We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at~1938.72 nm.The temporal pulse-to-pulse separation among the multiple solitons,10 in a single-pulse bunch,inc...We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at~1938.72 nm.The temporal pulse-to-pulse separation among the multiple solitons,10 in a single-pulse bunch,increases from 0.89 ns to1.85 ns per round trip.In addition,with the increasing pump power,the number of bunched solitons increases from 3 up to 24linearly,while the average time separation in the soliton bunch varies irregularly between~0.80 and~1.52 ns.These results contribute to a more profound comprehension of nonlinear pulse dynamics in ultrafast fiber lasers.展开更多
基于光滑粒子动力学和有限元法(smoothed particle hydrodynamics-finite element method,SPH-FEM)耦合算法,建立了截断式脉冲水射流冲蚀煤岩的数值计算模型。通过对比数值模拟结果与相同工况下的实验结果,验证了该模型的有效性。在此...基于光滑粒子动力学和有限元法(smoothed particle hydrodynamics-finite element method,SPH-FEM)耦合算法,建立了截断式脉冲水射流冲蚀煤岩的数值计算模型。通过对比数值模拟结果与相同工况下的实验结果,验证了该模型的有效性。在此基础上,探究了在截断式脉冲水射流冲击作用下,煤岩沿射流轴向的损伤演化过程,分析了煤岩围压、脉冲长度、脉冲间距及射流速度对煤岩冲蚀深度及速度的影响规律。结果表明:煤岩的冲蚀深度随着围压增大而减小;随着脉冲长度的增加,煤岩的冲蚀深度逐渐减小,冲蚀速度经历了先增大后减小的过程;脉冲间距对冲蚀深度的影响较小,煤岩的冲蚀速度随脉冲间距的增大呈现出线性减小的变化趋势;脉冲速度对冲蚀深度及速度影响较为显著,且随着脉冲速度的增加,冲蚀深度及速度整体呈增长趋势。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 study of the evolution of the pulse width in homogeneous dielectric barrier dis- charge at atmospheric pressure with helium as the working gas is reported by using a one- dimensional fluid model. In this paper, a ne...A study of the evolution of the pulse width in homogeneous dielectric barrier dis- charge at atmospheric pressure with helium as the working gas is reported by using a one- dimensional fluid model. In this paper, a new computational method is presented to estimate the pulse width through calculating the time interval between the breakdown voltage and the extinguishing voltage. The effects on the discharge characteristics of the applied voltage and exci- tation frequency are studied based on the computational data. The results of the simulation show that the pulse width is observed to be narrower and the time intervals between two consecutive current pulses decrease with increasing amplitude and excitation frequency, which indicates that the homogeneous discharge is susceptible to the filamentary mode. The simulation results support the conclusion that in order to restrain the transition from the glow mode to filamentary mode, the applied voltage and excitation frequency should be kept within an appropriate range.展开更多
基金supported by the National Natural Science Foundation of China(Nos.61935013,61975133,and62005178)the Guangdong Major Project of Basic and Applied Basic Research(No.2020B0301030009)+3 种基金the Natural Science Foundation of Guangdong Province(No.2023A1515010093)the Science and Technology Innovation Commission of ShenzhenShenzhen Peacock Plan(Nos.KQTD20170330110444030,JCYJ20200109114018750,and JCYJ20220809170611004)Shenzhen University(No.2019075)。
文摘We demonstrate the generation of a unique regime of multiple solitons in a Tm-doped ultrafast fiber laser at~1938.72 nm.The temporal pulse-to-pulse separation among the multiple solitons,10 in a single-pulse bunch,increases from 0.89 ns to1.85 ns per round trip.In addition,with the increasing pump power,the number of bunched solitons increases from 3 up to 24linearly,while the average time separation in the soliton bunch varies irregularly between~0.80 and~1.52 ns.These results contribute to a more profound comprehension of nonlinear pulse dynamics in ultrafast fiber lasers.
文摘基于光滑粒子动力学和有限元法(smoothed particle hydrodynamics-finite element method,SPH-FEM)耦合算法,建立了截断式脉冲水射流冲蚀煤岩的数值计算模型。通过对比数值模拟结果与相同工况下的实验结果,验证了该模型的有效性。在此基础上,探究了在截断式脉冲水射流冲击作用下,煤岩沿射流轴向的损伤演化过程,分析了煤岩围压、脉冲长度、脉冲间距及射流速度对煤岩冲蚀深度及速度的影响规律。结果表明:煤岩的冲蚀深度随着围压增大而减小;随着脉冲长度的增加,煤岩的冲蚀深度逐渐减小,冲蚀速度经历了先增大后减小的过程;脉冲间距对冲蚀深度的影响较小,煤岩的冲蚀速度随脉冲间距的增大呈现出线性减小的变化趋势;脉冲速度对冲蚀深度及速度影响较为显著,且随着脉冲速度的增加,冲蚀深度及速度整体呈增长趋势。
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.
基金supported by National Natural Science Foundation of China(No.51077089)
文摘A study of the evolution of the pulse width in homogeneous dielectric barrier dis- charge at atmospheric pressure with helium as the working gas is reported by using a one- dimensional fluid model. In this paper, a new computational method is presented to estimate the pulse width through calculating the time interval between the breakdown voltage and the extinguishing voltage. The effects on the discharge characteristics of the applied voltage and exci- tation frequency are studied based on the computational data. The results of the simulation show that the pulse width is observed to be narrower and the time intervals between two consecutive current pulses decrease with increasing amplitude and excitation frequency, which indicates that the homogeneous discharge is susceptible to the filamentary mode. The simulation results support the conclusion that in order to restrain the transition from the glow mode to filamentary mode, the applied voltage and excitation frequency should be kept within an appropriate range.
