Fast Signal Processing Algorithms Research Articles

Assessment of non-negative matrix factorization for the preprocessing of long-term ECG

Background. With the advent of health information technology and wearable acquisition systems, long-term ECG are more and more used in long-term cardiac tolerability studies of new compounds. Nevertheless, the accurate analysis of such long signals requires reliable and fast signal processing algorithms. Objectives. The objective of this study is to assess the practical relevance of innovative matrix factorization methods for the preprocessing of long-term ECG. Those signals are generally noisy with complex baseline wander and require preprocessing, such as filtering, to perform a correct analysis. Our goal is to present two innovative algorithms of matrix factorization to detect R-peaks in long-term ECG. Methods. The two tested methods are called Independent Component Analysis (ICA) and Non-Negative Matrix Factorization (NMF). They are both source separation methods whose goal is to isolate each component of an ECG: R-peak, P and T waves, noise, baseline wander etc. On the one hand, ICA assumes that all subcomponents of the signal are statistically independent from each other and on the other hand, Non-Negative Matrix Factorization is a method that uses the non-negativity of the spectrogram of the ECG to separate the different time-frequency patterns. The two signal processing methods were implemented in the Matlab computing environment. Results. The proposed approaches are tested on the MIT-BIH Arrythmia and Noise Stress Test databases: ICA shows a strong drawback by returning the different sources in a random order making compulsory a reconnaissance step or the action of a specialist. Whereas NMF achieves high results in terms of sensitivity and specificity in general even in case of complex baseline wander and highly noisy signals. Conclusion. This study emphasizes promising results of a new long-term ECG preprocessing technique based on a matrix factorization method. This approach simultaneously undertakes three tasks: denoising, baseline wander removal and peak R detection.

Label free high throughput screening for apoptosis inducing chemicals using time-lapse microscopy signal processing.

Label free time-lapse microscopy has opened a new avenue to the study of time evolving events in living cells. When combined with automated image analysis it provides a powerful tool that enables automated large-scale spatiotemporal quantification at the cell population level. Very few attempts, however, have been reported regarding the design of image analysis algorithms dedicated to the detection of apoptotic cells in such time-lapse microscopy images. In particular, none of the reported attempts is based on sufficiently fast signal processing algorithms to enable large-scale detection of apoptosis within hours/days without access to high-end computers. Here we show that it is indeed possible to successfully detect chemically induced apoptosis by applying a two-dimensional linear matched filter tailored to the detection of objects with the typical features of an apoptotic cell in phase-contrast images. First a set of recorded computational detections of apoptosis was validated by comparison with apoptosis specific caspase activity readouts obtained via a fluorescence based assay. Then a large screen encompassing 2,866 drug like compounds was performed using the human colorectal carcinoma cell line HCT116. In addition to many well known inducers (positive controls) the screening resulted in the detection of two compounds here reported for the first time to induce apoptosis.

A fast algorithm for the reconstruction of a layered acoustic medium from its transmission response

We derive a layer‐recursive algorithm for reconstructing an equal‐travel‐time layered acoustic medium from its transmission response to an impulsive plane wave incident from below. The medium is bounded below by an infinite half‐space from which it is probed, and it is bounded above by a free surface at which its transmission response is measured. This problem arises in the nondestructive evaluation of layered composite materials, in which the transmission response is measured. The algorithm is similar in form to the Levinson algorithm, which reconstructs a layered medium from its reflection response; it is closely related to the lattice algorithm for computing the QR factorization of a matrix. We relate the new algorithm to the Levinson, fast Cholesky, and lattice algorithms, all of which are well‐known fast algorithms for signal processing.

On the synthesis of fast algorithms for signal processing

Nonstandard transformations over matrices allow the derivation of different, optimal algorithms in digital signal processing.

Fast algorithms for estimation and signal processing: an inverse scattering framework

The inverse scattering problem for a lossless transmission line has been used as a framework for deriving the Levinson and Schur fast algorithms for Toeplitz matrices. Here, the same framework is used to derive and attach novel simple scattering interpretations to the lattice algorithm and the split algorithms. This demonstrates that the scattering and interpretation is more fundamental to fast signal-processing algorithms than previously noted.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

AN/FQM‐12(V) sonar test set. II: signal generation and processing for an automated acoustical measurement system

This paper describes the signal generation and processing capabilities of an automated acoustical measurement system. The basic design goals for the signal generation and timing capabilities of the system were to provide the maximum flexibility for signal generation and reception while using sampling techniques that allow fast signal processing algorithms to be used in the data processing and analysis. The waveform and timing generator was designed to generate the conventional sinusoidal pulse waveforms used in many acoustical measurements along with special purpose arbitrary waveforms which can either be used directly as the transmit signal or to modulate the sinusoidal transmit pulses. The system timing technique allows a user to make simple single pulse measurements or to make multiple pulse measurements where data samples are summed either coherently or incoherently to maximize the signal‐to‐noise ratio. [Work sponsored by NAVSEA 06H4D.]