1,721,024 research outputs found
Ceramic electrolytes and electrochemical sensors
No full textThe electrochemical method involving solid electrolytes has been known as a selective and an accurate way of sensing chemical species in the environment and even in liquid metal for some time. The most successful among the electrochemical sensors are the emission control sensor (lambda-sensor) for the automobile engine and the oxygen sensor used in steelmaking, both made of stabilized zirconia. This article presents an overview of basic principles of various types of electrochemical sensors including active (potentiometric) and passive (amperometric) sensors. Recent advances in oxygen (O-2), carbon dioxide (CO2) and hydrogen (H-2) sensors are also presented. (C) 2003 Kluwer Academic Publishers
Crystal structure revision and identification of Li+-ion migration pathways in the garnet-like Li5La3M2O12 (M = Nb, Ta) oxides
No full textBond valence sums for the ion positions in single-crystal structure data of the garnet-like fast lithium ion conductors Li5La3M2O12 (M = Nb, Ta) exhibit unusually large deviations from the ideal valences. The root-mean-square bond valence mismatch (commonly termed "global instability index" GII) and the chemical plausibility of the structure model can be significantly improved by optimizing the light atoms (oxygen and lithium) positions using a bond valence mismatch minimization procedure in the previously suggested space group I2(1)3 or its centrosymmetric counterpart Ia (3) over bar Possible pathways for lithium ion migration in Li5La3M2O12 are identified by a bond valence analysis. Li-bond valence mismatch isosurface models for Li+-ion transport pathways are found to be nearly the same in both compounds Li5La3Nb2O12 and Li5La3Ta2O12. The characteristic feature of the three-dimensional Li+-ion pathway network is a nonplanar square of partially occupied Li sites
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
Development of hydrogen sensors based on polymeric and ceramic proton conductors
Get PDFAn all-solid-state hydrogen sensor working under short circuit amperometric conditions at low temperature with minor water maintenance has been developed. A simple and upscaleable method for the preparation of platinum metal nanoparticles were deposited onto the surface of a perfluorinated ion-exchange membrane without a binder by impregnation-reduction (I-R) of a cationic precursor salt. The I-R method, utilizes reactions of a tetraammine platinum(II) chloride hydrate [Pt(NH3)4]Cl2 solution as an impregnating salt with sodium borohydride NaBH4 and potassium borohydride KBH4 as a reducing agent on the membrane surface. The possibility of electroless deposition on layered perovskite Dion-Jacobson (D-J) phase materials was demonstrated by a multistep-impregnation-reduction (M-I-R) method. A series of A-site ordered D-J phase layered oxide perovskite compound A´[An-1BnX3n+1] (where A´ = H, Na, K, Rb, Cs; A = Ca, Sr; B = Nb, Ta) was synthesised by both solid state and soft chemical ion exchange reactions. High proton conductivity of 6.3x10-5 Scm-1 at 45 oC was obtained with KCa2Nb3O10 in H2 containing atmospheres. Electrode and electrolyte surfaces were characterized by XRD, optical microscopy, SEM, EDX and AFM. The chemically reduced sensing electrode from NaBH4 reductant was found to be suitable for high H2 concentration detection. The average max. sensitivity was observed to be 0.01, 0.007, and 0.008 µA cm-2 ppm-1 in the H2 partial pressure range from 1-2, 3-7 and 8-10%, respectively. For leak detection purposes, the sensing electrode prepared by using KBH4 reductant was found to be suitable in low ppm level H2 detection. An average max. sensitivity of the sensor 0.0046 µA cm-2 ppm-1 was achieved within 10-50 s. A reproducible, identical max. output current was observed upon changing the H2 concentration from 0 to 50 ppm. The sensing performance of proton conducting niobate KCa2Nb3O10 was proved in the presence of H2 concentration from 0.005 to 8 % at 45 oC. The max. sensitive current of 9.32 µA cm-2 was achieved within 5 s. The polymer based sensor has shown a relatively slow response yielding higher sensitive current, in contrast, the response of ceramic based sensor was fast and resulted in a lower current. Hydrogen gas detection of up to 80 % could be detected in the presence of 10-20 % CO2 gas. Interface models have been proposed for both polymer and ceramic based ionic conducting systems. The dissociated H2 molecule species transport along the surface was faster than the bulk diffusion process. The simple construction of the cell and its performance characteristics make the device very promising for portable and compact H2 sensor applications
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