1,721,024 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
Nonlinear vibration energy harvesting : fundamental limits, robustness issues, and practical approaches
No full textThesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 119-130).The problem of a scalable energy supply is one of the biggest issues in miniaturizing electronic devices. Advances in technology have reduced the power consumption of electronic devices such as wireless sensors, data transmitters, and medical implants to the point where harvesting ambient vibration, a universal and widely available source of energy, has become a viable alternative to costly and bulky traditional batteries. However, implementation of vibratory energy harvesters is currently impeded by three main challenges: broadband harvesting, low-frequency harvesting at small (micro) scales, and robust energy harvesting at presence of parametric uncertainties. This thesis investigates two main directions for effective vibration energy harvesting: (i) fundamental limits to nonlinear energy harvesting and techniques to approach them, and (ii) robust energy harvesting under uncertainties. As well as being of fundamental scientific interest, understanding maximal power limits is essential for assessment of the technology potential and it also provides a broader perspective on the current harvesting mechanisms and guidance in their improvement. We begin by developing a general framework and model hierarchy for the derivation of fundamental limits of the nonlinear energy harvesting rate based on Euler-Lagrangian variational approach. The framework allows for an easy incorporation of almost any constraints and arbitrary forcing statistics and represents the maximal harvesting rate as a solution of either a set of DAEs or a standard nonlinear optimization problem. Closed-form expressions are derived for two cases of damping-dominated and displacement-constrained motion. Stemming from the study of fundamental limits, we present an almost-universal strategy termed buy-low-sell-high (BLSH) to maximize the harvested energy for a wide range of set-ups and excitation statistics. We further propose two techniques to realize the non-resonant BLSH strategy, namely latch-assisted harvester and adaptive bistable harvester. To validate the efficacy of the proposed strategy and practical techniques, we perform a simulation experiment by exposing the said harvesters to harmonic and experimental, random walking-motion excitations; it is shown that they outperform their linear and conventional bistable counterparts in a wide range of harmonic excitation and random vibration. Furthermore, we propose to harvest energy by exploiting surface instability or in general instability in layered composites which is, in part, motivated by the BLSH strategy. Instabilities in soft matter and composite structures e.g. wrinkling allow large local strains to take place throughout the entire structure and at regular patterns. Unlike conventional harvesting techniques, this allows to harvest energy from the entire volume of the structure e.g. by attaching piezoelectric patches at large-strain locations throughout the structure. We show that this significantly improves the power to volume ratios of the harvesting devices. In addition, these structural instabilities are non-resonant that consequently enhances robustness of such harvesters with respect to excitation characteristics. The high efficacy of energy harvesting via structural instabilities, in part, is attributed to its ability to approximately follow the BLSH logic. Additionally, we put forth the idea of extending this idea to control the instability; and hence, extend the application of the aforementioned idea from energy harvesting to a whole new level of tunable material/structures with a myriad of applications from electromechanical sensors and amplifiers to fast-motion actuators in soft robotics. And last but not least, to more specifically address the robustness issues of passive harvesters, we propose a new modeling philosophy for optimization under uncertainty; optimization for the worst-case scenario (minimum power) rather than for the ensemble expectation of the power. The proposed optimization philosophy is practically very useful when there is a minimum requirement on the harvested power. We formulate the problems of uncertainty propagation and optimization under uncertainty in a generic and architecture-independent fashion. Furthermore, to resolve the ubiquitous problem of coexisting attractors in nonlinear energy harvesters, we propose a novel robust and adaptive sliding mode controller for active harvesters to move the harvester to any desired attractor by a short entrainment on the desired attractor. The proposed controller is robust to disturbances and unmodeled dynamics and adaptive to the system parameters.by Ashkan Haji Hosseinloo.Ph. D
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
Efficient algorithm for online N - 2 power grid contingency selection
No full textThesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.Includes bibliographical references (pages 55-57).Multiple element outages (N - k contingencies) have caused some of the most massive blackouts and disturbances in the power grid. Such outages affect millions of people and cost the world economy billions of dollars annually. The impact of the N - k contingencies is anticipated to grow as the electrical power grid becomes increasingly more loaded. As the result power system operators face the need for advanced techniques to select and mitigate high order contingencies. This study presents a novel algorithm for the fast N - 2 contingency selection to address this problem. The developed algorithm identifies all potentially dangerous contingencies with zero missing rate. The complexity of the algorithm is shown to be of the same order as the complexity of N - 1 contingency selection, which makes it much more efficient than brute force enumeration. The study first derives the equations describing the set of the dangerous N - 2 contingencies in the symmetric form and presents an effective way to bound them. The derived bounding technique is then used to develop an iterative pruning algorithm. Next, the performance of the algorithm is validated using various grid cases under different load conditions. The efficiency of the algorithm is shown to be rather promising. For the Summer Polish grid case with more than 3500 lines it manages to reduce the size of the contingency candidates set by the factor of 1000 in just 2 iterations. Finally, the reasons behind the efficiency of the algorithm are discussed and intuition around the connection of its performance to the grid structure is provided.by Petr A. Kaplunovich.S.M
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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