References of "Verly, Jacques"
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See detailDevelopment and validation of an accelerometer-based method for quantifying gait events
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Stamatakis, Julien et al

in Medical Engineering & Physics (2015)

An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO ... [more ▼]

An original signal processing algorithm is presented to automatically extract, on a stride-by-stride basis, four consecutive fundamental events of walking, heel strike (HS), toe strike (TS), heel-off (HO), and toe-off (TO), from wireless accelerometers applied to the right and left foot. First, the signals recorded from heel and toe three-axis accelerometers are segmented providing heel and toe flat phases. Then, the four gait events are defined from these flat phases. The accelerometer-based event identification was validated in seven healthy volunteers and a total of 247 trials against reference data provided by a force plate, a kinematic 3D analysis system, and video camera. HS, TS, HO, and TO were detected with a temporal accuracy ± precision of 1.3 ms ± 7.2 ms, ‒4.2 ms ± 10.9 ms, ‒3.7 ms ± 14.5 ms, and ‒1.8 ms ± 11.8 ms, respectively, with the associated 95% confidence intervals ranging from ‒6.3 ms to 2.2 ms. It is concluded that the developed accelerometer-based method can accurately and precisely detect HS, TS, HO, and TO, and could thus be used for the ambulatory monitoring of gait features computed from these events when measured concurrently in both feet. [less ▲]

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See detailSegmentation of gait cycles using foot-mounted 3D accelerometers
Boutaayamou, Mohamed ULg; Bruls, Olivier ULg; Denoël, Vincent ULg et al

in Proceedings of the IEEE International Conference on 3D Imaging 2015 (2015)

We describe a new gait segmentation method based on the continuous wavelet transform to identify stride-by-stride gait cycles from measurements of foot-mounted three-dimensional (3D) accelerometers. The ... [more ▼]

We describe a new gait segmentation method based on the continuous wavelet transform to identify stride-by-stride gait cycles from measurements of foot-mounted three-dimensional (3D) accelerometers. The detection of such gait cycles is indeed a crucial step for an accurate extraction of relevant gait events such as heel strike, toe strike, heel-off, and toe-off. We demonstrate the ability of this segmentation method, used in conjunction with a validated extraction algorithm, to calculate the following gait (duration) parameters for each gait cycle during the gait of a healthy young subject and of an elderly subject with Parkinson’s disease (PD) in OFF and ON states: durations of (1) loading response, (2) mid-stance, (3) push-off, (4) stance, (5) swing, (6) stride, (7) step, and (8) double support phases. The experimental results show that the proposed method can extract relevant refined gait parameters to quantify subtle gait disturbances in subjects with PD. [less ▲]

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See detailAmbulatory system using wearable accelerometers for gait analysis in Parkinson’s disease
Boutaayamou, Mohamed ULg; Demonceau, Marie ULg; Schwartz, Cédric ULg et al

in Proceedings of the 14th Belgian Day on Biomedical Engineering (2015)

We describe a signal-processing algorithm for gait analysis in Parkinson’s disease (PD) using an ambulatory system with wearable accelerometers. This algorithm is versatile enough to detect, on a stride ... [more ▼]

We describe a signal-processing algorithm for gait analysis in Parkinson’s disease (PD) using an ambulatory system with wearable accelerometers. This algorithm is versatile enough to detect, on a stride-by-stride basis, refined gait parameters that quantify subtle gait disturbances in PD in a rater-independent way. [less ▲]

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See detailOrganizer and General Chair of 2014 International Conference on 3D Food Printing
Verly, Jacques ULg

Book published by University of Liège (2014)

Detailed reference viewed: 23 (0 ULg)
See detailGeneral Chair and Co-Organizer of (2014) "3D Stereo MEDIA: The International 3D Summit for Science, Technology, Art, and Business". Held in Liège, Belgium, on 9-11 Dec 2014, at Theater of Liège and University of Liège. 6th edition. J. G. Verly initiated event in 2008.
Verly, Jacques ULg

Book published by Image&3D Europe ASBL (2014)

3D Stereo MEDIA 2014 was held in Liège, Belgium, on 9-11 Dec 2014, and comprised the following sub-events: 3D Workshop in Cannes (Festival de Cannes, American Pavilion, Cannes, France, 16 May 2015 ... [more ▼]

3D Stereo MEDIA 2014 was held in Liège, Belgium, on 9-11 Dec 2014, and comprised the following sub-events: 3D Workshop in Cannes (Festival de Cannes, American Pavilion, Cannes, France, 16 May 2015), Scientific Conference: 2014 International Conference on 3D Imaging (IC3D 2014), 3D Content Financing Market, International 3D Festival, Professional Conference, B2B Meetings, Awards Evening. [less ▲]

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See detailOrganizer, General Chair, and Editor of 2014 International Conference on 3D Imaging
Verly, Jacques ULg

Book published by Institute of Electrical and Electronics Engineers (IEEE) (2014)

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See detailDevelopment and validation of a 3D kinematic-based method for determining gait events during overground walking
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Denoël, Vincent ULg et al

in IEEE International Conference on 3D Imaging (IC3D) (2014, December 09)

A new signal processing algorithm is developed for quantifying heel strike (HS) and toe-off (TO) event times solely from measured heel and toe coordinates during overground walking. It is based on a rough ... [more ▼]

A new signal processing algorithm is developed for quantifying heel strike (HS) and toe-off (TO) event times solely from measured heel and toe coordinates during overground walking. It is based on a rough estimation of relevant local 3D position signals. An original piecewise linear fitting method is applied to these local signals to accurately identify HS and TO times without the need of using arbitrary experimental coefficients. We validated the proposed method with nine healthy subjects and a total of 322 trials. The extracted temporal gait events were compared to reference data obtained from a force plate. HS and TO times were identified with a temporal accuracy ± precision of 0.3 ms ± 7.1 ms, and –2.8 ms ± 7.2 ms in comparison with reference data defined with a force threshold of 10 N. This algorithm improves the accuracy of the HS and TO detection. Furthermore, it can be used to perform stride-by-stride analysis during overground walking with only recorded heel and toe coordinates. [less ▲]

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See detailEvaluation of pairwise calibration techniques for range cameras and their ability to detect a misalignment
Lejeune, Antoine ULg; Grogna, David ULg; Van Droogenbroeck, Marc ULg et al

in International Conference on 3D Imaging (IC3D) (2014, December)

Many applications require the use of multiple cameras to cover a larger volume. In this paper, we evaluate several pair-wise calibration techniques dedicated to range cameras. We compare the precision of ... [more ▼]

Many applications require the use of multiple cameras to cover a larger volume. In this paper, we evaluate several pair-wise calibration techniques dedicated to range cameras. We compare the precision of a self-calibration technique based on the movement in front of the cameras to object based calibration. While the self-calibration method is less precise than its counterparts, it yields a first estimation of the transformation between the cameras and permits to detect when the cameras become mis-aligned. Therefore it is useful in a practical situations. [less ▲]

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See detailDesign and implementation of a T impedance matching network for the radiocommunication subsystem aboard the OUFTI-1 nanosatellite
Boutaayamou, Mohamed ULg; Crosset, Nicolas ULg; Werner, Xavier ULg et al

in Proceedings of the URSI Forum 2014 (2014, November 18)

We describe how we handled an unexpected impedance matching issue on the receiver side (at UHF) of the radiocommunication system aboard the OUFTI-1 nanosatellite of the University of Liège. Our approach ... [more ▼]

We describe how we handled an unexpected impedance matching issue on the receiver side (at UHF) of the radiocommunication system aboard the OUFTI-1 nanosatellite of the University of Liège. Our approach relied on a combination of novel analytical developments combined with experimentation. [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 ULg; Wertz, Jérôme ULg; Kirkove, Murielle ULg et al

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

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See detailValidation of a new automatic drowsiness quantification system for drivers
Wertz, Jérôme ULg; François, Clémentine ULg; Verly, Jacques ULg

Poster (2014, July)

Drowsiness is a major cause of various types of accidents, and particularly of driving accidents. Scientific studies report that drowsiness would be responsible for 20 to 30% of driving accidents ... [more ▼]

Drowsiness is a major cause of various types of accidents, and particularly of driving accidents. Scientific studies report that drowsiness would be responsible for 20 to 30% of driving accidents. Drowsiness can result from, among others, sleep deprivation, sleep disorders, alcohol, some medications, or performing a monotonous task. While all persons are likely to be drowsy at some point during the day, some persons are more prone than others to being drowsy at almost any time of the day; e.g. 6 to 11% of the population suffers from severe chronic excessive daytime sleepiness. Three main classes of methods can be used to characterize the level of drowsiness of a driver without disturbing him. These classes are respectively related to vehicle behavior (e.g. via lateral movements), driver behavior (e.g. via steering wheel movements), and driver physiological state (e.g. via eye movements). Since drowsiness is a physiological state, it seems particularly meaningful to use physiology-based methods to characterize it. Among these, the most significant ones rely on polysomnography and/or oculography. Polysomnography is viewed by some practitioners as the reference in the domain, but it is very sensitive to artifacts, and it is not very practical for use while driving. Ocular parameters are recognized to be good and reliable physiological indicators of drowsiness, and, thus, oculography seems to be the most sensible way to characterize drowsiness in practice. We have thus developed an experimental, fully automatic drowsiness monitoring system (software/algorithms) based on the physiological state of a person. This system uses ocular parameters extracted from images of the eye (i.e. photooculography) to determine a level of drowsiness on a continuous numerical scale from 0 to 10, with 0 corresponding to "very awake" (or "very vigilant") and 10 to "very drowsy". The ultimate goal of this system is to prevent drowsiness-related accidents for driving and other applications. The reported study shows that our system exhibits promising capability for road safety. Fourteen healthy volunteers (7 M, 7 F, mean age 23.7, range 21-33 years) participated in an experiment in a driving simulator, where they were asked to perform three driving sessions/runs (two of 45 minutes and one of 60 minutes) in different sleep-deprivation conditions (with up to 28 hours of complete sleep deprivation). During each session, we recorded both a high frame rate video of one eye and a set of driving parameters. Subsequently, for each successive minute in the session, we used our algorithms to extract ocular parameters from the video images and to produce a level of drowsiness, and we computed the standard deviation of lateral position (SDLP) from the driving parameters. The results show (1) that the (computed) SDLP increases when the (computed) level of drowsiness increases, and (2) that the level of drowsiness increases when the level of sleep deprivation increases. These results indicate that our algorithms for producing a level of drowsiness work in a meaningful way. The experiment protocol was approved by the Ethics Committee of our university. [less ▲]

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See detailDetection of eye movements specific to drowsiness and their relation with subjective assessment: A cognitive ergonomic approach.
Blavier, Adelaïde ULg; Montagnino, Cédric; Wertz, Jérôme ULg et al

Poster (2014, May 27)

Drowsiness is one of the major factors explaining accidents, particularly in traffic accidents but also in work situations with serious consequences (e.g. medicine). The drowsiness may be assessed by ... [more ▼]

Drowsiness is one of the major factors explaining accidents, particularly in traffic accidents but also in work situations with serious consequences (e.g. medicine). The drowsiness may be assessed by diverse measures that vary from physiological and unconscious data (e.g. EEG) to subjective and conscious evaluation. In their daily life, people are used to evaluate their drowsiness by subjective assessment and research observes a great inter-individual variation in this evaluation. Moreover, the subjective evaluation is dependent on the situation and the risk perceived by the person (e.g., new versus usual situations, simple versus complex environments, etc.). In this theoretical context, our purpose was to investigate the links between 1) objective performance (reaction time) measured by a psychomotor vigilance task (PVT), 2) data from eye movements and 3) subjective assessment of drowsiness (measured with Karolinska Sleepiness Scale, KSS). 12 persons, aged from 20 to 56, participated individually. They were asked to respect a 60% sleep deprivation during the night before the experiment and to not drink any energy drinks the day of the experiment. The experiment was conducted between 1 and 3 PM after a heavy lunch in order to increase the circadian effect. Moreover, the temperature of the room was 25° in order to increase drowsiness. Each participant was asked to perform 4 PVT. However, although 100% of participants performed the first two PVT, only 66% were able to perform the third PVT and only 33% of participants performed the fourth and last PVT. Our results showed an effect of time on objective performance, eye movements and subjective assessment of drowsiness in PVT 1 and 2: significant increase of reaction time, increase of eye closure and perclos, reduction of pupil diameter and increase of subjective drowsiness estimation (KSS). Only the frequency and duration of blinks remained constant across time. In PVT 3 and 4, data from eye movements and objective performance (reaction time) did not vary anymore across the time. Only the subjective estimation of drowsiness (KSS) continued to increase. Furthermore, subjective estimation of drowsiness was differently correlated with eye movements and objective performance across the PVT; it was significantly correlated with reaction time (PVT 1,2,3), blink frequency and duration (PVT 1,2,3), perclos (PVT 1,2,3,4), eye closure (PVT 2,3), pupil diameter (PVT 1,2,3,4). These results are discussed and integrated in an ergonomic approach in order to analyze the links between objective performance, eye movements and subjective assessment of drowsiness. [less ▲]

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See detailFrom Sputnik to Beanie Babies & CubeSats to OUFTI
Verly, Jacques ULg

Conference given outside the academic context (2014)

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See detailDetection of eye movements specific to drowsiness and their relation with subjective assessment of sleepiness in PVT: A cognitive ergonomic approach
Blavier, Adelaïde ULg; Montagnino, Cédric; Wertz, Jérôme ULg et al

Conference (2014, February 24)

Drowsiness is one of the major factors explaining accidents, particularly in traffic accidents but also in work situations with serious consequences (e.g. medicine). The drowsiness may be assessed by ... [more ▼]

Drowsiness is one of the major factors explaining accidents, particularly in traffic accidents but also in work situations with serious consequences (e.g. medicine). The drowsiness may be assessed by diverse measures that vary from physiological and unconscious data (e.g. EEG) to subjective and conscious evaluation. In their daily life, people are used to evaluate their drowsiness by subjective assessment and research observes a great inter-individual variation in this evaluation. Moreover, the subjective evaluation is dependent on the situation and the risk perceived by the person (e.g., new versus usual situations, simple versus complex environments, etc.). In this theoretical context, our purpose was to investigate the links between 1) objective performance (reaction time) measured by a psychomotor vigilance task (PVT), 2) data from eye movements and 3) subjective assessment of drowsiness (measured with Karolinska Sleepiness Scale, KSS). 12 persons, aged from 20 to 56, participated individually. They were asked to respect a 60% sleep deprivation during the night before the experiment and to not drink any energy drinks the day of the experiment. The experiment was conducted between 1 and 3 PM after a heavy lunch in order to increase the circadian effect. Moreover, the temperature of the room was 25° in order to increase drowsiness. Each participant was asked to perform 4 PVT. However, although 100% of participants performed the first two PVT, only 66% were able to perform the third PVT and only 33% of participants performed the fourth and last PVT. Our results showed an effect of time on objective performance, eye movements and subjective assessment of drowsiness in PVT 1 and 2: significant increase of reaction time, increase of eye closure and perclos, reduction of pupil diameter and increase of subjective drowsiness estimation (KSS). Only the frequency and duration of blinks remained constant across time. In PVT 3 and 4, data from eye movements and objective performance (reaction time) did not vary anymore across the time. Only the subjective estimation of drowsiness (KSS) continued to increase. Furthermore, subjective estimation of drowsiness was differently correlated with eye movements and objective performance across the PVT; it was significantly correlated with reaction time (PVT 1,2,3), blink frequency and duration (PVT 1,2,3), perclos (PVT 1,2,3,4), eye closure (PVT 2,3), pupil diameter (PVT 1,2,3,4). These results are discussed and integrated in an ergonomic approach in order to analyze the links between objective performance, eye movements and subjective assessment of drowsiness. [less ▲]

Detailed reference viewed: 77 (6 ULg)