Automatic diagnosis from electrocardiograms (ECGs)

This paper deals with the development of a new algorithm for electrocardiogram (ECG) analysis for automatic diagnostic purposes. The frequency characteristic of each segment of the ECG signal is computed via a fast Fourier transform. The phase characteristic of the segments is used to identify the cardiac abnormalities. The accuracy, reliability, and consistency of the algorithm have been verified by carrying out a classification of various normal and abnormal ECG waveforms. This work is a useful step towards the goal of automatic and computerized ECG interpretation and diagnosis.     

Automatic diagnosis of cardiac arrhythmia in electrocardiograms via multigranulation computing

The automatic and accurate arrhythmia diagnosis in the electrocardiogram (ECG) signals is significant for cardiac health. Typically, the arrhythmia diagnosis is automatically detected depending on single-lead signals or a simple combination of multilead signals from the ECG. However, it ignores the inter-lead correlation and the significance of different leads for different heart beats detection, which decreases the performance of arrhythmia diagnosis. In this paper, arrhythmia diagnosis is converted to a problem of multigranulation computing in the view of granular computing, and thus different lead signals can be captured to improve the effectiveness of abnormal heart beats detection. To this end, multilead ECG signals are firstly granulated into different fuzzy information granules by the fuzzy equivalence relation. An objective decision-making model based on fuzzy set theory is then proposed for describing and analyzing these granulated multilead ECG signals, which brings a self-adaptive and unsupervised decision making. As a result, the significance and correlation of different leads are analyzed by granularity selection and granular structures to make a better decision for arrhythmia diagnosis. Extensive experimental results show that the proposed algorithm can significantly improve the performance of arrhythmia diagnosis, especially better robustness to several types of cardiac arrhythmia.     

Towards inverse modeling of turbidity currents: The inverse lock-exchange problem

A new approach is introduced for turbidite modeling, leveraging the potential of computational fluid dynamics methods to simulate the flow processes that led to turbidite formation. The practical use of numerical flow simulation for the purpose of turbidite modeling so far is hindered by the need to specify parameters and initial flow conditions that are a priori unknown. The present study proposes a method to determine optimal simulation parameters via an automated optimization process. An iterative procedure matches deposit predictions from successive flow simulations against available localized reference data, as in practice may be obtained from well logs, and aims at convergence towards the best-fit scenario. The final result is a prediction of the entire deposit thickness and local grain size distribution. The optimization strategy is based on a derivative-free, surrogate-based technique. Direct numerical simulations are performed to compute the flow dynamics. A proof of concept is successfully conducted for the simple test case of a two-dimensional lock-exchange turbidity current. The optimization approach is demonstrated to accurately retrieve the initial conditions used in a reference calculation.     

The inverse internal model†

The paper studies the servo problem when a disturbance signal is applied at the compensator's input. It is shown that the compensator must provide an ‘ inverse internal model’ (defined in a precise sense) of the disturbance signal besides the (direct) internal model of the signal to be tracked.     

The perturbation of the Drazin inverse

In this paper, we present the explicit expressions of the perturbation of the Drazin inverse under different conditions. Also, we give the upper bounds of ‖(A+E)^D?A ^D‖ _P /‖A ^D‖ _P for these cases.     

The inverse electromagnetic shaping problem

The inverse problem concerning electromagnetic casting of molten metals consists of looking for an electric current density distribution such that the induced electromagnetic field makes a given mass of liquid metal acquire a predefined shape. This problem is formulated here as an optimization problem where the positions of a finite set of inductors are the design variables. Two different formulations for this optimization problem for the two-dimensional case are proposed. The first one minimizes the difference between the target and the equilibrium shapes while the second approach minimizes the L ² norm of a fictitious surface pressure that makes the target shape to be in mechanical equilibrium. The optimization problems are solved using Feasible Arc Interior Point Algorithm, a line search interior-point algorithm for nonlinear optimization. Some examples are presented to show the effectiveness of the proposed approaches.     

Algorithms for the detection of events in electrocardiograms

The detection of events in electrocardiograms (ECGs) and vectorcardiograms (VCGs) is an essential processing step in systems for computer-assisted ECG/VCG interpretation. This paper describes various algorithms for the detection of QRS complexes, atrial activity and artefacts. These algorithms have been used in various versions of the TNO Modular ECG/VCG Interpretation System including its latest version, MEANS. Evaluation results are presented.     

The modality effect tested in children in a user‐paced multimedia environment

The modality learning effect proposes that learning is enhanced when information is presented in both the visual and the auditory domains (e.g. pictures and spoken information) compared with presenting information solely in the visual channel (e.g. pictures and written text). Most of the evidence for this effect comes from adults in a laboratory setting. Therefore, we tested the modality effect with 80 children in the highest grade of elementary school in a naturalistic setting. In a between‐subjects design, the children either saw representational pictures with speech or representational pictures with text. Retention and transfer knowledge was tested at three moments: immediately after the intervention, one day after and after one week. The present study did not find any evidence for a modality effect in children when the lesson was learner‐paced. Instead, we found a reversed modality effect directly after the intervention for retention. A reversed modality effect was also found for the transfer questions one day later. This effect was robust, even when controlling for individual differences.     

The generalized inverse in parametric programming

In this paper we are concerned with parametric programming problems. The main results are two: the first one is an explicit representation of the general optimal solution of particular parametric programming problems; the second one is an unified approach to general parametric programming problems. The method suggested here is based on the utilization of the generalized inverse of a matrix: it allows a fast and simple solution of parametric problems and has several advantages over the classical parametric methods. We refer to interval linear programming problems but a fruitful direction of research may be its application to linear programming problems in the standard from. Research supported in part by the Gruppo Nazionale per l'Analisi Funzionale e le sne applicazioni del C. N. R.     

The inverse problem for compartmental systems

The current state of the inverse problem for compartmental systems is reviewed and analyzed in terms of three major phases, viz. model specification, identifiability and parameter estimation. Emphasis is given to a review of identifiability for linear compartmental systems and the need to put identifiability in perspective in the context of the inverse problem.     

The inverse Liapunov problem of finite time stability

In this paper three theorems for finite time stability and uniform finite time stability are presented. The inverse Liapunov problem is considered and solved for each of these theorems. This consists of determining the class of systems which can be proven stable using a given Liapunov function and a given stability theorem.