1,720,969 research outputs found
Design of a chemical reactor under microwave irradiation in resonance conditions
No full textIn this paper the development of a multi-tube reactor for chemical processing, running in a microwave irradiated field, is presented. It is known that reaction processes are often improved by microwave application, but the enhancing effect is not always due only to the temperature increasing in the medium, which is produced by the radiation exposure. Thus, to study the evolution of such kind of processes needs a strict control of the irradiation conditions and the use of a proper reaction apparatus in which the interaction between radiation and irradiated materials can be precisely defined. The present work is made necessary by the need of operating with well known and reproducible experimental conditions, and the aim was to design a resonant cavity inside which the tubes with the fluid to be processed are positioned. The main choice was to operate with a resonant cavity. In fact, working in resonance conditions allows the irradiated fluid to be exposed to constant microwave power, and the field intensity and power absorption can be accurately calculated and mapped. The cavity was designed by the authors using a proper commercial software for 3D electromagnetic simulation, then the reactor operation was tested by another commercial multiphysic simulation software. The results here presented show the proper geometrical characteristics of the cavity and of the internal tubes to work at 2.45 GHz of frequency while the irradiation power can be varied depending on the needs of the process. The reactor can work with different homogeneous systems, both chemical and biological (enzyme reactions). The future development will be the construction and the real operation of the designed apparatus in order to confirm the simulation results
Design and optimization of a microwave irradiated and resonant continuous biochemical reactor
No full textThe design of a microwave irradiated enzyme (biochemical) reactor is here presented. It consists of a suitable higher-order mode resonant cavity which contains several tubes where the solution containing reagents and products flow in the laminar flow regime. The process evolution under irradiation has then been simulated using the COMSOL multiphysics environment. As an example, the enzymatic hydrolysis reaction of sucrose has been considered. The results of the multiphysics simulation show that such a reactor can be used to effectively perform the reaction process in the optimal conditions for maximizing the reaction rate and preventing the enzyme deactivation by a precise knowledge of the temperature distribution and its strict control
Microwave resonant cavity as a reactor for the enzymatic hydrolysis of sucrose
No full textWe present here the design and analysis of a microwave resonant cavity to evaluate the effect of RF electromagnetic field on enzyme reactions. The cavity has been first designed using CST. Then, its behaviour in the actual use has been evaluated using the COMSOL multiphysics
A numerical estimation of a RFID reader field and SAR inside a blood bag at UHF
No full textIn this paper, the effects of UHF electromagnetic fields produced by a RFID reader on a blood bag are evaluated numerically in several configurations. The results of the simulation, field level and distribution, specific absorption rate (SAR), and heating time show that an exposure to a typical reader field leads to a temperature increase smaller than 0.1 C and to a SAR smaller than 1 W/kg. As a consequence, no adverse biological effects occur during a typical UHF RFID reading cycle on a blood bag. Therefore, the blood contained in a bag traced using UHF-RFID is as safe as those traced using barcodes. The proposed analysis supports the use of UHF RFID in the blood transfusion supply chain
A simple model for SE evaluation of MWCNT composite
No full textComposites material made form Carbon NanoTubes have attracted much interest as shielding materials. A new model for the full-wave simulation of the shielding effectiveness is presented. The full-wave evaluation of that effectiveness is also discussed
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
Use of microwaves for disinfection of farmland: A feasibility study
No full textThis work focuses on the heat transfer dynamics in agricultural soils when exposed to microwave (MW) fields, in order to disinfect them and to eliminate dangerous organisms without using pesticides. The work managed with the design of a horn antenna, with fixed feeding power, to be used to irradiate the superficial layer of soils for a fixed depth. The soil was approximated with a transmission line model, i.e. a lumped electrical model. By this model, after evaluating the relevant physical parameters such as the dielectric constant (as a function of the soil water content), it was possible to evaluate the power absorption and, finally, the increase in temperature and its profile as a function of the irradiation time. The latter information, strictly connected to the heat transfer process, demonstrated the feasibility of the methodology here proposed to achieve difficult conditions for microbial and pathogens life and so an effective disinfection of the treated farmland
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