[Objective] The aim was to compare and analyze microwave coherent and incoherent scattering models in a corn field. [Method] In the research, based on a coherent scattering model （Stile）, we proposed a coherent scat...[Objective] The aim was to compare and analyze microwave coherent and incoherent scattering models in a corn field. [Method] In the research, based on a coherent scattering model （Stile）, we proposed a coherent scattering model exclusive for corn, in which, physical optics （PO） and infinite-length dielectric cylinder were used to calculate single-scattering matrices of corn leaves and stalks. In addition, coherent components produced from interaction among the scattering mechanisms were also considered and this coherent model was compared with the Michigan Mi- crowave Canopy Scattering （MIMICS） model. The measured data in a corn filed in Gongzhuling in Jilin Province were used as the input parameters of the coherent and incoherent models. We simulated backscattering coefficients of VV and HH po- larization at L and C bands and made a comparison between the simulation results. [Result] The simulation results at L-band were poor, which indicated that we could not find regularity at early growth stage of vegetation. In addition, comparisons be- tween coherent and incoherent scattering models proved that the coherence triggered by the scattering mechanism was small. [Conclusion] In the research, we analyzed differences between coherent and incoherent scattering models with change of incident angle, and further analysis on the differences with change of vegetation and soil needed to be made in future.展开更多
Coherent and incoherent internal tides(CITs and ICITs) in the southern South China Sea were investigated from two sets of _18-month mooring current records. The CITs were mainly composed of diurnal Q _1, O _1, P _1 an...Coherent and incoherent internal tides(CITs and ICITs) in the southern South China Sea were investigated from two sets of _18-month mooring current records. The CITs were mainly composed of diurnal Q _1, O _1, P _1 and K _1 and semidiurnal M_2. The observed diurnal internal tides(ITs) were more coherent than the semidiurnal constituents. Coherent diurnal variance accounted for approximately 58% of the diurnal motion, whereas semidiurnal tides contained a much smaller fraction(35%) of coherent motion. The ICITs mainly consisted of motion at non-tidal harmonic frequencies around the tidal frequency, and showed clear intermittency. The modal decomposition of CITs and ICITs showed that CITs were dominated by mode-1, whereas mode-1 and higher modes in ICITs signals showed comparable amplitudes. CITs and ICITs accounted for approximately 64% and 36% of the total kinetic energy of internal tides, respectively.展开更多
This paper studies numerically the dark incoherent spatial solitons propagating in logarithmically saturable nonlinear media by using a coherent density approach and a split-step Fourier approach for the first time. U...This paper studies numerically the dark incoherent spatial solitons propagating in logarithmically saturable nonlinear media by using a coherent density approach and a split-step Fourier approach for the first time. Under odd and even initial conditions, a soliton triplet and a doublet are obtained respectively for given parameters. Simultaneously, coherence properties associated with the soliton triplet and doublet are discussed. In addition, if the values of the parameters are properly chosen, five and four splittings from the input dark incoherent spatial solitons can also form. Lastly, the grayness of the soliton triplet and that of the doublet are studied, in detail.展开更多
A scheme for generating the giant enhancement of the Kerr nonlinearity in a four-level system with the quantum coherences from the decays and the incoherent pumping is proposed. Compared with that generated in a gener...A scheme for generating the giant enhancement of the Kerr nonlinearity in a four-level system with the quantum coherences from the decays and the incoherent pumping is proposed. Compared with that generated in a general four- level system, the Kerr nonlinearity can be enhanced by several orders of magnitude with vanishing linear absorption. By using the numerical results, we show that the remarkable enhancement should be attributed to the interaction of the quantum coherences from the decays and the incoherent pumping.展开更多
In this paper, we studied incoherent and coherent beam combining for the master oscillator/power amplifier （MOPA） system with stimulated Brillouin scattering （SBS） mirror. Optic field intensity distributions in th...In this paper, we studied incoherent and coherent beam combining for the master oscillator/power amplifier （MOPA） system with stimulated Brillouin scattering （SBS） mirror. Optic field intensity distributions in the near and far field are numerically calculated for the two kinds of system. The results show that good beam quality in the far field could be obtained. It provides a theoretical basis for experimental research in the future.展开更多
The effects from quantum coherence via decays and incoherent pumping on the lasing without inversion(LWI) are investigated in a four-level system.By analyzing the transient and steady-state behaviors of the absorption...The effects from quantum coherence via decays and incoherent pumping on the lasing without inversion(LWI) are investigated in a four-level system.By analyzing the transient and steady-state behaviors of the absorption,we find that the gain occurs when both spontaneously generated coherence(SGC) and coherence induced by incoherent pumping(IPC) are considered.We attribute the occurrence of the gain to the interaction of quantum coherence via decays and incoherent pumping.展开更多
An explicit evaluation of the deuteron spin asymmetry and the associated Gerasimov-Drell Hearn （GDH） integral for coherent and incoherent π-photoproduction channels with inclusion of rescattering effects is present...An explicit evaluation of the deuteron spin asymmetry and the associated Gerasimov-Drell Hearn （GDH） integral for coherent and incoherent π-photoproduction channels with inclusion of rescattering effects is presented. The helicity-dependent total inclusive photoabsorption cross section on the deuteron and the helicity-dependent semiexclusive channels γd→π± NN and γd→π0X （X = pn or d） are explicitly evaluated up to 1.5 GeV. Our model calculations indicate that convergence of the GDH integral is reached for π-production, while it is not completely reached for π-production. For the sum of 7d → πNN and γd→ π0d contributions to the finite GDH integral by explicit integration up to 1.5 GeV, a value of 249.73μb is obtained. The extracted results are compared with available experimental data from MAMI and ELSA. We find that our predictions fairly well reproduce the data in the μ±NN case, while fail to predict the measured shape of the μ0X channel.展开更多
Constrained by complex imaging mechanism and extraordinary visual appearance,change detection with synthetic aperture radar(SAR)images has been a difficult research topic,especially in urban areas.Although existing st...Constrained by complex imaging mechanism and extraordinary visual appearance,change detection with synthetic aperture radar(SAR)images has been a difficult research topic,especially in urban areas.Although existing studies have extended from bi-temporal data pair to multi-temporal datasets to derive more plentiful information,there are still two problems to be solved in practical applications.First,change indicators constructed from incoherent feature only cannot characterize the change objects accurately.Second,the results of pixel-level methods are usually presented in the form of the noisy binary map,making the spatial change not intuitive and the temporal change of a single pixel meaningless.In this study,we propose an unsupervised man-made objects change detection framework using both coherent and incoherent features derived from multi-temporal SAR images.The coefficients of variation in timeseries incoherent features and the man-made object index(MOI)defined with coherent features are first combined to identify the initial change pixels.Afterwards,an improved spatiotemporal clustering algorithm is developed based on density-based spatial clustering of applications with noise(DBSCAN)and dynamic time warping(DTW),which can transform the initial results into noiseless object-level patches,and take the cluster center as a representative of the man-made object to determine the change pattern of each patch.An experiment with a stack of 10 TerraSAR-X images in Stripmap mode demonstrated that this method is effective in urban scenes and has the potential applicability to wide area change detection.展开更多
A typical precipitation hardened alloy, Cu-Co dilute alloy was selected to study the precipitation behavior and irradiation effect on precipitates. It is found that the principal effect of ion irradiation on the coher...A typical precipitation hardened alloy, Cu-Co dilute alloy was selected to study the precipitation behavior and irradiation effect on precipitates. It is found that the principal effect of ion irradiation on the coherent precipitates is loss of coherency, and TEM cross-section observations show that the fraction of the incoherent precipitates is dependent on dose but not on dose rate during heavy ion irradiation.展开更多
The temperature effect on tunnelling splitting in the spin boson model with a super-ohmic bath is studied by the small polaron theory. The coherent-incoherent transition temperature is calculated and its dependence on...The temperature effect on tunnelling splitting in the spin boson model with a super-ohmic bath is studied by the small polaron theory. The coherent-incoherent transition temperature is calculated and its dependence on dissipation strength and bare tunnelling splitting is analysed. In additional to the traditional transition point described in textbooks, a new kind of transition is found in the low dissipation region, showing different temperature dependence in the transition. The relation to the corresponding transition in the polaron-phonon system is also discussed.展开更多
Public-key encryption is essential for secure communications,eliminating the need for pre-shared keys.However,traditional schemes such as RSA(Rivest-Shamir-Adleman)and elliptic curve cryptography rely on computational...Public-key encryption is essential for secure communications,eliminating the need for pre-shared keys.However,traditional schemes such as RSA(Rivest-Shamir-Adleman)and elliptic curve cryptography rely on computational complexity,making them increasingly susceptible to advances in computing power and algorithms.Physical-layer encryption,which leverages the intrinsic properties of physical systems,offers a promising alternative with security rooted in physics.Despite progress in this field,public-key encryption at the optical layer remains largely unexplored.Here,we propose a novel optical public-key encryption scheme based on partially coherent light sources.The cryptographic keys are encoded in the incoherent optical transmission matrix of an on-chip Mach-Zehnder interferometer mesh,providing high complexity and resilience to computational attacks.We experimentally demonstrate encrypted image transmission over 40 km of optical fiber with high decryption fidelity and achieve a 10 Gbit/s optical encryption rate using a lithium niobate photonic chip.This represents the first implementation of public-key encryption at the physical optical layer.The approach offers key advantages in security,cost,energy efficiency,and compatibility with commercial optical communication systems.By integrating public-key encryption into photonic hardware,this work opens a new direction for secure and high-speed optical communications in next-generation networks.展开更多
The incoherent control of finite-level quantum systems is investigated.Following a brief introduction to coherent control paradigms in quantum control,a control problem that can not be accomplished using only coherent...The incoherent control of finite-level quantum systems is investigated.Following a brief introduction to coherent control paradigms in quantum control,a control problem that can not be accomplished using only coherent control is presented.For such a control problem,it is proved that it can be accomplished using incoherent control based on projective measurement and coherent control for two classes of finite-level quantum systems,i.e.,eigenstate controllable quantum systems and wavefunction controllable quantum systems.展开更多
We report a theoretical investigation of coherent-to-incoherent heat conduction in multilayer nanostructures.In the coherent regime where the phonon motion is quasi-harmonic,the elastic continuum model gives accurate ...We report a theoretical investigation of coherent-to-incoherent heat conduction in multilayer nanostructures.In the coherent regime where the phonon motion is quasi-harmonic,the elastic continuum model gives accurate cross-plane thermal conductivity predictions of upper limits and demonstrates that the coherent transport is the result of the interplay between intrinsic wave effects.As the temperature or system size increases,the phonon dephasing scattering results in the deviation of thermal conductivity from the coherent-limit calculation.By further introducing the incoherence of phonons,we reproduce the classical minimum thermal conductivity,indicating the feasibility of extending the pure wave model into the wave-particle crossing regime.展开更多
It is well known that the adaptive line enhancer (ALE) is effective detector of CW signal with unknown frequency in the background of white noise. The system processing gain of ALE, when the LMS algorithm is used, how...It is well known that the adaptive line enhancer (ALE) is effective detector of CW signal with unknown frequency in the background of white noise. The system processing gain of ALE, when the LMS algorithm is used, however, is not satisfactory because of the presence of iterative noise and weight noise. In this paper, the coherent accumulation algorithm of ALE, called as ALECA, is suggested. It is shown that the adaptive filter employing this new algorithm possesses the ARMA structure. The experimental results also show that the processing gain of ALECA is about 14dB higher than that of conventional ALE.展开更多
基金Supported by Hunan Provincial Natural Science Foundation(10JJ4027)Opening Fund of State Key Laboratory of Information Engineering in Surveying,Mapping and Remote Sensing(10R01)~~
文摘[Objective] The aim was to compare and analyze microwave coherent and incoherent scattering models in a corn field. [Method] In the research, based on a coherent scattering model （Stile）, we proposed a coherent scattering model exclusive for corn, in which, physical optics （PO） and infinite-length dielectric cylinder were used to calculate single-scattering matrices of corn leaves and stalks. In addition, coherent components produced from interaction among the scattering mechanisms were also considered and this coherent model was compared with the Michigan Mi- crowave Canopy Scattering （MIMICS） model. The measured data in a corn filed in Gongzhuling in Jilin Province were used as the input parameters of the coherent and incoherent models. We simulated backscattering coefficients of VV and HH po- larization at L and C bands and made a comparison between the simulation results. [Result] The simulation results at L-band were poor, which indicated that we could not find regularity at early growth stage of vegetation. In addition, comparisons be- tween coherent and incoherent scattering models proved that the coherence triggered by the scattering mechanism was small. [Conclusion] In the research, we analyzed differences between coherent and incoherent scattering models with change of incident angle, and further analysis on the differences with change of vegetation and soil needed to be made in future.
基金Supported by the Special Fund of the Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA11010202)the National Basic Research Program of China(973 Program)(No.2013CB430303)+1 种基金the National Natural Science Foundation of China(NSFC)(Nos.41376022,41276021)the CAS/SAFEA International Partnership Program for Creative Research Teams
文摘Coherent and incoherent internal tides(CITs and ICITs) in the southern South China Sea were investigated from two sets of _18-month mooring current records. The CITs were mainly composed of diurnal Q _1, O _1, P _1 and K _1 and semidiurnal M_2. The observed diurnal internal tides(ITs) were more coherent than the semidiurnal constituents. Coherent diurnal variance accounted for approximately 58% of the diurnal motion, whereas semidiurnal tides contained a much smaller fraction(35%) of coherent motion. The ICITs mainly consisted of motion at non-tidal harmonic frequencies around the tidal frequency, and showed clear intermittency. The modal decomposition of CITs and ICITs showed that CITs were dominated by mode-1, whereas mode-1 and higher modes in ICITs signals showed comparable amplitudes. CITs and ICITs accounted for approximately 64% and 36% of the total kinetic energy of internal tides, respectively.
基金Project supported by the Major Program of the National Natural Science Foundation of China (Grant No 10674176)
文摘This paper studies numerically the dark incoherent spatial solitons propagating in logarithmically saturable nonlinear media by using a coherent density approach and a split-step Fourier approach for the first time. Under odd and even initial conditions, a soliton triplet and a doublet are obtained respectively for given parameters. Simultaneously, coherence properties associated with the soliton triplet and doublet are discussed. In addition, if the values of the parameters are properly chosen, five and four splittings from the input dark incoherent spatial solitons can also form. Lastly, the grayness of the soliton triplet and that of the doublet are studied, in detail.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10904015,61008063,11004030,and 11074036)
文摘A scheme for generating the giant enhancement of the Kerr nonlinearity in a four-level system with the quantum coherences from the decays and the incoherent pumping is proposed. Compared with that generated in a general four- level system, the Kerr nonlinearity can be enhanced by several orders of magnitude with vanishing linear absorption. By using the numerical results, we show that the remarkable enhancement should be attributed to the interaction of the quantum coherences from the decays and the incoherent pumping.
文摘In this paper, we studied incoherent and coherent beam combining for the master oscillator/power amplifier （MOPA） system with stimulated Brillouin scattering （SBS） mirror. Optic field intensity distributions in the near and far field are numerically calculated for the two kinds of system. The results show that good beam quality in the far field could be obtained. It provides a theoretical basis for experimental research in the future.
基金Supported by National Natural Science Foundation of China under Grant Nos. 10904015,11074036,and 11004030
文摘The effects from quantum coherence via decays and incoherent pumping on the lasing without inversion(LWI) are investigated in a four-level system.By analyzing the transient and steady-state behaviors of the absorption,we find that the gain occurs when both spontaneously generated coherence(SGC) and coherence induced by incoherent pumping(IPC) are considered.We attribute the occurrence of the gain to the interaction of quantum coherence via decays and incoherent pumping.
文摘An explicit evaluation of the deuteron spin asymmetry and the associated Gerasimov-Drell Hearn （GDH） integral for coherent and incoherent π-photoproduction channels with inclusion of rescattering effects is presented. The helicity-dependent total inclusive photoabsorption cross section on the deuteron and the helicity-dependent semiexclusive channels γd→π± NN and γd→π0X （X = pn or d） are explicitly evaluated up to 1.5 GeV. Our model calculations indicate that convergence of the GDH integral is reached for π-production, while it is not completely reached for π-production. For the sum of 7d → πNN and γd→ π0d contributions to the finite GDH integral by explicit integration up to 1.5 GeV, a value of 249.73μb is obtained. The extracted results are compared with available experimental data from MAMI and ELSA. We find that our predictions fairly well reproduce the data in the μ±NN case, while fail to predict the measured shape of the μ0X channel.
基金supported by the National Natural Science Foundation of China(41774006)the Comparative Study of Geo-environment and Geohazards in the Yangtze River Delta and the Red River Delta Projectthe Shanghai Science and Technology Development Foundation(20dz1201200)。
文摘Constrained by complex imaging mechanism and extraordinary visual appearance,change detection with synthetic aperture radar(SAR)images has been a difficult research topic,especially in urban areas.Although existing studies have extended from bi-temporal data pair to multi-temporal datasets to derive more plentiful information,there are still two problems to be solved in practical applications.First,change indicators constructed from incoherent feature only cannot characterize the change objects accurately.Second,the results of pixel-level methods are usually presented in the form of the noisy binary map,making the spatial change not intuitive and the temporal change of a single pixel meaningless.In this study,we propose an unsupervised man-made objects change detection framework using both coherent and incoherent features derived from multi-temporal SAR images.The coefficients of variation in timeseries incoherent features and the man-made object index(MOI)defined with coherent features are first combined to identify the initial change pixels.Afterwards,an improved spatiotemporal clustering algorithm is developed based on density-based spatial clustering of applications with noise(DBSCAN)and dynamic time warping(DTW),which can transform the initial results into noiseless object-level patches,and take the cluster center as a representative of the man-made object to determine the change pattern of each patch.An experiment with a stack of 10 TerraSAR-X images in Stripmap mode demonstrated that this method is effective in urban scenes and has the potential applicability to wide area change detection.
文摘A typical precipitation hardened alloy, Cu-Co dilute alloy was selected to study the precipitation behavior and irradiation effect on precipitates. It is found that the principal effect of ion irradiation on the coherent precipitates is loss of coherency, and TEM cross-section observations show that the fraction of the incoherent precipitates is dependent on dose but not on dose rate during heavy ion irradiation.
基金Project supported by the National Natural Science Foundation of China (Grant No 10575045)
文摘The temperature effect on tunnelling splitting in the spin boson model with a super-ohmic bath is studied by the small polaron theory. The coherent-incoherent transition temperature is calculated and its dependence on dissipation strength and bare tunnelling splitting is analysed. In additional to the traditional transition point described in textbooks, a new kind of transition is found in the low dissipation region, showing different temperature dependence in the transition. The relation to the corresponding transition in the polaron-phonon system is also discussed.
基金supported by the Fundamental Research Funds for the Central Universities.National Natural Science Foundation of China(62425504,U21A20511,62275088).
文摘Public-key encryption is essential for secure communications,eliminating the need for pre-shared keys.However,traditional schemes such as RSA(Rivest-Shamir-Adleman)and elliptic curve cryptography rely on computational complexity,making them increasingly susceptible to advances in computing power and algorithms.Physical-layer encryption,which leverages the intrinsic properties of physical systems,offers a promising alternative with security rooted in physics.Despite progress in this field,public-key encryption at the optical layer remains largely unexplored.Here,we propose a novel optical public-key encryption scheme based on partially coherent light sources.The cryptographic keys are encoded in the incoherent optical transmission matrix of an on-chip Mach-Zehnder interferometer mesh,providing high complexity and resilience to computational attacks.We experimentally demonstrate encrypted image transmission over 40 km of optical fiber with high decryption fidelity and achieve a 10 Gbit/s optical encryption rate using a lithium niobate photonic chip.This represents the first implementation of public-key encryption at the physical optical layer.The approach offers key advantages in security,cost,energy efficiency,and compatibility with commercial optical communication systems.By integrating public-key encryption into photonic hardware,this work opens a new direction for secure and high-speed optical communications in next-generation networks.
基金supported by the National Natural Science Foundation of China(60805029and60703083)the project from the State KeyLaboratory of Industrial Control Technology,Zhejiang University
文摘The incoherent control of finite-level quantum systems is investigated.Following a brief introduction to coherent control paradigms in quantum control,a control problem that can not be accomplished using only coherent control is presented.For such a control problem,it is proved that it can be accomplished using incoherent control based on projective measurement and coherent control for two classes of finite-level quantum systems,i.e.,eigenstate controllable quantum systems and wavefunction controllable quantum systems.
文摘We report a theoretical investigation of coherent-to-incoherent heat conduction in multilayer nanostructures.In the coherent regime where the phonon motion is quasi-harmonic,the elastic continuum model gives accurate cross-plane thermal conductivity predictions of upper limits and demonstrates that the coherent transport is the result of the interplay between intrinsic wave effects.As the temperature or system size increases,the phonon dephasing scattering results in the deviation of thermal conductivity from the coherent-limit calculation.By further introducing the incoherence of phonons,we reproduce the classical minimum thermal conductivity,indicating the feasibility of extending the pure wave model into the wave-particle crossing regime.
文摘It is well known that the adaptive line enhancer (ALE) is effective detector of CW signal with unknown frequency in the background of white noise. The system processing gain of ALE, when the LMS algorithm is used, however, is not satisfactory because of the presence of iterative noise and weight noise. In this paper, the coherent accumulation algorithm of ALE, called as ALECA, is suggested. It is shown that the adaptive filter employing this new algorithm possesses the ARMA structure. The experimental results also show that the processing gain of ALECA is about 14dB higher than that of conventional ALE.
