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Анализ параметров качества входного тока модульного AC-DC зарядного устройства SEPIC на основе ряда Фурье двух переменных
Get PDFУ статті розглянуто можливі топології зарядних пристроїв змінного струму з активною корекцією коефіцієнта потужності. Виділено одноланкові і дволанкові топології зарядних пристроїв та обґрунтовано доцільність використання першої групи перетворювачів через менші габарити та простішу структуру. Серед одноланкових перетворювачів наголошено на перевагах модульних перетворювачів з чергуванням фаз на основі топології SEPIC, що мають мінімальні динамічні втрати, простий алгоритм та схемну реалізацію корекції коефіцієнта потужності у граничному режимі протікання струму (ГРП) та невеликі габарити. Функціонування модульних перетворювачів проаналізовано на прикладі двокоміркового перетворювача та показано принцип покращення форми вхідного струму за умови зсуву імпульсів керування кожної комірки. Як результат, встановлено функціональну залежність параметрів якості електроенергії (коефіцієнт потужності PF і коефіцієнт нелінійних спотворень THD) від коефіцієнта заповнення імпульсів кожної комірки перетворювача. Оскільки у реальних перетворювачах складно дотримуватись ГРП, а в неперервному режимі форма вхідного струму спотворюється, такі перетворювачі працюють у переривчастому режимі протікання (ПРП) струму. На основі аналізу схем заміщення для трьох інтервалів роботи перетворювача SEPIC – інтервал наростання вхідного струму, інтервал спадання вхідного струму та інтервалу нульової паузи – створено його математичну модель. Показано, що збільшення тривалості нульової паузи протікання струму суттєво погіршує значення коефіцієнта потужності PF і коефіцієнта нелінійних спотворень THD. Внаслідок цього параметри PF і THD є функціями коефіцієнта заповнення імпульсів і тривалості паузи і мають складну залежність. Тому для оцінки кількості комірок перетворювача, що забезпечують необхідні значення PF і THD доцільно вивести ці залежності в аналітичній формі, що здійснено на основі використання ряду Фур’є двох змінних. Отримані залежності спрощують вибір кількості комірок перетворювача для заданого діапазону коефіцієнта заповнення імпульсів і значення відносної нульової паузи. На основі отриманих формул побудовано залежність PF і THD для двох, трьох і чотирьох комірок.Review of AC chargers topologies with active power factor correction are considered in the paper. Single and double-stage charger topologies are highlighted and the feasibility of using the first group of converters is substantiated because of its smaller size and simpler structure. Among single-stage converters, the advantages of modular converters based on SEPIC topologies are emphasized because of minimal dynamic losses, a simple algorithm, and circuit implementation of power factor correction at the boundary condition mode (BCM) of input current and small dimensions. The operation of modular converters is analyzed on the example of a two-cell converter and the principle of improving the shape of the input current under the condition of shifting control pulses of each cell is shown. As a result, the functional dependence of the electricity quality parameters (power factor PF and the total harmonic distortion THD) on the pulse ratio of each converter cell is established. Since it is difficult to comply BCM in real converters, and in continuous mode the shape of the input current is distorted, such converters operate in the discontinuous conduction mode (DCM) of input current. Based on the analysis of equivalent circuits in three intervals of operation of the SEPIC converter - interval of increase of input current, interval of decrease of input current and interval of zero pause - its mathematical model was created. It is shown that the increase of relative zero current interval duration significantly worsens the value of the power factor PF and the total harmonic distortion THD. As a result, the PF and THD parameters are functions of duty cycle and the relative zero current interval duration and have a complex relationship. Therefore, in order to estimate the number of converter cells that provide the required PF and THD values, it is advisable to derive these dependencies in analytical form, based on the use of a Double Fourier series. The obtained dependencies simplify the selection of the number of cells of the converter for a given range of duty cycle and the relative zero current interval duration. PF and THD dependencies for two, three and four cells are constructed on the basis of the derived formulas.В статье рассмотрены возможные топологии зарядных устройств переменного тока с активной коррекцией коэффициента мощности. Выделено однозвенных и двухзвенных топологии зарядных устройств и обоснована целесообразность использования первой группы преобразователей через меньшие габариты и простую структуру. Среди однозвенного преобразователей отмечена преимуществах модульных преобразователей с чередованием фаз на основе топологии SEPIC, имеющих минимальные динамические потери, простой алгоритм и схемную реализацию коррекции коэффициента мощности в предельном режиме протекания тока (ГРП) и небольшие габариты. Функционирование модульных преобразователей проанализированы на примере двухячеестого преобразователя и показано принцип улучшения формы входного тока при сдвига импульсов управления каждой ячейки. Как результат, установлено функциональную зависимость параметров качества электроэнергии (коэффициент мощности PF и коэффициент нелинейных искажений THD) от коэффициента заполнения импульсов каждой ячейки преобразователя. Поскольку в реальных преобразователях сложно придерживаться ГРП, а в непрерывном режиме форма входного тока искажается, такие преобразователи работают в прерывистом режиме протекания (ПРП) тока. На основе анализа схем замещения для трех интервалов работы преобразователя SEPIC - интервал нарастания входного тока, интервал падения входного тока и интервала нулевой паузы - создано его математическую модель. Показано, что увеличение продолжительности нулевой паузы протекания тока существенно ухудшает значение коэффициента мощности PF и коэффициента нелинейных искажений THD. В результате параметры PF и THD являются функциями коэффициента заполнения импульсов и длительности паузы и имеют сложную зависимость. Поэтому для оценки количества ячеек преобразователя, обеспечивающих требуемые значения PF и THD целесообразно вывести эти зависимости в аналитической форме, осуществлено на основе использования ряда Фурье двух переменных. Полученные зависимости упрощают выбор количества ячеек преобразователя для заданного диапазона коэффициента заполнения импульсов и значение относительной нулевой паузы. На основе полученных формул построено зависимость PF и THD для двух, трех и четырех ячеек
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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