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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.
221

A class of weighted Bergman spaces, reducing subspaces for multiple weighted shifts, and dilatable operators

Liang, Xiaoming 14 August 2006 (has links)
This thesis consists of four chapters. Chapter 1 contains the preliminaries. We give the background, notation and some results needed for this work, and we describe our main results of this thesis. In Chapter 2 we will introduce a class of weighted Bergman spaces. We then will discuss some properties about the multiplication operator, Mz , on them. We also characterize the dual spaces of these weighted Bergman spaces. In Chapter 3 we will characterize the reducing subspaces of multiple weighted shifts. The reducing subspaces of the Bergman and the Dirichlet shift of multiplicity N are portrayed from this characterization. In Chapter 4 we will introduce the class of super-isometrically dilatable operators and describe their elementary properties. We then will discuss an equivalent description of the invariant subspace lattice for the Bergman shift. We will also discuss the interpolating sequences on the bidisk. Finally, we will examine a special class of super-isometrically dilatable operators. One corollary of this work is that we will prove that the compression of the Bergman shift on two compliments of two invariant subspaces are unitarily equivalent if and only if the two invariant subspaces are equal. / Ph. D.
222

Influence of cultivar, topping height, and harvest treatment on physical and chemical characteristics of flue-cured tobacco

Mullins, Seth David 14 April 2006 (has links)
There has been an increased interest among the tobacco industry in the production of tip leaves in flue-cured tobacco. Different harvest treatments of flue-cured tobacco were compared across six cultivars and two topping heights with the objective of identifying tip grade tobacco. Agronomic and cured leaf chemistry data were collected. Cultivar had significant influences on yield, average price, grade index, and value in three growing seasons. NC 71 and RG H51 were the highest yielding cultivars, with grade indices among the highest as well. Increasing topping height increased tobacco yield in two of three years. As topping height increased there was a significant increase in the percentage of tobacco receiving a tip grade. The four harvest treatments focused on the ten uppermost leaves of the plant. Harvest treatments that allowed proper separation of stalk positions (5&5L and 7&3L treatments) resulted in increased yields and tip grades. Harvest treatments that separate upper stalk position tobacco resulted in a higher percentage of tip grades from a tobacco company grader. Chemical analysis identified differences between stalk positions at the top of the plant. In order for cigarette manufacturers to properly blend the tobacco used to make American blend cigarettes, this separation of stalk positions is important. Harvest treatments that combined stalk positions resulted in the loss of these chemical differences. By topping flue-cured tobacco four to five leaves higher than current extension recommendations and separating stalk positions correctly, tobacco growers can meet the crop throw requirements of tobacco marketing contracts. / Master of Science
223

Cost effectiveness of a weight reduction program in reducing the pregnancy risks of obese clients of family planning clinics

Abeson, Mars January 1983 (has links)
M.S.
224

Towards a more sustainable surface transport infrastructure: a case study of applying multi criteria analysis techniques to assess the sustainability of transport noise reducing devices.

Oltean-Dumbrava, Crina, Watts, Gregory R., Miah, Abdul H.S. 22 September 2015 (has links)
Yes / The surface transport infrastructure (i.e. road and rail) has seen increasing pressure in recent years to achieve better sustainability performance. Transport Noise Reducing Devices (NRDs) form a major part of the surface transport infrastructure system in mitigating undesirable surface noise pollution to impacted communities. Their sustainability is a growing interest for practitioners and policy makers in this area as NRDs projects now have to balance integrating and assessing social, environmental, and economic objectives besides meeting key technical requirements. This paper presents an account of the first study carried out to assess the absolute sustainability of NRDs via the application of multi criteria analysis (MCA) techniques. The general procedure, selection of criteria, data gathering, and the use of three MCA techniques, SAW (Simple Additive Weighting), PROMETHEE (Preference Ranking Organisation MeTHod for Enrichment Evaluations), and ELECTRE III (Elimination et Choice Translating Reality), to assess the absolute sustainability of two built and operating European NRDs projects (one in Spain, and one in Italy) is presented. The novel concept of defining an Optimal Hypothetic Ideal Solution (OHIS) to assess the sustainability of NRDs in absolute terms to achieve this end is also introduced and discussed. The presented case studies will thus provide a useful model for practitioners to adopt or amend to conduct their own assessments of NRDs' sustainability. The paper further concludes that the generation of index values by the three MCA techniques to denote the overall absolute sustainability of solutions is a useful feature for communicating the sustainability of NRDs across a broad range of stakeholders, and for conducting “what-if” analyses. The presented research could also support broader aims of developing harmonized sustainability standards for the NRDs industry to adopt and so forward the sustainability transport agenda.
225

“Top-Down-Bottom-Up” Methodology as a Common Approach to Defining Bespoke Sets of Sustainability Assessment Criteria for the Built Environment

Oltean-Dumbrava, Crina, Watts, Gregory R., Miah, Abdul H.S. 04 January 2013 (has links)
Yes / The top-down-bottom-up (TDBU) methodology for defining bespoke sets of sustainability criteria for specific civil engineering project types is introduced and discussed. The need to define sustainability criteria for specific civil engineering project types occurs mainly in one or both of the following cases: (1) when a more comprehensive and indicative assessment of the sustainability of the project type in question is required; and/or (2) there is no readily available bespoke sustainability assessment tool, or set of criteria, for assessing the sustainability of the project type. The construction of roads, buildings, airports, tunnels, dams, flood banks, bridges, water supply, and sewage systems and their supporting systems are considered to be unique civil engineering/infrastructure project types. The normative definition of sustainable civil engineering/infrastructure projects and the framework for assessing its sustainability is defined and provided by the authors. An example of the TDBU methodology being applied to define sustainability criteria for transport noise reducing devices is presented and discussed. The end result of applying the methodology is a systematically researched and industry validated set of criteria that denotes assessing the sustainability of the civil engineering/infrastructure project type. The paper concludes that the top-down-bottom-up will support stakeholders and managers involved in assessing sustainability to consider all major research methods to define general and unique sustainability criteria to assess and so maximize sustainability.
226

Low energy dense diet and high-intensity exercise : impact on weight and waist circumference in abdominally obese women

Sweat, Whitney M. 17 November 2011 (has links)
Aging, obesity and increased waist circumference (WC) increases risk for metabolic syndrome (MetS). MetS is a cluster of symptoms (elevated WC, triglycerides, blood pressure, fasting glucose, and decreased high-density lipoprotein cholesterol [HDL-C]) increasing risk for chronic disease. Low-energy dense (LED) diets, emphasizing whole food eating patterns, have not been examined in combination with moderate (mod)/high-intensity physical activity (PA) or dietary protein levels to determine their impact on changes in body weight (BW) and WC in premenopausal, abdominally obese women. PURPOSE: To determine the effect of two 16-wk diet and PA interventions, differing in protein intake, on BW, WC, MetS risk factors, dietary patterns, energy density (ED), and min of Mod-Hi PA. METHODS: Healthy, abdominally obese (WC≥80cm) women (n=38; 34±10y) were randomly assigned to either a 15 or 25% (+18 g/d whey protein) en from protein diet. Individualized LED diets plans decreased energy intake (EI) by ~300kcal/d; PA 5 d/wk (30-60 min/d) consisted of supervised, high-intensity Zumba classes 3d/wk (≥65%HRmax; ≥6METs) and self-selected mod-intensity PA (≥3METs) 2d/wk. Servings of fruits/vegetables, whole grains, and low-fat/fat-free dairy (LFD), fiber, high calorie beverages (BEV), ED, and PA were monitored before (T1), during (T2) and after (T3) the intervention using repeated measures ANOVA. Bonferroni simultaneous testing procedure was used in analysis of multiple comparisons. RESULTS: At T1, groups did not differ in dietary patterns, PA, BW, WC, or MetS risk. Groups responded similarly to the interventions so data were combined, with BW and WC decreasing (p<0.0001) by -4.8±2.7kg and -7.1±3.6cm, respectively. Comparing T1 vs. T2, there were increases (p<0.0001) in fruits/vegetables, (Δ=+1.5 ser/d), whole grains (Δ=+1.0 ser/d), LFD (Δ=+0.5 ser/d), fiber (Δ=+5.7g/1000 kcal), and decreases in BEV (Δ=-165 kcal/d) and ED (Δ=-0.55 kcal/g). During the intervention high-intensity Zumba PA was 87min/wk; total min of all mod-intensity PA increased by 75 min/d (p<0.0001); VO2max improved from 29.3±4.7 (T1) to 34.4±5.3 (T3) mL/kg/min (p<0.0001). Triglycerides significantly decreased (-24±52 mg/dl; p=0.006), no other significant changes occurred in MetS risk factors. Exploratory analysis indicated that increases in fruits/vegetables and LFD, and decreases ED were associated with BW loss, while increases in whole grains, fiber, LFD, and min/wk of high-intensity PA (Zumba) were associated with WC reductions. CONCLUSION: For abdominally obese women, an intervention focused on LED foods and high-intensity PA significantly reduced BW and WC and improved dietary patterns regardless of protein intake. Helping clients identify a few key factors that positively promote reductions in BW and WC may improve weight loss success, while reducing MetS risk factors. / Graduation date: 2012
227

Rôle de différents compartiments microbiens (biofilms, matières en suspension, sédiments de surface) et de leurs constituants (bactéries, polymères extracellulaires et biominéraux) sur la méthylation et la réduction de HgII / Role of different microbial compartments (biofilms, suspended matters, surface sediment) and some of them components (bacterial cells, extracellular polymeric substances and biominerals) on HgII methylation and reduction

Remy, Paul-Philippe 01 July 2015 (has links)
La formation de méthylmercure, la forme la plus toxique du mercure, est due à l’activité bactérienne anaérobie. Afin de connaître la contribution des compartiments microbiens (biofilms, eaux brutes, sédiments) dans la méthylation du mercure, nous avons évalué les vitesses de méthylation d’échantillons de mares de région tempérée (Lorraine) et subarctique (Québec, Canada). Si les bactéries des biofilms ne semblent pas plus méthylantes que d’autres, le sédiment apparait comme le compartiment le plus méthylant en lien avec la concentration en nutriments ainsi qu’avec la température. Ainsi, les changements climatiques actuels, en augmentant la température de l’eau et en favorisant l’activité biologique, peuvent faire de ces mares des sites préférentiels de la méthylation du mercure en milieu subarctique. Enfin, l’activité des biofilms a mené à la formation de rouille verte, un minéral capable de réduire HgII en mercure élémentaire, concurrençant ainsi la méthylation bactérienne / Monomethylmercury formation, the neurotoxic form of mercury, is mainly linked to anaerobic microbial activity. In order to assess the relative contribution of several microbial compartments (biofilms, raw water and sediment) we evaluated methylation of samples from ponds of temperate area (Lorraine, France) and from subarctic ponds (Nunavik, Quebec). Biofilms were not found to specifically promote mercury methylation, whereas sediment emerges as the main compartment involved in mercury methylation. The formation of methylmercury is positively linked to the temperature and to nutrients. Thus, by increasing the open water period, the water temperature and of the microbial activity, current climate changes may turn these ponds in preferential location for mercury methylation in the subarctic ecosystem. Finally, the reactivity of green rust, a mineral which can be produced by bacterial activity of environmental biofilms, may compete with mercury methylation by reducing HgII into Hg0
228

Estudo da redução carbotérmica de minérios de ferro na forma de pelotas ou misturas autorredutoras em forno rotativo. / Study of carbothermic reduction of iron ore in the form of self-reducing pellets or mixtures in rotary kiln.

Nogueira, Alberto Eloy Anduze 31 August 2010 (has links)
A finalidade deste trabalho é estudar a redução carbotérmica de minério hematítico com misturas e pelotas autorredutoras em um forno rotativo experimental. Trabalhou-se com duas temperaturas, a 1673 e 1773 K (1400 a 1500 °C), em fluxo de argônio de 1Nl/min, em um forno rotativo experimental aquecido por resistências, com uma rotação fixa de 5 rpm. Foram realizadas diversas experiências, alterando variáveis como a temperatura, composição e quantidade da escória, tipo de redutor, e tipo de conformação. Foi estudado o tempo de residência das pelotas e misturas autorredutoras dentro do forno e sua interrelação com a inclinação do mesmo. Mediu-se a resistência a compressão de diferentes composições de pelotas. Foi analisada a fração de redução atingida nas experiências com ajuda de um método indireto proposto neste trabalho, atingindo-se frações de redução acima de 98%. Especial atenção foi dada para os casos limites estudados, o primeiro com uma mistura autorredutora de 81% de minério hematítico de baixo teor, 19% de coque de petróleo,+10% cimento ARI, processada a 1773 K (1500 °C) com 33% de escória final, a qual, apesar da grande quantidade de escória, atingiu uma fração de redução de 98,7%; e o segundo, para uma mistura autorredutora de 43,5% de minério hematítico de baixo teor, 56,5% de pó de serragem, processada a 1773 K (1500 °C), a qual atingiu uma fração de redução de 99,2%, provando, com as ressalvas cabíveis, a factibilidade de reduzir diretamente com pó de serragem. Com base nas observações experimentais sugeriram-se modelos do processo de redução-fusão tanto das misturas como das pelotas autorredutoras no forno rotativo. Analisaram-se a composição da escória e a composição da fase metálica obtida. Para comparar o grau de coalescimento entre as amostras, foram levantadas as análises granulométricas de cada uma delas, comparando-se as porcentagens em massa dos nódulos de ferro-carbono com diâmetro superior a 7,93 mm. Atenção especial foi dada ao método de desagregação do produto; pela ausência de normas técnicas especificas para processos autorredutores, foi empregada uma adaptação do método de desagregação por tambor (ASTM E279-95), e validada por moagem manual. Estudou-se o efeito das variáveis: temperatura de processamento, temperatura liquidus da escória, da quantidade de escória de alta temperatura liquidus, da quantidade de voláteis do redutor, da quantidade do redutor, e da ausência de conformação. Entre os resultados destas experiências tem-se que a maior temperatura de processamento leva a maior grau de coalescimento. Na medida em que a escória do sistema não se liquefaz, o processo de coalescimento é prejudicado. Na medida em que a quantidade de escória com alta temperatura liquidus aumenta, o grau de coalescimento decresce. Ao se aumentar a quantidade do redutor acima do necessário para a correta redução, carburação e colaescimento, prejudica-se o processo de formação dos nódulos de ferro-carbono. Ao se comparar o grau de coalescimento obtido entre as misturas e as pelotas autorredutoras, temse que o desempenho das misturas autorredutoras é superior. Para aclarar o efeito da temperatura liquidus da escória no processo de carburação e coalescimento, foram realizadas experiências paralelas para estudar como a temperatura liquidus da escória e a ausência do FeO afetava o coalescimento. Ao estudar o transporte de carbono pelas escórias sem e com a presença de um óxido redutível, tem-se que o transporte do óxido de ferro na escória sem agitação é um fenômeno difusivo. / The purpose of this work is to study the carbothermal reduction of hematite ore as self-reducing mixtures or pellets in an experimental rotary kiln. Two different temperatures were employed, 1673 and 1773 K (1400-1500 ° C) in an experimental rotary kiln heated by resistors, with a fixed rotation of 5 rpm and under an argon flow of 1Nl/min. Several experiments were performed by changing variables such as temperature, composition and quantity of slag, type of carbonaceous material, and type of conformation. The residence time inside the furnace and its interrelation with the slope of the kiln containing self-reducing pellets or mixtures was studied. It was measured the compressive strength of pellets of different compositions. It has been analyzed the fractional reduction achieved in the experiments with the help of an indirect method proposed in this work, reaching fractional reduction above 98%. Special attention was given to some cases, the first one with a self-reducing mixture of 81% low grade ore, 19% petroleum coke, ARI +10%, processed to 1773 K (1500 ° C) with 33% final slag, which despite the large amount of slag reached a fractional reduction of 98.7%, and the second for a self-reducing mixture of 43.5% low-grade ore, 56.5% of sawdust processed to 1773 K (1500 ° C) which reached a fractional reduction of 99.2%, proving, with reasonable exceptions, the feasibility of reducing directly with sawdust. Based on experimental observations, process models of both the reduction-melting of self-reducing mixtures and pellets in the rotary kiln were proposed. The composition of slag and composition of the metallic phase obtained were analyzed. To compare the degree of coalescence between the samples, particle size analysis of each one was performed, comparing the percentages by weight of iron-carbon nuggets with a diameter greater than 7.93 mm. Regarding the method of disintegration of the product, due to the lack of technical standards for specific self-reducing processes, the drum method (ASTM E279-95) was adapted and validated by manual grinding. It was studied the effect of the following parameters: processing temperature, slag liquidus temperature, the amount of high liquidus temperature slag, amount of volatile matter of the reducing agent, the amount of reducing agent, and the absence of conformation. These experiments have shown that the higher the processing temperature, the greater the degree of coalescence, and also that as long as the slag does not melt, the coalescence process is impaired. As the amount of slag with high liquidus temperature increases, the degree of coalescence decreases. Increasing the amount of carbonaceous material above to that necessary to reduction and carburization undermines the process of formation of iron-carbon nuggets. When comparing the degree of coalescence obtained between the self-reducing mixtures and pellets, it has been shown that the performance of self-reducing mixtures is superior. To clarify the effect of the slag liquidus temperature in the carburization and coarsening process, experiments were conducted to study how the liquidus temperature of the slag and the absence of FeO affected the coarsening. By studying the transport of carbon in slags with and without the presence of a reducible oxide, it has been shown that the transport of iron oxide in the slag without agitation is a diffusive phenomenon.
229

Changes in body composition and metabolic syndrome risk factors : response to energy-restriction, protein intake, and high intensity interval training

Pilolla, Kari D. 28 March 2014 (has links)
Metabolic syndrome (MetS) and abdominal obesity (AbOb) increase the risk of developing cardiovascular disease and diabetes. Energy restriction (ER), highprotein (PRO) intake and high-intensity interval training (HIT) can independently improve MetS and AbOb. However, ER reduces metabolically active lean body mass (LBM) in addition to body fat (BF). Purpose: To determine the effects of a 16-wk ER diet with 2 levels of PRO (15% or 25% of energy), plus HIT, on MetS risk factors, AbOb, and body composition in women. Methods: Sedentary, premenopausal women (age=35±10y) with AbOb (waist circumference [WC] ≥80cm) were randomized to a 16-wk ER diet (-300kcals/d) with 15% (15PRO; n=17) or 25% (25PRO; n=18) of energy from PRO, plus 45min/d, 3d/wk HIT and 45min/d, 2d/wk continuous moderate-intensity exercise (CME) (-200kcals/d). Diet and physical activity (PA) were assessed using 4-d weighed food and PA records, respectively; diet and exercise compliance were assessed monthly with multiple-pass 24-h recalls and weekly tracking logs. Body weight (BW), WC, DXA-assessed body composition (BF [%], BF [kg], trunk fat [kg], and LBM [kg]), blood lipids (total cholesterol [TC], high-density lipoprotein cholesterol [HDL-C], low-density lipoprotein cholesterol [LDL-C], triglycerides [TG]), glycemic markers (fasting plasma glucose [FPG], insulin, and homeostatic model assessment for insulin resistance [HOMA-IR], beta cell function [HOMA-%β] and insulin sensitivity [HOMA-%S]) and resting blood pressure (BP) (systolic BP [SBP]; diastolic BP [DBP]) were assessed pre/post-intervention. Repeated measures analysis of variance and two sample t-tests were used at analyze the date. Results are reported as means±standard deviations. Results: There were significant time, but not group, differences in BW (-5.1±2.6kg, p=0.0141), WC (- 7.3±3.6cm, p<0.0001), TC (-18.1±17.4mg/dL, p<0.0001), LDL-C (12.2± 16.2mg/dL, p<0.0001), TG (-25.3±56.2mg/dL, p=0.0064), insulin (-2.1±4.2mg/dL, p=0.0048), HOMA-IR (-0.2±0.5, p=0.0062), HOMA-%β (-12.1±35.2%, p=0.0497), HOMA-%S (28.5±78.4%, p=0.0357), and SBP (-3±9mmHg, p=0.214). There were significant group x time differences in DBP (15PRO=-5±8mmHg, 25PRO=- 2±8mmHg; p=0.0024). There were no time or group differences in FPG or HDLC. There were significant time, but not group, effects on changes in BW (-5.1kg± 2.6, p<0.0001), BF (-3.3±1.6%, p<0.0001), and LBM (-0.6kg±1.5, p=0.0283). The 15PRO group lost more absolute whole BF (-5.2kg vs. -3.9kg, p=0.0355) and trunk fat (-3.1kg vs. -2.2kg) vs. the 25PRO group. Conclusion: Both diets significantly improved BW, AbOb, MetS risk factors, glycemic control, and BF (%); LBM (kg) loss was similar in both groups. Compared to the 15PRO diet had significantly greater absolute BF-kg and trunk fat-kg losses. Increased PRO intake did not improve AbOb or MetS risk beyond ER and HIT/CME. The impact of HIT/CME and the greater (-1.3kg) changes in BW in the 15PRO group may have contributed significantly to the changes in absolute BF and trunk fat. More research is needed to separate the impact of HIT/CME and weight loss from the impact of PRO during ER. / Graduation date: 2013 / Access restricted to the OSU Community at author's request from March 28, 2013 - March 28, 2014
230

Estudo da redução carbotérmica de minérios de ferro na forma de pelotas ou misturas autorredutoras em forno rotativo. / Study of carbothermic reduction of iron ore in the form of self-reducing pellets or mixtures in rotary kiln.

Alberto Eloy Anduze Nogueira 31 August 2010 (has links)
A finalidade deste trabalho é estudar a redução carbotérmica de minério hematítico com misturas e pelotas autorredutoras em um forno rotativo experimental. Trabalhou-se com duas temperaturas, a 1673 e 1773 K (1400 a 1500 °C), em fluxo de argônio de 1Nl/min, em um forno rotativo experimental aquecido por resistências, com uma rotação fixa de 5 rpm. Foram realizadas diversas experiências, alterando variáveis como a temperatura, composição e quantidade da escória, tipo de redutor, e tipo de conformação. Foi estudado o tempo de residência das pelotas e misturas autorredutoras dentro do forno e sua interrelação com a inclinação do mesmo. Mediu-se a resistência a compressão de diferentes composições de pelotas. Foi analisada a fração de redução atingida nas experiências com ajuda de um método indireto proposto neste trabalho, atingindo-se frações de redução acima de 98%. Especial atenção foi dada para os casos limites estudados, o primeiro com uma mistura autorredutora de 81% de minério hematítico de baixo teor, 19% de coque de petróleo,+10% cimento ARI, processada a 1773 K (1500 °C) com 33% de escória final, a qual, apesar da grande quantidade de escória, atingiu uma fração de redução de 98,7%; e o segundo, para uma mistura autorredutora de 43,5% de minério hematítico de baixo teor, 56,5% de pó de serragem, processada a 1773 K (1500 °C), a qual atingiu uma fração de redução de 99,2%, provando, com as ressalvas cabíveis, a factibilidade de reduzir diretamente com pó de serragem. Com base nas observações experimentais sugeriram-se modelos do processo de redução-fusão tanto das misturas como das pelotas autorredutoras no forno rotativo. Analisaram-se a composição da escória e a composição da fase metálica obtida. Para comparar o grau de coalescimento entre as amostras, foram levantadas as análises granulométricas de cada uma delas, comparando-se as porcentagens em massa dos nódulos de ferro-carbono com diâmetro superior a 7,93 mm. Atenção especial foi dada ao método de desagregação do produto; pela ausência de normas técnicas especificas para processos autorredutores, foi empregada uma adaptação do método de desagregação por tambor (ASTM E279-95), e validada por moagem manual. Estudou-se o efeito das variáveis: temperatura de processamento, temperatura liquidus da escória, da quantidade de escória de alta temperatura liquidus, da quantidade de voláteis do redutor, da quantidade do redutor, e da ausência de conformação. Entre os resultados destas experiências tem-se que a maior temperatura de processamento leva a maior grau de coalescimento. Na medida em que a escória do sistema não se liquefaz, o processo de coalescimento é prejudicado. Na medida em que a quantidade de escória com alta temperatura liquidus aumenta, o grau de coalescimento decresce. Ao se aumentar a quantidade do redutor acima do necessário para a correta redução, carburação e colaescimento, prejudica-se o processo de formação dos nódulos de ferro-carbono. Ao se comparar o grau de coalescimento obtido entre as misturas e as pelotas autorredutoras, temse que o desempenho das misturas autorredutoras é superior. Para aclarar o efeito da temperatura liquidus da escória no processo de carburação e coalescimento, foram realizadas experiências paralelas para estudar como a temperatura liquidus da escória e a ausência do FeO afetava o coalescimento. Ao estudar o transporte de carbono pelas escórias sem e com a presença de um óxido redutível, tem-se que o transporte do óxido de ferro na escória sem agitação é um fenômeno difusivo. / The purpose of this work is to study the carbothermal reduction of hematite ore as self-reducing mixtures or pellets in an experimental rotary kiln. Two different temperatures were employed, 1673 and 1773 K (1400-1500 ° C) in an experimental rotary kiln heated by resistors, with a fixed rotation of 5 rpm and under an argon flow of 1Nl/min. Several experiments were performed by changing variables such as temperature, composition and quantity of slag, type of carbonaceous material, and type of conformation. The residence time inside the furnace and its interrelation with the slope of the kiln containing self-reducing pellets or mixtures was studied. It was measured the compressive strength of pellets of different compositions. It has been analyzed the fractional reduction achieved in the experiments with the help of an indirect method proposed in this work, reaching fractional reduction above 98%. Special attention was given to some cases, the first one with a self-reducing mixture of 81% low grade ore, 19% petroleum coke, ARI +10%, processed to 1773 K (1500 ° C) with 33% final slag, which despite the large amount of slag reached a fractional reduction of 98.7%, and the second for a self-reducing mixture of 43.5% low-grade ore, 56.5% of sawdust processed to 1773 K (1500 ° C) which reached a fractional reduction of 99.2%, proving, with reasonable exceptions, the feasibility of reducing directly with sawdust. Based on experimental observations, process models of both the reduction-melting of self-reducing mixtures and pellets in the rotary kiln were proposed. The composition of slag and composition of the metallic phase obtained were analyzed. To compare the degree of coalescence between the samples, particle size analysis of each one was performed, comparing the percentages by weight of iron-carbon nuggets with a diameter greater than 7.93 mm. Regarding the method of disintegration of the product, due to the lack of technical standards for specific self-reducing processes, the drum method (ASTM E279-95) was adapted and validated by manual grinding. It was studied the effect of the following parameters: processing temperature, slag liquidus temperature, the amount of high liquidus temperature slag, amount of volatile matter of the reducing agent, the amount of reducing agent, and the absence of conformation. These experiments have shown that the higher the processing temperature, the greater the degree of coalescence, and also that as long as the slag does not melt, the coalescence process is impaired. As the amount of slag with high liquidus temperature increases, the degree of coalescence decreases. Increasing the amount of carbonaceous material above to that necessary to reduction and carburization undermines the process of formation of iron-carbon nuggets. When comparing the degree of coalescence obtained between the self-reducing mixtures and pellets, it has been shown that the performance of self-reducing mixtures is superior. To clarify the effect of the slag liquidus temperature in the carburization and coarsening process, experiments were conducted to study how the liquidus temperature of the slag and the absence of FeO affected the coarsening. By studying the transport of carbon in slags with and without the presence of a reducible oxide, it has been shown that the transport of iron oxide in the slag without agitation is a diffusive phenomenon.

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