1,720,986 research outputs found
Radio frequency treatment of foods: review of recent advances
Get PDFRadio frequency (RF) heating is a technology on which quite a number of publications have emerged in recent years. The current paper reviews the history of this form of heating and introduces the basic principle of this technology including how it is applied and how it differs from other forms of heating. Recent literature on RF heating applications is examined, highlighting the impact of this form of heating on general quality aspects of foods. An understanding of physical characteristics which influence food heating including geometry, shape, product position and dielectric properties is extremely important in the design of RF heating systems and recent publications in these areas are discussed in addition to the most recent developments on mathematical modelling. In the final section the authors give their opinion on future trends and prospects for this form of heating
Effects of geometry and orientation of food products on heating uniformity during radio frequency heating
No full textIn radio frequency (RF) assisted heat treatment of food products, heating behavior depends on the composition and geometry of a product. In this study, the effect of salt added to a food simulant on its dielectric properties and penetration depth (dp) were determined across a temperature range from 5 to 80 °C. Three primitive geometries (cube, cylinder and sphere) of a food simulant having a standardised volume (3.98 × 10−4 m3) heated in a custom-built 50 Ω RF system to investigate the impact of sample geometry and orientation on power absorption and heating uniformity. Experimental results revealed vertical oriented cylinder samples followed by cubes showed better temperature uniformity. The temperature at the core of food simulant samples after 6 min RF heating using 500 W power was 44 ± 7.1 °C, 45.3 ± 0.9 °C and 52.9 ± 3.5 °C in cube, cylinder, and sphere sample, respectively. However, the sphere sample was characterized by having the hottest spot at the bottom section. RF power level also played a significant role in heating uniformity with lower power input resulting not only in a slower heating rate but also in less uniform temperature distribution. This study provided a potential insight on the use of food simulants for evaluating RF heating design and performances
Radio-Frequency heating of foodstuff: solution and validation of a mathematical model
No full textRadio-frequency (RF) heating is based on the interaction between the electric field produced by the electrodes of a capacitor and the dipoles and ionic-charges contained within a food product. In this paper, the temperature profiles and, particularly, the non-uniformity of temperature distribution occurring during RF heating of cylindrical meat batters, were analysed by mathematical modelling of both electromagnetic and thermal phenomena. Meat batters were chosen as sample food, with dielectric and physical property data available as a function of temperature. Temperature profiles were experimentally measured along the sample axes, for RF output powers of 100, 200, 300 and 400 W, while electromagnetic and heat equations were simultaneously solved by means of the finite element software FEMLAB. The goodness of fit of the model was evaluated by comparing numerical results with measured temperature profiles. Results showed different heating rates within the samples and, therefore, an uneven temperature distribution. The closer the temperature measurement point was to the bottom of the sample, the higher was the heating velocity. Unevenness of temperature distribution was emphasised by the applied RF output power: the higher the applied power the more uneven was the temperature distribution
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
Get PDF“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
Get PDFWe 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
Get PDFWe 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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