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
Using China Health and Nutrition Survey(CHNS) data between 1989 and 2011, this paper measures the returns to education in China based on the Mincer earnings function and reaches the following findings through an analy...Using China Health and Nutrition Survey(CHNS) data between 1989 and 2011, this paper measures the returns to education in China based on the Mincer earnings function and reaches the following findings through an analysis of the tendency of continuous variations over a long timeframe: returns to education are on the rise within the range of samples both under relative and absolute scenarios; returns to different levels of education are characterized by increasing marginal return; no significant difference exists between the returns to junior middle school and the returns to primary school education. Further discussions consider that the requirements of job positions for the overall competence of personnel, differentiated decline of corporate demand for recruitment, lack of an evaluation system in the labor market, information asymmetry in the job market, the development strategy adopted in a particular stage of history and the current slow progress of economic transition have jointly led to the underemployment of college graduates and the great enthusiasm of parents investing in higher education for their children. Conclusions of this paper not only have important practical relevance to the ongoing implementation of China's innovation-driven development strategy, but offer inspirations for the new round of educational reform as well.展开更多
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.
文摘Using China Health and Nutrition Survey(CHNS) data between 1989 and 2011, this paper measures the returns to education in China based on the Mincer earnings function and reaches the following findings through an analysis of the tendency of continuous variations over a long timeframe: returns to education are on the rise within the range of samples both under relative and absolute scenarios; returns to different levels of education are characterized by increasing marginal return; no significant difference exists between the returns to junior middle school and the returns to primary school education. Further discussions consider that the requirements of job positions for the overall competence of personnel, differentiated decline of corporate demand for recruitment, lack of an evaluation system in the labor market, information asymmetry in the job market, the development strategy adopted in a particular stage of history and the current slow progress of economic transition have jointly led to the underemployment of college graduates and the great enthusiasm of parents investing in higher education for their children. Conclusions of this paper not only have important practical relevance to the ongoing implementation of China's innovation-driven development strategy, but offer inspirations for the new round of educational reform as well.
