Multi-technique radiometric assessment of a desert-marine ecosystem facilitating radiological-environmental safety in hyper-arid regions

International audienceThis paper presents a rigorous, multi-technique assessment of radiometric and physiochemical characteristics of a desert-marine ecosystem in the United Arab Emirates (UAE). Current models and empirical data on the release, dispersion, retention and migration of radionuclides in hyper-arid regions are inadequate. This is a critical gap in the radiological-environmental assessments in the Arabian Peninsula, where industries producing radioactivity, such as oil and gas, mining, and both thermal and nuclear power generations, are expanding rapidly. This study offers the most diverse baseline data to date, laying the groundwork for an evidence-based radionuclide transport modeling in hyper-arid environments. It identifies the key isotopes to track and carefully selects a representative region for a comprehensive sampling. The Al Dhafra region of Abu Dhabi was chosen due to its importance in hosting oil, gas, and nuclear industries, and because it covers 71 % of the total area of the emirate. Around 30 different samples were collected, including rock, sand, groundwater, seawater, plants, and farm products. A tailored combination of advanced radiometric methods with XRD, ICP-MS, IC, and gamma spectrometry was developed for this complex and rare sample set. Majority of the instrumentation for this project were hosted in the Subatech Laboratories (France). The study yielded radioactivity compositions in the main arid environmental matrices, consistent with the previous research, and introduced novel findings on the probable host rocks to study for nuclear waste storage, desert shrubs as bioindicators, and camel milk as a medium for transfers to humans. •Diverse and multi-method radiometric characterization of an expansive hyper-arid desert region.•Baseline radionuclide concentrations measured for rocks, sand, waters, plants, and farm produces.•Identified primary rock types, groundwater chemistry and salinity, and plants for transport mechanisms.•Vital empirical data for nuclear and radioactivity-producing industries in hyper-arid ecosystems

An approximate dynamic programming approach for multi-stage stochastic lot-sizing under a Decision-Hazard-Decision information structure

International audienceThis work studies a combinatorial optimization problem encountered in industrial production planning: the single-item multi-resource lot-sizing problem with inventory bounds and lost sales. The demand to be satisfied by the production plan is subject to uncertainty and only probabilistically known. We consider a multi-stage decision process with a Decision-Hazard-Decision information structure in which decisions are made at each stage both before and after the uncertainty is revealed. Such a setting has not yet been studied for stochastic lot-sizing problems, and the resulting problem is modeled as a multi-stage stochastic integer program. We propose a solution approach based on an approximate stochastic dynamic programming algorithm. It relies on a decomposition of the problem into single-stage sub-problems and on the estimation at each stage of the expected future costs. Due to the Decision-Hazard-Decision information structure, each nested single-stage sub-problem is itself a two-stage stochastic integer program. We therefore introduce a Benders decomposition scheme to reduce the computational effort required to solve each nested sub-problem, and present a specialpurpose polynomial-time algorithm to efficiently solve the single-scenario second-stage sub-problems involved in the Benders decomposition. The results of extensive simulation experiments carried out on large-size randomly generated instances are reported. They demonstrate the practical benefit, in terms of the actual production cost, of using the proposed approach as compared to a naive deterministic optimization approach based on the expected demand

Proton beam monitoring through water scintillation in radiobiology experiments

International audienceNon-invasive methods based on the detection of secondary particles generated in the irradiated medium are being investigated to monitor ion beams without disturbing the beam. This study investigates the use of water scintillation as a beam monitoring tool, taking into account the challenges posed by the radiobiology experiment constraints. An experimental setup has been designed to measure the depth deposited energy profile produced by protons of (67.5 ± 0.4) MeV entering a water tank, through the water scintillation detected with a photomultiplier. The beam current during the experiment was around 100 pA, and beam intensity fluctuations were monitored using a parallel plate ionization chamber and a Faraday cup. The experiment was repeated with a second ionization chamber as a reference detector placed inside the water tank, and simulated with the GATE Monte Carlo code. The position of the Bragg peak, measured with the water scintillation, shows significant agreement (deviation of 0.5 mm) with the positions obtained from the ionization chamber and the Monte Carlo simulation within a submillimeter uncertainty. The ionization quenching effect was also observed and corrected using the Birks and Chou models. A new value of the key parameter for these models (k · B = (8.0 ± 4.0) × 10−3 g/MeV.cm2) has been determined for water, which is in good agreement with the data available in the literature for organic scintillators. This study demonstrated the feasibility of using water scintillation measured with a collimated photomultiplier as a tool for monitoring the depth deposited energy profile in water. •Water scintillation is used to monitor proton beams in radiobiological experiment.•The Bragg peak is localized with submillimeter uncertainty.•The Chou model allows for correction of ionization quenching for water.•The Birks and Chou parameters were determined for water

Development of a numerical model for measuring the electrical conductivity (EC) of a cake batter

International audienceThe electrical conductivity (EC) of materials represents their ability to conduct electrical current and determines the power dissipated within the material. This parameter can be temperature and electric field dependent. When EC is measured in the electric fields used for ohmic heating, the increase in temperature results in heating nonuniformity in the measuring cell. As a result, the relationship between EC and temperature cannot be accurately determined. In addition, for cake batter, starch gelatinization occurs during the measurement, leading to more complex EC curves. To address these issues, this study proposes a numerical method for determining EC that accounts for temperature non-uniformity. This model is coupled with a starch gelatinization model. The principle is based on the estimation of the EC using the method of least squares between the experimental temperature and the numerical one. The estimation of the EC of the cake batter consists of two steps: first, the device was characterized with xanthan and potassium chloride solutions of known electrical conductivities. A conversion efficiency of 0.77 was found. This efficiency was used to estimate the EC of the cake batter as a function of temperature and for different electric fields. Results showed that EC became independent of the electric field from 34.57 V/cm

The grammar of ‘unanalyzable’ sentences in early child language production: Production mismatches in the development of Recursion in English

International audienc

Respirer avec K. Méthodes et enjeux cartographiques

National audienceCe texte se propose de mener une discussion avec et autour d’une cartographie , celle de l’itinéraire de K., un homme, asthmatique et allergique. Nous - deux chercheurs et une architecte cartographe - avons expérimenté avec K. un itinéraire en marchant centré sur sa respiration et son expérience ordinaire de l’air, en nous donnant l’objectif suivant : produire une cartographie qui non seulement exprime l’expérience de l’itinéraire, mais aussi constitue un outil réflexif et critique des espaces publics contemporain

Kinematic modeling and task-based design of a URRR-URR parallel mechanism for percutaneous interventions

International audiencePercutaneous interventions, including biopsies, thermal ablations, and regional anesthesia, involve the insertion of an instrument into the patient's body to remove tissue or manage pain. In this context, the use of a robotic assistant is suitable to guide the medical gestures, leading to a more time effective intervention and better patient care. For this purpose, this paper introduces a novel URRR-URR parallel mechanism. The constraint and mobility analysis of the mechanism is performed using screw theory. A methodology for determining the solution to its Direct and Inverse Geometric Models is presented. The forward and inverse kinematic Jacobian matrices of the mechanism are then expressed. Some singularities of the mechanism are identified and illustrated. Additionally, the design problem of the parallel manipulator (PM) under study is formulated as a bi-objective optimization problem. The first objective function is expressed in terms of the condition number of the forward and inverse Jacobian matrices. The second objective function deals with the mechanism size. Lastly, the non-dominated Pareto-optimal solutions are obtained and three Pareto-optimal solutions are detailed

Direction-of-Arrival Estimation of Coherent Sources with Leaky-Wave Antennas using Spatially Filtered Interpolation

International audienceWith their frequency-beam scanning behavior, leaky-wave antennas (LWAs) are promisingsolutions to develop accurate and cost-effective direction-of-arrival (DoA) estimationsystems. However, DoA estimators such as MUSIC face challenges with coherent sourcesdue to the non-Vandermonde LWA steering matrix. Leveraging the unique radiation propertiesof LWAs, this paper first divides the entire field of view into several angular sectors,and then introduces a robust and accurate sectorized spatially-filtered interpolation (SFI)method to transform the LWA steering matrix into a Vandermonde matrix in each sectorwhile minimizing the issue of out-of-sector interference. The proposed method allowsthus the estimation of DoAs of coherent sources with LWAs. The simulation results showthat the DoAs of multiple coherent sources across the entire field-of-view, regardless theirangular sector, can be correctly estimated. The performance of the proposed method isshown be close to the Cramér-Rao Bound