1,720,956 research outputs found
Identificazione di schiume in polipropilene e relazione tra densità e parametri dei modelli
Full text linkLa varietà praticamente infinita di solidi cellulari rende particolarmente ardua la modellazione di questi materiali, per ognuno dei quali è in genere necessaria una specifica identificazione. La ricerca di legami tra i parametri dei modelli e le caratteristiche note della schiuma è utile per ridurre il lavoro di identificazione ed evitare una eccessiva quantità di esperimenti. Prove sperimentali di compressione uniassiale statica su schiume rigide di EPP a cinque densità diverse sono state utilizzate per identificare i modelli di Gibson e Rush. I parametri identificati per il modello di Gibson sono stati confrontati con quelli dati dalle espressioni dello stesso autore in funzione della densità. I parametri identificati per il modello di Rush sono stati studiati per individuare relazioni analitiche simili a quelle di Gibson tra i parametri e la densit
Topology optimisation of an automotive component without final volume constraint specification
No full textThe paper shows the results obtained by using a topology optimisation code to solve a three-dimensional problem concerning a real automotive component. The implemented optimisation method is based on the maximisation of the total potential energy with a volume constraint by optimality criteria. The volume of the optimal solution depends on the imposed static (displacement, stress, stiffness) and dynamic (natural frequency) constraints and has not to be specified a priori. The optimisation process converges toward a quite well defined structure made of the base material with a very little percentage of elements characterised by intermediate material properties
Mechanical models of cellular solids: parameters identification from experimental tests
No full textCellular materials have large use in many components acting as impact energy absorbers. These components have to be designed on the basis of the kind of impact, of the involved energy amount and of the maximum admissible load. The choice of the most suitable density for the selected type of foam is based on stress-strain behaviour, obtained by means of experimental tests and/or models. Only a few micro-mechanical models, as the Gibson model, take into account the density effects. These models could result quite complex to manage because of the need of, at least, a rough analysis of the actual foam structure. Conversely, most of the models used for numerical simulations are phenomenological models and have simple parameter identification based on fitting of experimental data, but they do not account for density effect. Experimental uniaxial compression tests performed for several types of foams, namely EPP, PUR (Bayfill EA), EPS and PPO/PS (Noryl GTX), at different density levels are used in order to identify, with an optimisation procedure devoted to the minimisation of the fitting residual evaluated by the least square method, the parameters of four cellular solid models. The considered models are four: the Gibson model [Gibson LJ, Ashby MF. Cellular solids. Structure and properties. Cambridge: Cambridge University Press; 1997], the Rusch model [Rusch KC. Load-compression behavior of flexible foams. J Appl Polym Sci 1969;13:2297-311; Rusch KC. Energy-absorbing characteristics of foamed polymers. J Appl Polym Sci 1969;14:1133-47; Rusch KC. Load-compression behavior of brittle foams. J Appl Polym Sci 1970;14:1263-73], a modified version of the Gibson model and a new empirical model. The third and fourth models have been developed in order to better fit the experimental stress-strain curve. The obtained improvements in terms of weighted sum of the squared errors are shown. The experimental data are a good representation of the typical behaviour of these kinds of foams and can be useful for the validation of models and the comparison of their performance. Moreover the large basis of experimental data for different types of foams at different densities could be used for the analysis of the influence of the density on the model parameters. Explicit empirical formulations are proposed to express the dependency of the phenomenological model parameters on the foam density. These relationships permit the identification of whatever density foam derived from the same solid material and with the same micro-structure by means of a minimum set of experimental tests. At the same time the availability of a large quantity of experimental data is helpful to reach a higher level of confidence in the model parameter values. Finally the identified parameters vs. density laws for the considered types of foam could be used in order to assist the design of a given absorber and to find the optimum density for the specific application. Closed form expression for the specific energy W and the efficiency E can be obtained, based on the resulting identified phenomenological model
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
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
- …
