Optimizing the Use of an Artificial Tongue-Placed Tactile Biofeedback for Improving Ankle Joint Position Sense in Humans

The performance of an artificial tongue-placed tactile biofeedback device for improving ankle joint position sense was assessed in 12 young healthy adults using an active matching task. The underlying principle of this system consists of supplying individuals with supplementary information about the position of the matching ankle relative to the reference ankle position through a tongue-placed tactile output device generating electrotactile stimulation on a 36-point (6 X 6) matrix held against the surface of the tongue dorsum. Precisely, (1) no electrodes were activated when both ankles were in a similar angular position within a predetermined "angular dead zone" (ADZ); (2) 12 electrodes (2 X 6) of the anterior and posterior zones of the matrix were activated (corresponding to the stimulation of the front and rear portion of the tongue) when the matching ankle was in a too plantarflexed and dorsiflexed position relative to the reference ankle, respectively. Two ADZ values of 0.5 degrees and 1.5 degrees were evaluated. Results showed (1) more accurate and more consistent matching performances with than without biofeedback and (2) more accurate and more consistent ankle joint matching performances when using the biofeedback device with the smaller ADZ valu

Postural destabilization induced by trunk extensor muscles fatigue is suppressed by use of a plantar pressure-based electro-tactile biofeedback

Separate studies have reported that postural control during quiet standing could be (1) impaired with muscle fatigue localized at the lower back, and (2) improved through the use of plantar pressure-based electro-tactile biofeedback, under normal neuromuscular state. The aim of this experiment was to investigate whether this biofeedback could reduce postural destabilization induced by trunk extensor muscles. Ten healthy adults were asked to stand as immobile as possible in four experimental conditions: (1) no fatigue/no biofeedback, (2) no fatigue/biofeedback, (3) fatigue/no biofeedback and (4) fatigue/biofeedback. Muscular fatigue was achieved by performing trunk repetitive extensions until maximal exhaustion. The underlying principle of the biofeedback consisted of providing supplementary information related to foot sole pressure distribution through electro-tactile stimulation of the tongue. Centre of foot pressure (CoP) displacements were recorded using a force platform. Results showed (1) increased CoP displacements along the antero-posterior axis in the fatigue than no fatigue condition in the absence of biofeedback and (2) no significant difference between the no fatigue and fatigue conditions in the presence of biofeedback. This suggests that subjects were able to efficiently integrate an artificial plantar pressure information delivered through electro-tactile stimulation of the tongue that allowed them to suppress the destabilizing effect induced by trunk extensor muscles fatigue

Energy aware unicast geographic routing

Abstract — In this paper, we are investigating the optimal radio range minimizing the energy globally consummed by a geographical routing process. Considering a geographical greedy routing protocol and a uniform distribution of nodes in the network area, we analytically evaluate the energy cost of a multi-hop communication. This cost evaluation corresponds to the asymptotic behavior of the routing protocol and turns out to be very accurate compared to the results obtained by simulations. We show that this cost is function of the node intensity and we use this result to deduce the optimal radio range. We evaluate this range with two energy consumption models, the first one considering the energy consumed by transmission operations only and the second one considering both transmission and reception operations. These results can be used in two ways. First, the nodes range can be tuned in advance as a function of the expected node intensity during an off-line planning. Second, we propose an adaptative algorithm where nodes tune their powers according to an on-line evaluation of the local node intensity. I

Traces mobiles afin de caractériser les usages et la mobilité des utilisateurs

National audienceCellular communications are evolving quickly to constantly adapt and tolerate the load induced by the increasing number of phones. Understanding the traffic is crucial to refine models and improve experiments. In this context, one has to understand the temporal and spatial user behavior at different levels. At the user scale, the usage is not only define by the amount of calls but also by the user’s mobility and type of communication. At a higher level, the BS have a key role on the flow quality. In this paper, we propose a 1-year Call Detail Records (CDR) analysis in Mexico in order to catch on usage turnovers and investigate overlooked parameters such as the call duration. Moreover, we look into handovers (switching from a station to an other one). Our study suggests that user mobility is pretty dependant to user calls.Les communications mobiles évoluent rapidement afin de s'adapter et de tolérer la charge qu'implique le nombre croissant de téléphones. Il est crucial de comprendre le trafic pour redéfinir les modèles et améliorer les expériences. Dans ce contexte, il faut prendre en compte le comportement temporel et spatial de l'utilisateur à différents niveaux. A l'échelle de l'utilisateur, son usage n'est pas défini seulement par la quantité d'appels, mais aussi par sa mobilité et son type d'utilisation. A un niveau supérieur, les stations de base jouent un rôle clé sur la qualité du flux. Dans ce papier nous proposons une analyse de traces téléphoniques d'un an au Mexique afin de comprendre les handovers et de considérer les paramètres négligés, comme la durée d'appel. Nous traitons les handovers. Notre étude suggère que la mobilité de l'utilisateur est assez dépendante de leurs appels

Utiliser la densité des utilisateurs mobiles dans les grandes villes afin de délivrer des SMS

International audienceDans cet article nous proposons un protocole de réseau semblable à un DTN afin d'acheminer les SMS en se basant sur une étude de mesures et une analyse des SMS provenant d'une trace sur une période de deux mois. Plus précisément nous réalisons une analyse spatiale et temporelle du réseau cellulaire de Mexico en prenant en compte les messages géo-localisés. L'analyse temporelle nous permet de détecter les évènements et de vérifier les périodes de surcharge comprenant un trafic anormal ou inattendu et d'étudier l'évolution de paramètres classiques tels que l'activité ou la distance entre l'expéditeur et le receveur. L'analyse spatiale est basée sur le diagramme Voronoï des stations de base couvrant la ville de Mexico. Nous expliquons comment le trafic de SMS peut être caractérisé. Une telle caractérisation clef nous permet de répondre à la question suivante : est-il possible de transmettre des SMS en utilisant les téléphones comme des relais dans une grande ville comme Mexico ? Nous avons défini un protocole de réseaux simple afin de transmettre des SMS d'un point de départ à un point d'arrivée. Ce protocole semblable à un DTN ne nécessite pas de routage ni de connaissance globale. Le protocole profite de la localité des SMS, de la densité de téléphone à Mexico et de la mobilité des utilisateurs. Nous avons étudié une base de données de téléphones portables incluant 8 millions d'utilisateurs vivant à Mexico. Cela nous a donné une estimation précise du temps de transmission moyen et de la performance globale de notre approche. Après 30 minutes, la moitié des messages ont atteint leur destination avec succès

On-line Human Activity Recognition from Audio and Home Automation Sensors: comparison of sequential and non-sequential models in realistic Smart Homes

International audienceAutomatic human Activity Recognition (AR) is an important process for the provision of context-aware services in smart spaces such as voice-controlled smart homes. In this paper, we present an on-line Activities of Daily Living (ADL) recognition method for automatic identification within homes in which multiple sensors, actuators and automation equipment coexist, including audio sensors. Three sequence-based models are presented and compared: a Hidden Markov Model (HMM), Conditional Random Fields (CRF) and a sequential Markov Logic Network (MLN). These methods have been tested in two real Smart Homes thanks to experiments involving more than 30 participants. Their results were compared to those of three non-sequential models: a Support Vector Machine (SVM), a Random Forest (RF) and a non-sequential MLN. This comparative study shows that CRF gave the best results for on-line activity recognition from non-visual, audio and home automation sensors

Call Detail Records to Characterize Usages and Mobility Events of Phone Users

National audienceCellular communications are evolving quickly to constantly adapt and tolerate the load induced by the increasing number of phones. Understanding the traffic is crucial to refine models and improve experiments. In this context, one has to understand the temporal and spatial user behavior at different levels. At the user scale, the usage is not only defined by the amount of calls but also by the user's mobility and type of communication. At a higher level, the BS have a key role on the flow quality. In this paper, we propose a 1-year Call Detail Records (CDR) analysis in Mexico in order to catch on usage turnovers and investigate overlooked parameters such as the call duration. Moreover, we look into handovers (switching from a station to an other one). Our study suggests that user mobility is pretty dependent to user calls

iBalance-ABF: a Smartphone-Based Audio-Biofeedback Balance System

International audienceThis article proposes an implementation of a Kalman Filter, using inertial sensors of a Smartphone, to estimate 3D angulation of the trunk. The developped system monitors the trunk angular evolution during bipedal stance and helps the user to improve balance through a configurable and integrated auditory-biofeedback loop. A proof-of-concept study was performed to assess the effectiveness of this so-called iBalance-ABF - smartphone-based audio-biofeedback system - in improving balance during bipedal standing. Results showed that young healthy individuals were able to efficiently use ABF on sagittal trunk tilt to improve their balance in the ML direction. These findings suggest that iBalance-ABF system as a Telerehabilitation system which could represent a suitable solution for Ambient Assisted Living technologies