1,721,221 research outputs found
Nonlinear High Gain Separation Principles and Fast Sampling Results ensuring Robust Stability
No full textA semi-global nonlinear separation principle is described which presents conditions under which a stabilizing controller based on the output and its derivatives (typically the state or partial state) can be replaced by a controller based on measurement of the output only. The results include the case of high gain observer reconstruction of the output derivatives and the case of approximating the output derivatives via numerical derivatives for which various realizable schemes based on discrete sampling are given. The same sampling constructions and results are also applied directly to the output measurement itself, giving rise to fast sampling theorems. The proofs are based on estimating gap distances between the original controller and the reconstructed approximation and conditions based on the robust stability margin
Robust stabilization by linear output delay feedback
Full text linkThe main result establishes that if a controller (comprising of a linear feedback of the output and its derivatives) globally stabilizes a (nonlinear) plant , then global stabilization of can also be achieved by an output feedback controller where the output derivatives in are replaced by an Euler approximation with sufficiently small delay h>0. This is proved within the conceptual framework of the nonlinear gap metric approach to robust stability. The main result is then applied to finite dimensional linear minimum phase systems with unknown coefficients but known relative degree and known sign of the high frequency gain. Results are also given for systems with non-zero initial conditions
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
A smart energy management system for battery-supercapacitor in electric vehicles based on the discrete wavelet transform and deep learning
No full textThe Discrete Wavelet Transform (DWT) is used to distribute power between the battery and supercapacitor in an electric vehicle so that the fast dynamic power demand is met by the supercapacitor and the slow dynamic is met by the battery. This results in a decline in battery ageing as the supercapacitor absorbs the high charge and discharge stress that would otherwise be imposed on the battery. However, implementing DWT introduces a time delay that increases as the level of decomposition increases. This time delay makes real time implementation difficult. This paper proposes the use of Deep Learning Recurrent Neural Networks with Long-Short Term Memory (LSTM) units to predict the power demand from raw data and compensate for the time delay so that DWT based energy management strategy can be implemented in real time. To compensate for the delay introduced by a second level DWT, the LSTM obtained a prediction root mean squared error of 3.69KW for the federal test procedure 72 (FTP72) driving cycle. Simulation results are presented to validate the design
Assessment of supercapacitor performance in a hybrid energy storage system with an EMS based on the discrete wavelet transform
No full textWhen battery and supercapacitor (SC) Energy Storage Systems (ESSs) coexist in electric vehicles, energy management is imperative to ensure efficient power distribution based on the strengths and weaknesses of each ESS.The decoupling of highly dynamic power demands into components that match the dynamic nature of each ESS is essential. The Discrete Wavelet Transform (DWT) has been widely recommended for this purpose as part of real time energy management systems. However, due to DWT signal processing, delays in the frequency components can undermine the benefits of hybridization. This paper analyses the contribution of the SC to alleviate the battery when the DWT is used with and without time delay compensation using future demand prediction. Four different implementation strategies for a DWT based EMS have been evaluated using different metrics to quantify energy circulation and SC assistance during acceleration and braking. Simulation results using urban and highway driving cycles, show that obtaining the SC current reference as the difference between the real time current demand and the DWT low frequency component enhances SC assistance during acceleration and braking at the expense of higher energy circulation. The complexity added by future demand prediction does not reap SC performance benefits
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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