Accounting for Risk: Conceptualizing a Robust Greenhouse Gas Inventory for Financial Institutions

Outlines objectives, options, and challenges for financial firms and stakeholders in accounting for greenhouse gas emissions from their investments and services as part of climate change risk management. Discusses methods, scope, reporting, and use

Fast Cloth Simulation with Implicit Contact and Exact Coulomb Friction

International audienceCloth dynamics plays an important role in the visual appearance of moving characters. Properly accounting for frictional contact is of utmost importance to avoid cloth-body penetration and to capture folding behavior due to dry friction. We present here the first method able to account for contact with exact Coulomb friction between a cloth and the underlying character. Our key contribution is to formulate and solve the frictional contact problem merely on velocity variables, by leveraging some tools of convex analysis. Our method is both fast and robust, allowing us to simulate full-size garments with more realistic body-cloth interactions compared to former methods, while maintaining similar computational timings

Simulation par éléments discrets de fibres flexibles avec frottement de Coulomb

National audienceOn présente ici une méthode pour la simulation d'ensembles de fibres basée sur une discrétisation du modèle de Kirchhoff ( modèle des Super-Hélices ). Le contact avec frottement de Coulomb exact entre les fibres est résolu grâce à un algorithme itératif de type Gauss-Seidel faisant intervenir un solveur local hybride. La méthode est appliquée à l'informatique graphique, et en particulier à la simulation réaliste de chevelures

Simulation of Drucker–Prager granular flows inside Newtonian fluids

Granular-fluid interactions appear in a variety of real-life scenarios ranging from immersed avalanches to ash clouds. We present a continuum-based numerical method for the simulation of such phenomena. Our approach avoids the heavy computational cost inherent to a fluid-solid coupling at the grain scale, while still being able to capture the distinctive regimes governing the collapse of an immersed granular column. To the best of our knowledge, the method presented here is the first to combine fully-coupled two-phase equations for immersed granular flows with an implicit nonsmooth treatment of the Drucker–Prager rheology

Revisiting the role of friction coefficients in granular collapses: confrontation of 3-D non-smooth simulations with experiments

In this paper, transient granular flows are examined both numerically and experimentally. Simulations are performed using the continuous 3D granular model introduced in Daviet & Bertails-Descoubes (2016), which represents the granular medium as an inelastic and dilatable continuum subject to the Drucker-Prager yield criterion in the dense regime. One notable feature of this numerical model is to resolve such a non-smooth rheology without any regularisation. We show that this non-smooth model, which relies on a constant friction coefficient, is able to reproduce with high fidelity various experimental granular collapses over inclined erodible beds, provided the friction coefficient is set to the avalanche angle - and not to the stop angle, as generally done. In order to better characterise the range of validity of the fully plastic rheology in the context of transient frictional flows, we further revisit scaling laws relating the shape of the final collapse deposit to the initial column aspect ratio, and accurately recover established power-law dependences up to aspect ratios in the order of 10. The influence of sidewall friction is then examined through experimental and simulated collapses with varying channel widths. The effective flow thickness is estimated in relation to the channel width, thereby challenging previously held assumptions on its estimation. Finally, we discuss the potential extension of the constant coefficient model with a hysteretic model to refine predictions of early-stage collapse dynamics, illustrating the impact of such phenomenology on transient flows and paving the way to more elaborate analysis.Comment: 25 figures and 6 movie

Inverse Elastic Cloth Design with Contact and Friction

Physically based cloth modeling is classically achieved through a trial and error process. The rest (undeformed) configuration of the cloth, often represented as a 2D pattern assembly, is edited geometrically and adjusted iteratively depending on the feedback provided by a static cloth simulator, which predicts the deformed 3D shape under gravity and contacts. Matching a reference 3D shape while keeping the time of the modeling process reasonable is thus difficult , unless the user possesses advanced skills in real cloth tailoring. In contrast, in this paper we investigate a new, inverse strategy for modeling realistic cloth intuitively. Our goal is to take as input a target (deformed) 3D shape, and to interpret this configuration automatically as a stable equilibrium of a cloth simulator, by retrieving the unknown rest shape. In the presence of gravity and frictional contact, such an inverse problem formulates as an ill-posed nonlinear system subject to nonsmooth constraints. To select and compute a plausible solution, we design an iterative two-step solving process. In a first step, contacts are reduced to frictionless bilateral constraints, and starting from an as-flat-as possible pose, a unique rest pose is retrieved using the adjoint method on a regularized energy. The second step modifies this rest pose so as to project bilateral forces onto the admissible Coulomb friction cone, for each contact. We show that our method converges well in most cases towards a plausible rest configuration, and demonstrate practical inversion results on various cloth geometries modeled by an artist

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)