1,721,144 research outputs found
Analysis of Different Energy Management Strategies for Complex Hybrid Electric Vehicles
No full textThe performance of Hybrid Electric Vehicles (HEVs) is strongly affected by their powertrain control strategies, in particular when complex architectures are concerned. Therefore the purpose of this paper is to analyze, through numerical simulation, different methodologies to develop an energy management strategy aiming to minimize the overall CO2 emissions of the vehicle. In order to perform a comprehensive comparison, different optimization algorithms were selected among the available solutions in the control theory. Foremost a global optimization strategy, the Dynamic Programming (DP), was used to benchmark the performance of the energy management systems. Then a local optimization strategy, the Equivalent Consumption Minimization Strategy (ECMS), was evaluated, to prove its suboptimal performance and to evaluate the possibility to be implemented on a real Engine Control Unit (ECU). Finally, the potential of heuristic control techniques was evaluated due to their low computational requirements and since they represent the most common solution in real applications.
The analysis focused on the case study architecture of the Chevrolet Volt, for which a Simulink model was built and tested on both regulatory driving cycles and real world driving conditions, emphasizing pro and cons of each method
Super D-branes
Full text linkWe present a manifestly Lorentz invariant, space-time supersymmetric, and 'κ-invariant' world-volume action for all type II Dirichlet p-branes, p ≤ 9, in a general type II supergravity background, including massive backgrounds in the IIA case. The p = 0, 2 cases are rederived from D = 11. The p = 9 case provides a supersymmetrization of the D = 10 Born-Infeld action.
Couplings of self-dual tensor multiplet in six dimensions
Full text linkThe (1, 0) supersymmetry in six dimensions admits a tensor multiplet which contains a second-rank antisymmetric tensor field with a self-dual field strength and a dilaton. We describe the fully supersymmetric coupling of this multiplet to a Yang–Mills multiplet, in the absence of supergravity. The self-duality equation for the tensor field involves a Chern–Simons modified field strength, the gauge fermions and an arbitrary dimensionful parameter.
Heterotic-Type II duality and wrapping rules
Full text linkWe show how the brane wrapping rules, recently discovered in closed oriented string theories compactified on tori, are extended to the case of the Type IIA string compactified on K3. To this aim, a crucial role is played by the duality between this theory and the Heterotic string compactified on a four-dimensional torus T4. We first show how the wrapping rules are applied to the T4/ZN orbifold limits of K3 by relating the D0 branes, obtained as D2 branes wrapping two-cycles, to the perturbative BPS states of the Heterotic theory on T4. The wrapping rules are then extended to the solitonic branes of the Type IIA string, finding agreement with the analogous Heterotic states. Finally, the geometric Type IIA orbifolds are mapped, via T-duality, to non-geometric Type IIB orbifolds, where the wrapping rules are also at work and consistent with string dualities.
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
Massive IIA supergravity from the topologically massive D-2-brane
Full text linkThe superfield equations of massive IIA supergravity, in the form of constraints on the superspace geometry, are shown to be implied by κ-symmetry of the topologically massive D-2-brane.
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
Generating Geodesic Flows and Supergravity Solutions
No full textWe consider the geodesic motion on the symmetric moduli spaces that arise after timelike and spacellike reductions of supergravity theories. The geodesics correspond to timelike respectively spacelike p-brane Solutions when they are lifted over a p-dimensional flat space. In particular, we consider the problem of constructing the minimal generating solution: A geodesic with the minimal number of free parameters such that all other geodesics are generated through isometrics. We give an intrinsic characterization of this solution in a wide class of orbits for various supergravities in different dimensions. We apply our method to three cases: (i) Einstein vacuum solutions, (ii) extreme and non-extreme D = 4 black holes in N = 8 supergravity and their relation to N = 2 STU black holes and (iii) Euclidean wormholes in D >= 3. In case (iii) we present an easy and general criterium for the existence of regular wormholes for a given scalar coset
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
- …
