A robust nonsingular fixed time terminal sliding mode control scheme with a time delay disturbance observer is proposed for atmospheric pollution detection lidar scanning mechanism(APDL-SM)system.Distinguished from th...A robust nonsingular fixed time terminal sliding mode control scheme with a time delay disturbance observer is proposed for atmospheric pollution detection lidar scanning mechanism(APDL-SM)system.Distinguished from the conventional terminal sliding mode control methods,the authors design a novel fixed-time terminal sliding surface,the convergence time of sliding mode phase of which has a constant upper bound that is designable by adjusting only one parameter.Moreover,in order to overcome the problem of unknown upper bound of lumped uncertainty including model uncertainty,friction effect and external disturbances from the port environment,the authors propose a time delay disturbance observer to provide an estimation for the system lumped uncertainty.By using the Lyapunov synthesis,the explicit analysis of the convergence time upper bound are performed.Finally,simulation studies are conducted on the APDL-SM system to show the fast convergence rate and strong robustness of the proposed control scheme.展开更多
In certain environments and under some conditions, the video images taken by the intelligent mobile video phones seem dark, and the colors are not bright or saturated enough.This paper presents an adaptive method to e...In certain environments and under some conditions, the video images taken by the intelligent mobile video phones seem dark, and the colors are not bright or saturated enough.This paper presents an adaptive method to enhance the video image brightness visualization and the color performance depending on the certain hardware property and function parameters. The experimental results prove that this method can enhance the colors and the contrast of the video images, based on the estimated quality feature values of each frame, without using the extra Digital Signal Processor (DSP).展开更多
Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparamet...Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparametric mixed effect model with time-varying latent effects in the analysis of longitudinal data with informative observation times and a dependent terminal event. Estimating equation approaches are developed for parameter estimation, and asymptotic properties of the resulting estimators are established. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a bladder cancer study is provided.展开更多
The dynamic behavior of entangled poly(methyl methacrylate)(PMMA)chains in both the traditional monocationic ionic liquid(MIL)and synthetic dicationic ionic liquid(DIL)with the same anion bis[(trifluoromethyl)sulfonyl...The dynamic behavior of entangled poly(methyl methacrylate)(PMMA)chains in both the traditional monocationic ionic liquid(MIL)and synthetic dicationic ionic liquid(DIL)with the same anion bis[(trifluoromethyl)sulfonyl]imide([TFSI]−)has been examined over the wide composition range using differential scanning calorimetry and rheological measurements.PMMA/DIL and PMMA/MIL systems exhibit two glass transitions in the midrange of composition due to self-concentration effects.PMMA in DIL shows slower relaxation behavior,however,after the iso-free-volume correction,the terminal relaxation timeτ_(0)of PMMA in both the DIL and MIL presents the power law behaviorτ_(0)∼ϕ^(v)with exponent v conforming to experimental results for conventional polymer solutions(v=2.0±0.2).At high ILs concentration(70%),the entanglement molecular weight M_(e)of PMMA/DIL system is lower than that of PMMA/MIL system owing to the formation of additional physical network in DIL,while the difference of M_(e)is reversed at low ILs content.The composition dependence might be related to the fact that the probability of formation of physical cross-linking points in linked double imidazolium ring increases with the increase of DIL content.The recovered creep strain of PMMA/DIL is almost 18 times of PMMA/MIL,exhibiting significantly better viscoelastic behavior.展开更多
基金supported by the National Key Research and Development Project of China under Grant Nos.2018AAA0100800 and 2018YFE0106800the National Natural Science Foundation of China under Grant Nos.61903353,61725304,and 1761673361+2 种基金Major Science and Technology Project of Anhui Province under Grant No.912198698036SINOPEC Programmes for Science and Technology Development under Grant No.PE19008-8the Fundamental Research Funds for the Central Universities under Grant No.WK2100000013。
文摘A robust nonsingular fixed time terminal sliding mode control scheme with a time delay disturbance observer is proposed for atmospheric pollution detection lidar scanning mechanism(APDL-SM)system.Distinguished from the conventional terminal sliding mode control methods,the authors design a novel fixed-time terminal sliding surface,the convergence time of sliding mode phase of which has a constant upper bound that is designable by adjusting only one parameter.Moreover,in order to overcome the problem of unknown upper bound of lumped uncertainty including model uncertainty,friction effect and external disturbances from the port environment,the authors propose a time delay disturbance observer to provide an estimation for the system lumped uncertainty.By using the Lyapunov synthesis,the explicit analysis of the convergence time upper bound are performed.Finally,simulation studies are conducted on the APDL-SM system to show the fast convergence rate and strong robustness of the proposed control scheme.
文摘In certain environments and under some conditions, the video images taken by the intelligent mobile video phones seem dark, and the colors are not bright or saturated enough.This paper presents an adaptive method to enhance the video image brightness visualization and the color performance depending on the certain hardware property and function parameters. The experimental results prove that this method can enhance the colors and the contrast of the video images, based on the estimated quality feature values of each frame, without using the extra Digital Signal Processor (DSP).
基金supported by National Natural Science Foundation of China (Grant Nos. 11231010, 11171330 and 11201315)Key Laboratory of Random Complex Structures and Data Science, Chinese Academy of Sciences (Grant No. 2008DP173182)Beijing Center for Mathematics and Information Interdisciplinary Sciences
文摘Longitudinal data often occur in follow-up studies, and in many situations, there may exist informative observation times and a dependent terminal event such as death that stops the follow-up. We propose a semiparametric mixed effect model with time-varying latent effects in the analysis of longitudinal data with informative observation times and a dependent terminal event. Estimating equation approaches are developed for parameter estimation, and asymptotic properties of the resulting estimators are established. The finite sample behavior of the proposed estimators is evaluated through simulation studies, and an application to a bladder cancer study is provided.
基金the National Natural Science Foundation of China(Nos.51873125,52073184 and 51721091)Scientific Research Foundation of International Cooperation and Exchanges of Sichuan Province(No.2019YFH0027).
文摘The dynamic behavior of entangled poly(methyl methacrylate)(PMMA)chains in both the traditional monocationic ionic liquid(MIL)and synthetic dicationic ionic liquid(DIL)with the same anion bis[(trifluoromethyl)sulfonyl]imide([TFSI]−)has been examined over the wide composition range using differential scanning calorimetry and rheological measurements.PMMA/DIL and PMMA/MIL systems exhibit two glass transitions in the midrange of composition due to self-concentration effects.PMMA in DIL shows slower relaxation behavior,however,after the iso-free-volume correction,the terminal relaxation timeτ_(0)of PMMA in both the DIL and MIL presents the power law behaviorτ_(0)∼ϕ^(v)with exponent v conforming to experimental results for conventional polymer solutions(v=2.0±0.2).At high ILs concentration(70%),the entanglement molecular weight M_(e)of PMMA/DIL system is lower than that of PMMA/MIL system owing to the formation of additional physical network in DIL,while the difference of M_(e)is reversed at low ILs content.The composition dependence might be related to the fact that the probability of formation of physical cross-linking points in linked double imidazolium ring increases with the increase of DIL content.The recovered creep strain of PMMA/DIL is almost 18 times of PMMA/MIL,exhibiting significantly better viscoelastic behavior.
