1,720,960 research outputs found
Battery Conditional Reliability Function under an Inverse Gaussian model and its Bayes Estimation
No full textThis paper proposes a new methodological approach in the field of studies devoted to proper and accurate selection of a reliability model for battery systems. The study is performed with particular emphasis on the modeling and estimation of the Conditional Reliability Function, conceived as a key analytical tool in predicting the "Remaining useful life" of the battery, which is in turn an important information in order to identify the best maintenance strategy selection, or for inspection optimization, and also spare parts provision. Estimation of the Conditional Reliability Function is developed by means of a method based on the Inverse Gaussian Distribution and its Bayes Estimation. The performances of this estimation are developed and validated by means of extensive simulations and available experimental data. A brief account is reported of robustness analyses of the method with respect to the assumed prior Distribution
Investigating Electric Cars Charging Behaviour in Italian Urban Areas
No full textOne of the most relevant factors for the widespread adoption of battery electric vehicles is an effective recharge infrastructure, in terms of location, power and costs for users. This is an ambitious objective mainly in urban areas, where recharge networks can assume diverse alternative configurations. In such contexts, private and public infrastructure can overlap or have deficiencies, causing investment waste or supply shortages. Generally, surveys are powerful tools for investigating demand preferences and guiding offer development, mainly at its early stages. In Italy, electric mobility struggles to catch on, so we considered it useful to investigate Italian attitudes toward electric car recharging. With this aim, we carried out a first survey addressed to electric car early adopters, performed with the Revealed Preferences technique, and a second one addressed to potential electric car users, set on the Stated Preferences technique. Both surveys were mainly focused on urban context and daily mobility, with special attention on the choice of recharge location with respect to the stopping places (home, work, other destinations). This paper describes only the Stated Preference survey, which is more significant for the setting up and calibration of a behavioral model on electric car recharge in urban areas. Results on the representativeness of the sample are reported, as well as the charging behaviour expressed in different situations of battery level, recharge time, and costs
On line Bayes Estimation of Capacity Fading for Battery Lifetime Assessment
No full textThis study is devoted to a proper modeling and estimation method of battery capacity fading under the widely adopted exponential decay model, in view of an efficient lifetime assessment of battery. The method is based upon recursive online Bayes estimation of capacity fading. It is also shown how a degradation-based modeling of battery reliability can be adopted, leading to a Bernstein lifetime distribution. The performances of the proposed method are successfully evaluated by means of extensive Monte Carlo simulations based upon available literature and experimental data. A brief account is also given of a robustness analysis of the proposed methodology with respect to departures from the assumption of Gaussian noise
Life cycle estimation of battery energy storage systems for primary frequency regulation
No full textAn increasing share of renewable energy sources in power systems requires ad-hoc tools to guarantee the closeness of the system’s frequency to its rated value. At present, the use of new technologies, such as battery energy storage systems, is widely debated for its participation in the service of frequency containment. Since battery installation costs are still high, the estimation of their lifetime appears crucial in both the planning and operations of power systems’ regulation service. As the frequency response of batteries is strongly dependent on the stochastic nature of the various contingencies which can occur on power systems, the estimation of the battery lifetime is a very complex issue. In the present paper, the stochastic process which better represents the power system frequency is analyzed first; then the battery lifetime is properly estimated on the basis of realistic dynamic modeling including the state of the charge control strategy. The dynamic evolution of the state of charge is then used in combination with the celebrated rain-flow procedure with the aim of evaluating the number of charging/discharging cycles whose knowledge allows estimating the battery damage. Numerical simulations are carried out in the last part of the paper, highlighting the resulting lifetime probabilistic expectation and the impact of the state of the charge control strategy on the battery lifetime. The main findings of the present work are the proposed autoregressive model, which allows creating accurate pseudo-samples of frequency patterns and the analysis of the incidence of the control law on the battery lifetime. The numerical applications clearly show the prominent importance of this last aspect since it has an opposing impact on the economic issue by influencing the battery lifetime and technical effects by modifying the availability of the frequency regulation servic
Experimental Analysis of NMC Lithium Cells Aging for Second Life Applications
No full textNowadays the electric power system is facing new challenges related to the integration of renewable sources, more and more frequently combined with energy storage systems. The use of these technologies is very promising, although it requires sophisticated control architectures in order to successfully balance the intermittence and unpredictability of renewables, and provide the power grid with new services. The presence of a storage state estimator is absolutely required to correctly identify the storage performance and present conditions, in terms of stored energy, aging or possible failures; this is crucial to assess the real exploitability of the battery, both during its first or second life application. This paper focuses in particular on aging mechanisms, describing and comparing three possible models and their deployment procedures. Flexibility of implementation, accuracy in aging determination, and ease of use of each technique have been deeply analysed and compared
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
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