No description available.

L'extrapolation des réacteurs catalytiques nécessite l'acquisition des données cinétiques sur des réacteurs à petite échelle dans les conditions opératoires industrielles. Le critère de dimensionnement utilisé lors de la réduction d'échelle est la conservation de la vitesse volumique horaire, ce qui conduit à des vitesses de circulation très faibles dans les réacteurs pilotes à lit-fixe. A ces vitesses, les flux de transfert de matière externes peuvent devenir limitant par rapport au flux de réaction. Dans ce contexte, une nouvelle géométrie de réacteur a été imaginée pour intensifier les transferts de matière et chaleur et pour augmenter les vitesses de circulation des fluides : le réacteur "filaire". Il s'agit d'un réacteur dont le diamètre est égal ou proche de celui des grains de catalyseur et avec un ratio longueur sur diamètre très élevé. Le principal objectif de cette thèse est de caractériser ce réacteur en termes d'hydrodynamique et de transferts de matière externes pour définir ses limites d'utilisation. En écoulement diphasique, ce réacteur est relativement piston et la rétention liquide est élevée, ce qui permet d'assurer un mouillage total du catalyseur. En ce qui concerne les vitesses des transferts de matière externe, celles-ci sont proches de celles d'un réacteur agité avec panier et sont supérieures à celles caractéristiques d'un réacteur pilote à lit-fixe conventionnel. Cette observation est liée à l'augmentation des vitesses locales du liquide et à la présence d'un écoulement du type Taylor modifié. En conclusion, le réacteur "filaire" constitue une alternative efficace aux réacteurs pilotes à lit-fixe pour l'étude de catalyseurs mis en forme.

Approved for public release; distribution in unlimited. / Night Vision Devices (NVD) using Image Intensification (II) technology are among the most important sensors used by ground troops and aviators in night operations for modern combat. With the intensified images from these devices, soldiers can see an enemy's movement better and further in darkness. This thesis explores different test methods in evaluating the performances and sensitivities of several NVDs for future image fusion studies. Specification data such as sensitivity, resolution (Modulation Transfer Function) and pixel size are obtained. Comparative analyses of the collected results are made to characterize the performances of the different NVDs. A new method using MATLAB programming to objectively analyze digitized images for characterization of II based NVDs is proposed. This test method can also be extended to the evaluation of Thermal Imaging (TI) systems for comparative analysis with II NVDs. In addition, the feasibility of testing NVDs using both II and TI technologies, with common operating conditions and target boards is discussed. Finally, the potential of using these digitized images for image fusion studies is verified with the test and evaluation results. / Republic of Singapore

Ce travail de thèse a porté sur la prise en compte de la phase juvénile des peuplements forestiers du Sud-Ouest de la France dans la caractérisation des échanges sol-végétation-atmosphère. L’étude s’est focalisée sur des structures de peuplements contrastées de jeunes peuplements de Pins maritimes et d’Eucalyptus. La première partie de ces recherches a consisté à étudier de façon expérimentale les échanges de masse et d’énergie de jeunes plantations d’Eucalyptus et de Pins maritimes du Sud-Ouest. Trois sites instrumentés pour la détermination en continu des échanges de CO2 et H2O, bilan d’énergie, flux de sève et de croissance et production des arbres ont été suivis durant deux années marquées par des épisodes répétés de sécheresse. Le comportement des essences présentes a été comparé ainsi que les effets de l’environnement et des pratiques culturales sur le fonctionnement de ces écosystèmes. Les bilans annuels d’eau, de carbone et la croissance et la production des trois peuplements ont été établis et comparés. A partir de ces mesures enrichies par des données déjà disponibles et en se basant sur le modèle de production forestière et de transfert sol-végétation-atmosphère GRAECO (INRA-EPHYSE), modèle mécaniste biophysique monodimensionnel, la deuxième partie a consisté à développer une nouvelle évolution de ce modèle pour l’adapter au cas des systèmes de culture de biomasse forestière à croissance rapide. L’approche proposée en couplant ce modèle avec le modèle MAESTRA (Medlyn 2004) a permis de dépasser les hypothèses d’homogénéités verticale et horizontale du couvert pour rendre compte de l’effet de la structure en trois dimensions de peuplements jeunes à couronnes disjointes et sous-étage développé sur les transferts radiatifs, de CO2 et vapeur d’eau. De plus, le modèle a été complété par trois nouveaux modules décrivant respectivement la dynamique du carbone du sol (Roth-C) et la croissance et fonctionnement du sous-étage et du taillis. Il a été évalué sur les données existantes couvrant différents sites et séries temporelles et incluant une série d’interventions de type labour, désouchage, disquage superficiel, semis, dépressages, éclaircies et recépées. Enfin, ce modèle a été implémenté sur un jeu de données décrivant le climat local sous le forçage du scénario climatique A2 régionalisé sur un point de la grille SAFRAN de Météo-France pour trois itinéraires sylvicoles de Pin maritime et Eucalyptus, afin d’évaluer, à titre exploratoire, les potentialités de productivité de ces itinéraires. / In this thesis, the juvenile phase of forest stands of southwestern France was studied in order to characterise soil-vegetation-atmosphere exchanges. The study focused on contrasted structures of young pines and Eucalyptus stands. The first part of this research was to study experimentally the mass and energy exchanges of young plantations of pines and Eucalyptus growing in southwestern France. Continuous measurements of CO2 and H2O fluxes, energy balance, sapflow and tree growth and production were carried out for two years, a period marked by repeated episodes of drought. The behavior of these species was compared, as well as the effects of the environment and cultural practices on these ecosystems. The annual water and carbon balances, growth and production of the three stands were established and compared. These measurements were enriched by data already available and were based on the 1D-mechanistic model of forest production and soil-vegetation-atmosphere transfer GRAECO (INRA-EPHYSE). The second part of the thesis focused on developing a new version of the model to be applied to crop systems for fast-growing forest biomass. By coupling this evolution of the model with the 3D-model MAESTRA (Medlyn 2004), the assumptions of vertical and horizontal homogeneities in the canopy can be exceeded thus accounting for the effect of the three-dimensional structure on the radiative, CO2 and water vapor transfers in young stands, where crowns are separate and the understorey is well-developed. In addition, the model was supplemented by three new modules describing the dynamics of soil carbon (Roth-C) and the growth and functioning of the understory and coppice. It was evaluated on existing data covering different sites and time series and including a series of forest practices, such as plowing, stump removal, superficial disking, seeding, early thinning, thinnings and cutting down close to the ground. Finally, as an exploratory work, this model has been implemented on a data set describing the local climate forced by the A2 climate scenario which was regionalized on a SAFRAN grid point (‘Météo-France’) for three forest itineraries of maritime pine and Eucalyptus, in order to assess the potential productivity of these systems.

Neste trabalho foram desenvolvidos sistemas microfluídicos para aplicações na produção de micro e nanopartículas. Os dispositivos microfluídicos foram microfabricados em vidros do tipo borosilicato e em cerâmica verde LTCC (Low Temperature Co-fired Ceramic). Para os dispositivos em vidro foram utilizadas técnicas de fotolitografia, corrosão úmida e soldagem por cola UV. Com estas técnicas foram produzidos sistemas planares com diversas geometrias, sistemas com dispositivos em paralelo com duas e três camadas de vidros. Além disso, dois polímeros o Benzociclobuteno (BCB) e o Parylene-C foram apresentados como ferramenta para a modificação da superfície do vidro de hidrofílica para hidrofóbica. A cerâmica LTCC foi utilizada para a produção de um sistema microfluídico para focalização hidrodinâmica em 3 dimensões. Os dispositivos microfabricados foram utilizados para estudos sobre a produção de emulsões simples e duplas, observando a influência de parâmetros como taxa de fluxo, razão entre fluxos e diferentes tipos de emulsificantes no tamanho das gotas e no tipo de corte obtido em cada situação. Observou-se que o tamanho máximo das gotas obtidas fica restringido ao tamanho do canal microfabricado, cerca de 50m e o tamanho mínimo obtido foi de 15m. Além da produção de emulsões, foi estudada a produção de nanosuspensões pela técnica de nanoprecipitação anti-solvente. Para este estudo, além das geometrias planares, foram testadas as geometrias 3D e também sistemas para o aumento de escala de produção, onde o sistema integrado possuía 4 dispositivos para nanoprecipitação. Os resultados obtidos indicaram que os sistemas microfluídicos permitem a produção de nanopartículas amorfas, na faixa de 100 a 1000 nm, com baixa polidispersão, sendo ainda reprodutíveis em sistema de maior escala. O desenvolvimento deste trabalho mostrou que a microfluídica oferece ferramentas importantes na obtenção de micro e nanopartículas. / In this work microfluidic systems were developed for applications in micro and nanoparticles production. Microfluidic devices were microfabricated in borosilicate glasses substrates and LTCC ceramic (Low Temperature Co-fired Ceramic). For glass devices were used techniques such as photolithography, wet etching and UV glue for sealing glass wafers. With these techniques were manufactured planar systems with various geometries, systems with devices in parallel with two and three glass layers. In addition, two polymers, BCB and Parylene-C, were presented as a tool for glass surface modification, from hydrophilic to hydrophobic. The ceramic LTCC was used for the production of a microfluidic system for hydrodynamic focusing in three dimensions. The devices were used for studies on the single and double emulsions production, observing the influence of parameters such as flow rate, ratio between flows and different types of surfactants at the droplet size and droplet cut type obtained in each situation. It was observed that the maximum size of the droplets obtained is restricted by the channel size, the maximum was about 50m and the minimum size of 15m. Besides, the devices were used to produce nanoparticles using anti-solvent nanoprecipitation technique. For these studies, besides the planar geometries, 3D geometries were tested and also systems for increasing scale production, where 4 devices were integrated in one system for nanoprecipitation. The results indicated that the microfluidic systems allow the production of amorphous nanoparticles in the range of 100 to 1000 nm with low polydispersity, being also reproducible in a larger scale system. The development of this work has shown that microfluidics offers valuable tools in obtaining micro-and nanoparticles.

Este estudo é dedicado à análise da redução da jornada de trabalho no Brasil. O trabalho inicia-se por uma narrativa histórica da evolução da jornada de trabalho no mundo e no Brasil. Em seguida, apresenta-se a divergência doutrinária sobre os termos: duração do trabalho, jornada de trabalho e horário de trabalho. São, então, observadas as jornadas especiais de certas categorias profissionais que, por força de circunstâncias particulares da profissão, assumem jornadas de trabalho diferenciadas. Posteriormente, estuda-se a Organização Internacional do Trabalho, suas convenções quanto a jornada de trabalho, bem como a Recomendação 116, sobre a possibilidade da redução progressiva da jornada de trabalho. Por fim, aborda-se a experiência francesa, que diz respeito à redução da jornada de trabalho para 35 horas. Chega-se à conclusão da dissertação, com os argumentos finais e o posicionamento de que a redução da jornada de trabalho, ainda que seja medida essencial para proteção da saúde do trabalhador, não gera emprego e não reduz o desemprego, porém suscita a intensificação do trabalho. / This study is dedicated to the analysis of the working hours reduction in Brazil. The dissertation begins with a historical narrative of the evolution of the working hours in the world and Brazil; with an emphasis on the doctrinal disagreement over the terms: hours of work, working hours and work schedule. Then, it analyzes the working hours for certain professional categories under particular circumstances. Moreover, it studies the International Labour Organization; the conventions and Recommendation 116 about the possibility of progressive working hours reduction. Subsequently, it analyzes the French experience highlighting on the working hours reduction to 35 hours. The dissertation is concluded with the exposition of the final arguments and the position that the working hours reduction does not reduce unemployment and does not increase employment, but cause work intensification. However, it is an essential measure to protect the worker health.

Afrikanisches einheimisches Gemüse (AIVs) hat in letzter Zeit in ganz Afrika südlich der Sahara (SSA) aufgrund des zunehmenden Bewusstseins für deren Ernährung und gesundheitlichen Nutzen größere Anerkennung gefunden. Dieses wachsende Verbraucherbewusstsein hat zu einer erhöhten Nachfrage nach AIV-Verbrauch geführt, was wiederum zu einer verstärkten Produktion von AIV geführt hat. Das Ziel dieser Arbeit war es daher, das Ausmaß und die zugrunde liegenden Faktoren zu bewerten, die Einfluss auf die Einführung nachhaltiger Intensivierungsmethoden (SIPs) haben (Einsatz von verbesserten Bewässerungssystemen, integrierte Bodendüngung, organischer Dünger und AIV - Diversifizierung) (2) Die Übernahme von SIP in Bezug auf den Lebensunterhalt der Landwirte und (3) eine Bewertung der wirtschaftlichen Leistung und der ökologischen Ergebnisse von Bodendüngungsstrategien, um Bodenbewirtschaftungsstrategien zu empfehlen, die die Produktion, den Lebensunterhalt und den Klimaschutz optimieren. Die Ergebnisse zeigten, dass der Einsatz von organischem Dünger und die Diversifizierung der AIV in ländlichen und stadtnahen Produktionsgebieten weit verbreitet waren, wohingegen verbesserte Bewässerungssysteme und ein integriertes Bodenfruchtbarkeitsmanagement eher gering waren und in ländlichen Gebieten sogar erheblich niedriger waren als in Stadtrandgebieten. Darüber hinaus wurden Komplementaritäten und Substituierbarkeiten zwischen SIPs identifiziert, was darauf hindeutet, dass eine Änderung der Richtlinien, die sich auf ein einzelnes SIP auswirkt, Auswirkungen auf andere verwandte SIPs haben kann. Die Ergebnisse der Determinanten von SIP zeigen, dass die Marktintegration, das Haushaltseinkommen und die städtischen Gemüseproduktionsumgebungen die Haupttreiber der Akzeptanz waren. Darüber hinaus erhöht die Einführung von SIPs sowohl das Gesamteinkommen der Haushalte als auch die Ernte. Darüber hinaus optimiert die integrierte Strategie zur Bodenfruchtbarkeit die Wirtschafts- und Umweltleistung. Daher ist ein integriertes Bodenfruchtbarkeitsmanagement ein möglicher Weg, um die AIV-Produktion nachhaltig zu intensivieren. / African indigenous vegetables (AIVs) have recently gained greater recognition across sub-Sahara Africa (SSA) because of increased awareness on their nutrition and health benefits. This rising consumer consciousness has caused an increase in demand for consumption of AIVs, which in turn has led to increased intensification of AIV production. The aim of this thesis was therefore, to evaluate the level and underlying factors influencing the adoption of sustainable intensification practices (SIPs) (use of improved irrigation systems, integrated soil fertilisation, organic manure and AIV diversification), (2) examined the impacts of SIP adoption on farmers’ livelihoods, and (3) assessed economic performance and ecological outcomes of soil fertilisation strategies in order to recommend soil fertility management strategies which optimises production, livelihood and climate trade-offs. The results revealed that use of organic manure and AIV diversification were widely adopted across rural and peri-urban production areas while improved irrigation systems and integrated soil fertility management was rather low, and even significantly lower in rural areas than in peri-urban areas. Moreover, complementarities and substitutabilities between SIPs were also identified indicating that a change in policy affecting a single SIP might have a spill over effect on other related SIPs. The results of determinants of SIPs shows that market integration, household income and peri-urban vegetable production environments were the major drivers of adoption. In addition, adoption of SIPs significantly increases both total household and crop incomes. Furthermore, integrated soil fertility manage strategy optimises economic and environmental performance. Therefore, integrated soil fertility management is a potential pathway to sustainably intensify AIV production.

Made available in DSpace on 2016-08-10T10:32:21Z (GMT). No. of bitstreams: 1 SANDRA LUCIA GONCALVES.pdf: 2162767 bytes, checksum: 01220947a07e437c83d3e3e851272d92 (MD5) Previous issue date: 2014-06-30 / This work includes research and analysis on the expansion and reconfiguration of education, science and technology and its implications for relations and working conditions at the Federal Institute of Education, Science and Technology State of Goiás (IFG), with emphasis on national scene, in the vocational and technological education policies, its implications relations and working conditions and forms of resistance and oppositions of teachers and technical and administrative workers. Studies undertaken in the examination of the implementation of Law in 9394-1996 (BRAZIL, 1996) Guidelines of the National Education (LDB), and creation of Ifets to Law 11,892 - 2008 (BRAZIL, 2008), were guided by perspective of the capital relation, work and education in the light of categories and concepts developed by Marx, Engels, addressing the main mediations that contributed to the establishment of a close relationship between education and the capitalist mode of production. It analyzes also the dimensions problematized by the analysis of corporate transformations and their expressions in contrarreforma state in Brazil, and their implications for public social policies and the main axes of political and legal contrarreforma process performed in education policy, science and technology highlighting two legal instruments, Decree No 2208-1997 and Decree No. 5,154 - 2004. The analysis rests with the network expansion process and its double face today - the technological improvement and the commodification of knowledge according to the guidelines of international organizations. In the study seized the process and the connections with the precariousness and intensification of work and the new institutional framework of the network, with the study of their specific at the Federal Institute of Goiás. The main changes undertaken since 2008, the policy guidelines "people management" in IFG add to the problem of intensification and job insecurity. / Esta dissertação compreende a investigação e a análise sobre a expansão e a reconfiguração da educação profissional, científica e tecnológica e suas implicações nas relações e condições de trabalho no Instituto Federal de Educação, Ciência e Tecnologia do Estado de Goiás (IFG), com ênfase ao cenário nacional, nas políticas de educação profissional e tecnológica, suas implicações relações e condições de trabalho e formas de resistência e contraposições dos trabalhadores docentes e técnico-administrativos. Os estudos empreendidos no exame da implementação da Lei no 9.394-1996 (BRASIL, 1996) de Diretrizes de Bases da Educação Nacional (LDB), e de criação dos Ifets com a Lei no 11.892-2008 (BRASIL, 2008), foram norteados pela perspectiva da relação capital, trabalho e educação à luz de categorias e conceitos desenvolvidos por Marx, Engels, abordando as principais mediações que contribuíram para a constituição de uma estreita relação entre educação profissional e o modo de produção capitalista. Analisam-se ainda as dimensões problematizadas pelas análises das transformações societárias e suas expressões na contrarreforma do Estado no Brasil, e suas implicações nas políticas sociais públicas e os principais eixos políticos e legais do processo de contrarreforma realizada na política de educação profissional, científica e tecnológica com destaque para dois instrumentos legais, o Decreto no 2.208-1997 e o Decreto no 5.154-2004. A análise recai sobre o processo de expansão da rede e sua dupla face na atualidade a tecnificação e a mercadorização do conhecimento conforme as diretrizes dos organismos internacionais. No estudo apreendeu-se o processo e os nexos com a precarização e intensificação do trabalho e a nova institucionalidade da rede, com o estudo das suas especificidades no Instituto Federal de Goiás. As principais mudanças empreendidas a partir de 2008, as orientações da política de gestão de pessoas no IFG somam-se à problemática da intensificação e precarização do trabalho.

Made available in DSpace on 2016-08-10T10:47:18Z (GMT). No. of bitstreams: 1 PAULA FERNANDES TEIXEIRA CANEDO.pdf: 878688 bytes, checksum: 1c7e640a0551070d789c379291f4b625 (MD5) Previous issue date: 2013-12-10 / The new ways of existing work in the XXI century, the result of neoliberal economics and globalization, generate a reflection on the figure of the worker in the context of modern society, which is the protection of human dignity of the worker, especially regarding the intensification of work that the employee is submitted to assist the economic goals of the employer. In Brazil, the Constitution of 1988 reflects, in its Article 7, the worker protection and, as a social right, is considered as a fundamental right, supporting the idea that the capitalist system must maintain a dependent relationship with the social rights in order to the free initiative established by Magna Carta should be carried out with social justice and strengthening of the work in a fair and caring society. The practice of hard work equates to moral harassment when a worker is submitted to conditions that confront his-her physical or mental health so that his-her work activities are summarized in a presentation of positive results to the employer in order to increase the company s profit, which entails moral and social security damage as a way to seek redress against the injury he-she suffered. In this sense, this work takes the form of a investigative and bibliographic research that aims to analyze the human dignity of the worker within the neoliberalism forward to new forms of work brought by global society, focusing on the intensification of work and the need of compensation of his-her moral by the action of Judiciary granting moral and social security compensation for the injured worker, in view of the critical study of the right to work, as well as the interpretation in the social, political and economic context. Therefore, it analyzes, beyond the formal element (the rules of worker protection), also the materiality of protecting the dignity of the worker face to the Brazilian courts in order to presents some considerations about the effective legal protection of the right to work as fundamental right. / As novas formas de trabalho existentes no século XXI, fruto da economia neoliberal e da globalização, geram uma reflexão acerca da figura do trabalhador no contexto da sociedade moderna, qual seja, a proteção da dignidade humana do trabalhador, principalmente no que tange a intensificação do trabalho a qual o trabalhador é submetido para atender aos objetivos econômicos do empregador. No Brasil, a Constituição de 1988 reflete, em seu Art. 7º, a proteção ao trabalhador e, como direito social, trata tal direito como fundamental, entendendo que o sistema capitalista deve manter uma relação de dependência com os direitos sociais para que a livre iniciativa presente na Carta Magna seja realizada com justiça social e fortalecimento do trabalho, numa sociedade justa e solidária. A prática do trabalho intenso equipara-se ao assédio moral quando o trabalhador é submetido a condições que afrontam sua saúde física ou psíquica de modo que suas atividades laborais são resumidas à apresentação de resultados positivos para o empregador com o objetivo de aumentar o lucro da empresa, o que enseja o dano moral trabalhista e previdenciário como forma de buscar o ressarcimento frente à lesão por ele sofrida. Nesse sentido, este trabalho tem a forma de uma pesquisa bibliográfica investigativa que objetiva analisar a dignidade humana do trabalhador dentro do neoliberalismo frente às novas formas de trabalho trazidas pela sociedade globalizada, focando na intensificação do trabalho e a necessidade de ressarcimento de sua moral mediante atuação do Poder Judiciário concedendo indenização por dano moral e previdenciário para o trabalhador lesado, tendo em vista o estudo crítico do direito ao trabalho, bem como a interpretação dentro do contexto social, político e econômico. Para tanto, analisa-se, além do elemento formal (as normas de proteção ao trabalhador), igualmente a materialidade da proteção à dignidade do trabalhador perante os Tribunais brasileiros a fim de apresentar algumas considerações acerca da efetiva proteção jurídica ao direito ao trabalho como direito fundamental.

A agricultura de corte-e-queima é praticada há milhares de anos nas áreas florestadas do planeta, principalmente nas regiões tropicais. Muitos estudos atestam a sustentabilidade desses sistemas quando praticados tradicionalmente e sob baixas densidades populacionais, mantendo, ou mesmo, promovendo a biodiversidade local e garantindo a subsistência de milhões de pessoas pobres rurais. No entanto, é crescente na literatura acadêmica e no debate político o papel que a agricultura de corte-e-queima vem desempenhando no desmatamento e demais impactos ambientais e sócio-econômicos. Esse processo é conseqüência das mudanças no uso do solo, intensificação agrícola e aumento demográfico que estão alterando as práticas e comprometendo a sustentabilidade desses sistemas agrícolas tradicionais. No Vale do Ribeira, sudeste do Estado de São Paulo, comunidades quilombolas têm sofrido um processo acelerado de mudanças nos seus padrões de subsistência. Dessa forma, esse estudo traz uma revisão da literatura sobre a agricultura de corte-equeima com o objetivo de traçar um panorama geral do que foi produzido até o momento, identificar as principais correntes teóricas envolvidas e apontar as alternativas propostas para sua manutenção. Em seguida, são caracterizados o perfil demográfico e sócio-econômico de nove comunidades quilombolas do Vale do Ribeira e identificados os principais fatores responsáveis pelas mudanças recentes nos seus padrões de subsistência. Por fim, é feita uma análise etnográfica, através de informações levantadas em três comunidades quilombolas pré-selecionadas, para a caracterização das atividades agrícolas praticadas atualmente e no passado recente, bem como o processo de mudanças ocorridas e os impactos causados no sistema agrícola de corte-equeima. Os resultados mostram que as restrições impostas pela legislação ambiental, os conflitos de terra, a construção de uma rodovia na região, a crescente inserção no mercado regional, e a atuação de órgãos governamentais e não-governamentais de desenvolvimento são os principais fatores responsáveis pelas mudanças observadas no sistema agrícola de corte-e-queima e, conseqüentemente, na organização socioeconômica destas populações. / Slash-and-burn agriculture has been practiced for thousands of years in the forests around the world, especially in the tropics, where it provides for the livelihood of countless poor rural populations. Many studies claim that slash-andburn agriculture is sustainable when performed under conditions of low human demographic density, maintaining or even increasing local biodiversity. However, it is growing in the academic literature, as well as in development debates, the concern regarding the role that this system has been playing in the deforestation of the planet´s tropical forests. This process appears to be closely linked to changes in land use patterns (agricultural intensification) and urban and rural demographic growth. In Ribeira Valley, State of São Paulo, Quilombola communities have had a significant increase of changes in their subsistence system. On the thread of these concerns, this study presents a critical review of the international and national academic literature on slash-and-burn agriculture. Thus, this review intends to draw a broad scenario of the current academic debate on this issue, as well as to identify the main alternatives strategies proposed to maintain or replace this cultivation system. Following this study aims to characterize the socioeconomic and demographic profile of nine Quilombola populations in the Ribeira Valley, and to identify the main factors responsible for the recent changes in their subsistence system. Por fim, an ethnographic analysis is done, through informations gathered in three pre-selected Quilombola communities, to characterize the agricultural activities practiced nowadays and in the recent past, besides the change process and impacts on the slash-and-burn agriculture. The results show that restrictions imposed by environmental laws, conflict over land, the construction of a major road in the region, the growing insertion into a market economy, and the intervention of governmental and nongovernmental development agencies are the main factors behind the changes observed in the subsistence system and, consequently, in the socioeconomic organization of these populations.