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in subjects: "Fractures"  
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Micromorphology, mineralogy, and genesis of soils and fracture fills and the Pajarito Plateau, New Mexico

Description: The town of Los Alamos, and the Los Alamos National Laboratory (LANL), are located on the Pajarito Plateau in north-central New Mexico. Environmental concerns have recently focused attention on the numerous fractures in the Bandelier Tuff, the series of volcanic rock units that make up most of the plateau. These fractures have come into question as possible conduits for transport of contaminants downward through the tuff. This, study arose out of a need to evaluate the potential for contaminant… more
Date: December 1, 1993
Creator: Davenport, D. W.
Partner: UNT Libraries Government Documents Department
open access

Dislocation dynamics simulations of plasticity at small scales

Description: As metallic structures and devices are being created on a dimension comparable to the length scales of the underlying dislocation microstructures, the mechanical properties of them change drastically. Since such small structures are increasingly common in modern technologies, there is an emergent need to understand the critical roles of elasticity, plasticity, and fracture in small structures. Dislocation dynamics (DD) simulations, in which the dislocations are the simulated entities, offer a w… more
Date: December 15, 2010
Creator: Zhou, Caizhi
Partner: UNT Libraries Government Documents Department
open access

Theoretical studies of non-Newtonian and Newtonian fluid flow through porous media

Description: A comprehensive theoretical study has been carried out on the flow behavior of both single and multiple phase non-Newtonian fluids in porous media. This work is divided into three parts: development of numerical and analytical solutions; theoretical studies of transient flow of non-Newtonian fluids in porous media; and applications of well test analysis and displacement efficiency evaluation to field problems. A fully implicit, integral finite difference model has been developed for simulation … more
Date: February 1, 1990
Creator: Wu, Yu-Shu.
Partner: UNT Libraries Government Documents Department
open access

Theoretical Studies of Non-Newtonian and Newtonian Fluid Flowthrough Porous Media

Description: A comprehensive theoretical study has been carried out on the flow behavior of both single and multiple phase non-Newtonian fluids in porous media. This work is divided into three parts: (1) development of numerical and analytical solutions; (2) theoretical studies of transient flow of non-Newtonian fluids in porous media; and (3) applications of well test analysis and displacement efficiency evaluation to field problems. A fully implicit, integral finite difference model has been developed for… more
Date: February 1, 1990
Creator: Wu, Y.S.
Partner: UNT Libraries Government Documents Department
open access

Mechanisms for fatigue and wear of polysilicon structural thinfilms

Description: Fatigue and wear in micron-scale polysilicon structural films can severely impact the reliability of microelectromechanical systems (MEMS). Despite studies on fatigue and wear behavior of these films, there is still an on-going debate regarding the precise physical mechanisms for these two important failure modes. Although macro-scale silicon does not fatigue, this phenomenon is observed in micron-scale silicon. It is shown that for polysilicon devices fabricated in the MUMPs foundry and SUMMiT… more
Date: December 1, 2006
Creator: Alsem, Daniel Henricus
Partner: UNT Libraries Government Documents Department
open access

Ambient and elevated temperature fracture and cyclic-fatigue properties in a series of Al-containing silicon carbides

Description: A series of in situ toughened, Al, B and C containing, silicon carbide ceramics (ABC-SiC) has been examined with Al contents varying from 3 to 7 wt%. With increasing Al additions, the grain morphology in the as-processed microstructures varied from elongated to bimodal to equiaxed, with a change in the nature of the grain-boundary film from amorphous to partially crystalline to fully crystalline. Fracture toughness and cyclic fatigue tests on these microstructures revealed that although the 7 w… more
Date: August 30, 2004
Creator: Yuan, Rong
Partner: UNT Libraries Government Documents Department
open access

Hydrogeologic characterization of a fractured granitic rock aquifer, Raymond, California

Description: The hydrogeologic properties of a shallow, fractured granitic rock aquifer in the foothills of the Sierra Nevada, California were investigated via the analysis of borehole geophysical logs and pumping tests. The drawdowns produced during these tests are not indicative of any simple conceptual aquifer model, and borehole logs show that the granite is intensely fractured. These observations are suggestive of a complex fracture-flow geometry which is extremely difficult to decipher. However, throu… more
Date: October 1, 1993
Creator: Cohen, A. J. B.
Partner: UNT Libraries Government Documents Department
open access

Solid state NMR method development and studies of biological and biomimetic nanocomposites

Description: This thesis describes application and development of advanced solid-state nuclear magnetic resonance techniques for complex materials, in particular organic-inorganic nanocomposites and thermoelectric tellurides. The apatite-collagen interface, essential for understanding the biomineralization process in bone and engineering the interface for controlled bio-mimetic synthesis and optimized mechanical properties, is buried within the nanocomposite of bone. We used multinuclear solid-state NMR to … more
Date: February 7, 2011
Creator: Hu, Yanyan
Partner: UNT Libraries Government Documents Department
open access

On the Mechanical Properties and Microstructure of Nitinol forBiomedical Stent Applications

Description: This dissertation was motivated by the alarming number of biomedical device failures reported in the literature, coupled with the growing trend towards the use of Nitinol for endovascular stents. The research is aimed at addressing two of the primary failure modes in Nitinol endovascular stents: fatigue-crack growth and overload fracture. The small dimensions of stents, coupled with their complex geometries and variability among manufacturers, make it virtually impossible to determine generic m… more
Date: December 15, 2006
Creator: Robertson, Scott W.
Partner: UNT Libraries Government Documents Department
open access

A study of particle generation during laser ablation withapplications

Description: A study has been made of the generation of particles during laser ablation and has included size distribution measurements and observation of the formation processes. The particle size distribution with respect to different laser parameters was obtained in-line using a differential mobility analyzer (DMA) and a particle counter. The experimental results show that the particle size varies with laser energy, laser pulsewidth, ambient gas flow rate and sample properties. The results serve as a bas… more
Date: August 12, 2005
Creator: Liu, Chunyi
Partner: UNT Libraries Government Documents Department
open access

Water infiltration and intermittent flow in rough-walled fractures

Description: Flow visualization experiments were conducted in transparent replicas of natural rough-walled fractures. The fracture was inclined to observe the interplay between capillary and gravity forces. Water was introduced into the fracture by a capillary siphon. Preferential flow paths were observed, where intermittent flow frequently occurred. The water infiltration experiments suggest that intermittent flow in fractures appears to be the rule rather than the exception. In order to investigate the me… more
Date: May 1, 1995
Creator: Su, G.
Partner: UNT Libraries Government Documents Department
open access

Statistical analysis of liquid seepage in partially saturated heterogeneous fracture systems

Description: Field evidence suggests that water flow in unsaturated fracture systems may occur along fast preferential flow paths. However, conventional macroscale continuum approaches generally predict the downward migration of water as a spatially uniform wetting front subjected to strong inhibition into the partially saturated rock matrix. One possible cause of this discrepancy may be the spatially random geometry of the fracture surfaces, and hence, the irregular fracture aperture. Therefore, a numerica… more
Date: December 1, 1999
Creator: Liou, T.S.
Partner: UNT Libraries Government Documents Department
open access

The use of synthetic colloids in tracer transport experiments in saturated rock fractures

Description: Studies of groundwater flow and contaminant transport in saturated, fractured geologic media are of great interest to researchers studying the potential long-term storage of hazardous wastes in or near such media. A popular technique for conducting such studies is to introduce tracers having different chemical and physical properties into a system and then observe the tracers at one or more downstream locations, inferring flow and transport mechanisms from the breakthrough characteristics of th… more
Date: August 1, 1995
Creator: Reimus, Paul William
Partner: UNT Libraries Government Documents Department
open access

Simulation of a field scale tritium tracer experiment in a fractured, weathered shale using discrete-fracture/matrix-diffusion and equivalent porous medium models

Description: Simulations of a tritium tracer experiment in fractured shale saprolite, conducted at the Oak Ridge National Laboratory, were performed using 1D and 2D equivalent porous medium (EPM) and discrete-fracture/matrix-diffusion (DFMD) models. The models successfully reproduced the general shape of the breakthrough curves in down-gradient monitoring wells which are characterized by rapid first arrival, a slow-moving center of mass, and a persistent ``tail`` of low concentration. In plan view, the plum… more
Date: May 1, 1996
Creator: Stafford, Paige L.
Partner: UNT Libraries Government Documents Department
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