Corn crop is essential for Brazilian agriculture, due to economic and social importance for the country. Grain yield has been increasing gradually over the years, in part due to genetic gain from selection. The objectives of this work were to evaluate the behavior of some agronomic traits in parents and their single-cross hybrids and reciprocals, and the relationship of these characters with grain yield and plant density; and to study the performance of corn hybrids in high yield environments based upon the analysis of phenotypic adaptability and stability. The first part of the work was conducted in an experimental field in Cruz Alta/RS, during 2010/2011 growing season. Five inbred parents and eight hybrids synthesized from the inbred lines were evaluated. The experiments were carried out in a factorial (genotype x densities x planting dates) in a randomized complete block design with four replications. The evaluations were: plant height, leaf area index, ear index, thousand grain weight, number of grains per ear and grain yield. Heterosis was obtained from the parent s average. In the second part of the work, 48 environments were used to evaluate the grain yield from ten maize hybrids. The hybrid s behavior was studied according to the average yield in poor and/or high-quality environments, the parameters estimates of the discontinuous bi-segmented equation, and the equation adjustment. The plant density was an important management practice to maximize the maize hybrids yield and heterosis estimates showed that the inbreeds have a higher tolerance to increased plant density. The yield potential of hybrids was influenced by the specific combining ability and reciprocal effect was observed for the traits plant height, leaf area index, grain weight, number of grains per ear and grain yield. The reciprocal effect was randomly controlled, sometimes by male or female parent, thus there was not a standard behavior for all traits. If there is no reciprocal effect, we can choose the female parent with higher seeds yield for a particular cross, otherwise, the parent needs to be chosen according to the best specific combination. There was a really good phenotypic stability in single-cross hybrids, with high yield potential. Adaptability and stability characteristics are intrinsic from each hybrid combination. / A cultura do milho tem papel fundamental na agricultura brasileira, devido à importância econômica e social para o país. O rendimento de grãos vem aumentando gradativamente ao longo dos anos, em parte, graças ao melhoramento genético. Os objetivos deste trabalho foram avaliar o comportamento de alguns caracteres agronômicos em genitores e em seus híbridos simples e recíprocos e a relação destes caracteres com o rendimento de grãos e a densidade de plantas; e estudar o desempenho de híbridos de milho em ambientes manejados para altos níveis de rendimento, através da análise de adaptabilidade e estabilidade fenotípica. A primeira parte do trabalho foi conduzida em área experimental localizada no município de Cruz Alta/RS, no ano agrícola 2010/2011. Foram estudados cinco genitores endogâmicos e oito híbridos simples sintetizados a partir dos genitores. Os experimentos foram conduzidos em um trifatorial (genótipos x densidades x épocas de semeadura) em blocos completos ao acaso, com quatro repetições. As avaliações realizadas foram: altura média de planta, índice de área foliar, índice de espiga, massa de mil grãos, grãos por espiga e rendimento de grãos. A heterose foi obtida em relação à média dos genitores. Na segunda parte do trabalho, 48 ambientes foram utilizados para a avaliação do rendimento de grãos de dez híbridos de milho. O comportamento dos híbridos foi estudado em função do rendimento médio nos ambientes inferiores e/ou superiores, das estimativas dos parâmetros da equação bi-segmentada descontínua, e da qualidade do ajustamento. A densidade de plantas foi uma prática de manejo muito importante para maximizar o rendimento de híbridos de milho e as estimativas de heterose comprovaram que os genitores possuem uma maior tolerância ao aumento da densidade de plantas do que os híbridos. O potencial de rendimento dos híbridos foi influenciado pela capacidade específica de combinação e houve efeito recíproco para os caracteres altura de planta, índice de área foliar, massa de grãos, grãos por espiga e rendimento de grãos. Dependendo do caráter, o efeito recíproco foi controlado pelo genitor masculino ou pelo feminino, ou seja, não houve um comportamento padrão. Se não houver efeito recíproco, pode-se escolher o genitor feminino de maior rendimento de sementes para um determinado cruzamento, caso contrário, o genitor deve ser escolhido de acordo com a melhor combinação específica. Houve estabilidade fenotípica muito boa em híbridos simples, de alto potencial produtivo. A adaptabilidade e estabilidade são intrínsecas a cada combinação híbrida.

In African folklore, there is a Swahili tale which depicts the relationship between a monkey and a shark; a story about the needs of two creatures living in two different worlds. The shark needs the heart of the monkey to give to his king and the monkey agrees to go on the journey to learn and experience new things. Unaware of each other’s intentions and goals they fall prey to a relationship of mutual distrust and suspicion. Many opportunities to use art as a tool for social engagement through service-learning exist in Higher Education. However, good intentions do not always equal good outcomes. The story above illustrates the importance of open communication around goals and motives. My past experiences in community engagement projects have taught me that more harm than good can result when communities are not involved in relationship-building and decision-making processes which affect them. It is therefore imperative that students collaborate with communities in every phase of the engagement process, so that they will learn and benefit from each other in meaningful ways. This qualitative research explores and describes the engagement between Intermediate Phase education students and community youth, the findings of which will be used to design a service-learning module in Creative Arts. The aims of the study were (i) to explore what the students and the community participants can learn from such a process, (ii) to explore what aspects of the engagement process can enhance the attainment of mutually beneficial learning outcomes, and which detract from it, and (iii) based on the findings, to suggest recommendations that can inform the development and design of a future service-learning module in Creative Arts programmes for teacher educators. A qualitative design situated within a critical theoretical paradigm employing a participatory action research approach to inquiry was utilised to achieve the aims of the study. Availability sampling was used to select participants in the engagement between the campus students from the Creative Arts department in the faculty of Education Sciences at the North West University (NWU) Potchefstroom, and the community youths from a nearby township area. The data generation process consisted of four cycles which embraced seven interactive activities, including visual, oral, art, and text-based techniques that were employed in a participatory process. Semi-structured reflective interviews towards the end concluded the research study. Data documentation was obtained through verbatim transcriptions of video clips, visual diaries, and visual charts. The engagement process was systematically monitored, inductively analysed, and thematically interpreted. Trustworthiness was verified by overlapping and multiple data generation strategies, and maintained by reflective member checking and own critical reflections on the process. Ethical requirements included the approval of the Ethics Committee of the NWU Faculty of Educational Sciences, Potchefstroom campus. Signed consent of participants was obtained in writing before the data generation began. Consent was obtained from the participants for visual material to be used for the research study and the presentations thereof. Three themes emerged from the data collection. Theme 1: the process allowed participants to gain insight into each other’s worlds. Theme 2: the participatory action research (PAR) process shifted power relations. Theme 3: the participants experienced personal and professional development through the interactive process. My findings on the student-community youth engagement suggest that the participatory (PAR) process is well suited for socially engaged art-based practices in service-learning as it promotes reciprocal learning through interactive activities. The activities unlocked value-laden and meaningful learning between the participants. Working collaboratively and in groups benefitted the participants in several ways. They gained confidence and self-determination, began to understand each other, improved personal and working relations, and increased their level of professional development. Limiting aspects included language barriers, short time frames, and unpredictable community events. The role of the researcher as change agent required shared leadership of collaborative groupwork, and it was necessary to structure topics in service-learning that evoke challenging and critical responses between participants from diverse backgrounds. These findings have significance for the design and development of a service-learning module for Creative Arts education, provide recommendations for future community partnerships in art-based practices, and for further research in service-learning. / MEd (Curriculum Development), North-West University, Potchefstroom Campus, 2015

In African folklore, there is a Swahili tale which depicts the relationship between a monkey and a shark; a story about the needs of two creatures living in two different worlds. The shark needs the heart of the monkey to give to his king and the monkey agrees to go on the journey to learn and experience new things. Unaware of each other’s intentions and goals they fall prey to a relationship of mutual distrust and suspicion. Many opportunities to use art as a tool for social engagement through service-learning exist in Higher Education. However, good intentions do not always equal good outcomes. The story above illustrates the importance of open communication around goals and motives. My past experiences in community engagement projects have taught me that more harm than good can result when communities are not involved in relationship-building and decision-making processes which affect them. It is therefore imperative that students collaborate with communities in every phase of the engagement process, so that they will learn and benefit from each other in meaningful ways. This qualitative research explores and describes the engagement between Intermediate Phase education students and community youth, the findings of which will be used to design a service-learning module in Creative Arts. The aims of the study were (i) to explore what the students and the community participants can learn from such a process, (ii) to explore what aspects of the engagement process can enhance the attainment of mutually beneficial learning outcomes, and which detract from it, and (iii) based on the findings, to suggest recommendations that can inform the development and design of a future service-learning module in Creative Arts programmes for teacher educators. A qualitative design situated within a critical theoretical paradigm employing a participatory action research approach to inquiry was utilised to achieve the aims of the study. Availability sampling was used to select participants in the engagement between the campus students from the Creative Arts department in the faculty of Education Sciences at the North West University (NWU) Potchefstroom, and the community youths from a nearby township area. The data generation process consisted of four cycles which embraced seven interactive activities, including visual, oral, art, and text-based techniques that were employed in a participatory process. Semi-structured reflective interviews towards the end concluded the research study. Data documentation was obtained through verbatim transcriptions of video clips, visual diaries, and visual charts. The engagement process was systematically monitored, inductively analysed, and thematically interpreted. Trustworthiness was verified by overlapping and multiple data generation strategies, and maintained by reflective member checking and own critical reflections on the process. Ethical requirements included the approval of the Ethics Committee of the NWU Faculty of Educational Sciences, Potchefstroom campus. Signed consent of participants was obtained in writing before the data generation began. Consent was obtained from the participants for visual material to be used for the research study and the presentations thereof. Three themes emerged from the data collection. Theme 1: the process allowed participants to gain insight into each other’s worlds. Theme 2: the participatory action research (PAR) process shifted power relations. Theme 3: the participants experienced personal and professional development through the interactive process. My findings on the student-community youth engagement suggest that the participatory (PAR) process is well suited for socially engaged art-based practices in service-learning as it promotes reciprocal learning through interactive activities. The activities unlocked value-laden and meaningful learning between the participants. Working collaboratively and in groups benefitted the participants in several ways. They gained confidence and self-determination, began to understand each other, improved personal and working relations, and increased their level of professional development. Limiting aspects included language barriers, short time frames, and unpredictable community events. The role of the researcher as change agent required shared leadership of collaborative groupwork, and it was necessary to structure topics in service-learning that evoke challenging and critical responses between participants from diverse backgrounds. These findings have significance for the design and development of a service-learning module for Creative Arts education, provide recommendations for future community partnerships in art-based practices, and for further research in service-learning. / MEd (Curriculum Development), North-West University, Potchefstroom Campus, 2015

The bonding power of the gift has been the subject of much social scientific research. My dissertation adds to this by examining the relationship between gift giving and commitment to a social network or an employing organization. Ideas and concepts from social exchange and identity theories provide the theoretical underpinnings for this investigation. Social exchange theory views human interaction as a series of resource exchanges, and I contend that how people exchange resources may have ramifications for the bonds that develop between them and for their commitment to particular social relations. This study has two parts. In the first half of the dissertation, I ask whether the greater relational solidarity that results from direct reciprocal exchange, as opposed to negotiated exchange, differentially affects whether actors choose to leave their existing exchange networks for new ones and if so, why? Direct reciprocal exchange involves actors directly and independently giving resources to others without knowing whether the recipients of those resources will reciprocate in kind. Negotiated exchange involves actors jointly bargaining over the terms of an agreement. Differences between these two forms of exchange inform my causal argument about why actors are more like to stay in social networks if they participate in direct reciprocal exchange. I test this argument using an experiment. The second half of the dissertation continues this investigation into reciprocal exchange by examining the factors that affect gift giving in the workplace as well as the effects of gift giving on organizational commitment. Here, gift giving is defined broadly to include any act that involves people freely and independently volunteering to provide either tangible or intangible benefits to others without knowing if others will reciprocate. Data from a survey distributed to registered nurses working for a large healthcare organization provides the empirical basis for this investigation. Together the experiment and survey allow for an in-depth investigation into how exchange processes affect commitments to social networks and organizations. As such, the findings reported herein advance sociological understanding about how micro-level processes shape macro-level structures. They also speak to the practical issue of organizational retention.

Reciprocal teaching comprehension-monitoring is a reading comprehension instructional procedure that combines four instructional strategies: predicting, summarizing, questioning, and clarifying to enhance students' comprehension of text. The procedure is a dialogue between the teacher and the students. During reciprocal teaching instruction, the teacher and students take turns leading the dialogue in order to enhance the students' comprehension-monitoring skills. The research on reciprocal teaching has included meta-analyses, group designs, qualitative designs, and single-subject research designs. These studies have identified gaps in the literature to include the measurement of treatment fidelity and treatment acceptability, as well as the psychometric properties of the instruments used to measure daily reading comprehension growth. These gaps were investigated in this study. The purpose of this study was to investigate the effects of reciprocal teaching comprehension-monitoring with a group of fifteen 3rd grade students reading at grade level. Specifically, this study investigated the use of curriculum-based measurement maze probes (CBM-maze probes) to formatively assess the reading comprehension growth of the students. Additionally, this study implemented treatment integrity procedures and investigated the acceptability of reciprocal teaching and the CBM-maze probes through a treatment acceptability rating scale. A multiple baseline across groups with three phases (baseline, intervention, follow-up) was employed. Overall, visual analysis of the data suggested reciprocal teaching was an effective intervention in increasing reading comprehension abilities in students as measured by the CBM-maze probes. All three groups exhibited continual growth on the daily comprehension measures across all three phases. Implications for practice, cautions in interpreting the results, and future directions are discussed.

Research on family influences on adolescents’ aggression has revealed a relation between maternal depressive symptoms and adolescents’ frequency of aggression. A recent cross-sectional study of these relations (Pugh & Farrell, 2011) indicated that maternal depressive symptoms had a significant relation with teachers,’ students,’ and mothers’ reports of adolescents’ aggression. This effect was mediated by parenting practices and family functioning. The cross-sectional designs used in previous studies examining relations between maternal depressive symptoms and adolescents’ aggression make it difficult to draw clear inferences regarding the causal nature of this association. The present study used longitudinal data across five waves of data from a large multi-site study to explore reciprocal relations between maternal depressive symptoms and adolescents’ aggression and the role of parenting practices and family functioning as a mediator of this relation. Participants were 521 mother-adolescent dyads (64% Male; 69% African American) from 18 schools from four different sites throughout the United States representing a range of socioeconomic backgrounds. About 40% of the mothers met criteria for clinically elevated depressive symptoms. Data were collected across five waves from fall of the sixth grade to spring of the eighth grade. Maternal depressive symptoms were assessed using the Center for Epidemiologic Studies Depression scale and adolescents’ aggression was assessed using adolescents’ reports on the Problem Behavior Frequency Scales and mothers’ and teachers’ ratings on the Behavior Assessment System for Children. Analyses revealed positive correlations between maternal depressive symptoms and adolescents’ aggression within each time point (p < .01). Autoregressive path models revealed the reciprocal nature of maternal depressive symptoms and mothers’ report of aggression among female adolescents (significant paths at the majority of time points, p < .05), but not among male adolescents. Hence, findings provide support for the reciprocal relation between maternal depressive symptoms and female adolescents’ aggression. With few exceptions, support was not found for parenting and family variables mediating this relation.

Master of Science / Department of Family Studies and Human Services / Jared R. Anderson / The present study tests the reciprocal relationships between marital attitudes, time spent together, and marital satisfaction in a sample of newlyweds (N = 1220). Using cognitive dissonance theory and the investment model, this study tests two sets of theoretically derived unidirectional pathways to provide empirical evidence for longitudinal associations between these three constructs. Two separate models were tested, one for husbands, and one for wives. For both husbands and wives, results of the panel models indicated significant autoregressive paths among all three variables from T1 to T2, T2 to T3, and T1 to T3. Among husbands, significant cross-lagged paths emerged between T1 marital satisfaction and T2 marital attitudes, T1 marital satisfaction and T2 time spent together, T1 time spent together and T2 marital satisfaction, T2 time spent together and T3 marital satisfaction, and T2 time spent together and T3 marital attitudes. For wives, cross-lagged paths between T1 marital satisfaction and T2 time spent together, T1 time spent together and T2 marital satisfaction, and T2 time spent together and T3 marital satisfaction were found to be significant. Bootstrap test for indirect effects resulted in no significant mediating effects in the models. The results of these models are discussed and implications for future research and intervention are given.

A presente tese procura expor as linhas gerais do projeto estético de Hölderlin, tal como ele procurou realizá-lo entre 1793 e 1797. Anunciado em diversas cartas como uma tentativa de encontrar o princípio esclarecedor das oposições do espírito, tais como natureza e liberdade, sujeito e objeto, eu e não-eu, esse projeto estético toma por base a relação entre filosofia e poesia tal como a estabeleceu Kant na Crítica da Faculdade de Julgar, em especial na seção em que trata das ideias estéticas, da imaginação produtiva e do gênio, bem como aquela estabelecedia por Schiller em Sobre graça e dignidade, na medida em que este último procura fundar uma estética objetiva a partir dos esforços iniciados por Kant nesse mesmo sentido. Mas é principalmente ao entrar em contato com a filosofia da Doutrina-da-ciência, de Fichte, que Hölderlin vislumbra todo o potencial dessa relação entre filosofia e poesia. Em sua obra, afinal, Fichte atribui à imaginação criadora um papel ainda mais importante do que Kant, na medida em que, para aquele, a imaginação constitui a origem das separações encontradas no eu. O fato, porém, de que Hölderlin não realiza sua anunciada estética na forma teórica não impede de vê-la executada poeticamente em seu romance de formação Hipérion ou o eremita na Grécia. Assim como o filósofo da Doutrina-da-ciência reduz as oposições encontradas no eu à imaginação por meio do método da determinação recíproca, também Hipérion, na medida em que realiza a passagem da natureza para o âmbito da liberdade e da poesia, é capaz de unificar as oposições próprias da via excêntrica. / This thesis is intended to render an outline of the aesthetic project Hölderlin sought to carry out between 1793 and 1797. His aesthetic project, which in a number of letters he addressed as an attempt to find the principle enlightening such oppositions of spirit as nature and freedom, subject and object, self and not-self, is based upon the philosophy-poetry relationship as established by Kant in the Kritik der Urteilskraft, especially in the section dealing with aesthetic ideas, productive imagination, and genius, as well as the one Schiller establishes in Über Anmut und Würde to the extent he succeeds in founding an objective Aesthetics upon Kant\'s efforts to this effect. However, it was not before he got in touch with Fichte´s Wissenschaftslehre philosophy that Hölderlin realizes the entire potential of this philosophy-poetry relationship. After all, throughout his work Fichte assigns creative imagination a more important role than Kant does, as imagination, for the former, is the origin of the separations residing in the self. Hölderlin\'s failure to perform his announced Aesthetics in the form of theory, however, did not prevent him from accomplishing it poetically in his novel Hyperion or the Hermit in Greece. Just as the philosopher of the Wissenschaftslehre reduces unto imagination the oppositions in the self using the reciprocal determination method, Hyperion is also capable of unifying the oppositions pertaining to the eccentric path as it leads from nature into the realm of freedom and poetry.

A atribuição de uma marca a um elemento não influencia o consumidor somente com relação ao elemento em si. Os efeitos dessa atribuição também podem recair sobre a própria marca, incidindo indiretamente sobre outros elementos que carregam esse símbolo de identificação. O efeito do produto que recebe a marca sobre o comportamento do consumidor em relação à própria marca tem sido chamado de \"efeito recíproco\". Até o presente, o efeito recíproco da atribuição de marcas foi estudado principalmente no contexto da extensão de marcas para novos bens e serviços. A presente pesquisa estuda o efeito recíproco em um contexto ainda não explorado, o das marcas turísticas de países. O objetivo da pesquisa é analisar de que forma o poder da marca turística do país é afetado pelos valores subjetivos dos destinos contidos em seu território. Para tanto, foi elaborado um modelo teórico baseado na perspectiva de marcas como símbolos de identificação que permitem a categorização de produtos por meio de esquemas mentais. Em termos empíricos, foram estudadas a valência e a linearidade da relação entre o valor subjetivo dos destinos e poder da marca turística do país. Foi examinada também a influência sobre o poder da marca turística do país exercida pela similaridade dos destinos do país. Além disso, foi analisado ainda o efeito moderador que o conhecimento do consumidor acerca das características turísticas do país exerce sobre o efeito recíproco dos valores subjetivos dos destinos. Os objetivos desta pesquisa são úteis para embasar uma série de decisões relativas à gestão de marcas, especialmente de marcas turísticas de países e regiões. Para alcançar os objetivos definidos, a presente pesquisa utilizou o método experimental. O primeiro experimento abordou o efeito dos valores subjetivos dos destinos sobre o poder da marca turística do país em um contexto formado por destinos e países hipotéticos, utilizando dados coletados a partir de uma amostra de 230 estudantes universitários brasileiros. O segundo experimento enfocou o caso do Brasil como destino de viagens turísticas a partir de uma amostra de 363 consumidores norte-americanos. Os resultados alcançados comprovaram a existência do efeito recíproco dos valores subjetivos dos destinos sobre o poder da marca turística do país. As evidências coletadas mostraram também que esse efeito não é linear, mas sim crescente em função dos valores subjetivos dos destinos. O efeito da similaridade dos destinos do país sobre o poder da marca turística deste não foi suportado pelos dados empíricos. Da mesma forma, o efeito moderador do conhecimento acerca das características turísticas do país incidente sobre o efeito recíproco dos valores subjetivos dos destinos também não foi evidenciado. / Assigning a brand to an element influences the consumer not only with respect to the element itself. The effects of this assignment may also fall on the consumer behavior regarding the brand, indirectly affecting other elements that display this symbol of identification. The effect of the product that receives the brand on consumer behavior towards the brand itself have been named reciprocal effects. To date, reciprocal effects were mainly studied in the context of brand extensions to new goods and services. The present research studies reciprocal effects in a context that has not been examined yet: the tourism brand of the country. The objective of this research is to analyze how the power of the tourism brand of the country is affected by the subjective values of destinations situated in its territory. To do that, a conceptual model was developed based on the perspective of brands as identification symbols that enable categorization of products through mental schemes. In empirical terms, the study focused on the valence and the linearity of this relationship. It also analyzed the effect of the similarity across country\'s destinations on the power of the national brand. A final analysis focused on the moderating role of consumer knowledge about tourism characteristics of the country falling upon the reciprocal effect of the subjective values of destinations. These objectives are useful to support a number of branding decisions, especially those regarding countries and regions\' tourism brands. Two experiments were conducted in order to achieve these objectives. The first experiment addressed the effects of subjective values of destinations on the power of the tourism brand of the country in a context of hypothetical destinations and countries. It used data collected from a sample of 230 Brazilian undergraduate students. The second experiment focused on the Brazilian case by using a sample of 363 US consumers. The results evidenced the existence of the reciprocal effect of subjective values of destinations on the power of the tourism brand of the country. The experiments also showed that this effect is not linear, but increasing with respect to the subjective values of destinations. The effect of the similarity across destinations on the power of the national tourism brands was not supported by empirical data. Similarly, the moderating effect of knowledge about tourism characteristics of the country on the reciprocal effect of subjective values of destinations was not evidenced.

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / The use of biogas, with high concentrations of carbon dioxide (CO2) in its composition, in thermal systems of conventional combustion can result in combustion instabilities, leading to a decrease of the flame front propagation velocity, resulting even to the flame extinction. In addition, this contaminant can increase greenhouse gas levels in the exhaust, such as carbon monoxide (CO), unburned hydrocarbons (UHC), nitrogen oxides (NOx) among others. Thus, this research aims to demonstrate the effectiveness of "Filtration Combustion" (FC) to deal with fuels of low heat content, such as biogas. CF is a non-conventional technology capable of producing ultra-low emissions of CO, HC and NOx. The experimental apparatus used in this research consists of a porous burner constituted of ceramic spheres (alumina) that fill the combustion chamber, where heat exchangers are inserted at the porous matrix ends. The FC allows even the application of a reciprocating gas flow system, which periodically switches the direction of the gas flow in the chamber. The reciprocal filtration combustion allows the operation with several fuels and providing a stable combustion process with temperature distribution on trapezoidal profile, with temperature peaks between 1300 and 1600 K. In this context, the present experimental study tries to identify and to analyze the effects of carbon dioxide in FC, which covers energy extraction efficiency, emissions, reaction stability, and flammability limits using several air-fuel mixtures, altering both the CO2 concentration in the biogas composition as the equivalence ratio (ER), in which the technical methane is taken as the reference gas. The results have pointed out significant benefits of the reversal on the combustion process, allowing operation in a wide equivalence ratio range (0.1 <&#1060; <1.0), and achieving energy extraction efficiencies above 90%, with ultra-low CO and NOx emissions (below 1 ppm). However, when the burner operates on only flow direction, it is possible to realize a drastic reduction of the flammability limit, as the CO2 content in the biogas composition is increased. / A utilizaÃÃo do biogÃs, com elevadas concentraÃÃes de diÃxido de carbono (CO2) em sua composiÃÃo, em sistemas tÃrmicos de combustÃo convencionais pode resultar em instabilidades na reaÃÃo, levando a uma diminuiÃÃo da velocidade de propagaÃÃo da frente de chama (onda de combustÃo), ocasionando inclusive a sua extinÃÃo. AlÃm disso, este contaminante pode aumentar os Ãndices de gases poluentes na exaustÃo, tais como: monÃxido de carbono (CO), hidrocarbonetos nÃo queimados (HC), Ãxidos de nitrogÃnio (NOx), dentre outros. Por esta razÃo, esta pesquisa tem como objetivo demonstrar a eficÃcia da "CombustÃo de FiltraÃÃo" (CF) em lidar com os combustÃveis de baixo poder calorÃfico, como o biogÃs. CF à uma tecnologia nÃo-convencional capaz de produzir emissÃes ultrabaixas de CO, HC e NOx. O aparato experimental empregado nessa pesquisa consistiu de um queimador poroso, constituÃdo de esferas cerÃmicas (alumina) que preenchem a cÃmara de combustÃo, onde trocadores de calor estÃo inseridos nas extremidades dessa matriz porosa. A CF possibilitou, inclusive, a aplicaÃÃo de um sistema de escoamento recÃproco, que alternou periodicamente a direÃÃo do escoamento dos gases na cÃmara. A combustÃo de filtraÃÃo recÃproca permitiu a operaÃÃo com diversos combustÃveis e proporciona um processo de combustÃo estÃvel com a distribuiÃÃo de temperatura em perfil trapezoidal, com picos de temperatura entre 1300 e 1600 K. Neste contexto, o presente estudo experimental buscou identificar e analisar os efeitos do diÃxido de carbono na CF, o que engloba eficiÃncia de extraÃÃo de energia, emissÃes, estabilidade da reaÃÃo, e limites de inflamabilidade, utilizando vÃrias misturas ar-combustÃvel, alterando tanto a concentraÃÃo de CO2 na composiÃÃo do biogÃs como a razÃo de equivalÃncia (RE), tendo como gÃs de referÃncia o metano tÃcnico. Os resultados apontaram benefÃcios significativos da reversÃo sobre o processo de combustÃo, permitindo a operaÃÃo em uma ampla faixa de razÃo de equivalÃncia (0,1<&#1060;<1,0), e alcanÃando uma eficiÃncia de extraÃÃo de energia acima de 90%, com emissÃes ultrabaixas de CO e NOx (abaixo de 1 ppm). Em contrapartida, quando o queimador operou em apenas um sentido do escoamento, foi possÃvel perceber uma reduÃÃo no limite de inflamabilidade à medida que foi incrementado o teor de CO2 na composiÃÃo do biogÃs.