1,720,995 research outputs found
Heterogeneous oxidation of different atomic clusters in amorphous SiBCN ceramic associated with phase separation
No full textIn this study, the microstructure of amorphous SiBCN ceramic derived from polyborosilazane and the crystalline SiBCN ceramic heat treated at 1600 degrees C was investigated and their oxidation behavior and kinetics involving different atomic clusters or phases during the non-isothermal oxidation process up to 1500 degrees C were analyzed to obtain their different micro mechanisms. Due to higher oxidation activity, the atomic clusters in amorphous structure can be oxidized at lower temperatures and exhibit lower activation energy than the crystal phases in crystalline structure, but have much higher oxidation resistance due to the phase separation-coupled heterogeneous oxidation of different atomic clusters
Heterogeneous oxidation behavior and kinetic mechanisms of SiBCN ceramic with structure of MA-SiBCN coated by PDCs-SiBCN
No full textIn this study, SiBCN ceramics with a structure of three-dimensional PDCs-SBCN network structure coated MASiBCN (MA@PDCs-SiBCN) were fabricated, which significantly improved the sintering activity and oxidation performance. The effect of MA@PDCs-SiBCN structure on oxidation behaviors and kinetics of oxide layer growth of the SiBCN ceramics at 1500 degrees C was investigated, indicating that the significantly improved oxidation resistance is attributed to the different heterogeneous oxidation behaviors, especially in the initial stage. Therefore, the heterogeneous oxidation behaviors and kinetic laws of different phases in MA@PDCs-SiBCN ceramics at different temperature ranges and their effects on structural evolution and oxide layer composition were analyzed by comparison with the MA-SiBCN ceramics. The significantly improved oxidation resistance of MA@PDCsSiBCN ceramics should be attributed to the inhibition of MA@PDCs-SiBCN structure to heterogeneous oxidation, especially the consumption of t-C, and different oxide layer composition generated from microcrystalline structure rather than nanocapsule-like crystalline structure
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
Additive manufacturing of geopolymers with hierarchical porosity for highly efficient removal of Cs<sup>+</sup>
No full textGeopolymers (GPs) have emerged as promising adsorbents for wastewater treatment due to their superior adsorption stability, tunable porosity, high adsorption capacity, and low-energy production. Despite their great promise, developing GPs with well-controlled hierarchical structures and high porosity remains challenging, and the mechanism underlying the ion adsorption process remains elusive. Here we report a cost-effective and universal approach to fabricate Na or K GPs with sophisticated architectures, high porosity, and arbitrary cation species exchange by means of additive manufacturing and a surfactant. The introduction of sodium lauryl sulfate (SLS) enhanced the porosity of the GP adsorbents, yielding NaGP-lattice-10%SLS adsorbent with a high total porosity of 80.8 vol%. Combining static and dynamic adsorption tests, the effects of morphology, surfactant content, and cation species on Cs+ adsorption performance were systemically investigated. With an initial Cs+ concentration of 900 mg/L, the printed NaGP exhibited a maximum Cs+ adsorption capacity of 80.1 mg/g, outperforming other adsorbents reported so far. The quasi-second-order fit of the NaGP adsorbent showed overall higher R2 values than the quasi-first-order fit, indicating that the adsorption process was dominated by ion exchange. Combined with first-principles calculations, we verified that the content of water in the GP sod cages also affected the ion-exchange process between Na+ and Cs+
Exploiting bifunctional 3D-Printed geopolymers for efficient cesium removal and immobilization: An approach for hazardous waste management
No full text3D-printed geopolymer lattices (3DGPLs) have recently been considered as promising candidates for hazardous waste management due to their low cost, porous nature, and excellent environmental stability. However, the ion adsorption capacity influenced by usage conditions such as multi-ion systems and radiation remains largely unexplored. Furthermore, effective strategies to immobilize adsorbed ions for long-term disposal are still lacking. This work tackles these questions by studying the Cs+ adsorption and immobilization properties of 3DGPLs in the presence of competing ions and gamma-ray radiation. Our results reveal the inhibitory intensity of Cs+ adsorption capacity by five common metal cations in seawater, ranked in the following order: Na+ > K+ > Ca2+ > Mg2+ > Sr2+. After exposure to different doses of gamma-ray radiation, the Cs+ adsorption capacity of 3DGPLs shows no significant change, demonstrating their outstanding radiation resistance. By encapsulating the Cs-containing 3DGPL with a homologous GP coating, the Cs+ immobilization rate reaches 98.545% after leaching in NaCl solution at 60 degrees C for 5 days. The already-high Cs+ immobilization rate can be further increased to 99.228% by sintering treatment due to the densification effect. This study not only provides microscopic insights into the adsorption of hazardous ions by 3DGPLs under usage conditions, but also offers a feasible approach to prevent the leakage of loaded ions through GP coating technology
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