1,721,064 research outputs found
Experimental investigation and performance analysis of nano enhanced phase change material based photovoltaic thermal system / Mohammed Moinul Islam
No full textPhotovoltaic systems suffer from a paradoxical problem that they need sun light for their operation, but their performance abates with increasing temperature. Commercially available photovoltaic modules (PV) converts less than 20% of the approaching solar energy into power, the rest being dissipated as heat which further affects the conversion efficiency of the module by augmenting its temperature. Co-generation of electricity and heat from a single module, known as photovoltaic thermal (PVT) module, offers a hands-on solution to this problem. However, the major shortcoming with PVT collectors consists in its inefficacy in heat removal and storage of mostly employed heat transfer fluids (HTF) – air and water. As such both fluids suffer from low thermal conductivity and poor specific heat, PVT/air and PVT/water collectors cannot achieve a sustained low cell temperature with considerable electrical efficiency. Phase change materials (PCM) having very good latent heat capacity can be used for thermal control of these collectors, but their poor thermal properties turns out to be barrier in effective heat removal. Hence, incorporation of highly conductive nanoparticles such as carbon nanotube may offer a credible solution to this problem. In the present research, multi-walled carbon nanotube (MWNT) has been used to develop a very new nano enhanced PCM (NePCM) and thus apply this composite material in PVT systems to achieve better thermal control through enhanced thermal properties. Four NePCMs with concentration of functionalized MWNT (f-CNT) ranging from 0.25%wt to 0.01%wt have been synthesized. Detailed characterization of these nano composite materials has been performed by field emission scanning electron microscopy (FESEM), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy and thermal conductivity analysis. With a 3% increase in heat storage capacity and 15% upsurge in thermal conductivity NePCM RT44HC-0.01%fCNT has been confirmed as the best nano composite material for photovoltaic thermal application. Hence, this NePCM has been integrated with a commercially popular parallel-flow PVT and real-time performance of this PVT-NePCM system has been investigated in the outdoor conditions of Kuala Lumpur, Malaysia. To observe whether PVT-NePCM system perform better than other conventional PV and PVT systems four other panels, viz., a reference PV, a PVT with same collector design, a PV-PCM and a PVT-PCM system have been erected in line with the novel PVT-NePCM system to ensure the same ambience. All operating and ambient parameters (different temperatures, solar irradiance, HTF flow rate, wind speed, etc.) have been measured and recorded concurrently by digital data acquisition system from June to September 2019. Thermal performance has been analyzed from both energy and exergy viewpoints. Results show that PVT-NePCM system achieved, at least, 4oC lower cell temperature than other systems and it operates with an energy efficiency of 85.3% and exergy efficiency of 13%. Moreover, PVT-NePCM system extends the cooling period of the solar cells by 37.5% as compared with PVT only system. Extensive application of such system can abate dependence on fossil fuels and help to improve the environment as well
Compact wrench-shaped resonator loaded UWB antenna with notched frequency characteristics
No full textIn the manuscript, the design of a wrench-shaped
resonator loaded ultra-wideband (UWB) antenna has been
proposed using notched frequency characteristics. The antenna is
composed of the patch with microstrip feed line, a wrench-shaped
resonator, and a slotted partial ground plane. A notched
frequency is created due to the electromagnetic coupling of
wrench-shaped resonator. In order to observe the effects of
wrench-shaped resonator, a parametric study has been executed.
Measured results are compared with simulations (with and
without notched bands) and a stable similarity has been
observed. The surface current, radiation patterns and the
impedance (imaginary and real) have ensured the compression of
wanted notched frequency bands
Compact wrench-shaped resonator loaded UWB antenna with notched frequency characteristics
No full textIn the manuscript, the design of a wrench-shaped resonator loaded ultra-wideband (UWB) antenna has been proposed using notched frequency characteristics. The antenna is composed of the patch with microstrip feed line, a wrench-shaped resonator, and a slotted partial ground plane. A notched frequency is created due to the electromagnetic coupling of wrench-shaped resonator. In order to observe the effects of wrench-shaped resonator, a parametric study has been executed. Measured results are compared with simulations (with and without notched bands) and a stable similarity has been observed. The surface current, radiation patterns and the impedance (imaginary and real) have ensured the compression of wanted notched frequency band
Automated short answer scoring
Get PDFThis thesis report is submitted in partial fulfillment of the requirements for the degree of Bachelor of Science in Computer Science and Engineering, 2016.Cataloged from PDF version of thesis report.Includes bibliographical references (page 62-64).In our thesis we have worked to analyses text short answers then predict the score accordingly by using different extracted features. In our research we have used around 1700 data for each dataset and are scored by two different humans provided by the Hewlett foundation available in Kaggle. We have used different NLP techniques to process the data in order to use it to the classifiers. Sckit was used to implement the algorithms of the different classifiers. The data were divided into two different data sets, one of them was the training set and the test set. The training set data was used to train the different classifiers afterwards the test set data was given to the classifiers to predict the score. The predicted score was compared with the score given by the humans to find the efficiency and accuracy of the different classifiers.M. Rayhan Ahmed MithuMoumita KamalSyed Mohammad Moinul Islam RobinB. Computer Science and Engineerin
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
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