References of "Pierard, Sébastien"
     in
Bookmark and Share    
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 115 (23 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 142 (25 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 99 (36 ULg)
Full Text
Peer Reviewed
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)

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 ▲]

Detailed reference viewed: 11 (3 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 25 (6 ULg)
Full Text
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 ▲]

Detailed reference viewed: 34 (1 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 16 (1 ULg)
Full Text
See detailReal-time processing of depth and color video streams to improve the reliability of depth maps
Pierard, Sébastien ULg; Leens, Jérôme ULg; Van Droogenbroeck, Marc ULg

Poster (2009, November)

Depth is a useful information in vision to understand the geometrical properties of an environment. Depth is traditionally computed in terms of a disparity map acquired by a stereoscopic system but, over ... [more ▼]

Depth is a useful information in vision to understand the geometrical properties of an environment. Depth is traditionally computed in terms of a disparity map acquired by a stereoscopic system but, over the last few years, several manufacturers have released single-lens cameras that directly capture depth information (also called range). This is an important technological breakthrough although range signals remain difficult to handle in practice, due to many reasons (low resolution, noise, low framerate, . . . ). Practitioners still struggle to use range data in their applications. The purpose of this paper is to give a brief introduction to range data (captured with a camera), discuss common limitations, and propose techniques to cope with difficulties typically encountered with range cameras. These techniques are based on a simultaneous view of the scene by a color and a depth camera that are combined to improve their interpretation in real time. [less ▲]

Detailed reference viewed: 87 (16 ULg)
Full Text
See detailA technique for building databases of annotated and realistic human silhouettes based on an avatar
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in Annual Workshop on Circuits, Systems and Signal Processing (ProRISC) (2009, November)

The real-time interpretation of video scenes and human motion is a research field with a lot of applications. Awidely used pre-processing step is the background subtraction, which highlights silhouettes ... [more ▼]

The real-time interpretation of video scenes and human motion is a research field with a lot of applications. Awidely used pre-processing step is the background subtraction, which highlights silhouettes. In addition, example-based and learning-based approaches are attractive for the interpretation of complex scenes. But to be effective, such techniques need to be trained on samples of realistic human silhouettes. This paper presents a method to automatically build databases of artificial, realistic, and annotated human silhouettes. Our method, based on a 3D human avatar, allows to save additional data with the silhouettes, and to highlight the different body parts. These supplementary data may be application-driven. To help in evaluating the relevance of automatically generated databases, we suggest some practical solutions based on a visual signature of the databases. [less ▲]

Detailed reference viewed: 156 (8 ULg)
Full Text
See detailTechniques to improve the foreground segmentation with a 3D camera and a color camera
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

(2009, November)

Nowadays, techniques for real-time interpretation of video scenes are widespread. Amongst these techniques, the foreground segmentation is one of the favorite. It can be applied to color images as well as ... [more ▼]

Nowadays, techniques for real-time interpretation of video scenes are widespread. Amongst these techniques, the foreground segmentation is one of the favorite. It can be applied to color images as well as depth maps. The point of using depth maps is straightforward as a single color camera is not able to provide depth information. Technologies capable to acquire 3D informations are thus adequate to complement color cameras in consumer products. Practice has shown that 3D or RGB signals, taken alone, are unreliable to extract the foreground under arbitrary conditions. Therefore we combine both modalities to counter the intrinsic limitations of both modalities, which is only possible if the problems specific to a technology are handled appropriately. This paper presents a new global approach for enhanced foreground segmentation that handles limitations to 3D and RGB in a combined way. [less ▲]

Detailed reference viewed: 127 (17 ULg)
Full Text
Peer Reviewed
See detailCombining Color, Depth, and Motion for Video Segmentation
Leens, Jérôme ULg; Pierard, Sébastien ULg; Barnich, Olivier et al

in Computer Vision Systems (2009)

This paper presents an innovative method to interpret the content of a video scene using a depth camera. Cameras that provide distance instead of color information are part of a promising young technology ... [more ▼]

This paper presents an innovative method to interpret the content of a video scene using a depth camera. Cameras that provide distance instead of color information are part of a promising young technology but they come with many diff culties: noisy signals, small resolution, and ambiguities, to cite a few. By taking advantage of the robustness to noise of a recent background subtraction algorithm, our method is able to extract useful information from the depth signals. We further enhance the robustness of the algorithm by combining this information with that of an RGB camera. In our experiments, we demonstrate this increased robustness and conclude by showing a practical example of an immersive application taking advantage of our algorithm. [less ▲]

Detailed reference viewed: 169 (31 ULg)
Full Text
See detailLa biodiversité, reflet des soubresauts de la biosphère et de l'équilibre géophysiologique.
Pierard, Sébastien ULg; Franchimont, Claudine ULg; Pierard, Gérald ULg

in Association des Géologues Amateurs de Belgique Minibul (2009), 42

Detailed reference viewed: 10 (4 ULg)
Full Text
See detailGénération automatique d'une base de données de silhouettes humaines au moyen d'un avatar humain tridimensionnel
Pierard, Sébastien ULg

Master's dissertation (2007)

Pour la conception de systèmes de vidéo-surveillance, il est avantageux d’avoir un système de détection automatique d’êtres humains. Certains de ces systèmes sont basés sur la reconnaissance de la forme ... [more ▼]

Pour la conception de systèmes de vidéo-surveillance, il est avantageux d’avoir un système de détection automatique d’êtres humains. Certains de ces systèmes sont basés sur la reconnaissance de la forme de silhouettes humaines. L’utilisation de méthodes d'apprentissage pour la reconnaissance nécessite une base de données de silhouettes humaines, dont il est intéressant d’automatiser la génération. Dans ce travail, nous utilisons un avatar humain tridimensionnel, celui du projet open-source MakeHuman, afin de générer automatiquement la base de données. Le choix des configurations (positions, orientations et poses) à donner à l’avatar pour obtenir une base de données adéquate est central. Dans un premier temps, nous tentons une étude de l’impact de modifications dans le mode tridimensionnel sur la silhouette. Cet impact est quantifié par la distance de Hausdorff. Parmi les modifications envisagées se trouvent le déplacement, la rotation et le changement de pose de l’avatar. Nous espérions déterminer, à partir de ces impacts, les pas par lesquels doivent varier les différents paramètres. Les configurations que doit prendre l’avatar, pour obtenir une base de données suffisamment riche sans être trop volumineuse, seront obtenues en prenant toutes les combinaisons des valeurs des différents paramètres. Le nombre de configurations est exponentiel en le nombre de degrés de liberté, ce qui rend l’approche inutilisable en pratique, même si nous sommes indifférents à la translation et à la mise à l’échelle des silhouettes. Dans un deuxième temps, nous avons opté pour une approche radicalement différente. Cette fois, nous n’espaçons plus les silhouettes, mais les poses. La position de l’avatar est fixée et il ne peut tourner qu’autour de l’axe vertical. Les poses sont choisies en effectuant des tirages aléatoires des différents paramètres. Cette approche aléatoire du problème a mené à l’élaboration d’un nouveau logiciel, Silhouette. Il est écrit en Java et une interface écrite en C lui permet, grâce à Java Native Interface d’exploiter efficacement le moteur de pose de MakeHuman. Parmi les fonctionnalités de Silhouette, notons la possibilité de restreindre les poses à un ensemble voulu, de ne générer que des silhouettes correspondant à des poses licites et d’annoter les silhouettes. Grâce au logiciel mis en place, nous avons été en mesure de générer diverses bases de données. Nous avons étudié l'impact de l'utilisation de celles-ci sur les performances d'un système de détection de personnes existant. Nous obtenons des résultats encourageants, 73% des silhouettes humaines étant correctement détectées. Un raffinement et un paramétrage soigneux de la méthode devraient mener à des résultats excellents. [less ▲]

Detailed reference viewed: 26 (3 ULg)
Full Text
See detailImpact du stress géoclimatique sur la peau.
Franchimont, Claudine ULg; Pierard, Sébastien ULg; Pierard, Gérald ULg

in Dermatologie Actualité (2006), 100

Detailed reference viewed: 23 (11 ULg)
Full Text
See detailStress écologique et chronobiologique de la dérive géoclimatique.
Pierard, Sébastien ULg; Franchimont, Claudine ULg; Pierard, Gérald ULg

in Revue Verviétoise d'Histoire Naturelle (2002), 59

Detailed reference viewed: 64 (2 ULg)
Full Text
See detailLes rudistes de la Mésogée. Anatomie et biotope.
Pierard, Sébastien ULg; Franchimont, Claudine ULg; Pierard, Gérald ULg

in Revue Verviétoise d'Histoire Naturelle (2001), 58

Detailed reference viewed: 30 (1 ULg)
Full Text
See detailLes Scarabées.
Pierard, Sébastien ULg; Franchimont, Claudine ULg; Pierard, Gérald ULg

in Revue Verviétoise d'Histoire Naturelle (2000), 57

Detailed reference viewed: 12 (1 ULg)
Full Text
See detailL'appareil aptychial chez les ammonoïdes.
Pierard, Sébastien ULg; Franchimont, Claudine ULg; Pierard, Gérald ULg

in Association des Géologues Amateurs de Belgique Minibul (2000), 33

Detailed reference viewed: 10 (1 ULg)