1,720,954 research outputs found
Influence of pressurization for fuel cell systems fed with alternative fuels for maritime applications.
No full textThe maritime sector, characterized by its reliance on conventional fossil fuels, is undergoing a decarbonization process towards cleaner and more sustainable energy sources. This thesis investigates the potential utilization of fuel cells as alternative energy power systems for maritime applications, with a particular emphasis on both low-temperature Proton Exchange Membrane Fuel Cells (PEMFC) and high-temperature Solid Oxide Fuel Cells (SOFC).
The study begins with a comprehensive review of the current composition of power energy systems in the maritime field, analysing existing propulsion systems and their environmental impact. To complete this first part, the software HELM (developed by the Thermochemical Power Group) was adopted to carry out a multicriteria analysis on few case studies to have a better understanding on the range of applicability of these innovative technologies.
The work includes the simulation of the fuel cells system through numerical models to evaluates the feasibility, advantages, and challenges associated with integrating PEMFC and SOFC systems into maritime vessels. Special attention is given to the study of pressurization of both PEMFC and SOFC systems. The performance of the system increases but the complexity of the BoP, the costs and the volumes and weights are influenced negatively. The pressurization is achieved for both cases, hybridizing the fuel cell with a turbocharger.
The PEMFC-TC system was analysed using the commercial software GT-Power while the SOFC was investigated with the use of TRANSEO which relies on MATLAB-Simulink.
The actual state of art for SOFC provides for the use of methane that is converted with a reforming process into hydrogen but in the recent years other hydrocarbons or hydrogen carriers are considered as alternative fuels. The last chapter of this thesis explores the potential of utilizing innovative fuels such as ammonia in SOFC systems. The feasibility and advantages of using ammonia as a fuel source are examined, considering its potential for reducing greenhouse gas emissions relying on the fact that its production is widely diffused.
Overall, this thesis contributes to the research on alternative systems that will be part of the energy mix of the next years to reach the emissions limits imposed by regulations for a more sustainable maritime transportation by offering a comprehensive analysis of the opportunities and challenges associated with fuel cell technologies in this field
Investigation of an Ammonia-Fuelled SOFC-mGT Hybrid System: Performances Analysis and Comparison With Natural Gas-Based System
No full textAmong power generation systems, Hybrid Systems (HS) are very attractive due to the opportunity to reach higher power outputs and efficiencies by coupling different technologies. Among Solid Oxide Fuel Cell plants, one of the most studied innovative HS is the SOFC-Micro-Gas Turbine (mGT) integrated system: in the pressurized configuration, the Fuel Cell (FC) is in the place of the mGT combustion chamber, and an afterburner is used to complete the fuel combustion upstream the expander. Several system configurations, designs, and control system challenges have been studied in the last decades, and prototypes have been already developed around the world with satisfactory results in terms of system efficiency. However, these systems have been deeply studied feeding the FC with Natural Gas (NG) and Biogas, not completely allowing to reach zero carbon emissions. The growing global demand for carbon-free energy production is increasing, highlighting the importance of alternative fuels in the power generation sector: among them, thanks to its chemical and physical properties, ammonia is gaining more and more interest. In the present work, the authors want to investigate an innovative Ammonia-to-Power (A2P) system based on a SOFC-mGT HS, focusing on the main thermodynamic parameters, the system’s features, and critical aspects, from a technical and environmental point of view. To perform this analysis, a MATLAB/Simulink model has been developed, starting from a fully validated model of the HS fueled by NG and considering the FC operating with an anodic ejector recirculation. In the new plant configuration, the SOFC pre-reformer has been substituted by an ammonia cracker, permitting to investigate the effects of the anode gas recirculation and properly design the whole system. In particular, the operating parameters, such as anodic recirculation factor, fuel utilization, performance, gas turbine size, and features are presented and discussed. Finally, a comparison between hybrid systems and mGT fed by methane, biogas, and ammonia is carried out. Copyright © 2024 by ASME
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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