Potential yield simulated by global gridded crop models: using a process-based emulator to explain their differences

How global gridded crop models (GGCMs) differ in their simulation of potential yield and reasons for those differences have never been assessed. The GGCM Intercomparison (GGCMI) offers a good framework for this assessment. Here, we built an emulator (called SMM for simple mechanistic model) of GGCMs based on generic and simplified formalism. The SMM equations describe crop phenology by a sum of growing degree days, canopy radiation absorption by the Beer–Lambert law, and its conversion into aboveground biomass by a radiation use efficiency (RUE). We fitted the parameters of this emulator against gridded aboveground maize biomass at the end of the growing season simulated by eight different GGCMs in a given year (2000). Our assumption is that the simple set of equations of SMM, after calibration, could reproduce the response of most GGCMs so that differences between GGCMs can be attributed to the parameters related to processes captured by the emulator. Despite huge differences between GGCMs, we show that if we fit both a parameter describing the thermal requirement for leaf emergence by adjusting its value to each grid-point in space, as done by GGCM modellers following the GGCMI protocol, and a GGCM-dependent globally uniform RUE, then the simple set of equations of the SMM emulator is sufficient to reproduce the spatial distribution of the original aboveground biomass simulated by most GGCMs. The grain filling is simulated in SMM by considering a fixed-in-time fraction of net primary productivity allocated to the grains (frac) once a threshold in leaves number (nthresh) is reached. Once calibrated, these two parameters allow for the capture of the relationship between potential yield and final aboveground biomass of each GGCM. It is particularly important as the divergence among GGCMs is larger for yield than for aboveground biomass. Thus, we showed that the divergence between GGCMs can be summarized by the differences in a few parameters. Our simple but mechanistic model could also be an interesting tool to test new developments in order to improve the simulation of potential yield at the global scale

Exploring Cosmic Origins with CORE: Cosmological Parameters

We forecast the main cosmological parameter constraints achievable with theCORE space mission which is dedicated to mapping the polarisation of the CosmicMicrowave Background (CMB). CORE was recently submitted in response to ESA'sfifth call for medium-sized mission proposals (M5). Here we report the resultsfrom our pre-submission study of the impact of various instrumental options, inparticular the telescope size and sensitivity level, and review the great,transformative potential of the mission as proposed. Specifically, we assessthe impact on a broad range of fundamental parameters of our Universe as afunction of the expected CMB characteristics, with other papers in the seriesfocusing on controlling astrophysical and instrumental residual systematics. Inthis paper, we assume that only a few central CORE frequency channels areusable for our purpose, all others being devoted to the cleaning ofastrophysical contaminants. On the theoretical side, we assume LCDM as ourgeneral framework and quantify the improvement provided by CORE over thecurrent constraints from the Planck 2015 release. We also study the jointsensitivity of CORE and of future Baryon Acoustic Oscillation and Large ScaleStructure experiments like DESI and Euclid. Specific constraints on the physicsof inflation are presented in another paper of the series. In addition to thesix parameters of the base LCDM, which describe the matter content of aspatially flat universe with adiabatic and scalar primordial fluctuations frominflation, we derive the precision achievable on parameters like thosedescribing curvature, neutrino physics, extra light relics, primordial heliumabundance, dark matter annihilation, recombination physics, variation offundamental constants, dark energy, modified gravity, reionization and cosmicbirefringence. (ABRIDGED

Microstructures et textures d'alliages d'aluminium déformés par forgeage croisé (compression multidirectionnelle)

Un nouveau montage de compression multidirectionnelle, dont l'intérêt principal réside dans la bonne maîtrise de la température tout au long de l'essai, a été développé au cours de cette thèse. Des essais de forgeage croisé ont été réalisés sur deux alliages d'aluminium polycristallins (AA 3103 et AlMgScZr) et sur des monocristaux Al-0,3%Mn dans des gammes de températures et de vitesses de déformation assez larges, jusqu'à une déformation cumulée de l'ordre de 3. Ces essais ont été caractérisés en termes de rhéologie, de microstructures et de textures de déformation. Enfin, des simulations de texture (hypothèse de Taylor couplée à une interaction entre grains) ont permis de retrouver et d'expliquer une partie des résultats expérimentaux, notamment la saturation rapide de la contrainte pour les températures inférieures à 200C et l'apparition de trois composantes de forgeage croisé (maille cubique tournée de 45 autour des 3 axes de compression).A new cross-forging device has been developed to enable high strain deformations up to 450C. Its main advantage is the control of the deformation temperature by means of an original flip mechanism which avoids temperature variations between each compression. Cross-forging tests have been carried out on two polycrystalline aluminium alloys (AA 3103 and AlMgScZr) and on Al-0,3%Mn single crystals over large temperature and strain rate ranges, up to a cumulative strain of about 3. The results were characterised in terms of rheology, microstructures and textures, and a comparison with plane strain compression tests established. Original 3D texture simulations (Taylor model combined with a grain interaction scheme) enabled us to explain some experimental results, namely the rapid stress saturation observed for the polycrystalline alloys strained below 200C, and the appearance during the test of three texture components (unit cell flip of 45 around each of the three axes).ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

Microstructures et textures d'alliages d'aluminium déformés par forgeage croisé (compression multidirectionnelle)

Un nouveau montage de compression multidirectionnelle, dont l'intérêt principal réside dans la bonne maîtrise de la température tout au long de l'essai, a été développé au cours de cette thèse. Des essais de forgeage croisé ont été réalisés sur deux alliages d'aluminium polycristallins (AA 3103 et AlMgScZr) et sur des monocristaux Al-0,3%Mn dans des gammes de températures et de vitesses de déformation assez larges, jusqu'à une déformation cumulée de l'ordre de 3. Ces essais ont été caractérisés en termes de rhéologie, de microstructures et de textures de déformation. Enfin, des simulations de texture (hypothèse de Taylor couplée à une interaction entre grains) ont permis de retrouver et d'expliquer une partie des résultats expérimentaux, notamment la saturation rapide de la contrainte pour les températures inférieures à 200C et l'apparition de trois composantes de forgeage croisé (maille cubique tournée de 45 autour des 3 axes de compression).A new cross-forging device has been developed to enable high strain deformations up to 450C. Its main advantage is the control of the deformation temperature by means of an original flip mechanism which avoids temperature variations between each compression. Cross-forging tests have been carried out on two polycrystalline aluminium alloys (AA 3103 and AlMgScZr) and on Al-0,3%Mn single crystals over large temperature and strain rate ranges, up to a cumulative strain of about 3. The results were characterised in terms of rheology, microstructures and textures, and a comparison with plane strain compression tests established. Original 3D texture simulations (Taylor model combined with a grain interaction scheme) enabled us to explain some experimental results, namely the rapid stress saturation observed for the polycrystalline alloys strained below 200C, and the appearance during the test of three texture components (unit cell flip of 45 around each of the three axes).ST ETIENNE-ENS des Mines (422182304) / SudocSudocFranceF

How is P added and what are future trends ?

International audienc

Phosphate in agricultural soils in the world : where is lacking, where in excess ?

International audienc

Texture and microtexture development in an Al–3Mg–Sc(Zr) alloy deformed by triaxial forging

International audienceThe texture and microstructure evolutions of a triaxially forged Al–3% Mg–0.25% Sc–0.12% Zr alloy are described for strains up to 3 and temperatures in the range 20–400 °C. A clear deformation texture develops and is composed of three symmetrical variants of a component. A three-dimensional spatially resolved crystal plasticity analysis also predicts the same texture evolution. At room temperature, significant grain fragmentation leads to substructure refinement and weaker textures. However, at 300 °C and above, more homogeneous intragranular deformation and rotations lead to stronger textures and, ultimately, the formation of interpenetrating ‘orientation chains' as a result of grain coalescence to common orientations, a new type of microstructure

A novel high straining process for bulk materials—The development of a multipass forging system by compression along three axes

International audienceA new triaxial forging equipment has been designed and built to enable sequential forging of near cube samples up to strains of 3–4 and temperatures up to 450 °C. This paper presents a technical and analytic description of the system and its application to a standard AA 3103 alloy. Some first results in terms of stress–strain curves, microstructures and textures are given

Relationship Between Microstructure, Strength, and Fracture in an Al-Zn-Mg Electron Beam Weld: Part II: Mechanical Characterization and Modeling

International audienceThis paper presents an experimental and modeling study of the mechanical behavior of an electron beam welded EN-AW 7020 aluminum alloy. The heterogeneous distribution of mechanical properties is characterized by micro-tensile tests and by strain field measurements using digital image correlation technic. These results are related to the microstructural observation presented in the companion paper. The mechanical behavior of the weld is simulated by a finite element model including a Gurson-type damage evolution model for void evolution. The model is shown to be capable of describing accurately experimental situations where the sample geometry is varied, resulting in stress triaxiality ratios ranging from 0.45 to 1.3

Carbon and phosphorus allocation in annual plants: an optimal functioning approach

Phosphorus (P) is the second most important nutrient after nitrogen (N) and can greatly diminish plant productivity if P supply is not adequate. Plants respond to soil P availability by adjusting root biomass to maintain uptake and productivity due to P use. In spite of our vast knowledge on P effects on plant growth, how to functionally model enhanced root biomass allocation in low P environments is not fully explored. We develop a dynamic plant model based on the principle of optimal carbon (C) and P allocation to investigate growth and functional response to contrasting levels of soil P availability. By describing plant growth as a balance of growth and respiration processes, we optimize C and P allocation in order to maximize leaf productivity and drive plant response. We compare our model to a field trial and a set of hydroponic experiments which describe plant response at varying P availabilities. The model is able to reproduce long-term plant functional response to different P levels like change in root-shoot ratio (RSR), total biomass and organ P concentration. But it is not capable of fully describing the time evolution of organ P uptake and cycling within the plant. Most notable is the underestimation of organ P uptake during the vegetative growth stage which is due to the model's leaf productivity formalism. In spite of the model's parsimonious nature, which optimizes for and predicts whole plant response through leaf productivity alone, the optimal growth hypothesis can provide a reasonable framework for modelling plant response to environmental change that can be used in more physically driven vegetation models