Long-time coherent integration(LTCI)can remarkably improve the detection ability of radar for moving target.To increase the processing efficiency,this paper proposes a novel LTCI method based on segment time reversing...Long-time coherent integration(LTCI)can remarkably improve the detection ability of radar for moving target.To increase the processing efficiency,this paper proposes a novel LTCI method based on segment time reversing transform(STRT)and chirp z-transform(CZT).In this method,STRT operation is first presented to estimate the Doppler ambiguity factor,and keystone transform(KT)is used to correct the whole range migration(RM).Then,CZT and non-uniform fast Fourier transform(NUFFT)are used to estimate the parameters as well as correct the second and third order Doppler frequency migration(DFM).Compared with the existing methods,the proposed method can achieve RM correction and DFM correction without repetitive operation.The effectiveness of the proposed method is validated by both simulated and real data.展开更多
Long-time coherent integration(LTCI)is an effective way for radar maneuvering target detection,but it faces the problem of a large number of search parameters and large amount of calculation.Realizing the simultaneous...Long-time coherent integration(LTCI)is an effective way for radar maneuvering target detection,but it faces the problem of a large number of search parameters and large amount of calculation.Realizing the simultaneous compensation of the range and Doppler migrations in complex clutter back-ground,and at the same time improving the calculation efficiency has become an urgent problem to be solved.The sparse transformation theory is introduced to LTCI in this paper,and a non-parametric searching sparse LTCI(SLTCI)based maneuvering target detection method is proposed.This method performs time reversal(TR)and second-order Keystone transform(SKT)in the range frequency&slow-time data to complete high-order range walk compensation,and achieves the coherent integra-tion of maneuvering target across range and Doppler units via the robust sparse fractional Fourier transform(RSFRFT).It can compensate for the nonlinear range migration caused by high-order motion.S-band and X-band radar data measured in sea clutter background are used to verify the detection performance of the proposed method,which can achieve better detection performance of maneuvering targets with less computational burden compared with several popular integration methods.展开更多
The traversal search of multi-dimensional parameter during the process of hypersonic target echo signal coherent integration,leads to the problem of large amounts of calculation and poor real-time performance.In view ...The traversal search of multi-dimensional parameter during the process of hypersonic target echo signal coherent integration,leads to the problem of large amounts of calculation and poor real-time performance.In view of these problems,a modified polynomial Radon-polynomial Fourier transform(MPRPFT)hypersonic target coherent integration detection algorithm based on Doppler feedback is proposed in this paper.Firstly,the Doppler estimation value of the target is obtained by using the target point information obtained by subsequent non-coherent integration detection.Then,the feedback adjustment of the coherent integration process is performed by using the acquired target Doppler estimation value.Finally,the coherent integration is completed after adjusting the search interval of compensation.The simulation results show that the algorithm can effectively reduce the computational complexity and improve the real-time performance on the basis of the effective coherent integration of hypersonic target echo signals.展开更多
The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m s...The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m series to do non-coherent integration. It is indicated that the power in- creasing times of larger target sidelobe is less than the power increasing times of smaller target main- lobe because of the larger target＇ s pseudo-randomness. Smaller target is integrated from larger tar- get sidelobe, which strengthens the detection capability of radar for smaller targets. According to the sidelobes distributing characteristic, a method is presented in this paper to remove the estimated sidelobes mean value for signal detection after non-coherent integration. Simulation results present that the SNR of small target can be improved approximately 6. 5 dB by the proposed method.展开更多
To verify the effectiveness of the integrated importance measure （IIM） for multi-state coherent systems of k level, the definition and physical meaning of IIM are demonstrated. Then, the improvement potential and Δ...To verify the effectiveness of the integrated importance measure （IIM） for multi-state coherent systems of k level, the definition and physical meaning of IIM are demonstrated. Then, the improvement potential and Δ-importance measures are generalized to multi-state coherent systems based on the system performance level, and the relationships between IIM and traditional importance measures are discussed. The characteristics of IIM are demonstrated in both series and parallel systems. Also, an application to an oil transportation system is given. The comparison results show that： （i） IIM has some useful properties that are not possessed by traditional importance measures; （ii） IIM is effective in evaluating the component role in multi-state systems when the component reliability and the failure rate are simultaneously considered.展开更多
We construct a general form of propagator in arbitrary dimensions and give an exact wavefunction of a time- dependent forced harmonic oscillator in D（D ≥ 1） dimensions. The coherent states, defined as the eigenstat...We construct a general form of propagator in arbitrary dimensions and give an exact wavefunction of a time- dependent forced harmonic oscillator in D（D ≥ 1） dimensions. The coherent states, defined as the eigenstates of annihilation operator, of the D-dimensional harmonic oscillator are derived. These coherent states correspond to the minimum uncertainty states and the relation between them is investigated.展开更多
Using improved homogeneous balance method, we obtain new exact solutions for the coupled integrable dispersionless equation. On the basis of these exact solutions, we find some new interesting coherent structures by s...Using improved homogeneous balance method, we obtain new exact solutions for the coupled integrable dispersionless equation. On the basis of these exact solutions, we find some new interesting coherent structures by selecting arbitrary functions appropriately.展开更多
The SU（1,1） coherent states for a relativistic model of the linear singular oscillator are considered. The corresponding partition function is evaluated. The path integral for the transition amplitude between SU（1,...The SU（1,1） coherent states for a relativistic model of the linear singular oscillator are considered. The corresponding partition function is evaluated. The path integral for the transition amplitude between SU（1,1） coherent states is given. Classical equations of the motion in the generalized curved phase space are obtained. It is shown that the use of quasiclassical Bohr Sommerfeld quantization rule yields the exact expression for the energy spectrum.展开更多
To detect highly maneuvering radar targets in low signal-to-noise ratio conditions, a hybrid long-time integration method is proposed, which combines Radon-Fourier Transform(RFT), Dynamic Programming(DP), and Binary I...To detect highly maneuvering radar targets in low signal-to-noise ratio conditions, a hybrid long-time integration method is proposed, which combines Radon-Fourier Transform(RFT), Dynamic Programming(DP), and Binary Integration(BI), named RFT-DP-BI. A Markov model with unified range-velocity quantification is formulated to describe the maneuvering target’s motion. Based on this model, long-time hybrid integration is performed. Firstly, the whole integration time is divided into multiple time segments and coherent integration is performed in each segment via RFT. Secondly, non-coherent integration is performed in all segments via DP. Thirdly, 2/4 binary integration is performed to further improve the detection performance. Finally, the detection results are exported together with target range and velocity trajectories. The proposed method can perform the long-time integration of highly maneuvering targets with arbitrary forms of motion.Additionally, it has a low computational cost that is linear to the integration time. Both simulated and real radar data demonstrate that it offers good detection and estimation performances.展开更多
The evolution of a pure coherent state into a chaotic state is described very well by a master equation, as is validated via an examination of the coherent state＇s evolution during the diffusion process, fully utiliz...The evolution of a pure coherent state into a chaotic state is described very well by a master equation, as is validated via an examination of the coherent state＇s evolution during the diffusion process, fully utilizing the technique of integration within an ordered product （IWOP） of operators. The same equation also describes a limitation that maintains the coherence in a weak diffusion process, i.e., when the dissipation is very weak and the initial average photon number is large. This equation is dp/dt = -κ[a＋ap -a＋pa -apa＋ ＋ paa＋]. The physical difference between this diffusion equation and the better-known amplitude damping master equation is pointed out.展开更多
The concept of partially coherent nonparaxial modified Bessel Gauss （MBG） beams is proposed. Based on the generalized Rayleigh-Sommerfeld diffraction integral, the analytical propagation equations of nonparaxial MBG...The concept of partially coherent nonparaxial modified Bessel Gauss （MBG） beams is proposed. Based on the generalized Rayleigh-Sommerfeld diffraction integral, the analytical propagation equations of nonparaxial MBG beams in free space are derived and analysed, and some special cases are discussed. In particular, under the paraxial approximation our results reduce to the corresponding paraxial ones. Numerical calculation examples are given to illustrate the dependence of intensity and spectral degree of coherence on the beam order m, ζ and f parameters, and to compare the difference between the paraxial and nonparaxial results.展开更多
The evolution laws of the large-eddy coherent structure of the wind turbine wake have been evaluated via wind tunnel experiments under uniform and turbulent inflow conditions.The spatial correlation coefficients,the t...The evolution laws of the large-eddy coherent structure of the wind turbine wake have been evaluated via wind tunnel experiments under uniform and turbulent inflow conditions.The spatial correlation coefficients,the turbulence integral scales and power spectrum are obtained at different tip speed ratios(TSRs)based on the time-resolved particle image velocity(TR-PIV)technique.The results indicate that the large-eddy coherent structures are more likely to dissipate with an increase in turbulence intensity and TSR.Furthermore,the spatial correlation of the longitudinal pulsation velocity is greater than its axial counterpart,resulting into a wake turbulence dominated by the longitudinal pulsation.With an increase of turbulence intensity,the integral scale of the axial turbulence increases,meanwhile,its longitudinal counterpart decreases.Owing to an increase in TSR,the integral scale of axial turbulence decreases,whereas,that of the longitudinal turbulence increases.By analyzing the wake power spectrum,it is found that the turbulent pulsation kinetic energy of the wake structure is mainly concentrated in the low-frequency vortex region.The dissipation rate of turbulent kinetic energy increases with an increase of turbulence intensity and the turbulence is transported and dissipated on a smaller scale vortex,thus promoting the recovery of wake.展开更多
1. Introduction In quantum optics, optical frequency conversion is a typical nonlinear process and is worth studying, for example, a second harmonic frequency generation will generate a squeezed state.[1＇2l In this ...1. Introduction In quantum optics, optical frequency conversion is a typical nonlinear process and is worth studying, for example, a second harmonic frequency generation will generate a squeezed state.[1＇2l In this work, we tackle the evolution of an initial coherent state in a Raman dispersion process which is also a nonlinear process. The process involves the inelastic scattering of a pho- ton when it is incident on a molecule. The photon loses some of its energy to the molecule or gains some from it, and so leaves the molecule with a lower or a higher frequency. The lower frequency components of the scattered radiation are called the Stokes lines and the higher frequency components are called the anti- Stokes lines. The Hamiltonian governing its dynamics is[3]展开更多
When two representations of the Lie algebra are coupled, the coupling integral kernels are presented to relate the coupled to uncoupled group-related coherent states. These kernels have a connection with usual couplin...When two representations of the Lie algebra are coupled, the coupling integral kernels are presented to relate the coupled to uncoupled group-related coherent states. These kernels have a connection with usual coupling coefficients. The explicit expressions of these kernels for and are given. When the direct product of three representations is formed in two ways, the recoupling integral kernels relating to the coupled group-related coherent states corresponding to two different schemes are introduced, and the relations between these kernels and the general recoupling coefficients are obtained. The properties of these kernels are discussed.展开更多
A beam splitter operator is a very important linear device in the field of quantum optics and quantum information.It can not only be used to prepare complete representations of quantum mechanics,entangled state repres...A beam splitter operator is a very important linear device in the field of quantum optics and quantum information.It can not only be used to prepare complete representations of quantum mechanics,entangled state representation,but it can also be used to simulate the dissipative environment of quantum systems.In this paper,by combining the transform relation of the beam splitter operator and the technique of integration within the product of the operator,we present the coherent state representation of the operator and the corresponding normal ordering form.Based on this,we consider the applications of the coherent state representation of the beam splitter operator,such as deriving some operator identities and entangled state representation preparation with continuous-discrete variables.Furthermore,we extend our investigation to two single and two-mode cascaded beam splitter operators,giving the corresponding coherent state representation and its normal ordering form.In addition,the application of a beam splitter to prepare entangled states in quantum teleportation is further investigated,and the fidelity is discussed.The above results provide good theoretical value in the fields of quantum optics and quantum information.展开更多
The detection of hypersonic targets usually confronts range migration(RM)issue before coherent integration(CI).The traditional methods aiming at correcting RM to obtain CI mainly considers the narrow-band radar condit...The detection of hypersonic targets usually confronts range migration(RM)issue before coherent integration(CI).The traditional methods aiming at correcting RM to obtain CI mainly considers the narrow-band radar condition.However,with the increasing requirement of far-range detection,the time bandwidth product,which is corresponding to radar’s mean power,should be promoted in actual application.Thus,the echo signal generates the scale effect(SE)at large time bandwidth product situation,influencing the intra and inter pulse integration performance.To eliminate SE and correct RM,this paper proposes an effective algorithm,i.e.,scaled location rotation transform(ScLRT).The ScLRT can remove SE to obtain the matching pulse compression(PC)as well as correct RM to complete CI via the location rotation transform,being implemented by seeking the actual rotation angle.Compared to the traditional coherent detection algorithms,Sc LRT can address the SE problem to achieve better detection/estimation capabilities.At last,this paper gives several simulations to assess the viability of ScLRT.展开更多
The text-based and reader-based are two contrasting groups of approaches existed in the field of textual coherence study.On the basis of the integration of the two kinds of approaches,an integrative interpretation of ...The text-based and reader-based are two contrasting groups of approaches existed in the field of textual coherence study.On the basis of the integration of the two kinds of approaches,an integrative interpretation of the nature of coherence is proposed,that is,coherence is both a text-related and reader-related phenomenon.In order to construct coherent interpretation of text meaning more efficiently,readers should not only be able to identify and use text-immanent coherence cues,but also be capable of drawing coherence-related information by perceiving the contextual features and by engaging actively in activating their background knowledge and in using their cognitive skills.Coherence construction based on the integrative interpretation is the key to success in reading comprehension,so it can generate important pedagogical implications in the college English intensive reading classroom.展开更多
Using the technique of integration within an ordered product of operators, we find a new kind of coherent-entangled state （CES）, which exhibits both coherent and entangled state properties. The set of CESs makes up ...Using the technique of integration within an ordered product of operators, we find a new kind of coherent-entangled state （CES）, which exhibits both coherent and entangled state properties. The set of CESs makes up a complete and partly nonorthogonal representation. Using a beam splitter, we propose a simple experimental scheme to produce the CES. Finally~ we present some applications of CESs in quantum optics.展开更多
The rapid advancement of the thin-film lithium niobate(LiNbO_(3))platform has established it as a premier choice for high-performance photonics integrated circuits.However,the scalability and cost-efficiency of this p...The rapid advancement of the thin-film lithium niobate(LiNbO_(3))platform has established it as a premier choice for high-performance photonics integrated circuits.However,the scalability and cost-efficiency of this platform are hindered by the reliance on chip-level fabrication and integration for passive and active components,necessitating a robust wafer-level LiNbO_(3)heterogeneous integration platform.Despite its critical role in enabling ultrahigh-speed optical interconnects,as well as optical mmWave/THz sensing and communication,the realization of ultrahigh-speed photodiodes and optical coherent receivers on the LiNbO_(3)platform remains an unresolved challenge.This is primarily due to the challenges associated with the large-scale integration of direct-bandgap materials.To address these challenges,we have developed a scalable,high-speed InP-LiNbO_(3)wafer-level heterogeneous integration platform.This platform facilitates the fabrication of ultrahigh-speed photodiodes with a bandwidth of 140 GHz,capable of receiving high-quality 100-Gbaud pulse amplitude modulation(PAM4)signals.Moreover,we demonstrate a sevenchannel,single-polarization I–Q coherent receiver chip with an aggregate receiving capacity of 3.584 Tbit s^(-1).This coherent receiver exhibits a balanced detection bandwidth of 60 GHz and a common mode rejection ratio(CMRR)exceeding 20 dB.It achieves receiving capacities of 600 Gbit s^(-1)λ^(-1)with a 100-Gbaud 64-QAM signal and 512 Gbit s^(-1)λ^(-1)with a 128-Gbaud 16-QAM signal.Furthermore,energy consumption as low as 9.6 fJ bit^(-1) and 13.5 fJ bit^(-1) is achieved for 200 Gbit s^(-1)and 400 Gbit s^(-1)capacities,respectively.Our work provides a viable pathway toward enabling Pbps hyperscale data center interconnects,as well as optical mmWave/THz sensing and communication.展开更多
Ubiquitous radar is a new radar system that provides continuous and uninterrupted multifunction capability within a coverage volume.Continuous coverage from close-in"pop-up"targets in clutter to long-range t...Ubiquitous radar is a new radar system that provides continuous and uninterrupted multifunction capability within a coverage volume.Continuous coverage from close-in"pop-up"targets in clutter to long-range targets impacts selection of waveform parameters.The coherent processing interval(CPI)must be long enough to achieve a certain signal-to-noise ratio(SNR)that ensures the efficiency of detection.The condition of detection in the case of low SNR is analyzed,and three different cases that would occur during integration are discussed and a method to determine the CPI is presented.The simulation results show that targets detection with SNR as low as-26 dB in the experimental system can possibly determine the CPI.展开更多
基金the National Natural Foundation of China(Nos.61771046,61731023 and 62171029).
文摘Long-time coherent integration(LTCI)can remarkably improve the detection ability of radar for moving target.To increase the processing efficiency,this paper proposes a novel LTCI method based on segment time reversing transform(STRT)and chirp z-transform(CZT).In this method,STRT operation is first presented to estimate the Doppler ambiguity factor,and keystone transform(KT)is used to correct the whole range migration(RM).Then,CZT and non-uniform fast Fourier transform(NUFFT)are used to estimate the parameters as well as correct the second and third order Doppler frequency migration(DFM).Compared with the existing methods,the proposed method can achieve RM correction and DFM correction without repetitive operation.The effectiveness of the proposed method is validated by both simulated and real data.
基金supported by the National Natural Science Foundation of China(62222120,61871391,U1933135)Shandong Provincial Natural Science Foundation(ZR2021YQ43).
文摘Long-time coherent integration(LTCI)is an effective way for radar maneuvering target detection,but it faces the problem of a large number of search parameters and large amount of calculation.Realizing the simultaneous compensation of the range and Doppler migrations in complex clutter back-ground,and at the same time improving the calculation efficiency has become an urgent problem to be solved.The sparse transformation theory is introduced to LTCI in this paper,and a non-parametric searching sparse LTCI(SLTCI)based maneuvering target detection method is proposed.This method performs time reversal(TR)and second-order Keystone transform(SKT)in the range frequency&slow-time data to complete high-order range walk compensation,and achieves the coherent integra-tion of maneuvering target across range and Doppler units via the robust sparse fractional Fourier transform(RSFRFT).It can compensate for the nonlinear range migration caused by high-order motion.S-band and X-band radar data measured in sea clutter background are used to verify the detection performance of the proposed method,which can achieve better detection performance of maneuvering targets with less computational burden compared with several popular integration methods.
基金supported by the National Natural Science Foundation of China(6173102361701519+1 种基金61671462)the Distinguished Taishan Scholars in Climbing Plan
文摘The traversal search of multi-dimensional parameter during the process of hypersonic target echo signal coherent integration,leads to the problem of large amounts of calculation and poor real-time performance.In view of these problems,a modified polynomial Radon-polynomial Fourier transform(MPRPFT)hypersonic target coherent integration detection algorithm based on Doppler feedback is proposed in this paper.Firstly,the Doppler estimation value of the target is obtained by using the target point information obtained by subsequent non-coherent integration detection.Then,the feedback adjustment of the coherent integration process is performed by using the acquired target Doppler estimation value.Finally,the coherent integration is completed after adjusting the search interval of compensation.The simulation results show that the algorithm can effectively reduce the computational complexity and improve the real-time performance on the basis of the effective coherent integration of hypersonic target echo signals.
基金Supported by the National Natural Science Foundation of China(Youth Science Fund)(61001190)
文摘The m series with 511 bits is taken as an example being applied in non-coherent integra- tion algorithm. A method to choose the bi-phase code is presented, which is 15 kinds of codes are picked out of 511 kinds of m series to do non-coherent integration. It is indicated that the power in- creasing times of larger target sidelobe is less than the power increasing times of smaller target main- lobe because of the larger target＇ s pseudo-randomness. Smaller target is integrated from larger tar- get sidelobe, which strengthens the detection capability of radar for smaller targets. According to the sidelobes distributing characteristic, a method is presented in this paper to remove the estimated sidelobes mean value for signal detection after non-coherent integration. Simulation results present that the SNR of small target can be improved approximately 6. 5 dB by the proposed method.
基金supported by the National Natural Science Foundation of China (7110111671271170)+2 种基金the National Basic Research Program of China (973 Progrom) (2010CB328000)the National High Technology Research and Development Program of China (863 Progrom) (2012AA040914)the Basic Research Foundation of Northwestern Polytechnical University (JC20120228)
文摘To verify the effectiveness of the integrated importance measure （IIM） for multi-state coherent systems of k level, the definition and physical meaning of IIM are demonstrated. Then, the improvement potential and Δ-importance measures are generalized to multi-state coherent systems based on the system performance level, and the relationships between IIM and traditional importance measures are discussed. The characteristics of IIM are demonstrated in both series and parallel systems. Also, an application to an oil transportation system is given. The comparison results show that： （i） IIM has some useful properties that are not possessed by traditional importance measures; （ii） IIM is effective in evaluating the component role in multi-state systems when the component reliability and the failure rate are simultaneously considered.
基金Project supported by the National Natural Science Foundation of China （Grant No 60261004） and Yunnan Province Science Foundation （Grant No 2002E0008M）.
文摘We construct a general form of propagator in arbitrary dimensions and give an exact wavefunction of a time- dependent forced harmonic oscillator in D（D ≥ 1） dimensions. The coherent states, defined as the eigenstates of annihilation operator, of the D-dimensional harmonic oscillator are derived. These coherent states correspond to the minimum uncertainty states and the relation between them is investigated.
基金Supported by Colleges and Universities Scientific Research Foundation of Inner Mongolia Autonomous Region under Grant N0. NJZY07139Natural Science Foundation of Inner Mongolia Autonomous Region under Grant No. 200408020113
文摘Using improved homogeneous balance method, we obtain new exact solutions for the coupled integrable dispersionless equation. On the basis of these exact solutions, we find some new interesting coherent structures by selecting arbitrary functions appropriately.
文摘The SU（1,1） coherent states for a relativistic model of the linear singular oscillator are considered. The corresponding partition function is evaluated. The path integral for the transition amplitude between SU（1,1） coherent states is given. Classical equations of the motion in the generalized curved phase space are obtained. It is shown that the use of quasiclassical Bohr Sommerfeld quantization rule yields the exact expression for the energy spectrum.
基金supported by the National Natural Science Foundation of China(No.6157010118)。
文摘To detect highly maneuvering radar targets in low signal-to-noise ratio conditions, a hybrid long-time integration method is proposed, which combines Radon-Fourier Transform(RFT), Dynamic Programming(DP), and Binary Integration(BI), named RFT-DP-BI. A Markov model with unified range-velocity quantification is formulated to describe the maneuvering target’s motion. Based on this model, long-time hybrid integration is performed. Firstly, the whole integration time is divided into multiple time segments and coherent integration is performed in each segment via RFT. Secondly, non-coherent integration is performed in all segments via DP. Thirdly, 2/4 binary integration is performed to further improve the detection performance. Finally, the detection results are exported together with target range and velocity trajectories. The proposed method can perform the long-time integration of highly maneuvering targets with arbitrary forms of motion.Additionally, it has a low computational cost that is linear to the integration time. Both simulated and real radar data demonstrate that it offers good detection and estimation performances.
基金Project supported by the National Basic Research Program of China(Grant No.2012CB922103)the National Natural Science Foundation of China(GrantNos.11175113 and 11274104)the Natural Science Foundation of Hubei Province of China(Grant No.2011CDA021)
文摘The evolution of a pure coherent state into a chaotic state is described very well by a master equation, as is validated via an examination of the coherent state＇s evolution during the diffusion process, fully utilizing the technique of integration within an ordered product （IWOP） of operators. The same equation also describes a limitation that maintains the coherence in a weak diffusion process, i.e., when the dissipation is very weak and the initial average photon number is large. This equation is dp/dt = -κ[a＋ap -a＋pa -apa＋ ＋ paa＋]. The physical difference between this diffusion equation and the better-known amplitude damping master equation is pointed out.
基金Project supported by the National High Technology Development Program of China （Grant No 823070） and the National Natural Science Foundation of China （Grant No 10574097）.
文摘The concept of partially coherent nonparaxial modified Bessel Gauss （MBG） beams is proposed. Based on the generalized Rayleigh-Sommerfeld diffraction integral, the analytical propagation equations of nonparaxial MBG beams in free space are derived and analysed, and some special cases are discussed. In particular, under the paraxial approximation our results reduce to the corresponding paraxial ones. Numerical calculation examples are given to illustrate the dependence of intensity and spectral degree of coherence on the beam order m, ζ and f parameters, and to compare the difference between the paraxial and nonparaxial results.
基金supported by the Inner Mongolia Autonomous Region Natural Science Foundation Research Project(Grant No.2020MS05026)the Doctor Fund Project of Inner Mongolia University of Technology(Grant No.BS2020033)the National Natural Science Foundation of China(Grant Nos.52066014 and 51966013).
文摘The evolution laws of the large-eddy coherent structure of the wind turbine wake have been evaluated via wind tunnel experiments under uniform and turbulent inflow conditions.The spatial correlation coefficients,the turbulence integral scales and power spectrum are obtained at different tip speed ratios(TSRs)based on the time-resolved particle image velocity(TR-PIV)technique.The results indicate that the large-eddy coherent structures are more likely to dissipate with an increase in turbulence intensity and TSR.Furthermore,the spatial correlation of the longitudinal pulsation velocity is greater than its axial counterpart,resulting into a wake turbulence dominated by the longitudinal pulsation.With an increase of turbulence intensity,the integral scale of the axial turbulence increases,meanwhile,its longitudinal counterpart decreases.Owing to an increase in TSR,the integral scale of axial turbulence decreases,whereas,that of the longitudinal turbulence increases.By analyzing the wake power spectrum,it is found that the turbulent pulsation kinetic energy of the wake structure is mainly concentrated in the low-frequency vortex region.The dissipation rate of turbulent kinetic energy increases with an increase of turbulence intensity and the turbulence is transported and dissipated on a smaller scale vortex,thus promoting the recovery of wake.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.10775097 and 10475056)
文摘1. Introduction In quantum optics, optical frequency conversion is a typical nonlinear process and is worth studying, for example, a second harmonic frequency generation will generate a squeezed state.[1＇2l In this work, we tackle the evolution of an initial coherent state in a Raman dispersion process which is also a nonlinear process. The process involves the inelastic scattering of a pho- ton when it is incident on a molecule. The photon loses some of its energy to the molecule or gains some from it, and so leaves the molecule with a lower or a higher frequency. The lower frequency components of the scattered radiation are called the Stokes lines and the higher frequency components are called the anti- Stokes lines. The Hamiltonian governing its dynamics is[3]
文摘When two representations of the Lie algebra are coupled, the coupling integral kernels are presented to relate the coupled to uncoupled group-related coherent states. These kernels have a connection with usual coupling coefficients. The explicit expressions of these kernels for and are given. When the direct product of three representations is formed in two ways, the recoupling integral kernels relating to the coupled group-related coherent states corresponding to two different schemes are introduced, and the relations between these kernels and the general recoupling coefficients are obtained. The properties of these kernels are discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.11964013,11664017)the Training Program for Academic and Technical Leaders of Major Disciplines in Jiangxi Province(20204BCJL22053)。
文摘A beam splitter operator is a very important linear device in the field of quantum optics and quantum information.It can not only be used to prepare complete representations of quantum mechanics,entangled state representation,but it can also be used to simulate the dissipative environment of quantum systems.In this paper,by combining the transform relation of the beam splitter operator and the technique of integration within the product of the operator,we present the coherent state representation of the operator and the corresponding normal ordering form.Based on this,we consider the applications of the coherent state representation of the beam splitter operator,such as deriving some operator identities and entangled state representation preparation with continuous-discrete variables.Furthermore,we extend our investigation to two single and two-mode cascaded beam splitter operators,giving the corresponding coherent state representation and its normal ordering form.In addition,the application of a beam splitter to prepare entangled states in quantum teleportation is further investigated,and the fidelity is discussed.The above results provide good theoretical value in the fields of quantum optics and quantum information.
基金supported by the National Natural Science Foundation of China(62101099)the Chinese Postdoctoral Science Foundation(2021M690558,2022T150100,2018M633352,2019T120825)+3 种基金the Young Elite Scientist Sponsorship Program(YESS20200082)the Aeronautical Science Foundation of China(2022Z017080001)the Open Foundation of Science and Technology on Electronic Information Control Laboratorythe Natural Science Foundation of Sichuan Province(2023NSFSC1386)。
文摘The detection of hypersonic targets usually confronts range migration(RM)issue before coherent integration(CI).The traditional methods aiming at correcting RM to obtain CI mainly considers the narrow-band radar condition.However,with the increasing requirement of far-range detection,the time bandwidth product,which is corresponding to radar’s mean power,should be promoted in actual application.Thus,the echo signal generates the scale effect(SE)at large time bandwidth product situation,influencing the intra and inter pulse integration performance.To eliminate SE and correct RM,this paper proposes an effective algorithm,i.e.,scaled location rotation transform(ScLRT).The ScLRT can remove SE to obtain the matching pulse compression(PC)as well as correct RM to complete CI via the location rotation transform,being implemented by seeking the actual rotation angle.Compared to the traditional coherent detection algorithms,Sc LRT can address the SE problem to achieve better detection/estimation capabilities.At last,this paper gives several simulations to assess the viability of ScLRT.
文摘The text-based and reader-based are two contrasting groups of approaches existed in the field of textual coherence study.On the basis of the integration of the two kinds of approaches,an integrative interpretation of the nature of coherence is proposed,that is,coherence is both a text-related and reader-related phenomenon.In order to construct coherent interpretation of text meaning more efficiently,readers should not only be able to identify and use text-immanent coherence cues,but also be capable of drawing coherence-related information by perceiving the contextual features and by engaging actively in activating their background knowledge and in using their cognitive skills.Coherence construction based on the integrative interpretation is the key to success in reading comprehension,so it can generate important pedagogical implications in the college English intensive reading classroom.
基金Project supported by the National Natural Science Foundation of China (Grant No. 10574060)the Natural Science Foundation of Shandong Province,China (Grant Nos. Y2008A23 and ZR2010AQ027)the Shandong Provincial Higher Educational Science and Technology Program,China (Grant Nos. J09LA07 and J10LA15)
文摘Using the technique of integration within an ordered product of operators, we find a new kind of coherent-entangled state （CES）, which exhibits both coherent and entangled state properties. The set of CESs makes up a complete and partly nonorthogonal representation. Using a beam splitter, we propose a simple experimental scheme to produce the CES. Finally~ we present some applications of CESs in quantum optics.
基金supported by the National Key Research and Development Program(Grant No.2022YFB2803800)the National Natural Science Foundation of China(Grant No.U23A20376,62431024).
文摘The rapid advancement of the thin-film lithium niobate(LiNbO_(3))platform has established it as a premier choice for high-performance photonics integrated circuits.However,the scalability and cost-efficiency of this platform are hindered by the reliance on chip-level fabrication and integration for passive and active components,necessitating a robust wafer-level LiNbO_(3)heterogeneous integration platform.Despite its critical role in enabling ultrahigh-speed optical interconnects,as well as optical mmWave/THz sensing and communication,the realization of ultrahigh-speed photodiodes and optical coherent receivers on the LiNbO_(3)platform remains an unresolved challenge.This is primarily due to the challenges associated with the large-scale integration of direct-bandgap materials.To address these challenges,we have developed a scalable,high-speed InP-LiNbO_(3)wafer-level heterogeneous integration platform.This platform facilitates the fabrication of ultrahigh-speed photodiodes with a bandwidth of 140 GHz,capable of receiving high-quality 100-Gbaud pulse amplitude modulation(PAM4)signals.Moreover,we demonstrate a sevenchannel,single-polarization I–Q coherent receiver chip with an aggregate receiving capacity of 3.584 Tbit s^(-1).This coherent receiver exhibits a balanced detection bandwidth of 60 GHz and a common mode rejection ratio(CMRR)exceeding 20 dB.It achieves receiving capacities of 600 Gbit s^(-1)λ^(-1)with a 100-Gbaud 64-QAM signal and 512 Gbit s^(-1)λ^(-1)with a 128-Gbaud 16-QAM signal.Furthermore,energy consumption as low as 9.6 fJ bit^(-1) and 13.5 fJ bit^(-1) is achieved for 200 Gbit s^(-1)and 400 Gbit s^(-1)capacities,respectively.Our work provides a viable pathway toward enabling Pbps hyperscale data center interconnects,as well as optical mmWave/THz sensing and communication.
文摘Ubiquitous radar is a new radar system that provides continuous and uninterrupted multifunction capability within a coverage volume.Continuous coverage from close-in"pop-up"targets in clutter to long-range targets impacts selection of waveform parameters.The coherent processing interval(CPI)must be long enough to achieve a certain signal-to-noise ratio(SNR)that ensures the efficiency of detection.The condition of detection in the case of low SNR is analyzed,and three different cases that would occur during integration are discussed and a method to determine the CPI is presented.The simulation results show that targets detection with SNR as low as-26 dB in the experimental system can possibly determine the CPI.
