Estimating a CBRN atmospheric release in a complex environment using Gaussian Processes

International audienceIn this paper, we present a new methodology for the estimation and the prediction of the concentration of pollutant in a complex environment. We take benefit of a semi-parametric formulation of the problem to perform a faster and more efficient estimation of the pollutant cloud. In a first part, we present how we use the Gaussian process to model the interactions between position and time given the observations. Then, we introduce the expansion as a function of the observations through the time, and we construct an estimator of the time of release from it within change-point detection framework. Then, we use this time estimate to obtain the position (or more likely, a confidence region of the position) of the source. Several simulations are provided in a complex city scenario that demonstrate the accuracy of the proposed technique

A METHODOLOGY TO CHARACTERISE THE SOURCES OF UNCERTAINTIES IN ATMOSPHERIC TRANSPORT MODELLING

The atmospheric dispersion modelling of pollutants is based on models, but also on data and users, who lead to uncertainties, i.e. to differences between the results of the models and the physical reality to describe. The question of the uncertainty of dispersion models is a subject of increasing interest for primarily two reasons: • In spite of the significant number of research works on atmospheric dispersion in the last 30 years, results of simulations preserve an important level of uncertainty. Since the reduction of this uncertainty will be more and more difficult, it thus seems today necessary to characterize it and, if possible, to quantify it. • The development of computer performances allows today the use of models in real time for decision-making aid, e.g. for the control of an industrial facility or for the management of an accident. In this context, where important decisions must be made quickly, it becomes extremely important to provide to the results of models an information on the uncertainty associated with these results. For better characterising uncertainties associated with atmospheric dispersion models, we propose a methodology of analysis which led us to make an inventory of all the sources of uncertainties of a model, considering all kind of models (Gaussian, Lagrangian, Eulerian). This methodology is based on a decomposition of the modelling process in four steps: • The collection of input data (sources, meteorology, topography, land cover…), with uncertainties in the measurement of these data, in their treatment and in their representativeness. • The modelling of the meteorological field, with uncertainties associated with intrinsic nature of atmospheric phenomena and with the quality of the models/approaches used to describe these phenomena. • The modelling of dispersion processes and of the physicochemical transformations. • The statistical treatment of results: it is shown that the choice of the output parameters (average annual or hourly maximum, maximum ground value or position of this maximum, etc.) modify, in an important way, the uncertainty of the results and how to evaluate it. The methodology proposed in this work should make it possible to progress towards a more systematic quantification of uncertainties associated with modelling of atmospheric dispersion

Micro-evaporators for kinetic exploration of phase diagrams

We use pervaporation-based microfluidic devices to concentrate species in aqueous solutions with spatial and temporal control of the process. Using experiments and modelling, we quantitatively describe the advection-diffusion behavior of the concentration field of various solutions (electrolytes, colloids, etc) and demonstrate the potential of these devices as universal tools for the kinetic exploration of the phases and textures that form upon concentration

A METHODOLOGY TO CHARACTERISE THE SOURCES OF UNCERTAINTIES IN ATMOSPHERIC TRANSPORT MODELLING

The atmospheric dispersion modelling of pollutants is based on models, but also on data and users, who lead to uncertainties, i.e. to differences between the results of the models and the physical reality to describe. The question of the uncertainty of dispersion models is a subject of increasing interest for primarily two reasons: • In spite of the significant number of research works on atmospheric dispersion in the last 30 years, results of simulations preserve an important level of uncertainty. Since the reduction of this uncertainty will be more and more difficult, it thus seems today necessary to characterize it and, if possible, to quantify it. • The development of computer performances allows today the use of models in real time for decision-making aid, e.g. for the control of an industrial facility or for the management of an accident. In this context, where important decisions must be made quickly, it becomes extremely important to provide to the results of models an information on the uncertainty associated with these results. For better characterising uncertainties associated with atmospheric dispersion models, we propose a methodology of analysis which led us to make an inventory of all the sources of uncertainties of a model, considering all kind of models (Gaussian, Lagrangian, Eulerian). This methodology is based on a decomposition of the modelling process in four steps: • The collection of input data (sources, meteorology, topography, land cover…), with uncertainties in the measurement of these data, in their treatment and in their representativeness. • The modelling of the meteorological field, with uncertainties associated with intrinsic nature of atmospheric phenomena and with the quality of the models/approaches used to describe these phenomena. • The modelling of dispersion processes and of the physicochemical transformations. • The statistical treatment of results: it is shown that the choice of the output parameters (average annual or hourly maximum, maximum ground value or position of this maximum, etc.) modify, in an important way, the uncertainty of the results and how to evaluate it. The methodology proposed in this work should make it possible to progress towards a more systematic quantification of uncertainties associated with modelling of atmospheric dispersion

Why aren't they locked in waiting games? Unlocking rules and the ecology of concepts in the semiconductor industry.

International audienceIn a multi-level perspective, regimes can be clearly described as long as they remain stable. To understand how regimes and niches interact during transition, the article contrasts two models of regimes in transition(s). The classical model of evolutionary niches suggests misalignments between rules and competition between niches. Transition management, technological innovation systems and works on transition pathways suggest a second model based on "unlocking rules", which support collective work on a structured set of emerging technologies. The latter model is illustrated with a case study on the International Technology Roadmap for Semiconductors (ITRS)

3D SIMULATION OF THE DISPERSION IN THE URBAN ENVIRONMENT IN CASE OF AN EXPLOSION USING TESATEX PRE-PROCESSOR AND MICRO-SWIFT-SPRAY MODELLING SYSTEM

TESATEX was developed to evaluate the source term generated by an open-air explosion with or without obstacles. It lies on deeply modified SARRIM and HOTSPOT models. TESATEX can take account of the wind field influenced by buildings. It was operated with Micro-SPRAY but could be run with any other dispersion model. Experimental validation of TESATEX and Micro-SPRAY was successfully carried out using ‘Double Tracks’ in-field test measurements. Applications of TESATEX – Micro- SWIFT-SPRAY modelling system are shown in the paper. Explosions of Radiological Dispersal Devices (RDD) or ‘dirty bombs’ have been simulated in Oklahoma City (downtown) and Paris (Concorde square district). The radiological pollutants dispersion is strongly influenced by the streets network and the initial cloud configuration. Dispersion results have been post-processed to assess the radiological impact of the considered hypothetical events

Large contraction conducting polymer molecular actuators

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, February 2005.Vita. Leaf 239 blank.Includes bibliographical references.The development of powerful and efficient artificial muscles that mimic Nature will profoundly affect engineering sciences including robotics and prosthetics, propulsion systems, and microelectromechanical systems (MEMS). Biological systems driven by muscle out-perform human-engineered systems in many key aspects. For example, muscle endows animals with a level of dexterity and speed that has yet to be emulated by even the most complex robotic system to date. Conducting polymers were chosen for research as actuators, based on a review of the relevant properties of all known actuators and active materials. Key features of conducting polymer actuators include low drive voltages (1 - 2 V) and high active strength (10 - 40 MPa) but moderate active strains (2 %). Active strains of 20 %, which human skeletal muscle is capable of, are desirable for applications in life-like robotics, artificial prostheses or medical devices. This thesis focuses on two approaches to create large contraction in conducting polymer actuators. The first strategy utilizes polypyrrole (PPy), a conducting polymer actuator material that contracts and expands based on a bulk ion swelling mechanism. Optimization of the polymer activation environment via room temperature ionic liquids enables PPy actuators to generate large contractions (16.3 % recoverable strain at 2.5 MPa, 21 % max) at slow speeds (0.4 %/s). In addition, cycle life can reach 10⁵ cycles without significant polymer degradation. This thesis presents an in-depth characterization of the behavior of polypyrrole actuators in room temperature 1-butyl-3-methyl imidazolium tetrafluoroborate liquid salt electrolyte.(cont.) The characterization includes the assessment of passive and electroactive mechanical properties as well as electrical and morphological properties. Using Nature's actin-myosin molecular engine as a source of inspiration, the second approach uses molecular mechanisms to create motion. In this bottom-up approach molecules are rationally designed from the molecular level for specific actuation properties. Such active molecular building blocks include shape changing, load bearing, passively deformable or hinge-like molecular elements. Several novel materials based on contractile molecular design were synthesized and their active properties characterized.by Patrick A.T. Anquetil.Ph.D

Synchronisation cyclique globale entre les économies subsahariennes et les économies avancées

The intensification of international trade, reinforced by the interconnection of financial markets and the appearance of common economic shocks are the elements that contribute to explaining the co-movements of advanced and sub-Saharan economies. In this study, it is a question of measuring the global cyclical synchronization of the economies referred to above, over the period going from 1981.T1 to 2021.T1, from the concordance index of Harding and Pagan (2006). Overall, this analysis shows that the level of cyclical synchronization between the economies of sub-saharan and advanced countries is high enough to justify the strong economic dependence between these two groups of countries