Point processes and time series analysis : theory and applications to complex physiological problems

Summary available: p. vii

A Bayesian Logistic Regression approach in Asthma Persistence Prediction

Background: A number of models based on clinical parameters have been used for the prediction of asthma persistence in children. The number and significance of factors that are used in a proposed model play a cardinal role in prediction accuracy. Different models may lead to different significant variables. In addition, the accuracy of a model in medicine is really important since an accurate prediction of illness persistence may improve prevention and treatment intervention for the children at risk. Methods: Data from 147 asthmatic children were analyzed by a new method for predicting asthma outcome using Principal Component Analysis (PCA) in combination with a Bayesian logistic regression approach implemented by the Markov Chain Monte Carlo (MCMC). The use of PCA is required due to multicollinearity among the explanatory variables. Results: This method using the most appropriate models seems to predict asthma with an accuracy of 84.076% and 86.3673%, a Sensitivity of 84.96% and 87.25% and a Specificity of 83.22% and 85.52%, respectively. Conclusion: Our approach predicts asthma with high accuracy, gives steadier results in terms of positive and negative patients and provides better information about the influence of each factor (demographic, symptoms etc.) in asthma prediction

Modeling andsimulationofspeedselectiononleftventricular assist devices

The control problem for LVADs is to set pump speed such that cardiac output and pressure perfusion are within acceptable physiological ranges. However, current technology of LVADs cannot provide for a closed-loop control scheme that can make adjustments based on the patient\u27s level of activity. In this context, the SensorART Speed Selection Module (SSM) integrates various hardware and software components in order to improve the quality of the patients\u27 treatment and the workflow of the specialists. It enables specialists to better understand the patient-device interactions, and improve their knowledge. The SensorART SSM includes two tools of the Specialist Decision Support System (SDSS); namely the Suction Detection Tool and the Speed Selection Tool. A VAD Heart Simulation Platform (VHSP) is also part of the system. The VHSP enables specialists to simulate the behavior of a patient?s circulatory system, using different LVAD types and functional parameters. The SDSS is a web-based application that offers specialists with a plethora of tools for monitoring, designing the best therapy plan, analyzing data, extracting new knowledge and making informative decisions. In this paper, two of these tools, the Suction Detection Tool and Speed Selection Tool are presented. The former allows the analysis of the simulations sessions from the VHSP and the identification of issues related to suction phenomenon with high accuracy 93%. The latter provides the specialists with a powerful support in their attempt to effectively plan the treatment strategy. It allows them to draw conclusions about the most appropriate pump speed settings. Preliminary assessments connecting the Suction Detection Tool to the VHSP are presented in this paper

Control of the single phase AC/DC/AC converter in order to operate as a power amplifier in a real time simulation

129 σ.Στην παρουσα διπλωματικη εργασία εξεταζεται η δομή ενός πειράματος προσομοίωσης σε πραγματικό χρόνο με το εργαστηριακό μικροδίκτυο διεσπαρμένης παραγωγής σε ρόλο δοκιμίου.Η προσομοίωση αυτή ονομάζεται Power Hardware in Loop (PHIL) ή συσκευή ισχύος σε βρόχο στα ελληνικά.Αρχικά περιγράφονται συνοπτικά τα στοιχεία του πειράματος όπως είναι το εργαστηριακό μικροδίκτυο, ο εξομοιωτής πραγματικού χρόνου (RTDS) που θα προσομοιώσει το ηλεκτρικό δίκτυο στο οποίο θα συνδέσουμε το δοκίμιο και τον ενδιάμεσο (Interface) που θα επιτελέσει τη σύνδεση των δύο προηγούμενων στοιχείων.Παρουσιάζονται οι τρεις διαφορετικοί μέθοδοι υλοποίησης του Interface που γενικά μπορεί να χαρακτηριστεί ως ενισχυτής ισχύος. Έπειτα παρουσιάζεται εκτενέστερα η χρήση του AC/DC/AC μετατροπέα 3 κλάδων.Αφού αναλυθεί η διάταξη αυτή σημειώνονται τα πλεονεκτήματα της τοπολογίας σε σχέση με την συμβατική τοπολογία με τους 4 κλάδους.Εξαιτίας της ιδιαίτερης τοπολογίας του μετατροπέα 3 κλάδων παρουσιάζονται λεπτομερώς, το σχήμα ελέγχου του, που σχεδιάστηκε με τη βοήθεια του Simulink/Matlab, καθώς και τεχνικές βελτίωσης των επιδόσεων του.Για την βελτωση αυτή επιλέγεται μια μέθοδος συγχρονισμού με χρήση PLL με γενικευμένο ολοκληρωτή δεύτερης τάξηςκαι παρουσιάζονται τα αποτελέσματα του.Έπειτα αναλύεται ο ενισχυτής της εταιρείας Triphase που θα χρησιμοποιηθεί στο πείραμα PHIL του εργαστηρίου Συστημάτων ηλεκτρικής ενέργειας (ΣΗΕ).Ο ενισχυτής αυτός στηρίζεται στον μονοφασικό μετατροπέα 3 κλάδων που αναλύθηκε νωρίτερα.Επίσης περιγράφεται λεπτομερώς το κύκλωμα ισχύος του και τα περιφερειακά συστήματα που χρησιμοποιεί για την επικοινωνία με τον χρήστη και την εκτέλεση του αλγορίθμου σε πραγματικό χρόνο.Ο αλγόριθμος ελέγχου που είναι σχεδιασμένος μέσω του Simulink, παρουσιάζεται λεπτομερώς στη συνέχεια και επισημαίνονται τα ιδιαίτερα στοιχεία του καθώς και οι απαιτούμενες τροποποιήσεις που έπρεπε να γίνου για να είναι εφικτή η σύνδεση του με το RTDS.Τέλος πραγματοποιούνται πειραματικές μετρήσεις για την επιβεβαίωση της ορθής λειτουργίας του για διαφορετικά είδη φορτίων κι παρατίθενται οι αντίστοιχες γραφικές παραστάσεις.This Diploma Thesis presents the structure of a real-time simulation project where a laboratory microgrid is tested. This kind of simulation is called PHIL (Power Hardware In Loop). Initially the key parts of this simulation such as the microgrid, the RTDS (Real Time Digital Simulator which simulates the electrical network that will be connected with the Hardware Under Test (HUT)) and the Interface which will make feasible the connection between the two previous parts, are mentioned. Three different methods of the implementation of the Interface which acts as a power amplifier are described. Furthermore the use of the AC/DC/AC converter in PHIL applications is described extensively and the operation of the single phase three leg AC/DC/AC converter is discussed. After analyzing this converter topology, the advantages compared to the conventional converter topology with four legs are mentioned .Because of the particular topology of the three leg converter, its control algorithm (which was designed in Simulink/Matlab) as well as specific techniques that can improve its performance are presented. In order to achieve this improvement, a synchronization method implemented by a PLL scheme with a second order generalized integrator is chosen and the results were shown. Afterwards the power amplifier of the Triphase company which will be used as an amplifier in the PHIL simulation of the NTUA power systems laboratory, is analyzed. This amplifier is based on the single phase three leg converter mentioned before. The power circuit and the peripheral devices which are used for the interaction with the user and the real time execution of the control algorithm are also described. The control algorithm which is designed using Simulink is shown. Also its specific elements and the necessary amendments should be made in order to allow the connection with the RTDS, are described. Finally experimental measurements were made in order to verify the proper functioning of the amplifier for different types of loads and the corresponding graphs are shown.Αλέξανδρος Ε. Ρήγα

Current Trends of Insect Physiology and Population Dynamics: Modeling Insect Phenology, Demography, and Circadian Rhythms in Variable Environments

The current eBook collection includes substantial scientific work in describing how insect species are responding to abiotic factors and recent climatic trends on the basis of insect physiology and population dynamics. The contributions can be broadly split into four chapters: the first chapter focuses on the function of environmental and mostly temperature driven models, to identify the seasonal emergence and population dynamics of insects, including some important pests. The second chapter provides additional examples on how such models can be used to simulate the effect of climate change on insect phenology and population dynamics. The third chapter focuses on describing the effects of nutrition, gene expression and phototaxis in relation to insect demography, growth and development, whilst the fourth chapter provides a short description on the functioning of circadian systems as well as on the evolutionary dynamics of circadian clocks

International Conference on Risk Analysis

This book covers the latest results in the field of risk analysis. Presented topics include probabilistic models in cancer research, models and methods in longevity, epidemiology of cancer risk, engineering reliability and economical risk problems. The contributions of this volume originate from the 5th International Conference on Risk Analysis (ICRA 5). The conference brought together researchers and practitioners working in the field of risk analysis in order to present new theoretical and computational methods with applications in biology, environmental sciences, public health, economics and finance

Evaluation of Bayesian classifiers in asthma exacerbation prediction after medication discontinuation

Abstract Objective The achievement of the optimal control of the disease is of cardinal importance in asthma treatment. As the control of the disease is sustained the medication should be gradually reduced and then stopped. Nevertheless, the discontinuation of asthma medication may lead to loss of disease control and eventually to an exacerbation of the disease. The goal of this paper is to examine the performance of Bayesian network classifiers in predicting asthma exacerbation based on several patient’s parameters such as objective measurements and medical history data. Results In this study several Bayesian network classifiers are presented and evaluated. It is shown that the proposed semi-naive network classifier with the use of Backward Sequential Elimination and Joining algorithm is able to predict if a patient will have an exacerbation of the disease after his last assessment with 93.84% accuracy and 90.9% sensitivity. In addition, the resulting structure and the conditional probability tables give a clear view of the probabilistic relationships between the used factors. This network may help the clinicians to identify the patients who are at high risk of having an exacerbation after stopping the medication and to confirm which factors are the most important