Coded excitation technology （CET） can effectively enhance the penetration and resolution of ultrasonic testing. To analyze the influence of rock properties on pulse compression performance （PCP） of coded excitatio...Coded excitation technology （CET） can effectively enhance the penetration and resolution of ultrasonic testing. To analyze the influence of rock properties on pulse compression performance （PCP） of coded excitation signals （CES）, a numerical simulation, and an ultrasonic experiment on different rock samples are performed; and the detection ability of several CESs are also investigated and compared. The results of experiments showed that the loss of the signal-to-noise ratio （SNR） of Barker coded signal with tapered linear frequency modulated carrier （BTLFM） is always less than Barker coded signal with sine carrier （BS）, while the resolution loss of BTLFM is lower than tapered linear frequency modulated signal （TLFM）. In sum, the results not only verifiy the effectiveness of CET, but also provide a basis for the parameter settings of coded signals used in rock ultrasonic testing.展开更多
Begonia L.is the sixth biggest genus of flowering plants in the world and a major genus in the family Begoniaceae.It is complicated in current section delimitation and more morphological characters are needed for crit...Begonia L.is the sixth biggest genus of flowering plants in the world and a major genus in the family Begoniaceae.It is complicated in current section delimitation and more morphological characters are needed for critical revaluation within the genus.In present study,we selected 21 species from sections Coelocentrum,Begonia,Platycentrum and Reichenheimia of Begonia mainly distributed in China.Using the method of scanning electron microscopy(SEM),the pollen morphology was carefully examined and its systematic significance was discussed.The results showed that the common palynological characters of studies taxa were exhibited as monads,radially symmetrical,isopolar,3-zono-colporate and perprolate to prolate.For non-metric multidimensional scaling(NMDS)analysis,nine stable pollen characters were selected and coded as unordered and unweighted.The results supported that these sections were not monophyletic groups and the useful palynological features for this study were the pollen sides,outline of the poles,colpus,exine ornamentation,and margo.According to the omamentation of margo,the studied taxa can be divided into two groups:(A)without margo and psilate margo,(B)regulate,exquisitely regulate and coarsely regulate margo.In relation to Group B,the taxa with regulate and exquisitely regulate grains were gathered while the taxa with coarsely regulate margo were located between Group A and B.It indicated that the feature of margo was exhibited as a transition,from without margo and psilate margo,along coarsely regulate margo to exquisitely regulate.Therefore,it is worthy to pay more attention on the feature of margo and increase more taxa of the genus in further studies.展开更多
基金supported by the National Natural Science Foundation of China(41104117)
文摘Coded excitation technology （CET） can effectively enhance the penetration and resolution of ultrasonic testing. To analyze the influence of rock properties on pulse compression performance （PCP） of coded excitation signals （CES）, a numerical simulation, and an ultrasonic experiment on different rock samples are performed; and the detection ability of several CESs are also investigated and compared. The results of experiments showed that the loss of the signal-to-noise ratio （SNR） of Barker coded signal with tapered linear frequency modulated carrier （BTLFM） is always less than Barker coded signal with sine carrier （BS）, while the resolution loss of BTLFM is lower than tapered linear frequency modulated signal （TLFM）. In sum, the results not only verifiy the effectiveness of CET, but also provide a basis for the parameter settings of coded signals used in rock ultrasonic testing.
文摘Begonia L.is the sixth biggest genus of flowering plants in the world and a major genus in the family Begoniaceae.It is complicated in current section delimitation and more morphological characters are needed for critical revaluation within the genus.In present study,we selected 21 species from sections Coelocentrum,Begonia,Platycentrum and Reichenheimia of Begonia mainly distributed in China.Using the method of scanning electron microscopy(SEM),the pollen morphology was carefully examined and its systematic significance was discussed.The results showed that the common palynological characters of studies taxa were exhibited as monads,radially symmetrical,isopolar,3-zono-colporate and perprolate to prolate.For non-metric multidimensional scaling(NMDS)analysis,nine stable pollen characters were selected and coded as unordered and unweighted.The results supported that these sections were not monophyletic groups and the useful palynological features for this study were the pollen sides,outline of the poles,colpus,exine ornamentation,and margo.According to the omamentation of margo,the studied taxa can be divided into two groups:(A)without margo and psilate margo,(B)regulate,exquisitely regulate and coarsely regulate margo.In relation to Group B,the taxa with regulate and exquisitely regulate grains were gathered while the taxa with coarsely regulate margo were located between Group A and B.It indicated that the feature of margo was exhibited as a transition,from without margo and psilate margo,along coarsely regulate margo to exquisitely regulate.Therefore,it is worthy to pay more attention on the feature of margo and increase more taxa of the genus in further studies.
