1,721,013 research outputs found
Comparing different processing methods in apple slice drying. Part 1. Performance of microwave, hot air and hybrid methods at constant temperatures
Full text linkThe drying curves, energy efficiency and colour variations of sliced apples dried at various temperatures and using different techniques were evaluated, i.e. microwave (35, 55 and 65 °C), hot air (35, 55, 65 and 75 °C) and combination of both (65 °C). The microwave (MW) tests also included comparison between air recirculation and continuous inlet of fresh air. Each drying method was evaluated at a fixed temperature level by means of a control system based on infrared thermography. The time required to complete the drying process at 65 °C varied from about 44 min for MW with fresh air ventilation (double with air recirculation), to 122 min for hybrid heating and 238 min for hot air. Drying kinetics was analysed by introducing a new semi-empirical model, capable of recovering the drying behaviour in terms of both mass loss and drying speed. The results showed that the hybrid drying mode, thanks to the reduced power of the microwaves, led to a lower drying rate than the microwave mode alone. Overall colour variations were minor in samples heated with MW to 65 °C (ΔE=19.8). No significant differences were found between the drying methods with regard to energy consumption. As expected, the fastest drying occurs as the temperature increases, which requires more heat generation within the test samples
PROCESS INTENSIFICATION OF TOMATO RESIDUES DRYING BY MICROWAVE HEATING: EXPERIMENTS AND SIMULATION
No full textDrying of wet wastes from tomato processing industry was investigated as a critical step prior to their valorization to energy and/or to value-added chemicals. Microwave drying (MWD) was considered because of its advantages over conventional drying. A lab-scale MW oven equipped with automatic temperature control allowed operating at “constant temperature” rather than at “constant magnetron power”, as occurred in past research. MWD tests were performed in batch mode at three temperatures (50, 60 and 70 °C) and the results were compared with those from hot air drying (HAD) experiments. Based on experimental data, an empirical kinetic equation was developed for the microwave drying of tomato wastes as a function of moisture content and temperature. The rate equation was incorporated into a lumped-parameter mathematical model for a steady-state MWD process, which in turn was embedded in an Aspen PlusTM flowsheet used for the gross sizing of a continuous microwave belt dryer. Compared with HAD, MWD allows reducing the drying time up to one order of magnitude (i.e., from 320 to 100 min at 50 °C and from 190 to 60 min at 70 °C), but implies an investment cost one order of magnitude larger (i.e., from about 0.2 to 0.9 M€)
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
Analytical solutions for tomato peeling with combined heat flux and convective boundary conditions
No full textPeeling of tomatoes by radiative heating is a valid alternative to steam or lye, which are expensive and pollutant methods. Suitable energy densities are required in order to realize short time operations, thus involving only a thin layer under the tomato surface. This paper aims to predict the temperature field in rotating tomatoes exposed to the source irradiation. Therefore, a 1D unsteady analytical model is presented, which involves a semi-infinite slab subjected to time dependent heating while convective heat transfer takes place on the exposed surface. In order to account for the tomato rotation, the heat source is described as the positive half-wave of a sinusoidal function. The problem being linear, the solution is derived following the Laplace Transform Method. In addition, an easy-to-handle solution for the problem at hand is presented, which assumes a differentiable function for approximating the source while neglecting convective cooling, the latter contribution turning out to be negligible for the context at hand. A satisfying agreement between the two analytical solutions is found, therefore, an easy procedure for a proper design of the dry heating system can be set up avoiding the use of numerical simulations
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
Analytical Solutions for Tomato Peeling with Combined Heat Flux and Convective Boundary Conditions
No full textPeeling of tomatoes by radiative heating is a valid alternative to steam or lye, which are expensive and pollutant methods. Suitable energy densities are required in order to realize short time operations, thus involving only a thin layer under the tomato surface. This paper aims to predict the temperature field in rotating tomatoes exposed to the source irradiation. Therefore, a 1D unsteady analytical model is presented, which involves a semi-infinite slab subjected to time dependent heating while convective heat transfer takes place on the exposed surface. In order to account for the tomato rotation, the heat source is described as the positive half-wave of a sinusoidal function. The problem being linear, the solution is derived following the Laplace Transform Method. In addition, an easy-to-handle solution for the problem at hand is presented, which assumes a differentiable function for approximating the source while neglecting convective cooling, the latter contribution turning out to be negligible for the context at hand. The thermal response fully recovers the temperature field due to a sinusoidal varying heat source as a limiting case. A satisfying agreement between the two analytical solutions is found, therefore, an easy procedure for a proper design of the dry heating system can be set up avoiding the use of numerical simulations
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