Dissertations / Theses on the topic 'Self-reduction'

CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Neste trabalho, foram feitas experiências de redução em temperaturas na faixa de 900°C a 1300°C, usando briquetes auto-redutores contendo óxidos de manganês e carvão vegetal, visando investigar o processo de redução de MnO2 para MnO. É apresentado um panorama geral do manganês, indicando os principais produtos, entre eles, o MnO para uso agropecuário e a liga FeMn, insumo siderúrgico e evidenciando os aspectos termodinâmicos e cinéticos no processamento para a obtenção destes produtos. Cabe assinalar que o MnO é um produto intermediário no processo de fabricação da liga ferro-manganês. Mostram-se também detalhes do procedimento experimental, caracterização dos materiais utilizados e as discussões sobre os resultados obtidos. Na determinação das conversões de MnO foi utilizado o método de análise química de titulação por complexometría com EDTA. A partir dos resultados experimentais foi proposto um modelo para determinação dos parâmetros cinéticos. Pelos resultados da redução de Mn+4 para Mn+2, foi possível distinguir dois estágios nas temperaturas ensaiadas. O primeiro estágio foi marcado por altas velocidades de reação, a até aproximadamente 10 minutos de experimentação, alcançando conversões elevadas de MnO; como foi o caso dos ensaios nas temperaturas de 1000°C e 1200°C, que já indicavam em 10 minutos valores de conversões iguais a 0.94. Já para o segundo estágio, após os 10 minutos iniciais de experimentação, as velocidades e os valores da conversão apresentaram uma queda, sugerindo que o produto do primeiro estágio, o MnO, poderia estar começando a se transformar em outra substancia ( provavelmente o Mn3C ). Por não ser objetivo desta dissertação determinar a natureza da citada transformação, apenas a evidência de sua ocorrência foi aqui explicitada, ficando os estudos mais detalhados para outro trabalho. O modelo cinético concluiu que o processo se passava essencialmente em duas etapas : uma para tempos curtos e outra para tempos longos, sendo o tempo de experimentação em torno de 10 minutos a fronteira destas etapas . O valor da energia de ativação para a etapa em tempos menores, ou seja, inferiores a 10 minutos, foi, nas temperaturas estudadas, 1000, 1100, 1150 e 1200°C, de 11,50 KJ/mol e o fator de freqüência pré-exponencial 0,057 mHz, sugerindo um controle difusional.. Já para os tempos maiores que 10 minutos, os experimentos nas temperaturas de 900, 1000, 1100, 1150, 1200 e 1300°C, muito embora não se tenha pesquisado a natureza do novo composto ( possivelmente o carboneto de manganês ), forneceu para a energia de ativação o valor de 46,10 KJ/mol e para o fator de freqüência pré-exponencial 48,045 Hz, sugerindo, em conseqüência, um mecanismo predominantemente misto, ou seja, equilibradamente difusional e químico.<br>In this work, aiming at the investigation on the reduction process of manganese dioxide to manganese oxide, experiments were made using selfreducing briquettes containing manganese oxides and charcoal, at temperatures ranging from 900 to 1300oC. A general overview of the manganese is presented, indicating its principal products such as, the farming usage of MnO and the steelmaking application of the FeMn alloys, also emphasizing the thermodynamical and kinectical aspects of their productions. It is worthwhile to emphasize that MnO is an intermediary product in the production of the FeMn alloy. Experimental details concerning materials characterization and discussion on the obtained results, are also presented. In the determination of the MnO conversion the complexometric titration with EDTA chemical procedure was applied. From these determinations a model was proposed for the calculation of the kinectic parameters. The experimental results of reduction, from Mn+4 towards Mn+2 , it was possible to identify two stages for the reactions in the temperature range from 900 to 1300 C. An onset stage was marked by high reaction rates, lasting for the first 10 minutes, achieving high MnO conversions. In the experiments carried out in the range of 1000 to 1200oC, for instance, a 0,94 conversion was attained within just 10 minutes. As for the second stage, beginning after 10 minutes, the conversion showed a decrease, suggesting that the product of the first stage, the MnO, could be suffering a transformation, generating an other substance - probably Mn3C. Being this a new process, out of the scope of this work, its elucidation is left here as a suggestion for later works. Wrapping up the kinetic model, a time frontier between the two processes, around 10 minutes, was considered . Below this limit, i.e., in the temperatures - 1000, 1100, 1150 and 1200oC -, the process exhibited an apparent activation energy of 11.50 kJ x mol -1 and a pre-exponential frequency factor of 57 µHz, inferring a diffusion control. As for times beyond 10 minutes, in experiments at 900, 1000, 1100, 1150, 1200 e 1300°C, though the nature of a new compound was not probed - possibly a manganese carbide - it was possible to measure a new apparent activation energy, 46.10 kJ x mol -1 , with a pre- exponential frequency factor of 48 Hz, values coherent with a mixed control, i.e., between the diffusional and the chemical mechanisms.

This is a post-test only experimental design using an uncertainty reduction video to alleviate patient uncertainty, desire for information and increase self-concept to improve overall patient satisfaction with health care experience. The subjects were 80 cardiac consultation patients in a cardiology clinic in Northern California. Forty people were randomly assigned to a control group and forty people to the experimental group. A scale was given to each group which measured the patients' level of self-concept, level of uncertainties (medical setting, relational and illness), and desire for information. The experimental group received an uncertainty reduction video prior to filling out the questionnaire. The uncertainty reduction video was designed to debrief the patient on subjects that may be causing uncertainty for the patient. In conclusion, this study found that the uncertainty reduction video significantly reduced the patient's level of medical setting uncertainty. The study showed a relationship between medical setting uncertainty and relational uncertainty and a relationship between relational uncertainty and illness uncertainty. The study also indicated that patients have high levels of uncertainties in all uncertainty areas: illness, relational, and medical setting, and high a desire for information. However, the video did not show an ability to reduce a patient's level of relational or illness uncertainty. The study also did not show a relationship between self-concept and level of uncertainty and desire for information. Future areas of research suggest that for a similar study a series of illness specific videotapes may be more beneficial at reducing illness uncertainty. The patient's level of previous knowledge, its source, depth and credibility was also suggested for future research. Another area suggested for future research would be the correlation between uncertainties and anxieties.

<p> This thesis encompasses a suite of coordination-driven self-assembled porphyrin prisms differing in the molecular clips linking two porphyrin faces in a cofacial arrangement. The goal of this work was to apply the facile synthesis methods to rationally design cofacial catalysts and analyze the activity towards the oxygen reduction reaction (ORR). Specifically, we have explored how different molecular clips affected the prisms&rsquo; activity, selectivity, overpotential, and kinetics. High selectivity towards H₂O and low overpotential are key requirements of an oxygen reduction catalyst for applications in fuel cells. </p><p> We have demonstrated the first coordination-driven self-assembled porphyrin catalyst (<b>Benzo-Co</b>) used for small molecule activation, specifically ORR. The first report includes the characterization, along with catalytic chemical and electrochemical reduction studies. The selectivity and rate constants of this catalyst (H₂O vs. H₂O₂) were compared to the mononuclear <b>CoTPyP</b>. After these findings, the goal was to optimize the catalyst using alternative bridging ligands in the molecular clips that held the porphyrin subunits in a cofacial offset and analyze the selectivity towards H₂O. We hypothesized that if the metal centers of <b>CoTPyP</b> were held at a shorter distance, the selectivity of the catalyst would improve. The distance of the metals is critical to the O&ndash;O bond cleavage step. If there is not a secondary metal to interact with O₂, for example mononuclear <b>CoTPyP</b>, O&ndash;O cannot be cleaved. If the M&ndash;M distance is too large, the secondary metal may not interact with O₂ to participate in the bond cleavage step. The catalyst series were immobilized on the electrode surface and the selectivities of <b>Ox-Co</b>, <b>Oxa-Co</b>, and <b>Benzo-Co</b> prisms towards H₂O₂ as determined by rotating ring-disk electrode studies. Rotating disk electrode studies showed Levich current responses. Kouteck&yacute;-Levich and Tafel analyses, were used to obtain kinetic information and estimation of rate constants. This thesis highlights how coordination-driven self-assembly can be used to address difficult multi-electron multi-proton transformations, like oxygen reduction, using cofacial polynuclear catalyst. </p><p>

Através de revisão bibliográfica e estudo experimental, o presente trabalho apresenta uma análise da influência de diversos parâmetros sobre a velocidade da reação entre minério de ferro e carbono, aglomerados na forma de pelotas auto-redutoras. Os parâmetros estudados foram: temperatura, tipo e quantidade de redutor, uso de adições, composição e vazão dos gases no recipiente de reação, tamanho da pelota. A técnica experimental consistiu em medi-se a velocidade de reação por análise termogravimétrica, complementada por análise do gás de saída e difração de Raios-X em pelotas parcialmente reduzidas. Verificou-se que o mecanismo controlador da velocidade de reação é determinado por um conjunto de parâmetros inter-relacionados, e que pode mudar o progresso de reação. A etapa química da reação é controlada pela gaseificação do carbono por CO2. Transporte de calor e difusão gasosa através dos poros da pelota exercem forte influência sobre a velocidade; os fatores que favorecem a influência de transporte de calor são: aumento de temperatura; aumento da reatividade do redutor; uso de catalisador; diminuição do diâmetro da pelota; início de reação; redução sob atmosfera CO/CO2 de composição próxima ao equilíbrio wustitaferro. A influência de difusão gasosa se faz sentir quando a reação é efetuada sob atmosfera de gás inerte, que penetra nos poros da pelota, diluindo a atmosfera CO/CO2 reinante no interior da mistura de partículas. Nessas condições, esta influência é maior quanto menor for a temperatura de reação, quanto menos reativo for o redutor, quanto menor for a pelota, e nos estágios finais de reação. Verificou-se ainda que parâmetros relacionados à composição das pelotas, bem como a temperatura do processo, tem grande influência sobre o comportamento dimensional dos aglomerados.Assim, pelotas com ganga básica (com carvão vegetal e adições básicas) tendem a inchar catastroficamente, ao passo que pelotas com ganga ácida (com coque ou carvão mineral como redutores) não apresentam este fenômeno. Microscopia eletrônica de varredura indicou a presença de ferro filamentar em pelotas que apresentaram inchamento catastrófico. Analisou-se ainda como a presença de matéria volátil no redutor afeta a cinética de reação e o comportamento dimensional das pelotas, e também sob que condições o ferro formado na redução catalisa a reação.<br>The factors that affect the rate of reaction between iron oxides and carbon were analysed by means of literature review and experimental investigation. The iron ore and the carbon were agglomerated in the form of self-reducing pellets. The investigated variables were: temperature, type and amount of redactor, presence of additives, gas composition and flow in the reactor vessel, and pellet\'s size. The experimental technique employed was thermogravimetric analysis, complemented by gas analysis and X-ray diffraction. It was shown that the rate control may change in the course of the reaction, and it depends on a number of interrelated varibles. The slowest reaction of the chemical step is the carbon gaseification by CO2. Heat transfer and gaseous diffusion through pellets pores play an important role in the rate; the factors that favours the heat transfer influence are: temperature increase, reducto\'s reactivity increase, the use of catalyst, pellet\'s size decrease, start up the reaction; reduction under CO/CO2 atmosphere near wustite-iron equilibrium. When the reaction is performed under inert gas atmosphere, gaseous diffusion through pellet\'s pores can dilute the CO/CO2 atmosphere prevailing in the pallet\'s core. Under these conditions, this effect is more pronounced for lower temperature, lower carbon reactivity, smaller pellets and at the end of the reaction. It was also found that variables related to pellet composition as well as process temperature greatly affect the pellet\'s dimensional behavior. In fact, pellets containing basic guangue (e.g.wood charcoal and/or basic additives) show catastrophic swelling; in contrast, pellets containing acid gangue (e.g. coke or coal) have good dimensional stability. Iron whiskers were observed with scanning electron microscope on pellets that swell catastrophically. The influence of reductor\'s volatile matter upon kinetics and dimensional behavior of pellets was also analysed as well as the catalysis of the reaction by the iron formed in the course of the reduction.

Flow metering plays a major role in modern life. In the process industry, flow metering is critical in industries ranging from food processing to cosmetics. It is also essential in custody transfer or billing, as flow meters are present in gas pumps and district heating substations. In the district heating industry, the ultrasonic flow meter has become the desired meter in many of its applications because it has a low cost while being accurate. This accuracy is however sensitive to installation effects and other sources of errors. This thesis stems from research that addresses the recognition of these installation effects, informs when they are unacceptable and considers reducing the measurement errors. To present these concepts, the thesis details the estimation of the mean flow velocity, the calibration of the meter and the measurement noise properties. Once installed, any kind of meter provides larger errors than in the facility where it has been calibrated and compensated. It is particularly true for ultrasonic flow meters as they are very sensitive to installation effects. Installation effects can either be static or dynamic. Special attention is paid to errors generated by temperature and velocity profile variations. Velocity profile variations can be due to pipe bends or flow pulsations. Such disturbances often induce a bias error and change the properties of the measurement noise. It is therefore with help of the change in noise that velocity profile disturbances can be detected. The detection of such abnormal behaviour of the measurement process constitutes a diagnosis. A diagnosis of the sensitivity of the meter to installations effects would allow for compensations for the errors. Signal analysis allows detection of specific noise properties, characteristic of installation effects. An example of self-diagnosis showing the detection of real pulsations in a flow is described in details. The detection of the flow pulsations and the estimation of their frequency allow to reduce the error of estimation on the flow rate. This technique is confirmed by the simulations of a pulsating flow. To empower one with the decision whether a flowmeter performance is normal or abnormal, a study of the relative error as a function of flow rate and temperature has been conducted.<br><p>Godkänd; 2004; 20080708 (evan)</p>

This quantitative study explored the impact of the Family Self-Sufficiency (FSS) program on welfare dependency over time, by evaluating participant income 5 years after completing the FSS program. The study was guided using the framework of the Personal Responsibility and Work Opportunity Reconciliation Act, which initiated welfare reform in an effort to decrease dependency on government assistance; and the Quality Housing and Work Responsibility Act, the law that initiated Public housing reform by reducing the high concentration of poverty. The research question examined whether the FSS Program in Los Angeles County reduced dependency on welfare overtime. The sample size for this study included 256 participants who received housing assistance payments from the Los Angeles County Housing Authority between 2010 and 2019. The results of this study demonstrate that Los Angeles County FSS program graduates are indeed, self-sufficient over time, thus reducing dependency on welfare. Implications for positive social change imply that cities across the nation could experience a decrease in poverty while benefiting from increased tax revenue resulting from higher employment rates. Working adults tend to be less prone to crime if they are making decent wages that can provide for their family.

Competence based self-esteem (CBSE) refers to a disposition where an individual strives for self-worth by achievements to compensate a low basic self-esteem (BSE). This kind of self-attitude is linked to burnout. The purpose of the study was to examine the effects of an 8-week mindfulness based stress reduction (MBSR) intervention on self-ratings of CBSE, BSE, burnout and mindfulness. Four MBSR groups were enrolled and a total sample comprised 29 participants. Results of repeated measures ANOVAs showed a significant decrease in CBSE and burnout as well as significant increases in BSE and mindfulness. It was further found that pre test - post test change in mindfulness was significantly associated with reduced CBSE. These results indicate the effectiveness of MBSR to reduce burnout and suggest the program’s applicability in treating self-esteem related problems.

<p> The purpose of this study was to explore treatment options for aggression-related disorders. Two activities were examined to validate their use as frustration-reduction techniques --yoga and therapeutic drumming. Twenty-two college students were randomly assigned to participate in one of three groups--yoga, drumming, or silence (control)--following experimentally-induced frustration using a computerized Stroop color-word technique. Self-reported emotion levels and physiological responses were tracked at baseline, post-frustration, and post-treatment to measure responses to treatment. Results indicate that self-reported frustration levels were significantly reduced in all experimental groups, but physiologic responses showed no significant changes. A Multivariate Analysis of Variance (MANOVA) indicated no significant difference in lowered frustration for any of the treatment groups, suggesting that they are equally effective. These results also suggest that the passage of time may be key to successful emotion regulation. Further study should examine control variables and methodology to identify other factors that may be involved in regulating aggressive emotions. </p>

Thesis (Ph.D.)--Indiana University, School of Education, 2006.<br>Source: Dissertation Abstracts International, Volume: 68-11, Section: A, page: 4607. Advisers: Jack Cummings; Samuel Odom. Title from dissertation home page (viewed May 21, 2008).

This dissertation explores the self-help initiatives of the poor in Egypt and articulates their perceptions of well-being. It argues that an increased role of the poor in the alleviation of their own poverty can render poverty reduction strategies more sustainable. Using Egypt as a case study, the dissertation compares the poor’s perceptions of well-being in two Egyptian sites (a rural village and an urban slum); and compares different patterns of self-help initiatives in Egypt: (i) an Islamic model of self-help in a rural village in the Delta; (ii) an anti-Female Genital Mutilation (FGM) women’s self help group and a semi syndicate for quarry workers in rural villages in Upper Egypt; and (iii) different cases of self-help in Manshiet Nasser, a slum area in Cairo. The case studies are drawn on to understand the role of religion and civil society in promoting these initiatives. At the conceptual level, the research adopts the capability approach and combines it with the literatures on collective action, institutions and social capital. It emphasizes the importance of collectivities for the expansion of human capabilities and develops a new integrated analytical framework that captures the interactive relationship between individual capabilities and social structures. Through the example of self-help, the research demonstrates how the poor- by pooling their resources together – are usually able to gain new capabilities that each individual alone would neither have nor be able to achieve, i.e. new ‘collective capabilities’. The research depends on qualitative research methods, such as an open-ended well-being questionnaire, semi-structured interviews and participant observation to articulate the poor’s voices and analyse their self-help initiatives. The research challenges the conventional top-down model of development by encouraging governments, donors and NGOs to build upon these existing initiatives of the poor thus promoting a new bottom-up model whereby the ideas of the poor come <i>first</i> and assistance is provided accordingly.

The purpose of this study is to determine the effect of Mindfulness-Based Stress Reduction (MBSR) on flow state and self-compassion in musicians while practicing. Specifically, the following research questions were addressed: (1) What effects, if any, will MBSR have on musicians' flow state and self-compassion during individual practice? and (2) What is the relationship between the constructs of flow and self-compassion? A two-group pre-test/post-test experimental design was used to address these research questions. Participants (N = 63) included students enrolled in an ensemble at a large comprehensive university in the Pacific Northwest. Results from a repeated measure ANOVA found non-significant changes in flow and self-compassion. Additionally, analysis from a Pearson’s Correlation found non-significant correlations between flow and self-compassion. Further implications from this study have the potential to aid music teachers with a better understanding of some methods and techniques to help students improve their focus and attention while playing music.

A redução carbotérmica do minério de ferro é a mais importante reação na fabricação do ferro, e tem sido obtida principalmente em Alto-Forno. Nos últimos anos, muitos processos novos foram propostos como alternativas e vários tipos de reatores foram testados. O processo mais promissor foi aquele em que a mistura minério de ferro e material carbonáceo eram aquecidos a altas temperaturas, promovendo a reação com formação do ferro metálico. Tornou-se claro que um dos principais obstáculos para a rápida reação é a transferência de calor da região externa para o centro da mistura. Por outro lado, muitos estudos têm mostrado que o aquecimento por microondas é muito efetivo em processos industriais, como secagem e sinterização de cerâmicos. No aquecimento por microondas, o material é aquecido a partir de seu interior, logo evita a obrigação de um aquecimento de fora para dentro do material. Neste trabalho, o aquecimento por microondas foi aplicado para a redução carbotérmica da hematita. Os resultados obtidos mostraram que é possível aquecer a mistura minério de ferro - carbono acima da temperatura de reação e que a taxa de reação é comparável à obtida por aquecimento convencional utilizando-se a mesma mistura.<br>The carbothermic reduction of iron ores is the most important reaction in ironmaking, and has been performed mainly in the Blast Furnace. In the last years, several new processes have been proposed as alternatives, and many types of reactors have been tested. The most promising processes are those in which a mixture of iron ore and carbonaceous material is heated at high temperatures, promoting the reaction with formation of metallic iron. It became clear that one of the main obstacles to a fast reaction is heat transfer from the surroundings to the core of the mixture. On the other hand, several studies have shown that microwave heating is very effective in some industrial processes, like drying and sintering of ceramics. In the microwave heating, the material is heated from the inside, thus avoiding the constraints of heat transfer from the surroundings to the inner part of the material. In this work, microwave heating has been applied to the carbothermic reduction of hematite. The obtained results have show that it is possible to heat iron-carbon mixture above the reduction temperature, and the reaction rates have been compared to those obtained employing conventional heating with the same mixtures .

Stress and stress-related disorders have been on the increase both in the UK and worldwide. UK Governmental bodies have proposed guidelines for managing stress at work; however most are aimed at reducing and preventing stress in employees. There are also a number of stress management programmes in place (including self-help), but very few have been empirically validated in a middle management population. A novel stress self-help manual based on cognitive behavioural therapy was developed for middle managers and evaluated in this randomised controlled trial (RCT; N = 102). Four outcome measures were used to measure change: Brief Symptom Inventory (BSI; primary outcome measure), Symptom Assessment-45 (SA45), Coping Inventory for Stressful Situations (CISS), and the Job Stress Survey (JSS). Treatment effects were evaluated using analyses of covariance (ANCOVA) with post- treatment scores as dependent variables and pre-treatment scores as covariates. Significant changes were obtained on the BSI (P<0.001) at post-treatment, as well as on the SA45 (P<0.001) indicating intervention effectiveness regardless of the frequency of work stressors and lack of organisational support remaining unchanged. Measures of coping indicated that the intervention increased task, emotion, and distraction-oriented coping styles (P<0.001). The intervention was not found to effect the avoidance- oriented or social diversion coping styles. Regression analyses indicated that discussing the manual with others during the treatment protocol had a significant effect on outcomes, suggesting that future interventions should encourage groups within organisations rather than individual participation, or using the manual as an adjunct to various forms of psychological therapy. Qualitative data was also collated, which revealed that the participants felt more in control and confident after working through the manual. While further evaluation by independent researchers is recommended, including cost effectiveness analysis, the manual has shown initial effectiveness and is considered a potentially useful tool for the development of improvements towards managing and preventing stress.

Neste trabalho estudou-se a evolução da redução da pelota auto-redutora de cromita contendo coque de petróleo, ferro-silício, cal hidratada, sílica e cimento Portland ARI (alta Resistência Inicial), para a obtenção da liga ferro-cromo alto carbono (FeCrAC). As principais variáveis estudadas foram: influência das adições de Fe-75%Si em sinergismo com coque de petróleo, adição de fluxantes, temperatura e tempo de redução. Além disso, foram realizadas experiências para confirmação dos resultados de auto-redução num forno rotativo de laboratório. Inicialmente os materiais (cromita, ferro-silício, coque de petróleo, cal dolomitica, sílica e cimento Portland ARI), foram caracterizados por análise química e análise granulométrica. Após a caracterização, os materiais, foram aglomerados na forma de pelotas (P1, P2, P3, P4 e P5), com adições de 0, 1, 2 e 4% Fe-75%Si, e adições de 2% Fe-75%Si e de fluxantes (3,83% cal dolomitica e 2,88% sílica), respectivamente. A redução das pelotas foi feita num forno de indução podendo atingir temperaturas de até 1973K (1700oC). Os ensaios experimentais foram realizados nas temperaturas de 1773K (1500°C), 1823K (1550oC) e 1873K (1600oC), utilizando-se cadinhos de grafite. Após os ensaios de redução os produtos obtidos (escória e metal) foram analisados por microscopia ótica, por microscopia eletrônica de varredura (MEV) e por análise de espectro de dispersão de energia (EDS). O processo de redução nas pelotas 1, 2, 3 e 4 segue os seguintes fenômenos i) via intermediários gasosos (CO/cromita) formam-se glóbulos metálicos nucleados na superfície das partículas de cromita, inicialmente rico em ferro; ii) estes crescem, pela redução na superfície da cromita deixando óxidos refratários na periferia da partícula de cromita original; iii) uma escoria incipiente se forma com os componentes da pelota (aglomerantes inorgânicos, cinza do redutor e fluxantes) e com a dissolução da ganga das partículas pequenas reduzidas da cromita; iv) a escória incipiente dissolve parte refratária da superfície da cromita, liberando a fase metálica e a escória vai se tornando cada vez mais refratária; v) o nódulo metálico segue crescendo e enriquecendo-se de cromo, reduzindo os óxidos de cromo e eventualmente de ferro dissolvido na escória incipiente; vi) o coalescimento da fase metálica é favorecido pela formação de escória e dissolução da ganga refrataria da cromita. O processo de redução da pelota 5 pela presença de fluxantes forma uma quantidade maior de escória inicial e apresenta os seguintes fenômenos: i) as reações indireta e direta reduzem as partículas finas de cromita, com formação de nódulos metálicos e fase escória nos primeiros instantes de redução; ii) os nódulos metálicos são formados pela redução das partículas finas de cromita. As partículas grandes sofrem pequena redução superficial e são encobertas pela escória, permanecendo dispersas na mesma; iii) a formação de escória encobrindo a cromita prejudica a redução gasosa aumentando o tempo de redução da mesma, porem facilita o coalescimento da fase metálica; iv) o nódulo metálico segue crescendo e enriquecendo-se de cromo, reduzindo aos poucos as partículas grandes de cromita. Existe regeneração do gás redutor (Boudouard) que pode ser diretamente com C do redutor ou com C dissolvido na fase metálica. A auto-redução carbotérmica das pelotas de cromita, na faixa de temperatura 1773K (1500oC) a 1873K (1600°C), sofre grande influência da temperatura, seja com ou sem adição de Fe-75%Si. O aumento da temperatura de 1773K (1500°C) para 1873K (1600°C) diminui o tempo para atingir redução completa conforme segue: i) 8 vezes para pelota sem Fe-75%Si; ii) 4 vezes para pelota com 1% de Fe-75%Si; e iii) 3 vezes para pelota com 2% de Fe-75%Si. Há um efeito significativo de adições de Fe-75%Si em pelotas auto-redutoras de cromita no tempo para atingir redução completa. O teor benéfico destas adições foi de 2%, contribuindo com aproximadamente 9% de calor necessário para redução completa, para as temperaturas ensaiadas de 1873K (1600ºC), 1823K (1550ºC) e 1773K (1500ºC). A evolução da redução é altamente sensível (diminui) com adição de fluxantes formadores de escória com temperatura líquidus abaixo de 1773K (1500ºC). A evolução da redução pela reação indireta (CO/cromita) é notavelmente mais rápida que a redução pela reação direta (C/cromita e C dissolvido na fase metálica/óxido de cromo na escória). A redução gasosa atuante nos primeiros estágios de redução, vai sendo prejudicada à medida que aumenta a quantidade de escória. As pelotas (1, 2, 3 e 4) sem adição de fluxantes (sílica e cal dolomítica), após reduzidas, são altamente porosas e têm pequena formação de fase escória se comparar com aquelas com adição de fluxantes com formação maior de fase escória (pelota 5). A pelota 3 com 2% de Fe-75%Si apresentou melhores resultados em relação ao tempo de redução. A pelota com adição de 4% Fe-75%Si (pelota 4), não apresentou diminuição do tempo de redução, devido a uma maior formação de escória que prejudica a reação indireta (mais rápida). As evidências micrográficas, auxiliadas por análises por EDS, mostraram que as reduções das partículas de cromita, foram praticamente completas quando as frações de reação se aproximam da unidade, confirmando a confiabilidade da metodologia utilizada. A redução da pelota auto-redutora, independente da sua composição, acontece de forma não isotérmica apesar de ser ensaiada numa temperatura isotérmica, apresentando-se um gradiente de temperatura entre a superfície e o centro da pelota, ao longo do tempo, mas esta desaparece conforme a reação progride tornando-se uniforme ao final da reação; evidenciando que a transferência de calor é a etapa lenta do processo devido: às reações de redução serem bastante endotérmicas; ao tamanho das pelotas; às altas temperaturas; e por ser um material poroso e refratário. A resistência a compressão das pelotas (1, 2, 3, 4 e 5) após 28 dias de cura e antes de serem reduzidas foi de ~4 kgf/pelota, porém tornou-se bastante alta após reduzidas (150 a 400 kgf/pelota); tornando-as aptas para carga em reatores de fusão. Estes resultados foram confirmados com ensaios no forno rotativo de laboratório, utilizando-se a pelota 2 (2% de Fe-75%Si), evidenciando: i) que as reduções de Cr e Fe foram praticamente completas (fração média de reação de 0,99) em 30 minutos de ensaio a 1500ºC; ii) a coalescência das partículas metálicas, obtidas por redução depende da capacidade da escória de dissolver os óxidos remanescentes na partícula de cromita reduzida; iii) há formação de fase incipiente de escória não-continua, aos 5 minutos de ensaio, pela parte da ganga do minério de cromita com os componentes de aglomerantes e/ou fluxantes; iv) a recuperação do teor metálico é alto (99%), em 30 minutos de ensaio, a 1500º C. Os resultados mostram um grande potencial do processo de auto-redução na produção de ferro-cromo alto carbono (FeCrAC).<br>The evolution of reduction of the self-reducing pellets of chromite for obtaining ferro-chromium high carbon (FeCrHC) was analyzed. The influences of Fe-75%Si additions, addition of fluxing agents, temperature and time of reduction were studied. The materials (chromite, ferro-silicon, petroleum coke, dolomite lime, silica and cement Portland), were characterized by chemical and particle size analysis. After characterization, the materials were agglomerated in the form of pellets (P1, P2, P3 and P4), with additions of 0, 1, 2 and 4% Fe-75%Si, respectively, and P5 with additions of 2% Fe-75%Si and fluxing agents (3.83% dolomite lime and 2.88% silica). The reduction of pellets was made using induction furnace with capability to reach temperatures up to 1973K (1700ºC). The experiments were performed at temperatures of 1773K (1500ºC), 1823K (1550ºC) and 1873K (1600ºC), using graphite crucibles. After the reduction the products (slag and metal) were analyzed by optical microscopy, scanning electronic microscopy (MEV) and energy dispersion spectrum analysis (EDS). The reduction process in pellets 1, 2, 3 and 4 followed phenomena as: i) gaseous reduction (CO/chromite) produces metallic globules on the surface of chromite particles, initially rich in iron; ii) these globules grow continuing the reduction at the periphery of chromite particles, leaving refractory oxides at this area of the original chromite particle; iii) an incipient slag is formed with the components of the pellet (inorganic binders, ash of reducer and fluxing agents) and with the dissolution of gangue from small particles of the reduced chromite; iv) the incipient slag dissolves refractory oxides remaining at the periphery of the chromite particles, liberating the metallic phase and the slag becomes more refractory; v) the metallic phase grows and becomes richer in chromium by reducing chromium oxides and eventually of iron dissolved in the incipient slag; vi) the coalescence of the metallic phase is favored by the slag formation and dissolution of refractory gangue of the chromite. The reduction process of pellet 5 follows as: i) indirect and direct reactions reduce fine particles of chromite, with formation of metallic nodules and slag phase at the beginning of reduction; ii) the metallic nodules are formed by the reduction of fine particles of chromite. Large chromite particles are reduced at the peripherical surfaces and are embebeded by the slag and remain dispersed in it; iii) the slag formed is harmful for the gaseous reduction and the time for completing the reduction is increased, but facilitates the coalescence of the metallic phase; iv) the metallic nodule follows growing and becomes richer in chromium. The carbothermic self-reduction pellets of the chromite at the temperature range of 1773K (1500ºC)-1873K (1600ºC), presents great influence of the temperature, either, with or without addition of Fe-75%Si. The increase of the temperature from 1773K (1500ºC) to 1873K (1600ºC) decreases the time for completing the reduction as: i) 8 times for pellet without Fe-75%Si; ii) 4 times for pellet with 1% of Fe-75%Si; and iii) 3 times for pellet with 2% of Fe-75%Si. A significant effect of additions of Fe-75%Si in self-reducing pellets of chromite in the reduction time was observed. The best addition was with 2% and its contribution was approximately 9% of necessary heat for complete the reduction, for the temperatures of 1873K (1600ºC), 1823K (1550ºC) and 1773K (1500ºC). The evolution of reduction is highly sensitive (it decreases) with addition of fluxing agents which form the slag with liquidus temperature below 1500ºC. The evolution of reduction for the indirect reaction (CO/chromites) is remarkably faster than that of the reduction by the direct reaction (C/chromite and C dissolved in the metallic phase/chromium oxide in the slag). At the beginning the gaseous reduction is predominant but it becomes less important with formation of larger amount of slag. The pellets (1, 2, 3 and 4) without addition of fluxing agents (silica and dolomite lime), after reduced, are highly porous and have small formation of slag phase than pellet 5 with addition of fluxing agents. Pellet 3 with 2% of Fe-75%Si presented the best results with relation to time for completing the reduction of chromite. The pellet with addition of 4% Fe-75%Si (pellet 4) did not present advantage with relation to that of 2% addition due to larger volume of slag formation. The micrograph analysis showed that the reductions of chromite particles practically were complete when the reaction fractions approach to the unit, confirming the confidence of the methodology used for determining the reaction fraction. The reduction of the self-reducing pellet, regardless its composition, happens by not isothermal way although it is submitted at isothermal temperature. The temperature gradient between surface and the core of the pellet is larger at the beginning but it disappears as the reaction progresses, becoming uniform with time. The heat transfer showed to be the slowest step of the process due to, the endothermic reactions of reduction, the size of the pellets, the high temperatures and porous nature and refractory material. The compression strength of the pellets (1, 2, 3, 4 and 5), after 28 days of curing, before of the reduction was ~4kgf/pellet but it increased up to 150 - 400 kgf/pellet; which are acceptable for charging the melting furnace for metal/slag separation. These results were confirmed by using laboratory rotating furnace, with pellet 2 (2% of Fe-75%Si), as: i) the reductions of Cr and Fe were practically complete (fraction of reaction 0,99) after 30 minutes of experiment at 1500ºC; ii) the coalescence of metallic particles, depends the capability of the slag to dissolve remaining oxides in the reduced chromite particle; iii) incipient not-continuous slag phase forms, at 5 minutes of experiment, from the gangue of the chromite and from the components of binders and/or fluxing agents; iv) the yield of metallic recovery is high (99%), after 30 minutes of experiment at1500º C. The results show that the self-reduction process presents a great potential for the ferro-chromium high carbon production (FeCrHC).

Background: Alongside experiencing physical symptoms with no identifiable organic cause, patients with MUS commonly experience comorbid anxiety and depression. They also have high health utilisation costs, which has implications for the health service. Interventions which target these symptoms in a cost effective way need to be developed and evaluated. Objective: To develop and evaluate a self-help mindfulness-based stress reduction (MBSR) intervention for patients with medically unexplained symptoms (MUS). Methods: A systematic review of the literature was carried out to evaluate the effectiveness of MBSR for reducing psychological distress in people with MUS. Study 1 developed and evaluated a self-help MBSR intervention in a clinical setting. Fifteen participants were recruited from eight practice, however only five completed post-intervention measures. A combination of t-tests and descriptive statistics were used to compare changes in levels of psychological distress, quality of life, symptoms and mindfulness at post-intervention. Pearson‘s correlations were used to identify relationships between improvements in mindfulness and improvements in outcomes. Study 2, exploring the reasons for the difficulties recruiting participants to Study 1, was then carried out through questionnaires to GPs. Results: Though more evidence is needed, the systematic review found MBSR to have moderate effects on psychological distress, which are largely maintained or improved at follow-up. Study 1 found symptom frequency and levels of acceptance to have improved at post-intervention. Study 2 found that the main reasons for GPs not recruiting participants was that they were busy and found it difficult to prioritise given other demands. Conclusions: Evidence to date suggests that MBSR is an effective intervention for patients with MUS. Future studies may benefit from recruiting participants from relevant organisations or using alternative methods such as database searches. No firm conclusions can be made about the self-help MBSR intervention‘s efficacy due to the study‘s limitations, however changes seen in the completer group suggest that further research would be warranted.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>PROGRAMA DE SUPORTE À PÓS-GRADUAÇÃO DE INSTS. DE ENSINO<br>O pó de aciaria (fração Fina-F e fração Grossa-G) gerado no sistema de despoeiramento à seco dos gases de exaustão do conversor LD, e o pó de alto forno-AF recuperado pelo sistema de tratamento de gases do setor de redução (coletor de gases), têm papel relevante entre os materiais secundários gerados nos vários elos da cadeia produtiva de uma siderúrgica integrada, seja pelas quantidades produzidas, seja por suas composições. Por serem portadores principalmente de unidades de ferro e carbono e algumas vezes zinco, esses resíduos são sempre alvo de iniciativas tecnológicas que objetivem recuperá-los ou reciclá-los. Além disso, os materiais particulados gerados pelo sistema de despoeiramento a seco, diferentemente dos à úmido, ainda carecem de estudos aprofundados para suas reciclagens. Embora antiga, a briquetagem atualmente vem se tornando uma tecnologia cada vez mais importante entre os processos de aglomeração. Assim, nesta Tese foi estudado, numa primeira etapa, a viabilidade de fabricação dos chamados briquetes F-G simples, constituídos apenas pelos pós Finos e Grossos, nas proporções percentuais de 50-50 e 70-30, respectivamente, e o exame teórico e experimental de seus usos como carga ferrosa nos processos de redução e como materiais alternativos às sucatas e pelotas, quando adicionados ao aço líquido do conversor LD para o controle de sua temperatura. Na fabricação dos briquetes F-G simples, também buscou-se testar os aglomerantes cimento ARI e melaço de cana de açúcar, isoladamente ou quando misturados, atendendo às relações água/cimento de 0,5 e água/melaço de 0,7. O processo experimental de cura a frio dos aglomerados se estendeu até 28 dias. A resistência à compressão obtida em prensa hidráulica instrumentada foi o principal parâmetro para avaliar a qualidade mecânica dos briquetes. A metodologia experimental envolveu a técnica do planejamento fatorial, 2(k), níveis (mínimo e máximo), com três variáveis (resíduos, aglomerantes e água). Nos resultados verificou-se que a resistência à compressão dos briquetes F-G simples, usando o binômio cimento-melaço sempre apresentou valores mais elevados do que os briquetes quando aglutinados com as duas substancias isoladamente. Além disso, dentre os aglomerados produzidos os de teores mais elevados de fração Grossa (briquetes 50-50), apresentaram maior resistência mecânica que os briquetes tipo 70-30. Em relação aos efeitos de resfriamento que provocam quando adicionados ao aço liquido, os balanços térmicos mostraram que os briquetes do tipo 70-30 apresentariam melhores índices no controle da temperatura do banho de aço, que os do tipo 50-50. A fim de verificar como se comportariam os briquetes F-G anteriores, quando se adicionava o pó de coletor de AF nas suas constituições como fonte supridora de carbono e apenas o cimento ARI como aglutinante, foram produzidos os denominados briquetes autorredutores, também dos tipos F-G, 50-50 e 70-30. Além da viabilidade de fabricação desses aglomerados, foram determinadas suas qualidades mecânicas e levantadas suas metalizações em ensaios de redução nas temperaturas de 1100 graus Celsius e 1150 graus Celsius. O estudo cinético da autorredução foi realizado avaliando-se o grau de conversão a ferro metálico e examinada a fenomenologia de sua evolução. Os resultados evidenciaram que o grau de conversão metálica cresceu com o aumento da temperatura e com a quantidade da fonte de carbono, que a metalização apresentou uma morfologia final do tipo shell layer e que o modelo cinético testado, tipo reação continua, apresentou uma correlação acima de 99 por cento. Além disso, os balanços de energia mostraram que o efeito de resfriamento imposto ao aço liquido pelos briquetes F-G autorredutores, sempre se mostrou superior aos dos briquetes F-G simples. Adicionalmente, afim de melhor interpretar os resultados obtidos foram realizados testes adicionais, como o de reatividade do coque metalúrgico, via a norma ASTM D5341-99 e por aná<br>The steel dusts (fine-F and coarse-G fractions) generated in the dry dedusting equipment of the LD converter exhaust system, and in the blast furnace-AF dust collector, play a relevant role among secondary materials generated in the various steps of the integrated steelmaking chain, either by the quantities produced and their compositions. Because they mainly contain iron and carbon units and sometimes zinc in their compositions, actually these wastes are being the target of several technological initiatives, aiming to recover or recycle them. Moreover, the particulate materials generated by the LD dry dedusting system, unlike those collected in the wet system of the same LD processes, still lack in-depth studies for recycling. Nowadays briquetting is increasing in importance among agglomeration processes, mainly due to its feature in treat particulate materials with a wide range of size. This thesis studied, in a first stage, the feasibility of manufacturing the so-called simple F-G briquettes, in the proportions of 50-50 and 70-30, respectively, as well as their theoretically and experimentally possibilities to be charged as a ferrous burden in reduction processes and as an alternative material to the scrap and pellets, when used to control the liquid steel temperature in LD converters. In the manufacture of the simple F-G briquettes, was also tested the binders ARI cement and sugarcane molasses, alone or when mixed, taking into account the water / cement ratio of 0,5 and the water / molasses ratio of 0,7. For the briquettes studied in this research, all cure operations lasted for up to 28 days and the compressive strength parameter obtained to evaluate the mechanical quality of the briquettes. The experimental methodology involved the technique of factorial planning, 2(k) levels (minimum and maximum), with three variables (residues, agglomerates and water). The results showed that the compressive strengths of the simple F-G briquettes, when using the cement-molasses mixture, always achieved higher values than that for briquettes using the cement or molasses separately. Moreover, the higher content of coarser fraction (briquettes 50-50) always leads to higher mechanical resistance than the finer one (70-30). On the other hand, the energy balances showed that the simple F-G briquettes 70-30, have presented the better cooling indexes for the liquid steel temperature control than the 50-50 briquettes. Regarding the second part of the thesis, two types of F-G self-reducing briquettes were also produced, containing stoichiometric and 10 percent excess of BF-collector dusts. After curing, they were tested on compression and reduced in temperatures of 1100 Celsius degrees and 1150 Celsius degrees. The kinetic study of the self-reducing briquettes was carried out evaluating the metallic iron conversion and the metallic iron phenomenology and morphology formation. The results showed: a) that the iron conversion increased as higher the temperature and amount of carbon; b) that the iron metallization presented a shell-layer type morphology and, c) that the continuous-reaction type kinetic model, adjusted very well the experimental reduction results, with a correlation factor above 99 percent. Additionally, in order to better understand the experiment results, the metallurgical coke reactivity was obtained using the ASTM D5341-99 test and the Differential Thermogravimetric analyzes (DTG), as well as confirmed the hydrated water amount in the passivated F and G dusts, also using the DTG methodology. Finally, considering the manufacturing feasibility of the both, simple and self-reducing F-G briquettes, the following could be also marked: I) The use of both briquettes type for liquid steel temperature control in LD converters, as effective alternative materials to scraps and pellets, considering the following comparative cooling indexes: a) 2,1 and 2,4 times the scrap, for the self-reducing briquettes 50-50 and 70-30, respectively, both with 10 percent excess; b) 1,7 and 1,9 times the scrap, for the simple briquettes, 50-50 and 70

The current study examined the relative effectiveness of motivational feedback compared to cognitive-behavioral skills training delivered in bibliotherapy format to college students. The effectiveness of matching alcohol abuse interventions with participant's stage of change was also explored. The study's design utilized an assessment only control group and collateral informants to strengthen the validity of the conclusions. Participation in the cognitive-behavioral skills training and motivational feedback interventions did not lead to greater reductions in participants' alcohol use and alcohol related problems than assignment to an assessment only control group. No significant differences were found between these three groups on any of the drinking measures from pre-test to l-month and from pre-test to the 2- month follow-up. Only time effects were observed on alcohol related problems and frequency of heavy alcohol use across the 3 experimental conditions. Tentative explanations for the lack of support for the effectiveness of these interventions are discussed in the paper including sample size and statistical power, intervention compliance, and intervention fidelity. A number of changes which might enhance the effectiveness of these interventions are also discussed in the paper. The study also found no significant Intervention X stage of Change X Time interactions to support the effectiveness of matching intervention to participants' stage of change. Tentative hypotheses for this finding are discussed in the paper including issues related to the measurement of stages of change. Competing hypothesis regarding the relative and incremental utility of outcome and self-efficacy expectancies were also examined in the study. Pre-test efficacy expectancies consistently predicted a significant proportion in participants' frequency of alcohol use and moderate use at 1 and 2-month follow-ups beyond concurrent use outcome expectancies were unable to add to the prediction of drinking behavior beyond self-efficacy and concurrent drinking behavior. This pattern of results support Bandura's (1986) view that efficacy expectancies subsume most of the predictive power of outcome expectancies. Further, as predicted by Bandura, prior drinking behavior alone did not fully explain future use, rather students perceptions of efficacy also guided future use.<br>Ph. D.

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.<br>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.

In Australia, up to 53 women will be diagnosed with breast cancer every day of 2019. With improved screening, diagnosis and treatment, survival rates are over 90% for 5 years after diagnosis. Notably, even when individuals are cancer-free following treatment for breast cancer, it is considered a chronic illness with recurrence a constant possibility. Many individuals adapt to this uncertainty; however, some are at risk of ongoing psychosocial distress. For individuals diagnosed with cancer, from the time of diagnosis, throughout treatment and into survivorship, maintenance of wellbeing is critical. Mindfulness and self-compassion are two positive constructs known to protect against distress, particularly during times of adversity. This research had three aims: 1) to identify the unique and common contributions made by dispositional facets of mindfulness and positive and negative self-compassion, to protect against anxiety and depression and promote quality of life in a sample of individuals with breast cancer; 2) to determine the stability and reliability of dispositional mindfulness and self-compassion over time; and 3) to evaluate the feasibility and efficacy of a facilitator-supported online mindfulness-based stress reduction (eMBSR) programme for women with breast cancer, many of whom were reporting significant psychological distress. To address these aims, three studies were conducted to explore facets of mindfulness and self-compassion that might protect against distress and promote wellbeing for people with breast cancer, incorporating cross-sectional, longitudinal, and interventional methods to examine these associations. In Study 1 the associations between the dispositional facets of mindfulness, positive and negative self-compassion, and reports of anxiety, depression, and quality of life were investigated in a sample (N = 199) of individuals diagnosed with breast cancer who were in or had completed treatment for breast cancer within the past 36 months. Whilst there was considerable overlap between these constructs, regression analysis found that the mindfulness facets, act with awareness and being non-judgemental of inner experience, together with positive self-compassion, were uniquely associated with lower reported symptoms of depression and anxiety and better quality of life. Higher reports of negative self-compassion were associated with higher reports of anxiety and depression and symptoms of poorer quality of life. Study 2 examined the influence of dispositional mindfulness and positive and negative self-compassion on ongoing levels of anxiety, depression, and quality of life over time. Participants (N = 79) completed two additional questionnaires, three (Time 2) and six months (Time 3) following participation in Study 1. The associations between the facets of mindfulness and outcome variables were also stable over time. When examining trends over time, anxiety, depression, all facets of mindfulness, and positive and negative self-compassion were stable, showing evidence of high reliability. Time 3 quality of life significantly improved from Time 1 and 2. Increased mindful non-judgement and decreased negative self-compassion consistently predicted lower levels of anxiety and depression. Increased mindful non-judgement and lower negative self-compassion, and to a lesser degree increased reports of acting with awareness and positive self-compassion, were also associated with improved quality of life over time. When examined together, Studies 1 and 2 indicated that being more mindful, particularly less judgemental of the self, as well as identifying less with difficulties and being less self-critical, were associated with reduced anxiety and depression and better wellbeing in a distressed sample. Study 3 evaluated the feasibility and efficacy of an eMBSR programme for women with breast cancer, most of whom reported significant psychological distress (81.3%). All 16 participants were recruited from Study 1 and split across two parallel eMBSR programme groups using quasi-random allocation. A single case multiple baseline design was used. In addition, a normative control (N = 79) sample was taken from Study 2 for comparison. Feasibility results showed an acceptable intervention completion rate (62.7%) and good participant engagement with the programme. Results of the study were very positive and compelling. Analysis of case series data suggested participants reported positive personal benefits from programme participation. Further, analysis of pre-, post-, and follow-up intervention data found significant improvements in anxiety, mindful non-reactivity and observe, and positive self-compassion. No significant changes were found for depression, the other mindfulness facets, or negative self-compassion. This study provides promising results for further investigation of eMBSR delivery format. Overall, the findings provide insights into how being more mindful, and showing more positive and less negative compassion toward the self, promotes wellbeing in individuals diagnosed with breast cancer. Dispositional mindfulness and self-compassion were stable over time in the absence of intervention, indicating that training to enhance these skills might be helpful in improving wellbeing over time. The mindfulness facet of non-judgement and negative self-compassion were found to be the strongest and most consistent unique predictors of anxiety, depression, and quality of life. Mindful acting with awareness and positive self-compassion were also found to predict anxiety, depression, and quality of life. These findings could be used to inform creation of more targeted interventions. Finally, the results for eMBSR provide very promising and compelling initial feasibility and preliminary efficacy data that show patterns of improvement consistent with past face-to-face MBSR research. Several avenues for further research are suggested, including more representative samples and improvements to the intervention interface by using updated software solutions. This thesis represents a significant contribution to the understanding of how mindfulness and self-compassion can protect against distress and promote wellbeing during times of adversity work, and how they can be influenced using a novel internet version of an evidence-based programme.<br>Thesis (Professional Doctorate)<br>Doctor of Philosophy in Clinical Psychology (PhD ClinPsych)<br>School of Applied Psychology<br>Griffith Health<br>Full Text

Neste trabalho estuda-se o comportamento de redução para a obtenção da liga FeCrAC a partir da pelota auto-redutora feita de minério de cromita, coque de petróleo, ferro-silicio, cal hidratada, sílica e cimento portland ARI. As principais variáveis consideradas são: teor de redutor na composição da pelota, quantidade do redutor, temperatura e tempo. Inicialmente os materiais (cromita, ferro-silício, coque de petróleo, cal hidratada, sílica e cimento Portland ARI), foram caracterizados por: análise química e análise granulométrica. Após a caracterização os materiais (cromita, ferro-silício, coque de petróleo e cimento Portland ARI) foram aglomerados na forma de pelotas juntamente com cal hidratada e sílica para ajuste da basicidade quaternária da escória. A redução das pelotas foi feita num forno de indução que pode atingir temperaturas de até 1973K (1700oC). Todos os experimentos de redução foram realizados no aparato experimental utilizando-se cadinhos de grafite nas temperaturas de 1773K (1500oC), 1823K (1550oC) e 1873K (1600oC). Após os ensaios de redução os produtos obtidos (escória e metal) foram analisados por microscopia ótica, por microscopia eletrônica de varredura (MEV) e análise por EDS. O efeito do aumento da temperatura na redução da cromita é significativo. Houve aumento na velocidade de redução de 4 a 6 vezes com o aumento de 1773K (1500oC) para 1873K (1600oC). Os resultados indicam um efeito marcante de pequenas adições de Fe-Si na velocidade de redução da cromita. Na temperatura de 1773K (1500oC) as adições até ~2% de Fe-Si são benéficas e para adições maiores praticamente não há vantagens técnicas e econômicas. Os tempos necessários para atingir a fração unitária de redução foram 12, 7,5 e 5 minutos para adições de Fe-Si de 0, ~1%, e ~2%, respectivamente; a temperatura de 1823K (1550oC). À temperatura de 1873K (1600oC) as adições de Fe-Si na pelota apresentam também efeitos significativos na velocidade de redução, porém adições de ~1%, e ~2% mostraram os mesmos resultados, indicando que o teor ótimo de adição de Fe- Si na pelota deve estar em torno de 1%. Verificou-se que a utilização de pelotas auto-redutoras contendo 26% em excesso, sobre o estequiométrico, de coque de petróleo aumentou o rendimento de recuperação de Cr de 96% para 98%. O rendimento e a eficiência do processo de auto-redução supera aos processos convencionais de produção de FeCrAC, obtendo-se altas recuperações de cromo na faixa de 96% até 98% para Cr.<br>The reduction behaviors, at high temperature, of the self-reducing pellets of chromites for production of high carbon ferro-chromium are studied in this work. The influences of the temperature, of the excess of reductant and the small addition of the Fe-Si were analyzed. The materials used (chromites, petroleum coke, Portland cement, hydrated lime and silica) were characterized chemically and by size distribution. The composite pellets (self-reducing) were produced aiming a quaternary basicity of 0.91. The reductant was calculated considering a stoichiometry of reduction and dissolution of 4wt%C in the final metallic phase. The reduction experiments were made in a special system, in argon atmosphere, heated by induction and at temperatures of 1773, 1823 and 1873K. The dried pellets were placed into a pre-heated graphite crucible and left there along up to no gas evolution was observed. The results of the reacted fraction with time were plotted and the obtained product (metallic and slag phases) after experiments were analyzed by optical and by electron micrograph. The chemical estimations were made by micro-analysis (EDS) The effect of increasing the temperature of reduction was sensitive, such that, the reduction rate increased 4 to 6 times with increase of temperature from 1773 to 1873. The small additions, up to 2% of Fe-Si, for substituting the equivalent fixed carbon of the petroleum coke showed to improve substantially the reduction rate, almost doubling it in comparison with pellets without any addition. The use of excess of 26%, over the stoichiometry, of the petroleum coke decreased around 50% of the chromium content in the slag, with relation to pellet without excess. The chromium recovery yield reached 98%. This result coupled with very high reduction rate of self-reducing pellets show the potential for self-reducing processes for ferro-chromium production.

O ferro-esponja ou DRI (Direct Reduced Iron) é obtido pelo processo de redução direta onde o minério de ferro é transformado em ferro metálico através de reações químicas envolvendo o estado sólido (minério) e o gasoso (gases redutores). Neste processo o minério de ferro não passa pelo estado líquido como ocorre com o ferro-gusa. Isto confere ao ferro-esponja algumas desvantagens que prejudicam o seu desempenho nas aciarias. Pode-se citar a redução no rendimento metálico e o maior consumo de energia elétrica como principais impactos de sua utilização intensiva. O ferro-esponja apresenta menor quantidade de ferro total (maior quantidade de impurezas) do que o ferro-gusa e também apresenta óxidos de ferro remanescentes em sua estrutura (menor metalização). Para torná-lo mais competitivo, inúmeras melhorias no processo têm sido promovidas para aumento da metalização. No entanto, o limite superior alcançado na prática tem ficado ao redor de 95%. Visando contribuir para melhorar a qualidade do ferro-esponja este trabalho apresenta uma proposta inovadora a partir da técnica de auto-redução. O objetivo é aumentar o grau de metalização do ferro-esponja através de seu aquecimento. Para isso, foram realizadas análises termogravimetrias e aquecimentos em forno mufla; análises químicas por via úmida, difração de raios-x, espectroscopia mössbauer e análise de microssonda de raios-x. As análises estruturais foram realizadas utilizando microscópio eletrônico de varredura para confirmar a efetividade da técnica apresentada. Nesta dissertação pode-se comprovar que, através da técnica de auto-redução, o ferro-esponja alcança metalizações acima de 98% em detrimento da queda do teor de carbono total. Um aumento de 4% na metalização traz um ganho estimado de 5 a 10% no consumo de energia elétrica nos fornos de fusão e um acréscimo proporcional na produção horária das aciarias.<br>The direct reduced iron is obtained by direct reduction process, where iron ore is transformed in metallic iron via chemical reactions involving solid (ore) and gaseous (reductant gases) states. In this process the iron ore does not pass by liquid state like pig iron. This become to direct reduced iron some disadvantages, which decrease its performance in the steelmaking process. It can be mentioned the reduction of metallic yield and the higher consumption of electric energy as the main impacts of its intensive use. The direct reduced iron presents lower amount of total iron (higher amount of impurities) than pig iron and presents iron oxides remained in its structure (lower metallization). To become more competitive, several improvements in the reduction process have been carried out to increase its metallization. However, the highest level of metallization, which has been reached, is 95%. To improve the direct reduced iron quality, the present work evaluates, in an innovative way, using the technique of self reduction. The objective is increase of metallization of the direct reduced iron through its heating. Thermal, chemical and structural characterization was carried out to check the effectiveness of the investigated technique. The research confirms that the direct reduced iron can reach a metallization higher than 98% with a decrease of total carbon amount using the technique presented in this work. An improvement of 4% in the metallization brings savings of 5 to 10% in the electric energy consumption of the electric arc furnaces and a proportional increase of the production in the steelmaking plants.

Ensuring the resilience of self-adaptive systems used in critical infrastructure systems is a concern as their failure has severe societal and financial consequences. The current trends in the growth of the scale and complexity of society's workload demands and the systems built to cope with these demands increases the anxiety surrounding service disruptions. Self-adaptive mechanisms instill dynamic behavior to systems in an effort to improve their resilience to runtime changes that would otherwise result in service disruption or failure, such as faults, errors, and attacks. Thus, the evaluation of a self-adaptive system's resilience is critical to ensure expected operational qualities and elicit trust in their services. However, resilience benchmarking is often overlooked or avoided due to the high cost associated with evaluating the runtime behavior of large and complex self-adaptive systems against an almost infinite number of possible runtime changes. Researchers have focused on techniques to reduce the overall costs of benchmarking while ensuring the comprehensiveness of the evaluation as testing costs have been found to account for 50 to 80% of total system costs. These test suite minimization techniques include the removal of irrelevant, redundant, and repetitive test cases to ensure that only relevant tests that adequately elicit the expected system responses are enumerated. However, these approaches require an exhaustive test suite be defined first and then the irrelevant tests are filtered out, potentially negating any cost savings. This dissertation provides a new approach of defining a resilience changeload for self-adaptive systems by incorporating goal-oriented requirements engineering techniques to extract system information and guide the identification of relevant runtime changes. The approach constructs a goal refinement graph consisting of the system's refined goals, runtime actions, self-adaptive agents, and underlying runtime assumptions that is used to identify obstructing conditions to runtime goal attainment. Graph theory is then used to gauge the impact of obstacles on runtime goal attainment and those that exceed the relevance requirement are included in the resilience changeload for enumeration. The use of system knowledge to guide the changeload definition process increased the relevance of the resilience changeload while minimizing the test suite, resulting in a reduction of overall benchmarking costs. Analysis of case study results confirmed that the new approach was more cost effective on the same subject system over previous work. The new approach was shown to reduce the overall costs by 79.65%, increase the relevance of the defined test suite, reduce the amount of wasted effort, and provide a greater return on investment over previous work by a factor of two.

Battery energy storage systems are a key factor for enabling a continuous increase of the fraction of photovoltaics in the Swedish electricity grid. One big challenge is to utilise all potential services of such a storage system. The aim of this study was to improve the supervisory controller for an existing battery storage and photovoltaic solution marketed by the Swedish company Ferroamp AB. This has been done by developing a combined peak reduction and time-of-use bill management algorithm, together with a simulation and evaluation software for optimisation of algorithm parameters. The algorithms and tools were evaluated using an installation made by Ferroamp AB and Vattenfall Eldistribution AB as a case study. Sensitivity analyses has been performed on economic parameters and length of the algorithm training data set. Improvement of economic profit, in this case study, were 300 % compared to the currently used algorithm and 32 % compared to a conventional threshold peak reduction algorithm. Despite this improvement, the battery energy storage system is shown to be non-profitable, with the economic profit only covering 36 % of the investment costs, not taking interest rate into account. Like in many other studies, power storage was found more profitable than energy storage. An increase of the grid power tariff and the grid energy fee of 30 % to 40 % is found to make the system viable. One interesting finding is that by using the proposed optimal algorithm, 55 % of the cycle life of the battery storage is still accessible for other services when considering 10 years of economic depreciation time for the system.

In this thesis, I defend a non-egologic pure consciousness which is the initial position of Husserl in the Logical Investigations. There is anti transcendental ego argumentations in which I claim that self alienation of the &quot<br>transcendental ego&quot<br>, incomplete reduction, the presence of the pre-reflective transcendental ego are the reasons to leave the claim about the existence of the &quot<br>transcendental ego&quot<br>. I also claim that the possible solution of the mind-body problem depends on the denial of the &quot<br>transcendental ego&quot<br>in the frame of phenomenology. I defend the non-egologic pure consciousness which is not identical and reducible to whatever is material, including brain. Qualia, intentionality, intuition, philosophizing constitution acts of pure consciousness are used to support the claim about immaterial nature of non-egologic pure consciousness.

Bakgrund och problem: Majoriteten av försäljningen mellan företag, samt mellan företag och offentlig sektor sker via handelskrediter. Detta leder till att företagen ofta blir utsatta för risker i form av sena och uteblivna betalningar. I sådana situationer finns det behov av riskreduceringsmekanismer som ska reducera och minimera dessa risker. Mekanismerna för reducering av risker har vi fördelat i två kategorier, privata och offentliga. Avsikten med uppsatsen är att undersöka vilka av dessa mekanismer som har störst inverkan på beviljandet av handelskrediter. Den här studien är den första av sitt slag som genomförts i Sverige. Syfte: Uppsatsens syfte är att undersöka, analysera och utvärdera vilka av de privata eller offentliga riskreduceringsmekanismerna som har störst inverkan på beviljandet av handelskrediter. Metod: Den kunskapsteoretiska uppfattningen som har legat till grund för vår undersökning är positivism. Den positivistiska ansatsen har lett till att en hypotetisk-deduktiv ansats med en kvantitativ metod valdes för att få fram resultat och analys. Teoretiska ramverk: Vår studie utgår från ett eklektiskt teoretiskt angreppssätt och tidigare forskning inom området. Vi använder teori som disposition och som en beskrivande del av vår studie. Våra teorier om de privata och offentliga riskreduceringsmekanismerna kommer även att presenteras i detta kapitel. Empirism: Det empiriska materialet är baserat på en enkätundersökning där enkäten skickades som webbenkät och delades ut för hand till olika företag. Materialet har sedan analyserats med hjälp av statistiska tes Resultat: Majoriteten av respondenterna svarade att de offentliga riskreduceringsmekanismerna inte påverkar deras beviljande av handelskrediter i Sverige medan de privata riskreduceringsmekanismerna till en viss grad har påverkan på beviljandet av handelskrediter. Det råder relativt låg risk i den svenska ekonomin vilket kan förklara riskreduceringsmekanismernas relativt låga inverkan på beviljandet av handelskrediter.<br>Background and problem: Today, the biggest sales between businesses and between businesses and the public sector are through trade credit. As a result, companies are often exposed to risk in the form of late and missing payments. In such situations, there is a need for mechanisms of risk reduction to reduce and minimize these risks. The mechanisms of risk reduction are divided into private and public risk reduction. The point with this dissertation is to show which of these mechanisms that have the greatest impact on the decision making of trade credit. This study is the first in Sweden to implement this type of investigation. Purpose: The point with this paper is to investigate, analyze and evaluate which of the private or public mechanisms of risk reduction those have the greatest impact on decision making on trade credit. Method: The epistemological view which has been the basis for our study is positivism. The positivistic approach has led to a hypothetical-deductive approach with a quantitative method, chosen to obtain the results and analysis. Theoretical perspective: Our study is based on an eclectic theoretical approach and previous research in the area. We use theory to outline the descriptive part of our study. Our theory about the private and public mechanisms of risk reduction will also be included in this chapter. Empirical: The empirical material is based on a survey where a web-questionnaire was distributed to various companies. The material was then analyzed by statistical tests. Results: The majority of respondents replied that the public mechanisms of risk reduction did not affect their decision making on trade credit while the private mechanisms of risk reduction to some degree did affect the decision making on trade credit. There is a relatively low risk in the Swedish economy, which can explain why the mechanisms of risk reduction had relatively low impact on decision making on credit trade.

This thesis explored the relationships between 1) Self-compassion 2) Cognitive Emotion Regulation and 3) Mindfulness Based Stress Reduction (MBSR) and teacher stress in a foreign international school setting. The retrospective, multi-tiered study investigated a total of 177 expatriated teachers working in multiple international schools around the globe; at least 17 of whom indicated that they had completed a MBSR course. A mixed-methods approach was used over three stages utilising the following instruments: 1) an adapted stress impact survey, 2) Teacher Interview Protocol (TIP), 3) the short forms of the Cognitive Emotion Regulation Questionnaire (CERQ-SF), the Self-Compassion Scale (SCS-SF), and the Perceived Stress Scale (PSS-4). Results suggest that teachers’ beliefs about stress correlate with job satisfaction; 82.6% of respondents who reported that stress has ‘hardly any effect’ also reported that they liked their job overall; whereas, 76.9% and 36.4% of respondents that believed stress had affected their teaching ‘some’ or ‘a lot’ reported liking their job, respectively. Results also indicate that higher perceived stress is strongly correlated with both 1) decreased self-compassion (r = -.491, p < .001) and 2) increased use of non-adaptive cognitive emotion regulation strategies, such as Catastrophizing (r= < 0.392, p < .001). All five adaptive cognitive coping strategies were positively correlated with Self-Compassion, four were significant; only Refocus on Planning failed to reach significance at p < .05. The data indicated no statistically significant differences between MBSR and non-MBSR participants, regarding perceptions of stress (PSS-4), self-compassion (SCS-SF), and eight of the nine coping strategies (CERQ-S), with the exception being that MBSR participants experienced reduced Self-Blame (p < 0.007). Conclusions find that policies and practices aimed at supporting the three aspects of self-compassion offer one possible avenue to reducing teacher stress and maladaptive thinking strategies, and thereby increasing job satisfaction, for teachers working in a foreign country.

Thesis (Ph. D.)--Ohio State University, 2005.<br>Title from first page of PDF file. Document formatted into pages; contains xxxiv, 429 p.; also includes graphics (some col.). Includes bibliographical references (p. 402-429). Available online via OhioLINK's ETD Center

The ability to reduce flexural vibrations of lightweight structures has been a goal for many researchers. A type of transducer-controller system that accomplishes this is a piezoelectric patch connected to an electrical impedance, or shunt. The piezoelectric patch converts the vibrational strain energy of the structure to which it is bonded into electrical energy. This converted electrical energy is then modified by the shunt to influence to mechanical response. There are many types of shunt circuits which have demonstrated effective control of flexural systems. Of interest in this work is the negative capacitance shunt, which has been shown to produce significant reduction in vibration over a broad frequency range. A negative capacitance circuit produces a current that is 180̊ out of phase from a traditional, passive capacitor. In other words, the voltage of the capacitor decreases as charge is added. The negative capacitance shunt consists of a resistor and an active negative capacitance element. By adding a resistor and negative capacitor to the electrical domain, the shunt acts as a damper and negative spring in the mechanical domain. The performance of the negative capacitance shunt can be increased through proper selection of the shunt's electrical components. Three aspects of component selection are investigated: shunt efficiency, maximum suppression, and stability. First, through electrical modeling of the shunt-patch system, the components can be chosen to increase the efficiency of the shunt for a given impedance. Second, a method is developed that could be utilized to adaptively tune the magnitude of resistance and negative capacitance for maximum control at a given frequency. Third, with regard to stability, as the control gain of the circuit is increased, by adjusting the circuit parameters, there is a point when the shunt will become unstable. A method to predict the stability of the shunt is developed to aid in suppression prediction. The negative capacitance shunt is also combined with a periodic piezoelectric patch array to modify the propagating wave behavior of a vibrating structure. A finite element method is utilized to create models to predict both the propagation constant, which characterizes the reduction in propagating waves, and the velocity frequency response of a full system. Analytical predictions are verified with experimental results for both a 1- and 2-D periodic array. Results show significant attenuation can be achieved with a negative capacitance shunt applied to a piezoelectric patch array. Three electromechanical aspects are developed: design for maximum suppression, more accurate stability prediction, and increased power-output efficiency. First, a method is developed that may be used to adaptively tune the magnitude of resistance and negative capacitance for maximum suppression. Second, with regard to stability, a method is developed to predict the circuit components at which the circuit will obtain a stable output. Third, through electrical modeling of the shunt-patch system, the components are chosen to increase the power output efficiency of the shunt circuit for a given impedance. The negative capacitance shunt is also combined with a periodic piezoelectric patch array to modify the propagating wave behavior of a vibrating structure. Analytical predictions are verified with experimental results for both a 1- and 2-D periodic array. Results show significant attenuation can be achieved with a negative capacitance shunt applied to a piezoelectric patch array.

A presente tese teve como objetivo fornecer subsídios teóricos e experimentais com vistas à reciclagem da carepa gerada em usinas mini-mills através de briquetes autorredutores para uso em FEA. Para atingir os objetivos vislumbrados, o trabalho foi estruturado em quatro principais tópicos: estudo de caracterização e de redutibilidade da carepa, escolha e caracterização do redutor para uso nos briquetes, elaboração e caracterização da mistura e ensaios de laboratório para avaliação do desempenho dos briquetes autorredutores. Os estudos de caracterização da carepa indicaram que este resíduo é constituído principalmente de wustita e se apresenta estratificada em três camadas: camada externa fina e porosa composta de hematita e magnetita, camada intermediária de wustita densa e camada interna de wustita porosa. A cinética de redução da carepa foi investigada em termobalança no intervalo de temperatura entre 830 e 1200°C com CO puro e mistura 90%CO-10%CO2. A energia de ativação aparente encontrada nesses ensaios variou de 71 a 80 kJ/mol e as observações microscópicas demonstraram que a redução da carepa segue um modelo topoquímico. A escolha do agente redutor para compor o briquete se deu através de ensaios de gaseificação ao CO2 e de autorredução em termobalança com três tipos de material carbonoso. A partir desses ensaios observou-se a seguinte ordem decrescente de reatividade e respectivas energias aparentes de ativação: Carvão Vegetal (Ea = 237 kJ/mol), Carvão Mineral (Ea = 214 kJ/mol) e Coque de Petróleo (Ea = 335 kJ/mol). Em virtude da maior reatividade do Carvão Vegetal frente aos demais, este redutor foi escolhido para uso nos briquetes. A mistura utilizada na confecção dos briquetes autorredutores teve como constituintes principais a carepa, os finos de carvão vegetal e aglomerantes (melaço e cal). Ensaios de caracterização em termobalança com atmosfera oxidante e aquecimento rápido indicaram uma perda de massa de cerca de 40%, referente às etapas de secagem, desvolatilização e autorredução da mistura. Nesses ensaios, observou-se elevadas taxas de perda de massa da mistura e uma notável complexidade dos fenômenos envolvidos, com reações simultâneas de combustão, autorredução e de oxidação do ferro, prevalecendo uma ou outra, dependendo da temperatura e da fração reagida de amostra. Através de procedimentos que buscaram reduzir a complexidade dos fenômenos envolvidos nas condições oxidantes, foi possível estimar que a energia de ativação aparente de autorredução está entre 62 e 69 kJ/mol. Os briquetes produzidos em escala industrial foram submetidos a ensaios isotérmicos e não-isotérmicos de alta temperatura. Tais ensaios buscaram determinar os gradientes térmicos no interior do briquete, a energia de ativação aparente e o desempenho cinético do aglomerado em condições de temperatura que se aproximam da prática industrial. A partir das constatações concernentes às taxas das reações químicas individuais (redução e gaseificação), às medidas do perfil de temperatura no interior dos aglomerados, à energia de ativação estimada para o briquete (93 kJ/mol) e ao modelo de redução encontrado nos ensaios de alta temperatura, acredita-se que tanto a cinética de redução da carepa como a transferência de calor sejam obstáculos limitantes da cinética global dos briquetes em estudo. Finalmente, os resultados de metalização obtidos nos testes de alta temperatura dão indícios da possibilidade de uso destes briquetes em FEA.<br>This dissertation aimed to provide theoretical and experimental basis for recycling of mill scale generated in mini-mill plants through the use of self-reducing briquettes in EAF. To reach these goals, the work was structured around four main topics: characterization and reducibility study of scale, choice and characterization of the reductant to use in briquettes, elaboration and characterization of the mixture and laboratory tests to performance evaluation of self-reducing briquettes. The characterization studies of mill scale have indicated that this waste is composed mainly of wustite and is stratified into three layers with different morphologies: fine porous external layer composed of hematite and magnetite, intermediate layer of dense wustite and inner layer of porous wustite. The kinetics of scale reduction was investigated in thermobalance in a temperature range from 830 to 1200°C with pure CO and a mixture of 90% CO and 10% CO2. The apparent activation energy obtained in these tests ranged from 71 to 80 kJ/mol and the microscopic observations showed that the mill scale reduction corresponds to a topochemical model. The choice of the reductant for composing the briquette was made through tests of gasification with CO2 and of self-reduction in thermobalance with three different carbonaceous materials. From the results, it was observed the following decreasing reactivity order and the related apparent activation energy: Charcoal (Ea = 237 kJ/mol), Mineral Coal (Ea = 214 kJ/mol) and Petroleum Coke (Ea = 335 kJ/mol). Due to the higher reactivity of Charcoal in relation to the others, this reducer was chosen to be used in the briquettes. The main constituents of the mixture used in the manufacture of self-reducing briquettes were scale, charcoal and binders (melasse and lime). The characterization tests in thermobalance with oxidizing athmosfere and rapid heating indicated a mass loss of about 40%, referring to the stages of drying, devolatilization and self-reduction of the mixture. During these tests, it were observed high rates of mixture loss mass and a remarkable complexity of the phenomena, with simultaneous combustion, self-reduction and iron oxidation reactions, where their importance changes according to temperature and fractional reaction of the sample. Through the procedures that aimed to reduce the complexity of the related phenomena in oxidant conditions, it was possible to estimate that the self-reduction apparent activation energy ranges between 62 to 69 kJ/mol. The briquettes produced in the industrial plant were submitted to isothermal and nonisothermal tests of high temperatures. Such tests aimed to determine the thermal gradients into the briquette, the apparent activation energy and kinetic performance of the agglomerate in temperature conditions similar to the ones used in industrial practice. Based on the findings concerning the individual rates of chemical reactions (reduction and gasification), the measures of the temperature profile inside the briquettes, the activation energy estimated (93 kJ/mol) and the reduction model found in high-temperature tests, it is assumed that both the kinetics of mill scale reduction and heat transfer limit the overall kinetic rates of these briquettes. Finally, the results of metallization obtained in the tests conducted at high temperatures indicate the possibility of using these briquettes into the EAF.