An IMC-PID controller was proposed for unstable second-order time delay system which shows the characteristics of inverse response(RHP zero). A plot of Ms versus λ was suggested to calculate the suitable tuning param...An IMC-PID controller was proposed for unstable second-order time delay system which shows the characteristics of inverse response(RHP zero). A plot of Ms versus λ was suggested to calculate the suitable tuning parameter λ, which provides a trade-off between performance and robustness. Six different forms of process models were selected from literature to show the applicability of the present method. Performance of controller was calculated by ITAE and total variation TV and compared with recently published tuning rules. Undesirable overshoot was removed by using a set-point weighting parameter. Robustness was tested by introducing a perturbation into the various model parameters and closed-loop results show that the designed controller is robust in the case of model uncertainty. The proposed method shows an overall better closed-loop response as compared to other recently reported methods.展开更多
Based on data of cloud-to-ground lightning detected by a lightning location system in Jiangsu Province from 2007 to 2012and data of thunderstorm days from seven meteorological observation stations in Huai'an durin...Based on data of cloud-to-ground lightning detected by a lightning location system in Jiangsu Province from 2007 to 2012and data of thunderstorm days from seven meteorological observation stations in Huai'an during 1961-2012,the spatial and temporal distribution characteristics of cloud-to-ground lightning in Huai'an were analyzed.The results show that the total frequency of cloud-to-ground lightning in one day was closely related to the intensity and frequency of thunder and lightning.The seasonal variations in the total frequency of cloud-to-ground lightning in Huai'an.The total frequency was shown in unimodal distribution,and the extreme values always appeared in July or August.Most cloud-to-ground lightning was negative,and its frequency accounted for about95.3% of the total frequency.Cloud-to-ground lightning density was high in the south of Huai'an and low in the north,and the serious and very serious ground flash zones concentrated in the south of Hongze County,and most parts of Xuyi and Jinhu County,so lightning protection should be an important task particularly in these regions.展开更多
Motion compensation based on the parameter estimation of a moving target has a strong influence on the inverse synthetic aperture radar(ISAR)imaging quality.For the target with built-in disturbance components or under...Motion compensation based on the parameter estimation of a moving target has a strong influence on the inverse synthetic aperture radar(ISAR)imaging quality.For the target with built-in disturbance components or under an extremely low signal-to-noise ratio(SNR),conventional parameter estimation methods based on cross-correlation processing of adjacent profiles,such as the cross-correlation method and the accumulated cross-correlation method,give sizable aligned errors and subsequently produce low-quality ISAR images.The fractional Fourier transform is capable of concentrating the signal power;however,a large computational complexity is induced by searching the matched order.In view of the problems above,a time-weighting symmetric accumulated cross-correlation method is proposed herein.This method maps the spectrum of the range profile into a single-peak envelope to reduce range alignment errors,and presents a symmetric accumulated manner to offset the accumulated error.The simulation results demonstrate that the proposed method yields much better estimation precision than other methods,and yields extremely low computational complexity.展开更多
This paper is concerned with the construction of globally smooth solutions near a given global Maxwellian to the Cauchy problem of tile Vlasov-Poisson-Boltzmann system for non-cutoff hard potentials in three space dim...This paper is concerned with the construction of globally smooth solutions near a given global Maxwellian to the Cauchy problem of tile Vlasov-Poisson-Boltzmann system for non-cutoff hard potentials in three space dimensions without the neutral condition imposed on the initial perturbation. Our analysis is based on the time-weighted energy method and some delicate estimates.展开更多
基金India (MHRD, India) for providing financial support
文摘An IMC-PID controller was proposed for unstable second-order time delay system which shows the characteristics of inverse response(RHP zero). A plot of Ms versus λ was suggested to calculate the suitable tuning parameter λ, which provides a trade-off between performance and robustness. Six different forms of process models were selected from literature to show the applicability of the present method. Performance of controller was calculated by ITAE and total variation TV and compared with recently published tuning rules. Undesirable overshoot was removed by using a set-point weighting parameter. Robustness was tested by introducing a perturbation into the various model parameters and closed-loop results show that the designed controller is robust in the case of model uncertainty. The proposed method shows an overall better closed-loop response as compared to other recently reported methods.
文摘Based on data of cloud-to-ground lightning detected by a lightning location system in Jiangsu Province from 2007 to 2012and data of thunderstorm days from seven meteorological observation stations in Huai'an during 1961-2012,the spatial and temporal distribution characteristics of cloud-to-ground lightning in Huai'an were analyzed.The results show that the total frequency of cloud-to-ground lightning in one day was closely related to the intensity and frequency of thunder and lightning.The seasonal variations in the total frequency of cloud-to-ground lightning in Huai'an.The total frequency was shown in unimodal distribution,and the extreme values always appeared in July or August.Most cloud-to-ground lightning was negative,and its frequency accounted for about95.3% of the total frequency.Cloud-to-ground lightning density was high in the south of Huai'an and low in the north,and the serious and very serious ground flash zones concentrated in the south of Hongze County,and most parts of Xuyi and Jinhu County,so lightning protection should be an important task particularly in these regions.
基金This work is supported in part by the National Science Foundation for the Distinguished Young Scholars of China(No.61525103)the Shenzhen Fundamental Research Project(No.JCYJ20150930150304185).
文摘Motion compensation based on the parameter estimation of a moving target has a strong influence on the inverse synthetic aperture radar(ISAR)imaging quality.For the target with built-in disturbance components or under an extremely low signal-to-noise ratio(SNR),conventional parameter estimation methods based on cross-correlation processing of adjacent profiles,such as the cross-correlation method and the accumulated cross-correlation method,give sizable aligned errors and subsequently produce low-quality ISAR images.The fractional Fourier transform is capable of concentrating the signal power;however,a large computational complexity is induced by searching the matched order.In view of the problems above,a time-weighting symmetric accumulated cross-correlation method is proposed herein.This method maps the spectrum of the range profile into a single-peak envelope to reduce range alignment errors,and presents a symmetric accumulated manner to offset the accumulated error.The simulation results demonstrate that the proposed method yields much better estimation precision than other methods,and yields extremely low computational complexity.
基金supported by National Natural Science Foundation of China(Grant Nos.10925103,11261160 and 11271160)the Fundamental Research Funds for the Central Universities
文摘This paper is concerned with the construction of globally smooth solutions near a given global Maxwellian to the Cauchy problem of tile Vlasov-Poisson-Boltzmann system for non-cutoff hard potentials in three space dimensions without the neutral condition imposed on the initial perturbation. Our analysis is based on the time-weighted energy method and some delicate estimates.
