1,720,956 research outputs found
Experimentelle Untersuchung des Stofftransports im mikroblasenbegasten Rührreaktor unter der Berücksichtigung von Gegendiffusionseffekten
No full textViele chemische und biologische Reaktionen in wässriger Phase benötigen gasförmige Komponenten, welche über Begasungseinrichtungen bereitgestellt werden. Für schnelle chemische und biologische Reaktionen ist der Stofftransport von der Gas- in die Flüssigphase häufig limitierend, was eine kontinuierliche Prozessoptimierung notwendig macht. Für diese Prozessoptimierung wird im Labor der Stofftransport über den volumenspezifischen Stoffdurchgangskoeffizienten kLa quantifiziert. Für die Bestimmung des kLa-Wertes wird in der Regel die Messmethode des Gasstrippings mit Stickstoff verwendet.
Die vorliegende Arbeit konzentriert sich auf die Charakterisierung von Gegendiffusionseffekten und deren Einfluss auf den Stofftransport. Hierbei ist vor allem der Einfluss unterschiedlicher Strippinggase bei der Bestimmung des kLa-Wertes von Interesse. Die Grundlage dieser Arbeit bildet ein 2 L Rührreaktor sowie drei Begasungseinrichtungen (Opentube, L-Begaser und Sinterstein), welche sich primär über ihre Blasengröße und -form differenzieren lassen. Der Stofftransport bei unterschiedlichen Entgasungsmethoden wird mit dem Sauerstoff-kLa-Wert für unterschiedliche Gasvolumenströme und Begaser analysiert. Hierbei wird das Reaktionsmedium über Stickstoff oder Argon gestrippt, zudem wird physikalisch entgastes Medium verwendet. Neben den Stofftransportmessungen werden die Blasen über endoskopische Messungen aufgenommen.
Als ein entscheidendes Ergebnis der Untersuchungen zeigt das physikalisch entgaste Medium um 56% höhere Stofftransportraten als das mit Stickstoff desorbierte Medium. Als Hauptgrund kann die vorliegende Gegendiffusion und der dadurch niedrigere Sauerstoffpartialdruck in den Blasen identifiziert werden, welcher den Stofftransport negativ beeinflusst. Zudem steigt die Gegendiffusion mit höherer Gaslöslichkeit des Strippinggases, während die Stofftransportrate von Sauerstoff sinkt. Außerdem sind über die endoskopischen Messdaten und die kLa-Werte die jeweiligen flüssigseitigen Stoffdurchgangskoeffizienten kL berechnet worden, welche charakteristisch für jede Entgasungsmethode sind. Auf Basis der kL-Werte konnte ein Modell zur Quantifizierung der Gegendiffusionseffekte entwickelt werden.Many chemical and biological liquid phase reactions require gaseous components provided by aeration via gassed stirred tanks. For fast chemical and biological reactions mass transfer from the gas to the liquid phase is often limited making a continuous process optimisation necessary. For this process optimisation, the mass transfer is usually quantified in the laboratory via the volumetric mass transfer coefficient kLa using the measurement method of gas stripping with nitrogen.
The present work focuses on the characterisation of counter-diffusion effects and their influence on mass transport. The influence of different stripping gases on the determination of the kLa-value is particular important. The basis of this work is a 2 L stirred reactor and three gassing devices (opentube, L-sparger and sintered frit). These sparger can be differentiated primarily by their bubble size and shape. The analysis of mass transfer with different degassing methods is performed by the oxygen kLa-value for different gas volume flows and gassing devices. The reaction medium is stripped via nitrogen or argon. A physically degassed medium is used as well. In addition to mass transport measurements, endoscopic measurements are used to record the micro-bubbles generated by the sintered frit.
As a key-result of the investigations, the physically degassed medium shows 56% higher mass transport rates than the medium desorbed with nitrogen. The main reason is the counter-diffusion and the resulting lower oxygen partial pressure in the bubbles, which has a negative influence on the mass transport. Moreover, the counter-diffusion effects increase with higher gas solubility of the stripping gas and mass transfer rate of oxygen decreases.
In addition, the endoscopic measurement data and the kLa-values were used to calculate the respective mass transfer coefficients kL. These are characteristic for each degassing method. On the basis of the kLa-values a model for quantifying the counter-diffusion effects could be developed
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Author Under Sail The Imagination of Jack London, 1893-1902
No full textIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Intro -- Title Page -- Copyright Page -- Dedication -- Contents -- Acknowledgments -- Introduction -- 1. Spirit Truth -- 2. From Absorption to Theatricality and Back Again -- 3. "I Will Build a New Present" -- 4. Sons as Authors -- 5. Fathers as Publishers -- 6. The Daughter as Author -- 7. Lovers as Authors -- 8. At Sea with the Family -- 9. Yellow News, Yellow Stories -- 10. The Return Home -- Notes -- Bibliography -- Index -- About Jay WilliamsIn Author Under Sail, Jay Williams offers the first complete literary biography of Jack London as a professional writer engaged in the labor of writing. It examines the authorial imagination in London's work, the use of imagination in both his fiction and nonfiction, and the ways he defined imagination in the creative process in his business dealings with his publishers, editors, and agents. In this first volume of a two-volume biography, Williams traverses the years 1893 to 1902, from London's "Story of a Typhoon" to The People of the Abyss. The Jack London who emerges in the pages of Author Under Sail is a writer whose partnership with publishers, most notably his productive alliance with George Brett of Macmillan, was one of the most formative in American literary history. London pioneered many author models during the heyday of realism and naturalism, blurring the boundaries of these popular genres by focusing on absorption and theatricality and the representation of the seen and unseen. London created an impassioned, sincere, and extremely personal realism unlike that of other American writers of the time. Author Under Sail is a literary tour de force that reveals the full range of London as writer, creative citizen, and entrepreneur at the same time it sheds light on the maverick side of machine-age literature.Description based on publisher supplied metadata and other sources.Electronic reproduction. Ann Arbor, Michigan : ProQuest Ebook Central, YYYY. Available via World Wide Web. Access may be limited to ProQuest Ebook Central affiliated libraries
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