A novel chiral conjugated polymer with chiral 1,1-binaphthyl and 2,2-bipyridyl units was prepared. The ion responsive properties of the polymer were measured in tetrahydrogenfuran by using absorption, emission spectra...A novel chiral conjugated polymer with chiral 1,1-binaphthyl and 2,2-bipyridyl units was prepared. The ion responsive properties of the polymer were measured in tetrahydrogenfuran by using absorption, emission spectra and optical rotation. The results show that absorption, emission spectra and optical rotation of the polymer solutions have different responses with interactions of different transition metal ions. The mechanism is that different changes of electrical and steric effects of the polymer can cause different changes of the properties of the polymer when interacting with different transition metal ions. The novel chiral polymer could be used for metal ion sensing.展开更多
The wind stress acquired from European Centre for Medium-Range Weather Forecasts （ECMWF）, National Centers for Environmental Prediction （NCEP） climate models and QSCAT satellite observations are analyzed by using ...The wind stress acquired from European Centre for Medium-Range Weather Forecasts （ECMWF）, National Centers for Environmental Prediction （NCEP） climate models and QSCAT satellite observations are analyzed by using frequency-wavenumber spectrum method. The spectrum of two climate models, i.e., ECMWF and NCEP, is similar for both 10 m wind data and model output wind stress data, which indicates that both the climate models capture the key feature of wind stress. While the QSCAT wind stress data shows the similar characteristics with the two climate models in both spectrum domain and the spatial distribution, but with a factor of approximately 1.25 times larger than that of climate models in energy. These differences show the uncertainty in the different wind stress products, which inevitably cause the atmospheric faction torque uncertainties on solid Earth with a 60% departure in annual amplitude, and furtherly affect the precise estimation of the Earth＇s rotation.展开更多
Line-Spectrum noise of counter-rotation propellers has constructed the main part of the radiated noise of high speed vehicles in water. The line-spectrum noise of the counter-rotation propellers is due to the interact...Line-Spectrum noise of counter-rotation propellers has constructed the main part of the radiated noise of high speed vehicles in water. The line-spectrum noise of the counter-rotation propellers is due to the interaction between fore or aft propeller and wake of the vehicle,and the interaction between fore and aft propeller. Based on a combination of the lifting surface theory and acoustic method, the prediction of line-spectrum noise is presented in this paper.Theoretical calculation method, characteristics and numerical prediction of the line-spectrum noise are detailed too. The effect of different wake and different distance between fore and aft propeller on the propeller noise is also studied by numerical method. The agreement of predicted results compared with existing experimental data is quite satisfactory.展开更多
文摘针对大斜视条件下合成孔径雷达(synthetic aperture radar,SAR)地面运动目标成像存在的聚焦困难、几何形变严重、十字旁瓣大等问题,提出一种基于频谱旋转ωk算法的大斜视SAR动目标成像算法。首先,在推导具有精确斜距表达式的斜视动目标回波信号模型的基础上,获得了初步成像结果并提取动目标的感兴趣区域(region of interest,ROI)数据。然后,构造相位补偿函数并利用最小熵算法完成动目标参数估计,再根据估计的参数对ROI数据进行相位补偿,获得聚焦的动目标图像。进一步利用频谱旋转消除了几何形变,利用稀疏增强方法减小了动目标旁瓣,最终得到聚焦、无几何形变、低旁瓣的动目标图像。仿真实验验证了所提算法的有效性。
文摘A novel chiral conjugated polymer with chiral 1,1-binaphthyl and 2,2-bipyridyl units was prepared. The ion responsive properties of the polymer were measured in tetrahydrogenfuran by using absorption, emission spectra and optical rotation. The results show that absorption, emission spectra and optical rotation of the polymer solutions have different responses with interactions of different transition metal ions. The mechanism is that different changes of electrical and steric effects of the polymer can cause different changes of the properties of the polymer when interacting with different transition metal ions. The novel chiral polymer could be used for metal ion sensing.
基金supported by research projects of National Basic Research Program of China (2012CB957802)the National Natural Science Foundation of China (41321063, 41374087)Open Fund of the State Key Laboratory of Geodesy and Earth's Dynamics (2014-2-1-E)
文摘The wind stress acquired from European Centre for Medium-Range Weather Forecasts （ECMWF）, National Centers for Environmental Prediction （NCEP） climate models and QSCAT satellite observations are analyzed by using frequency-wavenumber spectrum method. The spectrum of two climate models, i.e., ECMWF and NCEP, is similar for both 10 m wind data and model output wind stress data, which indicates that both the climate models capture the key feature of wind stress. While the QSCAT wind stress data shows the similar characteristics with the two climate models in both spectrum domain and the spatial distribution, but with a factor of approximately 1.25 times larger than that of climate models in energy. These differences show the uncertainty in the different wind stress products, which inevitably cause the atmospheric faction torque uncertainties on solid Earth with a 60% departure in annual amplitude, and furtherly affect the precise estimation of the Earth＇s rotation.
文摘Line-Spectrum noise of counter-rotation propellers has constructed the main part of the radiated noise of high speed vehicles in water. The line-spectrum noise of the counter-rotation propellers is due to the interaction between fore or aft propeller and wake of the vehicle,and the interaction between fore and aft propeller. Based on a combination of the lifting surface theory and acoustic method, the prediction of line-spectrum noise is presented in this paper.Theoretical calculation method, characteristics and numerical prediction of the line-spectrum noise are detailed too. The effect of different wake and different distance between fore and aft propeller on the propeller noise is also studied by numerical method. The agreement of predicted results compared with existing experimental data is quite satisfactory.
