We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs),no spontaneous lasing even with high gain,in longdistance fiber-optic time ...We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs),no spontaneous lasing even with high gain,in longdistance fiber-optic time and frequency(T/F)synchronization system.It is found that the Rayleigh scattering noise can be suppressed due to the high isolation design,but the amplified spontaneous emission(ASE)noise generated by the high isolation Bi-EDFA and the bidirectional asymmetry of the transmission link caused by the high isolation Bi-EDFA will deteriorate the stability of the system.The calculated results show that under the influence of ASE noise,the frequency instability of a 1200 km system composed of 15 high isolation Bi-EDFAs is 1.773×10^(-13)/1 s.And the instability caused by asymmetry is 2.6064×10^(-16)/30000–35000 s if the total asymmetric length of the bidirectional link length is 30 m.The intensity noises originating from the laser and detector,the transfer delay fluctuations caused by the variation in ambient temperature and the jitter in laser output wavelength are also studied.The experiment composed of three high isolation Bi-EDFAs is done to confirm the theoretical analysis.In summary,the paper shows that the short-term instability of the T/F synchronization system composed of high isolation Bi-EDFAs is limited by the accumulation of ASE noise of amplifiers and the laser frequency drift,while the long-term instability is limited by the periodic variation in ambient temperature and the asymmetry of the amplifiers.The research results are useful for pointing out the direction to improve the stability of the fiber-optic T/F synchronization system.展开更多
In recent years,the rapid development of large-scale satellite constellations has challenged the mass production capabilities of satellite manufacturers.Assembly is the last and critical phase of satellite production....In recent years,the rapid development of large-scale satellite constellations has challenged the mass production capabilities of satellite manufacturers.Assembly is the last and critical phase of satellite production.Achieving satellite mass assembly is the key to realizing satellite mass production.To this end,satellite manufacturers are working to construct the satellite mass assembly shop-floor(SMAS)to enable moving assembly.However,there is still a lack of a modularized manufacturing system oriented to flexible production for SMAS,as well as disturbance detection methods and production-logistics synchronization methods to deal with various disturbances.Therefore,this paper proposes a digital twin-based production-logistics synchronization system(DT-PLSS)for SMAS.The framework of DT-PLSS is introduced first.In this framework,DT-PLSS can achieve modular construction,as well as distributed management and control.Based on the proposed framework,the construction methods of resource level digital twin(DT),workstation level DT,and shop-floor level DT in SMAS are discussed.The DT-based disturbance detection method for SMAS is presented,aiming to detect or predict di erent types of disturbances and to analyze the e ect of disturbances.Then,a DT enhanced production-logistics synchronization mechanism for SMAS is proposed.With this mechanism,the logistics distribution in the dynamic shop-floor environment and production-logistics synchronization under various disturbances can be realized.Finally,a case study in a real SMAS verifies the feasibility and e ectiveness of the proposed system and methods.This research proposes a practical framework and system which could realize disturbance detection,logistics distribution,and the production-logistics synchronization in complex SMAS scenario e ectively.展开更多
The distributed time-keeping and synchronization system （DTSS） underwent an upgrade for EAST during the last shutdown. The upgraded DTSS, designed based on PXI bus and reconfigurable I/O devices, synchronizes all ot...The distributed time-keeping and synchronization system （DTSS） underwent an upgrade for EAST during the last shutdown. The upgraded DTSS, designed based on PXI bus and reconfigurable I/O devices, synchronizes all other sub-systems by using a reference clock and trigger. It can produce a uniform clock up to 80 MHz, provide a delayed trigger from 1 ms to 6872 s in 1 ms steps with 10 ns accuracy, and acquire the outputs of itself for self-inspection. The new DTSS was successfully applied in the 2012 spring EAST campaign, and has proven to be stable and reliable, giving an effective performance. The system structure and software development will be illustrated in detail in this paper.展开更多
Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color （RGB） digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital ...Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color （RGB） digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital image with 8 bits into unrecognizable disorder codes and then transforms the disorder codes into an RGB digital image with 16 bits for transmitting. A receiver uses a non-symmetric key to verify the authentication of the received data origin, and decrypts the ciphertext. The scheme can encrypt and decz：Fpt most formatted digital RGB images recognized by computers, and recover the plaintext almost without any errors. The scheme is suitable to be applied in network image communications. The analysis of the key space, sensitivity of key parameters, and correlation of encrypted images imply that this scheme has sound security.展开更多
OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication...OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication applications. Based on the theoretic a analysis of the OFDM technology, the impact of phase noise that introduced by the bit and symbol timing mechanism is discussed. Then a pilot correction and the cyclic prefix protection method are put forwarded to deal with the problem. These methods have been used in our experimental OFDM cable modem system to cope with the impulse noise and narrow band interference in the HFC (hybrid fiber and coax) upstream channel.展开更多
The intelligent substation realizes the digitization of information in the whole substation and thus time synchronization system becomes more and more important. This paper introduces time synchronization technology o...The intelligent substation realizes the digitization of information in the whole substation and thus time synchronization system becomes more and more important. This paper introduces time synchronization technology of intelligent substation and puts forward the principles for designing intelligent substation time synchronization system. According to some relay protection malfunction examples caused by time synchronization system fault, analyze the influence of time synchronization system fault to relay protection and correspondingly put forward some improving measures.展开更多
As the rapid development of Wireless Communications and the popularity of the Intelligent Terminal, data synchronization has been a social focus, meanwhile, user terminal devices are increasingly diversified, traditio...As the rapid development of Wireless Communications and the popularity of the Intelligent Terminal, data synchronization has been a social focus, meanwhile, user terminal devices are increasingly diversified, traditional synchronization technology based C/S mode has such deficiencies as insufficient amount of transmitting data and bad Real-time efficiency. It has become increasingly unable to meet the needs of future development. In this paper, we proposed and designed a new method and system by separating control with transmission to synchronize data to ensure Real-time data and improve efficiency.展开更多
White Rabbit(WR)is a multi-laboratory,multi-company collaboration for the development of an Ethernet based network ensuring sub-nanosecond synchronization and deterministic data transfer.WR technology is a combination...White Rabbit(WR)is a multi-laboratory,multi-company collaboration for the development of an Ethernet based network ensuring sub-nanosecond synchronization and deterministic data transfer.WR technology is a combination of PTP(Precision time protocol)using Synchronous Ethernet and Digital Dual-Mixer Time Difference(DDMTD)phase detection.A WR link is formed by master and slave,each WR Master and WR Slave has some constant transmission and reception delays(ΔTXM,ΔRXM,ΔTXS,ΔRXS)presented in Fig.1.Additional reception delay is also caused on both sides by aligning the recovered clock signal to the inter-symbol boundaries of the data stream.This is called the bit-slide value and is marked in Fig.1 asεM andεS.Packets transmitted in fiber are affected with propagation latencies in both directions(εMS,εSM)so the round-trip delay(delayMM)is defined as the sum of all delay factors described above。展开更多
Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and ev...Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and even a chaotic or hyperchaotic system,the response network is complex system coupled by N nodes,and every node is showed by the approximately linear part of the drive system.Only controlling any one node of the response network by designed controller can achieve the projective synchronization.Some numerical examples were employed to verify the effectiveness and correctness of the designed controller.展开更多
The dynamics of chaotic memristor-based systems offer promising potential for secure communication.However,existing solutions frequently suffer from drawbacks such as slow synchronization,low key diversity,and poor no...The dynamics of chaotic memristor-based systems offer promising potential for secure communication.However,existing solutions frequently suffer from drawbacks such as slow synchronization,low key diversity,and poor noise resistance.To overcome these issues,a novel fractional-order chaotic system incorporating a memristor emulator derived from the Shinriki oscillator is proposed.The main contribution lies in the enhanced dynamic complexity and flexibility of the proposed architecture,making it suitable for cryptographic applications.Furthermore,the feasibility of synchronization to ensure secure data transmission is demonstrated through the validation of two strategies:an active control method ensuring asymptotic convergence,and a finite-time control method enabling faster stabilization.The robustness of the scheme is confirmed by simulation results on a color image:χ^(2)=253/237/267(R/G/B);entropy≈7.993;correlations between adjacent pixels in all directions are close to zero(e.g.,-0.0318 vertically);and high number of pixel change rate and unified average changing intensity(e.g.,33.40%and 99.61%,respectively).Peak signal-to-noise ratio analysis shows that resilience to noise and external disturbances is maintained.It is shown that multiple fractional orders further enrich the chaotic behavior,increasing the systems suitability for secure communication in embedded environments.These findings highlight the relevance of fractional-order chaotic memristive systems for lightweight secure transmission applications.展开更多
This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser.We analyze the controller input/output data of phase-locked loops in length-s...This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser.We analyze the controller input/output data of phase-locked loops in length-stabilized links,focusing on the response to earthquakes,ocean-generated microseism and civilization noise.By comparing the controller data with external data,we were able to identify disturbances and their effects on the control signals.Our results show that seismic events influence the stability of the phase-locked loops.Even earthquakes that are approximately 5000 km away cause remarkable fluctuations in the in-loop control signals.Ocean-generated microseism in particular has an enormous influence on the in-loop control signals due to its constant presence.The optical synchronization system is so highly sensitive that it can even identify vibrations caused by civilization,such as road traffic or major events like concerts or sport events.The phase-locked loops manage to eliminate more than 99%of the existing interference.展开更多
While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,du...While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,due to continuously varied geometries of laser-matter incidence.In the present work,we propose a novel manufacturing system of 7-axis on-the-fly LST for complex curved surface,based on the integrated synchronization of 5-axis linkage motion platform with 2-axis galvanometer.Specifically,the algorithm for decomposing spatial texture trajectory on curved surface into low-frequency and high-frequency parts is established,based on which the kinematic model of synchronized 7-axis system is developed to derive the motion of each axis in both 5-axis linkage motion platform and 2-axis galvanometer simultaneously.Subsequently,the synchronized 7-axis LST system is experimentally realized,including the setup of mechanical stages integrated with optical path,the configuration of numerical control unit,and the development of processing software.Finally,case study of 7-axis on-the-fly LST of freeform aluminum surface is performed,and the advantages in terms of processing efficiency and texturing accuracy over 5-axis linkage LST are demonstrated.The correlation of reduced following errors between mechanical stages with the promoted performance of curved surface texturing by the 7-axis on-the-fly LST is further analyzed.Current work provides a feasible solution for establishing the manufacturing system for high performance LST of complex curved surface.展开更多
Nanogenerators provide important freedom for future electronic system design by collecting dispersed mechanical energy to power devices such as Internet of Things.Although researchers have focused on breaking through ...Nanogenerators provide important freedom for future electronic system design by collecting dispersed mechanical energy to power devices such as Internet of Things.Although researchers have focused on breaking through the design of high energy density nanogenerators,the whole system energy consumption design can effectively improve the convenience and effectiveness of the self-powered system design by reducing the use area of nanogenerators.In this study,we use the brightness change of an light-emitting device(LED)powered by a nanogenerator to convert the vibration of an instrument into a light signal(LS).This method effectively eliminates the additional phase difference commonly encountered in traditional sound signal(SS)transmission,thereby providing a significant phase verification technique for symphony orchestra coordination and related applications.This system does not rely on chip conversion signals,and does not require a Bluetooth transceiver system,so it can achieve long-distance signal transmission.The system implements a fully self-powered design,so this work has an important impact on the design of related systems in the future.展开更多
This paper presents a detailed technical overview of the femtosecond precision timing and synchronization systems implemented at the Shanghai high repetition rate XFEL and extreme light facility(SHINE).These systems a...This paper presents a detailed technical overview of the femtosecond precision timing and synchronization systems implemented at the Shanghai high repetition rate XFEL and extreme light facility(SHINE).These systems are designed to deliver stabilized optical references to multiple receiver clients,ensuring high-precision synchronization between the optical master oscillator(OMO)and optical/RF subsystems.The core components include an OMO,fiber length stabilizers and laser-to-laser synchronization modules that achieve femtosecond-level accuracy.Our discussion extends to the various subsystems that comprise the synchronization infrastructure,including the OMO,fiber length stabilizer and advanced phase detection techniques.Finally,we highlight ongoing research and development efforts aimed at enhancing the functionality and efficiency of these systems,thereby contributing to the advancement of X-ray freeelectron laser technology and its applications in scientific research.展开更多
The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas...The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas such as Positioning,Navigation,and Timing,lunar navigation,and cutting-edge fundamental physics research.This study presents an improved carrier-phase-based method for time synchronization,which was demonstrated through both laboratory and satellite-ground experiments via the China Space Station(CSS)-ground synchronization system.Initial laboratory experiments confirmed the system’s stability,achieving picosecond-level accuracy,highlighting the robustness of the method in controlled environments.Then,preliminary satellite-to-ground synchronization experiments were conducted using the CSS and ground stations,validating the effectiveness of the carrier-phase-based method.The time synchronization accuracy reached the picosecond-level,significantly surpassing traditional pseudocode techniques,which typically achieve sub-nanosecond level accuracy.Additionally,the Allan Deviation results indicated an improvement in stability by about an order of magnitude compared to traditional pseudocode-based methods.This demonstrates that the carrier-phase-based method can effectively mitigate common sources of system errors and enhance time synchronization capabilities.Therefore,this method can provide an effective technical reference for future applications requiring higher precision in time synchronization.展开更多
Optical non-reciprocity is a fundamental phenomenon in photonics.It is crucial for developing devices that rely on directional signal control,such as optical isolators and circulators.However,most research in this fie...Optical non-reciprocity is a fundamental phenomenon in photonics.It is crucial for developing devices that rely on directional signal control,such as optical isolators and circulators.However,most research in this field has focused on systems in equilibrium or steady states.In this work,we demonstrate a room-temperature Rydberg atomic platform where the unidirectional propagation of light acts as a switch to mediate time-crystalline-like collective oscillations through atomic synchronization.展开更多
This paper is dedicated to fixed-time passivity and synchronization for multi-weighted spatiotemporal directed networks.First,to achieve fixed-time passivity,a type of decentralized power-law controller is developed,i...This paper is dedicated to fixed-time passivity and synchronization for multi-weighted spatiotemporal directed networks.First,to achieve fixed-time passivity,a type of decentralized power-law controller is developed,in which only one parameter needs to be adjusted in the power-law terms;this greatly decreases the inconvenience of parameter adjustment.Second,several fixed-time passivity criteria with LMI forms are derived by using a Gauss divergence theorem to deal with the spatial diffusion of nodes and by applying the Hölder’s inequality to dispose rigorously the power-law term greater than one in the designed control scheme;this improves the previous theoretical analysis.Additionally,the fixed-time synchronization of spatiotemporal directed networks with multi-weights is addressed as a direct result of fixed-time strict passivity.Finally,a numerical example is presented in order to show the validity of the theoretical analysis.展开更多
Neuromorphic circuits based on superconducting tunnel junctions have attracted much attention due to their highspeed computing capabilities and low energy consumption.Josephson junction circuits can effectively mimic ...Neuromorphic circuits based on superconducting tunnel junctions have attracted much attention due to their highspeed computing capabilities and low energy consumption.Josephson junction circuits can effectively mimic biological neural dynamics.Leveraging these advantages,we construct a Josephson junction neuron-like model with a phasedependent dissipative current,referred to as a memristive current.The proposed memristive Josephson junction model exhibits complex dynamical behaviors.Furthermore,considering the effect of a fast-modulated synapse,we explore synchronization phenomena in coupled networks under varying coupling conductances and excitatory/inhibitory interactions.Finally,we extend the neuromorphic Josephson junction model—exhibiting complex dynamics—to the field of image encryption.These results not only enrich the understanding of the dynamical characteristics of memristive Josephson junctions but also provide a theoretical basis and technical support for the development of new neural networks and their applications in information security technology.展开更多
Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchroniza...Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchronization method based on pulse-coupled oscillators(PCOs)provides an effective solution for clock synchronization in wireless networks.However,the existing clock synchronization algorithms in multi-agent ad hoc networks are difficult to meet the requirements of high precision and high stability of synchronization clock in group cooperation.Hence,this paper constructs a network model,named DAUNet(unsupervised neural network based on dual attention),to enhance clock synchronization accuracy in multi-agent wireless ad hoc networks.Specifically,we design an unsupervised distributed neural network framework as the backbone,building upon classical PCO-based synchronization methods.This framework resolves issues such as prolonged time synchronization message exchange between nodes,difficulties in centralized node coordination,and challenges in distributed training.Furthermore,we introduce a dual-attention mechanism as the core module of DAUNet.By integrating a Multi-Head Attention module and a Gated Attention module,the model significantly improves information extraction capabilities while reducing computational complexity,effectively mitigating synchronization inaccuracies and instability in multi-agent ad hoc networks.To evaluate the effectiveness of the proposed model,comparative experiments and ablation studies were conducted against classical methods and existing deep learning models.The research results show that,compared with the deep learning networks based on DASA and LSTM,DAUNet can reduce the mean normalized phase difference(NPD)by 1 to 2 orders of magnitude.Compared with the attention models based on additive attention and self-attention mechanisms,the performance of DAUNet has improved by more than ten times.This study demonstrates DAUNet’s potential in advancing multi-agent ad hoc networking technologies.展开更多
To realize the data synchronization between the inertial measurement unit （IMU） and the global positioning system （GPS）, the synchronization technology in the IMU/GPS integrated measurement system of vehicle motio...To realize the data synchronization between the inertial measurement unit （IMU） and the global positioning system （GPS）, the synchronization technology in the IMU/GPS integrated measurement system of vehicle motion parameters is studied. According to the characteristics of the output signals of the IMU and the GPS, without the IMU synchronization signal, the synchronization circuit based on CPLD is designed and developed, which need not alter the configurations of the IMU and GPS. Experiments of measuring vehicle motion parameters, which rely on the synchronization circuit to realize IMU/GPS data synchronization, are made. The driving routes in experiments comprise a curve and a straight line. Experimental results show that the designed circuit can accurately measure the synchronization time difference and the IMU period, and can effectively solve the data synchronization in IMU/GPS integration. Furthermore, the IMU/GPS integrated measurement system based on the synchronization circuit can measure and calculate many vehicle motion parameters in high frequency mode.展开更多
基金the National Natural Science Foundation of China(Grant Nos.61701040,61771062,and 61871044)the Youth Program of the National Natural Science Foundation of China(Grant No.61901046)+1 种基金the Fundamental Research Funds for the Central Universities,China(Grant Nos.2019XD-A18and 2019PTB-004)the Youth Research and Innovation Program of BUPT(Grant No.2017RC13)。
文摘We propose a physical model of estimating noise and asymmetry brought by high isolation Bi-directional erbiumdoped fiber amplifiers(Bi-EDFAs),no spontaneous lasing even with high gain,in longdistance fiber-optic time and frequency(T/F)synchronization system.It is found that the Rayleigh scattering noise can be suppressed due to the high isolation design,but the amplified spontaneous emission(ASE)noise generated by the high isolation Bi-EDFA and the bidirectional asymmetry of the transmission link caused by the high isolation Bi-EDFA will deteriorate the stability of the system.The calculated results show that under the influence of ASE noise,the frequency instability of a 1200 km system composed of 15 high isolation Bi-EDFAs is 1.773×10^(-13)/1 s.And the instability caused by asymmetry is 2.6064×10^(-16)/30000–35000 s if the total asymmetric length of the bidirectional link length is 30 m.The intensity noises originating from the laser and detector,the transfer delay fluctuations caused by the variation in ambient temperature and the jitter in laser output wavelength are also studied.The experiment composed of three high isolation Bi-EDFAs is done to confirm the theoretical analysis.In summary,the paper shows that the short-term instability of the T/F synchronization system composed of high isolation Bi-EDFAs is limited by the accumulation of ASE noise of amplifiers and the laser frequency drift,while the long-term instability is limited by the periodic variation in ambient temperature and the asymmetry of the amplifiers.The research results are useful for pointing out the direction to improve the stability of the fiber-optic T/F synchronization system.
基金Supported by National Natural Science Foundation of China(Grant Nos.52275471,52120105008)New Cornerstone Science Foundation through the Xplorer Prize。
文摘In recent years,the rapid development of large-scale satellite constellations has challenged the mass production capabilities of satellite manufacturers.Assembly is the last and critical phase of satellite production.Achieving satellite mass assembly is the key to realizing satellite mass production.To this end,satellite manufacturers are working to construct the satellite mass assembly shop-floor(SMAS)to enable moving assembly.However,there is still a lack of a modularized manufacturing system oriented to flexible production for SMAS,as well as disturbance detection methods and production-logistics synchronization methods to deal with various disturbances.Therefore,this paper proposes a digital twin-based production-logistics synchronization system(DT-PLSS)for SMAS.The framework of DT-PLSS is introduced first.In this framework,DT-PLSS can achieve modular construction,as well as distributed management and control.Based on the proposed framework,the construction methods of resource level digital twin(DT),workstation level DT,and shop-floor level DT in SMAS are discussed.The DT-based disturbance detection method for SMAS is presented,aiming to detect or predict di erent types of disturbances and to analyze the e ect of disturbances.Then,a DT enhanced production-logistics synchronization mechanism for SMAS is proposed.With this mechanism,the logistics distribution in the dynamic shop-floor environment and production-logistics synchronization under various disturbances can be realized.Finally,a case study in a real SMAS verifies the feasibility and e ectiveness of the proposed system and methods.This research proposes a practical framework and system which could realize disturbance detection,logistics distribution,and the production-logistics synchronization in complex SMAS scenario e ectively.
基金supported by the National Magnetic Confinement Fusion Science Program of China(No.2012GB105000)
文摘The distributed time-keeping and synchronization system （DTSS） underwent an upgrade for EAST during the last shutdown. The upgraded DTSS, designed based on PXI bus and reconfigurable I/O devices, synchronizes all other sub-systems by using a reference clock and trigger. It can produce a uniform clock up to 80 MHz, provide a delayed trigger from 1 ms to 6872 s in 1 ms steps with 10 ns accuracy, and acquire the outputs of itself for self-inspection. The new DTSS was successfully applied in the 2012 spring EAST campaign, and has proven to be stable and reliable, giving an effective performance. The system structure and software development will be illustrated in detail in this paper.
基金the National Natural Science Foundation of China under，the Foundation for University Key Teachers，高等学校博士学科点专项科研项目，教育部科学技术研究项目
文摘Based on a generalized chaos synchronization system and a discrete Sinai map, a non-symmetric true color （RGB） digital image secure communication scheme is proposed. The scheme first changes an ordinary RGB digital image with 8 bits into unrecognizable disorder codes and then transforms the disorder codes into an RGB digital image with 16 bits for transmitting. A receiver uses a non-symmetric key to verify the authentication of the received data origin, and decrypts the ciphertext. The scheme can encrypt and decz：Fpt most formatted digital RGB images recognized by computers, and recover the plaintext almost without any errors. The scheme is suitable to be applied in network image communications. The analysis of the key space, sensitivity of key parameters, and correlation of encrypted images imply that this scheme has sound security.
文摘OFDM (the orthogonal frequency division multiplexing) and its variety DMT (the discrete multitone) as delegates of the multicarrier modulation technology have given a big impact on the conventional data communication applications. Based on the theoretic a analysis of the OFDM technology, the impact of phase noise that introduced by the bit and symbol timing mechanism is discussed. Then a pilot correction and the cyclic prefix protection method are put forwarded to deal with the problem. These methods have been used in our experimental OFDM cable modem system to cope with the impulse noise and narrow band interference in the HFC (hybrid fiber and coax) upstream channel.
文摘The intelligent substation realizes the digitization of information in the whole substation and thus time synchronization system becomes more and more important. This paper introduces time synchronization technology of intelligent substation and puts forward the principles for designing intelligent substation time synchronization system. According to some relay protection malfunction examples caused by time synchronization system fault, analyze the influence of time synchronization system fault to relay protection and correspondingly put forward some improving measures.
文摘As the rapid development of Wireless Communications and the popularity of the Intelligent Terminal, data synchronization has been a social focus, meanwhile, user terminal devices are increasingly diversified, traditional synchronization technology based C/S mode has such deficiencies as insufficient amount of transmitting data and bad Real-time efficiency. It has become increasingly unable to meet the needs of future development. In this paper, we proposed and designed a new method and system by separating control with transmission to synchronize data to ensure Real-time data and improve efficiency.
文摘White Rabbit(WR)is a multi-laboratory,multi-company collaboration for the development of an Ethernet based network ensuring sub-nanosecond synchronization and deterministic data transfer.WR technology is a combination of PTP(Precision time protocol)using Synchronous Ethernet and Digital Dual-Mixer Time Difference(DDMTD)phase detection.A WR link is formed by master and slave,each WR Master and WR Slave has some constant transmission and reception delays(ΔTXM,ΔRXM,ΔTXS,ΔRXS)presented in Fig.1.Additional reception delay is also caused on both sides by aligning the recovered clock signal to the inter-symbol boundaries of the data stream.This is called the bit-slide value and is marked in Fig.1 asεM andεS.Packets transmitted in fiber are affected with propagation latencies in both directions(εMS,εSM)so the round-trip delay(delayMM)is defined as the sum of all delay factors described above。
基金Supported by the National Natural Science Foundation of China (11161027)。
文摘Projective synchronization problems of a drive system and a particular response network were investigated,where the drive system is an arbitrary system with n+1 dimensions;it may be a linear or nonlinear system,and even a chaotic or hyperchaotic system,the response network is complex system coupled by N nodes,and every node is showed by the approximately linear part of the drive system.Only controlling any one node of the response network by designed controller can achieve the projective synchronization.Some numerical examples were employed to verify the effectiveness and correctness of the designed controller.
文摘The dynamics of chaotic memristor-based systems offer promising potential for secure communication.However,existing solutions frequently suffer from drawbacks such as slow synchronization,low key diversity,and poor noise resistance.To overcome these issues,a novel fractional-order chaotic system incorporating a memristor emulator derived from the Shinriki oscillator is proposed.The main contribution lies in the enhanced dynamic complexity and flexibility of the proposed architecture,making it suitable for cryptographic applications.Furthermore,the feasibility of synchronization to ensure secure data transmission is demonstrated through the validation of two strategies:an active control method ensuring asymptotic convergence,and a finite-time control method enabling faster stabilization.The robustness of the scheme is confirmed by simulation results on a color image:χ^(2)=253/237/267(R/G/B);entropy≈7.993;correlations between adjacent pixels in all directions are close to zero(e.g.,-0.0318 vertically);and high number of pixel change rate and unified average changing intensity(e.g.,33.40%and 99.61%,respectively).Peak signal-to-noise ratio analysis shows that resilience to noise and external disturbances is maintained.It is shown that multiple fractional orders further enrich the chaotic behavior,increasing the systems suitability for secure communication in embedded environments.These findings highlight the relevance of fractional-order chaotic memristive systems for lightweight secure transmission applications.
基金support by DASHH(Data Science in Hamburg-Helmholtz Graduate School for the Structure of Matter)with grant No.HIDSS-0002。
文摘This study investigates the influence of seismic activities on the optical synchronization system of the European X-ray Free-Electron Laser.We analyze the controller input/output data of phase-locked loops in length-stabilized links,focusing on the response to earthquakes,ocean-generated microseism and civilization noise.By comparing the controller data with external data,we were able to identify disturbances and their effects on the control signals.Our results show that seismic events influence the stability of the phase-locked loops.Even earthquakes that are approximately 5000 km away cause remarkable fluctuations in the in-loop control signals.Ocean-generated microseism in particular has an enormous influence on the in-loop control signals due to its constant presence.The optical synchronization system is so highly sensitive that it can even identify vibrations caused by civilization,such as road traffic or major events like concerts or sport events.The phase-locked loops manage to eliminate more than 99%of the existing interference.
基金the support by the Harbin Manufacturing Science and Technology Innovation Talent Project(No.2023CXRCGD035)the Open Research Foundation of State Key Laboratory of Digital Manufacturing Equipment and Technology in Huazhong University of Science and Technology,China(No.IMETKF2023012).
文摘While laser surface texturing(LST)is a promising manufacturing technique for surface functionalization,simultaneously realizing high precision and high efficiency in the LST of complex curved surface is challenging,due to continuously varied geometries of laser-matter incidence.In the present work,we propose a novel manufacturing system of 7-axis on-the-fly LST for complex curved surface,based on the integrated synchronization of 5-axis linkage motion platform with 2-axis galvanometer.Specifically,the algorithm for decomposing spatial texture trajectory on curved surface into low-frequency and high-frequency parts is established,based on which the kinematic model of synchronized 7-axis system is developed to derive the motion of each axis in both 5-axis linkage motion platform and 2-axis galvanometer simultaneously.Subsequently,the synchronized 7-axis LST system is experimentally realized,including the setup of mechanical stages integrated with optical path,the configuration of numerical control unit,and the development of processing software.Finally,case study of 7-axis on-the-fly LST of freeform aluminum surface is performed,and the advantages in terms of processing efficiency and texturing accuracy over 5-axis linkage LST are demonstrated.The correlation of reduced following errors between mechanical stages with the promoted performance of curved surface texturing by the 7-axis on-the-fly LST is further analyzed.Current work provides a feasible solution for establishing the manufacturing system for high performance LST of complex curved surface.
基金supported by the National Natural Science Foundation of China(NSFC)(Nos.U2330126 and 12104249)the Youth Innovation Team Project of Shandong Provincial Education Department(No.2021KJ013)State Key Laboratory of Bio-Fibers and Eco-Textiles(Qingdao University)(No.GZRC202011&ZKT46).
文摘Nanogenerators provide important freedom for future electronic system design by collecting dispersed mechanical energy to power devices such as Internet of Things.Although researchers have focused on breaking through the design of high energy density nanogenerators,the whole system energy consumption design can effectively improve the convenience and effectiveness of the self-powered system design by reducing the use area of nanogenerators.In this study,we use the brightness change of an light-emitting device(LED)powered by a nanogenerator to convert the vibration of an instrument into a light signal(LS).This method effectively eliminates the additional phase difference commonly encountered in traditional sound signal(SS)transmission,thereby providing a significant phase verification technique for symphony orchestra coordination and related applications.This system does not rely on chip conversion signals,and does not require a Bluetooth transceiver system,so it can achieve long-distance signal transmission.The system implements a fully self-powered design,so this work has an important impact on the design of related systems in the future.
基金supported by the National Natural Science Foundation of China(Nos.12105348 and 12275341)the SHINE project(National Major Scientific and Technological Infrastructure,No.NDRC[2017]825).
文摘This paper presents a detailed technical overview of the femtosecond precision timing and synchronization systems implemented at the Shanghai high repetition rate XFEL and extreme light facility(SHINE).These systems are designed to deliver stabilized optical references to multiple receiver clients,ensuring high-precision synchronization between the optical master oscillator(OMO)and optical/RF subsystems.The core components include an OMO,fiber length stabilizers and laser-to-laser synchronization modules that achieve femtosecond-level accuracy.Our discussion extends to the various subsystems that comprise the synchronization infrastructure,including the OMO,fiber length stabilizer and advanced phase detection techniques.Finally,we highlight ongoing research and development efforts aimed at enhancing the functionality and efficiency of these systems,thereby contributing to the advancement of X-ray freeelectron laser technology and its applications in scientific research.
基金funded by National Key Research and Development Program(NO.2023YFB3906500)Space Application System of China Manned Space Programthe National Nature Science Foundation of China(Grant NO.42030105 and NO.12273045).
文摘The development of precise time synchronization technology is key to the effective application of time-frequency standards.It will significantly promote the application of precise time-frequency standards in the areas such as Positioning,Navigation,and Timing,lunar navigation,and cutting-edge fundamental physics research.This study presents an improved carrier-phase-based method for time synchronization,which was demonstrated through both laboratory and satellite-ground experiments via the China Space Station(CSS)-ground synchronization system.Initial laboratory experiments confirmed the system’s stability,achieving picosecond-level accuracy,highlighting the robustness of the method in controlled environments.Then,preliminary satellite-to-ground synchronization experiments were conducted using the CSS and ground stations,validating the effectiveness of the carrier-phase-based method.The time synchronization accuracy reached the picosecond-level,significantly surpassing traditional pseudocode techniques,which typically achieve sub-nanosecond level accuracy.Additionally,the Allan Deviation results indicated an improvement in stability by about an order of magnitude compared to traditional pseudocode-based methods.This demonstrates that the carrier-phase-based method can effectively mitigate common sources of system errors and enhance time synchronization capabilities.Therefore,this method can provide an effective technical reference for future applications requiring higher precision in time synchronization.
基金supported by the National Natural Science Foundation of China (Grant No.12274131)the Innovation Program for Quantum Science and Technology (Grant No.2024ZD0300101)。
文摘Optical non-reciprocity is a fundamental phenomenon in photonics.It is crucial for developing devices that rely on directional signal control,such as optical isolators and circulators.However,most research in this field has focused on systems in equilibrium or steady states.In this work,we demonstrate a room-temperature Rydberg atomic platform where the unidirectional propagation of light acts as a switch to mediate time-crystalline-like collective oscillations through atomic synchronization.
基金supported by the National Natural Science Foundation of China(62373317)the Tianshan Talent Training Program(2022TSYCCX0013)+3 种基金the Key Project of Natural Science Foundation of Xinjiang(2021D01D10)the Basic Research Foundation for Universities of Xinjiang(XJEDU2023P023)the Xinjiang Key Laboratory of Applied Mathematics(XJDX1401)the Intelligent Control and Optimization Research Platform in Xinjiang University.
文摘This paper is dedicated to fixed-time passivity and synchronization for multi-weighted spatiotemporal directed networks.First,to achieve fixed-time passivity,a type of decentralized power-law controller is developed,in which only one parameter needs to be adjusted in the power-law terms;this greatly decreases the inconvenience of parameter adjustment.Second,several fixed-time passivity criteria with LMI forms are derived by using a Gauss divergence theorem to deal with the spatial diffusion of nodes and by applying the Hölder’s inequality to dispose rigorously the power-law term greater than one in the designed control scheme;this improves the previous theoretical analysis.Additionally,the fixed-time synchronization of spatiotemporal directed networks with multi-weights is addressed as a direct result of fixed-time strict passivity.Finally,a numerical example is presented in order to show the validity of the theoretical analysis.
基金supported by the National Natural Science Foundation of China(Grant No.12302070)the Natural Science Foundation of Ningxia(Grant No.2024AAC05002)+1 种基金the Youth Science and Technology Talent Cultivation Project of Ningxiathe Ningxia Science and Technology Leading Talent Training Program(Grant No.2022GKLRLX04)。
文摘Neuromorphic circuits based on superconducting tunnel junctions have attracted much attention due to their highspeed computing capabilities and low energy consumption.Josephson junction circuits can effectively mimic biological neural dynamics.Leveraging these advantages,we construct a Josephson junction neuron-like model with a phasedependent dissipative current,referred to as a memristive current.The proposed memristive Josephson junction model exhibits complex dynamical behaviors.Furthermore,considering the effect of a fast-modulated synapse,we explore synchronization phenomena in coupled networks under varying coupling conductances and excitatory/inhibitory interactions.Finally,we extend the neuromorphic Josephson junction model—exhibiting complex dynamics—to the field of image encryption.These results not only enrich the understanding of the dynamical characteristics of memristive Josephson junctions but also provide a theoretical basis and technical support for the development of new neural networks and their applications in information security technology.
文摘Clock synchronization has important applications in multi-agent collaboration(such as drone light shows,intelligent transportation systems,and game AI),group decision-making,and emergency rescue operations.Synchronization method based on pulse-coupled oscillators(PCOs)provides an effective solution for clock synchronization in wireless networks.However,the existing clock synchronization algorithms in multi-agent ad hoc networks are difficult to meet the requirements of high precision and high stability of synchronization clock in group cooperation.Hence,this paper constructs a network model,named DAUNet(unsupervised neural network based on dual attention),to enhance clock synchronization accuracy in multi-agent wireless ad hoc networks.Specifically,we design an unsupervised distributed neural network framework as the backbone,building upon classical PCO-based synchronization methods.This framework resolves issues such as prolonged time synchronization message exchange between nodes,difficulties in centralized node coordination,and challenges in distributed training.Furthermore,we introduce a dual-attention mechanism as the core module of DAUNet.By integrating a Multi-Head Attention module and a Gated Attention module,the model significantly improves information extraction capabilities while reducing computational complexity,effectively mitigating synchronization inaccuracies and instability in multi-agent ad hoc networks.To evaluate the effectiveness of the proposed model,comparative experiments and ablation studies were conducted against classical methods and existing deep learning models.The research results show that,compared with the deep learning networks based on DASA and LSTM,DAUNet can reduce the mean normalized phase difference(NPD)by 1 to 2 orders of magnitude.Compared with the attention models based on additive attention and self-attention mechanisms,the performance of DAUNet has improved by more than ten times.This study demonstrates DAUNet’s potential in advancing multi-agent ad hoc networking technologies.
文摘To realize the data synchronization between the inertial measurement unit （IMU） and the global positioning system （GPS）, the synchronization technology in the IMU/GPS integrated measurement system of vehicle motion parameters is studied. According to the characteristics of the output signals of the IMU and the GPS, without the IMU synchronization signal, the synchronization circuit based on CPLD is designed and developed, which need not alter the configurations of the IMU and GPS. Experiments of measuring vehicle motion parameters, which rely on the synchronization circuit to realize IMU/GPS data synchronization, are made. The driving routes in experiments comprise a curve and a straight line. Experimental results show that the designed circuit can accurately measure the synchronization time difference and the IMU period, and can effectively solve the data synchronization in IMU/GPS integration. Furthermore, the IMU/GPS integrated measurement system based on the synchronization circuit can measure and calculate many vehicle motion parameters in high frequency mode.
