| 1. |
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| 2. |
- Stavrou, Photios A., et al.
(författare)
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Asymptotic Reverse-Waterfilling Characterization of Nonanticipative Rate Distortion Function of Vector-Valued Gauss-Markov Processes with MSE Distortion
- 2018
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Ingår i: 2018 IEEE Conference on Decision and Control (CDC). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781538613955 ; , s. 14-20
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Konferensbidrag (refereegranskat)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.
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| 3. |
- Stavrou, P. A., et al.
(författare)
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Filtering with fidelity for time-varying Gauss-Markov processes
- 2016
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Ingår i: Proceedings of the 55th IEEE Conference on Decision and Control (CDC 2016). - 0743-1546. - 9781509018376 ; , s. 5465-5470
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Konferensbidrag (refereegranskat)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.
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| 4. |
- Stavrou, Photios A., et al.
(författare)
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OPTIMAL ESTIMATION VIA NONANTICIPATIVE RATE DISTORTION FUNCTION AND APPLICATIONS TO TIME-VARYING GAUSS-MARKOV PROCESSES
- 2018
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Ingår i: SIAM Journal of Control and Optimization. - : SIAM PUBLICATIONS. - 0363-0129 .- 1095-7138. ; 56:5, s. 3731-3765
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Tidskriftsartikel (refereegranskat)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.
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| 5. |
- Charalambous, Andreas, et al.
(författare)
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Content of Orthopedic Patient Education Provided by Nurses in Seven European Countries
- 2018
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Ingår i: Clinical Nursing Research. - : SAGE PUBLICATIONS INC. - 1054-7738 .- 1552-3799. ; 27:7, s. 770-789
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Tidskriftsartikel (refereegranskat)abstract
- Patients and their significant others education during the perioperative phase is an important and challenging aspect of care. This study explored the content of education provided by nurses to arthroplasty patients and their significant others. Data were collected with the Education of Patients-NURSE content (EPNURSE-Content), Received Knowledge of Hospital Patient (RKhp), and Received Knowledge of Significant Other (RKso) scales. The results showed that the content of education emphasized biophysiological and functional needs, differed between countries, and was related to how physically demanding nurses found their job to be and the amount of education provided. There is congruence between the received knowledge of patients and their significant others in relation to the content of education provided by nurses. The findings can support nurses in developing aid material for patients and significant others explaining the nature of education and advising them what to expect and how to optimize their participation in the process.
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| 6. |
- Csikos, A, et al.
(författare)
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Network traffic flow optimization under performance constraints
- 2017
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Ingår i: Transportation Research, Part C: Emerging Technologies. - : Elsevier BV. - 0968-090X. ; 83, s. 120-133
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a model-based perimeter control policy for large-scale urban vehicular networks is proposed. Assuming a homogeneously loaded vehicle network and the existence of a well-posed Network Fundamental Diagram (NFD), we describe a protected network throughout its aggregated dynamics including nonlinear exit flow characteristics. Within this framework of constrained optimal boundary flow gating, two main performance metrics are considered: (a) first, connected to the NFD, the concept of average network travel time and delay as a performance metric is defined; (b) second, at boundaries, we take into account additional external network queue dynamics governed by uncontrolled inflow demands. External queue capacities in terms of finite-link lengths are used as the second performance metric. Hence, the corresponding performance requirement is an upper bound of external queues. While external queues represent vehicles waiting to enter the protected network, internal queue describes the protected network’s aggregated behavior.By controlling the number of vehicles joining the internal queue from the external ones, herewith a network traffic flow maximization solution subject to the internal and external dynamics and their performance constraints is developed. The originally non-convex optimization problem is transformed to a numerically efficiently convex one by relaxing the performance constraints into time-dependent state boundaries. The control solution can be interpreted as a mechanism which transforms the unknown arrival process governing the number of vehicles entering the network to a regulated process, such that prescribed performance requirements on travel time in the network and upper bound on the external queue are satisfied. Comparative numerical simulation studies on a microscopic traffic simulator are carried out to show the benefits of the proposed method.
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| 7. |
- Csikos, A, et al.
(författare)
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Traffic flow optimization with QoS constrained network admission control
- 2017
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Ingår i: IFAC-PapersOnLine. - : Elsevier BV. - 2405-8963. ; 50:1, s. 5275-5280
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Konferensbidrag (refereegranskat)abstract
- The paper proposes a control design method in order to gate input flow to a protected urban vehicular network such that travel time Quality of Service (QoS) constraints are preserved within the network. In view of the network to be protected (also called the region), two types of queues are distinguished: external and internal. While external queues represent vehicles waiting to enter the protected network, an internal queue can be used to describe the network's aggregated behaviour. By controlling the number of vehicles entering the internal queue, the travel time within the network subject to the vehicular conservation law and the Network Fundamental Diagram (NFD) can be subsequently controlled. The admission controller can thus be interpreted as a mechanism which transforms the unknown arrival process governing the number of vehicles entering the network to a regulated process, such that prescribed QoS requirements on travel time in the network and upper bound on the external queue are satisfied. The admission control problem is formulated as a constrained convex optimization problem and a Model Predictive Control (MPC) problem. A case study demonstrates the benefits of the admission control mechanisms proposed.
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| 8. |
- Karat, Aaron S., et al.
(författare)
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Measuring mortality due to HIV-associated tuberculosis among adults in South Africa : Comparing verbal autopsy, minimally-invasive autopsy, and research data
- 2017
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Ingår i: PLOS ONE. - : Public Library of Science (PLoS). - 1932-6203. ; 12:3
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Tidskriftsartikel (refereegranskat)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.
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| 9. |
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| 10. |
- Stavrou, Photios A., et al.
(författare)
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Zero-Delay Rate Distortion via Filtering for Vector-Valued Gaussian Sources
- 2018
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Ingår i: IEEE Journal on Selected Topics in Signal Processing. - : Institute of Electrical and Electronics Engineers (IEEE). - 1932-4553 .- 1941-0484. ; 12:5, s. 841-856
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Tidskriftsartikel (refereegranskat)abstract
- We deal with zero-delay source coding of a vector-valued Gauss-Markov source subject to a mean-squared error (MSE) fidelity criterion characterized by the operational zero-delay vector-valued Gaussian rate distortion function (RDF). We address this problem by considering the nonanticipative RDF (NRDF), which is a lower bound to the causal optimal performance theoretically attainable function (or simply causal RDF) and operational zero-delay RDF. We recall the realization that corresponds to the optimal "test-channel" of the Gaussian NRDF, when considering a vector Gauss-Markov source subject to a MSE distortion in the finite time horizon. Then, we introduce sufficient conditions to show existence of solution for this problem in the infinite time horizon (or asymptotic regime). For the asymptotic regime, we use the asymptotic characterization of the Gaussian NRDF to provide a new equivalent realization scheme with feedback, which is characterized by a resource allocation (reverse-waterfilling) problem across the dimension of the vector source. We leverage the new realization to derive a predictive coding scheme via lattice quantization with subtractive dither and joint memoryless entropy coding. This coding scheme offers an upper bound to the operational zero-delay vector-valued Gaussian RDF. When we use scalar quantization, then for r active dimensions of the vector Gauss-Markov source the gap between the obtained lower and theoretical upper bounds is less than or equal to 0.254r + 1 bits/vector. However, we further show that it is possible when we use vector quantization, and assume infinite dimensional Gauss-Markov sources to make the previous gap to be negligible, i.e., Gaussian NRDF approximates the operational zero-delay Gaussian RDF. We also extend our results to vector-valued Gaussian sources of any finite memory under mild conditions. Our theoretical framework is demonstrated with illustrative numerical experiments.
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| 11. |
- Suhonen, Riitta, et al.
(författare)
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Hospitalised cancer patients' perceptions of individualised nursing care in four European countries
- 2018
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Ingår i: European Journal of Cancer Care. - : Hindawi Limited. - 0961-5423 .- 1365-2354. ; 27:1
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this study was to describe hospitalised cancer patients' perceptions of individualised care in four European countries and compare these perceptions using the patients' socio-demographic characteristics and the Individualized Care Scale. The patients' socio-demographic characteristics used were: education, age, gender, type of hospital admission, previous hospitalisation and hospital length of stay. The Individualized Care Scale has two parts (1) nurses' support of individuality and (2) patients' receipt of individuality. Data (n = 599) were collected in Cyprus (n = 150), Finland (n = 158), Greece (n = 150) and Sweden (n = 141). Multivariate analysis of variance models were constructed and differences in perceptions of individualised care were analysed using the patients' socio-demographic characteristics as covariates. The level of support for individuality and receipt of individualised care was reported as moderate and good respectively. Generally, the highest assessments were made by the Swedish respondents and the lowest by those in Greece. This study revealed some between-country differences in patients' perceptions of care individualisation. These differences, for example, conceptual, educational, based in clinical practice or in the health organisation, require further research. Enquiry into the individualised care perceptions of health care providers and the families of cancer patients would also be useful.
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| 12. |
- Suhonen, R., et al.
(författare)
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Older cancer patients' perceptions of care guality - an international study
- 2016
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Ingår i: Journal of Advanced Nursing. - 0309-2402 .- 1365-2648. ; 72:S1, s. 29-29
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cancer is considered as chronic condition, especially in the older people. Prevalence of cancer is especially high in the Nordic countries and Mediterranean countries. People with cancer are a common patient group in the healthcare system.Introduction: User perspective, such as patient assessments of care and care quality are central in developing healthcare services. These assessments have a high value in time when there are reforms in social and healthcare services. One core principle in these reforms is patient-centeredness. Earlier studies have shown that older patients differ from other age-based patient groups in their assessments of care quality elements. They were reported to be more positive in their evaluations.Aim: The aim of this study was to analyse cancer patients’ perceptions of patient-centered quality and individuality in care and trust in nurses, and to compare these perceptions between patients in the working age and older people. The research questions were: To what extent cancer patients perceive their care is patient-centered quality care, individualised and do they trust in nurses? Are there differences between older cancer patients and those in working age in their perceptions of person-centered quality of care, individuality in care and trust in nurses?Materials and methods: The study employed a cross-sectional comparative survey design. Data were collected using questionnaires among hospitalised cancer patients (N = 876, n = 599, 68%) in four countries: Greece, Cyprus, Sweden and Finland. The following instruments were used: The Oncology Patients perceptions of the Quality of Nursing Care Scale (OPPQNCS), the Individualised care Scale (ICS-patient) and Trust in Nurses. The data were divided into two sub-samples based on age (cut point 65 years): Older patients (n = 209) and patients in the working age (n = 387). Data were analysed statistically using cross-tabulation and chi-square statistics, or paired samples t-test.Results: In this study cancer patients’ perceptions about individualization and coordination of care, support of individuality and perceived individuality in care were only moderate. Proficiency and responsiveness as part of care quality were reported well realised. Trust in nurses was strong. Older patients and those patients in the working age did not differ in their perceptions of either patient-centered quality of care, individualised care or trust in nurses.Conclusions: The results of this study point out topics that need development in order to provide individualised and patient-centered nursing care. Contradictory to many earlier study results, age was not associated with cancer patients’ assessment.
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| 13. |
- Suhonen, R., et al.
(författare)
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Older cancer patients' perceptions of care guality - an international study
- 2016
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Ingår i: Journal of Advanced Nursing. - : Wiley-Blackwell Publishing Ltd. - 0309-2402 .- 1365-2648. ; 72:S1, s. 29-29
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Tidskriftsartikel (refereegranskat)abstract
- Background: Cancer is considered as chronic condition, especially in the older people. Prevalence of cancer is especially high in the Nordic countries and Mediterranean countries. People with cancer are a common patient group in the healthcare system. Introduction: User perspective, such as patient assessments of care and care quality are central in developing healthcare services. These assessments have a high value in time when there are reforms in social and healthcare services. One core principle in these reforms is patient-centeredness. Earlier studies have shown that older patients differ from other age-based patient groups in their assessments of care quality elements. They were reported to be more positive in their evaluations. Aim: The aim of this study was to analyse cancer patients’ perceptions of patient-centered quality and individuality in care and trust in nurses, and to compare these perceptions between patients in the working age and older people. The research questions were: To what extent cancer patients perceive their care is patient-centered quality care, individualised and do they trust in nurses? Are there differences between older cancer patients and those in working age in their perceptions of person-centered quality of care, individuality in care and trust in nurses? Materials and methods: The study employed a cross-sectional comparative survey design. Data were collected using questionnaires among hospitalised cancer patients (N = 876, n = 599, 68%) in four countries: Greece, Cyprus, Sweden and Finland. The following instruments were used: The Oncology Patients perceptions of the Quality of Nursing Care Scale (OPPQNCS), the Individualised care Scale (ICS-patient) and Trust in Nurses. The data were divided into two sub-samples based on age (cut point 65 years): Older patients (n = 209) and patients in the working age (n = 387). Data were analysed statistically using cross-tabulation and chi-square statistics, or paired samples t-test. Results: In this study cancer patients’ perceptions about individualization and coordination of care, support of individuality and perceived individuality in care were only moderate. Proficiency and responsiveness as part of care quality were reported well realised. Trust in nurses was strong. Older patients and those patients in the working age did not differ in their perceptions of either patient-centered quality of care, individualised care or trust in nurses. Conclusions: The results of this study point out topics that need development in order to provide individualised and patient-centered nursing care. Contradictory to many earlier study results, age was not associated with cancer patients’ assessment.
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| 14. |
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| 15. |
- Zou, Zhuo, et al.
(författare)
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Optimal Radio Frequency Energy Harvesting with Limited Energy Arrival Knowledge
- 2016
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Ingår i: IEEE Journal on Selected Areas in Communications. - : Institute of Electrical and Electronics Engineers (IEEE). - 0733-8716 .- 1558-0008. ; 34:12, s. 3528-3539
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Tidskriftsartikel (refereegranskat)abstract
- We develop optimal sleeping and harvesting policies for radio frequency (RF) energy harvesting devices, formalizing the following intuition: when the ambient RF energy is low, devices consume more energy being awake than what can be harvested and should enter sleep mode; when the ambient RF energy is high, on the other hand, it is essential to wake up and harvest. Toward this end, we consider a scenario with intermittent energy arrivals described by a two-state Gilbert-Elliott Markov chain model. The challenge is that the state of the Markov chain can only be observed during the harvesting action, and not while in sleep mode. Two scenarios are studied under this model. In the first scenario, we assume that the transition probabilities of the Markov chain are known and formulate the problem as a partially observable Markov decision process (POMDP). We prove that the optimal policy has a threshold structure and derive the optimal decision parameters. In the practical scenario where the ratio between the reward and the penalty is neither too large nor too small, the POMDP framework and the threshold-based optimal policies are very useful for finding non-Trivial optimal sleeping times. In the second scenario, we assume that the Markov chain parameters are unknown and formulate the problem as a Bayesian adaptive POMDP and propose a heuristic posterior sampling algorithm to reduce the computational complexity. The performance of our approaches is demonstrated via numerical examples.
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