1,720,959 research outputs found
The Evolution of Large Pleasure Vessel Towards a Green Future
No full textThe future of transportation means is quickly moving towards green solutions in order to reduce the emission of COx and SOx firstly and, secondly, to progressively abandon the fossil fuels. In this perspective, alternative propulsion such as fully electric engine, biofuels, hydrogen, LNG are now largely used in the automotive field and for mass transportation means. The naval field is now moving on the same trend by using hybrid and fully electric engine especially for pleasure vessels, where the relatively small engine power allows the installation of battery stacks onboard without adding unreasonable weight for only few navigation miles. In this paper, the transformation of a traditional pleasure vessel towards a new hybrid version is proposed; after a more comprehensive view of the modifications that are necessary to install hybrid engine and battery onboard, highlighting all the critical aspects of these new design, a FE numerical analysis of the basement of electric variable speed generators is presented
A simplified method for the evaluation of inertial loads on sailing yachts
No full textThe aim of this work was to improve the understanding of dismasting, in view of the development of a new set of Rig Certification Rules specifically aimed at sailing yacht design, In the first phase of this project a preliminary systematic analysis of the dismastings of a large set of boats of different type and size has been carried out. By examining all these events, typical collapse modes have been identified, showing that whereas the traditional approach to mast scantlings is based on static loads, many of the failures took place as a result of severe dynamic loads. For this reason attention has been focused on the dynamic loads acting on the rigging caused by the response of the sailing yacht to waves. Especially in the case of boats with large displacement, these loads could be of a greater magnitude than static ones, and their evaluation must be earned out through seakeeping analysis. In particular pitching motions are extremely important, since they can cause severe accelerations to mast and rigging, possibly leading to mast collapse. Indeed dismasting is a significant event, very dangerous for the crew and very expensive to be repaired. In this paper a systematic study of the pitching behaviour of a database of sailing yachts was carried out. Using these results a simplified formulation is given to quickly evaluate the longitudinal acceleration at the mast centre of gravity. A state-of-the-art process is then used to obtain results in irregular sea states and to compute time series. Despite the small size of the database, this could be regarded as a first step towards the formulation of a simplified method based only on the boat length; this method would be able rapidly to estimate inertial loads due to waves
Assessing the Potential of Hybrid Systems with Batteries, Fuel Cells and E-Fuels for Onboard Generation and Propulsion in Pleasure Vessels
Full text linkElectro-fuels (E-fuels) represent a potential solution for decarbonizing the maritime sector, including pleasure vessels. Due to their large energy requirements, direct electrification is not currently feasible. E-fuels, such as synthetic diesel, methanol, ammonia, methane and hydrogen, can be used in existing internal combustion engines or fuel cells in hybrid configurations with lithium batteries to provide propulsion and onboard electricity. This study confirms that there is no clear winner in terms of efficiency (the power-to-power efficiency of all simulated cases ranges from 10% to 30%), and the choice will likely be driven by other factors such as fuel cost, onboard volume/mass requirements and distribution infrastructure. Pure hydrogen is not a practical option due to its large storage necessity, while methanol requires double the storage volume compared to current fossil fuel solutions. Synthetic diesel is the most straightforward option, as it can directly replace fossil diesel, and should be compared with biofuels. CO2 emissions from E-fuels strongly depend on the electricity source used for their synthesis. With Italy’s current electricity mix, E-fuels would have higher impacts than fossil diesel, with potential increases between +30% and +100% in net total CO2 emissions. However, as the penetration of renewable energy increases in electricity generation, associated E-fuel emissions will decrease: a turning point is around 150 gCO2/kWhel
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
UNDERWATER RADIATED NOISE FROM A LARGE PLEASURE CRAFT
No full textThe impact of underwater radiated noise (URN) by ship traffic has gained an increasing interest among scientists, ship designers and builders. It is now recognized that the underwater noise generated by human activities and in particular shipping noise can be harmful for the marine fauna and therefore urgent actions must be taken to tackle the problem. To this aim a virtuous example is represented by the Port Authority of Vancouver (CA) that, since 2017, has introduced important incentives and tax relief for those ships that prove to be particularly virtuous in terms of noise emissions radiated into the water. Up to now, most of the attention has been paid to study and characterize the noise emissions of large commercial ships due their worldwide diffusion. To this aim several measurements protocols have been issued both by international bodies (ISO, ANSI/ASA) both by the main classification societies. A lack of data is on the contrary present regarding pleasure crafts both as regards small boast and large yachts. In the present paper data coming from an experimental campaign for the measurement of the underwater radiated noise of one large yacht built by the SanLorenzo shipyards is presented. Noise has been measured for several operative conditions and speeds ranging from zero to maximum speed
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
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