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  • 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.
261

Engineering geology of the Patonga Claystone, Central Coast, New South Wales, with particular reference to slaking behaviour

Nunt-jaruwong, Sorawit, School of Biological, Earth & Environmental Sciences, UNSW January 2006 (has links)
The Patonga Claystone, a red bed facies in the Narrabeen Group of the Sydney Basin, is one of the most unfavorable rock units in the basin from a geotechnical point of view. This rock unit is composed of sandstone, siltstone, mudstone and claystone. One of the unfavorable characteristics is the low shear strength, which causes instability of cut slopes; another is its slaking-prone behaviour. Numerous measurements of geotechnical properties, along with extensive mineralogical and geochemical determinations, were carried out to identify cause of this slaking behaviour. Key techniques were the use of quantitative X-ray diffractometry for mineralogical analysis, and the determination of slake durability index and related properties to evaluate the slaking behaviour under both standard and more extended conditions. Standard (two cycle) slake durability test results indicate a range from low to high slake durability index values, with some mudstone samples having very low durability and some sandstones having very high slake durability indices. Jar slake test results indicate that the rock samples break rapidly and/or develop several fractures (Ij = 4) in an as-received state, but degrade to a pile of flakes or mud (Ij = 1) if the samples are oven dried before testing. The results for jar slake testing of oven-dried material are comparable, for individual samples, to those obtained from the more comprehensive slake durability tests. The mineralogy of the samples was evaluated by quantitative X-ray diffraction techniques using the Rietveld-based Siroquant processing system. Comparison to independent chemical data show a generally good level of agreement, suggesting that the mineralogical analysis results are consistent with the chemical composition of the individual rock samples. Good correlations were also obtained between clay mineralogy determined from orientedaggregate XRD analysis of the &lt2 micron fraction and the results from powder diffractometry and Siroquant analysis of the whole-rock samples. Evaluation of the slake durability characteristics and other geotechnical properties in relation to the quantitative mineralogy suggests that quartz and feldspar form a rigid framework in the rocks that resists the disruptive pressures that cause slaking. Expansion of the clay minerals by various processes, including the incorporation of water into the interlayer spaces of illite/smectite as well as changes in pore pressures associated with entry of water into micro-fractures in the clay matrix, are thought to produce the disruptions that cause slaking and degradation. An abundant clay matrix also reduces the strength of the rock materials, probably because of the less rigid nature of the clay minerals relative to the quartz and feldspar particles. As well as the mineralogy, the loss on ignition (LOI) and water absorption percentage were found to provide good indicators of longer-term slaking behaviour. Both properties are also related to the overall clay content. Rock samples with water absorption values of &lt10, 10-15 and &gt15% behave as highly durable, intermediate and less durable materials respectively. Rocks with LOI values of greater than 5% by weight behave as less durable rock materials, at least for the strata encompassed by the present study. The water absorption and LOI values were also used to develop a predictive model of slake durability characteristics for the different rock materials in the Patonga Claystone, providing a relatively simple basis for predicting longer-term stability in a range of geotechnical studies.
262

A compositional study of the lunar global megaregolith using clementine orbiter data

Jackson, Noel William January 2005 (has links)
This thesis presents new information about the global megaregolith of the Moon, using 2059 craters (5 to 50 km diameter) as natural probes. Iron (FeO) and titanium (TiO2) concentrations were obtained from crater ejecta blanket data over an area between 600 North to 600 South latitude derived from the 1994 Clementine mission. The average iron and titanium weight percentages for lunar crater ejecta were calculated using the US Geological Survey's ISIS software, and used to determine the variation with depth of iron (FeO) and titanium (TiO2) in the highlands, mare areas and the South Pole Aitken basin. In addition, megaregolith compositional Iron (FeO) and Titanium (TiO2) Maps and compositional Province Maps were generated, and studied in detail. The Lunar Megaregolith Iron Province Map divides the Highland areas into 2 distinct provinces of low-iron Highland I (0-3.7 FeO weight percentage) and low-medium level iron Highland II (3.8-6.4%), and the Mare and South Pole Aitken Basin each into 3 distinct provinces (6.5-9.7%, 9.8-13.6%, and 13.7-18.3%). Similarly, a Titanium Megaregolith Province Map divides the Moon globally into 5 provinces based on weight percentages of TiO2. A new finding is the Highland II Province of elevated iron concentration which surrounds basins. These elevated iron levels may be explained in terms of an "Intrusion Model". In this model, basin formation fractures the surrounding anorthositic bedrock, and the middle level anorthositic crust allows mafic (basaltic?) magma to intrude. This intrusion into the megaregolith is in the form of sills and dykes from deep mafic sources but generally does not intrude into the surface regolith. In some places however, the mafic (basaltic?) lava may have extruded onto the surface, such as near Crater 846 (15.6N 92.2W). The megaregolith, which consists of large volume breccia, would have voids and vacancies in this structure into which mafic or basaltic material could intrude. "Islands" of Highland I Province material surrounded by Highland II Province indicate this intrusion was non-uniform. Another possible explanation for the Highland II Province iron levels comes from the "Thrust Block" model, where deep mafic material has been broken into large blocks by the basin-forming events, and "thrusted" or uplifted to displace most of the overlying anorthosite bedrock, thereby mechanically mixing with the megaregolith to provide the additional iron input. However, this does entirely fit comfortably with the data in this study. A third explanation for the Highland II Province arises from the "Basin Impact Ejecta Model" such as the Imbrium Impact described by Haskin (1998). The Basin Impact Ejecta model describes the effect of basin impacts around 4.0 billion to 3.8 billion years ago in the Moon's history (Ryder, 1990; Taylor, 2001)). This model implies that basin material was ejected and deposited on a global or similar scale. However, the results of this study place severe limitations on the feasibility of the "Basin Impact Ejecta" model to explain any significant mafic input from such ejecta in forming the Highland II megaregolith material. These Province Maps provide a new dimension to the study of the Moon's crustal development and reveal a highly complex history, providing a basis for future study.
263

Western juniper encroachment into aspen communities in the Northwest Great Basin

Wall, Travis G. 30 June 1999 (has links)
In the Northwest Great Basin, aspen (Populus tremuloides) communities uniquely contribute to the biodiversity of a semi-arid, sagebrush-dominated landscape. In this same region, western juniper (Juniperus occidentalis) is encroaching into aspen stands. This study determined the timing, extent, and some of the effects of this expansion. Aspen stands below 2,133 m elevation were sampled in northwest Nevada, northeast California, and southeast Oregon for density, canopy cover, age, stand structure, and recruitment of western juniper and aspen. Soils and tree litter from both species were collected to analyze the effects of western juniper in areas previously influenced by aspen. Additionally, two large aspen complexes in southeast Oregon were intensively aged to determine disturbance (fire) frequencies. Western juniper encroachment into aspen stands peaked from 1920 to 1939 with 77% of all juniper trees sampled establishing during this period. Five percent were greater than 100 years and none exceeded 145 years. Three-fourths of aspen stands sampled have established populations of western juniper. Twenty-three percent have a dominant canopy of western juniper. Twelve percent of aspen stands sampled were completely replaced by western juniper. Average density of western juniper was 1,573 trees per hectare of aspen. Seventy percent of aspen stands sampled had zero recruitment of new aspen. Within the study area aspen stands averaged 98 years old. Forty-eight percent of stands were greater than 100 years old. There was an inverse correlation between aspen canopy cover and western juniper canopy cover (r��=.80, p=.0001). Soils influenced by western juniper had a higher C:N ratio and pH; higher amounts of salts, lime, and sulfate; and lower amounts of magnesium, iron, copper, and manganese (p<.05). Aspen litter had a lower C:N ratio than western juniper litter (p<.05). Prior to 1870, the two major aspen complexes sampled had mean fire return intervals of 10 and 11 years. However, the most recent disturbance in either complex was 80 to 90 years ago. This lack of disturbance (fire) coupled with aspen stand decadence and low recruitment levels leaves aspen communities in the Northwest Great Basin vulnerable to western juniper encroachment and replacement. / Graduation date: 2000
264

Using Osteological Evidence to Assess Biological Affinity: A Re-evaluation of Selected Sites in East Tennessee

McCarthy, Donna M 01 May 2011 (has links)
TVA/WPA excavations in East Tennessee in the 1930s uncovered archaeological sites critical for shaping theories about the prehistory of the region. Based on the archaeology of three of these sites, Hixon (AD 1155-1285), Dallas (AD 1350-1450), and Rymer (AD 1400-1600) in the Chickamauga Basin, early researchers concluded that each settlement resulted from migrations of biologically unrelated people into the area (Lewis and Lewis, 1941, 1946). Testing of this supposition using biological distance analysis (Weston, 2005) suggested that the sites instead represented biological continuity in the Chickamauga Basin. In this study, cranial and postcranial non-metric traits are used to examine biological distance between the three Chickamauga Basin sites and an extra-regional site from the Watts Bar Basin, using Mahalanobis D2 with a tetrachoric correlation matrix. Results of this four-group study differed dramatically from the expected structure of biological relationships between the sites, suggesting that the Hixon population was completely unrelated biologically to the populations in both the Chickamauga and Watts Bar Basins. In fact, these results combined with ceramic decorative styles present at the Hixon site suggest the population may have immigrated from Etowah in Bartow County, Georgia, with a continued shared cultural identity with Etowah providing sufficient barrier to mate exchange with the other East Tennessee sites examined here. Results of both cranial and postcranial non-metric biological distance analyses indicate the strongest genetic affiliations for all four sites to be between Dallas in the Chickamauga Basin and DeArmond in Watts Bar, despite great geographical separation of the settlements. In addition, an introduction to the skeletal biology of Watts Bar is presented via osteological examination of pathology and trauma of the DeArmond site. Smith (2003) recorded low levels of interpersonal and high levels of intrapersonal violence during the Dallas phase in the Chickamauga Basin. Results from DeArmond demonstrate similar rates and patterns, most likely reflecting a temporal trend in the region. The DeArmond skeletal remains exhibit low levels of metabolic stress but remarkably high levels of infectious disease. It appears that while all of the DeArmond individuals had access to high protein food resources regardless of status, status had little effect on preventing the spread of infection at the site.
265

Fast Stochastic Global Optimization Methods and Their Applications to Cluster Crystallization and Protein Folding

Zhan, Lixin January 2005 (has links)
Two global optimization methods are proposed in this thesis. They are the multicanonical basin hopping (MUBH) method and the basin paving (BP) method. <br /><br /> The MUBH method combines the basin hopping (BH) method, which can be used to efficiently map out an energy landscape associated with local minima, with the multicanonical Monte Carlo (MUCA) method, which encourages the system to move out of energy traps during the computation. It is found to be more efficient than the original BH method when applied to the Lennard-Jones systems containing 150-185 particles. <br /><br /> The asynchronous multicanonical basin hopping (AMUBH) method, a parallelization of the MUBH method, is also implemented using the message passing interface (MPI) to take advantage of the full usage of multiprocessors in either a homogeneous or a heterogeneous computational environment. AMUBH, MUBH and BH are used together to find the global minimum structures for Co nanoclusters with system size <em>N</em>&le;200. <br /><br /> The BP method is based on the BH method and the idea of the energy landscape paving (ELP) strategy. In comparison with the acceptance scheme of the ELP method, moving towards the low energy region is enhanced and no low energy configuration may be missed during the simulation. The applications to both the pentapeptide Met-enkephalin and the villin subdomain HP-36 locate new configurations having energies lower than those determined previously. <br /><br /> The MUBH, BP and BH methods are further employed to search for the global minimum structures of several proteins/peptides using the ECEPP/2 and ECEPP/3 force fields. These two force fields may produce global minima with different structures. The present study indicates that the global minimum determination from ECEPP/3 prefers helical structures. Also discussed in this thesis is the effect of the environment on the formation of beta hairpins.
266

Identification Of Morphometric Properties Of Basins Located On Western Part Of Nafz

Sarp, Gulcan 01 February 2012 (has links) (PDF)
This study aims to investigate tectonic activity levels and development stages of the tectonic and hydrologic basin areas located on western part of the main trace of the North Anatolian Fault Zone (NAFZ) using quantitative measurement techniques. The basins investigated are Bolu, Yeni&ccedil / aga, D&ouml / rtdivan, &Ccedil / erkes, Ilgaz and Tosya. The methodology includes application of six morphometric indices (Basin Shape, Hypsometric curve and Hypsometric Integral, Sinuosity of Mountain Fronts, Stream Length Gradient Index, Valley width to height ratio, and Asymmetry Factor) to Digital Elevation Model (DEM) of the region generated from 1:25000 scale topographic maps. The analyses indicate that the basins located in the study area have different characteristics of tectonic activity. According to the results of the applied indices relative order of the activity for tectonic basins is, in decreasing order, Bolu, Tosya, Ilgaz, &Ccedil / erkes, Yeni&ccedil / aga and D&ouml / rtdivan. For hydrologic basins, on the other hand, the same order is observed except for a swap in &Ccedil / erkes and Yeni&ccedil / aga basins. Among the basins located to the north of the NAFZ, the activity decreases eastward whereas to the south the fault zone it decreases towards the west.
267

Regional tectonics, sequence stratigraphy and reservoir properties of Eocene clastic sedimentation, Maracaibo Basin, Venezuela

Escalona, Alejandro 28 August 2008 (has links)
Not available / text
268

Integrated sequence stratigraphy, depositional environments, diagenesis, and reservoir characterization of the Cotton Valley Sandstones (Jurassic), East Texas Basin, USA

Elshayeb, Tarek Abu Serie 28 August 2008 (has links)
Not available / text
269

Paleogene sedimentation patterns and basin evolution during Andean orogenesis, Middle Magdalena Valley basin, Colombia

Moreno, Christopher John 23 December 2010 (has links)
The Central Cordillera and Eastern Cordillera of the northern Andes form the western and eastern flanks of the north-trending Middle Magdalena Valley basin. Previous estimates for the timing of initial exhumation of the two cordilleras range from ~100 to ~10 Ma. Accurately constraining the spatial and temporal distribution of deformation in Colombia has implications for the shortening history of the Andean convergent margin and the prediction of rapid lateral facies changes in sedimentary basins in close proximity to sediment sources. This study applies sandstone petrographic point counts, field sedimentological analyses of basin fill, and paleocurrent measurements of trough cross-stratification, clast imbrication, and flute casts to provide new insights into the tectonic history of the flanks of the Middle Magdalena Valley basin. Between the lower and upper Paleocene strata of the Lisama Formation, paleocurrent orientations show a shift from northward to eastward transport. This change in sediment dispersal coincides with a shift from a cratonic (Amazonian) to orogenic (Andean) sediment source, as recorded by published U-Pb detrital zircon geochronological results (Nie et al. 2010), suggesting initial uplift of the Central Cordillera by mid-Paleocene time. Later in the basin’s history, establishment of an alluvial-plain system with meandering-channel deposits is recorded in lower–middle Eocene strata of the lower La Paz Formation. Consistent eastward paleocurrents characterize mid-Paleocene through uppermost Eocene strata, indicating a continuous influence of western sediment source areas. However, within the upper middle Eocene succession (~40 Ma), at the boundary between the lower and upper La Paz Formation, sandstone compositions show a dramatic decrease in lithic content. This compositional change is accompanied by a facies shift to amalgamated fluvial channels, reflecting changes in both the composition and proximity of the western sediment source. We attribute these changes to the growing influence of the exhumed La Cira/Infantas paleohighs off the western flank of the present-day Nuevo Mundo syncline. In the uppermost Eocene strata of the Esmeraldas Formation, paleocurrents show a switch to dominantly westward transport that persisted through the Neogene. In addition, deposits show a contemporaneous decrease in the amount of coarse-grained channel deposits. These changes are interpreted to reflect the onset of exhumation in the Eastern Cordillera. The lack of a significant change in sandstone compositions at this boundary suggests a compositional similarity between strata uplifted by the Lisama structure and the Eastern Cordillera. These data support and further refine previous thermochronologic and provenance studies which suggest that uplift-induced exhumation of the Central Cordillera and Eastern Cordillera commenced by mid-Paleocene and late Eocene–early Miocene time, respectively. / text
270

Islamic foundations for effective water management : four case studies

Walz, Jonathan David 16 February 2011 (has links)
This thesis project addresses Islamic water management by presenting case studies on regional water issues and analyzing the extent to which Muslim-majority states behave in a way consistent with Islamic shariah law. The case studies presented in this thesis address both international cooperation related to the management of trans-boundary water basins (the Nile and Tigris-Euphrates River Basins) and domestic water management strategies employed by Muslim-majority states in the MENA region (Jordan and Yemen). In each case, it is not clear that there is consistency between the Islamic ideals discussed by academics and the actual techniques employed by various states. In international attempts at managing the shared waters of the Nile and Tigris-Euphrates Basins, the fact that many riparian states have Muslim-majority populations does not appear to make the management of trans-boundary resources any easier or more successful. The implications for Islamic water management at the domestic level is also unclear – with shariah playing a positive role in Jordanian attempts at water conservation but promoting the over-exploitation of resources in Yemen. Although shariah appears to play a limited role in the management of trans-boundary water resources, it seems to be better suited for informing how states internally manage their endowments of freshwater resources. / text

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