1,720,995 research outputs found
Statistical analysis of biological monitoring data
No full textGuttorp, Peter. (1992). Statistical analysis of biological monitoring data. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/2276
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
The statistical analysis of wildfire growth
No full textThesis (Master's)--University of Washington, 2017-01Understanding and quantifying wildfire behavior is of interest to the scientific community, as well as public health and fire management professionals. To achieve this end, there is a demand for statistical descriptions of wildfire behavior and its relationship to the environment. However, wildfire behavior can be complex, described by multiple characteristics such as final size, duration and growth rates, and influenced by processes that can be regionally dependent. Further challenges arise due to the poor quality and availability of cumulative burn area time series data, which often contain missing and erroneous measurements. To address these issues, a variety of methods are presented. Multiple wildfire behaviors are represented using a simple decomposition of cumulative burn area time series that measures four meaningful quantities from the growth curve. The relationship between wildfire activity and the environment are approximated using regionally specific generalized linear models. Weather and landscape data are used to predict various measures of wildfire behavior. Validation results suggested that most of the models generalized well to independent data, and have potentially useful applications in climatological research. Data quality issues common to cumulative burn area time series are addressed using Bayesian state-space models, which reconstruct growth curves from multiple corrupted burn area time series. Two state space models are presented, a stationary version that assumes idealized fire growth, and a non-stationary version that produces reconstructions with time-varying growth rates. The relative computational costs and goodness-of-fit is illustrated by reconstructing the growth curves of 13 wildfires from 2014 wildfire season using growth data coming from two sources, fire perimeters from the Geospatial Multi-Agency Coordination (GeoMAC) and cumulative hotspot detects from the Hazard Mapping System (HMS). The stationary model had minimal computational costs, but rarely produced adequate descriptions of the burn area observations. The non-stationary model had much higher computational costs, but produced realistic estimates of the time series. An informal sensitivity analysis suggested that the reconstructed curves would be robust to changes in the priors. The main application of the state-space models is to reconstruct burn area time series, which can in turn be used for statistical analysis or validation of currently existing growth models. The framework can be modified for other purposes as well including forecasting burn area, and predicting the extinguishment date of a fire
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
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
Improving Uncertainty Quantification and Visualization for Spatiotemporal Earthquake Rate Models for the Pacific Northwest
Full text linkThesis (Ph.D.)--University of Washington, 2021The Pacific Northwest (PNW) has substantial earthquake risk, both due to the offshore Cascadia megathrust fault but also other fault systems that produce earthquakes under the region's population centers. Forecasts of aftershocks following large earthquakes are thus highly desirable and require statistical models of a catalog of the PNW’s past earthquakes and aftershock sequences. This is complicated by the fact that the PNW contains multiple tectonic regimes hypothesized to have different aftershock dynamics as well as two types of earthquake clustering (aftershock sequences and swarms). The Epidemic-Type Aftershock Sequence (ETAS) model is a top-performing spatiotemporal point process model which describes the dynamics of earthquakes and aftershocks in a seismic region using a set of parameters. Typically, maximum likelihood estimation is used to fit ETAS to an earthquake catalog; however, the ETAS likelihood suffers from flatness near its optima, parameter correlation and numerical instability, making likelihood-based estimates less reliable. We present a Bayesian procedure for ETAS estimation, such that parameter estimates and uncertainty can be robustly quantified, even for small and complex catalogs like the PNW. The procedure is conditional on knowing which earthquakes triggered which aftershocks; this latent structure and the ETAS parameters are estimated iteratively. The procedure uses a Gibbs sampler to conditionally estimate the posterior distributions of each part of the model. We simulate several synthetic catalogs and test the modelling procedure, showing well-mixed posterior distributions centered on true parameter values. We also use the procedure to model the continental PNW, using a new catalog formed by algorthmically combining US and Canadian data sources and then, identifying and removing earthquake swarms. While MLEs are unstable and depend on both the optimization procedure and its initial values, Bayesian estimates are insensitive to these choices. Bayesian estimates also fit the catalog better than do MLEs. We use the Bayesian method to quantify the uncertainty in ETAS estimates when including swarms in the model or modelling across different tectonic regimes, as well as from catalog measurement error. Seismicity rate estimates and the earthquake forecasts they yield vary spatially and are usually represented as heat maps. While the visualization literature suggests that displaying forecast uncertainty improves understanding in users of forecast maps, research on uncertainty visualization (UV) is missing from earthquake science. In a pre-registered online experiment, we test the effectiveness of three UV techniques for displaying uncertainty in aftershock forecasts. Participants completed two map-reading tasks and a comparative judgment task, which demonstrated how successful a visualization was in reaching two key communication goals: indicating where many aftershocks and no aftershocks are likely (sure bets) and where the forecast is low but the uncertainty is high enough to imply potential risk (surprises). All visualizations performed equally well in the goal of communicating sure bet situations. But the visualization mapping the lower and upper bounds of an uncertainty interval was substantially better than the other map designs at communicating potential surprises. We discuss the implications of these experimental results for the communication of uncertainty in aftershock forecast maps
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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