为了进一步提高自主水下机器人(AUV)纯方位目标跟踪能力,从AUV轨迹优化方面进行了研究.采用基于距离的分段轨迹优化方法:在跟踪目标的初始阶段以定位的位置误差GDOP(geometrical dilution of precision)作为优化对象,以期在定位跟踪的...为了进一步提高自主水下机器人(AUV)纯方位目标跟踪能力,从AUV轨迹优化方面进行了研究.采用基于距离的分段轨迹优化方法:在跟踪目标的初始阶段以定位的位置误差GDOP(geometrical dilution of precision)作为优化对象,以期在定位跟踪的各个时刻能得到最优的定位精度;针对目标运动要素(位置、速度、航向等)估计趋于收敛的情况,提出了一种基于短期预测的轨迹优化方法,AUV根据物理条件限制预测双方短期状态,计算能够反映跟踪态势特征的收益函数,根据收益函数对自身某状态进行评估,估算出自身各个预测状态的综合收益后,选出综合收益最大的那个状态作为短期目标,执行能到达该状态的行为.目标运动要素估计中使用扩展卡尔曼滤波(EKF).最后,将该轨迹优化方法与基于GDOP的轨迹优化进行仿真对比,结果表明该方法能够实现AUV与目标较快汇合.展开更多
In order to realize the aircraft trajectory prediction,a modified interacting multiple model(M-IMM) algorithm is proposed,which is based on the performance analysis of the standard interacting multiple model(IMM) algo...In order to realize the aircraft trajectory prediction,a modified interacting multiple model(M-IMM) algorithm is proposed,which is based on the performance analysis of the standard interacting multiple model(IMM) algorithm.In the proposed M-IMM algorithm,a new likelihood function is defined for the sake of updating flight mode probabilities,in which the influences of interacting to residual's mean error are taken into account and the assumption of likelihood function being a zero mean Gaussian function is discarded.Finally,the proposed M-IMM algorithm is applied to the simulation of the aircraft trajectory prediction,and the comparative studies are conducted to existing algorithms.The simulation results indicate the proposed M-IMM algorithm can predict aircraft trajectory more quickly and accurately.展开更多
Background： The cognitive function of children with either attention deficit hyperactivity disorder （ADHD） or learning disabilities （LDs） is known to be impaired. However, little is known about the cognitive func...Background： The cognitive function of children with either attention deficit hyperactivity disorder （ADHD） or learning disabilities （LDs） is known to be impaired. However, little is known about the cognitive function of children with comorbid ADHD and LD. The present study aimed to explore the cognitive function of children and adolescents with ADH D and learning difficulties in comparison with children with ADHD and healthy controls in different age groups in a large Chinese sample. Methods： Totally, 1043 participants with ADHD and learning difficulties （the ADHD ＋ learning difficulties group）, 870 with pure ADHD （the pure ADHD group）, and 496 healthy controls were recruited. To investigate the difference in cognitive impairment using a developmental approach, all participants were divided into three age groups （6-8, 9-11, and 12-14 years old）. Measurements were the Chinese-Wechsler Intelligence Scale for Children, the Stroop Color-Word Test, the Trail-Making Test, and the Behavior Rating Inventory of Executive Function-Parents （BRIEF）. Multivariate analysis of variance was used. Results： The results showed that after controlling for the effect of ADHD symptoms, the A DHD ＋ learning difficulties group was still significantly worse than the pureADHD group, which was, in turn, worse than the control group on full intelligence quotient （98.66 ± 13.87 vs. 105.17 ± 14.36 vs. 112.93 ± 13.87, P 〈 0.001 ）. The same relationship was also evident for shift function （shifting time of the Trail-Making Test, 122.50 [62.00, 194.25] s vs. 122.00 [73.00, 201.50] s vs. 66.00 [45.00, 108.00] s, P 〈 0.001） and everyday life executive function （BRIEF total score, 145.71 ± 19.35 vs. 138.96± 18.00 vs. 122.71 ± 20.45, P 〈 0.001 ） after controlling for the effect of the severity of ADHD symptoms, intelligence quotient, age, and gender. As for the age groups, the differences among groups became nonsignificant in the 12-14 years old group for inhibition （meaning interference of 展开更多
文摘应用常规观测资料、自动站资料、加密观测降雪资料和GFS 0.5°×0.5°间隔6 h的再分析资料,对2011年11月29日发生在华北南部的暴雪过程进行动力诊断分析。结果表明:该暴雪天气的影响系统为高空槽和地面回流冷锋;水汽轨迹结果显示在暴雪过程中存在三股气流,即东北干冷气流、东南暖湿气流和西南暖湿气流;低层水汽主要来自东海,中层的水汽来自孟加拉湾和南海,暖湿气流在干冷空气之上爬升,在800 h Pa左右形成锋区;冷平流是引起锋生的主要因子,锋生函数各项对锋生的贡献不同,垂直运动作用项对锋生贡献最大。
文摘为了进一步提高自主水下机器人(AUV)纯方位目标跟踪能力,从AUV轨迹优化方面进行了研究.采用基于距离的分段轨迹优化方法:在跟踪目标的初始阶段以定位的位置误差GDOP(geometrical dilution of precision)作为优化对象,以期在定位跟踪的各个时刻能得到最优的定位精度;针对目标运动要素(位置、速度、航向等)估计趋于收敛的情况,提出了一种基于短期预测的轨迹优化方法,AUV根据物理条件限制预测双方短期状态,计算能够反映跟踪态势特征的收益函数,根据收益函数对自身某状态进行评估,估算出自身各个预测状态的综合收益后,选出综合收益最大的那个状态作为短期目标,执行能到达该状态的行为.目标运动要素估计中使用扩展卡尔曼滤波(EKF).最后,将该轨迹优化方法与基于GDOP的轨迹优化进行仿真对比,结果表明该方法能够实现AUV与目标较快汇合.
基金National Natural Science Foundation of China(No.71401072)Natural Science Foundation of Jiangsu Province,China(No.BK20130814)Fundamental Research Funds for the Central Universities,China(No.NS2013064)
文摘In order to realize the aircraft trajectory prediction,a modified interacting multiple model(M-IMM) algorithm is proposed,which is based on the performance analysis of the standard interacting multiple model(IMM) algorithm.In the proposed M-IMM algorithm,a new likelihood function is defined for the sake of updating flight mode probabilities,in which the influences of interacting to residual's mean error are taken into account and the assumption of likelihood function being a zero mean Gaussian function is discarded.Finally,the proposed M-IMM algorithm is applied to the simulation of the aircraft trajectory prediction,and the comparative studies are conducted to existing algorithms.The simulation results indicate the proposed M-IMM algorithm can predict aircraft trajectory more quickly and accurately.
文摘Background： The cognitive function of children with either attention deficit hyperactivity disorder （ADHD） or learning disabilities （LDs） is known to be impaired. However, little is known about the cognitive function of children with comorbid ADHD and LD. The present study aimed to explore the cognitive function of children and adolescents with ADH D and learning difficulties in comparison with children with ADHD and healthy controls in different age groups in a large Chinese sample. Methods： Totally, 1043 participants with ADHD and learning difficulties （the ADHD ＋ learning difficulties group）, 870 with pure ADHD （the pure ADHD group）, and 496 healthy controls were recruited. To investigate the difference in cognitive impairment using a developmental approach, all participants were divided into three age groups （6-8, 9-11, and 12-14 years old）. Measurements were the Chinese-Wechsler Intelligence Scale for Children, the Stroop Color-Word Test, the Trail-Making Test, and the Behavior Rating Inventory of Executive Function-Parents （BRIEF）. Multivariate analysis of variance was used. Results： The results showed that after controlling for the effect of ADHD symptoms, the A DHD ＋ learning difficulties group was still significantly worse than the pureADHD group, which was, in turn, worse than the control group on full intelligence quotient （98.66 ± 13.87 vs. 105.17 ± 14.36 vs. 112.93 ± 13.87, P 〈 0.001 ）. The same relationship was also evident for shift function （shifting time of the Trail-Making Test, 122.50 [62.00, 194.25] s vs. 122.00 [73.00, 201.50] s vs. 66.00 [45.00, 108.00] s, P 〈 0.001） and everyday life executive function （BRIEF total score, 145.71 ± 19.35 vs. 138.96± 18.00 vs. 122.71 ± 20.45, P 〈 0.001 ） after controlling for the effect of the severity of ADHD symptoms, intelligence quotient, age, and gender. As for the age groups, the differences among groups became nonsignificant in the 12-14 years old group for inhibition （meaning interference of
