Mathieu Lemay

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Due to the much higher amplitude of the electrical activity of the ventricles in the surface electrocardiogram (ECG), its cancellation is crucial for the analysis and characterization of atrial fibrillation. In this paper, two different methods are proposed for this cancellation. The first one is an average beat subtraction type of method. Two sets of(More)
This paper describes two initiatives aiming at improving code reusability for programming mobile robots: robotflow/flowdesigner, a data-flow programming environment; MARIE (mobile and autonomous robotics integration environment), a programming environment allowing multiple applications, programs and tools, to operate on one or multiple machines/OS and work(More)
We propose a new method for ventricular cancellation and atrial modelling in the ECG of patients suffering from atrial fibrillation. Our method is based on dictionary learning. It extends both the average beat subtraction and the sparse source separation approaches. Experiments on synthetic data show that this method can almost completely suppress the(More)
Real life deployment of robot formation cannot assume that robots are going to be correctly positioned to move in a particular configuration. To do so, we propose an approach that allows the group to determine autonomously the most appropriate assignment of positions in the formation. Our approach is distributed and uses directional visual perception to(More)
Ion channels exhibit stochastic conformational changes determining their gating behavior. In addition, the process of protein turnover leads to a natural variability of the number of membrane and gap junctional channels. Nevertheless, in computational models, these two aspects are scarcely considered and their impacts are largely unknown. We investigated(More)
Today, Data Center Networks (DCNs) are re-architected in different new architectures in order to alleviate several emergent issues related to server virtualization and new traffic patterns, such as the limitation of bi-section bandwidth and workload migration. However, these new architectures will remain either proprietary or hidden in administrative(More)
AIM This study aims at developing methods for extracting spatiotemporal information about the electric activity of the atria from electrocardiographic signals, in particular during atrial fibrillation. METHODS A biophysical model of the atria and a volume conductor model of the thorax were used to simulate the atrial electrical activity as expressed on(More)
The problem of efficiently representing and approximating digital data is an open challenge and it is of paramount importance for many applications. This dissertation focuses on the approximation of natural signals as an organized combination of mutually connected elements, preserving and at the same time benefiting from their inherent structure. This is(More)
Electrical impedance tomography (EIT) is a non-invasive imaging technique that can measure cardiac-related intra-thoracic impedance changes. EIT-based cardiac output estimation relies on the assumption that the amplitude of the impedance change in the ventricular region is representative of stroke volume (SV). However, other factors such as heart motion can(More)
Phase-rectified signal averaging (PRSA) is a technique recently introduced to enhance quasi-periodic signal components. An important parameter that can be extracted from surface ECG is the dominant frequency (DF) of atrial fibrillation (AF). AF signal components are always highly contaminated by the ventricular complexes, and the cancellation of these(More)