20,605 research outputs found

    Target Detection Using Fractal Geometry

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    The concepts and theory of fractal geometry were applied to the problem of segmenting a 256 x 256 pixel image so that manmade objects could be extracted from natural backgrounds. The two most important measurements necessary to extract these manmade objects were fractal dimension and lacunarity. Provision was made to pass the manmade portion to a lookup table for subsequent identification. A computer program was written to construct cloud backgrounds of fractal dimensions which were allowed to vary between 2.2 and 2.8. Images of three model space targets were combined with these backgrounds to provide a data set for testing the validity of the approach. Once the data set was constructed, computer programs were written to extract estimates of the fractal dimension and lacunarity on 4 x 4 pixel subsets of the image. It was shown that for clouds of fractal dimension 2.7 or less, appropriate thresholding on fractal dimension and lacunarity yielded a 64 x 64 edge-detected image with all or most of the cloud background removed. These images were enhanced by an erosion and dilation to provide the final image passed to the lookup table. While the ultimate goal was to pass the final image to a neural network for identification, this work shows the applicability of fractal geometry to the problems of image segmentation, edge detection and separating a target of interest from a natural background

    Traditional vocations and modern professions among Tamil Brahmans in colonial and post-colonial south India

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    Since the nineteenth century, Tamil Brahmans have been very well represented in the educated professions, especially law and administration, medicine, engineering and nowadays, information technology. This is partly a continuation of the Brahmans’ role as literate service people, owing to their traditions of education, learning and literacy, but the range of professions shows that any direct continuity is more apparent than real. Genealogical data are particularly used as evidence about changing patterns of employment, education and migration. Caste traditionalism was not a determining constraint, for Tamil Brahmans were predominant in medicine and engineering as well as law and administration in the colonial period, even though medicine is ritually polluting and engineering resembles low-status artisans’ work. Crucially though, as modern, English-language, credential-based professions that are wellpaid and prestigious, law, medicine and engineering were and are all deemed eminently suitable for Tamil Brahmans, who typically regard their professional success as a sign of their caste superiority in the modern world. In reality, though, it is mainly a product of how their old social and cultural capital and their economic capital in land were transformed as they seized new educational and employment opportunities by flexibly deploying their traditional, inherited skills and advantages

    Supplanting crystallography or supplementing microscopy? A combined approach to the study of an enveloped virus

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    The recent advances in the resolution obtained by single-particle reconstructions from cryo-electron microscopy (cryo-EM) have led to an increase in studies that combine X-ray crystallographic results with those of electron microscopy (EM). Here, such a combination is described in the determination of the structure of an enveloped animal virus, Semliki Forest virus, at 9 Å resolution. The issues of model bias in determination of the structure, the definition of resolution in a single-particle reconstruction, the effect of the correction of the contrast-transfer function on the structure determined and the use of a high-resolution structure of a subunit in the interpretation of the structure of the complex are addressed
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