1,721,196 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
Computational modelling and simulation of ductile damage in metals
No full textThis thesis deals with the development of a novel continuum damage modelling framework which enables the accurate prediction of the phenomenological effects of ductile damage on the mechanical properties of metals.
The proposed modelling framework establishes a relation between the macroscopic strain and stress states and is embedded into a finite element method regularised by adopting the micromorphic approach.
Thereby, the simulation of (cold) forming processes with more accurate predictions of the resulting mechanical properties and, especially, of the safety margin of the produced part becomes possible.
The process of developing the modelling framework is set forth by means of three separate models which increase in complexity.
At first, a regularised, isotropic, three-dimensional, ductile damage model is established at finite strains.
The analysis focuses on the coupling of damage and plasticity by means of a multisurface approach as well as on the applicability of the material model to resemble the behaviour of the dual-phase steel DP800, i.e.\ experiments are performed and parameters are identified by using full-field displacement data.
Secondly, a regularised anisotropic ductile damage model is implemented by adopting the fictitious configuration concept, where damage is described by a mapping related to a fictitiously undamaged configuration.
The coupling of damage and plasticity is further enriched by introducing effective driving forces controlling onset and evolution of damage and plasticity, respectively.
Different possibilities of regularisation are analysed and the results are underlined by illustrative examples.
The final stage of material model development incorporates the micro-crack closure and reopening effect.
Motivated from micro-mechanical considerations where mechanical stiffness in tension and in compression may evolve differently, two separate damage variables are introduced.
Previous stages of the material model are formulated with thermodynamically consistent associated evolution equations.
In contrast, the recovery of stiffness on crack closure is modelled in terms of a non-associated approach where special attention is paid towards fulfilling the dissipation inequality.
For all discussed models, the algorithmic implementation encompasses an implicit and monolithic solution of the model equations.
Furthermore, the characteristic behaviour of the developed models is demonstrated in terms of illustrative examples
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
A framework for geometrically non-linear gradient extended crystal plasticity coupled to heat conduction and damage
No full textGradient enhanced theories of crystal plasticity enjoy great research interest. The focus of this work is on thermodynamically consistent modeling of grain size dependent hardening effects. In this contribution, we develop a model framework for damage coupled to gradient enhanced crystal thermoplasticity. The damage initiation is directly linked to the accumulated plastic slip. The theoretical setting is that of finite strains. Numerical results on single-crystalline metal showing the development of damage conclude the paper
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
Modeling of Inelastic Response of Metals with Emphasis on Cyclic Viscoplasticity
No full textThis thesis is concerned with the continuum modeling of the macroscopic behavior of engineering metals, in particular as part of life prediction strategies. Focus is primarily placed on the formulation and numerics of models for cyclic rate-dependent response. <p />A thermodynamically consistent viscoplastic model based on the Duvaut-Lions concept with coupling to damage is proposed and various aspects of it are discussed. To extend the application range of the model with respect to loading rates, the unconventional feature of a bounding dynamic yield surface is introduced by a particular choice of overstress function. The dynamic yield surface prevents the response of the model to become purely elastic for high loading rates; instead the response will be almost rate-independent and resembles elastic-plastic response. The Backward Euler rule is used to integrate the constitutive equations, and the efficiency of a multi-level iteration technique for solving the arising system of equations is demonstrated. Further, the algorithmic tangent stiffness is derived and the model is implemented in the commercial FE code Abaqus. A sensitivity analysis is performed and used within a gradient-based optimization method to determine the model parameters. An example showing the capability of the model to mimic cyclic and softening experimental data of stainless steel is given. <p />The issue of thermo-elastic-viscoplastic modeling of the high-strength alloy IN792, used at high temperatures, is then addressed. Within the Perzynaviscoplasticity different overstress functions are examined. Among these, two functions are taken from the literature and one function, that includes the concept of dynamic yield surface, is proposed. Numerical issues such as integration, sensitivity analysis and parameter identification are discussed. Experimental data for step-relaxation tests and stationary creep for different temperatures are simulated and, finally, predicted. <p />Elastic and plastic anisotropy at large inelastic strains, modeled within the framework of hyperelasto-plasticity, is also part of this thesis. A kinematic hardening rule is proposed, and its predictive capability is investigated. Numerical investigations of the consequences of anisotropy are presented. In addition, it is shown that truncation errors introduced by linearizations in the case of non-coaxiality may be significant
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