• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 44
  • 4
  • 3
  • 2
  • 2
  • 1
  • Tagged with
  • 67
  • 11
  • 11
  • 10
  • 10
  • 9
  • 8
  • 7
  • 7
  • 7
  • 6
  • 6
  • 6
  • 6
  • 6
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Struktur, Eigenschaften und Gefährdungspotentiale des oberflächennahen Untergrunds in historischen Erzbergbaugebieten des zentraleuropäischen Mittelgebirgsraums

Russow, Frank 24 October 2005 (has links) (PDF)
Thema der vorliegenden Arbeit ist die Identifikation, Differenzierung und Bewertung von vorhandenen Schwermetallreservoirs im Hangbereich historischer Erzbergbaugebiete im Nordpfälzer Bergland und dem Spessart. Dazu wurden auf Grundlage von 115 Bodenprofilen entlang von 14 Hangsequenzen die holozäne Umweltgeschichte, die Verbreitung und Struktur sowie ausgewählte ökologische Eigenschaften der quartären Hangsedimente erstmalig integrativ analysiert. Besondere Beachtung fanden hierbei die Schwermetallgehalte der quartären Hangsedimente und ihr immanentes Gefährdungspotential, das für die Untersuchungsgebiete zum ersten mal auf Grundlage der aktuellen rechtlichen Grundlagen bestimmt wurde. Die Auflösung einer hochauflösenden Boden- und Sedimentaufnahme mit exemplarischer Beprobung ermöglichte die Analyse vieler Details, Merkmale und Eigenschaften der Sedimente und Bodenbildungen dieser (stark) gestörten Standorte im Mittelgebirgsbereich.
22

Regolith-landform and mineralogical mapping of the White Dam Prospect, eastern Olary Domain, South Australia, using integrated remote sensing and spectral techniques.

Lau, Ian Christopher January 2004 (has links)
The research contained within this thesis was directed at examining the spectral properties of regolith-dominated terrains using airborne and proximal hyperspectral instruments. The focus of the investigation was to identify the mineralogy of the regolith and determine if surficial materials were indicative of the underlying bedrock in the regolithdominated terrain of the eastern Olary Domain, South Australia. The research area was constrained to a 250 km2 area around the Cu-Au mineralisation of the White Dam Prosect. Integrated remote sensing, using airborne hyperspectral datasets (HyMap), Landsat imagery and gamma-ray spectroscopy data, was performed to map regolith-landforms and extract information on surficial materials. Detailed calibration of the HyMap dataset, using a modified model-based/empirical line calibration technique, was required prior to information extraction. The White Dam area was able to be divided into: alluvial regolith-dominated; in situ regolith-dominated; and bedrock-dominated terrains, based on mineralogical interpretations of the regolith, using the remotely sensed hyperspectral data. Alluvial regions were characterised by large abundances of vegetation and soils with a hematite-rich mineralogy. Highly weathered areas of in situ material were discriminated by the presence of goethite and kaolinite of various crystallinities, whereas the bedrock-dominated regions displayed white mica-/muscovite-rich mineralogy. Areas flanking bedrock exposures commonly consisted of shallow muscovite-rich soils containing regolith carbonate accumulations. Traditional mineral mapping processes were performed on the HyMap data and were able to extract endmembers of regolith and other surficial materials. The Mixture Tuned Matched Filter un-mixing process was successful at classifying regolith materials and minerals. Spectral indices performed on masked data were effective at identifying the key regolith mineralogical features of the HyMap imagery and proved less time consuming than un-mixing processes. Processed HyMap imagery was able to identify weathering halos, highlighted in mineralogical changes, around bedrock exposures. Proximal spectral measurements and XRD analyses of samples collected from the White Dam Prospect were used to create detailed mineralogical dispersion maps of the surface and costean sections. Regolith materials of the logged sections were found to correlate with the spectrally-derived mineral dispersion profiles. The HyLogger drill core scanning instrument was used to examine the mineralogy of the fresh bedrock, which contrasted with the weathering-derived near-surface regolith materials. The overall outcomes of the thesis showed that hyperspectral techniques were useful for charactering the mineralogy of surficial materials and mapping regolith-landforms. / Thesis (Ph.D.)--School of Earth & Environmental Sciences, 2004.
23

The character and genesis of pedogenic calcrete in southern Australia

Grevenitz, Paul. January 2006 (has links)
Thesis (Ph.D.)--University of Wollongong, 2006. / Typescript. Includes bibliographical references: p. 129-148.
24

Regolith-landform and mineralogical mapping of the White Dam Prospect, eastern Olary Domain, South Australia, using integrated remote sensing and spectral techniques /

Lau, Ian Christopher. January 2004 (has links) (PDF)
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Geology and Geophysics, 2005? / "December 2004" Bibliography: p. 330-369. Also available electronically.
25

Regolith-landform and mineralogical mapping of the White Dam Prospect, eastern Olary Domain, South Australia, using integrated remote sensing and spectral techniques

Lau, Ian Christopher. January 2004 (has links)
Thesis (Ph.D.)--University of Adelaide, School of Earth and Environmental Sciences, Discipline of Geology and Geophysics, 2005? / Title from cover of source document (viewed July 22, 2005). "December 2004" Bibliography: p. 330-369 of source document. Also available in print version.
26

Pyrolyse von Metalloxiden und Silikaten unter Vakuum mit konzentrierter Solarstrahlung

Sauerborn, Markus. Unknown Date (has links) (PDF)
Universiẗat, Diss., 2005--Bonn.
27

Mécanismes et taux de dénudation d'un bassin versant élémentaire (Strengbach, France) : apport de l'étude couplée des méthodes de datation isotopique (déséquilibres U-Th-Ra, 10Be in situ) et des méthodes de modélisation hydrogéochimique (KIRMAT) / Mechanisms and denudation rates of an elementary watershed (Strengbach, France) : contribution of the isotopic dating approaches (U-Th-Ra disequilibria, in situ 10Be) and of the hydrogeochemical modeling approaches (KIRMAT) coupled study

Ackerer, Julien 07 June 2017 (has links)
Lors de ce travail de thèse, la combinaison des méthodes de la géochimie analytique et isotopique avec les approches modélisatrices a permis d’apporter de nouvelles connaissances à la compréhension de la zone critique et du régolithe. Pour l’étude du régolithe, ce travail présente une méthodologie permettant de réaliser sur un même profil d’altération les analyses de la géochimie élémentaire, de la minéralogie, ainsi que des isotopes de la série de l’uranium (U-Th-Ra) et de l’isotope cosmogénique du 10Be in situ. Les résultats obtenus montrent l’importance de la bonne résolution spatiale de l’échantillonnage pour pouvoir pleinement exploiter les outils de la série U-Th-Ra et du 10Be in situ, notamment pour déterminer d’une manière indépendante les paramètres clés que sont les taux de production et de dénudation du régolithe à long terme. Les deux profils d’altération réalisés dans cette étude montrent de plus que (1) la structure du régolithe est relativement simple sur les positions sommitales et permet une interprétation continue des données géochimiques et minéralogiques et (2) les processus de pente tendent à augmenter l’hétérogénéité spatiale du régolithe et des processus d’altération. D’une façon complémentaire, le suivi et la modélisation hydrogéochimique des eaux de surface permettent d’étudier les processus d’altération actuels, et de comprendre les mécanismes impliqués dans leurs variabilités récentes. Ce travail a notamment montré le lien pouvant exister entre les modifications enregistrées en surface dans les solutions de sol et l’évolution temporelle des certaines propriétés chimiques des eaux de source (pH, concentration en calcium). Les simulations réalisées ont également permis de comprendre la faible variabilité des flux d’altération globaux exportés par les sources, en relation avec la relative stabilité des concentrations de sodium et de silice dissoute sur la période récente allant de 1990 à 2010. Cette étude a finalement montré l’importance du couplage des méthodes apportant des informations sur les processus d’altération et d’érosion à différentes échelles de temps et d’espace, en particulier pour évaluer correctement la dynamique du régolithe et pour replacer le fonctionnement actuel d’un bassin versant vis-à-vis de son évolution à long terme. / In this PhD work, the combination of the geochemical analytic and isotopic approaches with the modeling approaches has allowed to bring new insights to the understanding of the critical zone and the regolith. Concerning the regolith, this work presents a methodology to perform the analyses of the elemental geochemistry, of the mineralogy, as well as of the U-Th-Ra isotopes and of the in situ 10Be cosmogenic isotope along a single weathering profile. The obtained results highlight the importance of the sampling spatial resolution for an exhaustive interpretation of the U-Th-Ra and of the in situ 10Be data, especially to independently determine the key parameters of the long term regolith production and denudation rates. The two weathering profiles realized in this study furthermore show that (1) the regolith structure is relatively simple on ridge-tops and allows a continuous interpretation of the geochemical and of the mineralogical data and (2) the slope processes tend to increase the spatial heterogeneity of the regolith and of the weathering processes. In addition, the monitoring and the modeling of the surface waters allow to investigate the current weathering processes, and to understand the mechanisms involved in their recent variability. This work shows the relationship that can exist between the modifications recorded at the surface in the soil solutions and the temporal evolution of some chemical properties of the spring waters (pH, calcium concentration). The simulations also allow to understand the weak variability of the global weathering fluxes exported by the springs, in relation with the relative stability of the sodium and of the dissolved silica concentrations over the period 1990-2010. This study also demonstrates the interest of the coupling of methods providing information on the weathering and the erosion processes at different time and space scales, in particular to correctly evaluate the regolith dynamic and to position the present-day functioning of a watershed with respect to its long term evolution.
28

Optimisation of selective extraction techniques as a tool for geochemical mapping in the Southern Africa region

Akinyemi, Segun Ajayi January 2008 (has links)
Magister Scientiae - MSc / The complex nature and composition of regolith cover in Southern Africa is a major challenge to geochemical mapping for concealed mineralization. Some of the setbacks to successful geochemical exploration may be ascribed to the use of various partial extraction techniques,without a profound understanding of the regolith components and their composition. This investigation therefore focuses on the use of hydroxylamine partial extraction geochemistry for geochemical mapping in regolith over two contrasting environments viz; aeolian sand-calcrete regolith over Au mineralization at Amalia Blue Dot Mine in South Africa and lateritic regolith covering the Ni-Cu deposit at Kabanga Main and Luhuma in Tanzania. Regolith samples from the above areas were sieved and extracted with hydroxylamine hydrochloride solution and analyzed for multi-element by AAS and ICP-MS techniques. A stepwise optimization of the hydroxylamine extraction technique of samples from both areas was carried out and incorporated into the analytical programme (in a pilot study). Results of hydroxylamine partial extraction generally gave better anomaly contrast and reflection of bedrock mineralization than the conventional aqua regia techniques that were previously used in the region. The results however show that lateritic regolith may be best extracted using 0.25M hydroxylamine while 0.1M concentration appears most suitable for extraction of aeolian-calcrete regolith. The above results are corroborated by principal component analysis of the analytical data that show various element associations, e.g. with Fe-Mn oxides while others possibly belong to the loosely adsorbed or exchangeable group. The gochemical maps in the pilot study areas at Amalia, Kabanga and Luhuma show elevated element contents or clusters of anomalies of diverse elements associated with Fe-Mn oxides. Geochemical mapping at Kabanga with deeply concealed mineralization however shows variability of subdued element patterns over mineralized areas. Geochemical signatures associated with hydroxylamine hydrochloride partial leach are therefore characterized by a lower geochemical background than that using conventional aqua regia leach. This study leads recommending for further investigations into partial extraction of the exchangeable group of elements, possibly using ammonium acetate. / South Africa
29

Understanding the Pressure-Sinkage Relationship for Simulated Lunar Regolith and Implications on Bearing Capacity and Trafficability

Millwater, Catherine A 01 January 2023 (has links) (PDF)
The intent of this thesis is to explore the pressure-sinkage relationship for simulated lunar regolith (simulant). The simulants used in this experiment emulate the lunar highlands (LHS-1) and the lunar mare (LMS-1). The ultimate ability of a terrain or regolith to support a load without shear failure is vital to the planning and construction of permanent infrastructure. This relationship can be measured by applying a normal load to the regolith until shear failure, from which allowable and ultimate bearing capacity can be deduced. An understanding of the pressure-sinkage of lighter loads on the higher ‘fluffy' layer of regolith is of great importance to low mass projects. The experimental hardware consisted of a test bed filled with simulated lunar regolith. The focus was to create a mechanism to apply a known load to a simulant surface normal to a square box filled with a regolith simulant. A known mass of each simulant was placed into the bearing capacity box and gently agitated to encourage natural settling and the density was measured. The simulant was only packed as much as was caused by gravity and settling. Normal loads of increasing weight were put into the box, putting pressure on the simulant. It was determined that widely accepted models for pressure-sinkage reasonably anticipate sinkage in both LHS-1 and LMS-1, though this study recommends improvements to the experimental design.
30

Estimation of Hydraulic Properties of the Shallow Aquifer System for Selected Basins in the Blue Ridge and the Piedmont Physiographic Provinces of the Southeastern U.S. Using Streamflow Recession and Baseflow Data

Baloochestani, Farshad 21 April 2008 (has links)
The objectives of this research are to measure the aquifer properties (S, T, and K) of selected watersheds delineated to the U.S. Geological Survey gauging stations using streamflow recession and baseflow data and to describe the relations among the properties of shallow aquifers and the physical properties of the basins, such as slope, regolith type and thickness, and land use type. Geographic Information System (GIS) techniques are utilized to investigate critical physiographic controls on transmissivity and storage coefficients on a regional basis. Moreover, the effect of evapotranspiration on recession index is illustrated. Finally, a detailed quantitative comparison of results for the Piedmont and the Blue Ridge Physiographic Provinces in southeast of the U.S. is provided. Recession index, annual groundwater recharge, and annual baseflow data were obtained from 44 USGS-gauging stations with drainage areas larger than 2 (mi2) and less than 400 (mi2). These gauging stations are located in Georgia and North Carolina. Analyses of data focused on GIS techniques to estimate watershed parameters such as total stream length, drainage density, groundwater slope, and aquifer half-width. The hydraulic diffusivity, transmissivity, and storage coefficient of watersheds were computed using hydrograph techniques and the Olmsted and Hely, and Rorabaugh mathematical models. Median recession index values for the Blue Ridge and Piedmont Provinces are 87.8 and 74.5 (d/log cycle), respectively. Median areal diffusivity values for the Blue Ridge and Piedmont are 35,000 and 44,200 (ft2/d), respectively. Median basin-specific estimates of transmissivity for basins in the Blue Ridge and Piedmont are 150 and 410 (ft2/d), respectively. The large values of transmissivity obtained for the Piedmont regolith may be attributed to the thick regolith, low values of basin relief, and voids that develop as a result of fracturing, foliation, weathering, and fractured quartz veins in the saprolite. Median basin-specific estimates of storage coefficient for basins in the Blue Ridge and Piedmont are 0.005 and 0.009, respectively. In general, the results from this study reveal great differences in basin-specific hydraulic parameters of the regolith material within the Piedmont compared to that of the Blue Ridge Physiographic Province.

Page generated in 0.014 seconds