Maria Livada - Academia.edu (original) (raw)

Papers by Maria Livada

The thesis deals with aspects of Systems Re-engineering specialised to the case of passive electr... more The thesis deals with aspects of Systems Re-engineering specialised to the case of passive electrical networks. Re-engineering is a problem different from traditional control problems and this emerges when it is realised that the systems designed in the past cannot perform according to the new performance requirements and such performance cannot be improved by traditional control activities. Re-engineering implies that we intervene in early stages of system design involving sub-processes, values of physical elements, interconnection topology, selection of systems of inputs and outputs and of course retuning of control structures. This is a very challenging problem which has not been addressed before in a systematic way and needs fundamental new thinking, based on understanding of structure evolution during the stages of integrated design. A major challenge in the study of this problem is to have a system representation that allows study of evolution of system properties as well as s...

Redesigning systems by changing elements, topology, organization, augmenting the system by the ad... more Redesigning systems by changing elements, topology, organization, augmenting the system by the addition of subsystems, or removing parts, is a major challenge for systems and control theory. A special case is the redesign of passive electric networks which aims to change the natural dynamics of the network (natural frequencies) by the above operations leading to a modification of the network. This requires changing the system to achieve the desirable natural frequencies and involves the selection of alternative values for dynamic elements and non-dynamic elements within a fixed interconnection topology and/or alteration of the interconnection topology and possible evolution of the network (increase of elements, branches). The use of state-space or transfer function models does not provide a suitable framework for the study of this problem, since every time such changes are introduced, a new state space or transfer function model has to be recalculated. The use of impedance and admit...

IFAC-PapersOnLine, 2021

Abstract Early stages modelling of processes involves issues of classification of variables into ... more Abstract Early stages modelling of processes involves issues of classification of variables into inputs, outputs and internal variables, referred to as Model Orientation Problem (MOP) which may be addressed on state space implicit, or matrix pencil descriptions. Defining orientation is equivalent to producing state space models of the regular or singular type. In this paper we consider autonomous differential descriptions defined by matrix pencils and then search for strict equivalence transformations which introduce the partitioning of the implicit vector into states and possible inputs and outputs, referred to as system orientation. The Kronecker invariant structure of the matrix pencil description is shown to be central to the solution of system orientation and this is expressed as a problem of classification and partitioning of the Kronecker invariants. It is shown that the types of Kronecker invariants characterise the nature of the system orientation solutions. Studying the conditions, under which such oriented models may be derived, as well as their structural properties in terms of the Kronecker structure, is the issue considered here.

Springer Optimization and Its Applications, 2020

Presented study aimed to assess wastewater treatment installation using near infrared technology.... more Presented study aimed to assess wastewater treatment installation using near infrared technology. Wastewater samples obtained in eight different districts in Aceh Province and spectral data were acquired in wavenumbers range from 4,000-10,000 cm-1. On the other hand, actual nitrogen, phosphor and potassium contents were measured using standard laboratory procedures. Spectra data were corrected by applying average smoothing algorithm. The wastewater quality was assessed by constructing prediction models using partial least square regression approach. The results showed that all chemical properties can be determined rapidly and simultaneously with maximum coefficient of determination are: 0.85 for nitrogen, 0.93 for phosphor, and 0.94 for potassium content prediction respectively. Spectra data using average smoothing algorithm found to be more accurate and robust for determining those three quality parameters. Based on obtained performances, it may conclude that near infrared technology was feasible to assess wastewater quality parameters rapidly and without direct contact with the samples.

Ο σκοπός της διπλωματικής εργασίας ήταν η ανάπτυξη της μεθοδολογίας υπολογισμού της ωριαίας ακτιν... more Ο σκοπός της διπλωματικής εργασίας ήταν η ανάπτυξη της μεθοδολογίας υπολογισμού της ωριαίας ακτινοβολίας που προσπίπτει στην επιφάνεια ενός κεκλιμένου συλλέκτη σε οποιαδήποτε κλίση και τυχαίο προσανατολισμό λαμβανομένων υπόψιν και τυχόν σκιάσεων από φυσικά εμπόδια. Το δεύτερο μέρος της εργασίας περιλαμβάνει εφαρμογή των παραπάνω σε κτίριο γραφείων στον Ταύρο. Αναπτύχθηκαν δύο μοντέλα υπολογισμού. Το πρώτο μοντέλο υπολογίζει την μέση ωριαία ακτινοβολία κεκλιμένου συλλέκτη για την αντιπροσωπευτική μέρα του μήνα. Η βάση δεδομένων για την υλοποίηση αυτού του μοντέλου προήλθε από την Εθνική Μετεωρολογική υπητεσία. Το δεύτερο μοντέλο υπολογίζει την ωριαία ακτινοβολία κεκλιμένου συλλέκτη για κάθε μέτα του μήνα. Η βάση δεδομένων που χρησιμοποιήθηκε ήταν του Εθνικού Μετσόβιου Πολυτεχνείου. Στην συνέχεια αυτά τα δύο μοντέλα συγκρίθηκαν με στατιστικούς ελέγχους για να διαπιστωθεί αν τα αποτελέσματα διαφέρουν σημαντικά ή όχι. Τα αποτελέσματα από το μοντέλο που θεωρήθηκε πιο αξιόπιστο χρησιμοποι...

IFAC-PapersOnLine, 2016

Creative Commons Legal Code AttributionNonCommercialNoDerivatives 4.0 International Official tran... more Creative Commons Legal Code AttributionNonCommercialNoDerivatives 4.0 International Official translations of this license are available in other languages. Creative Commons Corporation ("Creative Commons") is not a law firm and does not provide legal services or legal advice. Distribution of Creative Commons public licenses does not create a lawyer client or other relationship. Creative Commons makes its licenses and related information available on an "asis" basis. Creative Commons gives no warranties regarding its licenses, any material licensed under their terms and conditions, or any related information. Creative Commons disclaims all liability for damages resulting from their use to the fullest extent possible. Using Creative Commons Public Licenses Creative Commons public licenses provide a standard set of terms and conditions that creators and other rights holders may use to share original works of authorship and other material subject to copyright and certain other rights specified in the public license below. The following considerations are for informational purposes only, are not exhaustive, and do not form part of our licenses.

22nd Mediterranean Conference on Control and Automation, 2014

Multi-parameter structural transformations of passive electrical networks and natural frequency a... more Multi-parameter structural transformations of passive electrical networks and natural frequency assignment. In: 22nd Mediterranean Conference of Control and Automation (MED). (pp. 984-989). IEEE. ISBN 9781479959006 This is the accepted version of the paper. This version of the publication may differ from the final published version.

2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2014

Circuits, Systems, and Signal Processing, 2018

The McMillan degree of an implicit network transfer function defines the minimum number of dynami... more The McMillan degree of an implicit network transfer function defines the minimum number of dynamic elements which are necessary to fully describe the network. It is therefore a measure for the complexity of a network. Using modified nodal analysis models, which are linked directly to the natural network topology, we show that the McMillan degree equals the sum of the number of capacitors and inductors minus the number of fundamental loops of capacitors and fundamental cutsets of inductors. Exploiting this representation we derive a minimal realization of a RLC network, that is one where the number of involved (independent) differential equations equals the McMillan degree.

We utilize systems theory in the study of the implementation of non pharmaceutical strategies for... more We utilize systems theory in the study of the implementation of non pharmaceutical strategies for the mitigation of the COVID-19 pandemic. We present two models. The first one is a model of predictive control with receding horizon and discontinuous actions of unknown costs for the implementation of adaptive triggering policies during the disease. This model is based on a periodic assessment of the peak of the pandemic (and, thus, of the health care demand) utilizing the latest data about the transmission and recovery rate of the disease. Consequently, the model seems to be suitable for discontinuous, non-mechanical (i.e. human) actions with unknown effectiveness, like those applied in the case of COVID-19. Secondly, we consider a feedback control problem in order to contain the pandemic at the capacity of the NHS (National Health System). As input parameter we consider the value \begin{document}$ p $\end{document} that reflects the intensity-effectiveness of the measures applied and...

J. Optim. Theory Appl., 2021

Structural Methods in the Study of Complex Systems

IEEE Transactions on Automatic Control

2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2014

ABSTRACT The paper examines the problem of systems redesign within the context of passive electri... more ABSTRACT The paper examines the problem of systems redesign within the context of passive electrical networks by considering the problem of multi-parameter and topology changes, and their representation. This representation may be used to investigate the impact of such changes on properties such as characteristic frequencies. The general problem area is the modelling of systems, whose structure is not fixed but evolves during the system life-cycle. The specific problem we are addressing is the study of effect of changing the topology of an electrical network that is changing individual elements of the network into elements of different type and value, augmenting / or eliminating parts of the network and developing a framework that allows the study of the effect of such transformations on the natural frequencies. This problem is a special case of the more general network redesign problem. We use the Impedance-Admittance models and we establish a representation of the different types of transformations on such models. The representation of the structural transformations is given in terms of the companion pencil that preserves the natural topologies of the RLC network.

The thesis deals with aspects of Systems Re-engineering specialised to the case of passive electr... more The thesis deals with aspects of Systems Re-engineering specialised to the case of passive electrical networks. Re-engineering is a problem different from traditional control problems and this emerges when it is realised that the systems designed in the past cannot perform according to the new performance requirements and such performance cannot be improved by traditional control activities. Re-engineering implies that we intervene in early stages of system design involving sub-processes, values of physical elements, interconnection topology, selection of systems of inputs and outputs and of course retuning of control structures. This is a very challenging problem which has not been addressed before in a systematic way and needs fundamental new thinking, based on understanding of structure evolution during the stages of integrated design. A major challenge in the study of this problem is to have a system representation that allows study of evolution of system properties as well as s...

Redesigning systems by changing elements, topology, organization, augmenting the system by the ad... more Redesigning systems by changing elements, topology, organization, augmenting the system by the addition of subsystems, or removing parts, is a major challenge for systems and control theory. A special case is the redesign of passive electric networks which aims to change the natural dynamics of the network (natural frequencies) by the above operations leading to a modification of the network. This requires changing the system to achieve the desirable natural frequencies and involves the selection of alternative values for dynamic elements and non-dynamic elements within a fixed interconnection topology and/or alteration of the interconnection topology and possible evolution of the network (increase of elements, branches). The use of state-space or transfer function models does not provide a suitable framework for the study of this problem, since every time such changes are introduced, a new state space or transfer function model has to be recalculated. The use of impedance and admit...

IFAC-PapersOnLine, 2021

Abstract Early stages modelling of processes involves issues of classification of variables into ... more Abstract Early stages modelling of processes involves issues of classification of variables into inputs, outputs and internal variables, referred to as Model Orientation Problem (MOP) which may be addressed on state space implicit, or matrix pencil descriptions. Defining orientation is equivalent to producing state space models of the regular or singular type. In this paper we consider autonomous differential descriptions defined by matrix pencils and then search for strict equivalence transformations which introduce the partitioning of the implicit vector into states and possible inputs and outputs, referred to as system orientation. The Kronecker invariant structure of the matrix pencil description is shown to be central to the solution of system orientation and this is expressed as a problem of classification and partitioning of the Kronecker invariants. It is shown that the types of Kronecker invariants characterise the nature of the system orientation solutions. Studying the conditions, under which such oriented models may be derived, as well as their structural properties in terms of the Kronecker structure, is the issue considered here.

Springer Optimization and Its Applications, 2020

Presented study aimed to assess wastewater treatment installation using near infrared technology.... more Presented study aimed to assess wastewater treatment installation using near infrared technology. Wastewater samples obtained in eight different districts in Aceh Province and spectral data were acquired in wavenumbers range from 4,000-10,000 cm-1. On the other hand, actual nitrogen, phosphor and potassium contents were measured using standard laboratory procedures. Spectra data were corrected by applying average smoothing algorithm. The wastewater quality was assessed by constructing prediction models using partial least square regression approach. The results showed that all chemical properties can be determined rapidly and simultaneously with maximum coefficient of determination are: 0.85 for nitrogen, 0.93 for phosphor, and 0.94 for potassium content prediction respectively. Spectra data using average smoothing algorithm found to be more accurate and robust for determining those three quality parameters. Based on obtained performances, it may conclude that near infrared technology was feasible to assess wastewater quality parameters rapidly and without direct contact with the samples.

Ο σκοπός της διπλωματικής εργασίας ήταν η ανάπτυξη της μεθοδολογίας υπολογισμού της ωριαίας ακτιν... more Ο σκοπός της διπλωματικής εργασίας ήταν η ανάπτυξη της μεθοδολογίας υπολογισμού της ωριαίας ακτινοβολίας που προσπίπτει στην επιφάνεια ενός κεκλιμένου συλλέκτη σε οποιαδήποτε κλίση και τυχαίο προσανατολισμό λαμβανομένων υπόψιν και τυχόν σκιάσεων από φυσικά εμπόδια. Το δεύτερο μέρος της εργασίας περιλαμβάνει εφαρμογή των παραπάνω σε κτίριο γραφείων στον Ταύρο. Αναπτύχθηκαν δύο μοντέλα υπολογισμού. Το πρώτο μοντέλο υπολογίζει την μέση ωριαία ακτινοβολία κεκλιμένου συλλέκτη για την αντιπροσωπευτική μέρα του μήνα. Η βάση δεδομένων για την υλοποίηση αυτού του μοντέλου προήλθε από την Εθνική Μετεωρολογική υπητεσία. Το δεύτερο μοντέλο υπολογίζει την ωριαία ακτινοβολία κεκλιμένου συλλέκτη για κάθε μέτα του μήνα. Η βάση δεδομένων που χρησιμοποιήθηκε ήταν του Εθνικού Μετσόβιου Πολυτεχνείου. Στην συνέχεια αυτά τα δύο μοντέλα συγκρίθηκαν με στατιστικούς ελέγχους για να διαπιστωθεί αν τα αποτελέσματα διαφέρουν σημαντικά ή όχι. Τα αποτελέσματα από το μοντέλο που θεωρήθηκε πιο αξιόπιστο χρησιμοποι...

IFAC-PapersOnLine, 2016

Creative Commons Legal Code AttributionNonCommercialNoDerivatives 4.0 International Official tran... more Creative Commons Legal Code AttributionNonCommercialNoDerivatives 4.0 International Official translations of this license are available in other languages. Creative Commons Corporation ("Creative Commons") is not a law firm and does not provide legal services or legal advice. Distribution of Creative Commons public licenses does not create a lawyer client or other relationship. Creative Commons makes its licenses and related information available on an "asis" basis. Creative Commons gives no warranties regarding its licenses, any material licensed under their terms and conditions, or any related information. Creative Commons disclaims all liability for damages resulting from their use to the fullest extent possible. Using Creative Commons Public Licenses Creative Commons public licenses provide a standard set of terms and conditions that creators and other rights holders may use to share original works of authorship and other material subject to copyright and certain other rights specified in the public license below. The following considerations are for informational purposes only, are not exhaustive, and do not form part of our licenses.

22nd Mediterranean Conference on Control and Automation, 2014

Multi-parameter structural transformations of passive electrical networks and natural frequency a... more Multi-parameter structural transformations of passive electrical networks and natural frequency assignment. In: 22nd Mediterranean Conference of Control and Automation (MED). (pp. 984-989). IEEE. ISBN 9781479959006 This is the accepted version of the paper. This version of the publication may differ from the final published version.

2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2014

Circuits, Systems, and Signal Processing, 2018

The McMillan degree of an implicit network transfer function defines the minimum number of dynami... more The McMillan degree of an implicit network transfer function defines the minimum number of dynamic elements which are necessary to fully describe the network. It is therefore a measure for the complexity of a network. Using modified nodal analysis models, which are linked directly to the natural network topology, we show that the McMillan degree equals the sum of the number of capacitors and inductors minus the number of fundamental loops of capacitors and fundamental cutsets of inductors. Exploiting this representation we derive a minimal realization of a RLC network, that is one where the number of involved (independent) differential equations equals the McMillan degree.

We utilize systems theory in the study of the implementation of non pharmaceutical strategies for... more We utilize systems theory in the study of the implementation of non pharmaceutical strategies for the mitigation of the COVID-19 pandemic. We present two models. The first one is a model of predictive control with receding horizon and discontinuous actions of unknown costs for the implementation of adaptive triggering policies during the disease. This model is based on a periodic assessment of the peak of the pandemic (and, thus, of the health care demand) utilizing the latest data about the transmission and recovery rate of the disease. Consequently, the model seems to be suitable for discontinuous, non-mechanical (i.e. human) actions with unknown effectiveness, like those applied in the case of COVID-19. Secondly, we consider a feedback control problem in order to contain the pandemic at the capacity of the NHS (National Health System). As input parameter we consider the value \begin{document}$ p $\end{document} that reflects the intensity-effectiveness of the measures applied and...

J. Optim. Theory Appl., 2021

Structural Methods in the Study of Complex Systems

IEEE Transactions on Automatic Control

2014 6th International Symposium on Communications, Control and Signal Processing (ISCCSP), 2014

ABSTRACT The paper examines the problem of systems redesign within the context of passive electri... more ABSTRACT The paper examines the problem of systems redesign within the context of passive electrical networks by considering the problem of multi-parameter and topology changes, and their representation. This representation may be used to investigate the impact of such changes on properties such as characteristic frequencies. The general problem area is the modelling of systems, whose structure is not fixed but evolves during the system life-cycle. The specific problem we are addressing is the study of effect of changing the topology of an electrical network that is changing individual elements of the network into elements of different type and value, augmenting / or eliminating parts of the network and developing a framework that allows the study of the effect of such transformations on the natural frequencies. This problem is a special case of the more general network redesign problem. We use the Impedance-Admittance models and we establish a representation of the different types of transformations on such models. The representation of the structural transformations is given in terms of the companion pencil that preserves the natural topologies of the RLC network.