Ceticismo ou reputação nas recompras de ações?

Este trabalho investiga as recompras de ações no Brasil pelo prisma da reputação das empresas anunciadoras. Por meio de uma base de dados ainda inexplorada, o formulário de referência anual, que possibilita a diferenciação dos anúncios de recompras pelas quantidades efetivamente compradas. Com metodologia de estudo de evento e regressão, foram analisados os anúncios de recompras de ações da própria companhia em mercado aberto para o período compreendido entre os anos de 2007 a 2014. Os principais resultados encontrados foram à existência de reputação para empresas que apresentam uma taxa efetiva de recompra mais elevada e uma penalização para as empresas que apresentam baixas taxas efetivas de recompra em anúncios anteriores, quanto mais próximo de zero a taxa efetiva de recompra do anuncio anterior, menor é o efeito de um novo anúncio. Por fim, foi encontrado retorno anormal acumulado significativo no mercado acionário brasileiro para empresas que anunciam recompra de ações próprias no mercado aberto de 1,12% no primeiro dia, 1,56% no quinto dia e 1,97% ao final do primeiro mês. Para eventos com histórico, foi de 0,98% no primeiro dia, 1,33% no quinto dia e 1,38% ao final do primeiro mês. Já para o caso nos quais os eventos foram antecedidos imediatamente por anúncios de recompra com taxas efetivas de recompras de no mínimo 70%, foi de 1,42% no primeiro dia, 2,70% no quinto dia e 5,09% ao final do primeiro mês.

Environmental regulation, technology adoption and structural transformation: evidence from Brazilian sugarcane industry

We estimate the effects of the adoption of mechanized agriculture led by a new environmental regulation on structural change of local labor markets within a large emerging country, Brazil. In 2002, the state of S\~{a}o Paulo passed a law outlying the timeline to end sugarcane pre-harvest burning in the state. The environmental law led to the fast adoption of mechanized harvest. We investigate if the labor intensity of sugarcane production decreases; and, if so, if it leads to structural changes in the labor market. We use satellite data containing the type of sugarcane harvesting -- manual or mechanic harvest -- paired with official labor market data.%, also geomorphometric data base for our instrumental variable correction. We find suggestive evidence that mechanization of the field led to an increase in utilization of formal workers and a reduction in formal labor intensity in the sugarcane sector. This is partially compensated by an increase in the share of workers in other agricultural crops and in the construction and services sector. Although we find a reduction in employment in the manufacturing sector, the demand generated by the new agro-industries affected positively the all sectors via an increase in workers' wage.

Recomendações para o desenvolvimento de uma ferramenta de suporte às primeiras decisões projetuais visando ao desempenho energético de edificações de escritório em clima quente

PEDRINI, Aldomar; SZOKOLAY, Steven. Recomendações para o desenvolvimento de uma ferramenta de suporte às primeiras decisões projetuais visando ao desempenho energético de edificações de escritório em clima quente. Ambiente Construído, Porto Alegre, v. 5, n. 1, p.39-54, jan./mar. 2005. Trimestral. Disponível em: . Acesso em: 04 out. 2010.

Caminhos que estruturam cidades: redes técnicas de transporte sobre trilhos e a conformação intra-urbana de Natal

The railroad, from 1870 and on, becomes an usual complaining in the press s and politician elite s speeches, especially because of Natal s geographic isolation. The implantation of two railroads in the capital territory Estrada de Ferro de Natal a Nova Cruz, afterwards part of Great Western Railway Company network, and Estrada de Ferro Central do Rio Grande do Norte had serious implications in the urban environment. While railroad s structures were already consolidated, other transportation mechanisms were being implanted in the first decades of the 20th century, such as trams lines, which, by the way, was a transport modal that also used rails as a dislocation meaning. Considering these questions, we may ask: how come railroads and tramways demands, roads and buildings had influenced the internal organization of Natal? We work with the general hypothesis that the influence of technical networks, composed by tramways and railroads, over Natal s urban space happened in a diversified way, sometimes consolidating social aspects in certain areas, sometimes improving the occupation of others. The impact over the city s territory also happens in a diversified way between the buildings/railroad s complexes and the pathways. The different scale of the train in comparison to the trams velocity, size, noise level, flow, among others is also a cause to the different consequences in urban environment. The main objective of this work is to understand the role of circulation technical networks in the construction process of urban space in Natal, as a way to contribute to the urban historiography about the subject. The time frame adopted, between 1881 and 1937, marks the time path of railroads and tramways in Rio Grande do Norte: 1881 is the year of railroad s first section inauguration from Natal to São José do Mipibu as well of the railroad complex in the Republic Square in Natal; the year of 1937 marks the beginning of tramways declination process in the city. At this time railroads and tramways had to face more intensively the competition of motor vehicles. The theory reference adopted is based on concepts and analysis of authors, such as Flávio Villaça and Roberto Lobato Corrêa references to the concepts of urban structure , localization and accessibility and Gabriel Dupuy to explain the concept of urban technical networks . These references reveal the conflict of different realities in the urban universe interests and values which is an important factor about the construction of urban space. The information sources used were from two distinctive natures: primary, journals of the time studied and official government reports, and secondary, based on other works about the subject. It was also used by this study iconographic source, especially images from the data base of the research group História da Cidade, do Território e do Urbanismo .

Coeficientes de difusão de metais em materiais não convencionais (agarose e acetato de celulose) usados na técnica de difusão em filmes finos por gradientes de concentração

The DGT technique allows one to measure quantitatively free and labile metal species in aquatic systems. Nevertheless, for this approach, knowledge is required of the diffusion coefficients of the analytes in a diffusive layer. In this study, the diffusion coefficients of Hg(II), As(III), Mn(II), Mg(II), Cu(II), Cd(II) were determined in agarose gel and those of Ba(II), Cd(II), Cu(II), Mg(II), Mn(II) e Zn(II) in cellulose acetate membranes. These materials presented good performance and the reported results can be used as a data base for further DGT studies.

A casa própria: sonho ou realidade? : um olhar sobre os conjuntos habitacionais em Natal

This dissertation is about housing provision under a capitalist system. It aims at analyzing the economic relevance of the Brazilian housing policy, in particular, looking at the housing estates built in Natal city. It also draws on a data-base about living and housing conditions in Natal, produced in the wake of a more comprehensive research of the 50 largest housing estates in the city. Theoretically, the dissertation discusses: the symbolic dimension of housing; housing as a commodity; the alleged social and economic stability of homeownership; and the urban dynamic of housing estates. It also discusses the historic and conceptual references of the Brazilian housing policy and its consequences to Natal city. From the 1960s, polilcy under the BNH privileged the production of large housing estates. Although this was more closely related to economic rather than social objectives, this policy helped expand the urban limits. This was the case for Natal. At the end, this policy was not targeted towards the poorest in society but towards those low income house buyers who could afford to pay for the mortgages on offer

Aplicação de sistemas multi-classificadores no diagnóstico de falhas em motores de indução trifásicos

Equipment maintenance is the major cost factor in industrial plants, it is very important the development of fault predict techniques. Three-phase induction motors are key electrical equipments used in industrial applications mainly because presents low cost and large robustness, however, it isn t protected from other fault types such as shorted winding and broken bars. Several acquisition ways, processing and signal analysis are applied to improve its diagnosis. More efficient techniques use current sensors and its signature analysis. In this dissertation, starting of these sensors, it is to make signal analysis through Park s vector that provides a good visualization capability. Faults data acquisition is an arduous task; in this way, it is developed a methodology for data base construction. Park s transformer is applied into stationary reference for machine modeling of the machine s differential equations solution. Faults detection needs a detailed analysis of variables and its influences that becomes the diagnosis more complex. The tasks of pattern recognition allow that systems are automatically generated, based in patterns and data concepts, in the majority cases undetectable for specialists, helping decision tasks. Classifiers algorithms with diverse learning paradigms: k-Neighborhood, Neural Networks, Decision Trees and Naïves Bayes are used to patterns recognition of machines faults. Multi-classifier systems are used to improve classification errors. It inspected the algorithms homogeneous: Bagging and Boosting and heterogeneous: Vote, Stacking and Stacking C. Results present the effectiveness of constructed model to faults modeling, such as the possibility of using multi-classifiers algorithm on faults classification

Contribuições para a análise de sinais neuronais e biomédicos

Following the new tendency of interdisciplinarity of modern science, a new field called neuroengineering has come to light in the last decades. After 2000, scientific journals and conferences all around the world have been created on this theme. The present work comprises three different subareas related to neuroengineering and electrical engineering: neural stimulation; theoretical and computational neuroscience; and neuronal signal processing; as well as biomedical engineering. The research can be divided in three parts: (i) A new method of neuronal photostimulation was developed based on the use of caged compounds. Using the inhibitory neurotransmitter GABA caged by a ruthenium complex it was possible to block neuronal population activity using a laser pulse. The obtained results were evaluated by Wavelet analysis and tested by non-parametric statistics. (ii) A mathematical method was created to identify neuronal assemblies. Neuronal assemblies were proposed as the basis of learning by Donald Hebb remain the most accepted theory for neuronal representation of external stimuli. Using the Marcenko-Pastur law of eigenvalue distribution it was possible to detect neuronal assemblies and to compute their activity with high temporal resolution. The application of the method in real electrophysiological data revealed that neurons from the neocortex and hippocampus can be part of the same assembly, and that neurons can participate in multiple assemblies. (iii) A new method of automatic classification of heart beats was developed, which does not rely on a data base for training and is not specialized in specific pathologies. The method is based on Wavelet decomposition and normality measures of random variables. Throughout, the results presented in the three fields of knowledge represent qualification in neural and biomedical engineering

Desenvolvimento de um sistema para aplicação dos conceitos da tecnologia cad3d-bim na indústria moveleira

In this work was developed an information system to apply the concepts of CAD3D-BIM technology for the design activities of the furniture industry. The development of this system was based in an architecture comprised of two modules: a web interface to management the metadata of models from furniture's library and the combination of three-dimensional CAD software with a specific plugin to access the information from this model. To develop this system was also used a Data Base Management System (DBMS) designed to storage the information from models in a hierarchical way, based on concepts of Group Technology (GT). The centralization of information in a single database allows the automatic availability of any changes to all participants involved in a particular project when it‟s happens. Each module from system has its own connection to this database. Finally was developed a prototype from a 3D virtual environment to help create Virtual Reality projects in the web. A study from available technologies to create 3D web applications for execution in websites was done to support this development. The interconnection between modules and the database developed allowed the assembly of a system architecture to support the construction and exhibition of projects of the furniture industry in accordance with the concepts proposed by BIM (Building Information Modeling), using as object of study the furniture industry of state of Rio Grande do Norte

Teores de metais na biomassa de Egeria densa, Egeria najas e Ceratophyllum demersum

Este estudo foi realizado com o objetivo de se estimar o conteúdo de elementos metálicos presentes em três macrófitas aquáticas submersas, procurando avaliar a participação destas plantas na remoção destes elementos na água e criar base de dados que permita prever o impacto ambiental do descarte delas em solo ou na própria água. As amostras foram desidratadas, moídas e encaminhadas aos laboratórios para análise e quantificação dos elementos. Para as três espécies, a maior concentração de elementos foi observada durante o verão, ocorrendo declínio nas concentrações durante o inverno, principalmente para os elementos vanádio e chumbo. Não foi detectada presença do elemento mercúrio em nenhuma das amostras.

Determinação de dados de equilíbrio de fases para sistemas aquosos com eletrólitos

In the present work are established initially the fundamental relationships of thermodynamics that govern the equilibrium between phases, the models used for the description of the behavior non ideal of the liquid and vapor phases in conditions of low pressures. This work seeks the determination of vapor-liquid equilibrium (VLE) data for a series of multicomponents mixtures of saturated aliphatic hydrocarbons, prepared synthetically starting from substances with analytical degree and the development of a new dynamic cell with circulation of the vapor phase. The apparatus and experimental procedures developed are described and applied for the determination of VLE data. VLE isobarics data were obtained through a Fischer s ebulliometer of circulation of both phases, for the systems pentane + dodecane, heptane + dodecane and decane + dodecane. Using the two new dynamic cells especially projected, of easy operation and low cost, with circulation of the vapor phase, data for the systems heptane + decane + dodecane, acetone + water, tween 20 + dodecane, phenol + water and distillation curves of a gasoline without addictive were measured. Compositions of the equilibrium phases were found by densimetry, chromatography, and total organic carbon analyzer. Calibration curves of density versus composition were prepared from synthetic mixtures and the behavior excess volumes were evaluated. The VLE data obtained experimentally for the hydrocarbon and aqueous systems were submitted to the test of thermodynamic consistency, as well as the obtained from the literature data for another binary systems, mainly in the bank DDB (Dortmund Data Bank), where the Gibbs-Duhem equation is used obtaining a satisfactory data base. The results of the thermodynamic consistency tests for the binary and ternary systems were evaluated in terms of deviations for applications such as model development. Later, those groups of data (tested and approved) were used in the KijPoly program for the determination of the binary kij parameters of the cubic equations of state original Peng-Robinson and with the expanded alpha function. These obtained parameters can be applied for simulation of the reservoirs petroleum conditions and of the several distillation processes found in the petrochemistry industry, through simulators. The two designed dynamic cells used equipments of national technology for the determination of VLE data were well succeed, demonstrating efficiency and low cost. Multicomponents systems, mixtures of components of different molecular weights and also diluted solutions may be studied in these developed VLE cells

Determinação de Dados de Equilíbrio Líquido-Vapor para Sistemas Hidrocarbonetos e Desenvolvimento de uma Nova Célula Dinâmica

In the present work are established initially the fundamental relationships of thermodynamics that govern the equilibrium between phases, the models used for the description of the behavior non ideal of the liquid and vapor phases in conditions of low pressures. This work seeks the determination of vapor-liquid equilibrium (VLE) data for a series of multicomponents mixtures of saturated aliphatic hydrocarbons, prepared synthetically starting from substances with analytical degree and the development of a new dynamic cell with circulation of the vapor phase. The apparatus and experimental procedures developed are described and applied for the determination of VLE data. VLE isobarics data were obtained through a Fischer's ebulliometer of circulation of both phases, for the systems pentane + dodecane, heptane + dodecane and decane + dodecane. Using the two new dynamic cells especially projected, of easy operation and low cost, with circulation of the vapor phase, data for the systems heptane + decane + dodecane, acetone + water, tween 20 + dodecane, phenol + water and distillation curves of a gasoline without addictive were measured. Compositions of the equilibrium phases were found by densimetry, chromatography, and total organic carbon analyzer. Calibration curves of density versus composition were prepared from synthetic mixtures and the behavior excess volumes were evaluated. The VLE data obtained experimentally for the hydrocarbon and aqueous systems were submitted to the test of thermodynamic consistency, as well as the obtained from the literature data for another binary systems, mainly in the bank DDB (Dortmund Data Bank), where the Gibbs-Duhem equation is used obtaining a satisfactory data base. The results of the thermodynamic consistency tests for the binary and ternary systems were evaluated in terms of deviations for applications such as model development. Later, those groups of data (tested and approved) were used in the KijPoly program for the determination of the binary kij parameters of the cubic equations of state original Peng-Robinson and with the expanded alpha function. These obtained parameters can be applied for simulation of the reservoirs petroleum conditions and of the several distillation processes found in the petrochemistry industry, through simulators. The two designed dynamic cells used equipments of national technology for the determination Humberto Neves Maia de Oliveira Tese de Doutorado PPGEQ/PRH-ANP 14/UFRN of VLE data were well succeed, demonstrating efficiency and low cost. Multicomponents systems, mixtures of components of different molecular weights and also diluted solutions may be studied in these developed VLE cells

Fiscal policy contradiction: a perspective on Brazil and Mexico

The aim of this paper is to discuss the quality of fiscal policy in Brazil and Mexico and investigate whether fiscal policy influence is favorable to reduce the unemployment rate. Public spending, which has a positive effect on the level of employment when results in additional aggregate demand, may cause a negative effect on employment, if its financing depends on persistent high interest rates. Brazil and Mexico have engaged in a long effort to control public spending and to reduce the public deficit to zero. Does this policy bring a positive result to the economic activity no matter how actual public deficit has been financed? We select variables related to public budget as public sector borrowing requirements, taxes, public debt and others to form a data base. The fiscal institutional arrangement and the data allow us to evaluate the fiscal policy as a whole and to discuss the importance of credibility and reputation of the government.

Uso de técnicas de Geoprocessamento e Sensoriamento Remoto no levantamento e integração de dados necessários a gestão ambiental dos campos de extração de óleo e gás do Canto do Amaro e Alto da Pedra no município de Mossoró - RN

The objective of this work is to identify, to chart and to explain the evolution of the soil occupation and the envirionment vulnerability of the areas of Canto do Amaro and Alto da Pedra, in the city of Mossoró-RN, having as base analyzes it multiweather of images of orbital remote sensors, the accomplishment of extensive integrated works of field to a Geographic Information System (GIS). With the use of inserted techniques of it analyzes space inserted in a (GIS), and related with the interpretation and analyzes of products that comes from the Remote Sensoriamento (RS.), make possible resulted significant to reach the objectives of this works. Having as support for the management of the information, the data set gotten of the most varied sources and stored in digital environment, it comes to constitute the geographic data base of this research. The previous knowledge of the spectral behavior of the natural or artificial targets, and the use of algorithms of Processing of Digital images (DIP), it facilitates the interpretation task sufficiently and searchs of new information on the spectral level. Use as background these data, was generated a varied thematic cartography was: Maps of Geology, Geomorfológicals Units soils, Vegetation and Use and Occupation of the soil. The crossing in environment SIG, of the above-mentioned maps, generated the maps of Natural and Vulnerability envirionmental of the petroliferous fields of I Canto do Amaro and Alto da Pedra-RN, working in an ambient centered in the management of waters and solid residuos, as well as the analysis of the spatial data, making possible then a more complex analysis of the studied area

Diagnóstico geoambiental com uso do geoprocessamento visando a determinação de potencialidades de uso do solo para a área estuarina do Rio Curimataú - Canguaretama(RN)

The activities developed in the coastal zone always arise the researchers interest, mainly when it is developed in fragile ecological areas, not observing the sustenable development laws. In this context, the analysis presented developed around the estuary of Curimatau river, located in the Eastern coast of Rio Grande do Norte state, integrates information provided by high resolution images of orbital remote sensing (IKONOS II, dated of July of 2003) and images of not-orbital remote sensing (Air photographs of DPU, dated of March of 1997) in a multitemporary perspective, diagnosising patterns of use and occupation, evaluating the main area´s impacts, together with the estuarian region fisiograph of Curimatau river. The use of high resolution images consequently allowed generates a precision cartography, facilitating the quantification of the evolution of the landscape and supporting decisions. Was possible yet, the definition of use areas, conservation areas and preservation areas; that were inserted in the concept of Potentialities: a fundamental element to management of vulnerable areas of the natural point of view. The information provided during the research had been stored in an Enviromental Georreferenced Data Base, constructed under the optics of Geographical Information Systems (GIS), that they facilitate the environment management Through fast access to information. The results were satisfactory, because permits the quantification of evolution of the landscape and the mapping. Beyond the geoenviromental diagnosis, was possible develop maps and matrixes that support the Rio Grande do Norte state costal Management.