Controle feedback de nível baseado em sensor de imagem aplicado ao equipamento misturador-decantador à inversão de fases (MDIF®)

The treatment of wastewaters contaminated with oil is of great practical interest and it is fundamental in environmental issues. A relevant process, which has been studied on continuous treatment of contaminated water with oil, is the equipment denominated MDIF® (a mixer-settler based on phase inversion). An important variable during the operation of MDIF® is the water-solvent interface level in the separation section. The control of this level is essential both to avoid the dragging of the solvent during the water removal and improve the extraction efficiency of the oil by the solvent. The measurement of oil-water interface level (in line) is still a hard task. There are few sensors able to measure oil-water interface level in a reliable way. In the case of lab scale systems, there are no interface sensors with compatible dimensions. The objective of this work was to implement a level control system to the organic solvent/water interface level on the equipment MDIF®. The detection of the interface level is based on the acquisition and treatment of images obtained dynamically through a standard camera (webcam). The control strategy was developed to operate in feedback mode, where the level measure obtained by image detection is compared to the desired level and an action is taken on a control valve according to an implemented PID law. A control and data acquisition program was developed in Fortran to accomplish the following tasks: image acquisition; water-solvent interface identification; to perform decisions and send control signals; and to record data in files. Some experimental runs in open-loop were carried out using the MDIF® and random pulse disturbances were applied on the input variable (water outlet flow). The responses of interface level permitted the process identification by transfer models. From these models, the parameters for a PID controller were tuned by direct synthesis and tests in closed-loop were performed. Preliminary results for the feedback loop demonstrated that the sensor and the control strategy developed in this work were suitable for the control of organic solvent-water interface level

Avaliação de indicadores de impactos ambientais no perímetro irrigado Cruzeta-Região semi-árida do RN

Environmental impacts are defined as the processes of social and ecological changes caused by nuisance ambient. In agriculture are diverse, and the intensive use of land and inappropriate agricultural practices causes negative effect on the environment besides affecting crop productivity and quality of life of man. So this study was objective to analyze parameters indicators of environmental impacts in the Cruzeta the Discrict Irrigation. During the period July 2007 to March 2008 samples were collected in lot 01 and 02 of the irrigation district. The monitoring was conducted in four sampling points, three (3) located in the irrigation channels and 1 (one) located in a cacimbão. Were monitored pH, CE, STD, SS, NO3-, OD, DT, PST, RAS, CT, Ca+2, Mg+2, Na+ and K+ and heavy metals. Analysis was performed, soil fertility, determining the infiltration rate, moisture content of soil and flow measurement. The results showed that the parameters considered most effective in evaluating the indicators of environmental impacts were: Suspended solid, turbidity, dissolved oxygen and Coliform termotelerantes. The concentrations of nitrate were below the limit established by CONAMA (2005). High levels of STD were found in the point P4. The risk of salinity in cacimbão Lot 02, the water was classified as Class II, or medium risk of salinity in the remaining points was classified as Class I. The iron and aluminum were found high concentrations in four sampling points independent of the dry or rainy. On the ground, found high levels of phosphorus in both samples collected in the batch 01, as the lot 02. The pH levels found in samples of soil, the soil can be classified as neutral and moderate alkalinity. The high infiltration rate obtained in the tests performed in lots 01 and 02 indicated the high permeability of soil at these points

Análise da vulnerabilidade de Natal/RN frente às mudanças climáticas

The interaction between land and water, resulting from dynamic agents, such as wind, waves and tides, characterizes the coastal zone as a dynamic environment that is constantly disturbed and that may alter the balance of natural and man-made environment. Such modifications may be intensified when considering the climate change. This environment is highly attractive for the development of economic activities and urbanization, current scenario of the city of Natal. Weighing the economic importance for the state and the physical environment in which the capital of Rio Grande do Norte is inserted, this study aims to identify and analyze vulnerabilities and impacts caused by the rising sea level in the municipality. To that end, we defined a coastline, delimited areas susceptible to flooding and presented some flood scenarios. This way we could identify and analyze the impacts of each flood scenario in its respective section. Finally, it appears that the coastal zone in which Natal is inserted is a fragile area that requires actions aimed at mitigating vulnerabilities and facing the problem that caused the rise in the mean sea level (MSL), and mitigating the presented vulnerability framework; it is necessary to implement actions that effectively contribute to the protection and adaptation of the most fragile areas

Identificação de áreas com precipitação pluvial homogênea no Estado do Rio Grande do Norte

O estudo da variabilidade da precipitação é importante para o planejamento das atividades econômicas, possibilitando o uso mais eficiente e racional dos recursos hídricos. Dessa forma, o objetivo desta pesquisa é caracterizar o estado do Rio Grande do Norte com relação à variabilidade temporal da precipitação, agrupá-lo em regiões homogêneas e comparar diferentes técnicas de agrupamento. Para o estudo da variabilidade pluvial foram utilizados os índices: Grau de Concentração de Precipitação (PCD), que representa o grau em que a precipitação é distribuída ao longo do ano; e o Período de Concentração de Precipitação (PCP), que reflete o período no qual a precipitação está mais concentrada. Para a realização dos agrupamentos foram escolhidas as variáveis: PCD, PCP, médias da precipitações anuais e médias das precipitações mensais. Posteriormente, foi aplicada a análise de agrupamento para obter grupos com características similares. Os resultados mostraram que as precipitações são melhor distribuídas na região leste do estado, neste caso, os meses mais chuvosos são de maio a agosto. Os municípios localizados nessa área possuem dois picos de chuvas, devido à atuação de dois sistemas: Perturbações Ondulatórias dos Alísios (POA s) e Zona de Convergência Intertropical (ZCIT). Nas regiões localizadas a oeste os meses que possuem maior concentração de chuvas são março e abril, neste caso temos apenas um pico de precipitação, devido a atuação da ZCIT. A identificação de áreas homogêneas favorece o planejamento adequado de acordo com as características de cada grupo formado e o RN pode foi dividido em 4 (quatro) regiões homogêneas. As técnicas de agrupamento utilizadas apresentaram resultados semelhantes, porém, sugere-se o uso de mais de uma técnica para que se possa analisar qual delas reflete melhor a realidade local. O estudo da variabilidade de precipitação, através dos índices estudados e do agrupamento realizado, são ferramentas adequadas ao planejamento ambiental e econômico

A melancolia em A Asa Esquerda do Anjo

O termo melancolia, como foi mostrado em todo o decorrer do nosso trabalho, principalmente no histórico da melancolia, é um termo, por excelência, escorregadio. De várias facetas, a melancolia pode vir a designar desde patologia, passando por inspiração filosófica, para desaguar num modo de ver a vida, como bem nos coloca Denílson Lopes em seu livro Nós os mortos: melancolia e neo Barroco (1999). A Asa Esquerda do Anjo (LUFT, 2005) é uma obra que já nos acompanha há algum tempo, pois desde a graduação estudamo-la. Em torno da protagonista, chamada de Gisela pela mãe e Guísela pela avó, circula toda a trama desse romance moderno. Tentamos visualizá-la nos três capítulos da dissertação. No primeiro, focalizamos a obra sob o aspecto de uma possível estética da melancolia, tendo por base teórica Marie Claude Lambotte (2000). Depois, elaboramos algumas linhas sobre as perdas da protagonista que do enredo emergem. Por fim, demonstramos Gisela pelo aspecto de múltiplas faces. Sabendo que uma obra literária é infinita em seus significados, cremos que A Asa Esquerda do Anjo (2005) suscita outras nuances. Isto nos dá a certeza que não é um texto acabado, finalizado. Estas nuances poderão ser estudadas, pesquisadas em uma outra oportunidade por nós ou por outros leitores de Luft. A fim de estudar a melancolia em Gisela, fundamentamos nossa dissertação com os estudos de Freud (1980) a respeito do tema. Este faz uma análise comparando a melancolia ao luto, para poder chegar, assim, a um denominador comum, já que o termo é flexível em seus significados. Freud e alguns outros autores no campo, tais como, Bataille (1980); Benjamin (1984); Erickson (2003); Klein (1971); Kristeva (1989); Lino (2004); Peres (2003); Santos (2005), Scliar (2003), pois, nos auxiliaram em nossas pesquisas e direcionaram melhor o nosso olhar sobre a obra. Acreditamos ter alcançado nosso objetivo estudar a obra A Asa Esquerda do Anjo (LLUFT, 2005) pelo foco da melancolia e suas nuances. Gisela é um personagem inacabado. Em seu discurso ela deixa isto bem nítido. Assim também, não buscamos respostas prontas, com teor de acabamento. O fechar da história está nas mãos do leitor. Mas, à medida que reiniciamos nova leitura, percebemos algo novo, que pode ser extraído da obra, do personagem, da trama. É neste abrir/fechar que a própria Gisela sussurra: Vem, vem, vem.... Ao chamar a todos nós, chama também para um novo caminhar com ela, em suas perturbações subjetivas e sua ausência de respostas. Ao aceitarmos este convite, fica difícil retornarmos pelo mesmo caminho de antes. É necessário, então, junto com este ser de papel, rever nossos passos, para, enfim, redimensionarmos nossa escrita acerca de nós mesmos e (por que não dizer?) do mundo que nos circunda

Evolução top-hat hidrodinâmica em campos de velocidades peculiares primordiais

We investigate the cosmology of the vacuum energy decaying into cold dark matter according to thermodynamics description of Alcaniz & Lima. We apply this model to analyze the evolution of primordial density perturbations in the matter that gave rise to the first generation of structures bounded by gravity in the Universe, called Population III Objects. The analysis of the dynamics of those systems will involve the calculation of a differential equation system governing the evolution of perturbations to the case of two coupled fluids (dark matter and baryonic matter), modeled with a Top-Hat profile based in the perturbation of the hydrodynamics equations, an efficient analytical tool to study the properties of dark energy models such as the behavior of the linear growth factor and the linear growth index, physical quantities closely related to the fields of peculiar velocities at any time, for different models of dark energy. The properties and the dynamics of current Universe are analyzed through the exact analytical form of the linear growth factor of density fluctuations, taking into account the influence of several physical cooling mechanisms acting on the density fluctuations of the baryonic component of matter during the evolution of the clouds of matter, studied from the primordial hydrogen recombination. This study is naturally extended to more general models of dark energy with constant equation of state parameter in a flat Universe

Efeitos não-gaussianos em astrofísica e cosmologia

The recent astronomical observations indicate that the universe has null spatial curvature, is accelerating and its matter-energy content is composed by circa 30% of matter (baryons + dark matter) and 70% of dark energy, a relativistic component with negative pressure. However, in order to built more realistic models it is necessary to consider the evolution of small density perturbations for explaining the richness of observed structures in the scale of galaxies and clusters of galaxies. The structure formation process was pioneering described by Press and Schechter (PS) in 1974, by means of the galaxy cluster mass function. The PS formalism establishes a Gaussian distribution for the primordial density perturbation field. Besides a serious normalization problem, such an approach does not explain the recent cluster X-ray data, and it is also in disagreement with the most up-to-date computational simulations. In this thesis, we discuss several applications of the nonextensive q-statistics (non-Gaussian), proposed in 1988 by C. Tsallis, with special emphasis in the cosmological process of the large structure formation. Initially, we investigate the statistics of the primordial fluctuation field of the density contrast, since the most recent data from the Wilkinson Microwave Anisotropy Probe (WMAP) indicates a deviation from gaussianity. We assume that such deviations may be described by the nonextensive statistics, because it reduces to the Gaussian distribution in the limit of the free parameter q = 1, thereby allowing a direct comparison with the standard theory. We study its application for a galaxy cluster catalog based on the ROSAT All-Sky Survey (hereafter HIFLUGCS). We conclude that the standard Gaussian model applied to HIFLUGCS does not agree with the most recent data independently obtained by WMAP. Using the nonextensive statistics, we obtain values much more aligned with WMAP results. We also demonstrate that the Burr distribution corrects the normalization problem. The cluster mass function formalism was also investigated in the presence of the dark energy. In this case, constraints over several cosmic parameters was also obtained. The nonextensive statistics was implemented yet in 2 distinct problems: (i) the plasma probe and (ii) in the Bremsstrahlung radiation description (the primary radiation from X-ray clusters); a problem of considerable interest in astrophysics. In another line of development, by using supernova data and the gas mass fraction from galaxy clusters, we discuss a redshift variation of the equation of state parameter, by considering two distinct expansions. An interesting aspect of this work is that the results do not need a prior in the mass parameter, as usually occurs in analyzes involving only supernovae data.Finally, we obtain a new estimate of the Hubble parameter, through a joint analysis involving the Sunyaev-Zeldovich effect (SZE), the X-ray data from galaxy clusters and the baryon acoustic oscillations. We show that the degeneracy of the observational data with respect to the mass parameter is broken when the signature of the baryon acoustic oscillations as given by the Sloan Digital Sky Survey (SDSS) catalog is considered. Our analysis, based on the SZE/X-ray data for a sample of 25 galaxy clusters with triaxial morphology, yields a Hubble parameter in good agreement with the independent studies, provided by the Hubble Space Telescope project and the recent estimates of the WMAP

Análise de redes do cotidiano a partir do encontro entre usuários e profissionais da estratégia saúde da família

O presente estudo discute a formação de Redes Sociais no cotidiano da Estratégia Saúde da Família, a partir de aportes da teoria sociológica sobre redes, interações, dádiva e reconhecimento. O objetivo geral é analisar as redes sociais locais em saúde a partir da interação de usuários e profissionais da Estratégia Saúde da Família na Unidade de Saúde de Ligéia, em Natal, RN. Seus objetivos específicos são: Mapear as redes sociais locais em saúde existentes no território adscrito; Identificar os tipos de interações cotidianas entre os sujeitos; Compreender a percepção dos sujeitos sobre o processo de formação de redes sociais a partir das interações. Caracteriza-se enquanto pesquisa qualitativa exploratória cujos sujeitos foram profissionais e usuários vinculados à referida unidade de saúde. Para a coleta de dados foram utilizadas entrevistas individuais semiestruturadas e debates em grupos focais, estimulados pela Metodologia de Análise de Redes do Cotidiano (MARES), pertinente para abordar a complexidade das relações sociais e mapear os diferentes conteúdos expressos e as formas de mobilização coletiva. A análise dos dados foi realizada através da Técnica de Análise Temática de Conteúdo, proposta por Minayo. Os resultados foram interpretados à luz das Teorias da Dádiva (Mauss) e do Reconhecimento (Honneth). Os sujeitos visualizaram: Rede Virtual (28,20%); Rede de Atenção à Saúde (25,64%); Redes de Usuários (17,95%); Rede Pessoal (10,26%); Conselho Comunitário (10,26%); Escolas (7,69%). Os participantes não perceberam os arranjos familiares enquanto Redes Sociais. Os tipos de interações sociais identificadas foram: Confrontação/Negociação (41.02%); Harmônicas (25,70%); Correlativas (17,90%); Definidas pela Organização (15,38%). A formação de redes sociais ocorre a partir de interações cotidianas entre pessoas, pela articulação inseparável de conteúdos e formas, catalisadas pelo contexto, experiência e cognição, valorizando a liberdade, a expressividade e a diversidade dos parceiros de significação. Foram encontradas duas categorias, na percepção dos sujeitos, sobre a formação de redes sociais do cotidiano: Diálogo e Encontro. Validamos e recomendamos o uso da metodologia MARES: Na formação, para despertar uma visão mais tolerante e humana de si e do outro; Na avaliação qualitativa dos serviços, por facilitar a reflexão sobre a prática e (re)organização do processo de trabalho; Na comunidade, para estimular movimentos sociais existentes ou emergentes. A aposta no circuito da dádiva e do reconhecimento recíproco, durante o trânsito nas redes sociais em saúde, pode ser capaz de tecer uma práxis transformadora, pela busca e alcance de confiança, respeito e estima, nos espaços de encontro entre usuários e profissionais da Estratégia Saúde da Família

Identificação e comparação entre controle preditivo com modelo não linear e PI sintonizados com PSO em sistema de separação gravitacional de águia-óleo

The separation methods are reduced applications as a result of the operational costs, the low output and the long time to separate the uids. But, these treatment methods are important because of the need for extraction of unwanted contaminants in the oil production. The water and the concentration of oil in water should be minimal (around 40 to 20 ppm) in order to take it to the sea. Because of the need of primary treatment, the objective of this project is to study and implement algorithms for identification of polynomial NARX (Nonlinear Auto-Regressive with Exogenous Input) models in closed loop, implement a structural identification, and compare strategies using PI control and updated on-line NARX predictive models on a combination of three-phase separator in series with three hydro cyclones batteries. The main goal of this project is to: obtain an optimized process of phase separation that will regulate the system, even in the presence of oil gushes; Show that it is possible to get optimized tunings for controllers analyzing the mesh as a whole, and evaluate and compare the strategies of PI and predictive control applied to the process. To accomplish these goals a simulator was used to represent the three phase separator and hydro cyclones. Algorithms were developed for system identification (NARX) using RLS(Recursive Least Square), along with methods for structure models detection. Predictive Control Algorithms were also implemented with NARX model updated on-line, and optimization algorithms using PSO (Particle Swarm Optimization). This project ends with a comparison of results obtained from the use of PI and predictive controllers (both with optimal state through the algorithm of cloud particles) in the simulated system. Thus, concluding that the performed optimizations make the system less sensitive to external perturbations and when optimized, the two controllers show similar results with the assessment of predictive control somewhat less sensitive to disturbances

Efeitos de tempestades magnéticas em sinais de gps, em Natal, Brasil

Satellites signals present disturbances (scintillations), due to presence of irregularities in the ionospheric plasma. In the present work, we dedicate to the study of the attenuation of these scintillations that is, an improvement in the signal, during the main magnetic storm phase during the period of October 2006 to February 2007. Using amplitude of scintillation 1.5GHz (L1) data of the net of satellites GPS, in the ionospheric station of Natal (5.84o S, 35.20o O, -20o dip) and geomagnetic indices, during the minimum solar cycle (referred to as cycle 23), demonstrating its anti-correlation between magnetic activity (Kp) and index of scintillation () (Bonelli2005 method, that works for solar maximum, Bonelli(2005)). These results show that these storms correspond to category I of Aarons (1991). The magnetic storms can generate irregularities when the electric feld of penetration eastward on the pre-reversal hour intensificating that and can too generate irregularities on midnight and sunlight period. The limitation of the method applied here is that it is not considering some storms that had also occurred during equinox and summer in the Brazilian region. For this reason, we will use additional data of the stations of São João de Cariri (Imager and Photometer) and of the station at Fortaleza (Digissonde data), as aid to analyze these storms. The storms that had been left out by the applied method, fit in the other two categories of Aarons, with one only exception (storm of January, 02). We show that in the day of the main phase of the magnetic storm, and with presence of bubbles (according to data of the Imager and Photometer), the speed of vertical drift ~E ~B (hF=t) is below 20m/s, that is the threshold found for Anderson al., (2004) (>20m/s as condition favorable to the formation of irregularities and increase in the scintillation index). This reduction of the speed is due to solar minimum

Parâmetro de regularização em problemas inversos: estudo numérico com a transformada de Radon

In general, an inverse problem corresponds to find a value of an element x in a suitable vector space, given a vector y measuring it, in some sense. When we discretize the problem, it usually boils down to solve an equation system f(x) = y, where f : U Rm ! Rn represents the step function in any domain U of the appropriate Rm. As a general rule, we arrive to an ill-posed problem. The resolution of inverse problems has been widely researched along the last decades, because many problems in science and industry consist in determining unknowns that we try to know, by observing its effects under certain indirect measures. Our general subject of this dissertation is the choice of Tykhonov´s regulaziration parameter of a poorly conditioned linear problem, as we are going to discuss on chapter 1 of this dissertation, focusing on the three most popular methods in nowadays literature of the area. Our more specific focus in this dissertation consists in the simulations reported on chapter 2, aiming to compare the performance of the three methods in the recuperation of images measured with the Radon transform, perturbed by the addition of gaussian i.i.d. noise. We choosed a difference operator as regularizer of the problem. The contribution we try to make, in this dissertation, mainly consists on the discussion of numerical simulations we execute, as is exposed in Chapter 2. We understand that the meaning of this dissertation lays much more on the questions which it raises than on saying something definitive about the subject. Partly, for beeing based on numerical experiments with no new mathematical results associated to it, partly for being about numerical experiments made with a single operator. On the other hand, we got some observations which seemed to us interesting on the simulations performed, considered the literature of the area. In special, we highlight observations we resume, at the conclusion of this work, about the different vocations of methods like GCV and L-curve and, also, about the optimal parameters tendency observed in the L-curve method of grouping themselves in a small gap, strongly correlated with the behavior of the generalized singular value decomposition curve of the involved operators, under reasonably broad regularity conditions in the images to be recovered

O território das novas economias e suas implicações socioambientais na comunidade pesqueira de Barra do Cunhaú

This dissertation aims to analyze the territory of the new economies and their social implications in the district of Barra do Cunhaú / Canguaretama. We used techniques of qualitative research (document analysis, interviews and observations in situ). It was found that the changes occurring in the territory are linked to the pressures caused by factors internal and external orders, such as the deployment and expansion of projects for development of tourism and shrimp in place, which led to the advancement of real estate speculation and intensification of the deforestation of areas of mangroves along the estuary of the river Curimataú / Cunhaú, contributing to the abandonment of fishing and agriculture for livelihood in this community, therefore, the loss of traditional knowledge applied in the conduct of this activity. It was also found that changes in the use of territory and resources threaten biodiversity and have contributed to the reduction of fish stocks of the Municipality of Canguaretama and thus bar the Cunhaú, especially the stock of crab, Uca (ucides cardatus ). The results indicated that the production in large scale in a market economy, as is the shrimp, ignores the search for balance in regional settings. Thus the environmental disturbances resulting from the shrimp and tourism have consequences for social and cultural aspects, directly affecting the livelihood of the residents of Barra do Cunhaú. Companies of shrimp and related to tourism have absorbed the fishermen who are leaving the fishing activity. However, the low level of education associated with age are factors that make them far outside the framework of employees of these companies. Therefore, it is necessary to create conditions that allow the development of the shrimp and tourism without putting at risk the sustainability of the region

Análise dos microssismos registrados no arquipélago de São Pedro e São Paulo (ASPSP) e suas relações com variáveis oceanográficas

Microseisms are continuous vibrations pervasively recorded in the mili Hertz to 1 Hz frequency range. These vibrations are mostly composed of Rayleigh waves and are strongest in the 0.04 to 1 Hz frequency band. Their precise source mechanisms are still a matter of debate but it is agreed that they are related to atmospheric perturbations and ocean gravity waves. The Saint Peter Saint Paul Archipelago (SPSPA) is located in the equatorial region of the Atlantic Ocean about 1,100 km distant from the Brazilian northeastern coast. The SPSPA is composed by a set of several small rocky formations with a total area of approximately 17,000 m². Due to its remote distance from the continent and the lack of cultural noise, this location is a unique location for measuring microseismic noise and to investigate its relation with some climate and oceanographic variables. In the SPSPA we have recorded both primary microseisms (PM) at 0.04 – 0.12 Hz and the secondary microseisms (SM) at 0.12 – 0.4 Hz during 10 months in 2012 and 2013. Our analysis indicates a good correlation between the microseismic noise in the region and a seasonal dependency. In particular, the winter in the northern hemisphere. We have also shown that most of the PM is generated in the SPSPA itself. The SM source location depends with the seasonal climatic and oceanographic variables in the northern hemisphere

Indicadores do nível relativo do mar e evolução costeira durante o holoceno tardio no litoral oeste do Ceará, NE do Brasil

In the coastal region of Ceará, between the municipalities of Acaraú and Itapipoca, thirteen sites were identified containing indicators of relative sea level, six of these being dated by optically stimulated luminescence (OSL) and radiocarbon. Ages obtained supports that were formed prograding beaches in the study area. In the eastern portion, beaches in coastal plain deposits occur while a system lagoon/barrier paleomangrove occurs in the western portion of the study area. In both cases the coastal deposits prograde from east to west. Higher sea levels were identified between the current: (a) 3.110-2.830 cal. yr. BP; (b) 1.830 yr. BP (OSL) - 1.490 cal. yr. BP; (c) between 1.240-1.060 cal. yr. BP; (d) 845-715 yr. BP (OSL). Since then the sea level suffered by lowering the current level. Variations in sea level are interpreted as responses to changes in the pattern of marine circulation and do not exclude possible tectonic disturbances in the basin of the continental margin. The indicators of relative sea level west coast of Ceará present differently from other curves constructed in the coastal northeast, suggesting that local factors mentioned above contributed to sea level fluctuations.

Estudo da estrutura subsuperficial da província Borborema com correlação de ruído sísmico

Ambient seismic noise has traditionally been considered as an unwanted perturbation in seismic data acquisition that "contaminates" the clean recording of earthquakes. Over the last decade, however, it has been demonstrated that consistent information about the subsurface structure can be extracted from cross-correlation of ambient seismic noise. In this context, the rules are reversed: the ambient seismic noise becomes the desired seismic signal, while earthquakes become the unwanted perturbation that needs to be removed. At periods lower than 30 s, the spectrum of ambient seismic noise is dominated by microseism, which originates from distant atmospheric perturbations over the oceans. The microsseism is the most continuous seismic signal and can be classified as primary – when observed in the range 10-20 s – and secondary – when observed in the range 5-10 s. The Green‘s function of the propagating medium between two receivers (seismic stations) can be reconstructed by cross-correlating seismic noise simultaneously recorded at the receivers. The reconstruction of the Green‘s function is generally proportional to the surface-wave portion of the seismic wavefield, as microsseismic energy travels mostly as surface-waves. In this work, 194 Green‘s functions obtained from stacking of one month of daily cross-correlations of ambient seismic noise recorded in the vertical component of several pairs of broadband seismic stations in Northeast Brazil are presented. The daily cross-correlations were stacked using a timefrequency, phase-weighted scheme that enhances weak coherent signals by reducing incoherent noise. The cross-correlations show that, as expected, the emerged signal is dominated by Rayleigh waves, with dispersion velocities being reliably measured for periods ranging between 5 and 20 s. Both permanent stations from a monitoring seismic network and temporary stations from past passive experiments in the region are considered, resulting in a combined network of 33 stations separated by distances between 60 and 1311 km, approximately. The Rayleigh-wave, dispersion velocity measurements are then used to develop tomographic images of group velocity variation for the Borborema Province of Northeast Brazil. The tomographic maps allow to satisfactorily map buried structural features in the region. At short periods (~5 s) the images reflect shallow crustal structure, clearly delineating intra-continental and marginal sedimentary basins, as well as portions of important shear zones traversing the Borborema Province. At longer periods (10 – 20 s) the images are sensitive to deeper structure in the upper crust, and most of the shallower anomalies fade away. Interestingly, some of them do persist. The deep anomalies do not correlate with either the location of Cenozoic volcanism and uplift - which marked the evolution of the Borborema Province in the Cenozoic - or available maps of surface heat-flow, and the origin of the deep anomalies remains enigmatic.