1,720,978 research outputs found
Process simulator-based optimization of biorefinery downstream processes under the Generalized Disjunctive Programming framework
No full textDownstream processing of biofuels and bio-based chemicals represents a challenging problem for process synthesis and optimization, due to the intrinsic nonideal thermodynamics of the liquid mixtures derived from the (bio) chemical conversion of biomass. In this work, we propose a new interface between the process simulator PRO/II (SimSci, Schneider-Electric) and the optimization environment of GAMS for the structural and parameter optimization of this type of flowsheets with rigorous and detailed models. The optimization problem is formulated within the Generalized Disjunctive Programming (GDP) framework and the solution of the reformulated MINLP problem is approached with a decomposition strategy based on the Outer-Approximation algorithm, where NLP subproblems are solved with the derivative free optimizer belonging to the BzzMath library, and MILP master problems are solved with CPLEX/GAMS. Several validation examples are proposed spanning from the economic optimization of two different distillation columns, the dewatering task of diluted bio-mixtures, up to the distillation sequencing with simultaneous mixed-integer design of each distillation column for a quaternary mixture in the presence of azeotropes
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
Alkylation of isopropanol with ethanol over heterogeneous catalysts
Full text linkThe importance of synthesis of carbon-carbon bonds is reflected by the fact that Nobel Prizes in Chemistry have been given to this area: The Grignard reaction (1912), the Diels-Alder reaction (1950), the Witting reaction (1979), the olefin metathesis Y. Chauvin, R.H. Grubbs and R.R. Schrock (2005), the palladiumcatalyzed cross-coupling reactions to R. F. Heck, A. Suzuki, E. Negishi (2010). For the first time ever alkylation of isopropanol with ethanol was carried out over heterogeneous 0.2-1 wt.% Au and/or 0.02-0.3 wt. %Ni - containing catalysts without any sacrificial agents and/or presence of acidic/base additives. The catalyst containing 0.2 wt.% Au and 0.18 wt.% Ni supported on γ-Al2O3 was found to be the most selective in the cross-coupling route. Total selectivity of coupling products reached up to 70 %, conversion of the both initial alcohols was 50 %. Structural investigations of the Au, Ni - containing catalysts permitted to determine probable active sites peculiarities that provide effective one-pot alkylation of isopropanol with ethanol
Robust optimization of the heteroextractive distillation column for the purification of water/acetic acid mixtures using p-xylene as entrainer
No full textThe separation of water and acetic acid mixtures is a challenging task in the terephthalic acid production process. This study addresses the techno-economical optimization of an heteroextractive distillation column that uses p-xylene as entrainer. The optimization of this column is performed by means of robust optimizers belonging to the BzzMath library, coupled with the detailed process simulation of the downstream section performed with the commercial software SimSci PRO/II. A comparison with respect to the commercial simulator optimizer and a quantification of benefits are given. Results show that the BzzMath robust optimizer reaches a lower Total Annual Cost (−3.5%) with respect to the commercial software optimization. Finally, the comparison with other entrainers proposed in literature for the advanced distillation of the water/acetic acid mixtures demonstrates the economical and operational appeal of this process configuration
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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