1,720,993 research outputs found
Development Of Redox Tolerant Solid Oxide Fuel Cells
No full textAnode supported solid oxide fuel cells (SOFCs) having various properties are developed and the effects of fabrication parameters on the cell performance and redox behavior of the cell are investigated experimentally and theoretically. In the experimental program, an yttria stabilized zirconia based anode supported membrane electrode group (MEG) is developed with the tape casting, co-sintering and screen printing methodology. For comparison, various anode supported cells with different electrolyte thickness and anode support porosities are also fabricated. An experimental setup is devised for the performance measurement of the cells before and after redox cycling. The effects of anode fabrication parameters on the cell performances and the redox stability of the cells are investigated. The mechanical performance of the cell before and after redox cycling is also measured via three point bending tests. Experimental results reveal that the porosity of the anode support and the thickness of the electrolyte should be carefully decided by considering not only the cell performances but also the redox stability. In theoretical study a mathematical model is developed to represent the fluid flow, the heat transfer, the species transport and the electrochemical reaction in solid oxide fuel cells. In addition, a redox model representing the mechanical damage in the v electrochemical reaction zones due to redox cycling is developed by defining a damage function as a function of strains and a damage coefficient. The differential equations are solved numerically with a commercial code which employs a finite element based approach. The effects of anode porosity and the electrolyte thickness on the cell performance and redox stability of the cells are numerically investigated. The experimental and numerical results are compared to validate the mathematical model. The mathematical model is found to agree reasonable with experimental data.Farklı özelliklere sahip anot destekli katı oksit yakıt pilleri (KOYP) geliştirilmiş ve anot destek üretim parametrelerinin hücre performansına ve redoks dayanımına olan etkisi deneysel ve teorik olarak incelenmiştir. Deneysel programda itriyum oksit ile stabilize edilmiş zirkonyum oksit (YSZ) temelli anot destekli membran elektrot grupları (MEG) şerit döküm, birlikte sinterleme ve ipek baskı teknikleri kullanılarak geliştirilmiştir. Karşılaştırma amaçlı, farklı anot gözenenekliliğine ve elektrolit kalınlığına sahip anot destekli hücreler de imal edilmiştir. Hücrelerin redoks öncesi ve sonrasındaki performanslarının ve redoks dayanımlarının belirlenmesi için bir deneysel düzenek hazırlanmıştır. Deneysel sonuçlar anot destek gözenekliliği ve elektrolit kalınlığının hem hücre performansı hem de redoks dayanımını göz önüne alarak belirlenmesi gerektiğini ortaya koymuştur. Teorik programda KOYP içerisinde akış, ısı transferi, madde transferi, elektrokimyasal reaksiyonları ifade eden matematiksel bir model geliştirilmiştir. Ayrıca, elektrokimyasal reaksiyon bölgelerinde redoks kaynaklı mekanik hasarları ifade eden bir redoks modeli de geliştirilmiştir. Modelde tanımlanan hasar fonksiyonu gerinme bağımlı olarak ifade edilmiştir. Diferansiyel denklemler ticari bir sonlu elemanlar programı yardımı ile sayısal olarak çözülmüştür. Anot destek gözenekliliği ve elektrolit kalınlığının hücre performans ve redoks dayanımı üzerindeki etkileri sayısal olarak incelenmiştir. Deneysel ve sayısal sonuçlar, matematiksel modeli doğrulamak için karşılaştırılmıştır. Matematiksel modelin deneysel datalarla uyumlu olduğu belirlenmiştir
Investigation of parameters effecting on the performance of electrochemical hydrogen compressor
No full textTez kapsamında, hidrojen gazını mekanik kompresörlere ihtiyaç duymadan yüksek basınçlara çıkarabilen, sessiz ve gürültüsüz çalışan ve yüksek saflık değerlerinde hidrojen gazının elde edilebilmesine olanak sağlayan tek hücreli bir elektrokimyasal hidrojen kompresörü (EHK) geliştirilmiş ve performansa etki eden parametreler deneysel olarak incelenmiştir. Deneylerin daha kontrollü ve güvenli bir şekilde gerçekleştirilebilmesi için EHK sistemine uyumlu özel bir elektronik kontrol ünitesi (data logger/kontrolör) ve yüksek basınç test istasyonu imal edilmiştir. EHK sisteminin performansına etki eden basınç, sıcaklık, hidrojen debisi, nemlilik ve akım yoğunluğu gibi parametreler deneysel olarak incelenmiştir. Sıcaklığın artmasıyla hücre performansının arttığı gözlemlenirken debi değişimimin belirli bir değerden sonra performansa etki etmediği tespit edilmiştir.An electrochemical hydrogen compressor which can compress hydrogen at high purity without needing a mechanical pump is developed and parameters affecting its performance are experimentally investigated. A fully electrochemically control experimental set up is developed to improve accuracy of measurement and processes control. Experiments are performed in a safe pressure chamber. The effects of operating pressure, temperature and humidity of incoming hydrogen on the performance are investigated. The operating temperature is found to be most effective on the performance while efficiency is found to be insensitive to mass flow rate
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
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
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
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