1,720,976 research outputs found
Il ruolo delle misure di flusso di gas e di pressione nella ricerca delle perdite
No full textLe prove di tenuta, siano esse eseguite a livello di collaudo del prodotto o siano più sofisticate per quantificare la tenuta di un prodotto, richiedono la misura di varie grandezze quali la pressione, il flusso di gas, la temperatura, la concentrazione del gas utilizzato per la prova. Per queste grandezze, così come per tutte le grandezze fondamentali e derivate del sistema SI (Sistema Internazionale delle unità di misura), è stata realizzata la catena della riferibilità che parte dai campioni primari, conservati presso l’INRIM, passa attraverso i campioni di riferimento dei Laboratori Secondari e si diffonde ai campioni di lavoro utilizzati dall’industria.
Nella prima parte del lavoro vengono presentati in modo sintetico i campioni primari per la misura della pressione e del flusso di gas e vengono indicate le caratteristiche metrologiche salienti dei trasduttori di trasferimento di pressione e delle fughe di riferimento. Nella seconda parte del lavoro si mette in rilievo l’importanza che assume ai fini della qualità del prodotto la corretta riferibilità delle grandezze (pressione e flusso gassoso) al sistema SI
Flussometro primario per la misura di piccole portate di gas con riferimento alla pressione atmosferica
No full textAlcuni prodotti devono garantire una certa ermeticità e quindi devono essere sottoposti ad un controllo che consiste nella misurazione del flusso di gas in ingresso o uscita attraverso possibili cricche, porosità, microfessure.
Tra le diverse metodologie applicabili per la ricerca delle perdite, alcune sono molto semplici e permettono analisi qualitative, mentre altre, più sofisticate, consentono di quantificare la perdita. È comunque necessario disporre di rivelatori tarati in grado di misurare il flusso di gas. Le fughe di riferimento, componenti essenziali per la taratura dei rivelatori, sono in genere capillari in acciaio e generano un flusso di gas quando ai lori estremi vi è una differenza di pressione.
Per garantire la corretta riferibilità delle fughe di riferimento l’INRIM ha progettato e realizzato un flussometro, campione primario per la misura di portate di gas < 1x10-4 Pa m3/s con riferimento alla pressione atmosferica.
Recentemente è stato progettato e realizzato un sistema di controllo termico attivo al fine di migliorare l’accuratezza del flussometro ed estendere il limite inferiore di misura. Le modifiche apportate hanno portato tale limite a 1x10-6 P am3/s con incertezza estesa inferiore al 3%
Biobased Vitrimeric Epoxy Networks
Full text linkThe scientific strategies reported in the literature for developing biobased epoxy vitrimers are summarized. Biomass resources such as lignin, cellulose, or different vegetable oils can be exploited as biobased building blocks for epoxy thermosets as an alternative to the bisphenol-A-based ones. Biorenewable resources have been synthesized introducing dynamic covalent bonds in the cross-linked networks. This combination allows to achieve cross-linked biobased epoxy networks with thermoset-like properties at a temperature of use, but showing (re)processability, recyclability, and self-healing properties above a well-defined temperature named topology freezing transition temperature (Tv).Here, all the scientific strategies reported in the literature for developing biobased epoxy vitrimers are summarized. The strategy for achieving sustainable and recyclable epoxy thermosets is exploiting monomers from biorenewable resources by introducing dynamic covalent bonds in the cross-linked networks. This combination allows to achieve cross-linked biobased epoxy networks with thermoset-like properties at a temperature of use, but showing (re)processability, recyclability, and self-healing properties.imag
Impatto dell'accordo di mutuo riconoscimento (MRA) sulle misure di pressione in Italia (IMGC-CNR e Centri SIT)
No full text
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
DLP Fabrication of Mullite Structures: Flaw Mitigation Through Powder Thermal Processing
Full text linkDigital Light Processing (DLP), which operates through a layer-by-layer deposition, has proven to be a promising technique for obtaining complex and customized architectures. However, there are still numerous unresolved challenges in ceramics additive manufacturing, among which is delamination due to suboptimal adhesion between the layers, which threatens the structural integrity and properties of samples. According to recent findings, excess surface hydroxyl groups were identified as being responsible for this defect; a suitable calcination pre-treatment of the ceramic powder could be effective in significantly mitigating delamination flaws in mullite DLP printed bodies. Therefore, in addition to optimizing the printable slurry formulation and printing parameters (mainly in terms of curing energy and layer resolution), this work aimed at investigating the influence of the calcination of a commercial mullite powder (added with magnesium nitrate hexahydrate, as a precursor of the sintering aid MgO) as a simple and effective treatment to additively shape ceramic bodies with limited flaws and enhanced density. The surface characteristics evolution of the mullite powder was investigated, specifically comparing samples after magnesium nitrate hexahydrate addition and ball-milling in water (labeled as BM), and after an additional calcination (BMC). In particular, the effect of the superficial -OH groups detected by FTIR analysis in the BM powder, but not in the BMC sample, was studied and correlated to the properties of the respective ceramic slurry in terms of rheological behavior and curing depth. The hydrophilicity of BM powders, due to superficial hydroxyls groups, affects ceramic powder dispersion and wettability by the resin, causing a weak interface. At the same time, it promotes photopolymerization of the light-sensitive resin, thus inducing the as-printed matrix embrittlement. Anyhow, its photopolymerization degree, equal to 67% and 55% for BM and BMC, respectively, was enough to guarantee the printability of both slurries. However, the use of BMC significantly reduced flaw occurrence in the as-printed bodies and the final density of the samples sintered at 1450 °C (without an isothermal step) was increased (approx. 60% and 50% of the theoretical value for BMC and BM, respectively). Thus, the target porosity of the ceramic bodies was guaranteed, and their structural integrity achieved without any increase in sintering temperature but with a simple powder treatment
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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