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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
Designs, Syntheses, Characterizations and Device Applications of 2nd and 3rd Generation OLED Materials
No full text磷光有機發光二極體(Phosphorescent OLEDs, PhOLEDs)因其具有100%激子利用效率的潛力，是近年OLED研究領域中的主流。利用適當的主體材料以及妥切的元件設計，不同光色的PhOLED元件效率已逼近其理論最大值。然而，當前報導的藍光主體材料其元件效率以及操作壽命仍具許多改善空間，成為PhOLEDs在正式商業化前一個關鍵課題。熱激活化延遲螢光有機發光二極體(Thermal activated delayed fluorescent OLEDs, TADF OLEDs)與PhOLEDs在具有相同最大理論放光效能及相似元件結構下，前者利用調降具有高放光特質的單純有機結構其單重態-三重態能隙取代了後者對有機金屬發光體的依賴，而成為近期OLED研究領域中最新的研究對象。
在本論文中，個人藉由設計與合成一系列具有雙極性特色的有機芳香材料，在引入共同電子予體−咔唑下與各式不同的電子受體進行結合，以期待實際應用於二代(PhOLEDs)或三代(TADF OLEDs)有機發光二極體的發光層中。透過各式物理分析以及元件應用，進而詳細探討與剖析分子結構−物質特性−元件效能之間系統性的關係。各章節內容簡要如下: 第一章中，主要概括OLED的近代發展、發光原理與機制及其主體材料的設計要點；第二章論述磷光有機發光二極體的主體分子在具有相同電子予體−咔唑和電子受體−噁二唑的情況下，如何透過彼此比例間的微調，逐步達到性質與元件效能的最佳化；第三章介紹一系列具有高扭性的雙極性主體材料，如何透過分子共軛及結構拓撲的操縱，進而改變其物理性質並平衡載子傳輸能力，最後成功應用於多種不同色光的磷光有機發光二極體元件之中；第四章始於簡介當前TADF材料的發展與設計，並探討第三章中符合TADF分子設計概念的潛力分子於新領域的應用性。接著，透過新分子架構進行電子予體和受體的組合，並藉由探討其各項物理性質以及元件上的應用，探求新材料於TADF OLEDs中應用的可能性。Phosphorescent OLEDs (PhOLEDs), known for their 100% exciton utilization efficiency, are the mainstream of the current OLED development. The proper host materials and finely tuned device structure have envisaged the theoretical maximum quantum efficiencies of 20-30% for PhOLEDs. However, nowadays blue PhOLED hosts are still deficient due to the below average device performances and operational longevities. Therefore, the device improvement for blue devices has become the most pivotal issue for OLEDs before commercialization. In this regard, thermally activated delayed fluorescent OLEDs (TADF OLEDs), possessing equally high emitting capability and similar device configuration in comparison with PhOLEDs, have become the latest novel research topic in organic optoelectronic fields. The use of pure aromatic compounds with small singlet-triplet energy gap (∆EST) as emitters exempts the dependence on noble metals and therefore reduce the production cost, which is especially attractive for academia and industries.
The main attribute in this dissertation are the design, synthesis, and characterization of novel bipolar pure aromatic materials comprising of common electron-donating group − carbazole and various electron-deficient groups as emitting layer materials for 2nd and/or 3rd generation OLEDs. Their physical properties and device applications were fully investigated to explore their structure-property- performance relationship. The essence of each chapter is briefly outlined as follows. The 1st chapter provides an overview of modern development of OLEDs, emitting mechanisms, and design criteria of host materials. The 2nd chapter focuses on the carbazole (D)/1,3,4-oxadiazole (A) ratio manipulation of bipolar hosts for PhOLEDs to finely tune and balance their physical properties rendering the devices with better performances. The 3rd chapter introduces three groups of highly twisted bipolar hosts featuring different conjugation length and/or structural topology. The reduced electronic coupling between D and A via twisted conformation gives each of the compounds unique optical characters and balanced charge transporting ability and thus, PhOLEDs based on such materials exhibit remarkable EL performance. The 4th chapter commences with the recent TADF literature survey and, later on, redeems the potential TADF character of the highly twisted molecule introduced in Chapter 3. Last, but not the least, the novel bipolar molecules based on carbazole and 1,3,5-trazine/CN moieties were redesigned, synthesized and characterized. From the preliminary physicochemical investigations and device applications of these materials, their roles as efficient TADF materials is going to unambiguously disclose.Content
中文摘要 i
Abstract iii
Content v
Index of Figure ix
Index of Scheme xix
Index of Table xxi
Molecule Index xxv
Chapter 1. Prologue of Organic Light-Emitting Diodes (OLEDs) 1
1.1 Introduction 1
1.2 Development and Recent Progress on OLEDs 4
1.2.1 The 1st Generation — OLEDs 5
1.2.2 The 2nd Generation — PhOLEDs 9
1.2.3 The 3rd Generation — TADF OLEDs 12
1.3 Principle of Electroluminescence Generation 15
1.4 Mechanism of Electroluminescence 18
1.5 Energy Transfer 21
1.5.1 Fӧrster Energy Transfer 22
1.5.2 Dexter Energy Transfer 23
1.6 Host-Guest System 24
1.7 Host Materials 25
1.10 References 29
Chapter 2. Fine-tuning the balance between carbazole and oxadiazole units in bipolar hosts to realize highly efficient green PhOLEDs 35
2.1 Introduction 35
2.2 Molecular Design and Synthesis 38
2.3 Photophysical Properties 40
2.4 Theoretical Calculation 44
2.5 Electrochemical Properties 45
2.6 Thermal Properties 46
2.7 Crystal Structure Analysis 47
2.8 Carrier-transport Properties 48
2.9 Application in PhOLEDs 50
2.10 Conclusions 53
2.11 Experimental Details 54
2.11.1. General Methods 54
2.11.2. Synthesis and Characterization 56
2.12 References 60
Chapter3. Highly Twisted Host Materials for Highly Efficient PhOLEDs 63
3.1 Introduction 63
3.2 Molecular Design and Synthetic Strategy 69
3.3 Cz-Azine Series 72
3.3.1 Synthesis 72
3.3.2 Crystal Structures 73
3.3.3 Thermal Properties 75
3.3.4 Optical Properties 76
3.3.5 Electrochemical Properties 80
3.3.6 Charge Carrier Mobility 82
3.3.7 Application in PhOLEDs29 84
3.4 Cz-BI Series 91
3.4.1 Synthesis 92
3.4.2 Crystal Structures 93
3.4.3 Thermal Properties 95
3.4.4 Optical Properties 96
3.4.5 Electrochemical Properties 102
3.4.6 Charge Carrier Mobility29 104
3.4.7 Application in PhOLEDs29 109
3.5 Cz-OXA Series 117
3.5.1 Synthesis 118
3.5.2 Crystal Structures 120
3.5.3 Thermal Properties 122
3.5.4 Optical Properties 124
3.5.5 Electrochemical Properties 127
3.5.6 Charge Carrier Mobility29 130
3.5.7 Application in PhOLEDs29 133
3.6 Conclusion 145
3.7 Experimental Details 147
3.7.1 General Methods 147
3.7.2 Synthesis and Characterization 151
3.8 References 164
Chapter 4. Thermally Activated Delayed Fluorescence 172
4.1. Introduction……………………………………………………………….172
4.2. Highly Twisted Bipolar Materials20………………………………………188
4.2.1. Optical Properties 188
4.3. C3-Symmetric Bipolar Materials…………………………………………192
4.3.1. Synthesis 194
4.3.2. Thermal Properties 197
4.3.3. Optical Properties 198
4.3.4. Electrochemical Properties 206
4.3.5. Electroluminescent Properties 208
4.4. Summary………………………………………………………………….216
4.5. Experimental Details……………………………………………………..217
4.5.1. General Methods 217
4.5.2. Synthesis and Characterization 219
4.6. References…………………………………………………………………224
Appendix A 1H and 13C NMR Spectrum…………………………………….…... 229
Appendix B TGA and DSC Thermogram…………………………………….…...257
Appendix C X-ray Crystallography Data……………………………………….....27
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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