1,721,055 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
Statistical Downscaling of Climate Model Outputs for Hydrological Extremes
Full text linkChanging climate poses an unprecedented challenge for hydrology. The quantification of knowledge
on occurrence, circulation and distribution of the waters of the Earth becomes increasingly complex
under climate projections because of uncertain effects due to anthropogenic emissions. Traditional
understanding of the hydrological cycle needs to be re-examined, and new tools and frameworks for
modelling hydrological series with non-stationary characteristics are required for assessing climate
change impacts. The aims of this thesis are to (i) understand the relationship between climate
change and hydrology at a catchment scale and (ii) develop tools to support climate change
adaptation and mitigation.
To achieve the aims, this thesis employs a stochastic rainfall model based on generalised linear
models (GLMs) to downscale information from regional and global climate models for projecting
drought conditions and annual rainfall extremes. Using a state space approach, important global
circulation variables for catchment drought characteristics in the Midlands and South East of
England are investigated. For annual rainfall extremes, a new approach for studying rainfall
simulation series ensemble is proposed based on extreme value theory. Using a statistical modelling
methodology related to GLMs, a novel potential evaporation model has been put forward and
evaluated. In UK catchment scale application, the results provide insight into possible changes and
implications in the shift of rainfall and drought patterns under scenarios of climate in the 2080s. The
quality of potential evaporation estimation is shown to be sensitive to the interrelationship of global
climate variables. For monthly maxima of potential evaporation, the projected change is high in the
southern UK (~25%) but is low in the northern UK (~0%). Furthermore, 2080s streamflows have also
been projected. The results show that uncertainty in streamflow projections depend on which GCMs
and RCMs are used. Overall, this dissertation provides improved methods for further development in
understanding our non-stationary water cycle
Effects of tree shelterbelts on the hydrology of upland areas
No full textRecent large flood events in the UK have focused attention on the effects of agricultural intensification and de-intensification on flood risk. Possible detrimental factors for these floods are thought to be the degradation of soil structure through compaction from grazing animals and agricultural machinery; while possible ameliorating factors may be the re-introduction of natural landscape features such as woodland and wetlands.
In order to address this issue in an upland setting a multi-scale experimental programme has been implemented at Pontbren, a sheep-farmed headwater catchment of the River Severn, UK. The research aimed to evaluate the impact of different land management regimes on hydrological response. An integral component of this was to determine the role that native, broadleaf trees, planted as shelterbelts on intensively grazed pasture, may have in the reduction of flooding. Effects of trees on soil properties, soil moisture status, rainfall interception and overland flow were investigated
Comparisons of soil hydraulic properties show significant increases in saturated moisture content and hydraulic conductivity of soil under trees compared to adjacent improved pasture. These effects, combined with increased interception and water use by the trees, have led to the soil under the trees being considerably drier than that under the pasture. The influence of the tree strips on rainfall patterns in the wider landscape is determined by the wind direction and inclination angle of the rain during rainfall events. The results show seasonal variation. Overland flow results show substantial differences in surface runoff between the grazed pasture and the ungrazed tree-planted area. Manipulation experiments reveal that, excluding sheep has a significant influence on surface hydrology at the plot scale, which is enhanced by planting trees. Data were used to underpin the conceptual understanding of the hydrological response, to support model development and thus make predictions under speculative land management scenarios.Open Acces
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
Traditional irrigation strategies and their implication for sustainable livelihoods in semi-arid areas
No full textDispelling 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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