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performance evaluation of evolutionary designed conventional AGC controllers for interconnected electric power system studies in a deregulated market environment
Y Karnavas, K Dedousis
International Journal of Engineering, Science and Technology , 2010,
Abstract: Electric power industry is currently in transition from vertically integrated utilities to an industry that will incorporate competitive companies. This increases the complexity of the load frequency issue and calls for more insight and research. In this context, the tuning of a multi-area automatic generation control (AGC) system after deregulation and furthermore, the effect of reheat turbines dynamics in the power system performance, are not yet discussed in depth and are studied in this work. The effect of bilateral contracts on the dynamics of the system is taken into account and the concept of DISCO participation matrix for these bilateral contracts is simulated. Genetic algorithms are adopted in order to obtain the optimal parameters of the load-frequency controllers as well as of the frequency biases of thermal systems with reheat turbines. Also, since the optimum parameter values of the classical AGC have been obtained in the literature by minimizing the popular integral of the squared errors criterion (ISE) only, an effort is made in this study to show that this criterion does not give always the best system performance especially in a deregulated environment. In this work, we investigate the optimum adjustment of the load frequency controllers using a set of performance indices which are various functions of error and time. In this way, someone can observe the various performances that such a kind of power system might have when a different performance index is used. It should be noted that to the extent of the authors' knowledge, this kind of optimization has not been done yet in the literature. The performances of the tuned two–area AGC system are obtained using appropriate Matlab/Simulink models. Finally, it is envisaged that the synthesis procedure highlighted in this paper could be of practical significance for tuning conventional AGC controllers for an interconnected thermal-electric power system in a deregulated environment.
MODELOS SOCIALES DE ALUMNOS DE DOCE A?OS DE LA ESCUELA PRIMARIA DE LA EDUCACIóN PúBLICA EN GRECIA
Karnavas,Vassilis; Tzani,María;
Byzantion nea hellás , 2011, DOI: 10.4067/S0718-84712011000100013
Abstract: the, mainly political, multiplex crisis which greece is going through during the last years, is also reflects, to our opinion, on the way the twelve year old students choose their social models. the following research is included in the area of early political socialization. the research concludes that greek students of that age choose their social models mainly from the entertainment industry, while politics and science are in a very low level among their preferences.
MODELOS SOCIALES DE ALUMNOS DE DOCE A OS DE LA ESCUELA PRIMARIA DE LA EDUCACIóN PúBLICA EN GRECIA SOCIAL MODELS OF TWELVE YEARS OLD STUDENTS OF THE PUBLIC PRIMARY SCHOOL IN GREECE
Vassilis Karnavas,María Tzani
Byzantion Nea Hellás , 2011,
Abstract: La multifacética crisis social que está sufriendo Grecia durante los últimos a os, se imprenta, según nuestra opinión, en la manera que los alumnos de doce a os optan por sus modelos sociales. La siguiente investigación se enmarca en el ámbito de la temprana socialización política. De los datos que se han coleccionado, se hace evidente que los alumnos griegos en esta edad recogen sus modelos sociales, principalmente, del mundo del espectáculo, mientras áreas como la política y la ciencia se encuentran en nivel bajo entre sus preferencias. The, mainly political, multiplex crisis which Greece is going through during the last years, is also reflects, to our opinion, on the way the twelve year old students choose their social models. The following research is included in the area of Early Political Socialization. The research concludes that Greek students of that age choose their social models mainly from the entertainment industry, while politics and science are in a very low level among their preferences.
Development of a Practical Low-Cost μC based Brushless DC Motor Controller using Proteus
Y. L. Karnavas,Ch. L. Liagkos
International Journal of Electronics and Computer Science Engineering , 2012,
Abstract: Simulation, design and prototype construction of a low cost three phase permanent magnet (PM) brushless DC (BLDC) motor controller for low power applications is studied in this paper. The drive circuitry is based on the PIC16F877A microcontroller (μC), which –among others- performs pulse width modulation (PWM) control for a 6-step, 120-degree trapezoidal PM BLDC motor drive. The specific processor is a widely used one and its characteristics are judged excellent in conjunction with its low cost. The prototype controller developed can perform rotation direction control, commutation sequence, speed control and reading Hall sensor signals. The controlling technique chosen is a “sensored type” one. The main reason for that, except control simplicity is the need for both low-speed and high-speed applications. The application of Proteus Virtual System Modelling (VSM) software is also introduced in the paper. This software is used as a real-time simulation tool, in order to verify the performance of the BLDC motor drive, prior to its hardware implementation. Through virtual simulation of all the components used, the relevant results can be analyzed and monitored. Verification of the experimental results and validation of the simulated circuit has been done through the comparison of the results.
Histone content increases in differentiating embryonic stem cells
Theodoros Karnavas,Alessandra Agresti,Marco E. Bianchi
Frontiers in Physiology , 2014, DOI: 10.3389/fphys.2014.00330
Abstract: Mouse Embryonic Stem Cells (ESCs) are pluripotent mammalian cells derived from the Inner Cell Mass (ICM) of mouse blastocysts, which give rise to all three embryonic germ layers both in vivo and in vitro. Mouse ESCs have a distinct epigenetic landscape and a more decondensed chromatin compared to differentiated cells. Numerous studies have shown that distinct histone modifications in ESCs serve as hallmarks of pluripotency. However, so far it is still unknown whether the total histone content (as opposed to histone modifications) remains the same in cells of different developmental stage and differentiation capacity. In this work we show that total histone content differs between pluripotent and differentiated cells. In vitro spontaneous differentiation from ESCs to Embryoid Bodies (EBs) and directed differentiation toward neuronal and endodermal cells entails an increase in histone content. Primary MEFs also contain more histones than ESCs. We suggest that the difference in histone content is an additional hallmark of pluripotency, in addition to and besides histone modifications.
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