滤波反投影算法具有快速实时成像的特点,因此被广泛用于工业和医学超声成像系统中,如何使其在快速实时成像的同时具有较高的清晰度,一直是学术界的研究热点。针对滤波反投影(filtered back projection,FBP)算法重建后图像质量较差的问题...滤波反投影算法具有快速实时成像的特点,因此被广泛用于工业和医学超声成像系统中,如何使其在快速实时成像的同时具有较高的清晰度,一直是学术界的研究热点。针对滤波反投影(filtered back projection,FBP)算法重建后图像质量较差的问题,利用投影中经过Radon变换图像高频信号变少的特点,通过给滤波函数加修正因子的方法对常用于反投影重建算法的斜坡滤波器(ram-lak,R-L)进行改进,通过实验分析验证,改进后的滤波反投影重建算法在不增加运算时间的前提下,提升了重建图像的质量。当修正因子为0.1时,与常用的滤波反投影算法相比,均方误差(MSE)降低了99.0125%,峰值信噪比(PSNR)增加了75.9634%,信噪比(SNR)增加了44.8616%。展开更多
Response surface methodology, according to CCD （central composite design）, was used to determine the optimum processing conditions giving maximum water loss and minimum solid gain during osmotic dehydration of medla...Response surface methodology, according to CCD （central composite design）, was used to determine the optimum processing conditions giving maximum water loss and minimum solid gain during osmotic dehydration of medlars in sucrose solution. The independent variables of osmotic dehydration were temperature （25-65 ℃）, processing time （20-240 min）, sugar concentration （45%-65% w/w） and blanching time （0-180 s）. The optimum conditions were found to be： temperature = 55 ℃, time = 180 min, concentration = 60° Brix and blanching time = 30 s. At this optimum point, water loss, weight reduction and solid gain were found to be 74.12% and 7.136%, respectively.展开更多
In this paper,we propose a method to realize microwave photonic filter(MPF) with complex coefficient,whose central frequency f 0 and 3 dB bandwidth are tunable.The complex coefficient is realized by multi-wavelength o...In this paper,we propose a method to realize microwave photonic filter(MPF) with complex coefficient,whose central frequency f 0 and 3 dB bandwidth are tunable.The complex coefficient is realized by multi-wavelength optical source and stimulated Brillouin scattering(SBS).The central frequency of the filter is tuned by adjusting the phase shift caused by SBS without changing its frequency response.The frequency selectivity of filter can be improved through increasing the bandwidth of broadband optical source(BOS) or decreasing wavelength separation to increase the taps of MPF.The mainlobeto-sidelobe suppression ratio(MSSR) of the filter is affected by the weight of each tap.When the length of fiber is 0.5544 m in birefringence fiber loop mirror(FLM),the MSSR is improved by 18.55 dB compared with that without the weight controlling.展开更多
文摘滤波反投影算法具有快速实时成像的特点,因此被广泛用于工业和医学超声成像系统中,如何使其在快速实时成像的同时具有较高的清晰度,一直是学术界的研究热点。针对滤波反投影(filtered back projection,FBP)算法重建后图像质量较差的问题,利用投影中经过Radon变换图像高频信号变少的特点,通过给滤波函数加修正因子的方法对常用于反投影重建算法的斜坡滤波器(ram-lak,R-L)进行改进,通过实验分析验证,改进后的滤波反投影重建算法在不增加运算时间的前提下,提升了重建图像的质量。当修正因子为0.1时,与常用的滤波反投影算法相比,均方误差(MSE)降低了99.0125%,峰值信噪比(PSNR)增加了75.9634%,信噪比(SNR)增加了44.8616%。
文摘Response surface methodology, according to CCD （central composite design）, was used to determine the optimum processing conditions giving maximum water loss and minimum solid gain during osmotic dehydration of medlars in sucrose solution. The independent variables of osmotic dehydration were temperature （25-65 ℃）, processing time （20-240 min）, sugar concentration （45%-65% w/w） and blanching time （0-180 s）. The optimum conditions were found to be： temperature = 55 ℃, time = 180 min, concentration = 60° Brix and blanching time = 30 s. At this optimum point, water loss, weight reduction and solid gain were found to be 74.12% and 7.136%, respectively.
基金supported by the National Natural Science Foundation of China (No.60808004)
文摘In this paper,we propose a method to realize microwave photonic filter(MPF) with complex coefficient,whose central frequency f 0 and 3 dB bandwidth are tunable.The complex coefficient is realized by multi-wavelength optical source and stimulated Brillouin scattering(SBS).The central frequency of the filter is tuned by adjusting the phase shift caused by SBS without changing its frequency response.The frequency selectivity of filter can be improved through increasing the bandwidth of broadband optical source(BOS) or decreasing wavelength separation to increase the taps of MPF.The mainlobeto-sidelobe suppression ratio(MSSR) of the filter is affected by the weight of each tap.When the length of fiber is 0.5544 m in birefringence fiber loop mirror(FLM),the MSSR is improved by 18.55 dB compared with that without the weight controlling.
