1,720,989 research outputs found
Complex permittivity measurements for moisture and salinity characterization of building materials
No full textIn this paper, preliminary results of complex permittivity measurements of clay-brick material will be presented. The general aim of the experimental project is to correlate the measured permittivity of construction materials with the content of water and salt, in order to obtain information on the condition of ancient walls by using non-invasive techniques. The complex permittivity values reported in this paper have been obtained by waveguide measurements on samples of clay-brick dried and then immersed in demineralized water or in a saturated solution of demineralized water and NaCl. © (2017) by the International Measurement Confederation (IMEKO)
Compact system for measuring the dielectric properties of biological tissues at extremely-low and ultra-low frequencies
No full textThe aim of this paper is to describe a system designed for measuring the dielectric properties of biological tissues at extremely-low frequencies (ELF) and ultra-low frequencies (ULF), in particular in the 0.1 Hz - 1 kHz range. In this frequency range, literature data are very limited or absent, since measurement techniques are strongly affected by systematic errors. In order to carry out the aforementioned measurements, the paper presents the system design and metrological tests for assessing accuracy in complex impedance measurements. The uncertainty of the measuring system was determined using reference R-C circuits, showing extremely low errors as compared to high-accuracy multimeters and LCR meters. In order to obtain the sample complex permittivity, the system was calibrated in saline solutions to determine the cell constant K. Then, experimental results on the bioimpedance and related complex permittivity of bovine liver are shown, performed with the 4-electrode measurement technique to limit the effect caused by the electrodes polarization. In particular, measurements were performed in 20 tissue samples, obtained from 5 different livers. Both conductivity and relative permittivity results have been compared with the few existing literature data, finding a satisfactory agreement between the values obtained from the literature and those achieved by measurements with the proposed system
Four-electrode system for the measurement of biological tissue conductivity at ELF and ULF
Full text linkThis article presents the metrological characterization of a four-electrode compact system able to measure the dielectric properties of biological tissues at extremely low and ultralow frequencies, where data available from the literature are very limited. The cell constant k of the system, together with its expanded uncertainty, is found measuring different saline solutions of known conductivity. Since the cell constant plays a key role in the determination of tissue dielectric properties, it has been further verified through tests on other saline solutions, containing a different type of solute, confirming the accuracy of the system. In particular, results on a saline solution with a given molar concentration of KCl and on a physiological solution (Eurospital 0.9% NaCl) show that the system maximum relative error is lower than 3.3%. Therefore, it can be concluded that the system correctly measures the conductivity in saline solutions, and the parameter k can be properly used for the measurement of dielectric properties of biological tissues. As an application example, the system is used to perform measurements on bovine liver. Liver conductivity measurements show a constant behavior as a function of frequency in the examined range. Furthermore, the comparison of our results with the few data found in the literature at low frequencies shows good agreement. These observations point out the feasibility and convenience of the proposed method for the measurement of the conductivity at very low frequency
Embedded split ring resonator network for health monitoring in concrete structures
Full text linkCivil infrastructure systems such as bridges, buildings, dams, pipelines, airports, and heritage structures are complex engineered systems that play a fundamental role for the economic and industrial prosperity of society [1]. In order to build structures that are safe for the community, standardized design methodologies have been developed [1]. However, these structures are often subjected to various external loads and problematic environmental conditions that are difficult to consider during the design phase, resulting in structural deterioration [2]
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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