| 1. |
|
|
| 2. |
- Adiels, Lars, et al.
(author)
-
A π0 and η spectrometer of lead glass and BGO for momenta up to 1 GeV/c
- 1986
-
In: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 244:3, s. 380-390
-
Journal article (peer-reviewed)abstract
- A spectrometer consisting of two sets of bismuth germanium oxide (BGO) crystals and a lead-glass array has been used to measure the [pi]0 and [eta] momentum spectra produced from proton-antiproton annihilations at rest. We describe the test of the BGO sets in electron beams of energies from 50 to 450 MeV. We discuss the method of construction and calibration of the lead-glass array, as well as procedures to extract the energy and position resolutions for detected photons. A momentum resolution ([sigma]) for [pi]0’s and [eta]’s of 4% and 3%, respectively has been achieved at momenta below 1 GeV/c.
|
|
| 3. |
- Adiels, L., et al.
(author)
-
Experimental determination of the branching ratios {Mathematical expression}, and 2γ at rest
- 1987
-
In: Zeitschrift für Physik C Particles and Fields. - : Springer. - 0170-9739 .- 1431-5858. ; 35:1, s. 15-19
-
Journal article (peer-reviewed)abstract
- The branching ratios of {Mathematical expression} annihilations into the neutral final states 2π 0, π 0γ, and 2γ are measured by stopping antiprotons in liquid hydrogen. They are {Mathematical expression}, {Mathematical expression}, and B γγ<1.7×10 -6 (95% c.l.).
|
|
| 4. |
- Adiels, L., et al.
(author)
-
Experimental determination of the branching ratios proton-antiproton -> 2pi0, pi0γ and γγ at rest
- 1987
-
In: Zeitschrift für Physik C Particles and Fields. - 0170-9739. ; 35:1, s. 15-19
-
Journal article (peer-reviewed)abstract
- The branching ratios of Mathematical expression annihilations into the neutral final states 2π0, π0γ, and 2γ are measured by stopping antiprotons in liquid hydrogen. They are Mathematical expression, Mathematical expression, and Bγγ<1.7×10-6 (95% c.l.). © 1987 Springer-Verlag.
|
|
| 5. |
- Adiels, L., et al.
(author)
-
Experimental study of the inclusive η-spectrum from p {Mathematical expression} annihilations at rest in liquid hydrogen
- 1989
-
In: Zeitschrift für Physik C Particles and Fields. - : Springer. - 0170-9739 .- 1431-5858. ; 42:1, s. 49-58
-
Journal article (peer-reviewed)abstract
- The inclusive η-momentum spectrum from {Mathematical expression} annihilations at rest in liquid hydrogen was measured at LEAR. Branching ratios were obtained for {Mathematical expression}, and ηη(8.1±3.1)×10 -5. An upper limit for {Mathematical expression} of 1.8×10 -4 at 95% CL was found. The ratio of the branching ratios is BR(ηρ{variant})/BR(ηω)=0.51 -0.06 +0.20. For the ratio of branching ratios into two pseudoscalar mesons, we have BR(ηπ 0)/BR(π 0π 0)=0.65±0.14, BR(ηη)/BR(π 0π 0), BR(ηη ′)/BR(π 0π 0) at 95% CL, and BR(ηη)/BR(ηπ 0). © 1989 Springer-Verlag.
|
|
| 6. |
- Adiels, Lars, et al.
(author)
-
Experimental study of the inclusive η-spectrum from proton-antiproton annihilations at rest in liquid hydrogen
- 1989
-
In: Zeitschrift für Physik C Particles and Fields. - 0170-9739 .- 1431-5858. ; 42, s. 49-58
-
Journal article (peer-reviewed)abstract
- The inclusive η-momentum spectrum from Mathematical expression annihilations at rest in liquid hydrogen was measured at LEAR. Branching ratios were obtained for Mathematical expression, and ηη(8.1±3.1)×10-5. An upper limit for Mathematical expression of 1.8×10-4 at 95% CL was found. The ratio of the branching ratios is BR(ηÏvariant)/BR(ηω)=0.51-0.06+0.20. For the ratio of branching ratios into two pseudoscalar mesons, we have BR(ηπ0)/BR(Ï€0Ï€0)=0.65±0.14, BR(ηη)/BR(Ï€0Ï€0), BR(ηη′)/BR(Ï€0Ï€0) at 95% CL, and BR(ηη)/BR(ηπ0). © 1989 Springer-Verlag.
|
|
| 7. |
|
|
| 8. |
|
|
| 9. |
- Adiels, L., et al.
(author)
-
Search for narrow signals in the [gamma]-spectrum from [Proton-antiproton] annihilation at rest
- 1986
-
In: Physics Letters B. - : Elsevier BV. - 0370-2693 .- 1873-2445. ; 182:3-4, s. 405-408
-
Journal article (peer-reviewed)abstract
- The [gamma]-spectrum originating from pp[combining macron] annihilations at rest in liquid hydrogen was measured with two BGO spectrometers. A total of 24 ï¿œ 106[gamma]’s were accumulated. No narrow peaks indicating exotic states such as baryonium were observed. The upper limit for the branching ratio with 1040 [less-than-or-equals, slant] mx [less-than-or-equals, slant] 1770 MeV/c2 and with [lambda]x [less-than-or-equals, slant] 25 MeV/c2 is less than 10-3 with more than 99.96% confidence.
|
|
| 10. |
- Adiels, L., et al.
(author)
-
Search for narrow signals in the γ-spectrum from pp̄ annihilation at rest
- 1986
-
In: Physics Letters B. - : Elsevier. - 0370-2693 .- 1873-2445. ; 182:3-4, s. 405-408
-
Journal article (peer-reviewed)abstract
- The γ-spectrum originating from pp̄ annihilations at rest in liquid hydrogen was measured with two BGO spectrometers. A total of 24 × 10 6 γ's were accumulated. No narrow peaks indicating exotic states such as baryonium were observed. The upper limit for the branching ratio p p ̄ → γ + X with 1040 ≤ m x ≤ 1770 MeV/c 2 and with λ x ≤ 25 MeV/c 2 is less than 10 -3 with more than 99.96% confidence. © 1986.
|
|
| 11. |
- Adiels, L, et al.
(author)
-
Some results of experiment PS182 at LEAR
- 1986
-
In: Antiproton 86. - Singspore : World Scientific Publishing. - 9971503131 ; , s. 199-204, s. 199-204
-
Conference paper (other academic/artistic)
|
|
| 12. |
|
|
| 13. |
- Adiels, L, et al.
(author)
-
π0 and η spectroscopy at LEAR
- 1985
-
In: Physics with antiprotons at LEAR in the ACOL era. - Gif sur Yvette : Editions Frontières. - 2863320351 ; , s. 359-360
-
Conference paper (other academic/artistic)
|
|
| 14. |
|
|
| 15. |
- Adiels, L., et al.
(author)
-
Investigations on baryonium and other rare pmacrp annihilation modes using high resolution pi0 spectrometers (PS 182)
- 1985
-
In: Antiproton 1984. Proceedings of the VII European Symposium on Antiproton Interactions. - : Institution of Electrical Engineers (IEE). ; , s. 297-304
-
Conference paper (peer-reviewed)abstract
- In the search for heavy, narrow exotic states such as baryonium or glueballs, carried out so far, various methods of high- and low-energy production, low-energy formation, and e+e- reactions were used. In particular, a search for baryonium states below threshold (mxlsimmppmacr) has shown some evidence [Richter et al., 1983, Brando et al., 1984] for a few states. However, the results of these measurements suffer from poor statistics. Among the possible methods which can be applied in the baryonium bound state research at LEAR, the authors consider the study of the reaction ppmacrrarrX+pi0 as the most promising. They have performed an experiment to study this reaction by means of an experimental set-up especially tailored for measuring monoenergetic pi0,s, allowing for both angular distribution measurements and high-resolution spectroscopy. They report on the preliminary results from our actual measurements of the inclusive pi0 and eta spectra following the antiproton annihilation at rest.
|
|
| 16. |
- Adiels, L., et al.
(author)
-
Pi0 And Eta Spectroscopy At Lear
- 1986
-
In: Tignes 1985, Proceedings, Physics With Antiprotons At Lear In The Acol Era. ; , s. 359-359
-
Conference paper (peer-reviewed)
|
|
| 17. |
- Adiels, Lars, 1952-, et al.
(author)
-
Test of CP violation with K0 and K‾0 at LEAR
- 1985
-
In: Physics with antiprotons at LEAR in the ACOL era. - Gif sur Yvette : Editions Frontières. - 2863320351 ; , s. 467-482
-
Conference paper (other academic/artistic)
|
|
| 18. |
|
|
| 19. |
- Charalambous, Charalambos D., et al.
(author)
-
Dynamic programming with total variational distance uncertaint
- 2012
-
In: Decision and Control (CDC), 2012 IEEE 51st Annual Conference on. - : IEEE. ; , s. 1909-1914
-
Conference paper (peer-reviewed)abstract
- The aim of this paper is to address optimality of stochastic control strategies via dynamic programming subject to total variational distance uncertainty on the conditional distribution of the controlled process. Utilizing concepts from signed measures, the maximization of a linear functional on the space of probability measures on abstract spaces is investigated, among those probability measures which are within a total variational distance from a nominal probability measure. The maximizing probability measure is found in closed form. These results are then applied to solve minimax stochastic control with deterministic control strategies, under a Markovian assumption on the conditional distributions of the controlled process. The results include: 1) Optimization subject to total variational distance constraints, 2) new dynamic programming recursions, which involve the oscillator seminorm of the value function.
|
|
| 20. |
- Charalambous, Charalambos D., et al.
(author)
-
Extremum Problems with Total Variation Distance
- 2013
-
In: 2013 IEEE 52nd Annual Conference on Decision and Control (CDC). - : IEEE conference proceedings. - 9781467357142 ; , s. 1204-1209
-
Conference paper (peer-reviewed)abstract
- The aim of this paper is to investigate extremum problems with pay-off the total variational distance metric subject to linear functional constraints both defined on the space of probability measures, as well as related problems. Utilizing concepts from signed measures, the extremum probability measures of such problems are obtained in closed form, by identifying the partition of the support set and the mass of these extremum measures on the partition. The results are derived for abstract spaces, specifically, complete separable metric spaces, while the high level ideas are also discussed for denumerable spaces endowed with the discrete topology.
|
|
| 21. |
- Charalambous, Charalambos D., et al.
(author)
-
Extremum Problems With Total Variation Distance and Their Applications
- 2014
-
In: IEEE Transactions on Automatic Control. - 0018-9286 .- 1558-2523. ; 59:9, s. 2353-2368
-
Journal article (peer-reviewed)abstract
- The aim of this paper is to investigate extremum problems with pay-off being the total variation distance metric defined on the space of probability measures, subject to linear functional constraints on the space of probability measures, and vice-versa; that is, with the roles of total variation metric and linear functional interchanged. Utilizing concepts from signed measures, the extremum probability measures of such problems are obtained in closed form, by identifying the partition of the support set and the mass of these extremum measures on the partition. The results are derived for abstract spaces; specifically, complete separable metric spaces known as Polish spaces, while the high level ideas are also discussed for denumerable spaces endowed with the discrete topology. These extremum problems often arise in many areas, such as, approximating a family of probability distributions by a given probability distribution, maximizing or minimizing entropy subject to total variation distance metric constraints, quantifying uncertainty of probability distributions by total variation distance metric, stochastic minimax control, and in many problems of information, decision theory, and minimax theory.
|
|
| 22. |
- Charalambous, Charalambos D., et al.
(author)
-
Team Optimality Conditions of Differential Decision Systems with Nonclasssical Information Structures
- 2014
-
In: 2014 European Control Conference (ECC). - : IEEE. - 9783952426913 ; , s. 2851-2856
-
Conference paper (peer-reviewed)abstract
- We derive team optimality conditions for differential decision systems with nonclassical information structures. The necessary conditions of optimality are given in terms of Hamiltonian system of equations consisting of a coupled backward and forward differential equations and a Hamiltonian projected onto the subspace generated by the information structures. Under certain global convexity conditions it is shown that person-by-person optimality implies team optimality.
|
|
| 23. |
- Charalambous, Themistoklis, et al.
(author)
-
Optimal Merging Algorithms for Lossless Codes With Generalized Criteria
- 2014
-
In: IEEE Transactions on Information Theory. - 0018-9448 .- 1557-9654. ; 60:9, s. 5486-5499
-
Journal article (peer-reviewed)abstract
- This paper presents lossless prefix codes optimized with respect to a payoff criterion consisting of a convex combination of maximum codeword length and average codeword length. The optimal codeword lengths obtained are based on a new coding algorithm, which transforms the initial source probability vector into a new probability vector according to a merging rule. The coding algorithm is equivalent to a partition of the source alphabet into disjoint sets on which a new transformed probability vector is defined as a function of the initial source probability vector and scalar parameter. The payoff criterion considered encompasses a tradeoff between maximum and average codeword length; it is related to a payoff criterion consisting of a convex combination of average codeword length and average of an exponential function of the codeword length, and to an average codeword length payoff criterion subject to a limited length constraint. A special case of the first related payoff is connected to coding problems involving source probability uncertainty and codeword overflow probability, whereas the second related payoff compliments limited length Huffman coding algorithms.
|
|
| 24. |
|
|
| 25. |
|
|
| 26. |
- Nomikos, N., et al.
(author)
-
Capacity improvement through buffer-aided successive opportunistic relaying
- 2013
-
In: 2013 3rd International Conference on Wireless Communications, Vehicular Technology, Information Theory and Aerospace and Electronic Systems, VITAE 2013 - Co-located with Global Wireless Summit 2013. - : IEEE. - 9781479902392 ; , s. 6617051-
-
Conference paper (peer-reviewed)abstract
- Abstract-In this work, we propose a buffer-aided successive opportunistic relaying scheme that aims to improve the average capacity of the network when inter-relay interference arises between relays that are selected for transmission and reception. In order to exploit the benefits of bufTering at the relays, we propose a relay-pair selection policy that decouples the receiving relay at the previous time slot from being the transmitting relay at the next slot. Furthermore, we impose an interference cancellation threshold allowing the relay that is selected for reception, to decode and subtract the inter-relay interference. The proposed relaying scheme selects the relaying pair that maximizes the average capacity of the relay network. The performance of the proposed scheme is evaluated via simulation and comparisons with other state-of-the-art half and full-duplex relay selection schemes, in terms of outage probability, average capacity and average delay. The results reveal the need for a tradeoff between improving the outage on the cost of reduced capacity and increased delay, and vice versa. Finally, conclusions are drawn and future directions are discussed, including the need for a hybrid scheme incorporating both half and full-duplex characteristics.
|
|
| 27. |
|
|
| 28. |
- Stavrou, Photios A., et al.
(author)
-
Asymptotic Reverse-Waterfilling Characterization of Nonanticipative Rate Distortion Function of Vector-Valued Gauss-Markov Processes with MSE Distortion
- 2018
-
In: 2018 IEEE Conference on Decision and Control (CDC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538613955 ; , s. 14-20
-
Conference paper (peer-reviewed)abstract
- We analyze the asymptotic nonanticipative rate distortion function (NRDF) of vector-valued Gauss-Markov processes subject to a mean-squared error (MSE) distortion function. We derive a parametric characterization in terms of a reverse-waterfilling algorithm, that requires the solution of a matrix Riccati algebraic equation (RAE). Further, we develop an algorithm reminiscent of the classical reverse-waterfilling algorithm that provides an upper bound to the optimal solution of the reverse-waterfilling optimization problem, and under certain cases, it operates at the NRDF. Moreover, using the characterization of the reverse-waterfilling algorithm, we derive the analytical solution of the NRDF, for a simple two-dimensional parallel Gauss-Markov process. The efficacy of our proposed algorithm is demonstrated via an example.
|
|
| 29. |
- Stavrou, P. A., et al.
(author)
-
Filtering with fidelity for time-varying Gauss-Markov processes
- 2016
-
In: Proceedings of the 55th IEEE Conference on Decision and Control (CDC 2016). - 0743-1546. - 9781509018376 ; , s. 5465-5470
-
Conference paper (peer-reviewed)abstract
- In this paper, we revisit the relation between Nonanticipative Rate Distortion (NRD) theory and real-time realizable filtering theory. Specifically, we give the closed form expression for the optimal nonstationary (time-varying) reproduction distribution of the Finite Time Horizon (FTH) Nonanticipative Rate Distortion Function (NRDF) and we establish its connection to real-time realizable filtering theory via a realization scheme utilizing time-varying fully observable multidimensional Gauss-Markov processes. As an application we provide the optimal filter with respect to a mean square error constraint. Unlike classical filtering theory, our filtering approach based on FTH NRDF is performed with waterfilling. We also derive a universal lower bound to the mean square error of any causal estimator to Gaussian processes based on the closed form expression of FTH NRDF. Our theoretical results are demonstrated via an illustrative example.
|
|
| 30. |
- Stavrou, Photios A., et al.
(author)
-
OPTIMAL ESTIMATION VIA NONANTICIPATIVE RATE DISTORTION FUNCTION AND APPLICATIONS TO TIME-VARYING GAUSS-MARKOV PROCESSES
- 2018
-
In: SIAM Journal of Control and Optimization. - : SIAM PUBLICATIONS. - 0363-0129 .- 1095-7138. ; 56:5, s. 3731-3765
-
Journal article (peer-reviewed)abstract
- In this paper, we develop finite-time horizon causal filters for general processes taking values in Polish spaces using the nonanticipative rate distortion function (NRDF). Subsequently, we apply the NRDF to design optimal filters for time-varying vector-valued Gauss-Markov processes, subject to a mean-squared error (MSE) distortion. Unlike the classical Kalman filter design, the developed filters based on the NRDF are characterized parametrically by a dynamic reverse-waterfilling optimization problem obtained via Karush-Kuhn-Tucker conditions. We develop algorithms that provide, in general, tight upper bounds to the optimal solution to the dynamic reverse-waterfilling optimization problem subject to a total and per-letter MSE distortion constraint. Under certain conditions, these algorithms produce the optimal solutions. Further, we establish a universal lower bound on the total and per-letter MSE of any estimator of a Gaussian random process. Our theoretical framework is demonstrated via simple examples.
|
|
| 31. |
- Tzortzis, I., et al.
(author)
-
Approximation of Markov processes by lower dimensional processes
- 2014
-
In: Proceedings of the IEEE Conference on Decision and Control. - : IEEE conference proceedings. ; , s. 4441-4446
-
Conference paper (peer-reviewed)abstract
- In this paper, we investigate the problem of aggregating a given finite-state Markov process by another process with fewer states. The aggregation utilizes total variation distance as a measure of discriminating the Markov process by the aggregate process, and aims to maximize the entropy of the aggregate process invariant probability, subject to a fidelity described by the total variation distance ball. An iterative algorithm is presented to compute the invariant distribution of the aggregate process, as a function of the invariant distribution of the Markov process. It turns out that the approximation method via aggregation leads to an optimal aggregate process which is a hidden Markov process, and the optimal solution exhibits a water-filling behavior. Finally, the algorithm is applied to specific examples to illustrate the methodology and properties of the approximations.
|
|
| 32. |
- Tzortzis, Ioannis, et al.
(author)
-
Approximation of Markov Processes by Lower Dimensional Processes via Total Variation Metrics
- 2017
-
In: IEEE Transactions on Automatic Control. - : IEEE Press. - 0018-9286 .- 1558-2523. ; 62:3, s. 1030-1045
-
Journal article (peer-reviewed)abstract
- The aim of this paper is to approximate a Finite-State Markov (FSM) process by another process defined on a lower dimensional state space, called the approximating process, with respect to a total variation distance fidelity criterion. The approximation problem is formulated as an optimization problem using two different approaches. The first approach is based on approximating the transition probability matrix of the FSM process by a lower-dimensional transition probability matrix, resulting in an approximating process which is a Finite-State Hidden Markov (FSHM) process. The second approach is based on approximating the invariant probability vector of the original FSM process by another invariant probability vector defined on a lower-dimensional state space. Going a step further, a method is proposed based on optimizing a Kullback-Leibler divergence to approximate the FSHM processes by FSM processes. The solutions of these optimization problems are described by optimal partition functions which aggregate the states of the FSM process via a corresponding water-filling solution, resulting in lower-dimensional approximating processes which are FSHM or FSM processes. Throughout the paper, the theoretical results are justified by illustrative examples that demonstrate our proposed methodology.
|
|
| 33. |
- Tzortzis, I., et al.
(author)
-
Approximation of Markov Processes by Lower Dimensional Processes via Total Variation Metrics
- 2017
-
In: IEEE Transactions on Automatic Control. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9286 .- 1558-2523. ; 62:3, s. 1030-1045
-
Journal article (peer-reviewed)abstract
- The aim of this paper is to approximate a Finite-State Markov (FSM) process by another process defined on a lower dimensional state space, called the approximating process, with respect to a total variation distance fidelity criterion. The approximation problem is formulated as an optimization problem using two different approaches. The first approach is based on approximating the transition probability matrix of the FSM process by a lower-dimensional transition probability matrix, resulting in an approximating process which is a Finite-State Hidden Markov (FSHM) process. The second approach is based on approximating the invariant probability vector of the original FSM process by another invariant probability vector defined on a lower-dimensional state space. Going a step further, a method is proposed based on optimizing a Kullback-Leibler divergence to approximate the FSHM processes by FSM processes. The solutions of these optimization problems are described by optimal partition functions which aggregate the states of the FSM process via a corresponding water-filling solution, resulting in lower-dimensional approximating processes which are FSHM or FSM processes. Throughout the paper, the theoretical results are justified by illustrative examples that demonstrate our proposed methodology.
|
|
| 34. |
- Tzortzis, Ioannis, et al.
(author)
-
Dynamic programming subject to total variation distance ambiguity
- 2015
-
In: SIAM Journal of Control and Optimization. - : Society for Industrial & Applied Mathematics (SIAM). - 0363-0129 .- 1095-7138. ; 53:4, s. 2040-2075
-
Journal article (peer-reviewed)abstract
- The aim of this paper is to address optimality of stochastic control strategies via dynamic programming subject to total variation distance ambiguity on the conditional distribution of the controlled process. We formulate the stochastic control problem using minimax theory, in which the control minimizes the payoff while the conditional distribution, from the total variation distance set, maximizes it. First, we investigate the maximization of a linear functional on the space of probability measures on abstract spaces, among those probability measures which are within a total variation distance from a nominal probability measure, and then we give the maximizing probability measure in closed form. Second, we utilize the solution of the maximization to solve minimax stochastic control with deterministic control strategies, under a Markovian and a non-Markovian assumption, on the conditional distributions of the controlled process. The results of this part include (1) minimax optimization subject to total variation distance ambiguity constraint; (2) new dynamic programming recursions, which involve the oscillator seminorm of the value function, in addition to the standard terms; and (3) a new infinite horizon discounted dynamic programming equation, the associated contractive property, and a new policy iteration algorithm. Finally, we provide illustrative examples for both the finite and infinite horizon cases. For the infinite horizon case, we invoke the new policy iteration algorithm to compute the optimal strategies.
|
|
| 35. |
- Tzortzis, I., et al.
(author)
-
Infinite horizon average cost dynamic programming subject to ambiguity on conditional distribution
- 2016
-
In: Proceedings of the IEEE Conference on Decision and Control. - 0743-1546 .- 2576-2370. - 9781479978861 ; 2016-February, s. 7171-7176
-
Conference paper (peer-reviewed)abstract
- This paper addresses the optimality of stochastic control strategies based on the infinite horizon average cost criterion, subject to total variation distance ambiguity on the conditional distribution of the controlled process. This stochastic optimal control problem is formulated using minimax theory, in which the minimization is over the control strategies and the maximization is over the conditional distributions. Under the assumption that, for every stationary Markov control law the maximizing conditional distribution of the controlled process is irreducible, we derive a new dynamic programming recursion which minimizes the future ambiguity, and we propose a new policy iteration algorithm. The new dynamic programming recursion includes, in addition to the standard terms, the oscillator semi-norm of the cost-to-go. The maximizing conditional distribution is found via a water-filling algorithm. The implications of our results are demonstrated through an example.
|
|
| 36. |
- Tzortzis, I., et al.
(author)
-
Infinite horizon discounted dynamic programming subject to total variation ambiguity on conditional distribution
- 2016
-
In: Proceedings of the 55th IEEE Conference on Decision and Control (CDC 2016); Las Vegas; United States; 12-14 December 2016. - 0743-1546. - 9781509018376 ; , s. Art no 7798559, Pages 2010-2015
-
Conference paper (peer-reviewed)abstract
- We analyze the infinite horizon minimax discounted cost Markov Control Model (MCM), for a class of controlled process conditional distributions, which belong to a ball, with respect to total variation distance metric, centered at a known nominal controlled conditional distribution with radius R ϵ [0, 2], in which the minimization is over the control strategies and the maximization is over conditional distributions. Through our analysis (i) we derive a new discounted dynamic programming equation, (ii) we show the associated contraction property, and (iii) we develop a new policy iteration algorithm. Finally, the application of the new dynamic programming and the corresponding policy iteration algorithm are shown via an illustrative example.
|
|
| 37. |
- Tzortzis, I., et al.
(author)
-
Robust Linear Quadratic Regulator for uncertain systems
- 2016
-
In: Proceedings of the 55th IEEE Conference on Decision and Control (CDC 2016); Las Vegas; United States; 12-14 December 2016. - 0743-1546. - 9781509018376 ; , s. Art no 7798481, Pages 1515-1520
-
Conference paper (peer-reviewed)abstract
- This paper develops a Linear Quadratic Regulator (LQR), which is robust to disturbance variability, by using the total variation distance as a metric. The robust LQR problem is formulated as a minimax optimization problem, resulting in a robust optimal controller which in addition to minimizing the quadratic cost it also minimizes the level of disturbance variability. A procedure for solving the LQR problem is also proposed and an example is presented which clearly illustrates the effectiveness of our developed methodology.
|
|
| 38. |
- Zioutas, K., et al.
(author)
-
Baryonium physics
- 1983
-
In: Proceedings of the 1st Hellenic School on Elementary Particle Physics. - : Institution of Electrical Engineers (IEE). ; , s. 437-466
-
Conference paper (peer-reviewed)abstract
- Various theoretical ideas on nuclear physics, quark models, and the dual topological unitarization lead to the expectation of massive mesons, called baryonium, coupled strongly to the ppmacr channel but weakly to mesons, thus resulting in a virtually high stability, particularly below the ppmacr threshold. Such states are relevant to nuclear physics owing to the fact that the badly explored short-range forces in the NN interactions are just the most relevant ones in the NNmacr systems. From the known NN potential, one is led to expect short-range attraction in NNmacr systems, and this should result in quasinuclear bound states in the vicinity of threshold.
|
|
| 39. |
- Charalambous, C. D., et al.
(author)
-
Directed Information Subject to a Fidelity. Applications to Conditionally Gaussian Processes
- 2018
-
In: 2018 European Control Conference, ECC 2018. - : Institute of Electrical and Electronics Engineers (IEEE). - 9783952426982 ; , s. 3071-3076
-
Conference paper (peer-reviewed)abstract
- This paper is concerned with the minimization of directed information over conditional distributions that satisfy a fidelity of reconstructing a conditionally Gaussian random process by another process, causally. This information theoretic extremum problem is directly linked, via bounds to the optimal performance theoretically attainable by non-causal, causal and zero-delay codes of data compression. The application example includes the characterization of causal rate distortion function for conditionally Gaussian random processes subject to a meansquare error fidelity.
|
|
| 40. |
|
|
| 41. |
- Karat, Aaron S., et al.
(author)
-
Measuring mortality due to HIV-associated tuberculosis among adults in South Africa : Comparing verbal autopsy, minimally-invasive autopsy, and research data
- 2017
-
In: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:3
-
Journal article (peer-reviewed)abstract
- Background The World Health Organization (WHO) aims to reduce tuberculosis (TB) deaths by 95% by 2035; tracking progress requires accurate measurement of TB mortality. International Classification of Diseases (ICD) codes do not differentiate between HIV-associated TB and HIV more generally. Verbal autopsy (VA) is used to estimate cause of death (CoD) patterns but has mostly been validated against a suboptimal gold standard for HIV and TB. This study, conducted among HIV-positive adults, aimed to estimate the accuracy of VA in ascertaining TB and HIV CoD when compared to a reference standard derived from a variety of clinical sources including, in some, minimally-invasive autopsy (MIA). Methods and findings Decedents were enrolled into a trial of empirical TB treatment or a cohort exploring diagnostic algorithms for TB in South Africa. The WHO 2012 instrument was used; VA CoD were assigned using physician-certified VA (PCVA), InterVA-4, and SmartVA-Analyze. Reference CoD were assigned using MIA, research, and health facility data, as available. 259 VAs were completed: 147 (57%) decedents were female; median age was 39 (interquartile range [IQR] 33-47) years and CD4 count 51 (IQR 22-102) cells/mu L. Compared to reference CoD that included MIA (n = 34), VA underestimated mortality due to HIV/AIDS (94% reference, 74% PCVA, 47% InterVA-4, and 41% SmartVA-Analyze; chance-corrected concordance [CCC] 0.71, 0.42, and 0.31, respectively) and HIV-associated TB (41% reference, 32% PCVA; CCC 0.23). For individual decedents, all VA methods agreed poorly with reference CoD that did not include MIA (n = 259; overall CCC 0.14, 0.06, and 0.15 for PCVA, InterVA-4, and SmartVA-Analyze); agreement was better at population level (cause-specific mortality fraction accuracy 0.78, 0.61, and 0.57, for the three methods, respectively). Conclusions Current VA methods underestimate mortality due to HIV-associated TB. ICD and VA methods need modifications that allow for more specific evaluation of HIV-related deaths and direct estimation of mortality due to HIV-associated TB.
|
|
| 42. |
- Karat, Aaron S., et al.
(author)
-
Performance of verbal autopsy methods in estimating HIV-associated mortality among adults in South Africa
- 2018
-
In: BMJ Global Health. - : BMJ Publishing Group Ltd. - 2059-7908. ; 3:4
-
Journal article (peer-reviewed)abstract
- Introduction: Verbal autopsy (VA) can be integrated into civil registration and vital statistics systems, but its accuracy in determining HIV-associated causes of death (CoD) is uncertain. We assessed the sensitivity and specificity of VA questions in determining HIV status and antiretroviral therapy (ART) initiation and compared HIV-associated mortality fractions assigned by different VA interpretation methods.Methods: Using the WHO 2012 instrument with added ART questions, VA was conducted for deaths among adults with known HIV status (356 HIV positive and 103 HIV negative) in South Africa. CoD were assigned using physician-certified VA (PCVA) and computer-coded VA (CCVA) methods and compared with documented HIV status.Results: The sensitivity of VA questions in detecting HIV status and ART initiation was 84.3% (95% CI 80 to 88) and 91.0% (95% CI 86 to 95); 283/356 (79.5%) HIV-positive individuals were assigned HIV-associated CoD by PCVA, 166 (46.6%) by InterVA-4.03, 201 (56.5%) by InterVA-5, and 80 (22.5%) and 289 (81.2%) by SmartVA-Analyze V.1.1.1 and V.1.2.1. Agreement between PCVA and older CCVA methods was poor (chance-corrected concordance [CCC] <0; cause-specific mortality fraction [CSMF] accuracy <= 56%) but better between PCVA and updated methods (CCC 0.21-0.75; CSMF accuracy 65%-98%). All methods were specific (specificity 87% to 96%) in assigning HIV-associated CoD.Conclusion: All CCVA interpretation methods underestimated the HIV-associated mortality fraction compared with PCVA; InterVA-5 and SmartVA-Analyze V. 1.2.1 performed better than earlier versions. Changes to VA methods and classification systems are needed to track progress towards targets for reducing HIV-associated mortality.
|
|
| 43. |
|
|
| 44. |
- Maraba, Noriah, et al.
(author)
-
Verbal autopsy-assigned causes of death among adults being investigated for TB in South Africa
- 2016
-
In: Transactions of the Royal Society of Tropical Medicine and Hygiene. - : Oxford University Press. - 0035-9203 .- 1878-3503. ; 110:9, s. 510-516
-
Journal article (peer-reviewed)abstract
- Background: Adults being investigated for TB in South Africa experience high mortality, yet causes of death (CoD) are not well defined. We determined CoD in this population using verbal autopsy (VA), and compared HIV- and TB-associated CoD using physician-certified verbal autopsy (PCVA) and InterVA-4 software. Methods: All contactable consenting caregivers of participants who died during a trial comparing Xpert MTB/RIF to smear microscopy were interviewed using the WHO VA tool. CoD were assigned using PCVA and InterVA-4. Kappa statistic (K) and concordance correlation coefficient (CCC) were calculated for comparison. Results: Among 231 deaths, relatives of 137 deceased were interviewed. Of the 137 deceased 76 (55.4%) were males, median age 41 years (IQR 33-50). PCVA assigned 70 (51.1%) TB immediate CoD (44 [62.8%] pulmonary TB; 26 [37.1%] extra-pulmonary TB); 21 (15.3%) HIV/AIDS-related; and 46 (33.5%) other CoD. InterVA-4 assigned 48 (35.0%) TB deaths; 49 (35.7%) HIV/AIDS-related deaths; and 40 (29.1%) other CoD. Agreement between PCVA and InterVA-4 CoD was slight at individual level (K=0.20; 95% CI 0.10-0.30) and poor at population level (CCC 0.67; 95% CI 0.38-0.99). Conclusions: TB and HIV are leading CoD among adults being investigated for TB. PCVA and InterVA agreement at individual level was slight and poor at population level. VA methodology needs further development where TB and HIV are common.
|
|
| 45. |
- Meisters, Rachelle, et al.
(author)
-
EULAR/eumusc.net standards of care for rheumatoid arthritis : cross-sectional analyses of importance, level of implementation and care gaps experienced by patients and rheumatologists across 35 European countries
- 2020
-
In: Annals of the Rheumatic Diseases. - : BMJ. - 0003-4967 .- 1468-2060. ; 79:11, s. 1423-1431
-
Journal article (peer-reviewed)abstract
- Objective As part of European League against Rheumatism (EULAR)/European Musculoskeletal Conditions Surveillance and Information Network, 20 user-focused standards of care (SoCs) for rheumatoid arthritis (RA) addressing 16 domains of care were developed. This study aimed to explore gaps in implementation of these SoCs across Europe. Methods Two cross-sectional surveys on the importance, level of and barriers (patients only) to implementation of each SoC (0-10, 10 highest) were designed to be conducted among patients and rheumatologists in 50 European countries. Care gaps were calculated as the difference between the actual and maximum possible score for implementation (ie, 10) multiplied by the care importance score, resulting in care gaps (0-100, maximal gap). Factors associated with the problematic care gaps (ie, gap≥30 and importance≥6 and implementation<6) and strong barriers (≥6) were further analysed in multilevel logistic regression models. Results Overall, 26 and 31 countries provided data from 1873 patients and 1131 rheumatologists, respectively. 19 out of 20 SoCs were problematic from the perspectives of more than 20% of patients, while this was true for only 10 SoCs for rheumatologists. Rheumatologists in countries with lower gross domestic product and non-European Union countries were more likely to report problematic gaps in 15 of 20 SoCs, while virtually no differences were observed among patients. Lack of relevance of some SoCs (71%) and limited time of professionals (66%) were the most frequent implementation barriers identified by patients. Conclusions Many problematic gaps were reported across several essential aspects of RA care. More efforts need to be devoted to implementation of EULAR SoCs.
|
|
| 46. |
- Nomikos, N., et al.
(author)
-
Hybrid cooperation through full-duplex opportunistic relaying and max-link relay selection with transmit power adaptation
- 2014
-
In: 2014 IEEE International Conference on Communications, ICC 2014. - : IEEE Computer Society. - 9781479920037 ; , s. 5706-5711
-
Conference paper (peer-reviewed)abstract
- In this work, we study a cooperative network with multiple full-duplex buffer-aided relays. A hybrid cooperative relaying policy is proposed that employs power adaptation and consists of two alternative schemes: (i) full-duplex transmission through the relay which requires the least total power expenditure and loop interference is mitigated through power adaptation; (ii) buffer-aided max - link selection with power adaptation, when full-duplexity is not feasible. Aiming to reduce the overhead of channel state information (CSI) acquisition and processing, we propose a suboptimal distributed method for relay selection, for which the network performance is not degraded significantly. We show that power adaptation offers reduced overhead of CSI acquisition. Numerical results and comparisons with other state-of-the-art relaying schemes are provided and performance evaluation in terms of throughput, power minimization and switching rate, show the benefits of the proposed hybrid scheme.
|
|
| 47. |
|
|
| 48. |
- Poulimeneas, Dimitrios, et al.
(author)
-
A delay-aware hybrid relay selection policy
- 2016
-
In: 2016 23rd International Conference on Telecommunications, ICT 2016. - : IEEE conference proceedings. - 9781509019908
-
Conference paper (peer-reviewed)abstract
- In this paper, we propose a novel relay selection policy based on the Hybrid Relay Selection (HRS) relay selection protocol that takes into account the state of the buffers and aims at reducing the average packet delays in the network. The proposed protocol, called the Delay-Aware HRS (DA - HRS) protocol is analyzed by means of Markov Chains and expressions for the outage probability, throughput and delay are derived. The distributed implementation of the protocol is also discussed. The performance of our proposed protocol is demonstrated via extensive simulations and comparisons with the classical HRS.
|
|
| 49. |
- Poulimeneas, Dimitrios, et al.
(author)
-
Delay-and diversity-Aware buffer-Aided relay selection policies in cooperative networks
- 2016
-
In: 2016 IEEE Wireless Communications and Networking Conference. - : Institute of Electrical and Electronics Engineers (IEEE). - 1525-3511. - 9781467398145
-
Conference paper (peer-reviewed)abstract
- In this paper, we propose novel relay selection policies that aim at reducing the average delay by incorporating the buffer size of the relay nodes into the relay selection process. More specifically, we propose two delay-Aware protocols that are based on the max-link relay selection protocol. First, a delay-Aware only approach while it reduces the delays considerably it starves the buffers and increases the outage probability of the system. Towards this end, we propose a delay-and diversity-Aware buffer-Aided relay selection policy that aims at reducing the average delay considerably and at the same time maintaining good diversity. The protocols are analyzed by means of Markov Chains and expressions for the outage, throughput and delay are derived. The performance and use of our proposed algorithms is demonstrated via extensive simulations and comparisons.
|
|
| 50. |
|
|
