•In-text citations from over five million full text articles from the PubMed Central Open Access subset and Elsevier journals are analyzed.•There are large field-level differences that are reflected ...in position within the text, citation interval, and citation counts of references.•In all fields the numbers of sentences, references, and in-text mentions per article have increased over time.•There are field-level and temporal differences in the numbers of in-text mentions per reference.•References mentioned only once tend to be much more highly cited than those mentioned multiple times.
We report characteristics of in-text citations in over five million full text articles from two large databases – the PubMed Central Open Access subset and Elsevier journals – as functions of time, textual progression, and scientific field. The purpose of this study is to understand the characteristics of in-text citations in a detailed way prior to pursuing other studies focused on answering more substantive research questions. As such, we have analyzed in-text citations in several ways and report many findings here. Perhaps most significantly, we find that there are large field-level differences that are reflected in position within the text, citation interval (or reference age), and citation counts of references. In general, the fields of Biomedical and Health Sciences, Life and Earth Sciences, and Physical Sciences and Engineering have similar reference distributions, although they vary in their specifics. The two remaining fields, Mathematics and Computer Science and Social Science and Humanities, have different reference distributions from the other three fields and between themselves. We also show that in all fields the numbers of sentences, references, and in-text mentions per article have increased over time, and that there are field-level and temporal differences in the numbers of in-text mentions per reference. A final finding is that references mentioned only once tend to be much more highly cited than those mentioned multiple times.
In public debates, climate change communication tends to polarize into communities for and against the scientific basis of global warming. We analyze mention networks on Twitter around the ...publication of the Fifth Assessment Report (AR5) of the Inter-governmental Panel on Climate Change (IPCC) Working Group 2 and 3 reports that were published in March–April 2014. Building upon earlier research into climate skepticism and polarization of climate change debate, we focus on the relative prominence of different types of Twitter user accounts, in terms of engagement with other users and their alignments towards the scientific basis of climate change. We distinguish a “heart” actively discussing IPCC from a “shadow”, which more anecdotally mentions IPCC and is likely to correspond to the remainder of a public space minimally interested in IPCC-related reports. We develop an original network analysis framework that enables us to analyze and deconstruct the inner structure of this heart’s strongly intertwined engagement dynamics. Interesting observations relate to the position of critical users, who are in the minority, but are in relative terms most engaged with and most engaging with other users in this arena, while the media, casual users and governmental agencies occupy relatively less prominent positions. We further qualify the various structural positions by demonstrating that they correspond to different types of vocabulary specific to user types and positions. This socio-semantic approach may be generally helpful to disentangle semantic and structural polarization in online conversation spaces where opposing poles precisely appear to be mixing.
•Users critical of anthropogenic climate change hold a prominent position on Twitter.•They dominate a heart of users discussing IPCC reports despite being in minority.•Their vocabulary distinctly relies on scientific rather than political terms.•Media, individuals and governmental organizations are less prominent in the debate.•The heart exhibits a socio-semantic hierarchy intertwining terms and positions.
Profinite Groups Ribes, Luis
2010, 20100213, 2014-07-30, Letnik:
40
eBook
This updated book serves both as an introduction to profinite groups and as a reference for specialists in some areas of the theory. This revised edition contains new results, improved proofs, ...typographical corrections, and an enlarged bibliography.
A modular approach to the kinematics of planar linkages is based on a structural analysis of the mechanisms. Kinematic chains that can be synthesized according to Assur principle are well classified ...by their structure. Such a classification allows the development of general methods of the kinematics of subchains that can be algorithmized and used for computer-aided design. The paper introduces a new method of the position analysis of Assur dyads based on vector algebra tools. Obtained in unified vector form formulas give the opportunity to calculate the radius-vectors of all points of the dyads in the standard basis for the three-dimensional space. The method can be applied to the position, complete kinematic and kinetostatic analyses of planar linkages of the 2nd class according to Artobolevsky.
•The vector based approach for position analyses of Assur dyads is presented.•Chace vector equation is applicable for position analyses of Assur dyads.•The kinematics of planar linkages of the 2nd class by Artobolevsky is covered.
Reconfigurable parallel mechanisms (RPMs) have the advantages of high stiffness, good dynamic performance due to their parallel structures, and can reconfigure themselves into various mobility ...configurations to accommodate different task requirements, which indicate that RPMs have the potential to be used in multidirectional additive manufacturing. Based on this application, this paper focuses on the design and analysis of a novel RPM. Degree of freedom (DOF) requirements in different stages of multidirectional additive manufacturing are analyzed. A hybrid limb that is composed of a planar metamorphic mechanism and a 4-DOF serial chain is presented, and then employed in the design of a three-legged RPM. Unified model for kinematic position analysis and the overall Jacobian matrix of the RPM are established. Singularity analysis including inverse kinematic singularity and direct kinematic singularity analysis are conducted. Workspaces of the RPM in different operation modes are evaluated. A prototype and some experiments are presented.
•A reconfigurable parallel mechanism for multidirectional AM is presented.•The proposed reconfigurable parallel mechanism has four operation modes.•Unified model for kinematic position solution is established.•Jacobian model for all the operation modes is built.•Inverse kinematic singularities and direct kinematic singularities are identified.
•A hybrid methodology for position analysis for complex Assur Groups.•A uniform discriminant to identify the singularities of complex Assur Groups.•A universal method is presented to determine ...branches and circuits of linkages.•Presenting the existence condition of cranks for all complex linkages.•An automatic analysis program is developed for planar linkage analysis.
Complex linkages refer to the linkages composed of 4-bar or more than 4-bar Assur Groups (AG). This paper presents a hybrid position analysis method for complex AG. Firstly, position solutions of an external link in AG are obtained by solving the position analysis polynomial, then all configurations of the AG corresponding to the solutions can be determined through solving 2-bar AG. Above is the position analysis process at a single input condition. With the increasement of the input angle, a series of discrete position solutions can be obtained. How to connect these solutions to form different branches and circuits, and determine the movement range of the linkage are the other problems to be solved. This paper presents an effective methodology to determine the branches and circuits as well as the movement range of the linkage and gives a novel discriminant for identifying singular configurations of complex AG. Finally, several numerical examples are presented to demonstrate the correctness, effectiveness and universality of the proposed methods and the practicability of the program compiled based on the formulations and methodology.
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