References of "Verly, Jacques"
     in
Bookmark and Share    
Peer Reviewed
See detailAdaptive method for detecting zero-velocity regions to quantify stride-to-stride spatial gait parameters using inertial sensors
Boutaayamou, Mohamed ULiege; Schwartz, Cédric ULiege; Joris, Laura ULiege et al

in Proceedings of the 12th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2019) (2019, February 25)

We present a new adaptive method that robustly detects zero-velocity regions to accurately and precisely quantify (1) individual stride lengths (SLs), (2) individual stride velocities (SVs), (3) the ... [more ▼]

We present a new adaptive method that robustly detects zero-velocity regions to accurately and precisely quantify (1) individual stride lengths (SLs), (2) individual stride velocities (SVs), (3) the average of SL, (4) the average of SV, and (5) the cadence during slow, normal, and fast overground walking conditions in young and healthy people. The measurements involved in the estimation of these spatial gait parameters are obtained using only one inertial measurement unit attached on a regular shoe at the level of the heel. This adaptive method reduced the integration drifts across consecutive strides and improved the accuracy and precision in the spatial gait parameter estimation. The validation of the proposed algorithm has been carried out using reference spatial gait parameters obtained from a kinematic reference system. The accuracy ± precision results were for SLs: 0.0 ± 4.7 cm, −0.7 ± 4.4 cm, and −5.8 ± 5.8 cm, during slow, normal, and fast walking conditions, respectively, corresponding to −0.1 ± 4.2 %, −0.5 ± 3.2 %, and −3.3 ± 3.0 % of the respective mean SL. The accuracy ± precision results were for SVs: 0.0 ± 2.9 cm/s, −0.7 ± 3.8 cm/s, and −6.7 ± 6.7 cm/s, during slow, normal, and fast walking conditions, respectively, corresponding to −0.6 ± 3.3 %, −0.1 ± 4.5 %, and −3.5 ± 3.1 % of the respective mean SV. These validation results show a good agreement between the proposed method and the reference, and demonstrate a fairly accurate and precise estimation of these spatial gait parameters. The proposed method paves the way for an objective quantification of spatial gait parameters in routine clinical practice. [less ▲]

Detailed reference viewed: 86 (36 ULiège)
Full Text
Peer Reviewed
See detailDescription of secondary payload of upcoming educational OUFTI-2 1U CubeSat for testing a new multilayer shield for protecting electronics against space radiations
Broun, Valery ULiege; De Dijcker, Sebastien; Werner, Xavier ULiege et al

Poster (2018, December)

We describe one of the secondary payloads of the educational OUFTI-2 satellite under development at the University of Liège, namely the one dedicated to the test of an innovative type of shielding that ... [more ▼]

We describe one of the secondary payloads of the educational OUFTI-2 satellite under development at the University of Liège, namely the one dedicated to the test of an innovative type of shielding that can protect electronic systems against space radiations, and that is well suited for small satellites. OUFTI-2 is a 1-U CubeSat, the main payload of which is a homemade radio repeater featuring D-STAR amateur-radio communications. We expect OUFTI-2 to be deployed from ISS, with a mission duration of about 6 months. The impact of space radiations on electronics depends mainly on the orbit/trajectory, mission duration, and possible protections. Such radiations cause well-known undesirable effects such as latch-ups. The protection against such effects is ideally achieved through a combination of device rad-hardening, physical shields, and defensive software. Here, we focus on the use of shields. One limitation with using such shields is the corresponding added volume and weight. The innovative type of shield to be tested aboard OUFTI-2 consists of a multilayer laminate structure, combining doped resin and Wolfram (tungsten) heavy alloy. It has the advantage of being light-weight, robust, and reliable. The part of the board containing the shields-test payload consists mainly of three identical electronic circuits, resp. without any shield, with a classical 2-mm aluminum shield, and with the new multilayer shield. The 1st part of each circuit is a RADFET (a p-channel MOSFET optimized for ionizing dose measurement), whose threshold voltage ΔV varies with the total dose D in a known way, essentially according to ∆V=A (1-e^(-B D) ), where A and B are parameters depending upon the RADFET used. One measures ΔV. The 2nd part contains 2 op-amp-based circuits. In one, one measures the offset voltage, and in the other the output noise voltage level. One also measures the temperature, T. ΔV, the two op-amp parameters, and T constitute the quadruplet of data measured periodically, and ultimately sent to the ground. During flight, we will use ΔV and T to deduce D at each sampling time. For each such time, we will also compute the total dose via the ESA SPENVIS simulation software using the known flight trajectory up to that time. Of course, we will also compare the protection provided by both types of shields, and in relation to the absence of a shield. The measurements of the two op-amp parameters will allow us to see how these parameters evolve as a function D. [less ▲]

Detailed reference viewed: 31 (5 ULiège)
See detailStereopsia, the World Immersion Forum
Verly, Jacques ULiege

Scientific conference (2018, September 04)

Detailed reference viewed: 19 (1 ULiège)
See detailSome novel applications of VR in the domain of health
Grogna, David ULiege; Stassart, Céline ULiege; Servotte, Jean-Christophe ULiege et al

Scientific conference (2018, September 04)

Detailed reference viewed: 41 (10 ULiège)
See detailTrends for immersion technologies and content
Verly, Jacques ULiege; Grogna, David ULiege

Scientific conference (2018, September 04)

Detailed reference viewed: 20 (3 ULiège)
Full Text
Peer Reviewed
See detailProbabilistic Framework for the Characterization of Surfaces and Edges in Range Images, with Application to Edge Detection
Lejeune, Antoine ULiege; Verly, Jacques ULiege; Van Droogenbroeck, Marc ULiege

in IEEE Transactions on Pattern Analysis and Machine Intelligence (2018), 40(9), 2209-2222

We develop a powerful probabilistic framework for the local characterization of surfaces and edges in range images, which is useful in many applications of computer vision, such as filtering, edge ... [more ▼]

We develop a powerful probabilistic framework for the local characterization of surfaces and edges in range images, which is useful in many applications of computer vision, such as filtering, edge detection, feature extraction, and classification. We use the geometrical nature of the data to derive an analytic expression for the joint probability density function (pdf) for the random variables used to model the ranges of a set of pixels in a local neighborhood of an image. We decompose this joint pdf by considering independently the cases where two real world points corresponding to two neighboring pixels are locally on the same real world surface or not. In particular, we show that this joint pdf is linked to the Voigt pdf and not to the Gaussian pdf as it is assumed in some applications. We apply our framework to edge detection and develop a locally adaptive algorithm that is based on a probabilistic decision rule. We show in an objective evaluation that this new edge detector performs better than prior art edge detectors. This proves the benefits of the probabilistic characterization of the local neighborhood as a tool to improve applications that involve range images. [less ▲]

Detailed reference viewed: 68 (21 ULiège)
Full Text
Peer Reviewed
See detailMulti-timescale drowsiness characterization based on a video of a driver’s face
Massoz, Quentin ULiege; Verly, Jacques ULiege; Van Droogenbroeck, Marc ULiege

in Sensors (2018), 18(9), 2801

Drowsiness is a major cause of fatal accidents, in particular in transportation. It is therefore crucial to develop automatic, real-time drowsiness characterization systems designed to issue accurate and ... [more ▼]

Drowsiness is a major cause of fatal accidents, in particular in transportation. It is therefore crucial to develop automatic, real-time drowsiness characterization systems designed to issue accurate and timely warnings of drowsiness to the driver. In practice, the least intrusive, physiology-based approach is to remotely monitor, via cameras, facial expressions indicative of drowsiness such as slow and long eye closures. Since the system’s decisions are based upon facial expressions in a given time window, there exists a trade-off between accuracy (best achieved with long windows, i.e., at long timescales) and responsiveness (best achieved with short windows, i.e., at short timescales). To deal with this trade-off, we develop a multi-timescale drowsiness characterization system composed of four binary drowsiness classifiers operating at four distinct timescales (5 s, 15 s, 30 s, and 60 s) and trained jointly. We introduce a multi-timescale ground truth of drowsiness, based on the reaction times (RTs) performed during standard Psychomotor Vigilance Tasks (PVTs), that strategically enables our system to characterize drowsiness with diverse trade-offs between accuracy and responsiveness. We evaluated our system on 29 subjects via leave-one-subject-out cross-validation and obtained strong results, i.e., global accuracies of 70%, 85%, 89%, and 94% for the four classifiers operating at increasing timescales, respectively. [less ▲]

Detailed reference viewed: 70 (33 ULiège)
Peer Reviewed
See detailSome novel applications of VR in the domain of health
Grogna, David ULiege; Stassart, Céline ULiege; Servotte, Jean-Christophe ULiege et al

in Proceedings of the 20th Congress of the International Ergonomics Association (IEA 2018) (2018, August)

Detailed reference viewed: 44 (11 ULiège)
Peer Reviewed
See detailTrends for immersion technologies and content
Verly, Jacques ULiege; Grogna, David ULiege

in Proceedings of the 20th Congress of the International Ergonomics Association (IEA 2018) (2018, August)

Detailed reference viewed: 20 (4 ULiège)
Peer Reviewed
See detailExcellent Potential of Geometric Brownian Motion (GBM) as a Random Process Model for Level of Drowsiness Signals
Ebrahimbabaie Varnosfaderani, Pouyan ULiege; Verly, Jacques ULiege

in Proceedings of the 11th International Joint Conference on Biomedical Engineering Systems and Technologies (2018, January 20)

We show that Geometric Brownian Motion (GBM) appears to be an excellent choice of random process model to describe mathematically the real-life signals that represent the evolution with time of the level ... [more ▼]

We show that Geometric Brownian Motion (GBM) appears to be an excellent choice of random process model to describe mathematically the real-life signals that represent the evolution with time of the level of drowsiness (LoD) of an individual, such as a driver. We collected data from thirty (30) healthy participants, who each underwent three tests (either driving in a simulator or performing Psychomotor Vigilance Tests) at successive levels of sleep deprivation. During each test, the LoD was produced by a photooculography (POG) based device designed and built by our team. We so obtained a total of 90 LoD signals. For each, we applied statistical methods to determine whether a GBM was a valid model for it. All 90 signals passed statistical tests of normality and independency, meaning that each can be modeled by GBM, thereby showing the excellent potential of GBM as a random process model for LoD signals. This finding could lead to the development of a number of innovative means for predicting the evolution of the LoD and the occurrence of related events beyond the present moment. The resulting technology should help reduce the number of accidents due to drowsy driving. [less ▲]

Detailed reference viewed: 47 (11 ULiège)
Full Text
Peer Reviewed
See detailValidated assessment of gait sub-phase durations in older adults using an accelerometer-based ambulatory system
Boutaayamou, Mohamed ULiege; GILLAIN, Sophie ULiege; Schwartz, Cédric ULiege et al

in Proceedings of the 11th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2018) (2018)

Validated extraction of gait sub-phase durations using an ambulatory accelerometer-based system is a current unmet need to quantify subtle changes during the walking of older adults. In this paper, we ... [more ▼]

Validated extraction of gait sub-phase durations using an ambulatory accelerometer-based system is a current unmet need to quantify subtle changes during the walking of older adults. In this paper, we describe (1) a signal processing algorithm to automatically extract not only durations of stride, stance, swing, and double support phases, but also durations of sub-phases that refine the stance and swing phases from foot-worn accelerometer signals in comfortable walking of older adults, and (2) the validation of this extraction using reference data provided by a gold standard system. The results show that we achieve a high agreement between our method and the reference method in the extraction of (1) the temporal gait events involved in the estimation of the phase/sub-phase durations, namely heel strike (HS), toe strike (TS), toe-off (TO), maximum of heel clearance (MHC), and maximum of toe clearance (MTC), with an accuracy and precision that range from ‒3.6 ms to 4.0 ms, and 6.5 ms to 12.0 ms, respectively, and (2) the gait phase/sub-phase durations, namely stride, stance, swing, double support phases, and HS to TS, TO to MHC, MHC to MTC, and MTC to HS sub-phases, with an accuracy and precision that range from ‒4 ms to 5 ms, and 9 ms to 15 ms, respectively, in comfortable walking of a thirty-eight older adults ( (mean ± standard deviation) 71.0 ± 4.1 years old). This demonstrates that the developed accelerometer-based algorithm can extract validated temporal gait events and phase/sub-phase durations, in comfortable walking of older adults, with a promising degree of accuracy/precision compared to reference data, warranting further studies. [less ▲]

Detailed reference viewed: 113 (33 ULiège)
See detailSome novel applications of virtual reality (VR) in the domain of health
Grogna, David ULiege; Stassart, Céline ULiege; Bragard, Isabelle ULiege et al

Conference (2017, December 12)

Detailed reference viewed: 50 (22 ULiège)