1,721,327 research outputs found
Multi-objective imperfect maintenance for dependent competing risk systems with multiple degradation processes
No full textMultiple competing risks are one of the important topics in reliability field, especially degradation processes and random shocks. This research aims to relax the independent assumption by considering that there exist dependent relationships not only among multiple degradation measures but also between degradation measure and random shocks. In reality, many systems have multiple components with more than one degradation measure which is dependent with each other due to their interplaying functions or common usage history. Independent assumption may underestimate system reliability estimation under many cases. Random shocks will also contribute to the system failure through two ways: (1) one is working directly on the degradation processes; (2) the other is causing immediate failure to the system. We develop a new methodology to formulate the reliability prediction model for the gradually degradating systems subject to multiple dependent competing risks of degradation processes and random shocks. Two kinds of random shocks are considered: (1) fatal shocks, which fail the system immediately; (2) non-fatal shocks, which exhibit two effects on the system degradation process, including sudden degradation increment and degradation rate acceleration. The dependency between degradation processes and random shocks are modulated by a time-scaled covariate factors while the dependency among degradation processes are fitted by copula method. Also the reliability and state probability estimation for the systems are derived under the research scope of multi-state system using both analytical and Monte Carlo simulation for the dependent competing-risk systems. Different maintenance policy models involving imperefect preventive maintenance for this dependent model are introducted and compared with each other. Multi-objective optimization is applied to consider two important targets simultaneously in maintenance issues, including long-run expected cost rate and system availability.Ph. D.Includes bibliographical referencesIncludes vitaby Yaping Wan
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
Supplemental Material - Study on properties of copolymers based on different types of benzoxazines and branched epoxy resins
No full textSupplemental Material for Study on properties of copolymers based on different types of benzoxazines and branched epoxy resins by Lele Liu, Fan Wang, Yaping Zhu and Huimin Qi in High Performance Polymers</p
Supplemental Material - Preparation and properties of benzoxazine precursors containing siloxane units and their epoxy copolymers
No full textSupplemental Material for Preparation and properties of benzoxazine precursors containing siloxane units and their epoxy copolymers by Lele Liu, Fan Wang, Yaping Zhu, Huimin Qi in High Performance Polymers</p
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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