• Article  

      Magnetohydrodynamic turbulence at moderate magnetic Reynolds number 

      Knaepen, B.; Kassinos, Stavros C.; Carati, D. (2004)
      We consider the case of homogeneous turbulence in a conducting fluid that is exposed to a uniform external magnetic field at low to moderate magnetic Reynolds numbers (by moderate we mean here values as high as 20). When ...
    • Article  

      A matrix decomposition MFS algorithm for biharmonic problems in annular domains 

      Tsangaris, T.; Smyrlis, Yiorgos-Sokratis; Karageorghis, Andreas (2004)
      The Method of Fundamental Solutions (MFS) is a boundary-type method for the solution of certain elliptic boundary value problems. In this work, we develop an efficient matrix decomposition MFS algorithm for the solution ...
    • Conference Object  

      Model reduction of modal representations 

      Louca, Loucas S.; Xydas, E. (American Society of Mechanical Engineers (ASME), 2006)
      Dynamic analysis is extensively used to study the behavior of continuous and lumped parameter linear systems. In addition to the physical space, analyses can also be performed in the modal space where useful frequency ...
    • Conference Object  

      Non-concurrent error detection and correction in discrete-time LTI dynamic systems 

      Hadjicostis, Christoforos N. (2001)
      In this paper we develop fault-tolerant constructions for discrete-time (DT) linear time-invariant (LTI) dynamic systems that are build out of appropriately interconnected delay, adder and gain elements. More specifically, ...
    • Conference Object  

      On optimal performance for linear time-varying systems 

      Djouadi, S. M.; Charalambous, Charalambos D. (2004)
      In this paper we consider the optimal disturbance attenuation problem and robustness for linear time-varying (LTV) systems. This problem corresponds to the standard optimal H ∞ problem for LTI systems. The problem is ...
    • Conference Object  

      Optimal state estimators for linear systems with unknown inputs 

      Sundaram, S.; Hadjicostis, Christoforos N. (2006)
      We present a method for constructing linear minimum-variance unbiased state estimators for discrete-time linear stochastic systems with unknown inputs. Our design provides a characterization of estimators with delay, which ...
    • Article  

      Partial state observers for linear systems with unknown inputs 

      Sundaram, S.; Hadjicostis, Christoforos N. (2008)
      We consider the problem of constructing partial state observers for discrete-time linear systems with unknown inputs. Specifically, for any given system, we develop a design procedure that characterizes the set of all ...
    • Article  

      Performance analysis for a changepoint problem 

      Hibey, J. L.; Charalambos, C. D. (1999)
      Nonlinear stochastic differential equations are used to model a version of the changepoint problem. State estimates of the minimum mean-square-error-type are used in likelihood-ratio tests to detect the time of change. ...
    • Conference Object  

      Performance of GMRES for the MFS 

      Karageorghis, Andreas; Smyrlis, Yiorgos-Sokratis (2009)
      In this work we present some preliminary numerical results regarding the performance of the Generalized Minimal Residual (GMRES) method when it is applied to the solution of the linear systems arising from the discretization ...
    • Article  

      Robust adaptive attenuation of unknown periodic disturbances in uncertain multi-input multi-output systems 

      Jafari, S.; Ioannou, Petros A. (2016)
      In high-performance high-accuracy systems, the attenuation of vibrational disturbances is essential. In this paper, we design and analyze a robust output-feedback adaptive control scheme to attenuate noise-corrupted ...
    • Conference Object  

      Robust control over uncertain communication channels 

      Charalambous, Charalambos D.; Farhadi, A.; Denic, S.; Rezaei, F. (2005)
      In this paper, the mathematical framework for studying robust control over uncertain communication channels is introduced. The theory is developed by generalizing the classical information theoretic measures of information ...
    • Article  

      Robustness of nonlinear control systems with respect to unmodeled dynamics 

      Zhang, Y.; Ioannou, Petros A. (1999)
      In theory, it can be established that nonlinear control laws for linear or nonlinear plants can be used to meet strict performance requirements. The success of these control designs in practical situations will very much ...
    • Conference Object  

      The singular function boundary integral method for Laplacian problems with boundary singularities in two and three-dimensions 

      Xenophontos, Christos A.; Christodoulou, Evgenia; Georgiou, Georgios C. (2010)
      We present a Singular Function Boundary Integral Method (SFBIM) for solving elliptic problems with a boundary singularity. In this method the solution is approximated by the leading terms of the asymptotic solution expansion, ...
    • Conference Object  

      Stability margins in adaptive mixing control via a Lyapunov-based switching criterion 

      Baldi, S.; Ioannou, Petros A. (2012)
      In all classes of linear adaptive control that involve switching or not there is no guarantee that after the switching stops or the adaptation is switched off the resulting closed loop linear time invariant system is stable ...
    • Article  

      Structural controllability and observability of linear systems over finite fields with applications to multi-agent systems 

      Sundaram, S.; Hadjicostis, Christoforos N. (2013)
      We develop a graph-theoretic characterization of controllability and observability of linear systems over finite fields. Specifically, we show that a linear system will be structurally controllable and observable over a ...
    • Article  

      The under-determined version of the MFS: Taking more sources than collocation points 

      Smyrlis, Yiorgos-Sokratis; Karageorghis, Andreas (2010)
      In this study we investigate the approximation of the solutions of certain elliptic boundary value problems by the Method of Fundamental Solutions (MFS). In particular, we study the case in which the number of singularities ...