A novel robot navigation algorithm with global path generation capability is presented. Local minimum is a most intractable but is an encountered frequently problem in potential field based robot navigation.Through ap...A novel robot navigation algorithm with global path generation capability is presented. Local minimum is a most intractable but is an encountered frequently problem in potential field based robot navigation.Through appointing appropriately some virtual local targets on the journey, it can be solved effectively. The key concept employed in this algorithm are the rules that govern when and how to appoint these virtual local targets. When the robot finds itself in danger of local minimum, a virtual local target is appointed to replace the global goal temporarily according to the rules. After the virtual target is reached, the robot continues on its journey by heading towards the global goal. The algorithm prevents the robot from running into local minima anymore. Simulation results showed that it is very effective in complex obstacle environments.展开更多
To improve localization accuracy, the spherical microphone arrays are used to capture high-order wavefield in- formation. For the far field sound sources, the array signal model is constructed based on plane wave deco...To improve localization accuracy, the spherical microphone arrays are used to capture high-order wavefield in- formation. For the far field sound sources, the array signal model is constructed based on plane wave decomposition. The spatial spectrum function is calculated by minimum variance distortionless response （MVDR） to scan the three-dimensional space. The peak values of the spectrum function correspond to the directions of multiple sound sources. A diagonal loading method is adopted to solve the ill-conditioned cross spectrum matrix of the received signals. The loading level depends on the alleviation of the ill-condition of the matrix and the accuracy of the inverse calculation. Compared with plane wave decomposition method, our proposed localization algorithm can acquire high spatial resolution and better estimation for multiple sound source directions, especially in low signal to noise ratio （SNR）.展开更多
In distributed cloud storage systems, inevitably there exist multiple node failures at the same time. The existing methods of regenerating codes, including minimum storage regenerating(MSR) codes and minimum bandwidth...In distributed cloud storage systems, inevitably there exist multiple node failures at the same time. The existing methods of regenerating codes, including minimum storage regenerating(MSR) codes and minimum bandwidth regenerating(MBR) codes, are mainly to repair one single or several failed nodes, unable to meet the repair need of distributed cloud storage systems. In this paper, we present locally minimum storage regenerating(LMSR) codes to recover multiple failed nodes at the same time. Specifically, the nodes in distributed cloud storage systems are divided into multiple local groups, and in each local group(4, 2) or(5, 3) MSR codes are constructed. Moreover, the grouping method of storage nodes and the repairing process of failed nodes in local groups are studied. Theoretical analysis shows that LMSR codes can achieve the same storage overhead as MSR codes. Furthermore, we verify by means of simulation that, compared with MSR codes, LMSR codes can reduce the repair bandwidth and disk I/O overhead effectively.展开更多
The scalability of routing architectures for large networks is one of the biggest challenges that the Internet faces today.Greedy routing,in which each node is assigned a locator used as a distance metric,recently rec...The scalability of routing architectures for large networks is one of the biggest challenges that the Internet faces today.Greedy routing,in which each node is assigned a locator used as a distance metric,recently received increased attention from researchers and is considered as a potential solution for scalable routing.In this paper,LMD—a local minimum driven method is proposed to compute the topology-based locator.To eliminate the negative effect of the " quasi" greedy property—transfer routes longer than the shortest routes,a two-stage routing strategy is introduced,which combines the greedy routing with source routing.The greedy routing path discovered and compressed in the first stage is then used by the following source-routing stage.Through extensive evaluations,based on synthetic topologies as well as on a snapshot of the real Internet AS(autonomous system)topology,it is shown that LMD guarantees 100%delivery rate on large networks with low stretch.展开更多
The characterization of friction in control systems and its restraint by localization method are analyzed. The minimum velocity and position precision of control systems with friction are obtained analytically. The co...The characterization of friction in control systems and its restraint by localization method are analyzed. The minimum velocity and position precision of control systems with friction are obtained analytically. The condition of global stability is given.展开更多
Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked t...Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked to equatorial plasma bubbles(EPBs),regions of depleted plasma density that form after sunset.Ionospheric scintillation typically occurs from post-sunset hours until midnight.Post-sunset EPBs can be enhanced or suppressed during geomagnetic storms,depending on local sunset timing and how it relates to the storm's main or recovery phases.This study analyzes ionospheric scintillation in Indonesia,located at low geomagnetic and geographic latitudes,during geomagnetic events from 2003 to 2024.Using the S4 index,scintillation was examined with data from seven observation stations during geomagnetic storm events.Geomagnetic activity was evaluated using Dst,SYM-H,and AE indices,employing Superposed Epoch Analysis(SEA)to assess scintillation occurrence linked to minimum SYM-H,defined as epoch 0 to represent the storm peak or the onset of recovery phase in each event.The analysis categorized geomagnetic storms into weak-moderate(–100 nT<min.Dst≤–30 nT)and strong(min.Dst≤–100 nT),and examined their dependence on the local time of minimum SYM-H.Results indicate that scintillation first appears~6 hours after epoch 0 in weak-moderate geomagnetic storms,and~12 hours after epoch 0 in strong geomagnetic storms.The average AE index returns to its baseline value(quiet condition)~6 and~12 hours after epoch 0 for weak-moderate and strong geomagnetic storms,respectively.Further analysis based on the classification of the local time of epoch 0 shows that scintillation occurrence is not observed in post-sunset hours when epoch 0 falls between 16:00 and 19:00 LT for weak-moderate geomagnetic storms.In strong geomagnetic storms,scintillation occurrence during post-sunset hours is absent when epoch 0 is between 10:00 and 19:00 LT.Notably,when the minimum SYM-H(epoch 0)nearly coincides with local sunset,scintillation activity occurs around sunset in both weak-moderate and strong geomagnetic storms.Furthermore,when epoch 0 falls within midnight until early morning,scintillation can be generated in the post-sunset hours before epoch 0.Still,post-midnight scintillation is not observed in the equatorial region during the recovery phase of either weak-moderate and strong storm events.Our findings show that when sunset falls before or coincide with epoch 0,the likelihood of post-sunset EPB and scintillation increases,due to the prompt-penetration electric field(PPEF)in the main phase of storm.The disturbance dynamo electric field(DDEF)in the recovery phase driven by equatorward winds from auroral Joule heating operates for at least 6-and 12-hours post-epoch 0 in the cases of weak-moderate and strong geomagnetic storms,respectively.When the local sunset falls within these operational DDEF periods,post-sunset EPBs will likely be suppressed,inhibiting ionospheric scintillation during post-sunset hours.Finally,this study provides essential information for developing more accurate ionospheric scintillation prediction models in space weather services in equatorial regions.展开更多
MEMS(Micro-Electro-Mechanical-System)陀螺仪是一种小型化的惯性传感器,广泛应用于导航、导弹制导、自动驾驶、虚拟现实和无人机等领域。然而MEMS陀螺仪常受到来自环境和硬件本身噪声的影响,降低了其性能,限制了MEMS陀螺仪在高精度场...MEMS(Micro-Electro-Mechanical-System)陀螺仪是一种小型化的惯性传感器,广泛应用于导航、导弹制导、自动驾驶、虚拟现实和无人机等领域。然而MEMS陀螺仪常受到来自环境和硬件本身噪声的影响,降低了其性能,限制了MEMS陀螺仪在高精度场合的应用。因此,信号去噪成为提高MEMS陀螺仪精度的重要手段之一。论文提出一种基于局部均值分解(LMD)和自适应最小均方误差(least mean squares,LMS)滤波算法。首先,使用局部均值分解对MEMS陀螺仪输出信号进行分解,然后应用多尺度排列熵将PF分量归类为混合分量和有用分量;再通过LMS对混合分量进行去噪,将MEMS陀螺仪的输出信号进行重建。并进行实验验证所提出的算法,实验结果表明,噪声均值、噪声方差有明显提升。展开更多
文摘A novel robot navigation algorithm with global path generation capability is presented. Local minimum is a most intractable but is an encountered frequently problem in potential field based robot navigation.Through appointing appropriately some virtual local targets on the journey, it can be solved effectively. The key concept employed in this algorithm are the rules that govern when and how to appoint these virtual local targets. When the robot finds itself in danger of local minimum, a virtual local target is appointed to replace the global goal temporarily according to the rules. After the virtual target is reached, the robot continues on its journey by heading towards the global goal. The algorithm prevents the robot from running into local minima anymore. Simulation results showed that it is very effective in complex obstacle environments.
基金Project supported by the National Natural Science Foundation of China (Grant No.61001160)the Doctoral Foundation of Ministry of Education (Grant No.20093108120018)the Shanghai Leading Academic Discipline Project (Grant No.S30108)
文摘To improve localization accuracy, the spherical microphone arrays are used to capture high-order wavefield in- formation. For the far field sound sources, the array signal model is constructed based on plane wave decomposition. The spatial spectrum function is calculated by minimum variance distortionless response （MVDR） to scan the three-dimensional space. The peak values of the spectrum function correspond to the directions of multiple sound sources. A diagonal loading method is adopted to solve the ill-conditioned cross spectrum matrix of the received signals. The loading level depends on the alleviation of the ill-condition of the matrix and the accuracy of the inverse calculation. Compared with plane wave decomposition method, our proposed localization algorithm can acquire high spatial resolution and better estimation for multiple sound source directions, especially in low signal to noise ratio （SNR）.
基金supported in part by the National Natural Science Foundation of China (61640006, 61572188)the Natural Science Foundation of Shaanxi Province, China (2015JM6307, 2016JQ6011)the project of science and technology of Xi’an City (2017088CG/RC051(CADX002))
文摘In distributed cloud storage systems, inevitably there exist multiple node failures at the same time. The existing methods of regenerating codes, including minimum storage regenerating(MSR) codes and minimum bandwidth regenerating(MBR) codes, are mainly to repair one single or several failed nodes, unable to meet the repair need of distributed cloud storage systems. In this paper, we present locally minimum storage regenerating(LMSR) codes to recover multiple failed nodes at the same time. Specifically, the nodes in distributed cloud storage systems are divided into multiple local groups, and in each local group(4, 2) or(5, 3) MSR codes are constructed. Moreover, the grouping method of storage nodes and the repairing process of failed nodes in local groups are studied. Theoretical analysis shows that LMSR codes can achieve the same storage overhead as MSR codes. Furthermore, we verify by means of simulation that, compared with MSR codes, LMSR codes can reduce the repair bandwidth and disk I/O overhead effectively.
基金Supported by the National High Technology Research and Development Program of China(No.2013AA013501)the National Program on Key Basic Research Project(No.2012CB315801)+1 种基金the National Natural Science Foundation of China(No.61133015)the Science and Technology on Information Transmission and Dissemination in Communication Networks Laboratory,CETC54
文摘The scalability of routing architectures for large networks is one of the biggest challenges that the Internet faces today.Greedy routing,in which each node is assigned a locator used as a distance metric,recently received increased attention from researchers and is considered as a potential solution for scalable routing.In this paper,LMD—a local minimum driven method is proposed to compute the topology-based locator.To eliminate the negative effect of the " quasi" greedy property—transfer routes longer than the shortest routes,a two-stage routing strategy is introduced,which combines the greedy routing with source routing.The greedy routing path discovered and compressed in the first stage is then used by the following source-routing stage.Through extensive evaluations,based on synthetic topologies as well as on a snapshot of the real Internet AS(autonomous system)topology,it is shown that LMD guarantees 100%delivery rate on large networks with low stretch.
文摘The characterization of friction in control systems and its restraint by localization method are analyzed. The minimum velocity and position precision of control systems with friction are obtained analytically. The condition of global stability is given.
文摘最小负载着色问题(minimum load coloring problem,MLCP)源于构建光通信网络的波分复用(wavelength division multiplexing,WDM)技术,是一个被证明的NP完全问题.由于NP完全问题有着随问题规模呈指数增长的解空间,因此启发式算法常被用来解决这类问题.在对国内外相关工作的深入分析基础上得知,现有的多类求解MLCP问题的启发式算法中局部搜索算法表现是最好的.研究针对当前求解MLCP问题的局部搜索算法在数据预处理和邻域空间搜索上的不足,提出了两点相应的优化策略:一是在数据的预处理阶段,提出一度顶点规则来约简数据的规模,进而减小MLCP问题的搜索空间;二是在算法的邻域空间搜索阶段,提出两阶段多重选择策略(twostage best from multiple selections,TSBMS)来帮助局部搜索算法在面对不同规模的邻域空间时可以高效地选择一个高质量的邻居解,它有效地提高了局部搜索算法在处理不同规模数据时的求解表现.将这个优化后的局部搜索算法命名为IRLTS.采用74个经典的测试用例来验证IRLTS算法的有效性.实验结果表明,无论最优解还是平均解,IRLTS算法在大多数测试用例上都明显优于当前表现最好的3个局部搜索算法.此外,还通过实验验证了所提策略的有效性以及分析了关键参数对算法的影响.
基金supported by the National Research and Innovation Agency(BRIN),Indonesia.
文摘Ionospheric scintillation refers to rapid radio signal amplitude and phase fluctuations due to small-scale irregularities in the ionosphere.Occurring primarily at equatorial and low latitudes,scintillation is linked to equatorial plasma bubbles(EPBs),regions of depleted plasma density that form after sunset.Ionospheric scintillation typically occurs from post-sunset hours until midnight.Post-sunset EPBs can be enhanced or suppressed during geomagnetic storms,depending on local sunset timing and how it relates to the storm's main or recovery phases.This study analyzes ionospheric scintillation in Indonesia,located at low geomagnetic and geographic latitudes,during geomagnetic events from 2003 to 2024.Using the S4 index,scintillation was examined with data from seven observation stations during geomagnetic storm events.Geomagnetic activity was evaluated using Dst,SYM-H,and AE indices,employing Superposed Epoch Analysis(SEA)to assess scintillation occurrence linked to minimum SYM-H,defined as epoch 0 to represent the storm peak or the onset of recovery phase in each event.The analysis categorized geomagnetic storms into weak-moderate(–100 nT<min.Dst≤–30 nT)and strong(min.Dst≤–100 nT),and examined their dependence on the local time of minimum SYM-H.Results indicate that scintillation first appears~6 hours after epoch 0 in weak-moderate geomagnetic storms,and~12 hours after epoch 0 in strong geomagnetic storms.The average AE index returns to its baseline value(quiet condition)~6 and~12 hours after epoch 0 for weak-moderate and strong geomagnetic storms,respectively.Further analysis based on the classification of the local time of epoch 0 shows that scintillation occurrence is not observed in post-sunset hours when epoch 0 falls between 16:00 and 19:00 LT for weak-moderate geomagnetic storms.In strong geomagnetic storms,scintillation occurrence during post-sunset hours is absent when epoch 0 is between 10:00 and 19:00 LT.Notably,when the minimum SYM-H(epoch 0)nearly coincides with local sunset,scintillation activity occurs around sunset in both weak-moderate and strong geomagnetic storms.Furthermore,when epoch 0 falls within midnight until early morning,scintillation can be generated in the post-sunset hours before epoch 0.Still,post-midnight scintillation is not observed in the equatorial region during the recovery phase of either weak-moderate and strong storm events.Our findings show that when sunset falls before or coincide with epoch 0,the likelihood of post-sunset EPB and scintillation increases,due to the prompt-penetration electric field(PPEF)in the main phase of storm.The disturbance dynamo electric field(DDEF)in the recovery phase driven by equatorward winds from auroral Joule heating operates for at least 6-and 12-hours post-epoch 0 in the cases of weak-moderate and strong geomagnetic storms,respectively.When the local sunset falls within these operational DDEF periods,post-sunset EPBs will likely be suppressed,inhibiting ionospheric scintillation during post-sunset hours.Finally,this study provides essential information for developing more accurate ionospheric scintillation prediction models in space weather services in equatorial regions.
文摘MEMS(Micro-Electro-Mechanical-System)陀螺仪是一种小型化的惯性传感器,广泛应用于导航、导弹制导、自动驾驶、虚拟现实和无人机等领域。然而MEMS陀螺仪常受到来自环境和硬件本身噪声的影响,降低了其性能,限制了MEMS陀螺仪在高精度场合的应用。因此,信号去噪成为提高MEMS陀螺仪精度的重要手段之一。论文提出一种基于局部均值分解(LMD)和自适应最小均方误差(least mean squares,LMS)滤波算法。首先,使用局部均值分解对MEMS陀螺仪输出信号进行分解,然后应用多尺度排列熵将PF分量归类为混合分量和有用分量;再通过LMS对混合分量进行去噪,将MEMS陀螺仪的输出信号进行重建。并进行实验验证所提出的算法,实验结果表明,噪声均值、噪声方差有明显提升。
