1,721,268 research outputs found
Synthesis of 8-MnO2 via ozonation routine for low temperature formaldehyde removal
No full textNowadays, it is still a challenge to prepared high efficiency and low cost formaldehyde (HCHO) removal catalysts in order to tackle the long-living indoor air pollution. Herein, 8MnO2 is successfully synthesized by a facile ozonation strategy, where Mn2 + is oxidized by ozone (O3 ) bubble in an alkaline solution. It presents one of the best catalytic properties with a low 100% conversion temperature of 85 degrees C for 50 ppm of HCHO under a GHSV of 48,000 mL/(g center dot hr). As a comparison, more than 6 times far longer oxidation time is needed if O3 is replaced by O2 . Characterizations show that ozonation process generates a different intermediate of tetragonal fi-HMnO2 , which would favor the quick transformation into the final product 8-MnO2 , as compared with the relatively more thermodynamically stable monoclinic y-HMnO2 in the O2 process. Finally, HCHO is found to be decomposed into CO2 via formate, dioxymethylene and carbonate species as identified by room temperature insitu diffuse reflectance infrared fourier transform spectroscopy. All these results show great potency of this facile ozonation routine for the highly active 8-MnO2 synthesis in order to remove the HCHO contamination. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy o
Controllable Synthesis of Different MnO<sub>2</sub> Phases by a Precipitation Method for Effective Ozone Decomposition
No full textIt is challenging to controllably synthesize manganese dioxide (MnO2) in a facile routine for structure-oriented applications. Herein, gamma-, alpha-, amorphous (a-), and delta-MnO2 are synthesized by the same liquid phase precipitation of KMnO4 and MnSO4 with tailored pH by KOH dosage and pH = 1 HCl washing. An ozone decomposition reaction is adopted as the catalytic activity evaluation probe, and a-MnO2 showed high efficiency of 80-90% to 100 ppm ozone during a 10 h test at weight hours space velocity of 1,200,000 mL g(-1) h(-1). The high activity can be attributed to its high specific surface area, low average Mn oxidation state, and abundant surface oxygen vacancy content. In addition, the activity decrease of a-MnO2 can be attributed to the accumulation of oxygen intermediates, as illustrated by in situ infrared spectroscopy, which however can be reactivated by simple 60 degrees C oven heating. These results provide a facile way to controllably synthesize differently crystallized MnO2, especially for highly efficient ozone decomposition catalysts
Co-templating synthesis of mesoporous hollow silica spheres and their application in catalytic oxidation with low Pt loading
No full textMesoporous hollow silica spheres (MHSS) with uniform size were successfully prepared by introducing monodispersed polystyrene (PS) spheres as hard template and selected surfactant as soft template in acid condition. With assistance of different surfactants, a series of mesoporous shells were created and the used surfactants have a significant effect on the structural properties of MHSS. The highest surface area was 690.3 m(2) g(-1) on the MHSS which was achieved by using P123 as a soft template. The MHSS was further used for loading active Pt through the reaction between chloroplatinic acid or and sodium borohydride. The as -prepared Pt/MHSS catalyst exhibited high activity for VOCs' deep oxidation. (C) 2016 Elsevier B.V. All rights reserved
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
Silicone rubber/hollow silica spheres composites with enhanced mechanical and electrical insulating performances
No full text
In this work, an experimental study was conducted to improve mechanical and electrical insulating properties of room temperature vulcanized silicone rubber (RTVSR) matrix by incorporating hollow silica spheres (HSS). The results showed that the addition of 5.0 wt% HSS in the RTVSR matrix noticeably improved the tensile strength. The volume resistivity of RTVSR nearly increased by one order of magnitude and the DC breakdown strength of RTVSR almost doubled when 5.0 wt% HSS were added. In contrast, commercial fumed silica (FS) with nanometre size showed relatively weak enhancing effects on RTVSR both in mechanical and electrical insulating performances at the same loading. (C) 2017 Elsevier B.V. All rights reserved.</p
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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