针对图像间存在不同形变、光照等情况下配准难度大的问题,基于尺度不变特征变换(SIFT)的配准方法计算量大、无法满足实时性的要求,提出一种基于Oriented FAST and Rotated Brief(ORB)与角点方向夹角约束的快速图像配准方法。首先在两幅...针对图像间存在不同形变、光照等情况下配准难度大的问题,基于尺度不变特征变换(SIFT)的配准方法计算量大、无法满足实时性的要求,提出一种基于Oriented FAST and Rotated Brief(ORB)与角点方向夹角约束的快速图像配准方法。首先在两幅图像中分块提取ORB特征点,采用一种基于双阈值的汉明距离进行特征点匹配,针对随机抽样一致性(RANSAC)算法无法剔除错误匹配的特征点,以角点方向夹角一致性为约束条件,有效剔除误配点;然后再用RANSAC算法计算出最佳变换矩阵,完成图像配准。实验表明,采用具有不同形变、光照等情况下的3组图像,该方法不仅能很好地配准图像,并且3组图像配准的平均时间为80.399 ms,不到SIFT配准方法所需时间的1/20,兼顾了图像配准的有效性和实时性。展开更多
Background:The Global Physical Activity Questionnaire(GPAQ)has been used to measure physical activity(PA)and sedentary time in France,but no study has assessed its psychometric properties.This study aimed to compare t...Background:The Global Physical Activity Questionnaire(GPAQ)has been used to measure physical activity(PA)and sedentary time in France,but no study has assessed its psychometric properties.This study aimed to compare the reliability as well as criterion and concurrent validity of the French version of the GPAQ with the French International Physical Activity Questionnaire long form(IPAQ-LF)and use of an accelerometer in a general adult population.Methods:We included 92 participants(students or staff)from the Medicine Campus at the University of Lorraine,Nancy(north-eastern France).The French GPAQ was completed twice,7 days apart,to study test-retest reliability.The IPAQ-LF was used to assess concurrent validity of the GPAQ,and participants wore an accelerometer(ActiGraph GT3X+)for 7 days to study criterion validity.Reliability as well as concurrent and criterion validity of the GPAQ were tested by the intraclass correlation coefficient(ICC),Spearman correlation coefficient for quantitative variables,and Kappa and Phi coefficients for qualitative variables.Both concurrent and criterion validity of GPAQ were assessed by Bland-Altman plots.Results:The GPAQ showed poor to good reliability(ICC=0.37-0.94;Kappa=0.50-0.62)and concurrent validity(Spearman r=0.41-0.86),but only poor criterion validity(Spearman r=-0.22-0.42).Limits of agreement for the GPAQ and accelerometer were wide,with differences between 286.5 min/week and 601.3 min/week.Conclusion:The French version of the GPAQ provides limited but acceptable reliability and validity for the measurement of PA and sedentary time.It may be used for assessing PA and sedentary time in a French adult population.展开更多
A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to fur...A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.展开更多
文摘针对图像间存在不同形变、光照等情况下配准难度大的问题,基于尺度不变特征变换(SIFT)的配准方法计算量大、无法满足实时性的要求,提出一种基于Oriented FAST and Rotated Brief(ORB)与角点方向夹角约束的快速图像配准方法。首先在两幅图像中分块提取ORB特征点,采用一种基于双阈值的汉明距离进行特征点匹配,针对随机抽样一致性(RANSAC)算法无法剔除错误匹配的特征点,以角点方向夹角一致性为约束条件,有效剔除误配点;然后再用RANSAC算法计算出最佳变换矩阵,完成图像配准。实验表明,采用具有不同形变、光照等情况下的3组图像,该方法不仅能很好地配准图像,并且3组图像配准的平均时间为80.399 ms,不到SIFT配准方法所需时间的1/20,兼顾了图像配准的有效性和实时性。
文摘Background:The Global Physical Activity Questionnaire(GPAQ)has been used to measure physical activity(PA)and sedentary time in France,but no study has assessed its psychometric properties.This study aimed to compare the reliability as well as criterion and concurrent validity of the French version of the GPAQ with the French International Physical Activity Questionnaire long form(IPAQ-LF)and use of an accelerometer in a general adult population.Methods:We included 92 participants(students or staff)from the Medicine Campus at the University of Lorraine,Nancy(north-eastern France).The French GPAQ was completed twice,7 days apart,to study test-retest reliability.The IPAQ-LF was used to assess concurrent validity of the GPAQ,and participants wore an accelerometer(ActiGraph GT3X+)for 7 days to study criterion validity.Reliability as well as concurrent and criterion validity of the GPAQ were tested by the intraclass correlation coefficient(ICC),Spearman correlation coefficient for quantitative variables,and Kappa and Phi coefficients for qualitative variables.Both concurrent and criterion validity of GPAQ were assessed by Bland-Altman plots.Results:The GPAQ showed poor to good reliability(ICC=0.37-0.94;Kappa=0.50-0.62)and concurrent validity(Spearman r=0.41-0.86),but only poor criterion validity(Spearman r=-0.22-0.42).Limits of agreement for the GPAQ and accelerometer were wide,with differences between 286.5 min/week and 601.3 min/week.Conclusion:The French version of the GPAQ provides limited but acceptable reliability and validity for the measurement of PA and sedentary time.It may be used for assessing PA and sedentary time in a French adult population.
基金Project(60873030) supported by the National Natural Science Foundation of China
文摘A new scheduling algorithm called deferrable scheduling with time slice exchange (DS-EXC) was proposed to maintain the temporal validity of real-time data. In DS-EXC, the time slice exchange method was designed to further defer the release time of transaction instances derived by the deferrable scheduling algorithm (DS-FP). In this way, more CPU time would be left for lower priority transactions and other transactions. In order to minimize the scheduling overhead, an off-line scheme was designed. In particular, the schedule for a transaction set is generated off-line until a repeating pattern is found, and then the pattern is used to construct the schedule on-line. The performance of DS-EXC was evaluated by sets of experiments. The results show that DS-EXC outperforms DS-FP in terms of increasing schedulable ratio. It also provides better performance under mixed workloads.
