1,720,995 research outputs found
Scatterometro a sfera integratrice, sensore di posizione e dimensione di oggetti, e relativi metodi di misura
No full textL’invenzione riguarda uno scatterometro a sfera integratrice per
la caratterizzazione superficiale di campioni di materiale o la
caratterizzazione di diffusione di sorgenti luminose di tipo
puntiforme, comprendente: nel caso della caratterizzazione superficiale di campioni di materiale, una sorgente di luce che produce un fascio di luce collimato modulato ad una frequenza f1 che incide sul campione sotto analisi ad un angolo dELTA rispetto alla direzione normale z; e una testa di misura comprendente un fotorivelatore per la rivelazione di una parte di luce diffusa indietro dal campione in risposta a detto fascio di luce collimato, in trasmissione o in riflessione, oppure diffusa dalla sorgente luminosa di tipo puntiforme, caratterizzato dal fatto che detta parte di luce è raccolta da una sfera integratrice presentante una finestra, posta su un asse zeta orientato ad un angolo psi rispetto a detta direzione normale z e a distanza x dal campione o dalla sorgente luminosa di tipo puntiforme, la distanza x potendo assumere anche valori negativi per iquali la sorgente di tipo puntiforme risulta all’interno della sfera integratrice, detta parte di luce essendo raccolta entro un angolo solido omega attorno a detto asse zeta, ovvero entro un semiangolo lineare teta, il
fotorilevatore misurando la luce integrata dalla sfera a partire dalla luce raccolta dalla sfera, l’angolo solido omega essendo funzione della distanza x. L’invenzione riguarda altresì un sensore utilizzante lo scatterometro nonché i relativi metodi di misura
EMITTER PASSIVATION MONITORING BY MEANS OF THE COMBINATE USE OF QSSPC MEASUREMENTS AND ANALYTICAL MODELLING OF THE EMITTER REGION
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Effect of alkylsulphanyl substituent on the performance of polythiophene as donor material for bulk heterojunction solar cells
No full textPolymer solar cells have evolved as a promising cost-effective alternative to siliconbasedsolar cells. However, low efficiency of these plastic solar cells limits their feasibility forcommercial use. The efficiencies of polymer photovoltaic cells got a major boost with theintroduction of the bulk heterojunction (BHJ) concept consisting of an interpenetrating network ofelectron donor and acceptor materials. In this work we describe the preparation of BHJ organic solarcells using blend films of poly[4,4’-bis(alkylsulfanyl)-2,2’-bithiophene] (PST) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM). Photovoltaic cells were prepared with a layersandwiched between electrodes with different work functions. We made a comparative study of theelectrical behaviour of different devices to investigate the influence of different fabricationconditions (donor/acceptor ratio, solvent, layer thickness, device annealing, etc.). The electricalperformance of the devices were compared with the corresponding one prepared using a blend ofcommercial poly(3-hexylthiophene) (P3HT) and PCBM. The quantum efficiency of the devicefabricated with PST/PCBM blend shows a better response in the visible region compared to the onewith P3HT/PCBM. Theoretical calculations on PST and P3HT were also carried out to explain theeffect of the alkylsulphanyl substituent (compared to hexyl one) on the geometry, band gap andHOMO/LUMO levels of polythiophene
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Full text linkWe 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
Organic Materials for Phovoltaics: Synthesis and Electrochemical Behaviour of a Thiophene Based Copolymer
No full textPolymer solar cells (PSCs) have recently attracted considerable attention due to their advantages of low cost, light weight, processability and compatibility with large scale flexible substrates [1]. Polythiophenes are quite interesting materials for this purpose, combining the above described advantages with an enhanced photochemical stability, compared with poly(p-phenylene vinylene) and poly p-phenylene.In this communication the synthesis, the spectroscopic, the electrochemical and photovoltaic characterization of a thiophene based copolymerare reported. The synthesis was performed in analogy to ref. [2] via Stille coupling of a brominated and a stannilated comonomer as illustrated in Fig.1. The copolymer was characterised through 1H and 13C NMR, Uv-Vis spectroscopy, Cyclic Voltammetry.References[1] S. Gunes, H. Neugebauer, N. S. Sariciftci, “Conjugated Polymer-Based Organic Solar Cells” Chem. Rev. 107, 1324 (2007) ; M. Helgesen, R. Søndergaard, F. C. Krebs, “Advanced materials and processes for polymer solar cell devices”, J. Mater. Chem. 20, 36 (2010) ; J. Peet, J. Y. Kim, N. E. Coates, W. L. Ma, D. Moses, A. J. Heeger, G. C. Bazan, “Efficiency enhancement in low-bandgap polymer solar cells by processing with alkane dithiols”, Nat. Mater. 6, 497 (2007) ; S. A. Gevorgyan and F. C. Krebs in Handbook of thiophene-Based materials, I. F. Perepichka and D. F. Perepichka ed. (John Wiley and Sons Ltd., 2009). [2]Yongye Liang, Danqin Feng, Yue Wu, Szu-Ting Tsai, Gang Li, Claire Ray and Luping Yu, “Highly Efficient Solar Cell Polymers Developed via Fine-Tuning of Structural and Electronic Properties”, JACS 131, 7792-7799 (2009
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