The sliding mode control method is used to study spatiotemporal chaos synchronization of an uncertain network.The method is extended from synchronization between two chaotic systems to the synchronization of complex n...The sliding mode control method is used to study spatiotemporal chaos synchronization of an uncertain network.The method is extended from synchronization between two chaotic systems to the synchronization of complex network composed of N spatiotemporal chaotic systems.The sliding surface of the network and the control input are designed.Furthermore,the effectiveness of the method is analysed based on the stability theory.The Burgers equation with spatiotemporal chaos behavior is taken as an example to simulate the experiment.It is found that the synchronization performance of the network is very stable.展开更多
Developing a comprehensive understanding of inter-city interactions is crucial for regional planning.We therefore examined spatiotemporal patterns of population migration across the Qinghai-Tibet Plateau(QTP)using mig...Developing a comprehensive understanding of inter-city interactions is crucial for regional planning.We therefore examined spatiotemporal patterns of population migration across the Qinghai-Tibet Plateau(QTP)using migration big data from Tencent for the period between 2015 and 2019.We initially used decomposition and breakpoint detection methods to examine time-series migration data and to identify the two seasons with the strongest and weakest population migration levels,between June 18th and August 18th and between October 8th and February 15th,respectively.Population migration within the former period was 2.03 times that seen in the latter.We then used a variety of network analysis methods to examine population flow directions as well as the importance of each individual city in migration.The two capital cities on the QTP,Lhasa and Xining,form centers for population migration and are also transfer hubs through which migrants from other cities off the plateau enter and leave this region.Data show that these two cities contribute more than 35%of total population migration.The majority of migrants tend to move within the province,particularly during the weakest migration season.We also utilized interactive relationship force and radiation models to examine the interaction strength and the radiating energy of each individual city.Results show that Lhasa and Xining exhibit the strongest interactions with other cities and have the largest radiating energies.Indeed,the radiating energy of the QTP cities correlates with their gross domestic product(GDP)(Pearson correlation coefficient:0.754 in the weakest migration season,WMS versus 0.737 in the strongest migration season,SMS),while changes in radiating energy correlate with the tourism-related revenue(Pearson correlation coefficient:0.685).These outcomes suggest that level of economic development and level of tourism are the two most important factors driving the QTP population migration.The results of this analysis provide critical clarification guidance regarding huge QTP development differences.展开更多
In this study, based on the data on the frequency of waterlogging events and the number of waterlogging days of 1,638 stations from 1961 to 2016, a variety of mathematical statistics methods were used to analyze the s...In this study, based on the data on the frequency of waterlogging events and the number of waterlogging days of 1,638 stations from 1961 to 2016, a variety of mathematical statistics methods were used to analyze the spatiotemporal evolution of waterlogging events in eastern China. The results showed that:① In terms of time, the annual frequency of waterlogging events and the number of waterlogging days in eastern China in 1961–2016 showed an increasing trend despite of fluctuations. In the interdecadal changes, the highest frequency of waterlogging events and the greatest number of waterlogging days occurred in the 1990s, and from the 1960s to the 1980s, the frequency of waterlogging events and the number of waterlogging days in eastern China showed a decreasing trend. There were 6-year and 30-year periodic variations in the frequency of waterlogging events and the number of waterlogging days in eastern China, and mutations occurred in 1991.② In terms of space, from 1961 to 2016, the areas with high frequency of waterlogging events in various years in eastern China were mainly South China, western and southern Yunnan, northern Jiangsu, southern Zhejiang, northern Fujian, junction areas between Hunan and Chongqing, northern Sichuan, and eastern Liaoning.③ In the spatial distribution of change trends and fluctuation characteristics, the frequency of waterlogging events and the number of waterlogging days in eastern China increased significantly in the southeastern coastal areas from 1961 to 2016, and the fluctuations of the frequency of waterlogging events and the number of waterlogging days in eastern China from 1961 to 2016 presented a spatial variation pattern of low in the southwest and high in the northwest.展开更多
Effective detection schemes for spatiotemporal light fields hold significant importance in the study of highdimensional spatiotemporal nonlinear systems.We propose a compact seven-core fiber spatiotemporal mapping sys...Effective detection schemes for spatiotemporal light fields hold significant importance in the study of highdimensional spatiotemporal nonlinear systems.We propose a compact seven-core fiber spatiotemporal mapping system(SCF-SMS)to investigate the transient dynamics within a spatiotemporal mode-locked(STML)fiber laser.By utilizing this system,we observed intriguing transient phenomena during STML processes,including beating dynamics and spatiotemporal soliton state transition dynamics.In the beating dynamics,two channels corresponding to distinct spatial sampling points exhibited different transient behaviors.Conversely,during the spatiotemporal soliton state transition dynamics,the transition processes of two channels were asynchronous,with observable discrepancies before and after the transitions.Compared with existing spatiotemporal light field acquisition methods,the SCF-SMS enables more compact spatiotemporal mapping within STML fiber lasers.This real-time,synchronous system for spatiotemporal soliton information measurement facilitates an in-depth study of nonlinear dynamical phenomena in STML fiber lasers.展开更多
Spatiotemporal mode-locked(STML)fiber lasers have emerged as a novel platform for investigating spatiotemporal solitons and three-dimensional nonlinear phenomena.In this work,we report the generation of synchronous du...Spatiotemporal mode-locked(STML)fiber lasers have emerged as a novel platform for investigating spatiotemporal solitons and three-dimensional nonlinear phenomena.In this work,we report the generation of synchronous dual-wavelength STML noise-like square pulses in a few-mode fiber laser,characterized by distinct pulse durations at each wavelength.To further explore the experimental results,numerical simulations are conducted,where the mode-related and wavelength-related characteristics of the dual-wavelength noise-like pulses are revealed.It is found that different modes have distinct transient time-frequency characteristics,and a broader spectrum correlates with a longer duration of the pulse envelope and a shorter duration of the sub-pulses.These findings enhance our understanding of the underlying mechanisms and characteristics of noise-like pulses in STML fiber lasers for better exploration of their potential applications.展开更多
Orbital angular momentum(OAM)beams,characterized by a helical phase structure and phase singularity,have emerged as a powerful resource for high-capacity optical communications through mode-division multiplexing(MDM)....Orbital angular momentum(OAM)beams,characterized by a helical phase structure and phase singularity,have emerged as a powerful resource for high-capacity optical communications through mode-division multiplexing(MDM).Traditional OAM multiplexing systems operating solely in the spatial domain face significant challenges,including increased system complexity,inter-modal crosstalk,and limited scalability.Recent advances have explored hybrid multiplexing schemes combining OAM with wavelength or polarization degrees of freedom,demonstrating Pbit/s level transmission capacities.However,these systems predominantly rely on continuous-wave lasers and external modulators,which constrain their applicability in challenging environments,whereas pulsed lasers provide superior peak power,enhanced transmission robustness,and the potential for implementation of OAM lasers,which generally emit pulsed OAM beams.Here,we report an OAM-based spatiotemporal multiplexing(OAM-STM)technique that synergistically implements pulsed OAM beams with a diffractive deep neural network(D^(2)NN)and optical fiber delay lines to project spatial mode information into the temporal domain.This approach leverages the full potential of pulsed laser sources by activating the underutilized time dimension,thereby overcoming the repetition-rate bottleneck and enhancing channel throughput.We experimentally demonstrate an OAM-based spatiotemporal demultiplexer achieving demultiplexing speed limited only by the bandwidth of the photodiode if OAM generation is fast enough.In the meantime,the architecture is intrinsically compatible with high-repetition-rate OAM sources,offering the entire system the scalability to GHz rates.This work establishes a foundational framework for high-speed,all-optical,and high-capacity OAM-STM systems,with promising implications for free-space optical communication,underwater communication links,and other complex environments.展开更多
Fault controlling petroleum accumulation is mainly reflected in hydrocarbon migration and sealing in accumulation periods.By fault activity rate analysis and fuzzy comprehensive sealing evaluation in different places ...Fault controlling petroleum accumulation is mainly reflected in hydrocarbon migration and sealing in accumulation periods.By fault activity rate analysis and fuzzy comprehensive sealing evaluation in different places of Linshang Fault Zone(LFZ),LFZ controlling petroleum accumulation shows a lot of spatiotemporal differences:(1) main branch of展开更多
目的综合考虑B型超声(B-mode ultrasound,B-US)和对比增强超声(contrast-enhanced ultrasound,CEUS)双模态信息有助于提升乳腺肿瘤诊断的准确性,从而利于提高患者生存率。然而,目前大多数模型只关注B-US的特征提取,忽视了CEUS特征的学...目的综合考虑B型超声(B-mode ultrasound,B-US)和对比增强超声(contrast-enhanced ultrasound,CEUS)双模态信息有助于提升乳腺肿瘤诊断的准确性,从而利于提高患者生存率。然而,目前大多数模型只关注B-US的特征提取,忽视了CEUS特征的学习和双模态信息的融合处理。为解决上述问题,提出了一个融合时空特征与时间约束的双模态乳腺肿瘤诊断模型(spatio-temporal feature and temporal-constrained model,STFTCM)。方法首先,基于双模态信息的数据特点,采用异构双分支网络学习B-US和CEUS包含的时空特征。然后,设计时间注意力损失函数引导CEUS分支关注造影剂流入病灶区的时间窗口,从该窗口期内提取CEUS特征。最后,借助特征融合模块实现双分支网络之间的横向连接,通过将B-US特征作为CEUS分支补充信息的方式,完成双模态特征融合。结果在收集到的数据集上进行对比实验,STFTCM预测的正确率、敏感性、宏平均F1和AUC(area under the curve)指标均表现优秀,其中预测正确率达88.2%,领先于其他先进模型。消融实验中,时间注意力约束将模型预测正确率提升5.8%,特征融合使得模型诊断正确率相较于单分支模型至少提升2.9%。结论本文提出的STFTCM能有效地提取并融合处理B-US和CEUS双模态信息,给出准确的诊断结果。同时,时间注意力约束和特征融合模块可以显著地提升模型性能。展开更多
The unique architectural form and decorative craftsmanship of Liao Pagodas serve as tangible evidence of the diverse unity of Chinese civilization.Research on the existing Liao Pagodas has revealed a clear linear spat...The unique architectural form and decorative craftsmanship of Liao Pagodas serve as tangible evidence of the diverse unity of Chinese civilization.Research on the existing Liao Pagodas has revealed a clear linear spatiotemporal differentiation.In the temporal dimension,the density and characteristics of their construction align with the rise and fall of the Liao Dynasty's national strength.In the spatial dimension,Liao Pagodas are centered around the five capitals of Liao and show a marked gradient of decline along major transportation routes and the Song-Liao border.This distribution is both constrained by natural geographical conditions and reflective of the Liao dynasty's political wisdom of"governing according to local customs"by implementing a dual-track system of governance that used national systems for the Khitan and Han systems for the Han people.However,in current cultural tourism development practices,Liao Pagodas are often developed in a"scenic spot"manner using a singular,isolated model,leading to their disconnection and fragmentation from the overall layout of Liao cities,regional religious networks,and even historical contexts.This weakens the comprehensive interpretation and depth of experience of their heritage value.To address these issues,this paper proposes a"linear corridor"cultural tourism development approach for Liao Pagoda cultural heritage based on a study of their spatiotemporal differentiation.This approach breaks the isolation of individual heritage sites and constructs a cross-regional cultural heritage corridor.It focuses on exploring operational implementation paths such as"series cultural creations","linked research studies",and"technological narratives".This perspective not only effectively avoids the risk of cultural context fragmentation caused by individual development but also provides a practical direction for the revitalization and utilization of Liao Pagoda heritage,which supports the coordinated development of the regional culture and economy.展开更多
农机轨迹行为模式识别是一项多变量时间序列分类(multivariate time series classification,MTSC)任务,旨在提取农机轨迹数据中蕴藏的时空特征来识别农机轨迹行为模式,并为每个轨迹点分配相应的语义标签。针对现有方法对轨迹时空信息捕...农机轨迹行为模式识别是一项多变量时间序列分类(multivariate time series classification,MTSC)任务,旨在提取农机轨迹数据中蕴藏的时空特征来识别农机轨迹行为模式,并为每个轨迹点分配相应的语义标签。针对现有方法对轨迹时空信息捕捉能力不足和识别精度不佳的问题,提出了多维时空交互网络(multidimensional spatio-temporal interaction network,MSINet)来识别农机轨迹的行为模式。提出了多维信息交互(multidimensional infor-mation interaction,MII)模块,其融合了图卷积与自注意力机制以捕捉轨迹点之间的局部关联与全局依赖,同时利用双向感知机制实现通道与空间维度的信息互补;设计了多路径特征提取(multipath feature extraction,MFE)模块,利用具有不同扩张率的卷积路径有效提取轨迹数据的多尺度时序特征。最后,开发了语义聚焦(semantic focus,SF)模块以高效地捕捉轨迹数据中的关键信息。为验证所提方法的有效性,在农业农村部农机作业监测与大数据应用重点实验室提供的轨迹数据集上展开了实验。实验结果表明,MSINet在水稻收割机和小麦收割机轨迹数据集上的准确率分别为91.62%和91.34%,F1 score分别为91.57%和86.98%,相较于当前表现最优的模型生成式对抗网络-双向长短期记忆网络(generative adversarial network-bidirectional long short-term memory network,GAN BiLSTM),F1 score分别提升了5.57和3.72个百分点。展开更多
基金Project supported by the Natural Science Foundation of Liaoning Province,China (Grant No. 20082147)the Innovative Team Program of Liaoning Educational Committee,China (Grant No. 2008T108)
文摘The sliding mode control method is used to study spatiotemporal chaos synchronization of an uncertain network.The method is extended from synchronization between two chaotic systems to the synchronization of complex network composed of N spatiotemporal chaotic systems.The sliding surface of the network and the control input are designed.Furthermore,the effectiveness of the method is analysed based on the stability theory.The Burgers equation with spatiotemporal chaos behavior is taken as an example to simulate the experiment.It is found that the synchronization performance of the network is very stable.
基金National Natural Science Foundation of China(41590845)Strategic Priority Research Program of the Chinese Academy of Sciences(XDA19040501)+2 种基金Strategic Priority Research Program of the Chinese Academy of Sciences(XDA20040401)National Key Research and Development Program of China(2017YFB0503605)National Key Research and Development Program of China(2017YFC1503003)。
文摘Developing a comprehensive understanding of inter-city interactions is crucial for regional planning.We therefore examined spatiotemporal patterns of population migration across the Qinghai-Tibet Plateau(QTP)using migration big data from Tencent for the period between 2015 and 2019.We initially used decomposition and breakpoint detection methods to examine time-series migration data and to identify the two seasons with the strongest and weakest population migration levels,between June 18th and August 18th and between October 8th and February 15th,respectively.Population migration within the former period was 2.03 times that seen in the latter.We then used a variety of network analysis methods to examine population flow directions as well as the importance of each individual city in migration.The two capital cities on the QTP,Lhasa and Xining,form centers for population migration and are also transfer hubs through which migrants from other cities off the plateau enter and leave this region.Data show that these two cities contribute more than 35%of total population migration.The majority of migrants tend to move within the province,particularly during the weakest migration season.We also utilized interactive relationship force and radiation models to examine the interaction strength and the radiating energy of each individual city.Results show that Lhasa and Xining exhibit the strongest interactions with other cities and have the largest radiating energies.Indeed,the radiating energy of the QTP cities correlates with their gross domestic product(GDP)(Pearson correlation coefficient:0.754 in the weakest migration season,WMS versus 0.737 in the strongest migration season,SMS),while changes in radiating energy correlate with the tourism-related revenue(Pearson correlation coefficient:0.685).These outcomes suggest that level of economic development and level of tourism are the two most important factors driving the QTP population migration.The results of this analysis provide critical clarification guidance regarding huge QTP development differences.
基金Sponsored by the National Natural Science Fund(41801064,71790611)China Postdoctoral Science Foundation(2019 T120114,2019M650756)the Central Asian Atmospheric Science Research Fund(CAAS201804)
文摘In this study, based on the data on the frequency of waterlogging events and the number of waterlogging days of 1,638 stations from 1961 to 2016, a variety of mathematical statistics methods were used to analyze the spatiotemporal evolution of waterlogging events in eastern China. The results showed that:① In terms of time, the annual frequency of waterlogging events and the number of waterlogging days in eastern China in 1961–2016 showed an increasing trend despite of fluctuations. In the interdecadal changes, the highest frequency of waterlogging events and the greatest number of waterlogging days occurred in the 1990s, and from the 1960s to the 1980s, the frequency of waterlogging events and the number of waterlogging days in eastern China showed a decreasing trend. There were 6-year and 30-year periodic variations in the frequency of waterlogging events and the number of waterlogging days in eastern China, and mutations occurred in 1991.② In terms of space, from 1961 to 2016, the areas with high frequency of waterlogging events in various years in eastern China were mainly South China, western and southern Yunnan, northern Jiangsu, southern Zhejiang, northern Fujian, junction areas between Hunan and Chongqing, northern Sichuan, and eastern Liaoning.③ In the spatial distribution of change trends and fluctuation characteristics, the frequency of waterlogging events and the number of waterlogging days in eastern China increased significantly in the southeastern coastal areas from 1961 to 2016, and the fluctuations of the frequency of waterlogging events and the number of waterlogging days in eastern China from 1961 to 2016 presented a spatial variation pattern of low in the southwest and high in the northwest.
基金National Natural Science Foundation of China(12274238,62205159,61835006)Natural Science Foundation of Tianjin Municipality(19JCZDJC31200)Special Project for Cooperation in Basic Research of Beijing,Tianjin and Hebei(21JCZXJC00010)。
文摘Effective detection schemes for spatiotemporal light fields hold significant importance in the study of highdimensional spatiotemporal nonlinear systems.We propose a compact seven-core fiber spatiotemporal mapping system(SCF-SMS)to investigate the transient dynamics within a spatiotemporal mode-locked(STML)fiber laser.By utilizing this system,we observed intriguing transient phenomena during STML processes,including beating dynamics and spatiotemporal soliton state transition dynamics.In the beating dynamics,two channels corresponding to distinct spatial sampling points exhibited different transient behaviors.Conversely,during the spatiotemporal soliton state transition dynamics,the transition processes of two channels were asynchronous,with observable discrepancies before and after the transitions.Compared with existing spatiotemporal light field acquisition methods,the SCF-SMS enables more compact spatiotemporal mapping within STML fiber lasers.This real-time,synchronous system for spatiotemporal soliton information measurement facilitates an in-depth study of nonlinear dynamical phenomena in STML fiber lasers.
基金supported by the National Natural Science Foundation of China(Nos.62375091 and 92050101)the Natural Science Foundation of Guangdong Province(Nos.2021A1515011608 and 2023A1515011870)。
文摘Spatiotemporal mode-locked(STML)fiber lasers have emerged as a novel platform for investigating spatiotemporal solitons and three-dimensional nonlinear phenomena.In this work,we report the generation of synchronous dual-wavelength STML noise-like square pulses in a few-mode fiber laser,characterized by distinct pulse durations at each wavelength.To further explore the experimental results,numerical simulations are conducted,where the mode-related and wavelength-related characteristics of the dual-wavelength noise-like pulses are revealed.It is found that different modes have distinct transient time-frequency characteristics,and a broader spectrum correlates with a longer duration of the pulse envelope and a shorter duration of the sub-pulses.These findings enhance our understanding of the underlying mechanisms and characteristics of noise-like pulses in STML fiber lasers for better exploration of their potential applications.
基金supported by the National Natural Science Foundation of China(no.62275167,62405287,61905147,92250304)the Natural Science Foundation of Zhejiang Province(no.LZYQ25F050001)the Key R&D Program of Zhejiang(no.2024SSYS0014).
文摘Orbital angular momentum(OAM)beams,characterized by a helical phase structure and phase singularity,have emerged as a powerful resource for high-capacity optical communications through mode-division multiplexing(MDM).Traditional OAM multiplexing systems operating solely in the spatial domain face significant challenges,including increased system complexity,inter-modal crosstalk,and limited scalability.Recent advances have explored hybrid multiplexing schemes combining OAM with wavelength or polarization degrees of freedom,demonstrating Pbit/s level transmission capacities.However,these systems predominantly rely on continuous-wave lasers and external modulators,which constrain their applicability in challenging environments,whereas pulsed lasers provide superior peak power,enhanced transmission robustness,and the potential for implementation of OAM lasers,which generally emit pulsed OAM beams.Here,we report an OAM-based spatiotemporal multiplexing(OAM-STM)technique that synergistically implements pulsed OAM beams with a diffractive deep neural network(D^(2)NN)and optical fiber delay lines to project spatial mode information into the temporal domain.This approach leverages the full potential of pulsed laser sources by activating the underutilized time dimension,thereby overcoming the repetition-rate bottleneck and enhancing channel throughput.We experimentally demonstrate an OAM-based spatiotemporal demultiplexer achieving demultiplexing speed limited only by the bandwidth of the photodiode if OAM generation is fast enough.In the meantime,the architecture is intrinsically compatible with high-repetition-rate OAM sources,offering the entire system the scalability to GHz rates.This work establishes a foundational framework for high-speed,all-optical,and high-capacity OAM-STM systems,with promising implications for free-space optical communication,underwater communication links,and other complex environments.
文摘Fault controlling petroleum accumulation is mainly reflected in hydrocarbon migration and sealing in accumulation periods.By fault activity rate analysis and fuzzy comprehensive sealing evaluation in different places of Linshang Fault Zone(LFZ),LFZ controlling petroleum accumulation shows a lot of spatiotemporal differences:(1) main branch of
文摘目的综合考虑B型超声(B-mode ultrasound,B-US)和对比增强超声(contrast-enhanced ultrasound,CEUS)双模态信息有助于提升乳腺肿瘤诊断的准确性,从而利于提高患者生存率。然而,目前大多数模型只关注B-US的特征提取,忽视了CEUS特征的学习和双模态信息的融合处理。为解决上述问题,提出了一个融合时空特征与时间约束的双模态乳腺肿瘤诊断模型(spatio-temporal feature and temporal-constrained model,STFTCM)。方法首先,基于双模态信息的数据特点,采用异构双分支网络学习B-US和CEUS包含的时空特征。然后,设计时间注意力损失函数引导CEUS分支关注造影剂流入病灶区的时间窗口,从该窗口期内提取CEUS特征。最后,借助特征融合模块实现双分支网络之间的横向连接,通过将B-US特征作为CEUS分支补充信息的方式,完成双模态特征融合。结果在收集到的数据集上进行对比实验,STFTCM预测的正确率、敏感性、宏平均F1和AUC(area under the curve)指标均表现优秀,其中预测正确率达88.2%,领先于其他先进模型。消融实验中,时间注意力约束将模型预测正确率提升5.8%,特征融合使得模型诊断正确率相较于单分支模型至少提升2.9%。结论本文提出的STFTCM能有效地提取并融合处理B-US和CEUS双模态信息,给出准确的诊断结果。同时,时间注意力约束和特征融合模块可以显著地提升模型性能。
文摘The unique architectural form and decorative craftsmanship of Liao Pagodas serve as tangible evidence of the diverse unity of Chinese civilization.Research on the existing Liao Pagodas has revealed a clear linear spatiotemporal differentiation.In the temporal dimension,the density and characteristics of their construction align with the rise and fall of the Liao Dynasty's national strength.In the spatial dimension,Liao Pagodas are centered around the five capitals of Liao and show a marked gradient of decline along major transportation routes and the Song-Liao border.This distribution is both constrained by natural geographical conditions and reflective of the Liao dynasty's political wisdom of"governing according to local customs"by implementing a dual-track system of governance that used national systems for the Khitan and Han systems for the Han people.However,in current cultural tourism development practices,Liao Pagodas are often developed in a"scenic spot"manner using a singular,isolated model,leading to their disconnection and fragmentation from the overall layout of Liao cities,regional religious networks,and even historical contexts.This weakens the comprehensive interpretation and depth of experience of their heritage value.To address these issues,this paper proposes a"linear corridor"cultural tourism development approach for Liao Pagoda cultural heritage based on a study of their spatiotemporal differentiation.This approach breaks the isolation of individual heritage sites and constructs a cross-regional cultural heritage corridor.It focuses on exploring operational implementation paths such as"series cultural creations","linked research studies",and"technological narratives".This perspective not only effectively avoids the risk of cultural context fragmentation caused by individual development but also provides a practical direction for the revitalization and utilization of Liao Pagoda heritage,which supports the coordinated development of the regional culture and economy.
