2,700 research outputs found
Design and implementation of fuzzy logic controllers
The main objectives of our research are to present a self-contained overview of fuzzy sets and fuzzy logic, develop a methodology for control system design using fuzzy logic controllers, and to design and implement a fuzzy logic controller for a real system. We first present the fundamental concepts of fuzzy sets and fuzzy logic. Fuzzy sets and basic fuzzy operations are defined. In addition, for control systems, it is important to understand the concepts of linguistic values, term sets, fuzzy rule base, inference methods, and defuzzification methods. Second, we introduce a four-step fuzzy logic control system design procedure. The design procedure is illustrated via four examples, showing the capabilities and robustness of fuzzy logic control systems. This is followed by a tuning procedure that we developed from our design experience. Third, we present two Lyapunov based techniques for stability analysis. Finally, we present our design and implementation of a fuzzy logic controller for a linear actuator to be used to control the direction of the Free Flight Rotorcraft Research Vehicle at LaRC
Design and Implementation of Fuzzy Logic Controllers. Thesis Final Report, 27 July 1992 - 1 January 1993
The main objectives of our research are to present a self-contained overview of fuzzy sets and fuzzy logic, develop a methodology for control system design using fuzzy logic controllers, and to design and implement a fuzzy logic controller for a real system. We first present the fundamental concepts of fuzzy sets and fuzzy logic. Fuzzy sets and basic fuzzy operations are defined. In addition, for control systems, it is important to understand the concepts of linguistic values, term sets, fuzzy rule base, inference methods, and defuzzification methods. Second, we introduce a four-step fuzzy logic control system design procedure. The design procedure is illustrated via four examples, showing the capabilities and robustness of fuzzy logic control systems. This is followed by a tuning procedure that we developed from our design experience. Third, we present two Lyapunov based techniques for stability analysis. Finally, we present our design and implementation of a fuzzy logic controller for a linear actuator to be used to control the direction of the Free Flight Rotorcraft Research Vehicle at LaRC
The Central American Question: Nicaraguan Cultural Production and Francisco Goldman\u27s The Ordinary Seaman
This study examines the cultural production and political history of Nicaragua from the 1960s to the early 1990s and interprets Francisco Goldman’s The Ordinary Seaman alongside Central America’s literary boom period, the nation-building project of the revolutionary letrados, and race relations between Nicaragua’s Pacific region and its two autonomous sectors of the Atlantic coast. It is argued that Central American ways of seeing are colored by the interplay between a revolutionary past, the myth of the pure Indio or mestizo, and the erasure of national identity in the US contact zone. Rather than recuperating a Central American identity, it is maintained that exposing the construction of said identity uncovers the hidden blackness and the heterogeneity of the Central American isthmus. Ultimately, the thesis aims at giving visibility to forgotten and ignored Central American narratives, histories, and people, and stresses the significance of studying the region within a literary and black Atlantic perspective
A panoramic VISTA of the stellar halo of NGC 253
Outskirts of large galaxies contain important information about the galaxy
formation and assembly process, and resolved star count studies can probe the
extremely low surface brightness of the outer halos. We use images obtained
with the VISTA telescope to construct spatially resolved J vs Z-J
colour-magnitude diagrams (CMDs) of NGC 253, a nearly edge-on disk galaxy in
the Sculptor group. The very deep photometry, down to J ~ 23.5, and the wide
area covered allows us to trace the red giant branch (RGB) and asymptotic giant
branch (AGB) stars that belong to the outer disk and the halo of NGC 253, out
to 50 kpc along the galaxy minor axis. We confirm the existence of an extra
planar stellar component of the disk, with a very prominent southern shelf and
a symmetrical feature on the north side. The only additional visible
sub-structure is an overdensity in the north-west part of the halo at about 28
kpc from the plane and extending over ~ 20 kpc parallel with the disk of the
galaxy. From the stellar count profile along the major axis we measure the
transition from the disk to the halo at a radial distance of about 25 kpc,
where a clear break appears in the number density profile. The isodensity
contours show that the inner halo is a flattened structure that blends with a
more extended, diffuse, rounder outer halo. Such external structure can be
traced to the very edge of our image out to 50 kpc from the disk plane. The
number density profile of the stars in the stellar halo follows a power law
with index -1.6, as function of radius. The CMD shows a very homogeneous
stellar population across the whole field; by comparison with theoretical
isochrones we conclude that the RGB stars are ~ 8 Gyr old or more, while the
AGB stars trace a population of about 2 x 10^8 Mo, formed from ~ 0.5 to a few
Gyr ago. Surprisingly, part of this latter population appears scattered over a
wide area.Comment: To appear on Astronomy and Astrophysic
Parallelizing the Sparse Matrix Transposition: Reducing the Programmer Effort Using Transactional Memory
AbstractThis work discusses the parallelization of an irregular scientific code, the transposition of a sparse matrix, comparing two multithreaded strategies on a multicore platform: a programmer-optimized parallelization and a semi-automatic parallelization using transactional memory (TM) support. Sparse matrix transposition features an irregular memory access pattern that de- pends on the input matrix, and thereby its dependencies cannot be known before its execution. This situation demands from the parallel programmer an important effort to develop an optimized parallel version of the code. The aim of this paper is to show how TM may help to simplify greatly the work of the programmer in parallelizing the code while obtaining a competitive parallel version in terms of performance. To this end, a TM solution intended to exploit concurrency from sequential programs has been developed by adding a fully distributed transaction commit manager to a well-known STM system. This manager is in charge of ordering transaction commits when required in order to preserve data dependencies
Higgs Boson Phenomenology in a Simple Model with Vector Resonances
In this paper we consider a simple scenario where the Higgs boson and two
vector resonances are supposed to arise from a new strong interacting sector.
We use the ATLAS measurements of the dijet spectrum to set limits on the masses
of the resonances. Additionally we compute the Higgs boson decay to two photons
and found, when compare to the Standard Model prediction, a small excess which
is compatible with ATLAS measurements. Finally we make prediction for
Higgs-strahlung processes for the LHC running at 14 TeV
Analytic solution of a magnetized tori with magnetic polarization around Kerr black holes
We present the first family of magnetically polarized equilibrium tori around
a Kerr black hole. The models were obtained in the test fluid approximation by
assuming that the tori is a linear media, making it is possible to characterize
the magnetic polarization of the fluid through the magnetic susceptibility
. The magnetohydrodynamic (MHD) structure of the models was solved by
following the Komissarov approach, but with the aim of including the magnetic
polarization of the fluid, the integrability condition for the magnetic
counterpart was modified. We build two kinds of magnetized tori depending on
whether the magnetic susceptibility is constant in space or not. In the models
with constant , we find that the paramagnetic tori () are
more dense and less magnetized than the diamagnetic ones () in the
region between the inner edge, , and the center of the disk, ;
however, we find the opposite behavior for . Now, in the models with
non-constant , the tori become more magnetized than the Komissarov
solution in the region where , and less
magnetized when . Nevertheless, it is worth
mentioning that in all solutions presented in this paper the magnetic pressure
is greater than the hydrodynamic pressure. These new equilibrium tori can be
useful for studying the accretion of a magnetic media onto a rotating black
hole.Comment: 7 pages, 15 .pdf figures, 1 table, Accepted for publication in
Astronomy & Astrophysics (A&A
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