Geomorphological processes on terrestrial planetary surfaces

This review deals with features and processes on planetary surfaces, first by examining the impact of photographic explorations of Moon, Mars, and Mercury on studies of surface processes on our own planet, and second by treating matters related to current deformation of Earth’s surface

Regional unit definition for the nucleus of comet 67P/Churyumov-Gerasimenko on the SHAP7 model

The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified

Regional unit definition for the nucleus of comet 67P/Churyumov-Gerasimenko on the SHAP7 model

Open Acces publication. This article is available under the Creative Commons CC-BY-NC-ND license and permits non-commercial use of the work as published, without adaptation or alteration provided the work is fully attributed.The previously defined regions on the nucleus of comet 67P/Churyumov-Gerasimenko have been mapped back onto the 3D SHAP7 model of the nucleus (Preusker et al., 2017). The resulting regional definition is therefore self-consistent with boundaries that are well defined in 3 dimensions. The facets belonging to each region are provided as supplementary material. The shape model has then been used to assess inhomogeneity of nucleus surface morphology within individual regions. Several regions show diverse morphology. We propose sub-division of these regions into clearly identifiable units (sub-regions) and a comprehensive table is provided. The surface areas of each sub-region have been computed and statistics based on grouping of unit types are provided. The roughness of each region is also provided in a quantitative manner using a technique derived from computer graphics applications. The quantitative method supports the sub-region definition by showing that differences between sub-regions can be numerically justified.© 2018 The AuthorsThe team from the University of Bern is supported through the Swiss National Science Foundation and through the NCCR PlanetS. The project has also received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 686709. This work was supported by the Swiss State Secretariat for Education, Research and Innovation (SERI) under contract number 16.0008-2

Integration of 3D geological and numerical models based on tetrahedral meshes for hydrogeological simulations in fractured porous media

Une nouvelle approche de modélisation des milieux géologiques fracturés représentés par un modèle conceptuel de fractures discrètes et déterministes est présentée dans cette thèse. L'objectif principal de l'étude est de reproduire l'hétérogénéité et la complexité des milieux poreux fracturés dans un modèle géométrique tridimensionnel afin d'effectuer des simulations numériques dans le but d'améliorer les capacités de modélisation en hydrogéologie. Ceci est réalisé à travers le couplage entre une plateforme de modélisation géologique (GOCAD) et un code numérique (HydroGeoSphere). Les principaux défis à relever sont: la représentation géométrique du réseau de fractures, la sélection d'un maillage approprié pour la discrétisation spatiale du domaine de simulation et l'adaptation du code numérique à ce maillage. La nouvelle approche est basée sur une première phase de modélisation géologique 3D, suivie par la génération d'un maillage tétraédrique 3D et par la simulation numérique de l'écoulement souterrain en conditions saturées et du transport de solutés. En général, le maillage tétraédrique s'avère plus adéquat que les maillages de blocs ou de prismes pour discrétiser les geometries complexes telles que les milieux fracturés. De plus, une définition alternative du maillage "dual", qui est essentiel pour appliquer la méthode numérique élément finis - volume de contrôle utilisée par HydroGeoSphere, est analysée et intégrée dans le code numérique. Le code numérique proposé est d'abord vérifié par l'intermédiaire de simples scénarios de simulation dont les solutions, analytiques et numériques, sont déjà connues. La complexité des simulations est augmentée de façon graduelle. L'approche de modélisation est finalement appliquée au site Olkiluoto (Finlande) où un laboratoire de recherche souterrain est en construction afin d'évaluer la faisabilité du stockage géologique profond de déchets nucléaires à haute activité. Les techniques de modélisation géologique mises au point permettent de modéliser facilement la géométrie des fractures identifiées à travers la caractérisation géologique in situ. De plus, le modèle numérique s'avère adéquat pour la simulation de l'écoulement et du transport de solutés dans ce site complexe. Ce travail de recherche présente une contribution au développement des techniques de modélisation hydrogéologique des milieux fracturés

Enceladus and the Icy Moons of Saturn : July 26-29, 2016, Boulder, Colorado

Topics include (but are not limited to) geology, geophysics, geochemistry and mineralogy, active jets and their properties and origins, formation and evolution, astrobiology, and future investigations of these bodies. Comparative planetology is encouraged. A major focus will be the new results from the 2015 Cassini encounters with Enceladus and the other icy moons. Contributions from Cassini, Voyager, and groundbased studies are welcomeUniversities Space Research Association (USRA), Lunar and Planetary Institute (LPI)Local Organizing Committee, Larry Esposito, University of Colorado Carly Howett, Southwest Research Institute Laura Bloom, University of Colorado ; Science Organizing Committee Paul Schenk, Lunar and Planetary Institute [and 12 others

The interpretation and characterisation of lineaments identified from Landsat TM imagery of SW England

Two Landsat TM scenes of SW England and a sub-scene of North Cornwall have been analysed visually in order to examine the effect of resolution on lineament interpretation. Images were viewed at several different scales as a result of varying image resolution whilst maintaining a fixed screen pixel size. Lineament analysis at each scale utilised GIS techniques and involved several stages: initial lineament identification and digitisation; removal of lineaments related to anthropogenic features to produce cleansed lineament maps; compilation of lineament attributes using ARC/INFO; cluster analysis for identification of lineament directional families; and line sampling of lineament maps in order to determine spacing. SW England lies within the temperate zone of Europe and the extensive agricultural cover and infrastructure conceal the underlying geology. The consequences of this for lineament analysis were examined using sub-images of North Cornwall. Here anthropogenic features are visible at all resolutions between 30m and 120m pixel sizes but lie outside the observation threshold at 150m. Having confidence that lineaments at this resolution are of non-anthropogenic origin optimises lineament identification since the image may be viewed in greater detail. On this basis, lineament analysis of SW England was performed using image resolutions of 150m. Valuable geological information below the observation threshold in 150m resolution images is likely, however, to be contained in the lineament maps produced from higher resolution images. For images analysed at higher resolutions, therefore, knowledge-based rules were established in order to cleanse the lineament populations. Compiled lineament maps were 'ground truthed' (primarily involving comparison with published geological maps but included phases of field mapping) in order to characterise their geological affinities. The major lineament trends were correlated to lithotectonic boundaries, and cross-cutting fractures sets. Major lineament trends produced distinct frequency/orientation maxima. Multiple minor geological structures, however, produced semi-overlapping groups. A clustering technique was devised to resolve overlapping groups into lineament directional families. The newly defined lineament directional families were further analysed in two ways: (i) Analysis of the spatial density of the length and frequency of lineaments indicates that individual and multiple lineament directional families vary spatially and are compartmentalised into local tectonic domains, often bounded by major lineaments. Hence, such density maps provide useful additional information about the structural framework of SW England. (ii) Lineament spacing and length of the lineament directional families were analysed for the effect of scale and geological causes on their frequency/size distributions. Spacing of fracture lineaments were found to be power-law, whereas lengths showed power-law and non-power-law distributions. Furthermore the type of frequency/size distribution for a lineament directional family can change with increasing resolution

Thermomechanical fatigue life investigation of an ultra-large mining dump truck tire

The cost benefits associated with the use of heavy mining machinery in the surface mining industry has led to a surge in the production of ultra-large radial tires with rim diameters in excess of 35 in. These tires experience fatigue failures in operation. The use of reinforcing fillers and processing aids in tire compounds results in the formation of microstructural inhomogeneity in the compounds and may serve as sources of crack initiation in the tire. Abrasive material cutting is another source of cracks in tires used in mining applications. It suffices, then, to assume that every material plane in the tire consists of a crack precursor of some known size likely to nucleate under the tire\u27s duty cycle loads. This assumption eliminates the need for prior knowledge of the location and geometry of crack features to be explicitly included in a tire finite element model, overcoming the key limitations of previous approaches. In this study, a rainflow counting algorithm is used to consistently count strain reversals present in the complex multiaxial variable amplitude duty-cycle loads of the tire to assess fatigue damage on its material planes. A critical plane analysis method is then used to account for the non-proportional loading on the tire material planes in order to identify the plane with the highest fatigue damage. The size of the investigated tire is 56/80R63, and it is typically fitted to ultra-class trucks with payload capacities in excess of 325 tonne (360 short ton). Experimental data obtained from extracted specimens of the tire were used to characterize the stress-strain and fatigue behavior of the tire finite element model in ABAQUS. A sequentially coupled thermomechanical rolling analysis of the tire provided stress, strains, and temperature data for the computation of the tire\u27s component fatigue performance in the rubber fatigue solver ENDURICA CL. The belt endings (tire shoulder), lower sidewall, and tread lug corners are susceptible to crack initiation and subsequent failure due to high stresses. This pioneering research effort contributes to the body of knowledge in tire durability issues in relation to mining applications. In addition, it provides a basis for off-road tire compounders and developers to design durable tires to minimize tire operating costs in the mining industry --Abstract, page iii

Computer aided process planning for multi-axis CNC machining using feature free polygonal CAD models

This dissertation provides new methods for the general area of Computer Aided Process Planning, often referred to as CAPP. It specifically focuses on 3 challenging problems in the area of multi-axis CNC machining process using feature free polygonal CAD models. The first research problem involves a new method for the rapid machining of Multi-Surface Parts. These types of parts typically have different requirements for each surface, for example, surface finish, accuracy, or functionality. The CAPP algorithms developed for this problem ensure the complete rapid machining of multi surface parts by providing better setup orientations to machine each surface. The second research problem is related to a new method for discrete multi-axis CNC machining of part models using feature free polygonal CAD models. This problem specifically considers a generic 3-axis CNC machining process for which CAPP algorithms are developed. These algorithms allow the rapid machining of a wide variety of parts with higher geometric accuracy by enabling access to visible surfaces through the choice of appropriate machine tool configurations (i.e. number of axes). The third research problem addresses challenges with geometric singularities that can occur when 2D slice models are used in process planning. The conversion from CAD to slice model results in the loss of model surface information, the consequence of which could be suboptimal or incorrect process planning. The algorithms developed here facilitate transfer of complete surface geometry information from CAD to slice models. The work of this dissertation will aid in developing the next generation of CAPP tools and result in lower cost and more accurately machined components