electric double layer capacitor
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Complexity ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
M. Saef Ullah Miah ◽  
Junaida Sulaiman ◽  
Talha Bin Sarwar ◽  
Kamal Z. Zamli ◽  
Rajan Jose

Keywords perform a significant role in selecting various topic-related documents quite easily. Topics or keywords assigned by humans or experts provide accurate information. However, this practice is quite expensive in terms of resources and time management. Hence, it is more satisfying to utilize automated keyword extraction techniques. Nevertheless, before beginning the automated process, it is necessary to check and confirm how similar expert-provided and algorithm-generated keywords are. This paper presents an experimental analysis of similarity scores of keywords generated by different supervised and unsupervised automated keyword extraction algorithms with expert-provided keywords from the electric double layer capacitor (EDLC) domain. The paper also analyses which texts provide better keywords such as positive sentences or all sentences of the document. From the unsupervised algorithms, YAKE, TopicRank, MultipartiteRank, and KPMiner are employed for keyword extraction. From the supervised algorithms, KEA and WINGNUS are employed for keyword extraction. To assess the similarity of the extracted keywords with expert-provided keywords, Jaccard, Cosine, and Cosine with word vector similarity indexes are employed in this study. The experiment shows that the MultipartiteRank keyword extraction technique measured with cosine with word vector similarity index produces the best result with 92% similarity with expert-provided keywords. This study can help the NLP researchers working with the EDLC domain or recommender systems to select more suitable keyword extraction and similarity index calculation techniques.


Author(s):  
Ashwini Swaminathan ◽  
◽  
Ranjithkumar Ravi ◽  
Sakunthala Ayyasamy ◽  
Vidhya Bhojan ◽  
...  

The PVA–NH4SCN polymer membranes were prepared by simple solution casting technique by passing ultrasound waves during the preparation. The polymer membranes were subjected to X-ray diffraction analysis and scanning electron microscopy. The X-ray diffraction pattern confirmed the incorporation of a salt into the polymer matrix. The scanning electron microscopy images showed the morphological changes of the polymer membrane. The polymer electrolyte (designated as UPVA20) incorporated with the 20 wt.% of the salt had the highest electrical conductivity in the order of 10–4 S cm–1. It was concluded from the dielectric, tangent and modulus spectra that the UPVA20 membrane was good at its properties. Thus, electric double layer capacitor was constructed with UPVA20 membrane as the separator. The capacitance value of the electric double layer capacitor determined from cyclic voltammetry was found to be 1652 mF g–1. The ultrasound assisted preparation of polymer membranes were good at performance when compared with the polymer membranes of ultrasound unassisted preparation. Among all the polymer electrolytes, UPVA20 polymer membrane had high conductivity, potential stability and capacitance.


Energies ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7671
Author(s):  
Toshiki Tsubota ◽  
Shion Tsuchiya ◽  
Tatsuya Kusumoto ◽  
Dimitrios Kalderis

Pine tree biochar produced by flame-curtain pyrolysis, an inexpensive and simple pyrolysis methodology, was used as the starting material for KOH-activated carbon. Flame-curtain pyrolysis is a simple, low-technology methodology that can be performed by non-specialized personnel. The elemental analysis of the biochars highlighted the high reproducibility of the process. The N2 adsorption isotherms indicated that KOH activation was effective for the preparation of high-surface-area activated carbons from the biochar. The BET specific surface area increased with the quantity of KOH added in the activation process, achieving a maximum value of 3014 m2 g−1 at 85.7 wt.% of KOH addition. The adsorption isotherms of all samples were IUPAC type I, establishing their microporous nature. Results from the Mikhail–Brunauer (MP) method and αs plot indicated that the pore size distribution became wider and the pore volume increased as the KOH content increased. The measured capacitance values followed the same dependence on KOH content. The maximum capacitance value at 1 mV s−1 was determined as 200.6 F g−1 for the sample prepared at 75 wt.% of KOH addition. Therefore, pine tree biochar prepared by simple pyrolysis equipment is a suitable precursor for the development of an electric double-layer capacitor.


Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3689
Author(s):  
Masatoshi Uno ◽  
Ziyan Lin ◽  
Kakeru Koyama

Voltages of electric double-layer capacitor (EDLC) modules vary rather wider than traditional secondary batteries. Although EDLCs should desirably be cycled in a voltage range as wide as possible to achieve a high energy utilization ratio, the wide voltage variation of EDLC modules impairs the performance of DC–DC converters. To address such issues, previous works reported series-parallel reconfiguration techniques, which are roughly divided into balance- and unbalance-shift circuits. However, conventional balance-shift circuits are not applicable to modules comprising odd number cells, impairing modularity. Unbalance-shift circuits, on the other hand, unavoidably cause cell voltage imbalance that reduces energy utilization ratio. This paper proposes a novel series-parallel reconfigurable EDLC module with cell voltage equalization capability. The proposed reconfigurable EDLC module is applicable to any number of cells, realizing good modularity. Furthermore, all cells in the proposed module can be charged and discharged uniformly without generating cell voltage imbalance, achieving an improved energy utilization ratio compared with conventional techniques. A five-cell module prototype was built for experimental verification. While the module voltage varied between 1.04 and 2.83 V, all cells discharged from 2.5 to 0.3 V. The result is equivalent to a 98.6% energy utilization ratio.


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