Thesis (Ph.D.)--University of Wyoming, 2008. / Title from PDF title page (viewed on Mar. 8, 2010). Includes bibliographical references.

Following the Second World War department stores transitioned from the downtown establishments of the first half of the century to the enclosed shopping malls of the second; however, for a period of about six years, from 1945 to 1951, the standalone department store fulfilled the needs of suburbanites. During this struggle to define the new suburban shopping experience, Welton Becket and Walter Wurdeman designed Bullock's Pasadena--the first embodiment of their research-based "total design" philosophy. Today, Becket is best known for his iconic Capitol Records building and the assembly line efficiency of Welton Becket and Associates, but he devoted much of the late 1940s and 1950s to designing department stores and shopping centers. As store managers and fellow architects strained to build department stores for automobile, Becket emerged with a research-based solution that he later termed "total-design." Similar to the concept of Gesamtkunstwerk, Becket's "total-design" was a philosophy that required attention to nuance and detail--in the case of department stores this included furniture, fixtures, carpet, and even price tags and restaurant menus. But he also sought to support his designs with research and study.1 Before Becket designed Bullock's Pasadena, his first department store, he dedicated a year to analyzing the customers, employees, and efficiency of Bullock's. This investigation resulted in an open-plan store with flexible furnishings and a sympathetic approach to the automobile, including parking lots that integrated with the store's layout. Becket was not alone in his exploration of suburban department stores. Architects from around the country, including Raymond Loewy, Victor Gruen, John Graham, and Morris Ketchum, created their own prototypes for this new building typology. But many found it difficult to compete with Becket's extensive research and empirical method. Several stores, such as B. Altman's Miracle Mile branch on Long Island (1947) and Bamberger's branch in Morristown, New Jersey (1949), had to be renovated or relocated within ten years of opening, unable to keep pace with growing storage and parking demands. Becket, by contrast, studied population densities and demographics, freeway connections and traffic congestion to establish the number of parking spaces and their location on site. Instead of utilizing parking space ratios, favored by his peers, he relied on a wider scope of analysis to inform his designs. Bullock's Pasadena provides the basis for this study and demonstrates the evolution of Becket's design process that would come to define one of the world's largest architecture firms. / text

Mid-infrared lasers in the 3-5 µm range are important for wide variety of applications including trace gas sensing, infrared counter measures, free space optical communications, etc. GaSb-based type-I quantum well (QW) diode lasers are an attractive choice due to their relatively simple design and growth tolerances, as compared with quantum cascade lasers and interband cascade lasers. Excellent diode lasers have been demonstrated for wavelengths up to ~3.0 µm, employing GaInAsSb/AlGaAsSb QW active regions. But, device performance tends to degrade at longer wavelengths, due to Auger recombination and decreasing QW valence band offsets. In this work we look into the feasibility of using highly strained GaInAsSb/GaSb QWs as active regions for diode lasers operating at wavelengths beyond 3.0 µm. Heavy strain in the QW can improve valence band offset and also increase the splitting between the heavy and light hole bands which can help minimize Auger recombination. Through optimized molecular beam epitaxy (MBE) growth conditions we were able to incorporate up to 2.45 % compressive strain in these QWs enabling laser operation up to 3.4 µm at room temperature. An alternate path to extend the emission wavelength is to incorporate dilute quantities of nitrogen into the QW. Incorporating dilute quantities of substitutional nitrogen into traditional III-V’s strongly reduces the bandgap of the alloy. The advantage for the case of GaSb based dilute-nitrides is that the bandgap reduction is almost exclusively due to the lowering of the conduction band leaving the valence band offsets unaffected; thus providing a path to mitigating hole leakage while extending the emission wavelength. Although GaSb-based dilute-nitrides are a potentially elegant solution for extending the operating wavelength of GaSb-based type-I QW diode lasers, the luminescence efficiency of this material system has been relatively poor. This is most likely due to the presence of a high concentration of point defects, like nitrogen substitutional clusters. Through careful optimization of MBE growth conditions and post growth annealing, we demonstrate improved luminescence efficiency. With further optimization this material system can potentially extend the emission wavelength of GaSb-based type-I QW diode lasers even further into the mid-infrared spectrum. / text

published_or_final_version / abstract / toc / Earth Sciences / Master / Master of Philosophy

This research quantifies the seismic vulnerability of older reinforced concrete frame structures located in Mid-America. After designing a representative three-story gravity load designed reinforced concrete frame structure, a nonlinear analytical representation was used evaluate inter-story drift demands from simulated earthquake time histories that were representative for the region. Limit state story drift capacities were identified for FEMA 273 guidelines, nonlinear pushover analyses, and incremental dynamic analyses. Integrating these two quantities allowed for the creation of fragility curves which relates the probability of exceeding a particular limit state given an imposed spectral acceleration at the fundamental building period. These curves were then used to evaluate the seismic vulnerability of the representatively designed structure. The structure as originally designed was found to be inadequate to resist large lateral loading that would be typical for the Memphis area. So structural retrofit performed by increasing the column-to-beam strength ratio was evaluated by increasing the strength of the column members in the analytical model. The first retrofit raised the column-to-beam strength ratio to 1.2, which is currently required by the ACI code provisions. The second retrofit raised the column-to-beam strength ratio to 1.8, as suggested in previous studies. The story capacity, demand, and fragility curves were once again created for these retrofitted structures. Comparison of these fragility curves is discussed in relation to the retrofit strategy of column strengthening for older reinforced concrete frame structures in Mid-America.

No description available.

No description available.

Iceland is the land-based expression of the Mid-Atlantic Ridge and is one of the most volcanically active regions of the world. Volcanic eruptions on Iceland are a source of geological hazard to humans and the environment due to the release of ash, gases and lava. The composition of the material released is determined by the chemical composition of the surrounding bedrock and the magma upwelling from the Earth’s crust. The effects of historical eruptions on Iceland have been locally devastating and of global impact. The eruption of Lakagígar in 1783-1784 is known to have been the largest eruption in historical time, and is responsible for the death of ~22 % of theIcelandic population. Skeletal fluorosis is a disease that is sometimes observed following large volcanic eruptions. Volcanic ash can travel great distances in the upper atmosphere and spread over vast areas far away from the erupting volcano. Volcanic ash can change incomposition in the atmosphere, and bring about climate-changing effects. Most notably in recent times, violent ash eruptions can also cause problems to the aviation industry, when ash enters and damages airplane engines. Iceland has many active volcanoes and needs to ensure plans for future eruptions are in place. One such measure is an evacuation plan that protects people living close to an active volcano, such as the most lively on Iceland: Hekla, Katla and Eyjafjallajökull.

At fast spreading ridges such as the East Pacific Rise (EPR) volcanic eruptions are predicted to occur on a decadal timescale. Due to the limited ability to observe submarine eruptions, little is known about the magmatic processes occurring in the underlying magma chamber leading up to a volcanic event, including differentiation and magma mixing. The recent 2005-06 eruption at 9˚46’N-9˚56’N along the EPR provides a unique opportunity to gain a better understanding of rates of magma transport and magma replenishment associated with a typical eruption. This study examines the geochemistry of phenocrysts from the 2005-06 eruption in order to determine if they are in equilibrium with their host melt, or if magma mixing occurred prior to eruption. A diffusion model is used to model those crystals which are out of equilibrium with their erupted host to determine timescales of magma mixing. The major and trace element contents of plagioclase and olivine phenocrysts provides evidence for melts both more evolved (> 3.5 wt % MgO) and more primitive (< 8.8 wt % MgO) than those found within the host lava (7.7-8.3 wt % MgO; Goss et al., 2010). Glomerocrysts and resorbed crystals in equilibrium with evolved melts (3.5-6.5 wt % MgO) suggests an origin in a roof mush zone, and were disrupted and entrained into their host melt within days of eruption. Modelling of the zoning profiles of phenocrysts suggest the 2005-06 eruption was likely triggered by an influx of hotter, more primitive melt (~ 9.0 wt % MgO) which was injected into the melt lens a few weeks to months prior to the eruption. With decreasing time before eruption, there is an overall increase in the number of crystals with modelled timescales representing mixing events in the magma chamber. This increase in modelled timescales appears to correlate with the increase in seismic activity recorded prior to the eruption (Tolstoy et al., 2006). This suggests magma mixing events within the underlying magma chamber may be linked to seismic activity at fast spreading ridges. / Graduate / 0372 / 0996

The mid-infrared (MIR) system presented in the thesis is based on a sub-100-fs erbium-doped fiber laser operating at 1.55 µm. The output of the laser is split in two, each arm seeding an erbium-doped fiber amplifier. The output of the first amplifier is sent to a grating-based stretcher to be stretched to 50 ps before seeding the optical parametric chirped-pulse amplifier (OPCPA). The output of the second amplifier is coupled to a highly nonlinear fiber to generate the 1 µm needed to seed the a neodymium-doped yttrium lithium fluoride (Nd:YLF) system. This work represents the first time this synchronization scheme is used, and the timing jitter between the two arms at the OPCPA is reduced to 333 fs. The pump laser for the OPCPA is a regenerative amplifier producing 1.6 W followed by a double-pass amplifier, for a final output power of 2.5 W at 1 kHz. Etalons were inserted into the cavity of the regenerative amplifier to stretch the pulses to 50 ps The OPCPA consists of two potassium titanyl arsenate crystals in a noncollinear configuration. With three passes, the gain is 3.8 · 10 6 . Using a grating compressor, the pulse duration is reduced to 140 fs, with a power of 300 mW. Because of the reduction of the timing jitter, the amplitude stability is 1 %, which is a great improvement compare to existing systems. To generate ultrafast light in the MIR, an optical parametric amplifier is used, pumped ii by the output of the OPCPA and seeded with its 3-µm idler. Two crystals were tested, both in a single-pass configuration. For the first crystal, a 4-mm thick silver thiogallate, an efficiency of 7.4 % was reached, with 8.76 mW in the signal and 7.2 mW in the idler. For the second crystal, a 2-mm thick lithium gallium selenide, the efficiency was higher, reaching 10.8 %. The power for the signal was 11.5 mW, and for the idler, 11.11 mW. Using this new scheme, energies on par with current systems are achieved with much higher efficiencies.