1,720,966 research outputs found
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
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
Relative performance of three phylogenetic methods based on complete mitochondrial genomes of barnacle
No full textAbstract Mitochondrial Genome analysis is essential for understanding phylogenetic relationships. However, few studies have compared the performance of phylogenetic approaches for marine invertebrates, which have a complex evolutionary history. This study compared three phylogenetic trees based on 34 complete mitochondrial genomes, including Amphibalanus eburneus, Fistulobalanus kondakovi, and Megabalanus rosa, in terms of (1) gene order, (2) concatenated protein-coding genes, and (3) universal cytochrome c oxidase subunit I (COX1) marker regions. Each phylogenetic tree exhibited significant topological differences (Robinson–Foulds distance of 0.55–0.92). The protein-coding genes (78.8%) performed significantly better in terms of monophyletic preservation than the COX1 marker region (61.3%) and gene order (50.0%). Gene order analysis identified two genomic regions (I and II) as hotspots (regions with concentrated rearrangement activity) with significantly elevated breakpoint densities (319 and 100 breakpoints, respectively; p < 0.001), indicating concentrated genome rearrangement activity. Although all three methods consistently preserved some families, they strongly suggested that taxonomic re-evaluation is necessary for Balanidae. In conclusion, gene order provides insights into genome evolution patterns, concatenated protein-coding genes are the most suitable for phylogenetic studies, and COX1 markers are useful for rapid species identification rather than phylogenic classification. This comparative analysis provides important insights into the effects of method selection on mitochondrial phylogeny, especially when addressing complex phylogenetic problems in marine invertebrates
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
가역성 향상을 위한 반응 기작 이해 및 전극 설계: 리튬티타네이트 전극과 리튬산소전지 사례 연구
No full text학위논문(박사)--서울대학교 대학원 :공과대학 화학생물공학부(에너지환경 화학융합기술전공),2019. 8. 최장욱.With the increasing demand for green energy, environmental-friendly power sources, like geothermal, wind and solar start to replace the fossil fuel. Electric vehicle (EV) is a representative example of this trend. The proportion of the EVs is small at this moment, however, the growth rate of the number of the EVs is very rapid. In addition, because the green energy sources suffer from a large supply fluctuation, energy storage system (ESS) is required to buffer the energy production. Enormous potential market of the EVs and the ESSs will lead to the increased consumption of the medium- and large-scale batteries. Lithium-ion batteries (LIBs) is the best system to store the energy with a large capacity due to its high energy capacity and power density. However, two problematic issues still remain to be solved for the LIBs. First, accidental explosions and fires of the EVs and ESSs are appeared occasionally. Second, despite of the high performance of LIBs, the market demands batteries with the higher energy density. To fulfill the requirement for the consumers, new type of electrodes should be developed. Here, lithium titanate (Li4Ti5O12, LTO) anode material with a high performance is proposed for the safe and high-power LIBs and lithium-oxygen battery (LOB) is studied to develop the next-generation battery system with the high energy density.
LTO anode is a replacement for the graphite anode of the LIBs. Spinel-framework structure of LTO induces a zero-strain lithium insertion/deinsertion and fast diffusion kinetics. Therefore, LTO exhibits a long lifespan and high power density. In addition, a high operating potential (1.55 V vs Li) and lacks of carbon material make the LTO battery safe. However, a low conductivity of LTO inhibits the operations at a high rate. Nanographene-surounded LTO hybridization structure is reported here for the high rate of lithium storage. The hybridization structure was arranged by the interfacial interactions from amphipathic solvent. The amphipathic solvent acted as a bridge between the hydrophilic LTO and the hydrophobic NG. The LTO-NG hybridization was synthesized via a redox coupling between adsorbed LTO and NG. The large contact area between the LTO core and the NG sheet resulted in a high electron-conducting path. It allowed the rapid kinetics for the lithium storage and also resulted in a cyclic performance stability.
LOB is expected to overcome the energy density issue of the large-scale batteries for EVs and ESSs due to its potential high energy density. However, an irreversibility of charge/discharge reactions induces a low coulombic efficiency and lifespan. To improve the reversibility of the reactions, two type of methods were studied to control the parasitic reaction: thermodynamic approach and kinetic approach.
For the thermodynamic approach, a platinum catalyst supported on zirconia is proposed as a cathode in LOBs. Superoxide and peroxide materials occurred during battery operation, decompose the electrolyte and the carbon electrode, resulting the low reversibility of LOBs. Experimental and theoretical studies show that zirconia suppresses the reactivity of these superoxide and peroxide materials. Therefore, it is able to enhance the reversibility and lifespan in LOBs.
For the kinetic approach, the composition of the discharge product is controlled by the blockage of the reaction pathway. Stacking process of the discharge products on the electrode was investigated. And it is revealed that morphological structure of the cathode catalyst influences the composition of the discharge products. During discharge, LiO2-like species with a low overpotential is converted to Li2O2 with a high overpotential. The catalyst with large pore (> 100 nm) can inhibit the development of Li2O2, because the conversion reaction is suppressed with the large pore. Therefore, catalyst with large pore results in the low overpotential and reversible reaction. This observation provides a clue to understand the behavior and kinetics of the discharge product for LOBs.녹색 에너지에 대한 수요와 관심의 증가에 따라 전지자동차와 에너지 그리드용 에너지 저장장치의 시장이 매우 커질 것으로 예상되며, 이는 곧 중·대형 배터리 시장의 확대로 이어질 것이다. 리튬이온배터리는 에너지와 출력 밀도가 높아 대용량 에너지를 저장하는 데에 가장 적합한 시스템이다. 그러나 중·대형 배터리로 사용되기 위해서는 안전 문제를 해결할 필요가 있으며, 더 높은 에너지 밀도를 확보하기 위한 방안이 필요하다. 본 논문에서는 안전한 리튬이온배터리를 위해 고성능의 리튬 티타네이트 (LTO) 양극재를 제안하고, 고에너지 밀도의 차세대 배터리 시스템으로 리튬산소전지를 연구하였다.
높은 안전성을 보이는 LTO의 단점인 낮은 전도성을 향상시키기 위하여 LTO-나노그래핀 혼성화 구조를 제안하였다. 양친매성 용매를 사용하여 친수성 LTO와 소수성 나노그래핀 사이에 가교를 이어줄 수 있었고, 산화환원쌍을 통하여 그래핀으로 뒤덮인 LTO를 합성하였다. 그 결과 만들어진 물질은 그래핀의 전도성으로 인하여 높은 출력 특성을 보였다.
리튬산소전지는 에너지 밀도가 높아, 한계에 다다른 리튬이온전지의 성능을 뛰어넘을 수 있을 것으로 예상된다. 그러나 충방전 반응의 가역성이 낮아 수명이 짧다는 문제점이 존재한다. 따라서 반응의 가역성을 개선하고 부반응을 억제하기 위하여 리튬산소전지의 반응기작에 대한 열역학적 접근법과 속도론적 접근법을 연구하였다.
열역학적 접근법에서는 백금을 지르코니아에 담지한 촉매를 사용하였다. 리튬산소전지의 충방전 과정 중, 친핵성이 높아 부반응을 일으키는 초과산화물과 과산화물이 생성되는데, 지르코니아 담지체가 두 물질과 결합하여 안정화시키고, 부반응을 억제시킨다는 것을 확인하였다.
운동학적 접근법에서는 방전 생성물의 조성을 변화시키는 방법을 연구하였다. 촉매의 구조적인 제어를 통하여 전해질의 확산을 억제하고 반응물 간의 접촉을 막아, 높은 과전압을 보이는 방전 생성물이 형성되는 속도를 감소시켰다. 그 결과 낮은 전압에서 충전이 진행되어 리튬산소전지의 수명이 증가하였다.Chapter 1. Introduction 1
1.1 Safe design of the lithium-ion batteries via advanced lithium titanate/graphene anode 1
1.2 Development of lithium-oxygen batteries for the next-generation batteries with high energy density 4
1.3. Objectives 8
Chapter 2. High Performance Graphene-Surrounded Lithium Titanate Anodes Using Amphipathic Solvent 10
2.1 Introduction 10
2.2 Experimental 12
2.2.1 Preparation of LTO-NG hybridization 12
2.2.2 Characterizations 14
2.2.3 Electrochemical characterizations 14
2.2.4 Computational Details 16
2.3 Results and Discussion 17
2.3.1 Mechanism of the graphene hybridization 17
2.3.2 Characterizations 19
2.3.3 Electrochemical measurement 23
Chapter 3. Stabilizing Discharge Products Using Electron-withdrawing Zirconia Support in Lithium-Oxygen Batteries 42
3.1 Introduction 42
3.2 Experimental 45
3.2.1 Fabrication of platinum deposited onto a zirconia support (Pt/ZrO2) 45
3.2.2 Characterization 45
3.2.3 Electrochemical characterization 46
3.2.4 Computational details 47
3.3 Results and discussion 48
3.3.1 Charcterization 48
3.3.2 Electrochemical measurement 49
3.3.3 Stability measurement of the discharge products 51
3.3.4 Calculation of Li2O2 stability on the catalyst 53
Chapter 4. Dependence of the Physicochemical Properties of Discharge Products in Lithium-Oxygen Batteries on the reaction kinetics 65
4.1 Introduction 65
4.2 Experimental 68
4.2.1 Preparation of porous carbon catalyst 68
4.2.2 Characterization 68
4.2.3 Electrochemical characterization 68
4.3 Results and discussion 70
4.3.1 Characterization 70
4.3.2 Morphology and kinetics analysis of the discharge product 70
4.3.2 Electrochemical measurement 72
Chapter 5. Summary and Conclusions 85
Chapter 6. Recommendations for Further Research 87
Bibliography 89
국문초록 97Docto
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