A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparis...A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.展开更多
A distributed fiber sensor was fabricated by splicing two single-mode fibers(SMFs)using the few-mode fiber(FMF)technique.A Brillouin optical time domain analysis(BOTDA)system was developed to measure the sensor’s tem...A distributed fiber sensor was fabricated by splicing two single-mode fibers(SMFs)using the few-mode fiber(FMF)technique.A Brillouin optical time domain analysis(BOTDA)system was developed to measure the sensor’s temperature and bending performance.Two-mode and four-mode step FMFs were combined to splice the few-mode segment.The results indicate that the temperature response coefficients of the few-mode segment are only slightly higher than those of the connected single-mode segment,measuring at 1.13 MHz/℃and 1.12 MHz/℃,respectively.The minimum bending radius for the sensor is 0.9 cm,and the four-mode bending response curve is superior to that of the two-mode one,proving that 4-SI-FMF offers better bending sensitivity.展开更多
In response to the requirements for large-scale device access and ultra-reliable and low-latency communication in the power internet of things,unmanned aerial vehicle-assisted multi-access edge computing can be used t...In response to the requirements for large-scale device access and ultra-reliable and low-latency communication in the power internet of things,unmanned aerial vehicle-assisted multi-access edge computing can be used to realize flexible access to power services and update large amounts of information in a timely manner.By considering factors such as machine communication traffic,MAC competition access,and information freshness,this paper develops a cross-layer computing framework in which the peak Age of Information(Ao I)provides a statistical delay boundary in the finite blocklength regime.We also propose a deep machine learning-based multi-access edge computing offloading algorithm.First,a traffic arrival model is established in which the time interval follows the Beta distribution,and then a business service model is proposed based on the carrier sense multiple access with collision avoidance algorithm.The peak Ao I boundary performance of multiple access is evaluated according to stochastic network calculus theory.Finally,an unmanned aerial vehicle-assisted multilevel offloading model with cache is designed,in which the peak Ao I violation probability and energy consumption provide the optimization goals.The optimal offloading strategy is obtained using deep reinforcement learning.Compared with baseline schemes based on non-cooperative game theory with stochastic learning automata and random edge unloading,the proposed algorithm improves the overall performance by approximately 3.52%and 20.73%,respectively,and provides superior deterministic offloading performance by using the peak Ao I boundary.展开更多
Atmospheric effects have significant influence on the performance of a free-space optical continuous variable quantum key distribution(CVQKD)system.In this paper,we investigate how the transmittance,excess noise and i...Atmospheric effects have significant influence on the performance of a free-space optical continuous variable quantum key distribution(CVQKD)system.In this paper,we investigate how the transmittance,excess noise and interruption probability caused by atmospheric effects affect the secret-key rate(SKR)of the CVQKD.Three signal wavelengths,two weather conditions,two detection schemes,and two types of attacks are considered in our investigation.An expression aims at calculating the interruption probability is proposed based on the Kolmogorov spectrum model.The results show that a signal using long working wavelength can propagate much further than that of using short wavelength.Moreover,as the wavelength increases,the influence of interruption probability on the SKR becomes more significant,especially within a certain transmission distance.Therefore,interruption probability must be considered for CVQKD by using long-signal wavelengths.Furthermore,different detection schemes used by the receiver will result in different transmission distances when subjected to individual attacks and collective attacks,respectively.展开更多
Collaborative vehicular networks is a key enabler to meet the stringent ultra-reliable and lowlatency communications(URLLC)requirements.A user vehicle(UV)dynamically optimizes task offloading by exploiting its collabo...Collaborative vehicular networks is a key enabler to meet the stringent ultra-reliable and lowlatency communications(URLLC)requirements.A user vehicle(UV)dynamically optimizes task offloading by exploiting its collaborations with edge servers and vehicular fog servers(VFSs).However,the optimization of task offloading in highly dynamic collaborative vehicular networks faces several challenges such as URLLC guaranteeing,incomplete information,and dimensionality curse.In this paper,we first characterize URLLC in terms of queuing delay bound violation and high-order statistics of excess backlogs.Then,a Deep Reinforcement lEarning-based URLLCAware task offloading algorithM named DREAM is proposed to maximize the throughput of the UVs while satisfying the URLLC constraints in a besteffort way.Compared with existing task offloading algorithms,DREAM achieves superior performance in throughput,queuing delay,and URLLC.展开更多
A dual-guided photonic crystal fiber(PCF) with low and flattened dispersion is designed, which can support a large number of orbital angular momentum(OAM) modes. The properties of the proposed PCF are systematically a...A dual-guided photonic crystal fiber(PCF) with low and flattened dispersion is designed, which can support a large number of orbital angular momentum(OAM) modes. The properties of the proposed PCF are systematically analyzed through the finite element method. The results show that the proposed PCF can support up to 84 OAM modes with 600 nm bandwidth ranging from 1000 to1600 nm. All values of mode purity are above 91.7%, the isolation parameters are larger than 67 dB and the maximum value up to 145 dB, the lowest confinement loss is only 5×10^(-13) dB·m^(-1).More importantly, the values of dispersion for all modes are less than 40 ps·km-1·nm-1, and the lowest dispersion variation is only 0.7 ps·km^(-1)·nm^(-1). These superior optical properties make the proposed PCF have great advantage in stable transmissions of data and long-distance optical fiber communication system with large capacity.展开更多
MIMO technique can provide higher information throughput and transmission reliability for the PLC system.However,the MIMO-PLC system based on three-conductor cable has a high correlation among its sub-channels.Spatial...MIMO technique can provide higher information throughput and transmission reliability for the PLC system.However,the MIMO-PLC system based on three-conductor cable has a high correlation among its sub-channels.Spatial multiplexing technology will be affected by the spatial correlation between MIMO-PLC sub-channels.To reduce the system bit error rate caused by MIMO-PLC correlation among sub-channels,this paper proposed a phase rotation precoding scheme for the 2×2 closed-loop MIMO-PLC system.According to the channel transfer function of high correlation MIMO-PLC system,the phase rotation precoding matrix F is calculated,and the transmission signal matrix S is modulated with the F,the code distance at the receiving point with smallest code distance is increased by phase rotation.Simulation results show that the scheme can effectively reduce the bit error rate of the 2×2 MIMO-PLC system based on ML detection,and significantly improve the system performance.展开更多
To solve the problems of small signal intensity and low signal-to-noise ratio(SNR)in single-ended Brillouin optical time domain analysis(BOTDA)system based on Fresnel reflection,we propose and experimentally demonstra...To solve the problems of small signal intensity and low signal-to-noise ratio(SNR)in single-ended Brillouin optical time domain analysis(BOTDA)system based on Fresnel reflection,we propose and experimentally demonstrate a pulse coding single-ended BOTDA system,which can improve the SNR and temperature measurement accuracy.A single-ended BOTDA temperature sensing system using single pulse and pulse coding is designed,and the Brillouin time domain signal and Brillouin frequency shift under different pulse coding bits are measured.The experimental results show that the fluctuations of Brillouin power and Brillouin frequency shift are gradually decreased with the increase of pulse coding bits,and the SNR under 32 bit Golay coding offers a 6.18 d B improvement with respect to traditional single pulse system.And the temperature measurement accuracy under 32 bit coding over a 9.35-km-long sensing fiber can be accurately measured as 1.59℃,while providing a 1.73℃ enhancement when compared to single pulse system.展开更多
In this paper,the influence of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection wavelength scanning Brillouin optical time domain reflectometer(WS-BOTDR)is theoretic...In this paper,the influence of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection wavelength scanning Brillouin optical time domain reflectometer(WS-BOTDR)is theoretically analyzed,and a local heterodyne detection WS-BOTDR system is built for experimental verification.The experimental results show that with the increase of sensing distance,the adverse effect of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection WS-BOTDR is gradually aggravated,which will lead to the broadening and distortion of the wavelength power spectrum(WPS),resulting in large errors in demodulated Brillouin central wavelength(BCW)and temperature.The average temperature measurement errors at the positions of 1 km,5 km,9 km non-heating section and 9.45 km heating section are 1.76℃,3.42℃,3.89℃and 4.3℃,respectively.展开更多
Intelligent reflecting surface(IRS) is regarded as a promising technology because it can achieve higher passive beamforming gain. In particular, the IRS assisted simultaneous wireless information and power transfer(SW...Intelligent reflecting surface(IRS) is regarded as a promising technology because it can achieve higher passive beamforming gain. In particular, the IRS assisted simultaneous wireless information and power transfer(SWIPT) system can make the information decoding receivers(IDRs) have a higher signal-to-noise ratio(SNR), and the energy harvesting receivers(EHRs) have the guarantee of minimum harvested energy threshold. Motivated by the above,in this paper, we use the power splitting(PS) at the user and introduce artificial noise(AN) into the access point(AP), so that the user in system can harvest energy and decode information simultaneously,further improve the security of user. We jointly optimize the beamforming matrix at AP, the reflection phase shift at IRS and the PS ratio, in order to maximize the user’s achievable secrecy rate, subject to the user’s minimum harvested energy threshold and AP’s transmission power. Due to the introduction of PS ratio, the coupling between variables is increased,and the complexity of the problem is significantly increased. Furthermore, the problem is non-convex, so we propose an efficient algorithm based on Taylor Formula, semi-definite relaxation(SDR) and alternating optimization(AO) to get the solution. Numerical results show that the proposed IRS-SWIPT system with PS and AN achieves significant performance improvement compared with other benchmark scheme.展开更多
Multi-mode power internet of things(PIoT)combines various communication media to provide spatio-temporal coverage for low-carbon operation in smart park.Edge-end collaboration is feasible to achieve the full utilizati...Multi-mode power internet of things(PIoT)combines various communication media to provide spatio-temporal coverage for low-carbon operation in smart park.Edge-end collaboration is feasible to achieve the full utilization of heterogeneous resources and anti-eavesdropping.However,edge-end collaboration-based multi-mode PIoT faces challenges of mutual contradiction in communication and security quality of service(QoS)guarantee,inadaptability of resource management,and multi-mode access conflict.We propose an Adaptive learning based delAysensitive and seCure Edge-End Collaboration algorithm(ACE_(2))to optimize multi-mode channel selection and split device power into artificial noise(AN)transmission and data transmission for secure data delivery.ACE_(2) can achieve multi-attribute QoS guarantee,adaptive resource management and security enhancement,and access conflict elimination with the combined power of deep actor-critic(DAC),“win or learn fast(WoLF)”mechanism,and edge-end collaboration.Simulations demonstrate its superior performance in queuing delay,energy consumption,secrecy capacity,and adaptability to differentiated low-carbon services.展开更多
Hybrid networking of power line and wireless communication can complement each other,save construction costs,improve network robustness,and has important value on the Internet of Things and smart grid.For power line a...Hybrid networking of power line and wireless communication can complement each other,save construction costs,improve network robustness,and has important value on the Internet of Things and smart grid.For power line and wireless dual-interface devices,a media access control(MAC)layer algorithm for hybrid communication is proposed,in which the stations can compete for two channels simultaneously.When a station obtains two channels at the same time,the station will randomly select a channel for transmission to ensure fairness,and reset the counters when the transmission is successful.In this paper,the performance of the unsaturated traffic model and counter spatial division is considered,and the throughput under coupling conditions is obtained.Finally,the simulation results show that the MAC layer algorithm based on the hybrid communication network can make full use of the advantages of the two channels,improve system throughput,and reduce transmission delay.展开更多
Long-term exposure to moisture leads to a gradual deterioration of performance and reduced service life of glass fibre-reinforced epoxy resin(GFRP)material in composite insulators.Therefore,it is necessary to analyse ...Long-term exposure to moisture leads to a gradual deterioration of performance and reduced service life of glass fibre-reinforced epoxy resin(GFRP)material in composite insulators.Therefore,it is necessary to analyse the moisture absorption characteristics of GFRP material and the evolution of damage to their internal interface properties.Moisture absorption tests on GFRP rod material used in composite insulators to obtain their three-dimensional diffusion coefficients are conducted.Atomic force microscopy was then employed to obtain the composite material system's fibre/matrix interfacial phase parameters.Furthermore,a finite element model incorporating representative volume elements with interfacial phases and a mesoscale transient moisture absorption finite element model for the composite material was established.Finally,the moisture absorption characteristics of GFRP material and the evolution of damage to the interfacial phase under thermal-humidity cycling conditions were investigated.The results showed that the diffusion coefficient along the fibre direction in GFRP material was higher than that in the perpendicular direction.The moisture diffusion finite element model,incorporating an anisotropic interfacial phase,fitted the anisotropic diffusion coefficients of GFRP material more accurately.As moisture invaded the GFRP material,the mismatch stresses continuously increased during the moisture absorption.Moreover,the non-uniform arrangement of fibres resulted in uneven distribution of moistureinduced stresses inside the material,leading to higher mismatch stresses in areas with dense fibre arrangements in the matrix.Prolonged high and low humidity cycles led to the development of micro-cracks,micro-porosity,and interface debonding along the fibre direction at the GFRP material interfaces,thereby affecting the anisotropic moisture absorption characteristics of the material.The findings of this study provide valuable insights into the mechanisms underlying the deterioration of GFRP material in composite insulator rods due to moisture degradation.展开更多
Facial attribute editing has mainly two objectives:1)translating image from a source domain to a target one,and 2)only changing the facial regions related to a target attribute and preserving the attribute-excluding d...Facial attribute editing has mainly two objectives:1)translating image from a source domain to a target one,and 2)only changing the facial regions related to a target attribute and preserving the attribute-excluding details.In this work,we propose a multi-attention U-Net-based generative adversarial network(MU-GAN).First,we replace a classic convolutional encoder-decoder with a symmetric U-Net-like structure in a generator,and then apply an additive attention mechanism to build attention-based U-Net connections for adaptively transferring encoder representations to complement a decoder with attribute-excluding detail and enhance attribute editing ability.Second,a self-attention(SA)mechanism is incorporated into convolutional layers for modeling long-range and multi-level dependencies across image regions.Experimental results indicate that our method is capable of balancing attribute editing ability and details preservation ability,and can decouple the correlation among attributes.It outperforms the state-of-the-art methods in terms of attribute manipulation accuracy and image quality.Our code is available at https://github.com/SuSir1996/MU-GAN.展开更多
A simple and inexpensive sensing structure,single mode fiber(SMF)alignment fusion to 62.5μm stepped index-multimode fiber(SI-MMF),combined with Brillouin optical time domain reflectometry(BOTDR)system,is used as a di...A simple and inexpensive sensing structure,single mode fiber(SMF)alignment fusion to 62.5μm stepped index-multimode fiber(SI-MMF),combined with Brillouin optical time domain reflectometry(BOTDR)system,is used as a distributed sensor in the field of structural safety and health monitoring(SSHM)of large infrastructures in terms of its prominent bending resistance.The bend loss principle and influencing factors of the fiber are analyzed,and the bending resistances of different fibers are discussed on the basis of theoretical and experimental comparisons.The bend-tolerant capacity and temperature sensing characteristics of the 5 km sensing structure are measured by using the self-developed frequency-shifted local heterodyne BOTDR system.The results show that the proposed sensing structure has excellent bend-tolerant capacity with a minimum bend radius and temperature measurement error of 1.25 mm and 0.69℃,respectively,which indicates that the proposed sensing structure has huge potential in the field of SSHM of large infrastructures.展开更多
At present,observing the temperature rise of composite insulators is an effective method for the detection of decay-like defects.However,ambient humidity will affect the temperature rise of composite insulators,which ...At present,observing the temperature rise of composite insulators is an effective method for the detection of decay-like defects.However,ambient humidity will affect the temperature rise of composite insulators,which will cause problems in screening the decaylike composite insulators.Therefore,it is urgent to study the temperature rise principle of decay-like insulators and find out the influence mechanism of humidity on temperature rise.In this study,a four-electrode system is designed to measure the surface current,volume current and interface current of the decay-like short sample and the intact short sample under different humidity.Then the equivalent circuit models of short samples and the 500 kV full-size decay-like composite insulator are built to analyse the contribution rates of leakage conductance loss and polarisation loss to temperature rise.The results show that the contribution rates of the polarisation loss to the temperature rise of two samples are 35.8%and 23.6%in low humidity,while they are 98.3%and 64.4%in high humidity.For the full-size decay-like composite insulator,the contribution rates of polarisation loss to its temperature rise in high or low humidity are more than 99%.In addition,the proportion of polarisation loss increases at first and then decreases with the increase of the length of the decay-like section.The conclusions of this study provide a theoretical basis for further understanding the corresponding relationship between decaylike defects and temperature rise and improve the detection rate of decay-like insulators.展开更多
Time-varying channel modeling plays an important role for many applications in time-variant scenarios,while most clustering algorithms focus on static channels and cannot accurately model the channel time-evolution pr...Time-varying channel modeling plays an important role for many applications in time-variant scenarios,while most clustering algorithms focus on static channels and cannot accurately model the channel time-evolution properties.In this paper,a fuzzy clustering algorithm based on multipath component(MPC)trajectory is proposed.Firstly,both the distance and velocity similarities of the MPCs in different snapshots are taken into account to track the MPC trajectory,in which the fuzzy scheme and a kernel function are used to calculate the distance and velocity similarities,respectively.Secondly,a fuzzy MPC trajectory clustering algorithm is proposed to cluster the MPCs in multiple snapshots.The MPCs in a snapshot are clustered according to the membership,which is defined as the probability that a MPC belongs to different clusters.Finally,time-varying channels at 28 GHz are simulated to validate the performance of our proposed algorithm.The results show that our proposed algorithm is able to accurately identify the clusters in time-varying channels compared with the existing clustering algorithms.展开更多
The signal is subjected to lots of interferences in vehicle-to-vehicle(V2V)channel propagation,resulting in receiving error codes.Two-dimensional(2D)and three-dimensional(3D)geometrical channel models are used to depi...The signal is subjected to lots of interferences in vehicle-to-vehicle(V2V)channel propagation,resulting in receiving error codes.Two-dimensional(2D)and three-dimensional(3D)geometrical channel models are used to depict the wideband V2V multiple-input multiple-output(MIMO)channels.Using the channel model,Turbo code and low-density parity-check(LDPC)code are investigated for wideband V2V MIMO system,and the encoding and the decoding schemes are investigated.The bit error rate(BER),channel capacity and outage probability of wideband V2V MIMO system using Turbo code and LDPC code are analyzed at different typical speeds.The results show that the performance of wideband V2V MIMO system using Turbo code outperform that using LDPC code.The performance is affected by transmitting and receiving speeds with the same coding scheme.And the channel capacity of the 3D channel is larger than that of 2D channel.展开更多
A geometry-based stochastic model(GBSM) for unmanned aerial vehicle to vehicle(UAV-V) multiple-input multiple-output(MIMO) wideband channel is proposed to investigate the characteristics of UAV-V channel. Based on the...A geometry-based stochastic model(GBSM) for unmanned aerial vehicle to vehicle(UAV-V) multiple-input multiple-output(MIMO) wideband channel is proposed to investigate the characteristics of UAV-V channel. Based on the proposed model, a three-dimensional(3D) wideband channel matrix regarding channel numbers, time and delay is constructed. And some important channel characteristics parameters, such as power delay profile(PDP), root mean square(RMS) delay spread, RMS Doppler spread, channel gain and Doppler power spectral density(PSD) are investigated with different vehicle velocities. It is much simpler and clearer compared with the complex analytical derivations. The results are compared with validated analysis to confirm the theoretical analysis.展开更多
Considering the significant expenses and power requirements associated with digital precoding and the low spectral efficiency(SE)of analog precoding,a hybrid precoding algorithm with efficient finite-resolution phase ...Considering the significant expenses and power requirements associated with digital precoding and the low spectral efficiency(SE)of analog precoding,a hybrid precoding algorithm with efficient finite-resolution phase shifters(PSs),named FRPS algorithm,was proposed for millimeter wave(mmWave)massive multi-input multi-output(MIMO)vehicle-to-vehicle(V2V)system.Digital and analog precoding matrix variables and non-convex constraints of the radio frequency(RF)precoder are decomposed into two independent optimization problems.Discrete iterative optimization is employed to solve for the analog and digital precoder alternately.In addition,the effect of finite-resolution PSs is considered in the precoding algorithm optimization.Simulation results show that the FRPS algorithm has a fast convergence speed,and it can approach the SE of fully digital precoding with only 3 bit resolution PS.The performance difference between the FRPS algorithm and the existing hybrid precoding algorithm with infinite-resolution PSs is almost negligible.Moreover,the FRPS algorithm performs superior to that of the infinite-resolution PS hybrid precoding algorithm and fully digital precoding algorithm.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No.11905076)S&T Program of Hebei (Grant No.SZX2020034)。
文摘A novel emissive probe consisting of an oxide cathode coating is developed to achieve a low operating temperature and long service life.The properties of the novel emissive probe are investigated in detail,in comparison with a traditional tungsten emissive probe,including the operating temperature,the electron emission capability and the plasma potential measurement.Studies of the operating temperature and electron emission capability show that the tungsten emissive probe usually works at a temperature of 1800 K-2200 K while the oxide cathode emissive probe can function at about 1200 K-1400 K.In addition,plasma potential measurements using the oxide cathode emissive probe with different techniques have been accomplished in microwave electron cyclotron resonance plasmas with different discharge powers.It is found that a reliable plasma potential can be obtained using the improved inflection point method and the hot probe with zero emission limit method,while the floating point method is invalid for the oxide cathode emissive probe.
基金supported by the National Science Foundation for Distinguished Young Scholars(No.62205105)the National Natural Science Foundation of China(Nos.61775057,52177141 and 62171185)。
文摘A distributed fiber sensor was fabricated by splicing two single-mode fibers(SMFs)using the few-mode fiber(FMF)technique.A Brillouin optical time domain analysis(BOTDA)system was developed to measure the sensor’s temperature and bending performance.Two-mode and four-mode step FMFs were combined to splice the few-mode segment.The results indicate that the temperature response coefficients of the few-mode segment are only slightly higher than those of the connected single-mode segment,measuring at 1.13 MHz/℃and 1.12 MHz/℃,respectively.The minimum bending radius for the sensor is 0.9 cm,and the four-mode bending response curve is superior to that of the two-mode one,proving that 4-SI-FMF offers better bending sensitivity.
基金supported in part by the National Natural Science Foundation of China(Nos.61601182)in part by the Fundamental Research Funds for the Central Universities under Grant 2023MS113。
文摘In response to the requirements for large-scale device access and ultra-reliable and low-latency communication in the power internet of things,unmanned aerial vehicle-assisted multi-access edge computing can be used to realize flexible access to power services and update large amounts of information in a timely manner.By considering factors such as machine communication traffic,MAC competition access,and information freshness,this paper develops a cross-layer computing framework in which the peak Age of Information(Ao I)provides a statistical delay boundary in the finite blocklength regime.We also propose a deep machine learning-based multi-access edge computing offloading algorithm.First,a traffic arrival model is established in which the time interval follows the Beta distribution,and then a business service model is proposed based on the carrier sense multiple access with collision avoidance algorithm.The peak Ao I boundary performance of multiple access is evaluated according to stochastic network calculus theory.Finally,an unmanned aerial vehicle-assisted multilevel offloading model with cache is designed,in which the peak Ao I violation probability and energy consumption provide the optimization goals.The optimal offloading strategy is obtained using deep reinforcement learning.Compared with baseline schemes based on non-cooperative game theory with stochastic learning automata and random edge unloading,the proposed algorithm improves the overall performance by approximately 3.52%and 20.73%,respectively,and provides superior deterministic offloading performance by using the peak Ao I boundary.
基金Project supported by the National Natural Science Foundation of China(Grant No.62071180)Fundamental Research Funds for the Central Universities,China(Grant No.2020MS099)。
文摘Atmospheric effects have significant influence on the performance of a free-space optical continuous variable quantum key distribution(CVQKD)system.In this paper,we investigate how the transmittance,excess noise and interruption probability caused by atmospheric effects affect the secret-key rate(SKR)of the CVQKD.Three signal wavelengths,two weather conditions,two detection schemes,and two types of attacks are considered in our investigation.An expression aims at calculating the interruption probability is proposed based on the Kolmogorov spectrum model.The results show that a signal using long working wavelength can propagate much further than that of using short wavelength.Moreover,as the wavelength increases,the influence of interruption probability on the SKR becomes more significant,especially within a certain transmission distance.Therefore,interruption probability must be considered for CVQKD by using long-signal wavelengths.Furthermore,different detection schemes used by the receiver will result in different transmission distances when subjected to individual attacks and collective attacks,respectively.
基金This work was partially supported by the Open Funding of the Shaanxi Key Laboratory of Intelligent Processing for Big Energy Data under Grant Number IPBED3supported by the National Natural Science Foundation of China(NSFC)under Grant Number 61971189supported by the Fundamental Research Funds for the Central Universities under Grant Number 2020MS001.
文摘Collaborative vehicular networks is a key enabler to meet the stringent ultra-reliable and lowlatency communications(URLLC)requirements.A user vehicle(UV)dynamically optimizes task offloading by exploiting its collaborations with edge servers and vehicular fog servers(VFSs).However,the optimization of task offloading in highly dynamic collaborative vehicular networks faces several challenges such as URLLC guaranteeing,incomplete information,and dimensionality curse.In this paper,we first characterize URLLC in terms of queuing delay bound violation and high-order statistics of excess backlogs.Then,a Deep Reinforcement lEarning-based URLLCAware task offloading algorithM named DREAM is proposed to maximize the throughput of the UVs while satisfying the URLLC constraints in a besteffort way.Compared with existing task offloading algorithms,DREAM achieves superior performance in throughput,queuing delay,and URLLC.
基金the Fundamental Research Funds for the Central Universities(2020YJ005,2021MS072,2019MS085)the Natural Science Foundation of Hebei Province(E2019502177,E2020502010)the National Natural Science Foundation of China(51607066,61775057)。
文摘A dual-guided photonic crystal fiber(PCF) with low and flattened dispersion is designed, which can support a large number of orbital angular momentum(OAM) modes. The properties of the proposed PCF are systematically analyzed through the finite element method. The results show that the proposed PCF can support up to 84 OAM modes with 600 nm bandwidth ranging from 1000 to1600 nm. All values of mode purity are above 91.7%, the isolation parameters are larger than 67 dB and the maximum value up to 145 dB, the lowest confinement loss is only 5×10^(-13) dB·m^(-1).More importantly, the values of dispersion for all modes are less than 40 ps·km-1·nm-1, and the lowest dispersion variation is only 0.7 ps·km^(-1)·nm^(-1). These superior optical properties make the proposed PCF have great advantage in stable transmissions of data and long-distance optical fiber communication system with large capacity.
基金supported by the National Natural Science Foundation of China (No.62001166)supported by the Natural Science Foundation of Hebei Province of China (E2019502186,F2019201362)supported by the Fundamental Research Funds for the Central Universities (2021MS073)。
文摘MIMO technique can provide higher information throughput and transmission reliability for the PLC system.However,the MIMO-PLC system based on three-conductor cable has a high correlation among its sub-channels.Spatial multiplexing technology will be affected by the spatial correlation between MIMO-PLC sub-channels.To reduce the system bit error rate caused by MIMO-PLC correlation among sub-channels,this paper proposed a phase rotation precoding scheme for the 2×2 closed-loop MIMO-PLC system.According to the channel transfer function of high correlation MIMO-PLC system,the phase rotation precoding matrix F is calculated,and the transmission signal matrix S is modulated with the F,the code distance at the receiving point with smallest code distance is increased by phase rotation.Simulation results show that the scheme can effectively reduce the bit error rate of the 2×2 MIMO-PLC system based on ML detection,and significantly improve the system performance.
基金supported by the Natural Science Foundation of Hebei Province of China(No.F2019502112)the National Natural Science Foundation of China(No.61775057)the Fundamental Research Funds for the Central Universities(No.2019MS086)。
文摘To solve the problems of small signal intensity and low signal-to-noise ratio(SNR)in single-ended Brillouin optical time domain analysis(BOTDA)system based on Fresnel reflection,we propose and experimentally demonstrate a pulse coding single-ended BOTDA system,which can improve the SNR and temperature measurement accuracy.A single-ended BOTDA temperature sensing system using single pulse and pulse coding is designed,and the Brillouin time domain signal and Brillouin frequency shift under different pulse coding bits are measured.The experimental results show that the fluctuations of Brillouin power and Brillouin frequency shift are gradually decreased with the increase of pulse coding bits,and the SNR under 32 bit Golay coding offers a 6.18 d B improvement with respect to traditional single pulse system.And the temperature measurement accuracy under 32 bit coding over a 9.35-km-long sensing fiber can be accurately measured as 1.59℃,while providing a 1.73℃ enhancement when compared to single pulse system.
基金supported by the National Natural Science Foundation of China(Nos.52177141,62171185 and 61775057)the Natural Science Foundation of Hebei Province of China(Nos.F2019502112 and E2020502010)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.2019MS086 and 2017MS112)the S&T Program of Hebei,China(No.SZX2020034)。
文摘In this paper,the influence of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection wavelength scanning Brillouin optical time domain reflectometer(WS-BOTDR)is theoretically analyzed,and a local heterodyne detection WS-BOTDR system is built for experimental verification.The experimental results show that with the increase of sensing distance,the adverse effect of laser wavelength instability,polarization fading and phase fluctuation on local heterodyne detection WS-BOTDR is gradually aggravated,which will lead to the broadening and distortion of the wavelength power spectrum(WPS),resulting in large errors in demodulated Brillouin central wavelength(BCW)and temperature.The average temperature measurement errors at the positions of 1 km,5 km,9 km non-heating section and 9.45 km heating section are 1.76℃,3.42℃,3.89℃and 4.3℃,respectively.
基金supported by the National Natural Science Foundation of China (No. 61971190)the Fundamental Research Funds for the Central Universities (No. 2019 MS089)+1 种基金the Hebei Province Natural Science Foundation (No. F2016502062)the Beijing Natural Science Foundation (No. 4164101)。
文摘Intelligent reflecting surface(IRS) is regarded as a promising technology because it can achieve higher passive beamforming gain. In particular, the IRS assisted simultaneous wireless information and power transfer(SWIPT) system can make the information decoding receivers(IDRs) have a higher signal-to-noise ratio(SNR), and the energy harvesting receivers(EHRs) have the guarantee of minimum harvested energy threshold. Motivated by the above,in this paper, we use the power splitting(PS) at the user and introduce artificial noise(AN) into the access point(AP), so that the user in system can harvest energy and decode information simultaneously,further improve the security of user. We jointly optimize the beamforming matrix at AP, the reflection phase shift at IRS and the PS ratio, in order to maximize the user’s achievable secrecy rate, subject to the user’s minimum harvested energy threshold and AP’s transmission power. Due to the introduction of PS ratio, the coupling between variables is increased,and the complexity of the problem is significantly increased. Furthermore, the problem is non-convex, so we propose an efficient algorithm based on Taylor Formula, semi-definite relaxation(SDR) and alternating optimization(AO) to get the solution. Numerical results show that the proposed IRS-SWIPT system with PS and AN achieves significant performance improvement compared with other benchmark scheme.
基金supported by the Science and Technology Project of State Grid Corporation of China under Grant Number 52094021N010 (5400202199534A-0-5-ZN)
文摘Multi-mode power internet of things(PIoT)combines various communication media to provide spatio-temporal coverage for low-carbon operation in smart park.Edge-end collaboration is feasible to achieve the full utilization of heterogeneous resources and anti-eavesdropping.However,edge-end collaboration-based multi-mode PIoT faces challenges of mutual contradiction in communication and security quality of service(QoS)guarantee,inadaptability of resource management,and multi-mode access conflict.We propose an Adaptive learning based delAysensitive and seCure Edge-End Collaboration algorithm(ACE_(2))to optimize multi-mode channel selection and split device power into artificial noise(AN)transmission and data transmission for secure data delivery.ACE_(2) can achieve multi-attribute QoS guarantee,adaptive resource management and security enhancement,and access conflict elimination with the combined power of deep actor-critic(DAC),“win or learn fast(WoLF)”mechanism,and edge-end collaboration.Simulations demonstrate its superior performance in queuing delay,energy consumption,secrecy capacity,and adaptability to differentiated low-carbon services.
基金supported in part by the National Natural Science Foundation of China (Nos. 61601182)in part Natural Science Foundation of Hebei Province (F2017502059)in part by the Fundamental Research Funds for the Central Universities under Grant 2021MS070
文摘Hybrid networking of power line and wireless communication can complement each other,save construction costs,improve network robustness,and has important value on the Internet of Things and smart grid.For power line and wireless dual-interface devices,a media access control(MAC)layer algorithm for hybrid communication is proposed,in which the stations can compete for two channels simultaneously.When a station obtains two channels at the same time,the station will randomly select a channel for transmission to ensure fairness,and reset the counters when the transmission is successful.In this paper,the performance of the unsaturated traffic model and counter spatial division is considered,and the throughput under coupling conditions is obtained.Finally,the simulation results show that the MAC layer algorithm based on the hybrid communication network can make full use of the advantages of the two channels,improve system throughput,and reduce transmission delay.
基金Hebei Provincial Department of Education Funding Project for Cultivating Innovation Ability of Postgraduate Students,Grant/Award Number:CXZZBS2024168Natural Science Foundation of Hebei Province,Grant/Award Number:E2021502025。
文摘Long-term exposure to moisture leads to a gradual deterioration of performance and reduced service life of glass fibre-reinforced epoxy resin(GFRP)material in composite insulators.Therefore,it is necessary to analyse the moisture absorption characteristics of GFRP material and the evolution of damage to their internal interface properties.Moisture absorption tests on GFRP rod material used in composite insulators to obtain their three-dimensional diffusion coefficients are conducted.Atomic force microscopy was then employed to obtain the composite material system's fibre/matrix interfacial phase parameters.Furthermore,a finite element model incorporating representative volume elements with interfacial phases and a mesoscale transient moisture absorption finite element model for the composite material was established.Finally,the moisture absorption characteristics of GFRP material and the evolution of damage to the interfacial phase under thermal-humidity cycling conditions were investigated.The results showed that the diffusion coefficient along the fibre direction in GFRP material was higher than that in the perpendicular direction.The moisture diffusion finite element model,incorporating an anisotropic interfacial phase,fitted the anisotropic diffusion coefficients of GFRP material more accurately.As moisture invaded the GFRP material,the mismatch stresses continuously increased during the moisture absorption.Moreover,the non-uniform arrangement of fibres resulted in uneven distribution of moistureinduced stresses inside the material,leading to higher mismatch stresses in areas with dense fibre arrangements in the matrix.Prolonged high and low humidity cycles led to the development of micro-cracks,micro-porosity,and interface debonding along the fibre direction at the GFRP material interfaces,thereby affecting the anisotropic moisture absorption characteristics of the material.The findings of this study provide valuable insights into the mechanisms underlying the deterioration of GFRP material in composite insulator rods due to moisture degradation.
基金supported in part by the National Natural Science Foundation of China(NSFC)(62076093,61871182,61302163,61401154)the Beijing Natural Science Foundation(4192055)+3 种基金the Natural Science Foundation of Hebei Province of China(F2015502062,F2016502101,F2017502016)the Fundamental Research Funds for the Central Universities(2020YJ006,2020MS099)the Open Project Program of the National Laboratory of Pattern Recognition(NLPR)(201900051)The authors gratefully acknowledge the support of NVIDIA Corporation with the donation of the GPU used for this research.
文摘Facial attribute editing has mainly two objectives:1)translating image from a source domain to a target one,and 2)only changing the facial regions related to a target attribute and preserving the attribute-excluding details.In this work,we propose a multi-attention U-Net-based generative adversarial network(MU-GAN).First,we replace a classic convolutional encoder-decoder with a symmetric U-Net-like structure in a generator,and then apply an additive attention mechanism to build attention-based U-Net connections for adaptively transferring encoder representations to complement a decoder with attribute-excluding detail and enhance attribute editing ability.Second,a self-attention(SA)mechanism is incorporated into convolutional layers for modeling long-range and multi-level dependencies across image regions.Experimental results indicate that our method is capable of balancing attribute editing ability and details preservation ability,and can decouple the correlation among attributes.It outperforms the state-of-the-art methods in terms of attribute manipulation accuracy and image quality.Our code is available at https://github.com/SuSir1996/MU-GAN.
基金supported by the National Natural Science Foundation of China(Nos.61775057 and 51607066)the Natural Science Foundation of Hebei Province of China(Nos.F2019502112 and E2019502177)+1 种基金the Fundamental Research Funds for the Central Universities(Nos.2019MS086 and 2021MS071)the S&T Program of Hebei(No.SZX2020034)。
文摘A simple and inexpensive sensing structure,single mode fiber(SMF)alignment fusion to 62.5μm stepped index-multimode fiber(SI-MMF),combined with Brillouin optical time domain reflectometry(BOTDR)system,is used as a distributed sensor in the field of structural safety and health monitoring(SSHM)of large infrastructures in terms of its prominent bending resistance.The bend loss principle and influencing factors of the fiber are analyzed,and the bending resistances of different fibers are discussed on the basis of theoretical and experimental comparisons.The bend-tolerant capacity and temperature sensing characteristics of the 5 km sensing structure are measured by using the self-developed frequency-shifted local heterodyne BOTDR system.The results show that the proposed sensing structure has excellent bend-tolerant capacity with a minimum bend radius and temperature measurement error of 1.25 mm and 0.69℃,respectively,which indicates that the proposed sensing structure has huge potential in the field of SSHM of large infrastructures.
基金National Key Research and Development Program of China,Grant/Award Number:2018YFF01011900。
文摘At present,observing the temperature rise of composite insulators is an effective method for the detection of decay-like defects.However,ambient humidity will affect the temperature rise of composite insulators,which will cause problems in screening the decaylike composite insulators.Therefore,it is urgent to study the temperature rise principle of decay-like insulators and find out the influence mechanism of humidity on temperature rise.In this study,a four-electrode system is designed to measure the surface current,volume current and interface current of the decay-like short sample and the intact short sample under different humidity.Then the equivalent circuit models of short samples and the 500 kV full-size decay-like composite insulator are built to analyse the contribution rates of leakage conductance loss and polarisation loss to temperature rise.The results show that the contribution rates of the polarisation loss to the temperature rise of two samples are 35.8%and 23.6%in low humidity,while they are 98.3%and 64.4%in high humidity.For the full-size decay-like composite insulator,the contribution rates of polarisation loss to its temperature rise in high or low humidity are more than 99%.In addition,the proportion of polarisation loss increases at first and then decreases with the increase of the length of the decay-like section.The conclusions of this study provide a theoretical basis for further understanding the corresponding relationship between decaylike defects and temperature rise and improve the detection rate of decay-like insulators.
基金supported by the National Key Laboratory of Electromagnetic Environment(No.202101004)the National Nature Science of China(NSFC)(No.61931001),respectively。
文摘Time-varying channel modeling plays an important role for many applications in time-variant scenarios,while most clustering algorithms focus on static channels and cannot accurately model the channel time-evolution properties.In this paper,a fuzzy clustering algorithm based on multipath component(MPC)trajectory is proposed.Firstly,both the distance and velocity similarities of the MPCs in different snapshots are taken into account to track the MPC trajectory,in which the fuzzy scheme and a kernel function are used to calculate the distance and velocity similarities,respectively.Secondly,a fuzzy MPC trajectory clustering algorithm is proposed to cluster the MPCs in multiple snapshots.The MPCs in a snapshot are clustered according to the membership,which is defined as the probability that a MPC belongs to different clusters.Finally,time-varying channels at 28 GHz are simulated to validate the performance of our proposed algorithm.The results show that our proposed algorithm is able to accurately identify the clusters in time-varying channels compared with the existing clustering algorithms.
基金supported by the National Natural Science Foundation of China(62001166,62172139)the Open Subject of Hebei Key Laboratory of Power Internet of Things Technology(2023KFKT002)。
文摘The signal is subjected to lots of interferences in vehicle-to-vehicle(V2V)channel propagation,resulting in receiving error codes.Two-dimensional(2D)and three-dimensional(3D)geometrical channel models are used to depict the wideband V2V multiple-input multiple-output(MIMO)channels.Using the channel model,Turbo code and low-density parity-check(LDPC)code are investigated for wideband V2V MIMO system,and the encoding and the decoding schemes are investigated.The bit error rate(BER),channel capacity and outage probability of wideband V2V MIMO system using Turbo code and LDPC code are analyzed at different typical speeds.The results show that the performance of wideband V2V MIMO system using Turbo code outperform that using LDPC code.The performance is affected by transmitting and receiving speeds with the same coding scheme.And the channel capacity of the 3D channel is larger than that of 2D channel.
基金supported by the National Natural Science Foundation of China (62001166, 62172139)the Natural Science Foundation of Hebei Province of China(F2022201055)。
文摘A geometry-based stochastic model(GBSM) for unmanned aerial vehicle to vehicle(UAV-V) multiple-input multiple-output(MIMO) wideband channel is proposed to investigate the characteristics of UAV-V channel. Based on the proposed model, a three-dimensional(3D) wideband channel matrix regarding channel numbers, time and delay is constructed. And some important channel characteristics parameters, such as power delay profile(PDP), root mean square(RMS) delay spread, RMS Doppler spread, channel gain and Doppler power spectral density(PSD) are investigated with different vehicle velocities. It is much simpler and clearer compared with the complex analytical derivations. The results are compared with validated analysis to confirm the theoretical analysis.
基金supported by the S&T Program of Hebei Province(2023KFKT002)the Natural Science Foundation of Hebei Province of China(F2024201053)。
文摘Considering the significant expenses and power requirements associated with digital precoding and the low spectral efficiency(SE)of analog precoding,a hybrid precoding algorithm with efficient finite-resolution phase shifters(PSs),named FRPS algorithm,was proposed for millimeter wave(mmWave)massive multi-input multi-output(MIMO)vehicle-to-vehicle(V2V)system.Digital and analog precoding matrix variables and non-convex constraints of the radio frequency(RF)precoder are decomposed into two independent optimization problems.Discrete iterative optimization is employed to solve for the analog and digital precoder alternately.In addition,the effect of finite-resolution PSs is considered in the precoding algorithm optimization.Simulation results show that the FRPS algorithm has a fast convergence speed,and it can approach the SE of fully digital precoding with only 3 bit resolution PS.The performance difference between the FRPS algorithm and the existing hybrid precoding algorithm with infinite-resolution PSs is almost negligible.Moreover,the FRPS algorithm performs superior to that of the infinite-resolution PS hybrid precoding algorithm and fully digital precoding algorithm.
