In this paper a local maximum principle for the singular discrete-time linear systemMx(k)=φx(k-1)+Bu(k-1)is investigated.By using this local maximum principle we can discussthe linear-quadratic optimal regulator prob...In this paper a local maximum principle for the singular discrete-time linear systemMx(k)=φx(k-1)+Bu(k-1)is investigated.By using this local maximum principle we can discussthe linear-quadratic optimal regulator problem and the minimum energy problem for singulardiscrete-time linear systems.展开更多
In this paper, we exploit the concept of data fusion in hybrid localization systems by combining different TOA (Time of Arrival) observables coming from different RATs (Radio Access Technology) and characterized by di...In this paper, we exploit the concept of data fusion in hybrid localization systems by combining different TOA (Time of Arrival) observables coming from different RATs (Radio Access Technology) and characterized by different precisions in order to enhance the positioning accuracy. A new Maximum Likelihood estimator is developed to fuse different measured ranges with different variances. In order to evaluate this estimator, Monte Carlo simulations are carried out in a generic environment and Cramer Rao Lower Bounds (CRLB) are investigated. This algorithm shows enhanced positioning accuracy at reasonable noise levels comparing to the typical Weighted Least Square estimator. The CRLB reveals that the choice of the number, and the configuration of Anchor nodes, and the type of RAT may enhance positioning accuracy.展开更多
为提升局部最大同步挤压变换估算瞬时频率的精度,本文结合2阶局部最大同步挤压变换(Second-order Local Maximum Synchrosqueezing Transform,SLMSST)和动态规划(Dynamic Optimization,DO)方法提出一种识别时变结构瞬时频率的新方法。...为提升局部最大同步挤压变换估算瞬时频率的精度,本文结合2阶局部最大同步挤压变换(Second-order Local Maximum Synchrosqueezing Transform,SLMSST)和动态规划(Dynamic Optimization,DO)方法提出一种识别时变结构瞬时频率的新方法。该方法首先通过引入2阶瞬时振幅与相位得到精度更高的2阶瞬时频率估算位置。其次,搜索频率方向上时频系数的局部最大值所对应的2阶瞬时频率位置并根据这些位置对时频系数进行重排,从而得到2阶局部最大同步挤压变换后的瞬时频带。再次,运用动态规划法在限定频带范围内提取瞬时频率曲线。通过一组数值算例和一个时变拉索试验验证了所提新方法的有效性,研究结果表明:相比既有的局部最大同步挤压变换算法,2阶局部最大同步挤压变换和动态规划的联合算法不仅具有较好的精度,而且具有更好的时频聚集性。展开更多
为解决局部最大同步挤压变换算法识别的频率精度不足及频带能量发散的问题,提出一种改进算法并将之命名为改进局部最大同步挤压变换方法(improved local maximum synchrosqueezing transform,ILMSST)。该方法首先对瞬时频率(instantaneo...为解决局部最大同步挤压变换算法识别的频率精度不足及频带能量发散的问题,提出一种改进算法并将之命名为改进局部最大同步挤压变换方法(improved local maximum synchrosqueezing transform,ILMSST)。该方法首先对瞬时频率(instantaneous freguency,IF)位置进行多次迭代,从而获得更高精度的瞬时频率位置。其次,搜索短时傅里叶系数模极大值的位置并上下平移该位置,得到初步估算的频带并将频带外的短时傅里叶系数归零。最后,搜索频率方向上短时傅里叶系数的局部最大值所对应的瞬时频率位置,根据这些位置对时频系数进行重排,进而得到细化的瞬时频带。通过2组数值算例、1个7层钢筋混凝土剪力墙振动台试验和1个时变拉索试验验证了所提新方法的有效性,研究结果表明:相比现有的局部最大同步挤压变换方法,改进算法不仅提高了瞬时频率的估算精度,而且改善了响应信号瞬时频带的时频聚集性。展开更多
局部阴影情况下,光伏阵列输出功率具有多峰值特性,针对最大功率点跟踪(Maximum power point tracking,MPPT)算法在实际应用中存在着收敛速度较慢,效率较低,且容易陷入局部功率极值的问题,将兼顾收敛速度、精度、功率稳定性的快速布谷鸟...局部阴影情况下,光伏阵列输出功率具有多峰值特性,针对最大功率点跟踪(Maximum power point tracking,MPPT)算法在实际应用中存在着收敛速度较慢,效率较低,且容易陷入局部功率极值的问题,将兼顾收敛速度、精度、功率稳定性的快速布谷鸟搜索(Fast cuckoo search,FCS)算法应用于光伏阵列最大功率追踪。FCS算法采用自适应步长和机会因子可避免过早收敛,全局搜索和跳出局部搜索能力强,收敛速度快,算法后期局部开发能力强,功率振荡小,功率输出稳定,最大功率追踪精度高。仿真表明,在静态阴影、动态阴影条件下,FCS算法较灰狼算法(Grey wolf optimizer,GWO)、粒子群算法(Particle swarm optimization,PSO)具有更快地收敛速度和更高的收敛精度,且稳定性好,有效地提升光伏阵列的输出效率。展开更多
A precise prediction of maximum scour depth around bridge foundations under ice covered condition is crucial for their safe design because underestimation may result in bridge failure and over-estimation will lead to ...A precise prediction of maximum scour depth around bridge foundations under ice covered condition is crucial for their safe design because underestimation may result in bridge failure and over-estimation will lead to unnecessary construction costs. Compared to pier scour depth predictions within an open channel, few studies have attempted to predict the extent of pier scour depth under ice-covered condition. The present work examines scour under ice by using a series of clear-water flume experiments employing two adjacent circular bridge piers in a uniform bed were exposed to open channel and both rough and smooth ice covered channels. The measured scour depths were compared to three commonly used bridge scour equations including Gao’s simplified equation, the HEC-18/Jones equation, and the Froehlich Design Equation. The present study has several advantages as it adds to the understanding of the physics of bridge pier scour under ice cover flow condition, it checks the validity and reliability of commonly used bridge pier equations, and it reveals whether they are valid for the case of scour under ice-covered flow conditions. In addition, it explains how accurately an equation developed for scour under open channel flow can predict scour around bridge piers under ice-covered flow condition.展开更多
As the basic work of image stitching and object recognition,image registration played an important part in the image processing field.Much previous work in registration accuracy and realtime performance progressed ver...As the basic work of image stitching and object recognition,image registration played an important part in the image processing field.Much previous work in registration accuracy and realtime performance progressed very slowly,especially in registrating images with line feature.An innovative method for image registration based on lines is proposed,it can effectively improve the accuracy and real-time performance of image registration.The line feature can deal with some registration problems where point feature does not work.Our registration process is divided into two parts.The first part determines the rough registration transformation relation between reference image and test image.Then the similarity degree among different transformation and modified nonmaximum suppression(MNMS)algorithms are obtained,which produce local optimal solution to optimize the rough registration transformation.The final optimal registration relation can be obtained from two registration parts according to the match scores.The experimental results show that the proposed method makes a more accurate registration relation and performs better in real-time situation.展开更多
文摘In this paper a local maximum principle for the singular discrete-time linear systemMx(k)=φx(k-1)+Bu(k-1)is investigated.By using this local maximum principle we can discussthe linear-quadratic optimal regulator problem and the minimum energy problem for singulardiscrete-time linear systems.
文摘In this paper, we exploit the concept of data fusion in hybrid localization systems by combining different TOA (Time of Arrival) observables coming from different RATs (Radio Access Technology) and characterized by different precisions in order to enhance the positioning accuracy. A new Maximum Likelihood estimator is developed to fuse different measured ranges with different variances. In order to evaluate this estimator, Monte Carlo simulations are carried out in a generic environment and Cramer Rao Lower Bounds (CRLB) are investigated. This algorithm shows enhanced positioning accuracy at reasonable noise levels comparing to the typical Weighted Least Square estimator. The CRLB reveals that the choice of the number, and the configuration of Anchor nodes, and the type of RAT may enhance positioning accuracy.
文摘针对传统无监督领域自适应方法扩展到多工况滚动轴承故障诊断场景适用性较弱的问题,提出了一种多源域自适应残差网络(multi-source domain adaptive residual network,MDARN),通过对齐来自多个源域的相关子域,从而提高模型在多工况下的故障诊断性能。首先,利用ResNeXt残差网络从源域和目标域充分提取可迁移特征;然后,引入局部最大平均差异(local maximum mean difference,LMMD)准则,以两个源域的子域为基础对齐目标域中相关子域,减少相关子域间和全局域间的分布差异;最后,利用美国凯斯西储大学轴承数据集和MFS机械综合故障试验台产生的真实的轴承振动数据集,对所提方法进行了试验验证。结果表明,该方法在多工况下的平均故障诊断精度高达99.76%。与现有代表性方法相比,所提方法具有更好的故障诊断效果。
文摘为提升局部最大同步挤压变换估算瞬时频率的精度,本文结合2阶局部最大同步挤压变换(Second-order Local Maximum Synchrosqueezing Transform,SLMSST)和动态规划(Dynamic Optimization,DO)方法提出一种识别时变结构瞬时频率的新方法。该方法首先通过引入2阶瞬时振幅与相位得到精度更高的2阶瞬时频率估算位置。其次,搜索频率方向上时频系数的局部最大值所对应的2阶瞬时频率位置并根据这些位置对时频系数进行重排,从而得到2阶局部最大同步挤压变换后的瞬时频带。再次,运用动态规划法在限定频带范围内提取瞬时频率曲线。通过一组数值算例和一个时变拉索试验验证了所提新方法的有效性,研究结果表明:相比既有的局部最大同步挤压变换算法,2阶局部最大同步挤压变换和动态规划的联合算法不仅具有较好的精度,而且具有更好的时频聚集性。
文摘为解决局部最大同步挤压变换算法识别的频率精度不足及频带能量发散的问题,提出一种改进算法并将之命名为改进局部最大同步挤压变换方法(improved local maximum synchrosqueezing transform,ILMSST)。该方法首先对瞬时频率(instantaneous freguency,IF)位置进行多次迭代,从而获得更高精度的瞬时频率位置。其次,搜索短时傅里叶系数模极大值的位置并上下平移该位置,得到初步估算的频带并将频带外的短时傅里叶系数归零。最后,搜索频率方向上短时傅里叶系数的局部最大值所对应的瞬时频率位置,根据这些位置对时频系数进行重排,进而得到细化的瞬时频带。通过2组数值算例、1个7层钢筋混凝土剪力墙振动台试验和1个时变拉索试验验证了所提新方法的有效性,研究结果表明:相比现有的局部最大同步挤压变换方法,改进算法不仅提高了瞬时频率的估算精度,而且改善了响应信号瞬时频带的时频聚集性。
文摘局部阴影情况下,光伏阵列输出功率具有多峰值特性,针对最大功率点跟踪(Maximum power point tracking,MPPT)算法在实际应用中存在着收敛速度较慢,效率较低,且容易陷入局部功率极值的问题,将兼顾收敛速度、精度、功率稳定性的快速布谷鸟搜索(Fast cuckoo search,FCS)算法应用于光伏阵列最大功率追踪。FCS算法采用自适应步长和机会因子可避免过早收敛,全局搜索和跳出局部搜索能力强,收敛速度快,算法后期局部开发能力强,功率振荡小,功率输出稳定,最大功率追踪精度高。仿真表明,在静态阴影、动态阴影条件下,FCS算法较灰狼算法(Grey wolf optimizer,GWO)、粒子群算法(Particle swarm optimization,PSO)具有更快地收敛速度和更高的收敛精度,且稳定性好,有效地提升光伏阵列的输出效率。
文摘A precise prediction of maximum scour depth around bridge foundations under ice covered condition is crucial for their safe design because underestimation may result in bridge failure and over-estimation will lead to unnecessary construction costs. Compared to pier scour depth predictions within an open channel, few studies have attempted to predict the extent of pier scour depth under ice-covered condition. The present work examines scour under ice by using a series of clear-water flume experiments employing two adjacent circular bridge piers in a uniform bed were exposed to open channel and both rough and smooth ice covered channels. The measured scour depths were compared to three commonly used bridge scour equations including Gao’s simplified equation, the HEC-18/Jones equation, and the Froehlich Design Equation. The present study has several advantages as it adds to the understanding of the physics of bridge pier scour under ice cover flow condition, it checks the validity and reliability of commonly used bridge pier equations, and it reveals whether they are valid for the case of scour under ice-covered flow conditions. In addition, it explains how accurately an equation developed for scour under open channel flow can predict scour around bridge piers under ice-covered flow condition.
文摘As the basic work of image stitching and object recognition,image registration played an important part in the image processing field.Much previous work in registration accuracy and realtime performance progressed very slowly,especially in registrating images with line feature.An innovative method for image registration based on lines is proposed,it can effectively improve the accuracy and real-time performance of image registration.The line feature can deal with some registration problems where point feature does not work.Our registration process is divided into two parts.The first part determines the rough registration transformation relation between reference image and test image.Then the similarity degree among different transformation and modified nonmaximum suppression(MNMS)algorithms are obtained,which produce local optimal solution to optimize the rough registration transformation.The final optimal registration relation can be obtained from two registration parts according to the match scores.The experimental results show that the proposed method makes a more accurate registration relation and performs better in real-time situation.