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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Comparing simple and complex native forage mixtures for grazing cattle in southwestern Saskatchewan

Kusler, Justin P 13 January 2010
Diverse forage mixtures have improved resilience to drought, improved persistence, ability to adapt to changing environmental conditions, reduced fertilizer costs, improved root mass and greater soil carbon sequestration but do they improve forage and animal production. The objective was to determine if complex native forage mixtures provide superior nutritional quality throughout the grazing season as compared to simple native mixtures. Three studies were conducted in 2007 at Swift Current, SK to evaluate forage production potentials, nutritive qualities and in vitro dry matter digestibility of native and tame forage species common to or having potential in Southwestern Saskatchewan. In study one, plots were seeded in 2006 on Chernozemic Orthic Brown Swinton Loam soils and consisted of 11 native and three tame monoculture species common to southwestern Saskatchewan. Clippings at a 5 cm stubble height occurred on June 20 and every 28 days after until October 10. Forage DM production, in vitro OMD, NDF, ADF, ADL, CP, Ca and P concentrations were measured. As species matured, production and OMD declined (P¡Ü0.05) but NDF, ADF and ADL concentrations increased (P¡Ü0.05). There were harvest date by species differences (P¡Ü0.05) in forage production and nutritional qualities of C3 and C4 grass and legume species. Study two examined the in situ CP, NDF and DM disappearance of six selected species harvested in the fall. EDNDF and ADDM values did not differ (P>0.05) among C3 grasses. The C4 grasses had higher (P<0.05) EDNDF and EDDM and the legume, Canadian milkvetch had the highest (P<0.05) EDDM but lowest EDNDF. Study three occurred in 2005, 2006 and 2007 to determine if complex native forage mixtures had superior forage and animal production as compared to simple forage stands. Grazing occurred from June through August to achieve 60% utilization. Animal weights and available, cage and residual forage yields were taken to determine production and utilization. Forage production and quality did not differ (P>0.05) between simple and complex forage mixtures but animal production (AUD ha-1) was higher on complex native mixtures. Overall results showed; 1) C3 and C4 grass and legume species have different growth patterns and qualities that can improve forage quality and degradability of the stand throughout the grazing season, 2) forage and animal production benefits associated with complex native forage mixtures largely depend on environmental conditions like temperature and moisture.
52

Comparing simple and complex native forage mixtures for grazing cattle in southwestern Saskatchewan

Kusler, Justin P 13 January 2010 (has links)
Diverse forage mixtures have improved resilience to drought, improved persistence, ability to adapt to changing environmental conditions, reduced fertilizer costs, improved root mass and greater soil carbon sequestration but do they improve forage and animal production. The objective was to determine if complex native forage mixtures provide superior nutritional quality throughout the grazing season as compared to simple native mixtures. Three studies were conducted in 2007 at Swift Current, SK to evaluate forage production potentials, nutritive qualities and in vitro dry matter digestibility of native and tame forage species common to or having potential in Southwestern Saskatchewan. In study one, plots were seeded in 2006 on Chernozemic Orthic Brown Swinton Loam soils and consisted of 11 native and three tame monoculture species common to southwestern Saskatchewan. Clippings at a 5 cm stubble height occurred on June 20 and every 28 days after until October 10. Forage DM production, in vitro OMD, NDF, ADF, ADL, CP, Ca and P concentrations were measured. As species matured, production and OMD declined (P¡Ü0.05) but NDF, ADF and ADL concentrations increased (P¡Ü0.05). There were harvest date by species differences (P¡Ü0.05) in forage production and nutritional qualities of C3 and C4 grass and legume species. Study two examined the in situ CP, NDF and DM disappearance of six selected species harvested in the fall. EDNDF and ADDM values did not differ (P>0.05) among C3 grasses. The C4 grasses had higher (P<0.05) EDNDF and EDDM and the legume, Canadian milkvetch had the highest (P<0.05) EDDM but lowest EDNDF. Study three occurred in 2005, 2006 and 2007 to determine if complex native forage mixtures had superior forage and animal production as compared to simple forage stands. Grazing occurred from June through August to achieve 60% utilization. Animal weights and available, cage and residual forage yields were taken to determine production and utilization. Forage production and quality did not differ (P>0.05) between simple and complex forage mixtures but animal production (AUD ha-1) was higher on complex native mixtures. Overall results showed; 1) C3 and C4 grass and legume species have different growth patterns and qualities that can improve forage quality and degradability of the stand throughout the grazing season, 2) forage and animal production benefits associated with complex native forage mixtures largely depend on environmental conditions like temperature and moisture.
53

Two-stage Ignition as an Indicator of Low Temperature Combustion in a Late Injection Pre-mixed Compression Ignition Control Strategy

Bittle, Joshua 2010 December 1900 (has links)
Internal combustion engines have dealt with increasingly restricted emissions requirements. After-treatment devices are successful in bringing emissions into compliance, but in-cylinder combustion control can reduce their burden by reducing engine out emissions. For example, oxides of nitrogen (NOx) are diesel combustion exhaust species that are notoriously difficult to remove by after-treatment. In-cylinder conditions can be controlled for low levels of NOx, but this produces high levels of soot potentially leading to increased particulate matter (PM). The simultaneous reduction of NOx and PM can be realized through a combustion process known as low temperature combustion (LTC). In this study, the typical definition of LTC as the defeat of the inverse relationship between soot and NOx is not applicable as a return to the soot-NOx tradeoff is observed with increasing exhaust gas recirculation (EGR). It is postulated that this effect is the result of an increase in the hot ignition equivalence ratio, moving the combustion event into a slightly higher soot formation region. This is important because a simple emissions based definition of LTC is no longer helpful. In this study, the manifestation of LTC in the calculated heat release profile is investigated. The conditions classified as LTC undergo a two-stage ignition process. Two-stage ignition is characterized by an initial cool-flame reaction followed by typical hot ignition. In traditional combustion conditions, the ignition is fast enough that a cool-flame is not observed. By controlling initial conditions (pressure, temperature, and composition), the creation and duration of the cool-flame event is predictable. Further, the effect that injection timing and the exhaust gas recirculation level have on the controlling factors of the cool-flame reaction is well correlated to the duration of the cool-flame event. These two results allow the postulation that the presence of a sufficiently long cool-flame reaction indicates a combustion event that can be classified as low temperature combustion. A potential method for identifying low temperature combustion events using only the rate of heat release profile is theorized. This study employed high levels of EGR and late injection timing to realize the LTC mode of ordinary petroleum diesel fuel. Under these conditions, and based on a 90 percent reduction in nitric oxide and no increase in smoke output relative to the chosen baseline condition, a two part criteria is developed that identifies the LTC classified conditions. The criteria are as follow: the combustion event of conventional petroleum diesel fuel must show a two-stage ignition process; the first stage (cool-flame reaction) must consume at least 2 percent of the normalized fuel energy before the hot ignition commences.
54

How the East Coast Rocks: A History of Hip Hop in Halifax: 1985 - 1998

McGuire, Michael 18 August 2011 (has links)
Between 1985 and 1997 a hip hop culture emerged in Halifax, Nova Scotia through rap music artists' live performances at various venues, and by releasing original music on commercial and non-commercial cassette tapes and compact discs. This thesis examines the evolution of this grassroots musical culture through the lenses of Halifax's geography, innovative musical and technological trends, ever-present racial politics, and a strong "do-it-yourself" ethic. This thesis argues that hip hop in Halifax during these years can be divided into two eras distinguished by dynamic racial and stylistic changes. While the 1980s saw a predominantly Black hip hop community take root around Uniacke Square and Gottingen Street, the 1990s saw a geographic and demographic shift as the rap music scene expanded and competed with the mainstream music scene of the city. In doing so, the integrated downtown hip hop community produced a significant amount of work, overcoming institutional opposition
55

EXAMINING VEGETATIVE GROWTH OF COOL-SEASON FORAGE GRASSES FOR DAIRY CATTLE GRAZING PREFERENCE

Billman, Eric D. 01 January 2015 (has links)
The objective of this study was to determine dairy cattle preference amongst four species of cool-season forage grasses: eight orchardgrasses (Dactylis glomerata L.), five tall fescues [Schedonorus arundinaceus (Schreb.) Dumort.], five perennial ryegrasses (Lolium perenne L.), and six festuloliums [xFestulolium braunii (K. Richt.) A. Camus.]; 24 cultivars in total. Each grazing trial utilized four Holstein-Friesian heifers over six hours. Maturity differences were eliminated by having animals graze only vegetative material. After six grazing trials (three each in 2014 and 2015), consistent results in animal preference were not found; three of the six trials did show preference (P
56

The Effect of High SRI Roofing Finishes Across Climate Zones in the U.S.

January 2011 (has links)
abstract: The intent of this research is to determine if cool roofs lead to increased energy use in the U.S. and if so, in what climates. Directed by the LEED environmental building rating system, cool roofs are increasingly specified in an attempt to mitigate urban heat island effect. A typical single story retail building was simulated using eQUEST energy software across seven different climatic zones in the U.S.. Two roof types are varied, one with a low solar reflectance index of 30 (typical bituminous roof), and a roof with SRI of 90 (high performing membrane roof). The model also varied the perimeter / core fraction, internal loads, and schedule of operations. The data suggests a certain point at which a high SRI roofing finish results in energy penalties over the course of the year in climate zones which are heating driven. Climate zones 5 and above appear to be the flipping point, beyond which the application of a high SRI roof creates sufficient heating penalties to outweigh the cooling energy benefits. / Dissertation/Thesis / M.S. Built Environment 2011
57

Estudo de durabilidade de pinturas \"frias\" e convencionais expostas ao envelhecimento natural. / Study of the durability of \"cool\" and convenctional paints exposed to natural aging.

Isabela Libório Martins da Silva 09 December 2016 (has links)
O uso de pinturas \"frias\", em coberturas e fachadas, é uma estratégia utilizada para melhorar a sensação térmica dos usuários por meio do aumento desempenho térmico das edificações, potencializar a eficiência energética e mitigar ilhas de calor. Por outro lado, a exposição ao longo do tempo pode alterar a capacidade refletiva dessas superfícies, devido à deposição de sujidades e crescimento microbiológico. Esse estudo tem o objetivo de avaliar a manutenção da capacidade refletiva, a alteração da cor, do aspecto e da emissividade de pinturas expostas por três anos ao envelhecimento natural. Para esse estudo foram produzidos, em laboratório, dois grupos de tintas tipo premium, para uso em superfícies externas de fachadas e coberturas, com dois acabamentos: acetinado (PVC 30%) e fosco (PVC 50%), nas cores: branco, cinza, amarelo e marrom, que são cores usualmente utilizadas em fachadas e coberturas no Brasil. Um grupo é composto por tintas convencionais, formuladas com pigmentos inorgânicos naturais e orgânicos. O outro grupo é composto por tintas formuladas com pigmentos, com alta capacidade de refletância solar na região do infravermelho próximo, conhecidos como pigmentos \"frios\". Ainda há um terceiro grupo de tintas que foi coletado do mercado e utilizado como referência. Na exposição ao envelhecimento natural o microclima é um dos fatores determinantes no tipo de degradação da pintura, por isso esse estudo contempla os três microclimas predominantes do Estado de São Paulo: rural (Pirassununga), urbano (São Paulo) e costeiro (Ubatuba). Nesse trabalho estão sendo apresentados os resultados obtidos com três anos de exposição e já foi possível observar redução da refletância inicial, alteração de cor (diminuição do índice L luminosidade) e indícios de crescimento microbiológico. / The application of cool paints, on roofs and facades components, is a strategy to improve indoor thermal comfort for users in rooms that are not air conditioned. Increasing the thermal performance of buildings, enhance thermal efficiency and mitigate urban heat island. On the other hand, the exposure of paints over time can change reflectance capability of the surface, due to dirty deposition and microbiological colonization. The objectives of this study is evaluate the level of maintenance of reflectance, emissivity, color and visual aspects of paints after three years of natural aging exposure. Two groups of \"premium\" type paints, formulation recommended for applications on facades and roofs, we prepared in laboratory. Each group of paints was produced with two sheen type, two ratios pigment to binder, gloss finish (PVC 30%) and silk finish (PVC 50%), for the colors white, yellow, grey and brown, which are the most used colors in facades and roofs in Brazil. One group, the standard paint, was produced with natural inorganic and organic pigments and the other group was produced with cool pigments, which has high solar reflectance capacity in the near-infrared spectrum. Additionally, a third group of paints was acquired from the market and used as reference data. The microclimate is one of the key factors for paint degradation by natural aging, so in this study was considered three major microclimates of São Paulo State: rural (Pirassununga City),urban (São Paulo city) and oceanic climate (Ubatuba). The present study shows the results of the paints after three years exposure, which was observed significant reduction in reflectance, color change (reduction of the luminance L index) and evidences of microbiological colonization.
58

Tectono-stratigraphic evolution of the Cenozoic Great Australian Bight

Sharples, Alexander Gabriel William david January 2014 (has links)
The Great Australian Bight (GAB) is an extensive W-E striking continental margin basin that drifted northwards during the Cenozoic following rifting and separation from Antarctica in the mid/late Cretaceous. Seafloor spreading accelerated in the mid-Eocene and was associated with local volcanism. The mid-Eocene succession of the GAB is conspicuously mounded and separates a dominantly siliciclastic succession below from a fully marine carbonate succession above. The mounded succession was penecontemporaneous with major changes in global climate, oceanographic conditions and tectonic re-organization in the region, and thus may hold important clues as to the palaeo-environmental changes associated with these changes. The mid Eocene has so far only been described locally or in passing, usually by studies focused on either the siliciclastics below or the carbonates above. It was therefore chosen as a major focus point for the research project reported herein. Exploration activity in the GAB has been limited despite the presence of a working petroleum system and large target structures, but industry interest has increased over the past few years leading to 3D seismic surveys being acquired in the GAB. The focus for exploration is the Cretaceous succession beneath the relatively thin Cenozoic cover, which however, is still important in terms of shallow hazards and as overburden to the anticipated productive sections. As is often the case, the new 3D seismic data shows many overburden features in great detail and thus affords new insights to be gained that improve our understanding of the post-rift evolution of the marginThis thesis expands upon and reinterprets a pre-existing sequence framework in the Cenozoic GAB based from ODP Leg 182 results. A vast database of 2D and 3D seismic surveys has been integrated with exploration wells and borehole data and several surfaces have been calibrated to borehole and well constraints, then mapped to the maximum lateral extent across the available dataset. Surface mapping provided new insight into sequence deposition and palaeoenvironmental settings. Structure maps and thickness maps highlight key depocentre locations and trends over the Cenozoic GAB as well as stacked mass debris aprons. The newly discovered sequences raise new questions regarding trigger mechanisms in a-seismic areas and feed into industry geohazard perception models. The base surface of the Cenozoic framework hosts a plethora of mounded features across shelf and basinal section. All mounds within the dataset have been mapped. A set a bryozoan reef mounds have been interpreted lying parallel to the margin as linear complexes over 500 km. They coincide with the underlying siliciclastic delta clinoform breakpoints and provide insight into the changing palaeoenvironment at the 43 Ma mark, cessation of siliciclastics and regional marine transgression. Further mound mapping aided by 3D attribute extractions along the base Cenozoic unconformity led to the interpretation of a series of enigmatic igneous-based mounded features. The discoveries have been included in a comparative study, comparing all mounded features (igneous or carbonate) and contrasting their individual characteristics of geometry, seismic facies, dimension in order to understand mound origin and emplacement. A new grouping of mounds in the GAB has been established, the origin and emplacement mechanisms of which contribute to the global knowledge base.
59

Low-mass stars as tracers of the milky way populations : investigating the effects of metallicity in cool atmosphere / Les étoiles de petite masse comme traceurs des populations de la voie lactée : étude des effets de la métallicité dans les atmosphères froides

Rajpurohit, Arvind Singh 13 September 2013 (has links)
Les étoiles de petite masse (naines M) forment la composante stellaire dominante de notre galaxie et contribuent à la majeure partie de la matière baryonique dans la galaxie. Notre compréhension de la galaxie repose donc sur la connaissance de cette composante peu lumineuse. Par ailleurs, un nombre grandissant d’exoplanètes sont découverte autour de naines M, y compris des super-terres. L’étude des naines M a ainsi des implications importantes sur la physique stellaire, permettant de comprendre les processus en jeu dans ces atmosphères froides. Ces astres restent cependant peu connus du fait de leur faible luminosité intrinsèque. La description de ces étoiles nécessite une validation empirique fort, notamment en ce qui concerne les effets de l’abondance chimique sur la physique des atmosphères froides.Le but de cette thèse est de déterminer les paramètres fondamentaux des naines M et de tester les modèles d’atmosphères d’étoiles froides.Dans la première partie nous comparons des spectres calibrés dans le visible et l’infrarouge des composantes de système triple LHS 1070 avec des spectres synthétiques. Cette étude permet d’améliorer notre compréhension de la formation de la poussière dans les atmosphères très froides. Ce travail est étendu à un échantillon de naines M et permet de déterminer l’échelle de température des naines M. La seconde partie présente l’analyse des spectres à haute résolution de 21 naines M de faible métallicité (sous naines). Nous analysons en détail les signature moléculaires et atomiques dans le spectre. La comparaison avec des spectres synthétiques permet de mesurer les paramètres stellaires des étoiles et de déterminer avec précision leur métallicité. Ce travail doit initier des recherches futures. En particulier nous voulons étendre cette étude dans le domaine proche-infrarouge pour s’assurer que les résultats obtenus sont cohérents du domaine optique jusqu’à l’infrarouge proche. / Very Low-Mass stars (M dwarfs) are an important source of information for probing the lowmass end of the main sequence, down to the hydrogen burning limit. They are the dominantstellar component of the Galaxy and make up the majority of baryonic matter in the Galaxy.Moreover, an increasing number of M dwarfs are now known to host exoplanets, includingsuper-Earth exoplanets. The determination of accurate fundamental parameters for M dwarfshas therefore relevant implications for both stellar and Galactic astronomy as well as planetology.Despite their large number in the Galaxy, M dwarfs remain elusive objects and themodelling of their photosphere has long remained a challenge (molecular opacities, dust cloudformation). The description of these stars therefore need a strong empirical basis, or validation.In particular, the effect of metallicity on the physics of cool atmospheres are still poorly known,even for early-type M-dwarfs.[...]
60

Autoignition chemistry of liquid and gaseous fuels in non-premixed systems

Alfazazi, Adamu 08 1900 (has links)
Heat-release in CI engines occurs in the presence of concentration and temperature gradients. Recognizing the need for a validation of chemical kinetic models in transport-affected systems, this study employs non-premixed systems to better understand complex couplings between low/high temperature oxidation kinetics and diffusive transport. This dissertation is divided into two sections. In the first section, a two-stage Lagrangian model compares model prediction of ignition delay time and experimental data from the KAUST ignition quality tester, and ignition data for liquid sprays in constant volume combustion chambers. The TSL employed in this study utilizes detailed chemical kinetics while also simulating basic mixing processes. The TSL model was found to be efficient in simulating IQT in long ignition delay time fuels; it was also effective in CVCC experiments with high injection pressures, where physical processes contributed little to ignition delay time. In section two, an atmospheric pressure counterflow burner was developed and fully validated. The counterflow burner was employed to examine the effects of molecular structure on low/high temperature reactivity of various fuels in transport-affected systems. These effects were investigated through measurement of conditions of extinction and ignition of various fuel/oxidizer mixtures. Data generated were used to validate various chemical kinetic models in diffusion flames. Where necessary, suggestions were made for improving these models. For hot flames studies, tested fuels included C3-C4 alcohols and six FACE gasoline fuels. Results for alcohols indicated that the substituted alcohols were less reactive than the normal alcohols. The ignition temperature of FACE gasoline was found to be nearly identical, while there was a slight difference in their extinction limits. Predictions by Sarathy et al. (2014) alcohol combustion model, and by the gasoline surrogate model (Sarathy et al., 2015), agreed with the experimental data. For cool diffusion flames studies, tested fuels included butane isomers, naphtha, gasolines and their surrogates. Results revealed that the addition of ozone successfully established cool flames in the fuels at low and moderate strain rates. Numerical simulations were performed to replicate the extinction limits of the cool flames of butane isomers. The model captured experimental trends for both fuels; but over-predicted their extinction limits.

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