Variable time scales, agent-based models, and role-playing games: The PIEPLUE river basin management game

This article presents a specific association of a role-playing game (RPG) and an agent-based model (ABM) aimed at dealing with a large range of time scales. Applications to the field of natural resource management lead one to consider the short time scale of resource use in practice at the same time as the longer ones related to resource dynamics or actors' investments. In their daily practice, stakeholders are translating their long-term strategies, a translation that is contextualized and combined with some cooccurring events. Long-term thinking is required for sustainable use of natural resources, but it should take into account its necessary adaptation on a short time scale. This raises the necessity for tools able to tackle jointly these various time scales. The similarity of architecture between computerized ABMs and RPGs makes them easy to associate in a hybrid tool, targeted at meeting this requirement. The proposition of this article is to allocate the representation of short time scales to computerized ABMs and the long ones to RPGs, while keeping the same static structural conceptual model, shared as a common root by both. This synergy is illustrated with PIEPLUE, an interactive setting tackling water-sharing issues.GESTION DE L'EAU;BASSIN VERSANT;RESSOURCE NATURELLE;MODELE;JEU DE ROLE;SYSTEME MULTIAGENTS;AGENT-BASED MODEL;CASE STUDY OF WATER SHARING;CONCEPTUAL MODEL;HYBRID TOOL;INVESTMENTS;LONG-TERM ISSUES;NATURAL RESOURCE MANAGEMENT;PIEPLUE;PARTICIPATORY MODELING;RESOURCE DYNAMICS;RESOURCE USE;ROLE-PLAYING GAME;STAKEHOLDERS;SUSTAINABLE USE OF NATURAL RESOURCES;TIME-SCALE DIVERSITY;VARIABLE TIME SCALES;WATER MANAGEMENT

Magnetocrystalline anisotropy of Fe and Co slabs and clusters on SrTiO_3\_3 by first-principles

In this work, we present a detailed theoretical investigation of the electronic and magnetic properties of ferromagnetic slabs and clusters deposited on SrTiO$\_3$ via first-principles, with a particular emphasis on the magneto-crystalline anisotropy (MCA). We found that in the case of Fe films deposited on SrTiO$\_3$ the effect of the interface is to quench the MCA whereas for Cobalt we observe a change of sign of the MCA from in-plane to out-of-plane as compared to the free surface. We also find a strong enhancement of MCA for small clusters upon deposition on a SrTiO$\_3$ substrate. The hybridization between the substrate and the $d$-orbitals of the cluster extending in-plane for Fe and out-of-plane for Co is at the origin of this enhancement of MCA. As a consequence, we predict that the Fe nanocrystals (even rather small) should be magnetically stable and are thus good potential candidates for magnetic storage devices.Comment: Physical ReviewB, 201

Using Social Simulation to Explore the Dynamics at Stake in Participatory Research

This position paper contributes to the debate on perspectives for simulating the social processes of science through the specific angle of participatory research. This new way of producing science is still in its infancy and needs some step back and analysis, to understand what is taking place on the boundaries between academic, policy and lay worlds. We argue that social simulation of this practice of cooperation can help in understanding further this new way of doing science, building on existing experience in simulation of knowledge flows as well as pragmatic approaches in social sciences.Participatory Research, Institutional Analysis and Design, Knowledge Flow, Agent Based Simulation

Magnetism of iron: from the bulk to the monoatomic wire

The magnetic properties of iron (spin and orbital magnetic moments, magnetocrystalline anisotropy energy) in various geometries and dimensionalities are investigated by using a parametrized tight-binding model in an $s$, $p$ and $d$ atomic orbital basis set including spin polarization and the effect of spin-orbit coupling. The validity of this model is well established by comparing the results with those obtained by using an ab-initio code. This model is applied to the study of iron in bulk bcc and fcc phases, $(110)$ and $(001)$ surfaces and to the monatomic wire, at several interatomic distances. New results are derived. The variation of the component of the orbital magnetic moment on the spin quantization axis has been studied as a function of depth, revealing a significant enhancement in the first two layers, especially for the $(001)$ surface. It is found that the magnetic anisotropy energy is drastically increased in the wire and can reach several meV. This is also true for the orbital moment, which in addition is highly anisotropic. Furthermore it is shown that when the spin quantization axis is neither parallel nor perpendicular to the wire the average orbital moment is not aligned with the spin quantization axis. At equilibrium distance the easy magnetization axis is along the wire but switches to the perpendicular direction under compression. The success of this model opens up the possibility of obtaining accurate results on other elements and systems with much more complex geometries