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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
Safe Connectivity Maintenance for a Fleet of Underactuated Seaweed Farms in Dynamic Oceanic Environments
No full textVariations 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
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Towards Operating Underactuated Robotic Systems by Going With the Flow
Get PDFOver the centuries, humanity has created ever more ingenious systems to traverse the oceans and skies of our planet. Modern ships and planes operate with powerful engines that require substantial amounts of fuel, leading to high operating costs. However, this approach becomes impractical for applications that require extended periods of autonomous operation without the possibility of refueling. This dissertation starts with the idea of operating systems by going with the flow: harnessing the wind and ocean currents by letting the system drift in favorable directions and strategically using a low-power engine to change flows when this is beneficial. As the power to counteract drag forces scales cubically with the relative velocity of the system, this new paradigm reduces the power required for operation by 2-3 orders of magnitude, thereby significantly reducing the system and operating costs. This could enable a host of novel applications that require low-cost and long-term operations, such as active environmental monitoring of the oceans and atmosphere or floating solar platforms. The primary case study used throughout this work is autonomous seaweed farms that roam the oceans while rapidly growing biomass for biofuel, bioplastic, or to sink it for carbon removal.In this dissertation, we systematically develop control techniques to tackle the four key challenges of operating by going with the flow: First, the system is severely underactuated with its own propulsion often being less than 1/10th of the magnitude of the surrounding flows. Second, to make strategic control decisions when to change flows, only coarse, deterministic forecasts are available. Third, the forecasts have a limited time horizon of 5-10 days, but realistic control objectives extend over weeks to months. Lastly, the forecast error defined as the difference between the forecasted and the true flows often exceeds the propulsion capabilities of the system, hence robust control is infeasible.We start by introducing techniques for continuous-time optimal control when the complex flows are known. We use dynamic programming for the objectives of navigation and maximizing seaweed growth. Next, we turn towards the challenge of operating with imperfect and short-term forecasts. Our insight is that the value functions obtained by the previously developed optimal control methods can be used as closed-loop control policies, which are equivalent to replanning on the forecast at every step. Through extensive simulation studies in realistic ocean conditions, we demonstrate that such frequent replanning allows for reliable operation despite significant forecast errors. To enable reasoning beyond the forecast horizon, we derive a discounted optimal control formulation and demonstrate how the value function can be extended by estimating the cost-to-go using historical flow averages. In the last part of this dissertation, we focus on how to handle constraints in these challenging environments. For that, we integrate time-varying obstacles into our value function and show empirically that this almost eliminates the risk of stranding. Moreover, we develop a hierarchical control approach to operate a fleet of underactuated autonomous systems while avoiding collisions and ensuring connectivity across the fleet.At the end of this dissertation, we summarize our techniques for operating by going with the flow which could enable a host of new applications of low-power autonomous systems in the oceans and skies. We also discuss promising ongoing and future research directions towards further improving the performance of underactuated robotic systems operating in flows
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
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