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Deforming generalized cylinders without self-intersection by means of a parametric center curve

Computational Visual Media 2018年第4期4卷 305-321页

作者： Ruibin Ma Qingyu Zhao Rui Wang James Damon Julian Rosenman stephen pizer Computer Science University of North Carolina at Chapel Hill Mathematics University of North Carolina at Chapel Hill Radiation Oncology University of North Carolina at Chapel Hill

Large-scale deformations of a tubular object, or generalized cylinder, are often defined by a target shape for its center curve, typically using a parametric target curve. This task is non-trivial for free-form deformations or direct manipulation methods because it is hard to manually control the centerline by adjusting control points. Most skeleton-based methods are no better, again due to the small number of manually adjusted control points. In this paper, we propose a method to deform a generalized cylinder based on its skeleton composed of a centerline and orthogonal cross sections. Although we are not the first to use such a skeleton, we propose a novel skeletonization method that tries to minimize the number of intersections between neighboring cross sections by means of a relative curvature condition to detect intersections. The mesh deformation is first defined geometrically by deforming the centerline and mapping the cross sections. Rotation minimizing frames are used during mapping to control twisting. Secondly, given displacements on the cross sections, the deformation is decomposed into finely subdivided regions. We limit distortion at these vertices by minimizing an elastic thin shell bending energy,in linear time. Our method can handle complicated generalized cylinders such as the human colon.

关键词： generalized cylinder deformation skeleton self-intersection

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McTeague

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作者： Frank Norris edited by Donald pizer.

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Sister Carrie

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作者： Theodore Dreiser edited by Donald pizer.

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The red badge of courage

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作者： edited by Donald pizer Eric Carl Link.

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Water Source Quality in Northern and Central Tanzania: Implications for Rural Communities

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Journal of Environmental Protection 2013年第5期4卷 389-404页

作者： Deborah M. Aller Kamazima M. M. Lwiza Michelle E. pizer Josephine Y. Aller School of Marine and Atmospheric Sciences Stony Brook University Stony Brook USA

Limited water availability coupled with the lack of hygienic and reliable water sources plague rural areas throughout the developing world. Tanzaniahas abundant fresh water sources, yet delivery, disinfection, and conservation outside of large towns is lacking or minimal at best. Here we examine drinking water sources in two climatologically distinct regions in Tanzania. We consider their chemical and microbiological characteristics specifically with respect to the potential for ultraviolet (UV) disinfection treatment. Interviews with local villagers provided information on collection means, frequency, storage, and incidences of water related illnesses. Total suspended solids, iron (Fe) and manganese (Mn) concentrations, total bacterial abundances, presence of fecal coliforms, and evidence of Escherichia coli contamination were measured in 31 water sources. Total suspended solids exceeded 15 mg/L, the limit for effective UV treatment, in more than half the sources. Principal component analysis indicated a positive correlation of bacterial abundances with levels of Fe. Water with elevated levels of Mn was associated with greater incidences of diseases. Levels of both Fe and Mn appeared to be more dependent on water source than on climatic differences with the chemical composition of the source rock and redox conditions of the water source at time of collection likely contributing to measured concentrations. E. coli was detected more frequently in water sources in the drier Kondoa district than in the wetter Arusha region. Water quality and socio-economic conditions within villages were linked to incidences of water-borne diseases. The maximum risk of exposure to diarrhea-causing pathogens, for example was strongly related to household income level. Nonetheless, incidences of diarrhea were reduced by more than 40% when the average monthly household expenses increased from US $10 to $20. Finally, to the best of our knowledge, this is the first study known to derive an

关键词： Tanzania Water-Related Diseases Water Quality UV Disinfection

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