1,721,101 research outputs found
Derivation of telegrapher's equations and field-to-transmission line interaction
No full textThe evaluation of electromagnetic field coupling to transmission lines is an important problem in electromagnetic compatibility. The use of the transmission line (TL) approximation theory has permitted the solution of a large range of problems (e. g. lightning and EMP interaction with power lines). However, the continual increase in operating frequency of products and higher-frequency sources of disturbances (such as UWB systems) makes TL basic assumptions no longer acceptable for a certain number of applications. In the last decade or so, the generalization of classical TL theory to take into account high frequency effects has emerged as an important topic of study in electromagnetic compatibility. This effort resulted in the elaboration of the so-called "generalized" or "full-wave" TL theory, which incorporates high frequency radiation effects, while keeping the relative simplicity of TL equations
Numerical solution of the Leader Progression Model by means of the Finite Element Method
No full textAs known the lightning incidence of a vertical structure is related to the physical processes involved in the final stage of the progression of the downward lightning leader to the structure and upward streamers, in case downward flashes are taken into account. Within this context, the paper presents and discusses a numerical implementation based on the Finite Element Method (FEM) of the Leader Progression Model (LPM): LPM-FEM. The obtained results are compared with those of the original implementation of the LPM based on the charge simulation method and the relevant differences analyzed and discussed
Voltage transient measurements in a distribution network and sequence of relay events associated to lightning strokes detected by LLS
Full text linkA two-year experimental campaign on lightning-originated
disturbances carried out in an Italian rural region
characterized by a high ground flash density (4
flashes/km2/yr) has provided a set of voltage transient
measurements in a medium voltage (MV) feeder that are
clearly correlated with both specific events detected by the
Italian lightning location system (LLS) CESI-SIRF and
sequences of relay operations. The paper describes the
sequence of relay events, reports the data of the correlated
LLS-detected stroke and presents the corresponding voltage
transients recorded at three different busses of the MV
feeder
Using of a cost-based Unit Commitment algorithm to assist bidding strategy decisions
No full textThe paper describes a procedure developed to assist a generating company in choosing the most convenient bidding strategies for a day-ahead electricity energy market. According to the proposed method, the profit maximization problem is transformed into a minimization problem that can be solved by a traditional hydro-thermal unit commitment program after implementing a few modifications. The paper describes the modifications introduced in a unit commitment program based on the Lagrangian relaxation approach and on a disaggregated Bundle method for the solution of the dual problem. It also presents some results obtained for a realistic data set of hydrothermal power plants. The results are discussed in order to emphasize how the method can be applied to assess the bidding strategy choice of a given company
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
On the influence of corona on lightning-induced overvoltages
No full textAn experimentally inferred charge-voltage (Q-V) diagram used to macroscopically model the corona phenomenon is adopted for the calculation of the lightning-induced transients in presence of corona. The paper aim at presenting the calculation procedure as well as the analysis of the corona Q-V diagram on the lightning-induced surges
Contributions to SC C4 Session on Paper C4-303 – “Lightning-Induced Voltages on Overhead Distribution Lines: Theoretical and Experimental Investigation of related Problems and their Impact on Power Quality”, by C.A. Nucci, A. Borghetti, M. Paolone, P. Boselli, M. Bernardi, S. Malgarotti, I. Mastandrea, F. Rachidi
No full textContributions to SC C4 Session on Paper C4-303 – PREFERENTIAL SUBJECT 3 - Lightning performance of MV systems
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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