The elastic wave localization in disordered periodic piezoelectric rods with initial stress is studied using the transfer matrix and Lyapunov exponent method. The electric field is approximated as quasi-static. The ef...The elastic wave localization in disordered periodic piezoelectric rods with initial stress is studied using the transfer matrix and Lyapunov exponent method. The electric field is approximated as quasi-static. The effects of the initial stress on the band gap characteristics are investigated. The numerical calculations of localization factors and localization lengths are performed. It can be observed from the results that the band structures can be tuned by exerting the suitable initial stress. For different values of the piezoelectric rod length and the elastic constant, the band structures and the localization phenomena are very different. Larger disorder degree can lead to more obvious localization phenomenon.展开更多
A localization method based on distance function of projected features is presented to solve the accuracy reduction or failure problem due to occlusion and blurring caused by smog, when dealing with vision based local...A localization method based on distance function of projected features is presented to solve the accuracy reduction or failure problem due to occlusion and blurring caused by smog, when dealing with vision based localization for target oil and gas wellhead （OGWH）. Firstly, the target OGWH is modeled as a cylinder with marker, and a vector with redundant parameter is used to describe its pose. Secondly, the explicit mapping relationship between the pose vector with redundant parameter and projected features is derived. Then, a 2D-point-to-feature distance function is proposed, as well as its derivative. Finally, based on this distance function and its derivative, an algorithm is proposed to estimate the pose of target OGWH directly according to the 2D image information, and the validity of the method is verified by both synthetic data and real image experiments. The results show that this method is able to accomplish the localization in the case of occlusion and blurring, and its anti-noise ability is good especially with noise ratio of less than 70%.展开更多
Terahertz （THz） random lazing is studied numerically for two-dimensional disordered media made of ruby grains with a three-level atomic system. A method via the adjustment of the pumping area to control the polariza...Terahertz （THz） random lazing is studied numerically for two-dimensional disordered media made of ruby grains with a three-level atomic system. A method via the adjustment of the pumping area to control the polarization of the THz wave is proposed. Computed results reveal that transverse electric THz lasing modes could occur if pumping is supplied on the whole medium, while transverse magnetic THz lasing modes could occur if pumping is appropriately supplied on a partial area of the medium.展开更多
Transverse localization of the optical Tamm plasmon （OTP） is studied in a metal-distributed Bragg reflector （DBR） structure with a one-dimensional disordered layer embedded at the interface between the metal and t...Transverse localization of the optical Tamm plasmon （OTP） is studied in a metal-distributed Bragg reflector （DBR） structure with a one-dimensional disordered layer embedded at the interface between the metal and the DBR. The embed- ded disordered layer induces multiple scattering and interference of light, forming the light localization in the transverse direction. This together with the formation of Tamm plasmonic modes at the metal-DBR interface （i.e., the confinement of light in the longitudinal direction）, gives birth to the so called transverse-localized Tamm plasmon. It is shown that for both transverse electric （TE） and transverse magnetic （TM） polarized light injection, the excited transverse-localized Tamm plas- mon broadens and splits the dispersion curve due to spatial incoherence in the transverse direction, thus proving the stronger light confinement especially in the TE polarized injection. By adding the gain medium, specific random lasing modes are observed. The proposed study could be an efficient way of trapping and locally enhancing light on a subwavelength scale, which is useful in applications of random lasers, optical sensing, and imaging.展开更多
基金supported by the National Natural Science Foundation of China(Grant Nos.10672017 and 10632020)the China Postdoctoral Science Foundation,Heilongjiang Province Postdoctoral Science Foundation Japan Society for the Promotion of Science(JSPS) to perform research work at Tokyo Institute of Technology,Japan.
文摘The elastic wave localization in disordered periodic piezoelectric rods with initial stress is studied using the transfer matrix and Lyapunov exponent method. The electric field is approximated as quasi-static. The effects of the initial stress on the band gap characteristics are investigated. The numerical calculations of localization factors and localization lengths are performed. It can be observed from the results that the band structures can be tuned by exerting the suitable initial stress. For different values of the piezoelectric rod length and the elastic constant, the band structures and the localization phenomena are very different. Larger disorder degree can lead to more obvious localization phenomenon.
基金supported by National Natural Science Foundation of China(No.61403226)the State Key Laboratory of Tribology of China(No.SKLT09A03)
文摘A localization method based on distance function of projected features is presented to solve the accuracy reduction or failure problem due to occlusion and blurring caused by smog, when dealing with vision based localization for target oil and gas wellhead （OGWH）. Firstly, the target OGWH is modeled as a cylinder with marker, and a vector with redundant parameter is used to describe its pose. Secondly, the explicit mapping relationship between the pose vector with redundant parameter and projected features is derived. Then, a 2D-point-to-feature distance function is proposed, as well as its derivative. Finally, based on this distance function and its derivative, an algorithm is proposed to estimate the pose of target OGWH directly according to the 2D image information, and the validity of the method is verified by both synthetic data and real image experiments. The results show that this method is able to accomplish the localization in the case of occlusion and blurring, and its anti-noise ability is good especially with noise ratio of less than 70%.
基金Project supported by the Fundamental Research Fund for the Central Universities of Ministry of Education of China (Grant No.2010MS041)the National Natural Science Foundation of China (Grant No.60778003)the Science Foundation of China Academy of Engineering Physics NSAF (Grant No.10876010)
文摘Terahertz （THz） random lazing is studied numerically for two-dimensional disordered media made of ruby grains with a three-level atomic system. A method via the adjustment of the pumping area to control the polarization of the THz wave is proposed. Computed results reveal that transverse electric THz lasing modes could occur if pumping is supplied on the whole medium, while transverse magnetic THz lasing modes could occur if pumping is appropriately supplied on a partial area of the medium.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61575040 and 61635005)the 111 Project,China(Grant No.B14039)
文摘Transverse localization of the optical Tamm plasmon （OTP） is studied in a metal-distributed Bragg reflector （DBR） structure with a one-dimensional disordered layer embedded at the interface between the metal and the DBR. The embed- ded disordered layer induces multiple scattering and interference of light, forming the light localization in the transverse direction. This together with the formation of Tamm plasmonic modes at the metal-DBR interface （i.e., the confinement of light in the longitudinal direction）, gives birth to the so called transverse-localized Tamm plasmon. It is shown that for both transverse electric （TE） and transverse magnetic （TM） polarized light injection, the excited transverse-localized Tamm plas- mon broadens and splits the dispersion curve due to spatial incoherence in the transverse direction, thus proving the stronger light confinement especially in the TE polarized injection. By adding the gain medium, specific random lasing modes are observed. The proposed study could be an efficient way of trapping and locally enhancing light on a subwavelength scale, which is useful in applications of random lasers, optical sensing, and imaging.
