1,720,959 research outputs found
Hocheffiziente photorefraktive Gläser auf Basis eines nicht aggregierenden elektrooptischen Chromophors
Get PDFIn dieser Arbeit wurden neue hocheffiziente photorefraktive Gläser auf Basis des Chromophors IDOP20 entwickelt. Der Chromophor wurde zunächst anhand der Kerr-Gütezahl auf seine Eignung für PR-Anwendungen überprüft. Es konnte eine relativ große Kerr-Gütezahl bestimmt werden. Durch die sterisch anspruchsvollen 3,3’-Dimethylmethylen-Gruppen wird in diesem Chromophor die Neigung zur Dimerenbildung weitgehend unterdrückt. Für mehrere photorefraktive Gläser mit IDOP20 als elektrooptischem Chromophor konnten sehr hohe Verstärkungskoeffizienten Gamma erzielt werden. Für das Glas der Zusammensetzung IDOP20:2BNCM:DPP:TPD:TNFM 30:25:20:24:1 Gew.-% wurde mit einer Nettoverstärkung von Gamma_net = 178 1/cm ein der bisher größten Werte bei einer Feldstärke von E = 45 V/µm erzielt. Weiterhin konnte der Polymeranteil in den photorefraktiven Gläsern vollständig durch glasbildende Co-Chromophore ersetzt werden. Dadurch wurde die Phasenseparation und Kristallbildung in den photorefraktiven Gläsern unterdrückt und die Stabilität und die optische Qualität der Gläser verbessert. Die glasbildenden Eigenschaften von IDOP20 wurden durch dynamische Differenz-Kalorimetrie-Messungen nachgewiesen werden. Der Chromophor bildet einen Charge-Transfer-Komplex mit dem Sensibilisator TNFM. Weitere quasistationäre und zeitabhängige holographische und ellipsometrische Messungen wurden an einem Glas mit zugesetztem Weichmacher DPP (zur Herabsetzung der Glasübergangstemperatur) der Zusammensetzung IDOP20:DPP:TNFM 69:30:1 Gew.-% durchgeführt. Dabei konnte eine Brechungsindexmodulation von Delta n = 0.009 bei einer Feldstärke 60 V/µm ermittelt werden. In zeitabhängigen Messungen wurde ein monoexponentieller Verlauf des photorefraktiven Gitteraufbaus beobachtet. Weiterhin wurde eine sehr starke Temperaturabhängigkeit der Antwortzeiten festgestellt und die Dynamik der Molekülorientierung als zeitbestimmender Prozess identifiziert. Die photorefraktive Leistung der IDOP20-Gläser wurde im Vergleich zu ATOP1-Gläsern diskutiert
Improved Principal Component Analysis and Linear Discriminant Analysis for the Determination of Origin of Coffee Beans using
No full textIn this work an improved Principal Component Analysis (pca) method is used for better determination of geographical origins of Ethiopian Green Coffee Beans. In the commercially available and widely employed pca methods the dataset is commonly normalized using Z-score procedure, which reduces the influence of the spread of data (or dispersion degree differences) on principal components (pcs). In the improved method, a new normalization procedure is introduced with the aim to improve the spread (dispersion) of data points around the mean. The pcs computed from the improved procedure could significantly better reflect information of the original dataset. The dispersion degree information in the original dataset was retained relatively much by using the improved pca than the Z-score-based pca. The improved pca was then used to identify the most discriminating variables corresponding to the coffee samples and, based on that, Linear Discrimination Analysis (lda) model was developed to classify and predict samples. The recognition and prediction abilities of the improved pca and lda at regional level respectively were 95.7% and 94% (using Chlorogenic Acids (cga s) content), 91% and 97% (using Fatty Acids (FA) content), 99% and 100% (and using the combined cga and FA contents). Mehari et al. (2016, 2019) reported recognition and prediction of the pca, they applied on the same dataset, at regional level were 91% and 90% (using cga s content) and 95% and 92 % (using fas content), respectively. The result reveals that the newly introduced method is superior and the best discriminations of coffee beans were achieved. The combined analysis of cga and fa concentrations is a useful tool for the determination of origin of coffee beans, and we recommend that the concerned bodies should use it to address the characterization, classification and authentication of Ethiopian coffee beans according to their geographical origin
Improved Principal Component Analysis and Linear Discriminant Analysis for the Determination of Origin of Coffee Beans using
Get PDFIn this work an improved Principal Component Analysis (pca) method is used for better determination of geographical origins of Ethiopian Green Coffee Beans. In the commercially available and widely employed pca methods the dataset is commonly normalized using Z-score procedure, which reduces the influence of the spread of data (or dispersion degree differences) on principal components (pcs). In the improved method, a new normalization procedure is introduced with the aim to improve the spread (dispersion) of data points around the mean. The pcs computed from the improved procedure could significantly better reflect information of the original dataset. The dispersion degree information in the original dataset was retained relatively much by using the improved pca than the Z-score-based pca. The improved pca was then used to identify the most discriminating variables corresponding to the coffee samples and, based on that, Linear Discrimination Analysis (lda) model was developed to classify and predict samples. The recognition and prediction abilities of the improved pca and lda at regional level respectively were 95.7% and 94% (using Chlorogenic Acids (cga s) content), 91% and 97% (using Fatty Acids (FA) content), 99% and 100% (and using the combined cga and FA contents). Mehari et al. (2016, 2019) reported recognition and prediction of the pca, they applied on the same dataset, at regional level were 91% and 90% (using cga s content) and 95% and 92 % (using fas content), respectively. The result reveals that the newly introduced method is superior and the best discriminations of coffee beans were achieved. The combined analysis of cga and fa concentrations is a useful tool for the determination of origin of coffee beans, and we recommend that the concerned bodies should use it to address the characterization, classification and authentication of Ethiopian coffee beans according to their geographical origins
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
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