Reproduction de : Thèse de doctorat : Chimie organique : Metz : 1984. / Titre provenant de l'écran-titre. Notes bibliographiques. Index.

The problem of performing complex maneuvers in challenging terrains is crucial to the advancement of legged robots and assistive devices, yet little progress has been made in exploring practical solutions to operate in these environments. In this thesis, we tackle the problem by developing strategies to predict a robot's center of mass (CoM) behavior based on contact constraints, and any arbitrary CoM path for situations in which the system has single or multiple points of contact through which external reaction forces may be applied. Our method consists of first leveraging previous work on multi-contact dynamics to derive reaction force behavior from internal tension force profiles and kinematic CoM trajectories. We then study the nonlinear dynamics of single contact phases along arbitrary paths and employ numerical integration to derive state-space approximations of CoM behavior. We use this theoretical framework to synthesize complex maneuvers in various terrains by means of a motion planner in which we determine step transition sequences for continuous motions involving contact profiles which vary with time. Furthermore, we validate our strategy through several comparative case studies, examining the motion of a human subject performing a difficult maneuver in an aggressive terrain. We then seed our motion planning algorithm with a limited set of parameters chosen to match those of a human subject and predict CoM behavior for the same motion pattern. These case studies show that the estimated CoM behaviors generated from our planning algorithm closely resemble the behavior of the human subject and therefore validate our methods. / text

Measuring physiological parameters or vital sign using camera has become popular in recent years. Contact-less monitoring and extraction of vital signs can be important source of information in situations like medical care system and safety control system. This paper presents the implementation of real-time, non-contact method for extraction of vital signs, heart rate in this case. A better face tracking method is used for efficient face detection. This study extends some of the previous works done and have a comparison study with several methods. The developed system used filtering with window over the green channel of the signal and then Converted to frequency domain to analyze the signal to detect heart rate. The developed system achieved high correlation and showed small error while referencing with actual heart signal from ECG. This method delivers better result in better light condition but gives fairly good result on lower light as well.

The aim of this thesis was to design, develop and evaluate a Non-Contact Corneal Aesthesiometer (NCCA), using a controlled pulse of air, of a pre-determined pressure. First, the system design and alterations are described, then in a series of model experiments, the standardisation and characteristics of the air-pulse were examined. These studies revealed that the NCCA could produce a repeatable stimulus of known volume and rate of air-flow. Furthermore, the air-flow exiting the stimulus air jet was of a laminar shape, with minimal dispersion. The control of the air-flow dispersion was further enhanced by using a 0.5mm diameter air jet and a working distance of lcm. Varying the stimulus duration was not found to influence these qualities of the air-pulse. The air-pulse stimulus was shown to possess the ability to produce corneal nerve stimulation either by surface deformation, temperature change, or both. Using thermal imaging equipment, a temperature drop in the ocular tear film was demonstrated that was localised, and limited to the cornea. A second series of experiments investigated the ability of the NCCA to measure a corneal sensitivity threshold. These studies indicated that a forced-choice, doublestaircase, Method of Limits experimental technique produced an accurate threshold, with low variability in the results, over a minimum time period. Further studies showed that this threshold measurement was repeatable to within 0.1 mbars. A database of typical normal sensitivity thresholds, under a number of physiological variables - corneal location, gender, age and iris colour, was developed. The results from these studies compared well qualitatively with those using invasive stimuli. A third series of experiments examined the ability of the NCCA to assess corneal nerve function when it was under a number of external influences. The first situation was that of anaesthesia,p roduced by 0.4% benoxinate hydrochloride. Non-contact corneal sensitivity loss and recovery were shown to return to normal levels 60mins after instillation of the anaesthetic. The second situation was that of long-term contact lens wear (i.e. longer than three years). Non-contact sensitivity was shown to be reduced with both soft and gas-permeable lens wear, although the extent of loss did not differ between them, nor was it influenced by the length of wear. Thirdly,corneal sensitivity loss and recovery was assessed in subjects following excimer laser photorefractive keratectomy (PRK). Three laser trials were completed: a longitudinal myopic study, a transverse myopic study, and a longitudinal hyperopic study. The results indicated that non-contact corneal sensitivity loss/recovery was not related to the attempted depth of ablation, and that sensitivity had still not returned to normal levels one year post-op.

No description available.

Awareness of biological invasions is becoming widespread and several mathematical tools have been used to study this problem. Interacting particle systems, specifically the contact process, have been used to study systems with invasion/infection type dynamics. The Propp-Wilson algorithm is a method for exact sampling from the stationary distribution of an ergodic monotone Markov chain using a method called coupling from the past. The contact process is monotone so we can sample exactly from the stationary distribution of a modified finite grid version using the Propp-Wilson algorithm. In order to study an invasion, we would like to include at least 2 species; however, monotonicity is not well defined for contact processes with more than 2 particle types. Here we develop a general theory of monotonicity for interaction map particle systems, which are interacting particle systems with contact process type dynamics. This allows us to create monotone models with any number of particles and to use the Propp-Wilson algorithm for not only sampling from the stationary distribution, but analyzing the path of invasion leading to equilibrium. Virtual particle invasion models that fall into this new theoretical framework, which we develop here, present a wide range of biological dynamics. Computer simulation of the stochastic system and mean field analysis are two powerful tools that we use for analyzing these types of models. Statistics gathered along the path to invasion help us understand the spatial dynamics of this ecological process and what the stationary behavior looks like. This allows us to understand when the invasion is successful or if coexistence occurs and how these depend on the transition rates and interactions within the process.

The present research examined how daily experiences of intergroup contact through social interaction (direct contact) and exposure to outgroups in media (media contact) facilitate improvements in intergroup attitudes. A longitudinal diary study was conducted whereby participants indicated the amount of direct contact and media contact they had each day, as well as their intergroup attitudes. Results indicated that direct contact and media contact both independently predicted improvements in intergroup attitudes. For direct contact, but not media contact, this relationship was moderated by the perceived negativity of the contact. Time-lagged analyses indicated that direct contact on a given day predicted improved intergroup attitudes on a subsequent day above and beyond direct contact on that day, but that media contact has little or no residual impact. This suggests that although media contact and direct contact may both be effective at promoting more positive intergroup attitudes, direct contact may have a more lasting impact.

The present research examined how daily experiences of intergroup contact through social interaction (direct contact) and exposure to outgroups in media (media contact) facilitate improvements in intergroup attitudes. A longitudinal diary study was conducted whereby participants indicated the amount of direct contact and media contact they had each day, as well as their intergroup attitudes. Results indicated that direct contact and media contact both independently predicted improvements in intergroup attitudes. For direct contact, but not media contact, this relationship was moderated by the perceived negativity of the contact. Time-lagged analyses indicated that direct contact on a given day predicted improved intergroup attitudes on a subsequent day above and beyond direct contact on that day, but that media contact has little or no residual impact. This suggests that although media contact and direct contact may both be effective at promoting more positive intergroup attitudes, direct contact may have a more lasting impact.

No description available.

No description available.