本着提高安徽省地面气温资料质量的宗旨,文中采用模糊C均值(Fuzzy C-Means,FCM)聚类法进行地面气温资料的质量控制研究。具体执行过程中,通过FCM将区域内各测温划分为若干气温相似的聚类,定义离群率(空间尺度)和离群速度(时间尺度)识别...本着提高安徽省地面气温资料质量的宗旨,文中采用模糊C均值(Fuzzy C-Means,FCM)聚类法进行地面气温资料的质量控制研究。具体执行过程中,通过FCM将区域内各测温划分为若干气温相似的聚类,定义离群率(空间尺度)和离群速度(时间尺度)识别出气温资料中的离群值。进一步基于专家场模型(Fields of Experts,FoEs)对识别出的气温离群值进行订正,FoEs考虑了邻近站和本站前后时次的气温信息。与传统方法相比,文中算法从整体气温出发,不需要设置气温参考值,FoEs不仅能够订正离群资料,还能对连续缺测资料进行插补。因而文中的方法具有实用性和科学性,较适合计算大样本的气温数据集。展开更多
In order to overcome the disturbance of noise,this paper presented a method to measure two-phase flow velocity using particle swarm optimization algorithm,nonlinear blind source separation and cross correlation method...In order to overcome the disturbance of noise,this paper presented a method to measure two-phase flow velocity using particle swarm optimization algorithm,nonlinear blind source separation and cross correlation method.Because of the nonlinear relationship between the output signals of capacitance sensors and fluid in pipeline,nonlinear blind source separation is applied.In nonlinear blind source separation,the odd polynomials of higher order are used to fit the nonlinear transformation function,and the mutual information of separation signals is used as the evaluation function.Then the parameters of polynomial and linear separation matrix can be estimated by mutual information of separation signals and particle swarm optimization algorithm,thus the source signals can be separated from the mixed signals.The two-phase flow signals with noise which are obtained from upstream and downstream sensors are respectively processed by nonlinear blind source separation method so that the noise can be effectively removed.Therefore,based on these noise-suppressed signals,the distinct curves of cross correlation function and the transit times are obtained,and then the velocities of two-phase flow can be accurately calculated.Finally,the simulation experimental results are given.The results have proved that this method can meet the measurement requirements of two-phase flow velocity.展开更多
Two types of the dual mode-locked fiber lasers for asynchronous absolute distance measurement are investigated, The lasers are linear and ring cavity with repetition rate of 70 MHz and 100 MHz, respectively. The group...Two types of the dual mode-locked fiber lasers for asynchronous absolute distance measurement are investigated, The lasers are linear and ring cavity with repetition rate of 70 MHz and 100 MHz, respectively. The group velocity dispersion is not compensated in the first type of the lasers, while the others are fully done. The timing jitter with the Allan deviation below averaging time of 0.2 s during the distance measurement for around 1 m of both types of lasers were 2.5 ps with 600 nm and 1.6 ps with 200 nm. We concluded that the phase noise resulted from the intra-cavity dispersion is the main contribution for the uncertainty of the ranging in these two types of the lasers.展开更多
文摘本着提高安徽省地面气温资料质量的宗旨,文中采用模糊C均值(Fuzzy C-Means,FCM)聚类法进行地面气温资料的质量控制研究。具体执行过程中,通过FCM将区域内各测温划分为若干气温相似的聚类,定义离群率(空间尺度)和离群速度(时间尺度)识别出气温资料中的离群值。进一步基于专家场模型(Fields of Experts,FoEs)对识别出的气温离群值进行订正,FoEs考虑了邻近站和本站前后时次的气温信息。与传统方法相比,文中算法从整体气温出发,不需要设置气温参考值,FoEs不仅能够订正离群资料,还能对连续缺测资料进行插补。因而文中的方法具有实用性和科学性,较适合计算大样本的气温数据集。
基金Supported by the National Natural Science Foundation of China (50736002,61072005)the Youth Backbone Teacher Project of University,Ministry of Education,China+1 种基金the Scientific Research Foundation of the Department of Science and Technology of Liaoning Province (20102082)the Changjiang Scholars and Innovative Team Development Plan (IRT0952)
文摘In order to overcome the disturbance of noise,this paper presented a method to measure two-phase flow velocity using particle swarm optimization algorithm,nonlinear blind source separation and cross correlation method.Because of the nonlinear relationship between the output signals of capacitance sensors and fluid in pipeline,nonlinear blind source separation is applied.In nonlinear blind source separation,the odd polynomials of higher order are used to fit the nonlinear transformation function,and the mutual information of separation signals is used as the evaluation function.Then the parameters of polynomial and linear separation matrix can be estimated by mutual information of separation signals and particle swarm optimization algorithm,thus the source signals can be separated from the mixed signals.The two-phase flow signals with noise which are obtained from upstream and downstream sensors are respectively processed by nonlinear blind source separation method so that the noise can be effectively removed.Therefore,based on these noise-suppressed signals,the distinct curves of cross correlation function and the transit times are obtained,and then the velocities of two-phase flow can be accurately calculated.Finally,the simulation experimental results are given.The results have proved that this method can meet the measurement requirements of two-phase flow velocity.
文摘Two types of the dual mode-locked fiber lasers for asynchronous absolute distance measurement are investigated, The lasers are linear and ring cavity with repetition rate of 70 MHz and 100 MHz, respectively. The group velocity dispersion is not compensated in the first type of the lasers, while the others are fully done. The timing jitter with the Allan deviation below averaging time of 0.2 s during the distance measurement for around 1 m of both types of lasers were 2.5 ps with 600 nm and 1.6 ps with 200 nm. We concluded that the phase noise resulted from the intra-cavity dispersion is the main contribution for the uncertainty of the ranging in these two types of the lasers.
