This paper investigates the path-following control problem with obstacle avoidance of autonomous surface vehicles in the presence of actuator faults,uncertainty and external disturbances.Autonomous surface vehicles in...This paper investigates the path-following control problem with obstacle avoidance of autonomous surface vehicles in the presence of actuator faults,uncertainty and external disturbances.Autonomous surface vehicles inevitably suffer from actuator faults in complex sea environments,which may cause existing obstacle avoidance strategies to fail.To reduce the influence of actuator faults,an improved artificial potential function is constructed by introducing the lower bound of actuator efficiency factors.The nonlinear state observer,which only depends on measurable position information of the autonomous surface vehicle,is used to address uncertainties and external disturbances.By using a backstepping technique and adaptive mechanism,a path-following control strategy with obstacle avoidance and fault tolerance is designed which can ensure that the tracking errors converge to a small neighborhood of zero.Compared with existing results,the proposed control strategy has the capability of obstacle avoidance and fault tolerance simultaneously.Finally,the comparison results through simulations are given to verify the effectiveness of the proposed method.展开更多
There is a lack of understanding about the bacterial,fungal and archaeal communities’composition of solid-phase denitrification(SPD)systems.We investigated four SPD systems with different carbon sources by analyzing ...There is a lack of understanding about the bacterial,fungal and archaeal communities’composition of solid-phase denitrification(SPD)systems.We investigated four SPD systems with different carbon sources by analyzing microbial gene sequences based on operational taxonomic unit(OTU)and amplicon sequence variant(ASV).The results showed that the corncob-polyvinyl alcohol sodium alginate-polycaprolactone(CPSP,0.86±0.04 mg NO_(3)^(−)-N/(g·day))and corncob(0.85±0.06 mg NO_(3)^(−)-N/(g·day))had better denitrification efficiency than polycaprolactone(PCL,0.29±0.11 mg NO_(3)^(−)-N/(g·day))and polyvinyl alcoholsodium alginate(PVA-SA,0.24±0.07 mg NO_(3)^(−)-N/(g·day)).The bacterial,fungal and archaeal microbial composition was significantly different among carbon source types such as Proteobacteria in PCL(OTU:83.72%,ASV:82.49%)and Rozellomycota in PVA-SA(OTU:71.99%,ASV:81.30%).ASV methods can read more microbial units than that of OTU and exhibit higher alpha diversity and classify some species that had not been identified by OTU such as Nanoarchaeota phylum,unclassified_f_Xanthobacteraceae genus,etc.,indicating ASV may be more conducive to understand SPD microbial communities.The co-occurring network showed some correlation between the bacteria fungi and archaea species,indicating different species may collaborate in SPD systems.Similar KEGG function prediction results were obtained in two bioinformatic methods generally and some fungi and archaea functions should not be ignored in SPD systems.These results may be beneficial for understanding microbial communities in SPD systems.展开更多
本文运用非对称随机波动(Asymmetric Stochastic Volatility,ASV)模型,以1997年为分界线,对我国沪深两市A股市场的市场波动反应模式进行了研究。实证结果表明:我国股票市场对外界信息的反应模式不仅存在非对称性,而且这种非对称反应特...本文运用非对称随机波动(Asymmetric Stochastic Volatility,ASV)模型,以1997年为分界线,对我国沪深两市A股市场的市场波动反应模式进行了研究。实证结果表明:我国股票市场对外界信息的反应模式不仅存在非对称性,而且这种非对称反应特征还具有阶段性:即在股市发展前期(1993～1996)市场波动反应具有非对称反转效应(Reversions in the Asymmetric Behavior of the Volatility);在股市发展后期(1997～2006)市场波动反应具有杠杆效应(Leverage Effect)。并且非对称反应强度随着时间的推移逐渐减小。展开更多
基金the National Natural Science Foundation of China(51939001,52171292,51979020,61976033)Dalian Outstanding Young Talents Program(2022RJ05)+1 种基金the Topnotch Young Talents Program of China(36261402)the Liaoning Revitalization Talents Program(XLYC20-07188)。
文摘This paper investigates the path-following control problem with obstacle avoidance of autonomous surface vehicles in the presence of actuator faults,uncertainty and external disturbances.Autonomous surface vehicles inevitably suffer from actuator faults in complex sea environments,which may cause existing obstacle avoidance strategies to fail.To reduce the influence of actuator faults,an improved artificial potential function is constructed by introducing the lower bound of actuator efficiency factors.The nonlinear state observer,which only depends on measurable position information of the autonomous surface vehicle,is used to address uncertainties and external disturbances.By using a backstepping technique and adaptive mechanism,a path-following control strategy with obstacle avoidance and fault tolerance is designed which can ensure that the tracking errors converge to a small neighborhood of zero.Compared with existing results,the proposed control strategy has the capability of obstacle avoidance and fault tolerance simultaneously.Finally,the comparison results through simulations are given to verify the effectiveness of the proposed method.
基金Thisworkwas supported by the National Key R&D Program of China(No.2019YFC0408602).
文摘There is a lack of understanding about the bacterial,fungal and archaeal communities’composition of solid-phase denitrification(SPD)systems.We investigated four SPD systems with different carbon sources by analyzing microbial gene sequences based on operational taxonomic unit(OTU)and amplicon sequence variant(ASV).The results showed that the corncob-polyvinyl alcohol sodium alginate-polycaprolactone(CPSP,0.86±0.04 mg NO_(3)^(−)-N/(g·day))and corncob(0.85±0.06 mg NO_(3)^(−)-N/(g·day))had better denitrification efficiency than polycaprolactone(PCL,0.29±0.11 mg NO_(3)^(−)-N/(g·day))and polyvinyl alcoholsodium alginate(PVA-SA,0.24±0.07 mg NO_(3)^(−)-N/(g·day)).The bacterial,fungal and archaeal microbial composition was significantly different among carbon source types such as Proteobacteria in PCL(OTU:83.72%,ASV:82.49%)and Rozellomycota in PVA-SA(OTU:71.99%,ASV:81.30%).ASV methods can read more microbial units than that of OTU and exhibit higher alpha diversity and classify some species that had not been identified by OTU such as Nanoarchaeota phylum,unclassified_f_Xanthobacteraceae genus,etc.,indicating ASV may be more conducive to understand SPD microbial communities.The co-occurring network showed some correlation between the bacteria fungi and archaea species,indicating different species may collaborate in SPD systems.Similar KEGG function prediction results were obtained in two bioinformatic methods generally and some fungi and archaea functions should not be ignored in SPD systems.These results may be beneficial for understanding microbial communities in SPD systems.
文摘本文运用非对称随机波动(Asymmetric Stochastic Volatility,ASV)模型,以1997年为分界线,对我国沪深两市A股市场的市场波动反应模式进行了研究。实证结果表明:我国股票市场对外界信息的反应模式不仅存在非对称性,而且这种非对称反应特征还具有阶段性:即在股市发展前期(1993～1996)市场波动反应具有非对称反转效应(Reversions in the Asymmetric Behavior of the Volatility);在股市发展后期(1997～2006)市场波动反应具有杠杆效应(Leverage Effect)。并且非对称反应强度随着时间的推移逐渐减小。
