References of "Pierard, Sébastien"
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See detailNeural networks for musical chords recognition
Osmalsky, Julien ULg; Embrechts, Jean-Jacques ULg; Van Droogenbroeck, Marc ULg et al

in Journées d'informatique musicale (2012, May)

In this paper, we consider the challenging problem of music recognition and present an effective machine learning based method using a feed-forward neural network for chord recognition. The method uses ... [more ▼]

In this paper, we consider the challenging problem of music recognition and present an effective machine learning based method using a feed-forward neural network for chord recognition. The method uses the known feature vector for automatic chord recognition called the Pitch Class Profile (PCP). Although the PCP vector only provides attributes corresponding to 12 semi-tone values, we show that it is adequate for chord recognition. Part of our work also relates to the design of a database of chords. Our database is primarily designed for chords typical of Western Europe music. In particular, we have built a large dataset filled with recorded guitar chords under different acquisition conditions (instruments, microphones, etc), but also with samples obtained with other instruments. Our experiments establish a twofold result: (1) the PCP is well suited for describing chords in a machine learning context, and (2) the algorithm is also capable to recognize chords played with other instruments, even unknown from the training phase. [less ▲]

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See detailRecognition of emotions in facial images
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

Report (2012)

This document reports about some work done in the field of emotions classification in facial images.

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See detailEstimation of human orientation based on silhouettes and machine learning principles
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in International conference on pattern recognition applications and methods (ICPRAM) (2012, February)

Estimating the orientation of the observed person is a crucial task for home entertainment, man-machine interaction, intelligent vehicles, etc. This is possible but complex with a single camera because it ... [more ▼]

Estimating the orientation of the observed person is a crucial task for home entertainment, man-machine interaction, intelligent vehicles, etc. This is possible but complex with a single camera because it only provides one side view. To decrease the sensitivity to color and texture, we use the silhouette to infer the orientation. Under these conditions, we show that the only intrinsic limitation is to confuse the orientation q with the supplementary angle (that is 180°-theta), and that the shape descriptor must distinguish between mirrored images. In this paper, the orientation estimation is expressed and solved in the terms of a regression problem and supervised learning. In our experiments, we have tested and compared 18 shape descriptors; the best one achieves a mean error of 5:24°. However, because of the intrinsic limitation mentioned above, the range of orientations is limited to 180°. Our method is easy to implement and outperforms existing techniques. [less ▲]

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See detailOn the human pose recovery based on a single view
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in International conference on pattern recognition applications and methods (ICPRAM) (2012, February)

Estimating the pose of the observed person is crucial for a large variety of applications including home entertainment, man-machine interaction, video surveillance, etc. Often, only a single side view is ... [more ▼]

Estimating the pose of the observed person is crucial for a large variety of applications including home entertainment, man-machine interaction, video surveillance, etc. Often, only a single side view is available, but authors claim that it is possible to derive the pose despite that humans evolve in a 3D environment. In addition, to decrease the sensitivity to color and texture, it is preferable to rely only on the silhouette to recover the pose. Under these conditions, we show that there is an intrinsic limitation: at least two poses correspond to the observed silhouette. We discuss this intrinsic limitation in details in this short paper. To our knowledge, this issue has been overlooked by authors in the past. We observe that this limitation has an impact on the way previous reported results should be interpreted, and it has clearly to be taken into account for designing new methods. [less ▲]

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See detailLe "cheetah-look". Le phénotype guépart, face cachée de la pigmentation mélanique innée du visage.
Hermanns-Le, Trinh ULg; AL RUSTOM, Kamil; FRANCHIMONT, Claudine ULg et al

in Dermatologie Actualité (2012), 131

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See detailMultimodal evaluation of gait and stride dynamics in relapsing and progressive forms of multiple sclerosis
Belachew, Shibeshih ULg; Pierard, Sébastien ULg; PHAN BA, Remy ULg et al

in Proceedings of the Belgian Royal Academies of Medicine (2012), 1

Ambulation measures are being increasingly recognized as highly relevant to the quantification of multiple sclerosis (MS) severity and response to treatment. Feet paths are highly informative for gait ... [more ▼]

Ambulation measures are being increasingly recognized as highly relevant to the quantification of multiple sclerosis (MS) severity and response to treatment. Feet paths are highly informative for gait analysis and we have recently designed a new system, which captures the position of the feet in real time. We use several range laser scanners (RLS) to analyze a horizontal slice of the scene in which each foot is considered as a point, and the vertical movements are ignored. Neat ambulation measures may be easily extracted such as walking speed, distance between feet over time, swing phase duration, and gait asymmetry in specific settings of walking recommendations. Our RLS platform is much cheaper than existing sensor-based and motion capture systems and may be more convenient for the development of multicentric clinical trials settings since patients can be easily and rapidly assessed without tags or sensors in the hallway of an outpatient clinic. We use 4 BEA LZR-i100 RLS arranged in a corridor of at least 10m long and 4m width, devoid of obstacle. The scanned plane is chosen to be located at 15 cm above the floor, which is right above the tibio-tarsal joint of the ankle in a barefoot configuration for adult individuals in stance phase. We expect further studies to validate and empower the meaning of non-intrusive RLS-derived gait measures that should pave the ground for major improvements in the way we will assess the efficacy of disease-modifying treatments (DMTs), physical therapy and symptomatic interventions on walking impairment, ataxia and fatigability in MS. RLS-derived gait measures may also reveal to be crucial in the near future for the development of treatments that would specifically target progressive forms of MS. [less ▲]

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See detailTélédermatopathologie et dermatopathologie virtuelle en temps réel.
REGINSTER, Marie-Annick ULg; Pierard, Sébastien ULg; PIERARD, Gérald ULg et al

in Dermatologie Actualité (2012), 129

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See detailA new jump edge detection method for 3D cameras
Lejeune, Antoine ULg; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg et al

in International Conference on 3D Imaging (IC3D) (2011, December)

Edges is a fundamental clue for analyzing, interpreting, and understanding 3D scenes: they describe objects boundaries. Available edge detection methods are not suited for 3D cameras such as the Microsoft ... [more ▼]

Edges is a fundamental clue for analyzing, interpreting, and understanding 3D scenes: they describe objects boundaries. Available edge detection methods are not suited for 3D cameras such as the Microsoft Kinect or a time-of-flight camera: they are slow and do not take into consideration the characteristics of the cameras. In this paper, we present a fast jump edge detection technique for 3D cameras based on the principles of Canny’s edge detector. We first analyze the characteristics of the range signal for two different kinds of cameras: a time-of-flight camera (the PMD[vision] CamCube) and the Microsoft Kinect. From this analysis, we define appropriate operators and thresholds to perform the edge detection. Then, we present some results of the developed algorithms for both cameras. [less ▲]

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See detailA new low-cost and non-intrusive feet tracker
Pierard, Sébastien ULg; PHAN BA, Remy ULg; Van Droogenbroeck, Marc ULg et al

in Workshop on Circuits, Systems and Signal Processing (ProRISC) (2011, November)

Capturing gait is useful for many applications, including video-surveillance and medical purposes. The most common sensors used to capture gait suffer from significant drawbacks. We have therefore ... [more ▼]

Capturing gait is useful for many applications, including video-surveillance and medical purposes. The most common sensors used to capture gait suffer from significant drawbacks. We have therefore designed a new low-cost and nonintrusive system to capture gait. Our system is able to track the feet on the horizontal plane in both the stance and the swing phases by combining measures of several range laser scanners. The number of sensors can be adjusted according to the target application specifications. The first issue addressed in this work is the calibration: we have to know the precise location of the sensors in a plane, and their orientations. The second issue addressed is how to calculate feet coordinates from the distance profiles given by the sensors. Our method has proven to be robust and precise to measure gait abnormalities in various medical conditions, especially neurological diseases (with a focus on multiple sclerosis). [less ▲]

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See detailEstimation of human orientation in images captured with a range camera
Pierard, Sébastien ULg; Leroy, Damien; Hansen, Jean-Frédéric et al

in Advanced Concepts for Intelligent Vision Systems (ACIVS) (2011, August)

Estimating the orientation of the observed person is a crucial task for some application fields like home entertainment, man-machine interaction, or intelligent vehicles. In this paper, we discuss the ... [more ▼]

Estimating the orientation of the observed person is a crucial task for some application fields like home entertainment, man-machine interaction, or intelligent vehicles. In this paper, we discuss the usefulness of conventional cameras for estimating the orientation, present some limitations, and show that 3D information improves the estimation performance. Technically, the orientation estimation is solved in the terms of a regression problem and supervised learning. This approach, combined to a slicing method of the 3D volume, provides mean errors as low as 9.2° or 4.3° depending on the set of considered poses. These results are consistent with those reported in the literature. However, our technique is faster and easier to implement than existing ones. [less ▲]

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See detailObject descriptors based on a list of rectangles: method and algorithm
Van Droogenbroeck, Marc ULg; Pierard, Sébastien ULg

in Soille, P., Pesarisi, M. (Ed.) International Symposium on Mathematical Morhology (ISMM) (2011, July)

Most morphological operators use a unique structuring element, possibly at different scales, to describe an object. In addition, morphological algorithms are often restricted to 1D structuring elements ... [more ▼]

Most morphological operators use a unique structuring element, possibly at different scales, to describe an object. In addition, morphological algorithms are often restricted to 1D structuring elements, combinations of 1D elements, or isotropic structuring elements (like circles), because of the lack of methods directly applicable to 2D structuring elements. While these descriptors have proved useful in the past, we propose an alternative that uses the list of maximal rectangles contained in a set X. In particular, we focus on an opening that preserves large rectangles contained in a set X and on its companion 2D algorithm that builds a list of all the maximal rectangles that fit inside an arbitrary set X. This list is the base of new descriptors that have been used successfully for machine learning tasks. [less ▲]

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See detailA probabilistic pixel-based approach to detect humans in video streams
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

in International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2011) (2011, May)

Human detection in video streams is an important task in many applications including video surveillance. Surprisingly, only few papers have been devoted to this topic. This paper presents a new approach ... [more ▼]

Human detection in video streams is an important task in many applications including video surveillance. Surprisingly, only few papers have been devoted to this topic. This paper presents a new approach to detect humans in video streams. Our approach is based on the temporal information present in videos. A background subtraction algorithm is first used to segment the silhouettes of the users and the moving objects. Then a classification process in two steps determines for each connected component if it corresponds to the silhouette of a human or not. During the first step, a probabilistic information is computed for each pixel independently. The information from a subset of pixels is then gathered to predict the class of the observed silhouette. This paper presents the principles and some results obtained on real silhouettes. It is shown that our approach is efficient for the detection of humans in video streams. [less ▲]

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See detailRecent trends in specular light reflectance beyond clinical fluorescence diagnosis.
Szepetiuk, Gregory; Pierard, Sébastien ULg; PIERARD-FRANCHIMONT, Claudine ULg et al

in European Journal of Dermatology (2011), 21(2), 157-61

Under specific light illumination, particularly ultraviolet (UV) and near-UV light stimulation, the skin produces both specular light reflectance and, possibly, specific fluorescent emission. These ... [more ▼]

Under specific light illumination, particularly ultraviolet (UV) and near-UV light stimulation, the skin produces both specular light reflectance and, possibly, specific fluorescent emission. These properties offer diagnostic clues and disclose some peculiar functions of the skin. A series of superficial infections (erythrasma, some tinea capitis types, tinea/pityriasis versicolor, dermatophytoses, etc.) and pilosebaceous follicles enriched in Propionibacterium spp show fluorescence. This latter characteristic is downgraded or lost while on some anti-acne treatments. A quenching effect of fluorescence is observed following the application of sunscreens. The (pre)neoplastic areas prepared for methylaminolevulinate photodynamic therapy (MAL-PDT) show reddish fluorescence following drug metabolisation producing porphyrins by the abnormal activated cells. Of note, when using a recording sensitive CCD camera instead of casual visual observation, skin fluorescence may be superimposed on the specular reflectance of the incident light. With the current technology, these situations are not distinguished with confidence. Any harsh and scaly lesion appears brighter following yellowish specular light reflectance. Stratum corneum samplings collected on clear self-adhesive discs or cyanoacrylate skin surface strippings are conveniently examined ex vivo, taking advantage of the same optical properties. [less ▲]

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See detail3D information is valuable for the detection of humans in video streams
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

in 3D Stereo Media (2010, December)

In this paper, we propose a technique based on 3D information (also called depth or range) for the detection of humans. First, a background subtraction technique operates to detect the silhouettes of ... [more ▼]

In this paper, we propose a technique based on 3D information (also called depth or range) for the detection of humans. First, a background subtraction technique operates to detect the silhouettes of humans and objects moving in the scene. Then, a machine learning algorithm is used to predict if a silhouette annotated with depth matches a human silhouette or not. The complete method is designed to cope with defects introduced during the segmentation step. Results, obtained on computer generated data, show that 3D depth data is a valuable information for detecting humans in that it improves over techniques based on binary silhouettes. In our experiments, we have reached an accuracy of 99.9% thanks to the depth information. [less ▲]

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See detailA virtual curtain for the detection of humans and access control
Barnich, Olivier; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in Advanced Concepts for Intelligent Vision Systems (ACIVS) (2010, December)

Biometrics has become a popular field for the development of techniques that aim at recognizing humans based upon one or more intrinsic physical or behavioral traits. In particular, many solutions ... [more ▼]

Biometrics has become a popular field for the development of techniques that aim at recognizing humans based upon one or more intrinsic physical or behavioral traits. In particular, many solutions dedicated to access control integrate biometric features like fingerprinting or face recognition. This paper describes a new method designed to interpret what happens when crossing an invisible vertical plane, called virtual curtain hereafter, at the footstep of a door frame. It relies on the use of two laser scanners located in the upper corners of the frame, and on the classification of the time series of the information provided by the scanners after registration. The technique is trained and tested on a set of sequences representative for multiple scenarios of normal crossings by a single person and for tentatives to fool the system. We present the details of the technique and discuss classification results. It appears that the technique is capable to recognize many scenarios which may lead to the development of new commercial applications. [less ▲]

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See detailA platform for the fast interpretation of movements and localization of users in 3D applications driven by a range camera
Pierard, Sébastien ULg; Pierlot, Vincent ULg; Barnich, Olivier ULg et al

in Proceedings of the 3DTV Conference (2010, June)

Interactivity is one of the key challenges for immersive applications like gaming. Manufacturers have been working towards interfaces that are driven by a device (e.g. a Wiimote) or interfaces that are ... [more ▼]

Interactivity is one of the key challenges for immersive applications like gaming. Manufacturers have been working towards interfaces that are driven by a device (e.g. a Wiimote) or interfaces that are controlled by a camera with a subsequent computer vision module. Both approaches have unique advantages, but they do not permit to localize users in the scene with an appropriate accuracy. Therefore, we propose to use both a range camera and accurate range sensors to enable the interpretation of movements. This paper describes a platform that uses a range camera to acquire the silhouettes of users, regardless of illumination, and to improve the pose recovery with range information after some image processing steps. In addition, to circumvent the difficult process of calibration required to map range values to physical distances, we complete the system with several range laser sensors. These sensors are located in a horizontal plane, and measure distances up to a few centimeters. We combine all these measurements to obtain a localization map, used to locate users in the scene at a negligible computational cost. Our method fills a gap in 3D applications that requires absolute positions. [less ▲]

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See detailIntroduction a l'analyse spectrale des reseaux microvasculaires du melanome cutane primitif.
Quatresooz, Pascale ULg; Pierard, Gérald ULg; FRANCHIMONT, Claudine ULg et al

in Pathologie Biologie (2010), 60

Cutaneous malignant melanoma represents one of the most dramatic skin cancers because its incidence is steadily growing in White populations. Of note, its metastatic risk and mortality dramatically ... [more ▼]

Cutaneous malignant melanoma represents one of the most dramatic skin cancers because its incidence is steadily growing in White populations. Of note, its metastatic risk and mortality dramatically increase when the primary neoplasm reaches about one millimeter thick. It is believed that angiogenesis and lymphangiogenesis associated with cutaneous melanoma potentially influence the neoplastic progression of the primary tumor and its metastases. In some instances, both the intratumoral and peritumoral microvasculature are correlated to booming of the tumoral growth fraction. In addition, the vascular network serves as a migration path for the intravascular and perivascular neoplastic spread. Hence, the quantification of the microvasculature might help establishing a prognostic factor of evolution. Among the available methods, spectral analysis of immunohistochemical sections highlighting vessels helps defining the microvasculature distribution. The benefit of using spectral analysis is discussed and the modalities of application of this analytical method are scrutinized. [less ▲]

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See detailIntroduction a l'analyse spectrale des reseaux microvasculaires du melanome cutane primitif.
Quatresooz, Pascale ULg; PIERARD, Gérald ULg; FRANCHIMONT, Claudine ULg et al

in Pathologie et Biologie (2010)

Cutaneous malignant melanoma represents one of the most dramatic skin cancers because its incidence is steadily growing in White populations. Of note, its metastatic risk and mortality dramatically ... [more ▼]

Cutaneous malignant melanoma represents one of the most dramatic skin cancers because its incidence is steadily growing in White populations. Of note, its metastatic risk and mortality dramatically increase when the primary neoplasm reaches about one millimeter thick. It is believed that angiogenesis and lymphangiogenesis associated with cutaneous melanoma potentially influence the neoplastic progression of the primary tumor and its metastases. In some instances, both the intratumoral and peritumoral microvasculature are correlated to booming of the tumoral growth fraction. In addition, the vascular network serves as a migration path for the intravascular and perivascular neoplastic spread. Hence, the quantification of the microvasculature might help establishing a prognostic factor of evolution. Among the available methods, spectral analysis of immunohistochemical sections highlighting vessels helps defining the microvasculature distribution. The benefit of using spectral analysis is discussed and the modalities of application of this analytical method are scrutinized. [less ▲]

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See detailGaïa, le stress géoclimatique et la peau.
Pierard, Sébastien ULg; Noel, Fanchon; Franchimont, Claudine ULg et al

in Dermo'Sphère (2010), 2

Le Soleil est à l’origine de la vie sur Terre. Le grand ensemble d’interactions biogéochimiques entre la vie, le sol, l’atmosphère et l’océan n’est pas sans rappeler la physiologie d’un grand organisme ... [more ▼]

Le Soleil est à l’origine de la vie sur Terre. Le grand ensemble d’interactions biogéochimiques entre la vie, le sol, l’atmosphère et l’océan n’est pas sans rappeler la physiologie d’un grand organisme unique. Ce dernier a reçu le nom de Gaïa. Tout le fonctionnement de la biosphère qui en fait partie est largement dépendant de l’apport énergétique solaire. Celui-ci est diversifié car le spectre des rayonnements électromagnétiques est large et variable en intensité et en nature. Le réchauffement global de la Terre et le « trou d’ozone » sont sous les feux de l’actualité. De tels bouleversements sont-ils la préfiguration d’une apocalypse ? L’écologie et la dérive géoclimatique vont-elles influencer la dermatologie de demain ? [less ▲]

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See detailEnvironmental dew point and skin and lip weathering.
Devillers, C.; Pierard, Gérald ULg; Quatresooz, Pascale ULg et al

in Journal of the European Academy of Dermatology & Venereology (2010), 24(5), 513-7

Xerosis represents a physiological response of the stratum corneum (SC) to environmental threats. The influence of the environmental dew point (DP) is not fully understood. This parameter is the air ... [more ▼]

Xerosis represents a physiological response of the stratum corneum (SC) to environmental threats. The influence of the environmental dew point (DP) is not fully understood. This parameter is the air temperature at which the relative humidity is maximum. This study aimed to assess the relationship between the environmental DP and the water-holding capacity of the skin and lower lip vermilion. For comparison, SC property was evaluated after occlusive application of cooled and uncooled hydrogel pads. Electrometric measurements using a dermal phase meter (DPM) device were performed on the back of the hands, the cheeks and the lower lip of 40 healthy menopausal women. Assessments were performed in the outdoor conditions during winter and spring. The same measurements were recorded after hydrogel pads, at room temperature or cooled to 4 degrees C, were placed for 15 min on the test sites. The environmental DP was recorded at each evaluation time. The SC water-holding capacity was discretely influenced by the DP. In the open-air environmental conditions, a positive linear relationship was found on the cheeks between the DP and DPM values. The relationship was weaker on the lips. Conversely, a consistent increase in DPM values was recorded immediately after removal of the cooled and uncooled hydrogel pads. The observations made in the open-air testing conditions are consistent with the predicted events following the Arrhenius law. By contrast, the combination of cooling and occlusion by the hydrogel pads is responsible for the reverse effect on the SC. [less ▲]

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