1,720,967 research outputs found
Rotational bifurcation of localized dissipative structures
No full textA topic of great interest for pattern-forming systems is the possibility of a spontaneous change in symmetry and dynamics as one slowly varies an external parameter. In this letter, we identify that a stationary localized structure without rotational symmetry, such as a pair of bound dissipative solitons, can spontaneously begin to rotate. The underlying mechanism is similar to the widely studied mechanism of the drift bifurcation in which structures begin to drift at constant velocity. We find a particular example of this new bifurcation for a 3-component reaction-diffusion system in 2 dimensions, and show that it can precede the drift bifurcation.
Voronoi diagrams in barrier gas discharge
No full textVoronoi diagrams are essential topics of modem physics, chemistry, biology and other fields. There is a great interest in generating Voronoi diagrams for real-time applications that can be made by means of parallel analog computation. We report the observation of self-organized Voronoi diagrams as a pattern arising in a barrier gas-discharge system. It is shown experimentally that this phenomenon provides an opportunity to generate Voronoi diagrams in a parallel way for a given set of reference points on submillisecond time scale. (C) 2002 American Institute of Physics.
Rotating bound states of dissipative solitons in systems of reaction-diffusion type
No full textWe report on the formation of stable rotating bound states consisting of self-organized well localized solitary structures with particle-like behaviour in systems of reaction-diffusion type. These dissipative solitons are detected in an experimental planar d.c. gas-discharge system with a high ohmic barrier, as well as in numerical solutions of related three-component reaction-diffusion equations where the formation of rotating bound states is investigated in the context of a particle ansatz.
Drift bifurcation of dissipative solitons due to a change of shape: experiment and theory
No full textThe subject of this paper is self-organized solitary current filaments being observed experimentally in a planar dc gas-discharge system with high-ohmic barrier. We report on the dynamical behavior of these objects which we refer to as dissipative solitons. An application of stochastic data analysis methods enables the separation of intrinsic dynamics from stochastic contributions. Using the externally applied voltage as control parameter, we observe a drift bifurcation that is accompanied by a change of shape of the bifurcating dissipative soliton. In order to interpret the experimental finding, a theoretical model in form of a three-component reaction-diffusion system is considered, allowing for a qualitative understanding of the obtained results. We discuss an analytical expression for the velocity of the dissipative soliton as a function of an appropriate control parameter and demonstrate that the change of the shape can induce the drift bifurcation. This analytical finding is supported by numerical simulations of the model equations. (C) 2004 Elsevier B.V. All rights reserved.
Healthcare Pathway Discovery, Conformance, and Enrichment
No full textFull Text is available to authenticated members of The University of Auckland only.Healthcare pathways define the execution sequence of clinical activities as patients move through a treatment process, and they are critical for maintaining quality of care and improving health outcome for all patients. Past studies show that there is potential for informative healthcare pathways to be extracted from hospital health records, but there is currently no consensus on a systematic healthcare pathway mining method that supports explicit design and conformance analysis of concise and comprehensible healthcare pathway models. This study investigates the utilization of business process modelling methods to design a process mining pipeline for healthcare pathway discovery, conformance analysis and enrichment using hospital records. The process mining pipeline is designed with emphasis on producing pathway models that are concise and easy to interpret for clinicians without a sufficient background in process mining. The proposed process mining pipeline is applied to an appendicitis and cholecystitis case study as an example of a simple pathway, and an ambulatory cardiac care case study as an example of a complex pathway. Results from the two case studies indicate that the proposed pipeline designed with business process mining tools is effective for healthcare pathways of different levels of complexity. The produced healthcare pathway models are easy for clinical interpretation and provide an unbiased overview of real patient movements through the treatment process. Preliminary analysis on building machine learning models to predict post-operation length of stay in hospital, using information extracted by the process mining pipeline, is showing promising results. This means that the proposed mining pipeline also has the potential to support the development of machine learning models to further relate healthcare pathways to performance indicators such as readmission rates and mortality rates. This study establishes the use of business process modelling methods for the improvement of healthcare pathway mining methods, and there is value in investigating the capabilities of other business process mining tools for healthcare pathway mining purposes
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
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