Submitted by Claudinei Pracidelli (cpracide@ipen.br) on 2015-03-17T11:00:01Z No. of bitstreams: 0 / Made available in DSpace on 2015-03-17T11:00:01Z (GMT). No. of bitstreams: 0 / Neste trabalho foram analisados diferentes parâmetros geométricos para canais de fluxo em células a combustível tipo PEMFC e sua influência no desempenho do sistema, utilizando a fluidodinâmica computacional. Na análise dos modelos matemáticos, verificou-se que o modelo de aglomerado inundado descreve com maior fidelidade o comportamento de células a combustível, enquanto as equações de Butler-Volmer não consideram as perdas por transporte de massa. Foram avaliadas as seções transversais retangular, trapezoidal e em degrau. O modelo com canais de seção retangular apresentou desempenho elétrico ligeiramente superior, porém os canais com seção trapezoidal propiciam um melhor gerenciamento de água. Em todos os aspectos estudados, os canais com seção em degrau se comportaram de forma análoga aos canais com seção trapezoidal, porém sua construção é menos complexa. Também foram analisadas as configurações serpentina e interdigitada em células de 5 cm², e sua influência na uniformidade da densidade de corrente. Não foram observadas diferenças significativas quanto à eficiência elétrica entre células com as duas configurações. A configuração interdigitada propiciou distribuição mais uniforme de geração de corrente, pois os reagentes são fornecidos em alta concentração por uma maior área da célula. Assim, esta configuração é preferível para aumento de escala. / Dissertação (Mestrado em Tecnologia Nuclear) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Arabidopsis arenosa represents a promising model for studying the mechanisms underlying the adaptation to serpentine soil. Genetic basis of serpentine adaptation is still poorly known and A. arenosa possesses many advantages as a tool to complete that knowledge. The first step of this study was to reveal the presence of a local adaptation to serpentine soil in a population of A. arenosa. To do so, I used the data from a reciprocal transplant experiment realized between a Czech pair of serpentine - non-serpentine populations and I explored the phenotypes associated with the adaptation. Subsequently, I produced the F2 hybrids coming from crosses between serpentine - non-serpentine parents and I studied the expression of fitness traits in F2 plants growing in serpentine in order to estimate the number of loci underlying the adaptation which I compared with other studies. I confirmed the presence of a local adaptation, with the population of serpentine origin performing better than the non-serpentine population in the serpentine substrate of origin, associated with accumulation of heavy metals in the leaves. Analyses of the soil composition revealed differences in heavy metals and nutrients contents, Ca/Mg ratio and pH between the two localities. Those results fitted with the function of the candidate...

The prevailing conditions in metalliferous soils are usually hostile for plant growth, but some plant species are still able to thrive in these substrates. Festuca arundinacea Schreb. plants were found to thrive on serpentine soils containing high concentrations of Cr and Ni. These plants contained higher concentrations of Ni in their roots than in their shoots. Hydroponic growth experiments with 350 µM and 650 µM Ni singularly and in combination revealed that more Cr was accumulated at the roots. The opposite was the case for Ni. The same experiments showed no difference between plants from serpentine and control soils in terms of growth and metal uptake. Ni was found to be toxic to control Festuca arundinacea plants at concentrations of at least 50 µM. The uptake of Ni in Festuca arundinacea was increased by an increase in the concentration of Ni and a decrease the pH of the substrate.

Serpentine diffusers have become a common feature in modern aircraft as they allow for certain benefits that are impossible with a traditional linear configuration. With the benefits, however, come certain disadvantages, namely flow distortions that reduce engine efficiency and decrease engine surge stability margins. These distortions are now being researched comprehensively to determine solutions for mitigating the adverse effects associated with them. This study investigates how varying the freestream turbulence intensity of the flow entering a serpentine diffuser affects the distortion patterns that are produced by the diffuser. Experiments were performed with a model serpentine diffuser on the Annular Cascade Facility of the Air Force Research Laboratory at Wright-Patterson Air Force Base. Hot wire anemometry was used to measure inlet turbulence, while static pressure probes located axially along the upper and lower surface of the model diffuser and total pressure probes located across the aerodynamic interface plane (AIP) were used to measure the distortion patterns of the flow passing through the diffuser. Varying levels of inlet freestream turbulence, ranging from 0 to 4%, were generated using square and round bar turbulence screens in three distinct test configurations. Axial static pressure measurements indicate that increasing turbulence slightly affects flow separation development downstream of the second turn. This effect is also seen at the AIP where the total pressure recovery increases with increasing level of inlet turbulence in the region of flow separation at the upper surface. The total pressure recovery along the lower surface is also seen to be increased with higher inlet turbulence. However, total pressure recovery increase across the entire AIP is almost negligible. Overall, the inlet freestream turbulence has a minor effect on the distortion patterns caused by the serpentine diffuser when compared with proven active inlet flow control methods.

This thesis examines the bioleaching of six different Canadian nickel sulphide ores at pH levels above what is generally considered optimum (~ 2). The majority of work discussed in this thesis was conducted with a low-grade metamorphosed ultramafic nickel sulphide ore from Manitoba, Canada (Ore 3), which is not currently exploitable with conventional technologies. The ore contains 21% magnesium and 0.3% nickel. Nickel is the only significant metal value, and is present primarily as pentlandite. A substantial fraction of the magnesium is present as the serpentine mineral lizardite, making processing difficult with conventional pyro- and biohydrometallurgical techniques. The work with this ore has two equally important objectives: to minimize magnesium mobilization and to obtain an acceptable level of nickel extraction. Batch stirred-tank bioleaching experiments were conducted with finely ground ore ( 147 µm) with temperature and pH control. The first phase of experimentation examined the effect of pH (2 to 6) at 30 °C, and the second phase examined all combinations of three pH levels (3, 4 and 5) and five temperatures (5, 15, 22.5, 30, and 45 °C).

Vacuum insulation panels, VIPs, constitute a new insulation material, 6 to 8 times better than traditional insulation materials, which utilizes the positive influence vacuum has on the thermal properties of certain materials. A VIP is a composite with a flat core enclosed by an envelope preventing the core to fill with gas. The vacuum in the core is vital to reach thermal conductivities down to 0,0035 W/(m K), if the vacuum is lost the panel has reached the end of its service life time. Metal sheets would the preferred material to create an impermeable envelope but would creates a large thermal bridge at the edges of a panel when it folds over the edges of the panel. A serpentine edge has been proposed in order to deal with this large thermal bridge. This serpentine edge has been evaluated first as a numeric model in software and then by measuring on a prototype edge element in a hot and cold plate instrument. Measured temperatures were used to validate the numerical model. Results show that a serpentine edge can greatly reduce the thermal bridge if designed correctly. Another direction taken in the development of the VIP barrier is to use very thin metal layers, metallization layer or coating, incorporated into multi layered polymer composite film. This creates barrier films with very good barrier properties and only small thermal bridges. The modeling of gas flux through films with more than one coating has only just started. Existing models for flux through multi coated films all assume that flux is only taking place through defects in the coating layers, that all defects are of the same size and that all defects are positioned in square lattices. The model discussed herein use the same assumption of flux through pinholes only but it does take defect sizes and positions into account. Barrier film, from a regular vacuum insulation panel, with double coatings has been evaluated in light microscopy to characterize the defects in each of the coatings. The data found have been fed into the model and the results comply well with reported permeabilities of similar barrier films. / QC 20101125

Lichens are among the most prominent and successful life forms of metal-rich habitats, including ultramafic rocks and soils; however, research on lichens of ultramafic habitats is limited, especially on the North American continent. A review of the published literature on lichens of ultramafic substrates in North America yielded a total of 437 lichen species reported from ultramafic rocks and soils. Lichen assemblages of ultramafic substrates vary in composition and are dominated by acidophytic (low pH preferring) taxa with a minor, but consistent, basiphytic (high pH preferring) component. Species lists from ultramafic habitats in different geographic regions varied widely, suggesting that factors unrelated to substrate, such as climate, have a large effect on lichen assemblage composition. However, several studies showed clear differentiation between lichen composition on nearby or adjacent ultramafic and nonultramafic habitats, suggesting that ultramafic substrates harbor regionally unique lichen assemblages. In a regional community ecology study, we sampled lichen biotas of eight ultramafic and eight sandstone outcrops along a 70 km maritime influence gradient in order to test three hypotheses: 1) a substrate effect hypothesis that saxicolous lichen communities of ultramafic and sandstone outcrops are compositionally distinct; 2) a maritime gradient hypothesis that coastal and inland communities are compositionally distinct; and 3) a maritime moderation hypothesis that coastal ultramafic and sandstone communities are more similar than those of inland ultramafic and sandstone. Relationships between lichen communities and abiotic variables were analyzed using perMANOVA. Ultramafic communities showed significant differentiation from sandstone communities in the study area. A total of 134 taxa were recorded - 81 taxa from ultramafic outcrops and 100 taxa from sandstone, with 47 taxa found on both rock types. Ultramafic outcrops were characterized by greater similarity between samples, lower lichen cover, larger differences in cover between north and south aspects, and higher abundance and diversity of cyanolichen taxa relative to sandstone. Coastal, intermediate, and inland communities were compositionally distinct from one another, and sandstone and ultramafic assemblages were significantly differentiated in all coastal distance groups. This study is one of few to quantitatively examine lichen communities of two rock types, and is unique in that it does so at a regional scale. These results add to our understanding of the interactive roles of substrate and maritime influence in lichen community assembly.

Reproductive barriers are vital to generating new species as well as maintaining distinct species. Investigating reproductive barriers between closely related plant taxa helps us to understand how these barriers are maintained, particularly between rare and widespread relatives. Layia jonesii, a rare San Luis Obispo County serpentine endemic, and L. platyglossa, a common coastal species, co-occur on serpentine derived hillsides and are interfertile. At these locations, L. jonesii is isolated to dry soils near serpentine rock outcrops and L. platyglossa is located on slightly deeper grassland soils surrounding the rock outcrops. On hillsides where they co-occur, I observe two morphologically distinct species, therefore the two species must be maintaining reproductive barriers, yet mechanisms that maintain this isolation are unknown. I studied this system to investigate possible mechanisms contributing to the maintenance of reproductive barriers. I hypothesize prezygotic reproductive isolation in this system is due to (1) habitat isolation due to local adaptation to differential edaphic environments on the hillside, (2) flowering time differences, and (3) reduced seed set resulting from hybrid crosses. To investigate the local adaptation of L. jonesii and L. platyglossa, I reciprocally transplanted both species into the center of each species’ distribution. I also conducted a competition experiment to determine if L. jonesii is sensitive to resource competition beyond its natural distribution. To investigate flowering time differences, I tracked flowering time of both wild and reciprocally transplanted populations. I also performed controlled crosses to determine if heterospecific, or hybrid crosses, result in lowered seed set than conspecific crosses. The reciprocal transplants showed L. platyglossa is locally adapted to the grassland habitat. Local adaptation likely prevents L. playtyglossa from dispersing into the rock outcrop habitat. Results of the competition experiment revealed L. jonesii is sensitive to competition and this may contribute to its constrained distribution to shallow soils. Local adaptation and competition likely contribute to habitat isolation between the two species. I also documented stark differences in flowering time between the species which contributes to reproductive isolation by reducing pollen flow. Hybrid crosses also resulted in lowered seed set than conspecific crosses. These results suggest prezygotic barriers to reproduction likely maintain the majority of isolation between the two species. These results provide insight into mechanisms that maintain reproductive barriers between closely related taxa existing in similar habitats. The results also contribute to our understanding of how rare plants preserve genetic integrity near common and interfertile relatives.

The use of serpentine boundary layer ingesting (BLI) diffusers offers a significant benefit to the performance of Blended Wing Body aircraft. However, the inherent diffuser geometry combined with a thick ingested boundary layer creates strong secondary flows that lead to severe flow distortion at the engine face, increasing the possibility of engine surge. This study investigated the use of enabling active flow control methods to reduce engine-face distortion. An ejector-pump based system of fluidic actuators was used to directly manage the diffuser secondary flows. This system was modeled computationally using a boundary condition jet modeling method, and tested in an ejector-driven wind tunnel facility. This facility is capable of simulating the high-altitude, high subsonic Mach number conditions representative of BWB cruise conditions, specifically a cruise Mach number of 0.85 at an altitude of 39,000 ft. The tunnel test section used for this experiment was designed, built, and tested as a validation tool for the computational methods. This process resulted in the creation of a system capable of efficiently investigating and testing the fundamental mechanisms of flow control in BLI serpentine diffusers at a minimum of time and expense. Results of the computational and wind tunnel analysis confirmed the large potential benefit of adopting fluidic actuators to control flow distortion in serpentine BLI inlets. Computational analysis showed a maximum 71% reduction in flow distortion at the engine face through the use of the Pyramid 1 ejector scheme, and a 68% reduction using the Circumferential ejector scheme. However, the flow control systems were also found to have a significant impact on flow swirl. The Pyramid 1 ejector scheme was found to increase AIP flow swirl by 64%, while the Circumferential ejector scheme reduced flow swirl by 30%. Computational analyses showed that this difference was the result of jet interaction. By keeping the jet flows separate and distinct, the diffuser secondary flows could be more efficiently managed. For this reason, the most practically effective flow control scheme was the Circumferential ejector scheme. Experimental results showed that the computational analysis slightly over-predicted flow distortion. However, the trends are accurately predicted despite slight variances in freestream Mach number between runs and a slightly lower tested altitude. / Master of Science

An innovative experimental facility was developed for testing flush-mounted, diffusing serpentine inlets intended for use on blended-wing-body aircraft. The static ground test facility was able to simulate the boundary layer profile expected to be ingested by inlets mounted on the aft sections of these aircraft. It generated Mach numbers ranging from 0.19 to 0.4 and boundary layer thicknesses between 36% and 45%. The circumferential distortions at the aerodynamic interface plane of the serpentine inlet were also calculated, and ranged between 0.0042 for the lowest Mach number, to 0.0098 for the highest Mach number. Reynolds numbers for the tests ranged between 1.2 million and 2.4 million depending on engine speed and Mach number. The results of the experiment were compared to a previous NASA report, and showed close agreement in distortion patterns and pressure losses at a Mach number of 0.25. / Master of Science