In this paper, a broadband unidirectional acoustic transmission based on inhomogeneous metamaterial shell with radial piecewise linear sound speed distribution is proposed. Acoustic rays in the case of external and in...In this paper, a broadband unidirectional acoustic transmission based on inhomogeneous metamaterial shell with radial piecewise linear sound speed distribution is proposed. Acoustic rays in the case of external and internal incidences from the shell are deduced by geometric acoustic theory to show the unidirectional acoustic propagation in the polar coordinate system. Numerical full-wave simulations reveal that one way transmission has the intensity-independent unidirectional transmission feature over a wide frequency range. Finally, a scheme for realization of the proposed one way transmission model is designed and simulated by using multilayered materials, suggesting its potential applications in noise control, acoustic rectifiers,wave absorption and related fields.展开更多
The principle, imaging condition and experimental method for obtaining high resolution composition contrast in secondary electron image were described. A new technique of specimen preparation for secondary electron co...The principle, imaging condition and experimental method for obtaining high resolution composition contrast in secondary electron image were described. A new technique of specimen preparation for secondary electron composition contrast observation was introduced and discussed. By using multilayer P+Si1-xGex/pSi heterojunction internal photoemission infrared detector as an example, the applications of secondary electron composition contrast imaging in microstructure studies on heterojunction semiconducting materials and devices were stated. The characteristics of the image were compared with the ordinary transmission electron diffraction contrast image. The prospects of applications of the imaging method in heterojunction semiconductor devices and multilayer materials are also discussed.展开更多
基金supported in part by the National Natural Science Foundation of China (41276040 and 11174240)the Natural Science Foundation of Fujian Province of China (2012J06010)the Fundamental Research Funds for the Central Universities (2011121010)
文摘In this paper, a broadband unidirectional acoustic transmission based on inhomogeneous metamaterial shell with radial piecewise linear sound speed distribution is proposed. Acoustic rays in the case of external and internal incidences from the shell are deduced by geometric acoustic theory to show the unidirectional acoustic propagation in the polar coordinate system. Numerical full-wave simulations reveal that one way transmission has the intensity-independent unidirectional transmission feature over a wide frequency range. Finally, a scheme for realization of the proposed one way transmission model is designed and simulated by using multilayered materials, suggesting its potential applications in noise control, acoustic rectifiers,wave absorption and related fields.
文摘The principle, imaging condition and experimental method for obtaining high resolution composition contrast in secondary electron image were described. A new technique of specimen preparation for secondary electron composition contrast observation was introduced and discussed. By using multilayer P+Si1-xGex/pSi heterojunction internal photoemission infrared detector as an example, the applications of secondary electron composition contrast imaging in microstructure studies on heterojunction semiconducting materials and devices were stated. The characteristics of the image were compared with the ordinary transmission electron diffraction contrast image. The prospects of applications of the imaging method in heterojunction semiconductor devices and multilayer materials are also discussed.
