Squeeze casting is the practise of solidifying metals under mechanically applied pressure via a slow displacement of a die volume. It has been shown that squeeze casting enhances the mechanical properties of cast metals. Research into other high integrity casting processes has shown that using techniques that enhance melt quality can further increase the mechanical properties. Therefore a bottom-tapped, bottom-fed squeeze casting machine was designed and built around a pre-existing squeeze casting die designed for uniaxial pressure application. This was used to obtain quantitative metallurgical and microstructural information on the squeeze castings produced, including the effects of common micro-alloying additions of strontium modifier and titanium modifier on the microstructure and hardness of a commercial aluminium silicon eutectic alloy. These were examined using a Taguchi design of experiments approach. It was found that squeeze casting reduced porosity and secondary dendrite arm spacing and increased hardness, and reduced or eliminated increases in porosity and secondary dendrite arm spacing associated with micro-alloying addition. The size of possibly deleterious iron-rich precipitates was reduced, and the morphology of such precipitates changed to a possibly less deleterious form without further alloy additions of manganese. It was also found that melt control and handling is essential for consistent quality of castings in the production of small volume squeeze castings, such as the ones produced in this experimental work.

Orientadores: Amauri Garcia, Jose Eduardo Spinelli / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-12T23:27:26Z (GMT). No. of bitstreams: 1 Silva_MariaAdrinaPaixaodeSouzada_M.pdf: 3527327 bytes, checksum: 88f3012a000dcdb2956852ed7fa40402 (MD5) Previous issue date: 2008 / Resumo: Ligas de alumínio dispersas com bismuto apresentam aplicações promissoras em componentes automotivos resistentes ao desgaste. Essas dispersões de elementos de baixa temperatura de fusão diminuem a dureza e escoam facilmente em condições de deslizamento, resultando em um comportamento tribológico favorável. Muitos estudos têm sido realizados a fim de melhor compreender as distintas morfologias obtidas pela reação monotética. Algumas pesquisas assumem que a evolução do espaçamento interfásico na liga monotética Al-Bi obedece à clássica relação utilizada para eutéticos: ?2v = C, onde v é a velocidade de solidificação e C é uma constante. Não há nenhum consenso a respeito dos valores de C encontrados. Além disso, tais estudos utilizaram fornos de aquecimento à resistência do tipo Bridgman para produzir a solidificação direcional de ligas monotéticas. Existe uma falta de estudos consistentes no desenvolvimento microestrutural de ligas monotéticas durante condições de fluxo de calor transitório, que são de importância primordial, uma vez que esse tipo de fluxo de calor engloba a maioria dos processos industriais de solidificação. No presente estudo, foram feitos experimentos de solidificação unidirecional em regime não-estacionário com as ligas hipomonotética Al-2,0%Bi e monotética Al-3,2%Bi. Os parâmetros térmicos como velocidades de crescimento, taxas de resfriamento e gradientes térmicos foram determinados experimentalmente por curvas de resfriamento adquiridas ao longo do comprimento do lingote. Os crescimentos celular e monotético foram caracterizados por técnicas metalográficas, e os espaçamentos celulares e interfásicos correlacionados com os parâmetros térmicos de solidificação. Verificou-se que a lei de crescimento ?2v = C pode ser expressa por um valor de C de 1,70 x10-12, que é em torno de duas ordens de magnitude maior do que aqueles reportados para o regime estacionário. Embora o fluxo convectivo induzido não tenha sido suficiente para mudanças consideráveis na magnitude dos espaçamentos interfásicos, as partículas ricas em bismuto foram afetadas pela direção do crescimento, diminuindo o diâmetro em condições de solidificação vertical descendente, quando comparadas com aquelas obtidas no modo vertical ascendente / Abstract: Aluminium alloys dispersed with bismuth show promising applications in wear-resistant automotive components. Such dispersions of low melting temperature elements decrease hardness and flow easily under sliding conditions, resulting in favorable tribological behavior. Much research has been devoted in order to better comprehend the distinct morphologies obtained by monotectic reaction. Some researches assume that the phase spacing evolution in the monotectic Al-Bi alloy follows the classical relationship used for eutectics: ?2v = C, where v is the solidification velocity and C a constant value. There is no consensus concerning the found C values. Other than, such studies have used Bridgman-type resistance heated furnaces to produce the directionally solidified monotectic samples. There is a lack of consistent studies on the microstructural development of monotectic Al-Bi alloy during transient heat flow conditions, which are of prime importance since this class of heat flow encompasses the majority of solidification industrial processes. In the present study, directional unsteady-state solidification experiments were carried out with hypomonotectic Al-2.0wt%Bi and monotectic Al-3.2wt%Bi alloys. The thermal parameters such as growth rates, cooling rates and thermal gradients were experimentally determined by cooling curves recorded along the casting length. The cellular and monotectic growths were characterized by metallography, being both the cell and the interphase spacing correlated with the thermal parameters. It is shown that the ?2v = C growth law can be expressed by a C value of 1,7x10-12, which is about two orders of magnitude higher than those reported for the steady-state regime. Although the induced convective flow was not enough to considerably change the interphase spacing's magnitude, the Bi-rich particle diameters have been affected by the direction of growth, decreasing in conditions of downward vertical solidification when compared with those grown vertically upwards / Mestrado / Materiais e Processos de Fabricação / Mestre em Engenharia Mecânica

Master of Science / Department of Agronomy / Kraig Roozeboom / High soybean [Glycine max.] commodity prices in recent years have led to an increase in use of yield enhancing and protecting products. These products need to be evaluated to determine if the use of multiple inputs has a positive impact on yield and how these inputs interact with agronomic practices. The objectives of this study were to evaluate products individually and collectively in input systems, examine interactions between varieties and input systems (IS), seeding rates (SR) and IS, and row spacing (RS) and IS. Field experiments were conducted at high-yielding locations in Kansas and Minnesota in 2012 to 2014 to meet these objectives. Sixteen treatments consisting of individual inputs and inputs combined in systems were evaluated in one experiment. A second experiment evaluated the variety by IS interaction by constructing 18 treatments from a factorial combination of six glyphosate [N-(phosphonomethyl) glycine] resistant varieties and three IS’s: untreated control (UTC), SOYA (combination of possible yield-enhancing products representative of those currently being marketed), and SOYA minus foliar fungicide (SOYA – foliar F). A third experiment evaluated the SR by IS interaction by constructing 12 treatments from a factorial arrangement of six SR’s and two IS’s: UTC and SOYA. A fourth experiment evaluated the RS by IS interaction by constructing 12 treatments from a factorial arrangement of three RS’s and four IS’s: UTC, fungicide and insecticide seed treatment plus foliar fungicide (STFF), SOYA, and SOYA – foliar F. Very few interactions between IS and agronomic practices were detected in any of the experiments. Varieties had an effect on multiple growth parameters but yield differences were marginal; linear-plateau and non-linear models found that seeding rates that maximized yield in this study were similar to University recommendations; and in general, narrow rows produced the greatest yields. The use of inputs and IS’s typically increased seed mass and yield above the UTC across all experiments. However, given current costs and soybean prices, yield response to IS’s was not great enough to cover the additional costs. Overall, it appears producers would be better served by focusing on agronomic practices rather than implementing input systems.

Call number: LD2668 .T4 1986 A47 / Master of Science / Agronomy

International Telemetering Conference Proceedings / October 20-23, 2003 / Riviera Hotel and Convention Center, Las Vegas, Nevada / This paper will present equations for calculating the minimum recommended frequency separation of two digital telemetry signals. The signals can be filtered continuous phase frequency shift keying (CPFSK), multi-h continuous phase modulation (CPM) [1], shaped offset quadrature phase shift keying-Telemetry Group (SOQPSK-TG, aka SOQPSK-A*) [2], or Feher’s patented quadrature phase shift keying FQPSK-B (or FQPSK-JR [3]). The equations are based on measured data in an adjacent channel interference (ACI) environment for filtered CPFSK (aka PCM/FM), multi-h CPM (or CPM for short), SOQPSK-TG, FQPSK-JR, and FQPSK-B. This paper is an extension of my 2001 and 2002 International Telemetering Conference papers on this topic [4, 5]. The quantity measured was bit error probability (BEP) versus frequency separation at a given signal energy per bit to noise power spectral density ratio (Eb/No). The interferers were CPFSK, CPM, SOQPSK-TG or FQPSK-B (-JR) signals. The results presented in this paper will be for a desired signal bit rate of 1 to 20 Mb/s, one interferer 20 dB larger than the desired signal (a few tests included two interferers), and various center frequency spacings, interfering signals, receivers, and demodulators. The overall ACI test effort has collected data sets at several bit rates and with one and two interferers. The results will be useful to system designers and range operators as they attempt to maximize the number of Mb/s that can be simultaneously transmitted with minimal interference in the telemetry bands.

This thesis entails a detailed microstructure analysis of directionally solidified (DS) Al-7Si alloys processed in microgravity aboard the International Space Station and similar duplicate ground based experiments at Cleveland State University. In recent years, the European Space Agency (ESA) has conducted experiments on alloy solidification in microgravity. NASA and ESA have collaborated for three DS experiments with Al- 7 wt. % Si alloy, aboard the International Space Station (ISS) denoted as MICAST6, MICAST7 and MICAST12. The first two experiments were processed on the ISS in 2009 and 2010. MICAST12 was processed aboard the ISS in the spring of 2014; the resulting experimental results of MICAST12 are not discussed in this thesis. The primary goal of the thesis was to understand the effect of convection in primary dendrite arm spacings (PDAS) and radial macrosegregation within DS aluminum alloys. The MICAST experiments were processed with various solidification speeds and thermal gradients to produce alloy with differences in microstructure features. PDAS and radial macrosegregation were measured in the solidified ingot that developed during the transition from one solidification speed to another. To represent PDAS in DS alloy in the presence of no convection, the Hunt-Lu model was used to represent diffusion-controlled growth. By sectioning cross-sections throughout the entire length of solidified samples, PDAS was measured and calculated. The ground-based (1-g) experiments done at Cleveland State University CSU were also analyzed for comparison to the ISS experiments (0-g). During steady state in the microgravity environment, there was a reasonable agreement between the measured and calculated PDAS. In ground-based experiments, transverse sections exhibited obvious radial macrosegregation caused by thermosolutal convection resulting in a non-agreement with the Hunt- Lu model. Using a combination of image processing techniques and Electron Microprobe Analysis, the extent of radial macrosegregation was found to be a function of processing conditions and PDAS.

International Telemetering Conference Proceedings / October 21, 2002 / Town & Country Hotel and Conference Center, San Diego, California / This paper will present measured data in an adjacent channel interference (ACI) environment for filtered continuous phase frequency shift keying (CPFSK or FM), multi-h continuous phase modulation (multi-h CPM or CPM for short) [1] and Feher’s patented quadrature phase shift keying (FQPSK-B) [2]. This paper is an extension of my 2001 International Telemetering Conference paper on this topic [3]. The quantity measured was bit error probability (BEP) versus signal energy per bit to noise power spectral density ratio (E(b)/N(o)). The interferers were CPFSK, CPM, or FQPSK-B signals. The results presented in this paper will be for a desired signal bit rate of 5 Mb/s, one interferer 20 dB larger than desired signal (a few tests included two interferers), and various center frequency spacings, interfering signals, receivers, and demodulators. The overall ACI test effort will collect data sets at several bit rates and with one and two interferers. The results will be useful to system designers and range operators as they attempt to maximize the number of Mb/s that can be simultaneously transmitted with minimal interference in the telemetry bands.

Recent attempts to elucidate a climatic effect on erosion rates at the catchment scale have generally found little or no correlation between precipitation and erosion rates, yet climate has been shown to exert a significant control on landscape properties such as drainage density, slope and relief. That erosion rates to do not directly reflect climatic conditions may not come as a surprise, since erosion rates will tend to keep pace with uplift rates in a tectonically active landscape. The interplay between erosion rates and climate may therefore be better understood with reference to the erosional efficiency of the landscape. Erosional efficiency governs how steep the landscape must become to balance uplift rates, and has also recently been postulated to affect the width to length (or spacing) ratio of first order basins, and the distribution of hillslopes within a landscape, via the relative inputs of diffusive and advective transport. This study constrains the efficiency of sediment transport along a climatic transect spanning a precipitation range of over two orders of magnitude in the Chilean Coastal Cordillera (26˚-41˚S), combining long-term erosion rates derived from concentrations of cosmogenic Be-10 in quartz in fluvial sediments with topographic metrics. The effects of changes in the relative input of diffusive and advective processes is investigated by studying the basin spacing ratios and distribution of hillslopes for a variety of natural landscapes and landscapes generated using the CHILD model. Sediment transport efficiency was found to peak at the transition between arid and semiarid climates, where herbaceous vegetation has almost entirely replaced bare ground, and to level off as climate becomes more humid, providing a background sediment transport efficiency value which will be applicable in both semi-arid and humid landscapes. Basin spacing ratios in natural landscapes show little variation along the transect, suggesting that changes in climate have little effect on this apparently universal catchment property, although maximum basin length attained appears to be linked to sediment transport efficiency. Slopes are consistently lower in the southern region where vegetation and sediment transport efficiency are uniform; here, lower slopes are maintained despite relatively high erosion rates thanks to higher sediment transport efficiency than in the north. Results from the CHILD landscapes show an increase in width to length ratio with decreasing sediment transport efficiency; this relationship is at odds with both the data from the study area and with data from previous studies. Results therefore indicate that, in natural landscapes, climate and vegetation cover exert a first order control on sediment transport efficiency. While climate and vegetation play little or no part in controlling the ratio of catchment dimensions, they may exert some control on the maximum dimensions of catchments and may help to modify the distribution of mean basin slope via their effects on hillslope processes.

The interwall spacing of multi-walled carbon nanotubes has an effect on their physical and chemical properties. Tubes with larger interwall spacing - compared to the spacing where the carbon atoms are in their natural distance to each other - are for instance expected to be mechanically less stable. Considering the MWCNT interwall spacing’s dependence on the tube size, three interesting previous studies with slightly different conclusions can be found. All of them conclude an increase of the interwall spacing with a decreasing tube size. We describe their analysis procedure, compare them to each other and to our own measured data. In the beginning of our analyses, we determine the expected inaccuracy for measured distances out of TEM images being up to 10 % and we show the impacts of the TEM’s defocus, a powerful setting in TEM imaging. Finally, we suppose that the interwall spacings are not as strongly varying as one previous study concludes, but our analyses are relatively in harmony with the two other studies. The interwall spacings from tubes with an inner diameter larger than 5 nm are relatively constant within the whole tube. Furthermore, it appears that the middle spacings (excluding the outer- and innermost ones) show values that are most consistent with the interlayer spacings of turbostratic graphite. In underfocused images, the outer- and innermost spacings tend to have values being slightly smaller than the middle ones from the same tube.

The search for alternative sources of energy has shown to be a global demand. Motivated by concern about climate change and the depletion of natural resources, the world market has attracted interest in the study and adoption of alternative renewable sources of energy. One possible alternative is the use of forest biomass. In this context, it is necessary to carry out studies that seek to evaluate the growth and yield of different forest species cultivated at different planting spacings. The aim of this study were: (i) to evaluate the production of biomass for energy; (ii) to determine carbon storage and partitioning in the forest system (above-belowground biomass + soil); (iii) to determine the radiation use efficiency of Eucalyptus grandis; and (iv) to characterize the elemental composition and properties of four forest species Eucalyptus grandis, Mimosa scabrella, Ateleia glazioviana, and Acacia mearnsii grown in four planting spacings in Southern Brazil. A field experiment was conducted from September 2008 to September 2018 in the city of Frederico Westphalen, Brazil. The forest biomass was determined by destructive method. Also, the calorific value, elemental composition, immediate chemical analysis, radiation use efficiency, light extinction coefficient, solar radiation interception, leaf area index, biomass yield and partitioning, carbon storage and potential energy yield were evaluated. Information generated in this study is relevant and provides information for companies interested in electricity generation from forest biomass and forest producers thereby assisting in the planning of optimal spacing to be used for biomass production for energy. The highest biomass production, carbon storage, and radiation use efficiency were obtained in the planting spacing (2.0×1.5 m) for the Eucalyptus grandis, which resulted in a higher amount of biomass for energy production. For the other forest species, the optimal planting spacing to produce biomass for energy was the (2.0×1.0 m). Therefore, the use of reduced planting spacing should be prioritized and recommended for future exploitation of forest energy plantations. / A busca por fontes alternativas de energia tem se mostrado uma demanda global. Motivado pela preocupação com as mudanças climáticas e pelo esgotamento dos recursos naturais, o mercado mundial tem despertado interesse no estudo e adoção de fontes alternativas renováveis de energia. Uma das alternativas possíveis é o uso da biomassa florestal. Neste contexto, surge a necessidade da realização de estudos que busquem avaliar o crescimento e produtividade de diferentes espécies florestais cultivadas em diferentes espaçamentos de plantio. Desse modo, os objetivos deste estudo são: (i) avaliar a produção de biomassa para energia; (ii) determinar a estocagem e partição de carbono no sistema florestal (biomassa florestal + solo); (iii) determinar a eficiência do uso da radiação solar da espécie Eucalyptus grandis; and (iv) caracterizar a composição elementar e as propriedades de quatro espécies florestais Eucalyptus grandis, Mimosa scabrella, Ateleia glazioviana e Acacia mearnsii cultivadas em quatro espaçamentos de plantio no sul do Brasil. Um experimento de campo foi realizado de setembro de 2008 a setembro de 2018 na cidade de Frederico Westphalen, Brasil. A biomassa florestal foi determinada pelo método destrutivo. Também foram avaliados o poder calorífico, composição elementar, análise química imediata, eficiência do uso da radiação, coeficiente de extinção luminosa, a interceptação da radiação solar, o índice de área foliar, o particionamento de biomassa, o armazenamento de carbono e o rendimento energético potencial. As informações geradas neste estudo são relevantes e fornecem informações importantes para empresas interessadas na geração de eletricidade a partir de biomassa florestal e produtores florestais, uma vez que auxiliam no planejamento da escolha do espaçamento ótimo a ser utilisado para produção de biomassa para energia. A maior produção de biomassa, armazenamento de carbono e eficiência de uso de radiação foi obtida para a espécie Eucalyptus grandis cultivada no espaçamento de plantio (2,0×1,5 m), que resultou em maior quantidade de biomassa para produção de energia. Para as demais espécies florestais, o espaçamento ótimo de plantio para produzir biomassa para energia foi (2,0×1,0 m). Portanto, o uso de espaçamento reduzido de árvores deve ser priorizado e recomendado para futuras explorações de plantações de energia florestal.