The characteristic of group delay is analyzed based on an electronic circuit, and its time-domain nature is studied with time-domain simulation and experiment. The time-domain simulations and experimental results show...The characteristic of group delay is analyzed based on an electronic circuit, and its time-domain nature is studied with time-domain simulation and experiment. The time-domain simulations and experimental results show that group delay is the delay of the energy center of the amplitude-modulated pulse, rather than the propagation delay of the electromagnetic field. As group velocity originates from the definition of group delay and group delay is different from the propagation delay, the superluminaiity or negativity of group velocity does not mean the supeduminal or negative propagation of the electromagnetic field.展开更多
This paper presents the application of the renormalization group （RG） methods to the delayed differential equation. By analyzing the Mathieu equation with time delay feedback, we get the amplitude and phase equation...This paper presents the application of the renormalization group （RG） methods to the delayed differential equation. By analyzing the Mathieu equation with time delay feedback, we get the amplitude and phase equations, and then obtain the approximate solutions by solving the corresponding RG equations. It shows that the approximate solutions obtained from the RG method are superior to those from the conventionally perturbation methods.展开更多
Real time prosody modification involves changing the prosody parameters such as pitch, duration and intensity of speech in real time without affecting the intelligibility and naturalness. In this paper prosody modific...Real time prosody modification involves changing the prosody parameters such as pitch, duration and intensity of speech in real time without affecting the intelligibility and naturalness. In this paper prosody modification is performed using instants of significant excitation (ISE) of the vocal tract system during production of speech. In the conventional prosody modification system the ISE are computed using group delay function, and it is computationally intensive task. In this paper, we propose computationally efficient methods to determine the ISE suitable for prosody modification in interactive (real time) applications. The overall computational time for the prosody modification by using the proposed method is compared with the conventional prosody modification method which uses the group delay function for computing the ISE.展开更多
The characteristics of frequency correlation and group time delay of ambient noise and ship radiated-noise in the sea are studied. The theoretical and experimental results show that the frequency correlation of ship r...The characteristics of frequency correlation and group time delay of ambient noise and ship radiated-noise in the sea are studied. The theoretical and experimental results show that the frequency correlation of ship radiated-noise is much greater than that of ambient noise,and the frequency correlation of ship radiated-noise at long distance has obvious group time delay展开更多
In this paper, the incorrect definition of VLBI coordinate time delay in solar system barycenter frame (B-frame) is clarified, thus correcting the error of sign of the individual term in VLBI relativistic time delay m...In this paper, the incorrect definition of VLBI coordinate time delay in solar system barycenter frame (B-frame) is clarified, thus correcting the error of sign of the individual term in VLBI relativistic time delay model of transformation published earlier. It is proved that the terms, i. e. the tropospheric refraction delay, the axis offset refraction delay, and the gravitational delay caused by the major planets which are respectively multiplied by the velocity and the acceleration vector of the geocenter, should be taken into account in the model mentioned above under the precision of 1 ps. Finally, the VLBI relativistic time delay model with precision of better than 1 ps is obtained.展开更多
The issue of stability and group consensus tracking is investigated for the discrete-time heterogeneous networked multi-agent systems with communication constraints(e.g.,time delays and data loss)in this paper.Firstly...The issue of stability and group consensus tracking is investigated for the discrete-time heterogeneous networked multi-agent systems with communication constraints(e.g.,time delays and data loss)in this paper.Firstly,the couple-group consensus tracking control is analyzed theoretically,the communication constraints are compensated by the prediction method,and the factor of leaders is introduced to make the system not lose generality.Secondly,the necessary and sufficient condition is given to ensure the stability of the system and achieve the couple-group consensus tracking control,and relax the topology constraint of in-degrees balance by cooperative-competitive interactions.In addition,the result of couple groups is extended to multiple groups based on the predictive control protocol.Numerical simulations with Matlab show that the proposed networked predictive control can effectively overcome the network constraints,the dynamic performance and control effect are better than the general control without the prediction.展开更多
Slowing a light pulse in a degenerate two-level system is observed with a double-frequency sweeping technique, The effects of coupling beam intensity, cell temperature and frequency detunings of the coupling and probe...Slowing a light pulse in a degenerate two-level system is observed with a double-frequency sweeping technique, The effects of coupling beam intensity, cell temperature and frequency detunings of the coupling and probe beams in resonance, on the slowing of light propagation in such a system are investigated. It is found that group velocities depend strongly on polarization combinations. A group velocity υg=6760m/s of light pulses in caesium vapour is obtained under the optimal parameters.展开更多
In this paper,the projective group consensus issue for second order multi-agent systems(MASs)in directed graphs with a dynamic leader is investigated.The proposed projective group consensus with arbitrary parameter in...In this paper,the projective group consensus issue for second order multi-agent systems(MASs)in directed graphs with a dynamic leader is investigated.The proposed projective group consensus with arbitrary parameter includes traditional consensus,reverse group consensus and cluster consensus as its special cases.Novel distributed control protocols are designed to obtain projective group consensus without analyzing signed directed graph as in most current literatures on bipartite consensus problem.On the basis of Lyapunov stability property,algebraic graph and some necessary matrix theory,sufficient conditions for delay and delay-free cases are derived.Finally,simulations of nonlinear chaotic MASs are adopted to testify the theoretical results.展开更多
基金Project supported by the National Basic Research Program of China(Grant No.2013CB329002)the National Natural Science Foundation of China(Grant No.61371012)
文摘The characteristic of group delay is analyzed based on an electronic circuit, and its time-domain nature is studied with time-domain simulation and experiment. The time-domain simulations and experimental results show that group delay is the delay of the energy center of the amplitude-modulated pulse, rather than the propagation delay of the electromagnetic field. As group velocity originates from the definition of group delay and group delay is different from the propagation delay, the superluminaiity or negativity of group velocity does not mean the supeduminal or negative propagation of the electromagnetic field.
文摘This paper presents the application of the renormalization group （RG） methods to the delayed differential equation. By analyzing the Mathieu equation with time delay feedback, we get the amplitude and phase equations, and then obtain the approximate solutions by solving the corresponding RG equations. It shows that the approximate solutions obtained from the RG method are superior to those from the conventionally perturbation methods.
文摘文章研究不同频点的无电离层组合模型中时间群延迟(time group delay,TGD)和差分码偏差(differential code bias,DCB)对定位结果影响的差异,给出了北斗卫星导航系统(BeiDou Navigation Satellite System,BDS)双频/三频无电离层组合TGD和DCB改正模型,利用IGS测站数据进行标准单点定位(standard point positioning,SPP)和精密单点定位(precise point positioning,PPP)实验。实验结果表明:对于SPP,定位精度平面方向小于5 m,U方向小于10 m,定位精度提升显著且精度改正为m级,经模型改正的平面方向精度提升大于70%,U方向精度提升大于28%,其中DCB改正效果略优于TGD改正;对于PPP,经模型改正后的定位精度提升并不明显,但加快了滤波的收敛速度;对于PPP,在未经模型改正的情况下,接收机钟差和模糊度参数吸收了绝大部分的误差改正,而对流层延迟参数受到的影响较小。
文摘Real time prosody modification involves changing the prosody parameters such as pitch, duration and intensity of speech in real time without affecting the intelligibility and naturalness. In this paper prosody modification is performed using instants of significant excitation (ISE) of the vocal tract system during production of speech. In the conventional prosody modification system the ISE are computed using group delay function, and it is computationally intensive task. In this paper, we propose computationally efficient methods to determine the ISE suitable for prosody modification in interactive (real time) applications. The overall computational time for the prosody modification by using the proposed method is compared with the conventional prosody modification method which uses the group delay function for computing the ISE.
文摘The characteristics of frequency correlation and group time delay of ambient noise and ship radiated-noise in the sea are studied. The theoretical and experimental results show that the frequency correlation of ship radiated-noise is much greater than that of ambient noise,and the frequency correlation of ship radiated-noise at long distance has obvious group time delay
文摘基于后处理精密产品,评估了2015-06-01—2018-06-30北斗广播星历的性能精度.对北斗系统性能精度评估的基准问题进行了讨论,统计分析了北斗系统不同星座卫星的轨道差值与星钟差值的长期变化趋势,表明北斗系统空间信号测距精度有逐年提升的趋势.还发现北斗广播星历在2017-01-17前后做出的调整具有较好的效果,不同卫星轨道径向产生一个非零均值的偏差,分析表明该径向偏差更好地实现了轨道径向与卫星星钟参数的自洽,进而大大提高了北斗系统空间信号测距精度.并且北斗系统在2017-07-22对广播星历TGD参数进行了更新,提高了卫星钟差精度.采用4个MGEX测站数据的伪距单点定位验证北斗空间信号精度提升对北斗系统基本导航定位服务的影响,结果表明北斗系统在2017年2次更新后,北斗基本导航定位精度在NEU三个方向分别提升41%、49%和39%.2018年1—6月的统计结果表明,目前北斗系统的IGSO卫星空间信号测距精度最高,优于0.8 m,GEO与MEO卫星次之,约为1 m.
文摘In this paper, the incorrect definition of VLBI coordinate time delay in solar system barycenter frame (B-frame) is clarified, thus correcting the error of sign of the individual term in VLBI relativistic time delay model of transformation published earlier. It is proved that the terms, i. e. the tropospheric refraction delay, the axis offset refraction delay, and the gravitational delay caused by the major planets which are respectively multiplied by the velocity and the acceleration vector of the geocenter, should be taken into account in the model mentioned above under the precision of 1 ps. Finally, the VLBI relativistic time delay model with precision of better than 1 ps is obtained.
基金supported by Natural Science Foundation of Heilongjiang Province of China under Grant No.LH2022F033the National Natural Science Foundation of China under Grant Nos.61903104,61773144 and 12071102Heilongjiang Postdoctoral Scientific Research Developmental Fund under Grant Nos.LBHQ20099 and LBH-Q20168。
文摘The issue of stability and group consensus tracking is investigated for the discrete-time heterogeneous networked multi-agent systems with communication constraints(e.g.,time delays and data loss)in this paper.Firstly,the couple-group consensus tracking control is analyzed theoretically,the communication constraints are compensated by the prediction method,and the factor of leaders is introduced to make the system not lose generality.Secondly,the necessary and sufficient condition is given to ensure the stability of the system and achieve the couple-group consensus tracking control,and relax the topology constraint of in-degrees balance by cooperative-competitive interactions.In addition,the result of couple groups is extended to multiple groups based on the predictive control protocol.Numerical simulations with Matlab show that the proposed networked predictive control can effectively overcome the network constraints,the dynamic performance and control effect are better than the general control without the prediction.
基金Project supported by the National Natural Science Foundation of China （Grant Nos 10174047 and 60378004）, the Natural Science Foundation of Shanxi Province （Grant No 20021032） and the Youth Science Foundation of Shanxi Province （Grant Nos 20031004 and 20041013）.
文摘Slowing a light pulse in a degenerate two-level system is observed with a double-frequency sweeping technique, The effects of coupling beam intensity, cell temperature and frequency detunings of the coupling and probe beams in resonance, on the slowing of light propagation in such a system are investigated. It is found that group velocities depend strongly on polarization combinations. A group velocity υg=6760m/s of light pulses in caesium vapour is obtained under the optimal parameters.
基金the National Natural Science Foundation of China under Grant Nos.61807016 and 61772013the Natural Science Foundation of Jiangsu Province under Grant Nos.BK20181342 and BK20171142。
文摘In this paper,the projective group consensus issue for second order multi-agent systems(MASs)in directed graphs with a dynamic leader is investigated.The proposed projective group consensus with arbitrary parameter includes traditional consensus,reverse group consensus and cluster consensus as its special cases.Novel distributed control protocols are designed to obtain projective group consensus without analyzing signed directed graph as in most current literatures on bipartite consensus problem.On the basis of Lyapunov stability property,algebraic graph and some necessary matrix theory,sufficient conditions for delay and delay-free cases are derived.Finally,simulations of nonlinear chaotic MASs are adopted to testify the theoretical results.
