186,395 research outputs found
Morphology and electrochemical properties of a gel blend polymer electrolyte based on PVDF-HFP/PEO blend
No full textHypothesis: In recent years, gel polymer electrolytes (quasi-solid state electrolytes) have attracted great attention as a suitable substitute for liquid electrolytes. On the other hand, ionic liquids could dramatically enhance the ionic conductivity of electrolytes. In this work, gel polymer electrolytes based on poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP)/poly(ethylene oxide) (PEO) blends (for application in dye-sensitized solar cells (DSSCs)) and imidazoliumbased ionic liquids were prepared. It is supposed that blending these two polymers could reduce the degree of crystallization and increase the porosity of the electrolyte blend to yield a higher electrolyte uptake and ionic conductivity. Methods: Polymer blend electrolytes were prepared in different blend ratios and in the presence of either one of the ionic liquids including BMII or BMIMBF4 through phase inversion method and their properties were investigated by differential scanning calorimetry (DSC), mercury porosimetry, electrolyte uptake, and morphology to optimize the blend ratio. Findings: It was found that the blend ratio of 60/40 (w/w) PVDF-HFP/PEO has the highest porosity and electrolyte uptake. Crystallization investigations by DSC showed that there is a direct relationship between the decrease of crystallinity of two polymers and the increment of electrolyte ionic conductivity. Electrolyte uptake gradually increased with increasing PEO component concentration up to 40 wt%, and reached a maximum of 98.49% and 89.48% for BMIMBF4 and BMII, respectively. Beyond this concentration, a decrease in electrolyte uptake was seen, which is an undesirable feature for the produced samples. In this blend ratio ionic conductivity was measured as 2.07 mS/cm and 1.78 mS/cm for PVDF-HFP/PEO/BMIMBF4 and PVDF-HFP/ PEO/BMII electrolytes, respectively
A study on the microstructural development of gel polymer electrolytes and different imidazolium-based ionic liquids for dye-sensitized solar cells
No full textQuasi-solid state electrolyte (gel-like) based on polymer matrix PVDF-HFP/PEO is considered as a suitable candidate for producing DSSC due to its essential influence on the performance of the device. In this work, PVDF-HFP/PEO membranes were prepared over the whole composition range in presence of either one of the ionic liquids (ILs) including BMII plus LiI, or BMIMBF4 via phase inversion and compared with liquid electrolyte and ILs individually. It was found that the blend ratio affected some of the membrane properties, such as porosity, pore size, pore connectivity, liquid uptake ability, and morphology. SEM analysis and mercury porosimetry were used to study the pore configuration and porosity of the membranes. The effects of two semicrystalline polymers on the morphology and crystallinity of the membrane were examined by DSC and also WAXD. It was found that there is a direct relationship between the crystallinity reduction and improvement of ionic conductivity of the samples. The photovoltaic performances of the fabricated DSSC at the highest ionic conductive optimized membrane revealed an improvement of Voc, Jsc, fill factor, and the solar conversion efficiency of 6.47%. The long-term durability of the quasi solid DSSC was increased compared to a liquid type electrolyte
Microstructural development and rheological study of a nanocomposite gel polymer electrolyte based on functionalized graphene for dye-sensitized solar cells
No full textFor a liquid electrolyte-based dye-sensitized solar cell (DSSC), long-term device instability is known to negatively affect the ionic conductivity and cell performance. These issues can be resolved by using the so called quasi-solid-state electrolytes. Despite the enhanced ionic conductivity of graphene nanoplatelets (GNPs), their inherent tendency toward aggregation has limited their application in quasi-solid-state electrolytes. In the present study, the GNPs were chemically modified by polyethylene glycol (PEG) through amidation reaction to obtain a dispersible nanostructure in a poly(vinylidene fluoride-co-hexafluoro propylene) copolymer and polyethylene oxide (PVDF-HFP/PEO) polymer-blended gel electrolyte. Maximum ionic conductivity (4.11 × 10-3 S cm-1) was obtained with the optimal nanocomposite gel polymer electrolyte (GPE) containing 0.75 wt% functionalized graphene nanoplatelets (FGNPs), corresponding to a power conversion efficiency of 5.45%, which was 1.42% and 0.67% higher than those of the nanoparticle-free and optimized-GPE (containing 1 wt% GNP) DSSCs, respectively. Incorporating an optimum dosage of FGNP, a homogenous particle network was fabricated that could effectively mobilize the redox-active species in the amorphous region of the matrix. Surface morphology assessments were further performed through scanning electron microscopy (SEM). The results of rheological measurements revealed the plasticizing effect of the ionic liquid (IL), offering a proper insight into the polymer-particle interactions within the polymeric nanocomposite. Based on differential scanning calorimetry (DSC) investigations, the decrease in the glass transition temperature (and the resultant increase in flexibility) highlighted the influence of IL and polymer-nanoparticle interactions. The obtained results shed light on the effectiveness of the FGNPs for the DSSCs
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
Going Beyond Counting First Authors in Author Co-citation Analysis
No full textThe 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
Appropriate Similarity Measures for Author Cocitation Analysis
No full textWe 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
Supplementary Material 1 - Supplemental material for Canadian Burden of Skin Disease From 1990 to 2017: Results From the Global Burden of Disease 2017 Study
No full textSupplemental material, Supplementary Material 1, for Canadian Burden of Skin Disease From 1990 to 2017: Results From the Global Burden of Disease 2017 Study by Alanna C. Bridgman, Christina Fitzmaurice, Robert P. Dellavalle, Chante Karimkhani Aksut, Ayman Grada, Mohsen Naghavi, Navid Manafi, Andrew T. Olagunju, Tinuke O. Olagunju, Ranjani Somayaji and Aaron M. Drucker in Journal of Cutaneous Medicine and Surgery</p
Dispelling the Myths Behind First-author Citation Counts
No full textWe 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
Dr. Edward P. Wimberly, ITC, July 2011
No full textThis video is a conversation with Dr. Edward P. Wimberly. Dr. Wimberly talks about his book, "No Shame in Wesley's Gospel: A Twenty-First Century Pastoral Gospel". Brad Ost, AUC Woodruff Library, is the interviewer
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