998 resultados para 1995_01310720 TM-68 4302812
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A pesquisa sobre empreendedorismo tem crescido de forma exponencial nos últimos anos. Este artigo teve como principal objetivo quantificar esta produção acadêmica, identificando os principais veículos de produção científica, os autores e artigos mais citados, os países e instituições mais produtivos, verificando a estrutura de co-citação entre os artigos. Dados relativos às citações foram coletados no site Web of Science presente na base de dados científicos do Institute for Scientific Information [ISI] da Thompson Reuters, considerado como o indicador de impacto científico mais reconhecido no mundo. Os dados foram importados e analisadas em um estudo bibliométrico usando o software HistCite. No total, foram encontrados 19.564 registros. Os resultados indicaram que a produção acadêmica e citações sobre empreendedorismo cresceu consideravelmente nos últimos anos. Os dados indicam que os dez países com artigos mais citados têm 68.586 citações, ou 79,50% do total, mostrando uma grande concentração. Concentrações semelhantes foram encontradas em relação a universidades e os principais periódicos. Outros achados e suas implicações, além de sugestões para futuras pesquisas são apresentadas.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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"March 1970."
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"25 January 1980."
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Remotely sensed imagery has been widely used for land use/cover classification thanks to the periodic data acquisition and the widespread use of digital image processing systems offering a wide range of classification algorithms. The aim of this work was to evaluate some of the most commonly used supervised and unsupervised classification algorithms under different landscape patterns found in Rondônia, including (1) areas of mid-size farms, (2) fish-bone settlements and (3) a gradient of forest and Cerrado (Brazilian savannah). Comparison with a reference map based on the kappa statistics resulted in good to superior indicators (best results - K-means: k=0.68; k=0.77; k=0.64 and MaxVer: k=0.71; k=0.89; k=0.70 respectively for three areas mentioned). Results show that choosing a specific algorithm requires to take into account both its capacity to discriminate among various spectral signatures under different landscape patterns as well as a cost/benefit analysis considering the different steps performed by the operator performing a land cover/use map. it is suggested that a more systematic assessment of several options of implementation of a specific project is needed prior to beginning a land use/cover mapping job.
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The objective of this work was to compare the soybean crop mapping in the western of Parana State by MODIS/Terra and TM/Landsat 5 images. Firstly, it was generated a soybean crop mask using six TM images covering the crop season, which was used as a reference. The images were submitted to Parallelepiped and Maximum Likelihood digital classification algorithms, followed by visual inspection. Four MODIS images, covering the vegetative peak, were classified using the Parallelepiped method. The quality assessment of MODIS and TM classification was carried out through an Error Matrix, considering 100 sample points between soybean or not soybean, randomly allocated in each of the eight municipalities within the study area. The results showed that both the Overall Classification (OC) and the Kappa Index (KI) have produced values ranging from 0.55 to 0.80, considered good to very good performances, either in TM or MODIS images. When OC and KI, from both sensors were compared, it wasn't found no statistical difference between them. The soybean mapping, using MODIS, has produced 70% of reliance in terms of users. The main conclusion is that the mapping of soybean by MODIS is feasible, with the advantage to have better temporal resolution than Landsat, and to be available on the internet, free of charge.
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The objective of this study was to analyze changes in the spectral behavior of the soybean crop through spectral profiles of the vegetation indexes NDVI and GVI, expressed by different physical values such as apparent bi-directional reflectance factor (BRF), surface BRF, and normalized BRF derived from images of the Landsat 5/TM. A soybean area located in Cascavel, Paraná, was monitored by using five images of Landsat 5/TM during the 2004/2005 harvesting season. The images were submitted to radiometric transformation, atmospheric correction and normalization, determining physical values of apparent BRF, surface BRF and normalized BRF. NDVI and GVI images were generated in order to distinguish the soybean biomass spectral response. The treatments showed different results for apparent, surface and normalized BRF. Through the profiles of average NDVI and GVI, it was possible to monitor the entire soybean cycle, characterizing its development. It was also observed that the data from normalized BRF negatively affected the spectral curve of soybean crop, mainly, during the phase of vegetative growth, in the 12-9-2004 image.