Underwater object identification using pressure sensors

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.Includes bibliographical references (p. 109-112).While the vast majority of underwater vehicles rely exclusively on sonar and vision to detect obstacles and maneuver, live fish also use their lateral line organ. The role played by the canal lateral line system is particularly important for hypogean fish, such as blind Mexican cave fish, who use it to avoid obstacles and navigate dexterously in complex environments. Similarly, pressure sensors could be used on underwater vehicles to expand their range of operability by filling the gap left by sonar and vision systems in turbid cluttered environments. To understand how much information can be extracted from the artificial lateral line of an underwater vehicle exploring an unknown environment, the case of a foil passing a static object in still water is analyzed. A two-dimensional potential flow approach based on a source panels method is used to characterize the spatio-temporal pressure signature of the object as sensed by the vehicle. Simulations are used to estimate the sensing range of an artificial lateral line and the appropriate density of pressure sensors. To emulate the object-detection and shape-recognition capabilities of the lateral line, an adapted unscented Kalman filter is combined with the hydrodynamic model. The method developed is experimentally tested in a water tank, using a hydrofoil instrumented with pressure sensors passing a static cylinder. The results show that location and shape informations of an elliptical cylinder can be successfully inferred from experimental pressure measurements. Performance of the proposed method for object identification using pressure sensors are discussed and ways to improve it are suggested.by Audrey Maertens.S.M

Designing role-play simulations for climate change decision-making: a step-by-step approach to facilitate cooperation between science and policy

Literature has demonstrated the benefits of role-play simulations (RPS) for decision-making and social learning in the field of climate change and environmental policy. Despite growing interest, step-by-step guidelines are still rare when it comes to the practical design and implementation of RPS, which hinders the adoption and implementation of this promising approach. This article aims to facilitate the development of RPS by proposing a step-by-step framework for designing role-play simulations around three stages – before, during, and after the simulation. To develop the methodology, we use as a starting point a pilot simulation on decision-making and knowledge production in contexts of uncertainty and complexity. Focusing on negative emission technologies in Switzerland, the pilot simulation involved 12 scientists and 12 politicians who role-played each other for half a day. Overall, we propose an actionable framework for RPS designed to facilitate cooperation between groups with different socialisations, timelines, and imperatives towards more informed and collaborative decision-making practices. Doing so, this article contributes to making RPS more accessible to a broad audience as a method supporting cooperation between science and policy in the field of climate and environmental politics and beyond

Finite Volume Particle Method for Fluid-Structure Interaction

We have recently developed a conservative finite volume particle method (FVPM) that can efficiently model 2-D and 3-D fluid flow with free-surfaces and complex geometries. Tn this paper we present an extension of the method to fluid-structure interaction. A new boundary condition enforcement is presented in which the hydrodynamic forces required in solid equations are computed directly. For validation, we study the 2-D motion of fluid through an elastic gate and compare the displacement of the gate with experimental and numerical data. We observe a very good agreement between FVPM and other numerical and experimental data

Impact erosion prediction using the finite volume particle method with improved constitutive models

Erosion damage in hydraulic turbines is a common problem caused by the high- velocity impact of small particles entrained in the fluid. In this investigation, the Finite Volume Particle Method is used to simulate the three-dimensional impact of rigid spherical particles on a metallic surface. Three different constitutive models are compared: the linear strain- hardening (L-H), Cowper-Symonds (C-S) and Johnson-Cook (J-C) models. They are assessed in terms of the predicted erosion rate and its dependence on impact angle and velocity, as compared to experimental data. It has been shown that a model accounting for strain rate is necessary, since the response of the material is significantly tougher at the very high strain rate regime caused by impacts. High sensitivity to the friction coefficient, which models the cutting wear mechanism, has been noticed. The J-C damage model also shows a high sensitivity to the parameter related to triaxiality, whose calibration appears to be scale-dependent, not exclusively material-determined. After calibration, the J-C model is capable of capturing the material’s erosion response to both impact velocity and angle, whereas both C-S and L-H fail

Self-Hypnosis for Phantom Limb Pain: A Multiple-Case Study

peer reviewe

Innovations in physical and rehabilitation medicine

peer reviewedAu cours de la dernière décennie, la Médecine Physique et Réadaptation (MPR) est une spécialité médicale qui a fortement évolué dans les différents domaines qui la concernent : de la prise en charge des lombalgies et lombosciatalgies ou encore de l’ostéoporose de manière pluridisciplinaire, en passant par l’utilisation des nouvelles technologies en rééducation neuro-locomotrice et de la robotisation en rééducation, chez les patients amputés par exemple, le développement de la médecine à vocation régénérative et la prévention en traumatologie du sport et, enfin, les progrès des techniques d’électrophysiologie pour le diagnostic des neuropathies à petites fibres. Ces différentes avancées seront abordées dans cet article.Over the last decade, Physical and Rehabilitation Medicine (PRM) is a medical specialty that has evolved considerably in the various fields that concern it : from the management of low back pain and lumbosciatalgia or osteoporosis in a multidisciplinary manner, through the use of new technologies in neuro-locomotor rehabilitation and robotisation in amputee patients for example, the development of regenerative medicine and prevention in sports traumatology and, finally, the progress of electrophysiology techniques for the diagnosis of small-fibre neuropathies. These various advances will be discussed in this article

Natalizumab treatment shows low cumulative probabilities of confirmed disability worsening to EDSS milestones in the long-term setting.

Abstract Background Though the Expanded Disability Status Scale (EDSS) is commonly used to assess disability level in relapsing-remitting multiple sclerosis (RRMS), the criteria defining disability progression are used for patients with a wide range of baseline levels of disability in relatively short-term trials. As a result, not all EDSS changes carry the same weight in terms of future disability, and treatment benefits such as decreased risk of reaching particular disability milestones may not be reliably captured. The objectives of this analysis are to assess the probability of confirmed disability worsening to specific EDSS milestones (i.e., EDSS scores ≥3.0, ≥4.0, or ≥6.0) at 288 weeks in the Tysabri Observational Program (TOP) and to examine the impact of relapses occurring during natalizumab therapy in TOP patients who had received natalizumab for ≥24 months. Methods TOP is an ongoing, open-label, observational, prospective study of patients with RRMS in clinical practice. Enrolled patients were naive to natalizumab at treatment initiation or had received ≤3 doses at the time of enrollment. Intravenous natalizumab (300 mg) infusions were given every 4 weeks, and the EDSS was assessed at baseline and every 24 weeks during treatment. Results Of the 4161 patients enrolled in TOP with follow-up of at least 24 months, 3253 patients with available baseline EDSS scores had continued natalizumab treatment and 908 had discontinued (5.4% due to a reported lack of efficacy and 16.4% for other reasons) at the 24-month time point. Those who discontinued due to lack of efficacy had higher baseline EDSS scores (median 4.5 vs. 3.5), higher on-treatment relapse rates (0.82 vs. 0.23), and higher cumulative probabilities of EDSS worsening (16% vs. 9%) at 24 months than those completing therapy. Among 24-month completers, after approximately 5.5 years of natalizumab treatment, the cumulative probabilities of confirmed EDSS worsening by 1.0 and 2.0 points were 18.5% and 7.9%, respectively (24-week confirmation), and 13.5% and 5.3%, respectively (48-week confirmation). The risks of 24- and 48-week confirmed EDSS worsening were significantly higher in patients with on-treatment relapses than in those without relapses. An analysis of time to specific EDSS milestones showed that the probabilities of 48-week confirmed transition from EDSS scores of 0.0–2.0 to ≥3.0, 2.0–3.0 to ≥4.0, and 4.0–5.0 to ≥6.0 at week 288 in TOP were 11.1%, 11.8%, and 9.5%, respectively, with lower probabilities observed among patients without on-treatment relapses (8.1%, 8.4%, and 5.7%, respectively). Conclusions In TOP patients with a median (range) baseline EDSS score of 3.5 (0.0–9.5) who completed 24 months of natalizumab treatment, the rate of 48-week confirmed disability worsening events was below 15%; after approximately 5.5 years of natalizumab treatment, 86.5% and 94.7% of patients did not have EDSS score increases of ≥1.0 or ≥2.0 points, respectively. The presence of relapses was associated with higher rates of overall disability worsening. These results were confirmed by assessing transition to EDSS milestones. Lower rates of overall 48-week confirmed EDSS worsening and of transitioning from EDSS score 4.0–5.0 to ≥6.0 in the absence of relapses suggest that relapses remain a significant driver of disability worsening and that on-treatment relapses in natalizumab-treated patients are of prognostic importance