1,720,963 research outputs found
Hydrophobic stabilizer-anchored fully inorganic perovskite quantum dots enhance moisture resistance and photovoltaic performance
No full textAdvances in surface chemistry and manipulation of fully inorganic CsPbI3 perovskite quantum dots (CsPbI3-QDs) have enabled improving the charge transport and photovoltaic performance of CsPbI3-QD thin films by replacing their native long-chain, insulating ligands with short-chain ligands. However, the conventional approach based on formamidinium (FA) replacement removes the hydrophobic protective layer, opening the path for moisture penetration and resulting in poor device stability. We demonstrate that short-chain and hydrophobic phenethylammonium (PEA) cations, instead of FA, are efficiently incorporated only onto CsPbI3-QD surfaces, confirmed by Fourier-transform infrared, H nuclear magnetic resonance and density functional theory calculations. PEA incorporation leads simultaneously to improved photovoltaic performance and moisture stability of resultant CsPbI3-QDs without any change in size, fully inorganic composition, and dimensionality of CsPbI3-QDs. Therefore, PEA-incorporated CsPbI3-QD solar cells show a high device power conversion efficiency of 14.1% and high moisture stability, retaining over 90% of the initial performance after 15 days under ambient conditions. © 2020 Elsevier Ltd1
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
Application and Development of Machine Learning for the Discovery of Novel Functional Materials: From Lithium Ion Battery Cathodes to Direct Band Gap Optoelectronics
Get PDFNearly every industry is seeking improvement in material performance such as strength, durability, efficiency, or cost. However, traditionally, material discovery has been a slow process and there is a large desire to speed it up. Recently, a method that has been gaining more attention for the screening of large datasets to find novel materials is machine learning (ML). In the first section of my thesis, I will review the material screening process along with fundamental concepts related to batteries, opto-electronics, and machine learning. In chapter 2, I will report on a pre-screening tool used to obtain equilibrium structures enabled by ML, and in chapters 3 and 4 I will report on ML models for the screening of cathode voltage and band gap type.
To obtain accurate ML predictions, optimized equilibrium structures are needed. However, these are not known for new materials and generally need to be obtained by computationally expensive optimization methods. In chapter 2, we demonstrate an ML-based geometry optimizer, capable of minimizing the energy of perturbed structures. The model was trained on both ground-state and systematically distorted structures. This allows our enhanced model to understand the effects local and global distortions have on crystal energy.
In chapter 3 we developed an ML model to predict the voltage of battery cathode materials, enabling the rapid screening of new materials. The model relied on the addition of extra data points, particularly materials with unfavorable lithium binding. We were able to identify 12 viable new cathode materials.
In chapter 4 we demonstrate two machine learning models, which are capable of classifying the band gap type of inorganic materials. We were able to train a model with a 90% true positive rate. We demonstrated its utility to discover new PV and LED materials, by identifying previously known materials as direct band gaps, and by converting known indirect materials to direct, by alloying.
Overall, this work demonstrates practical methods to improve the prediction of novel materials, however, several challenges remain. In chapter 5, I discuss potential applications of the presented work, along with strategies to further improve and validate the models.Ph.D
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
- …
