1,720,980 research outputs found
Micromechanical and microstructural analysis of Fe-rich plasma slag-based inorganic polymers
No full textThe development of new materials such as inorganic polymers (IPs) requires a deep understanding of the effect of the microstructural and the micromechanical properties on the strength. In this study, digital image processing technique were used to characterize SEM images of different IP microstructures. Via nanoindentation, the micromechanical properties were determined. Effects of changing the precursor fineness and the SiO2/Na2O (1.2–2.0) and H2O/Na2O (20.0–29.0) molar ratio of the activating solution (AS) on the properties of plasma slag-based IPs were studied. With a decreasing SiO2/Na2O molar ratio, the reactivity increased and more binder was formed not affecting the binder elastic properties, though leading to an increased strength. A decrease in H2O/Na2O molar ratio slightly favored the reactivity, with no extra binder formation, but with an increased elastic modulus of the binder. Damage initiation and propagation in the IP samples at the microscale was simulated using realistic microstructures and local mechanical properties. The effect of the elastic modulus of the binder phase on the strain softening was found to be negligible.sponsorship: The authors thank L. Arnout and L. Machiels from KU Leuven from providing the synthetic plasma slag. The authors also would like the express their appreciation to Danny Winant for the support with the TGAmeasurements and to Pavel Leonardo Lopez Gonzalez for the support with the calorimetry measurements. This study was partially supported by the Special Research Fund (BOF) of Hasselt University, by the ENEN+ project that has received funding from the Euratom research and training Work Programme 2 and by the Research Funding Flanders (FWO) . The research leading to these results was partially achieved through access to the Fuel and Materials (FMR) Laboratory (ActUsLab) under the Framework for open access to the Joint Research Centre Research Infrastructures of the European Commission. (Special Research Fund (BOF) of Hasselt University, ENEN+ project from the Euratom research and training Work Programme 2, Research Funding Flanders (FWO))status: Publishe
The effect of gamma irradiation on Fe-rich slag-based inorganic polymers
No full textIn search for alternative cementitious materials for radioactive waste encapsulation, geopolymers and inorganic polymers (IPs) have received wide attention. The absence of portlandite, the low water content and the high alkalinity, make IPs interesting candidates for the conditioning of certain radioactive waste streams. Moreover, Fe-rich IPs offer an interesting alternative to high density concretes for use in radiation shielding applications. Materials can though be altered when subjected to ionizing radiation, therefore the material's behaviour under irradiation have to be studied.
The effect of gamma irradiation was investigated on CaO-FexOy-SiO2 slag-based IPs. IPs with different curing times (1 h, 24 h and 28 days) prior to the irradiation were irradiated at a dose rate of 8.85 kGy/h, to a total absorbed dose of 200 kGy. The effects were evaluated by means of compressive strength, porosity measurements, thermogravimetric analysis, infrared spectrometry, nanoindentation and 57 Fe Mössbauer spectroscopy. For each irradiation test, non-irradiated samples were kept as a reference at the same environmental conditions as the irradiated samples.
The effect of gamma radiation is observed to be dependent on the curing time prior to irradiation. 28 days cured samples are found to be resistant to the gamma irradiation for the dose(rate) tested. No change was found in strength, indentation characteristics, porosity and Fe 3+ content. On the other hand, multiple effects were observed for the 1 hour cured samples: an increase of the compressive strength, a lower Young's-modulus, a lower creep in time, a decrease in porosity and an increased Fe 3+ /Fe ratio. The increased macromechanical strength is a result of radiation-induced heating and water radiolysis in the IPs. Both processes affect the oxidation reactions and the carbonation taking place leading to a changed microstructure/porosity eventually leading to an increased strength.Acknowledgements: BOF16DOC16 UHasselt, ENEN+, FWO, ActUsLa
The effect of gamma irradiation on Fe-rich slag-based inorganic polymers
No full textIn search for alternative cementitious materials for radioactive waste encapsulation, geopolymers and inorganic polymers (IPs) have received wide attention. The absence of portlandite, the low water content and the high alkalinity, make IPs interesting candidates for the conditioning of certain radioactive waste streams. Moreover, Fe-rich IPs offer an interesting alternative to high density concretes for use in radiation shielding applications. Materials can though be altered when subjected to ionizing radiation, therefore the material's behaviour under irradiation have to be studied.
The effect of gamma irradiation was investigated on CaO-FexOy-SiO2 slag-based IPs. IPs with different curing times (1 h, 24 h and 28 days) prior to the irradiation were irradiated at a dose rate of 8.85 kGy/h, to a total absorbed dose of 200 kGy. The effects were evaluated by means of compressive strength, porosity measurements, thermogravimetric analysis, infrared spectrometry, nanoindentation and 57 Fe Mössbauer spectroscopy. For each irradiation test, non-irradiated samples were kept as a reference at the same environmental conditions as the irradiated samples.
The effect of gamma radiation is observed to be dependent on the curing time prior to irradiation. 28 days cured samples are found to be resistant to the gamma irradiation for the dose(rate) tested. No change was found in strength, indentation characteristics, porosity and Fe 3+ content. On the other hand, multiple effects were observed for the 1 hour cured samples: an increase of the compressive strength, a lower Young's-modulus, a lower creep in time, a decrease in porosity and an increased Fe 3+ /Fe ratio. The increased macromechanical strength is a result of radiation-induced heating and water radiolysis in the IPs. Both processes affect the oxidation reactions and the carbonation taking place leading to a changed microstructure/porosity eventually leading to an increased strength.Acknowledgements: BOF16DOC16 UHasselt, ENEN+, FWO, ActUsLa
The effect of high dose rate gamma irradiation on the curing of CaO-FexOy-SiO₂ slag based inorganic polymers: Mechanical and microstructural analysis
No full textIn search for alternative cementitious materials for radioactive waste encapsulation, geopolymers and inorganic polymers (IPs) have received wide attention. Moreover, Fe-rich IPs offer an interesting alternative to high density concretes for use in radiation shielding applications. Materials can however be altered when subjected to ionizing radiation, creating the necessity to evaluate the material’s behaviour under irradiation conditions. In this study the effect of high dose rate (8.85 kGy/h) gamma irradiation is investigated on CaO-FexOy-SiO₂ slag-based IPs. Samples with different curing times (1 h, 24 h and 28 days) prior to the irradiation were irradiated to a dose of 200 kGy using a⁶⁰Co source.The effect of gamma radiation is observed to be highly dependent on the curing time prior to irradiation. 28 days cured samples are found to be resistant to the irradiation for the dose (rate) and properties tested without any significant change in strength, indentation characteristics, porosity and Fe³⁺ content. The IPs studied show a different behaviour when irradiated immediately after casting or after 24 h of curing. It is therefore thought that the mechanism behind the effect of irradiation is different for the non-hardened samples compared to hardened samples. For the 1 h cured samples prior to irradiation multiple effects were observed: an increase of the compressive strength by a factor 2.20, a decrease in hardness of the binder by a factor of 0.73, a lower Young’s-modulus of the binder by a factor of 0.67, a decrease of creep in time for the binder by a factor of 0.72, a decrease in porosity by a factor of 0.92 and an increase of the Fe3+/ΣFe ratio by a factor of 1.95.sponsorship: The authors express their appreciation to dr. ing. Krzystof Kierzek from Wroclaw University of Science and Technology to perform the MIP-analysis. The authors also thank L. Arnout and L. Machiels from KU Leuven from providing the synthetic plasma slag. This study was partially supported by the Special Research Fund (BOF) of Hasselt University, by the ENEN + project that has received funding from the Euratom research and training Work Programme 2 and by the Research Funding Flanders (FWO). The experimental data used in this research were partially generated through access to the ActUsLab-FMR under the Framework of access to the Joint Research Centre Physical Research Infrastructures of the European Commission (IP4NA project, Research Infrastructure Access Agreement Nr. 35433). APD acknowledges the partial support of this work by the project MIS 5002772, implemented under the Action "Reinforcement of the Research and Innovation Infrastructure", funded by the Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020) and cofinanced by Greece and the European Union (European Regional Development Fund). (Hasselt University, ENEN + project - Euratom research and training Work Programme 2, Research Funding Flanders (FWO), European Commission|35433, Operational Programme "Competitiveness, Entrepreneurship and Innovation" (NSRF 2014-2020)|MIS 5002772, European Union (European Regional Development Fund))status: Publishe
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
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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