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2,658 Matching Results
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A Study of Anti-collision Multi-tag Identification Algorithms for Passive RFID Systems
The major advantages of radio frequency identification (RFID) technology over barcodes are that the RFID-tagged objects do not require to be in line-of-sight with the reader for their identification and multiple objects can be read simultaneously. But when multiple objects are read simultaneously there is always a problem of collision which reduces the efficiency of the system. This thesis presents a comprehensive study of the dynamic framed slotted ALOHA (DFSA)-based anti-collision multi-tag identification algorithms for passive RFID system. Performance of various DFSA algorithms is compared through extensive simulation results. In addition, a number of simple performance improvement techniques have also been investigated in this thesis, including improved estimation techniques for the number of tags in each read cycle and a low-complexity heuristic stopping criterion that can be easily implemented in the practical system.
Date:
May 2010
Creator:
Kamineni, Neelima
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Speaking up: Applying the Theory of Planned Behavior to Bystander Intervention in Racism
Because racism remains a significant issue in society, and many victims of racism do not speak up for themselves when faced with racism, it is important to explore how witnesses to racist events may react and intervene upon observing racism toward others. Thus, the current study explored how participants (bystanders) reacted verbally to racist comments made by a confederate during a partner activity, as well as how participants discussed their reactions in post-interviews. Forty college students participated in the study, and three of the participants verbally intervened upon hearing the racist statements. Ajzen's theory of planned behavior was utilized as a framework, and examination of the results indicated that components of the theory as well as social constructions of racism and appropriateness of intervention behaviors affect intervention outcomes. Theoretical, methodological, and practical implications, as well as suggestions for future research are included.
Date:
May 2010
Creator:
Hall, Camille Ashley
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Comparison of Heteranthera Dubia (Jacq.) MacM.-associated Macroinvertebrates Between Georgraphical Regions in the United States
Macroinvertebrates associated with the aquatic plant, water stargrass (Heteranthera dubia), were sampled from 12 waterbodies in four regions of the United States from June to August 2005. Taxa richness, evenness, and diversity were lowest in the Lower Midwest (LMW) region, and higher in Northern sites, especially the Upper Midwest (UMW), and Northeast (NE). While relative abundance varied from site to site and region to region, utilization of the plant by functional groups remained fairly constant. Collector-gatherers consistently comprised the largest portion of invertebrates sampled. The shredder/ herbivore functional group comprised an average of 17 % of total groups. Through an exhaustive literature review, it was found that shredder/ herbivores of water stargrass have not been reported in the literature. Because of this, the herbivore group was analyzed separately and consisted of 2,383 specimens representing 23 species. The most common groups were Rhopalosiphum sp., Nectopsyche spp. and chironomids. No differences were found in herbivore diversity or evenness between sampling regions, but species richness was significantly different.
Date:
May 2010
Creator:
Harms, Nathan Earl
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Modulation of the Coelomic Fluid Protein Profile in the Earthworm, Lumbricus Terrestris, After Exposure to Copper as Copper Sulfate
Proteomic techniques were used to analyze the protein profile of earthworm, Lumbricus terrestris, coelomic fluid collected by either whole body dissection method or the coelomic cavity puncture method. Data demonstrated that collection of coelomic fluid using the coelomic cavity puncture method protocol resulted in a 32% reduction, 377 +/- 4.5 vs 253+/- 19.9 (p=0.0007), in the number of individual proteins. It was determined that the coelomic cavity puncture method yielded a "cleaner" preparation, one less contaminated with extraneous proteins from intestinal tissue, gut contents, and body wall materials. This protocol was used in all later studies. The same proteomic techniques were used to evaluate the effects that exposure to Cu (1.0 μg/cm2) as CuSO4 had on the earthworm coelomic fluid profile. Comparison of protein profile from exposed earthworms demonstrated a significant reduction in the number of proteins expressed (184 ± 2.64 vs 253 ±19.9 p=0.0192) when compared to control organisms. Cu exposure also resulted in a modulation of the protein profile with treated earthworms expressing 47 new proteins that were not identified in unexposed worm coelomic fluid. Additionally, 116 proteins found in coelomic fluid collected from normal worms were absent in Cu exposed organisms. Finally, 137 proteins were conserved or …
Date:
May 2010
Creator:
Herring, Reese
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Teaching Points in Comparing the Great Depression to the 2008-2009 Recession in the United States
For an introductory macroeconomics course, the discussion of historical relevance helps foster important learning connections. By comparing the Great Depression to the 2008-2009 recession, a macroeconomics instructor can provide students with connections to history. This paper discusses the major causes of each recession, major fiscal policy and monetary policy decisions of both recessions, and the respective relevance in teaching the relationship of each policy to gross domestic product. The teaching points addressed in this paper are directed towards an introductory college-level macroeconomics course, incorporating a variety of theories from historical and economic writers and data from government and central bank sources. A lesson plan is included in an appendix to assist the instructor in implementing the material.
Date:
May 2010
Creator:
Killian, Tiffany Noel
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Adaptive Advantages of Carotenoid Pigments in Alpine and Subalpine Copepod Responses to Polycyclic Aromatic Hydrocarbon Induced Phototoxicity
Alpine zooplankton are exposed to a variety of stressors in their natural environment including ultraviolet radiation. Physiological coping mechanisms such as the accumulation of photoprotective compounds provide these zooplankton protection from many of these stressors. Elevated levels of carotenoid compounds such as astaxanthin have been shown to help zooplankton survive longer when exposed to ultraviolet radiation presumably due to the strong antioxidant properties of carotenoid compounds. This antioxidant capacity is important because it may ameliorate natural and anthropogenic stressor-induced oxidative stress. While previous researchers have shown carotenoid compounds impart increased resistance to ultraviolet radiation in populations of zooplankton, little work has focused on the toxicological implications of PAH induced phototoxicity on zooplankton containing high levels of carotenoid compounds. This thesis discusses research studying the role that carotenoid compounds play in reducing PAH induced phototoxicity. By sampling different lakes at elevations ranging from 9,500' to 12,700' in the front range of the Colorado Rocky Mountains, copepod populations containing different levels of carotenoid compounds were obtained. These populations were then challenged with fluoranthene and ultraviolet radiation. Results discussed include differences in survival and levels of lipid peroxidation among populations exhibiting different levels of carotenoid compounds, and the toxicological and ecological implications of …
Date:
May 2010
Creator:
Kovach, Matthew James
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
X, An Analytical Approach to John Chowning's Phoné
The analysis of computer music presents new challenges to the field of music theory. This study examines the fixed media composition Phoné by John Chowning from its aesthetic perspective, compositional theory and computer sound synthesis techniques. Fast Fourier Transform analyses are used to create spectrograms. The findings from the spectrograms are juxtaposed with compositional philosophies of John Chowning, Jean-Claude Risset, Pierre Schaeffer and Arnold Schoenberg and the techniques are represented via PureData patches.
Date:
May 2010
Creator:
Krämer, Reiner
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
"Being" a Stickist: A Phenomenological Consideration of "Dwelling" in a Virtual Music Scene
Musical instruments are not static, unchanging objects. They are, instead, things that materially evolve in symmetry with human practices. Alterations to an instrument's design often attend to its ergonomic or expressive capacity, but sometimes an innovator causes an entirely new instrument to arise. One such instrument is the Chapman Stick. This instrument's history is closely intertwined with global currents that have evolved into virtual, online scenes. Virtuality obfuscates embodiment, but the Stick's world, like any instrument's, is optimally related in intercorporeal exchanges. Stickists circumvent real and virtual obstacles to engage the Stick world. Using an organology informed by the work of Heidegger and Merleau-Ponty, this study examines how the Chapman Stick, as a material "thing," speaks in and through a virtual, representational environment.
Date:
May 2010
Creator:
Hodges, Jeff
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Routine Leisure Activities and Adolescent Marijuana Use: Moderating Effects of Family Structure
How adolescents spend their time is a crucial predictor of their engagement in delinquency. Activities with peers away from direct supervision of adults are of concern as more opportunities and motivation to use marijuana exist in such situations. However, adolescents may vary in their propensity to use marijuana when faced the opportunity. Especially adolescents living with a single parent may have a higher propensity compared to those from two-parent households to use marijuana due to reduced parental monitoring and increased peer attachment. This thesis investigates the moderating effects of family structure on the routine leisure activities and adolescent marijuana use relationship, using data from Monitoring the Future Study 2007, 12th Grade Survey. The results provide partial support for the moderating effects.
Date:
May 2010
Creator:
Aksu, Gokhan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Environmental Philosophy and the Ethics of Terraforming Mars: Adding the Voices of Environmental Justice and Ecofeminism to the Ongoing Debate
Questions concerning the ethics of terraforming Mars have received some attention from both philosophers and scientists during recent decades. A variety of theoretical approaches have been supplied by a number of authors, however research pursuant to this thesis has indicated at least two major blindspots in the published literature on the topic. First, a broad category of human considerations involving risks, dangers, and social, political, and economic inequalities that would likely be associated with efforts to terraform Mars have been woefully overlooked in the published literature to date. I attempt to rectify that oversight by employing the interpretive lens of environmental justice to address questions of environmental colonialism, equality in terms of political participation and inclusion in decision making structures, risks associated with technological progressivism, and responses to anthropogenic climate change. Only by including the historically marginalized and politically disenfranchised "voices," of both humans and nonhumans, can any future plan to terraform Mars be deemed ethical, moral or just according to the framework provided by environmental justice. Furthermore, broader political inclusion of this sort conforms to what ecofeminist author Val Plumwood calls the "intentional recognition stance" and provides an avenue through which globally societies can include nonanthropocentric considerations in decision …
Date:
August 2013
Creator:
French, Robert Heath
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Military-diplomatic Adventurism: Communist China's Foreign Policy in the Early Stage of the Korean War (1950-1951)
The thesis studies the relations of Communist China's foreign policy and its military offensives in the battlefield in Korean Peninsula in late 1950 and early 1951, an important topic that has yet received little academic attention. As original research, this thesis cites extensively from newly declassified Soviet and Chinese archives, as well as American and UN sources. This paper finds that an adventurism dominated the thinking and decision-making of Communist leaders in Beijing and Moscow, who seriously underestimated the military capabilities and diplomatic leverages of the US-led West. The origin of this adventurism, this paper argues, lays in the CCP's civil war experience with their Nationalist adversaries, which featured a preference of mobile warfare over positional warfare, and an opportunist attitude on cease-fire. This adventurism ended only when Communist front line came to the verge of collapse in June 1951.
Date:
August 2013
Creator:
Zhong, Wenrui
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Finding Terroir in Southwest Iowa
Terroir combines the physical landscape of the vineyard with the grapevines and the methods and techniques used to produce wine from the grapes. This study used a GIS to identify the characteristics of the physical landscape in Pottawattamie, Mills, Montgomery, Fremont, and Page counties in southwestern Iowa. The components were combined in the GIS using a weighted linear index to identify areas suitable for vineyard development and to identify the general characteristics of the area. Vineyard owners were interviewed to help determine the weighting system to use in the GIS and to determine their perceptions of how the physical landscape impacts their vineyards, as well as to determine what grape varieties they plant in their vineyards and their decisions on making wine from these grapes. This information was collected to identify whether the vineyard owners had developed a sense of place for their vineyards and how this sense might aid them in the development of a terroir for their wines. The resulting perceptions about the individual wineries were then considered in conjunction with the results from the GIS modeling to understand how the physical landscape influences the concepts of sense of place and terroir in southwest Iowa. The physical landscape …
Date:
August 2013
Creator:
Deines, Dory
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
L'emploi variable des signes diacritiques dans le français tchaté : une étude variationniste en temps apparent .
After providing an historical overview of the French spelling system and orthographic variation, this study analyzes selected internal (i.e., linguistic) factors and one external (i.e., social) factor that can influence the use of diacritics in online French-language chat sessions. From a corpus of synchronous computer-mediated communication, 3,855 tokens of graphemes capable of bearing diacritics were coded with the following scheme: Letter, Diacritic, Grapheme (i.e., Letter and Diacritic combined), Date of Participation, and Age Group of Participant. A multivariate (VARBRUL) analysis determined that Grapheme exerts the most influence on variation.
Date:
May 2010
Creator:
Al-Rashdan, Omar
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Enemy of My Enemy Is What, Exactly? the British Flanders Expedition of 1793 and Coalition Diplomacy
The British entered the War of the First Coalition against Revolutionary France in 1793 diplomatically isolated and militarily unprepared for a major war. Nonetheless, a French attack on the Dutch Republic in February 1793 forced the British to dispatch a small expeditionary force to defend their ally. Throughout the Flanders campaign of 1793, the British expeditionary force served London as a tool to end British isolation and enlist Austrian commitment to securing British war objectives. The 1793 Flanders campaign and the Allied war effort in general have received little attention from historians, and they generally receive dismissive condemnation in general histories of the French Revolutionary Wars. This thesis examines the British participation in the 1793 Flanders campaign a broader diplomatic context through the published correspondence of relevant Allied military and political leaders. Traditional accounts of this campaign present a narrative of defeat and condemn the Allies for their failure to achieve in 1793 the accomplishments of the sixth coalition twenty years later. Such a perspective obscures a clear understanding of the reasons for Allied actions. This thesis seeks to correct this distortion by critically analyzing the relationship between British diplomacy within the Coalition and operations in Flanders. Unable to achieve …
Date:
August 2012
Creator:
Jarrett, Nathaniel W.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Examining the Role of Latitude and Differential Insolation in Asymmetrical Valley Development
Valley development through erosional processes typically tends to create symmetrical valleys. Over time, water cuts through the substrate to create valleys, gorges, and canyons for which the sides are the valley are evenly sloped. However, there are anomalies to this process. Asymmetrical valleys have been well-documented even in areas of uniform substrate or little tectonic uplift. One proposed explanation for the asymmetry of these valleys is differential insolation. This may lead to different microclimates from one slope to another which alter the rate and extent of erosion. Since the differences in received insolation vary with latitude (especially in streams that flow along an east/west axis), it follows that the degree of asymmetry should also vary with latitude if differential insolation is a primary driving factor in the development of these valleys. To evaluate if insolation plays a role in the development of asymmetrical valleys, this study examines variability in asymmetry across 447 valleys in nine study areas located at different latitudes. The degree of asymmetry for each valley was measured by using 30 meter resolution digital elevation models (DEMs) to determine the slope angle of each side of the valley. Asymmetry was measured by computing a ratio of the average …
Date:
August 2013
Creator:
Curran, Lorna L.
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Programming for the Latino Youth: a Content Analysis of Prime Time Television Programs By Three Spanish-language Broadcast Networks
This study reviews U.S. Spanish-language broadcast networks' prime time programming content targeted to the Latino youth audience. It explores the relationship between the Latino youth and prime time programming by Spanish-language broadcast networks and how they seek to attract this market as is reflected in the characteristics and quantity of their content and preferred formats by using the strategic management theory. This study identifies the amount and type of prime time programming that was catered to the Latino youth audience between 2003 and 2012 by the three major Spanish-language networks: Univision, Telemundo, and Telefutura. An observed pattern reveals that prime time programming targeting Latino teenagers is relatively smaller and older in comparison to programming delivered through the general programming.
Date:
August 2013
Creator:
Vazquez, Gabriel
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Comparative Phyto-uptake Across Distribution Coefficients of Pharmaceutical Compounds and Aquatic Macrophytes: Carbamazepine and Amiodarone Uptake in Lemna Spp
Few studies have been conducted on the effectiveness of phytoremediation of pharmaceutical compounds, although the persistent and non-acutely toxic nature of many of these compounds in today's water bodies may yield an ideal application for this practice. To quantify the potential effectiveness of plant uptake, kinetic and proportional bioconcentration factors (BCFk, and BCFp, respectively) in nanograms (ng) carbamazepine and amiodarone per gram (g) wet weight plant tissue for Lemna spp. were determined utilizing a 14-day continuous flow-through study. Samples were analyzed using isotope dilution liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) running in positive ion mode. Kinetic BCF was estimated at 0.538, while proportional BCF was estimated at 0.485. Kinetic BCF for the amiodarone study was estimated at 23.033, whereas proportional BCF was estimated at 41.340. Possible contamination of the C18 column and peristaltic pump failure may have impacted uptake results. In light of variability and current lack of research in the field, this work should be considered exploratory rather than conclusive.
Date:
August 2013
Creator:
Woodard, Jennifer Kristin
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Repetition and Difference: Parodic Narration in Kander and Ebb's "The Scottsboro Boys"
The American musical team John Kander and Fred Ebb created many celebrated works, yet musicologists have carried out little research on those works. This study examines the role of music in the parodic narration of Kander and Ebb's final collaboration, The Scottsboro Boys. Kander and Ebb use minstrelsy to tell the story of the historic Scottsboro Boys trials with actors portraying the Scottsboro Boys as minstrels; at the same time, they employ a number of devices to subvert minstrelsy stereotypes and thereby comment on racism. Drawing on African American literary theory, sociolinguistics, and Bakhtin's dialogism, this study illuminates how Signifyin(g), a rhetorical tradition used to encode messages in some African American communities, is the primary way the actors playing the Scottsboro Boys subvert through minstrelsy. This study not only contributes to the discussion of Signifyin(g) in African American musicals and theatre as a tool of subversion, but also provides an example of non-African American creators—Kander and Ebb—using Signifyin(g) devices. They use these in the music and the book; in particular, Kander and Ebb do some Signifyin(g) on Stephen Foster's plantation melodies.
Date:
August 2013
Creator:
Wolski, Kristin Anne
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A Vehicle-collision Learning System Using Driving Patterns on the Road
Demand of automobiles are significantly growing despite various factors, steadily increasing the average number of vehicles on the road. Increase in the number of vehicles, subsequently increases the risk of collisions, characterized by the driving behavior. Driving behavior is influenced by factors like class of vehicle, road condition and vehicle maneuvering by the driver. Rapidly growing mobile technology and use of smartphones embedded with in-built sensors, provides scope of constant development of assistance systems considering the safety of the driver by integrating with the information obtained from the vehicle on-board sensors. Our research aims at learning a vehicle system comprising of vehicle, human and road by employing driving patterns obtained from the sensor data to develop better systems of safety and alerts altogether. The thesis focusses on utilizing together various data recorded by the in-built embedded sensors in a smartphone to understand the vehicle motion and dynamics, followed by studying various impacts of collision events, types and signatures which can potentially be integrated in a prototype framework to detect variations, alert drivers and emergency responders in an event of collision.
Date:
August 2013
Creator:
Urs, Chaitra Vijaygopalraj
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Effects of Suspended Multi-Walled Carbon Nanotubes on Daphnid Growth and Reproduction
Multi-walled carbon nanotube aggregates can be suspended in the aqueous phase by natural organic matter. These aggregates are ingested by filter feeding zooplankton. Ingested aggregates result in decreased growth and decreased reproduction. These effects may be caused by reduction in energy input from normal feeding behavior. pH alters natural organic matter structure through changes in electrostatic repulsion. Altered natural organic matter structure changes multi-walled carbon nanotube aggregate size. This size variation with variation in pH is significant, but not large enough a change in size to alter toxicity, as the aggregate size range remains well within the particle size selection of the organisms.
Date:
May 2010
Creator:
Alloy, Matthew Michael
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Design and Application of Phased Array System
Since its invention, phased array has been extensively applied in both military and civil areas. The applications include target detecting and tracking, space probe communication, broadcasting, human-machine interfaces, and remote sensing. Although the phased array applications show a broad range of potential market, there are some limitations of phased array's development: high cost, complex structure, narrow bandwidth, and high power consumption. Therefore, novel ideas are needed to reduce these constraints. In this thesis, several new approaches about the design and application of phased array are presents. First, the principle of phased array and fundamental design equations are introduced. Second, a new application of phased array antenna for radar respiration measurement is presented. By integrating a 4×4 Butler matrix with four-element antenna array, there will be four distinct main beams in radiation pattern. This new approach can improve the measurement accuracy and realize a high detecting rate. Third, a compact phased array antenna system based on dual-band operations is introduced. Dual-band function can make N-antenna system obtain 2N unique radiation beams (N is an integer) and achieve a significant size reduction compared to the conventional single-band system. To verify the design concept, a four-element phased array antenna working at 5GHz and …
Date:
August 2013
Creator:
Ren, Han
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
The Ideological Appropriation of La Malinche in Mexican and Chicano Literature
La Malinche is one of the most controversial figures in Mexican and Chicano literature. The historical facts about her life before and after the Spanish Conquest are largely speculative. What is reliably known is that she had a significant role as translator, which developed into something of mythic proportions. The ideological appropriation of her image by three authors, Octavio Paz, Laura Esquivel and Cherríe Moraga, are explored in this thesis. The full extent of the proposed rendition of La Malinche by Octavio Paz is the basis of the second chapter. The conclusion drawn by Paz, in The Labyrinth of Solitude (1950) is that La Malinche is what he calls la chingada [the raped/violated one] and proposes that all women are always open to conquest, sexually and otherwise. Laura Esquivel's novel Malinche (2006) is a re-interpretation that focuses on the tongue as the source of power and language as the ultimate source of autonomy for La Malinche. This aspect of La Malinche and the contrast of Paz's understanding are the basis of the third chapter of this thesis. Cherríe Moraga, in Loving in the War Years (1983), proposes that if women are to be traitors, it is not each other that …
Date:
August 2013
Creator:
Moriel Hinojosa, Rita Daphne
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
Metabolic Engineering in Plants to Control Source/sink Relationship and Biomass Distribution
Traditional methods like pruning and breeding have historically been used in crop production to divert photoassimilates to harvested organs, but molecular biotechnology is now poised to significantly increase yield by manipulating resource partitioning. It was hypothesized that metabolic engineering in targeted sink tissues can favor resource partitioning to increase harvest. Raffinose Family Oligosaccharides (RFOs) are naturally occurring oligosaccharides that are widespread in plants and are responsible for carbon transport, storage and protection against cold and drought stress. Transgenic plants (GRS47, GRS63) were engineered to generate and transport more RFOs through the phloem than the wild type plants. The transgenic lines produced more RFOs and the RFOs were also detected in their phloem exudates. But the 14CO2 labeling and subsequent thin layer chromatography analysis showed that the RFOs were most likely sequestered in an inactive pool and accumulate over time. Crossing GRS47 and GRS63 lines with MIPS1 plants (that produces more myo-inositol, a substrate in the RFO biosynthetic pathway) did not significantly increase the RFOs in the crossed lines. For future manipulation of RFO degradation in sink organs, the roles of the endogenous α-galactosidases were analyzed. The alkaline α-galactosidases (AtSIP1 and AtSIP2 in Arabidopsis) are most likely responsible for digesting RFOs …
Date:
August 2013
Creator:
Lahiri, Ipsita
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library
A Study of Mechanisms to Engineer Fine Scale Alpha Phase Precipitation in Beta Titanium Alloy, Beta 21S
Metastable b-Ti alloys are titanium alloys with sufficient b stabilizer alloying additions such that it's possible to retain single b phase at room temperature. These alloys are of great advantage compared to a/b alloys since they are easily cold rolled, strip produced and can attain excellent mechanical properties upon age hardening. Beta 21S, a relatively new b titanium alloy in addition to these general advantages is known to possess excellent oxidation and corrosion resistance at elevated temperatures. A homogeneous distribution of fine sized a precipitates in the parent b matrix is known to provide good combination of strength, ductility and fracture toughness. The current work focuses on a study of different mechanisms to engineer homogeneously distributed fine sized a precipitates in the b matrix. The precipitation of metastable phases upon low temperature aging and their influence on a precipitation is studied in detail. The precipitation sequence on direct aging above the w solvus temperature is also assessed. The structural and compositional evolution of precipitate phase is determined using multiple characterization tools. The possibility of occurrence of other non-classical precipitation mechanisms that do not require heterogeneous nucleation sites are also analyzed. Lastly, the influence of interstitial element, oxygen on a precipitation …
Date:
August 2013
Creator:
Behera, Amit Kishan
Object Type:
Thesis or Dissertation
System:
The UNT Digital Library