The basic principle of pulsar timing model was introduced, and the general relativistic corrections were analyzed when pulse time of arrival (TOA) was transferred to coordinate TOA at the Solar System Barycentre. Base...The basic principle of pulsar timing model was introduced, and the general relativistic corrections were analyzed when pulse time of arrival (TOA) was transferred to coordinate TOA at the Solar System Barycentre. Based on the shifting, an iterative method of autonomous position determination for spacecraft was developed. Accordingly, the linear form of the position offset equation was evolved. Using the initial estimated value of spacecraft’s position as the input of pulsar timing equation, through calculation of the offset between measured or transferred and predicted TOA, the position offset can be solved by Least Squares. At last, the main error sources including modeling error and parameters error were discussed.展开更多
目的研究定量CT和磁共振成像(MRI)检查在测量腹部脂肪面积及分布的相关性及一致性。方法对44例健康研究对象空腹状态下同一天行腹部定量CT和MRI检查,选取腰椎4/5层面图像,CT图像采用定量CT分析软件QCT PRO v5.0测量,MRI图像采用图像分...目的研究定量CT和磁共振成像(MRI)检查在测量腹部脂肪面积及分布的相关性及一致性。方法对44例健康研究对象空腹状态下同一天行腹部定量CT和MRI检查,选取腰椎4/5层面图像,CT图像采用定量CT分析软件QCT PRO v5.0测量,MRI图像采用图像分析软件Analyze v12.0进行测量,半自动区分该层面腹内脂肪和皮下脂肪并测量其面积。统计分析两者测量结果的相关性和一致性。结果定量CT和MRI对腹部皮下脂肪面积(SFA)、腹内脂肪面积(SFA)、总脂肪面积(TFA)的测量呈明显正相关(r值分别为0.96、0.94、0.96,P<0.05)。Bland-Altman分析显示MRI和定量CT测得的腹部脂肪面积的差值很小(差值均数分别为8.6、-2.8、5.7cm2)。结论定量CT和MRI对腹部脂肪面积的测量结果具有明显相关性和较好的一致性,二者有可比性且在临床应用中可互相代替。展开更多
基金Supported by the National Defence Laboratory Foundation of China (Grant No. 9140C3601010901) Science Foundation of Shaanxi Province (Grant No. 2007F12)+1 种基金the Technology Specialism Foundation of Shaanxi Education Depart-ment of Shaanxi Province (Grant No. 07JK332)the Innovative Research Plan of Xi’an University of Technology (Grant No. 105-210714)
文摘The basic principle of pulsar timing model was introduced, and the general relativistic corrections were analyzed when pulse time of arrival (TOA) was transferred to coordinate TOA at the Solar System Barycentre. Based on the shifting, an iterative method of autonomous position determination for spacecraft was developed. Accordingly, the linear form of the position offset equation was evolved. Using the initial estimated value of spacecraft’s position as the input of pulsar timing equation, through calculation of the offset between measured or transferred and predicted TOA, the position offset can be solved by Least Squares. At last, the main error sources including modeling error and parameters error were discussed.
文摘目的研究定量CT和磁共振成像(MRI)检查在测量腹部脂肪面积及分布的相关性及一致性。方法对44例健康研究对象空腹状态下同一天行腹部定量CT和MRI检查,选取腰椎4/5层面图像,CT图像采用定量CT分析软件QCT PRO v5.0测量,MRI图像采用图像分析软件Analyze v12.0进行测量,半自动区分该层面腹内脂肪和皮下脂肪并测量其面积。统计分析两者测量结果的相关性和一致性。结果定量CT和MRI对腹部皮下脂肪面积(SFA)、腹内脂肪面积(SFA)、总脂肪面积(TFA)的测量呈明显正相关(r值分别为0.96、0.94、0.96,P<0.05)。Bland-Altman分析显示MRI和定量CT测得的腹部脂肪面积的差值很小(差值均数分别为8.6、-2.8、5.7cm2)。结论定量CT和MRI对腹部脂肪面积的测量结果具有明显相关性和较好的一致性,二者有可比性且在临床应用中可互相代替。
