The focus of this paper is on control design and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle（FAHV）.The model of interest includes flexibility effects and intricate couplings ...The focus of this paper is on control design and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle（FAHV）.The model of interest includes flexibility effects and intricate couplings between the engine dynamics and flight dynamics.To overcome the analytical intractability of this model,a nominal control-oriented model is constructed for the purpose of feedback control design in the first place.Secondly,the multi-input multi-output（MIMO） quasi-continuous high-order sliding mode（HOSM） controller is proposed to track step changes in velocity and altitude,which is based on full state feedback.The simulation results are presented to verify the effectiveness of the proposed control strategy.展开更多
This paper considers the problem of reference tracking control for the flexible air-breathing hypersonic flight vehicle with actuator delay and uncertainty.By constructing the Lyapunov functional including the lower a...This paper considers the problem of reference tracking control for the flexible air-breathing hypersonic flight vehicle with actuator delay and uncertainty.By constructing the Lyapunov functional including the lower and upper bounds of the time-varying delay,the non-fragile controller is designed such that the resulting closed-loop system is asymptotically stable and satisfies a prescribed performance cost index.The simulation results are given to show the effectiveness of the proposed control method,which is validated by excellent output reference altitude and velocity tracking performance.展开更多
A theoretical framework of nonlinear flight control for a flexible air-breathing hypersonic vehicle(FAHV)is proposed in this paper.In order to suppress the system uncertainty and external disturbance,an uncertainty an...A theoretical framework of nonlinear flight control for a flexible air-breathing hypersonic vehicle(FAHV)is proposed in this paper.In order to suppress the system uncertainty and external disturbance,an uncertainty and disturbance estimator(UDE)based back-stepping control strategy is designed for a dynamic state-feedback controller to provide stable velocity and altitude tracking.Firstly,the longitudinal dynamics of FAHV is simplified into a closure loop form with lumped uncertainty and disturbance.Then the UDE is applied to estimate the lumped uncertainty and disturbance for the purpose of control input compensation.While a nonlinear tracking differentiator is introduced to solve the problem of“explosion of term”in the back-stepping control.The stability of the UDE-based control strategy is proved by using Lyapunov stability theorem.Finally,simulation results are presented to demonstrate the capacity of the proposed control strategy.展开更多
This paper focuses on synthesizing a mixed robust H_2/H_∞ linear parameter varying（LPV） controller for the longitudinal motion of an air-breathing hypersonic vehicle via a high order singular value decomposition（H...This paper focuses on synthesizing a mixed robust H_2/H_∞ linear parameter varying（LPV） controller for the longitudinal motion of an air-breathing hypersonic vehicle via a high order singular value decomposition（HOSVD） approach.The design of hypersonic flight control systems is highly challenging due to the enormous complexity of the vehicle dynamics and the presence of significant uncertainties.Motivated by recent results on both LPV control and tensor-product（TP） model transformation approach,the velocity and altitude tracking control problems for the air-breathing hypersonic vehicle is reduced to that of a state feedback stabilizing controller design for a polytopic LPV system with guaranteed performances.The controller implementation is converted into a convex optimization problem with parameterdependent linear matrix inequalities（LMIs） constraints,which is intuitively tractable using LMI control toolbox.Finally,numerical simulation results demonstrate the effectiveness of the proposed approach.展开更多
Alterations in the respiratory epithelium of gills of a catfish, Heteropneustes fossilis by the sublethal and lethal concentrations of HgCl2 have been observcd using scanning electron microscope. Fish exposed to 0.1 ...Alterations in the respiratory epithelium of gills of a catfish, Heteropneustes fossilis by the sublethal and lethal concentrations of HgCl2 have been observcd using scanning electron microscope. Fish exposed to 0.1 ppm shows a thin coat ot mucus, but the continuous layer of mucus is not retained in 0.3 ppm after 24 h of exposure. Epithelial cells of the gill filament are hyperplastic. Other changcs in the respiratory epithelium are contraction of epithelium, formation of interlamellar bridge and diminishing number of microridges. Massive destruction of the respiratory epithelium by deep lesions and sloughing of epithelial layer in 0.5 and 1.0 ppm solutions after 6-12 h of exposure apparently causes death to the fish. SEM observations are well in conformity with the findings made at light microscopic level展开更多
Laser propulsion is a new concept technique of propulsion and will have important application in future space technology. There are two main driving types: the air-breathing mode and the rocket ablation mode. Vertical...Laser propulsion is a new concept technique of propulsion and will have important application in future space technology. There are two main driving types: the air-breathing mode and the rocket ablation mode. Vertical flight experiments have been carried out with a simple paraboloid type lightcraft in the air-breathing mode by TEA-CO_2 laser. In simulation a new model is used for LSD/LSC wave, the result shows that the momentum coupling coefficient increases with the increase of the pulse energy.展开更多
Air-Breathing Electric Thrusters (ABET) diagnostics is addressed, with on-ground prototypes in mind. It is based on detailed volume averaged Global Models and focuses on emission spectroscopy. Notably, the obtained op...Air-Breathing Electric Thrusters (ABET) diagnostics is addressed, with on-ground prototypes in mind. It is based on detailed volume averaged Global Models and focuses on emission spectroscopy. Notably, the obtained optical emission spectroscopy diagnostics tools give important information about the thruster propellant constitution and also the ionization degree of each constituent. This allows for trade-off between various prototypes on the basis of their characterization and optimization.展开更多
Histopathological effects of sublethal (0.1, 0.2, 0.3 ppm) and lethal (0.5, 1.0 ppm)solutions of mercuric chloride (HgCl2) have been studied on the gills of the air breathing catfish, Heteropneustes fossilis at the in...Histopathological effects of sublethal (0.1, 0.2, 0.3 ppm) and lethal (0.5, 1.0 ppm)solutions of mercuric chloride (HgCl2) have been studied on the gills of the air breathing catfish, Heteropneustes fossilis at the intervals ranging from 6h to 15 days. Thickening of the epithelium, swelling and hyperplasia of the mucous cells, fusion of secondary lamellae, formation of interlamellar bridge and deposition of mucous over the entire surface are some noteworthy features of mercury poisoning in sublethal concentrations. Acute pathological manifestations are formation of subepithelial space, sloughing of the epithelial layer, hemorrhage and hypertrophy of the mucous cells. Causes and impact of these cellular alterations affecting survival of the fish have been discussed展开更多
Fish skin acts as the first immune barrier against pathogens from external environments.Recently,fish skin immunity research has gradually become a hot topic in aquaculture disease control.Interestingly,the skin can d...Fish skin acts as the first immune barrier against pathogens from external environments.Recently,fish skin immunity research has gradually become a hot topic in aquaculture disease control.Interestingly,the skin can do air-breathing in some bimodal respiration fish.However,there is no comprehensive understanding of these two functions.In this study,the skin regeneration of loach(Paramisgurnus dabryanus)was investigated through morphological and histological observations.Then,original skins(OS)and the regenerated skins(RS)when their capillaries were the most abundant during healing,were collected for transcriptomic analysis.285,899,386 clean reads with a total length of 42.34 Gb were obtained.A total of 1282 differentially expressed genes(DEGs)were detected,including 1030 DEGs up-regulated and 252 DEGs down-regulated in the comparison of RS vs.OS.Fc gamma R-mediated phagocytosis(containing gelsolin(Gsn)),chemokine signaling pathway(containing C-C motif chemokine ligand 28(Ccl28)),and B cell receptor signaling pathway(containing CD80 molecule(Cd81))were closely related to skin immune response of the loach.PI3K-Akt signaling pathway[containing fibronectin 1(Fn1)and lysyl oxidase-like 2b(Loxl2b)],TGF-beta signaling pathway[containing thrombospondin 1(Thbs1)],ECM-receptor interaction[containing integrin alpha 7(Itga7),Itgb8,Itgb10 and Itgb5],and dilated cardiomyopathy[containing laminin subunit alpha1(Lama1)]were closely associated with skin air-breathing of the loach.This study is conducive to explore the molecular mechanisms of skin immune response during its regeneration and air-breathing of bimodal respiration fish.This study will benefit for the aquaculture of P.dabryanus and its related species.展开更多
A novel adaptive neural control strategy is exploited for the longitudinal dynamics of a generic flexible air-breathing hypersonic vehicle（FAHV）.By utilizing functional decomposition method, the dynamics of FAHV is ...A novel adaptive neural control strategy is exploited for the longitudinal dynamics of a generic flexible air-breathing hypersonic vehicle（FAHV）.By utilizing functional decomposition method, the dynamics of FAHV is decomposed into the velocity subsystem and the altitude subsystem.For each subsystem, only one neural network is employed for the unknown function approximation.To further reduce the computational burden, minimal-learning parameter（MLP）technology is used to estimate the norm of ideal weight vectors rather than their elements.By introducing sliding mode differentiator（SMD） to estimate the newly defined variables, there is no need for the strict-feedback form and virtual controller.Hence the developed control law is considerably simpler than the ones derived from back-stepping scheme.Finally, simulation studies are made to illustrate the effectiveness of the proposed control approach in spite of the flexible effects, system uncertainties and varying disturbances.展开更多
This article develops a polytopic linear pa- rameter varying （LPV） model and presents a non-fragile H2 gain-scheduled control for a flexible air-breathing hypersonic vehicle （FAHV）. First, the polytopic LPV model ...This article develops a polytopic linear pa- rameter varying （LPV） model and presents a non-fragile H2 gain-scheduled control for a flexible air-breathing hypersonic vehicle （FAHV）. First, the polytopic LPV model of the FAHV can be obtained by using Jacobian linearization and tensor-product （TP） model transfor- mation approach, simulation verification illustrates that the polytopic LPV model captures the local nonlinear- ities of the original nonlinear system. Second, based on the developed polytopic LPV model, a non-fragile gain- scheduled control method is proposed in order to reduce the fragility encountered in controller implementation, a convex optimisation problem with linear matrix in- equalities （LMIs） constraints is formulated for designing a velocity and altitude tracking controller, which guar- antees//2 control performance index. Finally, numerical simulations have demonstrated the effectiveness of the proposed approach.展开更多
Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine （APDE） are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gaso...Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine （APDE） are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gasoline/air mixture. Straight nozzle, converging nozzle, converging-diverging nozzle and diverging nozzle are tested. The results show that thrust augmentation of converging-diverging nozzle, diverging nozzle or straight nozzle is better than that of converging nozzle on the whole. Thrust augmentation of straight nozzle is worse than those of converging-diverging nozzle and diverging nozzle. Thrust augmentations of diverging nozzle with larger expansion ratio and converging-diverging nozzle with larger throat area range from 20% to 40% on tested frequencies and are better than those of congeneric other nozzles respectively. Nozzle effects on inlet pressure are also researched. At each frequency it is indicated that filling pressures and average peak pressures of inlet with diverging nozzle and converging-diverging nozzle with large throat cross section area are higher than those with straight nozzle and converging nozzle Pressures near thrust wall increase in an increase order from without nozzle, with diverging nozzle, straight nozzle and converging-diverging nozzle to converging nozzle.展开更多
The flight dynamics model of air-breathing hypersonic vehicles （AHVs） is highly nonlinear and multivariable cou- pling, and includes inertial uncertainties and external disturbances that require strong, robust, and ...The flight dynamics model of air-breathing hypersonic vehicles （AHVs） is highly nonlinear and multivariable cou- pling, and includes inertial uncertainties and external disturbances that require strong, robust, and high-accuracy controllers. In this paper, we propose a linear-quadratic regulator （LQR） design method based on stochastic robustness analysis for the longitudinal dynamics of AHVs. First, input/output feedback linearization is used to design LQRs. Second, subject to various system parameter uncertainties, system robustness is characterized by the probability of stability and desired performance. Then, the mapping rela- tionship between system robustness and LQR parameters is established. Particularly, to maximize system robustness, a novel hybrid particle swarm optimization algorithm is proposed to search for the optimal LQR parameters. During the search iteration, a Chernoff bound algorithm is applied to determine the finite sample size of Monte Carlo evaluation with the given prohabilily levels. Finally, simulation results show that the optimization algorithm can effectively find the optimal solution to the LQR parameters.展开更多
In this paper,a prescribed fast tracking control scheme is proposed for Flexible Airbreathing Hypersonic Vehicles(FAHV)subject to lumped disturbances and limited resources.To maintain tracking errors of velocity and a...In this paper,a prescribed fast tracking control scheme is proposed for Flexible Airbreathing Hypersonic Vehicles(FAHV)subject to lumped disturbances and limited resources.To maintain tracking errors of velocity and altitude converge to a predefined region with a prescribed time and release the transient intense fluctuations encountered in classical Prescribed Performance Control(PPC)using a fast decaying rate,a tracking differentiator-based PPC is presented,where the reaching time and the maximum time differentiation of preselected envelopes can be regulated as a prior via fixing an acceleration factor,so that a guaranteed fast convergence speed can be realized with reduced oscillations.Besides,to avoid the excessive occupation of limited resources(energy and communication)and guarantee a remarkable tracking accuracy,switching event-triggered mechanisms are constructed for FAHV control realization,which provide a promising way to pursue a desired level of tracking performance with a low energy consumption.Subsequently,Uncertainty and Disturbance Estimators(UDE)and Sigmoid function-based Tracking Differentiators(STD)are employed to provide disturbance estimation and reference derivation with a low computational complexity.Finally,robust control laws are designed to compensate for the sampling error induced by event-triggered conditions,meanwhile Zeno phenomena can be effectively eliminated.The simulation results and comparisons validate the effectiveness of the proposed scheme.展开更多
In this study, a membraneless, monolithic micro photocatalytic fuel cell with an air-breathing cathode was developed for simultaneous wastewater treatment and electricity generation. In this newly-developed micro phot...In this study, a membraneless, monolithic micro photocatalytic fuel cell with an air-breathing cathode was developed for simultaneous wastewater treatment and electricity generation. In this newly-developed micro photocatalytic fuel cell, the photoanode and cathode were arranged with a shoulder-to-shoulder design, forming two planar electrodes. Such design offers several advantages of enhanced mass transfer, uniform light distribution, short light transfer path, membrane elimination and easy fabrication, integration, and compatibility with other microdevices. The performance of this type fuel cell was evaluated by using methanol as a model pollutant under the alkaline condition. Experimental results indicated the developed micro photocatalytic fuel cell was able to show good photo-response to the illumination and satisfactory performance as well as durability. Parametric study on the cell performance was also performed. It was found that increasing the light intensity, methanol concentration andKOH concentration could improve the cell performance. But for the effect of the liquid flow rate, it was shown that the cell performance firstly increased with increasing the liquid flow rate and then decreased with further increasing the liquid flow rate. This study not only opens a new avenue for the design of the micro photocatalytic fuel cell but also is helpful for the optimization of the operating conditions.展开更多
Microbial fuel cells(MFCs)incorporating air-breathing cathodes have emerged as a promising ecofriendly wastewater treatment technology capable of operating on an energy-free basis.However,the inevitable biofouling of ...Microbial fuel cells(MFCs)incorporating air-breathing cathodes have emerged as a promising ecofriendly wastewater treatment technology capable of operating on an energy-free basis.However,the inevitable biofouling of these devices rapidly decreases cathodic catalytic activity and also reduces the stability of MFCs during long-term operation.The present work developed a novel microbial separator for use in air-breathing MFCs that protects cathodic catalytic activity.In these modified devices,microbes preferentially grow on the microbial separator rather than the cathodic surface such that biofouling is prevented.Trials showed that this concept provided low charge transfer and mass diffusion resistance values during the cathodic oxygen reduction reaction of 4.6±1.3 and 17.3±6.8 U,respectively,after prolonged operation.The maximum power density was found to be stable at 1.06±0.07 W m2 throughout a long-term test and the chemical oxygen demand removal efficiency was increased to 92%compared with a value of 83%for MFCs exhibiting serious biofouling.In addition,a cathode combined with a microbial separator demonstrated less cross-cathode diffusion of oxygen to the anolyte.This effect indirectly induced the growth of electroactive bacteria and produced higher currents in air-breathing MFCs.Most importantly,the present microbial separator concept enhances both the lifespan and economics of air-breathing MFCs by removing the need to replace or regenerate the cathode during longterm operation.These results indicate that the installation of a microbial separator is an effective means of stabilizing power generation and ensuring the cost-effective performance of air-breathing MFCs intended for future industrial applications.展开更多
Altitude characteristic is of great importance for studying when an air-breathing pulsed laser thruster works in the dense atmosphere condition of 0-30 km altitude. The experimental findings all over the world show th...Altitude characteristic is of great importance for studying when an air-breathing pulsed laser thruster works in the dense atmosphere condition of 0-30 km altitude. The experimental findings all over the world show that the similar relationship between impulse coupling coefficient and altitude. According to strong explosion theory and an ideal gas model,a dimensionless factor indicating energy law of similitude is introduced,and formula of impulse coupling coefficient is deducted. Then theoretical study of altitude characteristic is carried out and mechanism of altitude characteristic is further explained. The results indicate that there is a maximum value of impulse coupling coefficient if the dimensionless factor equals to 0.41 in theory, and whether the phenomena of maximum appear or not depends on the range of the dimensionless factor related to altitude. As to a conical nozzle with the fixed length of 120 mm, the relationship between the sonic velocity and the dimensionless factor causes the maximum phenomenon at the altitude of about 12.5 km,and maximum theoretical impulse coupling coefficient is also found in the experimental investigations. The mechanism of altitude characteristic for air-breathing pulsed laser thruster is discovered in this article, which will provide reference for further research on altitude characteristic.展开更多
Air-breathing proton exchange membrane fuel cells(PEMFCs) are very promising portable energy with many advantages. However, its power density is low and many additional supporting parts affect its specific power. In t...Air-breathing proton exchange membrane fuel cells(PEMFCs) are very promising portable energy with many advantages. However, its power density is low and many additional supporting parts affect its specific power. In this paper, we aim to improve the air diffusion and fuel cell performance by employing a novel condensing-tower-like curved flow field rather than an additional fan, making the fuel cell more compact and has less internal power consumption. Polarization curve test and galvanostatic discharge test are carried out and proved that curved flow field can strengthen the air diffusion into the PEMFC and improve its performance. With appropriate curved flow field, the fuel cell peak power can be 55.2%higher than that of planar flow field in our study. A four-layer stack with curved cathode flow field is fabricated and has a peak power of 2.35 W(120 W/kg).展开更多
Air-breathing mode laser propulsion experiment with a long-pulse transversely excited （TE） CO2 laser is carried out, and its ignition problem is solved with the ignition needle of lightcraft. Owing to the ignition n...Air-breathing mode laser propulsion experiment with a long-pulse transversely excited （TE） CO2 laser is carried out, and its ignition problem is solved with the ignition needle of lightcraft. Owing to the ignition needle, an order of magnitude reduction in the ignition threshold is demonstrated. The result is compared with previous study. The momentum coupling coefficient is also measured in the experiment and its dependence upon laser pulse energy （6 14 J） and pulse width （20, 32, and 40 μs） is discussed.展开更多
Purpose–The air-breathing hypersonic vehicle(AHV)includes intricate inherent coupling between the propulsion system and the airframe dynamics,which results in an intractable nonlinear system for the controller design...Purpose–The air-breathing hypersonic vehicle(AHV)includes intricate inherent coupling between the propulsion system and the airframe dynamics,which results in an intractable nonlinear system for the controller design.The purpose of this paper is to propose an H1 control method for AHV based on the online simultaneous policy update algorithm(SPUA).Design/methodology/approach–Initially,the H1 state feedback control problem of the AHV is converted to the problem of solving the Hamilton-Jacobi-Isaacs(HJI)equation,which is notoriously difficult to solve both numerically and analytically.To overcome this difficulty,the online SPUA is introduced to solve the HJI equation without requiring the accurate knowledge of the internal system dynamics.Subsequently,the online SPUA is implemented on the basis of an actor-critic structure,in which neural network(NN)is employed for approximating the cost function and a least-square method is used to calculate the NN weight parameters.Findings–Simulation study on the AHV demonstrates the effectiveness of the proposed H1 control method.Originality/value–The paper presents an interesting method for the H1 state feedback control design problem of the AHV based on online SPUA.展开更多
基金supported by the National Natural Science Foundation of China(9101601861273092+3 种基金61203012)the Foundation for Key Program of Ministry of Education of China(311012)the Key Program for Basic Research of Tianjin(11JCZDJC25100)the Key Program of Tianjin Natural Science(12JCZDJC30300)
文摘The focus of this paper is on control design and simulation for the longitudinal model of a flexible air-breathing hypersonic vehicle（FAHV）.The model of interest includes flexibility effects and intricate couplings between the engine dynamics and flight dynamics.To overcome the analytical intractability of this model,a nominal control-oriented model is constructed for the purpose of feedback control design in the first place.Secondly,the multi-input multi-output（MIMO） quasi-continuous high-order sliding mode（HOSM） controller is proposed to track step changes in velocity and altitude,which is based on full state feedback.The simulation results are presented to verify the effectiveness of the proposed control strategy.
基金supported by the National Natural Science Foundation of China(6082530390916005)+3 种基金the Aviation Science Fund of China (2009ZA77001)the Foundation for the Author of National Excellent Doctoral Dissertation of China(2007B4)the Key Laboratory Opening Funding(HIT.KLOF.2009099)the Key Laboratory of Integrated Automation for the Process Industry(Northeastern University),Ministry of Education
文摘This paper considers the problem of reference tracking control for the flexible air-breathing hypersonic flight vehicle with actuator delay and uncertainty.By constructing the Lyapunov functional including the lower and upper bounds of the time-varying delay,the non-fragile controller is designed such that the resulting closed-loop system is asymptotically stable and satisfies a prescribed performance cost index.The simulation results are given to show the effectiveness of the proposed control method,which is validated by excellent output reference altitude and velocity tracking performance.
基金Supported by National Natural Science Foundation of China(11672235)。
文摘A theoretical framework of nonlinear flight control for a flexible air-breathing hypersonic vehicle(FAHV)is proposed in this paper.In order to suppress the system uncertainty and external disturbance,an uncertainty and disturbance estimator(UDE)based back-stepping control strategy is designed for a dynamic state-feedback controller to provide stable velocity and altitude tracking.Firstly,the longitudinal dynamics of FAHV is simplified into a closure loop form with lumped uncertainty and disturbance.Then the UDE is applied to estimate the lumped uncertainty and disturbance for the purpose of control input compensation.While a nonlinear tracking differentiator is introduced to solve the problem of“explosion of term”in the back-stepping control.The stability of the UDE-based control strategy is proved by using Lyapunov stability theorem.Finally,simulation results are presented to demonstrate the capacity of the proposed control strategy.
基金supported by the National Natural Science Foundation of China(6120300761304239+1 种基金61503392)the Natural Science Foundation of Shaanxi Province(2015JQ6213)
文摘This paper focuses on synthesizing a mixed robust H_2/H_∞ linear parameter varying（LPV） controller for the longitudinal motion of an air-breathing hypersonic vehicle via a high order singular value decomposition（HOSVD） approach.The design of hypersonic flight control systems is highly challenging due to the enormous complexity of the vehicle dynamics and the presence of significant uncertainties.Motivated by recent results on both LPV control and tensor-product（TP） model transformation approach,the velocity and altitude tracking control problems for the air-breathing hypersonic vehicle is reduced to that of a state feedback stabilizing controller design for a polytopic LPV system with guaranteed performances.The controller implementation is converted into a convex optimization problem with parameterdependent linear matrix inequalities（LMIs） constraints,which is intuitively tractable using LMI control toolbox.Finally,numerical simulation results demonstrate the effectiveness of the proposed approach.
文摘Alterations in the respiratory epithelium of gills of a catfish, Heteropneustes fossilis by the sublethal and lethal concentrations of HgCl2 have been observcd using scanning electron microscope. Fish exposed to 0.1 ppm shows a thin coat ot mucus, but the continuous layer of mucus is not retained in 0.3 ppm after 24 h of exposure. Epithelial cells of the gill filament are hyperplastic. Other changcs in the respiratory epithelium are contraction of epithelium, formation of interlamellar bridge and diminishing number of microridges. Massive destruction of the respiratory epithelium by deep lesions and sloughing of epithelial layer in 0.5 and 1.0 ppm solutions after 6-12 h of exposure apparently causes death to the fish. SEM observations are well in conformity with the findings made at light microscopic level
文摘Laser propulsion is a new concept technique of propulsion and will have important application in future space technology. There are two main driving types: the air-breathing mode and the rocket ablation mode. Vertical flight experiments have been carried out with a simple paraboloid type lightcraft in the air-breathing mode by TEA-CO_2 laser. In simulation a new model is used for LSD/LSC wave, the result shows that the momentum coupling coefficient increases with the increase of the pulse energy.
文摘Air-Breathing Electric Thrusters (ABET) diagnostics is addressed, with on-ground prototypes in mind. It is based on detailed volume averaged Global Models and focuses on emission spectroscopy. Notably, the obtained optical emission spectroscopy diagnostics tools give important information about the thruster propellant constitution and also the ionization degree of each constituent. This allows for trade-off between various prototypes on the basis of their characterization and optimization.
文摘Histopathological effects of sublethal (0.1, 0.2, 0.3 ppm) and lethal (0.5, 1.0 ppm)solutions of mercuric chloride (HgCl2) have been studied on the gills of the air breathing catfish, Heteropneustes fossilis at the intervals ranging from 6h to 15 days. Thickening of the epithelium, swelling and hyperplasia of the mucous cells, fusion of secondary lamellae, formation of interlamellar bridge and deposition of mucous over the entire surface are some noteworthy features of mercury poisoning in sublethal concentrations. Acute pathological manifestations are formation of subepithelial space, sloughing of the epithelial layer, hemorrhage and hypertrophy of the mucous cells. Causes and impact of these cellular alterations affecting survival of the fish have been discussed
基金supported by the National Natural Science Foundation of China (32172962 and 31872579)the Fundamental Research Funds for the Central Universities of China (Project Number:2662020SCPY002).
文摘Fish skin acts as the first immune barrier against pathogens from external environments.Recently,fish skin immunity research has gradually become a hot topic in aquaculture disease control.Interestingly,the skin can do air-breathing in some bimodal respiration fish.However,there is no comprehensive understanding of these two functions.In this study,the skin regeneration of loach(Paramisgurnus dabryanus)was investigated through morphological and histological observations.Then,original skins(OS)and the regenerated skins(RS)when their capillaries were the most abundant during healing,were collected for transcriptomic analysis.285,899,386 clean reads with a total length of 42.34 Gb were obtained.A total of 1282 differentially expressed genes(DEGs)were detected,including 1030 DEGs up-regulated and 252 DEGs down-regulated in the comparison of RS vs.OS.Fc gamma R-mediated phagocytosis(containing gelsolin(Gsn)),chemokine signaling pathway(containing C-C motif chemokine ligand 28(Ccl28)),and B cell receptor signaling pathway(containing CD80 molecule(Cd81))were closely related to skin immune response of the loach.PI3K-Akt signaling pathway[containing fibronectin 1(Fn1)and lysyl oxidase-like 2b(Loxl2b)],TGF-beta signaling pathway[containing thrombospondin 1(Thbs1)],ECM-receptor interaction[containing integrin alpha 7(Itga7),Itgb8,Itgb10 and Itgb5],and dilated cardiomyopathy[containing laminin subunit alpha1(Lama1)]were closely associated with skin air-breathing of the loach.This study is conducive to explore the molecular mechanisms of skin immune response during its regeneration and air-breathing of bimodal respiration fish.This study will benefit for the aquaculture of P.dabryanus and its related species.
基金supported by the Aeronautical Science Foundation of China (No.20130196004)
文摘A novel adaptive neural control strategy is exploited for the longitudinal dynamics of a generic flexible air-breathing hypersonic vehicle（FAHV）.By utilizing functional decomposition method, the dynamics of FAHV is decomposed into the velocity subsystem and the altitude subsystem.For each subsystem, only one neural network is employed for the unknown function approximation.To further reduce the computational burden, minimal-learning parameter（MLP）technology is used to estimate the norm of ideal weight vectors rather than their elements.By introducing sliding mode differentiator（SMD） to estimate the newly defined variables, there is no need for the strict-feedback form and virtual controller.Hence the developed control law is considerably simpler than the ones derived from back-stepping scheme.Finally, simulation studies are made to illustrate the effectiveness of the proposed control approach in spite of the flexible effects, system uncertainties and varying disturbances.
文摘This article develops a polytopic linear pa- rameter varying （LPV） model and presents a non-fragile H2 gain-scheduled control for a flexible air-breathing hypersonic vehicle （FAHV）. First, the polytopic LPV model of the FAHV can be obtained by using Jacobian linearization and tensor-product （TP） model transfor- mation approach, simulation verification illustrates that the polytopic LPV model captures the local nonlinear- ities of the original nonlinear system. Second, based on the developed polytopic LPV model, a non-fragile gain- scheduled control method is proposed in order to reduce the fragility encountered in controller implementation, a convex optimisation problem with linear matrix in- equalities （LMIs） constraints is formulated for designing a velocity and altitude tracking controller, which guar- antees//2 control performance index. Finally, numerical simulations have demonstrated the effectiveness of the proposed approach.
基金National Natural Science Foundation of China(50976094, 51176158)Reseach Fund for the Doctoral Program of Higher Education of China(20096102110022)Doctorate Foundation of Northwestern Polytechnical University (CX200909)
文摘Nozzle effects on thrust and inlet pressure of a multi-cycle air-breathing pulse detonation engine （APDE） are investigated experimentally. An APDE with 68 mm in diameter and 2 050 mm in length is operated using gasoline/air mixture. Straight nozzle, converging nozzle, converging-diverging nozzle and diverging nozzle are tested. The results show that thrust augmentation of converging-diverging nozzle, diverging nozzle or straight nozzle is better than that of converging nozzle on the whole. Thrust augmentation of straight nozzle is worse than those of converging-diverging nozzle and diverging nozzle. Thrust augmentations of diverging nozzle with larger expansion ratio and converging-diverging nozzle with larger throat area range from 20% to 40% on tested frequencies and are better than those of congeneric other nozzles respectively. Nozzle effects on inlet pressure are also researched. At each frequency it is indicated that filling pressures and average peak pressures of inlet with diverging nozzle and converging-diverging nozzle with large throat cross section area are higher than those with straight nozzle and converging nozzle Pressures near thrust wall increase in an increase order from without nozzle, with diverging nozzle, straight nozzle and converging-diverging nozzle to converging nozzle.
基金the National Natural Science Foundation of China （No. 11672235）
文摘The flight dynamics model of air-breathing hypersonic vehicles （AHVs） is highly nonlinear and multivariable cou- pling, and includes inertial uncertainties and external disturbances that require strong, robust, and high-accuracy controllers. In this paper, we propose a linear-quadratic regulator （LQR） design method based on stochastic robustness analysis for the longitudinal dynamics of AHVs. First, input/output feedback linearization is used to design LQRs. Second, subject to various system parameter uncertainties, system robustness is characterized by the probability of stability and desired performance. Then, the mapping rela- tionship between system robustness and LQR parameters is established. Particularly, to maximize system robustness, a novel hybrid particle swarm optimization algorithm is proposed to search for the optimal LQR parameters. During the search iteration, a Chernoff bound algorithm is applied to determine the finite sample size of Monte Carlo evaluation with the given prohabilily levels. Finally, simulation results show that the optimization algorithm can effectively find the optimal solution to the LQR parameters.
基金supported by National Natural Science Foundation of China(No.61803348)National Nature Science Foundation of China as National Major Scientific Instruments Development Project(No.61927807)+5 种基金State Key Laboratory of Deep Buried Target Damage,China(No.DXMBJJ2019-02)Scientific and Technological Innovation Programs of Higher Education Institutions in Shanxi,China(No.2020L0266)Shanxi Province Science Foundation for Youths,China(No.201701D221123)Youth Academic North University of China(No.QX201803)Program for the Innovative Talents of Higher Education Institutions of ShanxiShanxi“1331 Project” Key Subjects Construction,China(1331KSC)。
文摘In this paper,a prescribed fast tracking control scheme is proposed for Flexible Airbreathing Hypersonic Vehicles(FAHV)subject to lumped disturbances and limited resources.To maintain tracking errors of velocity and altitude converge to a predefined region with a prescribed time and release the transient intense fluctuations encountered in classical Prescribed Performance Control(PPC)using a fast decaying rate,a tracking differentiator-based PPC is presented,where the reaching time and the maximum time differentiation of preselected envelopes can be regulated as a prior via fixing an acceleration factor,so that a guaranteed fast convergence speed can be realized with reduced oscillations.Besides,to avoid the excessive occupation of limited resources(energy and communication)and guarantee a remarkable tracking accuracy,switching event-triggered mechanisms are constructed for FAHV control realization,which provide a promising way to pursue a desired level of tracking performance with a low energy consumption.Subsequently,Uncertainty and Disturbance Estimators(UDE)and Sigmoid function-based Tracking Differentiators(STD)are employed to provide disturbance estimation and reference derivation with a low computational complexity.Finally,robust control laws are designed to compensate for the sampling error induced by event-triggered conditions,meanwhile Zeno phenomena can be effectively eliminated.The simulation results and comparisons validate the effectiveness of the proposed scheme.
基金Acknowledgments The authors gratefully acknowledge the financial support of the National Natural Science Foundation of China （51576021, 51222603, 51276208 and 51325602） and the National High-Tech R＆D Program of China （2015AA043503）.
文摘In this study, a membraneless, monolithic micro photocatalytic fuel cell with an air-breathing cathode was developed for simultaneous wastewater treatment and electricity generation. In this newly-developed micro photocatalytic fuel cell, the photoanode and cathode were arranged with a shoulder-to-shoulder design, forming two planar electrodes. Such design offers several advantages of enhanced mass transfer, uniform light distribution, short light transfer path, membrane elimination and easy fabrication, integration, and compatibility with other microdevices. The performance of this type fuel cell was evaluated by using methanol as a model pollutant under the alkaline condition. Experimental results indicated the developed micro photocatalytic fuel cell was able to show good photo-response to the illumination and satisfactory performance as well as durability. Parametric study on the cell performance was also performed. It was found that increasing the light intensity, methanol concentration andKOH concentration could improve the cell performance. But for the effect of the liquid flow rate, it was shown that the cell performance firstly increased with increasing the liquid flow rate and then decreased with further increasing the liquid flow rate. This study not only opens a new avenue for the design of the micro photocatalytic fuel cell but also is helpful for the optimization of the operating conditions.
基金supported by the National Nature Science Foundation of China(Grant No.52100021)the China Postdoctoral Science Foundation(Grants No.2022M720004 and No.2022M710208)。
文摘Microbial fuel cells(MFCs)incorporating air-breathing cathodes have emerged as a promising ecofriendly wastewater treatment technology capable of operating on an energy-free basis.However,the inevitable biofouling of these devices rapidly decreases cathodic catalytic activity and also reduces the stability of MFCs during long-term operation.The present work developed a novel microbial separator for use in air-breathing MFCs that protects cathodic catalytic activity.In these modified devices,microbes preferentially grow on the microbial separator rather than the cathodic surface such that biofouling is prevented.Trials showed that this concept provided low charge transfer and mass diffusion resistance values during the cathodic oxygen reduction reaction of 4.6±1.3 and 17.3±6.8 U,respectively,after prolonged operation.The maximum power density was found to be stable at 1.06±0.07 W m2 throughout a long-term test and the chemical oxygen demand removal efficiency was increased to 92%compared with a value of 83%for MFCs exhibiting serious biofouling.In addition,a cathode combined with a microbial separator demonstrated less cross-cathode diffusion of oxygen to the anolyte.This effect indirectly induced the growth of electroactive bacteria and produced higher currents in air-breathing MFCs.Most importantly,the present microbial separator concept enhances both the lifespan and economics of air-breathing MFCs by removing the need to replace or regenerate the cathode during longterm operation.These results indicate that the installation of a microbial separator is an effective means of stabilizing power generation and ensuring the cost-effective performance of air-breathing MFCs intended for future industrial applications.
基金National Natural Science Foundation of China(10672184)
文摘Altitude characteristic is of great importance for studying when an air-breathing pulsed laser thruster works in the dense atmosphere condition of 0-30 km altitude. The experimental findings all over the world show that the similar relationship between impulse coupling coefficient and altitude. According to strong explosion theory and an ideal gas model,a dimensionless factor indicating energy law of similitude is introduced,and formula of impulse coupling coefficient is deducted. Then theoretical study of altitude characteristic is carried out and mechanism of altitude characteristic is further explained. The results indicate that there is a maximum value of impulse coupling coefficient if the dimensionless factor equals to 0.41 in theory, and whether the phenomena of maximum appear or not depends on the range of the dimensionless factor related to altitude. As to a conical nozzle with the fixed length of 120 mm, the relationship between the sonic velocity and the dimensionless factor causes the maximum phenomenon at the altitude of about 12.5 km,and maximum theoretical impulse coupling coefficient is also found in the experimental investigations. The mechanism of altitude characteristic for air-breathing pulsed laser thruster is discovered in this article, which will provide reference for further research on altitude characteristic.
基金financial support granted by National Key R&D Program of China from Ministry of Science and Technology of China (Nos. 2020YFB1505700, 2016YFA0200700)China Postdoctoral Science Foundation (No. 2021M702408)+4 种基金the National Natural Science Foundation of China (No. 22172191)Dongyue Polymer Material Company of Dongyue FederationState Key Laboratory of Fluorinated Functional Membrane Materials(Dongyue Group institute)Dongyue Future Hydrogen Energy Materials Companysponsored by the Collaborative Innovation Center of Suzhou Nano Science and Technology。
文摘Air-breathing proton exchange membrane fuel cells(PEMFCs) are very promising portable energy with many advantages. However, its power density is low and many additional supporting parts affect its specific power. In this paper, we aim to improve the air diffusion and fuel cell performance by employing a novel condensing-tower-like curved flow field rather than an additional fan, making the fuel cell more compact and has less internal power consumption. Polarization curve test and galvanostatic discharge test are carried out and proved that curved flow field can strengthen the air diffusion into the PEMFC and improve its performance. With appropriate curved flow field, the fuel cell peak power can be 55.2%higher than that of planar flow field in our study. A four-layer stack with curved cathode flow field is fabricated and has a peak power of 2.35 W(120 W/kg).
文摘Air-breathing mode laser propulsion experiment with a long-pulse transversely excited （TE） CO2 laser is carried out, and its ignition problem is solved with the ignition needle of lightcraft. Owing to the ignition needle, an order of magnitude reduction in the ignition threshold is demonstrated. The result is compared with previous study. The momentum coupling coefficient is also measured in the experiment and its dependence upon laser pulse energy （6 14 J） and pulse width （20, 32, and 40 μs） is discussed.
基金supported by the National Basic Research Program of China(973 Program)(2012CB720003)the National Natural Science Foundation of China under Grants 91016004,61074057 and 61121003.
文摘Purpose–The air-breathing hypersonic vehicle(AHV)includes intricate inherent coupling between the propulsion system and the airframe dynamics,which results in an intractable nonlinear system for the controller design.The purpose of this paper is to propose an H1 control method for AHV based on the online simultaneous policy update algorithm(SPUA).Design/methodology/approach–Initially,the H1 state feedback control problem of the AHV is converted to the problem of solving the Hamilton-Jacobi-Isaacs(HJI)equation,which is notoriously difficult to solve both numerically and analytically.To overcome this difficulty,the online SPUA is introduced to solve the HJI equation without requiring the accurate knowledge of the internal system dynamics.Subsequently,the online SPUA is implemented on the basis of an actor-critic structure,in which neural network(NN)is employed for approximating the cost function and a least-square method is used to calculate the NN weight parameters.Findings–Simulation study on the AHV demonstrates the effectiveness of the proposed H1 control method.Originality/value–The paper presents an interesting method for the H1 state feedback control design problem of the AHV based on online SPUA.
