1,721,125 research outputs found
Performance Improvements of Power Management in CDMA Systems by Adaptive Modulation
No full textA signal processing procedure for distributed
resource allocation (power and rate management) in
telecommunication systems is here introduced. A generalized
approach towards adaptive modulation is discussed, as a noncooperative
joint modulation, rate and power control game for
the uplink of a single cell CDMA system. Then, an iterative
algorithm to select the best power and rate values for the desired
modulation is presented. Performance analysis is finally carried
out in comparison with conventional joint rate and power
control approach, also based on game theory
A Joint Modulation, Rate, and Power Control Game-Theoretic Approach for Uplink CDMA Communications
No full text
“American Studies in Europe/European American Studies: Local and Global Challenges”
No full textFifth contribution to the Serialized Forum Teaching American Studies in Europe: Challenges and New Directions for the 21st-Centur
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
Invariant Relative Satellite Motion
No full textThe paper investigates special orbital configuration which are invariant with respect to J2. Such configurations would have significant appplication as they can reduce the amount of propellant stored
Minimum Control for Spacraft Formation in a J2 perturbed environment
No full textLarge deltaV amounts are often required to maintain the relative geometry which is needed to implement a formation flying concept.Awise use of the orbital environmentmakes the orbit keeping phase easier, reducing the overall propellant consumption. A first important step in this direction is the selection of formation configurations and orbits which, while still satisfying the mission requirements, are less subject to perturbations resulting naturally in closed relative motion. Within this frame, a number of studies have been recently carried out in order to identify possible sets of invariant relative orbits under the effects of the Earth oblateness, a conservative force commonly referred to as J2 which is also the most important perturbation for LowEarth Orbit. These efforts clearly marked the difficulties connected with achieving genuine periodic relativemotion under J2 effect, but they also showed the existence of a set of conditions on the orbital parameters which allow for quasi-periodic J2 trajectories. This paper presents these particular trajectories, by means of deeper theoretical explanations, showing the dependency of the shape of the relative configurations on the orbital inclination. Since the quasi-periodic trajectories cannot be written analytically, and moreover, they are very sensitive with respect to the initial conditions, difficulties arise when trying to exploit these paths as reference for the control of a formation. This paper proposes a novel approach to find, from the actual quasi periodic natural trajectories, minimal control periodic reference trajectories. Next, it evaluates quantitatively the amount of propellant which is needed to control a spacecraft formation along these paths. The choice of Hill’s classical circular projected configuration as a nominal trajectory is considered as a comparison, showing the clear advantages of the proposed guidance design, which assumes low-perturbed periodic reference orbits as nominal trajectories
American Solitudes. International, National, Transnational
No full textProceedings of the XVIIII Biennial Conference of AISNA (Associazione Italiana di Studi nord-americani)Bari, October 6-8, 200
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
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