基于降低设备制造成本或辐射剂量等目的,计算机断层成像(Computer Tomography,CT)中的一个实际需求是以有限的探测器尺寸来获得更大的视野(Field of View,FOV),通过将探测器放置在横向偏移位置可以有效的扩大FOV。然而,常规的重建算法...基于降低设备制造成本或辐射剂量等目的,计算机断层成像(Computer Tomography,CT)中的一个实际需求是以有限的探测器尺寸来获得更大的视野(Field of View,FOV),通过将探测器放置在横向偏移位置可以有效的扩大FOV。然而,常规的重建算法无法精确重建偏置投影数据,针对这一问题,本文提出了一种基于自适应加权增强总变差最小化的偏置重建模型及CP(Chambolle-Pock)求解算法。具体来说,构建自适应加权增强总变差范数作为正则项,其中自适应权重根据局部增强梯度自适应调整权值,进而设计了一种基于自适应加权增强总变差最小化的偏置重建模型(Weighted Adaptive-weight reinforced Total Variation,WAwrTV),并推导出了相应的CP算法。实验结果表明,所提算法能有效的重建偏置投影数据并提高重建精度,且具有良好的抗噪性能。展开更多
The development of metamorphic petrology to metamorphic geology in China has a long history.Ancient basement metamorphic rocks are distributed primarily in the North China Craton,the Yangtze Block and Tarim Craton.The...The development of metamorphic petrology to metamorphic geology in China has a long history.Ancient basement metamorphic rocks are distributed primarily in the North China Craton,the Yangtze Block and Tarim Craton.They are mainly made up of plutonic gneiss and metamorphosed supercrust rock,transformed to granulite facies through Archean Paleoproterozoic.Many of the Paleoproterozoic metamorphic rocks have undergone high-pressure granulite facies metamorphism with a clockwise metamorphic evolution path.The ultrahigh temperature (UHT)granulites from the Late Paleoproterozoic are found in North China Craton.Many high-precision chronological data have allowed preliminary construction of the formation and evolutionary framework of different metamorphic basements.Primarily there are low-temperature and high-pressure blue schist,high-temperature and high-pressure granulite and ultrahigh-pressure (UHP)eclogite facies metamorphic rocks in the Phanerozoic orogenic belt.The discovery of eclogite in the Sulu orogen and a large quantity of coesite in its country rocks show that there was a deep subduction of voluminous continental materials during the collision process between the Yangtze block and the North China Craton in the Early Mesozoic phase.From the studies of,for instance,organic matter vitrinite reflectance,illite crystallinity,illite (muscovite)polytype and illite (muscovite)b dimension,the Late Paleozoic strata in the eastern region of Inner Mongolia and the north-central region of NE China have only experienced diagenesis to an extremely low-grade metamorphism.The discovery of impact-metamorphosed rocks in Xiuyan area of Liaoning province has enriched the type and category of metamorphic rocks in China.The phase equilibrium method has been widely used in the study of metamorphism of middle and high-grade metamorphic rocks.On the basis of existing geologic surveys and monographic study results, different scholars have respectively compiled 1:1500000 Metamorphic Geological Map and Specifications of Qinghai Tibet Plateau and its Adjacent Areas,1:2500000 Metamorphic Tectonic Map of China, and the 1:5000000 Metamorphic Geological Map and Specifications of China,among others repectively, which have systematically summarized the research results of metamorphic petrology and metamorphic geology in China.展开更多
文摘基于降低设备制造成本或辐射剂量等目的,计算机断层成像(Computer Tomography,CT)中的一个实际需求是以有限的探测器尺寸来获得更大的视野(Field of View,FOV),通过将探测器放置在横向偏移位置可以有效的扩大FOV。然而,常规的重建算法无法精确重建偏置投影数据,针对这一问题,本文提出了一种基于自适应加权增强总变差最小化的偏置重建模型及CP(Chambolle-Pock)求解算法。具体来说,构建自适应加权增强总变差范数作为正则项,其中自适应权重根据局部增强梯度自适应调整权值,进而设计了一种基于自适应加权增强总变差最小化的偏置重建模型(Weighted Adaptive-weight reinforced Total Variation,WAwrTV),并推导出了相应的CP算法。实验结果表明,所提算法能有效的重建偏置投影数据并提高重建精度,且具有良好的抗噪性能。
基金the National Natural Science Foundation of China (41203025)the Work Project of the China Geological Survey (1212010811048)the Fundamental Research Fund of the Institute of Geology of the Chinese Academy of Geological Sciences (J1615).
文摘The development of metamorphic petrology to metamorphic geology in China has a long history.Ancient basement metamorphic rocks are distributed primarily in the North China Craton,the Yangtze Block and Tarim Craton.They are mainly made up of plutonic gneiss and metamorphosed supercrust rock,transformed to granulite facies through Archean Paleoproterozoic.Many of the Paleoproterozoic metamorphic rocks have undergone high-pressure granulite facies metamorphism with a clockwise metamorphic evolution path.The ultrahigh temperature (UHT)granulites from the Late Paleoproterozoic are found in North China Craton.Many high-precision chronological data have allowed preliminary construction of the formation and evolutionary framework of different metamorphic basements.Primarily there are low-temperature and high-pressure blue schist,high-temperature and high-pressure granulite and ultrahigh-pressure (UHP)eclogite facies metamorphic rocks in the Phanerozoic orogenic belt.The discovery of eclogite in the Sulu orogen and a large quantity of coesite in its country rocks show that there was a deep subduction of voluminous continental materials during the collision process between the Yangtze block and the North China Craton in the Early Mesozoic phase.From the studies of,for instance,organic matter vitrinite reflectance,illite crystallinity,illite (muscovite)polytype and illite (muscovite)b dimension,the Late Paleozoic strata in the eastern region of Inner Mongolia and the north-central region of NE China have only experienced diagenesis to an extremely low-grade metamorphism.The discovery of impact-metamorphosed rocks in Xiuyan area of Liaoning province has enriched the type and category of metamorphic rocks in China.The phase equilibrium method has been widely used in the study of metamorphism of middle and high-grade metamorphic rocks.On the basis of existing geologic surveys and monographic study results, different scholars have respectively compiled 1:1500000 Metamorphic Geological Map and Specifications of Qinghai Tibet Plateau and its Adjacent Areas,1:2500000 Metamorphic Tectonic Map of China, and the 1:5000000 Metamorphic Geological Map and Specifications of China,among others repectively, which have systematically summarized the research results of metamorphic petrology and metamorphic geology in China.
