A novel strategy of probability density function （PDF） shape control is proposed in stochastic systems. The control er is designed whose parameters are optimal y obtained through the improved particle swarm optimiza...A novel strategy of probability density function （PDF） shape control is proposed in stochastic systems. The control er is designed whose parameters are optimal y obtained through the improved particle swarm optimization algorithm. The parameters of the control er are viewed as the space position of a particle in particle swarm optimization algorithm and updated continual y until the control er makes the PDF of the state variable as close as possible to the expected PDF. The proposed PDF shape control technique is compared with the equivalent linearization technique through simulation experiments. The results show the superiority and the effectiveness of the proposed method. The control er is excellent in making the state PDF fol ow the expected PDF and has the very smal error between the state PDF and the expected PDF, solving the control problem of the PDF shape in stochastic systems effectively.展开更多
Traditionally, it is widely accepted that measurement error usually obeys the normal distribution. However, in this paper a new idea is proposed that the error in digitized data which is a major derived data source in...Traditionally, it is widely accepted that measurement error usually obeys the normal distribution. However, in this paper a new idea is proposed that the error in digitized data which is a major derived data source in GIS does not obey the normal distribution but the p-norm distribution with a determinate parameter. Assuming that the error is random and has the same statistical properties, the probability density function of the normal distribution, Laplace distribution and p-norm distribution are derived based on the arithmetic mean axiom, median axiom and p-median axiom, which means that the normal distribution is only one of these distributions but not the least one. Based on this ideal distribution fitness tests such as Skewness and Kurtosis coefficient test, Pearson chi-square chi(2) test and Kolmogorov test for digitized data are conducted. The results show that the error in map digitization obeys the p-norm distribution whose parameter is close to 1.60. A least p-norm estimation and the least square estimation of digitized data are further analyzed, showing that the least p-norm adjustment is better than the least square adjustment for digitized data processing in GIS.展开更多
作为电力系统中的基本量测设备,电子式电压互感器(electronic voltage transformers,EVTs)的测量精度对系统的监控、控制与安全运行至关重要。为此,提出了一种基于混合深度模型和自适应窗宽概率密度估计的互感器测量误差区间预测模型。...作为电力系统中的基本量测设备,电子式电压互感器(electronic voltage transformers,EVTs)的测量精度对系统的监控、控制与安全运行至关重要。为此,提出了一种基于混合深度模型和自适应窗宽概率密度估计的互感器测量误差区间预测模型。首先,通过改进的集合经验模态分解对历史比差特征进行数据前处理。其次,提出了基于数据驱动的双向时序卷积网络、双向门控循环单元和多头注意力机制混合深度学习模型,对分解后的不同模态分量进行预测。此外,引入自适应选择最优窗宽的核密度概率估计方法,拟合预测结果构建不同置信度下的预测区间,并比较不同核函数对于预测区间的影响。通过算例分析,验证了所提模型在提高确定性预测和概率区间预测准确度方面的有效性。展开更多
针对随机激励下振动系统的减振问题,提出了考虑摩擦与非线性阻尼的混联Ⅱ型惯容非线性能量阱(nonlinear energy sink,简称NES),建立了含新型NES主系统的动力学控制方程。首先,采用蒙特卡洛数值方法,研究了非线性刚度对减振性能的影响,...针对随机激励下振动系统的减振问题,提出了考虑摩擦与非线性阻尼的混联Ⅱ型惯容非线性能量阱(nonlinear energy sink,简称NES),建立了含新型NES主系统的动力学控制方程。首先,采用蒙特卡洛数值方法,研究了非线性刚度对减振性能的影响,当非线性刚度比κ_(21)逐渐增大时,主结构和混联Ⅱ型惯容NES的位移概率密度函数出现了双峰变为单峰,以及速度概率密度函数由单峰变为双峰的随机跳跃现象。主结构的位移概率密度函数对非线性刚度κ_(22)的敏感性比κ_(21)更高,κ_(22)最佳取值区间为200~1 000。其次,研究了噪声强度、阻尼比和惯质比对减振性能的影响,当噪声强度小于0.1或惯质比μ在0.1左右时,惯容NES的减振效果较好。虽然线性阻尼比λ_(1)和非线性阻尼比λ_(21)、λ_(22)增大会导致主结构和混联Ⅱ型惯容NES的概率密度函数出现分岔不稳定现象,但增大非线性阻尼比有助于改善惯容NES的减振性能。最后,采用差分进化法对惯容NES的参数进行了优化。本研究可为受随机激励的振动系统减振研究提供技术参考。展开更多
海冰密集度数据是开展全球海洋监测和应对气候变化研究的重要数据源,为了研制出分辨率更高,误差更小的北极海冰密集度融合资料,本文使用了多源海冰密集度资料,以OSTIA(Operational Sea Surface Temperature and Ice Analysis)数据集为...海冰密集度数据是开展全球海洋监测和应对气候变化研究的重要数据源,为了研制出分辨率更高,误差更小的北极海冰密集度融合资料,本文使用了多源海冰密集度资料,以OSTIA(Operational Sea Surface Temperature and Ice Analysis)数据集为融合背景场,采用以下方案开展融合研究。首先,对现有5种海冰资料进行质量控制;其次,以OSI SAF(Ocean and Sea Ice Satellite Application Facility)资料为基准,采用概率密度匹配法订正各资料的系统误差;然后,利用小波分解将各资料分解为低频信息和高频信息,对低频信息和高频信息分别计算融合权重和卡尔曼滤波处理;最后,利用小波重构将各资料进行融合,生成0.05°分辨率的北极逐日海冰密集度融合资料。通过对比国际上广泛认可的OISST(Optimum Interpolation Sea Surface Temperature)、OSTIA海冰密集度资料,验证结果显示:融合资料与OISST、OSTIA海冰密集度资料在北极的空间分布上高度一致,相关系数均超过0.967。相对于前人的研究,本融合资料与OISST的偏差由–1.170%减少到–0.108%,与OSTIA的偏差由0.276%减少到–0.156%;与OISST和OSTIA的均方根误差分别由9.835%减少为8.010%以及由7.427%减少为5.140%。本融合资料的偏差以及均方根误差都得到了显著的提升,具有较高的质量。展开更多
基金supported by the National Natural Science Fundation of China(61273127)the Specialized Research Fund of the Doctoral Program in Higher Education(20106118110009+2 种基金20116118110008)the Scientific Research Plan Projects of Shaanxi Education Department(12JK0524)the Young Teachers Scientific Research Fund of Xi’an University of Posts and Telecommunications(1100434)
文摘A novel strategy of probability density function （PDF） shape control is proposed in stochastic systems. The control er is designed whose parameters are optimal y obtained through the improved particle swarm optimization algorithm. The parameters of the control er are viewed as the space position of a particle in particle swarm optimization algorithm and updated continual y until the control er makes the PDF of the state variable as close as possible to the expected PDF. The proposed PDF shape control technique is compared with the equivalent linearization technique through simulation experiments. The results show the superiority and the effectiveness of the proposed method. The control er is excellent in making the state PDF fol ow the expected PDF and has the very smal error between the state PDF and the expected PDF, solving the control problem of the PDF shape in stochastic systems effectively.
文摘Traditionally, it is widely accepted that measurement error usually obeys the normal distribution. However, in this paper a new idea is proposed that the error in digitized data which is a major derived data source in GIS does not obey the normal distribution but the p-norm distribution with a determinate parameter. Assuming that the error is random and has the same statistical properties, the probability density function of the normal distribution, Laplace distribution and p-norm distribution are derived based on the arithmetic mean axiom, median axiom and p-median axiom, which means that the normal distribution is only one of these distributions but not the least one. Based on this ideal distribution fitness tests such as Skewness and Kurtosis coefficient test, Pearson chi-square chi(2) test and Kolmogorov test for digitized data are conducted. The results show that the error in map digitization obeys the p-norm distribution whose parameter is close to 1.60. A least p-norm estimation and the least square estimation of digitized data are further analyzed, showing that the least p-norm adjustment is better than the least square adjustment for digitized data processing in GIS.
文摘作为电力系统中的基本量测设备,电子式电压互感器(electronic voltage transformers,EVTs)的测量精度对系统的监控、控制与安全运行至关重要。为此,提出了一种基于混合深度模型和自适应窗宽概率密度估计的互感器测量误差区间预测模型。首先,通过改进的集合经验模态分解对历史比差特征进行数据前处理。其次,提出了基于数据驱动的双向时序卷积网络、双向门控循环单元和多头注意力机制混合深度学习模型,对分解后的不同模态分量进行预测。此外,引入自适应选择最优窗宽的核密度概率估计方法,拟合预测结果构建不同置信度下的预测区间,并比较不同核函数对于预测区间的影响。通过算例分析,验证了所提模型在提高确定性预测和概率区间预测准确度方面的有效性。
文摘针对随机激励下振动系统的减振问题,提出了考虑摩擦与非线性阻尼的混联Ⅱ型惯容非线性能量阱(nonlinear energy sink,简称NES),建立了含新型NES主系统的动力学控制方程。首先,采用蒙特卡洛数值方法,研究了非线性刚度对减振性能的影响,当非线性刚度比κ_(21)逐渐增大时,主结构和混联Ⅱ型惯容NES的位移概率密度函数出现了双峰变为单峰,以及速度概率密度函数由单峰变为双峰的随机跳跃现象。主结构的位移概率密度函数对非线性刚度κ_(22)的敏感性比κ_(21)更高,κ_(22)最佳取值区间为200~1 000。其次,研究了噪声强度、阻尼比和惯质比对减振性能的影响,当噪声强度小于0.1或惯质比μ在0.1左右时,惯容NES的减振效果较好。虽然线性阻尼比λ_(1)和非线性阻尼比λ_(21)、λ_(22)增大会导致主结构和混联Ⅱ型惯容NES的概率密度函数出现分岔不稳定现象,但增大非线性阻尼比有助于改善惯容NES的减振性能。最后,采用差分进化法对惯容NES的参数进行了优化。本研究可为受随机激励的振动系统减振研究提供技术参考。
