1,720,976 research outputs found
Penetration Mechanics of Plant Roots and Related Inspired Robots
Full text linkThe ability of plant roots to penetrate soils is affected by several stimuli from the surrounding medium such as mechanical stresses and chemical changes. Therefore, roots have developed multiple responses to the several outer stimuli. Since plant roots have to face very complex problems to grow deeply into the ground, they are remarkable examples of problem-solving behaviour and adaptation to the outer constraints. The adaptation strategies of a natural root are not yet completely known and understood with exhaustive explanations. For this reason, mathematical models and experimental techniques applied to biological phenomena can perform a key role in translating the Nature adaptive solutions into engineering applications. The aim of this thesis is to provide further insights in understanding biological phenomena for the development of new technologies inspired by the adaptive ability of plant roots. Accordingly, both theoretical and experimental explanations to the adaptive behaviour of plant roots are proposed. The mathematical modelling is based on a modified version of the extended West, Brown and Enquist universal law, considering the root growth as an inclusion problem. The proposed equation has as a particular case a growth equation exploiting an approach similar to Lockhart taking into account the soil impedance. The influence of mechanical stresses and nutrient availability on the root growth are studied. The solutions of the analytical models are compared with experimental data collected in real and artificial soils. In addition, the theories and hypotheses of the root ability to grow in the apical region through nanoindentation, wettability, and photoelasticity are investigated. The first technique provided insights for the possible role and function at both different tissues levels and distances from the tip in the root movement and penetration during the growth. The investigation of root tissue properties revealed that the penetration and adaptation strategies adopted by plant roots could be enhanced by a combination of soft and stiff tissues. The second technique aimed to highlight the wettability of the apical zone and root hairs for the acquisition of water and nutrients. Finally, photoelastic experiments provided a non-invasive and in situ observation of plant roots growth and, by exploiting the fringe multiplication, a set up for the study of plant roots growing in edible gelatine is proposed
Modeling Tsunamis Generated by Submarine Landslides at Stromboli Volcano (Aeolian Islands, Italy): A Numerical Benchmark Study
Full text linkFlow of fluids with pressure-dependent viscosity down an incline: Long-wave linear stability analysis
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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
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
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