Based on Fermat’s principle, two-point ray tracing method was studied in three-dimensional structure. By means of first order Taylor’s incomplete series expansion (i.e. no expansion to the length of the ray), a symm...Based on Fermat’s principle, two-point ray tracing method was studied in three-dimensional structure. By means of first order Taylor’s incomplete series expansion (i.e. no expansion to the length of the ray), a symmetry block tridiagonal matrix equation set was deduced. Further, the positive definiteness of coefficient matrix was discussed, and the positive definiteness was accurately proved in a mathematical way. It assured that the algorithm was well-posed. Associated with iterative method, the solution to ray tracing can be got through step-by-step linearized iteration of the nonlinear problem. An algorithm of the whole path iterative ray tracing method in three-dimensional velocity structure was obtained. This method shows a clear and simple as well as explicit computation formula, which makes ray tracing computation easily applicable in practice. The correction vector is obtained through finding the solution to the positive definite block tridiagonal equation set, which ensures the method is robust convergence. This study offers a new kind of feasible and efficient ray tracing method for three dimensional seismic migration and tomography. Meanwhile, it also provides the prerequisite guarantee to design a fast algorithm.展开更多
【目的】果蝇是完全变态昆虫,蛹期经历了幼虫组织解离和成虫组织重塑的过程。本研究旨在利用细胞谱系追踪方法 G-TRACE(Gal4 technique for real-time and clonal expression)这一新的遗传学技术,检测果蝇幼虫后肠肠细胞在蛹期发育过程...【目的】果蝇是完全变态昆虫,蛹期经历了幼虫组织解离和成虫组织重塑的过程。本研究旨在利用细胞谱系追踪方法 G-TRACE(Gal4 technique for real-time and clonal expression)这一新的遗传学技术,检测果蝇幼虫后肠肠细胞在蛹期发育过程中是否发生细胞迁移。【方法】采用黑腹果蝇Drosophila melanogaster engrailed-Gal4(en-Gal4)品系和G-TRACE品系杂交,并引入tub-gal80ts控制Gal4的开启时间,分别在果蝇幼虫期和蛹期进行细胞谱系追踪。幼虫期追踪:亲代产卵后将卵置于30℃培养,3龄中期转入18℃培养,成虫羽化1 d内进行检测。蛹期追踪:亲代产卵后将卵置于18℃培养,在蛹期不同发育阶段转入30℃培养,待虫体羽化后检测成虫肠道。【结果】当在果蝇幼虫期启动细胞谱系追踪,在蛹期停止追踪,发现中肠靠近中后肠边界处以及马氏管存在绿色肠细胞。而当在果蝇幼虫期关闭细胞谱系追踪,在蛹期开始追踪,则发现虫体中肠各部位及马氏管分布着绿色肠细胞。en基因在果蝇蛹期肠道中表达。【结论】结果表明,在果蝇蛹形成过程中,后肠的部分肠细胞迁移至中肠和马氏管,参与中肠和马氏管的重塑。本研究对于探索昆虫在变态发育过程中成虫器官的重塑机制具有重要的意义。展开更多
炮检距向量片(offset vector tile,OVT)是一种新颖的叠前数据编排方式,当地震数据分选到OVT域后,地震资料的各种属性特征表现得更加明显,充分利用这些特征,可以改善噪声压制、振幅均衡、数据规则化等各种处理过程的效果。OVT道集偏移后...炮检距向量片(offset vector tile,OVT)是一种新颖的叠前数据编排方式,当地震数据分选到OVT域后,地震资料的各种属性特征表现得更加明显,充分利用这些特征,可以改善噪声压制、振幅均衡、数据规则化等各种处理过程的效果。OVT道集偏移后的CRP道集(CRP gather after OVT migration,OVG)含有方位各向异性信息,同相轴随观测方位的变化而明显起伏,典型表现形式是"蜗牛道",可以用于方位各向异性研究。采用非刚性匹配(non-rigid matching,NRM)技术能有效校平"蜗牛道",改善成像效果,提高AVO分析精度。实际的宽方位资料处理结果表明,经过OVT域预处理和道集校平,其处理成果可以分析振幅随倾角和方位角的变化(amplitude versus angle and azimuth,AVAZ),进行分方位裂缝预测。OVT域处理是宽方位三维地震资料的一种有效的处理方法。展开更多
基金Project(40674071) supported by the National Natural Science Foundation of Chinaproject(KFAS2002-2003) supported by Korea Foundation for Advanced Studies
文摘Based on Fermat’s principle, two-point ray tracing method was studied in three-dimensional structure. By means of first order Taylor’s incomplete series expansion (i.e. no expansion to the length of the ray), a symmetry block tridiagonal matrix equation set was deduced. Further, the positive definiteness of coefficient matrix was discussed, and the positive definiteness was accurately proved in a mathematical way. It assured that the algorithm was well-posed. Associated with iterative method, the solution to ray tracing can be got through step-by-step linearized iteration of the nonlinear problem. An algorithm of the whole path iterative ray tracing method in three-dimensional velocity structure was obtained. This method shows a clear and simple as well as explicit computation formula, which makes ray tracing computation easily applicable in practice. The correction vector is obtained through finding the solution to the positive definite block tridiagonal equation set, which ensures the method is robust convergence. This study offers a new kind of feasible and efficient ray tracing method for three dimensional seismic migration and tomography. Meanwhile, it also provides the prerequisite guarantee to design a fast algorithm.
文摘炮检距向量片(offset vector tile,OVT)是一种新颖的叠前数据编排方式,当地震数据分选到OVT域后,地震资料的各种属性特征表现得更加明显,充分利用这些特征,可以改善噪声压制、振幅均衡、数据规则化等各种处理过程的效果。OVT道集偏移后的CRP道集(CRP gather after OVT migration,OVG)含有方位各向异性信息,同相轴随观测方位的变化而明显起伏,典型表现形式是"蜗牛道",可以用于方位各向异性研究。采用非刚性匹配(non-rigid matching,NRM)技术能有效校平"蜗牛道",改善成像效果,提高AVO分析精度。实际的宽方位资料处理结果表明,经过OVT域预处理和道集校平,其处理成果可以分析振幅随倾角和方位角的变化(amplitude versus angle and azimuth,AVAZ),进行分方位裂缝预测。OVT域处理是宽方位三维地震资料的一种有效的处理方法。
