http://hdl.handle.net/10993/88 Search this channel search https://orbilu.uni.lu/simple-search http://hdl.handle.net/10993/41859 Title: Conventional EO Satellites vs. CubeSats; FDL - AI flood detection onboard a Nano Satellite <br/> <br/>Author, co-author: Backes, Dietmar; Schumann, Guy; Teferle, Felix Norman http://hdl.handle.net/10993/40936 Title: The legacy of coal mining – a view on examples in Belgium and France <br/> <br/>Author, co-author: Helfer, Malte <br/> <br/>Abstract: Following the end of coalmining in Belgium (1992) and France (2004), the year 2018 marks the end of hard coal mining in Germany as well. This contribution looks at the legacy of coalmining of Germany’s French-speaking neighbours and presents the most important remaining coal mining heritage sites as well as some extraordinary converted sites in France and the Belgian province Wallonia. http://hdl.handle.net/10993/39334 Title: Merging DEMs from VHR Optical Imagery with Drone Data - A High-resolution DEM for Tristan da Cunha <br/> <br/>Author, co-author: Backes, Dietmar; Teferle, Felix Norman <br/> <br/>Abstract: The extraction of high-resolution, Digital Elevation Models (DEM) from very high-resolution (VHR) optical satellite imagery, as well as low altitude drone images by Photogrammetric methods or modern Structure from Motion (SFM) engines, has rapidly matured. Today both data sources are representing cost-effective alternatives to dedicated airborne sensors, especially for remote and difficult to access regions. Ever-growing archives of high-resolution Satellite imagery, are providing a rich data source which covers even the most remote locations with high-resolution imagery up to 0.30m ground sample distance multiple times enabling the generation of high-resolution DEMS. Furthermore, low-cost, low weight and easy to use drones can easily be deployed in remote regions and capture limited areas with very high resolution. Dense point clouds derived from this method provide an invaluable data source to fill the gap between globally available low-resolution DEMs and highly accurate terrestrial surveys. The presented case study investigates the use of VHR archive imagery as well as low-cost drone imagery to generate high-quality DEMs using photogrammetric tools over a remote region which is difficult to access by manned airborne platforms. We highlight the potential and limitations of both data sources to provide high resolution, accurate elevation data. http://hdl.handle.net/10993/39324 Title: NASA-FDL Artificial Intelligence in Planetary Science; Lunar Resource Mission <br/> <br/>Author, co-author: Backes, Dietmar <br/> <br/>Commentary: More informations under: https://frontierdevelopmentlab.org/fdl-2017; https://www.youtube.com/watch?v=dXXtYdfVov0 http://hdl.handle.net/10993/29227 Title: Shear strength and stiffness degradation of geomaterials in cyclic loading <br/> <br/>Author, co-author: Pytlik, Robert Stanislaw; Van Baars, Stefan <br/> <br/>Abstract: Cyclic loading on civil structures can lead to a reduction of strength and stiffness in the loaded materials. The life span of many cyclically loaded structures such as wind turbines, high-speed train tracks and bridges strongly depends on the foundation. The soils and rocks in the foundation can be subjected to cyclic loads from natural and human sources. In order to evaluate the fatigue behaviour of geomaterials, this paper presents static and cyclic triaxial test results for several geomaterials. It was concluded that cyclic loading on different geomaterials can cause different types of effects. The shear strength of cohesionless crumbled limestone increases during cyclic loading; while for cohesive materials, such as gypsum and mortar, the strength decreases. The strength decrease can be seen as a degradation of the cohesion. The most significant factor in the cohesion reduction was found to be the number of applied cycles. It was also noticed that the friction angle for sands does not reduce under cyclic loading. A fatigue limit was not found for cohesive geomaterials; neither a dependence of the strength reduction on the cyclic loading ratios. <br/> <br/>Commentary: See: http://www.soilsandrocks.com.br/soils-androcks/SR39-3_273-283.pdf http://hdl.handle.net/10993/26773 Title: Hybrid mesh/particle meshless method for modeling geological flows with discontinuous transport properties <br/> <br/>Author, co-author: Bourantas, Georgios; Lavier, Luc; van Dam, Tonie; Bordas, Stéphane <br/> <br/>Abstract: In the present paper, we introduce the Finite Difference Method-Meshless Method (FDM-MM) in the context of geodynamical simulations. The proposed numerical scheme relies on the well-established FD method along with the newly developed “meshless” method and, is considered as a hybrid Eulerian/Lagrangian scheme. Mass, momentum, and energy equations are solved using an FDM method, while material properties are distributed over a set of markers (particles), which represent the spatial domain, with the solution interpolated back to the Eulerian grid. The proposed scheme is capable of solving flow equations (Stokes flow) in uniform geometries with particles, “sprinkled” in the spatial domain and is used to solve convection- diffusion problems avoiding the oscillation produced in the Eulerian approach. The resulting algebraic linear systems were solved using direct solvers. Our hybrid approach can capture sharp variations of stresses and thermal gradients in problems with a strongly variable viscosity and thermal conductivity as demonstrated through various benchmarking test cases. The present hybrid approach allows for the accurate calculation of fine thermal structures, offering local type adaptivity through the flexibility of the particle method. http://hdl.handle.net/10993/24564 Title: Eisen- und Stahlindustrie in der Großregion SaarLorLux <br/> <br/>Author, co-author: Thomes, Paul; Engels, Marc <br/> <br/>Editor: Pauly, Michel; Caruso, Geoffrey; Helfer, Malte <br/> <br/>Abstract: Die Wiege der kontinentaleuropäischen Industrialisierung stand in der Großregion. Die Schwerindustrie und der Maschinenbau, als Kernkomponenten des Industrialisierungsprozesses, entfachten seit den 1820er Jahren eine beachtliche, über die Region weit hinausreichende ökonomische Relevanz. Die Eisen- und Stahlindustrie prägte nach der Mitte des 19. Jahrhunderts über knapp 150 Jahre hinweg die wirtschaftlichen Strukturen der Großregion SaarLorLux. http://hdl.handle.net/10993/22357 Title: Laboratory tests on Dutch limestone (Mergel) <br/> <br/>Author, co-author: Pytlik, Robert Stanislaw; Van Baars, Stefan <br/> <br/>Abstract: In this note, results of triaxial laboratory tests on very weak sedimentary limestone from the construction of the “Geusselt A2” tunnel in Maastricht in the Netherlands are presented. The main purpose of the triaxial tests was to evaluate the strength of this rock. Particularly interesting was that the strength parameters obtained in the laboratory, were much lower than what was expected after preliminary visual inspections. The two most popular models in soil and rock mechanics, the Mohr-Coulomb and Hoek-Brown failure criteria, were used to estimate the strength parameters and both did not give satisfying results. Still the Mohr-Coulomb model is the best model to use. http://hdl.handle.net/10993/21330 Title: Enriched finite elements for branching cracks in deformable porous media <br/> <br/>Author, co-author: Sheng, M.; Li, G.; Shah, S.; Lamb, A. R.; Bordas, Stéphane <br/> <br/>Abstract: In this paper, we propose and verify a numerical approach to simulate fluid flow in deformable porous media without requiring the discretization to conform to the geometry of the sealed fractures (possibly intersecting). This approach is based on a fully coupled hydro-mechanical analysis and an extended finite element method (XFEM) to represent discrete fractures. Convergence tests indicate that the proposed scheme is both consistent and stable. The contributions of this paper include: (1) a new junction enrichment to describe intersecting fractures in deformable porous media; (2) the treatment of sealed fractures. We employ the resulting discretization scheme to perform numerical experiments, to illustrate that the inclination angles of the fractures and the penetration ratio of the sealed fractures are two key parameters governing the flow within the fractured porous medium.