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Short-term supply chain management in upstream natural gas systems
Get PDFThesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2009.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (p. 253-267).Natural gas supply chain planning and optimization is important to ensure security and reliability of natural gas supply. However, it is challenging due to the distinctive features of natural gas supply chains. These features arise from the low volumetric energy density of natural gas and the significance of gas quality and pressure in supply chain operations. Contracts play a central role in the entire supply chain due to high capital cost, specificity and investment risks associated with gas infrastructure. An upstream production planning framework is crucial for supply-side optimization and scenario evaluation in the natural gas supply chain. The technical features of upstream systems imply that the most efficient mode of operation is by single entity central control of the system, while their economics favor involvement of multiple parties in ownership. To resolve this conflict, upstream systems are generally operated by a single operator on the basis of governing rules that stem from agreements between the upstream operator, multiple stakeholders and consumer facilities. These agreements govern production sharing, operational strategy and gas sales in the upstream system. A short-term operational planning framework (with a 2-12 weeks planning horizon) for upstream natural gas systems is presented that can help to maximize production infrastructure utilization and aid in its management, minimize costs and meet production targets while simultaneously satisfying governing rules. Its requirements are inspired by the Sarawak Gas Production System (SGPS), an offshore gas production system in the South China Sea, which supplies the liquefied natural gas (LNG) plant complex at Bintulu in East Malaysia. This is the first attempt to formulate a comprehensive modeling framework for an upstream gas production system that includes a production infrastructure model and a methodology to incorporate governing rules.(cont.) The model has two components: the infrastructure model is a model of the physical system, i.e., of wells, trunkline network and facilities while the contractual model is a mathematical representation of the governing rules, e.g., production-sharing contracts (PSC), customer specifications and operational rules. The model formulation and objectives are from the perspective of the upstream operator. The infrastructure model incorporates the capability to track multiple qualities of gas throughout the network and determine the optimal routing and blending of gas such that the quality specifications are satisfied at the demand nodes. Nonlinear pressure-flowrate relationships in wells and the network are included for predicting a sufficiently accurate pressure-flowrate profile thereby facilitating implementation of the production strategy on the network. Modeling of complex platform configurations with reversible lines, lines that can be shut-off in normal operation and compression facilities, further improve the realistic representation of the network. A simplified prediction of natural gas liquids (NGL) production is included to maximize NGL revenue. The contractual model represents the framework for modeling the governing rules that are central to the operation of upstream systems. Modeling of productionsharing contracts is a two-fold challenge: accounting for gas volumes and converting the logical rules as stated in the system operations manual to binary constraints. A PSC network representation is proposed to account for gas volumes as well as interactions between different PSC. PSC rules are expressed as logical expressions in terms of availability, priority and transfer Boolean-states, and converted to binary constraints. Additional logical constraints are required to model the inference and intent of the rules. Operational rules can be modeled within the same framework.(cont.) The resulting mathematical program is a mixed-integer nonlinear program (MINLP) with nonconvex functions and can be solved with the current state-of-the-art global optimization approaches, provided careful attention is paid to the model formulation.A hierarchical multi-objective approach is proposed to address multiple objectives when operating upstream systems, by optimizing a lower priority objective over the multiple optimal solutions of a program with a higher priority objective to obtain a win-win scenario. A reproducible case study that captures all the features of natural gas upstream systems is constructed to facilitate future work in algorithm development for such problems. A preliminary comparison with the existing approach indicates that substantial benefits may be possible by using the proposed approach for short-term planning. The application of a reduced-space global optimization approach to planning in upstream gas networks has also been demonstrated, which can significantly lower the number of variables in the branch-and-bound algorithm. The lower bounding problem is implemented using McCormick (convex) relaxations of computer evaluated functions and solved by implementing a nonsmooth bundle solver as a linearization tool to obtain a linear programming relaxation. The upper bounding problem is implemented using automatic differentiation and a local NLP solver. Branch-and-bound with reduction heuristics and linearization propagation is used for global optimization.This approach has been found to be competitive with current state-of-the-art global optimization algorithms for upstream planning problems.by Ajay Selot.Ph.D
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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