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Realizzazione di sistemi ibridi organici/inorganici: formulazione, espansione e caratterizzazione
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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
PROCESSO PER DESTRUTTURARE UNA PASTA DI CELLULOSA, PRODOTTO OTTENUTO E UTILIZZI DEL PRODOTTO
No full textComparison of photo-oxidative degradation of polyamide 6,6 films stabilized with HALS and CuCl2+KI mixtures
No full textThe photo-oxidative stability of polyamide 6,6 (PA 6,6) doped with a hindered amine light stabilizer (HALS) and a mixture of cupric chloride and potassium iodide was examined.
Several analytical techniques were employed, in order to evaluate the correlation between chemical modifications, morphology and mechanical properties of PA 6,6 films irradiated at λ>300 nm, 90 °C, and 50% relative humidity.
Infrared spectroscopy showed a build-up of carbonyl absorption in the range 1700–1780 cm−1 due to primary and secondary photo-oxidation products. The increase in content of carbonyl groups was greatest in the case of the pure polymer, and it was also appreciable in the case of PA 6,6 stabilized with copper/KI system. On the other hand, the use of the HALS additive brought about a substantial increase in the amount of carboxylic acids formed.
The morphology of the samples was found to have an effect on the kinetics of the accumulation of carbonyls, and it was observed that at a later stage of exposure the crystalline phase was also involved in the oxidation process.
Tensile tests on films revealed a large reduction in ductility as a result of ageing for both neat polymer and HALS-doped polymer. Only a slight reduction in ductility was found for the polymer stabilized with the inorganic mixture.
This study evidenced that the mixture of CuCl2 and KI has a far better long-term stabilizing efficiency in comparison with the HALS stabilizer
Analisi Reologica del Processo Sol-Gel di Sistemi Inorganici a Base di Silicato di Sodio
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SOLUZIONE SILICATICA DI POLIOLI DA SCARTO PER LA PREPARAZIONE DI UN MATERIALE IBRIDO A MATRICE POLIURETANICA E/O POLI-ISOCIANURATICA-LEGANTE IDRAULICO, E RELATIVO METODO DI PREPARAZIONE
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