1,721,010 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
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
Understanding the spatial variability in catchment dynamics: a case study of 107 stream catchments in Victoria
No full textRivers and streams around the world are being affected by declining water quality. When designing remediation strategies, we must first understand the key factors affecting spatial and temporal variability in stream water quality. As such, the objective of this investigation was to investigate the relationships between in-stream constituent concentrations and streamflow and to understand how these relationships vary across space. We intend to use these findings to add a temporal component into existing statistical models of spatial variability in water quality. Monthly water quality data for total suspended solids (TSS), total phosphorus (TP), filterable reactive phosphorus (FRP), total Kjedahl nitrogen (TKN), nitrate-nitrite (NOx) and electrical conductivity (EC), in addition to streamflow collected between 1994 and 2014 from 107 water quality monitoring sites in Victoria were used for this study. Using these data, we characterized the interaction between constituent concentrations and streamflow in terms of (i) the ratio of the coefficient of variation (CV) of constituent concentrations to the CV of streamflow (CVC/CVQ) , and (ii) the slope of the linear regression between the log-transformed constituent concentrations and log-transformed streamflow (the C-Q slope). We then linked the spatial variations in CVC/CVQ and the C-Q slope to catchment characteristics (e.g., land use and climate). We found that the interaction between constituents and streamflow depends significantly on the reactivity of the constituent, and whether the constituent is in the dissolved or particulate state. TSS, TP, TKN, FRP and NOx demonstrated chemodynamic behavior, with the concentrations varying with streamflow (i.e., high CVC/CVQ and large absolute value in C-Q slope). On the other hand, EC demonstrated chemostatic behavior for the selected sites, with low CVC/CVQ values and C-Q slopes. The interaction between streamflow and constituents varied significantly across space. The variability in CVC/CVQ for TSS, nutrients and salts correlated positively with catchment characteristics such as mean catchment slope, average annual rainfall and woodland cover. This could be due to the weaker sources of TSS due to reduced erosion, nutrients due to zero or low application and salts due to high leaching in steeply sloping, vegetated and high rainfall catchments (as they tend to be less disturbed). Lower magnitude and less temporal consistency of constituent sources can lead to greater variability in constituent concentrations relative to streamflow. The spatial variability in C-Q slopes generally did not correlate strongly to catchment characteristics, likely due to the presence of major dams in approximately half of the water quality monitoring sites. However, once these sites were removed, we found that the TSS C-Q slope correlated strongly to average annual rainfall and the mean 7-day low flow. This suggests that there is a stronger positive linear relationship between TSS concentrations and streamflow in catchments with temporally consistent rainfall and streamflow. There were weak correlations between catchment characteristics and the C-Q slopes for nutrients regardless of the exclusion of the water quality monitoring sites with dams. This could be due to the reactive nature of these compounds, leading to less predictable interactions between streamflow and in-stream concentrations. The results of the analysis will be used to develop statistically-based predictive models of spatio-temporal variability in stream water quality
Dynamic modelling of complex systems under deep uncertainty using an exploratory multi-method approach
Get PDFThe decision making of complex systems is challenging because of the presence of non-linearities and time delays in their structure and their behaviour. This decision making over the system lifetime is also challenged by the presence of deep uncertainty in the future behaviour of systems and in their surrounding environment. Traditional modelling approaches are inclined to consolidate all facts into a single ultimate model and to take a deterministic, optimal and predictive approach in decision making. However, they proved to be inadequate for coping with complexity and uncertainty challenges. We argue that an exploratory multi-method approach to modelling is needed for making effective and robust decisions for complex systems; the decisions which remain valid under a diverse range of future conditions. This paper illustrates the combined use of multi-method modelling and exploratory analysis in the support of complex systems decision making, with an application to asset acquisition and management and using the case of aircraft fleet as an illustrative example. First, a framework is introduced for the implementation of this multi-method exploratory approach in practice, and the model structure, developed for the case of aircraft fleet, is explained. We then discuss how the use of our new approach can improve the robustness of decisions in asset acquisition and management. An initial exploratory analysis is performed on the model under deep uncertainty conditions and with three design strategies: High Acquisition – Low Maintenance, Low Acquisition – High Maintenance, and Medium Acquisition – Medium Maintenance. The analysis of the results shows that investing on the maintenance capacity of an aircraft fleet could result in more average flying hours compared to more acquisition of new aircraft. However, this could cause two side-effects: a higher total (acquisition and maintenance) costs and a wider uncertainty in the future performance of the system (in terms of average flying hours and total costs)
The role of deep flaming in violent pyroconvection
No full textViolent fire-driven convection can manifest as towering cumulus or cumulonimbus clouds, the latter of which are known as firestorms (pyroCb). These extreme fires can have devastating impacts on
environment and society, and appear to be a worsening problem. The major concerns surrounding these large pyroconvective events are that their associated fire spread is highly unpredictable and that they’re generally not suppressible. Indeed, current methods of fire spread prediction, including the use of empirical and semi-empirical modelling approaches, fall short when attempting to predict fire behaviour associated with these events. In particular, they commonly under-predict the rate of spread in such situations, when broader-scale
fire-atmosphere interactions are dominant. To date, research into large pyroconvective events has either
focused on the processes involved in normal atmospheric convection, or on surface fire weather and
associated fuel conditions. While some investigations have combined the two approaches, a definitive study
into both the effects of the surface conditions and the fire-atmosphere interactions is still needed to better
understand their respective role in the development of extreme fires.
This paper incorporates recent insights into dynamic fire propagation into a coupled fire-atmosphere fire
modelling framework to test the combined effects of fire behaviour and atmospheric structure on the
occurrence of violent pyroconvective events. In particular, we consider the role of factors such as the spatial
expanse and intensity of the fire, and the stability of the atmosphere (both in terms of temperature lapse and
moisture profile). The effects of these variables on extreme pyroconvective development are investigated in a
systematic way, varying these parameters using the coupled fire-atmosphere WRF-Fire (Weather Research
and Forecasting Model (WRF)). In the initial work presented in this paper we focus on the case where the fire
is represented by a static heat source of variable dimension and intensity.
Analyses were conducted to investigate how (a) the size of the fire (i.e. area of deep flaming) and (b) the
intensity of the sensible heat source affects the plume development. Results from preliminary analyses of dry,
static fires indicated that the areal expanse of the fire strongly influences the development of the column of
deep convection associated with violent pyroconvective events. This supports the hypothesis that plumes
above zones of deep flaming are less influenced by entrainment than plumes emanating from typical linear
fire fronts. While air is entrained at the plume boundary, the inner core of the plume is less able to entrain air.
As a consequence, the areal nature of the heat source driving convection has an influence on the dynamics of
the plume - in particular, the heights it can attain. The magnitude of the heat flux produced by the fire is also
important for areas of deep flaming up to a minimum of 2 km diameter, but as the size of the heat source
increases beyond a 2 km diameter, this appears to be less influential on the way the plume develops.
Our findings provide motivation for further investigation into the effect of the fire’s attributes on the
immediate atmosphere. They also have the potential to significantly improve forecasting of blow up fire
events. Indeed, by combining our findings with recent insights into dynamic fire propagation and improved
operational information relating to the atmospheric profile (e.g. through enhanced capability to conduct
atmospheric soundings) it is feasible to provide fire agency personnel with far more targeted methods and
tools that can be used to better distinguish fires that are likely to develop into violent pyroconvective events
Advances in multi-sensor systems for in situ remote sensing of Australian forest canopy processes
No full textRemote sensing has been the mainstay of much environmental research for many years. Data acquired from remote sensing systems deployed on spacecraft and aircraft have provided insight into environmental processes that are difficult or impossible to obtain otherwise. However, traditional remote sensing systems are expensive, highly specialised and may lack the ability to be moved or quickly deployed. Fortunately, the cost of sensors like those used in existing remote sensing systems has decreased over time, and their availability and capability has increased. It is now possible to build and deploy ground-based remote sensing systems with capabilities similar to those on traditional platforms. In this context we define in situ remote sensing systems to be within, above, or otherwise adjacent to the vegetation under study but not in direct contact with it. Such systems typically have a measurement range of a few tens of metres, can be deployed quickly and easily moved to new areas of study when required. This paper describes the development of in situ remote sensing systems as has occurred in Australia. The paper also outlines some of the challenges that were met during development and use of several generations of in situ remote sensing systems and presents contemporary work being done for the next generation of systems that will further expand our scientific measurement capability. Initial development of in situ remote sensing systems started in about 2003 with the deployment of the first single pixel multi-angle spectrometer at the CSIRO Tumbarumba field site in south-east New South Wales. Though this was a basic system, it provided much useful data, both in a scientific sense as well as providing information that would be useful in engineering the next generation of sensor systems. Early work in comparing acquired in situ data to satellite sensed data, and radiative modelling was complicated; difficulties included the effects of a non-homogenous forest canopy and the angular distribution of leaves. In 2013 a much more sophisticated system capable of hyperspectral and thermal imaging was installed at the same site, and this system continues to provide detailed and calibrated spectral and thermal time series images of forest canopy dynamics. The ability to examine specific and more uniform regions of interest within the forest canopy is the real value of imaging systems, as opposed to single footprint area-averaged measurements. Because of the high spatial resolution of the acquired data, it is now possible to examine within-tree variability as well as between-tree variability. The system provides much data for scientific analysis, and points to some of the engineering and data handling issues that influence the way future systems are developed. Building upon these earlier systems, the Australian National University has embarked on a project to build a state of the art sensor system that will extend the range of observed wavelengths and be deployable on various platforms for either short-term or extended observation campaigns. This new system uses a variety of sensors that cover the visible, short- and long-wave infrared wavelengths. In the first instance, scientific applications will focus on in situ remote sensing at the ANU Forest Research Facility at the National Arboretum in Canberra. Some important lessons have been learnt over the past 15 years. In situ remote sensing systems require careful design and engineering if they are to reach their full potential. Instrument calibration, handling the vast amount of acquired data and efficient data reduction are significant factors in the successful use of such systems. This contribution concludes with a speculative view of the future direction of science infrastructure in this field
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