1,721,012 research outputs found
Sample-Efficient Reinforcement Learning for Pose Regulation of a Mobile Robot
No full textReinforcement Learning (RL) has gained interest in the control and automation communities thanks to its encouraging results in many challenging control problems without requiring a model of the system and of the environment. Yet, it is well-known that employing such a learning-based approach in real scenarios may be problematic, as a prohibitive amount of data might be required to converge to an optimal control policy. In this work, we equip a popular RL algorithm with two tools to improve exploration effectiveness and sample efficiency: the Episodic Noise, that helps useful subsets of actions emerge already in the first few training episodes, and the Difficulty Manager, that generates goals proportioned to the current agent's capabilities. We demonstrate the effectiveness of such proposed tools on a pose regulation task of a four wheel steering four wheel driving robot, suitable for a wide range of industrial scenarios. The resulting agent learns effective sets of actions in just a few hundreds training epochs, reaching satisfactory performance during tests
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
Recent advances in metal-, organo-, and biocatalyzed one-pot tandem reactions under environmentally responsible conditions
Full text linkBecause of their handedness and wide scope, transitionmetal-,
organo-, and biocatalyzed tandem processes have
become routine and highly sought-after methodologies
because they dramatically increase synthetic efficiency, while
decreasing the number of laboratory operations, the quantities
of chemicals and solvents used, producing in a simpler way
highly complex organic molecules with the desired selectivity.
In this current opinion, recent examples of the use of metal-,
organo-, and biocatalyzed tandem processes run under environmentally
responsible conditions (e.g., use of water, biobased
solvents, or without additional solvents) are showcased,
highlighting practical and valuable aspects
A Hybrid Model of the Akamai Adaptive Streaming Control System
No full textVideo streaming is becoming the application generating the largest fraction of the Internet traffic. Adaptive video streaming adds to classic video streaming the feature of dynamically adapting the video bitrate to track the time-varying network available bandwidth, avoid playback interruptions and ensure the delivery of the best video quality. In this paper we focus on the adaptive video streaming control system employed by Akamai, a major CDN operator whose video delivery system is used by several video streaming platforms, including Livestream. Differently from the typical client-side control, Akamai employs an interesting and unique hybrid client/server control architecture. Our purpose is to derive and validate a closed loop mathematical model of the control system, which turns out to be a hybrid automaton. The model is then analyzed to derive key properties which can be used to properly tune the controller parameters
LSTM-based Viewport Prediction for Immersive Video Systems
No full textImmersive multimedia content delivery is becoming increasingly popular due to the spread of Head Mounted Displays. In particular, omnidirectional video streaming is gaining ground among video delivery platforms. Delivering 360° video content over the Internet requires much larger bandwidth compared to classic 2D videos. Therefore, for the purpose of reducing bandwidth consumption, the tiling technique breaks down the video into smaller portions so that those falling outside the user's viewport are encoded at a low resolution whereas those in the viewport are encoded at a higher resolution. This operation can be performed only when the user's future viewports are known in advance. Thus, it is necessary to provide a trustworthy prediction of future viewports. In this work, we show that users have a tendency to explore the environment at the beginning of the video and then to focus on one of the regions attracting more attention (Points of Interest). This insight is helpful when it comes to designing viewport-adaptive streaming techniques. On this basis, we propose a viewport prediction approach that combines Long Short-Term Memory (LSTM) networks and the classic naive technique. Preliminary simulative tests show promising results
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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