2013
Authors
Leite, A; Rocha, AP; Silva, ME;
Publication
CHAOS
Abstract
Heart Rate Variability (HRV) series exhibit long memory and time-varying conditional variance. This work considers the Fractionally Integrated AutoRegressive Moving Average (ARFIMA) models with Generalized AutoRegressive Conditional Heteroscedastic (GARCH) errors. ARFIMA-GARCH models may be used to capture and remove long memory and estimate the conditional volatility in 24 h HRV recordings. The ARFIMA-GARCH approach is applied to fifteen long term HRV series available at Physionet, leading to the discrimination among normal individuals, heart failure patients, and patients with atrial fibrillation. (C) 2013 AIP Publishing LLC
2013
Authors
Rocha, C; Mendonca, T; Silva, ME;
Publication
MATHEMATICAL AND COMPUTER MODELLING OF DYNAMICAL SYSTEMS
Abstract
During surgical interventions, a muscle relaxant drug is frequently administered with the objective of inducing muscle paralysis. Clinical environment and patient safety issues lead to a huge variety of situations that must be taken into account requiring intensive simulation studies. Hence, population models are crucial for research and development in this field.This work develops a stochastic population model for the neuromuscular blockade (NMB) (muscle paralysis) level induced by atracurium based on a deterministic individual model already proposed in the literature. To achieve this goal, a joint Lognormal distribution is considered for the patient-dependent parameters. This study is based on clinical data collected during general anaesthesia. The procedure developed enables to construct a reliable reference bank of parametrized models that not only reproduces the overall features of the NMB, but also the inter-individual variability characteristic of physiological signals. It turns out that this bank constitutes a fundamental tool to support research on identification and control algorithms and is suitable to be integrated in clinical decision support systems.
2013
Authors
Leite, A; Silva, ME; Rocha, AP;
Publication
Studies in Theoretical and Applied Statistics, Selected Papers of the Statistical Societies
Abstract
Long recordings of heart rate variability (HRV) display non-stationary characteristics and exhibit long- and short-range correlations. The nonparametric methodology detrended fluctuation analysis (DFA) has become a widely used technique for the detection of long-range correlations in non-stationary HRV data. Recently, we have proposed an alternative approach based on fractional integrated autoregressive moving average (ARFIMA) modelling. These models are an extension of the AR models usual in HRV analysis and have special interest for applications because of their ability for modelling both short- and long-term behaviour of a time series. In this work, DFA is used to assess also short-range scales, further characterizing the data. The methods are applied to 24 h HRV recordings from the Noltisalis database, collected from healthy subjects, patients suffering from congestive heart failure and heart transplanted patients. The analysis of short-range scales leads to a better discrimination between the different groups. © 2013, Springer-Verlag Berlin Heidelberg.
2013
Authors
Luz, N; Almeida, A; Anacleto, R; Silva, N;
Publication
ACM International Conference Proceeding Series
Abstract
Emergence of the social web has brought new powerful web applications that connect people in a global scale and allow them to reap the benefits of social life from online virtual environments. Taking into account the strengths and weaknesses of online social networks and tourism information systems, we propose an evolved version of the Toursplan information system, backed up by an online social network. This way, Toursplan can exploit social data to generate collective intelligence in the tourism and travel domains, and improve the quality of its recommendation and planning services. © 2013 ACM.
2013
Authors
Nascimento, V; Viamonte, MJ; Canito, A; Silva, N;
Publication
Advances in Intelligent Systems and Computing
Abstract
Agent technology has been applied in e-commerce to help coping with problems that arise due to its rapid growth. However, despite the amount of research in this area, the level of automation achieved is still limited. This is mainly due to the natural diversity existent in e-commerce environments, where agents may possess different conceptualizations about their needs and capabilities, giving rise to interoperability issues. In this paper we approach this problem and present the AEMOS system as a possible solution. AEMOS is an agent-based e-commerce platform that includes ontology matching services facilitating the interoperability between agents that have different conceptualizations about the same domain of knowledge. The system also explores emergent social networks in order to improve its efficiency by enhancing its ontology matching services and supporting agents in their decisions. © Springer International Publishing Switzerland 2013.
2013
Authors
Nascimento, V; Viamonte, MJ; Canito, A; Silva, N;
Publication
ICEIS: PROCEEDINGS OF THE 15TH INTERNATIONAL CONFERENCE ON ENTERPRISE INFORMATION SYSTEMS - VOL 2
Abstract
In this paper we approach the semantic heterogeneity problem which arises in agent mediated electronic commerce, presenting the AEMOS system as a promising answer. AEMOS is an agent mediated electronic commerce platform which main goal is to enable an efficient and transparent negotiation between agents even when they use different ontologies to represent the same domain of knowledge. The system provides ontology services, more specifically ontology matching services, which are improved by the exploitation of emergent social networks. In this paper we present the currently implemented system and demonstrate how an agent mediated electronic commerce system may benefit from the inclusion and combination of ontology services and social network based support.
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