Based mainly on TOGA-COARE data, that is, the CTD data from R/V Xiangyanghong No. 5 (Pu et al., 1993), the temperature and current data from the Woods Hole mooring and other deep current data, the layered numerical pr...Based mainly on TOGA-COARE data, that is, the CTD data from R/V Xiangyanghong No. 5 (Pu et al., 1993), the temperature and current data from the Woods Hole mooring and other deep current data, the layered numerical profiles of buoyancy frequency and mean current components are figured out. A numerical method calculating internal wave dispersion relation without background shear current, used by Fliegel and Hunkins (1975), is improved to be fit for the internal wave equation with mean currents and their second derivatives. The dispersion relations and wave functions of the long crested internal wave progressing in any direction can be calculated conveniently by using the improved method. A comparison between the calculated dispersion relation in the paper and the dispersion relation in GM spectral model of ocean internal waves (Garret and Munk, 1972) is performed. It shows that the mean currents are important to the dispersion relation of internal waves in the western equatorial Pacific Ocean and that the currents make the wave progressing co-directional with (against) the currents stretched (shrink). The influence of the mean currents on dispersion relation is much stronger than that of their second derivatives, but that on wave function is less than that of their second derivatives. The influences on wave functions result in the change of vertical wavenumber, that is, making the wave function stretch or shrink. There exists obvious turning depth but no significant critical layer absorption is found.展开更多
研究高斯光束经螺旋相位板和轴棱锥产生高阶贝塞尔-高斯涡旋光束的离轴传输情况,对于离轴高阶贝塞尔-高斯光束的成因、光强分布操控、光斑定位等实际应用具有一定的理论指导意义.利用菲涅尔衍射积分的卷积算法(Triple fast Fourier tran...研究高斯光束经螺旋相位板和轴棱锥产生高阶贝塞尔-高斯涡旋光束的离轴传输情况,对于离轴高阶贝塞尔-高斯光束的成因、光强分布操控、光斑定位等实际应用具有一定的理论指导意义.利用菲涅尔衍射积分的卷积算法(Triple fast Fourier transform,T-FFT)对离轴高阶贝塞尔-高斯涡旋光束进行仿真分析,着重研究了螺旋相位板和轴棱锥的错位参数、拓扑荷数以及传输距离等参数对光束带来的影响.分析表明:离轴高阶贝塞尔-高斯光束具有不均匀的光强分布,由于轴棱锥的偏移,光束会整体发生偏移,传输不同距离光强不均匀分布情况不同,不同的拓扑荷数只影响光斑的扩展,螺旋相位板和轴棱锥离轴参量值的多种组合会导致多种不同的光强分布情况,甚至出现暗核偏移.展开更多
In this paper, a plate shape perception technique based on quasi-distributed fiber Bragg grating(FBG) array and space surface reconstruction algorithm is proposed. Firstly, in order to make curvature continuous, the b...In this paper, a plate shape perception technique based on quasi-distributed fiber Bragg grating(FBG) array and space surface reconstruction algorithm is proposed. Firstly, in order to make curvature continuous, the bicubic plane interpolation algorithm is studied. Then, taking the simulated satellite bulkhead structure as the research object, we research the space surface reconstruction algorithm based on orthogonal curvature and coordinate transformation(translation and rotation). Finally, a four-sided fixed plate deformation monitoring system based on quasi-distributed FBG sensors network and surface reconstruction algorithm is built. Many experiments are conducted to verify the reliability and accuracy of the algorithm. The proposed algorithm provides a new method for three-dimensional reconstruction of spacecraft structure.展开更多
A visual reconstruction method was proposed based on fiber Bragg grating(FBG)sensors and an intelligent algorithm,aiming to solve the problems of low accuracy and complex reconstruction process in conventional reconst...A visual reconstruction method was proposed based on fiber Bragg grating(FBG)sensors and an intelligent algorithm,aiming to solve the problems of low accuracy and complex reconstruction process in conventional reconstruction methods of flexible structures.Firstly,the wavelength data containing structural strain information was captured by FBG sensors,together with deformation displacement information.Subsequently,a predicted model was built based on an extreme learning machine(ELM)and further optimized by the particle swarm optimization(PSO)algorithm.Different deformation patterns were tested on an aluminum alloy plate,indicating the ability of the predicted model to produce the deformation displacement for reconstruction.The experimental results show that the maximum error can be as low as 0.050 mm,which verifies that the proposed method is feasible and satisfied with the deformation monitoring of the spacecraft structure.展开更多
基金National Natural Science Foundation of China,Project under contract No.49676275,No.49976002 and Research Fund for the Docto
文摘Based mainly on TOGA-COARE data, that is, the CTD data from R/V Xiangyanghong No. 5 (Pu et al., 1993), the temperature and current data from the Woods Hole mooring and other deep current data, the layered numerical profiles of buoyancy frequency and mean current components are figured out. A numerical method calculating internal wave dispersion relation without background shear current, used by Fliegel and Hunkins (1975), is improved to be fit for the internal wave equation with mean currents and their second derivatives. The dispersion relations and wave functions of the long crested internal wave progressing in any direction can be calculated conveniently by using the improved method. A comparison between the calculated dispersion relation in the paper and the dispersion relation in GM spectral model of ocean internal waves (Garret and Munk, 1972) is performed. It shows that the mean currents are important to the dispersion relation of internal waves in the western equatorial Pacific Ocean and that the currents make the wave progressing co-directional with (against) the currents stretched (shrink). The influence of the mean currents on dispersion relation is much stronger than that of their second derivatives, but that on wave function is less than that of their second derivatives. The influences on wave functions result in the change of vertical wavenumber, that is, making the wave function stretch or shrink. There exists obvious turning depth but no significant critical layer absorption is found.
文摘研究高斯光束经螺旋相位板和轴棱锥产生高阶贝塞尔-高斯涡旋光束的离轴传输情况,对于离轴高阶贝塞尔-高斯光束的成因、光强分布操控、光斑定位等实际应用具有一定的理论指导意义.利用菲涅尔衍射积分的卷积算法(Triple fast Fourier transform,T-FFT)对离轴高阶贝塞尔-高斯涡旋光束进行仿真分析,着重研究了螺旋相位板和轴棱锥的错位参数、拓扑荷数以及传输距离等参数对光束带来的影响.分析表明:离轴高阶贝塞尔-高斯光束具有不均匀的光强分布,由于轴棱锥的偏移,光束会整体发生偏移,传输不同距离光强不均匀分布情况不同,不同的拓扑荷数只影响光斑的扩展,螺旋相位板和轴棱锥离轴参量值的多种组合会导致多种不同的光强分布情况,甚至出现暗核偏移.
基金supported by the National Natural Science Foundation of China(Nos.62073193 and 61873333)the Key Research and Development Plan of Shandong Province(Nos.2019TSLH0301 and 2019GHZ004)the Natural Science Foundation of Shandong Province(No.ZR2021MF041)。
文摘In this paper, a plate shape perception technique based on quasi-distributed fiber Bragg grating(FBG) array and space surface reconstruction algorithm is proposed. Firstly, in order to make curvature continuous, the bicubic plane interpolation algorithm is studied. Then, taking the simulated satellite bulkhead structure as the research object, we research the space surface reconstruction algorithm based on orthogonal curvature and coordinate transformation(translation and rotation). Finally, a four-sided fixed plate deformation monitoring system based on quasi-distributed FBG sensors network and surface reconstruction algorithm is built. Many experiments are conducted to verify the reliability and accuracy of the algorithm. The proposed algorithm provides a new method for three-dimensional reconstruction of spacecraft structure.
基金supported by the National Natural Science Foundation of China(Nos.62073193,61903224,61873333 and 61903225)the National Key Research and Development Project(Nos.2018YFE02013 and 2020YFE0204900)+1 种基金the Key Research and Development Plan of Shandong Province(Nos.2019TSLH0301 and 2019GHZ004)the Natural Science Foundation of Shandong Province,China(No.ZR2021MF041)。
文摘A visual reconstruction method was proposed based on fiber Bragg grating(FBG)sensors and an intelligent algorithm,aiming to solve the problems of low accuracy and complex reconstruction process in conventional reconstruction methods of flexible structures.Firstly,the wavelength data containing structural strain information was captured by FBG sensors,together with deformation displacement information.Subsequently,a predicted model was built based on an extreme learning machine(ELM)and further optimized by the particle swarm optimization(PSO)algorithm.Different deformation patterns were tested on an aluminum alloy plate,indicating the ability of the predicted model to produce the deformation displacement for reconstruction.The experimental results show that the maximum error can be as low as 0.050 mm,which verifies that the proposed method is feasible and satisfied with the deformation monitoring of the spacecraft structure.
