1,721,111 research outputs found
Physique et Modèles de Dispositifs Photovoltaïques Plastiques
No full textThis thesis discusses the operation and mechanisms of plastic solar cells made up using heterojunction/bulk-heterojunction of different donors and acceptors. Main emphasis is to highlight and address the forefront requirements for realization of efficient solar cells that would help develop new efficient donor-acceptor compositions. New class of efficient photovoltaic devices are prepared and electrically characterized. The results from these devices provide a better understanding of the exciton generation and dissociation phenomenon in organic solar cells. For the first time, highly luminescent organic semiconductor material rubrene is used as a donor in solar cell architecture, resulting in formation of an organic dual function device with photovoltaic (PV) and electroluminescence (EL) behavior integrated. The intriguing operation of extremely low voltage (< 1V) required for light emission from such dual function device is described as an energy up-conversion process; a phenomenon rarely observed in organic heterojunctions.Cette thèse discute le fonctionnement et les mécanismes mis en oeuvre dans les cellules solaires en plastique, composées de différents donneurs et accepteurs et dont l'architecture est décrite par hétérojonction/volume-hétérojonction. Une attention particulière a été portée à l'étude les conditions nécessaires pour la fabrication de cellules solaires à fort rendement, ceci de manière à aider au développement de compositions en donneur-accepteur nouvelles et plus efficaces. Une nouvelle classe de dispositifs photovoltaïques a été préparée et leurs rendements électriques ont été caractérisés. Les résultats expérimentaux obtenus avec ces dispositifs permettent une meilleure compréhension des phénomènes de génération et de dissociation d'excitons dans les cellules solaires organiques. Pour la première fois, le rubrene, un matériau organique, semiconducteur et fortement luminescent a été utilisé en tant que donneur dans l'architecture de systèmes organiques. Celui-ci nous a permis de fabriquer un appareil offrant 2 modes de fonctionnement intégrés et qui reposent sur l'utilisation respective de des propriétés photovoltaïques (PV) et électroluminescentes (EL) du rubrene. Un des résultats les plus importants a été obtenu lors de l'application de tensions extrêmement basses (< 1V) exigées pour l'émission de lumière d'un tel dispositif. Ce mode de fonctionnement est décrit comme un processus de conversion vers de plus hautes énergies (up-conversion), un phénomène rarement observé dans les hétérojonctions organiques
Web Proxy Server with Intelligent Prefetcher for Dynamic Pages Using Association Rules
No full textThe growth of the World Wide Web has emphasized the need for improved user latency. Primarily, two techniques, i.e. caching and prefetching are being used for improving user latency. Several studies have been conducted on cache replacement policies for improving cache hit ratio. On prefetching side, studies have been conducted on prefetching models based on decision tree, Markov chain, and path analysis. Increasing use of dynamic pages, frequent changes in the site structure and user access patterns on the internet have limited the efficacy of caching techniques and emphasized the need for prefetching with a predictive model which is easier to build and update and have improved predictive performance. In this project, we study the existing caching and prefetching techniques and explore as to how the knowledge of user access patterns discovered through Web Mining and the information on site structure can be used to predict future requests by an user. In a web site certain sets of pages exhibit strong correlation with each other, which manifest in user access patterns. Such set correlations can be discovered in the form association rules by Web Mining of server logs. We accordingly propose a prefetching model based association rules. We also present a predictive model based on site structure where certain number of children of the current page are prefetched. We also present a design and prototype implementation of a proxy server, which use these models for prefetching and conduct experiments to evaluate the performance of these two models. In our experiments we find that the association rules prefetching model has better predictive value than the site structure model and gives good cache hit ratio without much additional traffic load.Bhushan Pandey, Ajay; Srivastava, Jaideep; Shekhar, Shashi. (2001). Web Proxy Server with Intelligent Prefetcher for Dynamic Pages Using Association Rules. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/215499
Impact of selective thermal annealing on rubrene-C-60 heterojunction solar cells
No full textThe influence of thermal annealing at different fabrication stages on rubrene-C heterojunction organic solar cells is presented. Devices grown at room temperature showed s-shaped current density-voltage (J-V) characteristic. A pre- or post-fabrication thermal treatment step is found effective in elimination of s-shaped J-V. An exclusive gain in open-circuit voltage was measured when rubrene-C layer was fabricated at elevated substrate temperature of 80 °C. The results indicate that introduction of temperature at various stage of device fabrication allows selective control over organic layer growth and hence organic-organic interface formation. The 133 mV increase in open-circuit voltage in solar cells fabricated at substrate temperature is due to temperature induced molecular conformation change at the light in-coupling ITO/PEDOT interface
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
A Comparative Study on Web Prefetching
No full textThe growth of the World Wide Web has emphasized the need for improved user latency. Increasing use of dynamic pages, frequent changes in the site structure, and user access patterns on the internet have limited the efficacy of caching techniques and emphasized the need for prefetching. Since prefecthing increses bandwidth, it is important that the prediction model is highly accurate and computationally feasible. It has been observed that in a web environment, certain sets of pages exhibit stronger correlations than others, a fact which can be used to predict future requests. Previous studies on predictive models are mainly based on pair interactions of pages and TOP-N approaches. In this paper we study a model based on page interactions of higher order where we exploit set relationships among the pages of a web site. We also compare the performance of this approach with the models based on pairwise interaction and the TOP-N approach. We have conducted a comparative study of these models on a real server log and five synthetic logs with varying page frequency distributions to simulate different real life web sites and identified dominance zones for each of these models. We find that the model based on higher order page interaction is more robust and gives competitive performance in a variety of situations.Bhushan Pandey, Ajay; Vatsavai, Ranga R.; Ma, Xiaobin; Srivastava, Jaideep; Shekhar, Shashi. (2001). A Comparative Study on Web Prefetching. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/215470
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
Comparison of batteries charging time for standalone photovoltaic system
No full textThe general framework expense can be lessen by the utilization of proper battery, which accomplish less charging time, high battery SOC and thusly, more lifetime. The battery is the most ordinary and productive strategy for vitality stockpiling in standalone heavenly bodies because of its minimal effort and simplicity of accessibility. Photovoltaics are not a perfect hotspot for charging batteries as their yield is intensely subject to climate conditions. In this way, when batteries are utilized as a part of photovoltaic frameworks, the execution qualities (charging time) contrast essentially from batteries utilized as a part of more conventional applications and the battery life is normally abbreviated. This paper do examinations and think about the batteries charging time for stand-alone PV framework with time differing sunlight based insolation
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
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