Publications of Murielle Kirkove
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See detailSplit-Band SAR and Split Band InSAR principle and applications
De Rauw, Dominique ULiege; Kirkove, Murielle ULiege; Libert, Ludivine ULiege et al

Poster (2018, April 19)

Most recent SAR sensors use wide band signals to achieve metric range resolution. One can also take advantage of wide band to split it into sub-bands and generate several lower-resolution images, centered ... [more ▼]

Most recent SAR sensors use wide band signals to achieve metric range resolution. One can also take advantage of wide band to split it into sub-bands and generate several lower-resolution images, centered on slightly different frequencies, from a single acquisition (Bovenga & al. 2014). This process, named Multi Chromatic Analysis (MCA) corresponds to performing a spectral analysis of SAR images. From this spectral analysis, three potential applications are shown. First, this splitting allows performing a spectral analysis of observed scatterers. Spectral coherence is derived by computing the coherence between sub-images issued from a single SAR acquisition. It was shown that in the presence of a random distribution of surface scatterers, spectral coherence is proportional to sub-band intersection of sub-images. This model is fully verified when observing spectral coherence on open seas areas. If the scatterers distribution departs from this distribution, like for manmade structures, spectral coherence may be preserved to a certain degree and allows discriminating vessels from see clutter even in case of high sea state. This property can be used to perform vessel detection (Derauw & al., 2010). Second, Split-Band SAR interferometry (SBInSAR) is also based on this spectral analysis performed on each image of an InSAR pair, yielding a stack of sub-band interferograms. Scatterers keeping a coherent behaviour in each sub- band interferogram show a phase that varies linearly with the carrier frequency, the slope being proportional to the absolute optical path difference. This potentially solves the problems of phase unwrapping on a pixel-per-pixel basis (Libert & al.). Third, unwrapping classically two sub-band interferograms allows getting two phases of a same scene and same ionospheric components. Since these two components behave differently with frequency, SBInSAR allows discriminating both and remove the ionospheric artifacts if presents (Gomba & al. 2016, Furuya & al. 2016). [less ▲]

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See detailArtificial defects in CFRP composite structure for Thermography and Shearography nondestructive inspection
Blain, Pascal ULiege; Vandenrijt, Jean-François ULiege; Languy, Fabian ULiege et al

Poster (2017, April)

Locating defects in CFRP composite materials is a hot topic in nondestructive inspection (NDI). Beside classical NDI technique, such as ultrasound testing (UT), contactless techniques are actively studied ... [more ▼]

Locating defects in CFRP composite materials is a hot topic in nondestructive inspection (NDI). Beside classical NDI technique, such as ultrasound testing (UT), contactless techniques are actively studied. Generally manufacturers of CFRP structure incorporate artificial defects in the bulk, with different extents and depths, in order to study the performance of a specific NDI technique to detect the defect. One of the most common defects in CFRP is delamination between two layers. This is simulated by inserting teflon sheets which, like air, acts as ultrasound blocker in UT. When such reference part is used to assess NDI performance of thermography or shearography, we only observe respectively the thermal or mechanical response of teflon with respect to external loading used with these techniques. In this work, we assess other possibilities for artificial defects in CFRP matrix. For that a CFRP structure was developed and which incorporates teflon, flat-bottom holes and delamination obtained by the pull-out method. We experimentally studied the signals and we discuss the difference between the various artificial defects methods. [less ▲]

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See detailChange Detection Using Interferometric and Polarimetric Signatures in Argentina
Dadamia, Danilo; Thibeault, Marc; Palomeque, Mathias et al

in 8th International Workshop on Science and Applications of SAR Polarimetry and Polarimetric Interferometry (2017, January 23)

The two-satellite SAOCOM-1A/B SAR constellation to be deployed by Argentina shall provide full-polarimetric acquisitions at L-band, the main mission driver being the generation of soil moisture maps in ... [more ▼]

The two-satellite SAOCOM-1A/B SAR constellation to be deployed by Argentina shall provide full-polarimetric acquisitions at L-band, the main mission driver being the generation of soil moisture maps in the agriculture and hydrological contexts. The two satellites shall be incorporated, together with the Italian COSMO-Skymed satellites, in an X-L band constellation (referred to as SIASGE system) for risk management. Following an offer from CONAE, ESA has initiated the development of a passive receiving micro-satellite, SAOCOM-CS, for carrying out tomographic, interferometric, and bistatic imaging. SAOCOM-CS will fly in formation with SAOCOM-1B providing unique new single-pass measurements at L-band. The present paper reports the first results from an on-going study that comes in support to both the SAOCOM and SAOCOM-CS missions. The objective of this project is to accomplish a breakthrough in the development of algorithms and associated tools for change detection in Argentina, the core domain of focus being agriculture. The processing developments carried out in this project include a study of the polarimetric signature for different targets, and a multitemporal, spatial and angular analysis of the polarimetric parameters for different L band targets. The results are then applied in non-supervised algorithms for classification of SAR images and the development of simulated SAR images. Tests data sets include airborne and spaceborne SAR images and corresponding field measurements. [less ▲]

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See detailA TOPSAR Processor based on the Omega-K Algorithm: Evaluation with Sentinel-1 Data
Kirkove, Murielle ULiege; Orban, Anne ULiege; De Rauw, Dominique ULiege et al

in A TOPSAR Processor based on the Omega-K Algorithm: Evaluation with Sentinel-1 Data (2016, June)

This paper presents a processor for the TOPS (Terrain Observation by Progressive Scans) imaging mode. TOPS signals have two characteristics that make the use of Stripmap SAR processors inconvenient, i.e ... [more ▼]

This paper presents a processor for the TOPS (Terrain Observation by Progressive Scans) imaging mode. TOPS signals have two characteristics that make the use of Stripmap SAR processors inconvenient, i.e., azimuth frequency and azimuth time foldings. This paper describes a processor based on the Omega-K (Ω-k) algorithm, combined with pre-processing by frequency unfolding and post-processing by time unfolding. Raw data acquired by Sentinel-1 have been used to assess the quality of image reconstruction [less ▲]

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See detailEvaluation of the performance of an experimental somnolence quantification system in terms of reaction times and lapses
François, Clémentine ULiege; Wertz, Jérôme ULiege; Kirkove, Murielle ULiege et al

in Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society (2014, August)

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See detailComparative evaluation of existing and new methods for correcting ocular artifacts in electroencephalographic recordings
Kirkove, Murielle ULiege; François, Clémentine ULiege; Verly, Jacques ULiege

in Signal Processing (2014), 98(C), 102-120

EEG signals are often contaminated by ocular artifacts (OAs), in particular when they are recorded for a subject that is, in principle, awake, such as in a study of drowsiness. It is generally desirable ... [more ▼]

EEG signals are often contaminated by ocular artifacts (OAs), in particular when they are recorded for a subject that is, in principle, awake, such as in a study of drowsiness. It is generally desirable to detect and/or correct these OAs before interpreting the EEG signals. We have identified 11 existing methods for dealing with OAs. Their study allowed us to create 16 new methods. We performed a comparative performance evaluation of the resulting 27 distinct methods using a common set of data and a common set of metrics. The data was recorded during a driving task of about two hours in a driving simulator. This led to a ranking of all methods, with five emerging clear winners, comprising two existing methods and three new ones. [less ▲]

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See detailPerformance evaluation of methods for correcting ocular artifacts in electroencephalographic (EEG) recordings
Kirkove, Murielle ULiege; François, Clémentine ULiege; Libotte, Aurélie et al

Conference (2013, February)

The presence of ocular artifacts (OA) due to eye movements and eye blinks is a major problem for the analysis of electroencephalographic (EEG) recordings in most applications. A large variety of methods ... [more ▼]

The presence of ocular artifacts (OA) due to eye movements and eye blinks is a major problem for the analysis of electroencephalographic (EEG) recordings in most applications. A large variety of methods (algorithms) exist for detecting or/and correcting OA’s. We identified the most promising methods, implemented them, and compared their performance for correctly detecting the presence of OA’s. These methods are based on signal processing “tools” that can be classified into three categories: wavelet transform, adaptive filtering, and blind source separation. We evaluated the methods using EEG signals recorded from three healthy persons subjected to a driving task in a driving simulator. We performed a thorough comparison of the methods in terms of the usual performances measures (sensitivity, specificity, and ROC curves), using our own manual scoring of the recordings as ground truth. Our results show that methods based on adaptive filtering such as LMS and RLS appear to be the best to successfully identify OA’s in EEG recordings. [less ▲]

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See detailContrast and sensitivity performances of Elscint, General Electric, Siemens and SMV multi-heads cameras.
Kirkove, Murielle ULiege; Seret, Alain ULiege

in European Journal of Nuclear Medicine and Molecular Imaging (2007, October), 34(S2), 345

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See detailComparaison de techniques de débruitage des images scintigraphiques
Kirkove, Murielle ULiege; Seret, Alain ULiege

in Médecine Nucléaire: Imagerie Fonctionnelle et Métabolique (2007), 31(5), 219-234

Scintigraphic images are strongly affected by Poisson noise. This article presents the results of a comparison between denoising methods for Poisson noise according to different criteria: the gain in ... [more ▼]

Scintigraphic images are strongly affected by Poisson noise. This article presents the results of a comparison between denoising methods for Poisson noise according to different criteria: the gain in signal-to-noise ratio, the preservation of resolution and contrast, and the visual quality. The wavelet techniques recently developed to denoise Poisson noise limited images are divided into two groups based on: (1) the Haar representation, (2) the transformation of Poisson noise into white Gaussian noise by the Haar–Fisz transform followed by a denoising. In this study, three variants of the first group and three variants of the second, including the adaptative Wiener filter, four types of wavelet thresholdings and the Bayesian method of Pizurica were compared to Metz and Hanning filters and to Shine, a systematic noise elimination process. All these methods, except Shine, are parametric. For each of them, ranges of optimal values for the parameters were highlighted as a function of the aforementioned criteria. The intersection of ranges for the wavelet methods without thresholding was empty, and these methods were therefore not further compared quantitatively. The thresholding techniques and Shine gave the best results in resolution and contrast. The largest improvement in signal-to-noise ratio was obtained by the filters. Ideally, these filters should be accurately defined for each image. This is difficult in the clinical context. Moreover, they generate oscillation artefacts. In addition, the wavelet techniques did not bring significant improvements, and are rather slow. Therefore, Shine, which is fast and works automatically, appears to be an interesting alternative. [less ▲]

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See detailComparison of the current techniques used for the denoising of scintigraphic images
Kirkove, Murielle ULiege; Seret, Alain ULiege

in European Journal of Nuclear Medicine and Molecular Imaging (2006), 33(S2), 318

Detailed reference viewed: 30 (9 ULiège)
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See detailA Method for Spatial Deconvolution of Spectra
Courbin, F.; Magain, Pierre ULiege; Kirkove, Murielle ULiege et al

in Astrophysical Journal (2000), 529

A method for spatial deconvolution of spectra is presented. It follows the same fundamental principles as the ``MCS image deconvolution algorithm'' recently developed by Magain, Courbin, & Sohy and uses ... [more ▼]

A method for spatial deconvolution of spectra is presented. It follows the same fundamental principles as the ``MCS image deconvolution algorithm'' recently developed by Magain, Courbin, & Sohy and uses information contained in the spectrum of a reference point-spread function to spatially deconvolve spectra of very blended sources. An improved resolution rather than an infinite one is aimed at, overcoming the well-known problem of ``deconvolution artifacts.'' As in the MCS algorithm, the data are decomposed into a sum of analytical point sources and a numerically deconvolved background so that the spectrum of extended sources in the immediate vicinity of bright point sources may be accurately extracted and sharpened. The algorithm has been tested on simulated data including seeing variation as a function of wavelength and atmospheric refraction. It is shown that the spectra of severely blended point sources can be resolved while fully preserving the spectrophotometric properties of the data. Extended objects ``hidden'' by bright point sources (up to 4-5 mag brighter) can be accurately recovered as well, provided the data have a sufficiently high total signal-to-noise ratio (200-300 per spectral resolution element). Such spectra are relatively easy to obtain, even down to faint magnitudes, within a few hours of integration time with 10 m class telescopes. [less ▲]

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