1,721,099 research outputs found
Eni Carbon Silicates as crystalline and mesoporous hybrids for gas sensing
No full textNowadays, in order to satisfy market demands, materials and devices for sensors production must be increasingly miniaturized, eco-friendly, energetically efficient, reliably multitasking, and low-cost. Then, the research in material and technological sciences has gained a huge development to reach the expectations. Moving towards these requirements, hybrid nanomaterials are a fundamental alternative choice with respect to well-established materials. The purpose of this work is to satisfy both sciences, on the one hand implementing innovative hybrid materials referred to as ECS (Eni Carbon Silicate) in gas sensors manufacturing, and on the other hand verifying their possible operation at room temperature as a technological progress. Concerning the research in materials science, it is obvious that the employment of hybrids has represented a new challenge, especially because in ECS powders, with respect to the most hybrid materials, organic and inorganic components are not only anchored but perfectly merged to each other in a complex structure. The novelty of these materials concerns in fact their structures, crystalline aluminosilicate scaffoldings with long-range 3D order, which distinguish them from the previously reported amorphous and ‘‘crystal-like’’ silica-based PMOs (periodic mesoporous organosilicas). Regarding the research in technological science, room temperature operation is an extremely valuable goal in gas sensing, due to intrinsic safety of sensors working in harsh or industrial environment; moreover it is interesting to reduce high power consumption that characterized the wide used sensors based on metal-oxides semiconductors and consequently the size of associated electronics.
The research activity was divided in two parts: development of preliminary studies about the role of solvents and investigation on the suitability of ECS powders as suspensions for resulting film depositions. In the second part ECSs were used as functional material in screen-printable compositions. The samples were deposited by drop coating on glass, silicon and alumina substrates for morphological (optical and SEM microscopy), structural (XRD), and thermal (TG-DTA) or electrical (gas tests) characterizations, respectively. The measurements, carried out in a suitable test chamber with controlled atmosphere and standard electronic detection, allowed to study possible electrical and sensing properties. A significant response with sensors based on ECS 14 powders tested in humidity conditions and a calibration for an increasing RH% was obtained. Other powders showed an electrical activity, in particular ECS 13 gave a low response to acetaldehyde. The results were analyzed and compared with the literature to determine if ECSs represent an improvement in gas sensing field, and a possible interpretation of sensing mechanism was suggested. It was concluded that the electrically active films prepared with ECS powders by simple deposition technique can be employed as functional layers in gas sensors. The devices obtained with the ECS hybrids have the properties of speed, reversibility and selectivity fundamental for a good quality electrical response that makes them competitive with respect to systems currently in use. The technological advantage of room temperature operating and the selectivity are added to the novelty of the application of ECSs as active materials in gas sensing
Electrical, optical and sensing properties of photo-activated ZnO thin films
No full textZinc oxide is a wide gap semiconductor whose chemical activity at surface can be enhanced by proper electromagnetic radiation. This property opens the door to room temperature gas sensing with this material. In this work, nanosized ZnO powder was synthesized by sol-gel technique. Then, structural and morphological characterizations were carried out by means of X-Ray Diffraction and SEM techniques. Thin films were deposited by spin coating technique on both glass and alumina substrates, to perform optical absorption spectra and electrical conductance measurements, respectively. The electro-optical properties were studied on the photo-activated films, in air and in nitrogen conditions, to investigate first on the basic surface-oxygen interaction in photo-activated condition. Then, gas measurements were also performed in air and in nitrogen, to acquire information on the photo-enhanced surface chemistry, in order to be applied to gas sensing
Sensing of typical gaseous malodors in organic decomposition products
No full textWe approached the problem of sensing gaseous pollutants and malodors originated as a result of
decomposition of organic compounds via chemoresistive sensors. A set of four sensors based on
screen-printed films of mixed tin and titanium oxides, mixed tungsten and tin oxides, and zinc oxide
has been tested vs. the main gaseous components of these malodors. N-butanol was also considered
because of its importance as a reference gas in the odorimetric intensity scale. We found that, under
proper working conditions, the films can sensitively detect such gases either in dry or in wet
environments, within the range of concentrations of interest for monitoring
Materiale semiconduttore nanostrutturato per la rilevazione di anidride carbonica
No full textL’invenzione è relativa ad un materiale semiconduttore nanostrutturato per la rilevazione di anidride carbonica in un ampio intervallo di concentrazioni. Detto materiale semiconduttore nanostrutturato è a base di ossido di indio drogato con sodio (Na:In2O3)
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
- …
