**2011 (Volume 21)**Number 2

**Robust linear predictor as EEG fluctuation analyzer in diagnosis of Alzheimer's disease**D. Zachova, J. Kukal
*(FNSPE, CTU in Prague, Czech Rep.)* | O. Vysata
*(NEUROPS Ltd., Rychnov nad Kneznou, Czech Rep.)* |

The paper is oriented to EEG signal analysis, which is focused to quasi-stationarity hypothesis that the statistical properties of the channel signal fluctuate in time. Robust linear predictor is used for short segments of EEG as low-pass filter and the difference between the raw EEG and filter output was subject of statistical testing. Novelty is in the fluctuation measurement which enables to classify the Alzheimer's disease patients against controls.

**keywords:** Alzheimer’s disease, EEG, quasi-stationarity, linear predictor, robust identification

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**Spatial evolutionary games and radiation induced bystander effect**M. Krzeslak, A. Swierniak
*(Silesian University of Technology, Gliwice, Poland)* |

We present an application of evolutionary game theory to modeling of some processes important from oncological point of view. A studied phenomenon is a radiation induced bystander effect, in which three different strategies (phenotypes) of cells take part. The proposed payoff table of fitness, related to environment adaptation and genetic cell behavior, contains costs/profits of bystander effect, choice of apoptotic pathway, producing growth factors and resistance against bystander effect. We consider a game theory model including spatial cells allocation (the game is played on lattice). We discuss also different polymorphic equilibrium points dependent on model parameters, types of spatial games and players distribution.

**keywords:** evolutionary games, bystander effect, biomathematical modeling, cellular automata, cancer

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**Evaluation of maximum power point tracking methods for photovoltaic systems**A. Talha, H. Boumaaraf
*(University of Sciences and Technology Houari Boumediene, Algeria)* | O. Bouhali
*(Jijel University, Algeria)* |

The output characteristics of photovoltaic (PV) arrays are nonlinear and change with the solar irradiance and the cell's temperature. Therefore, a maximum power point tracking (MPPT) technique is needed to draw peak power from the solar array to maximize the produced energy. Among the hill climbing methods, the perturb and observe (P\&O) method tracks the maximum power point (MPP) by repeatedly increasing or decreasing the output voltage at the MPP of the PV module. The implementation of the method is relatively simple, but it cannot track the MPP when the irradiance varies quickly with time. In addition, it may cause system oscillation around the peak power points due to the effect of measurement noise. The incremental conductance (IncCond) method is also often used in PV systems. This method tracks the MPPs by comparing the incremental and instantaneous conductances of the solar array. This method requires longer conversion time, and a large amount of power loss results. In addition, extra hardware circuity is required to implement the system. In this paper, it is shown that the negative effects associated with such a drawback can be greatly reduced if the intelligent method is used to improve P&O and IncCond algorithms. The perturbation step is continuously approximated by using fuzzy logic controller (FLC). By the digital simulation, the validity of the proposed control algorithm is proved.

**keywords:** maximum power point tracking, PV, P&O, incremental conductance, fuzzy logic, converter

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**Positive stable realizations with system Metzler matrices**T. Kaczorek
*(Bialystok University of Technology, Poland)* |

Conditions for the existence of positive stable realizations with system Metzler matrices for linear continuous-time systems are established. A procedure for finding a positive stable realization with system Metzler matrix based on similarity transformation of proper transfer matrices is proposed and demonstrated on numerical examples. It is shown that if the poles of stable transfer matrix are real then the classical Gilbert method can be used to find the positive stable realization.

**keywords:** positive stable realization, system Metzler matrix, linear continuous-time systems

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**Self-tuning run-time reconfigurable PID controller**M. Pelc
*(Opole University of Technology, Poland)* |

Digital PID control algorithm is one of the most commonly used algorithms in the control systems area. This algorithm is very well known, it is simple, easily implementable in the computer control systems and most of all its operation is very predictable. Thus PID control has got well known impact on the control system behavior. However, in its simple form the controller have no reconfiguration support. In a case of the controlled system substantial changes (or the whole control environment, in the wider aspect, for example if the disturbances characteristics would change) it is not possible to make the PID controller robust enough. In this paper a new structure of digital PID controller is proposed, where the policy-based computing is used to equip the controller with the ability to adjust it's behavior according to the environmental changes. Application to the electro-oil evaporator which is a part of distillation installation is used to show the new controller structure in operation.

**keywords:** policy-based computing, reconfigurable systems, PID controller

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**Efficient face recognition based on weighted matrix distance metrics and 2DPCA algorithm**C. Rouabhia, H. Tebbikh
*(University 8 mai 45 de Guelma, Algeria)* |

In this paper, a new similarity measure is developed for human face recognition, namely, weighted matrix distance. The key difference between this metric and the standard distances is the use of matrices and weights rather than the vectors only. The two feature matrices are obtained by two-dimensional principal component analysis (2DPCA). The weights are the inverse of the eigenvalues sorted in decreasing order of the covariance matrix of all training face matrices. Experiments are performed under illumination and facial expression variations using four face image databases: ORL, Yale, PF01 and a subset of FERET. The results demonstrate the effectiveness of the proposed weighted matrix distances in 2DPCA face recognition over the standard matrix distance metrics: Yang, Frobenius and assembled matrix distance (AMD).

**keywords:** classification, similarity measure, two-dimensional PCA, weighted matrix distance, human face

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