We explore the thesis that resonances in trees result in forests acting as locally resonant metamaterials for Rayleigh surface waves in the geophysics context. A geophysical experiment demonstrates ...that a Rayleigh wave, propagating in soft sedimentary soil at frequencies lower than 150 Hz, experiences strong attenuation, when interacting with a forest, over two separate large frequency bands. This experiment is interpreted using finite element simulations that demonstrate the observed attenuation is due to bandgaps when the trees are arranged at the sub-wavelength scale with respect to the incident Rayleigh wave. The repetitive bandgaps are generated by the coupling of the successive longitudinal resonances of trees with the vertical component of the Rayleigh wave. For wavelengths down to 5 meters, the resulting bandgaps are remarkably large and strongly attenuating when the acoustic impedance of the trees matches the impedance of the soil. Since longitudinal resonances of a vertical resonator are inversely proportional to its length, a man-made engineered array of resonators that attenuates Rayleigh waves at frequency ≤10 Hz could be designed starting from vertical pillars coupled to the ground with longitudinal resonance ≤10 Hz.
It is undeniable that exposure to outdoor air pollution impacts the health of populations and therefore constitutes a public health problem. Any actions or events causing variations in air quality ...have repercussions on populations’ health. Faced with the worldwide COVID-19 health crisis that began at the end of 2019, the governments of several countries were forced, in the beginning of 2020, to put in place very strict containment measures that could have led to changes in air quality. While many works in the literature have studied the issue of changes in the levels of air pollutants during the confinements in different countries, very few have focused on the impact of these changes on health risks. In this work, we compare the 2020 period, which includes two lockdowns (March 16 - May 10 and a partial shutdown Oct. 30 - Dec. 15) to a reference period 2015–2019 to determine how these government-mandated lockdowns affected concentrations of NO2, O3, PM2.5, and PM10, and how that affected human health factors, including low birth weight, lung cancer, mortality, asthma, non-accidental mortality, respiratory, and cardiovascular illnesses. To this end, we structured 2020 into four periods, alternating phases of freedom and lockdowns characterized by a stringency index. For each period, we calculated (1) the differences in pollutant levels between 2020 and a reference period (2015–2019) at both background and traffic stations; and (2) the resulting variations in the epidemiological based relative risks of health outcomes. As a result, we found that relative changes in pollutant levels during the 2020 restriction period were as follows: NO2 (−32%), PM2.5 (−22%), PM10 (−15%), and O3 (+10.6%). The pollutants associated with the highest health risk reductions in 2020 were PM2.5 and NO2, while PM10 and O3 changes had almost no effect on health outcomes. Reductions in short-term risks were related to reductions in PM2.5 (−3.2% in child emergency room visits for asthma during the second lockdown) and NO2 (−1.5% in hospitalizations for respiratory causes). Long-term risk reductions related to PM2.5 were low birth weight (−8%), mortality (−3.3%), and lung cancer (−2%), and to NO2 for mortality (−0.96%). Overall, our findings indicate that the confinement period in 2020 resulted in a substantial improvement in air quality in the Grenoble area.
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•Global level changes in 2020: NO2 (−32%), PM2.5 (−22%), PM10 (−15%) and O3 (+10.6%).•Health risk impacts were mainly related to changes in PM2.5 and NO2 levels.•Short-term risks of child asthma (−3%) and hospitalization for respiratory diseases (−2%).•Long-term risks of low birth weight (−8%), mortality (−4%), and lung cancer (−2%).
The rise in homelessness in European cities linked to increased migration has led cities to face new challenges of providing shelter for precarious newcomers. During the COVID-19 pandemic, the French ...authorities required that all homeless people be sheltered. In order to meet this obligation, they recognised the voluntary actions of activist associations as a resource complementing state action. In this context, the long-standing demand of social movements that vacant buildings be used to house the homeless has gained momentum. This paper addresses the emergence of a non-profit temporary housing model, known as habitat intercalcaire (in-between homes), in France. It originates from the institutionalisation of squatting through regulated occupations of public or private properties that are temporarily unused, to accommodate people who do not qualify for mainstream shelters or social housing. These projects are often included in temporary urbanism strategies of areas undergoing urban renewal. In the academic literature, very few publications examine these practices, especially in France. In other European countries, such as the Netherlands and Switzerland, several authors have analysed temporary housing through the perspective of its commodification (Baloche, 2016; Debrunner, Gerber, 2021). This paper adds to this body of knowledge, through the study of the partnerships between different organisations, activist groups and local authorities in the creation of non-profit temporary housing that integrates rationales both from the social welfare sector and from urban development. By using an actor-centred perspective it complements other studies that have addressed mainstream emergency shelters and “alternative” accommodation for asylum seekers and migrants, such as squats and homestays (Agier et al., 2019; Bouillon, 2009; Damon, 2021; Dietrich-Ragon, 2011; Gardella, 2014, 2016; Lévy, 2021; Roche, 2021). Through an interdisciplinary approach, the paper focuses on the encounter between the discourses, values and practices from the two fields and questions the tactical dimension of these urban actions. It is based on empirical research including participant observation in meetings and seminars organised by the promoters of this non-profit temporary housing model. In addition, interviews with fifteen stakeholders – both from local governments and from the associative sector – were conducted in Rennes, Villeurbanne and Grenoble. The three cities were chosen owing to the involvement of their local political leaders, coming from left-wing or green parties, in reception policies and in housing issues.By focusing on the rationales of the emergence of this housing model, the main findings of the study show how contradictory political and ideological stances have been overcome through pragmatical means, and how the political commitment of elected representatives has fostered different strategies in the three cities. Values originating both from the social welfare and urban development realms, have been combined by advocates of the model, in order to encourage its adoption by property developers. In addition, by facilitating the management of properties by social welfare organisations, these practitioners show they can provide “creative” and financially sustainable long-term solutions for housing the homeless. Finally, the paper shows that these experiments attempt to pacify divergent logics and to include the social issue in urban management on a long-term basis. In doing so, it raises further questions on the future joint evolutions of social welfare and urban planning, when faced with challenges associated with international migration and housing crises.
We compare the fractal indices of the power grid of the city of Grenoble (France) to those computed on the spatial organization of the buildings and the road infrastructure. We assess the fractal ...dimensions and the curves of scaling behavior and conduct a concordance analysis. We study different districts within the city and compare the power and road networks with the built-up patterns. We show the importance of using carefully data sets from different sources and how it could sometimes make major differences ahead of further use. We conclude on the optimality of the spatial coverage of the distribution network in Grenoble.
•Importance of data cleaning before conducting fractal measurements on networks.•The box counting method is used to analyze the fractal behavior of the power grid.•A concordance analysis is conducted for two technical urban networks and buildings.•The analysis is conducted for the whole city and at district level.
The main scope of the InterPACIFIC (Intercomparison of methods for site parameter and velocity profile characterization) project is to assess the reliability of in-hole and surface-wave methods, used ...for estimating shear wave velocity. Three test-sites with different subsurface conditions were chosen: a soft soil, a stiff soil and a rock outcrop. This paper reports the surface-wave methods results. Specifically 14 teams of expert users analysed the same experimental surface-wave datasets, consisting of both passive and active data. Each team adopted their own strategy to retrieve the dispersion curve and the shear-wave velocity profile at each site. Despite different approaches, the dispersion curves are quite in agreement with each other. Conversely, the shear-wave velocity profiles show a certain variability that increases in correspondence of major stratigraphic interfaces. This larger variability is mainly due to non-uniqueness of the solution and lateral variability. As expected, the observed variability in VS,30 estimates is small, as solution non-uniqueness plays a limited role.
•Variability of surface wave analysis results are studied with a blind test.•Three subsoil conditions are considered: soft soil, stiff soil, rock outcrop.•Different methods are used to analyze active and passive data.•A low variability is observed on the estimates of the experimental dispersion curve.•Variability in VS profiles is due to parameterization and solution non-uniqueness.
So-called new technologies create imaginary worlds and give rise to attitudes and discourse with a decidedly deterministic tone. While mainstream and traditional media largely prefer to see only the ...bright side of new digital and information and communication technologies, some “alternative” media outlets take another tack, railing against the misdeeds of new technology and denouncing “false progress.” The article looks at one such outlet, Grenoble’s ultralocal Le Postillon, a little satirical magazine with alterglobalist leanings founded in 2009 to cover Grenoble local news. This leads into a reflection on the relationship between modern social myths and the media.
The InterPACIFIC project was aimed at assessing the reliability, resolution, and variability of geophysical methods in estimating the shear-wave velocity profile for seismic ground response analyses. ...Three different subsoil conditions, which can be broadly defined as soft-soil, stiff-soil, and hard-rock, were investigated. At each site, several participants performed and interpreted invasive measurements of shear wave velocity (Vs) and compression wave velocity (Vp) in the same boreholes. Additionally, participants in the project analysed a common surface-wave dataset using their preferred strategies for processing and inversion to obtain Vs profiles. The most significant difference between the invasive borehole methods and non-invasive surface wave methods is related to resolution of thin layers and abrupt contrasts, which is inherently better for invasive methods. However, similar variability is observed in the estimated invasive and non-invasive Vs profiles, underscoring the need to account for such uncertainty in site response studies. VS,30 estimates are comparable between invasive and non-invasive methods, confirming that the higher resolution provided by invasive methods is quite irrelevant for computing this parameter.
•Reliability of Vs models from geophysical tests is studied with a blind test.•Three subsoil conditions are considered: soft soil, stiff soil, rock outcrop.•In-hole methods and surface wave methods are considered.•In-hole methods provide high resolution and accuracy, but the precision is similar.There is a good match between estimates of VS,30, with comparable variability.
SUMMARY
We explored the potential of fibre optics coupled with distributed acoustic sensing (DAS) to measure the thickness and Young’s modulus of an ice layer, using the properties of guided seismic ...waves. During two winter seasons (2020 and 2021), an optical fibre was deployed over one of the frozen Roberts Mountain lakes (at 2400 m a.s.l) near Grenoble (France) and we measured both the continuous ambient seismic noise as well as signals generated by active sources (hammer), with a DAS interrogator. Following a Bayesian scheme, we inverted the dispersion curves of longitudinal and flexural guided waves retrieved from the analysis of active shot gathers and obtained Young’s modulus E = 3.4 ± 0.1 GPa and ice thickness h = 47 ± 1 cm from the second-year data. The ice thickness was consistent with field measurements. Field observations of porous and/or fracture ice may explain the relatively low effective Young’s modulus (relative to pure ice), which may also be affected by a snow layer not included in the model. The drastic improvements in the inversion results between the two years are related to better coupling conditions (drone deployment before early freezing), more appropriate acquisition parameters (2 m gauge length), and the upper snow layers (less thick and less heterogeneous in the second year). Moreover, we were able to use the non-dispersive low-frequency noise associated with gravity waves to estimate the lake depth H = 5 m which is compatible with independent observations. The use of DAS to record guided seismic waves could then appear as a relevant tool for monitoring environments like floating ice shelves and sea ice.
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