The Experts below are selected from a list of 26031 Experts worldwide ranked by ideXlab platform
Photios A Stavrou - One of the best experts on this subject based on the ideXlab platform.
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optimization of directed information and relations to Filtering Theory
2014Co-Authors: Charalambos D. Charalambous, Photios A StavrouAbstract:In this paper we generalize the relation between nonanticipative Rate Distortion Function (RDF) and Filtering Theory, to processes which are affected by the reproduction process, by utilizing the topology of weak convergence of probability measures. Specifically, this generalization is established via an optimization on the space of conditional distributions of the so-called directed information, subject to a fidelity constraint. Existence of the optimal reproduction distribution of the general nonanticipative RDF is shown, while the closed form expression of the optimal reproduction distribution is obtained for nonstationary processes. The expression of the optimal reproduction conditional distribution is recursively computed, backward in time. Finally, the realization procedure of the general nonanticipative RDF which is equivalent to joint-source channel matching for symbol-by-symbol transmission is described.
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on the relation of nonanticipative rate distortion function and Filtering Theory
2013Co-Authors: Charalambos D. Charalambous, Photios A StavrouAbstract:In this paper the relation between nonanticipative rate distortion function (RDF) and Bayesian Filtering Theory is investigated using the topology of weak convergence of probability measures on Polish spaces. The relation is established via an optimization on the space of conditional distributions of the so-called directed information subject to fidelity constraints. Existence of the optimal reproduction distribution of the nonanticipative RDF is shown, while the optimal nonanticipative reproduction conditional distribution for stationary processes is derived in closed form. The realization procedure of nonanticipative RDF which is equivalent to joint-source channel matching for symbol-by-symbol transmission is described, while an example is introduced to illustrate the concepts.
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nonanticipative rate distortion function and Filtering Theory a weak convergence approach
2012Co-Authors: Photios A Stavrou, Charalambos D. CharalambousAbstract:In this paper the relation between nonanticipative rate distortion function (RDF) and Bayesian Filtering Theory is further investigated on general Polish spaces. The relation is established via an optimization on the space of conditional distributions of the so-called directed information subject to fidelity constraints. Existence of the optimal reproduction distribution of the nonanticipative RDF is shown using the topology of weak convergence of probability measures. Subsequently, we use the solution of the nonanticipative RDF to present the realization of a multidimensional partially observable source over a scalar Gaussian channel. We show that linear encoders are optimal, establishing joint source-channel coding in real-time.
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nonanticipative rate distortion function and relations to Filtering Theory
2012Co-Authors: Charalambos D. Charalambous, Photios A Stavrou, N U AhmedAbstract:The relation between nonanticipative Rate Distortion Function (RDF) and Filtering Theory is discussed on abstract spaces. The relation is established by imposing a realizability constraint on the reconstruction conditional distribution of the classical RDF. Existence of the extremum solution of the nonanticipative RDF is shown using weak$^*$-convergence on appropriate topology. The extremum reconstruction conditional distribution is derived in closed form, for the case of stationary processes. The realization of the reconstruction conditional distribution which achieves the infimum of the nonanticipative RDF is described. Finally, an example is presented to illustrate the concepts.
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realizable rate distortion function and bayesian Filtering Theory
2012Co-Authors: Photios A Stavrou, Charalambos D. Charalambous, Christos K KourtellarisAbstract:The relation between rate distortion function (RDF) and Bayesian Filtering Theory is discussed. The relation is established by imposing a causal or realizability constraint on the reconstruction conditional distribution of the RDF, leading to the definition of a causal RDF. Existence of the optimal reconstruction distribution of the causal RDF is shown using the topology of weak convergence of probability measures. The optimal non-stationary causal reproduction conditional distribution of the causal RDF is derived in closed form; it is given by a set of recursive equations which are computed backward in time. The realization of causal RDF is described via the source-channel matching approach, while an example is briefly discussed to illustrate the concepts.
Massimo Ruzzene - One of the best experts on this subject based on the ideXlab platform.
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time periodic stiffness modulation in elastic metamaterials for selective wave Filtering Theory and experiment
2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Yiwei Xia, Massimo RuzzeneAbstract:Elastic waveguides with time-modulated stiffness feature a frequency-periodic dispersion spectrum, where branches merge at multiple integers of half the modulation frequency and over a finite wave number range. In this range, frequency becomes complex, with its real part remaining constant. The vanishing group velocity associated with these flat bands leads to frequency-selective reflection at an interface between a nonmodulated medium and a time-modulated one, which converts a broadband input into a narrow-band output centered at the half modulation frequency. This behavior is illustrated in an elastic waveguide in transverse motion, where modulation is implemented experimentally by an array of piezoelectric patches shunted through a negative electrical capacitance controlled by a switching circuit. The switching schedule defines the modulation frequency and allows the selection of the output frequency. This implementation is suitable for the investigation of numerous properties of time-space modulated elastic metamaterials, such as nonreciprocity and one-way propagation, and can lead to the implementation of novel functionalities for acoustic wave devices operating on piezoelectric substrates.
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time periodic stiffness modulation in elastic metamaterials for selective wave Filtering Theory and experiment
2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Massimo RuzzeneAbstract:We report on broadband-to-narrowband elastic wave Filtering resulting from time-periodic modulation of the stiffness of a one-dimensional elastic waveguide. Time modulation produces flat dispersion bands at frequencies that are multiple integers of half the modulation frequency. These flat bands lead to the selective reflection of a broadband incident wave at the interface between a non-modulated medium, and one with time-modulated stiffness properties. This results from the vanishing group velocity at the flat band frequencies, which prevents their propagation into the modulated domain. Thus, the considered modulated waveguide is understood as a single port system, in which a broadband incident wave (input) results in a narrowband reflected wave (output) at a frequency defined by modulation. The appearance of the flat bands for a time-modulated waveguide is here illustrated analytically and through numerical simulations. The Filtering characteristics of a non-modulate/modulated interface are observed experimentally by implementing a square-wave modulation scheme that employs an array of piezoelectric patches bonded to an elastic waveguide subject to transverse motion. The patches are shunted through a negative electrical capaticance that, when connected, implements a stiffness reduction for the resulting electromechanical waveguide. Switching the capacitance on and off effectively modulates the stiffness of the waveguide, and illustrates the Filtering characteristics associated with time-modulation of the equivalent elastic properties. We envision that a similar approach could be extended to investigate other properties of time-modulated elastic metamaterials, such as non-reciprocity and one-way Filtering of elastic waves.
Charalambos D. Charalambous - One of the best experts on this subject based on the ideXlab platform.
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optimization of directed information and relations to Filtering Theory
2014Co-Authors: Charalambos D. Charalambous, Photios A StavrouAbstract:In this paper we generalize the relation between nonanticipative Rate Distortion Function (RDF) and Filtering Theory, to processes which are affected by the reproduction process, by utilizing the topology of weak convergence of probability measures. Specifically, this generalization is established via an optimization on the space of conditional distributions of the so-called directed information, subject to a fidelity constraint. Existence of the optimal reproduction distribution of the general nonanticipative RDF is shown, while the closed form expression of the optimal reproduction distribution is obtained for nonstationary processes. The expression of the optimal reproduction conditional distribution is recursively computed, backward in time. Finally, the realization procedure of the general nonanticipative RDF which is equivalent to joint-source channel matching for symbol-by-symbol transmission is described.
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on the relation of nonanticipative rate distortion function and Filtering Theory
2013Co-Authors: Charalambos D. Charalambous, Photios A StavrouAbstract:In this paper the relation between nonanticipative rate distortion function (RDF) and Bayesian Filtering Theory is investigated using the topology of weak convergence of probability measures on Polish spaces. The relation is established via an optimization on the space of conditional distributions of the so-called directed information subject to fidelity constraints. Existence of the optimal reproduction distribution of the nonanticipative RDF is shown, while the optimal nonanticipative reproduction conditional distribution for stationary processes is derived in closed form. The realization procedure of nonanticipative RDF which is equivalent to joint-source channel matching for symbol-by-symbol transmission is described, while an example is introduced to illustrate the concepts.
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nonanticipative rate distortion function and Filtering Theory a weak convergence approach
2012Co-Authors: Photios A Stavrou, Charalambos D. CharalambousAbstract:In this paper the relation between nonanticipative rate distortion function (RDF) and Bayesian Filtering Theory is further investigated on general Polish spaces. The relation is established via an optimization on the space of conditional distributions of the so-called directed information subject to fidelity constraints. Existence of the optimal reproduction distribution of the nonanticipative RDF is shown using the topology of weak convergence of probability measures. Subsequently, we use the solution of the nonanticipative RDF to present the realization of a multidimensional partially observable source over a scalar Gaussian channel. We show that linear encoders are optimal, establishing joint source-channel coding in real-time.
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nonanticipative rate distortion function and relations to Filtering Theory
2012Co-Authors: Charalambos D. Charalambous, Photios A Stavrou, N U AhmedAbstract:The relation between nonanticipative Rate Distortion Function (RDF) and Filtering Theory is discussed on abstract spaces. The relation is established by imposing a realizability constraint on the reconstruction conditional distribution of the classical RDF. Existence of the extremum solution of the nonanticipative RDF is shown using weak$^*$-convergence on appropriate topology. The extremum reconstruction conditional distribution is derived in closed form, for the case of stationary processes. The realization of the reconstruction conditional distribution which achieves the infimum of the nonanticipative RDF is described. Finally, an example is presented to illustrate the concepts.
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realizable rate distortion function and bayesian Filtering Theory
2012Co-Authors: Photios A Stavrou, Charalambos D. Charalambous, Christos K KourtellarisAbstract:The relation between rate distortion function (RDF) and Bayesian Filtering Theory is discussed. The relation is established by imposing a causal or realizability constraint on the reconstruction conditional distribution of the RDF, leading to the definition of a causal RDF. Existence of the optimal reconstruction distribution of the causal RDF is shown using the topology of weak convergence of probability measures. The optimal non-stationary causal reproduction conditional distribution of the causal RDF is derived in closed form; it is given by a set of recursive equations which are computed backward in time. The realization of causal RDF is described via the source-channel matching approach, while an example is briefly discussed to illustrate the concepts.
Chengshang Chang - One of the best experts on this subject based on the ideXlab platform.
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a time varying Filtering Theory for constrained traffic regulation and dynamic service guarantees
1999Co-Authors: Chengshang Chang, R L CruzAbstract:By extending the Filtering Theory under the (min, +)-algebra to the time varying setting, we solve the problem of constrained traffic regulation and develop a calculus for dynamic service guarantees. For a constrained traffic regulation problem with maximum tolerable delay d and maximum buffer size q, the optimal regulator that generates the output traffic conforming to a subadditive envelope f and minimizes the number of discarded packets is a concatenation of the g-clipper with g(t)=min[f(t+d), f(t)+q] and the maximal f-regulator. The g-clipper is a bufferless device which optimally drops packets as necessary in order that its output be conformant to an envelope g. The maximal f-regulator is a buffered device that delays packets as necessary in order that its output be conformant to an envelope f. The f-regulator is a linear time invariant filter with impulse response f, under the (min, +)-algebra. To provide dynamic service guarantees in a network, we develop the concept of a dynamic server as a basic network element. Dynamic servers can be joined by concatenation, "filter bank summation" and feedback to form a composite dynamic server, we also show that dynamic service guarantees for multiple input streams sharing a work conserving link can be achieved by a dynamic SCED (service curve earliest deadline) scheduling algorithm, if an appropriate admission control is enforced.
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on deterministic traffic regulation and service guarantees a systematic approach by Filtering
1998Co-Authors: Chengshang ChangAbstract:We develop a Filtering Theory for deterministic traffic regulation and service guarantees under the (min, +)-algebra. We show that traffic regulators that generate f-upper constrained outputs can be implemented optimally by a linear time-invariant filter with the impulse response f/sub */ under the (min, +)-algebra, where f/sub */ is the subadditive closure defined in the paper. Analogous to the classical Filtering Theory, there is an associate calculus, including feedback, concatenation, "filter bank summation", and performance bounds. The calculus is also applicable to the concept of service curves that can be used for deriving deterministic service guarantees. Our Filtering approach not only yields easier proofs for more general results than those in the literature, but also allows us to design traffic regulators via systematic methods such as concatenation, filter bank summation, linear system realization, and FIR-IIR realization. We illustrate the use of the Theory by considering a window flow control problem and a service curve allocation problem.
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a Filtering Theory for deterministic traffic regulation
1997Co-Authors: Chengshang ChangAbstract:We develop a Filtering Theory for deterministic traffic regulators that generate f-constrained outputs. We show that such regulators can be implemented by a linear time invariant filter with the impulse response f under the (min,+)-algebra if the function f is increasing and subadditive. The Filtering approach not only yields easier proofs for more general results than those in the literature, but also allows us to design traffic regulators via systematic methods such as concatenation, filter bank summation, linear system realization, and FIR-IIR realization. The Theory has many applications, including leaky buckets, traffic regulation for periodic constraint functions, and service curves. In particular, we find a new linear system realization and a new FIR-IIR realization for a concatenation of leaky buckets. Moreover, we find an FIR-IIR realization for traffic regulators with periodic constraint functions. We also show that such regulators, in conjunction with maximum delay guarantee, guarantee shifted-subadditive service curves. Based on this, we provide a couple of rules for service curve allocation among a concatenation of servers.
Giuseppe Trainiti - One of the best experts on this subject based on the ideXlab platform.
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time periodic stiffness modulation in elastic metamaterials for selective wave Filtering Theory and experiment
2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Yiwei Xia, Massimo RuzzeneAbstract:Elastic waveguides with time-modulated stiffness feature a frequency-periodic dispersion spectrum, where branches merge at multiple integers of half the modulation frequency and over a finite wave number range. In this range, frequency becomes complex, with its real part remaining constant. The vanishing group velocity associated with these flat bands leads to frequency-selective reflection at an interface between a nonmodulated medium and a time-modulated one, which converts a broadband input into a narrow-band output centered at the half modulation frequency. This behavior is illustrated in an elastic waveguide in transverse motion, where modulation is implemented experimentally by an array of piezoelectric patches shunted through a negative electrical capacitance controlled by a switching circuit. The switching schedule defines the modulation frequency and allows the selection of the output frequency. This implementation is suitable for the investigation of numerous properties of time-space modulated elastic metamaterials, such as nonreciprocity and one-way propagation, and can lead to the implementation of novel functionalities for acoustic wave devices operating on piezoelectric substrates.
-
time periodic stiffness modulation in elastic metamaterials for selective wave Filtering Theory and experiment
2019Co-Authors: Giuseppe Trainiti, Jacopo Marconi, Gabriele Cazzulani, Alper Erturk, Massimo RuzzeneAbstract:We report on broadband-to-narrowband elastic wave Filtering resulting from time-periodic modulation of the stiffness of a one-dimensional elastic waveguide. Time modulation produces flat dispersion bands at frequencies that are multiple integers of half the modulation frequency. These flat bands lead to the selective reflection of a broadband incident wave at the interface between a non-modulated medium, and one with time-modulated stiffness properties. This results from the vanishing group velocity at the flat band frequencies, which prevents their propagation into the modulated domain. Thus, the considered modulated waveguide is understood as a single port system, in which a broadband incident wave (input) results in a narrowband reflected wave (output) at a frequency defined by modulation. The appearance of the flat bands for a time-modulated waveguide is here illustrated analytically and through numerical simulations. The Filtering characteristics of a non-modulate/modulated interface are observed experimentally by implementing a square-wave modulation scheme that employs an array of piezoelectric patches bonded to an elastic waveguide subject to transverse motion. The patches are shunted through a negative electrical capaticance that, when connected, implements a stiffness reduction for the resulting electromechanical waveguide. Switching the capacitance on and off effectively modulates the stiffness of the waveguide, and illustrates the Filtering characteristics associated with time-modulation of the equivalent elastic properties. We envision that a similar approach could be extended to investigate other properties of time-modulated elastic metamaterials, such as non-reciprocity and one-way Filtering of elastic waves.