement, and (5) to understand sorghum water and nutrient use and variations between hybrids in these regards. Fifty-two years of grain sorghum hybrid performance trial data (1957-2008), were analyzed and greenhouse and field studies were conducted on five selected hybrids to meet our objectives. The greenhouse and field studies were conducted from the summer of 2007 to the fall of 2009 on five selected hybrids, each representing a decade from the past fifty years. Results indicated that there was an increase in hybrid yield of nearly 50 kg ha-1 yr-1 in dryland sites over the 52 yrs (1957-2008) analyzed. Irrigated grain sorghum yields, however, remained unchanged over the same period. Agronomic practices such as planting date, phosphorus fertilizer use, and planting density changed over these years but were not found to contribute to increased dryland sorghum yields. There was no difference found between old and new hybrids tolerance to different densities. Hybrid advancement and increased nitrogen fertilizer application were responsible for changes in dryland yields. Total water use changed with hybrid advancement. New hybrids used the greatest total water and also had greater root-to-total biomass ratio than the old hybrids. Leaf biomass was also greater for the newest hybrid. There was a difference in amount of total nutrients extracted by hybrids, and there were differences among hybrids in allocation of nutrients to different tissues. In general the yield focus of sorghum hybrid development was effective in dryland sorghum production, likely because of intentional or inadvertent selection of hybrids with better drought tolerance. Results indicated that breeding programs created hybrids with improved morphological characteristics that might have resulted in better resource use (water and nutrient) and ultimately increased yield
Time series and spatial analysis of crop yield
Get PDFMaster of ScienceDepartment of StatisticsJuan DuSpace and time are often vital components of research data sets. Accounting for and utilizing the space and time information in statistical models become beneficial when the response variable in question is proved to have a space and time dependence. This work focuses on the modeling and analysis of crop yield over space and time. Specifically, two different yield data sets were used. The first yield and environmental data set was collected across selected counties in Kansas from yield performance tests conducted for multiple years. The second yield data set was a survey data set collected by USDA across the US from 1900-2009. The objectives of our study were to investigate crop yield trends in space and time, quantify the variability in yield explained by genetics and space-time (environment) factors, and study how spatio-temporal information could be incorporated and also utilized in modeling and forecasting yield. Based on the format of these data sets, trend of irrigated and dryland crops was analyzed by employing time series statistical techniques. Some traditional linear regressions and smoothing techniques are first used to obtain the yield function. These models were then improved by incorporating time and space information either as explanatory variables or as auto- or cross- correlations adjusted in the residual covariance structures. In addition, a multivariate time series modeling approach was conducted to demonstrate how the space and time correlation information can be utilized to model and forecast yield and related variables. The conclusion from this research clearly emphasizes the importance of space and time components of data sets in research analysis. That is partly because they can often adjust (make up) for those underlying variables and factor effects that are not measured or not well understood
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe 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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