143 documents found in 322ms
# 1
Falchi, Fabio • Cinzano, Pierantonio • Duriscoe, Dan • Kyba, Christopher C. M. • Elvidge, Christopher D. • (et. al.)
Abstract: These are maps of artificial night sky radiance that were produced by the Light Pollution Science and Technology Institute (ISTIL), and described in the paper "The New World Atlas of Artificial Night Sky Brightness" (Falchi et al. 2016). The data are stored in a 2.9 Gb geotiff file, on a 30 arcsecond grid. The map reports simulated zenith radiance data in [mcd/m^2]. The map is based on data from the VIIRS Day Night Band (DNB, MIller et al. 2013), which has been propagated through the atmosphere using the radiative transfer code reported in (Cinzano and Falchi, 2012). The upward emission function and the radiance calibration were obtained using data from Sky Quality Meters (including data from Duriscoe et al. 2007; Falchi 2010; Kyba et al 2013, 2015 and Zamorano et al. 2016). Note that the maps report artificial light only! The zenith radiance from natural sources such as stars and the Milky Way are not included, and must be added in order to match the data that would be obtained from an actual outdoor measurement. A kmz file for quick view of the data is also provided. Access to the FTP site to download the data can be requested via the data request form on the landing page. Version History:13 November 2019: change of the licence to CC BY NC 4.0 (after end of embargo period).
Artificial lights raise the night sky luminance, creating the most visible effect of light pollution, artificial sky glow. Despite the increasing interest among scientists in fields such as ecology, astronomy, healthcare, land use planning, light pollution lacks a current quantification of its magnitude on a global scale. To overcome this, here we present the World atlas of the artificial sky luminance, computed with our light pollution propagation software using new high resolution satellite data and new precision sky brightness measurements. This atlas shows that more than 80% of the World and more than 99% of the U.S.A. and Europe populations live under light polluted skies. The Milky Way is hidden for more than one third of humanity, including 60% of Europeans and nearly 80% of North Americans. Moreover, 23% of World's lands between 75°N and 60°S, 88% of Europe and almost half of U.S.A. experience light polluted nights.
# 2
Román-Berdiel, Teresa • Casas, Antonio M. • Pueyo, Emilio Luis • Peiro Chamarro, Alba • Soto, Ruth • (et. al.)
Abstract: This dataset provides friction data from ring-shear tests (RST) on different types of quartz sand used in the Laboratorio de modelización analógica of the Universidad de Zaragoza (UZ, Spain) as an analogue for brittle layers in the crust or lithosphere (Izquierdo-Llavall & Casas-Sainz, 2012; Calvín et al., 2013; Pueyo Anchuela et al., 2016; Peiro et al., 2018; Pueyo et al., 2018; Izquierdo-Llavall et al., submitted). The materials (quartz sand, green coloured quartz sand mixture, black coloured quartz sand) have been characterized by means of internal friction coefficients µ and cohesions C as a remote service by the Helmholtz Laboratory for Tectonic Modelling (HelTec) at the GFZ German Research Centre for Geosciences in Potsdam. According to our analysis the materials show a Mohr-Coulomb behaviour characterized by a linear failure envelope. Friction coefficients of the pure quartz sand and the green quartz sand mixture are similar (µP = 0.74 – 0.76, µD = 0.56 – 0.60, µR = 0.61 – 0.64), whereas friction coefficients of the black coloured quartz sand are lower (µP = 0.48, µD = 0.39, µR = 0.45). Cohesions of all sands range between 40 and 150 Pa. A minor rate-weakening of ~1 % per ten-fold change in shear velocity v is evident. The tested materials are quartz sands with a grain size of 0.063 – 0.4 mm and bulk densities of ρ = 1610-1800 kg m^-3. The data presented here are derived by ring shear testing using a SCHULZE RST-01.pc (Schulze, 1994, 2003, 2008) at the Helmholtz Laboratory for Tectonic Modelling (HelTec) of the GFZ German Research Centre for Geosciences in Potsdam. The RST is specially designed to measure friction coefficients µ and cohesions C in loose granular material accurately at low confining pressures and shear velocities similar to sandbox experiments.
# 3
Jatnieks, Janis • Sips, Mike • De Lucia, Marco • Dransch, Doris
Abstract: Geochemical models are used to seek answers about composition and evolution of groundwater, spill remediation, viability of geothermal resources and other important geoscientific applications. To understand these processes, it is useful to evaluate geochemical model response to different input parameter combinations. Running the model with varying input parameters creates a large amount of output data. It is a challenge to screen this data from the model to identify the significant relationships between input parameters and output variables. For addressing this problem we developed a Visual Analytics approach in an ongoing collaboration between Geoinformatics and Hydrogeology sections of GFZ German Research Centre for Geosciences. We implement our approach as an interactive data exploration tool called the GCex. GCex is a Visual Analytics approach and prototype that supports interactive exploration of geochemical models. It encodes many-to-many input/output relationships by the simple yet effective approach called Stacked Parameter Relation (SPR). GCex assists in the setup of simulations, model runs, data collection and result exploration, greatly enhancing the user experience in tasks such uncertainty and sensitivity analysis, inverse modeling and risk assessment. While in principle model-agnostic, the prototype currently supports and is tied to the popular geochemical code PHREEQC. Modification to support other models would not be complicated. GCex prototype was originally written by Janis Jatnieks at GFZ-Potsdam. It relies on Rphree (R-PHREEQC geochemical simulation model interface) written by Marco De Lucia at GFZ-Potsdam. A compatible version of Rphee is bundled with this installation.
https://gitext.gfz-potsdam.de/sec15pub/GCex/tags/1.0
# 4
Jatnieks, Janis • De Lucia, Marco • Sips, Mike • Dransch, Doris
Abstract: Surrogate playground is an automated machine learning approach written for rapidly screening a large number of different models to serve as surrogates for a slow running simulator. This code was written for a reactive transport application where a fluid flow model (hydrodynamics) is coupled to a geochemistry simulator (reactions in time and space) to simulate scenarios such as underground storage of CO2 or hydrogen storage for excess energy from wind farms. The challenge for such applications is that the geochemistry simulator is typically slow compared to fluid dynamics and constitutes the main bottleneck for producing highly detailed simulations of such application scenarios. This approach attempts to find machine learning models that can replace the slow running simulator when trained on input-output data from the geochemistry simulator. The code may be of more general interest as this prototype can be used to screen many different machine learning models for any regression problem in general. To illustrate this it also includes a demonstration example using the Boston housing standard data-set.
# 5
Warsitzka, Michael • Závada, Prokop • Pohlenz, Andre • Rosenau, Matthias
Abstract: This dataset provides friction data from ring-shear tests (RST) for a quartz sand used in analogue experiments at the Institute of Geophysics of the Czech Academy of Science (IGCAS) (Kratinová et al., 2006; Zavada et al., 2009; Lehmann et al., 2017; Krýza et al., 2019). It is characterized by means of internal friction coefficients µ and cohesion C. According to our analysis the materials show a Mohr-Coulomb behaviour characterized by a linear failure envelope. Peak friction coefficients µP of the tested material is ~0.75, dynamic friction coeffi-cients µD is ~0.60 and reactivation friction coefficients µR is ~0.64. Cohesions of the material range between 90 and 130 Pa. The material shows a minor rate-weakening of <1% per ten-fold change in shear velocity v.
# 6
Dietze, Elisabeth • Dietze, Michael
Abstract: EMMA – End Member Modelling Analysis of grain-size data is a technique to unmix multimodal grain-size data sets, i.e., to decompose the data into the underlying grain-size distributions (loadings) and their contributions to each sample (scores). The R package EMMAgeo contains a series of functions to perform EMMA based on eigenspace decomposition. The data are rescaled and transformed to receive results in meaningful units, i.e., volume percentage. EMMA can be performed in a deterministic and two robust ways, the latter taking into account incomplete knowledge about model parameters. The model outputs can be interpreted in terms of sediment sources, transport pathways and transport regimes (loadings) as well as their relative importance throughout the sample space (scores).
# 7
Deng, Bin • Schönebeck, Jan • Warsitzka, Michael • Rosenau, Matthias
Abstract: This dataset provides friction data from ring-shear tests (RST) on natural and artificial granular materials used for analogue modelling in the experimental laboratory of the Chengdu University of Technology (CDUT, China). Six samples, four types of quartz sands and two types of glass beads, have been characterized by means of friction coefficients µ and cohesions C. The material samples have been analysed at the Helmholtz Laboratory for Tectonic Modelling (HelTec) at the GFZ German Research Centre for Geosciences in Potsdam in the framework of the EPOS (European Plate Observing System) Transnational Access (TNA) call of the Thematic Core Service (TCS) Multi-scale Laboratories (MSL) in 2017 as a remote service for the CDUT. According to our analysis the materials show a Mohr-Coulomb behaviour characterized by a linear failure envelope. Peak friction coefficients µP of the quartz sand samples range between 0.62 and 0.79 and µP of the glass beads between 0.61 and 0.64. Except for one quartz sand sample, peak cohesions CP of all materials are smaller than or around zero meaning that these materials are cohesionsless. All materials show a minor rate-weakening of 1-2 % per ten-fold change in shear velocity v.
# 8
Willingshofer, Ernst • Sokoutis, Dimitrios • Kleinhans, Maarten • Beekmann, Fred • Schönebeck, Jan-Michael • (et. al.)
Abstract: This dataset provides friction data from ring-shear test (RST) on a plastic (polyester) sand material that has been used in flume experiments (Marra et al., 2014; Kleinhans et al., 2017) and is now used in the Tectonic Laboratory (TecLab) at Utrecht University (NL) as an analogue for brittle layers in the crust or lithosphere. Detailed information about the data, methodology and a list of files and formats is given in the data description and list of files that are included in the zip folder and also available via the DOI landing page. The material has been characterized by means of internal friction coefficient and cohesion as a remote service by GFZ Potsdam for TecLab (Utrecht University). According to our analysis the material behaves as a Mohr-Coulomb material characterized by a linear failure envelope and peak, dynamic and reactivation friction coefficients of 0.76, 0.60, and 0.66, respectively. Cohesions are in the order of few tens of Pa. A minor rate-weakening of 3% per ten-fold rate change is evident.
# 9
Warsitzka, Michael • Ge, Zhiyuan • Schönebeck, Jan-Michael • Pohlenz, Andre • Kukowski, Nina
Abstract: This dataset provides friction data from ring-shear tests (RST) for two types of foam glass beads and a mixture of foam glass beads with quartz sand (“G12”; Rosenau et al., 2019). These materials have been used in analogue experiments in Helmholtz Laboratory for Tectonic Modelling (HelTec) at the GFZ German Research Centre for Geosciences in Potsdam and in the Analogue laboratory of the Institute of Geosciences of the Friedrich Schiller University of Jena (FSU Jena). The materials have been characterized by means of internal friction coefficients µ and cohesion C. According to our analysis the materials show a Mohr-Coulomb behaviour characterized by a linear failure envelope. Peak friction coefficients µP of all tested materials range between 0.70 and 0.75, dynamic friction coefficients µD between 0.52 and 0.55 and reactivation friction coefficients µR between 0.60 and 0.62. Peak cohesions CP of all materials are negative indicating that they are cohesionless. All materials show a minor rate-weakening of ~1% per ten-fold change in shear velocity v. Further information about materical characteristics, measurement procedures, sample preparation, the RST (Ring-shear test) and VST (Velocity stepping test) procedure, as well as the analysed method is proviced in the data description file. The list of files explains the file and folder structure of the data set.
# 10
Purinton, Benjamin • Bookhagen, Bodo
Abstract: Grain-size distributions and their associated percentiles are a key geomorphic metric of gravel-bed rivers. Traditional measurement methods include manual counting or photo sieving, but these are typically achievable only at the patch (1 square meter) scale. With the advent of unmanned aerial vehicle systems and increasingly high-resolution cameras, we can now generate orthoimagery over large areas at resolutions of <1 cm. These scales, along with the complexity of many natural environments in high-mountain rivers, necessitate different approaches for photo sieving. Here, a new open-source algorithm is presented: PebbleCounts. As opposed to other image segmentation methods that use a watershed approach and automatically segment entire images, PebbleCounts relies on k-means clustering in the spatial and spectral (color) domain and rapid manual selection of well-outlined grains. This results in improved estimates for complex river-bed imagery without the need for post-processing.
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