Approved for public release; distribution is unlimited / Under meteorological conditions associated with extreme cold air outbreaks (CAO) off the U.S. East Coast, large ocean waves sometimes develop along the North Wall of the Gulf Stream. These wave events produce wave heights above those expected given the short fetch and moderate winds. The highest waves are often very localized, which suggests localized forcing by the atmosphere. In this study, results from four cases are examined to characterize the role of high resolution, mesoscale wind forcing in generating localized regions of large ocean waves during events with large air-sea temperature differences. A known "true" atmosphere is simulated through the use of the Navy's Coupled Oceanographic and Atmospheric Mesoscale Prediction System (COAMPS). Model surface wind output from COAMPS is used to generate a wave field using Wavewatch Three (WW3), which is then compared to buoy observations and ship reports. Results of these cases show the mesoscale wind forcing of ocean waves during CAO and the importance of mesoscale atmospheric modeling in localized generation of ocean wind waves. Additionally, empirical wave forecast techniques are compared to WW3 model output for these cases to further reinforce the mesoscale atmospheric forcing during rapid growth of wind wave events in fetch limited environments. / Lieutenant Commander, United States Navy

No description available.

Call number: LD2668 .T4 1952 H34 / Master of Science

During the Cold War, the inherent mistrust between the United States and the Soviet Union kept the two superpowers from cooperating even on many projects that might have proven mutually beneficial. Nevertheless, they were willing to work together at least occasionally; two such examples are the neutralizations of Austria (in 1955) and of Laos (in 1962). Despite very different world orders in those two countries at those times, the weaker superpowers in each contest, the Soviets in Austria and the Americans in Laos, took very similar actions. They followed the same three-stage process from the outbreak of the dispute to its negotiated conclusion. This process failed, however, in Vietnam. In trying to explain why neutralization failed so soon after its success, this thesis postulates a number of possible explanations. Ultimately, it was several factors coming to result in the failure of neutralization in Vietnam.

M.Ing. / The instability of partially stiffened stainless steel compression members due to local buckling of the flange element or flange and lip interaction has not been studied before. In this investigation the critical local buckling and post-buckling behavior of cold-formed partially stiffened stainless steel compression elements are studied in order to determine the applicability of the current design specification ...

In order to predict the strength of shear wall with cold-formed steel framing members, analytical models were reviewed. Multiple analytical models were studied, as well as twenty-one connection tests were performed. The connection tests consist of 50-ksi cold-formed steel framing track, different fastening configurations, and different sheathing thicknesses (1/8" and 1/2"). No.12 screw resulted in the highest peak load of all fastening configurations, while the rivet connection had the lowest peak load. In addition, failure modes were observed after conducting the connection tests including shear in fastening, screw pullout, and bearing in the sheathing. However, only the rivet and No.10 screw fastening configurations were used in the prediction analysis of the shear wall by the elastic model. Six shear wall tests were conducted on both panels (1/2"and 1/8" thickness). After doing the comparison between the experimental and the elastic model, the percentage difference for the 1/8" and the 1/2" polymer composite panels (3''along the edge and 6''along the chord stud), was very small. It was 6.2% for the 1/8" and 2.96% for the 1/2" panels. This means the analytical model can predict the shear wall peak load. However, the percentage difference was slightly higher being 7.4% for the 1/2" polymer composite panels with 6" along the perimeter with the 12" at the chord stud. After comparing the experimental values to the predicted value of shear walls, it was concluded that this model is the most appropriate analytical method for predicting the shear wall capacity framed with cold-formed steel sheathed with polymer composite panels. Many of these configurations were used in a prototype shelter that was constructed and built at the structural testing laboratory at the University of North Texas.

Memoria para optar al título de Ingeniero Civil Mecánico / Cold Spray es un proceso de manufactura aditiva en estado sólido, consistente en la deposición de material particulado en un substrato a altas velocidades. La gran ventaja de este proceso con respecto a otros procesos de Thermal Spray es que requiere de temperaturas de deposición bajo el punto de fusión, evitando problemas de difusión de gases y cambios microestructurales que limiten el rango de utilización de este proceso, además de disminuir la cantidad de calor necesario para realizar la adhesión. El objetivo principal de este trabajo de título fue estudiar la deformación por impacto de partículas de níquel y titanio en el proceso de Cold Spray a través de simulaciones numéricas. Los objetivos específicos fueron establecer una relación entre velocidad de impacto, temperatura y ángulo de impacto, con la adhesión de partículas con un substrato; analizar el impacto de las partículas con substratos de un mismo o diferente material; y determinar variables que permitan una deposición efectiva. Se realizaron simulaciones de impacto de una partícula esférica de 20 [µm] y un substrato, utilizando níquel y titanio. Se usaron como variables, las propiedades de los materiales, la temperatura, velocidad y ángulo antes del impacto, para obtener los esfuerzos, deformación y temperatura durante el impacto. Como recurso para realizar este trabajo de título, se trabajó con el software Abaqus/Explicit, con su módulo de análisis Abaqus/Explicit con un mallado Arbitrary Lagrangian Eulerian, para evitar la deformación excesiva. En total, se realizaron 40 simulaciones de impacto, analizados con 2 métodos distintos; el primero investigó la presencia de ASI (Adiabatic Shear Instability), no implicando la adhesión de la partícula con el substrato. El otro método logró obtener diferencias visibles a distintas velocidades (alrededor de los 500 y 600 [m/s] en los casos de níquel sobre níquel y titanio sobre titanio, y entre 600 y 700 [m/s] en los casos de níquel sobre titanio y titanio sobre níquel). A distintas temperaturas, aumentó la energía de adhesión a mayores temperaturas, y a distintos ángulos de impacto (disminuyendo la adhesión con un mayor ángulo de impacto). Si bien, las velocidades críticas logradas para níquel y titanio resultaron menores que las estimadas por la literatura [15] [28] [29], los resultados de la literatura estudiaron la presencia de ASI, lo cual no implica adhesión. Por lo tanto, existe la posibilidad de que los resultados obtenidos en este trabajo de título sean ciertos, sólo necesitarían demostración experimental para confirmar las velocidades críticas.

Thesis advisor: Robert Ross / Thesis advisor: Timothy Crawford / This paper examines the credibility issue in China's extended deterrent attempts during the Cold War. In its efforts to protect North Korea, North Vietnam and Kampuchea, how did China convey its threats, and why did these initiatives have differing results? First, I argue that signaling is the key explaining credibility of China's extended deterrent threats across space and time. While ambiguous signals ruined China's credibility in deterring challenges on North Korea and Kampuchea, clear-cut signals backed threats in China's attempts to save North Vietnam. Consequently, China's signals in the first two cases were disregarded or misunderstood but were perceived as expected in the last case. Secondly, the paper seeks to appraise the explanatory power of current theoretical approaches with regard to the effectiveness of extended deterrent threats. Balance of interests (BOI) and Balance of Capabilities (BOC) shed lights on sources of deterrence outcomes, but neither of them is sufficient to explain the cases. The paper concludes that China's peaceful rising is more likely if Beijing signals its interests and capabilities more clearly. / Thesis (MA) — Boston College, 2011. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Political Science.

A thesis submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Doctor of Philosophy Johannesburg 2017. / Introduction: Human rhinovirus (HRV) is the most prevalent virus detected in children with respiratory symptoms; however, its aetiological role during disease episodes remains unclear as detection of HRV is also ubiquitous among asymptomatic children. We evaluated the clinical epidemiology of HRV-associated disease among children hospitalised with severe and very severe pneumonia together with community control children living in Africa and Southeast Asia. In addition, we explored the associations between the molecular subtyping and nasopharyngeal viral loads of the HRV species and their ability to cause viraemia as potential markers for HRV disease. Methods: Using a case-control study conducted in seven countries, we compared the clinical characteristics of children (1-59 months of age) hospitalised with HRV-associated pneumonia between August 2011 - January 2014 and age-frequency matched controls. Nasopharyngeal swabs from the cases and controls were tested for HRV, together with 27 other respiratory pathogens, with quantitative real-time PCR assays. The 5’ NCR region of the HRV positive samples were sequenced to determine the species/strains of HRV and phylogenetic analysis was performed. Additionally, the blood samples from a limited number of cases (n=210) and controls (n=212) were tested for the presence of HRV viraemia and the 5’ NCR sequence of positive blood samples were further characterised. Results: Overall, HRV detection was 1.45-fold (aOR 95% CI: 1.29-1.62) higher among children hospitalised with pneumonia (24%) compared to controls (21%, P<0.005); including being 2.08-fold (28% vs 18%, aOR 95% CI: 1.75-2.47) more associated with case status among children 12-59 months of age. The HRV-associated cases were younger (13.1 months) than controls with HRV infection (15.4 months, P=0.001) and more likely to be malnourished (30% vs. 12%, P<0.001) and HIV-1 exposed (10% vs. 8%, P=0.046). HRV nasopharyngeal viral load was significantly higher among cases compared to controls (3.7 vs. 3.5 log10 copies/mL, P<0.001). Also, HRV viraemia was 7.02-fold (aOR 95% CI 1.70-28.94) more prevalent among cases (7%) compared to controls (2%, P=0.007). Moreover, HRV nasopharyngeal viral loads ≥4 log10 copies/mL differentiated between viraemia positive and negative cases. There was, however, no difference in the molecular subtyping of the HRV species prevalence among cases (HRV-A:48%; HRV-B:7%; HRV-C:45%) and controls (HRV-A:45%; HRV-B:10%; HRV-C:45%, P=0.496); as well as no evidence of seasonal or temporal clustering of the HRV species over time. Among cases, HRV detection was less likely to be associated with presence of radiographically confirmed pneumonia (40% vs 46%, P=0.001) or hospital stay >3 days (52% vs 61%, P=0.001). It was, however, positively associated with older age (13.1 months vs. 11.3 months, P<0.001) and presence of wheeze (46% vs. 31%, P<0.001) compared to the HRV uninfected cases. HRV was the sole virus detected in the 53% of cases and generally there were no differences in severity or clinical presentation among cases with HRV mono-infections compared to those with HRV-mixed infections. The HRV mono-infections, however, were associated with a 2.83-fold (aOR 95% CI: 1.44-5.53) higher case fatality ratio than cases with HRV and other viral mixed infections (10% vs. 5%, P=0.002). The HRV-associated case fatalities were more likely to have markers of bacterial co-infections compared to the HRV-associated cases that survived. Among the HRV species, HRV-C compared to HRV-A cases were older (12.1 vs. 9.4 months, P=0.033), more likely to present with wheeze (35% vs. 25%, P=0.031) and 2.59-fold (aOR 95% CI: 1.23-5.95) more likely to be associated with viraemia (12% vs. 2%, P=0.025). Conversely, the HRV-A infected cases were more likely to have radiographically confirmed pneumonia (46%) compared to HRV-C infected cases (36%, P=0.040) and HRV-A mono-infected cases were more likely to have hospital stay of >3 days (72%) than HRV-C mono-infected cases (54%, P=0.039). Conclusion: HRV detection, especially among children 1-5 years of age, was associated with severe lower respiratory tract infection; however, HRV detection was ubiquitous with a high degree of genetic diversity among both cases and controls. Thus the true etiologic role of HRV during childhood disease, especially among infants, remains uncertain. Nonetheless, HRV nasopharyngeal viral loads ≥4log10 copies/mL in conjunction with HRV viraemia are potential markers for HRV-associated severe respiratory disease. Among cases, HRV-A was associated with radiographically confirmed pneumonia and generally more severe disease than HRV-C which was more associated with viraemia and wheezing disease. / MT2017

Cold Spray is a solid-state additive manufacturing process that uses metallic feedstock powders to create layers on a substrate through plastic deformation. This process can be used for the repair of mechanical parts in the aerospace industry as well as for structural applications. Aluminum alloy powders, including Al 6061, 7075, 2024, and 5056, are typically used in this process as feedstock material. Since this process takes place all in the solid state, the properties and microstructure of the initial feedstock powder directly influence the properties of the final consolidated Cold Spray part. Given this, it is important to fully understand the internal powder microstructure, specifically the secondary phases as a function of thermal treatment. This work focuses on the understanding of the internal microstructure of Al 6061, 7075, 2024, and 5056 through the use of light microscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive x-ray spectroscopy, electron backscatter diffraction, and differential scanning calorimetry. Thermodynamic models were used to predict the phase stability in these powders and were calibrated using the experimental results to give a more complete understanding of the phase transformations during thermal processing.