1,721,069 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
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
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Smart simulation techniques for the evaluation of parametric uncertainties in black box systems
Full text linkWhen parameters of complex processes are uncertain, it is often necessary to perform exhaustive simulations to characterize the outputs of these processes. If simulations are computationally intensive, characterization of outputs through exhaustive simulations may be infeasible. In such cases, intelligent approaches for choosing simulations based on probabilistic descriptions of uncertainties may be valuable. The Probabilistic Collocation Method is a probabilistic technique that can model the deterministic relationship between the uncertain parameters and an output of interest with a small set of simulations. In this thesis, we review PCM, provide a new generalization of PCM for systems with multiple correlated uncertain parameters and also present an order selection algorithm for the technique. Although we tout PCM as a very economic technique, the number of simulation points nevertheless grows exponentially with the number of uncertain parameters. To overcome this difficulty, we develop some Information theory-based techniques that can allow us to apply PCM using only a subset of the uncertain input parameters. We conclude our analytical development by discussing the possibility of applying PCM to solve optimization problems. In the penultimate chapter we illustrate a possible PCM application in Computer Science (specifically, in queueing theory) and also develop a larger electric power system example. We conclude the thesis by summarizing our results and discuss future directions. In our work and previous work, PCM has been used in such diverse areas as global climate evolution studies, chemical engineering applications and power systems analysis, which indicates the versatile nature of this algorithm
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
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Security of autonomous-vehicle-team tracking dynamics a control-theoretic and graphical perspective
Full text linkRecently, distributed cooperative control of multiple autonomous vehicles, including for military reconnaissance, environmental protection, and health care applications, has become a very active research topic. In many of these applications, teams of autonomous agents with distributed sensing capabilities are required to cooperatively complete a tracking task. In addition, under the most general conditions, the autonomous vehicles systems operate in harsh, changing, and even adversarial environments. Hence, the security issue of AVNs has begun to become important. Although there are many papers related to information-security in the domain of communication networks, no serious attention seems to have been given to the role of communication and sensing among the network components and to the physical dynamics of these networks, which we think is central to AVNs control. On the other hand, control theorists' viewpoints on security/robustness almost always neglect that the complex and hybrid spatio-temporal characteristics of disturbance and adversaries may have an effect on AVNs. Hence, we are motivated to develop new definitions and analysis techniques for the security of AVNs which can cover both aspects. And then we expect to develop a systematic way to make the system secure or more secure by properly designing the gains of decentralized controllers in each vehicle using the methodology in this thesis. First, we abstract the AVNs and adversaries to a canonical model. In the model, we assume that each vehicle is governed by identical dynamics (double integrator dynamics), and the whole network dynamics is largely determined by the sensing capabilities of the AVNs. The task of an adversary is to estimate the initial condition of the AVNs by observing the position of one or a small set of vehicles. Whether or not the adversary can do this, and how well, is the security problem. Based upon the model and problem formulation, we develop several results. In the time invariant model, when the adversary's observation is noise-free, it is shown that we may derive the security of AVNs directly from the control gain of distributed controller and vehicle sensing capacity from both control-theoretical and graphical perspectives. In addition, when adversary observation is noisy, we define a security level matrix to present how secure the system is and use the knowledge of the control gain of distributed controller and vehicle sensing capacity to bound the value of security level matrix (performance of estimator of adversary). Furthermore, in time varying case, based upon the results before, we give some understandings of security for a special class of time varying systems
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A hypothesis-testing approach to low-overhead trajectory-based classification of aerial intruders
Full text linkMotivated by security concerns in the growing use of unmanned aerial vehicles (UAVs), a method for classifying aerial intrusions based on intrinsic flight characteristics is presented. In contrast to existing approaches, the presented method utilizes a coarse physical model to aid in the classification of measured data. A hypothesis testing problem is posed wherein aerial intruders are modelled as seeking to regulate their speed on a linear trajectory in the presence of a noisy disturbance (e.g. wind), and a maximum a posteriori (MAP) detector is developed to classify intruders as a function of measured velocity samples. A reduced, computationally efficient form of the detector is determined, which fundamentally relies on two points in the sample autocorrelation of the input, and readily lends itself toward linear classification techniques. Further, a method for computing the a priori probability of error as a function of intruder models is presented, and this probability is shown to approach zero as the number of input samples is increased. Additionally, the probability of error conditioned on an input measurement is found, providing a confidence metric for detection results. The detector and the presented error metrics are confirmed via simulation using synthesized data, and considerations for the detector’s practical implementation are discussed
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A study on the effects of a selfish agent in networked opinion dynamics
Full text linkThis thesis is concerned with manipulation of a network opinion dynamics by a selfish agent. To study manipulation, a canonical model for network opinion dynamics with local linear averaging updates is extended to include a manipulator (selfish) agent. The selfish agent uses a projection (statistic) of network opinions in feedback to regulate the dynamics, with the goal of driving other agents' opinions to a desired reference or goal. Specifically, the selfish agent in this work is modeled as either a proportional or proportional-integral feedback controller. An extension of the model with a nonlinear update rule, wherein all agents' opinions are capped or held between 0 and 1, is also considered. Analytical results are provided characterizing consensus behavior of the manipulated opinion dynamics model, including in the presence of a second stubborn agent with a fixed opinion. Additionally, an empirical study is conducted to identify the most influential nodes, and a novel centrality metric is proposed that closely correlates to the influence metric. Finally, simulations if the manipulated opinion dynamics are developed for a variety of scenarios. The empirical analyses and simulations were conducted using a real-world social network, representing frequent interactions between dolphins in the Doubtful Sound, a remote Fjord in New Zealand
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