Underwater quantum communication plays a crucial role in ensuring secure data transmission and extensible quantum networks in underwater environments.However,the implementation of such applications encounters challeng...Underwater quantum communication plays a crucial role in ensuring secure data transmission and extensible quantum networks in underwater environments.However,the implementation of such applications encounters challenges due to the light attenuation caused by the complicated natural seawater.This paper focuses on employing a model based on seawater chlorophyll-a concentration to characterize the absorption and scattering of light through quantum channels.We propose a multi-scattering random channel model,which demonstrates characteristics of the excess noise in different propagation directions of communication links.Furthermore,we consider the fidelity of a continuous-variable quantum teleportation through seawater channel.To enhance transmission performance,non-Gaussian operations have been conducted.Numerical simulations show that incorporating non-Gaussian operations enables the protocol to achieve higher fidelity transmission or lower fidelity fading rates over longer transmission distances.展开更多
There are many types of radar active deception false target jamming that are highly correlated with the real target.Recognizing the real and false targets under a low Signal-to-Noise Ratio(SNR)is difficult.To solve th...There are many types of radar active deception false target jamming that are highly correlated with the real target.Recognizing the real and false targets under a low Signal-to-Noise Ratio(SNR)is difficult.To solve the above problem,this article proposes a real/false target recognition method based on the features of multi-pulse joint frequency response by analyzing the differences in the scattering characteristics and modeling real target echoes as a synthesis of multi-scattering center echoes.Firstly,in the range-doppler domain,the real and false targets are truncated along the range dimension,and a fast Fourier transform is performed to extract the features of multi-pulse joint frequency response.Then,a two-channel feature fusion network is designed for real and false target recognition.Finally,a Multi-Coherent Processing Interval Joint Decision Method(M-CPIJDM)based on temporal information is proposed to improve the recognition performance.Experiments using the measured data show that the proposed method can well recognize real and false target signals under four jamming backgrounds:distance false target,velocity false target,distance-velocity composite false target,and forwarding dense false target.展开更多
A research is done for multipath effects of low-angle tracking in meter-wave radar, and the theory of multi-scattering centers of complex target is discussed as well as the character of reflected echoes. This points o...A research is done for multipath effects of low-angle tracking in meter-wave radar, and the theory of multi-scattering centers of complex target is discussed as well as the character of reflected echoes. This points out that the distribution and scattering properties of scattering centers are the prime reasons which cause the variation of muhipath effects, and all the changes of position, motion and attitude of the target can influence the muhipath effects. By building of muhipath model for multi-scattering centers for target, the analysis above is verified and a new method of elevation estimation for low-angle target is presented. The new method uses canceling vectors obtained by searching to cancel reflected waves in echoes and reduce the influence of reflected com- ponents, which can improve the accuracy of elevation estimation of low-angle target and the performance of low- angle tracking in meter-wave radar. Experimental results verify the availability of the method.展开更多
The theory of elastic wave scattering is a fundamental concept in the study of elastic dynamics and wave motion,and the wave function expansion technique has been widely used in many subjects.To supply the essential t...The theory of elastic wave scattering is a fundamental concept in the study of elastic dynamics and wave motion,and the wave function expansion technique has been widely used in many subjects.To supply the essential tools for solving wave scattering problems induced by an eccentric source or multi-sources as well as multi-scatters,a whole-space transform formula of cylindrical wave functions is presented and its applicability to some simple cases is demonstrated in this study.The transforms of wave functions in cylindrical coordinates can be classifi ed into two basic types: interior transform and exterior transform,and the existing Graf’s addition theorem is only suitable for the former.By performing a new replacement between the two coordinates,the exterior transform formula is fi rst deduced.It is then combined with Graf’s addition theorem to establish a whole-space transform formula.By using the whole-space transform formula,the scattering solutions by the sources outside and inside a cylindrical cavity are constructed as examples of its application.The effectiveness and advantages of the whole-space transform formula is illustrated by comparison with the approximate model based on a large cycle method.The whole-space transform formula presented herein can be used to perform the transform between two different cylindrical coordinates in the whole space.In addition,its concept and principle are universal and can be further extended to establish the coordinate transform formula of wave functions in other coordinate systems.展开更多
Jet ignition is an efficient way to achieve lean burn of the engine and a promising strategy to meet the stringent emission regulations in the future.This paper presents a distributed gas ignition(DGI)combustion conce...Jet ignition is an efficient way to achieve lean burn of the engine and a promising strategy to meet the stringent emission regulations in the future.This paper presents a distributed gas ignition(DGI)combustion concept and realizes a DGI combustion mode using a newly designed DGI igniter.The igniter integrates a fuel injector and a spark plug to achieve minimum volume and easy installation.As the mixture preparation within the jet chamber is essential for the performance of the igniter,different jet chamber injection strategies were tested with varying excess air-fuel ratio ranging from 1.4 to 2.0.By addressing the dual injection strategy,the ignition delay and combustion duration were improved evidently.Compared with the single injection strategy,dual injection strategy improves the flexibility when preparing the mixture inside the jet chamber and therefore retains more fuel.The increased energy density of the jet chamber helps to generate more energetic jets under dual injection strategy,resulting in the improvement of ignition and combustion performance with lean burn.A higher thermal efficiency and a leaner limit of the engine are attained with dual injection than that with single injection.Dual injection exhibits its potential in reducing CO and THC emissions to an acceptable level with leaner mixture.Based on dual injection strategy,the maximum indicated thermal efficiency of 45%is achieved.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.61871407)the Natural Science Foundation of Hunan Province,China(Grant No.2021JJ30878)the Key Research and Development Program of Hunan Province,China(Grant Nos.2020GK4063 and 2022GK2016)。
文摘Underwater quantum communication plays a crucial role in ensuring secure data transmission and extensible quantum networks in underwater environments.However,the implementation of such applications encounters challenges due to the light attenuation caused by the complicated natural seawater.This paper focuses on employing a model based on seawater chlorophyll-a concentration to characterize the absorption and scattering of light through quantum channels.We propose a multi-scattering random channel model,which demonstrates characteristics of the excess noise in different propagation directions of communication links.Furthermore,we consider the fidelity of a continuous-variable quantum teleportation through seawater channel.To enhance transmission performance,non-Gaussian operations have been conducted.Numerical simulations show that incorporating non-Gaussian operations enables the protocol to achieve higher fidelity transmission or lower fidelity fading rates over longer transmission distances.
基金supported by the Basic Research Program,China(No.514010503-208)the China Aerospace Science and Technology Corporation Stabilization Support Project(No.ZY0110020009)the Equipment Pre-research Project,China(No.304060201).
文摘There are many types of radar active deception false target jamming that are highly correlated with the real target.Recognizing the real and false targets under a low Signal-to-Noise Ratio(SNR)is difficult.To solve the above problem,this article proposes a real/false target recognition method based on the features of multi-pulse joint frequency response by analyzing the differences in the scattering characteristics and modeling real target echoes as a synthesis of multi-scattering center echoes.Firstly,in the range-doppler domain,the real and false targets are truncated along the range dimension,and a fast Fourier transform is performed to extract the features of multi-pulse joint frequency response.Then,a two-channel feature fusion network is designed for real and false target recognition.Finally,a Multi-Coherent Processing Interval Joint Decision Method(M-CPIJDM)based on temporal information is proposed to improve the recognition performance.Experiments using the measured data show that the proposed method can well recognize real and false target signals under four jamming backgrounds:distance false target,velocity false target,distance-velocity composite false target,and forwarding dense false target.
文摘A research is done for multipath effects of low-angle tracking in meter-wave radar, and the theory of multi-scattering centers of complex target is discussed as well as the character of reflected echoes. This points out that the distribution and scattering properties of scattering centers are the prime reasons which cause the variation of muhipath effects, and all the changes of position, motion and attitude of the target can influence the muhipath effects. By building of muhipath model for multi-scattering centers for target, the analysis above is verified and a new method of elevation estimation for low-angle target is presented. The new method uses canceling vectors obtained by searching to cancel reflected waves in echoes and reduce the influence of reflected com- ponents, which can improve the accuracy of elevation estimation of low-angle target and the performance of low- angle tracking in meter-wave radar. Experimental results verify the availability of the method.
基金the National Natural Science Foundation of China under Grand No.549974011
文摘The theory of elastic wave scattering is a fundamental concept in the study of elastic dynamics and wave motion,and the wave function expansion technique has been widely used in many subjects.To supply the essential tools for solving wave scattering problems induced by an eccentric source or multi-sources as well as multi-scatters,a whole-space transform formula of cylindrical wave functions is presented and its applicability to some simple cases is demonstrated in this study.The transforms of wave functions in cylindrical coordinates can be classifi ed into two basic types: interior transform and exterior transform,and the existing Graf’s addition theorem is only suitable for the former.By performing a new replacement between the two coordinates,the exterior transform formula is fi rst deduced.It is then combined with Graf’s addition theorem to establish a whole-space transform formula.By using the whole-space transform formula,the scattering solutions by the sources outside and inside a cylindrical cavity are constructed as examples of its application.The effectiveness and advantages of the whole-space transform formula is illustrated by comparison with the approximate model based on a large cycle method.The whole-space transform formula presented herein can be used to perform the transform between two different cylindrical coordinates in the whole space.In addition,its concept and principle are universal and can be further extended to establish the coordinate transform formula of wave functions in other coordinate systems.
基金This work is supported by NSFC.91541206The assistance of Professor Guang Hong of the University of Technology Sydney with improving language is gratefully acknowledged.
文摘Jet ignition is an efficient way to achieve lean burn of the engine and a promising strategy to meet the stringent emission regulations in the future.This paper presents a distributed gas ignition(DGI)combustion concept and realizes a DGI combustion mode using a newly designed DGI igniter.The igniter integrates a fuel injector and a spark plug to achieve minimum volume and easy installation.As the mixture preparation within the jet chamber is essential for the performance of the igniter,different jet chamber injection strategies were tested with varying excess air-fuel ratio ranging from 1.4 to 2.0.By addressing the dual injection strategy,the ignition delay and combustion duration were improved evidently.Compared with the single injection strategy,dual injection strategy improves the flexibility when preparing the mixture inside the jet chamber and therefore retains more fuel.The increased energy density of the jet chamber helps to generate more energetic jets under dual injection strategy,resulting in the improvement of ignition and combustion performance with lean burn.A higher thermal efficiency and a leaner limit of the engine are attained with dual injection than that with single injection.Dual injection exhibits its potential in reducing CO and THC emissions to an acceptable level with leaner mixture.Based on dual injection strategy,the maximum indicated thermal efficiency of 45%is achieved.
