Fluid-Structure Interaction with the Entropic Lattice Boltzmann Method

We propose a novel fluid-structure interaction (FSI) scheme using the entropic multi-relaxation time lattice Boltzmann (KBC) model for the fluid domain in combination with a nonlinear finite element solver for the structural part. We show validity of the proposed scheme for various challenging set-ups by comparison to literature data. Beyond validation, we extend the KBC model to multiphase flows and couple it with FEM solver. Robustness and viability of the entropic multi-relaxation time model for complex FSI applications is shown by simulations of droplet impact on elastic superhydrophobic surfaces

Hyperbolic Discounting with Environmental Outcomes across Time, Space, and Probability

Environmental discounting is a potentially important research area for climate change mitigation. We aimed to replicate and extend earlier work on the discounting of a negative environmental outcome. We measured ratings of concern, and willingness to act to mitigate, an outcome involving air pollution that would hypothetically affect the garden and drinking water of the participants over psychological distance represented by temporal (1 month, 6 months, and 1, 3, 5, 10, and 80 years), spatial (5, 20, 50, 100, 1000, and 5000 km), and probabilistic (95%, 90%, 50%, 30%, 10%, and 5% likelihood) dimensions. For our data from 224 first-year psychology students, of four potential models (an exponential, simple hyperbolic, and two hyperboloid functions), the Rachlin hyperboloid was the best-fitting model describing ratings of concern and action across all three dimensions. Willingness to act was discounted more steeply than concern across all dimensions. There was little difference in discounting for outcomes described as human-caused rather than natural, except that willingness to act was discounted more steeply than concern for human-caused environmental outcomes compared to natural outcomes across spatial (and, less conclusively, temporal) distance. Presenting values of the three dimensions in random or progressive order had little effect on the results. Our results reflect the often-reported attitudebehavior gap whereby people maintain concern about a negative event over dimensions of psychological distance, but their willingness to act to mitigate the event is lower and more steeply discounted

Two Variable Logic with Ultimately Periodic Counting

We consider the extension of FO² with quantifiers that state that the number of elements where a formula holds should belong to a given ultimately periodic set. We show that both satisfiability and finite satisfiability of the logic are decidable. We also show that the spectrum of any sentence is definable in Presburger arithmetic. In the process we present several refinements to the "biregular graph method". In this method, decidability issues concerning two-variable logics are reduced to questions about Presburger definability of integer vectors associated with partitioned graphs, where nodes in a partition satisfy certain constraints on their in- and out-degrees

Estimating the effects of non-discriminatory trade policies within structural gravity models

Abstract only in English and FrenchWe propose a simple method to identify the effects of unilateral and non‐discriminatory trade policies on bilateral trade within a theoretically consistent empirical gravity model. Specifically, we argue that structural gravity estimations should be performed with data that include not only international trade flows but also intra‐national trade flows. The use of intra‐national sales allows identification of the effects of non‐discriminatory trade policies such as most favoured nation tariffs, even in the presence of exporter and importer fixed effects. A byproduct of our approach is that it can be used to recover estimates of the trade elasticity, a key parameter for quantitative trade models. We demonstrate the effectiveness of our techniques in the case of most favoured nation tariffs and “time to export” as representative non‐discriminatory determinants of trade on the importer and on the exporter side, respectively. Our methods can be extended to quantify the impact on trade of any country‐specific characteristics as well as any non‐trade policies. = Évaluation de l’incidence des politiques commerciales non discriminatoires au sein de modèles de gravité structurels. Dans un modèle de gravité empirique théoriquement cohérent, nous proposons une méthode simple pour identifier les effets des politiques commerciales unilatérales et non discriminatoires sur le commerce bilatéral. Plus précisément, nous affirmons que les estimations basées sur des modèles de gravité structurels doivent être réalisées en tenant compte non seulement des données relatives aux flux commerciaux internationaux, mais aussi nationaux. L’utilisation de données relatives aux ventes domestiques permet d’identifier les effets des politiques commerciales non discriminatoires, par exemple les tarifs douaniers de la nation la plus favorisée (NPF), même en présence d’effets fixes importateur et exportateur. Notre approche peut être utilisée pour redresser les estimations relatives à l’élasticité des échanges, un paramètre clé des modèles commerciaux quantitatifs. Nous démontrons l’efficacité de nos techniques dans le cadre des tarifs douaniers NPF et des délais d’exportation, facteurs déterminants, représentatifs et non discriminatoires sur le commerce, à la fois pour l’importateur et l’exportateur. Il possible d’étendre nos méthodes pour quantifier les effets de n’importe quelle caractéristique spécifique à un pays sur le commerce, ainsi que de n’importe quelle politique non commerciale.Benedikt Heid, Mario Larch, Yoto V. Yoto