1,720,964 research outputs found
CARATTERIZZAZIONE ELETTRICA E SPETTROSCOPICA AD IMPEDENZA DI OSSIDI METALLICI NANOSTRUTTURATI PER IL RILEVAMENTO DI ALCANI VOLATILI
No full textChemoresistive gas sensors using semiconductor metal-oxides have proven to be excellent in important characteristics such as sensitivity, long-term stability, robustness and price. Solid solutions of mixed Sn and Ti oxides have shown promising results in combining the properties of the separate components. Basic science of these mixed oxides is far from being satisfactorily elucidated. Further progress in basic understanding is required to establish the principles to operate them as gas sensors.
Knowledge of the space charge width of the nanostructured powder grains is needed for the comparison of the mean grain radius to determine sensing properties of the nanostructure. A new method has been addressed using impedance spectroscopy technique to estimate the electric permittivity of these Sn and Ti oxides, which is fundamental for the determination of the space charge width and capacitive response.
A study of the sensing properties of chemoresistive metal-oxides vs. light alkanes has been undertaken under dry and wet conditions and even in presence of ethanol. Screen-printed films of pure Sn and Ti oxides and solid solutions of mixed Sn and Ti oxides have been selected for the purpose. It has been demonstrated that the films are capable of detecting 500ppm of methane or 100ppm of other light alkanes under either dry or wet condition, i.e. concentrations two levels by far lower than the alarm thresholds for such gases. Information about the working mechanism of chemical reactions on the surface has been discussed under either dry or wet condition. Ethanol is known to be a harmful interfering gas, though its concentration can be reduced to values lower than 10ppm by proper activated carbon filtering. It has been shown that, even in presence of 10ppm of ethanol, the films steadily responded to alkanes
Relative Permittivity of Nanostructured Solid Solutions of Tin and Titanium Oxides
No full textImpedance Spectroscopy technique was employed in order to characterize nanostructured powders based on solid solutions of SnO 2 and TiO 2, employed in thick-film chemoresistive gas sensors. The measurements were performed with a cylindrical capacitor, manufactured for this specific purpose, with the powders used as dielectric between the plates. Results were interpreted with the support of a theoretical model, which describes the electrical properties of the powders and allows us to estimate their relative permittivity. © 2012 Springer Science+Business Media, LLC
Monitoring HV transformer conditions: The strength of combining various diagnostic property observations
No full textEthanol interference in light alkane sensing by metal-oxide solid solutions
No full textReceived 29 July 2008
A study of the sensing properties of chemoresistive metal-oxides vs. light alkanes has been undertaken under wet condition and in presence of ethanol. Screen-printed films of a solid solution of mixed Sn and Ti oxides have been selected for the purpose. We demonstrated that the films are capable of detecting 100 ppm of light alkanes or 500 ppm of methane in wet condition, two concentration levels by far lower than their alarm thresholds, respectively. Ethanol is known to be a harmful interfering gas, though its concentration can be reduced to values lower than 10 ppm by proper filtering. We show that, even in presence of 10 ppm of ethanol, the films steadily responded to alkanes
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
Light alkane sensing by metal-oxide solid solutions
No full textSensing of light alkanes via chemoresistive gas
sensors has been addressed. Screen-printed films
of a solid solution of mixed Sn and Ti oxides have
been selected for the purpose. First of all, we
analysed the responses in dry and wet conditions at
different temperatures. We demonstrate that the
films sensitively detect a concentration of such
gases, which is by far lower than their alarm limits.
We achieved important information about the
working mechanism of chemical reaction with the
analyte at surface and the role played by humidity.
Moreover, we performed a study to compare
morphology to reactivity for all samples. All films
have the similar reactivity to each alkane and the
response differ to each other solely as a result of
morphology
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
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