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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.
151

A study of the fracture mechanism of concrete

Glancy, John James, 1941- January 1966 (has links)
No description available.
152

Stochastic Estimation of Hydraulic Spatial Properties

Xiang, Jianwei January 2007 (has links)
A tomographic survey provides different coverages and perspectives on subsurface heterogeneity--incompletely overlapping information about the subsurface. Fusion of these pieces of information expands and enhances the capability of a conventional survey, provides cross-validation, and constrains inherently ill-posed field-scale inverse problems. In this study, we explore the possibility of using river stage variation for basin-scale subsurface tomographic surveys. Basin-scale tomography requires energy sources of great strengths; spatially and temporally varying natural stimuli are ideal energy sources for this purpose. Specifically, we use numerical models to simulate groundwater level changes in response to temporal and spatial variations of river stage in a hypothetical groundwater basin. We then exploit the relation between temporal and spatial variations of well hydrographs and river stage to image the heterogeneous characteristics of the basin.Next, we apply the hydraulic tomography testing technique and analysis algorithm to synthetic fractured media. The application aims to explore the potential utility of the technique and the algorithm for characterizing fracture zone distribution and their connectivity. Results of this investigation show that using hydraulic tomography with a limited number of wells can map satisfactorily the fracture zone distribution and the general pattern of its connectivity although estimated hydraulic property fields are smooth. As the number of wells and monitoring ports increases, the fracture zone distribution and connectivity becomes more vivid and the estimated hydraulic properties approach the true values.Further we develop a new parameter identification method that allows for simultaneous inclusion of all observed hydrographs from hydraulic tomography to map aquifer heterogeneity. A procedure is then recommended to diagnose and denoise observed hydrographs. Subsequently, we introduce methods that exploit these processed hydrographs for estimating effective parameters, boundary conditions, and statistical spatial structures of heterogeneity, which are the required inputs for the new hydraulic tomography analysis method. This new method and the data processing procedure are tested in a synthetic aquifer and subsequently applied to a sand box experiment. The estimated parameter fields for the sand box experiment are validated by predicting the head distribution induced by an independent pumping test, which was not used in the hydraulic tomography analysis.
153

Modeling fluid flow through single fracture using experimental, stochastic, and simulation approaches

Alfred, Dicman 30 September 2004 (has links)
This research presents an approach to accurately simulate flow experiments through a fractured core using experimental, stochastic, and simulation techniques. Very often, a fracture is assumed as a set of smooth parallel plates separated by a constant width. However, the flow characteristics of an actual fracture surface are quite different, affected by tortuosity and the impact of surface roughness. Though several researchers have discussed the effect of friction on flow reduction, their efforts lack corroboration from experimental data and have not converged to form a unified methodology for studying flow on a rough fracture surface. In this study, an integrated methodology involving experimental, stochastic, and numerical simulations that incorporate the fracture roughness and the friction factor is shown to describe flow through single fractures more efficiently. Laboratory experiments were performed to support the study in quantifying the flow contributions from the matrix and the fracture. The results were used to modify the cubic law through reservoir simulations. Observations suggest that the fracture apertures need to be distributed to accurately model the experimental results. The methodology successfully modeled fractured core experiments, which were earlier not possible using the parallel plate approach. A gravity drainage experiment using an X-ray CT scan of a fractured core has also validated the methodology.
154

Functional Outcomes in the Aged with Hip Fractures: A Systematic Review of Randomized Clinical Trials

Hoang-Kim, Amy Milena 14 July 2009 (has links)
Hip fracture trials have used a wide range of patient-reported outcomes (PRO) suggesting a lack of consensus among clinicians on what are considered the most relevant functional outcomes. We conducted a systematic review to identify the outcomes used in hip fracture randomized controlled trials (RCTs). We hypothesized that there had been an increase in numbers of PROs over time and the health status measure, SF-36, would be used the most. A database search and screening yielded 86 original trials. The mean Detsky score (and standard error) for quality was: 75.8% ± 1.76%. There was a trend in the increase of functional outcome; however, the SF-36 was used only in (10 out of 86) 11.6% trials. Both the ADL-Katz Index and HHS have lower respondent burden than the SF36 which may contribute to their frequent use in hip RCTs. There is a lack of applicable measures suitable for patients with dementia.
155

Strength characterization of thin-wall hollow ceramic spheres from slurries

Adicks, Michael Kent 05 1900 (has links)
No description available.
156

Fracture mechanisms of an alumina ceramic at elevated temperatures

Britt, James Marcel 08 1900 (has links)
No description available.
157

A comparison atlas of electron and scanning electron fractrography.

Hubbard, James Lee 08 1900 (has links)
No description available.
158

An investigation of the effect of thermal gradients on fracture

Yu, Hui-Ming 12 1900 (has links)
No description available.
159

Effect of stress state and strain on particle cracking damage evolution in 5086 wrought al-alloy

Balasundaram, Arunkumar 12 1900 (has links)
No description available.
160

A simple model of dynamic cleavage

Kan, Han Pin 08 1900 (has links)
No description available.

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