Carbon nanotubes are known as ideal fillers for polymer systems; the main advantage of carbon nanotubes over other nano-reinforcing particles is the combination of superior strength and stiffness with large aspect ratio. Carbon nanotubes may improve the mechanical, electrical and thermal properties of polymers, but to realise their potential in polymer systems uniform dispersion, strong interfacial adhesion and alignment of nanotubes within the polymer matrix are necessary. These properties are not easy to achieve and they are key challenges in producing CNT/Polymer system. This research was carried out in an attempt to understand how the properties of CNT/Polymer composite can be optimised by manipulation of additives, compounding and postcompounding conditions. Polypropylene/Multi-Walled Carbon Nanotube (PP/MCNT) composites were prepared by conventional twin screw extrusion. Dispersants and compatibilisers were used to establish good interaction between filler and polymer. Several different extruder screw configurations were designed and the properties of PP/MCNT composite prepared by each configuration investigated. The results indicated that the addition of carbon nanotubes without additives enhanced mechanical, electrical and thermal properties of polypropylene polymer. Incorporation of compatibilisers into PP/MCNT improved the stiffness but decreased the strength of the nanocomposite, whilst addition of dispersants decreased the mechanical properties of the nanocomposite. Addition of both additives at high concentration improved electrical conductivity and induced electrical percolation in the nanocomposite. Extruder screw configuration was found to have significant effect on the electrical conductivity whilst only slightly affecting mechanical properties of the nanocomposite, possibly due to the competition between dispersion and degradation of polymer chains and possible reduction of carbon nanotube length by intensive shear during compounding. The use of screw configuration with high mixing intensity promoted the dispersion of nanotubes and favoured the conduction process in the nanocomposite. Finally in an attempt to improve dispersion and alignment of carbon nanotubes, compounded PP/MCNT composite was subjected to micromoulding, fibre spinning and biaxial stretching processes and the resultant properties investigated. Application of post-compounding process was found to have significant effect on mechanical and rheological properties of the nanocomposite. Stiffness and strength of the nanocomposites treated by post-compounding processes were found to increase by up to 160% and 300%, respectively. The reinforcement effect of carbon nanotubes in the stretched nanocomposites was found to be the greatest. Rheological analysis suggested that the application of post-compounding processes enhanced dispersion of carbon nanotubes within the nanocomposite. Overall, this finding of this research has shown that carbon nanotubes can be incorporated into polypropylene using conventional equipment to provide significant improvement in properties. By careful choices of additives, compounding and postcompounding conditions, specific properties can be further enhanced. / Ministry of higher education in Kurdistan region in Iraq.

No description available.

Existing models of the hydrogeology in the Blue Ridge Province in the eastern United States generally assume a simplified two-layered system consisting of shallow unconsolidated and relatively homogeneous and porous regolith with a water-table aquifer that slowly supplies water downward to the underlying variably fractured crystalline bedrock. In these models, interconnected fractures in the crystalline bedrock act as conduits for predominantly downward vertical and limited horizontal flow. Fracture density is depthà limited and correlated with proximity to topographic lineaments. Current models consider the porous regolith as the primary water storage reservoir for the entire aquifer system. In this research, detailed hydrogeologic studies in the Blue Ridge Province in Floyd County, Virginia reveal a substantially different framework for groundwater flow. Recent acquisition of two-dimensional surface resistivity profiles collected using a variety of array techniques combined with borehole geophysical logs revealed new insights into this geologically complex province. Dipole-dipole arrays were particularly important in gathering high resolution resistivity profiles that document horizontal and vertical resistivity variation reflecting changes in subsurface geology and anomalous low resistivity areas in crystalline bedrock associated with fault zones. The shallow regolith contains unsaturated areas and also localized sand and clay prone facies with water table and confined aquifer conditions residing locally. Hydraulic heads between the shallow aquifer and the deeper fractured bedrock aquifer can vary by 20 m vertically. Within the crystalline bedrock are anomalous lower resistivity intervals associated with ancient fault shear zones. Brecciated rock adjacent to the shear zones, and the shear zones themselves, can be hydraulically conductive and serve as pathways for groundwater movement. Aquifer testing of the regolith-bedrock fracture system occurred over a 6-day period and produced rapid and relatively uniform drawdowns in surrounding wells completed in the fractured bedrock aquifers. The shallow aquifers experienced minimal drawdowns from the aquifer test indicating low vertical hydraulic conductivity and limited communication between the shallow and deeper bedrock aquifers. Water chemistry and chlorofluorocarbon (CFC) age dating analyses indicated significant differences between water samples from the shallow and deep aquifers. A new conceptual model for Blue Ridge aquifers is proposed based on these research findings. / Ph. D.

2D inversion modeling of synthetic data is used to evaluate the performance of five electrical resistivity arrays, with the primary criteria being the reproduction of sharp model boundaries. 2D synthetic noise free data were calculated simulating a modern fixed spacing multi-electrode cable. Twelve 2D synthetic models, resembling a number of different geologic situations, were used to investigate performance of the dipole-dipole, pole-dipole, pole-pole, Wenner and Schlumberger arrays Although the synthetic, noise-free data were well matched for all inversions, many of the inversion results exhibit substantial mismatches from the true model. The greatest resistivity mismatches are near model discontinuities. Resistivity mismatches become worse with depth and the geometry of geologic boundaries in the deep portion of the models are not well reproduced by any of the arrays. Field surveys must be designed so that the geologic target is in the middle of the data constrained region. Different arrays performed best for different models and a practical table is presented allowing the practitioner to choose the optimal array for the particular geologic situation under investigation. Although the dipole-dipole and pole-dipole arrays may not be the optimal array for a given geology, they rarely fail for any model, and thus are recommended for reconnaissance or preliminary investigations in regions of unknown geology. Contrary to traditional advice found in textbooks, based on 1D profiling and sounding, and data plot comparison, this study, using 2D data and 2D inversion, finds the Wenner and Schlumberger arrays, thought to perform poorly for vertical boundaries, performed well for a vertical boundary and a thin vertical resistor. Similarly, the dipole-dipole and pole-dipole arrays, thought to perform poorly for horizontal and dipping boundaries, performed well for several models containing those geometries. Another interesting finding is that changing the polarity of geologic units from resistors to conductors changed relative array performance in most models. / Master of Science

Located in Giles County, Virginia, Mountain Lake has a documented history of dramatic water level fluctuations. Previous water balance studies have documented that the main cause of water loss is outflow to groundwater. However, the flow paths of water exiting the lake are unknown. This study applied hydrologic, geophysical, and dye tracer methods to examine the pathways for water loss and the possible geologic controls on these flow paths. Continuous lake level monitoring data show seasonal trends of draining and filling over a three year period. Electrical resistivity profiles suggest the presence of a large low-resistivity zone beneath the northern end of the lake. A dye tracer study yielded limited positive results, but dye detection in one stream and within the lake suggest complex flow dynamics. The most likely reasons for the lack of dye recovery include dilution of the dye during lake recovery, seepage of water below monitoring site locations, or formation of a temporary seal in the depressions created by influx of sediment during periods of lake bed exposure. / Master of Science

The Coles Hill uranium deposit in Pittsylvania County, VA, is the largest un-mined uranium deposit in the United States. The deposit is located in the Virginia Piedmont in a geologic unit located immediately west of the Chatham Fault, which separates the granitic rocks of the Virginia Piedmont to the west from the metasediments of the Danville Triassic basin to the east. Groundwater at the site flows through a complex interconnected network of fractures controlled by the geology and structural history of the site. In this study groundwater is characterized in a small study area just south of the main deposit. Methods used in this investigation include electrical resistivity profiling, bore hole logging, a pumping test, and age dating and water chemistry. In this thesis groundwater flow is confirmed to occur from the Piedmont crystalline rocks across the Chatham Fault and into the Triassic basin at the study area as evidenced by pumping test data and static water-level data from observation wells. Well logs have identified fractures capable of transmitting water in the granitic rocks of the Piedmont, the Triassic basin metasediments and the Chatham Fault but the largest quantities of flow appear to occur in the Triassic basin. A definable recharge area for the groundwater present at Coles Hill can not yet be determined due to the complexity of the fracture system, but age dating confirms that groundwater is composed of both young and old (>60 years) components, indicating that at least a portion of groundwater at Coles Hill originates from a more distant area. / Master of Science

No description available.

The Big Clifty (Jackson) Sandstone Member of the Golconda Formation is the most important of the Mississippian (Chesterian) heavy-oil reservoirs in the southeastern Illinois Basin. Heavy oil reservoirs, or asphalt rock deposits, have been studied extensively in south central and western Kentucky, and ~2 billion barrels of original oil in place (OOIP) have been proposed to occur in the Big Clifty Sandstone. Despite high OOIP estimates, heterogeneities in the reservoir negatively impact the production of heavy oil deposits. Heterogeneities related to depositional facies changes are poorly understood in the Big Clifty Sandstone of Kentucky, where it has been mostly described as a 60-120 feet thick sandstone unit. In some locations, the Big Clifty occurs as two distinct sand bodies with intercalated mud-rich units and, most typically, with the greatest clay- and silt-rich units present between sandstone bodies. Questions exist as to how such muddy facies occur in the reservoir. This study couples sedimentary facies analysis with sequence stratigraphy to assess how lithological factors affect the occurrence of petroleum in Big Clifty reservoirs. Multiple datasets were integrated to develop a depositional model for lithologic facies observed in this study. Datasets include core, exposure descriptions, petrographic analysis, bitumen concentrations, electrical resistivity tomography (ERT), and borehole geophysical analysis. This study occurred in Logan, Warren, and Butler counties, with emphasis on an active asphalt-rock mine in Logan County. Surface geophysical methods aided in demarcating Chesterian limestones, sandstone bodies and, in particular, highly resistive heavy-oil laden Big Clifty channel bodies. In Warren County, located E-NE of the Stampede Mine, the Big Clifty coalesces into a single amalgamated sandstone channel or a series of superimposed stacked channels as observed in outcrop along Indian Creek at McChesney Field Station and at Jackson’s Orchard. In these locations, the tidal influence is subtle with large-scale trough cross bedding dominating, and the contact on the Beech Creek Limestone is sharp. Facies changes related to the environment of deposition greatly impact the quality of heavy-oil reservoirs and must be taken into consideration during exploration and siting of asphalt rock mines.

Experiments using electrical resistivity tomography (ERT) have shown promising results in reducing the uncertainty of solute plume characteristics related to estimates based on the analysis of local point measurements only. To explore the similarities and differences between two cross-borehole ERT inversion approaches for characterizing salt tracer plumes, namely the classical smoothness-constrained inversion and a geostatistically based approach, we performed two-dimensional synthetic experiments. Simplifying assumptions about the solute transport model and the electrical forward and inverse model allowed us to study the sensitivity of the ERT inversion approaches towards a variety of basic conditions, including the number of boreholes, measurement schemes, contrast between the plume and background electrical conductivity, use of a priori knowledge, and point conditioning. The results show that geostatistically based and smoothness-constrained inversions of electrical resistance data yield plume characteristics of similar quality, which can be further improved when point measurements are incorporated and advantageous measurement schemes are chosen. As expected, an increased number of boreholes included in the ERT measurement layout can highly improve the quality of inferred plume characteristics, while in this case the benefits of point conditioning and advantageous measurement schemes diminish. Both ERT inversion approaches are similarly sensitive to the noise level of the data and the contrast between the solute plume and background electrical conductivity, and robust with regard to biased input parameters, such as mean concentration, variance, and correlation length of the plume. Although sophisticated inversion schemes have recently become available, in which flow and transport as well as electrical forward models are coupled, these schemes effectively rely on a relatively simple geometrical parameterization of the hydrogeological model. Therefore, we believe that standard uncoupled ERT inverse approaches, like the ones discussed and assessed in this paper, will continue to be important to the imaging and characterization of solute plumes in many real-world applications. (C) 2016 Hohai University. Production and hosting by Elsevier B.V.

Des mesures de résistivité électrique et des campagnes d’observations géologiques ont été menées pour cartographier le contact sédiment/roche basale ainsi que les structures d’impact associées au cratère d’impact Bosumtwi datant de 1,07 millions d’années. Le cratère de 10,5 km de diamètre s’est formé dans des roches métamorphiques du Précambrien (2,1 à 2,2 milliard d’années), d’origine sédimentaire et volcanique. Il est actuellement rempli par le lac Bosumtwi de 8,5 km de diamètre. Ce cratère est la source des tektites et microtektites dispersées jusqu’en Côte d’Ivoire et au large des côtes ouest africaine. La campagne de mesures éophysiques consiste en 16 tomographies de résistivité électrique effectuées radialement des rives du lac vers les bords du cratère d’impact. Chaque profil utilise un système d’acquisition multi – électrodes avec une distance minimum entre les électrodes de 5 m. Les données ont été corrigées des effets topographiques et inversées en utilisant le programme commercial d’inversion Res2DInv, avec la norme L1 considérée plus robuste. La zone comprise entre les rives du lac et le bord externe du cratère de divise en trois formations géologiques principales. Les régions de faibles résistivités (< 64 .m) représentent les sédiments de lac. Les zones de resistivités moyennes (entre 128 et 200 .m) sont interprétées comme des brèches liées à l’impact, en dikes, allochtones ou parautochtones. Les régions de hautes résistivités (> 128 .m) représentent les roches métamorphiques sous-jacentes, d’origine volcanique ou sédimentaire. Les profils de résistivités permettent de retrouver la géométrie et l’extension latérale de ces trois types de roches. Une correspondance directe entre la lithologie observée en surface et les structures mises en évidence par les mesures de résistivité électrique dans le sous-sol est observée à Dwamam au Sud-Est dulac. À Dwamam, les sédiments sont environ à 200 m de la rive du lac et s’étendent environ sur 400 m vers les les bords du cratère, à la différence des autres zones où ont pu être cartographiés les sédiments. La topographie du contact sédiment/roche basale présente une direction particulière NE-SO avec un pendage variant entre 16 degrés au NE et 36 degrés au SO. Une majorité de fractures ont été remarquées dans le SO, remplies par des clasts et des brèches d’impacts. Les failles sont surtout présentent à l’Ouest du lac. En moyenne elles présentent un pendage variant entre 60o à l’Est et 80 degrés à l’Ouest du cratère. Des analyses statistiques ont été effectuées sur les directions et les pendages des failles selon les loi de von Mises et Fisher. Elles démontrent que les failles s’alignent préférentiellement le long de deux directions principales. L’analyse cumulée de la surface de contact sédiment/roche, des failles et de la localisation du champ de dispersion des tektites indique que le bolide d’environ 0,8 à 1 km de diamètre responsable du cratère est arrivé du NE. Les résultats démontrent que les panneaux de résistivité électrique fournissent des informations utiles pour l’étude des cratères d’impact. / Electrical resistivity tomography (ERT) and geological field surveys have been used to map the sediment/bedrock contact and impact related structures of the 1.07 Myr old Bosumtwi impact crater. The 10.5 km complex crater excavated in 2.1–2.2 Gyr Precambrian metasedimentary and metavolcanic rocks is filled by the 8.5 km Lake Bosumtwi. It is the source crater of the tektites and microtektites of the Ivory Coast strewn field. Electrical resistivity survey was carried out sixteen (16) profiles running from the shore of the lake towards the rim of the crater. The multi-electrode gradient array method with minimum electrode separation of 5 m was used. The data were corrected for topography and inverted using the L1–norm (robust inversion) techniqueof the Res2DInv software. The area extending from the lake shore towards the crater rim contains essentially three formations. The low resistivity regions (< 64 .m) represent the lake sediments. The moderately high resistivity regions with values between 128 and 200 .m were interpreted as impact related breccias (dikes, allochthonous or parautochthonous) depending on their geometries. Lastly, the model clearly differentiate the resistive basement metamorphic rocks (> 128 .m) fromthe lake sediments and the breccias due to their geometry and lateral extent. Also observed was a direct correspondence between the lithology on the surface and the subsurface resistivity structures at Dwamam in the southeast section of the lake. At Dwamam, the sediments were about 200 m away from the shore and stretch about 400 m towards the crater rim unlike in other areas where the sediments were mapped from the shore. The gradient of the sediments/bedrock contact showsa symmetry in the NE–SW direction and dips between the lowest of 16 degrees in the NE to the highest 36 degrees in the SW. Majority of the fractures marked were in the southwest and were filled with clasts or impact breccia matrix. The faults were mostly delineated in the west. Averagely, the dips of the faults are about 60 degrees and 80 degrees for the east and west sections of the crater respectively. The dips of the faults were statistically treated using the von Mises and Fisher statistics, it was found that the faults have a preferred direction and it is possible to determine at least two different orientations. Theanalysis of the results of the sediments/bedrock surface and the faults combined with the location of the tektite strewn field indicate that the about 0.8–1 km bolide that created the complex crater came from the NE. The findings have shown that the ERT is efficient and a useful tool in impact cratering science research.