1,720,956 research outputs found
The autothermal reforming of artificial gasoline
Get PDFStringent legislation on control of vehicle exhaust emissions has led to consideration of alternative means of reducing emissions, with hydrogen fuel cell powered vehicles being accepted as one favoured possibility. However, the difficulties of storing and distributing hydrogen as a fuel are such that the conversion of more readily available fuels to hydrogen on board the vehicle may be required. The production of hydrogen by the partial oxidation of isooctane over Rh/Al2O3, Rh/CeO2-?l2O3 and Rh/CeO2-ZrO2 catalysts has been investigated. Oxidation was initiated at temperatures between 200 ?220 oC. The yield of hydrogen was 100%. CeO2-ZrO2 was found to be the best support. The production of hydrogen by the autothermal reforming of artificial gasoline has been studied. Part of gasoline is oxidised to produce heat and steam to promote the steam reforming of unburnt gasoline to produce hydrogen. The use of platinum impregnated on ceria supports (active for oxidation) and a commercial nickel based catalyst (Ni-com), for steam reforming of gasoline have been explored. Initiation of oxidation of artificial gasoline over unreduced platinum based catalysts occurred at temperature as low as 150 oC, depending on the oxygen:carbon ratio and the liquid hydrocarbon used. Detailed kinetic studies of the steam reforming of isooctane and artificial gasoline (a mix of cyclohexane, isooctane and octane) over pre-reduced Ni-com catalysts showed that the reaction was 0.17 order in isooctane and 0.54 order in steam, whilst the reaction was 0.08 order in artificial gasoline and 0.23 order in steam. Mechanisms have been proposed to account for the dual site surface reaction with dissociative adsorption of isooctane or artificial gasoline and steam. Combined oxidation and steam reforming systems (autothermal reforming) using Pt/CeO2 as a front catalyst bed and Ni-com as the rear bed at the feed conditions of oxygen:carbon (O:C) ratio of ca.1.2 and steam:carbon (S:C) ratio of ca.2, produces ca. 3.5 moles of hydrogen per mole of gasoline fed. The system reaction temperature could be controlled by adjusting the O:C and S:C ratios in feed
Deaktivasi Katalis Konverter-Hidrogen Di Pabrik Urea Kaltim-3
Get PDFDi pabrik urea, konverter-hidrogen adalah satu reaktor yang berfungsi untuk mengkonversi hidrogen yang terikut dalam karbondioksida dengan cara mengoksidasi dengan udara, sehingga karbondioksida umpan reaktor urea itu hanya mengandung tidak lebih dari 100 ppm hidrogen. Konversi dilangsungkan pada tekanan 145 kg/cm2 dan suhu umpan reaktor 130 C, menggunakan katalis platinum berpenyangga alumina (0,3%Pt/Al2O3). Dalam dua tahun terakhir, terjadi kenaikan kandungan hidrogen dalam karbondioksida umpan konverter-hidrogen Kaltim-3 yang menyebabkan peningkatan temperatur keluaran konverter dari biasanya sekitar 152oC menjadi sekitar 190 C. Hasil analisis kadar Pt, luas permukaan katalis dan dispersi Pt terhadap katalis-baru dan katalis-terpakai menunjukkan bahwa katalis konverter-hidrogen Kaltim-3 telah terdeaktivasi. Oleh karena itu, pada kesempatan perbaikan-tahunan Juli 2006 yang lalu, katalis tersebut telah diganti dengan yang baru. Selain itu telah dilakukan pula perbaikan kondisi operasi di pabrik amoniak Kaltim-3, sehingga kadar H2 dalam aliran CO2 umpan pabrik urea Kaltim-3 menjadi normal kembali (0,4%). Dengan tindakan-tindakan tersebut, sejak Agustus 2006 yang lalu konverter hidrogen Kaltim-3 dapat beroperasi secara normal kembali. © 2007 BCREC UNDIP. All rights reserved.[Presented at Symposium and Congress of MKICS 2007, 18-19 April 2007, Semarang, Indonesia][How to Cite: A. Subekti, A.S. Arief, P. Praharso, S. Subagjo. (2007). Deaktivasi Katalis Konverter-Hidrogen Di Pabrik Urea Kaltim-3. Bulletin of Chemical Reaction Engineering and Catalysis, 2 (2-3): 52-55. doi:10.9767/bcrec.2.2-3.10.52-55][How to Link/DOI: http://dx.doi.org/10.9767/bcrec.2.2-3.10.52-55 ] </p
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
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