Subproblem h-Conform Formulation for Accurate Thin Shell Models Between Conducting and Nonconducting Regions

peer reviewedA subproblem method (SPM) with h-formulation is developed for correcting the inaccuracies near edges and corners that arise from using thin shell (TS) models to replace thin volume regions by surfaces. The developed surface-to-volume correction problem is defined as a step of multiple SPs, with inductors and magnetic or conducting regions, some of them being thin. The TS model assumes that the fields in the thin regions are approximated by a priori 1-D analytical distributions along the shell thickness (C. Geuzaine et al., “Dual formulations for the modeling of thin electromagnetic shells using edge elements,” IEEE Trans. Magn., vol. 36, no. 4, pp. 799–802, 2000). Their interior is not meshed and ratherextracted from the studied domain, which is reduced to a zero-thickness double layer with interface conditions (ICs) linked to 1-D analytical distributions that however neglect end and curvature effects. This leads to inaccuracies near edges and corners that increase with the thickness. To cope with these difficulties, the authors have recently proposed a SPM based on the h-formulation for a thin region located between non-conducting regions (Vuong Q. Dang et al., “Subproblem Approach for Thin Shell Dual Finite Element Formulations”, IEEE Trans. Magn., vol. 48, no. 2, pp. 407–410, 2012). The magnetic field h is herein defined in nonconducting regions by means of a magnetic scalar potential , i.e. h = -grad{\phi} , with discontinuities of through the TS. In this paper, the SPM is extended to account for thin regions located between conducting regions or between conducting and nonconducting regions, in the general case of multiply connected regions. In these regions, the potential is not defined anymore on both sides of the TS and the problem has to be expressed in terms of the discontinuities of h, possibly involving on one side only, to be strongly defined via an IC through the TS. In the proposed SP strategy, a reduced problem with only inductors is first solved on a simplified mesh without thin and volume regions. Its solution gives surface sources (SSs) as ICs for added TS regions, and volume sources (VSs) for possible added volume regions. The TS solution is further improved by a volume correction via SSs and VSs that overcome the TS assumptions, respectively suppressing the TS model and adding the volume model. Each SP has its own separate mesh, which increases the computational efficiency. Details on the proposed method will be given in the extended paper, with practical applications

Exploring a possible energy transition in Vietnam; Scenarios for the electricity sector and cost assessment of de‐carbonisation

International audienceAs an emerging country in Southeast Asia, Vietnam has been experiencing strong economicgrowth over the past decades. Its rapid development is characterized by industrial and urbantransformations which translate into sustained demand for energy, and particularly electricity.Electricity production grew 14,1% over 1990-2010, and per capita consumption jumped from 93to 999 kWh/habitant.These trends for electricity sector expansion are to be considered in a policy and regulatoryframework with strong State intervention. Public intervention is proactive for the upgrading ofthe national capacity and the orientation of the electricity mix. The national electricity plan isconsidering a tremendous expansion of the national electricity capacity by 2030. By that time,the electricity capacity would be increased sevenfold (20.000 MW in 2010 upgraded to 146.800MW in 2030), according to offcial sources. The seventh Masterplan envisages a mix where hydropoweraccounts for 11.8%, energy storage hydropower 3.9%; coal thermal power 51.6%; andgas fired power 11, 8%; power using renewable energy 9.4%; nuclear power 6.6% ; and importedpower 4.9%.This is a considerable challenge in terms of investment, technology choice and prospects forreconciling energy, environment and climate policies. In this context, our research mobilizeseconomic analysis to investigate current trends with a view of characterizing a possible electricitytransition in Vietnam

Etude des mécanismes de rupture d'un assemblage boulonné

Cette étude expérimentale et numérique traite de l’analyse du comportement et de la rupture d’un assemblage ponctuel (boulonné) soumis à un chargement statique de cisaillement. La technique de l’émission acoustique a été utilisée pour prédire la chronologie des différents mécanismes d’endommagement. Une mesure de champs de déformations par corrélation d’images a été mise en œuvre. Les cas étudiés ont été simulé par la technique des éléments finis 3D

Inorganic, Organic, and Perovskite Halides with Nanotechnology for High-Light Yield X- and γ-Ray Scintillators

Trends in scintillators that are used in many applications, such as medical imaging, security, oil-logging, high energy physics and non-destructive inspections are reviewed. First, we address traditional inorganic and organic scintillators with respect of limitation in the scintillation light yields and lifetimes. The combination of high–light yield and fast response can be found in Ce 3+ , Pr 3+ and Nd 3+ lanthanide-doped scintillators while the maximum light yield conversion of 100,000 photons/MeV can be found in Eu 3+ doped SrI 2 . However, the fabrication of those lanthanide-doped scintillators is inefficient and expensive as it requires high-temperature furnaces. A self-grown single crystal using solution processes is already introduced in perovskite photovoltaic technology and it can be the key for low-cost scintillators. A novel class of materials in scintillation includes lead halide perovskites. These materials were explored decades ago due to the large X-ray absorption cross section. However, lately lead halide perovskites have become a focus of interest due to recently reported very high photoluminescence quantum yield and light yield conversion at low temperatures. In principle, 150,000–300,000 photons/MeV light yields can be proportional to the small energy bandgap of these materials, which is below 2 eV. Finally, we discuss the extraction efficiency improvements through the fabrication of the nanostructure in scintillators, which can be implemented in perovskite materials. The recent technology involving quantum dots and nanocrystals may also improve light conversion in perovskite scintillators

Large-scale gene discovery in the pea aphid Acyrthosiphon pisum (Hemiptera)

Aphids are the leading pests in agricultural crops. A large-scale sequencing of 40,904 ESTs from the pea aphid Acyrthosiphon pisum was carried out to define a catalog of 12,082 unique transcripts. A strong AT bias was found, indicating a compositional shift between Drosophila melanogaster and A. pisum. An in silico profiling analysis characterized 135 transcripts specific to pea-aphid tissues (relating to bacteriocytes and parthenogenetic embryos). This project is the first to address the genetics of the Hemiptera and of a hemimetabolous insect.Beatriz Sabater-Muñoz... et al

Policy framing and crisis narratives around food safety in Vietnam

While progress has been made recently in understanding food systems per se, much less is known about policies around those food systems. In this paper, we aim at understanding the food system policy context with the specific objective to look at policy dynamics—defined as the way policy agendas are identified, justified, and framed by decision-makers, and how they interact. Vietnam is used as a case study. Primary data were generated through face-to-face interviews complemented by an online survey. A policy framing approach was used to structure the research. The analysis reveals how the policy agenda is considered by many actors to be only partially evidence-based and highlights the extent to which the state government remains the most powerful actor in the setting of that agenda. The research also reveals the diffusion of the food safety crisis narrative beyond its original technical domain into a larger number of policy framings related to other issues of food systems, thus making it de facto the “center of gravity” of the current agenda on food systems in Vietnam. Yet, a comparison with data from other countries challenges this narrative, and reveals instead how the (legitimate) public concern about food safety is being instrumentalized by certain groups of actors to advance their own agenda. The implication of this “distorted” framing is the risk for the decision-makers to “overfocus” their attention on this short-term issue and lose sight of some other longer-term structural trends such as the emergence of obesity in Vietnamese urban population

Lithium-Doped Two-Dimensional Perovskite Scintillator for Wide-Range Radiation Detection

Two-dimensional lead halide perovskites have demonstrated their potential as high-performance scintillators for X- and gamma-ray detection, while also being low-cost. Here we adopt lithium chemical doping in two-dimensional phenethylammonium lead bromide (PEA)2PbBr4 perovskite crystals to improve the properties and add functionalities with other radiation detections. Li doping is confirmed by X-ray photoemission spectroscopy and the scintillation mechanisms are explored via temperature dependent X-ray and thermoluminescence measurements. Our 1:1 Li-doped (PEA)2PbBr4 demonstrates a fast decay time of 11 ns (80%), a clear photopeak with an energy resolution of 12.4%, and a scintillation yield of 11,000 photons per MeV under 662 keV gamma-ray radiation. Additionally, our Li-doped crystal shows a clear alpha particle/gamma-ray discrimination and promising thermal neutron detection through 6Li enrichment. X-ray imaging pictures with (PEA)2PbBr4 are also presented. All results demonstrate the potential of Li-doped (PEA)2PbBr4 as a versatile scintillator covering a wide radiation energy range for various applications