1,720,966 research outputs found
Variational Quantitative Phase-field Modeling and Simulation of Non-isothermal Sintering Process
Get PDFSintering, an important technique in the production of ceramics and metals has seen the emergence of novel methods (e.g., selective laser sintering) offering higher heating rates and flexibility in creating complex-shape components. However, achieving the desired material properties and underlying microstructure using these techniques is challenging due to the interplay of several mechanisms and complex non-isothermal factors. Phase-field modeling, a powerful tool in investigating microstructure evolution in sintering, has quantitative validity limitations when coupled with diffusive processes (e.g., mass and heat transfer). As one of the diffuse-interface approaches, abnormal interface effects may originate at the interfaces during simulations. On the other hand, models formulated to be quantitative, do not necessarily exhibit a thermodynamics variational nature. While variational quantitative models exist for liquid-solid interfaces, similar models are absent for sintering interfaces.
This study introduces a variational quantitative phase-field model formulated for the non-isothermal sintering process. The model, developed based on Onsager relations and variational principles is formulated to eliminate abnormal interface effects while ensuring thermodynamic consistency. Cross-coupling terms between the conserved kinetics (i.e., mass and thermal transfer) and the non-conserved one (grain growth), which are typically neglected in conventional models, are considered. These terms are shown via asymptotic analysis to be instrumental in ensuring the elimination of interface effects. In addition, it was obtained that the cross-coupling terms do not modify the thermodynamic equilibrium conditions. Furthermore, anisotropic interpolation of the kinetic mobilities is employed to ensure the model's quantitative validity.
Numerical simulations validate the importance of cross-coupling terms and anisotropic interpolation for accurate quantitative simulations. While the proposed model introduces these terms, necessitating a more complex numerical implementation, it offers a significant advantage. The model allows the usage of larger interface widths during simulations while maintaining quantitative accuracy. This enables the use of coarser meshes, leading to a better improvement in computational efficiency. Thermal-microstructural evolution results are also presented and compared between proposed and existing models. Furthermore, 3D simulations of yttria-stabilized zirconia micro-particles sintering demonstrate the model's ability to capture microstructure, density, and temperature profile evolution. The proposed modeling and simulation framework in this study provides a powerful tool for quantitative simulations of non-isothermal sintering and related processes
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
Investigation on temperature-gradient-driven effects in unconventional sintering via non-isothermal phase-field simulation
No full textkoamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Variational quantitative phase-field modeling of non-isothermal sintering process
No full textPhase-field modeling has become a powerful tool in describing the complex pore-structure evolution and the intricate multiphysics in nonisothermal sintering processes. However, the quantitative validity of conventional variational phase-field models involving diffusive processes is a challenge. Artificial interface effects, like the trapping effects, may originate at the interface when the kinetic properties of two opposing phases are different. On the other hand, models with prescribed antitrapping terms do not necessarily guarantee the thermodynamics variational nature of the model. This issue has been solved for liquid-solid interfaces via the development of the variational quantitative solidification phase-field model. However, there is no related work addressing the interfaces in nonisothermal sintering, where the free surfaces between the solid phase and surrounding pore regions exhibit strong asymmetry of mass and thermal properties. Also, additional challenges arise due to the conserved order parameter describing the free surfaces. In this work, we present a variational and quantitative phase-field model for nonisothermal sintering processes. The model is derived via an extended nondiagonal phase-field model. The model evolution equations have naturally cross-coupling terms between the conserved kinetics (i.e., mass and thermal transfer) and the nonconserved one (grain growth). These terms are shown via asymptotic analysis to be instrumental in ensuring the elimination of interface artifacts, while also examined to not modify the thermodynamic equilibrium condition (characterized by a dihedral angle). Moreover, we demonstrate that the trapping effects and the existence of surface diffusion in conservation laws are direction-dependent. An anisotropic interpolation scheme of the kinetic mobilities that differentiates between the normal and tangential directions along the interface is discussed. Numerically, we demonstrate the importance of the cross-couplings and the anisotropic interpolation by presenting thermal-microstructural evolutions
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