Mixing-scale dependent dispersion for transport in heterogeneous flows

Dispersion quantifies the impact of subscale velocity fluctuations on the effective movement of particles and the evolution of scalar distributions in heterogeneous flows. Which fluctuation scales are represented by dispersion, and the very meaning of dispersion, depends on the definition of the subscale, or the corresponding coarse-graining scale. We study here the dispersion effect due to velocity fluctuations that are sampled on the homogenization scale of the scalar distribution. This homogenization scale is identified with the mixing scale, the characteristic length below which the scalar is well mixed. It evolves in time as a result of local-scale dispersion and the deformation of material fluid elements in the heterogeneous flow. The fluctuation scales below the mixing scale are equally accessible to all scalar particles, and thus contribute to enhanced scalar dispersion and mixing. We focus here on transport in steady spatially heterogeneous flow fields such as porous media flows. The dispersion effect is measured by mixing-scale dependent dispersion coefficients, which are defined through a filtering operation based on the evolving mixing scale. This renders the coarse-grained velocity as a function of time, which evolves as velocity fluctuation scales are assimilated by the expanding scalar. We study the behaviour of the mixing-scale dependent dispersion coefficients for transport in a random shear flow and in heterogeneous porous media. Using a stochastic modelling framework, we derive explicit expressions for their time behaviour. The dispersion coefficients evolve as the mixing scale scans through the pertinent velocity fluctuation scales, which reflects the fundamental role of the interaction of scalar and velocity fluctuation scales in solute mixing and dispersion. © © 2015 Cambridge University Press.The authors thank three anonymous reviewers for their insightful comments. M.D. acknowledges the support of the European Research Council (ERC) through the project MHetScale (617511).Peer reviewe

Ecological fiscal transfers for biodiversity conservation policy: a transaction costs analysis of Minas Gerais, Brazil

This paper addresses the influence of ecological fiscal transfers (EFT) on the policy-making process of adopting local protected areas (PA) by municipal governments. Framed on the transaction-cost politics (TCP), it argues that an EFT schema designed at the state level may affect the expected payoff/costs of local level decisions and the time length to create PA. The mixed research design is composed of two parts: first, a descriptive analysis detailing the evolution of EFT in the state of Minas Gerais since the beginning until its current version; second, an event history analysis of municipal PA adoption from 1966 to 2013. The conclusion suggests that, while there is an overall increase in municipal PA after the introduction of EFT, some design aspects of the instrument such as uncertainty and monitoring costs slowed and flattened that increase.This work was conducted during a scholarship financed by CAPES (Brazilian Federal Agency). Process number: 000954/2015-02. Also, this study was conducted at Research Center in Political Science (UID/ CPO/0758/2019), University of Minho, and was supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds

The adoption of ecological fiscal transfers: an empirical analysis

The ecological fiscal transfers (EFT) from states to municipalities were adopted by 16 of the 26 Brazilian states since 1990s to stimulate and compensate districts for achieving some environmental goals. This study aims to understand the adoption of this economic-policy instrument by Brazilian states and argues that the vertical relations between the federal and state governments increase the EFT adoption. The hypotheses are derived from the transaction-costs politics and the institutional collective action frameworks, namely built in legislative decision-making costs and commitment costs, and are empirically tested using event history analysis for the period of 1990–2015. The conclusions point to the idea that the adoption rate increases in non-electoral years, suggesting that politicians tend to avoid conflicts during electoral years. They tend to minimize the costs related to the legislative decision-making process. Also, the coordination of the central government has the potential for facilitating the adoption of EFT. More broadly, the transaction cost-politics framework and the institutional collective action framework can explain EFT adoption partially.This work was conducted during a scholarship financed by CAPES (Brazilian Federal Agency). Process number: 000954/2015-02. Research Center in Political Science of the University of Minho and supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds (UID/CPO/00758/2013). Special acknowledgment is due to Dr. Irene Ring, received Felipe Paulo in her research group in July 2017. She introduced him to the literature of policy mix and ecological fiscal transfers (EFT). Many thanks also to Nils Droste for providing part of his database. Naturally, all possible shortcomings in this paper are the responsibility of the authors

An analysis of delay in implementing ecological fiscal transfers in Brazil

This paper sheds light on the cases of delay, in some cases interruptions and cancellations of criteria, that followed the adoption of ecological fiscal transfers (EFT) by Brazilian states. Using the transaction costs-politics framework to analyze the policy-making process, the central argument is that state legislatives are likely to weight benefits and costs at the formulation stage. At the implementation stage, legislatives delegate the role of refining EFT procedures to state agencies and, as such, increase the costs they incur. The empirical design is based on a set of case-studies, collecting data using questionnaires devised to describe the time-lags and the interruptions and cancellations of environmental criteria. The findings provide evidence of the presence of gridlocks in the formulation stage and delegation problems in the political-bureaucratic relationship at the implementation stage. Also, the absence of a gradual increase to implement the percentage dedicated to ecological criteria in each state is likely to explain the delays in the implementation of EFT schemes. In the end, we recommend flexibility in the design of scheme and the involvement of political actors in the policy process of adopting EFT.This work was conducted during a scholarship financed by CAPES (Brazilian Federal Agency). Process number: 000954/2015–02. Also, this study was conducted at Research Center in Political Science (UID/CPO/0758/2019), University of Minho, and was supported by the Portuguese Foundation for Science and Technology and the Portuguese Ministry of Education and Science through national funds