Experimental study of aqueous fluid infiltration into quartzite: implications for the kinetics of fluid redistribution and grain growth driven by interfacial energy reduction

To investigate the kinetics of interfacial energy‐driven fluid infiltration, experiments were carried out in a quartzite–water system at 621–925°C and 0.8 GPa. Infiltration couples were made by juxtaposing presynthesized dry quartzite cylinders and fluid reservoirs. The infiltration process was confirmed by the presence of pores at the quartzite grain edges. As predicted from theoretical considerations and previous experiments, wetting fluids such as pure water and NaCl aqueous solution infiltrated into quartzite, whereas nonwetting CO₂‐rich fluids did not. Newly precipitated quartz layers at the surfaces of the infiltrated sample proved that infiltration took place by a dissolution–precipitation mechanism. The enhancement of grain growth by fluid infiltration was observed over the entire range of experimental temperatures. The fluid fraction, gauged by the porosity of the run products, increases at the infiltration front and then decreases towards the fluid reservoir to form a high‐porosity zone with a maximum porosity of 2.3–2.9%. As infiltration proceeds, the high‐porosity zone advances like a travelling wave. This porosity wave is probably caused by a grain curvature gradient resulting from preferential grain growth in the infiltrated part of the quartzite, perhaps combined with other factors. The infiltration kinetics were modelled with a steady‐state diffusion model over the high‐porosity zone. The solubility difference between dissolving and precipitating grains was deduced to be 2 × 10^?2?3 × 10^?1 wt %. The experimentally obtained infiltration rate of aqueous fluid in the steady‐state diffusion regime (2 ± 0.5 × 10^?8 m sec^?1 at 823°C) is much faster than the estimated metamorphic fluid flux rates, so that interfacial energy‐driven fluid redistribution in quartz‐rich layers could significantly contribute to the fluid flux in high‐grade metamorphism, at least over a short distance. Cathodoluminescence observations of the run products revealed that the grain growth of quartzite in the presence of fluid proceeds extensively, which would promote the chemical equilibration between fluid and rock more effectively than would volume diffusion in quartz crystals.     

Hydrothermal,multiphase convection of H2O‐NaCl fluids from ambient to magmatic temperatures: a new numerical scheme and benchmarks for code comparison

Thermohaline convection of subsurface fluids strongly influences heat and mass fluxes within the Earth's crust. The most effective hydrothermal systems develop in the vicinity of magmatic activity and can be important for geothermal energy production and ore formation. As most parts of these systems are inaccessible to direct observations, numerical simulations are necessary to understand and characterize fluid flow. Here, we present a new numerical scheme for thermohaline convection based on the control volume finite element method (CVFEM), allowing for unstructured meshes, the representation of sharp thermal and solute fronts in advection‐dominated systems and phase separation of variably miscible, compressible fluids. The model is an implementation of the Complex Systems Modelling Platform CSMP++ and includes an accurate thermodynamic representation of strongly nonlinear fluid properties of salt water for magmatic‐hydrothermal conditions (up to 1000°C, 500 MPa and 100 wt% NaCl). The method ensures that all fluid properties are taken as calculated on the respective node using a fully upstream‐weighted approach, which greatly increases the stability of the numerical scheme. We compare results from our model with two well‐established codes, HYDROTHERM and TOUGH2, by conducting benchmarks of different complexity and find good to excellent agreement in the temporal and spatial evolution of the hydrothermal systems. In a simulation with high‐temperature, high‐salinity conditions currently outside of the range of both HYDROTHERM and TOUGH2, we show the significance of the formation of a solid halite phase, which introduces heterogeneity. Results suggest that salt added by magmatic degassing is not easily vented or accommodated within the crust and can result in dynamic, complex hydrologies.     

The Impact and Compensation of Offshore Wind Farm Development: Analysing the Institutional Discourse from a French Case Study

Abstract

In France, the public acceptability of marine renewable energies and their impacts on ecosystem services (ES) involves questions about compensation for stakeholders, who may perceive some of their activities and interests to be modified. This paper seeks to understand how impacts on ES are perceived by institutional stakeholders and what is expected in terms of compensation. It also seeks to identify the communities of practice affected. We focus our study on the planned offshore wind farm in the bay of Saint-Brieuc. Our results show that institutional discourse is heterogeneous, depending on sensitivities, interests, and who or what the stakeholders surveyed represent or defend. Stakeholders' discourse can be interpreted on various gradients of perception. Six distinct communities of practice have been identified, based on the impacts perceived by institutional stakeholders. Lastly, we show that the community of practice seems to be a proper level at which to study perceptions and assess the no-net-loss goal.     

Thermal springs and heat flow in North America

Thermal springs are commonly thought to be an indicator of geothermal resource potential. However, there have been few analyses of the relationship between thermal springs and the underlying thermal regime. An examination of temperature and discharge rates for a large database of thermal springs in North America demonstrates that there is not a simple relationship between these measurements made at the surface and subsurface heat flow. Hydrogeological factors appear to exert strong controls on the temperature and discharge at these springs and should be carefully considered in geothermal resource assessments.     

Advanced design of Chinese traditional materials for the conservation of historic stone buildings

The conservation of historic stone buildings and sculptures is recently receiving growing attention and becoming a focus of research because of rapid changes in weather conditions (pollution, acid rain, etc.). Presently, techniques for stone conservation primarily involve the use of organic coating treatments, but their side effects have been recognized. In contrast, some traditional materials used in historic stone buildings function well for thousands of years. In this paper, we report our research on the reasons why traditional protective materials can provide an unexpected long-term protection. First, calcium carbonate was prepared according to a formula for making Chinese traditional consolidating materials, and its structure and morphology were examined by different instruments. Second, the reinforcing effectiveness of the prepared CaCO₃ powders was tested and analyzed by investigating its surface characteristics. The experimental results reveal that a biocontrolled process occurs, in which an organic template can induce the precipitation of a mineral structure, which in turn results in a great improvement in the conservation of the historic stone buildings protected by these traditional protective materials. This provides a contribution toward the development of new researches on biocontrolled processes and on some protective materials with excellent performance through biocontrolled synthesis.     

浅谈现代生活中的电子技术新应用

随着社会进入信息化及电子智能化时代,电子技术发展越来越迅速,应用越来越广泛,对人类生活的影响也更加深远。节能减排、保护环境,是全世界、全人类共同关心的问题,也是我国社会经济发展的重要问题。     

Simulation of Shake Table Tests on Out-of-Plane Masonry Buildings. Part (VI): Discrete Element Approach

ABSTRACT

Although many experimental tests and numerical models are available in the literature, the numerical simulation of the seismic response of existing masonry buildings is still a challenging problem. While the nonlinear behavior of masonry structures is reasonably predictable when the out-of-plane behavior can be considered inhibited, when the in-plane and out-of-plane responses coexist and interact, simplified models seem unable to provide reliable numerical predictions. In this article, taking advantage of the experimental tests carried out in a shaking table on two masonry prototypes at LNEC, a macro-element approach is applied for the numerical simulations of their nonlinear response. The adopted approach allows simulating the nonlinear behavior of masonry structures considering the in-plane and out-of-plane responses. Since it is based on a simple mechanical scheme, explicitly oriented to representing the main failure mechanisms of masonry, its computational cost is greatly reduced with respect to rigorous solutions, namely nonlinear FEM approaches. Two modeling strategies are adopted, namely a regular mesh independent from the real texture of the prototypes and a detailed one coherent with the units disposal. The numerical results are discussed and the correlation between the nonlinear static analyses and the dynamic response is provided.     

A Review of the Environmental Policy Literature from 2014 to 2017 with a Closer Look at the Energy Justice Field

This review article documents and analyzes trends within the environmental policy literature published between 2014 and 2017. We find that environmental policy scholarship has recently shifted its focus from more traditional topics, such as watershed and ecosystem management, to other modern issues, such as climate change and energy. The environmental policy literature has increased in complexity and become more interdisciplinary in nature, which we illustrate with a discussion of the energy justice literature. The methodological approaches used by environmental policy scholars have also become increasingly diverse, with a notable uptick in statistical and modeling approaches. We find that some topics, such as policy failure, gender issues, and energy welfare policies are under‐explored, and certain regions within the world, such as developing countries, are less frequently studied. We encourage scholars to consider these gaps in the literature when developing future research.     

The Role of Pilot Projects in Urban Climate Change Policy Innovation

Cities are taking a leadership role in addressing global climate change and reducing greenhouse gas (GHG) emissions, but policy innovations are needed to help cities move from goals to outcomes. Pilot projects are one means by which cities are experimenting with new ways of governing and financing climate change mitigation. In this paper, we develop a framework for understanding the role of pilot projects in urban policy innovation: their emergence and rationale, and the means by which they ultimately scale up and out to reduce GHG emissions. We use this framework to evaluate a pilot project for retrofitting social housing buildings in Toronto. We find the initial pilot project helped address the challenges of pursuing deep retrofits of social housing. Scaling these lessons up to the city level required overcoming challenges to financing and coordinating a larger project; scaling out to the provincial level revealed institutional and political obstacles to pursuing the co-benefits of deep building retrofits in social housing. Bridging agents play an important role in both scaling processes. The analysis reveals the additive nature of urban policy innovation and the dynamic interplay of change agents and institutional and political context in innovation processes.     

A Micro Model of Problem Definition and Policy Choice: Issue Image,Issue Association,and Policy Support of Power Plants

Past research on problem definition and public policy primarily focuses on the macro-system level. In this study, we propose a micro model of problem definition and policy choice at the individual level. We argue that while individual citizens' problem definitions and policy preferences are rooted in and filtered through their predisposition characteristics (such as socioeconomic status, political orientation, and informational base), their policy choices also strongly depend on how they define public issues, particularly how they perceive the image of an issue at hand and how they associate the issue with other public issues. Our empirical analyses, based on data from a national public survey on energy and power plant issues, support the key propositions derived from our theoretical model. Key contributions to and implications for policy studies are discussed in conclusion.