A novel robust fault tolerant controller is developed for the problem of attitude control of a quadrotor aircraft in the presence of actuator faults and wind gusts in this paper.Firstly, a dynamical system of the quad...A novel robust fault tolerant controller is developed for the problem of attitude control of a quadrotor aircraft in the presence of actuator faults and wind gusts in this paper.Firstly, a dynamical system of the quadrotor taking into account aerodynamical effects induced by lateral wind and actuator faults is considered using the Newton-Euler approach. Then,based on active disturbance rejection control(ADRC), the fault tolerant controller is proposed to recover faulty system and reject perturbations. The developed controller takes wind gusts,actuator faults and measurement noises as total perturbations which are estimated by improved extended state observer(ESO)and compensated by nonlinear feedback control law. So, the developed robust fault tolerant controller can successfully accomplish the tracking of the desired output values. Finally, some simulation studies are given to illustrate the effectiveness of fault recovery of the proposed scheme and also its ability to attenuate external disturbances that are introduced from environmental causes such as wind gusts and measurement noises.展开更多
Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,a...Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,and the specific attenuation mechanism is still ambiguous.Therefore,in this work,a novel ultra-light egg-derived porous carbon foam(EDCF)structure has been successfully constructed by a simple carbonization combined with the silica microsphere template-etching process.Based on an equivalent substitute strategy,the influence of pore volume and specific surface area on the electromagnetic parameters and EMW absorption properties of the EDCF products was confirmed respectively by adjusting the addition content and diameter of silica microspheres.As a primary attenuation mode,the dielectric loss originates from the comprehensive effect of conduction loss and polarization loss in S-band and C band,and the value is dominated by polarization loss in X band and Ku band,which is obviously greater than that of conduction loss.Furthermore,in all samples,the largest effective absorption bandwidth of EDCF-3 is 7.12 GHz under the thickness of 2.13 mm with the filling content of approximately 5 wt%,covering the whole Ku band.Meanwhile,the EDCF-7 sample with optimized pore volume and specific surface area achieves minimum reflection loss(RL_(min))of−58.08 dB at 16.86 GHz while the thickness is 1.27 mm.The outstanding research results not only provide a novel insight into enhancement of EMW absorption properties but also clarify the dominant dissipation mechanism for the porous carbon-based absorber from the perspective of objective experiments.展开更多
In this paper,an active fault accommodate strategy is proposed for the plant in the presence of actuator fault and input constraints,which is a combination of a direct adaptive control algorithm with multiple model sw...In this paper,an active fault accommodate strategy is proposed for the plant in the presence of actuator fault and input constraints,which is a combination of a direct adaptive control algorithm with multiple model switching.The μ-modification is introduced in the model reference architecture to construct the adaptive controller.The proof of stability is based on the candidate Lyapunov function,while appropriate switching of multiple models guarantees asymptotic tracking of the system states and the boundedness of all signals.Simulation results illustrate the efficiency of the proposed method.展开更多
‘Lvyou No. 1',bred in Huasheng Agriculture Limited Liability Company of Shandong Province,is a new cucumber F1 hybrid developed by crossing two inbred lines HS267014 and HS6201. It is an early-maturing variety with ...‘Lvyou No. 1',bred in Huasheng Agriculture Limited Liability Company of Shandong Province,is a new cucumber F1 hybrid developed by crossing two inbred lines HS267014 and HS6201. It is an early-maturing variety with wide adaptability,high yield,and good commercial breeding. The plant has strong growth vigor and high resistance to white powder mildew. The first fruit sets on the 4 ^th-5^ th section,and the fruiting ratio of cucumber is 60%-80%. The cylindrical fruit is about 30-35 cm in length,3. 2-3. 5 cm in diameter with light green skin and glossy appearance. This plant has demonstrated adaptability in early-spring and late-autumn planting as well as spring and autumn tunnel planting.展开更多
In the last decade,electromagnetic pollution has caused people’s considerable attention.Developing absorbing material with low cost,lightweight,simple preparation,and high electromagnetic attenuation efficiency has b...In the last decade,electromagnetic pollution has caused people’s considerable attention.Developing absorbing material with low cost,lightweight,simple preparation,and high electromagnetic attenuation efficiency has become a feasible means to deal with this problem.In this work,core–shell SiC_(NWs)@MnO_(2)@PPy(NWs:nanowires,PPy:polypyrrole)heterostructures composed of SiC nanowires core,MnO_(2)nanosheets inter-layer,and PPy coating were successfully prepared through chemical vapor deposition and two-step electrodeposition process.Taking advantage of the interfacial polarization and dipole polarization,the obtained product displays excellent electromagnetic wave absorption performances with the minimum reflection loss(RLmin)of−50.59 dB when the matching thickness is 2.41 mm,and the optimal effective absorption bandwidth(EAB)value reaches to 6.64 GHz at a matching thickness of 2.46 mm,revealing that the SiC_(NWs)@MnO_(2)@PPy nanocomposite could be served as a promising electromagnetic wave absorbing material.On the basis of systematic analysis concerning the electromagnetic parameters,the dissipation process of the incident electromagnetic wave was demonstrated reasonably,which may provide a referable preparation strategy for novel heterostructures,especially nonmagnetic lightweight absorbing material.展开更多
Carbon-based electromagnetic wave absorbing materials(absorbers)adhered with metallic sulfide nanoparticles of good electrical conductivity attract increasing researchers’attention.In this study,on the basis of carbo...Carbon-based electromagnetic wave absorbing materials(absorbers)adhered with metallic sulfide nanoparticles of good electrical conductivity attract increasing researchers’attention.In this study,on the basis of carbon fiber(C_(f))@Fe_(3)O_(4) nanocomposites obtained by the electrostatic spinning and reflow method,C_(f)@FeS_(2)nanocomposite was successfully prepared during a further hydrothermal process.The products exhibit excellent electromagnetic wave absorption performances with a minimum reflection loss(RLmin)of-54.11 dB at 2.13 mm matching thickness.At the same time,the optimal effective absorption bandwidth(EAB)value of 6.04 GHz at a thickness of 1.98 mm covers the whole Ku band,suggesting its excellent electromagnetic wave absorption performances.In addition,the interlaced network structure constructed by carbon fiber,outstanding conductivity of FeS_(2)nanoparticles,and interfacial polarization from hetero-structure play significant parts in enhancing the electromagnetic parameters and absorption performances.All these results suggest that the C_(f)@FeS_(2)nanocomposites can be taken as a new electromagnetic wave-absorbing material under their low density,simple craft,and strong absorption characteristics.展开更多
Recently,developing carbon-based hybrid materials loaded with magnetic components has been generally regarded as a promising and practically feasible strategy when it comes to constructing lightweight electromagnetic ...Recently,developing carbon-based hybrid materials loaded with magnetic components has been generally regarded as a promising and practically feasible strategy when it comes to constructing lightweight electromagnetic wave absorbers.In the current work,reclaimed carbon black(CB)nanopowder was firstly produced by simple burning of wheat straw,which was then employed as sustainable carbon-based host materials(carrier)and successfully decorated Co@C nanoparticles via a simple thermal reduction process.Remarkably,both the as-fabricated nanocomposites and corresponding electromagnetic wave absorption performances could be effectively tuned by tailoring the dosage of the Co@C nanoparticles.The minimum reflection loss(RLmin)of–53.989 d B was achieved for CB/Co@C-2#at 2.28 mm thickness,meanwhile,CB/Co@C-3#was featured by a wide effective absorption band(EAB)of 6 GHz(6.72–12.72 GHz)at a 2.73 mm matching thickness,which covered the entire X band,suggesting that the CB/Co@C nanocomposites were an attractive candidate for electromagnetic wave absorber.According to the synergistic influence of dielectric loss and magnetic loss from CB and Co@C,respectively,as well as the properly matched impedance,a reasonable electromagnetic wave attenuation mechanism was illustrated.It is noteworthy that the preparation process of CB is a facile,recycled,and low-cost strategy for achieving nanoscale carbon-based absorbing materials,moreover,the CB/Co@C nanocomposites provide a reference for constructing lightweight dielectric-magnetic products with superb electromagnetic wave absorption performances.展开更多
The global urban area is expanding continuously,resulting in unprecedented emissions and deposition of reactive nitrogen(N)in urban environments.However,large knowledge gaps remain in the ecological effects of N depos...The global urban area is expanding continuously,resulting in unprecedented emissions and deposition of reactive nitrogen(N)in urban environments.However,large knowledge gaps remain in the ecological effects of N deposition on urban forests that provide key ecosystem services for an increasing majority of city dwellers.The current understanding of the spatial patterns and ecological effects of N deposition in urban forests was synthesized based on a literature review of observational and experimental studies.Nitrogen deposition generally increases closer to cities,resulting in an urban hotspot phenomenon.Chemical components of N deposition also shift across urban-suburban-rural gradients,showing higher ratios of ammonium to nitrate in and around urban areas.The ecological effects of N deposition on urban forest ecosystems are overviewed with a special focus on ecosystem N cycling,soil acidification,nutrient imbalances,soil greenhouse gas emissions,tree growth and forest productivity,and plant and soil microbial diversity.The distinct effects of unprecedented N deposition on urban forests are discussed in comparison with the common effects in natural forests.Despite the existing research efforts,several key research needs are highlighted to fill the knowledge gaps in the ecological effects of N deposition on urban forests.展开更多
基金supported by the National Natural Science Foundation of China(61573282)the Foundation of the Education Department of Sichuan Province(16ZA0132)the Foundation of Robot Technology Used for Special Environment,Key Laboratory of Sichuan Province(13zxtk06)
文摘A novel robust fault tolerant controller is developed for the problem of attitude control of a quadrotor aircraft in the presence of actuator faults and wind gusts in this paper.Firstly, a dynamical system of the quadrotor taking into account aerodynamical effects induced by lateral wind and actuator faults is considered using the Newton-Euler approach. Then,based on active disturbance rejection control(ADRC), the fault tolerant controller is proposed to recover faulty system and reject perturbations. The developed controller takes wind gusts,actuator faults and measurement noises as total perturbations which are estimated by improved extended state observer(ESO)and compensated by nonlinear feedback control law. So, the developed robust fault tolerant controller can successfully accomplish the tracking of the desired output values. Finally, some simulation studies are given to illustrate the effectiveness of fault recovery of the proposed scheme and also its ability to attenuate external disturbances that are introduced from environmental causes such as wind gusts and measurement noises.
基金supported by the National Natural Science Foundation of China under Grant No.52072196,52002199,52002200,52102106Major Basic Research Program of Natural Science Foundation of Shandong Province under Grant No.ZR2020ZD09+2 种基金the Natural Science Foundation of Shandong Province under Grant No.ZR2019BEM042,ZR2020QE063the Innovation and Technology Program of Shandong Province under Grant No.2020KJA004the Taishan Scholars Program of Shandong Province under No.ts201511034
文摘Three-dimensional(3D)ordered porous carbon is generally believed to be a promising electromagnetic wave(EMW)absorbing material.However,most research works targeted performance improvement of 3D ordered porous carbon,and the specific attenuation mechanism is still ambiguous.Therefore,in this work,a novel ultra-light egg-derived porous carbon foam(EDCF)structure has been successfully constructed by a simple carbonization combined with the silica microsphere template-etching process.Based on an equivalent substitute strategy,the influence of pore volume and specific surface area on the electromagnetic parameters and EMW absorption properties of the EDCF products was confirmed respectively by adjusting the addition content and diameter of silica microspheres.As a primary attenuation mode,the dielectric loss originates from the comprehensive effect of conduction loss and polarization loss in S-band and C band,and the value is dominated by polarization loss in X band and Ku band,which is obviously greater than that of conduction loss.Furthermore,in all samples,the largest effective absorption bandwidth of EDCF-3 is 7.12 GHz under the thickness of 2.13 mm with the filling content of approximately 5 wt%,covering the whole Ku band.Meanwhile,the EDCF-7 sample with optimized pore volume and specific surface area achieves minimum reflection loss(RL_(min))of−58.08 dB at 16.86 GHz while the thickness is 1.27 mm.The outstanding research results not only provide a novel insight into enhancement of EMW absorption properties but also clarify the dominant dissipation mechanism for the porous carbon-based absorber from the perspective of objective experiments.
基金supported by the Aeronautics Science Foundation of China(No.2007ZC52039)the National Natural Science Foundation of China(No.90816023)
文摘In this paper,an active fault accommodate strategy is proposed for the plant in the presence of actuator fault and input constraints,which is a combination of a direct adaptive control algorithm with multiple model switching.The μ-modification is introduced in the model reference architecture to construct the adaptive controller.The proof of stability is based on the candidate Lyapunov function,while appropriate switching of multiple models guarantees asymptotic tracking of the system states and the boundedness of all signals.Simulation results illustrate the efficiency of the proposed method.
文摘‘Lvyou No. 1',bred in Huasheng Agriculture Limited Liability Company of Shandong Province,is a new cucumber F1 hybrid developed by crossing two inbred lines HS267014 and HS6201. It is an early-maturing variety with wide adaptability,high yield,and good commercial breeding. The plant has strong growth vigor and high resistance to white powder mildew. The first fruit sets on the 4 ^th-5^ th section,and the fruiting ratio of cucumber is 60%-80%. The cylindrical fruit is about 30-35 cm in length,3. 2-3. 5 cm in diameter with light green skin and glossy appearance. This plant has demonstrated adaptability in early-spring and late-autumn planting as well as spring and autumn tunnel planting.
基金supported by the National Natural Science Foundation of China(Nos.52072196,52002199,52002200,and 52102106)Major Basic Research Program of Natural Science Foundation of Shandong Province(No.ZR2020ZD09)+2 种基金the Natural Science Foundation of Shandong Province(Nos.ZR202108180009,ZR2019BEM042,and ZR2020QE063)the Innovation and Technology Program of Shandong Province(No.2020KJA004)the Taishan Scholars Program of Shandong Province(No.ts201511034).
文摘In the last decade,electromagnetic pollution has caused people’s considerable attention.Developing absorbing material with low cost,lightweight,simple preparation,and high electromagnetic attenuation efficiency has become a feasible means to deal with this problem.In this work,core–shell SiC_(NWs)@MnO_(2)@PPy(NWs:nanowires,PPy:polypyrrole)heterostructures composed of SiC nanowires core,MnO_(2)nanosheets inter-layer,and PPy coating were successfully prepared through chemical vapor deposition and two-step electrodeposition process.Taking advantage of the interfacial polarization and dipole polarization,the obtained product displays excellent electromagnetic wave absorption performances with the minimum reflection loss(RLmin)of−50.59 dB when the matching thickness is 2.41 mm,and the optimal effective absorption bandwidth(EAB)value reaches to 6.64 GHz at a matching thickness of 2.46 mm,revealing that the SiC_(NWs)@MnO_(2)@PPy nanocomposite could be served as a promising electromagnetic wave absorbing material.On the basis of systematic analysis concerning the electromagnetic parameters,the dissipation process of the incident electromagnetic wave was demonstrated reasonably,which may provide a referable preparation strategy for novel heterostructures,especially nonmagnetic lightweight absorbing material.
基金The work reported here was supported by the National Natural Science Foundation of China(Nos.52072196,52002199,52002200,and 52102106)the Major Basic Research Program of Natural Science Foundation of Shandong Province(No.ZR2020ZD09)+2 种基金the Natural Science Foundation of Shandong Province(Nos.ZR2019BEM042 and ZR2020QE063)the Innovation and Technology Program of Shandong Province(No.2020KJA004)the Taishan Scholars Program of Shandong Province(No.ts201511034).We express our grateful thanks to them for their financial support.
文摘Carbon-based electromagnetic wave absorbing materials(absorbers)adhered with metallic sulfide nanoparticles of good electrical conductivity attract increasing researchers’attention.In this study,on the basis of carbon fiber(C_(f))@Fe_(3)O_(4) nanocomposites obtained by the electrostatic spinning and reflow method,C_(f)@FeS_(2)nanocomposite was successfully prepared during a further hydrothermal process.The products exhibit excellent electromagnetic wave absorption performances with a minimum reflection loss(RLmin)of-54.11 dB at 2.13 mm matching thickness.At the same time,the optimal effective absorption bandwidth(EAB)value of 6.04 GHz at a thickness of 1.98 mm covers the whole Ku band,suggesting its excellent electromagnetic wave absorption performances.In addition,the interlaced network structure constructed by carbon fiber,outstanding conductivity of FeS_(2)nanoparticles,and interfacial polarization from hetero-structure play significant parts in enhancing the electromagnetic parameters and absorption performances.All these results suggest that the C_(f)@FeS_(2)nanocomposites can be taken as a new electromagnetic wave-absorbing material under their low density,simple craft,and strong absorption characteristics.
基金the National Natural Science Foundation of China(Nos.51672144,51572137,51702181,52072196,52002199,52002200)the Major Basic Research Program of Natural Science Foundation of Shandong Province under Grant No.ZR2020ZD09+5 种基金the Shandong Provincial Key Research and Development Program(SPKR&DP)under Grant No.2019GGX102055the Natural Science Foundation of Shandong Province(Nos.ZR2019BEM042,ZR2020QE063)the Innovation and Technology Program of Shandong Province under Grant No.2020KJA004Guangdong Basic and Applied Basic Research Foundation(No.2019A1515110933)the China Postdoctoral Science Foundation(No.2020M683450)the Taishan Scholars Program of Shandong Province under No.ts201511034。
文摘Recently,developing carbon-based hybrid materials loaded with magnetic components has been generally regarded as a promising and practically feasible strategy when it comes to constructing lightweight electromagnetic wave absorbers.In the current work,reclaimed carbon black(CB)nanopowder was firstly produced by simple burning of wheat straw,which was then employed as sustainable carbon-based host materials(carrier)and successfully decorated Co@C nanoparticles via a simple thermal reduction process.Remarkably,both the as-fabricated nanocomposites and corresponding electromagnetic wave absorption performances could be effectively tuned by tailoring the dosage of the Co@C nanoparticles.The minimum reflection loss(RLmin)of–53.989 d B was achieved for CB/Co@C-2#at 2.28 mm thickness,meanwhile,CB/Co@C-3#was featured by a wide effective absorption band(EAB)of 6 GHz(6.72–12.72 GHz)at a 2.73 mm matching thickness,which covered the entire X band,suggesting that the CB/Co@C nanocomposites were an attractive candidate for electromagnetic wave absorber.According to the synergistic influence of dielectric loss and magnetic loss from CB and Co@C,respectively,as well as the properly matched impedance,a reasonable electromagnetic wave attenuation mechanism was illustrated.It is noteworthy that the preparation process of CB is a facile,recycled,and low-cost strategy for achieving nanoscale carbon-based absorbing materials,moreover,the CB/Co@C nanocomposites provide a reference for constructing lightweight dielectric-magnetic products with superb electromagnetic wave absorption performances.
基金supported by National Natural Science Foundation of China (41877328, 41630750 and 41425007)State Key Laboratory of Earth Surface Processes and Resource Ecology (2021-TS-02)Fok Ying-Tong Education Foundation (161015)。
文摘The global urban area is expanding continuously,resulting in unprecedented emissions and deposition of reactive nitrogen(N)in urban environments.However,large knowledge gaps remain in the ecological effects of N deposition on urban forests that provide key ecosystem services for an increasing majority of city dwellers.The current understanding of the spatial patterns and ecological effects of N deposition in urban forests was synthesized based on a literature review of observational and experimental studies.Nitrogen deposition generally increases closer to cities,resulting in an urban hotspot phenomenon.Chemical components of N deposition also shift across urban-suburban-rural gradients,showing higher ratios of ammonium to nitrate in and around urban areas.The ecological effects of N deposition on urban forest ecosystems are overviewed with a special focus on ecosystem N cycling,soil acidification,nutrient imbalances,soil greenhouse gas emissions,tree growth and forest productivity,and plant and soil microbial diversity.The distinct effects of unprecedented N deposition on urban forests are discussed in comparison with the common effects in natural forests.Despite the existing research efforts,several key research needs are highlighted to fill the knowledge gaps in the ecological effects of N deposition on urban forests.