文章提出了一种基于时空相关性的星图降噪方法,用于解决空间探测时星图峰值信噪比(Peak Signal to Noise Ratio,PSNR)低、星点提取难度大的问题。文章首先对真实星图中星点和背景噪声的能量特性进行了分析与建模。然后,基于该模型提出...文章提出了一种基于时空相关性的星图降噪方法,用于解决空间探测时星图峰值信噪比(Peak Signal to Noise Ratio,PSNR)低、星点提取难度大的问题。文章首先对真实星图中星点和背景噪声的能量特性进行了分析与建模。然后,基于该模型提出了一种可行的降噪算法,该算法以时空相关性检测为核心,并利用检测的结果对目标和噪声进行连续多帧定位。进一步利用定位的结果对目标进行匹配和平滑,对背景噪声进行抑制,从而在总体上提高图像的PSNR。最后,基于仿真平台对算法的有效性进行了测试验证。结果表明,该算法能够有效提升星图PSNR,尤其是点目标的PSNR,在一定噪声等级下,可提升1.6d B。降噪之后,在去除噪声的同时,星图的灰度直方图完好保留了高灰度值部分的目标点像素。该算法在相似的运算复杂度下,其降噪效果明显优于绝大多数的现有降噪算法,利于后续提取星图中恒星及点目标,应用于在轨空间探测系统中,具有广阔的应用前景。展开更多
AIM： To investigate the effects of gallbladder stones on motor functions of the gallbladder and the dynamics of bile flow in asymptomatic gallstone disease. METHODS： Quantitative hepatobiliary scintigraphy was perfo...AIM： To investigate the effects of gallbladder stones on motor functions of the gallbladder and the dynamics of bile flow in asymptomatic gallstone disease. METHODS： Quantitative hepatobiliary scintigraphy was performed to detect the parameters of gallbladder motor function [gallbladder ejection fraction （GBEF）, gallbladder visualization time （GBVT）, gallbladder time to peak activity （GBTmax）, gallbladder half emptying time （GBT1/2）, and transit time of bile to duodenum （TTBD）] in 24 patients with asymptomatic cholelithiasis who were diagnosed incidentally during routine abdominal ultrasonographic examination and 20 healthy subjects with normal gallbladder. RESULTS： Even though there was no significant difference in the clinical and laboratory parameters between the patient and control groups, all parameters of gallbladder function except TTBD were found to differ significantly between the two groups. GBEF in the patient group was decreased （P = 0.000） and GBVT, GBT GBT1/2 in the patient group were longer （P = 0.000, P = 0.015, P = 0.001, respectively）.there were not any clinical and laboratory findings, gallbladder filling and emptying could be impaired in patients with gallstone disease.展开更多
文摘文章提出了一种基于时空相关性的星图降噪方法,用于解决空间探测时星图峰值信噪比(Peak Signal to Noise Ratio,PSNR)低、星点提取难度大的问题。文章首先对真实星图中星点和背景噪声的能量特性进行了分析与建模。然后,基于该模型提出了一种可行的降噪算法,该算法以时空相关性检测为核心,并利用检测的结果对目标和噪声进行连续多帧定位。进一步利用定位的结果对目标进行匹配和平滑,对背景噪声进行抑制,从而在总体上提高图像的PSNR。最后,基于仿真平台对算法的有效性进行了测试验证。结果表明,该算法能够有效提升星图PSNR,尤其是点目标的PSNR,在一定噪声等级下,可提升1.6d B。降噪之后,在去除噪声的同时,星图的灰度直方图完好保留了高灰度值部分的目标点像素。该算法在相似的运算复杂度下,其降噪效果明显优于绝大多数的现有降噪算法,利于后续提取星图中恒星及点目标,应用于在轨空间探测系统中,具有广阔的应用前景。
文摘AIM： To investigate the effects of gallbladder stones on motor functions of the gallbladder and the dynamics of bile flow in asymptomatic gallstone disease. METHODS： Quantitative hepatobiliary scintigraphy was performed to detect the parameters of gallbladder motor function [gallbladder ejection fraction （GBEF）, gallbladder visualization time （GBVT）, gallbladder time to peak activity （GBTmax）, gallbladder half emptying time （GBT1/2）, and transit time of bile to duodenum （TTBD）] in 24 patients with asymptomatic cholelithiasis who were diagnosed incidentally during routine abdominal ultrasonographic examination and 20 healthy subjects with normal gallbladder. RESULTS： Even though there was no significant difference in the clinical and laboratory parameters between the patient and control groups, all parameters of gallbladder function except TTBD were found to differ significantly between the two groups. GBEF in the patient group was decreased （P = 0.000） and GBVT, GBT GBT1/2 in the patient group were longer （P = 0.000, P = 0.015, P = 0.001, respectively）.there were not any clinical and laboratory findings, gallbladder filling and emptying could be impaired in patients with gallstone disease.
