Stabilization of Rössler chaotic dynamical system using fuzzy logic control algorithm

This paper proposes a fuzzy logic control algorithm (FLCA) to stabilize the Rössler chaotic dynamical system. The fuzzy logic control system is based on a Takagi-Sugeno-Kang inference engine and the stability analysis in the sense of Lyapunov is carried out using Lyapunov’s direct method. The new FLCA is formulated to offer sufficient inequality stability conditions. The asymptotic complexity of our algorithm is analyzed and proved to be lower in comparison with that of linear matrix inequality-based FLCAs. A set of simulation results illustrates the effectiveness of the proposed FLCA.     

Iterative performance improvement of fuzzy control systems for three tank systems

This paper suggests the performance improvement of fuzzy control systems (FCSs) for three tank systems using iterative feedback tuning (IFT). The stable design of Takagi–Sugeno–Kang fuzzy controllers is guaranteed by means of a stability theorem based on LaSalle’s global invariant set theorem formulated for a class of multi input-multi output (MIMO) nonlinear processes. An IFT algorithm characterized by setting the step size to guarantee the FCS stability is proposed. The theoretical approaches are applied in a case study that deals with the IFT-based stable design of fuzzy controllers dedicated to the level control of a cylindrical three tank system as a representative MIMO system. A set of experimental results for a laboratory setup illustrates the performance improvement.     

Ultrastructural changes in cartilage after intra-articular administration of osmium tetroxide and the sodium salts of fish oil fatty acids (Varicocid)

A clinical and experimental study was carried out on knee joints of rabbits and in humans. In one knee joint of each rabbit 0.3 ml 1% osmic acid or 0.3 ml 5% Varicocid was injected, the remaining uninjected joints serving as controls. The animals were killed after 1 and 24 hours, 15, 45 and 90 days. Study with the electron microscope after osmic acid injection revealed necrosis of the chondrocytes in the superficial layer and upper middle zone. The articulations injected with Varicocid exhibited only slight lesions of the chondrocytes in the upper layer, consisting of dilated rough endoplasmatic reticulum, mitochondria lacking matrix and christae; the electron density of the layer seemed to be diminished. Biopsy of the non-weight-bearing cartilage of the lateral femoral condyle was performed in 4 patients with Rheumatoid Arthritis and arthritis of the knee in the onset stage. Two of these patients received one intra-articular injection of 10 ml 1% osmic acid, 5 ml 2% xylocaine and 50 mg hydrocortisone and the other 2 patients 6 ml 5% Varicocid. Biopsy of the cartilage in the areas adjacent to the site of the first biopsies 1 and 3 1/2 months after treatment with osmic acid and 2 and 3 1/2 months after treatment with Varicocid showed in the first two cases necrosis of the chondrocytes in the superficial layer and upper middle zone of the articular cartilage and depletion of the mucopolysaccharides in the ground substance, revealed by PAS and alcian blue staining. No lesion of the knee joint cartilage was observed in the other two cases. In view of the results obtained, chemical synovectomy with Varicocid can be considered as having received further support.     

Sur les cycles élémentaires dans les graphes et hypergraphesk-chromatiques

Résumé Le but de ce travail est celui d'obtenir une borne inférieure de la longueur des plus longues cycles élémentaires pour un graphe ou un hypergraphe de nombre chromatique donné. Ainsi on démontre que tout graphe qui n'a pas (r+1)-cliques, de degré minimal ≥d (ou de nombre chromatiqued+1) contient un cycle élémentaire de longueur ≥rd/(r−1) et tout hypergrapheH de nombre chromatique χ(H)=k contient un cycle élémentaire de longueur ≥k. On obtient aussi que tout grapheG de nombre chromatique γ(G)=k≥3 qui n'a pas de triangles contient un cycle élémentaire de longueur ≥2k−1, résultat qui est généralisé sous la forme suivante: Si le grapheG de degré minimal ≥d est 2-connexe et ne contient pas de triangles, alorsG=K _d,d′ oùd′≥d, ouG contient un cycle élémentaire de longueur ≥2d+1. On déduit que tout grapheG avec γ(G)=k≥3, qui n'a pask-cliques contient un cycle élémentaire de longueur ≥k+2, cette borne étant atteinte.

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The aim of this paper is that to obtain a lower bound of the length of the longest elementary cycles of ak-chromatic graph or hypergraph. It is proved that any graph without (r+1)-cliques, having the minimal degree of its vertices ≥d (or the chromatic number equal tod+1) has an elementary cycle of length ≥rd/(r−1) and any hypergraphH of chromatic number χ(H)=k has an elementary cycle of length ≥k. It is obtained also that any graphG without triangles, having chromatic number γ(G)=k≥3 contains an elementary cycle of length ≥2k−1. This result is generalized in the following way: IfG is 2-connected, has minimal degree ≥d and contains no triangle, thenG=K _d,d′ withd′≥d orG has an elementary cycle of length ≥2d+1. It is derived that any graphG with γ(G)=k≥3 which does not containk-cliques has an elementary cycle of length ≥k+2, this bound being attained.

     

Design and Experiments for a Class of Fuzzy Controlled Servo Systems

This paper proposes a new fuzzy control solution employing 2-DOF proportional-integral-fuzzy controllers dedicated to a class of servo systems. The controlled plants in these systems, widely used in mechatronics applications, can be characterized by second-order dynamics with integral type. The original design method suggested here starts with linear design results in terms of the extended symmetrical optimum method accompanied by an iterative feedback tuning (IFT) algorithm. Next, these results are transferred to the fuzzy case by the modal equivalence principle. The convergence of the IFT algorithm is guaranteed by the derivation of sufficient global asymptotic stability conditions based on Krasovskii-LaSalle's invariant set theorem with quadratic Lyapunov function candidate. Real-time experimental results corresponding to a low-cost fuzzy controlled servo system validate the theoretical approaches.     

Digital metrics: A graph-theoretical approach

Consider the following two graphs M and N, both with vertex set Z × Z, where Z is the set of all integers. In M, two vertices are adjacent when their euclidean distance is 1, while in N, adjacency is obtained when the distance is either 1 or √2. By definition, H is a metric subgraph of the graph G if the distance between any two points of H is the same as their distance in G. We determine all the metric subgraphs of M and N. The graph-theoretical distances in M and N are equal respectively to the city block and chessboard matrics used in pattern recognition.     

Structural and sensing properties of a novel Fe/Fe2O3/polyoxocarbosilane core shell nanocomposite powder prepared by laser pyrolysis

This paper reports about the synthesis and characterization of a novel Fe/Fe₂O₃/polyoxocarbosilane core shell nanocomposite as a material for gas-sensing applications. The nanocomposites (Fe-based nano cores enveloped with polymeric polyoxocarbosilane shells) were prepared by the IR laser co-pyrolysis of iron pentacarbonyl and hexamethyldisiloxane. The iron-based cores become superficially oxidized in atmosphere. The morphologies, chemical content and thermal behavior were studied by different analytical techniques. The sensing properties of the polymer-poor nanocomposite thick films were tested by measuring the variation of the electrical resistance in presence of CO and CH₄, at a working temperature of 450 °C. Preliminary results indicate that for CO toxic gas, an n–p transitional character of the semiconducting iron oxide appears in humid relatively to dry air.     

Path generated digital metrics

A new class of metrics, called path-generated metrics, is defined for the digital plane. There are essentially five different metrics in the class, including the classical city block and chessboard metrics.     

Improved large-signal performance of paralleled DC-DC converterscurrent sharing

This paper introduces fuzzy logic control as a technique for significantly improving the large-signal performance of paralleled DC-DC power converters with master-slave current sharing control. The control design for such systems is challenged by its high modeling complexity, and present approaches which come only from a small-signal perspective unable to give a good response for wide load and line transients. The fuzzy logic approach, by dealing naturally with nonlinearities, offers a good and parameter-insensitive transient response for the current sharing loop. The design methodology of the fuzzy compensator, simulation results, and a comparison with existing classical designs are shown