1,720,971 research outputs found
Multi-criteria (thermo-economic) optimization and environmental analysis of a food refrigeration system working with low environmental impact refrigerants
No full textIn order to cope with the performance requirements of the Eco-design and to the limitations of European regulations, manufacturers of refrigeration devices must find an optimum between performance and costs. In this paper, we propose a thermo-economic analysis based on calibrated models and real constraints to explore possible design options for a 2.5 kW commercial refrigeration unit including the effects of the refrigerant type (R404A as baseline, R454C, R449A, R452A, R455A and R290 as low environmental impact fluids). The results are proposed in two dimensions: the first one related to the manufacturer point of view with a Pareto front of costs and performance, and the second one related to the customer point of view with the environmental impact evaluation for each configuration that belongs to a Pareto front. The calibration of models is based on real and actual data for compressors, heat exchangers and costs. Different scenarios are proposed depending on the location and the related specific energy costs and emission factors (Italy, France, Germany). The results show that R449A performs better as mid-term scenario refrigerant in European market. Instead, R454C can be suitable as long-term replacement. Finally, the environmental analysis shows that the optimal configuration in terms of performance has not the lowest environmental impact. The latter aspect requires more attention by the regulatory panels
Defrosting frequency optimization in a cooling system: Minimization of energy consumption vs reduction of the number of on/off cycles per hour. Definition of a methodology and assessment of commercial methods based on experiments
No full textThis paper presents the definition of a new method to obtain the optimum defrosting start time for a medium temperature refrigeration system with hot-gas bypass defrosting technique. A series of experiments is performed for a monoblock prototype placed in a cold room with controlled temperature (from −4 °C to +2 °C) and relative humidity (from 70% to 90%), whereas the ambient temperature is set to 25 °C and monitored in a calorimetric chamber. Specific tests are carried out by leaving the machine in operating mode up to the complete blockage of the evaporator, measuring the corresponding defrosting phase period and frost accumulated mass.
A new method for data reduction of experimental data is presented to calculate the average energy consumption of the whole cycle (on–off operation and defrosting). With these results from experiments, firstly, the average energy consumption is used as one of the decisional parameters together with the number of hourly on–off cycles of a multi-criteria optimization under constrained heating load versus cooling capacity ratio. Secondly, an assessment of the results achievable with commercial defrosting method is carried out. The new method for data reduction could be used to collect performance maps under lab conditions and then use it as multi-criteria decisional basis for a control system. The commercial methods monitoring air-evaporator temperature difference or pressure drop across the evaporator do not allow to keep the heating load versus cooling capacity below a desired threshold value under all operating conditions. Conversely, a control system based on a defined maximum allowable heating load versus cooling capacity ratio permits to control the temperature of the cabinet
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
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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