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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.
341

Simulation of thermally active and pH-sensitive polymers for conformance control

Onbergenov, Ulan 02 August 2012 (has links)
A waterflood has been used as a secondary recovery process to maintain the reservoir pressure and displace the oil towards the producer. However, the existence of high-permeability zones (thief zones) can cause early water breakthrough and excessive water production, thus, leaving a significant amount of oil bypassed in heterogeneous reservoirs. In this work, thermally active (Bright Water®) and pH-sensitive polymers have been proposed as an in-depth conformance tool with detailed simulation studies. Thermally active polymers are triggered by temperature change, whereas pH-sensitive polymers are triggered by pH change. Upon activation, polymers provide high resistance to subsequent fluid flow and divert the flow into adjacent unswept zones. As a result, this leads to improved sweep efficiency, low oil-water-ratio, and incremental oil recovery. The modeling of a pH-sensitive polymer was based on the principles of the microgel modeling procedure developed by Huh et al. (2005). In addition, a modified model was developed to calculate equilibrium swelling ratio explicitly in terms of pH and ionic strength of solution instead of using a root-finding algorithm. Thermal active polymers were modeled in terms of gelation reaction, gel viscosity, gel adsorption, and permeability reduction factor. Thermally active and pH-sensitive polymers were coupled with UTGEL reservoir simulator in an attempt to assess applicability of these gels as a conformance tool. Sensitivity analysis studies were conducted through 3D synthetic models to investigate technical feasibility of thermally active and pH-sensitive polymers as an in-depth conformance tool. Results indicated that incremental oil recovery and conformance control depend on the polymer concentration, slug size, permeability contrast between matrix and thief zone, vertical to horizontal permeability ratio (kv/kh), treatment location, oil-to-water viscosity ratio, and adsorption level, among others. It is concluded in this study that the permeability contrast between matrix and thief zones appears to be one of the most important parameters that impacts treatment performance. Therefore, a high permeability contrast is a prerequisite to achieve technically and economically successful treatment. / text
342

Demographics and evolution of super massive black holes in quasars and galaxies

Salviander, Sarah Triplett, 1971- 04 September 2012 (has links)
This dissertation addresses the co-evolutionary relationship between central super-massive black holes and host galaxies. This relationship is suggested by observed correlations between black hole mass (M[subscript BH]) and properties of the host galaxy bulge. We first discuss investigation of the relationship between MBH and host galaxy velocity dispersion, [sigma subscript asterisk], for quasars in the Sloan Digital Sky Survey (SDSS). We derive MBH from the broad emission line width and continuum luminosity, and [sigma subscript asterisk] from the width of narrow forbidden emission lines. For redshifts z < 0.5, our results agree with the locally-observed M[subscript BH]- [sigma subscript asterisk] relationship. For 0.5 < z < 1.2, the M[subscript BH]- [sigma subscript asterisk] relationship appears to evolve with redshift in the sense that bulges are too small for their black holes. Part of this apparent trend can be attributed to observational biases, including a Malmquist bias involving the quasar luminosity. Accounting for these biases, we find approximately a factor of two evolution in the M[subscript BH]- [sigma subscript asterisk] relationship between the present and redshift z [approximately equal] 1. The second topic involves a search for the largest velocity dispersion galaxies in the SDSS. Black holes in quasars can have M[subscript BH]exceeding 5 billion M[mass compared to the sun], implying [sigma subscript asterisk] > 500 km s−1 by the local M[subscript BH]- [sigma subscript asterisk] relationship. We present high signal-to-noise HET observations for eight galaxies at redshift z < 0.3 from the SDSS showing large [sigma subscript asterisk] while appearing to be single galaxies in HST images. The maximum velocity dispersion we find is [sigma subscript asterisk] = 444 km s−1, suggesting either that quasar black hole masses are overestimated or that the black hole - bulge relationship changes at high black hole mass. The third topic involves work contributed to co-authored papers, including: (1) evidence for recoiling black holes in SDSS quasars, (2) the [sigma][O III] - [sigma subscript asterisk] relationship in active galactic nuclei (AGN), and (3) accretion disk temperatures and continuum colors in quasars. Lastly, we discuss research in progress, including: (1) possible physical influences on the width of narrow emission lines of SDSS AGN, including the gravitational effect of the black hole, and (2) a search for binary AGN in the SDSS using double-peaked [O III] emission lines. / text
343

A generalized method for rapid analysis of active interrogation systems for detection of special nuclear material

Armstrong, Hirotatsu 11 September 2013 (has links)
Detection of special nuclear material (SNM) being smuggled into the US through ports of entry has been identified as a crucial capability for ensuring the safety and security of the US from radiological threats. Programs such as the NNSA's Second Line of Defense aim to deploy detection systems, both domestically and abroad, in an attempt to interdict the SNM before it reaches its destination. Active interrogation (AI) is a technique that relies on the detection of emitted particles which are produced when SNM is bombarded with a source of high energy photons or neutrons. This work presents a general framework that allows for fast radiation transport modeling of AI scenarios by generating families of response functions which depict neutron, gamma, or electron radiation exiting various regions within the problem, per unit source of radiation entering the region. The solution for a given scenario, typically the detector count rate, is computed by injecting a source term into the first region and applying the appropriate response functions, in sequence, for each subsequent region. For the AI systems modeled in this work, the source is an electron beam in a linear accelerator. Subsequent response functions create and transport bremsstrahlung photons into the SNM, and transport neutrons born in the problem to a detector. The computed solution is comparable to that of a full Monte Carlo simulation, but is assembled in orders of magnitude less time from pre-computed response function libraries. The ability to rapidly compute detector spectra for complicated AI scenarios opens up research and analysis possibilities not previously possible, including conducting parametric studies of scenarios spanning a large portion of the threat space and generating detector spectra used for conditioning and testing of alarm algorithms. / text
344

The state of active living in Texas : understanding collaboration and capacity building

Atkins, Tracy Dour 14 November 2013 (has links)
This report addresses three important issues around active living and how planning, health and governmental agencies are addressing active living in their spheres of influence. Initially the report uses a literature review to determine if research shows that characteristics of the physical environment influence active lifestyle choices and behaviors. This review also includes whether state and local governments and non-profit agencies are incorporating active lifestyle goals in important planning and policy decisions affecting the local physical and natural environment. The literature review supports links between the physical environment and active living but does not establish a causal link. Regarding the question of whether state and local governments and non-profit agencies are incorporating active lifestyle goals in important planning and policy decisions, the research reveals that there is a low level of inclusion of health goals within planning efforts. The body of work in this report is focused on understanding the level of knowledge and the degree of cooperation among local actors around active living issues in Texas. The report explores this question through a survey targeted at public and non-profit organizations that have the potential to influence conditions supporting active lifestyles in Texas communities. While this survey and results focus on Texas communities, given the breadth of the responses, the results are likely applicable outside Texas. The research found collaboration around active living in Texas was widespread among the departments and organizations represented by the survey. Many communities have implemented active living programs or projects, however, most communities have not completed active living assessments to prioritize active living needs. Funding was the most important factor in addressing barriers to active living. Other important factors in addressing these barriers included education, sample policies and programs, best practices and case studies, and access to local experts and community groups. Strong community support and local government leadership were the most important factors in creating an environment that supports active learning. / text
345

Molecular dissection of reactive oxygen species-mediated oncotic cell death

Dong, Jing 28 August 2008 (has links)
Not available / text
346

Scanning electrochemical microscopy studies applied to biological systems

Mauzeroll, Janine 28 August 2008 (has links)
Not available / text
347

NEW MULTIFEEDBACK TYPE ACTIVE RC FILTERS

Sonu, Gene Ho, 1948- January 1978 (has links)
No description available.
348

An Accessible City An investigation using GIS into the potential for further development of the proposed major cycleways network for Christchurch, New Zealand

Martin, Aimee Selina January 2015 (has links)
As the future of the world’s oil reserves becomes progressively more uncertain, it is becoming increasingly important that steps are taken to ensure that there are viable, attractive alternatives to travel by private motor vehicle. As with many of New Zealand’s major urban centres, Christchurch is still exceptionally reliant on private motor vehicles; although a significant proportion of the population indicate that they would like to cycle more, cycling is still an underutilised mode of transport. Following a series of fatal earthquakes that struck the city in 2010 and 2011, there has been the need to significantly redevelop much of the city’s horizontal infrastructure – subsequently providing the perfect platform for significant changes to be made to the road network. Many of the key planning frameworks governing the rebuild process have identified the need to improve Christchurch’s cycling facilities in order to boost cycling numbers and cyclist safety. The importance of considering future growth and travel patterns when planning for transport infrastructure has been highlighted extensively throughout literature. Accordingly, this study sought to identify areas where future cycle infrastructure development would be advantageous based on a number of population and employment projections, and likely future travel patterns throughout the city. Through the use of extensive GIS analysis, future population growth, employment and travel patterns for Christchurch city were examined in order to attain an understanding of where the current proposed major cycleways network could be improved, or extended. A range of data and network analysis were used to derive likely travel patterns throughout Christchurch in 2041. Trips were derived twice, once with a focus on simply finding the shortest route between each origin and destination, and then again with a focus on cyclist safety and areas where cyclists were unlikely to travel. It was found that although the proposed major cycleways network represents a significant step towards improving the cycling environment in Christchurch, there are areas of the city that will not be well serviced by the current proposed network in 2041. These include a number of key residential growth areas such as Halswell, Belfast and Prestons, along with a number of noteworthy key travel zones, particularly in areas close to the central city and key employment areas. Using network analysis, areas where improvements or extensions to the proposed network would be most beneficial were identified, and a number of potential extensions in a variety of areas throughout the city were added to the network of cycle ways. Although it has been found that filling small gaps in the network can have considerable positive outcomes, results from the prioritisation analysis suggested that initially in Christchurch demand is likely to be for more substantial extensions to the proposed major cycleways network.
349

A case study of active traffic management : safety analysis and operations improvements using a queue warning system

Aung, Lily Kheng-Hwar 29 September 2011 (has links)
Active traffic management is a hot topic for addressing issues of highway congestion. It is the use of intelligent transportation systems to provide real time traffic information on highway conditions. In Austin, the segment of Interstate 35 between Riverside Drive and State Highway 71 experiences both congestion and safety issues. This report provides an introduction into the application of active traffic management through the use of a proposed queue warning system in the area. First, select crash data on the region is highlighted to present the safety conditions, particularly the type of collision and crash severity involved. Next, a proposed queue warning system design is described. This includes a description of the equipment used, methodology for system deployment, and expected outcomes. Finally, a computer simulation testing the operational performance of the queue warning system is performed using VISSIM, and the results are reported. This report aims to demonstrate the role that queue warning system and active traffic management may play in addressing metropolitan traffic needs. / text
350

Full-Scale Tilt Rotor Download Reduction

Beck, Stephen January 2013 (has links)
A large-scale model of a tiltrotor wing and flap was built and tested to determine how the size and spacing of fluidic actuators for active flow control should be scaled up from laboratory size models to aircraft size. Flow control was provided by sweeping jet actuators mounted in the flap follower. Chordwise pressure data was collected through pressure taps located along the model centerline. The maximum flap deflection to which the flow could be attached with actuation was compared to previous experiments on a 10% 3D model. An ideal actuator spacing was found and the momentum coefficient was comparable between the various sized models. These results were used in the design of an industrial wind tunnel-scale model of a wing built for cruise and tiltrotor-like download testing. These tests have shown that actuators located in the flap follower are effective in both the hover and cruise phases of flight.

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