The attitude stability control of under actuated spacecraft that used two reaction wheels in the presence of dynamic friction disturbance is handled. A novel improved control approach with a combination of a singular ...The attitude stability control of under actuated spacecraft that used two reaction wheels in the presence of dynamic friction disturbance is handled. A novel improved control approach with a combination of a singular control law based on quaternion and extended state observer (ESO) is employed to establish a stabilization control so as to restrain the effect of friction. The corresponding simulation results demonstrate the highly stable accuracy and performance compensated dynamic friction. Furthermore if there is a non zero initial condition in under actuated axis the attitude stability can be enhanced with a magnetic torquer. Simulations for a nano spacecraft denote a potential application value in pointing accuracy using two reaction wheels and a magnetic torquer.展开更多
The optimal guidance problem for an interceptor against a ballistic missile with active defense is investigated in this paper.A class of optimal guidance schemes are proposed based on linear quadratic differential gam...The optimal guidance problem for an interceptor against a ballistic missile with active defense is investigated in this paper.A class of optimal guidance schemes are proposed based on linear quadratic differential game method and numerical solution of Riccati differential equation.By choosing proper parameters, the proposed guidance schemes are able to drive the interceptor to the target and away from the defender simultaneously.Additionally, fuel cost, control saturation,chattering phenomenon and parameters selection were taken into account.Satisfaction of the proposed guidance schemes of the saddle point condition is proven theoretically.Finally, nonlinear numerical examples are included to demonstrate the effectiveness and performance of the developed guidance approaches.Comparison of control performance between different guidance schemes are presented and analysis.展开更多
Drug-associated reward memories are conducive to intense craving and often trigger relapse.Simvastatin has been shown to regulate lipids that are involved in memory formation but its influence on other cognitive proce...Drug-associated reward memories are conducive to intense craving and often trigger relapse.Simvastatin has been shown to regulate lipids that are involved in memory formation but its influence on other cognitive processes is elusive.Here,we used a mass spectrometry-based lipidomic method to evaluate the impact of simvastatin on the mouse brain in a cocaine-induced reinstatement paradigm.We found that simvastatin blocked the reinstatement of cocaine-induced conditioned place preference(CPP)without affecting CPP acquisition.Specifically,only simvastatin administered during extinction prevented cocaine-primed reinstatement.Global lipidome analysis showed that the nucleus accumbens was the region with the greatest degree of change caused by simvastatin.The metabolism of fatty-acids,phospholipids,and triacylglycerol was profoundly affected.Simvastatin reversed most of the effects on phospholipids induced by cocaine.The correlation matrix showed that cocaine and simvastatin significantly reshaped the lipid metabolic pathways in specific brain regions.Furthermore,simvastatin almost reversed all changes in the fatty acyl profile and unsaturation caused by cocaine.In summary,pre-extinction treatment with simvastatin facilitates cocaine extinction and prevents cocaine relapse with brain lipidome remodeling.展开更多
Based on a sample of Chinese A-share listed firms from 2015 to 2018,this paper studies the impact of annual report comment letters(ARCLs)on firm stock price synchronicity.We find that after firms receive ARCLs,their s...Based on a sample of Chinese A-share listed firms from 2015 to 2018,this paper studies the impact of annual report comment letters(ARCLs)on firm stock price synchronicity.We find that after firms receive ARCLs,their stock price synchronicity decreases.Moreover,the longer the ARCLs and the more negative the ARCLs’tone,the lower the resulting stock price synchronicity.The mechanism test shows that after firms receive ARCLs,the firms’information disclosure increases in quantity and quality,external media attention increases,and the firms’governance improves,reducing their stock price synchronicity.Further research shows that this negative association is more significant in firms with higher information asymmetry.This paper shows that the ARCL,an innovative application of the capital market supervision philosophy,is conducive to improving the quality of listed firms and to the healthy development of the capital market.展开更多
文摘The attitude stability control of under actuated spacecraft that used two reaction wheels in the presence of dynamic friction disturbance is handled. A novel improved control approach with a combination of a singular control law based on quaternion and extended state observer (ESO) is employed to establish a stabilization control so as to restrain the effect of friction. The corresponding simulation results demonstrate the highly stable accuracy and performance compensated dynamic friction. Furthermore if there is a non zero initial condition in under actuated axis the attitude stability can be enhanced with a magnetic torquer. Simulations for a nano spacecraft denote a potential application value in pointing accuracy using two reaction wheels and a magnetic torquer.
文摘The optimal guidance problem for an interceptor against a ballistic missile with active defense is investigated in this paper.A class of optimal guidance schemes are proposed based on linear quadratic differential game method and numerical solution of Riccati differential equation.By choosing proper parameters, the proposed guidance schemes are able to drive the interceptor to the target and away from the defender simultaneously.Additionally, fuel cost, control saturation,chattering phenomenon and parameters selection were taken into account.Satisfaction of the proposed guidance schemes of the saddle point condition is proven theoretically.Finally, nonlinear numerical examples are included to demonstrate the effectiveness and performance of the developed guidance approaches.Comparison of control performance between different guidance schemes are presented and analysis.
基金the National Natural Science Foundation of China(81871043 and 82071494)the National Science and Technology Major Project of China(2018ZX09201017 and 2018ZX09201018)the 1.3.5 Project for Disciplines of Excellence,West China Hospital,Sichuan University(ZYGD18024).
文摘Drug-associated reward memories are conducive to intense craving and often trigger relapse.Simvastatin has been shown to regulate lipids that are involved in memory formation but its influence on other cognitive processes is elusive.Here,we used a mass spectrometry-based lipidomic method to evaluate the impact of simvastatin on the mouse brain in a cocaine-induced reinstatement paradigm.We found that simvastatin blocked the reinstatement of cocaine-induced conditioned place preference(CPP)without affecting CPP acquisition.Specifically,only simvastatin administered during extinction prevented cocaine-primed reinstatement.Global lipidome analysis showed that the nucleus accumbens was the region with the greatest degree of change caused by simvastatin.The metabolism of fatty-acids,phospholipids,and triacylglycerol was profoundly affected.Simvastatin reversed most of the effects on phospholipids induced by cocaine.The correlation matrix showed that cocaine and simvastatin significantly reshaped the lipid metabolic pathways in specific brain regions.Furthermore,simvastatin almost reversed all changes in the fatty acyl profile and unsaturation caused by cocaine.In summary,pre-extinction treatment with simvastatin facilitates cocaine extinction and prevents cocaine relapse with brain lipidome remodeling.
文摘Based on a sample of Chinese A-share listed firms from 2015 to 2018,this paper studies the impact of annual report comment letters(ARCLs)on firm stock price synchronicity.We find that after firms receive ARCLs,their stock price synchronicity decreases.Moreover,the longer the ARCLs and the more negative the ARCLs’tone,the lower the resulting stock price synchronicity.The mechanism test shows that after firms receive ARCLs,the firms’information disclosure increases in quantity and quality,external media attention increases,and the firms’governance improves,reducing their stock price synchronicity.Further research shows that this negative association is more significant in firms with higher information asymmetry.This paper shows that the ARCL,an innovative application of the capital market supervision philosophy,is conducive to improving the quality of listed firms and to the healthy development of the capital market.
