In modern wireless communication and electromagnetic control,automatic modulationclassification(AMC)of orthogonal frequency division multiplexing(OFDM)signals plays animportant role.However,under Doppler frequency shi...In modern wireless communication and electromagnetic control,automatic modulationclassification(AMC)of orthogonal frequency division multiplexing(OFDM)signals plays animportant role.However,under Doppler frequency shift and complex multipath channel conditions,extracting discriminative features from high-order modulation signals and ensuring model inter-pretability remain challenging.To address these issues,this paper proposes a Fourier attention net-work(FAttNet),which combines an attention mechanism with a Fourier analysis network(FAN).Specifically,the method directly converts the input signal to the frequency domain using the FAN,thereby obtaining frequency features that reflect the periodic variations in amplitude and phase.Abuilt-in attention mechanism then automatically calculates the weights for each frequency band,focusing on the most discriminative components.This approach improves both classification accu-racy and model interpretability.Experimental validation was conducted via high-order modulationsimulation using an RF testbed.The results show that under three different Doppler frequencyshifts and complex multipath channel conditions,with a signal-to-noise ratio of 10 dB,the classifi-cation accuracy can reach 89.1%,90.4%and 90%,all of which are superior to the current main-stream methods.The proposed approach offers practical value for dynamic spectrum access and sig-nal security detection,and it makes important theoretical contributions to the application of deeplearning in complex electromagnetic signal recognition.展开更多
Lead scandium tantalate(PbSc_(0.5)Ta_(0.5)O_(3)(PST))is one of the most promising ferroelectric materials for electrocaloric(EC)refrigeration because of its large enthalpy change(ΔH)at room temperature(RT),whose prop...Lead scandium tantalate(PbSc_(0.5)Ta_(0.5)O_(3)(PST))is one of the most promising ferroelectric materials for electrocaloric(EC)refrigeration because of its large enthalpy change(ΔH)at room temperature(RT),whose properties are determined by the ordering arrangement of two kinds of heterovalent ions at B-sites.This work continuously adjusts the ordering degree(Ω)for PST ceramics on a large scale from 0.51 to 1 via multiple heat treatment processes.For the PST sample withΩ=1,large△H=1.06 J/g and very large EC adiabatic temperature change AT_(max)=4.26 K@60 kV/cm are obtained because of the highly ordered arrangement of the Sc^(3+)and Ta^(5+)ions.With decreasing,the Curie temperature(T)gradually shifts from RT to below 0℃,and the phase transition is diffused.A fairly large△T_(max)=1.57 K is obtained at a rather low temperature of 0℃in the ceramic with Q=0.51.This work proves that lattice ordering is another efficient route to modify ferroelectric features,and the achieved large Tmax in a wide temperature range near/below RT facilitates high-performance cooling devices with a cascade design toward the most urgent market needs.展开更多
The study of temperature-driven phase transitions is significant in phosphate chemistry,as these transitions often lead to unique physical properties for specific applications,such as catalysis,energy storage,ion cond...The study of temperature-driven phase transitions is significant in phosphate chemistry,as these transitions often lead to unique physical properties for specific applications,such as catalysis,energy storage,ion conduction,and nonlinear optics[1–3].The phase transition from room temperature(RT)to high temperature(HT)in phosphates is always from periodic structures to disordered or amorphous states[4–8].At RT,phosphates often maintain a highly ordered crystalline structure,which is stabilized by the lower thermal energy.As the temperature increases,the thermal energy disrupts the periodic arrangement of atoms and leads to a phase transition,where the once ordered structure becomes increasingly disordered or even amorphous.展开更多
In this letter, the problem of blind source separation of Multiple-Phase-Shift-Keying (MPSK) digital signal is considered. The geometry of received MPSK signals constellation is exploited. The column vectors of receiv...In this letter, the problem of blind source separation of Multiple-Phase-Shift-Keying (MPSK) digital signal is considered. The geometry of received MPSK signals constellation is exploited. The column vectors of received signals can be regarded as the points of hyper-cube. All the possible distinct vectors of received signals are found by clustering, and mixing matrix and sources are estimated by searching out the pairing vectors and eliminating redundant information in all possible distinct vectors. Simulation results give the polar diagram of estimated original signals. They show that the proposed algorithm is effective when the original signals is Quadrature-Phase-Shift-Keying (QPSK) or 8-Phase-Shift-Keying (8PSK).展开更多
To increase the spectral efficiency of the underwater acoustic(UWA)communication system,the high order quadrature amplitude modulations(QAM)are deployed.Recently,the prob-abilistic constellation shaping(PCS)has been a...To increase the spectral efficiency of the underwater acoustic(UWA)communication system,the high order quadrature amplitude modulations(QAM)are deployed.Recently,the prob-abilistic constellation shaping(PCS)has been a novel technology to improve the spectral efficiency.The PCS with high-order QAM is introduced into the UWA communication system.A turbo equal-ization scheme with PCS was proposed to cancel the severe inter-symbol interference(ISI).The non-zero a priori information is available for the equalizer and decoder before turbo iteration.A pri-ori hard decision approach is proposed to improve the detection performance and the equalizer con-vergence speed.At the initial turbo iteration,the relation between the a priori information and the probability of the amplitude of 16QAM symbols in one dimension is given.The simulation results verified the efficiency of the proposed method,and compared to the uniform distribution(UD),the PCS-16QAM had a significant improvement of the bit error rate(BER)performance with PCS-ad-aptive turbo equalization(PCS-ATEQ).The UWA communication experiments further verified the performance superiority of the proposed method.展开更多
基金supported by the National Natural Science Foundation of China(No.62027801).
文摘In modern wireless communication and electromagnetic control,automatic modulationclassification(AMC)of orthogonal frequency division multiplexing(OFDM)signals plays animportant role.However,under Doppler frequency shift and complex multipath channel conditions,extracting discriminative features from high-order modulation signals and ensuring model inter-pretability remain challenging.To address these issues,this paper proposes a Fourier attention net-work(FAttNet),which combines an attention mechanism with a Fourier analysis network(FAN).Specifically,the method directly converts the input signal to the frequency domain using the FAN,thereby obtaining frequency features that reflect the periodic variations in amplitude and phase.Abuilt-in attention mechanism then automatically calculates the weights for each frequency band,focusing on the most discriminative components.This approach improves both classification accu-racy and model interpretability.Experimental validation was conducted via high-order modulationsimulation using an RF testbed.The results show that under three different Doppler frequencyshifts and complex multipath channel conditions,with a signal-to-noise ratio of 10 dB,the classifi-cation accuracy can reach 89.1%,90.4%and 90%,all of which are superior to the current main-stream methods.The proposed approach offers practical value for dynamic spectrum access and sig-nal security detection,and it makes important theoretical contributions to the application of deeplearning in complex electromagnetic signal recognition.
基金supported by grants from the National Natural Science Foundation of China(Nos.52325208,92463311,and 52173217)the State Key Lab for Advanced Metals and Materials(No.2024-Z05).
文摘Lead scandium tantalate(PbSc_(0.5)Ta_(0.5)O_(3)(PST))is one of the most promising ferroelectric materials for electrocaloric(EC)refrigeration because of its large enthalpy change(ΔH)at room temperature(RT),whose properties are determined by the ordering arrangement of two kinds of heterovalent ions at B-sites.This work continuously adjusts the ordering degree(Ω)for PST ceramics on a large scale from 0.51 to 1 via multiple heat treatment processes.For the PST sample withΩ=1,large△H=1.06 J/g and very large EC adiabatic temperature change AT_(max)=4.26 K@60 kV/cm are obtained because of the highly ordered arrangement of the Sc^(3+)and Ta^(5+)ions.With decreasing,the Curie temperature(T)gradually shifts from RT to below 0℃,and the phase transition is diffused.A fairly large△T_(max)=1.57 K is obtained at a rather low temperature of 0℃in the ceramic with Q=0.51.This work proves that lattice ordering is another efficient route to modify ferroelectric features,and the achieved large Tmax in a wide temperature range near/below RT facilitates high-performance cooling devices with a cascade design toward the most urgent market needs.
基金supported by the National Natural Science Foundation of China(22105218)Science and Technology Project of Jiangxi Provincial Education Department(GJJ2201525).
文摘The study of temperature-driven phase transitions is significant in phosphate chemistry,as these transitions often lead to unique physical properties for specific applications,such as catalysis,energy storage,ion conduction,and nonlinear optics[1–3].The phase transition from room temperature(RT)to high temperature(HT)in phosphates is always from periodic structures to disordered or amorphous states[4–8].At RT,phosphates often maintain a highly ordered crystalline structure,which is stabilized by the lower thermal energy.As the temperature increases,the thermal energy disrupts the periodic arrangement of atoms and leads to a phase transition,where the once ordered structure becomes increasingly disordered or even amorphous.
基金Supported by the National Natural Science Foundation of China (No. 60872114, 60972056, 61132004)Shanghai Leading Academic Discipline Project and STCSM (S30108 and 08DZ2231100)
文摘In this letter, the problem of blind source separation of Multiple-Phase-Shift-Keying (MPSK) digital signal is considered. The geometry of received MPSK signals constellation is exploited. The column vectors of received signals can be regarded as the points of hyper-cube. All the possible distinct vectors of received signals are found by clustering, and mixing matrix and sources are estimated by searching out the pairing vectors and eliminating redundant information in all possible distinct vectors. Simulation results give the polar diagram of estimated original signals. They show that the proposed algorithm is effective when the original signals is Quadrature-Phase-Shift-Keying (QPSK) or 8-Phase-Shift-Keying (8PSK).
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDA22030101)the National Natural Science Foundation of China(No.61971472)the Institute of Acoustics,Chinese Academy of Sciences Free Exploration Project(No.ZYTS202003).
文摘To increase the spectral efficiency of the underwater acoustic(UWA)communication system,the high order quadrature amplitude modulations(QAM)are deployed.Recently,the prob-abilistic constellation shaping(PCS)has been a novel technology to improve the spectral efficiency.The PCS with high-order QAM is introduced into the UWA communication system.A turbo equal-ization scheme with PCS was proposed to cancel the severe inter-symbol interference(ISI).The non-zero a priori information is available for the equalizer and decoder before turbo iteration.A pri-ori hard decision approach is proposed to improve the detection performance and the equalizer con-vergence speed.At the initial turbo iteration,the relation between the a priori information and the probability of the amplitude of 16QAM symbols in one dimension is given.The simulation results verified the efficiency of the proposed method,and compared to the uniform distribution(UD),the PCS-16QAM had a significant improvement of the bit error rate(BER)performance with PCS-ad-aptive turbo equalization(PCS-ATEQ).The UWA communication experiments further verified the performance superiority of the proposed method.
