Based on the study of single pattern matching, MBF algorithm is proposed by imitating the string searching procedure of human. The algorithm preprocesses the pattern by using the idea of Quick Search algorithm and the...Based on the study of single pattern matching, MBF algorithm is proposed by imitating the string searching procedure of human. The algorithm preprocesses the pattern by using the idea of Quick Search algorithm and the already-matched pattern psefix and suffix information. In searching phase, the algorithm makes use of the!character using frequency and the continue-skip idea. The experiment shows that MBF algorithm is more efficient than other algorithms.展开更多
Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven a...Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven and damped nonlinear Schr?dinger equation indicate that an ultralow coupled pump power is required to excite the primary comb modes through a non-degenerate four-wave-mixing(FWM) process and, when the pump power is boosted, both the comb mode intensities and spectral bandwidths increase. At low pump powers, the field intensity profile exhibits a cosine variation manner with frequency equal to the separation of the two pumps, while a roll Turing pattern is formed resulting from the increased comb mode intensities and spectral bandwidths at high pump powers. Meanwhile, we found that the power difference between the two pump fields can be transferred to the newly generated comb modes, which are located on both sides of the pump modes, through a cascaded FWM process. Experimentally, the dual-pumped OFCs were realized by coupling two self-oscillating pump fields into a microring resonator. The numerically calculated comb spectrum is verified by generating an OFC with 2.0 THz mode spacing over 160 nm bandwidth. In addition, the formation of a roll Turing pattern at high pump powers is inferred from the measured autocorrelation trace of a 10 free spectral range(FSR) OFC. The experimental observations accord well with the numerical predictions. Due to their large and tunable mode spacing, robustness,and flexibility, the proposed dual-pumped OFCs could find potential applications in a wide range of fields,including arbitrary optical waveform generation, high-capacity optical communications, and signal-processing systems.展开更多
A low-frequency multi-mode ultrasonic Lamb wave method suitable for character- izing the thickness, the density and the elastic constants of the ultra-thin transversely isotropic laminate composite is presented. The &...A low-frequency multi-mode ultrasonic Lamb wave method suitable for character- izing the thickness, the density and the elastic constants of the ultra-thin transversely isotropic laminate composite is presented. The 'ultra-thin' here means that the thickness of the plate is much less than the wavelength of the ultrasonic wave so that the echoes from the front and back faces of the plate can't be separated in the time domain. The dispersion equations for the low frequency ultrasonic Lamb waves with the propagation directions parallel and vertical to the fiber direction are derived. In conjunction with the least square algorithm method, the secant algorithm is used to estimate the parameters of the ultra-thin fiber-reinforced composite layer. The evaluation errors and the sensitivity of the method to different paramters of the thin composite are analyzed. The technique has been used to characterize the ultra-thin grass fiber reinforced PES composite with thickness down to ten percents of the ultrasonic wavelength. It is observed that the agreement between the nominal and the estimation values is reasonably good.展开更多
The frequency mismatch caused by material defects and geometric errors during the manufacturing process is a critical factor limiting the performance of micro-shell resonator gyroscope(MSRG).Compared with other MEMS g...The frequency mismatch caused by material defects and geometric errors during the manufacturing process is a critical factor limiting the performance of micro-shell resonator gyroscope(MSRG).Compared with other MEMS gyroscopes,the frequency mismatch of MSRG can fundamentally be reduced by mechanical trimming.However,it is challenged by the precise characterization.Previous studies about the characterization of frequency mismatch are almost based on frequency spectrum analysis and sweeping,which can only meet the requirement of trimming efficiency of over 100 mHz,limited by the signal noise and temperature drift.In this paper,a novel characterization method of frequency mismatch based on the quadrature-control force under the self-precession mode is proposed to meet the requirement of high-precision mechanical trimming.Furthermore,the phase errors which affect the accuracy of characterization is analyzed,and methods for the correction of phase errors are proposed.Based on this characterization method,0.32 mHz frequency mismatch of micro-shell resonator is achieved by mechanical trimming,which is the best-reported performance for mechanical trimming of MEMS gyroscopes so far.More importantly,this novel characterization method can be applied for other kinds of resonators which can be mechanical trimmed.展开更多
文摘Based on the study of single pattern matching, MBF algorithm is proposed by imitating the string searching procedure of human. The algorithm preprocesses the pattern by using the idea of Quick Search algorithm and the already-matched pattern psefix and suffix information. In searching phase, the algorithm makes use of the!character using frequency and the continue-skip idea. The experiment shows that MBF algorithm is more efficient than other algorithms.
基金Strategic Priority Research Program of the Chinese Academy of Sciences(CAS)(XDB 24030600)National Key Research and Development Program of China(2016YFF0200702)+1 种基金National Natural Science Foundation of China(NSFC)(61690222,61308037,61635013)CASSAFEA International Partnership Program for Creative Research Teams
文摘Dual-pumped microring-resonator-based optical frequency combs(OFCs) and their temporal characteristics are numerically investigated and experimentally explored. The calculation results obtained by solving the driven and damped nonlinear Schr?dinger equation indicate that an ultralow coupled pump power is required to excite the primary comb modes through a non-degenerate four-wave-mixing(FWM) process and, when the pump power is boosted, both the comb mode intensities and spectral bandwidths increase. At low pump powers, the field intensity profile exhibits a cosine variation manner with frequency equal to the separation of the two pumps, while a roll Turing pattern is formed resulting from the increased comb mode intensities and spectral bandwidths at high pump powers. Meanwhile, we found that the power difference between the two pump fields can be transferred to the newly generated comb modes, which are located on both sides of the pump modes, through a cascaded FWM process. Experimentally, the dual-pumped OFCs were realized by coupling two self-oscillating pump fields into a microring resonator. The numerically calculated comb spectrum is verified by generating an OFC with 2.0 THz mode spacing over 160 nm bandwidth. In addition, the formation of a roll Turing pattern at high pump powers is inferred from the measured autocorrelation trace of a 10 free spectral range(FSR) OFC. The experimental observations accord well with the numerical predictions. Due to their large and tunable mode spacing, robustness,and flexibility, the proposed dual-pumped OFCs could find potential applications in a wide range of fields,including arbitrary optical waveform generation, high-capacity optical communications, and signal-processing systems.
基金the National Natural Science Foundation of China (No. 69631020) and theOffice of Naval Research of America (00014-93-1-0340).
文摘A low-frequency multi-mode ultrasonic Lamb wave method suitable for character- izing the thickness, the density and the elastic constants of the ultra-thin transversely isotropic laminate composite is presented. The 'ultra-thin' here means that the thickness of the plate is much less than the wavelength of the ultrasonic wave so that the echoes from the front and back faces of the plate can't be separated in the time domain. The dispersion equations for the low frequency ultrasonic Lamb waves with the propagation directions parallel and vertical to the fiber direction are derived. In conjunction with the least square algorithm method, the secant algorithm is used to estimate the parameters of the ultra-thin fiber-reinforced composite layer. The evaluation errors and the sensitivity of the method to different paramters of the thin composite are analyzed. The technique has been used to characterize the ultra-thin grass fiber reinforced PES composite with thickness down to ten percents of the ultrasonic wavelength. It is observed that the agreement between the nominal and the estimation values is reasonably good.
基金supported by the Key Projects of the National Natural Science Foundation of China(51935013,52205613)the Regional Innovative Development Joint Funds of the National Natural Science Foundation of China(U21A20505).
文摘The frequency mismatch caused by material defects and geometric errors during the manufacturing process is a critical factor limiting the performance of micro-shell resonator gyroscope(MSRG).Compared with other MEMS gyroscopes,the frequency mismatch of MSRG can fundamentally be reduced by mechanical trimming.However,it is challenged by the precise characterization.Previous studies about the characterization of frequency mismatch are almost based on frequency spectrum analysis and sweeping,which can only meet the requirement of trimming efficiency of over 100 mHz,limited by the signal noise and temperature drift.In this paper,a novel characterization method of frequency mismatch based on the quadrature-control force under the self-precession mode is proposed to meet the requirement of high-precision mechanical trimming.Furthermore,the phase errors which affect the accuracy of characterization is analyzed,and methods for the correction of phase errors are proposed.Based on this characterization method,0.32 mHz frequency mismatch of micro-shell resonator is achieved by mechanical trimming,which is the best-reported performance for mechanical trimming of MEMS gyroscopes so far.More importantly,this novel characterization method can be applied for other kinds of resonators which can be mechanical trimmed.
